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At least 1,171 records · Page 65Linked to original sources
PubMed1984

Susceptibility to DDT and some other insecticides of head lice (Pediculus capitis De Geer) in Czechoslovakia.

For testing the susceptibility of the head louse to insecticides impregnated bunches of polyamide fibres, whose diameter resembled that of human hair (0.1 mm) were used. In this manner a low mortality of control lice collected from infected persons was obtained (2.9% after 16 hours of exposure). Even after 25 years of DDT use no apparent resistance could be demonstrated in 25 tested louse populations and cross resistance to permethrin in 7 tested populations. The diagnostic concentration for resistance to pp'-DDT was established at 1%. Of the tested insecticides the highest toxicity was shown by malathion (LC50 = 0.000 018%), pirimiphos-methyl had on average a twice lower toxicity, trichlorphon 104 times lower, tetramethrin 1220 times lower, permethrin 2.5 times lower and pp'-DDT 630 times lower toxicity.

Adolescent↗
PubMed1994

Adult population differences in response to six insecticides in Culex fuscocephala Theobald.

Adult bioassay was conducted in the laboratory on two populations of Culex fuscocephala, a vector of Japanese encephalitis (JE) in India, against two organochloride compounds (DDT and dieldrin), an organophosphate compound (malathion), a carbamate pesticide (propoxur) and two synthetic pyrethroids (deltamethrin and cyfluthrin) using WHO techniques. The adult populations from Mandya an irrigated agricultural area, and Mysore, a non-agricultural place in Karnataka, India, have been employed for the experiments. JE outbreaks were reported from these places at different times. Among the insecticides used malathion in 5% concentration was found to be the most effective while, cyfluthrin (0.05%) and deltamethrin (0.025%) were very effective in much lesser concentration. For both propoxur (0.1%) and DDT (4.0%) the two populations of Cx. fuscocephala expressed least susceptibility in terms of the LT50. Against dieldrin (0.4%), cyfluthrin, DDT and malathion Mysore population showed relatively more susceptibility than Mandya population. However for deltamethrin and propoxur the Mandya population registered less tolerance than the Mysore population. Thus adult population responses to different insecticides are variable in the present study.

Animals↗
PubMedDate not supplied

[Susceptibility of Anopheles gambiae to insecticides in the Ivory Coast].

Studies on the susceptibility of Anopheles gambiae to insecticides were carried out in rice field areas of Côte-d'Ivoire. An. gambiae larvae populations from Côte-d'Ivoire were resistant to DDT but susceptible to organophosphorous insecticides. Adult populations from the surroundings of Bouake were resistant to DDT and permethrin. Resistance to propoxur was strongly suspected. The knock-down effect of both deltamethrin and lambdacyhalothrin was delayed and strongly decreased. The control strain from Bobo-Dioulasso and populations from rice fields of Katiola located far from the city were still susceptible to the three pyrethroids. It is likely that resistance to pyrethroids in Bouake has been promoted by the intensive use of domestic aerosol sprays.

Animals↗
PubMed1996

[Susceptibility of cockroaches Blattella germanica L. collected from hospitals to selected pyrethroid and carbamate insecticides].

The resistance to four pyrethroid insecticides: permethrin, deltamethrin, cypermethrin, etofenprox, and to two carbamate insecticides--bendiocarb, propoxur was investigated on field strains of German cockroaches (Blatella germanica L.) caught in hospitals from various parts of Poland. The tests were carried out only on males by the contact method recommended by the WHO. The resistance was evaluated on the basis of LT50S and resistance ratios (RRs). The tested fields strains showed high or moderate resistance to permethrin, deltamethrin, cypermethrin and bendiocarb: moderate resistance or tolerance to etofenproks (this compound has been never used in Poland before), and tolerance or susceptibility to propoxur.

Animals↗
PubMed1997

Insecticide resistance status and mechanisms in Malaysian Blattella germanica (Linnaeus).

