published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Nursing Studies / Master / Master of Nursing

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 5 uppsatser.

No description available.

Liu, Jian. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 127-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

Zhang, Yang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 147-169). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

This investigation was concerned with measuring aspects of cardiac function in conscious control, diabetic, hypertensive control, and hypertensive diabetic rats. Preliminary studies were conducted to determine catheter suitability and acute responses to atropine and angiotensin II in conscious animals. The catheter-manometer was tested using a square wave impact and was shown to accurately reproduce a left ventricular pressure pulse. Intravenous atropine caused both heart rate and left ventricular +dP/dt to rise. Intravenously administered angiotensin II caused systolic blood pressure to increase dramatically. In this case heart rate fell and +dP/dt was elevated. Hypertension was induced with deoxycorticosterone acetate (DOCA) and saline drinking water. Rats were first made diabetic with streptozotocin (60 mg/kg; i.v.). One week following this, subcutaneous DOCA (25 mg/kg) was administered twice weekly and all animals received saline drinking water. Following 2 and 5 weeks of DOCA treatment rats were catheterized and resting cardiovascular function was measured. DOCA treatment caused increased systolic and diastolic blood pressures to occur in control and diabetic rats at 2 and 5 weeks. Bradycardia was also observed in DOCA-diabetic and DOCA-control rats at 2 and 5 weeks of treatment. Two and 5 week hypertensive diabetic and control rats exhibited elevated -dP/dt and +dP/dt. The rate of contraction was shown to be proportional to the magnitude of systolic blood pressure in all treatment groups. It is concluded that diabetic rats and control rats did not differ in their response to hypertension after 5 weeks of DOCA treatment. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

The morbidity of and the mortality from cardiac disease are higher in diabetic patients. Clinical and experimental evidence suggests that diabetes-induced changes at the level of myocardium can, at least partially, contribute to these cardiac problems. The mechanism(s) involved in this diabetic cardiomyopathy is still unclear, but one defect appears to occur in the alpha₁-adrenoceptor system. Altered myocardial sensitivity and responsiveness to alpha₁-adrenoceptor agonists have been reported in experimental diabetes mellitus. Stimulation of alpha₁-adrenoceptors is known to produce a positive inotropic effect and has been recently shown to stimulate the hydrolysis of phosphoinositides. To evaluate the possibility that the changes in the inotropic responsiveness to alpha₁-adrenoceptor stimulation in the diabetic heart could be linked to altered alpha₁-adrenoceptor-stimulated phosphoinositide turnover and further to the development of diabetic cardiomyopathy, we studied contractility and receptor-stimulated phosphoinositide turnover following norepinephrine (in the presence of propranolol) stimulation in right ventricles from male Wistar rats (200-225 g) which were made diabetic with streptozotocin (55 mg/kg, i.v.). Rats were sacrificed six weeks after the induction of diabetes. Diabetic rats were characterized by decreased body weight gain, hypoinsulinemia, hyperglycemia and hyperlipidemia. Stimulation of alpha₁-adrenoceptors by norepinephrine (in the presence of propranolol) in right ventricles resulted in the formation of inositol monophosphate (measured with a radioisotope method) and inositol 1,4,5-trisphosphate (measured with an inositol 1,4,5-trisphosphate protein binding assay kit) in a time- and concentration-dependent manner in both control and diabetic rats. The increase in inositol 1,4,5-trisphosphate levels preceded the increase in the alpha₁-adrenoceptor-mediated positive inotropic effect. Diabetic hearts showed a greater maximum inotropic response to norepinephrine stimulation and also had a higher inositol 1,4,5-trisphosphate levels. However, with the radioisotope method, a decreased inositol monophosphate formation was shown in diabetic hearts compared with controls. Omega-3 fatty acids supplementation (Promega[symbol omitted], 0.5 ml/kg/day) had no significant effect on the changes in norepinephrine-stimulated inositol monophosphate formation in diabetic hearts. In the presence of the cyclooxygenase inhibitor indomethacin or the thromboxane synthetase inhibitor imidazole, the norepinephrine-stimulated positive inotropic effect and inositol 1,4,5-trisphosphate formation were significantly increased in control hearts, but were unaltered in the hearts from diabetics. The addition of the prostacyclin synthetase inhibitor tranylcypromine reduced the norepinephrine-stimulated positive inotropic effect and inositol 1,4,5-trisphosphate formation only in diabetic hearts and had no effect in the controls. While inositol 1,4,5-trisphosphate may be able to mediate only transient inotropic effects produced by alpha₁-adrenoceptor stimulation, diacylglycerol may provoke a sustained positive inotropic effect by activating slow Ca²⁺ channels through stimulation of protein kinase C. Our results showed that the diabetic hearts had a higher protein kinase C activity in the membrane fraction compared with controls and this was accompanied by a decrease in cytosolic protein kinase C activity. The present study suggests that the increases in inositol 1,4,5-trisphosphate levels and the membrane fraction protein kinase C activity may be implicated in the increased inotropic responsiveness to alpha₁-adrenoceptor stimulation in the hearts of the streptozotocin-diabetic rats. The increases in inositol 1,4,5-trisphosphate level and protein kinase C activity could induce Ca²⁺ overload in the diabetic heart which might be involved in the development of diabetic cardiomyopathy. The results from the omega-3 fatty acid study indicate that the changes in cardiac alpha₁-adrenoceptor-mediated inositol phosphates formation cannot contribute to the previously described improved cardiac function of omega-3 fatty acid-treated streptozotocin-diabetic rats. The nature and physiological significance of the enhanced positive inotropic effect and inositol 1,4,5-trisphosphate formation in the control heart with the addition of indomethacin and imidazole is still unclear. The effect of tranylcypromine may indicate the participation of prostaglandins in mediating the enhanced alpha₁-inotropic effect of norepinephrine in the diabetic heart. / Pharmaceutical Sciences, Faculty of / Graduate

