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PubMed1992

Selenium, glutathione peroxidase (GSH-Px) and lipid peroxidation products before and after selenium supplementation.

Treated phenylketonuric (PKU) children are at risk of selenium deficiency. We have studied 15 treated PKU children and 30 control children. We observed significantly lower (P less than 0.0005) plasma and erythrocyte selenium, as well as significantly lower (P less than 0.0005) plasma and erythrocyte glutathione peroxidase activities (GSH-Px) in PKU children than in controls. The lipid peroxidation products, evaluated as plasma malondialdehyde (MDA), was higher (P less than 0.0005) in PKU children than in controls. Specific oral sodium selenite supplementation (Selenium: 0.13 mumol/kg/day) resulted in a rapid increase of plasma selenium and GSH-Px activity, and after 10 days and 1 month respectively significant difference is no longer observed between PKU children and controls values. Statistically significant differences in erythrocyte selenium, erythrocyte GSH-Px activity and plasma MDA between PKU and control children disappear after respectively 2 months, 4 months and 6 months of selenium supplementation.

Child↗
PubMed1980

Dependence of the sister-chromatid exchange-inducing abilities of inorganic selenium compounds on the valence state of selenium.

Inorganic selenium (Se) compounds having Se of different valence states were tested for their abilities to induce sister-chromatid exchanges (SCEs) in human whole blood cultures. The Se compounds tested (and their Se valence states) were: sodium selenide (Se(2-)), selenium dioxide (Se(4+)), selenium (Se(0)), sodium selenate (Se(6+)), and sodium selenite (Se(4+)). Human whole blood cultures were exposed to concentrations of these compounds ranging from 1.12 X 10(-6)-8.00 X 10(-5) M for the final 18 h of the 96-h incubation period. Only sodium selenate failed to induce SCEs at high concentrations. Of the 4 SCE-inducing Se compounds studied selenium was the most potent inducer of SCEs, and sodium selenite was the least effective SCE-inducing agent. The SCE-inducing abilities of the Se compounds in decreasing order of their effectiveness were: selenium > selenium dioxide > solium selenide > sodium selenite > sodium selenate.

Blood Cells↗
PubMed2005

Bioaccumulation of waterborne selenium in the Asiatic clam Corbicula fluminea: influence of feeding-induced ventilatory activity and selenium species.

A set of experiments was performed to investigate the bioavailability and the effect of Se on the ventilatory activity of the bivalve Corbicula fluminea, under different conditions of both algal cell densities and dissolved Se chemical forms and concentrations. A first set of experiments was conducted without selenium to investigate the changes in the ventilatory flow rate as a function of the concentration of the unicellular alga Chlamydomonas reinhardtii (10(5)-10(6) cells mL(-1)). For algal concentrations below 2-3x10(5) cells mL(-1), ventilatory activity was highly stimulated whereas it was independent of algal densities for higher values (up to 10(6) cells mL(-1)). To investigate the influence of this first ventilatory drive on selenium contamination process, bivalves were exposed to waterborne selenium at two different algal concentrations, selected to provide contrasting reference ventilatory activities. Three different selenium forms were studied [selenite Se(+IV), selenate Se(+VI) and selenomethionine SeMet] and were added into the water at concentrations of 50 and/or 500 microg L(-1). Each selenium form induced a specific behavioural response, an increase, a decrease or no change of ventilation being observed for Se(+IV), SeMet and Se(+VI), respectively. Selenium accumulation by the organisms was investigated at the organ level for the different exposure conditions. Selenomethionine was the most bioaccumulated form, followed by selenate and selenite, respectively. Despite the bivalves displaying different ventilatory behaviours at low or high algal density, there was no evidence showing reduction or enhancement of Se uptake in the chemical domain investigated.

Analysis of Variance↗
PubMed1978

Selenium proteins in ovine tissues: III. Distribution of selenium and glutathione peroxidases in tissue cytosols.

