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Cutaneous and Ocular Toxicology Mar 2018The aim of this study was to determine optimal conditions for in vitro skin decontamination using water and detergents as decontamination agents and to test the...
The aim of this study was to determine optimal conditions for in vitro skin decontamination using water and detergents as decontamination agents and to test the cleansing efficiency of selected detergents. Experiments were performed using a peristaltic pump for showering of pig skin in modified static diffusion cells. Several conditions were tested including different flow rates (from 5 to 33 ml s), quantity of rinsing fluid (from 40 to 400 ml) and concentration of detergents (2; 5; 10%). Further, several types of detergents/commercial decontamination agents were evaluated under the selected conditions to find the most effective means of decontamination. The amount of paraoxon removed from the skin surface following wet-type decontamination was detected in the rinsing fluid spectrophotometrically after hydrolysis of paraoxon - a model contaminant. The efficacy of rinsing by water/Spolapon AES 253 increased with flow rate up to 25 ml s and a rinsing volume of 200 ml. Lutensol AT 25 achieved maximum efficacy at the lowest tested concentration (2%). A flow rate of 16 ml s, rinsing volume of 100 ml (values from the middle part of the sigmoid curve) and 5% concentration of decontaminant solution were used for further evaluation of detergents as cleansing agents under the selected conditions. Cetylpyridinium bromide (cationic surfactant), carbethopendecinii bromidum (cationic surfactant) and polyoxyethylene-10-tridecyl ether (non-ionic surfactant), SDS (anionic surfactant), althosan MB (cationic surfactant), sodium dodecylbenzene sulphonate (anionic surfactant), neodekont (mixture), tergitol NPX (non-ionic surfactant), Korynt P (non-ionic surfactant) were found to be the most effective. These decontaminants were able to wash away more than 92% of paraoxon from the contaminated skin.
Topics: Animals; Decontamination; Detergents; Female; Insecticides; Paraoxon; Skin; Surface-Active Agents; Swine; Water
PubMed: 28724312
DOI: 10.1080/15569527.2017.1354216 -
Immunological Investigations 2009In the present study, the synthesis of hapten for the organophosphorus (OP) pesticide paraoxon-methyl was developed, with a spacer arm (aminocarboxylic acid) attached at...
In the present study, the synthesis of hapten for the organophosphorus (OP) pesticide paraoxon-methyl was developed, with a spacer arm (aminocarboxylic acid) attached at the aromatic ring. It was conjugated to bovine serum albumin (BSA) for use as an immunogen and to ovalbumin (OVA) for coating antigen for ELISA testing. Rabbits were immunized with the immunogen and two polyclonal antisera were produced and screened against the coating antigen using competitive indirect enzyme-linked immunosorbent assay (ELISA). For application to textile samples, the influence of several factors such as organic solvent, ionic strength, and pH on the ELISA results were studied. Under optimized conditions, the quantitative working range was 0.012-1.158 microg/mL with a limit of detection (LOD) of 0.005 microg/mL and the IC(50) was 0.115 microg/mL.There was negligible cross reactivity (CR) with other OP pesticides. The recoveries obtained by standard paraoxon-methyl addition to the different textile samples such as cotton, wool and muslin delaine were all from 86.0% to 108.0%. Therefore, the optimized ELISA may become a new convenient and economical analytical tool for monitoring paraoxon-methyl residues in textile samples.
Topics: Animals; Antibodies; Cattle; Enzyme-Linked Immunosorbent Assay; Haptens; Organophosphorus Compounds; Ovalbumin; Paraoxon; Pesticides; Rabbits; Serum Albumin, Bovine; Textiles
PubMed: 19811409
DOI: 10.1080/08820130902803689 -
Analytica Chimica Acta May 2017In this work, a new colorimetric biosensor for the assay of paraoxon was developed via the conventional iodine-starch color reaction and multi-enzyme cascade catalytic...
In this work, a new colorimetric biosensor for the assay of paraoxon was developed via the conventional iodine-starch color reaction and multi-enzyme cascade catalytic reactions. In the presence of acetylcholine chloride, acetylcholinesterase (AChE) and choline oxidase (ChO) catalyzed the formation of HO, which then activated horseradish peroxidase (HRP) to catalyze the oxidation of KI to produce an iodine-starch color reaction. Upon exposure to paraoxon, the catalytic activity of AChE was inhibited and less HO generated, resulting in a decrease in the production of I and a drop in the intensity of solution color. This colorimetric biosensor showed high sensitivity for the assay of paraoxon with a limit of detection 4.7 ppb and was applied for the assay of paraoxon in spiked real samples. By employing the conventional iodine-starch color reaction, this biosensor has the potential of on-site assay of OPs residues in environmental samples.
