Democracy and party dominance in Kenya and South Africa : a comparative study of the Kenya African National Union and the African National Congres
- Authors: Mwangi, Oscar Gakuo
- Date: 2013-08-15
- Subjects: Kenya African National Union African National Congress Political parties -- South Africa Political parties -- Kenya Democracy -- South Africa Democracy -- Kenya South Africa -- Politics and government Kenya -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2876 , http://hdl.handle.net/10962/d1008431
- Description: Kenya and South Africa can be described as dominant party systems, under the dominance of the Kenya African National Union CKANU) and the African National Congress CANC) respectively. A dominant party system is in essence a democracy. The spirit of democracy may, however, apparently be contradicted by the weight of party dominance, thus questioning the content of and prospects for democracy under party dominance in both Kenya and South Africa. The study is a comparative analysis of party dominance in Kenya and South Africa. The main objective is to exan1ine the relationship between party dominance and democracy in both countries. It seeks to find out how party dominance is reproducing itself and surviving the post 1990 transition processes in Kenya and South Africa. More importantly, the study also seeks to find out how party dominance impacts upon institutions that support or uphold democratization and subsequently democracy. The findings of the study demonstrate that party dominance has reproduced itself and survived the post-1990 period, and is also impacting upon democratization and democracy. The dominant parties take a similar trajectory in pursuit of dominance over the state and its apparatuses. However, they differ when it comes to their relationship with the civil society. That between KANU and civil society is antagonistic, as the ruling party seeks to augment political power through authoritarian dominance of the latter to, while that of the ANC and civil society is responsive, as the former seeks to enhance political stability in the country. The impact of party dominance upon institutions that support democracy takes similar and different trajectories in both countries. Similarities arise with respect to the detrimental impact upon institutions of the Executive that ensure accountability and transparency, evident in the increasing cases of corruption, nepotism and political patronage appointments. Similarly, there has been a detrimental impact upon the Legislature regarding parliamentary proceedings. Parliamentary committees and opposition parties are being rendered ineffective as organs of ensuring transparency and accountability, and are often subject to delegitimation. The impact of party dominance on the Judiciary, however, differs in both countries. In Kenya, the judiciary continues to suffer from excessive interference from the Executive and the ruling party, whereas in South Africa the judicial system remains largely independent with regard to the application of justice, despite constant criticisms from the dominant party. The study concludes that South Africa is, gradually, going the Kenyan way. If this condition is left unchecked there is the possibility that South Africa could eventually end up a psuedo-democracy like Kenya, where formal democratic political institutions such as multiparty elections, exist to mask the reality of authoritarian dominance. The thesis recommends that strengthening civil society organizations, opposition political parties, and state institutions in both countries to ensure greater accountability and transparency, will reverse this detrimental effect of party dominance. It also recommends meaningful constitutional reforms that will guarantee greater independence of these institutions, and the decentralization of governmental and political power to check and limit the powers of the dominant party. Also recommended are areas for further research. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Mwangi, Oscar Gakuo
- Date: 2013-08-15
- Subjects: Kenya African National Union African National Congress Political parties -- South Africa Political parties -- Kenya Democracy -- South Africa Democracy -- Kenya South Africa -- Politics and government Kenya -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2876 , http://hdl.handle.net/10962/d1008431
- Description: Kenya and South Africa can be described as dominant party systems, under the dominance of the Kenya African National Union CKANU) and the African National Congress CANC) respectively. A dominant party system is in essence a democracy. The spirit of democracy may, however, apparently be contradicted by the weight of party dominance, thus questioning the content of and prospects for democracy under party dominance in both Kenya and South Africa. The study is a comparative analysis of party dominance in Kenya and South Africa. The main objective is to exan1ine the relationship between party dominance and democracy in both countries. It seeks to find out how party dominance is reproducing itself and surviving the post 1990 transition processes in Kenya and South Africa. More importantly, the study also seeks to find out how party dominance impacts upon institutions that support or uphold democratization and subsequently democracy. The findings of the study demonstrate that party dominance has reproduced itself and survived the post-1990 period, and is also impacting upon democratization and democracy. The dominant parties take a similar trajectory in pursuit of dominance over the state and its apparatuses. However, they differ when it comes to their relationship with the civil society. That between KANU and civil society is antagonistic, as the ruling party seeks to augment political power through authoritarian dominance of the latter to, while that of the ANC and civil society is responsive, as the former seeks to enhance political stability in the country. The impact of party dominance upon institutions that support democracy takes similar and different trajectories in both countries. Similarities arise with respect to the detrimental impact upon institutions of the Executive that ensure accountability and transparency, evident in the increasing cases of corruption, nepotism and political patronage appointments. Similarly, there has been a detrimental impact upon the Legislature regarding parliamentary proceedings. Parliamentary committees and opposition parties are being rendered ineffective as organs of ensuring transparency and accountability, and are often subject to delegitimation. The impact of party dominance on the Judiciary, however, differs in both countries. In Kenya, the judiciary continues to suffer from excessive interference from the Executive and the ruling party, whereas in South Africa the judicial system remains largely independent with regard to the application of justice, despite constant criticisms from the dominant party. The study concludes that South Africa is, gradually, going the Kenyan way. If this condition is left unchecked there is the possibility that South Africa could eventually end up a psuedo-democracy like Kenya, where formal democratic political institutions such as multiparty elections, exist to mask the reality of authoritarian dominance. The thesis recommends that strengthening civil society organizations, opposition political parties, and state institutions in both countries to ensure greater accountability and transparency, will reverse this detrimental effect of party dominance. It also recommends meaningful constitutional reforms that will guarantee greater independence of these institutions, and the decentralization of governmental and political power to check and limit the powers of the dominant party. Also recommended are areas for further research. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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An analysis of selected World Trade Organisation agreements to determine whether they discriminate unfairly against developing economices
- Authors: Grimett, Leticia Anthea
- Date: 2013-07-29
- Subjects: World Trade Organization Foreign trade regulation General Agreement on Tariffs and Trade (Organization) Free trade -- Developing countries Foreign trade regulation -- Developing countries Competition, Unfair -- Developing countries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3718 , http://hdl.handle.net/10962/d1008368
- Description: The focus of this thesis is the question whether or not the WTO discriminates unfairly against developing economies. In the absence of a test of guidelines for detennining unfairness or fairness of WTO provisions or Agreements has been drawn up using welfare economic and constitutional law principles as a foundation. Unfairness is therefore determined by asking whether the provisions of each Agreement are rational, proportional, efficient and whether they prevent the abuse of power amongst states. In addition, the economic effects of the provisions of the selected Agreements have been analysed to determine whether the relevant provisions are welfare enhancing and conclusive to promoting growth and development within developing economies. The Agreements chosed for analysis are the Agreements on Trade-related Investment Measures (TRIMS), Trade-related Intellectual Property (TRIPS), Agriculture and Services (GATS). The dispute settlement and negotiating process, labour standards and the impact of decreasing most-favoured nation rates on developing economy competitiveness is also discussed. Application of the test has shown that the WTO provisions do not reflect the interests of all members. Even though most member states are developing economies, the3 Agreements constantly cater foe developed country concerns and interests. Where provision is made for developing country interests, it is the LDC's who are favoured, with nonnal developing economies being bound by the same provisions as the developed economies. A fonnal, as opposed to a substantive, defmition has been adopted by the WTO, with a result that the process of equality is placed above the outcomes. While concessions have been made to development, members have not gone for enough. A main reason for the imbalance can be attributed to the negotiating process, which is based upon concessionary bargaining and trade-off. Those states with greater economic power are therefore at an advantage as they have the leverage needed to influence the outcomes of negotiations and hence the provisions of the various Agreements. Even with the LDC's, the WTO has been found to discriminate unfairly against developing economies because it does not adequately address developing country concerns. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Grimett, Leticia Anthea
- Date: 2013-07-29
- Subjects: World Trade Organization Foreign trade regulation General Agreement on Tariffs and Trade (Organization) Free trade -- Developing countries Foreign trade regulation -- Developing countries Competition, Unfair -- Developing countries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3718 , http://hdl.handle.net/10962/d1008368
- Description: The focus of this thesis is the question whether or not the WTO discriminates unfairly against developing economies. In the absence of a test of guidelines for detennining unfairness or fairness of WTO provisions or Agreements has been drawn up using welfare economic and constitutional law principles as a foundation. Unfairness is therefore determined by asking whether the provisions of each Agreement are rational, proportional, efficient and whether they prevent the abuse of power amongst states. In addition, the economic effects of the provisions of the selected Agreements have been analysed to determine whether the relevant provisions are welfare enhancing and conclusive to promoting growth and development within developing economies. The Agreements chosed for analysis are the Agreements on Trade-related Investment Measures (TRIMS), Trade-related Intellectual Property (TRIPS), Agriculture and Services (GATS). The dispute settlement and negotiating process, labour standards and the impact of decreasing most-favoured nation rates on developing economy competitiveness is also discussed. Application of the test has shown that the WTO provisions do not reflect the interests of all members. Even though most member states are developing economies, the3 Agreements constantly cater foe developed country concerns and interests. Where provision is made for developing country interests, it is the LDC's who are favoured, with nonnal developing economies being bound by the same provisions as the developed economies. A fonnal, as opposed to a substantive, defmition has been adopted by the WTO, with a result that the process of equality is placed above the outcomes. While concessions have been made to development, members have not gone for enough. A main reason for the imbalance can be attributed to the negotiating process, which is based upon concessionary bargaining and trade-off. Those states with greater economic power are therefore at an advantage as they have the leverage needed to influence the outcomes of negotiations and hence the provisions of the various Agreements. Even with the LDC's, the WTO has been found to discriminate unfairly against developing economies because it does not adequately address developing country concerns. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
An analysis of the impact of democratization on debt-led growth : the Nigerian experience, 1970-2000
- Authors: Dinneya, Godson Eze
- Date: 2013-05-22
- Subjects: Debts, External -- Nigeria Nigeria -- Politics and government -- 1960- Nigeria -- Economic policy Nigeria -- Economic conditions -- 1960-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1074 , http://hdl.handle.net/10962/d1007807
- Description: The debt-for democracy hypothesis is that undemocratic governments were largely responsible for not only the accumulation but also poor management of externally sourced capital resources. External borrowing had therefore failed to lead to growth of the economies of debtor countries under undemocratic political leadership. Despite this explanation of the debt problem conventional empirical analyses of the debt-growth relationship did not include political institutional variables. This study investigates the relationship between democratization and debt-led growth, using Nigeria, a typical debtor country whose politics was dominated by 'undemocratic ' governance, as a case study. Two broad research questions are investigated namely, whether available data support a negative or positive contribution of debt to the growth of the Nigeria economy during the period 1970-2000; and ifso was there any link between the levels of democratization in Nigeria and debt-led growth. Using a census of major political events in Nigeria around four dimensions of democratization, four primary indices of democratization and one composite index were constructed for the period. Using the Taylor (1983) marginal conditions to gauge the contribution of external debt to the growth of the Nigerian economy, the study found that external debt is capable of playing a double edged sword on the performance of the economy. Positive contributions coincided with the periods when Nigeria's oil dominated foreign exchange revenues were robust, and/ or when debt management strategies were better articulated and vice versa. The analyses of the link between democratization and debt-led growth using both correlation and regression techniques, yielded different results in two definitional contexts of debt-led growth. When defined purely in terms of the Taylor marginal conditions for a positive contribution of debt to the economy of a borrowing nation, the results support the pessimist view that democratization impeded growth. On the contrary, when debt-led growth was defined in a broader sense to incorporate variables such as domestic savings and investment, foreign direct investments, public and private consumption and debt burden, there was strong evidence that debt-led growth performed beller at higher levels of democratization than other wise. The result using the narrow definition was found to be a direct consequence of the overriding influence of export performance in the Taylor conditions. With Nigeria's exports almost entirely dominated by extractive industry the result derived using the narrow definition confirmed the theoretical links between natural resource endowment and regime type on the one hand, and external capital and the nature of the host country 's industry on the other. In the first resource dependence allowed the political leadership to be more detached and less accountable to the electorate since they did not need to levy taxes. Secondly foreign investors concerned with security of their sunk investments in the extractive oil induslly in particular favoured continuity of powerfol regimes with less democratic content. In both findings one thing was common: democratization was associated more with those factors whose decreases affect growth positively than with those whose increases improve growth. The conclusion from this is that the impact of democratization is stronger with negative than with positive growth factors. In other words, while democratization may be supportive of growth its greater impact appears to be in limiting the factors that themselves limit growth. To benefit from the favourable impact of democratisation on debt-led growth therefore the study suggests that improvements in the democratisation process in Nigeria is needed It identifies political education as central to this improvement. A model is developed to show how improvements in the political institutional framework may trickle down, through an enabling environment that is capable of engendering growth-enhancing domestic and international responses to lead in the direction of debt-led growth.
- Full Text:
An analysis of the impact of democratization on debt-led growth : the Nigerian experience, 1970-2000
- Authors: Dinneya, Godson Eze
- Date: 2013-05-22
- Subjects: Debts, External -- Nigeria Nigeria -- Politics and government -- 1960- Nigeria -- Economic policy Nigeria -- Economic conditions -- 1960-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1074 , http://hdl.handle.net/10962/d1007807
- Description: The debt-for democracy hypothesis is that undemocratic governments were largely responsible for not only the accumulation but also poor management of externally sourced capital resources. External borrowing had therefore failed to lead to growth of the economies of debtor countries under undemocratic political leadership. Despite this explanation of the debt problem conventional empirical analyses of the debt-growth relationship did not include political institutional variables. This study investigates the relationship between democratization and debt-led growth, using Nigeria, a typical debtor country whose politics was dominated by 'undemocratic ' governance, as a case study. Two broad research questions are investigated namely, whether available data support a negative or positive contribution of debt to the growth of the Nigeria economy during the period 1970-2000; and ifso was there any link between the levels of democratization in Nigeria and debt-led growth. Using a census of major political events in Nigeria around four dimensions of democratization, four primary indices of democratization and one composite index were constructed for the period. Using the Taylor (1983) marginal conditions to gauge the contribution of external debt to the growth of the Nigerian economy, the study found that external debt is capable of playing a double edged sword on the performance of the economy. Positive contributions coincided with the periods when Nigeria's oil dominated foreign exchange revenues were robust, and/ or when debt management strategies were better articulated and vice versa. The analyses of the link between democratization and debt-led growth using both correlation and regression techniques, yielded different results in two definitional contexts of debt-led growth. When defined purely in terms of the Taylor marginal conditions for a positive contribution of debt to the economy of a borrowing nation, the results support the pessimist view that democratization impeded growth. On the contrary, when debt-led growth was defined in a broader sense to incorporate variables such as domestic savings and investment, foreign direct investments, public and private consumption and debt burden, there was strong evidence that debt-led growth performed beller at higher levels of democratization than other wise. The result using the narrow definition was found to be a direct consequence of the overriding influence of export performance in the Taylor conditions. With Nigeria's exports almost entirely dominated by extractive industry the result derived using the narrow definition confirmed the theoretical links between natural resource endowment and regime type on the one hand, and external capital and the nature of the host country 's industry on the other. In the first resource dependence allowed the political leadership to be more detached and less accountable to the electorate since they did not need to levy taxes. Secondly foreign investors concerned with security of their sunk investments in the extractive oil induslly in particular favoured continuity of powerfol regimes with less democratic content. In both findings one thing was common: democratization was associated more with those factors whose decreases affect growth positively than with those whose increases improve growth. The conclusion from this is that the impact of democratization is stronger with negative than with positive growth factors. In other words, while democratization may be supportive of growth its greater impact appears to be in limiting the factors that themselves limit growth. To benefit from the favourable impact of democratisation on debt-led growth therefore the study suggests that improvements in the democratisation process in Nigeria is needed It identifies political education as central to this improvement. A model is developed to show how improvements in the political institutional framework may trickle down, through an enabling environment that is capable of engendering growth-enhancing domestic and international responses to lead in the direction of debt-led growth.
