Biochemical and structural characterization of β-lactamases tem-180 and tem-201

With the constant development of new antibiotics, selective pressure is a force to reckon when investigating antibiotic resistance. Although advantageous for medical treatments, it leads to increasing resistance. It is essential to use more potent and toxic antibiotics. Enzymes capable of hydrolyzing antibiotics are among the most common ways of resistance and TEM variants have been detected in several resistant isolates. Due to the rapid evolution of these variants, complex phenotypes have emerged and the need to understand their biological activity becomes crucial. To investigate the biochemical properties of TEM-180 and TEM-201 several computational methodologies have been used, allowing the comprehension of their structure and catalytic activity, which translates into their biological phenotype. In this work we intent to characterize the interface between these proteins and the several antibiotics used as ligands. We performed explicit solvent molecular dynamics (MD) simulations of these complexes and studied a variety of structural and energetic features. The interfacial residues show a distinct behavior when in complex with different antibiotics. Nevertheless, it was possible to identify some common Hot Spots among several complexes – Lys73, Tyr105 and Glu166. The structural changes that occur during the Molecular Dynamic (MD) simulation lead to the conclusion that these variants have an inherent capacity of adapting to the various antibiotics. This capability might be the reason why they can hydrolyze antibiotics that have not been described until now to be degraded by TEM variants. The results obtained with computational and experimental methodologies for the complex with Imipenem have shown that in order to this type of enzymes be able to acylate the antibiotics, they need to be capable to protect the ligand from water molecules.

Avaliação da proteção conferida pela via de sinalização do Nrf2 num modelo experimental de sobrecarga de ferro in vivo

O ferro é encontrado em praticamente todos os seres vivos, sendo um cofator para proteínas que desempenham funções essenciais à vida. Nos mamíferos, a maioria do ferro está incorporada na hemoglobina ou armazenado no fígado, ligado à ferritina. É absorvido pelos enterócitos, sendo a principal forma de controlo dos seus níveis. A sobrecarga de ferro pode levar a hemocromatose, podendo ser tóxica para vários órgãos. O fator de transcrição Nrf2 é importante na ativação de genes citoprotetores em situações de stress oxidativo/eletrofílico, colocando-se a hipótese de que poderá estar envolvido na resposta à progressão de doença devido à sobrecarga de ferro. Com o objetivo de determinar se a via do Nrf2 representa uma proteção contra a toxicidade do ferro a nível hepático, foram realizadas duas experiências nas quais murganhos C57BL/6 (B6) e Nrf2-/- machos foram alimentados com dieta standard ou com dieta enriquecida em ferro carbonilo (FeC) (0,5% ou 2,0%). Os resultados demonstram sobrecarga de ferro nos animais que receberam dieta enriquecida, sendo que os que receberam FeC 2,0% apresentaram níveis mais elevados de ferro hepático e sérico, bem como da saturação da transferrina. Os murganhos Nrf2-/- são mais suscetíveis a esta acumulação, mostrando evidências patológicas mais graves, nomeadamente necrose hepatocítica e infiltração de células inflamatórias. A deleção do Nrf2 associado a uma dieta suplementada com FeC 2,0% parece não ser suficiente para o desenvolvimento de fibrose hepática. O estudo da expressão de genes e proteínas do metabolismo do ferro mostrou que os animais B6 e Nrf2-/- são igualmente capazes de responder à sobrecarga de ferro, sugerindo que a sua diferente suscetibilidade à toxicidade do ferro não se deverá a uma regulação ineficiente da homeostasia do Fe. A dieta com FeC 2,0% aumentou a expressão de dois genes alvo do Nrf2, Nqo1 e Gsta1, o que não se verificou com os genes e proteínas GCLC e GCLM. A expressão de genes pró-inflamatórios não mostrou evidências de inflamação nestes animais. Foi demonstrado que os animais Nrf2-/- são mais suscetíveis à toxicidade do ferro, concluindo-se que a via do Nrf2 é ativada em resposta a uma dieta contendo quantidades excessivas de FeC e que confere proteção contra a acumulação de ferro em murganhos B6.

