Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Selenium biological function

Fig. 2. Periodic table indicating relative abundance and biological importance of elements. Highlighted elements are the 30 most abundant crustal elements with concentrations ranging from 46 % for oxygen to 0.1 yg/g for selenium. Bold faced elements have known biological functions with indicating limited data and controversy. Data taken from Wood and Wang, 1983. Fig. 2. Periodic table indicating relative abundance and biological importance of elements. Highlighted elements are the 30 most abundant crustal elements with concentrations ranging from 46 % for oxygen to 0.1 yg/g for selenium. Bold faced elements have known biological functions with indicating limited data and controversy. Data taken from Wood and Wang, 1983.
The growing interest in selenium speciation is due to its toxic and/or essential properties that depend on the actual physicochemical form of the element. Strong evidence exists on the adverse health effects related to selenium deficiency. It was also demonstrated that supplementation with different selenium forms might help to remove the symptoms of deficit. Selenium has been found in the active site of different antioxidant enzymes, protecting cells against the action of free radicals. The species-dependent cancer-preventive properties are well documented, yet the specific biological functions have not been ultimately elucidated. The list of small selenium compounds includes inorganic forms (two stable valence states), volatile alkylated species, and... [Pg.6095]

The precise biological function of selenium in KD is unclear, and seasonal variations in prevalence suggested the involvement of a virus. High levels of the Coxsackie B virus were found in KD patients (Li et al., 2000). Work by Beck (1999) showed that a normally benign strain of the Coxsackie B3 virus becomes virulent in selenium-or vitamin E-deficiency conditions. [Pg.4599]

One biological function for selenium is incorporation into the amino acid selenocysteine that is found in some proteins [174]. Microbial dissimilatory reduction of selenate to selenite and then to elemental... [Pg.885]

Diets that are low in protein, zinc, selenium, vitamin Bg, and fat may collectively depress immune function. This type of diet may be associated with either a low-caloric-intake diet or low-fat, low-meat-products diet. Zinc is an essential trace element for many biological functions, including immune functions. Indeed, zinc is required for the biological activity of a thymic hormone, called thymulin in its zinc-bound form, and is important for the maturation and differentiation of T-cells. With advancing age, zinc, thymic functions, and peripheral immune efficiency show a progressive decline. Supplementing zinc in old age restores immune efficiency. [Pg.88]

Stadtman TC. 1983. New biological functions-Selenium-dependent nucleic acids and proteins. Fundam Appl Toxicol 3 420-423. [Pg.390]

Y Shibata, M Morita, K Fuwa. Selenium and arsenic in biology Their chemical forms and biological functions. Adv Biophys 28 31-80, 1992. [Pg.91]

Some metals, including heavy metals, affect negatively people s health, either individually or forming metal compounds, and therefore they must be controlled. Moreover, there are toxic semi-metaUic elements the so-called metalloids, such as arsenic and selenium, which should also be monitored. Basically, this group of pollutants can be classified in (1) metals and metalloids that are necessary to support life in very small amounts, but toxic in larger amounts, e.g. copper, zinc, chromium, arsenic, or selenium (2) metals with unknown biological function which are extremely toxic even at trace levels, e.g. mercury, cadmium, or lead. [Pg.227]

If there is a difference in the biological function of the two sulfur loci in deamino-oxytocin, we may have detected this disparity through the use of a selenium marker. However, at present we have not excluded the possibility that the disparity in the biological activities of deamino-1-seleno-oxytocin and deamino-6-seleno-oxytocin result from an additional factor introduced by the "marker, namely its unequal interaction with the asymmetric environment. [Pg.104]

If future trials do demonstrate a reduction in chronic disease risk with antioxidant supplementation, this caimot be definitively attributed to the antioxidant effect of these nutrients because other biological functions may also play a role. For example, in addition to retarding LDL oxidation, vitamin E may help to protect against CVD via its action on platelet aggregation and adhesion or by inhibition of the proliferation of smooth muscle cells. Furthermore, although vitamin C, vitamin E, and selenium have been shown to decrease the concentration of some of the biomarkers associated with oxidative stress, the relationship between many of these biomarkers and chronic disease remains to be elucidated. [Pg.39]

