Desorption of sulphur mustard simulants methyl salicylate and 2-chloroethyl ethyl sulphide from contaminated scalp hair after vapour exposure

Chemical warfare agents have been used to incapacitate, injure or kill people, in a context of war or terrorist attack. It has previously been shown that hair could trap the sulphur mustard simulants methyl salicylate and 2-chloroethyl ethyl sulphide. In order to investigate simulants persistency in hair after intense vapour exposure, their desorption kinetics were studied by using two complementary methods: hair residual content measurement and desorbed vapour monitoring. Results showed that both simulants were detected in air and could be recovered from hair 2 h after the end of exposure. Longer experiments with methyl salicylate showed that it could still be recovered from hair after 24 h. Our data were fitted with several kinetic models and best correlation was obtained with a bimodal first-order equation, suggesting a 2-step desorption kinetics model: initial fast regime followed by a slower desorption. 2-chloroethyl ethyl sulphide was also detected in the immediate environment after hair exposure for 2 h, and hair simulant content decreased by more than 80%. Our results showed that hair ability to release formerly trapped chemical toxics could lead to health hazard. Their persistency however confirmed the potentiality of hair analysis as a tool for chemical exposure assessment.

Efficacy of scalp hair decontamination following exposure to vapours of sulphur mustard simulants 2-chloroethyl ethyl sulphide and methyl salicylate

Chemical warfare agents are an actual threat and victims' decontamination is a main concern when mass exposure occurs. Skin decontamination with current protocols has been widely documented, as well as surface decontamination. However, considering hair ability to trap chemicals in vapour phase, we investigated hair decontamination after exposure to sulphur mustard simulants methyl salicylate and 2-chloroethyl ethyl sulphide. Four decontamination protocols were tested on hair, combining showering and emergency decontamination (use of Fuller's earth or Reactive Skin Decontamination Lotion RSDL^®). Both simulants were recovered from hair after treatment, but contents were significantly reduced (42-85% content allowance). Showering alone was the least efficient protocol. Concerning 2-chloroethyl ethyl sulphide, protocols did not display significant differences in decontamination efficacy. For MeS, use of emergency decontaminants significantly increased showering efficacy (10-20% rise), underlining their usefulness before thorough decontamination. Our results highlighted the need to extensively decontaminate hair after chemical exposure. Residual amounts after decontamination are challenging, as their release from hair could lead to health issues.

New CeO2 nanoparticles-based topical formulations for the skin protection against organophosphates

To reinforce skin protection against organophosphates (OPs), the development of new topical skin protectants (TSP) has received a great interest. Nanoparticles like cerium dioxide (CeO₂) known to adsorb and neutralize OPs are interesting candidates for TSP. However, NPs are difficult to disperse into formulations and they are suspected of toxicological issues. Thus, we want to study: (1) the effect of the addition of CeO₂ NPs in formulations for the skin protection (2) the impact of the doping of CeO₂ NPs by calcium; (3) the effect of two methods of dispersion of CeO₂ NPs: an O/W emulsion or a suspension of a fluorinated thickening polymer (HASE-F) grafted with these NPs. As a screening approach we used silicone membranes as a skin equivalent and Franz diffusion cells for permeation tests. The addition of pure CeO₂ NPs in both formulations permits the penetration to decrease by a 3–4-fold factor. The O/W emulsion allows is the best approach to obtain a film-forming coating with a good reproducibility of the penetration results; whereas the grafting of NPs to a thickener is the best way to obtain an efficient homogenous suspension of CeO₂ NPs with a decreased of toxicological impact but the coating is less film-forming which slightly impacts the reproducibility of the penetration results.

