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At least 1,027 records · Page 57Linked to original sources
PubMed1997

Characterization of the acetylcholinesterase gene from insecticide-resistant houseflies (Musca domestica).

Acetylcholinesterase (AChE) is the target site for the organophosphates and carbamates in insects. Widespread use of these two classes of insecticides has led to the selection of resistance. Target modification was regarded as a molecular mechanism in some resistance species. The altered AChEs with reduced sensitivity to inhibition are related to this resistance. AChE genes from two insecticide-resistant housefly (Musca domestica) strains D3 and Kash were isolated and sequenced using RT-PCR and streptavidin-linked magnetic bead techniques. The cDNAs have a 2082-bp open reading frame from which the complete amino acid sequence of AChE has been deduced. Some differences in nucleotide sequence and four-point mutations of amino acid were found compared to a susceptible strain, i.e., the Cooper strain. Three substitutions are likely to confer insecticide insensitivity, which seems that D3 and Kash belong to CH2 pattern of resistance.

Acetylcholinesterase↗
PubMed1976

[Rapid enzymatic-colorimetric method for detecting organophosphorous insecticide residues in milk].

The authors developed a new enzymatic-colorimetric rapid method for testing milk for residues of organophosphorous insecticides. The test is based on the colour reaction of indoxyl acetate with the esterase of the OROSERAN (Dessau) horse serum which is inhibited by organophosphorous insecticides. Calibration curves were established for Trichlorphon and Dichlorphos (DDVP). The limit of detection lies at 0.02 mg/kg. The time actually needed per sample is about 15 min. The result is obtained within 90 min. Since this procedure requires no clean-up operations, it is labour-saving compared to other thin-layer or gas chromatographic methods. It may be recommended as a screening test for the detection of organophosphorous insecticides in milk samples.

Animals↗
PubMed1956

The significance of insecticide-resistant strains; with special reference to pests of medical importance.

The author discusses the meaning of insecticide resistance and the manner in which it should be detected and measured. From some recent data he gives a number of examples of measurements of resistance in mosquitos of different species in various areas. He then proceeds to a speculative discussion on the way in which insecticide resistance arises, whether it can be prevented and overcome, its importance in the past and at present, and finally its future prospects.

Animals↗
PubMed1957

Progress in physiological studies of insecticide resistance.

This study deals first with the progress recently made in investigations on the mode of toxic insecticidal action of DDT, lindane and other chlorinated hydrocarbons, pyrethrins and related chemicals, and organo-phosphates, and secondly with resistance mechanisms to the same insecticides.The author feels that, although good progress is being made towards understanding the physiological mechanisms of resistance, the gaps in present knowledge, the types of insecticide to which resistance is developing, and the number of medically important species involved lead inevitably to the conclusion that the general outlook for insect control is deteriorating. He considers that what is now needed is not so much continuation of the present empirical approach to the problem of resistance as intensification of basic studies of the biology, ecology and physiology of the insect species concerned to provide a foundation for more rational alternative control measures.

Insect Control↗
PubMed1985

The effects of the organophosphate insecticide malathion on very young chick embryos: malformations detected by histological examination.

This histological study sought to determine the nature and incidence of developmental abnormalities induced by one of the reportedly least teratogenic of insecticides injected into very young chick embryos. Using techniques to assure rapid contact between injectant and embryo, eggs incubated for 24, 48, or 72 hr were injected with corn oil or 125 micrograms-4.0 mg malathion. The embryos were recovered 48 hr later, paraffin-embedded, serially cross-sectioned, and examined in detail. Structures affected (and the nature of the defects) were as follows: wing level notochord and spinal cord (folded or undulated); trunk/leg level spinal cord (variously, neural folds unfused, roof infolded, canal partitioned, etc.); eye (lens misshapen or severely thinned, optic cup incompletely invaginated); diencephalon (epiphysis bifurcated or off-center, supernumerary outgrowths); cardiovascular structures (atrium and major blood vessels enlarged); and tailbud (curled into hindgut: ourentery). Overall incidence was both dose- and age-related, doubling for each doubling of dose and tripling for each 24 hr less age at exposure. For most (not all) individual structures, incidence was greatest when exposed at 24 hr and nil at 72 hr. Severity of effect was not consistently dose- or age-dependent. We conclude that contrary to previous reports, 24- to 72-hr embryos are highly vulnerable to insecticide exposure, with the youngest the most vulnerable, and many of the defects detected may be attributed to either of two mechanisms: failure in formation of the supportive sheath, or factors that cause epithelial morphogenesis (e.g., microtubules, microfilaments, extracellular material, cell-to-cell adhesion mechanisms). Previous observations that 1- to 3-day embryos are relatively unresponsive to insecticides are probably artifactual owing to imprecise techniques.

