Biorheology - Volume 26, issue 2

Article Type: Editorial

DOI: 10.3233/BIR-1989-26225

Citation: Biorheology, vol. 26, no. 2, pp. I-III, 1989

Authors: Copley, Alfred L.

Article Type: Editorial

DOI: 10.3233/BIR-1989-26201

Citation: Biorheology, vol. 26, no. 2, pp. 97-98, 1989

Authors: Goldsmith, Harry L.

Article Type: Editorial

DOI: 10.3233/BIR-1989-26202

Citation: Biorheology, vol. 26, no. 2, pp. 99-107, 1989

Authors: Fukushima, Takayoshi | Matsuzawa, Teruo | Homma, Tatsuji

Article Type: Research Article

Abstract: Pulsatile flows in glass models simulating fusiform and lateral saccular aneurysms were investigated by a flow visualization method. When resting fluid starts to flow, the initial fluid motion is practically irrotational. After a short period of time, the flow began to separate from the proximal wall of the aneurysm. Then the separation bubble or vortex grew rapidly in size and filled the whole area of the aneurysm circumferentially. During this period of time, the center of the vortex moved from the proximal end to the distal point of the aneurysm. The transient reversal flow, for instance, which may occur at …the end of the ejection period, passed between the wall of the aneurysm and the centrally located vortex. When the rate and pulsatile frequency of flow were high, the vortex broke down into highly disturbed flow (or turbulence) at the distal portion of the aneurysm. The same effect was observed when the length of the aneurysm was increased. A reduction in pulsatile amplitude made the flow pattern close to that in steady flow. A finite element analysis was made to obtain velocity and pressure fields in pulsatile flow through a tube with an axisymmetric expansion. Calculations were performed with the pulsatile flows used in the visualization experiment in order to study the effects of change in the pulsatile wave form by keeping the time-mean Reynolds number and Womersley’s parameter unchanged. Calculated instantaneous patterns of velocity field and stream lines agreed well with the experimental results. The appearance and disappearance of the vortex in the dilated portion and its development resulted in complex distributions of pressure and shear fields. Locally minimum and maximum values of wall shear stress occurred at points just upstream and downstream of the distal end of the expansion when the flow rate reached its peak. Show more

Keywords: pulsatile flow, flow visualization, finite element analysis vortex, shear stress, aneurysm

DOI: 10.3233/BIR-1989-26203

Citation: Biorheology, vol. 26, no. 2, pp. 109-130, 1989

Authors: Roach, Margot R. | Fletcher, Joan

Article Type: Research Article

Abstract: These experiments were designed to determine if male New Zealand white rabbits made mildly hypertensive (20–30 mm Hg increase) with bilateral renal artery clips developed more or less sudanophilic lesions than controls, and if the animals responded differently if hypercholesterolemia was produced soon (one week) or late (eight weeks) after the animals were operated on. Both groups received the diet of 2% cholesterol and 6% corn oil for six weeks. We also studied the distensibility of the carotid artery to determine if altered elastic behaviour played a role in lesion development. The experiments showed that the acute hypertensive group …developed most lesions (by area), but that the lesions in all groups had the same shape and location. The carotid arteries from the chronic hypertensives were least distensible, and most of the changes appeared to be in the elastance of collagen. The blood pressure actually dropped slightly in the chronic shams after the diet was started. These experiments suggest that, at least, in the rabbit, the duration of the hypertension may determine how the arterial wall responds to hypercholesterolemia. They show that mild hypertension, like hypercholesterolemia, alters the rate at which lesions develop, rather than altering their distribution. The changes do not appear to be related to altered distensibility. Show more

Keywords: Atherosclerosis, Hypertension, Elasticity, Mapping, Rabbits

DOI: 10.3233/BIR-1989-26204

Citation: Biorheology, vol. 26, no. 2, pp. 131-142, 1989

Authors: Tran-Son-Tay, R. | Coffey, B.E. | Hochmuth, R.M.

Article Type: Research Article

Abstract: Rheological properties of concentrated red blood cell suspensions are studied with a magneto acoustic microrheometer in which a ball is suspended in a vertically oriented cylindrical tube. The rheometer uses a conventional falling ball technique to measure steady state viscosity and a vertically oscillating, magnetically driven ball for viscoelastic measurements. The motion of the ball is tracked by ultrasound echo location in which sound waves are transmitted and received by an ultrasound transducer mounted at the base of the tube. The compact size of the rheometer allows rheological studies to be made with microliter quantities of opaque suspensions and permits …sudden and accurate changes in temperature. Also, values for the adiabatic compressibility are evaluated from measurements of the speed of sound. Show more

Keywords: red blood cell, rheology, compressibility, speed of sound, oscillating ball, rheometer

DOI: 10.3233/BIR-1989-26205

Citation: Biorheology, vol. 26, no. 2, pp. 143-151, 1989

Authors: Yardin, G. | Meiselman, H.J.

