Determination of selenium by GFAAS in slurries of fish feces to estimate the bioavailability of this micronutrient in feed used in pisciculture

This paper presents a simple, fast and sensitive method to determine selenium in samples of feces and of fish feed by graphite furnace atomic absorption spectrometry (GFAAS) through the direct introduction of slurries of the samples into the spectrometer's graphite tube. The limits of detection (LOD) and quantification (LOQ calculated for 20 readings of the blank of the standard slurries (0.50% m/v of feces or feed devoid of selenium) were 0.31 mu g 1(-1) and 1.03 mu g 1(-1), respectively, for the standard feces slurries and 0.35 mu g 1(-1) and 1.16 mu g 1(-1), respectively, for the standard feed slurries. The proposed method was applied in studies of bioavailability of selenium in different fish feeds and the results proved consistent with that obtained from samples mineralized by acid digestion using the microwave oven. (C) 2007 Elsevier Ltd. All rights reserved.

Elevated levels of selenium in the typical diet of Amazonian riverside populations

Selenium (Se) intake is generally from food, whose Se content depends on soil Se and plant accumulation. For humans, adequate Se intake is essential for several selenoenzymes. In the Lower Tapajos region of the Brazilian Amazon, Se status is elevated with large inter-community variability. Se intake in this region, where Hg exposure is among the highest in the world, may be important to counteract mercury (Hg) toxicity. The present study was conducted in 2006 with 155 persons from four communities of the Lower Tapajos. The objectives were: i) to evaluate Se content in their typical diet and drinking water; ii) to compare food Se concentrations with respect to geographic location; and iii) to examine the contribution of consumption of different food items to blood Se. More than 400 local foods and 40 drinking water samples were collected. Participants responded to an interview-administered food frequency questionnaire and provided blood samples. Food, water and blood Se levels were assessed by ICP-MS. Since Brazil nuts may also contain significant levels of barium (Ba) and strontium (Sr), these elements were likewise analyzed in nuts. The highest Se concentrations were found in Brazil nuts, but concentrations were highly variable (median: 13.9 mu g/g; range: 0.4-158.4 mu g/g). Chicken, game meat, eggs and beef also contained considerable levels of Se, with median concentrations from 0.3 to 1.4 mu g/g. There was no particular geographic distribution of food Se. Se concentration in drinking water was very low (<1.4 mu g/L). Blood Se covered a (103-1500 mu g/L), and was positively related to regular consumption of Brazil nuts, domestic chicken and game meat. Brazil nuts were found to contain highly variable and often very high concentrations of Ba (88.0 mu g/g, 1.9-1437 mu g/g) and Sr (38.7 mu g/g, 3.3-173 mu g/g). Further studies should address multiple nutrient/toxic interactions in the diet and related effects on health. (c) 2010 Elsevier B.V. All rights reserved.

In vivo bioavailability of selenium in enriched Pleurotus ostreatus mushrooms

The in vivo bioavailability of Se was investigated in enriched Pleurotus ostreatus mushrooms. A bioavailability study was performed using 64 Wistar male rats separated in 8 groups and fed with different diets: without Se, with mushrooms without Se, with enriched mushrooms containing 0.15, 0.30 or 0.45 mg kg(-1) Se and a normal diet containing 0.15 mg kg(-1) of Se using sodium selenate. The experiment was performed in two periods: depletion (14 days) and repletion (21 days), according to the Association of Official Analytical Chemists. After five weeks, the rats were sacrificed under carbon dioxide, and blood was drawn by heart puncture. Blood plasma was separated by centrifugation. The total Se concentration in the plasma of rats fed with enriched mushrooms was higher than in rats fed with a normal diet containing sodium selenate. The plasma protein profiles were obtained using size exclusion chromatography (SEC) and UV detectors. Aliquots of effluents (0.5 mL per minute) were collected throughout in the end of the chomatographic column. However, Se was determined by graphite furnace atomic absorption spectrometry (GF AAS) only in the aliquots where proteins were detected by SEC-UV. The plasma protein pro. le of rats fed with different diets was similar. The highest Se concentration was observed in a peptide presenting 8 kDa. Furthermore, the higher Se concentration in this peptide was obtained for rats fed with a diet using enriched mushrooms (7 mu g L(-1) Se) compared to other diets (2-5 mu g L(-1) Se). These results showed that Se-enriched mushrooms can be considered as an alternative Se food source for humans, due to their high bioavailability.

