Embryonic Development Effects of Basagran® Herbicide in Danio Rerio: A Preliminary Study.

Bentazon (Basagran®) belongs to the chemical group of benzothiadiazinones. Thus, this study aimed to estimate the influence of herbicide bentazon (3 µg.L-1, 6 µg.L-1, 12 µg.L-1, 300 µg.L-1) in Danio rerio embryos development. The study tested environmental relevant concentrations of bentazon as well as the limit established for drinking water (300 µg.L-1) in Brazil. We performed behavioral and developmental analyzes during 96 h of exposure. The bentazon measurements after experimental period showed reduction ranging from 5.0 to 18.93% between exposed groups. Our results showed significant differences in the heart rate, which was significantly higher in groups exposed to all bentazon concentrations compared to control groups. The absence of alterations in the behavioral parameters showing that the herbicide bentazon at the concentrations tested had few adverse effects on the development and behavior of the Danio rerio embryos. Considering the toxic point of view, there is a chance that bentazon acts together with other environmental contaminants as an additive or synergistic way.

Effects of glyphosate on zebrafish: a systematic review and meta-analysis.

Glyphosate herbicide is widely used in worldwide crop production. Consequently, its active ingredient, surfactants, and adjuvants commonly reach the aquatic ecosystem, thereby harming the biota. An investigation into how this herbicide affects aquatic species is important, especially in fish, as they have the ability to absorb and concentrate toxins. We aimed to evaluate the effects of glyphosate on the embryonic, larval and adult stages of zebrafish (Danio rerio), an appreciable organismal model. In this sense, we performed a meta-analysis using published articles from online databases (PubMed and ScienceDirect), which covered studies published until 2022. From a massive compilation of studies evaluating the effects of active substance glyphosate and Glyphosate-Based Herbicides (GBH) on zebrafish, we selected 36 studies used in downstream analyses. Overall, we report that glyphosate affects developmental stages and demonstrates toxicity and damage in zebrafish. We observed that embryos exposed to glyphosate exhibit increased mortality. There was also an increase in the number of morphological abnormalities related to yolk sac oedema, pericardial oedema, spinal curvature and body malformations, and a decrease in body size was observed. Furthermore, there was a decrease in the number of beats. The biochemical results demonstrated an increase in reactive oxygen species and antioxidant capacity against peroxyl radicals in the gills. The literature shows that glyphosate decreased the distance covered and the mean speed of the animals and increased the number of rotations. We concluded that glyphosate causes damage in the embryonic, larval and adult stages of this species. These results are valid for zebrafish and can be applied to other freshwater fish species. Graphical abstract.

Can Vitamin C Supplementation Improve the Antioxidant Capacity of Rhamdia quelen Fish Exposed to Atrazine?

Atrazine (ATZ) is one of the pesticides mostly widely used in Brazil; several studies have shown the toxic effects of this herbicide on aquatic organisms such as fish. Thus, it is absolutely necessary finding alternatives to protect the health of fish, mainly of species commercially important for aquaculture, which may be exposed to atrazine deriving from agricultural runoff. The aim of the current study was to investigate interactions between dietary supplementation with vitamin C (Vit C) antioxidant and exposure to ATZ in Rhamdia quelen fish exposed to this herbicide. R. quelen specimens were divided into four groups: (1) CTRL, (2) VitC, (3) ATZ, (4) ATZ + VitC. Groups 3 and 4 were exposed to ATZ (10 µg L-1) for 96 h, after 30 days of VitC supplementation (1 g kg-1). Liver samples were collected for biomarker assays. Group 4 was the only group presenting decreased protein carbonyl content. Non-protein thiol (NPSH) levels were significantly higher in groups VitC, ATZ and ATZ + VitC than in CTRL. Group ATZ + VitC presented significant increase in glutatione-peroxidase (GPx) activity in comparison to the other investigated groups. Ascorbic acid (AA) levels were significantly higher in group VitC and lower in group ATZ. Therefore, interactions between herbicide ATZ and dietary supplementation with Vit C have shown biochemical changes in R. quelen fish. Thus, dietary supplements with adequate amounts of Vit C can be added as antioxidants to the diet of fish bred in aquaculture systems in order to protect them from exposure to ATZ.

A mixture of pesticides at environmental concentrations induces oxidative stress and cholinergic effects in the neotropical fish Rhamdia quelen.

