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1.
House fly (Musca domestica L.) microsomes prepared from larvae, pupae, or adults contain three enzyme system which can metabolize juvenile hormone I: an esterase, an oxidase, and epoxide hydrase. The presence of the oxidase is indicated by the increased metabolism when microsomes are supplemented with NADPH and by the occurrence of additional metabolites tentatively identified as products arising from oxidation of the 6, 7 double bond. Additional evidence of the activity of the oxidase system is the increased metabolism of juvenile hormone I by the NADPH-dependent system from phenobarbital-induced insects, by inhibition of the oxidation by piperonyl butoxide and carbon monoxide, and by the greater metabolism of the hormone by microsomes from insecticide-resistant (high oxidase) strains. In vivo studies of house fly adults treated with 3H-labeled juvenile hormone I reveal a pattern of metabolism similar to that seen during NADPH-supplemented in vitro metabolism. The three enzymes have somewhat different patterns of activity during the larval stage of the house fly, juvenile hormone esterase and epoxide hydrase beginning at a high level of activity in the young larvae while the juvenile hormone oxidase is low at this stage. In the late larval stage all three enzymes show increased activity followed by declines during the pupal stage and further increases in the adult stage. Comparison of in vitro enzyme levels of the house fly, flesh fly (Sarcophaga bullata Parker), and blow fly [Phormia regina (Meigen)] showed that, although the enzymes were present in the latter two species, their activity on a per insect basis was considerably less than that of the house fly.  相似文献   

2.
Aliesterase, carboxylesterase, and phosphorotriester hydrolase activities in six house fly strains were studied in relation to malathion resistance. Selection of two susceptible strains with malathion for three generations resulted in an increase in both carboxylesterase activity and LD50 of malathion, indicating that the increased detoxication by the enzyme was the major mechanism selected for malathion resistance. With the highly resistant strains, however, the carboxylesterase activity alone was not sufficient to explain the resistance level, and the involvement of additional mechanisms, including phosphorotriester hydrolase activity, was suggested. The E1 strain, which had high phosphorotriester hydrolase activity but normal or low carboxylesterase activity, showed a moderate level, i.e., sevenfold resistance. Upon DEAE-cellulose chromatography, two or three esterase peaks were resolved from susceptible, moderately resistant, and highly resistant strains. The substrate specificity, the sensitivity to paraoxon inhibition, and the αβ ratio of malathion hydrolysis were studied for each esterase peak from the different strains. The results suggested the existence of multiple forms of esterases with overlapping substrate specificity in the house fly.  相似文献   

3.
Four major esterases in one susceptible (CSMA) and two resistant (Hirokawa, E1) house fly strains were separated by chromatofocusing. Of the four esterases, those with pI's of 5.1 and 5.3 accounted for 90% of the p-nitrophenyl butyrate hydrolyzing activity in the three house fly strains. They also accounted for 70% (Hirokawa, E1) and 40% (CSMA) of the paraoxon-hydrolyzing activity as well as 87% (Hirokawa), 39% (E1) and 66% (CSMA) of the malathion-hydrolyzing activity in microsomes as measured by esterase-antibody interaction. In the Hirokawa strain, the pI 5.1 esterase was the predominant esterase and was more active than that of the the CSMA strain. Different substrate specificities and a different Km toward acetylthiocholine, as well as different rates of malathion and paraoxon hydrolysis between the Hirokawa and CSMA strains, suggest a qualitative difference in the pI 5.1 esterase. For the pI 5.1 esterase from the E1 strain, a different substrate specificity, a different Km for p-nitrophenyl butyrate, a different sensitivity to inhibitors, and a different rate of paraoxon hydrolysis suggest that it is a modified esterase. This esterase is not a phosphorotriester hydrolase, nor does it lack nonspecific esterase activity. It is a modified esterase which has a different substrate specificity when compared to the esterases from the other strains. The molecular weight of the esterases studied was approximately 220,000, with pH optima of about 7.0.The ratio of malathion α-monoacid to β-monoacid formation was about 9.0 for the pI 5.1 and 5.3 esterases and 1.5 for the pI 4.8 and 5.6 esterases. The existence of a higher αβ ratio for the pI 5.1 and 5.3 esterases and their significant rate of malathion hydrolysis in the Hirokawa strain indicate that an increase in the αβ ratio in house flies reported was due to the increase in the pI 5.1 esterase in the resistant strain.  相似文献   

