Blood transport properties

Polysiloxane based block copolymers have also been examined with respect to their transport properties, because these copolymers are of special interest as membranes in various biomedical applications 376). The combination of good mechanical, dielectric, permeation and film formation properties of siloxane-carbonate segmented copolymers have led to their use as blood oxygenation, dialysis and microelectrode membranes 392 394. ... 

The biochemical properties of both the body and the drug have a lot to do with a drug s distribution to its sites of action. Because the blood transports a drug, it follows that regions of the body that receive the most blood get the most drug. 

Figure 2 Schematic illustration of the (transport) properties of the blood-brain barrier. Shown is the influence of astrocyte endfeet at the brain capillary endothelial cell. This cell has narrow tight junctions, low pinocytotic activity, many mitochondria, and luminal anionic sites that hinder the transport of negatively charged compounds. Passive hydrophilic transport occurs via paracellular diffusion (tight junctions), whereas passive lipophilic transport is a transcytotic process. Adsorptive-, receptor-, and carrier-mediated transport has been indicated. The metabolic properties of the BBB are illustrated by the various enzymes at the BBB [from (157), with permission].

A major objective of fundamental studies on hollow-fiber hemofliters is to correlate ultrafiltration rates and solute clearances with the operating variables of the hemofilter such as pressure, blood flow rate, and solute concentration in the blood. The mathematical model for the process should be kept relatively simple to facilitate day-to-day computations and allow conceptual insights. The model developed for Cuprophan hollow fibers in this study has two parts (1) intrinsic transport properties of the fibers and (2) a fluid dynamic and thermodynamic description of the test fluid (blood) within the fibers. 

Blood and lymphatic vessels are soft tissues with densities which exhibit nonlinear stress-strain relationships [1]. The walls of blood and lymphatic vessels show not only elastic [2, 3] or pseudoelastic [4] behavior, but also possess distinctive inelastic character [5, 6] as well, including viscosity, creep, stress relaxation and pressure-diameter hysteresis. The mechanical properties of these vessels depend largely on the constituents of their walls, especially the collagen, elastin, and vascular smooth muscle content. In general, the walls of blood and lymphatic vessels are anisotropic. Moreover, their properties are affected by age and disease state. This section presents the data concerning the characteristic dimensions of arterial tree and venous system the constituents and mechanical properties of the vessel walls. Water permeability or hydraulic conductivity of blood vessel walls have been also included, because this transport property of blood vessel wall is believed to be important both in nourishing the vessel walls and in affecting development of atherosclerosis [7-9]. 

Gases and vapors disperse with oxygen and nitrogen in normal air. Consequently, hazardous gases will travel with normal air deep into the lungs. Depending on solubility and other properties, a gas may go into solution in the blood or attach to red cells or elements of the blood. The blood transports the material to other tissues in the body for which there may be more affinity. 

Cd " and Mn may also be substrates for ion efflux mechanisms such as the Na-Ca exchanger (Frame and Milanick 1991). It has long been appreciated that a number of metals, and in particular and Mn ", inhibit this exchanger (Philipson 1985). Recent studies by Frame and Milanick (1991) demonstrate that this inhibition is competitive, and that these metals are in fact transported as substitutes for Ca. The for Ca, Cd ", and Mn uptake by ferret red blood cells is roughly similar, —10//M, as is the (Frame and Milanick 1991), indicating that the transport properties of cadmium and manganese are similar to those of calcium in this system. 

Skin forms a protective boundary layer between the body and its environment. With respect to transport properties, the nonvascularized epidermis, the outermost layer of which is formed by the stratum corneum (SC), serves as a barrier for the body. In the underlying vascularized dermis, the transport properties are strongly influenced by blood circulation. 

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