Hemodinamiese veranderinge as gevolg van eksperimentele hartversaking by skape soos waargeneem met 99m.-Technetium

MSc (Fisiologie), North-West University, Potchefstroom Campus1. Gousiekte is a congestive cardiomyopathy that occurs in ruminant animals. It is characterised by a latent period of 2-6 weeks followed by a sudden death. Typical symptoms such as arrhythmia, systolic murmurs and gallop rhythm can be heard by means of auscultation. It appears that during gousiekte the stroke volume decreases with about 40% and the PFI increases with more than a 100%. The decrease in stroke volume is observed by means of an electromagnetic bloodflow meter. The decrease in stroke volume during gousiekte is a sign that there is congestive failure of the left ventricle. A decrease in ejection fraction has been observed by a loss of value lower than 30% after the final congestive phase has been reached. The parameter ejection fraction is of more importance to accademic interest because it describes what takes place during congestive heart failure in sheep that have gousiekte, than what it is used for diagnostic criterion for heart failure during gousiekte. Normally 714 ~ 0,3 contractions of a sheep's heart are needed to pump the blood from the right to left side of the heart. Complete congestive fa i lure during gousiekte can decrease the effectiveness of the heart so that 50 contractions are needed, in other words a PFI value of 50. Two phases can be distinguished during the development of gousiekte namely a compensation phase and a decompensation phase. The PFI as criterion is used to establish the influence of certain medicines with aninotropie effect and to establish whether a gousiekte heart can potentiate after administration of the medicines. The findings are positive which shows that energy abnonnalities are not primary causes of gousiekte. As a model for heart failure gousiekte can be compared with other well known models of heart failure such as volume overload, pressure. overload and coronary ligatures in sheep. Similarity between volume overload as model and gousiekte has been found with a basic difference namely a limited compensation and pulmonary congestion with high PFI in sheep with gousiekte. Pressure overload as a model for heart failure has very little in common with gousiekte because the hypertrophy that is causes is obstructive and not dilating. Where gousiekte has been compared with a familiar criterion such as coronary arterie ligations it has been established that the rate of heart failure in gousiekte i.s much higher than during a drastic coronary ligature. 2. The by-product of this research is the development and possible application of the technetium isotope method to diagnose heart failure in sheep.Master

The role of renin in hypertension : an old dog with new bite / Johannes Marthinus van Rooyen

Foreword: Tigerstedt and Bergman discovered in 1898 the pressure-raising substance from saline rabbit kidney extracts and called the extract renin, however other scientists could not confirm their findings and in 1934, Harry Gold blatt published his results obtained in dog experiments where he clamped one or both renal arteries with a silver clamp. Numerous attempts showed no increases in plasma renin levels in patients with essential hypertension or that renin had any significant physiologic action of its own in humans. Braun-Menendez discovered that renin acted enzymatically on angiotensinogen (plasma protein) to form angiotensin I (inactive) and is further hydrolysed by converting enzyme to form angiotensin II (vasoconstrictor), which increases the blood pressure when it is low. This is the old dog and because renin is not even mentioned in the JNC-VII (US) and the ESH (European) guidelines and when one do a renin profiling on patients/participants and apply the laragh method to individualize the type of hypertension (volume or renin), it is evident that renin plays a large role in the maintenance of normal blood pressure and hypertension. In South African blacks whose hypertension is not under control. this will have a large impact on individualizing specific pathology and treatment and this will give the old dog new bite

Die beheer van die kardiopulmonêre bloedvolume en slagvolume by normale en versakende harte van skape

