1,720,987 research outputs found
Utility of isolated hepatocytes and radio-HPLC-MSn for the analysis of the metabolic fate of 19-nortestosterone laurate in cattle.
No full textThe metabolic fate of 19-nortestosterone laurate in cattle was investigated to evaluate target analyte(s) appropriate to surveillance for illicit use as a growth promoting agent. Bovine hepatocytes were incubated with either [3H]19-nortestosterone laurate (19-NTL; 4-estren-17 beta-laurate-3-one) or [3H]19-nortestosterone (19-NT; 4-estren-17 beta-ol-3-one; nandrolone). Hepatocyte medium was extracted with solid phase C18 media and analysed by narrow bore radio-HPLC-MSn (LCQ, Finnigan) to evaluate the structure of metabolites of 19-NTL and 19-NT. Radio-HPLC of hepatocyte medium extracts following incubation with [3H]19-NTL confirmed that the first step of biotransformation in liver was hydrolysis of the fatty acid ester to release [3H]19-NT, which, in turn, was converted into a range of metabolites of diverse polarity. Hydrolysis of hepatocyte medium extracts with beta-glucuronidase (Helix pomatia) indicated that some of these metabolites were glucuronide or sulfate conjugates. Structural analysis of unconjugated metabolities by positive-ion atmospheric pressure chemical ionisation MS2 and comparison with available reference preparations indicated biotransformation of 19-NT to 4-estren-17 alpha-ol-3-one, 4-estren-3, 17-dione (major metabolite after 1 h), n-hydroxy-4-estren-3, 17-dione, n-hydroxy-4-estren-17-ol-3-one, 5 beta-estran-3 alpha-ol-17-one (noretiocholanolone) and 5 beta-estran-3 alpha, 17 beta-ol (major metabolite after 4 h). Conjugated metabolites were analysed by electrospray ionization, which revealed the presence of glucuronide conjugates of alpha-(trace) and beta-epimers of 19-NT, n-hydroxy-4-estren-3, 17-dione, n-hydroxy-4-estren-17-ol-3-one and 5 beta-estran-3 alpha, 17 beta-diol. These studies provide a clear indication of the route of hepatic metabolism in the bovine, which may now be readily substantiated by reference to samples, such as urine or bile, derived from animals treated with unlabelled 19-NTL
Biotransformation of benzydamine by microsomes and precision-cut slices prepared from cattle liver
No full text1. Benzydamine (BZ), a non-steroidal anti-inflammatory drug used in human and veterinary medicine, is not licensed for use in food-producing species. Biotransformation of BZ in cattle has not been reported previously and is investigated here using liver microsomes and precision-cut liver slices. 2. BZ was metabolized by cattle liver microsomes to benzydamine N-oxide (BZ-NO) and monodesmethyl-BZ (Nor-BZ). Both reactions followed Michaelis-Menten kinetics (Km = 76.4 +/- 16.0 and 58.9 +/- 0.4 microM Vmax = 6.5 +/- 0.8 and 7.4 +/- 0.5 nmolmg(-1) min(-1) respectively); sensitivity to heat and pH suggested that the N-oxidation is catalysed by the flavin-containing monooxygenases. 3. BZ-NO and Nor-BZ were the most abundant products derived from liver slice incubations, and nine other BZ metabolites were found and tentatively identified by LC-MS. Desbenzylated and hydroxylated BZ-NO analogues and a hydroxylated product of BZ were detected, which have been reported in other species. Product ion mass spectra of other metabolites, which are described here for the first time, indicated the formation of a BZ N- -glucuronide and five hydroxylated and N+-glucuronidated derivatives of BZ, BZ-NO and Nor-BZ. 4. The results indicate that BZ is extensively metabolized in cattle. Clearly, differences in metabolism compared with, for example, rat and human, will need to be considered in the event of submission for marketing authorization for use in food animals
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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