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PubMed1987

Case histories of bald eagles and other raptors killed by organophosphorus insecticides topically applied to livestock.

Since 1982 when secondary poisoning of a red-tailed hawk (Buteo jamaicensis) was documented following the recommended use of famphur applied topically to cattle, the Patuxent Wildlife Research Center has tested dead birds of prey for poisoning by famphur and other pour-on organophosphorus (OP) insecticides. Brain cholinesterase (ChE) activity was first determined, then if ChE was depressed greater than or equal to 50%, stomach and/or crop contents were evaluated for anti-ChE compounds. This report presents the circumstances surrounding the OP-caused deaths of eight bald eagles (Haliaeetus leucocephalus), two red-tailed hawks, and one great horned owl (Bubo virginianus) between March 1984 and March 1985. OP poisoning of raptors by pour-on insecticides in the United States is widespread, but its magnitude is unknown.

Animals↗
PubMed1999

Relationship between amount of esterase and gene copy number in insecticide-resistant Myzus persicae (Sulzer).

Overproduction of the insecticide-degrading esterases, E4 and FE4, in peach-potato aphids, Myzus persicae (Sulzer), depends on both gene amplification and transcriptional control, the latter being associated with changes in DNA methylation. The structure and function of the aphid esterase genes have been studied but the determination of their copy number has proved difficult, a common problem with gene amplification. We have now used a combination of pulsed-field gel electrophoresis and quantitative competitive PCR to determine relative esterase gene copy numbers in aphid clones with different levels of insecticide resistance (R1, R2 and R3). There are approx. 4-fold increases between susceptible, R1, R2 and R3 aphids, reaching a maximum of approx. 80 times more genes in R3; this gives proportionate increases in esterase protein relative to susceptible aphids. Thus there is no overexpression of the amplified genes, in contrast with what was thought previously. For E4 genes, the loss of 5-methylcytosine is correlated with a loss of expression, greatly decreasing the amount of enzyme relative to the copy number.

5-Methylcytosine↗
PubMed1976

Pralidoxime as an insignificant reactivator in severe anticholinesterase (organophosphate insecticide) poisoning.

In acute severe anticholinesterase poisoning by organophosphate compounds, pralidoxime (P-2-AM, pyridine-2-aldoxime methiodide) used in the recommended doses, intravenously, has not been shown to reactivate the inhibited cholinesterase, as evidenced both clinically and biochemically. In vitro studies using pralidoxime iodide up to ten times the recommended concentrations, produced insignificant reactivation of cholinesterases inhibited by the organophosphate insecticide Bidrin (di-methyl-3-hydroxyl-N, N-dimethyl-crotonamide phosphate). This was even so despite prolonged exposure of the inhibited cholinesterases to the oxime. The value of pralidoxime as a reactivator of phosphorylated cholinesterases is therefore in doubt, and should not be used in preference to large doses of atropine and other supportive treatment in poisoning by organophosphate insecticides.

Acetylthiocholine↗
PubMedDate not supplied

[Research on some phosphorganic insecticide residues in olive oil in relation to techniques of Dacus oleae control. I. Results of total treatment to the foliage (author's transl)].

The research conducted to verify the presence and the amount of residues of organophosphorus insecticides in olive oil from olive trees sprayed against. Dacus oleae has shown that both hydrophilic (dimethoate, formathion, phosphamidon) and lypophilic (fenthion, medathion, prolate) substances tested leave more or less appreciable residues in the oil, either in a short time or in more than one month from the treatment. In the operative conditions reflecting antidacic practice, the amount of residue appears higher for the lypophilic organophosphorus insecticides.

Food Contamination↗
PubMed2000

Quantitative analysis of gene amplification in insecticide-resistant Culex mosquitoes.