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A critical analysis of governance and management in Zimbabwe's colleges of technical and vocational education: issues for revitalisation
- Authors: Mbizvo, Washington T
- Date: 2003
- Subjects: Education, Higher -- Zimbabwe Universities and colleges -- Zimbabwe Universities and colleges -- Zimbabwe -- Administration Vocational education -- Zimbabwe Technical education -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1469 , http://hdl.handle.net/10962/d1003350
- Description: This research was carried out in order to gain a better understanding of the practice of governance in a technical or vocationally oriented college and the critical role played by the principal as a college manager within the governance system in which industrialists and head office are also key players. Conceptual literature relating to issues of governance and management within the education scenario is examined. The wider issues of governance are critically analysed in the context of power and control mechanisms initiated by the Ministry of Higher Education as the responsible authority for the colleges. The influence of the industrial sector as the consumers of skilled labour force is analysed through college advisory councils set up in terms of the relevant pieces of legislation. The research is qualitative and takes the form of three case studies of technical and vocational colleges in Zimbabwe. Data were collected through multiple methods from varied sources with a view to ensuring triangulation. The multiple-case design enabled me to dig beneath the surface of what apparently happens in these organisations and unearth issues and concerns at the wider governance and management levels. Views and experiences of participants are captured and explained through in-depth interviews, observations and documentary sources. Results are discussed in relation to the relevant literature allowing grounded theory to emerge. The research highlights the roles of key players in governance and the issues of relationships among these actors. What emerges is a desperate situation of ineffectiveness, problematic processes in governance and poor responsiveness of these colleges to the labour market demands. The potential for generalisability and transferability is discussed in the report and possible corrective intervention strategies are recommended. The thesis demonstrates that managers of these colleges and indeed senior officers in head office who are at the centre of governance and will need transformational leadership development in order for them to come to terms with such things as people’s feelings, abandoning ‘outdated’ policies, managing change, and handling communication effectively. Various strategies for revitalisation of governance and management in technical and vocational colleges are suggested.
- Full Text:
- Date Issued: 2003
- Authors: Mbizvo, Washington T
- Date: 2003
- Subjects: Education, Higher -- Zimbabwe Universities and colleges -- Zimbabwe Universities and colleges -- Zimbabwe -- Administration Vocational education -- Zimbabwe Technical education -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1469 , http://hdl.handle.net/10962/d1003350
- Description: This research was carried out in order to gain a better understanding of the practice of governance in a technical or vocationally oriented college and the critical role played by the principal as a college manager within the governance system in which industrialists and head office are also key players. Conceptual literature relating to issues of governance and management within the education scenario is examined. The wider issues of governance are critically analysed in the context of power and control mechanisms initiated by the Ministry of Higher Education as the responsible authority for the colleges. The influence of the industrial sector as the consumers of skilled labour force is analysed through college advisory councils set up in terms of the relevant pieces of legislation. The research is qualitative and takes the form of three case studies of technical and vocational colleges in Zimbabwe. Data were collected through multiple methods from varied sources with a view to ensuring triangulation. The multiple-case design enabled me to dig beneath the surface of what apparently happens in these organisations and unearth issues and concerns at the wider governance and management levels. Views and experiences of participants are captured and explained through in-depth interviews, observations and documentary sources. Results are discussed in relation to the relevant literature allowing grounded theory to emerge. The research highlights the roles of key players in governance and the issues of relationships among these actors. What emerges is a desperate situation of ineffectiveness, problematic processes in governance and poor responsiveness of these colleges to the labour market demands. The potential for generalisability and transferability is discussed in the report and possible corrective intervention strategies are recommended. The thesis demonstrates that managers of these colleges and indeed senior officers in head office who are at the centre of governance and will need transformational leadership development in order for them to come to terms with such things as people’s feelings, abandoning ‘outdated’ policies, managing change, and handling communication effectively. Various strategies for revitalisation of governance and management in technical and vocational colleges are suggested.
- Full Text:
- Date Issued: 2003
A neural network based ionospheric model for the bottomside electron density profile over Grahamstown, South Africa
- Authors: McKinnell, L A
- Date: 2003
- Subjects: Neural networks (Computer science) Ionospheric electron density -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5477 , http://hdl.handle.net/10962/d1005262
- Description: This thesis describes the development and application of a neural network based ionospheric model for the bottomside electron density profile over Grahamstown, South Africa. All available ionospheric data from the archives of the Grahamstown (33.32ºS, 26.50ºE) ionospheric station were used for training neural networks (NNs) to predict the parameters required to produce the final profile. Inputs to the model, called the LAM model, are day number, hour, and measures of solar and magnetic activity. The output is a mathematical description of the bottomside electron density profile for that particular input set. The two main ionospheric layers, the E and F layers, are predicted separately and then combined at the final stage. For each layer, NNs have been trained to predict the individual ionospheric characteristics and coefficients that were required to describe the layer profile. NNs were also applied to the task of determining the hours between which an E layer is measurable by a groundbased ionosonde and the probability of the existence of an F1 layer. The F1 probability NN is innovative in that it provides information on the existence of the F1 layer as well as the probability of that layer being in a L-condition state - the state where an F1 layer is present on an ionogram but it is not possible to record any F1 parameters. In the event of an L-condition state being predicted as probable, an L algorithm has been designed to alter the shape of the profile to reflect this state. A smoothing algorithm has been implemented to remove discontinuities at the F1-F2 boundary and ensure that the profile represents realistic ionospheric behaviour in the F1 region. Tests show that the LAM model is more successful at predicting Grahamstown electron density profiles for a particular set of inputs than the International Reference Ionosphere (IRI). It is anticipated that the LAM model will be used as a tool in the pin-pointing of hostile HF transmitters, known as single-site location.
- Full Text:
- Date Issued: 2003
- Authors: McKinnell, L A
- Date: 2003
- Subjects: Neural networks (Computer science) Ionospheric electron density -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5477 , http://hdl.handle.net/10962/d1005262
- Description: This thesis describes the development and application of a neural network based ionospheric model for the bottomside electron density profile over Grahamstown, South Africa. All available ionospheric data from the archives of the Grahamstown (33.32ºS, 26.50ºE) ionospheric station were used for training neural networks (NNs) to predict the parameters required to produce the final profile. Inputs to the model, called the LAM model, are day number, hour, and measures of solar and magnetic activity. The output is a mathematical description of the bottomside electron density profile for that particular input set. The two main ionospheric layers, the E and F layers, are predicted separately and then combined at the final stage. For each layer, NNs have been trained to predict the individual ionospheric characteristics and coefficients that were required to describe the layer profile. NNs were also applied to the task of determining the hours between which an E layer is measurable by a groundbased ionosonde and the probability of the existence of an F1 layer. The F1 probability NN is innovative in that it provides information on the existence of the F1 layer as well as the probability of that layer being in a L-condition state - the state where an F1 layer is present on an ionogram but it is not possible to record any F1 parameters. In the event of an L-condition state being predicted as probable, an L algorithm has been designed to alter the shape of the profile to reflect this state. A smoothing algorithm has been implemented to remove discontinuities at the F1-F2 boundary and ensure that the profile represents realistic ionospheric behaviour in the F1 region. Tests show that the LAM model is more successful at predicting Grahamstown electron density profiles for a particular set of inputs than the International Reference Ionosphere (IRI). It is anticipated that the LAM model will be used as a tool in the pin-pointing of hostile HF transmitters, known as single-site location.
- Full Text:
- Date Issued: 2003
A phenomenological study of how South African entrepreneurs experience and deal with ethical dilemmas
- Authors: Robinson, David Alan
- Date: 2003
- Subjects: Entrepreneurship -- South Africa Business ethics -- South Africa Decision making -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1175 , http://hdl.handle.net/10962/d1002791
- Description: This research sets out to examine how entrepreneurs experience and deal with ethical dilemmas. An entrepreneur is defined as a person who creates something of value and assumes the risk of establishing and managing a business around it. An ethical dilemma comes about when the entrepreneur must choose between alternatives and where the morally correct choice is unclear. This may be due to conflicting personal values or loyalties, tensions arising out of the realization that the moral action is not in line with his self-interest, cross-cultural conflict, or moral ambiguity. Because of the nature of entrepreneurship, the entrepreneur typically lives with ever-present threats arising from limited resources, competition, and the risk of business failure. His actions must simultaneously ensure survival, maximize profit, limit risk, counter threats, optimize the use of resources, and reward him with a feeling of satisfaction. It is hardly surprising that conflicting priorities sometimes ensue. It is also widely believed that these entrepreneurial pursuits supersede the more general need to act in morally appropriate ways. This is a phenomenological study, based on interviews with seven entrepreneurs in established service-oriented ventures. They were asked to describe their business, any dilemmas they have experienced, how they were handled, and what challenges they experience as entrepreneurs in South Africa today. Using phenomenology as my vehicle for data collection and analysis, I sought to enter the lived-worlds of my participants to discover the essence of how ethical dilemmas are experienced in the entrepreneurial milieu. The study’s findings reflect that each entrepreneur has a distinctive world-view, which is represented by a complex mosaic of virtue ethics, deontology, utilitarianism and metaethical perspectives. The permutations are numerous, thus negating the possibility of typecasting entrepreneurs. Instead this research introduces the reader to aspects of entrepreneurial reality such as the complexity of cultural diversity, the freedom to limit the amount of personal energy given to business, and the existence of a more sensitive, searching inner soul beneath the apparent hard-nosed business-oriented public image. While examining entrepreneurial dilemmas in depth, this research introduces the dilemma drum as a tool to portray the argument form of any dilemma by making explicit the ethical component inherent in every business decision and facilitating its effective resolution in a non-prescriptive way. The findings identify certain individual characteristics of participant entrepreneurs that are unlike anything in the mainstream literature, dispelling notions of the entrepreneur as a societal misfit, an essential innovator with vision and flair, or a compulsive risk-taker, while confirming success as the key motivator rather than money per se, the importance of significant others, and the influence of culture and gender. They provide fresh insights into the psyche of the entrepreneur, which include: the existence of inner conviction - marrying the concept of goal-directedness with that of making a contribution to society; exercising the virtues in order to support a delicate balance between business and ethical imperatives; learning to respect energy flow; an alternative morality based on attracting and allowing benevolent or serendipitous events to happen naturally and redefining success as ‘being able to create what is needed as and when needed’; focusing one’s energy on the telos; developing a personal marketing formula suited to a culturallydiverse society; and the anxiety associated with being out-there on one’s own. The general statement, which is ultimately distilled from the seven situated descriptions, introduces a theory of entrepreneurial ethics that presents a new and different view of the lived-world of entrepreneurship, consisting of: Firstly, the key components of entrepreneurial success – having clear goals, energy, making a contribution to society, being connected, getting others on board, and work as an extension of self; secondly, what drives entrepreneurs – goal-orientation, sense of personal excitement, inner conviction, autonomy, and external recognition of success; thirdly, the entrepreneurial ethic – concern for credibility, commitment to service, contributing to quality of life; fourthly, the nature of entrepreneurial dilemmas - conflicting responsibilities, authenticity and credibility, risk and expansion, and awareness of diversity; fifthly, how entrepreneurs deal with ethical issues in their own distinctive ways – by holding fast to authentic virtues, bowing to community expectations, avoiding friction, adopting a ‘come-what-may’ or ‘what’s in it for me’ attitude, or pursuing a higher purpose where both parties benefit; sixthly, entrepreneurs’ world -views – beliefs, goals, ways of deriving satisfaction, virtuous behaviour; pen-ultimately, the challenges facing entrepreneurs in South Africa – overcoming the legacies of apartheid, containing crime, fostering an acceptable business ethic, and facilitating reconciliation between ethnic groups; and lastly, finding the power within – that illusive entrepreneurial spirit – self-reliance, looking beyond immediate obstacles, grasping opportunities, and understanding serendipity.
