1,720,997 research outputs found
Synthesis of Gaba in Schwann cells is induced by the neuroactive steroid allopregnanolone
No full textRecently we hypothesized that, in the PNS, the Schwann cells are the primary target for GABA’s action, as shown by the presence of mRNAs coding for a variety of GABA-A and GABA-B receptor subunits (Magnaghi, Curr. Neuropharmacol. 2007). Allopregnanolone (ALLO), a reduced metabolite of progesterone, modulates GABA-A receptor in Schwann cells and increases mRNA and protein levels of PMP22 (Magnaghi, Brain Res Rev. 2001). This observation is supported by the evidence that muscimol (a selective GABA-A agonist) similarly enhances PMP22 mRNA levels, whereas bicuculline (a specific GABA-A antagonist) counteracts such increase (Magnaghi, Brain Res Rev. 2001). Therefore, the expression of PMP22 in Schwann cells seems to be under control of GABA-A receptor. In addition, ALLO induces a robust stimulation of the mRNAs coding for some GABA-B receptor subunits. These effects are partially mimicked by muscimol, suggesting that ALLO controls GABA-B receptor expression through GABA-A mediated mechanism (Magnaghi, J Mol. Neurosci 2006). However, the general mechanism downstream ALLO activation of GABA-A is still elusive. Consequently, we aimed at elucidating ALLO’s-mediated mechanism(s) in Schwann cells, and its putative effects on GABA synthesis. By means of different approaches we demonstrated the presence of glutamic acid decarboxylase of 67 kDa (GAD67) in Schwann cells; additionally we demonstrated that GABA is synthesized and localized in Schwann cells. Finally, we suggested that PKA pathway, through enhanced cAMP levels and CREB phosphorylation is the intracellular signalling pathway responsible for such an allosteric action of ALLO at GABA-A receptor in Schwann cells. The knowledge of these mechanisms, therefore, might be important to establish new putative strategies to treat peripheral neuropathies
The neurosteroid allopregnanolone modulates specific functions in central and peripheral glial cells
Full text linkSince the first observations on the existence of neurosteroids in the 1980’s, our understanding of the importance of these endogenous steroids in the control of the central and peripheral nervous system has increased progressively. Although most of the observations were made in neuronal cells, equally important are the effects that neurosteroids exert on glial cells. Among the different classes of neurosteroids acting on glial cells, the progesterone 5α-3α metabolite, allopregnanolone, displays a particular mechanism of action involving primarily the modulation of classic GABA receptors. In this review, we focus our attention on allopregnanolone because its effects on the physiology of glial cells of the central and peripheral nervous system are intriguing and could potentially lead to the development of new strategies for neuroprotection and/or regeneration of injured nervous tissues
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
Expression of functional γ-aminobutyric acid type A receptors in Schwann-like adult stem cells.
No full textγ-Aminobutyric acid (GABA) receptors are present in peripheral and central glia and modulate important physiological parameters of glial cells. Schwann cells (SC), the peripheral nervous system glial cells, play essential roles in nerve regeneration, but they are unsuitable for bioengineering of nerve repair. Increasing interest has been focused on adult stem cells derived from bone marrow (BM-MSC) or adipose tissue (ASC), which can be differentiated into SC-like phenotype and used as SC replacements. SC-like adult stem cells express GABA-B receptors that can modulate their proliferation. The aim of this study was to investigate GABA-A receptors functional expression in differentiated stem cells. BM-MSC and ASC were found to express GABA-A α2 and β3, but not β1 mRNA transcripts. Protein expression levels of GABA-A α2 and β3 receptors were upregulated following SC-like differentiation as shown by Western blot studies. GABA-A receptor stimulation with muscimol increased the proliferation rate of SC, differentiated BM-MSC and differentiated ASC. In conclusion, GABA-A α2 and β3 receptor subunits are present in BM-MSC and ASC and upregulated following glial differentiation. GABA-A subunits in differentiated stem cells and SC assemble in functional receptors modulating cell proliferation. Functional GABA-A and GABA-B receptors represent a possible pharmacological target to modulate SC-like stem cells physiology
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
Anti-proliferative and anti-migratory effects are mediated by M2 muscarinic receptor in Schwannlike cells induced from adipose mesenchymal stem cells : implication in nerve regeneration
No full textDispelling 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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