Speciation analysis of selenium in human urine allowed for the first time the identification of a novel selenium metabolite, Se-methylselenoneine. Despite a concentration at low ppb level, its characterization was achieved after sample purification by solid phase extraction (SPE) followed by the parallel coupling of the bidimensional RP/HILIC chromatography with ICP-MS and ESI-LTQ Orbitrap MS detection. To confirm its biological significance with regards to selenoneine, the recently discovered analog of ergothioneine, and to discard the possibility of sample preparation artifacts, a new method was developed to monitor its actual presence, as well as the occurrence of its sulfur and/or non-methylated analogs, in non-preconcentrated urine and blood samples of non-supplemented humans. It consisted in a HILIC ESI-MS(3) method in high resolution mode (resolution 30 000 at m/z 400) with large isolation width windows for precursor ions. These two particular settings allowed respectively to keep observing the specific mass defect of selenium- and sulfur-containing molecules and to maintain the characteristic selenium pattern in product ions created through MS(n) fragmentations. As a result, all four metabolites were detected in blood and three of them in urine. Moreover, different ratios "methylated/non-methylated" were observed between urine and blood samples, which seemed to indicate their active metabolization. The analytical tool developed here will be of a great importance to further study the occurrence and the potential metabolic role in mammalian organelles, cells and fluids of these very particular and promising redox metabolites.

Se is an essential micronutrient required for normal growth, development and antioxidant defence. The objective of the present study was to assess the impact of dietary Se sources and levels on the antioxidant status of rainbow trout (Oncorhynchus mykiss) fry. First-feeding fry (initial body weight: 91 mg) were fed either a plant-or fishmeal-based diet containing 0·5 or 1·2 mg Se/kg diet supplemented or not with 0·3 mg Se/kg diet supplied as Se-enriched yeast or sodium selenite for 12 weeks at 178C. Growth and survival of rainbow trout fry were not significantly affected by dietary Se sources and levels. Whole-body Se was raised by both Se sources and to a greater extent by Se-yeast. The reduced:oxidised glutathione ratio was raised by Se-yeast, whereas other lipid peroxidation markers were not affected by dietary Se. Whole-body Se-dependent glutathione peroxidase (GPX) activity was enhanced in fish fed Se-yeast compared to fish fed sodium selenite or non-supplemented diets. Activity and gene expression of this enzyme as well as gene expression of selenoprotein P (SelP) were reduced in fish fed the non-supplemented plant-based diet. Catalase, glutamate -cysteine ligase and nuclear factor-erythroid 2-related factor 2 (Nrf2) gene expressions were reduced by Se-yeast. These results suggest the necessity to supplement plant-based diets with Se for rainbow trout fry, and highlight the superiority of organic form of Se to fulfil the dietary Se requirement and sustain the antioxidant status of fish. GPX and SelP expression proved to be good markers of Se status in fish.Key words: Selenium: Oxidative stress: Glutathione peroxidase: Rainbow trout fry Se is an essential micronutrient for animals and humans required for normal growth and development (1,2) . This role is attributed to low molecular weight Se compounds, as well as to the presence of Se within proteins and enzymes, named selenoproteins, in the form of the amino acid selenocysteine. Mammals have at least twenty-five selenoproteins, and fish probably more than thirty-two, although the functions of many selenoproteins are not yet elucidated (3,4) . Selenoproteins are involved in diverse physiological functions such as antioxidant defence, reduction of inflammation, thyroid hormone production, DNA synthesis, fertility and reproduction (1) . As a component of glutathione peroxidases (GPX), thioredoxin reductases (TR), and methionine sulphoxide reductases (MSR), Se plays, in particular, a pivotal role against oxidative cellular injury and lipid peroxidation. GPX can reduce H 2 O 2 and organic hydroperoxides to the corresponding alcohols with oxidation of glutathione to glutathione disulphide (5) . Seven GPX have been described in mammals, five of which are selenoproteins (2) . The GPX selenoproteins include the ubiquitously expressed cytosolic GPX1, a gastrointestinal-specific enzyme GPX2, a secreted protein found in plasma GPX3, a ubiquitously expressed enzyme that acts on oxidised lipids named * Corresponding author: S. Fontagné-Dicharry, fax þ33 55954515...

No abstract

No abstract

The highly toxic organotin compounds which have been used as biocides in ship antifouling paints have been introduced into aquatic ecosystems. Among them, tributyltin (TBT) is the most important organotin compound which has been produced on the largest scale. Understanding its fate in the environment is therefore of primary importance to prevent its migration. TBT sorption from aqueous solutions was studied at much lower concentrations (10 nM to 2 μM) than those used in previous studies. Experiments were performed using column reactors filled with a quartz sand. The influence of physicochemical parameters on TBT partitioning, i.e. ionic strength, pH, and nature of electrolyte cation was investigated. Equilibrium times were short as TBT retention appeared to be independent of the mean pore velocity. TBT sorption was affected strongly by the pH and slightly by the ionic strength of the solution. Competitions with monovalent alkaline cations showed a small influence of Li+, Na+, K+, Rb+, with respect to Cs+ on TBT retardation. Moreover, the injection of two different TBT concentrations accounted for the nonlinearity of TBT sorption. The theory of nonlinear chromatography was used for the calculation of convex adsorption isotherms. Retardation factors and distribution coefficients were estimated.

International audienceWater and 'soft' extractions (hydroxylammonium hydrochloride, ammonium oxalate and orthophosphoric acid) have been studied and applied to the determination of arsenic species (arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) in three environmental solid reference materials (river sediment, agricultural soil, sewage sludge) certified for their total arsenic content. The analytical method used was ion exchange liquid chromatography coupled online to atomic fluorescence spectroscopy through hydride generation. Very low detection limits for arsenic were obtained, ranging from 0.02 to 0.04 mg kg-1 for all species in all matrices studied. Orthophosphoric acid is the best extractant for sediment (mixed origin) and sludge samples (recent origin) but not for the old formation soil sample, from which arsenic is extracted well only by oxalate. Both inorganic forms (As(III) and As(V)) are significant in all samples, As(V) species being predominant. Moreover, organic forms are found in water extracts of all samples and are more important in the sludge sample. These organic forms are also present in the 'soft' extracts of sludge. Microwave-assisted extraction appears to minimize the risk of a redox interconversion of inorganic arsenic forms. This study points out the necessity of combining direct and sequential extraction procedures to allow for initial arsenic speciation and to elucidate the different mineralogical phases-species associations. Copyright © 2002 John Wiley & Sons, Ltd

No abstract

No abstract