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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: Preliminary assumption of this model is that interactions between actin and myosin presupposes an exact three-dimensional geometrical correspondence between sites, due to the very short time constants present under physiological conditions. Only small and controlled torsions of the actin filaments are accepted. The model uses geometrical information concerning orientations and dimensions of myosin crossbridges and actin monomeres to modelize the distribution of their inter-actions. An orientation map of actin sites in the crosssection perpendicular to the filament axis is proposed, adapted to the specific filament array of vertebrate muscle. Orientation of myosin crossbridges follows Luther’s rules (1). According to the…model, any interaction between actin and myosin implies the superimposition of their respective cross-sectional planes. The axial length of actin monomere is 55 Å; the distance between two crossbridges along the myosin filament axis is 143 Å. The following properties are derived: 1) The shortening step of the sliding actin filament must be a multiple of 11 Å (highest common factor). Taking into account the staggered disposition of the two actin strands and the presence of two heads for each cross-bridge, the most probable value for this shortening step is equal to 99 Å. A specific scheme is proposed to describe the shortening process. The behavior of the modelized crossbridge does not need any elastic structure - 2) Planes situated at 715 Å (lowest common multiple) of actin and myosin coinciding planes are also in coincidence. In a hemi-sarcomere the maximal number of these planes, referred to as simultaneously activable planes, is 10 (20 if both myosin heads are considered). The proportion of interactions authorized by the site orientations is 1/12. In the model, the concept of randomly recruited crossbridges is replaced by a discretized recruitment, based on geometrical properties at an ultrastructural level. The proposed distribution is homogeneous: it can be extended radially in the sarcomere and authorizes the actin filament sliding in the whole physiological range under the control of a dual activation function, reproducing Ca++ temporal and spatial distribution.
Keywords: 3-dimensional, geometrical correspondence, short time constant, shortening mechanism, simultaneously activable planes
vol. 28, no. 3-4, pp. 143-150, 1991
Abstract: We investigated the effects of l2-deoxyphorbol 13 isobutyrate 20 acetate (DPBA) on contractile function and intracellular calcium handling in normal human ventricular myocardium. The activation of protein kinase C by DPBA resulted in a decrease in sarcoplasmic reticulum calcium release and a reduction in isometric twitch. Force-Calcium relationships were obtained by tetanizing intact muscles or by chemically skinning muscle fibers. These relationships were fitted to a modified Hill function. In intact preparations, DPBA shifted the force-calcium relationship towards higher intracellular calcium concentrations by 0.12 μ M (n=5) and maximal force production was decreased 45.5 ± 6.1%. These experiments show that…protein kinase C activation affects intracellular calcium availability and myofibrillar calcium responsiveness.
Abstract: The relations between force, shortening velocity and sarcomere length (F-V-SL) during cardiac contraction, underlie Starling’s Law of the Heart. F-V-SL were investigated in isolated, intact and skinned trabeculae and myocytes from rat heart. SL and V were measured with laser diffraction techniques; F was measured with a silicon strain gauge. The “ascending” F-SL relation appeared to result from both length dependent sensitivity of the contractile system to activator calcium ions and the presence of restoring forces (Fr), residing in the collagen skeleton of the muscle. Fr increased exponentially with decreasing SL below slack length to 25% of maximal twitch force…(Ft) at SL=1.60μ m. V was inversely proportional to the load and attained a maximum at zero load (V0 ). V0 increased with factors that increased F: [Ca++ ], SL, and time during the twitch. VA reached a maximum and remained constant (13.5 μ m/s) when F attained or exceeded 50% of its maximum value. Viscous force in the passive muscle increased with V to a maximum of 4% of Ft at V=40 μ m/s. The relation between Vo and these factors could be predicted by a model of contraction in which the measured visco-elastic properties of myocardium were incorporated, while the truly unloaded maximal velocity of sarcomere shortening was assumed to be independent of the level of activation of the contractile filaments. A model of the cardiac cycle which explains the relation between Frank’s and Starling’s laws is presented.
Keywords: Cardiac muscle, sarcomere mechanics
vol. 28, no. 3-4, pp. 161-170, 1991
Abstract: The force-velocity relation for cardiac muscle fibers can be calculated from a proposed constitutive law based on force-time and force-length data. The calculated force-velocity relation agrees quite well with the measured force-velocity relation obtained from a quick release of sarcomere controlled rat cardiac trabeculae. The theory confirms the measured linear relationship between maximal velocity of sarcomere shortening and sarcomere length. The implication is that the force-velocity relation is not an independent property, and therefore need not be explicitly included as a rheological element in the constitutive law.
Abstract: The thixotropic parameters of whole blood from 314 healthy subjects (154 women, 160 men) were measured with our modified method by Low shear 30 Rheometer and calculated according Huang’s equation. This communication offered the reference range of thixotropic parameters from man and woman group. The results demonstrated that no significant differences existed in the plasma viscosity and fibrinogen between man and woman group. Man group had statistically higher values in HCT, yield stress (τ 0 ), Newtonian contribution of viscosity (μ ), non-Newtonian contribution of viscosity (η s –μ ),…apparent viscosity at 2.37 sec−1 (η s ), the equilibrium value of the structual parameter (A) and apparent kinetic rate constant of rouleaux breakdown (ARC) than those in woman group. The man and woman groups could be separately divided into five subgroups in terms of age. It was found that the levels of fibrinogen and plasma viscosity had a tendency of increasing with aging. In the old subgroup (>60 years) of men and women HCT, τ 0 , μ , η s , (η s –μ ) and A had significant lower values than those in young and middle-age subgroups. However, It was very interested that there were differences of ARC versus age between man group and woman group, i.e. ARC in the man subgroup III, IV had lower and the woman subgroup II, III, IV had higher values than their respective older subgroup did.
Keywords: Hemorheology, thixotropy of blood, hematocrit, aggregation of red blood cells
vol. 28, no. 3-4, pp. 177-183, 1991
Abstract: Ehrlich ascites cancer cells were compressed between glass microscope slides by the addition of weights. The projected areas of the cells were measured, and their surface membrane integrity determined by means of trypan-blue exclusion tests under different compression loads of 0 to 800g. The results are compatible with a two-step mechanism for surface rupture; first the cell membrane is unfolded and then stretched, with modest degrees of stretching associated with membrane rupture. It is calculated that lethal surface membrane rupture of the type produced here by compression, could also be produced when cancer cells are deformed by entry and…passage along relatively non-deformable capillaries. This would at least partially account for the rapid destruction of cancer cells in the microcirculation. The observation that isolated nuclei are less deformable than whole cells, may indicate that their nuclei may protect cancer cells from biomechanical trauma.