Method development and optimization for the determination of selenium in bean and soil samples using hydride generation electrothermal atomic absorption spectrometry

The present investigation is the first part of an initiative to prepare a regional map of the natural abundance of selenium in various areas of Brazil, based on the analysis of bean and soil samples. Continuous-flow hydride generation electrothermal atomic absorption spectrometry (HG-ET AAS) with in situ trapping on an iridium-coated graphite tube has been chosen because of the high sensitivity and relative simplicity. The microwave-assisted acid digestion for bean and soil samples was tested for complete recovery of inorganic and organic selenium compounds (selenomethionine). The reduction of Se(VI) to Se(IV) was optimized in order to guarantee that there is no back-oxidation, which is of importance when digested samples are not analyzed immediately after the reduction step. The limits of detection and quantification of the method were 30 ng L(-1) Se and 101 ng L(-1) Se, respectively, corresponding to about 3 ng g(-1) and 10 ng g(-1), respectively, in the solid samples, considering a typical dilution factor of 100 for the digestion process. The results obtained for two certified food reference materials (CRM), soybean and rice, and for a soil and sediment CRM confirmed the validity of the investigated method. The selenium content found in a number of selected bean samples varied between 5.5 +/- 0.4 ng g(-1) and 1726 +/- 55 ng g(-1), and that in soil samples varied between 113 +/- 6.5 ng g(-1) and 1692 +/- 21 ng g(-1). (C) 2011 Elsevier B.V. All rights reserved.

Nutritional status of selenium in Alzheimer`s disease patients

Studies have shown that various antioxidants are decreased in different age-related degenerative diseases and thus, oxidative stress would have a central role in the pathogenesis of many disorders that involve neuronal degeneration, including Alzheimer`s disease (AD). The present study aimed to assess the nutritional status of Se in AD patients and to compare with control subjects with normal cognitive function. The case control study was carried out on a group of elderly with AD (n 28) and compared with a control group (n 29), both aged between 60 and 89 years. Se intake was evaluated by using a 3-d dietary food record. Se was evaluated in plasma, erythrocytes and nails by using the method of hydride generation atomic absorption spectroscopy. Deficient Se intake was largely observed in the AD group. AD patients showed significantly lower Se levels in plasma, erythrocytes and nails (32.59 mu g/l, 43.74 mu g/l and 0.302 mu g/g) when compared with the control group (50.99 mu g/l, 79.16 mu g/l and 0.400 mu g/g). The results allowed us to suggest that AD has an important relation with Se deficiency.

Seedling responses of four Australian tree species to toxic concentrations of manganese in solution culture

Little is known about the responses of Australian plants to excess metal, including Mn. It is important to remedy this lack of information so that knowledgeable decisions can be made about managing Mn contaminated sites where inhabited by Australian vegetation. Acacia holosericea, Melaleuca leucadendra, Eucalyptus crebra and Eucalyptus camaldulensis were grown in dilute solution culture for 10 weeks. The seedlings ( 42 days old) were exposed to six Mn treatments viz., 1, 8, 32, 128, 512 and 2048 muM. The order of tolerance to toxic concentrations of Mn was A. holosericea congruent to = E. crebra < M. leucadendra < E. camaldulensis, the critical external concentrations being approximately 5.1, 5.0, 21 and 330 muM, respectively. The critical tissue Mn concentrations for the youngest fully expanded leaf and total shoots were, respectively, 265 and 215 mug g(-1) DM for A. holosericea, 445 and 495 mug g(-1) DM for M. leucadendra, 495 and 710 mug g(-1) DM for E. crebra and 7230 and 6510 mug g(-1) DM for E. camaldulensis. The high tolerance of E. camaldulensis ( as opposed to the sensitivity of E. crebra) to excess Mn raises concern about fauna feeding on the plant and is consistent with hypotheses suggesting the Eucalyptus subgenus Symphomyrtus is particularly tolerant of stress, including excess Mn. The results from this paper provide the first comprehensive combination of growth responses, critical external concentrations, critical tissue concentrations and plant toxicity symptoms for three important Australian genera, viz., Eucalyptus, Acacia and Melaleuca, for use in the management of Mn toxic sites.