The insecticides imidacloprid (IMI), a neonicotinoid, and propoxur (PRO), an N-methylcarbamate compound, are pesticides widely used throughout the world. Although they are not used together to combat pests, both are often found in freshwater near agricultural areas. Thereby, the goal of this study was to evaluate the additive effects of IMI and PRO mixtures at environmental concentrations in relation to isolated compounds on Rhamdia quelen, a neotropical fish. The fish was exposed to IMI (0.11 µg/L), PRO (0.039 µg/L), or Mix (0.11 µg/L IMI plus 0.039 µg/L PRO) during 96 h. Glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), acetylcholinesterase (AChE) activities were determined. To verify oxidative damage thiobarbituric acid reactive substances (TBARS), protein carbonyl (PC), reactive oxygen species contents (ROS), antioxidant capacity against peroxides (ACAP) were determined in gills, liver, brain and muscle. The results shows that a mixture of these pesticides at environmental concentrations inhibited acetylcholinesterase activity in the brain and induced oxidative damage in all analyzed tissues. These results reinforce the hypothesis that mixture of contaminants present in environment could induce additive or synergistic effects on fish species.

Environmentally relevant pesticides induce biochemical changes in Nile tilapia (Oreochromis niloticus).

The high demand for food consequently increases the entry of agricultural residues into water resources, and this phenomenon can affect non-target organisms in different ways. Environmentally relevant pesticide effects (per se or in combinations) are scarce in the scientific literature. Therefore, the aim of this study was to investigate: (1) the presence of pesticide residues in an important Brazilian source of water supply and power generation (Jacuí river), during 1 year of monitoring. (2) in a laboratory study verify the effects of the most frequently, herbicide, fungicide, and insecticide found in Jacuí river (individualized or in a mixture) on biochemical parameters in different tissues of Oreochromis niloticus. Twenty pesticide residues were detected in superficial water samples, and two of them are banned in Brazilian territory. Atrazine (0.56 µg L-1), azoxystrobin (0.024 µg L-1), and imidacloprid (0.11 µg L-1) were the most frequently herbicide, fungicide, and insecticide, respectively, found in the river and were used in the laboratory assay. O. niloticus exposed to the pesticide mixture exhibited more biochemical effects than individualized exposure groups. This response can be a result of the combined pesticide effects, culminating in an additive or synergistic effect, depending on the biomarker. In individual exposure groups, atrazine presented the most pronounced alterations, followed by azoxystrobin and imidacloprid. Overall, pesticide exposure increased levels of oxidative stress parameters, reduced antioxidant enzyme activities, and induced acetylcholinesterase activity. These findings highlight the threat to aquatic organisms which may be exposed to a miscellaneous of toxic compounds in the environment.

Biochemical and Behavioral Responses in Zebrafish Exposed to Imidacloprid Oxidative Damage and Antioxidant Responses.

Imidacloprid (IMI) is an insecticide used worldwide, a neonicotinoid that could cause toxicity in non-target organisms. Zebrafish (Danio rerio) is a model organism widely used in different fields of research such as behavioral studies, biochemical parameters as well as neurotoxicity research. Here, we investigate whether the exposure to three concentrations (0.15, 15, and 45 µg/L) of IMI for 96 h alters responses in zebrafish. Oxidative stress parameters and acetylcholinesterase activity (AChE) as well as the behavioral responses of locomotion were measured. IMI exposure decreased distance traveled in fish exposed to the 45 µg/L. In the exploratory activity, time spent and transitions to the top area of the water column decreased in fish exposed to all concentrations of IMI. In addition, exposures to 45 and 15 µg/L of IMI decreased episodes of erratic movement in the zebrafish. Exposures to IMI at a concentration of 45 µg/L decreased the time spent in erratic movements and increased the time spent with no movement (i.e., "freezing"). Glutathione S-transferase (GST) activity was increased in the brain of zebrafish exposed for 96 h to concentrations of 0.15 and 45 µg/L. Brain AChE activity was reduced and the levels of carbonyl protein (CP) increased in brain of zebrafish at concentrations of 15 and 45 µg/L. Lipid peroxidation measured by TBARS and, also non-protein thiols (NPSH) did not show any variation in the brain of zebrafish exposed to IMI. Changes in the activity of cholinergic neurotransmitters in the brain tissues of zebrafish indicate IMI toxicity. Exposures of fish over 96 h to IMI at a nominal concentration of 45 µg/L caused more extensive sublethal responses in zebrafish, but this concentration is well above those expected in the aquatic environment. Studies are warranted to evaluate the effects on behavior and biomarker responses in fish exposed over longer periods to IMI at environmentally relevant concentrations.

