Impacts of carbamate pesticides on olfactory neurophysiology and cholinesterase activity in coho salmon (Oncorhynchus kisutch)

Advances in Microfluidics Techniques for Rapid Detection of Pesticide Residues in Food

Food safety is a significant issue that affects people worldwide and is tied to their lives and health. The issue of pesticide residues in food is just one of many issues related to food safety, which leave residues in crops and are transferred through the food chain to human consumption. Foods contaminated with pesticide residues pose a serious risk to human health, including carcinogenicity, neurotoxicity, and endocrine disruption. Although traditional methods, including gas chromatography, high-performance liquid chromatography, chromatography, and mass spectrometry, can be used to achieve a quantitative analysis of pesticide residues, the disadvantages of these techniques, such as being time-consuming and costly and requiring specialist staff, limit their application. Therefore, there is a need to develop rapid, effective, and sensitive equipment for the quantitative analysis of pesticide residues in food. Microfluidics is rapidly emerging in a number of fields due to its outstanding strengths. This paper summarizes the application of microfluidic techniques to pyrethroid, carbamate, organochlorine, and organophosphate pesticides, as well as to commercial products. Meanwhile, the study also outlines the development of microfluidics in combination with 3D printing technology and nanomaterials for detecting pesticide residues in food.

Effects of the herbicide glyphosate on fish from embryos to adults: a review addressing behavior patterns and mechanisms behind them

The use of agrochemicals has grown in recent years following the increase in agricultural productivity, to eliminate weeds that can compromise crop yields. The intensive use of these products combined with the lack of treatment of agricultural wastewater is causing contamination of the natural environments, especially the aquatics. Glyphosate [N-(phosphonomethyl) glycine] is the most commonly used herbicide in agriculture worldwide. Studies have shown that this compound is toxic to a variety of fish species at the concentrations of environmental relevance. Glyphosate-based herbicides can affect fish biochemical, physiological, endocrine, and behavioral pathways. Changes in behaviors such as foraging, escaping from predators, and courtship can compromise the survival of species and even communities. The behavior patterns of fish has been shown to be a sensitive tool for risk assessment. In this sense, this review summarizes and discusses the toxic effects of glyphosate and its formulations on the behavior of fish in different life stages. Additionally, behavioral impairments were associated with other negative effects of glyphosate such as energy imbalance, stress responses, AChE inhibition, and physiological and endocrine disturbances, which are evidenced and described in the literature. Graphical abstract.

Isoprocarb causes neurotoxicity of zebrafish embryos through oxidative stress-induced apoptosis

Isoprocarb is a widely used carbamate insecticide in agriculture and aquaculture. Overuse of isoprocarb always leaves toxic residues in soil and water, however, the potential ecotoxicity of isoprocarb to organisms is still confusing. In this study, zebrafish embryo was used as a model to evaluate the toxicity of isoprocarb. Zebrafish embryos (96 hpf) were separately exposed at different concentrations of isoprocarb. The mortality rate, hatchability rate, average heart beat of the zebrafish embryo were separately calculated. Our results suggested that exposure to isoprocarb induced developmental toxicity in zebrafish embryos. HE staining showed that exposure to isoprocarb caused developmental defect in the hindbrain of zebrafish embryos. As expected, the behavioral analysis also showed that the motor ability of zebrafish embryos were significantly inhibited following exposure to isoprocarb. In terms of mechanism, The expressions of genes involved in neurodevelopment signaling pathways, such as foxo3a, gfap, syn2a, elavl3 and sox19b, were inhibited in zebrafish embryos after exposure to isoprocarb. The acetylcholinesterase (AChE) activity was also reduced in isoprocarb-treated zebrafish embryos. Moreover, oxidative stress was induced by increasing the reactive oxygen species (ROS) level and decreasing the activity of antioxidant enzyme (SOD) after exposure to isoprocarb. Expectedly, acridine orange (AO) staining and the detection of some apoptosis-related genes revealed that oxidative stress resulted in apoptosis. In short, the expressions of genes associated with the neurodevelopmental signaling pathway are inhibited, and oxidative stress is also induced in zebrafish embryos after exposure to isoprocarb, which may be the molecular basics of isoprocarb-induced neurotoxicity in zebrafish embryos.

Exposure to carbamate fungicide iodocarb does not affect reproductive behavior or milt volumes in precocious male brown trout (Salmo trutta L.) parr

Previous studies with olfactory-disturbing pesticides resulted after exposure in disturbed behavior and physiology in fish. In the present experiment, reproductive behavior and milt volumes of precocious brown trout (Salmo trutta L.) male parr were studied in a large stream aquarium after exposure to the olfactory-disturbing fungicide 15 μg l^-1 IPBC (iodocarb; 3-iodo-2-propynyl butyl carbamate) for 96 h. The statistical analyses did not reveal any significant differences for time attending females between controls and IPBC-exposed males. Furthermore, there were no significant differences in milt volumes. However, when taking all fish into consideration, there were significant differences in milt volumes between parr that had been attending females and those had not been attending females. Controls that had attended females had significantly higher milt volumes than controls or IPBC-exposed males that had not attended females. Taking all control and IPBC parr into consideration, there was a statistically significant positive correlation between time attended females and volume of milt and gonadosomatic index (GSI), respectively. In summary, 15 μg l^-1 IPBC did not have any significant effects on mature male parr reproductive behavior and milt volumes.