Seedling responses of three Australian tree species to toxic concentrations of zinc in solution culture

A frequently desired outcome when rehabilitating Zn toxic sites in Australia is to establish a self-sustaining native ecosystem. Hence, it is important to understand the tolerance of Australian native plants to high concentrations of Zn. Very little is known about the responses of Australian native plants, and trees in particular, to toxic concentrations of Zn. Acacia holosericea, Eucalyptus camaldulensis and Melaleuca leucadendra plants were grown in dilute solution culture for 10 weeks. The seedlings (42 days old) were exposed to six Zn treatments viz., 0.5, 5, 10, 25, 50 and 100 muM. The order of tolerance to toxic concentrations of Zn was E. camaldulensis > A. holosericea > M. leucadendra, the critical external concentrations being approximately 20, 12 and 1.5 muM, respectively. Tissue Zn concentrations increased as solution Zn increased for all species. Root tissue concentrations were higher than shoot tissue concentrations at all solution Zn concentrations. The critical tissue Zn concentrations were approximately 85 and 110 mug g(-1) DM for M. leucadendra, 115 and 155 mug g(-1) DM for A. holosericea and 415 and 370 mug g(-1) DM for E. camaldulensis for the youngest fully expanded leaf and total shoots, respectively. The results from this paper provide the first comprehensive combination of growth responses, critical external concentrations, critical tissue concentrations and plant toxicity symptoms for three important Australian genera, viz., Eucalyptus, Acacia and Melaleuca, for use in the rehabilitation of potentially Zn toxic sites.

Minimum detection limit of an in-house nested-PCR assay for herpes simplex virus and varicella zoster virus

Introduction Herpes simplex virus (HSV) and varicella zoster virus (VZV) are responsible for a variety of human diseases, including central nervous system diseases. The use of polymerase chain reaction (PCR) techniques on cerebrospinal fluid samples has allowed the detection of viral DNA with high sensitivity and specificity. Methods Serial dilutions of quantified commercial controls of each virus were subjected to an in-house nested-PCR technique. Results The minimum detection limits for HSV and VZV were 5 and 10 copies/µL, respectively. Conclusions The detection limit of nested-PCR for HSV and VZV in this study was similar to the limits found in previous studies.

Enhancing the selenium content of bovine milk through alteration of the form and concentration of selenium in the diet of the dairy cow

Since estimated dietary selenium intake in the UK has declined steadily from around 60 mug day(-1) in 1975 to 34 mug day(-1) in 1997, there is a need to increase selenium intake from staple foods such as milk and milk products. An experiment was therefore done to investigate the relationship between dietary source and concentration of selenium and the selenium content of bovine milk. In a 3 x 3 factorial design, 90 mid-lactation Holstein dairy cows were supplemented over 8 weeks with either sodium selenite (S), a chelated selenium product (Selenium Metasolate(TM)) (C) or a selenium yeast (Sel-plex(TM)) (Y) at three different dietary inclusion levels of 0.38 (L), 0.76 (M) and 1.14 (H) mg kg(-1) dry matter (DM). Significant increases in milk selenium concentration were observed for all three sources with increasing inclusion level in the diet, but Y gave a much greater response (up to +65 mug l(-1)) than the other two sources of selenium (S and C up to +4 and +6 mug l(-1) respectively). The Y source also resulted in a substantially higher apparent efficiency of transfer of selenium from diet to milk than S or C. Feeding Y at the lowest dietary concentration, and thus within the maximum level permitted under EU regulations, resulted in milk with a selenium concentration of 28 mug l(-1). If the selenium concentration of milk in the UK was increased to this value, it would, at current consumption rates, provide an extra 8.7 mug selenium day(-1), or 11 and 14% of daily recommended national intake for men and women respectively. (C) 2004 Society of Chemical Industry.

Ecto- and arbuscular mycorrhizal symbiosis can induce tolerance to toxic pulses of phosphorus in jarrah (Eucalyptus marginata) seedlings

