Biochemical characterisation of Pfj2, a Plasmodium falciparum heat shock protein 40 chaperone potentially involved in protein quality control in the endoplasmic reticulum
- Authors: Afolayan, Omolola Folasade
- Date: 2013
- Subjects: Plasmodium falciparum Endoplasmic reticulum Heat shock proteins Malaria , Mosquito-borne infectious disease
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3883 , http://hdl.handle.net/10962/d1001617
- Description: Plasmodium falciparum is a protozoan parasite that causes a severe form of malaria, a mosquito-borne infectious disease in humans. P. falciparum encodes a number of proteins to facilitate its life-cycle, including a type II heat shock protein 40 (Hsp40), Pfj2. Pfj2 shows a degree of homology to human ERdj5, a resident protein of the endoplasmic reticulum (ER) that promotes protein quality control by facilitating the degradation of misfolded proteins. The overall aim of this study was to further understand the function of Pfj2 in the P. falciparum cell by characterising it biochemically. A bioinformatic analysis of Pfj2 was carried out to enable the identification of a potential ER signal sequence and cleavage site. Furthermore, an analysis of Pfj2 protein sequence was performed to compare domain similarities and identities with typical type II Hsp40s namely, human ERdj5, S. cerevisiae Sis1, human Hsj1a and human DnaJB4. The method used included the insertion of the codon-optimised coding sequence for the processed ER form of Pfj2 into the prokaryotic expression vector, pQE30, to enable overproduction of a histidine-tagged protein. A 62 kDa His₆-Pfj2 was successfully expressed in Escherichia coli and purified using denaturing nickel affinity chromatography. ATPase assays were performed to determine the ability of His₆- Pfj2 to stimulate the chaperone activity of the ER Hsp70, also called immunoglobulin binding protein (BiP). Initial studies were conducted on readily available mammalian His₆-BiP as a control, which was shown to have an intrinsic activity of 12.07±3.92 nmolPi/min/mg. His₆- Pfj2 did not stimulate the ATPase activity of mammalian His₆-BiP, suggesting that it either could not act as a co-chaperone of mammalian His₆-BiP (specificity), or it required a misfolded substrate in the system. Therefore, ongoing studies are addressing the interaction of Pfj2 and misfolded substrates with P. falciparum BiP. The results of these studies will further our understanding of a poorly-studied parasite chaperone that represents a potential drug target for development of novel strategies for the control of a serious human disease
- Full Text:
- Date Issued: 2013
- Authors: Afolayan, Omolola Folasade
- Date: 2013
- Subjects: Plasmodium falciparum Endoplasmic reticulum Heat shock proteins Malaria , Mosquito-borne infectious disease
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3883 , http://hdl.handle.net/10962/d1001617
- Description: Plasmodium falciparum is a protozoan parasite that causes a severe form of malaria, a mosquito-borne infectious disease in humans. P. falciparum encodes a number of proteins to facilitate its life-cycle, including a type II heat shock protein 40 (Hsp40), Pfj2. Pfj2 shows a degree of homology to human ERdj5, a resident protein of the endoplasmic reticulum (ER) that promotes protein quality control by facilitating the degradation of misfolded proteins. The overall aim of this study was to further understand the function of Pfj2 in the P. falciparum cell by characterising it biochemically. A bioinformatic analysis of Pfj2 was carried out to enable the identification of a potential ER signal sequence and cleavage site. Furthermore, an analysis of Pfj2 protein sequence was performed to compare domain similarities and identities with typical type II Hsp40s namely, human ERdj5, S. cerevisiae Sis1, human Hsj1a and human DnaJB4. The method used included the insertion of the codon-optimised coding sequence for the processed ER form of Pfj2 into the prokaryotic expression vector, pQE30, to enable overproduction of a histidine-tagged protein. A 62 kDa His₆-Pfj2 was successfully expressed in Escherichia coli and purified using denaturing nickel affinity chromatography. ATPase assays were performed to determine the ability of His₆- Pfj2 to stimulate the chaperone activity of the ER Hsp70, also called immunoglobulin binding protein (BiP). Initial studies were conducted on readily available mammalian His₆-BiP as a control, which was shown to have an intrinsic activity of 12.07±3.92 nmolPi/min/mg. His₆- Pfj2 did not stimulate the ATPase activity of mammalian His₆-BiP, suggesting that it either could not act as a co-chaperone of mammalian His₆-BiP (specificity), or it required a misfolded substrate in the system. Therefore, ongoing studies are addressing the interaction of Pfj2 and misfolded substrates with P. falciparum BiP. The results of these studies will further our understanding of a poorly-studied parasite chaperone that represents a potential drug target for development of novel strategies for the control of a serious human disease
- Full Text:
- Date Issued: 2013
Uptake of liposomes into bacterial cells
- Authors: Oidu, Benjamin
- Date: 2013
- Subjects: Liposomes , Drug carriers (Pharmacy)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10165 , http://hdl.handle.net/10948/d1021010
- Description: Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. A variety of liposome formulations are presently under clinical trial exploration, while others have already been approved for clinical use. The aim of this study was to optimize liposome uptake into bacterial cells. Both gram-positive and gram-negative bacteria were used in the study as well as Candida albicans.Response surface methodology (RSM) using a central composite design (CCD) model was used to optimize liposomal formulations of carboxyfluorescien (CF) for each of the three microbes, and also the three microbes in combination namely; Staphylococcus aureus (Sa), Escherichia coli (Ec) and Candida albicans (Ca). Percentage of CF encapsulated and CF increase in Uptake were investigated with respect to two independent variables that were, cholesterol (CHOL) and stearylamine (SA) content. Design Expert 8 was used for the purpose of finding the combination of independent variables that would yield an optimal formulation for each microbe and the three microbes in combination. The model selected by the software managed to reasonably correlate the predicted models to the experimental data. Encapsulation of carboxyfluorescien (CF) into a liposome formulation enhanced its uptake by Staphylococcus aureus and Escherichia coli as well as Candida albicans. This was evident in the increase in CF uptake when the uptake rate of free CF was compared with that of liposomal CF.
- Full Text:
- Date Issued: 2013
- Authors: Oidu, Benjamin
- Date: 2013
- Subjects: Liposomes , Drug carriers (Pharmacy)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10165 , http://hdl.handle.net/10948/d1021010
- Description: Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. A variety of liposome formulations are presently under clinical trial exploration, while others have already been approved for clinical use. The aim of this study was to optimize liposome uptake into bacterial cells. Both gram-positive and gram-negative bacteria were used in the study as well as Candida albicans.Response surface methodology (RSM) using a central composite design (CCD) model was used to optimize liposomal formulations of carboxyfluorescien (CF) for each of the three microbes, and also the three microbes in combination namely; Staphylococcus aureus (Sa), Escherichia coli (Ec) and Candida albicans (Ca). Percentage of CF encapsulated and CF increase in Uptake were investigated with respect to two independent variables that were, cholesterol (CHOL) and stearylamine (SA) content. Design Expert 8 was used for the purpose of finding the combination of independent variables that would yield an optimal formulation for each microbe and the three microbes in combination. The model selected by the software managed to reasonably correlate the predicted models to the experimental data. Encapsulation of carboxyfluorescien (CF) into a liposome formulation enhanced its uptake by Staphylococcus aureus and Escherichia coli as well as Candida albicans. This was evident in the increase in CF uptake when the uptake rate of free CF was compared with that of liposomal CF.
- Full Text:
- Date Issued: 2013
Polyunsaturated fatty acid metabolism and effects on colon cancer cell biology in vitro.
- Authors: Bulcao, Candice
- Date: 2013
- Subjects: Unsaturated fatty acids , Unsaturated fatty acids in human nutrition , Colon (Anatomy)-- Cancer , Cancer -- Nutritional aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4137 , http://hdl.handle.net/10962/d1016128
- Description: Colon cancer is a leading cause of cancer related deaths worldwide. Lifestyle factors such as diet and exercise have been implicated as important agents in colon cancer development and progression. Epidemiological, in vivo and in vitro studies have found that n-3 polyunsaturated fatty acids (PUFAs) reduce colon carcinoma. The role of n-6 PUFAs remains a controversial topic, with studies indicating both promoting and preventing capabilities published. In order to better understand the effects of PUFAs on colon carcinoma, it is important to have an understanding of how they will be broken down in the body. During this study, in silico metabolism of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) predicted the formation of hydroxy-, di-hydroxy- and epoxy-FAs. A gas chromatography-mass spectrometry method was developed and validated for the detection of these PUFAs and their cytochrome P450 (CYP) metabolites. A human liver microsomal system for the in vitro metabolism of EPA, DHA and AA was optimised in terms of microsomal and PUFA concentration. The system resulted in the metabolism of the positive control, lauric acid, to 12-hydroxy-lauric acid but was unable to metabolise the PUFAs of interest. EPA, DHA and AA reduced cell viability in the colon carcinoma cell lines SW480 and SW620 in the micromolar concentration range (25 – 200 μM). The CYP epoxidation metabolite of EPA, 17, 18-epoxyeicosatetraenoic acid (17, 18-EpETE) resulted in a significant reduction in SW480 cell viability relative to the parent compound at lower concentrations (25 and 50 μM). Annexin V apoptosis analysis revealed that EPA and 17, 18- EpETE did not result in apoptosis in SW480 cells at a concentration of 25 μM and over an incubation period of 24 hours. A significant reduction in reactive oxygen species production was seen in SW480 cells after incubation with 25 μM 17, 18-EpETE for 24 hours. EPA and 17, 18-EpETE were implicated in the reduction of colon cancer metastasis since they were able to reduce SW480 migration and anchorage independent cell growth. These results indicate that the dietary intake of EPA, DHA and AA may be beneficial to one’s health due to the negative effects that these PUFAs had on colon carcinoma. Future studies are needed to confirm these benefits and compare the effects of the PUFAs to their CYP-metabolites.
- Full Text:
- Date Issued: 2013
- Authors: Bulcao, Candice
- Date: 2013
- Subjects: Unsaturated fatty acids , Unsaturated fatty acids in human nutrition , Colon (Anatomy)-- Cancer , Cancer -- Nutritional aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4137 , http://hdl.handle.net/10962/d1016128
- Description: Colon cancer is a leading cause of cancer related deaths worldwide. Lifestyle factors such as diet and exercise have been implicated as important agents in colon cancer development and progression. Epidemiological, in vivo and in vitro studies have found that n-3 polyunsaturated fatty acids (PUFAs) reduce colon carcinoma. The role of n-6 PUFAs remains a controversial topic, with studies indicating both promoting and preventing capabilities published. In order to better understand the effects of PUFAs on colon carcinoma, it is important to have an understanding of how they will be broken down in the body. During this study, in silico metabolism of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) predicted the formation of hydroxy-, di-hydroxy- and epoxy-FAs. A gas chromatography-mass spectrometry method was developed and validated for the detection of these PUFAs and their cytochrome P450 (CYP) metabolites. A human liver microsomal system for the in vitro metabolism of EPA, DHA and AA was optimised in terms of microsomal and PUFA concentration. The system resulted in the metabolism of the positive control, lauric acid, to 12-hydroxy-lauric acid but was unable to metabolise the PUFAs of interest. EPA, DHA and AA reduced cell viability in the colon carcinoma cell lines SW480 and SW620 in the micromolar concentration range (25 – 200 μM). The CYP epoxidation metabolite of EPA, 17, 18-epoxyeicosatetraenoic acid (17, 18-EpETE) resulted in a significant reduction in SW480 cell viability relative to the parent compound at lower concentrations (25 and 50 μM). Annexin V apoptosis analysis revealed that EPA and 17, 18- EpETE did not result in apoptosis in SW480 cells at a concentration of 25 μM and over an incubation period of 24 hours. A significant reduction in reactive oxygen species production was seen in SW480 cells after incubation with 25 μM 17, 18-EpETE for 24 hours. EPA and 17, 18-EpETE were implicated in the reduction of colon cancer metastasis since they were able to reduce SW480 migration and anchorage independent cell growth. These results indicate that the dietary intake of EPA, DHA and AA may be beneficial to one’s health due to the negative effects that these PUFAs had on colon carcinoma. Future studies are needed to confirm these benefits and compare the effects of the PUFAs to their CYP-metabolites.
