Elimite
Observations on the susceptibility of Ctenocephalides felis (Siphonaptera: Pulicidae) to malathion and permethrin in Tanzania.

Kilonzo BS, Gisakanyi ND.

Department of Veterinary Microbiology and Parasitology, Sokoine University of Agriculture Chuo Kikuu, Morogoro, Tanzania.

Laboratory-reared Ctenocephalides felis (Bouche) adults were tested with 0.5% malathion and 0.5% permethrin, using the standard WHO methods. After 24 h exposure to malathion (3.6 mg/cm2), 92% of the fleas died. The LT50 for malathion was approximately 8 h. Permethrin (0.45 mg/cm2) produced 100% mortality of exposed insects after 24 h while with a higher dose (0.9 mg/cm2) all fleas died after 8 h exposure. LT50 for the two doses of permethrin were 7.7 and 1.05 h, respectively. The failure of the diagnostic dose of malathion to kill 100% of the population was attributed to resistance. Permethrin is a suitable pesticide for controlling fleas of domestic animals in Tanzania.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2980190&dopt=Abstract permethrin Elimite



Elimite
Comparative effects of synthetic insecticides--endosulfan, phosalone and permethrin--on Chlamydomonas reinhardtii algal cells.

Gandhi SR, Kulkarni SB, Netrawali MS.

Food Technology and Enzyme Engineering Division, Bhabha Atomic Research Centre, Bombay, India.

Presence of insecticide-endosulfan, phosalone or permethrin in the growth medium caused concentration dependent inhibition in the vegetative growth of Chlamydomonas reinhardtii algal cells. The rate of inhibition produced by endosulfan was two-fold higher than that of phosalone or permethrin. Endosulfan affected the cell growth completely at 100 times less concentration as compared to that of phosalone or permethrin. Non-dividing cell populations encountered significant losses in cells during their exposure (2 h) to endosulfan and did not show further loss in the 72 h post-treatment period. The populations treated with phosalone exhibited losses of considerable magnitude in the post-treatment period. Permethrin treated non-diving cell populations did not lower the cell number, either after the treatment period (2 h) or the post-treatment period (72 h). However, these populations showed reduced levels of chlorophyll following the exposure of the insecticide and did not display recovery or further reduction in the levels in the post-treatment period. The chlorophyll levels of endosulfan or phosalone treated cell populations remained unaffected. The cells remaining intact after the treatment (2 h) of endosulfan or phosalone exhibited significant decreases in their post treatment vegetative growth abilities. The growth ability of such permethrin exposed cells was similar to that of untreated cells.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3188835&dopt=Abstract permethrin Elimite



Elimite
Chronic toxicity and carcinogenic evaluation of permethrin in rats and mice.

Ishmael J, Lithfield MH.

Imperial Chemical Industries PLC, Central Toxicology Laboratory, Macclesfield, Cheshire, England.

Groups of Alpk:AP (Wistar-derived) rats were fed diets containing 0, 500, 1000 or 2500 ppm permethrin for 2 years and Swiss-derived mice were maintained for their lifetime (80% mortality) on diets containing 0, 250, 1000, or 2500 ppm permethrin. Changes of toxicological significance were confined to the top dose level of 2500 ppm permethrin in both species. Tremors and hypersensitivity to noise were noted in rats at this dose during the first 2 weeks of study but such signs were not seen in mice. Pathological examination of the central and peripheral nervous systems did not reveal abnormalities attributable to permethrin administration. The effect on mice at 2500 ppm permethrin was shown by decreased body weight gain. Liver hypertrophy, associated with increase in liver weight, microsomal enzyme activity, and proliferation of smooth endoplasmic reticulum occurred in the rat with similar but less marked changes in the mouse. This was considered to be an adaptive response of no toxicological significance. No evidence of a carcinogenic effect was seen in the rat study. In the mouse study a slight elevation in benign lung tumor incidence in males only at 2500 ppm permethrin was observed but was not considered to represent a carcinogenic effect.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3220209&dopt=Abstract permethrin Elimite



Elimite
Pyrethroid effects on schedule-controlled behavior: time and dosage relationships.

Peele DB, Crofton KM.

Northrop Services, Inc., Environmental Sciences, Research Triangle Park, NC 27709.

Pyrethroid insecticides have been divided into Types I and II based on behavioral profiles of toxicity produced by life-threatening dosages. In order to assess potential alterations in acquired (operant) behavior, acute dosage-effect and time-course determinations for permethrin (Type I) and cypermethrin (Type II) were made. Long-Evans rats responded for food according to a multiple schedule consisting of four different variable-interval schedules. Permethrin (100-400 mg/kg) and cypermethrin (7.5-60 mg/kg) were administered PO 1.5 hr pre-session and their effects on response rates and between-component response patterning determined. Permethrin reduced responding in a manner which was independent of the baseline response rate, while the rate reductions following cypermethrin administration showed a dependence on the baseline levels of responding, with low response rates showing differential sensitivity to disruption. When select dosages of each compound were delivered at various pre-session times, onset of and recovery from the rate-decreasing effects were more rapid with cypermethrin, with rates returning to baseline levels by 12 hr post-dosing. Responding was maximally suppressed 24 hr after administration of permethrin and returned to baseline levels 48 hr after administration. The disruption of response patterning following cypermethrin was maximal at 1.5 hr after administration, with complete recovery 12 hr post-dosing. Differential effects on response patterning, in potency, and in the time-course of effects of permethrin and cypermethrin suggest a type-specificity for pyrethroid effects on schedule-controlled behavior at dosages far below those producing lethality in rats.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3696110&dopt=Abstract permethrin Elimite



Elimite
PK 11195 antagonism of pyrethroid-induced proconvulsant activity.

Devaud LL, Szot P, Murray TF.

The acute administration of 1R,cis, alpha S-cypermethrin, deltamethrin fenvalerate and permethrin produced a dose-dependent lowering of the dose of pentylenetetrazol required to elicit a seizure in rats. The proconvulsant action of cypermethrin displayed stereospecificity in that the 1R, cis, alpha S isomer of cypermethrin was the most potent compound tested, while the non-insecticidal isomer, 1S,cis, alpha R-cypermethrin, was devoid of proconvulsant activity. Pretreatment of rats with PK 11195, an antagonist of the peripheral-type benzodiazepine binding site, elicited a complete reversal of the proconvulsant actions of both deltamethrin and permethrin. In contrast, pretreatment with phenytoin did not alter the pyrethroid-induced proconvulsant activity. These results suggest that the effects of pyrethroids on pentylenetetrazol seizure threshold are mediated via an interaction with peripheral-type benzodiazepine binding sites.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3699096&dopt=Abstract permethrin Elimite