Organ volume

Sato et al. (1991) expanded their earlier PBPK model to account for differences in body weight, body fat content, and sex and applied it to predicting the effect of these factors on trichloroethylene metabolism and excretion. Their model consisted of seven compartments (lung, vessel rich tissue, vessel poor tissue, muscle, fat tissue, gastrointestinal system, and hepatic system) and made various assumptions about the metabolic pathways considered. First-order Michaelis-Menten kinetics were assumed for simplicity, and the first metabolic product was assumed to be chloral hydrate, which was then converted to TCA and trichloroethanol. Further assumptions were that metabolism was limited to the hepatic compartment and that tissue and organ volumes were related to body weight. The metabolic parameters, (the scaling constant for the maximum rate of metabolism) and (the Michaelis constant), were those determined for trichloroethylene in a study by Koizumi (1989) and are presented in Table 2-3. 

Powder Diffraction File Sets 31 to 32, Organic Volume, W. F. McClune, editor-in-chief, pattern number 32-1723, International Centre for Diffraction Data, Swarthmore, Pa., 1988, p. 254. 

Lanthanides Chemistry and Use in Organic Volume Editor S. Kobayashi... 

Measure bone length and organ volume, and statistically evaluate these parameters. 

Kinetics of Vinyl Hexanoate. A series of standard polymerizations was conducted using 10 ml of vinyl hexanoate in a total volume of 140 ml with varying amounts of emulsifier and initiator. The effect of varying initiator, particle number, and organic volume fraction in seeded runs, as well as for unseeded polymerizations, were also studied. The results are summarized in Table II. 

We can tentatively conclude, therefore, that the effect of chain transfer is still making itself felt in the polymerization of vinyl caproate in spite of its low water solubility. Except at the lowest particle concentrations, chain transfer is important. The polymerization in these regions is midway betwen Case I and Case II. When variables are considered separately, there is some dependence of polymerization rate on particle concentration, and also some dependence on initiator concentration. In addition, at constant organic volume, while the rate of polymerization increases as the particle concentration increases (Rp oc 2V- ), the rate per particle decreases as the particles get smaller. This shows that transferred radicals are mainly trapped in the particles, but some diffuse out and can undergo termination with other growing radicals. 

Sometimes filled adhesives will show better resistance to moisture resistance than unfilled adhesives simply because incorporating inert fillers into the adhesive lowers the organic volume that can be affected by moisture. Aluminum powder seems to be particularly effective, especially on aluminum substrates. The filler can provide a reduction of shrinkage on cure, a reduction of the thermal expansion coefficient, and a reduction of the permeability to water and other penetrants. However, fillers do not always produce more durable bonds. 

PBPK models require three different types of information (1) partition coefficients that describe the relative solubility or affinity of the compound for blood versus other tissues (2) physiological constants, such as tissue and organ volumes and the relevant blood flows and (3) rate constants for the key elimination pathways. 

Trifluoracetylacetone/toluene has been used for the extraction of indium (Fe, Co, Zn) from sea water, as mentioned in chapter 2.3.6 68). Indium is quantitatively and rapidly separated in a single extraction with an aqueous/organic volume ratio of 1 1. If this ratio is increased to 20 1 the extraction efficiency will decrease to 90%. The resins Chelex-100 and Permutit S 1005 may also be used for a complete retention of indium from sea water (refer to chapter 2.3.3) 56). 

Published data were used directly or to estimate values for the maternal and fetal extracellular space, maternal plasma volume and flow expansion during pregnancy, and maternal and fetal organ volumes and plasma flow. 

Parameter Values Aside from the dependent and independent variables in the equations above, a variety of parameters must be specified. These include physiological parameters (e.g., ventilation rates, cardiac output, organ volumes and masses), physicochemical parameters (e.g., tissue partition coefficients, protein binding constants), and biochemical parameters (e.g., Km and Vmax). 

Anatomical dimensions Organ blood flows Organ volumes Cardiac output Ventilation rate Body mass... 

The structure of PBPK models is fairly well defined and does not need to be changed, except for some particular chemicals, for which in vitro data would indicate unusual ADME properties. The major problem in PBPK modeling is thus the setting of parameter values. A first set of parameters is purely physiological and anatomical (e.g., organ volumes, blood flows, pulmonary ventilation, glomerular filtration rate). They can be specifically measured on... 

Physiologic parameters used, biochemical constants, and partition coefficients in the model are shown in Table 2-9. Physiologic constants (organ volume, blood flows, etc.) and tissue and blood coefficients were taken from literature sources (Astrand 1983 Fiserova-Bergerova 1983a). Elimination constants for the liver were taken from experiments in the perfused rat liver (Johanson et al. 1986b). Venous equilibrium was assumed, and competitive inhibition between ethanol and 2-butoxyethanol was assumed. 

Slaga, T. J. (ed.). (1983). Tumor Promotion in Internal Organs, Volume 1 of Mechanisms of Tumor Promotion, CRC Press, Boca Raton, FL, pp. 1-179. 

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