[Thermal homeostasis of the rabbit in thermoneutral zone (mathematic modeling)].

The thermal homeostasis of rabbits in thermoneutral zone were studied in the paper. Both in the experiment and in the model were shown that the temperature in the shell of the animal was changed without changing the core (nuclear) temperature when the temperature of the environment was changed and the heat production and delivery were remained unchanging. In the model was obtained this phenomenon was due to changing the shell and the core values, and was connected with blood flow variations in the shell.

[Mechanism of heat transfer in various regions of human body].

The processes of heat transfer in a human body were studied with the use of a mathematical model. It has been shown that only conductive or only convective heat transfer may occur in different body areas. The rate of blood-mediated heat transfer in the presence of blood circulation is many times higher than heat transfer due to temperature gradient; therefore, the convective process prevails over the conductive process.

[Effect of increased pressure of nitrogen on thermoregulation of mammals].

Consumption of oxygen in rats was studied under conditions of the gas different ambient temperatures and pressure. A dependence was revealed between the neutral temperature and the high gas pressure. Mathematical model revealed an increase oxygen consumption at an increase gas pressure.

[The efficiency of heat emission from skin vessels with different radii].

Important heat-physical parameters of the heat release by the blood in different vessels, were revealed enabling authors to estimate the effect of the vessel size on the heat release from the flowing blood. The skin arterial vessels of 0.05-0.

[The pattern of body temperature changes during cooling in relation to the properties of its covering (mathematical research)].

A sphere model simulating the rabbit organism was subjected to the effects of ice-cold water and cold air (0 degrees C). Distributions of the temperature within the sphere and its membrane depending on the thickness of the membrane, are presented. A 3.

[The efficiency of heat exchange between the tissues and the blood in blood vessels of different diameters].

Using mathematical calculations, the processes of heat radiation of the blood moving along skin vessels of different diameter, were studied. The temperature of the blood in capillaries, small arteries and venules was shown to be equal to that of surrounding tissue. The data show that, under normal physiological conditions, a situation occurs in the skin vascular bed when the vessels on the diameter lesser than 100 mcm cease to be able to be heat-exchanging means in the skin of the living organism.

[The oxygen supply of brain tissue under decreased oxygen tension in the capillary arterial blood].

Using mathematical model describing the oxygen transport in the brain three-dimensional microarea, the regularities of oxygen diffusion were studied in conditions of reduced oxygen content in the blood flowing through capillaries. Considering ordinary neuron-capillary spatial relationships and average values of the blood flow in the capillaries and oxygen consumption in neural tissues, the neural cells surrounding the capillaries can only function normally provided the oxygen tension is over 61 mm Hg at the arterial end of the capillaries. However, if the intercapillary distance is reduced, the neural cells have no hypoxia even at the oxygen tension of 40 mm Hg at the arterial and of capillaries.

[Oxygen diffusion through the walls of arterial vessels].

A newly developed mathematical model aided to study the regularities of the oxygen tension distribution in the wall of arterial vessels and in surrounding tissues at different physiological and morphological parameters determining the O2 transport in tissues. The model consists of a system of the second order differential equations. The maximal level of the oxygen tension in outer wall of the vessels was observed in arteriolar vessels of 80-160 mu diameter.

[Theoretical basis for the method of calculating blood-flow volume velocity from hydrogen clearance curves].

Two models: a hemodynamic one where the was out velocity is determined by means of the blood flow intensity alone, and a microcirculation one taking into consideration diffusion processes in tissue as well as architectonics of the vascular bed, gave ground for calculation of interrelationship between the time constant of the clearance curve and the local blood flow velocity. The data obtained showed the necessity of amendment depending on the time constant of the clearance curve when using the hemodynamic model.

[Mathematical model of the dynamics of transport of inert gases in the microcirculatory system].

A mathematical model imitating transport of inert gases in the system of microcirculation under increased pressures was constructed. It has been shown that saturation of microareas nucleus of the brain cortex of average dimensions proceeds in about 90 sec. Effect of the blood flow velocity, gases tension in arterial blood and density of the capillary net on the dynamics of mass transfer of gases in a tissue was investigated.

[Relation between morphologic reactive rearrangement of neuronal elements and their specific surface].

A great vuendorability of thin terminal neural processes as compared to thick fibers or neural cell bodies has been proved. This phenomenon does not depend on whether this very structure is pre- or postsynaptic. It is not connected with distance of the structures from the nucleus-containing area, and is, evidently, stipulated by their geometrical parameters, in particular, by their specific surface (dispersivity).

[Dynamics of oxygen transport in erythrocytes].

Distribution dynamics of oxygen tension throughout the erythrocyte volume was calculated by means of a mathematical model describing the dynamics of oxygen transport in the erythrocyte, its shape, diffusion resistance of hemoglobin solution. The pattern of the dissociation curve of oxyhemoglobin being taken into account. The model is presented as a system of differential equations in partial derivatives.

[Dynamics of brain oxygen saturation under increased pressure].

A mathematical model of the O2 transport within the brain aided to calculate the transitional processes of O2 tension in stepwise increase of the O2 amount in arterial blood as well as in alterations of the main physiological and morphological factors determining the O2 content and its changes in the organs and tissues under these conditions. The mathematical model took into consideration the actual data of mass-transfer in the microcirculation system and was described in the form of differential equations which had been solved by a digital computer with the aid of nets technique. The change of the pO2 mean level within the space of the modelled construction and under the conditions of the stepwise alterations of the above factors, was shown to be actualized during a period of time longer by order than in normoxia.

[Dynamics of oxygen transport from the capillaries to the cortical neurons].

A mathematical model describing the dynamics of oxygen transport in constructions with capillaries and pyramidal cells of the cat brain sensomotor cortex, aided to calculate the transitional processes of O2 tensions in neurons, capillaries and surrounding tissues during changes of the blood flow velocity in the capillaries and of the neurons respiration intensity. The model is represented in the form of a system of differential equations in particular derivatives, the solution of which was accomplished by the digital computer with the nets technique. Changes of pO2 levels within the space of modelled constructions in sharp shifts of the above parameters occurred within 2-5 sec.