Acetylcholinesterase inhibitory activity and chemical composition of commercial essential oils

Commercially available essential oils extracted from Artemisia dracunculus L., Inula graveolens L., Lavandula officinalis Chaix, and Ocimum sanctum L. and the components of these oils were screened by the microplate assay method for determining their acetylcholinesterase (AChE) inhibitory activity. The composition profiles of the oils were characterized by gas chromatography-mass spectrometry (GC-MS) analysis, and the relationships between the oil components and the AChE inhibitory activity of the oils were outlined. The results showed that all of the oils, except that of A. dracunculus from Hungary, exhibited AChE inhibitory activity, and the A. dracunculus oil from France showed the most potent inhibitory activity [50% inhibition concentration (IC(50)) = 0.058 mg/mL]. The AChE inhibitory activity of I. graveolens oil has not been reported to date, and this study is the first to reveal this activity in the oil. Among the essential oil components, five components, namely, 1,8-cineole, α-pinene, eugenol, α-terpineol, and terpinen-4-ol, showed AChE inhibitory activity, with IC(50) values of 0.015, 0.022, 0.48, 1.3, and 3.2 mg/mL, respectively. Eugenol, in particular, was found to be a potent AChE inhibitor along with determination of the IC(50) value, a finding that has been reported for the first time in this study. However, the ratio of the contribution of the active components, including a novel AChE inhibitor, to the observed AChE inhibitory activity of the essential oils was not very high. The results of this study raise concerns about the AChE inhibitory activity of widely produced and readily accessible commercial essential oils.

Acetylcholinesterase biosensor based on gold nanoparticles and cysteamine self assembled monolayer for determination of monocrotophos

In this paper, a simple method for immobilization of acetylcholinesterase (AChE) on cysteamine assembled glassy carbon electrode coupled with gold nanoparticles (GNPs) was proposed and thus a sensitive, fast and stable amperometric biosensor for quantitative determination of monocrotophos was developed. The fabrication procedure was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and contact angles. The presence of GNPs not only led to an increased effective surface to provide a sufficient amount of sites for binding enzyme, but also promoted electron transfer reactions and catalyzed the electro-oxidation of thiocholine, thus amplifying the detection sensitivity. Due to the notable decrease in voltammetric signal of the immobilized AChE, a simple method for determination of monocrotophos was established. The inhibition of monocrotophos was proportional to its concentration in two ranges, from 0.5 to 10 ng mL(-1) and from 10 to 600 ng mL(-1), with a detection limit lower than 0.3 ng mL(-1). The constructed biosensor processing prominent characteristics and performance such as good precision and reproducibility, acceptable stability and accuracy, fast response and low detection limit has potential application in detection of toxic compounds.

Continuous colorimetric assay for acetylcholinesterase and inhibitor screening with gold nanoparticles

We report herein a new colorimetric assay method for acetylcholinesterase (AChE) activity and its inhibitor screening by making use of the following facts: (1) the aggregation of gold nanoparticles (Au-NPs) results in the red-shift of the plasmon absorption due to interparticle plasmon interactions and (2) AChE can catalyze the hydrolysis of acetylthiocholine into thiocholine which can induce the aggregation of Au-NPs. With this convenient method, the activity of AChE with a concentration as low as 0.6 mU/mL can be assayed. Moreover, this assay method is also useful for screening inhibitors of AChE. Given its simplicity and easy-operation, this method may extend to high-throughput screening of AChE inhibitors and relevant drug discovery.

