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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 rather explosive advancement of the life sciences during the past few decades has been most surprising. This rapid advancement includes the science of biorheology and its different fields. The author pointed out that biorheology is the missing link in most life sciences. Biorheologists who are working in one of the fields of biorheology will need to acquaint themselves with other life sciences so that new techniques, instrumentations, methods and the needed skill can be developed successfully for rheological measurements to advance these sciences and biorheology. At the core of these developments are more adequate approaches for quantitative measurements of…the deformation and flow properties pertaining to biological phenomena and processes. Many of these new approaches are demonstrated in the presentations at this International Satellite Symposium of the 5. International Congress of Biorheology. These new technological developments promise to expand greatly the scope of biorheology, both fundamentally and in the applied fields of clinical biorheology including hemorheology. These new methods also concern the diagnosis and therapy of various diseases and pathological conditions as well as their prevention. All in all, this Symposium promises to be a milestone in the science of biorheology and to serve in securing and maintaining the health of the human species.
Abstract: In vitro rheological studies on clotting of fibrinogen solution, plasma and blood are reviewed. Multiple viscoelastorecorder (MVER) and viscoelastorecorder (VER) were developed for determining the dynamic rigidity modulus (G′) and loss modulus (G″) during clotting. The effect of some parameters on clotting and the properties of fibrin clot are discussed. The parameters include measuring frequency, measuring shear strain and surface coating of measuring cell. The change of dynamic rigidity during clotting was compared between normal plasma and plasma from patient with Glanzmann’s disease. By detecting the stress at the higher harmonic frequency, the non-linear terms of G′ and G″ were…determined.
Keywords: blood clotting, viscoelasticity, fibrinogen, platelet and plasma
Abstract: Resonance Thrombography is a method to follow up the coagulation process ex vivo from its very beginning up to its final consolidation phase resp. fibrinolysis. The mode of measurement is adopting the resonance effect of fibrin elasticity. The connection of a cylindric rod and outer cylinder by elastic fibrin fibres will increase the potential natural frequency (38 Hz) of the elastically suspended rod, to which a constant orbital drive of a very small radius is imported electronically. Change of difference between constant drive frequency and varying resonance frequency over time will result in sensitive registration of the Resonance Thrombogram (RTG).…The orbital movement of the rod causes a circular flow of blood as long as it is fluid. The speed of flow is comparable to that in a medium sized vein, resembling a physiological situation. The clinical application of RTGraphy is regarding the fact, that there is practically no disturbance of clotting process which is not represented in any change of clot construction. Diagnosis of DIC, demonstration of 5FMC as well as of fibrinolysis, differentiation between the effect of fibrin structure and of platelet activity are among the clinical assignments of RTGraphy.
Keywords: Resonance Thrombography
vol. 23, no. s1, pp. 15-22, 1984
Abstract: The theories and spatial concepts of Karl Weissenberg have been applied to the science of biorheology by employing the Weissenberg Rheogoniometer. Two main types of experimental methods have been used for the characterization of the bulk shear properties of biorheological fluids: (A) In continuous laminar shearing motion, the tangential and normal components of stress are measured at a series of rates of shear. From these parameters, the apparent viscosity, an elastic modulus and a recoverable strain, are calculated as functions of the rate of shear. In this continuous shear experiment, the physical structure present in the material at any given…rate of shear may be quite different from the material in its rest state or at other rates of shear. (B) In harmonic oscillatory motion, the material is subjected to a harmonic laminar shear about its rest state at a number of frequencies and small strain amplitudes. From these experiments the dynamic moduli of viscosity and elasticity are calculated. Preparations of biological materials, such as whole blood and systems of blood components, both in health and disease states, have been investigated using methods A and B, together with studies of surface layers of plasma proteins at interfaces.
Abstract: OP-Rheometer is a rotational viscometer of concentric type, which was developed to measure blood viscosity at low shear rate (0.2–40 sec−1 ) and viscoelasticity at 0.1–3.0 Hz in the context of clinical medicine. This system consists of a mechanical unit, a control unit (console), a data processing unit and a printer. The dynamic or steady state flow data are automatically printed out. An outer cylinder (sample container) is connected to a torsion wire assembly supported by a pair of magnetic bearings. The angular displacement is detected by a pair of variable differential transformers. In clinical application of this rheometer, authors…have confirmed that the viscosity and viscoelasticity of blood from diabetic patients are higher than for normal subjects.