Acute Silver Catfish (Rhamdia quelen) Exposure to Chlorantraniliprole Insecticide.

The aim of the current study is to investigate whether silver catfish (Rhamdia quelen) individuals exposed to commercial formulation of the chlorantraniliprole insecticide used in rice crops present changes in biochemical parameters. Fifty-four (54) silver catfish individuals were distributed in six units per tank (n = 6/repetition; triplicate/treatment) and subjected to the following treatments: T1-control, without insecticide; T2 (0.02 µg/L of insecticide) and T3 (0.20 µg/L of insecticide). Exposure time lasted 24 or 96 h, and it was followed by 96 h recovery in pesticide-free water. Results have indicated biochemical changes in cortisol, glucose, lactate and plasma protein levels, as well as few ionic changes in animals' gills during the exposure and recovery periods. Chlorantraniliprole incidence in water resulted in some biochemical changes in silver catfish specimens' plasma and gills throughout the acute exposure protocol (sub-lethal dose). Thus, chlorantraniliprole insecticide has caused osmoregulatory and/or biochemical imbalance in the investigated species under the herein adopted laboratory conditions; these changes did not get back to normal levels even after specimens were left to recover for 96 h in clean water.

Ecological risk of pesticide contamination in a Brazilian river located near a rural area: A study of biomarkers using zebrafish embryos.

Aquatic environments are affected by the use of pesticides in agricultural areas near rivers. To assess the impact of pesticide residues on affected environments Danio rerio (zebrafish) embryos have become an alternative model for biomonitoring studies. In the present study, zebrafish embryos were used as bioindicator of water quality in the Vacacaí river, located in the city of Santa Maria, southern Brazil. We hypothesized that it would be possible to observe changes in the biomarkers tested in the embryos. Exposures were performed over a total of eight months during the year 2018 using water collected in a river located near agricultural areas. Twenty-four pesticides were found in river water samples. The most frequently found were atrazine, quinclorac and clomazone. During exposure (96 h) spontaneous movement, the heart rate and hatching rate were evaluated. After the exposure time the embryos were euthanized for biochemical assays. We analyzed biomarkers such as thiobarbituric acid reactive substance (TBARS), acetylcholinesterase (AChE), glutathione S-transferase (GST) and catalase (CAT). We observed increases in GST and TBARS, especially during periods of major water contamination such as January, February, October, and November. Pesticides can affect the development of native species that reproduce during periods of high agricultural production. These results demonstrate the potential use of biochemical parameters combined with developmental and behavioral analyses in zebrafish embryos for biomonitoring studies.

Influence of pesticides and abiotic conditions on biochemical biomarkers in Aegla aff. longirostri (crustacea, anomura): Implications for conservation.

Freshwater ecosystems are constantly threatened by the advance of agricultural activities. Abiotic variables (such as temperature, ammonia, and nitrite) and contaminants (e.g. pesticides) can potentially interact, increasing metabolism and the absorption of toxic substances, which can alter the ability of organisms to establish adequate stress responses. This study aimed to verify which pesticides were most frequently found and in the greatest quantities in low-order streams, and whether the combination of these pesticides with the abiotic variables altered the biological metabolism of aeglids. These freshwater crustaceans are important shredders that inhabit low-order streams and are sensitive to disturbances and/or abrupt environmental variations. The animals were exposed in situ in four streams (reference site and sites 1, 2, and 3). The reference site is a preserved stream with no apparent anthropogenic interference where aeglids still occur, while the other sites no longer exhibit populations of these animals and are influenced by agricultural activities. The exposure was performed bimonthly from November 2017 to September 2018 and lasted 96 h. Measured abiotic data and water samples were collected through all days of exposure. The analyzed biochemical parameters were acetylcholinesterase activity in muscle; and glutathione S-transferase, lipid peroxidation, protein carbonylation, non-protein thiols, antioxidant capacity against peroxides, and reactive oxygen species (ROS) in muscle, gills, and hepatopancreas. We found 24 active principles of pesticides, the most frequently being clomazone, atrazine, and propoxur. Bentazone was present at the highest amounts. The parameters evaluated in this study, including biochemical biomarkers and abiotic factors measured from the water, provided a separation of the months as a function of environmental conditions. There was a difference in activity and biomarker levels throughout the year within the same site and in some months between sites. The greater concentration or variety of pesticides associated with extreme abiotic (very high temperatures) data generated increased oxidative stress, with high levels of protein damage and considerable lipid damage in all tissues, as well as elevation in ROS, even with high levels of antioxidant capacity and non-protein thiols. With these data, we intend to warn about the risks of exposure to these environmental conditions by trying to contribute to the preservation of limnic fauna, especially aeglid crabs, because most species are under some degree of threat.