Effect of Deepwater Horizon Crude Oil Water Accommodated Fraction on Olfactory Function in the Atlantic Stingray, Hypanus sabinus

The Deepwater Horizon oil spill was the largest accidental marine oil spill in history, releasing nearly 5 million barrels of crude oil. Crude oil causes both lethal and sublethal effects on marine organisms, and sensory systems have the potential to be strongly affected. Marine fishes rely upon the effective functioning of their sensory systems for detection of prey, mates, and predators. However, despite the obvious importance of sensory systems, the impact of crude oil exposure upon sensory function remains largely unexplored. Here we show that olfactory organ responses to amino acids are significantly depressed in oil exposed stingrays. We found that the response magnitude of the electro-olfactogram (EOG) to 1 mM amino acids decreased by an average of 45.8% after 48 h of exposure to an oil concentration replicating that measured in coastal areas. Additionally, in oil exposed individuals, the EOG response onset was significantly slower, and the clearing time was protracted. This study is the first to employ an electrophysiological assay to demonstrate crude oil impairment of the olfactory system in a marine fish. We show that stingrays inhabiting an area impacted by an oil spill experience reduced olfactory function, which would detrimentally impact fitness, could lead to premature death, and could cause additional cascading effects through lower trophic levels.

Mancozeb exposure results in manganese accumulation and Nrf2-related antioxidant responses in the brain of common carp Cyprinus carpio

Manganese (Mn)-containing dithiocarbamates such as Mancozeb (MZ) have been shown to induce oxidative stress-related toxicity in rodents and humans. However, little is known about the neurotoxic effects induced by MZ in fish. In this study, carp (Cyprinus carpio) were exposed to non-lethal waterborne concentrations of MZ, and oxidative stress parameters as well as metal accumulation in fish brains were evaluated. The experimental groups were as follows: control, MZ 5 mg/L, and MZ 10 mg/L. Fish were exposed for 7 days, and then brain was removed and prepared for subsequent analysis of antioxidant enzymes, reactive oxygen species (ROS), and expression of Nrf2 and phosphoNrf2. In parallel, manganese (Mn) levels were evaluated in blood and brain tissues. Mn levels were significantly increased in blood and brain of MZ-exposed carps. In addition, a concentration-dependent increase (p < 0.05) in ROS levels was observed in parallel to increments (p < 0.05) in the activity of major antioxidant enzymes, such as GPx, GR, and GST. On the other hand, significant decreases (p < 0.05) in CAT and SOD activities were observed. The expression of total and phosphorylated forms of Nrf2 was significantly (p < 0.05) upregulated in the brain of carps exposed to Mz when compared to the control, indicating an activation of the Nrf2 antioxidant pathway. Our study showed for the first time the activation of the Nrf2/ARE pathway and bioaccumulation of Mn induced by MZ exposure in fish species, highlighting important mechanisms of action and its toxicological impacts to aquatic organisms.

In situ toxicity and ecological risk assessment of agro-pesticide runoff in the Madre de Dios River in Costa Rica

The River Madre de Dios (RMD) and its lagoon is a biodiversity rich watershed formed by a system of streams, rivers, channels, and a coastal lagoon communicating with the Caribbean Sea. This basin sustains a large area of agricultural activity (mostly banana, rice, and pineapple) with intensive use of pesticides, continually detected in water samples. We investigated in situ the toxicological effects caused by pesticide runoff from agriculture and the relation of pesticide concentrations with different biological organization levels: early responses in fish biomarkers (sub-organismal), acute toxicity to Daphnia magna (organismal), and aquatic macroinvertebrate community structure. The evaluation was carried out between October 2011 and November 2012 at five sites along the RMD influenced by agricultural discharges and a reference site in a stream outside the RMD that receives less pesticides. Acute toxicity to D. magna was observed only once in a sample from the RMD (Caño Azul); the index of biomarker responses in fish exposed in situ was higher than controls at the same site and at the RMD-Freeman. However, only macroinvertebrates were statistically related to the presence of pesticides, combined with both physical-chemical parameters and habitat degradation. All three groups of variables determined the distribution of macroinvertebrate taxa through the study sites.

Orexin receptor expression is increased during mancozeb-induced feeding impairments and neurodegenerative events in a marine fish

Food intake ensures energy resources sufficient for basic metabolism, immune system and reproductive investment. It is already known that food-seeking performances, which are crucially controlled by orexins (ORXs), may be under the influence of environmental factors including pollutants. Among these, mancozeb (mz) is becoming an environmental risk for neurodegenerative diseases. Due to few studies on marine fish exposed to mz, it was our intention to correlate feeding latency, food intake and feeding duration to potential neurodegenerative processes in key diencephalic sites and expression changes of the ORX neuroreceptor (ORXR) in the ornate wrasses (Thalassoma pavo). Hence, fish exposed for 4 days (d) to mz 0.2 mg/l (deriving from a 0.07, 0.14, 0.2, 0.3 mg/l screening test) displayed a significant reduction (p < 0.05) of food intake compared to controls as early as 1d that became more evident (p < 0.01) after 3d. Moreover, significant enhancements of feeding latency were reported after 1d up to 3d (p < 0.001) and even feeding duration was enhanced up to 3d (p < 0.001), which instead moderately increased after 4d (p < 0.05). A reduction (-120%; p < 0.001) of mean body weight was also detected at the end of exposure. Likewise, a notable (p < 0.001) activation of ORXR protein occurred together with mRNA up-regulations in diencephalic areas such as the diffuse nucleus of the inferior lobe (+48%) that also exhibited evident degenerative neuronal fields. Overall, these results highlight an ORX role as a vital component of the neuroprotective program under environmental conditions that interfere with feeding behaviors.

