[Ultrastructure of the intercalary disks in cardiac muscle tissue of permanent and temporary residents at high altitudes].

In animals temporary adapted to the Alpine conditions, the intermembranous space of the intercalated disc is dilated 3-5 and more times, while in permanent inhabitants of the Alpine regions similar dilatation is not observed. Probably, in the latters numerous intercalated discs increase adhesive force of cardiomyocytes, extent of zones with low electrical resistance and increase contraction of myofibrills, thus promoting transmission of excitation from cell to cell.

[Morphologic characteristics of the hearts of argali continuously dwelling at high mountain altitudes].

The hearts of argali living at 3800-5000 m above the sea level were examined. Macroscopy showed complete absence of fatty tissue under the epicardium. Increased number of the capillaries surrounding cardiomyocytes, intercalated discs in many zones of the myocardium, sharp thickening giving pronounced cross lines of myofibrils were revealed on semithin and ultrathin sections.

[Change in the ultrastructure of rat myocardium under the influence of 12-months' adaptation to high altitude].

The right and left ventricle myocardium of rats was studied in the course of a 12-month period of adaptation to high altitude (3200 m above the sea level). A long-term exposure of the animals to the high altitude led the development of ventricular hypertrophy mostly of the right, and partly of the left ventricle. Hyperplasia and hypertrophy of individual organellae, particularly mitochondria, were found in most cardiomyocytes of both ventricles.

[Myocardial cell ultrastructure of yaks dwelling at high altitudes].

The ultrastructure of myocardial cells of the left, right ventricle, and the ventricular septum was studied in the Altai and Pamir Yaks permanently living at the altitude of 3000-3600 m. Electron microscopic studies of myocardial cells revealed, along with the normal mitochondria, the ones with a peculiar structure of the cristae; these had the appearance of polyhedral wavy membranes in some groups of the mitochondria, and of polyhedral netted structures - in the others. Considerable accumulations of glycogen granules were found beneath the sarcolemma, in the perinuclear cytoplasmic zone and between the myofibrils.