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Biomedical subjects

L I Osadchiĭ

Publications and source records attributed to L I Osadchiĭ.

At least 19 recordsLinked to original sources
PubMed2003

[Vascular factors of the orthostatic responses in systemic haemodynamic].

In anaesthetised rats, bending of the body for 30 degrees and 45 degrees entailed a reverse linear dependence between the systolic and diastolic pressures under conditions of initial blood pressure over 95 mm Hg, whereas in initial blood pressure lower than 95 mm Hg the dependence is direct. In bending of the body for 60 degrees the dependence was direct and only present in initial blood pressure lower than 95 mm Hg. Pressor effects of mesaton in orthostasis directly depended on the level of the initial blood pressure. Any dependence of the cardiac output shifts on the initial blood pressure was absent. The direction and the degree of the arterial system reactivity's changes in response to orthostasis and adrenergic effect of mesaton was found to depend on the bending angle and the initial blood pressure level.

Adrenergic alpha-Agonists↗
PubMed2003

[Effects of the endothelial relaxing factor on the orthostatic reaction of systemic hemodynamics in rats].

Experiments with unconscious rats showed that blocking of NO secretion intensifies orthostatic hypotension (mean arterial pressure drops by 72%) and reduces proportionally the calculated total peripheral resistance. A supposition has been made concerning involvement of the endothelial relaxing factor in orthostatic hypotension development, since in orthostasis cardiac output (systemic blood circulation) losses its influence on the endothelial NO secretion.

Animals↗
PubMed2003

[Endothelium-dependent mechanism of formation of the systemic hemodynamics responses].

In anaesthetised rats, effects of blockade of the NO-synthetase upon hemodynamic shifts were studied (arterial pressure, cardiac output, general peripheral vascular resistance), the shifts being evoked either by increase (infusion of polyglucon) or by decrease (orthostasis) in the cardiac output. Under the blockade of the NO-synthetase, the pressor effects of polyglucon increased by 27% and the orthostatic hypotension by 72%. Responses of general peripheral vascular resistance changed in the same direction. The findings suggest importance of the NO secretion by the vessels' endothelium for formation of the systemic hemodynamics responses.

Animals↗
PubMed2002

[Effect of hypervolemia on the adrenergic reactivity of the arterial system].

In anaesthetised rats, dependence of haemodynamics upon increase in the blood volume due to infusion of polyglucin in amounts 1.2 and 2.4 ml (8% and 16% of the blood volume in rats, respectively) < was studied. In the former case the initial blood pressure increased by 30%, in the latter case--by 42%; cardiac output--by 16% and 40%. The metasone pressor effects, at the were reliably decreased by 27% and 65%, and those of general peripheral resistance--by 40% and 80, respectively. The cardiac output changes did not differ significantly. The data obtained suggest an effect of the blood volume increase upon a drop of the arterial system's adrenoreactivity as a result of increase in initial blood pressure.

Adrenergic alpha-Agonists↗
PubMed2001

[Effect of initial (spontaneous) arterial pressure on systemic hemodynamic orthostatic responses].

In anesthetized rats, a reverse linear correlation of arterial pressure (AP) shifts was found within the range of initial AP over 95 mm Hg under the head-up tilts at 30 and 45 degrees. Within the range beneath 95 mm Hg this correlation was transformed into the direct one. Under 60 degrees tilt such correlation only occurred within the range beneath 95 mm Hg. The direction and degree of the arterial system responsiveness seems to depend on the tilt value as well as on the range of the initial AP.

Animals↗
PubMed2001

[Reactivity of the arterial system to orthostasis].

Reported are data of experiments with unconscious tilted rats (30 degrees, 45 degrees and 60 degrees) in which a dependence of orthostatic hypotensive reactions of systolic (APs) and diastolic (APd) pressure on spontaneous level of baseline mean arterial pressure (APb.mean) was established. Rats tilted at 30 degrees and 45 degrees, APs and APd were in inverse linear dependence with APb.mean above 95 mm Hg and in direct dependence with APb.mean below 95 mm Hg. Pressor effects of phenylephrine correlated directly and to the same extent with APb.mean only below 95 mm Hg in the 30 degrees and 45 degrees tilt and both above and below 95 mm Hg in the 60 degrees tilt. Mean values of the pressor effect before and after experiment were different in animals tilted at 60 degrees. No dependence of cardiac output on APb.mean was determined. Therefore, the trend and depth of changes in the arterial system reactivity to tilt are dependent on the degree of inclination and the APb.mean range. Reactivity to the adrenergic agent alters only when inclination is greater than 45 degrees.

Animals↗
PubMed2001

[Reactivity of the arterial system during vasodilation induced by sodium nitroprusside].

A stepwise decrease in the blood pressure by means of sodium nitroprusside infusion led to progressing diminishing of mesatone pressor effects in anaesthetised rats. Cardiac output changes due to mesatone administration did not depend on the initial blood pressure. The latter being lower than physiological limits, a direct linear correlation occurred between pressor responses and shifts of general peripheral resistance, on one hand, and the degree of the blood pressure initial drop, on the other hand. The constrictor responses under study are discussed in respect to their dependence on initial tone of arterial vessels.

Adrenergic alpha-Agonists↗
PubMed2000

[Effect of hypotension on the arterial system responsiveness].

The correlation analysis revealed no correlation within the range 110 to 80 mm Hg further transforming into a direct (within the range lower than 80 mm Hg) dependence of the pressure responses to mesatone on the reduction of initial mean arterial pressure under orthostatic hypotension in anaesthetised rats. Under paraverine hypotension a reverse correlation within the range 110-80 mm Hg transforming into a direct dependence (within the range lower than 80 mm Hg) of the responses to mesatone were observed. The dependence of cardiac shifts to mesatone on the initial arterial pressure was not occurred. The mechanisms of dependence of the systemic vascular responses on initial tone of arterial vessels, are discussed.

