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:3.1.1.7 (acetylcholinesterase)
28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acetylcholinesterase is released in a calcium-dependent manner when afferents of the cerebellar cortex are stimulated. Since cholinergic transmission is probably insignificant in the cerebellar cortex, the esterase itself might serve as a transmitter or modulator. Therefore, the effect of acetylcholinesterase in the cerebellum was investigated in slices of guinea-pig cerebella during intracellular recording from Purkinje cell somata or dendrites. Addition of acetylcholinesterase (20 U/ml) to the superfusion medium did not change the membrane potential or the input resistance of the Purkinje cells. Thus, esterase does not act like a classical transmitter. The threshold for Na+ spikes generated by intracellular current injection was unaffected, but the threshold for Ca2+ spikes was increased. This increase was abolished by tetrodotoxin (1 microM). Furthermore, when Ca2+ currents were blocked by substituting Mn2+ for Ca2+ (2 mM) a decrease in a Na+ plateau potential was seen in the presence of esterase. The effect of acetylcholinesterase of Ca2+ spikes is therefore most likely due to a reduction of the non-inactivating Na+ current of the Purkinje cell membrane. When present this current contributes to activation of Ca2+ spikes in dendrites. Acetylcholinesterase also enhanced the response of Purkinje cells to the excitatory amino acids glutamate and aspartate thought to be transmitters in the cerebellar cortex. The responses became larger and faster in the presence of esterase. Responses to climbing fibre stimulation were also enhanced by acetylcholinesterase. The late part of this synaptic response was increased. The potentiation by esterase of responses of Purkinje cells to excitatory amino acids and to climbing fibre stimulation may be mediated through interference with transmitter uptake, because it was prevented by treatment with DL-2-amino-4-phosphonobutyric acid (0.5 mM) and di-hydrokainate (0.1 mM). None of the effects of esterase was due to hydrolysis of acetylcholine because irreversible inhibition of the catalytic site of the enzyme with soman did not prevent the actions. The observations were specific for acetylcholinesterase. Butyrylcholinesterase (20-40 U/ml) showed none of the effects. It is concluded that acetylcholinesterase in the cerebellar cortex seems to mediate a novel type of modulation by two separate mechanisms. Esterase reduces the tendency towards Ca2+ spike generation in Purkinje cells. Ca2+ spikes are followed by afterhyperpolarizations and in their absence firing of Na+ spikes at higher frequencies is possible. Secondly, there is an enhancement of the action of excitatory transmitters so that the extended operating range can be utilized.
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PMID:Actions of acetylcholinesterase in the guinea-pig cerebellar cortex in vitro. 135 19

Some biological and neurochemical properties of the venom of stonefish (Syanceja horrida) were investigated. The venom exhibited oedema-inducing, haemolytic, hyaluronidase, thrombin-like, alkaline phosphomonoesterase, 5' nucleotidase, acetylcholinesterase, phosphodiesterase, arginine esterase, and arginine amidase activities. Recalcification clotting time, prothrombin, and kaolin-cephalin clotting times were increased 1.7-2.3- and 2.4-fold respectively. The LD50 (i.v. mouse) was 300 micrograms/Kg. Its effects on uptake and stimulation of neurotransmitter synthesis and release were observed in rat brain synaptosomes. In the presence of 100 micrograms venom, uptake of [methyl-3H] choline in rat brain synaptosomes was inhibited 70%, while that of 4-amino-n-[U-14C] butyric acid was inhibited 20%. The toxin also stimulated the release of [3H]-acetylcholine from the synaptosomes.
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PMID:Biological activities of Synanceja horrida (stonefish) venom. 136 68