Two-dimensional turbulent flow chromatography coupled on-line to liquid chromatography-mass spectrometry for solution-based ligand screening against multiple proteins

We present herein a novel bioseparation/chemical analysis strategy for protein-ligand screening and affinity ranking in compound mixtures, designed to increase screening rates and improve sensitivity and ruggedness in performance. The strategy is carried out by combining on-line two-dimensional turbulent flow chromatography (2D-TFC) with liquid chromatography-mass spectrometry (LC-MS), and accomplished through the following steps: (1) a reversed-phase TFC stage to separate the protein/ligand complex from the unbound free molecules, (2) an on-line dissociation process to release the bound ligands from the complexes, and (3) a second mixed-mode cation-exchange/reversed-phase TFC stage to trap the bound ligands and to remove the proteins and salts, followed by LC-MS analysis for identification and determination of the binding affinities. The technique can implement an ultra-fast isolation of protein/ligand complex with the retention time of a complex peak in about 5s, and on-line prepare the "clean" sample to be directly compatible with the LC-MS analysis. The improvement in performance of this 2D-TFC/LC-MS approach over the conventional approach has been demonstrated by determining affinity-selected ligands of the target proteins acetylcholinesterase and butyrylcholinesterase from a small library with known binding affinities and a steroidal alkaloid library composed of structurally similar compounds. Our results show that 2D-TFC/LC-MS is a generic and efficient tool for high-throughput screening of ligands with low-to-high binding affinities, and structure-activity relationship evaluation.

Analysis and integration of developmental neurotoxicity and ancillary data into risk assessment: a case study of dimethoate

Dimethoate is an organophosphate (OP) pesticide used to control a wide variety of insects on agricultural crops and ornamentals. To ensure that dimethoate is used safely, it is important to determine exposure levels that protect against adverse effects at all life stages, including the developing fetus, infant, and child. Based on an analysis of a developmental neurotoxicity (DNT) study, a cholinesterase (ChE) sensitivity study, a cross-fostering study, and several single- and multigenerational reproductive toxicity studies, two potential critical endpoints for dimethoate were identified: brain ChE inhibition (ChEI) in adult females, and pup mortality. An initial evaluation concluded that pup mortality was a preferable endpoint, based on an increased number of pup deaths born to dams dosed with > or =3 mg/kg dimethoate via oral gavage. Closer examination, however, revealed that the pup deaths were clustered in a small number of litters in which the dams providing postnatal care exhibited maternal care deficits. When the data were analyzed using the dam as the unit of statistical significance, a significant increase in the average litter proportion of pup deaths was observed only when the dams were dosed postnatally with 6 mg/kg dimethoate while they were raising the pups. Gestational exposure (i.e., during pregnancy only) to 6 mg/kg dimethoate exerted no effect on pup survival. This leads to the conclusion that it is postnatal exposure of the nursing dams that is associated with pup mortality. Furthermore, a previous benchmark dose (BMD) meta-analysis approach revealed that BMDL(10) for adult females (the lower 95% bound of the dose resulting in a 10% reduction in the parameter of interest) for ChEI was > 3-fold lower than the BMDL(10) for pup mortality (0.19 and 0.68 mg/kg, respectively). Overall, this study underscores the importance of using the dam as the unit of statistical significance when assessing data collected in the perinatal period, and it is concluded that adult brain ChEI is the correct critical endpoint for assessing risk of dimethoate toxicity.

Electrochemical biosensor technology: application to pesticide detection

In recent years, electrochemical sensors and biosensors are becoming an accepted part of analytical chemistry since they satisfy the expanding need for rapid and reliable measurements. An area in which electrochemical biosensors perhaps show the greatest diversity and potential for development involves the measurement of environmentally significant parameters. The increasing number of pollutants in the environment calls for fast and cost-effective analytical requirements. In this context, biosensors appear as suitable alternative or complementary analytical tools. The aim of this chapter is to review some basic concept concerning the electrochemical biosensors and to illustrate a protocol for the detection of environmental organic pollutants on the basis of electrochemical biosensors. In particular, a method based on the inhibition of the enzyme acetylcholinesterase (AChE) for the detection of organophosphorus and carbamate pesticides will be described in detail.

