Identifying the interdependence between South Africa's monetary policy and the stock market
- Authors: Muroyiwa, Brian
- Date: 2011
- Subjects: Monetary policy -- South Africa , Stock exchanges -- Law and legislation -- South Africa , Interest rates -- South Africa , Securities -- Prices -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:982 , http://hdl.handle.net/10962/d1002716 , Monetary policy -- South Africa , Stock exchanges -- Law and legislation -- South Africa , Interest rates -- South Africa , Securities -- Prices -- South Africa
- Description: This study estimates the interdependence between South Africa‟s monetary policy and stock market performance, utilising structural vector autoregression (SVAR) methodology. The study finds that a stock price shock which decrease stock prices by 100 basis points leads to 5 basis points decrease in interbank rate. A monetary policy shock that increases the interbank rate by l percent leads to decrease in real stock prices by 1 percent. This result for South Africa is similar to the result by Bjornland and Leteimo (2009) which earlier concluded that there was a high interdependence between interest rate setting and stock prices. However the magnitude of the relationship is relatively lower for South Africa compared to that of the United States of America (USA). The result of the current study is also very much consistent with the argument that the South African stock market is resource-based and so is influenced by external shocks, meaning monetary policy shock does not have as much impact on stock market in South Africa as in the USA. However the SARB may have to consider watching movements in stock prices so that booms in stock markets do not defeat central bank monetary policy thrusts. The stock price market is an essential source of information for monetary policy in South Africa.
- Full Text:
- Date Issued: 2011
- Authors: Muroyiwa, Brian
- Date: 2011
- Subjects: Monetary policy -- South Africa , Stock exchanges -- Law and legislation -- South Africa , Interest rates -- South Africa , Securities -- Prices -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:982 , http://hdl.handle.net/10962/d1002716 , Monetary policy -- South Africa , Stock exchanges -- Law and legislation -- South Africa , Interest rates -- South Africa , Securities -- Prices -- South Africa
- Description: This study estimates the interdependence between South Africa‟s monetary policy and stock market performance, utilising structural vector autoregression (SVAR) methodology. The study finds that a stock price shock which decrease stock prices by 100 basis points leads to 5 basis points decrease in interbank rate. A monetary policy shock that increases the interbank rate by l percent leads to decrease in real stock prices by 1 percent. This result for South Africa is similar to the result by Bjornland and Leteimo (2009) which earlier concluded that there was a high interdependence between interest rate setting and stock prices. However the magnitude of the relationship is relatively lower for South Africa compared to that of the United States of America (USA). The result of the current study is also very much consistent with the argument that the South African stock market is resource-based and so is influenced by external shocks, meaning monetary policy shock does not have as much impact on stock market in South Africa as in the USA. However the SARB may have to consider watching movements in stock prices so that booms in stock markets do not defeat central bank monetary policy thrusts. The stock price market is an essential source of information for monetary policy in South Africa.
- Full Text:
- Date Issued: 2011
The ichthyofauna in a small temporarily open/closed Eastern Cape estuary, South Africa
- Authors: Lukey, James Robert
- Date: 2006
- Subjects: Estuarine fishes -- South Africa -- Eastern Cape , Marine fishes -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Eastern Cape , Fishes -- Growth -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5287 , http://hdl.handle.net/10962/d1005131 , Estuarine fishes -- South Africa -- Eastern Cape , Marine fishes -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Eastern Cape , Fishes -- Growth -- South Africa -- Eastern Cape
- Description: The ichthyofaunal community structure, population dynamics and movement patterns in the small temporarily open/closed (TOCE) Grant’s Valley estuary, situated along the Eastern Cape coastline, were investigated over the period May 2004 to April 2005. Community structure in the littoral zone was assessed, while growth of selected ichthyofaunal species was investigated using the MULTIFAN model. Population size was assessed using mark recapture models and movement within the estuary using the Hilborn (1990) model. Total ichthyofaunal densities and biomass within the littoral zone ranged between 0.31 to 21.45 fish m⁻² and 0.20 to 4.67 g wwt m⁻², with the highest values typically recorded during the summer. Results of the study indicated that the ichthyofaunal community structure within the estuary was closely linked to the mouth phase and the establishment of a link to the marine environment via overtopping events. In the absence of any link to the sea, the ichthyofaunal community was numerically dominated by estuarine resident species, mainly Gilchristella aestuaria and to a lesser extent, by the river goby, Glossogobius callidus which collectively comprised ca. 88% of all fish sampled. The establishment of the link to the marine environment contributed to an increased contribution of marine breeding species (e.g. Rhabdosargus holubi, Myxus capensis and Atherina breviceps) to the total ichthyofaunal abundances. In contrast, total ichthyofaunal biomass was almost always dominated by marine breeding species by virtue of their larger sizes. Results of hierarchical cluster analyses did not identify any spatial patterns in the ichthyofaunal community within the littoral zone. Results of MULTIFAN analysis indicated estuarine resident fish species bred over an extended period with peaks occurring in the summer months. Conversely, marine breeding fish were shown to recruit into the estuary following overtopping and breaching events. Results of the mark-recapture experiment indicated a population of ca. 12 000 (11 219 – 13 311) individuals greater than 50mm SL. Marine-breeding species (R. holubi, Monodactylus falciformis, and two mullet species) numerically dominated the ichthyofauna, possibly as a result of their effective use of overtopping events. The two mullet species, M. capensis and Liza richardsonii, and the Cape stumpnose, R. holubi moved extensively throughout the estuary, while the remaining species exhibited restricted movement patterns possibly due to the preference for refuge and foraging areas associated with reed beds. The observed movement patterns of individual fish species appeared to be associated with both foraging behaviour and habitat selection.
