Author Report for: Abou-Donia MBContact information:Abou-Donia Mohamed BDepartment of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710USAPhone : Fax : Send E-Mail to Abou-Donia Mohamed B
Abou-Donia MB, Siracuse B, Gupta N, Sobel Sokol A Ref: Crit Rev Toxicol, :1, 2016 : PubMed ESTHER: Abou-Donia_2016_Crit.Rev.Toxicol__1 PubMedSearch: Abou-Donia 2016 Crit.Rev.Toxicol 1 PubMedID: 27705071 Abstract Sarin (GB, O-isopropyl methylphosphono fl uoridate) is a potent organophosphorus (OP) nerve agent that inhibits acetylcholinesterase (AChE) irreversibly. The subsequent build-up of acetylcholine (ACh) in the central nervous system (CNS) provokes seizures and, at sufficient doses, centrally-mediated respiratory arrest. Accumulation of ACh at peripheral autonomic synapses leads to peripheral signs of intoxication and overstimulation of the muscarinic and nicotinic receptors, which is described as "cholinergic crisis" (i.e. diarrhea, sweating, salivation, miosis, bronchoconstriction). Exposure to high doses of sarin can result in tremors, seizures, and hypothermia. More seriously, build-up of ACh at neuromuscular junctions also can cause paralysis and ultimately peripherally-mediated respiratory arrest which can lead to death via respiratory failure. In addition to its primary action on the cholinergic system, sarin possesses other indirect effects. These involve the activation of several neurotransmitters including gamma-amino-butyric acid (GABA) and the alteration of other signaling systems such as ion channels, cell adhesion molecules, and inflammatory regulators. Sarin exposure is associated with symptoms of organophosphate-induced delayed neurotoxicity (OPIDN) and organophosphate-induced chronic neurotoxicity (OPICN). Moreover, sarin has been involved in toxic and immunotoxic effects as well as organophosphate-induced endocrine disruption (OPIED). The standard treatment for sarin-like nerve agent exposure is post-exposure injection of atropine, a muscarinic receptor antagonist, accompanied by an oxime, an AChE reactivator, and diazepam. Title: DFP initiated early alterations of PKA/p-CREB pathway and differential persistence of beta-tubulin subtypes in the CNS of hens contributes to OPIDN Damodaran TV, Gupta RP, Attia MK, Abou-Donia MB Ref: Toxicol Appl Pharmacol, 240:132, 2009 : PubMed ESTHER: Damodaran_2009_Toxicol.Appl.Pharmacol_240_132 PubMedSearch: Damodaran 2009 Toxicol.Appl.Pharmacol 240 132 PubMedID: 19664648 Abstract Organophosphorus ester-induced delayed neurotoxicity (OPIDN) is a neurodegenerative disorder characterized by ataxia progressing to paralysis with a concomitant central and peripheral distal axonapathy. Diisopropylphosphorofluoridate (DFP) produces OPIDN in the chicken, which results in mild ataxia in 7-14 days and severe paralysis as the disease progresses with a single dose. White leghorn layer hens were treated with DFP (1.7 mg/kg, sc) after prophylactic treatment with atropine (1 mg/kg, sc) in normal saline and eserine (1 mg/kg, sc) in dimethyl sulfoxide. Control groups were treated with vehicle propylene glycol (0.1 mL/kg, sc), atropine in normal saline and eserine in dimethyl sulfoxide. The hens were sacrificed at different time points such as 2, 4, and 8 h, as well as 1, 2, 5, 10 and 20 days, and the tissues from cerebrum, midbrain, cerebellum brainstem and spinal cord were quickly dissected and frozen for protein (western) and mRNA (northern) studies. Subcellular fractionation, SDS-PAGE and immunoblotting of the nuclear and supernatant fractions using standard protocols from spinal cord and cerebrum showed differential expression of protein levels of PKA, CREB and phosphorylated CREB (p-CREB). There was an increase in PKA level in spinal cord nuclear fraction after 4 h (130+/-5%) and 8 h (133+/-6 %), while cerebrum nuclear fraction showed decrease (77+/-5%) at 4 h and remained at the same level at 8 h. No change was seen in either spinal cord or cerebrum soluble fraction at any time points. There was an increase in CREB level in the spinal cord supernatant (133+/-3%) after 5 days, while nuclear and supernatant fraction of the cerebrum did not show any alterations at any time point. p-CREB was induced in the spinal cord nuclear fraction at 1 day (150+/-3%) and 5 days (173+/-7%) of treatment, in contrast to the decreased levels p-CREB (72+/-4%) at 10 days in cerebrum nuclear fraction. Supernatant fraction of spinal cord and cerebrum did not show any changes in pCREB at time points studied. Similarly another set of animals were treated with DFP and perfused using standard protocols and immunohistochemistry for p-CREB in the brain and spinal cord confirmed the overall protein expression pattern identified by western analysis. Expression of beta-tubulin subtypes (1, 2, 3, and 4), studied by Northern blotting showed complex and differential pattern, while immunohistochemistry of the anti-beta-tubulin for the entire period of OPIDN developmental stages showed early induction and persistence even in the disintegrating axonal and non-neuronal structures of the CNS. These data thus strongly suggest that early cytoskeletal damage at molecular level mediated by PKA/p-CREB pathways leads to the culmination of gross (microscopically observable) level cytoskeletal changes in various components of central nervous system (CNS), consistent with our earlier findings. Thus, the differential protein expression of PKA, CREB, p-CREB and beta-tubulin subtypes appear to contribute to the initiation, progression and development of OPIDN, probably by recruiting other molecular pathways specific to various components of nervous system. Title: Imidacloprid induces neurobehavioral deficits and increases expression of glial fibrillary acidic protein in the motor cortex and hippocampus in offspring rats following in utero exposure Abou-Donia MB, Goldstein LB, Bullman S, Tu T, Khan WA, Dechkovskaia AM, Abdel-Rahman AA Ref: J Toxicol Environ Health A, 71:119, 2008 : PubMed ESTHER: Abou-Donia_2008_J.Toxicol.Environ.Health.A_71_119 PubMedSearch: Abou-Donia 2008 J.Toxicol.Environ.Health.A 71 119 PubMedID: 18080902 Abstract Imidacloprid, a neonicotinoid, is one of the fastest growing insecticides in use worldwide because of its selectivity for insects. The potential for neurotoxicity following in utero exposure to imidacloprid is not known. Timed pregnant Sprague-Dawley rats (300-350 g) on d 9 of gestation were treated with a single intraperitoneal injection (i.p.) of imidacloprid (337 mg/kg, 0.75 x LD50, in corn oil). Control rats were treated with corn oil. On postnatal day (PND) 30, all male and female offspring were evaluated for (a) acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity, (b) ligand binding for nicotinic acetylcholine receptors (nAChR) and muscarinic acetylcholine receptors (m2 mAChR), (c) sensorimotor performance (inclined plane, beam-walking, and forepaw grip), and (d) pathological alterations in the brain (using cresyl violet and glial fibrillary acidic protein [GFAP] immunostaining). The offspring of treated mothers exhibited significant sensorimotor impairments at PND 30 during behavioral assessments. These changes were associated with increased AChE activity in the midbrain, cortex and brainstem (125-145% increase) and in plasma (125% increase). Ligand binding densities for [3H]cytosine for alpha4beta2 type nAchR did not show any significant change, whereas [3H]AFDX 384, a ligand for m2mAChR, was significantly increased in the cortex of offspring (120-155% increase) of imidacloprid-treated mothers. Histopathological evaluation using cresyl violet staining did not show any alteration in surviving neurons in various brain regions. On the other hand, there was a rise in GFAP immunostaining in motor cortex layer III, CA1, CA3, and the dentate gyrus subfield of the hippocampus of offspring of imidacloprid-treated mothers. The results indicate that gestational exposure to a single large, nonlethal, dose of imidacloprid produces significant neurobehavioral deficits and an increased expression of GFAP in several brain regions of the offspring on PND 30, corresponding to a human early adolescent age. These changes may have long-term adverse health effects in the offspring. Title: Butyrylcholinesterase activity and lymphocyte subpopulations in peripheral blood of Kuwaiti women experiencing recurrent spontaneous abortion Mahmoud FF, Abul HT, Haines DD, Omu AE, Diejomaoh M, Wise JA, Abou-Donia MB Ref: J Reprod Immunol, 77:186, 2008 : PubMed ESTHER: Mahmoud_2008_J.Reprod.Immunol_77_186 PubMedSearch: Mahmoud 2008 J.Reprod.Immunol 77 186 PubMedID: 17884179 Abstract This study has evaluated the hypothesis that activity of the detoxifying enzyme butyrylcholinesterase (BuChE) correlates with levels of serum anti-cardiolipin antibodies (ACA) and T lymphocytes in peripheral blood of women experiencing recurrent spontaneous abortion (RSA). Peripheral venous blood from 16 non-pregnant, RSA-afflicted women and 8 healthy non-pregnant women was analyzed for frequency of T lymphocyte subpopulations by two-color flow cytometry and for serum BuChE using butyrylthiocholine iodide/spectrophotometry. RSA-afflicted women with high serum ACA, but not those with normal ACA levels, exhibited significantly increased percentages of CD4+CD25+ cells (p<0.01) and CD4+HLA-DR+ cells (p<0.05) relative to healthy women. CD4+CD25+(high) cells were significantly lower (p<0.05), while CD4+CD25+(low) cells were significantly higher (p<0.01), in women with elevated ACA compared to healthy women and to RSA women with normal ACA. Relative to healthy, non-pregnant subjects, serum BuChE activity in RSA patients was elevated, both for those with normal ACA (p<0.001) and elevated ACA levels (p<0.01). Among healthy controls, a significant positive correlation was observed between frequency of CD3+NK cells and BuChE activity (p<0.01), but not for RSA-afflicted subjects. A positive correlation between BuChE activity and frequency of CD4+CD25+ cells, as well as CD4+CD25+(high) cells, was observed in the RSA-afflicted subject group with elevated ACA (p<0.05), which may be related to induction of BuChE by toxic metabolites resulting from pathogenic T cell activity. It is concluded that, among RSA patients, high serum ACA correlates with elevated levels of activated T cells and reduced CD4+CD25+(high)/CD4+CD25+(low) cells in comparison to healthy women or those afflicted with RSA but with normal ACA. BuChE activity is observed to be elevated in RSA patients irrespective of serum ACA status. Title: In utero exposure to nicotine and chlorpyrifos alone, and in combination produces persistent sensorimotor deficits and Purkinje neuron loss in the cerebellum of adult offspring rats Abou-Donia MB, Khan WA, Dechkovskaia AM, Goldstein LB, Bullman SL, Abdel-Rahman A Ref: Archives of Toxicology, 80:620, 2006 : PubMed ESTHER: Abou-Donia_2006_Arch.Toxicol_80_620 PubMedSearch: Abou-Donia 2006 Arch.Toxicol 80 620 PubMedID: 16482470 Abstract This study was carried out to investigate the effect of in utero exposure to the cholinotoxicants, nicotine and chlorpyrifos, alone or in combination on neurobehavioral alterations and neuronal morphology latter in adult age. In the present study, 90 days old (corresponding to a human adult age) male and female offspring rats were evaluated for neurobehavioral, and neuropathological alterations following maternal, gestational exposure to nicotine and chlorpyrifos (O,O-diethyl-O-3,5,6-trichloro-2-pyridinyl phosphorothioate), alone and in combination. Female Sprague-Dawley rats (300-350 g) with timed-pregnancy were treated with nicotine (3.3 mg/kg/day, in bacteriostatic water via s.c. implantation of mini osmotic pump), chlorpyrifos (1.0 mg/kg, daily, dermal, in 75% ethanol, 1.0 ml/kg) or a combination of both chemicals, on gestational days (GD) 4-20. Control animals received bacteriostatic water via s.c. implantation of mini osmotic pump and dermal application of 70% ethanol. The offspring at postnatal day (PND) 90 were evaluated for neurobehavioral performance, changes in the activity of plasma butyrylcholinesterase (BChE) and acetylcholinesterase (AChE), and neuropathological alterations in the brain. Neurobehavioral evaluations included beam-walk score, beam-walk time, incline plane performance and forepaw grip time. Male and female offspring from mothers treated with nicotine and CPF, alone or in combination showed impairments in the performance of neurobehavioral tests, indicating sensorimotor deficits. Female offspring from mothers treated with a combination of nicotine and chlorpyrifos showed significant increase in plasma BChE activity. Brain regional AChE activity showed differential increases in male and female offspring. Brainstem and cerebellum of female offspring from mothers treated with nicotine or chlorpyrifos, alone or in combination showed increased AChE activity, whereas brainstem of male offspring from mothers treated with nicotine alone or a combination of nicotine and chlorpyrifos showed increase in AChE activity. Also, male offspring exposed in utero to nicotine exhibited increased AChE