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At least 775 records · Page 43Linked to original sources
PubMed1992

Joint action between binary mixtures of chlordimeform and insecticides.

Chlordimeform (CDF) was tested for its ability to act jointly with an organophosphorus insecticide (parathion) and a series of carbamate insecticides. Three arthropod species were used as test subjects: the two-spotted spider mite, Tetranychus urticae; the German cockroach, Blatella germanica; and the flour beetle, Tenebrio castaneum. However, CDF antagonized the toxicity of parathion toward B. germanica while it acted in a greater than additive fashion toward T. castaneum. No combination of CDF and insecticide tested acted jointly toward T. urticae. Species-specific differences in sensitivity, absorption, metabolism, and mode of delivery account for the varying results. Metabolic studies of pairs of compounds using two radiolabeled carbamates showed that CDF altered the metabolic detoxification of both carbaryl and aldicarb. The results suggest that CDF may inhibit MFOs as its mode of action.

Animals↗
PubMed1983

Mutagenic studies on the insecticide Metasystox-R with different genetic systems.

The insecticide Metasystox-R was tested for mutagenic activity by a multiple bioassay. Its potential ability to induce gene mutation in Salmonella, micronuclei formation in mice, and sister-chromatid exchange (SCE) in human lymphocytes was evaluated. The insecticide induced detectable genotoxic effects in these tests. The results support the view that the insecticide is genotoxic.

Animals↗
PubMed1996

Chemical constituents of essential oils of muña, Bolivian plants traditionally used as pesticides, and their insecticidal properties against Chagas' disease vectors.

The composition of essential oils from two muña, Bolivian medicinal plants, derived from Minthostachys andina and Hedomea mandonianum, were analyzed by gas chromatography/mass spectrometry. Major differences were observed in their chemical composition. Pulegone was the major component of H. mandonianum oil (44.6%) and M. andina oil (25.5%); menthone and isomenthone were around 33% of these oils. Differences were also observed in their insecticidal activity against the Chagas' disease vector, Rhodnius neglectus or Triatoma infestans bugs exposed on impregnated oil filter papers. While M. andina oil showed 30%-50% of mortality in both triatomine species after a period of 1 week, H. mandonianum oil did not show any insecticidal activity. Nevertheless, both species had insecticidal activity (33.3% and 50%) when oils were topically applied. The significance of these results is discussed in relation to the variability of the chemical composition and their potential use in Chasgas' disease vector control.

Animals↗
PubMed1996

Changes in the methylation of amplified esterase DNA during loss and reselection of insecticide resistance in peach-potato aphids, Myzus persicae.

Insecticide resistance in peach-potato aphids, Myzus persicae, results from the amplification of genes encoding an esterase that hydrolyses and sequesters insecticides. Resistance is normally stable, but highly resistant aphid clones sometimes lose resistance when insecticidal selection pressure is removed. This loss of resistance, termed reversion, arises from a loss of elevated esterase enzyme through transcriptional control, i.e. without loss of the amplified esterase DNA sequences. We have shown that loss of the elevated enzyme occurred simultaneously with loss of methylation at CCGG sites in the amplified DNA sequences. During reselection of resistance in these revertant clones, enzyme levels increased, but there was no corresponding return of methylation to DNA sequences. Thus, although DNA methylation is closely correlated with expression of the amplified esterase genes during reversion, it may not be a factor in the reverse process.

Animals↗
PubMed1996

Characterization of voltage-sensitive sodium channel gene coding sequences from insecticide-susceptible and knockdown-resistant house fly strains.

The kdr insecticide resistance trait of the house fly (Musca domestica .L.), which confers reduced neuronal sensitivity to DDT and pyrethroid insecticides, was previously shown to exhibit tight genetic linkage to restriction fragment length polymorphism markers lying within a voltage-sensitive sodium channel gene that is homologous to the para gene of Drosophila melanogaster. In the present study, the 6315 nucleotide coding sequences of this voltage-sensitive sodium channel gene from insecticide-susceptible (NAIDM strain) and kdr (538ge strain) house flies were determined by automated direct DNA sequencing of PCR fragments obtained by amplification on first strand cDNA from adult heads. The deduced 2105-residue amino acid sequence from each strain exhibited overall structure and organization typical of sodium channel alpha subunit genes and was 90.0% identical to that of the D. melanogaster para gene product. We did not detect any splice variants among voltage-sensitive sodium channel cDNAs obtained from adult house fly head preparations. Comparison of the coding sequence of the voltage-sensitive sodium channel gene of the kdr house fly strain to that of the NAIDM strain revealed 12 amino acid differences in the 538ge strain. The significance of these polymorphisms as candidate resistance-conferring mutations is discussed.

