Biorheology - Volume 28, issue 6

Authors: Silberberg, Alex | Copley, Alfred L.

Article Type: Editorial

DOI: 10.3233/BIR-1991-28601

Citation: Biorheology, vol. 28, no. 6, pp. 485-485, 1991

Authors: Copley, Alfred Lewin

Article Type: Editorial

DOI: 10.3233/BIR-1991-28602

Citation: Biorheology, vol. 28, no. 6, pp. 487-489, 1991

Authors: Sourander, Patrick

Article Type: Research Article

Abstract: The application of principles of biorheology, hemorheology and perihemorheology on problems of the nervous system in health and disease was suggested by Alfred L. Copley (1982, 1987). Late in 1988 Copley and Sourander considered neurobiorheology to be an appropriate term for a new branch of biorheology bridging the gap between biorheology and neurobiology. Neurobiorheology can be defined as a research field concerned with deformation behaviour of matter including flow and transportation in context with the structure and function of the nervous system at macroscopic, cellular, subcellular and molecular levels. It may be considered a basic life science with important …clinical applications. Its “raison d‘être” should be to apply various ways of thinking, calculations and techniques used in biorheology to treat and if possible to solve neurobiological problems. Show more

Keywords: Biorheology, hemorheology, neurobiology, neurobiorheology, perihemorheology

DOI: 10.3233/BIR-1991-28603

Citation: Biorheology, vol. 28, no. 6, pp. 491-525, 1991

Authors: Peslin, R. | Rotger, M. | Delaigue, N. | Duvivier, C.

Article Type: Research Article

Abstract: Lung pressure-volume hysteresis of cat lungs has been found by Hildebrandt (J. Appl. Physiol. 28, 365–372, 1970) to be 20–50% larger than predicted from stress adaptation data on the basis of a viscoelastic model. We have reinvestigated this phenomenon in isolated rat lungs with a different approach, in which the approximation inherent to using a model is avoided Lung transfer function was derived from the digitally-computed Laplace transform of the pressure decay following a step volume change and used to predict lung pressure-flow relationship in the frequency domain. The latter was expressed in terms of lung effective resistance (Rlc) and …effective elastance (Elc), and compared to the observed values (Rl and El) in the frequency range 0.01–0.5 Hz. The measurements were made in 5 lungs at a transpulmonary pressure (Pl) of 0.5 kPa and in 5 others at a Pl of 0.8 kPa. Rl was found to be 23–41% larger than Rlc at Pl=0.5 and 29–51% larger at Pl=0.8. El did not differ significantly from Elc at Pl=0.5 but was 14–28% larger at Pl=0.8. These results are in good agreement with previous findings. The differences between Rl and Rlc are proportional to the reciprocal of frequency and, thus, correspond to a rate-independent dissipation. They are consistent with a yield stress of 3–6 Pa. Show more

Keywords: Respiratory mechanics, lung, viscoelasticity plasticity, stress relaxation, impedance

DOI: 10.3233/BIR-1991-28604

Citation: Biorheology, vol. 28, no. 6, pp. 527-535, 1991

Authors: Reinhart, W.H. | Huang, C. | Vayo, M. | Norwich, G. | Chien, S. | Skalak, R.

Article Type: Research Article

Abstract: The geometric features of red blood cells in narrow channels in vivo and in vitro were studied by electron microscopy. In rabbit myocardial capillaries about half of the red cells were folded. In polycarbonate filters with pore diameters of 2.2–4.5 μ m approximately one third of the trapped red blood cells were folded. The frequency of folding did not depend on the applied pressure, which ranged from 0.1 to 8.0 cm H2 O. The folding of the red blood cells in filter pores was used to estimate the bending stiffness of the membrane. An analysis based on the …large deformation theory of bending of an elastic sheet was developed. Using pressures of 0.2 and 1.0 cm H2 O, the bending stiffness of human red cell membranes was estimated to be approximately 2.4–11.6 × 10−12 dyn-cm, which is in good agreement with other methods. A limiting radius of curvature of about 85 nm was found at higher pressures. Show more

Keywords: Erythrocyte, Red cell membrane, Bending modulus, Cell filtration

DOI: 10.3233/BIR-1991-28605

Citation: Biorheology, vol. 28, no. 6, pp. 537-549, 1991

Authors: Ohta, Kouichi | Fukuuchi, Yasuo | Tomita, Minoru | Tanahashi, Norio | Matsuoka, Shizuko | Takeda, Hidetaka