Abstract: Viscoelastic evaluation of aggregation and agglutination of red blood cells was attempted. A concentric double cylinder viscoelastometer was used for determining the dynamic rigidity modulus and loss modulus of blood sample. The dynamic rigidity modulus of horse blood were measured over a wide range of hematocrit. The relation between the viscoelastic behavior and the erythrocyte sedimentation was examined. The change in the amount of surface charge of enzyme treated red blood cells was qualitatively estimated from the measurements of dynamic viscoelasticity of red blood cells suspension with added poly-L-lysine. The dynamic rigidity modulus of red blood cells agglutinated by adding…lectin (concanavalin A) were also measured.
Keywords: viscoelasticity, rouleau, erythrocyte sedimentation, concanavalin A
vol. 23, no. s1, pp. 43-47, 1984
Abstract: The recent development of specific methods to measure directly the microrheological determinants of blood fluidity allows to complement or even substitute global measurements of whole blood apparent viscosity or filtrability through sieves containing restricted pores. While such differentiation is mandatory for practical and theoretical reasons, there is the danger of loosing coherence of measurements essential for correlating hemorheology to other sciences. In an attempt to document hemorheological data in a simple yet comprehensive fashion, a test profile for the display of normalized data from subtests on hematocrit, plasma viscosity, red cell “rigidity” and tendency to red cell aggregation is…proposed. Using procedures developed in the behavioural sciences, string end criteria for evaluating the validity, reliability, standardization, economy and usefulness of individual subtests for the blood viscosity determinants and a compounded hemorheology test profile are proposed. There is good evidence that abnormal hemorheological behaviour of red cell plasma mixtures manifest themselves exclusively in situations associated with grossly reduced in vivo driving pressures and thence shear stresses. In these situations, in which a low flow state is caused by general hemodynamic changes, there is a danger that the blood looses its normal fluidity and undergoes a reversible viscidation: We propose the hypothesis that in these situation abnormally blood poses a risk of a flow limitation (and even interruption) by rheological abnormalities described above. The test profile presented has been developed to supply a more valid experimental method for subjecting the above hypothesis to experimental tests in the clinical situation.
Keywords: Data processing in hemorheology, hematocrit measurement, plasma viscosity, red cell aggregometry, red cell rigidometry, standardization of tests, test profile, test battery, validation of tests
vol. 23, no. s1, pp. 49-62, 1984
Abstract: The aim of practice of clinical haemorheology is to study patients who might present themselves with or without any clinical symptoms but who might suffer from silent or overt cardiovascular disorders, some forms of cancer, anxiety, etc. A presence and a prognosis of these disorders are linked to an increase and/or abnormality of one or more of the blood viscosity factors: blood viscosity, plasma viscosity, red cell aggregation and rigidity, platelet aggregation, ability for formation of thrombi, flow instability, etc. Hyperviscosaemia might be present in spite of normal or low viscosity of the whole blood. Different disorders can be described…by ‘profiles of viscosity factors’ which form a rheological fingerprint specific to a particular disease or a group of disorders. Determination of viscosity factors is carried out utilizing a series of instruments: (a) rotational viscometers, (b) capillary viscometers, (c) erythrocyte sedimentation tubes in 20C and 37C water tanks, (d) variable frequency thrombo-viscometer, (e) slit-capillary photo-viscometer, etc. One known factor which is not measured routinely is ‘inversion phenomenon’, and this is due to complexity and expense of measurements. Biochemical studies, including fibrinogen assay and estimation of AB0 blood groups, are carried out. Effect of drugs on blood viscosity factors can be studied in vitro or in vivo.
Keywords: clinical haemorheology, viscometry, diagnosis and prognosis, aggregation of red cells, rigidity of red cells, thrombi
vol. 23, no. s1, pp. 63-69, 1984
Abstract: Patients with chronic arterial disorders (CAD) frequently exhibit rheological alterations of the blood beneath generalisated sclerosing of the vessels and restricted arterial diameters. Alterations of different rheological parameters were determined in more than 80% of the examined patients. The following parameters were measured: yield shear stress in the ESM, hematocrit level in the IHA, plasma viscosity in the CTPV, standardized erythrocyte aggregation index in the MEA and standardized erythrocyte rigidity index in the SER.
vol. 23, no. s1, pp. 71-74, 1984
Abstract: A new experimental method is described which permits estimation of flow ability of blood: measuring the yield shear stress with the erythrocyte-stasis-meter (ESM). This method is based on the phenomenon that pathological blood under low pressure behaves like a solid body. Knowing the pressure difference at the transition point from solid to fluid behavior and the geometry of the channel, the yield shear stress can be calculated.
vol. 23, no. s1, pp. 75-77, 1984
Abstract: Blood suspensions have been studied by using an air-bearing viscosimeter which is driven by a rotating magnetic induction. Each transient motion (rise, relaxation with zero or intermittent field) can be considered as a quasi-static motion, from which the curve viscosity-shear gradient can be obtained. Combining several transient motions allows an easier determination of the parameters describing a non newtonian fluid like blood.