activity. Histopathological evaluations using cresyl violet staining showed a decrease in surviving Purkinje neurons in the cerebellum in offspring of all treatments groups. An increase in glial fibrillary acidic protein (GFAP) immuno-staining was observed in cerebellum white matter as well as granular cell layer (GCL) of cerebellum following all exposures. These results indicate that in utero exposure to nicotine and chlorpyrifos, alone and in combination produced significant sensorimotor deficits in male and female offspring, differential increase in brain AChE activity, a decrease in the surviving neurons and an increased expression of GFAP in cerebellum in adult offspring rats at a corresponding human adult age. Collectively, this study demonstrates that maternal exposure to environmental neurotoxic chemicals, i.e., nicotine and chlorpyrifos leads to developmental abnormalities in the offspring that persist latter into adulthood. Title: Gene expression profiles of the rat brain both immediately and 3 months following acute sarin exposure Damodaran TV, Patel AG, Greenfield ST, Dressman HK, Lin SM, Abou-Donia MB Ref: Biochemical Pharmacology, 71:497, 2006 : PubMed ESTHER: Damodaran_2006_Biochem.Pharmacol_71_497 PubMedSearch: Damodaran 2006 Biochem.Pharmacol 71 497 PubMedID: 16376859 Abstract We have studied sarin-induced global gene expression patterns at an early time point (15 min; 0.5xLD50) and a later time point (3 months; 1xLD50) using Affymetrix: Rat Neurobiology U34 chips in male, Sprague-Dawley rats and have identified a total of 65 (early) and 38 (late) genes showing statistically significant alterations from control levels at 15 min and 3 months, respectively. At the early time point, those that are classified as ion channel, cytoskeletal and cell adhesion molecules, in addition to neuropeptides and their receptors predominated over all other groups. The other groups included: cholinergic signaling, calcium channel and binding proteins, transporters, chemokines, GABAnergic, glutamatergic, aspartate, catecholaminergic, nitric oxide synthase, purinergic, and serotonergic signaling molecules. At the late time point, genes that are classified as calcium channel and binding proteins, cytoskeletal and cell adhesion molecules and GABAnergic signaling molecules were most prominent. Seven molecules (Ania-9, Arrb-1, CX-3C, Gabab-1d, Nos-2a, Nrxn-1b, PDE2) were identified that showed altered persistent expression in both time points. Selected genes from each of these time points were further validated using semi quantitative RT-PCR approaches. Some of the genes that were identified in the present study have been shown to be involved in organophosphate-induced neurotoxicity by both other groups as well as ours. Principal component analysis (PCA) of the expression data from both time points was used for comparative analysis of the gene expression, which indicated that the changes in gene expression were a function of dose and time of euthanasia after the treatment. Our model also predicts that besides dose and duration of post-treatment period, age and possibly other factors may be playing important roles in the regulation of pathways, leading to the neurotoxicity. Title: Toxicogenomic studies of the rat brain at an early time point following acute sarin exposure Damodaran TV, Greenfield ST, Patel AG, Dressman HK, Lin SK, Abou-Donia MB Ref: Neurochem Res, 31:367, 2006 : PubMed ESTHER: Damodaran_2006_Neurochem.Res_31_367 PubMedSearch: Damodaran 2006 Neurochem.Res 31 367 PubMedID: 16733813 Abstract We have studied sarin-induced global gene expression patterns at an early time point (2 h: 0.5 x LD50) using Affymetrix Rat Neurobiology U34 chips and male Sprague-Dawley rats. A total of 46 genes showed statistically significant alterations from control levels. Three gene categories contained more of the altered genes than any other groups: ion channel (8 genes) and calcium channel and binding proteins (6 genes). Alterations were also found in the following gene groups: ATPases and ATP-based transporters (4), growth factors (4), G-protein-coupled receptor pathway-related molecules (3), neurotransmission and neurotransmitter transporters (3), cytoskeletal and cell adhesion molecules (2), hormones (2), mitochondria-associated proteins (2), myelin proteins (2), stress-activated molecules (2), cytokine (1), caspase (1), GABAnergic (1), glutamergic (1), immediate early gene (1), prostaglandin (1), transcription factor (1), and tyrosine phosphorylation molecule (1). Persistent alteration of the following genes also were noted: Arrb1, CaMKIIa, CaMKIId, Clcn5, IL-10, c-Kit, and Plp1, suggesting altered GPCR, kinase, channel, and cytokine pathways. Selected genes from the microarray data were further validated using relative RT-PCR. Some of those genes (GFAP, NF-H, CaMKIIa, Calm, and MBP) have been shown by other laboratories and ours, to be involved in the pathogenesis of sarin-induced pathology and organophosphate-induced delayed neurotoxicity (OPIDN). Induction of both proapoptotic (Bcl2l11, Casp6) and antiapoptotic (Bcl-X) genes, besides suppression of p21, suggest complex cell death/protection-related mechanisms operating early on. Principal component analysis (PCA) of the expression data confirmed that the changes in gene expression are a function of sarin exposure, since the control and treatment groups separated clearly. Our model (based on current and previous studies) indicates that both degenerative and regenerative pathways are activated early and contribute to the level of neurodegeneration at a later time, leading to neuro-pathological alterations. Title: Butyrylcholinesterase activity in gestational diabetes: correlation with lymphocyte subpopulations in peripheral blood Mahmoud FF, Haines DD, Abul HT, Omu AE, Abou-Donia MB Ref: Am J Reprod Immunol, 56:185, 2006 : PubMed ESTHER: Mahmoud_2006_Am.J.Reprod.Immunol_56_185 PubMedSearch: Mahmoud 2006 Am.J.Reprod.Immunol 56 185 PubMedID: 16911714 Abstract PROBLEM: Inefficient clearance of pregnancy-threatening toxins may contribute to gestational diabetes (GD) and Type II diabetes mellitus (DM) through mechanisms involving immune dysregulation. METHOD OF STUDY: Peripheral venous blood from pregnant Kuwaiti women in third trimester, including 15 GD and 17 DM patients, 14 healthy pregnant (HP) and eight non-pregnant subjects, was analyzed by two-color flow cytometery for number and percentage representation of T lymphocytes. Buterylcholinesterase (BuChE) activity was measured using buterylthiocholine iodide and spectrophotometry. Title: Antimuscarinic drugs for overactive bladder and their potential effects on cognitive function in older patients Kay GG, Abou-Donia MB, Messer WS, Jr., Murphy DG, Tsao JW, Ouslander JG Ref: J Am Geriatr Soc, 53:2195, 2005 : PubMed ESTHER: Kay_2005_J.Am.Geriatr.Soc_53_2195 PubMedSearch: Kay 2005 J.Am.Geriatr.Soc 53 2195 PubMedID: 16398909 Abstract Antimuscarinic agents are the predominant pharmacological treatment for patients with overactive bladder (OAB). These drugs are thought to act primarily through antagonism at muscarinic M3 receptors located at neuromuscular junctions in the human bladder detrusor muscle. Several of these drugs have been shown to be efficacious in ameliorating the symptoms of OAB in older patients, but most currently available agents lack selectivity for the M3 receptor subtype, and interaction with other muscarinic receptor subtypes throughout the body may adversely affect a variety of physiological functions and result in unwanted side effects, including cognitive dysfunction. With the recent availability of antimuscarinic agents that show increased selectivity for M3 receptors relative to other muscarinic subtypes, an invitational expert panel meeting was convened to review not only the mechanisms by which antimuscarinic agents could affect cognitive function, but also the published literature on cognitive adverse events. A review of the literature shows that the cholinergic system in the central nervous system (CNS) exerts a major influence on cognitive processes, in particular memory via M1 cholinergic receptors. In addition, recent evidence suggests a role for M2 receptors in mediating cognitive function. Thus, cognitive dysfunction (including memory loss) during treatment with nonselective antimuscarinic agents for OAB is of growing concern, particularly in older patients and those with mild cognitive impairment or dementia. Increased blood-brain barrier permeability, which can occur with advanced age and certain comorbidities, may also facilitate CNS access of antimuscarinic agents (regardless of their physiochemical properties) and add to antimuscarinic burden. On the basis of available evidence, antimuscarinic agents with selectivity for M3 over M1 and M2 receptors, limited CNS penetration, or both may therefore offer a favorable balance of efficacy in treating OAB together with a reduced risk of adverse cognitive events in the older population. Title: Stress and combined exposure to low doses of pyridostigmine bromide, DEET, and permethrin produce neurochemical and neuropathological alterations in cerebral cortex, hippocampus, and cerebellum Abdel-Rahman A, Abou-Donia S, El-Masry E, Shetty A, Abou-Donia MB Ref: J Toxicol Environ Health A, 67:163, 2004 : PubMed ESTHER: Abdel-Rahman_2004_J.Toxicol.Environ.Health.A_67_163 PubMedSearch: Abdel-Rahman 2004 J.Toxicol.Environ.Health.A 67 163 PubMedID: 14675905 Inhibitor(s) related to this paper: Pyridostigmine Abstract Exposure to a combination of stress and low doses of the chemicals pyridostigmine bromide (PB), DEET, and permethrin in adult rats, a model of Gulf War exposure, produces blood-brain barrier (BBB) disruption and neuronal cell death in the cingulate cortex, dentate gyrus, thalamus, and hypothalamus. In this study, neuropathological alterations in other areas of the brain where no apparent BBB disruption was observed was studied following such exposure. Animals exposed to both stress and chemical exhibited decreased brain acetylcholinesterase (AChE) activity in the midbrain, brainstem, and cerebellum and decreased m2 muscarinic acetylcholine (ACh) receptor ligand binding in the midbrain and cerebellum. These alterations were associated with significant neuronal cell death, reduced microtubule-associated protein (MAP-2) expression, and increased glial fibrillary acidic protein (GFAP) expression in the cerebral cortex and the hippocampal subfields CA1 and CA3. In the cerebellum, the neurochemical alterations were associated with Purkinje cell loss and increased GFAP immunoreactivity in the white matter. However, animals subjected to either stress or chemicals alone did not show any of these changes in comparison to vehicle-treated controls. Collectively, these results suggest that prolonged exposure to a combination of stress and the chemicals PB, DEET, and permethrin can produce significant damage to the cerebral cortex, hippocampus, and cerebellum, even in the absence of apparent BBB damage. As these areas of the brain are respectively important for the maintenance of motor and sensory functions, learning and memory, and gait and coordination of movements, such alterations could lead to many physiological, pharmacological, and behavioral abnormalities, particularly motor deficits and learning and memory dysfunction. Title: Neurological deficits induced by malathion, DEET, and permethrin, alone or in combination in adult rats Abdel-Rahman A, Dechkovskaia AM, Goldstein LB, Bullman SH, Khan W, El-Masry EM, Abou-Donia MB Ref: J Toxicol Environ Health A, 67:331, 2004 : PubMed ESTHER: Abdel-Rahman_2004_J.Toxicol.Environ.Health.A_67_331 PubMedSearch: Abdel-Rahman 2004 J.Toxicol.Environ.Health.A 67 331 PubMedID: 14713564 Abstract Malathion (O,O-dimethyl-S-[1,2-carbethoxyethyl]phosphorodithionate), DEET (N,N-diethyl-m-toluamide), and permethrin [(+/-)-cis/trans-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane carboxylic acid (3-phenoxyphenyl) methyl ester] are commonly used pesticides. To determine the effects of the dermal application of these chemicals, alone or in combination, the sensorimotor behavior, central cholinergic system, and histopathological alterations were studied in adult male Sprague-Dawley rats following a daily dermal dose of 44.4 mg/kg malathion, 40 mg/kg DEET, and 0.13 mg/kg permethrin, alone and in combination for 30 d. Neurobehavioral evaluations of sensorimotor functions included beam-walking score, beam walk time, inclined plane, and grip response assessments. Twenty-four hours after the last treatment with each chemical alone or in combination all behavioral measures were impaired. The combination of DEET and permethrin, malathion and permethrin, or the three chemicals together resulted in greater impairments in inclined performance than permethrin alone. Only animals treated with a combination of DEET and malathion or with DEET and permethrin exhibited significant increases in plasma butyrlcholinesterase (BChE) activity. Treatment with DEET or permethrin alone, malathion and permethrin, or DEET and permethrin produced