- Full Text:
- Date Issued: 2006
- Authors: Lukey, James Robert
- Date: 2006
- Subjects: Estuarine fishes -- South Africa -- Eastern Cape , Marine fishes -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Eastern Cape , Fishes -- Growth -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5287 , http://hdl.handle.net/10962/d1005131 , Estuarine fishes -- South Africa -- Eastern Cape , Marine fishes -- South Africa -- Eastern Cape , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- Habitat -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Eastern Cape , Fishes -- Growth -- South Africa -- Eastern Cape
- Description: The ichthyofaunal community structure, population dynamics and movement patterns in the small temporarily open/closed (TOCE) Grant’s Valley estuary, situated along the Eastern Cape coastline, were investigated over the period May 2004 to April 2005. Community structure in the littoral zone was assessed, while growth of selected ichthyofaunal species was investigated using the MULTIFAN model. Population size was assessed using mark recapture models and movement within the estuary using the Hilborn (1990) model. Total ichthyofaunal densities and biomass within the littoral zone ranged between 0.31 to 21.45 fish m⁻² and 0.20 to 4.67 g wwt m⁻², with the highest values typically recorded during the summer. Results of the study indicated that the ichthyofaunal community structure within the estuary was closely linked to the mouth phase and the establishment of a link to the marine environment via overtopping events. In the absence of any link to the sea, the ichthyofaunal community was numerically dominated by estuarine resident species, mainly Gilchristella aestuaria and to a lesser extent, by the river goby, Glossogobius callidus which collectively comprised ca. 88% of all fish sampled. The establishment of the link to the marine environment contributed to an increased contribution of marine breeding species (e.g. Rhabdosargus holubi, Myxus capensis and Atherina breviceps) to the total ichthyofaunal abundances. In contrast, total ichthyofaunal biomass was almost always dominated by marine breeding species by virtue of their larger sizes. Results of hierarchical cluster analyses did not identify any spatial patterns in the ichthyofaunal community within the littoral zone. Results of MULTIFAN analysis indicated estuarine resident fish species bred over an extended period with peaks occurring in the summer months. Conversely, marine breeding fish were shown to recruit into the estuary following overtopping and breaching events. Results of the mark-recapture experiment indicated a population of ca. 12 000 (11 219 – 13 311) individuals greater than 50mm SL. Marine-breeding species (R. holubi, Monodactylus falciformis, and two mullet species) numerically dominated the ichthyofauna, possibly as a result of their effective use of overtopping events. The two mullet species, M. capensis and Liza richardsonii, and the Cape stumpnose, R. holubi moved extensively throughout the estuary, while the remaining species exhibited restricted movement patterns possibly due to the preference for refuge and foraging areas associated with reed beds. The observed movement patterns of individual fish species appeared to be associated with both foraging behaviour and habitat selection.
