[Effects of tumor necrosis factor on the tonus of cerebral arteries]. / Vliianie tumornekrotiziruiushchego faktora na tonus arterii golovnogo mozga.

It was determined that tumor necrosis factor (TNF) is capable of decreasing the local brain's blood flow on 45.6% (in the concentration of 6 micrograms/kg); to make a spasm of the pial arteries on 39.6%. In vitro experiments TNF increased the amplitude of the rhythmical and the tonic contractions of the brain's arteries smooth muscles (3.6 X 10(-8) M). The direct action of the TNF in the vascular wall is endothelium-dependent.

[Velocity profiles in the microvessels dependent on the velocity and concentration of erythrocytes]. / Profil' skorostei v mikrososudakh v zavisimosti ot skorosti dvizheniia i kontsentratsii éritrotsitov.

Distribution of velocities of erythrocytes dependent upon their distance from the vascular axis were studied in 25-40 mu large microvessels of the frog mesentery. The method of in vivo cinemicrography with subsequent analysis revealed that with a mean axial velocity of blood flow higher than 0.3-0.4 mm/sec the velocity profile was parabolic, similar to the laminar flow of Newtonian fluids and independent of the erythrocytes concentration in microvessels. With velocities less than 0.3-0.4 mm/sec a chaotic distribution of erythrocytes velocities occurred and the parabolic form of the velocity profiles was rarely observed;--actually only at low erythrocyte concentration (less than 10-11%) in microvessels. The results suggest that an increase in vascular resistance to blood flow must appear during a considerable slow-down of blood flow velocity in microvessels.

[In vivo study of erythrocyte orientation in microvessels and the effect of different factors on it]. / Prizhiznennye issledovaniia orientatsii éritrotsitov v mikrososudakh i vliianiia na nee razlichnykh faktorov.

The orientation of erythrocytes in frogs' mesenteric microvessels (25--35 micrometer) depends on the following factors: a) linear velocity of erythrocytes, b) their concentration in the blood strain and c) character of the stream--its uniformity as well as presence of accelerations. At the velocity of red cells below 0.3 mm/sec the orientation of erythrocytes is essentially perpendicular to the vascular walls and readily affected by the stream character. The erythrocyte orientation becomes parallel to the stream direction and is not influenced by its character when the red cell velocity is over 0.3--0.4 mm/sec.