Arresting the heart with cardioplegia solution is the usual strategy to protect the myocardium during cardiac surgery. However, ischemia-reperfusion injury, due in part to Ca2+ overload, remains a clinical problem. Ca2+ influx during ischemia occurs through reverse mode action of the Na+/Ca2+ exchanger. We therefore tested the hypothesis that delivering the Na+/Ca2+ exchanger blocker SEA0400 to a cardioplegia solution would result in superior myocardial protection during ischemic-cardioplegic arrest. Studies were performed on isolated hearts and individual cardiomyocytes from young adult male Fisher Rats. Hearts arrested with cardioplegia containing SEA0400 showed improved recovery of left ventricular function after reperfusion. The onset of reperfusion arrhythmia was delayed, troponin release was reduced, and mitochondrial damage was minimized. In the isolated cell model, contraction amplitudes were higher during reperfusion in the SEA0400 group without a change in Ca2+ transients. This suggests that cells arrested with cardioplegia containing SEA0400 developed improved myofilament sensitivity to Ca2+.

Neste trabalho é descrito um sistema para aquisição e processamento do sinal de eletrocardiograma (ECG) para uso em experimentos de fisiologia cardíaca adaptativa de animais aquáticos (peixes). A aplicação imediata destina-se ao Laboratório de Zoofisiologia e Bioquímica Comparativa do Departamento de Ciências Fisiológicas da Universidade Federal de São Carlos. Um algoritmo de processamento do sinal de ECG é proposto, implementado e comparado com outros dois algoritmos, descritos na literatura especializada, tendo demonstrado ótimo desempenho. Um sistema de controle de experimentação, onde as condições do meio como temperatura e pressão de oxigênio, são mantidas constantes, também foi implementado. / In this work a system for signal acquisition and digital processing of the electrocardiogram (ECG) for adaptive cardiac physiology of fishes is described. The instrumentation has been developed to be used in the \"Laboratório de Zoofisiologia e Bioquímica do Departamento de Ciências Fisiológicas da Universidade Federal de São Carlos\". A new algorithm for signal processing of ECO is proposed, implemented and compares favourable with two others described in the literature. Also, a control system to keep constant the temperature and pressure has been designed.

Neste trabalho é descrito um sistema para aquisição e processamento do sinal de eletrocardiograma (ECG) para uso em experimentos de fisiologia cardíaca adaptativa de animais aquáticos (peixes). A aplicação imediata destina-se ao Laboratório de Zoofisiologia e Bioquímica Comparativa do Departamento de Ciências Fisiológicas da Universidade Federal de São Carlos. Um algoritmo de processamento do sinal de ECG é proposto, implementado e comparado com outros dois algoritmos, descritos na literatura especializada, tendo demonstrado ótimo desempenho. Um sistema de controle de experimentação, onde as condições do meio como temperatura e pressão de oxigênio, são mantidas constantes, também foi implementado. / In this work a system for signal acquisition and digital processing of the electrocardiogram (ECG) for adaptive cardiac physiology of fishes is described. The instrumentation has been developed to be used in the \"Laboratório de Zoofisiologia e Bioquímica do Departamento de Ciências Fisiológicas da Universidade Federal de São Carlos\". A new algorithm for signal processing of ECO is proposed, implemented and compares favourable with two others described in the literature. Also, a control system to keep constant the temperature and pressure has been designed.

