Biorheology - Volume 22, issue 1

Article Type: Editorial

DOI: 10.3233/BIR-1985-22108

Citation: Biorheology, vol. 22, no. 1, pp. I-III, 1985

Authors: Sugihara, Masako

Article Type: Research Article

Abstract: The motion and deformation of a single red blood cell in a simple shear flow between two parallel walls is studied theoretically. A two-dimensional deformable microcapsule is adopted as a model for the cell, which has a thin moving membrane, like a tank-tread, around the interior and is deformed into an elliptical shape with a constant area. Applying the finite element method to the Stokes equations, the tank-tread motion and deformation is determined in a stationary motion, under fluid dynamic interaction between the cell and the walls. It is shown that the motion and deformation of the microcapsule crucially …depends on the channel width between the two walls. As the width decreases, the microcapsule is more elongated and the frequency of tank-tread motion decreases at a constant shear rate. In addition, the angle of inclination decreases at the low range of the viscosity ratio of internal to external fluids and increases at the high range. The results obtained are compared with experimental observations and applied to the behavior of cells under mutual interaction. Show more

Keywords: deformability, red blood cell, shear flow, stationary motion, tank-tread motion, wall effect

DOI: 10.3233/BIR-1985-22101

Citation: Biorheology, vol. 22, no. 1, pp. 1-19, 1985

Authors: Schmukler, Robert | Chien, Shu

Article Type: Research Article

Abstract: A newly designed capillary deoxygenator has been constructed by using microporous polypropylene hollow fibers sealed into an airtight plexiglass housing. Oxygenated red cell suspensions and hemoglobin solutions flowing through the hollow fibers were subjected to deoxygenation with a gas mixture composed of 95 percent N2 and 5 percent CO2 passed through the housing. At a given flow rate of the oxygenated fluid, the outgoing fluid pO2 varied directly with hematocrit and inversely with the residence time. With a deoxygenator composed of 144 parallel 100-μ m fibers with an active length of 10 em, 2 ml of blood …at 10 percent hematocrit can be converted from arterial to venous pO2 in approximately 1 min. The design of this deoxygenator provides a method for rapid deoxygenation of blood without red cell membrane damage or hemolysis. Show more

Keywords: Deoxygenation, Erythrocytes, Hemoglobin

DOI: 10.3233/BIR-1985-22102

Citation: Biorheology, vol. 22, no. 1, pp. 21-29, 1985

Authors: Bitbol, M. | Quemada, D.

Article Type: Research Article

Abstract: We present two phenomenological models describing the flowing erythrocyte orientation rate. The first concerns the onset of a stable orientation in a very dilute erythrocyte suspension. It is based on a simple formula for erythrocyte elongation as a function of shear stress, and we assume that beyond a threshold of elongation, erythrocytes take on a stable orientation, while below this threshold, they have a flipping motion. We extend this model to high hematocrit values assuming that the effect of red cell collisions imposes a random moment to each erythrocyte, shifting it from its stable orientation. We obtain an approximate expression …for erythrocyte orientation rate as a function of shear rate and then we compare these results to our experimental data in part III of this series. Show more

Keywords: Models, erythrocyte orientation

DOI: 10.3233/BIR-1985-22103

Citation: Biorheology, vol. 22, no. 1, pp. 31-42, 1985

Authors: Bitbol, M. | Leterrier, F. | Dufaux, J. | Quemada, D.

Article Type: Research Article

Abstract: The measurements of erythrocyte orientation, obtained through a spin labeling technique, are compared with a phenomenological model. Several rheological conditions are varied: hematocrit, suspending medium viscosity, blood age, artificial reversible aggregation. We found that the onset of orientation is very sensitive to any variation of these conditions, and that its measurement would be a good method to assess erythrocyte deformability. A critical shear rate for the orientation process is then determined and compared to the corresponding parameter obtained from viscosity measurements of identical suspensions. A close qualitative relationship is found between the two sets of values of the critical shear …rate. Show more

Keywords: Erythrocyte orientation, blood ageing, aggregation, rheological parameters

DOI: 10.3233/BIR-1985-22104

Citation: Biorheology, vol. 22, no. 1, pp. 43-53, 1985

Authors: Delouche, A. | Dimicoli, J.L. | Péronneau, P.

Article Type: Research Article

Abstract: Velocity profiles obtained with atheromatous and normal bifurcation castings in the presence of various types of flows are proposed. In the atheromatous bifurcation, with steady flow, we observe radial positive or negative velocities at distance to the wall smaller than 1 mm, which may be attributed to small local eddy motions. The maximum of velocity needs a larger distance from the apex than in the case of the “normal” bifurcation to be again located on the axes. With periodical flows, the effects are strongly damped. The wall velocity gradients on several geometries of tubings are investigated to separate the …effects of the local rugosity of the wall from those incidental to the geometry of the bifurcation. The alterations caused by the atheroma do not seem to be induced by local modifications or rugosity, but by slow modifications of the local diameter. As a consequence, the variations of the velocity gradient caused by atheroma in the total bifurcation, are more likely due to distance effects of the geometry itself than to local effects of rugosity. Show more

Keywords: Atheroma, Bifurcation, Casting, Gradient, Rugosity, Velocity

DOI: 10.3233/BIR-1985-22105

Citation: Biorheology, vol. 22, no. 1, pp. 55-71, 1985

Authors: Nash, Gerard B. | Meiselman, Herbert J.

Article Type: Research Article

Abstract: The membrane shear elastic modulus (μ ) and the time constant for extensional shape recovery (tc) were measured for normal, control human red blood cells (RBC) and for RBC heat treated (HT) at 48°C. Three separate methods for the measurement of μ were compared (two used a micropipette and one employed a flow channel), and the membrane viscosity (n) was calculated from the relation n=μ .tc. The deformability of HT and control cells was evaluated using micropipette techniques, and the bulk viscosity of RBC suspensions at 40% hematocrit was measured. The shear elastic modulus, or “membrane rigidity”, was more …than doubled by heat treatment, although both the absolute value for μ and the estimate of the increase induced by heat treatment varied depending on the method of measurement. Heat treatment caused smaller increases in membrane viscosity and in membrane bending resistance, and only minimal changes in cell geometry. The deformability of HT cells was reduced: 1) the pressure required for cell entry (Pe) into 3μ m pipettes was increased, on average, by 170%; 2) at an aspiration pressure (Pa) exceeding Pe, longer times were required for cell entry into the same pipettes. However, when Pa was scaled relative to the mean entry pressure for a given sample (i.e, Pa/Pe), entry times were similar for control and HT cells. Bulk viscosity of HT RBC suspensions was elevated by approximately 12% on average (shear rates 75 to 1500 inverse seconds). These findings suggest that alteration of RBC membrane mechanical properties, similar to those induced by heat treatment, would most affect the in vivo circulation in regions where vessel dimensions are smaller than cellular diameters. Show more

Keywords: Erythrocytes Analysis, Membrane Viscoelasticity, Blood Rheology

DOI: 10.3233/BIR-1985-22106

Citation: Biorheology, vol. 22, no. 1, pp. 73-84, 1985

Article Type: Announcement

DOI: 10.3233/BIR-1985-22107

Citation: Biorheology, vol. 22, no. 1, pp. 85-85, 1985