Biorheology - Volume 32, issue 1

Authors: Prete, P.E. | Gurakar-Osborne, A. | Kashyap, M.L.

Article Type: Review Article

Abstract: Normal human synovial fluid contains extremely low concentrations of lipoproteins and apolipoproteins, in sharp contrast to those found in plasma. Increased amounts of cholesterol and other lipids have been found in the synovial fluid of a chronic inflammatory joint disorder, rheumatoid arthritis (RA). More recently, apolipoproteins AI, Band E have also been found in increased amounts in RA synovial fluid. Theories have been proposed to account for this increase in the amount of apolipoproteins and for the source of lipids and lipoproteins in normal synovial fluid; however, the mechanisms have not yet been established. Lipoproteins may play dual roles in …synovial fluid: A functional one in normal synovial fluid and, as some suggest, a pathologic one in the abnormal synovial fluid of certain arthritic diseases. The recent data prompt the need to define synovial fluid lipids, lipoprotein particle sub fractions and their constituent apolipoproteins, as well as their respective roles in synovial fluid. Show more

Keywords: Synovial fluid, lipoproteins, lipids, cholesterol, joint effusions, apolipoproteins

DOI: 10.3233/BIR-1995-32101

Citation: Biorheology, vol. 32, no. 1, pp. 1-16, 1995

Authors: Bert, J.L. | Reed, R.K.

Article Type: Research Article

Abstract: The flow rate of phosphate buffered saline through dermis was measured as a function of applied pressure. Hyaluronan and collagen, the two principal materials which confirm resistance to flow in dermis, were not lost from the tissue during the experiments which lasted up to two days. From Darcy’S Law, the average flow conductivities were 2 to 6 × 10 − 12 cm 4 / dyn × s and decreased with increasing applied pressure. We conclude that the tissue is compacted in proportion to the applied pressure during the flow experiments. The …hydraulic flow conductivity is described mathematically as a function of compaction induced by the applied pressure. Show more

Keywords: Flow conductivity, hydration, compaction, dermis, hyaluronan, interstitium

DOI: 10.3233/BIR-1995-32102

Citation: Biorheology, vol. 32, no. 1, pp. 17-27, 1995

Authors: Sutton, D.W. | Schmid-Schönbein, G.W.

Article Type: Research Article

Abstract: In spite of numerous investigations of erythrocyte rheology, there is limited information about the influence of erythrocyte suspensions on whole organ pressure-flow relationships. In this study, we present whole organ pressure-flow curves for resting vasodilated gracilis muscle of the rat, in which the microanatomy and vessel properties have been determined previously. For pure erythrocyte suspensions from donor rats, the organ resistance increases only mildly with perfusion time (less than a 5% shift over a one-hour perfusion time), while in contrast, erythrocyte suspensions containing leukocytes show an increases of resistance near 100% over a period of 25 min. Variation in pressure-flow …curves in the muscle at the same arterial hematocrit between different rats is less than 15%. The pressure-flow relation for pure erythrocyte suspensions depends on hematocrit. Shear thinning is exhibited at high hematocrits, while Newtonian behavior is approached at arterial hematocrits below 15%. The whole organ apparent viscosity for pure erythrocyte suspensions (normalized by cell-free plasma resistance) is a non-linear function of hematocrit; at physiological pressures, it reaches values comparable to those of apparent viscosities measured in rotational viscometers or in in vitro tube flow (diameters greater than 0.8 mm). The apparent viscosities estimated from the whole organ experiments tend to be higher than those measured in straight tubes under in vitro conditions. The pressure-flow curves for pure erythrocyte suspensions are shifted towards lower pressures than the curves for mixed suspensions of erythrocytes at the same hematocrit and with leukocytes at physiological cell counts. These acute experiments show that pure erythrocyte suspensions yield highly reproducible resistances in the skeletal muscle microcirculation with dilated arterioles. Relative apparent viscosities measured in vivo are higher than those measured in straight glass tubes of comparable dimesions. Show more

Keywords: Microcirculation, pressure, flow, resistance, hematocrit, erythrocytes

DOI: 10.3233/BIR-1995-32103

Citation: Biorheology, vol. 32, no. 1, pp. 29-42, 1995

Authors: Naiki, T. | Hayashi, K. | Takemura, S.

