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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: Various combinations of temperature have been used for freezing, storage and thawing in order to assess their effect on sputum viscosity estimated with the Ferranti–Shirley viscometer. The temperature of thawing was found not to be critical and so rapid thawing at 25°C was preferred. Degradation was prevented by (i) rapid freezing in liquid nitrogen and storage at −13°C or below, (ii) both freezing and storage at −70°C. This was found for mucoid, mucopurulent and purulent sputum specimens from patients with chronic bronchitis, bronchiectasis, asthma and cystic fibrosis.
vol. 10, no. 3, pp. 295-301, 1973
Abstract: Human erythrocytes in isotonic buffered (pH 7.4) saline/60 mM glucose containing 10% w/v Dextran 500 (a non-penetrating thickener) are reproducibly disrupted and/or fragmented when subjected to hydrodynamic shear stresses above a critical threshold. The haemoglobin-filled cell fragments (microspheres) resulting from cell break up closely resemble microdroplets formed from the break up of emulsion droplets, suggesting the possible application of elementary emulsion droplet theory. This theory provides an estimate of the tangential tension (Tm ) within the cell membrane at the point of rupture (Tm = 0.5–0.8 dyn/cm for the average cell, and 0.2–0.3 dyn/cm for the weakest cells after…5 min shear at 25°C). Erythrocyte fragmentation is due to the application of shear stress and not some other concomitant of the shearing process.
vol. 10, no. 3, pp. 303-311, 1973
Abstract: Tangential tensions are developed within the cell membranes of intact erythrocytes in viscous isotonic media, when they are subjected to large hydrodynamic shear stress. The magnitude of these tensions can be estimated by the application of elementary emulsion drop theory. The time taken for each cell membrane to rupture in response to a given tension enables an estimate to be made of the equivalent mechanical properties of the membrane. The values obtained are in excellent agreement with published estimates despite the fact that each author has used a different technique to apply the tension and a different theory to estimate…it.
vol. 10, no. 3, pp. 313-319, 1973
Abstract: The complete study of the rheological properties of human blood requires the use of a capillary viscometer. In a capillary viscometer, the blood in the feed reservoir must be continuously stirred in order to prevent sedimentation. The density difference between the plasma and the red cell that causes the red cells to settle in stationary blood may cause a radial concentration gradient when the blood is stirred with a rotating stirring bar. The radial concentration distribution of red cells in a healthy human blood sample contained in a capillary viscometer feed reservoir and stirred by a magnetic stirring bar…rotating on the bottom of the reservoir was investigated. The results indicate that centrifugal stirring can be used to agitate blood (and attain complete mixing and rouleaux breakup) in the feed reservoir of a capillary viscometer. This is accomplished at a fairly low rotational speed; plasma denaturation due to continuous production of fresh blood–air interface is negligible.
vol. 10, no. 3, pp. 321-323, 1973
Abstract: The mechanism of the decrease in erythrocyte volume on packing in a haematocrit centrifuge is considered. It is shown that experimental observations are inconsistent with the view that the change is caused, primarily, by a loss of intracellular medium. A possible mechanism is suggested.
vol. 10, no. 3, pp. 325-328, 1973
Abstract: Based on rheological data for blood at various hematocrits and temperatures, a characterizing parameter to describe the behavior of formed elements can be derived by a quasi-thermodynamic approach. Further development on this parameter should enable one to establish a better basis for distinction between normal and abnormal erythrocytes and/or blood.
vol. 10, no. 3, pp. 329-341, 1973
Abstract: The mechanism of rapid acceleration from rest (lunging) in fishes is studied by means of a slender-body theory adapted to deal with unsteady, curvilinear large amplitude movements in water at high Reynolds numbers. The vortex wake is represented here by the circulation shed from the fins and body, calculated by means of indicial aerodynamic theory. The caudal fin is shown to play a dominant role in the production of the thrust force required for the tremendous accelerations measured in various species of fish (50 msec−2 for pike and 40 msec−2 for trout). The theoretical analysis also shows…that an optimal value of the ratio of thrust produced to energy expenditure is obtained when the caudal fin moves perpendicularly to the direction of movement of the fish’s centre of gravity, while being at a small angle of incidence. Filmed sequences of accelerating fish were examined. showing that for species with good lunging ability, the starting process is made up of three stages. First the fish, which was initially stretched straight curls up into an L-shaped curve. At the end of this, the tail swings around and moves in the manner predicted by the theory. This second stage is repeated in some cases and finally the fish straightens out moving at an angle to its original orientation, roughly proportional to the acceleration. The forces and moments on the fish calculated by the present method are in good agreement with these experimental observations.
vol. 10, no. 3, pp. 343-350, 1973
Abstract: Through measurements of oscillatory flow birefringence of macromolecular solutions information on optical properties and relaxation effects are obtained for the molecules in a nearly unperturbed state. Small, oscillatory velocity gradients are used which are then directly proportional to the birefringence. Measurements are performed using an apparatus in which monochromatic light having circular polarization passes through a thin fluid layer which is confined between a fixed surface and an oscillating surface. The motion of the surface is monitored in amplitude and phase and from this the velocity gradient is determined. The light leaving the fluid now has an oscillating ellipticity which…is then monitored by passing it through a fixed plane analyzer and on to a photodetector. In the present apparatus the fluid is under precise temperature control and with its associated electronic instruments birefringence is measured in the frequency range from 0.02 to 1000 Hz. This apparatus is applied to the study of solutions of salmon sperm deoxyribonucleic acid, DNA. The relaxation times and magnitude of birefringence in solution are determined from measurements over a wide range of frequencies. This is done for several levels of shear degradation, the DNA being degraded by high speed chopping and by pressure cell induced flow. The ionic environment is considered as it influences the relaxation times. The method of oscillatory flow birefringence is also used to observe thermal denaturation of DNA. The birefringence undergoes a large change in magnitude and a reversal in sign as a consequence of the helix-coil transition. This method shows promise as a means for studying the kinetics of the process.
