Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.7 (acetylcholinesterase)
 28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Turkey, the mosquito Anopheles sacharovi has been under field selection pressure sequentially with DDT, dieldrin, malathion and pirimiphosmethyl over a period of 30 years for the purpose of malaria control. In 1984, the field population of An.sacharovi in the malarious Cukurova plain of Adana Province contained an altered acetylcholinesterase-based resistance gene giving broad spectrum resistance against organophosphorus and carbamate insecticides. The cross-resistance spectrum from this mechanism conferred resistance to malathion but not to the organophosphorus insecticide pirimiphos-methyl. Over the 6 years that pirimiphos-methyl has been applied for malaria vector control in this area, the frequency of the altered acetylcholinesterase resistance gene has declined, although in 1989 and 1990 it was still present at measurable frequencies in An.sacharovi from Cukurova. In addition to the acetylcholinesterase resistance mechanism there is evidence of an increased level of glutathione S-transferase in some of the An.sacharovi populations tested. This is known to be correlated with DDT resistance in other anophelines. In Turkish An.sacharovi, DDT resistance and elevated glutathione S-transferase occur in the same populations at similar frequencies. The continued prevalence of resistance to DDT and dieldrin, long after the 1971 cessation of DDT spraying for malaria control in Turkey, suggests that the DDT resistance gene has insufficient reduced fitness associated with it to have been lost from the field population during the past two decades. The implications of the slow decline in resistance gene frequencies in this field population are discussed in relation to mathematical models for managing resistance.
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PMID:Insecticide resistance gene frequencies in Anopheles sacharovi populations of the Cukurova plain, Adana Province, Turkey. 146 99

1. Interstrain differences in red blood cell enzyme activities were studied in mice (BALB/c, C57BL/6, C3H/He, DBA/2 and ddY) and rats (Donryu, F344/N, SD, Wistar and Wistar/ST), and were also compared with hamster, guinea-pig and rabbit. 2. The enzyme activities measured were: glutathione S-transferase (GST), glucose-6-phosphate dehydrogenase (G-6-PD), 6-phosphogluconate dehydrogenase (6-PGD), NADPH-diaphorase (ND), hexokinase (Hx), glutamate oxaloacetate transaminase (GOT), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE). 3. There were marked variations in the activities of some red cell enzymes (e.g. GST, Hx, ND), while others (e.g. G-6-PD, 6-PGD) were much less variable both within different strains and species.
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PMID:Interstrain differences in red cell enzyme activities in mice and rats. 178 55

The ontogeny and endocrine regulation of sex-differentiated hepatic metabolism is mediated via the hypothalamic-pituitary axis. Using in vitro-in vivo systems, we demonstrate alterations in activity levels of six sex-differentiated enzyme systems in male rats bearing ectopic pituitary tumors after the injection of a pituitary cell line, C811RAP. Activity levels of hepatic glutathione S-transferase, UDP-glucuronyltransferase, and aryl hydrocarbon hydroxylase are reduced to activity levels of control females, while histidase, 5 alpha-reductase, and serum cholinesterase levels are increased to levels of control females, i.e. feminization of all of these enzymes. RIAs of testosterone, estrogen, FSH, and PRL are similar in tumor-bearing and control animals, but GH levels are significantly higher in tumor-bearing animals than in the controls. It is suggested that GH may be the pituitary factor responsible for the expression of sex-differentiated hepatic metabolism.
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PMID:Modulation (feminization) of hepatic enzymes by an ectopic pituitary tumor. 392 55