Membrane selectivity versus sensor response in hydrogenated amorphous silicon CHEMFETs using a semi-empirical model

Toxic amides, such as acrylamide, are potentially harmful to Human health, so there is great interest in the fabrication of compact and economical devices to measure their concentration in food products and effluents. The CHEmically Modified Field Effect Transistor (CHEMFET) based onamorphous silicon technology is a candidate for this type of application due to its low fabrication cost. In this article we have used a semi-empirical modelof the device to predict its performance in a solution of interfering ions. The actual semiconductor unit of the sensor was fabricated by the PECVD technique in the top gate configuration. The CHEMFET simulation was performed based on the experimental current voltage curves of the semiconductor unit and on an empirical model of the polymeric membrane. Results presented here are useful for selection and design of CHEMFET membranes and provide an idea of the limitations of the amorphous CHEMFET device. In addition to the economical advantage, the small size of this prototype means it is appropriate for in situ operation and integration in a sensor array.

Synthesis of optimization of [11C] Pittsburgh compound B by the captive solvent method

Mestrado em Medicina Nuclear.

Cianobactérias e toxicidade: impacte na saúde pública em Portugal e no Brasil

Um aumento da concentração de nutrientes na água poderá desencadear fluorescências de cianobactérias (densidades >200 cel/mL). Sob determinadas condições as cianobactérias produzem toxinas responsáveis pelo envenenamento de animais e humanos. O objetivo deste estudo é relacionar a ocorrência de fluorescências toxicas em Portugal e no Brasil. Para tal, em 2005 e 2006 foi estudado o fitoplâncton em três reservatórios em Portugal (região sul) e dois no Brasil (Minas Gerais e Pará). Comparativamente foi verificado maior diversidade nos reservatórios portugueses, com dominância de cianobactérias em período de primavera/verão/outono, pertencentes a géneros produtores de hépato e neurotoxinas (Microcystis sp, Aphanizomenon sp, Oscillatoria sp e Planktothrix sp.). No Brasil observou-se dominância de cianobactérias ao longo de todo o ano, com presença de Microcystis aeruginosa, produtora de hepatotoxina. Conclui-se que os reservatórios estudados apresentam géneros produtores de toxinas, com risco para a saúde pública, sendo fundamental implementar medidas que contribuam para mitigar esta situação. - ABSTRACT - An increasing of nutrients in water can conduct to the development of cyanobacteria blooms (density>2000 cels/mL). Under specific conditions cyanobacteria produce toxins responsible for acute poisoning of animals and humans. The aim of this study is to describe toxic blooms in Portugal and Brazil. Therefore, phytoplankton from three Portuguese reservoirs (South region) and two from Brazil (Minas Gerais and Pará) were studied in 2005 and 2006. Portuguese reservoirs showed more diversity with dominance of hepatic and neurotoxin genera producers (Microcystis sp, Aphanizomenon sp, Oscillatoria sp e Planktothrix sp.) along spring/summer/autumn seasons. In Brazil dominance of cyanobacteria was observed all along the year with the presence of Microcystis aeruginosa hepatotoxic producer. The studied reservoirs present toxins producers’ genera, with risk for public health, being fundamental the implementation of mitigation measures to reverse this situation.

Toxicidade a cianobactérias: impacte potencial na saúde pública em populações de Portugal e Brasil

