Malathion specificity

Malathion specific resistance was also fully dominant in Indianmeal moth, while enzyme activity was semidominant, with hybrid offspring having one-half the activity of resistant homozygotes (25). These data in house flies and moths are consistent with a mechanism of catalytic hydrolysis with one resistance allele giving sufficient enzyme activity for survival. 

The reagent sequence is specific for endosulfan and phosphamidon. Other insecticides, e.g. organochlorine insecticides, such as endrin, aldrin, dieldrin, DDT and BHC, organophosphorus insecticides, such as malathion, parathion, dimethoate, quinalphos, phorate and fenitrothion, or carbamate insecticides, such as baygon, car-baryl and carbofuran do not react. Neither is there interference from amino acids, peptides or proteins which might be extracted from the biological material together with the pesticides. 

A nnmber of other examples are known in which genetically based resistance was dne to enhanced detoxication of OPs. These include malathion resistance in some stored product pests owing to high carboxylesterase activity, and resistance of strains of the housefly to diazinon due to detoxication by specific forms of a glutathione-S-transferase and monooxygenase (Brooks 1972). 

In the adsorption with Tenax alone satisfactory results were obtained, while in the presence of mineral oil a considerable proportion of the organophos-phorus pesticides (particularly Malathion and Parathion-methyl) was not adsorbed and was recovered in the filtered water. This drawback can be overcome by adding a layer of Celite 545 which, in order to prevent blocking of the column, is mixed with silanised glass wool plugs. A number of analyses of surface and estuarine sea waters were carried out by this modified Tenax column and simultaneously by the liquid-liquid extraction technique. To some of the samples taken, standard mixtures of pesticides were also added, each at the level of 1 xg/l (i.e., in concentration from 13 to 500 times higher than that usually found in the waters analysed). One recovery trial also specifically concerned polychlorobiphenyls. The results obtained in these tests show that the two extraction methods, when applied to surface waters that were not filtered before extraction, yielded very similar results for many insecticides, with the exception of compounds of the DDT series, for which discordant results were frequently obtained. 

Few epidemiologic studies of pesticide use in general, or specific pesticides, in relation to any autoimmune disease. Mechanistic research primarily for hexachlorobenzene and malathion. Mechanisms other than endocrine-disruption should be considered, even for pesticides with endocrine-disrupting properties. 

Several hundred-pesticide compounds of diverse chemical structures are widely used in the United States and Europe for agricultural and non-agricultural purposes (Fig. 10). Some are substitutes for organochlorines, which were banned due to their toxicity, persistence, and bioaccumulation in environmental matrices. According to a report published by the US-EPA, a total of 500,000 tons of pesticides was used in 1985 [144, 145, 148]. As far as specific pesticides are concerned, worldwide consumption of Malathion and Atrazine in 1980 amounted to 24,000 and 90,000 tons, respectively [149,150]. In the Mediterranean countries, 2100 tons of Malathion (active ingredient) were sprayed during the same period compared to 9700 tons in Asia [150]. 

Amidases can be found in all kinds of organisms, including insects and plants [24], The distinct activities of these enzymes in different organisms can be exploited for the development of selective insecticides and herbicides that exhibit minimal toxicity for mammals. Thus, the low toxicity in mammals of the malathion derivative dimethoate (4.44) can be attributed to a specific metabolic route that transforms this compound into the nontoxic acid (4.45) [25-27]. However, there are cases in which toxicity is not species-selective. Indeed, in the preparation of these organophosphates, some contaminants that are inhibitors of mammalian carboxylesterase/am-idase may be present [28]. Sometimes the compound itself, and not simply one of its impurities, is toxic. For example, an insecticide such as phos-phamidon (4.46) cannot be detoxified by deamination since it is an amidase inhibitor [24],... 

Methyl parathion is used primarily on cotton. It was one of the first insecticides restricted under the 1996 Food Quality Protection Act (FQPA), which developed new safety standards for human health, especially that of children. It can no longer be used on many fruits and vegetables. Malathion and parathion are the broadest spectrum organophosphate insecticides. There are many other organophosphate insecticides in use in the U.S. today. Many are produced at the 1-5 million Ib/yr level for specific applications. Three other leading organophosphates besides those mentioned already are chlorpyrifos, terbufos, and phorate. 

It Is well known that phosphorothlonate insecticides such as parathlon (, 0-diethyl p-nitrophenyl phosphorothloate) and malathion [0, -dimethyl -(l,2 -dlcarbethoxy)ethyl phosphoro-dithioate] are Intrinsically poor inhibitors of acetylcholinesterase and in vivo activation to the respective anticholinesterases paraoxon and malaoxon is required before animals exposed to the phosphorothionates are intoxicated. Since metabolic activation is essential to the biological activity of these thiono sulfur-containing organophosphorus insecticides, compounds of this type may be considered as propesticides or, more specifically, prolnsectlcldes. 

Inhibition of the cholinesterase enzymes depends on blockade of the active site of the enzyme, specifically the site that binds the ester portion of acetylcholine (Fig. 7.48). The organophosphorus compound is thus a pseudosubstrate. However, in the case of some compounds such as the phosphorothionates (parathion and malathion, for example), metabolism is necessary to produce the inhibitor. 

Nishi, K., Y. Imajuku, M. Nakata, et al. 2003. Preparation and characterization of monoclonal and recombinant antibodies specific to the insecticide malathion. J. Pestic. Sci. 28 301-309. 

Gas chromatography has been used [183] to determine the following at organophosphorus insecticides at the microgram per litre level in water and waste water samples Azinphos-methyl, Demeton-O, Demeton-S, Diazinon, Disulfoton, Malathion, Parathion-methyl and Parathion-ethyl. This method is claimed to offer several analytical alternatives, dependent on the analyst s assessment of the nature and extent of interferences and the complexity of the pesticide mixtures found. Specifically, the procedure uses a mixture of 15% v/v methylene chloride in hexane to extract... 

Pioneering work on immunochemical assays for pesticides involved the synthesis of haptens for DDT and malathion. Haas and Guardia (24) used the acid chlorides of malathion half ester and DDA (2,2-bis-[j)-chlorophenyl]acetic acid) for conjugation while Centeno et al. (25) used the anhydrides of DDA and malathion diacid (0,0-dimethyl S-[l,2-bis-carboxyethyl]phosphorodi-thioate). In retrospect, more specific antibodies of a higher titer may have been obtained had a spacer arm been used. 

WHO should review the specifications to consider clauses for iso-malathion for the TC, EC and DP. 

They experimented with four other proteins as carriers rabbit serum albumin, bovine serum albumin, bovine fibrinogen fraction I, and bovine )8-globulin fraction III. The structurally related derivatives of DDT and malathion, DDA, and 0,0-dimethyl S-carboxy-carboxyethyl phosphoro-dithioate (malathion half ester), respectively, were used as the specific haptens attached to these carrier proteins. These compounds contain free carboxyl groups, which when they reacted with thionylchloride, provide a means of coupling of the hapten to the amino groups of the protein carrier. 

Table 5 lists the half-lives of recovery for some OP-inhibited AChEs. In general OP-AChE complexes from dimethoxy-substituted OPs (e.g., malathion) spontaneously dephosphorylate faster than diethoxy (e.g., parathion) or diisopropoxy (e.g., DPP) complexes. Eto pointed out in 1974 that the stability of a phosphorylated AChE may be predicted from the stability of the specific OP inhibitor itself. One possibility is that methyl groups have less steric hindrance and greater electronegativity than ethyl or isopropyl groups. 

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