The gendered nature of intra-household decision making in the use of social grants and its impact on selected households in Zimbabwe and South Africa
- Authors: Makosa, Nigel
- Date: 2019
- Subjects: Social security Grants-in-aid
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15781 , vital:40523
- Description: The study aimed at undertaking a comparative investigation of the gendered nature of intra-household decision making in the use of social grants and to ascertain its impact on selected households in Zimbabwe and South Africa as a comparative study. A methodological triangulated approach was used in the study where both quantitative and qualitative approaches were adopted. A total of 250 heads of households were selected as a sample from the study population. Herein, 200 respondents were given the survey questionnaire (100 respondents from Zimbabwe and another 100 from South Africa). A larger number of respondents were sampled for quantitative data in order to improve validity and generalisability of the results. Interview participants for this study were conveniently selected from communities benefiting from cash transfers and social grants. The researcher then interviewed a total of 50 participants (25 from Zimbabwe plus another 25 from South Africa). The samples for the study were arrived at using the multi stage sampling techniques. From these samples two data sets were obtained namely quantitative and qualitative. The study yielded that there are more social grants that are targeted at benefiting older people in Zimbabwe whereas there are a variety of social grants that are aimed at benefiting people from all age groups in South Africa. The study also established that the nature of intrahousehold decision making is determined by the variations of the recipients’ age variations. In Zimbabwe It was revealed that most of the recipients who were younger than 65 years bought basic needs, while in South Africa the recipients mostly used the money for entertainment, savings and clothes. The current economic situations in these two countries determine their spending patterns. Both in Zimbabwe vi and South Africa, recipients older than 65 years used their money to buy agricultural inputs. In both countries most of the beneficiaries were female because there are the primary caregivers and also because of the increased number of female headed households precipitated by high divorce rates. It also emerged in the study that there are many factors that influencethe gendered nature of intra household decision making dynamics such as cultural, available resources, number of dependents. These factors have the potential to either reinforce or offset the impact of social grants. Furthermore, the decision-making roles for men and women in both Zimbabwe and South Africa were determined by income and economic activities, food security and basic needs; marital status, family and social structures. But on the whole, it was revealed in the study that the responsibility of the head of household to provide leadership and make crucial decisions such as using social grants money. In both countries members from outside the nucleus family were also involved in making decisions on behalf of the beneficiaries. Elderly people retained the majority of the decision-making power in most of the households in both Zimbabwe and South Africa. It also emerged that in most households in both countries, decision making on the use of social grant money was arrived at after consultations particularly between spouses. In order to enhance productive decision making and optimise the social grants usefulness, the study recommends that there should be monitoring and evaluation on how the social grants are being used and who is behind the decision-making process. More so, a conceptual framework was also suggested to explain intrahousehold decision dynamics.
- Full Text:
- Date Issued: 2019
- Authors: Makosa, Nigel
- Date: 2019
- Subjects: Social security Grants-in-aid
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15781 , vital:40523
- Description: The study aimed at undertaking a comparative investigation of the gendered nature of intra-household decision making in the use of social grants and to ascertain its impact on selected households in Zimbabwe and South Africa as a comparative study. A methodological triangulated approach was used in the study where both quantitative and qualitative approaches were adopted. A total of 250 heads of households were selected as a sample from the study population. Herein, 200 respondents were given the survey questionnaire (100 respondents from Zimbabwe and another 100 from South Africa). A larger number of respondents were sampled for quantitative data in order to improve validity and generalisability of the results. Interview participants for this study were conveniently selected from communities benefiting from cash transfers and social grants. The researcher then interviewed a total of 50 participants (25 from Zimbabwe plus another 25 from South Africa). The samples for the study were arrived at using the multi stage sampling techniques. From these samples two data sets were obtained namely quantitative and qualitative. The study yielded that there are more social grants that are targeted at benefiting older people in Zimbabwe whereas there are a variety of social grants that are aimed at benefiting people from all age groups in South Africa. The study also established that the nature of intrahousehold decision making is determined by the variations of the recipients’ age variations. In Zimbabwe It was revealed that most of the recipients who were younger than 65 years bought basic needs, while in South Africa the recipients mostly used the money for entertainment, savings and clothes. The current economic situations in these two countries determine their spending patterns. Both in Zimbabwe vi and South Africa, recipients older than 65 years used their money to buy agricultural inputs. In both countries most of the beneficiaries were female because there are the primary caregivers and also because of the increased number of female headed households precipitated by high divorce rates. It also emerged in the study that there are many factors that influencethe gendered nature of intra household decision making dynamics such as cultural, available resources, number of dependents. These factors have the potential to either reinforce or offset the impact of social grants. Furthermore, the decision-making roles for men and women in both Zimbabwe and South Africa were determined by income and economic activities, food security and basic needs; marital status, family and social structures. But on the whole, it was revealed in the study that the responsibility of the head of household to provide leadership and make crucial decisions such as using social grants money. In both countries members from outside the nucleus family were also involved in making decisions on behalf of the beneficiaries. Elderly people retained the majority of the decision-making power in most of the households in both Zimbabwe and South Africa. It also emerged that in most households in both countries, decision making on the use of social grant money was arrived at after consultations particularly between spouses. In order to enhance productive decision making and optimise the social grants usefulness, the study recommends that there should be monitoring and evaluation on how the social grants are being used and who is behind the decision-making process. More so, a conceptual framework was also suggested to explain intrahousehold decision dynamics.
