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Li W, Ehrich M Ref: Chemico-Biological Interactions, :110573, 2023 : PubMed ESTHER: Li_2023_Chem.Biol.Interact__110573 PubMedSearch: Li 2023 Chem.Biol.Interact 110573 PubMedID: 37263558 Abstract Chlorpyrifos (CPF; 0,0-diethyl 0-(3,5,6-trichloro-2-pyridinyl)-phosphorothioate), a cholinesterase inhibitor, compromised the integrity of the blood-brain barrier (BBB) when used at low concentrations during our previous experiments in vitro. To determine if BBB leakage would also occur in vivo, we used FITC-dextrans to evaluate BBB permeability in CPF-dosed mice. Results indicated BBB leakages that were evident at 2 h after treatment with 70 mg/kg CPF ip. Since vascular endothelial growth factor (VEGF), a potent vasopermeability factor, is a signaling protein that promotes the growth of new blood vessels, we investigated the possible involvement of VEGF in BBB disruption by CPF. We found that VEGF serum concentration was significantly increased at 24 h after CPF exposure. To further explore VEGF involving BBB disruption by CPF treatment, the receptor antagonist for VEGF (sFlt-1) was used for pretreatment before CPF exposure. After sFlt-1 pretreatment, gene expressions of the tight junction (TJ) proteins claudin5 and occludin were significantly downregulated at 1, 2, and 3 h, but returned to control levels at 24 h after CPF treatment. These results suggest that VEGF is involved in BBB disruption by CPF through BBB-TJs regulation. Title: Effects of chlorpyrifos on transient receptor potential channels Li W, Ehrich M Ref: Toxicol Lett, 358:100, 2022 : PubMed ESTHER: Li_2022_Toxicol.Lett_358_100 PubMedSearch: Li 2022 Toxicol.Lett 358 100 PubMedID: 35114315 Inhibitor(s) related to this paper: Chlorpyrifos Abstract The well-known toxicity of chlorpyrifos (CPF) occurs via inhibition of cholinesterase (ChE), but in recent years the detrimental effects of low-dose CPF exposure have been attributed to an unknown non-cholinergic mechanism of action. We previously showed that CPF can alter gene expression of transient receptor potential canonical (TRPC) channels in vitro. In this study, we analyzed the gene expression of TRPCs at various time points after CPF treatment in vivo. The results showed that TRPC1 mRNA expression in mouse brain was significantly reduced 2-8 h after CPF treatment, but the TRPC4 mRNA expression was not significantly changed. To investigate the possible involvement of Transforming Growth Factor-beta1 (TGF-beta1) in contributing to TRPCs gene alteration by CPF, we used TGF-beta receptor inhibitor (LY2109761) as a pretreatment prior to CPF treatment. The serum TGF-beta1 concentration was significantly increased 24 h after CPF treatment. After pretreatment with LY2109761, both TRPC1 and TRPC5 mRNAs were significantly downregulated 1 and 2 h after CPF treatment, but were significantly upregulated 3 and 24 h after CPF treatment. TRPC4 mRNA was also significantly downregulated at 1 h. These results suggest that interference with ion channels, a non-cholinergic mechanism of CPF, may contribute to the cellular neurotoxicity of CPF. Title: Effects of Polyhydroxyfullerenes on Organophosphate-Induced Toxicity in Mice Ehrich M, Hinckley J, Werre SR, Zhou Z Ref: Toxicology, :152586, 2020 : PubMed ESTHER: Ehrich_2020_Toxicology__152586 PubMedSearch: Ehrich 2020 Toxicology 152586 PubMedID: 32949634 Abstract Two polyhydroxyfullerenes, which decrease organophosphate (OP)-induced acetylcholinesterase (AChE) inhibition in vitro, were administered by the intraperitoneal (ip) route or applied topically at doses of 0.9-24 mg/kg to protect adult male mice from enzyme-inhibiting and behavioral effects indicative of OP toxicity resulting from exposure to 1.7 - 2 mg/kg diphosphorofluoridate (DFP) ip or 2.3 - 2.7 mg paraoxon topical. Dosing paradigms included OP-fullerene simultaneous administration by the ip route, and 20 min post-OP polyhydroxyfullerene treatment topically. Benefits of OP sequestration by the polyhydroxyfullerene were noted and were dependent on the OP compound as well as timing and route of the polyhydroxyfullerene treatment. Title: Studies Exploring the Interaction of the Organophosphorus Compound Paraoxon with Fullerenes Magnin G, Bissel P, Council-Troche RM, Zhou Z, Ehrich M Ref: ACS Omega, 4:18663, 2019 : PubMed ESTHER: Magnin_2019_ACS.Omega_4_18663 PubMedSearch: Magnin 2019 ACS.Omega 4 18663 PubMedID: 31737826 Abstract In vitro experiments previously published demonstrated the ability of fullerenes to decrease the capability of organophosphorus (OP) compounds to inhibit acetylcholinesterase. Experiments described herein demonstrate molecular level affinity interactions between fullerenes and the OP test compound paraoxon with NMR spectroscopy. The calculated binding constant of 19 M(-1) indicates that this binding was not covalent. Title: Mechanisms for consideration for intervention in the development of organophosphorus-induced delayed neuropathy Emerick GL, Deoliveira GH, Dos Santos AC, Ehrich M Ref: Chemico-Biological Interactions, 199:177, 2012 : PubMed ESTHER: Emerick_2012_Chem.Biol.Interact_199_177 PubMedSearch: Emerick 2012 Chem.Biol.Interact 199 177 PubMedID: 22819951 Abstract Organophosphorus-induced delayed neuropathy (OPIDN) is a neurodegenerative disorder characterised by ataxia progressing to paralysis with concomitant central and peripheral distal axonopathy. Symptoms of OPIDN in people include tingling of the hands and feet. This tingling is followed by sensory loss, progressive muscle weakness and flaccidity of the distal skeletal muscles of the lower and upper extremities and ataxia, which appear about 8-14 days after exposure. Some organophosphorus compounds (OPs) that are still used in worldwide agriculture have potential to induce OPIDN, including methamidophos, trichlorfon, dichlorvos and chorpyrifos. This review summarizes experimental attempts to prevent and/or treat OPIDN and the different mechanisms involved in each approach. The initial mechanism associated with development of OPIDN is phosphorylation and inhibition of neuropathy target esterase (NTE). The phosphorylated enzyme undergoes a second reaction known as "aging" that results in the loss of one of the "R" groups bound to the phosphorus of the OP. A second mechanism involved in OPIDN is an imbalance in calcium homeostasis. This can lead to the activation of calcium-activated neutral protease and increases in calcium/calmodulin-dependent protein kinases. These events contribute to aberrant phosphorylation of cytoskeletal proteins and protein digestion in the terminal axon that can proceed similarly to Wallerian-type degeneration. Several experimental studies demonstrated alleviation of the signs and symptoms of OPIDN by restoring calcium balance. Other studies have used preadministration of NTE inhibitors, such as carbamates, thiocarbamates, sulfonyl fluorides and phosphinate to prevent OPIDN. Progress is being made, but there is yet no single specific treatment available for use in clinical practice to prevent or alleviate the severe effects of OPIDN. Title: Comparative in vitro study of the inhibition of human and hen esterases by methamidophos enantiomers Emerick GL, Deoliveira GH, Oliveira RV, Ehrich M Ref: Toxicology, 292:145, 2012 : PubMed ESTHER: Emerick_2012_Toxicology_292_145 PubMedSearch: Emerick 2012 Toxicology 292 145 PubMedID: 22198100 Abstract The current Organisation for Economic Co-operation and Development (OECD) guidelines for evaluating organophosphorus-induced delayed neuropathy (OPIDN) require the observation of dosed animals over several days and the sacrifice of 48 hens. Adhering to these protocols in tests with enantiomers is difficult because large quantities of the compound are needed and many animals must be utilized. Thus, developing an in vitro screening protocol to evaluate chiral organophosphorus pesticides (OPs) that can induce delayed neuropathy is important. This work aimed to evaluate, in blood and brain samples from hens, human blood, and human cell culture samples, the potential of the enantiomeric forms of methamidophos to induce acetylcholinesterase (AChE) inhibition and/or delayed neurotoxicity. Calpain activation was also evaluated in the hen brain and SH-SY5Y human neuroblastoma cells. The ratio between the inhibition of neuropathy target esterase (NTE) and AChE activities by the methamidophos enantiomers was evaluated as a possible indicator of the enantiomers' abilities to induce OPIDN. The (-)-methamidophos exhibited an IC(50) value approximately 6 times greater than that of the (+)-methamidophos for the lymphocyte NTE (LNTE) of hens, and (+)-methamidophos exhibited an IC(50) value approximately 7 times larger than that of the (-)-methamidophos for the hen brain AChE. The IC(50) values were 7 times higher for the human erythrocyte AChE and 5 times higher for AChE in the SH-SY5Y human neuroblastoma cells. Considering the esterases inhibition and calpain results, (+)-methamidophos would be expected to have a greater ability to induce OPIDN than the (-)-methamidophos in humans and in hens. Title: Biochemical, histopathological and clinical evaluation of delayed effects caused by methamidophos isoforms and TOCP in hens: ameliorative effects using control of calcium homeostasis Emerick GL, Ehrich M, Jortner BS, Oliveira RV, Deoliveira GH Ref: Toxicology, 302:88, 2012 : PubMed ESTHER: Emerick_2012_Toxicology_302_88 PubMedSearch: Emerick 2012 Toxicology 302 88 PubMedID: 22974967 Abstract This work evaluated the potential of the isoforms of methamidophos to cause organophosphorus-induced delayed neuropathy (OPIDN) in hens. In addition to inhibition of neuropathy target esterase (NTE) and acetylcholinesterase (AChE), calpain activation, spinal cord lesions and clinical signs were assessed. The isoforms (+)-, (+/-)- and (-)-methamidophos were administered at 50mg/kg orally; tri-ortho-cresyl phosphate (TOCP) was administered (500mg/kg, po) as positive control for delayed neuropathy. The TOCP hens showed greater than 80% and