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Biorheology is an international interdisciplinary journal that publishes research on the deformation and flow properties of biological systems or materials. It is the aim of the editors and publishers of
Biorheology to bring together contributions from those working in various fields of biorheological research from all over the world. A diverse editorial board with broad international representation provides guidance and expertise in wide-ranging applications of rheological methods to biological systems and materials.
The aim of biorheological research is to determine and characterize the dynamics of physiological processes at all levels of organization. Manuscripts should report original theoretical and/or experimental research promoting the scientific and technological advances in a broad field that ranges from the rheology of macromolecules and macromolecular arrays to cell, tissue and organ rheology. In all these areas, the interrelationships of rheological properties of the systems or materials investigated and their structural and functional aspects are stressed.
The scope of papers solicited by
Biorheology extends to systems at different levels of organization that have never been studied before, or, if studied previously, have either never been analyzed in terms of their rheological properties or have not been studied from the point of view of the rheological matching between their structural and functional properties. This biorheological approach applies in particular to molecular studies where changes of physical properties and conformation are investigated without reference to how the process actually takes place, how the forces generated are matched to the properties of the structures and environment concerned, proper time scales, or what structures or strength of structures are required.
Biorheology invites papers in which such 'molecular biorheological' aspects, whether in animal or plant systems, are examined and discussed. While we emphasize the biorheology of physiological function in organs and systems, the biorheology of disease is of equal interest. Biorheological analyses of pathological processes and their clinical implications are encouraged, including basic clinical research on hemodynamics and hemorheology.
In keeping with the rapidly developing fields of mechanobiology and regenerative medicine,
Biorheology aims to include studies of the rheological aspects of these fields by focusing on the dynamics of mechanical stress formation and the response of biological materials at the molecular and cellular level resulting from fluid-solid interactions. With increasing focus on new applications of nanotechnology to biological systems, rheological studies of the behavior of biological materials in therapeutic or diagnostic medical devices operating at the micro and nano scales are most welcome.
Abstract: In the presence of macromolecules, e.g., dextrans, polylysines, heparin, or various plasma proteins, red blood cells (RBCs) aggregate to form rouleaux. Aggregation of RBCs results in an acceleration of erythrocyte sedimentation rate and an elevation of low-shear blood viscosity. The mechanism of RBC aggregation has been postulated to be due to macromolecular bridging between adjacent cell surfaces. The bridging energy is a function of the nature of binding and the number of binding sites between the macromolecules and the cell surfaces. RBC surface is negatively charged due to the presence of sialic acids. The interaction of surface potentials results in…a mutual repulsion between cells, especially in the presence of macromolecules. The magnitude of the repulsion is a function of the surface charge density and the ionic composition of the fluid medium. RBC aggregation occurs when the bridging force due to surface adsorption of macromolecules overcomes the electrostatic repulsive force and mechanical shearing force. The net aggregating energy is stored as a change in membrane strain energy. Studies on the ultrastructure of RBC aggregates have shown that the intercellular distance is a function of macromolecular dimensions and that the shape of RBC aggregates is determined by the net aggregating energy. understanding the force balance in RBC interactions serves to establish the physicochemical principles of cell-to-cell interactions induced by macromolecules. It also provides basic information for the understanding of micromechanics of RBC aggregation in blood rheology.
vol. 16, no. 3, pp. 137-148, 1979
Abstract: The rheological properties of blood, nonNewtonian viscosity in steady flow, frequency dependence and shear rate dependence of viscoelasticity in oscillatory flow, and thixotropy, are brought together by a unifying concept. Rheological states are defined which separate nonequilibrium properties, such as thixotropy, from equilibrium properties, such as steady flow viscosity and sustained oscillatory flow viscoelasticity. It is considered that the aggregation of erythrocytes is the primary process governing the conditions of equilibrium. A generalized Maxwell model is developed to provide a basis for quantitative analysis of equilibrium properties. A shear rate dependent degradation function serves to adjust the model elements to…the flow conditions. Characteristic relaxation times become significant rheological parameters for equilibrium viscosity and viscoelasticity while other characteristic times are important to thixotropy. Numerical data are evaluated for the several rheological properties by comparison with the theory using a computerized regression analysis. These determinations show that nonNewtonian viscosity and viscoelasticity can be calculated using the same numerical properties. Thus, the theory provides a rational framework into which several rheological tests of blood can be placed.
