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Biomedical subjects

R F Tuma

Publications and source records attributed to R F Tuma.

52 records · Page 3Linked to original sources
PubMed1977

Factors influencing leukocyte adherence in microvessels.

In vivo studies of the microcirculation of an untraumatized and unanesthetized animal preparation has shown that leukocyte adherence to vascular endothelium is an extremely rare occurrence. Induction of leukocyte adherence can be produced in a variety of ways including direct trauma to the vessels, remote tissue injury via laser irradiation, and denuding the epithelium overlying the observed vessels. The role of blood flow and local hemodynamics on the leukocyte adherence process is quite complex and still not fully understood. From the results reported it may be concluded that blood flow stasis will not produce leukocyte adherence but will augment pre-existing adherence. Studies using 2 quantitative measures of adherence, leukocyte flux and leukocyte velocity have shown these parameters to be affected differently by local hemodynamics. Initial adherence appears to be critically dependent on the magnitude of the blood shear stress at the vessel wall as evidenced by the lack of observable leukocyte flux above some threshold value. Subsequent behavior of the leukocytes as characterized by their average rolling velocity shows no apparent relationship to shear stress but, for low velocities, may be related to the linear blood velocity.

Cell Adhesion↗
PubMed1977

Comparison of arteriolar blood flow in the hamster cheek pouch at two different oxygen tensions.

Red cell velocity and diameter were measured in arterioles of the hamster cheek pouch microvasculature. The cheek pouch tissue was exposed to two different oxygen tensions, PO2 less than 30 mmHg and PO2 greater than 150 mmHg. Blood flow was calculated from velocity and diameter measurements and was found to be significantly reduced (44%) when cheek pouch was exposed to room oxygen superfusant. This reduction was the combined result of a significant decrease in both diameter (17%) and red cell velocity (17%) as compared to the measurements during the initial low oxygen period.

Animals↗
PubMed1977

Relationship between microvascular blood velocity and pressure distribution.

Red blood cell velocity and diameter were measured in vessels of the wing of the unanesthetized bat (Myotis lucifugus) from the supplying artery to the capillaries. These data were used to determine the manner in which velocity, shear rate, volume flow, and blood pressure depend on the vessel's hierarchical position within the vascular network. The results show that velocity decreases in an almost linear fashion as the capillary is approached but that the shear rate increases as one progresses distally from the supplying artery. Blood volume flow was found to decrease as an exponential function of the branching order. Comparison with available date in some animal species, including man, indicates some agreement in capillary velocity, although significantly lower values have been reported in some preparations. Using a method whereby blood pressure distribution could be obtained from anatomical data and center-line blood velocity, the rheologic alterations accompanying consecutive vessel branching were deduced and found to be in good agreement with data available in the literature.

Animals↗
PubMed1977

Dependence of reactive hyperemia in skeletal muscle on oxygen tension.

Red blood cell velocity was measured in capillaries of the rabbit tenuissimus muscle during exposure to a low-oxygen-tension (PO2 = 5 mmHg) and a high-oxygen-tension (room-air PO2 = 150 mmHg) suffusion solution. Control capillary red blood cell velocity was significantly reduced (44%) by elevating the suffusion solution PO2 from 5 to 150 mmHg. The reactive hyperemias that occurred after a 120-s aortic occlusion under these two conditions were compared. The mean RBC velocity during the hyperemia in the 1st min following the removal of occlusion was significantly reduced by increasing oxygen tension, as was the duration of the hyperemia. Peak capillary red blood cell velocities in the hyperemic phase during exposures to low and high PO2 were not significantly different. It can be concluded from this study that although oxygen tension does affect postocclusive reactive hyperemia, other factors such as myogenically induced vascular relaxation also contribute to the production of this phenomenon.

Animals↗
PubMedDate not supplied

The effect of intravenous lidoflazine on serotonin-induced cerebral vascular contraction--an in vivo study.

Lidoflazine, a piperazine derivative with known selectivity for vascular smooth muscle, was evaluated as a possible agent for prophylaxis of cerebral vascular contraction induced by subarachnoid perfusion with serotonin. The animals treated with serotonin (5 X 10(-6) M), had a 60% reduction in the diameter of basilar artery but when pretreated with Lidoflazine (1 mg/kg) intravenously, only had a 20% reduction in diameter (p less than 0.01). Lidoflazine, when administered intravenously at a slow rate will not adversely lower systemic blood pressure and can prevent the contraction of cerebral vessels when the stimulus for contraction is in the subarachnoid space.

Animals↗