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La majorité des Services d’incendie et de secours (SIS) disposent de cellules mobiles d’intervention radiologique (CMIR) dont les moyens en équipements de protection, de détection, de prélèvement, d’identification et de décontamination permettent d’évaluer les risques, de localiser et confiner une source radioactive, et d’en limiter les effets sur l’homme et son environnement. Les risques radiologiques les plus courants auxquels les sapeurs-pompiers font face comprennent la découverte fortuite de matières radioactives et les accidents de transport. L’utilisation malveillante de produits radioactifs est aussi prise en compte par les services d’intervention qui, en cas de plan d’urgence, s’appuieront notamment sur l’expertise de l’Institut de radioprotection et de sûreté nucléaire (IRSN). Certains SIS sont dotés de moyens nationaux, par exemple des portiques de contrôle de contamination, permettant de répondre à des accidents d’ampleur. La prise en charge médicochirurgicale de victimes radio-contaminées catégorisées UA est prioritaire sur la décontamination. La décontamination d’urgence ciblera en priorité les plaies et les muqueuses afin d’éviter que la contamination externe ne devienne interne. Des dispositifs spécifiquement développés telles que la crème Calixarene (CEVIDRA) et les lingettes imprégnées DECPOL®RAD (OUVRY) complètent les moyens de décontamination d’urgence mis à disposition des intervenants. L’information et la préparation des populations à la gestion des risques radiologiques et nucléaires sont cruciales pour améliorer l’efficience de la réponse.

In an effort to reduce CO2emissions, many countries throughout the world are initiating plans to transition to more sustainable forms of energy. Nuclear energy would appear to be a powerful contender to replace fossil fuels, or at least be an unavoidable option, from an energy-mix perspective. However, nuclear energy suffers from a poor image among certain populations, especially the young, who favor the development of renewable energies. We wanted to get a more accurate read of what was happening in France, one of the most nuclearized countries in the world, where the share of nuclear energy is greater than 70%. Since plans are underway to reduce this level to 50% by 2035, understanding popular perceptions on this matter is even more important. In order to gain a better understanding, we interviewed an “expert” population and compared the results obtained with a so-called young “non-expert” student population. The first group is composed of firefighters, about half of whom have attended training in radiological risks, and the other, a non-expert population, composed of students from Université Côte d’Azur (UCA), who are potentially influenced (for better or worse) by social media. The aim of this study is to compare and contrast any differences in perception that these two distinct populations may have on the subject of nuclear energy.

Human plasma paraoxonase (HuPON1) is a high density lipoprotein (HDL)-bound enzyme exhibiting antiatherogenic properties. The molecular basis for the binding specificity of HuPON1 to HDL has not been established. Isolation of HuPON1 from HDL requires the use of detergents. We have determined the activity, dispersity, and oligomeric states of HuPON1 in solutions containing mild detergents using nondenaturing electrophoresis, size exclusion chromatography, and cross-linking. HuPON1 was active whatever its oligomeric state. In nonmicellar solutions, HuPON1 was polydisperse. In contrast, HuPON1 exhibited apparent homogeneity in micellar solutions, except with CHAPS. The enzyme apparent hydrodynamic radius varied with the type of detergent and protein concentration. In C12E8micellar solutions, from sedimentation velocity, equilibrium analytical ultracentrifugation, and radioactive detergent binding, HuPON1 was described as monomers and dimers in equilibrium. A decrease of the detergent concentration shifted this equilibrium toward the formation of dimers. About 100 detergent molecules were associated per monomer and dimer. The assembly of amphiphilic molecules, phospholipids in vivo, in sufficiently large aggregates could be a prerequisite for anchoring of HuPON1 and then allowing stabilization of the enzyme activity. Changes of HDL size and shape could strongly affect the binding affinity and stability of HuPON1 and result in reduced antioxidative capacity of the lipoprotein.

Serum paraoxonase (PON1, EC 3.1.8.1.) is a high density lipid- (HDL)-associated, calcium-dependent enzyme whose 3D structure, active site residues and physiological substrates are not known. The kinetic parameters kcatand Km(relative to kcatand Kmof the wild-type), determined with four substrates (phenylacetate, paraoxon, diazoxon and chlorpyrifosoxon) were less than 1% and more than 100% for the W280A and W280F mutant enzymes, respectively. These results indicated that the aromatic/hydrophobic character of the amino acid in position 280 is essential for PON1 activity. In this study, we investigated whether this aromatic residue is in the PON1 active site. Group-specific labelling studies with N-bromosuccinimide, an oxidative agent of tryptophan, strongly suggested that one or several Trp could be in the active site of PON1 but we could not conclude either on the specificity of the labelling reaction or on the number of oxidized Trp. However, although PON activity was not altered by the hydrophilic tryptophan-modifying reagent 2-hydroxy-5-nitrobenzyl chloride (NBC), it was significantly reduced by the p-nitrophenylacetate analog 2-acetoxy-5-nitrobenzyl chloride (ANBC), whose hydrolysis by PON1 generated NBC in the active site. Moreover, since at least one calcium ion is present in the PON catalytic site, we attempted to probe the metal local environment using the calcium analog terbium. The luminescence spectrum of the PON–terbium complex exhibited an emission peak at 545 nm characteristic of an aromatic residue (Trp and/or Tyr)–terbium interaction. In conclusion, both the results obtained with the mechanism-based inhibitor of PON1 (ANBC) and the calcium-binding site luminescent probe terbium support the hypothesis of the presence of at least one Trp residue in the PON1 active site. Trp residue(s) may be involved in the binding of aromatic substrates.

Human serum paraoxonase/arylesterase (PON1, EC 3.1.8.1.) is a calcium-dependent enzyme which hydrolyzes a wide variety of organophosphates, including paraoxon, DFP, sarin and soman. Although the 3-D structure of PON has not yet been determined and its sequence shows no similarity with any other crystallized proteins, we undertook to identify some of its essential amino acid residues by two complementary approaches: group-specific labelling and site-directed mutagenesis. Group-specific labelling studies, performed on the purified native enzyme, indicated that one or more Trp, His and Asp/Glu are potentially important residues for PON activity. Based on these results, we identified some of these residues, conserved in the sequenced mammalian PON1, by site-directed mutagenesis. PON1 mutants were transiently expressed in 293T cells. The catalytic constants kcatand Km(relative to kcatand Kmof the wild-type) determined with four different substrates (phenylacetate, paraoxon, diazoxon, chlorpyrifos oxon), were not significantly changed for the following mutants: W193A, W201A, W253A, H160N, H245N, H250N, H347N, E32A, E48A, D88A, D107A, D121A, D273A. By contrast, kcatwas less than 1% for eight mutants: W280A, H114N, H133N, H154N, H242N, H284N, E52A and D53A. The essential amino acid residues identified in this work could be part of the PON1 active site, acting either as calcium ligands (E52 and D53?) or as substrate binding (W280?) or nucleophilic (His residues?) sites. However, we cannot rule out that the effects of mutations on catalytic properties resulted from a remote conformational change and/or misfolding of mutant proteins.

Dans le domaine judiciaire, les cheveux sont progressivement devenus un outil très utile pour contribuer à résoudre certaines enquêtes. Dans ce cadre, leur capacité de stockage des composés chimiques absorbés par l'organisme est mise à profit. Ils peuvent aussi capter certains produits toxiques présents dans l'air. Mais une fois contaminés, les cheveux deviennent à leur tour une source potentielle d'intoxication. Peuvent-ils être décontaminés ? [ABSTRACT FROM AUTHOR]