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Patrick Masson - One of the best experts on this subject based on the ideXlab platform.
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Polyclonal antibody to Soman-tyrosine.
Chemical research in toxicology, 2013Co-Authors: Ellen G. Duysen, Marie Thérèse Froment, Patrick Masson, Florian Nachon, Wei Jiang, Lawrence M. Schopfer, Geoffrey M. Thiele, Lynell Warren Klassen, John R. CashmanAbstract:Soman forms a stable, covalent bond with tyrosine 411 of human albumin, with tyrosines 257 and 593 in human transferrin, and with tyrosine in many other proteins. The pinacolyl group of Soman is retained, suggesting that pinacolyl methylphosphonate bound to tyrosine could generate specific antibodies. Tyrosine in the pentapeptide RYGRK was covalently modified with Soman simply by adding Soman to the peptide. The phosphonylated-peptide was linked to keyhole limpet hemocyanin, and the conjugate was injected into rabbits. The polyclonal antiserum recognized Soman-labeled human albumin, Soman-mouse albumin, and Soman human transferrin but not nonphosphonylated control proteins. The Soman-labeled tyrosines in these proteins are surrounded by different amino acid sequences, suggesting that the polyclonal recognizes Soman-tyrosine independent of the amino acid sequence. Antiserum obtained after 4 antigen injections over a period of 18 weeks was tested in a competition ELISA where it had an IC50 of 10(-11) M. The limit of detection on Western blots was 0.01 μg (15 picomoles) of Soman-labeled albumin. In conclusion, a high-affinity, polyclonal antibody that specifically recognizes Soman adducts on tyrosine in a variety of proteins has been produced. Such an antibody could be useful for identifying secondary targets of Soman toxicity.
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Binding and Hydrolysis of Soman by Human Serum Albumin
Chemical research in toxicology, 2007Co-Authors: Florian Nachon, Marie Thérèse Froment, Lawrence M. Schopfer, Laurent Verdier, Jean Claude Debouzy, Bernardo Brasme, Emilie Gillon, Oksana Lockridge, Patrick MassonAbstract:Human plasma and fatty acid free human albumin were incubated with Soman at pH 8.0 and 25 degrees C. Four methods were used to monitor the reaction of albumin with Soman: progressive inhibition of the aryl acylamidase activity of albumin, the release of fluoride ion from Soman, 31P NMR, and mass spectrometry. Inhibition (phosphonylation) was slow with a bimolecular rate constant of 15 +/- 3 M(-1) min (-1). MALDI-TOF and tandem mass spectrometry of the Soman-albumin adduct showed that albumin was phosphonylated on tyrosine 411. No secondary dealkylation of the adduct (aging) occurred. Covalent docking simulations and 31P NMR experiments showed that albumin has no enantiomeric preference for the four stereoisomers of Soman. Spontaneous reactivation at pH 8.0 and 25 degrees C, measured as regaining of aryl acylamidase activity and decrease of covalent adduct (pinacolyl methylphosphonylated albumin) by NMR, occurred at a rate of 0.0044 h (-1), indicating that the adduct is quite stable ( t1/2 = 6.5 days). At pH 7.4 and 22 degrees C, the covalent Soman-albumin adduct, measured by MALDI-TOF mass spectrometry, was more stable ( t1/2 = 20 days). Though the concentration of albumin in plasma is very high (about 0.6 mM), its reactivity with Soman (phosphonylation and phosphotriesterase activity) is too slow to play a major role in detoxification of the highly toxic organophosphorus compound Soman. Increasing the bimolecular rate constant of albumin for organophosphates is a protein engineering challenge that could lead to a new class of bioscavengers to be used against poisoning by nerve agents. Soman-albumin adducts detected by mass spectrometry could be useful for the diagnosis of Soman exposure.
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Soman inhibition of butyrylcholinesterase in the presence of substrate: pressure and temperature perturbations.
