Biorheology - Volume 21, issue 6

Article Type: Editorial

DOI: 10.3233/BIR-1984-21608

Citation: Biorheology, vol. 21, no. 6, pp. I-III, 1984

Authors: Sugihara, Masako | Niimi, Hideyuki

Article Type: Research Article

Abstract: The motion of a red blood cell in a plane Couette flow is studied theoretically, introducing a two-dimensional microcapsule model for the cell. It is assumed that the microcapsule is deformed into an elliptical shape with a constant area and that its membrane moves like a tank- tread around the interior. The flow fields both inside and outside the microcapsule are analyzed using the finite element method in the Stokes equations and the obtained viscous forces on the membrane are used to determine its deformation and tank-treading motion. It is shown that a decrease in viscosity ratio of internal …to external fluids causes the microcapsule to be more elongated, with its inclination angle increasing, whereas the microcapsule becomes more elongated at a smaller inclination angle with a longer tank-treading period as the elastic compliance of the membrane or the shear rate of the Couette flow increases. The force acting on the wall is also examined in relation to the abnormal viscosity of blood. Show more

Keywords: Couette flow, deformability, red blood cell, stationary orientation motion, tank-treading motion, unsteady flipping motion

DOI: 10.3233/BIR-1984-21601

Citation: Biorheology, vol. 21, no. 6, pp. 735-749, 1984

Authors: Tokita, Masayuki | Fujiya, Yoshinobu | Hikichi, Kunio

Article Type: Research Article

Abstract: The dynamic mechanical property of the vitreous body was studied as functions of frequency and temperature. The data at different temperatures were found to be superposable onto a single set of master relaxation curves. It was found that the shape of the composite master relaxation curves of the vitreous body resembles that of the network polymer system except for the very small absolute value of the shear modulus.

Keywords: Dynamic Viscoelasticity, Vitreous Body, Master Relaxation Curves, Very Lightly Cross-linked Gel, Hyaluronic Acid, Collagen

DOI: 10.3233/BIR-1984-21602

Citation: Biorheology, vol. 21, no. 6, pp. 751-756, 1984

Authors: Rogausch, H.

Article Type: Research Article

Abstract: Lysolecithin is formed by enzymatic processes in the blood plasma both in vivo and in vitro. Erythrocyte suspensions which are treated with lysolecithin, have a higher viscosity than normal erythrocytes. At high shear rates this may be attributed to a reduced deformability of these cells. At shear rates below 10 s−1 , however, these erythrocytes maintain their resting shape (which is that of a spiculated sphere) and their viscosity is 8 times higher than that of aldehyde-hardened erythrocytes. It is therefore concluded that the reduced deformability of lysolecithin-treated erythrocytes is not the cause of their high viscosity at low flow …velocities. The results of this paper suggest that lysolecithin-treated red cells have an increased functional volume due to the immobilization of fluid between their spicules. Furthermore the lysolecithin-treated erythrocytes, despite their sphered shape can attach to each other when the suspending medium contains long-chain molecules. Both the increased functional volume and the attachment of the cells can explain the high viscosity values at the lower shear rates. Show more

Keywords: Erythrocytes, lysolecithin, viscosity

DOI: 10.3233/BIR-1984-21603

Citation: Biorheology, vol. 21, no. 6, pp. 757-765, 1984

Authors: Schmid-Schönbein, Geert W. | Jan, Kung-Ming | Skalak, Richard | Chien, Shu

Article Type: Research Article

Abstract: Human leukocytes in a blood film exhibit a significantly larger diameter than in the circulation. This is due to the fact that white cells are highly deformed during preparation of a blood film. Instead of having the usual spherical shape, the cells are compressed to “pancake” forms with a thickness of about 1 µm. Hematological investigation is usually performed on these compressed cells, but in the circulation they are not observed. The deformation of the cells on a blood film is due to compression by the glass edge used to spread the blood. After deformation leukocytes do not have enough …time to recover since the blood film usually dries in a shorter period than is needed for cell recovery. The shape and size of the leukocyte on the blood film is not only determined by cell volume but also by the cell membrane area. This is shown for each kind of leukocyte by independent prediction of the pancake dimensions from previous measurements of cell volume and membrane area. Leukocytes which are strongly compressed during blood film preparation may exhibit mechanical damage with rupture of membranes. Show more

Keywords: Blood Smear, Leukocyte Deformation

DOI: 10.3233/BIR-1984-21604

Citation: Biorheology, vol. 21, no. 6, pp. 767-781, 1984

Authors: Sallam, Ahmed M. | Hwang, Ned H.C.

Article Type: Research Article

Abstract: Various previous models used in studying red blood cell (RBC) hemolysis in turbulent shear flows are reviewed from a fluid dynamic point of view. The effect of turbulent shear stress (Reynolds shear stress, τ R ) on RBC hemolysis is investigated utilizing a submerged axisymmetric jet flow field. A detailed survey of the flow field is made with a laser Doppler anemometer system to obtain contour maps of the mean velocity distributions, relative turbulence intensities, and τ R distributions in the field prior to conducting the experiment of sampling and analyzing the cells free-hemoglobin in the field. A new …two-point sampling technique, developed in this laboratory, allows collections of RBC samples from selected locations in the flow field so that a relationship between the local shear stress level and the cell damage may be established. The threshold level of τ R responsible for incipient hemolysis is found to be approximately 400 Newtons per square meter (N/m2 ), below which a sublethal region of zero hemolysis is observed. Show more

DOI: 10.3233/BIR-1984-21605

Citation: Biorheology, vol. 21, no. 6, pp. 783-797, 1984

Authors: Timanin, E.M.

Article Type: Research Article

Abstract: Stress relaxation regimes arising in a muscle subject to stepwise deformation are described on the basis of a recent phenomenological model of fully activated muscle tissue which is presented in the form of a second-order constitutive equation. It is shown that this model reproduces the qualitative form of relaxation curves observed experimentally. Relations between rheological parameters which correspond to different types of stress relaxation are found for the case where the jump duration is much smaller than the relaxation times of the sample. As illustrated by the simplest model of a slow length jump (linear deformation), the qualitative form of …the stress relaxation depends on the jump duration in this case. This effect can lead to rough errors in determination of rheological and molecular parameters of muscle tissue in mechanical experiments in which the relation between jump duration and relaxation times is not controlled. Show more

Keywords: fully activated muscle tissue, constitutive equation, stepwise deformation, stress relaxation, jump duration

DOI: 10.3233/BIR-1984-21606

Citation: Biorheology, vol. 21, no. 6, pp. 799-808, 1984

Article Type: Correction

DOI: 10.3233/BIR-1984-21607

Citation: Biorheology, vol. 21, no. 6, pp. 809-809, 1984