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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: We have examined phase differences between beating cilia measured in different directions on the surface. The measurements were performed on tissue cultures taken from frog palate epithelium. This experiment was based on a method developed earlier, which measures simultaneously scattered light from two different and relatively small areas. Moreover, the distance between the two small areas can be accurately defined and varied. Rotating the stage around the optical axis permits us to repeat these measurements at different space angles. It was found that: a) the phase gradient is a periodic function of the angle of rotation; b) the periodicity…can be described quantitatively by a cosine function; c) good agreement exists between Machemer’s findings in protozoa and our results, despite the differences between the two systems and techniques used. the phase gradient is a periodic function of the angle of rotation; the periodicity can be described quantitatively by a cosine function; good agreement exists between Machemer’s findings in protozoa and our results, despite the differences between the two systems and techniques used.
Abstract: We employ a structurally-motivated phenomenological formulation to identify biomechanical experiments which can be used to determine a vascular constitutive relation directly from data. Large deformations, nonlinear material behavior, load-dependent anisotropy, material heterogeneity and incompressibility are accounted for in the analysis. For purposes of illustration, we outline a procedure for studying elastic arteries wherein the behavior of the media and adventitia is considered separately. This general approach for identifying vascular constitutive relations can be applied to any vessel or airway, however, and should provide certain advantages over previous microstructural or purely phenomenological formulations.
Keywords: arteries, veins, stress-strain, large deformations
vol. 26, no. 4, pp. 687-702, 1989
Abstract: To discuss the decrease in the flow rate of blood experienced by astronauts, a theory of blood flow is presented taking account of the effect of gravity. The theory of two-dimensional Poiseuille flow is adopted. It is assumed that the flow is horizontal and that the width of the upper marginal layer filled with plasma thickens as gravity increases. The parameter ξ which mainly indicates the effect of thickening of the upper marginal layer is introduced. The extent of decrease in the flow rate of blood in the environment of weightlessness compared to that in the gravitational field is…calculated for various values of ξ . The decrease is more remarkable in the flow rate of the cell fraction than that of whole blood for the same value of ξ .
Abstract: A new filtration device and blood handling technique for the assessment of RBC deformability in small blqod samples is described and used to study RBC deformability in adult obese-hyperglycemic ob/ob -mice and normoglycemic controls. The new filtration device was designed to improve the time resolution during RBC incubation. Test and control RBC suspensions were directly filtered from two identical incubation chambers under a constant pressure of 1200 Pa. Nuclepore filters (3 μ m) were mounted on top of several standard test tubes into which the filtrate was subsequently collected and weighed. Because the RBCs were resuspended to a very low…(0.01 %) hematocrit, the average number of RBCs passing each pore was less than 10. Therefore, any detectable difference must reflect the physical properties of RBCs, e.g. shape or viscoelasticity, whereas the role of white blood cells is negligible. When ob/ob -mouse RBCs were studied with the new technique they showed impaired filtrability as compared with control RBCs, both when incubated without glucose and with glucose present at the same concentration as that recorded in the RBC donating mouse.
Abstract: The dynamics of aggregation and disaggregation of blood of varying hematocrit in oscillatory flow in a distensible horizontal tube was determined by measuring the developing echo intensity of the blood samples with a 10 MHz B-mode ultrasonic scanner. Early aggregation could be detected within 10 sec. of stoppage of flow. The rate of echo intensity buildup and thus, presumably the rate of aggregation when flow was stopped was inversely related to hematocrit, as was the rate of echo intensity reduction when flow was resumed. Polycythemic blood of 60% hematocrit showed no echo intensity increase over 5 min. Increasing the shear…stress when flow was resumed resulted in rapid decreases in aggregation. In all cases, disaggregation following flow resumption was faster than aggregation following flow stoppage.
Keywords: erythrocyte, aggregation, ultrasound
vol. 26, no. 4, pp. 723-736, 1989
Abstract: We investigated the role of the viscoelastic and adhesive properties of mucus gel simulants on the clearance of mucus by simulated cough. Mucus-like gels with widely varying viscoelastic properties were prepared from polysaccharides cross-linked with sodium borate. Cough was simulated by opening a solenoid valve connecting a model trachea to a pressurized tank. The clearance of gels lining the model trachea was quantified by observing marker particle transport. Viscosity elastic modulus, relaxation time and yield stress were measured with a steady-shear viscoelastometer. Spinnability (thread formation) was determined with a filancemeter. Adhesivity (surface tension) was measured by the platinum ring technique.…The viscoelastic and adhesive properties of the mucus gel simulants spanned the ranges observed for bronchial secretions from patients with COPD. The relationship between simulated cough clearance and the viscoelastic and adhesive properties of the gels was analyzed by stepwise linear regression of the non-zero data matrix. The major independent variable relating to clearance was viscosity. Secondary, but highly significant dependences, were also found for spinnability and adhesivity. Elastic modulus, relaxation time and yield stress had no independent effect on cough clearance over the investigated range. The results indicate that, in the absence of airway surface liquid, cough-type clearance relates primarily with mucus gel viscosity. For a given viscosity, clearance is also impaired by spinnability, i.e. the capacity of the mucus to form threads. At constant viscosity and spinnability, clearance is further impaired by an increase in the adhesivity of the mucus. The negative dependence of each of these physical factors can be rationalized in terms of their inhibitory effect on wave formation in the mucus lining layer during high velocity airflow interaction.
