Toxic Effects Of Chlorpyrifos Research Articles

Toxic effects of chlorpyrifos on biochemical composition, enzyme activity and gill surface ultrastructure of three species of small fishes from India.

The effects of chlorpyrifos, a frequently detected organophosphate in aquatic ecosystems, on biochemical (protein and glycogen) contents and oxidative enzyme activities (catalase and lipid peroxidation) in liver, muscle and gill tissues of three freshwater fish Trichogaster fasciata, Mystus vittatus and Heteropneustes fossilis were evaluated after 21-day exposure to 1 and 10% of 96h LC50 of this pesticide, which were 1.63 and 16.3µg L-1; 5.87 and 58.7µg L-1 and 2.12 and 21.2µg L-1, respectively. On comparing with control, significant reductions in protein concentration were found in liver, muscle and gill of the three fishes treated with both higher as well as lower concentrations of the pesticide except in gill of M. vittatus and liver of H. fossilis treated with the lower concentrations. Glycogen content reductions were significant in the liver and muscle of the fishes, as well as gill tissue of T. fasciata treated with the two pesticide concentrations. Significant elevations of catalase activity were found in liver of the three fishes treated with the higher concentrations, in muscle tissues of both T. fasciata and M. vittatus treated with both the concentrations and in gills of the three fishes except H. fossilis treated with the lower concentration of the pesticide. Significant elevations of lipid peroxidation level were also found in liver of all the three fish species treated with the higher concentrations, in the muscle tissue of M. vittatus as well as in the gill of T. fasciata and H. fossilis treated with both the concentrations of the pesticide. Chlorpyrifos exposed gill ultrastructure of T. fasciata, M. vittatus and H. fossilis revealed concentration-dependent effects of the pesticide on gill surface ultrastructure which include distortion of primary and secondary lamellae, deterioration of pavement cell and microridge structures, extrusion of red blood cells (RBCs), secretion of mucous layer on filament, sloughing of primary lamellae and clumping of secondary lamellae. The present study parameters could serve as useful biomarkers for evaluating the risk of pesticide toxicity to fish. These findings also point out the possible health risks to the consumers of these fish captured from contaminated water bodies.

Chlorpyrifos induced autophagy and mitophagy in common carp livers through AMPK pathway activated by energy metabolism disorder

Water pollution caused by widely used agricultural pesticide chlorpyrifos (CPF) has aroused extensive public concern. While previous studies have reported on toxic effect of CPF on aquatic animal, little is known about its effect on common carp (Cyprinus carpio L.) livers. In this experiment, we exposed common carp to CPF (11.6 μg/L) for 15, 30, and 45 days to establish a poisoning model. Histological observation, biochemical assay, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and integrated biomarker response (IBR) were applied to assess the hepatotoxicity of CPF in common carp. Our results displayed that CPF exposure damaged histostructural integrity and induced liver injury in common carp. Furthermore, we found that CPF-induced liver injury may be associated with mitochondrial dysfunction and autophagy, as evidenced by swollen mitochondria, broken mitochondrial ridges, and increased the number of autophagosomes. Moreover, CPF exposure decreased the activities of ATPase (Na+/K+-ATPase, Ca2+-ATPase, Mg2+-ATPase, and Ca2+Mg2+-ATPase), altered glucose metabolism-related genes (GCK, PCK2, PHKB, GYS2, PGM1, and DLAT), and activated energy-sensing AMPK, indicating that CPF caused energy metabolism disorder. The activation of AMPK further induced mitophagy via AMPK/Drp1 pathway, and induced autophagy via AMPK/mTOR pathway. Additionally, we found that CPF induced oxidative stress (abnormal levels of SOD, GSH, MDA, and H2O2) in common carp livers, which further contributed to the induction of mitophagy and autophagy. Subsequently, we confirmed a time-dependent hepatotoxicity caused by CPF in common carp via IBR assessment. Our findings presented a new insight into molecular mechanism of CPF induced-hepatotoxicity in common carp, and provided a theoretical basis for evaluating CPF toxicity to aquatic organisms.

