Página 12 dos resultados de 60878 itens digitais encontrados em 0.104 segundos

‣ Coordinated, network-based research as a strategic component of science in Brazil

Simpson, Andrew J.G.; Camargo, Anamaria A.; Ferro, Jesus Aparecido; Parra, Jucara; Vasconcelos, Ana Tereza
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 18-25
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Scientific research plays a fundamental role in the health and development of any society, since all technological advances depend ultimately on scientific discovery and the generation of wealth is intricately dependent on technological advance. Due to their importance, science and technology generally occupy important places in the hierarchical structure of developed societies, and they receive considerable public and private investment. Publicly funded science is almost entirely devoted to discovery, and it is administered and structured in a very similar way throughout the world. Particularly in the biological sciences, this structure, which is very much centered on the individual scientist and his own hypothesis-based investigations, may not be the best suited for either discovery in the context of complex biological systems, or for the efficient advancement of fundamental knowledge into practical utility. The adoption of other organizational paradigms, which permit a more coordinated and interactive research structure, may provide important opportunities to accelerate the scientific process and further enhance its relevance and contribution to society. The key alternative is a structure that incorporates larger organizational units to tackle larger and more complex problems. One example of such a unit is the research network. Brazil has utilized such networks to great effect in genome sequencing projects...

‣ The C-terminal domain of the regulatory protein NOVH is sufficient to promote interaction with fibulin 1C: A clue for a role of NOVH in cell-adhesion signaling

Perbal, Bernard; Martinerie, Cécile; Sainson, Richard; Werner, Michel; He, Bin; Roizman, Bernard
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 02/02/1999 Português
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The NOVH protein belongs to the emerging CCN [Connective tissue growth factor (CTGF), Cyr61/Cef10, nephroblastoma overexpressed gene] family of growth regulators sharing a strikingly conserved multimodular organization but exhibiting distinctive functional features. Two members of the family (CYR61 and CTGF) are positive regulators of cell proliferation, whereas NOVH and two other members (ELM1 and RCOP-1) exhibit features of negative regulators of growth. The multimodular structure of these proteins suggests that their biological role(s) may depend on interactions with several factors as well as proteins constitutive of the extracellular matrix. To gain insight into the functionality of these domains, we have used a two-hybrid system to identify proteins interacting with NOVH. We report here that the C-terminal domain confers on the full-length NOVH protein the capacity to bind fibulin 1C, a protein of the extracellular matrix that interacts with several other regulators of cell adhesion. Furthermore, we show that a natural N-truncated isoform of NOVH produced by cells expressing the full-length NOVH protein also binds fibulin 1C with a high affinity, and we hypothesize that the production of truncated isoforms of NOVH (and probably of other CCN proteins) may be a critical aspect in the modulation of their biological activity. These results set the stage for a study of NOVH–fibulin 1C interactions and their potential significance in cell-adhesion signaling in normal and pathological conditions.

‣ Structure-activity analysis of synthetic autoinducing thiolactone peptides from Staphylococcus aureus responsible for virulence

Mayville, Patricia; Ji, Guangyong; Beavis, Ronald; Yang, Hongmei; Goger, Michael; Novick, Richard P.; Muir, Tom W.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 16/02/1999 Português
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The synthesis of virulence factors and other extracellular proteins responsible for pathogenicity in Staphylococcus aureus is under the control of the agr locus. A secreted agr-encoded peptide, AgrD, processed from the AgrD gene product, is known to be an effector of self-strain activation and cross-strain inhibition of the agr response. Biochemical analysis of AgrD peptides isolated from culture supernatants has suggested that they contain an unusual thiol ester-linked cyclic structure. In the present work, chemical synthesis is used to confirm that the mature AgrD peptides contain a thiolactone structure and that this feature is absolutely necessary for full biological activity. The AgrD synthetic thiolactone peptides exhibited biological activity in vivo in a mouse protection test. Structure-activity studies have allowed key aspects of the peptide structure involved in the differential activation and inhibition functions to be identified. Accordingly, we propose a model for activation and inhibition of the agr response in which the former, but not the latter, involves specific acylation of the agr transmembrane receptor, AgrC.