Three 6 week-old lambs were injected with carrier-free selenium-75 as sodium selenite initially and again after 6 days. One lamb received no further injections whereas the other two received injections of either vitamin E or unlabeled Na2SeO3 when the first selenium-75 injection was given. Selected tissues were removed at autopsy 10 days after the first injection. The cytosol from homogenates of these tissues was subjected to gel chromatography, and the elution profiles determined for radioactivity, protein content, and glutathione peroxidase activity using either hydrogen peroxide or cumene hydroperoxide as substrates. The selenium-75 was found to be distributed mainly between 2 different MW peaks. The larger MW seleno-peak (90,000) possessed both glutathione:hydrogen peroxide oxidoreductase, and glutathione:cumene hydroperoxide oxidoreductase activities, but the smaller MW seleno-peak (about 10,000) possessed no glutathione peroxidase activity. A peak of about 60,000 daltons containing only glutathione:cumene hydroperoxide oxidoreductase activity and no selenium-75 was found primarily in the liver and kidney. Vitamin E had no effect on the elution profiles. Selenium status of the animal had only a minor effect on the selenium-75 distribution in the cytosol, but had a marked effect on the absolute amount of the label taken up by tissues.

Animals↗
PubMed2002

Development of new analytical methods for selenium speciation in selenium-enriched yeast material.

A sequential extraction allowing the discrimination of water-soluble and non-soluble selenium fractions has been developed to evaluate the availability of selenium (Se) in an Se-enriched yeast candidate reference material. The fractionation of selenium-containing compounds in the extracts was achieved on preparative grade 200 Superdex 75 and columns. It showed that water-soluble selenium is present in several fractions with a large mass distribution. Low-molecular- (< or = 10,000) and high-molecular-mass selenocompounds (range 10,000-100,000) were considered separately for further experiments. The analytical approach for low-molecular-mass selenocompounds was based onanion-exchange HPLC with on-line inductively coupled plasma (ICP) MS for quantitative analysis. Selenocystine, selenomethionine, selenite and selenate were quantified in the fractions isolated in preparative chromatography. The study revealed the existence of various unidentified Se species in yeast material. The Se-containing proteins in the yeast material have been further separated and selenium quantified by the combination of gel electrophoresis and electrothermal vaporization-ICP-MS. This new approach allows the separation of the proteins with high resolution by sodium dodecylsulfate-polyacrylamide gel electrophoresis and the sensitive determination of selenium in the protein bands.

Calibration↗
PubMed1986

Synthesis and characterization of a selenium-containing substrate of alpha-chymotrypsin. Selenium-77 nuclear magnetic resonance observation of an acyl-alpha-chymotrypsin intermediate.

The selenium-containing ester p-nitrophenyl (phenylselenyl)acetate, C6H5SeCH2C(O)-OC6H4-p-(NO2), has been synthesized, characterized as a substrate for alpha-chymotrypsin (k2/KM = 15.2 X 10(3) M-1 s-1, KMapp = 5.16 X 10(-6) M, pH 7.77, 33% CH3CN, 25 degrees C), and shown to be an active-site titrant for the enzyme. A synthesis of the selenium-77 enriched p-nitrophenyl (phenylselenyl)acetate in 53% yield from 94.4% elemental selenium-77, followed by its reaction with alpha-chymotrypsin (pH 5.0, 0-3 degrees C), permitted the observation of the (phenylselenyl)acetyl-alpha-chymotrypsin reaction intermediate by selenium-77 NMR spectroscopy. This acyl-enzyme species had a chemical shift of 275.1 ppm relative to dimethyl selenide. Accompanying this resonance was a lower intensity, pH-dependent resonance that is assigned to (phenylselenyl)acetate on the basis of a pH titration of the model compound. Deacylation in the presence of hydrazine sulfate produced a resonance at 332.3 ppm in addition to the 302.2 ppm resonance of (phenylselenyl)acetate at pH 7.85. Denaturation of the acyl-enzyme resulted in a shift of the 275.1 ppm resonance to 334.6 ppm at pH 4.90, in good agreement with the selenium-77 chemical shift of the model compound, methyl (phenylselenyl)acetate, in CDCl3 (333.3 ppm). The large shielding observed for the native acyl-enzyme in comparison to the denatured species can be attributed to a resonance-perturbed ester linkage and/or steric compression at a nonbonding orbital of the selenium nucleus.

