1,721,196 research outputs found
An interactive cranial nerve package for head and neck anatomy: bridging the gap between lecture and the lab
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Kainate is both trophic and proliferative for hippocampal precursors via AMPA receptors in-vitro and has differential effects on proliferation kinetics in the subgranular zone and granule cell layer after seizure induction in-vivo
No full textKainate enhances hippocampal precursor cell proliferation and survival in vitro, while Kainate induced seizures additionally recruits quiescent progenitors in vivo
No full textIt is widely accepted that hippocampal neurogenesis persists throughout life and is altered by acute seizures. Kainate is often used to model temporal lobe epilepsy and hippocampal damage. Kainate-induced status epilepticus transiently enhances hippocampal neurogenesis but the mechanisms are not well understood. Therefore, we examined the effects of Kainate on hippocampal precursors in vitro. We also investigated the acute effects of Kainate/seizures on a pre-labelled clone of proliferating hippocampal precursors in vivo.
Cultured hippocampal cells were prepared from Wistar rats P7-10 and exposed to 5µM Kainate. BrdU and Ki-67 were used to measure cell proliferation while caspase-3, Propidium iodide, MitoTracker, and Time-lapse microscopy were used to study cell survival. Nestin and TuJ1 were used to label precursor cells and neuroblasts, respectively. To examine Kainate effects in vivo, a clone of proliferating cells in the dentate gyrus was pre-labelled with BrdU 24 hours before Kainate-induced status epilepticus and examined 6-72 h later.
In vitro, we found that Kainate increased the proliferation rate of nestin-positive postnatal hippocampal precursors, via AMPA receptors. It also enhanced the survival of nestin and TuJ1 cells with a proportional increase in neuroblasts. Consistently, Kainate/seizures in vivo increased cell proliferation in the subgranular zone (SGZ) and granule cell layer (GCL) of the adult dentate gyrus, without enhancing cell death. Kainate/seizures recruited un-labelled quiescent cells in the SGZ. In contrast it increased the proliferation of the pre-labelled population only in the GCL. Kainate/seizures drove significantly more BrdU+ cells to become postmitotic in the GCL but not in the SGZ. Doublecortin positive cells increased in the GCL by 72 h after Kainate.
We conclude that Kainate enhances hippocampal precursor proliferation and survival without increasing cell death, while seizures recruit a quiescent cell population in the SGZ
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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