1,720,975 research outputs found
Good Egg or Bad Egg: Developing markers of oocyte competence for Assisted Reproductive Interventions.
Get PDFThe oocyte is the foundation of life. It develops from a single fertilized cell to a multicellular organism capable of an independent existence. Competence to achieve this maximum potential is acquired following the protracted, but, highly co-ordinated process of growth and subsequently, maturation. The environment in which all or part of these processes occur, can ultimately have long-term consequences for female fertility and the health of resulting offspring.The pressure to identify and select oocytes or embryos with the highest developmental potential has intensified as the number of patients and the range of options available to them have increased. In particular, as in vitro maturation and single embryo transfer become more routine in assisted reproductive technology, selection is critical to a successful outcome. Moreover, the identification of markers of oocyte health and quality is essential to monitor the impact of these technologies on gametes and embryos.Technologies, such as transcriptomics, proteomics and metabolomics, offer more sophisticated methods for oocyte and embryo selection, with the emphasis on the predictive value of non-invasive protocols which profile follicular fluid, follicle/ granulosa cells and cumulus cells, for assessment of oocyte quality. Using the bovine as a model, we have employed a range of approaches and identified many potential markers, such as oocyte and cumulus candidate proteins and transcripts and follicular fluid fatty acids and amino acids. The models, technologies, and future strategies will be discussed in detail
Genetic control of dairy cow reproduction
Get PDFThe decline in dairy cow reproductive performance compromised the productivity and profitability of dairy production worldwide. The phenotypic performance of lactating cows with similar proportions of Holstein genes, similar genetic merit for milk production traits, but either good (Fert+) or poor (Fert-) genetic merit for fertility traits managed in a standardised environment was compared. The objective of this study was to elucidate the physiological mechanisms contributing to suboptimal reproductive performance in lactating dairy cows. Fert+ cows had greater dry matter intake during the first five weeks postpartum, more favourable metabolic status during the transition period, better uterine health during early lactation, were more likely to have resumed cyclicity by week six postpartum, and had greater body condition score and milk production throughout lactation compared with Fert- cows. Preovulatory concentrations of oestradiol, corpus luteum volume and circulating concentrations of progesterone were greater in Fert+ cows compared with Fert- cows during the oestrous cycle. The metabolic clearance rate of progesterone was similar in both genotypes and differences in the hepatic mRNA abundance of genes responsible for progesterone metabolism were minor. Small differences in the abundance of fatty acids and amino acids were detected between genotypes on day seven of the oestrous cycle. Greater abundance of n-6 and total polyunsaturated fatty acids and lesser abundance of saturated fatty acids was observed in the serum of Fert+ cow compared with Fert- cows on day seven of the oestrous cycle. Fatty acid differences in follicular fluid and serum and amino acid differences in follicular fluid were highly predictive of fertility genotype. Combination of transcriptome analysis of the endometrium and corpus luteum on day 13 of the oestrous cycle with genome-wide association studies and whole genome sequence data identified quantitative trait loci regions and putative causal mutations associated with genetic variation in dairy cow fertility. The endometrial expression profile suggested prolonged uterine inflammation, greater prostaglandin F2α synthesis and secretion, and compromised energy status in Fert- cows. The luteal expression profile suggested reduced prostaglandin F2α response, greater steroidogenesis and mRNA processing in Fert+ cows. Collectively, the results highlight the importance of the uterine environment and ovarian activity for the phenotypic fertility differences between genotypes. The study has identified physiological mechanisms controlled by genetic merit for fertility traits that may support reproductive performance without antagonising milk production. This novel lactating cow genetic model of fertility represents a robust and valuable resource for on-going fertility research.Check date.issued and date.embargo: Flexible delayed release embargo added by autho
The contribution of the maternal immune system to the establishment of pregnancy in cattle
Get PDFImmune cells play an integral role in affecting successful reproductive function. Indeed, disturbed or aberrant immune function has been identified as primary mechanisms behind infertility. In contrast to the extensive body of literature that exists for human and mouse, studies detailing the immunological interaction between the embryo and the maternal endometrium are quite few in cattle. Nevertheless, by reviewing the existing studies and extrapolating from sheep, pig, mouse, and human data, we can draw a reasonably comprehensive picture. Key contributions of immune cell populations include granulocyte involvement in follicle differentiation and gamete transfer, monocyte invasion of the peri-ovulatory follicle and their subsequent role in corpus luteum formation and the pivotal roles of maternal macrophage and dendritic cells in key steps of the establishment of pregnancy, particularly, the maternal immune response to the embryo. These contributions are reviewed in detail below and key findings are discussed
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
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