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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Depressive behavioral effects of acetylcholine (10 mug ivtr) and physostigmine (0.3 mg/kg ip), and prolongation of the duration of electrogenic seizures produced by the drugs were prevented by intraperitoneal or intraventricular administration of FDP (0.5 mg/kg or 5 mug resp.). The peptides did not affect the brain acetylcholine level and did not influence the inhibitory effect of physostygmine on AChE activity.
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PMID:Influence of fibrinogen degradation products (FDP) on the central action of acetylcholine. 101 88

The present review was designed to integrate both experimental and clinical data and to focus on the problems of management of severe cases of acute organophosphate poisoning, which always show CNS involvement. AChE activity, in discrete regions of the human brain, was studied by quantitative histochemistry of 40 mu thick sections. The regional effects of AChE inhibition by organophosphates was examined in a comparative study of the brains of two victims and two control brains, matched for age and sex. The pattern of AChE inhibition was regionally selective. The most significant decreases were observed in the neocerebellum, thalamic nuclei and the cortex. This specific distribution of AChE inhibition may be correlated with some of the clinical characteristics of acute organophosphate poisoning. The diagnostic value of blood AChE levels was examined in a personal series of 53 patients, who needed artificial ventilation, intensive care monitoring and antidotal treatment. The effects and side-effects of the antidotal treatment were reassessed. Recommended regimen of therapy was outlined, based upon experience in this series and in recent animal studies. The logical therapy would be and almost always in the co-administration of an anticholinergic drug (usually atropine) and an AChE reactivator (oximes) in order to rapidly obtain the most beneficial effect in the critically ill patient. Seizures that do not respond to the specific antidotal therapy, should be treated with I.V. benzodiazepines. Artificial respiration and supportive measures are essential for patient' survival. They enable the patient to gain the necessary time for sufficient recovery of AChE activity.
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PMID:CNS involvement in acute organophosphate poisoning: specific pattern of toxicity, clinical correlates and antidotal treatment. 306 84

The ability of NBQX, a potent antagonist of AMPA glutamatergic receptors, to prevent or stop seizures induced by the organophosphate soman, an irreversible inhibitor of AChE, was studied in rats. NBQX administered concomitantly with soman prevents the onset of seizures (ED50: 29.2 mg kg-1, i.p.). Administered 5 min after the onset of seizures, NBQX greatly reduces the intensity of the epileptic activity. The same decrease of epileptic activity is observed, in the presence of atropine, when the administration of NBQX is delayed 15 min after the onset of seizures. NBQX thus appears as a promising antiepileptic candidate against soman-induced seizures. The roles of AMPA and muscarinic receptors in the onset and propagation of soman-induced epileptic activity are discussed.
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PMID:Antiepileptic effects of NBQX against soman-induced seizures. 800 67

We have assessed the efficacy of MAP-2 immunohistochemistry as a marker of seizure-related brain damage and its suitability for quantitation of the damage using densitometric and morphometric image analysis. Seizures were produced in rats by administration of 1.5 LD50 soman, an irreversible AChE inhibitor. Our results demonstrate that neuronal damage, assessed using hematoxylin and eosin, and cresyl violet staining, was colocalized on adjacent serial sections with clearly demarcated reductions in MAP-2 staining. The most severely damaged brain regions were devoid of MAP-2 staining. Reductions in MAP-2 immunostaining were found to be exceptionally well suited for quantitation using densitometric and morphometric image analysis. This study represents the first demonstration of seizure-induced excitotoxic alterations in MAP-2.
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PMID:Microtubule-associated protein 2 (MAP-2): a sensitive marker of seizure-related brain damage. 861 22

