A colorimetric phosphatase-inhibition bioassay was developed for the quantitative measurement of okadaic acid (OA) the main diarrhetic toxin responsible for diarrhetic shellfish poisoning. The assay used an artificial substrate, paranitrophenylphosphate, and a semi-purified protein phosphatase PP2Ac containing extract prepared from rabbit muscle. Calibration dose-inhibition curves were constructed using standard OA and they permitted easy determination of the enzyme concentration Et in their linear portion. In the range of linearity, the slope increased when Et decreased, thus giving a detecting limit of 0.04 pmol in the reaction mixture (1 ml). The lowest assayable concentration of OA was 4 ng/ml in aqueous solutions and 40 ng/ml (i.e., 100 ng of OA per g of mussel tissue) in crude methanol mussels extracts. The intra and interassay coefficients of variation in the measurement of OA for the toxin spiked aqueous samples averaged, respectively, 7.7% and 3.7%, and interexperiments coefficients of variation for the toxin spiked mussel extracts averaged 4.6%. The presence of OA was ascertained by a method in which one assay was performed at two or three different levels of enzyme concentration. The rapidity, accuracy, reproducibility, specificity, and simplicity of the procedure provides a simple way to assay okadaic acid in buffered or complex solutions.
Nous avons parcouru les rues de Brest le 27 novembre 2015 pour observer dans quelle mesure l’appel du Président de la République à pavoiser après les attentats du 13 novembre 2015 avait été suivi. Derrière ce qui a été perçu par nombre des personnes que nous avons interrogées sur leur geste comme un acte frappé au sceau de « l’extraordinaire », c’est bien une déclinaison, souvent oubliée, de l’échange politique qui s’est manifestée. L’article vise à comprendre le pouvoir de suggestion voire d’énonciation dont le drapeau a été doté à travers le trait d’union qu’il fut censé constituer au nom de la participation à une « communauté » nationale.
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