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COTRASPORTATORE NA+-GLUCOSIO NEL MESOTELIO PLEURICO E NELL'EPITELIO ALVEOLARE POLMONARE: ESPRESSIONE E CENNI DI REGOLAZIONE BETA ADRENERGICA
Get PDFSGLT1 (SLC5A1) is a Na+–glucose cotransporter belonging to the SLC5 family, expressed in several absorbing epithelia. Indirect evidence for a solute-coupled liquid absorption from rabbit pleural space indicated that it should be due to a Na+/H+-Cl-/HCO3- double exchanger and a Na+-glucose cotransporter (Agostoni and Zocchi, Clin Chest Med 19:241-60, 1998). Furthermore, functional evidence of Na+-glucose cotransport in rat lung has been provided by Basset (Basset et al., J Physiol 384:325-345, 1987). By autoradiography [3H]phloridzin binding has been found confined to alveolar type II cells in mouse and rabbit lungs (Boyd, J Physiol 422: 44P, 1990). In the alveolar airspace the active Na+ transport is regulated by beta adrenergic receptors, particularly the β2 subtype (Mutlu et. al., Am J Respir Crit Care Med 170:1270–1275, 2004). Experimental data suggest that beta adrenergic agonists, working via the β2AR, accelerate clearance of excess fluid from the alveolar airspace; activation of β2AR seems to increase both Na+/K+-ATPase and ENaC function and expression (Pesce et. al., FEBS Letters 486:310-314, 2000; Chen et. al., Am J Physiol Lung Cell Mol Physiol 282:609-620, 2002). In literature there are no data regarding a beta adrenergic regulation of Na+–glucose cotransport in the respiratory system, but in two cases is reported a beta adrenergic stimulation of SGLT1, in rat small intestine (Ishikawa et al., Biochimica et Biophysica Acta 1357: 306–318, 1997) and in ruminal epithelium of sheep (Aschernbach et al., J. Nutr. 132: 1254–1257, 2002).
In this research, we first tried to obtain molecular evidence for Na+-glucose cotransporter (SGLT1) in the respiratory system, particularly in pleural and alveolar epithelia. The expression of SGLT1 was identified by Western blot assays on total protein extracts of scraped mesothelium from visceral or parietal pleura, and from alveolar cells; in all experiments we obtained SGLT1 specific bands. Immunolocalization of SGLT1 was performed examining for fluorescence the pleural surface, the alveolar epithelium and isolated alveolar cells. Confocal immunofluorescence images of lamb pleural mesothelium showed that SGLT1 is located in the apical membrane; in alveolar sections of rats and lambs most alveolar surface was stained by anti-SGLT1 antibody; furthermore also alveolar type I and type II cells isolated from rat lung were stained by anti-SGLT1 antibody, so we can assume that SGLT1 is expressed on both types of alveolar cells. After that, we concentrated on beta adrenergic regulation of SGLT1; immunofluorescence assays were performed on A549 cells (alveolar epithelial cell line) treated for different times with the beta adrenergic agonist isoproterenol. Immunolabeling images showed an increased expression of the Na+-glucose cotransporter after treatment with the β-agonist isoproterenol; this increase appears to be reversible.
These findings provide evidence at molecular level, in pleural and alveolar epithelium, for Na+-glucose cotransporter (SGLT1); in the respiratory system, it seems to be involved in solute-coupled liquid absorption from the pleural space and from the alveolar airspace. Like other channels and trasporters that play a role in the solute-coupled liquid absorption, SGLT1 appears to be upregulated by β-adrenergic agonists
Evidence for Na(+)-glucose cotransporter in type I alveolar epithelium
No full textFunctional evidence of Na+/glucose cotransport in rat lung has been provided by Basset et al. (J. Physiol. 384:325–345, 1987). By autoradiography [3H]phloridzin binding has been found confined to alveolar epithelial type II cells in mouse and rabbit lungs (Boyd, J. Physiol. 422: 44P, 1990). In this research we checked by immunofluorescence whether Na+/glucose cotransporter (SGLT1) is also expressed in alveolar type I cells. Lungs of anesthetized rats and lambs were fixed by paraformaldehyde, perfused in pulmonary artery, or instilled into a bronchus, respectively. Tissue blocks embedded in paraffin or frozen were sectioned. Two specific anti-SGLT1 antibodies for rat recognizing aminoacid sequence 402–420, and 546–596 were used in both species. Bound primary antibody was detected by secondary antibody conjugated to fluorescein isothiocianate or Texas red, respectively. In some sections cellular nuclei were also stained. In rats alveolar type I cells were identified by fluorescent Erythrina cristagalli lectin. Sections were examined by confocal laser-scanning microscope. Both in rats and lambs alveolar epithelium was stained by either antibody; no labeling occurred in negative controls. Hence, SGLT1 appears to be also expressed in alveolar type I cells. This is functionally relevant because type I cells provide 95–97% of alveolar surface, and SGLT1, besides contributing to removal of lung liquid under some circumstances, keeps low glucose concentration in lining liquid, which is useful to prevent lung infection
Na+-glucose cotransporter is also expressed in mesothelium of species with thick visceral pleura
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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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