Showering effectiveness for human hair decontamination of the nerve agent VX

In this work, our goals were to establish whether hair decontamination by showering one hour post-exposure to the highly toxic organophosphate nerve agent VX was effective, whether it required the addition of a detergent to water and, if it could be improved by using the adsorbent Fuller's Earth (FE) or the Reactive Skin Decontamination Lotion (RSDL) 30 min prior to showering. Hair exposure to VX and decontamination was performed by using an in vitro model. Hair showering led to 72% reduction of contamination. Addition of detergent to water slightly increased the decontamination effectiveness. Hair treatment with FE or RSDL improved the decontamination rate. Combination of FE use and showering, which yielded a decontamination factor of 41, was demonstrated to be the most effective hair decontamination procedure. Hair wiping after showering was shown to contribute to hair decontamination. Altogether, our results highlighted the importance of considering hair decontamination as an important part of body surface decontamination protocols.

Human scalp permeability to the chemical warfare agent VX

The use of chemical warfare agents such as VX in terrorism act might lead to contamination of the civilian population. Human scalp decontamination may require appropriate products and procedures. Due to ethical reasons, skin decontamination studies usually involve in vitro skin models, but human scalp skin samples are uncommon and expensive. The purpose of this study was to characterize the in vitro permeability to VX of human scalp, and to compare it with (a) human abdominal skin, and (b) pig skin from two different anatomic sites: ear and skull roof, in order to design a relevant model. Based on the VX skin permeation kinetics and distribution, we demonstrated that (a) human scalp was significantly more permeable to VX than abdominal skin and (b) pig-ear skin was the most relevant model to predict the in vitro human scalp permeability. Our results indicated that the follicular pathway significantly contributed to the skin absorption of VX through human scalp. In addition, the hair follicles and the stratum corneum significantly contributed to the formation of a skin reservoir for VX.

Quadratic and Cubic Nonlinearities in Solution of Intramolecular Charge Transfer Aromatic Molecules A Quantum Two-Level Approach

A two-level expression of the second-order hyperpolarizability (y) is proposed, and shown to contain a negative charge transfer (CT) contribution. Frequency dispersed measurements of the quadratic and cubic susceptibility of N-(4-nitropheny1)-L-prolinol (NPP), N-(4-nitrophenyl)-N-methylaminoacetonitrile (NPAN) and 2-(N-prolinol)-5-nitropyridine (PNP) are reported. The electric field induced second-harmonic generation (EFISH) and third-harmonic generation (THG) techniques in solution are used. A two-level model dispersion of y as from THG measurements is shown to lead to a neglegible electronic contribution to the overall EFISH nonlinearity, as compared to the orientational contribution. The theoretical β-components of these molecules, obtained consistently by finite-field and perturbational approaches, clearly confirm that the β-tensor is one-dimensional along the donor-acceptor CT axis. The off resonance quadratic polarizabilities (β) of these molecules are sequenced as follows : β(NPP)> β(PNP)> β(NPAN). However this increased efficiency is obtained at the expense of the transparency range.

In vitro percutaneous penetration of organophosphorus compounds using full-thickness and split-thickness pig and human skin

Organophosphorus compounds (OPs), such as pesticides and chemical warfare agents like sarin (GB), soman (GD) and VX, are highly toxic compounds. The OP vapours and their liquid forms are readily absorbed through the skin, therefore, protecting the skin of people who are potentially exposed to these agents is crucial. The development of effective countermeasures relies on a better knowledge of the percutaneous penetration of such molecules. The purpose of this present study is to determine the in vitro percutaneous penetration parameters of two pesticides DSM and DFP, as potential simulants of V and G agents, respectively, using four in vitro systems: full-thickness and split-thickness human abdominal and pig-ear skin membranes mounted on static diffusion cells. Based on the toxicokinetic parameters of the percutaneous penetration of DSM and DFP, we demonstrated that (a) pig-ear skin is a relevant model to predict the in vitro human skin permeability taking into account a 2-fold difference between these two species (b) both full and split-thickness skin membranes could be used indiscriminately, (c) DSM and DFP would be appropriate surrogates for V and G agents to perform skin permeation studies.

