Biorheology - Volume 24, issue 3

Article Type: Editorial

DOI: 10.3233/BIR-1987-24309

Citation: Biorheology, vol. 24, no. 3, pp. I-III, 1987

Authors: Copley, Alfred L.

Article Type: Editorial

DOI: 10.3233/BIR-1987-24301

Citation: Biorheology, vol. 24, no. 3, pp. 285-286, 1987

Authors: Meier, Wolfgang | Lerche, Dietmar | Wendt, Max-Otto | Paulitschke, Manrico

Article Type: Research Article

Abstract: In micropipette experiments with small capillaries and moderate high pressure difference (≈1000 Pa) cell fragmentation (fission) of human red blood cells without hemolysis was observed by TV-system for a large number of fresh red blood cells of different donors. After separation, the fragment moves away from the residual cell. In seven cases this process was evaluated quantitatively and was shown that the rate of the fragment was constant in time. Two mechanisms for this phenomenon are discussed. In particular cases a spontaneous re-fusion with the residual cell body in the capillary can be observed. In our opinion probably protein-depleted …membrane surfaces arise and membrane fusion is possible simply by mechanical contact without additional electric fields and/or fusion agents. Show more

Keywords: RBC, fission, refusion, cell fragmentation

DOI: 10.3233/BIR-1987-24302

Citation: Biorheology, vol. 24, no. 3, pp. 287-296, 1987

Authors: More, R.B. | Thurston, G.B.

Article Type: Research Article

Abstract: The intrinsic viscoelasticity of erythrocyte suspensions holds great potential for specifying the deformability of the individual, noninteracting cells in an oscillatory shear flow field. In order to extrapolate to zero cell concentration, the complex viscoelastic modulus was measured as a function of hematocrit using 2 Hertz oscillatory flow and a shear rate of 10/sec. This was done for both normal cells and cells with severely reduced deformability when hardened with gluteraldehyde. Suspension media were blood plasma, isotonic saline, and Dextran solutions. The real parts of the complex intrinsic viscoelasticities were obtained by an extrapolation using a regression fit to Huggins’ …equation. For normal cells in native plasma the values ranged from 1.7 to 2, increasing to the range 2.4 to 3.1 when the plasma was diluted with isotonic saline solution. For hardened cells the value obtained was near 3.5. These results are compared with theories for suspensions of both rigid and deformable particles. Several theories for deformable particles predict an increase in intrinsic viscoelasticity with increases in the ratio of the viscosity of the interior of the particle to that of the suspending medium. This ratio controls the balance between rotational and deformational response of the cell in the flow field. The trends of these theories were observed in the measurements. Show more

Keywords: Blood Viscoelasticity, Intrinsic Viscosity, Deformability, Erythrocyte, Hematocrit

DOI: 10.3233/BIR-1987-24303

Citation: Biorheology, vol. 24, no. 3, pp. 297-309, 1987

Authors: Koyama, T. | Araiso, T. | Nitta, J.

Article Type: Research Article

Abstract: The dynamics of membrane microstructure was studied as molecular motions of phospholipids for bullfrog erythrocyte ghosts by the DPH fluorescence depolarization technique with a nanosecond fluorometer. The bullfrog erythrocyte ghosts were obtained by hypotonic lysis and collagenase treatment. The constituents of membrane proteins were confirmed by the disk gel electrophoresis. The viscosity of erythrocyte membrane ghosts was estimated to be 3.3±1.0 at 10°C, 2.1±0.1 at 20°C and 1.3±0.2 at 30°C in the unit of poise and the wobbling angle of lipid molecule was 35±1, 41±1 and 43±1 degree at the respective temperatures on an average and ±S.D. The …viscosity is lower than that of human erythrocytes. The relatively low viscous phospholipid bilayer may be one of the factors for the deform ability of bullfrog erythrocytes. Show more

Keywords: bullfrog erythrocyte, membrane viscosity, wobbling angle of phospholipid, temperature, electrophoresis, fluorescence depolarization

DOI: 10.3233/BIR-1987-24304

Citation: Biorheology, vol. 24, no. 3, pp. 311-317, 1987

Authors: Papenfuss, Heinz D. | Gross, Joseph F.

Article Type: Research Article

Abstract: A theoretical model of transvascular exchange of fluid ana plasma proteins in the microcirculation is developed based on fundamental laws of the fluid mechanics and on phenomenological transport equations of the irreversible thermodynamics. Intravascular axial changes of the pressure, flow and plasma protein concentration are taken into account as well as axial gradients of vascular permeability. Proper nondimensionalization of the resulting equations leads to the identification of dimensionless parameters which combine the transport characteristics of the endothelial wall and the intravascular flow resistance. In the theory, the dependence of the reflection coefficient on the transport coefficients of the vascular wall …and on the plasma protein concentration is established. The model is applied to the cat mesentery and the rat intestinal muscle. The numerical simulations indicate that taking into account vascular protein permeability yields considerable differences in the axial distribution of the plasma protein concentration and transvascular fluxes in comparison with the case of protein impermeability of the endothelial wall. The results show that the maximum of the transvascular fluid and plasma protein movement resides at the site of the small venules while a minimum of the exchange occurs at the site of the midcapillaries. Show more

Keywords: Microcirculation, Transvascular Exchange, Plasma Proteins, Reflection Coefficient, Irreversible Thermodynamics

DOI: 10.3233/BIR-1987-24305

Citation: Biorheology, vol. 24, no. 3, pp. 319-335, 1987

Authors: How, T.V. | Black, R.A.

Article Type: Research Article

Abstract: Pressure drop and pressure gradient were measured in steady Newtonian and non-Newtonian flow through tapered tubes having angles of taper, α , between 0.5° and 1.25°. Aqueous solutions of polyacrylamide, characterized as power law fluids, were used for the non-Newtonian flow measurements. These solutions had power law parameters similar in magnitude to those of blood. The pressure drop-flow rate data compared well with the predictions of a semi-empirical flow model over a large range of flow rate (Reα up to 10 for Newtonian flow and 5.7 for non-Newtonian flow). The pressure gradient increased with distance, z, into the taper …as the radius decreased. The linear relationship between pressure gradient and z, derived by Oka (Biorheology, 10, 207-212, 1973) was found to be valid only when α z was small. For the tapered tubes examined here, agreement was confined to the region near the inlet. If higher order terms in α z were taken into account the agreement was extended further into the taper. However, under higher flow conditions, when the inertial losses are not negligible, the semi-empirical model provides much better estimates of pressure gradient. Show more

Keywords: Taper, Non-Newtonian Flow, Pressure Drop, Pressure Gradient, Vascular Prosthesis

DOI: 10.3233/BIR-1987-24306

Citation: Biorheology, vol. 24, no. 3, pp. 337-351, 1987

Authors: Lerche, D.

Article Type: Book Review

DOI: 10.3233/BIR-1987-24307

Citation: Biorheology, vol. 24, no. 3, pp. 353-354, 1987

Article Type: Other

DOI: 10.3233/BIR-1987-24308

Citation: Biorheology, vol. 24, no. 3, pp. 355-355, 1987