significant increases in cortical acetylcholinesterase (AChE) activity. Combinations of malathion and permethrin or of DEET and permethrin produced significant decreases in midbrain AChE activity. Animals treated with DEET alone exhibited a significant increase in cortical m2 muscarinic ACh receptor binding. Quantification of neuron density in the dentate gyrus, CA1 and CA3 subfields of the hippocampus, midbrain, brainstem, and cerebellum revealed significant reductions in the density of surviving neurons with various treatments. These results suggest that exposure to real-life doses of malathion, DEET, and permethrin, alone or in combination, produce no overt signs of neurotoxicity but induce significant neurobehavioral deficits and neuronal degeneration in brain. Title: Maternal exposure to nicotine and chlorpyrifos, alone and in combination, leads to persistently elevated expression of glial fibrillary acidic protein in the cerebellum of the offspring in late puberty Abdel-Rahman A, Dechkovskaia AM, Mehta-Simmons H, Sutton JM, Guan X, Khan WA, Abou-Donia MB Ref: Archives of Toxicology, 78:467, 2004 : PubMed ESTHER: Abdel-Rahman_2004_Arch.Toxicol_78_467 PubMedSearch: Abdel-Rahman 2004 Arch.Toxicol 78 467 PubMedID: 15045467 Abstract We previously showed that maternal exposure to nicotine, alone or in combination with chlorpyrifos, caused an increase in glial fibrillary acidic protein (GFAP) immunostaining in the CA1 subfield of hippocampus and cerebellum in postnatal day (PND) 30 offspring. In the present study, PND 60 offspring were evaluated for histopathological and cholinergic effects following maternal exposure to nicotine and chlorpyrifos, alone and in combination. Timed-pregnant Sprague-Dawley rats (300-350 g) were treated daily with nicotine (1 mg/kg, s.c., in normal saline) or chlorpyrifos (0.1 mg/kg, dermal, in ethanol) or a combination of nicotine and chlorpyrifos from gestational days (GD) 4 to 20. Control animals were treated with saline and ethanol. On PND 60, the offspring were evaluated for cholinergic changes and pathological effects. Plasma butyrylcholinesterase (BChE) activity in the female offspring from chlorpyrifos treated mothers showed a significant increase (approximately 183% of control). Male offspring from mothers treated with either chlorpyrifos or nicotine alone showed a significant increase in the acetylcholinesterase (AChE) activity in the brainstem while female offspring from mothers treated with either nicotine or a combination of nicotine and chlorpyrifos showed a significant increase (approximately 134 and 126% of control, respectively) in AChE activity in the brainstem. No significant changes were observed in the ligand binding densities for alpha4beta2 and alpha7 nicotinic acetylcholine receptors in the cortex. Histopathological evaluation using cresyl violet staining showed a significant decrease in surviving Purkinje neurons in the cerebellum of the offspring from nicotine treated mothers. An increase in GFAP immunostaining in cerebellar white matter was observed in the offspring from the mothers treated with nicotine. These results suggest that maternal exposure to real-life levels of nicotine and/or chlorpyrifos causes differential regulation of brainstem AChE activity. Also, nicotine caused a decrease in the surviving neurons and an increased expression of GFAP in cerebellar white matter of the offspring on PND 60. These changes can lead to long-term neurological adverse health effects later in life. Title: Co-exposure to pyridostigmine bromide, DEET, and/or permethrin causes sensorimotor deficit and alterations in brain acetylcholinesterase activity Abou-Donia MB, Dechkovskaia AM, Goldstein LB, Abdel-Rahman A, Bullman SL, Khan WA Ref: Pharmacol Biochem Behav, 77:253, 2004 : PubMed ESTHER: Abou-Donia_2004_Pharmacol.Biochem.Behav_77_253 PubMedSearch: Abou-Donia 2004 Pharmacol.Biochem.Behav 77 253 PubMedID: 14751452 Inhibitor(s) related to this paper: Pyridostigmine Abstract Military personnel deployed in the Persian Gulf War (PGW) were exposed to a combination of chemicals, including pyridostigmine bromide (PB), DEET, and permethrin. We investigated the dose-response effects of these chemicals, alone or in combination, on the sensorimotor performance and cholinergic system of male Sprague-Dawley rats. Animals were treated with a daily dermal dose of DEET and/or permethrin for 60 days and/or PB (gavage) during the last 15 days. Neurobehavioral performance was assessed on day 60 following the beginning of the treatment with DEET and permethrin. The rats were sacrificed 24 h after the last treatment for biochemical evaluations. PB alone, or in combination with DEET, or DEET and permethrin resulted in deficits in beam-walk score and longer beam-walk times compared to controls. PB alone, or in combination with DEET, permethrin, or DEET and permethrin caused impairment in incline plane performance and forepaw grip strength. PB alone at all doses slightly inhibited plasma butyrylcholinesterase activity, whereas combination of PB with DEET or permethrin increased its activity. Brainstem acetylcholinesterase (AChE) activity significantly increased following treatment with combinations of either DEET or permethrin at all doses, whereas the cerebellum showed a significant increase in AChE activity following treatment with a combination of PB/DEET/permethrin. Co-exposure to PB, DEET, and permethrin resulted in significant inhibition in AChE in midbrain. PB alone or in combination with DEET and permethrin at all doses increased ligand binding for m2 muscarinic acetylcholine receptor in the cortex. In addition, PB and DEET together or a combination of PB, DEET, and permethrin significantly increased ligand binding for nicotinic acetylcholine receptor. These results suggest that exposure to various doses of PB, alone and in combination with DEET and permethrin, leads to sensorimotor deficits and differential alterations of the cholinergic system in the CNS. Title: Increased expression of glial fibrillary acidic protein in cerebellum and hippocampus: differential effects on neonatal brain regional acetylcholinesterase following maternal exposure to combined chlorpyrifos and nicotine Abdel-Rahman A, Dechkovskaia A, Mehta-Simmons H, Guan X, Khan W, Abou-Donia MB Ref: J Toxicol Environ Health A, 66:2047, 2003 : PubMed ESTHER: Abdel-Rahman_2003_J.Toxicol.Environ.Health.A_66_2047 PubMedSearch: Abdel-Rahman 2003 J.Toxicol.Environ.Health.A 66 2047 PubMedID: 14555401 Abstract Cigarette smoking and environmental exposure to chlorpyrifos during pregnancy could lead to developmental toxicity in the offspring. In the present study, pregnant female Sprague-Dawley rats (300-350 g) were treated daily with nicotine (1 mg/kg, sc) or chlorpyrifos (0.1 mg/kg, dermal) or a combination of nicotine and chlorpyrifos from gestational days (GD) 4-20. Control animals were treated with saline and ethanol. Male offspring from the mothers treated with nicotine alone gained significantly less weight on postnatal day (PND) 30 as compared to control. On PND 7, there was a significant increase in brain acetylcholinesterase (AChE) activity in pups from nicotine- and chlorpyrifos-treated dams, whereas plasma butyrylcholinesterase (BChE) activity was significantly elevated in pups of mothers treated with either chlorpyrifos alone or pesticide combined with nicotine. On PND 30 there was a significant increase in AChE activity in brainstem and cerebellum in all treated male pups. In female pups on PND 30 there was a significant rise in AChE activity in brainstem of chlorpyrifos alone and in cerebellum of the combination nicotine and chlorpyrifos group. Histopathological evaluation demonstrated an increased neuronal cell death in the cerebellum granular cell layer of female offspring from nicotine or combined nicotine with chlorpyrifos group. A rise in glial fibrillary acidic protein (GFAP) immunostaining was observed in the CA1 subfield of hippocampus and cerebellum on PND 30 in female and male offspring of mothers treated with either nicotine or nicotine in combination with chlorpyrifos, but to a lesser extent in males. Data suggest that maternal exposure to nicotine and chlorpyrifos, alone or in combination, produces differential alterations in brain regional AChE activity and expression of GFAP in cerebellum and hippocampus in offspring on PND 30. Title: Sensorimotor deficits and increased brain nicotinic acetylcholine receptors following exposure to chlorpyrifos and/or nicotine in rats Abou-Donia MB, Abdel-Rahman A, Goldstein LB, Dechkovskaia AM, Shah DU, Bullman SL, Khan WA Ref: Archives of Toxicology, 77:452, 2003 : PubMed ESTHER: Abou-Donia_2003_Arch.Toxicol_77_452 PubMedSearch: Abou-Donia 2003 Arch.Toxicol 77 452 PubMedID: 12937891 Abstract Despite well-known adverse effects associated with cigarette smoking, approximately 20% of the US population continues to smoke and many more are exposed to environmental tobacco smoke. Many of the same individuals are also exposed to environmental neurotoxic chemicals such as the organophosphorus insecticide chlorpyrifos. In the present study, the effects of exposure to low doses of nicotine and chlorpyrifos alone and in combination, were studied on the central cholinergic system and sensorimotor performance in rats. Male Sprague-Dawley rats (250-300 g) were treated with nicotine (1 mg/kg s.c., in normal saline), chlorpyrifos (0.1 mg/kg dermally, in 0.1 ml 70% ethanol), or a combination of both, daily for 30 days. Control rats were treated with saline and dermally with ethanol. Sensorimotor behavior was evaluated 24 h following the last dose using a battery of tests. There was a significant deficit in incline plane performance, beam-walk score and beam-walk time following exposure to each chemical, alone or in combination. The deficit in incline plane performance was greater when the two chemicals were given in combination than with either compound alone. Biochemical analysis showed a decrease in cerebellar and an increase in midbrain acetylcholinesterase (AChE) activity following combined exposure. Exposure to nicotine alone resulted in a significant increase in AChE activity in brainstem and midbrain, whereas there was no significant change after exposure to chlorpyrifos, alone. A significant increase in ligand binding to nicotinic acetylcholine receptors (nAChR) was observed in brainstem and cortex following exposure to nicotine or chlorpyrifos. This was further augmented with combined exposure, which caused a modest but significant increase in m2 muscarinic acetylcholine receptors (m2-mAChR) ligand binding in the cortex. These data suggest that exposure to either nicotine or chlorpyrifos or a combination of the two may impair neurobehavioral performance and affect the central nervous system cholinergic pathways. Title: Organophosphorus ester-induced chronic neurotoxicity Abou-Donia MB Ref: Archives of Environmental Health, 58:484, 2003 : PubMed ESTHER: Abou-Donia_2003_Arch.Environ.Health_58_484 PubMedSearch: Abou-Donia 2003 Arch.Environ.Health 58 484 PubMedID: 15259428 Abstract Organophosphorus compounds are potent neurotoxic chemicals that are widely used in medicine, industry, and agriculture. The neurotoxicity of these chemicals has been documented in accidental human poisoning, epidemiological studies, and animal models. Organophosphorus compounds have 3 distinct neurotoxic actions. The primary action is the irreversible inhibition of acetylcholinesterase, resulting in the accumulation of acetylcholine and subsequent overstimulation of the nicotinic and muscarinic acetylcholine receptors, resulting in cholinergic effects. Another action of some of these compounds, arising from single or repeated exposure, is a delayed onset of ataxia, accompanied by a Wallerian-type degeneration of the axon and myelin in the most distal portion of the longest tracts in both the central and peripheral nervous systems, and is known as organophosphorus ester-induced delayed neurotoxicity (OPIDN). In addition, since the introduction and extensive use of synthetic organophosphorus compounds in agriculture and industry half a century ago, many studies have reported long-term, persistent, chronic neurotoxicity symptoms in individuals as a result of acute exposure to high doses that cause acute cholinergic toxicity, or from long-term, low-level, subclinical doses of these chemicals. The author attempts to define the neuronal disorder that results from organophosphorus ester-induced chronic neurotoxicity (OPICN), which leads to long-term neurological and neurobehavioral deficits. Although the mechanisms of this neurodegenerative disorder have yet to be established, the sparse available data suggest that large toxic doses of organophosphorus compounds cause acute necrotic neuronal cell death in the brain, whereas sublethal or subclinical doses produce apoptotic neuronal cell death and involve oxidative stress. Title: Sarin (nerve agent GB)-induced differential expression of mRNA coding for the acetylcholinesterase gene in the rat central nervous system Damodaran TV, Jones KH, Patel