1,720,953 research outputs found
Investigating chromosome ageing in mouse dictyate oocytes
Get PDFAgeing mammalian oocytes are known to be prone to transmit an abnormal set of chromosomes to the next generation, a condition called aneuploidy. One of the potential contributory factors is the loss of chromosome cohesion during the oocytes' prolonged meiotic arrest. Mature oocytes from aged mice have decreased amounts of cohesin, a structural protein that helps maintaining chromosome cohesion, associated with their chromosomes. However, these studies on the age-dependent loss of chromosome cohesion in oocytes were based on mature oocytes due to the challenging task of accessing pre-ovulatory oocytes. Therefore, it is currently unknown at which stage of oogenesis age-dependent loss of chromosome cohesion occurs. It is essential to understand when this age-dependent loss of oocyte cohesion happens to help us avoid, prevent or even treat the subsequent complications. Thus, the main objective of my thesis is to investigate when age-dependent chromosome cohesion loss occurs during oogenesis in mice.
Before investigating mouse oocytes, I tested a fluorescence in-situ hybridisation (FISH) method to monitor sister chromatid separation in a simpler experimental model to ensure the method’s compatibility with the detection of chromosome cohesion loss. FISH was carried out on Tex19.1 mouse embryonic stem cells (mES cells) that were previously shown to have defects in chromosome cohesion at the mitotic stage. Here I show that FISH signals hybridised to specific regions on mES cell chromosomes were significantly further apart in Tex19.1-/- mES cells, indicating increased sister chromatid separation. More importantly, FISH on mES has proved to be a promising method to study chromosome cohesion loss in mammalian cells.
To carry out a more in-depth study of chromosome cohesion in oocytes in fixed tissue, FISH was performed on Tex19.1 and Ubr2 mouse ovarian sections, two genes implicated in regulating cohesion in oocytes. However, there was no detectable increase in chromatid distances at the peri-telomere in Tex19.1-/- and Ubr2-/- oocytes in primordial follicles. It is possible that Tex19.1 and Ubr2 regulate cohesion at later stage of oogenesis. Notably, these experiments showed the capability of FISH to probe chromatid separation in meiotic cells in fixed tissue.
To understand the effect of ageing on chromatid cohesion in mouse oocytes at different follicular stages, I then performed FISH on 3-month, 6-month, and 9-month mouse ovarian tissue sections. Dictyate oocytes, in primordial, primary, and secondary follicular stages, were analysed for chromatid separation at the peri-centromeric and peri-telomeric regions of two chromosomes. These ageing oocytes showed significant increases in inter-chromatid distances at chromosome 1 from 3-month and 6-month to 9-month oocytes in all three follicular stages and at both peri-centromere and peri-telomere. Surprisingly, inter-chromatid distance increases were also detected during follicle development from primordial to secondary. However, no significant inter-chromatid distance change was detected in chromosome 18 of oocytes in primordial follicles. Taken together, although ageing may have different effects on chromosomes, age-dependent effects on chromosome arm separation were detected in dictyate oocytes.
In conclusion, these findings have provided new insights into our understanding of chromatid cohesion in female mouse germ cells and suggest that combining FISH with high-resolution 3D microscopy can allow the investigation of age-dependent changes in chromosome cohesion in dictyate oocytes. Ultimately, this research serves as a beneficial resource for the future study of ageing chromosome cohesion in pre-ovulatory oocytes in mammals, including humans
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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