Animals↗
PubMed2003

Speciation of selenium compounds from high selenium broccoli is affected by the extracting solution.

The speciation of selenium compounds from high selenium broccoli (876 microg/g) depends on the extraction conditions. Twenty-seven extraction conditions were explored involving nine different buffering systems between pH 1 and pH 9. In nonbuffered extractions of broccoli, more than 40% of the spiked Se-methylselenocysteine was not recovered in the filtered solution. However, in buffered extractions, losses for Se-methylselenocysteine ranged from 10 to 20%. Mass balance indicated that approximately 30% of naturally occurring selenium in broccoli samples was volatilized and lost to the atmosphere when buffered extractions were made. Solid phase extractions indicated that the polarity of selenium compounds in solution was also dependent on the extracting solution. High-pressure liquid chromatography coupled to an inductively coupled plasma mass spectrometer was used to show that selenium compounds extracted from broccoli reacted with the extracting solution. Compound identities were assigned by matching retention times to standards of selenite, selenate, methylseleninic acid, Se-methylselenocysteine, selenomethionine, and the selenonic acids of Se-methylselenocysteine and selenomethionine. Changes in speciation were analyte-, pH-, and buffer-dependent, but generally, a higher pH resulted in more highly oxidized selenium compounds. For valid conclusions to be drawn from the analytical data, the extraction conditions should match the conditions present in the matrix or be specified for a particular application such as a simulated gastrointestinal digestion.

Brassica↗
PubMed2004

Effect of foliar application of selenium on the antioxidant activity of aqueous and ethanolic extracts of selenium-enriched rice.

Selenium fertilizer was foliar applied to determine the effects of antioxidant activity of selenium-enriched rice assessed by alpha,alpha-diphenyl-beta-picylhydrazyl (DPPH) radical scavenging and the ferric thiocyanate (FTC) method. Results showed that selenium concentration in rice was significantly enhanced dose dependently. Aqueous or ethanolic extracts of rice displayed significantly higher antioxidant activity against lipid peroxidation. The activities of aqueous extracts were significantly higher than those of ethanolic extracts and increased with the increasing selenium concentration in rice. The DPPH assay showed that the kinetic behaviors of aqueous extracts were complex and slow, while ethanolic extracts reacted quickly with DPPH radical. Aqueous extracts of rice exhibited higher antiradical efficiencies than ethanolic extracts, and rice (1.275 mg Se kg(-)(1)) presented the lowest EC(50) values of 533.46 +/- 0.58 microg mL(-)(1). As compared to rice extracts, all of the reference antioxidants showed more than 4-fold antiradical efficiencies than rice extracts. This radical scavenging activity was significantly correlated with selenium concentrations in rice (R = 0.862, p < 0.05), while ethanolic extracts were inversely correlated with selenium concentration in rice.

Antioxidants↗
PubMed2003

Sequential extractions of selenium soils from Stewart Lake: total selenium and speciation measurements with ICP-MS detection.

Different techniques have been employed in order to evaluate the most efficient procedure for the extraction of selenium from soil as required for speciation. Selenium contaminated sediments from Stewart Lake Wetland, California were used. A strong acid mineralization of the samples gives quantitative total selenium, which is then used to estimate recoveries for the milder extraction methods. The different extraction methodologies involve the sequential use of water, buffer (phosphate, pH 7) and either acid solution (e.g. HNO3 or HCl) or basic solutions (e.g. ammonium acetate, NaOH or TMAH). Pyrophosphate extraction was also evaluated and showed that selenium was not associated with humic acids. The extractants were subsequently analyzed by size exclusion chromatography (SEC) with UV (254 and 400 nm) and on-line ICP-MS detection; anion exchange chromatography, and ion-pair reversed phase chromatography with ICP-MS detection. For sequential extractions the extraction efficiencies showed that the basic extractions were more efficient than the acidic. The difference between the acidic and the basic extraction efficiency is carried to the sulfite extraction, suggesting that whatever is not extracted by the acid is subsequently extracted by the sulfite. The species identified with the different chromatographies were selenate, selenite, elemental selenium and some organic selenium.