Amino Acid Sequence↗
PubMed2006

Production of a novel recombinant Drosophila melanogaster acetylcholinesterase for detection of organophosphate and carbamate insecticide residues.

A novel recombinant Drosophila melanogaster acetylcholinesterase (R-DmAChE) produced in Pichia pastoris was first reported in this study. We cloned the DmAChE cDNA by reverse transcription PCR with removal of the signal for glycosylphosphatidylinositol (GPI) anchor attachment and the endogenous signal peptide coding sequence, and inserted it into P. pastoris vector pPIC9K under control of the alcohol oxidase gene AOX1 promoter (5'AOX1). The expression cassette of AChE cDNA was then introduced into methylotrophic yeast GS115 and several recombinant strains expressing R-DmAChE were obtained. The secreted R-DmAChE showed high stability in neutral phosphate buffer at 4 degrees C, and its kinetic parameters were identical to those of the native DmAChE. The bimolecular rate constants of R-DmAChE to dichlorvos, aldicarb and carbaryl were ranging from three to six times higher than of native DmAChE. Within six insecticides, the R-DmAChE was more sensitive than EeAChE, NbAChE and HuAChE. For 10 widely used insecticides, the IC50 values to the R-DmAChE were much lower than those to AChEs commonly used in China. With the R-DmAChE-based assay, samples spiked with three concentrations of pesticides caused enzymatic activity inhibition with R.S.D. of 0-13.7%. These results suggest that the R-DmAChE can be useful for detection of organophosphate and carbamate insecticide residues.

Acetylcholinesterase↗
PubMed2006

Insecticidal lead identification by screening benzopyrano[4,3-c] pyrazol-3(2H)-ones library constructed from multiple-parallel synthesis under microwave irradiation.

A rapid library-generation via liquid-phase multiple-parallel synthesis of 2-(substituted)benzyl-1-benzopyrano[4,3-c]pyrazol-3(2H)-ones, bearing two points of diversity, under microwave irradiation was successfully performed using chromenone-3-carboxylic acids as starting materials. Compared to an identical library generated by conventional parallel synthesis, microwave-assisted parallel synthesis dramatically decreased reaction times from an average of 16h to 13min, and the yields of products and intermediates were improved in most cases. A bioassay indicated that the compounds of the library exhibited excellent insecticidal activity against T. cinnabarinus at the dosage of 250mgL(-1), and some compounds still exhibited insecticidal activity when the dosage was reduced to 50mgL(-1). This shows that 2-(substituted) benzyl-1-benzopyrano[4,3-c]pyrazol-3(2H)-ones might be used as lead structures for further optimization. To our knowledge, this is the first report about the application of solution-phase multiple-parallel synthesis under microwave irradiation to construct libraries of benzopyrano-[4,3-c]pyrazol-3(2H)-ones with insecticidal activity. The coupling of microwave technology with liquid-phase parallel synthesis constitutes a novel and particularly attractive avenue for the rapid generation of structurally diverse libraries for lead discovery.

Animals↗
PubMed2006

Discovery of a new insecticide lead by optimizing a target-diverse scaffold: tetrazolinone derivatives.

In order to discover lead compounds with novel action mechanism, a series of tetrazolinone derivatives bearing structurally diverse substituents, 1-aryl-4-substituted-1,4-di-hydro-5H-tetrazol-5-ones 2, 1-((5-(alkylthio)-1,3,4-oxadiazol-2-yl)methyl)-4-(substituted)- phenyl-1H-tetrazol-5(4H)-ones 5, and 1-((5-(alkylthio)-1,3,4-thiadiazol-2-yl)methyl)-4- (substituted)phenyl-1H-tetrazol-5(4H)-ones 7, were designed and synthesized in good yields by a multiple-step synthetic procedure. The results of greenhouse in vivo test indicated that all the target compounds did not displayed herbicidal activity, however, some of them exhibited excellent in vivo insecticidal activity against Tetranychus cinnabarinus at the concentration of 250 mg L-1. To our knowledge, this is the first report about the insecticidal activity of tetrazolinone derivatives, which indicated that the tetrazolinone scaffold could be identified as a novel insecticidal lead structure. The present work demonstrated that optimizing a target-diverse scaffold is an effective way to discover new lead compounds with new action mechanism or biological activity.

Animals↗
PubMed2004

Dose-response relationship in lethal and behavioural effects of different insecticides on the parasitic wasp Aphidius ervi.

