Doctoral Degrees (Medical Physiology)

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

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    The dietary ionic effects on sex ratios in animal models
    (Stellenbosch : Stellenbosch University, 2016-03) Linge, Augustine Peter Kavoo; Du Plessis, S. S.; Kimwele, C.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Medical Physiology.
    ENGLISH ABSTRACT: X-linked disorders are more expressed in male offspring and prevention of these hereditary diseases is the only recourse to date. Influencing conception towards female offspring can circumvent this problem; however sex ratio adjustment remains highly contentious. Treatment of genetic disorders through sex ratio adjustments has been examined and adopted as acceptable, easier, cheaper, safer and legal. Historically, society has been rife with allegations that diet does influence sex ratios though this has not been proven fully. The dietary chemical compositions have been claimed to act as modulators that affect the electrical charges or potential of the membranes of the oocytes and cause allosteric modification or electrotactism through a process referred to as galvanotropism and cause selective attraction towards either of the male gametes and subsequently influence the gender of the conceptus. This study was performed in an attempt to address the various questions, allegations and speculations that have been rife in many societies concerning interplay between diet, fertilization and sex ratios so as to verify the validity of these social claims by taking them to the laboratory for experimental verification. Swiss Webster mice study In a double-blind fashion, nine double groups were set up comprising of 144 families of Swiss (Webster) mice, each receiving different ionic formulations in their drinking water: 1) water and 2) glucose as controls; high serum concentrations of single elements of 3) sodium, 4) potassium, 5) calcium and 6) magnesium; combined double elements 7) sodium + potassium and 8) calcium + magnesium; and finally a cocktail of the four elements 9) sodium + potassium + calcium + magnesium. Tests included the perinatal mortality rate; the relationship between high chemical composition diet and serum levels; the effects of the study chemicals on weight gains of the study models; the effects of birth order on sex ratios and the effects of seasonal variations on sex ratios. There were 1528 deliveries with 13,040 (6,348 females and 6,692 males) pups at 8.5 pups on average per litter. a) Glucose, sodium, potassium and sodium + potassium supplementation influenced the sex ratios towards male progeny (p<0.001). Calcium (p<0.014), magnesium (p<0.008) and calcium + magnesium (p<0.001) supplementation influenced sex ratios towards the female progeny. The water (p>0.61) and cocktail solutions (p>0.0609) had no influence. b) The perinatal mortality rate was 32/1000 and was female biased among the magnesium (p<0.005) and combined calcium + magnesium (p<0.044) groups only. c) Normal serum levels were observed in the control groups (p>0.165), while significant elevated serum levels were observed among the experimental groups (p<0.0001). d) The total mean weight gains were 11.12g and 10.55g among the females and males respectively. The weight trends were used to track the general wellbeing of the animal models. e) The mean litter size was 8.5 per delivery in all the groups and generations, while no influence due to birth order were detected. f) Seasons affect the litter size, in particular the rainy season, but not the gender ratios (p>0.061). Cat fish study Parallel double blind studies looking at the dietary chemical ionic effects on the oocyte membrane electrical potential were done utilising a cat fish model (n=108). The study sought to find out effects of the following solutions on the oocyte electrical charges: 1) plain electrolyte solution, 2) glucose solution 3) sodium solution 4) potassium solution 5) calcium solution 6) magnesium solution 7) sodium + potassium solution 8) calcium + magnesium solution and the 9) cocktail solution of the four elements combined. The results revealed that oocytes retrieved from the two control groups had baseline oval polar attraction significantly more towards the positive than the negative pole (p<0.0003). There was however more significant oocyte polar attraction towards the positive electrode among the oocytes retrieved from the sodium, potassium and the combined sodium + potassium solutions (p<0.0001). Oocytes retrieved from calcium, magnesium and combined calcium + magnesium solutions had significant affinity towards the negative electrode and minimal affinity towards the positive pole (p<0.0001). Oocytes harvested from the solutions constituted with all the salts demonstrated dual attraction with more attraction to the positive electrode than the negative electrode but of no statistical significance (p>0.0530). These study findings do confirm the social allegations that a positive relationship does exist between dietary components and sex ratios. The chemicals acted as the dietary modulators that ultimately influenced the electrical cellular gametal charges and subsequently the resulting progeny. Our platform of comfort is unlike artificial sex ratio adjustment methods; the natural sex ratio adjustment methods that include the dietary method under scrutiny in this study are practiced always at the comfort of many people’s homes and are difficult to quantify or have legislation on. However, this study shows that their long term effects conform to the Fishers principle of evolution towards 1:1 sex ratios and therefore do not have significant social gender skewing on a long term basis. The study clearly explains the molecular basis upon which ions of single valency attracts the Y-bearing sperm leading to a male conceptus and how cations of double valency attracts the X-bearing sperm leading to a female conceptus despite being positively charged. The study further reaffirms the natural feminine supremacy by demonstrating that it is the ova and by extension the woman who determines the sex of the conceptus. The study ultimately confirms that the dietary ionic effects on sex ratios can be used for prevention of X-linked disorders.
