List of Titles

Beginner teachers’ leadership development opportunities: an interventionist case study in a rural combined school in the Ohangwena region, Namibia

- Ndakolonkoshi, Klaudia

Authors: Ndakolonkoshi, Klaudia
Date: 2018
Subjects: School management and organization -- Namibia , Teacher participation in administration -- Namibia , Educational leadership -- Namibia , Teacher effectiveness -- Namibia
Language: English
Type: text , Thesis , Masters , MEd
Identifier: http://hdl.handle.net/10962/61603 , vital:28041
Description: The emergence of distributed leadership theory encourages multiple involvement of individuals in leadership of the school, regardless of their leadership positions (Spillane, 2006). The manifestation of teacher leadership through distributed leadership theory grants opportunities to teachers to enact leadership roles. This study explored how the notion of teacher leadership is understood, the leadership roles existing for the beginner teachers, and the constraining and enabling factors to the practice of teacher leadership in a rural combined school in Ohangwena region, in Namibia. The study is a formative intervention adopting a case study approach located in a critical paradigm since it aimed to bring changes in the activity system of the beginner teachers. The data were collected from ten participants: four beginner teachers, four experienced teachers, the principal and the Head of Department. The data were generated using the following techniques: document analysis, interview, questionnaires, observation and Change Laboratory workshops. The data were analysed thematically using second generation of Cultural Historical Activity Theory (CHAT) and Grant’s (2006, 2008, 2010) Teacher Leadership Model. The findings revealed that there were different understandings of the concept of teacher leadership. It was viewed as participation, influence, motivation and mentoring. It was also revealed that beginner teachers practiced leadership roles across the four zones of Grant’s (2006, 2008, 2010) Teacher Leadership Model, but to various extents. A high participation was noted in zone one within the classroom and zone two in curricular and extra-curricular activities and minimal participation was reported in zone three within the whole school development and zone four beyond the school into the community. Teacher leadership in the case study school was constrained by several factors, including teachers’ reluctance to lead, cultural beliefs, top-down leadership structure and lack of experience. Due to the minimal participation of beginner teachers in zone three and four, the findings suggested that the school should foster a collaborative culture, establish induction and mentoring committees in the school and encourage beginner teachers to take up leadership roles by providing opportunities for them to lead through delegation. In a series of Change Laboratory workshops (CLW) the principal and the Head of Department took up the responsibility of providing leadership training to the teachers to enable them to assume leadership roles in the school. In addition, participants agreed to establish induction and mentoring committees in the school to provide guidance and assistance to teacher leaders.
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Date Issued: 2018

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Behaviour of quiet time ionospheric disturbances at African equatorial and midlatitude regions

- Orford, Nicola Diane

Authors: Orford, Nicola Diane
Date: 2018
Subjects: Ionospheric storms , Ionospheric storms -- Africa , Ionosphere , Plasmasphere , Q-disturbances , Total electron content (TEC)
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/62672 , vital:28228
Description: Extreme ionospheric and geomagnetic disturbances affect technology adversely. Prestorm enhancements, considered a potential predictor of geomagnetic storms, occur during quiet conditions prior to geomagnetic disturbances. The ionosphere experiences general disturbances during quiet geomagnetic conditions and these Q- disturbances remain unexplored over Africa. This study used TEC data to characterize the morphology of Q-disturbances over Africa, exploring variations with solar cycle, season, time of occurrence and latitude. Observations from 10 African GPS stations in the equatorial and midlatitude regions show that Q-disturbances in the equatorial region are predominantly driven by E x B variations, while multiple mechanisms affect the midlatitude region. Q- disturbances occur more frequently during nighttime than during daytime and no seasonal trend is observed. Midlatitude Q-disturbance mechanisms are explored in depth, considering substorm activity, the plasmaspheric contribution to GPS TEC and plasma transfer between conjugate points. Substorm activity is not a dominant mechanism, although Q-disturbances occurring under elevated substorm conditions tend to have longer duration and larger amplitude than general Q-disturbances. Many observed Q-disturbances become non-significant once the plasmaspheric contribution to the TEC measurements is removed, indicating that these disturbances occur within the plasmasphere, and not the ionosphere. Transfer of plasma between conjugate points does not seem to be a mechanism driving Q-disturbances, as the corresponding nighttime behaviour expected between depletions in the summer hemisphere and enhancements in the winter hemisphere is not observed. Pre-storm enhancements occur infrequently, rendering them a poor predictor of geomagnetic disturbances. Pre-storm enhancement morphology does not differ significantly from general quiet time enhancement morphology, suggesting pre-storms are not a special case of Q-disturbances.
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Date Issued: 2018

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Beneficial effects of medicinal plants in fish diseases

