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At least 757 records · Page 42Linked to original sources
PubMed1999

The effect of insecticides on learning in the Africanized honey bee (Apis mellifera L.).

The present study was designed to examine the effects of endosulfan, decis, baytroid, and sevin on the learning ability of Africanized honey bees (Apis mellifera L.). Although these insecticides were recommended by the government of Brazil to control the cotton boll weevil, the effects on bees have been unknown. Results of the present research show that: (1) bees readily consume each of the pesticides when placed in a sucrose solution; (2) the odors of the pesticides are not repellent to bees, and such odors can serve as conditioned stimuli; (3) learning occurs to various degrees when the insecticides are combined with the sucrose solution and used as an unconditioned stimulus; and (4) feeding the insecticides to the bees 1 h prior to conditioning leads to differing mortality. Because of the importance of bees for honey production, as well as pollination of cotton and other crops, recommendations are made for the use of decis and other measures for boll weevil control.http://link. springer-ny.com/link/service/journals/00244/bibs/37n4p529.++ +html</HEA

Animals↗
PubMed2000

Correlation of the insecticidal activity of the Bacillus thuringiensis A4 strain against Bactrocera oleae (Diptera) with the 140-kDa crystal polypeptide.

The crystals of the soil-isolated Bacillus thuringiensis (Bt) strain A4 consist of two polypeptides with molecular mass of 140 kDa and 32 kDa that exhibit insecticidal activity against adult flies of Bactrocera oleae (Diptera). Plasmid curing applied to this strain resulted in the isolation of several subclones exhibiting alterations in their crystal polypeptides as well as two acrystalliferous subclones. The crystals of subclone 1.1 lacked the 32-kDa polypeptide and consisted uniquely of a 140-kDa polypeptide antigenically related to the parental 140-kDa crystal polypeptide. Additionally, the crystals of this subclone exhibited insecticidal activity against B. oleae equivalent to that of the parental strain. Therefore, the 32-kDa crystal polypeptide is dispensable for insecticidal activity, which appears to be dependent on the presence of the 140-kDa crystal polypeptide.

Animals↗
PubMed2006

Wide mutational spectrum of a gene involved in hormone action and insecticide resistance in Drosophila melanogaster.

The Methoprene-tolerant (Met) bHLH-PAS gene in Drosophila melanogaster is involved in the molecular action of juvenile hormone (JH), and mutants result in resistance to the toxic and morphogenetic effects of JH and JH agonist insecticides such as methoprene. A detailed study of Met mutants can shed light on the poorly understood action of JH as well as the molecular basis of Met resistance to JH insecticides. Nine mutant alleles bearing point mutations in Met were examined for penetrance and expressivity of three phenotypic characters: resistance, defective oogenesis, and a novel eye defect. The collection ranged from two weak alleles having less severe phenotypes to strong alleles with severe phenotypes similar to that of a null allele. The point mutations were located in both conserved and nonconserved domains. Both the eye defect, seen as severely malformed ommatidial facets in the posterior margin of the compound eye, and the oogenesis phenotype are nonconditional, whereas expression of the resistance phenotype requires treatment with JH or JH analogs (JHAs) during early metamorphosis. A proposed basis for all the phenotypic characters centers on MET action as a transcriptional regulator of ecdysone secondary-response target genes during metamorphosis. Disruption of MET function either by mutation or by JHA presence during early metamorphosis results in transcriptional misregulation of different target genes, resulting in the pathology seen in either instance. The variety of amino acid changes in MET that resulted in resistance may portend a rapid rise in resistance in response to increased use of JH insecticides in field insect populations.

Alleles↗
PubMed2005

The link between the insecticide heptachlor epoxide, estradiol, and breast cancer.

