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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 viscosity of whole blood (WB), plasma (P), and packed cells (PC) was measured in a Wells-Brookfield cone plate viscometer on blood from dogs undergoing surgical shock and hemodilution with different plasma substitutes and on human ACD-blood diluted in vitro to comparable concentrations of colloids. Erythrocyte sedimentation rate (ESR) and microscopic red cell aggregate count were used as in vitro indices of red cell aggregation. During three hours of intestinal shock WB viscosity increased by 20 %, hematocrit increased from 50.9 to 59. 1 %, P viscosity was unchanged and PC viscosity increased by 6 %. When compared at equal…hematocrit drop, Ringer’s acetate decreased WB viscosity more than albumin, ACD-plasma, dextran 70 and gelatin in this order both on blood diluted in vitro and in vivo. Since the duration of volume expansion in vivo after Ringer’s solution was very transient the absolute decrease of viscosity was less than that observed after all other solutions except gelatin. P viscosity increased with dextran 70, was unchanged with ACD-plasma, dextran 40, and gelatin and decreased with albumin and Ringer’s acetate dilution. A marked red cell aggregation occurred with dextran 70 and gelatin with increasing concentration. No aggregation of red cells was seen with dextran 40, albumin, or Ringer’s acetate. It is concluded that lasting hemodilution in vivo is best achieved with albumin and dextran 40 based on their viscosity influences, volume expansion duration and their lack of red cell aggregation properties.
vol. 17, no. 1-2, pp. 9-16, 1980
Abstract: A Couette viscometer with axial flow is proposed which allows blood to be exposed to defined shear stresses of short duration. A prototype of this viscometer is tested. By measurements and simple calculations the range of application is established. Measurements with blood show the possibility to control the flow conditions which may lead to haemolysis.
vol. 17, no. 1-2, pp. 17-24, 1980
Abstract: A capillary viscosmeter is described which allows measurement of the shear rate dependency of fresh blood viscosity at low shear rates. The instrument has been used in a preliminary study to evaluate differences between fresh and EDTA anticoagulated blood. In a shear rate range of 0.5 to 1.3 sec−1 the viscosity of fresh blood is more strongly dependent on hematocrit than is the viscosity of EDTA anticoagulated blood. Also, the viscosity of anticoagulated blood is more sensitive to day-to-day variations than is that of fresh blood. For some subjects, such variations may amount to as much as 30%.
vol. 17, no. 1-2, pp. 25-35, 1980
Abstract: Enzymes are widely used to remove selectively various stress bearing components of connective tissues before, during or after application of stress. This paper surveys and critically reviews these techniques.
vol. 17, no. 1-2, pp. 45-50, 1980
Abstract: Crosslinking of collagen is a prerequisite for the collagen fibers to withstand the physical stresses to which they are exposed. Significant progress has been made in understanding the functional groups on the molecule which are involved in the formation of crosslinks. Chemical agents, in particular bifunctional aldehydes such as glutaraldehyde, have found applications in the area of bioprostheses. They increase the resistance of collagen to biological degradation while increasing its mechanical resistance and decreasing its immunogenicity. It is to be expected that our increasing understanding of the molecular structure of collagen will allow us to further modulate its process of…biosynthesis and turnover as well as to benefit from the use of chemically modified collagen fibers in the development of novel bioprostheses.
vol. 17, no. 1-2, pp. 51-82, 1980
Abstract: The purpose of this paper is to review the present knowledge of the effects of immobility on fibrous connective tissue and to outline present theories about the pathogenesis of joint contracture. A severe disordering of connective tissue homeostasis appears when the diarthrodial joints are subjected to prolonged immobilization. Not only are bone, muscle and cartilage affected by disuse, but the fibrous connective tissue structures are functionally disturbed. We found that the tissues lose significant lubricating and buffering volume of water and glycosaminoglycan in concert with increased inter- and intra-molecular cross-links of collagen which resulted in joint stiffness. The potential application…of D-penicillamine and 17β -estradiol in pharmacological doses are being investigated for the therapeutic manipulation of reduction of strength of contracture.