Biochimica et biophysica acta, 1992Co-Authors: Cécile Cléry, Patrick Masson, Irmgard Heiber-langer, Claude BalnyAbstract:Irreversible inhibition of butyrylcholinesterase by Soman was studied in the presence of the substrate (o-nitrophenyl butyrate). Inhibition was found of the competitive complexing type. Study at different temperatures and pressures showed that the behavior of the enzyme differs from that of the inhibitor-free enzyme. In the absence of inhibitor, enzyme kinetics displayed a non-linear temperature dependence with a break at 21 degrees C. In the presence of a non-inhibitor structural analog of Soman (pinacolyl dimethylphosphinate and methyl dimethylphosphinate), the Arrhenius plot break is slightly shifted (18 degrees C). On the other hand, in the presence of Soman this break is abolished. The pressure-dependence of the substrate hydrolysis revealed also differences between the native enzyme and the enzyme in the presence of Soman: the sign and magnitude of the apparent activation volume (delta V not equal to) were different for the two reactions. Beyond 300 bar, in the presence of Soman, a plateau (delta V not equal to approx. 0) was observed over a large pressure range depending on temperature. Such a behavior with respect to temperature and pressure can reflect a Soman-induced enzyme conformational state. Thus, temperature and pressure perturbations of the kinetics allow to complete the inhibition scheme of butyrylcholinesterase by Soman. Our data suggest that upon Soman binding, the enzyme undergoes a long-lived Soman-induced-fit conformational change preceding the phosphonylation step. However, an alternative hypothesis according to which the enzyme processes a secondary Soman-binding site cannot be ruled out.
Guy Lallement - One of the best experts on this subject based on the ideXlab platform.
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long term consequences of Soman poisoning in mice part 1 neuropathology and neuronal regeneration in the amygdala
Behavioural Brain Research, 2008Co-Authors: Jeanmarc Collombet, Catherine Masqueliez, Dominique Baubichon, Christophe Pierard, Daniel Beracochea, Stephanie Coubard, Mariefrance Burckhart, Elise Four, Guy LallementAbstract:Abstract To date, studies on Soman-induced neuropathology mainly focused on the hippocampus, since this brain region is a well-delimited area with easily detectable pyramidal neurons. Moreover, the hippocampus is severely damaged after Soman exposure leading to a substantial alteration of behavioral mnemonic processes. The neuropathology described in the hippocampus, however, and its behavioral consequences cannot be extrapolated to all other limbic damaged brain areas such as the amygdala. Accordingly, in this inaugural paper, using hemalun–phloxin staining and NeuN immunohistochemistry, the number of damaged and residual healthy neurons was quantified in the amygdala in mice over a 90-day period after Soman injection (1.2 LD 50 of Soman). On post-Soman day 1, a moderate neuronal cell death (about 23% of the whole neurons) was evidenced. In parallel, a large quantity of degenerating neurons (about 36% of the whole neurons) occurred in this brain region and survived from post-Soman day 1 to day 15. The death of these damaged neurons was initiated on post-Soman day 30, and ended on post-Soman day 90. Concomitantly, as quantified by NeuN immunohistochemistry, a clear neuronal regeneration was demonstrated in the amygdala of Soman-poisoned mice between 60 and 90 days after neurotoxicant exposure. In the companion paper (see part 2), the possible effects of both long-term neuropathology and delayed neuronal regeneration were evaluated on amygdala-driven emotional processes.
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long term consequences of Soman poisoning in mice part 2 emotional behavior
Behavioural Brain Research, 2008Co-Authors: Stephanie Coubard, Guy Lallement, Jeanmarc Collombet, Daniel Beracochea, Jeannicolas Philippin, Ali Krazem, Pierrette Liscia, Christophe PierardAbstract:Abstract The organophosphorus compound Soman produces long-lasting epileptic seizure activity which is associated to brain damage, more particularly in the hippocampus and the amygdala. The companion paper (see part 1 in the same journal issue) describes the neuropathology in the amygdala of Soman-poisoned mice. The present paper examines the long-term effects of Soman poisoning on emotional reactivity in mice, 30 or 90 days after intoxication using behavioral tasks involving amygdala function. The emotional behavior was estimated in animal tests of unconditioned fear (light/dark boxes, elevated plus-maze) and conditioned fear (auditory and contextual response). In the light/dark boxes and elevated plus-maze, mice intoxicated with Soman (110 μg/kg, 1.2 LD 50 ) showed an anxiety-like behavior profile at post-poisoning days 30 and 90. In conditioned fear, results showed that both auditory and contextual conditioned responses are increased on post-Soman day 30 but no longer on post-Soman day 90, evidencing behavioral recovery overtime. This latter behavioral result is in accordance with the delayed neuronal regeneration patterns described in the companion paper (part 1).
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The role of nitric oxide in Soman-induced seizures, neuropathology, and lethality.
