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Biomedical subjects

Iu I Levkovich

Publications and source records attributed to Iu I Levkovich.

At least 19 recordsLinked to original sources
PubMed1999

[Proliferative activity and structure-functional organization of chromosomes in cells from the developing brain in respect to genetically determined excitability of the rat nervous system].

Neuroblasts of developing hippocampus of 16-17-day old rat embryo of the line with high threshold excitability are characterised by a high level of proliferative activity and chromosome aberration, as well as high degree of brain chromatin concentration as compared with embryos of a line with low threshold excitability.

Animals↗
PubMed1996

[The antiulcer effect of corticosteroids and the blood flow in the gastric mucosa].

Intravital microfilming by means of dark-field contact epiobjective was used for investigation of the role of gastric microcirculation in antiulcerogenic action of corticosteroids in rats. Microvascular volume blood flow velocity was calculated from measurements of red cell velocity and vessel diameters. There was compared gastric submucosal and mucosal microcirculation as well as gastric ulceration after water-immersion stress in rats with normal function of hypothalamo-pituitary-adrenocortical (HPA) axis and in rats with insufficiency of corticosteroid production, induced by blockade of the HPA axis. The 3h stress induced gastric ulcerations, dilatation of mucosal microvessels and a significant decrease of volume blood flow in submucosal microvessels. These changes were greater in rats with blockade of HPA axis than in animals with normal corticosteroid production. Replacement corticosterone therapy decreased the effects of HPA axis blockade. Thus corticosteroids which are produced during stress restricted the reduction of volume blood flow in submucosal microvessels, the dilatation of mucosal microvessels as well as gastric ulcerations. These findings indicate that corticosteroids exert their antiulcerogenic action via the mechanism of improvement of gastric microcirculation.

Adrenal Cortex Hormones↗
PubMed1996

[Corticosteroids limit the decrease in blood flow velocity in the microvessels of the gastric submucosal layer during stress in rats].

To evaluate the influence of stress and corticosteroids on blood flow velocity in gastric submucosal microvessels it was used intravital microfilming by means of a dark-field contact epiobjective. The plasma filled "gap" in the continuous erythrocyte flow were used as the markers to measure linear blood flow velocity. In unstressed rats the linear blood flow velocity was equal to 2.0 +/- 0.08 mm/sec (156 microvessels, 6.4 +/- 0.14 micron in diameter), calculated volume blood flow--(6.9 +/- 0.48) x 10(-5) microliters/sec. Stress (water immersion and restraint) led to a decrease of blood flow velocity in microvessels to more than double. A stress-induced decrease of blood flow velocity was more greater in rats with insufficient corticosteroid production. The linear velocity of blood flow of these rats was lowered to 0.6 +/- 0.06 mm/sec, volume blood flow to (1.6 +/- 0.21) x 10(-5) microliters/sec. Replacement corticosterone therapy increased the blood flow velocity. It was concluded that stress decreases blood flow in microvessels of gastric submucosa. The results revealed that glucocorticoids take part in normalization of blood flow of gastric microvessels during stress and this action can provide antiulcerogenic effect of corticosteroids which was shown by us previously.

Adrenal Cortex Hormones↗
PubMed1996

[The adaptation-protective effect of corticosteroids on the rat gastric mucosa and its mechanism].

The influence of stress-induced corticosteroid production on gastric ulceration, blood flow velocity in gastric microvessels and blood pressure was studied in rats. The role of plasma corticosteroids was investigated by means of blockade of the pituitary-adrenocortical system (PACS) and following corticosterone replacement therapy (400 mu/100 g b.w.). The blockade which was induced by Fi. hydrocortisone administration (7 days before stress, 30 mg/100 g b. w.) resulted in an insufficient corticosteroid production. To evaluate the influence of corticosteroids on blood flow velocity in gastric microvessels of muscular, submucosal and mucosal coats it was used intravital microfilming by means of a dark-field contact epiobjective. Stress (water immersion + restraint) induces an ulceration, a decrease in the systemic arterial blood pressure (3 h after stress onset) and a decrease in blood flow velocity in the gastric microvessels (3 h after stress onset). In rats with insufficient corticosteroid production stress-induced ulceration, a decrease in blood pressure and gastric blood velocity were more greater than in rats with intact PACS. Replacement corticosterone therapy corrected all parameters. The results revealed that antiulcerogenic effect of stress-induced glucocorticoid production is realised owing to normalisation of gastric blood supply which is provided by an increase in systemic blood pressure.

Adaptation, Physiological↗
PubMed1995

[The effect of stress and corticosteroids on the rate of blood flow in the microvessels of the gastric muscular coat of rats].

In order to evaluate the influence of stress and corticosteroids on blood flow velocity in microvessels of muscular coat of the stomach we applied intravital microfilming by means of a dark-field contact epiobjective. The plasma filled "gap" in the continuous erythrocyte flow were used as the markers to measure linear flow velocity. In unstressed rats the velocity was equal to 1.76 +/- 0.07 mm/sec (182 microvessels, 3.7-8.7 mu in diameter). Stress (water immersion and restraint) led to a decrease of blood flow velocity in microvessels to more than double. A stress-induced decrease of blood flow velocity was greater in rats with insufficient corticosteroid production. The velocity of blood flow in these rats was lowered to 0.62 +/- 0.04 mm/sec. Replacement corticosterone therapy increased the blood flow velocity. It was concluded that stress decreases blood flow in microvessels of muscular coat of the stomach as well as in microvessels of mucosa. The results revealed that glycocorticoids take part in normalisation of blood flow of gastric microvessels during stress.

