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The breeding and reproductive biology of the vlei rat Otomys irroratus representing three allopatric populations (Committee's Drift, Hogsback and Karkloof) have been studied in the laboratory. The study attempted to establish whether the three populations differed in respect of selected reproductive parameters, and whether the populations are reproductively isolated from one another. The breeding biology of the Hogsback and Karkloof populations was similar while the Committee's Drift population differed from the other two in respect of its smaller litter size and increased interval between pairing and the production of the first litter. Pre-copulatory behaviour differed among populations, with a gradation of increasing intersexual aggression from Hogsback to Karkloof to Committee's Drift pairs. Postnatal growth and development patterns, as well as male reproductive morphology, were indistinguishable among the populations. Attempts at interpopulation breeding were successful. However, some hybrids died before weaning, while those that survived beyond weaning were sterile, particularly those resulting from cross-matings of Hogsback animals with individuals representing the other populations. Interpopulation pairs displayed higher levels of agonistic interaction than did the pure pairings. Growth and development and the reproductive morphology of male hybrids were indistinguishable from those of the parental populations. Interpopulation reproductive variation in o. irroratus appears to be due to a combination of environmental and phylogenetic constraints. 80th pre- and post-zygotic isolating mechanisms would impede gene flow between the populations should they meet in nature. All populations appear to be undergoing active speciation. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

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Multidrug resistance phosphoglycoprotein (P-gp) is expressed in the placenta and fetal blood-brain barrier (BBB) and plays a critical role in reducing fetal accumulation of xenobiotics. In other tissues, P-gp activity is inhibited by selective serotonin reuptake inhibitors (SSRIs) and by lethal doses of LPS modeling a bacterial infection. However, nothing is known with respect to the effects of SSRIs or nonlethal infection on P-gp activity in the placenta or fetal tissues. In the studies presented in this thesis, we hypothesized that (1) the SSRI sertraline and (2) a nonlethal maternal bacterial infection would decrease P-gp activity in the placenta and fetal BBB. The first study shows that sertraline affects P-gp activity at these barrier sites in a tissue-specific manner. The second study shows that nonlethal infection does not significantly affect P-gp activity at either site. However, nonlethal infection may still influence substrate biodistribution by altering hepatic elimination of these substrates.

Multidrug resistance phosphoglycoprotein (P-gp) is expressed in the placenta and fetal blood-brain barrier (BBB) and plays a critical role in reducing fetal accumulation of xenobiotics. In other tissues, P-gp activity is inhibited by selective serotonin reuptake inhibitors (SSRIs) and by lethal doses of LPS modeling a bacterial infection. However, nothing is known with respect to the effects of SSRIs or nonlethal infection on P-gp activity in the placenta or fetal tissues. In the studies presented in this thesis, we hypothesized that (1) the SSRI sertraline and (2) a nonlethal maternal bacterial infection would decrease P-gp activity in the placenta and fetal BBB. The first study shows that sertraline affects P-gp activity at these barrier sites in a tissue-specific manner. The second study shows that nonlethal infection does not significantly affect P-gp activity at either site. However, nonlethal infection may still influence substrate biodistribution by altering hepatic elimination of these substrates.

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No description available.

Obese females face a number of health challenges, including infertility. Obese females are three times more likely to present with infertility compared to normal weight females. Exercise improves infertility by interacting with hormones specific to reproduction. The hormones leptin and kisspeptin (KiSS) are crucial for reproduction. Research suggests leptin may increase production and secretion of KiSS. KiSS subsequently increases gonadotropin-releasing hormone, activating the menstrual cycle and reproduction. Interestingly, circulating levels of leptin and KiSS are altered in the obese state. Leptin levels significantly increase, whereas KiSS levels decrease. Studies demonstrate increases in leptin cause leptin resistances, which is followed by a decrease in KiSS mRNA concentrations. Exercise is associated with decreases in circulating leptin and infertility, however there is no research examining the changes in KiSS after an exercise intervention. Therefore the purpose of this research was to examine the effects of an exercise intervention on circulating KiSS and leptin levels in obese females. Ten obese females were randomized to an exercise intervention (n=5) or a non-exercise control group (n=5). The exercise intervention group completed a 12-week supervised, progressive, aerobic exercise program that involved walking a treadmill between 65 – 75% of their predicated maximum heart rate. The non-exercise control group maintained their current lifestyle habits. All participants had blood drawn at three different time points; baseline, mid-point and end-point; and KiSS and leptin levels were analyzed. The exercise group had a significant decrease in %BF (p<0.01) compared to the control group from baseline to end-point testing, whereas there was a significant increase in weight (p<0.01) and BMI (p<0.01) in the control group from baseline to mid-point testing. A group main effect for circulating leptin levels was found (p<0.01), however a pairwise comparison between the exercise and control group was not significant (p=0.81). For KiSS there was a main effect of time (p<0.05). Test of Within-Subjects Contrasts indicated that there was a significant decrease in KiSS between baseline and end-point testing (p=0.05). Individual participant data was also graphically represented for weight, leptin and KiSS level. Trends in the data suggest leptin levels in the exercise group corresponded with changes in weight; as weight decreased from baseline to mid-point testing, so did leptin levels. When individual participant KiSS levels were looked at in conjunction with leptin changes over the intervention potential trends did appear. All exercise participants experienced decreases in leptin from baseline to mid-point testing and all but one exercise participant saw increases in KiSS levels during the same time frame. Overall, results support a decrease in %BF in the exercise group compared to the control group. However, there was no evidence to support that an exercise intervention for obese females statistically significantly decreased circulating leptin levels and increases KiSS levels. Although there was a trend for hormone levels to be associated with body fat levels, the small sample size was problematic. A definitive study with increased numbers is now required to elucidate whether the trends become significant.