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Biomedical subjects

G I Mchedlishvili

Publications and source records attributed to G I Mchedlishvili.

At least 19 recordsLinked to original sources
PubMed1994

[An experimental analysis of the development of local capillary stasis].

Micro-application of NaCl induced a local slowdown to full stoppage of the blood flow in the lamina of individual capillaries in the Wistar rats mesenterium. The blood stasis resulted from local disturbances of the blood rheological properties. The erythrocyte aggregates obstructed the capillaries leaving no space for the parietal plasma layer. The findings suggest the intravascular erythrocyte aggregation to be the immediate cause of the blood flow disturbances and the blood stasis in the microvascular lumina.

Animals↗
PubMed1991

[The hematocrit in the microcirculatory bed of the brain].

Concentration of erythrocytes (hematocrit) was assessed in blood samples taken from small veins of the brain and the hindlimbs of rabbits. Its values were regularly found to be higher by 20% in cerebral vessels than in the hindlimbs. These results corroborate our previous conclusion about preferential distribution of erythrocytes along the arterial ramifications to the brain where the metabolic rate and the blood flow are higher than in other parts of the body. The hematocrit in capillaries of the cerebral cortex was found to be higher than in the veins draining blood from its networks. During ischemia in the cerebral hemispheres the erythrocyte concentration regularly decreased both in the cortex capillaries and in the veins. These changes were independent of the systemic hematocrit, which remained unchanged under these conditions.

Animals↗
PubMed1990

[Axial shift of erythrocytes in arteries supplying blood to the cerebral cortex].

In experiments with rabbits the widths of the axial flows of erythrocytes and of the parietal plasma layers were assessed in pial arterial ramifications supplying the cerebral cortex after their in vivo and in situ fixation under conditions of control and vasodilatation. A strict proportional relationship was revealed between the width of red cell flows and the diameter of pial arteries of 15-200 microns wide. However, the relative plasma volume in the microvessels below 50 microns in diameter was comparatively greater than in the larger vessels. The obtained results prove the feasibility of assessing the microvessels' diameters in tissues where one can see the red cell flow but the vascular walls are invisible. One of the reasons for the lower hematocrit in smaller blood vessels as compared to the larger ones was also elucidated.

Animals↗
PubMed1989

[The variously directed reactions of the pial and cortical arterial branches in postischemic hyperemia in the cerebral cortex].

In adult rabbits, functional behaviour of pial and cortical (radial) arteries was rather different: the pial arteries showed regular dilatation while the lumen of the cortical arteries underwent regular reduction. Despite the different responses of the arterial segments, the vascular resistance diminished entailing an increase of local blood flow in the cerebral cortex.

Animals↗
PubMed1989

[Features of physiologic mechanisms regulating microcirculation in the cerebral cortex of birds and mammals].

The responses of pial arteries to increased activity of the cerebral cortex as well as their innervation at various stages of phylogenic development, were studied with the aid of serial photomicrography with subsequent frame-to-frame analysis in adult rabbits and hens. Following the application of 0.5% isotonic strychnine solution to brain surface, the dilatation of all the segments of the pial artery ramifications was considerably more obvious in rabbits than in hens. The latencies of the vascular responses differed in a similar way. Histochemical studies revealed a considerably richer adren- and cholinergic innervation in rabbit pial arteries as compared with those of hens. The vascular responses and the neurogenic control of the pial arterial bed seem to become steadily refined, together with its anatomy, in the course of evolutionary development.

Animals↗
PubMed1986

[Ultrastructural characteristics of branch sphincters and precortical arteries in the rabbit pial arterial system].

Structural peculiarities of pial arteries and their active microvascular segments-sphincters in offshoots and precortical arteries have been investigated, using electron and light microscopy. Our studies have revealed that these vascular segments, which can independently change their lumen, possess multiple myoendothelial junctions, as well as neuro-muscular contacts. This gives evidence of their independent responses that might be determined by structural peculiarities and innervation of their walls.

Animals↗
PubMed1986

[Differences in the concentration of erythrocytes and the hematocrit value in the blood in relation to the location of the vessels and the intensity of the blood flow].

The experiments in adult rabbits revealed that in the blood flowing in cerebral veins the red cell concentration and hematocrit are much greater than in the veins of hind legs of the same animals. In blood samples taken from the heart these values are higher than in those taken from the hind leg, but usually lower than in blood samples taken from the brain. Under conditions of reduced cerebral blood flow (ischemia) the red cell concentration and hematocrit in the brain vessels decrease significantly as compared to the control conditions. Thus, the red cell distribution in arterial branching sequence is irregular, depending both on the localization of the vascular bed and the blood flow rate in it.

