Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 34-35.

Background: Risk factors for cardiovascular disease (CVD) include obesity, ethnicity and hypertension. High-density lipoprotein (HDL) has traditionally served as a marker for CVD risk. Latest studies, however, propose that the composition and subclass distribution and the anti-atherogenic function of HDL are more accurate predictors of CVD risk. We therefore explored whether obesity, ethnicity, exercise and hypertension may modulate HDL composition, subclass and function in three different sample populations of patients affected with these CVD risk factors. Methods: The first study sample population consisted of black and white obese and normal-weight South African women (n=40). In the second sample population, obese black South African women were randomly assigned to exercise (combined aerobic and resistance exercise 4 times/week) or control (sedentary) conditions for 12-weeks (n=32). The third sample population included Nigerian out-patients, divided into healthy controls, hypertensive patients and hypertensive patients with heart failure (HF) (n=80). HDL composition measurements included apolipoproteins A1 and M (ApoA1 and ApoM), paraoxonase (PON1) and platelet activating factor acetylhydrolase (PAF-AH) expression (using Western blotting) and sphingosine-1-phosphate (S1P) content (using mass spectometry). Levels of large, intermediate and small HDL subclasses were measured using the Lipoprint® system. HDL functionality was assessed by measuring PON1 activity, PAF-AH activity, reverse cholesterol efflux capacity, HDL-mediated activation of endothelial nitric oxide synthase (eNOS) and quantification of the expression of vascular cell adhesion molecule in endothelial cells. Results: In all sample populations, HDL-cholesterol concentration was not different between groups. PON1 activity was lower in white compared to black women (0.49±0.09 U/L vs 0.78±0.10 U/L, p<0.05). Obese black women had lower PAF-AH activity compared to obese white women (9.34±1.15 U/L vs 13.89±1.21 U/L, p<0.05). Compared to normal-weight women, obese women had lower large HDL, greater intermediate and small HDL. Compared to the sedentary control condition, exercise training was associated with a decrease in PON1 activity (-8.7±2.4% vs +1.1±3.0%, p<0.05), PAF-AH serum expression (-22.1±8.0% vs +16.9±9.8, p<0.005) and small HDL subclasses (-10.1±5.4% vs +15.7±6.6%, p<0.005). S1P content in HDL was lower in hypertensive and HF patients compared to controls (165 ± 55 vs 201 ± 73 pmol/mg, p < 0.05). HDL subclass distribution was different in hypertensive and HF patients with lower large HDL (48 ± 15 vs 63 ± 7%, p<0.005), higher intermediate (45 ± 7 vs 34 ± 5%, p<0.005) and small HDL (7 ± 9 vs 2 ± 4%, p<0.05). In contrast to HDL from control patients, HDL from all hypertensive patients failed to activate eNOS. Conclusions: In all three sample populations, there were associations between CVD risk factors and measures of HDL quality. HDL subclass distribution differences were associated with obesity and hypertensive heart failure, both in cross-sectional studies and in an exercise intervention study. In African sample populations, consideration of HDL quality rather than total HDL quantity may be a more sensitive marker to assess CVD risk.

The intramyocardial injection of biomaterials is an emerging therapy for myocardial infarction. Computational methods can help to study the mechanical effect s of biomaterial injectates on the infarcted heart s and can contribute to advance and optimise the concept of this therapy. The distribution of polyethylene glycol hydrogel injectate delivered immediately after the infarct induction was studied using rat infarct model. A micro-structural three-dimensional geometrical model of the entire injectate was reconstructed from histological micro graphs. The model provides a realistic representation of biomaterial injectates in computational models at macroscopic and microscopic level. Biaxial and compression mechanical testing was conducted for healing rat myocardial infarcted tissue at immediate (0 day), 7, 14 and 28 days after infarction onset. Infarcts were found to be mechanically anisotropic with the tissue being stiffer in circumferential direction than in longitudinal direction. The 0, 7, 14 and 28 days infarcts showed 443, 670, 857 and 1218 kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p= 0.0055, 0.028, and 0.018 for 0, 7 and 14 days groups). The biaxial mechanical data were utilized to establish material constitutive models of rat healing infarcts. Finite element model s and genetic algorithms were employed to identify the parameters of Fung orthotropic hyperelastic strain energy function for the healing infarcts. The provided infarct mechanical data and the identified constitutive parameters offer a platform for investigations of mechanical aspects of myocardial infarction and therapies in the rat, an experimental model extensively used in the development of infarct therapies. Micro-structurally detailed finite element model of a hydrogel injectate in an infarct was developed to provide an insight into the micromechanics of a hydrogel injectate and infarct during the diastolic filling. The injectate caused the end-diastolic fibre stresses in the infarct zone to decrease from 22.1 to 7.7 kPa in the 7 day infarct and from 35.7 to 9.7 kPa in the 28 day infarct. This stress reduction effect declined as the stiffness of the biomaterial increased. It is suggested that the gel works as a force attenuating system through micromechanical mechanisms reducing the force acting on tissue layers during the passive diastolic dilation of the left ventricle and thus reducing the stress induced in these tissue layers.

