Atrazine promotes biochemical changes and DNA damage in a Neotropical fish species

The effects of Atrazine, an herbicide used worldwide and considered as a potential contaminant in aquatic environments, were assessed on the Neotropical fish Prochilodus lineatus acutely (24 and 48 h) exposed to 2 or 10 μg L⁻¹ of atrazine by using a set of biochemical and genetic biomarkers. The following parameters were measured in the liver: activity of the biotransformation enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione S transferase (GST), antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), content of reduced glutathione (GSH), generation of reactive oxygen species (ROS) and occurrence of lipid peroxidation (LPO); in brain and muscle the activity of acetylcholinesterase (AChE) and DNA damage (comet assay) on erythrocytes, gills and liver cells. A general decreasing trend on the biotransformation and antioxidant enzymes was observed in the liver of P. lineatus exposed to atrazine; except for GR, all the other antioxidant enzymes (SOD, CAT and GPx) and biotransformation enzymes (EROD and GST) showed inhibited activity. Changes in muscle or brain AChE were not detected. DNA damage was observed in the different cell types of fish exposed to the herbicide, and it was probably not from oxidative origin, since no increase in ROS generation and LPO was detected in the liver. These results show that atrazine behaves as enzyme inhibitor, impairing hepatic metabolism, and produces genotoxic damage to different cell types of P. lineatus.     

Toxicity of the nerve agent tabun to Daphnia magna, a new experimental species in military toxicology

Daphnia magna, a freshwater microcrustacean, is currently tested as an alternative experimental species in research dealing with nerve agents poisonings treatment. Because of this, the toxicity of the nerve agent tabun (a cyanide-group containing organophosphate) to Daphnia had to be examined by estimating the EC₅₀ values. The immobilization of daphnids was chosen as the end-point. It was found that D. magna is sensitive to small amounts of tabun, even after 15 min exposure, and tabun toxicity increases with time. The estimated EC₅₀ values for 15, 30, 45, and 60 min exposure were as follows: 67.39, 38.10, 26.95, and 21.9 μg l^-1. In addition, the toxicity of media to which tabun was added 24 h before the start of experiments was examined. The results obtained indicate that daphnids can be used in experiments with nerve-agent intoxication treatment.     

Persistently elevated AFP and AChE in amniotic fluid from a normal fetus following demise of its twin

Intrauterine fetal demise (IUFD) in one of twins at 12 weeks of gestation was accompanied by markedly elevated maternal serum alpha-fetoprotein (AFP) at 17 and 18 weeks. Amniotic fluid AFP from the healthy surviving twin's sac at 18·5 and 23 weeks was also greatly increased along with a positive acetylcholinesterase (AChE) band. Persistently elevated AFP and positive AChE so long after fetal demise–-6·5 and 11 weeks post IUFD–-has not, to our knowledge, been previously described. In similar cases, high level ultrasound and careful placental examination at birth should be utilized to search for fetal abnormalities or multiple pregnancy with IUFD.     

Maternal serum alpha-fetoprotein and fetal triploidy

Fetal triploidy is commonly found in early pregnancy. The majority of these pregnancies spontaneously abort in the first trimester. Occasionally, the pregnancy progresses to the second and third trimesters. We reviewed the maternal serum alpha-fetoprotein (MSAFP), amniotic fluid alpha-fetoprotein (AFP), amniotic fluid acetylcholinesterase (ACHE), fetal pathology, and placental pathology in sex second-trimester pregnancies complicated by fetal triploidy. Four of these patients had MSAFP values greater than 7.5 multiples of the median (MoM). Five of six pregnancies had MSAFP values greater than 2.25 MoM. All five of these patients had a partial mole. Four patients had amniotic fluid AFP values greater than 2.0 MoM. Two fetuses had associated neural tube defects. These were the only patients with positive amniotic fluid ACHE. None of the other patients had fetuses with anomalies that are known to be associated with an elevated MSAFP. The elevated MSAFP appeared to be related to the presence of a partial mole. Two of the five cases with an MSAFP greater than 2.25 MoM did not have sonographic evidence of a significant anomaly. Therefore, karyotyping can be of benefit in evaluating patients with elevated MSAFP.     

Examining the joint toxicity of chlorpyrifos and atrazine in the aquatic species: Lepomis macrochirus, Pimephales promelas and Chironomus tentans

The joint toxicity of chlorpyrifos and atrazine was compared to that of chlorpyrifos alone to discern any greater than additive response using both acute toxicity testing and whole-body residue analysis. In addition, acetylcholinesterase (AChE) inhibition and biotransformation were investigated to evaluate the toxic mode of action of chlorpyrifos in the presence of atrazine. The joint toxicity of atrazine and chlorpyrifos exhibited no significant difference in Lepomis macrochirus compared to chlorpyrifos alone; while studies performed with Pimephales promelas and Chironomus tentans, did show significant differences. AChE activity and biotransformation showed no significant differences between the joint toxicity of atrazine and chlorpyrifos and that of chlorpyrifos alone. From the data collected, the combination of atrazine and chlorpyrifos pose little additional risk than that of chlorpyrifos alone to the tested fish species.     

