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Biomedical subjects

K P Ivanov

Publications and source records attributed to K P Ivanov.

At least 19 recordsLinked to original sources
PubMed1995

[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 0.05-0.2-mm radius were found to play the main role in the organism heat exchange with ambient environment.

Arteries↗
PubMed1994

[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.

Animals↗
PubMed1993

[The "thermoresponsive" neurons of the thermoregulation center and their functional characteristics].

The specific features of responses to thermal stimulation of the skin in neurons of the thermoregulation centre in the anterior and posterior hypothalamus were investigated in rabbits. Separate neurons were found to respond to temperature changes like skin thermoreceptors. A part of thermal signals from the skin is supposed to arrive to the thermoregulation centre without specific transformation.

Animals↗
PubMed1992

[The efficiency of thermoregulatory reactions in the cooling of the body].

Immersion of the rabbit body model in water of 4 degrees C temperature induced fast cooling of the model even though the heater of the model was 3-fold more powerful than the respective heat-production mechanism in a live rabbit. Only 10-11-fold more powerful heat production was able to keep the model temperature about 37 degrees C.

Animals↗
PubMed1992

[The temperature changes in different organs during immersion hypothermia].

Precise thermometry of the brain, liver, rectum, muscles and skin surface was performed in white rats in conditions of immersion of the body in water with the temperature 1 degree C. Breathing arrested within 15-18 min after immersion, their brain temperature being 16.7-18.2 degrees C, liver temperature 12.7-15.2 degrees C, rectum--10.4-15.5 degrees C, muscle 8.3-12.0 degrees C, skin surface--1.6-5.0 degrees C.

Animals↗
PubMed1992

[The temperature gradient values in the skin and their significance for thermoregulation].

The ambient temperature decrease from 32-35 degrees C to 15-17 degrees C was shown to increase the temperature gradient between the skin surface and its deep layers (2-3 mm from the surface) from 0.13 +/- 0.1 degrees C to 1.29 +/- 0.13 degrees C in humans. Considering the localisation of thermoreceptors in different skin layers, such a considerable gradient can be measured by the thermoregulation system and serve for determination of direction and intensity of heat flow across the skin.

Body Temperature↗
PubMed1992

[The microcirculatory changes in leukocytosis].

A moderate leucocytosis was found to decelerate the blood flow in the rat brain capillaries and to change the character of the blood flow. This seems to be due to a temporal obturation of the capillary lumen by one or several leucocytes.

Animals↗
PubMed1992

[The value and comparative analysis of the energy expenditures of newborn animals and children].

As opposed to adults, infants were found to have 5-fold differences in values of heat production per unit of mass and unit of body surface. Animals of the same age have these differences not over 20-50%. Newborn mature infants could have these differences to reach 50-60%. The data obtained suggest significant differences in the efficiency coefficient values for muscles contractile activity to play the role of the mechanism of heat production control in chemical thermoregulation and postnatal formation of the constancy of main (standard) metabolism.

Animals↗
PubMed1991

[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.

Animals↗
PubMed1991

[Characteristics of the distribution and reference values of 12 biochemical indices of the blood serum].

Twelve blood serum parameters: sodium, potassium, chlorine, total protein, cholesterol, glucose, urea nitrogen, creatinine, bilirubin, alkaline phosphatase, alanine and aspartate aminotransferases activities were measured in 488 normal subjects (male), residents of Leningrad, by the Technicon (USA) microanalyzer. Relationships between the estimated reference values and the distribution patterns of the referent blood parameters (variability, symmetric pattern) were analyzed. The authors compare the reference values of the Leningrad population with those obtained by this microanalyzer in the USA.

Blood Chemical Analysis↗
PubMed1990

[Separate flows of erythrocytes with different degrees of oxygenation in the venous vessels].

Having studied the structure of the blood flow in pial microvessels of the rat brain, the blood flow in venules was shown to consist of separate erythrocyte flows divided by the plasma layers Visualisation of these flows is facilitated after isovolume hemodilution until the 20-25% hematocrit. The blood flows in the same microvessel were found to differ from each other essentially by the oxygen tension level and by the velocity of their transition.

Animals↗