Ecological impacts of pesticides on Astyanax jacuhiensis (Characiformes: Characidae) from the Uruguay river, Brazil.

Brazilian freshwater ecosystems are continuously exposed to pesticides and domestic sewage. The Uruguay River was chosen for this study because of its international importance, as it flows through Brazil, Argentina, and Uruguay. It receives contaminants such as pesticides and domestic residues. Thus, the aim of this study to assess the accumulation of pesticides in muscle of the fish Astyanax jacuhiensis, its biochemical responses, and the presence of pesticides in water. In total, seven pesticides were registered in water from both river sites. Eight pesticides were detected in fish muscle. The biochemical responses showed that brain lipid peroxidation (LPO) and protein carbonyl (PC) in A. jacuhiensis were higher in the summer. Muscle showed the highest LPO levels in the spring and the highest PC in the summer. Liver LPO and PC levels were higher in the spring and summer. In the gills, the PC was higher in the spring and the LPO in the spring and winter. In the brain and in the gills, glutathione-S-transferase activity was high in the summer and autumn. Catalase activity was lower during the winter and spring. Non-protein thiol (NPSH) levels were lower in the brain in the winter and spring. Muscle tissue showed lower NPSH in the winter (site 1). Liver NPSH showed increased levels in liver in the spring and winter (site 2). The biochemical results clearly is related to pesticides and/or to the presence of other contaminants in the water such as metals or domestic sewage. The accumulation of pesticides in fish muscle added evidence that pesticides have been used in the area surrounding the Uruguay River. In conclusion, the biomarkers assayed in the present study could be used in future investigations considering other sampling sites along Uruguay River.

Toxicological response of silver catfish (Rhamdia quelen) after acute exposure to a commercial insecticide containing thiamethoxam.

This study assessed the hematological, enzymatic and osmoregulatory responses of silver catfish (Rhamdia quelen) exposed to sublethal concentrations (1.125 and 3.750 µg/L) of a commercial thiamethoxam-containing insecticide used on rice crops. Groups of 6 fish per tank (in triplicate, n = 3, total 54 fish) were exposed for up to 96 h to different concentrations of the compound. After this period, fish were placed in clean water for 48 h. Two fish from each tank (6 per treatment) that had been exposed to the insecticide for 24 h were anesthetized with eugenol and blood was collected to evaluate hematological and biochemical parameters. Blood, liver and muscle were collected for determination of metabolic parameters, plasma cortisol, Cl-, Na+ and K+ levels and H+-ATPase and Na+/K+-ATPase activity in the gill. H+-ATPase activity was higher in fish exposed to 1.125 µg/L insecticide at 24 h compared to control (0.0 µg/L). Differences in cortisol levels were evidenced throughout the experimental period. These results indicated that exposure to the insecticide changed the hematological, biochemical and metabolic profile of the animals, suggesting concern about environmental safety. Therefore, we discourage the use of this pesticide in areas that come into contact with water bodies inhabited by fish.

Assessment of River Water Quality in an Agricultural Region of Brazil Using Biomarkers in a Native Neotropical Fish, Astyanax spp. (Characidae).

Intensive agricultural and livestock activities demand high pesticide use and, consequently, contaminants reach aquatic ecosystems. In the lower Jacuí River, southern Brazil, there is a lack of knowledge about pesticide residues in water samples and the biochemical responses in native fish species. Thus, this study aimed to estimate the influence of pesticide residues and water parameters to biomarker responses in the native fish Astyanax spp. We performed seasonal biomonitoring in 2017 with water samples and fish collections. Biomarkers of oxidative stress, antioxidants, biotransformation, and neurotoxicity were analyzed in fish tissues. Fourteen pesticide residues were detected; they presented correlations with detoxification enzyme and oxidative stress biomarkers. These data indicate that most of variations can be related to the pesticide presence in water indicating high aquatic pollution in this place.