Reuse water: Exposure duration, seasonality and treatment affect tissue responses in a model fish

Partially remediated gray (reuse) water will likely find increasing use in a variety of applications owing to the increasing scarcity of freshwater. We aimed to determine if a model fish, the goldfish, could sense reuse water using olfaction (smell), and if 30min or 7d (acute) and 60d (sub-chronic) exposures would affect their olfactory responses to natural odorants. We examined olfaction as previous studies have found that numerous chemicals can impair the olfactory sense, which is critical to carrying out numerous life-sustaining behaviors from feeding to mating. We also examined if fish olfactory and liver tissues would mount a response in terms of biotransformation enzyme gene expression, and whether treatment of reuse water with UV/H₂O₂ ameliorated adverse effects following reuse water exposure. We found that fish olfactory tissue responded to reuse water as it would to a natural odorant and that UV/H₂O₂ treatment had no influence on this. With acute exposures, olfactory impairment was apparent regardless of water type (e.g. responses of 23-55% of control), but in sub-chronic exposures, only the untreated reuse water caused olfactory impairment. The exposure of fish to reuse water increased the expression of one enzyme (CYP1A; >2.5-6.5 fold change) and reuse water treatment with UV/H₂O₂ reversed the effect. There was a seasonal effect that was likely due to changes in water quality (60d summer exposure impaired olfaction whereas spring and fall exposures did not). Overall, the data suggest that reuse water may be detected by olfaction, impair olfactory responses in fish receiving unavoidable exposures, and that exposure duration and season are important factors to consider regarding adverse effects.

Effects of Glyphosate-Based Herbicide Sub-Lethal Concentrations on Fish Feeding Behavior

Glyphosate-based herbicides are widely used in agricultural systems. Although the target organism are particularly plant organisms, there are numerous studies showing adverse effects in aquatic animals, such as inhibition of acetyl cholinesterase, effects on kidney, liver, and gill and stressors effects. This study analyzed the effects of commercial formulation of glyphosate on feeding behavior in Pacu (Piaractus mesopotamicus). Fish were exposed to three glyphosate concentrations (0.2, 0.6, and 1.8 ppm) for 15 days. At concentrations of 0.2 and 0.6 ppm, food intake decreased on day 13 and then returned to normal on day 15. At the highest glyphosate-based herbicide concentration, 1.8 ppm, food consumption decreased dramatically and did not recover on day 15. This study showed that glyphosate-based herbicide at sub-lethal concentrations can affect feed intake in pacu and consequently inhibits its growth.

A meta-analysis synthesizing the effects of pesticides on swim speed and activity of aquatic vertebrates

Pesticide contaminants are ubiquitous in aquatic environments and pose a threat to biodiversity. Pesticides also have diverse mechanisms of action that make it difficult to identify impacts on exposed wildlife. Behavioral measures represent an important link between physiological and ecological processes, and are often used to generalize sub-lethal effects of pesticide exposure. In order to bridge the toxicological and behavioral literature, and identify chemical classes that denote the largest threat, we conducted a meta-analysis summarizing the effects of pesticides on swim speed and activity of aquatic vertebrates. We found that exposure to environmentally relevant concentrations of pesticides reduced the swim speed of exposed amphibians and fish by 35%, and reduced overall activity by 72%. There were also differences in the magnitude of this effect across chemical classes, which likely reflect underlying physiological processes. Pyrethroids, carbamates, and organophosphates all produced a large decrease in swim speed, where as phosphonoglycines and triazines showed no overall effect. Pyrethroids, carbamates, organophosphates, organochlorines, and organotins also produced a large decrease in activity, while phosphonoglycines had no overall effect, and triazines had the opposite effect of increasing activity. Our results indicate that even sub-lethal concentrations of pesticides have a strong effect on critical behaviors of aquatic vertebrates, which can affect fitness and alter species interactions. We expect our synthesis can be used to identify chemical classes producing the largest sub-lethal effects for further research and management.

Olfactory Transcriptional Analysis of Salmon Exposed to Mixtures of Chlorpyrifos and Malathion Reveal Novel Molecular Pathways of Neurobehavioral Injury

Pacific salmon exposed to sublethal concentrations of organophosphate pesticides (OP) have impaired olfactory function that can lead to loss of behaviors that are essential for survival. These exposures often involve mixtures and can occur at levels below those which inhibit acetylcholinesterase (AChE). In this study, juvenile Coho salmon were exposed for 24 h to either 0.1, 0.5, or 2.5 ppb chlorpyrifos (CPF), 2, 10, or 50 ppb malathion (MAL), or binary mixtures of 0.1 CPF:2 ppb MAL, 0.5 CPF:10 ppb MAL, or 2.5 CPF:10 ppb MAL to mimic single and binary environmental exposures. Microarray analysis of olfactory rosettes from pesticide-exposed salmon revealed differentially expressed genes involved in nervous system function and signaling, aryl hydrocarbon receptor signaling, xenobiotic metabolism, and mitochondrial dysfunction. Coho exposed to OP mixtures exhibited a more pronounced loss in detection of a predatory olfactory cue relative to those exposed to single compounds, whereas respirometry experiments demonstrated that exposure to OPs, individually and in mixtures, reduced maximum respiratory capacity of olfactory rosette mitochondria. The observed molecular, biochemical, and behavioral effects occurred largely in the absence of effects on brain AChE. In summary, our results provide new insights associated with the sublethal neurotoxic effects of OP mixtures relevant to environmental exposures involving molecular and cellular pathways of injury to the salmon olfactory system that underlie neurobehavioral injury.

Effects of chlorpyrifos on the transcription of CYP3A cDNA, activity of acetylcholinesterase, and oxidative stress response of goldfish (Carassius auratus)

Chlorpyrifos (CPF) is the widely used organophosphate pesticide in agriculture throughout the world. It has been found that CPF is relatively safe to human but highly toxic to fish. In this study, acute toxicity of CPF on goldfish was determined and then the transcription of goldfish cytochrome P450 (CYP) 3A was evaluated after 96 h of CPF exposure at concentrations of 15.3 [1/10 50% lethal concentration (LC50 )] or 51 μg L(-1) (1/3 LC50 ) of CPF. Meanwhile, the enzymatic activities of acetylcholinesterase (AChE), superoxide dismutase (SOD), and catalase (CAT), total antioxidant activity (T-AOC), and the contents of malondialdehyde (MDA) in the liver or brain of goldfish were also determined. The results of acute toxicity testing showed that the 96-h LC50 of CPF to the goldfish was 153 μg L(-1) . Moreover, a length sequence of 1243 bp CYP3A cDNA encoding for 413 amino acids from goldfish liver was cloned. Polymerase chain reaction results reveal that CPF exposure downregulates CYP 3A transcription in goldfish liver, suggesting that goldfish CYP 3A may be not involved in CPF bioactivation. Finally, the results of biochemical assays indicate that 96 h of CPF exposure remarkably inhibits AChE activity in fish liver or brain, alters hepatic antioxidant enzyme activities, decreases brain T-AOC, and causes lipid peroxidation in fish liver. These results suggest that oxidative stress might be involved in CPF toxicity on goldfish.

