1,721,049 research outputs found
GABA-A and GABA-B receptors participate in the axon-Schwann cell interactions
No full textThe g-aminobutyrric acid (GABA) is the major inhibitory neurotransmitter responsible of neuron-to-neuron communication and also of neuron-to-glia interactions in the nervous system. In fact, different mechanisms involving the GABA receptors (i.e. GABA-AA and GABA-B receptors) seem to play pivotal roles during the development and differentiation of glial precursor cells. In the rat peripheral nervous system (PNS), both the rat sciatic nerve and the Schwann cells express the GABA-A and the GABA-B receptor isoforms, which are proved to be functionally active. A physiological role for the GABA and its receptors in the PNS might be hypothesised. In particular, we have demonstrated that the selective ligands of the GABA-A and GABA-B receptors, respectively muscimol and baclofen, control the Schwann cell proliferation and the expression of some specific myelin proteins (e.g. glycoprotein P0, peripheral myelin protein 22, PMP22, connexin 32, myelin associated glycoprotein, MAG). Moreover, we have also reported that some neuroactive steroids, such as the allopregnanolone (THP) and androstenediol (3alpha-diol), known to be allosteric modulator of the GABA-A receptor, are able to control the PMP22 synthesis in the Schwann cell. In addition, we have recently observed that THP is the main modulator of the different GABA-B subunit (i.e. 1a, 1b, 2) expressions in the Schwann cells; some of these effects are mimicked by muscimol and GABA, indicating a GABA-A mediated effects in such a control.
Collectively, our observations suggest that, in the PNS, the cross-talk between the GABAergic system (via the GABA-A and GABA-B receptors) and the neuroactive steroids may play an important role in the neuron-Schwann cell interactions, which are modified in case of peripheral degenerative neuropathies. (Supported by E.C. QLK6-CT-2000-00179
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
2,2,6- and 2,3,5-trimethypiperazines as monocyclic analogues of the mu-opioid agonis 3,8-diazabicyclo[3.2.1]octanes: synthesis, modeling and activity
No full textGABA-A and GABA-B mediated effects in the peripheral nervous system : a cross-interaction with neuroactive steroids
No full text
The neurosteroid allopregnanolone upregulates glutamate transport in Schwann cells by changing the surface density of the EAAC1/EAAT3 glutamate transporter
No full textGlutamate has been recently involved in the proliferation and differentiation of Schwann cells, the myelinating cells of the Peripheral Nervous System. Thus, the control of extracellular glutamate level may be crucial for Schwann cell physiology.
We recently observed that functional glutamate transporters were expressed by Schwann cells and modulated by exposure to 10 nM allopregnanolone (ALLO), a progesterone's metabolite. Aim of this study was to identify the molecular mechanisms by which ALLO modulated glutamate uptake.
We found that transport up-regulation did not involve protein neo-synthesis and was prevented by actin depolimerization, suggesting a change in the transporters' trafficking. To verify this hypothesis, Schwann cells were transfected with the GFP-tagged EAAC1 transporter and its surface density was measured by Total Internal Reflection Microscopy (TIRFM). ALLO induced the actin cytoskeleton reorganization and caused the EAAC1 redistribution from intracellular compartments to the plasma membrane, at the tips of filopodia structures. Taken together, these data demonstrate that ALLO up-regulates glutamate transport by increasing the delivery of EAAC1 to the cell surface
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