Behavioural and biochemical parameters in guppy (Poecilia vivipara) following exposure to waterborne zinc in salt or hard water.

Zinc is an essential trace mineral that is involved in many biological processes. In elevated concentrations, this metal may have toxic effects for aquatic organisms. Physicochemical properties of water, such as salinity and hardness, can influence the bioavailability of zinc and, therefore its toxicity in aquatic environments. Therefore, this study aimed investigate the influence of salinity, hardness on Zn toxicity on the behaviours and biochemical parameters of the estuarine guppy (Poecilia vivipara). The fish were exposed to waterborne zinc (500 µg L-1) in salt water (25 ppt) or hard water (120 mg L-1 CaCO3). For behavioural analysis, the locomotive and exploratory parameters of fish in novel environment and light-dark tests were evaluated. We observed that exposure to hard water decreased the distance covered by the fish, and when zinc also present the vertical exploratory behavior decreased. When zinc was tested alone, an increase in the maximum speed of fish was recorded. Activities of antioxidant enzymes, levels of lipid peroxidation, protein carbonylation, total peroxidation and, reactive oxygen species content, antioxidant capacity against peroxyl radicals, non-proteins thiols levels, acetylcholinesterase and Na+/K+-ATPase activities were evaluated in the whole fish body. The integrated biomarker response was calculated for each parameter to aid in the interpretation of the results and indicated that hard water containing zinc had the greatest effect on the biochemical parameters of the fish. In general, neither salinity nor hardness were totally effective in protecting the guppy from the biochemical damage caused by exposure to zinc.

The bioaccumulation of waterborne zinc in tissues of silver catfish (Rhamdia quelen) and its effect on biochemical parameters.

Silver catfish (Rhamdia quelen) is a fish species with neotropical distribution, and is a potential model organism to study polluted environment. The aim of this study is to analyze the response of silver catfish to environmental concentrations of waterborne zinc (Zn) over 96 h. Significant metal accumulation was seen in gill, intestine and liver tissues. No significant accumulation was seen in muscle tissue. Lipid peroxidation increased in the brain, and decreased in the muscle and liver at all levels of exposure. Zinc exposure led to decreased protein carbonyl levels in the brain and increased levels in the liver. The activity of catalase in the liver was reduced for all exposed groups. Glutathione S-transferase activity decreased in the brain at the highest level of exposure and in the liver at all Zn concentrations tested. Non-protein thiols increased in the muscle and in the gills after exposure. Ascorbic acid levels increased in the brain and in the gills. Exposure to Zn also altered the metabolic parameters, causing decreased lactate and ammonia levels in the muscle, and decreased glycogen in the liver. Zinc exposure increased ammonia and amino acid levels in the liver, and increase glycogen and amino acid levels in muscle tissue. Our results demonstrate that exposure to environmentally relevant concentrations of Zn led to accumulation of metals in the tissues of silver catfish, with significant changes in biochemical parameters.

Effects of diphenyl diselenide diet on a model of mercury poisoning.

This work investigated the preventive effect of diphenyl diselenide [(PhSe)2] against the toxic effects of mercury in silver catfish (Rhamdia quelen). The animals were treated during 30 consecutive days with a (PhSe)2 supplemented feed (3.0 mg kg-1) or commercial feed. During the last 5 days the animals received a daily intraperitoneal dose of HgCl2 (1.7 mg kg-1) or Saline (0.9%). Twenty-four hours after the last HgCl2 injection, the animals were euthanized by spinal cord section to biological material obtainment. Hepatic (AST and ALT) and renal (ammonia and creatinine) toxicity biomarkers, δ-ALA-D activity, TBARS, total and non-protein thiols levels and hepatic, renal and blood mercury (Hg) and zinc (Zn) content were evaluated. Considering renal parameters, HgCl2 exposition increased serum creatinine levels and decreased δ-ALA-D activity, total and non-protein thiols and TBARS levels. HgCl2 exposure also decreased blood δ-ALA-D activity. With exception of blood δ-ALA-D activity and total thiols levels, (PhSe)2 supplementation partially prevented mercury induced alterations. Animals exposed to HgCl2 presented an increase in liver and kidney Hg content and a decrease in liver and blood Zn content. The alteration in blood Zn content was partially prevented with (PhSe)2 supplementation. With the exception of mercury and zinc content, no effects of HgCl2 exposure on hepatic tissue were observed. These results show that (PhSe)2 supplementation can represent a promising alternative to prevent the toxic effects presented by Hg exposure.

