Showing papers on "Selenium published in 2000"
TL;DR: Selenium is needed for the proper functioning of the immune system, and appears to be a key nutrient in counteracting the development of virulence and inhibiting HIV progression to AIDS.
3,359 citations
TL;DR: It is shown that at constant intakes in the nutritional range, tissue Se levels increase until a steady state is established, preventing the build-up to toxic levels, and for animals, DL-Se-met is acceptable.
Abstract: Although the need for selenium in human and animal nutrition is well recognized, the question concerning the proper form of selenium for supplemental use is still being debated. Ideally, selenium should be supplemented in the form in which it occurs naturally in foods. Because the L-isomer of selenomethionine (Se-met) is a major natural food-form of selenium, synthetic L-Se-met or enriched food sources thereof such as selenium yeast are appropriate supplemental forms of Se for humans; for animals, DL-Se-met is acceptable. Ingested Se-met is either metabolized directly to reactive forms of selenium or stored in place of methionine in body proteins. Se-met metabolism is closely linked to protein turnover. At constant intakes in the nutritional range, tissue Se levels increase until a steady state is established, preventing the build-up to toxic levels.
648 citations
TL;DR: In this paper, the toxicity of Se can be attributed to metabolic disturbances, in addition to its pro-oxidative effects, which can be explained by the changes in the total chlorophyll concentration.
Abstract: Selenium is an essential element for antioxidation reactions in human and animals. In order to study its biological role in higher plants, ryegrass (Lolium perenne) was cultivated in a soil without Se or amended with increasing dosages of H2SeO4 (0.1, 1.0, 10.0 and 30.0 mg Se kg−1). Ryegrass was harvested twice and the yields were analyzed for antioxidative systems and growth parameters. Selenium exerted dual effects: At low concentrations it acted as an antioxidant, inhibiting lipid peroxidation, whereas at higher concentrations, it was a pro-oxidant, enhancing the accumulation of lipid peroxidation products. The antioxidative effect was associated with an increase in glutathione peroxidase (GSH-Px) activity, but not with superoxide dismutase (SOD) and αα-tocopherol, which was the only tocopherol detected. In the second yield, the diminished lipid peroxidation due to a proper Se addition coincided with promoted plant growth. The oxidative stress found at the Se addition level ≥ 10 mg kg−1 resulted in drastic yield losses. This result indicates that the toxicity of Se can be attributed, in addition to metabolic disturbances, to its pro-oxidative effects. Neither the growth-promoting nor the toxic effect of Se could be explained by the changes in the total chlorophyll concentration.
492 citations
TL;DR: Results show that selenium is essential for the activity of thioredoxin reductase, explaining why this trace element is required for cell proliferation by effects on thiOREDoxin-dependent control of the intracellular redox state, ribonucleotide reduct enzyme production of deoxyribonucleotides, or activation of transcription factors.
Abstract: Selenium is an essential trace element with known antioxidant properties. Cytosolic thioredoxin reductase from mammalian cells is a dimeric flavin enzyme comprising a glutathione reductase-like equivalent elongated with 16 residues including the conserved carboxy-terminal sequence, Gly-Cys-SeCys-Gly, where SeCys is selenocysteine. Replacement of the SeCys residue by Cys in rat cytosolic thioredoxin reductase using site-directed mutagenesis and expression in Escherichia coli resulted in a functional mutant enzyme having about one percent activity with thioredoxin as a substrate through a major loss of Kcat and a shift in the pH optimum from 7 to 9. The truncated enzyme expected in selenium deficiency by the UGA mRNA codon for SeCys acting as a stop codon was also expressed. This enzyme lacking the carboxy-terminal SeCys-Gly dipeptide contained FAD but was inactive because the SeCys selenol is in the active site. These results show that selenium is essential for the activity of thioredoxin reductas...
483 citations
TL;DR: Several decades after the discovery of selenium as an essential trace element in vertebrates approximately 20 eukaryotic and more than 15 prokaryotic selenoproteins containing the 21st proteinogenic amino acid, selenocysteine, have been identified, partially characterized or cloned from several species as mentioned in this paper.
