Biomedical subjects

M Ehrich

Publications and source records attributed to M Ehrich.

At least 55 records · Page 3Linked to original sources

PubMed1993

Evaluation of knit glove fabrics as barriers to dermal absorption of organophosphorus insecticides using an in vitro test system.

Cotton and synthetic knit glove fabrics in combination with an in vitro skin model were used to examine the capability of fabric to decrease the dermal absorption of the organophosphorus insecticides azinphos-methyl, paraoxon, and malathion. Capability for inhibition of acetylcholinesterase was determined in samples of media taken from under the skin barrier after the skin model, with or without fabric protection, had been exposed to the test compounds for 4 h. Acetylcholinesterase inhibitions caused by the direct addition of organophosphorus insecticide to the media were also included in the comparison. Results indicated that the skin model system alone had some capability to serve as a barrier to the transfer of organophosphates. Fabric covering used on the test model increased the barrier between insecticide application and resultant acetylcholinesterase inhibition. The all-cotton, 7-cut knit was especially effective in preventing the absorption of azinphos-methyl, as this organophosphorus insecticide had no capability to cause acetylcholinesterase inhibition when this fabric was used to protect the skin model. Knit glove materials of 100% cotton were demonstrated to be effective in preventing the absorption of paraoxon and malathion. These studies indicate that an in vitro model system can be used in combination with fabrics to study the relationship between clothing and skin as barriers to the absorption of organophosphorus insecticides.

Gloves, Protective↗

PubMed1993

Differential cytotoxic sensitivity in mouse and human cell lines exposed to organophosphate insecticides.

Neuroblastoma cell lines were used to examine the differential interspecies response (i.e., species selectivity) to organophosphates (OPs). Baseline activities of the major target esterases, i.e., cholinesterase, carboxylesterase, and neurotoxic esterase, were assayed in mouse and several human neural candidate cell lines. These activities were found to be variable within individual cell lines and among the various tested cell lines. Cytotoxicity data using the neutral red fluorometric assay were collected on both human (SH-SY5Y) and mouse (NB41A3) neuroblastoma clones exposed to a variety of OP insecticides. IC50 data indicated that the tested mouse cell line was consistently more sensitive than the human cell line to equimolar doses of various OP compounds (e.g., mipafox, parathion, paraoxon, DFP, leptophos oxon, fenthion, and fenitrothion). This difference in cytotoxic sensitivity was most pronounced in response to compounds requiring metabolic bioactivation (i.e., protoxicants). Cytotoxicity data also demonstrated that the NB41A3 mouse neuroblastoma cell line was more metabolically competent than the SH-SY5Y human cell line in converting the protoxicant parathion to its neurotoxic metabolite, paraoxon. B-lymphoblastoids, genetically engineered with human P450 cDNAs, demonstrated higher cytotoxic sensitivity to parathion than unengineered cells, indicating that cytochrome P450-associated monooxidase activity could also influence cytotoxic sensitivity to parathion in culture. These data suggest that interspecies-selectivity in response to OP-related cytotoxicity is influenced by intercellular differences in metabolism and baseline esterase activities.

Animals↗

PubMed1993

Modification of mipafox-induced inhibition of neuropathy target esterase in neuroblastoma cells of human origin.

A neuroblastoma cell line of human origin was used as an in vitro model system to examine early effects on inhibition of neuropathy target esterase (NTE, also known as neurotoxic esterase) in the presence of agents belonging to classes of chemicals previously demonstrated to modify organophosphorus-induced delayed neuropathy in hens. For this study, differentiated SY-5Y cells were treated for up to 10 min with mipafox, an organophosphorus compound, and NTE inhibition was determined when cells exposed to mipafox were also exposed to the carbamate, aldicarb, and to the calcium channel blocker, verapamil. Cells were exposed to aldicarb or verapamil 5 min before, at the same time, or 2 min after mipafox. Less NTE inhibition was observed when either aldicarb or verapamil was included in the incubation of SY-5Y cells with mipafox. Effects of aldicarb and verapamil on NTE inhibition in differentiated SY-5Y cells were similar to effects in chicken brain homogenates. These results indicate that NTE inhibition can be detected in neuroblastoma cells, that these cells respond in a manner similar to chicken brain, and that mipafox-induced inhibition of NTE can be decreased in the presence of aldicarb or verapamil.

