In vitro Degradation of Poly-L-co-D, L-lactic Acid Membranes

Poly-L-co-D.L-lactic (PLDLA) is a bioresorbable polymer whose properties have been studied for degradation sensitivity and its application in medicine. In this study, the potential of PLDLA membranes for temporary implantation was evaluated. PLDLA membranes were prepared with the solvent evaporation technique and characterized by differential scanning calorimetry, gel permeation chromatography, thermogravimetric analysis, scanning electron microscopy and traction tests. The glass transition temperature of the membranes was 59 °C. Degradation started around 340 °C during the second week showing pores and fissures on the broken surface. Evident degradation was observed after 16 weeks. Microscopy showed that before degradation PLDLA membranes presented no pores. PLDLA properties of resistance to traction and elasticity module were maintained until the 8th week, and after the 16th week there was a sharp reduction of these properties due to degradation. PLDLA membranes present excellent potential as temporary implantation given their degradation characteristics

Lithograph-moulded poly-L-co-D,L lactide porous membranes for osteoblastic culture

Pore size, shape, wall morphology, porosity, and interconnectivity are important characteristics of the scaffolds. Lithography is a manufacturing technique that allows the production of tridimensional scaffolds with a controllable and reproducible inner architecture. The aim of this study was to use lithography to create a poly-L-co-D,L lactide (PLDLA) scaffold with symmetrical pore size and distribution, and to evaluate its biocompatibility with osteoblasts in vitro. Lithographic moulds were used to produce porous PLDLA membranes by a casting procedure. Osteoblasts were removed from calvarial bones and seeded onto porous and smooth PLDLA membranes after which cell viability and adhesion assays, cytochemical analysis and scanning electron microscopy were used to characterize the cells. Cell viability and adhesion assays, cytochemical analysis, and scanning electron microscopy were carried out. Cell viability was similar on porous and smooth PLDLA membranes but higher than on a polystyrene substrate (positive control). Although osteoblasts adhered to the surface of all the materials tested, cell adhesion to lithographed PLDLA was greater than to smooth PLDLA membranes. In conclusion, osteoblasts interacted well with PLDLA membranes, as shown by the viability and adhesion assays and by the enhanced collagen production17171

Cytocompatibility of poly(p-dioxanone)/ poly(hydroxybutic) (PPD/PHB) blends to cartilage tissue engineering

In order of seek strategies to improve the interaction between bioreabsorbable polymer materials and cellular growth, this work aimed at evaluating in vitro the influence of PPD/PHB blends on cell adhesion and fibrochondrocytes growth. Fibrochondrocytes cells were obtained by primary extraction from enzymatic digestion methods. The PPD/PHB blends were prepared by casting with 100/0, 60/40 and 50/50 compositions, and were characterized by scanning electron microscopy (SEM). After 6, 48, 120 and 168 hours in culture, ultrastructural observations showed changes in cell morphology, suggesting that the fibrochondrocytes can respond to substrate modifications, changing their phenotypic profile. The MTT analyses showed that the blends did not present cytotoxicity and allowed fibrochondrocytes adhesion and proliferation on the membranes in all compositions. The colorimetric Sirius Red test revealed the capability of extracellular matrix synthesis on the blends, from which one can conclude that the PPD/PHB blends are not cytotoxic and can be indicated for cell culture.Buscando estratégias que repercutam na melhoria da interação entre materiais poliméricos biorreabsorvíveis e o crescimento celular, o presente estudo in vitro teve como objetivo estudar a influência de blendas de PPD/PHB na adesão celular e crescimento de fibrocondrócitos obtidos a partir de cultura primária. As blendas de PPD/PHB foram preparadas pelo método de evaporação de solvente nas composições 100/0, 60/40 e 50/50 e caracterizadas por microscopia eletrônica de varredura (MEV). Observações ultra-estruturais mostraram alterações na morfologia celular, sugerindo que os fibrocondrócitos podem responder a alterações no substrato alterando seu perfil fenotípico. As análises com MTT demonstraram que as blendas não apresentaram citotoxicidade e permitiram a adesão e proliferação dos fibrocondrócitos sobre os substratos em todas as suas composições. O ensaio colorimétrico com Sirius Red evidenciou a capacidade de manutenção da síntese de matriz extracelular colágena sobre as amostras, concluindo-se que as blendas de PPD/PHB podem ser indicadas para o cultivo celular.383388Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

PLLA/Triethyl citrate membrane as an alternative for the treatment of skin wounds

