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Evaluation of horn flies (Diptera: Muscidae) from a pyrethroid susceptible colony for general and permethrin esterase activities.

Pruett JH, Oehler DD, Kammlah DM, Guerrero FD.

Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, TX 78028, USA.

In this study we describe a nonradioactive single-fly microassay for permethrin hydrolysis. We used this assay with a microplate assay for general esterase activity to evaluate the permethrin hydrolyzing and general esterase activities of aging pyrethroid-susceptible male and female horn flies, Haematobia irritans (L.). We found substantial gender- and age-related differences regarding general esterase activity, permethrin sensitivity, and permethrin hydrolyzing activity within the colony. Extracts of female flies collected 48 h after receiving their first blood meal yielded significantly greater esterase activity than male extracts. Aging female flies were more tolerant of permethrin than were male flies. In addition, a positive correlation was found to exist between the general esterase activity of aging females and their ability to hydrolyze permethrin.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10902350&dopt=Abstract permethrin Elimite



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Resistance of Musca domestica (L.) (Diptera: Muscidae) from Gamasa City to some insecticides.

Mostafa AA, Zayed AB.

Research Institute of Medical Entomology, Dokki, Giza, Egypt.

Susceptibility tests for house fly Musca domestica collected from Gamasa City and laboratory bred one were carried out. The data suggested that the levels of resistance in Gamasa population against malathion, diazinon, diamethoate (organophosphorus compounds) and permethrin (pyrethroid one) were developed while deltamethrin and cypermethrin were still effective. The highest homogenity response was for malathion followed by dimethoate, deltamethrin and cypermethrin. On the other hand, the highest homogenity response in laboratory population was that of cypermethrin and deltamethrin followed by malathion, dimethoate, permethrin and then diazinon. The EST activity was higher in laboratory population (three heavy bands), than Gamasa one (two faint bands), while the activity of LDH and G-6PDH were higher in Gamasa population than in laboratory one. The ADH activity was the same in both populations. This means that EST was not the main detoxifying target in Musca domestica.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12561899&dopt=Abstract permethrin Elimite



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Cis-urocanic acid increases immunotoxicity and lethality of dermally administered permethrin in C57BL/6N mice.

Prater MR, Gogal RM Jr, Blaylock BL, Holladay SD.

Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0442, USA. mrprater vt.edu

Immunomodulatory effects of a single topical permethrin exposure, 5-day exposure to cis-urocanic acid (cUCA), or a combination of the two chemicals were evaluated in 4- to 5-week-old female C57BL/6N mice. Permethrin alone decreased thymic weight and cellularity. Although cUCA alone did not affect thymic end points, coexposure to topical permethrin and cUCA exacerbated the thymolytic effects of permethrin. The single topical dose of permethrin also depressed several immune responses in isolated splenic leukocytes. This included splenic T-cell proliferative response to mitogen, splenic macrophage hydrogen peroxide production, and splenic B lymphocyte-specific antibody production. Unlike the effect of coexposure to these agents on thymic end points, cUCA did not exacerbate permethrin's adverse effect on any of the splenic end points examined. These results appear to suggest divergent mechanisms by which these compounds affect precursor and functionally mature T cells. At the doses used in this study, permethrin caused neurotoxic effects, including lethality, in a portion of the mice. For undetermined reasons, cUCA significantly increased the rate of lethality caused by permethrin. Although the permethrin doses used in this study exceed that typically used in human medicine, these results raise some concerns about the possibility that sunlight, via cUCA, may increase the risk of adverse central nervous system and immune effects caused by permethrin alone.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12573947&dopt=Abstract permethrin Elimite



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The synaptosomal membrane bound ATPase as a target for the neurotoxic effects of pyrethroids, permethrin and cypermethrin.

Kakko I, Toimela T, Tahti H.

Medical School, 33014 University of Tampere, Tampere, Finland. irma.kakko uta.fi

Pyrethroids are used widely as insecticides both in agriculture and in households. A cellular target of pyrethroids is the sodium channel in the membrane. In the present study, the activity of the membrane bound integral protein ATPase was studied as a biomarker for the membrane effect of the pyrethroids permethrin and cypermethrin. Male Sprague-Dawley rats were used for cerebral synaptosome preparation. The isolation of synaptosomes was performed with the Percoll gradient method. Both total ATPase and Mg(2+) activated ATPase were studied by determining inorganic phosphate liberated from the substrate ATP. One hour exposure to permethrin (Biokill) and cypermethrin (Ripcord) insecticide products affected ATPase activities. The activity of Na(+), K(+) ATPase decreased dose-dependently in 10-50 microM concentrations of permethrin, and Mg(2+) activated ATPase increased over twofold in the same concentrations of the active components. The effect of the cypermethrin compound Ripcord was not clearly dose-dependent. The activity of total ATPase was almost entirely lost in the concentrations of 100 microM of permethrin and cypermethrin. The results support the idea that membrane ATPases are one target of the neurotoxic effect of pyrethroid compounds.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12615099&dopt=Abstract permethrin Elimite



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Dissipation and mobility of permethrin in the field with repeated applications under tropical conditions.

Ismail BS, Kalithasan K.

School of Environmental and Natural Resource Sciences, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia. ismail pkrisc.cc.ukm.my

Studies on persistence, mobility and the effect of repeated application of permethrin on its half-life were carried out under field conditions. The half-life of permethrin in the top 20 cm of the soil increased from 11.5 to 23.6 days as the application rates increased from 35 to 140 g ha(-1). Induced by heavier rainfall, more residues moved downward in trial 2 than in trial 1. Repeated applications enhanced degradation rates and mobility of permethrin in the soil. The residue level in the 0-5-cm layer was reduced at day 28 after 17 consecutive applications to a level lower than after 5 applications. The half-life of permethrin was reduced from 15.9 days to 11.2 days after 5 and 17 applications, respectively. The residue reached the 15-20 cm layer much earlier (approximately 3 days after treatment) in soil that received 17 applications as compared to those with two applications.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12617552&dopt=Abstract permethrin Elimite