DSc (Fisiologie), North-West University, Potchefstroom CampusIn this study use was made of volume expansion with dextran on sheep with normal hearts and with cardiac failure in order to examine the mechanisms which are important in the control of the relation of the cardiopulmonary blood volume to stroke volume as well as to establish whether these mechanisms play a role in the overall hemodynamic control. A Swan-Ganz catheter was used for right heart catheterisation to establish pulmonary pressures and to establish the cardiac output after a cold five per cent dextrose injection was made. A radio-cardiogram was obtained by the injection of 1-5m Ci technetiumpertechnetate into the right atrium and the measuring of its activity with an Nal crystal. At the time the radio-cardiogram was taken an ECG was registered from which the cardio pulmonary flow index was calculated. The cardiopulmonary blood volume was calculated as the product of the cardiopulmonary flow index and the stroke volume. A cardiopulmonary flow index which under normal physiological conditions vary between five and 8,5 can be assumed as relative constant, if compared with changes from a control value of seven to values of 28 found with heart failure in sheep with gousiekte. The mean pulmonary intravascular pressure (approximate transmural pressure) is not homogeneous throughout the pulmonary circulation, because changes in the intrapleural pressure were not taken in account. In spite of this the approach of Oakley et al. ( 1962) and others were used in this study to show in vivo changes in pulmonary vasoactivity. Changes in pulmonary vasoactivity were established through changes in the cardiopulmonary blood volume and the mean pulmonary intravascular pressure (approximate transmural pressure). An increase in the cardiopulmonary blood volume and the mean pulmonary intravascular pressure indicates a passive pulmonary vasodilation and a decrease in the cardiopulmonary blood volume and increase in the mean pulmonary intravascular pressure indicate an active pulmonary vasoconstriction. This method is more suitable for the lung circulation than the measurement of resistance for the observance of changes in vasoactivity. The observance of vasoactivity in the lungs coupes great experimental and physiological problems because active and passive processes function in the pulmonary circulation. Sometimes these active and passive processes take place simultaneously and the more powerful dominates . In spite of this the in vivo method for the measurement of pulmonary vasoactivity is accompanied by great advantages over the in vitro methods because no nerve supply exists in the isolated specimen and manifestations like damage or unintensional rubbing of the vascular endothelium hamper the interpretation of results. It was pointed out that in the case of sheep with low initial heart rates active vasoconstriction of the pulmonary vessels take place after volume expansion in order to maintain the relation between the cardiopulmonary blood volume and the stroke volume at a value of about seven for normal hearts. Because the Bainbridge reflex also functions in the experimental animals with low initial heart rates, the active vasoconstriction apparently, and probably additionally functions in conjunct ion with the Bainbridge reflex. Another mechanism, the Starling mechanism, on the other hand functions in the case of high initial heart rates to maintain the relation of the cardiopulmonary blood volume to stroke volume . In the case of sheep with cardiac failure the different mechanisms do not function effectively and the cardiopulmonary flow index rises very steeply. A resting heart rate of 80 beats/min must not be seen as the approximate value for active pulmonary vasoconstriction to occur, whereas the resting heart rates may vary from sheep to sheep and as a consequence may show a spread in results. This study lends itself to statistical analysis of groups of experimental animals and not to an analysis of data from individual animals. With blocking receptors the problem arises that antagonists are not fully selective and it is uncertain whether receptors are fully blocked before an experiment. In spite of this problem agonists were injected intravenously to deter mine the extent of blockage before volume expansion. With the aid of blocking receptors it was shown that the active vasoconstriction functions via a parasympathetic efferent mechanism. The receptors which initiate this active vasoconstriction are probably seated in the walls of the pulmonary arteries and are probably dependent on the changes in pulmonary pressure and not on the absolute pressure It has been shown that the relation of the cardiopulmonary blood volume to stroke volume is not dependent upon the preload of the heart and relatively independent from the after-load of the heart when mean arterial pressures are lower than about 140nm Hg. The cardiopulmonary flow index can therefore be regarded as a good index to describe the pumping ability of the heart. The constancy of the cardiopulmonary flow index within the normal physiological range of five to 8,5 and the large increases in the cardiopulmonary flow index found in the event of cardiac failure, make it a good noninvasive criterion which in future can have certain diagnostic applications in veterinary science and medicine. From a physiological point of view this project yields more quantitative data regarding pulmonary reflexes and it has lent meaning to a mechanism which together with the Bainbridge and the Starling mechanism can possibly play an important role in hemodynami c control. With studying the relation of the cardiopulmonary blood volume to stroke volume, this project yields more quantitative data regarding the importance of in vivo control of the different volumes concerned, as well as the role of the different volumes in the overall hemodynamic control.Doctora

The impact of a 10-week physical activity intervention programme on selective metabolic syndrome markers in black adolescents

The purpose of this study was to determine the effects of a 10-week physical activity (PA) intervention on selective metabolic syndrome markers in black adolescents. All available adolescents (194 subjects), boys and girls, in the grade 9 class (15-19 years) attending a secondary school were recruited for the experimental group. A control group consisting of 57 adolescents from grade 9 of another secondary school in the same area was also recruited. The experimental group participated in a 10- week PA intervention. Body mass index (BMI), fasting insulin, fasting glucose, homeostasis model assessment of insulin resistance (HOMA-IR), systolic blood pressure (SBP), diastolic blood pressure (DBP), Windkessel arterial compliance (Cw), total peripheral resistance (TPR) and waist circumference were measured. After the 10-week PA intervention, adolescents from the control group had a significantly lower DBP compared to the intervention group (p=0.00005) and adolescents from the intervention group had a significantly lower SBP compared to the control group (p=0.000061). There was also a tendency towards a higher Cw and lower HOMA-IR in the intervention group compared to the control group. The findings of this study suggest that black adolescents had significantly lower SBP and a trend of lower HOMA-IR after a 10-week PA intervention.Key words: Physical activity; Metabolic syndrome; Adolescents