- Full Text:
- Date Issued: 2006
Population dynamics of selected ichthyofaunal components in the temperate, temporarily open/closed Kasouga Estuary, South Africa
- Authors: Tweddle, Gavin Paul
- Date: 2005
- Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5742 , http://hdl.handle.net/10962/d1005428 , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Description: The spatial and temporal pattern of ichthyofaunal community composition in relation to selected physico-chemical (temperature and salinity) and biological variables (chlorophyll-a and zooplankton) was investigated at ten stations in the temperate temporarily open/closed Kasouga estuary. In addition, the food web structure in the estuary was investigated using stable carbon isotope analysis. Results of the 5 metre seine net survey indicated that ichthyofaunal composition and biomass in the Kasouga estuary was largely determined by seasonality and mouth condition. Maximum abundance and biomass of ichthyofauna was recorded during summer or during those periods when overtopping occurred. Overtopping coincided with the recruitment of marine estuarine dependant species, which dominated the catches both numerically and in biomass. The recruitment of these species resulted in an increase in diversity of the ichthyofaunal community. There were no significant spatial patterns in the distribution of smaller ichthyofauna (<50mm SL) identified in Bray-Curtis similarity matrices using cluster analysis (Primer 5 v5.2.4). Spearman’s correlation analysis revealed that there were no significant correlations between abundance and biomass of ichthyofauna and selected physico-chemical and biological variables other than salinity (P>0.05 in all other cases). There were two distinct spatial patterns in the distribution of the larger ichthyofauna (>50mm SL). These corresponded to a grouping associated with the mouth region and a grouping associated with the remaining regions of the estuary. Stable isotope analysis indicated that the primary source of carbon utilised by the ichthyofauna of the Kasouga estuary was derived from the channel, most likely microphytobenthic algae. The contributions of the riparian and salt marsh vegetation to the total carbon flow appear to be minimal.
- Full Text:
- Date Issued: 2005
- Authors: Tweddle, Gavin Paul
- Date: 2005
- Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5742 , http://hdl.handle.net/10962/d1005428 , Estuaries -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
- Description: The spatial and temporal pattern of ichthyofaunal community composition in relation to selected physico-chemical (temperature and salinity) and biological variables (chlorophyll-a and zooplankton) was investigated at ten stations in the temperate temporarily open/closed Kasouga estuary. In addition, the food web structure in the estuary was investigated using stable carbon isotope analysis. Results of the 5 metre seine net survey indicated that ichthyofaunal composition and biomass in the Kasouga estuary was largely determined by seasonality and mouth condition. Maximum abundance and biomass of ichthyofauna was recorded during summer or during those periods when overtopping occurred. Overtopping coincided with the recruitment of marine estuarine dependant species, which dominated the catches both numerically and in biomass. The recruitment of these species resulted in an increase in diversity of the ichthyofaunal community. There were no significant spatial patterns in the distribution of smaller ichthyofauna (<50mm SL) identified in Bray-Curtis similarity matrices using cluster analysis (Primer 5 v5.2.4). Spearman’s correlation analysis revealed that there were no significant correlations between abundance and biomass of ichthyofauna and selected physico-chemical and biological variables other than salinity (P>0.05 in all other cases). There were two distinct spatial patterns in the distribution of the larger ichthyofauna (>50mm SL). These corresponded to a grouping associated with the mouth region and a grouping associated with the remaining regions of the estuary. Stable isotope analysis indicated that the primary source of carbon utilised by the ichthyofauna of the Kasouga estuary was derived from the channel, most likely microphytobenthic algae. The contributions of the riparian and salt marsh vegetation to the total carbon flow appear to be minimal.
- Full Text:
- Date Issued: 2005
Promotion of liberal values in South African foreign policy : beyond the structural imperatives of the international system?