Associations between tissue residues and toxicity to aquatic organisms were examined to evaluate the applicability of the critical body residue (CBR) approach across different chemical classes. Chemical classes and mode of action categories evaluated included narcotics (polar and nonpolar), excitatory agents, AChE inhibitors, reactives/irritants, CNS seizure agents, aryl hydrocarbon (Ah) receptor agonists, and inorganic metals and organometals. This evaluation indicated that empirical data do not support broad application of the CBR concept across chemical classes. This conclusion is particularly important for polar and nonpolar narcotics because the CBR concept was specifically developed for these chemical classes. The variability observed in tissue residues between chemicals within a given mode-of-action class appears to be generally of the same order of magnitude as the variability of aqueous measures of toxicity such as LC50 values (Table 3; Fig. 10). This observation suggests that either (a) the reported tissue residues were dependent on the aqueous dosing regime; (b) the tissue measurements do not accurately reflect the internal dose at target organs with substantially greater precision than water exposure measurements; or (c) many of the same sources of variability associated with aqueous exposures, such as chemical structure, individual species sensitivity, biotransformation processes, and lipid content, also apply to tissue-based measures of exposure. An additional source of uncertainty of CBRs is whether a chemical has been correctly assigned to a mode of action category. [figure: see text] The CBR approach outlined by McCarty (1986, 1987) and McCarty et al. (1993) underlines an important concept in aquatic toxicology, i.e., that internal chemical dose is the true measure of toxicity for many chemicals rather than imputed dose based on aqueous exposure. Nevertheless, without more refined and accurate examination of that actual internal dose and without additional consideration of differences in sensitivity between species, differences in toxic potency between chemicals, and differences in toxicity of environmentally modified or biotransformed compounds, the CBR approach may not offer practical advantages over conventional media-based exposure assessment.
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PMID:Association between contaminant tissue residues and effects in aquatic organisms. 1177 48

Acetylcholinesterase (AChE, EC3.1.1.7) functions in nerve impulse transmission, and possibly as a cell adhesion factor during neurite outgrowth. These functions predicted that a mouse with zero AChE activity would be unable to live. It was a surprise to find that AChE -/- mice were born alive and survived an average of 14 days. The emaciated appearance of AChE -/- mice suggested an inability to obtain sufficient nutrition and experiments were undertaken to increase caloric intake. Pregnant and lactating dams (+/-) were fed 11% high fat chow supplemented with liquid Ensure. AChE -/- pups were weaned early, on day 15, and fed liquid Ensure. Although nullizygous animals showed slow but steady weight gain with survival over 1 year (average 100 days), they remained small at all ages compared to littermates. They demonstrated delays in temperature regulation (day 22 vs. 15), eye opening (day 13 vs. 12), righting reflex (day 18 vs. 12), descent of testes (week 7-8 vs. 4), and estrous (week 15-16 vs. 6-7). Significant physical findings in adult AChE -/- mice included body tremors, abnormal gait and posture, absent grip strength, inability to eat solid food, pinpoint pupils, decreased pain response, vocalization, and early death caused by seizures or gastrointestinal tract ileus. Behavioral deficits included urination and defecation in the nest, lack of aggression, reduced pain perception, and sexual dysfunction. These findings support the classical role for AChE in nerve impulse conduction and further suggest that AChE is essential for timely physical development and higher brain function.
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PMID:Rescue of the acetylcholinesterase knockout mouse by feeding a liquid diet; phenotype of the adult acetylcholinesterase deficient mouse. 1212 53

The nerve agent soman, a powerful inhibitor of acetylcholinesterase (AChE; EC 3.1.1.7), causes an array of toxic effects in the central nervous system. Adamantyl tenocyclidine derivative Tamorf (1-[2-(2-thienyl)-2-adamantyl] morpholine), a compound with potential activity at the N-methyl-D-aspartate (NMDA) receptors and with neuroprotective properties, is effective against convulsions and brain lesions related to soman poisoning. The objective of this study was to evaluate the antidotal potency of Tamorf (2.5 mg kg(-1)), which was tested alone as a pretreatment or in combination with atropine (10.0 mg kg(-1)) as a therapy in rats poisoned with two different sub-lethal doses of soman (1/4 and 1/2 of LD50). The effect of Tamorf was compared with carbamate physostigmine (0.1 mg kg(-1)). The study also determined the possible genotoxic effects of Tamorf and physostigmine, especially primary DNA damage in white blood cells, liver and brain tissue. Tamorf administered 5 min before poisoning stopped soman-induced seizures, was successful against sub-lethal doses of soman and protected AChE activity in the brain (P = 0.0014, P = 0.0019), and in plasma (P = 0.0464, P = 0.0405). Compared with Tamorf, physostigmine was slightly effective in the elimination of soman-induced poisoning in rats. The pharmacological effect of Tamorf and atropine was less effective as therapy, but did not increase soman toxicity (P > 0.05 for all interactions). The results obtained indicate that Tamorf and physostigmine are not genotoxic to rats in the concentrations tested. Treatment with Tamorf seems to be a good alternative for current pretreatment in soman poisoning. Its antidotal mechanism is complex and is based on combined biochemical and receptor properties.
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PMID:Evaluation of antidotal effects of adamantyl derivative Tamorf in soman poisoning. 1616 15