- Stratev, Deyan, Zhelyazkov, Georgi, Noundou, Xavier S, Krause, Rui W M

Authors: Stratev, Deyan , Zhelyazkov, Georgi , Noundou, Xavier S , Krause, Rui W M
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/126177 , vital:35856 , https://doi.org/10.1007/s10499-017-0219-x
Description: Fish are constantly in contact with pathogens inhabiting water. High populationdensity as well as poor hydrodynamic conditions and feeding lead to an increased sensitivitytowards infections. In order to prevent major economic losses due to diseases, variousmedications are used for treatment and prevention of infections. The use of antimicrobialdrugs in aquacultures could lead to emergence of resistance in pathogenic microorganisms.Alternatives are being sought over the last few years to replace antibiotics, and medicinalplants are one of available options for this purpose. These plants are rich in secondarymetabolites and phytochemical compounds, which have an effect against viral, bacterial, andparasitic diseases in fish. Their main advantage is their natural origin and most of these plantsdo not represent threat for human health, the fish, and the environment. The goal of this reviewis to present information on the treatment of viral, bacterial, and parasitic diseases in fishthrough medicinal plants, with focus on the mechanisms of action of the identified secondarymetabolites, fractions, or plant extracts.
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Date Issued: 2018

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Beneficiary perceptions regarding farm worker equity share schemes in South Africa

- Xolo, Siyavuya Nicholas

Authors: Xolo, Siyavuya Nicholas
Date: 2018
Subjects: Investments -- South Africa , Investment analysis Land reform -- South Africa Agricultural laborers -- South Africa
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/36323 , vital:33920
Description: The study aimed to assess beneficiary perceptions regarding farm worker equity share schemes in South Africa. Farm worker equity share schemes started in the early 1990s with the aim of having a special arrangement pertaining to the ownership and operation of a farm between the farmer and the farm workers. This was intended to assist farm workers in not only remaining as farm workers but also to gain ownership of the farm. This could lead to the empowerment of farm workers, better working conditions, improved living standards and their rights to land ownership. Farm worker equity share schemes have been widely reported as having failed to meet their intended objectives, thus, in 2009, the Department of Rural Development and Land Reform initiated a study to assess the implementation of equity share schemes. Although the report was not made public, it reports that out of the 88 equity share schemes at the time, only nine managed to pay dividends ranging from R200 to R2000 per year. As a result, the Department of Rural Development and Land Reform put a moratorium on equity share schemes; this was however removed in 2011. It is against this background that this study was undertaken to assess beneficiaries’ perceptions regarding farm worker equity share schemes in South Africa. A positivistic research paradigm was employed in this study, by means of quantitative research. Secondary data in the form of textbooks, journal articles and Internet sources provided the theoretical framework for this study. Primary data was obtained using the survey method, by means of self-administered structured questionnaires. Convenience and purposive sampling were applied in order to select 20 farms that use equity share schemes. The farms selected for this study were located in the Eastern Cape, Gauteng, Mpumalanga and the Western Cape provinces, covering a variety of farming activities such as citrus fruits, crops, vegetables and wineries. Ideally, a total of 15 farm workers per farm were targeted. However, due to a variation in these farm worker equity share schemes, on some farms less than 15 workers and in others more than 15 workers were selected for the study; this resulted in a total sample size of 341 farm workers. Ten null-hypotheses and a hypothetical model of beneficiary perceptions regarding farm worker equity share schemes were tested. The influence of seven independent variables were tested, these are: stakeholder trust, operational risks, government interventions, two-way communication, farm worker empowerment, training and skills development, and access to resources on farm worker equity share schemes. In addition, the influence of farm worker equity share schemes on three dependent variables, namely, farming performance, sustainability and employee expectations were tested. The Statistica (version 13.2) computer programme was used to analyse the results by means of advanced statistical techniques (such as exploratory factor analysis, regression and correlation analyses) as well as descriptive analysis and frequency distributions. After various statistical procedures, the model was re-specified; some of the variables were then renamed and the hypotheses were adjusted accordingly. The empirical results showed that three key variables to the success of farm worker equity share schemes are stakeholder trust, government interventions and farm owner support. It was determined that these key variables could lead to increased farming performance, farming sustainability and meeting employee expectations. This study provided useful and practical guidelines to farm owners and administrators of equity share schemes, so as to ensure effective strategising that could enhance their competitiveness and long term survival. The findings of this study could inform strategy policy formulation and implementation in the agricultural sector, as pertaining to farm worker equity share schemes. The study used a sound and well-developed research design and methodology, which has been justified and successfully applied to this research; this method can be utilised by other similar studies to conduct empirical research in the field of farm worker equity share schemes. It is envisaged that the results and recommendations of this study could be used to implement effective strategies that could ensure the effective functioning of farm worker equity share schemes in South Africa.
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Date Issued: 2018

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Best simultaneous approximation in normed linear spaces