- Full Text:
- Date Issued: 2003
- Authors: Robinson, David Alan
- Date: 2003
- Subjects: Entrepreneurship -- South Africa Business ethics -- South Africa Decision making -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1175 , http://hdl.handle.net/10962/d1002791
- Description: This research sets out to examine how entrepreneurs experience and deal with ethical dilemmas. An entrepreneur is defined as a person who creates something of value and assumes the risk of establishing and managing a business around it. An ethical dilemma comes about when the entrepreneur must choose between alternatives and where the morally correct choice is unclear. This may be due to conflicting personal values or loyalties, tensions arising out of the realization that the moral action is not in line with his self-interest, cross-cultural conflict, or moral ambiguity. Because of the nature of entrepreneurship, the entrepreneur typically lives with ever-present threats arising from limited resources, competition, and the risk of business failure. His actions must simultaneously ensure survival, maximize profit, limit risk, counter threats, optimize the use of resources, and reward him with a feeling of satisfaction. It is hardly surprising that conflicting priorities sometimes ensue. It is also widely believed that these entrepreneurial pursuits supersede the more general need to act in morally appropriate ways. This is a phenomenological study, based on interviews with seven entrepreneurs in established service-oriented ventures. They were asked to describe their business, any dilemmas they have experienced, how they were handled, and what challenges they experience as entrepreneurs in South Africa today. Using phenomenology as my vehicle for data collection and analysis, I sought to enter the lived-worlds of my participants to discover the essence of how ethical dilemmas are experienced in the entrepreneurial milieu. The study’s findings reflect that each entrepreneur has a distinctive world-view, which is represented by a complex mosaic of virtue ethics, deontology, utilitarianism and metaethical perspectives. The permutations are numerous, thus negating the possibility of typecasting entrepreneurs. Instead this research introduces the reader to aspects of entrepreneurial reality such as the complexity of cultural diversity, the freedom to limit the amount of personal energy given to business, and the existence of a more sensitive, searching inner soul beneath the apparent hard-nosed business-oriented public image. While examining entrepreneurial dilemmas in depth, this research introduces the dilemma drum as a tool to portray the argument form of any dilemma by making explicit the ethical component inherent in every business decision and facilitating its effective resolution in a non-prescriptive way. The findings identify certain individual characteristics of participant entrepreneurs that are unlike anything in the mainstream literature, dispelling notions of the entrepreneur as a societal misfit, an essential innovator with vision and flair, or a compulsive risk-taker, while confirming success as the key motivator rather than money per se, the importance of significant others, and the influence of culture and gender. They provide fresh insights into the psyche of the entrepreneur, which include: the existence of inner conviction - marrying the concept of goal-directedness with that of making a contribution to society; exercising the virtues in order to support a delicate balance between business and ethical imperatives; learning to respect energy flow; an alternative morality based on attracting and allowing benevolent or serendipitous events to happen naturally and redefining success as ‘being able to create what is needed as and when needed’; focusing one’s energy on the telos; developing a personal marketing formula suited to a culturallydiverse society; and the anxiety associated with being out-there on one’s own. The general statement, which is ultimately distilled from the seven situated descriptions, introduces a theory of entrepreneurial ethics that presents a new and different view of the lived-world of entrepreneurship, consisting of: Firstly, the key components of entrepreneurial success – having clear goals, energy, making a contribution to society, being connected, getting others on board, and work as an extension of self; secondly, what drives entrepreneurs – goal-orientation, sense of personal excitement, inner conviction, autonomy, and external recognition of success; thirdly, the entrepreneurial ethic – concern for credibility, commitment to service, contributing to quality of life; fourthly, the nature of entrepreneurial dilemmas - conflicting responsibilities, authenticity and credibility, risk and expansion, and awareness of diversity; fifthly, how entrepreneurs deal with ethical issues in their own distinctive ways – by holding fast to authentic virtues, bowing to community expectations, avoiding friction, adopting a ‘come-what-may’ or ‘what’s in it for me’ attitude, or pursuing a higher purpose where both parties benefit; sixthly, entrepreneurs’ world -views – beliefs, goals, ways of deriving satisfaction, virtuous behaviour; pen-ultimately, the challenges facing entrepreneurs in South Africa – overcoming the legacies of apartheid, containing crime, fostering an acceptable business ethic, and facilitating reconciliation between ethnic groups; and lastly, finding the power within – that illusive entrepreneurial spirit – self-reliance, looking beyond immediate obstacles, grasping opportunities, and understanding serendipity.
- Full Text:
- Date Issued: 2003
A qualitative analysis of the need-satisfying experiences of the customers of a niche-restaurant
- Authors: Burger, John Michael
- Date: 2003
- Subjects: Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Language: English
- Type: Thesis , Doctoral , DTech (Marketing)
- Identifier: vital:10767 , http://hdl.handle.net/10948/260 , Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Description: Tradition dictates that marketing decision-makers remain accurately aligned with the dynamic and vacillating need structures of the target markets they serve. To comply with this caveat, a time-honoured and largely unchallenged philosophy of customer orientation has been applied. Theory further strongly contends that if such a business stance is vigilantly and diligently applied, any firm is bound to gain a competitive edge in the market place. A weakness in the above marketing mindset is the perception that when a spectrum of business elements are orchestrated and focussed on customers, target audience members will automatically be satisfied and return their patronage. This so-called marketing concept has undergone major reevaluations over the past decades, and it is now becoming ever more prevalent to witness varied permutations of new marketing architecture evolving in literature and practice. The unit of analysis selected for this research study is a niche restaurant that flouts many of the rudimentary traditional rules of marketing and iconoclastically succeeds despite all counter-logic. What such organisations have been practicing, albeit unknown to themselves, is a new way of business - a stance that has only recently been taken seriously by academics, writers and marketing professionals. These intuitive marketers are succeeding in niche businesses, despite going against the tide of the ingrained paradigm mindsets of conventional marketing stalwarts. Such niche business people have discovered is that there is more to satisfying consumer needs than simply honing in and understanding what the basic needs of designated audiences are. A growing band of new age marketers have been challenging orthodox marketing philosophy. Tofler, the visionary futurist, alluded to a host of unarticulated psychic consumer needs that would emerge as society drifted into a clinical and dispassionate ‘new’ millennium. In a world geared to instant gratification, fast-paced living and mechanistic social interactions, jaded consumers seek recognition as individuals (Tofler, 1970). They quest for inclusion rather than exclusion. They need a place to feel safe and find solace. Hence, it is now clear that simply attempting to satisfy the fundamental dimensions of consumers’ needs is no longer sufficient. Consumers rather seek the fulfilment of an holistic band of experience dimensions. Increasingly, phrases such as “winning consumer hearts and minds” are entering the vocabulary of marketers on a regular basis. The present vogue is to isolate and then include a range of intangible elements that are embodied in the process of satisfying customers needs. However, despite a growing awareness of the significance of mental-need satisfiers, in the specific domain of this investigation there is sparse evidence in literature of the mechanics of such novel thinking. The study unit is a second generation restaurant where many of the hollowed cornerstones of conventional marketing are inadvertently flouted. Different sets of rules of engagement seem to apply to their customers, who are also their most ardent advocates. A unique philosophy and business ethos also appears to prevail. In the study, the idiosyncratic characteristics which socially and competitively differentiate such a business were identified, explored and expiated. The constituents were then harmonised in an effort to establish what ‘it’ was that magnetically attracted patrons back despite the owner’s unintentional dismissive predisposition towards fundamental theory. As a result of this in-depth qualitative study, an holistic model encompassing all of the dimensions of a dining out experience at a niche restaurant have been proposed. Consequently the pillars upon which a sustained, enduring, loyal staunch customer base can be bed-rocked have been identified. Further, for the study unit, a typology of its diner corpse has been developed. The owners of the establishment under investigation have succeeded to provide an intimate family haven for their patrons. They, and their diners have collectively given strong, descriptive voice to the psychogenic need satisfying elements that have always existed, but to date have been unarticulated and unrecorded. This thesis brings the milieu of the iconoclast niche restaurant marketing practitioner to life.
- Full Text:
- Date Issued: 2003
- Authors: Burger, John Michael
- Date: 2003
- Subjects: Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Language: English
- Type: Thesis , Doctoral , DTech (Marketing)
- Identifier: vital:10767 , http://hdl.handle.net/10948/260 , Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Description: Tradition dictates that marketing decision-makers remain accurately aligned with the dynamic and vacillating need structures of the target markets they serve. To comply with this caveat, a time-honoured and largely unchallenged philosophy of customer orientation has been applied. Theory further strongly contends that if such a business stance is vigilantly and diligently applied, any firm is bound to gain a competitive edge in the market place. A weakness in the above marketing mindset is the perception that when a spectrum of business elements are orchestrated and focussed on customers, target audience members will automatically be satisfied and return their patronage. This so-called marketing concept has undergone major reevaluations over the past decades, and it is now becoming ever more prevalent to witness varied permutations of new marketing architecture evolving in literature and practice. The unit of analysis selected for this research study is a niche restaurant that flouts many of the rudimentary traditional rules of marketing and iconoclastically succeeds despite all counter-logic. What such organisations have been practicing, albeit unknown to themselves, is a new way of business - a stance that has only recently been taken seriously by academics, writers and marketing professionals. These intuitive marketers are succeeding in niche businesses, despite going against the tide of the ingrained paradigm mindsets of conventional marketing stalwarts. Such niche business people have discovered is that there is more to satisfying consumer needs than simply honing in and understanding what the basic needs of designated audiences are. A growing band of new age marketers have been challenging orthodox marketing philosophy. Tofler, the visionary futurist, alluded to a host of unarticulated psychic consumer needs that would emerge as society drifted into a clinical and dispassionate ‘new’ millennium. In a world geared to instant gratification, fast-paced living and mechanistic social interactions, jaded consumers seek recognition as individuals (Tofler, 1970). They quest for inclusion rather than exclusion. They need a place to feel safe and find solace. Hence, it is now clear that simply attempting to satisfy the fundamental dimensions of consumers’ needs is no longer sufficient. Consumers rather seek the fulfilment of an holistic band of experience dimensions. Increasingly, phrases such as “winning consumer hearts and minds” are entering the vocabulary of marketers on a regular basis. The present vogue is to isolate and then include a range of intangible elements that are embodied in the process of satisfying customers needs. However, despite a growing awareness of the significance of mental-need satisfiers, in the specific domain of this investigation there is sparse evidence in literature of the mechanics of such novel thinking. The study unit is a second generation restaurant where many of the hollowed cornerstones of conventional marketing are inadvertently flouted. Different sets of rules of engagement seem to apply to their customers, who are also their most ardent advocates. A unique philosophy and business ethos also appears to prevail. In the study, the idiosyncratic characteristics which socially and competitively differentiate such a business were identified, explored and expiated. The constituents were then harmonised in an effort to establish what ‘it’ was that magnetically attracted patrons back despite the owner’s unintentional dismissive predisposition towards fundamental theory. As a result of this in-depth qualitative study, an holistic model encompassing all of the dimensions of a dining out experience at a niche restaurant have been proposed. Consequently the pillars upon which a sustained, enduring, loyal staunch customer base can be bed-rocked have been identified. Further, for the study unit, a typology of its diner corpse has been developed. The owners of the establishment under investigation have succeeded to provide an intimate family haven for their patrons. They, and their diners have collectively given strong, descriptive voice to the psychogenic need satisfying elements that have always existed, but to date have been unarticulated and unrecorded. This thesis brings the milieu of the iconoclast niche restaurant marketing practitioner to life.
- Full Text:
- Date Issued: 2003
An evaluation of mentoring to develop a strategy for facilitating the objectives of the Employment Equity Act (Act 55 of 1998)
- Authors: Berry, David Michael
- Date: 2003
- Subjects: Mentoring in business , Employees -- Training of -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DTech (Human Resource Management)
- Identifier: vital:10858 , http://hdl.handle.net/10948/127 , Mentoring in business , Employees -- Training of -- Evaluation
- Description: The research problem in this study was to identify what mentoring strategies organisations can use to facilitate the objectives of the Employment Equity Act (Act 55 of 1998). To achieve this objective a nine-phase theoretical model for organisational mentoring was presented. The presentation of the theoretical model consisted of the following three sub-processes: -The first consisted of a survey of literature related to the development of the Employment Equity Act (Act 55 of 1998) and the implications of the Act for organisations: The second comprised surveying the literature dealing specifically with the impact of mentoring programmes on career development, organisational success and career satisfaction, particularly in terms of employees from designated groups; The third surveyed the literature dealing with various mentoring strategies and models used by organisations for facilitating management development. The theoretical model served as a basis for drawing up a survey questionnaire to establish the extent to which individuals at different levels in the organisations agree with the theoretical model developed in the study. The survey questionnaire was sent to a random sample of individuals employed in the automobile industries of the Nelson Mandela Metropolitan Municipality and the Buffalo City Metropole. The empirical results obtained from the survey indicated a strong concurrence with the theoretical organisational mentoring model presented in the study. These results were included in the theoretical model, leading to the development of an integrated model for organisational mentoring. From the survey literature and the study it became evident that if organisations plan to introduce mentoring strategies that will contribute towards facilitating their employment equity objectives, it is necessary to ensure that a transformational culture exists. Many South African organisations are currently experiencing problems in recruiting, training and retaining individuals from designated groups. The introduction of a mentoring programme based on the integrated model for organisational mentoring cannot be considered as the sole strategy for alleviating these problems and for facilitating management development to achieve the objectives of the Employment Equity Act (Act 55 of 1998). However, when this programme is effectively managed and incorporated into the overall development programme of an organisation committed to transformation, the potential to ease these problems and achieve the objectives of the Employment Equity Act (Act 55 of 1998) is greatly enhanced.
- Full Text:
- Date Issued: 2003
- Authors: Berry, David Michael
- Date: 2003
- Subjects: Mentoring in business , Employees -- Training of -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DTech (Human Resource Management)
- Identifier: vital:10858 , http://hdl.handle.net/10948/127 , Mentoring in business , Employees -- Training of -- Evaluation
- Description: The research problem in this study was to identify what mentoring strategies organisations can use to facilitate the objectives of the Employment Equity Act (Act 55 of 1998). To achieve this objective a nine-phase theoretical model for organisational mentoring was presented. The presentation of the theoretical model consisted of the following three sub-processes: -The first consisted of a survey of literature related to the development of the Employment Equity Act (Act 55 of 1998) and the implications of the Act for organisations: The second comprised surveying the literature dealing specifically with the impact of mentoring programmes on career development, organisational success and career satisfaction, particularly in terms of employees from designated groups; The third surveyed the literature dealing with various mentoring strategies and models used by organisations for facilitating management development. The theoretical model served as a basis for drawing up a survey questionnaire to establish the extent to which individuals at different levels in the organisations agree with the theoretical model developed in the study. The survey questionnaire was sent to a random sample of individuals employed in the automobile industries of the Nelson Mandela Metropolitan Municipality and the Buffalo City Metropole. The empirical results obtained from the survey indicated a strong concurrence with the theoretical organisational mentoring model presented in the study. These results were included in the theoretical model, leading to the development of an integrated model for organisational mentoring. From the survey literature and the study it became evident that if organisations plan to introduce mentoring strategies that will contribute towards facilitating their employment equity objectives, it is necessary to ensure that a transformational culture exists. Many South African organisations are currently experiencing problems in recruiting, training and retaining individuals from designated groups. The introduction of a mentoring programme based on the integrated model for organisational mentoring cannot be considered as the sole strategy for alleviating these problems and for facilitating management development to achieve the objectives of the Employment Equity Act (Act 55 of 1998). However, when this programme is effectively managed and incorporated into the overall development programme of an organisation committed to transformation, the potential to ease these problems and achieve the objectives of the Employment Equity Act (Act 55 of 1998) is greatly enhanced.
