1,721,057 research outputs found
Characterization of a CYP3A-like activity in the digestive gland of Mytilus galloprovincialis-inhibition by 17alfa ethynylestradiol
No full textCYP3A enzyme is a toxicologically relevant end-point; interactions between xenobiotics (e.g. pharmaceuticals and xenoestrogens) and CYP3A may compromise both the clearance of xenobiotics and endogenous molecules (e.g. steroid hormones), as they share common routes of metabolism through CYP3A enzymes. The purpose of this work was to better characterize CYP3A-like enzyme in microsomal fractions isolated from the digestive gland of mussels Mytilus galloprovincialis by using 7benzyloxy-4-trifluoromethylcoumarin as a substrate. The higher Km value in mussels collected from Barcelona harbor with respect to that collected from Ebro delta indicated lower affinity of the enzyme in polluted specimens. 17 alfa-ethynylestradiol (EE2)acted as mixed inhibitor of CYP3A activity. The study contributes to the better knowledge of CYP3A-like activity in mussels and shows potential interference between EE2 and possibly other pollutants, and CYP3A function
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
Triphenyltin alters androgen metabolism in the sea urchin Paracentrotus lividus
No full textAndrogen metabolism (androstenedione and testosterone) has been assessed in the digestive tube and gonads of the echinoderm Paracentrotus lividus exposed to different concentrations of the biocide triphenyltin (TPT) in a semi-static water regime for 4 weeks. Key enzymatic activities involved in both synthesis and metabolism of androgens, namely 17 beta-hydroxysteroid dehydrogenases (17 beta-HSDs), 3 beta-HSDs, 5 alpha-reductases, P450-aromatase, palmitoyl-CoA:testosterone acyltransferases (ATAT) and testosterone sulfotransferases (SULT), were investigated in digestive tube and/or gonads of control and TPT-exposed specimens in an attempt to see whether androgen metabolism was altered by exposure. In agreement with previous data for vertebrates, exposure to TPT led to a concentration dependent decrease of P450-aromatase that was statistically significant at the highest TPT concentration tested (225 ng/L). Additionally, increased metabolism of testosterone to form dihydrotestosterone (DHT) and 5 alpha-androstane-3 beta, 17 beta-diol was observed, suggesting increased 5 alpha-reductase activity in the gonads of TPT-exposed individuals. Interestingly, exposure to TPT induced testosterone conjugating activities in organisms exposed to medium (SULT) and high (ATAT and SULT) TPT concentrations. Despite the changes of androgen metabolizing enzymes, testosterone levels in gonads remained rather stable. In contrast, an increase in testosterone and a concomitant decrease in estradiol were observed in the coelomic fluid of TPT-exposed organisms. Overall, the data indicate the ability of TPT to modulate androgen metabolism and circulating steroid levels in R lividus and suggest the existence of regulatory mechanisms to maintain stable endogenous levels of testosterone in gonads. This study also contributes to a better knowledge of echinoderm endocrinology
Reproductive cycle and sex hormones in the feather star Antedon mediterranea
No full textIn the recent decades, the importance of echinoderm endocrinology has increased because of the use of echinoderms as models for aquatic ecotoxicology and due to their evolutionary closeness to chordates. Nonetheless, apart from asteroids and echinoids, there is limited information available on the reproductive physiology of echinoderm groups, particularly crinoids. This investigation focused on the reproductive cycle of Antedon mediterranea and was intended to elucidate the reproductive pattern occurring in this species. We observed spawning throughout the year, though there were preferential months. The sex ratio was biased in favour of females. Possible correlations between steroid level variations and gonad maturity were also evaluated: testosterone and 17β-estradiol mean levels were higher at the beginning of gametogenesis and during vitellogenesis, suggesting their possible involvement in nutrient supply for developing gametes. This study should stimulate further work on steroids and steroid derivatives as ancestral hormones characteristic of the animal kingdom
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
C. Porte de Mandjaq as-Silâhdâr
No full textFarnall Harry, Shafik Muhammad, Simaïka Marcus H., Sayed Metoualli, Omar Ahmad, 'Amrusi Ahmad Fahmi al-, Sayyed Ahmad el-. C. Porte de Mandjaq as-Silâhdâr. In: Comité de Conservation des Monuments de l'Art Arabe. Fascicule 34, exercice 1925-1926, 1933. p. 69
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