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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: Mechano-calorimetry involves temperature dependent mechanical experiments to decompose reversible changes in membrane free energy density into internal energy and entropy density contributions. The measurements required are the membrane surface elastic properties (area compressibility and shear moduli) as a function of temperature plus the thermal area expansivity of the membrane. The results include the reversible heats of expansion for the membrane as well as the energetic contributions. Consequently, the approach directly assesses the thermodynamic state of the membrane, in situ ; comparison with well defined chemical systems (i.e., specific vesicle combinations of lipids, proteins, etc.) provides insight into the chemical state…of the composite or natural membrane “mixture”. For the human red cell membrane, the thermal area expansivity has been found to be 1.2 × 10−3 C0–1 . The heat of expansion is determined to be 110–200 ergs/cm2 ; the heat of extension is 2 × 10−3 ergs/cm2 for unit extension of the red cell membrane. The heat of expansion is a measure of the thermal repulsive forces acting in the membrane surface; the heat of expansion measured for the red cell membrane is of the order anticipated for a lipid bilayer idealized as twice the behavior of a monolayer at an oil-water interface. On the other hand, the heat of extension measured for the red cell membrane is five orders of magnitude smaller than the heat of expansion. Assuming that the red cell membrane shear rigidity and heat of extension is associated with “spectrin”, unit extension of the membrane increases the configurational entropy of spectrin by about 500 cal/mole; this is opposed by enthalpic increases of 600–700 cal/mole produced by extension.
vol. 16, no. 4-5, pp. 279-283, 1979
Abstract: Treatment of intact fresh human red cells with phosphate and calcium ions, in that order, led to cell agglutination at room temperature, and hemolysis and fusion at 37°C within 30–60 minutes. During incubation, cell-associated calcium increased 70 fold, while ATP levels declined by 98%. Agglutination was much reduced after neuraminidase treatment, suggesting that surface negative charges play a role in phosphate-calcium bridging between cells. Incorporation of 10 mM EGTA into resealed ghosts increased the fusion index relative to control ghosts while the incorporation of 1 mM calcium had the opposite effect. Aggregation of membrane-associated proteins was demonstrated by freeze-fracture and…by glycoprotein labeling. In summary, phosphate and calcium ions cause agglutination of red cells and an increased permeability to cations resulting in hemolysis, an aggregation of membrane proteins and finally fusion of adjacent protein-free lipid bilayers.
Keywords: human red cells, fusion, ATP, phosphate, calcium, agglutination
vol. 16, no. 4-5, pp. 285-292, 1979
Abstract: Governed by a hierarchy of short-range and long-range physical forces, electrically neutral phospholipid molecules aggregate in water to form bilayer membranes which in turn form a multilayer lattice of bilayers alternating with aqueous layers. We use x-ray diffraction to determine the bilayer thickness dl , average molecular cross-sectional area A and bilayer separation dw . As water is removed from the lattice not only do the bilayers come closer together,but they deform to decrease area A and to thicken the bilayer. We measure the work of water removal and divide this work into that of overcoming long-range bilayer…repulsion and that of causing bilayer deformation. Electrically neutral membranes of egg lecithin, synthetic lecithins (above and below the melting temperature of their hydrocarbon chains), and egg phosphatidylethanolamine all exhibit a very strong repulsion at less than 20 to 30 Angstrom separation. For dw < 10 Angstroms the repulsive pressure exceeds 100 atmospheres. This force varies roughly exponentially with a decay distance of 2 to 3 Angstroms and presents a formidable barrier to close contact between membranes. The lattices are stabilized at 20 to 30 Angstroms separation by van der Waals attraction between bilayers whose magnitude can also be estimated. This attraction is of the correct magnitude expected from the general theory of van der Waals forces. Preliminary comparison of the work of membrane deformation with monolayer data suggest that the lateral pressure to compact molecules on the same bilayer is not related simply to the analogous surface pressure of lipids in monolayers. The lateral pressure is necessarily zero at the equilibrium packing area of the phospholipids and increases to the order of 25 dyne/cm for 25% change in area. The low work of lateral compression (relative to thermal energy) might permit fairly large lateral fluctuations in packing if the work of lateral expansion is comparably small. Our ability to measure the work of rearranging lipids mak.es it possible to test and compare theories of bilayer mechanical properties and their stability, phase transitions between disordered and ordered states of the hydrocarbon chains, and phase separation of lipids in mixed systems.
vol. 16, no. 4-5, pp. 293-295, 1979
Abstract: At the cellular level the continuum theories for hydrodynamic diffusion and membrane elastic deformation will be modified by long range molecular level forces of electrodynamic and/or electrostatic origin. This talk will examine two important applications, (a) the intracellular Brownian motion of plasmalemmal vesicles and (b) the formation of intercellular tight and gap junctions, where van der Waals and electric double layer forces are believed to cause significant changes in the mechanical behavior of the cell.