4.
Six to seven esterases from mouse, rat, and rabbit liver microsomes were resolved by chromatofocusing in the pH range 7–4. Each esterase peak showed a different substrate specificity pattern with the substrates evaluated. Malathion and paraoxon hydrolysis always corresponded with p-nitrophenyl acetate and methylthiobutyrate hydrolysis, whereas the pattern of fenvalerate hydrolysis was more complicated. Phosphorotriester hydrolase activity was isolated, and was found to be more specific toward paraoxon than toward the other insecticides. Time-course studies of paraoxon hydrolysis indicated that the hydrolysis of paraoxon by carboxylesterase was an inhibitory reaction. This reaction and phosphorotriester hydrolase activity can serve as a detoxication reaction toward organophosphate insecticides.  相似文献   

5.
Botanical pyrethrins and synthetic pyrethroids are highly potent and environmentally safe insecticides that are used to control a wide range of disease vector and pest arthropods. Unfortunately, resistance to these insecticides has been demonstrated in numerous medically important mosquito species. In this study, adult Culex pipiens sensu lato were captured in agricultural and urban locations in Fresno County, California, and subsequently exposed to a commercial formulation of pyrethrin insecticide by ultra-low-volume spraying. Following insecticide exposure, two pyrethroid-like, fluorescent substrates (4-methyl-2-oxo-2H-chromen-6-yl, cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate (cis-DCVC) and 4-methyl-2-oxo-2H-chromen-6-yl, cis-3-((Z)-2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2-dimethylcyclopropanecarboxylate (cis-TFMCVC)) and 1-chloro-2,4-dinitrobenzene (CDNB) were used to measure esterase and glutathione S-transferase (GST) activities in surviving mosquitoes. Elevated esterase activity (2.5-fold) was found in surviving urban mosquitoes at 12-h post-pyrethrin exposure (in comparison to non-insecticide-exposed control mosquitoes) when cis-TFMCVC was used as a substrate. Additionally, when CDNB was used as a substrate, 2.8-fold higher GST activity was found. A simple assay was established using our pyrethroid-like, fluorescent substrates that was able to detect low-level esterase activities in homogenates made from individual mosquitoes. The cis-TFMCVC-based assay suggested that esterase activity plays a role in pyrethrin resistance in urban mosquitoes in California.  相似文献   

6.
The relative potency to target and nontarget insects of ester pyrethroids and the analogous oxime ethers, and the degree of synergism of the esters with tributyl phosphorotrithioate, provide a useful guide to the importance of esterase detoxification in species specificity. These criteria indicate that esterase detoxification is a more important component of pyrethroid tolerance in Chrysopa carnea and Cryptolaemus montrouzieri larvae than in Exochomus flavipis larvae and Musca domestica adults. Studies with 3-phenoxybenzyl 2-(4-chlorophenyl)-2-cyclopropylacetate and the corresponding 2,3,4,5,6-pentafluorobenzyl ester, their oxime ether analogs, and permethrin and its thiol ester and amide analogs provide evidence that the high insecticidal activity of some ester and E-oxime ether pyrethroids, relative to that of the corresponding thiol ester and amide, is more closely associated with the dipole moment and polarizability of the central linkage and its resistance to esterase detoxification than with bond lengths or lipophilicities conferred by a specific linkage. Pentafluorobenzyl tetramethylcyclopropanecarboxylate is very effective in the vapor state for house fly control.  相似文献   

7.
Tralomethrin and tralocythrin undergo debromination, forming deltamethrin and cypermethrin, respectively, following topical administration to house flies, feeding to cabbage looper larvae, or incubation with house fly homogenates and cockroach nerve cords. The debromination is probably not an enzymatic process since it occurs rapidly on incubation with glutathione, cysteine, and albumin. Following debromination, an esterase(s) in house fly homogenate hydrolyzes delta-methrin and cypermethrin. The insecticidal activity of tralomethrin and tralocythrin may be due in part to the liberation of deltamethrin and cypermethrin in the insect or its nervous system.  相似文献   