AG, Abou-Donia MB Ref: Biochemical Pharmacology, 65:2041, 2003 : PubMed ESTHER: Damodaran_2003_Biochem.Pharmacol_65_2041 PubMedSearch: Damodaran 2003 Biochem.Pharmacol 65 2041 PubMedID: 12787884 Abstract We carried out a time-course study on the effects of a single intramuscular (i.m.) dose (0.5x LD(50)) of sarin (O-isopropyl methylphosphonofluoridate), also known as nerve agent GB, on the mRNA expression of acetylcholinesterase (AChE) in the brain of male Sprague-Dawley rats. Sarin inactivates the enzyme AChE which is responsible for the breakdown of the neurotransmitter acetylcholine (ACh), leading to its accumulation at ACh receptors and overstimulation of the cholinergic system. Rats were treated with 50 microg/kg of sarin (0.5x LD(50)) in 1 mL saline/kg and terminated at the following time points: 1 and 2 hr and 1, 3, and 7 days post-treatment. Control rats were treated with normal saline. Total RNA was extracted, and northern blots were hybridized with cDNA probes for AChE and 28S RNA (control). Poly-A RNA from both treated and control cortex was used for reverse transcription-polymerase chain reaction (RT-PCR)-based verification of the data from the northern blots. The results obtained indicate that a single (i.m.) dose of sarin (0.5x LD(50)) produced differential induction and persistence of AChE mRNA levels in different regions of the brain. Immediate induction of AChE transcripts was noted in the brainstem (126+/-6%), cortex (149+/-4%), midbrain (153+/-5%), and cerebellum (234+/-2%) at 1 hr. The AChE expression level, however, increased over time and remained elevated after a decline at 1 day in the previously shown more susceptible brainstem. The transcript levels remained elevated at a later time point (3 days) in the midbrain, after a dramatic decline at day 1 (110+/-2%). In the cortex, transcript levels came down to control values by day 1. The cerebellum also showed a decline of the elevated levels observed at 2 hr (275+/-2%) to control values by day 1. RT-PCR analysis of the AChE transcript at 30 min in the cortex showed an induction to 213+/-3% of the control level, confirming the expression pattern obtained by the northern blot data. The immediate induction followed by the complex pattern of the AChE mRNA time-course in the CNS may indicate that the activation of both cholinergic-related and unrelated functions of the gene plays an important role in the pathological manifestations of sarin-induced neurotoxicity. Title: Methyl parathion: a review of health effects Garcia S, Abu-Qare A, Meeker OW, Borton A, Abou-Donia MB Ref: J Toxicol Environ Health B Crit Rev, 6:185, 2003 : PubMed ESTHER: Garcia_2003_J.Toxicol.Environ.Health.B.Crit.Rev_6_185 PubMedSearch: Garcia 2003 J.Toxicol.Environ.Health.B.Crit.Rev 6 185 PubMedID: 12554434 Abstract Methyl parathion is an organophosphorus (OP) insecticide with insecticidal properties derived from acetylcholinesterase (AChE) inhibition; this same property is also the root of its toxicity in humans. Poisoning with methyl parathion leads to cholinergic overstimulation with signs of toxicity including sweating, dizziness, vomiting, diarrhea, convulsions, cardiac arrest, respiratory arrest, and, in extreme cases, death. Reports of methyl parathion intoxication, usually seen only in field pesticide applicators, have increased throughout the United States as a result of unauthorized application of methyl parathion inside homes. The health concerns of the use of methyl parathion have resulted in cancellation of its use in most food crops in the United States. This review examines the well-documented neurotoxicity of methyl parathion as well as effects on other organ systems. Title: Acute exposure to sarin increases blood brain barrier permeability and induces neuropathological changes in the rat brain: dose-response relationships Abdel-Rahman A, Shetty AK, Abou-Donia MB Ref: Neuroscience, 113:721, 2002 : PubMed ESTHER: Abdel-Rahman_2002_Neurosci_113_721 PubMedSearch: Abdel-Rahman 2002 Neurosci 113 721 PubMedID: 12150792 Abstract We hypothesize that a single exposure to an LD(50) dose of sarin induces widespread early neuropathological changes in the adult brain. In this study, we evaluated the early changes in the adult brain after a single exposure to different doses of sarin. Adult male rats were exposed to sarin by a single intramuscular injection at doses of 1, 0.5, 0.1 and 0.01 x LD(50). Twenty-four hours after the treatment, both sarin-treated and vehicle-treated (controls) animals were analyzed for: (i) plasma butyrylcholinesterase (BChE) activity; (ii) brain acetylcholinesterase (AChE) activity, (iii) m2 muscarinic acetylcholine receptor (m2 mAChR) ligand binding; (iv) blood brain barrier (BBB) permeability using [H(3)]hexamethonium iodide uptake assay and immunostaining for endothelial barrier antigen (EBA); and (v) histopathological changes in the brain using H&E staining, and microtubule-associated protein (MAP-2) and glial fibrillary acidic protein immunostaining. In animals treated with 1 x LD(50) sarin, the significant changes include a decreased plasma BChE, a decreased AChE in the cerebrum, brainstem, midbrain and the cerebellum, a decreased m2 mAChR ligand binding in the cerebrum, an increased BBB permeability in the cerebrum, brainstem, midbrain and the cerebellum associated with a decreased EBA expression, a diffuse neuronal cell death and a decreased MAP-2 expression in the cerebral cortex and the hippocampus, and degeneration of Purkinje neurons in the cerebellum. Animals treated with 0.5 x LD(50) sarin however exhibited only a few alterations, which include decreased plasma BChE, an increased BBB permeability in the midbrain and the brain stem but without a decrease in EBA expression, and degeneration of Purkinje neurons in the cerebellum. In contrast, animals treated with 0.1 and 0.01 x LD(50) did not exhibit any of the above changes. However, m2 mAChR ligand binding in the brainstem was increased after exposure to all doses of the sarin.Collectively, the above results indicate that, the early brain damage after acute exposure to sarin is clearly dose-dependent, and that exposure to 1 x LD(50) sarin induces detrimental changes in many regions of the adult rat brain as early as 24 hours after the exposure. The early neuropathological changes observed after a single dose of 1 x LD(50) sarin could lead to a profound long-term neurodegenerative changes in many regions of the brain, and resulting behavioral abnormalities. Title: Disruption of the blood-brain barrier and neuronal cell death in cingulate cortex, dentate gyrus, thalamus, and hypothalamus in a rat model of gulf-war syndrome Abdel-Rahman A, Shetty A, Abou-Donia MB Ref: Neurobiol Dis, 10:306, 2002 : PubMed ESTHER: Abdel-Rahman_2002_Neurobiol.Dis_10_306 PubMedSearch: Abdel-Rahman 2002 Neurobiol.Dis 10 306 PubMedID: 12270692 Abstract We investigated the effects of a combined exposure to restraint stress and low doses of chemicals pyridostigmine bromide (PB), N, N-diethyl-m-toluamide (DEET), and permethrin in adult male rats, a model of Gulf-War syndrome. Animals were exposed daily to one of the following for 28 days: (i) a combination of stress and chemicals (PB, 1.3 mg/kg/day; DEET, 40 mg/kg/day; and permethrin, 0.13 mg/kg/day); (ii) stress and vehicle; (iii) chemicals alone; and (iv) vehicle alone. All animals were evaluated for: (i) the disruption of the blood-brain barrier (BBB) using intravenous horseradish peroxidase (HRP) injections and endothelial barrier antigen (EBA) immunostaining; (ii) neuronal cell death using H&E staining, silver staining, and glial fibrillary acidic protein (GFAP) immunostaining; and (iii) acetylcholinesterase (AChE) activity and m2-muscarinic acetylcholine receptors (m2-AChR). Animals subjected to stress and chemicals exhibited both disruption of the BBB and neuronal cell death in the cingulate cortex, the dentate gyrus, the thalamus, and the hypothalamus. Other regions of the brain, although they demonstrated some neuronal cell death, did not exhibit disruption of the BBB. The neuropathological changes in the above four brain regions were highly conspicuous and revealed by a large number of HRP-positive neurons (21-40% of total neurons), a decreased EBA immunostaining (42-51% reduction), a decreased number of surviving neurons (27-40% reduction), the presence of dying neurons (4-10% of total neurons), and an increased GFAP immunostaining (45-51% increase). These changes were also associated with decreased forebrain AChE activity and m2-AchR (19-25% reduction). In contrast, in animals exposed to stress and vehicle or chemicals alone, the above indices were mostly comparable to that of animals exposed to vehicle alone. Thus, a combined exposure to stress and low doses of PB, DEET, and permethrin leads to significant brain injury. The various neurological symptoms reported by Gulf-War veterans could be linked to this kind of brain injury incurred during the war. Title: Sensorimotor deficit and cholinergic changes following coexposure with pyridostigmine bromide and sarin in rats Abou-Donia MB, Dechkovskaia AM, Goldstein LB, Bullman SL, Khan WA Ref: Toxicol Sci, 66:148, 2002 : PubMed ESTHER: Abou-Donia_2002_Toxicol.Sci_66_148 PubMedSearch: Abou-Donia 2002 Toxicol.Sci 66 148 PubMedID: 11861982 Inhibitor(s) related to this paper: Pyridostigmine Abstract A myriad of neurological symptoms including muscle and joint pain, ataxia, chronic fatigue, headache, and difficulty in concentration have been reported by Persian Gulf War (PGW) veterans. A large number of these veterans were prophylactically treated with pyridostigmine bromide (PB) and possibly exposed to sarin. In the present study we investigated the effects of PB and sarin, alone and in combination, on sensorimotor performance and the central cholinergic system of rats. Male Sprague-Dawley rats were treated with PB (1.3 mg/kg, 15 daily doses, oral) and sarin (50, 75, 90, and 100 microg/kg, single im dose on day 15), alone and in combination. The animals were evaluated for postural reflexes, limb placing, orienting to vibrissae touch, incline plane performance, beam-walk time, and forepaw grip time 7 and 15 days following treatment with sarin. Treatment with either PB or sarin alone resulted in significant sensorimotor impairments. Coexposure to sarin and PB resulted in significant sensorimotor deficits that worsened over time. By 15 days following sarin treatment, plasma butyrylcholinesterase (BChE) activity returned to normal levels in the animals treated with sarin alone, whereas in the animals exposed to PB or PB plus sarin, there was an increase in the enzyme activity. Cortical acetylcholinesterase (AChE) activity remained inhibited in the animals treated with sarin alone and in combination with PB. Muscarinic acetylcholine receptor (m2 mAChR) ligand binding with [(3)H]AFDX-384 in cortex and brain stem showed significant increases (approximately 120-130% of control) following coexposure to PB and sarin at higher doses. To evaluate the potential of PB for augmentation or inhibition of the toxicity induced by acute sarin exposure, the animals were exposed to either 10 or 100 microg/kg sarin (single im injection) with or without pretreatment with PB, and sacrificed 3 h after treatment with sarin. Pretreatment with PB offered slight protection in the plasma as well as brain regional enzyme activities. Pretreatment with PB did not have any effect on sarin-inhibited brain regional AChE activity following treatment with 100 microg/kg sarin. These results show that prophylactic treatment with PB offers some degree of protection in peripheral cholinesterase. Furthermore, these results show that treatment with either sarin or PB alone resulted in sensorimotor impairments, while coexposure to high doses of sarin with PB caused an exacerbated deficit. Title: Uranyl acetate-induced sensorimotor deficit and increased nitric oxide generation in the central nervous system in rats Abou-Donia MB, Dechkovskaia AM, Goldstein LB, Shah DU, Bullman SL, Khan WA Ref: Pharmacol Biochem Behav, 72:881, 2002 : PubMed ESTHER: Abou-Donia_2002_Pharmacol.Biochem.Behav_72_881 PubMedSearch: Abou-Donia 2002 Pharmacol.Biochem.Behav 72 881 PubMedID: 12062578 Abstract We investigated the effects of uranyl acetate on sensorimotor behavior, generation of nitric oxide and the central cholinergic system of rats. Male Sprague-Dawley rats were treated with intramuscular injection of 0.1 and 1 mg/kg uranyl acetate in water, daily for 7 days. Control animals received equivalent amount of water. The treatment was stopped after the seventh injection because the animals in the 1-mg/kg group appeared lethargic. The animals were maintained for an additional observation period of 30 days. The study was initiated as a dose-finding study that covered doses of 10 and 100 mg/kg, as well. However, all the animals in the 100-mg/kg treatment group died after the third and fourth injections, and all animals given 10 mg/kg died after the fifth and sixth injections. On Day 30 following the cessation of treatment, the sensorimotor functions of the animals