Metabolic activation, organic defined

The bowel, one of the largest and most metabolically active organs, contains bacteria that may change the chemical composition of the human body. In renal failure the altered bacterial flora cause the accumulation of aliphatic amines in the gut (09, S25). Bacteria transform part of the choline in the gut to trimethylamine, which is reabsorbed and then either oxidized or demethylated to dimethylamine in the liver (S24). Dimethylamine enters the circulation and is excreted in the bile and urine. The trimethylamine and dimethylamine in the exhaled air of uremic patients may contribute to the classic fishy breath, which can be improved by hemodialysis or by gut sterilization with nonabsorbable antibiotics (S23, S25). The overall role of these compounds as uremic toxins, however, remains to be defined. 

Cell growth and metabolic activities are similarly described as a simple chemical reaction. It is also necessary to establish a definite formula for dry cell matter. The elemental composition of certain strains of microorganism is defined by an empirical formula CHaO/3Ns. The general biochemical reaction for biomass production is based on consumption of organic substrate, as shown below. Substrate oxidation is simplified in the following biochemical oxidation ... 

A vitamin has been defined [399] as a biologically active organic compound that is essential for the organism s normal metabolic and physiologic functions. Vitamins are not produced by human body itself, thereby they have to be obtained from the diet. As micronutrients, in contrast to nonessential chemical substances, they present both a minimum and a maximum level of intake beyond which arise risks of deficiency conditions or adverse effects [400]. 

In most instances the test system will be self-evident (e.g., the animal to which the test article is administered or applied). Studies with micro-organisms, however, sometimes present difficulty in defining the test system. In the case of the Ames test, for example, the test system is not merely the colonies of salmonella or yeast, but includes in addition the culture medium, metabolic activation agent (if any), biotin, histidine, and buffer (if any). The last sentence of the definition makes it clear that untreated control groups also meet the definition of test system even though a test or control article is not administered or applied to such groups. 

It is the role of technical bioreactors in such advanced systems to create a specifically defined environment for the biochemical reaction system producing or modifying flavour substances. The most important purpose of such bioreactors is the well controlled combination of food raw material and flavour precursor, respectively, with the biological reaction centres. It also provides the means for survival and maintenance of the centre s metabolic activity. Presently there is laboratory and partially also industrial experience with mostly all kinds of different micro-organisms and isolated biocatalysts ... 

Soil DOM comprises a wide variety of organic substances. Specific microbial or plant exudates are released as a consequence of metabolic activity of soil biota. Transformations of biogenic compounds, through partial degradation and polymerization, result in the formation of a structurally ill-defined mixture of humic substances, a term used to include both humic and fulvic acids (20, 21). Nonuniform effects of DOM components on metal mobilization may be anticipated because of the heterogeneity of their chemical structures and properties. 

An attempt has been made to give an overview of all chemical aspects of plant protection, with the exception of analytical chemistry. We are fully aware that the designation chemistry of pesticides does not cover an unequivocally defined, uniform branch of science, because the fundamental sciences on which it is built, particularly organic chemistry and biochemistry, have maintained their independence and their original scope also within the frame of this special field. The chemistry of pesticides integrates these fundamental sciences only functionally, and not with respect to their methods. Our book attempts to achieve this functional unity. In the discussion of individual compounds and types of compound our aim has been to cover preparative and organic chemical and biochemical aspects, metabolism, activity-structure relationships, fields of application, and environmental and toxicological problems. 

The carbohydrate metabolic routes in various tissues of the organism discussed above differ in intensity, which is defined by metabolic features specific of each tissue and organ. However, from the standpoint of activity of the whole organism, certain specializations of the carbohydrate metabolic routes in individual tissues are profitably complementary. For example, strenuous muscular exertion requires energy which is initially supplied by the breakdown of glycogen to lactic acid. The latter compound is excreted into the blood to be supplied... 

Most tissues have well-defined patterns of esterase activity. Thus, the ESI synthesized in mouse liver constitutes the major esterase activity in murine plasma. It has been postulated that the ES2 present in the lymph plays an essential role in fat resorption [92], Four esterases designated ES5, SEI, SEII, and SEIII are restricted to serum and have not been identified in other tissues. The content of ES6 is highest in organs with active fat metabolism, but is absent in serum and erythrocytes. ES7 is present in erythrocytes, lung, tongue, testis, and most other tissues but not in plasma and brain. 

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