vol. 10, no. 3, pp. 351-360, 1973
Abstract: Sedimentation and aggregation of red cells were studied in the freshly shed blood, anticoagulated with EDTA, of 88 donors. including cancer and vascular patients. Tests were carried out in Westergren tubes at room temperature and at 37° and 40°C. Aggregation of red cells was estimated from ESR’s corrected for plasma viscosity and adjusted to 30 per cent haematocrit. Sedimentation rates and aggregation of red cells increase at higher temperatures. The degree of this effect depends on the type of disease, on the type of ABO blood group, and on the interplay between contradictory actions of albumin and fibrinogen. A negative correlation…between the temperature coefficient of aggregation of red cells and the fibrinogen concentration is shown by patients with vascular diseases and, to a much higher measure, by cancer patients of blood group A only. Temperature coefficient of aggregation of red cells appears to be a much more specific parameter than the aggregation of red cells.
vol. 10, no. 3, pp. 383-391, 1973
Abstract: In the present study, an investigation was into the changes in viscoelasticity of the clot formed during the process of blood coagulation of normal subjects and of patients with a variety of disease, in an effort to elucidate the rheological aspect of a thrombus formation. Dynamic viscoelasticity was measured by the viscoelastorecorder and was shown by absolute values, namely dynamic elastic modulus (E′) and loss modulus (E″). Experimental conditions were: temperature, 25.0°C; oscillation of outer cylinder, 3 c/s, amplitude; 60 μ m from peak to peak; and blood samples used diluted to 66.7 per cent of the original…by adding citrate and CaCl2 solutions which were used as an anticoagulant and for recalcification, respectively. Results of experiment were as follows: (1) Average saturated dynamic elastic modulus (E′s) and loss modulus (E″s) of normal subjects were 3393 and 252 dyn/cm2 , respectively. High viscoelasticity of blood clot was often recorded in patients with connective tissue disease, neoplasm, hematological disease (polycythemia vera and chronic granulocytic leukemia), infection and diabetes mellitus. (2) Investigation of causative factors of high E′s level. In high E′s group of patients, hematocrit was lower than that of the groups of which E′s was within normal limits, however, platelet count, plasma viscosity and erythrocyte sedimentation rate elicited high levels. Also, high E′s level was accompanied by high levels of maximum clotting gradient and E″s. (3) Correlation of factors related to clot strength was studied. Good correlations were found in E′s vs MCG, E′s vs plasma fibrinogen, E′s vs E″s, and tan δ vs E″s. (4) Effects of platelet on clot strength. In platelet rich plasma, levels of MCG, MCG′, E′s, E″s and tan δ were higher than those of whole blood or platelet poor plasma. It is of interest to note that tan δ was influenced by platelet count.
vol. 10, no. 3, pp. 411-424, 1973
Abstract: A fluid mechanical model for the interpretation of the intestinal activity is proposed. The intestinal contents are assumed to behave rheologically as a power law fluid. The intraluminal pressures are obtained in terms of the parameters characterizing the power law fluid and the geometry and the kinematics of the intestinal wall. The differences between peristaltic movement and isolated contraction of the wall are discussed.
vol. 10, no. 3, pp. 431-440, 1973
Abstract: In order to understand colonic activity, the rheological properties of the colonic contents are needed. A suitable tube viscometer was constructed and viscometric measurements on human feces were performed. The results indicate that, at sufficiently high shear rates, the feces behave as a power law fluid, i.e. Shear Stress ∼ (Shear Rate)m . For these shear rates the exponent m was approximately the same for all samples tested, regardless of their consisLcncy, and equal to 0.25.
vol. 10, no. 3, pp. 441-445, 1973
Abstract: Using the vitalmicrospectrophotometric technique the protein content was measured in exposed rat mesentery at 280 nm absorbance. In intravascular circulating blood plasma there was a linear relationship between the protein content and the measured absorbance which proved the methodical reliability of the technique. In cellfree perivascular tissue the protein content was higher around venules than around capillaries and arterioles. There was a decrease in the protein content of the interstitial tissue with increasing distance from the vessel wall. This concentration gradient is highest around venules. A change in the colloidosmotic pressure of blood leads to a change of the protein…content of the perivascular tissue. Accordingly a decrease in colloidosmotic pressure will result in loss of tissue protein while an increase in plasma protein will lead to an outward shift of proteins into the perivascular tissue.
vol. 10, no. 3, pp. 447-451, 1973
Abstract: L’analyse du comportement rhéologique typique de l’expectoration recueillie chez le bronchiteux chronique a été réalisée à l’aide d’un rhéomètre rotatif “Rotovisko” type Couette. Les courbes de la contrainte mesurée à différents taux de cisaillement reflètent le comportement viscoélastique complexe de l’expectoration comparable à celui de certains polymères chez qui l’application d’une contrainte entraînerait une modification de la structure moléculaire. Par ailleurs, l’analyse des courbes de recouvrance montre que la déformation élastique retardée peut être représentée par un modèle de Kelvin–Voigt généralisé à trois éléments. Toutefois, les variables rhéologiques à retenir dans l’analyse en routine des expectorations chez le malade…peuvent être valablement limitées à la mesure (1) de la viscosité apparente à l’état stable et à un taux de cisaillement faible (γ ˙ = 0 , 3 sec − 1 ), (2) de la recouvrance instantanée et retardée.
vol. 10, no. 3, pp. 481-487, 1973