1,720,970 research outputs found
Increased duodenal iron uptake and transfer in a rat model of chronic hypoxia is accompanied by reduced hepcidin expression
No full textBackground: Despite the requirement for increased iron delivery for erythropoiesis during hypoxia, there is very little information on how duodenal iron uptake and its transfer to the blood adapts to this condition.Aims: To assess the effects of 30 days of chronic hypoxia in rats on luminal iron uptake and transfer of the metal to blood, together with gene expression of hepcidin, a proposed negative regulator of iron transport.Methods: 59-Fe uptake by isolated duodenum and its transfer to blood by in vivo duodenal segments was measured after exposure of rats to room air or 10% oxygen for four weeks. Liver hepcidin expression was measured by real time reverse transcription-polymerase chain reaction. The effects of hypoxia on hepcidin gene expression by HepG2 cells was also determined.Results: Hypoxia did not affect villus length but enhanced (+ 192.6%) luminal iron uptake by increasing the rate of uptake by all enterocytes, particularly those on the upper villus. Hypoxia promoted iron transfer to the blood but reduced mucosal iron accumulation in vivo by 66.7%. Hypoxia reduced expression of hepcidin mRNA in both rat liver and HepG2 cells.Conclusions: Prolonged hypoxia enhances iron transport from duodenal lumen to blood but the process is unable to fully meet the iron requirement for increased erythropoiesis. Reduced secretion of hepcidin may be pivotal to the changes in iron absorption. The processes responsible for suppression of hepcidin expression are unknown but are likely to involve a direct effect of hypoxia on hepatocytes
Interactions between the gastrointestinal tract, kidney, and the liver in the regulation of body phosphate balance
Full text linkInorganic phosphate (Pi) is an essential element that fuels vital processes in the body. To date, there is discord regarding the mechanisms of Pi regulation and the proportion of transport attributed to active (sodium-driven), paracellular, or uncharacterized transcellular pathways. The present studies address this by comparing Pi transport in different segments of the intestine using in vitro, in situ, and ex vivo techniques. Potential Pi signalling between the intestine, kidney, and liver was also investigated using intestinal perfusion and in vivo renal clearance surgeries.
Regional differences in intestinal Pi transport were investigated using the in situ closed-loop, in vitro everted sleeve, and ex vivo intestinal perfusion techniques. These studies highlighted measured Pi transport discrepancies between methods, confirmed the jejunum as the site of highest Pi transport ability in the GI tract, and also revealed that the distal colon transported a significant amount of Pi both in vitro and in situ. An intestinal perfusion technique never applied to studies of Pi transport also exposed a concentrated amount of Pi transported directly across the rat intestinal epithelium.
Renal Pi clearance surgeries investigated a proposed Pi sensing mechanism between the small intestine and the kidney in which a high duodenal Pi load triggered rapid phosphaturia. Present data show no phosphaturia after a physiological 10mM Pi duodenal instillation. In contrast with previously published data, a high Pi load into the
duodenum increased plasma Pi and parathyroid hormone (PTH) levels resulting in correlated phosphaturia.
The role of the liver in Pi transport was investigated by removing the liver following instillation of 1, 5, 10, and 15mM 32P coupled Pi buffer into the jejunum. Data show a steady increase of Pi accumulated in the liver, which correlated with increased Pi concentration instilled into the jejunum. Between 10 and 15mM however, the Pi in the liver reached saturation, suggesting that the liver may only store physiological concentrations of Pi. Sodium-dependency of Pi uptake by the liver was also not apparent until 15mM Pi, in contrast with sodium-dependent Pi transport by the intestine at all four concentrations. This finding suggests a separate mechanism of liver Pi transport at this supraphysiological Pi concentration
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
The effect of dietary status on the structure and absorptive function of the rat small intestine
No full textVariations 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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