vol. 17, no. 1-2, pp. 95-110, 1980
Abstract: Linear and nonlinear theories are used to study the one-dimensional permeation problem of liquids flowing through soft tissues under applied pressure gradients. It is found that the strain field induced by the drag of permeation is nonuniform with respect to depth, causing nonuniform permeability in the tissue sample for which the permeability is to be measured. As a consequence, permeability experiments on soft, porous and permeable tissues can only measure their apparent permeabilities. The concept of “intrinsic” permeability is introduced to define the permeability of the tissue under an imposed, uniform clamping strain and a vanishly small imposed pressure gradient…during a flow permeation experiment. Extra-polating from our experimental results for decreasing pressure gradients, we obtained the following intrinsic permeability function: k intrisic = k o exp ( M o e ) where ko and Mo are constants and e is the true strain. By using a nonlinear theory which incorporates the above intrinsic permeability function to describe the permeation experiment, we found that the dependence of apparent permeability on pressure gradient observed in our experiments can be predicted reasonably well by the theory. The results thus show that the intrinsic permeability function could be used to provide a better biphasic model whenever fluid flow becomes an important factor during the deformation of a soft, porous, permeable medium such as articular cartilage.
Abstract: Although the internal structure of cilia on micro-organisms and in the lung is identical the mechanical principles of fluid (mucous) transport may be vastly different. Cilia on micro-organisms are generally quite long, less densely packed on the epithelium, have a pronounced aperiodic beating pattern and a highly coordinated metachronal wave compared to the short densely packed, multicellular coordination of cilia found in the lung. A simple hydrodynamic theory using two layers of Newtonian fluid of differing viscosity is developed to model muco-ciliary transport. Features include estimates for the mean force distribution, the likelihood that a cilium is located at a…given height above the epithelium for an idealised beat pattern, and allowance for the retardation of the serous layer by the cilia. Initial calculations suggest that if the cilia just penetrate the upper, much more viscous, layer that mucous transport rates are substantially enhanced. Other features of the results are the significant retardation of flow in the serous layer and the ‘plug’ flow in the mucous layer.
vol. 17, no. 1-2, pp. 125-134, 1980
Abstract: Cilia-generated fluid flow between two strips of frog palate epithelium has been measured and flow velocity profiles have been obtained from the data. The strips are mounted in a covered chamber so as to form a ciliated channel and fluid motion is marked by suspended 1.0 μ m polystyrene latex spheres which act as tracers. Results from a control non-mucus system and a 40% – 50% v/v mucus system are compared with predictions of a theoretical model. This theory for flow in mucociliated channels incorporates flow due to a static pressure drop between the channel ends and a difference in…the cilia tip speeds between the two strips.
vol. 17, no. 1-2, pp. 135-150, 1980
Abstract: A series of experiments have been carried out to investigate the muco-ciliary transport in the trachea of rat, rabbit and chicken with cinemicrographic analyses of the movement, beat pattern and metachrony of the tracheal cilia. As a principal test case of the cilia-tip-penetration-into-mucus hypothesis, detailed studies have been made on the transport of a biochemically viable mucous plug artificially introduced into the chicken trachea both with and without a pressure differential across the mucous plug. Guided by the result of these pilot experiments, a theoretical two-layer model of the muco-ciliary transport is introduced, in which the cilia are assumed to…penetrate shallowly into the overlaying mucous layer during the effective stroke and to withdraw from the mucous layer during the recovery stroke. Both the mucus and the serous fluid are assumed to be Newtonian and with widely differ ing viscosities. Based on this model the mucus transport rate is found to depend linearly on the ciliary beat frequency and also on the time of ciliary tip penetration in the mucus. Results are also given on the propulsive force contributed by each individual cilium and an estimate of shear and shear rates within the mucous layer.
vol. 17, no. 1-2, pp. 151-162, 1980
Abstract: In most instances where sliding transport has to occur over an epithelial tissue surface, the surface is covered by a system of cells capable of secreting a thick flowing fluid, mucus. The sliding motion can involve the transport of the whole organism, the transfer of food, the facilitation of sperm or ovum movement, the clearance of respiratory air ways, etc. There is considerable evidence that the major biopolymeric component involved is a glycoprotein, 80% of whose weight is carbohydrate and 20% is protein. The carbohydrate is attached in the form of short oligomeric side chains to about 4/5 of the…protein backbone leaving 1/5 of its length bare. The bare part of the protein involves disulphide bridges which mayor may not be intramolecular. These glycoproteins are crosslinked into a weak gel i.e. a system which is viscoelastic and is endowed with long, if not infinite, mechanical relaxation times. Where, as is often the case, mucus is in mechanical contact with an array of metachronously beating cilia it acts as coupler in facilitating transport by ciliary propulsion. In relation to the period of the ciliary beat its characteristic relaxation time is sufficiently long so that the response of the mucus layer lying on top of the bed of beating cilia is that of a semi-solid sheet having an essentially rigid interaction with the moving wave. The requirements are strongly linked to ciliary beat characteristics. While solid-like properties are essential they must fall into a certain class. The characteristics of an incipient gel are most favourable in establishing transport. Mucus also possesses properties whose effects and purposes are not yet understood. Mucus, for example is unstable and its gel-like structure declines with time. This occurs rather slowly at body, but more rapidly at higher temperature. Hence the crosslinks of mucus are labile and of a character not yet established. The glycoprotein molecules building the networks are but for the cross links molecularly disperse. This is indicated by measurements of the hydraulic permeability of mucus which is far too low for any other arrangement of the glycoprotein strands to be considered.
