Showing papers by "University of the Witwatersrand published in 2004"

Extinction risk from climate change

Abstract: Climate change over the past approximately 30 years has produced numerous shifts in the distributions and abundances of species and has been implicated in one species-level extinction. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15-37% of species in our sample of regions and taxa will be 'committed to extinction'. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction ( approximately 18%) than mid-range ( approximately 24%) and maximum-change ( approximately 35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration.

Finding your way in qualitative research, E. Henning, W. van Rensburg and B. Smit : book review

Abstract: Extracted from text ... 509 Title: Finding your way in qualitative research Authors: E. Henning, W. van Rensburg and B. Smit Year: 2004 Publisher: Van Schaik ISBN: 0-627-02545-5 (paperback, 179 pages) 'It's like trying to navigate a dangerous, and mainly uncharted raging river, full of hidden currents and submerged rocks, only no-one will give you a boat that doesn't leak.' This quote, taken from the diary of a postgraduate student attempting to conduct qualitative research for the first time, succinctly and trenchantly summarises the frustration and confusion often faced by 'novice' qualitative researchers. Whilst the use of qualitative methods in conducting research within ..

A role for Streptococcus pneumoniae in virus-associated pneumonia

Abstract: Here we show, in a double-blind, randomized, placebo-controlled trial in 37,107 fully immunized infants in Soweto, South Africa, that a 9-valent pneumococcal conjugate vaccine, PncCV, prevents 31% (95% confidence interval = 15-43%) of pneumonias associated with any of seven respiratory viruses in children in hospital. These data suggest that the pneumococcus has a major role in the development of pneumonia associated with these viruses and that viruses contribute to the pathogenesis of bacterial pneumonia.

Effective Stress in Unsaturated Soils: Review with New Evidence

Abstract: The application of the effective stress principle to unsaturated soils is critically reviewed, and the reasons underlying the difficulties in previous investigations of the effective stress in unsaturated soils are highlighted. The validity of the relationship proposed by Khalili and Khabbaz in 1998 for the determination of the effective stress parameter, χ, is examined using an extensive array of experimental data. It is shown that quantitative predictions of shear strength and volume change in unsaturated soils can be made using the effective stress concept. The uniqueness of the critical state line in the deviatoric stress–effective mean stress plane for saturated as well as unsaturated soils is investigated, and the incremental form of the effective stress parameter is derived.

Combination Antibiotic Therapy Lowers Mortality among Severely Ill Patients with Pneumococcal Bacteremia

Abstract: Retrospective studies have suggested that combination antibiotic therapy for severe bacteremic pneumococcal pneumonia may reduce mortality. We assessed this issue in a prospective, multicenter, international observational study of 844 adult patients with bacteremia due to Streptococcus pneumoniae. The effect of combination antibiotic therapy versus monotherapy on mortality was examined by univariate analyses and by logistic regression models. The 14-day mortality was not significantly different for the two groups. However, among critically ill patients, combination antibiotic therapy was associated with lower 14-day mortality (23.4 versus 55.3%, p = 0.0015). This improvement in survival was independent of country of origin, intensive care unit support, class of antibiotics, or in vitro activity of the antibiotics prescribed. Combination antibiotic therapy improved survival among critically ill patients with bacteremic pneumococcal illness.

Sexual Power and HIV Risk, South Africa

Abstract: Gender power inequities are believed to play a key role in the HIV epidemic through their effects on women's power in sexual relationships. We hypothesized that lack of sexual power, measured with a four-point relationship control scale and by a woman's experience of forced sex with her most recent partner, would decrease the likelihood of consistent condom use and increase the risk for HIV infection among sexually experienced, 15- to 24-year-old women in South Africa. While limited sexual power was not directly associated with HIV, it was associated with inconsistent condom use: women with low relationship control were 2.10 times more likely to use condoms inconsistently (95% confidence interval [CI] 1.17-3.78), and women experiencing forced sex were 5.77 times more likely to use condoms inconsistently (95% CI 1.86-17.91). Inconsistent condom use was, in turn, significantly associated with HIV infection (adjusted odds ratio 1.58, 95% CI 1.10-2.27).

