428 research outputs found

    Systemic Metabolism, Its Regulators, and Cancer:Past Mistakes and Future Potential.

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    There has been a resurgence of interest in cancer metabolism; primarily in the resetting of metabolism within malignant cells. Metabolism within cells has always been a tightly regulated process; initially in protozoans due to metabolic enzymes, and the intracellular signaling pathways that regulate these, being directly sensitive to the availability of nutrients. With the evolution of metazoans many of these controls had been overlaid by extra-cellular regulators that ensured coordinated regulation of metabolism within the community of cells that comprised the organism. Central to these systemic regulators is the insulin/insulin-like growth factor (IGF) system that throughout evolution has integrated the control of tissue growth with metabolic status. Oncological interest in the main systemic metabolic regulators greatly subsided when pharmaceutical strategies designed to treat cancers failed in the clinic. During the same period, however the explosion of new information from genetics has revealed the complexity and heterogeneity of advanced cancers and helped explain the problems of managing cancer when it reaches such a stage. Evidence has also accumulated implying that the setting of the internal environment determines whether cancers progress to advanced disease and metabolic status is clearly an important component of this local ecology. We are in the midst of an epidemic of metabolic disorders and there is considerable research into strategies for controlling metabolism. Integrating these new streams of information suggests new possibilities for cancer prevention; both primary and secondary

    K10-Montmorillonite as Support for a Cationic Manganese(III)-salen Complex

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    A argila K10, uma montmorilonita comercial, foi usada como suporte para a imobilização de um complexo catiônico do tipo manganês(III)-salen, o qual apresenta propriedades catalíticas na reação de epoxidação de alcenos. O complexo imobilizado na argila K10 foi testado na epoxidação de três alcenos (estireno, α-metilestireno e 6-ciano-2,2-dimetilcromeno) a 0 ºC, usando três sistemas oxidantes diferentes. Todas as amostras, antes e depois dos ensaios catalíticos, foram caracterizadas por várias técnicas, como adsorção de nitrogênio a baixa temperatura, DRX e FTIR. Foi ainda efetuada a análise química dos catalisadores, por espectroscopia de absorção atômica e por XPS, com o objetivo de avaliar a influência de cada sistema substrato/oxidante na integridade do respectivo catalisador. Os resultados catalíticos demonstraram uma forte influência do sistema substrato/oxidante na percentagem de excesso enantiomérico (%ee). Em alguns casos, os valores de %ee são comparáveis aos valores obtidos em fase homogênea. Os resultados também realçam a necessidade de otimização dos sistemas oxidantes, uma vez que alguns dos oxidantes usualmente utilizados podem conduzir à decomposição do complexo imobilizado, com a consequente lixiviação da fase ativa e desativação do catalisador. A commercial K10-montmorillonite was used as support for the immobilization of a cationic manganese(III)-salen complex. The catalytic behavior of the resulting material was tested in the enantioselective epoxidation of three different alkenes, viz.: styrene, α-methylstyrene and 6-cyano-2,2-dimethylchromene, at 0 ºC, using three different oxidant systems: m-chloroperoxybenzoic acid (m-CPBA) and N-methylmorpholine (NMO) as co-oxidant, iodosylbenzene (PhIO) and sodium hypochlorite. All samples, before and after the catalytic studies, were characterised by nitrogen adsorption at −196 ºC, DRX, FTIR and chemical analysis, in order to evaluate the influence of the substrate/oxidant system on catalyst integrity. The catalytic results demonstrated a strong influence of the substrate and oxidant system on the enantiomeric excess (%ee) values. In some cases, these values were comparable to those in the corresponding homogeneous phase reactions. The results also highlighted the importance of optimizing the oxidant systems, since they may lead to the disruption of the complex from the support, and the consequent catalyst deactivation

    Assessment of genotype imputation methods

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    Several methods have been proposed to impute genotypes at untyped markers using observed genotypes and genetic data from a reference panel. We used the Genetic Analysis Workshop 16 rheumatoid arthritis case-control dataset to compare the performance of four of these imputation methods: IMPUTE, MACH, PLINK, and fastPHASE. We compared the methods' imputation error rates and performance of association tests using the imputed data, in the context of imputing completely untyped markers as well as imputing missing genotypes to combine two datasets genotyped at different sets of markers. As expected, all methods performed better for single-nucleotide polymorphisms (SNPs) in high linkage disequilibrium with genotyped SNPs. However, MACH and IMPUTE generated lower imputation error rates than fastPHASE and PLINK. Association tests based on allele "dosage" from MACH and tests based on the posterior probabilities from IMPUTE provided results closest to those based on complete data. However, in both situations, none of the imputation-based tests provide the same level of evidence of association as the complete data at SNPs strongly associated with disease
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