Diabetes mellitus has been associated with both clinical and experimental cardiac dysfunction. Diabetic cardiomyopathy which is characterized by depressed cardiac contractility is accompanied by a variety of biochemical changes in Ca⁺⁺ metabolism. This cardiomyopathy may occur in the presence of normal coronary arteries and normal blood pressure. However, some studies have shown that hypertension is more prevalent among diabetics and can aggravate the cardiovascular abnormalities associated with diabetes. To understand the mechanisms of diabetic cardiomyopathy and consequences of combined hypertension and diabetes, experiments were designed to measure cardiac tissue responses to various inotropic agents in experimental diabetes. Six weeks following streptozotocin (STZ) administration, Wistar, spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats exhibited the 'classical signs' of diabetes which included: hyperglycemia, hypoinsulinemia, hyperlipidemia (except in WKY), and hypothyroidism. Decreased basal atrial rate and increased basal developed force (BDF) suggest a depressed SA node function and an alteration of Ca⁺⁺ utilization by diabetic ventricles. Decreased post quiescent potentiation (PQP) values (except in WKY) in ventricular tissues suggest a diminished amount of releasable Ca⁺⁺ from sarcoplasmic reticulum (SR). Decreased post stimulation potentiation (PSP) values in SHR papillary muscles (PM) are probably suggestive of a depressed sarcolemmal Na⁺-Ca⁺⁺ exchange function in this tissue. Diabetic rats show subsensitivity to β-adrenergic stimulation in ventricular tissues, supersensitivity and hyperresponsiveness to Ca⁺⁺ and α-adrenergic stimulation (except in WKY) in ventricular tissues and left atria (LA) and supersensitivity to BAY K 8644 in SHR LA and hyperresponsiveness to verapamil in ventricular strips. These alterations may be attributed to a change in receptor number and/or a post receptor alteration. Ryanodine decreased the PQP of Wistar and SHR PM and SHR LA in both controls and diabetics. It especially abolished PQP in SHR diabetic tissues, but had no effect on WKY tissues, which may suggest a difference in the SR function in these tissues. SR with impaired Ca⁺⁺ uptake may contribute to these phenomena in diabetic rats. Ryanodine also diminished (PQP + BDF) of SHR LA and (PQP/BDF) of Wistar and SHR PM, ˙but had no effects on control and other diabetic tissues. It appears that ryanodine has some influence on the Na⁺-Ca⁺⁺ exchange generated by sarcolemma (SL) of certain diabetic tissues. Further experiments are required to clarify this. SHR diabetic rats had greater changes in most of the measurements such as hyperlipidemia, depressed PQP and PSP values, and altered drug responses. This model exhibited very high mortality as compared to Wistar and WKY diabetic rats. As has been shown previously, the combination of hypertension and diabetes exerts a synergistic effect on the cardiac dysfunction in this model, and that altered lipid metabolism, SL and SR function are all involved in the development of cardiomyopathy. WKY diabetic rats, on the other hand, exhibited no significant changes in blood lipids, or in response to phenylephrine or to Ca⁺⁺ (LA) stimulation. Lack of change in these factors may explain the relatively normal cardiac function of this model as measured previously. / Pharmaceutical Sciences, Faculty of / Graduate

published_or_final_version / abstract / Physiology / Doctoral / Doctor of Philosophy