Abstract: Using a simulated cough machine, we analyzed the effect of adding tensio-active liquids as sol phase simulant on the clearance of gel mucus simulant by cough. Polysaccharides crosslinked with sodium tetra borate were used at different concentration as gel mucus simulant. A drop of gel mucus simulant was deposited either directly on the model trachea or on a sol phase layer simulant (2% sodium dodecyl sulfate in water). The clearance of the mucus simulants was quantified by observing the movement of marker particles in the gel layer. The viscoelastic properties of gel mucus simulants were determined by using a viscoelastometer…(SEFAM). The adhesive properties were analyzed by means of the platinum ring technique. The wettability of the mucus simulants was quantified by the automatic measurement of the contact angle of the drop of gel on the model trachea. We found that the addition of a sol phase significantly decreased by about 50% the adhesivity and wettability of the gel mucus simulants. This decrease was associated with a marked enhancement of cough clearance, whatever the viscoelastic properties of the gel mucus simulants. These results suggest that the sol phase is essential in bronchial respiratory mucus clearance by the cough mechanism.
Keywords: mucus clearance, sol phase, gel phase, adhesivity, wettability
vol. 26, no. 4, pp. 747-752, 1989
Abstract: Steady laminar flow of a non-Newtonian fluid based on couple stress fluid theory, through narrow tubes of varying cross-sections has been studied theoretically. Asymptotic solutions are obtained for the basic equations and the expressions for the velocity field and the wall shear stress are derived for a general cross-section. Computation and discussions are carried out for the geometries which occur in the/context of physiological flows or in particular blood flows. The tapered tubes and constricted tubes are of special importance. It is observed that increase in certain parameters results in erratic flow behaviour proximal to the constricted areas which is…further enhanced by the increase in the geometric parameters. This elucidates the implications of the flow in the development of vascular lesions.
Abstract: A rigidity index (RI) related to red blood cell deformability was measured by using the hemorheometre. The RI for 13 patients homozygous for sickle cell disease was 109 ± 44 at 37°C and at atmospheric pO2 . The filtration time curve as a function of pO2 is biphasic for sickle cell suspensions. The pO2 at which filtration time is maximum, pO2 max. , correlated with the rigidity index measured at atmospheric pO2 . This pO2 max. value was very sensitive to small changes in physico-chemical parameters such as osmolality, pH, temperature, hematocrit, and cell density. Conditions which…reduced the Hb S polymerization induced a leftward shift of pO2 max. . The experimental curves are in agreement with theoretical models based on the presence of two abnormal cell types: filtrable “slow cells” and infiltrable “sickled cells“ .
Keywords: RBC deformability, sickle cell disease, rigidity index
vol. 26, no. 4, pp. 771-784, 1989
Abstract: Reversible aggregation of red blood cells (RBC) plays an important role in determining the flow properties of blood. To study different factors affecting RBC aggregation we used a new commercially available erythro-aggregameter (SEFAM, Nancy, France). The method allows the photometric quantitation of the kinetics of RBC aggregation and the estimation of the shear resistance of the aggregates. Modification of the hematocrit acts mostly on the determination of the disaggregation shear rate, while plasma composition strongly affects all measurements. Anticoagulants per se do no influence the aggregation process, but can alter the value of the parameters through a plasma dilution effect.…Presence of white blood cells and platelets in the sample did not modify the data. Study on the effects of low concentration of heparin and low molecular weight heparin showed that at therapeutical doses these drugs did not alter the values of the aggregation parameters. Provided that precise guidelines are followed for the processing of blood samples, this method may serve to investigate RBC aggregation in various diseases and to search for adequate hemorheologic treatment.
Keywords: RBC aggregation, hematocrit, anticoagulants, plasma dilution, heparin, white cells and platelets
vol. 26, no. 4, pp. 785-797, 1989
Abstract: A study was conducted to investigate the hydrodynamics of branching flow in relation to the blood supply to the basal part of the brain. A series of measurements of the branching loss-coefficients under laminar steady flow were conducted using model branches with various geometries, and the effect of branching on blood supply to distal areas was described using a lumped-parameter model of the vascular structure. It was revealed that in the blood circulation, branching loss is important where a small artery divides off with a large branching angle from a large trunk. It was also indicated that the effect of…such branching on the distal blood supply might become more significant when the peripheral resistance is reduced, thereby increasing the blood velocity in the trunk.