approximately 20% inhibition of NTE and AChE in hen brain, respectively. Among the isoforms of methamidophos, only the (+)-methamidophos was capable of inhibiting NTE activity (approximately 60%) with statistically significant difference compared to the control group. Calpain activity in brain increased by 40% in TOCP hens compared to the control group when measured 24h after dosing and remained high (18% over control) 21 days after dosing. Hens that received (+)-methamidophos had calpain activity 12% greater than controls. The histopathological findings and clinical signs corroborated the biochemical results that indicated the potential of the (+)-methamidophos to be the isoform responsible for OPIDN induction. Protection against OPIDN was examined using a treatment of 2 doses of nimodipine (1mg/kg, i.m.) and one dose of calcium gluconate (5mg/kg, i.v.). The treatment decreased the effect of OPIDN-inducing TOCP and (+)-methamidophos on calpain activity, spinal cord lesions and clinical signs. Title: Organophosphorus compound effects on neurotrophin receptors and intracellular signaling Pomeroy-Black M, Ehrich M Ref: Toxicol In Vitro, 26:759, 2012 : PubMed ESTHER: Pomeroy-Black_2012_Toxicol.In.Vitro_26_759 PubMedSearch: Pomeroy-Black 2012 Toxicol.In.Vitro 26 759 PubMedID: 22449548 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Neurite outgrowth of SH-SY5Y neuroblastoma cells following the addition of spinal cord extracts from chickens exposed to a neuropathic organophosphorus (OP) compound suggests the presence of a growth factor during OP neuropathy. However, exposure of SH-SY5Y cells directly to neuropathic OP compounds results in apoptosis and/or decreased neurite outgrowth. These cellular effects may follow OP-induced interference with neurotrophin-receptor binding and/or intracellular signaling resulting from receptor binding. We hypothesized that sub-lethal concentrations of a neuropathic OP compound interferes with neurotrophin-receptor binding as well as specific intracellular signaling pathways in neuroblastoma cells which would not occur with a non-neuropathic OP compound. SH-SY5Y cells were exposed to a neuropathic OP compound (PSP; 0.01, 0.1, 1.0muM), a neuropathic OP compound with nerve growth factor (1.0muM PSP+1ng/ml NGF), a non-neuropathic OP compound (paraoxon; 100muM), and medium only for 4, 8, 24, and 48h. Western blots indicate that cells exposed to a low dose of PSP or the high dose of PSP+NGF contained the phosphorylated form of a common neurotrophin receptor (pp75) that was four times greater than that of the phosphorylated form of the high-affinity NGF receptor (pTrkA) suggesting that p75 activation may contribute to early cell death after exposure to OP compounds. Furthermore, events in signaling pathways after exposure to PSP differed from those after exposure to paraoxon, with activation of the MEK1/2 protein increasing significantly only after exposure to paraoxon. Both types of OP compounds, however, caused significant activation of Akt in the PI-3K cell-survival pathway. These results suggest that exposure to a non-neuropathic OP compound causes increased activity of the MAPK pathway whereas exposure to neuropathic OP compounds prevented upregulation of the pathway. Since this pathway is integral to neurite outgrowth and cell survival, this study has revealed molecular mechanisms implicated in neuronal response after exposure to neuropathic OP compounds. Title: Fullerene antioxidants decrease organophosphate-induced acetylcholinesterase inhibition in vitro Ehrich M, Van Tassell R, Li Y, Zhou Z, Kepley CL Ref: Toxicol In Vitro, 25:301, 2011 : PubMed ESTHER: Ehrich_2011_Toxicol.In.Vitro_25_301 PubMedSearch: Ehrich 2011 Toxicol.In.Vitro 25 301 PubMedID: 20888407 Abstract Although organophosphate (OP)-induced acetylcholinesterase (AChE) inhibition is the critical mechanism causing toxicities that follow exposure, other biochemical events, including oxidative stress, have been reported to contribute to OP toxicity. Fullerenes are carbon spheres with antioxidant activity. Thus, we hypothesized that fullerenes could counteract the effects of OP compounds and tested this hypothesis using two in vitro test systems, hen brain and human neuroblastoma SH-SY5Y cells. Cells were incubated with eight different derivatized fullerene compounds before challenge with paraoxon (0=control, 5x10(-8), 10(-7), 2x10(-7) or 5x10(-7) M) or diisopropylphosphorofluoridate (DFP, 0=control, 5x10(-6), 10(-5), 2x10(-5), and 5x10(-5) M) and measurement of AChE activities. Activities of brain and SH-SY5Y AChE with OP compounds alone ranged from 55-83% lower than non-treated controls after paraoxon and from 60-92% lower than non-treated controls after DFP. Most incubations containing 1 and 10 muM fullerene derivatives brought AChE activity closer to untreated controls, with improvements in AChE activity often >20%. Using dissipation of superoxide anion radicals as an indicator (xanthine oxidation as a positive control), all fullerene derivatives demonstrated significant antioxidant capability in neuroblastoma cells at 1 muM concentrations. No fullerene derivative at 1 muM significantly affected neuroblastoma cell viability, when determined using either Alamar Blue dye retention or a luminescent assay for ATP production. These studies suggest that derivatized fullerene nanomaterials have potential capability to ameliorate OP-induced AChE inhibition resulting in toxicities. Title: Comparison of two blood-brain barrier in vitro systems: cytotoxicity and transfer assessments of malathion/oxon and lead acetate Balbuena P, Li W, Magnin-Bissel G, Meldrum JB, Ehrich M Ref: Toxicol Sci, 114:260, 2010 : PubMed ESTHER: Balbuena_2010_Toxicol.Sci_114_260 PubMedSearch: Balbuena 2010 Toxicol.Sci 114 260 PubMedID: 20064834 Abstract Toxicity and integrity disruption in response to transport through the blood-brain barrier (BBB) of the organophosphates malathion and malaoxon and heavy metal lead acetate were assessed in two in vitro barrier systems. One system was constructed using bovine brain microvascular endothelial cells (BMEC), while the other system was constructed with rat brain microvascular endothelial cells (RBE4); both were cocultured with rat astrocytes. We hypothesized that these models would respond differently to neurotoxic compounds. Concentrations of malathion, malaoxon, and lead acetate between 0.01 microM and 1 mM were assessed for their capacity to cause cytotoxicity to the astrocytes and endothelial cells utilized to construct the BBB systems, with the least cytotoxic concentrations chosen for transfer assessments of neurotoxicants through the barrier systems. Concentrations of malathion at 10 microM, malaoxon at 1 microM, and lead acetate at 1 and 10 microM were selected. Lead concentrations were measured in media of the abluminal and luminal sides of both systems using graphite furnace atomic absorption at the beginning of the treatment (T0) and 14 h later (T14). Passage of organophosphate compounds was determined utilizing inhibition of acetylcholinesterase enzyme in a neuroblastoma cell line (SH-SY5Y) localized below the barrier system. Transendothelial electrical resistance was assessed as a measurement of integrity of the barrier systems, with baseline values higher with the RBE4-astrocyte system than with the BMEC-astrocyte system. Metabolic capability, as measured by esterase activity, was higher in BMECs, which were more likely to retain lead than RBE4 cells. Results suggest that differences in endothelial cell source can affect the outcome of studies on toxicant transfer through in vitro BBB systems. Title: Distribution of SH-SY5Y human neuroblastoma cells in the cell cycle following exposure to organophosphorus compounds Carlson K, Ehrich M Ref: J Biochem Mol Toxicol, 22:187, 2008 : PubMed ESTHER: Carlson_2008_J.Biochem.Mol.Toxicol_22_187 PubMedSearch: Carlson 2008 J.Biochem.Mol.Toxicol 22 187 PubMedID: 18561334 Abstract The current study investigated the relationship of the cell cycle phase (as G(0)/G(1), S, and G(2)/M) and cytotoxicity (as sub-G(1) DNA) to determine whether alterations in cell replication were associated with organophosphate (OP) compound induced cytotoxicity. Results demonstrated that, overall, OP compound--induced cell cycle changes were variable and depended on the OP compound, exposure concentration, and temporal relationship to cytotoxicity. Noncytotoxic OP compound treatments substantially decreased the percentage of cells in S phase of the cell cycle when compared to controls. A corresponding increase was seen in the percent of cells in G(0)/G(1) phase of the cell cycle. In the precytotoxic interval of exposure, most cytotoxic OP compound treatments substantially decreased the percentage of cells in G(2)/M phase of the cell cycle. Corresponding increases were seen primarily in G(0)/G(1) phase cells. Effects on cells in S stage of the cell cycle varied with the OP compound. In the during cytotoxic interval of exposure, most cytotoxic OP compound treatments substantially increased the percentage of cells in S phase of the cell cycle. A corresponding decrease in the percent of cells in G(0)/G(1) stage of the cell cycle was observed. Furthermore, treatments either increased or decreased the percentage of cells in G(2)/M phase of the cell cycle when compared to controls, with decreases more likely with the most cytotoxic OP compound exposures. Overall, the in vitro data suggest that exposure to OP compounds can alter the cell cycle status of SH-SY5Y neuroblastoma cells depending on compound, concentration, and interval from initial exposure. Changes in cell cycle, however, did not differentiate between OP compounds that are known for their ability to acutely inhibit acetylcholinesterase versus those inducing type I and type II delayed neurotoxicity. Title: The effect of stress on the acute neurotoxicity of the organophosphate insecticide chlorpyrifos Hancock S, Ehrich M, Hinckley J, Pung T, Jortner BS Ref: Toxicol Appl Pharmacol, 219:136, 2007 : PubMed