Given the suspected effects of estrogens on breast cancer, xenoestrogenic insecticides may be a risk factor. Studies of the weak xenoestrogen, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), have failed to demonstrate a causal relationship, though another estrogenic organochlorine insecticide, dieldrin, belonging to the cyclodiene family, has recently been linked to breast cancer. Other cyclodienes such as heptachlor epoxide (HE) and oxychlordane (OC) present in breast tissue have not been evaluated as rigorously, presumably due to their lower concentration and lower recovery using solvent extraction procedures. We used sparging extraction coupled with gas chromatography to determine the levels of HE, OC, and DDE in adipose tissue within breast biopsies in a series of 34 women evaluated for breast abnormality. Of the three insecticides tested, only HE (p=0.007) was positively associated with prevalence of breast cancer in the biopsies. In rapid, non-genomic studies using isolated human leukocytes, flow cytometric methods were used to measure HE-induced oxidants and DNA damage. These studies indicated that HE, at concentrations similar to those in breast biopsies, induced an inverted-U increase in intracellular oxidants and DNA strand breaks [both blocked by specific nitric oxide- (NO-) synthesis blockade withL: -NMMA] in human polymorphonuclear leukocytes (PMNs). HE-treated PMNs also induced damage to surrounding lymphocytes in mixed-leukocyte incubations (also inhibited by NO blockade). The HE-induced changes in NO were inhibited by 17beta-estradiol-(17beta-E2) receptor antagonists and were mimicked by similar concentrations of 17beta-E2. The addition of tumor necrosis factor-alpha (TNF-alpha) increased intracellular oxidants and DNA damage and shifted the responses to lower HE concentrations. This study, along with others, suggests that HE-induced NO production may contribute to initiation, promotion, and progression of cancer.

Adult↗
PubMed2005

Compatibility of the entomopathogenic fungus Lecanicillium muscarium and insecticides for eradication of sweetpotato whitefly, Bemisia tabaci.

The compatibility of the entomopathogenic fungus Lecanicillium muscarium and chemical insecticides used to control the second instar stages of the sweetpotato whitefly, Bemisia tabaci, was investigated. The effect on spore germination of direct exposure for 24 h to the insecticides imidacloprid, buprofezin, teflubenzuron and nicotine was determined. Only exposure to buprofezin was followed by acceptable spore germination. However, all chemicals significantly reduced spore germination when compared to a water control. Infectivity of L. muscarium in the presence of dry residues of buprofezin, teflubenzuron and nicotine (imidacloprid is a systemic pesticide) on foliage were also investigated. No significant detrimental effects on the level of control of B. tabaci was recorded when compared with fungi applied to residue free foliage on either tomato or verbena plants. Fungi in combination with imidacloprid gave higher B. tabaci mortality on verbena foliage compared to either teflubenzuron or nicotine and fungi combinations. Use of these chemical insecticides with L. muscarium in integrated control programmes for B. tabaci is discussed.

Animals↗
PubMed1979

Interaction of insecticides with lipid membranes.

The permeability of liposome membranes is increased by organophosphorus and organochlorinated insecticides at concentrations of 10(-5)--10(-4) M. The order of effectiveness is similar to the toxicity of the compounds to mammals, and is the following for permeation of non-electrolytes and for valinomycin-induced permeation of K+: parathion greater than 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT) approximately aldrin greater than malathion greater than lindane. The degree of effectiveness for X-537A-induced permeation of Ca2+ was the following: aldrin greater than or equal to DDT greater than parathion greater than malathion greater than lindane. The organophosphorus compound, ethyl azinphos (10(-4) M), dramatically increases the permeability of liposome membranes to all the tested substances, probably as a consequence of surfactant effects. Some organochlorinated insecticides appear to react with cation ionophores and modulate their motion across lipid membranes. It is suggested that the insecticides may exert some of their toxic actions by modifying certain mechanisms in the cell membrane.

Calcium↗
PubMed1985

Neurotoxic insecticides inhibit GABA-dependent chloride uptake by mouse brain vesicles.

The neurotoxic insecticides endrin, dieldrin, aldrin, lindane (gamma-1,2,3,4,5,6-hexachlorocyclohexane) and deltamethrin inhibited gamma-aminobutyric acid-dependent 36Cl- uptake by mouse brain vesicles. Of the insecticides examined, the chlorinated cyclodienes endrin and dieldrin were the most potent, producing 50% inhibition at 2.8 and 13.9 microM, respectively. Lindane and deltamethrin were less effective, and with deltamethrin the effect was incompletely stereospecific. These results demonstrate the disruption of gamma-aminobutyric acid receptor-chloride ionophore function in mammalian brain by neurotoxic insecticides and provide evidence that this complex is the principal site of cyclodiene action.

Animals↗
PubMed1992

Specific inhibition of calcineurin by type II synthetic pyrethroid insecticides.