Studies in the rabbit retina have shown that infusion of exogenous acetylcholine (ACh) into the vitreal chamber leads to an increase in the amount of substance P (SP) immunoreactivity (Goebel and Pourcho, submitted). This increase was determined to be independent of new peptide synthesis, suggesting that the elevated level of SP is the result of ACh inhibition of an SP-degrading protease. This phenomenon has now been confirmed in vitro in both tissue slice and retinal homogenate assays. These studies have shown that ACh decreases the rate of SP hydrolysis in a concentration dependent manner. Recovery of SP hydrolytic activity following ACh inhibition was found to be directly proportional to the amount of acetylcholinesterase (AChE) activity in the membrane fraction. Specific protease inhibitors were used to determine the relative contributions of membrane associated retinal enzymes to SP-hydrolysis. In the presence of 1 mM 1,10-phenanthroline or p-chloromercuribenzenesulfonic acid all SP-hydrolytic activity was abolished, indicating that the enzyme(s) responsible for the degradation of the peptide is a metallopeptidase. The ACh sensitive retinal enzyme was found to be concentrated in the membrane fraction where it accounts for approximately 70% of the SP hydrolytic activity. Although the precise identity of this enzyme remains to be determined, the present evidence indicates that it shares many of the characteristics of the enzyme substance P-degrading endopeptidase (Endo et al. 1988, 1989). Enkephalinase activity was also found, contributing to 28% of the hydrolytic activity in the membrane fraction. However, the activity of this enzyme was insensitive to elevated levels of ACh. After initial cleavage of SP by the primary hydrolytic enzymes, further degradation of the fragments appears to be carried out by membrane associated serine protease(s). The activity exhibited by this class of enzymes was inhibited by DFP treatment and was not sensitive to ACh. Although AChE does not make a major contribution to the hydrolysis of SP, it does participate in peptide degradation via its esterase activity which controls the level of ACh, thereby modulating the primary SP-hydrolytic enzyme.
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PMID:Hydrolysis of substance P in the rabbit retina: II. The role of a membrane-associated acetylcholine-sensitive metalloendopeptidase. An in vitro study. 137 Nov 83

1. The novel choline analogs selenonium choline (SeCh) and acetylselenonium choline (ASeCh) have been examined for selected biological activities. 2. ASeCh was found to be an alternative substrate for acetylcholine esterase with Km and Vmax values similar to acetylcholine. 3. ASeCh and SeCh inhibited acetylthiocholine hydrolysis by acetylcholinesterase with IC50 values similar to acetylcholine and choline. 4. SeCh exerted a protective action against physostigmine and DFP induced toxicity. 5. SeCh (85 mg/kg) was found to be 3 times more toxic in mice than choline.
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PMID:Selected biological activities of novel selenonium choline analogs. 139 75

In previous work, we studied, under conditions of ad libitum food consumption, the effect of amount and type of dietary fat on plasma esterase-1 (ES-1) and butyryl cholinesterase activity in rats. This was done by the isoenergetic replacement of dietary fat by carbohydrates or by another fat source. The observed change in enzyme activity could theoretically be determined by either the dietary omission or the addition or by the combination. In the present work, we studied under restricted feeding conditions the effect of supplemental energy in various forms to determine the effect of the supplement alone. Supplemental coconut fat, but not isoenergetic amounts of either glucose or casein, raised plasma ES-1 activity. None of these supplements influenced butyryl cholinesterase activity. In a second experiment, we demonstrated that the ES-1 enhancing effect of supplemental coconut fat also occurred with fish oil, whereas the stimulatory effects of olive oil and corn oil were less pronounced. Supplemental fish oil, but not the three other fats, significantly reduced the depression in butyryl cholinesterase activity. Plasma cholesterol concentration was negatively associated with butyryl cholinesterase activity, but was not related to ES-1 activity. The two esterases were not correlated with plasma triglyceride concentration. We conclude that both the amount and type of fat in the diet of rats have specific influences on plasma ES-1 activity and that butyryl cholinesterase activity is affected by the type of fat.
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PMID:Plasma esterase-1 (ES-1) activity in rats is influenced by the amount and type of dietary fat, and butyryl cholinesterase activity by the type of dietary fat. 143 52

