Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.8 (cholinesterase)
12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

2-Chloroethylphosphonic acid (ethephon) as the dianion phosphorylates butyrylcholinesterase (BChE) at its active site. In contrast, the classical organophosphorus esterase inhibitors include substituted-phenyl dialkylphosphates (e.g., paraoxon) with electron-withdrawing aryl substituents. The chloroethyl and substituted-phenyl moieties are combined in this study as 2-chloro-1-(substituted-phenyl)ethylphosphonic acids (1) to define the structure--activity relationships and mechanism of BChE inhibition by ethephon and its analogues. Phenyl substituents considered are 3- and 4-nitro, 3- and 4-dimethylamino, and 3- and 4-trimethylammonium. Phosphonic acids were synthesized via the corresponding O,O-diethyl phosphonate precursors followed by deprotection with trimethylsilyl bromide. They decompose under basic conditions about 100-fold faster than ethephon to yield the corresponding styrene derivatives. Electron-withdrawing substituents on the phenyl ring decrease the hydrolysis rate while electron-donating substituents increase the rate. The 4-trimethylammonium analogue has the highest affinity (K(i)=180 microM) and potency (IC(50)=19 microM) in first binding reversibly at the substrate site (possibly with stabilization in a dianion--monoanion environment) and then progressively and irreversibly inhibiting the enzyme activity. These observations suggest dissociation of chloride as the first and rate-limiting step both in the hydrolysis and by analogy in phosphorylation of BChE by bound at the active site.
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PMID:Novel irreversible butyrylcholinesterase inhibitors: 2-chloro-1-(substituted-phenyl)ethylphosphonic acids. 1188 91

Biosensors based on acetyl cholinesterase (AChE) inhibition have been known for monitoring of pesticides in food and water samples. However, strong inhibition of the enzyme is a major drawback in practical application of the biosensor which can be overcome by reactivation of the enzyme for repeated use. In the present study, enzyme reactivation by oximes was explored for this purpose. Two oximes viz., 1,1'-trimethylene bis 4-formylpyridinium bromide dioxime (TMB-4) and pyridine 2-aldoxime methiodide (2-PAM) were compared for the reactivation of the immobilized AChE. TMB-4 was found to be a more efficient reactivator under repeated use, retaining more than 60% of initial activity after 11 reuses, whereas in the case of 2-PAM, the activity retention dropped to less than 50% after only 6 reuses. Investigations also showed that reactivation must be effected within 10 min after each analysis to eliminate the ageing effect, which reduces the efficiency of reactivation.
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PMID:Reactivation of immobilized acetyl cholinesterase in an amperometric biosensor for organophosphorus pesticide. 1200 12

The acute lethal interaction that occurs in rodents when high doses of a peripherally restricted cholinesterase inhibitor, pyridostigmine bromide (PB), and the insect repellent N, N-diethyl-m-toluamide (DEET) are combined was first described during studies of chemical mixtures that were targeted as potential causative agents of Gulf War illnesses. This study was intended to provide insight into possible mechanisms of that lethal interaction. Following a single intraperitoneal injection of PB (2 mg/kg) and/or DEET (300 or 500 mg/kg), respiratory activity was measured in conscious freely moving rats using whole-body plethysmography. Cardiovascular function was also monitored simultaneously through an arterial catheter. PB (2 mg/kg) given alone stimulated respiration and increased blood pressure. Arterial pH levels were decreased, whereas pO(2) and pCO(2) remained at control levels. Administration of DEET (300 mg/kg) alone increased tidal volume and decreased blood pressure. Blood gases and pH levels were unaltered. A higher dose of DEET (500 mg/kg) also decreased respiratory and heart rate. Coadministration of PB (2 mg/kg) and DEET (300 mg/kg) increased tidal volume, decreased arterial pH, and elevated pCO(2). Heart rate and blood pressure declined progressively after drug coadministration. Pretreatment with atropine methyl nitrate (AMN), a peripherally selective competitive antagonist at nicotinic and muscarinic receptor sites, reduced the individual effects of PB or DEET, and significantly increased survival after coexposure to these agents. Although changes in respiratory function may have contributed to the lethal interaction, it was concluded that the primary cause of death was circulatory failure.
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PMID:Cardiorespiratory effects following acute exposure to pyridostigmine bromide and/or N,N-diethyl-m-toluamide (DEET) in rats. 1217 30