- Full Text:
- Date Issued: 2013
A standardised protocol for roadkill detection and the determinants of roadkill in the greater Mapungubwe Transfrontier Conservation Area, Limpopo Province, South Africa
- Authors: Collinson, Wendy Jane
- Date: 2013
- Subjects: Roadkill -- South Africa -- Mapungubwe Site , Traffic safety and wildlife -- South Africa -- Mapungubwe Site
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5606 , http://hdl.handle.net/10962/d1002056 , Roadkill -- South Africa -- Mapungubwe Site , Traffic safety and wildlife -- South Africa -- Mapungubwe Site
- Description: Despite evidence suggesting that road traffic is a major threat to biodiversity loss, very little is known about its actual impact on wildlife populations in South Africa. Globally, road density and traffic volumes are increasing, and although huge budgets are devoted to the construction and upgrading of roads, there is little or no allocation to mitigation measures for protecting fauna in most countries, particularly Africa. Further, no global standardised protocol exists for the rapid assessment of roadkill or the most economical and efficient approach for assessing roadkill rates. Using vehicle field trials, the reliability of detecting artificially deployed roadkill was assessed. Roadkill detection rates decreased significantly at speeds >50 km/h and were also significantly influenced by light conditions (i.e. detection success was greater when the sun was high) and the position of the roadkill on the road (i.e. smaller roadkill on verges were often missed). These results suggest that roadkill sampling was most effective between 1.5 hours after dawn and 1.5 hours before dusk and that driving at slower speeds (<50 km.h⁻ₑ) was required to detect roadkill. This protocol was implemented across three ecological seasons on a 100 km paved road and a 20 km unpaved road in the Greater Mapungubwe Transfrontier Conservation Area, Limpopo Province, South Africa. Driven daily over a 120-day period (three periods consisting each of 40 days), a total of 1,027 roadkill were recorded. These comprised 162 species from all terrestrial vertebrate groups with birds being the most commonly encountered roadkill (50% of all incidents). The high numbers of vertebrates identified as roadkill suggests that road traffic could have potentially unsustainable impacts on wildlife populations and hence the biodiversity of the area. Seventeen variables were identified as possible determinants of roadkill occurrence with season, rainfall, minimum and maximum temperature, habitat type, grass height, grass density, fence type and vehicle type significantly influencing roadkill numbers. Significantly more roadkill were detected on the paved road (9.91/100km) than on the unpaved road (1.8/100km) probably because of greater traffic volumes and the increased speed that vehicles travelled on the paved road. Warmer temperatures and increased rainfall in the preceding 24 hours also increased road mortality numbers as animals tended to become more active during these times. Interestingly, more roadkill was detected in open roadside habitats compared to dense roadside habitats on both the paved and unpaved roads and when grass on the roadside verge was of intermediate height. Open habitat possibly may provide a natural corridor for wildlife which ultimately end up on the road. Roadkill numbers increased when certain other physical barriers, such as cattle fences, were present, probably because these barriers were more penetrable than electric fencing. A series of mitigation measures are proposed to reduce the impacts of roads on wildlife in South Africa. These mitigation measures highlight the need to address the balance between the development of a country’s transport infrastructure and the conservation of its fauna. It is important that research on the impacts of roads becomes standardised to enable robust statistical comparisons which will provide a greater understanding of the potential threats to vertebrate biodiversity
- Full Text:
- Date Issued: 2013
- Authors: Collinson, Wendy Jane
- Date: 2013
- Subjects: Roadkill -- South Africa -- Mapungubwe Site , Traffic safety and wildlife -- South Africa -- Mapungubwe Site
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5606 , http://hdl.handle.net/10962/d1002056 , Roadkill -- South Africa -- Mapungubwe Site , Traffic safety and wildlife -- South Africa -- Mapungubwe Site
- Description: Despite evidence suggesting that road traffic is a major threat to biodiversity loss, very little is known about its actual impact on wildlife populations in South Africa. Globally, road density and traffic volumes are increasing, and although huge budgets are devoted to the construction and upgrading of roads, there is little or no allocation to mitigation measures for protecting fauna in most countries, particularly Africa. Further, no global standardised protocol exists for the rapid assessment of roadkill or the most economical and efficient approach for assessing roadkill rates. Using vehicle field trials, the reliability of detecting artificially deployed roadkill was assessed. Roadkill detection rates decreased significantly at speeds >50 km/h and were also significantly influenced by light conditions (i.e. detection success was greater when the sun was high) and the position of the roadkill on the road (i.e. smaller roadkill on verges were often missed). These results suggest that roadkill sampling was most effective between 1.5 hours after dawn and 1.5 hours before dusk and that driving at slower speeds (<50 km.h⁻ₑ) was required to detect roadkill. This protocol was implemented across three ecological seasons on a 100 km paved road and a 20 km unpaved road in the Greater Mapungubwe Transfrontier Conservation Area, Limpopo Province, South Africa. Driven daily over a 120-day period (three periods consisting each of 40 days), a total of 1,027 roadkill were recorded. These comprised 162 species from all terrestrial vertebrate groups with birds being the most commonly encountered roadkill (50% of all incidents). The high numbers of vertebrates identified as roadkill suggests that road traffic could have potentially unsustainable impacts on wildlife populations and hence the biodiversity of the area. Seventeen variables were identified as possible determinants of roadkill occurrence with season, rainfall, minimum and maximum temperature, habitat type, grass height, grass density, fence type and vehicle type significantly influencing roadkill numbers. Significantly more roadkill were detected on the paved road (9.91/100km) than on the unpaved road (1.8/100km) probably because of greater traffic volumes and the increased speed that vehicles travelled on the paved road. Warmer temperatures and increased rainfall in the preceding 24 hours also increased road mortality numbers as animals tended to become more active during these times. Interestingly, more roadkill was detected in open roadside habitats compared to dense roadside habitats on both the paved and unpaved roads and when grass on the roadside verge was of intermediate height. Open habitat possibly may provide a natural corridor for wildlife which ultimately end up on the road. Roadkill numbers increased when certain other physical barriers, such as cattle fences, were present, probably because these barriers were more penetrable than electric fencing. A series of mitigation measures are proposed to reduce the impacts of roads on wildlife in South Africa. These mitigation measures highlight the need to address the balance between the development of a country’s transport infrastructure and the conservation of its fauna. It is important that research on the impacts of roads becomes standardised to enable robust statistical comparisons which will provide a greater understanding of the potential threats to vertebrate biodiversity
- Full Text:
- Date Issued: 2013
A systematic study of Berkheya and allies (Compositae)
- Authors: Phaliso, Ntombifikile
- Date: 2013
- Subjects: Compositae -- Africa, Southern , Daisies -- Africa, Southern , Compositae -- Phylogeny -- Africa, Southern , Compositae -- Geographical distribution -- Africa, Southern , Compositae -- Classification -- Africa, Southern , Cladistic analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4179 , http://hdl.handle.net/10962/d1003054
- Description: Berkheya Ehrh. is a genus of daisies in the tribe Arctotideae, subtribe Gorteriinae with over 80 species, most of which occur in southern Africa. This genus has centres of diversity associated with the montane regions of South Africa, including the Drakensberg Alpine Centre and Mpumalanga escarpment regions. Previous molecular and morphological studies indicate that Berkheya is paraphyletic. I present phylogenies based on nrDNA (ITS; Internal Transcribed Spacer) and cpDNA (psbA-trnH) sequence data analysed with Bayesian Inference and Parsimony. A phylogeny of combined cp- and nrDNA is also presented. These phylogenies are used to assess generic limits and to investigate the biogeographic patterns of Berkheya and its allies. The ITS phylogeny shows five well supported clades of Berkheya, two of which (Clades I and 2) are monophyletic summer rainfall region clades. Clades 3 to 5 are all paraphyletic winter rainfall clades with Cullumia occurring in the third clade, Cuspida occurring in the fourth and Didelta in Clade 5. Both psbA-trnH and combined phylogenies show concordance with the clade distribution shown in the ITS phylogeny. The ITS phylogeny was used to analyse correspondence with Roessler’s (1959) Series. It was found that the phylogeny showed considerable agreement with Roessler’s series, but B. bipinnatifida and B. spinosa of Series Speciosae may require some revision as well as taxa of monotypic series Cruciatae and Angustae. It is suggested that the latter series be merged with Cullumia species to form a single series. Some consideration should be taken to include Didelta species into Series Fruticosae as Didelta occurs in subclade 5b of Clade 5 with other Series Fruticosae taxa. Achene morphology was examined from species from each of the five clades to investigate the relationships of Berkheya and its allies, as well as to determine if there were any consistent achene features for each clade. The structure of surface cells on the fruit, the presence, absence and morphology of twin hairs as well as the structure of the pappus scales were found to be most useful in reflecting phylogenetic relationships within the clades. When compared with the clades of the ITS phylogeny, achene morphology showed consistent characters between taxa occurring in the same clades. As the most comprehensive study involving Berkheya, this phylogenenetic investigation was able to confirm that Berkheya is a paraphyletic genus with Didelta, Cullumia and Cuspida needing to be subsumed into Berkheya. An alternative classification is that taxa of Clade 5 could possibly be erected as an expanded Didelta, separate and sister to Berkheya.
- Full Text:
- Date Issued: 2013
- Authors: Phaliso, Ntombifikile
- Date: 2013
- Subjects: Compositae -- Africa, Southern , Daisies -- Africa, Southern , Compositae -- Phylogeny -- Africa, Southern , Compositae -- Geographical distribution -- Africa, Southern , Compositae -- Classification -- Africa, Southern , Cladistic analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4179 , http://hdl.handle.net/10962/d1003054
- Description: Berkheya Ehrh. is a genus of daisies in the tribe Arctotideae, subtribe Gorteriinae with over 80 species, most of which occur in southern Africa. This genus has centres of diversity associated with the montane regions of South Africa, including the Drakensberg Alpine Centre and Mpumalanga escarpment regions. Previous molecular and morphological studies indicate that Berkheya is paraphyletic. I present phylogenies based on nrDNA (ITS; Internal Transcribed Spacer) and cpDNA (psbA-trnH) sequence data analysed with Bayesian Inference and Parsimony. A phylogeny of combined cp- and nrDNA is also presented. These phylogenies are used to assess generic limits and to investigate the biogeographic patterns of Berkheya and its allies. The ITS phylogeny shows five well supported clades of Berkheya, two of which (Clades I and 2) are monophyletic summer rainfall region clades. Clades 3 to 5 are all paraphyletic winter rainfall clades with Cullumia occurring in the third clade, Cuspida occurring in the fourth and Didelta in Clade 5. Both psbA-trnH and combined phylogenies show concordance with the clade distribution shown in the ITS phylogeny. The ITS phylogeny was used to analyse correspondence with Roessler’s (1959) Series. It was found that the phylogeny showed considerable agreement with Roessler’s series, but B. bipinnatifida and B. spinosa of Series Speciosae may require some revision as well as taxa of monotypic series Cruciatae and Angustae. It is suggested that the latter series be merged with Cullumia species to form a single series. Some consideration should be taken to include Didelta species into Series Fruticosae as Didelta occurs in subclade 5b of Clade 5 with other Series Fruticosae taxa. Achene morphology was examined from species from each of the five clades to investigate the relationships of Berkheya and its allies, as well as to determine if there were any consistent achene features for each clade. The structure of surface cells on the fruit, the presence, absence and morphology of twin hairs as well as the structure of the pappus scales were found to be most useful in reflecting phylogenetic relationships within the clades. When compared with the clades of the ITS phylogeny, achene morphology showed consistent characters between taxa occurring in the same clades. As the most comprehensive study involving Berkheya, this phylogenenetic investigation was able to confirm that Berkheya is a paraphyletic genus with Didelta, Cullumia and Cuspida needing to be subsumed into Berkheya. An alternative classification is that taxa of Clade 5 could possibly be erected as an expanded Didelta, separate and sister to Berkheya.