In common with many plants native to low P soils, jarrah (Eucalyptus marginata) develops toxicity symptoms upon exposure to elevated phosphorus (P). Jarrah plants can establish arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) associations, along with a non-colonizing symbiosis described recently. AM colonization is known to influence the pattern of expression of genes required for P uptake of host plants and our aim was to investigate this phenomenon in relation to P sensitivity. Therefore, we examined the effect on hosts of the presence of AM and ECM fungi in combination with toxic pulses of P and assessed possible correlations between the induced tolerance and the shoot P concentration. The P transport dynamics of AM (Rhizophagus irregularis and Scutellospora calospora), ECM (Scleroderma sp.), non-colonizing symbiosis (Austroboletus occidentalis), dual mycorrhizal (R. irregularis and Scleroderma sp.), and non-mycorrhizal (NM) seedlings were monitored following two pulses of P. The ECM and A. occidentalis associations significantly enhanced the shoot P content of jarrah plants growing under P-deficient conditions. In addition, S. calospora, A. occidentalis, and Scleroderma sp. all stimulated plant growth significantly. All inoculated plants had significantly lower phytotoxicity symptoms compared to NM controls 7 days after addition of an elevated P dose (30 mg P kg−1 soil). Following exposure to toxicity-inducing levels of P, the shoot P concentration was significantly lower in R. irregularis-inoculated and dually inoculated plants compared to NM controls. Although all inoculated plants had reduced toxicity symptoms and there was a positive linear relationship between rank and shoot P concentration, the protective effect was not necessarily explained by the type of fungal association or the extent of mycorrhizal colonization.

Determination of selenium in nutritionally relevant foods by graphite furnace atomic absorption spectrometry using arsenic as internal standard

A method has been developed for the direct determination of Se in nutritionally relevant foods by graphite furnace atomic absorption spectrometry. Tungsten/rhodium carbide coating on the integrated platform of a transversely heated graphite atomizer or W coating with co-injection of Pd(NO3)(2) were used as a permanent modifiers. Samples and reference solutions were spiked with 500 mu g L-1 As and absorbance variations due to changes in experimental conditions were minimized. For 20 mu L aqueous analytical solutions delivered into the graphite tube, analytical curves in the 5.0-40 mu g L-1 with good linear correlation were established. Pyrolysis and atomization temperatures were evaluated using pyrolysis and atomization curves, respectively. The optimized heating program (temperature, ramp time, hold time) of the graphite tube of the Perkin-Elmer SIMAA 6000 atomic absorption spectrometer was: dry steps (110 degrees C, 5 s, 10 s; 130 degrees C, 15 s, 15 s); air-assisted pyrolysis step (600 degrees C, 20 s, 40 s; 20 degrees C, 1 s, 40 s); pyrolysis step (1300 degrees C, 10 s, 20 s); atomization step (2100 degrees C, 0 s, 4 s); clean step (2550 degrees C, 1 s, 5 s). The method was applied for Se determination in coconut water, coconut milk, soybean milk, cow milk, tomato juice, mango juice, grape juice and drinking water samples and four standard reference materials and results were in agreement at 95% confidence level. The lifetime of the tube was 500 firings and the relative standard deviations of measurements of typical samples containing 25 mu gL(-1) Se were 3.0% and 6.0% (n = 12) with and without internal standardization, respectively. The limits of detection were in the 0.35 mu g L-1-0.7 mu g Se L-1 range. The accuracy of the proposed method was evaluated by an addition-recovery experiment and all recovered values were in the 98-109% range. (c) 2004 Elsevier Ltd. All rights reserved.

Studying the distribution of Selenium in buffalo and cow's milk whey

Neste estudo, a cromatografia por exclusão de tamanho (SEC) com detecção online ultravioleta (UV), espectrometria de absorção atômica em forno de grafite (GF AAS) e a espectrometria de massa por tempo de voo com dessorção/ionização de matriz assistida por laser (MALDI-TOF-MS) foram usadas para estudar a associação de selênio com macromoléculas e compostos presentes no soro de leite de búfala e bovino. Os perfis de SEC-UV obtidos para as amostras de soro de leite de búfala e soro de leite bovino indicaram a presença de espécies de alta e baixa massa molecular. A combinação das informações obtidas com SEC-UV, GF AAS e MALDI-TOF-MS para as frações < 10 kDa confirmou a associação de selênio com espécies de baixa massa molecular.

Effect of Brazil Nut Supplementation on Plasma Levels of Selenium in Hemodialysis Patients: 12 Months of Follow-up