Review on the use of enzymes for the detection of organochlorine, organophosphate and carbamate pesticides in the environment

Pesticides are released intentionally into the environment and, through various processes, contaminate the environment. Three of the main classes of pesticides that pose a serious problem are organochlorines, organophosphates and carbamates. While pesticides are associated with many health effects, there is a lack of monitoring data on these contaminants. Traditional chromatographic methods are effective for the analysis of pesticides in the environment, but have limitations and prevent adequate monitoring. Enzymatic methods have been promoted for many years as an alternative method of detection of these pesticides. The main enzymes that have been utilised in this regard have been acetylcholinesterase, butyrylcholinesterase, alkaline phosphatase, organophosphorus hydrolase and tyrosinase. The enzymatic methods are based on the activation or inhibition of the enzyme by a pesticide which is proportional to the concentration of the pesticide. Research on enzymatic methods of detection, as well as some of the problems and challenges associated with these methods, is extensively discussed in this review. These methods can serve as a tool for screening large samples which can be followed up with the more traditional chromatographic methods of analysis.     

Effects of atrazine on acetylcholinesterase activity in midges (Chironomus tentans) exposed to organophosphorus insecticides

Acetylcholinesterase activity was determined for midge larvae (Chironomus tentans) exposed to either organophosphorus insecticides (OPs) alone or OP insecticides in binary combination with atrazine (200 μg/l). Although atrazine by itself did not reduce the level of acetylcholinesterase activity, atrazine in combination with chlorpyrifos significantly decreased acetylcholinesterase activity as compared to chlorpyrifos only treatments. Although similar trends existed for malathion and methyl parathion, differences were not statistically significant. These results match previously published toxicity data where atrazine, although not acutely toxic even at much higher levels, decreased EC₅₀ values for chlorpyrifos by a magnitude of 4, decreased methyl parathion values by a magnitude of 2, and did not decrease values for malathion.     

The mechanism of delayed neuropathy caused by some organophosphorus esters: Using the understanding to improve safety

Abstract

The mechanism of delayed neurotoxicity of some OP (organophosphorus) esters such as DFP (di‐isopropyl phosphorofluoridate) and TOCP (tri‐o‐cresyl phosphate) involves an initial two‐step process affecting an esterase called NTE (neurotoxic esterase). This understanding permits the assessment of delayed neuropathic potential in terms of a quantitative measurement of inhibition of NTE in tissue taken from dosed hens. Structure/activity relationships have been rationalized and the neurotoxic potential of those OP esters which are direct inhibitors of esterases may now be assessed in vitro. The response of human NTE can usefully be compared with that of hen NTE. Nil delayed neurotoxic potential is associated with carbamate or phosphinate anticholinesterases which may be designed as insecticides.     

Endosulfan induces changes in spontaneous swimming activity and acetylcholinesterase activity of Jenynsia multidentata (Anablepidae, Cyprinodontiformes)

We assessed changes in spontaneous swimming activity and acetylcholinesterase (AchE) activity of Jenynsia multidentata exposed to Endosulfan (EDS). Females of J. multidentata were exposed to 0.072 and 1.4 μg L⁻¹ EDS. Average speed and movement percentage were recorded during 48 h. We also exposed females to EDS at five concentrations between 0.072 and 1.4 μg L⁻¹ during 24 h, and measured the AchE activity in brain and muscle. At 0.072 μg L⁻¹ EDS swimming motility decreased relative to the control group after 45 h, while at 1.4 μg L⁻¹ EDS swimming motility decreased after 24 h. AchE activity significantly decreased in muscle when J. multidentata were exposed to EDS above 0.072 μg L⁻¹, while no significant changes were observed in brain. Thus, changes in swimming activity and AchE activity in muscle are good biomarkers of exposure to EDS in J. multidentata.     

Inhibition and recovery of serum,liver and brain acetylcholinesterase activities in rats exposed to new groups of O-ethyl phosphoramidates and benzo-1,3,2-dioxaphospholenes

Searching for new organophosphorus compounds with minimum effects on acetylcholinesterase of non-target organism especially mammals has gained an increased attention in the public concern. In this effort, the effects of some recently introduced O-ethyl phosphoramidates and benzo-1,3,2-dioxaphospholenes on rat acetylcholinesterase in different tissues have been evaluated in vivo and compared with the effects of fenitrothion, a commercial pesticide with reported moderate toxicity to mammals. The tested compounds were introduced orally in a single dose of 85?mg/kg body weight. Results indicated that the tested phosphoramidates lowered the enzyme activity to 54–69, 36–71 and 70–76% of its normal activity in serum, liver and brain, respectively. Meanwhile, the enzyme activity was depressed by fenitrothion to 11, 2 and 11% in the mentioned organs respectively. The lower anticholinesterase activity of the examined phosphoramidates than that of fenitrothion was attributed to their low hydrophobicity and low electrophilicity of their phosphorus atom, which reduces their interaction with the enzyme active site.