A Sociological Investigation on the Influence of Gender Inequality in Agricultural Development: A Study of Koloni village, Raymond Mhlaba Municipality.
- Authors: Mxoli, Aviwe
- Date: 2019
- Subjects: Agricultural productivity
- Language: English
- Type: Thesis , Masters , MSoc (Sociology)
- Identifier: http://hdl.handle.net/10353/16373 , vital:40713
- Description: This study investigates the influence of gender inequality in agricultural development in Koloni village, Raymond Mhlaba Municipality, Eastern Cape Province, South Africa. The study explored the views of the agricultural active individual on the influence of gender inequality in agricultural development. Likewise, the study investigated the causes of gender inequality in agricultural productivity in the study area. Moreover, this study examined how gender inequality affect sale of agricultural production in Koloni Village. The study used theory triangulation and was guided by three theories namely: Women’s Empowerment Theory, Feminist Agrifood Systems Theory and the Agrarian Feminist Theory. The study used both quantitative and qualitative research methods embedded in pragmatic ontological and epistemological inquiry. Data collection process included the use of survey questionnaires, semi structured in-depth interviews and focus groups. The targeted participants of the study were obtained using non-probability sampling procedure. The quantitative data gathered were analysed using descriptive statistics, while the qualitative data were processed with the use of content analysis and the research findings are presented using sided by side comparison. The key findings of the study indicate that women do not reach their full potential in agriculture, owing to women’s lack of skill crucial in agriculture. Furthermore, gender inequality jeopardizes women’s chances of benefiting from workshops and trainings and that consequently affects women’s skills essential for agricultural production. The study concluded that gender inequality hinders agricultural development in Koloni village, Raymond Mhlaba municipality, South Africa. The findings of this study indicated that more women engage in agricultural activities than men nonetheless ii patriarchal systems within the agricultural sector that marginalises women is still dominant in Koloni village.
- Full Text:
- Date Issued: 2019
- Authors: Mxoli, Aviwe
- Date: 2019
- Subjects: Agricultural productivity
- Language: English
- Type: Thesis , Masters , MSoc (Sociology)
- Identifier: http://hdl.handle.net/10353/16373 , vital:40713
- Description: This study investigates the influence of gender inequality in agricultural development in Koloni village, Raymond Mhlaba Municipality, Eastern Cape Province, South Africa. The study explored the views of the agricultural active individual on the influence of gender inequality in agricultural development. Likewise, the study investigated the causes of gender inequality in agricultural productivity in the study area. Moreover, this study examined how gender inequality affect sale of agricultural production in Koloni Village. The study used theory triangulation and was guided by three theories namely: Women’s Empowerment Theory, Feminist Agrifood Systems Theory and the Agrarian Feminist Theory. The study used both quantitative and qualitative research methods embedded in pragmatic ontological and epistemological inquiry. Data collection process included the use of survey questionnaires, semi structured in-depth interviews and focus groups. The targeted participants of the study were obtained using non-probability sampling procedure. The quantitative data gathered were analysed using descriptive statistics, while the qualitative data were processed with the use of content analysis and the research findings are presented using sided by side comparison. The key findings of the study indicate that women do not reach their full potential in agriculture, owing to women’s lack of skill crucial in agriculture. Furthermore, gender inequality jeopardizes women’s chances of benefiting from workshops and trainings and that consequently affects women’s skills essential for agricultural production. The study concluded that gender inequality hinders agricultural development in Koloni village, Raymond Mhlaba municipality, South Africa. The findings of this study indicated that more women engage in agricultural activities than men nonetheless ii patriarchal systems within the agricultural sector that marginalises women is still dominant in Koloni village.
- Full Text:
- Date Issued: 2019
Bioavailability of nutrients in a diet enriched with moringa oleifera lam. Leaves using wistar rats
- Authors: Mhlomi, Yanga Nonelela
- Date: 2019
- Subjects: Moringa Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14594 , vital:40018
- Description: This study investigated the nutritional composition and bioavailability of nutrients in Moringa oleifera leaf meal from South African ecotype. Nutritional evaluation (proximate, mineral, vitamins and antinutrients, amino acids and fatty acids analyses) was performed using AOAC, ICP-OES and GC+MS techniques respectively. Bioavailability of nutrients involved formulation of diets deficient in minerals and vitamins; and proteins supplemented with Moringa oleifera leaf meal (MOLM) at 0, 3, 5 and 10% respectively. Growth performance, hematological, biochemical and histopathological evaluations were used to assess the effect of MOLM supplementation. Proximate and mineral evaluation revealed that the leaves were rich in protein (28.72%) and carbohydrate (28.84%), calcium content was (1603.33 mg/100g), potassium (1690 mg/100g), zinc (13.03 mg/100g) and iron (21.13 mg/100g). Vitamin E content was the highest (89.43 mg/100g) followed by vitamic C (24.9 mg/100g) and vitamin A (12.98 mg/100g). Fatty acids analysis detected were fifteen of which polyunsaturated fatty acid linoleic acid (56.36) and alpha-linolenic acid (687.58) were highest and behenic acid (22:0) characteristics of Moringa (4.11%) were detected. Seven of the detected fatty acids were saturated fatty acids, though relatively low, with stearic acid having the highest value. On the other hand fifteen of the amino acids, 7 were essential (valine, leucine, isoleucine, methionine, threonine and phenylalanine) were detected; while alanine, proline, serine, aspartic acid, cysteine, glutamic acid, asparagine and tyrosine were non- essential amino acid. Moringa oleifera had low quantities of antinutrients in relation to minerals, thus nutrients will easily ne available. Amino and fatty acids profile of nutrient deficient diets supplemented with MOLM revealed that six essential amino acids were detected in the diets. However, the essential amino acid (EAA) in MOLM with the highest value was threonine (500.47±23.03mg/L), while the lowest was methionine (75.65±5.31mg/L). Leucine was highest in PD10 (234.32±27.98 mg/l) 15 and lowest in PD3. Predominant amino acid in VMD diet was glutamic acid (966.76±208.92 mg/l), while methionine was lowest (197.14±35.90). Caproic acid was the most prominent unsaturated fatty acid in the diets and was highest in the PD diet. Palmitoleic acid was highest in the control diet (8.19±0.56 mg/L) and lowest in PD3 but an increase was observed as the levels of MOLM increased in the diets. Linoleic acid values obtained were significantly higher in PD diet, lower in control diet, compared to other diets. Linolenic acid (C18-3n6) was higher in PD10 (63.48±3.84 mg/L) compared to the control diet (6.05±0.14 mg/L). The highest unsaturated fatty acid in all the feed samples was linoleic acids ranging from 54.48±5.61 to 296.26±7.20 mg/L. the highest omega-3 (n-3) fatty acid content (63.48±3.38 mg/L) was in PD10 and was almost 10 times higher than the value recorded for control. Rats treated on vitamin mineral deficient (VMD) diet showed no significant changes in growth performances and blood parameters except in certain indices. Rats on VMD diet had lowest haemoglobin levels, whereas haemoglobin increased with MOLM levels. No significant differences in haematocrit, MCH, MCHC, platelets, RDW and MPV were observed in all treatments and control. However, VMD rats showed decrease in haemoglobin, increase in WBC and platelets. Electrolytes and glucose for all treatments and control were not significantly different, but, control and VMD10 diets rats showed significantly higher values for creatinine compared to MOLM diets; total protein and albumin increased with MOLM and were higher than in VMD and control rats. Serum activities of liver, cardiac, adrenal marker enzymes were significantly lower in MOLM rats compared to VMD and control. Mild congestion in VMD and VMD3 rat’s liver and diffused congestion in the kidney of VMD diet fed rats was observed. Protein deficient diets supplemented with MOLM had a negative impact on feed intake and growth parameters. Rats fed PD and PD5 consumed significantly less diet than those fed PD10, PD3 diets respectively. White blood cells decreased with increasing levels of MOLM 16 supplementation. Differential white cell count (Neutrophils, lymphocytes, monocytes, eosinophils and basophils) followed the same trend though not statistically significant (P>0.05). Furthermore, histopathological evaluation of organs revealed that no abnormalities were in heart and liver and kidney of rats fed on the control diet, while mild congestion in the liver and myocardium (heart) were observed in rats fed with protein deficient diet. No visible abnormalities were observed in the heart, kidney and liver of animals on the PD 10 diet, but myocardial fibres showing intense eosinophilia was detected in heart muscles of rats fed PD and PD3 diets. In this study, MOLM had a negative impact on feed intake and growth performance of animals and haematology. Blood biochemistry and histology suggest that MOLM has the potential of defending the body against infection with hematinic and blood enhancing qualities. Protein deficiency led to a significant elevation in the serum lipid profile of rats especially cholesterol even with increase in MOLM. PD10 had the highest triglycerides content when compared to the control but was lower (p>0.05) to that of PD. There was an increase in crude fat, ADF, NDF and protein in faecal samples of rats supplemented with MOLM diets while a decrease in moisture and ash was observed compared to the control.Vitamin and mineral deficiency resulted in significant decrease in serum cholesterol, triglycerides and HDL-C when compared to the control. There was a slight increase in excretion for all elements with increasing MOLM. Total removal of minerals and vitamins from the VMD experimental diets seemed not to have any visible negative impact on performance of the rats probably because of residual micronutrients present in other ingredients used in the feed formulation. MOLM could not replace protein in protein deficient diets.
