Azamethiphos Research Articles

Differentiated Neurons Are More Vulnerable to Organophosphate and Carbamate Neurotoxicity than Undifferentiated Neurons Due to the Induction of Redox Stress and Accumulate Oxidatively-Damaged Proteins.

Organophosphate (OP) and carbamate pesticides are toxic to pests through targeted inhibition of acetylcholinesterase (AChE). However, OPs and carbamates may be harmful to non-target species including humans and could induce developmental neurotoxicity if differentiated or differentiating neurons are particularly vulnerable to neurotoxicant exposures. Hence, this study compared the neurotoxicity of OPs, chlorpyrifos-oxon (CPO), and azamethiphos (AZO) and the carbamate pesticide, aldicarb, to undifferentiated versus differentiated SH-SY5Y neuroblastoma cells. OP and carbamate concentration-response curves for cell viability were undertaken using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and cellular bioenergetic capacity assessed via quantitation of cellular ATP levels. Concentration-response curves for inhibition of cellular AChE activity were also generated and the production of reactive oxygen species (ROS) was monitored using a 2',7'-dichlorofluorescein diacetate (DCFDA) assay. The OPs and aldicarb reduced cell viability, cellular ATP levels, and neurite outgrowth in a concentration-dependent fashion, from a threshold concentration of ≥10 µM. Neurotoxic potency was in the order AZO > CPO > aldicarb for undifferentiated cells but CPO > AZO > aldicarb for differentiated cells and this toxic potency of CPO reflected its more extensive induction of reactive oxygen species (ROS) and generation of carbonylated proteins that were characterized by western blotting. Hence, the relative neurotoxicity of the OPs and aldicarb in part reflects non-cholinergic mechanisms that are likely to contribute to developmental neurotoxicity.

Evaluation of azamethiphos and dimethoate degradation using chlorine dioxide during water treatment.

Chlorine dioxide (ClO2) degradation of the organophosphorus pesticides azamethiphos (AZA) and dimethoate (DM) (10 mg/L) in deionized water and in Sava River water was investigated for the first time. Pesticide degradation was studied in terms of ClO2 level (5 and 10 mg/L), degradation duration (0.5, 1, 2, 3, 6, and 24 h), pH (3.00, 7.00, and 9.00), and under light/dark conditions in deionized water. Degradation was monitored using high-performance liquid chromatography. Gas chromatography coupled with triple quadrupole mass detector was used to identify degradation products of pesticides. Total organic carbon was measured to determine the extent of mineralization after pesticide degradation. Real river water was used under recommended conditions to study the influence of organic matter on pesticide degradation. High degradation efficiency (88-100% for AZA and 85-98% for DM) was achieved in deionized water under various conditions, proving the flexibility of ClO2 degradation for the examined organophosphorus pesticides. In Sava River water, however, extended treatment duration achieved lower degradation efficiency, so ClO2 oxidized both the pesticides and dissolved organic matter in parallel. After degradation, AZA produced four identified products (6-chlorooxazolo[4,5-b]pyridin-2(3H)-one; O,O,S-trimethyl phosphorothioate; 6-chloro-3-(hydroxymethyl)oxazolo[4,5-b]pyridin-2(3H)-one; O,O-dimethyl S-hydrogen phosphorothioate) and DM produced three (O,O-dimethyl S-(2-(methylamino)-2-oxoethyl) phosphorothioate; e.g., omethoate; S-(2-(methylamino)-2-oxoethyl) O,O-dihydrogen phosphorothioate; O,O,S-trimethyl phosphorodithioate). Simple pesticide degradation mechanisms were deduced. Daphnia magna toxicity tests showed degradation products were less toxic than parent compounds. These results contribute to our understanding of the multiple influences that organophosphorus pesticides and their degradation products have on environmental ecosystems and to improving pesticide removal processes from water.

