Biorheology - Volume 30, issue 5-6

Authors: Sipkema, P. | van der Linden, P.J.W. | Westerhof, N.

Article Type: Research Article

Abstract: Perfusion of the heart takes place mainly in diastole. It is therefore important to study the factors that affect coronary diastolic flow. One of the factors that may limit coronary artery vasoactive responses is the surrounding cardiac tissue. We have therefore studied the intramyocardial septal artery, both when still embedded in the diastolic, unstretched myocardial tissue and after complete dissection (n = 6). In situ , the average external diameter was 351 ± 21 μ m; after dissection, it was 362 ± 21 μ m. These values were not significantly different. The average response of the vessel to KCl (125 …mM, receptor-independent constriction) reduced the diameter to 56.1 ± 5.0% and 69.4 ± 3.7% of the maximal diameter for in situ and dissected vessels, respectively. The reduction in diameter after dissection was significantly less than the reduction in situ . The response to vasopressin (1,000 μ U/ml, a receptor-dependent constrictor) was a reduction to 62.6 ± 4.7% and 70.4 ± 4.5%, respectively. The reduction in diameter of the dissected vessel is significantly smaller than that of the in situ vessel. The average values of the ratios of the diameter reductions for vasopressin and KCl were 0.85 ± 0.06 in the in situ condition and 0.95 ± 0.08 after dissection and were not significantly different (paired t-test). The results show that the dilated diameter and the diameter responses of intramyocardial conduit arteries are not affected by the surrounding diastolic cardiac tissue. Show more

Keywords: Vasopressin, diastolic heart tissue, cannulation, diastolic coronary flow

DOI: 10.3233/BIR-1993-305-609

Citation: Biorheology, vol. 30, no. 5-6, pp. 381-385, 1993

Authors: Oddou, C. | Razakamiadana, A.

Article Type: Research Article

Abstract: Intramyocardial stresses appear to be an important factor in the degree of compression of the coronary vasculature, directly influencing the peripheral impedance of the coronary hemodynamic network. A method is presented for predicting variation in the luminal area of small vessels embedded in myocardial tissue, due to changes in surrounding stresses. Such stresses and strains were calculated as those generated in the wall of a cylindrical structure, a model of the cardiac ventricular wall. Based on the classical theory of linear elasticity and assumptions of superposition of strains generated within the medium by the cyclic variation of tissue pressure and …fiber stress, changes in the inner cross-section area of microvessels were computed. Applied to coronary microvasculature, it was shown for the range of tested parameters that these microvessels are not likely to be subjected to instability phenomena and subsequent collapses, but rather show a small change in area. These results are in agreement with physiological observations concerning the degree of area reduction in arterioles and venules localized within the endocardial portion of the left ventricular wall. Based on this theory, analysis of variations in distensibility, compliance and resistance of microvessels, such as arterioles and venules, vs . internal pressure, and different cardiac states and locations within the myocardial wall is possible. Show more

Keywords: Myocardial stresses, microvessel rheology, coronary microcirculation, microvessel compressibility, coronary hemodynamics, mechanical model

DOI: 10.3233/BIR-1993-305-610

Citation: Biorheology, vol. 30, no. 5-6, pp. 387-396, 1993

Authors: Nash, G.B. | Gratzer, W.B.

Article Type: Review Article

Abstract: Although the stability and viscoelasticity of the red cell membrane are undoubtedly governed by the membrane’s underlying protein skeleton, the mechanism by which this network controls elasticity is uncertain. The structural constraints, that impose end-to-end spacing on the spectrin molecules well below that in free solution, may impart rubbery (entropic) elasticity to the system. However, other enthalpic and entropic contributions due to interactions between spectrin chains or between spectrin and other proteins, the lipid bilayer or the solvent must also prevail. To relate structural features to elasticity, explicit measurements of membrane rigidity are required. The most widely used measurement is …that of the membrane shear elastic modulus by micropipette aspiration. Analysis of genetic variants of membrane structure have shown that the density of spectrin is directly correlated with membrane rigidity. Although cross-linking of the skeleton increases rigidity, interruption of the continuity of the network by dissociating spectrin tetramers into dimers does not reduce rigidity as might be expected. On the other hand, external ligands that cause new interactions between integral proteins and the skeletal network do increase rigidity. Moreover, hereditary ovalocytes, which have a deletion of 9 amino acids from band 3 at the first point of entry into the membrane, are extremely rigid. This mutation is associated with decreased translational and rotational mobility of the band 3, and may impair flexural freedom of its cytoplasmic domain. It thus appears that elasticity may be regulated not only by the structure of the spectrin network, but also by its interactions with and freedom of motion relative to the lipid bilayer. Show more

Keywords: Erythrocyte, membrane, elasticity, protein skeleton, rheology

DOI: 10.3233/BIR-1993-305-611

Citation: Biorheology, vol. 30, no. 5-6, pp. 397-407, 1993

Authors: Gomez, J.E. | Thurston, G.B.

Article Type: Research Article

Abstract: Rheological and compositional properties of pathological synovial fluids were measured and compared in order to reveal differences between disease states. The cases include degenerative joint disease, rheumatoid arthritis, mixed connective tissue disease, and pseudo gout. Using an oscillatory flow capillary instrument, measurements were made of both the frequency and shear rate dependence of the complex viscoelasticity. The fluid types differ most in their elasticity, with the degenerative joint disease fluids having the greatest average viscosity, elasticity and intrinsic viscosity, followed by the rheumatoid arthritis fluids, and the fluids from cases of mixed connective tissue disease. Differences in the hyaluronate and …protein concentrations are not as great as those between rheological variables. The viscoelasticity of synovial fluid appears more strongly dependent on the degree of polymerization of hyaluronate than on its concentration. These synovial fluids conform well to a model of relaxation process truncation. Distinct types of elastic stres train behavior reveal the nature of the dynamic fluid structure. Show more

Keywords: Synovial fluid, viscoelasticity, shear rate dependence, intrinsic viscosity, rheumatoid arthritis, degenerative joint disease, mixed connective tissue disease, pseudogout

DOI: 10.3233/BIR-1993-305-612

Citation: Biorheology, vol. 30, no. 5-6, pp. 409-427, 1993

Authors: Taylor, T. | Okino, H. | Yamaguchi, T.