ESTHER: Hancock_2007_Toxicol.Appl.Pharmacol_219_136 PubMedSearch: Hancock 2007 Toxicol.Appl.Pharmacol 219 136 PubMedID: 17196233 Abstract A study was conducted to determine if multiple exposures to several stress paradigms might affect the anticholinesterase effect of subsequently administered organophosphate insecticide chlorpyrifos. Male Sprague-Dawley rats were subject to daily periods of restraint, swimming, a combination of the two, or neither of the two (controls) (n=8/group) for 5 days per week over a six-week period. The most profound stress, as measured by reduced body weight gain and elevated levels of plasma corticosterone, was swimming. On day 39 of the study, shortly after the daily stress episode, one half of the rats in each group was dosed with 60 mg/kg chlorpyrifos subcutaneously. This had no effect on subsequent levels of plasma corticosterone. There were no stress-related differences in the degree of chlorpyrifos-induced inhibition of brain acetylcholinesterase in animals sacrificed on day 43. Title: Examination of concurrent exposure to repeated stress and chlorpyrifos on cholinergic, glutamatergic, and monoamine neurotransmitter systems in rat forebrain regions Pung T, Klein B, Blodgett D, Jortner B, Ehrich M Ref: Int J Toxicol, 25:65, 2006 : PubMed ESTHER: Pung_2006_Int.J.Toxicol_25_65 PubMedSearch: Pung 2006 Int.J.Toxicol 25 65 PubMedID: 16510359 Abstract Repeated stress has been reported to cause reversible impairment in the central nervous system (CNS). It was proposed that alterations in glutamatergic, cholinergic, and monoamine neurotransmitter systems after exposure to stress are initial CNS events contributing to this impairment and that exacerbation could occur with concurrent exposure to cholinesterase inhibitors. Effects of concurrent exposure to repeated stress and chlorpyrifos on activities of acetylcholinesterase (AChE), carboxylesterase, and choline acetyltransferase (ChAT); concentrations of excitatory amino acids, monoamines, and their metabolites; and maximum binding densities (B(max)) and equilibrium dissociation rate constants (K(d)) of glutamatergic N-methyl-d-aspartate (NMDA) and total muscarinic cholinergic receptors were studied in the blood, hippocampus, cerebral cortex, or hypothalamus of adult Long-Evans rats. Stress treatments extended over 28 days included (1) control rats handled 5 days/week; (2) rats restrained 1 h/day for 5 days/week; (3) rats swum 30 min for 1 day/week; or (4) rats restrained 4 days/week and swum for 1 day/week. On day 24, each stress treatment group was randomly divided and injected either with corn oil or chlorpyrifos, 160 mg/kg subcutaneously (sc) (60% of the maximum tolerated dose), 4 h after restraint. Blood and brain tisssues were collected on day 28. Rats restrained and swum had a statistical trend toward increasing concentrations of glutamate in the hippocampus when compared to rats only swum (p = .064). Chlorpyrifos administration decreased restraint-induced elevated aspartate in the hippocampus, and decreased B(max) of total muscarinic receptors in the cerebral cortex. In addition, chlorpyrifos decreased B(max) and K(d) of total muscarinic receptors in the cerebral cortex of swum rats. Results demonstrated that chlorpyrifos inhibited AChE activity in blood, cerebral cortex, and hippocampus, but stress did not affect AChE activity. Carboxylesterase activity was inhibited by chlorpyrifos and by repeated restraint with swim. Swim stress decreased concentrations of norepinephrine in the hippocampus and hypothalamus, and increased concentrations of dopamine and its metabolite, DOPAC, in the hypothalamus. Both stress and chlorpyrifos altered serotonin concentrations, and the interactions of repeated stress and chlorpyrifos on serotonin approached significance in the hippocampus (p = .06) and hypothalamus (p = .08). Therefore, stress models were demonstrated to alter glutamatergic and monoamine responses, whereas chlorpyrifos alone had effects on cholinergic and monoamine systems in the rat CNS. However, the interactions between stress and chlorpyrifos significant at p < 0.05 were restricted to attenuation of elevated aspartate in the hippocampus of restrained with swim rats and decreased K(d) of acetylcholine receptors in the cerebral cortex of swum rats and restrained rats. Title: Effects of organophosphorus compounds on ATP production and mitochondrial integrity in cultured cells Massicotte C, Knight K, Van der Schyf CJ, Jortner BS, Ehrich M Ref: Neurotox Res, 7:203, 2005 : PubMed ESTHER: Massicotte_2005_Neurotox.Res_7_203 PubMedSearch: Massicotte 2005 Neurotox.Res 7 203 PubMedID: 15897155 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Recent studies in vivo and in vitro suggested that mitochondrial dysfunction follows exposure to organophosphorus (OP) esters. As mitochondrial ATP production is important for cellular integrity, ATP production in the presence of OP neurotoxicants was examined in a human neuronal cell line (SH-SY5Y neuroblastoma cells) and primary dorsal root ganglia (DRG) cells isolated from chick embryos and subsequently cultured to achieve maturation with axons. These cell culture systems were chosen to evaluate toxic effects on the mitochondrial respiratory chain associated with exposure to OP compounds that do and do not cause OP-induced delayed neuropathy (OPIDN), a disorder preceded by inhibition of neurotoxic esterase (NTE). Concentration- and time-response studies were done in neuroblastoma cells exposed to phenyl saligenin phosphate (PSP) and mipafox, both compounds that readily induce delayed neuropathy in hens, or paraoxon, which does not. Phenylmethylsulfonyl fluoride (PMSF) was included as a non-neuropathic inhibitor of NTE. Purified neuronal cultures from 9 day-old chick embryo DRG were treated for 12 h with 1 microM PSP, mipafox, or paraoxon. In situ evaluation of ATP production measured by bioluminescence assay demonstrated decreased ATP concentrations both in neuroblastoma cells and chick DRG neurons treated with PSP. Mipafox decreased ATP production in DRG but not in SH-SY5Y cells. This low energy state was present at several levels of the mitochondrial respiratory chain, including Complexes I, II, III, and IV, although Complex I was the most severely affected. Paraoxon and PMSF were not effective at all complexes, and, when effective, required higher concentrations than needed for PSP. Results suggest that mitochondria are an important early target for OP compounds, with exposure resulting in depletion of ATP production. The targeting of neuronal, rather than Schwann cell mitochondria in DRG following exposure to PSP and mipafox was verified by loss of the mitochondrial-specific dye, tetramethylrhodamine, in these cells. No such loss was seen in paraoxon exposed neurons isolated from DRG or in Schwann cells treated with any of the test compounds. Title: Chlorpyrifos alters functional integrity and structure of an in vitro BBB model: co-cultures of bovine endothelial cells and neonatal rat astrocytes Parran DK, Magnin G, Li W, Jortner BS, Ehrich M Ref: Neurotoxicology, 26:77, 2005 : PubMed ESTHER: Parran_2005_Neurotoxicol_26_77 PubMedSearch: Parran 2005 Neurotoxicol 26 77 PubMedID: 15527875 Abstract The blood-brain barrier (BBB) is a structural and functional interface between the circulatory system and the brain. Organophosphorous compounds such as chlorpyrifos (CPF) may cross the BBB and disrupt BBB integrity and function. To determine events that may contribute to CPF toxicity, we used an in vitro BBB model in which bovine microvascular endothelial cells (BMEC) and neonatal rat astrocytes were co-cultured. We hypothesized that CPF is metabolized by the BBB leading to an inhibition of esterase activity and a disruption of the BBB. The co-culturing of BMECs and astrocytes resulted in tight junction formation as determined by electron microscopy, electrical resistance and western blot analysis of two tight junction-associated proteins (ZO-1 and e-cadherin). We observed time dependent increases in ZO-1 and e-cadherin expression and electrical resistance during BBB formation, which were maximal after 9-13 days of co-culturing. The CPF concentration and production of its metabolites were monitored by HPLC following 24 h exposure to CPF on the luminal side of the BBB. We found that the BBB metabolized CPF, with the metabolite 2,3,6-trichloro-2-pyridinol being the major product. CPF and its metabolites were detected on the abluminal side of the BBB suggesting that CPF crossed this barrier. CPF was also detected intracellularly and on the membrane inserts. At tested concentrations (0.1-10 microM), CPF inhibited both carboxylesterase (CaE) and cholinesterase (ChE) activities in BMECs by 43-100%, while CPF-oxon totally inhibited CaE and ChE activity in concentrations as low as 0.1 microM. CPF also caused a concentration-dependent decrease in electrical resistance, with significant inhibition observed at 1 nM and complete loss at 1 microM. These data show that low concentrations of CPF and its metabolites are present within the BBB. CPF and its metabolites, especially CPF-oxon, contribute to the inhibition of CaE and ChE activity, as well as the alteration of BBB integrity and structure. Title: Neurologic and immunologic effects of exposure to corticosterone, chlorpyrifos, and multiple doses of tri-ortho-tolyl phosphate over a 28-day period in rats Ehrich M, Hancock S, Ward D, Holladay S, Pung T, Flory L, Hinckley J, Jortner BS Ref: J Toxicol Environ Health A, 67:431, 2004 : PubMed ESTHER: Ehrich_2004_J.Toxicol.Environ.Health.A_67_431 PubMedSearch: Ehrich 2004 J.Toxicol.Environ.Health.A 67 431 PubMedID: 14718179 Abstract An animal (rat) model of chronic stress (corticosterone in the drinking water) was used to study the interaction of stress and the organophosphorus (OP) neurotoxicants chlorpyrifos (60 mg/kg subcutaneously in a single dose) and tri-ortho-tolyl phosphate (TOTP, at 75, 150, or 300 mg/kg given 7 times orally in a 2-wk period). Adult male Long-Evans rats were provided with