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Synthetic Pyrethroids (synthetic + pyrethroid)
Terms modified by Synthetic Pyrethroids Selected AbstractsEstrogenic activity of lambda-cyhalothrin in the MCF-7 human breast carcinoma cell line,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2008Meirong Zhao Abstract Synthetic pyrethroids are widely used in both agricultural and urban environments for insect control. Lambda-cyhalothrin (LCT) is one of the most common pyrethroids and is used mainly for controlling mosquitoes, fleas, cockroaches, flies, and ants around households. Previous studies have addressed the environmental behaviors and acute toxicities of LCT, but little is known about its chronic toxicity, such as estrogen-like activity. In the present study, the estrogenic potential of LCT was evaluated using the MCF-7 human breast carcinoma cell line. The in vitro E-screen assay showed that 10,7 M LCT could significantly promote MCF-7 cell proliferation, with a relative proliferative effect ratio of 45%. The cell proliferation induced by LCT could be blocked completely, however, by the addition of 10,9 M of the estrogen receptor (ER)-antagonist ICI 182,780. The semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) results showed that the Trefoil factor 1 (pS2) and progesterone receptor gene expression were up-regulated by 10,7 M LCT for 2- and 1.5-fold, respectively. On the other hand, RT-PCR, Western blot analysis, and immunofluorescent assay demonstrated that LCT significantly repressed the mRNA and protein expression levels of ER, and ER,. These observations indicate that LCT possesses estrogenic properties and may function as a xenoestrogen, likely via a mechanism similar to that of 17,-estradiol. The endocrine-disruption potential of LCT should be considered when assessing the safety of this compound in sensitive environmental compartments. [source] Isomer selectivity in aquatic toxicity and biodegradation of bifenthrin and permethrinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Weiping Liu Abstract Synthetic pyrethroids are widely used insecticides, and contamination of surface aquatic ecosystems by pyrethroid residues from runoff is of particular concern because of potential aquatic toxicity. Pyrethroids also are chiral compounds consisting of multiple stereoisomers. In the present study, we evaluated the diastereomer and enantiomer selectivity of cis -bifenthrin (cis -BF) and permethrin (PM) in their aquatic toxicity and biodegradation. The 1R-cis enantiomer was the only enantiomer in cis -BF showing toxicity against Ceriodaphnia dubia. Incubation with pesticide-degrading bacteria showed that the trans diastereomer of PM was selectively degraded over the cis diastereomer, whereas the 1S-cis enantiomer in cis -BF or cis -PM was preferentially degraded over the corresponding 1R-cis enantiomer. The enantioselectivity was significantly greater for cis -PM than for cis -BF and also varied among different strains of bacteria. Isomer selectivity may be a common phenomenon in both aquatic toxicity and biodegradation of pyrethroids, and this should be considered when assessing ecotoxicological risks of these compounds in sensitive ecosystems. [source] Phase distribution of synthetic pyrethroids in runoff and stream waterENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Weiping Liu Abstract Synthetic pyrethroids (SPs) are a group of hydrophobic compounds with significant aquatic toxicity. Their strong affinity to suspended solids and humic materials suggests that SPs in natural surface water are distributed in solid-adsorbed, dissolved organic matter (DOM)-adsorbed, and freely dissolved phases. The freely dissolved phase is of particular importance because of its mobility and bioavailability. In the present study, we used solid-phase microextraction to detect the freely dissolved phase, and we evaluated the phase distribution of bifenthrin and permethrin in stream and runoff waters. In stream water, most SPs were associated with the suspended solids and, to a lesser extent, with DOM. The freely dissolved phase contributed only 0.4% to 1.0%. In runoff effluents, the freely dissolved concentration was 10% to 27% of the overall concentration. The predominant partitioning into the adsorbed phases implies that the toxicity of SPs in surface water is reduced because of decreased bioavailability. This also suggests that monitoring protocols that do not selectively define the freely dissolved phase can lead to significant overestimation of toxicity or water-quality impacts by SPs. [source] Dual enantioselective effect of the insecticide bifenthrin on locomotor behavior and development in embryonic,larval zebrafishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2010Meiqing Jin Abstract Bifenthrin (BF) is a synthetic pyrethroid that targets the nervous system of insects and may have adverse effects on the behavior and development of nontarget organisms. However, no reports have been issued on the effects of different enantiomers on locomotor behavior for synthetic pyrethroids (SPs) in zebrafish, and whether locomotor activity is associated with the developmental toxicities remains unclear. In this study, enantioselectivity of BF (1S and 1R) on the acute locomotor activity and developmental toxicities of embryonic,larval zebrafish