Aims There is a high prevalence of hypertension in the African population and it is known that vascular dysfunction (including nitric oxide (NO) bio-availability markers) play an important role in the development of cardiovascular diseases. Since very little is known regarding the role of markers of NO bio-availability in Africans, the aim of this study was to compare markers of NO bio-availability (namely L-arginine, L-citrulline, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA)), ambulatory blood pressure (BP) and markers of end organ damage between African and Caucasian school teachers. Additionally, we also aimed to determine whether these markers of NO bio-availability are associated with ambulatory BP and markers of end organ damage in both ethnic groups. Methods The SABPA (Sympathetic activity and Ambulatory Blood Pressure in Africans) study was a cross-sectional study, including urbanised African (N=181) and Caucasian (N=209) men and women, between the ages of 25 and 65 years. Cardiovascular measurements included ambulatory blood pressure, pulse wave velocity (PWV), electrocardiographic Cornell product and carotid intima media thickness (cIMT). Anthropometric measurements included height, weight and waist circumference. Various bio-markers were analysed, including glucose, L-arginine, ADMA, SDMA, Lcitrulline, reactive oxygen species, albumin-to-creatinine ratio (ACR) and estimated creatinine clearance (eCCR). Characteristics of groups were compared with independent T-tests and Chi-square tests. Single and partial analyses were used to investigate associations between NO bioavailability markers with ambulatory BP measurements and markers of end organ damage. Analyses of covariance (ANCOVA) were used for comparison of variables between groups to determine significant differences, while adjusting for age, body mass index and antihypertensive medication. Forward stepwise multiple regression analyses were performed to determine if independent associations exist between ambulatory BP measurements or markers of end organ damage with either- L-arginine, L-citrulline, ADMA or SDMA as the main independent variable. Results and conclusion The Africans and Caucasians were of similar ages. However, the Africans had higher blood pressure therefore their cardiovascular profile was unfavourable compared to that of the Caucasians. The inhibitors of NO biosynthesis, ADMA and SDMA, were significantly lower in the Africans (p=0.046; p<0.001, respectively). However, the NO bio-availability markers, L-arginine and L-citrulline, were higher in the African compared to the Caucasian participants (all p values <0.05) regarded as significant. When performing unadjusted analyses, we found significant negative associations between eCCR and L-citrulline in all four subgroups: African men (r=-0.27; p=0.013), African women (r=-0.24; p=0.021), Caucasian men (r=-0.21; p=0.044) and Caucasian women (r=-0.28; p=0.003). The association of eCCR with L-citrulline was confirmed to be independent of confounders in all groups: African men (R2=0.46; β=-0.23; p=0.006), African women (R2=0.68; β= -0.12; p=0.046), Caucasian men (R2=0.62; β= -0.24; p<0.001) and Caucasian women (R2=0.72; β= -0.13; p=0.029). This implicates that renal function may be detrimentally affected by L-citrulline concentrations. In the Caucasian men and women negative correlations between eCCR and SDMA were found before adjustments (r=-0.33; p=0.003 and r=-0.26; p=0.006, respectively). This phenomenon was confirmed in the forward stepwise multiple regression analysis in Caucasian men (R2=0.75; β= -0.27; p<0.001) and women (R2=0.73; β= -0.21; p<0.001), while no associations were found in the Africans. This result is not unexpected, since SDMA can only be eliminated by the kidneys and is therefore an important risk marker for the early detection of renal dysfunction. In Caucasian men we found that ADMA correlated with ACR (r=0.36; p=0.001), night-time SBP (r=0.34; p=0.002) and night-time DBP (r=0.25; p=0.023) with single linear regression analyses. A similar trend was shown in African men with night-time SBP (r= 0.20; p=0.089) and night-time DBP (r= 0.21; p=0.078) respectively, but this association was absent in the Caucasian and African women. After adjustments for age and body mass index, the associations with ADMA, ACR and SBP in the Caucasian men remained. However, a negative association between eCCR and ADMA also became evident in the African men (r=- 0.24; p=0.025) and remained significant in the forward stepwise multiple regression analysis (R2=0.44; β= -0.18; p=0.034). It is, however, not clear why our results were gender specific, but we could speculate that the female sex hormones may play a part in protecting the vascular endothelium. Apart from the associations described above, there were no significant independent associations between the markers of the NO cycle (such as L-arginine) and PWV, cIMT, eCCR, ACR or Cornell product. In conclusion, although Africans presented a more vulnerable cardiovascular profile, we found a consistent negative association between renal function and L-citrulline in all participants, which has only been reported previously in patients with chronic renal disease. Additionally we found a gender-specific link between renal function and ADMA in African and Caucasian men. Our results may indicate that in the general population, markers of NO bioavailability may be associated with early changes in renal function, accompanying elevated blood pressure. / Thesis (MSc (Physiology))--North-West University, Potchefstroom Campus, 2013

