Compartment, definition

Receptor assays, 251 Receptor compartment definition of, 35 drug removal from, 36f free drug concentration in, 39 Receptor density... 

Figure 21.8 Two-box model of trwo completely mixed environmental compartments. Definition of subscripts first subscript (7 or j) designs the compound, the second (1 or 2) the box. Transfer fluxes Tcarry three subscripts. For instance, T ll describes the interbox flux of variable i from box 1 to box 2. X and Y denote other chemicals which are not state variables.

Recently, some kinetic coefficients have been determined in electro-chemically initiated polymerizations [144]. Trioxane, dissolved in three different solvents (acetonitrile, benzonitrile, and nitrobenzene) with tetra-butylammonium perchlorate as background electrolyte, was polymerized in the anodic compartment. Definite solvent dependence was shown. When the current was turned off, polymerization in acetonitrile ceased in... 

The AUC is a measure of bioavailability, i.e. the amount of substance in the central compartment that is available to the organism. It takes a maximal value under intravenous administration, and is usually less after oral administration or parenteral injection (such as under the skin or in muscle). In the latter cases, losses occur in the gut and at the injection sites. The definition also shows that for a constant dose D, the area under the curve varies inversely with the rate of elimination kp and with the volume of distribution V. Figure 39.6 illustrates schematically the different cases that can be obtained by varying the volume of distribution Vp and the rate of elimination k both on linear and semilogarithmic diagrams. These diagrams show that the slope (time course) of the curves are governed by the rate of elimination and that elevation (amplitude) of the curve is determined by the volume of distribution. 

In the case of a one-compartment open model with single-dose intravenous administration, the mean residence time is simply the inverse of the elimination transfer constant kp, since according to the above definition we obtain ... 

Figure 3 Possible blood circulation connections in a physiologically based pharmacokinetic model. (A) Venous return incorporated into lung mass balance equation (B) separate venous blood compartment. See text for definition of symbols.

In whole tissue or cell monolayer experiments, transcellular membrane resistance (Rm = Pm1) lumps mucosal to serosal compartment elements in series with aqueous resistance (R = P ). The operational definition of Lm depends on the experimental procedure for solute transport measurement (see Section VII), but its magnitude can be considered relatively constant within any given experimental system. Since the Kp range dwarfs the range of Dm, solute differences in partition coefficient dominate solute differences in transcellular membrane transport. The lumped precellular resistance and lumped membrane resistance add in series to define an effective resistance to solute transport ... 

Equilibrium. Equilibrium between compartments can be expressed either as partition coefficients K.. (i.e. concentration ratio at equilibrium) or in the fugacity models as fugacity capacities and Z. such that K.. is Z./Z., the relationships being depicted in Figur 1. Z is dellned as tfte ratio of concentration C (mol/m3) to fugacity f (Pa), definitions being given in Table I. 

Summary. In summary, when modeling with the fugacity concept, all equilibria can be treated by Z values (one for each compartment) and all reaction, advection and transport processes can be treated by D values. The only other quantities requiring definition are compartment volumes and emission rates or initial concentrations. A major advantage is that since all D quantities are in equivalent units they can be compared directly and the dominant processes identified. By converting diverse processes such as volatilization, sediment deposition, fish uptake and stream flow into identical units, their relative importance can be established directly and easily. Further, algebraic manipulation... 

MTs serve multiple roles in neurons. Besides acting as the substrate for the transport of membrane-bounded organelles, MTs are necessary for the extension of neurites during development they provide the structural basis for maintaining neurites after extension and they also help maintain the definition and integrity of intracellular compartments. The diversity of these functions is reflected in differences in the biochemistry and metabolic stability of different MTs. 

There have been fuel processor configurations where a non-catalytic POX is placed in series with a steam reformer. Without catalyst, the POX reaction has to be at a higher temperature than the steam reformer reaction. These reactions have to take place in separate compartments with heat exchange and a wall between them (13). This configuration is not considered within the definition of autothermal reforming. 

Definition of the exposure scenarios describing 1° and 2° (direct/indirect) human exposure, the various emissions and the l°/2° environmental compartments exposed. 

Provide guidance on how to develop the most relevant hazard effects (PNEC) data i.e. the eco-toxicity testing strategy and methods definition per environmental compartment exposed. 

Industry is currently faced with the rather unfortunate situation of (1) not knowing exactly which environmental compartments are exposed for certain product types and thus cannot agree on what environmental fate/eco-toxicologi-cal testing needs to be done and (2) what tools to use to establish an agreed (between industry/Competent Authority) PEC per product type. It is important to repeat at this point that without the definition of the emission scenarios and... 

The intravenous curve is, by definition, a representation of 100% bioavailability as the drug was put in its entirety into the vein. The oral curve has an area under it approximately 75% the size of the intravenous curve, and this suggests that 25% of the oral dose failed to get into the circulation. The oral bioavailability of the drug is the proportion getting into the vascular compartment, and can be measured if there is an intravenous dose curve available for the same subject at the same dose. In this example, F (the fraction bioavailable) is 0.75. It might be as high as 1.0 (100%) for some steroids, or as low as 0.1 (10%) or even less for poorly absorbed aminoglycosides. 

Clearance (Cl) and volumes of distribution (VD) are fundamental concepts in pharmacokinetics. Clearance is defined as the volume of plasma or blood cleared of the drug per unit time, and has the dimensions of volume per unit time (e.g. mL-min-1 or L-h-1). An alternative, and theoretically more useful, definition is the rate of drug elimination per unit drug concentration, and equals the product of the elimination constant and the volume of the compartment. The clearance from the central compartment is thus VVklO. Since e0=l, at t=0 equation 1 reduces to C(0)=A+B+C, which is the initial concentration in VI. Hence, Vl=Dose/(A+B-i-C). The clearance between compartments in one direction must equal the clearance in the reverse direction, i.e. Vl.K12=V2-k21 and VVkl3=V3-k31. This enables us to calculate V2 and V3. 

Antilymphocyte antibody acts primarily on the small, long-lived peripheral lymphocytes that circulate between the blood and lymph. With continued administration, "thymus-dependent" lymphocytes from lymphoid follicles are also depleted, as they normally participate in the recirculating pool. As a result of the destruction or inactivation of T cells, an impairment of delayed hypersensitivity and cellular immunity occurs while humoral antibody formation remains relatively intact. ALG and ATG are useful for suppressing certain major compartments (ie, T cells) of the immune system and play a definite role in the management of solid organ and bone marrow transplantation. 

Risk assessment of chemicals does not, in practice, estimate the incidence and severity of the adverse effects likely to occur in the human population or environmental compartment due to actual or predicted exposure to a substance — the definition of risk characterization in Article 2 of Directive 93/67/EEC. The assessment process hinges on being able to say that there is a threshold below which the chemical has no adverse effects, in other words on being able to derive a no-effect level. Recent debates, discussed later, challenge the idea that there normally is such a threshold. 

Let us discuss the meaning of some of the expressions which appear in the above definition (see Box 21.1). A subunit of the environment can be any spatial compartment of the world, from the whole planet to a single algal cell floating in the ocean. The term state variable refers to those properties which are used to characterize the... 

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