The inhibitory action of synthetic pyrethroids and some chlorinated hydrocarbon insecticides on the neural calcium-calmodulin-dependent protein phosphatase, calcineurin, was studied using one radiotracer and two colorimetric methods. It was found that all insecticidal Type II pyrethroids (cypermethrin, deltamethrin and fenvalerate) are potent inhibitors of isolated calcineurin from bovine brain. Their IC50 values were approximately 10(-9) to 10(-11) M. By contrast, neither noninsecticidal chiral isomers of these pyrethroids, neuroactive Type I pyrethroids nor neuroactive chlorinated hydrocarbon insecticides showed comparable potencies against this enzyme. To confirm the action of Type II pyrethroid in situ, isolated intact rat brain synaptosomes were incubated with [32P]phosphoric acid and subsequently depolarized in the presence and absence of 0.1 microM deltamethrin. As expected, there was a sharp rise in protein phosphorylation due to the action of calcineurin. Deltamethrin caused a distinct delay in the dephosphorylation process. The results clearly indicate that calcineurin is specifically inhibited by Type II pyrethroids.

Animals↗
PubMed1995

Interaction of ethanol and the organophosphorus insecticide parathion.

Phosphorothioate insecticides such as parathion (O,O-diethyl-O-p-nitrophenyl phosphorothioate) undergo P450-dependent oxidative desulfuration, leading to both activation and detoxification of these compounds. Consequently, alterations in P450-dependent oxidative desulfuration may affect the acute toxicities of these insecticides. In the present study, pretreatment of mice with 15% ethanol in the drinking water for 6 days antagonized the acute toxicity of parathion, but not its toxic metabolite paraoxon (O,O-diethyl-O-p-nitrophenyl phosphate), suggesting that ethanol affected the oxidative desulfuration of this insecticide. The presence of ethanol within hepatic microsomal incubations did not alter the P450-dependent formation of paraoxon (activation) and p-nitrophenol (detoxification), although p-nitrophenol levels were increased in the presence of ethanol as a result of inhibition of its biotransformation to 4-nitrocatechol by CYP2E1. Ethanol exposure reduced hepatic pyruvate levels, but had no effect on levels of lactate, isocitrate, alpha-ketoglutarate, and malate. Calculation of cytosolic NAD+/NADH and cytosolic NADP+/NADPH redox ratios did not reveal any detectable difference in redox state between control and ethanol-treated mice. Since ethanol did not alter directly the P450-dependent activation or detoxification of parathion, and did not decrease NADPH levels, ethanol's antagonism of the acute toxicity of parathion may result from reduced availability of O2.

Animals↗
PubMed1981

Interaction of insecticides with human plasma lipoproteins.

The binding of chlorinated hydrocarbon, carbamate and organophosphate insecticides to human low density plasma lipoproteins (LDL) and high density plasma lipoproteins (HDL) was studied at pH 7.0 and 16 degrees C and 26 degrees C by equilibrium dialysis, difference spectra and fluorescence. The results suggest interaction to be a partitioning rather than a stoichiometric binding process. Distribution is related to lipid content and composition of the lipoproteins. The K-values vary from 3 x 10(5)M-1 for 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) to less than 10 M-1 for nicotine and aldicarb, and delta G degrees tr is in the range of 7400 cal for DDT to less than 1000 cal for aldicarb and nicotine. The K and delta G degrees tr are inversely related to the water solubility of the insecticides. A significant role of plasma lipoproteins in the transport of slightly water soluble insecticides is suggested.

Humans↗
PubMed1986

Polychlorocycloalkane insecticide-induced convulsions in mice in relation to disruption of the GABA-regulated chloride ionophore.

The toxicity to mice of intraperitoneally-administered polychlorocycloalkane (PCCA) insecticides is generally correlated with their potency as in vitro inhibitors of the brain specific [35S]t-butylbicyclophosphorothionate [( 35S]TBPS) binding site with correction for metabolic activation and detoxification. These findings from our earlier studies are extended here to in vivo investigations relating convulsant action to inhibition of the TBPS binding site in poisoned mice. Radioligand binding assays involved brain P2 membranes washed three times with 1 mM EDTA to remove endogenous gamma-aminobutyric acid (GABA) or other modulator(s) which otherwise serves as a noncompetitive inhibitor of [35S]TBPS binding at the GABA-regulated chloride ionophore. Examination of lindane, technical toxaphene, toxaphene toxicant A, and 10 polychlorocyclodiene insecticides revealed 62 +/- 4% binding site inhibition 30 min after their LD50 doses with 32 +/- 3% inhibition at one-half and 6 +/- 3% inhibition at one-quarter of their LD50 doses. This correlation between binding site inhibition and convulsant action is also evident in dose- and time-dependency studies with endosulfan sulfate. The brain P2 membranes of treated mice contain the parent compound with each of the PCCAs plus activation products of some of the cyclodienes, i.e. endosulfan sulfate from alpha- and beta-endosulfan and 12-ketoendrin from isodrin and endrin. The finding that the brains of treated mice contain sufficient PCCA or its activation products to achieve a magnitude of [35S]TBPS binding site inhibition correlated with the severity of the poisoning signs supports the hypothesis that the acute toxicity of PCCA insecticides to mammals is due to disruption of the GABA-regulated chloride ionophore.

