Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on September 23, 2009. Major professor: Robert Crockett, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering, with Specializations in Biomedical Engineering." "June, 2009." Includes bibliographical references (p. 54-55). Also available on microfiche.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: myocardium; microthreads; fibrin; infarct; human mesenchymal stem cells. Includes bibliographical references (leaves 71-77).

Thesis (M.A.)--San Francisco State University, 2003. / Includes bibliographical references (leaves 56-58). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (M.A.)--San Francisco State University, 2003. / Includes bibliographical references (leaves 56-58).

Thesis (M.D.)—Boston University

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Acute myocardial infarction (AMI) is one of the most common causes of death in our country. As population ages, such illness have its prevalence rates increased. In order to analyse drug effects over myocardial lesions as a result of AMI, the myocardial infarction induction model by means of the administration of isoproterenol in rats is one of the most used at all, given the capability of that substance of mimicking the myocardial injury observed in humans. In the present study, preconditioning with intra-peritoneal ternatin, at a dose of 1 mg/kg was used. Fourteen consecutive days were assessed in the isoproterenol-induced MI (120 mg/kg) in Wistar rats. Myocardial lesions induced by isoproterenol was indicated by the rise in biochemical markers levels, such as SGOT (serum glutamic oxaloacetic transaminase) and troponin I, reduction in the activity of catalase enzyme in the myocardial tissue, as well as by histopathological changes assessed in the apex of the left ventricle. It was also evaluated mortality rates, hemoglobin and SGPT (serum glutamic pyruvic transaminase) serum concentrations, leukocytes, neutrophils counts and renal function. Preconditioning with ternatin unveiled protective effects within the myocardial infarction induced by isoproterenol in rats, once it diminished mortality rates, attenuated SGOT and troponin I concentrations, preserved catalase levels in the myocardium and diminished histopathological changes in the apex of the left ventricle Possible pathways accountable for such good results, reducing the degree of myocardial injury in this experimental essay, might be related to the antioxidant properties attributable to ternatin. / O infarto agudo do miocÃrdio (IAM) à uma das principais causas de morte em nosso paÃs. Com o envelhecimento da populaÃÃo a tendÃncia à que se aumente a incidÃncia desta afecÃÃo. Para se estudar efeitos de drogas sobre a lesÃo miocÃrdica decorrente de IAM, um dos modelos experimentais mais utilizados à a induÃÃo de infarto do mocÃrdio (IM) com administraÃÃo de isoproterenol em ratos, uma vez que esta substÃncia causa uma lesÃo miocÃrdica semelhante à observada em IAM nos humanos. Nesse estudo o prÃ-condicionamento com ternatina administrada por via intraperitoneal, na dose de 1 mg/kg do animal, por catorze dias consecutivos, foi avaliado no IM induzido por isoproterenol (120 mg/kg do animal) em ratos Wistar. A lesÃo miocÃrdica induzida pelo isoproterenol foi indicada pela elevaÃÃo de marcadores bioquÃmicos, como transaminase glutÃmico-oxalacÃtica (TGO) e troponina I, reduÃÃo da atividade da enzima catalase no tecido miocÃrdico, bem como por alteraÃÃes histopatolÃgicas avaliadas na regiÃo do Ãpice do ventrÃculo esquerdo. Avaliou-se ainda a mortalidade, as concentraÃÃes sÃricas de transaminase glutÃmico-pirÃvica (TGP), hemoglobina, contagem de leucÃcitos e neutrÃfilos e marcadores da funÃÃo renal. O prÃ-tratamento com ternatina apresentou efeitos protetores no infarto do miocÃrdio induzido por isoproterenol em ratos, uma vez que dimunuiu a taxa de mortalidade, atenuou as elevaÃÃes de TGO e troponina I; preservou a atividade da enzima catalase e reduziu o grau de alteraÃÃes histopatolÃgicas. PossÃveis mecanismos de aÃÃo responsÃveis pelos efeitos benÃficos em reduzir o grau de lesÃo miocÃrdica neste modelo experimental podem estar relacionados a propriedades antioxidantes da ternatina.

