No abstract available.
Doxorubicin* ; Myocytes, Cardiac*

No abstract available.
Extracellular Space* ; Ischemia* ; Myocytes, Cardiac*

BACKGROUND: In response to numerous pathologic stimuli, the myocardium undergoes a hypertrophic response characterized by increased myocardial cell size and activation of fetal cardiac genes. Recently, the calcineurin inhibitor, cyclosporine has been reported to prevent the development of cardiac hypertrophy, however, others reported data which are disagreed to the cyclosporine effect on the prevention of cardiac hypertrophy. METHOD: To clarify whether the calcineurin signaling pathway is a critical for overloaded hypertrophy in vivo and to characterize the cyclosporine effect on the develpment of cardiac hypertrophy, I examined the effects of cyclosporine on the left ventricular overload in the experimental model of clipping of abdominal aorta between the diaphragm and renal artery for three weeks in rats. RESULTS: Left ventricular mass was larger in the group of clipping of abdominal aorta than in the group of cyclosporine injection after clipping of abdominal aorta, however, which had larger ventricular mass rather than control group. It means that cyclosporine suppress hypertrophic growth. Both treated and untreated animals showed increased nuclear polymorphism and euchromatin pattern, and also, ultrastructurally, showed degenerative changes in the cardiac myocytes such as swelling of subsarcolemmal cytoplasm with indistinct sarcoplasmic reticulum and "T" tubules, loosening of myofibril bundles with decreased electron density, and electron dense mitochondria with decreased number. Characteristically, the group of cyclosporine injection after clipping of abdominal aorta showed polymorphic electron dense unswollen giant mitochondria which was not characteristic in other groups. alpha-MyHC mRNA including non-spliced mRNA of the group of abdominal aortic clipping was downregulated in the both groups of clipping of abdominal aorta. beta-MyHC mRNA was upregulated in the group of clipping of abdominal aorta and downregulated in the group of cyclosporine injection after clipping of abdominal aorta. From the above results, initial response to overload is a degenerative changes of cardiac myocytes and cyclosporine may suppress hypertrophic response and the fetal gene reactivation such as beta-MyHC mRNA in this experiment.
Animals ; Aorta, Abdominal ; Calcineurin ; Cardiomegaly ; Cell Size ; Cyclosporine* ; Cytoplasm ; Diaphragm ; Euchromatin ; Heart Ventricles* ; Hypertrophy ; Mitochondria ; Models, Theoretical ; Myocardium* ; Myocytes, Cardiac ; Myofibrils ; Myosin Heavy Chains* ; Myosins* ; Rats* ; Renal Artery ; RNA, Messenger ; Sarcoplasmic Reticulum

Short period of ischemia and reperfusion protect heart against subsequent prolonged ischemia-reperfusion injury. This phenomenon was first described by Murry et al in 1986, who demonstrated that four 5-minute coronary artery occlusions followed by equal period of reflow at each time before a subsequent prolonged occlusion resulted in a reduction of infarct size in dog. Although the precise mechanism of preconditioning remains unknown, this phenome-non is present among different species of mammals, including dogs, rats, pigs, rabbits, and human. The objects of present study was to investigate effect of ischemic preconditioning on cell viability, structural changes and apoptosis during 60 min hypoxia and 60 min reoxygenation of the cell. In present study we investigated through cell culture system using myocyte of three days old neonatal rat cultured for three days. During hypoxia and reoxygenation, differences between preconditioned and nonpreconditioned of beating counts, morphological and structural changes are investigated through inverted phase contrast microscope and transmis-sion electron microscope. To detection of apoptotic cell, TUNEL (TdT-mediated dUTP-biotin nick end labeling) stain was accomplished, and through which we invesigate the effects of preconditioning on apoptosis. Viabiliy of each cell and it's mitochondria were measured quantitatively by MTT assay. After 60 min of hypoxia and 60 min of reoxygenation, beating rate decreased remarkably. But at the time of 60 min of reoxygenation, there was marked increase in beating count in pre-conditioned cell. Swollen mitochondria with amorphous granules in inner membrane, destroyed mitochondrial cristae, indented nuclear envelope, chromatin condensation, contracture of myofibril, fragmentation of myofilaments, cytoplasmic shrinkage were observed in both preconditioned cell and nonpreconditioned cell. But it is much less in pre-conditioned cell than in nonpreconditioned cell. MTT activity decreased in both experimental groups in compared with normal group, but in preconditioned group, MTT activity increased markedly in compared with nonpreconditioned group. And apoptosis is decreased by precontitioning in TUNEL staining. These results suggest that cardioprotective effects of ischemic preconditioning is mediated by attenuating structural destroy, increasing cell viability, decreasing apoptosis.
Animals ; Anoxia ; Apoptosis ; Cell Culture Techniques ; Cell Survival ; Chromatin ; Contracture ; Coronary Vessels ; Cytoplasm ; Dogs ; Heart ; Humans ; In Situ Nick-End Labeling ; Ischemia ; Ischemic Preconditioning* ; Mammals ; Membranes ; Mitochondria ; Muscle Cells ; Myocytes, Cardiac* ; Myofibrils ; Nuclear Envelope ; Rabbits ; Rats ; Reperfusion ; Reperfusion Injury ; Swine

