Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320120003&lang=en vol. 108 num. 5-6 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Purposeful support for health research in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300001&lng=en&nrm=iso&tlng=en <![CDATA[<b>What's new is old</b>: <b>Comments on (more) archaeological evidence of one-million-year-old fire from South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300002&lng=en&nrm=iso&tlng=en <![CDATA[<b>Exploring the significance of land-cover change in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300003&lng=en&nrm=iso&tlng=en <![CDATA[<b>Listening to distant thunder</b>: <b>The art of Peter Clarke</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300004&lng=en&nrm=iso&tlng=en <![CDATA[<b>Stem cell research engenders interdisciplinary collaboration in science, ethics and religion</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300005&lng=en&nrm=iso&tlng=en <![CDATA[<b>European Research Council scheme offers opportunities for Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300006&lng=en&nrm=iso&tlng=en <![CDATA[<b>Christina Scott</b>: <b>Science journalist (1961-2011)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300007&lng=en&nrm=iso&tlng=en <![CDATA[<b>A disturbing reminder</b>: <b>The experiences of conscripted soldiers in South Africa's Border War</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300008&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300009&lng=en&nrm=iso&tlng=en <![CDATA[<b>Natural products research in South Africa</b>: <b>1890-2010</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300010&lng=en&nrm=iso&tlng=en Having spent some 50 years as an organic chemist with an interest in medicinal plant chemistry in South Africa it was relevant now to ask three questions, (1) when were natural products first utilised, (2) who were the people involved, and (3) what is the status quo? Based on older literature published in the South African Journal of Chemistry, information gleaned from attendance at innumerable chemistry conferences, and relevant literature in university archives, a great deal of information was gathered to answer the first two questions. For example, that the first veterinarian to treat cattle diseases caused by poisonous plants in the Eastern Cape was Dr Jotella Soga in the 1890s. Contributions from other prominent scientists such as Marais, Rindl, Rimington and Warren followed. From about 1940 to the 1990s, researchers concentrated mainly on the isolation of new compounds from local plants for which some indigenous knowledge was recorded. Foreign chemists also arrived and did a fair amount of 'exploitation' of natural products. Thus, the anti-cancer compound combretastatin was first isolated from the indigenous tree Combretum caffrum. Plant chemistry in South Africa has blossomed in the last decade, with many students from previously disadvantaged backgrounds, but with a keen interest in muti or medicinal chemistry, entering the field. Recent findings have rekindled the belief that a major development in natural products would at last emerge from Africa. <![CDATA[<b>Overweight and obesity in children and adolescents</b>: <b>the South African problem</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300011&lng=en&nrm=iso&tlng=en Overweight and obesity in children and adolescents are on the increase worldwide. Overweight and obesity increase the risk for the development of non-communicable diseases during childhood and adolescence, and predispose the individual to the development of overweight, obesity, cardiovascular disease, and metabolic and other disorders in adulthood. In Africa the number of overweight or obese children has doubled since 1990. In South Africa, overweight and obesity in children and adolescents are on the increase, but the prevalence varies with age, gender and population group. These differences are important when intervention programmes and policies are considered. South Africa faces a double burden of disease where undernutrition and overweight or obesity are found in the same populations, in the same households and even in the same children. Malnutrition is a major contributor to the double burden of disease in South African children and adolescents. <![CDATA[<b>Antimicrobial properties of the skin secretions of frogs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300012&lng=en&nrm=iso&tlng=en Antimicrobial resistance results in increased morbidity and mortality, and increased health-care costs. Therefore the need to develop new classes of antibiotics is indispensable. Antimicrobial peptides are a relatively new class of potential antibiotics which are fast acting, possess broad-spectrum activity and are able to escape many of the currently known mechanisms of drug resistance. They have been shown to be active against Gram-negative and Gram-positive bacteria, fungi, enveloped viruses and even cancer cells. However, toxicity to healthy host cells remains a concern and has affected the clinical development of therapeutics based on antimicrobial peptides. The purpose of this review is to discuss recent advances in research focused on antimicrobial peptides from frogs and the challenges in conducting research in this area in southern Africa. An extensive literature review of relevant articles published between 1980 and the present was conducted using PubMed, ScienceDirect, Sabinet, Elsevier and GoogleScholar. There has been little research done on anurans from southern Africa which are endemic to the region, and there is therefore a need to focus on this group for the purposes of bioprospecting for potentially new antimicrobial peptide compounds. <![CDATA[<b>The use of civilian-type GPS receivers by the military and their vulnerability to jamming</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300013&lng=en&nrm=iso&tlng=en