Motivation - Brain-derived neurotrophic factor (BDNF) is a protein complex, synthesised and secreted mainly by the central nervous system and is involved in neuronal maintenance. Research suggests that BDNF is implicated in various neurological and psychiatric diseases, while recent evidence suggests a role for the neurotrophin on the periphery as well. Indeed, the specific functional role of BDNF and its action mechanism in the cardiovascular system, especially in that of Africans, is yet to be determined. The cardiovascular health profile of black South Africans is a major concern as research has shown that this group suffers from an array of cardiovascular risk factors that may result in organ damage. Sub-clinical atherosclerosis or structural endothelial dysfunction contributes to ever-increasing morbidity and mortality in the world. However, no studies regarding the associations between BDNF and structural vascular disease have been undertaken relating to black African participants. Objectives - The objective of this study was to determine whether BDNF is associated with changes in ambulatory blood pressure (BP) and whether a relationship between BDNF and structural endothelial dysfunction exists in black African male and female participants, determined by cross sectional wall area (CSWA) and albumin:creatinine ratio (ACR). Methodology - The study included 172 black African teachers (82 males and 90 females) who were employed by the Kenneth Kaunda Education district of the North-West Province, South Africa. Ambulatory blood pressure recordings were obtained with the use of a Meditech CE120 CardioTens ® apparatus. Blood pressure readings were measured at 30 min intervals during the day and 60 min intervals during the night. Anthropometric measurements were performed in triplicate by registered level II anthropometrists according to standardised procedures. A high-resolution ultrasound scan with carotid intima-media thickness (CIMT) images from at least two optimal angles of the left and right common carotid artery were obtained using a SonoSite Micromaxx ultrasound system. The lumen diameter between the near and far wall of the lumen-intima interface and the averages of both the left and right common carotid arteries were calculated. Subsequently, the carotid cross-sectional wall area (CSWA) was calculated. Participants, who fasted overnight, provided eight-hour blood and urine samples to determine serum BDNF and metabolic markers, for example, hyperglycaemia (HbA1c) and gamma glutamyl transferase (GGT). Urinary albumin and creatinine levels were determined by means of a turbidimetric method with the use of a Unicel DXC 800 analyser from Beckman and Coulter (Germany) and expressed as a ratio between albumin and creatinine (ACR). BDNF median split x Gender interaction effects for structural ED justified stratification of BDNF into low and high (≤ / > 1.37 ng/ml) gender groups. Results and Conclusion - On average, male participants were overweight (BMI 25-30kg/m2) and abused more alcohol.21 African men revealed a vulnerable cardiometabolic profile with values exceeding cut–points (European Society of Hypertension). These men demonstrated increased acute and chronic glucose (HbA1c) levels indicating a pre-diabetic state; as well as a disturbed lipid profile with lower HdL and increased triglycerides. Overall BDNF levels were lower than reference ranges (6.97 – 42.6 ng/ml). The men revealed mean lower BDNF levels, ambulatory BP values exceeding guideline cut-points (ambulatory SBP > 130mmHg; DBP > 80mmHg) as well as a hypertensive state compared to their female counterparts. Pertaining to structural endothelial dysfunction, the mean ACR value in men exceeded normal laboratory values (< 3.5mg/mmol). The African women displayed an obese state with low grade inflammation (CRP, 12.27 ± 11.67mg/l). A single two-way ANCOVA interaction on main effects (BDNF median split x Gender) demonstrated significant interaction for CIMTf [F (1,164); 3.99, p=0.05] and cholesterol [F (1,164); 4.12, p=0.05]. Therefore, a median split approach was followed which stratified gender groups into lower (≤ 1.37 ng/ml) and higher BDNF levels (>1.37 ng/ml). The low BDNF men revealed higher cholesterol than the high BDNF group, independent of BMI and age. Only the low BDNF women indicated significantly higher values for structural vascular markers (p< 0.05) than the high BDNF female group. In conclusion, we accept our hypothesis, as hypertrophic remodelling of the carotid artery was associated with lower BDNF levels. This may imply attenuated or possibly down-regulated BDNF levels acting as a compensatory mechanism for the mean higher BP levels. In women, metabolic risk and hypertrophic remodelling were evident within higher circulating levels of BDNF, underpinning different underlying mechanisms for impaired neurotrophin health in men and women. Novel findings of BDNF revealed the impact of central neural regulation on the circulatory system, which may contribute to cardiometabolic risk in Africans. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014

Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Forensiese assesseringstegnieke wat tydens ondersoeke na kinder seksuele misbruik benut word, het in n hoë mate mettertyd ontwikkel. Navorsing het n waardevolle bydrae gelewer tot effektiewe en geskikte assesseringstegnieke. Verdere navorsing is egter nodig om die bestaande tegnieke te ondersoek. Die persoon wat by forensiese assesserings betrokke is, kan baat vind by die leiding wat navorsing bied. Op grond hiervan het die navorser ondersoek ingestel na die forensiese assesseringstegnieke wat tans in die praktyk deur forensiese maatskaplike werkers benut word. Gedurende die ondersoek is verskeie tegnieke wat tydens forensiese assesseringsonderhoude benut word, geïdentifiseer en bespreek. Die sistematiese aanrakingseksplorasie is vir die doel van hierdie studie deur die navorser uitgesonder. Hierdie tegniek is aan die hand van n gevallestudie bestudeer en bespreek. Ondersoek is ook ingestel na die menings van maatskaplike werkers wat in die forensiese veld werksaam is, asook dié van justisie–amptenare, onder wie landdroste en staatsaanklaers, wat in die hof vir seksuele misdrywe werksaam is, ten opsigte van die benutting van die sistematiese aanrakingseksplorasie. Die justisie–amptenare was aanvanklik nie vertroud met die tegniek nie. Nadat literatuur vir bestudering aan hulle beskikbaar gestel is, is vasgestel dat hulle ontvanklik is vir en positief staan teenoor die benutting van die sistematiese aanrakingseksplorasie. Die ondersoek het ten doel gehad: * Om deur middel van n literatuurstudie die forensiese assesseringstegnieke wat tans in die praktyk benut word, te identifiseer en te bespreek; en * Om die sistematiese aanrakingseksplorasietegniek aan die hand van n literatuurstudie en empiriese navorsing te evalueer. Samevattend kan gestel word dat die tegnieke, soos in hierdie navorsing bespreek, deel behoort uit te maak van die protokol van die professionele persoon wat die seksueel misbruikte kind assesseer. Hierdie navorsing het bevind dat die sistematiese aanrakingseksplorasie n waardevolle forensiese assesseringstegniek is ten opsigte van die seksueel misbruikte kind. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2012.

Objectives: The aim of this study was to determine associations between physical activity (PA), blood pressure (BP) and renin in urban black Africans. Methods: The study sample included 137 urban African males (N=68) and females (N=69) (aged 41.53 ± 8.13 and 44.16 ± 7.37 years, respectively), from the North West Province, South Africa. Anthropometric measurements, ambulatory blood pressure and energy expenditure were determined. Actical® accelerometers were used to determine energy expenditure (METS) over a 24 hour period. Fasting blood samples were used to determine fasting blood glucose, serum cotinine (COT), gamma–glutamyl transferase (GGT) and plasma renin. Results: A greater percentage (64%) of African males were hypertensive compared to African females (33.33%). SBP (p<0.001) and DBP (p<0.001) were significantly higher in males than females. Female subjects were more obese (32.00±7.75 kg/m2) whereas males demonstrated an overweight status (27.28±5.86kg/m2). Male subjects displayed overall higher lifestyle risks (BP, smoking, alcohol consumption, HIV–status) than females. Multivariate regression analyses demonstrated an inverse relationship between BP and renin in both males and females, but no associations existed between renin and physical inactivity. Conclusion: PA appeared not to buffer elevated blood pressure in this specific African sample, as no significant associations supported this hypothesis. The results confirm that black Africans display lower renin levels associated with elevated blood pressure. Furthermore, low renin and physical inactivity was not related to indicate elevated BP through elevated SNS activity. / Thesis (M.Sc. (Biokinetics))--North-West University, Potchefstroom Campus, 2012.

