Topic
Selenium
About: Selenium is a research topic. Over the lifetime, 21192 publications have been published within this topic receiving 429715 citations. The topic is also known as: Se & selen.
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TL;DR: In this article, the results suggest metabolic involvement in the uptake and long distance transport of solenium supplied as selenite, despite lower Se concentrations in the xylem exudate than in the external solution.
Abstract: Selenate and selenite transport through tomato root systems were followed for periods up to 4 h after removal of the plant tops, using Se as a tracer.With selenate, Se concentrations in the xylem exudate were 6 to 13 times higher than in the external solution, and chromatographic analysis showed that the selenium was transported as inorganic selenate (SeO42-).With selenite, Se concentrations in the exudate were always lower than in the external solution. Analyses of exudate samples showed that negligible amounts of selenium were transported as inorganic selenite (HSeO3-except at very high external selenite concentrations (500 μM), when up to 7 per cent was transported as selenite. Most of the selenium transport in selenite-fed plants was as selenate or as an unknown selenium compound, the relative proportions of these two forms varying both with time and with external selenite concentration. Addition of a 5-fold excess of sulphate over selenite had no detectable effect on the concentrations of selenate in the exudate, but caused substantial decreases in the maximum concentrations of both total selenium (c. 47 per cent decrease) and the unknown selenium compound (c. 69 per cent decrease). Addition of a 5-fold excess of sulphite decreased the concentration of the unknown (c. 39 per cent) but caused a large (2.7-fold) increase in the maximum total selenium concentration in the exudate and a 7.9-fold increase in the maximum concentration of selenate. The results suggest metabolic involvement in the uptake and long distance transport of solenium supplied as selenite, despite lower Se concentrations in the xylem exudate than in the external solution. An attempt is made to incorporate the new and existing information into a selenium transport model.
102 citations
TL;DR: Both free-and protein-bound seleno-amino acids were identified and the initial steps of selenium incorporation seem to involve the use of the sulfur enzymatic machinery resulting in the replacement of some of the sulphur by selenum in both free amino acids and proteins.
102 citations
TL;DR: A demountable direct injection high efficiency nebulizer operating at low sample uptake rates was developed and used for coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) as discussed by the authors.
Abstract: A demountable direct injection high efficiency nebulizer operating at low sample uptake rates was developed and used for coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS). When the nebulizer was used for continuous sample introduction, detection limits of 20 and 1 ng L−1 were obtained for 82Se and 103Rh, respectively, at sample uptake rates of 10–30 μL min−1, based on three times the standard deviation of blank solution (3σb, n = 10). The nebulizer was used as part of the interface for coupling of CE with ICP-MS and applied for speciation of aqueous selenium standards. The interface was operated in the self-aspirating mode with a sheath liquid uptake of 10 μL min−1. The CE-ICP-MS system resulted in baseline separation of selenate, selenite, selenocystine and selenomethionine within a total analysis time of 5.4 min. Detection limits were in the sub µg Se L−1 range, corresponding to absolute detection limits in the range 25–125 fg selenium. Repeatability (n = 6) expressed as relative standard deviations with respect to migration times, peak heights and peak areas were better than 1.6, 6.7 and 6.0%, respectively.
102 citations
TL;DR: Toxicity was more pronounced when inorganic Se was applied than after subacute application of Sel‐Plex, nanoSe, or LactoMicroSe, and a comparison of lowest toxic doses of sodium selenite in mice and mallard indicates that birds are more resistant to Se than rodents.
Abstract: Sixteen groups of mice were fed diets containing different selenium species to compare their toxicity. Inorganic sodium selenate and sodium hydroselenite, elementary nanoSe, organic Sel-Plex, and Lacto-MicroSelenium were administered for 14 d at concentrations of 0.5, 5, and 50 ppm Se, equivalent to 0.5, 5, and 50 mg Se/kg food, corresponding to an estimated 4, 40, and 400 µg/kg body weight/d Se uptake, respectively. At the end of the treatment, body, liver, spleen, kidney, heart, and brain weights were measured, mice were subjected to necropsy, and histological examinations were performed on the liver. At lower Se doses (0.5 and 5 ppm) a moderate reduction was observed in the number of bone marrow and white blood cells and in granulocyte-macrophage colony-forming units (GM-CFUs) relative to the untreated control group of mice. A comparison of lowest toxic doses of sodium selenite in mice (0.5 ppm) and mallard (10 ppm) indicates that birds are more resistant to Se than rodents. In mice, a small but measurable weight loss was observed after 5 ppm selenate and LactoMicroSe treatment. The most significant changes took place after 50-ppm administration in body and spleen weight, hematology, and liver histology. Toxicity was more pronounced when inorganic Se was applied than after subacute application of Sel-Plex, nanoSe, or LactoMicroSe. To summarize the effects, the authors' 14-d murine subacute toxicity study showed that the toxicity of Se species decreased in the following order: selenate > selenite > nanoSe > Sel-Plex > LactoMicroSe.
102 citations
TL;DR: Differences in intake, speciation, or bioavailability of selenium from the yeast-based supplements in the population groups studied may explain this.
Abstract: This study investigated the speciation and bioavailability of selenium in yeast-based intervention agents from multiple manufacturers from several time points. Sources of selenized yeast included Nutrition 21 (San Diego, CA), which supplied the Nutritional Prevention of Cancer (NPC) Trial from 1981-1996; Cypress Systems (Fresno, CA; 1997-1999); and Pharma Nord (Vejle, Denmark; 1999-2000), which supplied the Prevention of Cancer by Intervention by Selenium (PRECISE) Trial pilot studies. The low-molecular-selenium species were liberated from the samples by proteolytic hydrolysis followed by separation by ion exchange liquid chromatography and detection by inductively coupled plasma-mass spectrometry. The results for the NPC tablets showed that selenomethionine, together with 3 unidentified selenium compounds, were predominant in the sample hydrolysates. The relative amounts of the 4 selenium species varied (p < 0.05) among several of the 7 tablet batches used during the course of the NPC Trial. In comparison, 5 batches of more recently produced selenized yeasts, which were used as a source of selenium in the PRECISE and other trials, contained less of the unknown compounds and more selenomethionine at 54-60% of the total selenium in the yeasts. One batch of yeast, however (from 1985), which originated from the same producer as the yeast used in the NPC tablets, contained only 27% of selenium in the sample as selenomethionine. Human subjects receiving 200 microg selenium/day in the UK PRECISE Pilot Trial showed a higher concentration (p < 0.01) and higher increase from baseline in plasma selenium than did the same dosage used in the NPC Trial. Differences in intake, speciation, or bioavailability of selenium from the yeast-based supplements in the population groups studied may explain this. Furthermore, the selenium concentration in whole blood from the Danish PRECISE Pilot Trial was higher (p < 0.001) than that obtained with synthetic L-selenomethionine in a comparable group of Danes, both groups having been treated with 300 microg selenium/day.
102 citations