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Biomedical subjects

A V Priezzhev

Publications and source records attributed to A V Priezzhev.

11 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

Reduction of erythrocyte deformability in rats with cerebral ischemia.

Erythrocyte deformability was studied by laser interferometry in rats with cerebral ischemia. Ninety minutes after ligation of both common carotid arteries the erythrocyte deformability coefficient decreased by 11+/-2% in experimental group in comparison with the baseline level and by 12% in comparison with sham-operated animals and remained 16% decreased after 4 days.

Animals↗
PubMed1998

Clinical application of the measurement of spontaneous erythrocyte aggregation and disaggregation. A pilot study.

Aggregation and disaggregation kinetics of erythrocytes in samples of whole blood were studied using a backscattering nephelometry technique. Blood was drawn from normal subjects and from patients suffering from different diseases: chronic glomerulonephritis, systemic lupus erythematosus, hereditary hypercholesterolemia, pulmonary hypertension, intestinal tumors preoperatively (age > 60 years), psoriasis, psoriatic arthritis, ischemia and ischemia with diabetes. Blood samples of healthy donors were used as controls. The backscattering signal in the erythroaggregometer was processed according to algorithms yielding quantitative data on the full amplitude of aggregation, characteristic times of spontaneous aggregation, average hydrodynamic strength of all aggregates and, whenever possible, additionally, strength of the largest aggregates. The obtained results confirm that the complexity of erythrocyte aggregation kinetics requires multiparametric description which, when applied to clinical material, enables the differentiation of aggregation characteristics between diseases.

Biomarkers↗
PubMed1997

On refraction in Monte-Carlo simulations of light transport through biological tissues.

To obtain reliable results from Monte-Carlo simulations of light scattering experiments, a statistically accurate procedure for positioning the photons after refraction between two different scattering media is necessary. Two statistically equivalent algorithms for calculating the position of the photons immediately after crossing an interface are described and justified.

Algorithms↗
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↗
PubMedDate not supplied

Self-localization of laser induced tumour coagulation limited by heat diffusion through active tissue.

We analyse necrosis growth due to thermal coagulation induced by laser light absorption and limited by heat diffusion into the surrounding live tissue. The tissue is assumed to contain a tumour in the undamaged tissue where the blood perfusion rate does not change during the action. By contrast, normal tissue responds strongly to an increase in the tissue temperature and the blood perfusion rate can grow by tenfold. We study in detail necrosis formation under conditions typical of a real course of thermal therapy treatment. The duration of the treatment is about 5 minutes when a necrosis domain of about 1 cm or above is formed. In particular, if the tumour size is sufficiently large, i.e. it exceeds 1 cm, and the tissue response is not too delayed, i.e. the delay time does not exceed 1 min, then there are conditions under which the relative volume of the damaged normal tissue is small in comparison with the tumour volume after the tumour is totally coagulated.

Body Temperature↗
PubMedDate not supplied

[Study of kinetic parameters of singlet molecular oxygen in aqueous porphyrin solutions. Effect of detergents and the quencher sodium azide].

The kinetic parameters of porphyrin-photosensitized formation and deactivation of singlet molecular oxygen (1O2) and their dependence on the concentration of the 1O2 quencher sodium azide were investigated in air-saturated water, ethanol, and aqueous micellar solutions of detergents using time-resolved measurements of oxygen phosphorescence under pulsed laser excitation. The lifetimes of 1O2 formation and deactivation and the rate constants of 1O2 quenching by sodium azide were determined. It was shown that, with no azide in the solutions, the rise in phosphorescence intensity after the laser flash corresponded to the kinetics of energy transfer from the porphyrin triplet molecules to oxygen, while the decay kinetics corresponded to the kinetics of 1O2 deactivation. In the presence of detergent, a considerable increase in the 1O2 lifetime was observed, which is likely due to the localization of 1O2 molecules mostly in lipophilic micelles and not in the water phase. If relatively high azide concentrations were used, the lifetime of the porphyrin triplet state did not change but the 1O2 lifetime decreased to values similar to those in living cells. In this case, the inversion of the phosphorescence kinetic phases was observed. The rise corresponded to 1O2 deactivation, and the decay, to the energy transfer from triplet porphyrin to oxygen. The data suggest that, in living cells, 1O2 molecules are also located mainly in lipophilic structures and the 1O2 lifetime determines the kinetics of the phosphorescence rise after the laser pulse.

Detergents↗
PubMedDate not supplied

[Reduction of erythrocyte deformability in Krushinskiĭ-Molodkina rats in acute hemorrhagic cerebrovascular circulation disorders].

The ability of erythrocytes to change their shapes in the shear flow under acute strokes of hemorrhagic type in rats of the Krushinsky-Molodkina line was studied. The rigidity of membranes and the internal viscosity of erythrocytes were investigated by the laser diffraction method. The method consists in obtaining diffraction images from a thin layer of a dilute suspension of erythrocytes moving in the shear flow and subsequent computer processing of these images. It was shown that strokes of hemorrhagical type in rats of the Krushinsky-Molodkina line cause a reduction in the ability of erythrocytes to change theirs shapes.

Acoustic Stimulation↗
PubMedDate not supplied

[Mathematical model of protoplasm flow in a viscous-elastic active strand of a myxomycete plasmodium].

A mathematical model is plotted of protoplasmic flow in long strands of Myxomycete plasmodium. An analytical relationship was obtained between the characteristics of protoplasmic flow: amplitude and contour of velocity in the strand channel with the amplitude and wave length of pressure developed by contractile filaments of the strand cortical layer. The model permitted a comparison to be made between the experimental data of protoplasmic flow obtained by optical methods and the evidence on contractile apparatus obtained by tensiometric measurements. A conclusion is drawn on the consistency of the basic hypothesis concerning an autowave pattern of the motive force of the cortical layer filaments.

Elasticity↗