Publications
185 results found
Warboys CM, Overby DR, Weinberg PD, 2010, Dendritic cells lower permeability of endothelial cell monolayers, Publisher: ELSEVIER IRELAND LTD, Pages: E17-E17, ISSN: 0021-9150
Vincent PE, Sherwin SJ, Weinberg PD, 2010, The Effect of the Endothelial Glycocalyx Layer on Concentration Polarisation of Low Density Lipoprotein in Arteries, Journal of Theoretical Biology, Vol: 265, Pages: 1-17, ISSN: 0022-5193
It has been postulated that a flow-dependent (and hence spatially varying) low density lipoprotein (LDL) concentration polarisation layer forms on the luminal surface of the vascular endothelium. Such a layer has the potential to cause heterogeneity in the distribution of atherosclerotic lesions by spatially modulating the rate of LDL transport into the arterial wall. Theoretical analysis suggests that a transmural water flux which is spatially heterogeneous at the cellular scale can act to enhance LDL concentration polarisation in a shear dependent fashion. However, such an effect is only observed if a relevant Peclet number (i.e. the ratio of LDL convection to LDL diffusion) is of order unity or greater. Based on the diffusivity of LDL in blood plasma, such a Peclet number is found to be far less than unity, implying that the aforementioned enhancement and shear dependence will not occur. However, this conclusion ignores the existence of the endothelial glycocalyx layer (EGL), which may inhibit the diffusion of LDL near the luminal surface of the endothelium, and hence raise any Peclet number associated with the transport of LDL. The present study numerically investigates the effect of the EGL, as well as a heterogeneous transmural water flux, on arterial LDL concentration polarisation. Particular attention is paid to measures of LDL concentration polarisation thought relevant to the rate of transendothelial LDL transport. It is demonstrated that an EGL is unlikely to cause any additional shear dependence of such measures directly, irrespective of whether or not LDL can penetrate into the EGL. However, it is found that such measures depend significantly on the nature of the interaction between LDL and the EGL (parameterised by the height of the EGL, the depth to which LDL penetrates into the EGL, and the diffusivity of LDL in the EGL). Various processes may regulate the interaction of LDL with the EGL, possibly in a flow dependent and hence spatially non-uniform f
Warboys CM, Berson RE, Mann GE, et al., 2010, Acute and chronic exposure to shear stress have opposite effects on endothelial permeability to macromolecules, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 298, Pages: H1850-H1856, ISSN: 0363-6135
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- Citations: 64
Bond AR, Ni C-W, Jo H, et al., 2010, Intimal cushions and endothelial nuclear elongation around mouse aortic branches and their spatial correspondence with patterns of lipid deposition, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 298, Pages: H536-H544, ISSN: 0363-6135
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- Citations: 10
Kazakidi A, Wylezinska M, Bohraus Y, et al., 2010, NUMERICAL MODELLING OF BLOOD FLOW IN THE MOUSE AORTIC ARCH USING INFLOW VELOCITIES OBTAINED BY PHASE-CONTRAST MRI, 12th ASME Summer Bioengineering Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 555-556
Palombo F, Danoux CB, Weinberg PD, et al., 2009, Measurement of drug and macromolecule diffusion across atherosclerotic rabbit aorta <i>ex vivo</i> by attenuated total reflection-Fourier transform infrared imaging, JOURNAL OF BIOMEDICAL OPTICS, Vol: 14, ISSN: 1083-3668
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- Citations: 15
Poelma C, Mari JM, Foin N, et al., 2009, 3D flow reconstruction using ultrasound PIV, Experiments in Fluids, Vol: 50, Pages: 777-785, ISSN: 1432-1114
Ultrasound particle image velocimetry (PIV)can be used to obtain velocity fields in non-transparent geometries and/or fluids. In the current study, we use this technique to document the flow in a curved tube, usingultrasound contrast bubbles as flow tracer particles. The performance of the technique is first tested in a straight tube, with both steady laminar and pulsatile flows. Bothexperiments confirm that the technique is capable of reliable measurements. A number of adaptations are introduced that improve the accuracy and applicability of ultrasound PIV. Firstly, due to the method of ultrasoundimage acquisition, a correction is required for the estimation of velocities from tracer displacements. This correction accounts for the fact that columns in the image are recorded at slightly different instances. The second improvement uses a slice-by-slice scanning approach to obtain three-dimensional velocity data. This approach is here demonstrated in a strongly curved tube. The resultingflow profiles and wall shear stress distribution shows a distinct asymmetry. To meaningfully interpret these threedimensionalresults, knowledge of the measurement thickness is required. Our third contribution is a method to determine this quantity, using the correlation peak heights. The latter method can also provide the third (out-of-plane) component if the measurement thickness is known, so that all three velocity components are available using a single probe.