Integrated biomarkers response confirm the antioxidant role of diphenyl diselenide against atrazine.

Atrazine (ATZ) is a herbicide worldwide used. That can cause oxidative damage in non-target organisms, such as fish. Furthermore, the threat of exposure to pesticides together with poor nutrition is hazardous to the normal development of fish, and supplementation of the fish diet with antioxidants compounds is an alternative approach to prevent the hazardous effects of pesticide exposure. Here we aimed to investigate the capacity of diphenyl diselenide (PhSe)2 diet supplementation to improve the antioxidant defense of Cyprinus carpio (carp) exposed to environmental concentrations of ATZ. To prove the efficiency of (PhSe)2, we used the Integrated Biomarkers Response (IBR) methodology. Therefore, carp were fed for 8 weeks diets either with or without (PhSe)2 and exposed to 2 or 10µg/L of ATZ for 96h, euthanized, and their liver, gills, and muscle tissues were removed for biochemical assays. ATZ was able to cause oxidative damage from reactive species production in all tissues of carp, as observed by the increase of lipid peroxidation and protein damage. The activity of some antioxidant enzymes was inhibited in carp exposed to ATZ. However, (PhSe)2 supplementation was able to prevent this ATZ-induced damage by improving the activities of antioxidant enzymes and through antioxidant competence of (PhSe)2per se. Furthermore, IBR was shown to be a useful tool to compare treatments, even at different concentrations, and identify the efficiently antioxidant behavior of the organoselenium compound.

Biochemical Responses in Freshwater Fish Exposed to Insecticide Propoxur.

Although designed to control pests selectively, there is some evidence that environmental contamination by pesticides increases risks for humans and wildlife. In the present study, we evaluated biomarkers of oxidative stress in Astyanax jacuhiensis exposed to (5, 15 and 30 µg L-1) of carbamate Propoxur (PPX) for 96 h. Glutathione S-transferase (GST) in liver and gills showed reduced activity in all PPX concentrations tested. Acetylcholinesterase (AChE) activities reduced in brain and muscle at concentrations 15 and 30 µg L-1 of PPX. Lipid peroxidation (LPO) and hydrogen peroxide (HP) had no significant differences. In the brain, protein carbonyl (PC) increased in all groups treated with PPX. Although PPX is a selective pesticide, it causes oxidative damage and enzyme alteration in fish. This study pointed out some biomarkers that could be used to assess effects of environmentally relevant concentrations of pesticides, and infer about studies using fish as bioindicator.

Hypothyroidism Enhanced Ectonucleotidases and Acetylcholinesterase Activities in Rat Synaptosomes can be Prevented by the Naturally Occurring Polyphenol Quercetin.

Thyroid hormones have an influence on the functioning of the central nervous system. Furthermore, the cholinergic and purinergic systems also are extensively involved in brain function. In this context, quercetin is a polyphenol with antioxidant and neuroprotective properties. This study investigated the effects of (MMI)-induced hypothyroidism on the NTPDase, 5'-nucleotidase, adenosine deaminase (ADA), and acetylcholinesterase (AChE) activities in synaptosomes of rats and whether the quercetin can prevent it. MMI at a concentration of 20 mg/100 mL was administered for 90 days in the drinking water. The animals were divided into six groups: control/water (CT/W), control/quercetin 10 mg/kg, control/quercetin 25 mg/kg, methimazole/water (MMI/W), methimazole/quercetin 10 mg/kg (MMI/Q10), and methimazole/quercetin 25 mg/kg (MMI/Q25). On the 30th day, hormonal dosing was performed to confirm hypothyroidism, and the animals were subsequently treated with 10 or 25 mg/kg quercetin for 60 days. NTPDase activity was not altered in the MMI/W group. However, treatment with quercetin decreased ATP and ADP hydrolysis in the MMI/Q10 and MMI/Q25 groups. 5'-nucleotidase activity increased in the MMI/W group, but treatments with 10 or 25 mg/kg quercetin decreased 5'-nucleotidase activity. ADA activity decreased in the CT/25 and MMI/Q25 groups. Furthermore, AChE activity was reduced in all groups with hypothyroidism. In vitro tests also demonstrated that quercetin per se decreased NTPDase, 5'-nucleotidase, and AChE activities. This study demonstrated changes in the 5'-nucleotidase and AChE activities indicating that purinergic and cholinergic neurotransmission are altered in this condition. In addition, quercetin can alter these parameters and may be a promising natural compound with important neuroprotective actions in hypothyroidism.

