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PubMed2001

Modification, by the insecticide chlorpyrifos, of the behavioral response to kairomones of a parasitoid wasp, Leptopilina boulardi.

Parasitoids are key species involved in the regulation of natural populations. Host parasitization is realized via some important steps in which kairomone perception is essential. Due to the wide use of insecticides and their contribution to environmental pollution, the determination of their sublethal effects on behaviors involved in the reproduction of parasitoids becomes a necessity. In this work, we analyzed the effects of a lethal dose 20% of chlorpyrifos, an organophosphorus insecticide, on the behavior of L. boulardi toward the kairomone of its host. The insecticide significantly modified the kinetics of the residence time of parasitoids on a patch marked by kairomones. Females exposed to the insecticide were less efficient in finding the kairomone patch than control females, and they tended to stay on that patch, whereas control females rapidly left it. These effects are discussed considering the mode of action of the insecticide. Because search time allocation of host is an important component for parasitism efficiency, this modification of behavior could interfere with the reproduction capacity of parasitoids. Therefore, in a context of environmental pollution, the repercussions of such sublethal effects on the population biology of insects need to be considered.

Animals↗
PubMed1982

Interactions of chlorinated hydrocarbon insecticides with membranes.

Chlorinated hydrocarbon insecticides quench the fluorescence of N-alkyl derivatives of carbazole. We used phospholipids with covalently attached carbazole as probes for the interactions of chlorinated hydrocarbon insecticides with lipid bilayers, the object being to understand better the toxicities of chlorinated hydro-carbons. Fluorescence quenching measurements revealed the lipid-water partition coefficients of the chlorinated hydrocarbons, their diffusion coefficients in the membranes, and the binding capacities of the membranes for the chlorinated hydrocarbons. Active insecticides were compared with inactive analogues to test whether activities correlated with chlorinated hydrocarbon-membrane interactions. Thus DDT and methoxychlor were compared with inactive DDE, and insecticidal gamma-lindane was compared with three less active stereoisomers. The partition coefficients, diffusion coefficients and membrane saturation capacities did not correlate with insecticidal potency. The partition coefficients of these chlorinated hydrocarbons were larger in bilayers containing unsaturated fatty acyl chains as compared to bilayers containing saturated fatty acyl chains. Interestingly, neural membranes are known to contain a large percentage of unsaturated lipids. Our results indicate that the activities of chlorinated hydrocarbons are not a result of specific interactions of these compounds with the lipids of membranes. However, the neurotoxicity of chlorinated hydrocarbons may be amplified by selective partitioning in the unsaturated neural membranes.

Diffusion↗
PubMed1984

Interference by DDT and cyclodiene types of insecticides with chloroplast-associated reactions.

The effects of DDT, some of its analogs, and selected cyclodiene insecticides on isolated spinach (Spinacea oleracea L.) thylakoids were identified, characterized, and compared to responses induced by selected herbicides. Except for endrin, the insecticides inhibited light-induced electron transport, altered chlorophyll fluorescence transients, and competitively displaced [14C]atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], a known photosystem II inhibitor, from the membranes. The insecticides appeared to act at, or near B, the secondary electron acceptor of photo-system II. Binding of DDT and dieldrin was estimated at 900 and 2200 molecules, respectively, per photosynthetic unit (490 chlorophyll molecules). The insecticides also inhibited valinomycin-induced swelling of the thylakoid membrane. Whereas inhibition of electron transport can be attributed to interaction by the insecticides with a proteinaceous component of the thylakoid membrane, interference with the action of valinomycin may involve interaction with lipoidal constituents of the membrane.

Binding, Competitive↗
PubMed1983

Influence of pretreatment with various insecticides on the N-demethylation of dimethylnitrosamine.

The effects of various classes of insecticides were studied on the N-demethylation of dimethylnitrosamine (DMN) by mouse liver enzymes. Organochlorine insecticides, represented by lindane, DDT, and endrin, increased the activities of DMN demethylase I and II. The latter enzyme was more susceptible to the inducive action of the tested chlorinated insecticides. On the other hand, the synthetic pyrethroids, fenvalerate and flucythrinate, did not alter the activity of either enzyme. While pretreatment with carbaryl, a carbamate derivative, was without effect, moderate elevation in the activity of both demethylases was observed following administration of carbofuran. Dimethoate, representing organophosphorus compounds, was the only insecticide tested to inhibit the N-demethylation of DMN, with more pronounced effect on DMN demethylase I. Since DMN requires metabolic activation for its hepatotoxic and carcinogenic actions, alterations in the activities of its metabolizing enzymes as a sequela of exposure to certain insecticides may change susceptibility to its toxicity and/or carcinogenicity.