We considered the impact of external influences on a GPS receiver and how these influences affect the capabilities of civilian-type GPS receivers. A standard commercial radio frequency signal generator and passive GPS antenna were used to test the sensitivity of GPS to intentional jamming; the possible effects of the terrain on the propagation of the jamming signal were also tested. It was found that the high sensitivity of GPS receivers and the low strength level of GPS satellite signals combine to make GPS receivers very vulnerable to intentional jamming or unintentional radio frequency interference. Terrain undulation was used to shield GPS antennas from the direct line-of-sight of the jamming antenna and this indicated that terrain characteristics can be used to mitigate the effects of jamming. These results illuminate the vulnerability of civilian-type GPS receivers to the possibility and the ease of disablement and establish the foundation for future work. <![CDATA[<b>Proportionality in enterprise development of South African towns</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300014&lng=en&nrm=iso&tlng=en We investigated proportionalities in the enterprise structures of 125 South African towns through examining four hypotheses, (1) the magnitude of enterprise development in a town is a function of the population size of the town; (2) the size of an enterprise assemblage of a town is a function of the town's age; (3) there are statistically significant relationships, and hence proportionalities, between the total number of enterprises in towns and some, if not all, of the enterprise numbers of different business sectors in towns; and (4) the implications of proportionalities have far-reaching implications for rural development and job creation. All hypotheses were accepted on the basis of statistically significant (p < 0.05) correlations, except for the second hypothesis - the age of a town does not determine the size of its enterprise assemblage. Analysis for the fourth hypothesis suggested that there are two broad entrepreneurial types in South African towns: 'run-of-the-mill' entrepreneurs and 'special' entrepreneurs, which give rise to different enterprise development dynamics. 'Run-of-the-mill' enterprises are dependent on, and limited by, local demand and if there is only a small demand, the entrepreneurial space is small. By comparison, 'special' enterprises have much larger markets because their products and/or services are exportable. We propose that the fostering of 'special' entrepreneurs is an imperative for local economic development in South African towns. <![CDATA[<b>Remote sensing land-cover change in Port Elizabeth during South Africa's democratic transition</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300015&lng=en&nrm=iso&tlng=en Urban population increase has caused significant urban landscape transformation globally. Before 1994, South Africa's highly regulated urban growth was shaped by the restrictive Prevention of Illegal Squatters Act of 1951. After the abolishment of the act in the 1980s, the period of transition to democracy in the 1990s was characterised by an unprecedented urban population influx that caused a myriad of socio-economic and environmental challenges. These challenges have consequently compounded the need to monitor urban growth for the planning and optimisation of urban spaces. The limitations of traditional mapping methods, such as surveying and photogrammetry, in urban mapping are well documented. In the recent past, satellite remote sensing has emerged as one of the most viable urban mapping tools. Using post-classification comparisons, we sought to monitor major land use and land cover (LULC) changes in the city of Port Elizabeth during South Africa's democratic transition (1990-2000). Images for 1990, 1995 and 2000 were acquired, geo-rectified and atmospherically corrected. An iterative self-organising data analysis (ISODATA) was then used to generate existing LULCs. Classes generated using ISODATA were then amalgamated to the city's major LULCs and resultant classes were validated using aerial photographs and field visits. Results showed that 'Built-up' and 'Bare surface' LULC classes had the highest increase and decrease, respectively. There was no change in the 'Beach or dune' LULC, whereas 'Green vegetation' and 'Water' classes had minimal changes. This study illustrates the efficacy of remote sensing in monitoring urban change and the potential of remote sensing to aid decision-making in rapidly changing urban landscapes. <![CDATA[<b>'God is my forest' </b>: <b>Xhosa cultural values provide untapped opportunities for conservation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300016&lng=en&nrm=iso&tlng=en In South Africa conservation is still largely framed in terms of Western scientific values, with a focus on material benefits to local communities, whilst little is known about the intangible values local people attach to nature and biodiversity. We explored the cultural, spiritual and emotional relationships with nature expressed by Xhosa people, within the Maputaland-Pondoland-Albany Hotspot, as well as the activities that mediate this relationship. A descriptive research approach was applied to document the emotions, meanings and values associated with landscape elements. This approach included group and individual interviews and 'walk-in-the-woods' interviews and participatory mapping exercises. Respondents portrayed a strong, although not always easily articulated, appreciation for nature, especially ihlathi lesiXhosa ('Xhosa forest', vegetation types within the Thicket Biome). Activities such as collecting fuelwood and other resources, hunting and time spent at initiation schools were described as key opportunities for spending time in nature. The benefits of being in nature were ascribed