Toxic effects of chlorpyrifos on the growth, hemocytes counts, and vital organ’s histopathology of freshwater mussel, Lamellidens marginalis

The Chlorpyrifos 20 EC (emulsifying concentration) is one of the extensively used agro-pesticide in Bangladesh, most of which are residual in nearby natural water reservoirs. The freshwater mussel, Lamellidens marginalis have been exposed to Chlorpyrifos 20 EC at varying concentrations of Tc 0 mgL-1, T1 2.53 mgL-1, T2 5.07 mgL-1 and T3 10.15 mgL-1 for 35 days to investigate its toxic effects on growth biometrics, hemocyte counts and histopathology of gill, muscle, and ovary. The 96-hour Chlorpyrifos 20 EC LC50 for L. marginalis has been computed as 25.37 mgL-1 from PROBIT analysis. Major water regulating parameters were recorded and analyzed for each treatment group. The specific growth rate (%) was reported statistically highest in TC (0.104 ± 0.412) and lowest in T3 (-0.52 ± 0.38). Similarly, the condition index (CI) and Fulton’s condition factor were decent at TC and downed at T3 (P < 0.05). A high mortality rate occurred in T3 and the lowest mortality in TC. The value of total hemocytes count were also reported to be highest for TC and gradually decreased as the dosage increased (P < 0.05). The histopathology of gill, muscle, and ovary also revealed moderate to severe pathological signs in treatment groups in comparison to control. Administration of Chlorpyrifos 20 EC results in detrimental growth, cytological and hematological alternation in L. marginalis.

Стан системи антиоксидантного захисту у риб Danio rerio за інтоксикації хлорпірифосом

The article presents the results of studies of acute intoxication in Danio Rerio fish by chlorpyrifos at concentrations 0.5 mg/L; 0.75 mg/L and 1 mg/L of aquarium water for 24 h and its influence on the content of TBK-active products, catalase activity (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPO), glutathione reductase (GR) in their tissues. After 24 h in the fish staying in water with chloropyrifos added in concentrations 0.75 mg/L and 1 mg/L we have revealed an increase of the content of TBK-active products in the studied tissues compared to the control values. The linear nature of the growth of the CAT enzymatic activity in the tissues of head and torso due to the effects of chloropyrifos in doses of 0.5 mg/L; 0.75 mg/L and 1 mg/L. was shown. On the background of the catalase activity growth in Danio rerio, in 24 h after the action of the toxicant, there was an inversely proportional dependence between the dose of chlorpyrifos and the activity of GPOs in both investigated parts of the fish body. In the tissues of the head and torso, inhibition of SOD activity for the action of chlorpyrifos has been established. The activity of this enzyme was the lowest at the chlorpyrifos concentration 0.75 mg/L. The obtained results complement the data on the toxic effect of chlorpyrifos on ichthyofauna and on the course of chlorpyrifos-induced oxidative stress in Danio rerio fish. The obtained data can be used in the development of additional biochemical markers of chlorpyrifos and other phosphor organic compounds intoxication and in toxicological and environmental experiments, taking into account the growing intensity of the use of insecticidal preparations in agricultural production and everyday life.

Chlorpyrifos caused necroptosis via MAPK/NF-κB/TNF-α pathway in common carp (Cyprinus carpio L.) gills

Chlorpyrifos (CPF) is an organophosphate insecticide and can cause cell death of animals. In the study, the common carp were exposed to CPF at 0 μg/L (the control group), 1.16 μg/L (the low dose group), 11.6 μg/L (the medium dose group), and 116 μg/L (the high dose group), respectively. The carp were euthanized at the 30th day and gills were collected immediately. The ultrastructural and histopathological observations showed obvious necrosis characteristics and inflammatory injury in the CPF-treated groups. CPF exposure activated the MAPK pathway, in which the mRNA and protein expressions of extracellular signal-regulated (ERK), p38 MAP kinase (p38), and c-Jun N-terminal kinase (JNK) were increased; the mRNAs and proteins of NF-κB and TNF-α were activated; and the mRNAs and proteins of necroptosis related genes were changed (the mRNA and protein expression of RIPK1, RIPK3, MLKL, and FADD were increased and caspase-8 was decreased) with concentration dependency. Taken together, we concluded that CPF exposure activated the MAPK/NF-κB/TNF-α pathway, promoted inflammatory injure and evoked necroptosis in common carp gills. In addition, CPF-induced inflammation and necroptosis was concentration dependency. The toxic effects of CPF on gills provided data for both aquaculture and toxicological studies.