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    The effects of a green rooibos extract on the reproductive function of obesity-induced insulin resistant or hypertensive male wistar rats
    (Stellenbosch : Stellenbosch University, 2019-12) Manirafasha, Claudine; Du Plessis, S. S.; Huisamen, Barbara; Aboua, Yapo Guillaume; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences: Medical Physiology.
    ENGLISH ABSTRACT: Diet-induced obesity (DIO) due to a high caloric diet (HCD) predisposes an individual to the development of diabetes and cardiovascular diseases, with high prevalence in young populations. Existing evidence supports the sentiment that insulin resistance and hypertension (HT) affect male reproduction. A greater understanding of the influence of insulin resistance and/or HT on male reproduction is required in order to prevent or treat male infertility. Due to the limitations of orthodox drugs, there is currently a strong movement towards and support for studies on phytomedicine. Rooibos (Aspalathus linearis) has been used in several studies and is known to have natural antioxidant effects and anti-obesogenic, antidiabetic, anti-hypertensive and anti-infertility activities. Currently, the company Afriplex (Pty) Ltd is producing an aspalathin-rich laboratory standardized extract prepared from green rooibos called Afriplex GRTTM (GRT). However, there is very little knowledge regarding the use of GRT in obesity-related insulin resistance and/or HT, and specifically, its effects on male reproductive health. Aim This study aimed to explore the effect of GRT on the reproductive function in obesity-induced insulin resistant and hypertensive male Wistar rats. Methods A prospective randomized control and experimental animal study design was used. Two different diets were used to induce obesity-related insulin resistance with or without HT in male Wistar rats. Subsequently, the possible protective properties of GRT on the male reproductive system were evaluated. Animals (weighing 120 ±10 g, approximately 7 weeks old) were randomly assigned to seven groups with seven rats each. All rats had unrestricted access to their respective diets and water for 16 weeks. At baseline (week 0–10), we had three groups: 1) lean control (LC) – animals that received standard rat chow; 2) obese (OB) – animals that received a diet to induce obesity associated with insulin resistance; and 3) obese with hypertension (OBHT) – animals were placed on a slightly modified DIO and additionally developed HT. From weeks 11 to 16, one LC, OB and OBHT group were each treated with GRT (prepared and supplied by Afriplex (Pty) Ltd) at 60 mg/kg/day as a dietary supplement in the form of jelly blocks. An additional group of OBHT animals was treated during the same period for 6 weeks with Captopril, an angiotensin-converting-enzyme (ACE) inhibitor (positive control for HT) at 60 mg/kg per day. Food and water intake were monitored on a daily basis. An oral glucose tolerance test was performed during the 10th week after the onset of the respective diets and during the 16th week, after which the animals were sacrificed. Blood pressure measurements were taken once per week throughout the experimental period. After the 16-week period, animals were killed and blood, testis and epididymal tissue were harvested for further analysis. Body weight, intra-peritoneal fat, non-fasting glucose levels, IL-1β, IL-6, IL-12, IL-18 and TNFα, oxidative stress (OS) markers (superoxide dismutase and catalase activity, malondialdehyde), testosterone and estradiol, sperm concentration, viability, morphology, total motility, progressive motility and various velocity parameters were measured. Results and conclusion Both diets successfully induced insulin resistance with or without hypertension and demonstrated detrimental effects on male reproductive function as evidenced by OS and hormone dysregulation. Treatment with GRT reversed OS and balanced the androgens. This study provided insight into the pharmacological effects of GRT in the treatment of pathophysiological changes that occur in DIO associated with insulin resistance or HT. These findings will hopefully inspire further research into the clinical setting related to the GRT and could possibly lead to the development of new drugs from this compound.
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    Effects of insulin and leptin on human spermatozoa function and their cross-talk with nitric oxide and cytokines
    (Stellenbosch : University of Stellenbosch, 2009-12) Lampiao, Fanuel; Du Plessis, S. S.; Strijdom, Hans; University of Stellenbosch. Faculty of Health Sciences. Dept. of Biomedical Sciences. Medical Physiology.