Acute heart failure is a potentially lethal clinical emergency without any effective therapy. Using an isolated rat heart model, we established and validated a model of de novo acute heart failure to study novel putative cardio protective therapies against acute heart failure, including glucose, insulin and the molecular agent sphingosine-1-phosphate(component of high density lipoprotein) for recovery. In isolated rat hearts, the protocol consisted of three phases: stabilization at normotensive perfusion pressure, hypotensive acute heart failure and recovery by restoring normotension. Low glucose (2.5mM) and high albumin-bound free fatty acids (1.3mM) (±adrenaline 10-M) were added in theperfusate. Molecular and metabolic agents were administered either alone or in combination in the acute heart failure or recovery phases. Effects of glucose, insulin and sphingosine-1-phosphatewere observed on heart function, cell death and mitochondrial respiration. In the absence of adrenaline, combination of glucose andsphingosine-1-phosphateduring acute heart failure improved functional recovery by increasing the heart rate. In the presence of adrenaline, glucose and sphingosine-1-phosphate administered separately were cardioprotective in the recovery phase by improving heart rate. The combination of glucose+insulin and glucose+sphingosine-1-phosphate in the recovery phase also increased heart rate. Glucos9+sphingosine-1-phosphate+insulin increased heart rate and left ventricular developed pressure.Sphingosine-1-phosphate reduced expression of cytochrome C, but metabolic agents had no effect.AG490 (inhibitor of signal transducer and activator of transcription 3) attenuated the cardio protective effect of sphingosine-1-phosphatewithincreased expression of the phosphorylated inactive form of this transcription factor protein. Conclusion: We have established and validated an ex-vivo model of de novoacute heart failure. The combination of metabolic and molecular treatments improved heart function by increasingsinus node activity_ Sphingosine-1-phosphate not only improved heart rate, but also reduced cell death, an effect mediated via activation of signal transducer and activator of transcription 3. Our data provide novel principles and approaches for the treatment of acute heart failure.

Introduction: Little is known about the molecular genetics of cardiomyopathy in Africans. Aims: to (I) determine the prevalence of desmosomal gene mutations in arrhythmogenic right ventricular cardiomyopathy (ARVC) and dilated cardiomyopathy (DCM) in desmosomal protein genes (i.e., plakophilin 2, desmocollin 2, desmoglein 2, and plakoglobin), (2) establish the presence of a founder effect in families with a recurrent mutation in the plakophilin 2 (PKP2) gene, (3) investigate whether single nucleotide polymorphisms found in desmosomal genes affect gene expression, and (4) search for new candidate genes for ARVC in families where no causal mutation was found in desmosomal protein genes. Methods: 177 participants with cardiomyopathy were screened for desmosomal gene mutations which were confumed by Sanger sequencing. The following methods were used: in the founder effect study we used haplotyping with microsatellite markers; for total gene expression we used real time polymerase chain reaction and allelic expression imbalance and exome sequencing was used for mutation screening in two siblings with severe early onset ARVC. To all novel variants identified prediction tools were used to predict the pathogenicity of the variant in uestion. Results: 21.5% of ARVC pro bands had a disease-causing mutation in one of four desmosomal genes; no disease-causing mutation was found in the 112 OCM index cases. A recurrent PKP2 mutation occurred on a common haplotype background in four white South African probands with cardiomyopathy. Investigation of a common PKP2 polymorphism had no effect on total gene expression nor was there evidence of allelic expression imbalance. Finally, rare mutations were found in PARVA and HMGXB3 by exome sequencing of two siblings.

