Biorheology - Volume 25, issue 6

Article Type: Editorial

DOI: 10.3233/BIR-1988-25612

Citation: Biorheology, vol. 25, no. 6, pp. I-III, 1988

Authors: Copley, Alfred L.

Article Type: Editorial

DOI: 10.3233/BIR-1988-25601

Citation: Biorheology, vol. 25, no. 6, pp. 823-825, 1988

Authors: Sourander, Patrick | Breimer, Lars H.

Article Type: Other

DOI: 10.3233/BIR-1988-25602

Citation: Biorheology, vol. 25, no. 6, pp. 827-832, 1988

Article Type: Other

DOI: 10.3233/BIR-1988-25603

Citation: Biorheology, vol. 25, no. 6, pp. 833-834, 1988

Authors: Holenstein, Rolf | Ku, David N.

Article Type: Research Article

Abstract: The arterial blood flow waveform is shown to change abruptly when passing from the thoracic aorta into the abdominal aorta in humans. Although this change has been accurately predicted by numerical solution of complicated pulse propagation equations, this paper demonstrates the ability of a simple lumped parameter model to explain this change in the waveforms using easily understood physical terms. The model correctly predicts changes in flow waveform under conditions of exercise and peripheral vascular disease. This analysis is useful in understanding abdominal artery physiology and explains the basis for clinical ultrasound Doppler examination of the legs.

Keywords: Pulsatile flow, aorta, capacitance, reverse flow, blood flow, human

DOI: 10.3233/BIR-1988-25604

Citation: Biorheology, vol. 25, no. 6, pp. 835-842, 1988

Authors: Kozlov, Michael M. | Lerche, Dietmar | Meier, Wolfgang

Article Type: Research Article

Abstract: Under conditions of high pressure difference micropipette aspiration experiments show a “pinch-off” phenomenon as observed by Rand (Mechanical properties of the red cell membrane: II. Viscoelastic breakdown of the membrane. Biophys. J. 4, 303–316, 1964). In a very recent paper, Meier et. al (Fission and refusion of red blood cells using a micropipette technique. Biorheology 24, 287–296, 1987) have reported about new data obtained with a modern electronic technique under moderate mechanical load. We have theoretically analysed the conditions necessary to form such a instability. In our approximations we have investigated the effective transmembrane pressure difference which is given both …by the true pressure drop, determined by the hydrodynamic flow through a small gap between the cell tongue and the pipette wall and the interaction between the tongue and the wall, as well as by the nonisotropic part of the membrane tension. When the membrane tongue is long enough (> 3Rp ) we have found a condition for the loss of membrane stability in a point where a minimum of the effective transmembrane pressure drop occurs. An expression for it and the vesicle size are given. Show more

Keywords: RBC, fission, fragmentation, membrane instability

DOI: 10.3233/BIR-1988-25605

Citation: Biorheology, vol. 25, no. 6, pp. 843-856, 1988

Authors: Hakim, T.S. | Macek, A.S.

Article Type: Research Article

Abstract: The contribution of erythrocyte deformability to the pulmonary vascular resistance during hypoxia indifferent animal species has not been examined. We hypothesized that the increase in pulmonary vascular resistance during hypoxia was partially due to erythrocytes (RBC’s) becoming less deformable during hypoxia, and therefore their transit in the capillaries becomes restricted. To test this, we measured an index of deformability of RBC’s from six animal species (dog, pig, cat, rabbit, hamster, rat) during normoxic and hypoxic condition, and compared the changes in deformability with the pulmonary hypoxic pressor response (HPR) which has been reported in the same species. Deformability was indexed …as the resistance that a Hemafil polycarbonate membrane (Nucleopore filter, 4.7 μ m pores) offers to a 10% suspension of RBC’s. The RBC suspension was either normoxic (PO2 = 150 torr) or hypoxic (PO2 = 50 torr). We found that hypoxia decreased RBC deformability; the largest decrease occurred in rat RBC’s, a small but significant decrease was observed in the RBC’s of cats, rabbits and hamsters, but no change was detected in RBC’s of dogs or pigs. In general, such changes in deformability do not correlate well with the HPR in intact or in isolated lungs, for example the pig, had the largest HPR but the smallest change in RBC deformability. In some species, however, there was a positive correlation between RBC deformability and HPR, for example rats, rabbits and cats are usually better responders than dogs and hamsters, similarly the deformability of RBC’s in rats, rabbits and cats were also more influenced by hypoxia than RBC’ s from dogs. The limiting factors in this relationship are the artificial conditions which were used to measure deformability and HPR, both may be different than in the intact conditions. Nevertheless the present data show that erythrocytes of some species can become less flexible during hypoxia, and hence may impede the transit in the capillaries. Therefore we propose that the hypoxic pressor response in the pulmonary vasculature may be partly due to smooth muscle contraction (vasoconstriction) and partly due to a decrease in erythrocyte deformability (capillary obstruction). Both components are likely to be species dependent. Show more

Keywords: Erythrocyte deformability, hypoxia, pulmonary vascular resistance

DOI: 10.3233/BIR-1988-25606

Citation: Biorheology, vol. 25, no. 6, pp. 857-868, 1988

Authors: Takamizawa, Keiichi | Hayashi, Kozaburo | Nakamura, Takao | Kato, Tadashi | Tsushima, Nobuko

Article Type: Research Article

Abstract: In the cholesterol-fed rabbits, we observed that the whole blood viscosity was maintained at the normal level in spite of the decrease in hematocrit. This phenomenon suggests that there exists some visco-regulatory mechanism, and we could simulate it by a simple integration type model.

Keywords: Whole Blood Viscosity, Hematocrit, Visco regulation, Cholesterol-fed Rabbits

DOI: 10.3233/BIR-1988-25607

Citation: Biorheology, vol. 25, no. 6, pp. 869-877, 1988

Authors: Rudraiah, N. | Vortmeyer, D. | Veena, B.H.

Article Type: Research Article

Abstract: The influence of electric field on unsteady convective diffusion in couple stress flow is studied using a time, dependent dispersion model. The electric field, arising as a body couple in the governing equations, is shown to increase the axial dispersion coefficient. This is useful in the control of haemolysis caused by artificial organs implanted or extracorporeal. The contribution of pure convection in the dispersion of concentration is singled out and investigated in detail. The results obtained are compared with those in the absence of electric field and some important conclusions are drawn.

Keywords: Haemolysis, Electric field, Dispersion, Biomechanics

DOI: 10.3233/BIR-1988-25608

Citation: Biorheology, vol. 25, no. 6, pp. 879-890, 1988

Article Type: Announcement

DOI: 10.3233/BIR-1988-25609

Citation: Biorheology, vol. 25, no. 6, pp. 891-891, 1988