Yes

Heart failure, as a result of myocardial infarction, is a major cause of mortality in human. The main cause of heart failure is that when adult cardiomyocytes die in the infarct site they do not regenerate. Instead the infract site is replaced by fibroblasts and collagen scar. It is generally believed that cardiomyocytes have terminally differentiated and can not divide to replace cardiomyocytes that have lost following injury. However, recently published data have provided new evidence that there is a small but continuously turnover of cardiomyocytes in the adult heart. These new findings provide a new theory that the heart does possess a limited ability to regenerate. / I also examined the regenerative ability of cardiomyocyte in adult heart. MRL mice were used because previously it has been reported that the cardiomyocyte could proliferate in response to injury. To understand how the cardiomyocytes in the MRL mouse heart, I used a cryo-injury approach. I discovered that the cardiomyoctyes in MRL mouse hearts were capable of dividing shortly after cryo-injury. These MRL hearts healed without scarring in contrast to C57BL/6 control mice. It was discovered that BMP-2, GATA4 and Nkx2.5 were involved in the healing process. The activation of these genes induced the cardiomyocyte to re-enter the cell cycle so that new cardiomyocytes could replace the cell that have been lost in the infarct site. I also discovered that stem cells may also play a minor role in the healing process. / In summary, my research findings revealed that cardiomyocytes regeneration in the heart is a very complex process that involves the participation of many cells and signalling pathway. There findings raise many intriguing and important questions and are worthy of being addressed in the future. / Stem cell therapy has been proposed as a potential treatment for various myocardial diseases. Chen et al. (2004) found small chemical called reversine that could dedifferentiate C2C12 cells to become stem-like cells. In this study, I demonstrated that reversine could inhibit the growth of C2C12 cell. The presence of reversine in cell culture could significantly inhibit muscle-specific genes MyoD, Myogenin and Myf5 expression. These 3 muscle specific transcriptional genes are essential for maintaining muscle differentiation. The down regulation of these gene showed that reversine could dedifferentiate C2C12 cells. We also discovered that reversine-treated C2C12 cells could differentiate into cardiomyocytes when they were cocultured with cardiomyocytes or when transplanted into the infarct site of a cryo-injured heart. / To investigate the regenerative potential of cardiomyoctyes in adult heart, we tried first to uncover the signals that direct post-natal cardiomyocytes to enter into growth arrest and differentiation. In the first part of my study, I established that the cardiomycytes divided extensively in 2 day-old post-natal hearts and that the majority of these cells entered into growth arrest and terminal differentiation at day 13. Comparative proteomic techniques were used in order to identify proteins that might be associated with cardiomyocytes proliferation during terminal differentiation the mouse heart. Several proteins were found to be differently expressed and amongst them was cyclin I protein. Cyclin I was found strongly expressed in 13 day old hearts. The protein is involved in signaling growth arrested in cells. / Liu, Ye. / "November 2006." / Adviser: Lee Ka Ho. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5658. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 142-172). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

