Biorheology - Volume 19, issue 1-2

Authors: Dimicoli, J.L. | Nakache, M. | Péronneau, P.

Article Type: Research Article

Abstract: A new method is developed for direct visualization of the local mass transfer at solid liquid interfaces. Peroxidase is immobilized by entrapment in a polyacrylamide gel coating the interior surface of a glass tube. The reaction of oxidation of luminol by H2 O2 catalyzed by this enzyme involves light emission. Furthermore at low H2 O2 concentration (≲ 5. × 10−5 M), this reaction is controlled by the diffusion of H2 O2 from the bulk flow to the wall, as evidenced by the Re1/3 dependence of the light flux V measured in the laminar case. It is …possible in these conditions to directly relate V as measured at each point of the wall, to the local properties of the flow: (i) a decrease of V is always observed when moving downstream from the input of the tube, but it is much more pronounced for laminar flows than for turbulent ones, as theoretically expected; (ii) the sensitivity of the method has been tested for evaluating the diffusion convection phenomena at the wall downstream from a stenosis. Furthermore the local hydrodynamic properties have been characterized by measuring through pulsed Doppler velocimetry the velocity of the moving liquid phase as a function of the position in the flow. The data obtained show the presence of a maximum of V in the vicinity of the reattachment point of the liquid streamlines at the wall. This constitutes the first experimental confirmation of calculations on diffusion convection phenomena downstream from stenoses. These first experiments show one the ability of the method to detect the local properties of the parietal mass transfer phenomena, as a function of the geometry of the wall and the hydrodynamic characteristics of the flow. Show more

Keywords: Diffusion convection, visualization, chemiluminescent enzymatic immobilized system

DOI: 10.3233/BIR-1982-191-231

Citation: Biorheology, vol. 19, no. 1-2, pp. 281-300, 1982

Authors: Stanwyck, T. Scott | Fischer, Richard | Pope, Malcolm | Seligson, David

Article Type: Research Article

Abstract: Pilot studies showed the occurrence of stress relief when a sawcut was made in cortical bone next to a foil strain gauge. In these experiments, strain gauges were cemented on the surface of bovine metatarsals or ovine tibiae to determine if the observed residual strain was an artifact caused by strain gauge application or by stress relief procedures. A consistent stress relief was recorded lending further support to the concept that bone is a prestressed material.

Keywords: Prestress, Hydroxyapatite, Collagen, Bone

DOI: 10.3233/BIR-1982-191-232

Citation: Biorheology, vol. 19, no. 1-2, pp. 301-306, 1982

Authors: Walburn, Frederick J. | Stein, Paul D.

Article Type: Research Article

Abstract: The purpose of this study was to determine the shear rate at the wall in a symmetrically branched tube with a branch-to-trunk area ratio and angle of branching that were comparable to the human abdominal aorta. Velocity profiles were measured with a laser Doppler anemometer during steady and pulsatile flow in which the mean Reynolds numbers were 500, 1000, and 1500. During both steady and pulsatile flow, as the Reynolds numbers increased, the shear rates at the inner wall of the branch increased. Only slight increments of the shear rates occurred along the outer wall of the branch, however, as …the Reynolds number increased. No reversal s of flow were observed at any Reynolds number during steady flow. Transient reversals of flow (causing negative shear rates) occurred along the outer wall of the branch at a Reynolds number of 500; but such transient flow reversals were not observed at the higher Reynolds numbers during pulsatile flow. Show more

Keywords: Shear rate, transient flow reversals, laser Doppler anemometry

DOI: 10.3233/BIR-1982-191-233

Citation: Biorheology, vol. 19, no. 1-2, pp. 307-316, 1982

Authors: Jackson, Graham W. | James, David F.

Article Type: Research Article

Abstract: An experimental system was developed to measure flow rates and pressure drops across hyaluronic acid solutions. The solutions were contained r:y membranes in a test cell, and solvent was perfused through the cell at flow rates comparable to physiological conditions. The pressure drop was found to be proportional to a steady flow rate for concentrations up to 1.5%, confirming that Darcy’s Law for porous media is valid for hyaluronic acid solutions (and indicating that the polymer chains did not pile up at one end of the test cell). From the flow data, the hydrodynamic permeability of each solution was calculated …and found to be 50 times higher that whole tissue having the same hyaluronic acid concentration; hyaluronic acid on its own, therefore, is not the source of resistance to flow in tissue. The results for hyaluronic acid were then used to show that all the glycosaminoglycans together cannot cause the high resistance of ground substance in tissue, and it is argued that mucoproteins are the most likely source. A hydrodynamic model of the polymer chains was developed to predict solution permeability; the theoretical values agree closely with the experimental data. Show more

Keywords: Hydrodynamic resistance, permeability, hyaluronic acid, Darcy’s Law

DOI: 10.3233/BIR-1982-191-234

Citation: Biorheology, vol. 19, no. 1-2, pp. 317-330, 1982

Authors: Sharikov, Alexander N. | Zaiko, Valery M.

