Organophosphate compounds pesticides

In addition to being found in the nervous system, acetylcholinesterase also occurs in the blood where it is bound to the surface of red blood cells (termed RBC-ChE or RBC-AChE). RBC-AChE activity, as well as the activity of a second type of cholinesterase found in blood plasma (butyrylchoUnesterase, or plasma cholinesterase) have been used to monitor exposure to organophosphate compounds (pesticides and nerve agents). Both RBC-AChE and plasma-ChE activity have been used as bioindicators of potential toxic effects. There is some evidence that RBC-AChE is as sensitive as brain ChE to the effects of nerve agents. Grob and Harvey (1958) reported that the in vitro concentrations producing 50% depression of brain-ChE and RBC-AChE activity were the same in the case of GA (1.5 x 10 mol/L),... 

Poisoning by pesticides that contain organophosphate compounds produces a variety of symptoms, including nausea, blurred vision, fatigue, muscle weakness and, potentially, death caused by paralysis of respiratory muscles. 

Pesticides used around the house and garden include insecticides, herbicides, rodenticides, fungicides, and fumigants. Toxic chemicals contained in pesticides include organochlorine and organophosphate compounds, carbamates, and arsenicals. The solvents used as carriers for these include aliphatic and aromatic hydrocarbons, alcohols, and glycol ethers. I34l... 

Delayed neurotoxicity results from degeneration of the axons followed by demyelination (14,15,23). Clinical manifestation includes sensory disturbances, ataxia, weakness, muscle twitching and, in severe cases, complete flaccid paralysis ( 15). A fair number of organophosphate compounds are capable of inducing delayed neurotoxicity. Of the 250 organophosphates (not all pesticides) tested for delayed neurotoxicity in chickens, 47% (117 chemicals) showed positive responses (23). Notable examples of pesticides which possess this neurotoxicity are leptophos, EPN, merphos, dichlorvos, and... 

EPA has a good website for information on organophosphate compounds at www.epa.gov/pesticides. 

In summary, studies intended to examine the neuropsychiatric effects of organophosphate compounds vary in their adequacy, and in some instances the results are contradictory. Most studies agree, however, that acute neuropsychiatric effects result from exposure to both insecticides and nerve agents. These effects include inability to concentrate, memory problems, sleep disturbances, anxiety, irritability, depression, and problems with information processing and psychomotor tasks. With pesticides, these effects do not occur in the absence of the conventional signs of poisoning. 

Organophosphate (OP) pesticides have been extensively nsed as insecticides in modem agriculture, but their potential to prodnce nenrotoxicity in animals and humans have raised concerns about their potential adverse impact on both the environment and human health (1,2). Some OP compounds have... 

Their toxicity justifies the crucial need of accurate and reliable methods to monitor the level of pesticides for safety considerations. Moreover, the area of biodefense is also interesting in this field of research, since several organophosphate compounds can be used as nerve agents (i.e., sarin and soman). The development and continual improvement of analytical methods for the determination of this large group of compounds, mostly at trace level, is a great challenge for analysts, and constimtes the subject of research and development for contemporary analytical chemistry. ... 

Pesticides are further subdivided into classes of compounds. Historically, insecticides included the organochlorine, methyl carbamate, and organophosphate classes of pesticides. Herbicides comprise about 10—12 principal classes of compounds. Within each class of pesticide there may be several hundred active ingredients. 

Organophosphate flame retardants and plasticisers Perfluorinated compounds Pharmaceuticals and personal care products Polar pesticides and their degradation/transformation products Surfactants and their metabolites... 

Organophosphate or Organophosphorus Compound—A phosphorus containing organic compound and especially a pesticide that acts by inhibiting cholinesterase. 

Each sample was analyzed for a specific set of compounds, corresponding to pesticide residues that might occur in the Suit or vegetable from use of one or more organophosphate insecticides on the growing crop. Insecticides of interest are listed in Table 1. 

In the OPMBS, all compounds were determined that occurred in the tolerance expression for organophosphate pesticides being supported by the registrants in each of the 13 commodities. Thus, compounds to be determined were those that might occur as residues of organophosphate pesticides whose continued use was supported by members of the OPMBS Task Force. 

Enzymes can be used not only for the determination of substrates but also for the analysis of enzyme inhibitors. In this type of sensors the response of the detectable species will decrease in the presence of the analyte. The inhibitor may affect the vmax or KM values. Competitive inhibitors, which bind to the same active site than the substrate, will increase the KM value, reflected by a change on the slope of the Lineweaver-Burke plot but will not change vmax. Non-competitive inhibitors, i.e. those that bind to another site of the protein, do not affect KM but produce a decrease in vmax. For instance, the acetylcholinesterase enzyme is inhibited by carbamate and organophosphate pesticides and has been widely used for the development of optical fiber sensors for these compounds based on different chemical transduction schemes (hydrolysis of a colored substrate, pH changes). 

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