Topics: Acetylcholine; Acetylcholinesterase; Alcohol Oxidoreductases; Biosensing Techniques; Colorimetry; Hydrogen Peroxide; Iodine; Paraoxon; Pesticides; Starch; Water Pollutants, Chemical
PubMed: 28390486
DOI: 10.1016/j.aca.2017.02.028 -
Chemico-biological Interactions Aug 2019Carbamates are esters of substituted carbamic acids that react with acetylcholinesterase (AChE) by initially transferring the carbamoyl group to a serine residue in the... (Review)
Review
Carbamates are esters of substituted carbamic acids that react with acetylcholinesterase (AChE) by initially transferring the carbamoyl group to a serine residue in the enzyme active site accompanied by loss of the carbamate leaving group followed by hydrolysis of the carbamoyl enzyme. This hydrolysis, or decarbamoylation, is relatively slow, and half-lives of carbamoylated AChEs range from 4 min to more than 30 days. Therefore, carbamates are effective AChE inhibitors that have been developed as insecticides and as therapeutic agents. In this report, we review recent data showing that decarbamoylation rate constants are independent of the ester leaving group for a series of carbamic acid esters with the same carbamoyl group and that decarbamoylation rate constants decreased by 800-fold when the alkyl substituents on the carbamoyl group increased in size from N-monomethyl- to N,N-diethyl-. We also review data showing that solvent deuterium oxide isotope effects for decarbamoylation decreased from 2.8 for N-monomethylcarbamoyl AChE to 1.1 for N,N-diethylcarbamoyl AChE, indicating a shift in the rate-limiting step from general acid-base catalysis to a likely conformational change in the distorted active site in N,N-diethylcarbamoyl AChE. The nature of such a conformational change is suggested from X-ray crystal structures of AChE phosphorylated by paraoxon.
Topics: Acetylcholinesterase; Carbamates; Catalytic Domain; Crystallography, X-Ray; Kinetics; Paraoxon
PubMed: 31175846
DOI: 10.1016/j.cbi.2019.06.004 -
Concentration-dependent kinetics of acetylcholinesterase inhibition by the organophosphate paraoxon.Toxicological Sciences : An Official... Apr 2006For decades the interaction of the anticholinesterase organophosphorus compounds with acetylcholinesterase has been characterized as a straightforward phosphylation of...
For decades the interaction of the anticholinesterase organophosphorus compounds with acetylcholinesterase has been characterized as a straightforward phosphylation of the active site serine (Ser-203) which can be described kinetically by the inhibitory rate constant k(i). However, more recently certain kinetic complexities in the inhibition of acetylcholinesterase by organophosphates such as paraoxon (O,O-diethyl O-(p-nitrophenyl) phosphate) and chlorpyrifos oxon (O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphate) have raised questions regarding the adequacy of the kinetic scheme on which k(i) is based. The present article documents conditions in which the inhibitory capacity of paraoxon towards human recombinant acetylcholinesterase appears to change as a function of oxon concentration (as evidenced by a changing k(i)), with the inhibitory capacity of individual oxon molecules increasing at lower oxon concentrations. Optimization of a computer model based on an Ordered Uni Bi kinetic mechanism for phosphylation of acetylcholinesterse determined k(1) to be 0.5 nM(-1)h(-1), and k(-1) to be 169.5 h(-1). These values were used in a comparison of the Ordered Uni Bi model versus a k(i) model in order to assess the capacity of k(i) to describe accurately the inhibition of acetylcholinesterase by paraoxon. Interestingly, the k(i) model was accurate only at equilibrium (or near equilibrium), and when the inhibitor concentration was well below its K(d) (pseudo first order conditions). Comparisons of the Ordered Uni Bi and k(i) models demonstrate the changing k(i) as a function of inhibitor concentrations is not an artifact resulting from inappropriate inhibitor concentrations.
