1,721,010 research outputs found
Presynaptic AMPA receptors : more than just ion channels?
No full textAMPA receptor ion channels are of paramount importance for postsynaptic excitation. Several reports demonstrate that AMPA receptors are present in the presynaptic compartment and point to a role of these receptors in the modulation of presynaptic function. We discuss here the possibility that not only ion influx through the receptor, but also biochemical cascades, activated by ligand binding and independent from ion flux, might contribute to AMPA mediated presynaptic modulation
Vesicle recycling in developing neurons : how to build a presynaptic terminal
No full textOver the past decade, evidence has accumulated indicating that, during development, the construction of synapses--the sites of communication between neurons--might rely on the utilization of preassembled sets of synaptic proteins, which have already accumulated in the axon and are highly mobile, before getting recruited to the sites of contact with the postsynaptic neuron. In this review, we discuss evidence from most recent publications pointing to the existence of active vesicle traffic and turnover in developing neurons, which lead to the construction of new synaptic sites
Purinergic P2X7 Receptor Drives T Cell Lineage Choice and Shapes Peripheral γδ Cells
No full textTCR signal strength instructs αβ versus γδ lineage decision in immature T cells. Increased signal strength of γδTCR with respect to pre-TCR results in induction of the γδ differentiation program. Extracellular ATP evokes physiological responses through purinergic P2 receptors expressed in the plasma membrane of virtually all cell types. In peripheral T cells, ATP released upon TCR stimulation enhances MAPK activation through P2X receptors. We investigated whether extracellular ATP and P2X receptors signaling tuned TCR signaling at the αβ/γδ lineage bifurcation checkpoint. We show that P2X7 expression was selectively increased in immature γδ +CD25 + cells. These cells were much more competent to release ATP than pre-TCR-expressing cells following TCR stimulation and Ca 2+ influx. Genetic ablation as well as pharmacological antagonism of P2X7 resulted in impaired ERK phosphorylation, reduction of early growth response (Egr) transcripts induction, and diversion of γδTCR- expressing thymocytes toward the αβ lineage fate. The impairment of the ERK-Egr-inhibitor of differentiation 3 (Id3) signaling pathway in γδ cells from p2rx7 -/- mice resulted in increased representation of the Id3-independent NK1.1-expressing γδ T cell subset in the periphery. Our results indicate that ATP release and P2X7 signaling upon γδTCR expression in immature thymocytes constitutes an important costimulus in T cell lineage choice through the ERK-Egr-Id3 signaling pathway and contributes to shaping the peripheral γδ T cell compartment. Copyrigh
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
Cell-autonomous regulation of hematopoietic stem cell cycling activity by ATP
No full textExtracellular nucleotides regulate many cellular functions through activation of purinergic receptors in the plasma membrane. Here, we show that in hematopoietic stem cell (HSC), ATP is stored in vesicles and released in a calcium-sensitive manner. HSC expresses ATP responsive P2X receptors and in vitro pharmacological P2X antagonism restrained hematopoietic progenitors proliferation, but not myeloid differentiation. In mice suffering from chronic inflammation, HSCs were significantly expanded and their cycling activity was sensitive to treatment with the P2X antagonist periodate-oxidized 2,3-dialdehyde ATP. Our results indicate that ATP acts as an autocrine stimulus in regulating HSCs pool size
- …