Introduction: The presence of melatonin in wine contributes to the cardioprotective effect of regular and moderate consumption of wine against lethal ischemia/reperfusion injury. Recently, the presence of melatonin isomers has been identified in red wine, but whether or not these isomers confer any physiological properties is unknown. Aim: The aim of our study was to establish a cell culture model of simulated ischemia to study and compare the possible cytoprotective effects of dietary melatonin and a melatonin isomer against an ischemic insult and to explore the possible role of melatonin receptors in this effect. Methods: H9C2 cardiac fibroblast cells were subjected to simulated ischemia by exposure to 1mM H₂O₂ following a 30min pre-treatment with 75ng/L (dietary concentration), 1μM (pharmacological concentration, 0.232mg/L) melatonin or/and 75mg/L (dietary concentration) melatonin isomer. To determine the role of melatonin receptors, cells were pre-treated with the melatonin receptor inhibitor, luzindole (10 μM) for 1h prior to H₂O₂ treatment. At the end of the simulated ischemic insult, cell viability was assessed using trypan blue staining. Mitochondrial respiration in permeabilized H9C2 cells was measured using the Oroboros Instrument, at two different time points: at the end of a 30min pre-treatment with either 75ng/L melatonin or 75mg/L melatonin isomer, or the afore mentioned pre-treatments prior to a 15min treatment of 1mM H₂O₂. Results: A simulated ischemic insult with 1mM H₂O₂ reduced cell viability from 92.9±1.5% to 28.4±1.4% (p<0.001 vs control). Pre-treatment with the dietary concentrations of melatonin or the melatonin isomer improved the cell viability to a similar extent as a pre-treatment with the pharmacological concentration of melatonin (74.4±3.1%, 73.9±2.7% and 69.0±1.2%, p<0.001 vs H₂O₂ and p<0.01 vs H₂O₂ respectively). A combined pre-treatment of melatonin and the melatonin isomer did not add further cytoprotective benefit. Addition of luzindole fully abolished the cytoprotective effect of dietary melatonin (29.7±2.4%, p<0.001 vs H₂O₂ + Mel), but only partially abolished the cytoprotective effect of the melatonin isomer (41.4±3.6%). Both dietary concentrations of melatonin and the melatonin isomer did not affect mitochondrial respiration in permeabilized H9C2 cells. Conclusion: Our findings suggest that both dietary melatonin and the melatonin isomer confer cytoprotection against a simulated ischemic insult, an effect which is mediated, at least in part, via the activation of melatonin receptors. Both melatonin and melatonin isomers present the advantage to be potentially safe and inexpensive therapies against ischemic heart disease.

Includes bibliographical references.

Sumaary in English. / Includes bibliographical references. / Background: Due to the geographic distance between abattoirs and commercial valve plants delays between harvest and fixation usually range from 48 to 72 hours. In order to assess the pre-fixation tissue damage arising from the hypoxic period and the resulting calcific degeneration after implantation, we used an ultrastructural damage score and transmission electron microscopy. Materials and Methods: In a step by step manner, three major issues were clarified: 1) The degree of pre-fixation tissue damage was determined in the four most widely used commercially produced tissue heart valves. Since stentless bioprostheses represent the latest promising trend in the development of biological heart valves, stentless models of the following makes were compared: Baxter, Medtronic, St. Jude and Biocor. Due to the fact that the aortic wall component of these valves proved most resistant to all anticalcification treatments, aortic wall tissue stood in the centre of our analyses. 2) Subsequently, three main determinants of the fixation process namely: delay, temperature and fixative-concentration were varied with the goal of significantly improving the ultrastructural preservation of the bioprosthetic tissue. 3) Eventually, the influence of improved ultrastructural preservation on calcific degeneration was evaluated under in vivo conditions in the non-human primate and the rat model. Results: The comparison of the four most commonly used stentless bioprosthetic heart valves revealed a disturbing degree of tissue damage in all valves. Using a damage score from 1 to 21 (21 being the worst), aortic wall tissue of commercial valves ranged from 10 to 18 and that of leaflet tissue from 12 to 20. When fixation conditions were permutated, tissue damage could almost be abolished by immediate fixation (within 30 minutes of slaughter), low-temperature fixation(4°C) and high glutaraldehyde concentrations (> 1 %). Our in vivo experiments confirmed that commercially used fixation (delayed fixation, room-temperature and I ow concentrations of glutaraldehyde) with its concomitant high degree of tissue damage results in high levels of calcification. Apart from a distinctly improved calcification potential in ultrastructurally well preserved tissue, there was also an inverse correlation between tissue calcification and the concentration of glutaraldehyde used for fixation. Conclusion: We could demonstrate that commercially produced bioprosthetic heart valves uniformly show badly damaged tissue and that tissue damage contributes to the calcific degeneration of these valves. We were also able to determine ideal fixation conditions which in turn significantly reduced tissue calcification.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.