[Systemic and regional hemodynamics in alert rats with increasing hyperthermia]. / Sistemnaia i regionarnaia gemodinamika u bodrstvuiushchikh krys v usloviiakh narastaiushchei gipertermii.

The changes in the parameters of systemic and regional hemodynamics during thermal stress were followed up in awake male Wistar rats. The cardiac output (CO) and blood flow in 16 zones of the body were measured by means of 15 microns microspheres labeled by 4 different isotopes. The blood flow increased in the skin of the tail, the liver, heart, adrenals, and skeletal muscles and reduced in the organs of the splanchnic region and kidneys. When body temperature reached 42 degrees C the CO decreased. The shifts in the regional blood flow maintained their direction, with the exception of a sharp increase of blood flow in the small intestine which preceded or coincided with the beginning of a fall in arterial pressure. The rate of increase of left ventricular pressure remained at a high level. It is assumed that the disruption of celiac vasoconstriction is among the earlier developing links of hemodynamic disorders in thermal affections and is caused by the vasodilative effect of the factors of local control of the vascular functions.

[Differences in the redistribution of cardiac output during hyperthermia in waking rats and guinea pigs]. / Razlichiia v pereraspredelenii serdechnogo vybrosa pri gipertermii u bodrstvuiushchikh krys i morskikh svinok.

The heat stress induced common responses in rats and guinea pigs: an increase in the blood flow at the sites of heat radiation and in the diaphragm, and its decrease in splanchnic area's organs and in kidneys while cardiac output remained constant. The species differences occurred in the responses of intestine and skeletal muscles' vessels. The differences seem to be due mainly to the differences in behavioral responses to the heat stress in these animals.

[Resistance, capacitance and exchange functions of the vessels of the small intestines and skeletal muscles during exposure of the body to intense heat]. / Rezistivnaia, emkostnaia i obmennaia funktsii sosudov tonkogo kishechnika i skeletnykh myshts v protsesse intensivnogo teplovogo vozdeistviia na organizm.

Rise of body temperature to 41.0-41.2 degrees C led to an increase of the integral, pre- and postcapillary resistance in the vascular bed of the cat small intestine and skeletal muscles. The increase of the resistance function in veins led to an increase of the mean capillary hydrostatic pressure. The above shifts enhanced with increasing of the hyperthermia. The latter was found to reduce distensibility of veins and the capillary filtration coefficient (CFC) in the small intestine vascular bed but to increase the CFC in skeletal muscles. The role of the small intestine and skeletal muscles venous vessels in the shifts of the filtration-absorption ration and the capacitance function in hyperthermia is discussed.

[Characteristics of vasomotor responses in the cat skeletal muscles and skin during heat stress]. / Kharakteristika vazomotornykh reaktsii v skeletnykh myshtsakh i kozhe u koshek pri teplovom stresse.

In anesthetized cats, resistography and the volumometry of extracorporeal blood flow revealed that even the first stages of hyperthermia decreased the resistance and increased the compliance of the skin venous vessels, whereas an essential increase in the resistance of skeletal muscles' arterial vessels only occurred in marked hyperthermia. The compliance of skeletal muscles' venous vessels underwent no considerable changes in hyperthermia. The data obtained suggest a significant redistribution of the blood flow and blood volume among the skin and muscles vessels during heat stress. The observed differences in the rate of development of the above responses suggest participation of different mechanisms in their formation.

[Stretching of the veins of skeletal muscles following changes in the level of hydrostatic venous pressure]. / Rastiazhimost' ven skeletnykh myshts pri sdvigakh urovnia gidrostaticheskogo venoznogo davleniia.

Acute experiments in cats revealed that the integral venous compliance of m. gastrocnemius' could be represented by a graphic curve with ascending front, peak and descending front. These parts of the curve corresponded mainly to those ranges of the venous pressure values: (-10)-0 mm Hg; 0-(+10) mm Hg and (+10)-(+25) mm Hg, resp. The neurogenic component of venous tone in the skeletal muscles has no obvious effect on formation of venous compliance values in response to hydrostatic loads whereas increasing of this tone with noradrenaline or decreasing of it with papaverinum induced, resp., a decrease or an increase in the venous compliance.

[Effect of high ambient temperature on regional redistribution of blood flow in the cat]. / Regionarnoe pereraspredelenie krovotoka u koshek v usloviiakh vysokoi vneshnei temperatury.

Supersound flowmetry revealed that the effect of heat (50 degrees C) involved an increase of the blood flow in skin vessels and its decrease in the vessels of small intestine and skeletal muscles. The blood flow resistance was diminished in skin vessels and increased in the vessels of small intestine and skeletal muscles. These shifts of the regional blood flow are due to the integral interaction of active and passive vascular responses. Specifics of the small intestine and skeletal muscle vessels' constrictory responses to hyperthermia suggest a difference in the mechanisms of their occurrence.

[Vasomotor responses of the small intestine during acute overheating of the body]. / Vazomotornye reaktsii tonkogo kishechnika pri ostrom peregrevanii organizma.

In anesthetized cats under conditions of acute overheating, resistance to the blood flow increased in arteries of the small intestine whereas compliance of the postcapillary vascular bed reduced in respective linear dependence. The correlation-regression analysis indicated a close linear dependence between changes in arterial vessels of the small intestine to heating and their responses to the pressor carotid sinus reflex. The mechanism responsible for splanchnic vasoconstriction under conditions of acute overheating of the organism seems to involve increased efferent impulses activity mediated by the adrenoreactive structures.