Como recurso natural fundamental à vida, a água e os ecossistemas aquáticos devem ser alvo de avaliação contínua, no que se reporta à sua qualidade física, química e biológica. Segundo a Organização Mundial de Saúde cerca de 1,1 biliões de pessoas estão impossibilitadas em aceder a qualquer tipo de água potável e, as populações residentes nas proximidades de rios, lagoas, e reservatórios utilizam estas águas para as suas necessidades de consumo, aumentando o risco de transmissão de doenças. Enquanto constituintes da comunidade fitoplanctónica, as cianobactérias são microrganismos procariotas, fotossintéticos, que obtêm os nutrientes diretamente da coluna de água e, um aumento da concentração de nutrientes (principalmente azoto e fósforo), associado a condições ambientais favoráveis, pode desencadear um crescimento rápido originando fluorescências. Sob determinadas condições as cianobactérias podem produzir toxinas existindo registos que evidenciam que fluorescências toxicas são responsáveis pelo envenenamento agudo e morte de animais e humanos pelo que, a água utilizada para consumo humano deverá ser regularmente monitorizada para este elemento biológico. O objetivo deste estudo é relacionar a ocorrência de fluorescências de cianobactérias (> 2000 cel/ml) e toxicidade associada, com o impacte potencial na Saúde Pública avaliado através do consumo direto ou indireto da água. Em Portugal foram selecionados oito reservatórios situados na região Sul, pertencentes às bacias hidrográficas do Sado e Guadiana e estudados entre 2000 e 2008. No Brasil foram selecionados os reservatórios de Três Marias (Estado de Minas Gerais) e de Tucuruí (Estado do Pará) e estudados em 2005 e 2006 respetivamente. Os reservatórios foram caracterizados em termos físicos e químicos, tendo-se igualmente procedido à caracterização da comunidade fitoplanctónica através da identificação e quantificação dos principais grupos presentes em diferentes épocas do ano. Em termos fitoplanctónicos os reservatórios portugueses apresentaram maior diversidade,verificando-se contudo dominância das cianobactérias na comunidade. Associados a fluorescências, foram registados nestes reservatórios géneros produtores de hepato e neurotoxinas como Aphanizomenon sp, Microcystis aeruginosa e Oscillatoria sp. No Brasil, em situação de fluorescências, os géneros produtores de neuro e hepatotoxinas foram Microcystis (> 350.000 cels/ml) e Cylindrospermopsis. A presença destes géneros, poderá constituir um risco potencial para a saúde pública, pelo que é importante a implementação de medidas de mitigação em todos os reservatórios objeto de estudo, devendo essa atuação passar pelo controle do estado trófico no sentido de evitar o desenvolvimento de fluorescências. Assim sugere-se a implementação de um tratamento adequado para a produção de água de consumo e a organização de ações de sensibilização e aviso e informação às populações que utilizam os reservatórios em Portugal e no Brasil para diversos usos. - ABSTRACT - As a life fundamental natural resource, water and aquatic ecosystems must be continuously evaluated in their physical, chemical and biological quality. According World Health Organization, 1.1 billion people has no chance to access any kind of potable water. Populations living near rivers, lagoons or reservoirs use those waters to content their needs, increasing risks disease transmission. As members of phytoplankton community, cyanobacteria are prokaryotic, photosynthetic microorganisms and get its nutrients directly from water column. The increase of this nutrients (especially nitrogen and phosphorus) associated with favorable environment conditions, can support a sudden grow and instigate blooms. Under specific conditions cyanobacteria can produce toxins and several records have shown that toxic blooms are responsible by acute poisoning and death in animals and humans so, water for human consumption must be regularly surveyed for this biologic element. The aim of this study is to correlate Cyanobacteria blooms (>2.000cels/ml) and connected toxicity with public health impact, evaluated through water consumption. In Portugal, eight reservoirs located in the South region were selected and study between 2000 and 2008. In Brazil, Três Marias reservoir (Minas Gerais Provence) and Tucuruí (Pará Provence) were selected and study in 2005 and 2006. Reservoirs were characterized in physical and chemical aspects, as well as phytoplankton community, through identification and counting of main present groups along study period. In bloom circumstances, liver toxins and neurotoxins producers like Aphanizomenon sp, Microcystis aeruginosa and Oscillatoria sp. were founded in Portuguese reservoirs. In Brazil, cyanobacteria genera involved in toxic bloom were Microcystis (> 350.000 cels/ml) and Cylindrospermopsis. This genera presence represents a potential risk for public health, and show the requirement to implement mitigation measures in all study reservoirs. These measures can be represented by water eutrophication control to avoid blooms, by appropriate treatments of water to human consumption, and public warnings or information to dose people in Portugal and Brazil that use these reservoirs to several activities.

