1,720,956 research outputs found
Effect of heparin-like compounds on the in vitro proliferation and protein synthesis of various cell types.
No full textPrevious studies have shown that heparin and heparin-like compounds inhibit the proliferation of arterial smooth muscle cells (SMC) both in vivo and in vitro. This anti-proliferative effect seems to be exerted almost exclusively on arterial SMC and related cell types. In the present study the effect of heparin (HTh) is compared with that of two sulfated glycosaminoglycans with low anticoagulant activity, sulodexide (SDX) and low molecular weight heparin (OP/LMWH) on cell proliferation and protein synthesis of 3 cell types: human arterial smooth muscle cells (SMC), fibroblast-like cells (BHK-21) and epithelial cells (rat hepatoma cells, FAO). HTh, SDX and OP/LMWH (5-100 micrograms/ml) are equally effective in reducing the proliferation of human arterial SMC. This inhibition is dose dependent and reversible. BHK-21 and FAO cells are even more sensitive than SMC to heparin-like compounds. For example 1 microgram/ml of heparin-like compounds is sufficient to produce 40-60% inhibition of FAO cell proliferation. In all types of cells HTh, SDX and OP/LMWH do not reduce the incorporation of 35S-methionine into cellular and medium proteins; they increase the radioactivity incorporated into some proteins secreted into the medium. In the case of SMC this effect is dependent on the concentration and the length of exposure to heparin-like compounds. These findings demonstrate that several cell types are sensitive to the anti-proliferative effect of heparin-like compounds
Modulation of the synthesis of apolipoproteins in rat hepatoma cells.
No full textThe present study was designed to investigate whether plasma lipoproteins and albumin can affect the basal synthetic rate of apolipoproteins in differentiated rat hepatoma cells (Fao) incubated in serum-free medium. The synthesis of apolipoproteins was measured by the incorporation of [35S]methionine into medium lipoproteins isolated by density gradient ultracentrifugation. Under all the experimental conditions used, Fao cells synthesized almost exclusively apolipoprotein E. When cells were incubated in the presence of 5-10% rat plasma the synthesis of apolipoprotein E increased 2-3-fold; lipoprotein-deficient serum had a negligible effect. Fatty acid-poor bovine serum albumin (BSA), which had been found to reduce very-low-density lipoprotein secretion in isolated rat hepatocytes, did not modify the synthesis of apolipoprotein E. When Fao cells were incubated in medium containing rat plasma lipoprotein fractions, the synthesis of apolipoprotein E increased. The d less than 1.090 g/ml plasma lipoprotein fraction had the major stimulatory effect. Increased apolipoprotein E synthesis was observed when cells were incubated in the presence of lipids extracted from rat plasma lipoproteins. These results suggest that the intracellular accumulation of lipoprotein-lipids plays an important role in regulating apolipoprotein E synthesis in Fao cells
Effect of heparin derived fractions on the proliferation and protein synthesis of cells in culture.
No full textWe investigated the effect of sulfated oligosaccharides derived from depolymerization of heparin on the proliferation and protein synthesis of smooth muscle cells (SMC), hamster kidney (BHK-21) and lung (V-79) fibroblasts, rat hepatoma cells (FAO) and human promyelocytes (HL-60). BHK-21 and FAO showed the highest sensitivity to heparin; V-79 and HL-60 cells were completely resistant. LMWH (Low Molecular Weight Heparin) (MW 4.5 kD) was as effective as unfractionated heparin in reducing cell proliferation. The oligo-derivative 381/1 (MW 2 kD) was effective only on FAO and BHK-21 cells; oligo-derivative 381/2 (MW 1KD) had a negligible effect. The anti-proliferative effect was associated with an increased secretion of some protein classes. This effect was not present in heparin-resistant cells. In conclusion when the molecular size of heparin derivative is reduced below 2 kD (i.e. the size of a hexasaccharide) the anti-proliferative activity decreases dramatically
Effect of the desulfation of heparin on its anticoagulant and anti-proliferative activity
No full textSome glycosaminoglycans (GAGs), such as heparin and heparin-like compounds inhibit the proliferation of several cell types, including smooth muscle cells, cervical epithelial cells and fibroblasts (1-3). In order to establish which domain of the hepar-in molecule is specifically responsible for the anti-proliferative activity, several strategies have been adopted such as: chemical modification or fractionation of the heparin molecule into low molecular weight fragments or synthesis of oligosaccharides with a defined chemical structure (4-6). In the present study we attempted to determine the role of N- and 0- linked sulfate groups on the anti-proliferative and anticoagulant effect of heparin. To that purpose we modified the molecule to produce N-desulfated, 0-desulfated compounds. The anti-proliferative activity of these modified heparins was compared to that of low molecular weight heparins obtained by depolymerization, heparan sulfate as N-acetylated compound with glucuronic acid and heparin. Since the anti-proliferative effect of heparin depends also on the cell type, we used two different cell types: BHK-21 (hamster fibroblasts) and human arterial SMC (smooth muscle cells), that were found to exhibit a high or intermediate sensitivity to heparin (3,7)
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
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