1,720,999 research outputs found
Isolation, identification and quality assessment of bovine round spermatids
No full textIn mice and humans, it is possible to generate full-term individuals by round spermatids intracytoplasmic injection (ROSI). In cattle, ROSI is possible but with very low efficiency and no offspring have been born with this technique so far. One of the reasons for the low success rate is the ambiguous definition of a spermatid that hampers their selection. This work aims to set up a procedure for isolating a pure spermatids population from bull testes (n = 3 subjects of 2 years old), define morphological features for proper identification of spermatids, and analyse isolated cells for viability and quality immediately after their isolation (0 h) and after 24 h of culture at 4°C and 37°C. To this end, after enzymatic tissue dissociation, spermatids were isolated using discontinuous Percoll gradient, followed by the use of a 10-μm mesh cell strainer. Morphological analyses were run using haematoxylin and eosin and DAPI staining. Cell quality was assessed by viability (LIVE/DEAD staining), DNA integrity (acridine orange) and mitochondrial activity (red CMXRos and green FM mitoTrackers), at 0 and 24 h after their isolation and culture at 4°C in air atmosphere and 37°C in 5% CO2 incubators. Statistical analysis was run using one-way analysis
of variance. The results show that 40% of cells collected from 35%–40% Percoll fractions were represented by round spermatids. After using a cell strainer, this value increased to 60% (P < 0.05). Morphological analysis revealed that round and elongated spermatids ranged between 7.0–12.0 μm in size. In round spermatids, nuclei were centrally located in the cell and had 1–3 nucleoli. In elongated spermatids, nuclei were darker and polarized and nucleoli were absent. At 0 h, all cells were viable and had an intact DNA. At 24 h after culture, the percentage of viable cells was 97.8 ± 1.2% at 4°C and 98.2 ± 2.0% at 37°C (P < 0.05). Interestingly, mitochondrial activity significantly increased in the spermatids cultured for 24 h at 4°C and 37°C compared with those analysed at 0 h (P < 0.05), suggesting the presence of oxidative stress. However, no
difference in DNA integrity was found in the isolated spermatids after 24 h at both temperatures. Overall, our results indicate that distinctive morphological features were determined for identifying individual spermatids. Moreover, all the spermatids were viable and preserved their morphology after 24 h of culture at both 4°C and 37°C, suggesting that spermatids can be stored before ROSI. This work provides some preliminary data for developing an effective ROSI protocol in cattle. If successful and if it will be possible to generate competent spermatids from spermatogonia or even embryonic cells, this combined approach would provide a possible alternative for reducing the generational interval in cattle
Shelf –life di preparazioni di carni avicole sezionate-riformate e ristrutturate
No full textGiornate scientifiche delle Facoltà di Medicina e Chirurgia, Farmacia e Medicina Veterinaria Università degli studi di Napoli Federico II, 20 – 21 settembre 2007
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
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