- Full Text:
- Date Issued: 2013
Selected physiological and perceptual responses of batsmen during a simulated one day international century : impact on performance
- Authors: Pote, Lee
- Date: 2013 , 2013-04-02
- Subjects: Cricket -- Batting , Sports -- Physiological aspects , Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5097 , http://hdl.handle.net/10962/d1001650
- Description: Background: Very few studies have examined the demands of prolonged batting on physical, psychophysical and performance responses. Objective: The purpose of this study was therefore to determine the physiological and perceptual responses of batsmen scoring a simulated One Day International century. Furthermore, the impact that these responses had on batting performance were also measured. Methods: Seventeen male cricketers currently playing for Rhodes University or the country districts side, performed a simulated bating innings (BATEX©), typical of scoring a One Day international century. The BATEX© protocol consisted of six, five over stages (21 minutes each), with each stage matched to a specific phase of play where batsmen were encouraged to bat with the mindset of that phase. During stages one, three and five players ran at a “self-selected cruise pace” whereas during stages two, four and six players were required to run at maximum speed. At set intervals, selected physiological, perceptual and performance measures were recorded. Results: Most physiological responses increased and decreased accordingly with the low and high intensity stages with the exception of respiratory exchange ratio and core temperature responses. Mean physiological responses however, showed a progressive rise over time. Central ratings of perceived exertion increased as a function of intensity and duration. Sprint times got slower as the protocol progressed, while accuracy (impact accuracy) improved significantly (p<0.05) after stage one and then stabilised for the remainder of the protocol. Conclusion: The simulated batting protocol significantly impacted the physiological and perceptual responses over time. This was due to both the intensity and the duration of the work-bout. Furthermore, the increased physiological load placed on the batsmen significantly impacted the physical performance of the batsmen. An increase in sprint times (players getting slower) towards the end of the protocol may indicate the presence of physical fatigue. This physical fatigue did not however seem to impact the batsmen cognitively as accuracy improved after the first stage and then remained constant over time.
- Full Text:
- Date Issued: 2013
- Authors: Pote, Lee
- Date: 2013 , 2013-04-02
- Subjects: Cricket -- Batting , Sports -- Physiological aspects , Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5097 , http://hdl.handle.net/10962/d1001650
- Description: Background: Very few studies have examined the demands of prolonged batting on physical, psychophysical and performance responses. Objective: The purpose of this study was therefore to determine the physiological and perceptual responses of batsmen scoring a simulated One Day International century. Furthermore, the impact that these responses had on batting performance were also measured. Methods: Seventeen male cricketers currently playing for Rhodes University or the country districts side, performed a simulated bating innings (BATEX©), typical of scoring a One Day international century. The BATEX© protocol consisted of six, five over stages (21 minutes each), with each stage matched to a specific phase of play where batsmen were encouraged to bat with the mindset of that phase. During stages one, three and five players ran at a “self-selected cruise pace” whereas during stages two, four and six players were required to run at maximum speed. At set intervals, selected physiological, perceptual and performance measures were recorded. Results: Most physiological responses increased and decreased accordingly with the low and high intensity stages with the exception of respiratory exchange ratio and core temperature responses. Mean physiological responses however, showed a progressive rise over time. Central ratings of perceived exertion increased as a function of intensity and duration. Sprint times got slower as the protocol progressed, while accuracy (impact accuracy) improved significantly (p<0.05) after stage one and then stabilised for the remainder of the protocol. Conclusion: The simulated batting protocol significantly impacted the physiological and perceptual responses over time. This was due to both the intensity and the duration of the work-bout. Furthermore, the increased physiological load placed on the batsmen significantly impacted the physical performance of the batsmen. An increase in sprint times (players getting slower) towards the end of the protocol may indicate the presence of physical fatigue. This physical fatigue did not however seem to impact the batsmen cognitively as accuracy improved after the first stage and then remained constant over time.
- Full Text:
- Date Issued: 2013
Updating the ionospheric propagation factor, M(3000)F2, global model using the neural network technique and relevant geophysical input parameters
- Oronsaye, Samuel Iyen Jeffrey
- Authors: Oronsaye, Samuel Iyen Jeffrey
- Date: 2013
- Subjects: Neural networks (Computer science) , Ionospheric radio wave propagation , Ionosphere , Geophysics , Ionosondes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5434 , http://hdl.handle.net/10962/d1001609 , Neural networks (Computer science) , Ionospheric radio wave propagation , Ionosphere , Geophysics , Ionosondes
- Description: This thesis presents an update to the ionospheric propagation factor, M(3000)F2, global empirical model developed by Oyeyemi et al. (2007) (NNO). An additional aim of this research was to produce the updated model in a form that could be used within the International Reference Ionosphere (IRI) global model without adding to the complexity of the IRI. M(3000)F2 is the highest frequency at which a radio signal can be received over a distance of 3000 km after reflection in the ionosphere. The study employed the artificial neural network (ANN) technique using relevant geophysical input parameters which are known to influence the M(3000)F2 parameter. Ionosonde data from 135 ionospheric stations globally, including a number of equatorial stations, were available for this work. M(3000)F2 hourly values from 1976 to 2008, spanning all periods of low and high solar activity were used for model development and verification. A preliminary investigation was first carried out using a relatively small dataset to determine the appropriate input parameters for global M(3000)F2 parameter modelling. Inputs representing diurnal variation, seasonal variation, solar variation, modified dip latitude, longitude and latitude were found to be the optimum parameters for modelling the diurnal and seasonal variations of the M(3000)F2 parameter both on a temporal and spatial basis. The outcome of the preliminary study was applied to the overall dataset to develop a comprehensive ANN M(3000)F2 model which displays a remarkable improvement over the NNO model as well as the IRI version. The model shows 7.11% and 3.85% improvement over the NNO model as well as 13.04% and 10.05% over the IRI M(3000)F2 model, around high and low solar activity periods respectively. A comparison of the diurnal structure of the ANN and the IRI predicted values reveal that the ANN model is more effective in representing the diurnal structure of the M(3000)F2 values than the IRI M(3000)F2 model. The capability of the ANN model in reproducing the seasonal variation pattern of the M(3000)F2 values at 00h00UT, 06h00UT, 12h00UT, and l8h00UT more appropriately than the IRI version is illustrated in this work. A significant result obtained in this study is the ability of the ANN model in improving the post-sunset predicted values of the M(3000)F2 parameter which is known to be problematic to the IRI M(3000)F2 model in the low-latitude and the equatorial regions. The final M(3000)F2 model provides for an improved equatorial prediction and a simplified input space that allows for easy incorporation into the IRI model.
- Full Text:
- Date Issued: 2013
- Authors: Oronsaye, Samuel Iyen Jeffrey
- Date: 2013
- Subjects: Neural networks (Computer science) , Ionospheric radio wave propagation , Ionosphere , Geophysics , Ionosondes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5434 , http://hdl.handle.net/10962/d1001609 , Neural networks (Computer science) , Ionospheric radio wave propagation , Ionosphere , Geophysics , Ionosondes
- Description: This thesis presents an update to the ionospheric propagation factor, M(3000)F2, global empirical model developed by Oyeyemi et al. (2007) (NNO). An additional aim of this research was to produce the updated model in a form that could be used within the International Reference Ionosphere (IRI) global model without adding to the complexity of the IRI. M(3000)F2 is the highest frequency at which a radio signal can be received over a distance of 3000 km after reflection in the ionosphere. The study employed the artificial neural network (ANN) technique using relevant geophysical input parameters which are known to influence the M(3000)F2 parameter. Ionosonde data from 135 ionospheric stations globally, including a number of equatorial stations, were available for this work. M(3000)F2 hourly values from 1976 to 2008, spanning all periods of low and high solar activity were used for model development and verification. A preliminary investigation was first carried out using a relatively small dataset to determine the appropriate input parameters for global M(3000)F2 parameter modelling. Inputs representing diurnal variation, seasonal variation, solar variation, modified dip latitude, longitude and latitude were found to be the optimum parameters for modelling the diurnal and seasonal variations of the M(3000)F2 parameter both on a temporal and spatial basis. The outcome of the preliminary study was applied to the overall dataset to develop a comprehensive ANN M(3000)F2 model which displays a remarkable improvement over the NNO model as well as the IRI version. The model shows 7.11% and 3.85% improvement over the NNO model as well as 13.04% and 10.05% over the IRI M(3000)F2 model, around high and low solar activity periods respectively. A comparison of the diurnal structure of the ANN and the IRI predicted values reveal that the ANN model is more effective in representing the diurnal structure of the M(3000)F2 values than the IRI M(3000)F2 model. The capability of the ANN model in reproducing the seasonal variation pattern of the M(3000)F2 values at 00h00UT, 06h00UT, 12h00UT, and l8h00UT more appropriately than the IRI version is illustrated in this work. A significant result obtained in this study is the ability of the ANN model in improving the post-sunset predicted values of the M(3000)F2 parameter which is known to be problematic to the IRI M(3000)F2 model in the low-latitude and the equatorial regions. The final M(3000)F2 model provides for an improved equatorial prediction and a simplified input space that allows for easy incorporation into the IRI model.