An overview of the noradrenergic system, including the identification of norepinephrine (NE) in animal tissue, its synthesis and metabolism, adrenoceptor classification, peripheral and central actions, uptake and storage, and mechanisms of NE release are presented. After characterizing the kinetic, ion dependence and inhibitor sensitivity of the norepinephrine transporter (NET) expressed in a recombinant cell line (LLC-NET cells), the influence of catecholamine (CA) metabolizing enzymes on studies of transport was assessed. Inhibitors of catechol-O-methyltransferase (COMT) potentiated the apparent uptake and retention of [3H]NE and [3H]DA. COMT inhibition had a greater influence on [3H]DA than [3H]NE uptake and retention, which corresponds to the higher spontaneous loss of radiolabel from cells exposed to [3H]DA than [3H]NE ([3H]methoxytyramine, is more lipophilic than [3H]normetanephrine). The monoamine oxidase inhibitor, pargyline, had no augmentary action on [3H]CA uptake, but actually inhibited substrate influx by blocking the NET. [3H]substrate specific differences were demonstrated for [3H]NE, [3H]DA and [3H]MPP+. For a given length of exposure to low Na+ or tyramine, [3H]NE release was the lowest, but most sensitive to NET inhibitors. Disparities in the kinetics of each [3H]substrate for the inwardly facing NET may account for this. Inhibitors of the NET were found to stimulate the efflux of [3H]substrates from preloaded cells incubated in a physiological HEPES buffer. Efflux was NET-dependent and differed greatly for each [3H]substrate. Inhibitor-induced release was greatest for [3H]MPP+ and least for [3H]NE. Finally, a functional model of carrier-mediated NE release in myocardial ischemia, was developed in this study. Release of [3H]MPP+ was stimulated by Na+-H+ exchanger (NHE) activation and modulated by inhibitors of the NET, NHE, Na+,K+-ATPase, and via a receptor-operated pathway. Excessive NE release contributes to severe myocardial arrhythmias, therefore an improved understanding of the carrier-mediated NE release process will ultimately enhance our ability to intervene and prevent the deleterious effects of excessive NE release.

Quinacainol, 1-[2-(1,1-dimethylethyl)-4-quinolyl]-3-(4-piperidyl)-1-propanol is a class I antiarrhythmic agent provisionally subclassified as Ic. Studies were carried out in order to (1) determine the actions of quinacainol in acute myocardial ischæmia, (2) ascertain the mechanism(s) responsible for these actions, and (3) ascertain the appropriateness of its subclassification. Toxicological, hæmodynamic, and ECG effects in chronically prepared conscious rats were determined following administration of 1, 2, 4, or 8 mg/kg of quinacainol given i.v. over 10 minutes on alternate days. Toxicity referable to the heart was seen at doses of 8 mg/kg and above. In rats given 8 or 16 mgkg, arrhythmias occurred. Quinacainol had no major effects on blood pressure, unlike most class I antiarrhythmics, but lowered heart rate (not statistically significantly) and prolonged P-R interval and QRS duration. In an attempt to protect against ischæmic arrhythmias, doses of 2 mg/kg and 4 mg/kg were given. The high dose gave the best protection. It reduced the incidence of ventricular tachycardia (VT) from a control value of 80% to 30%, and reduced the incidence of ventricular fibrillation (VF) from a control value of 60% to 10%. An increase in the incidence of premature ventricular contractions was seen at both doses. Blood pressure was not adversely effected although slight bradycardic effects as well as prolongation of the P-R interval were seen at both doses. Both doses reduced S-T segment and delayed onset of elevation of S-T segment and R-wave which were induced by coronary occlusion. Sensitivity to electrical stimulation was tested in pentobarbital anæsthetised rats using ventricular electrodes. Doses of 0.5, 1, 2, and 4 mg/kg were given cumulatively as a 10 min infusion every 25 min. Quinacainol did not affect QRS duration or the Q-Tc interval but dose-dependently widened P-R interval when compared to pretreatment. Quinacainol dose-dependently increased threshold current, threshold duration, and ventricular fibrillation threshold. In addition, quinacainol elevated effective refractory period while decreasing maximum following frequency. Open-chest rats under pentobarbital anæsthesia were used to record the effects of quinacainol on epicardial intracellular potentials. Recordings were made by conventional microelectrode techniques before and after cumulative doses of 0.5, 1, 2, 4, and 8 mg/kg i.v. Quinacainol dose-dependently reduced phase zero of the action potential (AP) and AP height but did not influence other phases of the AP (with the exception of prolonging repolarization at the highest dose); actions indicative of class Ic. Effects of quinacainol on isolated rat hearts were assessed using a modified Langendorff heart preparation and were compared with those of tetrodotoxin (TTX). Quinacainol widened the P-R interval and QRS duration without having major effect on the Q-Tc interval. In addition it slowed the sinus beating rate. Quinacainol was more potent than TTX. All findings indicated that quinacainol is a potent antiarrhythmic agent with Na⁺channel blocking properties. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

