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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: The dynamic mechanical properties of milk and milk gel were examined as functions of frequency, temperature, and concentration. The real and imaginary parts of the complex rigidity G′ and G″ measured at various frequencies were found to be superposable onto a single set of master relaxation curves by performing the horizontal shift along the logarithmic frequency axis except for milk gel which were prepared at different temperatures. The results show that the rigidity of milk gel depends on the concentration of milk C in such a way that G* ∝ C2 . It was found that G′ depends on…the temperature as G′ ∝ T. It was also found that the complex rigidity of skim milk solution depends on the angular frequency ω in such a way that G* ∝ ω 1/2 . The dependence of G* on frequency seems to indicate the formation of structure by casein micelle in solution.
Abstract: The time-dependent filtration pressure curves of cell suspensions pumped through 5 μ m polycarbonate filters at a constant flow rate were analyzed with the aid of a theoretical model developed in an accompanying paper. The cell suspensions contained mixtures of erythrocytes and leukocytes, the concentrations of which were systematically varied. The pressure-time (P-t) curves generally showed multiphasic components. Following the attainment of a quasi-steady state level, the pressure rose first rapidly and then more slowly. The rates of pressure rise in the fast and slow phases were normalized by using the steady state pressure reading (P0 ) obtained with Ringer…solution at the same flow rate, and are designated k1 and k2 , respectively. Both k1 and k2 increased with rising concentrations of leukocytes, [WBC], or erythrocytes, [RBC]. [WBC] is 700-1000 times more effective than [RBC] in affecting k1 and k2 . k1 is related to the dynamic plugging and unplugging of filter pores, primarily by leukocytes. k2 is attributable to the “permanent” plugging of filter pores, again predominantly by leukocytes. The experimental P-t curves can be fitted with the theoretical model by using appropriate constants for leukocyte plugging. The results indicate that nearly 2/3 of the entering leukocytes cause transient plugging of pores, with an unplugging rate of 4.1 percent/sec/unit pressure rise, and that approximately 2.2 percent of the entering leukocytes are “permanently” lodged. These results underscore the important role of leukocytes in determining the later phase of the P-t curve and support the concept that leukocyte plugging may have pathophysiological significance in causing microvascular occlusion in disease states.
Abstract: Pressure-time curves obtained by passing suspensions of blood cells in Ringer solution through a 5 μ m polycarbonate filter at constant flow (1.6 ml/min) were evaluated for their ability to reflect the deformability of the erythrocytes. The initial pressure reading (Pi ) obtained in a quasi-steady state during the first 1–2 sec of pumping was found to be reproducible for hematocrit values between 10 and 30 percent. This Pi value was normalized by the pressure generated by the cell-free suspending medium (P0 ) at the same flow rate. The ratio Pi /P0 was found to be linearly proportional…to hematocrit up to 30 percent but independent of leukocyte concentration up to 12,000/mm3 . Later portions of the curve did vary with leukocyte count. By using the equations developed from theoretical modeling of cells passing through a filter, the experimentally determined relation of Pi /P0 to hematocrit, and the known geometry of the filter pores, we were able to calculate parameters reflecting the deformability of red cells. These include a, the ratio of resistance in a pore containing a red cell to that in a pore containing only the suspending medium, and a, the proportion of pores filled by erythrocytes in transit. The application of theoretical analysis to experimental data has provided quantitative insights into the behavior of red cells during filtration tests in normal and disease states.
Abstract: A theoretical model of filtration of suspensions containing red blood cells (RBCs) and white blood cells (WBCs) has been developed. Equations are written for the pressure drop, the filtration flow and the fractions of filter pores containing RBCs (α ) and WBCs (α ∗ ). Because the relative resistances (ratios of resistance of cell to resistance of suspending fluid) of RBCs (β ) and WBCs (β ∗ ) through the filter pore are greater than one, the transit of these cells (especially WBCs) through the filter is slower than that…of suspending fluid; this leads to values of α and α ∗ higher than those simply expected from the hematocrit and leukocrit, respectively, in the entering and exiting suspensions. In the absence of pore plugging by the cells (steady flow), the pressure drop can be computed from α , α ∗ , β and β ∗ . In order to model unsteady flow, differential equations are written to include pore plugging and the subsequent unplugging by the rising filtration pressure at a constant flow. By specifying the fractions of entering RBCs (ε ) and WBCs (ε ∗ ) which would plug the pores and the rate at which the plugged pores would unplug in response to pressure rise (ε ˙ u ), as well as the fractions of entering RBCs (ε p ) and WBCs (ε p ∗ ) that would plug the pores permanently, theoretical pressure-time curves can be generated by numerical integration, and the results fit the experimental data well. From such fitting of theoretical curve to experimental data, information can be deduced for ε , ε ∗ , ε ˙ u , ε p and ε p ∗ .
Abstract: The present paper explores the implications of employing time-averaged true continuum fields to investigate blood rheology in “steady viscometric” flows. This approach is in contrast with the spatially-averaged interpretation of field variables which is generally employed. On the basis of four plausible constitutive assumptions it is then possible to deduce the qualitative in vivo behavior of all three of the material functions of whole mammalian blood from inspection of the corresponding velocity profile. Quantitative results, and the evaluation of the material constants for specific constitutive models, can be obtained through curve-fitting procedures, as is illustrated. The development reconfirms, and…puts on a formal basis, the earlier conclusion of Bugliarello, et al, that whole blood can have a dilatant response at low rates of shear. In addition, the normal stress forces are shown to have off-axis extrema in tube flow, and to be large enough to influence particle migration across streamlines. The existing data on particle migration in whole blood is reviewed, and shown to be in accord with these results.
Keywords: blood rheology, velocity profiles, normal stresses, immune response
Abstract: The effects of a wide range of mucolytic agents on the viscoelastic nature of a purified mucus glycoprotein gel have been investigated. The gel was produced by ultrafiltration of a solution containing high molecular weight glycoproteins obtained by gel chromatography in potassium thiocyanate. The fact that compounds as diverse as dithiothreitol and protease reduced the viscoelastic properties indicates that the model gel is appropriate for screening such compounds. Since it is homogenous and highly reproducible then it would appear to be ideal for such purposes. Also, it has been shown that mucus gels can be formed containing nothing but glycoproteins.
Keywords: mucus, viscoelasticity, mucolytic, glycoprotein, gel structure