were first evaluated. The results indicated that 1R -BF was more toxic, causing morphological impairments, with a 96-h median effective concentration (EC50) of 226,µg/L for pericardial edema and 145,µg/L for curved body axis. Administration of 20,µg/L of one enantiomer of BF had differential effects on the locomotor activity of zebrafish larvae at 4 d postfertilization (dpf) under alternating light and dark conditions. Larvae treated with 1R -BF were not sensitive to the alteration of light to dark, and the locomotor activities were reduced to a level similar to that observed in light, which otherwise increased rapidly and markedly. However, 1S -BF did not alter the general pattern of zebrafish response to the light or dark compared with the control. The results demonstrated that the differential effects on development might have contributed to the enantioselectivity in the locomotor activity. The consistency of enantioselectivity with insecticidal activity may also indicate a common mode of action. Furthermore, 1R -BF accelerated the spontaneous movement and hatching process, whereas 1S -BF seemed to be inhibitory. The results suggest the need to link behavioral changes to developmental toxicities in order to achieve more comprehensive health risk assessments of chiral pesticides. Environ. Toxicol. Chem. 2010;29:1561,1567. © 2010 SETAC [source] Biochemical mechanisms of insecticide resistance in the diamondback moth (DBM), Plutella xylostella L. (Lepidopterata: Yponomeutidae), in the Sydney region, AustraliaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2009Vincent Y Eziah Abstract Following the detection of resistant diamondback moth (DBM) populations to synthetic pyrethroid, organophosphorus and indoxacarb insecticides in the Sydney Basin, a study of the major biochemical mechanisms was conducted to determine the type of resistance in these populations. The activity of cytochrome P450 monooxygenases increased two- to sixfold when compared with the susceptible strain. Up to a 1.9-fold increase in esterase activity in resistant strains compared with the susceptible strain was observed. In vitro inhibition studies showed that profenofos, methamidophos and chlorpyrifos strongly inhibited the esterases while permethrin and esfenvalerate resulted in less than 30% inhibition. Qualitative analysis of the esterases using native polyacrylamide gel electrophoresis showed four bands in both the susceptible and resistant individuals with more intense staining in the resistant individuals. The development of these bands was inhibited by methamidophos and chlorpyrifos pretreatment of the protein extract while permethrin and esfenvalerate did not exhibit this effect. Glutathione S-transferase (GST) activity was significantly higher in two field populations compared with the remaining populations. Overall, the study showed that the mechanisms of insecticide resistance in the DBM populations in the area studied were due to cytochrome P450 monooxygenases, esterase and GSTs, and possibly other non-metabolic mechanisms that were not investigated in the present study. [source] Dual enantioselective effect of the insecticide bifenthrin on locomotor behavior and development in embryonic,larval zebrafishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2010Meiqing Jin Abstract Bifenthrin (BF) is a synthetic pyrethroid that targets the nervous system of insects and may have adverse effects on the behavior and development of nontarget organisms. However, no reports have been issued on the effects of different enantiomers on locomotor behavior for synthetic pyrethroids (SPs) in zebrafish, and whether locomotor activity is associated with the developmental toxicities remains unclear. In this study, enantioselectivity of BF (1S and 1R) on the acute locomotor activity and developmental toxicities of embryonic,larval zebrafish were first evaluated. The results indicated that 1R -BF was more toxic, causing morphological impairments, with a 96-h median effective concentration (EC50) of 226,µg/L for pericardial edema and 145,µg/L for curved body axis. Administration of 20,µg/L of one enantiomer of BF had differential effects on the locomotor activity of zebrafish larvae at 4 d postfertilization (dpf) under alternating light and dark conditions. Larvae treated with 1R -BF were not sensitive to the alteration of light to dark, and the locomotor activities were reduced to a level similar to that observed in light, which otherwise increased rapidly and markedly. However, 1S -BF did not alter the general pattern of zebrafish response to the light or dark compared with the control. The results demonstrated that the differential effects on development might have contributed to the enantioselectivity in the locomotor activity. The consistency of enantioselectivity with insecticidal activity may also indicate a common mode of action. Furthermore, 1R -BF accelerated the spontaneous movement and hatching process, whereas 1S -BF seemed to be inhibitory. The results suggest the need to link behavioral changes to developmental toxicities in order to achieve more comprehensive health risk assessments of chiral pesticides. Environ. Toxicol. Chem. 2010;29:1561,1567. © 2010 SETAC [source] Multiple stressor effects of methoprene, permethrin, and salinity on limb regeneration and molting in the mud