corticosterone in drinking water (400 microg/ml, w/v) for a total of 28 d, which led to significantly decreased weight and decreased cellularity of the thymus and spleen. Seven days after initiation of corticosterone treatment, half of the rats were given chlorpyrifos, and an additional 7 d later the 2-wk, 7-dose treatment of TOTP was initiated. During the 28-d test period, behavior of rats was evaluated using a functional observational battery (FOB), motor activity, and passive avoidance. Reductions in body weight, grip strength, and ambulatory movements occurred as a result of corticosterone treatment. Decreased body weight and grip strength were also elicited by TOTP, and the interactions of corticosterone and TOTP enhanced the effects on body weight and grip strength. Blood cholinesterase levels were obtained during the 28-d study period and found useful for monitoring OP exposure. At the end of the 28-d testing period, rats were sacrificed and activities of cholinesterase, neurotoxic esterase (neuropathy target esterase), and/or carboxylesterase were evaluated in blood, liver, and/or brain regions (basal forebrain, caudate putamen, cerebral cortex, hippocampus). All these esterases in brain were inhibited in a dose-related manner by TOTP, with some enhancement in rats drinking corticosterone-containing water. In addition, choline acetyltransferase, glial acidic fibrillary protein (GFAP), glutathione peroxidase, and superoxide dismutase were evaluated in one or more of the brain regions already identified. Choline acetyltransferase, glutathione peroxidase, and superoxide dismutase activities were unaffected by treatments. However, GFAP was elevated above control levels in the cerebral cortex of rats by all treatments (corticosterone, chlorpyrifos, TOTP). Neuropathological examination revealed early stages of dose-related increased distal myelinated fiber axonal degeneration seen in the medullary fasciculus gracilis at only the highest dose of TOTP (300 mg/kg). Title: Corticosterone in drinking water: altered kinetics of a single oral dose of corticosterone and concentrations of plasma sodium, albumin, globulin, and total protein Pung T, Zimmerman K, Klein B, Ehrich M Ref: Toxicol Ind Health, 19:171, 2003 : PubMed ESTHER: Pung_2003_Toxicol.Ind.Health_19_171 PubMedSearch: Pung 2003 Toxicol.Ind.Health 19 171 PubMedID: 15747778 Abstract Effects of chronic exposure to corticosterone in drinking water on corticosterone kinetics, blood chemistry, and concentrations of catecholamines in parts of brain were studied in Long-Evans rats. Rats were randomly grouped into 3 x 2 treatments (n=4), with three treatments of drinking water (tap water, or 2.5% ethanol, or 400 microg/mL of corticosterone in 2.5% ethanol) for 28 days and two treatments of gavage with a single dose of either corn oil or corticosterone 20 mg/kg on day 28. Blood samples were collected at 0, 15, 30, 60, 120, 240, 480, and 720 min after dosing to determine plasma corticosterone concentrations. Blood samples were collected for clinical pathology on day 42. Hippocampus, cerebral cortex, caudate-putamen, and pons were examined to determine concentrations of catecholamines and activities of esterases. Concentrations of plasma corticosterone before gavage of the corticosterone-drinking rats (47.61 +/- 1.13 ng/mL) were lower than the water (418.47 +/- 1.13 ng/mL) or the ethanol rats (383.71 +/- 1.13 ng/mL, P < 0.0001). Plasma corticosterone rose to peak concentrations by 15 min after gavage in all three groups of drinking rats. Corticosterone-drinking rats had concentrations of plasma corticosterone that returned to basal levels slower than water- and ethanol-drinking rats. Plasma sodium and chloride concentrations were lower in the corticosterone-drinking rats than the water-drinking rats (P < 0.01). Plasma albumin, globulin, and total protein were highest in the corticosterone-drinking rats when compared to the other groups of drinking rats (P < 0.001, P < 0.05, and P < 0.001, respectively). Corticosterone in drinking water did not affect activities of brain neurotoxic esterase, carboxylesterase, acetylcholinesterase, or concentrations of monoamines and their metabolites. A single oral dose of corticosterone reduced neurotoxic esterase activity in the cerebral cortex (P < 0.05) and increased norepinephrine concentrations in the hippocampus (P < 0.05). Title: Esterase Inhibition in SH-SY5Y Human Neuroblastoma Cells Following Exposure to Organophosphorus Compounds for 28 Days Barber DS, Ehrich M Ref: In Vitr Mol Toxicol, 14:129, 2001 : PubMed ESTHER: Barber_2001_In.Vitr.Mol.Toxicol_14_129 PubMedSearch: Barber 2001 In.Vitr.Mol.Toxicol 14 129 PubMedID: 11690566 Abstract Esterase inhibition was determined in SH-SY5Y human neuroblastoma cells grown in serum-free media and exposed to 10(-11) to 10(-7) M concentrations of organophosphorus (OP) compounds for 28 days. To examine metabolic activation in these exposures, pairs of pro- and active toxicants were studied, including chlorpyrifos and its oxon, parathion and paraoxon, and tri-ortho-tolyl phosphate and phenyl saligenin phospahte. Inhibition of acetylcholinesterase was greater in cells treated for 28 days with all active organophosphorus compounds than it was in cells treated only once with the same concentration of a given OP compound. The protoxicants chlorpyrifos and parathion produced acetylcholinesterase inhibition after multiple exposures although no inhibition was seen following a single exposure to these agents. Exacerbation of neurotoxic esterase inhibition by multiple exposures to the test compounds was not as pronounced as that of acetylcholinesterase. Exposure to the test compounds for 28 days did not significantly enhance esterase inhibition produced by a subsequent exposure to 10(-9) M chlorpyrifos-oxon. The results indicate that in vitro methods can be used to study the effect of multiple OP exposures on esterase activity. Title: Inhibition of calcium-stimulated ATPase in the hen brain P2 synaptosomal fraction by organophosphorus esters: relevance to delayed neuropathy Barber D, Hunt J, Ehrich M Ref: J Toxicol Environ Health A, 63:101, 2001 : PubMed ESTHER: Barber_2001_J.Toxicol.Environ.Health.A_63_101 PubMedSearch: Barber 2001 J.Toxicol.Environ.Health.A 63 101 PubMedID: 11393797 Abstract Organophosphorus (OP) compounds have been reported to inhibit Ca/Mg-ATPase, but the relevance of this inhibition to organophosphate-induced delayed neuropathy (OPIDN) has not been explored. To determine if inhibition of this enzyme was related to the development of OPIDN, neuropathic and nonneuropathic OP compounds were sted for their ability to inhibit Ca-stimulated ATPase activity in the P2 synaptosomal fraction from hen brain. Following in vitro exposure to 10(-3) to 10(-5) M OP compounds, Ca-stimulated ATPase activity was inhibited by chlorpyrifos, chlorpyrifos-oxon, phenyl saligenin phosphate (PSP), and tri-o-tolyl phosphate (TOTP), but not by parathion, paraoxon, or diisopropyl fluorophosphate (DFP). Further investigation of inhibition induced by chlorpyrifos determined that inhibition was noncompetitive with respect to calcium and ATP. OP compound hydrophobicity was well correlated with in vitro inhibition of Ca-stimulated ATPase, suggesting that OP compounds interact with membrane lipids, and this interaction may contribute to the noncompetitive inhibition of Ca-stimulated ATPase that was observed. Subsequent to in vivo exposure, DFP, but not PSP, produced inhibition of Ca-stimulated ATPase activity in the hen brain P2 synaptosomal fraction. These data indicate that inhibition of Ca-stimulated ATPase activity is not correlated to neuropathic potential and demonstrate that inhibition of Ca/Mg-ATPase is not responsible for OPIDN. Title: Nerve conduction and ATP concentrations in sciatic-tibial and medial plantar nerves of hens given phenyl saligenin phosphate Massicotte C, Barber DS, Jortner BS, Ehrich M Ref: Neurotoxicology, 22:91, 2001 : PubMed ESTHER: Massicotte_2001_Neurotoxicol_22_91 PubMedSearch: Massicotte 2001 Neurotoxicol 22 91 PubMedID: 11307855 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract To assess the relationship of nerve conduction and adenosine triphosphate (ATP) status in organophosphorus-induced delayed neuropathy (OPIDN), we evaluated both in adult hen peripheral nerves following exposure to a single 2.5 mg/kg dose of phenyl saligenin phosphate (PSP). ATP concentrations were determined at days 2, 4, 7, and 14 post-dosing, from five segments (n = 5 per group) representing the entire length of the sciatic-tibial and medial plantar nerve. Initial effects of PSP dosing were seen in the most distal segment at day 2, when a transient ATP concentration increase (388 +/- 79 pmol/ml/mg versus control value of 215 +/- 23, P < 0.05) was noted. Subsequently, ATP concentration in this distal segment returned to normal. In the most proximal nerve segment, ATP concentrations were decreased on day 7, and further decreased on day 14 post-dosing (P < 0.05). Changes in ATP concentration and nerve conduction velocity begin at post-dosing day 2, and were found prior to development of clinical neuropathy and axonopathic lesions. These results suggest that alterations in sciatic-tibial and medial plantar nerve conduction associated with sciatic-tibial and medial plantar nerve ATP concentration are early events in the development of OPIDN. Title: Comparison of oxime-initiated reactivation of organophosphorous-inhibited acetylcholinesterase in brains of avian embryos Lesser J, Blodgett D, Ehrich M Ref: J Toxicol Environ Health, 59:57, 2000 : PubMed ESTHER: Lesser_2000_J.Toxicol.Environ.Health_59_57 PubMedSearch: Lesser 2000 J.Toxicol.Environ.Health 59 57 PubMedID: 10681099 Abstract Organophosphorous (OP) insecticide-induced inhibition and oxime reactivation of acetylcholinesterase (AChE) was determined in whole-brain homogenates prepared from 15-d-old chick embryos. Doses of chlorpyrifos, parathion, acephate, and trichlorfon that inhibited AChE >70% were administered to the embryos. Following insecticide exposure, an in vitro system compared the capability of the oximes pralidoxime (2-PAM), obidoxime, TMB-4(Trimedoxime), and HI-6 to reactivate the OP-inhibited AChE. Concentration-related increases in AChE activities were noted in embryo brains reactivated with 2-PAM, TMB, and HI-6. 