1,720,955 research outputs found
Estudio de las roturas de cadena sencilla y de cadena doble en el ADN de espermatozoides microseleccionados y su efecto en ciclos de ICSI
Full text linkEl estudio de la fragmentación del ADN espermático para la evaluación de varones infértiles ha sido de gran interés en los últimos años. Este daño puede ser de cadena sencilla (SSB), mayoritariamente debido a la presencia de estrés oxidativo y relacionado con la capacidad de conseguir un embarazo y la tasa de fecundación; o de cadena doble (DSB), con un origen mayoritariamente enzimático y relacionado con una cinética embrionaria lenta, una menor tasa de implantación y un riesgo elevado de aborto. La fragmentación en el ADN de los espermatozoides se puede estudiar mediante diferentes técnicas como el test Comet (versiones alcalina y neutra), el test de dispersión de la cromatina o el test TUNEL.
El primer objetivo de la presente Tesis Doctoral ha sido encontrar una posible explicación a la falta de asociación entre los valores de fragmentación y los resultados reproductivos en tratamientos de Inyección intracitoplasmática de espermatozoides (ICSI). Para ello, se ha realizado un estudio multimetodológico de la fragmentación con protocolos adaptados para el estudio de espermatozoides microseleccionados bajo criterios de ICSI (ICSI-S). También se han estudiado espermatozoides descartables para ICSI por presentar alteraciones en su movilidad o morfología (ICSI-N).
Los resultados muestran la existencia de un sesgo diagnóstico al analizar los valores de SSB y DSB en la muestra de eyaculado en comparación con la subpoblación de espermatozoides candidatos para ICSI. Mientras que los valores de SSB se reducen significativamente en los ICSI-S en comparación con el eyaculado y la muestra tras realizar un Swim-up, los valores de DSB se mantienen en el mismo nivel. Por su parte, los espermatozoides ICSI-N muestran valores incrementados de SSB y DSB, posiblemente relacionado con la presencia de un nivel elevado de estrés oxidativo y de apoptosis abortiva.
El segundo objetivo ha sido estudiar el efecto de las roturas de cadena doble en ciclos de ICSI. Se han comparado las tasas de fecundación y euploidía, así como su efecto clínico, tras el uso de un método convencional de preparación seminal (Gradientes de densidad) y tras el uso de un
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nuevo método de selección microfluídico (dispositivo ZyMōt™ICSI). Previamente, el método convencional ha mostrado una reducción eficiente de los valores de SSB, pero no de DSB. Por el contrario, el dispositivo microfluídico sí ha mostrado resultados prometedores para reducir significativamente los niveles de ambos tipos de roturas.
Los resultados muestran que el uso del dispositivo microfluídico permite aumentar la tasa de fecundación en comparación a los Gradientes de densidad, posiblemente debido a la mayor reducción en los valores de SSB. El dispositivo microfluídico también ha permitido aumentar la tasa de euploidía de los embriones obtenidos, especialmente cuando la pareja femenina es menor de 35 años en comparación con el uso del sistema convencional, posiblemente debido a la reducción de los valores de DSB. En cuanto a resultados clínicos, los datos muestran que el uso del dispositivo ZyMōt™ICSI permite obtener mejores tasas de embarazo bioquímico y embarazo clínico y una menor tasa de aborto en comparación con métodos convencionales.The study of sperm DNA fragmentation to evaluate infertile men has been an emerging field during the last years. DNA breaks can affect one or both strands, resulting in Single-Strand Breaks (SSB) or Double-Strand Breaks (DSB). SSB in sperm DNA have an oxidative origin and showed to reduce the chances of achieving a natural pregnancy. DSB have an enzymatic origin and showed to reduce embryo’s kinetics, implantation rates and to increase the miscarriage risk. DNA breaks can be studied using different techniques such as the Comet assay (alkaline and neutral versions), the Sperm chromatin dispersion test or the TUNEL test.
The main objective of this Doctoral Thesis was to study the effect of sperm DNA damage on Intracytoplasmic sperm injection (ICSI) treatments. For this purpose, DNA breaks were analysed on microselected sperm candidates for ICSI (ICSI-S). Sperm presenting motility or morphological alterations were also studied (ICSI-N). The results revealed a diagnostic bias when SSB and DSB are measured on the ejaculate sample compared to those values found on ICSI-S. SSB were significantly reduced after semen preparation through a Swim-up procedure and after ICSI selection compared to the ejaculate. On the contrary, DSB were present in sperm after the Swim-up and after ICSI sperm selection in the same proportion than in the ejaculate sample. On the other hand, ICSI-N sperm showed significantly increased values of SSB and DSB compared to the ejaculate, the Swim-up sample and ICSI-S, probably related to high oxidative stress conditions and to the abortive apoptosis process.
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After showing that conventional methods based on sperm motility may reduce SSB values but do not affect DSB, the second objective of the present Doctoral Thesis was to study the effect of these breaks on reproductive outcomes after ICSI. Fertilization and euploidy rates were compared after using a conventional method for semen preparation (Density gradients) and using a novel microfluidic sperm sorting device (ZyMōt™ICSI). The conventional method has previously shown to reduce SSB values, but not DSB values. On the contrary, the microfluidic device has recently shown to reduce both types of damage. The use of the microfluidic device resulted in better fertilization rates compared to the use of Density gradients. These results might be attributed to a better reduction in SSB values after using the ZyMōt™ICSI. The use of this device also increased the euploidy rate of the obtained embryos after ICSI, especially when the female partner was under 35 years of age. This increase might be attributed to the reduction in DSB values. The use of the microfluidic device also increased the euploidy rate when women were older than 35 years, but the presence of aneuploidies related to women’s age persisted.
In addition to the second objective, the effect of the microfluidic sorting device on clinical outcomes after ICSI was studied. The use of this device when patients presented high DSB values resulted in better biochemical and clinical pregnancy rates and lower miscarriage rates compared to conventional methods.Universitat Autònoma de Barcelona. Programa de Doctorat en Biologia Cel·lula
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
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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