- Full Text:
- Date Issued: 2013
Medicinal properties of some plants used for the treatment of skin disorders in the O. R. Tambo and Amathole Municipalities of the Eastern Cape Province, South Africa
- Authors: Mahachi, Josia
- Date: 2013
- Subjects: Medicinal plants -- Skin -- Diseases -- Treatment , South Africa -- Eastern Cape Province
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18487 , http://hdl.handle.net/11260/101
- Description: The use of medicinal plants for treatment of skin infections and improvement of skin tone was assessed. The study covered Amathole and OR Tambo municipalities of the Eastern Cape Province of South Africa. The study sought to identify and document some medicinal plants which are used by the indigenous people on the skin, evaluate some biological properties which attribute to their use for therapeutic use. This report provides ethnobotanical data on some plant which were identified. Six medicinal plants (Kniphofia drepanophylla, Gnidia capitata, Hypoxis hemerocallidea, Syzgium cordatum, Macaranga capensis and Protorhus longifolia) which were implicated for treatment of skin diseases were screened for their antibacterial and antioxidant properties. Guided questionnaires were used to interview and gather ethnobotanical information from the traditional healers. Members of the communities which were indicated to be knowledgeable on use of medicinal plants in the areas were visited and interviewed. The results revealed that a total of 45 plant species distributed in 41 Genera belonging to 28 Families are used for treatment of skin infections and improvement of skin texture. The plant medicines were reported to be used as remedies against common skin problem such as wounds, pimples, acnes and itches. Some were reported to have anti-inflammatory effect on the skin while other were reported to oil dry skin and prevent skin dryness and dry eczematous conditions. Others like Cassipourea flanaganii, and Spirostachys africana were commonly used to enlighten skin and protect skin from ultra-violet radiation. The most common mode of preparation of these medicinal plants was pastes or decoctions. Sometimes crushed plant materials were put in bathing water or boiled and steamed on affected parts. It was reported that mixing pastes with oil, animal fat and milk improve medicinal properties. Water, methanol and acetone extracts of K. drepanophylla, G. capitata, H. hemerocallidea, S. cordatum, M. capensis and P. longifolia were screened against five strains of Gram negative bacteria. The results revealed that water extracts from five plant species inhibited two or more strains of bacteria with the most common minimum inhibitory concentrations (MICs) ranging between 5,0 to 10,0 mg/ml with the exception of aqueous extracts of K. drepanophylla which failed to inhibit all strains of bacteria. The screening of methanol extract of these plants for antioxidant and free radical activity revealed a significant activity with 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) free radical (DPPH). The extracts of P. longifolia, G. capitata, M. capensis, S. cordutum and H. hemerocallidea showed significantly higher free radical scavenging activity with IC50 of ranging from about 11.0 to 41.2 μg/ ml while the IC50 value for K. drepanophylla could not be determined at 100 μg/ ml. Generally the study showed that medicinal plants still play a very important role in the health care delivery system, especially in the O R Tambo and Amathole municipalities of the Eastern Cape. Botanical medicine remains pivotal in the treatment of skin ailments and improvement of the skin tone.
- Full Text:
- Date Issued: 2013
- Authors: Mahachi, Josia
- Date: 2013
- Subjects: Medicinal plants -- Skin -- Diseases -- Treatment , South Africa -- Eastern Cape Province
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18487 , http://hdl.handle.net/11260/101
- Description: The use of medicinal plants for treatment of skin infections and improvement of skin tone was assessed. The study covered Amathole and OR Tambo municipalities of the Eastern Cape Province of South Africa. The study sought to identify and document some medicinal plants which are used by the indigenous people on the skin, evaluate some biological properties which attribute to their use for therapeutic use. This report provides ethnobotanical data on some plant which were identified. Six medicinal plants (Kniphofia drepanophylla, Gnidia capitata, Hypoxis hemerocallidea, Syzgium cordatum, Macaranga capensis and Protorhus longifolia) which were implicated for treatment of skin diseases were screened for their antibacterial and antioxidant properties. Guided questionnaires were used to interview and gather ethnobotanical information from the traditional healers. Members of the communities which were indicated to be knowledgeable on use of medicinal plants in the areas were visited and interviewed. The results revealed that a total of 45 plant species distributed in 41 Genera belonging to 28 Families are used for treatment of skin infections and improvement of skin texture. The plant medicines were reported to be used as remedies against common skin problem such as wounds, pimples, acnes and itches. Some were reported to have anti-inflammatory effect on the skin while other were reported to oil dry skin and prevent skin dryness and dry eczematous conditions. Others like Cassipourea flanaganii, and Spirostachys africana were commonly used to enlighten skin and protect skin from ultra-violet radiation. The most common mode of preparation of these medicinal plants was pastes or decoctions. Sometimes crushed plant materials were put in bathing water or boiled and steamed on affected parts. It was reported that mixing pastes with oil, animal fat and milk improve medicinal properties. Water, methanol and acetone extracts of K. drepanophylla, G. capitata, H. hemerocallidea, S. cordatum, M. capensis and P. longifolia were screened against five strains of Gram negative bacteria. The results revealed that water extracts from five plant species inhibited two or more strains of bacteria with the most common minimum inhibitory concentrations (MICs) ranging between 5,0 to 10,0 mg/ml with the exception of aqueous extracts of K. drepanophylla which failed to inhibit all strains of bacteria. The screening of methanol extract of these plants for antioxidant and free radical activity revealed a significant activity with 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) free radical (DPPH). The extracts of P. longifolia, G. capitata, M. capensis, S. cordutum and H. hemerocallidea showed significantly higher free radical scavenging activity with IC50 of ranging from about 11.0 to 41.2 μg/ ml while the IC50 value for K. drepanophylla could not be determined at 100 μg/ ml. Generally the study showed that medicinal plants still play a very important role in the health care delivery system, especially in the O R Tambo and Amathole municipalities of the Eastern Cape. Botanical medicine remains pivotal in the treatment of skin ailments and improvement of the skin tone.
- Full Text:
- Date Issued: 2013
The effect of in vitro digestion on selected biological activities of Hypoxis sobolifera corms
- Authors: Van Rooyen, Anzel
- Date: 2013
- Subjects: Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10344 , http://hdl.handle.net/10948/d1020058
- Description: In South Africa part of the cultural and religious beliefs of the African people is the use of traditional remedies to treat diseases. These remedies are obtained from medicinal plants (Steenkamp, 2003). One of the most frequently traded plants in the Eastern Cape is Hypoxis, commonly known as Afrika patat, or African potato. South African traditional healers instruct patients to brew the fresh Hypoxis corm as a tea and then ingest it (Steenkamp, 2006a). This prompted an investigation into the digestive stability of a traditionally prepared Hypoxis extract. The H. sobolifera extracts were digested using a simulated gastric/small intestinal digestion and their biological activity determined. The hot water H. sobolifera extract before digestion only showed cytotoxic activity against cancer cell lines at very high concentrations which are not likely to be achieved under normal ingestion circumstances. In Chang liver cells on the other hand, chronic exposure to the hot water H. sobolifera extract increased glucose uptake in amounts similar to that of metformin. On the negative side, the glucose utilization stimulation was lost due to the simulated digestion process. The significant inhibition of AGEs by hot water H. sobolifera extract (IC50 of 6.3 Ig/ml) is a very encouraging result as treatment in the management of diabetes. This activity was only slightly reduced by the in vitro digestion process. Also observed was enzyme inhibition activity by traditionally prepared H. sobolifera, with ∝-amylase being inhibited (IC50 of approximately 250 Ig/ml) and therefore preventing or limiting starch breakdown. From the DPPH results it was clear that H. sobolifera, even when digested, is a potent anti-oxidant (IC50 of 134.4 Ig/ml when undigested compared to 162.9 when digested with β-glucosidase added to stomach digestive step). HPLC and TLC experiments revealed that rooperol which has previously been thought to be the compound responsible for the anti-oxidant activity in Hypoxis extracts, was absent from the traditional extract of H. sobolifera and therefore cannot be the sole compound exhibiting anti-oxidant activity; other compounds such as phenolics may be contributing. The phenolic and flavonoid content results revealed very highconcentrations of these compounds in the traditionally prepared H. sobolifera extract. These compounds may therefore play major roles in all of the biological activities observed from treatment with Hypoxis spp. The ROS results yielded interesting and promising results. Using standard or traditionally prepared H. sobolifera extracts, activation of differentiated U937 cells with PMA was greatly enhanced by cotreatment with the extracts, while extracts on their own did not cause significant activation. Future studies should investigate this property of the extracts as a promising immune boosterThe HPLC results showed that hypoxoside was undetectable in the hot water traditional extract and the TLC anti-oxidant experiment proved that rooperol is not present in the hot water traditional extract after treatment with β-glucosidase. This indicates that neither one of the Hypoxis compounds previously believed to be responsible for the biological activities observed are present in the extract when prepared the traditional way. Therefore, the biological activities observed in this study can be attributed to other phytochemical compounds.
- Full Text:
- Date Issued: 2013
- Authors: Van Rooyen, Anzel
- Date: 2013
- Subjects: Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10344 , http://hdl.handle.net/10948/d1020058
- Description: In South Africa part of the cultural and religious beliefs of the African people is the use of traditional remedies to treat diseases. These remedies are obtained from medicinal plants (Steenkamp, 2003). One of the most frequently traded plants in the Eastern Cape is Hypoxis, commonly known as Afrika patat, or African potato. South African traditional healers instruct patients to brew the fresh Hypoxis corm as a tea and then ingest it (Steenkamp, 2006a). This prompted an investigation into the digestive stability of a traditionally prepared Hypoxis extract. The H. sobolifera extracts were digested using a simulated gastric/small intestinal digestion and their biological activity determined. The hot water H. sobolifera extract before digestion only showed cytotoxic activity against cancer cell lines at very high concentrations which are not likely to be achieved under normal ingestion circumstances. In Chang liver cells on the other hand, chronic exposure to the hot water H. sobolifera extract increased glucose uptake in amounts similar to that of metformin. On the negative side, the glucose utilization stimulation was lost due to the simulated digestion process. The significant inhibition of AGEs by hot water H. sobolifera extract (IC50 of 6.3 Ig/ml) is a very encouraging result as treatment in the management of diabetes. This activity was only slightly reduced by the in vitro digestion process. Also observed was enzyme inhibition activity by traditionally prepared H. sobolifera, with ∝-amylase being inhibited (IC50 of approximately 250 Ig/ml) and therefore preventing or limiting starch breakdown. From the DPPH results it was clear that H. sobolifera, even when digested, is a potent anti-oxidant (IC50 of 134.4 Ig/ml when undigested compared to 162.9 when digested with β-glucosidase added to stomach digestive step). HPLC and TLC experiments revealed that rooperol which has previously been thought to be the compound responsible for the anti-oxidant activity in Hypoxis extracts, was absent from the traditional extract of H. sobolifera and therefore cannot be the sole compound exhibiting anti-oxidant activity; other compounds such as phenolics may be contributing. The phenolic and flavonoid content results revealed very highconcentrations of these compounds in the traditionally prepared H. sobolifera extract. These compounds may therefore play major roles in all of the biological activities observed from treatment with Hypoxis spp. The ROS results yielded interesting and promising results. Using standard or traditionally prepared H. sobolifera extracts, activation of differentiated U937 cells with PMA was greatly enhanced by cotreatment with the extracts, while extracts on their own did not cause significant activation. Future studies should investigate this property of the extracts as a promising immune boosterThe HPLC results showed that hypoxoside was undetectable in the hot water traditional extract and the TLC anti-oxidant experiment proved that rooperol is not present in the hot water traditional extract after treatment with β-glucosidase. This indicates that neither one of the Hypoxis compounds previously believed to be responsible for the biological activities observed are present in the extract when prepared the traditional way. Therefore, the biological activities observed in this study can be attributed to other phytochemical compounds.
- Full Text:
- Date Issued: 2013
The sustainability of rural sanitation facilities in municipalities
- Authors: Maxwele, Zukani
- Date: 2013
- Subjects: Sanitation, Rural -- South Africa -- Eastern Cape , Sanitary engineering -- South Africa -- Eastern Cape , Sewage disposal, Rural -- South Africa -- Eastern Cape , Rural development projects -- South Africa -- Citizen participation , Municipal services -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9713 , http://hdl.handle.net/10948/d1020580
- Description: Progress has been made in eradicating the backlog in sanitation. This is reflected by the 2011 Census results that reflect a 21 percent increase in the provision of sanitation between the 2001 Census and the 2011 Census. In the rural areas of O.R. Tambo District Municipality, the eradication of sanitation backlogs is done through the provision of VIPs for sanitation. Even with this progress, there are still challenges resulting from the previously constructed sanitation facilities. Some of the challenges relate to the poor quality of these facilities. Community members – via the IDP road shows have voiced their unhappiness with regard to some of the sustainability factors of these structures. Community members feel they were not involved in decisions related to the sanitation projects. It has also been observed that the municipality and its agents do not conduct environmental management studies; and some pits of these structures were not lined, and the health and hygiene training, together with post-construction assessment was not done. In this study, an assessment of the provision of sanitation facilities, in order to identify some of the key factors that are critical to the sustainability of rural sanitation facilities, was done. The research findings should be helpful in assisting local government to improve the provision of sanitation facilities, with the aim of ensuring sustainability, improving community satisfaction, and improving the quality of life for the people living in these villages. For the purpose of the study, a quantitative research approach was used. A research questionnaire was used to collect the data; and it was distributed through email to a sample of respondents that understood sanitation issues. The data were collected from municipal officials, consultants working on sanitation projects, as well as other stakeholders with influence and an interest in sanitation. The results were analysed to establish the findings and to propose recommendations, in order to improve the sustainability of rural sanitation facilities. From the research findings, the recommendations highlighted the need for an improved participatory approach in implementing sanitation projects. To ensure sustainability, the following issues are key: monitoring and supervision; community participation and adherence to design guidelines; a review of the sanitation provision policy; as well as the promotion of health and hygiene.
