Biorheology - Volume 42, issue 4

Authors: Vaidya, Vinayak S. | Back, Lloyd H. | Banerjee, Rupak K.

Article Type: Research Article

Abstract: The coupled oxygen transport in the avascular wall of a coronary artery stenosis is studied by numerically solving the convection–diffusion equations. Geometry, replicating residual stenosis after percutaneous transluminal coronary angioplasty (PTCA), is used for the analysis. Important physiological aspects, such as oxygen consumption in the wall, oxygen carried by the hemoglobin, non-Newtonian viscosity of the blood, and supply of oxygen from the vasa vasorum are included. Mean blood flow rate in the lumen is varied from basal to hyperemic conditions. The results show that the PO2 in the medial region of the arterial wall is ∼10 mmHg. The …oxygen flux to the wall increases in the flow acceleration region, whereas it decreases at the flow reattachment zone. Near the location of flow separation there is a small rise and a sharp fall in the oxygen flux. The minimum PO2 in the avascular wall, PO2 , min  , at the point of flow reattachment reduces to ∼6 mmHg for a 300 micron wall thickness. For a thinner wall of 200 micron, the PO2 , min  at the location of flow reattachment increases to 6 times that of a 300 micron wall. The PO2 , min  in the wall decreases by 60% when volumetric oxygen consumption is increased by 30% for the same avascular wall thickness. Show more

Keywords: Precutaneous transluminal coronary angioplasty (PTCA), oxygen transport, hypoxia, stenosis, coronary artery, angioplasty, computational fluid mechanics (CFD), numerical methods, oxygen consumption, arterial wall, hemodynamics, convective transport, diffusive transport

Citation: Biorheology, vol. 42, no. 4, pp. 249-269, 2005

Authors: Peng, Yuhua | Wu, Shigui | Geng, Shizhao | Liepsch, Dieter | Liao, Donghua | Qiao, Aike | Zeng, Yanjun

Article Type: Research Article

Abstract: An ejection dynamics mathematical model of human left ventricle (LV) based on physiological data of human heart is proposed in this study. The mathematical equations were expressed in terms of vorticity-stream function equations in a prolate spheroidal coordinate system. These equations combined with specified boundary conditions were numerically solved by using an alternating-direction-implicit (ADI) algorithm with second order accuracy. The unsteady aspects of the ejection process were subsequently introduced into the numerical simulation. The numerical results have shown that the present ellipsoidal model could be available to simulate the ejection process of the human LV. Such a model combined with …cardiac muscle mechanics could be studied further to determine altered left ventricular function in cardiac diseases. Show more

Keywords: Left ventricle, ejection dynamics, alternating direction implicit algorithm, unsteady flow

Citation: Biorheology, vol. 42, no. 4, pp. 271-281, 2005

Authors: Kerrigan, Mark J.P. | Hall, Andrew C.

Article Type: Research Article

Abstract: Articular chondrocytes are exposed to significant changes in extracellular osmolarity during normal joint activity, which can lead to changes in cell volume and metabolism of the extracellular matrix (ECM). Chondrocytes can respond to cell swelling/shrinking by volume regulatory pathways, but the signalling pathways are poorly understood although a role for the cytoskeleton is frequently implicated. Here, we have investigated the effects of disruption of the chondrocyte F-actin cytoskeleton on the recovery of cell volume by RVD. The cytoskeleton was perturbed using the relatively specific agent latrunculin B (5 μM; 30 min) and loss of F-actin integrity quantified using fluorescent phalloidin-labelling …and confocal laser scanning microscopy (CLSM). Imaging of isolated chondrocytes labelled with Fura-2 to measure the fluorescence associated with cell volume changes, showed that the extent of hypo-osmotic swelling was unaffected by latrunculin B treatment. Two categories of the chondrocyte RVD response were observed: ‘fast’ RVD where at 3 min post-osmotic challenge there was a recovery in cell fluorescence of ≥80%, whereas other cells exhibited ‘slow’ RVD. Latrunculin B increased the proportion of chondrocytes demonstrating ‘fast’ RVD by ∼10 fold and reduced those cells showing ‘slow’ RVD. An inhibitor of chondrocyte RVD (REV 5901) had no significant effect on the integrity of the cytoskeleton showing that the RVD response could be inhibited independent of the state of the F-actin cytoskeleton. These results suggest that the intact cortical F-actin cytoskeleton has a restraining effect on the RVD response of isolated bovine articular chondrocytes. Show more

Keywords: Articular chondrocyte, volume regulation, cytoskeleton, fluorescence, mechanotransduction

Citation: Biorheology, vol. 42, no. 4, pp. 283-293, 2005

Authors: Fam, H. | Kontopoulou, M. | Bryant, J.T.

Article Type: Research Article

Abstract: The purpose of this work is to design a rheological analogue to periprosthetic fluid, for potential use in wear testing of orthopaedic implants. Polymer solutions of sodium carboxymethyl cellulose (CMC), xanthan and mixtures thereof were prepared, and the experimentally determined viscosity–shear rate dependence was analyzed using the three-parameter modified Cross model. A mixture containing 0.185 wt% CMC and 0.075 wt% xanthan was identified as being the closest rheological match for periprosthetic fluid in both steady shear and oscillatory modes of deformation.

Keywords: Prosthesis, orthopaedic implants, wear testing, viscosity, carboxymethyl cellulose, xanthan, rheology

Citation: Biorheology, vol. 42, no. 4, pp. 295-306, 2005

Authors: Lekka, Malgorzata | Fornal, Maria | Pyka-Fościak, Grażyna | Lebed, Kateryna | Wizner, Barbara | Grodzicki, Tomasz | Styczeń, Jan

Article Type: Research Article

Abstract: The stiffness of erythrocytes in patients (N=45) suffering from certain disorders, such as coronary disease, hypertension, and diabetes mellitus has been assessed using the Atomic Force Microscopy (AFM) and compared with that in a group of healthy individuals (N=13). For each blood sample, around 20 erythrocytes were selected at random and the stiffness of each one was probed in 20–30 arbitrarily chosen points. From these results, distributions of the cell Young's modulus (YM) were determined. Average values and widths of YM distributions significantly increased in samples taken from diabetes mellitus patients and cigarette smokers, as compared to those taken from …healthy donors. At the same time, the average values of YM were found to increase as a function of the patient's age. We demonstrated that the atomic force microscope is a very sensitive tool for determination of cell stiffness with every prospect of a routine application as a diagnostic tool in quantitative analysis of the physiological and pathological states of red blood cells. Show more

Keywords: Atomic force microscopy, red blood cell, cell stiffness, diabetes mellitus

Citation: Biorheology, vol. 42, no. 4, pp. 307-317, 2005

Authors: Baskurt, Oguz K. | Hardeman, Max R. | Meiselman, Herbert J. | Shin, Sehyun

Article Type: Other

Citation: Biorheology, vol. 42, no. 4, pp. 319-319, 2005