Aldicarb↗

PubMed1993

Relationship of neuropathy target esterase inhibition to neuropathology and ataxia in hens given organophosphorus esters.

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.

Animals↗

PubMed1993

Comparison of toxicities of acrylamide and 2,5-hexanedione in hens and rats on 3-week dosing regimens.

Survival rates, changes in body weight, gait/ataxia scores, and neuropathological lesions were compared between adult Long-Evans rats and adult White Leghorn hens given equivalent dosages of the peripheral neurotoxicants acrylamide and 2,5-hexanedione (12, 25, and 50 mg/kg acrylamide 3 times per week; or 75, 105, 150, 225, or 350 mg 2,5-hexanedione/kg/d, with hens receiving the lowest 3 dosages of 2,5-hexanedione and rats receiving the highest 3 dosages of this test compound). All rats survived the 3-wk acrylamide study period, although those given 50 mg/kg did not gain weight and showed alterations in gait. Hens given 50 mg/kg acrylamide were moribund by 2 wk and were sacrificed before the end of the 3-wk study period. By this time they had lost 29 +/- 3% of their body weight, but none showed significant renal or hepatic lesions on necropsy. Hens given all doses of acrylamide showed dose-related ataxia, weakness, and depression. Gait changes were seen in rats given the high dose of acrylamide for the 3-wk test period. Neuropathological studies revealed that both rats and hens given acrylamide had distal myelinated fibers with dose-related neurofilament-rich axonal swelling and Wallerian-like degeneration, better developed in the rodents. In addition, high-dose acrylamide rats had recent necrosis of cerebellar Purkinje cells. Deaths occurred in all groups of hens given 2,5-hexanedione (75, 105, or 150 mg/kg) before sacrifice at 3 wk, but all rats given 2,5-hexanedione (150, 225, 350 mg/kg) survived a 4-wk study period, even though gait changes were evident in the 225 and 350 mg/kg dosage groups by 3 wk. Neither hens nor rats dosed with 2,5-hexanedione for 3 wk had significant neuropathic lesions, although the hens showed dose-related ataxia, weakness, and depression. Early neurofilamentous intraaxonal masses in distal levels of selected myelinated tracts were seen in rats given the high dose of 2,5-hexanedione for an additional week. These studies suggest that hens are sensitive to acrylamide and 2,5-hexanedione toxicities, and that the rat is more likely than the hen to develop neuropathological lesions.

Acrylamide↗

PubMed1993

Differences between genetic stocks of chickens in response to acute and delayed effects of an organophosphorus compound.

The influence of genotypes of the major histocompatibility complex (MHC) on susceptibility to acute and delayed effects of an organophosphorus ester was measured in adult White Leghorn chickens from lines differing in response to sheep red blood cell (SRBC) antigen. Chickens from lines selected for high (HA) or low (LA) antibody response to SRBC and homozygous for B13B13 or B21B21 genotypes at the MHC were administered a single subcutaneous injection of diisopropyl phosphorofluoridate (DFP) at dosages of 0, 0.25, 0.50, or 1.0 mg/kg body weight using corn oil as the carrier. Criteria for toxicological responses included clinical, biochemical, and pathological measures. Clinical signs of acute cholinergic poisoning and delayed neuropathy were dose related. Brain and blood cholinesterase and carboxylesterase activities were more sensitive to inhibition by DFP than were liver cholinesterase and carboxylesterase activities. Cholinergic signs 3 h after administration of DFP were more pronounced in line HA than in line LA chickens. Pathological evidence of delayed neuropathy 2 wk after DFP administration was also more evident in HA than LA chickens. Although less pronounced than that for lines, differences in neurotoxic manifestations following DFP administration were greater for chickens of B21B21 than B13B13 genotypes. Activity of A-esterases, which hydrolyze organophosphorus esters without being inhibited by them, was lower in plasma of line HA than line LA chickens. Differences among the genotypes in activity of other esterases were not found in chickens not receiving DFP. These results indicated that responses of chickens to the neurotoxicant DFP were influenced by the background genome of the chickens.

