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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
PubMed2001

[Cold-induced paralysis and recovery of lung respiration and heart contractions in newborn rats (inversion of Arrhenius law for physiological functions)].

Arrest of respiration and heart activity in new-born rats aged 3-4 days and 10-11 days was shown to occur at a body temperature 6-7 degrees C and 2-3 degrees C lower than in adult rats, resp. At room temperature the body temperature of profoundly cooled rat's litter gradually increases and the functions are restored. In 3-4-day old rats, at the body temperature rising from profound cooling to 15-18 degrees C, the respiration and heart rates are 2-4-fold more than at the same temperature attained from the normal body temperature. These differences in the respiration and heart rates at the same body temperature suggest an inversion of the Arrhenius law (the Q10 coefficient) for physiological functions in early ontogenesis. This effect completely disappears in 10-11-day old rats.

Animals↗
PubMed2000

[Blood physiological resources and their role in physiological adaptation of the body to blood loss (based on the experimental data and calculations)].

In white rats, loss of about 66 +/- 3% of the blood volume results in an abrupt drop of the BP and arrest of the lung respiration. Introduction of a plasma substitute in the volume equal to the lost blood resulted in an increase of the BP and restoration of rhythmical respiration in 9 out of 14 experimental rats. Haematocrit after the blood loss and subsequent administration of the substitute was about 15%. Previously obtained data show that the Ht of about 15% decreases the oxygen transport to tissues. However, an increase in the lung ventilation, a shift of the haemoglobin dissociation curve to the right, an increase of oxygen extraction from the blood, and an increase in the minute blood volume by 50-100%, allow a sufficient oxygen transport to the organism tissues to be ensured at the Ht of about 15%. Thus, the reserve of the blood respiration function of the blood remaining after a life-threatening blood loss plays an important physiological role in replenishing the volume of the lost blood with the plasma substitute and in survival of the organism.

Animals↗
PubMed2000

[Blocking of cold paralysis of physiological functions].

For more than 100-year history of studying hypothermia a rewarming of a cooled organism was always considered as the only method of restoring the cold-paralysed physiological functions and the vital activity of an overcooled organism of homoiothermal animals and humans. The paper gives the results of applying the method developed at our Laboratory, of restoring the cold-paralysed important physiological functions after a continuous cooling of rats, without rewarming the animals.

Animals↗
PubMed1999

[Oxygen transport in the cerebral cortex of rats breathing a hyperoxic gas mixture].

Oxygen dissolved in the arterial blood plasma at a high pressure was shown to pass into the brain tissue from the finest arterioles. Therefore only a thin layer of the tissue immediately adjacent to these vessels is affected by the increased oxygen tension pO2. Permeability of the arteriole walls for oxygen protects the neurones against the high pO2. A special physiological feature of the oxygen transport during normobaric hyperoxia in the brain tissue involves very "steep" gradients of the pO2 in tissues and of the transferring the oxygen fraction from arterioles to venules through the tissues. The findings allow to compare distribution of the pO2 over the whole brain vessel network with that during inhalation of air or pure oxygen.

Animals↗
PubMed1999

[Decrease in the lower limit of the rat brain vital activity by the physiological method].

The brain temperature, at which the cessation of the lung respiration occurs in the cooled animals, can be named the lower temperature limit of the brain functional competence, since at this temperature the spontaneous respiration is not restored on its own, and without special artificial undertakings the animals perish. In this study upon the total cooling of the rat bodies their lung respiration stopped completely as the temperature of the medulla oblongata in the region of the respiratory center decreased to 18.18 +/- 0.17 degrees C. This occurred simultaneously with an abrupt decrease in the heart rate and in the arterial blood pressure (AP) to 42 +/- 1 mm Hg. Upon an isolated cooling of the rat head the heart rate and AP were maintained at a comparatively high level. Under such conditions the lung respiration did not stop even as the temperature of the medulla oblongata decreased to 17.23 +/- 0.25 degrees C. It retained rhythmicallity, a particular rate, and a comparatively high amplitude. It is suggested that an intensive blood supply of the cooled brain decreases the lower temperature limit of its vital activity.

Animals↗
PubMed1999

[Ca(2+) level in the animal blood and their cold resistance].

Administration of small doses of the EDTA decreased by 15-20% the Ca2+ contentn in the blood plasma of rabbits and rats. The decrease coincided with an abrupt stimulation of the thermoregulation system of cooled animals. Restoration of the Ca2+ content in circulating blood coincided in time with repeated suppression of the system's functions. The findings corroborate the theory of a key role of the Ca2+ in sensitivity of the homoiothermal organism to cold and substantiates the method of restoring physiological functions in deep hypothermia without rewarming the body.

Animals↗
PubMed1998

[Analysis of the body heat condition during muscular work based on the heat physical model of the rabbit body].

Quantitative data on body weight, heat absorption and heat conduction, value of relative body surface, and other values reflecting the main heat-physical parameters of the rabbit body, were obtained for a heat-physical model. The model "body" revealed a comparatively great heat inertia capacity which explains a passive rise of the "body" temperature in light or moderate physical work. Conditions of increasing the heat-physical efficacy of thermoregulatory vascular responses in animals, were revealed.

Animals↗
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↗