Abstract: The viscometer described in this paper comprises a vertical cylinder containing the fluid to be tested and an inner, hollow cylinder floating in the fluid and filled with magnetic liquid. The magnetic liquid and inner cylinder are set in motion by applying a rotating magnetic field. Torque is balanced by the stresses in the fluid and the inertia of the rotating cylinder. The main characteristics of this new apparatus are: - possibility of applying various torques to the rotor. Measurements of angular velocity are made on the inner cylinder (in general, conventional viscometers are built on the opposite principle),…- study in transient flow. Various measurements on Newtonian fluids (water, plasma, oils, etc.) and on blood suspensions have made it possible to improve the accuracy of the method.
Keywords: Viscometer, Magnetic liquid, blood
vol. 23, no. s1, pp. 83-88, 1984
Abstract: A falling ball viscometer is used to measure whole blood and plasma viscosities. The principle of the device is to determine the fall time of a ball contained in a disposable syringe; the periodic run of the sphere prevents blood sedimentation during the measuring cycle but does not prevent the aggregation process which takes place with a short relaxation time. The analysis of the flow field is discussed relative to previous papers. The study of the dynamics of the falling ball provides two characteristic rates of deformation for the mixed extensional and shear flow field. The Reynolds numbers are calculated…using different velocities and radii. Results on blood and plasma viscosity of patients suffering from rheumatoid arthritis are given in relation with clinical and biological indexes.
Abstract: We have studied some rheological parameters in different clinical status by using two coaxial viscometers. The Contraves Low Shear sinus 30 allows available shear rates range from γ ˙ (128s-1 to 0.0175 s-1), and the parameters studied were viscoelastiticy, thixotropy and blood viscosity. The Ecktacytometer1 1 Technicon is another method for measuring cell deformation in couette flow. The aim of our study was to compare these two technics, to consider their clinical interest and finally to visualize an eventual correlation. Technicon
Abstract: Aggregation and sedimentation of the red cells in the viscometer makes it difficult to obtain good reproducibility at low shear rates. A simple method is described to obtain repeatable torque-time curves with the Contraves LS30. Before starting rotation, the blood sample is agitated by an up and down movement of the bob. This results in identical (within 1-2% of the actual amplitude) repeated tracings even at the lowest shear rates, even with extremely time-dependent samples. The subsequent torque-time curve of the disaggregated and unsettled samples provides an experimental basis for the quantitave description of blood viscoelasticity and for dynamic analysis…of red cell aggregation: furthermore it results in more accurate measurements when comparing different samples and testing therapeutic effects. The method is applicable to any coaxial cylinder type viscometer with manual lowering of the bob.
Keywords: Low shear viscometry, aggregation, sedimentation, time dependence
vol. 23, no. s1, pp. 99-101, 1984
Abstract: The weak interactions between plasma proteins are of possible importance both in haemorheology and in the pathology of several diseases. The use of surface rheology is a convenient way to study the forces arising between surface adsorbed protein molecules. A surface rheological measuring head has been designed for the Contraves LS-30 viscometer. Plasma samples of healthy human subjects showed a rapidly developing viscous surface layer with a mean peak value of 2.10−3 Ns/m surface viscosity at 30–60 seconds. After that the viscosity of the surface layer gradually decreased to zero between 8–20 minutes. The rate of the observed decrease…was not related to shearing. There was no difference between samples anticoagulated with heparin or EDTA. The time course of the described phenomenon coincides with that of thrombocyte and white cell adherence to solid surfaces exposed to plasma.
Keywords: surface rheology, plasma-air interface
vol. 23, no. s1, pp. 103-105, 1984
Abstract: The determination of a constitutive law of a fluid, the red blood can be obtained by fitting the parameters of a theorical law with experimental results. For an experience, several expressions can be agreed, each of them explain a particular property. The aim of my purpose is to describe some mathematical ans numerical methods, in relation with two experiences, able to give the value of an unknown quantity by computation and to fit it with measured quantity. The first method use finite element to modelize a couette nonlinear flow. It can be approach by a very simple model using only…the computation of a nonlinear differential equation. The second use the perturbation method and the expansion in power serie.
