Single and combined effects of Zn, Mn and Fe on the Neotropical freshwater bivalve Anodontites trapesialis: Bioaccumulation and biochemical biomarkers.

Important concentrations of Zn, Mn and Fe were detected in a stream near a coal mining area and promoted, in field, biomarkers alterations in the bivalve Anodontites trapesialis. In order to understand the isolated and mixed effects of these metals on these Neotropical bivalves, we run short-term experiments under laboratory controlled conditions. After 96 h-exposure, tissues (gills, mantle, digestive gland, muscle, hemolymph) were removed for metal bioaccumulation analysis, oxidative stress biomarkers (reactive oxygen species (ROS), total antioxidant capacity, lipoperoxidation (LPO), proteins carbonylation (PC), metallothionein (MT), activity of superoxide dismutase and glutathione S-transferase and hemocytes DNA damage) and cholinesterase (ChE versus ASCh activity) activity evaluation. We run three independent tests. In Zn test, clams were exposed to three concentrations of Zn (0.18 mg L-1, 1.0 mg L-1, 5.0 mg L-1); in Mn test, clams were exposed to three concentrations of Mn (0.1 mg L-1, 0.5 mg L-1, 5.0 mg L-1) and in Mix test, clams were exposed to the mixture Zn (1 mg L-1) + Mn (0.5 mg L-1), with and without Fe (5.0 mg L-1). After single exposure to 5.0 mg L-1, Zn bioaccumulated in all tissues, but only in mantle and hemolymph after exposure to 1.0 mg L-1. The increased MT in gills of A. trapesialis exposed to Zn appears to be sufficient to avoid damage, since LPO occurred only in digestive glands from animals exposed to 5.0 mg L-1. We suggested that A. trapesialis had a metabolic suppression in consequence of Mn presence, based on the following results: the decrease of ROS in gills, the decrease of the Zn and Mn concentrations in tissues and the decrease of ChE versus ASCh activity in muscle. Despite this, animals exposed to Mn suffer oxidative damages (LPO and PC) in the mantle and digestive gland and MT increased in the mantle. These results showed A. trapesialis responded differently to each metal and Mn caused more damage. When exposed to Fe, gills level of ROS was increased, despite no changes in metal accumulation occurred. On the other hand, after exposure to the mixtures, tissues bioaccumulated Zn and previously observed damages caused by Mn and Fe disappeared. Consequently, biomarkers were less affected under mixture treatments, demonstrating mixtures effects or responses were not simply a combination of single exposures to Zn, Mn and Fe, but depend on metals toxicokinetics.

Metals bioaccumulation and biomarkers responses in the Neotropical freshwater clam Anodontites trapesialis: Implications for monitoring coal mining areas.

As one of the most impactful industries, coal mining can promote several alterations at surrounding environment. In surface water, elevated concentrations of metals like Mn, Zn, Fe and Al are often observed. Thus, the aim of this study was to investigate the bioaccumulation and the sub-lethal effects of these metals on various organs of the Neotropical bivalve Anodontites trapesialis confined along a stream located near a coal mine, in order to assess a set of biomarkers that could be used for effectively monitoring coal mining areas. Clams were caged, for 96h, at two sites located upstream (Up1 and Up2) and two sites downstream (Dw1 and Dw2) from the mine. Metals bioaccumulation was determined in gills, mantle, digestive gland, muscle and hemolymph and the following biomarkers were measured in A. trapesialis tissues: total antioxidant capacity against peroxyl radicals, metallothionein content, lipid peroxidation (LPO), proteins carbonylation, glutathione S-transferase activity, superoxide dismutase activity and acetylcholinesterase (AChE) activity. The results showed that Al and Fe bioaccumulation in the gills and hemolymph, Al bioaccumulation in the mantle and muscle, increased LPO in the gills (Dw1 and Dw2) and mantle (Dw1), as well as reduced AChE activity in the muscle (Dw1 and Dw2) should be considered effective biomarkers for monitoring coal mining areas. A. trapesialis proved to be an efficient biological model, considering that biomarkers responses were observed in the clams after only 96h of confinement at Dw sites, accordingly this species could be a good candidate for monitoring Neotropical freshwaters.

In vitro minocycline activity on superinfecting microorganisms isolated from chronic periodontitis patients / Atividade in vitro de minociclina sobre microrganismos superinfectantes isolados de pacientes com periodontite crônica

Chronic periodontitis is the most common type of periodontitis and it is associated with various species of microorganisms. Enteric rods, Pseudomonas, Staphyloccocus and Candida have been retrieved from periodontal pockets of patients with chronic periodontitis and correlated to cases of superinfection. Local or systemic antibiotic therapy is indicated to reinforce the effects of the conventional mechanical therapy. Minocycline has been suggested as one of the most effective drugs against periodontal pathogens. The aim of this work was to evaluate the minimal inhibitory concentration (MIC) of minocycline on superinfecting microorganisms isolated from the periodontal pocket and the oral cavity of individuals with chronic periodontitis. Isolates of Enterobacteriaceae (n = 25), Staphylococcus spp. (n = 25), Pseudomonas aeruginosa (n = 9) and Candida spp. (n = 25) were included in the study. Minimal inhibitory concentrations (MIC) of minocycline were determined using the Müeller-Hinton agar dilution method. Staphylococcus spp. isolates were the most sensitive to minocycline with a MIC of 8 µg/mL, followed by Enterobacteriaceae with a MIC of 16 µg/mL. The concentration of 16 µg/mL inhibited 96 percent of Candida spp. isolates. The MIC for 88.8 percent of the isolates of Pseudomonas aeruginosa was 128 µg/mL. A concentration of 1,000 µg/mL was not enough to inhibit 100 percent of the tested isolates.

Periodontite crônica é a forma mais comum de periodontite e está associada a diversas espécies de microrganismos. Enterobactérias, Pseudomonas, Staphyloccocus e Candida têm sido recuperados de bolsas periodontais de indivíduos com periodontite crônica e implicados em casos de superinfecção. A terapia antimicrobiana local ou sistêmica pode ser utilizada para reforçar os efeitos da terapia mecânica convencional, e a minociclina tem sido sugerida como antimicrobiano eficaz frente a periodontopatógenos. O objetivo deste trabalho foi avaliar a concentração inibitória mínima (CIM) de minociclina sobre microrganismos superinfectantes isolados de bolsas periodontais e cavidade bucal de indivíduos com periodontite crônica. Foram utilizadas 84 cepas de microrganismos, incluindo Enterobacteriaceae (n = 25), Staphylococcus spp. (n = 25), Pseudomonas aeruginosa (n = 9) e Candida spp. (n = 25). A CIM foi determinada pelo método de diluição em ágar Müeller-Hinton. Staphylococcus foram os microrganismos mais sensíveis a minociclina com CIM de 8 µg/mL, seguidos por Enterobacteriaceae com CIM de 16 µg/mL. Entre as espécies de Candida, 96 por cento foram inibidas na concentração de 16 µg/mL. Para 88,8 por cento das cepas de Pseudomonas aeruginosa a CIM foi de 128 µg/mL. A concentração de 1.000 µg/mL não foi suficiente para inibir 100 por cento das cepas testadas.