Neurotoxic insecticides are widely used for crop protection and behavioural perturbations can be expected in surviving beneficial insects, including parasitoids of pest insects. The present study aims to investigate the relationship between the dose of insecticide parasitoids have been exposed to, and the subsequent ability of these parasitoids to respond to host-related cues. A four-armed olfactometer, a design widely used to observe orientation responses in various insects and parasitoids in particular, was chosen to investigate the dose-response relationship. The species studied was Aphidius ervi, a relatively generalist parasitoid of aphids, and commercialised for biological control and integrated pest management. Active ingredients with similar and different modes of action on the nervous system were compared: a pyrethroid (lambda-cyhalothrin), an organophosphate (chlorpyrifos), a carbamate (pirimicarb) and a carbamyltriazole (triazamate). Adult females were exposed to dry residues on glass for 24 h. LD50 were calculated and predicted a high risk of mortality at the field application rate. The effect of five increasing residual doses of each active ingredient was tested on responses to plant-host odour in the olfactometer, from sublethal doses to LD50, and up to LD70 for some products. It appeared that none of the doses of lambda-cyhalothrin, chlorpyriphos and pirimicarb had any effect on A. ervi responses to the odour from the aphid-infested plant (Myzus persicae on oilseed rape). But for triazamate, a significant dose-behavioural response was quantified and attraction to the odour was no longer significant in females surviving the LD50. The possible explanations for the presence or absence of effect, depending on the insecticide are discussed.

Animals↗
PubMed2005

Application of hollow fiber liquid phase microextraction for the determination of insecticides in water.

In the present work, a novel sample pre-treatment technique for the determination of trace concentrations of some insecticide compounds in aqueous samples has been developed and applied to the determination of the selected analytes in environmental water samples. The extraction procedure is based on coupling polypropylene hollow fiber liquid phase microextraction (HF-LPME) with gas chromatography by flame thermionic detection (GC-FTD). For the development of the method, seven organophosphorous insecticides (dichlorvos, mevinphos-cis, ethoprophos, chlorpyrifos methyl, phenthoate, methidathion and carbofenothion) and one carbamate (carbofuran) were considered as target analytes. Several factors that influence the efficiency of HF-LPME were investigated and optimized including agitation, organic solvent, sample volume, exposure time, salt additives and pH. The optimized methodology exhibited good linearity with correlation coefficient = 0.990. The analytical precision for the target analytes ranged from 4.3 to 11.1 for within-day variation and 4.6 to 12.0% for between-day variation. The detection limits for all analytes were found in the range from 0.001 to 0.072 microg/L, well below the limits established by the EC Drinking Water Directive (EEC 80/778). Relative recoveries obtained by the proposed method from drinking and river water samples ranged from 80 to 104% with coefficient of variations ranging from 4.5 to 10.7%. The present methodology is easy, rapid, sensitive and requires small sample volumes to screen environmental water samples for insecticide residues.

Chemical Fractionation↗
PubMed2006

Differential responses of eight cyanobacterial and green algal species, to carbamate insecticides.

In this study, five carbamate insecticides were subjected to 96 h acute toxicity tests to examine their effects on three cyanobacteria, Anabaena flos-aquae, Microcystis flos-aquae, and Mirocystis aeruginosa, and five green algae, Selenastrum capricornutun, Scenedesmus quadricauda, Scenedesmus obliquus, Chlorella vulgaris, and Chlorella pyrenoidosa. The average acute toxicity of the carbamate insecticides to the cyanobacteria and the green algae was in descending order carbaryl>carbofuran, propoxur, metolcarb > carbosulfan. Wide variations in response to the tested carbamate insecticides occurred among the eight individual species of cyanobacteria and green algae. The sensitivity of various species of algae exposed to carbofuran, propoxur, metolcarb, and carbaryl varied over one order of magnitude, and that of algae exposed to carbosulfan varied over two orders of magnitude. With regard to the diffrential sensitivity of cyanobacteria and green algae, the cyanobacteria were less sensitive than green algae to carbosulfan and propoxur. The pollutants may initiate a shift of algal group structure; especially, a shift from dominance by green algae to dominance by cyanobacteria, and may sustain cyanobacterial blooms at particular times. Therefore, the descending order of the ecosystem risk was carbosulfan > propoxur > carbofuran > carbaryl, metolcarb. There was a strong variance between toxicity and ecosystem risk; i.e., "low toxicity" does not imply "low ecosystem risk."

Carbamates↗
PubMed2004

Chronic illness as a result of low-level exposure to synthetic pyrethroid insecticides: a review of the debate.