- Full Text:
- Date Issued: 2019
The implementation of curriculum and assessment policy statement by economics grade twelve teachers and its influence on teaching methods in East London Education District, South Africa
- Authors: Rantsane, Twoboy Babini
- Date: 2017
- Subjects: Curriculum-based assessment -- South Africa -- Eastern Cape Curriculum planning -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/4970 , vital:28879
- Description: The introduction of the Economics CAPS policy ushered the introduction of the new principle of “active and critical learning” which implies fostering active learner participation in teaching and learning process. The revision of curriculum in 1997 and subsequent years has implications on how teachers teach. Since the introduction of Economics CAPS in Grade twelve in 2014, no study has been conducted to determine how teachers implement the curriculum. The aim of the study was to investigate the implementation of Curriculum and Assessment Policy Statement (CAPS) by Economics Grade twelve teachers and its influence on teaching methods in East London Education District. The theoretical framework of the study was Experiential Learning Theory (ELT), constructivism, and pragmatism. A mixed method which entails the combination of quantitative and qualitative research methods was used in this study. A sequential design was followed in the study where the first stage comprised of the administration of questionnaire as a component of quantitative method. The second stage focused on qualitative method which entailed the administration of the following data collection techniques: lesson observation, semi-structured interviews and document analysis. Purposeful random sampling where East London Education District was selected since it has the required categories of schools required for the research was used. All the 53 Grade 12 Economics schools served as the population for the study. Some of the participants did not return the questionnaire while others have phased out Economics. A total of 36 schools participated and two schools have 2 Grade 12 classes. A total of 38 teachers returned the questionnaires. A stratified random sampling of 8 teachers was done for the qualitative research. The schools or teachers were categorised as follows: one teacher from Ex - Model C schools, one from urban, one from rural and five teachers from township schools. The sample represented 22.2 % of schools offering Grade 12 economics in the East London Education District. Descriptive statistics and thematic analysis were used for quantitative and qualitative studies respectively. The study found out that economics teachers assert that they employ mixed methods when teaching, but classroom practice reveals that their teaching approach is predominately teacher - centred. While the CAPS policy propagates the adoption of “active and critical learning” practice indicates this principle is applied to a limited extent. Economics teachers should be developed in using active learning methods to ensure that the new principle find expression in the classroom. In respect of the training of teachers to implement CAPS curriculum, research reveals that short-term training workshops were conducted but Economics teachers have challenges in methodology and content. The recommendations to address the challenges entail: continuous professional development of Economics teachers on methodology; conduct content workshops and resourcing of schools.