8.
Of six juvenile hormone analogs of the alkyl 3,7,11-trimethyl-2,4-dodecadienate type, only the isopropyl ester was strongly morphogenic in the house fly, Musca domestica L. In vitro assays revealed that house fly microsomes contain B-esterases as well as oxidases which metabolize such analogs. However, these esterases did not hydrolyze the isopropyl ester, ZR-515. Enzymes prepared from larvae, pupae, and adults were all active and there was evidence that in the late larval stage the esterase activity was cyclic, showing a minimum in the early third instar and a maximum a few hours later. When microsomes from two susceptible and two resistant house fly strains were compared for metabolic activity against the juvenile hormone analogs, those from the resistant strains were 1.3 to 20 × higher in oxidase activity but there was no difference in esterase activity. The oxidative metabolism of two analogs ZR-515 and 512 was greatly enhanced when the flies were induced with phenobarbital but there was no enhancement in metabolism of three of the remaining analogs and only a slight enhancement of a fourth. It is concluded that the insecticidal action of ZR-515 is largely due to its stability in the presence of the house fly esterases.  相似文献   

9.
It had been reported that a Japanese multiple-resistant strain of house fly, Hirokawa, had a high malathion-carboxylesterase activity as well as a normal level of esterase activity to α-naphthylacetate (NA). This is different from the situation in several other malathion-resistant strains, where high malathion-carboxylesterase activity goes together with a low level of activity to α-NA. This had been explained by the so-called “mutant ali-esterase theory,” which assumed that the opposite changes in activity to malathion and α-NA were the result of one and the same change in an ali-esterase. In the Hirokawa strain the esterase degrading malathion seems to be responsible for about 64% of the activity to α-NA. This was concluded since the two activities were equally sensitive to denaturation and to two organophosphorus inhibitors. Moreover activity of malathion was inhibited by α-NA, and that of α-NA by malathion. Most of the latter activity was inhibited competitively. Inhibition of activity to malathion was lower, however, than to be expected on the basis of competitive mutual inhibition. This case of resistance to malathion therefore seems to involve a different kind of “mutant ali-esterase” than in other strains. Increased hydrolysis of the insecticide seems to be achieved without loss of activity to α-NA, although Km is different. The strain further showed an unusually high β-NA hydrolysis and malaoxon-carboxylesterase activity (about 3- and 200-fold, respectively, that of another malathion-resistant strain G).  相似文献   

10.
BACKGROUND: Frankliniella occidentalis (Pergande) is among the most important crop pests in the south‐east region of Spain; its increasing resistance to insecticides constitutes a serious problem, and understanding the mechanisms involved is therefore of great interest. To this end, F. occidentalis populations, collected from the field at different locations in south‐east Spain, were studied in terms of total esterase activity and esterase isoenzyme pattern. RESULTS: Individual thrips extracts were analysed by native polyacrylamide gel electrophoresis (PAGE) and stained for esterase activity with the model substrate α‐naphthyl acetate. Significant correlations were found between resistance to the insecticides acrinathrin and methiocarb and the presence of a group of three intensely stained bands, named Triplet A. For each individual thrips extract, total esterase activity towards the substrates α‐naphthyl acetate and α‐naphthyl butyrate was also measured in a microplate reader. Insects possessing Triplet A showed a significantly higher α‐naphthyl acetate specific activity and α‐naphthyl acetate/α‐naphthyl butyrate activity ratio. This observation allowed a reliable classification of susceptible or resistant insects either by PAGE analysis or by total esterase activity determination. CONCLUSION: The PAGE and microplate assays described can be used as a monitoring technique for detecting acrinathrin‐ and methiocarb‐resistant individuals among F. occidentalis field populations. Copyright © 2008 Society of Chemical Industry  相似文献   

11.
The low mixed-function oxidase activity of house fly microsomes has been associated with low cytochrome P-450 content and NADPH-cytochrome c reductase activity. The microsomal cytochrome P-450 content and NADPH-cytochrome c reductase activity could be decreased by the addition of catechol and increased by the addition of cyanide to the homogenates. Similar results were obtained with rat liver microsomes treated with tyrosinase and catechol. During the inactivation of rat liver microsomal enzymes by tyrosinase and catechol, crosslinking of microsomal proteins occurred. These results suggest that the instability of house fly microsomal mixed-function oxidase may be due in part to the action of contaminating tyrosinase on endogenous substrates.  相似文献   