Chromatography, High Pressure Liquid↗
PubMed1996

Use of selenium concentration in whole blood, serum, toenails, or urine as a surrogate measure of selenium intake.

We examined the validity of using the selenium level in a single biological specimen as a surrogate measure of usual intake. We used data from 77 free-living adults from South Dakota and Wyoming. Subjects provided multiple 1-day duplicate-plate food composites, repeated specimens of blood and toenails, and 24-hour urine collections. We developed a statistical calibration method that incorporated measurement error correction to analyze the data. The Pearson correlation coefficients between selenium intake and a single selenium status measure, after deattenuation to adjust for the effect of within-person variation in intake, were: 0.78 for whole blood, 0.74 for serum, 0.67 for toenails, and 0.86 for urine. We present formulas to estimate the intake of individuals, based on selenium levels in a single specimen of blood, toenails, or urine. In these data, the concentration of selenium in a single specimen of whole blood, serum, or toenails served reasonably well as a measure for ranking subjects according to long-term selenium intake but provided only a rough estimate of intake for each subject.

Adult↗
PubMed1988

The selenium status of children with phenylketonuria: results of selenium supplementation.

The selenium status of children with phenylketonuria on a synthetic low phenylalanine diet was assessed. Correlation between blood selenium and red cell glutathione peroxidase was unsatisfactory (r = 0.65) due to the poor discrimination of red cell glutathione peroxidase with a low selenium diet. No symptoms of deficiency were observed. Supplementation with 50 micrograms per week of selenium as brewers yeast tablets over a period of 6 months significantly increased the blood selenium of the phenylketonuric children. Plasma Vitamin E levels were within normal limits. The supplementation effectively doubled their selenium intake to 15-17 micrograms per day, which is probably sufficient for this group with an adequate Vitamin E status, though considerably lower than the recommended minimum intake of 50 micrograms per day.

Adolescent↗
PubMed1997

Dietary selenium repletion may reduce cancer incidence in people at high risk who live in areas with low soil selenium.

Studies examining the relationship between dietary selenium intake and risk of various cancers have shown that low selenium intake is associated with higher cancer rates. A recent well-controlled intervention trial studied whether selenium supplementation can prevent cancer in subjects who have a history of skin cancer and live in areas of the United States with low soil selenium levels. Selenium supplementation did not reduce skin cancer rates, but the incidence of total, lung, colorectal, and prostate cancers was significantly reduced by the intervention. Although these data need confirmation, they suggest that adequate selenium intake is essential for cancer prevention.

Diet↗
PubMed1992

Selenium and glutathione peroxidase levels in premature infants in a low selenium community (Christchurch, New Zealand).

By world standards, the selenium status of the adult population of Christchurch, New Zealand is low. To determine the status of infants undergoing neonatal intensive care, plasma and red cell selenium and glutathione peroxidase levels were measured in infants admitted to the regional neonatal unit. Plasma levels in all newborn infants were one third to one half those in adults. Premature infants had levels significantly lower than those in cord blood from term infants, but their levels were not different from those of term infants admitted to the unit. There were no differences between adult and infant red cell levels. The premature infants remaining in the neonatal unit showed dramatic decreases in plasma selenium and glutathione peroxidase with age, with many infants having selenium levels of less than 0.13 mumol/L (10 micrograms/L). Low levels were seen in infants fed orally as well as those on parenteral nutrition. Thus, the low selenium status of New Zealanders is associated with particularly low selenium levels in premature infants. Because these infants have a high risk for oxidative diseases such as bronchopulmonary dysplasia (chronic lung disease) and retinopathy of prematurity, the possibility that these conditions are more serious in the New Zealand population needs to be assessed and consideration given to dietary supplementation.

Adult↗
PubMed2006

Microarray analysis of selenium-depleted and selenium-supplemented mice.

