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1.
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   

2.
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   

3.
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   

4.
Most of the studies on insecticide impregnated bednets efficacy in malaria control have been undertaken in areas where mosquitoes are pyrethroid susceptible. The efficacy of pyrethroid-treated bednets was not compromised even when mosquitoes were kdr resistant. Here, we evaluate a case in which mosquitoes have kdr-like pyrethroid resistance coupled with metabolic mechanisms. Metabolic and kdr-resistance mechanisms in Anopheles stephensi were characterised in our previous study and this easily colonised species was used as a model to examine the efficacy of pyrethroid-treated bednets in the laboratory. Bioassays performed on adults of susceptible (Beech) and resistant (DUB-S) strains using WHO 0.75% permethrin-impregnated papers showed a resistance ratio of 9.75. The recovery rate of the mosquitoes of the DUB-S strain was significantly higher than that of the susceptible strain Beech. The overall permethrin metabolism rates by DUB-S, measured by HPLC method, were 1.5-fold more than by Beech strain. Bioassays performed on DUB-S mosquitoes using different pyrethroid-treated bednets showed that only deltamethrin at 25 mg/m2 and α-cypermethrin at 40 mg/m2 produced adequate mortality rates. Four other pyrethroids, including permethrin, were ineffective. The deterrency test performed on susceptible and resistant An. stephensi showed that there are significant differences between the entry rates of susceptible and resistant mosquitoes into the exposure tube containing permethrin-treated bednet. These data show that when mosquitoes have both kdr-type and metabolic resistance mechanisms, the efficacy of pyrethroid-treated bednets is questionable.  相似文献   

5.
The in vivo and in vitro metabolism of [14C]malathion was studied in susceptible (LS) and malathion resistant (RM) strains of the sheep blowfly, Lucilia cuprina (Wiedemann). No difference was found between strains in the penetration, excretion, storage, or inhibitory potency of the insecticide. However, RM degraded malathion to its α- and β-monocarboxylic acid metabolites more rapidly than LS, both in vivo and in vitro. This enhanced degradation of [14C]malathion occurred in vitro in both mitochondrial and microsomal fractions of resistant flies. Kinetic analysis revealed that these fractions degraded malathion by discrete mechanisms. The enzymes from the mitochondria of both strains had the same Km, whereas the microsomal enzyme from the RM strain had a fivefold higher Km than that from the LS strain. Studies of esterase activities and the effect of enzyme inhibitors showed that both the mitochondrial and microsomal resistance mechanisms were the result of enhanced carboxylesterase activity. It was concluded that increased carboxylesterase detoxification of malathion adequately explained the high level of malathion resistance in RM if rate-limiting factors such as cuticular penetration were taken into account.  相似文献   

6.
A survey in SE England showed that seven out of 17 populations of glasshouse whitefly were resistant to DDT. Resistance to malathion occurred in 15 populations and to resmethrin in eight. Mecarbam and methiocarb gave good kills in screening tests but some insect growth regulators gave variable results. The synthetic pyrethroid permethrin was slightly more effective against a population of whitefly resistant to both DDT and malathion than against a susceptible population. Parthenogenetic females from a population susceptible to DDT and malathion produced almost entirely male progeny. An unsuccessful attempt was made to lower the resistance level of a DDT/malathion resistant strain by introducing these males to resistant females.  相似文献   

7.
We have examined the chromosomal basis for reproductive and developmental defects that are associated with malathion resistance in a laboratory-selected population of Drosophila melanogaster. Strains homozygous for second or third chromosomes from this population were more resistant to malathion and had greater mixed-function oxidase activity, decreased fertility, and lower egg production when compared with first chromosome or susceptible strains. Some of the strains carrying resistant third chromosomes were developmentally delayed and required a significantly longer time to pupate. Delayed pupation was not associated with increased in vitro degradation of ecdysone by larvae having increased mixed-function oxidase activity, nor could it be reversed by feeding larvae ecdysone. Differences in mixed function oxidase activity among strains homozygous for second or third chromosomes were strongly correlated with malathion resistance but not with fitness. Although both second and third chromosome strains had high mixed-function oxidase activity, only fly extracts from the third chromosome strains oxidatively degraded [3H]juvenile hormone in vitro to a significant extent. A deficit of vitellogenic oocytes and increased egg laying by females in response to topically applied juvenile hormone-I supported the hypothesis that juvenile hormone titer was lower than normal in these strains. The results indicate that different polygenic systems control malathion resistance and associated fitness defects in this selected population of D. melanogaster. Although these systems are partly independent, they overlap due to pleiotropic effects of third chromosomal genes controlling mixed-function oxidase activity on female reproduction.  相似文献   

