Elimite
Neurotoxic action of six pyrethroid insecticides on the isolated sciatic nerve of a frog (Rana ridibunda).

Theophilidis G, Benaki M, Papadopoulou-Mourkidou E.

Department of Zoology, School of Biology, Aristotle University, Thessaloniki, Macedonia, Greece. theophil bio.auth.gr

The neurotoxic action of six pyrethroid insecticides, four type II, (flucythrinate, deltamethrin, fenvalerate, fluvalinate) and two type I (cis- and trans-permethrin) was compared on the isolated sciatic nerve of frog. The nerve was exposed to pyrethroids for 30 min and action potentials were recorded for more than 45 hr after exposure. From the plots of the amplitude of the compound action potential vs time, it was possible to estimate, for each compound, the minimum effective concentration, the concentration which is required to reduce the amplitude of the compound action potential to 50% of its control value (mEC50). Flucythrinate was the most toxic compound, while toxicity decreased in the value: deltamethrin > fenvalerate > fluvalinate >> cis-permethrin > trans-permethrin. Low neurotoxicity of cis-permethrin and trans-permethrin (type I pyrethroids) was expected. The neurotoxicity of type I pyrethroids is mainly due to an action at the synapse, which are not present in the frog sciatic nerve preparation. The relative potencies of the four type II compounds agree with their acute toxicity estimated using the LD50.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9366040&dopt=Abstract permethrin Elimite



Elimite
Development of Wuchereria bancrofti in Culex pipiens L. (Diptera: Culicidae) exposed in the larval instar to sublethal dosages of insecticides and one insect growth regulator and their influence on reproduction of filaria-infected mosquitoes.

Seif AI, Husseiny IM, Soliman BA, Soliman MA, el-Kady MA.

Department of Zoology, Faculty of Science, Tanta University, Egypt.

The effects of exposure of Culex pipiens larvae to sublethel concentrations of larvicides on uptake, development of Wuchereria bancrofti, survival rate and reproduction of filaria-infected mosquitoes were investigated. Fourth instar larvae of Cx. pipiens were exposed to LC40 of the surfactant Triton X-100, the insect growth regulator DPX alone or combined with LC10 of the surfactant and permethrin alone or combined with LC10 of the surfactant. Adults that survived insecticide treatments and controls were infected by allowing them to feed on microfilaremic volunteers. Significant reduction in the uptake of microfilaria was observed in groups treated with Triton X-100 alone or combined either with permethrin or DPX when compared to control. The overall infection and infective rates were significantly reduced in mosquitoes treated with Triton X-100 either alone or combined with permethrin. Treatment with Triton X-100 and DPX prolonged the extrinsic incubation period (EIP) and retarded the development of filarial larvae, while permethrin either alone or combined with Triton X-100 and DPX combined with Triton X-100 shortened the EIP. All larvicides reduced the number of infective larvae (L3)/mosquito and induced deformities among he different parasite stages, especially in mosquitoes treated with combination of permethrin and Triton X-100 or mixture of DPX and Triton X-100 where 36% and 54.9% respectively of L3S were deformed. In treated mosquitoes, a low percentage of L3S was detected in the head and proboscis region while the majority was trapped in the thoracic region. The survival rates of mosquitoes were reduced in cases treated with permethrin, DPX and Triton X-100 while treatment with mixture of DPX and Triton X-100 induced higher rate of mortalities when compared to control. Egg production of filaria- infected Cx. pipiens was significantly reduced in mosquitoes treated with DPX and Triton X-100. It was observed that the addition of Triton X-100 to DPX or to permethrin significantly reduced egg production. The results suggest that sublethal concentrations of larvicides especially Triton X-100 applied to 4th instar larvae of Cx. pipiens could effectively interfere with the development of W. bancrofti in Cx. pipiens and reduced the survival rate and fecundity of the vector.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9425827&dopt=Abstract permethrin Elimite



Elimite
[The effect of permethrin and DDT on the activity of cytochrome P-450 1A and 2B molecular forms in rat liver]

[Article in Polish]

Kostka G, Palut D, Wiadrowska B.

Zaklad Toksykologii Srodowiskowej, Panstwowy Zaklad Higieny.