Abnormalities, Drug-Induced↗
PubMed1993

Differences in the neuroexcitatory actions of pyrethroid insecticides and sodium channel-specific neurotoxins in rat and trout brain synaptosomes.

The effects of pyrethroid insecticides and other sodium channel-specific neurotoxins on synaptosomal membrane potential were investigated in rat and trout brain synaptosomes using the membrane-permeant lipophilic cation [3H]tetraphenylphosphonium (TPP+). Concentration-dependent and tetrodotoxin-sensitive decreases in TPP+ accumulation, indicative of membrane depolarization, were produced by veratridine, aconitine, scorpion (Leiurus quinquestriatus) venom, and type I and type II pyrethroids, in both species. Veratridine, aconitine, and Leiurus venom were more potent and efficacious membrane-depolarizing agents in rat synaptosomes than in trout synaptosomes. Type II (deltamethrin, cypermethrin) pyrethroids produced similar depolarizing responses in rat and trout synaptosomes; however, the 1R-cis-alpha R isomer of deltamethrin, which had no effect on membrane potential in rat synaptosomes, depolarized trout synaptosomes. This isomer of deltamethrin was also shown to produce toxicity in trout, but not in rats. The type I pyrethroids, permethrin and NRDC 157, exhibited significantly greater intrinsic activity in trout brain synaptosomes, producing maximal membrane depolarizations that were three times greater than those observed in rat brain synaptosomes. These results provide evidence of species-specific differences in the membrane-depolarizing properties of pyrethroid insecticides and sodium channel-specific neurotoxins. They also suggest that some of the neurotoxin binding domains of the voltage-sensitive sodium channel in trout brain differ from those in mammalian brain. The hypersensitivity of fish to the neurotoxic actions of pyrethroid insecticides may be related to these differences.

Alkaloids↗
PubMed1990

The organochlorine insecticide 1,2,3,4,5,6-hexachlorocyclohexane (lindane) but not 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) augments the nocturnal increase in pineal N-acetyltransferase activity and pineal and serum melatonin levels.

The effect of organochlorine insecticides lindane (1,2,3,4,5,6-hexachlorocyclohexane) and DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) were studied in terms of their effects on the rat pineal N-acetyltransferase (NAT) activity, hydroxyindole-O-methyltransferase (HIOMT) activity and pineal and serum melatonin levels during the day (2000h) and at night (2300 and 0100h). Additionally, pineal levels of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), and 5-hydroxyindole acetic acid (5-HIAA) were estimated. Nocturnal NAT activity was increased after lindane administration; likewise, lindane augmented pineal and serum melatonin levels at 2300h. Conversely, DDT was without a statistically significant effect on either NAT activity or on pineal or serum melatonin levels. Neither lindane nor DDT significantly influenced pineal HIOMT values either during the day or at night. Likewise, neither insecticide consistently influenced pineal levels of either 5-HTP, 5-HT or 5-HIAA. The results indicate that the organochlorine insecticide, lindane, modifies pineal melatonin synthesis in vivo.

5-Hydroxytryptophan↗
PubMed2006

Dermal insecticide residues from birds inhabiting an orchard.