The insecticide resistance status of 4 strains of adult male Blattella germanica, viz M (Malacca), E (England), F (restaurant) and K (cafeteria) against malathion and bendiocarb compared with a reference susceptible strain (S) was determined by using a modified WHO bioassay method. The results indicated that all the 4 strains were resistant to the insecticides albeit in different degrees. Resistance ratios for malathion ranged from 1.85-41.07-fold, whereas that of bendiocarb ranged from 1.68-4.83-fold. The biochemical microplate enzyme assays technique employed indicated that the resistance in M and E strains were attributed to acetylcholinesterase insensitivity. Multiple resistance was not detected in any of the 4 strains. Parameters of the identified resistance mechanism correlated well with the observed level of resistance. Agar gel electrophoresis showed that variations in esterase isoenzymes did not confer organophosphate and carbamate resistance to the 4 strains.

Animals↗
PubMed1997

[Determination of insecticide resistance and its biochemical mechanisms in 2 strains of Culex quinquefasciatus from Santiago de Cuba].

It was analyzed the behavior of the resistance of 3 organophosphated insecticides (malathion, clorpirifos and methyl-pyrimifos), 3 pyrethroids (deltamethrin, lambda-cyhalothrin and cypermethrin), and 1 carbamate (propuxur) in populations of Culex quinquefasciatus from 2 municipalities of the province of Santiago de Cuba. The values of the resistance factor proved that there is resistance to malathion and clorpirifos. However, in spite of the existence of a high frequency of the mechanisms of elevated esterases and altered acetylcholinesterase no resistance to methylpymirifos, was observed which demonstrated that this insecticide is not affected by these mechanisms selected in our populations of Culex quinquefasciatus. There was resistence to deltamethrin, and lambda-cyhalothrin in Santiago de Cuba, whereas it was moderate to cypermethrin in Santiago and San Luis. Resistance to deltamethrin was also found in San Luis, but it was mild to lambda-cyhalothrin. The results obtained from the use of the synergists S,S,S tributyl phosphotritiade (DBF) and piperonyl butoxide (PB) indicated that the mechanisms of resistance of unspecific esterases and oxidases of multiple function are involved in the resistance to pyrethroids in both strains from Santiago de Cuba and San Luis. It was determined by the biochemical tests that there existed a high frequency of the mechanisms of esterases and altered acetylcholinesterase. The results of the polyacrylamide gel electrophoresis (PAGE) showed that esterase B1 appears more frequently associated with esterases A6 and B6. It was inferred that this association could be connected with the resistance to pyrethroids.

Acetylcholinesterase↗
PubMed1996

[The evolution of resistance in a Culex quinquefasciatus strain starting from selection with the pyrethroid insecticide lambdacyhalothrin].

The resistance change to different insecticides in Culex quinquesfasciatus strain select at the laboratory with doses of pyrethroid lambdacyhalothrin that would cause a larva mortality of 90% were studied. It was attained an increase of the resistance to this insecticide of 144.5 times compared with the original level, and it was obtained a resistant strain (287x). There was an increase of the levels of resistance to methyl-pyrimifos (2.4 times), propoxur (6 times), DDT (5.2 times), clorpirifos (22 time), cypermethrin (67.5 times), and deltamethrin (20.2 times). The frequencies of the genes that codify for the elevated esterases enzymes and for the modified acetylcholinesterase reached their maximum value. Significant changes were observed in the phenotypes for esterases in the electrophoresis in polyacrylamide gels. It was detected synergism of DEF and PB with lambdacyhalothrin. Therefore, the elevated esterases and the esterases of multiple function may contribute to resistance.

Acetylcholinesterase↗
PubMed1999

Kinetic constants for the inhibition of camel retinal acetylcholinesterase by the carbamate insecticide lannate.

We have designed this study to determine various kinetic parameters of camel retinal membrane-bound acetylcholinesterase (AChE; EC 3.1.1.7) inhibition by carbamate insecticide lannate [methyl N-[[(methylamino)carbonyl]oxy] ethanimidothioate]. All these kinetic constants were derived by simple graphical methods. The value of kinetic parameters was estimated as follows: 0.061 microM)(-1), 1.14 (microM)(-1), 0.216 microM, 0.016 min(-1), 0.0741 (gammaM min)(-1) 0.746 microM, and 4.42 microM for velocity constant (Kv), new inhibition constant (Knic), dissociation constant (Kd), carbamylation rate constant (k2c), overall carbamylation rate constant (k'2), 50% inhibition constant (K150), and 99% inhibition constant (K199), respectively. These unique methods may be used to estimate such kinetic parameters for time-dependent inhibition of enzymes by variety of chemicals, insecticides, herbicides, and drugs.

