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Biomedical subjects

B I Tkachenko

Publications and source records attributed to B I Tkachenko.

At least 19 recordsLinked to original sources
PubMed1992

[Changes in gas composition of expired air during electric stimulation of the ventral medulla oblongata].

The experiments on urethane-anesthetized cats with the electrically stimulated ventral brain stem revealed that caudal ventral medulla at the depth of 1500 microns possesses structures whose electrical activation increases the level of carbon dioxide in arterial blood and in the end portion of expirate, on the one hand, and decreases the oxygen content in expirate and arterial blood, on the other hand.

Animals↗
PubMed1991

[The dependence of changes in the microhemodynamics and lymph formation in the liver on the level of the arterial and portal blood flows].

In cats, when perfusing hemodynamically isolated liver with a constant blood volume, an increasing of arterial as well as portal blood flows was shown to increase hydrostatic pressure in sinusoids and lymph production in the liver, whereas decreasing of the flows decreased these parameters. The above changes of the blood flows entailed various shifts of sinusoidal hydrostatic pressure and postsinusoidal resistance. When the volume blood flow in the liver artery increased, the coefficient of sinusoidal filtration increased too, whereas an increment of the blood flow in portal vein led to its diminishing. The resistance of liver artery and portal vein changed very little both in case of increasing and diminishing of the blood flow in these vessels.

Animals↗
PubMed1991

[The nature of the changes in the systemic hemodynamic parameters under the combined action of vasoactive substances].

The direction and obviousness of changes in systemic arterial and venous vascular beds occurring in combined action of two similarly acting pressor and depressor vasoactive drugs, were studied in acute experiments in cats. The changes of last and general peripheral resistance of vessels were greater under the action of the two drugs as compared to the effect of a single drug, and yet less obvious than their algebraic sum. The shifts in cardiac output and venous return were not greater than the most obvious response to a single drug. The same was true for the blood flow changes in v. v. cavae. Irrespective of the mechanism of action of vasoactive drugs and the direction of shifts of systemic AP, single and combined drugs increased the blood flow in the v. cava anterior whereas the v. cava posterior's blood flow changed in different directions.

Acetylcholine↗
PubMed1991

[Functional relationship of venous to metabolic vessels of muscles in experimental venous insufficiency].

Modelled venous insufficiency of the hind limbs of cats (ligation of the posterior vena cava for 4-6 weeks) led to structural reorganization of the venous walls of the gastrocnemius muscle, which was manifested by a sharp increase of stretchability of the venous bed of the muscle if the activity of the smooth muscles was removed by papaverine, and by significant loss of the sensitivity of the smooth muscles of the intramuscular veins to noradrenaline as regards function. The range of adrenergic changes of postcapillary resistance and capillary pressure was reduced sharply in animals with venous insufficiency. This may be among the causes of disorders of metabolic processes in the skeletal muscles in venous insufficiency.

Animals↗
PubMed1991

Direct recording of postcapillary resistance in cat skeletal muscle: measurement in the presence of humoral stimuli.

A procedure involving the parallel perfusion of deep veins in a cat shank preparation with endogenous blood and a constant volume of dextran solution has been devised. The dextran is supplied to these deep veins via superficial and communicator veins (venae communicantes). With this method it is possible to record dynamic changes in the resistance of the deep veins (postcapillary resistance) in response to intraarterial administration of vasoactive agents into the vascular bed of the shank. Data are presented which indicate that the number of deep veins involved in the changes in venous resistance is equivalent to 67% of the total capacity of the vascular bed of the shank. It is shown that the increase in venous perfusion pressure caused by infusion of noradrenaline into the vascular bed of the shank is essentially equivalent to the increase in mean capillary pressure as determined isovolumetrically. With this new method it is demonstrated for the first time that angiotensin II causes constriction of the deep veins of the shank and that isoproterenol causes dose-dependent dilatatory reactions in the veins within the muscle preparation.

Angiotensin II↗
PubMed1990

[The organic macro- and microhemodynamics and the systemic circulation under the combined action of hypoxia and hypothermia].

In regimen of the constant blood flow perfusion of shank and small intestine of cat combined effect of hypoxia (10% O2 in N2) and hypothermia (about 30 degrees C) involved a decrease in precapillary resistance, an increase in capillary filtration coefficient in both vascular regions, an increase in postcapillary resistance and in mean capillary pressure in the intestine, and their decrease in the shank. In hypothermia, the hypoxic stimulus induced insignificant shifts in all the parameters under study in both organs. Dependence of hypoxic changes of macro- and microhemodynamics on the activity of adrenergic receptors in the cooled organism was studied on decentralized shank of cat. After cooling of cat and blockade of alpha-adrenoreceptors hypoxic hypoxia caused much greater reduction of precapillary resistance of shank, more striking (by 3 times) increase of capillary filtration coefficient and the increase of capillary pressure and postcapillary resistance in contrast with their decrease to hypoxia under hypothermia before alpha-blockade. Beta-adrenoreceptor blockade had no influence on the changes of the resistance and exchange function of skeletal muscle (shank) blood vessels evoked by hypoxia under cooling. Systemic arterial pressure are diminished during hypoxia under the normothermic conditions of animals. Such kind shifts caused especially by the decreasing of the total peripheral resistance; cardiac output are small raised in this situation. But combined influence of hypoxia and hypothermia evoked the pressor shifts of the systemic arterial pressure because of less decrease of total peripheral resistance and more remarkable rise of cardiac output. Hypoxic stimulus caused both in normothermia and hypothermia conditions caused the rising of venous return.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

[Hemodynamic structure of pressor reactions to vasoactive substances].