Assessment of Clarias batrachus as a source of acetylcholinesterase (AchE) for the detection of insecticides

An inhibitive assay of insecticides using Acetylcholinesterase (AChE) from the local fish Clarias batrachus is reported. AChE was assayed according to the modified method of Ellman. Screening of insecticide and heavy metals showed that carbofuran and carbaryl strongly inhibited C. batrachus AChE. The inhibition concentration (IC) IC50 values (and the 95% confidence interval) for both carbofuran and carbaryl inhibition on C. batrachus AChE at 6.66 (5.97-7.52) and 130.00 (119.3-142.5) microg l(-1), respectively was within the IC50 range of Electrophorus electricus at 6.20 (6.03-6.39) and 133.01 (122.40-145.50) microg l(-1), respectively and were much lower than bovine AChE at 20.94 (19.53-22.58) and 418.80 (390.60-451.60) microg l(-1), respectively. The results showed that C. batrachus have the potential to be used as a cheaper and more readily available source of AChE than other more commercially available sources.

A mid-infrared flow-through sensor for label-free monitoring of enzyme inhibition

Label-free monitoring of acetylcholinesterase (AChE) activity was achieved with a mid-infrared flow-through sensor. The flow-through sensor comprised agarose beads, carrying covalently immobilized AChE, which were placed in a temperature-controlled (37 degrees C) CaF(2) flow cell with an optical path of 60 mum. The sensor was incorporated into a computer-controlled sequential injection (SI) system for automated liquid handling. Different mixtures of enzyme substrate acetylcholine (ACh) and inhibitor (tacrine) were prepared and fed into the flow-through sensor. The flow was stopped as soon as the prepared mixtures reached the sensor. Enzymatic hydrolysis of ACh by AChE was directly monitored as it took place in the flow-through sensor. The inhibition effect of tacrine was calculated from the reaction-induced spectral changes, revealing an important decrease in the activity of AChE, approaching zero when the inhibitor concentration is high enough. The developed mid-infrared flow-through sensor is flexible and can be used to study the inhibitor activity of different target molecules as well as different enzymes.

Assessing intermittent pesticide exposure from flea control collars containing the organophosphorus insecticide tetrachlorvinphos

Fleas are a persistent problem for pets that require implementation of control measures. Consequently, pesticide use by homeowners for flea control is common and may increase pesticide exposure for adults and children. Fifty-five pet dogs (23 in study 1; 22 in study 2) of different breeds and weights were treated with over-the-counter flea collars containing tetrachlorvinphos (TCVP). During study 1, fur of treated dogs was monitored for transferable TCVP residues using cotton gloves to pet the dogs during 5-min rubbings post-collar application. Plasma cholinesterase (ChE) activity was also measured in treated dogs. Average amounts of TCVP transferred from the fur of the neck (rubbing over the collar) and from the back to gloves at 3 days post-collar application were 23,700+/-2100 and 260+/-50 microg/glove, respectively. No inhibition of plasma ChE was observed. During study 2, transferable TCVP residues to cotton gloves were monitored during 5-min rubbings post-collar application. Transferable residues were also monitored on cotton tee shirts worn by children and in the first morning urine samples obtained from adults and children. Average amounts of TCVP transferred to gloves at 5 days post-collar application from the neck (over the collar) and from the back were 22,400+/-2900 and 80+/-20 microg/glove, respectively. Tee shirts worn by children on days 7-11 contained 1.8+/-0.8 microg TCVP/g shirt. No significant differences were observed between adults and children in urinary 2,4,5-trichloromandelic acid (TCMA) levels; however, all TCMA residues (adults and children) were significantly greater than pretreatment concentrations (alpha=0.05). The lack of ChE inhibition in dogs and the low acute toxicity level of TCVP (rat oral LD(50) of 4-5 g/kg) strongly suggest that TCVP is rapidly detoxified and excreted and therefore poses a very low toxicological risk, despite these high residues.