in the 0.1- and 1-mg/kg treatment groups were evaluated using a battery of tests that included measurements of postural reflexes, limb placing, orientation to vibrissae touch, grip time, beam walking and inclined plane performance. The animals were sacrificed the same day and the cerebral cortex, brainstem, cerebellum and midbrain were dissected. The levels of nitric oxide as marker for increased oxidative stress, and the integrity of the cholinergic system as reflected in acetylcholinesterase (AChE) activity and m2 muscarinic acetylcholine receptors ligand binding, were determined. The data from behavioral observations show that there was a dose-related deficit at the 0.1- and 1-mg/kg treatment groups for inclined plane performance. Both doses reduced grip time, but there was no significant difference between the two doses. Similarly, both beam-walk score and beam-walk time were impaired at both doses as compared with the controls. A significant increase in nitric oxide was seen at 0.1 mg/kg dose in cortex and midbrain, whereas brainstem and cerebellum showed an insignificant decrease at both the doses. Similarly, there was no significant change in nitric oxide levels in kidneys and liver of the treated animals as compared with the controls. There was a significant increase in AChE activity in the cortex of the animals treated with 1 mg/kg uranyl acetate, but not in other brain regions. Ligand binding densities for the m2 muscarinic receptor did not show any change. These results show that low-dose, multiple exposure to uranyl acetate caused prolonged neurobehavioral deficits after the initial exposure has ceased. Title: Sarin: health effects, metabolism, and methods of analysis Abu-Qare AW, Abou-Donia MB Ref: Food & Chemical Toxicology, 40:1327, 2002 : PubMed ESTHER: Abu-Qare_2002_Food.Chem.Toxicol_40_1327 PubMedSearch: Abu-Qare 2002 Food.Chem.Toxicol 40 1327 PubMedID: 12387297 Abstract Sarin (O-isopropylmethylphosphonofluoridate) is a highly toxic nerve agent produced for chemical warfare. Sarin is an extremely potent acetylcholinesterase (AchE) inhibitor with high specificity and affinity for the enzyme. Death by sarin is due to anoxia resulting from airway obstruction, weakness of the muscles of respiration, convulsions and respiratory failure. The main clinical symptoms of acute toxicity of sarin are seizures, tremors and hypothermia. Exposure to sarin during incidents in Japan in 1994, 1995 and 1998, and possible exposure to low levels of sarin during the Gulf War, resulted in the deaths and injury of many people in Japan and caused possible long-term health effects on Gulf War veterans. Symptoms related to sarin poisoning in Japan still exist 1-3 years after the incident and include fatigue, asthenia, shoulder stiffness and blurred vision. Sarin produced seizures in rats and pigs. Recent studies showed that long-term exposure to low levels of sarin caused neurophysiological and behavioral alterations. Toxicity from sarin significantly increased following concurrent exposure to other chemicals such as pyridostigmine bromide. Further research to examine effects of sarin on the cellular and the molecular levels, gene transcription, endocrine system as well as its long-term impact is needed. Title: Inhibition and recovery of maternal and fetal cholinesterase enzymes following a single oral dose of chlorpyrifos in rats Ashry KM, Abu-Qare AW, Saleem FR, Hussein YA, Hamza SM, Kishk AM, Abou-Donia MB Ref: Archives of Toxicology, 76:30, 2002 : PubMed ESTHER: Ashry_2002_Arch.Toxicol_76_30 PubMedSearch: Ashry 2002 Arch.Toxicol 76 30 PubMedID: 11875622 Abstract Pregnant Sprague-Dawley rats (14-18 days of gestation) were treated with a single dose of 50 mg/kg (61% of oral LD50 in female rats) of chlorpyrifos ( 0,0-diethyl- 0-3,5,6-trichloro-2-pyridyl phosphorothioate) by oral gavage. Animals treated on day 18 of gestation were sacrificed at 1, 2, 4, 12 h after dosing. Animals treated on days 17, 16, 15, and 14 of gestation were sacrificed at 24, 48, 72, and 96 h after dosing, respectively. Maternal and fetal brain acetylcholinesterase (AchE) and plasma butyrylcholinesterase (BuChE) activities were significantly inhibited 1 h after treatment. Activity of fetal brain AChE and plasma BuChE recovered faster than that of the maternal enzymes. Peak inhibition of maternal spinal cord AChE and BuChE activities occurred 2 h and 1 h after dosing, respectively. Maternal spinal cord BuChE activity was totally recovered by 96 h compared to the partial recovery of spinal cord AChE activity. Maternal liver BuChE activity was significantly decreased within 1 h of dosing. The individual molecular forms (10S and 4S) of maternal and fetal brain AChE and BuChE activities were significantly decreased 1 h after treatment. Recovery of both forms of fetal brain AChE activity was much faster than the maternal forms. Activity of the 10S form of maternal control brain AChE was significantly higher than in the fetus control. The rapid recovery of cholinesterase enzymes in the fetus is attributed to the de novo synthesis of AChE enzymes in the fetus compared to the mother. Title: Locomotor and sensorimotor performance deficit in rats following exposure to pyridostigmine bromide, DEET, and permethrin, alone and in combination Abou-Donia MB, Goldstein LB, Jones KH, Abdel-Rahman AA, Damodaran TV, Dechkovskaia AM, Bullman SL, Amir BE, Khan WA Ref: Toxicol Sci, 60:305, 2001 : PubMed ESTHER: Abou-Donia_2001_Toxicol.Sci_60_305 PubMedSearch: Abou-Donia 2001 Toxicol.Sci 60 305 PubMedID: 11248143 Inhibitor(s) related to this paper: Pyridostigmine Abstract Since their return from Persian Gulf War (PGW), many veterans have complained of symptoms including muscle and joint pain, ataxia, chronic fatigue, headache, and difficulty with concentration. The causes of the symptoms remain unknown. Because these veterans were exposed to a combination of chemicals including pyridostigmine bromide (PB), DEET, and permethrin, we investigated the effects of these agents, alone and in combination, on the sensorimotor behavior and central cholinergic system of rats. Male Sprague-Dawley rats (200-250 gm) were treated with DEET (40 mg/kg, dermal) or permethrin (0.13 mg/kg, dermal), alone and in combination with PB (1.3 mg/kg, oral, last 15 days only), for 45 days. Sensorimotor ability was assessed by a battery of behavioral tests that included beam-walk score, beam-walk time, incline plane performance, and forepaw grip on days 30 and 45 following the treatment. On day 45 the animals were sacrificed, and plasma and CNS cholinesterase, and brain choline acetyl transferase, muscarinic and nicotinic acetylcholine receptors were evaluated. Animals treated with PB, alone or in combination with DEET and permethrin, showed a significant deficit in beam-walk score as well as beam-walk time as compared with controls. Treatment with either DEET or permethrin, alone or in combination with each other, did not have a significant effect on beam-walk score. All chemicals, alone or in combination, resulted in a significant impairment in incline plane testing on days 30 and 45 following treatment. Treatment with PB, DEET, or permethrin alone did not have any inhibitory effect on plasma or brain cholinesterase activities, except that PB alone caused moderate inhibition in midbrain acetylcholinesterase (AChE) activity. Treatment with permethrin alone caused significant increase in cortical and cerebellar AChE activity. A combination of DEET and permethrin or PB and DEET led to significant decrease in AChE activity in brainstem and midbrain and brainstem, respectively. A significant decrease in brainstem AChE activity was observed following combined exposure to PB and permethrin. Coexposure with PB, DEET, and permethrin resulted in significant inhibition in AChE in brainstem and midbrain. No effect was observed on choline acetyl transferase activity in brainstem or cortex, except combined exposure to PB, DEET, and permethrin caused a slight but significant increase in cortical choline acetyltransferase activity. Treatment with PB, DEET, and permethrin alone caused a significant increase in ligand binding for m2 muscarinic acetylcholine receptor (mAChR) in the cortex. Coexposure to PB, DEET, and permethrin did not have any effect over that of PB-induced increase in ligand binding. There was no significant change in ligand binding for nicotinic acetylcholine receptor (nAChR) associated with treatment with the chemical alone; a combination of PB and DEET or coexposure with PB, DEET, and permethrin caused a significant increase in nAChR ligand binding in the cortex. Thus, these results suggest that exposure to physiologically relevant doses of PB, DEET, and permethrin, alone or in combination, leads to neurobehavioral deficits and region-specific alterations in AChE and acetylcholine receptors. Title: Inhibition of cholinesterase enzymes following a single dermal dose of chlorpyrifos and methyl parathion, alone and in combination, in pregnant rats Abu-Qare AW, Abdel-Rahman A, Brownie C, Kishk AM, Abou-Donia MB Ref: J Toxicol Environ Health A, 63:173, 2001 : PubMed ESTHER: Abu-Qare_2001_J.Toxicol.Environ.Health.A_63_173 PubMedSearch: Abu-Qare 2001 J.Toxicol.Environ.Health.A 63 173 PubMedID: 11405414 Abstract Pregnant Sprague-Dawley rats (14-18 d of gestation) were treated with either a single dermal subclinical dose of 30 mg/kg (15% of dermal LD50) chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridinyl] phosphorothioate) or a single dermal subclinical dose of 10 mg/kg (15% of dermal LD50) methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate) or the two in combination. Chlorpyrifos inhibited maternal and fetal brain acetylcholinesterase (AChE) activity within 24 h of dosing, (48% and 67% of control activity, respectively). Following application of methyl parathion, peak inhibition of maternal and fetal brain AChE activity occurred at 48 h and 24 h after dosing (17% and 48% of control activity, respectively). A combination of chlorpyrifos and methyl parathion produced peak inhibition of maternal and fetal brain AChE activity at 24 h postdosing (35% and 73% of control activity, respectively). Maternal and fetal brain AChE activity recovered to various degrees of percentage of control 96 h after dosing. Application of methyl parathion or chlorpyrifos alone or in combination significantly inhibited maternal plasma butyrylcholinesterase (BuChE) activity. No significant inhibition of fetal plasma BuChE activity was detected. Peak inhibition of maternal liver BuChE occurred 24 h after application of methyl parathion or chlorpyrifos alone or in combination (64%, 80%, and 61% of control activity, respectively). Significant inhibition of placental AChE occurred within 24 h after application of methyl parathion or chlorpyrifos alone or in combination. The results suggest that methyl parathion and chlorpyrifos, alone or in combination, were rapidly distributed in maternal and fetal tissues, resulting in rapid inhibition of cholinesterase enzyme activities. The lower inhibitory effect of the combination could be due to competition between chlorpyrifos and methyl parathion for cytochrome P-450 enzymes, resulting in inhibition of the formation of the potent cholinesterase inhibitor oxon forms. The faster recovery of fetal plasma BuChE is attributed to the de novo synthesis of cholinesterase by fetal tissues compared to maternal tissues. Title: Effects of sub-chronic in vivo chlorpyrifos exposure on muscarinic receptors and adenylate cyclase of rat striatum Huff RA, Abu-Qare AW, Abou-Donia MB Ref: Archives of Toxicology, 75:480, 2001 : PubMed ESTHER: Huff_2001_Arch.Toxicol_75_480 PubMedSearch: Huff 2001 Arch.Toxicol 75 480 PubMedID: 11757672 Abstract In this study dosing regimens were designed such that cholinesterase inhibition following exposure to chlorpyrifos was produced in one treatment group but was absent in the other The higher dosing regimen inhibited plasma and brain cholinesterase activities by 51 and 70 respectively and resulted in decreased 3H]cis-methyldioxolane 3H]CD binding which was attributable to a decrease in Bmax No concomitant loss of 3H]quinuclidinyl benzilate 3H]QNB binding sites was observed indicating that the M2 muscarinic receptor subtype to which 3H]CD binds is particularly susceptible to alterations induced by chlorpyrifos treatment As the M2 receptor subtype is surmised to be the muscarinic autoreceptor decreases in this receptor may exacerbate poisoning by organophosphorus agents as a result of decreased ability to terminate synaptic acetylcholine release The ability of carbachol to inhibit striatal adenylate cyclase which is an effector molecule associated with the M2 receptor was unaltered in chlorpyrifos-treated rats Decreases in M2 receptors occurred with the higher dosing regimen in the absence of any clinical manifestations Thus in the absence of overt clinical signs perturbations of the muscarinic receptor system did occur as a result of sub-chronic chlorpyrifos exposure Such alterations may contribute to neurological impairments that develop