[The tissue oxygen partial pressure in organs of hens in the second half of embryogenesis and in the first days after hatching].

The aim of the study was measure the development chick tissue partial pressure of oxygen (pO2) in the brain cerebral hemispheres, liver, M. pectoralis, M. gastrocnemius, and to estimate the correlation of this index with our previously measured values (laser-Doppler flowmetry) volume blood flow (BF) in these organs.

[Rat heat structural and functional characteristics and gas exchange parameters after experimental myocardial infarction].

Rat heart structural and functional changes and gas exchange parameters were investigated in six months after experimental myocardial infarction. Left ventricular end-systolic and end-diastolic dimensions in rats with chronic heart failure were 78 and 30% higher than in control respectively. Left ventricle cavity volume in systole and diastole were 5 and 2 times increased respectively.

[Changes of gas exchange parameters and of functional-biochemical properties of erythrocytes in dynamics of experimental anemia in rats].

In experiments on Wistar male rats, on a specially constructed computer installation, O2 consumption by the animals in comparison with changes of hematological, biochemical, and rheological blood properties is studied after anemization--acute bloodletting (12-15% of the total blood mass). An increase of the O2 consumption by the organism and tissues by 18-28% has been revealed for the first 7 days after the bloodletting, in spite of a pronounced decrease of hematocrit, and of the amount of erythrocytes and hemoglobin in peripheral blood by 20-25% of the initial level. There was a 5-10-fold increase of the content of immature erythrocyte forms--reticulocytes and a progressive rise of cell acidic resistance, which is characteristic of young erythrocyte forms.

[A mathematical model of O2 transport by erythrocytes in capillaries].

A model of diffusive O2 transport in erythrocyte and surrounding plasma is suggested which allows for the calculation of pO2 distribution in a 3-dimensional capillary region. The dynamic of O2 diffusion inside and outside erythrocyte and reaction kinetics of red blood cell are considered. The finite differential method is used to obtain a pO2 profiles as a solution of the differential equations.

[The microviscosity of the whole blood in rats with acute hypoxia].

The EPR spectrum was optimally recorded at 20 degrees C in the blood sample. The rotatory ability of the probe, expressing the microviscosity of the blood, was shown to depend on the dose of administered solution of the sodium nitrite and to correlate with the degree of hypoxic state. An analysis of probable causes of the changes in the blood microviscosity in acute hypoxia was carried out.

[Dynamic oxygen tension in the brain of rats under acute hypobaric hypoxia].

In unanesthetized rats at the "altitudes" of 4000 m (1st group) and 8000 m (2nd group), within 1.5 hrs the 1st group developed a 17-30% drop in the PO2 in 43% of cases, no changes occurred in 14% of cases, and in 43% the PO2 increased by 145-205%. In the 2nd group, the PO2 was decreased by 44-87%, on the average.

[Age-related dynamics of energy metabolism enzymes of neurons and microvessels of the brain in spontaneously hypertensive rats].

The age changes in the activity of some enzymes in neurons and in microvessels, revealed histochemically, as well as the volume of microvessels in spontaneously hypertensive (SH) rats differ from these changes in the controls. At the age of 3 months the activity of these enzymes and the number of active microvessels in SH rats increased. At the age of 6 months the activity of studied enzymes in SH rats decreased, while the number of active microvessels remained constant.

[The effect of an increased erythrocyte count on rapid blood flow fluctuations in the microvessels of the rat brain].

Polycythemia was achieved by means of substitution of the rat own blood (2 ml) with the same volume of washed out erythrocytes, the hematocrit increasing from 44 to 54%. Excessive erythrocytes altered the structure of the erythrocyte flow, its diameter being 3-13 mu. The rate of occurrence of the plasma lumens decreased.

[Blood flow dynamics in adjacent microvessels of the brain in hypertensive rats].

Significant alterations in the blood flow velocity, its amplitude and oscillations were found in cerebral cortex's microvessels of 5-12 mu diameter in normotensive and spontaneously hypertensive rats. Associated alterations of the blood flow shifted by a few seconds, were found in adjacent vessels. These alterations seem to be due to hemodynamic readjustments in proximal parts of the vascular net.

[The rate of blood flow in the cerebral microvessels of rats with an elevated blood leukocyte count].

