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a chemical element, atomic number 34, atomic weight 78.96, symbol Se. (See Appendix 6.) It is an essential mineral nutrient. Dietary sources of selenium include seafoods, kidney, and liver. Humans can adjust their homeostasis mechanism for selenium over a wide range of dietary intakes. Recommended intake levels are generally met from the diet, so that supplements are not necessary.
1. the sulfide salt of selenium, a topical antiseborrheic and antifungal applied topically to the scalp to control seborrheic dermatitis and dandruff; also used topically in the treatment of tinea versicolor.
A metallic element chemically similar to sulfur, atomic no. 34, atomic wt. 78.96; an essential trace element toxic in large quantities that is required for glutathione peroxidase and a few other enzymes; 75Se (half-life equal to 119.78 days) is used in scintography of the pancreas and parathyroid glands.
[G. selēnē, moon]
selenium/se·le·ni·um/ (sĕ-le´ne-um) a chemical element, at. no. 34, symbol Se; it is an essential mineral nutrient, being a constituent of the enzyme glutathione peroxidase.
Etymology: Gk, selene, moon
a metalloid element of the sulfur group. Its atomic number is 34, and its atomic mass is 78.96. Selenium occurs mainly in iron, copper, lead, and nickel ores in the form of metallic selenides. One of the chief commercial sources is the flue dust produced by the burning of pyrites to make sulfuric acid. Selenium occurs as a trace element in foods, and research continues to determine the most effective daily allowances for different age groups. Dietary experts say that the estimated safe, adequate intake of selenium for infants 6 months of age is 0.04 mg, for adults 0.05 to 0.2 mg. Although selenium deficiency can result in liver problems and degeneration of muscles in some animals, in humans its need has not yet been clearly defined. The bright orange insoluble powder selenium sulfide is used externally in the control of seborrheic dermatitis, dandruff, and other forms of dermatosis. Selenium sulfide, used as a lotion, is used in some therapeutic shampoos as 2.5% of selenium sulfide in a detergent vehicle; it is sold without prescription as a 1% detergent suspension in a scented detergent vehicle. Adverse effects may include conjunctivitis if the preparation enters the eyes, increased oiliness or dryness of the hair, and orange tinting of gray hair. The antidandruff effectiveness of selenium sulfide is thought to stem from its antimitotic activity and its residual adherence to the hair after shampooing. Normal skin absorbs very little of the drug, but inflamed or damaged skin absorbs it readily. Selenium is used in the nuclear medicine compound selenomethionine for diagnosing parathyroid tumors. The element is also used as a photoconductive layer of xeroradiographic plates. Burns and dermatitis venenata may result from prolonged skin contact.
seleniumA non-metallic element (atomic number 34; atomic weigh 8.96) that is required in trace amounts by certain enzymes (e.g., glutathione peroxidase); it interacts with vitamins A, C and E, serving as an antioxidant. Selenium is believed to be anticarcinogenic, to retard ageing, and has been used for arthritis, cataracts, connective tissue disease, dandruff and age-related vision loss.
Brewer’s yeast, cereals, dairy products, fish, fruits, liver, organ and muscle meats, seafood, vegetables and whole grains.
A metallic element chemically similar to sulfur; atomic no. 34, atomic wt. 78.96; an essential trace element toxic in large quantities; required for glutathione peroxidase and a few other enzymes; 75Se (half-life equal to 119.78 days) is used in scintography of the pancreas and parathyroid glands.
[G. selēnē, moon]
seleniumA trace element recently found to be an essential component of the enzyme deiodinase which catalyses the production of triiodothyronine (T3) from thyroxine (T4) in the thyroid gland. Selenium deficiency prevents the formation of T3.
seleniumfunctions as an antioxidant by serving as cofactor for the enzyme glutathione peroxidase. A few studies have suggested a benefit of selenium supple mentation in improving antioxidant capacity and dim inishing cancer occurrence. Selenium may possibly be effective in athletes who are ingesting insufficient amounts, but it is not known if marginally insufficient intake compromises efficiency of training. Excessive amounts of selenium could have toxic effects. See also minerals; appendix 4.3 .
n an essential element/mineral found in most vegetables, breads, and meats. Has been used in AIDS, asthma, car-diovascular conditions, cataracts, cervical dysplasia, multiple sclerosis, osteoarthritis, and rheumatism. No known precautions, but selenium supplementation is toxic at daily doses greater than 750 μg.
A metallic element used in scintography of pancreas and parathyroid glands.
[G. selēnē, moon]
selenium (Se) (səlē´nēum),
n a trace element used in the treatment of seborrhea and dandruff of the scalp. Selenium is toxic in large amounts.
n a genus of gram-negative, anaerobic, rod-shaped bacteria found in the oral cavity.
a chemical element, atomic number 34, atomic weight 78.96, symbol Se. See Table 6. It is an essential mineral nutrient and a very potent poison.
a radioisotope of selenium having a half-life of 120 days and a principal gamma ray photon energy of 265 keV; used in the radiopharmaceutical selenomethionine. Symbol 75Se.
selenium accumulator plants
see accumulator plants.
selenium converter plants
see converter plants.
selenium indicator plants
see indicator plants.
selenium-induced infection resistance
selenium deficiency in the diet may increase the patient's susceptibility to infection.
selenium nutritional deficiency
there are well-defined deficiency and poorly defined selenium responsive diseases. A nutritional deficiency of vitamin E has many of the same effects of selenium deficiency and it is often difficult to separate the two. See also enzootic muscular dystrophy, mulberry heart disease, hepatosis dietetica, iron poisoning, weaner illthrift.
can occur on pasture growing on selenium rich soil, especially if there are selenium indicator plants growing in it. Also when selenium supplementation is carried out carelessly and there is accidental access to poisonous amounts. Acute poisoning features diarrhea, dyspnea and death. Subacute poisoning is hallmarked by blind staggers (see dummy). Chronic poisoning produces a syndrome of stiff gait, loss of haircoat and separation, perhaps sloughing, of the hooves. Called also alkali disease.
diseases such as reproductive inefficiency and illthrift in sheep and cattle respond in some situations to dietary supplementation with selenium but the diseases are not proven to be caused by nutritional deficiency of the element.
selenium sulfide, selenium disulfide
a commonly used keratolytic in medicated shampoos employed in the treatment of skin disease in dogs and cats.