Animals↗
PubMed1977

Mutagenicity screening of five methyl carbamate insecticides and their nitroso derivatives using mutants of Salmonella typhimurium LT2.

The mutagenic activity of five methyl carbamate insecticides-carbaryl, baygon, BUX-Ten, landrin and methomyl-and their nitroso derivatives were investigated using histidine auxotrophs-his TA98, his TA100, his TA1535, his TA1537 and his TA1538--of Salmonella typhimurium LT2 derived by Ames. The methyl carbamate insecticides did not cause a signficant increase in the number of revertant colonies in any of the strains used. In contrast, the nitroso derivatives of the carbamate insecticides greatly increased the number of colonies on plates inoculated with strains his TA100 and his TA1535. We conclude that the nitroso derivatives of the tested methyl carbamate insecticides are potent mutagens; whereas, the parent insecticides are non-mutagenic.

Carbamates↗
PubMed1993

Evaluation of knit glove fabrics as barriers to dermal absorption of organophosphorus insecticides using an in vitro test system.

Cotton and synthetic knit glove fabrics in combination with an in vitro skin model were used to examine the capability of fabric to decrease the dermal absorption of the organophosphorus insecticides azinphos-methyl, paraoxon, and malathion. Capability for inhibition of acetylcholinesterase was determined in samples of media taken from under the skin barrier after the skin model, with or without fabric protection, had been exposed to the test compounds for 4 h. Acetylcholinesterase inhibitions caused by the direct addition of organophosphorus insecticide to the media were also included in the comparison. Results indicated that the skin model system alone had some capability to serve as a barrier to the transfer of organophosphates. Fabric covering used on the test model increased the barrier between insecticide application and resultant acetylcholinesterase inhibition. The all-cotton, 7-cut knit was especially effective in preventing the absorption of azinphos-methyl, as this organophosphorus insecticide had no capability to cause acetylcholinesterase inhibition when this fabric was used to protect the skin model. Knit glove materials of 100% cotton were demonstrated to be effective in preventing the absorption of paraoxon and malathion. These studies indicate that an in vitro model system can be used in combination with fabrics to study the relationship between clothing and skin as barriers to the absorption of organophosphorus insecticides.

Gloves, Protective↗
PubMed1988

Control of horn flies on cattle with insecticide pellets fired from a CO2-operated pistol.

A method is needed to control pyrethroid-resistant horn flies (Haematobia irritans) which would involve the intermittent application of insecticides to cattle without their confinement for treatment. Our objective was to test a CO2 gas-operated pistol, designed to shoot marking pellets, to determine the number of pellet applications required to obtain season-long control. Also, since horn fly resistance to pyrethroid insecticides is widespread, we tested ten other insecticides as concentrates in pellets. Six pellet pistol applications of 38% permethrin provided 84% control of horn flies for 15 weeks. Single pellet applications of ten non-pyrethroid insecticides indicated that none of these insecticides, at the concentrations tested, were as effective as permethrin for control of pyrethroid-resistant horn flies. Our field evaluation of the pellet-pistol method indicates that it has sufficient merit to justify further testing for horn fly control.

Animals↗
PubMed2006

The delayed genotoxic effect of N-nitroso N-propoxur insecticide in mammalian cells.

The N-nitroso derivative of an extensively used insecticide, propoxur, consistently induced dose-responsive chromosome aberrations and sister-chromatid exchanges (SCEs) in Chinese hamster ovary (CHO-W8) cells. Further investigations indicated that post-treatment incubation with a regular 1.5-cell-cycle period did not offer an unbiased estimation of the genotoxicity of N-nitroso carbamate insecticides. The scale of chromosome aberration induction increased with extension of the post-treatment incubation period. Comparable phenomena were not found in CHO-AGT cells proficient for O(6)-methylguanine-DNA-methyltransferase. In CHO-W8 cells, pulsed-treatment of the insecticide in the 1st replication cycle showed higher SCE induction than in the 2nd cycle. Similar phenomenon was also found in SCE induced by N-nitroso derivatives from other carbamate insecticides including aldicarb, carbofuran and methomyl. Treated cells did not show significantly perturbed cell cycle progression until 12 h after treatment removal. Based on the above observations, the O(6)-methylguanine-DNA adduct is suggested to be the major lesion caused by the delayed genotoxic effect of N-methyl carbamate insecticides as described in this report.