not only to the physical experience of the forest environment and its biota, but also to the presence of ancestral spirits. Being in nature thus contributes significantly to the physical, mental and spiritual well-being of local people, and is also integral to their sense of cultural identity. This study has made it clear that maintenance of biodiversity and natural vegetation is as much in the interest of the local community's well-being as it is in the interest of conservation planners. We recommend that cultural values be incorporated into local conservation plans. <![CDATA[<b>Molecular characterisation of human peripheral blood stem cells</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300017&lng=en&nrm=iso&tlng=en Peripheral blood mononucleated cells consist of haematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). To date there is no well-defined isolation or characterisation protocol of stem cells from human adult peripheral blood mononucleated cells. Our aim in this study was to isolate and characterise mononucleated cells from human peripheral blood. Peripheral blood mononucleated cells were isolated using the Ficoll-Paque density gradient separation method and cultured in complete medium. After 4 days of culture, adherent and suspension mononucleated cells were separated and cultured for 14 days in an in-vitro culture selection. Stem cells in the isolated mononucleated cells were characterised using a multidisciplinary approach which was based on the expression of stem cell markers, morphology and the capacity to self-renew or proliferate and differentiate into specialised cells. Reverse transcription polymerase chain reaction was used to identify the expression of an HSC marker (signalling lymphocytic activation molecule family member 1, SLAMF1) and a MSC marker (CD105). Results revealed that adherent mononucleated cells were positive for MSC markers, whereas mononucleated cells in suspension were positive for HSC markers. The isolated adherent and suspension mononucleated cells were able to maintain their stem cell properties during in-vitro culture by retaining their capacity to proliferate and differentiate into osteoclast and osteoblast cells, respectively, when exposed to the appropriate induction medium. The isolated mononucleated cells consisted of suspension HSCs and adherent MSCs, both of which have the capability to proliferate and differentiate into mature cells. We have shown that suspension HSCs and adherent MSCs can be obtained from an in-vitro culture of peripheral blood mononucleated cells. <![CDATA[<b>Bibliometric analysis of publications by South African viticulture and oenology research centres</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300018&lng=en&nrm=iso&tlng=en We analysed the production, impact factor of, and scientific collaboration involved in viticulture and oenology articles associated with South African research centres published in international journals during the period 1990-2009. The articles under scrutiny were obtained from the Science Citation Index database, accessed via the Web of Knowledge platform. The search strategy employed specific viticulture and oenology terms and was restricted to the field 'topic'. The results showed that 406 articles were published during the review period, with the most number of publications being in the South African Journal of Enology and Viticulture (n = 34), American Journal of Enology and Viticulture (n = 16) and Journal of Agricultural and Food Chemistry (n = 16). The articles were published by 851 authors from 236 institutions. The collaboration rate was 3.7 authors per article, having grown over the two decades examined. The most productive institutions (i.e. those receiving a greater number of citations) were Stellenbosch University (219 published articles and 2592 citations) and the Agricultural Research Council (49 published articles and 454 citations), both from South Africa. Graphical representation of co-authorship networks identified 18 groups of authors and a single network of institutions whose core is Stellenbosch University. In conclusion, we have identified a significant growth in South African viticulture and oenology research in recent years, with a high degree of internationalisation and a constant level of domestic collaboration. <![CDATA[<b>Detection and eradication of <i>Spongospora subterranea</i> in mini-tuber production tunnels</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532012000300019&lng=en&nrm=iso&tlng=en Powdery scab, a root and tuber disease caused by the pathogen Spongospora subterranea f.sp. subterranea (Sss), poses a major problem to potato producers worldwide because it affects potato quality. Inoculum can be seed-borne or originate from contaminated growing media or contaminated equipment. During 2006, a potato mini-tuber production facility in Ceres in the Western Cape Province of South Africa had an outbreak of powdery scab. The purpose of this study was to detect Sss in the production facility and identify the source or sources of contamination so that corrective measures could be taken to eradicate the pathogen. Swab samples were taken from numerous points in the facility in 2009 and Sss-specific primers (Spsl and Sps2) were used in a polymerase chain reaction to detect Sss. Of 11 surfaces tested, 6 were positive for Sss. A second set of swab samples was taken after efforts were made to eradicate the pathogen through improved facility hygiene measures to determine whether these corrective measures were efficient. Corrective measures resulted in a disease-free harvest from 2009 onwards. This novel study has value for the mini-tuber industry as production tunnels can be tested for the presence of Sss and other pathogens before planting to ensure that, where suitable control measures are available, disease-free mini-tubers are produced.