Selenium cancer

Selenium, an essential micronutrient for plants, animals and microorganisms, has a direct impact on human health and environmental safety. Thus, Se supplementation of populations with low or deficient Se intakes may improve health, and supplementation of Se to populations with adequate intakes may reduce the risk of cancer. Selenium levels in the body are relevant for protection against chronic degenerative, neurological or neoplastic diseases. 

This is due to nitrogen s ability to form strong tt bonds whereas heavier group 5A elements do not form strong tt bonds. Therefore, P2, AS2, and Sb2 do not form since two tt bonds are required to form these diatomic substances. 3. There are medical studies that have shown an inverse relationship between the incidence of cancer and the selenium levels in soil. The foods grown in these soils and eventually digested are assumed to somehow furnish protection from cancer. Selenium is also involved in the activity of vitamin E and certain enzymes in the human body. In addition, selenium deficiency has been linked... 

Selenium is widely sold as a dietary supplement. It is advertised to protect women from breast cancer. Write the nuclear symbol for naturally occurring selenium. It has 34 protons and 46 neutrons. 

There is considerable evidence to suggest that selenium compounds are anticarcinogens. For one thing, tests with laboratory animals show that the incidence and size of malignant tumors are reduced when a solution containing Na2Se03 is injected at the part per million level. Beyond that evidence, statistical studies show an inverse correlation between selenium levels in the soil and the incidence of certain types of cancer. 

Dorgan, J.F. et al.. Relationships of serum carotenoids, retinol, alpha-tocopherol, and selenium with breast cancer risk results from a prospective study in Columbia, Missouri (United States), Cancer Causes Control, 9, 89, 1998. 

Selenium is required, but levels must fall into a narrow window. Both deficiency and toxicity symptoms occur. The element is also used therapeutically in cancer treatment. It is the co-factor of the enzyme glutathione peroxidase which is thought to play an important role in oxygen toxicity. The determination of Se in blood or serum is not easy, as many incorrect, inaccurate and imprecise methods have been published (Magee and James 1994). A suggested procedure for Se in body fluids is based on GF-AAS (Thomassen et al. 1994)- For tissues SS-AAS may be used (Fler-ber 1994a). Recent developments by Turner et al. (1999) show that LC-ICP-MS is sensitive and reproducible at low levels. 

Currently, one of the most promising agents for the prevention of lung cancer is selenium, which appeared to prevent the development of lung tumors in patients with skin cancer.15 This has not yet been shown in patients without preexisting skin cancer, although studies are underway. 

The risk of colon cancer appears to be inversely related to calcium and folate intake. Calciums protective effect may be related to a reduction in mucosal cell proliferation rates or through its binding to bile salts in the intestine, whereas dietary folate helps in maintaining normal bowel mucosa. Additional micronutrient deficiencies have been demonstrated through several studies to increase colorectal cancer risk and include selenium, vitamin C, vitamin D, vitamin E, and 3-carotene however, the benefit of dietary supplementation does not appear to be substantial.11... 

Additional agents, including selenium, folic acid, and HMG-CoA reductase inhibitors (statins), show promise as chemopreventive agents in colon cancer, and preliminary and confirmatory studies evaluating their effectiveness have been completed or are ongoing, although none of these agents have been approved for the prevention of colon cancer.46... 

Other agents, including selenium, vitamin E, lycopene, green tea, nonsteriodal anti-inflammatory agents, isoflavones, and statins, are under investigsation for prostate cancer and show promise. Selenium is a naturally occurring trace element that is an essential nutrient in the human diet.8 However, none of these agents is currently recommended for routine use outside a clinical trial. 

Multicomponent reactions (MCRs) have been known to produce highly complex and diverse structures [76]. There is a considerable interest in the application of new multicomponent reactions to access biologically relevant molecules [77,78] and natural products [79]. A recent report has disclosed multicomponent Passerini and Ugi reactions to produce, rapid and efficiently, a library of redox-active selenium and tellurium compounds [80]. The compounds showed promising cytotoxicity against several cancer cell lines. 

Helzlsouer KJ, Comstock GW and Morris JS. 1989. Selenium, lycopene, alpha tocopherol, beta carotene, retinol, and subsequent bladder cancer. Cancer Res 49 6144-6148. 

Ip C, Lisk DJ. 1994. Enrichment of selenium in album vegetables for cancer prevention. Carcinogenesis 15 1881-1885. 

Ip C, Lisk DJ and Stoewasand GS. 1992. Mammary cancer prevention by regular garlic and selenium enriched garlic. Nutr Cancer 17 279-286. 

Glickstein, N. 1978. Acute toxicity of mercury and selenium to Crassostrea gigas embryos and Cancer magister larvae. Mar. Biol. 49 113-117. 

Schrauzer, G.N., Effects of selenium antagonists on cancer susceptibility New aspects of chronic heavy metal toxicity, J UOEH 9, 208, 1987. 

Probably the most effective use of XRF and TXRF continues to be in the analysis of samples of biological origin. For instance, TXRF has been used without a significant amount of sample preparation to determine the metal cofactors in enzyme complexes [86]. The protein content in a number of enzymes has been deduced through a TXRF of the sulfur content of the component methionine and cysteine [87]. It was found that for enzymes with low molecular weights and minor amounts of buffer components that a reliable determination of sulfur was possible. In other works, TXRF was used to determine trace elements in serum and homogenized brain samples [88], selenium and other trace elements in serum and urine [89], lead in whole human blood [90], and the Zn/Cu ratio in serum as a means to aid cancer diagnosis [91]. 

---