- Full Text:
- Date Issued: 2017
- Authors: Rantsane, Twoboy Babini
- Date: 2017
- Subjects: Curriculum-based assessment -- South Africa -- Eastern Cape Curriculum planning -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/4970 , vital:28879
- Description: The introduction of the Economics CAPS policy ushered the introduction of the new principle of “active and critical learning” which implies fostering active learner participation in teaching and learning process. The revision of curriculum in 1997 and subsequent years has implications on how teachers teach. Since the introduction of Economics CAPS in Grade twelve in 2014, no study has been conducted to determine how teachers implement the curriculum. The aim of the study was to investigate the implementation of Curriculum and Assessment Policy Statement (CAPS) by Economics Grade twelve teachers and its influence on teaching methods in East London Education District. The theoretical framework of the study was Experiential Learning Theory (ELT), constructivism, and pragmatism. A mixed method which entails the combination of quantitative and qualitative research methods was used in this study. A sequential design was followed in the study where the first stage comprised of the administration of questionnaire as a component of quantitative method. The second stage focused on qualitative method which entailed the administration of the following data collection techniques: lesson observation, semi-structured interviews and document analysis. Purposeful random sampling where East London Education District was selected since it has the required categories of schools required for the research was used. All the 53 Grade 12 Economics schools served as the population for the study. Some of the participants did not return the questionnaire while others have phased out Economics. A total of 36 schools participated and two schools have 2 Grade 12 classes. A total of 38 teachers returned the questionnaires. A stratified random sampling of 8 teachers was done for the qualitative research. The schools or teachers were categorised as follows: one teacher from Ex - Model C schools, one from urban, one from rural and five teachers from township schools. The sample represented 22.2 % of schools offering Grade 12 economics in the East London Education District. Descriptive statistics and thematic analysis were used for quantitative and qualitative studies respectively. The study found out that economics teachers assert that they employ mixed methods when teaching, but classroom practice reveals that their teaching approach is predominately teacher - centred. While the CAPS policy propagates the adoption of “active and critical learning” practice indicates this principle is applied to a limited extent. Economics teachers should be developed in using active learning methods to ensure that the new principle find expression in the classroom. In respect of the training of teachers to implement CAPS curriculum, research reveals that short-term training workshops were conducted but Economics teachers have challenges in methodology and content. The recommendations to address the challenges entail: continuous professional development of Economics teachers on methodology; conduct content workshops and resourcing of schools.
- Full Text:
- Date Issued: 2017
Mechanistic studies of unusual Miruta-Baylis-Hillman reactions
- Authors: Nyoni, Dubekile
- Date: 2012
- Subjects: Chemical reactions Benzaldehyde Acrylonitrile Methyl acrylate Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4400 , http://hdl.handle.net/10962/d1006692
- Description: This study has focussed on the application of synthetic, kinetic and exploratory theoretical methods in elucidating the reaction mechanisms of four Morita-Baylis-Hillman (MBH) type reactions, viz, i) the reactions of the disulfide 2,2'-dithiodibenzaldehyde with various activated alkenes in the presence of DBU and Ph₃P, ii) the reactions of chromone-3-carbaldehydes with MVK, iii) the reactions of chromone-2-carbaldehydes with acrylonitrile and iv) with methyl acrylate. Attention has also been given to the origin of the observed regioselectivity in Michaelis-Arbuzov reactions of 3-(halomethyl)coumarins. Cleavage of the sulfur-sulfur bond of aryl and heteroaryl disulfides by the nitrogen nucleophile DBU has been demonstrated, and a dramatic increase in the rate of tandem MBH and disulfide cleavage reactions of 2,2'-dithiodibenzaldehyde with the activated alkenes, MVK, EVK, acrylonitrile, methyl acrylate and tert-butyl acrylate has been achieved through the use of the dual organo-catalyst system, DBU-Ph₃P – an improvement accompanied by an increase in the yields of the isolated products. Detailed NMR-based kinetic studies have been conducted on the DBU-catalysed reactions of 2,2'-dithiodibenzaldehyde with MVK and methyl acrylate, and a theoretical kinetic model has been developed and complementary computational studies using Gaussian 03, at the DFT-B3LYP/6-31G(d) level of theory have provided valuable insights into the mechanism of these complex transformations. Reactions of chromone-3-carbaldehydes with MVK to afford chromone dimers and tricyclic products have been repeated, and a novel, intermediate MBH adduct has been isolated. The mechanisms of the competing pathways have been elucidated by DFT calculations and the development of a detailed theoretical kinetic model has ensued. Unusual transformations in MBH-type reactions of chromone-2-carbaldehydes with acrylonitrile and methyl acrylate have been explored and the structures of the unexpected products have been established using 1- and 2-D NMR, HRMS and X-ray crystallographic techniques. Attention has also been given to the synthesis of 3-(halomethyl)coumarins via the MBH reaction, and their subsequent Michaelis-Arbuzov reactions with triethyl phosphite. An exploratory study of the kinetics of the phosphonation reaction has been undertaken and the regio-selectivity of nucleophilic attack at the 4- and 1'-positions in the 3-chloro- and 3-(iodomethyl)coumarins has been investigated by calculating Mulliken charges, LUMO surfaces and Fukui condensed local softness functions.