Synthetic pyrethroid insecticides are widely used in public health and agriculture throughout the world and generally considered to be the safest class of insecticides available. In contrast to this belief stands a recent debate in Germany, around possible chronic effects of exposure to low levels of pyrethroid residues, particularly in the household. The debate is reviewed with a view to its potential implications on the use of synthetic pyrethroids on insecticide-treated nets (ITNs) for malaria control. Media coverage, rather than conclusive evidence from carefully planned scientific investigations, seems the underlying factor in the debate. However, chronic effects can presently not be excluded with certainty, as relevant toxicological data do not exist in the open scientific literature. Properly designed neuro-behavioural studies on groups with long-term exposure to low doses of synthetic pyrethroids should be conducted. This will require establishment of a working definition of "case" and "exposure". Meanwhile pyrethroids should continue to be used for public health interventions that contribute substantially to morbidity and mortality reduction, such as ITNs for malaria control.

Animals↗
PubMed2004

Molecular analysis of CYP321A1, a novel cytochrome P450 involved in metabolism of plant allelochemicals (furanocoumarins) and insecticides (cypermethrin) in Helicoverpa zea.

Cytochrome P450 monooxygenases play a significant role in the detoxification of hostplant allelochemicals and synthetic insecticides in Lepidoptera. In the corn earworm Helicoverpa zea, a noctuid of considerable economic importance, metabolisms of xanthotoxin, a toxic furanocoumarin, and alpha-cypermethrin, an insecticide, are mediated by at least one P450 with a catalytic site capable of accepting both substrates. To further the characterization of P450s in this species, we have cloned three full-length cDNAs encoding two CYP4M subfamily members and a novel CYP321A subfamily member. RNA analyses have demonstrated that the CYP321A1 gene is highly induced (51-fold) in larval midguts in response to xanthotoxin but not cypermethrin. Both CYP4M genes are expressed at negligible levels that are not increased by xanthotoxin or cypermethrin. Baculovirus-mediated expression of the full-length CYP321A1 cDNA has demonstrated that the CYP321A1 protein metabolizes xanthotoxin and angelicin, like the CYP6B1 protein in the furanocoumarin specialist Papilio polyxenes, and alpha-cypermethrin, like the CYP6B8 protein previously characterized in H. zea. In contrast, the CYP4M7 protein does not metabolize xanthotoxin at any detectable level. We conclude that at least two xanthotoxin-inducible P450s from highly divergent subfamilies (CYP6B and CYP321A) contribute to the resistance of H. zea larvae to toxic furanocoumarins and insecticides. Genomic PCR analysis indicates that the CYP321A1 gene has evolved independently from the CYP6B genes known to be present in this insect.

Amino Acid Sequence↗
PubMed2006

Reference values for metabolites of pyrethroid and organophosphorous insecticides in urine for human biomonitoring in environmental medicine.

Pesticides are widely used throughout the world in agriculture to protect crops, and in public health to control diseases transmitted by vectors or intermediate hosts. After the prohibition of organochlorines, such as DDT, today mainly pyrethroids and organophosphorous insecticides are used. With reliable and sensitive analytical methods for detecting metabolites of organophosphorous and pyrethroid insecticides in urinary specimens of the general population several studies have been published on internal exposure to these insecticides of the population in Germany. In total, data on levels of metabolites of organophosphorous acids in urine of about 1200 children and adults have been published, as well as data on levels of pyrethroid metabolites in urine of about 2100 children and adults. In Germany, reference values for environmental pollutants related to the population are established continuously by the Human Biomonitoring Commission of the German Federal Environmental Agency, preferably based on data gained by representative studies. Reference values are defined as the 95th percentile, rounded off within the 95% confidence interval of the population studied. Since there is a need for reference values to characterise the population's exposure to organophosphates and pyrethroids, and since there are different studies available from Germany that agree quite well with data from other industrialised countries, the Commission has derived reference values from the available data, though none of the studies had fulfilled criteria on representativity. Reference values for metabolites of organophosphorous acids are as follows: DMP 135 microg/l, DMTP 160 microg/l and DEP 16 microg/l and for metabolites of pyrethroids: cis-Cl2CA 1 microg/l, trans-Cl2CA 2 microg/l and 3-PBA 2 microg/l. As the volume-related concentrations of organophosphate and pyrethroid metabolites show no significant age-dependence, the reference values derived are not age-stratified. Though based merely on statistical and not on toxicological data, levels analysed above the reference levels, when reliably measured (verified several times), should prompt environmental health practitioners to search for sources, within the bounds of proportionality. In addition to accidental poisoning, possible sources include indoor contamination following improper pest control operations in homes as well as in pets and food products contaminated by these pesticides.