Abstract: Several decades after the discovery of selenium as an essential trace element in vertebrates approximately 20 eukaryotic and more than 15 prokaryotic selenoproteins containing the 21st proteinogenic amino acid, selenocysteine, have been identified, partially characterized or cloned from several species. Many of these proteins are involved in redox reactions with selenocysteine acting as an essential component of the catalytic cycle. Enzyme activities have been assigned to the glutathione peroxidase family, to the thioredoxin reductases, which were recently identified as selenoproteins, to the iodothyronine deiodinases, which metabolize thyroid hormones, and to the selenophosphate synthetase 2, which is involved in selenoprotein biosynthesis. Prokaryotic selenoproteins catalyze redox reactions and formation of selenoethers in (stress-induced) metabolism and energy production of E. coli, of the clostridial cluster XI and of other prokaryotes. Apart from the specific and complex biosynthesis of selenocysteine, selenium also reversibly binds to proteins, is incorporated into selenomethionine in bacteria, yeast and higher plants, or posttranslationally modifies a catalytically essential cysteine residue of CO dehydrogenase. Expression of individual eukaryotic selenoproteins exhibits high tissue specificity, depends on selenium availability, in some cases is regulated by hormones, and if impaired contributes to several pathological conditions. Disturbance of selenoprotein expression or function is associated with deficiency syndromes (Keshan and Kashin-Beck disease), might contribute to tumorigenesis and atherosclerosis, is altered in several bacterial and viral infections, and leads to infertility in male rodents.
302 citations
TL;DR: Comparison of biological activities of Se-garlic and Se-yeast was compared to elucidate how their disposition in tissues might account for the differences in cancer chemopreventive activity and the metabolism of these two compounds is discussed.
Abstract: A recent human intervention trial showed that daily supplementation with selenized yeast (Se-yeast) led to a decrease in the overall cancer morbidity and mortality by nearly 50%; past research has also demonstrated that selenized garlic (Se-garlic) is very effective in mammary cancer chemoprevention in the rat model. The goal of this study was to compare certain biological activities of Se-garlic and Se-yeast and to elucidate the differences based on the chemical forms of selenium found in these two natural products. Characterization of organic selenium compounds in yeast (1922 microg/g Se) and garlic (296 microg/g Se) was carried out by high-performance liquid chromatography with inductively coupled plasma mass spectrometry or with electrospray mass spectrometry. Analytical speciation studies showed that the bulk of the selenium in Se-garlic and Se-yeast is in the form of gamma-glutamyl-Se-methylselenocysteine (73%) and selenomethionine (85%), respectively. The above methodology has the sensitivity and capability to account for >90% of total selenium. In the rat feeding studies, supplementation of Se-garlic in the diet at different levels consistently caused a lower total tissue selenium accumulation when compared to Se-yeast. On the other hand, Se-garlic was significantly more effective in suppressing the development of premalignant lesions and the formation of adenocarcinomas in the mammary gland of carcinogen-treated rats. Given the present finding on the identity of selenomethionine and gamma-glutamyl-Se-methylselenocysteine as the major form of selenium in Se-yeast and Se-garlic, respectively, the metabolism of these two compounds is discussed in an attempt to elucidate how their disposition in tissues might account for the differences in cancer chemopreventive activity.
302 citations
TL;DR: It is concluded that the nutritional status of the laying hen determines the efficiency of the antioxidant system throughout embryonic and early postnatal development of the offspring.