Forensiese assesseringstegnieke wat tydens ondersoeke na kinder seksuele misbruik benut word, het in n hoë mate mettertyd ontwikkel. Navorsing het n waardevolle bydrae gelewer tot effektiewe en geskikte assesseringstegnieke. Verdere navorsing is egter nodig om die bestaande tegnieke te ondersoek. Die persoon wat by forensiese assesserings betrokke is, kan baat vind by die leiding wat navorsing bied. Op grond hiervan het die navorser ondersoek ingestel na die forensiese assesseringstegnieke wat tans in die praktyk deur forensiese maatskaplike werkers benut word. Gedurende die ondersoek is verskeie tegnieke wat tydens forensiese assesseringsonderhoude benut word, geïdentifiseer en bespreek. Die sistematiese aanrakingseksplorasie is vir die doel van hierdie studie deur die navorser uitgesonder. Hierdie tegniek is aan die hand van n gevallestudie bestudeer en bespreek. Ondersoek is ook ingestel na die menings van maatskaplike werkers wat in die forensiese veld werksaam is, asook dié van justisie–amptenare, onder wie landdroste en staatsaanklaers, wat in die hof vir seksuele misdrywe werksaam is, ten opsigte van die benutting van die sistematiese aanrakingseksplorasie. Die justisie–amptenare was aanvanklik nie vertroud met die tegniek nie. Nadat literatuur vir bestudering aan hulle beskikbaar gestel is, is vasgestel dat hulle ontvanklik is vir en positief staan teenoor die benutting van die sistematiese aanrakingseksplorasie. Die ondersoek het ten doel gehad: * Om deur middel van n literatuurstudie die forensiese assesseringstegnieke wat tans in die praktyk benut word, te identifiseer en te bespreek; en * Om die sistematiese aanrakingseksplorasietegniek aan die hand van n literatuurstudie en empiriese navorsing te evalueer. Samevattend kan gestel word dat die tegnieke, soos in hierdie navorsing bespreek, deel behoort uit te maak van die protokol van die professionele persoon wat die seksueel misbruikte kind assesseer. Hierdie navorsing het bevind dat die sistematiese aanrakingseksplorasie n waardevolle forensiese assesseringstegniek is ten opsigte van die seksueel misbruikte kind. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2012.

Objectives: The aim of this study was to determine associations between physical activity (PA), blood pressure (BP) and renin in urban black Africans. Methods: The study sample included 137 urban African males (N=68) and females (N=69) (aged 41.53 ± 8.13 and 44.16 ± 7.37 years, respectively), from the North West Province, South Africa. Anthropometric measurements, ambulatory blood pressure and energy expenditure were determined. Actical® accelerometers were used to determine energy expenditure (METS) over a 24 hour period. Fasting blood samples were used to determine fasting blood glucose, serum cotinine (COT), gamma–glutamyl transferase (GGT) and plasma renin. Results: A greater percentage (64%) of African males were hypertensive compared to African females (33.33%). SBP (p<0.001) and DBP (p<0.001) were significantly higher in males than females. Female subjects were more obese (32.00±7.75 kg/m2) whereas males demonstrated an overweight status (27.28±5.86kg/m2). Male subjects displayed overall higher lifestyle risks (BP, smoking, alcohol consumption, HIV–status) than females. Multivariate regression analyses demonstrated an inverse relationship between BP and renin in both males and females, but no associations existed between renin and physical inactivity. Conclusion: PA appeared not to buffer elevated blood pressure in this specific African sample, as no significant associations supported this hypothesis. The results confirm that black Africans display lower renin levels associated with elevated blood pressure. Furthermore, low renin and physical inactivity was not related to indicate elevated BP through elevated SNS activity. / Thesis (M.Sc. (Biokinetics))--North-West University, Potchefstroom Campus, 2012.

Thesis (doctoral)--Utrecht, 1979.

