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1.
Enzyme preparations from Drosophila melanogaster flies degraded [14C]malathion to α- and β-malathion monoacids and, hence, were considered to contain malathion carboxylesterase (ME) activity. Although ME- activity was stable during preincubation in the absence of malathion, it decreased dramatically during the course of the reaction, and could not be completely recovered by Sephadex G-25 chromatography. Furthermore, the protein fraction after chromatography still contained 14C, suggesting that the enzyme had become inhibited by a bound, 14C-labeled derivative. Extracts from a resistant (malathion-selected), an intermediate control, and the susceptible Canton S strains of D. melanogaster differed in the lability of ME activity during the reaction. This difference was partly attributed to the production of small amounts of malaoxon (2–8%) by the extracts from the more resistant strains. No consistent strain differences were found when the rate of malathion degradation was measured during the first minute of reaction, either with or without a microsomal oxidase inhibitor (metyrapone) present. These results, together with the cross-resistance of the malathion-selected strain to other insecticides and the lack of a synergistic effect of two carboxylesterase inhibitors (triphenyl phosphate and S,S,S-tributylphosphorotrithioate) suggested that malathion carboxylesterase does not contribute significantly to the observed differences in malathion resistance between strains.  相似文献   

2.
Malathion resistance in Anopheles stephensi from Pakistan was synergized by triphenyl phosphate, primarily a carboxylesterase inhibitor. There was a slight degree of antagonism with piperonyl butoxide. The major metabolite of malathion in larvae of both the resistant and susceptible strains was malathion monocarboxylic acid. Resistant larvae produced about twice as much of this product as the susceptible larvae. This suggests that a qualitative or a quantitative change in a carboxylesterase enzyme may be the basis of malathion resistance in this strain. Analysis of general esterase levels to α- and β-naphthyl acetate showed that there was no quantitative change in the amount of carboxylesterase enzyme present in the resistant strain as compared to the susceptible.  相似文献   

3.
A simple and rapid procedure is described for the qualitative and quantitative analysis of metabolites of malathion and other insecticides. The omission of an extraction at low pH, and mild conditions of anion-exchange chromatography on QAE-Sephadex prevent the degradation of a malathion metabolite, S-(1-carboxy-2-ethoxycarbonyl)-ethyl O,O-dimethyl phosphorothioate (malaoxon α-carboxylic acid), which takes place under strongly acid conditions. Disadvantages of the commonly used fractionation of malathion and malaoxon metabolites based on partitioning are discussed.  相似文献   

4.
A study was conducted to determine the extent of resistance to malathion in field populations of insects collected from nine granaries located in different regions of Israel. The results showed that the maximum resistance factor calcuated from the LCso s of the different insect species tested was:Tribolium castaneum (Herbst), x 538.0;Oryzaephilus surinamensis (L.), x 8.0;Sitophilus oryzae (L.), x 1.2; andRhyzopertha dominica (F.), x 9.0. There were significant differences between the resistance level among strains collected from different locations in Israel. By using triphenyl phosphate (TPP), an inhibitor of carboxyesterase, it was shown that, in the case ofT. castaneum andR. dominica, the resistance is a malathion-specific type and that in the case ofO. surinamensis it is partially non-specific to malathion. The significance of these findings in selecting new insecticides to replace malathion as a grain protectant was considered.  相似文献   

5.
Fourth instar larvae, the progeny from wild-caught Anopheles sacharovi females, were subjected to a number of biochemical tests and the results were compared to those from similar tests on laboratory insecticide resistant and susceptible strains of anopheline and culicine mosquitoes. DDT resistance in An. sacharovi is associated with the ability to rapidly metabolise DDT to DDE. The organophosphorus and carbamate resistance was not associated with quantitative changes in esterases, multifunction oxidases, or glutathione S-transferase. The acetylcholinesterase was less sensitive to malaoxon and propoxur than laboratory susceptible An. albimanus, and plots of inhibition suggest that the population was polymorphic for more than one form of acetylcholinesterase. Metabolism studies on malathion and pirimiphos methyl did not indicate resistance due to increased metabolism. There was no evidence of penetration barriers contributing to resistance to either DDT or malathion, and there was no indication of any resistance to pirimiphos methyl in our tests.  相似文献   