following chronic organophosphorus exposure Title: Subchronic effects following a single sarin exposure on blood-brain and blood-testes barrier permeability, acetylcholinesterase, and acetylcholine receptors in the central nervous system of rat: a dose-response study Jones KH, Dechkovskaia AM, Herrick EA, Abdel-Rahman AA, Khan WA, Abou-Donia MB Ref: J Toxicol Environ Health A, 61:695, 2000 : PubMed ESTHER: Jones_2000_J.Toxicol.Environ.Health.A_61_695 PubMedSearch: Jones 2000 J.Toxicol.Environ.Health.A 61 695 PubMedID: 11132698 Inhibitor(s) related to this paper: Hexamethonium Abstract Subchronic neurotoxic effects of sarin (O-isopropyl methylphosphonofluoridate) treatment at various doses in male Sprague Dawley rats were studied. The animals were treated with a single intramuscular (im) injection of 0.01, 0.1, 0.5, or 1 x LD50 (100 microg/kg). The animals were maintained for 90 d thereafter. [3H]Hexamethonium iodide was used to monitor the changes in blood-brain barrier (BBB) permeability in cortex, brainstem, midbrain, and cerebellum. Brainstem exhibited a significant decrease (approximately 58% of control) in uptake of [3H]hexamethonium iodide at 1 x LD50 dose. No significant changes were observed in BBB permeability in cortex, midbrain, and cerebellum at any dose. Plasma butyrylcholinesterase (BChE) activity remained unchanged, reflecting recovery of the enzyme activity from the initial inhibition following single exposure of 1 x LD50 sarin. Acetylcholinesterase (AChE) activity in the cortex remained inhibited (approximately 29%), whereas in the brainstem there was an increase (approximately 20%) at 1 x LD50 dose of sarin. The m2-selective muscarinic acetylcholine receptor (m2-mAChR) ligand binding was inhibited significantly at 1 x LD50 in the cortex, whereas brainstem showed significantly increased (approximately 45%) ligand binding at 1 x LD50 dose. Nicotinic acetylcholine receptor (nAChR), on the other hand, showed a biphasic response in ligand binding in the cortex with a decrease (approximately 30%) at 0.01 x LD50 but an increase (approximately 40%) at 1 x LD5O. Brainstem did not show any significant change in nAChR ligand binding. These results suggest that single exposure of sarin could lead to changes that may play an important role in neuropathological abnormalities in the central nervous system. Title: Acute sarin exposure causes differential regulation of choline acetyltransferase, acetylcholinesterase, and acetylcholine receptors in the central nervous system of the rat Khan WA, Dechkovskaia AM, Herrick EA, Jones KH, Abou-Donia MB Ref: Toxicol Sci, 57:112, 2000 : PubMed ESTHER: Khan_2000_Toxicol.Sci_57_112 PubMedSearch: Khan 2000 Toxicol.Sci 57 112 PubMedID: 10966517 Abstract Acute neurotoxic effects of sarin (O:-isopropylmethylphosphonoflouridate) in male Sprague-Dawley rats were studied. The animals were treated with intramuscular (im) injections of either 1 x LD(50) (100 microg/kg), and sacrificed at 0. 5, 1, 3, 6, 15, or 20 h after treatment, or with im injections of either 0.01, 0.1, 0.5, or 1 x LD(50) and sacrificed 15 h after treatment. Plasma butyrylcholinesterase (BChE) and brain regional acetylcholinesterase (AChE) were inhibited (45-55%) by 30 min after the LD(50) dose. BChE in the plasma and AChE in cortex, brainstem, midbrain, and cerebellum remained inhibited for up to 20 h following a single LD(50) treatment. No inhibition in plasma BChE activity was observed 20 h after treatment with doses lower than the LD(50) dose. Midbrain and brainstem seem to be most responsive to sarin treatment at lower doses, as these regions exhibited inhibition (approximately 49% and 10%, respectively) in AChE activity following 0.1 x LD(50) treatment, after 20 h. Choline acetyltransferase (ChAT) activity was increased in cortex, brainstem, and midbrain 6 h after LD(50) treatment, and the elevated enzyme activity persisted up to 20 h after treatment. Cortex ChAT activity was significantly increased following a 0.1 x LD(50) dose, whereas brainstem and midbrain did not show any effect at lower doses. Treatment with an LD(50) dose caused a biphasic response in cortical nicotinic acetylcholine receptor (nAChR) and muscarinic acetylcholine receptor (m2-mAChR) ligand binding, using [(3)H]cytisine and [(3)H]AFDX-384 as ligands for nAChR and mAChR, respectively. Decreases at 1 and 3 h and consistent increases at 6, 15, and 20 h in nAChR and m2-mAChR were observed following a single LD(50) dose. The increase in nAChR ligand binding densities was much more pronounced than in mAChR. These results suggest that a single exposure of sarin, ranging from 0.1 to 1 x LD(50), modulates the cholinergic pathways differently and thereby causes dysregulation in excitatory neurotransmission. Title: Enhanced mRNA expression of neurofilament subunits in the brain and spinal cord of diisopropyl phosphorofluoridate-treated hens Gupta RP, Lin WW, Abou-Donia MB Ref: Biochemical Pharmacology, 57:1245, 1999 : PubMed ESTHER: Gupta_1999_Biochem.Pharmacol_57_1245 PubMedSearch: Gupta 1999 Biochem.Pharmacol 57 1245 PubMedID: 10230768 Abstract Diisopropyl phosphorofluoridate (DFP) is an organophosphorus ester, and a single injection of this compound (1.7 mg/kg, s.c.) produces delayed neurotoxicity (OPIDN) in hens in 7-14 days. Clinically, the disease is marked by hindlimb ataxia followed by paralysis after some time. A characteristic feature of this neuropathy is axonal swelling in the initial stages and comparative dissolution of the accumulated material and degeneration of distal axons with disease progression. Axonal swelling consists of aggregated neurofilaments, microtubules, and proliferated smooth endoplasmic reticulum. We studied expression of neurofilament (NF) mRNAs in brain regions and spinal cord to elucidate their role in OPIDN. There was a 50-200% increase in NF transcripts in 24 hr after DFP administration. The NF-L mRNA level started falling after 1-5 days and came down to control level in susceptible brain regions (i.e. cerebellum and brainstem) and spinal cord, but not in cerebral cortex, which does not show degeneration of axons in OPIDN. Cerebral cortex exhibited elevated levels of both NF-L and NF-M transcripts in DFP-treated hens throughout the period of observation. The induction of NF messages is consistent with the previously reported effect on extension of neurites of human neuroblastoma cells in culture. The transient increase in NF messages in susceptible tissues either may be responsible for the delayed degeneration of axons in OPIDN or is the result of interruption of regulatory signal due to progressive degeneration of axons. Title: The organophosphate pesticide chlorpyrifos affects form deprivation myopia Geller AM, Abdel-Rahman AA, Peiffer RL, Abou-Donia MB, Boyes WK Ref: Invest Ophthalmol Vis Sci, 39:1290, 1998 : PubMed ESTHER: Geller_1998_Invest.Ophthalmol.Vis.Sci_39_1290 PubMedSearch: Geller 1998 Invest.Ophthalmol.Vis.Sci 39 1290 PubMedID: 9620094 Inhibitor(s) related to this paper: Chlorpyrifos Abstract PURPOSE: The effects of the anti-cholinesterase organophosphate pesticide chlorpyrifos (CPF) on the refractive development of the eye were examined. Form deprivation was used to induce eye growth to address the previously reported relationship between organophosphate pesticide use and the incidence of myopia. METHODS: Chickens, a well-established animal model for experimental myopia and organophosphate neurotoxicity, were dosed with chlorpyrifos (3 mg/kg per day, orally, from day 2 to day 9 after hatching) or corn oil vehicle (VEH) with or without monocular form deprivation (MFD) over the same period. The set of dependent measures included the refractive state of each eye measured using retinoscopy, axial dimensions determined with A-scan ultrasound, and intraocular pressure. RESULTS: Dosing with CPF yielded an inhibition of 35% butyrylcholinesterase in plasma and 45% acetylcholinesterase in brain. MFD resulted in a significant degree of myopia in form-deprived eyes resulting from significant lengthening of the vitreal chamber of the eye. CPF significantly reduced the effect of MFD, resulting in less myopic eyes (mean refraction: VEH-MFD = -16.2 +/- 2.3 diopters; CPF-MFD = -11.1 +/- 1.8 diopters) with significantly shorter vitreal chambers. Nonoccluded eyes were, on average, slightly hyperopic. Treatment with CPF for 1 week in the absence of MFD led to no significant change in ocular dimensions or refraction relative to controls. CONCLUSIONS: The use of form deprivation as a challenge suggests that CPF treatment interferes with the visual regulation of eye growth Title: Alteration in neurofilament axonal transport in the sciatic nerve of the diisopropyl phosphorofluoridate (DFP)-treated hen Gupta RP, Abdel-Rahman A, Wilmarth KW, Abou-Donia MB Ref: Biochemical Pharmacology, 53:1799, 1997 : PubMed ESTHER: Gupta_1997_Biochem.Pharmacol_53_1799 PubMedSearch: Gupta 1997 Biochem.Pharmacol 53 1799 PubMedID: 9256154 Abstract Diisopropyl phosphorofluoridate (DFP) is an organophosphorus ester that produces organophosphorus ester-induced delayed neurotoxicity (OPIDN) in hens 7-14 days after a single s.c. dose of 1.7 mg/kg. In this study, hens were treated with a single dose of DFP (1.7 mg/kg, s.c.) 24 hr after [35S]methionine injection into the sacrolumbar region of their spinal cord, and killed 3, 7, 14, or 27 days post-DFP treatment. The rates of transport of labeled high (NF-H), medium (NF-M), and low (NF-L) molecular weight neurofilaments, and tubulin were faster in DFP-treated birds than in controls after 3 days. Subsequently, the rate of transport of these proteins started falling, so that the peaks of labeled proteins in control and DFP-treated hens were overlapping after 7 days. At 14 days, the peaks of NF-H, NF-M, and NF-L in treated hens were distinctly behind the corresponding peaks in control hens. This was again followed by an increase in transport of NF-H and NF-L, but not of NF-M, so that the labeled NF-H and NF-L showed the same pattern in control and treated hens after 27 days. The transient decrease in NF-H and NF-L axonal transport rate, and recovery correlated in a temporal manner with the previously reported increase of Ca2+/calmodulin-dependent protein kinase-mediated phosphorylation of neurofilament proteins and inhibition of calpain activity in the sciatic nerve in OPIDN. Proteinase inhibition has been reported recently to result in enhanced phosphorylation of neurofilaments in some cells. The present study suggests that the enhanced phosphorylation of neurofilaments by DFP-increased Ca2+/calmodulin-dependent protein kinase activity may be contributing toward alteration in NF axonal transport and the development of OPIDN. Title: Neurotoxicity resulting from coexposure to pyridostigmine bromide, deet, and permethrin: implications of Gulf War chemical exposures Abou-Donia MB, Wilmarth KR, Jensen KF, Oehme FW, Kurt TL Ref: Journal of Toxicology & Environmental Health, 48:35, 1996 : PubMed ESTHER: Abou-Donia_1996_J.Toxicol.Env.Health_48_35 PubMedSearch: Abou-Donia 1996 J.Toxicol.Env.Health 48 35 PubMedID: 8637057 Inhibitor(s) related to this paper: Pyridostigmine Abstract Of the three-quarters of a million service personnel involved in the Persian Gulf War, approximately 30,000 have complained of neurological symptoms of unknown etiology. One contributing factor to the emergence of such symptoms may be the simultaneous exposure to multiple agents used to protect the health of service personnel, in particular, the anti-nerve agent pyridostigmine bromide (PB; 3-dimethylaminocarbonyloxy-N-methylpyridinium bromide), the insect repellent DEET (N,N-diethyl-m-toluamide), and the insecticide permethrin (3-(2,2-dichloro-ethenyl)-2,2-dimethylcyclopropanecarboxylic acid (3-phenoxyphenyl)methyl ester). This study investigated neurotoxicity produced in hens by individual or simultaneous exposure to these agents (5 d/wk for 2 months to 5 mg/kg/d PB in water, po; 500 mg/kg/d DEET, neat, sc; and 500 mg/kg/d permethrin in corn oil, sc). At these dosages, exposure to single compounds resulted in minimal toxicity. Combinations of two agents produced greater neurotoxicity than that caused by individual agents. Neurotoxicity was further enhanced following concurrent administration of all three agents. We hypothesize that competition for liver and plasma esterases by these compounds leads to their decreased breakdown and increased transport of the parent compound to nervous tissues. Thus, carbamylation of peripheral esterases by PB reduces the hydrolysis of DEET and permethrin and increases their availability to the nervous system. In effect, PB "pumps" more DEET and permethrin into the central nervous system. Consistent with this hypothesis, hens exposed to the combination of the three agents exhibited neuropathological lesions with several characteristics similar to those previously reported in studies of near-lethal doses of DEET and permethrin. If this hypothesis is correct, then blood and liver esterases play an important "buffering" role in protecting against neurotoxicity in the population at large. It