Biorheology - Volume 16, issue 1-2

Authors: King, Malcolm

Article Type: Research Article

Abstract: The relationship between the mechanical properties of tracheal mucus and its rate of transport on the mucus-depleted frog palate was investigated. Mucus samples were obtained from dogs subject to a variety of physiological interventions - barbiturate anesthesia, tranquilization, cholinergic stimulation, and dehydration. For each sample, the elastic modulus, G′, and the dynamic viscosity, η ′, were determined over the frequency range of 1 to 100 rad/sec by means of the magnetic rheometer technique, and the relative frog palate transport rate, Tr, was determined by previously described methods. For 102 control or near-control tracheal mucus samples, correlations were found relating the …relative transport rate to either the elastic modulus or the viscosity, and, in addition, to the loss tangent, tan δ . At constant tan δ , Tr vs. log G′ or log η ′ (determined at 1 rad/sec) gave partial correlation coefficients of −0.59; at constant G′, the partial correlation coefficient for Tr vs. tan δ was −0.45. Cholinergic stimulation and barbiturate anesthesia both induced rapid, gross changes in the tracheal mucus. With these acute interventions, the dependence of mucociliary transport on mucus mechanical properties was qualitatively similar to that seen in the chronic studies. The statistical variability was smaller, however, because the variation due to frog palate mucus was eliminated. Show more

DOI: 10.3233/BIR-1979-161-210

Citation: Biorheology, vol. 16, no. 1-2, pp. 57-68, 1979

Authors: Dintenfass, L.

Article Type: Research Article

Abstract: Our studies in theoretical, experimental and clinical haemorheology moved through a number of stages, but each of these stages contributed to a better insight into the microrheology of blood. While the first two stages dealt with instrumentation and comprehension of blood viscosity factors (i.e., concepts of the internal viscosity of the red cell, of the “inversion phenomenon” in the microcapillary flow, of spectra of coagulation times, viscosity and morphology of artificial thrombi), in the third stage these viscosity factors were correlated with protein levels or ratios, cholesterol, parathyroid hormone, SGOT, etc., and ABO blood groups. In the fourth stage a …correlation was sought between viscosity and clinical syndromes, physical fitness, ECG abnormality, etc. In recent studies the submaximal exercise work was found to be significantly related to the blood viscosity factors. Experimental work presented herewith shows a significant correlation between diastolic and/or systolic blood pressure and blood viscosity or blood viscosity factors. Of particular importance appears to be rigidity of red cells, and its role in blood pressure and viscosity homeostasis is considered. There is evidence for autoregulation of blood viscosity which might be involving a hypothetical “viscoreceptor” mechanism. Elevation of any of the blood viscosity factors is a ‘risk factor’ and a warning sign, the latter most important in the silent disorders. Show more

DOI: 10.3233/BIR-1979-161-211

Citation: Biorheology, vol. 16, no. 1-2, pp. 69-84, 1979

Authors: Cox, Robert H.

Article Type: Research Article

Abstract: Changes in passive arterial wall mechanical properties have been correlated with connective tissue composition during growth and development. These results indicate that passive arterial wall mechanics are determined in part by a) the total connective tissue content (collagen and elastin); b) the ratio of collagen to elastin; and c) the “concentration” of connective tissue in extracellular space. Studies of the mechanics and composition of arteries from different anatomical sites indicate that the low and high strain mechanics of these vessels correlates well with their elastin and collagen content, respectively. Differences in mechanics at moderate values of strain can be explained …on the basis of differences in the details of the recruitment of collagen fibers to support wall load with increasing strain in different arteries. Differences in the mechanics of carotid arteries from different species at high and low strain suggest that values of elastin and collagen elastic moduli may vary with amino acid composition, for example. Studies of stiffness during arterial smooth muscle activation (series elasticity, SE) in arteries from different anatomical locations revealed no correlation between values of SE and connective tissue composition. However, the results of these studies indicate that arteries with the stiffest SE had the most effective contractile apparatus producing relatively larger constriction responses for a given active stress response compared to other muscles. Smaller arteries from the same vascular bed exhibit similar characteristics with no differences in SE. The more effective contractile apparatus in this case is probably the result of a relatively larger wall thickness in the case of smaller arteries. Treatment of arteries with collagenase produces reductions in active stress development which parallel collagen removal. This suggests a role of collagen in the intercellular coupling of cellular force development. Thus, passive wall elements play a variety of roles in the arterial wall by contributing to both active and passive properties. Show more

