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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: An apparatus for measuring the concentration profile of erythrocytes of human whole blood in settling tubes was devised. Experiments were made on the blood of five healthy male donors. A two-region moving boundary mathematical model for the erythrocyte sedimentation under unsteady state condition was developed for the settling process. A solution was obtained to give the expression of the erythrocyte concentration as a function of settling time and the distance along. the settling tube. From the mathematical model, two parameters, the mean sedimentation velocity and the diffusivity of erythrocytes, are the two main factors which control the shape of the…erythrocyte concentration profile. A statistical method of parameter estimation was employed to determine these two parameters from five sets of concentration profiles experimentally secured. It was found that the diffusivity of erythrocyte varies between 1.5 × 10−4 –2.0 × 10−3 cm2 /sec. The range of variation of the mean sedimentation velocity is quite broad from 1.5 × 10−7 to 2.0 × 10−4 cm/sec among five blood samples. Also, the diffusivity of erythrocytes was found to be the predominant parameter which controls the erythrocyte concentration profile and the erythrocyte sedimentation rate (ESR).
vol. 14, no. 2-3, pp. 69-73, 1977
Abstract: Dextran (dx) in excess of 40,000 MW can induce weak cell aggregation of native human erythrocytes (RBC) and formaldehyde-fixed RBC (F-RBC) by macromolecular bridging. Cellular aggregation is measured both microscopically and by a rheological method in which the relative viscosity ratio, R = [ ( η / η 0 ) dx , I / ( η / η 0 ) saline ] estimated at sufficiently low shear rates gives an index of the degree of cellular aggregation. The observed aggregation increases to a maximum at…a characteristic dx concentration and then diminishes at higher concentrations until it is absent above a characteristic concentration. Elevation of bulk dextran concentration through this range gives proportional increases in adsorbed polymer and is accompanied by increases in the electrophoretically measured zeta potential of the cells. The correlation of the zeta potentials at disaggregation and the low shear behavior of RBC in the presence of dx support the notion that intercellular electrostatic interactions are an important opposing force to polymer bridging and that weak aggregation could be detected by low shear viscometry. To establish the role of cell deformation in the rheological estimation of aggregation, the degrees of aggregation, zeta potentials, and flow behaviors at low shear were compared for deformable RBC and nondeformable F-RBC in media of differing ionic strengths and dextran T-70 concentrations. In contrast to RBC, F-RBC aggregated weakly in the absence of dx at ionic strengths > 0.03 M and higher dx concentrations were required to disaggregate the cells. At high dx concentrations the zeta potentials associated with disaggregation of F-RBC at different ionic strengths were approximately constant but were consistently higher than for RBC. The rheological estimation of aggregation provided a satisfactory index of the extent of cell–cell cohesion for RBC, but it gave no indication of very weak aggregation of F-RBC under the measurement conditions employed.
vol. 14, no. 2-3, pp. 75-84, 1977
Abstract: Flow of blood into the microcirculation becomes progressively slower until, in the finest vessels, the average velocity approaches zero. The pressure gradient also falls progressively until it too approaches zero. The effect of pressure gradient on blood flow may be studied in tubes of any convenient size; in this report a tube 0.55 mm in diameter was used. Owing to the great variability in flow resistance of samples prepared in identical fashion from different subjects, simple viscosity measurements at a single pressure gradient will produce only an array of viscosities. An innovation was adopted: two pressure gradients, one…of which was the lowest practicable and the other two and one-half times greater, were employed to produce a basis for an “internal comparison”. The ratio between the two apparent viscosities is a dimensionless number that characterizes the sample. By our method all Newtonian liquids of whatever viscosity must yield a ratio of 2.5. Our experimental samples, which were 87% red cell suspensions, produced a range of ratios from 1.6 to 9.7. Normal subjects and patients with diseases other than cancer had ratios above 4.0, In marked contrast, patients with cancer occupied the range below 3.9.
vol. 14, no. 2-3, pp. 85-89, 1977
Abstract: Erythrocytes suspended in different viscosity solutions of dextran in Hanks’ solution have been exposed to shear stress in capillaries of radius ranging from 0.125 to 0.30 mm and lengths ranging from 1.0 to 100 cm. A high degree of lysis resulted when the cells were stressed at around 3 kN/m2 . Lysis occurred in a time less than 0.45 ms. Turbulence played no part in the cell breakage and it is shown that shear stress accounts well for the observed effects. When the stress was decreased to the region of 1.5 kN/m2 little lysis was observed even though the…exposure time was increased by orders of magnitude on 0.45 ms.