Abstract: 1. The effects of selenium and vitamin E supplementation of the maternal diet on their transfer to the egg yolk and tissues of the newly hatched chick and on the development of the antioxidant system in the chick liver in early postnatal life were investigated. 2. One hundred Cobb broiler breeder hens were divided into 10 equal groups and housed in pens at 25 weeks of age. Each hen received 1 of the treatment diets which included 0.2 or 0.4 mg/kg selenium, 40, 100, 200 mg/kg vitamin E or their combination. After 6 weeks, the hens were artificially inseminated once per week. From week 8, eggs were collected and placed in an incubator. After hatching, chicks from each group were reared (under standard commercial conditions) to 10 d of age. The chicks were fed on a standard starter commercial broiler diet. At the time of hatching, and at 5 and 10 days old, 4 chicks from each group were sacrificed and blood, liver and brain were collected for the subsequent biochemical analyses. 3. The inclusion of organic selenium or vitamin E in the commercial diet significantly increased their concentration in the egg and in the liver of 1-d-old chicks obtained from the eggs enriched with these substances. A positive effect of such dietary supplementation was seen at d 5 and d 10 of postnatal development. 4. There was a positive effect of selenium supplementation of the maternal diet on glutathione concentration in the liver of 1-d-old and 5-d-old chicks. A combination of a dietary selenium supplementation with high vitamin E doses further increased glutathione concentration in the liver. Dietary selenium supplementation significantly increased selenium-dependent glutathione peroxidase (Se-GSH-Px) activity in the liver of the 1-d-old and 5-d-old chicks and decreased liver susceptibility to peroxidation. 6. It is concluded that the nutritional status of the laying hen determines the efficiency of the antioxidant system throughout embryonic and early postnatal development of the offspring.
289 citations
TL;DR: Methylation of the p53 promoter region of Caco-2 cells decreased when cells were cultured in the absence of selenite and in the absent of arsenite, suggesting alterations in DNA methylation may be a potential mechanism, whereby deficient dietary selenium increases liver and colon tumorigenesis.
Abstract: Selenium is an essential trace element for human health, and it has received considerable attention for its possible role as an anticarcinogenic agent. The purpose of the present study was to determine whether changes in the amount and the chemical form of selenium would affect DNA methylation and whether this effect would be modified by arsenic. Caco-2 cells, a human colon cancer cell line, were exposed to 0, 1 or 2 micromol supplemental selenite/L and 0, 1 or 2 micromol supplemental arsenite/L for 7 d. DNA isolated from Caco-2 cells not treated with selenite was significantly (P: < 0. 0001) hypomethylated compared with that from cells treated with 1 or 2 micromol selenite/L. DNA isolated from Caco-2 cells not treated with arsenite was significantly (P: < 0.0001) hypomethylated compared with DNA isolated from cells treated with 1 or 2 micromol arsenite/L. In addition, methylation of the p53 promoter region of Caco-2 cells decreased when cells were cultured in the absence of selenite and in the absence of arsenite. Sixty weanling male Fischer 344 rats were fed a torula yeast-based diet supplemented with 0, 0.1 or 2 mg selenium/kg diet as either selenite or selenomethionine in the presence or absence of 5 mg arsenic/kg diet as arsenite for 6 wk. Similar to the results with Caco-2 cells, rats fed selenium-deficient diets had significantly (P: < 0.0001) hypomethylated liver and colon DNA compared with rats fed 0.1 or 2.0 microg selenium/g diets as either selenite or selenomethionine. Thus, alterations in DNA methylation may be a potential mechanism, whereby deficient dietary selenium increases liver and colon tumorigenesis.
252 citations
01 Sep 2000-Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment
TL;DR: Dietary exposure of the UK population to lead is falling as a result of measures taken to reduce lead contamination of the environment and food and is well below the PTWI.
Abstract: Concentrations of aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc were determined in samples from the 1997 UK Total Diet Study and used to estimate dietary exposures of the general UK population. Population average dietary exposures to aluminium (3.4mg/day), arsenic (0.065mg/day), cadmium (0.012mg/day), chromium (0.10mg/day), copper (1.2mg/day), mercury (0.003mg/day), nickel (0.13mg/day), tin (1.8mg/ day) and zinc (8.4mg/day) are similar to those from previous UK Total Diet Studies and are below the appropriate PTWIs, PMTDIs and TDIs. Dietary exposure of the UK population (0.026 mg/day) to lead is falling as a result of measures taken to reduce lead contamination of the environment and food and is well below the PTWI. There has been little change in UK estimates of selenium exposure since the 1994 Total Diet Study but current estimates (0.039mg/day) are lower than those derived from earlier Total Diet Studies.
252 citations
TL;DR: The action of selenium is compared to that of insulin and the available evidence in support ofselenium as an insulin mimetic is discussed.
