Development of a Pesticide Exclusion Technique for Assessing the Impact of Biological Control Agents for Chrysanthemoides monilifera

Seven biological control agents have been released on the environmental weed Chrysanthemoides monilifera in Australia and two are widely established on infestations of C. monilifera subsp. rotundata in New South Wales. Five pesticides were screened for their impact on seed production of C. monilifera and two on the survival of the agent Comostolopsis germana, a shoot tip-feeding lepidopteran. The insecticides carbaryl, carbofuran, dimethoate, fluvalinate and the fungicide benomyl had no significant effect on seed production of C. monilifera when applied over a period of four months. Numbers of C. germana larvae were readily suppressed after three months by applications of fluvalinate or a mixture of carbaryl, carbofuran and dimethoate. Shoot growth was not affected by applications of carbaryl, dimethoate and benomyl. It is concluded that exclusion by pesticides of biological control agents is a valid method of measuring the impact of agents on C. monilifera.     

Structure-based design and application of an engineered glutathione transferase for the development of an optical biosensor for pesticides determination

In the present work, a structure-based design approach was used for the generation of a novel variant of synthetic glutathione transferase (PvGmGSTU) with higher sensitivity towards pesticides. Molecular modelling studies revealed Phe117 as a key residue that contributes to the formation of the hydrophobic binding site (H-site) and modulates the affinity of the enzyme towards xenobiotic compounds. Site-saturation mutagenesis of position Phe117 created a library of PvGmGSTU variants with altered kinetic and binding properties. Screening of the library against twenty-five different pesticides, showed that the mutant enzyme Phe117Ile displays 3-fold higher catalytic efficiency and exhibits increased affinity towards α-endosulfan, compared to the wild-type enzyme. Based on these catalytic features the mutant enzyme Phe117Ile was explored for the development of an optical biosensor for α-endosulfan. The enzyme was entrapped in alkosixylane sol-gel system in the presence of two pH indicators (bromocresol purple and phenol red). The sensing signal was based on the inhibition of the sol-gel entrapped GST, with subsequent decrease of released [H⁺] by the catalytic reaction, measured by sol–gel entrapped indicators. The assay response at 562?nm was linear in the range pH?=?4–7. Linear calibration curves were obtained for α-endosulfan in the range of 0–30?μΜ. The reproducibility of the assay response, expressed by relative standard deviation, was in the order of 4.1% (N?=?28). The method was successfully applied to the determination of α-endosulfan in real water samples without sample preparation steps.     

Alterations in the general condition,biochemical parameters and locomotor activity in Cnesterodon decemmaculatus exposed to commercial formulations of chlorpyrifos,glyphosate and their mixtures

The Pampean region, an extensive area of South America is continuously impacted by agricultural activities and the pesticides related to them like chlorpyrifos and glyphosate. Both pesticides have been registered in freshwater bodies of the region. One of the most abundant and widely distributed fish species in Pampean streams is Cnesterodon decemmaculatus, which have to cope with this altered scenario.In the present study the toxicity of Clorfox^® and Roundup Max^®, the commercial formulations of chlorpyrifos and glyphosate, respectively, and their mixture where evaluated using a set of biomarkers at different biological organization levels in fish exposed to relevant environmentally pesticides concentrations. Somatic indexes such as the condition factor (K), and the hepato-somatic index (HSI), the locomotor activity through the distance traveled and the average speed, the enzymatic activities of acetylcholinesterase (AChE) in brain and muscle, catalase (CAT) in muscle and liver, glutathione-S-transferase (GST) in brain, liver, muscle and gills, aspartate amino-transferase (AST), alanine amino-transferase (ALT), AST/ALT ratio and alkaline phosphatase (ALP) in liver were measured on C. decemmaculatus. Adult females were exposed during 6 weeks to the following concentrations: 0.0084 μl/l and 0.00084 μl/l of Clorfox (CF), 0.2 and 2 mg/l of Roundup Max (RM) and all the combinations of these concentrations. The CF exposure caused a decrease in the condition factor and in the locomotor activity parameters and induced an increase brain AChE, liver CAT activity and AST/ALT ratio. On the other hand, the exposure to RM produced a decrease in liver GST, AST/ALT ratio and ALP activity. Finally, some pesticide combinations decrease general condition and liver GST activities, and increase brain GST and liver ALP activities. Different responses in biomarkers were observed in mixtures treatments, reflecting the complex interactions between these toxics and suggesting a suppressive action of RM on CF effects.Since the concentrations we tested are environmentally relevant and the overall fish health condition was affected, the presence of these pesticides in freshwater systems could impose a risk for populations by causing deleterious effects on C. decemmaculatus in Pampean region.     

Glutamic-dehydrogenase activity inhibition by phenoxyacilic acids

Summary Experiments were carried out on the effects of some phenoxyacilic acids, used as herbicides, on the glutamic-dehydrogenase (GLDH) activity. 2,4-D,2,4,5-T, MCPA and Dichlorprop inhibited GLDH activity in a competitive way. Phenoxyacilic acids were ranked in the following order of affinity for the enzyme on the basis of the values of the inhibition constants: 2,4,5-T>2,4-D>MCPA>Dichlorprop; on the basis of chemical structure, it was established that the carboxyl dissociation degree is instrumental in linking the herbicide with the active site of the enzyme.     