Prevalence and Patterns of Gender-based Violence and Revictimization among Women Attending Antenatal Clinics in Soweto, South Africa

Abstract: Gender-based violence is a key health risk for women globally and in South Africa. The authors analyzed data from 1,395 interviews with women attending antenatal clinics in Soweto, South Africa, between November 2001 and April 2002 to estimate the prevalence of physical/sexual partner violence (55.5%), adult sexual assault by nonpartners (7.9%), child sexual assault (8.0%), and forced first intercourse (7.3%). Age at first experience of each type of violence was modeled by the Kaplan-Meier method, and Cox hazard models with time-varying covariates were used to explore whether child sexual assault and forced first intercourse were associated with risk of violent revictimization in adulthood. Child sexual assault was associated with increased risk of physical and/or sexual partner violence (risk ratio = 2.43, 95% confidence interval: 1.93, 3.06) and with adult sexual assault by a nonpartner (risk ratio = 2.33, 95% confidence interval: 1.40, 3.89). Forced first intercourse was associated with increased risk of physical and/or sexual partner violence (risk ratio = 2.64, 95% confidence interval: 2.07, 3.38) and nonsignificantly with adult sexual assault by a nonpartner (risk ratio = 2.14, 95% confidence interval: 0.92, 4.98). This study confirms the need for increased attention by the public health community to primary and secondary prevention of gender-based violence, with a specific need to reduce risk among South African adolescents.

Prevalence of neutralizing antibodies to adenoviral serotypes 5 and 35 in the adult populations of The Gambia, South Africa, and the United States.

Abstract: One of the major limitations of the use of adenoviruses as gene therapy vectors is the existence of preformed immunity in various populations. Recent studies have linked failure of adenoviral gene therapy trials to the presence of antiadenoviral neutralizing antibodies (NAb). Understanding the distribution and specificity of such antibodies will assist in the design of successful recombinant adenoviral gene therapies and vaccines. To assess the prevalence of NAb to adenovirus serotypes 5 and 35 (Ad5 and Ad35), we analyzed serum samples from adult immunocompetent individuals living in The Gambia, South Africa, and the United States by using a neutralization assay. Serum samples were incubated with A549 lung carcinoma cells and adenoviruses encoding enhanced green or yellow fluorescent proteins; results were analyzed by fluorescence microscopy and flow cytometry. Using this technique, we found a high prevalence of NAb against Ad5 in Gambian, South African, and U.S. subjects at both low and high titers. Conversely, all subjects displayed a low prevalence of NAb to Ad35; when present, anti-Ad35 NAb were seen at low titers. Because of the ability of adenoviruses to elicit systemic and mucosal immune responses, Ad35 with its low NAb prevalence appears to be an attractive candidate vector for gene therapy applications.

Adherence to antiretroviral therapy in HIV-infected adults in Soweto, South Africa.

Abstract: Little is known about achievable levels of antiretroviral treatment (ART) adherence in resource-limited settings. We conducted a cross-sectional study of adherence among patients at Chris Hani Baragwanath Hospital's Adult HIV Clinic in Soweto, South Africa. Adherence was assessed using a 1-month, self-report questionnaire and was calculated as a ratio of doses taken to doses prescribed. The 66 patients studied had a mean age of 36.1 years, a median duration of ART use of 18 months, and an overall baseline median CD4+ cell count of 200/mm3 (IQR: 114–364). The adherence reported by these patients for the previous month was >95% for 58 patients (88%), 90–95% for 6 (9%) and, <90% for 2 (3%). The main reasons given for missing doses were being away from home (30%), difficulty with the dosing schedules (23%), and running out of pills (12%). Adherence decreased considerably with fear of being stigmatized by the sexual partner (OR = 0.13 95%, CI 0.02–0.70). Plasma HIV RNA levels were <400 copies/ml in the majorit...

Growth Impact and Determinants of Foreign Direct Investment into South Africa, 1956-2003

Abstract: The paper is concerned with the growth impact and the determinants of foreign direct investment in South Africa. Estimation is in terms of a standard spill-over model of investment, and in terms of a new model of locational choice in FDI between domestic and foreign alternatives. We find complementarity of foreign and domestic capital in the long run, implying a positive technological spill-over from foreign to domestic capital. While there is a crowd-out of domestic investment from foreign direct investment, this impact is restricted to the short run. Further we find that foreign direct investment in South Africa has tended to be capital intensive, suggesting that foreign direct investment has been horizontal rather than vertical. Determinants of foreign direct investment in South Africa lie in the net rate of return, as well as the risk profile of the foreign direct investment liabilities. Policy handles are both direct and powerful. Reducing political risk, ensuring property rights, most importantly bolstering growth in the market size, as well as wage moderation, lowering corporate tax rates, and ensuring full integration of the South African economy into the world economy all follow as policy prescriptions from our empirical findings.

The Mycobacterium tuberculosis protein serine/threonine kinase PknG is linked to cellular glutamate/glutamine levels and is important for growth in vivo.