‣ On the mechanism by which vascular endothelial cells regulate their oxygen consumption

Clementi, Emilio; Brown, Guy Charles; Foxwell, Neale; Moncada, Salvador
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 16/02/1999 Português
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Two enzymes, soluble guanylyl cyclase and cytochrome c oxidase, have been shown to be exquisitely sensitive to nitric oxide (NO) at low physiological concentrations. Activation of the soluble guanylyl cyclase by endogenous NO and the consequent increase in the second messenger cyclic GMP are now known to control a variety of biological functions. Cytochrome c oxidase, the terminal enzyme of the mitochondrial respiratory chain, is inhibited by NO. However, it is not clear whether NO produced by the constitutive NO synthase interacts with cytochrome c oxidase, nor is it known what the biological consequences of such an interaction might be. We now show that NO generated by vascular endothelial cells under basal and stimulated conditions modulates the respiration of these cells in response to acute changes in oxygen concentration. This action occurs at the cytochrome c oxidase and depends on influx of calcium. Thus, NO plays a physiological role in adjusting the capacity of this enzyme to use oxygen, allowing endothelial cells to adapt to acute changes in their environment.

‣ A strategy for rapid sequencing of heparan sulfate and heparin saccharides

Turnbull, Jeremy E.; Hopwood, John J.; Gallagher, John T.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 16/03/1999 Português
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Sulfated glycosaminoglycans (GAGs) are linear polysaccharides of repeating disaccharide sequences on which are superimposed highly complex and variable patterns of sulfation, especially in heparan sulfate (HS). HS and the structurally related heparin exert important biological functions, primarily by interacting with proteins and regulating their activities. Evidence is accumulating that these interactions depend on specific saccharide sequences, but the lack of simple, direct techniques for sequencing GAG saccharides has been a major obstacle to progress. We describe how HS and heparin saccharides can be sequenced rapidly by using an integrated strategy with chemical and enzymic steps. Attachment of a reducing-end fluorescent tag establishes a reading frame. Partial selective chemical cleavage at internal N-sulfoglucosamine residues with nitrous acid then creates a set of fragments of defined sizes. Subsequent digestion of these fragments with combinations of exosulfatases and exoglycosidases permits the selective removal of specific sulfates and monosaccharides from their nonreducing ends. PAGE of the products yields a pattern of fluorescent bands from which the saccharide sequence can be read directly. Data are presented on sequencing of heparin tetrasaccharides and hexasaccharides of known structure; these data show the accuracy and versatility of this sequencing strategy. Data also are presented on the application of the strategy to the sequencing of an HS decasaccharide of unknown structure. Application and further development of this sequencing strategy...

‣ A synthetic inhibitor of histone deacetylase, MS-27-275, with marked in vivo antitumor activity against human tumors

Saito, Akiko; Yamashita, Takashi; Mariko, Yukiyasu; Nosaka, Yasuhito; Tsuchiya, Katsutoshi; Ando, Tomoyuki; Suzuki, Tsuneji; Tsuruo, Takashi; Nakanishi, Osamu
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 13/04/1999 Português
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Synthetic benzamide derivatives were investigated for their ability to inhibit histone deacetylase (HDA). In this study, one of the most active benzamide derivatives, MS-27-275, was examined with regard to its biological properties and antitumor efficacy. MS-27-275 inhibited partially purified human HDA and caused hyperacetylation of nuclear histones in various tumor cell lines. It behaved in a manner similar to other HDA inhibitors, such as sodium butyrate and trichostatin A; MS-27-275 induced p21WAF1/CIP1 and gelsolin and changed the cell cycle distribution, decrease of S-phase cells, and increase of G1-phase cells. The in vitro sensitivity spectrum of MS-27-275 against various human tumor cell lines showed a pattern different than that of a commonly used antitumor agent, 5-fluorouracil, and, of interest, the accumulation of p21WAF1/CIP1 tended to be faster and greater in the cell lines sensitive to MS-27-275. MS-27-275 administered orally strongly inhibited the growth in seven of eight tumor lines implanted into nude mice, although most of these did not respond to 5-fluorouracil. A structurally analogous compound to MS-27-275 without HDA-inhibiting activity showed neither the biological effects in cell culture nor the in vivo therapeutic efficacy. These results suggest that MS-27-275 acts as an antitumor agent through HDA inhibition and may provide a novel chemotherapeutic strategy for cancers insensitive to traditional antitumor agents.