Background: Large amounts of reactive oxygen species are produced in hemodialysis (HD) patients, and, at higher concentrations, reactive oxygen species are thought to be involved in the pathogenesis of cardiovascular disease. It has been proposed that selenium (Se) may exert an antiatherogenic influence by reducing oxidative stress. The richest known food source of Se is the Brazil nut (Bertholletia excelsa, family Lecythidaceae), found in the Amazon region. Objective: The objective of this work was to determine if Se plasma levels in HD patients submitted to a program of supplementation during 3 months with 1 Brazil nut by day could be sustained after 12 months. Methods: A total of 21 HD patients (54.2 +/- 15.2 years old; average time on dialysis, 82.3 +/- 51.6 months; body mass index, 24.4 +/- 3.8 kg/m(2)) from the RenalCor Clinic in Rio de Janeiro, Brazil, were followed up 12 months after the supplementation study ended. The Se plasma levels were determined by atomic absorption spectrophotometry with hydride generation. Results: The Se Plasma levels (17.3 +/- 19.9 mg/L) were below the normal range (60 to 120 mu g/L) before nut supplementation, and after 3 months of supplementation, the levels increased to 106.8 +/- 50.3 mu g/L (P < .0001). Twelve months after supplementation, the plasma Se levels decreased to 31.9 +/- 14.8 mu g/L (P < .0001). Conclusions: The data showed that these patients were Se deficient and that the consumption of Brazil nut was effective to increase the Se parameters of nutritional status. Se levels 12 months after the supplementation period were not as low as presupplementation levels but yet significantly lower, and we needed to motivate patients to adopt different dietary intake patterns. (C) 2012 by the National Kidney Foundation, Inc. All rights reserved.

The isotope composition of selenium in chondrites constrains the depletion mechanism of volatile elements in solar system materials

Solar nebula processes led to a depletion of volatile elements in different chondrite groups when compared to the bulk chemical composition of the solar system deduced from the Sun's photosphere. For moderately-volatile elements, this depletion primarily correlates with the element condensation temperature and is possibly caused by incomplete condensation from a hot solar nebula, evaporative loss from the precursor dust, and/or inherited from the interstellar medium. Element concentrations and interelement ratios of volatile elements do not provide a clear picture about responsible mechanisms. Here, the abundance and stable isotope composition of the moderately- to highly-volatile element Se are investigated in carbonaceous, ordinary, and enstatite chondrites to constrain the mechanism responsible for the depletion of volatile elements in planetary bodies of the inner solar system and to define a δ(82/78)Se value for the bulk solar system. The δ(82/78)Se of the studied chondrite falls are identical within their measurement uncertainties with a mean of −0.20±0.26‰ (2 s.d., n=14n=14, relative to NIST SRM 3149) despite Se abundance depletions of up to a factor of 2.5 with respect to the CI group. The absence of resolvable Se isotope fractionation rules out a kinetic Rayleigh-type incomplete condensation of Se from the hot solar nebula or partial kinetic evaporative loss on the precursor material and/or the parent bodies. The Se depletion, if acquired during partial condensation or evaporative loss, therefore must have occurred under near equilibrium conditions to prevent measurable isotope fractionation. Alternatively, the depletion and cooling of the nebula could have occurred simultaneously due to the continuous removal of gas and fine particles by the solar wind accompanied by the quantitative condensation of elements from the pre-depleted gas. In this scenario the condensation of elements does not require equilibrium conditions to avoid isotope fractionation. The results further suggest that the processes causing the high variability of Se concentrations and depletions in ordinary and enstatite chondrites did not involve any measurable isotope fractionation. Different degrees of element depletions and isotope fractionations of the moderately-volatile elements Zn, S, and Se in ordinary and enstatite chondrites indicate that their volatility is controlled by the thermal stabilities of their host phases and not by the condensation temperature under canonical nebular conditions.

Responses of four Australian tree species to toxic concentrations of copper in solution culture

In Australia, metal-contaminated sites, including those with elevated levels of copper (Cu), are frequently revegetated with endemic plants. Little is known about the responses of Australian plants to excess Cu. Acacia holosericea, Eucalyptus crebra, Eucalyptus camaldulensis, and Melaleuca leucadendra were grown in solution culture with six Cu treatments (0.1 to 40 mu M). While A. holosericea was the most tolerant to excess Cu, all of the species tested were sensitive to excess Cu when compared with exotic tree and agricultural species. The critical external concentrations for toxicity were < 0.7 mu M for all species tested. There was little differentiation between shoot-tissue Cu concentrations in normal versus treated plants, thus, the derivation of critical shoot concentrations was possible only for the most tolerant species, A. holosericea. Critical root Cu concentrations were approximately 210 mu g g(-1) (A. holosericea), 150 mu g g(-1) (E. crebra), 25 mu g g(-1) (E. camaldulensis), and 165 mu g g(-1) (M. leucadendra). These results provide the first comprehensive combination of growth responses, critical concentrations, and toxicity symptoms for three important Australian genera for use in the management of Cu-contaminated sites.