Keywords: Blood, Viscosimeter
vol. 23, no. s1, pp. 107-110, 1984
Abstract: This work was done as the first part of a continuing study of neonatal blood. In a recent paper (1), two parameters, “A” (relative whole-blood viscosity at unit rate of shear and 1% haematocrit) and “β ” (shear-sensitivity exponent) were proposed, as characteristics of a given blood-sample. Here, some 60 placentae yielded (after plasma-manipulation) 130 sub-samples having haematocrits ranging from 3% to 90%. Their viscosities were measured in a capillary viscometer set for a constant wall shear-stress of 1855 mPa. “A” and “β ” were calculated by the method given in (1). Multiple calculations on a number of…sub - samples revealed systematic variations within anyone blood; but when every A/β ratio is plotted against the corresponding A, the results follow a smooth curve. This curve occupies a striking, almost central location when A-and-β values from adult normal and pathological bloods (rotational viscometry) are superimposed on the diagram. An analytic form for the close correlation between haematocrit and relative placental blood-viscosity is given by the adoption of a single “group A” and “group β ” for all 130 results.
Abstract: A new capillary viscometer was developed to eliminate the measuring errors due to insufficient cleaning or the residue of cleaning solution in the capillary. A disposable polyurethane tube which can be discarded after each determination is used as a measuring chamber. This device has been constructed for bed-side application (light weight, dry, thermostat-controlled measuring capillaries, short measuring period, automated process, and easy operation). The Pearson correlation coefficient for comparative measurements with the Coulter-Harkness viscometer was r = 0.979 .
vol. 23, no. s1, pp. 115-117, 1984
Abstract: In clinical practice, a wide variety of drugs are given to modify the rheological properties of bronchial mucus but they are frequently not correctly chosen because there is not a simple apparatus available for the routine measurement of the mucus viscoelasticity. We designed a new viscoelastometer which is easy to operate and permit accurate measurement of the viscoelastic properties of mucus. The system has a Couette geometry and requires a sample of 1 ml. The outer cylinder is thermostated and rotates at a constant rate. The resulting torque is measured on the inner cylinder using a microdisplacement transducer. The…inner cylinder is suspended by a special wire system which maintains a constant 0.75 mm gap between the two cylinders. The apparent viscosity is calculated up to 100 Pa.s. at a low shear rate (0.4 s−1 ) and the elasticity is analyzed by a stress relaxation method The characteristics of the apparatus and the typical viscoelasticity behaviour of several sputum samples are reported.
Abstract: Spinability is a rheological parameter which characterizes the property of fluids to be drawn into threads when stretched. It has been shown that this property is of particular importance in the mucus transport process. This paper describes an automatic apparatus which measures the spinability of a calibrated volume (2g μ l) of sample at a stretching rate of 10 mm.sec−1 . The reproducibility of the measurements is analyzed on mucus simulants and on different types of bronchial mucus. Using this technique, we observed that the spinability of bronchial secretions is significantly correlated (r = 0.69, p < 0.001) with…their transport rate measured on the depleted frog palate. This device is suitable for measuring the spinability of all conductive types of mucus and other biological fluids.
Keywords: Respiratory mucus, thread-forming property, spinability, mucociliary transport
vol. 23, no. s1, pp. 123-126, 1984
Abstract: In order to rationally test the efficacy of mucolytic and mucospissic compounds, their effects upon mucus viscoelasticity, ciliary beat frequency (c.b.f.) and total mucociliary transport rate (t.t.r.) must all be determined. Methods are described which allow the measurement of the viscoelastic modulii of small (10μ L) quantities of mucus, while c.b.f. and t.t.r. are determined using the frog palate model.
Abstract: A velocimeter for measurements of blood flow velocity in microvessels was constructed with a microscope, a grating, a photomultiplier and a wave-period measuring circuit. A differential detection system seemed to be useful when the probing area was extremely small. A pulsating flow velocity contour and the velocity reduction caused by an application of noradrenaline were on-line recorded in an arteriole of foot web of frogs.
Abstract: Capillary blood flow may be considered as the flow of two compartments a.) the low viscous cell free marginal layer, surrounding b.) the higher viscous axial core. If the flow of both compartments is calculated separately according to Poiseuille, the addition of the two calculations allows to adapt Poiseuille’s law to the non-Newtonian blood flow in small capillaries. The modified law correlates theoretical and experimental data with R2 =0.99. (H=0.3–0.7, τ W =0.1–1.2 Pa, blood viscosity 5 to 20 mPa·s, capillary I.D. 0.3 mm). The width of the marginal was calculated by relating the shear dependent change in electrical…resistance in blood perfused capillaries to the development of a cell free marginal layer. The viscosity of the core was determined with a bended glass fibre (⌀= 10 μ m).