- Full Text:
- Date Issued: 2012
- Authors: Nyoni, Dubekile
- Date: 2012
- Subjects: Chemical reactions Benzaldehyde Acrylonitrile Methyl acrylate Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4400 , http://hdl.handle.net/10962/d1006692
- Description: This study has focussed on the application of synthetic, kinetic and exploratory theoretical methods in elucidating the reaction mechanisms of four Morita-Baylis-Hillman (MBH) type reactions, viz, i) the reactions of the disulfide 2,2'-dithiodibenzaldehyde with various activated alkenes in the presence of DBU and Ph₃P, ii) the reactions of chromone-3-carbaldehydes with MVK, iii) the reactions of chromone-2-carbaldehydes with acrylonitrile and iv) with methyl acrylate. Attention has also been given to the origin of the observed regioselectivity in Michaelis-Arbuzov reactions of 3-(halomethyl)coumarins. Cleavage of the sulfur-sulfur bond of aryl and heteroaryl disulfides by the nitrogen nucleophile DBU has been demonstrated, and a dramatic increase in the rate of tandem MBH and disulfide cleavage reactions of 2,2'-dithiodibenzaldehyde with the activated alkenes, MVK, EVK, acrylonitrile, methyl acrylate and tert-butyl acrylate has been achieved through the use of the dual organo-catalyst system, DBU-Ph₃P – an improvement accompanied by an increase in the yields of the isolated products. Detailed NMR-based kinetic studies have been conducted on the DBU-catalysed reactions of 2,2'-dithiodibenzaldehyde with MVK and methyl acrylate, and a theoretical kinetic model has been developed and complementary computational studies using Gaussian 03, at the DFT-B3LYP/6-31G(d) level of theory have provided valuable insights into the mechanism of these complex transformations. Reactions of chromone-3-carbaldehydes with MVK to afford chromone dimers and tricyclic products have been repeated, and a novel, intermediate MBH adduct has been isolated. The mechanisms of the competing pathways have been elucidated by DFT calculations and the development of a detailed theoretical kinetic model has ensued. Unusual transformations in MBH-type reactions of chromone-2-carbaldehydes with acrylonitrile and methyl acrylate have been explored and the structures of the unexpected products have been established using 1- and 2-D NMR, HRMS and X-ray crystallographic techniques. Attention has also been given to the synthesis of 3-(halomethyl)coumarins via the MBH reaction, and their subsequent Michaelis-Arbuzov reactions with triethyl phosphite. An exploratory study of the kinetics of the phosphonation reaction has been undertaken and the regio-selectivity of nucleophilic attack at the 4- and 1'-positions in the 3-chloro- and 3-(iodomethyl)coumarins has been investigated by calculating Mulliken charges, LUMO surfaces and Fukui condensed local softness functions.
- Full Text:
- Date Issued: 2012
Strategy implementation: a critical assessment of the application of integrated risk management in the implementation of Eastern Cape Province provincial growth and development strategy (ECPGDS)
- Tshayingca-Mashiya, Nontsikelelo Valencia
- Authors: Tshayingca-Mashiya, Nontsikelelo Valencia
- Date: 2012
- Subjects: Risk assessment -- South Africa -- Eastern Cape -- Growth , Risk assessment -- Development -- South Africa -- Eastern Cape , Strategic planning , Risk management
- Language: English
- Type: Thesis , Doctoral , PhD (in Public Administration)
- Identifier: vital:11678 , http://hdl.handle.net/10353/d1007305 , Risk assessment -- South Africa -- Eastern Cape -- Growth , Risk assessment -- Development -- South Africa -- Eastern Cape , Strategic planning , Risk management
- Description: Strategic Management cycle consist of strategic planning, implementation, monitoring, evaluation and review of strategy. Strategy implementation has thus become the most significant management challenge. Yang et al. (2010) claim that although formulating a consistent strategy is a difficult task for any management team, making that strategy work and implementing it throughout the organisation is even more difficult. Yang further argues that Strategy implementation has been recorded as a key challenge for today’s organisations. According to Gurowitz (2008, there is evidence which shows that less than 10 percent of strategies formulated are effectively executed. Hrebiniak (2005) advances that; failure in organisations to effectively execute strategies is often as a result of limitation in linking organisational goals with objectives (operations). There are many other factors that influence the success of strategy implementation, ranging from the people who communicate or implement the strategy, to the systems or mechanisms in place for co-ordination. Brynard (2005) asserts that strategy implementation is equally challenging for management in Government departments, given that efforts of Government are aimed at improving service delivery. Poor strategy implementation is linked to poor service delivery. It is also worth noting that whilst implementation is acknowledged as a challenge, joint planning and joint implementation policies and strategies experience even a greater challenge in their implementation According to Young (2006), Debra and Yeates (2008), strategy implementation is in itself a risk because of its impact on the processes, people, and the systems. Strategy implementation is thus considered one of the main risk factors in organisations. In concurring with this view, Lorenzi et al. (2008) proposes that, strategy implementation implies change, and therefore poses risk to the processes, the people and the systems.
