Biorheology - Volume 26, issue 4

Authors: Chabanel, A. | Samama, M.

Article Type: Research Article

Abstract: Reversible aggregation of red blood cells (RBC) plays an important role in determining the flow properties of blood. To study different factors affecting RBC aggregation we used a new commercially available erythro-aggregameter (SEFAM, Nancy, France). The method allows the photometric quantitation of the kinetics of RBC aggregation and the estimation of the shear resistance of the aggregates. Modification of the hematocrit acts mostly on the determination of the disaggregation shear rate, while plasma composition strongly affects all measurements. Anticoagulants per se do no influence the aggregation process, but can alter the value of the parameters through a plasma dilution effect. …Presence of white blood cells and platelets in the sample did not modify the data. Study on the effects of low concentration of heparin and low molecular weight heparin showed that at therapeutical doses these drugs did not alter the values of the aggregation parameters. Provided that precise guidelines are followed for the processing of blood samples, this method may serve to investigate RBC aggregation in various diseases and to search for adequate hemorheologic treatment. Show more

Keywords: RBC aggregation, hematocrit, anticoagulants, plasma dilution, heparin, white cells and platelets

DOI: 10.3233/BIR-1989-26410

Citation: Biorheology, vol. 26, no. 4, pp. 785-797, 1989

Authors: Matsuo, Takashi | Okeda, Riki | Higashino, Fumio

Article Type: Research Article

Abstract: A study was conducted to investigate the hydrodynamics of branching flow in relation to the blood supply to the basal part of the brain. A series of measurements of the branching loss-coefficients under laminar steady flow were conducted using model branches with various geometries, and the effect of branching on blood supply to distal areas was described using a lumped-parameter model of the vascular structure. It was revealed that in the blood circulation, branching loss is important where a small artery divides off with a large branching angle from a large trunk. It was also indicated that the effect of …such branching on the distal blood supply might become more significant when the peripheral resistance is reduced, thereby increasing the blood velocity in the trunk. Show more

Keywords: Biofluid mechanics, branching flow, energy loss coefficient, cerebral circulation

DOI: 10.3233/BIR-1989-26411

Citation: Biorheology, vol. 26, no. 4, pp. 799-811, 1989

Authors: Zahm, J.M. | Pierrot, D. | Fuchey, C. | Levrier, J. | Duval, D. | Lloyd, K.G. | Puchelle, E.

Article Type: Research Article

Abstract: Methods for measuring the adhesiveness, plasticity, viscoelasticity and spinnability of mucus microsamples have been developed. The rheological properties of the rat gastric and duodenal gel mucus have been analyzed and compared. Using a controlled stress rheometer (Carri-Med), flow and creep experiments showed that gastroduodenal mucus exhibits a typically non-newtonian, pseudoplastic and viscoelastic behaviour. The apparent viscosity (7,800 ± 11,000 Pa.s) and yield stress (24.9 ± 8.5 Pa) of gastric mucus were significantly higher than the duodenal mucus viscosity (39 ± 160 Pa.s) and yield stress (12.9 ± 2 Pa). Spinnability of gastric mucus, measured with a Filancemeter (SEFAM), was significantly …lower (4.9 ± 2.5 mm) in comparison to duodenal mucus (6.9 ± 1.5 mm). Adhesive properties of gastric mucosa (analyzed with the platinum ring method) were not significantly different in comparison to duodenal mucus (99.9 ± 31.5 mN/m and 92.8 ± 11.2 mN/m, respectively). Show more

Keywords: gastroduodenal mucus, adhesiveness, yield stress, non-newtonian behaviour, spinnability

DOI: 10.3233/BIR-1989-26412

Citation: Biorheology, vol. 26, no. 4, pp. 813-822, 1989

Authors: Gallik, Stephen | Usami, Shunichi | Jan, Kung-Ming | Chien, Shu

Article Type: Research Article

Abstract: We employed a static-incubation assay to determine the intensity of wall shear stress (τ ) needed to detach human polymorphonuclear leukocytes (HPMNs) from human umbilical vein endothelial cell (HUVE) monolayers. Confluent monolayers of HUVE were placed in a parallel-plate flow chamber which was mounted on the stage of an inverted tissue culture microscope, attached to a perfusion system and maintained at 37°C. All events in the selected fields were recorded using videomicroscopy. HPMNs were co-incubated for 15 minutes with the HUVE monolayers under control conditions or in the presence of 10−7 M formyl-methionyl-leucyl-phenylalanine (FMLP). Following this static incubation, a series …of five individual flows, each 1 minute in duration, were driven through the flow channel, exposing the cells to 1.0, 2.0, 3.8, 7.6 and 14.8 dyn/cm2 wall shear stresses. Under control conditions, the percentage of HPMNs remaining attached to the HUVE monolayers following exposure to each shear stress was 61, 38, 25, 12 and 5, respectively. In the FMLP-treated condition, the percentage of HPMNs remaining attached to the monolayers was significantly greater than control at all five levels of τ . Thus, under control conditions, adherent HPMNs can be detached from endothelial cell monolayers in vitro with levels of shear stress normally found in the microcirculation (18). In the presence of FMLP, the level of shear stress needed to overcome the adhesions is increased significantly. Show more