Alastruey J, Nagel SR, Nier BA, et al., 2009, Modelling pulse wave propagation in the rabbit systemic circulation to assess the effects of altered nitric oxide synthesis, JOURNAL OF BIOMECHANICS, Vol: 42, Pages: 2116-2123, ISSN: 0021-9290
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- Citations: 22
Palombo F, Cremers SG, Weinberg PD, et al., 2009, Application of Fourier transform infrared spectroscopic imaging to the study of effects of age and dietary L-arginine on aortic lesion composition in cholesterol-fed rabbits, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 6, Pages: 669-680, ISSN: 1742-5689
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- Citations: 36
Vincent PE, Sherwin SJ, Weinberg PD, 2009, The Effect of a Spatially Heterogeneous Transmural Water Flux on Concentration Polarization of Low Density Lipoprotein in Arteries, Biophysical Journal, Vol: 96, Pages: 3102-3115, ISSN: 0006-3495
Uptake of low density lipoprotein (LDL) by the arterial wall is likely to play a key role in atherogenesis. A particular process that may cause vascular scale heterogeneity in the rate of transendothelial LDL transport is the formation of a flow-dependent LDL concentration polarization layer on the luminal surface of the arterial endothelium. In this study, the effect of a spatially heterogeneous transmural water flux (that traverses the endothelium only via interendothelial cell clefts) on such concentration polarization is investigated numerically. Unlike in previous investigations, realistic intercellular cleft dimensions are used here and several values of LDL diffusivity are considered. Particular attention is paid to the spatially averaged LDL concentration adjacent to different regions of the endothelial surface, as such measures may be relevant to the rate of transendothelial LDL transport. It is demonstrated in principle that a heterogeneous transmural water flux can act to enhance such measures, and cause them to develop a shear dependence (in addition to that caused by vascular scale flow features, affecting the overall degree of LDL concentration polarization). However, it is shown that this enhancement and additional shear dependence are likely to be negligible for a physiologically realistic transmural flux velocity of 0.0439 mu m s(-1) and an LDL diffusivity (in blood plasma) of 28.67 mu m(2) s(-1). Hence, the results imply that vascular scale studies of LDL concentration polarization are justified in ignoring the effect of a spatially heterogeneous transmural water flux.
Vincent PE, Hunt AAE, Grinberg L, et al., 2009, A Realistic Representation of the Rabbit Aorta for use in Computational Haemodynamic Studies, ASME Summer Bioengineering Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 985-986
Vincent P, 2009, A Cellular Scale Study of Low Denisty Lipoprotein Concentration Polarisation in Arteries
Uptake of Low Density Lipoprotein (LDL) by the arterial wall is likely to play a key role in the process of atherogenesis, which occurs non-uniformly within the ar- terial vasculature. A particular process that may cause vascular scale heterogeneity in the rate of transendothelial LDL transport is the formation of a flow-dependent LDL concentration polarisation layer adjacent to the luminal surface of the arte- rial endothelium. In this thesis the effects of cellular scale endothelial features on such LDL concentration polarisation are investigated using an idealised theoretical model. Specifically, the effect of a spatially heterogeneous transmural water flux is considered (flowing only through intercellular clefts), as well as the effect of the endothelial glycocalyx layer (EGL). The idealised model is implemented using both analytical techniques and the spectral/hp element method. A range of scenarios are considered, including those were no EGL is present, those where an EGL is present but LDL cannot penetrate into it, and finally those where an EGL is present and LDL can penetrate into it.For cases where no EGL is present, particular attention is paid to the spatially averaged LDL concentration adjacent to various regions of the endothelial surface, as such measures may be relevant to the rate of transendothelial LDL transport. It is demonstrated, in principle, that a heterogeneous transmural water flux alone can act to enhance such measures, and cause them to develop a shear dependence (in addition to that caused by vascular scale flow features affecting the overall degree of LDL concentration polarisation). However, it is shown that this enhancement and additional shear dependence are likely to be negligible for a physiologically realistictransmural flux velocity of 0.0439μms−1 and an LDL diffusivity in blood plasma of 28.67μm2 s−1 .For cases where an EGL is present, measures of LDL concentration polarisation relevant to the rate of transendo
Segers D, Weinberg P, Krams R, 2008, Atherosclerosis: cell biology and lipoproteins - shear stress and inflammation in plaque formation: new evidence, CURRENT OPINION IN LIPIDOLOGY, Vol: 19, Pages: 627-628, ISSN: 0957-9672
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- Citations: 2
