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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: A parallel-plate flow chamber was used to quantify the detachment of normal, transformed, and reverted rat fibroblasts from a confluent monolayer of normal fibroblasts. In this method, known shear stresses were applied to the adherent cells and the percent of cells detached from the monolayer was determined. Results indicate that the detachment of all cell types increased with increasing shear stress and detachment of highly metastatic ras-transformed cells was significantly higher than that of either nonmetastatic normal cells or transformed cells reverted with the Kirsten ras revertant (K-rev 1a) gene, which are lowly metastatic. From these results, it is concluded…that a correlation exists between the metastatic phenotype of the cell and its ability to detach from normal cells.
Abstract: An unsteady convective diffusion in a synovial fluid of human joints modeled as a power-law fluid is studied using the generalized dispersion model of Gill and Sankarasubramanian (Fan, L.T. and Wang, H.N. Dispersion of Matter in non-Newtonian Laminar Flow Through a Circular Tube, Proc. Roy. Soc. Lond. , A292, 203 - 208, 1966.). The contributions of convection and diffusion, and pure convection on the dispersion of nutrient are investigated in detail. It is shown that the effect of decrease in non-Newtonian parameter is to decrease the dispersion coefficient. The mean concentration distribution appears to increase as the non-Newtonian parameter decreases…upto a certain value of the axial distance. Beyond this point, however, the reverse pattern is observed.
Abstract: Plasmodia and other intraerythrocytic parasites reduce the deformability of the red cells they infect. One mechanism potentially responsible for this reduction in deformability is the decrease in the surface:volume (S/V) ratio of the red cell which occurs with parasite growth. To examine this hypothesis, normal red cells were allowed to phagocytize polylysine-coated latex spheres 1.0 to 2.9 μ m in diameter. Deformability decreased progressively with spheres of increasing size, consistent with the decreasing S/V ratios of those cells (from an initial length:width [L/W] ratio of 2.398 ± 0.549 for normal red cells to 1.559 ± 0.249 for red cells containing…2.92 μ m latex spheres at 40 dynes per cm2 , p < 0.001). Nevertheless, red cells containing latex spheres 2.0–2.9 μ m in diameter remained deformable and continued to tank tread, in contrast to red cells containing Plasmodium falciparum parasites of that size, which are not deformable and do not tank tread. The progressive decrease in S/V produced by the latex spheres is consistent with their effect on the L/W ratio. However, the total loss of deformability observed with red cells containing parasites of similar or smaller size cannot be explained on these grounds alone. It suggests an additional mechanism, such as calcium-induced crosslinking of the red cell cytoskeleton.
Keywords: Rheology, erythrocyte, erythrocyte deformability, malaria, P. falciparum
vol. 28, no. 3-4, pp. 221-229, 1991
Abstract: The ability of red cells to deform is essential to allow their circulation. However the degree of rheological abnormality which can be tolerated before flow is impaired is not so clear. Red cell rheology has been characterised in a number of physiological, pathological and genetic conditions, and some inferences can be drawn. In vivo ageing causes a small loss of cell deformability attributable to increased membrane and internal viscosity; volume and surface area are also lost. These changes cannot be sufficient to cause cellular removal, since the cells sampled had continued to circulate. In sickle cell disease, the oxygenated blood…contains dense cells that are more severely abnormal than dense, aged cells from normal individuals. Melanesian ovalocytes have comparable rigidity to dense SS cells, but this condition has no marked Circulatory pathology. Thus circulatory problems in SS disease probably stem from deoxygenation-induced sickling which causes extreme loss of deformability, rather than from the abnormal cells in oxygenated blood. In falciparum malaria, immature parasites cause appreciable loss of deformability but continue to circulate. Maturation of the parasites causes much greater rheological changes, including attachment to vascular endothelium, and the cells cease to circulate. In summary, quite marked changes in cell mechanics can occur without loss of ability to circulate. It thus seems that slight rheological alterations reported in some clinical studies are unlikely to cause appreciable flow disruption.
Abstract: Effects of the non-Newtonian viscosity of blood on a flow in a coronary arterial casting of man were studied numerically using a finite element method. Various constitutive models were examined to model the non-Newtonian viscosity of blood and their model constants were summarized. A method to incorporate the non-Newtonian viscosity of blood was introduced so that the viscosity could be calculated locally. The pressure drop, wall shear stress and velocity profiles for the case of blood viscosity were compared for the case of Newtonian viscosity (0.0345 poise). The effect of the non-Newtonian viscosity of blood on the overall pressure drop…across the arterial casting was found to be significant at a flow of the Reynolds number of 100 or less. Also in the region of flow separation or recirculation, the non-Newtonian viscosity of blood yields larger wall shear stress than the Newtonian case. The origin of the non-Newtonian viscosity of blood was discussed in relation to the viscoelasticity and yield stress of blood.