    ENGLISH ABSTRACT: In recent years there has been an increase in obesity and diabetes mellitus (DM). These conditions have for a long time been associated with infertility. Obesity is characterized by high levels of circulating leptin and cytokines as well as insulin resistance. Type I DM is associated with low or no insulin whereas, Type II DM is characterised by insulin resistance. As the prevalence of obesity and DM continues to rise, it is likely that the incidence of infertility associated with these pathological conditions will likewise increase. The effects of insulin and leptin on male reproductive function have been reported on the endocrine and spermatogenesis level, but their effects on cellular level of human ejaculated spermatozoa are yet to be elucidated. This study presents data on the role of insulin and leptin on human ejaculated spermatozoa and their interaction with cytokines and nitric oxide. In the first part of the study, we established the suitable concentrations of glucose, insulin and leptin that could be administered to human spermatozoa in vitro. Glucose concentration of 5.6 mM was chosen as the suitable concentration to be administered to human spermatozoa because it has previously been reported in the literature; furthermore, it is within the range of the physiological glucose levels found in the blood of fasting humans. Insulin and leptin concentrations of 10 μIU and 10 nmol were chosen respectively because they gave much improved sperm function and this was within the range of insulin and leptin levels previously measured in human ejaculated spermatozoa. This was followed by investigating the signalling pathway of insulin and its beneficial effects on human spermatozoa function. Endogenous insulin secretion from human ejaculated spermatozoa was blocked by nifedipine and its receptor tyrosine phosphorylation effects were inhibited by erbstatin while phosphatidylinositol 3-kinase (PI3K) phosphorylation activity was inhibited by wortmannin. Exogenous insulin administration significantly increased human sperm motility parameters as well as the sperm ability to acrosome react. The inhibition of endogenous insulin release from spermatozoa as well as the inhibition of the insulin receptor substrate (IRS) tyrosine phosphorylation significantly decreased motility parameters and the ability of spermatozoa to acrosome react. The study also investigated the effects of insulin and leptin on human sperm motility, viability, acrosome reaction and nitric oxide (NO) production. Both insulin and leptin significantly increased sperm motility parameters, acrosome reaction and NO production. The NO production induced by insulin and leptin was via PI3K signalling as evidenced by a reduction in NO levels when PI3K activity was inhibited by wortmannin. To investigate whether insulin and leptin could improve motility parameters of asthernozoospermic and teratozoospermic spermatozoa, the spermatozoa were separated into two fractions by means of a double density gradient technique. The gradient system was able to separate spermatozoa into high morphologically abnormal and less motile spermatozoa similar to that of asthernozoospermic and teratozoospermic patients as well as a more motile fraction. Insulin and leptin significantly increased the motility parameters of spermatozoa from the immature and less motile fraction. The fourth part of the study was aimed at investigating the effects of the cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), on human sperm motility, viability, acrosome reaction and NO production. The study shows that TNF-α and IL-6 significantly reduced motility parameters and acrosome reaction in a dose4 and time-dependent manner. These cytokines were also shown to significantly increase NO production from human spermatozoa. The decreased motility parameters induced by these cytokines could be attributed to their ability to induce excessive NO production. It is not yet clear how they inhibit spermatozoa to undergo the acrosome reaction. The fifth part of the study was to investigate the expression and localization of glucose transporter 8 (GLUT8) in human spermatozoa. This study shows that GLUT8 is constitutively expressed and located in the midpiece region of the human spermatozoa. The study also showed that stimulating spermatozoa with insulin led to an increase in GLUT8 expression as well as translocation to the acrosomal region. In the last part of the study we wanted to investigate why the increase in NO generation by spermatozoa due to insulin and leptin stimulation is accompanied with increased sperm function whereas NO increased due to TNF-α and IL-6 stimulation is accompanied with decreased sperm function. We observed that TNF-α and IL-6 not only increased NO production but also ROS production. This study speculates that the decrease in sperm motility and acrosome reaction when TNF-α and IL-6 were administered was due to the concomitant high increase in NO and ROS they induced. In conclusion, this study has established in vitro beneficial effects of insulin and leptin in normozoospermic and asthernozoospermic human sperm function. These hormones influence sperm function via the PI3K signalling pathway in two ways. Firstly, by increasing GLUT8 expression and translocation thereby possibly increasing glucose uptake and metabolism and secondly, by increasing NO production. The study has also established that TNF-α and IL-6 have detrimental effects on human spermatozoa in a dose and time dependent manner. These effects are mediated via their ability to stimulate both NO and ROS production in human spermatozoa. This study reports that GLUT8 is expressed in the midpiece region of human spermatozoa and that insulin stimulation upgrades its expression and leads to its translocation to the acrosomal region.