Animals↗
PubMedDate not supplied

Insecticide impregnation can restore the efficiency of torn bed nets and reduce man-vector contact in malaria endemic areas.

Three trials with torn bed nets impregnated with permethrin and deltamethrin were made under field conditions at the Soumousso Field Station and the Vallée du Kou rice-field area, both in Burkina Faso, and the Djoumouna fish pond area in the Congo Republic. Even a considerably torn correctly impregnated bed net could be an useful method for limiting human-anopheline contacts. But bed nets in poor condition, i.e. too little impregnated and too much torn, cannot protect the users against anopheline bites. Protection increases with insecticide concentration, but at a high dosage insecticide could have more a repellent than a killing effect. Therefore a balance has to be found for the optimum rate of insecticide treatment of bed nets to obtain a real reduction in malaria transmission and morbidity, in every epidemiological situation.

Animals↗
PubMed1993

A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of The Gambia, west Africa. 7. Impact of permethrin-impregnated bed nets on malaria vectors.

The impact of permethrin-impregnated bed nets on malaria vectors was studied in 6 pairs of villages during the rainy season in 1989. In each pair, the residents of one village had their nets treated whilst those of the other remained untreated. Routine collections of mosquitoes were made outdoors in the early evening using human-biting collections, and indoors with insecticide sprays, light traps and by searches under bed nets. Mosquitoes of the Anopheles gambiae complex, An. gambiae sensu stricto, An. arabiensis and An. melas, were present in large numbers for 5 months of the study period. These mosquitoes were susceptible to permethrin as judged by bioassay results. Outdoor human-biting rates in the early evening in communities with treated bed nets were similar to those in communities with untreated nets. In villages with treated bed nets most biting occurred outdoors in the early evening with little taking place under impregnated nets. The insecticidal activity of permethrin-impregnated bed nets, dipped by the local population, provided good individual protection against mosquitoes throughout the rainy season and bed nets remained effective even when washed up to 3 times. There was little to suggest that the use of insecticide-treated nets reduced the survival of mosquito populations in villages with impregnated nets. The absence of the expected village-wide effects of net impregnation may have resulted from the circulation of mosquitoes between villages with treated and untreated nets. The proportion of mosquitoes which fed on humans did not differ significantly between villages with treated and untreated nets.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Regional effect of organochlorine insecticides on cholinergic muscarinic receptors of rat brain.

In different brain regions of the rat we studied the effect of chronic feeding with the organochlorine insecticides p,p'-DDT and gamma-HCH on the cholinergic muscarinic receptors. Using [3H]quinuclidinyl benzylate binding to membranes from cerebral cortex, medulla pons, diencephalon, and cerebellum it was found that the two insecticides produced a decrease in the number of muscarinic receptor sites in cerebellum; while gamma-HCH also reduced these receptors in diencephalon. In both cases no changes in receptor affinity were observed. It is suggested that the chronic treatment with these organochlorine insecticides may cause an alteration in cholinergic transmission leading to a down regulation of the muscarinic receptor in certain brain regions.

Animals↗
PubMed1992

Separation of insecticidal components from an extract of the roots of male Piper guineense (west African black pepper) by gas chromatography.

A petroleum ether extract of Piper guineense male roots showed insecticidal activity when tested against Musca domestica. Gas chromatography of the extract yielded four active fractions, one of which was a pure component which was identified by spectral and chemical methods as pellitorine (N-isobutyl-2E,4E-decadienamide). The root extract lost about half of its insecticidal potency during passage down the GLC column, and much of the residual activity was due to the presence of pellitorine. It was concluded that GLC facilitates the isolation of active components in a pure form, but causes some insecticidal components of the root extract to be lost.

Africa, Western↗
PubMed1991

The effect of insecticide-treated bed nets on mortality of Gambian children.