Topics: Acetylcholinesterase; Acridines; Cholinesterase Inhibitors; Humans; Kinetics; Models, Biological; Paraoxon; Recombinant Proteins
PubMed: 16403852
DOI: 10.1093/toxsci/kfj094 -
Drug Metabolism and Disposition: the... 1984The inhibition of cholinesterase of human serum by paraoxon can be predicted by a mathematical model which considers two competing reactions for paraoxon: one, the...
The inhibition of cholinesterase of human serum by paraoxon can be predicted by a mathematical model which considers two competing reactions for paraoxon: one, the direct interaction with cholinesterase, and the other, enzymatic hydrolysis by paraoxonase. On the basis of the residual cholinesterase activity at various times during the incubation with paraoxon, it is possible to determine the rate constants for the reaction of paraoxon with cholinesterase (k1), and the reaction with paraoxonase (k2), the latter being directly proportional to paraoxonase activity. The percentage of initial activity remaining as residual cholinesterase depends primarily upon the paraoxonase level; it is influenced only slightly by variations in initial cholinesterase levels within the normal range. From these results, we conclude that the residual cholinesterase activity test is, in fact, an indirect measure of serum paraoxonase activity; it has the same limitations and is no more reliable a means of differentiating individual paraoxonase genotypes than measuring the level of serum paraoxonase activity directly. Our model suggests that there are conditions where paraoxonase genotype may alter the clearance of paraoxon and in turn the reaction of paraoxon with target sites. Whether similar results would be obtained in vivo is unknown. Since this model predicts the degradation of paraoxon well in vitro, it may be possible to extend the model and predict the effect of paraoxonase genotype on the clearance of paraoxon in vivo.
Topics: Aryldialkylphosphatase; Cholinesterases; Humans; Hydrolysis; Kinetics; Mathematics; Models, Biological; Paraoxon; Phenotype; Phosphoric Monoester Hydrolases
PubMed: 6141913
DOI: No ID Found -
Fortschritte Der Medizin Jan 1979Some examples of ecogenetics--including pharmacogenetics--demonstrate the tremendous variability in genetic constitution within a population as well as between different...
Some examples of ecogenetics--including pharmacogenetics--demonstrate the tremendous variability in genetic constitution within a population as well as between different populations. They are the reason for different atypical responses to xenobiotics, synthetics like drugs, pesticides, insecticides, herbicides, industrial irritation, smog, cigarettes, alcohol, as well as naturally occurring substances like aflatoxines. It is unknown to what extent individuals differ in their susceptibilities and which genetic consequences of exposure of the human population to toxic environmental agents will occur. It is referred to genetic traits causing a predisposition for atypical reactions against chemicals of different structure as well as to the mutagenic and inductive action of such compounds. In this connection, population genetic aspects will be considered. All examples have to be seen in the context of ecogenetics, the genetically determined individual differences in adverse responses to environmental pollutants, and they are of special interest for preventive and industrial medicine.
Topics: Carboxylic Ester Hydrolases; Cholinesterases; Drug Tolerance; Ecology; Ethanol; Gene Frequency; Genetics; Humans; Paraoxon; Pharmacogenetics; Polymorphism, Genetic; alpha 1-Antitrypsin Deficiency
PubMed: 311313
DOI: No ID Found -
Chemico-biological Interactions Aug 2019The recent intentional use of nerve agents and pesticides in Europe and Afghanistan highlights the need for an effective countermeasure against organophosphates (OP)...
The recent intentional use of nerve agents and pesticides in Europe and Afghanistan highlights the need for an effective countermeasure against organophosphates (OP) toxins. The most developed pretreatment candidate to date is plasma (native) human butyrylcholinesterase (HuBChE), which is limited in availability and because of its 1:1 stoichiometry with OPs, a large dose will present challenges when delivered parenterally both in terms of pharmacokinetics and manageability in the field. A tetrameric recombinant (r) form of human BChE produced in CHO-K1 cells with similar structure, in vivo stability and antidotal efficacy as the native form, has been developed to deliver rHuBChE as an aerosol (aer) to form a pulmonary bioshield capable of neutralizing inhaled OPs in situ and prevent AChE inhibition in the blood and in the brain; the latter associated with the symptoms of OP toxicity. Previous proof-of-concept macaque studies demonstrated that delivery of 9 mg/kg using a microsprayer inserted down the trachea, resulted in protection against an inhaled dose of 15ug/kg of aer-paraoxon (aer-Px) given 72 h later. In the present studies, pulmonary delivery of rHuBChE in macaques was achieved using Aerogen vibrating mesh nebulizers, similar to that used for human self-administration. The promising findings indicate that despite the poor lung deposition observed in macaques using nebulizers (13-20%), protective levels of RBC-AChE were still present in the blood even when exposure aer-Px (55 μg/kg) was delayed for five days. This long term retention of 5 mg/kg rHuBChE deposited in the lung bodes well for the use of an aer-rHuBChE pretreatment in humans where a user-friendly customized nebulizer with increased lung deposition up to 50% will provide even longer protection at a lower dose.