Pharmacology biochemistry and behavior, 1996Co-Authors: Guy Lallement, I. Pernot-marino, Dominique Baubichon, Tsung Ming Shih, Annie Foquin, John H. McdonoughAbstract:The effects of the inhibitors of endothelial and neuronal nitric oxide (NO) synthases, N-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI), respectively, and the precursor of NO, glyceryl trinitrate, on Soman-induced seizures, lethality, and neuropathology were studied in rats. It was found that pretreatment of rats with L-NAME and 7-NI potentiated the severity of motor convulsions and enhanced lethality produced by Soman. On the other hand, glyceryl trinitrate, administered transdermally at doses ranging from 2.5-5 mg/day 1 day before Soman, decreased seizure susceptibility and lethality in Soman-intoxicated animals. This was accompanied by a subsequent reduction of central neuronal damage 24 h after Soman treatment. Pretreatment with glyceryl trinitrate also reversed seizure latency produced by 7-NI treatment during Soman intoxication. These results indicate that neuronal NO may play a prominent role in seizures by acting as an anticonvulsant and neuroprotectant in Soman intoxication.
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Modulation of Soman-induced neuropathology with an anticonvulsant regimen.
Neuroreport, 1994Co-Authors: Guy Lallement, I. Pernot-marino, Dominique Baubichon, Pierre Carpentier, Mariefrance Burckhart, Guy BlanchetAbstract:Rat hippocampus and piriform cortex were examined for pathological changes 48 hours after exposure to a convulsant dose of Soman. Animals were treated with a low dose of atropine just after Soman and were then injected, after 10 or 40 minutes of seizures, with both the anticonvulsant drugs NBQX and TCP. Atropine given alone counteracted the extensive neuronal loss due to Soman in both areas without prevention of neuronal suffering. Comparatively, the complete anticonvulsant regimen, given before 40 minutes of seizures, totally prevented hippocampal Soman-induced neuropathology. Neurones of piriform cortex were still suffering whatever the time of injection of the drugs. This emphasizes the need for a rapid and definitive anticonvulsant treatment just after Soman intoxication to block the subsequent neurotoxic effect of nerve-agent exposure.
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Anticonvulsant and antilethal effects of the phencyclidine derivative TCP in Soman poisoning
Neurotoxicology, 1994Co-Authors: Pierre Carpentier, G. Blanchet, Jeanmarc Kamenka, Gérard Rondouin, A. Foquin-tarricone, N. Bodjarian, Mireille Lerner-natoli, M. Denoyer, Guy LallementAbstract:The protection afforded by TCP (thienylcylohexylpiperidine), a non-competitive blocker of N-methyl-D-aspartate (NMDA) receptors, against the seizures and lethality produced by 2 × LD50 of Soman (62 μg/kg, sc), an irreversible inhibitor of cholinesterase, was studied in guinea-pigs. In the presence of additional anticholinergic medication (pyridostigmine: 0.2 mg/kg, sc, 30 min prior to Soman; atropine sulphate: 5 mg/kg, im, 1 min post-Soman), TCP pretreatment (2.5 mg/kg, im, 30 or 15 min prior to Soman) did not generally prevent the appearance of Soman-induced status epilepticus but did arrest it after 30-40 min in 80% (TCP-30 min) or 100% (TCP-15 min) of the convulsing subjects. Moreover, in all subjects treated curatively, TCP was able to interrupt ongoing status epilepticus in approximately 20, 10 or 8 min when it was administered 5, 30 or 60 min respectively after the onset of epileptiform tracings on EEG. All of these curatively administered animals survived and recovered remarkably well. On every criteria examined (latency-to-seizure arrest, 24 hr-survival rate, clinical recovery), injection of 2.5 mg/kg TCP after 90 min of seizures appeared slightly less efficient compared to earlier curative administration. Therefore, our study (a) establishes that the previously reported capacity of MK-801 (dibenzocyclohepneimine) to counteract Soman toxicity is not unique and could be extended to other non-competitive inhibitors of NMDA receptors; (b) shows that TCP could easily prevent and, above all, interrupt Soman-induced seizures; furthermore, TCP appears the first compound ever tested on Soman poisoning that still displays satisfactory anticonvulsant activity after such a long duration of initial status epilepticus (90 min); therefore, TCP might be of special value for the delayed therapy for Soman poisoning; (c) confirms that NMDA receptors are involved in the maintenance of seizures and play an important role in other processes implicated in the overall toxicity (including the lethal respiratory effects) of Soman poisoning
J. G. Clement - One of the best experts on this subject based on the ideXlab platform.
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Chromodacryorrhea in rats: absence following Soman poisoning.
