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Biomedical subjects

G Mchedlishvili

Publications and source records attributed to G Mchedlishvili.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of erythrocyte aggregability changes during ischemic and hemorrhagic stroke.

The aim of this work was to perform a comparative investigation of erythrocyte aggregability changes in the peripheral and cerebral circulation during ischemic and hemorrhagic stroke. Subjects of the present study were patients with ischemic brain infarcts (14 patients) and with hemorrhagic stroke (21 patients) from the Intensive Care Unit of the Institute of Neurology and Neurosurgery. The blood samples were obtained from the following blood vessels: the common carotid artery carrying blood to the primarily damaged brain hemisphere, both jugular veins carrying blood from the primarily damaged and the contralateral hemispheres, as well as from the cubital vein to obtain specimens of the systemically circulating blood. Erythrocyte aggregation was evaluated by using the "Georgian technique". We found that the RBC aggregation indices increased in both the regional as well as the systemic circulation of the hemorrhagic stroke patients as compared to ischemic stroke patients. The results of the present study demonstrate different changes of erythrocyte aggregation in ischemic and hemorrhagic stroke patients. Therefore, the role of blood rheological properties in their pathogenesis seems also to be different.

Brain Ischemia↗
PubMed2001

Arteriolar resistance and hemorheological disorders related to Raynaud's phenomenon.

The functional condition of resistance arteries in human hands was monitored with a noninvasive test. Blood flow velocity changes (Doppler flow meter) were monitored in the radial artery before and after a 1-min stop flow in the hand under conditions of stable systemic arterial pressure. In addition, the most significant parameter of hemorheological disorders in microcirculation, RBC aggregability, was investigated in the same patients' blood samples. The muscular tone of the resistance arteries was found to be a mean of 35% higher during Raynaud's phenomenon than in the healthy controls tested. The raised vascular tone was not related to the patients' age and had a pronounced tendency to rise with disease duration. RBC aggregability was a mean of 4% higher in the patients than in the healthy controls, and the difference was not reliable. We concluded that, among principal pathogenic factors which might cause deficiency of the blood supply to fingers, it is the enhanced tone of resistance arteries that is primarily responsible for the development of Raynaud's phenomenon, while hemorheological disorders are not, or are considerably less, involved in the development of the principal symptom of the disease, deficient blood supply to the fingers.

Adult↗
PubMed2000

Comparative values of erythrocyte aggregability versus other indices of hemorheological disorders in patients with ischemic brain infarcts.

The aim of the present study is comparison of changes of principal hemorheological factors responsible for blood flow disorders in the microcirculation in patients with ischemic brain infarcts. It was found that in venous blood samples the erythrocyte aggregability (examined with a direct, highly sensitive, quantitative technique) was considerably more increased (by mean of 120%) than the blood plasma fibrinogen contents, blood plasma viscosity, and hematocrit which increased only by 23.7%, 7.4% and 3.6%, respectively, as compared to the same hemorheological factors in the healthy controls. These results led us to the following conclusion: among the other tests the enhanced erythrocyte aggregability, when measured with an appropriate technique, is the best diagnostic indicator of hemorheological derangements during development of the ischemic brain infarct.

Adult↗
PubMed1999

Microcirculatory stasis induced by hemorheological disorders: further evidence.

OBJECTIVE: Reinvestigate the microcirculatory alterations immediately responsible for blood rheological disorders and blood stases, which are related to red blood cell (RBC) aggregation in capillaries. METHODS: Blood rheological disorders were produced by significantly intensified intravascular red blood cell aggregation in the intestinal mesentery of Wistar rats and in the cerebral cortex of Chinchilla rabbits, either systemically (by intravascular administration of high molecular-weight dextran) or locally (by increase of high-molecular compounds in blood plasma inside individual or groups of capillaries). RESULTS: Under conditions where the microvascular lumina were not decreased and the arteriolovenular pressure gradients got even higher, the significantly enhanced intravascular RBC aggregation resulted in the slowing down of blood flow in the microvessels to a full stop. CONCLUSION: A significant increase in microvascular RBC aggregation results in local hemorheological disorders, which is, in all probability, related to derangement of the blood-flow structuring in microvessels.

