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Comparison of esterase between insecticide resistant and susceptible strains of German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae)

No-Joong Park, University of Nebraska - Lincoln

Abstract

The Crawford strain of German cockroach, Blattella germanica (L.) was determined to be highly resistant to chlorpyrifos, propoxur, cypermethrin, and permethrin and esterase activities were higher than susceptible CSMA strains at both nymphal and adult stages. The most mobile isozyme a and c that were stained more intensely in every developmental stage and sex of both strains showed much greater intensity in the Crawford strain. Another intensely stained isozyme b was observed only in homogenates from the Crawford strain. ^ The distribution and inhibition of esterase activity among body of the resistant Crawford and susceptible CSMA strains of male German cockroach, Blattella germanica (L.), were evaluated with α- and β-naphthyl esters using a spectrophotometric assay and native polyacrylamide gel electrophoresis. The esterase activities in the Crawford strain were significantly higher than in the CSMA strain in most tissues except midgut and male genitalia, where the activities were similar. In both strains, isozyme a was dominant in the brain and fat body and isozymes c and d were more abundant in the midgut; but isozyme b was observed only in the Crawford strain. In addition, the esterase b was observed from the whole body homogenates of several German cockroach resistant strains on native PAGE analysis. The complete inhibition by paraoxon was observed regardless of the strain, substrate type, and body part for enzyme source in spectrophotometric assay and native PAGE gels. ^ The brain esterase preferred ester substrates with chain length of carbons, less than 5 in carbon number. Maximum activity of the p-NPB esterase appeared at 40°C and pH 7.4 at 38°C in both strains. The addition of Triton X-100 into extraction buffer enhanced the p-NPB esterase activity. The addition of sucrose and dithiothreitol was also favorable in minimizing the spontaneous inactivation of enzyme activity during homogenization and storage. The p-NPB esterase in brain was extremely sensitive to paraoxon and strongly inhibited by eserine and propoxur. ^ The toxicity of chlorpyrifos was greatly reduced in decapitated CSMA male cockroaches with LD50 values 17.1-fold higher than that from normal CSMA roaches. The acetylcholinesterase activity from heads were significantly higher in Crawford stain than CSMA strain and were not changed till 24 h after in vivo treatment chlorpyrifos in both strains. The p-NPB esterase activities from both heads and decapitated bodies of resistant Crawford strain were significantly greater than those from susceptible CSMA strain. The p-NPB esterase activity was significantly inhibited after chlorpyrifos treatment, and the total p-NPB esterase activity was more significantly declined in the decapitated bodies than that in the heads of both strains. In native PAGE analysis, the isozyme d1 and d2 appear to be more sensitive to the chlorpyrifos intoxication than acetylcholinesterase and the isozyme c1 and c2 might be responsible for detoxification of chlorpyrifos. ^

Subject Area

Biology, Molecular|Biology, Entomology

Recommended Citation

Park, No-Joong, "Comparison of esterase between insecticide resistant and susceptible strains of German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae)" (2000). ETD collection for University of Nebraska - Lincoln. AAI9967401.
http://digitalcommons.unl.edu/dissertations/AAI9967401

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