1,720,972 research outputs found
Seasonal variations of Rana esculenta L. skin tyrosinase
Full text linkVarious enzymes are known to be involved in melanin biosynthesis, but the key role appertains to tyrosinase. In amphibians this enzyme displays peculiar characteristics: i) it requires an activation process; ii) its level of enzymatic activity in the animal skin changes depending on the season. In this work, by using chymotrypsin, subtilisin and SDS as putative activators, we studied the activation process of the skin pro-tyrosinase of Rana esculenta L. in different seasons over a period of two years. We found that chymotrypsin and subtilisin were able to yield an active enzyme, but not SDS. The maximum levels of tyrosinase activity were recorded in winter and the minimum in summer. We detected tyrosinase activity in the melanosomal fraction, where the enzyme form was least sensitive to proteolytic activation, probably corresponding to a "mature" tyrosinase. The enzyme forms found in the microsomal and soluble fractions were more sensitive to proteolytic activation, probably corresponding to "immature" tyrosinase. On SDS-PAGE, the tyrosinase activity assays showed a dopa-positive band at 200 kDa and a second aggregated band with a still higher molecular mass. The significance of these results in frog melanogenesis regulation is discussed
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
Analisi del sistema tirosinasico nella linea cellulare SHK-1 di Salmo Salar L. (Teleostei)
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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
Extracutaneous melanogenetic system in Dicentrarchus labrax and Sparus aurata (Linnaeus, 1758): a preliminary study.
No full textMelanogenesis has been mainly studied in mammalian melanocytes and melanoma cells. In heterothermic vertebrates, melanin-containing cells, named melano-macrophages, occur in visceral organs (1). In Teleosts, these cells are copious and dispersed in the stroma of haemopoietic tissues in kidney and spleen. In these organs, pigment content increases in particular states such as pathological and inflammatory conditions (1).
To gain a more extensive knowledge of the extracutaneous melanin-containg cell system, we investigated for the enzymes responsible of melanogenesis in two fish species: sea bass (Dicentrarchus labrax, L.) and gilthead seabream (Sparus aurata, L.). We looked for DOPA oxidase (DO) and peroxidase (POD) activity in kidney and spleen of breeding specimens caught in spring and winter.
Kidney melanosomal protein fractions revealed a very high DO activity in both species. A seasonal variation of the enzymatic activity (higher in winter and lower in spring) was found. Kidney melano-macrophages also showed a POD activity with seasonal variations similar to those observed in DO activity. Assays on spleen tissue extract revealed only a POD activity in spring, whereas in winter both activities were detected.
In conclusion we demonstrate, in these two fish species, that the melano-macrophages from kidney and spleen possess a melanogenetic capability that share common features with the melano-macrophages studied in other low vertebrate species.
The extracutaneous melanogenetic system could be used as a biomarker for the health status of farmed fishes. Great interest is directed to human diet because of the close relationship between nutrition and health.
References
1)Agius C., Roberts R. J., Journal of Fish Diseases, 200326, 499-509
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
Analisi del sistema tirosinasico nella linea cellulare SHK-1 di Salmo Salar L. (Teleostei)
No full textDispelling 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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