[Coronary blood flow during stochastic stimulation of the canine heart].

Changes of mechanical activity and coronary blood flow induced by haphazard uncorrelated sequence of stimuli, were studied in the dog heart. The total coronary blood flow did not differ from one during determined regimen of the same mean frequency. Whereas relative contribution of systolic coronary flow increased and that of diastolic one decreased.

[Effect of heterogeneity of the myocardium on its mechanical function].

The influence of the mechanical heterogeneity on the myocardium contractility was evaluated. The heterogeneity was imitated by parallel connection of two papillar muscles with different mechanical properties. The rate of muscle shortening was controlled by a feed-back from tension of each of the muscles or both muscles simultaneously in the precision ergometer.

[The activation and mechanical determinants of the rate of isometric relaxation of the heart muscle].

In experiments with sequential loads, the relative velocity of cardiac muscle relaxation was found to be affected by the calcium ions concentration, velocity of shortening and by the terminal systolic length. Mechano-chemical dissociation played a major role, too, in the relaxation determination. The shifts in mechanical relaxation seem to be based on the cooperation phenomena in the troponine regulation of contraction and relaxation.

[The characteristics of the effect of catecholamines on the relaxation of ventricular myocardium in warm-blooded and cold-blooded animals].

The relaxation of the frog myocardium is decelerated by addition of adrenaline (10(-8)-10(-6) M) into the perfusion solution. The catecholamines in low concentrations up to 5.10(-8) M decelerate the relaxation, and in higher concentrations accelerate the drop of mechanical tension in capillary muscles of the cat ventricular myocardium.

[The relationship between rigidity and strength in the skinned fiber of rabbit skeletal muscle].

In single chemically skinned fibers of the rabbit skeletal muscle in the state of rigour and the calcium activation, the interrelationship between the strength and rigidity, in change of the sarcomeres length from 2.4 to 3.0 microns, of free calcium concentration (pCa = 6.