Toxicology and applied pharmacology, 1994Co-Authors: J. G. ClementAbstract:Chromodacryorrhea is the secretion of so-called "bloody tears" from the harderian gland which nearly circumscribes the eye within the bony orbit. Direct-acting cholinergic agonists such as oxotremorine, carbachol, and pilocarpine caused chromodacryorrhea but nicotine did not. Atropine blocked chromodacryorrhea induced by systemic administration of direct-acting cholinergic agonists. Thus, chromodacryorrhea appears to be a muscarinic receptor-related event. Soman (pinacolyl methylphosphonofluoridate), a potent irreversible inhibitor of acetylcholinesterase which increases the synaptic concentration of the neurotransmitter acetylcholine, did not induce chromodacryorrhea in rats. Similarly, physostigmine, a tertiary, carbamate acetylcholinesterase inhibitor, did not induce chromodacryorrhea. In vivo Soman-induced inhibition of harderian gland acetylcholinesterase was independent of the Soman dose and the inhibition was significantly less than brain acetylcholinesterase. In vitro Soman-induced inhibition of harderian gland acetylcholinesterase was not significantly different from that of diaphragm acetylcholinesterase. The lack of inhibition of acetylcholinesterase in the harderian gland does not appear to be due to a difference in sensitivity to inhibition by Soman. The distribution of the various molecular forms of acetylcholinesterase between the diaphragm and harderian gland was different. There was a great deal more of the 4S form of acetylcholinesterase in the harderian gland than in the diaphragm. The lack of the following, inhibition of harderian gland acetylcholinesterase and elevation of the synaptic concentration of acetylcholine, could explain the absence of chromodacryorrhea following Soman poisoning. The discrepancy between the significant Soman-induced inhibition of brain acetylcholinesterase and the lack of inhibition of harderian gland acetylcholinesterase allows one to speculate that there may be a very efficient scavenger of Soman present in the rat harderian gland.
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Efficacy of diazepam and avizafone against Soman-induced neuropathology in brain of rats.
Neurotoxicology, 1993Co-Authors: J. G. Clement, B. BroxupAbstract:The purpose of this investigation was to compare the efficacy of diazepam and a water soluble pro-diazepam drug, avizafone (lysyl, peptido-aminobenzophenone diazepam pro-drug) in preventing or reducing the severity of Soman-induced neuropathology in rats and to determine the temporal relationship between seizure initiation, anticonvulsant administration and the incidence and severity of Soman-induced neuropathology. Brains from rats, treated with a convulsant dose of Soman (pinacolyl methylphosphonofluoridate) and anticonvulsants such as diazepam and avizafone, were evaluated by light microscopy for evidence of neuropathology. All rats received atropine methyl nitrate (20 mg/kg, ip)+the bispyridinium acetylcholinesterase reactivator HI-6 (125 mg/kg, ip; 1-(((4-(aminocarbonyl)pyridinio) methoxy)methyl)-2-((hydroxyimino)methyl)-pyridinium dichloride) in the same solution 10 min before Soman (130 micrograms/kg,sc). Three days later the rats were perfused and the tissue fixed for histological evaluation. Necrosis and/or malacia (degenerative changes) and hemorrhage were observed in some groups. The sites where pathology was most frequently observed and with greater severity were the piriform cortex, amygdala and (dorsal) thalamus. Less severe changes were observed in the cerebral cortex and hippocampus. There were no changes in the hypothalamus. Diazepam given 10 minutes before Soman prevented the occurrence of Soman-induced convulsions and neuropathology (i.e. degenerative changes were not then seen). Diazepam given at the start of the Soman-induced convulsions reduced considerably the convulsions and the degree of neuropathology. Avizafone given 10 minutes before Soman reduced slightly the effect of Soman. Other treatments (diazepam given 30, 60 and 120 minutes after the start of the convulsions and avizafone given at the start of convulsions) showed little or no effect on the neuropathology associated with Soman administration. The results of this study have demonstrated that the use of an anticonvulsant, such as diazepam, must be initiated shortly after Soman exposure in order for any therapeutic benefit to be realized.
John G. Clement - One of the best experts on this subject based on the ideXlab platform.
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Pharmacological nature of Soman-induced hypothermia in mice.