- Full Text:
- Date Issued: 2019
- Authors: Mhlomi, Yanga Nonelela
- Date: 2019
- Subjects: Moringa Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14594 , vital:40018
- Description: This study investigated the nutritional composition and bioavailability of nutrients in Moringa oleifera leaf meal from South African ecotype. Nutritional evaluation (proximate, mineral, vitamins and antinutrients, amino acids and fatty acids analyses) was performed using AOAC, ICP-OES and GC+MS techniques respectively. Bioavailability of nutrients involved formulation of diets deficient in minerals and vitamins; and proteins supplemented with Moringa oleifera leaf meal (MOLM) at 0, 3, 5 and 10% respectively. Growth performance, hematological, biochemical and histopathological evaluations were used to assess the effect of MOLM supplementation. Proximate and mineral evaluation revealed that the leaves were rich in protein (28.72%) and carbohydrate (28.84%), calcium content was (1603.33 mg/100g), potassium (1690 mg/100g), zinc (13.03 mg/100g) and iron (21.13 mg/100g). Vitamin E content was the highest (89.43 mg/100g) followed by vitamic C (24.9 mg/100g) and vitamin A (12.98 mg/100g). Fatty acids analysis detected were fifteen of which polyunsaturated fatty acid linoleic acid (56.36) and alpha-linolenic acid (687.58) were highest and behenic acid (22:0) characteristics of Moringa (4.11%) were detected. Seven of the detected fatty acids were saturated fatty acids, though relatively low, with stearic acid having the highest value. On the other hand fifteen of the amino acids, 7 were essential (valine, leucine, isoleucine, methionine, threonine and phenylalanine) were detected; while alanine, proline, serine, aspartic acid, cysteine, glutamic acid, asparagine and tyrosine were non- essential amino acid. Moringa oleifera had low quantities of antinutrients in relation to minerals, thus nutrients will easily ne available. Amino and fatty acids profile of nutrient deficient diets supplemented with MOLM revealed that six essential amino acids were detected in the diets. However, the essential amino acid (EAA) in MOLM with the highest value was threonine (500.47±23.03mg/L), while the lowest was methionine (75.65±5.31mg/L). Leucine was highest in PD10 (234.32±27.98 mg/l) 15 and lowest in PD3. Predominant amino acid in VMD diet was glutamic acid (966.76±208.92 mg/l), while methionine was lowest (197.14±35.90). Caproic acid was the most prominent unsaturated fatty acid in the diets and was highest in the PD diet. Palmitoleic acid was highest in the control diet (8.19±0.56 mg/L) and lowest in PD3 but an increase was observed as the levels of MOLM increased in the diets. Linoleic acid values obtained were significantly higher in PD diet, lower in control diet, compared to other diets. Linolenic acid (C18-3n6) was higher in PD10 (63.48±3.84 mg/L) compared to the control diet (6.05±0.14 mg/L). The highest unsaturated fatty acid in all the feed samples was linoleic acids ranging from 54.48±5.61 to 296.26±7.20 mg/L. the highest omega-3 (n-3) fatty acid content (63.48±3.38 mg/L) was in PD10 and was almost 10 times higher than the value recorded for control. Rats treated on vitamin mineral deficient (VMD) diet showed no significant changes in growth performances and blood parameters except in certain indices. Rats on VMD diet had lowest haemoglobin levels, whereas haemoglobin increased with MOLM levels. No significant differences in haematocrit, MCH, MCHC, platelets, RDW and MPV were observed in all treatments and control. However, VMD rats showed decrease in haemoglobin, increase in WBC and platelets. Electrolytes and glucose for all treatments and control were not significantly different, but, control and VMD10 diets rats showed significantly higher values for creatinine compared to MOLM diets; total protein and albumin increased with MOLM and were higher than in VMD and control rats. Serum activities of liver, cardiac, adrenal marker enzymes were significantly lower in MOLM rats compared to VMD and control. Mild congestion in VMD and VMD3 rat’s liver and diffused congestion in the kidney of VMD diet fed rats was observed. Protein deficient diets supplemented with MOLM had a negative impact on feed intake and growth parameters. Rats fed PD and PD5 consumed significantly less diet than those fed PD10, PD3 diets respectively. White blood cells decreased with increasing levels of MOLM 16 supplementation. Differential white cell count (Neutrophils, lymphocytes, monocytes, eosinophils and basophils) followed the same trend though not statistically significant (P>0.05). Furthermore, histopathological evaluation of organs revealed that no abnormalities were in heart and liver and kidney of rats fed on the control diet, while mild congestion in the liver and myocardium (heart) were observed in rats fed with protein deficient diet. No visible abnormalities were observed in the heart, kidney and liver of animals on the PD 10 diet, but myocardial fibres showing intense eosinophilia was detected in heart muscles of rats fed PD and PD3 diets. In this study, MOLM had a negative impact on feed intake and growth performance of animals and haematology. Blood biochemistry and histology suggest that MOLM has the potential of defending the body against infection with hematinic and blood enhancing qualities. Protein deficiency led to a significant elevation in the serum lipid profile of rats especially cholesterol even with increase in MOLM. PD10 had the highest triglycerides content when compared to the control but was lower (p>0.05) to that of PD. There was an increase in crude fat, ADF, NDF and protein in faecal samples of rats supplemented with MOLM diets while a decrease in moisture and ash was observed compared to the control.Vitamin and mineral deficiency resulted in significant decrease in serum cholesterol, triglycerides and HDL-C when compared to the control. There was a slight increase in excretion for all elements with increasing MOLM. Total removal of minerals and vitamins from the VMD experimental diets seemed not to have any visible negative impact on performance of the rats probably because of residual micronutrients present in other ingredients used in the feed formulation. MOLM could not replace protein in protein deficient diets.
- Full Text:
- Date Issued: 2019
The development, implementation and evaluation of a mental skills training programme for rowers at Rhodes University
- Authors: Wentworth, Tara E
- Date: 2017
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/5247 , vital:20797
- Description: In the ever increasingly competitive world of sport, there is a pressing need for training methods that have the potential to improve the performance of athletes. It is for this reason that practices associated with sport psychology (such as mental skills training) have increased in popularity. This desire for improved performance has seen a rising number of athletes seeking out the assistance of sport psychology methods. In this research, a mental skills training (MST) programme was developed and implemented into the training regime of Rhodes University rowers in Grahamstown, South Africa. The process of this research adhered to the Organisational Development Process Model’s format. Information collected from focus groups and performance profiling were utilised to design a MST programme tailored to the context of this group of athletes. This programme was implemented over one month and comprised of theoretical and practical sessions focussing on the topics of goalsetting, arousal regulation and imagery. After the programme had been completed, the participants evaluated the process in the form of individual interviews and were required to repeat the initial performance profile exercise. The results gathered from the various assessment and evaluation measures were used to compare and add to existing literature regarding MST and related disciplines. The benefits and effects of the programme have been detailed, and recommendations have been made which could possibly answer to the limitations of this research. These recommendations could provide insight into the manner in which MST programmes could possibly be more effectively implemented in future.
- Full Text:
- Date Issued: 2017
- Authors: Wentworth, Tara E
- Date: 2017
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/5247 , vital:20797
- Description: In the ever increasingly competitive world of sport, there is a pressing need for training methods that have the potential to improve the performance of athletes. It is for this reason that practices associated with sport psychology (such as mental skills training) have increased in popularity. This desire for improved performance has seen a rising number of athletes seeking out the assistance of sport psychology methods. In this research, a mental skills training (MST) programme was developed and implemented into the training regime of Rhodes University rowers in Grahamstown, South Africa. The process of this research adhered to the Organisational Development Process Model’s format. Information collected from focus groups and performance profiling were utilised to design a MST programme tailored to the context of this group of athletes. This programme was implemented over one month and comprised of theoretical and practical sessions focussing on the topics of goalsetting, arousal regulation and imagery. After the programme had been completed, the participants evaluated the process in the form of individual interviews and were required to repeat the initial performance profile exercise. The results gathered from the various assessment and evaluation measures were used to compare and add to existing literature regarding MST and related disciplines. The benefits and effects of the programme have been detailed, and recommendations have been made which could possibly answer to the limitations of this research. These recommendations could provide insight into the manner in which MST programmes could possibly be more effectively implemented in future.
