Search PubMed⌕ Search

Biomedical subjects

M I Timkina

Publications and source records attributed to M I Timkina.

At least 19 recordsLinked to original sources
PubMed2005

[A drop in "apparent" blood viscosity due to administration of high-molecular polymer capable of augmenting viscosity].

Influence of a high-molecular compound capable of augmenting viscosity, namely: polyethylene oxide Polyox WSR-301, on hemodynamic parameters in rat mesenteric microvessels was investigated. A substantial decrease in the arteriolar hemodynamic resistance caused by the polymer was revealed. Special research has shown that this reaction is not connected with a vasodilatation and, therefore, is caused by a reduction in the "apparent" viscosity of the blood, i.e., it is a consequence of changed properties of the blood flow.

Animals↗
PubMed2004

Microvessels of hamster buccal pouch under conditions of reduced systemic blood pressure.

Using implanted camera we studied hamster buccal pouch microvessels under conditions of reduced blood pressure. The correlation (R=0.30-0.85) between the diameter and pressure was observed in 42% vessels. During progressive decrease in blood pressure, R for the majority of left venules was below zero, while left arterioles had equal probability of having R<0 and R>0. For right venules the positive and negative correlations were equally probable, while right arterioles were predominantly characterized by R>0. Heterogeneous reactions in microvessels of different diameter were revealed.

Animals↗
PubMed2000

Myogenic tone and neurogenic vasoconstriction in microcirculatory bed of rat cerebral cortex.

The reaction of rat parietal cortical vessels to stimulation of the sympathetic ganglion was studied by intravital microscopy. stimulation induced constriction of cerebral arterioles. Clamping of one or both carotid arteries led to myogenic vasodilatation in the majority of cases. Constrictive response of brain arterioles to ganglion stimulation under conditions carotid occlusion did not differ from that under conditions of baseline cerebral blood supply.

Animals↗
PubMed1998

[Influence of polyethylene oxide Polyox WSR-301 on the pressure in mesenteric arterial microvessels in rats pre-adapted to anti-orthostatic states].

High-molecular polymers apt to directly influence flow microstructure were tested as a fundamentally new method for correcting microhemodynamics in microgravity. Pressure in the mesenteric arterial microvessels was measured two weeks in rats adapted to the head-down suspension. Intravenous polyethylene oxide (Polyox WSR-301, end-concentration in the order of 2.10(-7) g/ml), reduced the microvascular pressure by 26%, whereas in the control pressure was reduced by only 15%. Systemic arterial pressure showed an equal drop in the groups (by 10 to 11%). These results suggest that the biomechanical agent weakens resistance to the blood flow in the body region where blood supply is impaired by microgravity.

Adaptation, Psychological↗
PubMed1993

[Changes in the efficacy of vasoconstrictor stimuli in acute and chronic hypotension in the microcirculatory bed of rat skeletal muscle].

Microvascular diameters in m. extensor hallucis proprius of rats were measured by the image split method. The baseline diameters and responses to the electrical stimulation (20 Hz, 10 s) of the sympathetic tract were obtained in arterioles i. d. 7.8-88 microns. Measurements were made under baseline pressure into the right femoral artery, 1 min after local blood pressure drop (LBPD) produced by inflation of the cuff around descending aorta and in the rats with the chronic (1-2 months) regional hypotension (CRH) produced by implantation of a metal coil narrowing the aorta. Thirty five arterioles out of 45 showed reduction of responsiveness to sympathetic stimulation after LBPD (mean-19.1 +/- 2.1%), 6 arterioles reacted by insignificant enhancing of the constrictor responses and the reactions of 3 vessels were more pronounced (mean-21.1 +/- 9.1%). The responsiveness to sympathetic stimulation of the skeletal muscle arterioles i. d. 10-20 microns exposed to CRH did not differ from that in the sham-operated rats (11.6 +/- 1.3% vs 10.4 +/- 0.1%).

Acute Disease↗
PubMed1993

[A decrease in the hydrodynamic resistance in the mesenteric arterioles of rats injected with the polyethylene oxide Polyox WSR-301].