Structure/function analyses of human serum paraoxonase (HuPON1) mutants designed from a DFPase-like homology model

Human serum paraoxonase (HuPON1) is a calcium-dependent enzyme that hydrolyzes esters, including organophosphates and lactones, and exhibits anti-atherogenic properties. A few amino acids have been shown to be essential for the enzyme's arylesterase and organophosphatase activities. Until very recently, a three-dimensional model was not available for HuPON1, so functional roles have not been assigned to those residues. Based on sequence-structure alignment studies, we have folded the amino acid sequence of HuPON1 onto the sixfold beta-propeller structure of squid diisopropylfluorophosphatase (DFPase). We tested the validity of this homology model by circular dichroism (CD) spectroscopy and site-directed mutagenesis. Consistent with predictions from the homology model, CD data indicated that the structural composition of purified HuPON1 consists mainly of beta-sheets. Mutants of HuPON1 were assayed for enzymatic activity against phenyl acetate and paraoxon. Substitution of residues predicted to be important for substrate binding (L69, H134, F222, and C284), calcium ion coordination (D54, N168, N224, and D269), and catalytic mechanism of HuPON1 (H285) led to enzyme inactivation. Mutants F222Y and H115W exhibited substrate-binding selectivity towards phenyl acetate and paraoxon, respectively. The homology model presented here is very similar to the recently obtained PON1 crystal structure, and has allowed identification of several residues within the enzyme active site.

Oligomeric states of the detergent-solubilized human serum paraoxonase (PON1)

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 C(12)E(8) micellar 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.

The active site of human paraoxonase (PON1)

Ideally we would like to treat people exposed to nerve agents with an enzyme that rapidly destroys nerve agents. The enzymes considered for such a role include human butyrylcholinesterase (BChE), acetylcholinesterase (AChE), carboxylesterase and paraoxonase (PON1). Success has been achieved in endowing BChE with the ability to hydrolyze organophosphates. The G117H mutant of BCHE hydrolyzes sarin and VX, whereas the double mutant G117H/E197Q hydrolyzes soman (Millard et al. Biochemistry 1995; 34: 15925-15933; 1998; 37: 237-247). However, the rates of organophosphate hydrolysis are slow and a faster organophosphate hydrolase is being sought. Native PON1 hydrolyzes paraoxon with a catalytic efficiency, of 2.4 x 10(6) M(-1) x min(-1), and our goal is to improve the organophosphate hydrolase activity of PON1. To achieve this we need to identify the amino acids in the active site of PON1. Using site-directed mutagenesis and expression in human 293T cells, we have identified the following eight amino acids as being essential to PON1 activity: W280, H114, H133, H154, H242, H284, E52 and D53. Fluorescence of PON1 complexed to terbium ion shows that at least one tryptophan is close to the calcium binding site.

[Human plasma paraoxonase (HuPON1): an anti-atherogenic enzyme with organophosphate hydrolase activity]

Human plasma paraoxonase (PON1) is a calcium-dependent organophosphate-hydrolase. In plasma, PON1 is bound to high-density lipoproteins (HDL). PON1 prevents the oxidation of LDL and scavenges oxidized phospholipids, thus protecting from atherogenesis. Improving the prophylaxis and treatment of organophosphate (OP) poisoning is a public health concern that also interests the civilian safety and the military. In this context, engineering and formulation of enzymes able to scavenge or hydrolyze OPs, such as PON1, are widely studied. Determination of the PON1 three-dimensional structure is a key step toward improvement of the enzyme functional properties.

Polymer-based microcavity with photoencoded quadratic nonlinearity

Functional electro-optic polymer thin films embedded in microcavity structures have been poled by an all-optical procedure based on the interference of multiphoton absorption processes. The photoinduced X((2)) tensor was then further addressed at modal resonance for the fundamental wavelength, leading to significant enhancement of the second-harmonic-generation efficiency. An order-of-magnitude enhancement, which is due to electric field resonant conditions inside the microcavity, has been probed by an optical parametric oscillator, in comparison with a single-path thin-film configuration. This configuration opens new perspectives in the realm of nonlinear photonic device processing.

Tryptophan residue(s) as major components of the human serum paraoxonase active site

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 k(cat) and Km (relative to k(cat) and Km of 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 (PON1): identification of essential amino acid residues by group-selective labelling and site-directed mutagenesis

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 k(cat) and Km (relative to k(cat) and Km of 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, k(cat) was 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.