This study was designed to investigate the effects of the cholinesterase inhibitors soman and pyridostigmine bromide (PB) on synaptic transmission in the CA1 field of rat hippocampal slices. Soman (1-100 nM, 10-15 min) decreased the amplitude of GABAergic postsynaptic currents (IPSCs) evoked by stimulation of Schaffer collaterals and recorded from CA1 pyramidal neurons. It also decreased the amplitude and frequency of spontaneous IPSCs recorded from pyramidal neurons. Whereas the maximal effect of soman on evoked GABAergic transmission was observed at 10 nM, full cholinesterase inhibition was induced by 1 nM soman. After 10-15-min exposure of hippocampal slices to 100 nM PB, GABAergic transmission was facilitated and cholinesterase activity was not significantly affected. At nanomolar concentrations, soman and PB have no direct effect on GABA(A) receptors. The effects of soman and PB on GABAergic transmission were inhibited by the m2 receptor antagonist 11-[[[2-diethylamino-O-methyl]-1-piperidinyl] acetyl]-5,11-dihydrol-6H-pyridol[2,3-b][1,4]benzodiazepine-6- one (1 nM) and the m3 receptor antagonist 4-diphenylacetoxy-N-methyl-piperidine (100 nM), respectively, and by the nonselective muscarinic receptor antagonist atropine (1 microM). Thus, changes in GABAergic transmission are likely to result from direct interactions of soman and PB with m2 and m3 receptors, respectively, located on GABAergic fibers/neurons synapsing onto the neurons under study. Although the effects of 1 nM soman and 100 nM PB were diametrically opposed, they only canceled one another when PB was applied to the neurons before soman. Therefore, PB, acting via m3 receptors, can effectively counteract effects arising from the interactions of soman with m2 receptors in the brain.
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PMID:Low concentrations of pyridostigmine prevent soman-induced inhibition of GABAergic transmission in the central nervous system: involvement of muscarinic receptors. 1249 May 99

The physiological changes that occur with increasing age can have significant effects on the pharmacokinetics of neuromuscular-blocking drugs. Changes in cardiac output can affect drug distribution and therefore the speed of onset of neuromuscular block. A decrease in muscle mass and increase in body fat with age can also affect their distribution. The deterioration in renal and hepatic function associated with aging affects the clearance and elimination of many neuromuscular-blocking drugs. The effects of these physiological changes on the pharmacokinetics of neuromuscular-blocking agents may not become apparent clinically in healthy individuals until the age of at least 75 years. There is very little evidence to suggest any alteration in the sensitivity of the neuromuscular junction to neuromuscular-blocking drugs with increasing age. Neuromuscular-blocking drugs that undergo a significant degree of organ-dependent elimination, such as pancuronium bromide, vecuronium bromide, rocuronium bromide and doxacurium chloride, may have a significantly prolonged duration of action in elderly patients. These drugs can be used safely in elderly patients if the anaesthetist is aware of their altered pharmacokinetics in this patient group. Appropriate changes must be made to drug dosage and dose intervals. As the pharmacokinetic changes can be unpredictable, monitoring of neuromuscular block is strongly advised when using these drugs in such patients. The risk of residual block occurring postoperatively after the use of pancuronium bromide increases with age. The duration of action of mivacurium chloride may also be prolonged in the elderly; this change has not been demonstrated to be a result of an alteration in plasma cholinesterase activity. In contrast, there is no evidence of an alteration in the action of suxamethonium chloride (succinylcholine chloride) with increasing age. Atracurium besilate and cisatracurium besilate undergo predominantly organ-independent elimination. Onset of block with these two drugs may be prolonged in the elderly, but their clinical duration of action does not alter significantly with age, making them particularly suitable for use in this patient group. Although atracurium besilate may cause histamine release, there is little evidence of it producing haemodynamic changes in the elderly. Its (1R,1R')-isomer, cisatracurium besilate, has very little direct or indirect cardiovascular effect and is, therefore, the most suitable nondepolarising agent to use in elderly patients.
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PMID:Selecting neuromuscular-blocking drugs for elderly patients. 1253 13