Rimbach G, Boesch-Saadatmandi C, Frank J, et al., 2008, Dietary isoflavones in the prevention of cardiovascular disease - A molecular perspective, International Conference on Molecular and Physiological Effects of Bioactive Food Compounds, Publisher: PERGAMON-ELSEVIER SCIENCE LTD, Pages: 1308-1319, ISSN: 0278-6915
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- Citations: 139
Nier BA, Harrington LS, Carrier MJ, et al., 2008, Evidence for a specific influence of the nitrergic pathway on the peripheral pulse waveform in rabbits, EXPERIMENTAL PHYSIOLOGY, Vol: 93, Pages: 503-512, ISSN: 0958-0670
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- Citations: 12
Vincent PE, Sherwin SJ, Weinberg PD, 2008, Viscous Flow Over Outflow Slits Covered by an Anistropic Brinkman Medium: A Model of Flow Above Inter-Endothelial Cell Clefts, Physics of Fluids, Vol: 20
Kazakidi A, Sherwin SJ, Weinberg PD, 2008, Effect of Reynolds number and flow division on patterns of haemodynamic wall shear stress near branch points in the descending thoracic aorta, Interface, Vol: Submitted
Atherosclerotic lesions are non-uniformly distributed at arterial bends and branch sites, suggesting an important role for haemodynamic factors, particularly wall shear stress (WSS), in their development. The pattern of lesions at aortic branch sites depends on age and species. Using computational flow simulations in an idealised model of an intercostal artery emerging perpendicularly from the thoracic aorta, we studied the effects of Reynolds number and flow division under steady conditions. Patterns of flow and WSS were strikingly dependent on these haemodynamic parameters. With increasing Reynolds number, WSS, normalised by the fully developed aortic value, was lowered at the sides of the ostium and increased upstream and downstream of it. Increasing flow into the side branch exacerbated these patterns and gave rise to a stagnation region downstream of the ostium. Incorporation of more realistic geometric features had only minor effects. Aspects of the observed WSS patterns correlate with, and may explain, some but not all of the lesion patterns in human, rabbit and mouse aortas.
Staughton TJ, Weinberg PD, 2007, Arterial wall permeability at the left coronary bifurcation, ATHEROSCLEROSIS, Vol: 195, Pages: 207-209, ISSN: 0021-9150
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- Citations: 1
Kazakidi A, Sherwin SJ, Weinberg PD, 2007, Reverse flow in arterial branches influences wall shear stress patterns around branch ostia, Joint Autumn Meeting of the British-Society-for-Cardiovascular-Research/British-Atherosclerosis-Society, Publisher: B M J PUBLISHING GROUP, ISSN: 1355-6037
Vincent PE, Sherwin SJ, Weinberg PD, 2007, Computational investigation of a mechanism by which blood flow could control lipoprotein uptake by the arterial, Joint Autumn Meeting of the British-Society-for-Cardiovascular-Research/British-Atherosclerosis-Society, Publisher: B M J PUBLISHING GROUP, ISSN: 1355-6037
Bond AR, Weinberg PD, 2007, Variation in blood flow patterns around arterial branches with age, Joint Autumn Meeting of the British-Society-for-Cardiovascular-Research/British-Atherosclerosis-Society, Publisher: B M J PUBLISHING GROUP, ISSN: 1355-6037
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- Citations: 1
Weinberg PD, Ethier CR, 2007, Twenty-fold difference in hemodynamic wall shear stress between murine and human aortas, JOURNAL OF BIOMECHANICS, Vol: 40, Pages: 1594-1598, ISSN: 0021-9290
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- Citations: 59
Cremers SG, Weinberg PD, 2006, Use of a desktop scanner and spreadsheet software for mapping arterial disease, SCANNING, Vol: 27, Pages: 126-131, ISSN: 0161-0457
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- Citations: 4
Nier B, Weinberg PD, Rimbach G, et al., 2006, Differential gene expression in skeletal muscle of rats with vitamin E deficiency, IUBMB LIFE, Vol: 58, Pages: 540-548, ISSN: 1521-6543
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- Citations: 33
Hernandez-Montes E, Pollard SE, Vauzour D, et al., 2006, Activation of glutathione peroxidase via Nrf1 mediates genistein's protection against oxidative endothelial cell injury, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, Vol: 346, Pages: 851-859, ISSN: 0006-291X
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- Citations: 72
Ewins BA, Vassiliadou M, Minihane AM, et al., 2006, Techniques for quantifying effects of dietary antioxidants on transcription factor translocation and nitric oxide production in cultured cells, GENES AND NUTRITION, Vol: 1, Pages: 125-131, ISSN: 1865-3499
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- Citations: 9
Kazakidi A, Sherwin S J, Weinberg P D, 2006, Alteration of Reynolds number and flow partition modify wall shear stresses at arterial branches in a way that can explain age- and species-dependent patterns of arterial disease
Cremers S G, Weinberg P D, 2006, Changes with age in the pattern of high-permeability foci in the rabbit aortic endothelium near branch points
Bond AR, Weinberg PD, 2006, Haemodynamic stresses and wall structure can account for the pattern of lipid deposition around aortic branches in mice, London, XIV International Symposium on Atherosclerosis, Rome, Italy, 2006, Publisher: Elsevier, Pages: 200-200, ISSN: 1567-5688
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