[Investigation of osteoporotic changes of the long tubular leg bones for identification of human biological age].

The authors propose to introduce into expert practice a number of methods estimating age-related osteoporosis by such quantitative characteristics as coefficient of optical transmission, optic density, porosity. The data confirm nonlinear dependence of age dynamics of osteoporotic changes which can be more effectively described by equations of polynomial regression.

Sex differences in endothelium-dependent reactions of rabbit arteries to elevated blood flow.

Acute experiments on anesthetized rabbits were performed to compare dilator responses of the carotid arteries in a wide range of blood flow rates. In males, the reactivity of vessels to changes in blood flow rate was higher than in females. Thirty percent of the revealed sex differences are due to various blood viscosities in males and females. The main factor determining these differences is a higher vascular tone in males.

[Regional difference in endothelium-dependent vascular responses upon the flow rate elevation]. / Regionarnye razlichiia v zavisimykh ot éndoteliia sosudistykh reaktsiiakh na povysheniie skorosti potoka.

In anaesthetised rabbits, femoral artery manifested a maximal reserve capacity in its vasodilatory response to the flow speed acceleration. In order of the capacity diminishing, this artery is followed by renal artery, abdominal aorta, celiacus tube, common carotid artery. The endothelium-dependent flow-induced response is important for restricting the flow's linear speed.

[Endothelium-dependent regulation of the carotid artery diameter by the flow in rabbits of various age]. / Endotelii-zavisimaia reguliatsiia diametra sonnykh arterii potokom u raznykh vozrastnykh grupp krolikov.

Endothelium-dependent flow-induced regulation leads to a decrease in the flow-induced response of arteries in male rabbits from a newly-born period to one-month period of life.

[Analysis of the relationship between the rate and force of myocardial contractions in dogs, rats and frogs]. / Analiz zavisimosti mezhdu chastotoi i siloi sokrashchenii miokarda sobak, krys i liagushek.

Under maximally physiological conditions of arterial blood supply to isolated hearts of dogs, rats and frogs it was found that frequency potentiation of contractility was most distinct in the ventricles of frogs, less distinct in the left ventricle of dogs, and absent in rats. It was demonstrated that in connection with the rhythmic activity the myocardial cells accumulate quantities of calcium proportional to the degree of frequency potentiation. Amounts of calcium were determined that are necessary for a full activation of myocardial contractility proteins, and the amount of calcium entering the myocardial cells of a frog per one systole was calculated. A close approximation of both the values indicates that the activation of a contraction occurs at the expense of the entrance of extracellular calcium during the depolarization of a sarcolemoma.

[The "optimal rate" for the heart beat of a homeotherm]. / Ob "optimal'noi chastote" bienii serdtsa teplokrovnogo.

The optimal heart-rate was studied in natural conditions of hemodynamics and on stabilizing the left ventricle load and volume with a balloon. The coronary blood-flow was traced with the aid of electromagnetic fluorometer. Post-occlusion reactive hyperemia estimated reserves of the coronary blood-flow. On stabilizing the left ventricle load and volume, its contractility was higher with faster heart-rate. With the fastest heart-rate, a considerable reserve of the coronary blood-flow was still preserved. Apparently under conditions of natural hemodynamics, the optimal heart-rate (100-180/min) and the decline of contractility with fast heart-rate are due to decrease in filling of the heart caves with the blood per 1 sistole at a constant 1 min volume of the blood-flow.