1,722,411 research outputs found
Testicular cells lysostripped of H-Y antigen organize ovarian follicle-like aggregates
No full textA suspension of free testicular cells were obtained by mild trypsin treatment from newborn BALB/c testes, and their plasma membrane H-Y antigen sites were blocked (lysostripped) by an excess of H-Y antibody of proven specificity and potency (45 min in ice). Upon 16 h of the Moscona-type rotation culture, these treated testicular cells yielded primarily spherical aggregates, more than half of which demonstrated a strong resemblance to ovarian follicles. The resemblance was particularly striking between the smallest testicular folliculoids and primordial ovarian follicles that abound in the newborn female gonad. Under the same condition, control serum-treated testicular cells primarily yielded cylindrical tubular structures that can be very long. Over a critical range, concentrations of H-Y antibody apparently influenced the frequency of testicular folliculoid formation. The above directly supports the proposed testis-organizing function of H-Y antigen and is certainly compatible with the genetic situation encountered in the wood lemming (Myopus schisticolor), that in the functional absence of H-Y antigen, XY gonadal cells readily organize an ovary
The identification of human H-Y antigen and testicular transformation induced by its interaction with the receptor site of bovine fetal ovarian cells
No full textbeta 2m(-), HLA (-) Daudi human male Burkitt lymphoma cells excreted a group of protein subunits that shared three distinctive characteristics; their conspicuously longer half-lives compared to more hydrophilic Daudi excreted proteins, their tendency to form progressively larger polymers by means of interchain disulfide bridges, and the extreme hydrophobicity of these polymers. The plasma membrane of extragonadal somatic cells absorbed 1.2 to 2.8% of these hydrophobic proteins. The unoccupied H-Y receptor sites residing on the plasma membrane of bovine fetal ovarian cells, on the other hand, selectively absorbed polymers of 18,000 mol. wt. subunits, and this antigen-receptor interaction, if allowed to continue for five days, induced the formation of tunica albuginea and seminiferous tubules in bovine XX embryonic indifferent gonads. In this manner, human H-Y antigen excreted by Daudi cells has functionally been identified as a series of polymers derived from 18,000 mol. wt. subunits. While, the H-Y antigenic determinants were retained even by the largest polymeric form that became irreversibly water insoluble, the receptor binding activity was shown only by 36.8% of the available polymeric forms of 18,000 mol. wt. subunits, at the most. Nevertheless, once bound to the receptor site, these polymers were rapidly reduced to the monomeric form on the plasma membrane of bovine fetal ovarian cells. Accordingly, the 18,000 mol. wt. monomer might actually represent the functional form of H-Y antigen
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
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
H-Y antigen in testes of XX(BALB)/XY (C3H) chimaeric male mouse
No full textAmong experimentally produced BALB/C3H aggregation (Blastocyst fusion) chimaeras of the mouse, one fertile XX (BALB)/XY (C3H) male was identified who maintained 50% or more female cells in many parts of his body. Results of H-Y antibody absorption tests revealed an XY to XX transfer of testis-organizing H-Y antigen among testicular Sertoli and Leydig cells, but not among spleen and epidermal cells
Testis-organizing H-Y antigen and the primary sex-determining mechanism of mammals
No full textEmbryonic indifferent gonads of mammals have the inherent tendency to develop toward the ovary. The precise meaning of this general statement is likely to be the bisexual expression of the ovary-organizing plasma membrane component and its specific membrane-bound receptor. Testicular organogenesis that normally, but not always, depends upon the presence of the Y-chromosome is the responsibility of the two plasma membrane components; the male-specific but ubiquitously expressed H-Y antigen and its specific receptors expressed only by gonadal cells, but of both sexes. Of these four components for mammalian gonadal organogenesis, only the expression of H-Y antigen is confined to the heterogametic male sex. Accordingly, this plasma membrane component, which has been conserved in evolution to the extreme, emerges as the master regulator of the primary (gonadal) sex-determining mechanism of mammals. Its ubiquitous as well as constitutive expression in the male reflects its master regulatory role, since a master by definition is not under genetic subjugation. Testis-organizing H-Y antigen is not an integral component of the plasma membrane. Instaed, it utilizes β2-microglobulin-MHC (H-2 of the mouse and HLA of man) antigen dimers as its plasma membrane anchorage sites. This enables H-Y antigen to play a hormonelike role during testicular organogenesis. By so doing, H-Y antigen drives out the bisexually expressed, rival ovary-organizing antigen from the plasma membrane and virtually monopolizes the β2m-MHC antigen dimer anchorage sites of male gonadal cells. In the mouse, this monopolization by H-Y renders much of H-2 antigenic determinants inaccessible to anti-H-2 antibody. Hence, fetal and newborn testicular cells are totally resistant to the cytotoxic effect of anti-H-2 antibody
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