1,720,966 research outputs found
Influence of stress on lymphocyte subset distribution--a flow cytometric study in young student pilots.
No full textEffect of acute exposure to hypoxia on electrolytes and water metabolism regulatory hormones
No full textBackground: Many studies suggest the hypothesis that the pathology of high altitude could be due to an early alteration of the hormones that regulate sodium homeostasis. Hypothesis: The aim of this study was to evaluate the behavior of these hormones during an acute exposure to hypobaric hypoxia. Methods: We studied 26 young healthy pilot students (23.1 ± 29 yrs) in a hypobaric chamber, for 3 h (samples collected at time 0, 120, and 180 min), at 5000 m ASL. Results: The results show an early increase of plasma renin activity (PRA) paradoxically associated to a decrease of aldosterone plasma levels. This later returned to the baseline values at 180 min, whereas PRA remained increased throughout the exposure. Both arginine-vasopressin (ADH) and the atrial natriuretic peptide (ANP) significantly increased, while a new putative hormone, the so-called digoxin-like substance (DLS) did not show significant changes. Conclusions: Our data demonstrate a specific sensitivity of the hormonal systems to hypoxia, which may be influenced by the time of the exposure. The relationship with results previously reported is also addressed
Effects of beta-adrenergic blockade on insulin-mediated glucose disposal in hypertensive and normotensive rats
No full textObjective To evaluate the impact of beta-adrenergic blockade in spontaneously hypertensive rats (SHR) and in their normotensive controls, Wistar-Kyoto (WKY) rats, on whole-body glucose disposal under metabolic steady state conditions, in unrestrained and conscious animals, Method SHR (n = 13) and WKY rats (n = 12) underwent a 240 min insulinaemic clamp study with or without a superinfusion (120th to 240th minutes; second step) of propranolol. Results From 0 to 120 min (the first step) SHR showed significantly increased glucose uptake, muscle glycogen synthesis and glycogen synthase activity compared with WKY rats, When propranolol was superinfused, glucose uptake and muscle glycogen synthesis in SHR returned to levels similar to those observed in WKY rats during the first step, No significant differences were found for whole-body glycolysis in SHR and WKY in the first and second steps. Conclusion Hypertensive rats display an increased insulin sensitivity compared with controls, beta-Blockade is associated with a reduction in overall glucose metabolism in SHR, but not in WKY rats
Effects of acute and protracted hypoxia on plasma levels of atrial natriuretic factor
No full textAcute hypoxia stimulates the release of atrial natriuretic factor (ANF) from isolated rat and rabbit hearts. Increased ANF plasma levels have been found in rats exposed to chronic hypoxia and recently some studies have been conducted on men, with discordant results. The aim of the present study was to verify changes in ANF plasma levels during acute and prolonged hypoxia in young healthy men. We studied 22 subjects (aged 20-28 years, mean 22.7 years) during a simulated exposure to altitude (5000 m) in a hypobaric chamber for 3 hours (A), and 6 subjects (aged 24-51 years, mean 36.5 years) during the scientific expedition to mount Poumori (Nepal 4930 m altitude) with an exposure at maximum altitude for 20 days (B). ANF was measured by the radioimmunoassay method. Results (pg/ml): (A) baseline: 29.4 +/- 18.6; 120 min: 32.0 +/- 17.4 (NS); 180 min: 35.4 +/- 17.1 (p less than 0.05). (B) baseline: 39.6 +/- 13.3; third day: 38.2 +/- 14.1; fifth day: 31.3 +/- 11; seventh day: 29.1 +/- 13.5; tenth day: 32.2 +/- 20.8; fifteenth day: 37.9 +/- 20.2; twentieth day: 34.6 +/- 23.7 (all differences were not significant). In (B) we observed a higher dispersion of values perhaps due to individual variability. The different behaviour of ANF plasma levels in acute and chronic conditions might be due to the adaptive modification of different physiological parameters as loss of plasma volume, natriuresis and attenuation of tissue hypoxia by enhanced erythropoiesis, observed more evidently during prolonged exposure
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
The effects of hypobaric hypoxia on specific B cell responses following immunization in mice and humans.
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