1,721,445 research outputs found
Periodic links and manifolds
No full textWe consider orientable closed 3-manifolds obtained by Dehn surgery with rational coefficients along the components of certain periodic links. These manifolds were introduced in [Osaka J. Math. 39 (2002), 705-721] as natural generalizations of Takahashi manifolds. In this note we re-obtain the result of [Osaka J. Math. 39 (2002)] by a different approach based on a group-theoretic argument from [Tsukuba J. Math. 22 (1998), 723-739]. This permits to simplify some proofs of [Osaka J. Math. 39 (2002)] and to obtain some new related results
On branched coverings of lens spaces
No full textWe construct some series of polyhedral schemata which represent orientable closed connected 3-manifolds. We show that these manifolds have spines corresponding to certain balanced presentations of their fundamental groups. Then we study some covering properties of such manifolds and prove that many of them are cyclic branched coverings of lens spaces. Our theorems contain a number of published results from various sources as particular cases
Regulation of the spermatogonial niche factor GDNF by retinoic acid
Full text linkThe aim of this thesis was to clarify the mechanism behind RA-mediated GDNF regulation, which is a crucial factor, secreted by Sertoli cells, for spermatogonial stem cells self-renewal. We demonstrated that RA negatively regulates GDNF in murine Sertoli cells. RARα is the nuclear receptor involved in this regulation acting through a novel-identified Retinoic Acid Responsive Element (RARE) on Gdnf murine promoter. Data obtained with HDACi and ChIP-qPCR suggested that Gdnf promoter undergoes a de-acetylation after RA treatment. Regarding human testis, we found that in our culture conditions testis tissue positively responds to RA stimulation while RA effect on gdnf expression is heterogeneous. Our results can ameliorate the comprehension of the spermatogonial stem cell niche in its physiological conditions but also in relation to the increasing cases of male infertility
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
CONTACT SITES BETWEEN THE ENDOPLASMIC RETICULUM AND THE PLASMA MEMBRANE CONTROL EGFR ENDOCYTOSIS
Full text linkThe epidermal growth factor receptor (EGFR) can be internalized through different routes. While clathrin-mediated endocytosis destines EGFR for recycling and signaling, internalization through non-clathrin endocytosis (NCE) targets the receptor for degradation. Since NCE appears to be a major negative regulator of EGFR levels, a more complete picture of this pathway would likely reveal new insights into aberrant EGFR signaling observed in many types of cancer.
By combining a candidate gene approach with an unbiased proteomic approach, we have defined EGFR-NCE as molecularly distinct from other NCE pathways, relying on functional regulators not previously implicated in endocytosis. We found that reticulon 3 (RTN3), an endoplasmic reticulum (ER)-resident protein, is fundamental for NCE-mediated EGFR internalization, and that its ablation delays EGFR degradation, demonstrating that the NCE pathway is a critical regulator of the EGF-dependent cellular response. We show that, upon stimulation with high dose of EGF, RTN3 is localized in close proximity to EGFR and that it is crucial for the formation of contact sites between the ER and the plasma membrane (PM), which are needed for NCE to proceed efficiently. We also show that ER contact sites are involved in local Ca2+ release: high EGF doses induce a release of Ca2+ from the ER to the PM, which is strongly inhibited upon knockdown of RTN3. This calcium release depends on the inositol trisphosphate (IP3) cascade and is essential for the internalization of EGFR via NCE.
In conclusion, we have discovered a new clathrin-independent endocytic pathway that relies on the action of RTN3. RTN3 is necessary for the formation of contact sites between the ER and EGFR-NCE sites at the PM, which are required for IP3R-dependent local calcium release and the completion of EGFR internalization through NCE
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