Biorheology - Volume 7, issue 4

Authors: Ahuja, Avtar S. | Bugliarello, George

Article Type: Research Article

Abstract: The limited literature on the compressibility of blood and of the erythrocyte is reviewed. A disagreement is noted between the experimental values of compressibility obtained by direct measurements of pressure-volume changes and by those obtained by measurements of the velocity of sound propagation in blood.

DOI: 10.3233/BIR-1971-7401

Citation: Biorheology, vol. 7, no. 4, pp. 199-203, 1971

Authors: Whelan, James A. | Huang, Ching-Rong | Copley, Alfred L.

Article Type: Research Article

Abstract: An apparatus and method were devised for measuring the concentration profile of erythrocytes settling in whole blood. Experiments were made with this technique on the blood of five human donors and the results of the concentration profiles are presented. At the early stages of sedimentation, a linear relationship was found to exist between the location of the interface and the time. Wall effects were found to be negligible in the settling tubes of 0.62 cm diameter, used in these studies. An unexpected finding was an initial sharp drop of the interface concentration within the first hour of sedimentation. The occurrence …of this phenomenon emphasizes that the diffusion of erythrocytes plays a significant role in their sedimentation. Show more

DOI: 10.3233/BIR-1971-7402

Citation: Biorheology, vol. 7, no. 4, pp. 205-212, 1971

Authors: Cerny, Lawrence C.

Article Type: Research Article

Abstract: A model for the erythrocyte is proposed based upon the Ovals of Cassini. Calculations of the volume, surface area and “sphericity index” are given for this model. In order to evaluate drag coefficients, inverse prolate and inverse oblate spheroidal coordinates were used.

DOI: 10.3233/BIR-1971-7403

Citation: Biorheology, vol. 7, no. 4, pp. 213-220, 1971

Authors: Greene, Howard L. | Nokes, Richard F. | Thomas, Lindon C.

Article Type: Letter

DOI: 10.3233/BIR-1971-7404

Citation: Biorheology, vol. 7, no. 4, pp. 221-223, 1971

Authors: Copley, A.L. | Scott Blair, G.W.

Article Type: Introduction

DOI: 10.3233/BIR-1971-7405

Citation: Biorheology, vol. 7, no. 4, pp. 225-225, 1971

Authors: Schmid-Schönbein, H. | Wells, R.E. | Goldstone, J.

Article Type: Research Article

Abstract: A number of well established peculiarities of erythrocytes in flow (e.g. cell deformation, cell aggregation, diapedesis of cells) have recently been related to the equally well known “anomalous viscosity” of whole blood. By applying microrheological techniques, the relevance of the above mentioned phenomena to blood flow has been studied. It has been shown that the erythrocyte can act either as the basic unit of a three dimensional structure of rouleaux which greatly inhibit flow, or like a fluid drop thereby fully participating in the flow. Cell fluidity depends both on having a flexible membrane and liquid in the cell …interior. Membrane flexion is greatly helped by the surplus surface area the erythrocyte possesses compared to that of an isovolaemic sphere. The biconcave resting shape is also a consequence of this surplus: it should be noted, however, that under most flow conditions the red cell is being continuously deformed into a variety of shapes. In bulk blood flow, the membrane is continuously rotating around the cell content, the shear stresses are transmitted into the cell interior and the cell behaves much like a fluid drop. Cell fluidity can disappear either because the internal content becomes abnormally viscous or when the membrane becomes much stiffer. This is signalled by deviations from the normal biconcave shape such as occur in structural membrane defects or in unstable hemoglobins. Cell fluidity can also functionally disappear when the erythrocytes are immobilized into rouleaux or agglutinates of as few as two cells. Under all these conditions, the cells offer a much higher resistance to flow, especially in the restricted channels of the microcirculation. The cells then behave as solid particles and they can only pass channels larger than their resting diameter; any smaller pore is likely to trap the cell, leading to prolonged stagnation and eventual lysis. Show more

DOI: 10.3233/BIR-1971-7406

Citation: Biorheology, vol. 7, no. 4, pp. 227-234, 1971

Authors: Goldsmith, H.L.

Article Type: Research Article

Abstract: The flow behavior of single human red cells and rouleaux in plasma has been compared with that in viscous isotonic Ficoll and Dextran solutions, and in concentrated suspensions of reconstituted biconcave ghost cells. In the absence of particle interactions, marked deformation of red cells was not evident in plasma at shear stresses of 3 dyne cm−2 , even though the cells migrated inwards from the tube wall, a property of deformable particles such as previously observed with liquid droplets. In viscous media at shear stresses above 5 dyne cm−2 , the cells were deformed into ellipsoid-like structures but with the …dimple still present. In contrast, at volume concentrations above 30 per cent in plasma, deformation of erythrocytes and rouleaux was observed at shear stresses as low as 0.07 dyne cm−2 . This effect is due to crowding of the particles. Show more

DOI: 10.3233/BIR-1971-7407

Citation: Biorheology, vol. 7, no. 4, pp. 235-242, 1971