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Developing technological solutions that use yerba mate waste as precursors is key to reducing the environmental impact caused by the lack of treatment and its accumulation in landfills. Due to their physicochemical properties, these residues can be used to develop activated carbons. Activated carbon is a versatile material with a high surface area that can be used for energy storage. In this work, yerba mate residues were valued by producing chemically activated carbon to be used as electrode material in supercapacitors. Activated carbons were developed through chemical activation in two steps with KOH. Variables such as impregnation ratio and activation temperature are studied. The developed carbons were characterized by physicochemical and electrochemical techniques. They were found to have high surface areas, up to 1800 m 2  g -1 , with a hierarchical porous distribution. A maximum specific capacitance of 644 F g -1 at 0.1 A g -1 , and power values of ca 32,000 W kg -1 , at 33 A g -1 were found. All the synthesized carbons have excellent electrochemical properties and are suitable for use as active material in supercapacitors., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Marcela Alejandra Bavio reports financial support was provided by National University of the Center of the Province of Buenos Aires Faculty of Engineering. Gerardo Gabriel Acosta reports financial support was provided by National Agency for Scientific and Technological Promotion., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Saxitoxin (STX) is a neurotoxic cyanotoxin that also generate reactive oxygen species, leading to a situation of oxidative stress and altered metabolism. The Amazonian fruit açaí Euterpe oleracea possesses a high concentration of antioxidant molecules, a fact that prompted us to evaluate its chemoprotection activity against STX toxicity (obtained from samples of Trichodesmium sp. collected in the environment) in the shrimp Litopenaeus vannamei. For 30 days, shrimps were maintained in 16 aquaria containing 10 shrimps (15% salinity, pH 8.0, 24 °C, 12C/12D photoperiod) and fed twice daily with a diet supplemented with lyophilized açaí pulp (10%), in addition to the control diet. After, shrimps (7.21 ± 0.04 g) were exposed to the toxin added to the feed for 96 h. Four treatments were defined: CTR (control diet), T (lyophilized powder of Trichodesmium sp. 0.8 μg/g), A (10% of açaí) and the combination T + A. HPLC analysis showed predominance of gonyautoxin-1 concentrations (GTX-1) and gonyautoxin-4 concentrations (GTX-4). The results of molecular docking simulations indicated that all variants of STX, including GTX-1, can be a substrate of isoform mu of the glutathione-S-transferase (GST) enzyme since these molecules obtained similar values of estimated Free Energy of Binding (FEB), as well as similar final positions on the binding site. GSH levels were reduced in muscle tissues of shrimp in the T, A, and T + A treatments. Increased GST activity was observed in shrimp hepatopancreas of the T treatment and the gills of the A and T + A treatments. A decrease of protein sulfhydryl groups (P-SH) was observed in gills of shrimps from T + A treatment. A reduction in malondialdehyde (MDA) levels was registered in the hepatopancreas of the T + A treatment in respect to the Control, T, and A treatments. The use of açaí supplements in L. vannamei feed was able to partially mitigate the toxic effects caused by Trichodesmium sp. extracts, and points to mu GST isoform as a key enzyme for saxitoxin detoxification in L. vannamei, an issue that deserves further investigation., (Copyright © 2022. Published by Elsevier B.V.)

