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Excitotoxic lesions of the ventral anteroventral third ventricle and pressor responses to central sodium, ouabain and angiotensin II
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Ouabain- and central sodium-induced hypertension depend on the ventral anteroventral third ventricle region
No full textTo examine the role of the ventral anteroventral third ventricle (vAV3V) in the hypertension induced by chronic subcutaneous ouabain and intracerebroventricular hypertonic saline, neurons in this area were destroyed by microinjection of an excitotoxin, ibotenic acid. Sham-operated or lesioned Wistar rats were administered ouabain (50 μg/day) or placebo for 3 wk from subcutaneously implanted controlled release pellets or artificial cerebrospinal fluid (CSF) or CSF containing 0.8 mol/l NaCl (5 μl/h) infused intracerebroventricularly for 2 wk. At the end of the experiment, mean arterial pressure (MAP) and heart rate at rest and in response to ganglionic blockade by intravenous hexamethonium (30 mg/kg) were assessed. In rats infused with hypertonic saline, responses to air jet stress were also assessed. Baseline MAP in sham-operated rats receiving intracerebroventricular hypertonic saline or subcutaneous ouabain was significantly higher than in control rats (115 ± 1 vs. 97 ± 3 and 121 ± 3 vs. 103 ± 3 mmHg, respectively). vAV3V lesions abolished the increase in MAP elicited by chronic infusion of hypertonic saline or administration of ouabain. Sham-operated rats treated with hypertonic saline or ouabain exhibited significantly enhanced decreases in MAP to hexamethonium, but lesioned rats did not. Rats infused with hypertonic saline demonstrated enhanced responses to air jet stress that were similar in sham-operated and lesioned rats. These results demonstrate that neurons in the vAV3V are essential for the hypertension induced by intracerebroventricular hypertonic saline and subcutaneous ouabain, possibly by increasing sympathetic tone. Cardiovascular responses to air jet stress appear not to be mediated by the vAV3V.</jats:p
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
Brain “ouabain,” ANG II, and sympathoexcitation by chronic central sodium loading in rats
No full text Both brain ouabain-like activity (“ouabain”) and brain angiotensin II (ANG II) contribute to the sympathoexcitatory and pressor responses to high sodium intake in spontaneously hypertensive (SHR) and Dahl salt-sensitive (Dahl S) rats. To assess whether increases in cerebrospinal fluid (CSF) sodium can mimic this pattern of changes, Wistar rats were chronically infused with artificial CSF (aCSF) or sodium-rich aCSF (0.8 or 1.2 M sodium) intracerebroventricularly through osmotic minipumps for 14 days. Sodium-rich aCSF (0.8 M) was also infused intracerebroventricularly for 2 wk concomitantly with either antibody Fab fragments that bind ouabain and related steroids with high affinity, γ-globulins as control (200 μg/day for both), or the AT1blocker losartan (1 mg ⋅ kg−1 ⋅ day−1). Sodium-rich aCSF increased CSF sodium from 146 ± 2 to 152 ± 2 (0.8 M) and 160 ± 3 (1.2 M) mmol/l, and increased brain “ouabain” in the hypothalamus, pituitary, and pons. In conscious rats, sodium-rich aCSF increased baseline mean arterial pressure (MAP), enhanced MAP, heart rate (HR), and renal sympathetic nerve activity (RSNA) responses to intracerebroventricular α2-adrenoceptor agonist guanabenz and air stress, and desensitized arterial and cardiopulmonary baroreflex control of HR and RSNA. These effects were largely prevented by intracerebroventricular Fab fragments or losartan. Thus, in Wistar rats, both brain “ouabain” and the brain renin-angiotensin system contribute to sympathoexcitation, impairment of baroreflexes, and hypertension caused by chronically increased CSF sodium. The similar patterns of changes caused by CSF sodium in Wistar rats and by high sodium intake in SHR and Dahl S rats indicate that if high sodium intake increases central sodium, such changes may contribute to sympathoexcitation and hypertension. </jats:p
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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