GreenFix®: avaliação da morfologia em tecido mamário

Na última década têm desenvolvido fixadores para substituição do formol que é tóxico para o homem. O principal objectivo foi avaliar microscopicamente a histomorfologia e as características tintoriais de tecido mamário fixado em GreenFix®, durante 24 e 72 horas, comparativamente ao fixado em formol, através da coloração de Hematoxilina-Eosina. Uma análise global da histomorfologia revelou existir uma diferença estatisticamente significativa entre a fixação pelo GreenFix® e pelo formol (p=0,050), tendo-se registado uma melhoria da coloração e detalhe nuclear nos tecidos fixados com GreenFix® durante 24 (p=0,007) ou 72 horas(p=0,024). O GreenFix® é um potencial substituto do formol na rotina histológica.

Impact of Sahara dust transport on Cape Verde atmospheric element particles

The objectives of this study were to (1) conduct an elemental characterization of airborne particles sampled in Cape Verde and (2) assess the influence of Sahara desert on local suspended particles. Particulate matter (PM10) was collected in Praia city (14°94'N; 23°49'W) with a low-volume sampler in order to characterize its chemical composition by k0-INAA. The filter samples were first weighed and subsequently irradiated at the Portuguese Research Reactor. Results showed that PM10 concentrations in Cape Verde markedly exceeded the health-based air quality standards defined by the European Union (EU), World Health Organization (WHO), and U.S. Environmental Protection Agency (EPA), in part due to the influence of Sahara dust transport. The PM10 composition was characterized essentially by high concentrations of elements originating from the soil (K, Sm, Co, Fe, Sc, Rb, Cr, Ce, and Ba) and sea (Na), and low concentrations of anthropogenic elements (As, Zn, and Sb). In addition, the high concentrations of PM measured in Cape Verde suggest that health of the population may be less affected compared with other sites where PM10 concentrations are lower but more enriched with toxic elements.

Occupational exposure to poultry dust and effects on the respiratory system in workers

Farmers are occupationally exposed to many respiratory hazards at work and display higher rates of asthma and respiratory symptoms than other workers. Dust is one of the components present in poultry production that increases risk of adverse respiratory disease occurrence. Dust originates from poultry residues, molds, and feathers and is biologically active as it contains microorganisms. Exposure to dust is known to produce a variety of clinical responses, including asthma, chronic bronchitis, chronic airways obstructive disease (COPD), allergic alveolitis, and organic dust toxic syndrome (ODTS). A study was developed to determine particle contamination in seven poultry farms and correlate this with prevalence rate of respiratory defects and record by means of a questionnaire the presence of clinical symptoms associated with asthma and other allergy diseases by European Community Respiratory Health Survey. Poultry farm dust contamination was found to contain higher concentrations of particulate matter (PM) PM5 and PM10. Prevalence rate of obstructive pulmonary disorders was higher in individuals with longer exposure regardless of smoking status. In addition, a high prevalence for asthmatic (42.5%) and nasal (51.1%) symptoms was noted in poultry workers. Data thus show that poultry farm workers are more prone to suffer from respiratory ailments and this may be attributed to higher concentrations of PM found in the dust. Intervention programs aimed at reducing exposure to dust will ameliorate occupational working conditions and enhance the health of workers.

Effects of fungal contamination on respiratory symptoms of poultry workers

Exposure to certain fungi (molds) can cause human illness by 3 specific mechanisms: generation of a harmful immune response, direct infection by the organism or/and toxic-irritant effects from mold byproducts. Moulds are considered central elements in daily exposure of poultry workers and can be the cause of an increased risk of occupational respiratory diseases, like allergic and non-allergic rhinitis and asthma.

Occupational exposure to toxigenic Aspergillus versicolor in Portuguese swines

Biological factors associated with airbome dust are the most important hazards in pig buildings and include allergenic and/or toxic compounds, as well as infectious agents such as fungi and their metabolites, like mycotoxins. Inhalation of such agents can be a potential occupationai treat. Exposure of workers from swine confinement buildings to respiratory hazards has been reported elsewhere in Europe, Asia and America. Analogous data has not been reported for Portugal and this omission has hindered the development of policies in the area of occupational health and farm safety. Aspergilius versicolor is known as being the major producer of the hepatotoxic and carcinogenic mycotoxin sterigmatocystin. The toxicity of this mycotoxin is manifested primarily in liver and kidney. This study aimed to determine occupational exposure treat due to fungal contamination caused by A. versicolor in seven Portuguese swine.