Article Type: Research Article

Abstract: The structure of pulsatile flow in a rigid aortic bifurcation model was studied by means of a flow visualization technique and three-dimensional laser-Doppler anemometry. The model was made of glass, having the same shape as that of the average human aortic bifurcation. It was installed into a mock circulatory loop that generated physiological pulsatile flow. Flow separation was observed during accelerated and decelerated flow periods. Double helical flow existed inside the flow separation in the early accelerated flow period. In the decelerated flow period, disturbed flow appeared behind the separation zone. Flow was strongly disturbed during the back flow period, …and then was gradually stabilized in the forward flow period. The flow separation and the disturbances released from the flow separation zone greatly influenced near-wall velocities along the lateral wall. The wave form of the near-wall velocity in the flow separation zone was much different from that observed in the aortic portion and behind the separation zone; for example, the magnitude of the negative peak velocity in the direction of the tube axis was larger than that of the positive one, and mean velocity in a cycle was very low. This abnormal phasic change of the near-wall velocity may be associated with atherogenesis. The three-dimensional velocity measurement is very useful for the detailed analysis of near-wall velocity patterns. Show more

Keywords: Pulsatile flow, aortic bifurcation, laser-Doppler anemometer, velocity pattern

DOI: 10.3233/BIR-1995-32104

Citation: Biorheology, vol. 32, no. 1, pp. 43-59, 1995

Authors: Taylor, T.W. | Yamaguchi, T.

Article Type: Research Article

Abstract: A realistic model of the left ventricle of the heart was previously constructed, using a cast from a dog heart which was in diastole. Previous studies of the three-dimensional heart model were conducted in systole only. The purpose of this investigation was to extend the model to both systole and diastole, and to determine what the effect of a previous cardiac cycle was on the next cardiac cycle. The 25.8 cc ventricular volume was reduced by 40% in 0.25 seconds, then increased to the original volume in another 0.25 seconds and then allowed to rest for 0.25 seconds. Runs done …with an ejection fraction of 60% showed little variation from one cardiac cycle to another after the third cardiac cycle was completed; the maximum velocity could vary by over 30% between the first and second cardiac cycles. In systole, centerline and cross-sectional velocity vectors greatly increased in magnitude at the aortic outlet. Most of the pressure drop occurred in the top 15% of the heart. The diastolic phase showed complex vortex formation not seen in the systolic contractions; these complex vortices could account for experimentally observed turbulent blood flow fluctuations in the aorta. Show more

Keywords: Computational fluid dynamics, heart, blood flow, left ventricle, systole, diastole

DOI: 10.3233/BIR-1995-32105

Citation: Biorheology, vol. 32, no. 1, pp. 61-71, 1995

Authors: Konstantopoulos, K. | Wu, K.K. | Udden, M.M. | Bañez, E.I. | Shattil, S.J. | Hellums, J.D.

Article Type: Research Article

Abstract: The objective of this work was to evaluate quantitatively the effects of flow on platelet reactions using a flow cytometric technique. Whole blood was exposed to well defined, laminar shear stress in a cone-and-plate viscometer in the absence of added agonists. Blood specimens were fixed with formaldehyde and incubated with two monoclonal antibodies. Antibody 6D1, specific for platelet membrane glycoprotein Ib (GPIb), was used to identify and enumerate platelets and platelet aggregates on the basis of their characteristic forward scatter and 6D1-FITC fluorescence profilles. Anti-CD62 antibody, specific for the granule membrane protein-140 (GMP-140), was used to measure platelet activation. Results …showed platelet aggregation increasing with increasing shear stress with marked increase in this response for a pathophysiological stress level of 140 dyn/cm2 and higher. This stress level also was the apparent threshold for formation of large platelet aggregates (“large” refers to particles larger than 10 µm in equivalent sphere diameter). These platelet responses to shear stress were insensitive to aspirin, but strongly inhibited by agents that elevate platelet cyclic adenosine monophosphate (cAMP) levels. Moreover, pre-incubation of whole blood with monoclonal antibodies that inhibit von Wille brand factor binding to GPIb or von Willebrand factor and fibrinogen binding to GPIIb/IIIa inhibited platelet aggregation. Aggregation induced by shear at 37°C was less in extent than at 23°C. At physiological shear stresses, whole blood was more susceptible to shear-induced platelet aggregation than platelet-rich plasma. This study reaffirms that flow cytometric methods have several important advantages in studies of shear effects on platelets, and extends the methodology to whole blood unaltered by cell separation methods. Show more

Keywords: Flow cytometry, shear stress, platelet

DOI: 10.3233/BIR-1995-32106

Citation: Biorheology, vol. 32, no. 1, pp. 73-93, 1995

Article Type: Correction

DOI: 10.3233/BIR-1995-32107

Citation: Biorheology, vol. 32, no. 1, pp. 95-95, 1995

Article Type: Announcement

DOI: 10.3233/BIR-1995-32108

Citation: Biorheology, vol. 32, no. 1, pp. 97-98, 1995

Article Type: Other

DOI: 10.3233/BIR-1995-32109

Citation: Biorheology, vol. 32, no. 1, pp. 99-100, 1995