A corrosão do aço inoxidável austenítico 304 em biodiesel

As distribuidoras de combustíveis utilizam containers de aço inoxidável para o armazenamento de biocombustíveis, entretanto, na literatura, há poucos relatos sobre os aspectos corrosivos desse aço em biodiesel. O objetivo desse trabalho é estudar o comportamento corrosivo do aço inoxidável austenítico 304 na presença de biodiesel, não lavado e lavado com soluções aquosas de ácido cítrico, oxálico, acético e ascórbico 0,01 mol L-1e comparar com os resultados obtidos para o cobre (ASTM D130). Empregaram-se técnicas como: espectrometria de absorção atômica (EAA) e microscopia óptica (MO). Os resultados de EAA mostraram uma baixa taxa de corrosão para o aço inoxidável, os elementos de liga estudados foram Cr, Ni e Fe, a maior taxa observada foi para o cromo, 1,78 ppm/dia em biodiesel não lavado ou lavado. As MO do aço 304, quando comparados com as do cobre, comprovaram a baixa taxa de corrosão para o sistema aço 304/biodiesel, entretanto comprovaram que, tanto o aço 304, quanto o cobre, sofrem corrosão em amostras de biodiesel.

MiR-1 Is a Tumor Suppressor in Thyroid Carcinogenesis Targeting CCND2, CXCR4, and SDF-1 alpha

Context: Micro-RNA have emerged as an important class of short endogenous RNA that act as posttranscriptional regulators of gene expression and are constantly deregulated inhumancancer. MiR-1 has been found down-regulated in lung, colon, and prostate cancer. Objectives: In this study, we investigated the possible role of miR-1 in thyroid carcinogenesis. Design: We have analyzed miR-1 expression in a panel of thyroid neoplasias including benign and malignant lesions and searched for miR-1 targets. Results: Our results show that miR-1 expression is drastically down-regulated in thyroid adenomas and carcinomas in comparison with normal thyroid tissue. Interestingly, miR-1 down-regulation was also found in thyroid hyperproliferative nonneoplastic lesions such as goiters. We identified the CCND2, coding for the cyclin D2 (CCND2) protein that favors the G1/S transition, CXCR4, and SDF-1 alpha genes, coding for the receptor for the stromal cell derived factor-1 (SDF-1)/CXCL12 chemokine and its ligand SDF-1/CXCL12, respectively, as miR-1 targets. An inverse correlation was found between miR-1 expression and CXC chemokine receptor 4 (CXCR4) and SDF-1 alpha protein levels in papillary and anaplastic thyroid carcinomas. Consistent with a role of the CCND2 protein in cell proliferation and CXCR4 and SDF-1 alpha proteins in cell invasion and metastasis, functional studies demonstrate that miR-1 is able to inhibit thyroid carcinoma cell proliferation and migration. Conclusions: These results indicate the involvement of miR-1 in thyroid cell proliferation and migration, validating a role of miR-1 down-regulation in thyroid carcinogenesis. (J Clin Endocrinol Metab 96: E1388-E1398, 2011)

Metabolic oxidative stress elicited by the copper(II) complex [Cu(isaepy)(2)] triggers apoptosis in SH-SY5Y cells through the induction of the AMP-activated protein kinase/p38(MAPK)/p53 signalling axis: evidence for a combined use with 3-bromopyruvate in neuroblastoma treatment

We have demonstrated previously that the complex bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl)pyridine-N,N`]copper(II), named [Cu(isaepy)(2)], induces AMPK (AMP-activated protein kinase)-dependent/p53-mediated apoptosis in tumour cells by targeting mitochondria. In the present study, we found that p38(MAPK) (p38 mitogen-activated protein kinase) is the molecular link in the phosphorylation cascade connecting AMPK to p53. Transfection of SH-SY5Y cells with a dominant-negative mutant of AMPK resulted in a decrease in apoptosis and a significant reduction in phospho-active p38(MAPK) and p53. Similarly, reverse genetics of p38(MAPK) yielded a reduction in p53 and a decrease in the extent of apoptosis, confirming an exclusive hierarchy of activation that proceeds via AMPK/p38(MAPK)/p53. Fuel supplies counteracted [Cu(isaepy)(2)]-induced apoptosis and AMPK/p38(MAPK)/p53 activation, with glucose being the most effective, suggesting a role for energetic imbalance in [Cu(isaepy)(2)] toxicity. Co-administration of 3BrPA (3-bromopyruvate), a well-known inhibitor of glycolysis, and succinate dehydrogenase, enhanced apoptosis and AMPK/p38(MAPK)/p53 signalling pathway activation. Under these conditions, no toxic effect was observed in SOD (superoxide dismutase)-overexpressing SH-SY5Y cells or in PCNs (primary cortical neurons), which are, conversely, sensitized to the combined treatment with [Cu(isaepy)(2)] and 3BrPA only if grown in low-glucose medium or incubated with the glucose-6-phosphate dehydrogenase inhibitor dehydroepiandrosterone. Overall, the results suggest that NADPH deriving from the pentose phosphate pathway contributes to PCN resistance to [Cu(isaepy)(2)] toxicity and propose its employment in combination with 3BrPA as possible tool for cancer treatment.