Abstract: Summary The function of the Mycobacterium tuberculosis eukaryotic-like protein serine/threonine kinase PknG was investigated by gene knock-out and by expres- sion and biochemical analysis The pkn G gene (Rv0410c), when cloned and expressed in Escherichia coli , encodes a functional kinase An in vitro kinase assay of the recombinant protein demonstrated that PknG can autophosphorylate its kinase domain as well as its 30 kDa C-terminal portion, which contains a tetratricopeptide (TPR) structural signalling motif Western analysis revealed that PknG is located in the cytosol as well as in mycobacterial membrane The pkn G gene was inactivated by allelic exchange in M tuberculosis The resulting mutant strain causes delayed mortality in SCID mice and displays decreased viability both in vitro and upon infection of BALB/c mice The reduced growth of the mutant was more pronounced in the stationary phase of the mycobacterial growth cycle and when grown in nutri- ent-depleted media The PknG-deficient mutant accu- mulates glutamate and glutamine The cellular levels of these two amino acids reached approximately threefold of their parental strain levels Higher cellular levels of the amine sugar-containing molecules, GlcN- Ins and mycothiol, which are derived from glutamate, were detected in the D pknG mutant De novo glutamine synthesis was shown to be reduced by 50% This is consistent with current knowledge sug- gesting that glutamine synthesis is regulated by glutamate and glutamine levels These data support our hypothesis that PknG mediates the transfer of signals sensing nutritional stress in M tuberculosis and translates them into metabolic adaptation

Hierarchical Targeting of Subtype C Human Immunodeficiency Virus Type 1 Proteins by CD8+ T Cells: Correlation with Viral Load

Abstract: An understanding of the relationship between the breadth and magnitude of T-cell epitope responses and viral loads is important for the design of effective vaccines. For this study, we screened a cohort of 46 subtype C human immunodeficiency virus type 1 (HIV-1)-infected individuals for T-cell responses against a panel of peptides corresponding to the complete subtype C genome. We used a gamma interferon ELISPOT assay to explore the hypothesis that patterns of T-cell responses across the expressed HIV-1 genome correlate with viral control. The estimated median time from seroconversion to response for the cohort was 13 months, and the order of cumulative T-cell responses against HIV proteins was as follows: Nef > Gag > Pol > Env > Vif > Rev > Vpr > Tat > Vpu. Nef was the most intensely targeted protein, with 97.5% of the epitopes being clustered within 119 amino acids, constituting almost one-third of the responses across the expressed genome. The second most targeted region was p24, comprising 17% of the responses. There was no correlation between viral load and the breadth of responses, but there was a weak positive correlation (r = 0.297; P = 0.034) between viral load and the total magnitude of responses, implying that the magnitude of T-cell recognition did not contribute to viral control. When hierarchical patterns of recognition were correlated with the viral load, preferential targeting of Gag was significantly (r = 0.445; P = 0.0025) associated with viral control. These data suggest that preferential targeting of Gag epitopes, rather than the breadth or magnitude of the response across the genome, may be an important marker of immune efficacy. These data have significance for the design of vaccines and for interpretation of vaccine-induced responses.

Sexual selection, natural selection and the evolution of dimorphic coloration and ornamentation in agamid lizards

Abstract: Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sexual dimorphism in head and body size were used as indirect indicators of sexual selection, and habitat type (openness) as an index of natural selection. We examined separately the dichromatism of body regions ’exposed to‚ and ’concealed from‚ visual predators, because these body regions are likely to be subject to different selection pressures. Dichromatism of ’exposed‚ body regions was significantly associated with habitat type: males were typically more conspicuously coloured than females in closed habitats. By contrast, dichromatism of ’concealed‚ body regions and ornament dimorphism were positively associated with sexual size dimorphism (SSD). When we examined male and female ornamentation separately, however, both were positively associated with habitat openness in addition to snout–vent length and head SSD. These results suggest that natural selection constrains the evolution of elaborate ornamentation in both sexes as well as sexual dichromatism of body regions exposed to visual predators. By contrast, dichromatism of ’concealed‚ body regions and degree of ornament dimorphism appear to be driven to a greater degree by sexual selection.

Polymer stabilized silver nanoparticles: a photochemical synthesis route

Abstract: This study describes a novel and convenient way for the preparation of polymer stabilized colloidal silver by an ultra-violet irradiation technique. Methoxypolyethylene glycol (MPEG) generates free radicals in presence of ultra-violet radiation and acts as the reducing agent towards the silver ion. MPEG also serves as a stabilizer of the silver particles formed.