Ultraviolet Raman spectra and cross-sections of the G-series nerve agents

Ultraviolet (UV) Raman spectroscopy is being applied to the detection of chemical agent contamination of natural and man-made surfaces. In support of these efforts, we have measured the UV Raman signatures of the G-series nerve agents GA (tabun), GB (sarin), GD (soman), GF (cyclosarin), and the agent simulant diisopropyl methylphosphonate (DIMP) at 248 nm and 262 nm, as well as taking their UV Raman and UV absorption cross-sections. Of these chemicals, only GA exhibits any significant pre-resonance enhancement. We also show that reduction of the excitation wavelength from 262 nm to 248 nm effectively shifts the Raman spectrum away from a substantial sample fluorescence background, implying a significant improvement in detection capability.

New performance of biosensor technology for Alzheimer's disease drugs: in vitro comparison of tacrine and 7-methoxytacrine

Two drugs were tested using electrochemical biosensor with immobilized acetylcholinesterase (AChE). The first was commercialized drug tacrine (known also as Cognex) used for treatment of cognitive manifestation of Alzheimer\'s disease (AD). The second one was its 7-methoxy derivate (7-MEOTA) that has not been marketed. We determined the IC50 (6.67+/-0.92)x10-7 M for tacrine and (1.66+/-1.43)x10-9 M for 7-MEOTA. In this in vitro study, 7-MEOTA acts as stronger inhibitor of AChE and in this way could be more favorable for treatment of cognitive manifestation of AD. Our study shows that biosensor technology could be used as a quick and cheap tool for testing of promising AChE inhibitors (AD drug candidates).

Rapid TLC/GC-MS identification of acetylcholinesterase inhibitors in alkaloid extracts

Alkaloid extracts from 12 plant species of the families Amaryllidaceae, Fumariacae and Papaveraceae were studied with respect to their acetylcholinesterase inhibitory activity and alkaloid patterns. Fifty-three alkaloids were identified by GC-MS, including known acetylcholinesterase (AChE) inhibitors such as galanthamine, epigalanthamine, sanguinine and epinorgalanthamine in extracts of Amaryllidaceae plants and protopine in extracts of Fumariaceae and Papaveraceae plants. The galanthamine-containing extracts of the amaryllidaceous plants were found to be the most active while the extract of Corydalis bulbosa was the most active among the extracts of the tested plants from the Fumariaceae and Papaveraceae plants. TLC bioautographic assay, preparative TLC and GC-MS analysis were combined to identify the active compounds in the studied extracts. Galanthamine was isolated from the known AChE inhibitors in the extracts of Amaryllidaceae plants. Corydaline, bulbocapnine and stylopine were found to be active in the extracts of plant species of the families Fumariaceae and Papaveraceae. Available standards of deshydrocorydaline--a precursor of corydaline, corydaline and stylopine--were tested for AChE inhibitory activity. Deshydrocorydaline and corydaline showed potent inhibitory activity comparable with that of the positive control galanthamine.

Detection of pesticide by polymeric enzyme electrodes

Screen-printed electrodes (SPEs) containing immobilized acetylcholine esterase (AChE) enzyme were used for the electrochemical determination of organophosphorous (OP) and carbamate pesticides. The extent of AChE deactivation by the pesticide was determined in the presence of acetylcholine (AChCl) substrate. The unique nature of this approach lies in the enzyme immobilization procedure in which AChE was attached to the SPE by in situ bulk polymerization of acrylamide to ensure efficient adherence within the membrane with minimal losses in enzyme activity. Responses were observed for the pesticides Monocrotophos, Malathion, Metasystox and Lannate over the concentration range 0-10 ppb (microg L(-1)).