also suggests that individuals with low plasma esterase activity may be predisposed to neurologic deficits produced by exposure to certain chemical mixtures. Title: Increased neurotoxicity following concurrent exposure to pyridostigmine bromide, DEET, and chlorpyrifos Abou-Donia MB, Wilmarth KR, Abdel-Rahman AA, Jensen KF, Oehme FW, Kurt TL Ref: Fundamental & Applied Toxicology, 34:201, 1996 : PubMed ESTHER: Abou-Donia_1996_Fundam.Appl.Toxicol_34_201 PubMedSearch: Abou-Donia 1996 Fundam.Appl.Toxicol 34 201 PubMedID: 8954750 Inhibitor(s) related to this paper: Pyridostigmine Abstract The operating environment of the service personnel during the Persian Gulf War involved psychological, biological, and chemical elements including exposure to pesticides such as the insect repellent DEET (N,N-diethyl-m-toluamide) and the insecticide chlorpyrifos (O,O-diethyl O-3,5,6-trichloropyridinyl phosphorothioate) and to pyridostigmine bromide (PB,3-dimethylaminocarbonyloxy-N-methylpyridinium bromide) that was administered as a prophylactic agent against possible nerve gas attack. The present study was designed to determine the toxicity produced by individual or coexposure of hens 5 days/week for 2 months to 5 mg PB/kg/day in water, by gavage; 500 mg DEET/kg/day, neat, sc; and 10 mg chlorpyrifos kg/day in corn oil, sc. Coexposure to various binary treatments produced greater neurotoxicity than that caused by individual exposures and was characterized by severe neurologic deficit and neuropathological alterations. Also, neurotoxicity was further enhanced following concurrent administration of the three chemicals. Severe inhibition of plasma butyrylcholinesterase (BCHE) activity was produced in hens treated with PB (activity 17% of control) compared to those treated with chlorpyrifos (activity 51% of control) or DEET (activity 83% of control). BCHE inhibition was further increased in binary and tertiary treatment groups compared to individual treatment groups. In contrast, a significant inhibition of brain acetylcholinesterase (AChE) was produced in hens administered chlorpyrifos alone (activity 67% of control), while those given chlorpyrifos in combination with other compounds exhibited a significant inhibition of brain AChE activity ranging from 43 to 76%. Brain neurotoxicity target esterase (NTE) was not inhibited in any of the individual treatment groups or PB/DEET, but was significantly inhibited and had activity expressed as a percentage of control in groups administered combined chlorpyrifos with PB of 73% or DEET of 74% and in the tertiary treatment group of 71%. We hypothesize that test compounds may compete for xenobiotic metabolizing enzymes in the liver and blood and may also compromise the integrity of the blood-brain barrier, leading to an increase in their "effective concentrations" in the nervous system to levels equivalent to the toxic doses of individual compounds. This is consistent with the present observation of increases in (1) the inhibition of brain AChE and NTE, (2) the extent of neurologic dysfunction, and (3) the severity and frequency of neuropathologic lesions in the combined treatment groups compared to those administered individual compounds. Title: The cytoskeleton as a target for organophosphorus ester-induced delayed neurotoxicity (OPIDN) Abou-Donia MB Ref: Chemico-Biological Interactions, 87:383, 1993 : PubMed ESTHER: Abou-Donia_1993_Chem.Biol.Interact_87_383 PubMedSearch: Abou-Donia 1993 Chem.Biol.Interact 87 383 PubMedID: 8343995 Abstract Although the immediate action of organophosphorus esters is the inhibition of acetylcholinesterase, some of these compounds also produce a neurodegenerative disorder known as organophosphorus ester-induced delayed neurotoxicity (OPIDN). Tri-o-cresyl phosphate (TOCP) first produced this condition in humans and later in sensitive animal species. OPIDN is characterized by a delay period prior to onset of ataxia and paralysis. The neuropathologic lesions are Wallerian-type degeneration of the axon and myelin in the distal parts of the large tracts in both the central and peripheral nervous systems. In the past decade we have demonstrated that the pathognomonic features of OPIDN are an aberrant increase in autophosphorylation of calcium/calmodulin kinase II (CaM kinase II) and an increase in phosphorylation of cytoskeletal proteins, i.e., MAPs, tubulin, neurofilament triplet proteins, and myelin basic protein. Protein kinase-mediated phosphorylation of cytoskeletal proteins plays a critical role in regulating the growth and maintenance of the axon. We hypothesize that, in OPIDN, hyperphosphorylation of cytoskeletal proteins and axonal swelling are causally linked. Hyperphosphorylation of cytoskeletal proteins decreases their transport rate down the axon relative to their rate of entry into the axon, thus leading to their accumulation. Consistent with this hypothesis is our finding of the anomalous accumulation of phosphorylated neurofilament aggregates in the central and peripheral axons of hens treated with TOCP. Title: The effects of tri-o-cresyl phosphate and metabolites on rat Sertoli cell function in primary culture Chapin RE, Phelps JL, Burka LT, Abou-Donia MB, Heindel JJ Ref: Toxicol Appl Pharmacol, 108:194, 1991 : PubMed ESTHER: Chapin_1991_Toxicol.Appl.Pharmacol_108_194 PubMedSearch: Chapin 1991 Toxicol.Appl.Pharmacol 108 194 PubMedID: 1902005 Inhibitor(s) related to this paper: CBDP Abstract A neurotoxic organophosphate, tri-o-cresyl phosphate (TOCP) is also a testicular toxicant. Histopathologic damage in the testis is first seen in Sertoli cells. TOCP and its activated metabolite saligenin cyclic-o-tolyl phosphate (SCOTP) were evaluated for effects on rat Sertoli cells in primary culture. SCOTP, but not TOCP, caused minor morphologic effects on the cells and increased levels of lactate in the spent medium with no change in pyruvate levels, synthesis of cellular or secreted proteins, or the cyclic AMP response to FSH stimulation. SCOTP was the metabolite of TOCP that produced the largest decrease in nonspecific esterase activity in Sertoli cells (up to 80%), when tested in the concentration range found in vivo. This decrease is consistent with previous in vivo evidence. These in vitro experiments replicate previously observed in vivo biochemical effects and suggest that SCOTP is the metabolite responsible for at least some of the biochemical effects seen in the testis after TOCP exposure. Title: Assessment of the delayed neurotoxicity of tributyl phosphate, tributoxyethyl phosphate, and dibutylphenyl phosphate Carrington CD, Lapadula DM, Othman M, Farr C, Nair RS, Johannsen F, Abou-Donia MB Ref: Toxicol Ind Health, 6:415, 1990 : PubMed ESTHER: Carrington_1990_Toxicol.Ind.Health_6_415 PubMedSearch: Carrington 1990 Toxicol.Ind.Health 6 415 PubMedID: 2237927 Abstract Three industrial organophosphorus compounds were tested for their ability to cause organophosphorus compound-induced delayed neurotoxicity (OPIDN) in the adult hen. The compounds tested were tributyl phosphate (TBP), tributoxyethyl phosphate (TBEP), and dibutylphenyl phosphate (DBPP). The acute oral LD50 of TBP and DBPP were estimated to be 1,863 and 1,500 mg/kg, respectively, and the dose equal to the LD50 was used as a test dose. The acute oral LD50 of TBEP was greater than 5,000 mg/kg and 5,000 mg/kg was used as a test dose. An oral dose of 750 mg tri-o-cresyl phosphate (TOCP) was used as a positive control. For the acute delayed neurotoxicity test, hens were given two test doses of the test materials 21 days apart and killed 21 days after the second dose. None of the hens given TBP, TBEP, or DBPP exhibited nerve damage or clinical signs which distinguished them from untreated control animals. A single dose of TOCP resulted in paralysis and a histopathological profile typical of a distal neuropathy. For the assay of the inhibition of esterases, hens were killed 24 hours after a single dose equal to the greater of either the LD50 or 5000 mg/kg. TOCP administration resulted in over 90% inhibition of brain neurotoxic esterase (NTE), but none of the other three compounds inhibited NTE to an extent (greater than 70%) which would be expected to result in OPIDN. Administration of TOCP, TBEP, or DBPP resulted in approximately a 70% decrease in plasma butyrylcholinesterase (BCHE) activity. TBP caused a 2-3 fold increase in BCHE activity. TBEP administration resulted in about 45% inhibition of acetycholinesterase (AChE) in brain. These results indicate that TBP, TBEP, and DBPP are all unlikely to cause OPIDN with any single sublethal dose. Title: Absence of delayed neurotoxicity and increased plasma butyrylcholinesterase activity in triallate-treated hens Lapadula DM, Johannsen F, Abou-Donia MB Ref: Fundamental & Applied Toxicology, 14:191, 1990 : PubMed ESTHER: Lapadula_1990_Fundam.Appl.Toxicol_14_191 PubMedSearch: Lapadula 1990 Fundam.Appl.Toxicol 14 191 PubMedID: 2155148 Inhibitor(s) related to this paper: Triallate Abstract Triallate (S-2,3,3-trichloroallyl diisopropylthiocarbamate) was tested for the potential to produce delayed neurotoxicity. Hens were given single oral doses ranging from 312.5 to 2500 mg/kg of triallate, 750 mg/kg tri-o-cresyl phosphate (TOCP), or empty gelatin capsules on Days 1 and 21 and were killed on Day 42. In a second experiment, animals were administered daily oral doses of 25-300 mg/kg triallate or 10 mg/kg TOCP for 90 days. In a third experiment, animals were given single oral doses of 2500 mg/kg triallate, 750 mg/kg TOCP, or empty gelatin capsules and killed after 24 hr. Delayed neurotoxicity was observed only in TOCP-treated animals. Animals given daily doses of 300 mg/kg triallate became moribund after 30 days; however, histological examination revealed no lesions characteristic of organophosphorus-induced delayed neurotoxicity. Neurotoxic esterase was not significantly altered in triallate-treated animals while it was 95% inhibited in TOCP-treated animals. Plasma butyrylcholinesterase increased significantly 24 hr after treatment with triallate in a dose-dependent manner. In summary, triallate, a thiocarbamate, did not produce neurotoxicity which has been previously reported for some dithiocarbamates. Title: Brain acetylcholinesterase, acid phosphatase, and 2',3'-cyclic nucleotide-3'-phosphohydrolase and plasma butyrylcholinesterase activities in hens treated with a single dermal neurotoxic dose of S,S,S-tri-n-butyl phosphorotrithioate Abou-Donia MB, Abdo KM, Timmons PR, Proctor JE Ref: Toxicol Appl Pharmacol, 82:461, 1986 : PubMed ESTHER: Abou-Donia_1986_Toxicol.Appl.Pharmacol_82_461 PubMedSearch: Abou-Donia 1986 Toxicol.Appl.Pharmacol 82 461 PubMedID: 3952729 Abstract The changes in brain acetylcholinesterase (AChE), acid phosphatase (APase), and 2',3'-cyclic nucleotide-3'-phosphohydrolase (CNP), and plasma butyrylcholinesterase (BuChE) activities were investigated in hens treated with a single, dermal dose (100-1000 mg/kg) of S,S,S-tri-n-butyl phosphorotrithioate (DEF). Three control groups consisted of hens left untreated, given a single, dermal dose of 500 mg/kg tri-o-cresyl phosphate (TOCP, positive control for organophophorous compound-induced delayed neurotoxicity), or 10 mg/kg O,O-diethyl O-4-nitrophenyl phosphorothioate (parathion, negative control). Brain AChE activity, determined 28 days after application, was significantly inhibited in hens given 500-1,000 mg/kg DEF and in TOCP- and parathion-treated hens. In contrast, brain APase and CNP activities were significantly higher in all treatments as compared with those of the untreated hens. Parathion, however, caused the least increase in these enzymatic activities as compared to DEF or TOCP. A single, dermal dose of DEF or TOCP also caused an initial decrease in plasma BuChE activity with maximum depression of enzymatic activity observed 1 to 7 days after administration. This decrease was dose dependent and the enzymatic activity showed partial recovery with time. Hens treated with single, dermal doses of DEF, ranging from 250 to 1000 mg/kg, developed ataxia which progressed to paralysis in some hens. Histopathologic examination revealed axon and myelin degeneration of the spinal cord and peripheral nerves of some hens. The severity and frequency of the neuropathologic lesions were dose dependent. Neurologic dysfunctions and neuropathologic lesions seen in DEF-treated hens were similar to those exhibited in TOCP-treated hens. While parathion produced acute cholinergic effects, it did not cause delayed neurotoxicity. The changes in brain and plasma enzymes are discussed in relation to their role in the pathogenesis of DEF-induced delayed neurotoxicity. Title: Target size of neurotoxic esterase and acetylcholinesterase as determined by radiation inactivation Carrington CD, Fluke DJ, Abou-Donia MB Ref: Biochemical Journal, 231:789, 1985 : PubMed ESTHER: Carrington_1985_Biochem.J_231_789 PubMedSearch: Carrington 1985 Biochem.J 231 789 PubMedID: 4074337 Abstract The target size of neurotoxic esterase (NTE), the putative target site for the initiation of organophosphorus-compound-induced delayed