Despite therapeutic advance, the prevalence of ischemic heart disease continues to increase. Recently, cell transplantation of stem cell has been proposed as a strategy for cardiac repair following myocardial damage. However, low differentiation efficiency into cardiomyocyte and poor cell viability associated with transplantation have limited the reparative capacity of these cell. In this study, we engineered P19 embryonal carcinoma cells using plasmid vector to overexpress the transcription factor MEF2c, Nkx2.5 involved in cardiomyogenesis. We investigated 1) formation of intercellular junction of P19 in mono-culture and co-culture with cardiomyocyte for functional and structural synchronous contraction after transplantation, 2) differentiation into cardiomyocyte, 3) resistance to hypoxic condition. An P19 embryonal carcinoma cell line expressing GFP, MEF2c, Nkx2.5 was generated by gene transfection and clonal selection. Nkx2.5 overexpression induced connexin43 expression level decrease. Electron microscopy revealed myofibril organization and immunostaining with cTnT showed positive staining in P19-Nkx2.5, consistent with early stage cardiomyocyte. Connexin43 and N-cadherin was expressed between P19-MEF2c and cardiomyocyte, P19- Nkx2.5 and cardiomyocyte in co-culture. And beating rate of cardiomyocyte co-cultured with P19-Nkx2.5 increased much more than other group, even if P19-Nkx2.5 did not have synchronous contraction with cardiomyocyte. Additionally, P19-Nkx2.5 had a resistance against hypoxia. These result suggest that overexpression of Nkx2.5 induced differentiation of P19 into cardiomyocyte and would be electro-mechanical coupling with cardiomyocyte after transplantation. Futhermore, Nkx2.5 overexpression had protection potential to hypoxic injury. Therefore, P19 cell overexpressed Nkx2.5 would be promising cell source for further study of new therapy of myocardial disease and building up in vitro model.
Anoxia ; Cadherins ; Cardiomyopathies ; Cardiomyoplasty* ; Cell Survival ; Cell Transplantation ; Coculture Techniques ; Connexin 43 ; Embryonal Carcinoma Stem Cells ; Intercellular Junctions ; Microscopy, Electron ; Myocardial Ischemia ; Myocytes, Cardiac ; Myofibrils ; Plasmids ; Prevalence ; Stem Cells ; Transcription Factors* ; Transfection ; Transplants

Abrupt reoxygenation (or reperfusion) after anoxia (or ischemia)-induced injury resulted in the loss of contractile property, destruction of cell organelles, and ultimately, cell death in cardiac myocytes. This phenomenon has been called 'oxygen paradox' or 'reperfusion injury'. The purpose of this study was to investigate the changes of fine structures and enzyme activities associated with oxygen paradox during 60 min. of anoxia, followed by a 30 min. of reoxygenation. Cardiac myocytes were dissociated from neonatal rat ventricles and cultured for three days. While they were exposed to anoxia and reoxygenation, the cardiac myocytes were investigated through beating counts, enzyme cytochemistry, immunofluorescence, electron microscopy for morphological study. Activity staining and Western blot for Cu, Zn-SOD, NADPH-diaphorase stain and nitrite concentration mesurement for nitric oxide synthase, and catalase activity measurement were performed. After 60 min. of anoxia, the beating rate increased remarkably. Swollen mitochondria with amorphous dense clumps, mild contracture of myofibrils and retraction of cytoplasmic processes were observed in cardiac myocytes. Under confocal microscope, weak reaction of Mn-SOD and myosin were observed, whereas reaction of Cu, Zn-SOD was enhanced in perinuclear region. Cu, Zn-SOD and catalase activity in cardiac myocytes increased markedly. Nitric oxide synthase activity increased gradually with time. After 30 min. of reoxygenation following 60 min anoxia, structural changes of myocardial cells was more pronounced than in the cells of anoxic group. Beating rate was variable but decreased gradually. Myocardial cells showed evidence of severe structural alterations, including marginal clumping of chromatids, varying-sized bleb formation, many vacuoles, mitochondrial matrix exposed to cytoplasm and fragmen-tation of cristae, myofibrillar hypercontracture. Decline of immunocytochemical reaction of Mn-SOD, myosin and Cu, Zn-SOD were observed under confocal microscope. The declines of activity and quantity of Cu, Zn-SOD were severe compared to control. In contrast, nitric oxide synthase activity significantly increased. Catalase activity was lower than in anoxic group, but still higher than in control activity. These results suggested that there were two possible mechanisms for the drastic morphological changes induced by anoxia-reoxygenation; 1) direct effect of oxygen free radicals, and 2) reaction of nitric oxide with superoxide radicals, which resulted in generation of toxic metabolites of nitric oxide, exacerbated myocardial cellular damages.
Animals ; Anoxia ; Blister ; Blotting, Western ; Catalase ; Cell Death ; Chromatids ; Contracture ; Cytoplasm ; Fluorescent Antibody Technique ; Free Radicals ; Histocytochemistry ; Microscopy, Electron ; Mitochondria ; Myocytes, Cardiac* ; Myofibrils ; Myosins ; Nitric Oxide ; Nitric Oxide Synthase ; Organelles ; Oxygen ; Rats ; Superoxide Dismutase ; Superoxides ; Vacuoles

Autophagy ; Humans ; Myocytes, Cardiac ; Ventricular Remodeling

Adult Stem Cells ; Myocytes, Cardiac ; cytology

Apoptosis ; Inhibitor of Apoptosis Proteins ; Myocytes, Cardiac ; cytology

Studies have demonstrated that the occurrence of a variety of arrhythmias presents an obvious circadian rhythm,which may be regulated by circadian rhythm genes.Circadian cycle and light stimulation can affect circadian rhythm genes and proteins,which constitute a transcription-translation loop that can regulate the ion channels in myocardial cell membrane through nervous-humoral regulation and changes in central clock-sub-clock gene expression,thereby modulating arrhythmia.This article reviews the molecular basis,mechanism,and performance of circadian rhythm in regulating arrhythmia.
Humans ; Circadian Rhythm/genetics* ; Myocytes, Cardiac ; Arrhythmias, Cardiac