1,721,028 research outputs found
S-Nitrosothiols in blood: does photosensitivity explain a 4-order-of-magnitude concentration range?
No full textStudy of the effect of thiols on the vasodilatory potency of S-nitrosothiols by using a modified aortic ring assay
No full textBoth low-molecular-mass thiols (LMM-SH) and protein thiols (P-SH) can modulate the biological activity of S-nitrosothiols (RSNO) via S-transnitrosation reactions. It has been difficult to evaluate the entity of this effect in blood circulation by in vitro assays with isolated aorta rings so far, because media rich in proteins cannot be used due to the foaming as a consequence of the needed gas bubbling. We have modified the original apparatus for organ bioassay in order to minimize foaming and to increase analytical performance. By using this modified bioassay we investigated the vasodilatory potency of various endogenous RSNOs in the presence of physiologically relevant concentrations of albumin and LMM-SH. Our results show that the sulfhydryl group of the cysteine moiety of albumin and LMM-SH has a dramatic effect on the vasodilatory potency of RSNO. Considering the equilibrium constants for S-transnitrosation reactions and the concentration of P-SH and LMM-SH we measured in healthy humans (aged 18-85. years), we infer that the age-dependency of hematic levels of LMM-SH may have a considerable impact in RSNO-mediated vasodilation. S-Nitrosoproteins such as S-nitrosoalbumin may constitute a relatively silent and constant amount of circulating RSNO. On the other hand, LMM-SH may mediate and control the biological actions of S-nitrosoproteins via S-transnitrosation reactions, by forming more potent nitric oxide-releasing LMM- S-nitrosothiols. Lifestyle habits, status of health and individual age are proven factors that, in turn, may influence the concentration of these compounds. These aspects should be taken into consideration when testing the vasodilatory effects of RSNO in pre-clinical studies
On the mercapturic acid pathway of nitric oxide: is S-nitrosoglutathione present in the bile?
No full textN-Acetylcysteine ethyl ester (NACET): a novel lipophilic cell-permeable cysteine derivative with an unusual pharmacokinetic feature and remarkable antioxidant potential
No full textRecent large clinical trials failed to confirm the supposed beneficial effects of N-acetylcysteine (NAC) in preventing oxidative stress-related diseases. This may be due to its low bioavailability. We thought that esterification of the carboxyl group of NAC to produce N-acetylcysteine ethyl ester (NACET) would drastically increase the lipophilicity of NAC, thus greatly improving its pharmacokinetics. In the present work, we report on representative chemical, pharmacological and anti-oxidant properties of NACET, especially in direct comparison with its congener NAC. We found that NACET is rapidly absorbed in rats after oral administration but reaches very low concentrations in plasma. This is due to a unique feature of NACET: it rapidly enters the cells where it is trapped being transformed into NAC and cysteine. After oral treatment, NACET (but not NAC) was able to increase significantly the glutathione content of most tissues examined, brain included, and to protect from paracetamol intoxication in the rat. NACET has also the unique feature to accumulate in human erythrocytes where it behaves as a potent protector against hydroperoxide-induced oxidative damage. Our study shows that being able to enter cells and to produce NAC and cysteine, NACET increases circulating hydrogen sulfide (H2S), thus representing a good candidate for the oral use as an H2S producer, with clear advantages over NAC. NACET has the potential to substitute NAC as a mucolytic agent, as a paracetamol antidote and as a GSH-related antioxidant. © 2012 Elsevier Inc
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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