8.
BACKGROUND: Bromus rigidus is a common weed species that has increased in cropping fields owing to limited control options. During a random field survey in Western Australia, six B. rigidus populations that had survived in‐crop weed control programmes were collected. The study aimed to determine the resistance profile of these six populations. RESULTS: Based on dose–response studies, all six B. rigidus populations had a low‐level resistance to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) while remaining susceptible to herbicides with other modes of action. ALS in vitro activity assays revealed no differences in enzyme sensitivity between susceptible and resistant populations, while the use of malathion (a cytochrome P450 inhibitor) in combination with sulfosulfuron caused the resistant populations to behave like the susceptible population. CONCLUSION: This study established that these six B. rigidus populations have a low‐level resistance to the ALS‐inhibiting sulfonylurea herbicides, but are able to be controlled by other herbicide modes of action. The low‐level, malathion‐reversible resistance, together with a sensitive ALS, strongly suggest that a non‐target‐site enhanced metabolism is the mechanism of resistance. Copyright © 2012 Society of Chemical Industry  相似文献   

9.
The interactions of the synthetic pyrethroid, lambda-cyhalothrin and malathion were studied with purines, pyrimidines, caffeine and some other related nitrogenous compounds in resistant and susceptible strains of Triboliurn castaneum (Herbst.) The results were compared with those obtained with a known synergist, piperonyl butoxide (PBO) and precocene I. Adenine, cytosine, guanine, thymine and uracil synergised lambda-cyhalothrin, especially in the susceptible strain, with maximum effect at a 1:1 mass ratio, with the effect decreasing with increasing proportion of the heterocycle. The order of synergism of lambda-cyhalothrin was; precocene I > PBO > the nitrogenous compounds, in both resistant and susceptible strains. On the other hand, caffeine (lethal effect increased about twice), barbital (about twice), isobarbituric acid (less than twice) and bromacil (up to eight times) synergised malathion in malathion-resistant strains and antagonised in the susceptible strains. Total in-vivo esterases, carbox-ylesterases and cytochrome P450 of susceptible and resistant strains showed significantly increased activity or content when treated with either insecticide plus a heterocyclic compound. Exceptions were with bromacil and malathion and for the malathion-specific strain, Kano-C with malathion and the N-heterocycles.  相似文献   

10.
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   

11.
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12.
Females of a diazinon-resistant strain of German cockroach exhibiting cross resistance to propoxur were evaluated for resistance to diazinon and propoxur by six assays: LD50s for topical application and injection; LC50, KT50 and LT50 for deposits on wood and KT50 for deposits on glass. Also investigated were certain variables in the topical application technique and the experimental conditions for topical synergism studies. Among all assays, diazinon resistance ratios (resistant:susceptible) ranged from 3- to 145-fold; propoxur varied from 1- to 14-fold. Resistance ratios based on KT50 data were consistently low (<4x) for both insecticides. Resistance to diazinon was 13x when applied topically and 6x when injected. Resistance to propoxur was 14x by injection compared to 8x for topical application. The LC50 assay exhibited the greatest difference in resistance to the two insecticides: namely, 145x to diazinon and 1x(no resistance) to propoxur. By LT50 analysis, resistance to propoxur was 10x compared with 100x resistance to diazinon. Thus, the method used had a significant effect on the final value of the resistance ratio. Even though resistance ratios may vary widely among different techniques, the final choice of a method depends upon many factors. The LT50 method may provide a more realistic appraisal of resistance in wild populations of German cockroaches especially when experimental residues are similar to those used in control programmes.  相似文献   

13.
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   

14.
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   

15.
In the case where resistance to an insecticide is associated with increased metabolism of the insecticide, it should not be concluded that the resistance is due only to the increased metabolism (i.e. metabolic hypothesis). Here, we study theoretically the pharmacokinetic consequences of a resistance mechanism due to increased metabolism. We consider two cases: treatment with the initial dose D0 applied to the susceptible strain and the treatment with the initial dose αD0, with α>1, applied to the resistant strain. We show the conditions for which the metabolism hypothesis is conceivable. The time τ, from which the mortality of the susceptible strain is significantly higher than that of the resistant strain, is an important parameter in determining the validity of the metabolic hypothesis. The more τ increases, the more the conditions are favourable to this hypothesis. Our work suggests an approach to test the metabolic hypothesis from experimental results. © 1998 SCI  相似文献   

16.
Comparisons with standard susceptible insects showed that a strain of Tribolium castaneum, with a specific resistance to malathion and its carboxylic ester analogues, had no cross-resistance to topical applications of natural pyrethrins. Another strain of T. castaneum, showing resistance to many organophosphorus (OP) insecticides, was cross-resistant to pyrethrins ( × 34) and eight synthetic pyrethroids also applied topically; least cross-resistance occurred with resmethrin ( × 2.2), bioresmethrin ( × 3.3) and phenothrin ( × 4.0). Generally larger resistance factors were recorded with formulations synergised by piperonyl butoxide (PB). The greatest cross-resistance encountered was with unsynergised tetramethrin ( × 338). Apart from tetramethrin, factors of synergism did not exceed 5.7 with either the susceptible or multi-OP resistant strains. PB antagonised six of the nine pyrethroids against the multi-OP resistant strain. Antagonism also occurred with two of these six, permethrin (cis: trans ratio 1:3) and 5-prop-2-ynylfurfuryl ( 1RS)-cis,trans-chrysanthemate (‘Prothrin’), against the susceptible strain. Considering only formulations without the synergist, the most effective compounds against the susceptible strain, relative to pyrethrins, were bioresmethrin (2.7) and permethrin (2.4). Similarly with the multi-OP resistant strain the most effective compounds were bioresmethrin (28), resmethrin (14) and permethrin (6.6). Thus the LD50 (the dose required to kill 50% of the test species) for bioresmethrin against the resistant strain (0.14 μg) only slightly exceeded the LD50 for pyrethrins against the susceptible strain (0.12 μg).  相似文献   

