Biochemical and Toxicological Studies with Laboratory and Field Populations of Heliothis virescens (F.)

Ibrahim, S. A.; Ottea, James A.

doi:10.1006/pest.1995.1059

Cited by 22 publications

(13 citation statements)

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“…Fresh gut tissue from 50 fifth‐instar O nubilalis larvae was homogenized with a Teflon glass Potter–Elvehjem type homogenizer in sodium phosphate buffer (0.1 M , pH 7.6; 1 ml) containing glycerol (150 g liter −1 ) 25. 26 Gut homogenates were centrifuged at 10 000 g for 12 min at 4 °C in a microcentrifuge.…”

Section: Methodsmentioning

confidence: 99%

In vivo and in vitro metabolism of fipronil by larvae of the European corn borer Ostrinia nubilalis

Durham

Siegfried

Scharf

2002

Pest Management Science

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In vivo and in vitro metabolism of [14C]fipronil was examined in a susceptible European corn borer (Ostrinia nubilalis, Hübner) laboratory strain. [14C]Fipronil penetrated the larval integument slowly, with 71.5% of the applied radioactivity recovered from surface rinses 24 h after topical application. Despite this slow penetration, radioactivity was detected in both the excrement and internal organo-soluble fractions. Radioactivity in the internal aqueous fraction and tissue pellet accounted for less than 0.8% of total radioactivity. The in vivo studies suggest that fipronil oxidation to its sulfone metabolite is the major route of metabolic conversion. In vitro studies were performed using subcellular microsomal fractions isolated from European corn borer larval midguts. Cytochrome P450-dependent monooxygenase activity (methoxyresorufin O-demethylase) was consistently observed in midgut preparations, and formation and detection of the sulfone metabolite in the same midgut preparations was also NADPH-dependent and inhibited by piperonyl butoxide. In vitro metabolism results indicate microsomal monooxygenases are responsible for the conversion of fipronil to its sulfone form in the European corn borer.

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Section: Methodsmentioning

confidence: 99%

In vivo and in vitro metabolism of fipronil by larvae of the European corn borer Ostrinia nubilalis

Durham

Siegfried

Scharf

2002

Pest Management Science

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“…This is that it appears to involve cross-resistance to both CBs and SPs. Field caught strains of this species have shown quite high levels of resistance to all three chemistries 19) and laboratory selection experiments for enhanced resistance to any one of the three has led to enhanced resistance for either or both of the other two. [20][21][22][23][24] Moreover at least some of the cross-resistance appears to involve the esterases, since the esterase inhibitor S,S,S-tributylphosphorotrithioate (DEF) synergises the effects of all three chemistries on the laboratory-selected resistant lines.…”

Section: Heliothine Resistance To Opsmentioning

confidence: 99%

“…It is also notable that other workers have found no association between SP resistance and a -naphthyl acetate activities in this species. 19,74) On the other hand there is good evidence for higher esteratic degradation of a radiolabelled SP (permethrin) and an SP analogue amenable to spectrophotometric assay in resistant as compared to susceptible Hs. virescens.…”

Section: Heliothine Resistance To Spsmentioning

confidence: 99%

Esterase-based metabolic resistance to insecticides in heliothine and spodopteran pests

