Biorheology - Volume 31, issue 2

Authors: Goldsmith, Harry

Article Type: Editorial

DOI: 10.3233/BIR-1994-31201

Citation: Biorheology, vol. 31, no. 2, pp. iii-iv, 1994

Authors: Sato, M. | Ohshima, N.

Article Type: Research Article

Abstract: Changes in shape and cytoskeletal structure of vascular endothelial cells induced by fluid-imposed shear stress were studied in vivo and in vitro . In in vivo experiments, aortic tissue specimens including the flow dividers of the branching of the left subclavian artery and the aortic intercostal ostium were obtained and their endothelial cell shapes were observed using the scanning electron microscope. It was found that the shape and orientation of endothelial cells were strongly affected by blood flow conditions. In in vitro cell culture experiments, porcine aortic endothelial cells were cultured on glass coverslips and extracellular matrix …coated (ECM coated) glass coverslips and exposed to shear stress using a parallel plate flow chamber. When we applied a shear stress of 2 Pa for 24 hrs, the rearrangement of F-actin filaments occurred within 3 hrs and preceded the cell shape change in the early stage after shear exposure. The endothelial cells on ECM-coated coverslips exhibited more elongated cell shapes even under no-flow conditions. After exposure to shear stress, the endothelial cells on ECM-coated glass showed more retarded elongation and orientation to the direction of flow than those on no-coated glass, suggesting that the anchorage to the substrate was enhanced by ECMs. Show more

Keywords: Atherosclerosis, blood flow, endothelial cells, extracellular matrix, F-actin filament, shear stress

DOI: 10.3233/BIR-1994-31202

Citation: Biorheology, vol. 31, no. 2, pp. 143-153, 1994

Authors: Okano, M. | Yoshida, Y.

Article Type: Research Article

Abstract: To determine how hemodynamic forces influence the permeability of endothelial cells, we observed the composition of junction complexes of the endothelial cells at the flow dividers of bifurcations of the aorta in normolipidemic and hyperlipidemic rabbits by a freeze-fractured replica method. We found that the leading edge of the brachiocephalic flow dividers exposed to high shear stress in a laminar fashion was nonsudanophilic and was covered by long fusiform endothelial cells predominantly showing continuous tight junctions, rather than discontinuous forms, and smooth, regular gap junctions. In contrast, the “hip” of the brachiocephalic flow dividers, a region of relatively low shear …stress, was sudanophilic, and was covered by ellipsoidal cells. The tight junctions were primarily discontinuous and the gap junctions had an irregular shape. These findings suggest that exposure of the arterial wall to a relatively low wall shear stress, rather than to high shear stress, may functionally activate the endothelial cells, increasing intercellular permeability. These events may increase the vulnerability of these regions of the vessel to atherosclerosis. Show more

Keywords: Shear stress, freeze-fracture, permeability, atherosclerosis, rabbit

DOI: 10.3233/BIR-1994-31203

Citation: Biorheology, vol. 31, no. 2, pp. 155-161, 1994

Authors: Williams, J.L. | Iannotti, J.P. | Ham, A. | Bleuit, J. | Chen, J.H.

Article Type: Research Article

Abstract: Neonatal rat calvarial cells (osteoblast-enriched) were cultured in monolayer on glass slides and subjected to a step increase in shear stress ranging from 3 to 60 dyne/cm2 in a laminar flow chamber. The level of intracellular free calcium ion concentration was monitored using Fura-2 fluorescence during the application of stress. Application of a step increase in stress resulted in a transient increase in calcium starting about 10–20 s after turning on the pump, reaching a peak in about 35 s and declining thereafter, despite the continued shear stress, and reaching near baseline values in about 100 s. No change …in cytoplasmic calcium was observed with a step increase in shear stress of 3 dyne/cm2 . Between 6 dyne/cm2 and 60 dyne/cm2 , the magnitude of the calcium response increased with the applied shear stress. Show more

Keywords: Flow, signal transduction, mechanoreceptor, mechanical stimulation

DOI: 10.3233/BIR-1994-31204

Citation: Biorheology, vol. 31, no. 2, pp. 163-170, 1994

Authors: Masuda, Y. | Kamisaka, S. | Yamamoto, R. | Hoson, T. | Nishinari, K.