- Full Text:
- Date Issued: 2017
Refuse exchange: the design of of waste management and recycling facility for the 5th avenue, Walmer waste tip in Port Elizabeth/Nelson Mandela Bay Metro
- Authors: Hunter, Casey Lauren
- Date: 2016
- Subjects: Refuse disposal facilities -- South Africa -- Port Elizabeth Waste disposal sites -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/38808 , vital:34975
- Description: Our cities can be viewed as urban mines, full of resources that already exist within the urban fabric. This treatise focuses on the design of a recycling facility to be used as a tool for metabolising waste and separating it into valuable resources. It then goes further into the uses of waste and its up-cycling in the realms of (I would say industrial products, arts and crafts and even in the fabric of architecture. The treatise aims to perpetuate Regenerative Sustainability and its application in design and architecture. It tries to understand the impact waste has on social, economic and environmental aspects of the community and how the better management of waste can positively affect these aspects of modern urban life. The study is separated into two parts. The first part is research into the topic and the second part is the application of this research into the design. The research section is broken down into two main chapters that investigate various issues and processes relating to the nature of the program and the nature of the site. The main focus of part two is on the conceptual development that will lead to a final design. Chapter one is an introduction to the theoretical discourse to be discussed in this project. It also discuses the connotations, history and development in waste management. Chapter two discusses the various programmatic concerns relating to the Waste Management and Recycling Facility and a paradigm shift towards integrated infrastructural development in an urban environment. Chapter three analyses site criteria to choose a site best suited to this program. It then analyses precedent studies of projects done in similar contextual environments. Through this a conclusion is made about the nature of the site. It considers how this project can be developed from the organising elements and the opportunities for improvement and the re-scripting of the site. The final chapter of part two explains the process used to arrive at a final design. It starts with the development of an urban intervention and the vision for the project. It goes on to explain the nature of the spaces in the facility, their various connections and locations in relation to the site and other related spaces. This chapter then develops the plan and physical form as well as the tectonic and materials to be implemented in the facility. The themes of the project are to [RE] cycle, [RE]cover, [RE]manufacture and [RE]materialise. Recycle refer to the program of the building and the physical act of separating waste. Recover refers to the way the facility will try to extract energy and useful resources from the waste stream such as biogas, electricity and fertiliser from anaerobic digesters. Thirdly, remanufacture refers to the up-cycling of waste in order to improve its value by transforming it into art, crafts and even building materials. Finally, the ultimate goal of the project is to rematerialise the connotations of waste in society, changing its perception from a dirty, unwanted by-product of society to a minefield of possibilities.
- Full Text:
- Date Issued: 2016
- Authors: Hunter, Casey Lauren
- Date: 2016
- Subjects: Refuse disposal facilities -- South Africa -- Port Elizabeth Waste disposal sites -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/38808 , vital:34975
- Description: Our cities can be viewed as urban mines, full of resources that already exist within the urban fabric. This treatise focuses on the design of a recycling facility to be used as a tool for metabolising waste and separating it into valuable resources. It then goes further into the uses of waste and its up-cycling in the realms of (I would say industrial products, arts and crafts and even in the fabric of architecture. The treatise aims to perpetuate Regenerative Sustainability and its application in design and architecture. It tries to understand the impact waste has on social, economic and environmental aspects of the community and how the better management of waste can positively affect these aspects of modern urban life. The study is separated into two parts. The first part is research into the topic and the second part is the application of this research into the design. The research section is broken down into two main chapters that investigate various issues and processes relating to the nature of the program and the nature of the site. The main focus of part two is on the conceptual development that will lead to a final design. Chapter one is an introduction to the theoretical discourse to be discussed in this project. It also discuses the connotations, history and development in waste management. Chapter two discusses the various programmatic concerns relating to the Waste Management and Recycling Facility and a paradigm shift towards integrated infrastructural development in an urban environment. Chapter three analyses site criteria to choose a site best suited to this program. It then analyses precedent studies of projects done in similar contextual environments. Through this a conclusion is made about the nature of the site. It considers how this project can be developed from the organising elements and the opportunities for improvement and the re-scripting of the site. The final chapter of part two explains the process used to arrive at a final design. It starts with the development of an urban intervention and the vision for the project. It goes on to explain the nature of the spaces in the facility, their various connections and locations in relation to the site and other related spaces. This chapter then develops the plan and physical form as well as the tectonic and materials to be implemented in the facility. The themes of the project are to [RE] cycle, [RE]cover, [RE]manufacture and [RE]materialise. Recycle refer to the program of the building and the physical act of separating waste. Recover refers to the way the facility will try to extract energy and useful resources from the waste stream such as biogas, electricity and fertiliser from anaerobic digesters. Thirdly, remanufacture refers to the up-cycling of waste in order to improve its value by transforming it into art, crafts and even building materials. Finally, the ultimate goal of the project is to rematerialise the connotations of waste in society, changing its perception from a dirty, unwanted by-product of society to a minefield of possibilities.
- Full Text:
- Date Issued: 2016
“Just trying to live our lives”: gay, lesbian and bisexual students’ experiences of being “at home” in university residence life
- Authors: Munyuki, Chipo Lidia
- Date: 2016
- Subjects: Homosexuality and education -- South Africa , Gay students , Lesbian students , Bisexual students , Transsexual students , Student housing , Discrimination in higher education -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2893 , http://hdl.handle.net/10962/d1020341
- Description: Higher education in South Africa is faced with a paramount task to help erode the social and structural inequalities that have been inherited from the Apartheid system (Department of Education 1997; Council on Higher Education 2000:12). The findings from the Soudien Report (2008:116-117) point out that the post-Apartheid higher education system in South Africa is characterised by various forms of discrimination and institutional cultures that marginalise some members of institutions resulting in pervasive feelings of alienation. In the South African higher education field, the concept of a “home” for all has been used by a variety of commentators to depict a vision of what transformed, inclusive higher education institutional cultures might look like. In this thesis, I interpret the experiences of residence life on the part of gay, lesbian and bisexual students on a largely residential campus. I ask how gay, lesbian and bisexual students experience being “at home” in the campus’s residence system. The thesis is based on 18 in-depth qualitative interviews with students who self-identify as gay/lesbian or bisexual who have experienced residence life on the campus for a period longer than six months. A wide literature exists on the concept of “home”. Drawing from many different disciplines including anthropology, history, philosophy, geography, psychology, architecture and sociology, I distil the essential features of “at homeness” as incorporating comfort, privacy, security, acceptance, companionship and community. The research was concerned to inquire into how central the idea of home is to human flourishing and then into how gay, lesbian and bisexual students are routinely denied many of the essential comforts associated with being “at home” that heterosexual students have the privilege of taking for granted.
- Full Text:
- Date Issued: 2016
- Authors: Munyuki, Chipo Lidia
- Date: 2016
- Subjects: Homosexuality and education -- South Africa , Gay students , Lesbian students , Bisexual students , Transsexual students , Student housing , Discrimination in higher education -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2893 , http://hdl.handle.net/10962/d1020341
- Description: Higher education in South Africa is faced with a paramount task to help erode the social and structural inequalities that have been inherited from the Apartheid system (Department of Education 1997; Council on Higher Education 2000:12). The findings from the Soudien Report (2008:116-117) point out that the post-Apartheid higher education system in South Africa is characterised by various forms of discrimination and institutional cultures that marginalise some members of institutions resulting in pervasive feelings of alienation. In the South African higher education field, the concept of a “home” for all has been used by a variety of commentators to depict a vision of what transformed, inclusive higher education institutional cultures might look like. In this thesis, I interpret the experiences of residence life on the part of gay, lesbian and bisexual students on a largely residential campus. I ask how gay, lesbian and bisexual students experience being “at home” in the campus’s residence system. The thesis is based on 18 in-depth qualitative interviews with students who self-identify as gay/lesbian or bisexual who have experienced residence life on the campus for a period longer than six months. A wide literature exists on the concept of “home”. Drawing from many different disciplines including anthropology, history, philosophy, geography, psychology, architecture and sociology, I distil the essential features of “at homeness” as incorporating comfort, privacy, security, acceptance, companionship and community. The research was concerned to inquire into how central the idea of home is to human flourishing and then into how gay, lesbian and bisexual students are routinely denied many of the essential comforts associated with being “at home” that heterosexual students have the privilege of taking for granted.