neurotoxicity, and acetylcholinesterase (AChE) from hen brain were examined by determining the rate at which the activities of the esterases were destroyed by ionizing irradiation. Samples of hen brain were prepared by slowly drying a microsomal preparation under vacuum. The dried samples were then irradiated with electrons from a 1 MeV Van de Graaff generator. The doses ranged from 0 to 28 Mrad. The radiation doses were calibrated by the rate of inactivation of T1-bacteriophage plaque induction. Following the irradiation procedure, the samples were resuspended in buffer and enzymic activity was measured. The target size of NTE from hen brain was determined to be about 105 kDa, whereas hen brain AChE was found to have a target size of about 53 kDa. The target size of NTE was found to be similar in experiments with rat brain and cat brain. In addition, commercial preparations of electric-eel electric-organ AChE and horse serum butyrylcholinesterase were found to have target sizes that were identical with each other, and also were very similar to that of AChE from hen brain. Title: Characterization of delayed neurotoxicity in the mouse following chronic oral administration of tri-o-cresyl phosphate Lapadula DM, Patton SE, Campbell GA, Abou-Donia MB Ref: Toxicol Appl Pharmacol, 79:83, 1985 : PubMed ESTHER: Lapadula_1985_Toxicol.Appl.Pharmacol_79_83 PubMedSearch: Lapadula 1985 Toxicol.Appl.Pharmacol 79 83 PubMedID: 4049409 Inhibitor(s) related to this paper: Tri-o-cresylphosphate Abstract The sensitivity of the mouse to organophosphorus-induced delayed neurotoxicity (OPIDN) has been investigated. One group of five mice received two single 1000-mg/kg po doses of tri-o-cresyl phosphate (TOCP) at a 21-day interval (on Days 1 and 21 of the study); a second group of five mice was given 225 mg/kg of TOCP daily for 270 days. A third group of five animals served as an untreated control. All animals were killed 270 days after the start of the experiment. Daily po dosing of 225 mg/kg TOCP caused a decrease in body weight gain, muscle wasting, weakness, and ataxia which progressed to severe hindlimb paralysis at termination. On the other hand, po administration of two single 1000-mg/kg doses of TOCP at a 21-day interval produced no observable adverse effects. Brain acetylcholinesterase (AChE) and neurotoxic esterase (NTE) activity were 35 and 10% of the control, respectively, in daily dosed animals while AChE and NTE in mice receiving two single 1000-mg/kg doses of TOCP were not significantly altered from the control group. Plasma butyrylcholinesterase activity was 12% of the control group in daily dosed animals. Hepatic microsomal enzyme activities of aniline hydroxylase and p-chloro-N-methylaniline demethylase and NADPH-cytochrome P-450 content in daily dosed animals were increased (141 to 161% of the control group) when compared to controls and mice receiving two single 1000-mg/kg doses of TOCP; the latter being not significantly different from each other. Degeneration of the axon and myelin of the spinal cord and sciatic fascicle were observed and were consistent with OPIDN. This study demonstrates that chronic dosing of TOCP produces OPIDN and induces hepatic microsomal enzyme activity in mice. It is concluded that while the mouse is susceptible to OPIDN, it is a less sensitive and a less appropriate test animal for studying this effect when compared to the adult hen. Title: The significance of inhibition of nonspecific esterases in the development of organophosphorus-induced delayed neurotoxicity Abou-Donia MB, Lapadula DM, Carrington CD, Nomeir AA Ref: In: Cholinesterases, fundamental and applied aspects : proceedings of the Second International Meeting on Cholinesterases, (Brzin M, Barnard EA, Sket D, Eds) De Gruyter:447, 1984 : PubMed ESTHER: Abou-Donia_1984_2nd.ChE.Meeting.Bled__447 PubMedSearch: Abou-Donia 1984 2nd.ChE.Meeting.Bled 447 Title: Modulation of avian muscarinic cholinergic high affinity binding sites by a neurotoxic organophosphate Ali SF, Abou-Donia MB, Bondy SC Ref: Neurochem Pathol, 2:267, 1984 : PubMed ESTHER: Ali_1984_Neurochem.Pathol_2_267 PubMedSearch: Ali 1984 Neurochem.Pathol 2 267 PubMedID: 6537470 Abstract A systematic survey of a series of high affinity binding sites in the forebrain of hens treated with a neurotoxic organophosphate has been carried out. Fourteen month old laying hens were treated with 750 mg/kg body weight triorthocresyl phosphate (TOCP) orally in gelatin capsules. Control birds received empty capsules. After 21 d, hens were killed and forebrain membrane fractions prepared for binding studies using the nitrocellulose filtration method. Incubations were carried out in the presence of low concentrations of pharmacological agents selective for certain classes of receptor sites. Nonspecific binding was characterized by simultaneous incubations in the presence of excess competing unlabeled ligands. Binding criteria that were satisfied in a prior study included specificity, saturability, and attainment of equilibrium during incubation. No significant change was found in treated hens assayed for dopaminergic, GABA, glycinergic, beta-adrenergic, and benzodiazepine receptors. However, a 30% reduction in binding of 3H-quinuclidinyl benzilate was apparent in TOCP-treated hens. These data implied a selective reduction of muscarinic receptors, suggesting a down-regulation in response to cholinergic hyperactivity. This dose of TOCP also caused paralysis and ataxia in all treated hens 21 d after exposure to the toxicant. These data demonstrate that a selective lesion in cholinergic neurotransmitter circuitry can be caused by a single administration of TOCP. Title: Heinz body production and hematological changes in the hen after administration of a single oral dose of n-butyl mercaptan and n-butyl disulfide Abdo KM, Timmons PR, Graham DG, Abou-Donia MB Ref: Fundamental & Applied Toxicology, 3:69, 1983 : PubMed ESTHER: Abdo_1983_Fundam.Appl.Toxicol_3_69 PubMedSearch: Abdo 1983 Fundam.Appl.Toxicol 3 69 PubMedID: 6873530 Abstract n-Butyl mercaptan (nBM) is a breakdown product of S,S,S,-tri-n-butyl phosphorotrithioate (DEF) and S,S,S-tri-n-butyl phosphorotrithioite (merphos) in hens and in the environment. n-Butyl disulfide (nBD) is an oxidation product of nBM. A single 500 mg/kg dose of nBM and nBD was administered in gelatin capsules to groups of five 12-month old laying hens. A third group (five hens) was given gelatin capsules. One day after administration, the hens exhibited weakness which progressed to unsteadiness and inability to stand by the third day. These signs were accompanied by a pale comb 18--24 hr after dosing, which changed to dark color at 48 hr. Treated hens improved with time. Heinz bodies and extensive erythrocyte deformation and lysis were observed in blood smears taken from hens 24 and 48 hr after treatment. Hemoglobin concentration, packed cell volume, erythrocytes, and glucose-6-phosphate dehydrogenase activity were significantly lower than controls, while methemoglobin was significantly higher. As the clinical condition of these hens improved, these hematologic changes disappeared. nBM caused an initial increase in plasma butyrylcholinesterase activity which was dose-dependent and returned to normal by the end of the 28-day experiment. Also, brain acetylcholinesterase activity was not different from that of the control at termination. Title: Effects of a dermal dose of S,S,S,-tri-n-butyl phosphorotrithioate on brain acetylcholinesterase, acid phosphatase, and 2',3'-cyclic nucleotide-3' phosphohydrolase and plasma butyrylcholinesterase in hens Abdo KM, Timmons PR, Abou-Donia MB Ref: Developments in Toxicology & Environmental Sciences, 11:499, 1983 : PubMed ESTHER: Abdo_1983_Dev.Toxicol.Environ.Sci_11_499 PubMedSearch: Abdo 1983 Dev.Toxicol.Environ.Sci 11 499 PubMedID: 6329633 Title: Effect of subchronic dermal application of O-ethyl O-4-nitrophenyl phenylphosphonothioate on producing delayed neurotoxicity in hens Abou-Donia MB, Graham DG, Makkawy HA, Abdo KM Ref: Neurotoxicology, 4:247, 1983 : PubMed ESTHER: Abou-Donia_1983_Neurotoxicol_4_247 PubMedSearch: Abou-Donia 1983 Neurotoxicol 4 247 PubMedID: 6685263 Inhibitor(s) related to this paper: EPN, Isofenphos Abstract Daily dermal administration for 90 days of 0.01 to 10 mg/kg of O-ethyl O-4-nitrophenyl phenylphosphonothioate (EPN) technical grade (85%) in acetone (0.1 ml) on the unprotected back of the neck produced delayed neurotoxicity. Hens given 2.5 to 10 mg/kg daily doses also received daily doses of atropine sulfate for 5 or 6 days to protect against cholinergic acute toxicity. Severity of the clinical condition depended on the concentration of the daily dermal dose of EPN; i.e., while hens given small doses showed only ataxia, those treated with large doses progressed to paralysis and died. The most consistent histopathologic alteration was the degeneration of axons and myelin in the spinal cord which was identical to that found in positive control hens that received daily dermal doses of 5 or 10 mg/kg tri-o-cresyl phosphate (TOCP). Some of the hens treated daily with the smallest tested dose of EPN (0.001 mg/kg) which did not show clinical signs of delayed neurotoxicity showed equivocal histological changes in the spinal cord. EPN and TOCP treatments had a more profound effect on the activity of plasma butyrylcholinesterase than that of brain acetylcholinesterase (AchE). by contrast O,O,-diethyl O-4-nitrophenyl phosphorothioate (parathion) was more inhibitory to brain AChE. Negative control hens that were treated with 90 daily dermal doses of 1 mg/kg of parathion initially showed leg weakness followed by recovery. A group of hens that received the same volume of acetone (0.1 ml) daily remained normal. Title: Delayed neurotoxicity of leptophos and related compounds: differential effects of subchronic oral administration of pure, technical grade and degradation products on the hen Abou-Donia MB, Graham DG, Ashry MA, Timmons PR Ref: Toxicol Appl Pharmacol, 53:150, 1980 : PubMed ESTHER: Abou-Donia_1980_Toxicol.Appl.Pharmacol_53_150 PubMedSearch: Abou-Donia 1980 Toxicol.Appl.Pharmacol 53 150 PubMedID: 6155716 Inhibitor(s) related to this paper: Leptophos Title: Late acute, delayed neurotoxic and cholinergic effects of S,S,S- tributyl phosphorotrithioite (Merphos) in hens Abou-Donia MB, Graham DG, Timmons PR, Reichert BL Ref: Toxicol Appl Pharmacol, 53:439, 1980 : PubMed ESTHER: Abou-Donia_1980_Toxicol.Appl.Pharmacol_53_439 PubMedSearch: Abou-Donia 1980 Toxicol.Appl.Pharmacol 53 439 PubMedID: 7385244 Title: High-pressure liquid chromatography of neurotoxic phenylphosphonothioate esters and related compounds Lasker JM, Sivarajah K, Eling TE, Abou-Donia MB Ref: Analytical Biochemistry, 109:369, 1980 : PubMed ESTHER: Lasker_1980_Anal.Biochem_109_369 PubMedSearch: Lasker 1980 Anal.Biochem 109 369 PubMedID: 6164313 Title: Delayed neurotoxicity of phenylphosphonothioate esters Abou-Donia MB Ref: Science, 205:713, 1979 : PubMed ESTHER: Abou-Donia_1979_Science_205_713 PubMedSearch: Abou-Donia 1979 Science 205 713 PubMedID: 462181 Abstract Administration of a single oral dose of five phenylphosphonothioate esters produced delayed neurotoxicity in hens; their potency was, in descending order, cyanofenphos, EPN, desbromoleptophos, leptophos, and EPBP (Seven). Histological examination showed that in some hens there was marked axonal and myelin degeneration in the spinal cord and peripheral nerves. The results suggest that delayed neurotoxicity may be a general feature of phenylphosphonothioate insecticides. Title: Kinetics of inhibition of acetylcholinesterase by spin labeled acetylcholine analogs Abou-Donia MB, Rosen GM Ref: Biophysical Chemistry, 6:15, 1976 : PubMed ESTHER: Abou-Donia_1976_Biophys.Chem_6_15 PubMedSearch: Abou-Donia 1976 Biophys.Chem 6 15 PubMedID: 1035114 Abstract A series of spin labeled acetycholine analogs, in which the number of methylene groups between the quaternary nitrogen and the alcohol oxygen ranged between 1-5, have been examined as inhibitors of electric eel acetylcholinesterase. Evidence is presented suggesting that inhibition of acetylocholinesterase by the spin labeled ACH analogs is due to the high affinity of these compounds for the enzyme, inhibition is competitive and reversible. It has been shown that complex formation is of major importance in the reaction between spin labeled ACH analogs and acetylcholinesterase. The acetylation step has been shown to occur by demonstrating that the leaving group is released as the reaction proceeds. Complex formation has been demonstrated by means of kinetic criteria. Kinetic parameter have been measured for the five compounds, and correlations with alkaline hydrolysis are disussed. Title: Fish brain cholinesterase: its inhibition by carbamates and automatic assay Abou-Donia MB, Menzel DB Ref: Comparative Biochemistry & Physiology, 21:99, 1967 : PubMed ESTHER: Abou-Donia_1967_Comp.Biochem.Physiol_21_99 PubMedSearch: Abou-Donia 1967 Comp.Biochem.Physiol 21 99 PubMedID: 6033845 | |||||||
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