Article Type: Research Article

Abstract: The effect of thrombospondin, a major glycoprotein in the platelet a-granule, on the erythrocyte aggregation rate was investigated. Venous blood was sampled from 8 healthy male volunteers and anticoagulated with 1.1 mg/ml EDTA(K2 ). The erythrocyte aggregation rate of each blood sample was measured with a whole-blood erythrocyte aggregometer before and after incubation with murine monoclonal antibody against human platelet thrombospondin. After 15 min incubation, the erythrocyte aggregation rate exhibited a significant decrease to 0.055 ± 0.022/s, representing 71.9 ± 8.7% of the control value (0.075 ± 0.028/s) (p < 0.0005). The results obtained suggest that thrombospondin may participate in …the control of erythrocyte aggregability in the circulating blood. Show more

Keywords: Erythrocyte aggregation, Aggregability, Hemorheology, Thrombospondin, Platelet, Monoclonal antibody

DOI: 10.3233/BIR-1991-28606

Citation: Biorheology, vol. 28, no. 6, pp. 551-556, 1991

Authors: Dong, Cheng | Skalak, Richard | Sung, Kuo-Li Paul

Article Type: Research Article

Abstract: The rheological properties of leukocytes are important to their effectiveness in the microcirculation. Previous studies based on in vitro data from micropipette experiments suggest that a Maxwell fluid bounded by a cortical shell with persistent tension is a realistic model for non-activated neutrophils in both the rapid and slow deformation phases. However, various viscoelastic coefficients have been obtained depending on the degree of cell deformation. In the present paper it is demonstrated that the cytoplasmic apparent viscosity and elasticity vary continuously, depending on the degree of deformation. These apparent variations are due to the inhomogeneous nature of the neutrophil …internal structure. It is shown that the nucleus is much stiffer than the cytoplasm. The composite structure of the cell results in the deformation-dependent properties. Show more

Keywords: Neutrophils, Cytoplasmic Viscosity, Micropipette, Mathematical Model

DOI: 10.3233/BIR-1991-28607

Citation: Biorheology, vol. 28, no. 6, pp. 557-567, 1991

Authors: Brookshier, Kathleen K. | Tarbell, John M.

Article Type: Research Article

Abstract: Porcine blood was used to examine the relationship between hematocrit levels and wall shear rate patterns in straight and curved artery models under fixed oscillatory flow conditions characteristic of larger arteries. It is demonstrated that porcine blood models both the viscous and elastic components of the 2 Hz complex viscosity of human blood quite accurately over a broad range of shear rates (1–1000 s−1 ) and hematocrits (20% - 80%). For a fixed oscillatory flow waveform (Poiseuille peak shear rate = 168 s−1 ; mean shear rate 84 s−1 ), increases in hematocrit produced a decrease in the peak wall …shear rate in both the straight and curved artery models and a corresponding decrease in wall shear rate reversal on the inside wall of the curved artery model. The same trends were also observed for oscillatory flows of aqueous glycerin solutions of increasing viscosity in the range of viscosity of the blood samples tested. Aqueous glycerin solutions produced wall shear rate waveforms of the same magnitude and shape as the porcine blood. This indicates that variations in the shear rate, and therefore the shear stress, were caused primarily by changes in the viscous and not the elastic properties of blood. The results suggest that simple Newtonian fluids may be sufficient for in vitro determination of the first order effects to be expected of human blood flow in large vessels having complex geometries and shear rates in or above the range of the present study. Show more

Keywords: Wall shear rate, viscoelasticity, complex viscosity

DOI: 10.3233/BIR-1991-28608

Citation: Biorheology, vol. 28, no. 6, pp. 569-587, 1991

Authors: Guiffant, G. | Durussel, J.J. | Dufaux, J. | Roubaud, P.

Article Type: Brief Report

Keywords: blood and vessel rheology, microcirculatory network, transport phenomena

DOI: 10.3233/BIR-1991-28609

Citation: Biorheology, vol. 28, no. 6, pp. 589-594, 1991

Authors: Schmid-Schönbein, Geert W.

Article Type: Meeting Report

DOI: 10.3233/BIR-1991-28610

Citation: Biorheology, vol. 28, no. 6, pp. 595-596, 1991