Implementation of proton therapy in the portuguese context of radiotherapy

Cancer is a national and international health care concern. It’s important to find strategies for early diagnosis as well as for the optimization of the various therapeutic options currently existing in Portugal. Cancer is the second leading cause of death in Portugal, the choice of this study, is due to the importance of radiotherapy approach in cancer treatment and because is the therapy used in 40% of oncology patients. Radiation therapy has evolve data technological level, that allows new treatment techniques that are more efficient and that also promotes greater professional satisfaction. The hadrons are charged particles, used in cancer therapy. These particles can bring a paradigm shift regarding the therapeutic approach in radiotherapy. The technique used is proton therapy, that reveal to be more accurate, efficacious and less toxic to surrounding tissue. Proton therapy may be a promising development in the field of oncology and how the treatment is given in radiotherapy. Although there is awareness of the benefits of proton therapy in oncology it’s also important to take in consideration the costs of these therapy, because they are considerably higher than conventional treatments of radiotherapy. Given the lack of a proton therapy service in Portugal, this study aims to be a documentary analysis of clinical records that will achieve the following objectives: to identify the number of cancer patients diagnosed in 2010 in Portugal and to calculate the estimated number of patients that could have been treated with proton therapy according to the Health Council of the Netherlands registration document.

Are known cyanotoxins involved in the toxicity of picoplanktonic and filamentous north atlantic marine cyanobacteria?

Eight marine cyanobacteria strains of the genera Cyanobium, Leptolyngbya, Oscillatoria, Phormidium, and Synechococcus were isolated from rocky beaches along the Atlantic Portuguese central coast and tested for ecotoxicity. Strains were identified by morphological characteristics and by the amplification and sequentiation of the 16S rDNA. Bioactivity of dichloromethane, methanol and aqueous extracts was assessed by the Artemia salina bioassay. Peptide toxin production was screened by matrix assisted laser desorption/ionization time of flight mass spectrometry. Molecular analysis of the genes involved in the production of known cyanotoxins such as microcystins, nodularins and cylindrospermopsin was also performed. Strains were toxic to the brine shrimp A. salina nauplii with aqueous extracts being more toxic than the organic ones. Although mass spectrometry analysis did not reveal the production of microcystins or other known toxic peptides, a positive result for the presence of mcyE gene was found in one Leptolyngbya strain and one Oscillatoria strain. The extensive brine shrimp mortality points to the involvement of other unknown toxins, and the presence of a fragment of genes involved in the cyanotoxin production highlight the potential risk of cyanobacteria occurrence on the Atlantic coast.

Primary screening of the bioactivity of brackishwater cyanobacteria: toxicity of crude extracts to artemia salina larvae and paracentrotus lividus embryos

Cyanobacteria are a diverse group of Gram-negative bacteria that produce an array of secondary compounds with selective bioactivity against vertebrates, invertebrates, plants, microalgae, fungi, bacteria, viruses and cell lines. The aim of this study was to assess the toxic effects of aqueous, methanolic and hexane crude extracts of benthic and picoplanktonic cyanobacteria isolated from estuarine environments, towards the nauplii of the brine shrimp Artemia salina and embryos of the sea urchin Paracentrotus lividus. The A. salina lethality test was used as a frontline screen and then complemented by the more specific sea urchin embryo-larval assay. Eighteen cyanobacterial isolates, belonging to the genera Cyanobium, Leptolyngbya, Microcoleus, Phormidium, Nodularia, Nostoc and Synechocystis, were tested. Aqueous extracts of cyanobacteria strains showed potent toxicity against A. salina, whereas in P. lividus, methanolic and aqueous extracts showed embryo toxicity, with clear effects on development during early stages. The results suggest that the brackishwater cyanobacteria are producers of bioactive compounds with toxicological effects that may interfere with the dynamics of invertebrate populations.

Caracterização da exposição e eventuais efeitos para a saúde da exposição profissional ao estireno nos ortoprotésicos

Mestrado em Segurança e Higiene do Trabalho.