- Full Text:
- Date Issued: 2012
- Authors: Tshayingca-Mashiya, Nontsikelelo Valencia
- Date: 2012
- Subjects: Risk assessment -- South Africa -- Eastern Cape -- Growth , Risk assessment -- Development -- South Africa -- Eastern Cape , Strategic planning , Risk management
- Language: English
- Type: Thesis , Doctoral , PhD (in Public Administration)
- Identifier: vital:11678 , http://hdl.handle.net/10353/d1007305 , Risk assessment -- South Africa -- Eastern Cape -- Growth , Risk assessment -- Development -- South Africa -- Eastern Cape , Strategic planning , Risk management
- Description: Strategic Management cycle consist of strategic planning, implementation, monitoring, evaluation and review of strategy. Strategy implementation has thus become the most significant management challenge. Yang et al. (2010) claim that although formulating a consistent strategy is a difficult task for any management team, making that strategy work and implementing it throughout the organisation is even more difficult. Yang further argues that Strategy implementation has been recorded as a key challenge for today’s organisations. According to Gurowitz (2008, there is evidence which shows that less than 10 percent of strategies formulated are effectively executed. Hrebiniak (2005) advances that; failure in organisations to effectively execute strategies is often as a result of limitation in linking organisational goals with objectives (operations). There are many other factors that influence the success of strategy implementation, ranging from the people who communicate or implement the strategy, to the systems or mechanisms in place for co-ordination. Brynard (2005) asserts that strategy implementation is equally challenging for management in Government departments, given that efforts of Government are aimed at improving service delivery. Poor strategy implementation is linked to poor service delivery. It is also worth noting that whilst implementation is acknowledged as a challenge, joint planning and joint implementation policies and strategies experience even a greater challenge in their implementation According to Young (2006), Debra and Yeates (2008), strategy implementation is in itself a risk because of its impact on the processes, people, and the systems. Strategy implementation is thus considered one of the main risk factors in organisations. In concurring with this view, Lorenzi et al. (2008) proposes that, strategy implementation implies change, and therefore poses risk to the processes, the people and the systems.