The amplification of carboxylesterase structural genes followed by their overexpression is the most common mechanism of resistance to organophosphorus insecticides in Culex mosquitoes. Most resistant Culex quinquefasciatus mosquitoes have co-amplified estalpha2(1) and estbeta2(1) genes. Recently, Southern, DNA dot-blot analysis and phosphorimaging technology were used to quantify the est gene copy number in aphids and mosquitoes. Although more accurate than autoradiography, this method relies on probe hybridization, which can be variable. We have directly measured gene and mRNA copy number by using real-time quantitative PCRs in mosquitoes. The acquisition of fluorescence from incorporation of the double-strand-specific dye SYBR GreenI into a PCR product once per cycle is used to provide an absolute quantification of the initial template copy number. Thus it has been possible to show that estalpha2(1) and estbeta2(1) are co-amplified approx. 80-fold in the genome of the resistant PelRR strain of C. quinquefasciatus. The two genes, although co-amplified in a 1:1 ratio, are differentially transcribed: the estbeta2(1) gene from this amplicon has greater transcription than estalpha2(1) in all individual mosquito larvae tested, with an average ratio of 10:1. Purified esterases from mosquito homogenates were found in a ratio of 3:1, which, combined with the quantitative mRNA data, suggests the operation of both transcriptional and translational control mechanisms to regulate the expression of the amplified genes in C. quinquefasciatus insecticide-resistant mosquitoes.

Animals↗
PubMed2000

Insecticide susceptibility status of Culex tritaeniorhynchus giles, vector of Japanese encephalitis in Delhi.

Laboratory studies were carried out to ascertain the current susceptibility status of adult and larval stages of the Culex tritaeniorhynchus mosquito, vector of Japanese encephalitis, to various insecticides used under public health programs in India. The present study revealed that exposure of adult mosquitoes to diagnostic concentrations of DDT - 4.0%, malathion - 5.0%, fenitrothion - 1.0%, and propoxur - 0.1% could induce only 50.0, 10. 0, 15.0, and 5.0% mortality, respectively, indicating that the species was resistant to all of these insecticides. The LT50 and LT95 values calculated using diagnostic concentrations of DDT, malathion, fenitrothion, and propoxur were found to be 56.4 and 136, 138 and 272, 185 and 258, and 187 and 249 min, respectively. However, when adult mosquitoes were exposed to the diagnostic concentration of synthetic pyrethroids, viz., deltamethrin - 0.025%, permethrin - 0.25%, and lambdacyhalothrin - 0.1%, 100.0% mortality was observed, indicating that the species was highly susceptible to these adulticides. Larval susceptibility tests carried out using diagnostic dosages of DDT- 0.008, temephos- 0.02, fenthion- 0.008, fenitrothion- 0.125, and malathion- 0.005 mg/l failed to induce any mortality, indicating that larvae were resistant to these larvicides. The LC50 and LC90 values calculated for commonly used larvicides, viz., temephos and fenthion, were 0.1511 and 1.9098, and 0.6151 and 2.395 mg/l, respectively. Increase in tolerance level were estimated at 95.5- and 299.4-fold when these LC90 values were compared with diagnostic dosages of temephos and fenthion, respectively.

Animals↗
PubMedDate not supplied

Differential sensitivity of sodium channel isoforms and sequence variants to pyrethroid insecticides.

Pyrethroids are commonly regarded as safe insecticides. However, some widely used pyrethroids, particularly single neurotoxic isomers of potent Type II compounds, have acute oral toxicities comparable to many organophosphorus insecticides. The majority of studies of the action of pyrethroids on voltage-sensitive sodium channels, the principal target sites for these compounds, have not considered differences in sodium channel structure as determinants of sensitivity. In mammals, voltage-sensitive sodium channels are encoded by a multi-gene family and exhibit both anatomical and developmental regulation of expression. Studies in this laboratory using cloned rat sodium channel isoforms expressed in Xenopus oocytes have documented profound differences in pyrethroid sensitivity between isoforms. Although the role of sodium channel gene mutations in altering pyethroid sensitivity has not been addressed in the case of the mammalian sodium channel gene family, the potential significance of allelic variation is illustrated in studies of point mutations in a sodium channel gene of the house fly that confer resistance to the lethal actions of pyrethroids and modify the sensitivity of house fly sodium channels expressed in Xenopus oocytes to these compounds. It is of particular interest that some of these resistance-associated mutations in the fly sodium channel occur at amino acid residues that are also the sites of mutations in human skeletal muscle sodium channels that are associated with inherited paralytic disorders. These findings document the pharmacological significance of structural differences between sodium channel isoforms and between genetic variants of an individual isoform as determinants of pyrethroid sensitivity.

Animals↗
PubMed1975

Testing the susceptibility of Simulium damnosum (Diptera: Simuliidae) to insecticides in the laboratory and in the field.