Keywords: Biofluid mechanics, branching flow, energy loss coefficient, cerebral circulation
vol. 26, no. 4, pp. 799-811, 1989
Abstract: Methods for measuring the adhesiveness, plasticity, viscoelasticity and spinnability of mucus microsamples have been developed. The rheological properties of the rat gastric and duodenal gel mucus have been analyzed and compared. Using a controlled stress rheometer (Carri-Med), flow and creep experiments showed that gastroduodenal mucus exhibits a typically non-newtonian, pseudoplastic and viscoelastic behaviour. The apparent viscosity (7,800 ± 11,000 Pa.s) and yield stress (24.9 ± 8.5 Pa) of gastric mucus were significantly higher than the duodenal mucus viscosity (39 ± 160 Pa.s) and yield stress (12.9 ± 2 Pa). Spinnability of gastric mucus, measured with a Filancemeter (SEFAM), was significantly…lower (4.9 ± 2.5 mm) in comparison to duodenal mucus (6.9 ± 1.5 mm). Adhesive properties of gastric mucosa (analyzed with the platinum ring method) were not significantly different in comparison to duodenal mucus (99.9 ± 31.5 mN/m and 92.8 ± 11.2 mN/m, respectively).
Abstract: We employed a static-incubation assay to determine the intensity of wall shear stress (τ ) needed to detach human polymorphonuclear leukocytes (HPMNs) from human umbilical vein endothelial cell (HUVE) monolayers. Confluent monolayers of HUVE were placed in a parallel-plate flow chamber which was mounted on the stage of an inverted tissue culture microscope, attached to a perfusion system and maintained at 37°C. All events in the selected fields were recorded using videomicroscopy. HPMNs were co-incubated for 15 minutes with the HUVE monolayers under control conditions or in the presence of 10−7 M formyl-methionyl-leucyl-phenylalanine (FMLP). Following this static incubation, a series…of five individual flows, each 1 minute in duration, were driven through the flow channel, exposing the cells to 1.0, 2.0, 3.8, 7.6 and 14.8 dyn/cm2 wall shear stresses. Under control conditions, the percentage of HPMNs remaining attached to the HUVE monolayers following exposure to each shear stress was 61, 38, 25, 12 and 5, respectively. In the FMLP-treated condition, the percentage of HPMNs remaining attached to the monolayers was significantly greater than control at all five levels of τ . Thus, under control conditions, adherent HPMNs can be detached from endothelial cell monolayers in vitro with levels of shear stress normally found in the microcirculation (18). In the presence of FMLP, the level of shear stress needed to overcome the adhesions is increased significantly.
Abstract: The effects of polar nature of blood and pulsatility on flow through a stenosed tube have been analysed by assuming blood as a micropolar fluid. Linearized solutions of basic equations are obtained through consecutive applications of finite Hankel and Laplace transforms. The analytical expressions for axial and particle angular velocities, wall shear stress, resistance to flow and apparent viscosity have been obtained. The axial velocity profiles for Newtonian and micropolar fluids have been compared. The interesting observation of this analysis is velocity, in certain parts of cycle, for micropolar fluid is higher than Newtonian fluid. Variation of apparent viscosity η…a with tube radius shows both inverse Fahraeus-Lindqvist and Fahraeus-Lindqvist effects. Finally, the resistance to flow and wall shear stress for normal and diseased blood have been computed and compared.
Abstract: Aggregation of erythrocytes is studied as function of time during their sedimentation process under the gravitational field. The method is based on ultrasonic scattering from the various blood samples in presence and absence of inhomogeneous magnetic field (IMF) and dextran 70 (10%). The experimental arrangement is consisting of ultrasonic transmitter and receiver probes placed in mutually perpendicular direction intersecting at the sampling volume of blood located at the centre of the blood column. The temporal kinetic process is represented in terms of histograms of amplitudes and number of scattering fluctuations related to the size and motion of aggregates. The results…show that the application of IMF influences the aggregation and sedimentation of erythrocytes. The aggregates thus formed sediment faster than that of control sample. The aggregate formation and their movements in presence of dextran 70 are slower than that of normal blood which may be attributed to the enhanced suspending medium viscosity and their interaction with erythrocytes.
Keywords: Erythrocytes aggregation, ultrasound, scattering, histograms, dextran, inhomogeneous magnetic field
vol. 26, no. 4, pp. 847-862, 1989
Abstract: The effects of suspending medium osmolality (166 to 736 mosm/kg) on relative viscosity (η r ) and tube hematocrit (HT ) measured in 33 diameter tubes were studied for 40, 47 and 57% feed hematocrit (HF k) suspensions of human RBC in buffer. At all feed hematocrits, η r increased sharply for the hypertonic media, but was essentially insensitive to hypotonicity. HT /HF was less affected by osmolality (13% change over the entire range of osmolality and feed hematocrit). Viscosities could not be calculated from the experimental HT values. However, η r could be predicted from…RBC number concentration and the tube diameter/RBC volume ratio via a semi-empirical model. RBC transport efficiency depended on both feed hematocrit and osmolality, and was maximal at or near isotonic conditions. Our results appear applicable to non-isotonic regions of the microcirculation, and to estimation of flow resistance for RBC with abnormal cellular mechanical properties.
Keywords: Viscosity, Tube Hematocrit, Fåhraeus-Lindqvist effect, Fåhraeus effect, RBC Transport
vol. 26, no. 4, pp. 863-874, 1989