TOXICITY, NATURAL AND INDUCED DEGRADATION OF CHLORPYRIFOS

The increase in demand for agricultural products due to the growing population led to excessive inputs of pesticides in the agriculture field which resulted in contamination of the environmental segments of life i.e. air, water, and soil. Chlorpyrifos is one of the most extensively used broad-spectrum organophosphate insecticides. The usage and broad-spectrum applicability of chlorpyrifos lead to widespread contamination in the environment and serious damage to non-target organisms. Moreover, metabolites of chlorpyrifos i.e. chlorpyrifos-oxon and 3,5,6-trichloro-2-pyridinol are found to be more toxic than its parent compound. This review emphasizes on various toxic effects of chlorpyrifos and its metabolites on living organisms. The efforts put to develop the efficient methods for the degradation of the insecticide in soil and water i.e. photocatalytic, biodegradation, electrochemical and others have been discussed. Analytical techniques used for the study of degraded products and various intermediates formed during degradation under different conditions are summarized. It also includes the general pathway for the degradation of chlorpyrifos. The review will help in the development of tools for degradation and mineralization of organophosphate pesticides by knowing the mechanism of degradation and applicability of the developed process at a large scale.

Chlorpyrifos inhibits nitrogen fixation in rice-vegetated soil containing Pseudomonas stutzeri A1501

Chlorpyrifos, a common organophosphorus pesticide, is widely used for agricultural pest control and can inhibit nitrogen-fixing bacteria biomass in paddy. In this study, the additions of chlorpyrifos (1 and 8 mg kg−1) to soil, with or without Pseudomonas stutzeri A1501, resulted in a significant decrease in nitrogen fixation, despite insignificant effects on the abundances of P. stutzeri A1501 and bacteria in soil. Toxic effect of chlorpyrifos on P. stutzeri A1501 nitrogenase activity in medium was also observed, accompanied by a significant reduction in the expression of nitrogen-fixing related genes (nifA and nifH). Furthermore, rhizosphere colonization and biofilm formation by P. stutzeri A1501 were repressed by chlorpyrifos, leading to decreased nitrogenase activity in the rhizosphere. Biofilm formation in medium was inhibited by bacterial hyperkinesis and reduction of extracellular polymeric substance, including exopolysaccharides and proteins. Together, these findings showed that chlorpyrifos-induced production of reactive oxygen species (ROS) which was directly responsible for reduced nitrogenase activity in the medium, soil, and rhizosphere by inhibiting the expressions of nitrogen-fixing related genes. Furthermore, the inhibition of biofilm formation by chlorpyrifos or ROS likely aggravated the reduction in rhizospherere nitrogenase activity. These findings provide potentially valuable insights into the toxicity of chlorpyrifos on nitrogen-fixing bacteria and its mechanisms. Furthermore, for sustainable rice production, it is necessary to evaluate whether other pesticides affect nitrogen fixation and select pesticides that do not inhibit nitrogen fixation.

Comparative study of esterase activities in different tissues of marine fish species Trachurus trachurus, Merluccius merluccius and Trisopterus luscus

Pesticides are one of the most frequently anthropogenic xenobiotics detected in water. Among these, the organophosphorus pesticides (OPs) are very widely used in agriculture due to their broad spectrum of activity and their low price, but they also have high potent effects as neurotoxic compounds in non-target organisms. The aim of this study was to evaluate biomarkers acetylcholinesterase (AChE), butyrylcholinesterase (BChE), propionylcholinesterase (PChE) and carboxylesterase (CbE) in the representative Atlantic fish species Trachurus trachurus, Merluccius merluccius and Trisopterus luscus from “Rías Gallegas”, a traditional Spanish fishing area. These esterase activities were evaluated in the brain, muscle and liver to determine the most adequate tissue to measure such enzymatic activities. The sensitivity of AChE and CbE activities from different tissues the widely used organophosphorus insecticide chlorpyrifos (CP), and its toxic metabolite (CP-oxon) was also tested. AChE activity was predominant in all tissues of the analysed species (particularly in brain constituting from 78.33%, 89.83% and 88.43% of total ChEs in Trachurus trachurus, Merluccius merluccius and Trisopterus luscus, respectively). Under in vitro exposure, esterases were shown to be highly sensitive to CP and especially to CP-oxon. Moreover, a similar effect observed on AChE and CbE activities could suggest that CbE activity might contribute efficiently against the toxic effects of CP, especially in muscle and the liver. The presence of BChE, PChE and upper CbE activities in muscle and the liver and their OP-sensibilities can be used to study their function in the pesticide biochemical detoxification pathways with a prominent role as a safeguarding mechanism against pesticide toxicity.