Keywords: Viscosity, marginal layer, axial core, Poiseuille’s law
vol. 23, no. s1, pp. 135-143, 1984
Abstract: Blood platelets labeled in vivo with the fluorochrome acridine red can be localized objectively within a thin optical section, using fluorescence microscopy. This allows the study of the rheological behavior of platelets in vivo as exemplified by the assessment of the concentration distribution and the orientation of platelets flowing in small arterioles of the rabbit mesentery.
Keywords: blood platelets, rheology, in vivo, fluorescence
vol. 23, no. s1, pp. 145-149, 1984
Abstract: This text recalls the main sequences of a videofilm in which we have looked at the blood flow through small diameter tubes, varying from 200 to 500 μ m diameter, using a video equipment where the camera is fixed to a phase contrast microscope. Flows of two fluid model through converging-diverging small tubes have been studied both theoretically and experimentally, where we have considered the influence of tube diameter, stenosis, flow rate, haematocrit upon the red blood cells repartitions and the thickness of peripheral plasma layer.
vol. 23, no. s1, pp. 151-153, 1984
Abstract: An instrument was developed which can simultaneously determine the hematocrit and the total electrolyte concentration in blood and plasma respectively. It is possible to correct the hematocrit value for fluctuations of the total electrolyte concentration. Pilot studies of this device have been conducted on physiological and rigid erythrocyte suspensions and on plasma with various total electrolyte concentration. In the future, this device will be employed in analyzing blood and plasma of patients undergoing hemodialysis.
vol. 23, no. s1, pp. 155-157, 1984
Abstract: A fundamental problem of haemodynamics lies in the description of the rheological properties of arteries. The time and history dependency of stress and strain, the nonlinearity of the stress-radius relationship, and the activity of vascular smooth muscle complicate or even prevent a complete mathematical characterization of the arterial wall mechanics. Due to this nonlinearity, dynamic investigations were hitherto performed in excised arteries in vitro by means of small sinusoidal changes of stress and radius at different stress levels in a wide frequency range. To allow an analysis of the dynamic rheological properties of arteries in vivo, we have developed a…procedure which permits the separate determination of the elastic, the viscous, and the inertial forces acting on the arterial wall. The stress can be subdivided into an elastic stress which is a function of radius (r), a viscous stress which is a function of dr/dt, and an inertial stress which is a function of d2 r/dt2 . These stresses are formulated as polynomials. Under cyclic loading and unloading, hysteresis loops appear in the stress-radius diagrams of arteries. Since the elastic stress-radius diagram must be free from any loop, the coefficients of the viscous and the inertial stress can be found by a fitting procedure, using the criterion of loop elimination. Investigations were performed on exposed canine arteries in vivo. The main result was that the elastic stress-radius curve was markedly nonlinear at greater pulse pressures. The viscous wall behaviour, too, was nonlinear and depended mainly on the square of the vessel radius.
Abstract: Bone has been shown to be a viscoelastic material which is thermorheologically complex. This implies that multiple mechanisms determine the viscoelastic response of bone. New calculations of the contribution of fluid flow to the viscoelastic behavior of bone have been made. The calculation of the relaxation time was based on Biot’s model for the relaxation of fluid flow in porous materials while the relaxation strength was estimated from simple composite models. These models together with recent measurements of the permeability of bone predict that part of the relaxation due to fluid flow will occur at fairly high frequencies, perhaps above…10 kHz for in vitro samples. Measurements of ultrasonic wave propagation and attenuation in wet bone have been performed from 0.5 MHz to 15 MHz and the mechanical damping was measured from 100 Hz to 1 kHz with fluid viscosities ranging from 10−3 to 5 × 10−2 (MKS). However, a complete understanding of the rheological properties or bone will require additional experiments to bridge the gap between the low frequency measurements and the ultrasonic measurements.
vol. 23, no. s1, pp. 169-174, 1984
Abstract: Regional wall motion of the left ventricle (LV) has been analyzed from contrast ventriculograms by using 4 methods based on different geometrical frameworks. Two of them utilize moving internal reference systems, the center of mass (CMM) and the long axis (LAM) methods; the two other ones use fixed external reference systems, the area-based (ABM) and the Palo Alto (PAM) methods. The techniques were applied on a set of 81 patients: 42 were normal and composed the group I; 22 had a single vessel obstruction >75% of the left anterior descending coronary artery (group II) with old necrosis or active ischemia…of the LV anterior wall; 17 had a single vessel obstruction >75% of the right coronary artery (group III) with old necrosis or active ischemia of the LV inferior wall. ABM and PAM showed the highest specificities and sensitivities on the studied sample. Therefore, we believe these two methods, of the techniques tested, are the best to quantitate wall motion from cineangiograms.
