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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 effect of temperature on the relative viscosity of human blood was determined. Data were taken in a capillary viscometer, a GDM concentric cylinder viscometer and in a Wells–Brookfield cone and plate viscometer at 23° and 37°C. It was found that the relative viscosity is independent of temperature at high shear rates in all viscometers, but depends on the temperature at low shear rates only in the capillary viscometer. The reason for this dependence on shear rate is discussed. The reason for the dependence on viscometer type is not known, but the different type of shear field may be responsible.
Abstract: The grinding of minced muscle tissue with quartz sand followed by extraction of the resulting homogeneous mass with NaCl solution of low ionic strength (0.05) in ratio 1:2 leads to formation of extracts undergoing rapidly spontaneous gelatinization during storage. The strength (viscosity) of the gels formed was studied by the “falling ball” method and Weiler and Rhebinder’s method of tangential shear of plate. The effect of various factors such as temperature, Ca ions, ATP, ethyleneglycoldiamintetracetate (EGTA) was studied and in some instances estimated quantitatively. It was shown that Ca ion binding by the sarcoplasmic reticulum or EGTA was…accompanied by conversion of the sarcoplasmic proteins solution into solid gel. It is suggested that this phenomenon underlies the development of the smooth muscle catch function, “viscous after-effect” and tonic hardening of vertebrate skeletal muscles during catalopsy. This concept does not contradict Lowy and Hanson’s hypothesis according to which the development mechanism of the catch function is due to the fact that after cessation of active contraction linkages between thick and thin filaments are either locked in the attached state or they detach very slowly. It appears that both these mechanisms may co-exist and possibly supplement each other.
Abstract: Extensive rheogoniometric measurements of undiluted blood, anticoagulated with heparin, Paul’s oxalate mixture and ethylene diamine tetra acetate, are presented. The blood was secured from healthy adult human subjects and measurements were made at shear rates from 1000 to 0.0009 sec−1 . In the minimal shear rate range from 0.01 to 0.0009 sec−1 , and in some cases down to 0.0006 sec−1 , three different slopes were obtained in the shear stress versus the shear rate plots, as compared to merely a single slope which we reported earlier. No appreciable differences were found by the use of the three anticoagulants. Although…two different gap widths in the combined Couette and cone and plate geometry were employed on samples from different blood withdrawals, all three types of slopes were found. The typical data were plotted in 6 figures which characterize our findings. A discontinuity or slope change was observed in three out of the 6 figures, when the shear rate is below 10−2 sec−1 . This continuity appears to confirm the presence of a yield stress. The importance of minimal shear rates in the flow properties of blood concerns physiological and pathological conditions, in which the flow of blood approaches a standstill and the shear rate progresses to zero.
Abstract: The rheological properties of whole blood from healthy human subjects were measured over a wide range of shear rates from 1000 down to 0.0009 sec−1 . A rheological equation of state is proposed to characterize the flow properties of blood. The flow curves were divided into three regions of shear rates. In region I (between 50 and 1000 sec−1 ) the blood exhibits nearly Newtonian behavior and the viscosity is not dependent on time of shearing. In region II (between 10−2 and 50 sec−1 ) the blood shows thixotropic behavior as predicted by the rheological equation. It is contended…that the time-dependent behavior is caused by progressive desaggregation of aggregated erythrocytes, for which experimental evidence exists. In region III (between 10−3 and 10−2 sec−1 ) the associated shear stresses are considered to be below the yield stress of the blood. At these minimal shear rates the blood behaves as a solid and, therefore, the rheological equation of state for a fluid is not applicable. A tentative explanation is given for rheological behavior of blood in this region by using the basic principle of electrostatic stability between erythrocytes and by the possible occurrence of linkages at points along the chains of the rouleaux of erythrocytes, forming a three-dimensional structure.