Acetylcholine↗
PubMedDate not supplied

Cytogenetic effect of some insecticides in mouse spleen.

Several insecticides were tested for their ability to induce chromosomal aberrations in mouse spleen. They were injected i.p. in doses representing approximately 1/8-1/10 of the respective LD50 values. Doses were: DDT, 5.5 mg kg-1 body wt.; malathion, 30 mg kg-1 body wt.; Dursban, 4 mg kg-1 body wt.; Sevin, 7 mg kg-1 body wt.; and Lannate, 1 mg kg-1 body wt. 'Mitomycin C' at a dose of 1 mg kg-1 body wt. was used as a positive control. Mice were sacrificed 6, 24 and 48 h after treatment. DDT, malathion, dursban and lannate caused maximum chromosomal aberrations 24 h after injection, whereas Sevin induced its maximum effect 6 h after the treatment. All the insecticides induced statistically significant chromosomal aberrations even after excluding the number of metaphases with gaps. The results indicate genotoxicity in mouse spleen cells.

Animals↗
PubMed1998

CYP6D1 protects thoracic ganglia of houseflies from the neurotoxic insecticide cypermethrin.

CYP6D1 is a housefly cytochrome P450 known to metabolize neurotoxic pyrethroid insecticides. To determine if the nervous system was capable of metabolizing pyrethroids, we examined CYP6D1-mediated in vitro metabolism in thoracic ganglia from pyrethroid-resistant (LPR) and -susceptible (CS) strains of housefly. SDS-PAGE/immunoblotting revealed that CYP6D1 was expressed in all tagmata and in thoracic ganglia of both strains, but in all cases the levels of CYP6D1 were higher in the LPR strain. Using a CYP6D1-specific antiserum, we found CYP6D1 to be the major, and possibly the only, P450 isozyme involved in cypermethrin metabolism in thoracic ganglia homogenates. Additionally, thoracic ganglia homogenates from LPR houseflies metabolize more cypermethrin than preparations from susceptible flies. This metabolism was inhibited by piperonyl butoxide and a CYP6D1-specific antibody. Our results indicate that thoracic ganglia of LPR houseflies are protected from the neurotoxin cypermethrin by virtue of the higher levels of CYP6D1 compared to the susceptible houseflies. This P450-mediated detoxification of an insecticide at the level of the target tissue helps to explain the high levels of resistance to pyrethroids in the LPR strain.

Animals↗
PubMed2000

Modulation of a lectin insecticidal activity by carbohydrates.

Lectins from plants present an insecticidal activity most probably through their carbohydrate binding properties; as a consequence, their toxicity should vary with the presence of a competitive sugar in the ingested food. In order to test this hypothesis, we performed competition experiments between insecticidal activity and carbohydrate binding. For this purpose, we used a lectin from Lathyrus ochrus and the specific carbohydrate for this protein, glucose. In toxicological tests with Drosophila melanogaster, we observed a decrease of lectin toxicity when glucose was added to the larva-rearing medium. This result suggests that the toxicity of the lectin is correlated to its ability to bind sugar in the insect digestive tract and stresses the importance of sugar composition of the nutriment used for toxicological testing of lectins or in genetically modified plants.

Animals↗
PubMed2001

The chemical and biological properties of methoxyfenozide, a new insecticidal ecdysteroid agonist.

Methoxyfenozide [N-tert-butyl-N'-(3-methoxy-o-toluoyl)-3,5-xylohydrazide; RH-2485] is the newest diacylhydrazine insecticide to reach the marketplace. It binds with very high affinity to the ecdysone receptor complex (EcR:USP) in lepidopteran insects [Kd = 0.5 nM (Plodia)], where it functions as a potent agonist, or mimic, of the insect molting hormone, 20-hydroxyecdysone (20E). Methoxyfenozide exhibits high insecticidal efficacy against a wide range of important caterpillar pests, including many members of the family Pyralidae, Pieridae, Tortricidae and Noctuidae. It is most effective when ingested by the target caterpillar, but it also has some topical and ovicidal properties. It is modestly root systemic, but not significantly leaf-systemic. Evidence collected to date indicates that methoxyfenozide has an excellent margin of safety to non-target organisms, including a wide range of non-target and beneficial insects.