Animals↗
PubMed1998

Kinetics of beneficial effect of pentoxifylline on persistent forms of arterial hypertension.

In some hypertensive patients a high level of arterial pressure proved resistant to the effect of Ca-antagonists. However, the addition of therapeutic doses of Pentoxifylline caused a significant decrease of blood pressure. The arterial pressure changes were found to be correlated with the index of erythrocyte aggregability (investigated using a highly sensitive "Georgian technique") in these patients. Thus, a pathogenetic link between blood pressure and hemorheological disorders could be conjectured. For a better understanding of the mechanism of these events the direct effect of Pentoxifylline on erythrocyte aggregability was investigated in vitro by using the blood samples of hypertensive patients possessing hemorheological disorders. The obtained results showed that the effect of Pentoxifylline (in therapeutic doses) was direct and that the dose-effect dependence was linear. From the obtained results we concluded that the beneficial effect of Pentoxifylline in hypertensive patients resistant to Ca-blockers is attained by eliminating the immediate cause of blood rheological disorders, the enhanced erythrocyte aggregability.

Aged↗
PubMed1998

Disturbed blood flow structuring as critical factor of hemorheological disorders in microcirculation.

Blood flow structuring is a phenomenon of co-ordinated self-organization of RBCs in the normal flow in microvessels which actually defines the blood rheological properties in their lumina. Under conditions of undisturbed macrocirculation and normal conductance of microvessels the blood flow structuring is a determining factor of the fluidity of the driven blood. The dynamic structuring of blood flow prevails in advancing of the driven RBCs with plasma in the shear field induced in microvessels. Term "blood flow structuring" was introduced to describe the self-organised behavior of the RBCs and plasma advancing in the arterio-venular direction in the rapidly perfused microvessels. It implies primarily the availability of parietal plasma layer and of RBCs driven in the axial core, the tank treading, deformation and orientation of the red cells, i.e., of their self-optimizing adaptive behavior which minimizes energy dissipation. Many local hemorheological disturbances in the microvessels are related to intensified RBC aggregation and to the subsequent local accumulation in the microvascular lumina, thus entailing disorders of the blood flow structuring. This, in turn, results in the decrease of flow velocity, to full blood stasis, despite a preserved local arterio-venous driving pressure gradient. Elevated blood plasma viscosity and considerably curtailed RBC deformability might also entail retardation and even stoppage of the RBC flow in microvessels. The transition of blood flow to blood stasis and again to blood flow represents a synergetic process in the critically underperfused microvascular networks. As to the WBCs and thrombocytes, they are not involved in the normal blood flow structuring in microvessels, but they can largely affect both the blood flow normal structuring and the flow velocity under various pathological conditions. The presented theoretical concept accounts for a wide variety of transition patterns from the normal to the pathological hemorheological phenomena in the microcirculation.

Arterioles↗
PubMed1997

Blood flow structuring and its alterations in capillaries of the cerebral cortex.

Various manifestations of blood flow structuring were investigated in rabbit cerebral cortex capillaries, which possess the most narrow lumina of all parts of the body. Blood flow structuring in the capillaries was characterized by the presence of a stable and comparatively large parietal plasma layer, which changed insignificantly under control and ischemic conditions, but disappeared when blood stasis developed inside the capillaries. The axial core of the blood flow in the capillaries, which occupied almost two-thirds of the intracapillary volume under normal conditions, consisted of significantly deformed (stretched along the microvessels' axes) and nonaggregated erythrocytes. During ischemia the shape of the erythrocytes did not change appreciably; only the blood plasma intervals between them increased significantly, demonstrating reduction of the local hematocrit. During primary blood stasis caused by enhanced intravascular erythrocyte aggregation, typical blood flow structuring became significantly disturbed: red cells filled the whole, or almost the whole, capillary lumina and did not leave visible space for plasma inside the microvessel lumina. We concluded that normal blood flow structuring is a deciding factor in the blood rheological properties of microvessels. Its disturbance, caused by fast accumulation of erythrocytes in the capillary lumina, results in blood rheological disorders and in a slow down to a full stop of the blood flow, despite a preserved arteriolovenular pressure difference.