The US Environmental Protection Agency conducts risk assessments of insecticide applications to wild birds using a model that is limited to the dietary route of exposure. However, free-flying birds are also exposed to insecticides via the inhalation and dermal routes. We measured azinphos-methyl residues on the skin plus feathers and the feet of brown-headed cowbirds (Molothrus ater) in order to quantify dermal exposure to songbirds that entered and inhabited an apple (Malus x domestica) orchard following an insecticide application. Exposure to azinphos-methyl was measured by sampling birds from an aviary that was built around an apple tree. Birds sampled at 36 h and 7-day post-application were placed in the aviary within 1 h after the application whereas birds exposed for 3 days were released into the aviary 4-day post-application. Residues on vegetation and soil were also measured. Azinphos-methyl residues were detected from the skin plus feathers and the feet from all exposure periods. Our results underscore the importance of incorporating dermal exposure into avian pesticide risk assessments.

Animals↗
PubMed1983

Carcinogenesis with the insecticide rotenone.

Rotenone is an insecticide which has been used extensively for a long time, and is now widely used in the U.S.A. and other industrialized countries. Rotenone is used mainly as an agricultural insecticide, household garden insecticide and water plant pesticide. Through these uses, rotenone may now be reaching the human male and female in these countries in substantial amounts, carried by fresh or cooked vegetables, consumed fish and drinking water. A review of the existing published reports and unpublished official documents dealing with the capacity of rotenone to induce neoplastic, paraneoplastic and preneoplastic lesions in the rat is presented here. It is strongly suggested that rotenone is carcinogenic to the rat (at doses from 2 to 25 parts per million continuously in food, or from 0.8 to 2.5 mg/kg weight for 1 to 4 months by oral administration), above all, when the rats receive deficient diets, especially those poor in riboflavin. Rotenone carcinogenesis, among other things, seems to exhibit a peculiar dose response pattern, which could be explained by its possible hormonal mechanism of action. Further studies to assess definitively the role of rotenone as a possible environmental carcinogen are proposed as being highly necessary.

Animals↗
PubMed1982

Cytogenetic effects of pesticides. I. Induction of micronuclei in mouse bone marrow by the insecticide Dursban.

The induction of micronuclei in mouse bone marrow by the organophosphorous insecticide 'Dursban' was tested. 3 routes of administration were used for the pure insecticide: intraperitoneal, oral and dermal. The different routes of treatment with Dursban induced a statistically significant increase in the percentage of polychromatic erythrocytes over that of the control. Both intraperitoneal and oral treatments with the insecticide induced a high percentage of polychromatic erythrocytes with micronuclei, whereas dermal treatment did not induce micronuclei.

Administration, Oral↗
PubMed1988

Genotoxicity studies with four organophosphorus insecticides using the unstable white-zeste system of Drosophila melanogaster.

The present study was carried out to evaluate the suitability of the unstable white-zeste system in Drosophila melanogaster by testing 4 organophosphorus insecticides for potential genotoxic activity: dimethoate, fenitrothion, malathion, and methyl parathion. In view of the high sensitivity to insecticides of the unstable zeste strain used in this assay and the negative results obtained in this work, the white-zeste system does not appear to be sufficiently accurate for the evaluation of the mutagenic potential of specifically toxic chemicals, like insecticides.

Animals↗
PubMed1987

Exposure to insecticides of brushland wildlife within the Lower Rio Grande Valley, Texas, USA.

Brushland wildlife within the Lower Rio Grande Valley of south Texas were studied following applications of eleven insecticides to nearby sugarcane or cotton fields. During the study no wildlife were found dead. Mean brain acetylcholinesterase (AChE) activity of great-tailed grackles (Quiscalus mexicanus) and mourning doves (Zenaida macroura) was significantly lower than controls following application of some organophosphorous insecticides. Brain AChE activity varied significantly among chemicals, days after exposure and application rates. Mean brain AChE activity of white-winged doves (Zenaida asiatica) and three small mammal species was not significantly different than their respective controls following application of insecticides. Mean brain AChE activity of grackles was inhibited significantly more than white-winged doves after application of Bolstar, EPN-methyl parathion, and Azodrin and significantly more than that of mourning doves after applications of Bolstar and EPN-methyl parathion. Our data indicate that there were no adverse effects on most brushland wildlife. Exposure was probably dependent upon use of the agricultural fields as feeding or resting sites and only grackles and mourning doves were regularly present in the fields.