Study of the degradation behaviour of dimethoate under microwave irradiation

In this work, the degradation of dimethoate under microwave irradiation assisted advanced oxidation processes (MW/oxidants) were studied. The efficiencies of the degradation of dimethoate in dilute aqueous solutions for a variety of oxidants with or without MW irradiation were compared. The results showed that the synergistic effects between MW and K(2)S(2)O(8) had high degradation efficiency for dimethoate. Simultaneously, UV/TiO(2)/K(2)S(2)O(8) photocatalytic oxidation degradation of dimethoate was investigated. The experimental results indicated that the method of microwave degradation of organic pollutants in the presence of oxidant could reduce reaction time and improve product yield. Microwave irradiation was an advisable choice for treating organic wastewaters and has a widely application perspective for non- or low-transparent and fuscous dye wastewaters.

Biosensor system for continuous monitoring of organophosphate aerosols

An enzyme-based monitoring system provides the basis for continuous sampling of organophosphate contamination in air. The enzymes butyrylcholinesterase (BuChE) and organophosphate hydrolase (OPH) are stabilized by encapsulation in biomimetic silica nanoparticles, entrained within a packed bed column. The resulting immobilized enzyme reactors (IMERs) were integrated with an impinger-based aerosol sampling system for collection of chemical contaminants in air. The sampling system was operated continuously and organophosphate detection was performed in real-time by single wavelength analysis of enzyme hydrolysis products. The resulting sensor system detects organophosphates based on either enzyme inhibition (of BuChE) or substrate hydrolysis (by OPH). The detection limits of the IMERs for specific organophosphates are presented and discussed. The system proved suitable for detection of a range of organophosphates including paraoxon, demeton-S and malathion.

Immobilization of acetylcholinesterase on gold nanoparticles embedded in sol–gel film for amperometric detection of organophosphorous insecticide

A simple method to immobilize acetylcholinesterase (AChE) on silica sol-gel (SiSG) film assembling gold nanoparticles (AuNPs) was proposed, thus a sensitive, fast and stable amperometric sensor for quantitative determination of organophosphorous insecticide was developed. The large quantities of hydroxyl groups in the sol-gel composite provided a biocompatible microenvironment around enzyme molecule and stabilized its biological activity to a large extent. The immobilized AChE could catalyze the hydrolysis of acetylthiocholine chloride (ATCl) with a Kmapp value of 450 microM to form thiocholine, which was then oxidized to produce detectable single with a linear range of 10-1000 microM. AuNPs catalyzed the electro-oxidation of thiocholine, thus increasing detection sensitivity. Based on the inhibition of organophosphorous insecticide on the enzymatic activity of AChE, using monocrotophos as a model compound, the conditions for detection of the insecticide were optimized. The inhibition of monocrotophos was proportional to its concentration ranging from 0.001 to 1 microg/ml and 2 to 15 microg/ml, with the correlation coefficients of 0.9930 and 0.9985, respectively. The detection limit was 0.6 ng/ml at a 10% inhibition. The developed biosensor exhibited good reproducibility and acceptable stability, thus providing a new promising tool for analysis of enzyme inhibitors.

Assessment of diazinon toxicity in sediment and water of constructed wetlands using deployed Corbicula fluminea and laboratory testing

Constructed wetlands for mitigation of nonpoint agricultural runoff have been assessed for their ability to decrease potential toxicity from associated contaminants. After a simulated runoff event, constructed wetlands positioned in series were used to measure the effects of the organophosphate insecticide diazinon. Water, sediment, and plant samples from five sites were analyzed for diazinon concentrations from 0.5 hours to 26 days; peak concentrations were measured in sediment after 0.5 hours (268.7 microg/kg) and in water and plant tissue after 3 hours (121.71 microg/L and 300.7 microg/kg, respectively). Cholinesterase activity and changes in shell growth were measured from Corbicula fluminea deployed at corresponding sites. Water collected after 9 hours from all wetland sites contained diazinon concentrations sufficient to cause toxicity to Ceriodaphnia dubia, but not to Pimephales promelas. C. dubia survival was decreased in water sampled through 7 days from the site nearest runoff introduction, whereas C. fluminea deployed at this same site experienced 100% mortality after 26 days. Clams from lower sites survived wetland conditions, but growth and ChE activity were significantly decreased lower than that of clams from a control site. C. dubia exposed to water from these sites continued to have decreased survival throughout the 26-day sampling. Sediment sampled from 48 hours through 14 days at the lowest wetland site decreased the laboratory survival of Chironomus dilutus, and sediment from upper sites elicited an effect only on day 26. Although wetland concentrations of aqueous diazinon were decreased lower than toxic thresholds after 26 days, decreased ChE activity in deployed clams provided evidence of residual diazinon effects to deployed organisms.

