1,720,958 research outputs found
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
Melanoma cells release extracellular vesicles which contain H1° RNA and RNA-binding proteins
No full textG26/24 oligodendroglioma cells produce EVs that contain pro-apoptotic proteins, such as FasL and TRAIL, able to induce neuronal- [1] and astrocytic- [2] death. Cancer cells release EVs [3] through which transferring proteins, such as extracellular matrix remodelling proteases [4], and H1°, a differentiation-specific histone [5]. By releasing H1°, cells could escape differentiation cues [5]. To verify the role of EVs in releasing specific proteins and mRNAs, in this study we used A375 melanoma cells.
EVs were purified from cell culture media as previously reported [1, 2]. T1 RNase-protection assays were performed on total cell lysates and EVs, as described elsewhere [6]. RNA-binding proteins (RBPs) were isolated by using a biotinylated H1° RNA as a bait [7]. Melanoma cells were found to synthesize H1° and secrete it via EVs. Moreover, EVs also contain H1° mRNA. Interestingly, H1° histone sorted to vesicles seems to be sumoylated. By T1 RNase-protection assay, we evidenced in EVs three main H1° RNA-protein complexes, the most abundant of which has a molecular mass of around 65 kDa. By using as a bait biotinylated H1° RNA, we isolated a few proteins, then analyzed by mass spectrometry. The most abundant protein was myelin expression factor-2 (MYEF2), which has a molecular mass of about 60 kDa. Finally, we confirmed MYEF2 presence in EVs by western blot.
[1] D’Agostino et al. 2006, Int J Oncol 29:1075-85.
[2] Lo Cicero A et al. 2011, Int J Oncol 39:1353-7
[3] Di Liegro et al. 2015, Biomed Res Int, 2015, Article ID 152926.
[4] Lo Cicero A et al. 2012, Matrix Biol 31:229-33
[5] Schiera G et al. 2013, Int J Oncol 43:1771-6
[6] Scaturro et al. 1998, J Biol Chem 273:22788-91
[7] Scaturro et al. 2003, Int J Mol Med 11:509-51
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
Melanoma cells release extracellular vesicle which contain H1° linker histone as well as RNA-binding proteins which bind to the H1° mRNA
No full textWe previously demonstrated that G26/24 oligodendroglioma cells release EVs that contain proteins, such as FasL and TRAIL, which induce apoptosis in rat cortical neurons [1] and astrocytes [2]. We also reported that cancer cells use EVs for transferring, into the environment [3], proteins such as extracellular matrix remodelling proteases [4], and H1°, a differentiation-specific histone [5]. In particular, by releasing H1°, cells could escape differentiation cues [5]. To verify the role of EVs in releasing specific proteins and mRNAs, in this study we used as a model A375 melanoma cells.
METHODS
EVs were purified from cell culture media as previously reported [1, 2]. T1 RNase-protection assays were performed on total cell lysates and EVs, as described elsewhere [6]. RNA-binding proteins (RBPs) were isolated by using a biotinylated H1° RNA as a bait.
RESULTS
We found that also melanoma cells synthesize H1° and secrete it via EVs. Interestingly, H1° histone sorted to vesicles is probably sumoylated. By T1 RNase-protection assay, we evidenced in EVs three main H1° RNA-protein complexes, the most abundant of which has a molecular mass of around 65 kDa. By using as a bait biotinylated H1° RNA, we isolated a few proteins, then analyzed by mass spectrometry. The most abundant protein was myelin expression factor-2 (MYEF2), which has a molecular mass of about 60 kDa. Finally, we confirmed MYEF2 presence in EVs by western blot.
CONCLUSIONS
We demonstrated that EVs released from melanoma cells contain the H1° linker histone, which is probably sumoylated before sorting to the vesicles. In addition, EVs contain H1° RNA-binding proteins, one of which seems to be MYEF2.
[1] D’Agostino et al. 2006, Int J Oncol 29:1075-85.
[2] Lo Cicero A et al. 2011, Int J Oncol 39:1353-7
[3] Di Liegro et al. 2015, Biomed Res Int, in press
[4] Lo Cicero A et al. 2012, Matrix Biol 31:229-33
[5] Schiera G et al. 2013, Int J Oncol 43:1771-6
[6] Scaturro et al. 1998, J Biol Chem 273:22788-9
G26/24 extracellular microvesicles contain both H1° protein and RNA
No full textExtracellular vesicles (EVs) are released into the extracellular space from both tumor and normal brain cells. By releasing EVs which contain FGF2 and VEGF1-2, astrocytes and neurons, co-cultured with brain capillary endothelial cells, are for example able to induce them to form a blood-brain barrier-like monolayer. On the other hand, membrane microvesicles (MVs) shed from G26/24 oligodendroglioma cells, when added to primary cultures of rat cortical neurons, induce neuronal damage; the damaging effects include a strong reduction of neurite outgrowth, and apoptosis in about 75% of the cells3. The same amount of shed MVs induce apoptosis in about 40% of astrocytes4. These effects are probably due to Fas Ligand and TRAIL, two proteins, present in G26/24 vesicles, with well-known cell death inducing ability5-6. EV-mediated horizontal transfer of labeled proteins from oligodendroglioma cells to astrocytes in culture was also noticed4.