The phenotypes of three mouse strains that carry the acetylcholinesterase knockout (AChE KO) mutation have been compared. The AChE KO mouse was developed from embryonic stem (ES) cells, originating from a 129/Sv blastocyst. Animals generated from strain 129/Sv suffer from dysgenesis of the corpus callosum and possibly a number of other neuroanatomical deficiencies. To determine the contribution of background genes to phenotype, 129/Sv AChE heterozygote (AChE+/-) mice were backcrossed 10 generations with wild-type inbred C57/BL6 (C57) mice and with wild-type outbred CD1(R) mice. AChE-/- mice in strains C57 and CD1died during seizures before postnatal day (P) 21, whereas mice in strain 129/Sv lived to adulthood.
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PMID:Phenotype comparison of three acetylcholinesterase knockout strains. 1719 42

Organophosphate (OP) poisoning poses great danger to both military and civilian populations. OP-induced brain injury is characterized by rapid loss of consciousness, seizures, central respiratory inhibition as well as long-term behavioral changes in sub-lethal injuries. The pharmacological treatment of OP poisoning is based on anticholinergic and anticonvulsant drugs as well as oximes, which reactivate the non-aged inhibited enzyme. The commonly used oximes are quaternary compounds with questionable capacity to penetrate through the blood-brain barrier. This implies that the main beneficial effect of oximes may result from reactivation of AChE activity in respiratory muscles rather than in the brain. Importantly, data accumulated over the last few decades suggests a potential beneficial role for oximes in the brain, despite their polarity. Albeit the concentration of oximes in the central nervous system is significantly lower than in the plasma, they do gain access into the brain and are able to reactivate inhibited local AChE. Oximes may also attenuate OP-induced brain insult via different mechanisms other than AChE reactivation. In this review, we focus on the ability of oximes to act in the brain and protect the central nervous system from OP-induced injury, either by direct reactivation of AChE or by other pharmacological mechanisms. While this is a poorly investigated field we believe that the data supports the potential role of oximes in mitigating OP-induced neuronal injury, thus making them valuable in the treatment of severe casualties.
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PMID:The possible use of oximes as antidotal therapy in organophosphate-induced brain damage. 1915 Apr 63

Studies were conducted to investigate relationships among soman (pinacolyl methylphosphonofluoridate) induced seizure activity, central metabolic impairments and lethality in normal vs thyroid-deficient rats. Quantitative cytophotometric measurements of individual cerebrocortical (layer V) and striatal neuron RNA contents were made following dosages of 0.5, 0.9 and 1.5 LD(50) soman (LD(50) = 135 ?g/kg, sc). Hypothyroidism was associated with a marked diminution of overt convulsive activity and reduced susceptibility to lethal actions of soman as indicated by enhanced 24- and 48-h survival rates at 0.9, 1.2 and 1.5 LD(50). Hypothyroidism per se produced RNA depletion in both cortical and striatal neurons. Soman treatment diminished cortical RNA to essentially the same extent in thyroid-deficient rats as in euthyroids, whereas there was no further reduction of striatal neuron RNA. It was found that amelioration of convulsive activity and lethal- ity in hypothyroid rats was accompanied by reduced cerebral acetylcholinesterase (AChE, EC 3.1.1.7) inactivation, and that plasma cholinesterase (EC 3.1.1.8) and aliesterase (EC 3.1.1.1) levels were significantly higher in hypothyroid than in euthyroid saline-control rats. The overall data indicate that soman- induced central metabolic impairments can occur independent of paroxysmal neural activity and lethal actions of the agent. Resistance to soman observed with thyroid deficiency may be due in large part to increased binding to plasma enzymes and diminished delivery of soman to AChE in vital cholinergic sites.
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PMID:Soman intoxication in hypothyroid rats: alterations in brain neuronal RNA, acetylcholinesterase and survival. 2049 25


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