Animals↗
PubMed1984

[Structural and functional units in the pial microvascular system].

A study was made of the pial arterial microcircles formed upon successive branching and anastomosing of the terminal pial vessels on the brain cortex surface at different levels of the phylogenetic development of the vertebrata. It was discovered that the pial arterial microcircles progressively become more complicated in the following order: chicken, rabbit, cat, dog, monkey. The morphological signs of the microcircles undergo progressive development: 1) they are formed primarily from small pial arterial branches possessing high vasomotor activity; 2) the area of each circle becomes less and less and their amount per unit of the brain surface increases respectively; 3) the quantity of the feeding arterial branches rises despite the reduction of the circle size; 4) the number of outgoing precortical and radial arteries entering the brain cortex increases; 5) the areas of the brain cortex supplied by individual radial arteries become less and less. This ensures increasingly delicate regulation of adequate blood supply of the smallest areas of the brain cortex.

Animals↗
PubMed1984

[Spread of the dilatational reactions in the pial artery system to the microapplication of strychnine to the surface of the brain].

In anesthetized adult rabbits, organization of pial arterial bed and responses of its elements to microapplication of strychnine, were studied. The pial arterial responses were primarily related to the vessels' structural and functional features. The most considerable dilatation was characteristic of the precortical arteries. The reactions of sphincters of offshoots and smaller pial arteries were almost similar. The least dilatation occurred in larger pial arteries (over 100 mu in diameter). The limits of the vasodilatation were the microanastomoses which separated individual "terminal microvascular units" in the pial arterial bed. The data obtained show that the anatomy of the pial arterial bed provides a possibility for relatively independent regulation of microcirculation in rather small areas of cerebral neocortex.

Administration, Topical↗
PubMed1983

[Dynamics of local vascular reactions during increased brain activity].

The dynamics of dilatant responses of the pial microvascular system was investigated under conditions of increased cortical activity due to direct application of suprathreshold concentrations of strychnine in experiments on adult rabbits using direct cinemicrography. The diameter of the following interconnected segments of pial arteries was measured in every frame of the film: comparatively large pial arteries (LPA), sphincters at off-shoots of smaller branches (SO), minor pial arteries (MPA), and precortical arteries (PCA). The experiments showed that the order of values of dilatant responses was: PCA greater than SO greater than MPA greater than LPA. The order of the latencies was: PCA less than SO less than MPA less than LPA. The revealed behaviour of the pial microvascular system maintains the adequacy of local blood supply as well as the elimination of the "steal phenomenon" in the neighbouring cortical areas.

Animals↗
PubMed1983

[Mechanism of "autoregulation" of the cerebral circulation: role of neurogenic and myogenic vascular reactions].

The neurogenic and pure myogenic responses of the dog circulatory isolated internal carotid artery were studied under conditions of controlled intraluminal pressure changes. The artery was continuously perfused with the oxygenated bicarbonate Ringer-Krebs solution, and the vascular responses were estimated as changes in the perfusion fluid flow rate recorded with a drop-flowmeter. The quantitative analysis of the vascular responses showed that a comparatively constant perfusion fluid flow independent of the rate of perfusion pressure changes only occurred when the neurogenic control of the artery was preserved. The pure myogenic responses of the artery were only observed in 25% of tests, were four times weaker and present only within the narrow limits and at a specific rate of the intraluminal pressure changes.

Animals↗
PubMed1982

Pattern and innervation of pial microvascular effectors which control blood supply to cerebral cortex.

In experiments with adult rabbits the active microvascular segments located at particular sites of the minor pial arterial ramifications were investigated. These appeared as sphincters at off-shoots of the arterial branches, the precortical arteries, and the arterial microanastomoses. The sphincters and the precortical arteries were found plentifully supplied with the cholinergic and adrenergic nerves, but the innervation of the microanastomoses was not considerably different from that of the adjacent arterial branches. The nerves of the precortical arteries were in direct connection with the nerve fibers of the arterial branches located inside the cerebral cortex. The pattern of distribution and innervation of the active vascular portions in pial microvascular bed suggests the probability of a neurogenic control of the blood supply to the smallest areas of the cerebral cortex.

Animals↗