Effects of exposing shrimp larvae (Pandalus borealis) to aquaculture pesticides at field relevant concentrations, with and without food limitation

Anti-parasitic drugs used in the aquaculture industry are discharged to the sea after treatment of salmon. In this study, the effects of azamethiphos (AZA) in the Salmosan® formulation and deltamethrin (DEL) in the Alpha Max® formulation, have been assessed in Northern shrimp larvae (Pandalus borealis) when administered both separately and in combination. The exposure concentrations were 100 ng/L for AZA and 2 ng/L for DEL, each representing a 1000-fold dilution of the prescribed concentrations for salmon. These two chemicals were combined at these concentrations to give a third treatment (AZA + DEL). When larvae were exposed for two hours on the first, second and third days post hatch (dph), significantly increased mortality and reduced swimming activity were observed for larvae from the DEL and combined AZA + DEL treatments 4 dph, though not in larvae from the AZA treatment. A single pulse exposure, delivered on the first day post hatch, caused similar effects on mortality and swimming activity 4 dph as the three-pulse exposure. Mortality was driven by the presence of DEL in both experiments, with no amplification or reduction of effects observed when DEL and AZA were combined. Larvae were observed for 13 days following the single pulse exposure, with food limitation introduced as an additional stressor on day 4. In the DEL and AZA + DEL treatments mortality continued to increase regardless of food level, with no larvae completing development to stage II. The overriding toxicity of DEL masked any potential effects the reduced food ration may have exerted. Swimming activity was lower for AZA treated larvae than Control larvae 13 dph, when both groups were fed daily, though no other significant changes to mortality, development to stage II, feeding rate or gene expression were observed. Food limited Control and AZA larvae had lower swimming activity and feeding rate than daily fed Control larvae, with expression of pyruvate kinase and myosin genes also downregulated. However, there was no negative effect on survival or successful development to stage II in these treatments. In addition, mesencephalic astrocyte-derived neurotropic factor was downregulated in food limited Control larvae when compared with the daily fed Controls.Results from this study together with reported estimates of dispersion plume concentrations of discharged pesticides indicate that toxic concentrations of deltamethrin could reach shrimp larvae several kilometers from a treated salmon farm.

Pesticides Drive Stochastic Changes in the Chemoreception and Neurotransmission System of Marine Ectoparasites.

Scientific efforts to elucidate the mechanisms of chemical communication between organisms in marine environments are increasing. This study applied novel molecular technology to outline the effects of two xenobiotic drugs, deltamethrin (DM) and azamethiphos (AZA), on the neurotransmission system of the copepod ectoparasite Caligus rogercresseyi. Transcriptome sequencing and bioinformatics analyses were conducted to evaluate treatment effects on the glutamatergic synaptic pathway of the parasite, which is closely related to chemoreception and neurotransmission. After drug treatment with DM or AZA, stochastic mRNA expression patterns of glutamatergic synapse pathway components were observed. Both DM and AZA promoted a down-regulation of the glutamate-ammonia ligase, and DM activated a metabotropic glutamate receptor that is a suggested inhibitor of neurotransmission. Furthermore, the delousing drugs drove complex rearrangements in the distribution of mapped reads for specific metabotropic glutamate receptor domains. This study introduces a novel methodological approach that produces high-quality results from transcriptomic data. Using this approach, DM and AZA were found to alter the expression of numerous mRNAs tightly linked to the glutamatergic signaling pathway. These data suggest possible new targets for xenobiotic drugs that play key roles in the delousing effects of antiparasitics in sea lice.

Acute toxicity of some treatments commonly used by the salmonid aquaculture industry to Corophium volutator and Hediste diversicolor: Whole sediment bioassay tests