Abstract: Insulin or agents that can mimic its action (insulin mimetics) are necessary to promote the entry of glucose into tissues where the glucose can either be converted into energy or stored for later use. In recent years, selenium has been shown to mediate a number of insulin-like actions both in vivo and in vitro. These insulin-like actions include stimulating glucose uptake and regulating metabolic processes such as glycolysis, gluconeogenesis, fatty acid synthesis and the pentose phosphate pathway. The mechanism by which selenium is capable of mimicking insulin is not clear; however, reports indicate that selenium does activate key proteins involved in the insulin-signal cascade. Various proteins in the insulin-signal cascade have been shown to be necessary for different insulin-regulated events, and presumably data will be forthcoming soon that illustrate this similarly for selenium. This review compares the action of selenium to that of insulin and discusses the available evidence in support of selenium as an insulin mimetic.
234 citations
TL;DR: In this article, the authors studied selenate and selenite sorption by amorphous Fe oxide [am-Fe(OH){sub 3}] and goethite ({alpha}-feOOH) as a function of time, pH, ionic strength, and total Se concentration.
Abstract: The authors studied selenate and selenite sorption by amorphous Fe oxide [am-Fe(OH){sub 3}] and goethite ({alpha}-feOOH) as a function of time, pH, ionic strength, and total Se concentration. They examined sorbed selenate and selenite by in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and electrophoresis to deduce sorption mechanisms. Sorption of both selenate and selenite reached equilibrium in <25 min and the sorption isotherm was not reversible. Increasing ionic strength decreased selenate sorption but did not affect selenite sorption. The presence of either selenate or selenite lowered the electrophoretic mobility (EM) and decreased the point of zero charge (PZC) of both sorbents, suggesting inner-sphere complexation for both selenate and selenite species. Both in situ ATR-FTIR and DRIFT difference spectra showed bidentate complexes of selenate with am-Fe(OH){sub 3}. The structure of selenite complexes in am-Fe(OH){sub 3}-solution interface was uncertain due to insensitivity of the in situ ATR-FTIR technique. The DRIFT spectra of selenite on am-Fe(OH){sub 3} showed {nu}{sub 3} splitting as evidence of complexation. The DRIFT spectra of selenite on goethite showed bridging bidentate complex of selenite. The authors conclude that the influence of ionic strength on Se sorption cannot be usedmore » as a criterion for distinguishing outer- vs. inner-sphere complex formation.« less
TL;DR: Selenium-enriched plants, such as hyperaccumulative phytoremediation plants, and reference samples with natural selenium levels, including onion and garlic controls, cooking garlic powder, baking yeast powder and a commercial garlic supplement were analyzed by HPLC-ICP-MS for theirSelenium content and speciation after hot water and enzymatic extractions.
Abstract: Selenium-enriched plants, such as hyperaccumulative
phytoremediation plants (Astragalus praleongus, 517 μg
g−1 Se, and Brassica juncea, 138 μg
g−1 Se in dry sample), yeast (1200, 1922 and 2100, μg
g−1 Se in dry sample), ramp (Allium tricoccum,
48, 77, 230, 252, 405 and 524 μg g−1 Se in dry sample),
onion (Allium cepa, 96 and 140 μg g−1 Se in
dry sample) and garlic (Allium sativum, 68, 112, 135, 296, 1355
μg g−1 Se in dry sample) were analyzed by HPLC-ICP-MS
for their selenium content and speciation after hot water and enzymatic
extractions. Reference samples with natural selenium levels, such as onion
and garlic controls, cooking garlic powder, baking yeast powder and a
commercial garlic supplement were also analyzed. Selected samples were also
examined by HPLC-electrospray ionization (ESI)-MS. HPLC was mostly carried
out with 0.1% heptafluorobutanoic acid (HFBA) as ion-pairing agent in 1 +
99 v/v methanol–water solution, but 0.1% trifluoroacetic acid (TFA)
in 1 + 99 v/v methanol–water solution was also utilized to permit
chromatography for compounds that did not elute with HFBA. More than 75% of
the total eluting selenium compounds, based upon element specific
detection, were identified from retention time data and standard spiking
experiments, and between 60 and 85% of compounds were identified by MS,
with up to 25% of the total eluting molecular selenium species being
unidentified as yet. Limits of quantification (LOQ, defined as the
concentration giving an S/N of 10) for HPLC-ICP-MS were in the range
2–50 ng mL−1 Se in the injected extracts for the
selenium-enriched samples and 2–10 ng mL−1 Se for
the natural selenium level samples. LOQ values for HPLC-ESI-MS were
ca. 100 times higher than those measured by HPLC-ICP-MS.