- Johnson, Solomon Nathan

Authors: Johnson, Solomon Nathan
Date: 2018
Subjects: Normed linear spaces , Approximation theory , Mathematical analysis
Language: English
Type: text , Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10962/58985 , vital:27400
Description: In this thesis we consider the problem of simultaneously approximating elements of a set B C X by a single element of a set K C X. This type of a problem arises when the element to be approximated is not known precisely but is known to belong to a set.Thus, best simultaneous approximation is a natural generalization of best approximation which has been studied extensively. The theory of best simultaneous approximation has been studied by many authors, see for example [4], [8], [25], [28], [26] and [12] to name but a few.
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Date Issued: 2018

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Between blue and light

- Campbell, Jennifer

Authors: Campbell, Jennifer
Date: 2018
Subjects: South African fiction (English) -- 21st century , Short stories, South African (English) -- 21st century
Language: English
Type: text , Thesis , Masters , MA
Identifier: http://hdl.handle.net/10962/63570 , vital:28441
Description: My novella follows a narrator observing her life, as she struggles with what it is to live in a world that she finds simultaneously frightening and beautiful. The story touches on the limitations of human connection and with loss in various forms. Set in both Cape Town and small town South Africa, the story explores the inner life of a woman detached and adrift.
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Date Issued: 2018

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Bioinformatics tool development with a focus on structural bioinformatics and the analysis of genetic variation in humans

- Brown, David K

Authors: Brown, David K
Date: 2018
Subjects: Bioinformatics , Human genetics -- Variation , High performance computing , Workflow management systems , Molecular dynamics , Next generation sequencing , Human Mutation Analysis (HUMA)
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/60708 , vital:27820
Description: This thesis is divided into three parts, united under the general theme of bioinformatics tool development and variation analysis. Part 1 describes the design and development of the Job Management System (JMS), a workflow management system for high performance computing (HPC). HPC has become an integral part of bioinformatics. Computational methods for molecular dynamics and next generation sequencing (NGS) analysis, which require complex calculations on large datasets, are not yet feasible on desktop computers. As such, powerful computer clusters have been employed to perform these calculations. However, making use of these HPC clusters requires familiarity with command line interfaces. This excludes a large number of researchers from taking advantage of these resources. JMS was developed as a tool to make it easier for researchers without a computer science background to make use of HPC. Additionally, JMS can be used to host computational tools and pipelines and generates both web-based interfaces and RESTful APIs for those tools. The web-based interfaces can be used to quickly and easily submit jobs to the underlying cluster. The RESTful web API, on the other hand, allows JMS to provided backend functionality for external tools and web servers that want to run jobs on the cluster. Numerous tools and workflows have already been added to JMS, several of which have been incorporated into external web servers. One such web server is the Human Mutation Analysis (HUMA) web server and database. HUMA, the topic of part 2 of this thesis, is a platform for the analysis of genetic variation in humans. HUMA aggregates data from various existing databases into a single, connected and related database. The advantages of this are realized in the powerful querying abilities that it provides. HUMA includes protein, gene, disease, and variation data and can be searched from the angle of any one of these categories. For example, searching for a protein will return the protein data (e.g. protein sequences, structures, domains and families, and other meta-data). However, the related nature of the database means that genes, diseases, variation, and literature related to the protein will also be returned, giving users a powerful and holistic view of all data associated with the protein. HUMA also provides links to the original sources of the data, allowing users to follow the links to find additional details. HUMA aims to be a platform for the analysis of genetic variation. As such, it also provides tools to visualize and analyse the data (several of which run on the underlying cluster, via JMS). These tools include alignment and 3D structure visualization, homology modeling, variant analysis, and the ability to upload custom variation datasets and map them to proteins, genes and diseases. HUMA also provides collaboration features, allowing users to share and discuss datasets and job results. Finally, part 3 of this thesis focused on the development of a suite of tools, MD-TASK, to analyse genetic variation at the protein structure level via network analysis of molecular dynamics simulations. The use of MD-TASK in combination with the tools developed in the previous parts of this thesis is showcased via the analysis of variation in the renin-angiotensinogen complex, a vital part of the renin-angiotensin system.
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Date Issued: 2018

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Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: an antimalarial, antitrypanosomal and cytotoxity evaluation

- Meyer, Franck, Isaacs, Michelle, Noundou, Xavier S, Krause, Rui W M, Teinkela, J E M, Hoppe, Heinrich C, Mpondo, Albert E M, Azebaze, Anatole G B, Nguemfo, Edwige L, Wintjens, Rene

Authors: Meyer, Franck , Isaacs, Michelle , Noundou, Xavier S , Krause, Rui W M , Teinkela, J E M , Hoppe, Heinrich C , Mpondo, Albert E M , Azebaze, Anatole G B , Nguemfo, Edwige L , Wintjens, Rene
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/126142 , vital:35853 , https://doi.org/10.1016/j.sjbs.2017.07.002
Description: The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC50 value 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC50 of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC50 value of 9.5 μg/mL) and trypanocidal (IC50 value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.
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Date Issued: 2018