Effects of carbofuran and deltamethrin on acetylcholinesterase activity in brain and muscle of the common carp

This work investigated the effect from exposure to insecticides carbofuran and deltamethrin on acetylcholinesterase (AChE) activity in the brain and muscle of common carp (Cyprinus carpio). Both pesticides were evaluated through two separate experiments, and carp were exposed in a semi-static system to three different concentrations of carbofuran (10, 50, and 100 μg/L) and deltamethrin (0.08, 0.4, and 0.8 μg/L) during a month with sampling times at 0, 4, 15, and 30 days (n = 7 from each aquarium). AChE activity was significantly inhibited in both organs of carps exposed to carbofuran at all sampling times depending on dose and time, reaching inhibition values of 73.5 and 67.1%, in brain and muscle tissues respectively, after 30 days with the highest concentration. On the contrary, AChE activity was not significantly affected after deltamethrin exposure at all concentrations and times of the assay. This study shows that the measurement of brain and muscle AChE activity in Cyprinus carpio is a useful biomarker of carbamates exposure and/or effects, but has no application with pyrethroids.

In situ exposure history modulates the molecular responses to carbamate fungicide Tattoo in bivalve mollusk

The aim of the present study was the investigation of the effect of in situ exposure history on the responses of freshwater mussels to thiocarbamate fungicide. Male bivalve mollusks Anodonta anatina (Unionidae) from polluted (A) and unpolluted (F) sites were subjected to 14 days of exposure to fungicide Tattoo (mixture of propamocarb and mancozeb, 91 μg L(-1)). When unexposed mussels were compared, chronic effect of toxic environment in site A was confirmed by oxidative stress indices (high levels of superoxide dismutase and catalase activities, lipid peroxidation, protein carbonyls and oxyradical production, low level of total glutathione (GSH)), genotoxicity (high levels of DNA-strand breaks and caspase-3 activity in digestive gland), and cytotoxicity (low lysosomal membrane stability in hemocytes), elevated vitellogenin-like proteins (Vtg-LP) concentration in gonads, high levels of Cu, Zn, Cd, metallothionein (MT)-bound metals (MT-Me) and MT-related thiol (MT-SH), and low ethoxyresorufin-O-deethylase (EROD) activity in digestive gland. The major differences in the responses of the two exposed groups were related to antioxidant defense and MT: in the group A, prominent oxidative stress response with the participation of MT-SH and GSH in the gills, EROD activation, but decrease of MT-Me level was shown, whereas in group F exposure provoked the elevation of MT-Me, caspase-3 and Vtg-LP values. Carbamate did not cause cholinesterase depletion and cytotoxicity. However, genotoxic and pro-oxidant effects (increased levels of hemocytes with micronuclei and nuclear abnormalities, DNA-strand breaks and oxyradical in digestive gland), were common responses for both the exposed groups.

Kinetic and physicochemical properties of brain acetylcholinesterase from the peacock bass (Cichla ocellaris) and in vitro effect of pesticides and metal ions

Brain acetylcholinesterase (AChE; EC 3.1.1.7) from peacock bass (Cichla ocellaris) was characterized and the effect of organophosphorus and carbamate pesticides as well as ions and heavy metals was evaluated. The kinetic parameters K(m) and V(max) were determined as 0.769 mM and 0.189 U/mg of protein respectively. Optimal pH and temperature were found to be 8.0 and 45°C. The enzyme retained approximately half of the activity after incubation at 50°C for 30 min. Total cholinesterase activity on brain of this species can be ascribed to AChE according to selective inhibitors analysis (neostigmine, eserine and BW284c5 reduced its activity whereas no effect was noticed for Iso-OMPA). Seven pesticides (five organophosphates: dichlorvos, diazinon, chlorpyrifos, temephos, tetraethyl pyrophosphate - TEPP and two carbamates: carbaryl and carbofuran) showed inhibitory effects on C. ocellaris AChE. However, the strongest effect was observed with carbofuran (IC(50)=0.21 μM and K(i)=2.57 × 10(-3) μM). The following ions (1 mM) showed to inhibit its activity (decrescent order): Hg(2+)>As(3+)>Cu(2+)>Zn(2+). EDTA(2-) did not affect enzyme activity. The present study provides assay conditions and data to suggest this enzyme as in vitro biomarker of organophosphorus and carbamate pesticides in routine environmental screening programs.

Using physiology and behaviour to understand the responses of fish early life stages to toxicants

The use of early life stages of fishes (embryos and larvae) in toxicity testing has been in existence for a long time, generally utilizing endpoints such as morphological defects and mortality. Behavioural endpoints, however, may represent a more insightful evaluation of the ecological effects of toxicants. Indeed, recent years have seen a considerable increase in the use of behavioural measurements in early life stages reflecting a substantial rise in zebrafish Danio rerio early life-stage toxicity testing and the development of automated behavioural monitoring systems. Current behavioural endpoints identified for early life stages in response to toxicant exposure include spontaneous activity, predator avoidance, capture of live food, shoaling ability and interaction with other individuals. Less frequently used endpoints include measurement of anxiogenic behaviours and cognitive ability, both of which are suggested here as future indicators of toxicant disruption. For many simple behavioural endpoints, there is still a need to link behavioural effects with ecological relevance; currently, only a limited number of studies have addressed this issue. Understanding the physiological mechanisms that underlie toxicant effects on behaviour so early in life has received far less attention, perhaps because physiological measurements can be difficult to carry out on individuals of this size. The most commonly established physiological links with behavioural disruption in early life stages are similar to those seen in juveniles and adults including sensory deprivation (olfaction, lateral line and vision), altered neurogenesis and neurotransmitter concentrations. This review highlights the importance of understanding the integrated behavioural and physiological response of early life stages to toxicants and identifies knowledge gaps which present exciting areas for future research.