‣ Assembly and activation of site-specific recombination complexes

Peña, Carol E. A.; Kahlenberg, J. Michelle; Hatfull, Graham F.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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Site-specific recombination is responsible for a broad range of biological phenomena, including DNA inversion, resolution of transposition intermediates, and the integration and excision of bacteriophage genomes. Integration of mycobacteriophage L5 is catalyzed by a phage-encoded integrase with recombination occurring between specific attachment sites on the phage and mycobacterial chromosomes (attP and attB, respectively). Although some site-specific recombination systems simply involve binding of the recombinase to the sites of strand exchange, synapsis, and recombination, phage systems typically require the assembly of higher-order structures within which the recombinational potential of integrase is activated. The requirement for these structures derives from the necessity to regulate the directionality of recombination—either integration or excision—which must be closely coordinated with other aspects of the phage growth cycles. We show herein that there are multiple pathways available for the assembly of L5 recombination complexes, including the early synapsis of the attP and attB DNAs. This process is in contrast to the model for lambda integration and illustrates the different usage of molecular machineries to accomplish the same biological outcome.

‣ Demonstration of the in vivo interaction of key cell death regulators by structure-based design of second-site suppressors

Parrish, Jay; Metters, Helen; Chen, Lin; Xue, Ding
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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Demonstrating in vivo interaction of two important biomolecules and the relevance of the interaction to a biological process have been difficult issues in biomedical research. Here, we report the use of a homology modeling approach to establish the significance of protein interactions in governing the activation of programmed cell death in Caenorhabditis elegans. A protein interaction cascade has been postulated to mediate activation of cell death in nematodes, in which the BH3-domain-containing (Bcl-2 homology region 3) protein EGL-1 binds the cell-death inhibitor CED-9 and induces release of the death-activating protein CED-4 from inhibitory CED-4/CED-9 complexes. We show here that an unusual gain-of-function mutation in ced-9 (substitution of glycine 169 to glutamate) that results in potent inhibition of most nematode cell deaths impairs the binding of EGL-1 to CED-9 and EGL-1-induced release of CED-4 from CED-4/CED-9 complexes. Based on a modeled EGL-1/CED-9 complex structure, we generated second-site compensatory mutations in EGL-1 that partially restore the binding of EGL-1 to CED-9(G169E) and EGL-1-induced release of CED-4 from CED-4/CED-9(G169E) complexes. Importantly, these mutations also significantly suppress the death-protective activity of CED-9(G169E) in vivo. These results establish that direct physical interaction between EGL-1 and CED-9 is essential for the release of CED-4 and the activation of cell death. The structure-based design of second-site suppressors via homology modeling should be widely applicable for probing important molecular interactions that are implicated in fundamental biological processes.

‣ Coupled two-way clustering analysis of gene microarray data

Getz, Gad; Levine, Erel; Domany, Eytan
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
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We present a coupled two-way clustering approach to gene microarray data analysis. The main idea is to identify subsets of the genes and samples, such that when one of these is used to cluster the other, stable and significant partitions emerge. The search for such subsets is a computationally complex task. We present an algorithm, based on iterative clustering, that performs such a search. This analysis is especially suitable for gene microarray data, where the contributions of a variety of biological mechanisms to the gene expression levels are entangled in a large body of experimental data. The method was applied to two gene microarray data sets, on colon cancer and leukemia. By identifying relevant subsets of the data and focusing on them we were able to discover partitions and correlations that were masked and hidden when the full dataset was used in the analysis. Some of these partitions have clear biological interpretation; others can serve to identify possible directions for future research.

‣ An engineered lipocalin specific for CTLA-4 reveals a combining site with structural and conformational features similar to antibodies

Schönfeld, D.; Matschiner, G.; Chatwell, L.; Trentmann, S.; Gille, H.; Hülsmeyer, M.; Brown, N.; Kaye, P. M.; Schlehuber, S.; Hohlbaum, A. M.; Skerra, A.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Biomolecular reagents that enable the specific molecular recognition of proteins play a crucial role in basic research as well as medicine. Up to now, antibodies (immunoglobulins) have been widely used for this purpose. Their predominant feature is the vast repertoire of antigen-binding sites that arise from a set of 6 hypervariable loops. However, antibodies suffer from practical disadvantages because of their complicated architecture, large size, and multiple functions. The lipocalins, on the other hand, have evolved as a protein family that primarily serves for the binding of small molecules. Here, we show that an engineered lipocalin, derived from human Lcn2, can specifically bind the T cell coreceptor CTLA-4 as a prescribed protein target with subnanomolar affinity. Crystallographic analysis reveals that its reshaped cup-like binding site, which is formed by 4 variable loops, provides perfect structural complementarity with this “antigen.” Furthermore, comparison with the crystal structure of the uncomplexed engineered lipocalin indicates a pronounced induced-fit mechanism, a phenomenon so far considered typical for antibodies. By recognizing the same epitope on CTLA-4 that interacts with the counterreceptors B7.1/B7.2 on antigen-presenting cells the engineered Lcn2 exhibits strong...