Behavior of the organophosphorus insecticide fenitrothion in stored faba beans and its biological effects towards experimental animals

Sound whole-seed faba beans were treated with (methyl-(14)C) fenitrothion [O, O-dimethyl-O-(3-methyl-4-nitrophenyl) phosphorothioate] at 5 and 10 mg insecticide/kg seeds, a dose normally used in practice. During the 30 weeks of storage period, the penetration and distribution of insecticide residues were studied. The amount of surface residues, internal residues and bound insecticide residues was estimated. Surface residues were found to decrease with the increase in time of storage, whereas internal residues showed a gradual increase with time apparently not dose dependent. Grain-bound residues increased with time and reached to its maximum (14-18%) after 24 weeks of storage. Chromatographic analysis of the internal extracts revealed the presence of the parent compound together with three main metabolites which were found in both free and conjugated form. Feeding mice for 90 days with a diet mixed with total internal fenitrothion residues in stored faba beans led to a reduction in body weight gain, and an appreciable decrease in cholinesterase activity of 32% for plasma and 15% for red blood cells (RBC(S)) after two months of experiment. Also, a significant decrease was showed in both total protein and albumin concentration at the end of feeding period (90 days). Liver and kidney function, as well as lipid profile of treated mice significantly increased at the end of feeding period. After a one-month recovery period, all the examined blood parameters returned to about the control values except blood urea and serum triglyceride.

Contamination of vegetables of different seasons with organophosphorous pesticides and related health risk assessment in northern India

India is an agrarian country. The use of pesticides, herbicides and fungicides were introduced in India during the mid-sixties, which are now being used on a large scale and is a common feature of Indian agriculture. The main intention of the introduction of pesticides was to prevent and control insects, pests and diseases in the field crops. Initially the use of pesticides reduced pest attack and paved way for increasing the crop yield as expected. Simultaneously, increased use of chemical pesticides has resulted in contamination of environment and also caused many long-term affect on the society. In the present study an effort has been made to evaluate the residual concentration of selected organophosphorous pesticides (methyl parathion, chlorpyriphos and malathion) in vegetables grown in different seasons (summer, rainy and winter). Data obtained was then used for estimating the potential health risk associated with the exposure to these pesticides. The pesticides residue concentrations in vegetables of different season shows that the winter vegetables are the most contaminated followed by summer and rainy vegetables. The concentration of the various pesticides were well below the established tolerances but continuous consumption of such vegetables even with moderate contamination level can accumulate in the receptor's body and may prove fatal for human population in the long term. The analysis of health risk estimates indicated that chlorpyriphos and malathion did not poses a direct hazard, however, exposure to methyl parathion has been found to pose some risk to human health.

Binding of acetylcholinesterase to multiwall carbon nanotube-cross-linked chitosan composite for flow-injection amperometric detection of an organophosphorous insecticide