- Full Text:
- Date Issued: 2016
Photophysicochemical properties and in vitro photodynamic therapy activities of zinc phthalocyanine conjugates with biomolecules and single-walled carbon nanotubes
- Authors: Ogbodu, Racheal O
- Date: 2015
- Subjects: Photochemotherapy , Phthalocyanines , Biomolecules
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4544 , http://hdl.handle.net/10962/d1017924
- Description: The synthesis, photophysicochemcial properties, in vitro dark toxicity and photodynamic therapy (PDT) activities of different derivatives of zinc phthalocyanine (ZnPc) conjugates with biomolecules (folic acid, bovine serum albumin (BSA), ascorbic acid, uridine or spermine) and single-walled carbon nanotubes (SWCNTs) are presented in this work. The fluorescence quantum yields (ΦF) (Subscript F) of the ZnPc derivatives or ZnPc-biomolecule conjugates remained relatively the same as compared to the precursor Pcs. Slight increases were observed in the ΦF (Subscript F) values of conjugates containing substituents such as pyrene, folic acid or BSA with intrinsic fluorescence properties. The triplet quantum yield (ΦT ) (Subscript T) values for some ZnPc conjugates increases compared to the precursor ZnPcs due to extended π conjugation (for the conjugate with pyrene) and the presence of phenyl ring that support spin-orbit charge transfer intersystem crossing to triplet state. While some conjugates showed decreases in the ΦT (Subscript T) values compared to precursor ZnPcs due to the presence of substituents that could quench photo-excited state properties. The singlet oxygen quantum yield (ΦΔ ) values follow the trends of the triplet quantum yield values. The conjugates containing BSA also show increases in the ΦΔ values without corresponding increases in ΦT (Subscript T) values due to the ability of BSA to generate free radicals including singlet oxygen. The presence of SWCNTs decreases the photophysicochemcial properties of some ZnPc-SWCNT conjugates compared to the precursor ZnPcs due to photo-induced electron transfer from an excited Pc complex (electron donor) to SWCNTs (electron acceptor). However, increases were observed in some ZnPc-SWCNT conjugates as a result of fast charge recombination process due to highly short-lived radical ion pair produced. These phenomena affected the ΦF (Suscript F) values, ΦT (Suscript T) values, and the ΦΔ values. Increases or decreases in ΦT (Suscript T) values resulted in corresponding increases or decreases in ΦΔ values
- Full Text:
- Date Issued: 2015
- Authors: Ogbodu, Racheal O
- Date: 2015
- Subjects: Photochemotherapy , Phthalocyanines , Biomolecules
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4544 , http://hdl.handle.net/10962/d1017924
- Description: The synthesis, photophysicochemcial properties, in vitro dark toxicity and photodynamic therapy (PDT) activities of different derivatives of zinc phthalocyanine (ZnPc) conjugates with biomolecules (folic acid, bovine serum albumin (BSA), ascorbic acid, uridine or spermine) and single-walled carbon nanotubes (SWCNTs) are presented in this work. The fluorescence quantum yields (ΦF) (Subscript F) of the ZnPc derivatives or ZnPc-biomolecule conjugates remained relatively the same as compared to the precursor Pcs. Slight increases were observed in the ΦF (Subscript F) values of conjugates containing substituents such as pyrene, folic acid or BSA with intrinsic fluorescence properties. The triplet quantum yield (ΦT ) (Subscript T) values for some ZnPc conjugates increases compared to the precursor ZnPcs due to extended π conjugation (for the conjugate with pyrene) and the presence of phenyl ring that support spin-orbit charge transfer intersystem crossing to triplet state. While some conjugates showed decreases in the ΦT (Subscript T) values compared to precursor ZnPcs due to the presence of substituents that could quench photo-excited state properties. The singlet oxygen quantum yield (ΦΔ ) values follow the trends of the triplet quantum yield values. The conjugates containing BSA also show increases in the ΦΔ values without corresponding increases in ΦT (Subscript T) values due to the ability of BSA to generate free radicals including singlet oxygen. The presence of SWCNTs decreases the photophysicochemcial properties of some ZnPc-SWCNT conjugates compared to the precursor ZnPcs due to photo-induced electron transfer from an excited Pc complex (electron donor) to SWCNTs (electron acceptor). However, increases were observed in some ZnPc-SWCNT conjugates as a result of fast charge recombination process due to highly short-lived radical ion pair produced. These phenomena affected the ΦF (Suscript F) values, ΦT (Suscript T) values, and the ΦΔ values. Increases or decreases in ΦT (Suscript T) values resulted in corresponding increases or decreases in ΦΔ values
- Full Text:
- Date Issued: 2015
The design, synthesis and antiplasmodial activity of a series of halogenated fosmidomycin analogues and hybrid drugs
- Authors: Afolayan, Anthonia Folake
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64370 , vital:28538
- Description: Malaria continues to be a devastating disease and a major cause of death in sub-Saharan Africa. With resistance against most of the available antimalarial drugs, there is a need for ongoing research and development of antimalarial agents. Fosmidomycin and its acetyl analogue FR900098 have been identified as potent inhibitors of Plasmodium falciparum, the causative agent of the most deadly form of malaria. Clinical trials of these agents have revealed poor absorption due to their high hydrophilicity. In the present studies the effect of halogenation of the acyl chain as well as the biological effect of extending the acyl sidechain was explored. This provided the basis on which fosmidomycin hybrids were designed to investigate the feasibility of hybrid extending into NADPH binding pocket. Synthesis of a series of halogenated FR900098 analogues was carried out in three stages. This included i) The introduction of the phosphonate group by reaction with 1,3dibromopropane in an Arbuzov reaction, ii) The introduction of a hydroxamate group by reaction of the propyl phosphonate by means of a nucleophilic substitution reaction with BocNHOBn and iii) The introduction of a halogenated acyl side chain on a protected fosmidomycin backbone. The synthesis of fosmidomycin-hybrids for which chloroquinefosmidomycin hybrids were used as the prototype, involved convergence of the two separately constructed moieties i.e. fosmidomycin and the quinoline moieties in a covalent linkage. The quinoline moiety was easily synthesized from the reaction of 4,7dichloroquinoline with 1,2-diamino ethane. The aminoquinoline so formed resulted in chloroquine-fosmidomycin hybrids 3.8 and 3.9 when reacted with halogenated FR900098 analogues. Antiplasmodial assays were conducted on the chloroquine-fosmidomycin hybrids and the halogenated fosmidomycin derivatives against the chloroquine resistant Gambian FCR-3 strain of P. falciparum. The most potent iodoacetyl fosmidomycin analogues 2.21 gave an IC50 value of 5.54 µM which is eight times more potent than the known antiplasmodial FR900098 which gave an IC50 value of 41.67 µM. All the halogenated FR900098 analogues showed better antiplasmodial activity than their non-halogenated derivatives. This indicated that the presence of halogens in the FR900098 analogues contributes to their biological Chapter 1 Literature review activity. The acetyl and propyl linked hybrids 3.8 and 3.9 showed potent antiplasmodial activity with IC50 values of 0.18 and 0.82 µM respectively. These were by far the most potent hybrids synthesized and provided leads for a new class of promising antimalarial agents. Preliminary E. coli DXR enzyme inhibition assays were carried out on the halogenated fosmidomycin analogues. The results showed good inhibition of the enzyme by the phosphonic acids of the chloroacetyl and chloropropyl analogues 2.1 and 2.2 respectively. Molecular modelling of the compounds on E. coli (PDB code: 2EGH) and P. falciparum (PDB code: 3AUA) DXR showed strong binding of the halogenated fosmidomycin analogues while the hybrids in the absence of docked NADPH showed minimum binding to the enzymes.
- Full Text:
- Date Issued: 2012
- Authors: Afolayan, Anthonia Folake
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64370 , vital:28538
- Description: Malaria continues to be a devastating disease and a major cause of death in sub-Saharan Africa. With resistance against most of the available antimalarial drugs, there is a need for ongoing research and development of antimalarial agents. Fosmidomycin and its acetyl analogue FR900098 have been identified as potent inhibitors of Plasmodium falciparum, the causative agent of the most deadly form of malaria. Clinical trials of these agents have revealed poor absorption due to their high hydrophilicity. In the present studies the effect of halogenation of the acyl chain as well as the biological effect of extending the acyl sidechain was explored. This provided the basis on which fosmidomycin hybrids were designed to investigate the feasibility of hybrid extending into NADPH binding pocket. Synthesis of a series of halogenated FR900098 analogues was carried out in three stages. This included i) The introduction of the phosphonate group by reaction with 1,3dibromopropane in an Arbuzov reaction, ii) The introduction of a hydroxamate group by reaction of the propyl phosphonate by means of a nucleophilic substitution reaction with BocNHOBn and iii) The introduction of a halogenated acyl side chain on a protected fosmidomycin backbone. The synthesis of fosmidomycin-hybrids for which chloroquinefosmidomycin hybrids were used as the prototype, involved convergence of the two separately constructed moieties i.e. fosmidomycin and the quinoline moieties in a covalent linkage. The quinoline moiety was easily synthesized from the reaction of 4,7dichloroquinoline with 1,2-diamino ethane. The aminoquinoline so formed resulted in chloroquine-fosmidomycin hybrids 3.8 and 3.9 when reacted with halogenated FR900098 analogues. Antiplasmodial assays were conducted on the chloroquine-fosmidomycin hybrids and the halogenated fosmidomycin derivatives against the chloroquine resistant Gambian FCR-3 strain of P. falciparum. The most potent iodoacetyl fosmidomycin analogues 2.21 gave an IC50 value of 5.54 µM which is eight times more potent than the known antiplasmodial FR900098 which gave an IC50 value of 41.67 µM. All the halogenated FR900098 analogues showed better antiplasmodial activity than their non-halogenated derivatives. This indicated that the presence of halogens in the FR900098 analogues contributes to their biological Chapter 1 Literature review activity. The acetyl and propyl linked hybrids 3.8 and 3.9 showed potent antiplasmodial activity with IC50 values of 0.18 and 0.82 µM respectively. These were by far the most potent hybrids synthesized and provided leads for a new class of promising antimalarial agents. Preliminary E. coli DXR enzyme inhibition assays were carried out on the halogenated fosmidomycin analogues. The results showed good inhibition of the enzyme by the phosphonic acids of the chloroacetyl and chloropropyl analogues 2.1 and 2.2 respectively. Molecular modelling of the compounds on E. coli (PDB code: 2EGH) and P. falciparum (PDB code: 3AUA) DXR showed strong binding of the halogenated fosmidomycin analogues while the hybrids in the absence of docked NADPH showed minimum binding to the enzymes.
