1,721,023 research outputs found
A closed cell for voltammetric measurement of oxygen consumption in biological material
No full textThe rate of oxygen consumption by the amine oxidases present in seminal plasma was determined by a new voltammetric measurement in a closed cel
Identification of calcitonin receptors in human spermatozoa.
No full textCalcitonin (CT) is a powerful hypocalcemic hormone which regulates calcium balance in cells. The presence of CT and CT receptors has been demonstrated in many extrathyroidal tissues, including the male genital tract. CT immunoreactivity has also been found in human seminal fluid, and an inhibitory effect of salmon CT on human sperm motility in vitro was recently reported. In this study the presence of specific binding sites for synthetic salmon CT in intact human spermatozoa was investigated using [125I]salmon CT. Binding experiments demonstrated a CT-sperm interaction involving a receptor-mediated mechanism. The binding was very rapid and minimally reversible, with the maximal site saturation occurring at approximately 2 nM labeled peptide. The dissociation of the CT-receptor complex was only slightly influenced by the addition of unlabeled hormone. Increasing concentrations of unlabeled salmon, eel, and human CT produced a dose-dependent inhibition of [125I]salmon CT binding. These data fulfill the major criteria for demonstration of specific receptors for salmon CT in human spermatozoa. Owing to the key role of calcium ions in regulating sperm motility and the onset of the acrosomal reaction, CT receptors could be important in male gamete physiology
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
Oocytes preserve the ability of mouse cumulus cells in culture to synthesize hyaluronic acid and dermatan sulfate
No full textA soluble factor(s) produced by fully grown oocytes is essential, together with follicle stimulating hormone (FSH), to stimulate in vitro hyaluronic acid (HA) synthesis by mouse cumulus cells (CCs). The stability of the response to this stimulus by CCs in culture was investigated. The data showed that preculture for 8 hr in basal medium reduced to approximately 30% the ability of CCs to synthesize HA in response to FSH or dibutyryl cyclic AMP (Bt2cAMP) and soluble oocyte factor(s). However, if CCs were precultured for the same period of time as intact cumulus cell-oocyte complexes, or in the presence of fully grown oocytes, or in medium conditioned by fully grown oocytes, their ability to synthesize HA was 75-95% preserved. In vitro stimulation of dermatan sulfate (DS) synthesis by CCs does not require oocyte factors and is induced by FSH or Bt2cAMP treatment alone. However, the preservation of such activity, like that of HA synthesis, depended on the presence of a soluble oocyte factor(s) during preculture. The presence of isolated oocytes or of oocyte-conditioned medium also prevented the spreading of CCs in culture. However, inhibiting CC spreading by culture on agar-coated plates or in serum-free medium did not preserve their HA or DS synthetic activity, thus suggesting that the two oocyte actions on CCs are independent. Growing oocytes were unable both to induce HA synthesis in freshly isolated CCs stimulated with FSH and to preserve the ability to synthesize HA and DS in 8-hr precultured CCs. The results suggest that the stability of the differentiated state of mouse CCs in vitro depends upon continued exposure to a soluble factor(s) produced by fully grown oocytes
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
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