Article Type: Research Article

Abstract: In this review article, we discuss the changes in the mechanical properties of the primary cell wall of different organs of several species of plant seedlings grown under simulated microgravity conditions. We compared growth and tropistic responses of these organs growing under different microgravity conditions, namely: 1) 3-D clinostat (three-dimensional clinostat with two axes); 2) water-submergence for rice seedlings, and 3) for comparison, an accelerated gravity using a specifically designed centrifuge. We measured the minimum stress-relaxation time as the parameter representing the mechanical property of the cell wall. We also measured extensibility, in mm/g. The 3-D clinostat condition disturbed the …normal gravitropic response of organs but affected growth rate and mechanical properties of the cell wall very little. Water-submergence of rice seedlings caused an acceleration of coleoptile elongation in the dark and caused a marked change in the mechanical property of the cell wall. However, the additional gravity of 30–135 xg showed only a small effect on growth and the mechanical property of the cell wall. Show more

Keywords: Microgravity, clinostat, water-submergence, hypergravity, plant growth, cell wall extensibility

DOI: 10.3233/BIR-1994-31205

Citation: Biorheology, vol. 31, no. 2, pp. 171-177, 1994

Authors: Thurston, C.B.

Article Type: Research Article

Abstract: Flow-induced changes in the red cell microstructure of human blood are identified from mechanical and optical evidence. On initiation of steady flow, a new microstructure develops as the shear strain increases through unit strain. This structure is identified with the formation of layers of red cells that slide on plasma layers (Thurston, 1989). At low shear rates, the cell layers are composed of aggregated cells, but at higher shear rates, the aggregates degrade to form thinner layers of oriented, compacted cells. The viscosity is determined by the hematocrit, the degree of compaction and viscosity within the cell layers, and the …plasma viscosity. Degradation of cell aggregates is controlled by 1) the time required for the strain to increase by one unit (Δt1 = 1/shear rate) and 2) the dominant viscoelastic relaxation times of the red cell structures. Structures having relaxation times > Δt1 are degraded by cell disaggregation; when Δt1 is less than the shortest relaxation time of the layered cells, disaggregation and (cell and plasma) layer formation are nearly complete. Analyses of the non-Newtonian viscosity and cell layer characteristics are given for both normal and hardened cells. Show more

Keywords: Blood, non-Newtonian, viscosity, viscoelasticity, shear strain

DOI: 10.3233/BIR-1994-31206

Citation: Biorheology, vol. 31, no. 2, pp. 179-192, 1994

Authors: Deng, L.H. | Barbenel, J.C. | Lowe, G.D.O.

Article Type: Research Article

Abstract: The influence of hematocrit on red blood cell aggregation was investigated using a modified automated Myrenne Aggregometer System. Hematocrit values ranged from 20–70% at 10% increments, and were produced by resuspending washed red cells in autologous plasma. The Myrenne System produced seven kinetic parameters of red cell aggregation. The results indicate that hematocrit (Hct) had a strong and nonlinear effect on erythrocyte aggregability. At both low and high hematocrit, the aggregation intensity (AI) tends to decrease, reaching a plateau at 40% hematocrit. The disaggregation shear rate demonstrates an exponential relationship as ln γ TMIN = 3.29 – …0.0837 Hct . Time constants of the aggregation process such as T1/2 TSLOW and TFAST were rather inconsistent. The increase of hematocrit increased the rate of the fast phase aggregation and slightly slowed the secondary aggregation. Show more

Keywords: Erythrocyte aggregation, hematocrit, cell interaction, rouleaux structure

DOI: 10.3233/BIR-1994-31207

Citation: Biorheology, vol. 31, no. 2, pp. 193-205, 1994

Authors: Friederichs, E. | Meiselman, H.J.

Article Type: Research Article

Abstract: Although many RBC rheological properties have been previously described in detail, the biochemical mechanisms leading to premature destruction of red blood cells are less clear. However, several biochemical processes have been suggested as possible mechanisms for membrane structural alterations (e.g. , crosslinking of membrane proteins, oxidant damage, binding of cytoplasmic proteins, and altered intracellular ion composition). We have carried out a series of studies aimed at evaluating the effects of calcium-regulated membrane-bound hemoglobin (Hbm ) on RBC and derived ghost rheologic behavior. Intracellular calcium was elevated by 10 μ M A23187, with cell deformability determined via the Cell Transit …Analyzer (CTA). Our results indicate: 1) Linear, positive correlations between Hbm and average RBC rigidity and 2) a marked influence of heterogeneous calcium concentration on both Hbm and rheologic properties for various subpopulations. These findings therefore suggest the importance of hemoglobin-membrane interactions as a determinant of erythrocyte deformability, and may be relevant to RBC aging as well as to diseases such as sickle cell anemia, hereditary spherocytosis and thalassemia. Show more

Keywords: Calcium, hemoglobin, deformability, ionophore

DOI: 10.3233/BIR-1994-31208

Citation: Biorheology, vol. 31, no. 2, pp. 207-215, 1994

Article Type: Correction

DOI: 10.3233/BIR-1994-31209

Citation: Biorheology, vol. 31, no. 2, pp. 217-218, 1994

Article Type: Other

DOI: 10.3233/BIR-1994-31210

Citation: Biorheology, vol. 31, no. 2, pp. 219-220, 1994