Aims There is a high prevalence of hypertension in the African population and it is known that vascular dysfunction (including nitric oxide (NO) bio-availability markers) play an important role in the development of cardiovascular diseases. Since very little is known regarding the role of markers of NO bio-availability in Africans, the aim of this study was to compare markers of NO bio-availability (namely L-arginine, L-citrulline, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA)), ambulatory blood pressure (BP) and markers of end organ damage between African and Caucasian school teachers. Additionally, we also aimed to determine whether these markers of NO bio-availability are associated with ambulatory BP and markers of end organ damage in both ethnic groups. Methods The SABPA (Sympathetic activity and Ambulatory Blood Pressure in Africans) study was a cross-sectional study, including urbanised African (N=181) and Caucasian (N=209) men and women, between the ages of 25 and 65 years. Cardiovascular measurements included ambulatory blood pressure, pulse wave velocity (PWV), electrocardiographic Cornell product and carotid intima media thickness (cIMT). Anthropometric measurements included height, weight and waist circumference. Various bio-markers were analysed, including glucose, L-arginine, ADMA, SDMA, Lcitrulline, reactive oxygen species, albumin-to-creatinine ratio (ACR) and estimated creatinine clearance (eCCR). Characteristics of groups were compared with independent T-tests and Chi-square tests. Single and partial analyses were used to investigate associations between NO bioavailability markers with ambulatory BP measurements and markers of end organ damage. Analyses of covariance (ANCOVA) were used for comparison of variables between groups to determine significant differences, while adjusting for age, body mass index and antihypertensive medication. Forward stepwise multiple regression analyses were performed to determine if independent associations exist between ambulatory BP measurements or markers of end organ damage with either- L-arginine, L-citrulline, ADMA or SDMA as the main independent variable. Results and conclusion The Africans and Caucasians were of similar ages. However, the Africans had higher blood pressure therefore their cardiovascular profile was unfavourable compared to that of the Caucasians. The inhibitors of NO biosynthesis, ADMA and SDMA, were significantly lower in the Africans (p=0.046; p<0.001, respectively). However, the NO bio-availability markers, L-arginine and L-citrulline, were higher in the African compared to the Caucasian participants (all p values <0.05) regarded as significant. When performing unadjusted analyses, we found significant negative associations between eCCR and L-citrulline in all four subgroups: African men (r=-0.27; p=0.013), African women (r=-0.24; p=0.021), Caucasian men (r=-0.21; p=0.044) and Caucasian women (r=-0.28; p=0.003). The association of eCCR with L-citrulline was confirmed to be independent of confounders in all groups: African men (R2=0.46; β=-0.23; p=0.006), African women (R2=0.68; β= -0.12; p=0.046), Caucasian men (R2=0.62; β= -0.24; p<0.001) and Caucasian women (R2=0.72; β= -0.13; p=0.029). This implicates that renal function may be detrimentally affected by L-citrulline concentrations. In the Caucasian men and women negative correlations between eCCR and SDMA were found before adjustments (r=-0.33; p=0.003 and r=-0.26; p=0.006, respectively). This phenomenon was confirmed in the forward stepwise multiple regression analysis in Caucasian men (R2=0.75; β= -0.27; p<0.001) and women (R2=0.73; β= -0.21; p<0.001), while no associations were found in the Africans. This result is not unexpected, since SDMA can only be eliminated by the kidneys and is therefore an important risk marker for the early detection of renal dysfunction. In Caucasian men we found that ADMA correlated with ACR (r=0.36; p=0.001), night-time SBP (r=0.34; p=0.002) and night-time DBP (r=0.25; p=0.023) with single linear regression analyses. A similar trend was shown in African men with night-time SBP (r= 0.20; p=0.089) and night-time DBP (r= 0.21; p=0.078) respectively, but this association was absent in the Caucasian and African women. After adjustments for age and body mass index, the associations with ADMA, ACR and SBP in the Caucasian men remained. However, a negative association between eCCR and ADMA also became evident in the African men (r=- 0.24; p=0.025) and remained significant in the forward stepwise multiple regression analysis (R2=0.44; β= -0.18; p=0.034). It is, however, not clear why our results were gender specific, but we could speculate that the female sex hormones may play a part in protecting the vascular endothelium. Apart from the associations described above, there were no significant independent associations between the markers of the NO cycle (such as L-arginine) and PWV, cIMT, eCCR, ACR or Cornell product. In conclusion, although Africans presented a more vulnerable cardiovascular profile, we found a consistent negative association between renal function and L-citrulline in all participants, which has only been reported previously in patients with chronic renal disease. Additionally we found a gender-specific link between renal function and ADMA in African and Caucasian men. Our results may indicate that in the general population, markers of NO bioavailability may be associated with early changes in renal function, accompanying elevated blood pressure. / Thesis (MSc (Physiology))--North-West University, Potchefstroom Campus, 2013

No description available.