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Biological activities of tulbaghia violacea against cryptococcus species

- Mitradev, Pattoo

Authors: Mitradev, Pattoo
Date: 2018
Subjects: Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Medicinal plants -- South Africa
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/32772 , vital:32357
Description: Cryptococcus neoformans and Cryptococcus gattii, which are environmental yeasts, are the etiological agents of cryptococcosis in both immunocompromised and immunocompetent individuals, and account for high mortality and morbidity rates in sub-Saharan Africa. The current antifungal agents used for treatment of cryptococcal infections either target the fungal cell wall (β-(1,3) glucan and chitin) or cell membrane directly or ergosterol biosynthetic pathways or fungal DNA and RNA. Gaps in antifungal therapy include the unavailability and exhorbitant costs of these drugs especially to patients in the developing world. Drug resistance to conventional drugs is also an ever-increasing problem. It is therefore essential to find alternative natural compounds from medicinal plants that are safer, cheaper and more widely available. Tulbaghia violacea, also known as wild garlic, has been used as a traditional remedy in South Africa for the treatment of several ailments. Aqueous and organic extracts of the plant have been demonstrated to have antimicrobial and antifungal activity against several pathogens. However, there is a huge gap in our current knowledge in that the mechanism/s of action/s of these extracts have not been fully investigated. The focus of the current study therefore was to determine whether T. violacea extracts from the roots, rhizome, leaves and tubers exhibited antifungal activity against C. neoformans and C. gattii and to evaluate the ability of the rhizome extract to induce changes in key fungal virulence factors. Three mechanisms (ergosterol, β-(1,3) glucan and chitin production) regulating the antifungal activity of the rhizome extract were also examined. In the current study, phytochemical analysis of aqueous extracts of the roots, leaves, rhizomes and tubers showed that the rhizomes had the highest phenolic, saponin and tannin content when compared to the other plant organs. Fingerprinting by GC-MS revealed identical compounds in the different plant parts with the detection of 4 H Pyran-4-one DDMP (known antifungal), previously unreported in studies on T. violacea. The bulk of the extract comprised of 40% sulphur-containing and 20% furan-containing compounds. The remaining minor compounds comprised of 2x alcohols (13.3%), 1x pyran (6.7%), 1x ketone (6.7%), 1x halogen (6.7%) and 1x acid (6.7%) compounds. The rhizomes also had highest content of 2 methyl methioacetic acid, benzophenone and chloromethyl methylsulfide compared to the other plant parts. The rhizomes were found to be more potent against both pathogenic fungi tested here with an MIC and MFC of 1.25 mg/ml. Nystatin was included as a positive control when determining the MIC’s and MFC’s of the different plant extracts. The antifungal nature of the T. violacea extracts in the current study may be due to the synergistic effects of the sulphide, furan, pyran and ketone compounds present in the extracts, but this still remains to be verified in future studies. An investigation of the effects of an aqueous rhizome extract of T. violacea on Cryptococcus virulence factors showed that phospholipase activity of C. neoformans and C. gattii remained unaffected with increasing sub-lethal doses of the plant extract. There was significant reduction in urease production in both fungi in a dose dependent manner relative to the untreated cultures after 24 hr exposure to the extract. However, urease production reverted to normal after 48 hr post exposure implying that the cultures were able to recover due to temporary inhibition of urease activity. A significant decrease in melanin production was observed in both C. neoformans and C. gattii with increasing sub-inhibitory concentrations of the rhizome extract. Investigation of the effect of the plant extract on the ultrastucture of the fungi via Transmission Electron Microscopy showed the induction of cytomorphological changes in C. neoformans and C. gattii. Changes included thickening of the cell wall, an increase in the number of vacuoles, mitochondrial swelling and occasional detachment of the membrane from the cell wall. These changes suggest the activation of possible defence mechanisms to compensate for the loss of cellular materials or an effort to sequester toxic T. violacea components or toxic intermediates generated from inhibited cellular pathways. The capsule size and architecture remained unaltered in the presence of sub-lethal doses of the rhizome extract. To study the mechanism of action of the rhizome extract on ergosterol biosynthesis, total sterols were extracted and ergosterol, squalene, 2,3-oxidosqualene and lanosterol were quantified using Reverse Phase High Performance Liquid Chromatography. Ergosterol concentration declined in a dose dependent manner for both pathogenic yeasts similar to the positive control terbinafine, while there was a slight accumulation of squalene in C. gattii only. 2,3-oxidosqualene levels accumulated in both fungi relative to the untreated control. Lanosterol production showed an oscillatory trend for the two microorganisms. Together, these findings indicate that the rhizome extract is capable of inhibiting squalene epoxidase and 2,3-oxidosqualene/ lanosterol cyclase causing a decrease in ergosterol production.
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Date Issued: 2018