The commercial farming of Atlantic salmon, Salmo salar, typically requires the periodic application of copper-based anti-foulants and chemotherapeutic treatments, including Slice ®, Excis ®, Salmosan ® and Aquatet ®/Tetraplex ® to reduce the effects of biological pests. Information on the environmental safety of any chemical agent released into the aquatic environment must be obtained before a product can be licensed for use, but such information typically exists only in confidential technical reports which can be difficult to obtain. Furthermore, different test organisms, experimental protocols and reporting procedures make comparison of the various compounds/studies difficult. Here we present a series of 10-day, whole sediment bioassay tests that determined the concentrations of emamectin benzoate (EB), cypermethrin (CP), azamethiphos (AZ) and oxytetracycline hydrochloride (OTC), the active ingredients of the aforementioned chemotherapeutants, and copper, that caused 50% mortality (LC 50) in the non-target benthic crustacean, Corophium volutator. Additional whole sediment bioassays of identical design were conducted with the non-target polychaete worm, Hediste diversicolor exposed to copper and EB. C. volutator demonstrated similar sensitivity to EB and AZ, with LC 50s of 153 (95% confidence intervals, CI = 119–198) and 182 (95% CI = 152–217) µg active ingredient [kg wet sediment] − 1 respectively. OTC caused 50% mortality of C. volutator at a concentration of 414 (95% CI = 233–734) µg OTC [kg wet sediment] − 1 . The LC 50 for H. diversicolor exposed to EB was 1368 (95% CI = 744–2516) µg EB [kg wet sediment] − 1 , an order of magnitude greater than that for C. volutator. Conversely, C. volutator was able to tolerate much higher concentrations of copper than H. diversicolor, with LC 50s of 193,326 (95% CI = 171,034–218,523) and 74,988 (95% CI = 61,192–91,895) µg Cu [kg wet sediment] − 1 respectively. CP was the most toxic to C. volutator of all compounds investigated, causing 50% mortality at a concentration of 5 (95% CI = 4–6) µg CP [kg wet sediment] − 1 . These data allow direct inter-comparison of the toxicities of some of the commonly applied treatments used by the global salmonid aquaculture industry.

Safety of azamethiphos in eel, seabass and trout

The safety of azamethiphos (AZA), an organophosphorous insecticide and the active ingredient of Salmosan ®, was evaluated in the European eel, seabass and rainbow trout. Fish were bathed in 0.1 ppm AZA for a period of 60, 120 or 240 min. After termination of each treatment fish were transferred to clean aquaria and randomly sampled over 21 days. Compared to controls, brain acetylcholinesterase (AChE) was inhibited up to 44, 56 and 62% in eels, seabass and trout, respectively, with the inhibition being significant for up to 4 days in eels and seabass and 7 days in trout. As result of the AChE depression, fish displayed motor hyperactivity and erratic jumping at the onset of treatment. Mortality was observed only in trout following exposure for 240 min. A variable correlation observed among species between the level of exposure, the reduced activity of brain AChE and the signs of toxicity suggest that brain AChE should be considered as an indicator of exposure rather than as an index of toxicity of AZA. The present data indicate that at the therapeutic dosage of 0.1 ppm AZA for 1 h can be safely used in eels, seabass and trout. The extended treatment times up to 240 min were equally safe for eels and seabass but not for trout.

Determination of Residues of Azamethiphos in Salmon Tissue by Liquid Chromatography with Fluorescence Detection

A liquid chromatographic (LC) method with fluorescence detection (FLD) is described for determining residues of the pesticide azamethiphos (AZA) in salmon tissue. The sample is extracted with ethyl acetate, centrifuged, dehydrated with anhydrous sodium sulfate, evaporated, reconstituted in water, and defatted with hexane. The aqueous phase is passed through a C18 solid-phase extraction (SPE) column. The SPE column is eluted with methanol, and the eluate is evaporated to dryness and then taken up in 10% acetonitrile (ACN) in water. The analyte is determined by LC using a C18 column, ACN-H2O (32 + 68) mobile phase, and FLD with excitation at 230 nm and emission at 345 nm. Composited salmon tissues were fortified with AZA at 5, 10, 21, 42, and 83 ng/g or ppb (target level, X = 10 ng/g). Overall recoveries were 86%, with between-day variability of 5.3%. The method detection limit was calculated as 1.2 ppb AZA based on a 5 g sample. The limit of quantitation as determined empirically by this method is the lower limit of the standard curve, approximately 5 ppb.