1,720,992 research outputs found
Human leukemia K562 cells: induction to erythroid differentiation by guanine, guanosine and guanine nucleotides
No full textBACKGROUND AND OBJECTIVE: Human leukemic K562 cells are able to undergo erythroid differentiation in vitro when cultured with a variety of inducers, leading to increased expression of embryo-fetal globin genes such as the zita, epsilon and gamma-globin genes. Therefore the K562 cell line has been proposed as a very useful in vitro model system for determining the therapeutical potential of new differentiating compounds as well as for studying the molecular mechanism(s) that regulate changes in the expression of embryonic and fetal human globin genes. In this study we explored whether nucleoside triphosphates and related compounds are able to induce differentiation of K562 cells. METHODS: K562 cell differentiation was studied using the benzidine test; hemoglobins were characterized by cellulose acetate gel electrophoresis and mRNA accumulation was investigated by Northern blot analysis. RESULTS: The main conclusion of this paper is that guanine, guanosine and guanine ribonucleotides are effective inducers of K562 cell differentiation. Expression of both Hb Portland and Hb Gower 1 is increased in GTP-induced K562 cells. This increase is associated with greater gamma-globin mRNA accumulation. By contrast, ATP, CTP and UTP are not able to induce erythroid differentiation. INTERPRETATION AND CONCLUSIONS: These findings suggest that guanine, guanosine and guanine ribonucleotides are inducers of erythroid differentiation of K562 cells. This is of some relevance since differentiating compounds have been proposed as antitumor agents. In addition, inducers of erythroid differentiation that stimulate gamma-globin synthesis might be considered in the experimental therapy of hematological diseases associated with a failure in the expression of adult beta-globin genes
Effects of periodate-oxidized ribonucleotides on tumor cell growth
No full textWe have studied the effects of periodate-oxidized ribonucleotides on the in-vitro cell proliferation of human myleoid leukemia K562, T-leukemic Jurkat, promyelocytic HL60 and transformed chinese hamster FH06T1-1 cell lines. oATP inhibits 50% at 5-20 microM, oGTP, oCTP and oUTP only at higher than 100 microM. Different cell lines are differentially affected. oADP, oAMP and o-adenosine were also found effective, even with a different efficiency
Dimensioni sociali dell'analisi di impatto ambientale: il caso della diga sul Basso Flumendosa
No full textDifferential Inhibitory effects of periodate-oxidized ribonucleotides on in vitro proliferation of human leukemic K562 cells
No full textTrans-resveratrol and leaf symptom expression in Esca of grapevine
No full textEsca of grapevine is a serious disease which in some aspects is still lacking full understanding, including the nature of foliar symptoms. Leaves collected at different phenological growth stage from esca symptomatic grapevines cv. Trebbiano d'Abruzzo showed the presence of higher concentrations of trans-resveratrol, the major stilbene produced in grapevine, compared to leaves from healthy plants. The increased levels of trans-resveratrol were supposed to be associated with the host-plant defence response, thought it also raises new questions on a possible role of the stilbene in the foliar symptom development. In 2009, symptomatic leaves were collected from the above mentioned grapevines and were divided into 4 classes calculating symptom severity as the percentage of chlorosis and necrosis on the total leaf area. For each class, leaves were collected at pre-bunch closure, post-veraison and harvest, and the level of trans-resveratrol was determined. The results showed higher concentrations of trans-resveratrol in symptomatic leaves collected at pre-bunch closure compared to what observed at the other growth stages. These results are in agreement with our previous findings and the stronger response of leaves might be correlated with the leaf functioning at the different phenological growth stages; moreover, the increasing of concentrations of trans-resveratrol with the increasing of the severity of leaf symptoms seems to exclude an involvement of the stilbene in the formation of symptoms. Further investigations on cut leaves inoculated with pathogen culture filtrates and/or trans-resveratrol may lead to a better understanding of the relationship between the stilbene and the foliar symptom expression.[...
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
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