- Full Text:
- Date Issued: 2003
An investigation into the physico-chemical and neuroprotective properties of melatonin and 6-hydroxymelatonin
- Authors: Maharaj, Deepa Sukhdev
- Date: 2003
- Subjects: Melatonin Nervous system -- Degeneration -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3768 , http://hdl.handle.net/10962/d1003246
- Description: Until the beginning of this decade the antioxidant, melatonin, had been considered as little more than a tranquilizing hormone, responsible for regulating certain circadian and circannual rhythms. However, it is the discovery of melatonin as a free radical scavenger that has generated the most interest in recent years. The reduction of melatonin with age has been associated with neurodegenerative diseases such as Alzheimer’s disease (AD)and therefore, melatonin has been implicated to have an important clinical role in neuroprotection. Thus, for several years melatonin has attracted increasing attention from the general press with many advertisements touting this indoleamine to act as an aphrodisiac, rejuvenator, protector against diseases and a general wonder drug. However, melatonin formulations appear with no labelling for the correct storage conditions, dosage and side effects, as well as no control for purity and self-medicating with an unregulated product. In addition, there is much controversy surrounding the antioxidative properties of the indolemaine, 6-hydroxymelatonin (6-OHM). Therefore, the first part of this study aims to elucidate the physico-chemical and various stability characteristics of the pineal antioxidant, melatonin, while the second part is devoted to investigating the neuroprotective properties of the primary hepatic metabolite of melatonin, 6-OHM. The physical properties of melatonin were determined using various chemical techniques. This information served to both characterize and confirm the identity of melatonin raw material used in this study. In addition, this information serves to be essential as the physical properties of melatonin have not been reported in detail in literature, to date. Thereafter, using a validated high performance liquid chromatography (HPLC) method, the various physico-chemical and stability characteristics of melatonin were determined. Melatonin was shown to be extremely lipophilic, while the hygroscopic study indicates that melatonin raw material is extremely hygroscopic at temperatures above 40°C, whereas melatonin tablets are hygroscopic when left out of the original container. This study highlights the need for consumers to be aware of the proper storage of melatonin tablets to improve the stability and ensure long term integrity of the compound. Since, melatonin is most often administered orally, thus exposing it to a large variations in pH, within the gastrointestinal tract, it was decided to investigate the stability of melatonin over a range of pH’s and temperatures. The findings imply that melatonin is relatively stable at body temperature when ingested orally and that orally administered slow release preparations of melatonin should be relatively stable and therefore exhibit favourable bioavailability. However melatonin was shown to be unstable in solution. This provides important information and a challenge to the formulators of this drug substance in a liquid dosage form. An assessment of the photostability of melatonin dosage forms using International Committee on Harmonization (ICH) conditions revealed melatonin to be light sensitive and thus indicates a need for careful consideration of the packaging of these drug products. In addition a detailed assessment of the photochemistry and photoproducts formed during the UV photodegradation of melatonin is reported. Melatonin is shown to rapidly degrade in the presence of UV light, with the presence of oxygen accelerating the photodegradation. N1-acetyl-N2-formyl-5-methoxykynurenamine(AFMK) and 6-OHM were identified as the major photoproducts formed and these agents have been shown previously to retain antioxidant activity. One of the concerns of using melatonin in sunscreens is its photostability. However, it is reported in this study that the degraded solution of melatonin still possesses equipotent free radical scavenging ability as melatonin, despite the absence of melatonin in solution. In addition, melatonin is shown to reduce UV-induced oxidative stress in rat skin homogenate. Thus, these results make melatonin a likely candidate for inclusion in sunscreen preparations. Neuronal damage due to oxidative stress has been implicated in several neurodegenerative disorders. 6-OHM is not only formed as the major hepatic metabolite of melatonin, but also when melatonin reacts with toxic radicals as well as UV light. Thus the second part of the study aims to elucidate and further characterize the mechanism behind 6-OHM’s neuroprotection. The results show 6-OHM to be a more potent singlet oxygen and superoxide anion scavenger than melatonin. In addition, the results show 6-OHM to offer protection against, oxidative stress and lipid peroxidation induced by several neurotoxins in the rat brain and hippocampus. The hippocampus is an important region of the brain responsible for the formation of memory and any agent that induces stress in this area has detrimental effects and could lead to various types of dementia. Such agents include quinolinic acid (QA) and iron (II). Histological studies undertaken reveal that 6-OHM is able to protect hippocampal neurons against QA and iron (II) induced necrotic cell death. Immunohistochemical investigations showed that QA moderately induces apoptotic cell death in the hippocampus which is inhibited by both melatonin and 6-OHM. The study sought to elucidate possible mechanisms by which 6-OHM exerts its neuroprotective capabilities and the results show 6-OHM to inhibit the action of cyanide on the mitochondrial electron transport chain (ETC), one of the most common sources of free radicals. In addition, 6-OHM treatment alone, increased ETC activity above basal control levels and the results show 6-OHM to increase complex I activity in the mitochondrial ETC. Electrochemical, ultraviolet/visible spectroscopy (UV/Vis) and HPLC assessment show that an interaction exists between 6-OHM and iron (III) and 6-OHM is able to reduce iron (III) to a more biologically usable form viz. iron (II) which can be incorporated into important biomolecules such as heme. One dire consequence of this interaction is the ready provision of iron (II) to drive the Fenton reaction. However the biological and histological assessments show 6-OHM to prevent iron (II)-induced lipid peroxidation and necrotic cell death and thus, provide evidence of its antioxidant properties. The results also show 6-OHM to promote Hsp70 induction in the hippocampus. Heat shock proteins, especially Hsp 70 plays a role in cytoprotection by capturing denatured proteins and facilitating the refolding of these proteins once the stress has been relieved. 6-OHM treatment alone and together with QA was shown to increase the level of expression of Hsp70, both inducible and cognate forms of the protein. This suggests that 6-OHM helps to protect against cellular protein damage induced by any form of stress the cell may encounter. Melatonin treatment alone and in combination with QA was shown to prevent increases in the level of Hsp70 in the hippocampus, indicating that melatonin was able to reduce oxidative stress induced by QA such that Hsp70 expression was not required. The discovery of neuroprotective agents, such as melatonin and 6-OHM, is becoming important considering the rapid rise in the elderly population and the proportionate increase in neurological disorders. The findings of this study indicate the need for important information regarding the correct storage conditions and stability characteristics of melatonin dosage forms. In addition, the results indicate that 6-OHM has a definite role to play as an antioxidant. Thus further research may favour the use of these agents in the treatment of several neurodegenerative disorders.
- Full Text:
- Date Issued: 2003
- Authors: Maharaj, Deepa Sukhdev
- Date: 2003
- Subjects: Melatonin Nervous system -- Degeneration -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3768 , http://hdl.handle.net/10962/d1003246
- Description: Until the beginning of this decade the antioxidant, melatonin, had been considered as little more than a tranquilizing hormone, responsible for regulating certain circadian and circannual rhythms. However, it is the discovery of melatonin as a free radical scavenger that has generated the most interest in recent years. The reduction of melatonin with age has been associated with neurodegenerative diseases such as Alzheimer’s disease (AD)and therefore, melatonin has been implicated to have an important clinical role in neuroprotection. Thus, for several years melatonin has attracted increasing attention from the general press with many advertisements touting this indoleamine to act as an aphrodisiac, rejuvenator, protector against diseases and a general wonder drug. However, melatonin formulations appear with no labelling for the correct storage conditions, dosage and side effects, as well as no control for purity and self-medicating with an unregulated product. In addition, there is much controversy surrounding the antioxidative properties of the indolemaine, 6-hydroxymelatonin (6-OHM). Therefore, the first part of this study aims to elucidate the physico-chemical and various stability characteristics of the pineal antioxidant, melatonin, while the second part is devoted to investigating the neuroprotective properties of the primary hepatic metabolite of melatonin, 6-OHM. The physical properties of melatonin were determined using various chemical techniques. This information served to both characterize and confirm the identity of melatonin raw material used in this study. In addition, this information serves to be essential as the physical properties of melatonin have not been reported in detail in literature, to date. Thereafter, using a validated high performance liquid chromatography (HPLC) method, the various physico-chemical and stability characteristics of melatonin were determined. Melatonin was shown to be extremely lipophilic, while the hygroscopic study indicates that melatonin raw material is extremely hygroscopic at temperatures above 40°C, whereas melatonin tablets are hygroscopic when left out of the original container. This study highlights the need for consumers to be aware of the proper storage of melatonin tablets to improve the stability and ensure long term integrity of the compound. Since, melatonin is most often administered orally, thus exposing it to a large variations in pH, within the gastrointestinal tract, it was decided to investigate the stability of melatonin over a range of pH’s and temperatures. The findings imply that melatonin is relatively stable at body temperature when ingested orally and that orally administered slow release preparations of melatonin should be relatively stable and therefore exhibit favourable bioavailability. However melatonin was shown to be unstable in solution. This provides important information and a challenge to the formulators of this drug substance in a liquid dosage form. An assessment of the photostability of melatonin dosage forms using International Committee on Harmonization (ICH) conditions revealed melatonin to be light sensitive and thus indicates a need for careful consideration of the packaging of these drug products. In addition a detailed assessment of the photochemistry and photoproducts formed during the UV photodegradation of melatonin is reported. Melatonin is shown to rapidly degrade in the presence of UV light, with the presence of oxygen accelerating the photodegradation. N1-acetyl-N2-formyl-5-methoxykynurenamine(AFMK) and 6-OHM were identified as the major photoproducts formed and these agents have been shown previously to retain antioxidant activity. One of the concerns of using melatonin in sunscreens is its photostability. However, it is reported in this study that the degraded solution of melatonin still possesses equipotent free radical scavenging ability as melatonin, despite the absence of melatonin in solution. In addition, melatonin is shown to reduce UV-induced oxidative stress in rat skin homogenate. Thus, these results make melatonin a likely candidate for inclusion in sunscreen preparations. Neuronal damage due to oxidative stress has been implicated in several neurodegenerative disorders. 6-OHM is not only formed as the major hepatic metabolite of melatonin, but also when melatonin reacts with toxic radicals as well as UV light. Thus the second part of the study aims to elucidate and further characterize the mechanism behind 6-OHM’s neuroprotection. The results show 6-OHM to be a more potent singlet oxygen and superoxide anion scavenger than melatonin. In addition, the results show 6-OHM to offer protection against, oxidative stress and lipid peroxidation induced by several neurotoxins in the rat brain and hippocampus. The hippocampus is an important region of the brain responsible for the formation of memory and any agent that induces stress in this area has detrimental effects and could lead to various types of dementia. Such agents include quinolinic acid (QA) and iron (II). Histological studies undertaken reveal that 6-OHM is able to protect hippocampal neurons against QA and iron (II) induced necrotic cell death. Immunohistochemical investigations showed that QA moderately induces apoptotic cell death in the hippocampus which is inhibited by both melatonin and 6-OHM. The study sought to elucidate possible mechanisms by which 6-OHM exerts its neuroprotective capabilities and the results show 6-OHM to inhibit the action of cyanide on the mitochondrial electron transport chain (ETC), one of the most common sources of free radicals. In addition, 6-OHM treatment alone, increased ETC activity above basal control levels and the results show 6-OHM to increase complex I activity in the mitochondrial ETC. Electrochemical, ultraviolet/visible spectroscopy (UV/Vis) and HPLC assessment show that an interaction exists between 6-OHM and iron (III) and 6-OHM is able to reduce iron (III) to a more biologically usable form viz. iron (II) which can be incorporated into important biomolecules such as heme. One dire consequence of this interaction is the ready provision of iron (II) to drive the Fenton reaction. However the biological and histological assessments show 6-OHM to prevent iron (II)-induced lipid peroxidation and necrotic cell death and thus, provide evidence of its antioxidant properties. The results also show 6-OHM to promote Hsp70 induction in the hippocampus. Heat shock proteins, especially Hsp 70 plays a role in cytoprotection by capturing denatured proteins and facilitating the refolding of these proteins once the stress has been relieved. 6-OHM treatment alone and together with QA was shown to increase the level of expression of Hsp70, both inducible and cognate forms of the protein. This suggests that 6-OHM helps to protect against cellular protein damage induced by any form of stress the cell may encounter. Melatonin treatment alone and in combination with QA was shown to prevent increases in the level of Hsp70 in the hippocampus, indicating that melatonin was able to reduce oxidative stress induced by QA such that Hsp70 expression was not required. The discovery of neuroprotective agents, such as melatonin and 6-OHM, is becoming important considering the rapid rise in the elderly population and the proportionate increase in neurological disorders. The findings of this study indicate the need for important information regarding the correct storage conditions and stability characteristics of melatonin dosage forms. In addition, the results indicate that 6-OHM has a definite role to play as an antioxidant. Thus further research may favour the use of these agents in the treatment of several neurodegenerative disorders.