2-PAM was the most effective reactivator of trichlorfon-inhibited AChE; 2-PAM and obidoxime were relatively similar in effectiveness for reactivation of AChE inhibited with the other OP insecticides used as test agents. All oximes were similarly effective against acephate, but HI-6 was the least effective reactivator of AChE in chick embryo brain homogenates inhibited by the other OP insecticides. These results suggest that both the OP insecticide inhibiting AChE and the oxime reactivating this enzyme can contribute to the effectiveness of the avian brain AChE reactivation. Title: Comparative effectiveness of organophosphorus protoxicant activating systems in neuroblastoma cells and brain homogenates Barber D, Correll L, Ehrich M Ref: J Toxicol Environ Health, 57:63, 1999 : PubMed ESTHER: Barber_1999_J.Toxicol.Environ.Health_57_63 PubMedSearch: Barber 1999 J.Toxicol.Environ.Health 57 63 PubMedID: 10321902 Inhibitor(s) related to this paper: Leptophos Abstract The ability of bromine and rat liver microsomes (RLM) to convert organophosphorus (OP) protoxicants to esterase inhibitors was determined by measuring acetylcholinesterase (AChE) and neuropathy target esterase (NTE) inhibition. Species specific differences in susceptibility to esterase inhibition were determined by comparing the extent of esterase inhibition observed in human neuroblastoma cells and hen, bovine, and rodent brain homogenates. OP protoxicants examined included tri-o-tolyl phosphate (TOTP), O-ethyl O-p-nitrophenyl phenylphosphonothioate (EPN), leptophos, fenitrothion, fenthion, and malathion. Bromine activation resulted in greater AChE inhibition than that produced by RLM activation for equivalent concentrations of fenitrothion, malathion, and EPN. For EPN and leptophos, bromine activation resulted in greater inhibition of NTE than RLM. Only preincubation with RLM activated TOTP; resultant inhibition of AChE was less in hen brain (13 +/- 3%) than in neuroblastoma cells (73 +/- 1%) at 10(-6) M. In contrast, 10(-6) M RLM-activated TOTP produced more inhibition of hen brain NTE (89 +/- 6%) than NTE of human neuroblastoma cells (72 +/- 7%). Human neuroblastoma cells and brain homogenates from hens, the accepted animal model for study of OP-induced neurotoxicity, were relatively similar in sensitivity to esterase inhibition. Homogenates from hens were more sensitive to NTE inhibition induced by phenyl saligenin phosphate (PSP), an active congener of TOTP, than were homogenates from less susceptible species (mouse, rat, bovine). AChE of hen brain homogenates was also more sensitive than homogenates from other species to malaoxon, the active form of malathion. Title: Immunohistochemical study of phosphorylated neurofilaments during the evolution of organophosphorus ester-induced delayed neuropathy (OPIDN) Jortner BS, Perkins SK, Ehrich M Ref: Neurotoxicology, 20:971, 1999 : PubMed ESTHER: Jortner_1999_Neurotoxicol_20_971 PubMedSearch: Jortner 1999 Neurotoxicol 20 971 PubMedID: 10693978 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Organophosphorus ester-induced delayed neuropathy (OPIDN) is manifest by delayed degeneration of distal levels of long myelinated fibers following an appropriate neurotoxic exposure. We investigated the dynamics of cytoskeletal changes during nerve fiber degeneration in this condition, focusing on the immunohistochemistry of axonal phosphorylated neurofilaments. OPIDN was produced in 5-month-old White Leghorn hens using a single 2.5 mg/kg intramuscular dose of phenyl saligenin phosphate. Hens were sacrificed on days 4, 7, 9, 15, and 20, and the tibial nerve branch to the gastrocnemius muscle was studied by light microscopy and immunohistochemistry (using the SMI 31 monoclonal primary antibody to phosphorylated neurofilaments). At post-dosing days 9, 15, and 20 various stages of OPIDN lesions were noted, including axonal swelling and myelinated nerve fiber degeneration. These were associated with intra-axonal cytoskeletal lysis, manifest by loss of immunolabeled phosphorylated neurofilaments, a process consistent with proteolysis. Aggregations of excess axonal phosphorylated neurofilaments were not observed. Title: Inhibition of carboxylesterases in SH-SY5Y human and NB41A3 mouse neuroblastoma cells by organophosphorus esters Ehrich M, Correll L Ref: J Toxicol Environ Health, 53:385, 1998 : PubMed ESTHER: Ehrich_1998_J.Toxicol.Environ.Health_53_385 PubMedSearch: Ehrich 1998 J.Toxicol.Environ.Health 53 385 PubMedID: 9515941 Inhibitor(s) related to this paper: Chlorpyrifos-oxon, DFP, Dibutyl-dichlorovinyl-phosphate~DBVP, Dichlorvos, Dioctyl-dichlorovinyl-phosphate~DOVP, Malaoxon, Mipafox, Paraoxon, Phenyl-saligenin-phosphate~PSP, Tri-o-cresylphosphate, Trichlorfon~Metrifonate Abstract Carboxylesterases (CbxE) can be inhibited by organophosphorus esters (OPs) without causing clinical evidence of toxicity. CbxE are thought to protect the critical enzyme acetylcholinesterase (AChE) from OP inhibition in animals. CbxE and AChE are both present in neuroblastoma cells, but, even though these cells have potential to be an in vitro model of OP toxicity, the effect of OPs on CbxE and the relationship of CbxE inhibition and AChE inhibition have not yet been examined in these cells. Therefore, this study examined concentration-related OP-induced inhibition of CbxE in human SH-SY5Y and mouse NB41A3 neuroblastoma cells with 11 active esterase inhibitors: paraoxon, malaoxon, chlorpyrifos-oxon, tolyl saligenin phosphate (TSP), phenyl saligenin phosphate (PSP), diisopropyl phosphorofluoridate (DFP), mipafox, dichlorvos, trichlorfon, dibutyryl dichlorovinyl phosphate (DBVP), and dioctyl dichlorovinyl phosphate (DOVP). All could inhibit CbxE, although the enzyme was less likely to be inhibited than AChE following exposure to 9 of the test compounds in the human cell line and to all 11 of the test compounds in the murine cell line. Species differences in concentration-related inhibitions of CbxE were evident. When cells were exposed first to an OP with a low IC50 toward CbxE (PSP), followed by an OP with high affinity for AChE (paraoxon or malaoxon), inhibitions of CbxE and AChE were additive. This indicated that CbxE did not protect AChE from OP-induced inhibition in this cell culture model. Title: Common mechanism of toxicity: a case study of organophosphorus pesticides Mileson BE, Chambers JE, Chen WL, Dettbarn W, Ehrich M, Eldefrawi AT, Gaylor DW, Hamernik K, Hodgson E and Wallace KB <7 more author(s)> Mileson BE, Chambers JE, Chen WL, Dettbarn W, Ehrich M, Eldefrawi AT, Gaylor DW, Hamernik K, Hodgson E, Karczmar AG, Padilla S, Pope CN, Richardson RJ, Saunders DR, Sheets LP, Sultatos LG, Wallace KB (- 7) Ref: Toxicol Sci, 41:8, 1998 : PubMed ESTHER: Mileson_1998_Toxicol.Sci_41_8 PubMedSearch: Mileson 1998 Toxicol.Sci 41 8 PubMedID: 9520337 Abstract The Food Quality Protection Act of 1996 (FQPA) requires the EPA to consider "available information concerning the cumulative effects of such residues and other substances that have a common mechanism of toxicity ... in establishing, modifying, leaving in effect, or revoking a tolerance for a pesticide chemical residue." This directive raises a number of scientific questions to be answered before the FQPA can be implemented. Among these questions is: What constitutes a common mechanism of toxicity? The ILSI Risk Science Institute (RSI) convened a group of experts to examine this and other scientific questions using the organophosphorus (OP) pesticides as the case study. OP pesticides share some characteristics attributed to compounds that act by a common mechanism, but produce a variety of clinical signs of toxicity not identical for all OP pesticides. The Working Group generated a testable hypothesis, anticholinesterase OP pesticides act by a common mechanism of toxicity, and generated alternative hypotheses that, if true, would cause rejection of the initial hypothesis and provide criteria for subgrouping OP compounds. Some of the alternative hypotheses were rejected outright and the rest were not supported by adequate data. The Working Group concluded that OP pesticides act by a common mechanism of toxicity if they inhibit acetylcholinesterase by phosphorylation and elicit any spectrum of cholinergic effects. An approach similar to that developed for OP pesticides could be used to determine if other classes or groups of pesticides that share structural and toxicological characteristics act by a common mechanism of toxicity or by distinct mechanisms. Title: Acetylcholinesterase and neuropathy target esterase inhibitions in neuroblastoma cells to distinguish organophosphorus compounds causing acute and delayed neurotoxicity Ehrich M, Correll L, Veronesi B Ref: Fundamental & Applied Toxicology, 38:55, 1997 : PubMed ESTHER: Ehrich_1997_Fundam.Appl.Toxicol_38_55 PubMedSearch: Ehrich 1997 Fundam.Appl.Toxicol 38 55 PubMedID: 9268605 Inhibitor(s) related to this paper: Mipafox, Phenyl-saligenin-phosphate~PSP Abstract The differential inhibition of the target esterases acetylcholinesterase (AChE) and neuropathy target esterase (NTE, neurotoxic esterase) by organophosphorus compounds (OPs) is followed by distinct neurological consequences in exposed subjects. The present study demonstrates that neuroblastoma cell lines (human SH-SY5Y and murine NB41A3) can be used to differentiate between neuropathic OPs (i.e., those inhibiting NTE and causing organophosphorus-induced delayed neuropathy) and acutely neurotoxic OPs (i.e., those highly capable of inhibiting AChE). In these experiments, concentration-response data indicated that the capability to inhibit AChE was over 100x greater than the capability to inhibit NTE for acutely toxic, nonneuropathic OPs (e.g., paraoxon and malaoxon) in