Cellular constituent

Many procedures have been studied for detoxification of aflatoxkis, including heat and treatment with ammonia, methylamine, or sodium hydroxide coupled with extraction from an acetone—hexane—water solvent system. Because ki detoxification it is important to free the toxki from cellular constituents to which it is bound, a stabifi2ation of protekis uskig a tanning compound such as acetaldehyde (qv) or glutaraldehyde may be a solution to the problem (98). 

To be biocompatible is to interact with all tissues and organs of the body in a nontoxic manner, not destroying the cellular constituents of the body fluids with which the material interfaces. In some appHcations, interaction of an implant with the body is both desirable and necessary, as, for example, when a fibrous capsule forms and prevents implant movement (2). 

Biosynthesis- Production of needed cellular constituents from other, usually simpler, molecules. 

Indeed, cellular constituents or biomolecules must conform to the chemical and physical principles that govern all matter. Despite the spectacular diversity of life, the intricacy of biological structures, and the complexity of vital mechanisms, life functions are ultimately interpretable in chemical terms. Chemistry is the lo e of biolo eal phenomena. 

The sensitivity of cellular constituents to environmental extremes places another constraint on the reactions of metabolism. The rate at which cellular reactions proceed is a very important factor in maintenance of the living state. However, the common ways chemists accelerate reactions are not available to cells the temperature cannot be raised, acid or base cannot be added, the pressure cannot be elevated, and concentrations cannot be dramatically increased. Instead, biomolecular catalysts mediate cellular reactions. These catalysts, called enzymes, accelerate the reaction rates many orders of magnitude and, by selecting the substances undergoing reaction, determine the specific reaction taking place. Virtually every metabolic reaction is served by an enzyme whose sole biological purpose is to catalyze its specific reaction (Figure 1.19). 

A rather limited collection of simple precursor molecules is sufficient to provide for the biosynthesis of virtually any cellular constituent, be it protein, nucleic acid, lipid, or polysaccharide. All of these substances are constructed from appropriate building blocks via the pathways of anabolism. In turn, the building blocks (amino acids, nucleotides, sugars, and fatty acids) can be generated from metabolites in the cell. For example, amino acids can be formed by amination of the corresponding a-keto acid carbon skeletons, and pyruvate can be converted to hexoses for polysaccharide biosynthesis. 

Certain of the central pathways of intermediary metabolism, such as the citric acid cycle, and many metabolites of other pathways have dual purposes—they serve in both catabolism and anabolism. This dual nature is reflected in the designation of such pathways as amphibolic rather than solely catabolic or anabolic. In any event, in contrast to catabolism—which converges to the common intermediate, acetyl-CoA—the pathways of anabolism diverge from a small group of simple metabolic intermediates to yield a spectacular variety of cellular constituents. 

Connett PH, Wetterhahn KE (1983) Metabolism of the Carcinogen Chromate by Cellular Constituents. 54 93-124... 

The rice bran phytochemicals and antioxidants induce several antioxidant enzymes at the cellular level which protects the DNA and other cellular constituents from damage. 

One goal of our current investigation is to show that genetically important cellular constituents can initiate the release of an alkylating agent from the N-nitrosamide. This might explain how highly reactive diazohydroxide metabolites effect the alkylation of nucleic acids within the cell nucleus. Preliminary evidence ( ) summarised in Table II shows that the decomposition of... 

Hydroxyl radicals are the most reactive free-radical species known and have the ability to react with a wide number of cellular constituents including amino-acid residues, and purine and pyrimidine bases of DNA, as well as attacking membrane lipids to initiate a free-radical chain reaction known as lipid peroxidation. 

Four processes are concerned in the isolation of a nucleic acid. First is the destruction of the tissue structure (stage 1). A nucleoprotein complex is then separated from other cellular constituents (stage 2). This complex is dissociated and the protein is removed (stage 3) and, finally, the nucleic acid is precipitated from the resulting solution (stage 4). Disintegration of... 

The lysosome is the subcellular organelle responsible for physiological turnover of cellular constituents. Their combined incidence is estimated to be 1 8,000 [2]. Knowledge about the molecular and cellular defects has advanced a great deal in recent years. Platt and Walkley [3] have proposed a new classification based on the nature of the molecular defects (Table 41-1). This system will be used here. 

There are two sources of biochemicals in soil one is the cellular constituents released when cells are destroyed during the extraction process. It should be kept in mind that any handling of a soil sample will cause the destruction of some of the cells it contains. The simple act of sieving, air drying, and weighing soil will cause some lyses of cells and release of their contents. Extraction will typically cause complete destruction of all cells in soil, with the release of all their constituent parts. Some parts such as enzymes may continue to function after release from the cell and continue to change the makeup of soil components for some time. 

An inevitable consequence of ageing is an elevation of brain iron in specific brain regions, e.g. in the putamen, motor cortex, pre-frontal cortex, sensory cortex and thalamus, localized within H- and L-ferritin and neuromelanin with no apparent adverse effect. However, ill-placed excessive amounts of iron in specific brain cellular constituents, such as mitochondria or in specific regions brain, e.g. in the substantia nigra and lateral globus pallidus, will lead to neurodegenerative diseases (Friedreich s ataxia and Parkinson s disease (PD), respectively). We discuss here a few of the examples of the involvement of iron in neurodegenerative diseases. From more on iron metabolism see Crichton, 2001. 

There is great interest in the mechanisms of cell death since better understanding might lead to therapy that slows the rate of aging and prevents or treats human disease. Two major processes of cell death have been described, apoptosis and neaosis other alternative pathways generally are variations of these (Formigli et al, 2000 Sperandio et al, 2000 Reed, 1999). Some of the intracellular events related to these types of death have been discovered (Reed, 2000). After exposure to noxious stimuli, the balance between antiapoptotic and proapoptotic influences can result in either survival or death. Many of these variable influences and the subsequent downstream concatenated events involve oxidation, which targets cellular components such as DNA, cellular proteins and membrane phospholipids. Our laboratory and others have studied the role of the redox-active cellular constituents nitric oxide ( NO) and membrane phospholipid... 

All these rapidly reacting intermediates are potentially harmful to the cell and might play a role in ozone toxicity. Furthermore, the potential for ozone-induced free-radical chain reactions exists. It appears likely that more than one radical is formed, either directly from ozone or as a result of the interaction of ozone with normal cellular constituents. 

Catabolic pathways are degradative. Molecules of varying degrees of complexity are broken down to simpler cellular constituents or excretory products. These pathways... 

---