- Full Text:
- Date Issued: 2012
Synthetic and bioactivity studies of antiplasmodial and antibacterial marine natural products
- Authors: Young, Ryan Mark
- Date: 2012
- Subjects: Antibacterial agents Marine natural products Marine pharmacology Plasmodium falciparum Staphylococcus aureus Isocyanides Imidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4378 , http://hdl.handle.net/10962/d1005043
- Description: This thesis is divided into two parts, assessing marine and synthetic compounds active firstly against Plasmodium falciparum (Chapter 3 and 4) and secondly active against methicillin resistant Staphylococcus aureus (MRSA, Chapter 5). In Chapter 3 the synthesis of nine new tricyclic podocarpanes (3.203-3.207 and 3.209-3.212) from the diterpene (+)-manool is described. Initial SAR study of synthetic podocarpanes concluded that the most active compound was a C-13 phenyl substituted podocarpane (3.204, IC₅₀ 6.6 μM). By preparing analogues with varying halogenated substituents on the phenyl ring (3.209-3.212) the antiplasmodial activity was improved (IC₅₀ 1.4 μM), while simultaneously decreasing the haemolysis previously reported for this class of compounds. Inspired by the antiplasmodial activity of Wright and Wattanapiromsakul’s tricycle marine isonitriles (2.16-2.21 and 2.24-2.27) an unsuccessfully attempt was made to convert tertiary alcohol moieties to isonitrile functionalities in compounds 3.188, 3.204-3.207 and 3.209-3.212. Over a decade ago Wright et al. proposed a putative antiplasmodial mechanism of action for marine isonitriles (2.4, 2.9, 2.15, 2.19 and 2.35) and isothiocyanate (2.34) which involved interference in haem detoxification by P. falciparum thus inhibiting the growth of the parasite. In Chapter 4 we describe how we successfully managed to scale down Egan’s β-haematin inhibition assay for the analyses of small quantities of marine natural products as potential β-haematin inhibitors. Our modified assay revealed that the most active antiplasmodial marine isonitrile 2.9 (IC₅₀ 13 nM) showed total β-haematin inhibition while 2.15 (IC₅₀ 81 nM) and 2.19 (IC₅₀ 31 nM) showed partial inhibition at three equivalents relative to haem. Using contempary molecular modelling techniques the charge on the isonitrile functionality was more accurately describe and the modified charge data sets was used to explore docking of marine isonitriles to haem using AutoDock. In Chapter 5 we describe how a lead South African marine bisindole MRSA pyruvate kinase inhibitor (5.8) was discovered in collaboration with colleagues at the University of British Columbia (UBC) and how this discovery inspired us to design a synthetic route to the dibrominated bisindole, isobromotopsentin (5.20) in an attempt to increase the bioactivity displayed by 5.8. We devised a fast and high yielding synthetic route using microwave assited organic synthesis. We first tested this synthesis using simple aryl glyoxals (5.27-5.32) as precursors to synthesize biphenylimidazoles (5.21-5.26), which later allowed us to synthesize the ascidian natural product 5.111. This method was sucessfully extended to the synthesis of deoxytopsentin (5.33) from an N-Boc protected indole methyl ketone (5.89). We subsequently were able to effectively remove the carbamate protection via thermal decomposition by heating the protected bisindole imidazole (5.90) in a microwave reactor for 5 min under argon. The synthesis of 5.20 resulted in an inseparable mixture of monoprotected and totally deprotected topsentin products, and due to time constraints we were not able to optimise this synthesis. Nonetheless our synthesis of the marine natural product 5.33 which was faster and higher yielding than previously reported routes could be extended to the synthesis of other topsentin bisindoles (5.138-5.140). Work towards this goal continues in our laboratory.
- Full Text:
- Date Issued: 2012
- Authors: Young, Ryan Mark
- Date: 2012
- Subjects: Antibacterial agents Marine natural products Marine pharmacology Plasmodium falciparum Staphylococcus aureus Isocyanides Imidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4378 , http://hdl.handle.net/10962/d1005043
- Description: This thesis is divided into two parts, assessing marine and synthetic compounds active firstly against Plasmodium falciparum (Chapter 3 and 4) and secondly active against methicillin resistant Staphylococcus aureus (MRSA, Chapter 5). In Chapter 3 the synthesis of nine new tricyclic podocarpanes (3.203-3.207 and 3.209-3.212) from the diterpene (+)-manool is described. Initial SAR study of synthetic podocarpanes concluded that the most active compound was a C-13 phenyl substituted podocarpane (3.204, IC₅₀ 6.6 μM). By preparing analogues with varying halogenated substituents on the phenyl ring (3.209-3.212) the antiplasmodial activity was improved (IC₅₀ 1.4 μM), while simultaneously decreasing the haemolysis previously reported for this class of compounds. Inspired by the antiplasmodial activity of Wright and Wattanapiromsakul’s tricycle marine isonitriles (2.16-2.21 and 2.24-2.27) an unsuccessfully attempt was made to convert tertiary alcohol moieties to isonitrile functionalities in compounds 3.188, 3.204-3.207 and 3.209-3.212. Over a decade ago Wright et al. proposed a putative antiplasmodial mechanism of action for marine isonitriles (2.4, 2.9, 2.15, 2.19 and 2.35) and isothiocyanate (2.34) which involved interference in haem detoxification by P. falciparum thus inhibiting the growth of the parasite. In Chapter 4 we describe how we successfully managed to scale down Egan’s β-haematin inhibition assay for the analyses of small quantities of marine natural products as potential β-haematin inhibitors. Our modified assay revealed that the most active antiplasmodial marine isonitrile 2.9 (IC₅₀ 13 nM) showed total β-haematin inhibition while 2.15 (IC₅₀ 81 nM) and 2.19 (IC₅₀ 31 nM) showed partial inhibition at three