In cats, similar changes of the blood pressure had different hemodynamic structures under the influence of catecholamines or angiotensin. Adrenalin was able to evoke a pressor response by means to either caridac or vascular factor. In the former case, the increase in the cardiac output was induced both by an increasing blood flow towards the heart and by an additive outflow of the blood from the minor to the major circulation; in the latter case, the increase in the general peripheral resistance entailed a decrease in the cardiac output in spite of the augmentation of the venous return which determined a delay of the blood in the minor circulation. The latter variant of interrelationships among hemodynamic parameters can occur under the influence of noradrenaline as well. A combined similarly rendered participation of the cardiac and the vascular factors in the increasing the blood pressure occurs under the influence of angiotensin and sometimes of noradrenaline. The participation of cardiac output in the pressor response may depend on hemodynamic shifts in the minor circulation which either limit or facilitate, or leave unchanged the rate of increment of the cardiac output.

Angiotensin II↗
PubMed1978

[Reactions of the microcirculatory bed of cat mesentery during exposure to heat].

The TV-microscopy in cats revealed that, by the 30th minute of 2-hr overheating, the arterioles are dilated and venules constricted. In the course of raise of body temperature from 36 degrees to 40 degrees C, the number of dilatory and constrictory responses of venules remains the same while the number of arteriole dilatory responses diminishes and of constrictory responses increases. At 40 degrees C of body temperature, the number of dilatory responses of the mesenteric arterioles and venules makes about 20--30% while the number of constrictory responses--70--80%. The extent of dilation of arterioles and venules increases with the heating while the extent of constriction, having achieved a certain level, starts to diminish. The greatest responses occurred in the microvessels with initial diameter 60 and more microns. The responses of microvessels with a lesser diameter could be different. The data obtained using hexonium, dihydroergotoxin, inderal, atropin, dezeril, methyamide, and tavegil, suggest participation of adrenergic and histamingergic substances in vasomotor responses of the microvessels to the hyperthermia.

Animals↗
PubMed1978

[Relationship between central and peripheral mechanisms in regulating capacitance vessels].

In acute experiments on cats, responses of the resistance and capacitance vessels of the spleen and hindlimbs to local electric stimulation of the medulla oblongata, of the sympathetic nerves, and pressor reflexes during different pressure of the venous outflow, were studied. No structures were revealed which could selectively affect the capacitance vessels. The bulbar structures affected both the resistance and the capacitance vessels. The reflex responses aof the pre- and post-capillary portions of the vascular bed could be different, the transmural pressure being one of the factors for dilatory responses of the capacitance vessels. The different responses of the capacitance vessels could occur on account of both local and central mechanisms, their participation, however, being unequal.

Animals↗
PubMed1978

Blood supply and O2 consumption of the small intestine in low flow.

Blood flow and O2 consumption of the small intestine were studied anaesthetized cats in two series of experiments. Two-step haemorrhagic shock was applied in the first one; the intestinal vascular bed was locally hypoperfused in the other. Resistance to blood flow decreased in both haemorrhage and hypoperfusion. Intestinal blood flow was 12.6 ml/min . 100 g in haemorrhage (blood pressure 60 mm Hg) and 13.3 ml/min . 100 g at 50% perfusion. O2 consumption was only slightly reduced (93% and 89% of the control, respectively). Decrease in resistance showed a similar character to the "autoregulatory escape" phenomenon. Two types of regulation of O2 supply took place during low flow. The first one tended to maintain O2 supply to the gut in the face of flow reduction; in the other O2 consumption depended upon blood upon blood flow. The lower was blood flow, the more dominant became the second mechanism.

Animals↗
PubMed1977

[Character of organ volume vessels during pressor reflexes].

In acute experiments on cats, responses of the resistance and capacity vessels of small intestine, spleen, kidneys, and m. gastrocnemius were studied during pressor sinocarotid reflex and electrical stimulation of the sciatic and brachial afferents. It was shown that, against the background of constrictory responses of the resistance vessels in these organs, both the constrictory and the dilatory responses of the capicitance vessels could occur or not. Correlation analysis revealed no dependence between the markedness and character of the capacitance vessel responses and the changes of the venous blood oxygenation during pressor reflexes. The regulatory mechanisms determining, different characters of the capacitance vessels during neurogenic effects and the methodical conditions revealing the true nature of changes occurring in the postcapillary bed, are discussed.

Animals↗
PubMed1977

[Comparative characteristics of changes in the diameters of microvessels and blood flow within them during systemic shifts in hemodynamics].

In anesthetized cats, with the aid of the method of television line single out, the diameters of mesenteric microvessels and their blood flow were studied. The diameter of the flow in arterioles and venules was shown to undergo greater changes than the diameter of the microvessels proper, although a close correlation was revealed between both parameters. The above differences of the changes of diameters are more obvious during dilatory responses. The changes depend on the initial caliber of the arterioles and venules.

Animals↗