6.
The in-vitro metabolism of O,O-diethyl S-(N-methylcarbamoymethyl) phosphorodithioate in mouse liver was studied. The major route of metabolism was via the mixed-function oxidases present in the microsomal fraction, which formed the oxygen analogue, O,O-diethyl hydrogen phosphorothioate and diethyl hydrogen phosphate upon addition of nicotinamide-adenine dinucleotide phosphate (NADPH). In the absence of NADPH, the carboxylic acid analogue (S-carboxymethyl O,O-diethyl phosphorodithioate) was isolated only from the microsomal fraction. Addition of glutathione to the 100 000 g supernatant resulted in no metabolism of the parent compound. However, addition of glutathione to the 10 000 g supernatant resulted in the carboxylic acid formed by amidase activity being further metabolised to O,O-diethyl hydrogen phosphorodithioate by a glutathione-dependent reaction.  相似文献   

7.
The role of esterases in malathion resistance in Culex tarsalis has been investigated. When larvae of a resistant and a sensitive strain were placed in water containing [14C]malathion, malathion penetrated to give initially similar internal levels. With resistant mosquitoes, after 15 min the internal malathion concentration decreased to low levels while the monoacid degradation products accumulated in the larvae and were excreted into the surrounding water, whereas in susceptible larvae the internal malathion level stayed high and was lethal. It is suggested that the decrease in internal malathion and the resulting resistance were caused by an active malathion carboxylesterase in the resistant strain. A specific assay for malathion carboxylesterase with [14C]malathion showed 55 times more activity in resistant than in susceptible larvae, whereas when general esterase activity was assayed with α-naphthyl acetate only 1.7 times the activity was found. Analyses by starch gel electrophoresis showed a peak of malathion carboxylesterase, 60-fold higher from resistant than from susceptible larvae, in a gel zone which did not stain for general esterase activity. General esterases that did not hydrolyze malathion showed different electrophoretic patterns in the two populations, which are likely due to the nonisogenic character of the strains. These results show that use of a specific assay and the demonstration of degradation of malathion in vivo are essential for assessment of the contribution of esterase activity to the malathion-resistant phenotype in mosquito populations.  相似文献   

8.
The metabolism of etrimfos, O,O-dimethyl-O-(6-ethoxy-2-ethyl-4-pyrimidinyl) phosphorothioate was studied in vitro in a diazinon-resistant (Rutgers) and a susceptible (CSMA) strain of house flies. Practically no metabolism of etrimfos occurred without the addition of cofactors. However, the addition of the cofactor, reduced glutathione, resulted in a substantial amount of metabolism in both strains, the metabolism being higher in the resistant strain. The major route of metabolism was via the glutathione transferase system and the predominant metabolite was desmethyl etrimfos. Although the oxygen analog could not be isolated, microsomal oxidation of etrimfos resulted in the inhibition of acetylcholinesterase, suggesting the formation of the oxygen analog. Bovine serum albumin also degraded etrimfos yielding desmethyl etrimfos and 6-ethoxy-2-ethyl-4-hydroxypyrimidine.  相似文献   

9.
Pyrethroid carboxyesterase which hydrolyzes the esters of chrysanthemumic acid was purified from rat liver microsome by cholic acid solubilization, ammonium sulfate fractionation, heat treatment, and DEAE-Sephadex A-50 column chromatography. The 45-fold purified enzyme (38% yield) is likely to consist of single protein, as evidenced by polyacrylamide gel disc electrophoresis and Sephadex G-100 column chromatography, and had a molecular weight of approximately 74,000 and a Km of 0.21 mM. It is susceptible to inhibition by organophosphates and carbamate insecticides and insensitive to pCMB, mercuric ion, and cupric ion. It is capable of hydrolyzing trans isomers of synthetic pyrethroids much more rapidly (five to ten times) than the cis counterparts. The purified pyrethroid carboxyesterase is apparently identical in nature with malathion carboxyesterase and with p-nitrophenyl acetate carboxyesterase.  相似文献   

10.
A Tetranychus cinnabarinus strain was collected from Chongqing, China. After 42 generations of selection with abamectin and 20 generations of selection with fenpropathrin in the laboratory, this T. cinnabarinus strain developed 8.7- and 28.7-fold resistance, respectively. Resistance to abamectin in AbR (abamectin resistant strain) and to fenpropathrin in FeR (fenpropathrin resistant strain) was partially suppressed by piperonyl butoxide (PBO), diethyl maleate (DEM) and triphenyl phosphate (TPP), inhibitors of mixed function oxidase (MFO), glutathione S-transferases (GST), and hydrolases, respectively, suggesting that these three enzyme families are important in conferring abamectin and fenpropathrin resistance in T. cinnabarinus. The major resistant mechanism to abamectin was the increasing activities of carboxylesterases (CarE), glutathione-S-transferase (GST) and mixed function oxidase (MFO), and the activity in resistant strain developed 2.7-, 3.4- and 1.4-fold contrasted to that in susceptible strain, respectively. The activity of glutathione-S-transferase (GST) in the FeR strain developed 2.8-fold when compared with the susceptible strain, which meant the resistance to fenpropathrin was related with the activity increase of glutathione-S-transferase (GST) in T. cinnabarinus. The result of the kinetic mensuration of carboxylesterases (CarE) showed that the structure of CarE in the AbR has been changed.  相似文献   