Keywords: Left ventricular wall motion, cineangiography, computer-based analysis methods
vol. 23, no. s1, pp. 175-182, 1984
Abstract: Up to now, not so much attention has been paid concerning the dynamic rheological behaviour of soft tissues although non linear viscoelastic effects have often been reported when mechanical properties of biomaterials are concerned. In order to characterize such properties different rheological tests have been proposed, the two principal being the study of the sample stresses responses to applied strains which are either harmonic with time or of step function type. Two different apparatus have been designed in our laboratory which allow specific rheological tests on biological materials under controlled environmental conditions. With one of them, harmonic uniaxial extension…tests are performed in a large domain of frequencies (.001 Hz to 100 Hz) and forces (up to 20 daN); with the other, the samples are submitted to relaxation tests in uniaxial elongation up to 5 cm deformation within time duration of the order of 20 ms. The principal characteristics, limitations and performances of such apparatus are presented and few examples of data thus obtained are given. On the basis of quasi linear viscoelasticity models, it can be shown that both two types of tests with their proper limitations are leading to the same rheological parameters.
Abstract: A system of equations, describing the excitation-contraction coupling in cardiac muscle is obtained on the basis of a physiological model and of a thermodynamical one of a system with external control, the latter model being proposed by the authors. A single isometric contraction is modelled for latent, activation and relaxation periods. The obtained theoretical results coincide qualitatively with the experimental data.
Abstract: We have developed a device for the determination of the minimum shear force necessary to maintain complete disaggregation of erythrocytes and to simultaneously determine the hematocrit of blood samples (red cells in autologous plasma). A functional relationship between this shear force and the hematocrit was determined. The first derivative of the (measured) γ Tmin as a function of the hematocrit was found to be identical (within limits) for all normal blood samples tested.
vol. 23, no. s1, pp. 213-215, 1984
Abstract: A viscometric technique is outlined for the measurement of red cell aggregation (RCA). Samples are submitted to a constant shear rate of 2,4 s−1 . The resulting time dependent torque signal reaches a peak soon after starting the rotation and falls within seconds to a constant baseline, thereby describing an area “F” with the baseline. The shear history of the sample being strictly controlled, “F” is reproducible and shows a direct, positive correlation with RCA as determined for instance in the “aggregometer”.
Keywords: hemorheology, red cell aggregation, viscometry
vol. 23, no. s1, pp. 217-219, 1984
Abstract: From a clinical point of view, the approach to erythrocyte aggregate or rouleau formation and cohesion is undeniably of great interest. A large number of methods have been suggested for studying this parameter such as: back-scattering of light, nephelometry, ultrasound, etc... In this paper the authors have compared three methods to approach rouleau formation: direct observation of rouleau formation (rheoscope); ‘erythrocyte aggregometer’: with this technique, the light transmitted by the sample is integrated over a period of time and provides an index (IA ); laser reflectometer based on studying the light that is back-scattered by the blood sheared in the…gap of a viscometer. The results show that the indexes measured by both reflexion and transmission vary according to hematocrit and reach a maximum value at hematocrit levels of between 30 and 40 %. In contrast, observation using the rheoscope did not provide qualitative evidence of this phenomenon.
vol. 23, no. s1, pp. 221-226, 1984
Abstract: Flow resistance of EDTA or defibrinized blood was measured in a vertical capillary viscometer. (Capillary I.D. = 0.3 mm, l = 475 mm, τ W = 0.27 to 0.036 Pa). With decreasing shear forces the apparent viscosity increased from 12 to 16 mPa·s, i.e. by about 30%. There was no significant difference in flow resistance between red cells suspended in plasma or serum. The apparent viscosity of the same blood sample increased from 14 to 45 mPa·s for RBC in plasma i.e. by about 320% if measured with a rotational viscometer. The attempt is made to explain this…difference in flow resistance with the different effect of shear resistant RBC-aggregates upon a parabolic streaming profile in a capillary, or upon the quasi linear profile within the annular Gap of a rotational viscometer.
vol. 23, no. s1, pp. 227-230, 1984
Abstract: We present a device for the routine measurement of the deformability of individual red blood cells, the so called Single-Erythrocyte-Rigidometer (SER). The time required for individual erythrocytes to traverse a single pore membrane (pore diameter = 5 μ m, pore length = 25 μ m) is taken as an index of red cell deformability. For example we present the results from patients with insult, polyneuropathy and morbus binswanger. Compared to the results of erythrocytes of healthy probands a significantly increased rigidity of the RBC of the patients can be diagnosed.