This study evaluated the effect of dietary inclusion of lyophilized açaí Euterpe oleracea (LEO) on redox status of shrimp Litopenaeus vannamei (initial weight 1.5 ± 0.39 g) upon exposure to cyanotoxin nodularin (NOD) in bioflocs system. Three hundred juvenile shrimps were randomly divided into two groups and fed twice a day with two diets: one containing 0.00 (control diet) and the other 10.0% LEO (w/w) for 30-days. After the feeding period, both shrimp groups were submitted to three treatments (14 L; 7 shrimp/tank) with different concentrations of cyanotoxin NOD (0.00; 0.25; and 1.00 μg/L) dissolved in water with 96 h of exposure. Then, the shrimps were sampled (n = 15/treatment) for the determination of reduced glutathione (GSH), the activity of glutathione-S-transferase (GST), sulfhydryl groups associated to proteins (P-SH), and lipid peroxidation (TBARS) in the hepatopancreas, gills and muscle. The NOD accumulation was measured in the muscle. The results revealed that dietary LEO significantly increased GSH levels in the hepatopancreas and gills of the shrimps exposed to NOD. Toxin exposure did not modify GST activity in all organs. Muscle TBARS levels were lower in the shrimp fed with the LEO diet and exposed to NOD. The NOD toxin did not accumulate in the muscle but notably was detected in the control groups fed or not with dietary LEO. Açaí was able to induce the antioxidant system of L. vannamei, as well as lowered the oxidative damage in shrimps exposed to NOD, suggesting its use as a chemoprotectant against cyanotoxins., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Blooms of the saxitoxin-producing cyanobacterium Cylindrospermopsis raciborskii have been contaminating drinking water reservoirs in Brazil for many years. Although acute effects of saxitoxin intoxication are well known, chronic deleterious outcomes caused by repeated saxitoxin exposure still require further investigation. The aim of the present work is to investigate the effects of consumption of drinking water contaminated with C. raciborskii for 30 days on learning and memory processes in rats., Methods: The effects of saxitoxin (3 or 9 μg/L STX equivalents) or cyanobacteria on behavior was determined using the open field habituation task, elevated plus maze anxiety model task, inhibitory avoidance task, and referential Morris water maze task., Results: No effects of saxitoxin consumption was observed on anxiety and motor exploratory parameters in the elevated plus maze and open field habituation tasks, respectively. However, groups treated with 9 μg/L STX equivalents displayed a decreased memory performance in the inhibitory avoidance and Morris water maze tasks., Conclusions: These results suggest an amnesic effect of saxitoxin on aversive and spatial memories.

Introduction: This study aimed to analyze antioxidant responses and oxidative damage induced by two inorganic forms of arsenic (As; As(III) and As(V)) in an estuarine polychaete species, Laeonereis acuta (Nereididae). The capacity of arsenic biotransformation was also evaluated through the methylation process considering the activity of a key enzyme involved in the metabolization process., Materials and Methods: Worms were exposed to 50 μg (As(III) or As(V))/l during 2 or 7 days, plus a control group. Endpoints analyzed included concentration of reactive oxygen species (ROS), activities of antioxidant enzymes such as glutathione reductase (GR), total glutathione-S-transferase (GST), and omega isoform (GST Ω), glucose-6-phosphate deshydrogenase (G6PDH), levels of the antioxidant glutathione (GSH), and lipid peroxides concentration (TBARS)., Results and Discussion: Results showed: (1) GR inhibition after 2-day exposure to both As forms (p < 0.05); (2) GST Ω inhibition after 7-day exposure to As(III) paralleled by an increase in total GST activity (p < 0.05); (3) augmented G6PDH activity after 7-day exposure to both As forms (p < 0.05); (4) no differences in terms of ROS and TBARS; and (5) inhibition of GST Ω activity in As(III) exposed worms, which was concomitant with a lowering of mono- and dymethylated arsenic species., Conclusion: These results confirm the reactivity of some biochemical variables of L. acuta to As and indicates its importance as a sentinel species in estuarine regions with presence of arsenic.