vol. 16, no. 4-5, pp. 297-307, 1979
Abstract: Cell membrane can be considered as a two-dimensional solution. Membrane components may undergo molecular movements in the plane of the membrane. In the present report, we summarize our studies on two types of these movements, namely, electrophoretic migration and Brownian diffusion, for two types of cell surface receptors: a heterogeneous group of concanavalin A receptors and a specific membrane protein/ionic channel, acetylcholine (ACh) receptors.
vol. 16, no. 4-5, pp. 309-315, 1979
Abstract: The viscoelastic response of human intervertebral disc material is studied. It is shown that the water concentration in the material has a dominant effect on the relaxation behavior. The studies are performed on small specimens cut from laminae which are excised from the anterior portion of an L4-L5 disc. Some consequences of this water sensitivity for laboratory testing and in-vivo response are discussed.
Abstract: The effects of the divalent ions calcium, magnesium and copper on the rheologic and mucociliary transport properties of canine tracheal mucus have been investigated. A maximum in the viscoelastic moduli of the mucus gel was observed for each ion around a concentration of 5 × 10−4 M and this corresponded to an optimum in transport on the toad palate (Bufo marinus). Since no demonstrable change occurred in the charge on the glycoprotein molecule as indicated by constant electrophoretic mobility, it is assumed that the effect is produced by a change in conformation of the molecule. Similar effects in vivo may…he of consequence in clearance from the lung and in the reproductive function of cervical mucus.
Keywords: tracheal mucus, viscoelasticity, calcium, ciliary transport, gel structure
vol. 16, no. 4-5, pp. 331-337, 1979
Abstract: Two promising methods of assessing the removal of blood microaggregates or other particulates from stored blood by microfilters, namely electronic particle size distribution analysis and screen filtration pressure (SFP) measurements, were compared. Microaggregate counts and size distributions have been difficult to quantitate because of a lack of reproducibility of the measurements. This problem has now been largely eliminated by the use of a red cell lysing solution containing hexadecyltrimethyl-ammonium bromide (CTAB), acetic acid and glutaraldehyde which permits destruction of the red cells yet stabilizes the microaggregate counts. As a consequence it has been possible to make a quantitative comparison with…the screen filtration pressure method. The correlation between the SFP values obtained with screens having pore sizes of 20 × 20, 30 × 30, and 40 × 40 μ and the number of microaggregates measured electronically has been examined for outdated blood bank blood. The 30 μ screen was found to offer advantages over the 20 and 40 μ m screens. Samples containing different relative concentrations of microaggregates were prepared by mixing various proportions of repeatedly filtered and unfiltered blood such that the maximum SFP was ⩽ 450 mm Hg using the 30 μ screen. When SFPs > 250 mm Hg were extrapolated from the straight line trace between ∼ 20 to 250 mm Hg, it was shown that the SFP values were linearly related to the relative quantity of filtrable material. A linear relationship was also observed between the relative quantity of microaggregates and the particles counted electronically. The simplicity and reproducibility of the SFP procedure offer advantages over electronic particle size distribution analysis for the evaluation of the performance of blood microfilters.
Abstract: This work examines the biophysical properties of two commercially available perfluorochemical artificial bloods with whole blood. The two per fluorocarbon emulsions used were Fluosol-DA and Fluosol-43. The experimental studies included shear viscometry, osmotic pressure, erythrocyte sedimentation rate, osmotic fragility and malonamide induced hemolysis. The results of this investigation are interpreted in terms of the composition of the artificial blood and its interaction with the components of whole blood.
vol. 16, no. 4-5, pp. 347-356, 1979
Abstract: Local velocity was measured with a hot film probe in the main pulmonary artery and ascending aorta of 10 adults in whom the valves were normal. The maximal intensity of turbulence was higher in the aorta (4.2 ± 0.4 cm/sec) (mean ± SEM) than in the pulmonary artery (1.6 ± 0.2 cm/sec) (P < .001). Maximal velocity in the aorta (75 ± 7 cm/sec) was also higher than in the pulmonary artery (43 ± 5 cm/sec) (P < .001). These observations indicate that the aorta rather than the pulmonary artery is the site of greater disturbances of flow, partially due…to a higher blood velocity in that vessel.
vol. 16, no. 4-5, pp. 357-362, 1979
Abstract: The influences of the membrane cholesterol on the rheological and functional properties of the human erythrocytes were studied. As the cholesterol/phospholipid molar ratio is artificially increased, (i) the viscosity of the erythrocyte suspension slightly increases, (ii) the deformability, expressed by the “easiness” to enter into a small orifice, decreases and (iii) the rate of the oxygen egress from the erythrocytes is retarded. These changes may be primarily due to the condensing effect of cholesterol in the lipid portion of the cell membrane, because of the similarity of the other biochemical and morphological factors among the samples.