The principal biochemical mechanisms of resistance to insecticides involve either modified, less sensitive cholinesterase, esterase action, glutathione S-transferase action or cytochrome P-450-dependent monooxygenation. Both quantitative and qualitative differences in cytochrome P-450 isozymes are under genetic control and both are related to resistance. Recent characterization studies involving ligand binding and multiplicity of isozymes in Musca domestica (the housefly) are discussed in relation to resistance. The recent demonstration that multiple isozymes of glutathione S-transferase exist in susceptible and resistant insects is of interest, and some re-examination of their role in the mechanism of resistance is required. Esterases are a heterogeneous group of enzymes whose role in resistance has often been suggested but seldom rigorously defined. Purification studies in the green rice leafhopper, Nephotettix cincticeps, have involved an enzyme with carboxylesterase, phosphotriesterase and pyrethroid esterase activities. A similar enzyme, but without pyrethroid esterase activity, is also found in the housefly. In resistance such enzymes may serve either to catalyse hydrolysis or as binding proteins. It has been suggested, from time to time, that regulator genes, enzyme induction and gene magnification all play a part in controlling biochemical mechanisms of resistance, although clearly defined evidence has not always been brought forward. These hypotheses are re-examined.
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PMID:Biochemical mechanisms of resistance to insecticides. 655 14

The resistance status of 14 strains of Blattella germanica (L.) from four countries was determined for chlorpyrifos and propoxur compared with a standard reference susceptible strain. Thirteen strains were resistant to chlorpyrifos; 12 strains were resistant to propoxur. Resistance ratios for chlorpyrifos ranged from 8- to 462-fold at LC90; for propoxur, resistance ratios ranged from 4- to 46-fold. One cockroach strain from Denmark had negative cross-resistance to chlorpyrifos, and one strain from the United States had negative cross-resistance to propoxur. Slopes of probit regressions indicated that all resistant strains were heterogeneous for resistance to both chlorpyrifos and propoxur. Synergist studies with piperonyl butoxide indicated that multifunction mono-oxidases are probably involved in resistance to chlorpyrifos in six strains and in resistance to propoxur in seven strains. Esterase activity was elevated in 10 strains; of these strains, two had only slightly elevated esterase activity as measured with the substrates 1- and 2-naphthyl acetate. The remainder had higher levels of elevated esterase activity to both substrates. Strains with elevated esterase activity were resistant to a broad spectrum of organophosphates, pyrethroids, or both. Increased levels of glutathione S-transferase activity were found in four strains. Another two strains had a low frequency (1%) of individuals with high glutathione S-transferase activity. Elevated glutathione S-transferase activity was not correlated with the observed levels of organophosphate or carbamate resistance. One strain from Dubai had an altered acetylcholinesterase-based mechanism that conferred broad-spectrum resistance to a range of organophosphates and carbamates.
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PMID:Possible mechanisms of organophosphorus and carbamate insecticide resistance in German cockroaches (Dictyoptera: Blattelidae) from different geographical areas. 750 2

Rats and chickens were given single oral doses of 50 mg chlorpyrifos/kg to compare toxic effects in these 2 species. Oral administration resulted in decreased cytochrome P-450 and aminopyrine N-demethylase activities and increased cytosolic glutathione S-transferase activity in rats. On the contrary, there was increased cytochrome P-450 and aminopyrine N-demethylase activities in chickens. A significantly higher inhibition of serum cholinesterase (82%) was noted in rats than in chickens (55%). Serum gamma-glutamyl transferase, a marker of hepatotoxicity, remained unchanged in both species, indicating the absence of hepatotoxicity. These studies project chlorpyrifos to be an inhibitor of hepatic microsomal drug-metabolizing enzymes in rats and an inducer in chickens, and a non-hepatotoxic organophosphate insecticide in both species when given at the dosage of 50 mg/kg.
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PMID:Comparative toxicological studies of chlorpyrifos in rats and chickens. 753 64

Baseline entomological surveillance was carried out in a rural area of The Gambia during the rainy season in 1988, one year before the implementation of a malaria control programme using insecticide-impregnated nets and targeted chemoprophylaxis in villages with a primary health care (PHC) system. Mosquito collections took place in 6 pairs of settlements each with untreated bed nets; within each pair there was a large PHC village with a resident village health worker (VHW) and traditional birth attendant (TBA) and a smaller non-PHC village without either a VHW or a TBA. The most common vectors in the study area were Anopheles gambiae sensu stricto and, to a lesser extent, An. arabiensis. These mosquitoes were found in appreciable numbers for at least 4 months of the year (geometric mean/bedroom/night = 32.5, 95% confidence interval 18.2-57.3). Numbers of mosquitoes collected in PHC villages or non-PHC villages were not significantly different. Greater numbers of mosquitoes were found in villages closer to the River Gambia than in those further away. Evidence for DDT resistance due to elevated glutathione S-transferase activity was found in one of the 12 villages, but there was no evidence of resistance to organophosphate or carbamate insecticides as suggested by the low esterase levels and carbamate sensitive acetylcholinesterase.
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PMID:A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of The Gambia, west Africa. 3. Entomological characteristics of the study area. 821 5