both cell lines. Inhibition of AChE was greater than inhibition of NTE, without overlap of the concentration-response curves, for OPs which are more likely to cause acute, rather than delayed, neurotoxic effects in vivo (e.g., chlorpyrifos-oxon, dichlorvos, and trichlorfon). In contrast, concentrations inhibiting AChE and NTE overlapped for neuropathy-causing OPs. For example, apparent IC50 values for NTE inhibition were less than 9.6-fold the apparent IC50 values for AChE inhibition when cells were exposed to the neuropathy-inducing OPs diisopropyl phosphorofluoridate, cyclic tolyl saligenin phosphate, phenyl saligenin phosphate, mipafox, dibutyl dichlorovinyl phosphate, and di-octyl-dichlorovinyl phosphate. In all cases, esterase inhibition occurred at lower concentrations than those needed for cytoxicity. These results suggest that either mouse or human neuroblastoma cell lines can be considered useful in vitro models to distinguish esterase-inhibiting OP neurotoxicants. Title: Effect of laundering on ability of glove fabrics to decrease the penetration of organophosphate insecticides through in vitro epidermal systems Keeble VB, Correll L, Ehrich M Ref: Journal of Applied Toxicology, 16:401, 1996 : PubMed ESTHER: Keeble_1996_J.Appl.Toxicol_16_401 PubMedSearch: Keeble 1996 J.Appl.Toxicol 16 401 PubMedID: 8889792 Abstract Two knit glove fabrics, one of 100% cotton and one of 100% polypropylene, were examined for their capability to decrease the penetration of the organophosphate insecticides (OPs), azinphos-methyl and paraoxon after 4 h at field concentrations (3000 and 15 ppm, respectively) through an in vitro epidermal system (Skin2, Advanced Tissue Systems, LaJolla, CA). The glove fabrics were examined under three different conditions of use: new, after they had been abraded and after they had been abraded and then laundered. New and laundered cotton fabric was also examined for its capability to decrease the penetration of azinphos-methyl through another in vitro epidermal system (Epiderm, MatTek Corp., Ashland, MA), after 4 and 24 h of exposure. Capability of the media under the in vitro epidermal systems to inhibit brain acetylcholinesterase (AChE) was used as the indicator of penetration. Results were compared to OP-caused inhibitions seen in media under the fabric alone and in media under the in vitro epidermal systems alone. Incubations of azinphos-methyl suspensions and the in vitro epidermal systems covered with fabric indicated that both the epidermal cells and fabric provided protection against AChE inhibition caused by this OP and that the protective effects were additive, whether measured after 4 or 24 h of exposure. Therefore, neither laundering nor abrasion followed by laundering altered the capability of the in vitro epidermal systems to absorb azinphos-methyl suspension. For paraoxon solution, however, new cotton glove fabric prevented absorption, and this protective effect, noted after 4 h of exposure, was lost when the fabric was laundered. Abrading the fabric did not cause a greater effect than laundering alone. These results suggest that the pesticide as well as its formulation may be factors of consideration when protective fabrics are chosen, and that, for cotton glove fabric, the protection against some OPs may best be provided before the fabric is laundered. Title: Catecholamine concentrations and contractile responses of isolated vessels from hens treated with cyclic phenyl saligenin phosphate or paraoxon in the presence or absence of verapamil McCain WC, Flaherty DM, Correll L, Jortner B, Ehrich M Ref: Journal of Toxicology & Environmental Health, 48:397, 1996 : PubMed ESTHER: McCain_1996_J.Toxicol.Env.Health_48_397 PubMedSearch: McCain 1996 J.Toxicol.Env.Health 48 397 PubMedID: 8691509 Abstract Blood samples and vascular segments from the ischiadic artery of hens treated with either cyclic phenyl saligenin phosphate (PSP; 2.5 micrograms/kg, im) or paraoxon (PXN; 0.1 micrograms/kg, im) in the presence or absence of verapamil, a calcium channel antagonist (7 micrograms/kg, im, given 4 consecutive days beginning the day before PSP or PXN administration), were examined 1, 3, 7, and 21 d after PSP or PXN administration in order to determine the contribution of catecholamines and peripheral blood vessel physiology and morphology to organophosphorus-induced delayed neuropathy (OPIDN). The levels of plasma catecholamines were measured by high-performance liquid chromatograpy (HPLC) and indicated a different effect with PSP, which causes OPIDN, and PXN, which does not. PSP treatment elevated the levels of norepinephrine and epinephrine throughout the study, while PXN treatment depressed the levels of these catecholamines. Verapamil treatment attenuated the OP response by approximately 50% for both compounds. Ischiadic vessel segments were isolated from OP-treated hens and perfused at a constant flow rate of 12 ml/min, then examined for their response to potassium chloride (KCl, 3 x 10(-3) M), acetylcholine (ACh), phenylephrine (PE), an alpha 1 adrenergic agonist, and salbutamol (SAL), a beta 2 adrenergic agonist. Agents were delivered in concentrations of 10(-8) to 10(-3) M. Vascular segments did not respond to ACh or SAL at any concentration used. Vessels displayed a significant reduction in contractile response to both KCl (3 x 10(-3) M) and PE (10(-8) to 10(-3) M) 3 and 21 d after exposure to either PSP or PXN. This reduced response was not altered by the presence of verapamil. Innervation of the peripheral vasculature was unchanged after OP treatment. This study indicates that plasma catecholamine levels could be differentially altered by treatment with OPs that do and do not cause OPIDN and suggests that the alterations involve intracellular calcium. In contrast, vascular response of the ischiadic artery was altered following OP treatment, but the effect was not specific for the neuropathy-inducing OP, PSP, and response was not mediated by Ca 2+, nor was it the result of autonomic nerve deterioration. Title: Comparison of the relative inhibition of acetylcholinesterase and neuropathy target esterase in rats and hens given cholinesterase inhibitors Ehrich M, Jortner BS, Padilla S Ref: Fundamental & Applied Toxicology, 24:94, 1995 : PubMed ESTHER: Ehrich_1995_Fundam.Appl.Toxicol_24_94 PubMedSearch: Ehrich 1995 Fundam.Appl.Toxicol 24 94 PubMedID: 7713347 Inhibitor(s) related to this paper: DFP, Mipafox, Phenyl-saligenin-phosphate~PSP Abstract Inhibition of neuropathy target esterase (NTE, neurotoxic esterase) and acetylcholinesterase (AChE) activities was compared in brain and spinal cords of adult While Leghorn hens and adult male Long Evan rats 4-48 hr after administration of triortho-tolyl phosphate (TOTP po, 50-500 mg/kg to hens; 300-1000 mg/kg to rats), phenyl saligenin phosphate (PSP im 0.1-2.5 mg/kg to hens; 5-24 mg/kg to rats), mipafox (3-30 mg/kg ip to hens and rats), diisopropyl phosphorofluoridate (DFP sc, 0.25-1.0 mg/kg to hens; 1-3 mg/kg to rats), dichlorvos (5-60 mg/kg ip to hens; 600-2000 mg/kg to rats), and carbaryl (300-560 mg/kg ip to hens; 30-170 mg/kg to rats). Inhibitions of NTE and AChE were dose-related after administration of all compounds to both species. Hens and rats given TOTP, PSP, mipafox, and DFP demonstrated delayed neuropathy 3 weeks later, with spinal cord lesions and clinical signs more notable in hens. Ratios of NTE/AChE inhibition in hen spinal cord, averaged over the doses used, were 2.6 after TOTP, 5.2 after PSP, 1.3 after mipafox, and 0.9 after DFP, which contrast with 0.53 after dichlorvos, 1.0 after malathion, and 0.46 after carbaryl. Rat NTE/AChE inhibition ratios were 0.9 after TOTP, 2.6 after PSP, 1.0 after mipafox, 0.62 after DFP, 1.3 after dichlorvos, 2.2 after malathion, and 1.1 after carbaryl. The lower NTE/AChE ratios in rats given dosages of the four organophosphorus compounds that caused delayed neuropathy interferred with survival, an effect that was not a problem in hens. Title: Esterase comparison in neuroblastoma cells of human and rodent origin Ehrich M, Veronesi B Ref: Clinical & Experimental Pharmacology & Physiology, 22:385, 1995 : PubMed ESTHER: Ehrich_1995_Clin.Exp.Pharmacol.Physiol_22_385 PubMedSearch: Ehrich 1995 Clin.Exp.Pharmacol.Physiol 22 385 PubMedID: 7554440 Abstract 1. Activities of acetylcholinesterase (AChE), neuropathy target esterase (NTE), and carboxylesterase (CbxE) were compared in neuroblastoma cells of human origin (SH-SY5Y) and murine origin (NB41A3). 2. Mouse neuroblastoma cells had lower specific activities of NTE and CbxE than did human neuroblastoma cells; specific activities in the murine cells correlated with specific activities in mouse brain. 3. AChE activities in mouse and human neuroblastoma cells were considerably lower than AChE activities in mouse or hen brain. 