1,721,012 research outputs found
Gender-dependent effect of P2X7 antagonism on motor neuron dysfunction in a mouse model of ALS
No full textGABAA and glycine strychnine-sensitive receptor modulate NMDA-evoked acetylcholine release from rat spinal motor neurons: A possible role in neuroprotection
No full text
GABA(A) and strychnine-sensitive glycine receptors modulate N-methyl-d-aspartate-evoked acetylcholine release from rat spinal motoneurons: A possible role in neuroprotection
No full textIncreasing experimental and clinical evidence suggests
that abnormal glutamate transmission might play a
major role in a vast number of neurological disorders.
As a measure of glutamatergic excitation, we have studied
the acetylcholine (ACh) release induced by N-methyl-D-aspartate
(NMDA) receptor stimulation in primary cultured rat
ventral horn spinal neurons and we have evaluated the possibility
to limit the consequences of the hyperactivation of
glutamatergic receptors, by recruiting the inhibitory transmission
mediated by GABA and glycine. For this purpose, we have
exposed cell cultures, previously loaded with [3H]choline, to
NMDA, which increased the spontaneous tritium efflux in a
concentration-dependent manner. Tritium release is dependent
upon external Ca2+, tetrodotoxin, Cd2+ ions and w-conotoxin
GVIA, but not on w-conotoxin MVIIC nor nifedipine, suggesting
the involvement of N-type voltage-sensitive calcium channels.
NMDA-mediated [3H]ACh release was completely prevented by
MK-801, 5,7-diclorokynurenic acid and ifenprodil, while it was
strongly inhibited by a lower external pH, suggesting that the
involved NMDA receptors contain NR1 and NR2B subunits.
Muscimol inhibited NMDA-evoked [3H]ACh release and its effect
was antagonized by SR95531 and potentiated by diazepam,
indicating the involvement of benzodiazepine-sensitive GABAA
receptors. Also glycine, via strychnine-sensitive receptors, inhibited
the effect of NMDA.
It is concluded that glutamate acts on the NMDA receptors
situated on spinal motoneurons to evoke ACh release, which
can be inhibited through the activation of GABAA and glycine
receptors present on the same neurons. These data suggest
that glutamatergic overload of receptors located onto spinal
cord motoneurons might be decreased by activating GABAA and glycine receptors
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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