A stress correction procedure for the analysis of inelastic frames under transient dynamic loads

This paper attempts to present an algorithm (as a set of conditions and equations) for the correction of stresses of both strain-hardening and perfectly-plastic materials, for the analysis of frames under transient dynamic loadings. The validity of the proposed conditions and equations is verified through numerical experiments

Dietary Omega-3 Fatty Acids Do Not Change Resistance of Rat Brain or Liver Mitochondria to Ca2+ and/or Prooxidants

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) block apoptotic neuronal cell death and are strongly neuroprotective in acute and chronic neurodegeneration. Theoretical considerations, indirect data, and consideration of parsimony lead to the hypothesis that modulation of mitochondrial pathway(s) underlies at least some of the neuroprotective effects of n-3 PUFAs. We therefore systematically tested this hypothesis on healthy male FBFN1 rats fed for four weeks with isocaloric, 10% fat-containing diets supplemented with 1, 3, or 10% fish oil (FO). High resolution mass spectrometric analysis confirmed expected diet-driven increases in docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3) in sera, liver and nonsynaptosomal brain mitochondria. We further evaluated the resistance of brain and liver mitochondria to Ca2+ overload and prooxidants. Under these conditions, neither mitochondrial resistance to Ca2+ overload and prooxidants nor mitochondrial physiology is altered by diet, despite the expected incorporation of DHA and EPA in mitochondrial membranes and plasma. Collectively, the data eliminate one of the previously proposed mechanism(s) that n-3 PUFA induced augmentation of mitochondrial resistance to the oxidant/calcium-driven dysfunction. These data furthermore allow us to define a specific series of follow-up experiments to test related hypotheses about the effect of n-3 PUFAs on brain mitochondria

Drought tolerance and antioxidant enzymatic activity in transgenic ?Swingle? citrumelo plants over-accumulating proline.

In this study we investigated the effects of the high endogenous proline level on water relations, gas exchange and antioxidant enzymatic activity in leaves of transgenic ?Swingle? citrumelo rootstocks transformed with the P5CSF129A gene coding for the key-enzyme for proline synthesis, under water deficit. Leaf total water, osmotic and pressure potentials, stomatal conductance, photosynthetic rates and xylem sapflowwere evaluated in non-transformed control and transgenic plants during water deficit treatment. Malondialdehyde (MDA) content, catalase (CAT; EC 1.11.1.6), superoxide dismutase (SOD; EC 1.15.1.1) and ascorbate peroxidase (APX; EC 1.11.1.11) activities were quantified in leaves collected based on their total water potential, representing the following conditions: irrigated (w =−1.3 MPa), moderate stress (w =−2.3 to −2.5 MPa), severe stress (w =−3.8 to −3.9 MPa) and recovery (24 h after re-irrigation: w =−1.3 to −1.9 MPa). Osmotic adjustment was observed in transgenic plants until 11 days after withholding water, while pressure potential in non-transformed controls was close to zero after nine days of water deprivation. This superior maintenance of turgor pressure in leaves of transgenic plants led to higher stomatal conductance, photosynthetic and transpiration rates when compared to non-transgenic plants. Drought caused a significant decrease in APX and SOD activities in control plants, followed by an increase after re-watering. On the other hand, CAT was more active in control than in transgenic plants under irrigated condition and both stress levels. Our results suggest that transgenic plants were able to cope with water deficit better than non-transformed controls since the high endogenous proline level acted not only by mediating osmotic adjustment, but also by contributing to gas exchange parameters and ameliorating deleterious effects of drought-induced oxidative stress

Análise proteômica do estresse hídrico em cafeeiro.

Déficit hídrico é um dos fatores ambientais mais importantes para a diminuição da produtividade do cafeeiro, tanto no Brasil quanto em outros países produtores. O estabelecimento de estratégias para obtenção de cultivares tolerantes ao estresse hídrico depende da compreensão das respostas biológicas ao nível genético, molecular e bioquímico. Para estudar a resposta ao estresse hídrico no gênero Coffea, foi estabelecida uma rede de pesquisa em proteômica (PROTEOPAR ? Programa Proteoma do Paraná) constituída de oito laboratórios. Quatro genótipos de Coffea, com diferentes respostas fisiológicas à seca, foram analisados: C. canephora (Clone 14, tolerante e Clone 109A, sensível) e C. arabica (BA10, tolerante e Geisha, sensível). Proteínas foram extraídas de folhas e raízes de plantas (18 meses de idade) mantidas em casa-de-vegetação, utilizando-se o método de SDS-Fenol modificado. Os regimes hídricos constituíram-se dos seguintes tratamentos: controle irrigado, estresse hídrico severo (-4,0 MPa de potencial de água) e recuperação pós-estresse (36 horas após irrigação). Os extratos protéicos foram distribuídos aos laboratórios do PROTEOPAR para obtenção e análise do padrão de expressão protéica diferencial via eletroforese bidimensional. O método de identificação de proteínas PMF (?Peptide mass fingerprinting?) foi aplicado utilizando-se um espectrômetro de massa (MS) do tipo MALDI-TOF e comparando os espectros de digestão tríptica contra bancos de dados baseados em ESTs de Coffea