1,720,955 research outputs found
GAS2 and GAS4 : a pair of developmentally regulated genes involved in spore wall assembly in yeast
No full textThe GAS multigene family comprehends 5 paralogs encoding GPI-anchored proteins endowed with glucanosyltransferase activity. Gas1p, the best characterized protein of the family, is expressed during vegetative growth and plays a crucial role in cell wall assembly. In order to study the role of GAS2 and GAS4 genes, that were previously classified as middle meiotic genes, we analysed their expression profiles during the entire sporulation process by Quantitative RT-PCR in a SK1 strain. GAS2 and GAS4 expression profiles were periodic and overlapping. A peak occurred at 7 h from induction of sporulation and at 10 h the mRNA levels were already decreased. Immunoblot analysis using polyclonal antibodies raised against the purified Gas4p revealed that Gas4p is a GPI-anchored 60 kDa membrane protein that is absent at the moment of induction of sporulation and reaches a maximum at 11 h from transfer of the cells to sporulation medium. The double null mutant gas2 gas4/ gas2 gas4 showed a severe reduction of the efficiency of sporulation whereas the single null mutants, gas2/gas2 and gas4/gas4 were similar to the isogenic strain. These results indicate that GAS2 and GAS4 are redundant genes which play partially overlapping functions in spore morphogenesis. To determine if meiosis was affected in the double null mutant, we monitored the kinetics of nuclei formation. Meiotic progression occurred normally when Gas2 and Gas4 proteins were absent A detailed analysis of the spore wall defects was performed using different kinds of assays. Spores of the double null mutant resulted to be morphologically aberrant, less viable, highly permeable to Zymolyase and Calcofluor. TEM and SEM analysis of the spores of the double mutant indicated that the glucan and chitosan layers are dissociated and an abnormal accumulation of spore wall material occurs. These results suggests that Gas2 and Gas4 proteins play a crucial role in spore morphogenesis by direecting the attachment of the inner and outer spore wall layers to each other
The sporulation-specific GAS2 and GAS4 genes are essential for the proper assembly of spore wall in Saccharomyces cerevisiae
No full textThe GAS family comprehends 5 paralogs encoding GPI-anchored proteins endowed with glucanosyltransferase activity. GAS1 is expressed during vegetative growth and plays a crucial role in cell wall assembly. In order to study the role of GAS2 and GAS4, we analysed the expression profiles during the entire sporulation process by use of Quantitative RT-PCR. GAS2 and GAS4 expression was periodic and overlapping. A peak occurred at 7 h from induction of sporulation and at 10 h the mRNA levels were already decreased. Immunoblot analysis using polyclonal antibodies raised against the purified Gas4p revealed that Gas4p is a GPI-anchored 60 kDa-membrane protein that was absent at the moment of induction of sporulation and reached a maximum at 11 h from transfer of the cells to sporulation medium. The double null mutant gas2 gas4/gas2 gas4 showed a severe reduction of the efficiency of sporulation whereas the single null mutants, gas2/gas2 and gas4/gas4 were similar to the isogenic strain. Only 4% of mature asci were present in the double mutant after 24 h of sporulation. These results indicate that GAS2 and GAS4 are redundant genes which play partially overlapping functions in spore morphogenesis. To determine if meiosis was affected in the double null mutant, we monitored the kinetics of nuclei formation. Meiotic progression occurred normally when Gas2 and Gas4 proteins were absent. A detailed analysis of the spore wall defects was performed using different kinds of assays. Spores of the double null mutant resulted to be highly permeable to Calcofluor. The spores released by a zymolyase treatment of the asci were unviable. Detailed analysis by electron microscopy of the spore walls of the double mutant indicated that the glucan and chitosan layers were dissociated and an abnormal accumulation of spore wall material occurred. These results suggests that Gas2 and Gas4 proteins play a crucial role in spore morphogenesis by directing the cross-linking between the inner and outer spore wall layers to each other
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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