Organ systems, transport

Recently the effect of intrinsic traps on hopping transport in random organic systems was studied both in simulation and experiment [72]. In the computation it has been assumed that the eneigy distribution of the traps features the same Gaussian profile as that of bulk states. 

Most of the actual reactions involve a three-phase process gas, liquid, and solid catalysts are present. Internal and external mass transfer limitations in porous catalyst layers play a central role in three-phase processes. The governing phenomena are well known since the days of Thiele [43] and Frank-Kamenetskii [44], but transport phenomena coupled to chemical reactions are not frequently used for complex organic systems, but simple - often too simple - tests based on the use of first-order Thiele modulus and Biot number are used. Instead, complete numerical simulations are preferable to reveal the role of mass and heat transfer at the phase boundaries and inside the porous catalyst particles. 

Estimation of parameters. Model parameters in the selected model are then estimated. If available, some model parameters (e.g. thermodynamic properties, heat- and mass-transfer coefficient, etc.) are taken from literature. This is usually not possible for kinetic parameters. These should be estimated based on data obtained from laboratory expieriments, if possible carried out isothermal ly and not falsified by heat- and mass-transport phenomena. The methods for parameter estimation, also the kinetic parameters in complex organic systems, and for discrimination between models are discussed in more detail in Section 5.4.4. More information on parameter estimation the reader will find in review papers by Kittrell (1970), or Froment and Hosten (1981) or in the book by Froment and Bischoff (1990). 

Heijn, M., Oude Elferink, R. and Jansen, P. (1992). ATP-dependent multispecific organic anion transport system in rat erythrocyte membrane vesicles. Am. J. Physiol. 262, 104-110. 

Thermal conduction (also referred to as electrical conductive heating or in situ thermal desorption) supplies heat to the soil through steel wells or with a blanket that covers the ground surface. As the polluted area is heated, the contaminants are destroyed or evaporated. Steel wells are used when the polluted soil is deep. The blanket is used where the polluted soil is shallow. Typically, a carrier gas or vacuum system transports the volatilized water and organics to a treatment system. 

An appropriate starting point for any discussion of drug transport in the gastrointestinal (GI) tract at the cellular level requires some introductory remarks on the structure and function of GI tissue. As a class of tissue, epithelia demarcate body entry points (skin, eye, respiratory, urinary, and GI organ systems), predisposing a general barrier function with respect to solute entry and translocation. In addi-... 

All of the organ systems in the body, except the reproductive system, contribute to the maintenance of homeostasis (see Table 1.1). For example, the gastrointestinal tract digests foods to provide nutrients to the body. The respiratory system obtains oxygen and eliminates carbon dioxide. The circulatory system transports all of these materials and others from one part of the body to another. The renal system eliminates wastes and plays a role in regulating blood volume and blood pressure. 

Soil solution is the aqueous phase of soil. It is in the pore space of soils and includes soil water and soluble constituents, such as dissolved inorganic ions and dissolved organic solutes. Soil solution accommodates and nourishes many surface and solution reactions and soil processes, such as soil formation and decomposition of organic matter. Soil solution provides the source and a channel for movement and transport of nutrients and trace elements and regulates their bioavailability in soils to plants. Trace element uptake by organisms and transport in natural systems typically occurs through the solution phase (Traina and Laperche, 1999). 

Cell lines, such as the Caco-2 and MDCK cells [27, 35, 47, 49, 57, 67, 128-133], have been used frequently to study different transporters in the GI tract. These cell lines have been evaluated for transport both in absorptive and secretory direction and in addition also been transfected with specified transporter systems of interests to yield new clones [23, 31, 72, 79, 80, 134] or co-cultures [135], Some of the uptake transporters belonging to the organic cation transporter (OCT) family have also been identified in cell lines such as the pig kidney cell line LLC-PK1, and MDCK [67, 136]. In fact, its presence in Caco-2 cells needs to be further elucidated as reports have shown both the absence and presence of transporters from this family of transporters [136-138],... 

Lahjouji, K., G. A. Mitchell, and I. A. Qureshi. Carnitine transport by organic cation transporters and systemic carnitine deficiency. Mol. Genet. Metab. 2001, 73, 287-297. 

Results of the experimental and theoretical investigations on bridging electrolyte-water systems as to thermodynamic and transport properties of aqueous and organic systems. Revised version of chapter four in Number 35. 

In vitro stndies have shown that there are distinct transport systems for both baso-lateral and apical uptake of nicotine (Takami et al. 1998). Nicotine has been shown to be actively transported by kidney cells, most likely by the organic ion transporter OCT2 (Zevin et al. 1998 Urakami et al. 1998). Cimetidine decreases renal clearance of nicotine by 47% in nonsmoking volunteers (Bendayan et al. 1990). This is consistent with the inhibition of basolateral uptake by cimetidine detected in vitro. Mecamylamine reduces renal clearance of nicotine in smokers dosed with intra-venons nicotine when urine is alkalinized, but not when nrine is acidified (Zevin et al. 2000). 

Pattern of distribution of an agent, its derivatives, or metabolites in an organism, system, compartment, or (sub)population of concern as a result of transport, partitioning, transformation, or degradation. 

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