The effect of permethrin on relative liver weight (RLW) and the activity of hepatic monooxygenase system related to cytochrome P-4502B and 2A was studies. The effect of permethrin was compared with DDT used as phenobarbital-type of monooxygenase inducer (induces cyt. P-4502B). Male Wistar rats received permethrin and DDT for 4 days at 24 h intervals in daily oral doses of 1/10, 1/50 and 1/100 LD50. 3-methylocholantrene and phenobarbital which served as inducers of cytochrome P-4501A and 2B, respectively and were used as positive controls. The activities of cytochrome(s) P-450 were measured by 7-pentoxy- and 7-etoxyresofurin O-dealkylation by S-9 fraction of rat liver; these two compounds have been shown to be the substrates for reactions mediated by cytochrome P-4502B and 2A. Thus this biochemical procedure permits to determine whether tested compound belongs to one of two main types of inducers of the cytochrome P-450 monoxygenase system. Treatment of rats with both pesticides resulted in significant increase in RLW, to 30 and 15% of control, respectively. In animals treated with permethrin the metabolism of 7-pentoxyresofurin increased in a dose dependent manner. Phenobarbital and the highest dose of permethrin (620 mg/kg b.w. x day-1) induced similar (about 30-fold) increase in O-dealkylation of 7-pentoxyresofurin. DDT stimulated metabolism of 7-pentoxyresofurin to much higher degree as compared with phenobarbital. It should be noted that both pesticides induced only slight increase in O-dealkylation of 7-etoxyresofurin (cyt. P-4501A-mediated reaction). The present results indicate that permethrin as well as DDT shows the ability to induce the phenobarbital-type of cytochrome P-4502B.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9432699&dopt=Abstract permethrin Elimite



Elimite
Comparison of bednets treated with alphacypermethrin, permethrin or lambdacyhalothrin against Anopheles gambiae in the Gambia.

Jawara M, McBeath J, Lines JD, Pinder M, Sanyang F, Greenwood BM.

Medical Research Council Laboratories, Fajara, The Gambia.

In the Gambian village of Saruja, where malaria is transmitted mainly by mosquitoes of the Anopheles gambiae complex, a trial was undertaken of the acceptability and efficacy of bednets treated with one of three pyrethroid insecticides--alphacypermethrin 40 mg/m2, permethrin 500 mg/m2 and lambdacyhalothrin 10 mg/ m2. Fewer mosquitoes were found alive under nets treated with insecticide than under control nets. Significantly more dead mosquitoes were found under nets treated with alphacypermethrin than under nets treated with permethrin or lambdacyhalothrin. Side-effects were reported by a proportion of the users of nets treated with each of the insecticides, but none were severe and their prevalence was similar between treatment groups. Unwashed nets treated with alphacypermethrin were more effective at killing anopheline mosquitoes in bioassays than nets treated with permethrin or lambdacyhalothrin. Killing activity was reduced when nets were washed, irrespective of which insecticide was used. Bednets treated with alphacypermethrin are well accepted, effectively killed anopheline mosquitoes and should therefore be evaluated for personal protection against malaria transmission.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9513940&dopt=Abstract permethrin Elimite



Elimite
[Pyrethroids in house dust of the German housing population--results of 2 nationwide cross-sectional studies]

[Article in German]

Friedrich C, Becker K, Hoffmann G, Hoffmann K, Krause C, Nollke P, Schulz C, Schwabe R, Seiwert M.

Institut fur Wasser-, Boden- und Lufthygiene des Umweltbundesamtes, Berlin.

As a part of the German Environmental Surveys performed in 1985/86 (West Germany), 1990/91 (West Germany) and 1991/92 (East Germany), dust samples were collected in the households of about 1600 randomly selected adults (25 to 69 years) and an analysis of these samples was performed in respect of their content of 8 different pyrethroids and of the synergist piperonyl butoxide (PBO). In the 1990-92 survey about 90% of the samples contained permethrin in concentrations above the limit of quantification. This showed permethrin to be the most widespread of the 8 compounds investigated. The geometric mean of the permethrin content in domestic dust was 0.22 mg/kg. Only about 8% of the samples contained one or more of the other investigated substances (cyfluthrin, lambda-cyhalothrin, cypermethrin, alpha-cypermethrin, deltamethrin, empenthrin, d-phenothrin) in quantifiable amounts. About 76% of the samples contained quantifiable amounts of PBO. In East Germany the geometric mean of the PBO content (0.21 mg/kg) was significantly higher than in West Germany (0.07 mg/kg), but no difference for permethrin was found. Significant associations could be shown for the permethrin content and the application of biocides as well as for the PBO content and regional factors (size of community, type of dwelling area). Samples collected in 1985/86 (West Germany) showed a geometric mean for permethrin of 0.06 mg/kg and for PBO of 0.07 mg/kg. Comparing the values of 1985/86 and 1990/91, a significant increase can be observed for permethrin, whereas the PBO concentration remained constant.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9553309&dopt=Abstract permethrin Elimite