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    ABSTRACT: Organophosphates (OPs) are widely used in agriculture. Many studies have investigated the capability of personal protective equipment (PPE) to reduce chemical exposure; however, investigations into the protective effect of 'every-day' clothing are rare. The purpose of this study was to investigate the protective effect of 'every-day' clothing against dermal exposure, and to measure early decontamination of skin following exposure to chlorpyrifos and dichlorvos. Using human skin in vitro, absorption of (14)C-labelled chlorpyrifos (500ng/cm(2)) was shown to be significantly reduced when applied to clothed skin (cotton shirt), regardless of application vehicle (isopropanol (IPA) or propylene glycol (PG)). The majority of applied dose was retained within the clothing after 4h exposure. Significant reduction in absorption of chlorpyrifos (in PG) was seen through clothed skin when supplemented with skin decontamination at 4h, compared with clothed skin decontaminated after 24h, however, this was not observed with IPA. Absorption of dichlorvos (5μg/cm(2)) was greater through unclothed skin than chlorpyrifos for all vehicles (IPA, isopropyl myristate (IPM) and PG). Significant reduction in absorption was observed when decontaminating clothed skin at 30min, compared with decontamination at 24h (post-exposure) for all vehicles.
    Toxicology Letters 06/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: To date, there has been little research investigating low-level human exposure to chemicals, and so the aim of this study was to examine the percutaneous penetration of organophosphates (dichlorvos and chlorpyrifos) using low-level exposure scenarios in vitro. Dermal absorption of chlorpyrifos applied in different vehicles was measured at 0, 4, 8 and 24hours, after dose application for 4 and 24hour exposure (finite dose, 500ng/cm(2)) in isopropanol (IPA), isopropyl myristate (IPM) and propylene glycol (PG). Dichlorvos was applied to the skin for 24hours (infinite dose, 1mg/cm(2) and 10mg/cm(2), finite dose, 5μg/cm(2)) using the same vehicles. Human skin was mounted in flow through diffusion cells ith minimum essential medium eagle pH. 7.4 (supplemented with 2% BSA) as receptor fluid. Following exposure, the skin surface dose was removed by tissue swabbing, the stratum corneum removed by sequential tape stripping, and the skin digested prior to scintillation counting (chlorpyrifos), or GC/MS analysis (dichlorvos). Dermal absorption of chlorpyrifos was greatest following application in PG (19.5% of dose), when compared with absorption from IPA and IPM vehicles (10.3% and 1.9% absorbed respectively). However, dichlorvos showed greater dermal absorption than chlorpyrifos from all vehicles used, with greatest absorption from the IPA vehicle (38.6% absorbed). Although dichlorvos exhibited a short lag time (0.6 hours from IPA and IP vehicles, and 0.4 hours from PG), chlorpyrifos displayed greater propensity to accumulate in the stratum corneum and epidermis/dermis. These results demonstrate that prompt skin surface decontamination would be required for both dichlorvos and chlorpyrifos (and chemicals with similar properties) in the event of skin contact. The magnitude of the skin reservoir formed with chlorpyrifos was time dependent, therefore prompt decontamination of this and similar chemicals would be required to reduce delayed systemic absorption.
    Toxicology Letters 06/2014;
  • Toxicology. 12/2011; 290(s 2–3):117.
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    ABSTRACT: Sulphur mustard (SM) is a blistering agent that causes debilitating damage to the skin, eyes and respiratory system. In cases of severe exposure, immunodepletion can occur as well as death, due to secondary infections. The toxicity of SM is thought to be mediated in part by the alkylation of nucleic acids and proteins, although the exact mechanisms are not clear. In addition, although the first known use of SM was in military conflict nearly 100 years ago, there are still no effective treatments or preventative measures. In order to develop treatments it is necessary to have a detailed understanding of the cellular biochemical changes induced by SM as well as information on the mechanisms that cells employ to protect against SM toxicity. We have previously demonstrated that the homologous recombination (HR) DNA repair pathway promotes cell survival after SM. This study investigated the role of other DNA repair pathways in the cellular response to SM, specifically base excision repair (BER), nucleotide excision repair (NER) and non-homologous end joining (NHEJ) as well as studying the activation and regulation of DNA damage signalling pathways. Our data confirmed that HR is the major repair pathway protecting against acute SM toxicity, with NER and NHEJ also contributing to cell survival. In addition, this study demonstrated the dose- and time-dependent activation of DNA damage signalling pathways after SM in human TK6 lymphoblastoid cells, in particular the phosphorylation of CHK1, CHK2 and p53. These phosphorylation events were orchestrated by a combination of the ATM and ATR protein kinases.