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Biological activity of macrofungi in South Africa against respiratory and lung disease

- Didloff, Jenske

Authors: Didloff, Jenske
Date: 2018
Subjects: Macrofungi , Microbiology Medical microbiology
Language: English
Type: Thesis , Masters , MSc
Identifier: http://hdl.handle.net/10948/30138 , vital:30835
Description: Macrofungi represent an untapped source of natural bioactive compounds for various diseases, which have been targeted as potential therapeutic agents. The medicinal uses of macrofungi discovered to date include anticancer, antidiabetic, antioxidant, antimicrobial, and immunomodulatory properties. The knowledge regarding the medicinal uses of macrofungi in Africa is limited; however, it is believed that Africa may contain a large number of unidentified species of macrofungi. The objectives of this study were to: (i) screen the macrofungal extracts for antimicrobial activity against microorganisms responsible for respiratory diseases (e.g. Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Mycobacterium tuberculosis, HIV-1), (ii) determine the effect of macrofungal extracts on bacterial morphology, (iii) investigate the cytotoxicity of macrofungal extracts against human lung carcinoma cells, and to elucidate the mechanism/s of action of cytotoxicity/anticancer activity. In vitro bioassays for antimicrobial activity included: ρ-iodonitrotetrazolium chloride assays and microplate alamar blue assay (MABA), while the HIV-1 reverse transcriptase colorimetric ELISA and HIV-1 protease fluorometric assay kits were used for anti-HIV activity. Cytotoxicity of the macrofungal species against A549 lung cancer cell line was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and the IC50 values determined for the most cytotoxic macrofungal spp. The mechanism of cytotoxicity was investigated by cell cycle analysis and fluorescent staining to observe morphological and biochemical changes (i.e. acridine orange, caspase activation). Ethanol extracts of Amanita foetidissima, Gymnopilus junonius, Pisolithus tinctorius, Fomitopsis lilacinogilva, Stereum hirsutum and Pycnoporus sanguineus showed higher antimicrobial activity against the Gram-positive bacteria than aqueous extracts, with S. pneumoniae being the most susceptible. The ethanol extracts of Agaricus campestris, Chlorophyllum molybdites, Gymnopilus penetrans, Pseudophaeolus baudonii and Laetiporus sulphureus exhibited anti-TB (tuberculosis) activity with minimum inhibitory concentrations (MICs) ranging between 500-1,000 μg/mL. C. molybdites ethanol extract inhibited HIV-1 protease activity (IC50: 49.7 μg/mL). The macrofungal extracts did not inhibit HIV-1 reverse transcriptase activity. Ethanol extracts of F. lilacinogilva, G. junonius, P. sanguineus and the aqueous extract iv of P. baudonii were cytotoxic against A549 lung cancer cells at IC50 values of 69.2±3.6, 57±5, 7.4±1.1 and 53.6±1.1 μg/mL, respectively. Cell cycle arrest was observed in the G2 phase for both P. sanguineus and P. baudonii, and G2/M and early M phases for G. junonius and F. lilacinogilva, respectively. Apoptosis induced by macrofungal extracts was confirmed by fluorescent staining. Morphological and biochemical changes included chromatin condensation, membrane blebbing, loss of cytoskeletal structure, caspase activation and phosphatidylserine translocation. This study demonstrates the biological activities of selected macrofungal extracts and their potential mechanisms of action. Isolation and identification of active compounds require further analysis.
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Date Issued: 2018

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Biological activity of plant extracts and isolated compounds from Alchornea laxiflora: Anti-HIV, antibacterial and cytotoxicity evaluation

- Ndinteh, Derek T, Olivier, Denise K, Noundou, Xavier S, Krause, Rui W M, Mnkandhla, D, Isaacs, Michelle, Hoppe, Heinrich C, Muganza, F M, Mbafor, J T, Van Vuuren, S F, Patnala, S

