D. Tech. Nursing / Cardiovascular disease is the most common and yet one of the most preventable causes of death in the world. Risk factors for cardiovascular disease are numerous and well known. These risk factors are amongst others, hypertension, diabetes, physical inactivity, obesity, smoking and behaviour patterns. The intention of the study was to use the concept of a wellness clinic to promote cardiovascular wellness in the community. Packaging multiple interventions in a single visit would enable the research team to identify risk factors and educate the person regarding their own risk factors. The objectives of the study were to determine the prevalence of risk factors for cardiovascular disease in Soshanguve, determine personnel time and direct cost for promoting cardiovascular wellness taking into consideration screening, diagnostic testing and teaching including time, travel and personnel; and develop the optimal package of cardiovascular wellness interventions as determined by a binary Integer Programming model that maximizes cardiovascular wellness subject to constrains of shortage of funds and human resources in a resource poor setting.

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.

The effects of angiotensinsI and II on pump-perfusion pressure were examined in the hindlimb vasculature and in the vasculature supplied by the circumflex coronary artery in dogs. In both vasculatures angiotensins I and II caused dosedependent increases in perfusion pressure reflecting directionally similar changes in resistance to blood flow. Responses to angiotensin I were blocked with SQ 20881, a nonapeptide that specifically inhibits conversion of angiotensin I to angiotensin II. In contrast, P-113, a specific anglotensin II antagonist, abolished increases in perfusion pressure produced by angiotensins I and II. These results suggest that increases caused by local administration of angiotensin I in hindlimb or coronary vasculatures are largely ascribable to its enzymatic conversion to angiotensin II. Such conversion appears to occur to the extent of 31% in the hindlimb vasculature, and 26% in the coronary vasculature.

Cephalopods have one of the most sophisticated cardiovascular systems among the invertebrates; they have an enclosed high pressure blood system, characterised by a double circulation, with one main systemic heart and two gill hearts. The cephalopod cardiac tissues are basically myogenic, but there is evidence for both nervous and hormonal regulation of most parts of the cardiovascular system, although the details of the control systems remain unknown. This study investigated the physiology and innervation of the cardiac tissues of the squid Alloteuthis subulata, Loligo forbesii and L vulgaris. Histological staining techniques established that the cardiac organs in squid are innervated from the palliovisceral lobe of the brain via the paired visceral nerves. The nerves to the ventricle, branch off from each of the visceral nerves, close to a commissure that connects the two visceral nerves. The auricles of the systemic heart are innervated from a cardiac ganglion, situated at the base of the gills. Other branches, also given off at this level, innervate the lateral vena cava, afferent and efferent branchial blood vessels, branchial hearts and the muscular valve region between the branchial heart and afferent branchial vessel. Electron microscopical studies have shown the structure and number of fibres in these nerves. Pharmacological studies of isolated and perfused squid branchial hearts showed that acetylcholine had an inhibitory effect on cardiac activity, acting on both nicotinic and muscarinic receptors. An aminergic receptor system may be present in squid branchial hearts, although the transmitter substance is still unknown. The catecholamines adrenaline and noradrenaline excite the heart, although in an inconsistent manner. Whole cell patch clamp studies revealed that individual squid heart cells operated, using a combination of at least six different ionic currents; three outward potassium currents (delayed rectifier, A-current, calcium-activated current) and three inward currents (sodium current, L- and T -type calcium currents). An understanding of the functions of the various currents was obtained by recording electrically stimulated and spontaneous action potentials, using conventional intracellular recording and stimulation techniques. The ionic currents were isolated by applying known channel antagonists, and each antagonist's effect on the action potential was studied.

An integrated description of the respiratory system of the abalone Haliotis iris is presented. These animals are believed to be inherently primitive and still bear the ancestral gastropod gill arrangement, thus allowing physiological examination of a 'living fossil'. Ventilation, gaseous diffusion, blood transport and the anatomical arrangement of the vascular system are examined under a range of conditions. Resting H. iris consume an average of 0.47 µmol 0₂.g live weight⁻¹ .h⁻¹, 87% of which is taken up across the gills, the remainder diffuses directly into the foot and epipodium. A 300g abalone ventilates its gills at a rate of 28mL.min⁻¹, a rate which, due to low resistance to diffusion (diffusion limitation index = 0.47) and a well matched ventilation/perfusion conductance ratio, is adequate to support the quiescent animal. Increased oxygen demand is accommodated by an increase in cardiac stroke volume, elevating output from 9.1 to 24.4 µL.g⁻¹.min⁻¹. At rest the right gill is the predominant gas exchanger, receiving 95.7% of the branchial blood flow, when cardiac output is elevated the left gill becomes equally perfused, effectively doubling the diffusing surface. Ventilation does not increase, and an increased reliance on assistance from external water currents is seen. Previously undescribed components of the vascular system, notably an extensive sinus of mixed venous and arterial blood surrounding the gut and a large vessel that offers a bypass to the right kidney, provide a low resistance circuit between the heart and gills, bypassing the major organs and muscles. The low resistance circuit allows haemolymph to pass from the aorta to the base of the gills with minimal loss of pressure and no phase shift in the pulse, allowing blood to cross the gills with maximal inertia and instantaneous pressure gradient. Haliotis iris therefore appears to have exploited its limited physiological resources to the maximum in the routine operation of its gas exchange system. It is concluded that further improvement could not occur without substantial remodeling of the body plan, which may account for the abandonment of the system by higher gastropods.

Thesis (M. P. H.)--University of Hong Kong, 2007.

Thesis (M. P. H.)--University of Hong Kong, 2007. / Also available in print.