Browsing by Issue Date, starting with "2013-03-15"
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- Assessment of the genotoxicity of a titanium dioxide nanomaterial using a combination of in vitro and in vivo assaysPublication . Tavares, Ana; Louro, Henriqueta; Vital, Nádia; Antunes, Susana; Lavinha, João; Silva, Maria JoãoHuman exposure to manufactured nanomaterials such as titanium dioxide (TiO2), often used in sunscreens and cosmetics, has increased worldwide. Their specific properties, such as size and high surface area/mass, render them attractive for many applications, but may also be associated to higher toxicity in biological systems and adverse effects in humans. In the context of EU Joint Action NANOGENOTOX (www.nanogenotox.com), the present work aimed to analyse the potential genotoxic effects of a well-characterized TiO2 nanomaterial, correlating in vitro and in vivo effects. TiO2 dispersions were prepared according to a standardized protocol and were used for exposure of human cells (in vitro) or mice (in vivo). The cytokinesis-block micronucleus assay (OECD guideline 487) was performed in human bronchial epithelial cells (BEAS-2B) and primary cultures of human lymphocytes. Additionally, Comet assay was conducted in BEAS-2B cells. In vivo testing was carried out on a mouse model after exposure of groups of mice intravenously. The mammalian erythrocyte micronucleus test in mouse blood (OECD guideline 474) and comet assay in mouse organs were performed. Concurrent positive chemical controls and a nanoparticle control (ZnO) were included. While the results obtained in BEAS-2B cells showed no induction of micronucleated cells, a significant increase was observed in human lymphocytes at the dose of 125 μg/ml. Exposure of BEAS-2B to TiO2 caused an increase in DNA damage detected by comet assay (3-fold increase, p< 0.006) although no dose-response effect was seen. In mice, there was no genotoxicity in both assays. In summary, using a standardized preparation of nanomaterials, results obtained were mostly negative after TiO2 exposure, in both in vitro and in vivo assays. However, somewhat different genotoxicity outcomes may reflect tissue-specific effects affecting, e.g., cellular uptake of the nanomaterial.
- Vamos conhecer os micróbiosPublication . Furtado, RosáliaNoções básicas de Microbiologia Alimentar adequadas ao 1º e 2º ciclos do ensino básico.
- Genotoxicity and oxidative stress induced by sediments from the Sado Estuary and potential antimutagenic effects of quercetinPublication . Pinto, Miguel; Sacadura, Joana; Louro, Henriqueta; Costa, Pedro Manuel; Costa, Maria Helena; Caeiro, Sandra; Lavinha, João; Silva, Maria JoãoThe Sado Estuary is affected by various sources of pollution, such heavy-industry, urbanism, mining, agriculture and maritime traffic and sizable amounts of organic and inorganic contaminants were identified in the sediments. These compounds can be accumulated in the edible parts of estuarine species and agricultural products, thus entering the human food chain and posing a public health problem. This study had two objectives: i) to study genotoxic effects of sediments from the Sado Estuary in a human liver-derived cell line; and ii) to analyze oxidative DNA damage (produced by the same samples) and try to reverse it by treatment with quercetin, as an antioxidant. Sediments were collected from four distinct sites of the Sado Estuary: Sites P and C from the northern area and sites A and E from the southern area. Contaminants were extracted with dichloromethane:methanol (2:1) and genotoxicity was evaluated by the comet assay; oxidative damage was quantified using the DNA repair endonuclease FPG-modified comet assay. HepG2 cells were exposed (48h) to concentrations of each extract (10 - 200 mg SEQ/ml). To confirm oxidative stress, cells were co-exposed for 48h to the concentrations of each extract that were able to produce oxidative DNA damage. A significant increase in total DNA strand breakage was observed following cells exposure to extract P (with and without FPG). Significant DNA damage was only observed following FPG treatment for extracts E and A, suggesting induction of oxidative DNA damage. Extract C failed to induce genotoxicity. Co-exposure to quercetin did not reverse the observed oxidative DNA damage, but rather increased it, suggesting a possible co-mutagenicity. The differential genotoxicity observed in samples from the northern (P) and southern areas (E and A) of the Sado Estuary probably reflects different pressures from an industrialized and urban area versus an agricultural area, respectively.
- Como medir os poluentes do ar ambiente que nos rodeia?Publication . Pires, Ana Filipa