Animals↗
PubMed2006

Role of the transcriptional repressor mdGfi-1 in CYP6D1v1-mediated insecticide resistance in the house fly, Musca domestica.

Gfi-1 is a C(2)H(2)-type zinc finger protein that is a transcriptional repressor in vertebrates and has been implicated in control of CYP6D1 expression in house flies (Musca domestica). A 15 bp insert, which disrupts a putative mdGfi-1 binding site in the CYP6D1v1 promoter has been implicated as a cause of increased expression of CYP6D1, and thus insecticide resistance. Using electrophoretic mobility shift assays we demonstrate that the CYP6D1 promoter from susceptible strains binds mdGfi-1. The 15 bp insert that interrupts the mdGfi-1-binding site in insecticide-resistant strains reduces the amount of mdGfi-1 binding by 9- to 20-fold, consistent with the role of mdGfi-1 in resistance. Partial sequences of mdGfi-1 (spanning the first intron) from individual houseflies from 11 different strains revealed the presence of 23 alleles. There was no consistent difference in the mdGfi-1 alleles between susceptible and CYP6D1-mediated insecticide-resistant strains, indicating that mdGfi-1 alleles were not likely involved in resistance. Polymorphisms were used to map mdGfi-1 to autosome 1. Quantitative real time PCR (qRT-PCR) revealed Gfi-1 expression was higher in the thorax compared to the head and abdomen, and varied between life stages and between strains. However, similar levels of mdGfi-1 were detected in susceptible and resistant adults suggesting that altered levels of mdGfi-1 were not likely a cause of insecticide resistance. The significance of these results to understanding insecticide resistance is discussed.

Alleles↗
PubMed2003

Influence and persistence of phorate and carbofuran insecticides on microorganisms in rice field.

An experiment was conducted in microplots (4 m x 4 m) with two insecticides, phorate and carbofuran at rates of 1.5 and 1.0 kga.i.ha(-1) respectively, to investigate its effect on the population and distribution of bacteria, actinomycetes and fungi as well as the persistence of the insecticidal residues in rhizosphere soils of rice (Oryza sativa L., variety IR-50). Application of the insecticides stimulated the population of bacteria, actinomycetes and fungi in the rhizosphere soils, and the stimulation was more pronounced with phorate as compared to carbofuran. Both the insecticides did not have marked effect on the numbers of Streptomyces and Nocardia in the rhizosphere soils. However, the growth of Bacillus, Escherichia, Flavobacterium, Micromonospora, Penicillium, Aspergillus and Trichoderma with phorate and that of Bacillus, Corynebacterium, Flavobacterium, Aspergillus and Phytophthora with carbofuran were increased. On the other hand, the numbers of Staphylococcus, Micrococcus, Fusarium, Humicola and Rhizopus under phorate and Pseudomonas, Staphylococcus, Micrococcus, Klebsiella, Fusarium, Humicola and Rhizopus under carbofuran were inhibited. Both the insecticides persisted in the rhizosphere soil for a short period of time and the rate of dissipation of carbofuran was higher than that of phorate in the soil depicting the half-life (T1/2) 9.1 and 10.4 days, respectively.

Bacteria↗
PubMed1997

[125I]Azidonicotinoid photoaffinity labeling of insecticide-binding subunit of Drosophila nicotinic acetylcholine receptor.

The novel synthetic nicotinoid insecticide imidacloprid is a high affinity ligand for the insect nicotinic acetylcholine receptor (nAChR). The goal of this study is to identify the ligand- and insecticide-binding subunit of Drosophila nAChR with a novel [125I]azidonicotinoid ([125I]AN) photoaffinity probe modeled on imidacloprid. [125I]AN photoaffinity labels a single polypeptide in Drosophila head membranes corresponding in molecular mass to 66 kDa at a specific site inhibited by various cholinergic ligands including (-)-nicotine, cytisine, carbachol, alpha-bungarotoxin and d-tubocurarine as well as the insecticides imidacloprid and acetamiprid, pharmacologically consistent with the ligand- and insecticide-binding subunit. The Drosophila nAChR, isolated with three putative subunits (69, 66 and 61 kDa) using a nicotinoid-agarose affinity column, is labeled by [125I]AN primarily at the 66 kDa subunit and secondarily at the 61 kDa subunit. Clearly, the novel synthetic nicotinoid insecticides are valuable contributors in exploring the structure and function of the Drosophila nAChR.

Animals↗
PubMed2001

Measurement of insecticide uptake and effective fraction in a beneficial insect using solid-phase microextraction.

