The State of the Art of Flow-Through Solid-Phase Spectrometry

Sample pretreatment is one of the bottlenecks in analytical chemistry, especially when dealing with complex matrices like environmental samples. When performed in a batch mode, sample handling methods are tedious and time consuming. Therefore, the hyphenation of these methods with flow-injection techniques yields many advantages. The possibility of automation not only increases the determination rate, but also decreases sample and reagent consumption. As a consequence, analyte separation, enrichment, and elimination of sample matrix becomes possible with an increase in selectivity and sensitivity. This is a significant contribution for the analysis of environmental samples because the analyte is usually present at trace levels in a complex matrix. In this scenario, the state of the art of solid-phase spectrometry (SPS) with a focus on the lab-on-valve (LOV) platform is discussed. LOV facilitates the manipulation of bead suspension for SPS with lower reagents consumption and waste production.info:eu-repo/semantics/publishedVersio

Enhanced mitochondrial testicular antioxidant capacity in Goto-Kakizaki diabetic rats: role of coenzyme Q

Because diabetes mellitus is associated with impairment of testicular function, ultimately leading to reduced fertility, this study was conducted to evaluate the existence of a cause-effect relationship between increased oxidative stress in diabetes and reduced mitochondrial antioxidant capacity. The susceptibility to oxidative stress and antioxidant capacity (in terms of glutathione, coenzyme Q, and vitamin E content) of testis mitochondrial preparations isolated from Goto-Kakizaki (GK) non-insulin-dependent diabetic rats and from Wistar control rats, 1 yr of age, was evaluated. It was found that GK mitochondrial preparations showed a lower susceptibility to lipid peroxidation induced by ADP/Fe(2+), as evaluated by oxygen consumption and reactive oxygen species generation. The decreased susceptibility to oxidative stress in diabetic rats was associated with an increase in mitochondrial glutathione and coenzyme Q9 contents, whereas vitamin E was not changed. These results demonstrate a higher antioxidant capacity in diabetic GK rats. We suggest this is an adaptive response of testis mitochondria to the increased oxidative damage in diabetes mellitu

Membrane-based separation in flow analysis for environmental and food applications

Membrane-based separation techniques have been used as an efficient process for analyte separation or enrichment and matrix removal. By coupling these techniques to flow-based analysis, sample preparation and analyte detection can be automated and miniaturized. Different membrane separation techniques are available but the most used in flow analysis are gas diffusion, dialysis, supported liquid membranes and polymer inclusion membranes. The current state of the art of membrane-based separations hyphenated with flow techniques is presented along with a discussion of the applications to environmental and food analysis. Moreover, a brief description of gas diffusion, dialysis and membrane extraction techniques is also included.info:eu-repo/semantics/publishedVersio

Yeast as a model organism for studying the evolution of non-standard genetic codes

During the last 30 years, a number of alterations to the standard genetic code have been uncovered both in prokaryotes and eukaryotic nuclear and mitochondrial genomes. But, the study of the evolutionary pathways and molecular mechanisms of codon identity redefinition has been largely ignored due to the assumption that non-standard genetic codes can only evolve through neutral evolutionary mechanisms and that they have no functional significance. The recent discovery of a genetic code change in the genus Candida that evolved through an ambiguous messenger RNA decoding mechanism is bringing that naive assumption to an abrupt end by showing, in a rather dramatic way, that genetic code changes have profound physiological and evolutionary consequences for the species that redefine codon identity. In this paper, the recent data on the evolution of the Candida genetic code are reviewed and an experimental framework based on forced evolution, molecular genetics and comparative and functional genomics methodologies is put forward for the study of non-standard genetic codes and genetic code ambiguity in general. Additionally, the importance of using Saccharomyces cerevisiae as a model organism for elucidating the evolutionary pathway of the Candida and other genetic code changes is emphasised.publishe

Os labirintos da memória, da história e da representação do sujeito feminino em El Dock, de Matilde Sánchez