Article Type: Research Article

Abstract: During the recent years various investigators have developed the technique of kryophotometric measurements of oxyhemoglobin saturation with oxygen (Ψ) in small vessels. In this paper, on the basis of the statistical model of the organ developed by the authors, a theoretical relationship is established between the distributions of measured in various groups of experiments in the capillaries and the distributions of Ψ in the arterioles and venules. It is shown that for the description of the distribution of Ψ in a separate multicapillary unit, lying between the arteriole and the venule, it is possible to introduce a special distribution function. …In some cases this function may be determined analytically. Statistical distributions of other microcirculation parameters may be included into the statistical model of the organ using the similar procedure described in this paper for the parameters Ψa , Ψv -arteriolar and venular Ψ. Show more

Keywords: Microcirculation, Oxygen transport

DOI: 10.3233/BIR-1982-191-235

Citation: Biorheology, vol. 19, no. 1-2, pp. 331-339, 1982

Authors: Ramcharan, J.E. | Shoja, H.S. | Piggott, M. | Taylor, D.E.M.

Article Type: Research Article

Abstract: It has long been established that vibration can produce vasospastic disease with associated hyperviscosity. More recently it has been shown that short-term exposure to vibration may lead to increased blood-flow; the associated blood rheology of this has not been studied. The vibration used in this study was of the three dimensional type known as “cycloid” vibration. It is often used in physiotherapy departments and is therefore of particular interest. Investigations have been carried out to determine the effects on blood-viscosity at shear rates between 230 s−1 and 0.0734 s−1 of whole-body vibration, at a frequency of 50 Hz …for 15 minutes in the rabbit and of the effects of in vitro vibration on both human and rabbit blood. Haematocrit, yield stress, erythrocyte electrophoretic mobility and zeta-potential were also estimated. Three studies were carried out:- I. Comparison of blood with and without in vitro vibration from human volunteers with hyperviscosity (N = 5). II. Comparison of blood from lop-eared rabbits before and after whole-body vibration (N = 11). III. Comparison of blood from lop-eared rabbits after in vitro vibration and after whole-body vibration (N = 10). The frequency of vibration was 50 Hz, the amplitude was 0.8 mm and the duration was 15 minutes. It was shown that vibration of either human or rabbit blood in vitro has no effect on blood-viscosity at any shear rate, on red cell mobility, on zeta-potential or on yield stress. Whole-body vibration produced no significant effect on rheology at rates of shear above 2 s−1 , but low-shear viscosity (<1 s−1 Shear rate) became more nearly Newtonian after vibration, with a significant reduction in yield stress from 5.71 ± 0.14 mNm−2 to 3.54 ± 0.32 mNm−2 (p < 0.005). There were no significant changes in electrophoretic mobility (i.e. zeta-potential). Show more

Keywords: Vibration, Blood-Viscosity, Red Cell Mobility

DOI: 10.3233/BIR-1982-191-236

Citation: Biorheology, vol. 19, no. 1-2, pp. 341-352, 1982

Authors: Gaillard, S. | Delhon, A. | Laurresergues, H. | Stoltz, J.F.

Article Type: Research Article

Abstract: The essential part played by rheological factors in genesis of thrombosis and atherosclerosis has often been mentioned. Thus the authors have carried out a study of rheological and biochemical parameters on a genetic animal model with modifications in plasma lipids (homozygous obese “Fatty” rat) compared to the non obese heterozygous animal. The results obtained for the evolution of biochemical parameters (blood glucose, cholesterol, triglycerids) over a 16 months period confirm those published earlier. Further, a significant increase in fibrinogen level was observed in homozygous animals, and correlated with plasma viscosity. These results are also connected with changes in apparent …blood viscosity which is considerably increased in homozygous rats, particularly at low shear rates (γ ˙ < 20 s−1 ). These results show the value of this animal model and the authors suggest the application of such a genetic animal model and of its heterozygous control population to both theoretical rheological and pharmacological studies on atherogenesis and hyperlipoproteinaemia. Show more

Keywords: hemorheology, animal model, Fatty rat, fibrinogen

DOI: 10.3233/BIR-1982-191-237

Citation: Biorheology, vol. 19, no. 1-2, pp. 353-362, 1982

Authors: Kiesewetter, H. | Radtke, H. | Jung, F. | Schmid-Schönbein, H. | Wortberg, G.

Article Type: Review Article

Abstract: The question whether blood exhibits pseudoelastic behavior i.e. if it behaves like a solid under negligible external forces, is of great theoretical interest for the clarification of stasis phenomena in the microcirculation. The determination of yield point, that is the change from the solid to the fluid phase, was at first only of abstract scientific importance for blood. In the diagnosis and treatment of patients with flow anomalies this phenomenon is increasingly important, as numerous possibilities now exist to modify the flow behavior of blood by therapeutical changes of composition. Therefore it seems to be of high priority to review …and discuss the numerous methods for the quantification of a yield shear stress. Show more

Keywords: Yield shear stress, Rotational viscometer, Capillary viscometer, Sedimentation, Plug flow, Microcirculation

DOI: 10.3233/BIR-1982-191-238

Citation: Biorheology, vol. 19, no. 1-2, pp. 363-374, 1982

Article Type: Abstract

DOI: 10.3233/BIR-1982-191-239

Citation: Biorheology, vol. 19, no. 1-2, pp. 375-382, 1982

Authors: Church, Michael J.

Article Type: Announcement

DOI: 10.3233/BIR-1982-191-240

Citation: Biorheology, vol. 19, no. 1-2, pp. 383-383, 1982