We evaluated the effects of aqueous extracts of the cyanobacterium-producing microcystin (MC), Microcystis aeruginosa (strain RST9501), on detoxification capacity and glutathione (GSH) synthesis in liver, brain, gill, and muscle-as well as apoptotic protease (calpain) activity in liver and brain-in the common carp Cyprinus carpio (Teleostei: Cyprinidae). Experimental groups were defined as follows: (1) control (CTR); (2) carp treated with an aqueous extract from the toxic cyanobacteria M. aeruginosa in a final MC concentration of 25 μg/kg (MC 25); and (3) carp treated with an aqueous extract from the toxic cyanobacteria M. aeruginosa in a final MC concentration of 50 μg/kg (MC 50). Carp were gavaged with a cyanobacterial aqueous solution or MilliQ water (CTR group). The experiment was conducted for period of 48 h comprising two gavages with a 24-h interval between them. Some of the parameters analyzed in liver, brain, gill, and muscle included activity of the enzymes glutathione-S-transferase (GST), glutamate cysteine ligase (GCL), glutathione reductase (GR), and GSH concentration. We also evaluated GST pi concentration by Western blot as well as calpain activity in liver and brain samples. In carp liver from the MC 50 group, we observed a decrease in GST and GCL activity, which was accompanied by a decreased GSH concentration. In addition, liver calpain activity was highly induced in carp at both MC doses. Thus, MC ingestion affected the liver antioxidant status through decreasing the GSH concentration and the activity of the enzyme involved in its synthesis (GCL). It also decreased the MC detoxification capacity of the liver because total GST activity decreased, a result that cannot be ascribed to GST pi levels. Because GSH acts as an uncompetitive inhibitor of calpain, its decrease should explain the higher activity of this apoptotic enzyme. The main goal of this study was to show that a decrease in GSH concentration is related to decreased activity of GCL, the limiting enzyme involved in GSH synthesis. Because MCs are phosphatase inhibitors and GCL is allosterically inhibited by phosphorylation, the cellular hyperphosphorylation state induced by MC exposure could act as a modulator factor for antioxidant defenses.

Determination of total antioxidant capacity, instead of the measurements of limited number of antioxidants, is very important for the understanding of how antioxidants interact with reactive oxygen species (ROS). Several techniques already exist with this propose, although some of them are extremely time-consuming. A new methodology is proposed, based on the detection of ROS by fluorometry (ex/em: 485/520 nm) employing 2',7'-dichlorofluorescein diacetate (H(2)DCF-DA) as substrate. Supernatant of homogenized samples from different organs (gill, muscle, liver, and brain) of the teleost fish Jenynsia multidentata (Anaplebidae) were exposed to peroxyl radicals generated by thermal (35 degrees C) decomposition of 2,2'-azobis (2 methylpropionamidine) dihydrochloride (ABAP, 4 mM). Different protein concentrations (0.5, 1, 2 and 8 mg/ml) were assayed to get the best signal and curve fitting of fluorescence data over time (30 min). Total antioxidant capacity against peroxyl radicals was estimated as the difference in ROS area with and without ABAP, relative to the fluorescence registered without ABAP. For application of this methodology, J. multidentata specimens were exposed for 24 h to microcystins, cyanotoxins known to induce oxidative stress. Almost all organs showed a lower antioxidant capacity (p<0.05) in samples with 8 mg proteins/ml, when compared to protein content of 1-2 mg/ml. In liver samples, higher (p<0.05) free iron content was determined in samples with 8 mg proteins/ml. Sensitivity test employing GSH spiked in homogenized samples showed the protocol efficiency in detecting total antioxidant capacity. In the test with microcystins a dose-dependent decrease (p<0.05) of antioxidant competence in gills and brain and an inverse result with liver samples were observed. The use of antioxidant defenses was efficient in avoiding oxidative damage, as the content of oxidized proteins was not altered. Data obtained show the potential of this new methodology to be used in ecotoxicological studies.

Lipoic acid (LA) has been reported as a potential therapeutic agent due its antioxidants proprieties. It was considered its effect in different organs (gills, brain, muscle and liver) of the fish Corydoras paleatus (Callychthyidae). LA (70 mg/kg of body mass) was added to a commercial fish diet, organisms being fed daily (1% body weight). Sixty animals (mean mass: 2.37+/-0.09 g) were placed randomly in aquariums and received (+LA) or not (-LA) lipoic acid enriched diet during four weeks. After, fish were killed and the brain, muscle, gills and liver were dissected. LA treatment reduced significantly (p<0.05) reactive oxygen species concentration in brain and increased (p<0.05) glutamate-cysteine ligase activity in brain and liver of the same experimental group. LA fed organisms showed higher (p<0.05) brain glutathione-S-transferase activity, indicating that LA improves the detoxification and antioxidant capacity face components that waste glutathione in phase II reactions. A conspicuous reduction of protein oxidation was observed in muscle and liver of +LA organisms, indicating that the treatment was also effective in reducing oxidative stress parameters.