‣ Archaeopteryx feathers and bone chemistry fully revealed via synchrotron imaging

Bergmann, U.; Morton, R. W.; Manning, P. L.; Sellers, W. I.; Farrar, S.; Huntley, K. G.; Wogelius, R. A.; Larson, P.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Evolution of flight in maniraptoran dinosaurs is marked by the acquisition of distinct avian characters, such as feathers, as seen in Archaeopteryx from the Solnhofen limestone. These rare fossils were pivotal in confirming the dinosauria-avian lineage. One of the key derived avian characters is the possession of feathers, details of which were remarkably preserved in the Lagerstätte environment. These structures were previously simply assumed to be impressions; however, a detailed chemical analysis has, until now, never been completed on any Archaeopteryx specimen. Here we present chemical imaging via synchrotron rapid scanning X-ray fluorescence (SRS-XRF) of the Thermopolis Archaeopteryx, which shows that portions of the feathers are not impressions but are in fact remnant body fossil structures, maintaining elemental compositions that are completely different from the embedding geological matrix. Our results indicate phosphorous and sulfur retention in soft tissue as well as trace metal (Zn and Cu) retention in bone. Other previously unknown chemical details of Archaeopteryx are also revealed in this study including: bone chemistry, taphonomy (fossilization process), and curation artifacts. SRS-XRF represents a major advancement in the study of the life chemistry and fossilization processes of Archaeopteryx and other extinct organisms because it is now practical to image the chemistry of large specimens rapidly at concentration levels of parts per million. This technique has wider application to the archaeological...

‣ 2D luminescence imaging of pH in vivo

Schreml, Stephan; Meier, Robert J.; Wolfbeis, Otto S.; Landthaler, Michael; Szeimies, Rolf-Markus; Babilas, Philipp
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Luminescence imaging of biological parameters is an emerging field in biomedical sciences. Tools to study 2D pH distribution are needed to gain new insights into complex disease processes, such as wound healing and tumor metabolism. In recent years, luminescence-based methods for pH measurement have been developed. However, for in vivo applications, especially for studies on humans, biocompatibility and reliability under varying conditions have to be ensured. Here, we present a referenced luminescent sensor for 2D high-resolution imaging of pH in vivo. The ratiometric sensing scheme is based on time-domain luminescence imaging of FITC and ruthenium(II)tris-(4,7-diphenyl-1,10-phenanthroline). To create a biocompatible 2D sensor, these dyes were bound to or incorporated into microparticles (aminocellulose and polyacrylonitrile), and particles were immobilized in polyurethane hydrogel on transparent foils. We show sensor precision and validity by conducting in vitro and in vivo experiments, and we show the versatility in imaging pH during physiological and chronic cutaneous wound healing in humans. Implementation of this technique may open vistas in wound healing, tumor biology, and other biomedical fields.

‣ Arabidopsis hybrid speciation processes

Schmickl, Roswitha; Koch, Marcus A.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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The genus Arabidopsis provides a unique opportunity to study fundamental biological questions in plant sciences using the diploid model species Arabidopsis thaliana and Arabidopsis lyrata. However, only a few studies have focused on introgression and hybrid speciation in Arabidopsis, although polyploidy is a common phenomenon within this genus. More recently, there is growing evidence of significant gene flow between the various Arabidopsis species. So far, we know Arabidopsis suecica and Arabidopsis kamchatica as fully stabilized allopolyploid species. Both species evolved during Pleistocene glaciation and deglaciation cycles in Fennoscandinavia and the amphi-Beringian region, respectively. These hybrid studies were conducted either on a phylogeographic scale or reconstructed experimentally in the laboratory. In our study we focus at a regional and population level. Our research area is located in the foothills of the eastern Austrian Alps, where two Arabidopsis species, Arabidopsis arenosa and A. lyrata ssp. petraea, are sympatrically distributed. Our hypothesis of genetic introgression, migration, and adaptation to the changing environment during the Pleistocene has been confirmed: We observed significant, mainly unidirectional gene flow between the two species...