Characterization of phospholipid hydroperoxide glutathione metabolizing peroxidase (gpx4) isoforms in Coho salmon olfactory and liver tissues and their modulation by cadmium

Exposure to environmental contaminants, including various pesticides and trace metals, can disrupt critical olfactory-driven behaviors of fish such as homing to natal streams, mate selection, and an ability to detect predators and prey. These neurobehavioral injuries have been linked to reduced survival and population declines. Despite the importance of maintaining proper olfactory signaling processes in the presence of chemical exposures, little is known regarding chemical detoxification in the salmon olfactory system, and in particular, the antioxidant defenses that maintain olfactory function. An understudied, yet critical component of cellular antioxidant defense is phospholipid hydroperoxide glutathione peroxidase (PHGPx/GPx4), an isoform within the family of selenium-dependent glutathione peroxidase (GPx) enzymes that can directly reduce lipid peroxides and other membrane-bound complex hydroperoxides. In this study, we cloned two gpx4 isoforms (gpx4a and gpx4b) from Coho salmon olfactory tissues and compared their modulation in olfactory and liver tissues by cadmium, an environmental pollutant and olfactory toxicant that cause oxidative damage as a mechanism of toxicity. Amino acid sequence comparisons of the two gpx4 isoforms shared 71% identity, and also relatively high sequence identities when compared with other fish GPx4 isoforms. Sequence comparisons with human GPx4 indicated conservation of three important active sites at selenocysteine (U46), glutamine (Q81), and tryptophan (W136), suggesting similar catalytic activity between fish and mammalian GPx4 isoforms. Tissue profiling confirmed the expression of gpx4a and gpx4b in all ten Coho tissues examined. The expression of gpx4 mRNAs in the Coho olfactory system was accompanied by comparably high initial rates of GPx4 enzymatic activity in mitochondrial and cytosolic fractions. Exposure to low (3.7 ppb) and high (347 ppb) environmental Cd concentrations for 24-48 h significantly decreased gpx4a expression in Coho olfactory rosettes, whereas olfactory gpx4b mRNA expression was not modulated by exposures at these concentrations. In summary, Coho salmon express two paralogs of gpx4, a key enzyme in the maintenance of signal transduction processes that protect against cellular oxidative damage. The Cd-associated downregulation of salmon olfactory gpx4a expression in particular, may be associated with the loss of olfactory signal transduction that accompanies metal-associated loss of olfaction in salmonids.

Population-related molecular responses on the effect of pesticides in Carassius auratus gibelio

The aim of this study was to evaluate population-related peculiarities of the adaptive responses of Carassius auratus gibelio. In order to do this, male specimens from polluted (B) and clean (Z) sites were exposed to commercial pesticides thiocarbamate Tatoo (9.1 μg·L(-1)and 91 μg·L(-1)) or tetrazine Apollo (2 μg·L(-1) and 10 μg·L(-1)) during fourteen days. The control fish from site B was distinguished by weakness of antioxidant defence (measured from superoxide dismutase and catalase activities, redox index of glutathione (GSH), superoxide anion (O(2)) and lipid peroxidation levels), imbalance of the concentrations of protein metallothionein (MT-SH) and MT-related metals (MT-Me) and neurotoxicity. Differences in glutathione-S-transferase activity in the liver and vitellogenin-like proteins in the serum were also showed between B and Z control groups. Common effects of pesticides were related to a decrease in GSH, an increase in O(2) production, ethoxyresorufin O-deethylase activity and hepatosomatic index. Apollo provoked particular elevation of MT-SH/MT-Me ratio. Population-related difference in the response was the activation of antioxidant defence in fish from site B and its inhibition in fish from site Z. The genotoxic effect of exposures was more expressed in fish from site B. Principal component analysis combine all exposed groups from site Z and control group from site B in one set, and separated each exposed group from site B. The main distinguishing index of each population selected by classification and regression tree analysis was MT-SH.

Effects of carbofuran on the sea bass (Dicentrarchus labrax L.): study of biomarkers and behaviour alterations

The objective of this study was to investigate the acute effects of the pesticide carbofuran on the sea bass (Dicentrarchus labrax) using parameters at different levels of biological organisation (swimming behaviour and several biomarkers) and possible relationships between alterations found in different effect criteria. In a bioassay, sea bass juveniles were individually exposed to different doses of carbofuran (31, 63, 125 and 250 μg/L) for 96 h. At the end of the bioassay, the swimming performance and 11 biomarkers were determined. Biomarkers were: hepatosomatic index (HSI), lipid peroxidation (LPO), reduced glutathione and the activities of the enzymes ethoxyresorufin O-deethylase (EROD), glutathione S-transferases, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, brain acetylcholinesterase (AChE) and muscle cholinesterases (ChE). After 96 h of exposure, carbofuran induced a decrease of the swimming velocity and inhibition of EROD activity at all concentrations tested, and inhibition of muscle ChE and brain AChE activities at 250 μg/L. No relevant alterations in any of the other tested parameters were found. These results show that carbofuran induced adverse effects on fish by interfering with neurofunction, capability of detoxication and swimming velocity. In addition, positive and significant correlations between the swimming velocity and (i) brain AChE activity, (ii) muscle ChE activity and (iii) EROD activity suggest that the inhibition of these enzymes may somehow be related to the behavioural changes observed. Since these functions are determinant for the survival and performance of the fish in the wild, the findings of the present study suggest that adverse effects may occur in populations exposed to carbofuran if a sufficient number of animals is affected.

