Elimination pool

Figure 39.4a represents schematically the intravenous administration of a dose D into a central compartment from which the amount of drug Xp is eliminated with a transfer constant kp. (The subscript p refers to plasma, which is most often used as the central compartment and which exchanges a substance with all other compartments.) We assume that mixing with blood of the dose D, which is rapidly injected into a vein, is almost instantaneous. By taking blood samples at regular time intervals one can determine the time course of the plasma concentration Cp in the central compartment. This is also illustrated in Fig. 39.4b. The initial concentration Cp(0) at the time of injection can be determined by extrapolation (as will be indicated below). The elimination pool is a hypothetical compartment in which the excreted drug is collected. At any time the amount excreted must be equal to the initial dose D minus the content of the plasma compartment Xp, hence ...

Fig. 39.4. (a) One-compartment open model with single-dose intravenous injection of a dose D. The transfer constant of elimination (excretion and metabolism) is kp - (b) Time course of the plasma concentration Cp and of the contents in the elimination pool Xp. 

Fig. 39.7. (a) Two-compartment catenary model for extravascular (oral or parenteral) administration of a single dose D which is completely absorbed. The transfer constant of absorption is (b) Time courses of the amount in the extravascular compartment Xa, the concentration in the plasma compartment Cp and the content in the elimination pool X. ... 

In the catenary model of Fig. 39.14a we have a reservoir, absorption and plasma compartments and an elimination pool. The time-dependent contents in these compartments are labelled X, X, and X, respectively. Such a model can be transformed in the 5-domain in the form of a diagram in which each node represents a compartment, and where each connecting block contains the transfer function of the passage from one node to another. As shown in Fig. 39.14b, the... 

Description of the model. The Leggett Model includes a central compartment, 15 peripheral body compartments, and 3 elimination pools, as illustrated in Figure 2-9. Transport of lead between... 

Preconditioning is used commercially by chip-potato processors to compensate the unpredictable nature of reconditioning of process varieties and to achieve market flexibility (Brook et al., 1995). During this phase, the storage environment is maintained at conditions similar to the wound healing phase (12-16°C) with the pulp temperature actively controlled in order to eliminate pools of reducing sugars in process potatoes. The duration of this phase is dependent... 

Adenosine is not active orally, but adrninistered as an iv bolus dmg adenosine rapidly eliminates supraventricular tachycardias within 1—2 min after dosing. The dmg slows conduction through the AV node. Adenosine is rapidly removed from the circulation by uptake into red blood ceUs and vascular endothehal ceUs. Thus the plasma half-life is less than 10 s. Adenosine is rapidly metabolized to inosine or adenosine monophosphate and becomes part of the body pool for synthesis of adenosine-triphosphate. 

For laboratory purposes it is sometimes convenient to recycle the foamate directly to the pool in a manner analogous to an equihbrium still. This eliminates the feed and bottoms streams and makes for a more reliable approach to steady-state operation. However, this recycling may not be advisable for colligena measurements in the presence of slowly dissociating collector micelles. 

The scrubbing liquid is fed into the pool at the bottom of the scrubber and later recirculated from the entrainment separator baffles by gravity instead of being circulated by a pump as in venturi scrubbers. Many devices using contactor ducts of various shapes are offered commercially. The principal advantage of this scrubber is the elimination of a pump for recirculation of the scrubbing liquid. 

Pooling the information gathered under headings (2) and (3), a final selection will be made of the method of determination and of the procedure for eliminating interferences. 

Although products of fat digestion, including cholesterol, are absorbed in the first 100 cm of small intestine, the primary and secondary bile acids are absorbed almost exclusively in the ileum, and 98—99% are returned to the liver via the portal circulation. This is known as the enterohepatic circulation (Figure 26—6). However, lithocholic acid, because of its insolubility, is not reabsorbed to any significant extent. Only a small fraction of the bile salts escapes absorption and is therefore eliminated in the feces. Nonetheless, this represents a major pathway for the elimination of cholesterol. Each day the small pool of bile acids (about 3-5 g) is cycled through the intestine six to ten times and an amount of bile acid equivalent to that lost in the feces is synthesized from cholesterol, so that a pool of bile acids of constant size is maintained. This is accomplished by a system of feedback controls. 

Mo, J.Y., Maki, H. and Sekiguchi, M. (1992). Hydrolytic elimination of a mutagenic nucleotide, 8-oxodGTP, by human 18-kilodalton protein sanitization of nucleotide pool. Proc. Natl Acad. Sci. USA 89, 11021-11025. 

Fig. 39.14. (a) Catenary compartmental model representing a reservoir (r), absorption (a) and plasma (p) compartments and the elimination (e) pool. The contents X, Xa, Xp and X,. are functions of time t. (b) The same catenary model is represented in the form of a flow diagram using the Laplace transforms Xr, Xa and Xp in the j-domain. The nodes of the flow diagram represent the compartments, the boxes contain the transfer functions between compartments [1 ]. (c) Flow diagram of the lumped system consisting of the reservoir (r), and the absorption (a) and plasma (p) compartments. The lumped transfer function is the product of all the transfer functions in the individual links. 

Skeletal deposition is assumed to distribute into two pools 50% goes to the trabecular bone surface and 50% to the cortical bone surface. A first order rate coefficient for elimination of americium from liver to plasma is assumed to be 0.0019 day 1 (half-time, 365 days). 

Strictly, disinfection means removing the risk of infection, but in the context of swimming pools the water cannot be sterile all the time. A few living, but normally harmless microorganisms will always be present, especially in open pools. Disinfection aims to keep their number to an acceptable minimum and to ensure that any harmful organisms entering the pool water are rapidly inactivated and eliminated so that the water will not transmit infection to the bathers. 

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