1,721,044 research outputs found
In vitro developmental competence of horse embryos derived from oocytes with a different corona radiata cumulus-oocyte morphology
Full text linkThe increase in demand for in vitro produced horse embryos is fostering the development of commercial laboratories for this purpose. Nevertheless, blastocyst production after intracytoplasmic sperm injection (ICSI) is still not as great as desired in most of these laboratories. In relation to horse oocyte classification, both expanded and compact cumulus-oocyte-complexes (COCs) are used for in vitro embryo production. The aim of this study was to compare in vitro embryo developmental capacity of COCs from horses including those with only the corona radiata, frequently collected after aspiration procedures. Horse oocytes were collected by follicular aspiration of abattoir-derived ovaries. After classification as expanded, compact or corona radiata COCs, these were in vitro matured, fertilized by ICSI and in vitro cultured for 7.5 days. Maturation rate, cleavage rate and morula/blastocyst rates were recorded. No significant differences (P > 0.05) were detected among groups in maturation rate. Cleavage rate was less (P < 0.05) for embryos derived from oocytes with a corona radiata as compared to compact-derived embryos, but embryo development after 7.5 days of culture was similar among groups (P > 0.05). In conclusion, even if embryos derived from oocytes with corona radiata had a lesser cleavage rate after ICSI, the developmental capacity was similar to embryos derived from oocytes with a compact and expanded cumulus morphology, indicating these can be an useful source of embryos in horses
Overnight holding aids in selection of developmentally competent equine oocytes
Full text linkThe demand for equine in vitro produced embryos has increased over the last decade. The aim of this study was to compare the effects of an extended IVM or a prolonged period before fertilization, including holding time, on equine immature oocyte developmental competence. Oocytes, collected from abattoir-derived ovaries, were divided into 4 groups: H0/24 (n = 165) 0 h holding + standard 24-26 h IVM; H8/36 (n = 160) 8 h holding + 36 h IVM; H20/24 (n = 187) 20 h holding + 24 h IVM; H0/44 (n = 164) 0 h holding + 44 h IVM. Oocytes matured to MII were fertilized by intracytoplasmic sperm injection (ICSI) and cultured for 10 days. The oocyte degeneration rate was higher (P 0.05). Timing of blastocyst development was not different among groups. Overnight holding of equine immature oocytes followed by a standard IVM interval may induce a pre-selection of the most competent oocytes thereby improving cleavage and embryo development rates after ICSI
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
Seasonal changes in ROS concentrations and sperm quality in unfrozen and frozen-thawed stallion semen
Full text linkOxidative stress is regarded as an important cause of sperm damage during cryopreservation. However, seasonal changes in oxidative status in unfrozen and frozen-thawed stallion sperm have not been well established. We tested the hypothesis that sperm ROS concentrations and lipid peroxidation change between breeding and non-breeding seasons and influence quality of unfrozen and frozen-thawed sperm. Eighteen ejaculates from six Warmblood stallions (8 to 21 y) known to be fertile, were collected in winter and summer and processed for freezing. After 90 min at +4°C, some straws from each ejaculate were not frozen (unfrozen), whereas the remainder were frozen by N2 vapors and plunged in N2 (frozen). Rapid cells (RAP; determined by CASA), plasma membrane-acrosome integrity (PMAI), high mitochondrial membrane potential (Mpos), low intracellular Ca2+ concentration (Fneg), membrane lipid peroxidation (BODIPY), intracellular ROS concentrations (DCFH, MitoSOX) and chromatin fragmentation (DFI%) were evaluated by flow cytometry in both groups and at intervals during incubation at +37°C for 24 h. Overall, ROS concentrations and lipid peroxidation were higher and faster (P < 0.0001) in winter versus summer, DFI% was lower in winter versus summer (P < 0.0001), but similar between the two groups within season. There were moderate positive correlations in both seasons between DFI% and MitoSOX, DCFH, BODIPY in both groups, whereas a negative correlation, stronger in winter, was evident between sperm quality (RAP, PMAI, Mpos, Fneg) and BODIPY, DCFH, MitoSOX. There were no differences between seasons for RAP, PMAI, Mpos and Fneg. In conclusion, ROS-related parameters were higher in winter than in summer, without a negative effect on sperm quality. We concluded that increased ROS concentrations were less deleterious to sperm than freezing-thawing. Furthermore, incubation at +37°C and sequential analysis were useful to assess sperm resistance
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
Is Resveratrol Effective in Protecting Stallion Cooled Semen?
No full textThe aim of this work was to evaluate the effect of resveratrol (RSV) during liquid storage of
stallion sperm for 24 hours at either 10C or 4C. The antioxidant RSV was added to reduce
the oxidative damage that occurs during cold storage. Aliquots of 2 mL of diluted semen
were stored either at 4C or 10C under anaerobic conditions, in the absence (control
group) or presence of RSV at different concentrations (10, 20, 40, and 80 mM). Sperm
quality parameters were assessed at 0 hours and after 24 hours of storage. Resveratrol
treatment did not affect sperm quality parameters at 0 hours. At 24-hour storage, a significant
(P < .01) decrease of sperm quality was observed independently from RSV supplementation
and storage temperature. A significant decrease of viable spermatozoa with
high mitochondrial membrane potential (SYBRþ/PI/JC-1þ) was evident at 24-hour
storage in 40- and 80-mM RSV groups compared with control group. Moreover, a decline
of total motility in 80-mM RSV group compared with the control group and a decrease of
progressive motility and average path velocity in 80-mM RSV group compared with control
and 20-mM RSV groups were observed. In conclusion, our findings demonstrate that RSV
supplementation does not enhance sperm quality of stallion semen after 24 hours of
storage. Moreover, 40- and 80-mM RSV concentrations could damage sperm functional
status, probably acting as pro-oxidant. Finally, although 24-hour storage significantly
affected most of the sperm quality parameters, no significant differences were found in
groups maintained at 4C or 10C, suggesting that stallion semen could be equally preserved
at these different temperatures
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
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