Cholinesterase inhibition and behavioral toxicity of carbofuran on Oreochromis niloticus early life stages

Nile tilapia Oreochromis niloticus at 9 days post-hatch were exposed in semi-static experiments to the carbamate insecticide carbofuran, which is applied in agricultural systems in Brazil. Although the molecular mechanism of carbofuran toxicity is well known, a detailed understanding of the ecological mechanisms through which carbofuran effects can propagate towards higher levels of biological organization in fish is incomplete. Mortality rates were quantified for larvae exposed for 96 h to 8.3, 40.6, 69.9, 140, 297 and 397 μg/L carbofuran, and the LC(50) 96 h was 214.7 μg/L. In addition, the biochemical biomarker cholinesterase inhibition and behavioral biomarkers related to vision, swimming, prey capture and predator avoidance were quantified in individual larvae, as well as their growth in weight. The behavioral parameters were quantified by analysis of digitally recorded videos of individual larvae within appropriate experimental setups. The activity of the enzyme cholinesterase decreased after exposure to carbofuran with a lowest observed effects concentration (LOEC) of 69.9 μg/L. Visual acuity deficits were detected after carbofuran exposure with a LOEC of 40.6 μg/L. Swimming speed decreased with carbofuran exposure, with a LOEC of 397.6 μg/L. The number of attacks to prey (Daphnia magna nauplii) decreased in larvae exposed to carbofuran, with a LOEC of 397.6 μg/L. Growth in weight was significantly reduced in a dose dependent manner, and all carbofuran groups exhibited a statistically significant decrease in growth when compared to controls (p<0.05). The number of predator attacks necessary to capture larvae decreased after exposure to carbofuran, and the LOEC was 69.9 μg/L. These results show that exposure of sensitive early life stages of tilapia O. niloticus to sublethal concentrations of carbofuran can affect fundamental aspects of fish larval ecology that are relevant to recruitment of fish populations, and that can be better understood by the application of behavioral biomarkers.

Hypersalinity acclimation increases the toxicity of the insecticide phorate in coho salmon (Oncorhynchus kisutch)

Previous studies in euryhaline fish have shown that acclimation to hypersaline environments enhances the toxicity of thioether organophosphate and carbamate pesticides. To better understand the potential mechanism of enhanced toxicity, the effects of the organophosphate insecticide phorate were evaluated in coho salmon (Oncorhynchus kisutch) maintained in freshwater (<0.5 g/L salinity) and 32 g/L salinity. The observed 96-h LC50 in freshwater fish (67.34 ± 3.41 μg/L) was significantly reduced to 2.07 ± 0.16 μg/L in hypersaline-acclimated fish. Because organophosphates often require bioactivation to elicit toxicity through acetylcholinesterase (AChE) inhibition, the in vitro biotransformation of phorate was evaluated in coho salmon maintained in different salinities in liver, gills, and olfactory tissues. Phorate sulfoxide was the predominant metabolite in each tissue but rates of formation diminished in a salinity-dependent manner. In contrast, formation of phorate-oxon (gill; olfactory tissues), phorate sulfone (liver), and phorate-oxon sulfoxide (liver; olfactory tissues) was significantly enhanced in fish acclimated to higher salinities. From previous studies, it was expected that phorate and phorate sulfoxide would be less potent AChE inhibitors than phorate-oxon, with phorate-oxon sulfoxide being the most potent of the compounds tested. This trend was confirmed in this study. In summary, these results suggest that differential expression and/or catalytic activities of Phase I enzymes may be involved to enhance phorate oxidative metabolism and subsequent toxicity of phorate to coho salmon under hypersaline conditions. The outcome may be enhanced fish susceptibility to anticholineterase oxon sulfoxides.

Alterations in mRNA expression of acetylcholinesterase in brain and muscle of common carp exposed to atrazine and chlorpyrifos

The uses of pesticides and herbicides have become an integral part of modern agricultural systems. The intensive use of pesticides chlorpyrifos (CPF) and herbicides atrazine (ATR) has resulted in serious environmental problems. Herein, we have developed real-time quantitative polymerase chain reaction assays for common carp (Cyprinus carpio L.) mRNA. The levels of AChE mRNA were evaluated in brain and muscle collected from common carp by treatment of ATR, CPF, and their mixture. The decreased transcription of AChE was detected in both tissues at different doses of the toxicants in the end of exposure tests, and the changes were improved in the end of recovery tests in varying degrees. It is suggested that transcription inhibition of AChE might be significant in long-playing single or associated exposure of ATR and CPF in common carp. Alteration in transcription of AChE caused by ATR, CPF, and their mixture could reveal the toxic mechanisms related to cholinergic signaling.

Bioaccumulation of micropollutants and biomarker responses in caged carp (Cyprinus carpio)

At four different aquatic sites in Flanders (Belgium) with different types and degrees of contamination, juvenile carp (Cyprinus carpio) were exposed in cages for 4 weeks. After exposure, metals, polychlorinated biphenyls (PCBs), and selected organochlorine pesticides (OCPs) were analyzed in the tissues of the carp. Besides pollutant accumulation, several effects were measured as well. Condition measures such as changes in weight, condition factor (CF), and hepatosomatic index (HSI) were assessed. In addition, activity of acetylcholinesterase (AChE) and a set of blood biochemical parameters were measured. At all sites, accumulation of metals in the fish tissues was observed. Levels of cadmium and lead at some of the exposure sites were higher than the levels at the start and comparable to levels in fish from moderately metal-contaminated sites. For most organic pollutants, however, levels were not significantly higher than at the start. Only for two PCB congeners, levels had slightly increased but were still lower than levels in carp captured at noncontaminated sites. Although food limitation probably caused some of the observed effects, significant relationships were found between metal load in tissues and CF, AChE, plasma osmolality and HSI. This study shows that caged carp might be useful for the assessment of bioaccumulation and some effects of micropollutants in aquatic ecosystems.