A novel method for immobilization of acetylcholinesterase (AChE) by binding covalently to a cross-linked chitosan-multiwall carbon nanotube (MWNT) composite is described. In addition a sensitive, fast, cheap and automatizable flow injection detection of an organophosphorous insecticide was developed. The MWNTs were homogeneously distributed in the chitosan membrane which showed a homogeneous porous structure. The immobilized AChE could catalyze the hydrolysis of acetylthiocholine with a K(M)app value of 177 microM to form thiocholine, which was then oxidized to produce detectable signal in a linear range of 1.0-500 microM and fast response. MWNTs could catalyze the electrooxidation of thiocholine, thus increasing detection sensitivity. Based on the inhibition of an organophosphorous insecticide on the enzymatic activity of AChE, using Sulfotep as a model compound, the conditions for the flow-injection detection of the insecticide were optimized. Both biocompatibility of chitosan and inherent conductive properties of MWNTs favored the detection of the insecticide from 1.5 to 80 microM along with good stability and reproducibility. 95 % reactivation from inhibited AChE could be regenerated by using 2-pyridinealdoxime methiodide within 15 min for 15 times. The detection of Sulfotep samples exhibited satisfactory results. The proposed flow-injection analysis device can be applied to automated determination and characterization of enzyme inhibitors.

Fluorescent method for evaluation of cholinesterase inhibitors

The sensitivity of detection of anticholinesterase compounds (e.g. tacrine) by the biochemical method significantly increased when fluorogenic compound N-(4-(7-diethylamino-4-methylcoumarine-3-yl)phenyl)maleimide was used instead of Ellman's reagent. A kinetic fluorescent method for evaluating cholinesterase inhibitors is proposed.

Inhibition of rainbow trout acetylcholinesterase by aqueous and suspended particle-associated organophosphorous insecticides

Spraydrift and edge-of-field runoff are important routes of pesticide entry into streams. Pesticide contamination originating from spraydrift usually resides in the water phase, while pesticides in contaminated runoff are to a large extent associated with suspended particles (SPs). The effects of two organophosphorous insecticides (OPs), chloropyrifos (CPF) and azinphos-methyl (AZP), on acetylcholinesterase (AChE) activity in rainbow trout were compared between two exposure scenarios, simulating spraydrift- and runoff-borne contamination events in the Lourens River (LR), Western Cape, South Africa. NOECs of brain AChE inhibition, determined after 1h of exposure followed by 24h of recovery, were 0.33microgl(-1) for aqueous CPF, 200mgkg(-1) for SP-associated CPF and 20mgkg(-1) for SP-associated AZP (at 0.5gl(-1) SP). The highest aqueous AZP concentration tested (3.3microgl(-1)) was without significant effects. Previously reported peak levels of aqueous CPF in the LR ( approximately 0.2microgl(-1)) are close to its NOEC (this study), suggesting a significant toxicological risk to fish in the LR. By contrast, reported levels of SP-associated OPs in the LR are 20-200-fold lower than their NOECs (this study). In a comparative in situ study, trout were exposed for seven days at agricultural (LR2, LR3) and upstream reference (LR1) sites. No runoff occurred during the study. Brain AChE was significantly inhibited at LR3. However, OP levels at LR3 (CPF 0.01microgl(-1); AZP 0.14microgl(-1)) were minor compared to concentrations having effects in the laboratory (see above). Additionally, muscle AChE activity was significantly higher in caged trout from LR1 than in animals maintained in laboratory tanks.

Enzyme-linked immunosorbent assays for the insecticide fenitrothion. Influence of hapten conformation and sample matrix on assay performance

This study aimed at developing competitive enzyme-linked immunosorbent assays (ELISAs) for the organophosphorus (OP) insecticide fenitrothion using a monoclonal antibody. The hapten used to obtain the antibody had an ideal structural feature that allowed minimal functional group sacrifice. By using the antibody and a coating antigen, a competitive indirect ELISA was developed, which showed an IC50 of 14 ng mL(-1) with a detection limit of 3.0 ng mL(-1). A competitive direct ELISA using an enzyme tracer was also developed, which showed an IC50 of 17 ng mL(-1) with a detection limit of 1.6 ng mL(-1). The antibodies in both assays showed negligible cross-reactivity with the metabolites of fenitrothion and other OP pesticides except with the insecticides parathion-methyl and parathion-ethyl. Recoveries of fenitrothion from fortified rice and lettuce samples were determined and the bias in the recovery values was rationalized by using the standard curves obtained in the matrix extract.