Polymorphisms have been detected in a variety of xenobiotic-metabolizing enzymes at both the phenotypic and genotypic level. In the case of four enzymes, the cytochrome P450 CYP2D6, glutathione S-transferase mu, N-acetyltransferase 2 and serum cholinesterase, the majority of mutations which give rise to a defective phenotype have now been identified. Another group of enzymes show definite polymorphism at the phenotypic level but the exact genetic mechanisms responsible are not yet clear. These enzymes include the cytochromes P450 CYP1A1, CYP1A2 and a CYP2C form which metabolizes mephenytoin, a flavin-linked monooxygenase (fish-odour syndrome), paraoxonase, UDP-glucuronosyltransferase (Gilbert's syndrome) and thiopurine S-methyltransferase. In the case of a further group of enzymes, there is some evidence for polymorphism at either the phenotypic or genotypic level but this has not been unambiguously demonstrated. Examples of this class include the cytochrome P450 enzymes CYP2A6, CYP2E1, CYP2C9 and CYP3A4, xanthine oxidase, an S-oxidase which metabolizes carbocysteine, epoxide hydrolase, two forms of sulphotransferase and several methyltransferases. The nature of all these polymorphisms and possible polymorphisms is discussed in detail, with particular reference to the effects of this variation on drug metabolism and susceptibility to chemically-induced diseases.
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PMID:Metabolic polymorphisms. 836 90

The enzymes acetylcholinesterase, glutathione S-transferase (GST), glucose 6-phosphate dehydrogenase (G6PD), and general esterases were assayed in four strains of Aedes aegypti mosquitoes aged between 1 and 30 days. Microtitre plate methods were used to assay activity in the homogenates of individual mosquitoes. The levels of GST and G6PD declined with the age of the mosquitoes, while the activity for the other enzymes remained constant. Soluble protein content was also found to decline with mosquito age in all the strains. Insecticide bioassays showed that two strains (Trinidad and Virtudes) of Ae. aegypti were resistant to DDT, deltamethrin and malathion, whereas two other strains (Bangkok and Indian) were susceptible to all four classes of insecticides tested. Higher esterase activity levels in the resistant compared to the susceptible strains were assumed to be the cause of organophosphate resistance. The combination of DDT and deltamethrin resistance in two strains with normal GST and G6PD characteristics suggests that a kdr-type nerve insensitivity mechanism may be involved.
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PMID:Changes in enzyme titres with age in four geographical strains of Aedes aegypti and their association with insecticide resistance. 843 83

Etofenprox is a non-ester pyrethroid insecticide with comparable toxicity and a similar mode of action to other pyrethroids. Cross-resistance studies on mosquitoes showed no effect of carboxylesterase, elevated esterase, altered acetylcholinesterase or glutathione S-transferase-based resistance mechanisms on etofenprox toxicity, when compared to standard susceptible strains of Anopheles and Culex. Cross-resistance to etofenprox occurred in a pyrethroid-resistant strain of Culex quinquefasciatus with both oxidase and 'kdr'-like resistance mechanisms. Dose-response data for susceptible mosquito strains suggest that, in standard W.H.O. susceptibility tests of adult mosquitoes, appropriate discriminating concentrations of etofenprox for detection of resistance would be 0.1% for Culex and 0.25% for Anopheles.
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PMID:Efficacy of etofenprox against insecticide susceptible and resistant mosquito strains containing characterized resistance mechanisms. 854 96


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