DOI: 10.3233/BIR-1979-161-212

Citation: Biorheology, vol. 16, no. 1-2, pp. 85-94, 1979

Authors: Houbouyan, L. | Gaillard, S. | Goguel, A. | Stoltz, J.F.

Article Type: Research Article

DOI: 10.3233/BIR-1979-161-213

Citation: Biorheology, vol. 16, no. 1-2, pp. 95-100, 1979

Authors: Sabbah, Hani N. | Stein, Paul D.

Article Type: Research Article

Abstract: The purpose of this study is to determine if the normal semilunar valve leaflets contribute to turbulence in the region of the semilunar valves. Measurements of turbulence distal to a porcine aortic valve were made using an in vitro model of the cardiovascular system in which fluctuating velocities indicative of turbulence were measured with a hot film probe. The distribution of turbulence across the simulated aortic root was shown to relate to the location of the free margin of the aortic valve during systole. This indicates that turbulence resulted from the formation of eddies at the free margins of the …semilunar cusps which acted as projections in the stream of flow. Therefore, it is insufficient to rely upon the peak Reynolds number when attempting to determine when turbulence would occur in the region of the aortic or pulmonary valves. These observations are pertinent to understanding the genesis of cardiac murmurs that originate in the region of semilunar valves. Show more

DOI: 10.3233/BIR-1979-161-214

Citation: Biorheology, vol. 16, no. 1-2, pp. 101-108, 1979

Authors: Chaturani, P. | Upadhya, V.S.

Article Type: Research Article

Abstract: The present problem deals with a two-fluid model for blood flow through small diameter tubes. The two-fluid model consists of a core (suspension of red cells) and a peripheral red cell free plasma layer. The core has been considered as a couple stress fluid and the plasma layer as a Newtonian fluid. Using appropriate boundary conditions, analytic expressions for velocity profile, flow rate, percentage marginal flow rate and effective viscosity have been obtained. It is found that the velocity profiles obtained from this model are in better agreement with the experimental results of Bugliarello and Sevilla than the velocity profiles …given by other models. A critical study of other models and their comparison with the present model have been presented. It is observed that, for some reason, in these models, only one aspect of the flow, i.e., either velocity profiles or viscosity, has been studied, whereas for blood flow, both are equally important. It is shown that many of the existing two-fluid models are included in the present model as its special cases. It is of interest to note that the effective viscosity computed from the present model increases with tube radius; thus this model exhibits ‘Fahraeus-Lindquist Effect’ (FLE). Perhaps, the most important feature of this model is: it gives an analytic formula to determine the core viscosity experimentally, which so far, at least to authors’ knowledge, has not been determined. Finally, some biological implications of this theoretical investigation have been indicated. Show more

DOI: 10.3233/BIR-1979-161-215

Citation: Biorheology, vol. 16, no. 1-2, pp. 109-118, 1979

Authors: Singh, Megha | Coulter Jr., N.A.

Article Type: Short Communication

DOI: 10.3233/BIR-1979-161-216

Citation: Biorheology, vol. 16, no. 1-2, pp. 119-120, 1979

Authors: Chaturani, P. | Upadhya, V.S.

Article Type: Short Communication

DOI: 10.3233/BIR-1979-161-217

Citation: Biorheology, vol. 16, no. 1-2, pp. 121-122, 1979

Article Type: Abstract

DOI: 10.3233/BIR-1979-161-218

Citation: Biorheology, vol. 16, no. 1-2, pp. 123-132, 1979

Article Type: Announcement

DOI: 10.3233/BIR-1979-161-219

Citation: Biorheology, vol. 16, no. 1-2, pp. 133-133, 1979