The quality of the experimental evidence for nutritional essentiality varies widely for the ultratrace elements. The evidence for the essentiality of three elements, iodine, molybdenum and selenium, is substantial and noncontroversial specific biochemical functions have been defined for these elements. The nutritional importance of iodine and selenium are such that they have separate entries in this encyclopedia. Molybdenum, however, is given very little nutritional attention, apparently because a deficiency of this element has not been unequivocally identified in humans other than individuals nourished by total parenteral nutrition or with genetic defects causing disturbances in metabolic pathways involving this element. Specific biochemical functions have not been defined for the other 15 ultratrace elements listed above. Thus, their essentiality is based on circumstantial evidence, which most often is that a dietary deprivation in an animal model results in a suboptimal biological function that is preventable or reversible by an intake of physiological amounts of the element in question. Often the circumstantial evidence includes an identified essential function in a lower form of life, and biochemical actions consistent with a biological role or beneficial action in humans. The circumstantial evidence for essentiality is substantial for arsenic, boron, chromium, nickel, silicon, and vanadium. The evidence for essentiality for the... [Pg.397]

There are numerous synthetic and natural compounds called antioxidants which regulate or block oxidative reactions by quenching free radicals or by preventing free-radical formation. Vitamins A, C, and E and the mineral selenium are common antioxidants occurring naturally in foods (104,105). A broad range of flavonoid or phenoHc compounds have been found to be functional antioxidants in numerous test systems (106—108). The antioxidant properties of tea flavonoids have been characterized using models of chemical and biological oxidation reactions. [Pg.373]

Selenium is readily available in a variety of foods including shrimp, meat, dairy products, and grains, with a recommended daily intake of 55 to 70 jug. It occurs in several forms with Se+6 being biologically most important. Selenium is readily absorbed by the intestine and is widely distributed throughout the tissues of the body, with the highest levels in the liver and kidney. It is active in a variety of cellular functions and interacts with vitamin E. Selenium appears to reduce the toxic effects of metals such as cadmium and mercury and to have anticarcinogenic activity. Selenium produces notable adverse effects both in deficiency and excess thus recommended daily intake for adults is approximately 70 Jg/day but should not exceed 200 pg/day. [Pg.124]

The synthesis and preliminary biological activity of substituted 7-alkylseleno-l,4-dihydro[l,6]naphthyridines have been reported <2000DOC218> along with their further synthetic ttansformations <2001RCB122>. There have also been reports of the preparation of selenium-containing fused heterocycles. The C=0 function in benzothiophen-3-ones, 3,4-dihydrothiopyrano[3,2-. ]benzothiophen-4(2//)-ones, and 3,4-dihydro-2//,5//-thiopyrano[2, 3 4,5]thiopyrano[3,2-/ ]ben-zothiophen-4-ones reacts with selenium dioxide and thionyl chloride to give fused 1,2,3-selena and thiadiazoles via their semicarbazones <1999IJB308>. [Pg.748]


See other pages where Selenium biological function is mentioned: [Pg.69]    [Pg.1633]    [Pg.2]    [Pg.1679]    [Pg.682]    [Pg.41]    [Pg.267]    [Pg.119]    [Pg.536]    [Pg.682]    [Pg.54]    [Pg.927]    [Pg.390]    [Pg.927]    [Pg.6827]    [Pg.667]    [Pg.268]    [Pg.27]    [Pg.493]    [Pg.1489]    [Pg.262]    [Pg.1039]    [Pg.55]    [Pg.135]    [Pg.368]    [Pg.5]    [Pg.51]    [Pg.709]    [Pg.1581]    [Pg.1]    [Pg.403]    [Pg.145]    [Pg.709]   
See also in sourсe #XX -- [ Pg.60 ]




SEARCH



Biological functionalization

Biology functional

Functional biological

Functions biological

© 2024 chempedia.info