Alternative tissue engineering scaffolds based on starch: processing methodologies, morphology, degradation and mechanical properties

http://www.sciencedirect.com/science/journal/09284931An ideal tissue engineering scaffold must be designed from a polymer with an adequate degradation rate. The processing technique must allow for the preparation of 3-D scaffolds with controlled porosity and adequate pore sizes, as well as tissue matching mechanical properties and an appropriate biological response. This communication revises recent work that has been developed in our laboratories with the aim of producing 3-D polymeric structures (from starch-based blends) with adequate properties to be used as scaffolds for bone tissue engineering applications. Several processing methodologies were originally developed and optimised. Some of these methodologies were based on conventional melt-based processing routes, such as extrusion using blowing agents (BA) and compression moulding (combined with particulate leaching). Other developed technologies included solvent casting and particle leaching and an innovative in situ polymerization method. By means of using the described methodologies, it is possible to tailor the properties of the different scaffolds, namely their degradation, morphology and mechanical properties, for several applications in tissue engineering. Furthermore, the processing methodologies (including the blowing agents used in the melt-based technologies) described above do not affect the biocompatible behaviour of starch-based polymers. Therefore, scaffolds obtained from these materials by means of using one of the described methodologies may constitute an important alternative to the materials currently used in tissue engineering

Extended BRST invariance in topological Yang Mills theory revisited

Extended BRST invariance (BRST plus anti-BRST invariances) provides in principle a natural way of introducing the complete gauge fixing structure associated to a gauge field theory in the minimum representation of the algebra. However, as it happens in topological Yang Mills theory, not all gauge fixings can be obtained from a symmetrical extended BRST algebra, where antighosts belong to the same representation of the Lorentz group of the corresponding ghosts. We show here that, at non interacting level, a simple field redefinition makes it possible to start with an extended BRST algebra with symmetric ghost antighost spectrum and arrive at the gauge fixing action of topological Yang Mills theory.Comment: Interaction terms heve been included in all the calculations. Two references added. Version to be published in Phys. Rev. D. 7 pages, Latex, no figure

Energy efficiency in olive oil mills

The paper presents some statistical data from olive oil mills in Portugal and Spain, presents the TESLA project and gives some information about energy consumption in olive oil mills

Desempenho agronômico e estabilidade fenotípica de híbridos de sorgo granífero.

O sorgo granífero é uma das culturas que vêm apresentando significativo aumento de produtividade e área plantada no Brasil, com isso vem a importância de cultivares com rendimento estável. O trabalho teve o objetivo de avaliar o rendimento de grãos e a interação entre genótipos e ambiente (GxA) de 25 híbridos simples de sorgo granífero, em distintos ambientes. Para o estudo, foram conduzidos sete experimentos: um em Acreúna-GO, um em Itumbiara-GO, três com diferentes saturações por alumínio, em Sete Lagoas-MG, um em Vilhena-RO e um em Teresina-PI. Os experimentos seguiram o delineamento de blocos casualizados, com três repetições. Os genótipos avaliados foram: 0307401; 0090061; 0307363; 0307343; 0090035; 0307509; 0307421; 0307511; 0307541; 0577393; 0144015; 0307167; 0144013; 0307689; 9920045; 0307561; 307671; 0577337; 0441347 e 0577335, esses provenientes do programa de melhoramento genético da Embrapa Milho e Sorgo e as cultivares comerciais 1G220; Dow 822; BRS 308; 1G150 e BRS 310. Para a avaliação estatística, foi realizada a análise de variância e teste F. Para a realização de comparações múltiplas de médias, foi realizado o teste de Scott & Knott (1974) e a estabilidade fenotípica foi mensurada pela análise de Annicchiarico (1992). O rendimento de grãos foi dependente do ambiente. Os híbridos 0307689, 0307671, 1G220 0307343, 1G150, 0307363, BRS 308, 0009061, 9920045, BRS 310, 0307541 0441347, 0144015, 0307421 e 0307401,obtiveram destaque, por possuírem rendimento de grãos superior à média geral (4,10 t.ha-1) e apresentaram maior estabilidade fenotípica, considerando todos os ambientes

Click-modified cyclodextrins as non-viral vectors for neuronal siRNA delivery

RNA interference (RNAi) holds great promise as a strategy to further our understanding of gene function in the central nervous system (CNS) and as a therapeutic approach for neurological and neurodegenerative diseases. However, the potential for its use is hampered by the lack of siRNA delivery vectors, which are both safe and highly efficient. Cyclodextrins have been shown to be efficient and low toxicity gene delivery vectors in various cell types in vitro. However, to date they have not been exploited for delivery of oligonucleotides to neurons. To this end, a modified β-cyclodextrin (CD) vector was synthesised, which complexed siRNA to form cationic nanoparticles of less than 200nm in size. Furthermore, it conferred stability in serum to the siRNA cargo. The in vitro performance of the CD in both immortalised hypothalamic neurons and primary hippocampal neurons was evaluated. The CD facilitated high levels of intracellular delivery of labelled siRNA, whilst maintaining at least 80% cell viability. Significant gene knockdown was achieved, with a reduction in luciferase expression of up to 68% and a reduction in endogenous glyceraldehyde phosphate dehydrogenase (GAPDH) expression of up to 40%. To our knowledge, this is the first time that a modified CD has been used as a safe and efficacious vector for siRNA delivery into neuronal cells

The effects of death and post-mortem cold ischemia on human tissue transcriptomes

Post-mortem tissues samples are a key resource for investigating patterns of gene expression. However, the processes triggered by death and the post-mortem interval (PMI) can significantly alter physiologically normal RNA levels. We investigate the impact of PMI on gene expression using data from multiple tissues of post-mortem donors obtained from the GTEx project. We find that many genes change expression over relatively short PMIs in a tissue-specific manner, but this potentially confounding effect in a biological analysis can be minimized by taking into account appropriate covariates. By comparing ante- and post-mortem blood samples, we identify the cascade of transcriptional events triggered by death of the organism. These events do not appear to simply reflect stochastic variation resulting from mRNA degradation, but active and ongoing regulation of transcription. Finally, we develop a model to predict the time since death from the analysis of the transcriptome of a few readily accessible tissues.Peer ReviewedPostprint (published version

Fractional Dirac Bracket and Quantization for Constrained Systems

So far, it is not well known how to deal with dissipative systems. There are many paths of investigation in the literature and none of them present a systematic and general procedure to tackle the problem. On the other hand, it is well known that the fractional formalism is a powerful alternative when treating dissipative problems. In this paper we propose a detailed way of attacking the issue using fractional calculus to construct an extension of the Dirac brackets in order to carry out the quantization of nonconservative theories through the standard canonical way. We believe that using the extended Dirac bracket definition it will be possible to analyze more deeply gauge theories starting with second-class systems.Comment: Revtex 4.1. 9 pages, two-column. Final version to appear in Physical Review