Animals↗

PubMed1992

Development of a model cell culture system in which to study early effects of neuropathy-inducing organophosphorus esters.

Certain organophosphorus (OP) compounds produce a delayed neuropathy in man and susceptible animal species after early inhibition and aging of the enzyme, neurotoxic esterase (NTE). In this study, the human neuroblastoma cell line, SY-5Y, was used to examine the time course of inhibition and aging of NTE after toxicant treatment. The time course and extent of detrimental effects on this enzyme were similar in the SY-5Y cells to those observed in homogenized chicken brain tissue after the same treatments. The results indicate that the SY-5Y model system shows promise for use in the determination of initial mechanisms contributing to the development of organophosphorus-induced delayed neuropathy.

Animals↗

PubMed1992

Toxicity and toxicokinetics of carbaryl in chickens and rats: a comparative study.

Carbaryl, a carbamate insecticide, exerts its toxic effect in animals by inhibiting the activity of neural acetylcholinesterase. Differences in sensitivity of this enzyme to inhibition were studied after intraperitoneal administration to chickens and rats. A dose of 900 mg/kg to chickens and 70 mg/kg to rats caused equivalent inhibition of brain cholinesterase activities (57% +/- 6 and 47% +/- 4, respectively) 60 min after administration, which was the time of maximal cholinergic signs. Signs of toxicity (salivation, respiratory distress, muscle tremors and weakness) were more pronounced in rats than in chickens when brain acetylcholinesterase was inhibited to the same extent in both species. Carboxylesterase activities in brain, liver, and plasma were also inhibited 60 min after administration of carbaryl to chickens and rats. Activities of enzymes associated with hepatic microsomes were unaffected. Specific activities of brain esterases, including acetylcholinesterase, carboxylesterase and neurotoxic esterase, were higher in untreated chickens than in untreated rats. Specific activities of liver esterases (carboxylesterase, A-esterase) were, however, 4- and 10-fold lower in untreated chickens than in untreated rats. Total clearance of carbaryl in the chicken, determined after intravenous administration of 5 mg/kg, was 0.26 +/- 0.02 l/kg/min. This value is 5.7 times higher than that reported for the rat, indicating that the relatively lower activities of esterases in the liver of chickens did not affect the clearance of this chemical in the avian species.

Animals↗

PubMed1992

Comparative evolution of mipafox-induced delayed neuropathy in rats and hens.

Adult male Long-Evans rats and White Leghorn hens were given 30 mg/kg mipafox ip. Administration of this organophosphorus ester resulted in > or = 89% inhibition of brain and spinal cord neurotoxic esterase activity in both species 4 hr after dosing. Our sequential, comparative study of the bilateral mipafox-induced neuropathy in the medulla and cervical spinal cord in hens and rats demonstrated that the rats had well-developed, vacuolar axonopathic lesions in the fasciculus gracilis by post-dosing day 7. Severely affected rats with such lesions were noted through day 21, but not subsequently (days 28 and 35). The hen had a slower developing, but more severe, consistent and longer lasting neuropathy than the rat. In these birds, lesions in the medulla and rostral cervical spinal cord levels were more extensive, involving large regions of both the spinocerebellar tracts and fasciculus gracilis. Neuropathic changes, including myelinated fiber axonopathy and Wallerian-like degeneration, were prominent from days 14 - 35 in hens, and were associated with prominent gliosis in the later stages.

Animals↗

PubMed1992

Comparative dose-response studies of organophosphorus ester-induced delayed neuropathy in rats and hens administered mipafox.