- Full Text:
- Date Issued: 2012
Sign language in South Africa language planning and policy challenges
- Authors: Ganiso, Mirriam Nosiphiwo
- Date: 2011
- Subjects: Sign language -- Study and teaching -- South Africa Deaf -- Education -- South Africa Deaf -- Means of communication
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3588 , http://hdl.handle.net/10962/d1002163
- Description: This thesis sets out to undertake research into the very important topic of sign language and its usage, particularly in the Western Cape Province of South Africa. Three schools are used in this study. Interviews and questionnaires were used to conduct research with teachers, students and deaf teacher assistants within this context. The analysis of this data is presented in Chapter five of this thesis.
- Full Text:
- Date Issued: 2011
- Authors: Ganiso, Mirriam Nosiphiwo
- Date: 2011
- Subjects: Sign language -- Study and teaching -- South Africa Deaf -- Education -- South Africa Deaf -- Means of communication
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3588 , http://hdl.handle.net/10962/d1002163
- Description: This thesis sets out to undertake research into the very important topic of sign language and its usage, particularly in the Western Cape Province of South Africa. Three schools are used in this study. Interviews and questionnaires were used to conduct research with teachers, students and deaf teacher assistants within this context. The analysis of this data is presented in Chapter five of this thesis.
- Full Text:
- Date Issued: 2011
An investigation of IgE regulation by recombinant soluble IgE receptors and co-receptors in human cell culture models
- Authors: Bowles, Sandra Lyn
- Date: 2010
- Subjects: Immunoglobulin E , Allergy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10321 , http://hdl.handle.net/10948/1231 , Immunoglobulin E , Allergy
- Description: Type I hypersensitivities are mediated by the IgE antibody. The effector functions and synthesis of IgE result from interactions with a network of proteins that include a high affinity (FcRIα) and a low affinity (CD23, FcRII) Fc receptor in conjunction with the B lymphocyte receptor, CD21. CD23 is a multifunctional type II transmembrane protein that binds its known ligands through its ectodomain either as a membrane-bound or soluble receptor generated in vivo by specific proteolytic cleavages. IgE production is primarily regulated by interactions between IgE, CD23 and CD21. Despite its importance for development of strategies to limit hypersensitivity, precise information about the molecular interactions remains limited. During this study, I engineered, expressed and purified from bacteria three soluble human CD23 fragments that are normally formed in vivo and shed from the cell surface (1) derCD23, amino acids 156-298 (2) sCD23, amino acids 150-321 and (3) the entire ectodomain, exCD23, amino acids 48-321 to examine the comparative binding of recombinant human CD21 SCR 1-2 and native human IgE to these fragments. Gel filtration HPLC revealed that derCD23 and sCD23 were monomeric whereas exCD23 assembled as a heterogeneous mixture that included trimers and monomers. At the concentrations utilized, CD23 fragments sCD23 and exCD23 bound CD21 with similar affinity, whereas interaction between derCD23 and CD21 was minimal when analyzed by surface plasmon resonance (SPR) spectroscopy. These findings suggest that penultimate “tail” amino acids between 298 and 321 stabilize CD21 attachment, although it cannot be ruled out, the region between Met 150 and Ser 156 may also play a role in binding CD21 SCR 1-2. In contrast, there is a progressive increment in the affinity of soluble fragments (exCD23>sCD23>derCD23) for IgE, upon increasing length of the proximal CD23 “stalk” domain. These findings highlight the differences in both the structural basis and affinity of the three physiological fragments of human CD23 for the ligands CD21 and IgE and underscore the complexity of CD23-mediated regulatory networks. It was found that B-cells only make up ~5% of the PBMC population, and that these cells were able to be activated, via STAT-6 phosphorylation, to enter class switch recombination (CSR) by the addition of switch factors (IL-4 and anti-CD40). Titration experiments dictated that 25 ng/mL of CD23 was the most efficient concentration to up-regulate IgE synthesis in PBMCs; furthermore, soluble CD23 proteins were incubated with PBMCs in the presence and absence of CD21 SCR 1-2 to investigate the effect that these recombinant proteins have on IgE synthesis. Results showed that the influence of recombinant proteins (both CD23 and CD21) on IgE synthesis was slight. It was shown that while derCD23 had no significant effect, monomeric sCD23 down-regulated, and the mixture of monomeric and oligomeric exCD23 up-regulated IgE synthesis. On addition of CD21 SCR 1-2 to the cells switched and treated with soluble CD23, it was found that in both cases for sCD23 and exCD23, IgE synthesis was increased, while for derCD23, there was no noticeable difference in IgE synthesis. This confirmed previous data showing the lack of binding between derCD23 and CD21 SCR 1-2. The exact binding site for CD21 on the CD23 molecule is unknown, and incompletely represented in the NMR and crystal structures. It is thought that CD21 binds to the C-terminal tail section, not present in derCD23. It is therefore likely that only a negative-feedback mechanism operates with derCD23 to regulate IgE synthesis. Further investigation of the binding of CD23 fragments to SCR 5-8 of CD21 and the effect of this on IgE synthesis may lead to a potential therapeutic role for derCD23 in the treatment of allergic disease. Data accumulated in this study suggests that investigating the modulation of oligomeric state and thus the activity of soluble CD23 fragments may be important in the construction of new regulators of IgE synthesis.
- Full Text:
- Date Issued: 2010
- Authors: Bowles, Sandra Lyn
- Date: 2010
- Subjects: Immunoglobulin E , Allergy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10321 , http://hdl.handle.net/10948/1231 , Immunoglobulin E , Allergy
- Description: Type I hypersensitivities are mediated by the IgE antibody. The effector functions and synthesis of IgE result from interactions with a network of proteins that include a high affinity (FcRIα) and a low affinity (CD23, FcRII) Fc receptor in conjunction with the B lymphocyte receptor, CD21. CD23 is a multifunctional type II transmembrane protein that binds its known ligands through its ectodomain either as a membrane-bound or soluble receptor generated in vivo by specific proteolytic cleavages. IgE production is primarily regulated by interactions between IgE, CD23 and CD21. Despite its importance for development of strategies to limit hypersensitivity, precise information about the molecular interactions remains limited. During this study, I engineered, expressed and purified from bacteria three soluble human CD23 fragments that are normally formed in vivo and shed from the cell surface (1) derCD23, amino acids 156-298 (2) sCD23, amino acids 150-321 and (3) the entire ectodomain, exCD23, amino acids 48-321 to examine the comparative binding of recombinant human CD21 SCR 1-2 and native human IgE to these fragments. Gel filtration HPLC revealed that derCD23 and sCD23 were monomeric whereas exCD23 assembled as a heterogeneous mixture that included trimers and monomers. At the concentrations utilized, CD23 fragments sCD23 and exCD23 bound CD21 with similar affinity, whereas interaction between derCD23 and CD21 was minimal when analyzed by surface plasmon resonance (SPR) spectroscopy. These findings suggest that penultimate “tail” amino acids between 298 and 321 stabilize CD21 attachment, although it cannot be ruled out, the region between Met 150 and Ser 156 may also play a role in binding CD21 SCR 1-2. In contrast, there is a progressive increment in the affinity of soluble fragments (exCD23>sCD23>derCD23) for IgE, upon increasing length of the proximal CD23 “stalk” domain. These findings highlight the differences in both the structural basis and affinity of the three physiological fragments of human CD23 for the ligands CD21 and IgE and underscore the complexity of CD23-mediated regulatory networks. It was found that B-cells only make up ~5% of the PBMC population, and that these cells were able to be activated, via STAT-6 phosphorylation, to enter class switch recombination (CSR) by the addition of switch factors (IL-4 and anti-CD40). Titration experiments dictated that 25 ng/mL of CD23 was the most efficient concentration to up-regulate IgE synthesis in PBMCs; furthermore, soluble CD23 proteins were incubated with PBMCs in the presence and absence of CD21 SCR 1-2 to investigate the effect that these recombinant proteins have on IgE synthesis. Results showed that the influence of recombinant proteins (both CD23 and CD21) on IgE synthesis was slight. It was shown that while derCD23 had no significant effect, monomeric sCD23 down-regulated, and the mixture of monomeric and oligomeric exCD23 up-regulated IgE synthesis. On addition of CD21 SCR 1-2 to the cells switched and treated with soluble CD23, it was found that in both cases for sCD23 and exCD23, IgE synthesis was increased, while for derCD23, there was no noticeable difference in IgE synthesis. This confirmed previous data showing the lack of binding between derCD23 and CD21 SCR 1-2. The exact binding site for CD21 on the CD23 molecule is unknown, and incompletely represented in the NMR and crystal structures. It is thought that CD21 binds to the C-terminal tail section, not present in derCD23. It is therefore likely that only a negative-feedback mechanism operates with derCD23 to regulate IgE synthesis. Further investigation of the binding of CD23 fragments to SCR 5-8 of CD21 and the effect of this on IgE synthesis may lead to a potential therapeutic role for derCD23 in the treatment of allergic disease. Data accumulated in this study suggests that investigating the modulation of oligomeric state and thus the activity of soluble CD23 fragments may be important in the construction of new regulators of IgE synthesis.