Adolescent↗
PubMed2004

Fusion proteins containing insect-specific toxins as pest control agents: snowdrop lectin delivers fused insecticidal spider venom toxin to insect haemolymph following oral ingestion.

The mannose-specific snowdrop lectin (Galanthus nivalis agglutinin: GNA), when fed to insects, binds to the gut epithelium and passes into the haemolymph. The ability of GNA to act as a carrier protein to deliver an insecticidal spider venom neurotoxin (Segestria florentina toxin 1: SFI1) to the haemolymph of lepidopteran larvae was investigated. Constructs encoding SFI1 and an SFI1/GNA fusion protein were expressed in Pichia pastoris. The insecticidal activity of purified recombinant proteins on injection was found to be comparable to published values for SfI1 purified from spider venom [Toxicon 40 (2002) 125]. Whereas neither GNA nor SFI1 alone showed acute toxicity when fed to larvae of tomato moth (Lacanobia oleracea), feeding SFI1/GNA fusion at 2.5% of dietary proteins was insecticidal to first stadium larvae, causing 100% mortality after 6 days. The protein also showed a significant, dose dependent, toxicity towards fourth and fifth stadium larvae, with growth reduced by up to approximately 90% over a 4-day assay period compared to controls. Delivery of intact SFI1/GNA to the haemolymph in these insects was shown by western blotting; haemolymph samples from fusion-fed larvae contained a GNA-immunoreactive protein of the same molecular weight as the SFI1/GNA fusion. SFI1/GNA and similar fusion proteins offer a novel and effective approach for delivering haemolymph active toxins by oral administration, which could be used in crop protection by expression in transgenic plants.

Animals↗
PubMed2005

Bacillus cereus produces several nonproteinaceous insecticidal exotoxins.

Bacillus cereus is mainly known as a human food-borne opportunistic pathogen. Here, we used biological assays and HPLC to investigate the ability of B. cereus to produce insecticidal exotoxins during the stationary growth phase. None of the 575 B. cereus strains screened produced detectable levels of beta-exotoxin I, a small, heat-stable insecticidal nucleotide analogue. However, six out of a subset of 270 B. cereus strains produced several small, nonproteinaceous insecticidal exotoxins different from beta-exotoxin I. Thus, B. cereus can secrete a large array of proteinaceous and nonproteinaceous toxins acting on insects and mammals.

Animals↗
PubMed2006

The stability of organophosphorus insecticides in fresh blood.

We investigated the stability of 14 organophosphorus insecticides: dichlorvos, fenitrothion, cyanophos, malathion, phenthoate, methidathion, dimethoate, thiometon, isoxathion, diazinon, trichlorfon, EPN, acephate and sulprofos, in fresh blood. The organophosphorus compounds, except for sulprofos, decomposed over time at 37 degrees C, with varying decomposition speed for each compound. Methyl phosphate types (dichlorvos) decomposed most rapidly, followed by methyl thiophosphate types (fenitrothion and cyanophos) and methyl dithiophosphate types (methidathion, dimethoate and thiometon). Methyl thiophosphate types decomposed faster than ethyl thiophosphate types (isoxathion and diazinon). Of the five methyl dithiophosphate type insecticides (malathion, phenthoate, methidathion, dimethoate and thiometon), the compounds with a carboxylic ester bond (malathion and phenthoate) decomposed faster than the others. Compounds left standing at 37 degrees C decomposed faster than those left standing at 4 degrees C. Temperature has a great effect on the decomposition of organophosphorus insecticides in blood. However, the order of the decomposition speeds of each compound was approximately the same at different temperatures. In cases of suspected organophosphate poisoning, it should be considered that the blood concentration of the compound might decrease during the postmortem interval.

Chromatography, High Pressure Liquid↗
PubMed2005

Synergistic effect of entomogenous fungi on some insecticides against Bihar hairy caterpillar Spilarctia obliqua (Lepidoptera: Arctiidae).

A number of fungal parasites infect a wide range of insects and cause epizootics from time to time. Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) Sorokin are two of the major disease-causing fungi in insects. Investigations were carried out to study the effect of these fungi on the toxicity of endosulfan, imidacloprid, lufenuron, diflubenzuron, dimethoate and oxydemeton methyl against 10-11 days old larvae of Spilarctia obliqua (Walker). For some products the combination treatments showed higher dose mortality response than the sole treatment of fungal conidia or the insecticide. The combination of insecticides with B. bassiana showed 1.26-35.8 fold increase in toxicity of insecticides over sole treatment, while the increase was 1.05-72.0 fold in case of M. anisopliae. Imidacloprid 17.8 SL and oxydemeton methyl 25EC may be used in combination with these fungi for management of S. obliqua.

Animals↗