A single injection of mipafox was administered to both Long-Evans hooded rats and White Leghorn hens in dosages which inhibited the activity of brain neurotoxic esterase 30-50%, 60-80%, or greater than 80% four hr after intoxication. All animals were monitored for clinical evidence of organophosphorus induced delayed neuropathy for 21 days, euthanatized, and regions of the nervous system were histologically evaluated. Only hens manifested clinical signs of neuropathy; however, light and electron microscopic lesions were present in the nervous systems of both species. In rats, these lesions were well developed in only the highest dosage group and confined to the rostral level of the fasciculus gracilis in the medulla oblongata. Swollen axons containing a single vacuole filled with flocculent material were the most prominent lesion in rats. Hens manifested more extensive and varied fiber breakdown in multiple spinal cord tracts, with the intensity of degeneration increasing with increasing dosages of mipafox. Both marked Wallerian-like degeneration and swollen axons filled with aggregates of cellular debris were observed in the nervous systems of hens. This study indicates that both rats and hens are susceptible to OPIDN. However, there are qualitative and quantitative differences in both clinical manifestations and histologic appearances between the two species.

Animals↗

PubMed1992

Role of socialization, stress and sex of chickens on response to anesthesia and on response to an organophosphate neurotoxicant.

The influence of socialization of chickens on response to exogenous substances in the presence and absence of stress was examined. Chickens of both sexes were habituated to human beings (socialized) by being talked to and offered food from the hand of the caretaker. After 19 w, half the socialized group and half the unsocialized group were subjected to stress (loud noises for 120 sec twice daily) for 2 w. At the end of this period, response to 37 mg pentobarbital/kg iv was evaluated by length of sleeping time. Males slept longer than females, and males that were socialized but not stressed slept significantly longer than other males. Stress and socialization did not significantly affect pentobarbital sleeping time in females. This indicated that response to pentobarbital was dependent on sex and on socialization, with the most notable effects occurring in socialized males. Socialized and nonsocialized, stressed and unstressed male and female chickens were also administered a single po dose of 360 mg tri-ortho-tolyl phosphate (TOTP)/kg. This organophosphorus ester induced a delayed neuropathy that caused ataxia in all the chickens. The ataxia was significantly more pronounced earlier in males than in females, although the sex difference became insignificant 18 d after dosing. Socialized chickens were ultimately more affected. Noise stress did not affect TOTP-induced ataxia. This indicated that response to an organophosphate neurotoxicant was also dependent on sex and socialization, with the most notable effects again seen in socialized males. Response to endogenous substances in chickens depends both on sex and on familiarity to humans.

Anesthesia↗

PubMed1991

A microassay method for neurotoxic esterase determinations.

A microtiter plate reader with an associated computer to average triplicate samples and subtract blanks was used for reading and calculating neurotoxic esterase (NTE, also known as neuropathy target esterase) activities in spinal cord regions of hens 4 hr after administration of diisopropylphosphorofluoridate (DFP, 0.5 mg/kg sc). Although NTE inhibition is an early indicator of organophosphorus ester-induced delayed neuropathy. DFP-induced inhibition was not greater in regions of the spinal cord where pathological changes are most notable. Acetylcholinesterase (AChE) activities and protein determinations were also done on these tissues using microassay methods. DFP-induced AChE inhibition was similar to NTE inhibition. In addition to the capability to be used for small regional esterase activity measurements, the microassay was advantageous because the number of samples incorporated into a single assay was increased and the time needed for the NTE assay was reduced by 50%. Total volume of incubate in each well was 0.3 ml; the incubate contained 1/20 quantities of sample and reagents necessary in more conventional assays. Validation of the microassay was performed by comparison with more conventional assays when measuring inhibition of NTE and AChE in brains of control and experimental hens of two different genetic strains (B13B13 and B21B21 white leghorns). Experimental birds were given DFP, 0.5 mg/kg sc, 24 hr before samples were collected. NTE activities in brains of control hens were similar using both types of NTE analytical procedures. Percentage inhibition of NTE caused by DFP was within 4% using both assay procedures in both strains of hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗

PubMed1990

Protease activity in brain, nerve, and muscle of hens given neuropathy-inducing organophosphates and a calcium channel blocker.