TL;DR: Comparative studies showed, that Pyrobaculum aerophilum was also able to grow organotrophically under anaerobic culture conditions in the presence of arsenate, selenate and selenite, and in contrast to P. arsenaticum, P. aerophILum could use selenates or arsenate for lithoautotrophic growth with carbon dioxide and hydrogen.
TL;DR: Hg and Se near-edge X-ray absorption spectroscopy of erythrocytes, plasma, and bile of rabbits that had been injected with solutions of sodium selenite and mercuric chloride showed that HG and Se in plasma samples exhibited X-rays that were essentially identical to those of the synthetic Hg-Se-S species.
Abstract: Mercuric chloride toxicity in mammals can be overcome by co-administration of sodium selenite We report a study of the mutual detoxification product in rabbit plasma, and of a Hg-Se-S-containing species synthesized by addition of equimolar mercuric chloride and sodium selenite to aqueous, buffered glutathione Chromatographic purification of this Hg-Se-S species and subsequent structural analysis by Se and Hg extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of four-coordinate Se and Hg entities separated by 261 A Hg and Se near-edge X-ray absorption spectroscopy of erythrocytes, plasma, and bile of rabbits that had been injected with solutions of sodium selenite and mercuric chloride showed that Hg and Se in plasma samples exhibited X-ray absorption spectra that were essentially identical to those of the synthetic Hg-Se-S species Thus, the molecular detoxification product of sodium selenite and mercuric chloride in rabbits exhibits similarities to the synthetic Hg-Se-S species The underlying molecular mechanism for the formation of the Hg-Se-S species is discussed
TL;DR: Findings support previous results found in liver tissue of marine mammals, suggesting that methyl mercury is detoxified by a chemical mechanism involving selenium, and should be monitored to elucidate whether this protective mechanism can be maintained in target organs.
TL;DR: Using X-ray absorption spectroscopy, a new arsenic−selenium compound is identified in the bile of rabbits injected with aqueous selenite and arsenite solutions, which provides a molecular basis for the antagonistic interaction between these metalloid compounds and a potential explanation of the association of cancer with prolonged intake of inorganic arsenic in humans.
Abstract: Among the most startling observations in mammalian toxicology is that a lethal dose of selenium can be overcome by an otherwise lethal dose of arsenic. We report the molecular basis of this antagonism. Using X-ray absorption spectroscopy we have identified a new arsenic−selenium compound in the bile of rabbits injected with aqueous selenite and arsenite solutions. This compound contains equimolar arsenic and selenium and exhibits X-ray absorption spectra which are essentially identical with those of a synthetic species in solution which we have identified spectroscopically as the seleno-bis(S-glutathionyl) arsinium ion. The in vivo detection of this compound links the mammalian metabolism of arsenite, selenite, and sulfur. It provides a molecular basis for the antagonistic interaction between these metalloid compounds, and a potential explanation of the association of cancer with prolonged intake of inorganic arsenic in humans.
Book•
01 Jan 2000
TL;DR: In this paper, Selenium compounds as ligands and catalysts are used as catalysts for carbanions in higher Oxidation State.and general Aspects.- Electrophilic Selenium, Selenocyclization, Nucleophilic and Nucleic Selenium.
Abstract: and General Aspects.- Electrophilic Selenium, Selenocyclizations.- Nucleophilic Selenium.- Radical Reactions Using Selenium Precursors.- Selenium-Stabilized Carbanions.- Selenium at Higher Oxidation State.- Selenocarbonyls.- Selenoxide Elimination and [2,3]Sigmatropic Rearrangement.- Selenium Compounds as Ligands and Catalysts.
TL;DR: The different and contrasting effects that Se supplementation had on blood selenoenzyme activities may be indicative of a difference in metabolic need for Se regulated at the level of Se-dependent cell function.
