Effect of pyrethroid insecticides

Riviere, J.L., J. Bach, and G. Grolleau. 1983. Effect of pyrethroid insecticides and N-(3,5-dichlorophenyl) dicarboximide fungicides on microsomal drug-metabolizing enzymes in the Japanese quail (Cotumix cotumix). Bull. Environ. Contam. Toxicol. 31 479-485. 

Vijverberg, H.P.M., G.S.F. Ruigt, and J.V.D. Bercken. 1982. Structure-related effects of pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis. Pestic. Biochem. Physiol. 18 315-324. 

Hossain MM, Suzuki T, Sato N, Sato I, Takewaki T, Suzuki K, Tachikawa E, Kobayashi H (2006) Differential effects of pyrethroid insecticides on extracellular dopamine in the striatum of freely moving rats. Toxicol Appl Pharmacol 217 25-34... 

Stein EA, Washburn M, Walczak C et al (1987) Effects of pyrethroid insecticides on operant responding maintained by food. Neurotoxicol Teratol 9 27-31... 

Direct effects of pyrethroid insecticides on giant axons in the abdominal nerve cord (microelectrode recordings). 

Tateno C, Ito S, Tanaka M, Yoshitake A (1993) Effects of pyrethroid insecticides on gap junctional intercellular communications in Balb/c3T3 cells by dye-transfer assay. Cell Biol Toxicol 9 215-221... 

Muir, D.C.G., B.R. Hobden, and M.R. Servos. 1994. Bioconcentration of pyrethroid insecticides and DDT by rainbow trout uptake, depuration, and effect of dissolved organic carbon. Aquat. Toxicol. 29 223-240. 

In a study of men living in an agricultural setting, it was shown that higher exposures to mixtures of organophosphorus and pyrethroid insecticides resulted in lower sperm concentrations. F61 Pyrethroid insecticides are known to enhance the toxic effects of organophosphorus insecticides and apparently also enhance male infertility. 

Enantioselection can be controlled much more effectively with the appropriate chiral copper, rhodium, and cobalt catalyst.The first major breakthrough in this area was achieved by copper complexes with chiral salicylaldimine ligands that were obtained from salicylaldehyde and amino alcohols derived from a-amino acids (Aratani catalysts ). With bulky diazo esters, both the diastereoselectivity (transicis ratio) and the enantioselectivity can be increased. These facts have been used, inter alia, for the diastereo- and enantioselective synthesis of chrysan-themic and permethrinic acids which are components of pyrethroid insecticides (Table 10). 0-Trimethylsilyl enols can also be cyclopropanated enantioselectively with alkyl diazoacetates in the presence of Aratani catalysts. In detailed studies,the influence of various parameters, such as metal ligands in the catalyst, catalyst concentration, solvent, and alkene structure, on the enantioselectivity has been recorded. Enantiomeric excesses of up to 88% were obtained with catalyst 7 (R = Bz = 2-MeOCgH4). 

In view of the very critical role calcium channels play in a variety of nerve and muscle function, possible effects of various insecticides on calcium channels are too important to be overlooked. It was indeed shown that neurosecretory cells of the stick insect generate action potentials by inward calcium currents (48), and that permethrin increases the electrical activity of these cells at a concentration as low as 5 x 10 " M (49). Although direct demonstration still remains to be seen, it is possible that pyrethroids act on calcium channels to exert their toxic effects (48.50). 

It is noteworthy that the insecticidal effect of pyrethroids depends strongly on their absolute configuration (cf. Section 8.3). Thus, for this class of compounds one had to attempt, for the first time in the history of plant protection, to prepare enantiomerically pure agrochemicals. 

A number of studies have examined the role of various factors such as volatility and solubility on the efficacy of soil insecticides.(14) While the soil itself affects the efficacy of soil insecticides, the major determinate of biological activity is the amount of organic material in the soil.(15) Simmons, Lew, Silverman and Ali studied the effect of pyrethroids and some commercial insecticides on 3 instar southern com rootworm larva (Diabrotica undecimpunctata howardii).(16) They found that a combination of calculated lipophilicity and calculated volatility could predict soil pLCso based on the topical pLDso. The volatility was expressed as the log of the vapor pressure in nun Hg. We re-plotted the difference of the topical pLDso - soil pLCso with the calculated logP and calculated log volatility in a 3D graph shown in Figure 9. It can be seen as the compounds become more volatile (logVp < 5) that is a marked increase in soil toxicity. As the compounds become less lipophilic (more hydrophilic), they also become more toxic in the soil. 

Vijverberg HPM, Van den Bercken J (1990) Neurotoxicological effects and the mode of action of pyrethroid insecticides. Grit Rev Toxicol 21 105... 

Synthetic Pyrethroid Insecticides. Elucidation of the chemical stmctures of the naturally occurring pyrethmm esters, their rapid and selective insecticidal action, and their high cost stimulated the search for effective synthetic derivatives (13,17,21). Since the 1940s, stmctural optimisation has produced an array of broad-spectmm insecticides with activity 10- to 20-fold greater than other types of insecticides, and with extended residual action. These synthetic pyrethroids have become one of the most important classes of insecticides with world aimual production estimated at 6000 t (21). 

Godin et al. (10), working on the effect of insecticidal activity of pyrethrum flowers from fresh and dried flowers, showed that extracts from fresh flowers had little or no greater effect on pyrethroid content and insecticidal activity than extracts from dried flowers with drying temperatures up to 80 °C. However, some of all the pyrethrin was lost at 120°C. The principal loss was in pyrethin I and not pyrethin II. 

Since 1945 the use of synthetic pesticides in the United States has grown 33-fold. The amounts of herbicides, insecticides, and fungicides used have changed with time due, in large part, to changes in agricultural practices and cosmetic standards (14, 15). At the same time, the toxicity and biological effectiveness of these pesticides have increased at least 10-fold (15). For example, in 1945 DDT was applied at a rate of about 2 kg/ha. With the more potent insecticides available now, similar effective insect control is achieved with pyrethroids and aldicarb applied at 0.1 kg/ha and 0.05 kg/ha, respectively. 

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