Biorheology - Volume 34, issue 3

Article Type: Obituary

DOI: 10.3233/BIR-1997-34301

Citation: Biorheology, vol. 34, no. 3, pp. v-viii, 1997

Authors: Chien, Shu

Article Type: Obituary

DOI: 10.3233/BIR-1997-34302

Citation: Biorheology, vol. 34, no. 3, pp. ix-x, 1997

Authors: Sugihara-Seki, Masako | Skalak, Richard

Article Type: Research Article

Abstract: To study the rheological behavior of blood cells in various flow patterns through narrow vessels, we analyzed numerically the motion of blood cells arranged in one row or two rows in tube flow, at low Reynolds numbers. The particles are assumed to be identical rigid spheres placed periodically along the vessel axis at off-axis positions with equal spacings. The flow field of the suspending fluid in a circular cylindrical tube is analyzed by a finite element method applied to the Stokes equations, and the motion of each particle is simultaneously determined by a force-free and torque-free condition. In both cases …of single- and two-me arrangements of the particles, their longitudinal and angular velocities are largely affected by the radial position and the axial spacing between neighboring particles. The apparent viscosity of the asymmetric flows is higher than that of the symmetric flow where particles are located on the tube centerline, and this is more pronounced when particles are placed farther from the tube centerline and when the axial distance between neighboring particles is reduced. Show more

Keywords: Red cells, Stokes flow, two-me flow, apparent viscosity

DOI: 10.3233/BIR-1997-34303

Citation: Biorheology, vol. 34, no. 3, pp. 155-169, 1997

Authors: Pawlowski, P. | Poznanska, A. | Fikus, M.

Article Type: Research Article

Abstract: The influence of cytochalasin B on the mechanical properties of Neurospora crassa cells subjected to a periodic electric field was investigated. Shear and extensional deformations were considered and studied separately. Conditions were found under which shear deformations become irreversible. Rheological models helped in the interpretation of the results in terms of the different response to the shear stress of the three hypothetical supramolecular regions of the membrane-skeleton network (F, S and 0). Rheological parameters for the above regions related to the proposed models were calculated. The models were satisfactorily fitted to the experimental results. The influence of cytochalasin B on …the course of extensional deformation of cells was investigated and characterized semiquantitatively. Show more

Keywords: Cellular rheology, electric field, shear, extensional deformation, membrane skeleton, cell disruption, cytochalasin B

DOI: 10.3233/BIR-1997-34304

Citation: Biorheology, vol. 34, no. 3, pp. 171-193, 1997

Authors: Barakat, Abdul I. | Karino, Takeshi | Colton, Clark K.

Article Type: Research Article

Abstract: Arterial fluid mechanics may play a role as a localizing factor for early atherosclerosis. Flow patterns in natural rabbit aortas rendered transparent were studied using a microcinematographic visualization technique. The aortic arch exhibited a single cell of clockwise-rotating helical secondary flow along the ventral and inner walls. Flow separation occurred proximal to the two arch branches with flow reversal proximal to the brachiocephalic artery. Sinusoidal flow rendered the helical motion more pronounced in systole, while the reverse flow zone periodically expanded and contracted. Steady flow in the abdominal aorta revealed streamlines which follow slow looping trajectories lateral to ostia before …tracing helical paths into the branches. Flow separation was present along the dorsal wall of the aorta opposite the superior mesenteric artery. With the exception of the left renal artery, steady flow wall shear stresses were higher distal to ostia than proximal. Spatial gradients of wall shear stress were larger around branches than elsewhere. Similar to observed flow patterns, sites of enhanced macromolecular permeability, as observed previously in the normal rabbit aorta, follow a clockwise helical pattern in the arch and exhibit a distribution around ostia that correlates to some degree with regions of elevated shear stress gradients. Show more

Keywords: Atherosclerosis, hemodynamics, flow patterns, shear stress, rabbit aorta

DOI: 10.3233/BIR-1997-34305

Citation: Biorheology, vol. 34, no. 3, pp. 195-221, 1997

Authors: Flieger, R. | Grebe, R.

Article Type: Research Article

Abstract: A new method for measuring erythrocyte membrane elasticity in physiological media is presented. Cells are loaded with well-defined centrifugal forces and the resulting change in shape is observed indirectly by laser diffractometry. Only a small amount of data has to be acquired and evaluated to follow up all the shape information contained in the diffraction pattern. This method has been proven using native and chemically altered cells (glutaraldehyde and diamide treatment). Advantages of the proposed method are the ease of handling, the small blood volume (10 µl) needed per measurement, a high sensitivity and the rational experimental setup.

Keywords: Erythrocyte, membrane, centrifugation, diffraction, elasticity, deformability

DOI: 10.3233/BIR-1997-34306

Citation: Biorheology, vol. 34, no. 3, pp. 223-234, 1997

Authors: Baskurt, Oguz K. | Meiselman, Herbert J.

Article Type: Research Article

Abstract: Low-shear viscometry is one of the methods commonly used to estimate the degree of red blood cell (RBC) aggregation in various bloods and RBC suspensions. However, it has been previously shown that alterations in RBC morphology and mechanical behavior can affect the low-shear apparent viscosity of RBC suspensions; RBC aggregation is also sensitive to these cellular factors. This study used heat treatment (48°C, 5 min), glutaraldehyde (0.005–0.02%) and hydrogen peroxide (1 mM) to modify cell geometry and deformability. Red blood cell aggregation was assessed via a Myrenne Aggregometer (“M” and “M1” indexes), RBC suspension viscosity was measured using a Contraves …LS-30 viscometer, and RBC shape response to fluid shear stresses (i.e., deformability) was determined by ektacytometry (LORCA system). Our results indicate that low-shear apparent viscosity and related indexes may not always reflect changes of RBC aggregation if cellular properties are altered: for situations where RBC aggregation has been only moderately affected, cellular mechanical factors may be the major determinant of low-shear viscosity. These findings thus imply that in situations which may be associated alterations of RBC geometry and/or deformability, low-shear viscometry should not be the sole measurement technique used to assess RBC aggregation. Show more

Keywords: Aggregation, deformability, red blood cell, viscosity, viscometry

DOI: 10.3233/BIR-1997-34307

Citation: Biorheology, vol. 34, no. 3, pp. 235-247, 1997