Abstract: The blood selenium (Se) concentration in the U.K. population has declined by approx. 50% between 1974 and 1991, reflecting a large decrease in dietary Se supply, with intakes only half the reference nutrient intake of 1 microg/kg body weight. Tissue levels of Se are readily influenced by dietary intake. Therefore selenoprotein activity may be sub-optimal due to low Se status, and thus compromise normal cell function. To examine the effects of changing Se intake on selenoproteins, we have determined the relative effectiveness of organic selenomethionine and inorganic sodium selenite (50 microg of Se daily for 28 days) in modulating glutathione peroxidase activities in blood cells from 45 healthy men and women, from a U.K. population. Transient and acute changes in lymphocyte, granulocyte and platelet phospholipid-hydroperoxide glutathione peroxidase (GPx4) activity occurred by day 7 or 14 of sodium selenite treatment and by day 7 in lymphocytes from selenomethionine-treated subjects compared with controls taking a placebo. In contrast, GPx4 activity in granulocytes and platelets in the selenomethionine group increased gradually over the 28 days. Cytosolic glutathione peroxidase (GPx1) activity in these blood cells from both treatment groups increased gradually over the 28 days. For each cellular selenoenzyme activity a significant inter-individual difference (P<0.001) in the extent of the response to Se supplementation was observed, but this was not related to blood Se concentrations either before or after treatments. Significant inverse correlations were evident between baseline enzyme activities and percentage change in activity after 28 days of supplementation [e.g. lymphocyte GPx4, r=-0.695 (P<0.001)], indicating that pre-treatment activity may be sub-optimal as a result of poor Se status. The different and contrasting effects that Se supplementation had on blood selenoenzyme activities may be indicative of a difference in metabolic need for Se regulated at the level of Se-dependent cell function.
TL;DR: Topical hypotheses on the biological role of selenium in general and of individual selenoproteins in respect to antioxidant defense, redox regulation of metabolic processes, thyroid function, spermatogenesis, oncogenesis, and atherogenesis are critically evaluated.
Abstract: The present status of selenium biochemistry is reviewed with particular emphasis on biomedical problems related to the selenium status of humans and experimental animals. Historical milestones of selenium biochemistry starting from the identification of the first selenoenzymes up to the elucidation of prokaryotic and eukaryotic selenoprotein biosynthesis are compiled. Topical hypotheses on the biological role of selenium in general and of individual selenoproteins in respect to antioxidant defense, redox regulation of metabolic processes, thyroid function, spermatogenesis, oncogenesis, and atherogenesis are critically evaluated.
TL;DR: In vitro and in vivo data suggest that METH-induced neurotoxicity is mediated by the production of peroxynitrite, and selenium plays a protective role in Meth- induced neurotoxicity.
TL;DR: Under suitable conditions the undesirable inorganic selenium content of the yeast could be suppressed to as low as 5-6% at the expense, however, of approximately a 20% decrease in the final biomass.
TL;DR: The effects of a variety of parameters on the reduction of soluble selenium by a Bacillus sp.
TL;DR: Inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was characterised for the detection of the six naturally occurring selenium isotopes as mentioned in this paper.
Abstract: Inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was characterised for the detection of the six naturally occurring selenium isotopes. The potentially interfering argon dimers at the selenium masses m/z 74, 76, 78 and 80 were reduced in intensity by approximately five orders of magnitude by using methane as reactive cell gas in the DRC. By using 3% v/v methanol in water for carbon-enhanced ionisation of selenium, the sensitivity of 80Se was 104 counts s−1 per ng ml−1 of selenium, and the estimated limit of detection was 6 pg ml−1. The precision of the isotope ratios was close to the theoretical values for selenium concentrations at 1 and 10 ng ml−1. The accuracy of the isotope ratios, however, was improved by correcting the count rate of all selenium isotopes equivalent to the formation of SeH at 9.6 ± 0.5% one mass unit above the selenium isotopes. A linear relationship (r < 0.98) was found between the error of the corrected isotope ratios and the difference in mass from the 80Se reference isotope. This indicated that the error was caused by mass bias. The slope of the curve at −3.0% error per mass unit can be used for correction of the measured ratios. Deuterated methane used as the DRC gas showed that hydrogen transfer from methane was not involved in the formation of SeH as SeD was absent in the mass spectrum. The almost interference-free detection of selenium by ICP-DRC-MS made the detection of the 80Se isotope possible for detection of selenoamino acids separated by cation exchange HPLC. The limit of detection of the HPLC-ICP-DRC-MS method was in the range 3–5 pg as selenium.