4. Inhibition of esterases did not demonstrate interspecies differences for 12 of the 17 anti-esterase compounds tested with human and mouse neuroblastoma cells. Title: Effect of cyclic phenyl saligenin phosphate and paraoxon treatment on vascular response to adrenergic and cholinergic agents in hens McCain WC, Wilcke J, Lee JC, Ehrich M Ref: J Toxicol Environ Health, 44:167, 1995 : PubMed ESTHER: McCain_1995_J.Toxicol.Environ.Health_44_167 PubMedSearch: McCain 1995 J.Toxicol.Environ.Health 44 167 PubMedID: 7853421 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract The response of peripheral blood vessels to adrenergic and cholinergic agonists was examined 1, 3, 7, and 21 d after hens were treated with a single intramuscular injection of 2.5 mg/kg cyclic phenyl saligenin phosphate (PSP) or 0.10 mg/kg paraoxon (PXN). These two organophosphates (OPs) cause different clinical effects in exposed animals, as PSP causes organophosphate-induced delayed neuropathy (OPIDN) and PXN causes acute poisoning through inhibition of acetylcholinesterase. For these studies, the ischiadic artery was cannulated both prograde and retrograde and the blood was shunted through a pump to maintain a constant flow. Alterations in pressure measured at the pump outflow were used to indicate changes in limb vascular resistance. Dose-response curves were generated for the response to intravenous administration of acetylcholine (ACh), phenylephrine (PE), or salbutamol (SAL) (10(-8) to 10(-4) mol/kg). Acetylcholine at 10(-8) to 10(-7) mol/kg caused an increase in vascular resistance, whereas concentrations of 10(-5) to 10(-4) mol/kg caused a decrease in vascular resistance in hens given PSP 1 and 3 d previously. The response of PXN-treated hens to ACh was not significantly altered from that of vehicle-treated hens. The resistance generated in response to PE, an alpha 1-adrenergic agonist, in PSP-treated hens was greater than levels in vehicle-treated hens on d 1 and 3 and greater than the response seen in hens treated with PXN. Salbutamol, a beta 2-adrenergic agonist, at concentrations of 10(-7) to 10(-4) mol/kg caused an increase in resistance 1 and 3 d after PSP and a decrease on d 7. The responses to SAL were different in PXN-treated hens, as these hens demonstrated a lesser increase in resistance at concentrations of 10(-8) to 10(-7) mol/kg and a decrease in resistance at 10(-5) to 10(-4) mol/kg 1 d after administration of PXN. These observations indicate that response to vasoactive agents is altered in OP-treated hens and that responses differ between a compound capable of causing OPIDN (PSP) and a compound that only causes acute effects (PXN). Title: Interaction of organophosphorus compounds with muscarinic receptors in SH-SY5Y human neuroblastoma cells Ehrich M, Intropido L, Costa LG Ref: J Toxicol Environ Health, 43:51, 1994 : PubMed ESTHER: Ehrich_1994_J.Toxicol.Environ.Health_43_51 PubMedSearch: Ehrich 1994 J.Toxicol.Environ.Health 43 51 PubMedID: 8078092 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Human neuroblastoma cells (line SH-SY5Y) were used to examine the interaction of single exposure to organophosphorus compounds (OPs) with muscarinic receptors. In this study, SH-SY5Y cells were exposed for 30 min to concentrations of paraoxon, diisopropyl phosphorofluoridate (DFP), phenyl saligenin cyclic phosphate (PSP), and mipafox (N,N'-diisopropyl phosphorodiamide fluoridate) that ranged between 10(-9) M and 10(-3) M (10(-2) M for mipafox). Ability to interfere with muscarinic receptor binding was determined by change in the binding of the nonspecific antagonist [3H]-N-methylscopolamine (3H-NMS). Concentrations of paraoxon > 0.5 x 10(-3) M and PSP 1 x 10(-3) M significantly inhibited the binding of a saturating concentration of 3H-NMS. Concentrations of > 10(-5) M paraoxon or PSP could significantly inhibit the binding of a half-saturating concentration of 3H-NMS. Studies using specific antagonists for muscarinic subtypes (pirenzepine for M1, AFDX-116 for M2, and 4-DAMP for M3) indicated that SH-SY5Y cells have muscarinic receptors most sensitive to the specific antagonist for the M3 subtype (IC50 of 10(-8) M for 4-DAMP compared to 2.5 x 10(-6) M and 2.7 x 10(-5) M for pirenzepine and AFDX-116, respectively). As M3 receptor stimulation results in formation of inositol phosphates from membrane phosphoinositides the capability of OPs to alter levels of inositol phosphates and agonist-stimulated increases in inositol phosphate formation was examined. Intact cells were prelabeled with [3H]myo-inositol and then incubated for 15 min with the OPs before addition of 10(-5) M to 10(-3) M carbachol. Levels of inositol phosphates were determined as the amount of aqueous soluble radiolabeled product extracted from the reaction mixture. Paraoxon and PSP, but not mipafox or DFP, decreased basal levels of inositol phosphates in a concentration-related manner. This could be overcome in cells stimulated with carbachol, a muscarinic agonist, and with sodium fluoride, which does not act at muscarinic receptors. These results indicate that certain OPs, upon acute exposure, interact with muscarinic receptors, but that they also have effects on levels of inositol phosphates that may be associated with another site of action in SH-SY5Y cells. Title: Relationship of neuropathy target esterase inhibition to neuropathology and ataxia in hens given organophosphorus esters Ehrich M, Jortner BS, Padilla S Ref: Chemico-Biological Interactions, 87:431, 1993 : PubMed ESTHER: Ehrich_1993_Chem.Biol.Interact_87_431 PubMedSearch: Ehrich 1993 Chem.Biol.Interact 87 431 PubMedID: 8343999 Abstract Adult White Leghorn hens were acutely exposed to 3 dosages of the following organophosphorus compounds: mipafox, tri-ortho-tolyl phosphate (TOTP), phenyl saligenin phosphate, and diisopropylphosphorofluoridate (DFP). Neuropathy target esterase (NTE) activity was measured in brain and spinal cord 4 or 48 h after exposure. Ataxia was assessed using an 8-point rating scale on days 9 through 21 after administration, and neuropathological examination was conducted on samples collected from perfusion-fixed animals on day 21. Morphological alterations were indicated by lesion scores between 0 (no lesions) and 4 (diffuse involvement of spinal cord tracts and > 25% degeneration of peripheral nerve fibers). Dosages of mipafox (30 mg/kg i.p.), TOTP (500 mg/kg p.o.), phenyl saligenin phosphate (2.5 mg/kg i.m.) and DFP (1 mg/kg s.c.) that were capable of inhibiting NTE > 80% in both brain and spinal cord preceded ataxia which reached maximal levels (scores of 7-8), and development of lesions scored as 4. Hens were notably impaired (ataxia scores of 3-4) 21 days after administration of dosages of mipafox (3 and 6 mg/kg), TOTP (90 mg/kg), phenyl saligenin phosphate (0.1 and 0.2 mg/kg), and DFP (0.4 mg/kg) when spinal cord NTE was inhibited 40-75%. Lesions were, however, only noted in spinal cord and peripheral nerves of hens given TOTP or DFP (scores 1-3). These data indicate that inhibition of spinal cord NTE > 80% was predictive of severe ataxia and extensive pathology in the hen and that less NTE inhibition was indicative of less severe ataxia and a lower score for neuropathological damage. Title: The Effect of Phenyl Saligenin Cyclic Phosphate Induced Delayed Neuropathy on Selected Hemodynamic and Hematologic Parameters in the Hen McCain WC, Lee JC, Wilcke JR, Ehrich M Ref: Pesticide Biochemistry and Physiology, 45:220, 1993 : PubMed ESTHER: Mccain_1993_Pestic.Biochem.Physiol_45_220 PubMedSearch: Mccain 1993 Pestic.Biochem.Physiol 45 220 Abstract Cardiovascular parameters, including limb venous flow and arterial blood pressure, were measured 1, 3, 7, and 15-21 days after a single 2.5 mg/kg intramuscular injection of phenyl saligenin cyclic phosphate (PSP) was administered to hens. All hens given the organophosphate developed clinical signs of delayed neuropathy by Day 10 and these signs were maximal by Day 20 after PSP administration. Resistance to blood flow was increased in the legs of hens given PSP prior to the onset of clinical signs of organophosphorus-induced delayed neuropathy (OPIDN). This did not occur in hens given an OP that did not cause OPIDN (paraoxon). PSP administration also resulted in significant decreases in the activities of brain neurotoxic esterase (NTE) and plasma cholinesterase, as well as decreases in body weight prior to evidence of clinical signs of OPIDN. When maximal signs of OPIDN were present, activities of brain NTE and plasma cholinesterase had returned to control levels. Limb venous flow and arterial blood pressure were elevated in PSP-treated hens when maximal clinical signs were evident (Days 15-21). Body weight and arterial PCO2 were also significantly decreased in hens with OPIDN and hematocrit significantly increased. Administration of this neuropathy-inducing organophosphate was, therefore, capable of altering hemodynamic and hematologic parameters before and after onset of OPIDN. Title: Nerve conduction studies in chickens given phenyl saligenin phosphate and corticosterone Lidsky TI, Manetto C, Ehrich M Ref: J Toxicol Environ Health, 29:65, 1990 : PubMed ESTHER: Lidsky_1990_J.Toxicol.Environ.Health_29_65 PubMedSearch: Lidsky 1990 J.Toxicol.Environ.Health 29 65 PubMedID: 2299688 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Clinical signs of delayed neuropathy were induced in adult white leghorn chickens given the organophosphorus ester phenyl saligenin phosphate (PSP, 2.5 mg/kg im) 22-24 d before assessment of nerve conduction parameters. Damage to the myelinated sensory portion of the sciatic nerve was indicated by abnormal compound action potentials in treated chickens. In particular, the amplitude of the A beta response was markedly reduced. In addition, the A beta fibers did not respond normally to increasing stimulation intensity. These parameters were more like controls in chickens that had been given PSP and 30 ppm corticosterone for 11 d, beginning 1 d before PSP administration. These studies indicated that nerve conduction parameters could distinguish peripheral nerve damage in chickens given PSP and improvement could be noted in chickens treated with corticosterone. Title: Use of the biventer cervicis nerve-muscle preparation to detect early changes following exposure to organophosphates inducing delayed neuropathy el-Fawal HA, Jortner BS, Ehrich M Ref: Fundamental & Applied Toxicology, 15:108, 1990 : PubMed ESTHER: el-Fawal_1990_Fundam.Appl.Toxicol_15_108 PubMedSearch: el-Fawal 1990 Fundam.Appl.Toxicol 15 108 PubMedID: 2373292 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Indices of organophosphorus (OP)-induced delayed neuropathy (OPIDN) in the hen model have traditionally been restricted to the early inhibition of neuropathy target esterase (NTE) and ataxia with associated pathological changes in hind limb peripheral nerve which occur more than 7 days after OP exposure. The biventer cervicis nerve-muscle preparation was used to evaluate OPIDN in adult hens at various time periods after treatment with either the protoxicant tri-o-tolyl phosphate (TOTP), 360 mg/kg po, or the active congener phenyl saligenin phosphate (PSP), 2.5 mg/kg im. NTE activity was 21 and 48% of control for TOTP and PSP, respectively, 