Mechanotransduction and flow across the endothelial glycocalyx.
Item
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Title
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Mechanotransduction and flow across the endothelial glycocalyx.
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Identifier
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AAI3187444
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identifier
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3187444
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Creator
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Zhang, Xiaobing.
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Contributor
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Adviser: Sheldon Weinbaum
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Biomedical
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Abstract
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While the endothelial glycocalyx layer (EGL) was first identified by special electron microscopic staining techniques nearly forty years ago (Luft, 1967), it is only relatively recently that this surface layer has been observed in vivo (Vink and Duling, 1996), and the importance of its multifaceted physiological functions recognized. In this dissertation we quantitatively investigate the physiological functions of the EGL as a mechanotransducer of fluid shearing stress, and as a transport barrier, using models for the quasi-periodic structure of the EGL proposed in Squire et al. (2001) and Weinbaum et al. (2003). We also develop a simplified 1-D model to describe the revised Starling principle using the structural parameters for the interendothelial cleft measured in rat mesenteric capillaries (Adamson et al., 2004).;We first present a mathematical model for estimating the mechanical properties of the endothelial glycocalyx fibers based on existing experimental data (Vink and Duling, 1999). The predicted value of EI, 700 pN·nm 2, indicates that the glycocalyx is stiff to resist large deformations due to both fluid shear stresses in the physiological range and shear stresses due to the passage of red blood cells, yet its fibers can easily buckle due to the normal forces when red cell motion is arrested in tightly fitting capillaries. Second, we use the detailed morphological data for rat mesenteric capillaries obtained by our collaborator at UC Davis, Dr. Adamson, to construct a 3-D model for water and protein transport in rat mesenteric microvessels, and use this to confirm the Michel and Weinbaum hypothesis for a revised Starling principle in mammalian tissue. We also use this 3-D model to show that when the EGL covers the entrance to the cleft one cannot treat the hydraulic resistance of the EGL and cleft as two linear resistances in series. We then develop a much simpler, multilayer, 1-D theoretical model that can be solved analytically to provide most of the important results predicted by its complex numerical 3-D counterpart. Finally, we shall present an approximate model to describe the mechanism of oncotic flow across the EGL based upon the fiber matrix structure proposed in Squire et al. (2001) and Weinbaum et al. (2003). This model extends the theory in Anderson and Malone (1974) for cylindrical pores to a sieving fiber layer.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
