1,720,960 research outputs found
Identification of a bipotential precursor cell in hepatic cell lines derived from transgenic mice expressing cyto-Met in the liver.
No full textMet murine hepatocyte (MMH) lines were established from livers of transgenic mice expressing constitutively active human Met. These lines harbor two cell types: epithelial cells resembling the parental populations and flattened cells with multiple projections and a dispersed growth habit that are designated palmate. Epithelial cells express the liver-enriched transcription factors HNF4 and HNF1alpha, and proteins associated with epithelial cell differentiation. Treatments that modulate their differentiation state, including acidic FGF, induce hepatic functions. Palmate cells show none of these properties. However, they can differentiate along the hepatic cell lineage, giving rise to: (a) epithelial cells that express hepatic transcription factors and are competent to express hepatic functions; (b) bile duct-like structures in three-dimensional Matrigel cultures. Derivation of epithelial from palmate cells is confirmed by characterization of the progeny of individually fished cells. Furthermore, karyotype analysis confirms the direction of the phenotypic transition: palmate cells are diploid and the epithelial cells are hypotetraploid. The clonal isolation of the palmate cell, an immortalized nontransformed bipotential cell that does not yet express the liver-enriched transcription factors and is a precursor of the epithelial-hepatocyte in MMH lines, provides a new tool for the study of mechanisms controlling liver development
Inhibition of MMH (Met Murine Hepatocyte) cell differentiation by TGFbeta is abrogated by pre-treatment with the heritable differentiation effector FGF1
No full textMMH (Met murine hepatocyte) liver cells derived from transgenic mice expressing a truncated constitutively active form of human c-Met are non-transformed immortalized cell lines. We have previously shown that they harbor: (1) epithelial cells that express the liver-enriched transcription factors HNF4 and HNF1 alpha, and that can be stably induced by FGF1 to express liver functions, and (2) fibroblast-like bi-potential palmate cells that can differentiate into bile duct-like structures in Matrigel cultures, or into epithelial cells competent to express hepatic functions. Low concentrations of TGF beta have been found to inhibit growth and differentiation of MMH cells. The factor stabilized the palmate cell phenotype, and it provoked epithelial cells to acquire palmate-like morphological characteristics, in parallel with down-regulation of expression of HNF4 and HNF1 alpha and activation of Snail transcripts. The effects of TGF beta were dominant if it was added with FGF1, but the effects on differentiation were abrogated if cells had been pre-treated with FGF1, This work identifies TGF beta as a factor that could be implicated in maintaining bi-potential precursor cells in the liver, FGF1 as one that could override the TGF beta effects and Snail as a candidate for mediation of the signal
IDENTIFICAZIONE DI UN PRECURSORE BIPOTENZIALE IN LINEE CELLULARI EPATOCITARIE (MMH) DERIVATE DA TOPI TRANSGENICI PER CYTO-MET.
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
MMH (MET MURINE HEPATOCYTES): UN NUOVO STRUMENTO BIOTECNOLOGICO PER LO STUDIO DELLA FUNZIONE E DEL DIFFERENZIAMENTO EPATOCITARIO IN VITRO
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
- …