TL;DR: In this paper, the new development and application of this technique for speciation and analysis of mercury, arsenic and selenium are discussed, as well as its application for the determination of environmentally and biomedically important elements.
Abstract: Atomic fluorescence spectrometry is a very sensitive and selective method for the determination of a number of environmentally and biomedically important elements. The new development and application of this technique for speciation and analysis of mercury, arsenic and selenium are discussed here.
TL;DR: In this paper, a garlic sample was leached with water and the aqueous extract was fractionated by preparative size-exclusion chromatography and the chromatographic purity of the fraction was verified by reversed phase chromatography with inductively coupled mass spectrometric detection.
TL;DR: In this paper, the available phase-diagram data for the Cu-Se system are critically evaluated, and the T-x and p-T phase diagrams are optimized, and thermodynamic properties and polymorphism of copper selenides are analyzed.
Abstract: The available phase-diagram data for the Cu-Se system are critically evaluated, and theT-x andp-T phase diagrams are optimized. The thermodynamic properties and polymorphism of copper selenides are analyzed.
TL;DR: The stability of arsenic, selenium, antimony and tellurium species in water and urine as well as in extracts of fish and soil certified reference materials has been investigated and losses and species transformations during extraction processes were investigated.
Abstract: The stability of arsenic, selenium, antimony and tellurium species in water and urine (NIST SRM 2670n) as well as in extracts of fish and soil certified reference materials (DORM-2 and NIST SRM 2710) has been investigated. Stability studies were carried out with As(III), As(V), arsenobetaine, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), phenylarsonic acid (PAA), Se(IV), Se(VI), selenomethionine, Sb(III), Sb(V) and Te(VI). Speciation analysis was performed by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Best storage of aqueous mixtures of the examined species was achieved at 3 degrees C whereas at -20 degrees C species transformation especially of selenomethionine and Sb(V) took place and a new selenium species appeared within a period of 30 days. Losses and species transformations during extraction processes were investigated. Extraction of the spiked fish material with methanol/water led to partial conversion of Sb(III), Sb(V) and selenomethionine to two new antimony and one new selenium species. The other arsenic, selenium and tellurium species were almost quantitatively extracted. For soil spiked with MMA, PAA, Se(IV) and Sb(III), recoveries after extraction with water and sulfuric acid (0.01 mol/L) were below 20%.
TL;DR: It is concluded that selenium acts on granulosa cells by modulating their proliferation and E2 synthesis; moreover, its effect could be mediated, at least in part, through an inhibition of nitric oxide.
TL;DR: It was shown that sunflower sprouts were the most resistant and had the highest uptake rates, but almost 100% of the selenium was extracted with water and found to be nonmetabolized selenate, indicating a high metabolism rate.
Abstract: The selenium supply in almost all European countries, including Austria and Germany, is below the recommended daily intake. In these countries, selenium fortification of foods and the use of selenium supplements are quite popular to compensate for low Se intake from diets. In general, wheat (Triticum aestivum) is known to be a good source for bioavailable selenium, and many studies have been performed to enrich selenium in wheat by selenium fertilization of the soil. In the present work, the process of sprouting was investigated as an alternative to enrich selenium in wheat. Sprouting was chosen because it additionally improves the nutritional value of seeds, for example, by a higher vitamin content, a better quality of protein, and some other parameters. Wheat, alfalfa (Medicago sativa), and sunflower (Helianthus annuus) seeds were germinated for 5 and 7 days in solutions containing selenate. The selenium sensitivity of the sprouts was tested by measuring visible germination levels and seedling developme...
TL;DR: In this paper, the authors used double spike (82Se and 74Se) thermal ionization mass spectrometry technique to quantify the isotopic fractionation achieved by three different species of anaerobic bacteria.