Coenzyme q10 confers cardiovascular protection against acute mevinphos intoxication by ameliorating bioenergetic failure and hypoxia in the rostral ventrolateral medulla of the rat

Coenzyme Q10 (CoQ10, ubiquinone) is a highly mobile electron carrier in the mitochondrial respiratory chain that also acts as an antioxidant. We evaluated the cardiovascular protective efficacy of CoQ10 at the rostral ventrolateral medulla (RVLM), a medullary site where sympathetic vasomotor tone originates and where the organophosphate poison mevinphos (Mev) acts to elicit cardiovascular intoxication. Experiments were carried out in adult male Sprague-Dawley rats that were maintained under propofol anesthesia. Microinjection bilaterally of Mev (10 nmol) into the RVLM induced progressive hypotension and minor bradycardia, alongside significant depression of the activity of NADH cytochrome c reductase (enzyme marker for Complexes I and III) or cytochrome c oxidase (enzyme marker for Complex IV) in the mitochondrial respiratory chain, reduction in ATP concentration, or tissue hypoxia in the RVLM. On the other hand, the activity of succinate cytochrome c reductase (enzyme marker for Complexes II and III) remained unaltered. The Mev-induced hypotension, bioenergetic failure, or hypoxia was significantly reversed when CoQ10 (4 microg) was coadministered bilaterally into the RVLM with the organophosphate poison. We conclude that CoQ10 confers cardiovascular protection against acute Mev intoxication by acting on the RVLM, whose neuronal activity is intimately related to the "life-and-death" process. We also showed that amelioration of the selective dysfunction of respiratory enzyme Complexes I and IV in the mitochondrial respiratory chain, the reduced ATP level, and the induced tissue hypoxia in the RVLM are among some of the underlying mechanisms for the elicited protection.

Spectral changes in systemic arterial pressure signals during acute mevinphos intoxication in the rat

We investigated the cardiovascular consequences of acute intoxication by the organophosphate poison, mevinphos (Mev), and delineated the underlying mechanism. Based on on-line power spectral analysis of systemic arterial pressure (SAP) signals in rats anesthetized and maintained by propofol, we identified two distinct phases after intravenous administration of Mev (160 or 320 microg/kg). Phase I was characterized by transient hypertension and mild tachycardia, concurrent with an increase in the very high-frequency (BVHF; 5-9 Hz), high-frequency (BHF; 0.8-2.4 Hz), low-frequency (BLF; 0.25-0.8 Hz),and very low-frequency (BVLF; 0-0.25 Hz) components of SAP signals. Phase II exhibited significant hypotension, a reversal of the BVHF and BVLF power to control levels, and further reduction in the power density of both BHF and BLF components to below baseline. Microinjection of Mev (2 microg) into the bilateral nucleus reticularis ventrolateralis (NRVL), the medullary origin of sympathetic neurogenic vasomotor tone, essentially duplicated those phasic cardiovascular changes. Similarly, sympathoexcitatory NRVL neurons exhibited respectively an elevation and a decline in their spontaneous activities during Phase I and Phase II Mev intoxication. We conclude that the progressive accumulation of acetylcholine over time induced by a direct inhibition of Mev on cholinesterase in the NRVL may be responsible for the phasic changes in cardiovascular events over the course of acute Mev intoxication. Whereas the initial amount of acetylcholine is excitatory to NRVL neurons, overstimulation by the amassed acetylcholine results instead of an inhibitory action.

[Importance of reactivation of fosdrin-inhibited acetylcholinesterase in the brain and diaphragm for the in vivo therapeutic effect of oximes in rats poisoned with fosdrin]

BACKGROUND

The composition of the causal antidotal therapy of subjects, poisoned with organophosphorus insecticides, has not been satisfactorily solved till now in spite of the knowledge of the basic mechanism of action of these toxic substances. The purpose of this study is to evaluate which of currently used or perspective acetylcholinesterase reactivators seems to be the most efficacious to protect poisoned subjects.

METHODS AND RESULTS

In experiments on white laboratory rats, the reactivating efficacy of selected acetylcholinesterase reactivators (oximes), administered at equimolar doses, was evaluated in target tissue of toxic effects of organophosphorus insecticides (diaphragm, brain) and compared with their therapeutic efficacy in the case of prophylactic administration with the help of the evaluation of mean efficacy dose of oximes, possible to protect rats exposed to supralethal dose of organophosphorus insecticide fosdrin for 24 hours. Our findings confirm that there are not statistically significant differences in reactivating and therapeutic efficacy of oximes tested against fosdrin in rats.

CONCLUSIONS

The perspective acetylcholinesterase reactivators (H oximes) seem to be as suitable as currently used oximes for the therapy of acute poisonings with organophosphorus insecticides although they are not significantly more efficacious than currently used oximes as in the case of the treatment of poisoning with highly toxic organophosphorus compounds.