Administration, Oral↗
PubMed2003

Neurological symptoms among Sri Lankan farmers occupationally exposed to acetylcholinesterase-inhibiting insecticides.

BACKGROUND: In many agricultural districts in Sri Lanka, pesticide poisoning is a leading cause of death. This study aims to evaluate the impact of pesticide use on Sri Lankan farmers' health. METHODS: A total of 260 subjects were surveyed in both a low and a high exposure period. Acetylcholinesterase activity was measured and data on symptoms were collected with questionnaires. RESULTS: Twenty-four percent of surveyed farmers had suffered at least once from acute pesticide poisoning. Farmers showed significantly more inhibition of cholinesterase activity than controls. Acute symptoms indicative for exposure to cholinesterase-inhibiting pesticides were associated with farming and a higher degree of cholinesterase suppression (more than 13% inhibition). Integrated Pest Management (IPM) training seemed to result in less insecticide use, and less cholinesterase inhibition. CONCLUSIONS: Our results suggest that occupational acetylcholinesterase-inhibiting insecticide exposures have a negative impact on Sri Lankan farmers' health. Overall reduction in pesticide use seems the best option to protect farmers from the adverse effects of pesticides.

Acetylcholinesterase↗
PubMed1990

Chronic neuropsychological sequelae of occupational exposure to organophosphate insecticides.

The early (immediate and delayed) neurotoxic effects of acute organophosphate intoxication are well documented in the scientific literature; lack of recognition and inappropriate treatment of occupational poisonings continue. Less well understood is the potential development of chronic neuropsychological sequelae from exposures to insecticides. We undertook two cohort studies to assess chronic neuropsychologic effects of insecticide poisoning. Based, in part, on our clinical evaluation of several patients, these studies included: 1) a retrospective cohort study assessing function at least 1 year following moderate to severe poisonings among farm workers; and 2) a prospective cohort study assessing neuropsychological function before and after a season of organophosphate exposures among pesticide applicators. A typical case description, the study design, methodologic problems, and preliminary findings of these ongoing studies are presented.

Agricultural Workers' Diseases↗
PubMed1985

Teratogenic effects of the organophosphate insecticide dicrotophos (Bidrin): histological characterization of defects.

White Leghorn chicken eggs, specific pathogen free, were treated with the organophosphate insecticide dicrotophos and the early defects thus induced were characterized histologically. Eggs were incubated for 24, 48, 72, or 96 hr, injected with doses of dicrotophos ranging from 250 micrograms to 2.0 mg per egg, and observed after an additional 48 hr of incubation. Treated embryos displayed general developmental retardation as well as unilateral retardation of the cranial sense organs, the youngest embryos being most severely affected. Many embryos injected with insecticide at 24 hr, and all but one injected at 48 or 72 hr, displayed notochordal folding, usually restricted to the cervical region; most of these also showed deformities of the adjacent spinal cord. Other defects, seen on a less consistent basis, included branching of the neural canal in the lumbar region, bifurcation of the neural epiphysis, deformation of the lens vesicle, and distention of the major blood vessels. The incidence and severity of epiphyseal, lens, and vascular defects were greatest among embryos treated at 24 hr, whereas notochordal and both types of neural defects were greatest among those treated at 48 hr. The incidence and severity of the abnormalities diminished with increasing age such that by 96 hr the only defect noted was a weak notochordal folding in one embryo. To a lesser extent, incidence and severity were dose-related also. Histological similarities between embryos displaying vascular distention and recently dead treated embryos suggested that this abnormality is a precursor to death.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗
PubMed1995

Characterization of a novel esterase conferring insecticide resistance in the mosquito Culex tarsalis.