- Authors: Mkalipi, Zanethemba
- Date: 2002
- Subjects: South Africa -- Foreign relations
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2865 , http://hdl.handle.net/10962/d1007662 , South Africa -- Foreign relations
- Description: The end of the Cold War in the early 1990s led to a multilateral international system no longer divided by contending forces of capitalism and communism. In the context of South Africa, the end of the Cold War occurred at a juncture where the apartheid government was being challenged by pro-democracy forces that have fought against it for decades. The developments in the international system and in the country led to South Africa adopting universal liberal values not only in its constitution, but also in its international relations. Foreign policy documents and statements by the ministry of Foreign Affairs also reflected the country's aspiration of becoming a mediator, a facilitator for democracy and a peacemaker especially in the context of Africa. International expectation mounted as South Africa was perceived as possessing the capacity to act in a manner that advances democratic values and which gives voice to the weak nations of the world. However, the aura of a post-apartheid South Africa that would act not only in its interest, but also in the interest of the world community never fully materialised. South Africa failed to act in a manner consistent with its stated commitment to democratic values when it recognised Peoples Republic of China, an undemocratic and repressive government. It also marched into Lesotho in 1998, resulting in the destabilisation of this tiny Southern African country. These events led to an increasing criticism of the South African government. Some argued that South Africa was still inexperienced given its recent emergence as a world player. Others blamed the inconsistency on a too broad and ambitious foreign policy that set itself for failure. This study seeks to contribute to the conceptual understanding of the debate regarding the ambiguous nature of South Africa's foreign policy behaviour. It situates the conceptualisation of South Africa's foreign policy within the predominant debates in international relations between realism, political structuralism and pluralism. Firstly, it holds that the end of the Cold War and ascendancy of globalist conceptions of international relations did not lead to the inadequacy of political structuralism as an organising framework. Secondly, it attempts to clarify the gap between South Africa's foreign policy and foreign policy behaviour by employing the assumptions advanced by political structuralism, Thirdly, a case study of South Africa's foreign policy towards China, Lesotho, the Great Lakes and Swaziland is carried out. Here it is demonstrated that the ambiguities of South Africa's foreign policy are a function of the constraints imposed by the political and economic structure of the international system, It draws its conclusion by providing methodological recommendations to South Africa's foreign policy makers and future researchers in the field of foreign policy analysis.
- Full Text:
- Date Issued: 2002
- Authors: Mkalipi, Zanethemba
- Date: 2002
- Subjects: South Africa -- Foreign relations
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2865 , http://hdl.handle.net/10962/d1007662 , South Africa -- Foreign relations
- Description: The end of the Cold War in the early 1990s led to a multilateral international system no longer divided by contending forces of capitalism and communism. In the context of South Africa, the end of the Cold War occurred at a juncture where the apartheid government was being challenged by pro-democracy forces that have fought against it for decades. The developments in the international system and in the country led to South Africa adopting universal liberal values not only in its constitution, but also in its international relations. Foreign policy documents and statements by the ministry of Foreign Affairs also reflected the country's aspiration of becoming a mediator, a facilitator for democracy and a peacemaker especially in the context of Africa. International expectation mounted as South Africa was perceived as possessing the capacity to act in a manner that advances democratic values and which gives voice to the weak nations of the world. However, the aura of a post-apartheid South Africa that would act not only in its interest, but also in the interest of the world community never fully materialised. South Africa failed to act in a manner consistent with its stated commitment to democratic values when it recognised Peoples Republic of China, an undemocratic and repressive government. It also marched into Lesotho in 1998, resulting in the destabilisation of this tiny Southern African country. These events led to an increasing criticism of the South African government. Some argued that South Africa was still inexperienced given its recent emergence as a world player. Others blamed the inconsistency on a too broad and ambitious foreign policy that set itself for failure. This study seeks to contribute to the conceptual understanding of the debate regarding the ambiguous nature of South Africa's foreign policy behaviour. It situates the conceptualisation of South Africa's foreign policy within the predominant debates in international relations between realism, political structuralism and pluralism. Firstly, it holds that the end of the Cold War and ascendancy of globalist conceptions of international relations did not lead to the inadequacy of political structuralism as an organising framework. Secondly, it attempts to clarify the gap between South Africa's foreign policy and foreign policy behaviour by employing the assumptions advanced by political structuralism, Thirdly, a case study of South Africa's foreign policy towards China, Lesotho, the Great Lakes and Swaziland is carried out. Here it is demonstrated that the ambiguities of South Africa's foreign policy are a function of the constraints imposed by the political and economic structure of the international system, It draws its conclusion by providing methodological recommendations to South Africa's foreign policy makers and future researchers in the field of foreign policy analysis.