- Full Text:
- Date Issued: 2003
An investigation of the isolation, characterisation and application of hydantoinases for the industrial production of amino acids
- Authors: Kirchmann, Shaun
- Date: 2003
- Subjects: Hydantoin Amino acids Hydrolysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3969 , http://hdl.handle.net/10962/d1004028
- Description: This thesis describes a series of investigations into the hydantoin-hydrolysing activity of bacterial strains RU-KM1 and RU-OR, which were previously isolated for their ability to hydrolyse hydantoins to amino acids. The main aim of the study was to develop biotransformations with potential application in the production of enantiomerically pure amino acids using a bioreactor based system utilising the hydantoin hydrolysing enzymes of the two isolated microorganisms. Different substituted hydantoins may be used as substrates by these enzymes for the production of a variety of amino acids. These are not only important for amino acid production, but they may be used for production of other industrially important compounds, such as semisynthetic penicillin/ampicillin, L-aspartame (sweetener), Fluvalinate (insecticide), Enalapril (ACE inhibitor). Thus, the ability of the above-mentioned strains to hydrolyse these substrates was investigated, with the view to utilizing the maximum potential of these biocatalysts. Hydantoin conversion involves a two-step hydrolysis reaction which yields, initially, an N-carbamylamino acid intermediate, and subsequently, an amino acid. The hydantoin-hydrolysing enzymes of a Pseudomonas sp. RU-KM1, and an Agrobacterium sp. RU-OR were characterised as whole cells and in a crude extract preparation, and reaction conditions for its biocatalytic application were optimised. The optimum conditions for conversion of hydantoin to glycine were found to be 1 hour at 40 °C, with conversion yields greater than 30 % achieved. The enzymes of RU-KM1 demonstrated considerable stability, retaining 80 % of their activity after storage for 2 weeks at 4 °C. The activities of the enzymes were increased by the addition of a detergent to the extraction medium, suggesting that the enzymes might be membrane-bound. The results of the determination of the metal-dependence of the hydantoinase and N-carbamoylase of RU-KM1 suggested that these enzymes required metal ions for activity, with metal ions such as Cu[superscript (2+)], Fe[superscript (2+)], and Co[superscript (2+)] resulting in no significant change in enzyme activity, however there was an activation of the enzymes when Mn[superscript (2+)] was added to the enzymes. The stereoselectivity of the enzymes was investigated, and the results suggested that the hydantoinase was D-selective, whereas the N-carbamoylase was shown to be L-selective by other researchers. The hydantoin substrate selectivity of RU-KM1 and RU-OR was investigated, and the organisms were shown to be able to hydrolyse all of the seven substrates tested. However, there was a difference in activity levels between crude extract preparations and whole cells, with crude extracts generally showing slightly lower activity than whole cells in RU-KM1, and the whole cells or RU-OR showing the lower activity than its crude extract. Some difference was also observed in the order of preference of substrates between whole cells and crude extracts. The preferred substrate for RU-KM1 whole cells was isopropylhydantoin, whereas the crude extract preparation preferentially hydrolysed p-hydroxyphenylhydantoin, achieving 57 % and 52 % conversions respectively. RU-OR whole cells preferred methylhydantoin where as the crude extract preferred isopropylhydantoin, and showed 49 % and 51 % conversions respectively. The enzymes were characterised in terms of their temperature and pH optima, inducer requirements, and product inhibition studies. The hydantoinase of RU-KM1 was shown to be inducible with low levels of hydantoin, and thermostable upto 75 °C with its optima between 60 and 70 °C. The N-carbamoylase was shown to have its optima at 50 °C. The addition of ATP (0.5 mM), DTT (1 mM) and a protease inhibitor (2 mg.mL[superscript (-1)]) all increased the hydantoinase activity of RU-KM1 crude extract, however they had very little effect on the N-carbamoylase activity. The hydantoinase enzyme from extracts of RU-KM1 was partially purified by development of cell disruption methods using mechanical and lysing enzymes, followed by precipitation and chromatographic resolution. The results obtained showed a hydantoinase enzyme of between 48 and 66 kDa. RU-KM1 was grown under fermentation conditions using different minimal media. The activity and yields under these conditions were low. Previous attempt to grow the organism in a rich medium had resulted in an increase in biomass but no hydantoinase activity. A rich medium was developed by carbon and nitrogen optimisation and yielded biomass up to 30 g.L[superscript (-1)] dry cell weight. The hydantoinase activity was restored by nitrogen starvation in stationary phase. This resulted in high biomass with increased activity. This data is currently in press. Crude extract and whole cells were immobilised on flat sheet membranes, hollow fibre membranes and in alginate beads. Low hydantoinase activity was measured in bioreactors using membranes in different configurations. A significant increase in hydantoinase activity was measured when the crude extract was immobilised in sodium alginate, as a result of stabilisation of the N-carbamoylase. Temperature and pH optima were unaffected by the immobilisation procedure, however the durability of the enzymes increased 2-fold. Different configurations of the bioreactor were investigated, as well as a hydroxyphenylhydantoin as an alternative substrate in this study. The bioreactors showed a near 95 % conversion of the hydantoin to glycine, and a 99 % conversion using HPG. In conclusion, the hydantoin-hydrolysing enzymes of RU-KM1 have been shown to be possibly membrane associated, which is a novel finding. This study has shown that the hydantoinase of RU-KM1 is D-stereoselective, with high temperature stability. A growth medium was developed for the rapid production of active biomass. A bioreactor was developed using a single and a dual biocatalyst configuration, which was capable of hydrolysing hydantoin and monosubstituted hydantoins to produce amino acids. To our knowledge this system is the first such dual biocatalyst system reported for the production of amino acids.
- Full Text:
- Date Issued: 2003
- Authors: Kirchmann, Shaun
- Date: 2003
- Subjects: Hydantoin Amino acids Hydrolysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3969 , http://hdl.handle.net/10962/d1004028
- Description: This thesis describes a series of investigations into the hydantoin-hydrolysing activity of bacterial strains RU-KM1 and RU-OR, which were previously isolated for their ability to hydrolyse hydantoins to amino acids. The main aim of the study was to develop biotransformations with potential application in the production of enantiomerically pure amino acids using a bioreactor based system utilising the hydantoin hydrolysing enzymes of the two isolated microorganisms. Different substituted hydantoins may be used as substrates by these enzymes for the production of a variety of amino acids. These are not only important for amino acid production, but they may be used for production of other industrially important compounds, such as semisynthetic penicillin/ampicillin, L-aspartame (sweetener), Fluvalinate (insecticide), Enalapril (ACE inhibitor). Thus, the ability of the above-mentioned strains to hydrolyse these substrates was investigated, with the view to utilizing the maximum potential of these biocatalysts. Hydantoin conversion involves a two-step hydrolysis reaction which yields, initially, an N-carbamylamino acid intermediate, and subsequently, an amino acid. The hydantoin-hydrolysing enzymes of a Pseudomonas sp. RU-KM1, and an Agrobacterium sp. RU-OR were characterised as whole cells and in a crude extract preparation, and reaction conditions for its biocatalytic application were optimised. The optimum conditions for conversion of hydantoin to glycine were found to be 1 hour at 40 °C, with conversion yields greater than 30 % achieved. The enzymes of RU-KM1 demonstrated considerable stability, retaining 80 % of their activity after storage for 2 weeks at 4 °C. The activities of the enzymes were increased by the addition of a detergent to the extraction medium, suggesting that the enzymes might be membrane-bound. The results of the determination of the metal-dependence of the hydantoinase and N-carbamoylase of RU-KM1 suggested that these enzymes required metal ions for activity, with metal ions such as Cu[superscript (2+)], Fe[superscript (2+)], and Co[superscript (2+)] resulting in no significant change in enzyme activity, however there was an activation of the enzymes when Mn[superscript (2+)] was added to the enzymes. The stereoselectivity of the enzymes was investigated, and the results suggested that the hydantoinase was D-selective, whereas the N-carbamoylase was shown to be L-selective by other researchers. The hydantoin substrate selectivity of RU-KM1 and RU-OR was investigated, and the organisms were shown to be able to hydrolyse all of the seven substrates tested. However, there was a difference in activity levels between crude extract preparations and whole cells, with crude extracts generally showing slightly lower activity than whole cells in RU-KM1, and the whole cells or RU-OR showing the lower activity than its crude extract. Some difference was also observed in the order of preference of substrates between whole cells and crude extracts. The preferred substrate for RU-KM1 whole cells was isopropylhydantoin, whereas the crude extract preparation preferentially hydrolysed p-hydroxyphenylhydantoin, achieving 57 % and 52 % conversions respectively. RU-OR whole cells preferred methylhydantoin where as the crude extract preferred isopropylhydantoin, and showed 49 % and 51 % conversions respectively. The enzymes were characterised in terms of their temperature and pH optima, inducer requirements, and product inhibition studies. The hydantoinase of RU-KM1 was shown to be inducible with low levels of hydantoin, and thermostable upto 75 °C with its optima between 60 and 70 °C. The N-carbamoylase was shown to have its optima at 50 °C. The addition of ATP (0.5 mM), DTT (1 mM) and a protease inhibitor (2 mg.mL[superscript (-1)]) all increased the hydantoinase activity of RU-KM1 crude extract, however they had very little effect on the N-carbamoylase activity. The hydantoinase enzyme from extracts of RU-KM1 was partially purified by development of cell disruption methods using mechanical and lysing enzymes, followed by precipitation and chromatographic resolution. The results obtained showed a hydantoinase enzyme of between 48 and 66 kDa. RU-KM1 was grown under fermentation conditions using different minimal media. The activity and yields under these conditions were low. Previous attempt to grow the organism in a rich medium had resulted in an increase in biomass but no hydantoinase activity. A rich medium was developed by carbon and nitrogen optimisation and yielded biomass up to 30 g.L[superscript (-1)] dry cell weight. The hydantoinase activity was restored by nitrogen starvation in stationary phase. This resulted in high biomass with increased activity. This data is currently in press. Crude extract and whole cells were immobilised on flat sheet membranes, hollow fibre membranes and in alginate beads. Low hydantoinase activity was measured in bioreactors using membranes in different configurations. A significant increase in hydantoinase activity was measured when the crude extract was immobilised in sodium alginate, as a result of stabilisation of the N-carbamoylase. Temperature and pH optima were unaffected by the immobilisation procedure, however the durability of the enzymes increased 2-fold. Different configurations of the bioreactor were investigated, as well as a hydroxyphenylhydantoin as an alternative substrate in this study. The bioreactors showed a near 95 % conversion of the hydantoin to glycine, and a 99 % conversion using HPG. In conclusion, the hydantoin-hydrolysing enzymes of RU-KM1 have been shown to be possibly membrane associated, which is a novel finding. This study has shown that the hydantoinase of RU-KM1 is D-stereoselective, with high temperature stability. A growth medium was developed for the rapid production of active biomass. A bioreactor was developed using a single and a dual biocatalyst configuration, which was capable of hydrolysing hydantoin and monosubstituted hydantoins to produce amino acids. To our knowledge this system is the first such dual biocatalyst system reported for the production of amino acids.
- Full Text:
- Date Issued: 2003
Aplousobranch ascidians (Tunicata: Ascidiacea) from Southern Africa
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
- Full Text:
- Date Issued: 2003
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
- Full Text:
- Date Issued: 2003
Applications of the Baylis-Hillman reaction in the synthesis of coumarin derivatives
- Authors: Musa, Musiliyu Ayodele
- Date: 2003
- Subjects: Coumarins Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4403 , http://hdl.handle.net/10962/d1006705
- Description: The reaction of specially prepared salicylaldehyde benzyl ethers with the activated alkenes, methyl acrylate or acrylonitrile, in the presence of the catalyst, DABCO, has afforded Baylis-Hillman products, which have been subjected to conjugate addition with either piperidine or benzylamine. Hydrogenolysis of these conjugate addition products in the presence of a palladium-on-carbon catalyst has been shown to afford the corresponding 3-substituted coumarins, while treatment of O-benzylated Baylis-Hillman adducts with HCl or HI afforded the corresponding 3-(halomethyl)coumarins directly, in up to 94%. The 3-(halomethyl)coumarins have also been obtained in excellent yields (up to 98%) and even more conveniently, by treating the unprotected Baylis-Hillman products with HCl in a mixture of AcOH and Ac₂O, obtained from tert-butyl acrylate and various salicylaldehydes. The generality of an established route to the synthesis of coumarins via an intramolecular Baylis-Hillman reaction, involving the use of salicylaldehyde acrylate esters in the presence of DABCO, has also been demonstrated. Reactions between the 3-(halomethyl)coumarins and various nitrogen and carbon nucleophiles have been shown to proceed with a high degree of regioselectivity at the exocyclic allylic centre to afford 3-substituted coumarin products. The electronimpact mass spectra of selected coumarin derivatives have been investigated using high-resolution and B/E linked scan data. Fragmentation pathways have been proposed and fragmentation modes associated with different coumarin-containing analogues have been compared. A series of coumarin-containing analogues of ritonavir (a clinically useful HIV-1 protease inhibitor) have been prepared and characterized. The synthetic approach has involved the coupling of coumarin derivatives with a hydroxyethylene dipeptide isostere to afford ritonavir analogues containing coumarin termini. An interactive docking procedure has been used to explore the docking of ritonavir and a coumarincontaining analogue into the enzyme active site.
- Full Text:
- Date Issued: 2003
- Authors: Musa, Musiliyu Ayodele
- Date: 2003
- Subjects: Coumarins Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4403 , http://hdl.handle.net/10962/d1006705
- Description: The reaction of specially prepared salicylaldehyde benzyl ethers with the activated alkenes, methyl acrylate or acrylonitrile, in the presence of the catalyst, DABCO, has afforded Baylis-Hillman products, which have been subjected to conjugate addition with either piperidine or benzylamine. Hydrogenolysis of these conjugate addition products in the presence of a palladium-on-carbon catalyst has been shown to afford the corresponding 3-substituted coumarins, while treatment of O-benzylated Baylis-Hillman adducts with HCl or HI afforded the corresponding 3-(halomethyl)coumarins directly, in up to 94%. The 3-(halomethyl)coumarins have also been obtained in excellent yields (up to 98%) and even more conveniently, by treating the unprotected Baylis-Hillman products with HCl in a mixture of AcOH and Ac₂O, obtained from tert-butyl acrylate and various salicylaldehydes. The generality of an established route to the synthesis of coumarins via an intramolecular Baylis-Hillman reaction, involving the use of salicylaldehyde acrylate esters in the presence of DABCO, has also been demonstrated. Reactions between the 3-(halomethyl)coumarins and various nitrogen and carbon nucleophiles have been shown to proceed with a high degree of regioselectivity at the exocyclic allylic centre to afford 3-substituted coumarin products. The electronimpact mass spectra of selected coumarin derivatives have been investigated using high-resolution and B/E linked scan data. Fragmentation pathways have been proposed and fragmentation modes associated with different coumarin-containing analogues have been compared. A series of coumarin-containing analogues of ritonavir (a clinically useful HIV-1 protease inhibitor) have been prepared and characterized. The synthetic approach has involved the coupling of coumarin derivatives with a hydroxyethylene dipeptide isostere to afford ritonavir analogues containing coumarin termini. An interactive docking procedure has been used to explore the docking of ritonavir and a coumarincontaining analogue into the enzyme active site.
