Biorheology - Volume 24, issue 1

Article Type: Editorial

DOI: 10.3233/BIR-1987-24111

Citation: Biorheology, vol. 24, no. 1, pp. I-III, 1987

Authors: Copley, Alfred L.

Article Type: Editorial

DOI: 10.3233/BIR-1987-24101

Citation: Biorheology, vol. 24, no. 1, pp. 1-1, 1987

Authors: Fukushima, T. | Homma, T. | Azuma, T. | Harakawa, K.

Article Type: Research Article

Abstract: Steady and pulsatile flow in a glass model simulating an arterial bifurcation was investigated by flow visualization techniques. Secondary flow generated at the bifurcation has a similar pattern to a vortex, called the horseshoe vortex, produced around a wall-based protuberance in a circular tube. The same flow disturbance was clearly observed during the decelerating phase of pulsatile flow. The vortex produces a stagnation point on the top and bottom wall just upstream from the bifurcation apex. When aluminium dust was suspended in the test fluid perfusing the blood vessel model, particles deposited over an area spreading from the stagnation point …to the lateral corners of the bifurcation. Comparison between the present results and topographical patterns of atherosclerosis reported in the literature suggests that it is in such low shear regions that lipid deposition tends to occur most. Show more

Keywords: pulsatile flow, secondary flow, flow separation, arterial bifurcation, particle deposition, atherosclerosis

DOI: 10.3233/BIR-1987-24102

Citation: Biorheology, vol. 24, no. 1, pp. 3-12, 1987

Authors: Schneditz, D. | Rainer, F. | Kenner, T.

Article Type: Research Article

Abstract: Red blood cell (REC) aggregation is known to be of deciding influence on erythrocyte sedimentation-rate (ESR) and on whole blood viscoelastic properties. The rheological behaviour of blood collected from a control-group with normal ESR is compared to the viscoelastic behaviour of blood collected from two groups with high to very high ESR, whose individuals are suffering from chronical polyarthritis and Morbus Bechterew, respectively. The rheological properties are evaluated by means of an oscillating-flow capillary-rheometer where the viscous (η ′ ) and elastic (η ″ ) component of the complex viscosity …(η ∗ ) is measured at a constant frequency of 2 Hz. Correcting for the varying hematocrit of the different blood samples according to an exponential equation, the viscoelastic data are found to be elevated in the groups with high ESR. For the viscous properties this is only due to the increase of the plasma viscosity. A correction for the plasma viscosity, however, shows that the viscous properties at low shear-rates (2s−1 ) are significantly reduced, whereas elastic properties in a range of medium shear-rates (10s−1 to 50s−1 ) are significantly increased (P < 0.001, t-test of Student). This result is discussed to be due to the high packing density of the RBC in fast sedimenting aggregates. High packing density reduces the effective volume of the REC but increases the stiffness of the aggregates. Show more

Keywords: erythrocyte-aggregation, erythrocyte sedimentation-rate, viscoelasticity

DOI: 10.3233/BIR-1987-24103

Citation: Biorheology, vol. 24, no. 1, pp. 13-22, 1987

Authors: Lerche, D. | Kozlov, M.M. | Markin, V.S.

Article Type: Research Article

Abstract: A biophysical model for the equilibrium curvature of a composite membrane element is derived taking into account the mechanical bilayer properties and the adjacent charged protein layers. The minimum of the total free energy density with respect to the curvature of such a membrane curved was estimated from the sum of the electrostatic free energy density of the charges of the membrane and the elastic surface energy density due to bending the lipid bilayer membrane. It was shown that the equilibrium curvature, i.e. the spontaneous curvature, of such a charged composite sandwich-like membrane depends inversely on the bending stiffness of …the lipid membrane itself and directly on the charge amount inside and outside the membrane to the second power. Furthermore the geometric and electrostatic structure of the protein layers and the physico-chemical environment conditions are involved. Corresponding to the model developed a “standard RBC” membrane element has a negative spontaneous curvature, accounting for a discocyte RBC shape. The shape change from a discocyte to a more stomatocytic shape (increase in the negative spontaneous curvature) after reducing the charges in the glycocalyx is also explained within this model. Show more