fiddler crab (UCA pugnax)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Todd A. Stueckle Abstract Exposure to multiple stressors from natural and anthropogenic sources poses risk to sensitive crustacean growth and developmental processes. Applications of synthetic pyrethroids and insect growth regulators near shallow coastal waters may result in harmful mixture effects depending on the salinity regime. The potential for nonadditive effects of a permethrin (0.01,2 ,g/L), methoprene (0.03,10 ,g/L), and salinity (10,40 ppt) exposure on male and female Uca pugnax limb regeneration and molting processes was evaluated by employing a central composite rotatable design with multifactorial regression. Crabs underwent single-limb autotomy followed by a molting challenge under 1 of 16 different mixture treatments. During the exposure (21,66 d), individual limb growth, major molt stage duration, abnormal limb regeneration, and respiration were monitored. At 6 d postmolt, changes in body mass, carapace width, and body condition factor were evaluated. Dorsal carapace tissue was collected, and protein and chitin were extracted to determine the composition of newly synthesized exoskeleton. The present results suggest chronic, low-dose exposures to multiple pesticide stressors cause less-than-additive effects on U. pugnax growth processes. Under increasing concentrations of methoprene and permethrin, males had more protein in their exoskeletons and less gain in body mass, carapace width, and body condition compared to females. Females exhibited less gain in carapace width than controls in response to methoprene and permethrin. Females also displayed elevated respiration rates at all stages of molt, suggesting a high metabolic rate. Divergent growth and fitness between the sexes over the long term could influence crustacean population resilience. [source] Effects of dietary esfenvalerate exposures on three aquatic insect species representing different functional feeding groupsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2008Katherine R. Palmquist Abstract Given the chemical properties of synthetic pyrethroids, it is probable that compounds, including esfenvalerate, that enter surface waters may become incorporated into aquatic insect food sources. We examined the effect of dietary esfenvalerate uptake in aquatic insects representing different functional feeding groups. We used three field-collected aquatic insect species: A grazing scraper, Cinygmula reticulata McDunnough (Ephemeroptera: Heptageniidae); an omnivorous filter feeder, Brachycentrus americanus Banks (Trichoptera: Brachycentridae); and a predator, Hesperoperla pacifica Banks (Plecoptera: Perlidae). Laboratory-cultured algae were preexposed for 24 h to esfenvalerate concentrations of 0, 0.025, 0.05, and 0.1 ,g/L and provided to two C. reticulata age classes (small and final-instar nymphs). Reduction in small nymph growth was observed following three weeks of feeding on algae exposed to 0.05 and 0.1 ,g/L of esfenvalerate, and the highest dietary exposure reduced egg production in final-instar nymphs. The diet for B. americanus and H. pacifica consisted of dead third-instar Chironomus tentans larvae preexposed for 24 h to esfenvalerate concentrations ranging between 0.1 and 1.0 ,g/L. Consumption of larvae exposed to 0.5 to 1.0 ,g/L of esfenvalerate caused case abandonment and mortality in B. americanus caddisfly larvae. Although H. pacifica nymphs readily consumed esfenvalerate-exposed larvae, no adverse effects were observed during the present study. Furthermore, no evidence of esfenvalerate-induced feeding deterrence was found in any of the species tested, suggesting that aquatic insects may not be able to distinguish between pyrethroid-contaminated and uncontaminated food sources. These findings indicate that feeding deterrence is not a factor in regulating aquatic insect dietary exposures to synthetic pyrethroids. [source] Microbial transformation of pyrethroid insecticides in aqueous and sediment phasesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Sangjin Lee Abstract Recent studies showed that synthetic pyrethroids(SPs)can move via surface runoff into aquatic systems. Fifty-six of SP-degrading bacteria strains were isolated from contaminated sediments, of which six were evaluated for their ability to transform bifenthrin and permethrin in the aqueous phase and bifenthrin in the sediment phase. In the aqueous phase, bifenthrin was rapidly degraded by strains of Stenotrophomonas acidaminiphila, and the half-life (t1/2) was reduced from >700 h to 30 to 131 h. Permethrin isomers were degraded by Aeromonas sobria, Erwinia carotovora, and Yersinia frederiksenii. Similar to bifenthrin, the t1/2 of cis - and trans -permethrin was reduced by approximately 10-fold after bacteria inoculation. However, bifenthrin degradation by S. acidaminiphila was significantly inhibited in the presence of sediment, and the effect was likely caused by strong adsorption to the solid phase. Bifenthrin t1/2 was 343 to 466 h for a field sediment, and increased to 980 to 1200 h for a creek sediment. Bifenthrin degradation in the inoculated slurry treatments was not greatly enhanced when compared with the noninoculated system. Therefore, although SP-degrading bacteria may be widespread in aquatic systems, adsorption to