Resistance to the organophosphate insecticide, malathion, in a strain of Culex tarsalis mosquitoes is due to increased activity of a malathion carboxylesterase (MCE). To determine whether resistance was due to a qualitative or quantitative change in the MCE, the enzyme was purified from both malathion-resistant and -susceptible mosquitoes. Enzyme kinetic measurements revealed that the two strains have one MCE in common, but resistant mosquitoes also have a unique MCE which hydrolyses malathion 18 times faster. Interestingly, this MCE does not hydrolyse alpha-naphthyl acetate, a substrate commonly used to detect increased levels of esterases in other organophosphate-resistant insects. Unlike the over-produced esterase of some related mosquito species, each MCE in C. tarsalis accounts for only a small fraction (0.015%) of the total extractable protein in either strain. Therefore, resistance in these insects is due to the presence of a qualitatively different enzyme, and not to a quantitative increase of a non-specific esterase. This study therefore demonstrates that the underlying biochemical mechanisms of insecticide resistance in one insect cannot necessarily be predicted from those of another, even closely related species.

Animals↗
PubMed2006

Synthesis of new thiazolylthiazolidinylbenzothiazoles and thiazolylazetidinylbenzothiazoles as potential insecticidal, antifungal, and antibacterial agents.

A series of 2-{[2'-(3''-chloro-2''-oxo-4''-substitutedaryl-1''-azetidinyl)-1',3'-thiazol-4'-yl] thio}benzothiazoles (4a-4e) and 2-{[(2'-(2''-substitutedaryl-4''-thiazolidinon-3''-yl)-1',3'-thiazol-4'-yl]thio}benzothiazoles (5a-5e) have been synthesized from 2-[(2'-substitutedarylidenylimino-1',3'-thiazol-4'-yl)thio]benzothiazoles (3a-3e). The structure of these compounds has been elucidated by elemental (C, H, N) and spectral (IR, (1)H-NMR, Mass) analysis. Furthermore, compounds 3a-3e, 4a-4e, and 5a-5e were screened for insecticidal activity against Periplaneta americana and antifungal, antibacterial activities in vitro against different strains of fungi and bacteria. Out of the fifteen compounds tested, compound 5b, 2-{[2'-(2''-p-hydroxy-m-methoxyphenyl)-4''-thiazolidinon-3''-yl)-1',3'-thiazol-4'-yl]thio}benzothiazole, was found to possess most prominent insecticidal activity.

Animals↗
PubMed2006

Comparison of the biotransformation of the 14C-labelled insecticide carbaryl by non-transformed and human CYP1A1-, CYP1A2-, and CYP3A4-transgenic cell cultures of Nicotiana tabacum.

Transgenic tobacco-cell-suspension cultures expressing separately the human cytochrome P450 monooxygenases CYP1A1, CYP1A2, and CYP3A4 were utilized to study the biotransformation of the 14C-labelled insecticide carbaryl (=naphthalen-1-yl methylcarbamate). The resulting data were compared to similar data from the corresponding non-transformed (NT) tobacco-cell culture and commercially available membrane preparations (Bactosomes) of genetically modified bacteria separately containing the same human P450s. A rapid conversion rate of carbaryl was observed with the CYP1A1 and CYP1A2 cells, where only 49.7 and 0.2% of applied carbaryl (1 mg/l), respectively, remained after 24 h, as compared to 77.7% in the non-transformed culture. Unexpectedly, the corresponding results obtained from the CYP3A4 cultures were not definite. With 25 mg/l of carbaryl and 96 h of incubation, it was proven that the insecticide is also substrate of CYP3A4. This finding was supported by GC/EI-MS analysis of the primary metabolite pattern produced by the isozyme. This consisted of naphthalene-1-ol, N-(hydroxymethyl)carbaryl, 4-hydroxycarbaryl, and 5-hydroxycarbaryl, whereas the main product in non-transformed cells was N-(hydroxymethyl)carbaryl. Data obtained from the CYP1A1, CYP1A2, or CYP3A4 Bactosomes agreed with those of the P450-transgenic tobacco cells. Problems with GC/EI-MS analysis of carbaryl and its metabolites are discussed.

Carbaryl↗