The infusion of polyethylene oxide in anesthetised rats in a total dose of 10(-7) g/ml caused a 10-16% reduction in blood pressure. This injection has been associated with 17% decreased pressure (servo-nulling method) and 54% increased blood velocity (laser Doppler fluxmetry) in mesenteric arterioles (d - about 24 mu), but no increase in their internal diameter was observed (image-split method). Vasodilatation (adenosine, 10(-5) M) did not change the hemodynamic response of the arterioles to polymer infusion. These results suggest that microdisturbances of blood flow which can be diminished by drug-reducing polymers are more important for the vascular resistance to blood than it has been previously.

Animals↗
PubMed1991

[A comparison of the efficiency of vasoconstricting effects in spontaneously hypertensive and normotensive rats under different perfusion conditions].

The in vivo biomicroscopy of the m. extensor hallucis proprius revealed thickening of the arterioles walls in spontaneously hypertensive rats (SHRs) as compared with normotensive ones. However, the constrictor responses of the arterioles to standard sympathetic stimulation were 35-50% lesser in the SHRs. The experiments with perfusion of the hind-part of the body revealed reduced responses in the SHRs as well. Therefore, the specifics of morphofunctional structure of the resistive vessels' walls hinders a considerable increase in constrictor responses in the RHRs at a reduced transmural pressure.

Animals↗
PubMed1987

[Wall thickness of skeletal muscle microvessels and their reactivity to vasoconstrictor stimuli in normal rats and rats with spontaneous hypertension].

Wall thickness (w), wall thickness to lumen radius ratio (w/r) and vasomotor reactions produced by electrical stimulation of the sympathetic tract were studied by intravital microscopy of the skeletal muscle (extensor hallucis proprius) and compared in normal Wistar rats (NWR) and spontaneously hypertensive rats (SHR). It was established that w and w/r of arterioles with an equal lumen was greater in SHR than in NWR. Sympathetic stimulation with 6 mA, 3 imp/sec for 10 sec produced an almost 50% reduced arteriolar constriction in SHR, as compared to NWR. Linear positive correlation was shown between w/r and the degree of the lumen narrowing in both groups of animals. A bias for the increase in arteriolar response to neurogenic stimuli was manifested after a drop in blood pressure due to an acute hemorrhage in SHR. It is suggested that high blood pressure in SHR ensures the perfusion of the microcirculatory bed with a constant blood volume and prevents arteriolar constriction.

Animals↗
PubMed1986

[Role of arteriolar heterogeneity on the development of the organ response of the vasculature of the skeletal muscles of the rat to constrictor stimuli].

A correlation was found between the initial relative thickness of vascular wall and the extent of vasoconstriction in response to standard stimulation of sympathetic strings. The distribution of vessels within the wall was comprised in mathematical model which estimated interrelationships among three variables: pressure perfusate expenditure and a conventional dose of vasoconstricting agent. The model revealed that intense vasoconstrictory responses entailed a decrease in the number of functioning vessels. When perfusing the rat hindlimbs with a constant expenditure in maximal vasoconstriction, the number of functioning microvessels decreased by 46 +/- 11.9%.

Animals↗
PubMed1985

[Effect of elevated systemic arterial pressure on neurogenic vasoconstriction in the microcirculatory bed of rat skeletal muscles].

Vasomotor reactions produced by electrical stimulation of the sympathetic tract were studied in anesthetized rats by intravital microscopy of the skeletal muscle (extensor hallucis proprius). Experiments were made in normal and elevated blood pressure. The stimulation itself did not change BP but led to an appreciable decrease in the initial diameter of the arterioles (28.6 +/- 1.4 m). The constriction amounted to 21%. The lumen decreased by 38.9%. Injection of felypressin (Sandoz) in a dose of 6 to 8 IU/100 g produced the pressor reaction. The 27.4% rise of BP during primary phase of the pressor response inhibited the development of the neurogenic vasoconstriction which was 11.5% for arteriolar diameter and 20.4% for lumen. The data suggest that inhibition of the neurogenic vasoconstriction is caused by an increase in arteriolar pressure. Consequently the elevation of intralumen pressure is considered as a protective mechanism of the drop of the tissue blood flow because of the sympathetic vasoconstriction.