- Full Text:
- Date Issued: 2013
- Authors: Maxwele, Zukani
- Date: 2013
- Subjects: Sanitation, Rural -- South Africa -- Eastern Cape , Sanitary engineering -- South Africa -- Eastern Cape , Sewage disposal, Rural -- South Africa -- Eastern Cape , Rural development projects -- South Africa -- Citizen participation , Municipal services -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9713 , http://hdl.handle.net/10948/d1020580
- Description: Progress has been made in eradicating the backlog in sanitation. This is reflected by the 2011 Census results that reflect a 21 percent increase in the provision of sanitation between the 2001 Census and the 2011 Census. In the rural areas of O.R. Tambo District Municipality, the eradication of sanitation backlogs is done through the provision of VIPs for sanitation. Even with this progress, there are still challenges resulting from the previously constructed sanitation facilities. Some of the challenges relate to the poor quality of these facilities. Community members – via the IDP road shows have voiced their unhappiness with regard to some of the sustainability factors of these structures. Community members feel they were not involved in decisions related to the sanitation projects. It has also been observed that the municipality and its agents do not conduct environmental management studies; and some pits of these structures were not lined, and the health and hygiene training, together with post-construction assessment was not done. In this study, an assessment of the provision of sanitation facilities, in order to identify some of the key factors that are critical to the sustainability of rural sanitation facilities, was done. The research findings should be helpful in assisting local government to improve the provision of sanitation facilities, with the aim of ensuring sustainability, improving community satisfaction, and improving the quality of life for the people living in these villages. For the purpose of the study, a quantitative research approach was used. A research questionnaire was used to collect the data; and it was distributed through email to a sample of respondents that understood sanitation issues. The data were collected from municipal officials, consultants working on sanitation projects, as well as other stakeholders with influence and an interest in sanitation. The results were analysed to establish the findings and to propose recommendations, in order to improve the sustainability of rural sanitation facilities. From the research findings, the recommendations highlighted the need for an improved participatory approach in implementing sanitation projects. To ensure sustainability, the following issues are key: monitoring and supervision; community participation and adherence to design guidelines; a review of the sanitation provision policy; as well as the promotion of health and hygiene.
- Full Text:
- Date Issued: 2013
An investigation into control mechanisms of driving performance : resource depletion and effort-regulation
- Authors: Louw, Tyron Linton
- Date: 2013
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5101 , http://hdl.handle.net/10962/d1001842 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Description: Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand
- Full Text:
- Date Issued: 2013
- Authors: Louw, Tyron Linton
- Date: 2013
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5101 , http://hdl.handle.net/10962/d1001842 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Description: Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand
- Full Text:
- Date Issued: 2013
The fitting of statistical distributions to wind data in coastal areas of South Africa
- Authors: Moodley, Kirshnee
- Date: 2013
- Subjects: Winds -- South Africa -- Port Elizabeth -- Speed -- Measurement , Wind power -- South Africa -- Port Elizabeth , Winds -- South Africa -- Port Elizabeth -- Measurement -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10584
- Description: Coastal South African cities like Port Elizabeth are said to have a strong potential for wind energy. This study aims to model wind data in order to be able assess the power potential belonging to a given site. The main challenge in modelling wind direction data is that it is categorized as circular data and therefore requires special techniques for handling that are different from usual statistical samples. Statistical tools such as descriptive measures and distribution fitting, were re-invented for directional data by researchers in this field. The von Mises distribution is a predominant distribution in circular statistics and is commonly used to describe wind directions. In this study, the circular principles described by previous researchers were developed by using the statistical software, Mathematica. Graphical methods to present the wind data were developed to give an overview of the behaviour of the winds in any given area. Data collected at Coega, an area near Port Elizabeth, South Africa, was used to illustrate the models which were established in this study. Circular distributions were fit to the directional data in order to make appropriate conclusions about the prevailing wind directions in this area.
- Full Text:
- Date Issued: 2013
- Authors: Moodley, Kirshnee
- Date: 2013
- Subjects: Winds -- South Africa -- Port Elizabeth -- Speed -- Measurement , Wind power -- South Africa -- Port Elizabeth , Winds -- South Africa -- Port Elizabeth -- Measurement -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10584
- Description: Coastal South African cities like Port Elizabeth are said to have a strong potential for wind energy. This study aims to model wind data in order to be able assess the power potential belonging to a given site. The main challenge in modelling wind direction data is that it is categorized as circular data and therefore requires special techniques for handling that are different from usual statistical samples. Statistical tools such as descriptive measures and distribution fitting, were re-invented for directional data by researchers in this field. The von Mises distribution is a predominant distribution in circular statistics and is commonly used to describe wind directions. In this study, the circular principles described by previous researchers were developed by using the statistical software, Mathematica. Graphical methods to present the wind data were developed to give an overview of the behaviour of the winds in any given area. Data collected at Coega, an area near Port Elizabeth, South Africa, was used to illustrate the models which were established in this study. Circular distributions were fit to the directional data in order to make appropriate conclusions about the prevailing wind directions in this area.
- Full Text:
- Date Issued: 2013
Spatial and temporal patterns in the population and the feeding of Palaemon peringueyi (MacPherson 1990) (Decapoda, Palaemonidae) in the Kariega estuary, South Africa
- Nyalungu, Nonhlanhla Precotia Dudu
- Authors: Nyalungu, Nonhlanhla Precotia Dudu
- Date: 2013
- Subjects: Palaemonidae -- Food -- South Africa , Palaemonidae -- Behavior -- South Africa , Palaemonidae -- Habitat -- South Africa , Estuarine biology -- South Africa , Shrimp populations -- South Africa , Shrimps -- South Africa , Decapoda (Crustacea) -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5584 , http://hdl.handle.net/10962/d1001576 , Palaemonidae -- Food -- South Africa , Palaemonidae -- Behavior -- South Africa , Palaemonidae -- Habitat -- South Africa , Estuarine biology -- South Africa , Shrimp populations -- South Africa , Shrimps -- South Africa , Decapoda (Crustacea) -- South Africa
- Description: The spatial and temporal patterns in the population demographs and feeding ecology of the caridean shrimp, Palaemon peringueyi, was investigated over a 12 month period in the permanently open Kariega Estuary situated on the south-east coastline of South Africa. Shrimps were sampled monthly from three stations corresponding to the lower, middle and upper reaches of the Kariega Estuary. The shrimps were collected at the different stations using a pull net. Temperature, salinity, dissolved oxygen and % cover of submerged vegetation were measured at each sampling station. Finally, the feeding ecology of the shrimp was investigated employing stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes analysis. Temperature, salinity, dissolved oxygen and vegetation cover showed distinct seasonal patterns. The shrimps attained total abundances and biomass of between 0 and 245.6 individuals per m² (ind.m⁻²) and between 0 and 13.6 grams wet weight per m² (g wwt.m⁻²), respectively. Mean abundance ranged between 2.3 (± 3.0) and 88 (± 27.3) ind.m⁻² in the lower reach, between 0.9 (± 0.4) to 21.5 (± 4.5) ind.m⁻² in the middle reach and 0 to 1.6 (± 0.5) ind.m⁻² in the upper reach. Mean biomass ranged between 0.4 (± 0.5) and 4.4 (± 1.4) g wwt.m⁻² in the lower reach, between 0.1 (± 0) to 4.3 (± 0.9) g wwt.m⁻² in the middle reach and between 0 to 1.6 (± 0.5) g wwt.m⁻² in the upper reach. Greatest abundances and biomasses were recorded in winter following heavy rainfall within the catchment area. Freshwater inflow which is due to rainfall is thought to provide a cue for the recruitment of marine breeding organisms. The spatial patterns in the distribution of the shrimps showed that juveniles occupied the lower and middle reaches and adults the entire length of the estuary. There were no significant relationships between the abundance and biomass of the shrimps and the selected physico-chemical variables (p > 0.05 in all cases). Results of the stable isotope study indicated that the mean δ¹³C of the shrimps in the lower, middle and upper reaches were -12.4 (± 1.3) ‰, -15.6 (± 0.5) ‰ and -17.5 (± 0.5) ‰, respectively. The δ¹⁵N isotopes of the shrimps in the lower reach was 11.6 (± 0.5) ‰ with middle and upper reaches having similar δ¹⁵N values, 13.5 (± 0.4) ‰ and 13.4 (± 0.4) ‰, respectively. There was no significant difference in the δ¹³C and δ¹⁵N isotope (p > 0.05) between the sexes of the shrimps. Two-way ANOVA indicated a significant difference in the δ¹³C isotope of the shrimps between the sites (p < 0.05). The difference in the δ¹³C and δ¹⁵N ratios of the shrimps suggests spatial variability in the diet of P. peringueyi within the Kariega Estuary. The diet of the shrimps in the lower reach is primarily composed of Nanozostera capensis epibionts. In the middle reach the diet of the shrimps is likely comprised of the detritus of benthic algae. In the upper reach of the estuary, P. peringueyi likely derives its carbon from a combination of epibionts, benthic algae and detritus derived from Codium.