Insecticide treatment of bed nets ("mosquito nets") may be a cheap and acceptable method of reducing the morbidity and mortality caused by malaria. In a rural area of The Gambia, bed nets in villages participating in a primary health-care (PHC) scheme were treated with permethrin at the beginning of the malaria transmission season. Additionally, children aged 6 months to 5 years were randomised to receive weekly either chemoprophylaxis with maloprim or a placebo throughout the malaria transmission season. We measured mortality in children in PHC villages before and after the interventions described, and compared this with mortality in villages where no interventions occurred (non-PHC villages). About 92% of children in PHC villages slept under insecticide-treated bed nets. In the year before intervention, mortality in children aged 1-4 years was lower in non-PHC villages. After intervention, the overall mortality and mortality attributable to malaria of children aged 1-4 in the intervention villages was 37% and 30%, respectively, of that in the non-PHC villages. Among children who slept under treated nets, we found no evidence of an additional benefit of chemoprophylaxis in preventing deaths. Insecticide-treated bed nets are simple to introduce and can reduce mortality from malaria.

Antimalarials↗
PubMed1984

Toxicity of anticholinesterase insecticides to birds: technical grade versus granular formulations.

The acute toxicities of 13 granular anticholinesterase insecticides were compared with their technical grade active ingredients by administering single oral doses of chemical to adult Northern bobwhites (Colinus virginianus) and evaluating resultant LD50 values and dose-response curves. Similar tests with ringed turtledoves (Streptopelia risoria) were conducted with five of the granular formulations to check for interspecific differences. The test chemicals were Amaze 15G (isofenphos), Counter 15G (terbufos), Dasanit 15G (fensulfothion), Diazinon 14G (diazinon), Di-Syston 15G (disulfoton), Dyfonate 20G (fonofos), Furadan 10G (carbofuran), Lorsban 15G (chlorpyrifos), Nemacur 15G (fenamiphos), Parathion 10G (parathion), Tattoo 10G (bendiocarb), Temik 15G (aldicarb), and Thimet 15G (phorate). Information is also presented on dose-response relations and their use in hazard assessment, granule size and hazard, response patterns, and toxic signs. The general conclusions were: (1) The organophosphates (fenamiphos and fensulfothion) and the carbamate (aldicarb) were the most toxic of the insecticides tested. (2) The granular formulation and its technical grade active ingredient were of equivalent toxicity, or the granular was significantly less toxic. (3) The dose-response curve enhances hazard assessment. (4) Ingestion of a single granule of Temik 15G was shown to be life threatening to bobwhite-sized birds, and ingestion of fewer than five granules could be lethal to sparrow-sized birds for Dasanit 15G, Diazinon 14G, Dyfonate 20G, Furadan 15G, and Nemacur 15G. (5) It is therefore suggested that the hazard associated with granular insecticides may be more dependent on which species (cf. size and feeding behavior) inhabit a treated area than on the actual application rate.

Animals↗
PubMed1991

Impact of insecticides on nontarget microarthropod fauna in agricultural soil.

Ecologically important soil microarthropods were used to evaluate the direct and residual toxicities of some insecticides under field and laboratory conditions. The density of total microarthropods and major groups, namely Acarina and Collembola, suffered a statistically significant and persistent decline in the aldrin 30 EC (0.25%)- and endosulfan 35 EC (0.33%)-treated soil of wheat fields. But dimethoate 30 EC (0.125%) and phosphamidon 85 EC (0.03%) applied in mustard fields produced only a temporary decline. Laboratory studies showed that all the above insecticides and monocrotophos 36 EC (0.2%), methyl parathion 50 EC (0.05%), chlordane 20 EC (0.125%), and carbaryl 50 WP (0.625%) had a direct knockdown effect on Cyphoderus sp. but another collembolan species, Xenylla sp., appeared to be somewhat resistant. Only endosulfan was toxic to a common soil Acarina species, Lancetoppia sp. Among four soil media, toxicity was maximum in pure sand, followed by sandy loam, clay, and organic soil. The residual toxicity of phosphamidon, dimethoate, methyl parathion, and endosulfan was more prolonged for Cyphoderus sp. than for Xenylla sp. Only the larval stage of Lancetoppia sp. was susceptible to the residual effect of endosulfan. LD50 and bioassay studies showed that Cyphoderus sp. can be employed as a potential biomonitor of insecticide pollution in soil.

Animals↗