Pharmacology biochemistry and behavior, 1993Co-Authors: John G. ClementAbstract:The object of the study was to determine the pharmacological nature of pinacolyl methylphosphonofluoridate (Soman)-induced hypothermia in mice. This was accomplished by examining the Soman hypothermia dose response and the effect of various pharmacological antagonists in comparison to the hypothermia responses of muscarinic and nicotinic cholinergic agonists such as oxotremorine and nicotine and another anticholinesterase, physostigmine. Core temperature in mice was monitored by telemetry. In general, atropine antagonized oxotremorine, physostigmine, and Soman hypothermia but not nicotine hypothermia whereas mecamylamine antagonized nicotine hypothermia but not that produced by the other agonists. Soman hypothermia was not affected significantly by various pharmacological antagonists, suggesting that other neurotransmitters were not involved in the expression of Soman hypothermia. Soman hypothermia appears to be due to muscarinic receptor stimulation and can be effectively antagonized, but not completely, by the use of atropine. Acetylcholinesterase oxime reactivators, such as HI-6 and toxogonin, were ineffective in antagonizing Soman-induced hypothermia and reactivating hypothalamic acetylcholinesterase, whereas HI-6 was effective in reactivating Soman-inhibited diaphragm acetylcholinesterase when administered up to 10 min after Soman, indicating that aging of the Soman-inhibited acetylcholinesterase had not occurred. Soman hypothermia appears to be primarily a muscarinic receptor-related event.
Zoran Grubič - One of the best experts on this subject based on the ideXlab platform.
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The influence of Soman simulator on reactivation by HI-6 of Soman-inhibited acetylcholinesterase in preparations of rat and human skeletal muscle
Biochemical pharmacology, 1993Co-Authors: Martina Brank, Marjeta Šentjurc, Anton Štalc, Zoran GrubičAbstract:The aim of our study was to elucidate the phenomenon called "Soman depot". Our investigations were focused on the depot formed in the skeletal muscle and on the effects of 1,2,2-trimethylpropyl dimethylphosphonate (PDP), a reported blocker of Soman depot formation. The following questions were addressed: (1) how much of acetylcholinesterase (EC 3.1.1.7, AChE) activity can additionally be recovered by Hagedorn bispiridinium oxime reactivator 2-hydroxyimino-methylpyridinium-1-methyl-4'-carbamoyl-pyridinium-1 '-methylether dichloride monohydrate (HI-6) in the skeletal muscle preparations if they are pretreated by PDP prior to incubation in Soman (1,2,2-trimethylpropyl methylphosphonofluoridate)? (2) Is this effect uniform along the muscle fibre or different in the endplate in comparison to the endplate-free region? (3) Is the effect of PDP species specific, i.e. does it differ between rat and human muscle? (4) What are the molecular mechanisms of the effects of PDP? PDP pretreatment increased the reactivation of Soman-inhibited AChE by HI-6 in both regions of rat skeletal muscle. This increase was smaller in human skeletal muscle. The PDP-mediated increase in HI-6 reactivation was most efficient in the endplate-rich region of rat diaphragm as demonstrated biochemically and histochemically, but it could not be explained by the blockade of Soman depot alone since it was also observed at low Soman concentrations, at which Soman depot is not supposed to form. This PDP effect could be better explained by the direct interactions of PDP with AChE resulting in decreased AChE phosphorylation. Soman concentration-dependent increase in HI-6 reactivation by PDP, which was more efficient at a high than a low Soman concentration and could therefore originate from blockade of Soman depot, was observed in the endplate-free region of rat diaphragm. It was also found in human muscle but was again smaller in this species. According to our EPR study, solubilization of Soman in the lipophilic cell membrane compartment can be excluded as a mechanism producing significant Soman depot. In general, our results suggest a more complex mechanism of PDP action than reported previously.
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The effects of pretreatment with Soman simulator in the skeletal muscle : direct interactions with acetylcholinesterase
Chemico-biological interactions, 1993Co-Authors: Zoran Grubič, Martina Brank, Miro BrzinAbstract:Soman simulator PDP is a compound that has a chemical structure identical to Soman, except that the fluorine atom is replaced by a methyl group which makes PDP unable to bind covalently to the AChE active center. In rats, late mortality observed after treatment with high doses of Soman could be prevented by PDP pretreatment. Such pretreatment has been much less efficient in primates. The effect of PDP in rats has been explained by blocking the deposition of Soman in so-called Soman depots in which Soman is stored intact and subsequently released. In this paper we demonstrate that in the presence of PDP, inhibition of rat muscle AChE by Soman is reduced in rat but not in human muscle homogenates. This result suggests that at least part of the beneficial effects of PDP pretreatment in rat might be due to the direct interaction of PDP with AChE resulting in reduced AChE phosphorylation by Soman.