11.
Thirteen methylenedioxyphenyl (MDP) compounds, including commercial insecticide synergists and juvenile hormone analogs, were compared in their effect on detoxifying enzymes in the housefly (Musca domestica). Flies were fed a diet containing 1% of the compounds for 3 days. Enzymes were then assayed in vitro for their activity using aldrin and DDT as substrates. Piperonyl butoxide (PB), sesamex, propyl isome, sulfoxide, safrole, isosafrole, 6,7-epoxy-3,7-diethyl-1-[3-4(methylenedioxy) phenoxy]-2-octene (MDP-JH I) and 6,7-epoxy-3-methyl-7-ethyl-1-[3,4-(methylenedioxy) phenoxy]-2-octene (MDP-JH II) all caused a bimodal effect, inhibiting microsomal epoxidase and inducing DDT-dehydrochlorinase in the resistant Isolan-B strain. Two of these, PB and MDP-JH I, gave similar results with the susceptible strain, stw;w5 and two resistant strains, Fc-B and Orlando-DDT. However, o-safrole, piperonylic acid, piperonal, 3,4-methylenedioxybenzyl acetate and methyl-(3,4-methylenedioxy) benzoate had little or no effect on the enzyme systems studied. The standard susceptible strain (WHO-SRS) responded to these compounds very differently. Among those tested, piperonyl butoxide, sesamex, safrole, and isosafrole were inducers of microsomal epoxidase, a 4-fold increase occurring after treatment with sesamex. Only MDP-JH II showed a marked inhibition of the epoxidase. These treatments did not effect DDT-dehydrochlorinase activity in this strain.The enhancement of DDT-dehydrochlorinase activity by the MDP compounds is associated with an increased rate of DDT dehydrochlorination in vivo. The stimulatory effect could be blocked by treatment with actinomycin D or cycloheximide.  相似文献   

12.
Resistance in a dual malathion- and permethrin-resistant head louse strain (BR-HL) was studied. BR-HL was 3.6- and 3.7-fold more resistant to malathion and permethrin, respectively, compared to insecticide-susceptible EC-HL. S,S,S-Tributylphosphorotrithioate synergized malathion toxicity by 2.1-fold but not permethrin toxicity in BR-HL. Piperonyl butoxide did not synergize malathion or permethrin toxicity. Malathion carboxylesterase (MCE) activity was 13.3-fold and general esterase activity was 3.9-fold higher in BR-HL versus EC-HL. There were no significant differences in phosphotriesterase, glutathione S-transferase, and acetylcholinesterase activities between strains. There was no differential sensitivity in acetylcholinesterase inhibition by malaoxon. Esterases from BR-HL had higher affinities and hydrolysis efficiencies versus EC-HL using various naphthyl-substituted esters. Protein content of BR-HL females and males was 1.6- and 1.3-fold higher, respectively, versus EC-HL adults. Electrophoresis revealed two esterases with increased intensity and a unique esterase associated with BR-HL. Thus, increased MCE activity and over-expressed esterases appear to be involved in malathion resistance in the head louse.  相似文献   

13.
Resistance to malathion in Anopheles stephensi from Pakistan was measured at intervals during the first week of adult life. LT50 values for homozygous resistant females decreased four-fold during the first 7 days of adulthood. A decrease in resistance with age also occurred in heterozygotes; the LT50 values of males and females fell sevenfold during the first 5 days of adulthood. The sensitivity to malathion of a susceptible strain increased with age. A biochemical basis for the declining resistance levels was investigated. Resistant and susceptible adults were homogenized at intervals during the first week of adulthood and soluble extracts were incubated with [14C]malathion. The rate of malathion metabolism to mono- and dicarboxylic acids was faster in resistant than in susceptible mosquitoes. The rate of malathion metabolism decreased with age in both strains. A decrease in carboxylesterase activity with age in resistant and susceptible mosquitoes is thus responsible for the increasing sensitivity to malathion. Implications for the monitoring of resistance in the field by diagnostic dosages and for the future use of malathion in mosquito control are discussed.  相似文献   