We tested the hypothesis that pyridostigmine bromide (PB) intake and/or low-level sarin exposure, suggested by some as causes of the symptoms experienced by Persian Gulf War veterans, induce neurobehavioral dysfunction that outlasts their effects on cholinesterase. Adult male Sprague-Dawley rats were treated during 3 weeks with s.c. saline, PB in drinking water (80 mg/l), sarin (62.5 microg/kg; 0.5x LD(50), three times/week s.c.), or PB in drinking water + sarin. Animals were tested for passive avoidance, nociceptive threshold, acoustic startle, and open field activity 2, 4, or 16 weeks after treatment. Two weeks after sarin, acoustic startle was enhanced, whereas distance explored in the open field decreased. These effects were absent with PB + sarin or PB by itself. No effect on any variable was found at 4 weeks, whereas at 16 weeks sarin induced a decrease and PB + sarin induced an increase in habituation in the open field test. Nociceptive threshold was elevated in the PB + sarin group at 16 weeks. No effect of treatment on passive avoidance was noted in any group. Brain regional acetylcholinesterase and cholineacetyltransferase activities were not affected at any time after treatment, but muscarinic receptors were down-regulated in hippocampus, caudate putamen, and mesencephalon in the sarin group at 2 weeks. In conclusion, this study gives further support to the use of PB against nerve agent poisoning and does not support the hypothesis that delayed symptoms experienced by Persian Gulf War veterans could be due to PB, alone or in association with low-level sarin exposure.
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PMID:Delayed neurologic and behavioral effects of subtoxic doses of cholinesterase inhibitors. 1260 88

Mentally or emotionally stressful situations occur throughout our lives and cause physiological haemodynamic responses. In patients with coronary artery disease, such events can also induce myocardial ischaemia and ventricular arrhythmias, increasing mortality rates. The purpose of the present study was to determine the acute effects of the oral administration of pyridostigmine, a reversible cholinesterase inhibitor and thus an indirect cholinomimetic drug, on echocardiographic variables during mental stress in healthy subjects. A total of 18 healthy young volunteers were subjected to mental stress tests (mental arithmetic and the Stroop colour-word test) 2 h after the oral administration of either placebo or pyridostigmine bromide (45 mg), using a balanced-randomized, double-blind, crossover protocol. During mental stress, heart rate (pyridostigmine, 64+/-1 beats/min; placebo, 70+/-1 beats/min; P =0.0003) and diastolic blood pressure (pyridostigmine, 66+/-2 mmHg; placebo, 79+/-3 mmHg; P =0.01) were lower in the pyridostigmine group, but systolic pressure was not (pyridostigmine, 124+/-3 mmHg; placebo, 123+/-3 mmHg; P =0.40). There were no detectable abnormalities in the left ventricular wall motion score during mental stress, but left ventricular outflow tract mean velocity (pyridostigmine, 0.68+/-0.02 m/s; placebo, 0.64+/-0.02 m/s; P <0.05) and mitral inflow velocity deceleration (placebo, 4.05+/-0.18 m/s(2); pyridostigmine, 4.41+/-0.16 m/s(2); P <0.05) were higher in the pyridostigmine group. In conclusion, cholinergic stimulation with pyridostigmine seems to increase left ventricular diastolic function during mental stress in healthy subjects.
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PMID:Cardiac function during mental stress: cholinergic modulation with pyridostigmine in healthy subjects. 1262 98