- Full Text:
- Date Issued: 2003
Binding and transcriptional activation by Uga3p, a zinc binuclear cluster protein of Saccharomyces cerevisiae redefining the UAS [subscript GABA] and the Uga3p binding site
- Authors: Idicula, Anu Mary
- Date: 2003
- Subjects: Saccharomyces cerevisiae GABA
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3933 , http://hdl.handle.net/10962/d1003992
- Description: Uga3p, a member of the zinc binuclear cluster transcription factor family, is required for [gamma]-aminobutyric acid-dependent transcription of the UGA genes in Saccharomyces cerevisiae. Crystallographic data of some of the protein-DNA complexes of this family reveal that members of this family bind to CGG triplets. A conserved 19-nucleotide activation element in certain UGA gene promoter regions contains a CCG-N4-CGG everted repeat, proposed to be the binding site of Uga3p, UAS[subscript GABA]. The spacer region (N4) between the CGG triplets has been suggested to be the specificity determinant for binding to UAS[subscript GABA]. The data available from the Saccharomyces genome database indicates that there are multiple repeats of -CCG-N4-CGG- regions within the genome. These transcription factors are involved in the activation of specific pathways and the question arises as to how their specificity of binding is determined. The aim of this study was to understand the binding characteristics of Uga3p to UAS[subscript GABA] and to determine the affinity and specificity of this interaction. In this study, full-length (tagged and untagged) and truncated (1-124 a.a.) Uga3p was produced in a heterologous expression system (E. coli). The interaction of Uga3p with UAS[subscript GABA] in Saccharomyces cerevisiae was characterized in terms of binding in vitro and the transcriptional activation of lacZ reporter genes in vivo. The Uga3p was capable of binding to these sites in vitro independent of exogenous GABA. Electrophoretic mobility shift assays (EMSA) of the full-length Uga3p with the wild type UAS[subscript GABA] sequences produced two distinct mobility complexes. The complexes formed in the EMSA of the full-length Uga3p were those specific to the interaction of the Uga3p to UAS[subscript GABA]. The truncated Uga3p(1-124 a.a.), which has the DNA-binding zinc cluster domain, the linker region and the putative coiled-coil domain was not functionally equivalent to the full-length protein with respect to binding in vitro because the EMSAs of the UAS[subscript GABA] with the truncated Uga3p produced indistinct complexes. EMSAs using mutant UAS[subscript GABA] sequences and heterologously-produced full-length Uga3p, demonstrated that UAS[subscript GABA] consists of two, independent Uga3p-binding sites. This work presents evidence that the two Uga3p molecules bound to UAS[subscript GABA] most likely interact with each other. Unlike other zinc cluster binding sites the Uga3p-binding site is an asymmetric site of 5’-SGCGGNWWT-3’ (S= G or C, W = A or T and N = no nucleotide or G or C). UAS[subscript GABA] is a palindrome containing the two asymmetric Uga3p-binding sites. The two-site consensus sequence required for the binding of Uga3p to the UAS[subscript GABA] is present upstream of UGA1 (region -387 to -370) and UGA4 (region -403 to -387). Furthermore, a single Uga3p-binding site was identified in the 5’ untranslated regions of UGA2 (region -219 to -211). GABA-dependent transcriptional activation by UAS[subscript GABA] in vivo could be directly correlated to a high affinity, specific interaction of two Uga3p molecules to this UAS. Binding with high affinity required the conserved sequences flanking the everted repeat. This study provided evidence that the binding pattern of Uga3p is novel compared to other zinc cluster motifs investigated, as the sequences flanking the everted repeat are important regions for recognition by Uga3p. The studies with the truncated Uga3p (1 –124 a.a.), also suggested that the regions C-terminal to the DNA-binding motif and putative coiled-coil area of this protein are important for Uga3p-specific interactions with UAS[subscript GABA]. Investigation of regions C-terminal to the zinc cluster, linker and putative coiledcoil revealed an eight-motif regulatory region similar to that in other zinc cluster proteins. This indicated that the regions C-terminal to these domains are important for the regulation and activity of these proteins. A putative seven repeat WD40-like motif was identified within this region. This putative domain has been speculated to be important for protein-protein interactions. Phosphorylation and dephosphorylation in other proteins of this class have been indicated to be important for the regulation of the activity of these proteins. The bioinformatic analysis of Uga3p revealed two possible cAMP/cGMP-dependent protein kinase phosphorylation sites, four putative protein kinase C phosphorylation motifs and four putative casein kinase II phosphorylation motifs. This study has contributed to the understanding of the nature of interactions between Uga3p and its specific UAS [subscript GABA] and how the regions flanking the everted repeat determine its specificity. The comparison of the nature of the binding of truncated and full-length Uga3p in vitro provided evidence for the role played by the full-length protein in determining this specific interaction. This evidence suggested that the in vitro binding evidence for other proteins of this family, using truncated peptides that carry the DNA-binding domain, might not reflect the true nature of interactions between the proteins of this class and their specific UASs in vivo.
- Full Text:
- Date Issued: 2003
- Authors: Idicula, Anu Mary
- Date: 2003
- Subjects: Saccharomyces cerevisiae GABA
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3933 , http://hdl.handle.net/10962/d1003992
- Description: Uga3p, a member of the zinc binuclear cluster transcription factor family, is required for [gamma]-aminobutyric acid-dependent transcription of the UGA genes in Saccharomyces cerevisiae. Crystallographic data of some of the protein-DNA complexes of this family reveal that members of this family bind to CGG triplets. A conserved 19-nucleotide activation element in certain UGA gene promoter regions contains a CCG-N4-CGG everted repeat, proposed to be the binding site of Uga3p, UAS[subscript GABA]. The spacer region (N4) between the CGG triplets has been suggested to be the specificity determinant for binding to UAS[subscript GABA]. The data available from the Saccharomyces genome database indicates that there are multiple repeats of -CCG-N4-CGG- regions within the genome. These transcription factors are involved in the activation of specific pathways and the question arises as to how their specificity of binding is determined. The aim of this study was to understand the binding characteristics of Uga3p to UAS[subscript GABA] and to determine the affinity and specificity of this interaction. In this study, full-length (tagged and untagged) and truncated (1-124 a.a.) Uga3p was produced in a heterologous expression system (E. coli). The interaction of Uga3p with UAS[subscript GABA] in Saccharomyces cerevisiae was characterized in terms of binding in vitro and the transcriptional activation of lacZ reporter genes in vivo. The Uga3p was capable of binding to these sites in vitro independent of exogenous GABA. Electrophoretic mobility shift assays (EMSA) of the full-length Uga3p with the wild type UAS[subscript GABA] sequences produced two distinct mobility complexes. The complexes formed in the EMSA of the full-length Uga3p were those specific to the interaction of the Uga3p to UAS[subscript GABA]. The truncated Uga3p(1-124 a.a.), which has the DNA-binding zinc cluster domain, the linker region and the putative coiled-coil domain was not functionally equivalent to the full-length protein with respect to binding in vitro because the EMSAs of the UAS[subscript GABA] with the truncated Uga3p produced indistinct complexes. EMSAs using mutant UAS[subscript GABA] sequences and heterologously-produced full-length Uga3p, demonstrated that UAS[subscript GABA] consists of two, independent Uga3p-binding sites. This work presents evidence that the two Uga3p molecules bound to UAS[subscript GABA] most likely interact with each other. Unlike other zinc cluster binding sites the Uga3p-binding site is an asymmetric site of 5’-SGCGGNWWT-3’ (S= G or C, W = A or T and N = no nucleotide or G or C). UAS[subscript GABA] is a palindrome containing the two asymmetric Uga3p-binding sites. The two-site consensus sequence required for the binding of Uga3p to the UAS[subscript GABA] is present upstream of UGA1 (region -387 to -370) and UGA4 (region -403 to -387). Furthermore, a single Uga3p-binding site was identified in the 5’ untranslated regions of UGA2 (region -219 to -211). GABA-dependent transcriptional activation by UAS[subscript GABA] in vivo could be directly correlated to a high affinity, specific interaction of two Uga3p molecules to this UAS. Binding with high affinity required the conserved sequences flanking the everted repeat. This study provided evidence that the binding pattern of Uga3p is novel compared to other zinc cluster motifs investigated, as the sequences flanking the everted repeat are important regions for recognition by Uga3p. The studies with the truncated Uga3p (1 –124 a.a.), also suggested that the regions C-terminal to the DNA-binding motif and putative coiled-coil area of this protein are important for Uga3p-specific interactions with UAS[subscript GABA]. Investigation of regions C-terminal to the zinc cluster, linker and putative coiledcoil revealed an eight-motif regulatory region similar to that in other zinc cluster proteins. This indicated that the regions C-terminal to these domains are important for the regulation and activity of these proteins. A putative seven repeat WD40-like motif was identified within this region. This putative domain has been speculated to be important for protein-protein interactions. Phosphorylation and dephosphorylation in other proteins of this class have been indicated to be important for the regulation of the activity of these proteins. The bioinformatic analysis of Uga3p revealed two possible cAMP/cGMP-dependent protein kinase phosphorylation sites, four putative protein kinase C phosphorylation motifs and four putative casein kinase II phosphorylation motifs. This study has contributed to the understanding of the nature of interactions between Uga3p and its specific UAS [subscript GABA] and how the regions flanking the everted repeat determine its specificity. The comparison of the nature of the binding of truncated and full-length Uga3p in vitro provided evidence for the role played by the full-length protein in determining this specific interaction. This evidence suggested that the in vitro binding evidence for other proteins of this family, using truncated peptides that carry the DNA-binding domain, might not reflect the true nature of interactions between the proteins of this class and their specific UASs in vivo.
- Full Text:
- Date Issued: 2003
Biogeography and community structure of fishes in South African estuaries
- Authors: Harrison, Trevor D
- Date: 2003
- Subjects: Estuarine ecology -- South Africa Estuarine fishes -- South Africa Fish communities -- South Africa Biogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5235 , http://hdl.handle.net/10962/d1005078
- Description: The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
- Full Text:
- Date Issued: 2003
- Authors: Harrison, Trevor D
- Date: 2003
- Subjects: Estuarine ecology -- South Africa Estuarine fishes -- South Africa Fish communities -- South Africa Biogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5235 , http://hdl.handle.net/10962/d1005078
- Description: The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
- Full Text:
- Date Issued: 2003
Biological control initiatives against Lantana camara L. (Verbenaceae) in South Africa : an assessment of the present status of the programme, and an evaluation of Coelocephalapion camarae Kissinger (Coleoptera: Brentidae) and Falconia intermedia (Distant) (Heteroptera: Miridae), two new candidate natural enemies for release on the weed
- Authors: Baars, Jan-Robert
- Date: 2003
- Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
- Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
- Full Text:
- Date Issued: 2003
- Authors: Baars, Jan-Robert
- Date: 2003
- Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
- Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
- Full Text:
- Date Issued: 2003
Change and continuity : perceptions about childhood diseases among the Tumbuka of Northern Malawi
- Munthali, Alister Chaundumuka
- Authors: Munthali, Alister Chaundumuka
- Date: 2003
- Subjects: Tumbuka (African people) Ethnology -- Malawi Diseases -- Causes and theories of causation Health behavior -- Malawi Health attitudes -- Malawi Children -- Diseases -- Malawi
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2114 , http://hdl.handle.net/10962/d1007718
- Description: The objectives of this study were to determine what the Tumbuka people of northern Malawi consider to be the most dangerous childhood diseases, to explore their perceptions about the aetiology, prevention and treatment of these diseases, and to determine how such perceptions have changed over the years. The study was done in Chisinde and surrounding villages in western Rumphi District, northern Malawi. Although a household questionnaire was used to collect some quantitative data, the major data collection methods comprised participant observation, in-depth interviews with mothers with children under five and old men and women, and key informant interviews with traditional healers, traditional birth attendants, village headmen, health surveillance assistants and clinical officers. Informants in this study mentioned chikhoso chamoto, diarrhoea, malaria, measles, and conjunctivitis as the most dangerous childhood diseases in the area. Old men and women added that in the past smallpox was also a dangerous disease that affected both children and adults. Apart from measles and smallpox, community-based health workers and those at the local health centre also mentioned the same list of diseases as the most dangerous diseases prevalent among under-five children. Though health workers and informants mentioned the same diseases, the informants' perspectives about the aetiology and prevention of these diseases and the way they sought treatment during childhood illness episodes, in some cases, differed significantly from those of biomedicine. For example, while health workers said that the signs and symptoms presented by a child suffering from "chikhoso chamoto" were those of either kwashiorkor or marasmus, both young and elderly informants said that a child could contract this illness through contact with a person who had been involved in sexual intercourse. Biomedically, diarrhoea is caused by the ingestion of pathogenic agents, which are transmitted through, among other factors, drinking contaminated water and eating contaminated foods. While young men and women subscribed to this biomedical view, at the same time, just like old men and women, they also believed that if a breastfeeding mother has sexual intercourse, sperms will contaminate her breast milk and, once a child feeds on this milk, he or she will develop diarrhoea. They, in addition, associated diarrhoea with the process of teething and other infections, such as malaria and measles. In malaria-endemic areas such as Malawi, the occurrence of convulsions, splenomegaly and anaemia in children under five may be biomedically attributed to malaria. However, most informants in this study perceived these conditions as separate disease entities caused by, among other factors, witchcraft and the infringement of Tumbuka taboos relating to food, sexual intercourse and funerals. Splenomegaly and convulsions were also perceived as hereditary diseases. Such Tumbuka perceptions about the aetiology of childhood diseases also influenced their ideas about prevention and the seeking of therapy during illness episodes. Apart from measles, other childhood vaccine-preventable diseases (i.e. tetanus, diphtheria, tuberculosis, pertussis and poliomyelitis) were not mentioned, presumably because they are no longer occurring on a significant scale, which is an indication of the success of vaccination programmes. This study reveals that there is no outright rejection of vaccination services in the study area. Some mothers, though, felt pressured to go for vaccination services as they believed that non-vaccinated children were refused biomedical treatment at the local health centres when they fell ill. While young women with children under five mentioned vaccination as a preventative measure against diseases such as measles, they also mentioned other indigenous forms of 'vaccination', which included the adherence to societal taboos, the wearing of amulets, the rubbing of protective medicines into incisions, isolation of children under five (e.g. a newly born child is kept in the house, amongst other things, to protect him or her against people who are ritually considered hot because of sexual intercourse) who are susceptible to disease or those posing a threat to cause disease in children under five. For example, since diarrhoea is perceived to be caused by, among other things, a child feeding on breast milk contaminated with sperms, informants said that there is a strong need for couples to observe postpartum sexual intercourse. A couple with newly delivered twins is isolated from the village because of the belief that children will swell if they came into contact with them. Local methods of disease prevention seem therefore to depend on what is perceived to be the cause of the illness and the decision to adopt specific preventive measures depends on, among other factors, the diagnosis of the cause and of who is vulnerable. The therapy-seeking process is a hierarchical movement within and between aetiologies; at the same time, it is not a random process, but an ordered process of choices in response to negative feedback, and subject to a number of factors, such as the aetiology of the disease, distance, social costs, cost of the therapeutic intervention, availability of medicines, etc. The movement between systems (i.e. from traditional medicine to biomedicine and vice-versa) during illness episodes depends on a number of factors, including previous experiences of significant others (i.e. those close to the patient), perceptions about the chances of getting healed, the decisions of the therapy management group, etc. For example, febrile illness in children under five may be treated using herbs or antipyretics bought from the local grocery shops. When the situation worsens (e.g. accompanied by convulsions), a herbalist will be consulted or the child may be taken to the local health centre. The local health centre refers such cases to the district hospital for treatment. Because of the rapidity with which the condition worsens, informants said that sometimes such children are believed to be bewitched, hence while biomedical treatment is sought, at the same time diviners are also consulted. The therapeutic strategies people resort to during illness episodes are appropriate rational decisions, based on prevailing circumstances, knowledge, resources and outcomes. Boundaries between the different therapeutic options are not rigid, as people move from one form of therapy to another and from one mode of classification to another. Lastly, perceptions about childhood diseases have changed over the years. Old men and women mostly attribute childhood illnesses to the infringement of taboos (e.g. on . sexual intercourse), witchcraft and other supernatural forces. While young men and women also subscribe to these perceptions, they have at the same time also appropriated the biomedical disease explanatory models. These biomedical models were learnt at school, acquired during health education sessions conducted by health workers in the communities as well as during under-five clinics, and health education programmes conducted on the national radio station. Younger people, more frequently than older people, thus move within and between aetiological models in the manner described above.