- Full Text:
- Date Issued: 2010
The effects of elephants at low densities and after short occupation time on the ecosystems of the Eastern Cape Province, South Africa
- Authors: Parker, Daniel Matthew
- Date: 2008
- Subjects: Elephants -- South Africa -- Eastern Cape Biotic communities -- South Africa -- Eastern Cape Animal populations -- South Africa -- Eastern Cape Plant communities -- South Africa -- Eastern Cape Mammals -- Ecology -- South Africa -- Eastern Cape Animal-plant relationships -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5678 , http://hdl.handle.net/10962/d1005363
- Description: Elephants (Loxodonta africana, Blumenbach) are recognised as keystone herbivores and ecosystem engineers in African ecosystems due to the noticeable impact they have on plant communities. This impact can influence other animal taxa and ecosystem processes, especially within enclosed systems. I investigated the effects of elephants in four vegetation types and the cascade effect on three associated taxa and two ecosystem processes at five sites with elephants and five paired sites without elephants in the Eastern Cape Province, South Africa, between April 2005 and July 2007. In grassland habitats, the physical structure of the vegetation was neither enhanced nor degraded in the presence of elephants. Within the locally important Thicket Biome, elephant browsing transformed relatively homogeneous stands of vegetation into more heterogeneous units. However, although seeds from thicket plant species were recorded in elephant dung, elephants did not promote the viability and germination success of these plants. In addition, elephant foraging on aloes caused declines in their populations. By contrast, the size of bushclumps was not reduced in the presence of elephants in bushclump savanna. The associated insect, bird and mammal communities appeared to benefit from elephant foraging in all vegetation types assessed, whereas vegetation patch dynamics and soil surface processes were neither enhanced nor degraded in the presence of elephants. I conclude that, at current densities, elephants do not (in most cases) negatively affect plant and animal communities or ecosystem processes in enclosed reserves. However, elephants have only been present at each site for a relatively short period and it is likely that their impact will be cumulative, increasing over time in these closed systems. Thus, future research along a continuum of elephant density and time since re-introduction is recommended.
- Full Text:
- Date Issued: 2008
- Authors: Parker, Daniel Matthew
- Date: 2008
- Subjects: Elephants -- South Africa -- Eastern Cape Biotic communities -- South Africa -- Eastern Cape Animal populations -- South Africa -- Eastern Cape Plant communities -- South Africa -- Eastern Cape Mammals -- Ecology -- South Africa -- Eastern Cape Animal-plant relationships -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5678 , http://hdl.handle.net/10962/d1005363
- Description: Elephants (Loxodonta africana, Blumenbach) are recognised as keystone herbivores and ecosystem engineers in African ecosystems due to the noticeable impact they have on plant communities. This impact can influence other animal taxa and ecosystem processes, especially within enclosed systems. I investigated the effects of elephants in four vegetation types and the cascade effect on three associated taxa and two ecosystem processes at five sites with elephants and five paired sites without elephants in the Eastern Cape Province, South Africa, between April 2005 and July 2007. In grassland habitats, the physical structure of the vegetation was neither enhanced nor degraded in the presence of elephants. Within the locally important Thicket Biome, elephant browsing transformed relatively homogeneous stands of vegetation into more heterogeneous units. However, although seeds from thicket plant species were recorded in elephant dung, elephants did not promote the viability and germination success of these plants. In addition, elephant foraging on aloes caused declines in their populations. By contrast, the size of bushclumps was not reduced in the presence of elephants in bushclump savanna. The associated insect, bird and mammal communities appeared to benefit from elephant foraging in all vegetation types assessed, whereas vegetation patch dynamics and soil surface processes were neither enhanced nor degraded in the presence of elephants. I conclude that, at current densities, elephants do not (in most cases) negatively affect plant and animal communities or ecosystem processes in enclosed reserves. However, elephants have only been present at each site for a relatively short period and it is likely that their impact will be cumulative, increasing over time in these closed systems. Thus, future research along a continuum of elephant density and time since re-introduction is recommended.
- Full Text:
- Date Issued: 2008
Teacher motivation in a South African school
- Authors: Kovach, John C
- Date: 2007
- Subjects: Teacher morale -- South Africa -- Eastern Cape Teachers -- Professional ethics -- South Africa -- Eastern Cape Teacher-administrator relationships -- South Africa -- Eastern Cape Educational leadership -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1790 , http://hdl.handle.net/10962/d1003675
- Description: This study explores and attempts to shed light on what motivates teachers and how teacher motivation is affected by a principal's leadership style. The worldviews of pragmatism and critical realism were used as the basis for exploring teacher motivation in a South African school. A primary school in the Eastern Cape of South Africa was chosen for the case study. Three data gathering tools, a leadership questionnaire, teacher survey, and interviews were used to generate data on teacher motivation and the interaction between leadership style and teacher motivation. In regards to teachers, religion, social justice, and self-efficacy were all identified as motivators. The principal was strongly charismatic in her leadership and along with transformational and social justice leadership played a major role in influencing teacher behaviors. Self-determination theory was identified as helping to explain different levels of intrinsic and extrinsic motivation and thereby to better understand varying degrees of teacher motivation. There are many difficulties in South African education and around the world in general and this study is premised on the belief that if teacher motivation can be studied and advanced there will be an improvement in education and learning. This thesis was limited in its scope and ability to fully explore the different levels of ontology as outlined by the critical realist and this is identified as a possible future course of action for not only studying teacher motivation but getting to the 'heart of the matter'.
- Full Text:
- Date Issued: 2007
- Authors: Kovach, John C
- Date: 2007
- Subjects: Teacher morale -- South Africa -- Eastern Cape Teachers -- Professional ethics -- South Africa -- Eastern Cape Teacher-administrator relationships -- South Africa -- Eastern Cape Educational leadership -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1790 , http://hdl.handle.net/10962/d1003675
- Description: This study explores and attempts to shed light on what motivates teachers and how teacher motivation is affected by a principal's leadership style. The worldviews of pragmatism and critical realism were used as the basis for exploring teacher motivation in a South African school. A primary school in the Eastern Cape of South Africa was chosen for the case study. Three data gathering tools, a leadership questionnaire, teacher survey, and interviews were used to generate data on teacher motivation and the interaction between leadership style and teacher motivation. In regards to teachers, religion, social justice, and self-efficacy were all identified as motivators. The principal was strongly charismatic in her leadership and along with transformational and social justice leadership played a major role in influencing teacher behaviors. Self-determination theory was identified as helping to explain different levels of intrinsic and extrinsic motivation and thereby to better understand varying degrees of teacher motivation. There are many difficulties in South African education and around the world in general and this study is premised on the belief that if teacher motivation can be studied and advanced there will be an improvement in education and learning. This thesis was limited in its scope and ability to fully explore the different levels of ontology as outlined by the critical realist and this is identified as a possible future course of action for not only studying teacher motivation but getting to the 'heart of the matter'.