Activity of calcium-activated neutral protease (CANP or calpain), an enzyme responsible for degradation of axonal and muscle cytoskeletal elements, was determined in brain, sciatic nerve, and gastrocnemius muscle of hens given tri-ortho-tolyl phosphate (TOTP, 360 mg/kg po) or active congener phenyl saligenin phosphate (PSP, 2.5 mg/kg im) with and without a calcium channel blocker which ameliorated clinical signs of organophosphate-induced delayed neuropathy (nifedipine 1 mg/kg/day x 5). Calcium channel blocker administration was initiated 1 day prior to administration of organophosphate (OP). OP administration caused an increase in CANP activity in brain within 4 days and in sciatic nerve and gastrocnemius muscle within 2 days of administration. This increase did not occur if nifedipine was administered to PSP-treated hens. Total sciatic nerve calcium concentrations were also increased by PSP, but not until OP-treated hens were no longer being administered calcium blockers. This indicates that calcium channel blockers may contribute to amelioration of organophosphate-induced delayed neuropathy by attenuation of calcium-mediated disruption of axonal and muscle cytoskeletal homeostasis.

Animals↗

PubMed1990

A comparative study of drug metabolizing enzymes in adrenal glands and livers of rats and chickens.

1. Drug metabolizing enzymes (cytochrome P450, glutathione-S-transferase, carboxylesterase) were compared in livers and adrenal glands from rats and chickens. 2. Quantities of cytochrome P450 in chicken liver and adrenal glands were less than in rat liver and adrenals. 3. Activities of carboxylesterase and of glutathione-S-epoxide transferase were similar in livers of rats and chickens. 4. In the chicken, activities of carboxylesterase and of glutathione-S-epoxide transferase were less in adrenal glands than in livers. 5. Carboxylesterase enzyme activities in adrenal glands of chickens were more sensitive to inhibition by antiesterase agents than were carboxylesterase enzyme activities in liver.

Adrenal Glands↗

PubMed1990

Nerve conduction studies in chickens given phenyl saligenin phosphate and corticosterone.

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.

Action Potentials↗

PubMed1990

Modification of phenyl saligenin phosphate-induced delayed effects by calcium channel blockers: in vivo and in vitro electrophysiological assessment.

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.

Acetylcholine↗

PubMed1990

Use of the biventer cervicis nerve-muscle preparation to detect early changes following exposure to organophosphates inducing delayed neuropathy.

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.

Acetylcholine↗

PubMed1989

Effect of verapamil on organophosphorus-induced delayed neuropathy in hens.

Verapamil, a calcium channel blocker, was administered to adult white leghorn hens to determine if inhibition of calcium entry could alter delayed neuropathy induced by administration of phenyl saligenin phosphate (PSP). Verapamil was given im in doses of 7 mg/kg/day for 4 days beginning 24 hr before administration of PSP (2.5 mg/kg im). Ataxia was less pronounced in hens given PSP plus verapamil than in hens given PSP alone during observations made 8-28 days after PSP administration. Myelinated fiber lesions were less extensive and regeneration more notable in the biventer cervicis nerve in chickens given PSP plus verapamil, with samples obtained both 17 and 28 days after PSP. In the absence of verapamil, rheobase and chronaxie values of strength-duration curves were higher and shorter, respectively, and sensitivity to acetylcholine was increased in biventer cervicis nerve-muscle preparations from hens given PSP. Verapamil did not alter PSP-induced inhibition of neurotoxic esterase, indicating that the mechanism involved in amelioration of these indices of delayed neuropathy was not associated with initial enzyme inhibition caused by this organophosphorus ester.

Acetylcholine↗