Toxic Effects of Chronic Chlorpyrifos Exposure on Jejunum of Adult Male Albino Rats and the Possible Ameliorative Role of Propolis

Chlorpyrifos (CPF), as an extensively used organophosphorus pesticide, has many toxic hazards on health. There is a lack of data regarding the toxic effect of CPF on Gut. Aim of the work: to investigate the toxic effect of chronic oral exposure to chlorpyrifos on jejunum of adult male albino rats and to evaluate the ameliorative role of propolis. Methodology: The study extended for 12 weeks and included fifty male albino rats that were divided into 4 groups as follows: control group (I) consisted of 20 rats equally and randomly subdivided into 2 subgroups: Ia (-ve control) & Ib (+ve control). propolis group (II) 10 rats treated with 400 mg/kg body weight of propolis dissolved in corn oil by oral gavage. chlorpyrifos group (III): 10 rats treated with CPF at a daily dose of 6.75 mg/kg {1/20 of the oral LD50 of CPF (135mg/kg)} dissolved in corn oil. CPF+propolis group (IV) 10 rats each was gavaged orally with CPF (6.75 mg/kg body weight) with simultaneous administration of propolis (400 mg/kg body weight) once daily. The levels of serum citrulline, circulating endotoxin core antibodies (Endocab IgG) were assessed, GSH & MDA in jejunal mucosa were measured. Histopathological and morphological analysis of the jejunal mucosa was also evaluated. Results: Significant decrease in serum citrulline level, increase Endocab IgG with a significant decrease in tissue GSH and increase in MDA in CPF group when compared with control and CPF+Propolis groups with disruption of jejunal epithelium and decrease in both height and width of villi. CPF+propolis group showed no significant difference in MDA levels when compared with control, but significant difference regarding other biochemical and histopathological parameters was detected on comparison with CPF group. Conclusion: CPF induced disruption and increased permeability of epithelial barrier in the jejunum with bacterial translocation and chronic endotoxemia evidenced by Endocab IgG. This may be due to induction of oxidative stress. Propolis as a natural, cheap and available product could partially ameliorate the toxic effect of CPF on jejunum.

Possible Protective Role of Propolis and Nigella Sativa Oil against the Toxic Effects of Chlorpyrifos on the Liver and Testes of Adult Albino Rats

Objective: Pesticides are major contaminants of our environment. Chlorpyrifos (CPF), a broad spectrum organophosphate insecticide, is one of the most used organophosphate pesticides in domestic and industrial applications all over the world. This work was undertaken to evaluate the protective effect of propolisand nigella sativa oil against the toxic effects of Chlorpyrifos on the liver and testes of adult male albino rats. Material and methods: Eighty adult male albino rats were used in this study. They were divided into 8 equal groups: Group I (negative control group); Group II (positive control group); Group III gavaged with propolis (400mg/Kg b. w.); GroupIVgavaged with nigellasativa oil (100 mg/Kg b.w.); Group V with CPF 6.75 mg/ Kg b. w. / (1/20 of the oral LD50); while group VI gavaged with propolis and CPF, group VII gavaged with nigella sativa oil and CPF, and groupVIII gavaged with both propolis and nigella sativa oil and CPF in the same previous doses. All treatments were given by oral gavage once daily for 12 weeks. Blood samples were obtained for assessment of total antioxidant capacity (TAC). Liver and testicular specimens were obtained for assessment of malondialdehyde (MDA) and histopathological examination by light and electron microscopes. Results: CPF induced chronic toxic effects in the liver and testes which were evidenced by significant increases in hepatic and testicular MDA and significant decrease in TAC serum levels. These results were confirmed by structural and ultra-structural alterations in liver and testes of CPF treated rats. Administration of propolis or nigella sativa alone or in combination ameliorated CPF induced toxic effects, but the most remarkable effects were observed in rats treated with combination of Propolis and nigella sativa. Conclusion: Combination of propolis and nigella sativa had marked protective effects against CPF-induced toxicity in liver and testes of adult albino rats.

In vitro protection of human lymphocytes from toxic effects of chlorpyrifos by selenium-enriched medicines.

