Masters Degrees (Medical Physiology)

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Acrosome size and kinematics of human spermatozoa
(Stellenbosch : University of Stellenbosch, 2007-03) Murray, George M.; Du Plessis, S. S.; Franken, D. R.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Biomedical Sciences. Medical Physiology.
For spermatozoa to gain access to the oocyte for fertilization, lytic enzymes need to be released during the acrosome reaction. These enzymes, which are stored and transported within an organelle termed the acrosome, make it possible for spermatozoa to collectively penetrate the layers of cells and glycoproteins that surround and protect an oocyte. Acrosomes may thus be viewed as essential for fertilization and their shape, size and volume were examined morphometrically by utilizing automated morphometric analysis equipment. In addition to the acrosome being necessary for normal unassisted fertilization, spermatozoa also need the ability to migrate to the oocyte. Following zona pellucida binding, sperm tail thrust movement initiates zona penetration into the space created by the digestive action of the acrosomal enzymes. Therefore the motion characteristics of spermatozoa were also quantified in terms of kinematic properties. In the treatment of male sub fertility, assisted reproductive techniques are applied. In the application of such techniques, a motile sub-population of spermatozoa was obtained by employing a procedure (swim-up selection) that selects cells on the basis of their kinematic ability. This study presents an analysis of the morphometric and kinematic qualities of spermatozoa populations that are subjected to swim-up selection and investigates the relationship of these morphometrical and kinematic qualities. Computer-assisted semen analysis, swim-up selection and automated sperm morphology analysis tests were all used to evaluate spermatozoa populations. Results indicated that, irrespective of acrosome size, higher kinematic parameter measurements were observed post-swim-up. A significant inverse relationship between the population’s average acrosome size and a number of kinematic parameters was observed. Our results indicated that for a post-swim-up population of spermatozoa an increase in the average acrosome size was significantly related to a decrease in the kinematic parameters VAP, VCL and the VSL within the same population.
Gender selection: separation techniques for X- and Y-chromosome bearing human spermatozoa
(Stellenbosch : Stellenbosch University, 2013-12) Van der Linde, Michelle; Du Plessis, S. S.; Stellenbosch University. Faculty of Medicine & Health Sciences. Dept. of Biomedical Sciences, Medical Physiology.
ENGLISH ABSTRACT: Preconceptual sex selection is an ethically justifiable process whereby X- and Y-chromosome bearing spermatozoa are isolated prior to fertilization of the oocyte in order to generate either a male or a female offspring. Although various separation techniques are available, none can guarantee 100% accuracy. There are various physiological differences between X- and Y-chromosome bearing spermatozoa which can be used to separate these two populations of sperm. For the purpose of this study, X- and Y-chromosome bearing spermatozoa were separated based on (1) their respective abilities to remain viable when subjected to adverse environments, including extreme pH values, increased temperatures and various hydrogen peroxide (H2O2) concentrations; (2) the ability of Y-chromosome bearing spermatozoa to swim faster and/or more progressively than X-chromosome bearing spermatozoa; and (3) the X-chromosome bearing spermatozoa’s increased size and weight when compared to the Y-chromosome bearing spermatozoa. The efficacy of live and dead cell separation through (i) Magnetic Antibody Cell Separation (MACS) and (ii) a modified swim-up technique was also assessed and compared. Changes in the sex-chromosome ratio of samples were established by double-label fluorescent in situ hybridization (FISH) before and after processing. Sperm motility (CASA) and viability (eosin/nigrosin) was assessed before and after each intervention. Ethical clearance for this study was granted by the Health Research Ethics Committee 1 (Ethics #: S13/04/068). The results indicated successful enrichment of X-chromosome bearing spermatozoa upon incubation in acidic media, increased temperatures, and H2O2. In contrast, Y-chromosome bearing spermatozoa were successfully enriched through a direct swim-up method as well as discontinuous gradient centrifugation. In conclusion, this study demonstrated the potential role for physiological differences between X- and Y-chromosome bearing spermatozoa in the development of preconceptual gender selection through sperm sorting.
The impact of oocyte meiotic spindle and automated zona pellucida score and sperm chromatin packaging on fertilization and pregnancy for assisted reproduction techniques
(Stellenbosch : Stellenbosch University, 2016-03) Raubenheimer, Kara; Du Plessis, S. S.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Medical Physiology.