- Full Text:
- Date Issued: 2013
- Authors: Nyalungu, Nonhlanhla Precotia Dudu
- Date: 2013
- Subjects: Palaemonidae -- Food -- South Africa , Palaemonidae -- Behavior -- South Africa , Palaemonidae -- Habitat -- South Africa , Estuarine biology -- South Africa , Shrimp populations -- South Africa , Shrimps -- South Africa , Decapoda (Crustacea) -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5584 , http://hdl.handle.net/10962/d1001576 , Palaemonidae -- Food -- South Africa , Palaemonidae -- Behavior -- South Africa , Palaemonidae -- Habitat -- South Africa , Estuarine biology -- South Africa , Shrimp populations -- South Africa , Shrimps -- South Africa , Decapoda (Crustacea) -- South Africa
- Description: The spatial and temporal patterns in the population demographs and feeding ecology of the caridean shrimp, Palaemon peringueyi, was investigated over a 12 month period in the permanently open Kariega Estuary situated on the south-east coastline of South Africa. Shrimps were sampled monthly from three stations corresponding to the lower, middle and upper reaches of the Kariega Estuary. The shrimps were collected at the different stations using a pull net. Temperature, salinity, dissolved oxygen and % cover of submerged vegetation were measured at each sampling station. Finally, the feeding ecology of the shrimp was investigated employing stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes analysis. Temperature, salinity, dissolved oxygen and vegetation cover showed distinct seasonal patterns. The shrimps attained total abundances and biomass of between 0 and 245.6 individuals per m² (ind.m⁻²) and between 0 and 13.6 grams wet weight per m² (g wwt.m⁻²), respectively. Mean abundance ranged between 2.3 (± 3.0) and 88 (± 27.3) ind.m⁻² in the lower reach, between 0.9 (± 0.4) to 21.5 (± 4.5) ind.m⁻² in the middle reach and 0 to 1.6 (± 0.5) ind.m⁻² in the upper reach. Mean biomass ranged between 0.4 (± 0.5) and 4.4 (± 1.4) g wwt.m⁻² in the lower reach, between 0.1 (± 0) to 4.3 (± 0.9) g wwt.m⁻² in the middle reach and between 0 to 1.6 (± 0.5) g wwt.m⁻² in the upper reach. Greatest abundances and biomasses were recorded in winter following heavy rainfall within the catchment area. Freshwater inflow which is due to rainfall is thought to provide a cue for the recruitment of marine breeding organisms. The spatial patterns in the distribution of the shrimps showed that juveniles occupied the lower and middle reaches and adults the entire length of the estuary. There were no significant relationships between the abundance and biomass of the shrimps and the selected physico-chemical variables (p > 0.05 in all cases). Results of the stable isotope study indicated that the mean δ¹³C of the shrimps in the lower, middle and upper reaches were -12.4 (± 1.3) ‰, -15.6 (± 0.5) ‰ and -17.5 (± 0.5) ‰, respectively. The δ¹⁵N isotopes of the shrimps in the lower reach was 11.6 (± 0.5) ‰ with middle and upper reaches having similar δ¹⁵N values, 13.5 (± 0.4) ‰ and 13.4 (± 0.4) ‰, respectively. There was no significant difference in the δ¹³C and δ¹⁵N isotope (p > 0.05) between the sexes of the shrimps. Two-way ANOVA indicated a significant difference in the δ¹³C isotope of the shrimps between the sites (p < 0.05). The difference in the δ¹³C and δ¹⁵N ratios of the shrimps suggests spatial variability in the diet of P. peringueyi within the Kariega Estuary. The diet of the shrimps in the lower reach is primarily composed of Nanozostera capensis epibionts. In the middle reach the diet of the shrimps is likely comprised of the detritus of benthic algae. In the upper reach of the estuary, P. peringueyi likely derives its carbon from a combination of epibionts, benthic algae and detritus derived from Codium.
- Full Text:
- Date Issued: 2013
The diet of the Subantarctic (A. Tropicalis) and Antarctic (A. Gazella) Fur seal at Marion Island
- Mgibantaka, Nonkoliso Felicia
- Authors: Mgibantaka, Nonkoliso Felicia
- Date: 2013
- Subjects: Southern fur seals -- Feeding and feeds -- Antarctica , Seals (Animals) -- Antarctica , Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10729 , http://hdl.handle.net/10948/d1021104
- Description: Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.
- Full Text:
- Date Issued: 2013
- Authors: Mgibantaka, Nonkoliso Felicia
- Date: 2013
- Subjects: Southern fur seals -- Feeding and feeds -- Antarctica , Seals (Animals) -- Antarctica , Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10729 , http://hdl.handle.net/10948/d1021104
- Description: Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.
- Full Text:
- Date Issued: 2013
The medicinal plant Sutherlandia Frutescens regulates gene expression to reverse insulin resistace in rats
- Authors: Fortuin, Melissa
- Date: 2013
- Subjects: Insulin resistance , Medicinal plants , Genetic regulation , Insulin resistance -- Animal models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10349 , http://hdl.handle.net/10948/d1020823
- Description: Obesity can lead to Type 2 Diabetes, both conditions increase in association with physical inactivity and high-energy diets, resulting in elevated blood glucose, decreased insulin sensitivity and increased insulin resistance. Sutherlandia frutescens (S.frutescens), an anti-diabetic plant, reverses and prevents insulin resistance in a rat model and human cell culture model. Gene expression analysis in hepatocyte cultures, identified genes down regulated in insulin resistance and up regulated by S.frutescens. These included genes encoding vesicle transporter proteins, hypothesised to be linked to hepatic lipid accumulation and lipid droplet formation during insulin resistance. The aim of this study was to investigate critical genes involved in lipid droplet formation, vesicle assembly and transport in high fat diet (HFD)-induced insulin resistant rat liver tissue during the development of insulin resistance and the reversal of these changes by S.frutescens. Rats were fed a low fat diet (LFD) or HFD supplemented with S.frutescens for 2, 4 and 8 weeks. Rats fed a HFD for 12 weeks developed insulin resistance, confirmed by plasma glucose and insulin levels (compared to normal controls). Groups of these rats were gavaged with S. frutescens (50mg/kg BW), Metformin (13mg/kg BW) or water for a further 4 weeks and starved for 12 hours, anaesthetized and blood removed by heart puncture. Liver was stored in RNA-Later™ for qRT-PCR and snap-frozen in liquid nitrogen for western blotting and confocal microscopy analysis. Changes in expression of vesicle transporter genes VAMP3 and NSF were analysed by qRT-PCR and changes in the protein expression by western blotting analysis. Proteins were localised within the liver by confocal immunohistochemistry using ZEN lite™ software. Statistical analysis was performed using One-Way ANOVA and unpaired t-test. mRNA gene expression of vesicle transport components VAMP3, NSF and SNAP25 showed relatively moderate changes with considerable individual variation within control or experimental groups. Uncorrelated changes in mRNA and protein products were found and may be due to differential regulation by siRNA. Proteins also showed altered staining patterns in high fat diet rats that reverted towards normal on S. frutescens treatment, potentially reflecting functional changes associated with transport of lipid-filled vesicles.
- Full Text:
- Date Issued: 2013
- Authors: Fortuin, Melissa
- Date: 2013
- Subjects: Insulin resistance , Medicinal plants , Genetic regulation , Insulin resistance -- Animal models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10349 , http://hdl.handle.net/10948/d1020823
- Description: Obesity can lead to Type 2 Diabetes, both conditions increase in association with physical inactivity and high-energy diets, resulting in elevated blood glucose, decreased insulin sensitivity and increased insulin resistance. Sutherlandia frutescens (S.frutescens), an anti-diabetic plant, reverses and prevents insulin resistance in a rat model and human cell culture model. Gene expression analysis in hepatocyte cultures, identified genes down regulated in insulin resistance and up regulated by S.frutescens. These included genes encoding vesicle transporter proteins, hypothesised to be linked to hepatic lipid accumulation and lipid droplet formation during insulin resistance. The aim of this study was to investigate critical genes involved in lipid droplet formation, vesicle assembly and transport in high fat diet (HFD)-induced insulin resistant rat liver tissue during the development of insulin resistance and the reversal of these changes by S.frutescens. Rats were fed a low fat diet (LFD) or HFD supplemented with S.frutescens for 2, 4 and 8 weeks. Rats fed a HFD for 12 weeks developed insulin resistance, confirmed by plasma glucose and insulin levels (compared to normal controls). Groups of these rats were gavaged with S. frutescens (50mg/kg BW), Metformin (13mg/kg BW) or water for a further 4 weeks and starved for 12 hours, anaesthetized and blood removed by heart puncture. Liver was stored in RNA-Later™ for qRT-PCR and snap-frozen in liquid nitrogen for western blotting and confocal microscopy analysis. Changes in expression of vesicle transporter genes VAMP3 and NSF were analysed by qRT-PCR and changes in the protein expression by western blotting analysis. Proteins were localised within the liver by confocal immunohistochemistry using ZEN lite™ software. Statistical analysis was performed using One-Way ANOVA and unpaired t-test. mRNA gene expression of vesicle transport components VAMP3, NSF and SNAP25 showed relatively moderate changes with considerable individual variation within control or experimental groups. Uncorrelated changes in mRNA and protein products were found and may be due to differential regulation by siRNA. Proteins also showed altered staining patterns in high fat diet rats that reverted towards normal on S. frutescens treatment, potentially reflecting functional changes associated with transport of lipid-filled vesicles.
- Full Text:
- Date Issued: 2013
Movement patterns and genetic stock delineation of an endemic South African sparid, the Poenskop, Cymatoceps nasutus (Castelnau, 1861)
- Authors: Murray, Taryn Sara
- Date: 2013
- Subjects: Fish stock assessment -- South Africa , Sparidae -- South Africa , Fishes -- Reproduction -- South Africa , Fishing -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa , Marine fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5178 , http://hdl.handle.net/10962/d1001514 , Fish stock assessment -- South Africa , Sparidae -- South Africa , Fishes -- Reproduction -- South Africa , Fishing -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa , Marine fishes -- South Africa
- Description: Poenskop Cymatoceps nasutus (Pisces: Sparidae), an endemic South African sparid, is an important angling species being predominantly targeted by the recreational shore and skiboat sector. This species is slow-growing, long-lived, late-maturing and sex-changing, making poenskop acutely sensitive to over-exploitation. Despite interventions, such as the imposition of size and bag limits (currently 50 cm TL and one per licensed fisher per day) by authorities, catch-per-unit-effort trends reflect a severe and consistent stock decline over the last two decades. Poenskop has been identified as a priority species for research and conservation. Although the biology and population dynamics of this species have been well-documented, little is known about the movement behaviour of poenskop. Furthermore, there is a complete lack of information on its genetic stock structure. This thesis aimed to address the current knowledge gaps concerning movement behaviour and genetic stock structure of poenskop, making use of a range of methods and drawing on available information, including available fishery records as well as published and unpublished survey and research data, and data from long-term monitoring programmes. Analysis of available catch data (published and unpublished) revealed a decline in the number of poenskop caught as well as size of fish taken over the last two decades, ultimately reflecting the collapse of the stock (estimated to be at 20% of their pristine level). Improved catch-per-unit-effort data from the Tsitsikamma National Park Marine Protected Area (MPA), and larger poenskop being caught in the no-take areas than adjacent exploited areas of the Pondoland MPA confirmed that MPAs can be effective for the protection and management of poenskop. The current MPA network in South Africa is already wellestablished, and encompasses considerable reef areas, being preferable for poenskop habitation. Conventional dart tagging and recapture information from three ongoing, long-term fishtagging projects, conducted throughout the poenskop’s distribution, indicated high levels of residency at all life-history stages. Coastal region, seasonality and time at recapture did not appear to have a significant effect on the level of movement or distance moved. However, on examining the relationship among coastal movements and fish size and ages, larger and older fish (adults) moved greater distances, with juveniles and sub-adults showing high degrees of residency. An estimation of home-range size indicated smaller poenskop to hold smaller home-ranges, while larger poenskop hold larger home-ranges. Large easterly displacements of a number of adult poenskop is in accordance with previous findings that this species may undertake a unidirectional migration up the coastline of South Africa where they possibly settle in Transkei waters for the remainder of their lives. This high level of residency makes poenskop vulnerable to localised depletion, although they can be effectively protected by suitable MPAs. Despite considerable tagging effort along the South African coastline (2 704 poenskop tagged with 189 recaptures, between 1984 and 2010), there remains limited information on the connectivity of different regions along the South African coastline. This was addressed using mitochondrial DNA sequencing. The mitochondrial DNA control region was used due to its high substitution rate, haploid nature, maternal inheritance and absence of recombination. The mtDNA sequencing showed no evidence of major geographic barriers to gene flow in this species. Samples collected throughout the core distribution of poenskop showed high genetic diversity (h = 0.88, π = 0.01), low genetic differentiation among regions, no spatial structure (ɸST = 0.012, p = 0.208) and no evidence of isolation by distance. The collapsed stock status of poenskop as well as the fact that it is being actively targeted by recreational and commercial fishers suggests that this species requires improved management, with consideration given to its life-history style, residency and poor conservation status. Management recommendations for poenskop, combined with increasing South Africa’s existing MPA network, include the possibility of setting up a closed season (during known spawning periods) as well as the decommercialisation of this species. The techniques used and developed in this study can also be adopted for other overexploited linefish species.
