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added section on selenium ingestion and aversion
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Aasif Mandvi ran a [http://www.thedailyshow.com/watch/thu-june-14-2012/a-simple-plot story] on selenium pollution of Idaho rivers as a consequence of phosphate mining.
Aasif Mandvi ran a [http://www.thedailyshow.com/watch/thu-june-14-2012/a-simple-plot story] on selenium pollution of Idaho rivers as a consequence of phosphate mining.
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+==Selenium Ingestion and Aversions==
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+Selenium is an essential micronutrient. The mammalian selenoproteome consists of some 2 dozen selenocysteine-containing proteins (24 in rodents, 25 in human) including the glutathione peroxidase, thioredoxin reductase and iodothyronine deiodinase enzymes [PMID 12775843]. However, at doses not much higher than the dietary requirement, selenium is also toxic [PMID 3527390]. Selenium toxicity is due to the generation of superoxide and other reactive oxygen species, the oxidation of thiols, and by substituting for sulfur in methionine to form selenomethione which then may be incorporated into many sulfur containing proteins [PMID 11879936].
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+Reduced intake and avoidance of toxic diets containing selenium compounds has been demonstrated in many species. Because selenium is concentrated by certain species of plants in selenium-rich geographies, selenosis is a potential hazard for livestock and native herbivores. Waste from mining or agricultural run-off can also introduce selenium into the environment and hence into the food-chain. It has therefore been of interest to determine whether species can avoid selenium-rich food sources due to an aversive taste or odor of selenium compounds, or acute toxic effects, or learned food aversions. Aphids [PMID 17831208, JSTOR 1514562], crickets and grasshoppers [PMID 17635224], southern armyworms [PMID 10467057] mallard ducks [Heinz 1990], owls [Wiemeyer 1996], prairie dogs [PMID 21628258], sheep [Pfister 2010, PMID 3527390], and cattle [PMID 3527390] have been shown to reduce intake of selenium-containing foods, or show reduced preference for selenium-containing foods over control diets.
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+In laboratory studies, rats show a preference for control or low selenium-diets over high selenium diets [PMID 17788901][Franke and Potter 1935]. Consistent with the effects of other selenium compounds, selenate adulteration also causes a reduction of food [Franke and Moxon 1937] [Smith Stohlman Lillie 1937] or water intake [PMID 6053743, PMID 1255264] Acute injection of selenate can also reduce food intake and body weight gain [PMID 2609019]
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+Only a few of these studies (e.g. [Pfister 2010, PMID 3527390, Heinz & Sanderson 1990] ) have determined if animals were responding to an acute perception of selenium compounds, or if the animals used food-associated cues, to avoid consumption, after acquiring a selenium-induced conditioned food aversion. Selenium absorbing plants may themselves have salient taste or odor: for example, Provenza et al. have demonstrated that the odor of Astragalus bisulcatus, a sulfur-containing selenium-absorbing plant, can serve as a CS that reduced preference for CS+barley-straw after pairing with oral-intubation of LiCl. [Oikos 88(2000)424-432.] Selenium compounds may also present distinctive cues, e.g., the volatile dimethyldiselenide, a major metabolite of selenite and selenate, has a pungent garlic odor to humans, that may be innately aversive or serve as an indicative CS in learned selenium aversions.
==Government Documents on Selenium Safety==
==Government Documents on Selenium Safety==