Effect of diphenyl diselenide diet supplementation on oxidative stress biomarkers in two species of freshwater fish exposed to the insecticide fipronil.

The ability of diphenyl diselenide [(PhSe)2] to attenuate oxidative damage was evaluated in the liver, gills, brain, and muscle of carp (Cyprinus carpio) and silver catfish (Rhamdia quelen) experimentally exposed to fipronil (FPN). Initially, the fish were fed a diet without (PhSe)2 or a diet containing 3.0 mg/kg of (PhSe)2 for 60 days. After the 60-day period, the fish were exposed to 0.65 µg/L of FPN for 192 h. The results showed that carp exposed to FPN and not fed with (PhSe)2 exhibited acetylcholinesterase (AChE) inhibition in brain and muscle, and increased thiobarbituric acid-reactive substance (TBARS) in liver, gills, and brain. Furthermore, FPN decreased nonprotein thiols (NPSH) and δ-aminolevulinate dehydratase (δ-ALA-D) in carp liver and gills, and increased plasma glucose and protein levels. In silver catfish, FPN inhibited AChE and increased TBARS levels in muscle. In addition, glutathione S-transferase (GST) decreased in liver and muscle, and plasma glucose was increased. (PhSe)2 reversed some of these effects. It prevented the increase in TBARS levels in liver, gills, and brain in carp and in silver catfish muscle, and reversed the increase in plasma glucose levels in both species. Additionally, (PhSe)2 increased the NPSH levels in carp and silver catfish that had decreased in response to FPN exposure. However, (PhSe)2 was not effective in reversing the AChE inhibition in brain and muscle or the δ-ALA-D decrease in carp liver. Thus, (PhSe)2 protects tissues of both species of fish, mainly by preventing or counteracting the effects of FPN, on TBARS levels, antioxidants, and present anti-hyperglycemic property.

Early biochemical biomarkers for zinc in silver catfish (Rhamdia quelen) after acute exposure.

Contamination of aquatic ecosystems by metals causes various biochemical changes in aquatic organisms, and fish are recognized as indicators of environmental quality. Silver catfish were exposed to six concentrations of zinc (Zn): 1.0, 2.5, 5.0, 7.5, 10.0 and 12.5 mg/L for 96 h to determine the mean lethal concentration (LC50). The value obtained was 8.07 mg/L. In a second experiment, fish were exposed to concentrations of 1.0 or 5.0 mg/L Zn and a control for 96 h. Afterward, the tissues were collected for biochemical analysis. Lipid peroxidation, as indicated by thiobarbituric acid-reactive substance (TBARS), decreased in the liver and brain for all Zn concentrations tested, while in the gills TBARS levels increased at 1.0 mg/L and declined at 5.0 mg/L. Zn increased protein carbonyls in the muscle of silver catfish and decreased it in the other tissues. The enzyme superoxide dismutase increased in both exposed groups. However, catalase did not change. Glutathione S-transferase decreased in the liver and increased in the gills (1.0 mg/L), muscle (5.0 mg/L) and brain (1.0 and 5.0 mg/L). Nonprotein thiols changed only in brain and muscle tissue. Zn exposure inhibited acetylcholinesterase (AChE) activity in the brain at both concentrations tested, but did not change it in muscle. Exposure to Zn inhibited the activity of Na(+)/K(+)-ATPase in the gills and intestine at both concentrations tested. Our results demonstrate that Zn alters biochemical parameters in silver catfish and that some parameters such as AChE and Na(+)/K(+)-ATPase could be considered as early biomarkers of waterborne Zn toxicity.