No description available.

The interaction between the embryo and fetus with the maternal environment can have both short- and long-term consequences on health and development after birth. In some cases, these changes may be detrimental to the individual, but in other cases these developmental changes may be beneficial and manipulated to produce desired effects. Our interest is to use this concept of fetal programming to improve skeletal muscle development and meat production in ruminants. To achieve this, we targeted the period of gestation when fetal muscle fiber formation occurs. Primary muscle fibers form during embryonic development, and it is this small number of primary muscle fibers that will serve as templates for secondary fiber formation that occurs in the fetus during mid-gestation. Supplementing amino acids that influence blood flow within the reproductive tract is one potential way to provide fetuses with added nutrients during gestation, and this supplementation strategy may be especially useful when the maternal diet is compromised. L-citrulline was chosen for this work because of its long half-life in maternal circulation. This work utilized twin-bearing ewes with a moderate dietary energy restriction to assess the effects of mid-gestational L-citrulline supplementation on umbilical blood flow, placental function, neonatal lamb size, and lamb performance. We hypothesize that i.v. administration of L-citrulline will increase uterine and placental blood flow in gestating ewes and this will improve fetal growth, development, and overall postnatal performance. Blood flow parameters were not influenced by treatment (P>0.05). Circulating levels of progesterone and pregnancy-specific protein B (PSPB) were used as indicators of placental function and were unaffected by treatment administration (P>0.05). A treatment by time interaction was detected in both analyses, but no differences between treatments were detected within any time points. There was no effect of treatment on lamb weights or survival to weaning (P>0.05). Lamb sex effects are absent with the exception that body weights were greater in ewe lambs (P>0.05). There was no effect of treatment on any carcass traits or visceral organ weights assessed, though there was an effect of sex on dressing percentage and pancreas weight with wethers having a greater dressing percentage and heavier pancreases per kg body weight than that of ewes (P<0.05). In summary, contrary to our hypothesis L-citrulline supplementation to pregnant ewes under a minor to moderate metabolic challenge had no impact on blood flow and provided no programming benefit to the lambs. / Master of Science / The global population continues to grow, along with the consumption of animal protein. This can be met with increasing the numbers of animals within our food production systems, however, there is also increasing pressure for livestock production systems to produce more while utilizing less space and resources. And simultaneously, we face growing concerns about climate change, its impacts on agriculture, and the role of agriculture in both the cause and any future solution. To combat both these issues, the efficiency of our livestock systems needs to improve with each individual animal becoming much more efficient. This increase in efficiency can occur in many ways including reproductive efficiency, feed efficiency, and in overall producing more meat per individual. The improvement in efficiency of an animal can begin in the womb. Livestock in meat production spend 35-40% of their life within the uterus being nourished by their mother. The interactions the embryo and fetus have with the maternal environment during this time can have both short- and long-term impacts on health and development after birth. In some cases, these changes may be detrimental to the individual, but in other cases these developmental changes may be beneficial and manipulated to produce the desired effects. Thus, it is important to understand the impact of these fetal-maternal interactions as it directly affects both fetal growth and growth and development after birth. This concept is known as fetal programming. Our interest is to use this concept to improve skeletal muscle development and meat production in cattle and sheep. To achieve this, we targeted the period of pregnancy when fetal muscle formation occurs. Primary muscle fibers form early in pregnancy, and it is this small number of primary muscle fibers that will serve as templates for secondary fiber formation that occurs in the fetus during mid-pregnancy. Supplementing amino acids that influence blood flow within the reproductive tract is one potential way to provide fetuses with added nutrients during pregnancy, and this supplementation strategy may be especially useful when the maternal diet is compromised. L-citrulline was chosen for this work because of its long half-life in maternal circulation. This work utilized twin-bearing ewes with a moderate dietary energy restriction to assess the effects of L-citrulline supplementation on blood flow, placental function, newborn lamb size, and lamb performance. We hypothesize that intravenous administration of L-citrulline will increase uterine and placental blood flow in pregnant ewes and this will improve fetal growth, development, and overall postnatal performance. There was no beneficial effect on blood flow to the fetus and on placental function. Additionally, there were very minimal effects on carcass traits or internal organ weights assessed. In summary, contrary to our hypothesis L-citrulline supplementation to pregnant ewes under a moderate metabolic challenge had no impact on blood flow and provided no programming benefit to the lambs. We can conclude that the potential benefit of amino acid supplementation was not realized in our sheep model.

No description available.