There are several methods for measuring the susceptibility of blackfly larvae to insecticides. In 1970 the provisional method suggested by the World Health Organization was used with a view to establishing baseline data on the susceptibility of S. damnosum larvae to insecticides; this method was found to be unsuitable. Thereafter, attempts were made to develop a reliable susceptibility testing method for S. damnosum. This report describes the method that yielded the best results in the laboratory; a second method suitable for use in the field is also described. The results from several replicates of such tests gave reasonably straight log-dosage-probit-mortality curves from which values of LC(50) could be calculated. The overall control mortality in the laboratory series of tests was about 9% and that in the field series was about 4%.

Animals↗
PubMed2000

Insecticide resistance in Anopheles sacharovi Favre in southern Turkey.

We report the resistance to 12 insecticides of specimens of Anopheles sacharovi, both in laboratory cultures and those collected in the malarious areas of Adana, Adiyaman, Antalya, Aydin, and Muğla in southern Turkey. Mortality was higher 24 h after exposure than immediately after exposure but was unaffected by temperature (24 degrees C or 29 degrees C) or the position of the test kit (horizontal or vertical). In Adana, Adiyaman and Antalya, A. sacharovi was susceptible only to malathion and pirimiphos-methyl. In Aydin it was susceptible to both these insecticides as well as to dieldrin, lambda-cyhalothrin, and etofenprox; and in Muğla it was susceptible to dieldrin, fenitrothion, lambda-cyhalothrin, cyfluthrin and etofenprox, as well as to malathion and pirimiphos-methyl.

Animals↗
PubMed1999

Susceptibility of Phlebotomus argentipes and P. papatasi (Diptera: Psychodidae) to insecticides.

Field collected fully fed adults of Phlebotomus argentipes and P. papatasi were screened in the laboratory for susceptibility to DDT, BHC, malathion, deltamethrin, permethrin, lambdacyhalothrin and bendiocarb. Pondichery strain of P. papatasi and P. argentipes showed variations in their susceptibility to insecticides. Both the species were resistant to permethrin but tolerant to DDT and malathion with LD99.99 values of 13.88, 1.92, 1.08 and 34.63, 4.69, 16.32 times more than the deterministic doses respectively. However, they were susceptible to bendiocarb with LD99.99 7.6 and 1.6 times lower than the deterministic doses. While P. papatasi was susceptible to BHC, P. argentipes showed tolerance (1.6 times). The former showed tolerance to deltamethrin and the latter exhibited resistance (34 times). It was reverse in case of lamdacyhalothrin. High susceptibility of the vector sandflies to bendiocarb suggests that this insecticide could be used effectively against OP and pyrethroid resistant populations for Kalaazar control.

Animals↗
PubMed1999

Influence of the insecticide dimethoate on arbuscular mycorrhizal colonization and growth in soybean plants.

Application to the soil of the insecticide dimethoate had no effect on the growth of soybean colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae and by the indigenous AM fungus. The application of the recommended concentration of dimethoate decreased the percentage of colonization of soybean by the indigenous AM population, but no significant effect was observed on the colonization of soybean inoculated with G. mosseae. The insecticide did not affect the germination of G. mosseae spores; however, 0.5 mg/l of dimethoate increased the germination of Gigaspora roseae and 5 mg/l of dimethoate decreased the germination of Scutellospora castaneae spores.

Dimethoate↗
PubMed2000

Neurotoxic effects of insecticides--current and future research: a review.

The clinical manifestations and mechanism of acute effects of organophosphate, carbamate and pyrethroid insecticides on the central and peripheral nervous systems are reviewed. The controversies of persistent effects following acute pesticide poisoning and the effects of long-term low level pesticide exposure are discussed. Based on the current issues of insecticide neurotoxicity, future research needs are recommended.

Agricultural Workers' Diseases↗
PubMed2000

[Chlorinated hydrocarbon insecticides(DDT, methoxychlor, HCH etc.)].

Endocrine disrupting properties of organochlorine(chlorinated hydrocarbon) insecticides are reviewed. Physicochemical properties such as water solubility and partition coefficient of the organochlorine insecticides greatly influence their environmental fates. Insolubility in water and high partition coefficient usually enhance the environmental persistence of the compounds. On the endocrine disrupting properties, an important metabolite of p,p'-DDT, p,p'-DDE, is known to exhibit weak anti-androgenic properties. An isomer o,p'-DDT is estrogenic. Metabolites of methoxychlor, mono-demethylated and di-demethylated methoxychlor derivatives, are weakly estrogenic. Their dehydochlorinated product also exhibits estrogenicity. HCH isomers are environmentally persistent compounds, but there is few reports on their endocrine disrupting properties. Some other organochlorine pesticides such as cyclodienes and chlordecone is reported to be estrogenic.