Chlorpyrifos (CP) is a broad-spectrum organophosphorus pesticide used extensively in agricultural and domestic pest control, accounting for 50% of the global insecticidal use. In the present study, protective effects of two selenium-enriched strong antioxidative medicines IMOD and Angipars were examined in human lymphocytes treated with CP in vitro. Isolated lymphocytes were exposed to 12 µg/ml CP either alone or in combination with effective doses (ED50) of IMOD (0.2 µg/ml) and Angipars (1 µg/ml). After 3 days incubation, the viability and oxidative stress markers including cellular lipid peroxidation (LPO), myeloperoxidase (MPO), total thiol molecules (TTM), and total antioxidant power (TAP) were evaluated. Also, the levels of tumor necrosis factor-α (TNF-α), as inflammatory index along with acetylcholinesterase (AChE) activity and cell apoptosis were assessed by flow cytometry. Results indicated that effective doses of IMOD and Angipars reduced CP-exposed lymphocyte mortality rate along with oxidative stress. Both agents restored CP-induced elevation of TNF-α and protected the lymphocytes from CP-induced apoptosis and necrosis. Overall, results confirm that IMOD and Angipars reduce the toxic effects associated with CP through free radical scavenging and protection from apoptosis and necrosis.

Protective effects of curcumin and vitamin E against chlorpyrifos-induced lung oxidative damage.

There are increasing concerns regarding the toxic effects of chlorpyrifos (CPF) on human health. Curcumin (CUR) is a yellow pigment isolated from turmeric ground rhizome of Curcuma longa Linn., which has been identified as an antioxidant agent. This study was designed to examine the protective effect of CUR and vitamin E (Vit E) on CPF-induced lung toxicity. Rats were divided into seven groups: control, CPF (13.5 mg/kg, orally), CPF + CUR (100 and 300 mg/kg, respectively, orally), CPF + α-tocopherol (Vit E, 150 mg/kg, intraperitoneally), CPF and CUR (100 and 300 mg/kg, respectively) in combination with α-tocopherol. The regimens were administered once daily for 28 days. At the end of the treatment period, lungs were collected for evaluation of oxidative factors and histopathological parameters. CUR and Vit E led to a decrease in lipid peroxidation in the lungs of the CPF-injected animals (48% and 51%, respectively). Glutathione peroxidase inhibited by CPF (91.9 nmol/min/mg protein) was induced again by CUR and Vit E (167.1 and 171.8 nmol/min/mg protein). CUR and Vit E caused a significant induction of superoxide dismutase (103.4 U/mg protein). Catalase activity almost returned to normalcy in CPF-intoxicated rats subjected to CUR + Vit E treatment (p < 0.001). Lung sections from CPF-treated rats displayed histopathological damages, while coadministration of CUR and Vit E resulted in apparently normal morphology with a significant decrease in injuries (p < 0.05). Our findings revealed that coadministration of Vit E and CUR to CPF-treated animals prevents the oxidative damages in the lung tissues.

Clinico-haemato-biochemical changes due to the induced acute toxicity of chlorpyrifos in rabbits (Oryctolagus Cuniculus)

The present study was aimed to assess the acute toxic effects of chlorpyrifos using rabbits as mammalian model. Chlorpyrifos @ 1000 mg kg−1 body weight as single oral dose (Lara-909 containing 50% chlorpyrifos) caused marked clinical changes with 50% mortality over 24 hr. Death was associated with muscular spasms and unconsciousness. Haematology showed a significant increase in mean lymphocyte and basophil counts. The blood glucose, total protein, albumin, globulin, alanine transaminase, aspartate aminotransferase, blood urea nitrogen and creatinine were not altered significantly. It was concluded that acute chlorpyrifos toxicity was characterized by marked clinical changes and mortality without any marked alterations in the haemato-biochemical indices.

Toxic effects of chlorpyrifos on lysozyme activities, the contents of complement C3 and IgM, and IgM and complement C3 expressions in common carp (Cyprinus carpio L.)