Authors: Ndinteh, Derek T , Olivier, Denise K , Noundou, Xavier S , Krause, Rui W M , Mnkandhla, D , Isaacs, Michelle , Hoppe, Heinrich C , Muganza, F M , Mbafor, J T , Van Vuuren, S F , Patnala, S
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/126634 , vital:35907 , https://doi.org/10.1016/j.sajb.2018.08.010
Description: This study was designed to assess the cytotoxicity, anti-HIV and antibacterial efficacy of various solvent extracts of roots, stem and leaves of Alchornea laxiflora, as well as five compounds isolated from its methanolic stem extract viz.; ellagic acid (1); 3-O-methyl-ellagic acid (2), 3-O-β-d-glucopyranosyl-β-sitosterol (3), 3-O-acetyl-oleanolic acid (4) and 3-O-acetyl-ursolic acid (5). The tested crude extracts were prepared from several solvent polarities including: hexane (Hex), chloroform (CHCl3), ethyl acetate (EtOAc), ethanol (EtOH), methanol (MeOH) and water (H2O). The anti-HIV properties were assessed on HIV-1 subtype C integrase while the cytotoxicity was tested against Hela cells. The antibacterial activity was studied on a panel of pathogens including gastrointestinal, skin, respiratory and urinary-tract infection causing Gram positive bacteria viz.; Bacillus cereus (ATCC 11778), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 25923) and Staphylococcus saprophyticus (ATCC 15305)] and Gram-negative bacteria, i.e., Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Moraxella catarrhalis (ATCC 23246). All the tested samples were determined to be non-toxic due to the low inhibitions observed. The most potent anti-HIV activity was observed for the methanolic extract of A. laxiflora root (ALR4) with an IC50 value of 0.21 ng/ml, which was more active than chicoric acid used as reference drug (6.82 nM). Roots, stem and leaves of A. laxiflora extracts exhibited antibacterial activities against most of the Gram-positive bacteria with the minimum inhibitory concentrations (MIC) ranging between 50 and 63 μg/ml. Compounds 1–5 displayed antibacterial activities against S. saprophyticus with MIC values as low as 4 μg/ml. The results inferred from this study demonstrate the potential of A. laxiflora root as a source for new anti-HIV drugs and scientifically validate the traditional use of A. laxiflora in the treatment of gastrointestinal, skin, respiratory and urinary tract related infections. These results reaffirm the ethnopharmacological significance of African traditional medicines.
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Date Issued: 2018

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Biological control of Salvinia molesta in South Africa revisited

- Martin, Grant D, Coetzee, Julie A, Weyl, Philip S R, Parkinson, Matthew C, Hill, Martin P

Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
Date: 2018
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
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Date Issued: 2018

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Bioprospecting for amylases, cellulases and xylanases from ericoid associated fungi, their production and characterisation for the bio-economy

- Adeoyo, Olusegun Richard

Authors: Adeoyo, Olusegun Richard
Date: 2018
Subjects: Mycorrhizal fungi , Hydrolases , Ericaceae South Africa , Ericaceae Molecular aspects
Language: English
Type: Doctoral theses , text
Identifier: http://hdl.handle.net/10962/64327 , vital:28533
Description: South Africa is one of the most productive areas for ericaceous plants with about 850 identified species in the Cape Floral Region. The Albany Centre of Endemism where all fungi used in this study were isolated from, falls within this region. Ericaceous plants interact with some fungi via an association called the ericoid mycorrhizal (ERM) association. All fungi used in this study were isolated from roots of six ericaceous plants; Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Fungal enzymes are known to play a significant role in the food, brewing, detergent, pharmaceutical and biofuel industries. The enzyme industry is among the major sectors of the world, and additional novel sources are being explored from time to time. This study focussed on amylases (amyloglucosidase, AMG), cellulases (endoglucanase) and xylanases (endo-1,4-P-xylanase) production from ERM fungal isolates. Out of the fifty-one (51), fungal isolates screened, ChemRU330 (Leohumicola sp.), EdRU083 and EdRU002 were among the fungi that had the highest activities of all the enzymes. They were tested for the ability to produce amylases and cellulases under different pH and nutritional conditions that included: carbon sources, nitrogen sources and metal ions, at an optimum temperature of 28°C in a modified Melin-Norkrans (MMN) liquid medium. Cellulase specific activity of 3.99, 2.18 and 4.31 (U/mg protein) for isolates EdRU083, EdRU002 and ChemRU330, respectively, was produced at an optimal pH of 5.0. For amylase, ChemRU330 had the highest specific activity of 1.11 U/mg protein while EdRU083 and EdRU02 had a specific activity of 0.80 and 0.92 U/mg protein, respectively, at the same pH with corresponding biomass yield of 113, 125 and 97 mg/50 ml, respectively. Increased enzyme activities and improved mycelial biomass production were obtained in the presence of supplements such as potassium, sodium, glucose, maltose, cellobiose, tryptone and peptone, while NaFe-EDTA and cobalt inhibited enzyme activity. ChemRU330 was selected to determine the consistency and amount of amylase, cellulase and xylanase formed after several in vitro subculturing events. AMG and endo-1,4-P-xylanase were found to have the most consistent production throughout the study period. The AMG was stable at 45oC (pH 5.0), retaining approximately 65% activity over a period of 24 h. The molecular mass of AMG and endo-1,4-P-xylanase were estimated to be 101 kDa and 72 kDa, respectively. The Km and kcat were 0.38 mg/ml and 70 s-1, respectively, using soluble starch (AMG). For endo-1,4-P-xylanase, the Km and Vmax were 0.93 mg/ml and 8.54 U/ml, respectively, using beechwood xylan (endo-1,4-P-xylanase) as substrate. Additionally, crude extracts of five root endophytes with unique morphological characteristics were screened for antibacterial properties and was followed by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). L. incrustata (ChemRU330) and Chaetomium sp. extracts exhibited varying degrees of inhibition against two Gram-positive and Gram-negative bacteria. The crude extract of L. incrustata was the most effective which was found to inhibit Staphylococcus aureus (MIC: 1 mg/ml), Bacillus subtilis (MIC: 2 mg/ml) and Proteus vulgaris (MIC: 16 mg/ml). The L. incrustata displayed potential for antibacterial production and could be considered as an additional source of new antimicrobial agents in drug and food preservation. Also, the three isolates used for enzyme production were identified to genus and species levels, i.e., Leohumicola incrustata (ChemRU330), Leohumicola sp. (EdRU083) and Oidiodendron sp. (EdRU002) using both ITS and Cox1 DNA regions. The molecular analysis results indicated that these ERM mycorrhizal fungi were similar to those successfully described by some researchers in South Africa and Australia. Therefore, this study opens new opportunities for exploring ERM fungal biomolecules for the bio-economy. The promising physicochemical properties, starch and xylan hydrolysis end- products, and being non-pathogenic make AMG and endo-1,4-P-xylanase potential candidates for future applications as additives in the food industry for the production of glucose, glucose syrups, high-fructose corn syrups, and as well as the production of bioethanol. Finally, the findings of this study revealed that it is possible to produce hydrolytic enzymes from ERM fungi in vitro using chemically defined media. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2018
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Date Issued: 2018