ENGLISH ABSTRACT: Non-invasive selection of developmentally competent human oocytes may provide information on the true fertilization potential of the spermatozoon in the absence of oocyte limitations. The objective was to measure 856 oocyte’s competence by assessing oocyte metaphase 2 (M2) maturity, zona pellucida score (ZS) and presence of the meiotic spindle (SPp) using birefringent imaging software. ICSI was performed and fertilization (n=90 patients) and pregnancy rates (n=89) were measured and compared to the oocyte competence and sperm DNA chromatin via Chromomycin A3 (CMA3) (n=89). Fisher’s exact and odds ratio’s (OR) were used to determine effect. In total, 856 oocytes were harvested of which 568 (66%) were M2 stage of development. SPp oocytes were (384/730) 52.60%, OR was performed on the SP to determine its relevance to fertilization, its presence in the oocyte prior to ICSI, resulted in fertilization 1.5:1 times more than when it was absent, p=0.01. SPp embryos selected for embryo transfer resulted in a 65% expanded blastocyst rate, full blastocyst rate of 58% and early blastocyst rate of 54%. A negative development competence on day 5 was also correlated to absence of meiotic spindle (SPa) prior to ICSI with 56% of day 5 embryos transferred reaching only the compacted morula stage; while 50% of SPa embryos reached the morula stage at time of embryo transfer on day 5. Although there were no statistical differences between the pregnancy rates of SPp and SPa embryos, there were slight tendencies for better embryo quality. The SPp had a pregnancy rate (PR) of 40.91% (36/88). Random effects logistic regression OR performed on 768 oocytes from 90 patients indicated pregnancy to succeed 1.4:1 when SPp (p=0.89). The mean average automated ZS was 18.96 μm (95% CI: 15.75; 22.16; n=625 positive ZS from 90 patients). The ZS revealed a GLS linear regression with p=0.04 to fertilize when the ZS was 19.20 μm (16.60; 21.79). There was no statistical difference between ZS of the pregnant and non-pregnant groups. The main objective was to prove that when oocyte quality is optimized, that fertilization rates and by implication, pregnancy rates would be improved. If not, failure to fertilize or implant would most probably be due to decreased spermatozoa capacity to fertilize possibly due to damaged chromatin packaging. The chromatin packaging (CMA3) of the study population was 74% semen samples with >40% immature DNA. The OR for CMA3 underlines the hypothesis, that when oocyte competence for fertilization is controlled to a degree, the success or failure of treatment can be indicated by the CMA3 value. In this instance, the OR is highly predictive for success with pregnancy when ICSI is performed on CMA3 values that are immature (≥41%). Logistic regression calculated the OR for immature DNA (CMA3≥41%) to predict pregnancy to be likely with odds of 1.6:1, p=0.39. Hypothesis OR: If ICSI is performed on an oocyte with: M2 and SPp, and this embryo develops to day 5 for embryo transfer, the odds of pregnancy, if working with a semen sample with >40% immature DNA, would be 1.9: 1.
Investigating the ameliorative potential of Aspalathus linearis and Cyclopia intermedia against lipid accumulation, lipolysis, oxidative stress and inflammation
(Stellenbosch : Stellenbosch University, 2020-03) Mamushi, Mokadi Peggy; Pheiffer, Carmen; Jack, B. U.; Du Plessis, S. S.; Stellenbosch University. Faculty of Health and Medical Sciences. Dept. of Biomedical Sciences: Medical Physiology.
Background Despite the availability of several treatment regimens, obesity continues to be one of the greatest health challenges of the 21st century. In recent years, plant polyphenols have attracted increasing attention as nutraceuticals that are able to prevent or treat obesity and its co-morbidities. However, the first-line screening of these compounds is hampered by the shortage of in vitro experimental models that mimic the complex pathophysiology of obesity (excess lipid accumulation, basal lipolysis, inflammation and oxidative stress) in vivo. The aim of this study was two-fold. Firstly, establish a 3T3-L1 adipocyte in vitro model that more closely mimics obesity in vivo, and secondly to investigate the ameliorative properties of Aspalathus linearis, Cyclopia intermedia and their major polyphenols against these conditions. Methods For the experimental model, 3T3-L1 pre-adipocytes were differentiated in 5.5 mM, 25 mM or 33 mM glucose concentrations for 7 or 14 days. Lipid accumulation, basal lipolysis, oxidative stress, inflammation, mitochondrial activity and gene expression were assessed using Oil Red O staining, glycerol release, 2',7'-dichlorfluorescein-diacetate fluorescence to quantify reactive oxygen species, monocyte chemoattractant protein-1 secretion, the 3- [4, 5-Dimethylthiazol-2-yl]-2, 5 diphenyltetrazolium bromide assay and quantitative real time polymerase chain reaction, respectively. The ameliorative effects of Aspalathus linearis (Afriplex GRTTM) and Cyclopia intermedia (CPEF) against these conditions were investigated by acute and chronic treatment of the optimised experimental model with various concentrations of these plant extracts and their major