Rats were fed for 15 d purified diets with different amounts of coconut fat, and with or without clofibrate. Fat was added at the expense of an isoenergetic amount of glucose. The hypolipidemic action of clofibrate was not influenced by the amount of fat in the diet. Clofibrate did not affect liver cholesterol concentration in rats fed the low fat diet, but it counteracted the rise in liver cholesterol seen in rats fed the high fat diet. This could relate to the observed raised intestinal clofibrate-hydrolyzing activity of rats fed the high fat diet, because hydrolysis of clofibrate gives rise to its biologically active form. In rats fed the low fat diet, but not in those fed the high fat diet, clofibrate raised the activity of serum esterase-1, which (unlike esterase-2) does not hydrolyze clofibrate. Possibly, the dramatic stimulatory effect of fat feeding on serum esterase-1 activity had overruled any influence of clofibrate. Clofibrate elevated serum butyryl cholinesterase activity, with this effect being amplified by fat feeding. High levels of dietary fat in the absence of dietary clofibrate did not alter serum butyryl cholinesterase activity. Clofibrate did not change butyryl cholinesterase and esterase-1 activities in small intestine. The high fat diet caused slightly higher levels of butyryl cholinesterase activity in small intestine, but markedly raised intestinal esterase-1 activity. This study shows that certain effects of clofibrate and a high fat diet are interrelated.
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PMID:Fat intake and clofibrate administration have interrelated effects on liver cholesterol concentration and serum butyryl cholinesterase activity in rats. 143 66

The nervous system of Cysticercus cellulosae, the metacestode stage of the tapeworm Taenia solium, was delineated using histochemical methods for the localization of the enzyme markers; nonspecific esterase and acetylcholinesterase. The main features of the nervous system include a pair of cerebral ganglia, a circumcerebral nerve ring, a rostellar nerve ring, and anterior and posterior nerves and their branches. The posterior nerves form a subtegumental network in the strobila and the bladder wall. A nerve network around excretory tubules could also be demonstrated, suggesting neuronal control of excretion in the metacestode. No sheath was observed around the nervous system. The morphological features described suggest "cephalization" of the nervous system in this parasite.
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PMID:Neuroanatomy of Cysticercus cellulosae (Cestoda) as revealed by acetylcholinesterase and nonspecific esterase histochemistry. 143 50

Rapid enzyme microassays for the detection of resistance due to organophosphate and carbamate in individual field-collected strains of Culex quinquefasciatus adults were conducted. These tests allowed accurate differentiation by eye, on the basis of color changes of susceptible and resistant individuals. Two separate tests were conducted for the biochemical assays. In the insensitive acetylcholinesterase (AChE) test, acetylthiocholine iodide (ACTH) and 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) were used as substrate and coupling agent respectively. The resulting yellow chromophore indicated AChE activity. Test results showed that the color intensity decreased as increasing concentrations of propoxur were added, thereby confirming the susceptibility of the enzyme to inhibitor. Assay of non-specific esterase however, indicated elevated levels which were correlated with degree of malathion resistance. Electrophoretic data revealed the presence of 2 esterase bands in all strains. It was concluded that such a pattern was not contributory to malathion resistance in adults.
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PMID:Determination of insecticide susceptibility in Culex quinquefasciatus Say adults by rapid enzyme microassays. 148 1

4-Amino-3-pyridyl carbamates (2a-c) were synthesized as potential acetylcholinesterase inhibitors and acetylcholine releasers on the basis of the reported activity of the analogous N-(4-amino-3-pyridyl)-N',N'-dimethylurea (1). Although 4-amino-3-pyridyl N,N-dimethylcarbamate (2b) showed good cholinesterase inhibition [concentration that elicited a 50% reduction in the maximal enzyme response (IC50) was 13.4 microM], it had no effect on the stimulated release of [3H]acetylcholine from rat striatal slices. 4-[[(Dimethylamino)methylene]amino]-3-pyridyl N,N-dimethylcarbamate (7a), an intermediate in the synthesis of 2b, demonstrated surprisingly good cholinesterase inhibition (IC50 was 9.4 microM) but showed no activity as a release. A precursor to 7a, N-(3-hydroxy-4-pyridyl)-N',N'-dimethylformamidine (6a), showed some activity in release but was not an esterase inhibitor, whereas the precursor to 6a, 4-amino-3-pyridinol (5a), was a potent releaser. A new synthesis of 5a, based on an ortho-directed lithiation strategy, is also reported.
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PMID:Aminopyridine carbamic acid esters: synthesis and potential as acetylcholinesterase inhibitors and acetylcholine releasers. 150 Oct 77

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.
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PMID:Toxicity and toxicokinetics of carbaryl in chickens and rats: a comparative study. 150 71


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