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Biotic and abiotic drivers of macroinvertebrate assemblages in a South African river

- Bellingan, Terence Andrew

Authors: Bellingan, Terence Andrew
Date: 2018
Subjects: Aquatic insects -- South Africa -- Eastern Cape , Stream ecology -- South Africa -- Eastern Cape , Freshwater ecology -- South Africa -- Eastern Cape , Riparian areas -- Management , Ecosystem management -- South Africa -- Eastern Cape , Mayflies -- South Africa -- Eastern Cape , Stoneflies -- South Africa -- Eastern Cape , Keiskamma River
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/61839 , vital:28067
Description: Aquatic insects are the most numerically abundant and diverse group of organisms found in lotic ecosystems in South Africa and the world over. They play vital roles in freshwater ecosystem functioning, processing nutrients and in turn forming integral links in stream food-webs. This thesis focussed on examining the macroinvertebrate fauna within three reaches of headwater streams of the Keiskamma River system: reaches that were considered to be fishless; reaches that were invaded by non-native salmonid species; and reaches that were dominated by native fish. I described the effects of predatory fish presence through detailed examination of macroinvertebrate assemblage composition; macroinvertebrate drift timing and density; and through niche utilisation determined from stable isotope data. Patterns in the macroinvertebrate assemblages of the headwaters of the Keiskamma River appear to be driven more strongly by flow rate and seasonal influences, but fish presence and biotope availability were also significant drivers. Niche shifts due to predator presence were not easy to detect and, while patterns of influence may have been evident, they were not found to be significant. However, I demonstrated that salmonids selectively feed on native fish species when the opportunity is presented, occupying significantly higher trophic levels when co-occurring with native fish than in invaded reaches where native fish are absent. Drift timing and density were demonstrated to be significantly different between reach for specific macroinvertebrate species from the Ephemeroptera and Plecoptera, under differing fish predation regimes, in agreement with what has been observed from studies in rivers elsewhere. In freshwater ecosystems of South Africa and worldwide, mitigation of negative effects of alien fishes through their removal using piscicides may also affect non-target organisms. To better understand the effects of just such a removal operation, employed for the first time in the history of freshwater conservation in South Africa, macroinvertebrate communities were assessed for non-target effects of rotenone. The fish eradication operations were demonstrated to have a short-term negative effect on the macroinvertebrate assemblage, through water quality index measurements and alteration of densities of macroinvertebrate taxa collected from stone surfaces. However, no long-term detrimental impact was observed as macroinvertebrate faunas returned to a comparable pre-treatment state within a year of each rotenone application.
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Date Issued: 2018

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Bird responses to land use change: Guild diversity in a Kenyan coastal forest and adjoining habitats

