1,721,033 research outputs found
Polyoxygenated steroids of marine origin
No full textA review, with 386 refs., on polyoxygenated steroids of marine origin, e.g. marine algae, Porifera, Coelenterata, Bryozoa, Mollusca, Echinodermata, Arthropoda, tunicates, and vertebrates (fish)
Starfish Saponins. Part XLII. Isolation of Twelve Steroidal Glycoides from the Pacific Ocean Starfish Henricia leviuscula
No full textCallipeltosides B and C, two novel cytotoxic glycoside macrolides from a marine Lithistida sponge Callipeltasp.
No full textFollowing the characterization of callipeltoside A, the first member of a novel class of marine glycoside macrolides, two
more bioactive constituents, callipeltoside B (I) and C, were isolated from Callipelta sp. in very low amts. The structures,
assigned on the basis of spectral anal., include the same 14-membered macrolide in a callipeltoside A but differed in the
saccharide moieties
Microfilament depletion and circumvention of multiple drug resistance by sphinxolides
No full textSphinxolides, a newly described family of cytotoxins from the New Caledonian sponge Neosiphonia superstes, bear
structural resemblance to scytophycins. We now demonstrate that the cytotoxicity of sphinxolides is assocd. with cell
cycle arrest in G2-M and induction of apoptosis. Like scytophycins and cytochalasins, sphinxolides caused rapid loss of
microfilaments in cultured cells, without affecting microtubule organization. Microfilament reassembly was very slow after
removal of the sphinxolide, consistent with the slow recovery of cellular proliferation. Sphinxolides potently inhibited actin
polymn. in vitro and the microfilament-dependent ATPase activity of purified actomyosin, indicating a direct effect on
actin. Importantly, sphinxolides were equally cytotoxic toward MCF-7 human breast carcinoma cells and a subline which
overexpresses P-glycoprotein (MCF-7/ADR). Similarly, overexpression of the multidrug resistance-assocd. protein MRP
by HL-60 cells did not confer resistance to the sphinxolides. These studies demonstrate that sphinxolides are potent new
antimicrofilament compds. that circumvent multidrug resistance mediated by overexpression of either P-glycoprotein or
MRP. Therefore, these agents may be useful in the treatment of drug-resistant tumors
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
Steroidal oligoglycosides and polyhydroxysteroids from echinoderms.
No full textA review, with 193 refs., on steroidal oligoglycosides and polyhydroxysteroids found in starfish and brittle stars
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
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