- Full Text:
- Date Issued: 2002
The goddess, the witch and the bitch : three studies in the perception of women
- Authors: Hare, Nicola Tracy
- Date: 2001
- Subjects: Feminism in literature , Women's rights in literature , Feminism and literature , Patriarchy in literature
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10986 , http://hdl.handle.net/10948/278 , Feminism in literature , Women's rights in literature , Feminism and literature , Patriarchy in literature
- Description: In the minds of many people all over the world, women are ‘second class citizens’, standing accused of the downfall of mankind ever since Eve allegedly ate the apple. Even amongst those who do not openly denigrate women, there are many who do so in other, more subtle ways even if they are unaware of it. This study proposes to challenge such a view of women by exposing the ways in which perceptions of women are constructed by society, which frequently wants to maintain the status quo of male dominance. This study employs a feminist approach in examining this gynocentric theme, along with cultural studies which, with its focus on power relations and ways of decentring power structures, is also clearly of use. In addition, this multidisciplinary approach of cultural studies offers the possibility of studying literary texts as well as popular culture. Three specific time periods are examined, with a view to uncovering negative perceptions of women and ways that women can resist such attempts to control them. In chapter one, the focus turns to contemporary perceptions of prehistoric women and the ways that so-called ‘objective’ science has failed to represent women accurately. Similarly, ‘objective’ accounts of Goddess-worship – which frequently fail to examine this phenomenon adequately – are revisited. Alice Walker’s The Temple of My Familiar (1989) is discussed as a text which acts as a site of resistance to societally-informed perceptions. Chapter two continues this investigation by turning to the concept of the witch and its maligned association with women. Woman and witchcraft, having been associated for centuries, are investigated as a pairing which frequently results because iii of attempts to control women by androcentric society. In such situations, the practising of witchcraft can actually become a form of resistance to patriarchy. The pernicious effect of society’s need to purge itself – by witch hunts – of witches is also investigated. The Devil’s Chimney (1997) by Anne Landsman and “The prophetess” (1994) by Njabulo S. Ndebele are discussed as texts which examine fictionalised South African versions of this phenomenon. Sinead O’Connor, the Irish singer, is the ‘bitch’ discussed in chapter three. She is examined as a woman who offers strong and on-going resistance to patriarchal ways of thinking which would ‘box’ women in. This singer refuses to accept societal roles which are offered to women and so offers means of resistance to patriarchy, many of which are discussed in this chapter. This study concludes that it is the responsibility of women to resist patriarchy and to define roles for themselves. The three chapters examine various means of resistance and offer women insight into the forms of opposition they themselves can take.
- Full Text:
- Date Issued: 2001
- Authors: Hare, Nicola Tracy
- Date: 2001
- Subjects: Feminism in literature , Women's rights in literature , Feminism and literature , Patriarchy in literature
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10986 , http://hdl.handle.net/10948/278 , Feminism in literature , Women's rights in literature , Feminism and literature , Patriarchy in literature
- Description: In the minds of many people all over the world, women are ‘second class citizens’, standing accused of the downfall of mankind ever since Eve allegedly ate the apple. Even amongst those who do not openly denigrate women, there are many who do so in other, more subtle ways even if they are unaware of it. This study proposes to challenge such a view of women by exposing the ways in which perceptions of women are constructed by society, which frequently wants to maintain the status quo of male dominance. This study employs a feminist approach in examining this gynocentric theme, along with cultural studies which, with its focus on power relations and ways of decentring power structures, is also clearly of use. In addition, this multidisciplinary approach of cultural studies offers the possibility of studying literary texts as well as popular culture. Three specific time periods are examined, with a view to uncovering negative perceptions of women and ways that women can resist such attempts to control them. In chapter one, the focus turns to contemporary perceptions of prehistoric women and the ways that so-called ‘objective’ science has failed to represent women accurately. Similarly, ‘objective’ accounts of Goddess-worship – which frequently fail to examine this phenomenon adequately – are revisited. Alice Walker’s The Temple of My Familiar (1989) is discussed as a text which acts as a site of resistance to societally-informed perceptions. Chapter two continues this investigation by turning to the concept of the witch and its maligned association with women. Woman and witchcraft, having been associated for centuries, are investigated as a pairing which frequently results because iii of attempts to control women by androcentric society. In such situations, the practising of witchcraft can actually become a form of resistance to patriarchy. The pernicious effect of society’s need to purge itself – by witch hunts – of witches is also investigated. The Devil’s Chimney (1997) by Anne Landsman and “The prophetess” (1994) by Njabulo S. Ndebele are discussed as texts which examine fictionalised South African versions of this phenomenon. Sinead O’Connor, the Irish singer, is the ‘bitch’ discussed in chapter three. She is examined as a woman who offers strong and on-going resistance to patriarchal ways of thinking which would ‘box’ women in. This singer refuses to accept societal roles which are offered to women and so offers means of resistance to patriarchy, many of which are discussed in this chapter. This study concludes that it is the responsibility of women to resist patriarchy and to define roles for themselves. The three chapters examine various means of resistance and offer women insight into the forms of opposition they themselves can take.