The determination of insecticide uptake in beneficial insects is important for quantifying the doses that are responsible for the toxicological effects and to compare them with the doses that insects may absorb in treated fields. Because of the small size of some beneficial species, the amount of insecticide absorbed may be very low. Herein, we present a method that relies on the sensitivity and specificity of SPME (solid-phase microextraction) as a sampling technique that can be used to measure very small amounts of an organophosphorus insecticide in small insects. In our study, the method was applied to quantify the internal dose and free dissolved fraction of chlorfenvinphos in beneficial parasitoids exposed through a topical application. Up to 0.5 ng of the insecticide could be quantified in these fractions, that is, 10 times less than when using solvent extraction techniques. The penetration and elimination rates of the insecticide in the insect were also determined. The method proved to be suitable to quantify internal doses in parasitoids collected in a treated field.

Animals↗
PubMed2006

Organophosphorus insecticides in agricultural and residential runoff: field observations and implications for total maximum daily load development.

Development of total maximum daily loads (TMDLs) for nonpoint source pollutants requires mass flux estimates for targeted compounds from contributing sources. We measured organophosphorus insecticide concentrations in surface runoff from agricultural and residential land-use sites in a southern Californian watershed over the course of runoff-producing irrigation and rainfall events. Event mean concentrations (EMCs) for chlorpyrifos, diazinon, and malathion exhibited considerable variability among irrigation and storm runoff events at agricultural sites; residential storm runoff EMCs for these compounds were considerably less variable. Event loads and EMCs were higher for runoff events following reported insecticide applications. Organophosphorus insecticide EMCs were not consistently correlated with hydrologic characteristics of runoff events. Our results indicate that on an area basis, loads from residential land may exceed those from sites planted in row crops for a given rainfall depth, suggesting that residential land use warrants explicit consideration in TMDL development and implementation. No consistent first flush effect was discernible for organophosphorus insecticides in storm or irrigation runoff. A relative potency factor approach is introduced to permit evaluation of organophosphorus insecticides on a common toxicological basis and allow development of TMDLs and pollutant control strategies for these compounds as a class.

Agriculture↗
PubMed2000

Insecticidal sesquiterpene from Alpinia oxyphylla against Drosophila melanogaster.

In the course of screening for novel naturally occurring insecticides from Chinese crude drugs, an MeOH extract of Alpinia oxyphylla was found to possess insecticidal activity against larvae of Drosophila melanogaster Meigen. From the extract, an insecticidal compound was isolated by bioassay-guided fractionation and identified as nootkatone (1) by GC, GC-MS, and (1)H and (13)C NMR spectroscopy. In bioassays for insecticidal activity, 1 showed an LC(50) value of 11.5 micromol/mL of diet against larvae of D. melanogaster and an LD(50) value of 96 microg/adult against adults. Epinootkatol (1A), however, showed slight insecticidal activity in both assays, indicating that the carbonyl group at the 2-position in 1 was the important function for enhanced activity of 1.

Animals↗
PubMed2002

Effects of a mixture of two insecticides in freshwater microcosms: I. Fate of chlorpyrifos and lindane and responses of macroinvertebrates.

Effects of chronic application of a mixture of the insecticides chlorpyrifos and lindane were studied in indoor freshwater microcosms. The exposure concentrations (based on 0, 0.005, 0.01, 0.05, 0.1 and 0.5 times the LC50 of the most sensitive standard test organism for each compound) were kept at a constant level for four weeks. The calculated mean concentrations for chlorpyrifos were found to be almost at their corresponding nominal level during the treatment period. The mean calculated lindane concentrations, however, were found to be 15-40% higher than intended. In the post treatment period both insecticides dissipated fast (t 1/2: chlorpyrifos 9 days, lindane 22 days) from the water phase. The concentrations of the mixture at the highest treatment level corresponded to 0.53 toxic units (TU) for Daphnia magna and 0.61 TU for the most sensitive fish. The decomposition of Populus leaves in litter bags was significantly lower at the three highest insecticide concentrations. The macroinvertebrate community was seriously affected at the three highest treatment levels, with Crustacea and the Chironomidae Corynoneura proving to be the most sensitive groups. Gastropoda and Oligochaeta were relatively insensitive and some taxa (e.g. Valvata piscinalis, juvenile Physa fontinalis, Nemertea and Stylaria lacustris) increased in numbers. The observed effects could be explained from the individual toxicity of the insecticides to the invertebrates, and did not indicate synergistic effects. A second paper (Van den Brink et al., 2002) addresses the effects on other endpoints, as well as the overall risk assessment of the insecticide mixture.