17.
Penetration, metabolism and excretion of [14C]DDT and [3H]transpermethrin were studied in three strains of Aedes aegypti L. after topical application of 10 nl of a solution of the insecticide in 2-ethoxyethanol. The standard susceptible strain was compared with a DDT-selected strain (BKS) and a permethrin-selected strain (BKPM). No significant penetration resistance was observed in either resistant strain, but both showed high DDT-dehydrochlorinase activity which contributed to the DDT resistance. A non-metabolic factor was also involved. Rates of transpermethrin metabolism were very similar in all three strains and substantially higher internal concentrations of transpermethrin were required to produce toxic effects in both BKS and BKPM mosquitoes. By analogy with other insect species, it is concluded that transpermethrin resistance in these strains is of the kdr type, while the DDT resistance is a mixture of kdr and DDT-dehydrochlorinase.  相似文献   

18.
The relative rates of cytochrome P450 selection in southern Mexican Anopheles albimanus populations were investigated during a 3 years indoor residual house spraying intervention with a pyrethroid (PYR) or DDT, a mosaic of organophosphate (OP)-PYR, and the annual rotation of OP-PYR-carbamate (CARB). This insecticide resistance mechanism, initially evenly spread in the mosquito population, correlated with PYR resistance during the second treated year, when cytochrome P450 contents increased in most villages of the PYR, rotation and mosaic schemes. However, by the third year, mean cytochrome P450 contents declined to susceptible levels in mosquitoes of the rotation and one mosaic group but not in the PYR-treated villages. In DDT-treated villages, a continuous decrement of cytochrome P450 levels occurred since the first treatment year, and susceptible levels were observed at the end of the intervention. Most correlations of cytochrome P450 levels and PYR resistance were lost during the third year, indicating that another mechanism evolved in resistant mosquito populations.  相似文献   

19.
A population of Bromus tectorum infesting an olive grove at Córdoba (Spain) survived simazine use rates of 3.0 kg a.i. ha−1 over two consecutive years. Non‐tillage olive monoculture and two annual simazine applications had been carried out for 10 years. The resistant biotype showed a higher ED50 value (7.3 kg a.i. ha−1) than that of the susceptible control (0.1 kg a.i. ha−1), a 73‐fold increase in herbicide tolerance. The use of fluorescence, Hill reaction, absorption, translocation and metabolism assays showed that simazine resistance in this biotype was caused by a modification of the herbicide target site, since chloroplasts from the resistant biotype of B. tectorum were more than 300 times less sensitive to simazine than those from the susceptible biotype. In addition, non‐treated resistant plants of B. tectorum displayed a significant reduction in the QA to QB electron transfer rate when compared with the susceptible biotype, a characteristic that has been linked to several mutations in the protein D1 conferring resistance to PS II inhibiting herbicides. Resistant plants showed cross‐resistance to other groups of triazine herbicides with the hierarchy of resistance level being methoxy‐s‐triazines ≥chloro‐s‐triazines > methylthio‐s‐triazines > cis‐triazines. The results indicate a naturally occurring target‐site point mutation is responsible for conferring resistance to triazine herbicides. This represents the first documented report of target site triazine resistance in this downy brome biotype.  相似文献   

20.
BACKGROUND: Knockdown resistance (kdr) mutation (L1014F) is a well‐defined mechanism of resistance to pyrethroids and DDT in many insect species. Sensitive detection of the mutations associated with resistance is a prerequisite for resistance management strategies. The authors have developed a new real‐time molecular diagnostic assay based on SimpleProbe®/melting curve analysis for large‐scale kdr genotyping in the wild population of Culex quinquefasciatus Say, the principal vector of bancroftian filariasis. Melting curve analysis is based on the thermal stability difference between matched and mismatched DNA duplexes. The application of SimpleProbe® chemistry in insects described here is novel in entomology research. RESULTS: The mosquitoes homozygous for knockdown‐resistant and knockdown‐susceptible allele showed melting peaks at 60.45 °C ( ± 0.25) and 64.09 °C ( ± 0.24) respectively. The heterozygous mosquitoes yielded both peaks at approximately 60.5 °C ( ± 0.2) and 64.20 °C ( ± 0.23). Among the 92 samples genotyped, 16 were found to be homozygous resistant, 44 homozygous susceptible and 32 heterozygous. Comparative assessments were made of all the reported methods for kdr genotyping. CONCLUSION: The present method is cheaper, faster, more reliable and versatile than other alternatives proposed in detecting correct kdr genotypes in mosquitoes. This is the first report using a single‐labelled hybridisation probe to detect point mutations in insect populations. Copyright © 2010 Society of Chemical Industry  相似文献   

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