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Biomedical subjects

V Ia Izakov

Publications and source records attributed to V Ia Izakov.

At least 37 records · Page 2Linked to original sources
PubMed1982

[Inotropic effect of rhythm dispersion].

The influence of rhythm dispersion on the mean amplitude of rat and rabbit papillary muscle contractions and isovolumic contractions of canine heart has been investigated. In rabbit ventricular myocardium which shows a steep force-frequency relationship in the 0.3--1.0 s-1 range of frequencies, the increased rhythm dispersion of stimulation produces a rise in the mean amplitude of contractions. The inotropic effect of rhythm dispersion is more pronounced at higher frequencies of stimulation. The inotropic effect of activation may reach 30-40%. The increased rhythm dispersion reduces the mean value of systolic pressure in isovolumic canine heart. It is suggested that the inotropic effect of rhythm dispersion may be due to non-linearity of the force-frequency relationships.

Animals↗
PubMed1982

[Static and dynamic components of length-dependent regulation of contraction of the atrial and ventricular myocardium].

The influence of changes in length of the frog isolated atrium and ventriculus upon the isometric twitches was investigated. The length-tension relationship of the first contraction following the step of stretch was independent of the inotropic agents (Ca20+, adrenaline). The stretch to 0,35 induced the 5.04 +/- 051 fold increment of active tension in ventriculus and 1.75 +/- 0.12-fold increment of active tension in atrium. The length-tension relationship of the first contraction seems to depend on the degree of myofilaments overlapping A long-lasting transition-process occurred after step of deformation. The influence of inotropic agents upon the length tension relationship was shown for steady state contractions. An additional effect of activation by the length in normal solution was estimated for ventriculus as 22 +/- 5% and for atrium as 30 +/- 7%. The data suggest that the steady component-myofilament overlapping and dynamic component-calcium activations by the length change may participate in heterometric regulation of myocardial contractions.

Animals↗
PubMed1979

[Correlation of atrial and ventricular contractility. The possibility of using the atria for controlling the artificial heart].

A possibility of the artificial ventricle regulation using information on the atrial contraction is discussed. Correlations between atrial wall tension and ventricle tension as well as the pressure under radom heart rhythm variations were studied. The wall tension of the appropriate heart portion was recorded by the arched tensiometers, and intraventricular pressure under cavity catheterization by the electric manometer. The cardiac rhythm varied between 2.0 c-1 and 4.0 c-1. A correlation between the tension and interpulse interval, (correlation coefficient being 0.62 +/- 0.05) was established. The close relationships "atrial wall tension-intramuscular pressure" were observed. For such relationships the correlation coefficient changed from 0.713 +/- 0,09 to 0,874 +/- 0.02 depending on the average value of interpulse interval. It is concluded that the information on the atrial contraction can be used for artificial heart regulation.

Animals↗
PubMed1978

[Effect of adrenaline on rat atrial and ventricular chronoinotropy].

The atria and ventricles were shown to differ from each other in: temporal course of contractions, relations between the strength of contractions and the interstimuli interval, resting potentiation, transitional processes after intermissions, character of response to adrenaline. For the first time the adrenaline was shown to annihilate differences in restitution processes occurring in atria and ventricles. The differences of responses in atria and ventricles seem to be due to concentration of endogenous catecholamines which modulate the electromechanical coupling of the rhythmically working myocardium.

Animals↗
PubMedDate not supplied

[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 "force-velocity" and "length-force" relations were registered for each muscle independently, and in case of parallel connection of two muscles. It was shown that connection of two muscles in parallel influenced significantly the distribution of load in the muscles, maximal and mean velocity of their shortening. It is stated that the key phenomenon controlling the value and the heterogeneity influence sign is mechano-chemical uncoupling (inactivation).

Animals↗