Mixture toxicity assessment of wood preservative pesticides in the freshwater amphipod Gammarus pulex (L.)

All over the world, insecticides and fungicides are used to protect wood against pathogens. To document the environmental toxicity of wood preservative mixtures, freshwater amphipods Gammarus pulex (L.) were submitted to organic pesticides given independently or in mixtures. When given independently at environmentally realistic concentrations, propiconazole and tebuconazole (triazoles fungicides) were not toxic for G. pulex, 3-iodo-2-propinyl butyl carbamate (IPBC, fungicide) was moderately toxic, and cypermethrin (pyrethroid insecticide) was extremely toxic. 96-h LC50 were, respectively, 4703, 1643, 604, and 0.09 microg L(-1). When amphipods were submitted to a mixture mimicking the composition of a commercial solution (18.2% of cypermethrin, 45.8% propiconazole, 17.2% tebuconazole, 18.8% IPBC), the overall toxicity was equal to that of the most toxic component, namely cypermethrin. But, when organisms were submitted to the real commercial mixture containing pesticides, solvents and additives, the toxic effects were markedly higher. Moreover, a third mixture with only 0.002% cypermethrin showed lethality 2.5-18-fold higher than those predicted by the commonly used models. The present results show that toxicity of wood preservative mixtures cannot be assessed starting only from the toxicities of each single component. Furthermore, the present data strongly suggest that the environmental impacts of wood preservative mixtures might be frequently underestimated.

Salmon olfaction is impaired by an environmentally realistic pesticide mixture

Many of the salmon-producing waterways of the world contain pesticides known to harm olfactory sensory neurons (OSNs) that are critically important throughout the salmon lifecycle. The ability of OSNs to retain functionality after exposure to complex pesticide mixtures remains unknown. Here we show that a 96-h exposure to an environmentally realistic concentration of a mixture made from the ten most frequently occurring pesticides in British Columbia's Nicomekl River reduced the OSN responses of rainbow troutto a behaviorally relevant odorant. Odor-evoked responses were not altered by exposure to one-fifth of the realistic concentration, and this may have been due an upregulation in detoxification enzymes, since glutathione-S-transferase activity reached a maximum (> 32% above control) at this concentration. Mixture exposure did not help to prevent OSN impairment from a second, brief (5 min) exposure to a higher (20 x) concentration of the mixture, suggesting longer-term, low-concentration exposures may not prevent damage from brief, high-concentration pulse exposures. This study demonstrates that environmentally observed pesticide mixtures can injure salmon olfactory tissue, and by extension, contribute to the threatened and endangered status of many salmon stocks.

Chemosensory deprivation in juvenile coho salmon exposed to dissolved copper under varying water chemistry conditions

Dissolved copper is an important nonpoint source pollutant in aquatic ecosystems worldwide. Copper is neurotoxic to fish and is specifically known to interfere with the normal function of the peripheral olfactory nervous system. However,the influence of water chemistry on the bioavailability and toxicity of copper to olfactory sensory neurons is not well understood. Here we used electrophysiological recordings from the olfactory epithelium of juvenile coho salmon (Oncorhynchus kisutch) to investigate the impacts of copper in freshwaters with different chemical properties. In low ionic strength artificial fresh water, a short-term (30 min) exposure to 20 microg/L dissolved copper reduced the olfactory response to a natural odorant (10(-5) M L-serine) by 82%. Increasing water hardness (0.2-1.6 mM Ca) or alkalinity (0.2-3.2 mM HCO3-) only slightly diminished the inhibitory effects of copper. Moreover, the loss of olfactory function was not affected by a change in pH from 8.6 to 7.6. By contrast, olfactory capacity was partially restored by increasing dissolved organic carbon (DOC; 0.1-6.0 mg/L). Given the range of natural water quality conditions in the western United States, water hardness and alkalinity are unlikelyto protect threatened or endangered salmon from the sensory neurotoxicity of copper. However, the olfactory toxicity of copper may be partially reduced in surface waters that have a high DOC content.

A comparative study on the relationship between various toxicological endpoints in Caenorhabditis elegans exposed to organophosphorus insecticides

The toxicity of 10 organophophorus (OP) insecticides-acephate, dimethoate, dichlorvos, dicrotophos, monocrotophos, methamidophos, phosphamidon, omethoate, phosdrin, and trichlorfon-was evaluated in Caenorhabditis elegans using lethality, movement, and acetylcholinesterase (AChE) activity as the endpoints after a 4-hr- exposure period. The OP insecticides tested showed LC50 values ranging from 0.039 mM (for dichlorovs) to 472.8 mM (for methamidophos). The order of toxicity for lethality and movement was not significantly different when tested using the rank order correlation coefficient. AChE activity was markedly affected by all the OP insecticide exposures that caused significant inhibition in movement, indicating that the mechanism of toxicity of OP insecticides in C. elegans is the same as in higher animals. All OP insecticides induced greater than 50% inhibition of AChE at the lowest tested OP insecticide concentration resulting in inhibition in movement. While a significant correlation was evident between LC50 values in C. elegans and the LD50 values in rats for the 10 OP insecticides studied, a correlation was not evident between EC50 values in C. elegans and LD50 values in rats. Overall, the two endpoints, LC50 and movement, were more reliable and easier to perform than measurement of AChE activity in C. elegans for determining the toxicity of OP insecticides. Further, ranking of these endpoints with respect to the OP insecticides studied indicates that these parameters in C. elegans are predictive of OP insecticides mammalian neurotoxicity.