- Full Text:
- Date Issued: 2007
Participants' perceptions of Computer-Mediated Communication: a case study of the Global Teenager Project
- Authors: Turyagyenda, Joy Kyarimpa
- Date: 2003
- Subjects: Global Teenager Project Computer networks -- Social aspects Communication Telematics Learning -- Technological innovations
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1687 , http://hdl.handle.net/10962/d1003570
- Description: The study outlines general trends evident in Computer-Mediated Communication (CMC), participants’ perceptions and the promotion of CMC across the curriculum in a South African Secondary School. This case study focuses on the Global Teenager Project (GTP), which started as a bi-national pilot project in April 1999 between secondary schools in South Africa and the Netherlands. The study sets out to investigate how well the GTP can be incorporated into the existing school curriculum through the teacherresearcher’s direct involvement in facilitating the project at a school where she is a fulltime teacher. The main purpose of the study is to review existing literature to establish how collaborative learning could be achieved through a CMC environment between teenagers from various countries based on the research done at an international level and link the practice at this school to the existing international trends. It was found that the GTP has great potential in enhancing collaborative learning within various learning areas at Nathaniel Nyaluza Secondary School (NNSS). Despite the usefulness of the GTP and the overwhelming enthusiasm learners displayed, its success at NNSS depended on the motivation of teachers and how easily the activities of the GTP could be incorporated within day-to-day teachers’ activities. , Hodgkinson, Cheryl
- Full Text:
- Date Issued: 2003
- Authors: Turyagyenda, Joy Kyarimpa
- Date: 2003
- Subjects: Global Teenager Project Computer networks -- Social aspects Communication Telematics Learning -- Technological innovations
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1687 , http://hdl.handle.net/10962/d1003570
- Description: The study outlines general trends evident in Computer-Mediated Communication (CMC), participants’ perceptions and the promotion of CMC across the curriculum in a South African Secondary School. This case study focuses on the Global Teenager Project (GTP), which started as a bi-national pilot project in April 1999 between secondary schools in South Africa and the Netherlands. The study sets out to investigate how well the GTP can be incorporated into the existing school curriculum through the teacherresearcher’s direct involvement in facilitating the project at a school where she is a fulltime teacher. The main purpose of the study is to review existing literature to establish how collaborative learning could be achieved through a CMC environment between teenagers from various countries based on the research done at an international level and link the practice at this school to the existing international trends. It was found that the GTP has great potential in enhancing collaborative learning within various learning areas at Nathaniel Nyaluza Secondary School (NNSS). Despite the usefulness of the GTP and the overwhelming enthusiasm learners displayed, its success at NNSS depended on the motivation of teachers and how easily the activities of the GTP could be incorporated within day-to-day teachers’ activities. , Hodgkinson, Cheryl
- Full Text:
- Date Issued: 2003
Design, synthesis and evaluation of silver-specific ligands
- Authors: Daubinet, André
- Date: 2001
- Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
- Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
- Full Text:
- Date Issued: 2001
- Authors: Daubinet, André
- Date: 2001
- Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
- Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
- Full Text:
- Date Issued: 2001
An assessment of the monkfish resource of Namibia
- Authors: Maartens, Lima
- Date: 2000
- Subjects: Lophius -- Namibia Lophius
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5231 , http://hdl.handle.net/10962/d1005074
- Description: Two monkfish species are caught off the coast of Namibia. These are Lophius vomerinus Valenciennes (1837) and L. vaillanti Regan (1903). L. vomerinus is the more abundant of the two and contributes approximately 99% to the total Namibian monkfish landings. The Namibian monkfish fishery is one of the largest and most valuable of its kind in the world. Two fishing fleets harvest the resource, viz. the monkfish and sole fleet and the hake directed fleet. In 1998 and 1999, monkfish were also harvested by one gillnet vessel that had an experimental right. In this study, the biology, abundance and exploitation patterns of monkfish were investigated and used as inputs into a stock assessment framework as a contribution towards the development of a management procedure for this species. Ground and sectioned otoliths and sectioned illicia were used to age Lophius vomerinus. The illicia provided more precise estimates of age, and growth was subsequently modelled using these age estimates. Growth in length and weight was best described by the threeparameter specialised von Bertalanffy model as Lt (cm TL) = 72.29 (1-e⁻°·¹⁴⁽t⁺°·³°⁾) and Wt (kg) = 3.96 (1-e⁻°·¹⁸⁽t⁺°·¹°⁾)²·⁹⁹ for males, and Lt (cm TL) = 111.98 (1-e⁻°·°⁸⁽t⁺°·³⁶⁾) and Wt (kg) = 6.92 (1-e⁻°·¹⁸⁽t⁻°·⁶⁴⁾)³·°³ for females. L. vomerinus is a slow-growing species with a life span in excess of 10 years. Reproductive activity was shown to occur throughout the year, with a slight peak during the winter months. The adult sex ratio of fish > 37 cm TL was biased towards females. Length-at-50% sexual maturity was attained at 32.1 cm TL for females and 23.7 cm TL for males. The rate of natural mortality was estimated at 0.15 year⁻¹, while fishing mortality rates during the 1970s, 1980s and 1990s were estimated at 0.01 year⁻¹, 0.04 year⁻¹ and 0.14 year⁻¹, respectively. Gillnetting for monkfish (300 mm stretched mesh) was highly efficient with a moderate bycatch of around 20% during the two years of operation. The main bycatch species were red crab, spider crab, squalid sharks, rays and Cape and Deep-water hake. The mean length of the monkfish caught in gillnets (67 cm TL) was significantly larger than the monkfish landed by the trawlers (38 cm TL) and less than 1% of immature fish were landed. Gillnet catch-per-unit-effort for monkfish fluctuated between 0.03 and 0.67 kg.day⁻¹.50 m net panel⁻¹, with a soak time of between one and sixteen days. More than 50% (by weight) of monkfish landed by monkfish and sole trawlers, consisted of fish below 36 cm TL. There was a significant increase in catches of juvenile monkfish during 1997 and 1998 in comparison to the period 1994 to 1996. Various types of rigid sorting grids were tested to release juvenile monkfish below 32 cm TL. Five grid designs were tested. These included an “Ex-it” grid with horizontal bars spaced at 55 mm, single grids with vertical and horizontal bars spaced at 55 mm and grids with circular openings of 110 and 168 mm in diameter. The most efficient design was the grid with circular openings of 110 cm in diameter, which ensured the escape of 66% of monkfish smaller than 31 cm TL. However, studies need to be undertaken to quantify the survival of released fish and to test the feasibility of using grid sorters on commercial monkfish and sole trawling gear. The monkfish resource was assessed by means of length cohort analyses, the Thompson and Bell predictive model and by way of a deterministic age-structured production modelling approach. The length cohort analysis models were sensitive to the rate of natural mortality and insensitive to changes in the terminal fishing mortality rate. These biases may, however, not be serious provided that estimates of abundance are used to reflect relative changes. Fish ranging between 26 and 59 cm TL are the most heavily exploited. The Thompson and Bell model predicted that the monkfish resource is exploited above MSY -levels and a reduction of approximately 40% in fishing effort would provide a higher yield. Yield-per-recruit ranged between 10 000 and 14 000 tonnes. Results should, however, be treated with caution, as the condition of steady state was not satisfied. The age-structured production model was tuned using trends in catch-per-unit-effort data, estimated by Generalised Linear Modeling, as well as relative abundance indices calculated from hake biomass surveys. The model was found to be sensitive to both the ‘steepness’ parameter h and estimates of natural mortality. The ‘depletion’ level of the monkfish resource is currently estimated to be 49%. Estimated coefficients of variation were high (> 63%) due to the lack of a consistent trend within the abundance indices to tune the model. Overall productivity of the monkfish resource was estimated to be approximately 16%, similar to other southern African demersal resources. Results of the risk analyses suggest that catches in excess of 7 000 tonnes may be unsustainable and that catches of 5 000 or 6 000 tonnes would decrease the risk of stock collapse and possibly lead to a recovery in the stock. Monkfish management strategies were reviewed and these were considered in relation to the results of this study. The following management recommendations were made: to follow the precautionary approach and implement a total allowable catch for monkfish; to implement rigid sorting grids as these would be the most appropriate way in which to reduce catches of juvenile monkfish; to restrict soak time, depth of operation and implement means to reduce ‘ghost fishing’ by gillnetting and finally, to develop a management procedure for Namibian monkfish with the main objective being the sustainable exploitation of the resource.
