1,720,972 research outputs found
Correlation between evans blue dye and radiolabeled albumin in guinea pig airways in vivo
No full textWe quantified the tissue exudation and luminal transudation of two plasma markers, Evans blue (EB) dye and [125I]-human serum albumin (HSA), into the airways of the anesthetized guinea pig in response to platelet activating factor (PAF). There was a highly significant correlation between the tissue content of EB and [125I]-HSA in all airways studied. Significant correlation for transudation of the two markers was limited to high rates of plasma leakage. [125I]-HSA was the more sensitive marker for the association between exudation and transudation and the effect of PAF on transudation. EB was the better marker for assessing the relationship between the dose of PAF and plasma exudation. © 1989
Effect of anti-asthma drugs on microvascular leakage in guinea-pig airways
No full textWe have studied the effects of intravenous epinephrine, albuterol, verapamil, and aminophylline on airway microvascular leakage in guinea pigs. Microvascular leakage was induced by platelet-activating factor (PAF; 50 ng/kg intravenously), which acts directly on venular endothelial cells, and measured by quantifying extravasation of Evans blue (EB) dye. Epinephrine (20 μg/kg) inhibited PAF-induced changes in dye leakage in larynx and main bronchi; at 80 and 160 μg/kg, significant inhibition was observed in all airways studied. This effect was reversed by phentolamine (2.5 mg/kg) or prazosin (100 μg/kg). By contrast, albuterol (20 to 320 μg/kg) and aminophylline (12.5 to 50 mg/kg) failed to inhibit dye leakage at any dose studied. Verapamil inhibited PAF-increased leakage in larynx, main bronchi, and intrapulmonary airways at the lowest dose tested (125 μg/kg), although inhibition was not dose dependent. These results suggest that the antiedema effect of epinephrine may be due to vasocon..
Corticosteroid inhibition of airway microvascular leakage
No full textWe studied the effect of dexamethasone on microvascular leakage (using Evans blue dye as a marker of plasma exudation) induced in rat airways by platelet-activating factor (PAF). Intravenously administered PAF caused a dose-related increase in plasma leakage over the range 0.1 to 1 micrograms/kg. At 500 ng/kg PAF, the response was maximal in the extrapulmonary airways examined with increases in leakage above those in control animals of 312% in the larynx, 295% in the trachea, and 167% in the main bronchi. A maximal response was not achieved in the intrapulmonary airways at the doses of PAF tested: at 1 microgram/kg the increase was 206% above that in control animals. Dexamethasone, given by intraperitoneal injection 24 h and 4 h before PAF at a dose of 0.2 mg/kg on each occasion, partially inhibited leakage induced by PAF (1 microgram/kg) in all airway levels studied by 43 to 65%. At each level the tissue concentration of dye was reduced to a value that was significantly (p less than 0.05) different from either PAF or control values. We also determined whether a high dose (8 mg/kg) of dexamethasone given intraperitoneally would inhibit plasma leakage of dye induced by either PAF or antigen-challenge of sensitized rats. When given 4 h before antigen, dexamethasone completely prevented allergen-induced leakage in the airways showing significant leakage (larynx, trachea, and intrapulmonary airways). Similarly, dexamethasone (4 h before) partially inhibited PAF-induced leakage in the trachea and main bronchi. In summary, in rat airways, both low and high doses of dexamethasone markedly inhibit mediator-induced plasma exudation
Effect of platelet activating factor on formation and composition of airway fluid in the guinea-pig trachea
No full textWe studied the effect of platelet activating factor (PAF) on leakage of albumin, and secretion of fucose (a marker for mucus glycoprotein) and protein into the tracheal lumen of the guinea-pig isolated in situ, and on bioelectric properties and fluxes of mannitol in vitro. We also studied the effect of PAF on mucus secretion in human bronchi in vitro. 2. In guinea-pig, intravenous PAF markedly increased the luminal concentration of protein but did not significantly increase fucose concentrations. Increased albumin leakage (274% above controls at a dose of 50 ng/kg PAF) was associated with the increased luminal content of protein (248% above controls at the same dose of PAF). 3. Leakage of albumin was maximal 10 min after PAF, was significantly reduced by 20 min and had returned to baseline by 30 min. This pattern of leakage could be repeated with successive administrations of PAF. 4. PAF induced small but significant biphasic changes in bioelectric properties in vitro. The initial response was rapid in onset and characterized by maximal increases in short-circuit current (Isc) of 6.5% above controls at 7.5 min and in conductance (G) of 7% at 20 min. Both responses were blocked by the PAF receptor antagonist WEB 2086. Amiloride blocked the increase in Isc. Permeability of the tissue to mannitol (Pmann) was unaltered. The delayed response was characterized by maximal increases in Isc and G of 10% above controls at 60-90 min which were not significantly affected by WEB 2086 or amiloride. Pmann was increased by 38% at 90 min. 5. PAF increased fucose secretion in human bronchi in vitro. 6. Lyso-PAF in vitro caused changes similar to those induced by PAF on bioelectric properties and mucus secretion, but had no significant effects in vivo. 7. Light microscopy showed no evidence of epithelial disruption in animals given intravenous PAF at a dose causing significant albumin transudation. 8. We conclude that PAF increases the protein content of guinea-pig tracheal fluid principally by inducing plasma leakage rather than mucus secretion and that the small changes in ion transport and epithelial conductance may reduce the tendency to epithelial disruption during plasma leakage
Effects of treatment on airway microvascular leakage
No full textMicrovascular leakage, an essential component of inflammation, probably plays a critical role in asthma in producing plasma exudation and thickening of the bronchial mucosa which may underlie airway hyperresponsiveness. Several therapeutic approaches are possible to reduce this leakage, by blocking either the effects or the release of inflammatory mediators which induce the leakage. Drugs with these actions might be too specific to be of therapeutic value if many mediators are involved, as seems increasingly likely. Reduction of blood flow using selective vasoconstrictors is a more attractive approach and α1-adrenoceptor agonists may be of value. Drugs that act directly on endothelial cells are probably the most useful, since they would be effective irrespective of the mechanism of leakage. Corticosteroids probably have this property, but whether β-agonists or theophylline are clinically effective against airway microvascular leakage is not yet certain. The development of new drugs whi..
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
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