Pyridostigmine bromide (PB), a peripheral cholinesterase inhibitor, has been shown to have central cholinesterase inhibition properties under certain conditions (such as when ingested with other chemical compounds or following a high level of stress). Here we tested if stressing rats, using an intermittent 1 hr tailshock protocol, affected the degree of brain acetylcholinesterase (AChE) inhibition caused by a subsequent single injection of PB (2.0 mg/kg) or neostigmine bromide (NB, 0.32 mg/kg), another peripheral carbamate cholinesterase inhibitor. Stressed rats treated with PB had lower levels of AChE activity in the basal forebrain/striatum, but not in other brain areas. Stressed rats treated with NB did not show basal forebrain/striatum AChE activity changes but did show minor reductions of AChE activity in the cortex and cerebellum. These results confirm that prior stress can change the characteristic actions of certain peripherally acting drugs, thus possibly leading to unexpected central nervous system effects. Possible causes for these effects are discussed.
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PMID:Stress interacts with peripheral cholinesterase inhibitors to cause central nervous system effects. 1272 85

Sixteen compounds of the general structure {HON: CH.C(5)H(4)N(+).[CH(2)](n).R(+)}2Br(-) have been synthesized in which the position of the oxime group in the pyridine ring, the second charged group R(+) and the number of methylene groups between the charged atoms have been varied. The rate at which these compounds reactivate cholinesterase inhibited by ethyl pyrophosphate has been studied and a number have been found which are more active than 2-hydroxyiminomethyl-N-methylpyridinium methanesulphonate. Since considerable variation in structure was found among those compounds which are better reactivators than the latter, the concept that 2-hydroxyiminomethyl-N-methylpyridinium salts are unique in their ability to fit the surface of the inhibited enzyme is no longer tenable. The reactivating power of these oximes correlated well with their ability, when given in conjunction with atropine, to save the lives of mice poisoned by ethyl pyrophosphate. The most effective compounds, NN'-trimethylenebis-(4-hydroxyiminomethylpyridinium bromide) and NN'-hexamethylenebis(2-hydroxyiminomethylpyridinium bromide), contained a further oxime group in R(+), but the second oxime group was not essential for high activity. These new oximes were also superior in saving the lives of mice poisoned with sarin (isopropyl methylphosphonofluoridate), but the improvement was not as dramatic as when the mice were poisoned with ethyl pyrophosphate. The toxicity of the compounds varied with both n and R(+) and was unrelated to the therapeutic potency.
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PMID:Oximes of alpha omega-diquaternary alkane salts as antidotes to organophosphate anticholinesterases. 1366 72

The effects of four organophosphorous compounds, three oximes and atropine sulphate, injected through an indwelling cannula into the third ventricle of unanaesthetized dogs were examined. The effects of 200 mug of dyflos were involuntary micturition, defaecation, akinesia of hind limbs and pronounced disturbances of awareness; those of 100 mug of ethyl pyrophosphate were tremor, restlessness and signs of fear; 500 mug to 5 mg of dyflos and 250 mug to 500 mug of ethyl pyrophosphate caused vomiting, salivation, twitches of facial muscles and recurrent epileptiform seizures. The injection of 40 to 80 mg of dimefox and of 50 mg of schradan elicited involuntary micturition, vomiting, salivation and defaecation. These effects occur probably after these substances have passed into the blood stream and have been converted in the liver to potent anticholinesterases. This view is supported by the finding of reduced blood cholinesterase activity. At a dose level of 12.5 mg, 1,1'-trimethylenebis(4-hydroxyiminomethylpyridinium bromide) produced strong convulsions. At this dose level pralidoxime iodide and diacetyl monoxime produced no observable effects. Atropine sulphate in a dose of 1 mg caused disturbances in consciousness and behaviour followed by convulsions. Intraventricular atropine and to a minor extent intraventricular oximes were able to antagonize the effects of intraventricular ethyl pyrophosphate. Pralidoxime iodide exerted a strong antagonistic effect also on intravenous injection.
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PMID:Effects of organophosphorous compounds, oximes and atropine injected into the third ventricle of unanaesthetized dogs. 1388 82


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