1,720,955 research outputs found
Expression of hypoxia-inducible factor-1 in the cochlea of newborn rats
No full textHypoxia/ischemia is a major pathogenetic factor in the development of hearing loss. An important transcription factor involved in the signaling and adaptation to hypoxia/ischemia is the hypoxia-inducible factor-1 (HIF-1). To study HIF-1 expression we used an in vitro hypoxia model of explant and dissociated cultures of the stria vascularis, the organ of Corti with limbus and the modiolus from the cochlea of 3-5-day-old Wistar rats. Hypoxia differentially increased HIF-1 activity as measured by a reporter gene. Twenty-four hour hypoxia increased HIF-1 activity 14.1 +/- 3.5-fold in the modiolus, 9.4 +/- 3.0-fold in the organ of Corti with limbus, and 6.4 +/- 1.5-fold in the stria vascularis. The HIF-1alpha mRNA level was measured by quantitative reverse transcription polymerase chain reaction and showed a lower expression in the modiolus (1.3 +/- 0.2 pg/mug RNA) than in both the organ of Corti with limbus and the stria vascularis (2.7-3.2 +/- 1.3, P < 0.01). Hypoxia had no effect on the HIF-1 alpha mRNA levels. The region-specific regulation of HIF-1 expression on the transcriptional and posttranslational levels may expand the possibilities for adaptation of the cochlea to hypoxia. (C) 2003 Elsevier B.V. All rights reserved
Apoptosis, necrosis and hypoxia inducible factor-1 in human head and neck squamous cell carcinoma cultures
No full textThe objective of this study was to examine the mode of cell death and the hypoxia inducible factor-1 (HIF-1) expression of human head and neck squamous cell carcinoma (HNSCC) exposed to hypoxia in vitro. Apoptosis and necrosis rates were examined using flow cytometry. The findings suggest that HNSCC cells show a considerable heterogeneity in cell size and in response to hypoxia. A small-cell population showed a high spontaneous apoptosis and necrosis rate which was in-sensitive to hypoxia. A large-cell population responded to hypoxia by increase of apoptosis rate in parallel to recruitment of HIF-1. Hypoxia led to increased HIF-1 alpha protein levels in nuclear extract using ELISA-binding activity. In all cells, accumulation of HIF-1 in the nuclei during hypoxia and a rapid degradation of HIF-1 in the post-hypoxic period were observed immunocytochemically. The HIF-1 alpha mRNA level showed an expression of 10-40 pg/mu g total RNA and remained unchanged in one cell line, while slightly decreasing in the other. Remarkably, no increased luciferase activity response was found on the reporter gene level using pGL3 reporter gene with three erythropoietin hypoxia responsive elements, either by hypoxia or by application of lactacystin, desferrioxamine or CoCl2. These findings suggest that, in HNSCC cells, hypoxia induces HIF-1 alpha to stabilize and accumulate in the cell nuclei but have a cell-specific transcriptional complex
Apoptosis, necrosis and hypoxia inducible factor-1 in human head and neck squamous cell carcinoma cultures
No full textThe objective of this study was to examine the mode of cell death and the hypoxia inducible factor-1 (HIF-1) expression of human head and neck squamous cell carcinoma (HNSCC) exposed to hypoxia in vitro. Apoptosis and necrosis rates were examined using flow cytometry. The findings suggest that HNSCC cells show a considerable heterogeneity in cell size and in response to hypoxia. A small-cell population showed a high spontaneous apoptosis and necrosis rate which was in-sensitive to hypoxia. A large-cell population responded to hypoxia by increase of apoptosis rate in parallel to recruitment of HIF-1. Hypoxia led to increased HIF-1 alpha protein levels in nuclear extract using ELISA-binding activity. In all cells, accumulation of HIF-1 in the nuclei during hypoxia and a rapid degradation of HIF-1 in the post-hypoxic period were observed immunocytochemically. The HIF-1 alpha mRNA level showed an expression of 10-40 pg/mu g total RNA and remained unchanged in one cell line, while slightly decreasing in the other. Remarkably, no increased luciferase activity response was found on the reporter gene level using pGL3 reporter gene with three erythropoietin hypoxia responsive elements, either by hypoxia or by application of lactacystin, desferrioxamine or CoCl2. These findings suggest that, in HNSCC cells, hypoxia induces HIF-1 alpha to stabilize and accumulate in the cell nuclei but have a cell-specific transcriptional complex
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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