- Full Text:
- Date Issued: 2001
Metabolic responses to in vitro zinc supplementation
- Authors: Steel, Helen Carolyn
- Date: 1994
- Subjects: Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4040 , http://hdl.handle.net/10962/d1004101 , Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Description: The present study was carried out to determine the effects and possible mechanism of action of zinc supplementation on the in vitro growth of malignant murine melanoma (B16) and non-malignant monkey kidney (LLCMK) cells. Cell culture studies showed that zinc supplementation significantly inhibited B16 growth at all the concentrations studied (1, 3, 5 and lOμg/ml). Zinc was also found to inhibit the growth of the LLCMK cells, although to a lesser extent than the B16 cells. Possible evidence of mobilisation of the essential fatty acids from the membrane phospholipid stores was noted in both cell types. This effect was, however, greater in the B16 cells. Δ⁶-desaturase activity was found to be significantly lower in the B16 cells than in the LLCMK cells (p ≥ 0.05). Zinc supplementation resulted in an increase in the enzymes activity in the LLCMK cells and, at high concentrations, in the B16 cells. An estimation of elongase and Δ⁶-desaturase activity with zinc supplementation indicated that zinc had little or no effect on the activity of these enzymes. B16 cells were found to have higher levels of free radicals than the LLCMK cells. Zinc supplementation resulted in increased free radical formation in the B16 cells, while no effect was observed in the LLCMK cells. Lipid peroxidation increased in both cell types with increased zinc concentrations. The observed effect of zinc supplementation on cell growth may involve these elevated levels of lipid peroxides. CycIo-oxygenase activity was found to be greater in the B16 cells than the LLCMK cells. The activity of the enzyme increased with higher concentrations of zinc (lOμg/ml) in both cell types. Prostaglandin E, levels were found to be lower in the B16 cells compared to the LLCMK cells. The levels of prostaglandin E, in both cell types appeared to be dependent on the levels of the polyunsaturated fatty acid precursors to the prostaglandins. Zinc was found to inhibit the activity of the enzyme adenylate cyclase in both cell types. The cAMP levels in the LLCMK cells were also found to decrease with zinc supplementation. In the case of the B16 cells, cAMP levels increased at low concentrations of zinc despite a decrease in adenyl ate cyclase activity, suggesting a possible inhibition of cAMP phosphodiesterase activity at these concentrations of zinc. It is concluded that although zinc supplementation does have an effect on cell growth, this effect is not mediated through the activation of adenylate cyclase by the prostaglandins resulting in elevated levels of cAMP. A possible mechanism involving lipid peroxidation is proposed.
- Full Text:
- Date Issued: 1994
- Authors: Steel, Helen Carolyn
- Date: 1994
- Subjects: Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4040 , http://hdl.handle.net/10962/d1004101 , Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Description: The present study was carried out to determine the effects and possible mechanism of action of zinc supplementation on the in vitro growth of malignant murine melanoma (B16) and non-malignant monkey kidney (LLCMK) cells. Cell culture studies showed that zinc supplementation significantly inhibited B16 growth at all the concentrations studied (1, 3, 5 and lOμg/ml). Zinc was also found to inhibit the growth of the LLCMK cells, although to a lesser extent than the B16 cells. Possible evidence of mobilisation of the essential fatty acids from the membrane phospholipid stores was noted in both cell types. This effect was, however, greater in the B16 cells. Δ⁶-desaturase activity was found to be significantly lower in the B16 cells than in the LLCMK cells (p ≥ 0.05). Zinc supplementation resulted in an increase in the enzymes activity in the LLCMK cells and, at high concentrations, in the B16 cells. An estimation of elongase and Δ⁶-desaturase activity with zinc supplementation indicated that zinc had little or no effect on the activity of these enzymes. B16 cells were found to have higher levels of free radicals than the LLCMK cells. Zinc supplementation resulted in increased free radical formation in the B16 cells, while no effect was observed in the LLCMK cells. Lipid peroxidation increased in both cell types with increased zinc concentrations. The observed effect of zinc supplementation on cell growth may involve these elevated levels of lipid peroxides. CycIo-oxygenase activity was found to be greater in the B16 cells than the LLCMK cells. The activity of the enzyme increased with higher concentrations of zinc (lOμg/ml) in both cell types. Prostaglandin E, levels were found to be lower in the B16 cells compared to the LLCMK cells. The levels of prostaglandin E, in both cell types appeared to be dependent on the levels of the polyunsaturated fatty acid precursors to the prostaglandins. Zinc was found to inhibit the activity of the enzyme adenylate cyclase in both cell types. The cAMP levels in the LLCMK cells were also found to decrease with zinc supplementation. In the case of the B16 cells, cAMP levels increased at low concentrations of zinc despite a decrease in adenyl ate cyclase activity, suggesting a possible inhibition of cAMP phosphodiesterase activity at these concentrations of zinc. It is concluded that although zinc supplementation does have an effect on cell growth, this effect is not mediated through the activation of adenylate cyclase by the prostaglandins resulting in elevated levels of cAMP. A possible mechanism involving lipid peroxidation is proposed.