Animals↗
PubMed2000

The effect of insecticide aerosols on lung function, airway responsiveness and symptoms in asthmatic subjects.

The object of this study was to compare the effect of standard and "low irritant" insecticide aerosols on lung function, airway hyperresponsiveness (AHR) and symptoms in asthmatic subjects. A double blind randomized, crossover study was conducted in 25 asthmatic subjects who reported sensitivity to insecticide aerosols. All subjects were exposed for 30 min, on separate occasions, to two standard insecticide formulations (A and B), one low irritant formulation (C) and a negative control aerosol. Spirometric function and chest, nose and eye symptoms were recorded during, and for 90 min after, the exposure. AHR to methacholine was measured 90 min after the exposure. Compared to the negative control, the maximum fall in forced expiratory volume in one second (FEV1) was slightly greater after standard insecticides (mean differences from control +/-95% confidence interval: aerosol A, 3.3+/-3.6%, p=0.08; aerosol B, 5.1+/-4.7%, p=0.04), AHR was significantly more severe (mean difference from control: aerosol A, 0.35+/-0.29 doubling doses, p=0.028; aerosol B, 0.52+/-0.43 doubling doses, p=0.028), and symptoms were more severe. The low irritant test aerosol (C) did not differ significantly from the negative control with respect to FEV1, AHR or symptoms. It is concluded that some insecticide aerosols trigger symptoms and falls in lung function in some people with asthma. Furthermore, these aerosols may also increase airway hyperresponsiveness, although the mechanism of this effect has not been determined. The low irritant formulation did not appear to have the same effects.

Adult↗
PubMed2000

Role of loop D of the alpha7 nicotinic acetylcholine receptor in its interaction with the insecticide imidacloprid and related neonicotinoids.

1. The nitroguanidine insecticide imidacloprid along with a second generation of related compounds including nitenpyram, all nicotinic acetylcholine (ACh) receptor ligands, are used increasingly in many countries. Site-directed mutagenesis and heterologous expression in Xenopus laevis oocytes have been deployed to investigate mutants (G189D and G189E) of the chicken alpha7 homomer-forming nicotinic receptor subunit which are predicted to enhance the negative charge at the negative subsite (loop D) of the ACh binding site. 2. Xenopus oocytes expressing wild-type alpha7 nicotinic receptors respond to imidacloprid with rapid inward currents. Imidacloprid and nitenpyram are partial agonists, whereas ACh, (-)-nicotine and (+)-epibatidine are full agonists. 3. Compared to wild-type alpha7, the mutant G189D and G189E receptors are much less sensitive to the insecticides, whereas their sensitivity to (-)-nicotine, ACh and (+)-epibatidine is only slightly reduced. In contrast, G189N and G189Q mutants are sensitive not only to ACh, (-)-nicotine and (+)-epibatidine, but also to the two insecticides. Thus reduction of the insecticide-sensitivity by the mutations G189D and G189E are attributed to an increase in negativity of loop D. Desnitro-imidacloprid (DN-IMI), an imidacloprid derivative lacking the nitro group is a potent agonist on the G189D and G189E mutants suggesting an important role of loop D in nicotinic receptor interactions with the nitro group of nitroguanidine insecticides.

Animals↗
PubMed2005

Does insecticide resistance alone account for the low genetic variability of asexually reproducing populations of the peach-potato aphid Myzus persicae?

The typical life cycle of aphids includes several parthenogenetic generations and a single sexual generation (cyclical parthenogenesis), but some species or populations are totally asexual (obligate parthenogenesis). Genetic variability is generally low in these asexually reproducing populations, that is, few genotypes are spread over large geographic areas. Both genetic drift and natural selection are often invoked to account for this low genetic variability. The peach-potato aphid, Myzus persicae, which encompasses both cyclical and obligate parthenogens, has developed several insecticide resistance mechanisms as a consequence of intense insecticide use since the 1950s. We collected asexually reproducing M. persicae from oilseed rape and examined genetic variability at eight microsatellite loci and three insecticide resistance genes to determine whether their genetic structure was driven by drift and/or selection. We identified only 16 multilocus microsatellite genotypes among 255 individuals. One clone, which combined two insecticide resistance mechanisms, was frequently detected in all populations whatever their location over a large geographical area (the northern half of France). These unexpected findings suggest that drift is not the unique cause of this low variability. Instead, the intensification of both insecticide treatments and oilseed rape cultivation may have favored a few genotypes. Thus, we propose that selective pressures resulting from human activities have considerably modified the genetic structure of M. persicae populations in northern France in a relatively short period of time.

Alleles↗