Trace metals metabolism

Calhoun, B. A., J. Overmeyer, and W. Sunderman Jr. Studies of trace metal metabolism Electron paramagnetic resonance of manganese in ribonucleic acids. Proc. Soc. Exptl. Biol. Med. 119, 1089 (1965). 

Certain inherited diseases are associated with abnormal trace metal metabolism, and this may be linked to MT synthesis, either directly or indirectly. Zinc, copper, and iron are the target elements in several diseases, and their concentrations may be altered in disorders of the central nervous system or other physiological systems, including Alzheimer-type dementia, amyotrophic lateral sclerosis, acrodermatitis enteropathica, biliary cirrhosis, Wilson s and Menke s diseases (Bremner 1987), epi-... 

A book dealing with alkaloids in foods contains an account on caffeine and related compounds. The synthesis of caffeine, the conversion of uric acid into xanthine, and various syntheses of related heterocyclic compounds form subject matters in a review of broad scope. The role of purine alkaloids in trace-metal metabolism, disease resistance, mutagenesis, and chemotaxonomic considerations in plants has been reviewed. 

For a discussion of the consequences of trace metal deficiency as well as genetically determined disturbances in trace metal metabolism, see Sec. 6.1. 

It is clearly understood that severe acute clinical situations like severe infections, thermal injury, shock, postsurgical stages, polytrauma, etc., affect trace metal metabolism in an extremely intense way. Each of the known trace metals may be implicated. Primarily losses of trace metals or a shift from one compartment to another caused by acute phase proteins are of prominent clinical significance [58]. For this reason in infusion therapy in intensive care the solutions should contain a sufflcient amount of trace metals for substitution to promote recovery. 

Total parenteral nutrition (TPN) can produce trace metal deficiency associated with different clinical symptoms. Therefore trace metal supplementation (Fe, Cu, Zn, Se, Cr, Mo, Mn) in TPN solutions is necessary to disclose complications [59]. In addition, hemodialysis treatment influences trace metal metabolism and may derange trace metal balance (Zn, Cu, Se, and Mg). Complications in hemodialysis caused by aluminum treatment to prevent hyperphosphatemia include dialysis encephalopathy, osteomalacia, and anemia. Aluminum determination in blood serum is one of most important tests in therapy monitoring [60]. 

Pabo CO, Sauer RT (1992) Transcription factors structural families and principles of DNA recognition. Annu Rev Biochem 61 1053-1095 Packman S, O Toole T (1984) Trace metal metabolism in cultured skin fibroblasts of the mottled mouse response to metallothionein inducers. Pediatr Res 18 1282-1286... 

Season of collection (Fowler and Oregioni 1976 Sanders etal. 1991) and latitude (Anderlini 1974) also influenced silver accumulations. Seasonal variations in silver concentrations of Baltic clams (Macoma balthica) were associated with seasonal variations in soft tissue weight and frequently reflected the silver content in the sediments (Cain and Luoma 1990). Oysters from the Gulf of Mexico vary considerably in whole-body concentrations of silver and other trace metals. Variables that modify silver concentrations in oyster tissues include the age, size, sex, reproductive stage, general health, and metabolism of the animal water temperature, salinity, dissolved oxygen,... 

No carrier is completely specific for a given trace metal metals of similar ionic radii and coordination geometry are also susceptible to being adsorbed at the same site. The binding of a competing metal to an uptake site will inhibit adsorption as a function of the respective concentrations and equilibrium constants (or kinetic rate constants, see below) of the metals. Indeed, this is one of the possible mechanisms by which toxic trace metals may enter cells using transport systems meant for nutrient metals. The reduced flux of a nutrient metal or the displacement of a nutrient metal from a metabolic site can often explain biological effects [92]. 

Marine organisms concentrate metals in their tissues and skeletal materials. Many of these trace metals are classified as micronutrients because they are required, albeit in small amounts, for essential metabolic functions. Some are listed in Table 11.4, illustrating the role of metals in the enzyme systems involved in glycolysis, the tricarboxylic acid cycle, the electron-transport chain, photosynthesis, and protein metabolism. These micronutrients are also referred to as essential metals and, as discussed later, have the potential to be biolimiting. 

The trace metals listed in Table 11.2 (with the inclusion of Sn) are of particular concern as they are toxic at low concentrations. For historical reasons, these elements are commonly referred to as the heavy metals. The degree to which the heavy metals cause toxic effects is dependent on their concentration, chemical speciation, and other environmental conditions, such as temperature. As illustrated in Table 28.6, the type and physiological state of the target organism are also important as these fectors determine the degree to which internal metabolic processes can detoxify or eliminate the pollutant. 

Trace metals Zinc Red meats, shellfish, wholegrain cereals Involved in many metabolic reactions stabilisation of structure RNA, DNA and ribosomes Binding of some transcription factors to DNA Stabilisation of insulin complex in storage granules... 

Iron is an essential trace metal nutrient required by practically all living organisms for a wide variety of fundamental cell functions ranging from oxygen metabolism and electron transfer processes to DNA and RNA synthesis . ... 

Heavy metals stimulate or inhibit a wide variety of enzyme systems (16, 71, 72), sometimes for protracted periods (71, 73). These effects may be so sensitive as to precede overt toxicity as in the case of lead-induced inhibition of 8 ALA dehydrase activity with consequential interference of heme and porphyrin synthesis (15, 16). Urinary excretion of 8 ALA is also a sensitive indicator of lead absorption (74). Another erythrocytic enzyme, glucose-6-phosphatase, when present in abnormally low amounts, may increase susceptibility to lead intoxication (75), and for this reason, screens to detect such affected persons in lead-related injuries have been suggested (76). Biochemical bases for trace element toxicity have been described for the heavy metals (16), selenium (77), fluoride (78), and cobalt (79). Heavy metal metabolic injury, in addition to producing primary toxicity, can adversely alter drug detoxification mechanisms (80, 81), with possible secondary consequences for that portion of the population on medication. 

Deferoxamine is isolated from Streptomycespilosus. It binds iron avidly but essential trace metals poorly. Furthermore, while competing for loosely bound iron in iron-carrying proteins (hemosiderin and ferritin), it fails to compete for biologically chelated iron, as in microsomal and mitochondrial cytochromes and hemoproteins. Consequently, it is the chelator of choice for iron poisoning (Chapters 33 and 59). Deferoxamine plus hemodialysis may also be useful in the treatment of aluminum toxicity in renal failure. Deferoxamine is poorly absorbed when administered orally and may increase iron absorption when given by this route. It should therefore be administered intramuscularly or, preferably, intravenously. It is believed to be metabolized, but the pathways are unknown. The iron-chelator complex is excreted in the urine, often turning the urine an orange-red color. 

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