Biorheology - Volume 31, issue 4

Authors: Goldsmith, Harry

Article Type: Editorial

DOI: 10.3233/BIR-1994-31401

Citation: Biorheology, vol. 31, no. 4, pp. iii-iii, 1994

Authors: Miftakhov, R. | Wingate, D.

Article Type: Research Article

Abstract: A mathematical model and results of numerical simulation of the peristaltic reflex development of the small bowel are presented. The organ is modeled as a soft orthotropic cylindrical biological shell, reinforced by the smooth muscle elements. Their mechanical activity is under the control of a simple reflex arc represented by a single cholinergic neurone. The dynamical reaction starts as a response to the depolarization wave propagating along the smooth muscle layers. The muscle layers contract independently but in a coordinated way with the generation of active forces. The mechanical properties of the wall are supposed to be nonlinear. Deformations of …the bioshell are finite. The governing system of equations is obtained and solved numerically. The finite-difference method of second-order accuracy over the time and space variables has been used. The dynamics of stress-strain distribution in the biological shell and shape changes are analyzed. It is shown that there is no axial symmetry in the organ’s deformation during the first (preliminary) stage of motor reaction. Only with the development of propulsive contractions is the symmetry observed. Show more

Keywords: Small bowel, peristaltic reflex, biomechanical model, numerical simulation

DOI: 10.3233/BIR-1994-31402

Citation: Biorheology, vol. 31, no. 4, pp. 309-325, 1994

Authors: Lee, B. | Litt, M. | Buchsbaum, G.

Article Type: Research Article

Abstract: The viscoelastic properties of the vitreous body from bovine and porcine eyes were determined by microrheometry. Each vitreous sample was sectioned into anterior, central and posterior segments. The rheological properties of each species and region were compared with each other and with the viscoelastic properties of human vitreous reported earlier. The results showed significant variations among species, as well as between regions in all species. All regions of human vitreous have significantly different rheological properties from those of the cow, and from the anterior and posterior regions of the pig; however, the viscoelastic behavior of the central porcine region closely …resembles that of the human. In comparing the three species, the major differences found are in those parameters characterizing “viscous” or dissipative properties; values of “elastic” or energy storage properties were similar. Show more

Keywords: Vitreous body, viscoelasticity, compliance, bovine eye, porcine eye

DOI: 10.3233/BIR-1994-31403

Citation: Biorheology, vol. 31, no. 4, pp. 327-338, 1994

Authors: Lee, B. | Litt, M. | Buchsbaum, G.

Article Type: Research Article

Abstract: The vitreous body from bovine, porcine, and human eyes was analyzed for concentration of selected components. Each vitreous sample was sectioned into anterior, central, and posterior segments. The segments were analyzed for concentration of Ca+2 , Cl− , Na+ , and K+ , as well as of Collagen and Hyaluronic acid. The four electrolytes showed significant differences between species, but no significant regional variations. The two macromolecules showed significant differences with respect to both species and region within the vitreous. Comparison of these results with previously determined rheological values for the three species revealed a number of unexpected results, such …as higher polymer concentrations on average being associated with lower values of viscosity parameters. The results are analyzed in terms of possible compositional differences among species and effects of electrolytes on the viscoelastic behavior of the vitreous’ macromolecules. Show more

Keywords: Vitreous body, electrolytes, collagen, hyaluronic acid, rheology

DOI: 10.3233/BIR-1994-31404

Citation: Biorheology, vol. 31, no. 4, pp. 339-351, 1994

Authors: Sung, L.A. | Kabat, E.A.

Article Type: Research Article

Abstract: The adhesive energy in lectin-induced agglutination can be assessed by the deformation of erythrocytes in aggregates. Helix pomatia (HPA) and Dolichos biflorus (DBA) specifically agglutinated blood group A erythrocytes and induced a change in curvatures of cells at the end of the aggregates. The curvatures changed from concavity to convexity with increasing lectin concentrations. HPA-induced aggregates achieved the theoretical maximal end cell curvature of 0.27 μ m−1 at 2–3 μ g/ml; DBA-induced aggregates approached 0.23 μ m−1 , requiring 400 μ g/ml. At any given lectin concentration, HPA showed greater surface binding, caused higher cell curvatures, induced …larger aggregate size, and had greater adhesive energies, as compared to DBA. HPA and DBA are globular proteins with a diameter of ∼5.5 nm and ∼6.1 nm, respectively, as revealed by the negative staining electron microscopy. The former induced uniform intercellular spacing (∼15 nm), whereas the latter induced both smooth (∼20 nm) and ruffled spacings. The uniform intercellular spacing was not a function of lectin concentrations. Microscopic studies of erythrocyte deformation provided morphological correlates of biophysical findings of differential adhesive energies induced by these two blood group A-specific lectins. Show more

Keywords: Lectin, agglutination, deformation, erythrocytes, blood-group, electron microscopy

DOI: 10.3233/BIR-1994-31405

Citation: Biorheology, vol. 31, no. 4, pp. 353-364, 1994

Authors: Matsumoto, T. | Naiki, T. | Hayashi, K.