Heptachlor and o‐p′DDT effects on protein kinase activities associated with human placenta particulate fractions

Organochlorine pesticides have been detected in placenta. The ability of heptachlor (HC) and 1,1,1‐tricholoro‐2‐(2‐chlorophenyl)‐2‐4‐chlorophenyl)ethane (o‐p′DDT) to interfere with protein phosphorylation was evaluated. In vitro incubations of cell‐free placental villi homogenates with a concentration range 1–100 µM were performed. In particulate fractions, total serine/threonine kinase activity was increased by 10 µM HC and o‐p′ DDT (59% and 82%, respectively). Maximum eightfold increase was observed with 10 µM o‐p′ DDT on protein kinase A activity. By contrast, protein kinase C activity was reduced by 10 µM HC and o‐p′ DDT (40% and 52%, respectively). Endogenous substrate phosphorylation studies demonstrated that slight but significant increase in 24‐kDa band labeling was produced in nuclear samples with 1, 10, and 100 µM HC and 100 µM o‐p′ DDT. Exposition to 100 µM HC increased 85‐kDa band labeling. In mitochondrial fractions, 10 µM HC and o‐p′ DDT increased 24‐ and 65‐kDa bands' labeling. These data indicate that both pesticides affect protein kinase activities in particulate fraction. Nuclear compartmentalization of these compounds, insertion in membranes, and chemical stress production may be associated to the observed effects, thus suggesting deleterious consequences in signaling pathways. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:185–192, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20277     

Assessment of the genotoxicity of imidacloprid and metalaxyl in cultured human lymphocytes and rat bone-marrow

Imidacloprid and metalaxyl are two pesticides that are widely used in agriculture, either separately, or in combination. These agents were studied for their possible genotoxic effects with respect to the following cytogenetic end-points: (1) in vitro micronucleus (MN) formation and sister-chromatid exchange (SCE) induction in human lymphocytes and (2) in vivo micronucleus induction in polychromatic erythrocytes (PCEs) of the rat bone-marrow. The results of the MN analysis indicate that MN frequencies after treatment with both pesticides, separately or as a mixture, do not significantly differ from those in the controls except after treatment with metalaxyl alone at 50 μg/ml (p < 0.05). The results of the SCE analysis show that SCE frequencies after treatment with imidacloprid do not differ significantly from those in the controls. A statistically significant increase (p < 0.05) in SCE frequency resulted from treatments with metalaxyl at 5, 10 and 100 μg/ml and with the combination of imidacloprid and metalaxyl at 100 and 200 μg/ml. Finally, the in vivo micronucleus assay with rat bone-marrow polychromatic erythrocytes showed a statistically significant effect upon separate treatments with imidacloprid and metalaxyl at doses of 300 mg/kg body weight (b.w.) (p < 0.01) or upon combined treatment with 200 mg/Kg b.w. (p < 0.001) and 400 mg/kg b.w. (p < 0.05).     

Endocrine-mediated effects of UV-A irradiation on grass shrimp (Palaemonetes pugio) reproduction

Although much is known regarding photoperiodic effects on crustacean egg production, the effects of ultraviolet (UV) light on reproduction has not been investigated. Likewise, little is known concerning the interaction between UV and xenobiotic exposure on crustacean reproductive cycles. In this study, male and female grass shrimp, Palaemonetes pugio, were exposed to sublethal concentrations of endosulfan (200 ng/l and 400 ng/l ES) under both white fluorescent (WF) and UV-A (315-400 nm) light conditions for 50 days in laboratory bioassays. Female endocrine (vitellogenin, ecdysteroids, and cholesterol), reproductive (percent gravid, clutch size), and embryo (days to hatch, hatching success, and hatching survival) responses were assessed. UV-exposure alone caused a significant (>4-fold) increase in total Palaemonetes pugio female egg production over the course of 50 days. Exposure to ES and UV significantly lowered the percentage of gravid females relative to UV controls, whereas ES-exposed shrimp under WF lighting did not exhibit these trends. Although higher vitellogenin concentrations and lower ecdysteroid titers were correlated with increased female egg production, cholesterol titers only exhibited a dose-dependent change when exposed to ES. Embryos from females exposed to UV had significantly lower ecdysteroid titers and shorter hatching times but there were no differences in embryo vitellogenin concentrations, hatching success, or hatching survival. These results indicate that UV-A exposure has a pronounced effect on grass shrimp (Palaemonetes pugio) reproduction and is likely mediated through 5-hydroxytrptamine (5-HT)-related neuroendocrine pathways. The implications for decapod aquaculture and evaluating chronic contaminant effects are discussed.     

不同农药对海南山蛭毒力测定及其防治研究

在室内,利用速灭杀丁,叶蝉散,杀虫双,乐果,三氯杀螨,草甘膦等6种农药对海南山蛭（Haemadipsa hainane)进行毒力测定,比较各种农药LK50表明,速灭杀丁＞叶蝉散＞三氯杀螨醇＞杀虫双＞乐果,除草剂草苷膦对海南山蛭完全无毒杀作用,草甘膦＋速灭杀丁对海南山蛭仍有很强的毒杀作用,海南山蛭对速灭杀丁的敏感性为,成体＞幼体＞亚成体,在田间小区试验表明,1．5％速灭杀丁防治效果为95．08％,大面积应用表明“草苷膦药液＋0．5％速灭杀丁”防治效果最好,达94．74％,“草甘膦药液＋1％叶蝉散乳油”防治效果次之,达90．5％,草甘膦＋灭蛭农药是防治山蛭好药剂,达到灭蛭除草的目的。     

In vitro human phase I metabolism of xenobiotics I: pesticides and related chemicals used in agriculture and public health, September 2001

Human phase I enzymes and their isoforms that metabolize pesticides are listed in a database that will be updated periodically. This initial version includes enzymes and isoforms that metabolize organophosphorus insecticides, chloroacetamide herbicides and triazine herbicides.