Chlorpyrifos is one of the organophosphate pesticides widely used in agricultural practices throughout world. It has resulted in a series of toxicological and environmental problems, such as impacts on many non-target aquatic species, including fish. In the present study, toxic effects of chlorpyrifos on lysozyme activities, contents of IgM and complement C3, and the expressions of IgM and complement C3 at mRNA level in common carp were evaluated by acute exposure of 15 (1/10 LC50) or 75μgL−1 (1/2 LC50) of chlorpyrifos for 7d. The results of acute toxicity tests showed that the 96h-LC50 of chlorpyrifos for common carp was determined to be 149μgL−1. We also found that chlorpyrifos promoted lysozyme activities at the earlier stages of exposure but inhibited it at the late stages in the serum, hepatopancreas, and spleen of common carp. Furthermore, it was observed that chlorpyrifos-exposure decreased IgM contents in fish serum and spleen while increased it in kidney. No obvious change was found in the contents of complement C3 in fish spleen, while a slight increase of complement C3 was observed in fish serum and kidney after 1d of chlorpyrifos-exposure. In addition, the results of quantitative real-time PCR showed that IgM and complement C3 expressions were up-regulated at the earlier stage of exposure but down-regulated at later stage. Our results indicate that chlorpyrifos causes immunotoxicity to common carp.

Sub-chronic exposure to chlorpyrifos induces hematological, metabolic disorders and oxidative stress in rat: Attenuation by glutathione

The current work aimed to investigate the different toxic effects of chlorpyrifos (CPF) in subchronic exposure. Two groups of Sprague-Dawley male rats were exposed to CPF alone in a dose of 30mg/kg body weight, or CPF dose as previous plus glutathione (GSH) in a dose of 100mg/kg body weight, for 90 days, twice weekly, orally. Another two groups of rat were given corn oil (control) or GSH. There is a significant decrease in hemoglobin concentration, haematocrit percentage, thrombocytic indices, total protein and albumin levels in CPF-exposed group. CPF induced hyperglycemia and significant increase in total cholesterol, but a significant decrease in triglyceride levels was obtained. A significant increase in the levels of lipid peroxidation was obtained while a significant decrease of the total antioxidant was recorded. The decrease in glycogen content and some histopathological changes were observed in liver after CPF exposure. Furthermore, co-administration of GSH can restore some of these alterations.

Use of organic amendments as a bioremediation strategy to reduce the bioavailability of chlorpyrifos insecticide in soils. Effects on soil biology

The sorption capacity of both an organic municipal solid waste by-product (MSW) and a cow manure (CM) in a soil polluted with chlorpyrifos, as well as its effect on soil microbial activity, and weight, reproductive parameters and glutathione-S-transferase activity of two earthworm species ( Eisenia fetida and Lumbricus terrestris) were studied. Chlorpyrifos was added at the recommended application rate (5 L ha −1; 768 mg chlorpyrifos kg −1) and treated with MSW at a rate of 10% and CM at a rate of 5.8% in order to apply the same amount of organic matter to the soil. An unamended polluted soil was used as control. Earthworm cocoon number, average weight of cocoon, and number of juveniles per cocoon were measured after 30 days of incubation, whereas soil enzymatic activities, earthworm weight, and glutathione-S-transferase activity of earthworms were measured after 3, 45 and 90 days. Soil enzymatic activities, reproductive and glutathione-S-transferase activity in both worms decreased in polluted soil. The inhibition percentage of soil enzymatic activities, reproductive and glutathione-S-transferase activity in both worms was lower in MSW-amended soil than for CM-amended soil. The toxic effect of chlorpyrifos on E. fetida was lowest compared to L. terrestris. This suggested that the addition of organic wastes with higher humic than fulvic acid concentration is more beneficial for remediation of soils polluted with chlorpyrifos.

Investigation of the Acute Toxic Effect of Chlorpyrifos on Pseudomonas putida in a Sterilized Soil Environment Monitored by Microcalorimetry

Chlorpyrifos (CPF) is moderately persistent in soils. In our study, microcalorimetry was introduced for the first time to explore the acute toxic effect of CPF on a Pseudomonas strain in sterilized soil. Firstly, it was determined by microcalorimetry that P. putida failed to degrade CPF. Then the acute toxicity of increasing concentrations of CPF to P. putida was determined by its temporal effects on metabolism and counts of colony forming units. Results revealed that the increase of CPF concentration could induce a decrease of the growth rate constant (k) and the total thermal effect (Q (T)), representing an inhibiting action on P. putida. In addition, the colony forming units (CFU) for P. putida were counted. Results showed that the number of P. putida decreased with increasing CPF dose after 18 h of incubation in sterilized soil. Interestingly, the trend of the number of CFU was similar to the growth rate constant k, whereas the trend became irregular after 36 h of incubation. This indicated that P. putida resisted and also expresses high metabolic activity during the exponential growth phase of 18 h; thereafter the microorganisms showed a certain adaptation, even declining in number and activity.