Androgen Antagonists↗
PubMed2000

Evaluation of the in-vitro pediculicidal action of four known insecticides and three medicinal plant extracts.

Human lice is an increasing community health problem worldwide. This is particularly true among school children who spend most of their daytime in crowded areas. Four commercially known insecticides and three medicinal plant extracts were studied to evaluate their pediculicidal activities in-vitro. The best result with insecticides was achieved with malathion (Lt5o 10.396 and slope function 1.183). The best result with medicinal plant extracts was achieved with neem oil (A. indica) (Lt5o 85.27 and slope function 1.480). Although, neem oil extract was less active than malathion, yet it is more safe for human usage.

Adult↗
PubMed1975

Inhibition of hepatic drug-metabolizing enzymes by thiophaophate insecticides and its toxicological evaluation.

Thiophosphate insecticides, fenitrothion, diazinon and methylparathion, inhibit hepatic drug-metabolizing enzyme activity which was assayed using aminopyrine and aniline as substrates. About 50% inhibition was observed 4 hrs after the injection of fenitrothion into mice in a dose of 25 mg/kg. The addition in vitro of thiophosphates into a reaction mixture of drug metabolizing enzyme also produced an effective inhibition and IC50 was around 10(-5)M for fenitrothion. DDVP and oxygenated metabolite of fenitrothion did not show any inhibiting effect either in vitro or in vivo. The inhibition of thiophosphates in vitro was competitive while the kinetics of in vivo inhibition was shown as non-competitive. The drug metabolism in the rat liver preparation was also inhibited by thiophosphate in vitro, but in vivo treatment to male rats resulted in only slight inhibition. Female rats exhibited the similar response as mice. The administration of fenitrothion to mice prolonged the hexobarbital sleeping time and, consequently, suppressed the oxidative metabolism of parathion in liver preparation. These effects reveal that the biological half life of thiophosphate insecticides could be altered by the mode of administration or by co-existing thiophosphates.

Aminopyrine N-Demethylase↗
PubMed2002

Increased toxicity to invertebrates associated with a mixture of atrazine and organophosphate insecticides.

This study examined the joint toxicity of atrazine and three organophosphate (OP) insecticides (chlorpyrifos, methyl parathion, and diazinon) exposed to Hyalella azteca and Musca domestica. A factorial design was used to evaluate the toxicity of binary mixtures in which the lethal concentration/lethal dose (LC1/LD1, LC5/LD5, LC15/LD15, and LC50/LD50) of each OP was combined with atrazine concentrations of 0, 10, 40, 80, and 200 microg/L for H. azteca and 0, 200, and 2,000 ng/mg for M. domestica. Atrazine concentrations (> or = 40 microg/L) in combination with each OP caused a significant increase in toxicity to H. azteca compared with the OPs dosed individually. Acetylcholinesterase (AChE) activity also was examined for the individual OPs with and without atrazine treatment. Atrazine in combination with each of the OPs resulted in a significant decrease in AChE activity compared with the OPs dosed individually. In addition, H. azteca that were pretreated with atrazine (> or = 40 microg/L) were much more sensitive to the OP insecticides compared with H. azteca that were not pretreated with atrazine before being tested. Topical exposure to atrazine concentrations did not significantly increase OP toxicity to M. domestica. The results of this study indicate the potential for increased toxicity in organisms exposed to environmental mixtures.

Acetylcholinesterase↗
PubMed1975

[Pathogenesis of disorders of cardiac rhythm and conductivity in acute organophasphate insecticide poisoning].

A dynamic examination of ECG and K and Na level in plasma and erythrocyte was conducted in 73 patients during the acute period of poisoning with phosphorus-organic insecticides -- thiophos, chlorophos, carbophos. In 18.6% of the cases severe rhythm and conductivity disorders were revealed that caused cardiac arrest and death in 29 patients. Besides, a sharp increase in the electric systole on the ECG was noted in all the patients during the acute period of poisoning. A study of the electrolytes revealed hypokalemia, hypernatremia and an increased content of K and Na in the erythrocytes. The authors believe that the disturbances in the cardiac activity during acute poisonings with phosphorus-organic insecticides are due to the effect of the excessive acetylcholine upon the ion permeability towards increasing intracellular potassium.

Acute Disease↗