equivalents relative to haem. Using contempary molecular modelling techniques the charge on the isonitrile functionality was more accurately describe and the modified charge data sets was used to explore docking of marine isonitriles to haem using AutoDock. In Chapter 5 we describe how a lead South African marine bisindole MRSA pyruvate kinase inhibitor (5.8) was discovered in collaboration with colleagues at the University of British Columbia (UBC) and how this discovery inspired us to design a synthetic route to the dibrominated bisindole, isobromotopsentin (5.20) in an attempt to increase the bioactivity displayed by 5.8. We devised a fast and high yielding synthetic route using microwave assited organic synthesis. We first tested this synthesis using simple aryl glyoxals (5.27-5.32) as precursors to synthesize biphenylimidazoles (5.21-5.26), which later allowed us to synthesize the ascidian natural product 5.111. This method was sucessfully extended to the synthesis of deoxytopsentin (5.33) from an N-Boc protected indole methyl ketone (5.89). We subsequently were able to effectively remove the carbamate protection via thermal decomposition by heating the protected bisindole imidazole (5.90) in a microwave reactor for 5 min under argon. The synthesis of 5.20 resulted in an inseparable mixture of monoprotected and totally deprotected topsentin products, and due to time constraints we were not able to optimise this synthesis. Nonetheless our synthesis of the marine natural product 5.33 which was faster and higher yielding than previously reported routes could be extended to the synthesis of other topsentin bisindoles (5.138-5.140). Work towards this goal continues in our laboratory.
- Full Text:
- Date Issued: 2012
Ecological effects of impoundments in the Buffalo River, Eastern Cape, with particular reference to the distribution of blackflies (Diptera : simuliidae)
- Authors: Palmer, Robert William
- Date: 1992
- Subjects: Stream ecology -- South Africa -- Buffalo River (Eastern Cape) Dipter -- South Africa -- Buffalo River (Eastern Cape)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6028 , http://hdl.handle.net/10962/d1006157
- Description: This thesis examines the extent and intensity of the effects of impoundments on selected physical, chemical and biotic conditions in an impounded southern African river. Life-history characteristics and environmental requirements which determine the success of impoundment-outlet blackflies in southern Africa were studied. Difficulties with the identification of immature blackflies led to a search for additional diagnostic characters, the description of larvae of seven species previously unknown, and the development of new keys to the species of Simulium (larvae and pupae) in southern Africa. Distribution records for each species are presented, and their ecology is summarised. Three pairs of closely related species, which were formerly indistinguishable, can now be recognised by differences between the structure of their cephalic fan microtrichia. Monthly physical, chemical and invertebrate samples at 16 sites upstream and downstream of four impoundments in the Buffalo River, eastern Cape, were taken over a period of two years. The downstream effects of impoundments on these parameters depended on the variable examined, the position of the impoundment along the river profile, the depth from which water was released, and the quality of the inflowing water. Impoundments in the Buffalo River caused an upstream shift of the thermal and suspended organic conditions, and the distribution of blackfly species. Surface-release impoundments in the clean, upper-reaches of the river caused increases in water temperature (by as much as 8ºC) and chlorophyll a (by as much as 600%). Recovery to riverine conditions was within 2.6 to 18.4 km, depending on flow. A polluted, surface-release impoundment in the middle-reaches of the river had a slight dampening effect on river temperatures, converted the particle size spectrum of the river from small (<80 μm) to large (250-1000 μm), and improved the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). An impoundment in the lower reaches caused reductions in maximum temperature of up to 6ºC when releasing water from the surface, and up to 16ºC when releasing water from the bottom. Bottom-released water carried high concentrations (36 to 190 g m³) of small (<5 μm) and largely inorganic (86 to 93%) material.Twenty species of blackflies were found in the Buffalo River, of which 18 were distinguishable as larvae. They were divided into those which were widespread (5 taxa), those restricted to waterfalls and mountain torrents (2 taxa), those found in the foothill stony run zone (6 taxa), and rare taxa (5 taxa). Impoundments in the Buffalo River did not alter population densities of blackfly larvae, but did alter blackfly species composition, favouring five species commonly found in mid-order streams in southern Africa (s. meduseaforme, S. hargreavesi, S. nigritarse, S. adersi and s. damnosum s.l.) at the expense of upper-reach species (s. rutherfoordi, S. letabum and s. impukane). These five species are regarded as typical of impoundment-outlets, and were small, multivoltine flies whose larvae shared a generalised cephalic fan microtrichial structure, consisting of a single row of moderately differentiated microtrichia. A strong relation was found between cephalic fan microtrichial structure and larval habitats: Taxa found in fast-flowing, clear water had a more complex fan structure compared to those found in slow-flowing, turbid water. It is concluded that impoundment-induced changes to hydrodynamics and transported material (food) are important factors which have changed the distribution of blackflies in southern Africa in recent times. These changes are more severe downstream of upper-reach impoundments than middle or lower-reach impoundments.