The structural and functional consequences of the interaction of various antiarrhythmics with human erythrocyte membranes, guinea pig brain synap-tosomes and myocardial sarcolemmal membranes were studied at drug concentrations affecting the stability of intact erythrocytes to hypotonic lysis. It was assumed that such stabilization might bear some molecular resemblance to the electrical stabilizing properties of these drugs in excitable tissues. Membrane perturbational actions of these drugs were measured in terms of the specific incorporation of the chromophoric probes, 5,51-dithio-bis-(2-nitrobenzoic acid) (DTNB) and trinitrobenzenesulfonic acid (TNBS) into membrane sulfhydryl and amino groups respectively. Most drugs tested, including lidocaine, quinidine, the verapamil analogue D-600 and the quaternary analogues QX 572 and pranolium, exhibited a concentration-dependent stimulation of DTNB and TNBS incorporation. At drug concentrations producing erythrocyte stabilization, the protein perturbational properties of quinidine, lidocaine, D-600 and QX 572 as viewed in terms of DTNB labelling were equivalent while differences were apparent with quinidine, D-600 and lidocaine at high concentrations in the destabilizing range. Most agents, with the exception of pranolium, showed a similar pattern of DTNB incorporation in brain synaptic membranes as in erythrocytes. Studies of the incorporation of TNBS into erythrocyte membranes indicated that antiarrhythmics induce greater structural alterations in membrane phospholipids as compared with membrane proteins. Bretylium and practolol, two substances with minimal direct cardiodepressant properties, did not enhance DTNB or TNBS incorporations into erythrocyte membranes, although both agents, especially practolol, possessed marked antihemolytic properties. It appeared, therefore, that the membrane perturbational actions of antiarrhythmics as analyzed here by means of group-specific chemical probes are a better index of their direct myocardial membrane actions than erythrocyte stabilization. The functional consequences of drug-membrane interaction as reflected in the inhibition of membrane-associated enzymes by antiarrhythmics were shown to be critically dependent on the drug and membrane in question. The activity of erythrocyte membrane ouabain-sensitive K+-stimulated p-nitrophenyl-phosphatase (K+-NPPase) was more readily inhibited than that of Mg++-independent and Mg++-stimulated NPPase by most drugs examined. In myocardial sarcolemmal membranes, lidocaine was stimulatory to the K+-NPPase whereas all other agents exhibited stimulatory actions only at the lowest drug concentrations. The Ca++-ATPase system in the erythrocyte membrane was also inhibited by antiarrhythmics with propranolol, pranolium and lidocaine showing a relatively higher degree of inhibition of the high Ca++ affinity component while quinidine and D-600 exerted equal inhibitory actions on both high and low Ca++ affinity components of the enzyme. A comparison of the perturbational actions of antiarrhythmics in isolated erythrocyte membranes, in the membranes of the intact erythrocyte and in brain synaptic membranes was made by analyzing the effects of drugs on the activity of the membrane acetylcholinesterase present in these preparations. Inhibitory actions of all drugs tested were comparable in both intact and isolated erythrocyte membranes but differed in the excitable tissue membrane. The nature of the inhibition exerted by the antiarrhythmics on acetylcholinesterase of intact erythrocytes was of a mixed type for most drugs except practolol which inhibited non-competitively. The transmembrane chloride gradient had no influence on the inhibition by bretylium, lidocaine and D-600 of the acetylcholinesterase activity of the intact cells but the inhibition produced by quinidine and propranolol was enhanced when erythrocytes were suspended in a low chloride medium. The foregoing results, therefore, indicate that the membrane perturbational actions of antiarrhythmics vary with the agent in question and with the particular membrane system. It is suggested that the molecular mechanisms by which these drugs alter cardiac automaticity may not be identical and may differ in various regions of the myocardium. This in turn may underlie the differing spectra of clinical effectiveness exhibited by these pharmacological agents. / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