vol. 16, no. 3, pp. 149-162, 1979
Abstract: Velocity profile in the arteriole (diameter 80 to 90 µm) of anesthetized frog web was studied by means of a laser Doppler microscope. Since the laser Doppler microscope yields a particle biased mean of flow velocity, a method was postulated to estimate approximately the virtual velocity. The flow velocity at the central, median and marginal portions as well as the pressure gradient along the stream axis varied in response to the cardiac cycle and with a certain time lag. The virtual velocity profile differed from the one predicted from a Newtonian fluid.
vol. 16, no. 3, pp. 163-170, 1979
Abstract: Vascular diseases and risk factors such as smoking are accompanied by an increase in blood viscosity due to the enhancement of aggregation of the red blood cells. This is demonstrated both for smokers and for patients with peripheral vascular disease by comparing the viscoelasticity of the blood with that from healthy donors. Also, the hematocrit values measured by centrifugation for the smokers and patients were found to be significantly higher than for the healthy donors, this difference being attributed to the effects of aggregation. A new unit, the calculated hematocrit, is recommended. This unit, calculated from measured values of blood…and plasma densities, is independent of the conditions of aggregation.
vol. 16, no. 3, pp. 171-178, 1979
Abstract: The viscoelastic parameters of synovial fluids (SF) from various joint diseases and pure hyaluronic acid (HA) solutions of various concentrations were investigated. The complex coefficient of viscosity for these fluids confirmed to show non newtonian flow effects and to be also a function of the HA content. HA solutions at higher concentrations and SF with meniscus defects and degenerative joint disease show higher elastic components than the viscous. This effect is reversed in the case of traumatic and rheumatic arthritis. The latter display a decrease in both viscous and elastic components. The elastic component proved to be a more sensitive…indicator of the changes in joint effusions.
vol. 16, no. 3, pp. 179-184, 1979
Abstract: The complex rheological behavior of the sy.in under biaxial deformations is exhibited in terms of its experimental stress-strain relationships under constant strain level. The stress-strain relationships are anisotropic, nonlinear, strain rate dependent and have considerable hysteresis. The stress-relaxation modes are strain dependent and different for different components of the stress. The sY.in is therefore nonlinear viscoelastic. An attempt is made to develop a rheological model for the skin which is based on the observed structure of its constituents and their mechanical properties. The model emphasizes the importance of the nonuniformities in the skin’s structure as the possible sources of…the skin’s nonlinear and anistropic behavior. It is shown that these nonuniformities can indeed account for the skin rheological behavior. The model consists of two material parameters and four material functions which can be determined for each specimen from results of specific experiments.
vol. 16, no. 3, pp. 191-202, 1979
Abstract: The experimental findings hitherto reported on the permeability of serum albumin have been interpreted theoretically. Serum albumin may be transported either by vesicles through the protoplasm of endothelial cells or through intercellular junctions. Based on a new molecular picture of protoplasm and the junction, it is concluded that there exist weak bonds between protein molecules in the system and that a part of the bonds is broken down by mechanical disturbances. This facilitates the transport of serum albumin across the endothelium. Thus it is expected that the permeability is enhanced by wall shear stress, oscillatory flow, stretch and vibration. It…is further expected that positive circumferential tension of a blood vessel wall enhances its permeability. This prediction is in good agreement with the experimental finding that hypertensive arterial lesion is apt to develop in those regions where positive circumferential tension is easily induced.
vol. 16, no. 3, pp. 203-209, 1979
Abstract: In order to explain the pathogenesis of regional atherosclerotic plaques, the solid-dynamical force is emphasized. The regi.onal stress and deformation in the arterial wall near the ostium hole for branching is analyzed within the framework of shallow shell approximation. A high concentration in the stress and deformation is demonstrated. Following making a theoretical explanation how the regional stress and deformation could be involved for the transport of molecules across the endothelium, a new factor of the regional initiation of atherosclerosis is proposed.