Topics: Aerosols; Animals; Butyrylcholinesterase; CHO Cells; Cricetinae; Cricetulus; Female; Humans; Lung; Macaca; Male; Nebulizers and Vaporizers; Paraoxon; Recombinant Proteins
PubMed: 31201777
DOI: 10.1016/j.cbi.2019.06.025 -
Talanta Jan 2013A label-free immunosensor based on SWNTs modified GC electrodes has been developed for the direct detection of paraoxon. Based on aryldiazonium salt chemistry, forest of...
A label-free immunosensor based on SWNTs modified GC electrodes has been developed for the direct detection of paraoxon. Based on aryldiazonium salt chemistry, forest of SWNTs can be vertically aligned on mixed monolayers of aryldiazonium salt modified GC electrodes by C-C bonding, which provides an interface showing efficient electron transfer between biomolecules. PEG molecules were introduced to the interface to resist non-specific protein adsorption. Ferrocenedimethylamine (FDMA) was subsequently attached to the ends of SWNTs through the amide bonding followed by the attachment of epitope i.e., paraoxon hapten to which a paraoxon antibody would bind. This immunosensor shows good selectivity and high specificity to paraoxon, and is functional for the detection of paraoxon in both laboratory and field by a displacement assay. There is a linear relationship between electrochemical signal of FDMA and the concentration of paraoxon over the range of 2-2500 ppb with a lowest detected limit of 2 ppb in 0.1 M phosphate buffer at pH 7.0. The SWNTs based amperometric immunosensor provides an opportunity to develop the sensing system for on-site sensitive detection of a spectrum of insecticides.
Topics: Animals; Antibodies, Monoclonal; Biosensing Techniques; Electrochemistry; Electrodes; Haptens; Immunoglobulin G; Insecticides; Nanotubes, Carbon; Paraoxon; Rabbits; Serum Albumin, Bovine
PubMed: 23597895
DOI: 10.1016/j.talanta.2012.11.039 -
Journal of Biomolecular Structure &... Feb 2017Phosphotriesterase-like lactonases (PLLs) have received much attention because of their physical and chemical properties. They may have widespread applications in...
Phosphotriesterase-like lactonases (PLLs) have received much attention because of their physical and chemical properties. They may have widespread applications in various fields. For example, they show potential for quorum-sensing signaling pathways and organophosphorus (OP) detoxification in agricultural science. However, the mechanism by which PLLs hydrolyze, which involves OP compounds and lactones and a variety of distinct catalytic efficiencies, has only rarely been explored. In the present study, molecular dynamics (MD) simulations were performed to characterize and contrast the structural dynamics of DrPLL, a member of the PLL superfamily in Deinococcus radiodurans, bound to two substrates, δ-nonanoic lactone and paraoxon. It has been observed that there is a 16-fold increase in the catalytic efficiency of the two mutant strains of DrPLL (F26G/C72I) vs. the wild-type enzyme toward the hydrolysis of paraoxon, but an explanation for this behavior is currently lacking. The analysis of the molecular trajectories of DrPLL bound to δ-nonanoic lactone indicated that lactone-induced conformational changes take place in loop 8, which is near the active site. Binding to paraoxon may lead to conformational displacement of loop 1 residues, which could lead to the deformation of the active site and so trigger the entry of the paraoxon into the active site. The efficiency of the F26G/C72I mutant was increased by decreasing the displacement of loop 1 residues and increasing the flexibility of loop 8 residues. These results provide a molecular-level explanation for the experimental behavior.
Topics: Binding Sites; Hydrogen Bonding; Lactones; Ligands; Molecular Dynamics Simulation; Mutation; Paraoxon; Phosphoric Triester Hydrolases; Protein Binding
PubMed: 26775655
DOI: 10.1080/07391102.2016.1142899