Background: Autophagy is a conserved physiological process in the body that functions to maintain homeostasis via degradation and recycling of dysfunctional proteins and even entire organelles. It is typically triggered by nutritional stress and/or growth factor deprivation and ultimately results in the packaging of cellular components into autophagosomes. These autophagosomes then fuse with lysosomes to be degraded. Autophagy is suggested to play a significant role in cardiac remodeling, particularly following myocardial infarction (MI). Ataxia-telangiectasia mutated kinase (ATM) is a cell cycle checkpoint protein activated in response to DNA damage. Mutations in ATM cause a multi-systemic disease known as Ataxia-telangiectasia (AT). The present study aims to investigate the relationship between ATM and autophagy in the heart, particularly post-MI. Methods: Wild-type (WT) and ATM heterozygous (hKO; aged ~4 months) were injected with either bafilomycin (Baf; autophagy inhibitor) or rapamycin (Rap; autophagy activator) for 30 minutes. MI was then induced mice by ligation of the left anterior descending coronary artery. Heart function was measured using M-mode echocardiography 4 hours post-MI. For cellular analysis of autophagy, confluent cultures of cardiac fibroblasts were isolated from adult male rats and treated with KU-55933 (KU; specific ATM inhibitor) in serum-free media for 4 hours. Cardiac fibroblasts were also isolated from ATM WT, heterozygous (hKO), and knockout (KO) mice, grown to confluency, and serum-starved for 4 hours. Levels of microtubule-associated protein light chain 3-II (LC3-II), a marker for autophagy, was examined in the heart and cell lysates using western blots. Results: M-mode echocardiography revealed that MI decreases heart function in both genotypes as measured by decreased %FS and EF. No change in heart function was observed between WT-MI and hKO-MI groups following Baf treatment. Rap treatment resulted in the functional recovery of the heart in WT-MI, not in hKO-MI group. Levels of LC3-II protein were higher in hKO-sham versus WT-sham hearts. MI decreased LC3-II protein in hKO-MI, not in WT-MI group. Baf treatment further decreased LC3-II protein levels in hKO-MI group. LC3-II levels were lower in KU-treated rat cardiac fibroblasts when compared to control. Cardiac fibroblasts isolated from hKO and KO hearts exhibited decreased LC3-II levels versus those isolated from WT hearts. Conclusion: Although further investigations are needed to confirm our findings, these data provide evidence that ATM deficiency hinders improvement in heart function post-MI following activation of autophagy. ATM deficiency results in reduced autophagy post-MI, an effect that appears to be exaggerated following autophagy inhibition. ATM deficiency also reduces autophagy in rat and mouse cardiac fibroblasts.