- Full Text:
- Date Issued: 1994
The geology, mineralogy and chemistry of the Grahamstown clay deposits
- Authors: Smuts, Johann, 1951-
- Date: 1984
- Subjects: Clay minerals -- South Africa -- Grahamstown , Mineralogy -- South Africa -- Grahamstown , Geochemistry -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5080 , http://hdl.handle.net/10962/d1015969
- Description: The Grahamstown clay deposits extend in a broad belt from 26°23 to 26°50 East longitude and from 33°15 to 33°22 South latitude along two distinct geomorphological features, the Grahamstown Peneplane (650 m) and the Coastal Plain (520m). The clay deposits traverse four different lithologies including the Bokkeveld Shale, Witteberg Shale, Dwyka Tillite and Ecca Shale. The two planes invariably have a covering of silcrete which is also present over most of the clay deposits except where erosion has taken place. X-ray fluorescence analysis shows that chemically there is a fairly wide variation between and witnin the deposits. The greatest variation is in the Si0₂/Al₂0₃ ratio which appears to be controlled by the parent lithology and to some extent by the amount of leaching. K²0 shows an increase in concentration with depth and therefore indicates the limits of hydrolysis and leaching and of the clay. X-ray diffraction study shows the Peneplane and Coastal Plain deposits to be quite distinct. The Peneplane deposits consist of kaolinite, illite and quartz and the Coastal Plain deposits of kaolinite, illite, quartz and pyrophyllite. The presence of pyrophyllite is not fully understood as there is no indication of major faulting, metamorphism or pyrophyllite in the parent rock. The pyrophyllite most probably represents a transformation product of kaolinite. The kaolinite from the various deposits shows a considerable variation in crystallinity in both the X-ray diffraction traces and electron photomicrographs. The most poorly crystalline kaolinites are from the Coastal Plain deposits and the difference in crystallinity is most probably due to differences in the degree of hydrolysis and the parent rock material in the case of the tillite. Genetically all of the deposits are residual types generated by hydrolysis and subsequent leaching of micas and feldspars. The principal elements leached are silicon, iron and potassium. The hydrolysis and leaching took place over a long period of time in the flat lying areas of the Peneplane and Coastal Plain. The deposits are exploited economically and the clay is used principally in the tile, pottery and whiteware industries with some usage in the paper, refractory and brickmaking industries. The price commanded by raw kaolin is not very high and as a result the clay industry in Grahamstown is not as viable economically as it could be.
- Full Text:
- Date Issued: 1984
- Authors: Smuts, Johann, 1951-
- Date: 1984
- Subjects: Clay minerals -- South Africa -- Grahamstown , Mineralogy -- South Africa -- Grahamstown , Geochemistry -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5080 , http://hdl.handle.net/10962/d1015969
- Description: The Grahamstown clay deposits extend in a broad belt from 26°23 to 26°50 East longitude and from 33°15 to 33°22 South latitude along two distinct geomorphological features, the Grahamstown Peneplane (650 m) and the Coastal Plain (520m). The clay deposits traverse four different lithologies including the Bokkeveld Shale, Witteberg Shale, Dwyka Tillite and Ecca Shale. The two planes invariably have a covering of silcrete which is also present over most of the clay deposits except where erosion has taken place. X-ray fluorescence analysis shows that chemically there is a fairly wide variation between and witnin the deposits. The greatest variation is in the Si0₂/Al₂0₃ ratio which appears to be controlled by the parent lithology and to some extent by the amount of leaching. K²0 shows an increase in concentration with depth and therefore indicates the limits of hydrolysis and leaching and of the clay. X-ray diffraction study shows the Peneplane and Coastal Plain deposits to be quite distinct. The Peneplane deposits consist of kaolinite, illite and quartz and the Coastal Plain deposits of kaolinite, illite, quartz and pyrophyllite. The presence of pyrophyllite is not fully understood as there is no indication of major faulting, metamorphism or pyrophyllite in the parent rock. The pyrophyllite most probably represents a transformation product of kaolinite. The kaolinite from the various deposits shows a considerable variation in crystallinity in both the X-ray diffraction traces and electron photomicrographs. The most poorly crystalline kaolinites are from the Coastal Plain deposits and the difference in crystallinity is most probably due to differences in the degree of hydrolysis and the parent rock material in the case of the tillite. Genetically all of the deposits are residual types generated by hydrolysis and subsequent leaching of micas and feldspars. The principal elements leached are silicon, iron and potassium. The hydrolysis and leaching took place over a long period of time in the flat lying areas of the Peneplane and Coastal Plain. The deposits are exploited economically and the clay is used principally in the tile, pottery and whiteware industries with some usage in the paper, refractory and brickmaking industries. The price commanded by raw kaolin is not very high and as a result the clay industry in Grahamstown is not as viable economically as it could be.
