PubMed Health⌕ Search

Biomedical subjects

N Ohshima

Publications and source records attributed to N Ohshima.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effects of pentoxifylline and prostaglandin E1 on cold blood perfusion studied by red blood cell deformability.

The effects of pentoxifylline and prostaglandin E1 (PGE1) on red blood cell deformability during cold blood perfusion were studied by means of a filtration method. The deformability of normal red blood cells decreased with the temperature transition from 20 degrees to 15 degrees C (transit time: 3.5, 5.8, 25, and 99 seconds at 37 degrees, 20 degrees, 15 degrees, and 10 degrees C respectively). The effects of both pentoxifylline and PGE1 were not noticeable at 37 degrees C but became significant with hypothermia (5.0, 12, and 48 seconds at 20 degrees, 15 degrees, and 10 degrees C, respectively, in samples with pentoxifylline of 0.3 mg/ml; 5.3, 13, and 46 seconds at 20 degrees, 15 degrees, and 10 degrees C, respectively, in those with PGE1 of 40 ng/ml). The results in this study suggest that pretreatment of blood by pentoxifylline or PGE1 could improve coronary microcirculation perfused with cold blood cardioplegic solutions owing to significant improvement of the deformability of red blood cells.

Alprostadil↗
PubMed1986

Hemodynamics at stenoses formed by growing platelet thrombi in mesenteric microvasculature of rat.

Quantitative analyses of the dynamics of stenosis development were expressed in terms of the time course for changes in blood flow velocity in a stenosed region and thrombus configuration in the microvasculature of rat mesentery. The platelet thrombus was induced in microvessels by irradiation of filtered light in combination with intravascular administration of fluorescent dye. The blood flow velocity began to increase soon after the initiation of thrombus formation and continued to increase progressively with the growth of the thrombus in the radial direction. After the velocity reached an almost constant level, the velocity fluctuation became significant due to the frequent detachment of platelet aggregates. Meanwhile, the blood flow velocity precipitously dropped. Two different definitions of a critical stenosis were proposed. The first definition was the condition that the blood flow velocity reached a maximum. The critical area stenosis based on this definition had almost a constant value, i.e., 75-95% of the lumen area. The second definition of critical stenosis was given as the condition that the blood flow rate decreased by more than 15%. In the higher velocity range the values of critical stenosis based on the second definition were almost constant, i.e., 70-90% of the lumen area. However, in the lower velocity range, the critical condition seemed to occur in smaller stenosis.

Animals↗
PubMed1985

Relationship between mechanical and hydrodynamic properties of bioprosthesis produced from canine aortic valve.

Static tensile, stress relaxation, and hydrodynamic tests were carried out to investigate the relationships between the mechanical deformation or stiffness of heart valve leaflets and the opening behavior of bioprosthetic valves. The specimens used were fresh and glutaraldehyde (GA)-treated canine aortic valves. The tensile strength depended on the fiber orientation in the leaflet. The deformability of fresh and 0.05% GA-treated tissues was significantly larger than that induced by 0.1-5.0% GA concentrations according to the stress-strain curves. The stress relaxation function, which expresses the viscoelastic property, did not show significant differences in the 0.05-5.0% range of GA concentrations. In the hydrodynamic tests, the opening resistance of fresh and 0.05% GA-treated valves was less than that of 0.1-5.0% GA-treated valves. Thus, it was shown that the hydrodynamic valve functions were closely related to the material properties of aortic valve leaflets.

Animals↗
PubMed1984

Platelet thrombus induced in vivo by filtered light and fluorescent dye in mesenteric microvessels of the rat.

Intravascular platelet aggregation and subsequent thrombus formation were produced in the microvasculature by irradiation using filtered light from a mercury lamp in combination with the intravascular administration of a fluorescent dye. The effects of several factors, such as light intensity, dye concentration, and vessel diameter were examined in venules and arterioles of the rat mesentery with respect to the time required for the initiation of thrombus formation; the time to totally occlude the lumen; and the volume of the thrombus formed. It was found that the combined conditions of light intensity and dye concentration at specific values had a critical effect on the rate of platelet aggregation. In the arterioles and venules examined, the thrombus formation time was prolonged as a function of increasing vessel diameter. The time required for the initiation of thrombus formation and complete occlusion of the vessel lumen was greater in arterioles than in venules. This result may suggest the dependence of the kinetics of intravascular thrombus formation on blood flow conditions.

Animals↗
PubMed1981

Effect of pentoxifylline on microvascular blood flow velocity.

Pentoxifylline (PF), known to increase red blood cell (RBC) deformability, has recently attracted much attention because of its possible effect of reducing capillary resistance. There has been practically no reliable demonstration of an increase in capillary blood flow by this drug. This study was intended to examine the effect of PF and hence deformability changes on microvascular hemodynamics and the rheological mechanisms underlying such an effect. Mesentery microvessels of 15 rats were subjected to intravital microscopic observation under transillumination. Capillary blood flow was measured using a newly developed 2-channel sample-hold scanner incorporated into a video display system. Changes in whole blood viscosity were also measured in order to investigate hemorheological changes. It was found that a significant increase in capillary blood flow (as much as 140%) was brought about by PF administration. The increase in blood flow was particularly remarkable in capillaries of about 13 microns in diameter, while whole blood viscosity measured in vitro showed a reduction of 40% at most. In view of these results and the reported effect of PF on increasing the RBC deformability, increased capillary blood flow can be attributed to the increased RBC deformability.

Animals↗