sediment could render SPs unavailable to the degraders, thus prolonging their persistence. [source] Phase distribution of synthetic pyrethroids in runoff and stream waterENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Weiping Liu Abstract Synthetic pyrethroids (SPs) are a group of hydrophobic compounds with significant aquatic toxicity. Their strong affinity to suspended solids and humic materials suggests that SPs in natural surface water are distributed in solid-adsorbed, dissolved organic matter (DOM)-adsorbed, and freely dissolved phases. The freely dissolved phase is of particular importance because of its mobility and bioavailability. In the present study, we used solid-phase microextraction to detect the freely dissolved phase, and we evaluated the phase distribution of bifenthrin and permethrin in stream and runoff waters. In stream water, most SPs were associated with the suspended solids and, to a lesser extent, with DOM. The freely dissolved phase contributed only 0.4% to 1.0%. In runoff effluents, the freely dissolved concentration was 10% to 27% of the overall concentration. The predominant partitioning into the adsorbed phases implies that the toxicity of SPs in surface water is reduced because of decreased bioavailability. This also suggests that monitoring protocols that do not selectively define the freely dissolved phase can lead to significant overestimation of toxicity or water-quality impacts by SPs. [source] Pattern of cross-resistance in pyrethroid-selected populations of Helicoverpa armigera Hübner (Lep., Noctuidae) from IndiaJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2004T. Ramasubramanian Abstract:, In Helicoverpa armigera, withdrawal of selection pressure resulted in a two- to fourfold increase in susceptibility to synthetic pyrethroids and continuous selection enhanced the resistance level by four- to fivefold to the respective pyrethroids at the end of the 14th generation. Populations selected for resistance to one pyrethroid showed positive cross-resistance to all other pyrethroids, but no cross-resistance to endosulfan and thiodicarb. There was a significant increase in mixed-function oxidase activity with advancing generation suggesting its possible role in the positive cross-resistance among the pyrethroids. The induction of carboxyl esterases in pyrethroid-selected populations may have resulted in the activation of indoxacarb, thereby accounting for the observed negative cross-resistance. [source] Knockdown resistance to DDT and pyrethroids: from target-site mutations to molecular modellingPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2008TG Emyr Davies Abstract Naturally derived insecticides such as pyrethrum and man-made insecticides such as DDT and the synthetic pyrethroids act on the voltage-gated sodium channel proteins found in insect nerve-cell membranes. The correct functioning of these channels is essential for the normal transmission of nerve impulses, and this process is disrupted by binding of the insecticides, leading to paralysis and eventual death. Some insect pest populations have evolved modifications of the sodium channel protein that inhibit the binding of the insecticide and result in the insect developing resistance. This perspective outlines the current understanding of the molecular processes underlying target-site resistance to these insecticides (termed kdr and super-kdr), and how this knowledge may in future contribute to the design of novel insecticidal compounds. Copyright © 2008 Society of Chemical Industry [source] Temporal synergism can enhance carbamate and neonicotinoid insecticidal activity against resistant crop pestsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 1 2008Georgina Bingham Abstract BACKGROUND: Piperonyl butoxide (PBO) effectively synergises synthetic pyrethroids, rendering even very resistant insect pests susceptible, provided a temporal element is included between exposure to synergist and insecticide. This concept is now applied to carbamates and neonicotinoids. RESULTS: A microencapsulated formulation of PBO and pirimicarb reduced the resistance factor in a clone of Myzus persicae (Sulzer) from > 19 000- to 100-fold and in Aphis gossypii (Glover) from > 48 000- to 30-fold. Similar results were obtained for a strain of Bemisia tabaci Gennadius resistant to imidacloprid and acetamiprid, although a second resistant strain did not exhibit such a dramatic reduction, presumably owing to the presence of target-site insensitivity and the absence of metabolic resistance. Synergism was also observed in laboratory susceptible insects, suggesting that, even when detoxification is not enhanced, there is degradation of insecticides by the background enzymes. Use of an analogue of PBO, which inhibits esterases but has reduced potency against microsomal oxidases, suggests that acetamiprid resistance in whiteflies is largely oxidase based. CONCLUSION: Temporal synergism can effectively enhance the activity of carbamates and neonicotinoids against resistant insect pests. Although the extent of this enhancement is dependent upon the resistance mechanisms present, inhibition of background enzymes can confer increased sensitivity against target-site resistance as well as increased metabolism. Copyright © 2007 Society of Chemical Industry [source] | ||||||||||