PubMed Health⌕ Search

Biomedical subjects

M de Villiers

Publications and source records attributed to M de Villiers.

12 recordsLinked to original sources
PubMed2005

Refugia, dispersal and divergence in a forest archipelago: a study of Streptocarpus in eastern South Africa.

We describe a scenario of plant speciation across a relict forest archipelago in South Africa involving Pleistocene habitat expansion-contraction cycles, dispersal and adaptation to lower temperatures. This is the first population level study using molecular data in South African forests and has significant implications for conservation efforts in this area. Populations of the mesophytic forest floor herbs Streptocarpus primulifolius sensu lato and Streptocarpus rexii were sampled throughout their range in the naturally fragmented forests of eastern South Africa in order to investigate population genetic and phylogenetic patterns within the species complex, using nuclear microsatellites, nuclear ribosomal ITS (internal transcribed spacer) sequences and chloroplast genome sequences. S. primulifolius harbours high levels of genetic diversity at both the nuclear (mean HE = 0.50) and the chloroplast level (each population fixed for a unique haplotype). This is consistent with populations of these coastal species being Pleistocene relicts. In contrast, populations of S. rexii in cooler habitats at higher altitudes and lower latitudes harbour little or no nuclear genetic diversity (mean HE = 0.09) and most share a common chloroplast haplotype. The split of S. rexii from populations intermediate between the two species (S. cf. primulifolius) occurred between 0 and 0.44 million years ago according to the calibrated ITS phylogeny of the taxa. The low genetic diversity and homogeneity of S. rexii is congruent with this species having reached its current range during the Holocene. We found no evidence of monophyly of any of the taxa in this study, which we consider a consequence of recent evolution in a fragmented habitat.

Conservation of Natural Resources↗
PubMed2000

Learning in primary care--a report.

A symposium on Learning in Primary Care was held in Cape Town, South Africa, as a pre-conference workshop to the 9th International Ottawa Conference on Medical Education. The aim of this report is to inform medical educationalists of important issues in learning in primary care and to stimulate further debate. Four international speakers gave presentations on their experiences in teaching and learning in primary care. Objective positive outcome measures include acquiring clinical skills equally well in general practice as in hospital, and improved history taking, physical examination and communication skills learning. Students regard the course as an essential requirement for learning and are appreciative of the wider aspect to learning provided by the community, giving a more holistic view of health. A SWOT analysis (strengths, weaknesses, opportunities and threats) of teaching and learning in primary care identified that learning in primary care is of a generalist nature and reality based, but is hampered by a lack of resources. The increased professionalization of teaching in primary care results in better training, cost containment, and improved quality of health care at community level. It is important to focus on turning threats into opportunities. Academic credibility needs to be established by conducting research on learning in primary care and developing the conceptual basis of primary care.

Clinical Competence↗
PubMed1999

Community-based training in family medicine--a different paradigm.

INTRODUCTION: Community-based education is an important strategy for training students appropriately for delivering primary health care services. A community-based training rotation in Family Medicine and Primary Care was introduced at the University of Stellenbosch, South Africa, in January 1998. OBJECTIVE: The aim of this study was to explore the perceptions of final year medical students about the new rotation and to provide feedback on the value of this experience to the Faculty. In this article we explore the influence of differing world views held by biomedically oriented training institutions and the systems view of life adhered to by the discipline of Family Medicine on attempts to reform medical education. METHOD: Quantitative and qualitative curriculum evaluation methods, including a questionnaire and focus groups discussions, were used. Students rated the value of the block as 7.8 out of 10. RESULTS: Eighty-eight percent of students felt that there should be an earlier exposure to Family Medicine and Primary Care in their training. The main themes identified from the qualitative results supported the literature findings and included the difference in type of practice between tertiary and primary levels of care and the value of learning a new approach to patient care. Despite the fact that the results emphasized the importance of including community-based training in Family Medicine and Primary Care at an early stage in the medical curriculum, resistance to implementation was encountered. This led to reflection on possible reasons on why the recommendations of the study were not immediately adopted into the curriculum.

Adult↗
PubMed1989

Phosphatidylcholine biosynthesis in myocardial ischaemia.

In this study the effect of myocardial ischaemia was evaluated on two aspects of phospholipid metabolism: (i) the de novo synthesis of myocardial phospholipids, as indicated by the incorporation of (methyl-3H) choline and (ii) the incorporation of radiolabelled long chain fatty acids into tissue phospholipids. Two models of ischaemia were used namely normothermic ischaemic arrest and hypoxic, low-flow perfusion of the isolated rat heart. The results showed that within 10 min, hypoxic low-flow perfusion significantly inhibited the incorporation rate of (methyl-3H) choline into tissue phospholipids. Since the tissue choline content remained unaltered under these conditions, the results suggested that the de novo synthesis of phosphatidylcholine is very susceptible to ischaemic damage. Inhibition of (methyl-3H) choline incorporation into tissue phospholipids appeared to be due to both a reduction in choline uptake and specific inhibition of the CDP pathway. Perfusion with glucose (10 mM) as substrate completely abolished the ischaemia-induced reduction in (methyl-3H) choline incorporation, indicating that glycolytically produced ATP played an important role in phosphatidylcholine biosynthesis. In contrast to these results, myocardial ischaemia stimulated the incorporation of long-chain saturated and unsaturated fatty acids into tissue phospholipids. In summary, the results obtained showed that myocardial ischaemia profoundly affected phospholipid metabolism which, in turn, might contribute to membrane damage.

Adenosine Triphosphate↗
PubMed1987

Mitochondrial Ca2+ fluxes and levels during ischaemia and reperfusion: possible mechanisms.

It has been shown that myocardial ischaemia depresses the uptake and enhances the release of Ca2+ by mitochondria. Reperfusion of the ischaemic areas may result in a further deterioration of the above processes. Despite these marked changes in Ca2+ fluxes, reperfusion has been shown always to be associated with a marked increase in mitochondrial Ca2+ content. To explain the latter observation, it has been proposed that reperfusion promotes respiration-supported mitochondrial Ca2+ uptake in preference to ADP phosphorylation. To evaluate this hypothesis, the effect of exogenous ADP on mitochondrial respiration-linked Ca2+ uptake was investigated in control, ischaemic and ischaemic-reperfused hearts. The results show that ADP significantly depresses mitochondrial Ca2+ uptake in all three preparations, indicating that Ca2+ is not taken up preferentially to ADP phosphorylation in reperfused tissue. It is suggested that reperfusion-induced increased mitochondrial Ca2+ levels are probably not due to increased respiration-linked Ca2+ uptake, but rather to augmented conversion of ionized Ca2+ to calcium phosphate which does not participate in ionic fluxes.

Adenosine Diphosphate↗