- Full Text:
- Date Issued: 2003
- Authors: Munthali, Alister Chaundumuka
- Date: 2003
- Subjects: Tumbuka (African people) Ethnology -- Malawi Diseases -- Causes and theories of causation Health behavior -- Malawi Health attitudes -- Malawi Children -- Diseases -- Malawi
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2114 , http://hdl.handle.net/10962/d1007718
- Description: The objectives of this study were to determine what the Tumbuka people of northern Malawi consider to be the most dangerous childhood diseases, to explore their perceptions about the aetiology, prevention and treatment of these diseases, and to determine how such perceptions have changed over the years. The study was done in Chisinde and surrounding villages in western Rumphi District, northern Malawi. Although a household questionnaire was used to collect some quantitative data, the major data collection methods comprised participant observation, in-depth interviews with mothers with children under five and old men and women, and key informant interviews with traditional healers, traditional birth attendants, village headmen, health surveillance assistants and clinical officers. Informants in this study mentioned chikhoso chamoto, diarrhoea, malaria, measles, and conjunctivitis as the most dangerous childhood diseases in the area. Old men and women added that in the past smallpox was also a dangerous disease that affected both children and adults. Apart from measles and smallpox, community-based health workers and those at the local health centre also mentioned the same list of diseases as the most dangerous diseases prevalent among under-five children. Though health workers and informants mentioned the same diseases, the informants' perspectives about the aetiology and prevention of these diseases and the way they sought treatment during childhood illness episodes, in some cases, differed significantly from those of biomedicine. For example, while health workers said that the signs and symptoms presented by a child suffering from "chikhoso chamoto" were those of either kwashiorkor or marasmus, both young and elderly informants said that a child could contract this illness through contact with a person who had been involved in sexual intercourse. Biomedically, diarrhoea is caused by the ingestion of pathogenic agents, which are transmitted through, among other factors, drinking contaminated water and eating contaminated foods. While young men and women subscribed to this biomedical view, at the same time, just like old men and women, they also believed that if a breastfeeding mother has sexual intercourse, sperms will contaminate her breast milk and, once a child feeds on this milk, he or she will develop diarrhoea. They, in addition, associated diarrhoea with the process of teething and other infections, such as malaria and measles. In malaria-endemic areas such as Malawi, the occurrence of convulsions, splenomegaly and anaemia in children under five may be biomedically attributed to malaria. However, most informants in this study perceived these conditions as separate disease entities caused by, among other factors, witchcraft and the infringement of Tumbuka taboos relating to food, sexual intercourse and funerals. Splenomegaly and convulsions were also perceived as hereditary diseases. Such Tumbuka perceptions about the aetiology of childhood diseases also influenced their ideas about prevention and the seeking of therapy during illness episodes. Apart from measles, other childhood vaccine-preventable diseases (i.e. tetanus, diphtheria, tuberculosis, pertussis and poliomyelitis) were not mentioned, presumably because they are no longer occurring on a significant scale, which is an indication of the success of vaccination programmes. This study reveals that there is no outright rejection of vaccination services in the study area. Some mothers, though, felt pressured to go for vaccination services as they believed that non-vaccinated children were refused biomedical treatment at the local health centres when they fell ill. While young women with children under five mentioned vaccination as a preventative measure against diseases such as measles, they also mentioned other indigenous forms of 'vaccination', which included the adherence to societal taboos, the wearing of amulets, the rubbing of protective medicines into incisions, isolation of children under five (e.g. a newly born child is kept in the house, amongst other things, to protect him or her against people who are ritually considered hot because of sexual intercourse) who are susceptible to disease or those posing a threat to cause disease in children under five. For example, since diarrhoea is perceived to be caused by, among other things, a child feeding on breast milk contaminated with sperms, informants said that there is a strong need for couples to observe postpartum sexual intercourse. A couple with newly delivered twins is isolated from the village because of the belief that children will swell if they came into contact with them. Local methods of disease prevention seem therefore to depend on what is perceived to be the cause of the illness and the decision to adopt specific preventive measures depends on, among other factors, the diagnosis of the cause and of who is vulnerable. The therapy-seeking process is a hierarchical movement within and between aetiologies; at the same time, it is not a random process, but an ordered process of choices in response to negative feedback, and subject to a number of factors, such as the aetiology of the disease, distance, social costs, cost of the therapeutic intervention, availability of medicines, etc. The movement between systems (i.e. from traditional medicine to biomedicine and vice-versa) during illness episodes depends on a number of factors, including previous experiences of significant others (i.e. those close to the patient), perceptions about the chances of getting healed, the decisions of the therapy management group, etc. For example, febrile illness in children under five may be treated using herbs or antipyretics bought from the local grocery shops. When the situation worsens (e.g. accompanied by convulsions), a herbalist will be consulted or the child may be taken to the local health centre. The local health centre refers such cases to the district hospital for treatment. Because of the rapidity with which the condition worsens, informants said that sometimes such children are believed to be bewitched, hence while biomedical treatment is sought, at the same time diviners are also consulted. The therapeutic strategies people resort to during illness episodes are appropriate rational decisions, based on prevailing circumstances, knowledge, resources and outcomes. Boundaries between the different therapeutic options are not rigid, as people move from one form of therapy to another and from one mode of classification to another. Lastly, perceptions about childhood diseases have changed over the years. Old men and women mostly attribute childhood illnesses to the infringement of taboos (e.g. on . sexual intercourse), witchcraft and other supernatural forces. While young men and women also subscribe to these perceptions, they have at the same time also appropriated the biomedical disease explanatory models. These biomedical models were learnt at school, acquired during health education sessions conducted by health workers in the communities as well as during under-five clinics, and health education programmes conducted on the national radio station. Younger people, more frequently than older people, thus move within and between aetiological models in the manner described above.
- Full Text:
- Date Issued: 2003
Correlates and outcomes of emotional intelligence in organisations
- Authors: Bosman, Leon Abraham
- Date: 2003
- Subjects: Leadership , Emotional intelligence , Organizational behavior
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:11006 , http://hdl.handle.net/10948/337 , Leadership , Emotional intelligence , Organizational behavior
- Description: Emotional Intelligence and Leadership are two very important constructs to organizations. Likewise concepts like OCB, conflict handling and intention to quit of employees are equally important constructs to organizations. The primary aim of the present study was to determine how well Organisational Citizenship Behaviour and intention to quit as well as the conflict handling style of subordinates could be predicted by means of leadership style, and the emotional intelligence of leaders. A secondary aim was to determine whether a causal model could be built to represent the relationships among the variables included in the study. Relationships among these constructs were investigated in a South African sample of employees (N=470) working for various organisations. The construct validity and internal consistency of the measuring instruments were investigated. The finally accepted factor structure of not one of the measuring instruments matched the original structure as found by the authors/developers of the measuring instruments. It was therefore decided that in all cases the factor pattern as determined on the responses of the present sample would be used in further analyses of the data. Emotional intelligence of leaders as seen by subordinates and the self - perceived conflict handling styles of subordinates seem to be related in the case of Integrating and Obliging conflict handling styles and both the emotional intelligence sub-scales, i.e. Motivation and Vigilance. The Multiple Regression analysis indicated that the emotional intelligence sub-scales scores played a minor role in the prediction of Organizational Citizenship Behaviour. Models of the relationships among the variables were built by studying the results of v previous as well as the present study. The model, in which emotional intelligence is depicted as a causal variable influencing - through leadership behaviour – organizational citizenship behaviour and the integrating style of handling interpersonal conflict represented a good fit with the data. These results seem to provide some structure for thinking about the relationships among the variables and can possibly serve as frames of reference in future studies.
- Full Text:
- Date Issued: 2003
- Authors: Bosman, Leon Abraham
- Date: 2003
- Subjects: Leadership , Emotional intelligence , Organizational behavior
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:11006 , http://hdl.handle.net/10948/337 , Leadership , Emotional intelligence , Organizational behavior
- Description: Emotional Intelligence and Leadership are two very important constructs to organizations. Likewise concepts like OCB, conflict handling and intention to quit of employees are equally important constructs to organizations. The primary aim of the present study was to determine how well Organisational Citizenship Behaviour and intention to quit as well as the conflict handling style of subordinates could be predicted by means of leadership style, and the emotional intelligence of leaders. A secondary aim was to determine whether a causal model could be built to represent the relationships among the variables included in the study. Relationships among these constructs were investigated in a South African sample of employees (N=470) working for various organisations. The construct validity and internal consistency of the measuring instruments were investigated. The finally accepted factor structure of not one of the measuring instruments matched the original structure as found by the authors/developers of the measuring instruments. It was therefore decided that in all cases the factor pattern as determined on the responses of the present sample would be used in further analyses of the data. Emotional intelligence of leaders as seen by subordinates and the self - perceived conflict handling styles of subordinates seem to be related in the case of Integrating and Obliging conflict handling styles and both the emotional intelligence sub-scales, i.e. Motivation and Vigilance. The Multiple Regression analysis indicated that the emotional intelligence sub-scales scores played a minor role in the prediction of Organizational Citizenship Behaviour. Models of the relationships among the variables were built by studying the results of v previous as well as the present study. The model, in which emotional intelligence is depicted as a causal variable influencing - through leadership behaviour – organizational citizenship behaviour and the integrating style of handling interpersonal conflict represented a good fit with the data. These results seem to provide some structure for thinking about the relationships among the variables and can possibly serve as frames of reference in future studies.
- Full Text:
- Date Issued: 2003
Development of integrated algal ponding systems in the treatment of wine distillery wastewaters
- Authors: Dekker, Leendert Gideon
- Date: 2003
- Subjects: Sewage -- Purification -- Anaerobic treatment Wine and wine making -- Waste disposal -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4062 , http://hdl.handle.net/10962/d1004530
- Description: In South Africa, wastewater disposal in the wine and distilling industry is undergoing a profound transformation as a result of fundamental changes in regulations and license requirements. To deal with this problem conventional Waste Stabilisation Ponding systems have been used by the industry together with irrigation and evaporation disposal practises. Although effective in the evaporation and containment disposal functions, these pond systems are generally not properly designed and/or managed, resulting in overloading and, at times, the generation of seriously offensive odour problems. Preliminary studies on the feasibility of utilising the Advanced Integrated Wastewater Ponding System as a core treatment technology in winery wastewater treatment were conducted. Results indicated that specific problems had to be addressed before successful ponding treatment could be achieved. This research programme undertook an investigation of the performance of a demonstration ponding system treating household sewage, which formed the basis of the research due to limited experience reported on ponds treating wine industry wastewaters. Malfunctions identified were in correlation with the preliminary winery waste ponding survey, which included unstable fermentation pit functions and inadequate nutrient removal. Retrofitting the fermentation pit with a nylon net across the rising water column resulted in improved retention of active anaerobic sludge, especially during periods of system start-up and/or organic overloading. An investigation into nutrient removal utilising algal biomass provided a valuable contribution towards development of an independent nutrient removal system. Harvested algal biomass was passively manipulated to release polysaccharides under anoxic conditions, with subsequent use as a carbon source by denitrifying organisms. Following denitrification, the still viable algal cells were introduced into a High Rate Algal Pond raceway for photosynthetically produced alkalinity. This high pH environment resulted in induced calcium phosphate mineral formation and subsequent precipitation, as well as effective ammonia stripping from the water. Based on the novel positive research outcomes a decision was made to proceed to the construction of a pilot-scale integrated ponding system treating wastewater from a wine lees factory. The system linked the Anaerobic Baffle Reactor, for pre-treatment, with the improved Advanced Integrated Wastewater Ponding System. The potential of this system has shown that a Waste Stabilisation Ponding system can be engineered to treat wine industry wastewaters and thereby effectively reduce the organic and nutrient loads, by using low-cost retrofitted upgrading unit operations. Valuable algal biomass may also be recovered as a by-product of the treatment process.
- Full Text:
- Date Issued: 2003
- Authors: Dekker, Leendert Gideon
- Date: 2003
- Subjects: Sewage -- Purification -- Anaerobic treatment Wine and wine making -- Waste disposal -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4062 , http://hdl.handle.net/10962/d1004530
- Description: In South Africa, wastewater disposal in the wine and distilling industry is undergoing a profound transformation as a result of fundamental changes in regulations and license requirements. To deal with this problem conventional Waste Stabilisation Ponding systems have been used by the industry together with irrigation and evaporation disposal practises. Although effective in the evaporation and containment disposal functions, these pond systems are generally not properly designed and/or managed, resulting in overloading and, at times, the generation of seriously offensive odour problems. Preliminary studies on the feasibility of utilising the Advanced Integrated Wastewater Ponding System as a core treatment technology in winery wastewater treatment were conducted. Results indicated that specific problems had to be addressed before successful ponding treatment could be achieved. This research programme undertook an investigation of the performance of a demonstration ponding system treating household sewage, which formed the basis of the research due to limited experience reported on ponds treating wine industry wastewaters. Malfunctions identified were in correlation with the preliminary winery waste ponding survey, which included unstable fermentation pit functions and inadequate nutrient removal. Retrofitting the fermentation pit with a nylon net across the rising water column resulted in improved retention of active anaerobic sludge, especially during periods of system start-up and/or organic overloading. An investigation into nutrient removal utilising algal biomass provided a valuable contribution towards development of an independent nutrient removal system. Harvested algal biomass was passively manipulated to release polysaccharides under anoxic conditions, with subsequent use as a carbon source by denitrifying organisms. Following denitrification, the still viable algal cells were introduced into a High Rate Algal Pond raceway for photosynthetically produced alkalinity. This high pH environment resulted in induced calcium phosphate mineral formation and subsequent precipitation, as well as effective ammonia stripping from the water. Based on the novel positive research outcomes a decision was made to proceed to the construction of a pilot-scale integrated ponding system treating wastewater from a wine lees factory. The system linked the Anaerobic Baffle Reactor, for pre-treatment, with the improved Advanced Integrated Wastewater Ponding System. The potential of this system has shown that a Waste Stabilisation Ponding system can be engineered to treat wine industry wastewaters and thereby effectively reduce the organic and nutrient loads, by using low-cost retrofitted upgrading unit operations. Valuable algal biomass may also be recovered as a by-product of the treatment process.