Article Type: Research Article

Abstract: Effects of wall compliance on the flow characteristics were studied by visualizing pulsatile flow in two straight elastic tubes having different compliance and in a rigid tube. The elastic tubes were made of segmented polyether polyurethane and their compliance was adjusted by varying the wall thickness. Their diameter changes were ±3.3 and ±4.9% for the pressure pulsation between 20 and 250 mm Hg. An acrylic pipe was used for the rigid model. An air-driven artificial heart was used to generate the pulsatile flow having the mean Reynolds number and frequency parameter of 740 and 11.4, respectively. The flow was …visualized by the hydrogen bubble method at every 5% of the pulsatile flow cycle. Velocity distributions along the tube diameter were determined from still images of time lines taken with a CCD camera. The ratio of the wall shear rate in the elastic tubes to that in the rigid tube at each phase correlated well with the radial velocity of tube wall, while it had no significant correlation with the instantaneous tube diameter. These results suggest that the wall compliance either increases or decreases the wall shear rate depending on the phasic relation between the flow and pressure waves. When studying the hemodynamic effects on vascular diseases by model experiments, it may be important to take wall elasticity into account. Show more

Keywords: Pulsatile flow, elastic tube, blood flow, wall shear rate

DOI: 10.3233/BIR-1994-31406

Citation: Biorheology, vol. 31, no. 4, pp. 365-381, 1994

Authors: Dobashi, T. | Idonuma, A. | Toyama, Y. | Sakanishi, A.

Article Type: Research Article

Abstract: The enhanced rate of sedimentation of erythrocytes in an inclined rectangular vessel was measured under microscopic and macroscopic conditions. The velocity profile, V(x), and the thickness, δ , of the upflow layer generated below the downward-facing wall in the sedimentation vessel were measured under a microscope with polystyrene latex as a tracer particle. Here, x is the distance from the vessel wall. All the data of the velocity profile are represented by a single curve, [ V max − V ( x ) ] / V max …= [ ( δ − x ) / δ ] 2 , irrespective of the volume fraction, H, and tilt angle, θ , in the range of 0.05 < H < 0.30 and 10°< θ < 40°, where Vmax is the maximum velocity found at the upflow boundary. The rate of fall of the top surface of the suspension v(H, θ ) fits the function, v ( H , θ ) = v ( 0 , θ ) ( 1 − H ) exp [ − ( aH + bH 2 ) ] , well, irrespective of H and θ . These experimental results are compared with the theory of Acrivos and Herbolzheimer. Show more

Keywords: Erythrocyte sedimentation rate, Boycott effect, upflow layer, velocity profile, master curve

DOI: 10.3233/BIR-1994-31407

Citation: Biorheology, vol. 31, no. 4, pp. 383-393, 1994

Authors: Maeda, N. | Nakajima, T. | Izumida, Y. | Suzuki, Y. | Tateishi, N. | Senama, A.

Article Type: Research Article

Abstract: Rheological characteristics of red cells in two patients with refractory anemia (with single chromosomal abnormality of 20q− or 13q− , respectively) were investigated with the hematological and biochemical properties. (1) Whole blood viscosity was remarkably increased, and the red cell deformability was greatly impaired (the impairments were prominent in patient with 20q− ). (2) The hematocrit of both patients was about half of the normal value. Remarkable anisocytosis with elliptocytes and poikilocytes was observed in the patient with 20q− , but the anisocytosis was not so prominent in the patient with 13q− . (3) 2,3-diphosphoglycerate content in red cells …was markedly increased in both patients, but adenyl ate content was not. (4) The red cells were slightly resistant to osmotic hemolysis, but they were not heat-labile. (5) Structural abnormality of spectrin was suggested from the impaired dimer-dimer association in red cell membrane and from the different susceptibility of spectrin to tryptic digestion. In conclusion, the rheological impairments and the abnormal shape of red cells in refractory anemia probably originated from the structural abnormality of cytoskeletal proteins in membrane, and the functional and structural abnormality may be different among patients. Show more

Keywords: Erythrocyte deformability, refractory anemia, erythrocyte membrane, spectrin, blood viscosity, osmotic hemolysis

DOI: 10.3233/BIR-1994-31408

Citation: Biorheology, vol. 31, no. 4, pp. 395-405, 1994

Authors: Gudmundsson, M. | Oden, A. | Bjelle, A.

Article Type: Research Article

Abstract: Different methods of measuring whole blood viscosity using a couette rotational viscometer were compared to establish its use in clinical rheumatological practice. The relationship between blood viscosity and hematocrit was approximately exponential and no significant differences in the slopes were found between healthy controls and rheumatoid arthritis patients. Correction of native blood viscosity to a standard hematocrit of 40% by extrapolation from a standard regression curve, established by concentration/dilution of samples from healthy persons to correct for hematocrit differences and at shear rate 92s−1 , was the best method for differentiating between viscosities of patients and controls. It was also …the least laborious method, requiring the smallest amounts of blood and having the lowest method error. Native blood viscosity, corrected blood viscosity, plasma viscosity and red cell aggregation were all significantly higher and hematocrit significantly lower in rheumatoid arthritis patients than in controls. Show more

Keywords: Blood viscosity, plasma viscosity, hematocrit, red cell aggregation, rheumatoid arthritis, blood donors

DOI: 10.3233/BIR-1994-31409

Citation: Biorheology, vol. 31, no. 4, pp. 407-416, 1994

Article Type: Abstract

DOI: 10.3233/BIR-1994-31410

Citation: Biorheology, vol. 31, no. 4, pp. 417-503, 1994