vol. 16, no. 3, pp. 223-230, 1979
Abstract: Fluid mechanical factors are probably involved in the localization of atherosclerotic lesions and the deposition of platelet thrombi at arterial branches where secondary flows and vortices develop. Hence, we have studied the flow patterns in glass models of 3 mm diameter right angled T-junctions with square or rounded corners. With flow entering through the main tube, cine films of the paths of microspheres in dilute suspensions were taken at inflow Reynolds number Reo from 15 to 420 and flow ratios Q1 /Q2 main: side tube from 0.05 to 4.0. In the square T-junction, paired vortices symmetrical about the common…median plane formed at the entrances of the main and side daughter tubes over a wide range of Reo and Q1 /Q2 . Particles spiralled in open streamlines through the large main vortex; some then crossed above or below the mainstream to the side tube and through the side vortex, downstream of which there was a double helical flow. At high Q1 /Q2 , only the side vortex was present. At Q1 /Q2 < 0.1 and Re0 > 100, a third vortex formed downstream of the main vortex. In the rounded T-junction, the main vortex was formed at a lower, and the side vortex at a higher Reo than in the square T-junction. When flow entered through the side tube, paired connected vortices were also formed, but only when one daughter tube was severely occluded.
vol. 16, no. 3, pp. 231-248, 1979
Abstract: In view of a possible contribution of turbulent flow upon atherogenesis, particularly at bifurcations of vessels, an evaluation of the nature of flow in man in the abdominal aorta and common iliac artery was made. Velocity was measured in eight resting patients with a hot film velocity probe. A particular effort was made to record velocity in the region of the bifurcation of the aorta at the common iliac arteries. No high frequency disturbances of velocity were observed in the abdominal aorta or common iliac arteries, either during systole or diastole in any of the patients. Peak velocity in the…aorta, at the level of the renal artery, was 28 ± 4 cm/sec (mean ± SEM), at the aortic bifurcation it was 27 ± 4 cm/sec and at the common iliac artery it was 24 ± 4 cm/sec. The peak Reynolds number, measured at the aortic bifurcation (in four patients), ranged from 400 to 1100, and in the common iliac artery it ranged from 390 to 620. Absence of turbulent flow in the abdominal aorta and common iliac arteries in resting patients suggests that turbulence does not initiate atherosclerosis in these areas. However, a possible contribution of turbulence to atherosclerosis, once plaque formation has caused an irregularity of arterial walls, cannot be excluded.
vol. 16, no. 3, pp. 249-255, 1979
Abstract: It is now recognized that relations exist between mechanical factor of blood and occurrence of atheromatous plates. Various phenomena can interfere, such as parietal friction, separated zones and instabilities. In particular, measurement of parietal flow depends on the instruments available and few of them are able to give an accurate evaluation of instantaneous local velocities without perturbing the blood flow. For this purpose, an ultrasonic Doppler method is proposed associating echo graphic and Doppler techniques whereby local velocities and gradient on the vascular wall can be obtained in vivo and in vitro. Specific procedures are established i) to get a…convenient spatial resolution, ii) to provide calibrated values of the longitudinal component of velocities, involving a biangulation method.
vol. 16, no. 3, pp. 257-263, 1979
Abstract: The study described is intended to demonstrate the relation which can exist in the parietal microenvironment between blood flow and metabolic surface phenomena. For this purpose modelisation technique is used. An enzymatic protein (beta galactosidase EC-220.127.116.11) is fixed on the internal surface of a nylon tube, throught which a calibrated flow of substrate (orthonitrophenyl β -D galactoside (ON PG) is generated by a pump. Variations in catalytic activity under influence of flow is monitored by enzymatic kinetic measurement. The influence of wall stresses GM induced by continuous flow of substrate is studied. Distinction should be made between Michaelis behavioural…reaction rate and reaction rate controlled by diffusion; for GM values less than 125 s−1 , the process of substrate transfer to the wall depending on diffusion.
vol. 16, no. 3, pp. 265-276, 1979