Animals↗
PubMed1985

[Changes in the microcirculatory bed and tissue metabolism in chronic regional arterial hypotension].

Blood pressure was reduced in the hind part of rats by narrowing the aorta in regions distal to renal artery ostium. Resetting of microcirculatory bed (m. extensor hallicis propius) was revealed in arterial hypotension, characterized by resistance vessel dilatation ensuring the decrease in hydravlic resistance, thus facilitating blood supply and tissue metabolism normalization, irrespective of marked reduction in perfusion pressure.

Animals↗
PubMed1976

[Effect of bradykinin on the microcirculatory bed of the rat small intestine mesentery].

The effect of application and of intravenous injection of bradykinin on the rat mesenteric microcirculation was studied by direct microscopy methods in vivo. Electrophysiological experiments failed to reveal the reaction of the vascular smooth muscle cells to bradykinin. Under the same conditions the dynamics of vasomotions was studied by the image-splitter method. It appeared that the microvascular response to bradykinin application varied and primarily depended on whether the application was primary or repeated. It is suggested that the action of bradykinin on the mesenteric vessels was mediated through the other vasoactive agents.

Animals↗
PubMedDate not supplied

[The different vascular reactions of intact and ischemic brain to adrenergic exposures].

Electrical stimulation of the cervical sympathetic ganglion and norepinephrine increase the tonus of the cerebral vessels in intact animals. This points to the significant role of adrenergic mechanisms in regulation of blood circulation in the brain. Local ischemic affection of the brain removes the vasoconstrictor effects of stimulation of the cervical sympathetic ganglion and norepinephrine. Analysis by means of dihydroergotamine suggests that ischemia of the brain disturbs the property of alpha-adrenoceptors of the cerebral vessels to increase the tonus of the latter in response to adrenergic effects.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

[Effects of perftoran on experimental acute intestinal ischemia].

The studies were carried out on 76 albino noninbred male rats weighing 210-420 g. Ischemia of a jejunal segment was induced by applying a tourniquet to the base of a loop with the mesentery until the circulation fully stopped. Nonoxygenated perfluorane (an experimental group) or saline solution (a control group) was injected in a dose of 0.8-1.0 ml/100 g intraarterially 15 minutes before the termination of ischemia. During 90 min of reperfusion, there was a progressive decline of blood pressure (BP) with reference to the ischemic period by 39.8 +/- 20.9 and 20.8 +/- 14.6% in an experimental and control groups, respectively (p > 0.05). Biomicroscopy indicated that by min 5 of reperfusion, a relative reduction in the diameter (50-400 microns) of nutrient mesenteric arteries was half as large as that in the control group (24.0 +/- 5.5 and 45.1 +/- 3.6%; p < 0.05); by min 90, differences decreased (41.5 +/- 4.2 and 50.3 +/- 2.8%, respectively; p > or = 0.05). In the experimental group, perfluorane prevents the development of irreversible structural changes in the reperfusion period: the remaining cryptal epithelium is a source of regeneration of the integumentary epithelium of forming villi of the small intestinal mucosa.

Acute Disease↗
PubMedDate not supplied

[Pathogenesis of diffuse fecal peritonitis].

Mongrel albino rats were given intraperitoneal injections of blue pus bacillus endotoxin and human, rat, and guinea-pig fetal suspensions. Analysis of central and peripheral hemodynamics and the indices of the blood coagulation system showed that the severity of the animals' condition was determined by the degree of peripheral hemodynamic disorders associated with changes of the blood rheologic properties. Control of the presence of bacteremia in peritonitis showed that it is encountered both in severe intoxication (injection of human fecal suspension) and in a relatively favourable process (injection of rat fecal suspension). The shifts in the blood coagulation system were characterized by marked individual variability.

Animals↗