1,720,999 research outputs found
EFFECTS OF SEMINAL PLASMA AND 3 EXTENDERS ON CANINE SEMEN STORED AT 4-DEGREES-C
No full textSemen preservation and artificial insemination (Al) in the canine has become a common practice in veterinary medicine. Chilled dog semen is easy to handle, and several extenders can be used. The aim of this study was to compare the effects on canine spermatozoa of seminal plasma and 3 extenders commonly used for chilled semen preservation in clinical practice. The characteristics evaluated were sperm motility; velocity; plasma membrane status (assessed with a fluorescence staining technique and hypo-osmotic swelling test); acrosome morphology; semen pH; and semen osmolarity. These criteria were monitored daily in the ejaculates of ii dogs. The ejaculates were divided into 4 aliquots. Each aliquot was extended in autologous seminal plasma, egg-yolk Tris, egg-yolk milk or egg-yolk cream and preserved at 4 degrees C for 4 d. In 10 of 11 semen samples extended in autologous seminal plasma, motility had already decreased to 0% by Day 2, and the percentage of spermatozoa with intact membranes was lower than in the 3 extenders (P0.05). Egg-yolk Tris extender seems to be superior to the other extenders tested, to preserve dog semen at 4 degrees C, although differences were not significant for all the parameters
In vitro characteristics of canine spermatozoa subjected to two methods of cryopreservation
No full textThe in vitro Viability of canine spermatozoa was evaluated after freezing-thawing using the Andersen method, and the commercial CLONE method. These methods differ in the extenders used, number of dilution steps, and equilibration times as well as in both freezing and thawing techniques and rates. Insemination with semen frozen-thawed by either method gives high whelping rates in practice, implying that dog spermatozoa can retain their fertilizing ability after being subjected to widely different preservation methods. The in vitro viability of spermatozoa processed by these methods has not been previously evaluated in detail. Three ejaculates were collected from each of 5 fertile dogs. Each ejaculate was divided into 2 parts and frozen in medium straws according to the 2 methods. Two straws were thawed and examined from each freezing batch. Sperm motility was assessed in the undiluted semen, and in frozen-thawed semen immediately after thawing, and after storage for 3, 6 and 24 h at room temperature (Straw 1) or 1, 2 and 3 h at 37 degrees C (Straw 2, thermoresistance test). The integrity of the sperm plasma membrane was evaluated in undiluted, in equilibrated (diluted and chilled), and in frozen-thawed spermatozoa using fluorophore probes. The acrosome morphology of frozen-thawed spermatozoa was assessed using a commercial stain (Spermac(R)). Motility immediately after thawing was significantly higher with the CLONE method (75.3% [SD=4.0] for Straw 1 and 73.7% [SD=3.2] for Straw 2) than with the Andersen method (70.0% [SD=5.1] and 69.7% [SD=3.2]). Motility decreased during storage after thawing. Spermatozoa frozen-thawed using the CLONE method showed a significantly lower thermoresistance. The proportion of spermatozoa with intact plasma membrane was not affected by the equilibration procedure used with either method but was significantly decreased (P<0.001) after thawing with both methods. The percentage of spermatozoa exhibiting changes thought to represent different stages of acrosomal degradation, was 45.7% (SD=5.3) using the Andersen method and 44.1% (SD=9.2) using the CLONE method. Both cryopreservation methods thus resulted in high initial post-thaw sperm motility and membrane integrity but low thermoresistance, and under both methods a large proportion of sperm cells were undergoing acrosomal degradation. The methods differed significantly in terms of their effect on sperm motility but not on plasma membrane integrity or acrosomal morphology. (C) 1997 by Elsevier Science Inc
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
Effects of Equex STM paste on viability of frozen-thawed dog spermatozoa during in vitro incubation at 38 degrees C
No full textIn the canine, artificial insemination with cryopreserved semen generally yields lower pregnancy rates with vaginal deposition than with uterine deposition, one of the reasons being the shortened life span of frozen-thawed spermatozoa. The incubation of spermatozoa at body temperature partially mimics the situation in vivo, and evaluation of the kinetics of viability loss under these conditions can be used to measure the damage caused by freezing and thawing procedures. In this study, 2 aliquots were separated from split ejaculates collected from 7 dogs and were frozen by lowering the straws, in 3 steps, into an LN(2) tank after dilution with egg yolk Tris-citrate-glucose extender with or without the addition of 0.5% Equex STM paste. Motility and plasma membrane integrity (evaluated with the combined fluorescent probes 6-carboxyfluorescein diacetate and propidium iodide) were assessed immediately after thawing and over the next 3 h at 38 degrees C. The addition of Equex STM paste significantly increased the proportion of spermatozoa having an intact plasmalemma immediately after thawing compared with the control. It also increased the longevity of the thawed spermatozoa, prolonging the maintenance of both motility and plasma membrane integrity. (C) 1997 by Elsevier Science Inc
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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