- Full Text:
- Date Issued: 2013
- Authors: Murray, Taryn Sara
- Date: 2013
- Subjects: Fish stock assessment -- South Africa , Sparidae -- South Africa , Fishes -- Reproduction -- South Africa , Fishing -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa , Marine fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5178 , http://hdl.handle.net/10962/d1001514 , Fish stock assessment -- South Africa , Sparidae -- South Africa , Fishes -- Reproduction -- South Africa , Fishing -- South Africa , Fish populations -- South Africa , Fishes -- Behavior -- South Africa , Marine fishes -- South Africa
- Description: Poenskop Cymatoceps nasutus (Pisces: Sparidae), an endemic South African sparid, is an important angling species being predominantly targeted by the recreational shore and skiboat sector. This species is slow-growing, long-lived, late-maturing and sex-changing, making poenskop acutely sensitive to over-exploitation. Despite interventions, such as the imposition of size and bag limits (currently 50 cm TL and one per licensed fisher per day) by authorities, catch-per-unit-effort trends reflect a severe and consistent stock decline over the last two decades. Poenskop has been identified as a priority species for research and conservation. Although the biology and population dynamics of this species have been well-documented, little is known about the movement behaviour of poenskop. Furthermore, there is a complete lack of information on its genetic stock structure. This thesis aimed to address the current knowledge gaps concerning movement behaviour and genetic stock structure of poenskop, making use of a range of methods and drawing on available information, including available fishery records as well as published and unpublished survey and research data, and data from long-term monitoring programmes. Analysis of available catch data (published and unpublished) revealed a decline in the number of poenskop caught as well as size of fish taken over the last two decades, ultimately reflecting the collapse of the stock (estimated to be at 20% of their pristine level). Improved catch-per-unit-effort data from the Tsitsikamma National Park Marine Protected Area (MPA), and larger poenskop being caught in the no-take areas than adjacent exploited areas of the Pondoland MPA confirmed that MPAs can be effective for the protection and management of poenskop. The current MPA network in South Africa is already wellestablished, and encompasses considerable reef areas, being preferable for poenskop habitation. Conventional dart tagging and recapture information from three ongoing, long-term fishtagging projects, conducted throughout the poenskop’s distribution, indicated high levels of residency at all life-history stages. Coastal region, seasonality and time at recapture did not appear to have a significant effect on the level of movement or distance moved. However, on examining the relationship among coastal movements and fish size and ages, larger and older fish (adults) moved greater distances, with juveniles and sub-adults showing high degrees of residency. An estimation of home-range size indicated smaller poenskop to hold smaller home-ranges, while larger poenskop hold larger home-ranges. Large easterly displacements of a number of adult poenskop is in accordance with previous findings that this species may undertake a unidirectional migration up the coastline of South Africa where they possibly settle in Transkei waters for the remainder of their lives. This high level of residency makes poenskop vulnerable to localised depletion, although they can be effectively protected by suitable MPAs. Despite considerable tagging effort along the South African coastline (2 704 poenskop tagged with 189 recaptures, between 1984 and 2010), there remains limited information on the connectivity of different regions along the South African coastline. This was addressed using mitochondrial DNA sequencing. The mitochondrial DNA control region was used due to its high substitution rate, haploid nature, maternal inheritance and absence of recombination. The mtDNA sequencing showed no evidence of major geographic barriers to gene flow in this species. Samples collected throughout the core distribution of poenskop showed high genetic diversity (h = 0.88, π = 0.01), low genetic differentiation among regions, no spatial structure (ɸST = 0.012, p = 0.208) and no evidence of isolation by distance. The collapsed stock status of poenskop as well as the fact that it is being actively targeted by recreational and commercial fishers suggests that this species requires improved management, with consideration given to its life-history style, residency and poor conservation status. Management recommendations for poenskop, combined with increasing South Africa’s existing MPA network, include the possibility of setting up a closed season (during known spawning periods) as well as the decommercialisation of this species. The techniques used and developed in this study can also be adopted for other overexploited linefish species.
- Full Text:
- Date Issued: 2013
Morphology, patterns and processes in the Oyster Bay headland bypass dunefield, South Africa
- Authors: McConnachie, Lauren Bernyse
- Date: 2013
- Subjects: Sand dune conservation -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Sedimentation and deposition -- South Africa -- Eastern Cape Beach erosion -- South Africa -- Eastern Cape Coastal zone management -- South Africa -- Eastern Cape Shore protection -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4804 , http://hdl.handle.net/10962/d1001904
- Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed , Maiden name: Elkington, Lauren
- Full Text:
- Date Issued: 2013
- Authors: McConnachie, Lauren Bernyse
- Date: 2013
- Subjects: Sand dune conservation -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Sedimentation and deposition -- South Africa -- Eastern Cape Beach erosion -- South Africa -- Eastern Cape Coastal zone management -- South Africa -- Eastern Cape Shore protection -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4804 , http://hdl.handle.net/10962/d1001904
- Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed , Maiden name: Elkington, Lauren
- Full Text:
- Date Issued: 2013
A marine chemical ecology study of the sea hare, Bursatella leachii in South Africa
- Authors: D'Souza, Nicole
- Date: 2013 , 2013-03-22
- Subjects: Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4283 , http://hdl.handle.net/10962/d1002952 , Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Description: The large cosmopolitan sea hare Bursatella leachii is a common resident in Eastern Cape river mouths during summer and late autumn where they congregate in beds of Zostera capensis to breed. In this thesis, the previously known toxic formamide marine secondary metabolite (-)-bursatellin (2.2), which may deter predators of South African specimens of the globally distributed sea hare Bursatella leachii, was isolated and identified (Chapter 2). There have been no previous chemical ecology studies of B. leachii and the latter half of this thesis is devoted to chemical ecology studies of this organism. Interestingly, the isolation of the (-)-diastereomer of 2.2 from specimens of B. leachii collected from the Kariega River mouth (near Kenton-on-Sea) suggests that the South African specimens of this species are similar to specimens collected from Puerto Rico and from the Mediterranean Sea. Two different chromatographic techniques for isolating 2.2 were compared in order to maximize the amount of 2.2 isolated from the Kariega River mouth sea hares. The doubling of selected resonances observed in both the ¹H and ¹³C NMR spectra of the bursatellin isolated in this study suggest one of three possibilities; either firstly, the presence of closely related compound(s), secondly, the presence of diastereomers or thirdly the presence of rotamers. Through NMR kinetic studies, we were able to establish that the presence of rotamers was very unlikely due to no change in the relative ratio (3:1) of the ¹H NMR signals with an increase in temperature. Although the attempted synthesis of the acetate derivative (2.28), as a means of separating a diastereomeric mixture was successful, the chromatographic separation of the proposed acetylated diastereomers was not successful. Preparation of the camphanate ester derivatives (e.g. 2.30) proved to be unsuccessful. Five B. leachii specimens were dissected, their organs separated and individually extracted with methanol. The methanol extracts were individually chromatographed on HP-20 media, and the distribution of bursatellin determined by isolation and NMR. It was evident from this investigation that the distribution of 2.2 within individual B. leachii specimens was found to be highest within the B. leachii ink gland. The lower amounts of 2.2 contained in the digestive system, relative to other organs, was hypothesized to occur because 2.2 is sequestered from the diet of the sea hare and efficiently moved from the gut to various organs around the body where it is stored. The absence of 2.2 from the skin was surprising and may be a result of a smaller mass of skin relative to other organs coupled with the limitations of the chromatographic separation techniques employed. Surprisingly, no bursatellin was found within juvenile sea hares. Chapter three discusses the isolation of ilimaquinone (3.1) and pelorol (3.19) from the sponge Hippospongia metachroma and the structure elucidation of each compound using computer modeling to illustrate the conformation. It was deemed necessary to isolate these well known and abundant bioactive marine natural products from a sponge as standard compounds in the bioassays given the paucity of 2.2 available for this study. Chapter four describes the assays used to test the biological activity of the bursatellin 2.2 compared to the generally bioactive ilimaquinone and the structurally related and commercially available broad spectrum antibiotic chloramphenicol. B. leachii, a shell-less marine mollusc inhabits a variety of intertidal habitats and, therefore, is exposed to several different predators, yet does not appear to have any specific predators. Potential predators of this sea hare in the Kariega Estuary could be fish and amphipods which are found in close proximity to these sea hares. Results of the assays showed that at roughly natural concentrations, (calculated from the isolated chromatographic yield) feeding was deterred by the fish and amphipods, which implied that 2.2 may confer a defensive role within the organism. The relatively high concentration present within the ink gland of B. leachii may support this hypothesis. Surprisingly, given its structural similarity to chloramphenicol, 2.3 did not show any antimicrobial action against five of the six bacterial strains against which it was screened [chloramphenicol inhibited the growth of all the bacterial strains at very low concentrations (0.25 mg/mL)]. Bursatellin was found to be only active against Staphylococus aureus at high concentrations ca. 2 mg/mL when compared to chloramphenicol. Neither bursatellin nor chloramphenicol showed anti-fungal activity. Although this study suggests that the sea hares may use chemical defences in addition to opaline ink to defend themselves, they also live within the seagrass Z. capensis, which possibly provides the sea hare with a cryptic form of physical defence against several predators that are unable to swim freely within the weed beds in the littoral zone of the estuary. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: D'Souza, Nicole
- Date: 2013 , 2013-03-22