polyphenol Aspalathin and Mangiferin respectively. Results Collectively lipid accumulation, basal lipolysis, oxidative stress, inflammation and expression of associated genes were higher after differentiation in 33 mM for 14 days compared to lower glucose concentrations and 7 days, thus these conditions were selected as the experimental model. Neither acute nor chronic treatment with 0.1 to 100 µg/ml of Aspalathus linearis and Cyclopia intermedia, and 0.1 to 100 µM of Aspalathin and Mangiferin significantly decreased lipid content. However, all treatments decreased basal lipolysis and increased mitochondrial activity. Conclusion Differentiation of 3T3-L1 pre-adipocytes in 33 mM glucose for 14 days increased basal lipolysis, oxidative stress and inflammation compared to lower glucose concentrations and differentiation for 7 days. Aspalathus linearis, Cyclopia intermedia, Aspalathin and Mangiferin ameliorated the increased basal lipolysis under these conditions. This study showed that differentiation in 33 mM glucose for 14 days may offer potential as an experimental model that more closely mimics obesity in vivo and may thus improve first-line screening for anti-obesity therapeutics. Aspalathus linearis, Cyclopia intermedia and their major polyphenol Aspalathin and Mangiferin, respectively may have potential as antilipolytic agents that are able to ameliorate obesity-associated basal lipolysis.
Measurement of free radicals and their effects on human spermatozoa
(Stellenbosch : University of Stellenbosch, 2006-03) Lampiao, Fanuel; Du Plessis, S. S.; Strijdom, Hans; University of Stellenbosch. Faculty of Health Sciences. Dept. of Biomedical Sciences. Medical Physiology.
In this study, we presented data on the role of free radicals in human spermatozoa, particularly in the context of centrifugation and the potential development of defective sperm function. In order to achieve this, methods were developed to directly measure intracellular free radicals in human sperm and the effects of exogenously applied free radicals on sperm function were established. The role of brief and prolonged centrifugation and the associated generation of free radicals was also investigated.
Violence against women : impact on reproductive health and pregnancy outcome
(Stellenbosch : Stellenbosch University, 2003-03) Schoeman, Jeanne; Du Plessis, S. S.; Odendaal, H. J.; Stellenbosch University. Faculty of Medicine & Health Sciences. Dept. of Interdisciplinary Health Sciences.
ENGLISH ABSTRACT: Introduction Worldwide, up to 25% of women are assaulted during pregnancy, with estimates varying between populations. Violence has been associated with adverse pregnancy outcome, including preterm birth, abruptio placentae and low birth weight. Among the Coloured population of the Western Cape the incidence of spontaneous preterm birth is 20%, compared to the global figure of 10%. Overall, the rate of preterm labour has not dropped over the past 40 years and no clearer answer as to a specific cause has been found. The objective of this study was to determine whether patients who deliver preterm experience more domestic violence than those who deliver at term. Methods Two groups of patients were assessed. Firstly, patients who spontaneously delivered between 24 and 33 weeks (24wOd - 33w6d), who were admitted for suppression of active labour after 24 weeks, or who experienced placental abruption before 34 weeks, were screened for domestic violence using the "Abuse Assessment Screen". A second group of women, attending a local Midwife Obstetric Unit with uncomplicated pregnancies, completed the same questionnaire. The questionnaires were all administered by the same person (J.S.) after written informed consent was given. Results A total of 229 patients were interviewed, 99 in the low risk (LR) and 130 in the preterm labour (PTL) group, which included 23 women with abruptio placentae. The PTL group experienced significantly more violence throughout their lives than the LR group (59.7% vs. 40.4%, p = 0.038). Experiences of violence within the last year or during the pregnancy did not reach statistical significance between the two groups, although the numbers were higher for the PTL group. The PTL group smoked significantly more cigarettes per day (p = 0.009), used more alcohol (p < 0.001) and had a higher incidence of syphilis than the LR group (p = 0.005). These differences remained the same when the abruptio's were analyzed as a separate group. Conclusions: Women who delivered preterm did experience more violence at some point in their lives and were also more likely to engage in high-risk behaviour. Violence alone does not seem to cause PTL directly, but is part of a low socioeconomic lifestyle. The fact that the alcohol use is so high among these women is a problem that needs to be addressed, but once again, it is possibly the result of deeper social problems. The need for education on values and respect, family planning use and low risk sexual behaviour is once again challenged.

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Browsing Masters Degrees (Medical Physiology) by browse.metadata.advisor "Du Plessis, S. S."

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