Abstract: A new model was developed to characterize the hydrodynamics of the interaction between spermatoza and cervical mucus. In this model the local environment about a length element of a spermatozoon in the mucus is represented as a cell consisting of a Newtonian fluid within a rigid, cylindrical no-slip boundary. Such a cell models the mucous microstructure in the sense of “hydrodynamically equivalent” properties. A simple resistive force theory for sperm hydrodynamics was developed and applied to a human spermatozoon swimming within a mucous cell . The results included the prediction that the drag on the sperm head has…a substantial effect on swimming speed. This prediction was tested experimentally, by analyzing high-speed cine films of normal and headless human spermatozoa swimming in mucus. The theoretical result was confirmed, and a cell size of the order of 2 μ m was suggested.
vol. 17, no. 1-2, pp. 169-175, 1980
Abstract: The flow curves of rabbit blood, human fetal blood, and human adult blood show no hysteresis, a little hysteresis and considerable hysteresis, corresponding to their capacity of forming rouleaux. After the cessation of the steady flow, which was used to remove the original aggregation of cells, the time variations of the rigidity modulus G′ and the loss modulus G″ were determined at 1 Hz. For rabbit blood, almost no time change for G′ and G″ and no erythrocyte sedimentation was observed. For human adult blood, G′ and G″ first increased to a maximum value and then decreased. The rate of…erythrocyte sedimentation was correlated to the rates of increase and decrease of G′ and G″. These observations were accounted for by considering the change of structure of blood: i.e. the formation of rouleux, the association of rouleux, and the formation of nonhomogeneous structure.
vol. 17, no. 1-2, pp. 177-182, 1980
Abstract: The dynamic volume concentration of red cells in a narrow: capillary tube is a resultant of several mechanisms which take place either at the capillary orifice or within the tube. Both types of mechanisms have been studied in experiments in vitro. Human red cell suspensions were perfused through glass capillaries (I.D. 3.3 – 12μ m) branching from a larger feed channel. In addition, relative apparent viscosity was measured as a function of tube hematocrit. The results indicate that the red cell flow fraction is determined by the flow rate distribution at the branching point, and may even be reduced to…zero if the fraction of flow diverted into the capillary orifice is decreased. At any discharge hematocrit the hematocrit within the tube is further reduced due to the velocity difference between cells and plasma. At equal tube hematocrit, the relative apparent viscosity showed a minimum at a tube diameter of approx. 5μ m, whereas the dynamic hematocrit reduction was maximal at approx. 15μ m. These results were correlated with observations of the dynamic flow behaviour of the red cells in a “travelling capillary” which indicate that red cells tend to travel in groups rather than equally spaced, show a hematocrit dependent transition from single-file to multi-file arrangement in tubes larger than 6μ m, and, even in the smallest capillaries, exhibit a distinctly non-symmetric shape, regardless of flow rate and hematocrit.
vol. 17, no. 1-2, pp. 183-189, 1980
Abstract: A Couette type servo-controlled microviscometer associated with a low frequency generator modulating the rotational speed of the viscometer outer cylinder has been used to plot the rheological hysteresis curves of blood. It has been shown that the shape of these curves largely depends on the values of the parameters α and tm characterizing the linear variation of the rate of shear with time: γ ˙ = α t for 0 < t < t m and γ ˙ = α ( 2 t m…− t ) for t m < t < 2 t m . Two sets of α and tm have been selected in order to obtain rheograms showing preferentially the viscoelastic or the thixotropic behaviour of blood. This technic is used to compare normal human bloods with bloods submitted to various physical or chemical treatments, or with different pathological bloods. Some interpretations are proposed from considerations on changes in the deformability or aggregability of blood cells.
vol. 17, no. 1-2, pp. 191-203, 1980