- Subjects: Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4283 , http://hdl.handle.net/10962/d1002952 , Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Description: The large cosmopolitan sea hare Bursatella leachii is a common resident in Eastern Cape river mouths during summer and late autumn where they congregate in beds of Zostera capensis to breed. In this thesis, the previously known toxic formamide marine secondary metabolite (-)-bursatellin (2.2), which may deter predators of South African specimens of the globally distributed sea hare Bursatella leachii, was isolated and identified (Chapter 2). There have been no previous chemical ecology studies of B. leachii and the latter half of this thesis is devoted to chemical ecology studies of this organism. Interestingly, the isolation of the (-)-diastereomer of 2.2 from specimens of B. leachii collected from the Kariega River mouth (near Kenton-on-Sea) suggests that the South African specimens of this species are similar to specimens collected from Puerto Rico and from the Mediterranean Sea. Two different chromatographic techniques for isolating 2.2 were compared in order to maximize the amount of 2.2 isolated from the Kariega River mouth sea hares. The doubling of selected resonances observed in both the ¹H and ¹³C NMR spectra of the bursatellin isolated in this study suggest one of three possibilities; either firstly, the presence of closely related compound(s), secondly, the presence of diastereomers or thirdly the presence of rotamers. Through NMR kinetic studies, we were able to establish that the presence of rotamers was very unlikely due to no change in the relative ratio (3:1) of the ¹H NMR signals with an increase in temperature. Although the attempted synthesis of the acetate derivative (2.28), as a means of separating a diastereomeric mixture was successful, the chromatographic separation of the proposed acetylated diastereomers was not successful. Preparation of the camphanate ester derivatives (e.g. 2.30) proved to be unsuccessful. Five B. leachii specimens were dissected, their organs separated and individually extracted with methanol. The methanol extracts were individually chromatographed on HP-20 media, and the distribution of bursatellin determined by isolation and NMR. It was evident from this investigation that the distribution of 2.2 within individual B. leachii specimens was found to be highest within the B. leachii ink gland. The lower amounts of 2.2 contained in the digestive system, relative to other organs, was hypothesized to occur because 2.2 is sequestered from the diet of the sea hare and efficiently moved from the gut to various organs around the body where it is stored. The absence of 2.2 from the skin was surprising and may be a result of a smaller mass of skin relative to other organs coupled with the limitations of the chromatographic separation techniques employed. Surprisingly, no bursatellin was found within juvenile sea hares. Chapter three discusses the isolation of ilimaquinone (3.1) and pelorol (3.19) from the sponge Hippospongia metachroma and the structure elucidation of each compound using computer modeling to illustrate the conformation. It was deemed necessary to isolate these well known and abundant bioactive marine natural products from a sponge as standard compounds in the bioassays given the paucity of 2.2 available for this study. Chapter four describes the assays used to test the biological activity of the bursatellin 2.2 compared to the generally bioactive ilimaquinone and the structurally related and commercially available broad spectrum antibiotic chloramphenicol. B. leachii, a shell-less marine mollusc inhabits a variety of intertidal habitats and, therefore, is exposed to several different predators, yet does not appear to have any specific predators. Potential predators of this sea hare in the Kariega Estuary could be fish and amphipods which are found in close proximity to these sea hares. Results of the assays showed that at roughly natural concentrations, (calculated from the isolated chromatographic yield) feeding was deterred by the fish and amphipods, which implied that 2.2 may confer a defensive role within the organism. The relatively high concentration present within the ink gland of B. leachii may support this hypothesis. Surprisingly, given its structural similarity to chloramphenicol, 2.3 did not show any antimicrobial action against five of the six bacterial strains against which it was screened [chloramphenicol inhibited the growth of all the bacterial strains at very low concentrations (0.25 mg/mL)]. Bursatellin was found to be only active against Staphylococus aureus at high concentrations ca. 2 mg/mL when compared to chloramphenicol. Neither bursatellin nor chloramphenicol showed anti-fungal activity. Although this study suggests that the sea hares may use chemical defences in addition to opaline ink to defend themselves, they also live within the seagrass Z. capensis, which possibly provides the sea hare with a cryptic form of physical defence against several predators that are unable to swim freely within the weed beds in the littoral zone of the estuary. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
Isocyanide complexes of rhenium
- Authors: Schoultz, Xandri
- Date: 2013
- Subjects: Isocyanides , Rhenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10360 , http://hdl.handle.net/10948/d1021069
- Description: This study investigates the synthesis of rhenium(III)-isocyanide complexes with potentially bidentate ligands, as well as the reactivity of isocyanide ligands toward rhenium(I) and (V). The crystal structures of all the complexes have been determined by X-ray diffraction methods. The coordination behaviour of trans-[ReIIICl3(t-BuNC)(PPh3)2] with aniline and its derivatives were investigated. The isocyanide-containing rhenium(V) complexes [ReCl3(t-BuNC)(L)(PPh3)] were isolated, with the ligands H2L (aniline, o-phenylenediamine and anthranilic acid). In all these complexes the dianionic ligands L are coordinated monodentately as the imide. However, with 2-aminophenol the complexes [ReVCl2(t-BuNC)(L)(PPh3)2](ReO4) and [ReIIICl2(t-BuNC)(ibq)(PPh3)2] (ibq- = 2-iminobenzoquinonate) were identified as the products. [ReCl2(t-BuNC)(L)(PPh3)2](ReO4) is the product of a disproportionation reaction from Re(III) to Re(VII) and Re(V). All the above complexes show a distorted octahedral geometry around the rhenium. The products of the reaction of the Re(I) complex [Re(CO)5Cl] with isocyanides (tert-butyl- and cyclohexylisocyanide) are reported. Rhenium(I) tricarbonyl complexes of the form [Re(CO)3(CNR)2Cl] were isolated and they were characterized structurally and spectroscopically. The tricarbonyls are coordinated in the typical facial-fashion, whereas the isocyanides are coordinated cis to each other. The reaction of [Re(CO)3(t-BuNC)2Cl] with H2O led to the formation of the rhenium(I) complex [Re(CO)3(t-BuNC)2(OH2)] in which the aquo ligand can readily be substituted by a more complex ligand. The reaction of the rhenium(V) complexes cis-[ReO2I(PPh3)2] and mer-[ReOCl3(SMe2)(OPPh3)] with isocyanides were studied. The seven-coordinate trigonal prismatic, square faced monocapped rhenium(III) complex [ReI3(t-BuNC)3(PPh3)] was surprisingly isolated upon reacting cis-[ReO2I(PPh3)2] with tert-butyl isocyanide. The dimeric complex (μ-O)[ReOCl2(CNC6H11)2]2 was obtained from the reaction of mer-[ReOCl3(SMe2)(OPPh3)] with cyclohexyl isocyanide.
- Full Text:
- Date Issued: 2013
- Authors: Schoultz, Xandri
- Date: 2013
- Subjects: Isocyanides , Rhenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10360 , http://hdl.handle.net/10948/d1021069
- Description: This study investigates the synthesis of rhenium(III)-isocyanide complexes with potentially bidentate ligands, as well as the reactivity of isocyanide ligands toward rhenium(I) and (V). The crystal structures of all the complexes have been determined by X-ray diffraction methods. The coordination behaviour of trans-[ReIIICl3(t-BuNC)(PPh3)2] with aniline and its derivatives were investigated. The isocyanide-containing rhenium(V) complexes [ReCl3(t-BuNC)(L)(PPh3)] were isolated, with the ligands H2L (aniline, o-phenylenediamine and anthranilic acid). In all these complexes the dianionic ligands L are coordinated monodentately as the imide. However, with 2-aminophenol the complexes [ReVCl2(t-BuNC)(L)(PPh3)2](ReO4) and [ReIIICl2(t-BuNC)(ibq)(PPh3)2] (ibq- = 2-iminobenzoquinonate) were identified as the products. [ReCl2(t-BuNC)(L)(PPh3)2](ReO4) is the product of a disproportionation reaction from Re(III) to Re(VII) and Re(V). All the above complexes show a distorted octahedral geometry around the rhenium. The products of the reaction of the Re(I) complex [Re(CO)5Cl] with isocyanides (tert-butyl- and cyclohexylisocyanide) are reported. Rhenium(I) tricarbonyl complexes of the form [Re(CO)3(CNR)2Cl] were isolated and they were characterized structurally and spectroscopically. The tricarbonyls are coordinated in the typical facial-fashion, whereas the isocyanides are coordinated cis to each other. The reaction of [Re(CO)3(t-BuNC)2Cl] with H2O led to the formation of the rhenium(I) complex [Re(CO)3(t-BuNC)2(OH2)] in which the aquo ligand can readily be substituted by a more complex ligand. The reaction of the rhenium(V) complexes cis-[ReO2I(PPh3)2] and mer-[ReOCl3(SMe2)(OPPh3)] with isocyanides were studied. The seven-coordinate trigonal prismatic, square faced monocapped rhenium(III) complex [ReI3(t-BuNC)3(PPh3)] was surprisingly isolated upon reacting cis-[ReO2I(PPh3)2] with tert-butyl isocyanide. The dimeric complex (μ-O)[ReOCl2(CNC6H11)2]2 was obtained from the reaction of mer-[ReOCl3(SMe2)(OPPh3)] with cyclohexyl isocyanide.
- Full Text:
- Date Issued: 2013
Microsatellite and morphometric analysis of chokka squid (Loligo reynaudi) from different spawning aggregations around the South African coast
- Authors: Stonier, Terence Anthony
- Date: 2013
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5344 , http://hdl.handle.net/10962/d1006779
- Description: Accurate information on stock structure is very important to the effective management of any commercially exploited species (Angel et al. 1994), particularly in annual species like Loligo reynaudi. Previous molecular work on a number of fish and cephalopod species has shown that stock structuring may be more complex than originally believed and while much scientific work has been conducted on Loligo reynaudi to date, molecular work has been lacking and this species’ fishery is currently managed as a single stock. The primary aim of this project was to examine the population genetics of Loligo reynaudi on a molecular level, by looking at the levels of genetic variation between different spawning aggregations along the inshore distribution of the chokka squid, with particular attention being paid to any variation between Eastern Cape and Agulhas Bank groups. The secondary aim was to conduct a morphological analysis on samples from the same major areas in order to see if any genetic variation observed would be complemented by phenotypic variation. Two separate sample sets were collected; Genetic samples were collected from 6 different spawning sites along the South African Coast between April and July, 2006 and whole individuals for morphometric analysis were collected from 4 spawning sites between April and July 2007. Samples were screened for genetic variation between different spawning aggregations along the inshore distribution of chokka squid, from Port Alfred in the Eastern Cape, to the western Agulhas Bank. After this a morphometric analysis on samples from the same major areas, Eastern Cape, Agulhas Bank and Angola, was carried out. Genetic results showed significant variation between some of the sample groups. As expected, the Angolan outgroup consistently showed significant variation from other samples, while there was evidence of differentiation between the South African samples themselves. These results could have implications for the previously documented life cycle model of Loligo reynaudi and provide a basis for further study at a finer resolution into where exactly the boundaries of these different groupings can be found. This stock structuring has implications for the management of the species and warrants further genetic research with microsatellites proving to be a powerful tool in the explanation of stock structuring. Unfortunately, due to possible errors in taking measurements, morphometric analysis did not yield useful results which can be described and interpreted in this study. It is felt that further genetic study conducted on a finer scale, should be accompanied by a repeat of the morphometric analysis.
- Full Text:
- Date Issued: 2013
- Authors: Stonier, Terence Anthony
- Date: 2013
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5344 , http://hdl.handle.net/10962/d1006779
- Description: Accurate information on stock structure is very important to the effective management of any commercially exploited species (Angel et al. 1994), particularly in annual species like Loligo reynaudi. Previous molecular work on a number of fish and cephalopod species has shown that stock structuring may be more complex than originally believed and while much scientific work has been conducted on Loligo reynaudi to date, molecular work has been lacking and this species’ fishery is currently managed as a single stock. The primary aim of this project was to examine the population genetics of Loligo reynaudi on a molecular level, by looking at the levels of genetic variation between different spawning aggregations along the inshore distribution of the chokka squid, with particular attention being paid to any variation between Eastern Cape and Agulhas Bank groups. The secondary aim was to conduct a morphological analysis on samples from the same major areas in order to see if any genetic variation observed would be complemented by phenotypic variation. Two separate sample sets were collected; Genetic samples were collected from 6 different spawning sites along the South African Coast between April and July, 2006 and whole individuals for morphometric analysis were collected from 4 spawning sites between April and July 2007. Samples were screened for genetic variation between different spawning aggregations along the inshore distribution of chokka squid, from Port Alfred in the Eastern Cape, to the western Agulhas Bank. After this a morphometric analysis on samples from the same major areas, Eastern Cape, Agulhas Bank and Angola, was carried out. Genetic results showed significant variation between some of the sample groups. As expected, the Angolan outgroup consistently showed significant variation from other samples, while there was evidence of differentiation between the South African samples themselves. These results could have implications for the previously documented life cycle model of Loligo reynaudi and provide a basis for further study at a finer resolution into where exactly the boundaries of these different groupings can be found. This stock structuring has implications for the management of the species and warrants further genetic research with microsatellites proving to be a powerful tool in the explanation of stock structuring. Unfortunately, due to possible errors in taking measurements, morphometric analysis did not yield useful results which can be described and interpreted in this study. It is felt that further genetic study conducted on a finer scale, should be accompanied by a repeat of the morphometric analysis.
- Full Text:
- Date Issued: 2013