- Full Text:
- Date Issued: 1984
An investigation of compounds occurring in leonotis species
- Authors: Naidu, Krishna
- Date: 1970
- Subjects: Leonotis -- Analysis , Chemistry -- Analytic , Nuclear magnetic resonance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3852 , http://hdl.handle.net/10962/d1012934
- Description: Two labdane diterpenoids 8-hydroxymarrubiin and leonitin were isolated from Leonotis dysophylla (Benth.) and Leonotis leonitis respectively. Spectral studies of 8-hydroxymarrubiin, C₂₀H₂₈ O₅ʻ showed the presence of a β -substituted furan, a Ϫ-lactone, three tertiary methyl groups and tertiary hydroxyl group (s). The NMR spectrum of 8-hydroxymarrubiin and marrubiin C₂₀H₂₈O₄ʻ were almost identical with the exception of the C₁₇- methyl group which appeared as a singlet in 8-hydroxymarrubiin and as a doublet in marrubiin. The extra oxygen atom was therefore assumed to be present as a hydroxyl group substituted in the C₈₋ position. This was further confirmed by the formation of an epoxide and a Ϫό-dilactone. Leonitin, C₂₀H₂₈O₇ʻ was shown by spectral and chemical evidence to be a diterpenoid dilactone possessing an ester function and an ether linkage. Comparison of the NMR spectra of compound X and leonitin suggested that the acetoxy function occurs in the C₂₀- position. This was further supported by the formation of a 'Ϫό -dilactone. The absence of a β -furan moiety was apparent from chemical and spectral evidence, A structure for leonitin is proposed and aspects of its stereochemistry discussed.
- Full Text:
- Date Issued: 1970
- Authors: Naidu, Krishna
- Date: 1970
- Subjects: Leonotis -- Analysis , Chemistry -- Analytic , Nuclear magnetic resonance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3852 , http://hdl.handle.net/10962/d1012934
- Description: Two labdane diterpenoids 8-hydroxymarrubiin and leonitin were isolated from Leonotis dysophylla (Benth.) and Leonotis leonitis respectively. Spectral studies of 8-hydroxymarrubiin, C₂₀H₂₈ O₅ʻ showed the presence of a β -substituted furan, a Ϫ-lactone, three tertiary methyl groups and tertiary hydroxyl group (s). The NMR spectrum of 8-hydroxymarrubiin and marrubiin C₂₀H₂₈O₄ʻ were almost identical with the exception of the C₁₇- methyl group which appeared as a singlet in 8-hydroxymarrubiin and as a doublet in marrubiin. The extra oxygen atom was therefore assumed to be present as a hydroxyl group substituted in the C₈₋ position. This was further confirmed by the formation of an epoxide and a Ϫό-dilactone. Leonitin, C₂₀H₂₈O₇ʻ was shown by spectral and chemical evidence to be a diterpenoid dilactone possessing an ester function and an ether linkage. Comparison of the NMR spectra of compound X and leonitin suggested that the acetoxy function occurs in the C₂₀- position. This was further supported by the formation of a 'Ϫό -dilactone. The absence of a β -furan moiety was apparent from chemical and spectral evidence, A structure for leonitin is proposed and aspects of its stereochemistry discussed.
- Full Text:
- Date Issued: 1970
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