- Full Text:
- Date Issued: 1992
- Authors: Palmer, Robert William
- Date: 1992
- Subjects: Stream ecology -- South Africa -- Buffalo River (Eastern Cape) Dipter -- South Africa -- Buffalo River (Eastern Cape)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6028 , http://hdl.handle.net/10962/d1006157
- Description: This thesis examines the extent and intensity of the effects of impoundments on selected physical, chemical and biotic conditions in an impounded southern African river. Life-history characteristics and environmental requirements which determine the success of impoundment-outlet blackflies in southern Africa were studied. Difficulties with the identification of immature blackflies led to a search for additional diagnostic characters, the description of larvae of seven species previously unknown, and the development of new keys to the species of Simulium (larvae and pupae) in southern Africa. Distribution records for each species are presented, and their ecology is summarised. Three pairs of closely related species, which were formerly indistinguishable, can now be recognised by differences between the structure of their cephalic fan microtrichia. Monthly physical, chemical and invertebrate samples at 16 sites upstream and downstream of four impoundments in the Buffalo River, eastern Cape, were taken over a period of two years. The downstream effects of impoundments on these parameters depended on the variable examined, the position of the impoundment along the river profile, the depth from which water was released, and the quality of the inflowing water. Impoundments in the Buffalo River caused an upstream shift of the thermal and suspended organic conditions, and the distribution of blackfly species. Surface-release impoundments in the clean, upper-reaches of the river caused increases in water temperature (by as much as 8ºC) and chlorophyll a (by as much as 600%). Recovery to riverine conditions was within 2.6 to 18.4 km, depending on flow. A polluted, surface-release impoundment in the middle-reaches of the river had a slight dampening effect on river temperatures, converted the particle size spectrum of the river from small (<80 μm) to large (250-1000 μm), and improved the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). An impoundment in the lower reaches caused reductions in maximum temperature of up to 6ºC when releasing water from the surface, and up to 16ºC when releasing water from the bottom. Bottom-released water carried high concentrations (36 to 190 g m³) of small (<5 μm) and largely inorganic (86 to 93%) material.Twenty species of blackflies were found in the Buffalo River, of which 18 were distinguishable as larvae. They were divided into those which were widespread (5 taxa), those restricted to waterfalls and mountain torrents (2 taxa), those found in the foothill stony run zone (6 taxa), and rare taxa (5 taxa). Impoundments in the Buffalo River did not alter population densities of blackfly larvae, but did alter blackfly species composition, favouring five species commonly found in mid-order streams in southern Africa (s. meduseaforme, S. hargreavesi, S. nigritarse, S. adersi and s. damnosum s.l.) at the expense of upper-reach species (s. rutherfoordi, S. letabum and s. impukane). These five species are regarded as typical of impoundment-outlets, and were small, multivoltine flies whose larvae shared a generalised cephalic fan microtrichial structure, consisting of a single row of moderately differentiated microtrichia. A strong relation was found between cephalic fan microtrichial structure and larval habitats: Taxa found in fast-flowing, clear water had a more complex fan structure compared to those found in slow-flowing, turbid water. It is concluded that impoundment-induced changes to hydrodynamics and transported material (food) are important factors which have changed the distribution of blackflies in southern Africa in recent times. These changes are more severe downstream of upper-reach impoundments than middle or lower-reach impoundments.
- Full Text:
- Date Issued: 1992
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