- Chiawo, David O, Kombe, Wellington N, Craig, Adrian J F K

Authors: Chiawo, David O , Kombe, Wellington N , Craig, Adrian J F K
Date: 2018
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/448820 , vital:74763 , https://doi.org/10.1080/01584197.2018.1431052
Description: Land use change can have profound effects on forest ecology, particularly on the avian community. Arabuko-Sokoke Forest, one of the Important Bird Areas (IBAs) in Kenya, is under threat due to ongoing land use change in the surroundings that could affect species composition of many bird guilds. However, information on the response of different guilds in tropical land use systems is sparse in Africa. We examined the effects of land use on bird guilds in primary forest (Arabuko-Sokoke Forest), adjoining plantations, and neighbouring farmland. Point counts were distributed equally in the three land use systems to survey bird populations. A total of 2600 bird observations was recorded, representing 97 species in five main feeding guilds (frugivores, nectarivores, insectivores, carnivores, and granivores). Granivores were most abundant and diverse in farmland, while carnivores (primarily raptors) utilised all habitats. Insectivores were most diverse in primary forest where vertical heterogeneity of the vegetation and the presence of large fruiting trees significantly influenced their occurrence. Specialist nectarivores were most frequent in primary forest, whereas occasional nectarivores were less abundant there. Contrary to expectation, frugivore diversity showed no significant effect of land use.
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Date Issued: 2018

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Black South African men’s adjustment to divorce: a divorce-stress-adjustment model

- Muchena, Kudakwashe Christopher

Authors: Muchena, Kudakwashe Christopher
Date: 2018
Subjects: Divorce -- Psychological aspects , Social psychology Men -- Psychology
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/50121 , vital:42048
Description: The decision to divorce marks a turning point for each individual involved. It can be viewed as more than just a legal process. From a psychological perspective, it does not matter who initiated the divorce, it always comes with emotional ramifications for all those involved. Statistically there is a high rate of divorce in South Africa and there have been significant shifts in trends over time. However, black South African men’s experience of, action in, and adjustment to divorce has been relatively neglected in the divorce research, yet it is important for understanding contemporary social arrangements and processes, as well as for broadening the understanding of black South African men’s lives. How black South African men describe their situations and respond to marital dissolution may point to their positions in the gender-structured community and to how they interpret the nature of social practice, marriages, divorce and their position in society. The present study aimed at exploring black South African men’s experience of, and adjustment to, divorce. More specifically, the study developed a divorce-stress-adjustment model for divorced black South African men. The theoretical framework underpinning this study was that of Symbolic Interactionism that was complemented and enhanced by Erikson’s Psychosocial Theory, focusing specifically on identity development in adulthood. This was a qualitative study using an Interpretative Phenomenological Analysis (IPA) as both the research design and data analytic theory and process. The eight participants were volunteers who were recruited purposively. In accordance with IPA guidelines, data for the study was collected using biographical questionnaires and semi-structured interviews. The emerging themes were grouped into four superordinate themes, that is, pre-divorce experiences, experiencing divorce, adjustment process and post-divorce experience. Each superordinate theme had corresponding subordinate themes and subthemes. The themes were then used to develop the divorce-stress adjustment model indicating that the experience of divorce is an interconnected process. Weed’s recommendations for interpretative synthesis of interview data were used.
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Date Issued: 2018

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Black South African men’s adjustment to divorce: a divorce-stress-adjustment model

- Muchena, Christopher Kudakwashe

Authors: Muchena, Christopher Kudakwashe
Date: 2018
Subjects: Divorced men -- Psychological aspects , Adjustment (Psychology)
Language: English
Type: Thesis , Doctoral , DPhil
Identifier: http://hdl.handle.net/10948/17933 , vital:28543
Description: The decision to divorce marks a turning point for each individual involved. It can be viewed as more than just a legal process. From a psychological perspective, it does not matter who initiated the divorce, it always comes with emotional ramifications for all those involved. Statistically there is a high rate of divorce in South Africa and there have been significant shifts in trends over time. However, black South African men’s experience of, action in, and adjustment to divorce has been relatively neglected in the divorce research, yet it is important for understanding contemporary social arrangements and processes, as well as for broadening the understanding of black South African men’s lives. How black South African men describe their situations and respond to marital dissolution may point to their positions in the gender-structured community and to how they interpret the nature of social practice, marriages, divorce and their position in society. The present study aimed at exploring black South African men’s experience of, and adjustment to, divorce. More specifically, the study developed a divorce-stress-adjustment model for divorced black South African men. The theoretical framework underpinning this study was that of Symbolic Interactionism that was complemented and enhanced by Erikson’s Psychosocial Theory, focusing specifically on identity development in adulthood. This was a qualitative study using an Interpretative Phenomenological Analysis (IPA) as both the research design and data analytic theory and process. The eight participants were volunteers who were recruited purposively. In accordance with IPA guidelines, data for the study was collected using biographical questionnaires and semi-structured interviews. The emerging themes were grouped into four superordinate themes, that is, pre-divorce experiences, experiencing divorce, adjustment process and post-divorce experience. Each superordinate theme had corresponding subordinate themes and subthemes. The themes were then used to develop the divorce-stress-adjustment model indicating that the experience of divorce is an interconnected process. Weed’s recommendations for interpretative synthesis of interview data were used.
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Date Issued: 2018

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