La literatura de autoria feminina, en América Latina, a partir de la segunda mitad del siglo XX se fortaleció con miras al inicio de la representación de una mujer a través del texto de ficción, basado, en varias obras, de hechos históricos y de conflictos presentes en algunos países, incluyendo los temas de los regímenes dictatoriales. En este contexto, Por medio de un enfoque interpretativo y analítico, con los aportes de los Estudios Culturales de Género, Postcolonialismo y Regionalidad, se busca, a través de la memoria, revelar un pasado aún presente, centrándose en la representación del sujeto femenino, cambiando el tamaño del discurso, en El Dock, de Matilde Sánchez , que cuenta con un narrador que se mueve entre ayer y hoy en un intento de (re)organizarse como sujeto femenino.A literatura de autoria feminina, na América Latina, a partir da segunda metade do século XX, fortaleceu-se, tendo em vista o início de um movimento de representação da mulher por meio do texto ficcional, partindo, em diversas obras, de fatos históricos conflituosos presentes em alguns países, entre os quais as problemáticas provenientes de regimes ditatoriais. Em tal contexto, por meio de uma abordagem interpretativa e analítica, conforme as contribuições dos Estudos Culturais de Gênero, do Pós-Colonialismo e da Regionalidade, busca-se, através da memória, desvelar um passado ainda presente, com foco na representação do sujeito feminino, redimensionando o discurso, através da obra El Dock, de Matilde Sánchez, de modo que a narradora transita entre o ontem e o hoje na tentativa de (re)organizar-se na condição de sujeito feminino

Brain and liver mitochondria isolated from diabeticGoto-Kakizaki rats show different susceptibility to induced oxidative stress

Increased oxidative stress and changes in antioxidant capacity observed in both clinical and experimental diabetes mellitus have been implicated in the etiology of chronic diabetic complications. Many authors have shown that hyperglycemia leads to an increase in lipid peroxidation in diabetic patients and animals reflecting a rise in reactive oxygen species production. The aim of the study was to compare the susceptibility of mitochondria from brain and liver of Goto-Kakizaki (12-month-old diabetic) rats (GK rats), a model of non-insulin dependent diabetes mellitus, to oxidative stress and antioxidant defenses.Brain and liver mitochondrial preparations were obtained by differential centrifugation. Oxidative damage injury was induced in vitro by the oxidant pair ADP/Fe2+ and the extent of membrane oxidation was assessed by oxygen consumption, malondialdehyde (MDA) and thiobarbituric acid reactive substances (TBARS) formation. Coenzyme Q and alpha-tocopherol contents were measured by high-performance liquid chromatography (HPLC).Brain mitochondria isolated from 12-month-old control rats displayed a higher susceptibility to lipid peroxidation, as assessed by oxygen consumption and formation of MDA and TBARS, compared to liver mitochondria. In GK rats, mitochondria isolated from brain were more susceptible to invitro oxidative damage than brain mitochondria from normal rats. In contrast, liver mitochondria from diabetic rats were less susceptible to oxidative damage than mitochondria from normal rats. This decreased susceptibility was inversely related to their alpha-tocopherol and coenzyme Q (CoQ) content.The present results indicate that the diabetic state can result in an elevation of both alpha-tocopherol and CoQ content in liver, which may be involved in the elimination of mitochondrially generated reactive oxygen species. The difference in the antioxidant defense mechanisms in the brain and liver mitochondrial preparations of moderately hyperglycemic diabetic GK rats may correspond to a different adaptive response of the cells to the increased oxidative damage in diabetes. Copyright © 2001 John Wiley & Sons, Ltd

Impact of tRNA modifications and tRNA-modifying enzymes on proteostasis and human disease

Transfer RNAs (tRNAs) are key players of protein synthesis, as they decode the genetic information organized in mRNA codons, translating them into the code of 20 amino acids. To be fully active, tRNAs undergo extensive post-transcriptional modifications, catalyzed by different tRNA-modifying enzymes. Lack of these modifications increases the level of missense errors and affects codon decoding rate, contributing to protein aggregation with deleterious consequences to the cell. Recent works show that tRNA hypomodification and tRNA-modifying-enzyme deregulation occur in several diseases where proteostasis is affected, namely, neurodegenerative and metabolic diseases. In this review, we discuss the recent findings that correlate aberrant tRNA modification with proteostasis imbalances, in particular in neurological and metabolic disorders, and highlight the association between tRNAs, their modifying enzymes, translational decoding, and disease onset.publishe