Article Type: Research Article

Abstract: Using a constant-amplitude (± 1°) oscillatory Couette viscometer (f=0.01–1.0 Hz), we have measured the viscous (η ′ ) and elastic (η ″ ) components of the complex viscosity at 25°C for shape-transformed human RBC suspended in isotonic buffer at 80% hematocrit. Morphology-altering drugs employed were: ECHINOCYTIC AGENT 2,4-dinitrophenol (DNP, 0.1–5 mM); STOMATOCYTIC AGENT chlorpromazine hydrochloride (CPZ, 0.01–0.1 mM). All suspensions exhibited decreasing η ′ and η ″ with increasing frequency. Compared to biconcave, control RBC suspensions, salient effects …of shape transformation included: 1) for DNP, a dose-related elevation of both η ′ and η ″ , with a 850% increase in η ′ and a 2500% increase in η ″ at 5 mM and the lowest frequency; 2) for CPZ, a dose-related elevation of both η ′ and η ″ , with a 170% increase in η ′ and a 280% increase in η ″ at 0.1 mM and the lowest frequency; 3) for both DNP and CPZ, the elevations of η ′ and η ″ were inversely related to frequency. Using 2 mM DNP and various concentrations of CPZ, both η ′ and η ″ could be returned to control with 0.08 mM CPZ; further increases of CPZ at constant DNP led to elevations of both components. Comparisons of η ′ and η ″ to steady shear viscometric data indicated that neither a nominal shear rate approach nor a RMS complex viscosity technique was able to completely reconcile these data; a modified Kelvin-Voigt model proved useful in evaluating cellular versus membrane contributions to η ″ . These results indicate that RBC morphology is an important determinant of the oscillatory behavior of RBC suspensions and suggest the usefulness of the technique for studies of drug-membrane interactions. Show more

Keywords: Complex Viscosity, Echinocyte, RBC Morphology, Stomatocyte, Viscoelasticity

DOI: 10.3233/BIR-1989-26206

Citation: Biorheology, vol. 26, no. 2, pp. 153-175, 1989

Authors: Sutera, S.P. | Pierre, P.R. | Zahalak, G.I.

Article Type: Research Article

Abstract: Measurements of the dimensions and membrane rotational frequency of individual erythrocytes steadily tank-treading in a Rheoscope are used to deduce the surface shear viscosity (η m ) and the shear elastic modulus (μ m ) of the membrane. Previously published algorithms (Trans-Son-Tay et al., Biophys. J. 46 : 65, 1984, and 51 : 915, 1987) plus an assumed area-conserving membrane velocity field (Secomb and Skalak, Q.J. Mech. Appl. Math. XXXV 2 : 233, 1982) are applied to calculate η m as a function of the second invariant of the surface strain rate and μ m as a function …of the second invariant of membrane strain. The results indicate density-related increases in membrane stiffness and viscosity, shear-thinning viscous behavior, and strain-stiffening elastic behavior. Show more

Keywords: Rheoscope, erythrocyte membrane, viscoelastic properties, tank-treading

DOI: 10.3233/BIR-1989-26207

Citation: Biorheology, vol. 26, no. 2, pp. 177-197, 1989

Authors: Thurston, George B.

Article Type: Research Article

Abstract: Significant internal structural changes occur in flowing blood when shear strain exceeds the critical value of 1 (unit strain), forcing alignment of the erythrocytes and releasing trapped plasma, which in turn leads to the formation of multiple layers of plasma on which oriented and compacted cells slide. These effects are identified in the inflections in the shear rate dependence of viscoelasticity of normal blood and in the viscous and elastic stress-to-strain relationships. Theoretical factors for plasma release and cell compaction allow calculation of the viscous and elastic properties of the cell layers from measured whole blood viscoelasticity and plasma viscosity. …The new plasma release-cell layering theory encompasses, reinterprets and unifies many diverse previous observations relating to how blood flows, and provides a new understanding of the roles of red cell deformability and aggregation tendency. Show more

Keywords: Blood flow theory, shear strain, viscoelasticity, trapped plasma, cell layering, erythrocyte deformability, aggregation, plasma viscosity

DOI: 10.3233/BIR-1989-26208

Citation: Biorheology, vol. 26, no. 2, pp. 199-214, 1989

Authors: Schmid-Schönbein, G.W. | Lee, S.Y. | Sutton, D.

Article Type: Research Article

Abstract: Blood flow in the microcirculation of the rat skeletal muscle during transient changes of arterial pressure is analyzed theoretically. Although flow in such small vessels is quasi-steady and has a very low Reynolds number, time-dependent nonuniform flows along the length of the blood vessels can be observed due to vessel distensibility. The governing equations for a single microvessel are derived using previously measured microvessel elasticity, and several solutions to different inflow and outflow pressures and flow conditions are investigated. The results indicate that when such distensible microvessels are subjected to a step increase of arterial pressure, the arterial flow shows …a rapid overshoot followed by a progressive decay to steady-state. An arterial step flow induces a different response which takes the form of a monotonically increasing pressure. Pressure and flows are nonuniform along the vessel length during such transients. In-vitro whole organ pressure-flow data are presented in the dilated rat gracilis muscle which qualitatively agree with the theoretical predictions. Show more

Keywords: skeletal muscle, microcirculation, vessel distensibility, dynamic flow, transient pressures

DOI: 10.3233/BIR-1989-26209

Citation: Biorheology, vol. 26, no. 2, pp. 215-227, 1989