    Toxicology Letters 11/2011; 209(1):1-10.
  • Brain 04/2011; 134(Pt 4):924-7.
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    ABSTRACT: Acetylcholinesterase inhibition by organophosphorus pesticides or organophosphate nerve agents can cause acute parasympathetic system dysfunction, muscle weakness, seizures, coma, and respiratory failure. Prognosis depends on the dose and relative toxicity of the specific compound, as well as pharmacokinetic factors. METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments for acute organophosphorus poisoning? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2010 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). We found 62 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. In this systematic review we present information relating to the effectiveness and safety of the following interventions: activated charcoal (single or multiple doses), alpha(2) adrenergic receptor agonists, atropine, benzodiazepines, butyrylcholinesterase replacement therapy, cathartics, extracorporeal clearance, gastric lavage, glycopyrronium bromide (glycopyrrolate), ipecacuanha (ipecac), magnesium sulphate, milk or other home remedy immediately after ingestion, N-methyl-D-aspartate receptor antagonists, organophosphorus hydrolases, oximes, removing contaminated clothes and washing the poisoned person, and sodium bicarbonate.
    Clinical evidence 01/2011; 2011.
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    ABSTRACT: Parkinson's disease (PD) is a progressive, neurodegenerative condition that has increasingly been linked with mitochondrial dysfunction and inhibition of the electron transport chain. This inhibition leads to the generation of reactive oxygen species and depletion of cellular energy levels, which can consequently cause cellular damage and death mediated by oxidative stress and excitotoxicity. A number of genes that have been shown to have links with inherited forms of PD encode mitochondrial proteins or proteins implicated in mitochondrial dysfunction, supporting the central involvement of mitochondria in PD. This involvement is corroborated by reports that environmental toxins that inhibit the mitochondrial respiratory chain have been shown to be associated with PD. This paper aims to illustrate the considerable body of evidence linking mitochondrial dysfunction with neuronal cell death in the substantia nigra pars compacta (SNpc) of PD patients and to highlight the important need for further research in this area.
    Parkinson's disease. 01/2011; 2011:716871.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sulphur mustard (SM) is a blistering agent that has been used several times as a weapon during military conflict. Interest in this compound persists due to its ease of production and potential threat as an agent of warfare/terrorism. In addition, there are increasing reports of long-term health effects in individuals previously exposed to this compound, including an increased incidence of certain cancers. It is therefore important to elucidate the toxic mechanisms of SM and how the cell responds to any damage produced. This will allow for better healthcare planning in the event of an exposure and aid in the development of a therapeutic strategy, which is currently lacking. SM is a bifunctional alkylating agent, producing both DNA monoadducts and crosslinks, although the cellular response to these lesions is not well understood. This study aimed to investigate the DNA repair pathways employed by cells exposed to SM. It was found that DNA double strand breaks were generated after SM exposure and cells lacking the homologous recombination DNA repair pathway were more sensitive to the toxicity of SM than wild type cells. Finally, we demonstrate that chemical activation of the HR protein RAD51 offers cellular protection against SM toxicity and thus could be a novel target for therapeutic intervention.
    Toxicology Letters 05/2010; 197(1):12-8.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sulphur mustard (SM) is a blistering agent that is directly toxic to the skin and mucosal surfaces of the eye and respiratory system. Symptoms take several hours to develop and the mechanism of action is poorly understood although SM is able to alkylate nucleic acids and proteins. The ability of SM to form adducts with DNA has been documented, although there are limited data demonstrating how cells respond to this insult to repair the damage. This study used the sulphur mustard surrogate 2-chloroethyl ethyl sulphide (CEES) to identify DNA damage repair pathways and signalling events that are activated after exposure to the agent. A dose-dependent increase in DNA damage was observed in TK6 lymphoblastoid cells, which was associated with a loss of cell viability. Using both model human lymphoblastoid cell lines and pharmacological inhibitors, it was found that DNA damage induced by CEES was repaired by base excision repair (BER) and nucleotide excision repair (NER) pathways. Finally, CEES was found to induce the phosphorylation of p53 and Chk2 and these events were mediated by both the ATM ataxia telangiectasia mutated and ATR (ATM and Rad-3 related) protein kinases.
    Toxicology 01/2009; 257(3):105-12.
  • Principles and Practice of Skin Toxicology, 09/2008: pages 69 - 82; , ISBN: 9780470773093
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