A comparison of the efficacy of new monopyridinium oximes with the oxime HI-6 against mevinphos in mice

1. The therapeutic efficacy of three new monopyridinium oximes (2,4-PAEtM, 2,5-PAEtM, 2,5-PAAM) and the bispyridinium oxime HI-6 was evaluated in combination with benactyzine against acute poisoning with the organophosphorus insecticide mevinphos in mice. 2. When mice were treated two min after mevinphos poisoning, no significant differences in the therapeutic effectiveness of tested oximes were observed. They increased the 24h LD50 values of mevinphos about three times in comparison with non-treated intoxicated animals. 3. On the other hand, there were significant differences in their therapeutic efficacy when they were administered 30 sec following mevinphos challenge. The monopyridinium oxime 2,5-PAEtM seems to be the most efficacious against mevinphos toxicity. 4. Use of new monopyridinium oxime 2,5-PAEtM appears to be the improvement in the antidotal treatment of poisoning with organophosphorus insecticide mevinphos in comparison with HI-6.

Positron emission tomography scan in cortical visual loss in patients with organophosphate intoxication

OBJECTIVE

To determine the cerebral metabolism of patients with cortical visual loss.

DESIGN

Two observational case studies.

TESTING

Two patients who survived acute organophosphate poisoning with respiratory failure experienced severe visual loss despite relatively normal ophthalmic examination results. Magnetic resonance imaging of the brain revealed no abnormality of the visual system in either patient. Positron emission tomography (PET) was performed in these 2 patients and in 12 normal subjects with fluorine-18 fluorodeoxyglucose (FDG) as a tracer to measure cerebral glucose metabolism for the estimation of neurologic deficit in the visual cortex.

MAIN OUTCOME MEASURES

The FDG uptake values were measured as nanoCurie per cubic centimeters of tissue (nCi/cc). The relative uptake index in visual cortex was computed as the ratio of uptake of FDG in each region of visual cortex to that of cerebellum (regional visual cortex/cerebellum).

RESULTS

Hypometabolism was observed in the visual cortex of both patients. The relative uptake index of FDG in visual cortex (visual cortex/cerebellum) was significantly decreased in those patients compared with normal subjects.

CONCLUSIONS

In patients with cortical visual loss, conventional neuroimaging techniques can fail to visualize damage that can be detected by PET scanning, and PET analysis may be helpful in estimating the metabolic deficit of visual cortex and in establishing the organic nature of cortical visual loss in these patients.

[Comparison of the effect of selected cholinesterase reactivators combined with atropine on soman and fosdrin toxicity in mice]

The efficacy of cholinesterase reactivators tetroxime, HI-6 and obidoxime in combination with atropine against highly toxic organophosphate soman as well as organophosphorus insecticide fosdrin was evaluated in male mice using median lethal dose (LD50) for 48 hours. Oxime HI-6 appears to be considerably more effective than tetroxime as well as obidoxime for the treatment of acute poisonings by soman or fosdrin, although the difference in effect is not significant in the case of poisoning by fosdrin. These findings suggest that HI-6 has definite advantage over obidoxime as well as tetroxime in the treatment of poisoning with not only highly toxic organophosphates but also organophoshorus insecticides.

[Comparison of the therapeutic effectiveness of selected cholinesterase reactivators with atropine in acute fosdrine poisoning in mice]

In experiments on male mice, the effect of the cholinesterase reactivators obidoxime, methoxime and HI-6 in combination with atropine sulfate on the acute intoxication with the organophosphorous insecticide fosdrine was tested in dependence on the period of administration of drugs after intoxication and on the dose of oxime by influencing the LD50 value in 48-hour survival of experimental animals. It has been demonstrated that the rate of the therapeutic intervention is a much more important factor influencing the effect of oximes than the dose of oximes. A shortening of the period of drug administration from 2 minutes to 30 seconds substantially increases the effects of all three oximes. A comparison of the effects of all three reactivators has shown that the oxime HI-6 is significantly more effective than the remaining two reactivators in the case of therapy of intoxication 30 seconds after the application of the noxa. In the therapy of intoxication 2 minutes after the exposure of experimental animals to fosdrine, the effect of the antidotal therapy was relatively low regardless of the selected oxime.

Acute pancreatitis following organophosphate intoxication

BACKGROUND

Acute pancreatitis as a complication of organophosphate intoxication has been infrequently addressed. Previous reports have suggested that acute pancreatitis may follow the oral ingestion of several organophosphates, including parathion, malathion, difonate, coumaphos, and diazinon, or after cutaneous exposure to dimethoate. No cases of acute pancreatitis following mevinphos (CAS 7786-34-71) poisoning have been reported to date. The possible pathogeneses of the pancreatic insult in organophosphate intoxication are excessive cholinergic stimulation of the pancreas and ductular hypertension.

CASE REPORT

We describe a patient presenting with painless acute pancreatitis following an intentional ingestion of large amounts of mevinphos. Serum amylase and lipase values were increased and determination of amylase isoenzymes confirmed a pancreatic origin. A computerized tomograph of the abdomen showed diffuse swelling of the pancreas. The patient was discharged after a seven week clinical course, complicated by a delayed neuropathy.

CONCLUSIONS

As acute pancreatitis in organophosphate intoxication may be more common than reported, serum pancreatic enzymes and appropriate imaging studies should be more liberally utilized. Early recognition and appropriate therapy for acute pancreatitis may lead to an improved prognosis.