Muscular and brain cholinesterase sensitivities to azinphos methyl and carbaryl in the juvenile rainbow trout Oncorhynchus mykiss

The organophosphate azinphos methyl (AzMe) and the carbamate carbaryl are the insecticides mostly used in the irrigated valley of Río Negro and Neuquén, Patagonia, Argentina. Juvenile rainbow trout were exposed to AzMe and carbaryl and the sensitivity of skeletal muscular cholinesterase (ChE) and the time course of inhibition and recovery were evaluated. EC50 values demonstrated that AzMe was a stronger in vivo inhibitor of muscular ChE (1.05+/-0.23 microg/L) than carbaryl (270+/-62.23 microg/L). Muscular ChE was significantly less sensitive to both insecticides than brain ChE. EC50 values obtained for muscular ChE were closer than those for brain ChE to the respective pesticide lethal concentrations, pointing out the relevance of the muscular enzyme in determining acute toxicity. The recovery process of ChE activity after carbaryl exposure (500 microg/L) was fast, whereas no significant recovery was observed with AzMe (1 microg/L) after 21 days in uncontaminated media. Brain and muscular ChE were inhibited and showed a significant but not complete recovery after three consecutive 48-h exposures to AzMe (1 microg/L) followed by a recovery period of 7 days. This scheme mimics the periodical application of the insecticides in the region and suggests a certain probability of a sustained ChE inhibition under field conditions, affecting fish development and survival.

Relating olfactory neurotoxicity to altered olfactory-mediated behaviors in rainbow trout exposed to three currently-used pesticides

Odor-evoked neurophysiological responses can form the basis for behavioral responses. Here we first characterized olfactory-mediated behavioral and neurophysiological responses of juvenile rainbow trout to the amino acid l-histidine, then looked at whether there were similar responses to the carbamate antisapstain IPBC and the herbicides atrazine and Roundup, and lastly explored how exposures to these pesticides modified the l-histidine responses. Trout were behaviorally attracted to 10(-7)M l-histidine (as assayed in a counter-current olfactometer), but this preference behavior switched to indifference with higher histidine concentrations. Neurophysiologically, the summed electrical responses of peripheral olfactory neurons, as measured using electro-olfactogram (EOG), was 0.843+/-0.252 mV to 10(-7)M l-histidine. Of the pesticides, only Roundup evoked EOGs, indicating the amino acid-based pesticide may have acted as an odorant, and generated a behavioral response: it was avoided at active ingredient [AI; glyphosate isopropyl amine] concentrations > or =10 mg/l. With 30 min pesticide exposures, 10(-7)M l-histidine preference behavior was eliminated following exposure to 1 microg/l IPBC and atrazine, and 100 microg/l AI Roundup. Similarly, 10(-7)M l-histidine-evoked EOGs were significantly reduced by exposure to 1 microg/l IPBC, 10 microg/l atrazine, and 100 microg/l AI Roundup. When combined together, the results demonstrate that typical preference behavior can be abolished when neurophysiological responses are reduced by >60% of control. This asymmetry in response thresholds suggests that behavioral responses may be more sensitive toxicological endpoints than neurophysiological responses.

The alarm reaction of coho salmon parr is impaired by the carbamate fungicide IPBC

To determine whether the carbamate fungicide IPBC alters the olfactory-mediated behavioral and physiologic alarm responses of coho salmon parr (Oncorhynchus kisutch), groups of coho were exposed to skin extract (an alarm pheromone source) under a variety of conditions. In the 3min following skin extract exposure, freezing behavior was significantly increased (In the 3 min following skin extract exposure, freezing behavior was significantly increased under darkness (IR lighting) but not ambient lighting (25.3+/-2.6% and 7.5+/-5.7%, respectively; Delta calculated as: [(time (s) after/time (s) before)-1]x100%), and so IR was used for further experiments. Physiologically, following skin extract exposure, plasma cortisol concentration was increased at 0.5h (58.1+/-14.6ng/ml versus 4.32+/-1.31ng/ml, exposed versus control), hematocrit (Hct) was increased at 2h (50.4+/-1.0% versus 41.7+/-1.6%), and leucocrit (Lct) was decreased at 0.5 and 2h (0.534+/-0.114 and 0.13+/-0.01% versus 1.23+/-0.20%). After 0.5h exposures to 0, 1, 10 and 100microg/l IPBC and skin extract, the time spent dashing (>5cm/s) increased significantly (323+/-118%) in the first minute after skin extract exposure, but was absent in IPBC-exposed coho. Freezing behavior increased after skin extract exposure with control and 1microg/l IPBC exposures (11.0+/-3.0% and 17.7+/-11.0%, respectively), but was absent after 10microg/l and decreased after 100microg/l IPBC. Physiologically, Hct and plasma lactate concentration were significantly increased above controls after 1microg/l IPBC exposure (Hct: 45.7+/-1.6% versus 34.0+/-1.6%, lactate: 12.8+/-1.2mM versus 3.30+/-1.2mM). After 10microg/l exposure, IPBC alone elicited a stress response similar to skin extract. However in the 100microg/l treatment group the stress parameters were not different from controls. These findings suggest that the behavioral and physiologic alarm responses of juvenile salmonids may be impaired by acute exposure to > or =1microg/l IPBC.

Cholinesterase inhibition and impacts on behavior of the Asian clam, Corbicula fluminea, after exposure to an organophosphate insecticide

This study assessed the effects of exposure to an insecticide formulation containing the organophosphate, chlorpyrifos on cholinesterase activity, siphoning and burrowing ability in the Asian clam, Corbicula fluminea. Clams were exposed to concentrations of the pesticide ranging from 0.05 to 50 mg/L (as chlorpyrifos) in a series of 96-h static bioassays. Those organisms exposed to pesticide concentrations at or above 3.13 mg/L avoided exposure through valve closure during the 96-h test period, with no resultant effects on cholinesterase activity or behavior. Similarly, no effect was observed at low-test concentrations ranging from 0.05 to 0.1 mg/L, even though clams actively siphoned in these treatments. Asian clams exposed to the mid-range of concentrations, 0.5-1.0 mg/L, experienced a significant reduction in cholinesterase activity and a reduced capacity to burrow into the substrate. While these data indicate that cholinesterase activity in C. fluminea could be used as a biomarker of organophosphorous pesticide exposure, valve closure can clearly influence exposure profiles and biomarker response.