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Results for “Organothiophosphorus Compounds”

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At least 19 recordsLinked to original sources
PubMed2001

The status and development of insecticide resistance in Danish populations of the housefly Musca domestica L.

Samples of housefly (Musca domestica) field populations were collected from Danish livestock farms in 1997. The tolerance of the first-generation offspring was determined for a number of insecticides. Dose-response values were obtained by topical application for the pyrethroids bioresmethrin and pyrethrum, both synergised with piperonyl butoxide, and the organophosphate dimethoate. The organophosphates azamethiphos and propetamphos and the carbamate methomyl were tested in discriminating dose feeding bioassays. Resistance was low to moderate in most of the populations for most of the compounds tested, but this study also revealed the existence of high resistance to pyrethroid, organophosphate and carbamate insecticides in some populations. The resistance factors at LD50 for bioresmethrin/piperonyl butoxide ranged between 2 and 98, and for pyrethrum/piperonyl butoxide between 2 and 29. Our results indicate that pyrethroid resistance in Denmark is increasing, since four of the 21 farms showed more than 100-fold resistance at LD95, a level of resistance only observed once before. Resistance factors at LD50 for dimethoate ranged from 9 to 100, and showed two distinct trends: populations with either decreasing or increasing resistance. Resistance to azamethiphos was found to be widespread and high. Although two strains with high methomyl and propetamphos resistance were observed, methomyl and propetamphos resistance is moderate and appears not to be increasing.

Animals↗
PubMedDate not supplied

The biological importance of organophosphorus compounds containing a carbon-phosphorus bond.

Organophosphorus anticholinesterase compounds may be derivatives of phosphoric acid or of a phosphonic acid. The phosphonic acid derivatives are usually more reactive and more toxic than the phosphoric acid derivatives. Examples are given to show that differences in the chemical and biological reactivity of phosphates and phosphonates reflect many different aspects of their chemical structure. Some recently discovered naturally-occurring phosphonates are described, together with some synthetic phosphonate analogues of naturally-occurring phosphates. The utility of these synthetic phosphonates as tools for probing enzymic reaction sequences is discussed.

Animals↗
PubMed1986

Neurotoxicity assessment of O-ethyl-O'-(2-diisopropylaminoethyl) methylphosphonite (QL) in hens.

O-ethyl-O'-(2-diisopropylaminoethyl) methylphosphonite (QL), an intermediate in the formation of ethyl S-2-diisopropylaminoethyl methylphosphonothiolate, was evaluated for neurotoxicity in the adult hen. Birds were given a single oral dose of QL ranging from 635 to 6080 mg kg-1. The QL-treated hens were observed for up to 24 h after dosing for acute toxicologic effects and over a 24 d post-dose period for evaluation of delayed neurotoxicity. The oral LD50 in hens is 1186 mg kg-1. Neurologic dysfunction, as evidenced by motor incapacitation, was observed at 6 days and thereafter after treatment with QL. Neurotoxic esterase (NTE) activity was not inhibited at 24 h after exposure to compound. Neural damage, multifocal in nature, was noted in the peripheral nervous system of QL-treated hens at dose levels greater than or equal to 635 mg kg-1, oral dose. These findings indicate neural damage tendencies following QL exposure.

Animals↗
PubMed2001

Sex-related differences in the tolerance of Oriental fruit moth (Grapholita molesta) to organophosphate insecticides.

In vivo toxicity assays have shown that organophosphate insecticides are less toxic to male than to female Oriental fruit moths Grapholita molesta. While male moths have higher levels of acetylcholinesterase and general esterase activities, female moth acetylcholinesterase enzymes are less sensitive to aromatic and aliphatic organophosphates than male enzymes. Elevated esterase and acetylcholinesterase activities in male moths explain their greater tolerance to aromatic and aliphatic organophosphates. Male and female acetylcholinesterase enzymes are equally tolerant to heteroaromatic organophosphates, the most widely used of this class of insecticides in G molesta control. This observation, in contrast to the greater sensitivity of male acetylcholinesterases to aromatic and aliphatic organophosphates, shows the potential for the evolution of insensitive target sites in male moths, which would increase male G molesta tolerance to these insecticides. Significant sex-linked differences in insecticide tolerance have not been reported previously in lepidopterans. The practical implications of the observed differences in tolerance in male and female G molesta question the practice of using pheromone traps to monitor populations of these moths in orchards.

Acetylcholinesterase↗
PubMed1999

Low concentrations of the organophosphate VX affect spontaneous and evoked transmitter release from hippocampal neurons: toxicological relevance of cholinesterase-independent actions.

In the present study, the patch-clamp technique was applied to cultured hippocampal neurons to evaluate the effects of the nerve agent VX on evoked and spontaneous postsynaptic currents mediated by gamma-aminobutyric acid (GABA) and glutamate. At 0.01 nM, VX reduced the amplitude of evoked GABAergic currents, and only at concentrations >1 nM did it decrease the amplitude of evoked glutamatergic currents. The effect of VX on GABAergic currents, which was partially reversible upon washing of the neurons with VX-free external solution, could be prevented by the muscarinic antagonist atropine. In contrast, the effect of VX on glutamatergic currents, which was not reversible upon washing, appears to be related to the VX-induced reduction of the amplitude and frequency of repetitively firing by action potentials. In the presence of the Na(+)-channel blocker tetrodotoxin (TTX), VX (>/=10 nM) increased the frequency of GABA- and glutamate-mediated miniature postsynaptic currents (MPSCs). This effect of VX was unrelated to cholinesterase inhibition and was Ca(2+) dependent. The lack of effect of VX on MPSC kinetics indicates that VX-induced alterations of evoked and spontaneous currents are exclusively due to alterations of the transmitter release processes. The ability of VX to affect transmitter release in the brain may underlie some of its neurotoxic effects and may provide the basis for the development of therapeutic countermeasures to treat and/or prevent VX-induced neurotoxicity.

Animals↗
PubMed1984

Cytogenetic and genetic effects of subchronic treatments with organophosphorus insecticides.

Male mice (Q strain) received 5 days a week for 7 weeks drinking water containing dichlorvos (2 ppm), dimethoate (0.6 ppm), malathion (8 ppm), methylparathion (0.15 ppm), or trichlorfon (0.5 ppm). At the end of the treatment, no chromosome damage was observed in bone marrow cells, spermatogonia, and primary spermatocytes. Dominant lethal mutation assays were performed to investigate the pre- and postimplantation foetal lethality. Only negative results were obtained.

Animals↗
PubMed1975

Organophosphorus esters causing delayed neurotoxic effects: mechanism of action and structure activity studies.

Evidence is reviewed that the initial biochemical event leading to delayed neurotoxicity is phosphorylation of the active site of a specific enzyme called Neurotoxic Esterase. This is followed by a bondcleavage (? hydrolytic) leading to formation of a mono-substituted phosphoric acid residue on the protein. The mechanism by which some phosphinates protect hens against neurotoxic compounds is explained. Screening Assay. Assay of effects of compounds on Neurotoxic Esterase activity of hen brain in vitro and in vivo provides a quick biochemical screen to supplement the 3-week clinical test. This test provides an estimate of safety margin for compounds which give negative results in the clinical test and are currently used as pesticides, plasticisers, etc. Simplified assay procedures are being developed. Structure/Activity Studies. Data is now available for the biochemical and neurotoxic activity of many compounds. This provides a basis for structure/activity predictions; neurotoxicity data published since 1930 has been assessed in this light.

Animals↗