14.
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15.
Malathion resistance of a field-collected population of Rhizopertha dominica (Coleoptera: Bostrichidae) from Mexico was evaluated and the resistance mechanisms were characterized both in vivo and in vitro. The Mexican population showed a resistance level of 50-fold at LC50 as compared with that of a susceptible laboratory population. Malathion bioassays with the synergists triphenyl phosphate, piperonyl butoxide and diethyl maleate suggested that esterases were likely to contribute to the resistance whereas cytochrome P450 monooxygenases and glutathione S-transferases were not. In-vitro assays of esterases indicated that the general esterase activity was 1·3-fold higher in the Mexican population than in the susceptible population. However, the phosphotriesterase activity in the resistant population was 3·7-fold higher than in the susceptible population. Significantly higher phosphotriesterase activity in the resistant population was further indicated by 3·4-fold increase of Vmax in enzyme kinetics and higher frequency of individuals with high phosphotriesterase activity in this population. All these findings suggested that phosphotriesterases play a role in malathion resistance in the Mexican population of lesser grain borer. © 1998 SCI  相似文献   

16.
The inhibitory effects on liver microsomal carboxylesterases and erythrocyte membrane esterases produced by an impurity of malathion was investigated. Treatment of rats with an impurity of malathion, O,O,S-trimethyl phosphorothioate (OOS-Me), and its structural analog O,O-dimethyl S-ethyl phosphorothioate (OOS-Et) inhibited liver microsomal malathion and phenthoate carboxylesterases. The inhibition lasted for at least 7 days following a single oral administration of OOS-Me. These treatments inhibited acetylcholinesterase (AChE) and (Na+ + K+)-dependent ATPase of erythrocyte membranes which persisted at least 3 days. OOS-Et was a more potent inhibitor of all the esterases examined than OOS-Me. Pretreatment of rats with a metabolic inducer, phenobarbital, or a metabolic inhibitor, piperonyl butoxide, had no effect on such inhibitory effects on liver microsomal carboxylesterases produced by OOS-Me or OOS-Et.  相似文献   

17.
The earthworm, Eisenia foetida, eliminated parathion and carbofuran at first order rates when continually rinsed in water after treatment with the pesticides. This experiment was also carried out on Lumbricus rubellus for comparison. Carbofuran which is more soluble in water, was eliminated quicker than parathion. The later rate of elimination was very similar for the two species, but immediately after injection the rate was much higher in E. foetida. The metabolism of 1-ethyl14C labelled parathion and paraoxon (diethyl 4-nitrophenyl phosphate) was studied in E. foetida. The worm was able to convert parathion to paraoxon by a rather slow process although this metabolite could not be detected in the worms due to its rapid transformation to diethyl hydrogen phosphate. Indirectly, paraoxon can be postulated as a parathion metabolite because of a progressive depression of cholinesterase level observed after treatment with parathion. Small amounts of diethyl hydrogen phosphate were detected as a metabolite of parathion; this is also an indication of paraoxon formation. During the 30 h following injection of parathion, only 4.4% of the applied dose was recovered as water-soluble metabolites (2.8% in the worms and 1.6% in the sand surrounding them), while 52% was recovered as unmetabolised parathion. Because of inefficient injection, only 70-59% of the dose thought to be injected was recovered. Therefore the part of the actual applied dose that remained unmetabolised was probably even greater (88%). Five days after injection of parathion, 15 and 9.3 % of the recovered radioactivity in the surrounding sand and in the worm extracts, respectively, was identified as O,O-diethyl O-hydrogen phosphorothioate, 3.7 and 7.0% as diethyl hydrogen phosphate, 8.8 and 3.3% as O-ethyl O-4-nitrophenyl O-hydrogen phosphorothioate (desethylparathion) and/or O-4-aminophenyl O,O-diethyl phosphorothioate, while 70.3 and 80.4% was unmetabolised parathion. Paraoxon was very quickly hydrolysed to diethyl hydrogen phosphate in vivo and in vitro. The in-vitro hydrolysis was associated with a microsomal fraction and was not inhibited by ethylenediaminetetra-acetic acid or 4-(chloromercuri)benzoic acid, and incompletely by aldicarb. Cholinesterase and arylesterase were therefore excluded as enzymes responsible for the activity.  相似文献   

