130,516 research outputs found
Identification of two regulatory elements within the high mobility group box transcription factor XTCF-4
No full textSome members of the Wnt family of extracellular glycoproteins regulate target gene expression by inducing stabilization and nuclear accumulation of beta -catenin, which functions as a transcriptional activator after binding to transcription factors of the T-cell factor! lymphoid enhancer factor (TCF/LEF) family. Three different members of this family have been identified in Xenopus laevis thus far that differ in their ability to influence mesodermal differentiation and to activate expression of the Wnt target gene fibronectin, Here we report on the isolation and characterization of additional variants of XTCF-4. We:show that the differential ability of these proteins and other members of the TCF family to activate target genes is neither due to preferential interaction with transcriptional cofactors of the groucho family or SMAD4 nor to different DNA binding affinities, Expression of these proteins in an epithelial cell line reveals differences in their ability to form a ternary complex with DNA and beta -catenin. Interestingly, formation of this ternary complex was not sufficient to activate target gene expression as previously thought. Our experiments identify two amino acid sequence motifs, LVPQ and SFLSS, in the central domain of XTCF-4 that regulate the formation of the DNA-TCF-beta -catenin complex or activation of target genes, respectively Biochemical studies reveal that the phosphorylation state of these XTCF-4 variants correlates with their ability to form a ternary complex with beta -catenin and DNA but not to activate target gene expression, The described variants of XTFC-4 with their different properties in complex formation provide strong evidence that in addition to the regulation of beta -catenin stability the isoforms of TCF/LEF transcription factors and their posttranslational modifications define the cellular response of a Wnt/wingless signal
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Funktionalisierung strukturierter Oberflächen mit E-Cadherin Ektodomänen
No full textIn dieser Arbeit wurde SNAP-getaggtes E-Cadherin hergestellt und auf mittels µCP strukturierten Thiol-Monoschichten immobilisiert. Thiol-Monoschichten wurden mittels XPS, AFM, ToF-SIMS und QCM-D charakterisiert. E-Cadherin funktionalisierte Oberflächen wurden in Zelladhäsionsassays eingesetzt um die Cadherin-Funktionalität nachzuweisen
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Antagonistic regulation of convergent extension movements in Xenopus by Wnt/β-catenin and Wnt/Ca2+ signaling
No full textConvergent extension movements are the main driving force of Xenopus gastrulation. A fine-tuned regulation of cadherin-mediated cell-cell adhesion is thought to be required for this process. Members of the Wnt family of extracellular glycoproteins have been shown to modulate cadherin-mediated cell-cell adhesion, convergent extension movements, and cell differentiation. Here we show that endogenous Wnt/beta -catenin signaling activity is essential for convergent extension movements due to its effect on gene expression rather than on cadherins. Our data also suggest that XLEF-1 rather than XTCF-3 is required for convergent extension movements and that XLEF-1 functions in this context in the Wnt/beta -catenin pathway to regulate Xnr-3. In contrast, activation of the Wnt/Ca2+, pathway blocks convergent extension movements, with potential regulation of the Wnt/beta -catenin pathway at two different levels. PKC, activated by the Wnt/Ca2+ pathway, blocks the Wnt/beta -catenin pathway upstream of beta -catenin and phosphorylates Dishevelled. CamKII, also activated by the Wnt/Ca2+ pathway, inhibits the Wnt/beta -catenin signaling cascade downstream of beta -catenin. Thus, an opposing cross-talk of two distinct Wnt signaling cascades regulates convergent extension movements in Xenopus. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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