Motivation Hypertension and type 2 diabetes mellitus are common in the black population of South Africa. The literature also shows that elevated blood glucose concentrations can lead to an increase in blood pressure and a blunted decline in nocturnal blood pressure. Therefore, the motivation for this study was to determine if blood glucose may play a role regarding the blunted nocturnal decline in blood pressure in African and Caucasian men. Aim The aim of this study was to investigate the relationship between a blunted nocturnal decline in blood pressure and blood glucose in African and Caucasian men. Methodology A comparative population study was preformed that consisted of 202 school teachers (101 African and 101 Caucasian) between the ages of 25–60 years from the North West Province, South Africa. Subjects were excluded if their body temperature was elevated, had a dependence or abuse of psychotropic substances, were regular blood donors and/or vaccinated in the previous three months. Ambulatory systolic (SBP) and diastolic blood pressure (DBP) were measured. Blood samples from the antebrachial vein were collected in sodium fluoride tubes to determine the serum glucose level and glycosylated hemoglobin A1c (HbA1c) percentage. Estimated average glucose (eAG) was determined from the percentage HbA1c by means of a regression formula. Means and proportions were compared by standard t–test and the chi–square test, respectively. Pearson correlations were used to determine unadjusted associations and multiple regression analysis to determine adjusted associations between variables. Results and Conclusion African men had an elevated HbA1c (p<0.001), eAG (p<0.001), nighttime SBP (p<0.001) and DBP (p<0.001). These results remained similar when non–dipping African and Caucasian men were compared. The Africans also smoked more (p=0.012), consumed more alcohol (p=0.049), had a higher percentage of non–dippers (p=0.054), HIV infected subjects (p<0.001) and a larger number of subjects that used anti–hypertensive medication (p=0.049). The unadjusted analysis showed positive correlations between all the blood pressure measurements and serum glucose, HbA1c and eAG in the African non–dipper men. While in the non–dipper Caucasian men, only daytime SBP and nighttime SBP (22:00–06:00) correlated positively with serum glucose, HbA1c and eAG. Furthermore, when viewing the relationship between carotid intima–media thickness (CIMT) and the blood pressure measurements in the African population, only nighttime (00:00– 04:00) SBP (r=0.581, p<0.001) and DBP (r=0.566, p<0.001) showed positive associations. After adjustments were made for age and body mass index the associations between the various blood pressure measurements and blood glucose disappeared in the non–dipper Caucasian men. However, in the non–dipper African men both nighttime (22:00–06:00) SBP and (00:00– 04:00) SBP showed positive correlations with serum glucose, HbA1c and eAG. After full adjustments (age, BMI, smoking, alcohol intake, physical activity, C–reactive protein and baroreceptor sensitivity) were made, nighttime (00:00–04:00) SBP was the only measure of blood pressure that correlated positively with HbA1c (p=0.069) and eAG (p<0.001) in the nondipper African men. No significant relationships were found for Caucasian men. Furthermore, to determine if the association between nighttime (00:00–04:00) SBP and eAG were independent of CIMT, we adjusted for CIMT. By doing so the positive association between SBP and eAG remained significant in the non–dipper African men (R2=0.617; =0.438; p=0.008) and nonsignificant in the non–dipper Caucasian men (R2=0.423; =0.169; p=0.33). However, the relationship between CIMT and eAG disappeared when we adjusted for SBP, suggesting that the SBP and eAG relationship drives CIMT. In conclusion, the association between the early morning SBP (00:00–04:00) and the blood glucose in non–dipping African men suggests that the blunted decline in nocturnal blood pressure during the early morning hours is associated with chronically elevated blood glucose. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2011.

Motivation: Recently, with urbanisation becoming an increasing trend, the African population have been introduced to the westernised lifestyle. This contributed to severe health implications and a rapid increase in cardiovascular morbidity and mortality in the African population. In South Africa and other sub–Saharan African countries, the prevalence of cardiovascular disease is increasing rapidly. The African population is thus regarded as a high risk group, and we deem it necessary and important to investigate additional possible cardiovascular risk markers in the attempt to improve the diagnosis of cardiovascular diseases and the treatment thereof. We investigate double product as a possible cardiovascular risk marker in African and Caucasian men from South Africa. Recent studies have suggested that increased double product values might be an independent predictor of cardiovascular morbidity and mortality. However, investigations on double product and endorgan damage are limited in this population group. The strength of associations between double product and various measurements of end–organ damage, including intima–media thickness, left ventricular hypertrophy and albumin–to–creatinine ratio, are compared with the associations between the more traditional risk factor, systolic blood pressure, and the measurements of end–organ damage. Aim: The aim of this study is to investigate the usability of double product as a possible cardiovascular risk marker in African and Caucasian men from South Africa. Methodology: The manuscript presented in Chapter 3 made use of the cross–sectional SABPA (Sympathetic Activity and Ambulatory Blood Pressure in Africans) study, where 101 urbanised African and 101 Caucasian male school teachers from the North West Province of South Africa were recruited. Anthropometric measurements were taken in triplicate using standard methods. The cardiovascular measurements included 24–hour ambulatory blood pressure and electrocardiogram measurements. Double products were calculated as the product of 24–hour, daytime and night–time mean systolic blood pressure and mean heart rate values. The carotid intima–media thickness was also obtained following the prescribed protocols. A registered nurse collected blood samples and the biochemical measurements were performed by independent laboratories, blinded to the subject’s cardiovascular profile. Means and proportions were compared by standard t–tests and the x2 –tests, respectively. The association between markers of end–organ damage and double product were investigated using single, partial and multiple regression analyses. All p–values <= 0.05 were deemed significant. Results and conclusions: Results from this study showed that Africans displayed significantly higher systolic blood pressure values, heart rate values and subsequent double product values compared to the Caucasians. Despite these significant differences, double product only showed borderline significant correlations with the markers of end–organ damage in African men, while no correlations were evident in Caucasian men. In African men, systolic blood pressure displayed stronger and significant correlations with intimamedia thickness, left ventricular hypertrophy, and albumin–to–creatinine ratio than double product. These findings suggest that double product may not be a good marker of increased risk for end–organ damage and subsequent cardiovascular–related mortality. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2011.