Biorheology - Volume 22, issue 2

Article Type: Editorial

DOI: 10.3233/BIR-1985-22208

Citation: Biorheology, vol. 22, no. 2, pp. I-III, 1985

Authors: Karino, Takeshi | Goldsmith, Harry L.

Article Type: Research Article

Abstract: To further elucidate the role of fluid mechanical factors in the localization of atherogenesis and thrombogenesis, we have studied the 3-dimensional flow patterns in square T-junctions with branching angles θ from 30° to 150° and diameter ratios d/D (side: main tube) from 1.05/3.0 to 1.0. Cine films of the motions of tracer microspheres in dilute suspensions were taken at inflow Reynolds numbers from 15 to 400 and flow ratios (main: side tube) from 0.1 to 4.0. Flow patterns with suspension entering through the main tube were similar to those previously described in uniform 3 mm diameter T-junctions: paired vortices (spiral secondary …flows) symmetrical about the common median plane formed at the entrances of the main and side daughter tubes. Particles circulated through the main vortex, some crossing above and below the mainstream into and through the side vortex. At the geometrical flow ratio, the main vortex became smaller and smaller as the branching angle (θ < 90°) and diameter ratio decreased, and was confined to a thin layer adjacent to the tube wall, while the flow disturbance in the side tube was a minimum. In obtuse angle T-junctions the stagnation point shifted from the flow divider into the side tube, enhancing the flow disturbance there. The velocity distributions in main and side tubes were skewed towards the inner walls close to the flow divider. When flow entered through the side tube, a pair of recirculation zones formed in the main tube at the inner wall of the bend with a sharper angle. Show more

Keywords: T-junction, flow patterns, vortex, recirculation zone, stagnation point, localization of atherogenesis, thrombogenesis

DOI: 10.3233/BIR-1985-22201

Citation: Biorheology, vol. 22, no. 2, pp. 87-104, 1985

Authors: Kon, K. | O’Bryan, E.R. | Kon, H.

Article Type: Research Article

Abstract: The effect of the presence of hardened red blood cells (HRBC) in a mixed suspension on the deformation-orientation characteristics of normal cells in flow is experimentally probed by the electron spin resonance (ESR) spin label method, using a phosphatidylcholine label which does not transfer between the cells. The average deformation-orientation of the normal cells is generally suppressed by the presence of HRBC to different degrees, depending upon the shape and the way the HRBC are prepared. The effects are qualitatively explained by disturbance of laminar shear flow due to the random tumbling of the HRBC.

Keywords: Spin label, Erythrocyte, Deformation-orientation, Cell-cell interaction, Hardened cells

DOI: 10.3233/BIR-1985-22202

Citation: Biorheology, vol. 22, no. 2, pp. 105-117, 1985

Authors: Koutsouris, D. | Delatour-Hanss, E. | Hanss, M.

Article Type: Research Article

Abstract: The aim of this study is to assess the role of different physicochemical factors on the deformability measurements by using the initial filtration flow rate method, and to differentiate between the membrane or internal origin of some rigidity changes. The deformability is maximum for the physiological pH value and it decreases sharply for hypotonic and hypertonic buffer. For normal RBC, the deformability is independent of the pO2 level and a small decrease is observed for increasing pCO2 values (with constant pH). A theoretical model of filtration for the “Hemorheometre” will be also developed.

Keywords: RBC deformability, RBC filterability, initial flow rate, physiological conditions

DOI: 10.3233/BIR-1985-22203

Citation: Biorheology, vol. 22, no. 2, pp. 119-132, 1985

Authors: Kerr, H.R. | Warburton, B.

Article Type: Research Article

Abstract: Using an oscillating ring surface rheometer,surface shear rheological studies of hyaluronic acid solutions at physiological pH have demonstrated the elastico-viscous nature of the surface films. The properties of these surface films change with time and are shown to be related to bulk concentration, ionic strength and pH. This ageing behaviour can be explained on the basis of molecular conformational changes and molecular segmental kinetics. The results are discussed in relation to the postulated function of hyaluronic acid in synovial fluid.

Keywords: Rheology, Hyaluronic Acid, Surface

DOI: 10.3233/BIR-1985-22204

Citation: Biorheology, vol. 22, no. 2, pp. 133-144, 1985

Authors: Urban, J.P.G. | McMullin, J.F.

Article Type: Research Article

Abstract: In this study we have considered how equilibrium water content of the human nucleus pulposus varies with applied pressure for discs of various spinal levels and of various ages. In all cases hydration decreased as pressure increased but the level of equilibrium hydration depended on the relative amounts of collagen and PG in the tissue. Provided we accounted for the exclusion of PGs from the intra-fibrillar space, the swelling pressure curve and the osmotic pressure curve of equivalent PGs were found to coincide. The result implies that under physiological hydrations the mechanical forces exerted by the collagen network of the …nucleus are insignificant and that the osmotic pressure of the proteoglycans is balanced by the applied pressure arising from body weight and muscle and ligament tension alone. Since aged discs often have a low proteoglycan to collagen ratio, their equilibrium hydration also tends to be low. Moreover a far larger proportion of the total water is associated with the collagen than in the younger disc. Show more

Keywords: Disc, nucleus pulposus, swelling pressure, hydration, proteoglycan osmotic pressure, collagen water, extra-fibrillar water, intra-fibrillar water

DOI: 10.3233/BIR-1985-22205

Citation: Biorheology, vol. 22, no. 2, pp. 145-157, 1985

Authors: Maroudas, A. | Ziv, I. | Weisman, N. | Venn, M.

Article Type: Research Article

Abstract: An experimental study was carried out which involved comparing cartilage from normal and osteoarthritic joints with respect to (a) swelling pressure and (b) variation of hydrati.on with applied pressure. The main conclusion was that whilst osteoarthritic cartilage is undoubtedly less able to resist water loss under a given applied pressure than normal cartilage, this is not due to a change in the “quality” of the proteoglycans, resulting in a change in the osmotic pressure of the latter, but simply to a decreased fixed charge density. The latter decrease is either caused by an increase in the water content - and …this we attribute to a weakened collagen network - and/or to a loss of part of the proteoglycans from the tissue. Show more

Keywords: Hydration, osteoarthritic cartilage, proteoglycans

DOI: 10.3233/BIR-1985-22206

Citation: Biorheology, vol. 22, no. 2, pp. 159-169, 1985

Article Type: Announcement

DOI: 10.3233/BIR-1985-22207

Citation: Biorheology, vol. 22, no. 2, pp. 171-171, 1985