12.
The insecticidal properties of 1-(7-ethoxygeranyl)-2-methylbenzimidazole (EGMB) were investigated on larval and adult house flies. Unsynergised EGMB gave topical LD50 values of 0.53 μg per female fly on NAIDM strain house flies. When flies were pretreated with 5.2 μg piperonyl butoxide, susceptibility was increased (LD50 0.12 μg per female fly). House fly larvae were less susceptible to EGMB (LD50 2.2 μg). Poisoning with EGMB resulted in a rapid reduction in locomotor activity of both larval and adult house flies. This reduction in locomotion was progressive and led to complete paralysis. Various parameters of larval nervous system function were investigated in larvae during these early phases of poisoning. As early as 15 min after dosing larvae with LD95 doses of EGMB, sensory nerves were less responsive. Over a somewhat longer time (2–4 h), neurally evoked contractures were adversely affected by EGMB. In some cases, this effect appeared to be due to reduced postsynaptic potential amplitude; in other instances, it appeared to be due to an effect independent of neuromuscular transmission. The close temporal correlation between behavioural and electrophysiological observations suggests that the nervous and muscular systems are important sites of action of EGMB.  相似文献   

13.
The metabolism of carbosulfan, 2,3-dihydro-2,2-dimethylbenzofuran-7-yl (di-n-butylaminothio)-methylcarbamate, was studied in the rat and house fly. Carbosulfan was metabolized via at least two major pathways in the rat, by initial oxidation of the sulfur atom and by NS bond cleavage. The principal rat metabolites were the conjugated keto-phenol from the ring-labeled carbo-sulfan, carbon dioxide from the carbonyl-labeled carbosulfan, and dibutylamine from the dibutylamino-labeled carbosulfan. In house flies, carbosulfan was converted primarily into carbofuran and related oxidation products. The lower mammalian toxicity of carbosulfan compared to its insecticidal activity is explained on the basis of differences in routes and rates of metabolism of carbosulfan in mammals and insects.  相似文献   

14.
The metabolism of a selectively toxic derivative of carbofuran, 2,2-dimethyl-2,3-dihydrobenzofuranyl-7 N-dimethoxyphosphinothioyl N-methylcarbamate (PSC), was examined in the house fly, rat, and mouse. In house flies, PSC is metabolized mainly to carbofuran and related oxidation products containing the intact N-methylcarbamyl ester moiety. Degradation to phenolic products was the principal route of metabolism in rodents. The results indicate that the selective toxicity of PSC between insects and mammals is attributable to differing pathways of metabolism.  相似文献   

15.
In vitro inhibition of house cricket head, house fly head, and bovine erythrocyte acetylcholinesterase by O,O-dimethyl S-aryl phosphorothioates was studied by Main's kinetic treatment. The potency of the compounds as reflected by the bimolecular reaction constants (ki) indicated that house fly head acetylcholinesterase was the most sensitive to the inhibition followed by house cricket head and bovine erythrocyte acetylcholinesterase. There are no linear relationships between the phosphorylation rate constants and the total binding energies for the inhibition of three enzymes by this series of compounds, suggesting that the initial binding and the phosphorylation rate are not related. The structure and activity relationships were analyzed by multiple regression analyses with the use of Hammett's sigma, alkaline hydrolysis rates of the compounds, and pi constants. The hydrophobic bonding of the compound on the enzyme surface as reflected by the pi constant played a significant role in the determination of the potency of the inhibition of house cricket head and house fly head acetylcholinesterase by those compounds. However, the alkaline hydrolysis rates of the compounds, or the Hammett's sigma values seems to play a more important role in the determination of the inhibition of bovine erythrocyte acetylcholinesterase. Moderate insecticidal activity toward house crickets, house flies, and mosquito larvae were found.  相似文献   

