http://hdl.handle.net/10400.18/67 2013-05-17T10:04:23Z http://hdl.handle.net/10400.18/673 Title: Comparative study of the cytotoxic effects of microcystin-LR in mammalian cell lines: Vero, HepG2, Caco2 and MDCK Authors: Menezes, Carina Abstract: Microcystin-LR (MCLR) is a natural occurring freshwater cyanotoxin, recognized as one of the most toxic microcystin variants. It is thought to be responsible for cases of livestock and human intoxication due to consumption of toxic cyanobacteria-contaminated water. Although considered a hepatotoxin, MCLR also targets other organs such as the kidneys and intestines. In spite the cellular mechanisms associated with the toxicity of MCLR are still unclear, a previous work in a monkey kidney cell line suggested that the endoplasmic reticulum was an early target of MCLR toxicity and that autophagy was triggered as a cell defense mechanism at subcytotoxic concentrations of MCLR. In the present work, cytotoxic, morphological and ultrastructural effects of MCLR were compared in HepG2 (human liver), Vero (monkey kidney), MDCK (dog kidney) and Caco2 (human intestine) cell lines. MCLR induced a concentration-dependent decrease in cell viability by the NR assay in all cell lines, with HepG2 and Vero showing the lowest cytotoxic thresholds of 25 and 50 μM MCLR, respectively. In these cells, MCLR exposure induced lysosomal damages previously to mitochondrial disruption, reinforcing the role of lysosomes in MCLR-induced toxicity. Immunolabelling and ultrastructural visualization of autophagosomes, showed that autophagy was a response transversal to both cell lines, triggered at subcytotoxic MCLR concentrations, confirming its importance as a defense mechanism to early damages inflicted by the toxin. The analysis of GRP94, an ER stress protein, did not undoubtedly demonstrate that MCLR targets the ER. However, together with the ultrastructural data, suggested that in both HepG2 and Vero cells, the ER has a role in autophagy induction. Additionally, in HepG2 cells, GRP94 down-regulation with increasing MCLR concentrations supported the ER role in the triggering of apoptosis. At high toxin concentrations, ultrastructural alterations consistent with apoptosis were observed for all four cell lines, proving that this is a general MCLR-induced mechanism. Description: Dissertação de Mestrado em Biologia Humana e Ambiente apresentada à Faculdade de Ciências da Universidade de Lisboa, 2009; Tese orientada por: Professora Doutora Ana Amorim (Professora Auxiliar da Faculdade de Ciências da Universidade de Lisboa); Doutora Elsa Alverca (Investigadora do Laboratório de Biologia e Ecotoxicologia, Departamento de Saúde Ambiental,Instituto Nacional de Saúde Doutor Ricardo Jorge) 2009-01-01T00:00:00Z http://hdl.handle.net/10400.18/471 Title: Condições de Iluminação em Ambiente de Escritório: Influência no conforto visual [dissertações de mestrado] Authors: Pais, Aida Maria Garcia Abstract: Com o aumento da população laboral na actividade de escritório surge a necessidade de adequar estes espaços ao homem de forma a tornar o ambiente de trabalho motivante, e a melhorar o desempenho laboral. A adequada iluminação do posto de trabalho é um importante factor que contribui directamente para a segurança, saúde, bem-estar e conforto do trabalhador. As condições de iluminação condicionam a percepção do trabalhador face ao conforto visual, que se traduz em fadiga visual, stress e esforço físico. Este estudo pretendeu identificar condições anómalas e avaliar as condições de iluminação que influenciam o conforto visual dos trabalhadores em ambientes de escritório. A amostra do estudo é constituída por 143 indivíduos do sector administrativo, de 3 empresas. Os instrumentos usados para recolha de informação foram questionário, checklist, luxímetro e máquina fotográfica. Para tratar os dados foi usado o SPSS, versão 18. Efectuou-se análise descritiva, análise de inferência estatística sendo aplicados os testes de Kruskal-Wallis e de comparações múltiplas. Para a medição da iluminância e a uniformidade foram seguidas as normas europeias EN 12464 (2002), DIN 5035 (1990) e ISO 8995 (2002). Os resultados do estudo revelam desconforto visual (fadiga visual, irritabilidade ocular, dores de cabeça, dores musculares, dificuldade de concentração e de SVC) relacionado com o tempo de trabalho em computador sem pausas, com valores de iluminância inferiores aos valores recomendados e com a existência de brilhos e reflexos.; With increasing population in the labor office activity comes the need to adapt these workplaces to man in order to make the work environment motivating, and improve task performance. Adequate lighting of the workplace is an important factor that directly contributes to the health, well-being and worker comfort. The lighting conditions affect the perception of the worker towards visual comfort, which results in eyestrain, stress and physical exertion. This study aims to identify anomalous conditions and evaluate the lighting conditions that influence the visual comfort of workers in office environments. The study sample is composed of 143 individuals from three companies, of the administrative sector. The data collection instruments were a questionnaire, a checklist, a light meter and a camera. To process the data SPSS software, version 18 was used. A descriptive analysis and a statistical inference analysis were carried and Kruskal-Wallis tests and multiple comparisons tests were applied. For measuring the illuminance and uniformity European standards EN 12464 (2002), DIN 5035 (1990) and ISO 8995 (2002) were followed. The study results revealed visual discomfort (eyestrain, irritated eyes, headaches, muscle aches and Computer Visual Syndrome) related to working time with computer without breaks, with illuminance below the recommended values and with the existence of glare and reflections. Description: Dissertação elaborada com vista à obtenção do Grau de Mestre em Ergonomia na Segurança no Trabalho, apresentada à Universidade Técnica de Lisboa, Faculdade de Motricidade Humana. 2011-03-01T00:00:00Z