1,354,107 research outputs found
Sorting of two polytopic proteins, the gamma-aminobutyric acid and betaine transporters, in polarized epithelial cells
No full textThe g-aminobutyric acid transporter (GAT-1) isoform of the g-aminobutyric acid and the betaine (BGT) transporters exhibit distinct apical and basolateral distributions when introduced into Madin-Darby canine kidney
cells (Pietrini, G., Suh, Y. J., Edelman, L., Rudnick, G.,and Caplan, M. J. (1994) J. Biol. Chem. 269, 4668–4674). We have investigated the presence of sorting signals in their COOH-terminal cytosolic domains by expression in Madin-Darby canine kidney cells of mutated and chimeric transporters. Whereas truncated GAT-1 (DC-GAT)
maintained the original functional activity and apicallocalization, either the removal (DC-myc BGT) or the substitution (BGS chimera) of the cytosolic tail of BGT generated proteins that accumulated in the endoplasmic reticulum. Moreover, we have found that the cytosolic tail of BGT redirected apical proteins, the polytopic
GAT-1 (GBS chimera) and the monotopic human
nerve growth factor receptor, to the basolateral surface.These results suggest the presence of basolateral sorting information in the cytosolic tail of BGT. We have further shown that information necessary for the exit of BGT from the endoplasmic reticulum and for the basolateral
localization of the GBS chimera is contained in a short segment, rich in basic residues, within the cytosolic tail of BGT
Evidence for a functional nitric oxide synthase system in brown adipocyte nucleus
No full textAbstractThe intracellular localization and activity of the nitric oxide synthase (NOS) isoforms were investigated in rat brown adipocytes. Immunohistochemistry showed cytoplasmic and nuclear staining for the endothelial NOS (eNOS) and inducible NOS (iNOS) isoforms; accordingly, anti-L-citrulline antibody, a marker of NOS activity, immunostained both the cytoplasm and the nucleus. The presence of metabolically active NOS in the nucleus was further confirmed by immunoblotting analyses of subcellular fractions of homogenates from cultured brown adipocytes and by measurements of NOS activity in the cytosol and nucleus. Sympathetic stimulation in vivo (i.e. cold exposure or β3-adrenergic agonist treatment) and in vitro (i.e. noradrenaline treatment of cultured cells) significantly increased both cytosolic and nuclear eNOS and iNOS expression and activities. By contrast, the number of iNOS-positive, but not eNOS-positive, nuclei was significantly lower in the functionally impaired brown fat of genetically obese Zucker fa/fa rats. These data suggest the existence of a noradrenaline-modulated functional NOS system in the nucleus of brown adipocytes
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
White adipocytes are less prone to apoptotic stimuli than brown adipocytes in rodent
No full textObesity in rodents is related to a functional atrophy of brown adipose tissue (BAT), and consequent impairment of adaptive thermogenesis and increased white adipose tissue (WAT) mass.1 Further to defects in molecular processes of the adaptive thermogenesis, the BAT atrophy may be due to an increased rate of brown fat cell death.2 The expression of tumor necrosis factor (TNF)- is elevated in WAT of a variety of obese animals3 and humans,4 and TNF-receptor 1 (TNFR-1) stimulation induces brown adipocyte apoptosis both in vitro and in vivo.2, 5 Although there is some evidence that apoptosis of white adipocytes may be relevant in certain situations,6, 7 its role in WAT accumulation is not clearly defined. Here, a different sensitivity to apoptotic stimuli is reported in brown and white adipocytes, concomitant with a cell-specific expression of pro- and anti-apoptotic molecules. This difference is evident also in BAT and WAT of rats either subjected to starvation or genetically obese
Variations on the Author
No full text“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
No full textWe 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
Prion protein structure is affected by pH-dependent interaction with membranes: A study in a model system
No full textAbstractInteraction of full length recombinant hamster prion protein with liposomes mimicking lipid rafts or non-raft membrane regions was studied by circular dichroism, chemical cross-linking and sucrose gradient ultracentrifugation. At pH 7.0, the protein bound palmitoyloleoylphosphatidylcholine/cholesterol/sphingomyelin/monosialoganglioside GM1 (GM1) ganglioside liposomes but not palmitoyloleoylphosphatidylcholine alone (bound/free=0.33 and 0.01, respectively), maintaining the native α-helical structure and monomeric form. At pH 5.0, though still binding to quaternary mixtures, in particular GM1, the protein bound also to palmitoyloleoylphosphatidylcholine (bound/free 0.35) becoming unfolded and oligomeric. The pH-dependent interaction with raft or non-raft membranes might have implication in vivo, by stabilizing or destabilizing the protein
Ischemic conditions and beta-secretase activation: The impact of membrane cholesterol enrichment as triggering factor in rat brain endothelial cells
No full textAmong harmful conditions damaging the blood-brain barrier, cerebral stroke and reperfusion injuries were proposed as contributing factors to Alzheimer's disease etiology. Indeed it was reported that ischemic conditions promote beta-amyloid peptide production in brain endothelial cells, although implicated mechanisms are yet not fully understood.
Oxidative injury related to ischemia affects membrane-lipids profile by altering their biochemical properties and structural dynamics, which are also believed to play significant role in the amyloid precursor protein processing, suggesting a link between alterations in lipid membrane composition and beta-amyloid peptide production enhancement.
Using brain microvascular endothelial cells, here we demonstrate how oxygen and glucose deprivation followed by normal conditions restoration, mimicking ischemic environment, increases cell cholesterol amount (+20%), reduces membrane fluidity and results in strong activation (+40%) of beta-secretase 1 enzymatic activity. Moreover, we observed an increase of amyloid precursor protein and beta-secretase 1 protein levels with altered localization in non-discrete (Triton X-100 soluble) membrane domains, leading to an enhanced production of amyloid precursor protein beta-carboxyl-terminal fragment. Therefore, lipid alterations induced by oxygen and glucose deprivation enhance beta-secretase 1 activity, favor its proximity to amyloid precursor protein and may concur to increased amyloidogenic cleavage. The latter, represents a detrimental event that may contribute to beta-amyloid homeostasis impairment in the brain and to Alzheimer's disease-related BBB dysfunctions
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
- …