‣ Microfluidic Western blotting

Hughes, Alex J.; Herr, Amy E.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Rapid, quantitative Western blotting is a long-sought bioanalytical goal in the life sciences. To this end, we describe a Western blotting assay conducted in a single glass microchannel under purely electronic control. The μWestern blot is comprised of multiple steps: sample enrichment, protein sizing, protein immobilization (blotting), and in situ antibody probing. To validate the microfluidic assay, we apply the μWestern blot to analyses of human sera (HIV immunoreactivity) and cell lysate (NFκB). Analytical performance advances are achieved, including: short durations of 10–60 min, multiplexed analyte detection, mass sensitivity at the femtogram level, high-sensitivity 50-pM detection limits, and quantitation capability over a 3.6-log dynamic range. Performance gains are attributed to favorable transport and reaction conditions on the microscale. The multistep assay design relies on a photopatternable (blue light) and photoreactive (UV light) polyacrylamide gel. This hydrophilic polymer constitutes both a separation matrix for protein sizing and, after brief UV exposure, a protein immobilization scaffold for subsequent antibody probing of immobilized protein bands. We observe protein capture efficiencies exceeding 75% under sizing conditions. This compact microfluidic design supports demonstration of a 48-plex μWestern blot in a standard microscope slide form factor. Taken together...

‣ Improving spinning disk confocal microscopy by preventing pinhole cross-talk for intravital imaging

Shimozawa, Togo; Yamagata, Kazuo; Kondo, Takefumi; Hayashi, Shigeo; Shitamukai, Atsunori; Konno, Daijiro; Matsuzaki, Fumio; Takayama, Jun; Onami, Shuichi; Nakayama, Hiroshi; Kosugi, Yasuhito; Watanabe, Tomonobu M.; Fujita, Katsumasa; Mimori-Kiyosue, Yuko
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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A recent key requirement in life sciences is the observation of biological processes in their natural in vivo context. However, imaging techniques that allow fast imaging with higher resolution in 3D thick specimens are still limited. Spinning disk confocal microscopy using a Yokogawa Confocal Scanner Unit, which offers high-speed multipoint confocal live imaging, has been found to have wide utility among cell biologists. A conventional Confocal Scanner Unit configuration, however, is not optimized for thick specimens, for which the background noise attributed to “pinhole cross-talk,” which is unintended pinhole transmission of out-of-focus light, limits overall performance in focal discrimination and reduces confocal capability. Here, we improve spinning disk confocal microscopy by eliminating pinhole cross-talk. First, the amount of pinhole cross-talk is reduced by increasing the interpinhole distance. Second, the generation of out-of-focus light is prevented by two-photon excitation that achieves selective-plane illumination. We evaluate the effect of these modifications and test the applicability to the live imaging of green fluorescent protein-expressing model animals. As demonstrated by visualizing the fine details of the 3D cell shape and submicron-size cytoskeletal structures inside animals...

‣ Global meta-analysis reveals no net change in local-scale plant biodiversity over time

Vellend, Mark; Baeten, Lander; Myers-Smith, Isla H.; Elmendorf, Sarah C.; Beauséjour, Robin; Brown, Carissa D.; De Frenne, Pieter; Verheyen, Kris; Wipf, Sonja
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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A major advance of the last 20 y at the interface of biological, environmental, and conservation sciences has been the demonstration that plant biodiversity positively influences ecosystem function. Linking these results to applied conservation efforts hinges on the assumption that biodiversity is actually declining at the local scale at which diversity–function relationships are strongest. Our compilation and analysis of a global database of >16,000 repeat survey vegetation plots from habitats across the globe directly contradict this assumption. We find no general tendency for local-scale plant species diversity to decline over the last century, calling into question the widespread use of ecosystem function experiments to argue for the importance of biodiversity conservation in nature.

‣ Computational and biological studies of mechanical prophylaxis against deep venous thrombosis

Dai, Guohao, 1970-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 151 p.; 8072342 bytes; 8092977 bytes; application/pdf; application/pdf
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Deep vein thrombosis (DVT) of the lower extremity and induced pulmonary embolism are common complications resulting from prolonged periods of bed-rest or immobilization of the limbs. One of the most effective methods of prophylaxis against DVT is external pneumatic compression (EPC). In spite of its wide acceptance as an effective means of prophylaxis, its mechanism remains poorly understood and optimal compression conditions have not been defined. Understanding the biological consequences of EPC is an important goal for optimizing the performance of compression device and providing guidance for clinical use. In the first part of this thesis, a computational model of the leg was developed to simulate hemodynamic conditions under EPC and the influence of different modes of compression were analyzed and compared. Then, a new in vitro cell culture system was developed that can be used to examine the effect of hemodynamic conditions during EPC on endothelial cell (EC) function. The biologic response was assessed through changes in cell morphology and the expression of various pro-thrombotic and anti-thrombotic factors related to EC.; (cont.) The results show that intermittent flow associated with EPC up-regulates EC fibrinolytic potential and vasomotor function. Using DNA microarray technology...