Bioresorbable polymers can be applied as membranes to sustain and guide cell growth through the regeneration process. This study evaluated poly(acid lactide), PLLA, membranes with addition of 10% triethyl citrate as skin wound healing in Wistar rats. Initially a 2cm² skin wound was exercised of the back of 24 animals. The animals were divided into two groups: treated, whose the polymer membrane was implanted, and control, in which the wound was kept exposed. The results obtained after 1, 3, 7 and 15 days showed an inflammatory response more satisfactory in the implanted wounds, with early repair and collagen more organized when compared to exposed wounds. In addition to, the protected areas showed no irritant inflammatory response which could be attributed to the membrane. Thus, we conclude that the PLLA/Triethyl citrate membrane has effectively protected the wounds, allowing the repair and presenting itself as a promising skin dressing.Polímeros sintéticos biorreabsorvíveis podem ser utilizados sob a forma de membranas para sustentar e guiar o crescimento celular, através do processo de reparação tecidual. Este trabalho avaliou membranas de poli(ácido lático), PLLA, com adição de 10% de trietil-citrato usadas como curativos de feridas cutâneas agudas em ratos Wistar. Inicialmente uma ferida de 2cm² foi provocada na região dorsal de 24 animais. Estes foram divididos em 2 grupos: tratamento, nos quais as feridas foram recobertas pela membrana polimérica e controle, com feridas permanecendo cruentas. Os resultados obtidos em 1, 3, 7 e 15 dias mostraram uma resposta inflamatória mais satisfatória nas feridas protegidas pelas membranas, com reparação precoce e colágeno mais organizado quando comparadas com as áreas incialmente mantidas sem proteção. Além do que, as áreas protegidas pelas membranas não mostraram alterações inflamatórias irritativas que pudessem ser imputadas ao uso da membrana polimérica. Diante disso, conclui-se que a membrana de PLLA/Trietil-citrato protegeu efetivamente as feridas, permitindo o processo de reparação e mostrando-se promissora como curativo cutâneo.798806Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Measurement of the Electric Form Factor of the Neutron at Q^2=0.5 and 1.0 (GeV/c)^2

The electric form factor of the neutron was determined from measurements of the \vec{d}(\vec{e},e' n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G_E^n = 0.0526 +/- 0.0033 (stat) +/- 0.0026 (sys) and 0.0454 +/- 0.0054 +/- 0.0037 at Q^2 = 0.5 and 1.0 (GeV/c)^2, respectively.Comment: 5 pages, 2 figures, as publishe

HFR1 Is Crucial for Transcriptome Regulation in the Cryptochrome 1-Mediated Early Response to Blue Light in Arabidopsis thaliana

Cryptochromes are blue light photoreceptors involved in development and circadian clock regulation. They are found in both eukaryotes and prokaryotes as light sensors. Long Hypocotyl in Far-Red 1 (HFR1) has been identified as a positive regulator and a possible transcription factor in both blue and far-red light signaling in plants. However, the gene targets that are regulated by HFR1 in cryptochrome 1 (cry1)-mediated blue light signaling have not been globally addressed. We examined the transcriptome profiles in a cry1- and HFR1-dependent manner in response to 1 hour of blue light. Strikingly, more than 70% of the genes induced by blue light in an HFR1-dependent manner were dependent on cry1, and vice versa. High overrepresentation of W-boxes and OCS elements were found in these genes, indicating that this strong cry1 and HFR1 co-regulation on gene expression is possibly through these two cis-elements. We also found that cry1 was required for maintaining the HFR1 protein level in blue light, and that the HFR1 protein level is strongly correlated with the global gene expression pattern. In summary, HFR1, which is fine-tuned by cry1, is crucial for regulating global gene expression in cry1-mediated early blue light signaling, especially for the function of genes containing W-boxes and OCS elements

The UniProt-GO Annotation database in 2011

The GO annotation dataset provided by the UniProt Consortium (GOA: http://www.ebi.ac.uk/GOA) is a comprehensive set of evidenced-based associations between terms from the Gene Ontology resource and UniProtKB proteins. Currently supplying over 100 million annotations to 11 million proteins in more than 360 000 taxa, this resource has increased 2-fold over the last 2 years and has benefited from a wealth of checks to improve annotation correctness and consistency as well as now supplying a greater information content enabled by GO Consortium annotation format developments. Detailed, manual GO annotations obtained from the curation of peer-reviewed papers are directly contributed by all UniProt curators and supplemented with manual and electronic annotations from 36 model organism and domain-focused scientific resources. The inclusion of high-quality, automatic annotation predictions ensures the UniProt GO annotation dataset supplies functional information to a wide range of proteins, including those from poorly characterized, non-model organism species. UniProt GO annotations are freely available in a range of formats accessible by both file downloads and web-based views. In addition, the introduction of a new, normalized file format in 2010 has made for easier handling of the complete UniProt-GOA data set

FHY1 Mediates Nuclear Import of the Light-Activated Phytochrome A Photoreceptor

The phytochrome (phy) family of photoreceptors is of crucial importance throughout the life cycle of higher plants. Light-induced nuclear import is required for most phytochrome responses. Nuclear accumulation of phyA is dependent on two related proteins called FHY1 (Far-red elongated HYpocotyl 1) and FHL (FHY1 Like), with FHY1 playing the predominant function. The transcription of FHY1 and FHL are controlled by FHY3 (Far-red elongated HYpocotyl 3) and FAR1 (FAr-red impaired Response 1), a related pair of transcription factors, which thus indirectly control phyA nuclear accumulation. FHY1 and FHL preferentially interact with the light-activated form of phyA, but the mechanism by which they enable photoreceptor accumulation in the nucleus remains unsolved. Sequence comparison of numerous FHY1-related proteins indicates that only the NLS located at the N-terminus and the phyA-interaction domain located at the C-terminus are conserved. We demonstrate that these two parts of FHY1 are sufficient for FHY1 function. phyA nuclear accumulation is inhibited in the presence of high levels of FHY1 variants unable to enter the nucleus. Furthermore, nuclear accumulation of phyA becomes light- and FHY1-independent when an NLS sequence is fused to phyA, strongly suggesting that FHY1 mediates nuclear import of light-activated phyA. In accordance with this idea, FHY1 and FHY3 become functionally dispensable in seedlings expressing a constitutively nuclear version of phyA. Our data suggest that the mechanism uncovered in Arabidopsis is conserved in higher plants. Moreover, this mechanism allows us to propose a model explaining why phyA needs a specific nuclear import pathway