A leading cause of morbidity and mortality in the developed world is cardiovascular disease (CVD). Like many other disease processes the etiology of CVD has origins in both genetic and environmental factors. These factors affect the development of the heart and vasculature and how they respond to physiological and pathological stress. Abnormal heart development can lead to cardiac pathologies that manifest in a shift from normal cardiac geometry and physiology to what is called pathological cardiac remodeling. Often though, pathological remodeling can result from cardiovascular stress even when heart development is normal. Growth factors are essential mediators of cardiac development and physiology and a good number of clinical and experimental studies have implicated growth factors and their signaling effectors as potential therapeutic targets for pathological cardiac remodeling. Of those is Fibroblast Growth Factor 2 (FGF2) which is a potent inducer of fibroblast and cardiomyocyte proliferation in vitro. FGF2 is made in high molecular weight and low molecular weight isoforms (Hi FGF2 and Lo FGF2, respectively). It has already been demonstrated that, in the context of the heart, FGF2 modulates cardiac hypertrophy, cardiac fibrosis and mediates protection against cardiac injury. However, the isoform specific role of FGF2 in cardiac development, physiology and pathological remodeling has not been disclosed, and in this dissertation I address the hypothesis that FGF2 has isoform-specific function in cardiac physiology and remodeling. To test this hypothesis I used mice that are either deficient in Hi FGF2 (Hi KO) or Lo FGF2 (Lo KO) and subjected them to echocardiographic analysis and isoproterenol (Iso) treatment and compared them to wildtype (WT) cohorts. At baseline echocardiographic measurements, female Lo KO hearts are smaller and present with increased peak E-wave velocity, a diminutive A wave, and shortened mitral-flow deceleration time consistent with a restricted filling pattern and myocardial stiffness. Conversely, male Lo KO hearts present with a lower E wave and a higher A-wave velocity and a prolonged isovolumic-relaxation time consistent with impaired left ventricular (LV) relaxation. Female Hi KO hearts display no significant deviation from WT, while male Hi KO hearts exhibit increased systolic function. Hence, a deficiency in Lo FGF2 results in a shift from normal diastolic parameters and geometric measurements which is gender specific. Conversely, a deficiency in Hi FGF2 produces a phenotype in male hearts only. Histological and gravimetric analysis of Lo KO and Hi KO hearts post-Iso treatment reveals that female Lo KO hearts remain smaller even though their cardiomyocytes are hypertrophied while female Hi KO hearts present with a blunted hypertrophic response indicating a hypoplastic myocardium. Male Lo KO hearts present with an exacerbated fibrotic response and increased alpha-smooth muscle actin protein expression while Hi KO hearts exhibit a resistance to the fibrotic response and an induction of atrial natriuretic factor protein expression. Thus, in female hearts Hi FGF2 mediate cardiac hypertrophy while in male hearts Lo FGF2 and Hi FGF2 display an antithetical role in cardiac fibrosis where Lo FGF2 is protective while Hi FGF2 is damaging. Hence, cardiac remodeling following catecholamine overactivation is modulated by FGF2 in isoform- and gender-specific manners. In conclusion, the results presented here provide novel evidence on the interaction of gender and endogenous FGF2 isoforms as modulators of cardiac development, physiology and remodeling. Lo FGF2 signaling is necessary in the male heart for normal myocardial relaxation and for amelioration of the fibrotic response induced by beta-adrenergic stress, while in female hearts Lo FGF2 is necessary for normal cardiac growth and normal myocardial compliance. Hi FGF2 is necessary only in female hearts for mediating the hypertrophic response. Hence, I demonstrate that Lo FGF2 and Hi FGF2 have non-redundant roles in cardiac physiology and remodeling which are gender-specific.