The effect of additional administration of leucocytes into the vascular bed upon average velocities of the blood flow in the brain cortex microvessels with the erythrocyte flow diameter 5-15 mu, was studied by means of cine-TV-technique in rats. The 25-55% increase of the leucocytes concentration did not change the average blood flow velocity in the vascular net equal to 1186 +/- 306.8 and 1152 +/- 280.

[Effect of the ion composition and osmotic properties of blood plasma on the erythrocytes of normotensive and hypertensive rats].

Size of the erythrocytes was shown to change depending on the osmolality of "own" plasma in normotensive rats (WKY). Size of the erythrocytes was unaltered in hypoosmotic (the H2O load) and enhanced in hyperosmotic (the NaCl load) and isoosmotic (the KCl load) media in hypertensive rats (SHR). These specific properties of the erythrocytes are supposed to be due to differences in the transport mechanisms of ion transition through membranes.

[Mechanisms of O2 transport in the microcirculatory system].

The O2 transport in erythrocytes was shown to depend mostly on the form of erythrocyte, concentration of hemoglobin and its interaction with O2. The O2 transport in microvessels and capillaries depends on distribution of erythrocytes over the blood flow and their velocity, whereas intensity of O2 consumption and architectonics of capillary net determine the velocity and amount of O2 supply in tissues. Study of intricate processes of the O2 transport in microcirculation is only possible when using modern physical-chemical and mathematical techniques revealing the complicated interactions among the parameters under study.

[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.

[Effect of systemic hematocrit on blood supply in microvessels of the cerebral cortex].

The rat systemic hematocrit was increased by 44-54% by means of substitution of 2 ml of the rat own blood with the same volume of washed erythrocytes. Cine-TV technique revealed that the linear velocity of blood flow decreased by 20% immediately after the erythrocytes administration in most vessels under study. Changes of the blood flow were different in some microvessels: in 89% of cases the velocity decreased by 100-1600 mu/sec; no changes occurred in 5% of cases; and in 6% of cases the velocity increased by 100-500 mu/sec.

[Rate of blood flow in the microvessels of the brain of the rat with spontaneous arterial hypertension].

In normal and hypertensive rats, hematological indices were studied as well as the linear blood flow velocity in the microvessels with diameter 6-12 mu. Both groups of animals were shown to develop obvious oscillations of the blood velocity coinciding neither with heart beats nor with respiratory movements. In rats with spontaneous arterial hypertension, the mean velocity was 844 mu/sec and the amplitude of blood flow oscillations was 175 mu/sec which was higher by 35% and 33.

[Formation of gas bubbles in biological tissues in decompression (a mathematical model)].

A mathematical model simulating transport of gases between a bubble resulted from decompression and tissue around is presented. With the help of the model the influence of gas mixture and density of the bubble forming centres upon the growth rate was studied. An important part of CO2 in the bubble forming was found out.

[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.

[Mathematical model of fluid transport in the convoluted portion of the proximal kidney tubules and surrounding capillaries].

Simulating transport of fluid and ions among proximal tubule, interstice and capillaries the mechanism of fluid transport in the kidney was studied. A mathematical model as a system of differential equations was processed with a numerical method by a digital computer. The results showed that 96% of fluid from the proximal convolution into interstice were reabsorbed because of the difference of osmotic pressures caused by HCO3-, ions and 4% -- at the expense of oncotic pressure gradient.

[Blood flow fluctuations in the microvessels of the rat temporal muscle].

Dynamic characteristics of the blood flow linear velocity in microvessels on the surface of rat's temporal muscle were determined by means of accelerated cinemicrography. The blood flow velocity varied from 200 to 5000 microseconds in microvessels with diameter 4-13 mu. The blood flow fluctuated with period of 0.

[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.

[Blood flow in the microvessels of the cerebral cortex].

To measure dynamic characteristics of linear velocity of the blood flow in microvessels on the surface of rat's brain, the method of accelerated cinemicrography was used. The blood flow velocity varied from 500 to 5000 mu/sec in microvessels with diameter of 7-15 mu. The blood flow fluctuated with the rate of 1-3 oscillations per second and the amplitude 20-50% of the average value.

[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.