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This paper reports the results of a mercury (Hg) and selenium (Se) metallomic study in the liver tissues of Psectrogaster amazonica and Raphiodon vulpinus from the Brazilian Amazon. Two-dimensional electrophoresis, graphite furnace atomic absorption spectrometry, and liquid chromatography-tandem mass spectrometry were performed. Hg and Se determinations allowed the calculation of Hg:Se and Se:Hg molar ratio and Se values for health benefits (Se HBVs). The Se:Hg values were >1 for both fish species, whereas the Se HBVs were >5 for P. amazonica and >10 for R. vulpinus , indicating that both possess Se reserves to control Hg toxicity. The metallomic data allowed the identification of 11 Hg/Se-associated protein spots in the two fish species, with concentrations in the range of 9.70 ± 0.14 and 28.44 ± 0.31 mg kg -1 of Hg and 16.15 ± 0.21 and 43.12 ± 0.51 mg kg -1 of Se. Five metal binding proteins ( MBP ) in the Hg/Se-associated protein spots in the liver proteome of P. amazonica and eight in R. vulpinus were identified, indicating the possible formation of Hg/Se complexes on the MBP structures. The activities analysis of catalase, superoxide dismutase, GPx enzymes, and lipoperoxide concentrations demonstrated that Hg-induced oxidative stress did not occur, possibly because both fish species possess Se reserves necessary to inhibit the Hg's deleterious effects.

Aquatic biota are exposed to toxic substances resulting from human activities, reducing environmental quality and can compromise the health of the organisms. This study aimed to employ Danio rerio as an environmental bioindicator, analyzing the effects of water from distinct urban aquatic environments. An active biomonitoring system was set up to compare the temporal dynamics of histological biomarkers for gill and liver and the patterns of non-protein thiols (NPSH) in muscle in specimens exposed for 3, 6, and 12 days. Three large urban basins in the city of Campo Grande (Midwest of Brazil) were selected. Two sites are in a very populous area (i.e Lagoa and Bandeira) and another on in an area with agricultural activities (i.e Anhanduí). All the streams displayed distinct qualitative characteristics. The presence of metals, including Mn, Zn, Fe, and Al, as well as pH, temperature, and dissolved oxygen, accounted for 38% of the variability (PC1), while total solids, conductivity, ammonia, nitrite, and explained 24 % (PC2). Degree tissue changes index (DTC) in gill and the concentration of NPSH increased in all streams during 3, 6 and 12 days of exposure. DTC in liver increases in all exposure times in most populous stream (i.e Lagoa and Bandeira). Histopathological evidence in the gill, including proliferation, desquamation, and necrosis of the primary lamellar epithelium; fusion and aneurysms in the secondary lamellar epithelium were observed after three days of exposure. Degenerative nuclear figures were noted in the liver after three days of exposure, followed by hepatocellular hypertrophy, lipidosis, and necrosis at twelve days. Our findings showing time-dependent effects of urban aquatic environments in histopathological (i.e DTC) and biochemical biomarkers in zebrafish. The biomonitoring model enabled a comparison of the temporal dynamics of various health markers, using zebrafish as bioindicator. Future studies might use this experimental model and biomarkers for environmental biomonitoring program., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Carlos Eurico dos Santos Fernandes reports financial support and equipment, drugs, or supplies were provided by Federal University of Mato Grosso do Sul. Carlos Eurico dos Santos Fernandes reports a relationship with Foundation for Support and Development of Education Science and Technology of Mato Grosso do Sul State that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The most recent dam rupture in Brazil released tons of mining tailings into the upper course of the Paraopeba River, affecting this river in an unprecedented way. The present study aimed to evaluate the influence of heavy metals on Prochilodus costatus, an important commercial species in Brazil, four years after the dam colapse. To this end, biomarkers of heavy metals, oxidative stress, and environmental stress were analyzed, and histological analyses of target organs were performed. The results demonstrated critical contamination of fish from the Paraopeba River. Increased expression of Metallothioneins - MTs, Heat Shock Protein - HSP70, and inducible nitric oxide synthase - iNOS, as well as greater rates of histological changes in the liver, spleen, and gonads, were observed in P. costatus. These findings demonstrate that, despite past contamination, the metals present in mining tailings have significantly increased the contamination of the Paraopeba River basin., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Improperly managed care conditions for reptiles can lead to clinical problems, including those of nutritional origin. A diagnostic tool to aid in the assessment of hepatic lipidosis is warranted. Evaluation of attenuation using quantitative computed tomography has a variety of indications in animals and permits the standardization of hepatic computed tomography (CT) reference values, aiding in the diagnosis of lipidosis. The objective of this paper was to estimate hepatic quantitative CT reference values for boas because of the lack of data in the literature for this species. CT scans were performed in 13 boas ( Boa constrictor constrictor ): 5 under managed care and 8 that were free ranging. Results show that the mean hepatic attenuation in the captive boa group was well below the mean for the free-ranging animals ( P < 0.05) with respective values of 48.78 ± 6.57 and 61.76 ± 7.11 HU. These results suggest an influence of managed care on liver attenuation. These results were observed despite the lack of clinical or laboratory changes. This imaging technique is useful to detect early hepatic changes; however, clinical relevance is unknown at this point. Further studies and standardization of species-specific values for hepatic quantitative CT would contribute to better understanding of the physiologic, physiopathologic, environmental, and nutritional processes.

Glutathione S-transferase (GST) assays in non-mammalian organisms are usually conducted inappropriately, since no previous standardization of the optimal concentrations of proteins and substrates and adequate pH is conducted. Standardization is a key task to adjust enzyme assays at their kinetically correct maximal initial velocities, if one wants these velocities to indicate the amount of enzyme in a sample. In this paper GST assays were standardized in liver cytosol to compare seasonal GST levels in liver of mullet from two contaminated lagoons in the Rio de Janeiro to those from a reference bay. GST potential as a biomarker of sublethal intoxication in this species was also evaluated. Mullet liver GST levels assayed with substrates that corresponded to three different GST isoenzymes varied throughout the year. The differences indicated that mullets are suffering from sublethal intoxication from contaminants in these lagoons. Seasonal variations of activity were relevant, since these could indicate differences in xenobiotic input into the areas. An analysis of overall mullet health condition using a morphological index (the Fulton Condition Factor) and macroscopic abnormalities corroborated the differences in GST levels, with fish from one of the sites in worse overall health condition showing lower and significantly different FCF when compared to the reference site. Therefore, GST standardized activity levels are useful biomarkers of environmental contamination for mullet., (Copyright © 2012 Elsevier B.V. All rights reserved.)