1,720,977 research outputs found
The role of aquaporin-4 in the blood-brain barrier development and integrity: Studies in animal and cell culture models
No full textAquaporin-4 (AQP4) is the major water channel expressed in brain perivascular astrocyte processes. Although the role of AQP4 in brain edema has been extensively investigated, little information exists regarding its functional role at the blood-brain barrier (BBB). The purpose of this work is to integrate previous and recent data regarding AQP4 expression during BBB formation and depending on BBB integrity, using several experimental models. Results from studies on the chick optic tectum, a well-established model of BBB development, and the effect of lipopolysaccharide on the BBB integrity and on perivascular AQP4 expression have been analyzed and discussed. Moreover, data on the BBB structure and AQP4 expression in murine models of Duchenne muscular dystrophy are reviewed. In particular, published results obtained from mdX(3cv) mice have been analyzed together with new data obtained from mdx mice in which all the dystrophin isoforms including DP71 are strongly reduced. Finally, the role of the endothelial component on AQP4 cellular expression and distribution has been investigated using rat primary astrocytes and brain capillary endothelial cell co-cultures as an in vitro model of BBB. (C) 2004 IBRO. Published by Elsevier Ltd. All rights reserved.
Accession Number: WOS:000225726000008
Document Type: Article
Language: English
Author Keywords: aquaporins; brain edema; co-cultures; astrocytes; mdx; muscular dystrophy
KeyWords Plus: DYSTROPHIC MDX-MICE; INSENSITIVE WATER CHANNEL; MIDDLE-T ONCOGENE; RAT-BRAIN; CHICK-EMBRYO; GLIAL-CELLS; PERIVASCULAR ASTROCYTES; MUSCULAR-DYSTROPHY; ORTHOGONAL ARRAYS; PLASMA-MEMBRANES
Reprint Address: Friger, A (reprint author), Univ Bari, Dept Gen & Environm Physiol, Via Amendola 165-A, I-70126 Bari, Italy
Addresses
Automated cell-based assay for screening of aquaporin inhibitors
No full textAquaporins form water channels that play major roles in a
variety of physiological processes so that altered expression
or function may underlie pathological conditions. In order
to identify compounds that modulate aquaporin function,
we have implemented a functional assay based on rapid
measurement of osmotically induced cell volume changes
to screen several libraries of diverse drugs. The time course
of fluorescence changes in calcein-loaded cells was analyzed
during an osmotic challenge using a 96-multiwell fluorescence
plate reader. This system was validated using astrocyte
primary cultures and fibroblasts that strongly express
endogenous AQP4 and AQP1 proteins, respectively, as well
as AQP4-transfected cells. We screened 3575 compounds,
including 418 FDA-approved and commercially available
drugs, for their effect on AQP-mediated water transport.
Primary screening yielded 10 compounds that affected
water transport activity in both astrocytes and AQP4-
transfected cells and 42 compounds that altered cell volume
regulation in astrocytes. Selected drugs were then analyzed
on AQP1-expressing erythrocytes and AQP4-expressing
membrane vesicles by stopped-flow light scattering. Four
molecules of the National Cancer Institute’s chemical library
(NSC164914, NSC670229, NSC168597, NSC301460)
were identified that differentially affected both AQP4 and
AQP1 mediated water transport, with EC50 values between
20 and 50 μM. This fluorescence microplate readerbased
assay may, thus, provide a platform for highthroughput
screening which, when coupled to a secondary
evaluation to confirm target specificity, should allow
discovery of AQP-specific compounds for novel therapeutic
strategies in the treatment of water balance
disorders
Biomarkers of Astrocyte Microdomains - Focus on Gap Junctions, Purinergic Receptors, and Aquaporins
No full textEffect of microgravity on gene expression in mouse brain
No full textChanges in gravitational force such as that experienced by astronauts during space flight induce a redistribution of fluids from the caudad to the cephalad portion of the body together with an elimination of normal head-to-foot hydrostatic pressure gradients. To assess brain gene profile changes associated with microgravity and fluid shift, a large-scale analysis of mRNA expression levels was performed in the brains of 2-week control and hindlimb-unloaded (HU) mice using cDNA microarrays. Although to different extents, all functional categories displayed significantly regulated genes indicating that considerable transcriptomic alterations are induced by HU. Interestingly, the TIC class (transport of small molecules and ions into the cells) had the highest percentage of up-regulated genes, while the most down-regulated genes were those of the JAE class (cell junction, adhesion, extracellular matrix). TIC genes comprised 16% of those whose expression was altered, including sodium channel, nonvoltage-gated 1 beta (Scnn1b), glutamate receptor (Grin1), voltage-dependent anion channel 1 (Vdac1), calcium channel beta 3 subunit (Cacnb3) and others. The analysis performed by GeneMAPP revealed several altered protein classes and functional pathways such as blood coagulation and immune response, learning and memory, ion channels and cell junction. In particular, data indicate that HU causes an alteration in hemostasis which resolves in a shift toward a more hyper-coagulative state with an increased risk of venous thrombosis. Furthermore, HU treatment seems to impact on key steps of synaptic plasticity and learning processes
Contribution of Aquaporins and TRPV4 to astrocyte cell volume regulation
No full textRegulatory Volume Decrease (RVD) is a process by which cells restore their volume when swollen by hypo-osmotic stress. In this study, we have focused on the role played by two different Aquaporins (AQPs), AQP4 and AQP1, in mediating Ca2+ signaling after hypotonic shock and in triggering RVD, together with the Transient Receptor Potential Vanilloid 4 (TRPV4), a Ca2+-permeable channel activated by the membrane stretching.
Using biophysical techniques to measure the water plasma membrane permeability of WT and AQP4 KO astrocytes and of cells transfected with AQP4 or AQP1, we showed that both AQPs play a key role in RVD by affecting the initial kinetics of the swollen phase that is faster and higher in amplitude in the presence of AQPs. By calcium imaging we showed that AQP4 and AQP1-mediated cell swelling significantly increases the amplitude of Ca2+ influx inhibited by the TRPV4 inhibitors, Gadolinium (Gad) and Ruthenium Red (RR). Finally, the effect of Ca2+ influx through TRPV4 on the cell volume regulation was analyzed by measuring RVD in the presence of Gad and RR or removing the external Ca2+.
Our results show that the RVD kinetic was unchanged in all these conditions, indicating that the TRPV4 mediated Ca2+ influx does not play a role in RVD. All together these results show that 1) AQPs play a key role in mediating Ca2+ signaling after hypotonic shock together with TRPV4, 2) AQPs are the main trigger for RVD, and 3) Ca2+is not fundamental for RVD to occur
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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