Identification of residues essential for human paraoxonase (PON1) arylesterase/organophosphatase activities

Human serum paraoxonase (PON1) is a calcium-dependent organophosphatase. To identify residues essential for PON1 activity, we adopted complementary approaches based on chemical modification and site-directed mutagenesis. To detect 45Ca2+ binding to native and chemically modified PON1, we performed nondenaturating gel electrophoresis. The environment of calcium-binding sites was probed using the Ca2+ analogue, terbium. Tb3+ binds to calcium-binding sites as shown by displacement of 45Ca2+ by Tb3+. Binding of Tb3+ is accompanied by a complete loss of enzyme activity. PON1 chemical modification with the Trp-selective reagent, N-bromosuccinimide, and the Asp/Glu-selective, dicyclohexylcarbodiimide, established that Trp and Asp/Glu residues are components of the PON1 active center and calcium-binding sites. Additional evidence for the presence of a Trp residue in the PON1 calcium-binding sites was a characteristic fluorescence emission at 545 nm from the PON1-Tb3+ complex and abolishment of that fluorescence upon modification by N-bromosuccinimide. The importance of aromatic/hydrophobic character of the residue 280 was demonstrated by site-directed mutagenesis: the W280F mutant was fully active while the W280A and W280L mutants had markedly reduced activity. Twelve amino acids among conserved His and Asp/Glu residues were found essential for PON1 arylesterase and organophosphatase activities: H114, H133, H154, H242, H284, D53, D168, D182, D268, D278, E52, and E194. Finally, the cysteines constituting the PON1 disulfide bond (C41 and C352) were essential, but the glycan chains linked to Asn 252 and 323 were not essential for PON1 secretion and activity.

Enzymes hydrolyzing organophosphates as potential catalytic scavengers against organophosphate poisoning

Enzymes hydrolyzing organophosphates could be used as catalytic scavengers for treatment of organophosphate poisoning and for decontamination. Two organophosphorus hydrolases (OPH) were selected: the Flavobacterium sp/Pseudomonas diminuta phosphotriesterase (PTE) and human paraoxonase (HuPON). Genes encoding these enzymes were cloned and functional recombinant enzymes expressed. PTE was expressed in E. coli. Natural HuPON was purified from human plasma; recombinant HuPON was expressed in human embryonic kidney 293 T cells. Although HuPON displays interesting catalytic properties, a site-directed mutagenesis program was undertaken to improve its catalytic efficiency. PTE has high efficiency in hydrolysis of organophosphates, including nerve agents. PTE injected in rat has a half-life of 100 min. However, to overcome pharmacokinetic problems of injected OPH and/or immunological incompatibility, the model enzyme (recombinant PTE) was immobilized onto a hollow-fiber reactor. This reactor designed for extracorporeal blood circulation is under experimentation for post-exposure detoxification.

[Evaluation of coronary risk: a new technique of measuring lipoprotein (a)]

The aim of this study was to assess the reliability of immuno-nephelemetric assay (INA) of lipoprotein (Lp(a)) compared with immuno-radiometric (IRMA) and immuno-enzymologic (ELISA) assays in a coronary (P1) and a non-coronary (P2) populations. The serums of 66 coronary subjects (P1) with an average age of 61.5 +/- 10 years and 137 non-coronary subjects (P2) with an average age of 54 +/- 12 years were analysed by the 3 techniques. The technical characteristics of the INA were: negligeable interference with plasminogen (PLG) (< 1/100) for PLG < 375 mg/l; excellent repeatability and reproducibility at low, medium and high concentrations, respectively 12.3 and 7.5%. 1.2 and 1.2%, 1.3 and 1.1%, low dependance on sample conservation (stable 5 days at +4 degrees C), excellent practicability (simple and quick automised analysis: 10 min). The linear correlations with the concentrations of Lp(a) were: excellent with INA/IRMA P1 and P2: 0.99; very good with INA/ELISA P1: 0.88 and P2: 0.85; very good between IRMA/ELISA P1: 0.91 and P2: 0.87. The average values of Lp(a) were 386 mg/l (INA), 339 mg/l (IRMA), 316 mg/l (ELISA) for P1, and 231 mg/l (INA), 212 mg/l (IRMA) and 153 mg/l (ELISA) for P2, with a significant difference between P1 and P2 with all three techniques: 0.0138 (INA), 0.0207 (IRMA) and 0.0001 (ELISA). The authors concluded that measuring Lp(a) by INA is reliable with respect to IRMA and ELISA techniques, as accurate, quicker, automatised and cheaper, compensating for a lower sensitivity, a calculated risk of a non-specific reaction and the necessity of a shorter delay of analysis. The comparative results in two populations demonstrate it to be an excellent marker of coronary risk for epidemiological studies, independant of other risk factors.