vol. 14, no. 2-3, pp. 91-97, 1977
Abstract: Studies of red cell aggregation have suffered from the lack of a satisfactory definition of the degree of aggregation. On the basis of hundreds of observations involving normal and diseased samples of blood under various conditions, a definition is presented which relates to the variance in light intensity as one scans the field of view. The approach has led to separation into five classes in increasing order of aggregation. The five classes can be described in qualitative terms and can be distinguished by eye. This procedure offers a direct measure of red cell aggregation which lends itself to automation and…quantification on a continuous scale using scanner and computer techniques.
vol. 14, no. 2-3, pp. 99-103, 1977
Abstract: A brief review of the linear theory of viscoelasticity is given for both steady flow behavior and sinusoidal deformations. The causes and the molecular interpretation for departure from linear theory is discussed. A discussion is presented as to why one might expect molecules of biological importance to be more prone to non-linear behavior than synthetic polymers which have been the focal point of much of the experimental work performed in the area, to date. Examples are given for dispersions of lecithin in water. The concept of a weak structure in the material is presented such that Bingham-like behavior is…obtained. Often the nature of the experiment destroys the structure and hence obscures the Bingham-like behavior.
vol. 14, no. 2-3, pp. 105-109, 1977
Abstract: Earlier reports of increased blood viscosity and greatly increased RBC membrane rigidity consequent to adenosine triphosphate (ATP) depletion have been followed by studies demonstrating minimal or nonexistent alterations in the mechanical properties of depleted RBC membranes. The present study was undertaken to provide additional information on the rheological behavior of ATP-depleted human erythrocytes and to examine the influence of RBC morphology on the flow behavior of these cell suspensions. ATP depletion via 24 hr incubation at 37°C caused: (1) RBC crenation (discocyte-echinocyte): (2) increased low shear rate viscosity; (3) enhanced non-Newtonian flow behavior. Virtually identical flow data were obtained with…fresh ATP-rich RBC which were crenated via 2,4-dinitrophenol (DNP); shape change and viscometric behavior were dose related. Both ATP-depleted and fresh DNP-treated cells could be returned to near-normal morphology and to normal flow behavior with the addition of the stomatocytic agent chlorpromazine hydrochloride. These morphology-rheology results thus offer an alternative interpretation of the earlier viscometric data and suggest that decreased in vivo cell survival and disturbed microcirculatory flow associated with ATP-poor RBC may be related to altered cellular morphology.
vol. 14, no. 2-3, pp. 111-126, 1977
Abstract: Sialic acid was removed enzymatically from whole and fractionated lyophilized canine tracheal mucus. The intrinsic viscosity of the desialized and original mucus was determined at several values of pH and ionic strength. Removal of sialic acid did not have a significant effect on the intrinsic viscosity of the mucus at physiologic conditions of pH and ionic strength. Measurement of the viscoelastic shear moduli in solutions whose concentration was typical of whole mucus showed increases in the shear moduli as a result of desialization. The transport velocity of desialized mucus on the frog palate showed a small decrease consistent with the…increase in elasticity. Zeta potential measurements indicated that desialization did indeed significantly reduce the molecular charge of the mucus.
vol. 14, no. 2-3, pp. 127-132, 1977
Abstract: An experimental set up, wherein the flow of blood and red blood cell (RBC) suspensions through narrow glass capillaries can be studied, has been designed and fabricated. The set up has the facility for simultaneous measurements of various flow parameters like rate of flow, pressure drop, feed reservoir, cup-mixing and tube hematocrits. Measurements with plasma, whole blood and RBC suspensions in saline have been made in tubes of different sizes, at different flow rates and hematocrits. The anomalous effects (viz. Fahraeus–Lindquist effect and Fahraeus effect) that occur in blood flow through narrow tubes have been quantitatively studied. The experimental measurements…have been analysed with the help of analytical models, to calculate the wall layer thickness and velocity profiles. Two analytical models have been used in the analysis and their range of application is discussed. The wall layer thickness at any given hematocrit is found to increase with decreasing tube size. Further, the extent of plug flow is seen to increase with increase in hematocrit.
vol. 14, no. 2-3, pp. 133-143, 1977
Abstract: A sedimentation recorder including an optical tracking head controlled to track the liquid-solid separation boundary in a tube containing a sample of liquid-solid mixture is described. The tracking head is controlled by a pulse operated servomotor which responds to the output of a photodetector mounted in the tracking head. A two-pen plotter is provided to record the sedimentation behavior of the sample. One pen is connected to the tracking head and continuously records the position of the liquid–solid separation boundary to provide a settling curve. The other pen is driven by a rate of change mechanism and records the approximate…rate of change of the separation boundary position. The rate of change mechanism operates by measuring the excursion of the tracking head during each of a series of successive time intervals. The difference between each excursion measurement and the preceding measurement is calculated and each difference value is converted into a corresponding number of pulses. The pulses are applied to drive a second pulse operated stepping motor which in turn drives the rate of change recording pen. The approximate cost of construction of this unit is $1800.
vol. 14, no. 2-3, pp. 145-149, 1977