1,720,977 research outputs found
Hyperplasia and squamous metaplasia in the tracheobronchial epithelium: alterations in the balance of growth and differentiation factors.
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Positive and negative regulation of proliferation and differentiation in tracheobronchial epithelial cells.
No full textThe lung (in particular the bronchial epithelium) is a major site for tumor formation in humans. Environmental factors in conjunction with genetic factors are important determinants in this disease. The acquisition of defects in the control of proliferation and differentiation appears to constitute crucial steps in the transition of a normal to a neoplastic cell. Several factors have been identified that control positively or negatively the proliferation and differentiation of tracheobronchial epithelial cells. These factors include EGF/TGF alpha, TGF beta, insulin/IGFI, KGF, certain cytokines, retinoids, and activators of protein kinase C. Studies with neoplastic cells have identified several protooncogenes and tumor suppressor genes whose gene products are involved in the regulation of cell growth of normal tracheobronchial epithelial cells, and when mutated, lost, or activated, bring about a neoplastic phenotype. Future studies on the precise function of these genes will help to elucidate the mechanisms by which proliferation and differentiation in normal tracheobronchial epithelial cells are regulated and help to understand the molecular changes involved in diseases such as cancer
Identification and characterization of nuclear retinoic acid-binding activity in human myeloblastic leukemia HL-60 cells.
No full textSpecific [3H]retinoic acid (RA)-binding sites
in nuclear and cytosolic extracts prepared from human myeloblastic
leukemia HL-60 cells have been detected by sucrose
density gradient sedimentation and size-exclusion highperformance
liquid chromatography (HPLC) analyses. This
RA-binding activity migrated as a single peak with an apparent
molecular weight of 50,000 and >95% of the total binding
activity was associated with the nuclear extract. Nuclear extracts
prepared from COS-1 cells transfected with an expression
vector for the nuclear RA receptors RARa or RARE were
enriched (20- to 100-fold) with a RA-binding activity that
coeluted by size-exclusion HPLC with the putative RAR from
HL-60 cells. The HL-60 nuclear receptor exhibited high
affinity binding ofRA and its benzoic acid analogs ChS5, Ch3O,
Ro 13-7410, and SRI 6409-40 and low-affinity binding of
retinol, Ro 8-8717, and SRI 5442-60, correlating well with the
biological activity of these compounds in HL-60 cells. Saturation
binding and Scatchard plot analyses of the binding of RA
to the nuclear HL-60 receptor yielded an apparent dissociation
constant of -0.46 nM and 1400 ± 100 receptor sites per cell.
Northern blot analyses of poly(A)+ RNA with cDNA probes
specific for RARa and RARf indicated that HL-60 cells
contain predominantly transcripts encoded by the RARa gene.
Our results suggest that the observed nuclear RA-binding
activity in HL-60 cells might mediate the action of RA in these
cells
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
Variations 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
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