1,720,979 research outputs found
Hormonal effects of prohormones : novel approaches towards effect based screening in veterinary growth promoter control
No full textWithin the European Union the use of growth promoting agents in cattle fattening is prohibited according to Council Directive 96/22/EC. Interestingly, there is not a black list of substances, but 96/22/EC states that all substances having thyrostatic, estrogenic, androgenic or gestagenic activity are prohibited. Besides abuse of the “classical” synthetic steroids there is a tendency towards misuse of natural steroids and prohormones. Prohormones are compounds that exhibit limited or no hormonal activity but are direct precursors of bioactive hormones and are intended to be converted to full active hormones via enzymatic processes in the body. However, knowledge about metabolism, the mode of action and excretion profiles in cattle is often unclear, and methods to detect abuse of prohormones in livestock production are lacking. Therefore, the aim of this thesis was to get insight into the hormonal action of prohormones and to develop novel in vitro and in vivo screening methods allowing effective surveillance on the illegal use of prohormones in livestock production. Hereby the emphasis was on developing effect based approaches to better meet Council Directive 96/22/EC. The bioactivity of a wide variety of supplements which contained prohormones were tested using a yeast androgen bioassay. For supplements containing solely prohormones the value of this bioactivity based screening appeared to be limited as they require metabolism to become active. Therefore, screening methods for animal feed, supplements and preparations were set-up by using the same yeast androgen bioassay in combination with bovine liver models as well as enzymatic and chemical deconjugation procedures to mimic in vivo metabolic bioactivation. The use of either bovine liver S9, liver slices, pure enzymes or alkaline hydrolysis showed that prohormones could be activated, resulting in a significant increase in bioactivity as determined by the androgen yeast bioassay. For the detection of prohormone abuse at the farm and/or slaughterhouse the usefulness of ‘omics’ based profiling techniques was investigated. Within this scope a comprehensive metabolomics based screening strategy for steroid urine profiling was developed. Comparison of urinary profiles revealed large differences between the profiles of controls and dehydroepiandrosterone (DHEA) as well as pregnenolone treated animals. Moreover this steroid urine profiling approach allowed identification of biomarkers for treatment by specific prohormones. This resulted in respectively 7 and 12 specific mass peak loadings which could potentially be used as biomarkers for pregnenolone and DHEA treatment. In addition, the feasibility of a liver gene expression profiling approach was investigated to monitor the effects of DHEA treatment at the transciptome level. It was shown that identification and application of genomic biomarkers for screening of DHEA abuse in cattle is substantially hampered by biological variation. On the other hand, it was demonstrated that comparison of pre-defined gene sets versus the whole genome expression profile of an animal allows to distinguish DHEA treatment effects from variations in gene expression due to inherent biological variation. Altogether the results of this thesis increase the knowledge about the metabolism and bioactivation of prohormones in vitro as well as in vivo. Based on this knowledge, a panel of new effect based concepts and screening methods was developed that complement and improve the current testing programs. These new concepts will facilitate better implementation of the European ban on growth promoters in livestock production as described in Council Directive 96/22/EC. <br/
Transcription profiling by array of Bos taurus liver from control and either orally or intramuscularly DHEA treated animals
No full textComparing gene expression profiles of bovines treated orally or intramuscularly with DHEA versus control 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
- …