We found that, in cultured astrocytes, as previously found in developing rat brain, the amount of the H1° linker histone increases during differentiation, while the level of its mRNA decreases, suggesting that its expression is mainly regulated at the post-transcriptional level7. On the other hand, G26/24 maintain high levels of both H1° protein and mRNA.
We recently found that these tumor cells release both H1° protein and mRNA, through EVs, into the culture medium8. We suggest that G26/24 oligodendroglioma cells, and possibly other tumor cells, can escape differentiation cues, and continue to proliferate by eliminating proteins, such as the H1° linker histone (and its mRNA) into the extracellular space.
Schiera G et al. J Cell Mol Med 2007, 138-94.
Proia P et al. Int J Mol Med 2008, 21: 63-7.
D’Agostino S et al. Int J Oncol 2006, 29:1075-85.
Lo Cicero A et al. Int J Oncol 2011, 39: 1353-57.
Albanese J et al. Blood 1998, 91: 3862-74.
Abrahams VM et al. Cancer Res 2003, 63: 5573-81.
Castiglia D et al. Neurochem Res 1994, 19:1531-37.
Schiera G et al. Int J Oncol. 2013, 43:1771-76
Extracellular vesicles released from melanoma cells contain H1° mRNA-binding proteins, one of which is (probably) MYEF2.
No full textRelease of extracellular vesicles (EVs) is a process conserved from prokaryotes to eucaryotes. Although EVs are produced from both normal and cancer cells, malignant cells release a much higher amount of EVs, which contain tumour-specific proteins and RNAs.
We previously found that G26/24 oligodendroglioma cells shed EVs that contain the pro-apoptotic factors FasL and TRAIL and are able to inhibit neurite outgrowth, and induce apoptosis in about 75% of rat cortical neurons [1] and 40% of astrocytes [2] in culture. By labelling proteins synthesized in one cell type, we also demonstrated EV-mediated horizontal transfer of proteins among brain cells. Interestingly, G2624 release, via EVs, extracellular matrix remodelling proteases [3], and H1° histone protein [4]. We suggested that by releasing H1°, a differentiation-specific histone, cancer cells may escape differentiation cues [4].
To shed further light on the role of EVs in discarding proteins and mRNAs otherwise able to counteract proliferative signals, we studied a melanoma cell line (A375). We found that also these cancer cells produce H1° and release it into EVs. Interestingly, H1° sorted to vesicles shows a molecular mass higher than expected, and is probably sumoylated. By T1 RNase-protection assay with the H1° RNA, three main complexes were evidenced in EVs, the most abundant of which has a molecular mass of about 65 kDa. By using a biotinylated H1°RNA to fish interacting factors, we isolated from EVs a few proteins which have been then identified by mass spectrometry: the most abundant is a protein of about 60 kDa, recognized as myelin expression factor-2 (MYEF2). Western blot analyses confirmed the presence of MYEF2 in EVs released from A375 melanoma cells.
[1] D’Agostino et al- 2006. Int J Oncol 29:1075-85.
[2] Lo Cicero A et al. 2011, Int J Oncol 39:1353-7
[3] Lo Cicero A et al. 2012, Matrix Biol 31:229-33
[4] Schiera G et al. 2013, Int J Oncol 43:1771-
Melanoma cells release extracellular vesicles which contain RNA-binding proteins able to bind the mRNA encoding histone H1°
No full textExtracellular vesicles (EVs) are produced by most prokaryotic and eukaryotic cells; tumour cells, however, release much higher amounts of EVs, which contain cancer-specific proteins and RNAs. Molecules carried by EVs are captured by surrounding cells, which then undergo profound phenotypic modifications. G26/24 oligodendroglioma cells release, for example, EVs containing FasL and TRAIL, which induce apoptosis in rat cortical neurons and astrocytes in culture. By metabolic labelling of cells, EV-mediated horizontal transfer of radioactive proteins was clearly demonstrated. Among the proteins present in EVs produced by oligodendroglioma cells, extracellular matrix remodelling proteases, and the linker histone H1°, a differentiation-specific histone, were identified. We also found that A375 melanoma cells release EVs which, like the once produced by oligodendroglioma cells, contain H1°. Interestingly, H1° histone sorted to vesicles has a molecular mass higher than expected, and is probably sumoylated.
More recently, by a T1 RNase-protection assay, done by mixing an in-vitro transcribed, H1°- encoding RNA, and EVs, three main RNA-protein complexes were evidenced, the most abundant of which had an apparent molecular mass of about 65 kDa. We then synthesized a biotinylated H1° RNA, with the aim to fish, by affinity chromatography, the evidenced proteins. The RNA-bound fraction was finally analysed by mass spectrometry. The most abundant protein identified was the myelin expression factor-2 (MYEF2), which has indeed a molecular mass of about 60 kDa. The presence of MYEF2 in EVs released from A375 melanoma cells was finally confirmed by Western blot 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
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