Animals↗
PubMed1993

Effect of intensified red blood cell aggregability on arterial pressure and mesenteric microcirculation.

Intensified aggregability of red blood cells (RBC) was produced in adult white rats by the step-by-step intravascular administration of a high-molecular-weight dextran, with a molecular weight approximating that of blood fibrinogen. As a result, the systemic arterial pressure was elevated by more than one-third of the initial level, whereas the diameter of arterioles in the intestinal mesentery remained practically unchanged. This provided sufficient grounds for the conclusion that the increase in the total peripheral resistance was due to disturbances in blood rheological properties. Despite the elevated arterial pressure, the blood flow velocity in mesenteric arterioles displayed a clear-cut tendency to slow down. Simultaneously, a large number of RBC aggregates appeared in the mesenteric microvessels. In patients with a stable form of arterial hypertension the RBC aggregability index was found to be significantly increased as compared with that of the healthy control group. Following treatment with Ca(2+)- and beta-adrenergic blockers the index decreased significantly in parallel with the lowering of arterial pressure. The obtained results suggest that the intensified RBC aggregation in microvessels causing a disturbance of normal blood flow structure, and hence of blood rheological properties, might be an important factor responsible for the elevation of systemic arterial pressure in humans with arterial hypertension.

Animals↗
PubMed1992

Cerebral microcirculation: heterogeneity of pial arterial network controlling microcirculation of cerebral cortex.

Analysis of the functional behaviour of pial arterial ramifications feeding small areas of the cerebral cortex of rabbits uncovered well-defined heterogeneity of vascular responses during development of functional hyperemia. In the network of the smaller pial arteries, under 100 microns in diameter, the most active segments, the sphincters of offshoots of smaller arterial branches from larger trunks and the precortical arteries just before their penetration as the radial arteries into the cerebral cortex, have been discovered. The frequency of their dilatation was found to be higher, the latent periods of the vascular responses significantly shorter, and the degree of vasodilatation greater than of the adjacent arterial segments. An abundant amount of cholinergic nerve plexuses (containing the cholinesterase) was found in the walls of these active vascular segments, and microapplication of atropine resulted in a considerable decrease of their dilatation. These experimental results indicate the involvement of the cholinergic neurogenic mechanism in the functional vasodilatation, as distinct from the largely accepted effect of the humoral mechanism accomplished by diffusion of active vasodilatory substances from tissue elements to the walls of the feeding arterial branches.

Animals↗
PubMed1991

Dynamic structure of blood flow in microvessels.

The present article summarizes the author's perennial research on the flow of red blood cells in microvessels, the major determinant of rheological properties of blood in the microcirculation. Two main patterns of blood flow structure in microvessels, in the smallest arteries and veins and in the capillaries are described. The red cell concentration (hematocrit) in the blood flowing in microvessels undergoes regular alterations with changes of blood flow rate and vessel diameter in the microvascular beds. Further, the red blood cell concentration and flow velocity gradients are found in the cross-section of microvessels that should considerably affect the blood rheological properties in the microcirculation. In addition, radial displacements and blood velocity fluctuations of red cells in the flow are discovered in the larger microvessels during ischemic decrease of blood flow rate. The main factor disturbing the normal blood flow structure, and hence the normal rheological properties of blood, is the intravascular aggregation of red blood cells, which is to be diagnosed and eliminated in patients with blood rheological disturbances.

Erythrocyte Aggregation↗
PubMed1989

Mechanical properties of brain tissue related to oedema development in rabbits.

We studied the mechanical properties of the brain in anaesthetized rabbits by application of a standard external load to the exposed cerebral surface. The experimental model used allows one to eliminate potential circulatory factors. Brain oedema was produced by repeated episodes of ischaemia secondary to a decrease of the arterial blood pressure to zero. The development of brain oedema was assessed by an increase of the cerebral water content. In the course brain oedema development brain fluidity was found to steadily rise, while the brain compliance and the index of hysteresis decreased from the control value found at the onset of the experiment. Most important both, brain compliance and the index of hysteresis were already markedly elevated prior to the manifestation of brain oedema.

Animals↗