Journal Article↗
PubMed1987

Pyrolysing insecticidal coils: air pollution by polycyclic aromatic hydrocarbons and other mutagens detected by the Salmonella/microsome test.

Pyrolysing insecticidal coils, which are used commonly for their evaporative release of insecticidal amounts of pyrethrins, have been investigated with respect to the emission of airborne particles, their mutagenic activity in the Salmonella/microsome mutagenicity test and their polycyclic aromatic hydrocarbons (PAH) content. Emitted particles contain compounds that are mutagenic in the absence of exogenous activation, as well as components that require mammalian activation. The particles also contain a range of PAH, but their concentration cannot account for the mutagenic response with mammalian activation. The use of pyrolysing insecticidal coils in semi-enclosed spaces may cause air pollution by releasing mutagenic and carcinogenic compounds that are of a magnitude similar to that found in other air pollution situations.

Journal Article↗
PubMed1989

Seasonal variations of organochlorine insecticide residues in air from Porto Novo, South India.

Air samples collected from Porto Novo (11 degrees 29' N, 79 degrees 46' E), Tamil Nadu State, South India from December, 1987 to January, 1989 were analysed to determine the seasonal variations of the levels of organochlorine insecticides such as HCH (BHC) and DDT. Both these insecticides showed higher levels from August to January, although this trend was more marked in HCH than DDT, reflecting the application of HCH largely, and probably small quantities of DDT during the flowering season of rice. The alpha-HCH was detected as a dominant isomer for all seasons monitored followed by gamma-HCH. Among DDT compounds, p,p'-DDT was the highest except in dry season (January to April) when p,p-DDE showed higher percentage. The levels and percentage composition of these insecticides recorded in the present study may aid in interpreting the role of a 'point source' area since India is one of the countries still using the persistent organochlorine pesticides in large quantities.

Journal Article↗
PubMed1991

Modulation of interleukin-2-driven proliferation of human large granular lymphocytes by carbaryl, an anticholinesterase insecticide.

Studies in other laboratories have provided evidence that the interleukin-2 (IL2) signaling pathway in lymphocytes includes essential, serine proteases. Since the anticholinesterase (antiCHE) insecticides are potent serine hydrolase (esterase and protease) inhibitors, we assessed the ability of carbaryl (CA, a widely used antiCHE insecticide) and alpha-naphthol (NA, a major metabolite of carbaryl) to modulate IL2-driven proliferation of large granular lymphocytes (LGL) purified from human peripheral blood. These cells express nearly all of the natural killer (NK) activity of human peripheral blood. NK cells are normal lymphocytes that respond to IL2 by proliferating and increasing their tumoricidal activity on a per cell basis. Cultures of purified LGL, initiated in the presence of human recombinant IL2, were harvested on culture Day 4, then proliferation was measured as [3H]thymidine incorporation. When added only at the time cultures were initiated. CA inhibited incorporation 10-32%, 35-53%, and 54-57% at 0.5, 5.0, and 50 microM, respectively. In contrast, NA had no effect at 0.5 and 5.0 microM, but was inhibitory (16-17%) at 50 microM. Reexposure to CA or NA, during the incorporation assay, had little effect on the observed inhibition profiles. Chemically induced changes in cell number during an 8-day culture period reflect the chemically induced changes in [3H]thymidine incorporation. Neither CA nor NA produced cell death. Quantitation of both CA and NA by HPLC indicated a rapid loss of CA (ca. 95% in 24 hr) and a much slower loss of NA from the culture medium. CA inhibited human LGL proliferation at concentrations producing little or no inhibition of serum CHE, an indicator of exposure to antiCHE insecticides.

Adult↗
PubMed1992

Inhibition of interleukin-2-stimulated enhancement of human natural killer (NK) cell activity by carbaryl, an anticholinesterase insecticide.

