1,720,963 research outputs found
A revised view of the central nervous system microenvironment and major histocompatibility complex class II antigen presentation
No full textThere are numerous observations reporting that phagocytes expressing major histocompatibility complex (MHC) Class II molecules are associated with the central nervous system (CNS) in normal and pathological conditions. Although MHC Class II expression is necessary for antigen presentation to CD4 + T-cells, it is not sufficient and co-stimulatory molecules are also required. We review here recent in vivo studies demonstrating that the microglia and perivascular macrophages are unable to initiate a primary immune response in the CNS microenvironment, but may support secondary immune responses. Although in vitro studies show that microgila do not support a primary immune response leading to T-cell proliferation, they do show that microglia may protect the CNS from the unwanted attentions of autoreactive T- cells by inducing their apoptosis. The lack of cells in the CNS parenchyma with the ability to initiate a primary immune response has a cost, namely that pathogens may persist in the CNS undetected by the immune system.</p
Cat and monkey retinal ganglion cells and their visual functional roles
No full textRetinal ganglion cells, the integrative-output neurons of the retina, can be sorted into functional classes. In the cat, two ganglion cell classes are labelled X and Y. These are distinguished by the different retinal subnetworks that provide their input. X cells are driven by a single linear receptive field center mechanism. Y cells receive center and surround signals and additional signals from nonlinear subunits in their receptive fields. Both X and Y cells are highly sensitive to contrast. X cells project almost exclusively to the A or A1 layers of the lateral geniculate nucleus (LGN). Y cell axons terminate in the A or A1 layers and also the more ventral C layers, and also the superior colliculus. In the monkey, P cells connect the retina to the parvocellular layers of the LGN, have small receptive fields, are wavelength-selective, and are insensitive to contrast. M cells are ganglion cells that send axons to the magnocellular layers of the LGN, are not wavelength-selective, have somewhat larger receptive fields than P cells, and are very sensitive to contrast. Comparisons between cat and monkey ganglion cell classes reveal several important similarities between M cells and X cells.</p
Silencing synapses: A route to understanding synapse degeneration in chronic neurodegenerative disease
No full textThe degeneration of pre-synaptic boutons in the stratum radiatum of the dorsal hippocampus is one of earliest components of neurodegeneration in several models of murine prion disease. We recently showed that blockade of synaptic transmission by infusion of botulinum neurotoxin A (BoNT/A) into the hippocampus several weeks prior to the onset of degeneration, had no detectable impact on the extent of the synaptic degeneration.1 We elaborate here on the rationale for these experiments and highlight why we believe that this negative result is interesting and important. We also discuss new observations that might provide insights into the molecular events that underlie synapse degeneration.</p
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
Microglia and the urokinase plasminogen activator receptor/uPA system in innate brain inflammation
No full textThe urokinase plasminogen activator (uPA) receptor (uPAR) is a GPI-linked cell surface protein that facilitates focused plasmin proteolytic activity at the cell surface. uPAR has been detected in macrophages infiltrating the central nervous system (CNS) and soluble uPAR has been detected in the cerebrospinal fluid during a number of CNS pathologies. However, its expression by resident microglial cells in vivo remains uncertain. In this work, we aimed to elucidate the murine CNS expression of uPAR and uPA as well as that of tissue plasminogen activator and plasminogen activator inhibitor 1 (PAI-1) during insults generating distinct and well-characterized inflammatory responses; acute intracerebral lipopolysaccharide (LPS), acute kainate-induced neurodegeneration, and chronic neurodegeneration induced by prion disease inoculation. All three insults induced marked expression of uPAR at both mRNA and protein level compared to controls (naïve, saline, or control inoculum-injected). uPAR expression was microglial in all cases. Conversely, uPA transcription and activity was only markedly increased during chronic neurodegeneration. Dissociation of uPA and uPAR levels in acute challenges is suggestive of additional proteolysis-independent roles for uPAR. PAI-1 was most highly expressed upon LPS challenge, whereas tissue plasminogen activator mRNA was constitutively present and less responsive to all insults studied. These data are novel and suggest much wider involvement of the uPAR/uPA system in CNS function and pathology than previously supposed.</p
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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