Article Type: Research Article

Abstract: The effect of supravalvular aortic stenosis on cardiac left ventricular ejection was determined from a realistic left ventricle (LV) model built from the profile of a diastolic dog LV. The ejection fraction was considered to be 75% of the diastolic volume. The maximum blood ejection velocities and ventricular pressure occurred at the start of the diastolic flow since the ventricular walls moved the fastest at this point. Going from a healthy non-stenotic LV to one with 64% stenosis increased the maximum ejection velocity from 117 cm/sec to 269 cm/sec, and the maximum relative pressure increased from 10,420 dynes/cm2 to …33,550 dynes/cm2 (7.82 to 25.16 mm Hg). The supravalvular stenotic aorta showed major flow disturbances as the degree of stenosis increased. The computational technique using a realistic model gives predictions in general agreement with observed experimental results, and allows a complex determination of the three-dimensional flow patterns. Show more

Keywords: Computational fluid dynamics, heart blood flow, left ventricle, supravalvular stenosis

DOI: 10.3233/BIR-1993-305-613

Citation: Biorheology, vol. 30, no. 5-6, pp. 429-434, 1993

Authors: Matsumoto, T. | Kawai, M. | Masuda, T.

Article Type: Research Article

Abstract: Rheological properties and fractal structure of the polyion complex between chitosan and alginate have been studied using IR spectra, dynamic viscoelasticity and SAXS measurements. The complexation seems to occur between a carboxyl anion of the alginate and an amino group of the chitosan. The complex develops most markedly at a mixing ratio in weight of the chitosan/alginate from ca . 1/1 to 1/2 (in molar ratio), at which the dynamic viscoelastic functions of the systems manifest a plateau region due to a heterogeneous structure at a low frequency range. The heterogeneous structure shows a surface fractal structure having a fractal …dimension of ca . 2.4. Show more

Keywords: Polyion complex, chitosan, alginate, rheological property, fractal

DOI: 10.3233/BIR-1993-305-614

Citation: Biorheology, vol. 30, no. 5-6, pp. 435-441, 1993

Authors: Cloutier, C. | Shung, K.K.

Article Type: Research Article

Abstract: Human red cell aggregability and disaggregability represent important hemorheological parameters of blood. Several techniques have been proposed to evaluate the tendency of red cells to form aggregates and to disrupt in the presence of shear stress. One of the most recent approaches is based on the characterization of the intensity of ultrasonic scattered signals. A pulsatile flow loop model is used in the present study to demonstrate the potential applicability of Doppler ultrasound to detect and characterize the hemodynamic behavior of red cell aggregates. Porcine whole blood specimens collected from 20 different pigs were circulated in the flow model (tube …diameter of 0.476 cm) at different mean velocities and pulsation rates. At a pulsation of 70 beats/min for mean velocities of 13 cm/sec and 63 cm/sec, no cyclic variation of the Doppler power was observed, suggesting the absence of rouleaux build-up and rouleaux disruption. At a pulsation of 20 beats/min and mean velocities of 11 cm/sec and 38 cm/sec, statistically significant cyclic variations (p < 0.01) were measured. It is suggested that aggregate size enlargement, rouleaux orientation with the flow field and the effect of shear stress on rouleaux disruption are possible causes for the observed cyclic variation of the Doppler power within the flow cycle at a pulsation of 20 beats/min. A discussion of the potential application of this technique for in vivo study in large vessels is given. Show more

Keywords: Erythrocyte aggregation, biorheology in large vessels, rouleaux orientation, ultrasonics, Doppler ultrasound, power spectrum

DOI: 10.3233/BIR-1993-305-615

Citation: Biorheology, vol. 30, no. 5-6, pp. 443-461, 1993

Authors: Donath, E. | Pomorski, T. | Pastushenko, V.F.

Article Type: Research Article

Abstract: Human erythrocytes were transformed to advanced stages of echinocytes by means of an increase of the pH, by addition of 2,4-dinitrophenol or by an increase in temperature. Scanning electron microscopy pictures were taken and the lateral distribution of the spicula was analyzed. Regardless of the method of the production of the echinocytes, no correlation of the spatial distribution of the spicula was detected. Except for the exclusion due to the finite size of the spicula basis, the distribution was random. The conclusion was drawn that the generation of spicula is a local process. No long-range ordering interaction between the spicula …could be detected. Show more

Keywords: Human erythrocytes, echinocytes, spicula distribution, shape transformation

DOI: 10.3233/BIR-1993-305-616

Citation: Biorheology, vol. 30, no. 5-6, pp. 463-470, 1993

Authors: Zahalak, G.I.

Article Type: Short Communication

DOI: 10.3233/BIR-1993-305-617

Citation: Biorheology, vol. 30, no. 5-6, pp. 471-472, 1993

Article Type: Correction

DOI: 10.3233/BIR-1993-305-618

Citation: Biorheology, vol. 30, no. 5-6, pp. 473-473, 1993

Article Type: Other

DOI: 10.3233/BIR-1993-305-619

Citation: Biorheology, vol. 30, no. 5-6, pp. 475-475, 1993