Farnsworth

Teese

Yuan

et al. 2010

Journal of Pesticide Science

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IntroductionCarboxylesterases have been implicated in metabolic resistance to several classes of insecticide in a wide variety of pest insect species. [1][2][3] The classes most commonly involved are synthetic pyrethroids (SPs) and organophosphates (OPs), and carbamates (CBs) are also involved in several cases. There are also occasional reports of carboxylesterase phenotypes associated with resistance to benzoylureas, the oxadiazine indoxacarb, the diacylhydrazine tebufenozide, the organochlorine endosulfan and the proteinaceous Cry1Ac toxin of Bacillus thuringiensis that is expressed in transgenic crops. Figure 1 gives structures for some key compounds among these various classes of insecticide.It might be expected that carboxylesterases would be involved in SP resistance because the great majority of SPs are carboxylesters. However, no precise molecular mechanisms for esterase-based SP resistance have yet been elucidated in any insect. OPs are generally phosphotriesters rather than carboxylesters but nevertheless they bind many carboxylesterases with high affinity and this provides a basis for two forms of resistance, both now elucidated at a molecular level in several species. One form involves substantial overexpression of the esterase, allowing for effective sequestration of the insecticide. The other involves specific mutations in the active site of the enzyme which convert it to an OP hydrolase (the so-called "mutant ali-esterase" mechanism). CBs are carbamic acid (NH 2 COOH) derivatives, in which a functional group has been added as an ester; these esters are chemically similar to carboxylesters. Carbamates bind carboxylesterases with quite high affinity, but as yet the molecular mechanisms by which a (mutant) carboxylesterase confers CB resistance have not been elucidated in any species. Of the other insecticide classes occasionally linked to esterase-based resistance only indoxacarb has ester bonds (two Elevated esterase activities and increased band intensities of multiple esterase isozymes after electrophoresis are commonly associated with resistance to organophosphate, pyrethroid and carbamate insecticides in various heliothine and spodopteran pests. One possible explanation for this involves a 'master regulator' mutation in a more general chemical stress response. An association between elevated esterase activities and isozyme intensities has also been reported for resistance to the Cry1Ac toxin of Helicoverpa armigera. The basis for this is unclear albeit some involvement of esterases could be mediated by the toxin's affinity for N-acetyl galactosamine glycans on certain gut-expressed esterases in this species.

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“…In the tobacco budworm, Heliothis virescens F., esterase activity was correlated (r 2 ϭ 0.87) with increased frequencies of resistance in 15 populations examined across Louisiana (Harold and Ottea 2000). However, in other studies no such correlation was found (Brown andBrogdon 1987, Ibrahim andOttea 1995). Thus, the validity of enzyme activities measured with model substrates as indicators of metabolic resistance to insecticides cannot be assumed.…”

Section: Discussionmentioning

confidence: 57%

Association of Esterases With Insecticide Resistance in <I>Culex quinquefasciatus</I> (Diptera: Culicidae)

Gordon

Ottea

2012

jnl. econ. entom.

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The southern house mosquito, Culex quinquefasciatus Say, is a competent vector of human disease and an important target of mosquito abatement programs. However, these management programs have been compromised by development of insecticide resistance. In the current study, susceptibilities to naled and resmethrin, two adulticides used in mosquito abatement, were monitored using a topical and contact bioassay, respectively, in five field- collected populations of C. quinquefasciatus (MARC, HOOD1, HOOD2, MINLOVE, and THIB). Frequencies of resistance, measured as survival after treatment with discriminating concentrations (i.e., sufficient to kill > 90% of a reference susceptible strain) were high (88.0-96.8%) in all field collections treated with naled, but were variable (3.3-94.2%) with resmethrin. In addition, esterase activities in mosquitoes from these collections were quantified using alpha-naphthyl acetate and ranged from 1.08 to 3.39 micromol alpha-naphthol produced min(-1) mg prot(-1). Heightened activities were associated with decreased insecticide susceptibility in HOOD1, THIB, and MINLOVE but not HOOD2. Esterases were visualized using native polyacrylamide gel electrophoresis, and intra- and interstrain differences in banding patterns were detected. In addition, esterases from MINLOVE mosquitoes were more numerous and intensely staining when compared with those from a laboratory-susceptible strain. Finally, naled synergized the toxicity of resmethrin in populations with decreased insecticide susceptibility and increased esterase activity by 2.5-(MINLOVE) to three-fold (THIB). Results from this study will allow management strategies for populations of C. quinquefasciatus to be optimized, and provide a foundation for further studies exploring use of esterase inhibitors as synergists of pyrethroid toxicity.

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Biochemical and Toxicological Studies with Laboratory and Field Populations of Heliothis virescens (F.)

Cited by 22 publications

References 0 publications

In vivo and in vitro metabolism of fipronil by larvae of the European corn borer Ostrinia nubilalis

In vivo and in vitro metabolism of fipronil by larvae of the European corn borer Ostrinia nubilalis

Esterase-based metabolic resistance to insecticides in heliothine and spodopteran pests

Association of Esterases With Insecticide Resistance in <I>Culex quinquefasciatus</I> (Diptera: Culicidae)

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