Identification of a selenium-dependent glutathione peroxidase in the blood-sucking insect Rhodnius prolixus.

The selenium-dependent glutathione peroxidase (SeGPx) is a well-studied enzyme that detoxifies organic and hydrogen peroxides and provides cells or extracellular fluids with a key antioxidant function. The presence of a SeGPx has not been unequivocally demonstrated in insects. In the present work, we identified the gene and studied the function of a Rhodnius prolixus SeGPx (RpSeGPx). The RpSeGPx mRNA presents the UGA codon that encodes the active site selenocysteine (Sec) and a corresponding Sec insertion sequence (SECIS) in the 3' UTR region. The encoded protein includes a signal peptide, which is consistent with the high levels of GPx enzymatic activity in the insect's hemolymph, and clusters phylogenetically with the extracellular mammalian GPx03. This result contrasts with all other known insect GPxs, which use a cysteine residue instead of Sec and cluster with the mammalian phospholipid hydroperoxide GPx04. RpSeGPx is widely expressed in insect organs, with higher expression levels in the fat body. RNA interference (RNAi) was used to reduce RpSeGPx gene expression and GPx activity in the hemolymph. Adult females were apparently unaffected by RpSeGPx RNAi, whereas first instar nymphs showed a three-day delay in ecdysis. Silencing of RpSeGPx did not alter the gene expression of the antioxidant enzymes catalase, xanthine dehydrogenase and a cysteine-GPx, but it reduced the levels of the dual oxidase and NADPH oxidase 5 transcripts that encode for enzymes releasing extracellular hydrogen peroxide/superoxide. Collectively, our data suggest that RpSeGPx functions in the regulation of extracellular (hemolymph) redox homeostasis of R. prolixus.

Análise histológica da limpeza apical de canais radiculares após instrumentaçäo / Histological analysis of the apical cleaning of the root canal system after instrumentation

A limpeza do sistema de canais radiculares assume especial relevância no sucesso do tratamento endodôntico. O objetivo deste trabalho foi avaliar histologicamente a capacidade das técnicas step-back, movimentos contínuos de rotaçäo alternada (MRA) e do sistema Quantec de promover a limpeza do terço apical de canais radiculares. Os resultados demonstraram que näo houve diferença estatisticamente significante entre as técnicas testadas, sendo que, na maioria das vezes, os canais ainda apresentavam remanescentes teciduais, mormente em áreas de variaçöes da anatomia interna