- Full Text:
- Date Issued: 2003
Effects of sustained Russian wheat aphid (Diuraphis noxia Mordvilko) feeding on leaf blades of wheat (Triticum aestivum L. cv Adamtas)
- Authors: Matsiliza, Babalwa
- Date: 2003
- Subjects: Russian wheat aphid Wheat -- Diseases and pests
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4213 , http://hdl.handle.net/10962/d1003782
- Description: Penetration of sink as well as source leaves of wheat plants by the Russian wheat aphid, Diuraphis noxia (Mordvilko) was investigated using light, fluorescence and transmission electron techniques, to determine the feeding strategies adopted by the aphid in penetrating and successfully feeding from the phloem, and to assess the structural effects of the probing and feeding behaviour of D. noxia on the feeding sites. Examination of aphid-infested sink, as well as source leaf tissue, showed that D.noxia probed in cells of the vascular bundle more frequently than mesophyll cells. Within the vascular bundle, thin-walled sieve tubes were visited (probed) more than the other cells. In sink leaf material, 68 of 82 (83%) stylets and stylet tracks encountered during the examination of 1000 serial sections (from 5 different plants) terminated in thin-walled sieve tubes and only 14 (17%) in thick-walled sieve tubes. Thin-walled sieve tubes were visited more significantly than thick-walled sieve tubes. However, examination of the aphid.,.infested sink leaf on a per centimetre basis, from the tip of the leaf, revealed that thick-walled sieve tubes in the area closest to the tip (0-2cm from the tip) were as attractive to the aphid as were thin-walled sieve tubes, with no significant difference in the number of times thick- and thin-walled sieve tubes were probed in this area. Some 2-4cm from the tip however, thinwalled sieve tubes were significantly more probed and therefore more attractive than thick-walled sieve tubes. Examination of 2000 serial sections using aphid-infested source leaf tissue, showed that the thin-walled sieve tubes were significantly more probed than thickwalled sieve tubes, along the whole leaf, expressed as a total of all leaves, as well as on a per centimetre basis along the length of the leaf, with 212 (95%) of 222 terminations within the thin-walled sieve tubes and only 10 (5%) in thick-walledsieve tubes. The aphid probed the small vascular bundles (loading bundles) many more times than intermediate or large transport vascular bundles, in sink as well as source leaf. Of a total of 82 stylets and stylet tracks encountered in sink leaf tissue, 31 terminated in small vascular bundles ang the remaining 28 and 16 were located within large and intermediate vascular bundles respectively. In source leaf tissue 121 of 222 stylets and stylet tracks encountered were associated with small vascular bundles and only 58 tracks and 43 tracks with intermediate and large vascular bundles, respectively. The effect of sustained RWA feeding on the transport capacity was examined after the application of 5,6 carboxyfluoresceine diacetate (5,6-CFDA) in control (sink and source leaf tissue) and aphid-infested (source) wheat leaves, using fluorescence microscopy. After 3h acropetal longitudinal transport of 5,6-CF had occurred in sink leaves in longitudinal veins, as well as a lateral transfer via cross veins and subsequent unloading into mesophyll cells close to the tip of the leaf was observed. In control leaf tissue, the fluorescence front was detected up to about 5cm from the point of application and was only associated with the phloem and not unloaded. In contrast, aphid-infested leaf tissue showed very little 5,6-CF transport, being limited to 2cm or less from the point of application. Structural damage to the phloem in general and to the sieve tubes in particular within of control and infested wheat leaves was investigated using transmission electron microscopy (TEM). In addition, leaf strips were mounted in aniline blue to visualise callose deposition using the fluorescence microscopy. At the TEM level. infested leaf tissue showed various abnormalities, which included destruction of cell contents, membrane damage and subsequent loss of cell contents. TEM studies suggest severe osmotic shock resulted from the aphid's probing. Examination of leaf tissue using fluorescence microscopy showed that there was very little characteristic aniline blue-stained callose visible in control leaf tissue, other than the thin diffuse patches along the sieve plates and punctate spots associated with pore plasmodesmatal areas and plasmodesmatal aggregates. In contrast, the aphid-infested leaf tissue was heavily callosed, with callose deposited not only within the phloem tissue but also in neighbouring vascular parE:}nchyma cells as well. The data collectively suggest that D. noxia feeds preferentially within thin-walled sieve tubes, within the small longitudinal vascular bundles in sink , as well source leaf tissue. Based upon the data presented here the thin-walled sieve tubes in the wheat leaf appear to be more attractive to the aphid and that they are probably more functional in terms of transport system and unlo?lding in sink leaves. Aniline blue stained leaf material that had previously hosted large aphid colonies showed evidence of extensive callose deposits 24 to 36h after the aphids were removed, suggesting that the aphids caused severe mechanical damage to the vascular tissue and mesohyll cells as well. Damage (transient or more permanent) and the subsequent deposition of wound callose, disrupted phloem transport and hence the export of photoassimilate from the leaves.
- Full Text:
- Date Issued: 2003
- Authors: Matsiliza, Babalwa
- Date: 2003
- Subjects: Russian wheat aphid Wheat -- Diseases and pests
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4213 , http://hdl.handle.net/10962/d1003782
- Description: Penetration of sink as well as source leaves of wheat plants by the Russian wheat aphid, Diuraphis noxia (Mordvilko) was investigated using light, fluorescence and transmission electron techniques, to determine the feeding strategies adopted by the aphid in penetrating and successfully feeding from the phloem, and to assess the structural effects of the probing and feeding behaviour of D. noxia on the feeding sites. Examination of aphid-infested sink, as well as source leaf tissue, showed that D.noxia probed in cells of the vascular bundle more frequently than mesophyll cells. Within the vascular bundle, thin-walled sieve tubes were visited (probed) more than the other cells. In sink leaf material, 68 of 82 (83%) stylets and stylet tracks encountered during the examination of 1000 serial sections (from 5 different plants) terminated in thin-walled sieve tubes and only 14 (17%) in thick-walled sieve tubes. Thin-walled sieve tubes were visited more significantly than thick-walled sieve tubes. However, examination of the aphid.,.infested sink leaf on a per centimetre basis, from the tip of the leaf, revealed that thick-walled sieve tubes in the area closest to the tip (0-2cm from the tip) were as attractive to the aphid as were thin-walled sieve tubes, with no significant difference in the number of times thick- and thin-walled sieve tubes were probed in this area. Some 2-4cm from the tip however, thinwalled sieve tubes were significantly more probed and therefore more attractive than thick-walled sieve tubes. Examination of 2000 serial sections using aphid-infested source leaf tissue, showed that the thin-walled sieve tubes were significantly more probed than thickwalled sieve tubes, along the whole leaf, expressed as a total of all leaves, as well as on a per centimetre basis along the length of the leaf, with 212 (95%) of 222 terminations within the thin-walled sieve tubes and only 10 (5%) in thick-walledsieve tubes. The aphid probed the small vascular bundles (loading bundles) many more times than intermediate or large transport vascular bundles, in sink as well as source leaf. Of a total of 82 stylets and stylet tracks encountered in sink leaf tissue, 31 terminated in small vascular bundles ang the remaining 28 and 16 were located within large and intermediate vascular bundles respectively. In source leaf tissue 121 of 222 stylets and stylet tracks encountered were associated with small vascular bundles and only 58 tracks and 43 tracks with intermediate and large vascular bundles, respectively. The effect of sustained RWA feeding on the transport capacity was examined after the application of 5,6 carboxyfluoresceine diacetate (5,6-CFDA) in control (sink and source leaf tissue) and aphid-infested (source) wheat leaves, using fluorescence microscopy. After 3h acropetal longitudinal transport of 5,6-CF had occurred in sink leaves in longitudinal veins, as well as a lateral transfer via cross veins and subsequent unloading into mesophyll cells close to the tip of the leaf was observed. In control leaf tissue, the fluorescence front was detected up to about 5cm from the point of application and was only associated with the phloem and not unloaded. In contrast, aphid-infested leaf tissue showed very little 5,6-CF transport, being limited to 2cm or less from the point of application. Structural damage to the phloem in general and to the sieve tubes in particular within of control and infested wheat leaves was investigated using transmission electron microscopy (TEM). In addition, leaf strips were mounted in aniline blue to visualise callose deposition using the fluorescence microscopy. At the TEM level. infested leaf tissue showed various abnormalities, which included destruction of cell contents, membrane damage and subsequent loss of cell contents. TEM studies suggest severe osmotic shock resulted from the aphid's probing. Examination of leaf tissue using fluorescence microscopy showed that there was very little characteristic aniline blue-stained callose visible in control leaf tissue, other than the thin diffuse patches along the sieve plates and punctate spots associated with pore plasmodesmatal areas and plasmodesmatal aggregates. In contrast, the aphid-infested leaf tissue was heavily callosed, with callose deposited not only within the phloem tissue but also in neighbouring vascular parE:}nchyma cells as well. The data collectively suggest that D. noxia feeds preferentially within thin-walled sieve tubes, within the small longitudinal vascular bundles in sink , as well source leaf tissue. Based upon the data presented here the thin-walled sieve tubes in the wheat leaf appear to be more attractive to the aphid and that they are probably more functional in terms of transport system and unlo?lding in sink leaves. Aniline blue stained leaf material that had previously hosted large aphid colonies showed evidence of extensive callose deposits 24 to 36h after the aphids were removed, suggesting that the aphids caused severe mechanical damage to the vascular tissue and mesohyll cells as well. Damage (transient or more permanent) and the subsequent deposition of wound callose, disrupted phloem transport and hence the export of photoassimilate from the leaves.
- Full Text:
- Date Issued: 2003
Evaluating people-environment relationships : developing appropriate research methodologies for sustainable management and rehabilitation of riverine areas by communities in the Kat River Valley, Eastern Cape Province, South Africa
- Authors: Motteux, Nicole
- Date: 2003
- Subjects: Water-supply -- South Africa -- Kat River Valley -- Management Rural development -- Environmental aspects -- South Africa -- Kat River Valley Kat River Valley (South Africa) Human ecology -- South Africa -- Kat River Valley Stream ecology -- South Africa -- Kat River Valley
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4828 , http://hdl.handle.net/10962/d1005503
- Description: International evidence clearly indicates that water shortages and the enhanced value attached to water and aquatic ecosystems are key concerns faced by many countries. International experience, since the mid-1980s, has emphasised the importance of addressing political, social, environmental and economic issues through active stakeholder participation in riverine and water resource management. These trends and issues are relevant to South Africa, where integrated water resource management (IWRM) is now a cornerstone of water resource policy and the National Water Act (NWA). Apartheid excluded communities in former homelands (racial reserves) from participation in IWRM. The research presented in this thesis was based on the search for philosophies and methods to involve the rural, former homeland people of the Kat River Valley in South Africa in IWRM. Post-modern, humanist and some logical positivist geographical philosophies were used during the research. This research applied Participatory Rural Appraisal (PRA) philosophy and methods and was influenced by the seminal work of Paolo Freire (1972). In addition, the use of innovative methods for engagement of the oppressed, using theatre methods developed by Augusto Boal (1995, 2000) was explored to add value to PRA. In addition, the application of Action Research ensured that community participants were actively involved in the research being conducted for this thesis. The applied research in the Kat River Valley in South Africa evolved through three key phases. In Phase One quantifiable data on the Kat River Valley and its residents was sought. This investigation did not empower the resident communities of Fairbairn and Hertzog – a lesson that influenced the move to more participatory methods in subsequent phases of the research. Lessons learned from using surveys encouraged exploration of participatory methods to enable participants to become “co-learners”. Phase Two of the research commenced with a series of feedback meetings, in which participants recognised that they faced an environmental crisis. Through a series of participatory workshops, residents came to acknowledge and affirm their environmental knowledge. Residents then committed themselves to gaining a deeper understanding of their environment and their lives. My role changed from that of a researcher to a facilitator. Phase Three of the research and the shift to Action Research commenced after local residents identified the need to personally take charge of their environmental challenges in the Kat River Valley and recognised the need to collaborate at a catchment scale for effective IWRM. This eventually led to the formation of a Water User Association and Catchment Forum. The key theoretical contribution of the thesis relates to the identified relationship between the development orientation and ecological paradigm, and an assessment of the impact this has on the inputs, processes, outputs and outcomes of IWRM. This theoretical contribution is equally valid in other countries, where the tradeoffs are essentially the same, but the framework for making the choices is different because of varying socio-economic and biophysical circumstances
- Full Text:
- Date Issued: 2003
- Authors: Motteux, Nicole
- Date: 2003
- Subjects: Water-supply -- South Africa -- Kat River Valley -- Management Rural development -- Environmental aspects -- South Africa -- Kat River Valley Kat River Valley (South Africa) Human ecology -- South Africa -- Kat River Valley Stream ecology -- South Africa -- Kat River Valley
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4828 , http://hdl.handle.net/10962/d1005503
- Description: International evidence clearly indicates that water shortages and the enhanced value attached to water and aquatic ecosystems are key concerns faced by many countries. International experience, since the mid-1980s, has emphasised the importance of addressing political, social, environmental and economic issues through active stakeholder participation in riverine and water resource management. These trends and issues are relevant to South Africa, where integrated water resource management (IWRM) is now a cornerstone of water resource policy and the National Water Act (NWA). Apartheid excluded communities in former homelands (racial reserves) from participation in IWRM. The research presented in this thesis was based on the search for philosophies and methods to involve the rural, former homeland people of the Kat River Valley in South Africa in IWRM. Post-modern, humanist and some logical positivist geographical philosophies were used during the research. This research applied Participatory Rural Appraisal (PRA) philosophy and methods and was influenced by the seminal work of Paolo Freire (1972). In addition, the use of innovative methods for engagement of the oppressed, using theatre methods developed by Augusto Boal (1995, 2000) was explored to add value to PRA. In addition, the application of Action Research ensured that community participants were actively involved in the research being conducted for this thesis. The applied research in the Kat River Valley in South Africa evolved through three key phases. In Phase One quantifiable data on the Kat River Valley and its residents was sought. This investigation did not empower the resident communities of Fairbairn and Hertzog – a lesson that influenced the move to more participatory methods in subsequent phases of the research. Lessons learned from using surveys encouraged exploration of participatory methods to enable participants to become “co-learners”. Phase Two of the research commenced with a series of feedback meetings, in which participants recognised that they faced an environmental crisis. Through a series of participatory workshops, residents came to acknowledge and affirm their environmental knowledge. Residents then committed themselves to gaining a deeper understanding of their environment and their lives. My role changed from that of a researcher to a facilitator. Phase Three of the research and the shift to Action Research commenced after local residents identified the need to personally take charge of their environmental challenges in the Kat River Valley and recognised the need to collaborate at a catchment scale for effective IWRM. This eventually led to the formation of a Water User Association and Catchment Forum. The key theoretical contribution of the thesis relates to the identified relationship between the development orientation and ecological paradigm, and an assessment of the impact this has on the inputs, processes, outputs and outcomes of IWRM. This theoretical contribution is equally valid in other countries, where the tradeoffs are essentially the same, but the framework for making the choices is different because of varying socio-economic and biophysical circumstances
- Full Text:
- Date Issued: 2003