Keywords: RBC shape change, glycocalyx, cytoskeleton, free electrostatic and bending energy, spontaneous curvature

DOI: 10.3233/BIR-1987-24104

Citation: Biorheology, vol. 24, no. 1, pp. 23-34, 1987

Authors: Skalak, R. | Soslowsky, L. | Schmalzer, E. | Impelluso, T. | Chien, S.

Article Type: Research Article

Abstract: A theory is developed for the flow of suspensions of blood cells through filters in which the properties of the cells are defined by statistical distributions. It is shown that conditions are generally transient, and computational procedures are developed to compute the pressure drop and the fraction of the pores of the filter containing cells of various types as a function of time. The computations show a large influence of very small concentrations of stiff cells which gradually collect in the filter and effectively plug the filter during the time of a typical test. It is also shown that the …mean value of the resistance offered by a cell population with a limited distribution of resistances is more important than dispersion of resistances about the mean in determining the observable pressure curve. Experimental data are presented demonstrating that the drug pentoxifylline reduces the stiffness of leukocytes. Show more

Keywords: Filtration, Blood rheology, Erythrocytes, Leukocytes, Theoretical Modeling, Transient flow

DOI: 10.3233/BIR-1987-24105

Citation: Biorheology, vol. 24, no. 1, pp. 35-52, 1987

Authors: Singh, Megha | Joseph, K. Paul

Article Type: Research Article

Abstract: The erythrocytes sedimentation profiles (ESP) of normal blood and of blood mixed with saline, albumin (7%), and various molecular weight dextrans of different concentrations, at various height and widths of the sample holder are determined. These observations show that the sedimentation characteristics of the erythrocytes depend on the influence of these substitutes on the plasma and cellular constituents. The normalised aggregation and the sedimentation rate, as determined from these profiles, show that the dextran 40 and dextran 70 retard the erythrocytes sedimentation, for high molecular weight it is similar to that of normal blood and is the maximum for saline. …This change for high molecular weight dextrans could be attributed to the enhanced aggregation tendency of erythrocytes and for saline to the enhanced sedimentation due to decrease in the viscosity and density of suspending medium. The influence of the various concentrations of dextrans on these parameters has been determined. Show more

Keywords: Erythrocytes sedimentation profiles, transmitted laser intensity, dextrans, aggregation, sedimentation rate

DOI: 10.3233/BIR-1987-24106

Citation: Biorheology, vol. 24, no. 1, pp. 53-61, 1987

Authors: Crawford, Ralph G. | Moss, Richard D. | Gruemer, H.-D.

Article Type: Research Article

Abstract: A mathematical model was developed that describes the effects of filter plugging on flow through 3 μ m pore polycarbonate filters as a function of time, pressure, and cell concentration, both under stirring and nonstirring conditions. The mathematical constants for the model were derived from experimental data generated with a filtration apparatus, and were tested by using various concentrations of cells that are able to plug filter pores. A computer simulation program was written to test the model over a wide range of nonfilterable cell concentrations.

Keywords: Microsieving, plugging, Nuclepore filters, non-filterable cells

DOI: 10.3233/BIR-1987-24107

Citation: Biorheology, vol. 24, no. 1, pp. 63-76, 1987

Article Type: Announcement

DOI: 10.3233/BIR-1987-24108

Citation: Biorheology, vol. 24, no. 1, pp. 77-77, 1987

Article Type: Other

DOI: 10.3233/BIR-1987-24109

Citation: Biorheology, vol. 24, no. 1, pp. 79-84, 1987

Article Type: Other

DOI: 10.3233/BIR-1987-24110

Citation: Biorheology, vol. 24, no. 1, pp. 85-85, 1987