Toxic effects of chlorpyrifos on antioxidant enzymes and target enzyme acetylcholinesterase interaction in mosquito fish, Gambusia affinis

The recovery effect of chlorpyrifos (CPF) on antioxidant enzymes, locomotor behaviour and the target enzyme acetylcholinesterase (AChE) interaction were studied after exposure to 297 μg L −1 (LC 50 for 96 h) in mosquito fish, Gambusia affinis. Activities of the antioxidant enzymes—superoxide dismutase, catalase, glutathione reductase in viscera, and AChE in brain were inhibited at 96 h of exposure. However, induction in lipid peroxidation was observed. The antioxidant levels were restored to near control by 16–18 days. Similarly, swimming speed and AChE were also recovered but comparatively needs longer period. In vitro AChE study indicated that CPF alters the apparent K m values, resulting in a competitive type of inhibition and the inhibitory constant K i was found to be 4.57 × 10 −4 M. The results showed that the organophosphate CPF besides its inhibitory effect on target enzyme AChE also inhibits antioxidant enzymes, which can be used as biomarkers in the pesticide-contaminated aquatic streams.

Toxic effects of chlorpyrifos on morphology and acetylcholinesterase activity in the earthworm, Eisenia foetida

The acute toxicity of chlorpyrifos ( O, O-diethyl- O-(3,5,6-trichloro-2-pyridyl) phosphorothioate) was determined in the earthworm, Eisenia foetida. A 48-h contact test as described by the Organization for Economic Cooperation and Development (OECD) guideline 207 was carried out. The LC 50 of chlorpyrifos was 0.063 μg/cm 2. Inhibition of acetylcholinesterase (AChE: EC 3.1.1.7) activity indicated by in vitro neurotoxic potentiality revealed competitive inhibition and altered K m values widely in a dose-dependent manner. The K i value of chlorpyrifos was 4.20×10 −6 M. AChE activity of LC 50-exposed worms was 62%, 79%, 85%, and 91% inhibited at 12, 24, 36, and 48 h, respectively. Scanning electron microscopic studies revealed the morphological abnormalities in the worms. The present study demonstrates a dose- and time-dependent exposure of chlorpyrifos through skin results, morphological abnormalities, and inhibition of AChE in the earthworm, E. foetida.

The Effects of a Chronic Application of Chlorpyrifos on the Macroinvertebrate Fauna in an Outdoor Artificial Stream System: Species Responses

An outdoor artificial stream system was used to examine the effects of a chronic application of the organophosphate pesticide chlorpyrifos on the invertebrate fauna of the system. Two replicate streams received chlorpyrifos for 21 days at the high dose (5 μg · liter −1) or low dose (0.1 μg · liter −1) or only the carrier solution with which chlorpyrifos is mixed for commercial sale (1,1,1-trichloroethane and xylene). Streams behaved as replicates with respect to five water quality parameters. Seventy-four nonchironomid and 24 chironomid taxa were recorded during the study. The number of taxa and total invertebrate abundance were significantly reduced by both high and low doses of the pesticide. Shannon-Weaver diversity was also reduced by both high and low doses of the pesticide whereas evenness increased in high dose streams. The individual abundances of 9/36 nonchironomid and 13/19 chironomid taxa were significantly reduced by pesticide application; the abundance of one taxon, the gastropod Physastra, increased. The biomass of periphyton in the streams was affected by changes in the abundance of chironomid grazers and Physastra, and the slow recovery of grazers from mortality due to chlorpyrifos appeared to result in a higher biomass of periphyton in the high dose streams than in controls and low dose streams 21 days after dosing ceased. Inverse relationships between the amounts of fine particulate organic matter (FPOM) and the sum of the numbers of all taxa of collector-gatherers (as well as numbers of four individual taxa) were interpreted as disruption of the processing of FPOM by members of this trophic group following toxic effects of chlorpyrifos. The implications of the study for biological monitoring of the direct and indirect effects of chronic doses of chlorpyrifos on streams are discussed, and the use of chironomid larvae and periphyton in biomonitoring to detect pesticide impacts is particularly recommended.