1,720,960 research outputs found
Silencing of endogenous IGFBP-5 by micro RNA interference affects proliferation, apoptosis and differentiation of neuroblastoma cells
No full textSignal transduction through the IGF axis is implicated in proliferation, differentiation and survival during development and adult life. The IGF axis includes the IGF binding proteins (IGFBPs) that bind IGFs with high affinity and modulate their activity. In neuroblastoma (NB), a malignant childhood tumor, we found that IGFBP-5 is frequently expressed. Since NB is an IGF2-sensitive tumor, we investigated the relevance and the function of endogenous IGFBP-5 in LAN-5 and in SY5Y(N) cell lines transfected with micro and small interfering RNAs directed to IGFBP-5 mRNA. Cells in which IGFBP-5 expression was suppressed were growth-inhibited and more prone to apoptosis than the parental cell line and controls. Apoptosis was further enhanced by X-ray irradiation. The ability of these cells to undergo neuronal differentiation was impaired after IGFBP-5 inhibition but the effect was reversed by exposure to recombinant IGFBP-5. Together, these data demonstrate the importance of IGFBP-5 for NB cell functions and suggest that IGFBP-5 might serve as a novel therapeutic target in NB
Electrostatically driven interaction of silica-supported lipid bilayer nanoplatforms and a nerve growth factor-mimicking peptide
No full textAbstract: The interaction between lipid vesicles and NGF(1-14) peptide, mimicking nerve growth factor, was addressed to fabricate peptide-associated supported lipid bilayers (SLBs). According to a model of predominant electrostatic interactions, zwitterionic and anionic lipid vesicles were used to optimize the peptide association with the lipid membranes. Both planar silica and core-shell nanoparticles (NPs) were used as polar hydrophilic substrates to form the SLBs functionalized with the NGF peptide. The hybrid biointerface was scrutinized by a multitechnique approach with QCM-D, FRAP and fluorescence spectroscopy in terms of self-assembling kinetics, lipid lateral diffusion, and energy transfer processes in the SLB-wrapped silica NPs dye-doped in the core. The response of neuronal cells to the NGF(1-14)-SLBs highlighted their promising application as a drug delivery nanoplatform for ageing-related diseases
C/EBP alpha and beta mimic retinoic acid activation of IGFBP-5 in neuroblastoma cells by a mechanism independent from binding to their site.
No full textSignal transduction mediated by insulin-like growth factors is implicated in the aggressive behavior of neuroblastoma (NB), a childhood tumor originating from the neural crest. IGFBP-5, a protein that binds IGFs with high affinity, is expressed in many NB cell lines exerting opposite effects, depending on its concentration. We found that IGFBP-5 expression increased during retinoic acid (RA)-mediated differentiation of NB cells. This was due to transcriptional activation as demonstrated by reporter assays carried out in basal and differentiating conditions. We defined the shortest region of the human IGFBP-5 promoter (from nucleotide -83 to +53) which is sensitive to RA. Mutation of a CCAAT enhancer binding protein (C/EBP) element inside this region increased transcription, suggesting a repressive role of this sequence. DNA Affinity Precipitation Assays (DAPA) and chromatin immunoprecipitation demonstrated that the binding of C/EBPalpha and beta to the C/EBP site decreased upon treatment with RA. C/EBPalpha and beta induced an increase in IGFBP-5 transcription in human and murine NB cells similar to that obtained upon RA treatment. Activation by C/EBP alpha and beta did not depend on their binding to the C/EBP site, since they still activated IGFBP-5 promoter carrying a mutation in the C/EBP site. Of interest, we found that both transcription factors were able to interact with the TATA box, but only C/EBPalpha interaction increased during RA-induced differentiation
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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