Abstract: An in vitro experimental system was developed to study the interaction between endothelial cells and blood as an early event in coagulation. A designed vascular vessel model tube is composed of a monolayer of bovine aorta endothelial cells (BAECs) cultured on an inner surface of a glass tube by means of a rotatory cultivation method. The change of fluidity during coagulation of blood in the tube was measured by a rheological technique. The rate of coagulation of blood in contact with endothelial cells was affected by cell culture conditions such as cell age, passage number of BAECs and substrate beneath…endothelial cells. Fibrinolytic activity of the cells was examined by the rheological method. The present experimental system would be useful in examining the mechanism of blood coagulation based on the interaction between blood and endothelial cells as well as in evaluating endothelial cell functions.
Abstract: A vasomotion activity in the mesentery of anesthetized rabbits were studied by simultaneous measurements of inside diameters at multiple sites in arterioles, precapillaries and their bifurcations. A frame-by-frame diameter determination technique was used with a microcomputer-assisted laser video disk recorder and a video-image analysis system. Simultaneous intensity profiles across microvessels were continuously obtained. Applying an automatic wall surface tracer and a graphic editor to construct temporal sequences of intensity profiles, we obtained digitized data of inside diameters of microvessels, and implemented cross-correlation analysis between data sets to calculate phase differences of vasomotion at separated sites. The present analysis of the…propagation of vasomotion showed that the vasomotion originated from the orifice of precapillaries at the bifurcations, spreading downstream in the precapillary. The vasomotion wave spreads both upstream and downstream along single arterioles from various origins of the vasomotion activity. The propagation velocity of vasomotion was 0.17±0.03 mm/sec (n=19), and it became significantly slower through the branching points than along the arterioles. It is suggested that the vasomotion in terminal arterioles and precapillaries may spread through some mechanical transmission factors.
Abstract: So far, it has been hypothesized that numerical data obtained in steady flow conditions apply to pulsatile flows. In order to study the modifications of the velocity fields due to pulsatility, jets were produced by 8 orifices (with a diameter “D” of 4.4 to 11.3 mm) included in a chamber of 50 mm. The velocity was measured using laser Doppler anemometry with a pulsatile flow (“pf”) and compared to the values obtained in steady (“sf”): at maximum velocity, the longitudinal velocity profile is qualitatively similar to this observed in steady flow: it is made of a plateau followed by an…hyperbolic velocity decay in the turbulent area. The length of the core (“Lpf”) is strongly related to “D” (Lpf = 3.72 D + 5.49, r = .99) and the velocity decay depends on the ratio between the distance “x” from the orifice and “D” (V/Vo = 2.83D/x + 3.46, r = .85, where V is the velocity at “x” and Vo the initial velocity). During the acceleration and the deceleration, the laminar core is disturbed by turbulences. The comparison of “pf” data with “sf” data demonstrated similar diameters at the origin of the jets (Dpf = 0.96 Dsf + .12, r = .99), but significant (p < .0001) differences both for “L” and “V/Vo ”: Lpf = .91Lsf + 6.58, r = .97, V/Vopf = .63 V/Vosf + .34, r = .76. Thus, pulsatility modifies velocity fields and the results obtained in steady flow conditions do not apply to pulsatile jets.
Abstract: The micropipette aspiration technique was used to investigate the deformation properties of a panel of nontransformed and transformed rat fibroblasts derived from the same normal cell line. In this method, a step negative pressure is applied to the cell via a micropipette and the aspiration distance into the pipette as a function of time is determined using video techniques. A standard solid viscoelastic model was then used to analyze the viscoelastic properties of the cell. From these results, it is concluded that a direct correlation exists between an increase in deformability and progression of the transformed phenotype from a nontumorigenic…cell line into a tumorigenic, metastatic cell line.
Abstract: The assessment of vessel patency can be substantially improved by serial microvessel diameter measurements taken successively along an extensive length of the vessel. It is possible to avoid making the a priori assumptions about the existence or location of local constriction sites implicit in single diameter measurements. The problem then becomes one of making sense of tens or hundreds of measurements for each vessel. Equivalent diameter is defined here as as the diameter of a uniform circular cylinder of the same length as the original vessel, and having the same total resistance. Direct computation of the equivalent diameter, without…taking measurement errors into account, leads to an underestimation of the true equivalent diameter even if the individual diameter measurements were not biased. We have developed a method for effectively eliminating this bias. It has been applied to serial microvessel diameter measurements of the guinea pig cochlea, automatically measured using an image analysis system (1). In this report, the results were developed for diameter estimates with an approximate gaussian distribution; however the method is readily extended to other error distributions. Convergence of the bias compensation was rapid. Use of the new method is advisable with as few as three diameter estimates per vessel.