Abstract: Elastic and viscous properties of fibrin clots were measured in the cone-plate test section of a Weissenberg Rheogonimeter. The tests applied included forced oscillations, free vibrations, and stress relaxation, all in shear. Two classes of clots were studied: (i) ligated clots, formed with the presence of the enzyme fibrinoligase, and (ii) non-ligated clots, formed in the absence of fibrinoligase. The clots, formed in a cone-plate test section, gradually became stiffer over a period of about 1 hr, thereafter being stable for 2 additional hr. The present study deals with quantities measured during this stable period. Compared to the non-ligated…clots, the ligated clots, representing physiologic conditions, were found to be stiffer and less viscous. Furthermore, the former clots became even less stiff when they were cyclically strained for 30 min; the loss of rigidity, however, was mostly recoverable if they were left undisturbed subsequently for 40–60 min. For the strain range tested (up to 20 per cent), stress-strain curves for all clots were nonlinear, the main non-linearities being at small strains. The tangent modulus at large strains was constant for most clots. The storage modulus of all clots is strongly dependent on the fibrinogen concentration and on the total ionic strength of the clotting mixtures: The stiffest ligated clots are obtained at an ionic strength of 0.17. Less rigid clots are produced at smaller and greater ionic strengths. Non-ligated clots, tested at 0.03 Hz, dissipated 20–30 per cent of the input energy, whereas the ligated clots dissipated less than 5 per cent. Both ligated and non-ligated clots are more rigid if test frequencies above 1 Hz are applied. Below 1 Hz, the storage modulus is fairly constant. Clots cyclically strained during the formation period seem to be only one-fourth as rigid as clots formed undisturbed.
Abstract: Rotational viscometers have become important tools for measurement of blood viscosity. The present data reveal a potential source of error in such measurements, namely an elevation in viscosity produced by shearing in the viscometer. The viscosity of mouse blood and of human blood was measured in a GDM viscometer over a range of 300–0.3 sec−1 . When the same aliquot of blood was used for a subsequent series of viscosity measurements, it was found that viscosity had risen, uniformly with mouse blood, and occasionally with human blood. A lag period was present before the rise in viscosity appeared. Subsequent series…of measurements then revealed further increments in viscosity values until a plateau was reached. Refrigeration prior to any shearing, prevented the shear-dependent rise in viscosity. Results are interpreted in terms of possible damage to cells in the viscometer, producing a rise in blood viscosity, or resulting in release of some constituent of the cell which would in turn elevate blood viscosity.
Abstract: Measurements were made on erythrocyte-plasma suspensions in a concentric-cylinder viscometer with two different gap sizes. The experimental shear stress-shear rate relationship for any given red cell-plasma suspension was found to be independent of the viscometer gap size. This finding contradicts results reported by others; the contradiction arises because of the use of different methods of interpreting a given set of raw data. Viscometers with different characteristics will provide a different set of raw data for a particular blood sample at shear rates below about 1 sec−1 .
Abstract: The use of slip as a mechanism in explaining the predicting blood flow is shown to lead to inconsistent results when the over-all rheological properties as well as the velocity profile is considered. The evidence for slip is also considered and shown not to be a proper interpretation of observed characteristics of red blood cell motion.
Abstract: A reaction order for the formation of fibrin network in the fibrinogen–thrombin solution is determined by an analysis of clotting curves obtained by measurements of dynamic viscoelasticity at the various concentrations of fibrinogen and thrombin. It is concluded from a rheological point of view that clotting curves of elastic modulus and loss modulus can be represented by superposition of two first-order reaction processes with different rate constants respectively. The same conclusion is obtained for human and bovine plasma with different rate constants. The rate constants obtained from the loss modulus are larger than those from the elastic modulus. The saturated…values of the elastic moduli in the two processes increase with the increase of the concentrations of fibrinogen and thrombin. The amplitude dependence of the elastic modulus of the gel also supports the presence of the two processes. The elastic modulus in the first process is proportional to the number of cross links between fibrin fibers, and that in the second process is related to the non-linear elongation of fibrin fibers between crosslinks. The loss modulus in the first process is associated with the polymerization of fibrin, that in the second process is related to the increasing interaction between crosslinked fibrin fibers.