Nutritional selenium deficiency is associated with Keshan disease in humans and white muscle disease in ruminant livestock. In this study, mice were fed a selenium-deficient diet for three generations. Female mice from the third depleted generation of these mice were given water containing either no added selenium or 0.1 or 1.0 ppm selenium as sodium selenate; DNA microarrays were used to compare gene expression in the muscle from mice fed the selenium diets to that from mice remaining on the depleted diet. The most prominent expression increases were observed with Ptger2 (a prostaglandin E receptor), Tcrb-V13 (a T-cell receptor beta), Tcf-7 (a T-cell transcription factor), and Lck (lymphocyte protein tyrosine kinase), and the major consistent decrease was Vav2, an oncogene in mice consuming the selenium containing diets.

Animals↗
PubMed2004

Pharmacokinetics of selenium following oral administration selenium preparation in rabbits.

The aim of study was to investigate the bioavailability of selenium after oral administration of selenium yeast. As a reference preparation was used sodium selenite. The preparations were investigated in rabbits, according to a randomized two way crossover design in the fasted state. Each animal was given selenium preparation in the form of the single oral dose 0.5 mg Se/kg body weight. A washout period of one week separated both treatment periods. The selenium concentration was determined in serum spectrofluorometry. The divalent equation of one-compartment model was the simplest formula describing the course of selenium changes in serum of rabbits and giving the pharmacokinetic parameters. Pharmacokinetic variables (mean maximum plasma concentration, mean time to reach maximum plasma concentration, and the mean area under the plasma concentration-time curve) were not statistically different for the two preparations. It can be concluded that the two selenium preparations are likely to be bioequivalent.

Animals↗
PubMed1984

Effect of maternal dietary selenium intake on selenium levels in breast milk.

The average dietary selenium intake in Finland is naturally low, approximately 30 micrograms/d, when domestic grain is exclusively consumed. Selenium concentrations were determined in 46 individual breast milk samples collected after 1, 2, and 3 months of lactation in 1980, when the average Finnish dietary selenium intake was approximately 50 micrograms/d due to consumption of high selenium US grain. Selenium concentrations were characterized by a pattern of slight decline with advancing stages of lactation: 11.8 +/- 1.7 micrograms/l (n = 13), 10.9 +/- 1.9 micrograms/l (n = 18) and 10.0 +/- 1.9 micrograms/l (n = 15) at 1, 2 and 3 months post partum, respectively. This pattern, however, contrasts strongly to that found in a 1976 set of breast milk samples: 10.7 +/- 1.6 micrograms/l (n = 13) and 5.8 +/- 1.2 micrograms/l (n = 13) at 1 and 3 months post partum, respectively. The dietary selenium intake of the subjects was determined to be 33 +/- 13 micrograms/d during the course of lactation. Analytically, the results of these studies are analogous, as the same investigator determined both sets of samples by exactly the same analytical procedure.

Diet↗
PubMed1981

Annual variations in the average selenium intake in Finland: cereal products and milk as sources of selenium in 1979/80.

Grain, flour and milk samples were collected in spring 1980 and analysed for selenium. The selenium content of flour was approximately 10 times higher than in 1975-1977, and that of milk twice as high. The increase in the selenium content of flour is a reflection of the massive grain imports in 1979/80. The increased selenium level in milk was more unexpected, and may at least partly be due to the increased use of fodders enriched with selenium. The average intake of selenium in 1980 may have been between 50 and 60 micrograms/d/person, while the mid seventies it was found to be substantially lower, about 30 microns/d.

Animals↗
PubMed1980

Increasing selenium in bovine blood by feed supplements or selenium injections.

A study was made of the relative effectiveness of including various feed supplements or selenium injections on increasing the blood level of selenium in pregnant Holstein cows. The dietary treatment included the addition of soft coal fly ash, western grown grains, high selenium sweet clover or sodium selenite to the rations. Whereas each of the treatments caused a progressive increase in blood selenium the addition of 4% by weight of fly ash to the ration raised the concentration of selenium in blood the highest. Increases in the concentration of selenium in milk as a result of the treatments were very small.

Administration, Oral↗