18.
The cross-resistance and biochemical mechanism of the beet armyworm, Spodoptera exigua (Hübner), to spinosad was studied in the laboratory. S. exigua population were collected from Shanghai suburb. After five generations of selection, the resistance of S. exigua to spinosad increased 345.4 times compared with the susceptible strain. There was no cross-resistance between spinosad and fenvalerate, phoxim, methomyl, abamectin, and cyfluthrin. When the inhibitors, PBO, TPP, DEF, and DEM were used as synergist in the susceptible strain and resistant strain, the synergistic ratio was 0.7-, 0.5-, 1.0-, and 0.6- fold for the susceptible strain, and 9.8-, 1.5-, 2.6-, and 1.5-fold for the resistant strain, respectively. The results revealed that PBO had significant synergistic effect on the resistant strain. The activity in vitro of microsomal-O-demethylase and glutathione S-transferase in the resistant strain was 5.2- and 1.0-fold of the susceptible strain, respectively. The results implied that microsomal-O-demethylase might be important in conferring spinosad resistance in the S. exigua population.  相似文献   

19.
The brown planthopper (BPH), Nilaparvata lugens Stål, is a primary insect pest of cultivated rice, and its effective control is essential for crop production. However, in recent years, outbreaks of the brown planthopper have occurred more frequently in China. In order to determine the causes and mechanisms of insecticide-induced BPH resurgence and perform population management, we conducted the following studies. By the topical application method, our results showed that, fenvalerate acted as stimulus of fecundity from 3.50 × 10−3 to 2.02 × 10−2 μg/female in the BPH. Apart from 7.00 × 10−3 μg/female, the number of hatched nymphs was increased gradually with an increase in application dose from 3.50 × 10−3 to 1.74 × 10−2 μg/female. After continuous selection with fenvalerate for 11 generations by the rice-stem dipping method, a resistant strain was achieved with medium resistance to fenvalerate (RR 39.22). Life table study indicated that the resistant strain (G4 and G8) showed reproductive advantages, including increased female ratio, copulation rate and fecundity. But the hatchability of resistant strain was lower. The survival rate and emergence rate were significantly lower in G4 and G8 resistant strain. Resistant strains in G4 and G8 showed a fitness advantage (1.04 and 1.11), and the number of offspring in G8 generation was higher than that in G4 generation. The significant difference detected between resistant insects (G4, G5, G8 and G9) and S-strain contains not only the effect of resistant selection but also the effect of continuous rearing itself. Hence it was concluded that the BPH had the potential to develop high resistance against fenvalerate and the induction of the nymphs by sublethal doses of fenvalerate was of importance in the BPH population management, particularly in the predicting. Further studies demonstrated that triphenyl phosphate (TPP) and diethyl maleate (DEM) had no synergism on fenvalerate. However, piperonyl butoxide (PBO) displayed significant synergism in susceptible strain (1.97) and resistant strain (2.73). We concluded that esterase and glutathione S-transferase play little role in fenvalerate detoxification. The increase of the P450-monooxygenases detoxification is an important mechanism for fenvalerate resistance. Because their resistant populations had a fitness advantage, we should pay close attention to the occurrence of BPH and use other functionally different insecticides to control the BPH.  相似文献   

20.
The toxicological and biochemical characteristics of acetylcholinesterases (AChE) in the resistant and susceptible strains (SS) of Liposcelis bostrychophila were investigated. The two resistant strains were the dichlorvos-resistant strain (DDVP-R) and the phosphine-resistant strain (PH3-R) with resistance ratios of 22.36 and 4.51, respectively. Compared to their susceptible counterpart, the AChE activity per insect and the specific activity of AChE in DDVP-R and PH3-R were significantly higher. There were also significant kinetic differences between DDVP-R and PH3-R. The apparent Michaelis-Menten constant (Km) for acetylthiocholine iodide (ATChI) was obviously lower in SS than that in PH3-R, indicating a higher affinity to the substrate ATChI in the susceptible strains. The affinity for the substrate ATChI in DDVP-R and SS were not significantly different. The Vmax value of the PH3-R was significantly greater when compared to the Vmax for the SS suggesting a possible over expression of AChE in this resistant strain. The inhibition of AChE to insecticide exposure in vitro revealed that all six insecticides were inhibitory for the extracted AChE’s. Based on the I50 values, AChE of the SS were more sensitive to dichlorvos, paraoxon-ethyl, malaoxon and demeton-S-methyl than those of the two resistant strains. As for carbaryl and eserine, the PH3-R suggested a significantly higher I50s compared to the susceptible strain, while, no significant differences were found between SS and DDVP-R.  相似文献   

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