1,720,959 research outputs found
Monitoring the microtubule nucleation dynamics of sperm centriole after IFV and ICSI in sheep zygotes.
Get PDFIntracytoplasmic sperm injection (ICSI) is an assisted reproductive (ART) technique that is less efficient in ruminant, comparing to other species. In mammals, the spermatozoa proximal centriole nucleates the microtubule and generates the functional cell centriole of the resulting organism. Our study aimed to investigate eventual difference in the centriole microtubular nucleation in ICSI fertilized oocytes, comparing to control In Vitro Fertilized ones (IVF). In fact, we made the hypothesis that the tail severing step achieved in our ICSI protocol through applying a few piezo pulses, might mechanically damage the proximal centriole. On this basis, Sheep oocytes were in vitro maturated (IVM) for 24 h then were injected by piezo-pulsed spermatozoa, chemically activated by 5 min of incubation with 5 mg/ml ionomycin, washed in H199 for 5 min and cultured in 50 μl drops of Synthetic Oviductal Fluid (SOF) with estrus sheep serum and 16 μM isoproterenol, covered by mineral oil. Fertilization has been arrested around 5h after ICSI, and the presumptive zygotes were processed for immunological detection of tubulin. Zona Pellucida (ZP) was removed with a combined treatment of acid Tyrode and trypsin and zygotes were then fixed with 4% paraformaldehyde (pH7.2) and permeabilized by 0.5% Triton X-100, for 20 min each. Microtubular nucleation was assessed with anti-α-tubulin immunofluorescence under confocal microscopy. No difference was noticed in the dynamics and timing of sperm microtubular aster nucleation, that started around 5h post ICSI (5h30). Therefore, we conclude that abnormal microtubular nucleation by the centriole is not responsible for the low development of ICSI fertilized sheep oocytes
MICROTUBULAR NUCLEATING CENTER DYNAMICS IN ASSISTED REPRODUCTION TECHNOLOGY (ICSI, SHEEP MODEL)
Get PDFThe scope of this thesis is to investigate abnormal sperm centriole function during the early stages of Intra Cytoplasmic Sperm Injection (ICSI) embryo development using sheep as an animal model. The main focus was on evaluating the timing and dynamics of the sperm mi-crotubular aster nucleation and organization as a possible factor that undermines early em-bryonic development following ICSI. The main finding was that ICSI derived embryos using freeze-dried spermatozoa displayed a delay in their aster nucleation and a noticeable ham-pered embryo development. We also noticed that ICSI-derived embryos failed to undergo subsequent development and were blocked at the pronuclear stage. In this work, we demon-strated that embryo development failure following ICSI in sheep is not actually related to a centriole dysfunction; rather, the major problem recorded is the lack of syngamy. Thus, besides our objective data ruling out centriole dysfunction as a cause of developmental fail-ure in sheep/ruminant embryos, we have opened a worth theme to investigation, that is the perfecting of artificial protocols in sheep oocytes fertilized by ICSI
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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