Biochemical and genetic definition of the cellular protease required for HIV-1 gp160 processing

The surface glycoproteins of enveloped viruses bind to target cell receptors and trigger membrane fusion for infection. The human immunodeficiency virus 1 (HIV-1) envelope glycoprotein gp120 (CD4 binding protein) and gp41 (transmembrane fusion protein) are initially synthesized as a gp160 precursor. The intracellular cleavage of gp160 by a host cell protease during transit through the secretory pathway is essential for viral activities such as infectivity, membrane fusion, and T-cell syncytium formation. We report that gp160 biogenesis, protein processing, and cell-surface expression have been successfully reproduced in the yeast Saccharomyces cerevisiae. Genetic and biochemical approaches are used for defining that the unique cellular protease, Kex2p, is directly responsible for HIV-gp160 processing in yeast, in vivo and in vitro. The yeast system described in this report represents a powerful strategy for identifying, characterizing and inhibiting the host T-cell protease essential for HIV infectivity and AIDS.

Maternal reactions to the birth of triplets

This study examines the reactions of 14 women to the birth of triplets. Home interviews and observations were conducted at 4 months and 1 year after the birth. The findings indicate that the triplet situation constitutes a real source of psychological stress for the women in this study. Reactions depend on two factors: individual makeup, in that some women become depressed whereas others develop defenses, and amount of support from family and friends. These variables, along with mothers' ability to overcome phantasms of abnormality generated by the exceptionality of a multiple maternity, serve to define a set of predictors of good/poor prognosis for the establishment of triplet-mother relationships.

Forms of family reorganization following the birth of twins

A survey questionnaire of 200 families with 2-month-old twins assesses the economic, social and psychological impact of the arrival of twins on family life. The study shows the extent of material difficulties mothers of twins are confronted with, and the ways they cope with them--recourse to mother's helpers, assistance from the father and other members of the family (analyzed in terms of parity and socioeconomic/cultural status), twincare organization strategies, and impact on the decision to stop working. The findings provide an overall picture of the real situation, a necessary prerequisite to an understanding of psychological problems.

Mother-twin interaction during early childhood

The components of a research program focusing on early mother-twin interaction is described. Preliminary data obtained from a questionnaire at two months post term, cross-sectional observations at the age of one year, a follow-up study involving home observation and parental interviews from birth to the age of 3, point to the specificity of this triadic situation. During the first months of life, the burden of material tasks and the increase in baby care leave little time for starting a relationship based on pleasure or play. The impossibility of responding simultaneously to the needs of two babies and the difficulty of forming relationships on an individual basis foster early concerns for egalitarianism. The degree of physical resemblance between the babies creates the problem of differentiating them. To tell twins apart, mothers rapidly tend to rely on behavioral characteristics to which they attribute a genetic basis. In contrast, differences in development between the babies that introduce the eventuality of the dominance of one of the twins are often denied. In this highly specific situation, mothers arrive at personal solutions of adjustment over the first 3 years, manifest in a certain number of psychological and educational attitudes. Analysis of these maternal attitudes may help to shed light on some of the features of later psychoemotional development in twins.