Keywords: RBC-Deformability, Single-Erythrocyte-Rigidometer(SER, Single Pore
vol. 23, no. s1, pp. 241-243, 1984
Abstract: Employing the “Singlepore Erythrocyte Rigidometer” (SER) in which small pore diameters were used, significant differences were measured between red blood cells from adjuvant arthritic rats compared to control from non-diseased animals. The results changed to opposite values using higher pore diameters, which may be due to differences in cell “rigidity” and MCV.
Keywords: RBC-Deformability, Single Erythrocyte Rigidometer, Pore Geometry, Passage Time
vol. 23, no. s1, pp. 245-247, 1984
Abstract: In order to follow the filtration of a red cell suspension with time, the filtration technique described (1) has been modified. The red cell suspension is filtered through a polycarbonate membrane filter (pore diameter 5μ m) under gravitational force. The filtrate is collected in a plastic tube connected to an isometric transducer, the output of Which is registered on a chart recorder. The linear part of the curve obtained is used to calculate the slope and the relative filterability (HF) ie the ratio of the rate of flow of the red cell suspension to the rate of flow of the…suspending medium. The reproducibility of the technique is demonstrated by a <5% coefficient of variation in one blood sample <5% interobserver variation and a weekly variation from the same donor of <5%. The fast filtration rate of a highly diluted red cell suspension (0.5–1%) may be followed with this technique, taking the first 15 seconds to calculate it. The technique has proved useful in detecting differences in red cell deformability in connective tissue disorders (Scleroderma, Raynaud’s phenomenon) also between stored and freshly prepared red cell suspension and its improvement by drugs (pentoxifylline, dipyridamole).
Keywords: Red cell filterability, filtration technique
vol. 23, no. s1, pp. 249-253, 1984
Abstract: The Erythrometer is a new device capable of determining both red blood cell filterability and plasma viscosity. In the case of filterability measurements, a suspension of washed red blood cells is filtered at a steady flow rate through a 3 or 5 μ m pore-diameter membrane. Pressure drop across the membrane is recorded and a red blood cell filterability index can be calculated according to the change in pressure. The authors describe the instrument’s operating principle and performance and present some of the results obtained.
Keywords: Deformability, filterability, red blood cells, plasma, viscosity
vol. 23, no. s1, pp. 255-259, 1984
Abstract: The authors have tested a new device that records the filtration pressure of a suspension of red blood cells (R.B.C) passing through a 3μ m pore diameter filter. As the flow rate is constant, the pressure increase allows to appreciate an index of the R.B.C deformability. In order to test the performances of this new equipment, the authors have studied the influence of the variation of the following parameters. - Haematocrit from 0.5 to 2%, Buffer composition; time elapsing from drawing to measurement: from hour 0 to hour 3. This analysis has been performed on donors; on packed red cells…preserved in CPD, from D0 to D21 and on patients specimens and the results have been compared to the whole blood filtration according to the Reid and Dormandy method. The following parameters were simultaneously measured: - Whole blood viscosity by means of a Low Shear 30 viscosimeter, Intraerythrocyte ATP by bioluminescence, Membrane lipid composition (cholesterol, phospholipids), Scanning electron microscopy. This new apparatus, measuring the filtration pressure seems to be a more insensitive and reproductible method allowing to approach the RBC deformability, and quite useful in clinical haemorheology. Haematocrit from 0.5 to 2%, Buffer composition; time elapsing from drawing to measurement: from hour 0 to hour 3. This analysis has been performed on donors; on packed red cells preserved in CPD, from D0 to D21 and on patients specimens and the results have been compared to the whole blood filtration according to the Reid and Dormandy method. The following parameters were simultaneously measured: Whole blood viscosity by means of a Low Shear 30 viscosimeter, Intraerythrocyte ATP by bioluminescence, Membrane lipid composition (cholesterol, phospholipids), Scanning electron microscopy. This new apparatus, measuring the filtration pressure seems to be a more insensitive and reproductible method allowing to approach the RBC deformability, and quite useful in clinical haemorheology.