Centers for Disease Control and Prevention (CDC). Occupational pesticide poisoning in apple orchards--Washington, 1993

During July-December 1993, the Washington Department of Health (WDOH) received and conducted follow-up investigations of 26 reports of occupational illness related to exposure to mevinphos (Phosdrin), an organophosphate (OP) insecticide. The reports involved illnesses during June 13-August 18, 1993, in persons working in 19 different apple orchards; all involved use of mevinphos to control apple aphids. This report summarizes the results of these investigations by WDOH.

Chromatographic analysis of cis- and trans-mevinphos in poisoned wildlife

A method is described for the analysis of the cis- and trans-isomers of mevinphos in baits and avian tissues. The procedure involves extraction of the mevinphos isomers with acetone-dichloromethane (1:1) followed by clean-up on alumina. Bait samples were initially screened by thin-layer chromatography and identity of extracts confirmed by infrared spectrophotometry and gas chromatography-mass spectrometry.

Clinical confirmation of organophosphate poisoning by serial cholinesterase analyses

Three groups of agricultural workers with a history of exposure to organophosphate pesticides were followed up to evaluate the utility of sequential postexposure cholinesterase analyses to confirm organophosphate intoxication in the absence of baseline cholinesterase values. Three or more cholinergic symptoms were reported by 50 of the 72 patients. Initial plasma and red blood cell cholinesterase values of 45 of the workers were above the lower limit of the laboratory normal range. Follow-up examinations, including cholinesterase analyses, were conducted on 57 patients. When final postexposure cholinesterase determinations were taken as estimates of individual normal baseline values, the plasma and red blood cell activity of the three groups was shown to have been inhibited. The data support the use of sequential postexposure plasma cholinesterase analyses to confirm the diagnosis of organophosphate-induced illness in the absence of baseline values.

Rapid death by mevinphos poisoning while under observation

A case report of fatal ingestion of mevinphos with several points of interest: There was a known ingested dosage of 28 g. Several observers witnessed events from ingestion to death. Death was rapid--apparently within 1 min and certainly within 14 min.

Observations on the accidental poisoning of birds by organophosphate insecticides and other toxic substances

Details of cases involving the inadvertent exposure of birds to eight toxic substances are recorded. The organophosphate insecticides dichlorvos, diazinon and malathion produced respiratory symptoms which in the former and latter cases were initially thought to be caused by infectious disease. Birds which consumed feed containing fenitrothion showed nervous signs before death. On three separate occasions feral starlings (Sternus vulgaris) were found dead and their gizzard contents contained mevinphos. The rodenticide warfarin was associated with petechial haemorrhages in the skeletal muscles and on the serosal surfaces of one hen. Cyanogenic glycosides from Eucalyptus cladocalyx were responsible for the sudden deaths of ducks and guinea fowl. 'Ornamental dough' containing sodium chloride was fed to birds which were deprived of water and they showed diarrhoea and nervous disorders before death.

Electroretinographic study of the white mouse intoxicated by organo-phosphorus: mevinphos and malathion

Evidence is given that the organo-phosphates mevinphos and malathion perturb the retinal functioning of the white mouse by acting 1. directly on the photoreceptors; 2. by a synaptolytic effect due to the inhibition of cholinesterases; 3. likely by a damage of the bipolar and/or the ganglion neurones.

[Disturbance of equilibrium due to poisoning with organophosphate pesticides (author's transl)]

An organic phosphate insecticide poisoning is described, and the otologic findings elaborated. Disturbances of equilibrium were observed through a four-month period and documented by electronystagmography. Although damage of the central vestibular system was found, subjective complaints by the patient resolved completely within four months of the poisoning. However, thereafter both positional nystagmus and nystagmus after passive movements of the head could be observed. During the entire study period, neither hearing loss nor tinnitus occurred. After a review of the literature, the disturbances of equilibrium were designated as a sequela of the organic phosphate insecticide poisoning.

The effects of mevinphos on appetitive operant behavior in the gerbil

The need for study of the effects on performance of non-lethal organophosphate insecticide exposure is founded on many reports of behavioral difficulties in aerial applicators following exposure. In this study, a different pair of gerbils served in each of the following schedules of reinforcement: FR 25, FR 75, DRL 12-sec, DRL 20-sec, and VI 1-min. Baseline performance in these tasks tended to be comparable to that of more common laboratory species, but was more variable in the case of the VI 1-min task. Mevinphos doses of 0.20 mg/kg and above produced observable somatic signs of poisoning and also produced dose-related decrements in performance in FR and VI tasks. Performance in the DRL schedule was affected only at a dose of 0.30 mg/kg. No performance deficits or overt somatic signs of poisoning were present at mevinphos doses of 0.10 mg/kg or lower. These results do not agree with those of an earlier study which decrements in VI performance of pigeons and squirrel monkeys appeared at low mevinphos doses which did not produce overt somatic signs of poisoning. The possibility of variations in mevinphos effect as a function of species and task was discussed.