Keywords: cell adhesion, endothelium, leukocytes, neutrophils, shear stress

DOI: 10.3233/BIR-1989-26413

Citation: Biorheology, vol. 26, no. 4, pp. 823-834, 1989

Authors: Chaturani, P. | Palanisamy, V.

Article Type: Research Article

Abstract: The effects of polar nature of blood and pulsatility on flow through a stenosed tube have been analysed by assuming blood as a micropolar fluid. Linearized solutions of basic equations are obtained through consecutive applications of finite Hankel and Laplace transforms. The analytical expressions for axial and particle angular velocities, wall shear stress, resistance to flow and apparent viscosity have been obtained. The axial velocity profiles for Newtonian and micropolar fluids have been compared. The interesting observation of this analysis is velocity, in certain parts of cycle, for micropolar fluid is higher than Newtonian fluid. Variation of apparent viscosity η …a with tube radius shows both inverse Fahraeus-Lindqvist and Fahraeus-Lindqvist effects. Finally, the resistance to flow and wall shear stress for normal and diseased blood have been computed and compared. Show more

Keywords: Pulsatile blood flow, Blood rheology, Stenosed tubes

DOI: 10.3233/BIR-1989-26414

Citation: Biorheology, vol. 26, no. 4, pp. 835-846, 1989

Authors: Swarnamani, S. | Singh, Megha

Article Type: Research Article

Abstract: Aggregation of erythrocytes is studied as function of time during their sedimentation process under the gravitational field. The method is based on ultrasonic scattering from the various blood samples in presence and absence of inhomogeneous magnetic field (IMF) and dextran 70 (10%). The experimental arrangement is consisting of ultrasonic transmitter and receiver probes placed in mutually perpendicular direction intersecting at the sampling volume of blood located at the centre of the blood column. The temporal kinetic process is represented in terms of histograms of amplitudes and number of scattering fluctuations related to the size and motion of aggregates. The results …show that the application of IMF influences the aggregation and sedimentation of erythrocytes. The aggregates thus formed sediment faster than that of control sample. The aggregate formation and their movements in presence of dextran 70 are slower than that of normal blood which may be attributed to the enhanced suspending medium viscosity and their interaction with erythrocytes. Show more

Keywords: Erythrocytes aggregation, ultrasound, scattering, histograms, dextran, inhomogeneous magnetic field

DOI: 10.3233/BIR-1989-26415

Citation: Biorheology, vol. 26, no. 4, pp. 847-862, 1989

Authors: McKay, Colin B. | Meiselman, Herbert J.

Article Type: Research Article

Abstract: The effects of suspending medium osmolality (166 to 736 mosm/kg) on relative viscosity (η r ) and tube hematocrit (HT ) measured in 33 diameter tubes were studied for 40, 47 and 57% feed hematocrit (HF k) suspensions of human RBC in buffer. At all feed hematocrits, η r increased sharply for the hypertonic media, but was essentially insensitive to hypotonicity. HT /HF was less affected by osmolality (13% change over the entire range of osmolality and feed hematocrit). Viscosities could not be calculated from the experimental HT values. However, η r could be predicted from …RBC number concentration and the tube diameter/RBC volume ratio via a semi-empirical model. RBC transport efficiency depended on both feed hematocrit and osmolality, and was maximal at or near isotonic conditions. Our results appear applicable to non-isotonic regions of the microcirculation, and to estimation of flow resistance for RBC with abnormal cellular mechanical properties. Show more

Keywords: Viscosity, Tube Hematocrit, Fåhraeus-Lindqvist effect, Fåhraeus effect, RBC Transport

DOI: 10.3233/BIR-1989-26416

Citation: Biorheology, vol. 26, no. 4, pp. 863-874, 1989

Article Type: Announcement

DOI: 10.3233/BIR-1989-26417

Citation: Biorheology, vol. 26, no. 4, pp. 875-875, 1989

Article Type: Other

DOI: 10.3233/BIR-1989-26418

Citation: Biorheology, vol. 26, no. 4, pp. 877-880, 1989