Abstract: When filtering red blood cells (RBC) resuspended into buffer at constant flow, the pressure-time curve is dependent on erythrocyte deformability (E.D) and also on the plugging of pores by RBC or leukocytes (WBC). To understand the influence of these 3 factors, we used an apparatus with: 1) a constant flow syringe (Bioblock) (1.56 ml/mn); 2) a pressure transducer (Statham P23 ID); 3) a recorder (Gould); 4) a 5 μ m polycarbonate filter (Nuclepore) housed in a lucite block according to Usami & al.(1). Resuspensions of RBC from 4 to 14 % haematocrit with 0 to 600 WBC/mm3 were investigated. Results…indicate that: 1/ The first inflexion point of the pressure-time curve (initial pressure leading to calculation of β ) is related to the RBC’s deformability; 2/β is (in our experimental conditions) dependent on the WBC number; 3/β seems very sensitive to deformability changes as shown by rapid increases induced by osmolarity changes.
Abstract: A new version of the Hemorheometre is presented. The main improvements are: 1) The measurements can be performed at constant temperature. 2) The apparatus operation is automated. The accuracy of the apparatus is thus significantly increased.
vol. 23, no. s1, pp. 275-277, 1984
Abstract: Positive-pressure and initial-flow-rate (Hémorhéomètre) filtration systems were used to study the deformability of erythrocytes from whole blood stored in EDTA or heparin. When all contaminating platelets and leucocytes were removed from the erythrocyte suspension there was no significant anticoagulant effect on erythrocyte filtration. Blood may therefore be stored in K2 EDTA (1.5 mg/ml blood) or lithium heparin (15 IU/ml blood) for up to 6 hours at room temperature prior to measurement of erythrocyte filterability.
Abstract: Posit.ive-pressure and initial-flow-rate (Hémorhéomètre) methods for the study of erythrocyte filtration through 5 μ m diameter pores are highly sensitive to the presence of contaminating leucocytes in the erythrocyte test suspension. A pre-filtration step, in which heparinised or EDTA-anticoagulated whole-blood was passed through a column of Imugard IG500 cotton wool, was therefore developed. This procedure removed contaminating platelets and leucocytes, but not erythrocyte sub-populations, and is likely to improve the sensitivity and specificity of erythrocyte filtration techniques.
Abstract: The physical optics approximation has been used to compute small angle light scattering patterns from spheroids regarded as models for deformed red cells. According to their orientation, diagrams have been obtained whose fine structure can be very different from that resulting of the classical diffraction (existence of maxima and minima of intensity along the rings). Some experimental results for red cells suspensions under shear are shown which exhibit features very similar to the theoretical ones.
vol. 23, no. s1, pp. 287-290, 1984
Abstract: The Ektacytometer is a visco-diffractometric method to preferentially examine the functional properties of erythrocytes. The realization of this method in the form of an automated laboratory instrument, the Technicon Ektacytometer, is described. A suspension of RBC is submitted to a uniform shear stress. The resulting deformation of the cells is seen as an elongation of the diffraction image and expressed as the Elongation Index or EI. EI may be traced on an X–Y recorder as a function of stress, time and of suspending medium osmolality. The osmolality is varied automatically in the viscometer and automatically measured via its conductivity, resulting…in an “Osmoscan”. The Osmoscan is highly reproducible and requires only 150 μ l of blood and 5 minutes per sample. Its high sensitivity to small changes in erythrocyte properties permits the separation of factors affecting RBC deformability, and provides a measure of the osmotic fragility which correlates very well with the traditional test. Other applications are described, including mechanical fragility assays on whole cells, relaxation times of ghosts and the automatic variation of PO2 . Possible future applications are suggested.
vol. 23, no. s1, pp. 291-295, 1984
Abstract: Erythrocyte deformability is an important determinant of red cell life span and depends on at least three key factors: shape, internal viscosity and membrane mechanical properties. In this paper we describe three viscometric methods for assessing red cell deformability and fragmentation: 1) Plasma and whole blood are sheared with a coneplate viscometer at high shear rates. A mathematical model for liquid behaviour is applied to the results from plasma and whole blood viscosity, and a rheological parameter called internal viscosity is obtained. 2) Shearing packed red cells(Haematocrit ⩾ 95%)at high shear rates, a mechanical fragmentation curve is obtained, and a…new rheological parameter called rupture stress is determined. 3) Shearing whole blood at 230 Sec−1 and increasing continuously the temperature from 37°C to 57°C, a thermic curve is obtained. A viscosity increase is observed at about 48°C and thermic curve changes are related to effects of heat on the red cell membrane. Internal viscosity, mechanical fragmentation curve and thermic curve assess red cell deformability and fragmentation and can be used as diagnostic tools in diseases with red cell abnormalities.
Keywords: Red cell deformability, Red cell fragmentation, Internal viscosity, Red cell membrane
vol. 23, no. s1, pp. 297-301, 1984