The potency of the anticholinesterase (antiCHE) insecticides as serine hydrolase inhibitors, and evidence for serine hydrolase activity in interleukin-2 (IL2) signalling suggest that the natural killer (NK) cell may be a target for dysregulation by antiCHE insecticides. NK cells are large granular lymphocytes (LGL) that respond to IL2 by proliferating and increasing their cytolytic efficiency. In the present study, we assessed the effects of carbaryl (CA, an antiCHE insecticide) and alpha-naphthol (NA, the major metabolite of CA) on both target cell killing per se and IL2 enhancement of target cell killing by human NK cells. Human LGL, collected from the peripheral blood of normal donors, were cultured for 4 days with human recombinant IL2 (HRIL2), then assayed by a 51Chromium (51Cr) release assay for lytic activity against human K562 cells. When added at the beginning of the culture period, CA inhibited enhancement of cytolytic efficiency in a concentration-dependent manner; at concentrations (0.5 and 5.0 microM) compatible with no cholinergic toxicity. Reduction of the effector/target cell (E/T) ratio in the 51Cr release assay markedly enhanced the observed inhibition by CA. In one experiment, inhibition increased from 6% to 20%, 17% to 35%, and 53% to 73% at 0.5, 5.0, and 50 microM CA, respectively, when E/T was reduced from 10:1 to 2.5:1. This result is consistent with reduced cytolytic efficiency of individual NK cells exposed to CA. NA had no effect at 0.5 or 5.0 microM but caused some inhibition at 50 microM. Neither CA nor NA produced LGL death. When CA or NA was added directly to the 51Cr release assay, inhibition was not observed. The mechanism of inhibition of IL2-stimulated enhancement of target cell killing is not yet known, however, the results are consistent with impairment of IL2 signalling, by CA.

Adult↗
PubMed1995

Inhibition of erythrocyte membrane (Ca2+ + Mg2+)-ATPase by the organophosphorus insecticides parathion and methylparathion.

Organophosphorus insecticides parathion and methylparathion non-competitively inhibited the activity of (Ca2+ + Mg2+)-ATPase bound to and solubilized from pig erythrocyte membrane. Both enzyme preparations exhibited biphasic substrate curves displaying the existence of two functional active sites with low and high affinity to ATP. Also, the relationship between the activity of bound enzyme and Ca2+ concentration was biphasic. The activity reached maximum at 20 microM then dropped progressively as the Ca2+ concentration was raised. The inhibition of the activity was more pronounced for parathion than for methylparathion and the solubilized enzyme preparation was more affected than the bound one. The inhibition constants (Ki) for parathion for bound enzyme were 55 and 158 microM for high- and low-affinity active sites, respectively; for methylparathion these values equalled 74 and 263 microM, respectively. Ki values for parathion were 36 and 118 microM for solubilized enzyme (high- and low-affinity sites, respectively), for methylparathion -62 and 166 microM, respectively. The magnitude of the effect was greater for a low Ca2+ concentration, which could arise from different conformational states of the enzyme at different calcium concentrations. The results of the experiment suggest that the insecticides inhibited the ATPase by binding to a site on the enzyme rather than by the interaction with associated lipids, although lipids could weaken the action of the compounds due to the strong affinity of organophosphorus insecticides to lipids.

Adenosine Triphosphate↗
PubMed2003

Relocating expression of vegetative insecticidal protein into mother cell of Bacillus thuringiensis.

Vegetative insecticidal protein (VIP) is a class of insecticidal proteins produced by some strains of Bacillus thuringiensis during the vegetative stage of their growth. Unlike delta-endotoxins which are produced as parasporal inclusion bodies within the cell during sporulation, VIP is secreted into the culture medium. Here we report the relocation of the expression of VIP into the mother cell compartment in a manner similar to well-characterized Cry proteins. Relocation of VIP is directed to mother cell by placing its synthesis under sporulation-dependent promoters, BtI and BtII. The insertion of cry preferred transcription termination sequence at the 3(') region and a STAB-SD sequence at the 5(') region of the gene provided stability to the vip transcript and enhanced its yield. The demonstrated expression of VIP within the cells in the form of inclusion bodies would facilitate development of a suitable formulation for the application of this class of insecticidal proteins in the field.

Bacillus thuringiensis↗