Adrenergic alpha-Agonists↗
PubMed1999

[The initial tone of arteries determines the magnitude of depressor responses caused by nitroglycerin].

The correlation analysis revealed a direct (within the range 80 to 120 mm Hg) further transforming into a reverse (within the range 121 to 160 mm Hg) dependence of the blood pressure depressor shifts on the initial mean arterial pressure in anaesthetised rats. Within the physiological range of arterial pressure (70 to 130 mm Hg) there is no difference in responses to nitro-glycerine from their initial values. The mechanisms of dependence of the systemic vascular responses on initial tone of arterial vessels, are discussed.

Angiotensin II↗
PubMed1997

[Effects of the tone of arterial vessels on the antiorthostatic response of hemodynamics].

Contribution of the original angiotensin-2 controlled arterial tone to the shifts in systolic and diastolic arterial pressure (AP) was assessed in unconscious rats during tail-suspension. With this technique, values of original mean AP were elevated from 80-110 to 111-140 mm Hg. In the head-down position, rise in the tone was concurrent to a twofold increase in the number of "uncompensated" responses and a similar decrease in the number of test-resistant responses. The original arterial tone high, maximum decline of diastolic pressure was significantly less pronounced. Recovery of both systolic and diastolic arterial pressures was more dynamic against the background of high original tone. Magnitude of the diastolic AP variation dominated over that of systolic AP. These results are being analyzed in comparison with the data about orthostatic compensatory reactions.

Angiotensin II↗
PubMed1997

[Hemodynamic structure of antiorthostatic reactions: relationship of mechanical activity of the heart and arterial pressure].

In acute experiments with antiorthostatic rats tilt-induced changes in the parameters of cardiac activity (left ventricle systolic pressure (LVPs), its first derivative dp/dt, end-diastolic pressure (EDP) were compared in relation to the directionality and extent of systolic (sAP) and diastolic arterial pressure (dAP) shifts. Rise of the tilt angle by 15-45 degrees reduced sAP and dAP, increased LVPs and EDP and did not influence dp/dt. Changes in the cardiac parameters and AP were not unidirectional; sAP and dAP shifts were asynchronous. In a special experimental series, higher tilt angle was found to bring about opposite changes in cardiac ejection (CE) and total peripheral resistance (TPR). Growth in CE was concurrent to a progressive decline in TPR. Discussed is the response of the vascular system to antiorthostasis the unique character of which is vasodilatation.

Animals↗
PubMed1997

[The dependence of shifts in arterial pressure and cardiac output during alpha-adrenoreceptor stimulation on the initial (controlled) tonus of arterial vessels in rats].

A significant decrease in arterial pressure and total peripheral resistance occurred following elevation of the initial blood pressure to 160 mm Hg with mesathone in anesthetised rats. The increase in the cardiac output remaining unchanged. Vascular and cardiac mechanisms of the revealed relationships are discussed.

Adrenergic alpha-Agonists↗
PubMed1995

[The correlation of cardiac mechanical activity and arterial pressure in the hemodynamic postural reactions of rats].

In orthostasis, an increase in the body incline angle led to a decrease in the systolic AP, systolic pressure in the left ventricle and a progressive decrease of the final diastolic pressure in rats. The same incline in antiorthostasis decreases the systolic AP, increase the systolic and final diastolic pressure in the left ventricle. These and some other findings show that compensatory responses are mainly manifested in the vascular system both in ortho- and antiorthostasis, whereas shifts in the cardiac activity correspond to the type of blood redistribution.

Animals↗
PubMed1994

[The influence of baroreceptor reflexes on the effects of rapid changes in blood volume in rats].

The effect of suppression of the sinocarotid and cardioaortal areas on systemic pressor responses were studied during fast administration of fluid. The data obtained does not corroborate the traditional ideas of the universal buffer role of the baroreflexes in regulation of arterial pressure under live conditions of formation of systemic pressor responses as the suppression of the baroreceptor areas tells not on the increment of the pressor responses but either suppresses them or preserves them intact.

Animals↗
PubMed1994

[The relationship of systemic pressor reactions to the initial (spontaneous) blood pressure level].

Relative responses of the systolic and diastolic pressure to polyglukine and mesatone administration were found to be more obvious in anesthetised rats with initial blood pressure less than 100 mm Hg. A reverse linear correlation was found between the above parameters at the high level of connexion for both agents. Exclusion of sinocarotid or cardioaortic areas did not affect the dependence of the responses to measatone on the initial blood pressure, whereas such a dependence was found for polyglukine at intact baroreceptors.

Adrenergic alpha-Agonists↗
PubMed1993

[The systemic vascular reactions during different methods of assessing the hydraulic resistance of the vascular system].

The ratio of the resistance shifts as estimated by the pressure under conditions of stabilised expenditure, in respect to the resistance shifts as estimated by the blood flow, was for the electrical stimulation of a somatic nerve and occlusion of the carotid artery 1:3.3; for the noradrenaline administrations--from 1:3 to 1:3.5; for the papaverine administrations--from 1:2.2 to 1:3.6. In the perfusion with established pressure the vasomotor responses were devoid of the baroreflectory control whereas in perfusion with constant blood volume the conditions for stimulation of baroreceptors with altered pressure were preserved.

Animals↗
PubMed1993

[Postural systemic vascular reactions].

Changes of hydraulic resistance of the vascular system were studied under conditions of stabilised blood expenditure in response to ortho- and antiorthostatic effects. The first type effects involved an increase in the resistance whereas the antiorthostasis decreased the resistance. Both ways of estimation of vascular responses are discussed from the standpoint of conditions for baroreflex control of vasomotor responses.

Animals↗