[Optical and electron microscopic analysis of changes in loach myocardium after local heart injuries]

The myocardium of the cardiac ventricle was studied light optically and electron microscopically in the loach (Misgurnus fossilis). After the cardiac wall was cut, it could be observed that the wound was filling with a blood clot, the muscular tissue of its edges was in the state of necrosis and necrobiosis, richly infiltrated with the blood forming elements. The tissue mentioned was surrounded with a bordering zone, its cells were undergoing peculiar reversible distrophic and reactive changes. On the 5--7th day after the injury, in the bordering zone, a reversible development of the distrophic changes and a partial structural dedifferentiation of the cardiomyocytes occurred and, as the result, they acquired a resemblance with the cells of the embryonal myocardium. In myocytes all the stages on formation of the contractile system and hypertrophy of the preserving myofibrils could be observed. In no experiment the muscular tissue was newly formed; local regeneration of the cardiac muscle in the place of its destruction did not occur. The integrity of the cardiac wall was restored at the expense of the connective tissue.