Investigating mathematics teacher learning within an in-service community of practice: the centrality of confidence

Abstract: This paper is part of a broader study that draws on Wenger's (Wenger, E.:1998, Communities of Pratice: Learning, Meaning, and Identity, Cambridge University Press, New Work) social practice perspective to investigate teacher learning. The study extends Wenger's complex model of interrelated components of learning (as meaning, practice, identity and community) to describe and explain teacher learning that occurs within a mathematics senior-phase in-service program that was stimulated by curriculum change. The study uses qualitative ethnography in which the researcher performs the dual role of both coordinator and researcher of the in-service practice. In a longitudinal study the phenomenon of confidence emerged in teachers' descriptions and explanations of their learning. In this paper I explore this phenomenon both empirically and theoretically. The extension of Wenger's (1998) theory to include the overarching and interacting component of confidence is embedded in and derived from data analysis of 10 teachers' learning, over a 2-year period, during a time of radical curriculum change. Since it would be incoherent within this framework to draw on psychological explanations of confidence I set out to explore confidence from within a social practice frame in a way that is grounded in data of the teachers in this study. The paper offers a concept of confidence in relation to teacher learning as ‘learning as mastery’, and confidence as both a product and a process of learning. Teachers can at once state their confidence as mathematics teachers, and their confidence to admit to what they do not know and still need to learn. It is argued that this is a primary condition for ongoing learning in a profession like mathematics teaching. In addition, the paper provides a critique of the applicability of Wenger's work to the context of teacher education and in particular highlights the absence of the notion of confidence within his work.

Volunteer tourism: The case of Habitat for Humanity South Africa

Abstract: Volunteer tourism as a subset of alternative tourism is the focus of analysis. This paper contributes to the limited writings on volunteer tourism by investigating the activities in South Africa of Habitat for Humanity, a grassroots ecumenical Christian organization that works in partnership with communities to eliminate poverty through the provision of shelter. A profile of the volunteer tourist and of their tourism experience in South Africa is presented which is based largely upon the return of 123 questionnaires from volunteer tourists in South Africa working with the local branch of Habitat for Humanity.

Global strategies to prevent bacterial pneumonia in adults with HIV disease

Abstract: Summary We examined the peer-reviewed literature on the burden of bacterial pneumonia and the effectiveness of interventions for its prevention among HIV-infected adults in developed and developing countries. Bacterial pneumonia rates were up to 25-fold higher among HIV-infected adults than in the general community, with rates increasing as CD4+ T-cell count decreases. In developed countries, cohort studies showed that highly active antiretroviral therapy (HAART) had the most consistent effect on reducing pneumonia. In a prospective cohort and case-control studies from these regions, pneumococcal polysaccharide vaccine reduced pneumococcal disease in certain subgroups, particularly those with higher CD4+ T cells/μL. In patients with fewer than 200 CD4+ T cells/μL, antimicrobial prophylaxis was usually effective in reducing pneumonia. In sub-Saharan Africa, randomised controlled trials concluded that co-trimoxazole prophylaxis decreased rates of bacterial pneumonia, but pneumococcal polysaccharide vaccine prevented neither pneumonia nor invasive pneumococcal disease. Although not yet fully evaluated in Africa, based on experience in industrialised nations, use of HAART in Africa may have substantial potential to prevent bacterial pneumonia.

Ochre in hafting in Middle Stone Age southern Africa: a practical role

Abstract: Ochre is well-known as a substance used in Stone Age symbolism, but it can be shown to have had practical functions too. The authors used microscopic examination of Middle Stone Age tools to show they had been hafted, making use of an adhesive compound which included ochre in its recipe.

Prevalence of stroke survivors in rural South Africa: results from the Southern Africa Stroke Prevention Initiative (SASPI) Agincourt field site.

Abstract: Background and purpose The importance of stroke in low-income regions such as sub-Saharan Africa has recently been emphasized. However, little is known about the burden of stroke in sub-Saharan Africa. We investigated the prevalence of stroke survivors in the Agincourt Health and Population Unit, a demographic surveillance site in the rural northeast of South Africa. Methods Census workers asked household informants 2 screening questions for stroke during the annual census. If either question was answered positively, a clinician visited individuals aged > or =15 years to confirm the likely diagnosis of stroke. We performed a detailed assessment and defined stroke according to the World Health Organization criteria. Results A total of 42 378 individuals were aged > or =15 years. There were 982 positive responses to the questionnaire, and we examined 724 individuals (74%). We identified 103 strokes (crude prevalence, 243/100 000). After adjustment for those we did not examine, the prevalence was 300/100 000 (95% CI, 250 to 357). Sixty-six percent of stroke survivors needed help with at least 1 activity of daily living (Segi age-standardized prevalence, 200/100 000). Conclusions Stroke prevalence in rural South Africa is higher than previously documented in Africa but lower than in high-income countries. However, the prevalence of stroke survivors requiring help with at least 1 activity of daily living is already at high-income country levels. South Africa suffers from a huge burden of HIV/AIDS and diseases of poverty and violence and now faces the challenge of adapting its health systems to face the coming epidemic of vascular disease.