16.
The average heartbeat rate of female adult Musca domestica was near 250 beats/min in vivo at 23°C. However, standard deviation values ranged from ±35 to ±60 depending on the individual house fly. Heartbeat rates in tethered house flies fluctuated between cessation to over 300 beats/min. The heartbeat rate was temperature dependent with a Q10 of 2.3. Either a bite by the Lynx spider, Peucetia vividans (Hentz), or severing the abdomen from the thorax caused the heartbeat to become extremely steady at near 300 beats/min which gradually decreased over several minutes.Application of lethal doses of Monitor or Lindane to the house fly caused thoracic temperature to increase by at most 3°C in conjunction with increased convulsive activity and increased average heartbeat rate. In late stages of poisoning, the heartbeat was relatively uniform indicating a disruption in cardioregulatory nervous activity. Response of the house fly to carbofuran or its N-thiomethyl analog was similar to that of Monitor and Lindane except in late stages of poisoning where the heartbeat continued to exhibit large variations in average rate.  相似文献   

17.
A spectrophotometer interfaced with a microcomputer to collect and analyse data automatically was used to study the inhibition kinetics of house fly acetylcholinesterase by malaoxon and dichlorvos in the presence of substrate. This system simply and unequivocally identified insecticide-insensitive enzymes from single fly heads, even when these enzymes were hitherto uncharacterised. As well as identifying individual insects homozygous for a particular form of acetylcholinesterase, the method also recognised heterozygotes because the mixture of enzymes then present gave a heterogeneous response to inhibitors. In the latter case, each component enzyme present could be identified. The technique is valuable for characterising heterogeneous insect populations collected from the field, for establishing homozygous strains, and for more detailed biochemical study.  相似文献   

18.
Two cytochrome P-450-containing fractions were isolated from detergent-solubilized house fly microsomes by hydrophobic chromatography on a tryptamine-Sepharose gel. These fractions (designated P-450-1 and P-450-2) were distinctive in their spectral characteristics and in their profiles following electrophoresis in the presence of sodium dodecyl sulfate. Both fractions exhibited NADPH-dependent epoxidase activity when reconstituted with purified house fly cytochrome P-450 reductase and phospholipid. The aldrin epoxidase activity of fraction P-450-1 was twice that of P-450-2 even though heptachlor epoxidase activity of the fractions was equivalent. O-Demethylase activity with 7-methoxy-4-methylcoumarin was detectable only in the P-450-2 fraction.  相似文献   

19.
The degradation of the pyrethroid insecticide cypermethrin and the geometric isomers NRDC 160 (cis-) and NRDC 159 (trans-) in three soils has been studied under laboratory conditions. Samples of the insecticides labelled separately with 14C in the cyclopropyl and benzyl rings were used. The rate of degradation was most rapid on sandy clay and sandy loam soils, 50% of the NRDC 160 and NRDC 159 applied to both soils being decomposed in 4 weeks and 2 weeks respectively. The major degradative route in all soils was hydrolysis of the ester linkage leading to the formation of 3-phenoxybenzoic acid and 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid; soil treated with the cis-isomer (NRDC 160) was found to contain both cis- and trans-isomer forms of the cyclopropanecarboxylic acid. Further degradation of these carboxylic acids was evident since 14CO2 was released from cyclopropyl- and benzyllabelled cypermethrin in amounts equivalent to 24 and 38% of the applied radioactivity over a 22 week period. A minor degradative route was ring-hydroxylation of the insecticide to give an α-cyano-3-(4-hydroxyphenoxy)benzyl ester followed by hydrolysis of the ester bond. Under waterlogged conditions the rate of hydrolysis of cypermethrin on sandy loam soil was slower than under aerobic conditions and 3-phenoxybenzoic acid accumulated in the anaerobic soil.  相似文献   

20.
Glutathione transferases have been purified to a high degree of homogeneity from three strains of house fly by a procedure involving affinity chromatography on glutathione-sulfobromophthalein conjugate immobilized on Sepharose 4B, followed by preparative isoelectrofocusing. The affinity chromatography yielded purifications of between about 10- and 100-fold, depending on the strain and the substrate with which activity was measured. Each strain was shown to possess several proteins with glutathione S-transferase activity which fell into two clearly defined groups. The first group, of relatively low isoelectric point, showed activity with CDNB but little with DCNB, p-nitrobenzylchloride, or 1,2-epoxy-3-(p-nitrophenoxy)propane, whereas the second group, of higher isoelectric points, showed substantial activity with all substrates tested. Studies on the subunit structure of these enzymes demonstrated the existence of three different sized subunits of Mr 20,000, 22,000, and 23,500. From the experimental evidence recorded here, the existence of at least three functionally different glutathione transferases is inferred.  相似文献   

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