1,720,958 research outputs found
ELECTRON-MICROSCOPIC LOCALIZATION OF F-ACTIN IN ACROSOME REACTED BOAR SPERMATOZOA BY MEANS OF A PHALLOIDIN-FITC COMPLEX
No full text7. L. Castellani Ceresa, M. F. Brivio, G. Radaelli. Electron Microscopic Localization of F actin in Acrosome Reacted Boar Spermatozoa by Means of a Phalloidin FITC Complex. J. Submicrosc. Cytol. Phatol., 23, n°2, 347 349, 1991.An immunocytochemical study at the ultrastructural level has been performed in boar spermatozoa in order to clarify the aggregation state of actin before and after the acrosome reaction. A new phalloidin probe has been used to detect F-actin: a phalloidin derivative conjugated with FITC, followed by incubation with an anti-FITC antibody. The protein A-gold technique was then applied for the localization of the antigenic sites. Gold particles were localized on the sperm surface only after the acrosome reaction which was induced by the ionophore A23187
F-ACTIN IN ACROSOME-REACTED BOAR SPERMATOZOA
No full text8. L. Castellani Ceresa, M. F. Brivio, G. Radaelli. F Actin in Acrosome Reacted Boar Spermatozoa. Molecular Reproduction and Development, 33, 99 107, 1992.Biochemical and immunoelectron microscopic methods have been used to analyze the distribution of actin in boar spermatozoa and its state of aggregation before and after acrosome reaction. F-actin was detected on sperm head and tail by electron microscopy using an improved phalloidin probe: incubation with a fluorescein-phalloidin complex and an anti-fluorescein antibody, followed by labeling with protein A-gold complex. Gold particles, indicating the presence of F-actin, were localized on the sperm surface of the acrosome-reacted spermatozoa. Specific labeling was localized (1) between the outer acrosomal membrane and the plasma membrane in the equatorial region, (2) between the outer surface of the fibrous sheath and the plasma membrane in the postacrosomal region, (3) around the connecting piece and the neck region, and (4) on the external surface of the fibrous sheath in the principal piece of the tail. Furthermore, after NP-40 extraction, the SDS-PAGE revealed a difference in solubility between reacted and unreacted boar spermatozoa, reflecting actin polymerization. We conclude that most actin in the acrosome reacted boar spermatozoa is polymeric
LOCALIZATION AND DISTRIBUTION OF ACTIN IN MAMMALIAN SPERM HEADS
No full textActin was identified in boar and mole spermatozoa by utilizing indirect immunofiuorescence, immunoelectron microscopy, and SDS-PAGE, followed by blot and screening with an anti-actin monoclonal antibody. Actin was detected in two places in the sperm head: the equatorial segment of the acrosome and the postacrosomal region. The protein was present in a nonfilamentous form and was localized under the plasma membrane. A small amount of actin was also detected in the sperm tail. The function of actin in the sperm head is discussed. © 1986
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
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