- Full Text:
- Date Issued: 2000
- Authors: Maartens, Lima
- Date: 2000
- Subjects: Lophius -- Namibia Lophius
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5231 , http://hdl.handle.net/10962/d1005074
- Description: Two monkfish species are caught off the coast of Namibia. These are Lophius vomerinus Valenciennes (1837) and L. vaillanti Regan (1903). L. vomerinus is the more abundant of the two and contributes approximately 99% to the total Namibian monkfish landings. The Namibian monkfish fishery is one of the largest and most valuable of its kind in the world. Two fishing fleets harvest the resource, viz. the monkfish and sole fleet and the hake directed fleet. In 1998 and 1999, monkfish were also harvested by one gillnet vessel that had an experimental right. In this study, the biology, abundance and exploitation patterns of monkfish were investigated and used as inputs into a stock assessment framework as a contribution towards the development of a management procedure for this species. Ground and sectioned otoliths and sectioned illicia were used to age Lophius vomerinus. The illicia provided more precise estimates of age, and growth was subsequently modelled using these age estimates. Growth in length and weight was best described by the threeparameter specialised von Bertalanffy model as Lt (cm TL) = 72.29 (1-e⁻°·¹⁴⁽t⁺°·³°⁾) and Wt (kg) = 3.96 (1-e⁻°·¹⁸⁽t⁺°·¹°⁾)²·⁹⁹ for males, and Lt (cm TL) = 111.98 (1-e⁻°·°⁸⁽t⁺°·³⁶⁾) and Wt (kg) = 6.92 (1-e⁻°·¹⁸⁽t⁻°·⁶⁴⁾)³·°³ for females. L. vomerinus is a slow-growing species with a life span in excess of 10 years. Reproductive activity was shown to occur throughout the year, with a slight peak during the winter months. The adult sex ratio of fish > 37 cm TL was biased towards females. Length-at-50% sexual maturity was attained at 32.1 cm TL for females and 23.7 cm TL for males. The rate of natural mortality was estimated at 0.15 year⁻¹, while fishing mortality rates during the 1970s, 1980s and 1990s were estimated at 0.01 year⁻¹, 0.04 year⁻¹ and 0.14 year⁻¹, respectively. Gillnetting for monkfish (300 mm stretched mesh) was highly efficient with a moderate bycatch of around 20% during the two years of operation. The main bycatch species were red crab, spider crab, squalid sharks, rays and Cape and Deep-water hake. The mean length of the monkfish caught in gillnets (67 cm TL) was significantly larger than the monkfish landed by the trawlers (38 cm TL) and less than 1% of immature fish were landed. Gillnet catch-per-unit-effort for monkfish fluctuated between 0.03 and 0.67 kg.day⁻¹.50 m net panel⁻¹, with a soak time of between one and sixteen days. More than 50% (by weight) of monkfish landed by monkfish and sole trawlers, consisted of fish below 36 cm TL. There was a significant increase in catches of juvenile monkfish during 1997 and 1998 in comparison to the period 1994 to 1996. Various types of rigid sorting grids were tested to release juvenile monkfish below 32 cm TL. Five grid designs were tested. These included an “Ex-it” grid with horizontal bars spaced at 55 mm, single grids with vertical and horizontal bars spaced at 55 mm and grids with circular openings of 110 and 168 mm in diameter. The most efficient design was the grid with circular openings of 110 cm in diameter, which ensured the escape of 66% of monkfish smaller than 31 cm TL. However, studies need to be undertaken to quantify the survival of released fish and to test the feasibility of using grid sorters on commercial monkfish and sole trawling gear. The monkfish resource was assessed by means of length cohort analyses, the Thompson and Bell predictive model and by way of a deterministic age-structured production modelling approach. The length cohort analysis models were sensitive to the rate of natural mortality and insensitive to changes in the terminal fishing mortality rate. These biases may, however, not be serious provided that estimates of abundance are used to reflect relative changes. Fish ranging between 26 and 59 cm TL are the most heavily exploited. The Thompson and Bell model predicted that the monkfish resource is exploited above MSY -levels and a reduction of approximately 40% in fishing effort would provide a higher yield. Yield-per-recruit ranged between 10 000 and 14 000 tonnes. Results should, however, be treated with caution, as the condition of steady state was not satisfied. The age-structured production model was tuned using trends in catch-per-unit-effort data, estimated by Generalised Linear Modeling, as well as relative abundance indices calculated from hake biomass surveys. The model was found to be sensitive to both the ‘steepness’ parameter h and estimates of natural mortality. The ‘depletion’ level of the monkfish resource is currently estimated to be 49%. Estimated coefficients of variation were high (> 63%) due to the lack of a consistent trend within the abundance indices to tune the model. Overall productivity of the monkfish resource was estimated to be approximately 16%, similar to other southern African demersal resources. Results of the risk analyses suggest that catches in excess of 7 000 tonnes may be unsustainable and that catches of 5 000 or 6 000 tonnes would decrease the risk of stock collapse and possibly lead to a recovery in the stock. Monkfish management strategies were reviewed and these were considered in relation to the results of this study. The following management recommendations were made: to follow the precautionary approach and implement a total allowable catch for monkfish; to implement rigid sorting grids as these would be the most appropriate way in which to reduce catches of juvenile monkfish; to restrict soak time, depth of operation and implement means to reduce ‘ghost fishing’ by gillnetting and finally, to develop a management procedure for Namibian monkfish with the main objective being the sustainable exploitation of the resource.
- Full Text:
- Date Issued: 2000
Zinc inhibition of cell division : its relevance to cancer cells and possible mechanism of action
- Authors: Skeef, Noel Samuel
- Date: 1989
- Subjects: Cell division , Cancer cells -- Growth -- Regulation , Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4144 , http://hdl.handle.net/10962/d1016266
- Description: A description of two techniques used extensively in this study namely cell counting with a "cell counting plate" and argentation TLC for the separation of ω -6 -fatty acids is given. Zn supplementation into GM of two malignant (BL-6 and Hep- 350) and a non-malignant (LLC-MK) cell line/s resulted in an increased uptake of Zn by the cells and progressively suppressed proliferation of particularly the malignant cells. Zn chelation by EDTA suppressed in vitro proliferation of all 3 cell line, this effect being more pronounced in the malignant cells. A dietary Zn deficiency resulted in alopecia in mice and both a dietary Zn deficiency and Zn excess reduced growth of BL-6 tumours implanted subcutaneously in mice. Zn supplementation into GM progressively increased the uptake of [1-¹⁴C]-LA by BL-6 and LLC-MK cells but had a very slight though irregular effect on this parameter in the Hep- 350 cells. Zn supplementation also stimulated desaturase activity in the BL-6 cells. These results suggested that there are select cell lines whose Δ⁶-desaturase activity responds positively to Zn supplementation (e.g. the BL-6 cells). Delta-6-desaturase activity was also assayed in microsome preparations from different tissues. No enzyme activity was detected in the microsomes prepared from the BL-6 tumours. There was no significant effect with the addition of Zn or EDTA, on Δ⁶-desaturase activity of the regenerating liver microsomes. In the resting liver microsomes this enzyme activity was reduced only when EDTA and Zn were added together and when EDTA was added to the reaction medium as well as to the microsome preparations 2 hr before the enzyme activity assay was initiated. The results of these experiments suggested that the Δ⁶-desaturase enzyme in the microsome preparations may have had an adequate amount of Zn with further additions having no stimulatory effect on the enzyme. Two independent mechanisms of control of cell proliferation by low and high Zn are suggested to operate.
- Full Text:
- Date Issued: 1989
- Authors: Skeef, Noel Samuel
- Date: 1989
- Subjects: Cell division , Cancer cells -- Growth -- Regulation , Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4144 , http://hdl.handle.net/10962/d1016266
- Description: A description of two techniques used extensively in this study namely cell counting with a "cell counting plate" and argentation TLC for the separation of ω -6 -fatty acids is given. Zn supplementation into GM of two malignant (BL-6 and Hep- 350) and a non-malignant (LLC-MK) cell line/s resulted in an increased uptake of Zn by the cells and progressively suppressed proliferation of particularly the malignant cells. Zn chelation by EDTA suppressed in vitro proliferation of all 3 cell line, this effect being more pronounced in the malignant cells. A dietary Zn deficiency resulted in alopecia in mice and both a dietary Zn deficiency and Zn excess reduced growth of BL-6 tumours implanted subcutaneously in mice. Zn supplementation into GM progressively increased the uptake of [1-¹⁴C]-LA by BL-6 and LLC-MK cells but had a very slight though irregular effect on this parameter in the Hep- 350 cells. Zn supplementation also stimulated desaturase activity in the BL-6 cells. These results suggested that there are select cell lines whose Δ⁶-desaturase activity responds positively to Zn supplementation (e.g. the BL-6 cells). Delta-6-desaturase activity was also assayed in microsome preparations from different tissues. No enzyme activity was detected in the microsomes prepared from the BL-6 tumours. There was no significant effect with the addition of Zn or EDTA, on Δ⁶-desaturase activity of the regenerating liver microsomes. In the resting liver microsomes this enzyme activity was reduced only when EDTA and Zn were added together and when EDTA was added to the reaction medium as well as to the microsome preparations 2 hr before the enzyme activity assay was initiated. The results of these experiments suggested that the Δ⁶-desaturase enzyme in the microsome preparations may have had an adequate amount of Zn with further additions having no stimulatory effect on the enzyme. Two independent mechanisms of control of cell proliferation by low and high Zn are suggested to operate.
- Full Text:
- Date Issued: 1989
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