Metabolism species

When clearance is dependent upon metabolism, species-specific differences in the enzymes of metabolism can clearly prevent any such allometric relationship. An example of this is the absence of a close homologue of the human CYP2C9 enzyme in the dog, hence its inability to hydroxylate drugs such as tolbutamide and tienilic acid [13]. This said, many compounds cleared by metabolism do exhibit allometric relationships (e.g. N-nitrosodimethylamine, [14]). In an extensive analysis of the allometric relationship between clearance in the rat and man for 54 extensively cleared... 

Initiation 3. The metabolic species actually responsible for carcinogenesis... 

Metabolic fluxes are responsible for maintaining the homeostatic state of the cell. This condition may be translated into the assumption that the metabolic network functions in or near a non-equilibrium steady state (NESS). That is, all of the concentrations are treated as constant in time. Under this assumption, the biochemical fluxes are balanced to maintain constant concentrations of all internal metabolic species. If the stoichiometry of a system made up of M species and N fluxes is known, then the stoichiometric numbers can be systematically tabulated in a... 

Illustrated here was a different use of a computational model. It should be noted that even a model using somewhat more limited data (no adequate time course concentration disposition in humans, especially for metabolic species) was stUl a valuable tool for predicting a dose metric of choice for which there wctc more data (parent compound) and for predicting across different routes of exposure and between different species. Furthermore, the model was used to assess potential impact on that risk from variability in a hiunan population of inteest. Thus it sawed as an in silica laboratory. 

Tarka wrote an extensive review of the toxicology of cocoa and the methylxanthenes, theobromine, caffeine and theophyllin. The review involved biological and behavioral effects, metabolism, species variation, pregnancy. 

Downton,W.J.S. Adaptive and evolutionary aspects of C4 photosynthesis. In Photosynthesis and photorespiration. Hatch,M.D., Osmond,C.B., Slatyer,R.O. (eds.), pp. 3-17. New York, London, Sydney, Toronto Wiley-Interscience 1971 Eickmeier,W.G., Bender, M.M. Carbon isotope ratios of Crassulacean Acid Metabolism species in relation to climate and phytosociology. Oecologia 25,341-347 (1976) Enama,M. Molecular weight variations of phosphoenolpyruvate carboxylase from C4 plants. Carnegie Inst. Yearb. 75,409-413 (1976)... 

Shull, L. R., Buchmaster, G. W, and Cheeke, P. R. 1976. Factors Influencing Pyrrolizidine (Senecio) Alkaloid Metabolism Species, Liver Sulfhydryls and Rumen Fermentation. Journal of Animal Science 43 1247-1253. 

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