4 days after administration. Clinical signs were notable by 10 days and progressed in severity to paralysis by 21 days. Partial clinical recovery was evident at 37 days. Denervation hypersensitivity of biventer cervicis muscle to acetylcholine (ACh) was evident as early as 4 days following TOTP or PSP treatment. The sensitivity to ACh was greatest 21 days after OP administration, with partial recovery at 37 days. Strength-duration curves (SDC) of preparations from OP-treated hens showed an increase in excitability thresholds and elevated rheobase with shorter chronaxie than did preparations from controls as early as 4 days following treatment with either compound. SDC at 37 days indicated partial reinnervation. Peripheral nerve myelinated fiber degeneration and regeneration consistent with these physiological changes was seen on histopathological examination. This study suggests that the biventer cervicis nerve-muscle preparation may prove useful for detection of functional and morphological changes that occur during the interval between NTE inhibition and appearance of clinical deficits. Title: Modification of phenyl saligenin phosphate-induced delayed effects by calcium channel blockers: in vivo and in vitro electrophysiological assessment el-Fawal HA, Jortner BS, Ehrich M Ref: Neurotoxicology, 11:573, 1990 : PubMed ESTHER: el-Fawal_1990_Neurotoxicol_11_573 PubMedSearch: el-Fawal 1990 Neurotoxicol 11 573 PubMedID: 2087284 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Effects of organophosphorus esters (OPs) inducing delayed neuropathy in the adult hen have traditionally been evaluated by assessment of morphology and function of nerve and muscle in the rear limbs of animals exposed. In this study, organophosphorus-induced delayed neuropathy (OPIDN), including neuromuscular function and histology, were studied in vivo using sciatic nerve, tibial nerve and gastrocnemius muscle in anesthetized hens that had been administered phenyl saligenin phosphate (PSP), 2.5 mg/kg by intramuscular injection. In addition, OPIDN was examined in vitro using the biventer cervicis nerve and muscle of the same adult hens. Both nerve-muscle preparations were used for construction of strength duration curves (SDC) on days 4-5, 7-8, and 15-16 after PSP; the biventer cervicis preparation was also used 21-22, 37 and 64 days after PSP administration. Histological examination was done at these same time periods. SDC revealed significant increases in excitability thresholds for preparations from hens receiving PSP only compared to preparations from control hens, or compared to preparations from hens treated with PSP and either nifedipine (1 mg/kg intramuscularly for 5 days), or verapamil (7 mg/kg intramuscularly for 4 days), with treatment beginning 24 hours before administration of PSP. Ataxia, which appeared 7-10 days after hens were given PSP, was less pronounced in hens given PSP plus either calcium channel blocker than in hens given PSP alone. Whether treatment was initiated before or after PSP, verapamil, a phenylalkylamine, reduced sensitivity of the biventer cervicis muscle to acetylcholine-induced stimulation. The dihydropyridine, nifedipine, was less effective at reducing muscle sensitivity to acetylcholine post-exposure than when used as a pretreatment. Lesions were extensive in the biventer cervicis nerve after PSP administration and modification by treatment with calcium channel blockers was evident. Title: Effect of beta-naphthoflavone on o-tolyl saligenin phosphate-induced delayed neuropathy in two lines of chickens Bursian SJ, Lehning EJ, Correll L, Ehrich M Ref: J Toxicol Environ Health, 28:461, 1989 : PubMed ESTHER: Bursian_1989_J.Toxicol.Environ.Health_28_461 PubMedSearch: Bursian 1989 J.Toxicol.Environ.Health 28 461 PubMedID: 2593176 Inhibitor(s) related to this paper: CBDP Abstract The effect of the microsomal enzyme inducer beta-naphthoflavone (beta NF) on the development of organophosphorus-induced delayed neuropathy (OPIDN) was examined in two laboratories (VPI and MSU), utilizing two strains of White Leghorn hens. A single intraperitoneal injection of beta NF at 80 mg/kg body weight 48 h prior to administration of o-tolyl saligenin phosphate (TSP), the neuroactive metabolite of tri-o-tolyl phosphate (TOTP), caused a significant increase in hepatic microsomal cytochrome P-450 concentrations and aniline hydroxylase activities after 72 h in both strains. Hepatic carboxylesterase and cholinesterase activities were not affected by beta NF treatment in either strain. Administration of TSP in single subcutaneous doses of 20 and 25 mg/kg body weight (VPI) or 30 and 60 mg/kg body weight (MSU) caused significant inhibition of whole-brain neuropathy target esterase (NTE) activity 24 h postdosing, and hens subsequently developed clinical signs characteristics of OPIDN. beta NF had no significant effect on NTE inhibition or on initiation or severity of OPIDN clinical signs. However, OPIDN clinical signs were less severe in the strain of bird (MSU) with the higher intrinsic hepatic carboxylesterase activity and the higher beta NF-induced cytochrome P-450 concentration. The study indicates that microsomal enzyme induction, which has been shown to alleviate TOTP-induced delayed neuropathy, could not alleviate OPIDN resulting from exposure to TSP. This study also suggests that strain may affect susceptibility to TSP-induced delayed neuropathy. Title: The biventer cervicis nerve-muscle preparation of adult hens: effects of phenyl saligenin phosphate administration el-Fawal HA, Jortner BS, Eyre P, Ehrich M Ref: Neurotoxicology, 9:625, 1988 : PubMed ESTHER: el-Fawal_1988_Neurotoxicol_9_625 PubMedSearch: el-Fawal 1988 Neurotoxicol 9 625 PubMedID: 3244445 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract A biventer cervicis nerve-muscle preparation was used to assess in vitro neuromuscular function in adult white leghorn hens with clinical signs of delayed neuropathy induced by phenyl saligenin phosphate (PSP). Denervation of fast-twitch muscle fibers 13-15 days after PSP was indicated by higher excitability thresholds and by discontinuities of the strength-duration curves. Nerve degeneration was also indicated by significantly elevated rheobase values for all three experimental groups (2, 6 and 10 mg/kg PSP, im) and by shorter chronaxie for preparations from hens receiving 6 and 10 mg/kg. Chronaxie values for preparations from hens given 2 mg/kg PSP were longer than controls, indicating only partial denervation. Biventer cervicis muscle from all PSP-treated hens was 100-1000x more sensitive to acetylcholine (ACh) than muscle from untreated hens, a response typical of denervated slow-tonic muscle. Tension development in response to ACh was 20-45x greater than control in muscle of PSP-treated hens. The greatest sensitivity and tension development in response to ACh was encountered in muscles from hens given 10 mg/kg PSP. Denervation was also indicated histologically by the extensive degeneration and loss of larger myelinated nerve fibers. This study indicates that alteration in neuromuscular function and morphology occurs in the neck region of chickens during OPIDN and that deficits in nerves innervating both fast-twitch and slow-tonic muscles can be differentiated by nerve stimulation and by denervation hypersensitivity to ACh. Title: Neuropathological effects of phenyl saligenin phosphate in chickens [corrected and republished article originally printed in Neurotoxicology 1987 Spring;8(1):98-108] Jortner BS, Ehrich M Ref: Neurotoxicology, 8:303, 1987 : PubMed ESTHER: Jortner_1987_Neurotoxicol_8_303 PubMedSearch: Jortner 1987 Neurotoxicol 8 303 PubMedID: 3601242 Inhibitor(s) related to this paper: Phenyl-saligenin-phosphate~PSP Abstract Cyclic phenyl saligenin phosphate (PSP) proved to be a potent delayed neurotoxin, eliciting clinical disease and lesions, and depressing neuropathy target esterase and plasma cholinesterase at much lower doses than the protoxicant tri-ortho-tolyl phosphate (TOTP). Using adult White Leghorn chickens, we noted qualitative similarities in clinical signs and peripheral nerve and spinal cord lesions elicited by PSP and the TOTP. Ataxia and weakness were prominent clinical effects. Lesions began as a distal axonopathy affecting larger myelinated fibers in spinal cord white matter and peripheral nerve. The latter were studied in detail. Major features of the lesion were intra-axonal collections of mitochondria, dense and lamellar bodies, and granular degeneration of neurofilaments. These led to Wallerian-like degeneration. Percentages of teased peripheral nerve fibers demonstrating such degeneration correlated with severity of clinical signs. Title: Neurotoxicity of triorthotolyl phosphate in chickens of different genotypes in the presence and absence of deoxycorticosterone Ehrich M, Briles RW, Briles WE, Dunnington EA, Martin A, Siegel PB, Gross WB Ref: Poult Sci, 65:375, 1986 : PubMed ESTHER: Ehrich_1986_Poult.Sci_65_375 PubMedSearch: Ehrich 1986 Poult.Sci 65 375 PubMedID: 3703783 Abstract Indices of acute and delayed toxicity following administration of triorthotolyl phosphate (TOTP) were measured in roosters from lines of chickens originating from the Cornell randombred population. Matings were designed to produce individuals that had presence or absence of allele 21 of the B blood system. Non-B21 individuals had allele 13 or 31. Acute inhibition of esterases (neurotoxic esterase, liver cholinesterase, plasma cholinesterases, and plasma carboxylesterases) occurred in all birds within 24 hr of a single oral dose of 360 mg/kg TOTP. Clinical signs of delayed neuropathy were evident within 12 days of TOTP administration, with no significant difference between genotypes. Dietary deoxycorticosterone (40 to 200 ppm) appeared incapable of statistically significant modification of the strong effects of TOTP. Activities of blood esterases were different between roosters having B21/B21 and those with B13 and/or B31. | |||||||
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