‣ Blinking and nonradiant dark fraction of water-soluble quantum dots in aqueous solution

Yao, Jie; Larson, Daniel R.; Vishwasrao, Harshad D.; Zipfel, Warren R.; Webb, Watt W.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Water-soluble quantum dots (qdots) are now being used in life sciences research to take advantage of their bright, easily excited fluorescence and high photostability. Although the frequent erratic blinking and substantial dark (never radiant) fractions that occur in all available qdots may interfere with many applications, these properties of individual particles in biological environments had not been fully evaluated. By labeling Qdot-streptavidin with organic dyes, we were able to distinguish individual dark and bright qdots and to observe blinking events as qdots freely diffused in aqueous solution. Bright fractions were measured by confocal fluorescence coincidence analysis (CFCA) and two-photon cross-correlation fluorescence correlation spectroscopy (FCS). The observed bright fractions of various preparations were proportional to the ensemble quantum yields (QYs), but the intrinsic brightness of individual qdots was found to be constant across samples with different QYs but the same emission wavelengths. Increasing qdots' illuminated dwell time by 10-fold during FCS did not change the fraction of apparently dark qdots but did increase the detected fraction of blinking qdots, suggesting that the dark population does not arise from millisecond blinking. Combining CFCA with wide-field imaging of arrays of qdots localized in dilute agarose gel...

‣ Capture Hi-C reveals novel candidate genes and complex long-range interactions with related autoimmune risk loci

Martin, Paul; McGovern, Amanda; Orozco, Gisela; Duffus, Kate; Yarwood, Annie; Schoenfelder, Stefan; Cooper, Nicholas J.; Barton, Anne; Wallace, Chris; Fraser, Peter; Worthington, Jane; Eyre, Steve
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Article; published version
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This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/ncomms10069; Genome-wide association studies have been tremendously successful in identifying genetic variants associated with complex diseases. The majority of association signals are intergenic and evidence is accumulating that a high proportion of signals lie in enhancer regions. We use Capture Hi-C to investigate, for the first time, the interactions between associated variants for four autoimmune diseases and their functional targets in B- and T-cell lines. Here we report numerous looping interactions and provide evidence that only a minority of interactions are common to both B- and T-cell lines, suggesting interactions may be highly cell-type specific; some disease-associated SNPs do not interact with the nearest gene but with more compelling candidate genes (for example, FOXO1, AZI2) often situated several megabases away; and finally, regions associated with different autoimmune diseases interact with each other and the same promoter suggesting common autoimmune gene targets (for example, PTPRC, DEXI and ZFP36L1).; We thank Frank Dudbridge for providing the R scripts to analyse the interaction data. We would like to acknowledge the Faculty of Life Sciences Genomics Facility...

‣ Analysis of the Stability of a Type III Secretion System Containing Pathogenicity Island (PII-3) in the Human Pathogen Vibrio Cholerae

Peters, Molly
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Fidelma Boyd; Vibrio cholerae is an enteric pathogen that is the causative agent of the secretory diarrhea, cholera, that affects millions of people each year. While the V. cholerae O1 serogroup pathovar strains are well studied due to their propensity to cause epidemic and pandemic cholera, a second pathovar has been identified that causes inflammatory diarrhea. Strains of this pathovar encode a Type III Secretion system (T3SS) that is present on a Pathogenicity Island (PAI), a mobile genetic element integrated into the chromosome of some non-O1 serogroup strains. Our hypothesis is that this PAI was horizontally acquired and was an essential acquisition in the emergence of this pathovar. The aims of this study were to investigate the genetic structure of T3SS island regions, examine the excision behavior of the region in strain NRT36S and reconstruct the evolutionary history of the region. To accomplish this, we first performed a bioinformatics analysis among a group of strains that contain a T3SS. We constructed a genetic deletion of cognate T3SS island integrase, intV2, and determined the excision phenotype of the island using a two stage nested PCR assay. We showed that intV2 is necessary for the excision of the region. Lastly...