During the last two decades, since the heart has become a direct target for various surgical procedures for the correction of several abnormalities, interest in understanding its basic regulatory mechanisms and performance has increased considerably. Many experiments have been devised to study cardiac performance, under different circumstances, as an isolated preparation or as an integrated part of a functioning system. The results derived from these investigations not only proved to be important conceptual tools in making many observed phenomena more readily comprehensible, but also provided us with valuable basic principles to treat cardiac patients before and after open heart operations. The purpose of this paper is to investigate the control of the function of the heart in dogs with the chest and pericardium open, and under strictly controlled conditions. In spite of all the work j done in this field, there still exists some degree of confusion regarding the relative importance of autoregulatory mechanisms and extrinsic factors governing cardiac performance. Without trying to take sides as to the priority of either of these mechanisms, we have made an effort to confine our interest mainly to the intrinsic autoregulation of the heart.

The high metabolic demand of the heart makes it essential that an efficient and tightly controlled system be in place to regulate energy production. Contractility is mediated by a variable flux in intracellular calcium (iCa2+), which is proposed to be integrated into mitochondria to regulate cardiac energetics. Moreover, mitochondrial Ca2+ (mCa2+)-overload is known to activate the mitochondrial permeability transition pore (MPTP) and induce cell death. However, the true function of cardiac mCa2+ in physiology remains unknown. Recent studies have reported that the Mcu gene encodes the channel-forming portion of the mitochondrial calcium uniporter (MCU) and is required for mCa2+ uptake (Baughman et al., 2011; De Stefani, Raffaello, Teardo, Szabo, & Rizzuto, 2011). To examine the role of mCa2+ in the heart, we generated a conditional, cardiac-specific knockout model and deleted Mcu in adult mice (Mcu-cKO). Loss of Mcu protected against myocardial ischemia-reperfusion (IR) (40 min occlusion of the left coronary artery (LCA) followed by 24h reperfusion) injury by preventing the activation of the MPTP. We observed a 45% reduction in infarct size per area-at-risk and a 65% reduction in cardiac troponin-I serum levels from 24h post-IR. In addition, while we found no baseline phenotype or change in baseline mCa2+ content, Mcu-cKO mice lacked contractile responsiveness to β-adrenergic receptor stimulation (isoproterenol infusion) as assessed by invasive hemodynamics, and, in parallel, were unable to activate mitochondrial dehydrogenases, thereby decreasing tricarboxylic acid (TCA) cycle flux and cardiac NADH. We found that Mcu-cKO mice had a 3-fold increase in pyruvate dehydrogenase (PDH) phosphorylation and a 50% decrease in PDH activity post-isoproterenol infusion. Further experimental analyses in isolated adult cardiomyocytes confirmed a lack of energetic responsiveness to acute sympathetic stress (isoproterenol failure to mediate an increase in oxidative phosphorylation capacity) supporting the hypothesis that the physiological function of the MCU in the heart is to modulate Ca2+-dependent metabolism during the ‘fight or flight’ response. However, questions still remain on how basal mCa2+ levels are regulated and if it contributes to cardiac disease. The mitochondrial sodium/calcium exchanger (mNCX) is hypothesized as the primary mechanism of mCa2+ efflux, but to date no study has confirmed its identity or function in an in vivo system (Palty et al., 2010). To investigate the role of mNCX in the heart, we generated mutant mice with loxP sites flanking exons 5-7 of the candidate gene, Slc8b1, and crossed them with a tamoxifen-inducible, cardiomyocyte-specific, αMHC-Cre mouse to delete mNCX in the adult heart (mNCX-cKO). Biophysical study of cardiomyocytes isolated from mNCX-cKO mice revealed a significant reduction in mCa2+ efflux rate. Tamoxifen-induced deletion of Slc8b1 in adult hearts caused sudden death with less than 15% of mice surviving after 10 days. Echocardiographic evaluation of mNCX-cKO hearts 3d post-tamoxifen revealed significant left ventricular (LV) remodeling, characterized by significant dilation and a substantial decrease in function. In addition, mNCX-cKO hearts exhibited increased reactive oxygen species generation when assessed by DHE imaging of live myocardial tissue and mitoSOX Red imaging in isolated adult cardiomyocytes. Using an Evan’s blue dye exclusion technique, we found that mNCX-cKO hearts displayed significant sarcolemmal rupture (~8% of all myocytes at a single time point 3d post-tamoxifen), indicative of cellular necrosis. To rescue the sudden death phenotype and acute loss of cells, we crossed our mNCX-cKO mice with the cyclophilin d (a mediator of MPTP-opening) knockout mice. mNCX-cKO x CypD-KO mice had a significant improvement in survival and LV-function. In addition, loss of MPTP activation also rescued mitochondrial pathology on the subcellular level. Since deletion of mNCX was detrimental on cardiac function, we thought that increasing mNCX could protect cardiomyocytes by reducing mCa2+-overload during cardiac disease. To test this, we generated a conditional, cardiac-specific mNCX overexpression mouse model (mNCX-Tg) to assess if increasing mCa2+ efflux would prevent cardiac injury in multiple pathological surgical models. mNCX-Tg and controls were subjected to in vivo IR injury followed by 24h reperfusion and myocardial infarction (MI) (permanent LCA ligation). mNCX-Tg mice displayed reduced cell death (a 43% reduction in infarct size 24h post-IR and a 33% reduction in scar size 4w post-MI), preserved LV function, a reduction in ROS generation, and a decrease in numerous HF indices. For the first time, we showed that mNCX is essential for maintenance of the mCa2+ microdomain in cardiomyocytes and that mNCX represents a novel therapeutic target in HF. / Biomedical Sciences

No description available.

Calmodulin is a prevalent calcium sensing protein found in all cells. Three genes exist for calmodulin and all three of these genes encode for the exact same protein sequence. Recently mutations in the amino acid sequence of calmodulin have been identified in living human patients. Thus far, patients harboring these mutations in the calmodulin sequence have only displayed an altered cardiac related phenotype. Calcineurin is involved in many key physiological processes and its activity is regulated by calcium and calmodulin. In order to assess whether or not calcineurin contributes to calmodulinopathy (a pathological state arising from dysfunctional calmodulin), a comprehensive search of relevant literature has been performed. Herein, the physiological roles of calcineurin and consequences of dysfunction have been reviewed for literature focused on the heart.