Browsing by Issue Date, starting with "2011-10-19"
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- A importância da especiação na avaliação da exposição a contaminantes químicosPublication . Coelho, Inês; Gueifão, Sandra; André, Catarina; Castanheira, IsabelNesta comunicação é feita uma revisão bibliográfica das estratégias analíticas mais adequadas para a identificação das espécies químicas dos contaminantes eventualmente existentes nos alimentos ou nos materiais em contacto com alimentos. Os trabalhos publicados na última década têm demonstrado de forma inequívoca que as formas químicas dos elementos, nos sistemas biológicos, são cruciais para se conhecer a sua toxicidade e biodisponibilidade. As técnicas hifenadas como acoplação de um cromatógrafo líquido de alta resolução a um espectrómetro de massa com plasma indutivo acoplado permitem aliar o poder de separação do primeiro à elevada selectividade e sensibilidade do segundo, tornando-se assim nas técnicas de eleição para a especiação química. È feita depois uma breve apresentação dos trabalhos mais recentes publicados sobre a especiação do Arsénio, Crómio, Vanádio, Selénio, Mercúrio e Antimónio. È apresentado o Laboratório de ICP-MS, em funcionamento no INSA, sendo discutidos os trabalhos desenvolvidos no âmbito dos Projectos de Investigação, a decorrer. Serão debatidas as abordagens escolhidas para a extracção das espécies de Arsénio em função da sua reactividade e tipo de amostra e os métodos de controlo de qualidade seleccionados para monitorar a estabilidade das espécies e impedir a interconversão das mais reativas. Por fim serão apresentados os projectos a iniciar em 2012 e as tarefas acometidas ao Laboratório de ICP-MS do INSA.
- Ulcerogenic Helicobacter pylori Strains Isolated from Children: A Contribution to Get Insight into the Virulence of the BacteriaPublication . Vitoriano, Inês; Saraiva-Pava, Kathy; Rocha-Gonçalves, Alexandra; Santos, Andrea; Lopes, Ana Isabel; Oleastro, Mónica; Roxo-Rosa, MónicaInfection with Helicobacter pylori is the major cause for the development of peptic ulcer disease (PUD). In children, with no other etiology for the disease, this rare event occurs shortly after infection. In these young patients, habits of smoking, diet, consumption of alcohol and non-steroid anti-inflammatory drugs and stress, in addition to the genetic susceptibility of the patient, represent a minor influence. Accordingly, the virulence of the implicated H. pylori strain should play a crucial role in the development of PUD. Corroborating this, our in vitro infection assays comparing a pool of five H. pylori strains isolated from children with PUD to a pool of five other pediatric clinical isolates associated with non-ulcer dyspepsia (NUD) showed the greater ability of PUD strains to induce a marked decrease in the viability of gastric cells and to cause severe damage in the cells cytoskeleton as well as an impairment in the production/secretion of mucins. To uncover virulence features, we compared the proteome of these two groups of H. pylori strains. Two-dimensional gel electrophoresis followed by mass-spectrometry allowed us to detect 27 differentially expressed proteins between them. In addition to the presence of genes encoding well established virulence factors, namely cagA, vacAs1, oipA "on" status, homB and jhp562 genes, the pediatric ulcerogenic strains shared a proteome profile characterized by changes in the abundance of: motility-associated proteins, accounting for higher motility; antioxidant proteins, which may confer increased resistance to inflammation; and enzymes involved in key steps in the metabolism of glucose, amino acids and urea, which may be advantageous to face fluctuations of nutrients. In conclusion, the enhanced virulence of the pediatric ulcerogenic H. pylori strains may result from a synergy between their natural ability to better adapt to the hostile human stomach and the expression of the established virulence factors.
- Nanosized Titanium Dioxide Particles: Evaluation of Genotoxic Effects in Human LymphocytesPublication . Tavares, Ana; Antunes, Susana; Louro, Henriqueta; Lavinha, João; Silva, Maria JoãoThe number of consumer products containing nanomaterials (NM) in the European market showed a 6-fold increase in 2010 (RIVM report, 2010), reflecting the growing relevance of nanotechnology and the broad field of applications of NM across consumer, medical and industrial products. Although the use of NM may offer enormous benefits, it may also pose risks to human health, especially to workers who may face higher exposure, and to environment. Several studies have reported that the greater surface area per mass renders NM more reactive than larger-sized particles of similar chemistry. Size, surface properties, agglomeration state, biopersistence and dose are also likely to modify cell responses to NM, presenting a challenge to the assessment of their potential hazards to human health. Titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NP) are frequently used in sunscreens and cosmetics. Although cytotoxic and genotoxic properties of TiO2-NP and ZnO-NP have been investigated, conflicting results have been reported. Differences inherent to cell lines, NPs characterization, dispersion protocols, exposure times and assays, together with the lack of positive NM controls have lead to difficulties in the toxicity assessment of those NM. As a part of a larger project (www.nanogenotox.eu), aimed at establishing a robust methodology to evaluate the potential genotoxicity of manufactured NM, the objective of the present work was to characterize the potential genotoxic effects of TiO2-NP (anatase, hydrophilic rutile, hydrophobic rutile and rutile/anatase) in primary cultures of human lymphocytes. The cytokinesis-block micronucleus (CBMN) assay was carried out according to OECD guidelines. Dispersions of each NP were freshly prepared and cultures were exposed to NP concentrations (5-250 μg/mL), during 30h. Concurrent control cultures were processed: vehicle control, positive control (mytomicin C, MMC) and a reference NP (ZnO-NP). The results show that none of the four TiO2-NP tested induced a dose-related increase in MN frequency in lymphocytes. Likewise, the cytokinesis-block proliferation index (CBPI) was not significantly affected by TiO2-NP treatments, indicating no influence on cell cycle progression. As to the positive control, MMC induced a significant increase in the frequency of MN and a concomitant decrease in the CBPI, whereas ZnO-NP caused a decrease in the CBPI without affecting the frequency of MN. In conclusion, the results suggest that the tested TiO2-NP are not clastogenic or aneugenic in human lymphocytes, under the selected test conditions. Further data using different cell types and other endpoints, together with the study of in vivo genotoxic and toxicokinetics parameters, are expected to clarify if these TiO2-NP can be considered as non-genotoxic to humans.