Recent Submissions

  • Item
    Inducing controlled cell cycle arrest and re-entry during asexual proliferation of Plasmodium falciparum malaria parasites
    (Springer Nature, 2018-11-08) van Biljon, R; Niemand, J; van Wyk, R; Clark, K; Verlinden, B; Abrie, C; von Grüning, H; Smidt, W; Smit, A; Reader, J; Painter, H; Llinás, M; Doerig, C; Birkholtz, L.M
    The life cycle of the malaria parasite Plasmodium falciparum is tightly regulated, oscillating between stages of intense proliferation and quiescence. Cyclic 48-hour asexual replication of Plasmodium is markedly different from cell division in higher eukaryotes, and mechanistically poorly understood. Here, we report tight synchronisation of malaria parasites during the early phases of the cell cycle by exposure to DL-α-difluoromethylornithine (DFMO), which results in the depletion of polyamines. This induces an inescapable cell cycle arrest in G (~15 hours post-invasion) by blocking G/S transition. Cell cycle-arrested parasites enter a quiescent G-like state but, upon addition of exogenous polyamines, re-initiate their cell cycle. This ability to halt malaria parasites at a specific point in their cell cycle, and to subsequently trigger re-entry into the cell cycle, provides a valuable framework to investigate cell cycle regulation in these parasites. We subsequently used gene expression analyses to show that re-entry into the cell cycle involves expression of Ca-sensitive (cdpk4 and pk2) and mitotic kinases (nima and ark2), with deregulation of the pre-replicative complex associated with expression of pk2. Changes in gene expression could be driven through transcription factors MYB1 and two ApiAP2 family members. This new approach to parasite synchronisation therefore expands our currently limited toolkit to investigate cell cycle regulation in malaria parasites.
  • Publication
    South African Medical Research Council Annual Report 1996-1997
    (South African Medical Research Council, 1997-03-31) South African Medical Research Council
  • Publication
    Prevalence and sociodemographic correlates of common mental disorders among first-year university students in post-apartheid South Africa: Implications for a public mental health approach to student wellness
    (BMC, 2019-07-10) Bantjes, J; Lochner, C; Saal, W; Roos, J; Taljaard, L; Page, D; Auerbach, R.P; Mortier, P; Bruffaerts, R; Kessler, R.C; Stein, D.J; Christine Lochner, Janine Roos, Lian Taljaard, Dan J. Stein: MRC Unit on Risk and Resilience in Mental Disorders and Mental Health Information Centre of South Africa, Department of Psychiatry, Stellenbosch University, Stellenbosch, South Africa
    Background There is growing awareness of the need for effective prevention, early detection, and novel treatment approaches for common mental disorders (CMDs) among university students. Reliable epidemiological data on prevalence and correlates are the cornerstones of planning and implementing effective health services and adopting a public health approach to student wellness. Yet, there is a comparative lack of sound psychiatric epidemiological studies on CMDs among university students in low- and middle-income countries, like South Africa (SA). It is also unclear if historically marginalised groups of students are at increased risk for mental health problems in post-apartheid SA. The objective of the study was to investigate the prevalence and sociodemographic correlates of lifetime and 12-month CMDs among university students in SA, with a particular focus on vulnerability among students in historically excluded and marginalised segments of the population. Methods Data were collected via self-report measures in an online survey of first-year students registered at two large universities (n = 1402). CMDs were assessed with previously-validated screening scales. Data were weighted and analysed using multivariate statistical methods. Results A total of 38.5% of respondents reported at least one lifetime CMD, the most common being major depressive disorder (24.7%). Twelve-month prevalence of any CMD was 31.5%, with generalised anxiety disorder being the most common (20.8%). The median age of onset for any disorder was 15 years. The median proportional annual persistence of any disorder was 80.0%. Female students, students who reported an atypical sexual orientation, and students with disabilities were at significantly higher risk of any lifetime or 12-month disorder. Female gender, atypical sexual orientation, and disability were associated with elevated risk of internalising disorders, whereas male gender, identifying as White, and reporting an atypical sexual orientation were associated with elevated risk of externalising disorders. Older age, atypical sexual orientation, and disability were associated with elevated risk of bipolar spectrum disorder. Conclusions Despite advances to promote greater social inclusion in post-apartheid SA, students who identify as female, students with atypical sexual orientations, and students with disabilities are nonetheless at increased risk of CMDs, although students who identify as Black and first-generation students are not.
  • Publication
    Strategies for screening cord blood for a public cord blood bank in high HIV prevalence regions
    (Cambridge University Press, 2018-05-15) Meissner-Roloff, M; Gaggia, L; Vermeulen, M; Mazanderani, A.F.H; du Plessis, N.M; Steel, H.C; Pepper, M.S; M Meissner-Roloff: SAMRC Extramural Unit for Stem Cell Research and Therapy, University of Pretoria, Pretoria, South Africa
    The probability of a Black African finding a matched unrelated donor for a hematopoietic stem cell transplant is minimal due to the high degree of genetic diversity amongst individuals of African origin. This problem could be resolved in part by the establishment of a public cord blood (CB) stem cell bank. The high prevalence of human immunodeficiency virus (HIV) amongst women attending antenatal clinics in sub-Saharan Africa together with the risk of mother-to-child transmission increases the risk of transplant transmissible infection. In addition to screening the mother in a period inclusive of 7 days prior to the following delivery, we propose that all CB units considered for storage undergo rigorous and reliable screening for HIV. The Ultrio-plus® assay is a highly specific and sensitive test for detecting HIV, hepatitis-B and hepatitis-C viruses in peripheral blood. We validated the Ultrio-plus® assay for analytical sensitivity in detecting HIV in CB at the level of detection of the assay. Until more comprehensive and sensitive methods are developed, the sensitivity and reliability of the Ultrio-plus® assay suggest that it could be used for the routine screening of CB units in conjunction with currently recommended maternal screening to reduce the risk of transplant transmissible infection.
  • Publication
    Family planning and fertility decline in Africa: From 1950-2010
    (Intechopen, 2018-06-13) Garenne, M; Michel Garenne: MRC/Wits Rural Public Health and Health Transitions Research Unit, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
    The study analyzes the links between family planning programs, contraceptive prevalence and fertility trends in sub-Saharan Africa. It is based on case studies of countries with demographic surveys. The study reveals a variety of situations. Some countries have completed their fertility transition, while others have reduced their fertility level rapidly in urban areas, but less so in rural areas. In some countries, fertility remained very high, or declined very little, in rural areas, when population policies and family planning programs remained insufficient or almost non-existent. The role of family planning programs in fertility decline is highlighted by contrasting countries with similar characteristics, one of which experiencing a sharp drop in fertility, while the other one is showing a small decline or no decline at all. In each case, the political, economic, and social context is presented in order to explain the differences between family planning programs and their outcomes. These case studies make it possible to draw conclusions about the conditions of fertility control in African countries.

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