Adrenal Cortex Hormones↗
PubMed1995

[The microcirculation in the cerebral cortex of rats at different stages of deep immersion hypothermia].

A 25-30 degrees C hypothermia significantly increased the capillary blood flow in the rat cerebral cortex. A deeper hypothermia (17-15 degrees C) led to a stable decrease in the blood flow up to initial level. Breathing ceased at this stage, the cardiac activity being evident for 30-40 minutes after this. Deep hypothermia also led to a reversible aggregation phenomenon which seemed not to hinder the blood flow.

Animals↗
PubMed1993

[The circadian rhythm of the formation of stress stomach ulcers in rats].

Areas of stress-induced gastric ulceration vary parallels with changes of corticosterone levels. The ulceration was greater in the morning during low basal corticosterone level than in the evening during high one. Adrenalectomy ceased the circadian basal rhythm of corticosterone and the rhythm of stress-induced ulceration. The decrease of ulceration in the evening seems to indicate an increase of the body adaptability resulting from the circadian corticosterone increase.

Adrenalectomy↗
PubMed1992

[A quantitative analysis of primate motor activity in a situation of delayed spatial choice. The individual behavioral reactions].

Speed of movements in food getting responses of baboons, total time of the response, trajectories of the movements and other parameters revealed obvious changes during formation of conditioned activity. The data obtained suggest that many quantitative characteristics of the primate motor activity are specifically related to various aspects of complex behavioral responses.

Animals↗
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

[An analysis of the joint activities of primates in a situation of delayed spatial choice].

A leader-dominant baboon of a couple took practically all the food in the situation of spatial delayed choice. The subdominant baboon managed to get some food, too, using fast changes of behavioral tactics during the experimental session. The obvious negative state of the subdominant baboon resulted in a severe neurotic breakdown. Long delays in the experimental scheme enabled the subdominant to get up to 50% of the food reinforcement due to the dominant baboons mistakes. The role of changes in the tactics of the monkeys is discussed.

Animals↗
PubMed1991

[Changes in the blood flow velocity in the capillaries of the rat cerebral cortex in acute massive blood loss].

A statistically significant drop in the blood flow velocity in capillaries of the rat cerebral cortex occurred in 50-60% loss of the blood volume: from 1.32 +/- 0.1 mm/sec to 0.2-0.8 mm/sec even in 30-40% loss, resp. A more massive blood loss (50-60%) decreased the blood flow velocity with no subsequent restoration. Aggregates of elements were formed in the capillaries with subsequent hemostasis in this part of the vessel.

Acute Disease↗
PubMed1991

[The function of the precortical arteries].

In anesthetized adult rabbits, the responses of pial and precortical arteries to retinal photostimulation and the application of 0.5% strychnine solution to the brain surface were studied, as well as the distribution of cholinergic and adrenergic nerve fibres in these microvessels. The precortical arteries showed the highest degree of dilatation and frequency of responses. Dense innervation was mostly in evidence in the precortical arteries. Upon atropin application, the response suppression was also more obvious in the precortical arteries. The data suggest that the precortical arteries play an important role in regulation of the adequate blood supply to the brain tissue.

Adrenergic Fibers↗
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↗
PubMed1989

[Cerebral blood flow function during altered cholinergic mediation].

The study of cerebral blood flow was performed with the aid of hydrogen clearance technique and the cinema-television method in alteration of cholinergic transmission by means of phosphorus-organic inhibitors of cholinesterase and a cholinolytic agent in unanesthetized rats. The enzyme inhibition by 60-70% sharply increased the velocity of blood flow in the microvessels of cerebral cortex and in the sagittal sinus. A considerable vasodilation of pial vessels occurred. Atropine administration reduced the velocity of both the cortical and the total blood flow, increasing the lumen of pial vessels in intact animals. Whereas atropine administration against the background of the inhibitors action normalized the blood low velocity with no elimination of the vasodilation of pial arteries. The findings suggest that atropine widely used in poisoning with various inhibitors of cholinesterase, does not normalize the tonus of cerebral vessels.

Animals↗
PubMed1989

[Blood flow dynamics in adjacent microvessels of the brain in hypertensive rats].

Significant alterations in the blood flow velocity, its amplitude and oscillations were found in cerebral cortex's microvessels of 5-12 mu diameter in normotensive and spontaneously hypertensive rats. Associated alterations of the blood flow shifted by a few seconds, were found in adjacent vessels. These alterations seem to be due to hemodynamic readjustments in proximal parts of the vascular net. The absence of these alterations in adjacent vessels suggests no significant redistribution of the blood flow in resting in cerebral cortex's microvessels.

Animals↗
PubMed1989

[The effect of an increased erythrocyte count on rapid blood flow fluctuations in the microvessels of the rat brain].

Polycythemia was achieved by means of substitution of the rat own blood (2 ml) with the same volume of washed out erythrocytes, the hematocrit increasing from 44 to 54%. Excessive erythrocytes altered the structure of the erythrocyte flow, its diameter being 3-13 mu. The rate of occurrence of the plasma lumens decreased. The hematocrit increase, however, did not affect the amplitude and period of the oscillations. The character of distribution of periodic components of the fluctuations of the blood flow linear velocity did not change either in the vessels under study. The data obtained suggests that the erythrocytes do not affect the occurrence of the blood flow oscillations in the microcirculation system. The main part in their formation seems to be played by the leucocytes differing by their rheological features from erythrocytes.

Animals↗