Biorheology - Volume 24, issue 4

Article Type: Editorial

DOI: 10.3233/BIR-1987-24409

Citation: Biorheology, vol. 24, no. 4, pp. I-III, 1987

Authors: Goldsmith, Harry L.

Article Type: Obituary

DOI: 10.3233/BIR-1987-24401

Citation: Biorheology, vol. 24, no. 4, pp. 357-366, 1987

Authors: Gaehtgens, P.

Article Type: Research Article

Abstract: Pressure-velocity relations were obtained in vertical and horizontal glass tubes (I.D. 26 to 83 μ m) perfused with normal human blood at feed hematocrits between 0.25 and 0.65. Perfusion pressures used corresponded to wall shear stresses up to 0.27 dyn cm−2 Red cell velocity measurements were made both immediately following implementation of perfusion pressure (with red cells still desaggregated) and in a steady state situation (with red cells aggregated). Analysis of the slopes of the linear relations between perfusion pressure and velocity showed apparent viscosity to decrease with the manifestation of red cell aggregation. In horizontal tubes, sedimentation and …aggregation occurred simultaneously, and apparent viscosity increased due to axial asymmetry of cell concentration. Evidence for a yield shear stress (flow stagnation at positive driving pressure) was not observed. Show more

Keywords: viscosity, aggregation, sedimentation, yield stress

DOI: 10.3233/BIR-1987-24402

Citation: Biorheology, vol. 24, no. 4, pp. 367-376, 1987

Authors: Hovav, Elli | Halle, David | Yedgar, Saul

Article Type: Research Article

Abstract: The effect of medium viscosity on lysis of red blood cells (REC) induced by snake venom phospholipase A2 (PLA2 ) was examined. The medium viscosity was modified by the addition of various macromolecules which differ in their chemical nature and in their capacity to increase fluid viscosity. PLA2 and Ca++ were applied to cells suspended in viscous medium to induce hemolysis. It was found that the hemolysis is inhibited in direct proportion to increasing viscosity of the extracellular fluid. This phenomenon was observed with aggregated as well as disaggregated RBC. To examine whether the viscosity interferes with …the accessibility of the enzyme to the cell, the medium viscosity was modified after binding of the enzyme to the cells; PLA2 was added to a RBC suspension in the presence of Ba++ which binds the enzyme to the cell membrane but does not activate it. The cell-enzyme complex was separated by gel filtration and suspended in viscous medium in the presence of Ca++ which activates the reaction. Also in this case RBC lysis was inhibited as the medium viscosity was increased. It is proposed that the action of PLA2 on RBC membrane is regulated by the viscosity of the cell surface aqueous environment. Show more

Keywords: Red blood cells, snake venom phospholipase A2, medium viscosity

DOI: 10.3233/BIR-1987-24403

Citation: Biorheology, vol. 24, no. 4, pp. 377-384, 1987

Authors: Schurz, J. | Ribitsch, V.

Article Type: Research Article

Abstract: After a discussion of the role of synovial fluid as a joint lubricant, rheological measurements are described with both normal (healthy) synovial fluids and pathological ones. Shear stress and first normal stress difference are measured as a function of shear gradient to calculate the apparent shear viscosity η ′ and the apparent normal viscosity ψ 1 as well as an apparent Shear modulus G′. It is found, that in case of diseased synoviae all rheological parameters deteriorate. Most significant changes are observed with the zero shear viscosity η …0 , the shear modulus G′, and a characteristic time θ which is the reciprocal of the critical shear rate Dc which determines the onset of shear thinning. The rheological deterioration of synovial fluids is explained in terms of solute structure. whereby a molecular rmass of the backbone hyaluronic acid of at least 107 g.mol−1 is required for satisfactory function. A theory of the rheological performance of normal synovial fluid as well as its pathological deterioration is proposed. Show more

Keywords: synovial fluid, rheumatic joint diseases, viscosity curves, viscoelasticity, shear modulus, hyaluronic acid

DOI: 10.3233/BIR-1987-24404

Citation: Biorheology, vol. 24, no. 4, pp. 385-399, 1987

Authors: McMillan, D.E. | Strigberger, J. | Utterback, N.G.

Article Type: Research Article

Abstract: When the inner cylinder of a fluid-filled Couette viscometer is rotated rapidly, a vortical flow pattern develops when a dimensionless value referred to as the critical Taylor number (Tc) is reached. We have determined its magnitude in our viscometer for three Newtonian fluids and for blood at 37°C, using the inflection point of torque/RPM vs. RPM (sudden rise in apparent viscosity). Its position was identified by least squares line fitting. Because blood was studied, the viscosity used in Tc calculation was the apparent bob shear stress/shear rate ratio at the inflection marking vortical flow onset. For glycerol-water mixtures Tc was …41.8 ±0.3 (N=11), for propylene glycol 42.0 ±0.2 (N=14), for silicone oil 41.8 +0.2 (N=11). For healthy blood Tc was 40.7 ±0.9 (N=140). This evidence against blood’s increased resistance to flow instability was accompanied by a slower rate of rise in torque both above and below Tc compared to the three Newtonian fluids. Newtonian fluids and blood both developed wavy vortical flow at a rotation rate moderately higher than Tc. Blood resisted this unstable flow behavior more than the Newtonian fluids but it also experienced a slower rate of rise in torque with increasing rotation rate above the critical Taylor number. Shear-thinning is the simplest explanation for blood’s mildly altered Taylor vortex behavior; blood’s resistance to flow instability is otherwise not found to be sufficient to affect its flow stability in man. Show more

Keywords: hemorheology, fluid mechanics, hydrodynamic instability, vorticity, blood

DOI: 10.3233/BIR-1987-24405

Citation: Biorheology, vol. 24, no. 4, pp. 401-410, 1987

Authors: Puchelle, E.

Article Type: Other

DOI: 10.3233/BIR-1987-24406

Citation: Biorheology, vol. 24, no. 4, pp. 411-412, 1987

Article Type: Abstract

DOI: 10.3233/BIR-1987-24407

Citation: Biorheology, vol. 24, no. 4, pp. 413-423, 1987

Authors: Fung, Y.C.

Article Type: Book Review

DOI: 10.3233/BIR-1987-24408

Citation: Biorheology, vol. 24, no. 4, pp. 425-426, 1987