1,721,037 research outputs found
Use of Non Thermal Treatments to Improve the Safety, Quality, and Shelf-life of Products of Animal Origin
No full textMODULATION OF THE ENZYMATIC ACTIVITY AND MEMBRANE BINDING PROPERTIES OF SOYBEAN LIPOXYGENASE-1 THROUGH LIMITED PROTEOLYSIS AND METAL SUBSTITUTION
No full textLipoxygenases are non-heme, non-sulfur iron containing enzymes that catalyze the dioxygenation of polyunsatured fatty acids containing one or more pentadiene systems to the corresponding hydroperoxy derivatives. Structural studies in solution of the mammalian and plant enzyme revealed that the latter has a more stable and compact conformation1. As yet, metal atom extraction, reconstitution and substitution with vicariate metals have not been successfully applied to soybean lipoxygenase-1, because of the highly buried position of the iron atom within the active site. Tryptic digestion of lipoxygenase-1 and the subsequent isolation of the 60 kDa C-terminal region allowed to generate a “mini-lipoxygenase-1 (miniLOX)” that retains the catalytically active iron, but in a more accessible position2. In this study, we investigated by near-UV-circular dichroism and fluorescence spectroscopies the structural and functional effects of iron removal, reconstitution and vicariation in miniLOX. Moreover, we report the kinetic analysis and the membrane binding ability of the apo- and metal-substituted forms of miniLOX, using fluorescence resonance energy transfer and monolamellar vesicles. Taken together, these data demonstrate an unprecedented structural role of iron, which is involved not only in the catalytic activity but also in the membrane binding ability of lipoxygenase-1.1. Dainese E. Sabatucci A. van Zadelhoff G. Angelucci C. B. Vachette P., Veldink G. Finazzi Agrò A. and Maccarrone M. (2005). J. Mol. Biol. 349, 143-152.2. Maccarrone M. Salucci M. L. van Zadelhoff G. Malatesta F. Veldink, G. Vliegenthart J. F. and Finazzi Agrò A. (2001). Biochemistry 40, 6819-6827.[...
Oncogene expression is modulated by recombinant human interferon-beta in human breast-cancer cells
Full text linkThe effect of recombinant human interferon-beta on growth and oncoprotein expression was investigated in several human breast-cancer cell lines with different characteristics. All cell lines tested were sensitive to the antiproliferative action of the drug, regardless of their estrogen sensitivity. The maximal inhibition of cell proliferation was seen after 6 days of treatment. In estrogen-sensitive CG-5 and ZR-75-1 cells, but not in MDA-MB-453 estrogen-insensitive cells, a reduction in c-myc and c-erbB2 oncoproteins occurred after 48-72 hr and became more pronounced after 120-168 hr of treatment, suggesting that this down-regulation is not direct but is mediated by undefined molecular mechanisms. The time-course of the IFN-mediated decrease in oncoproteins seems to indicate that this event is not strictly related to the IFN-regulation of cell proliferation. The expression of c-erbB2 and c-myc was also analyzed, after recombinant human interferon-beta treatment, at the mRNA level in CG-5 cells. Surprisingly, no statistically significant variation of c-erbB2 or of c-myc mRNA was found either before or after 120-168 hr. Thus, we surmise that the observed reduction of oncoproteins may be due to post-transcriptional mechanisms
The growth of malignant and nonmalignant human cells is modulated by a human placental extract
No full textBackground: In the present paper, malignant and nonmalignant human cells were compared in their response to a fraction (fraction D, FD) of a human placental extract.
Materials and methods: The activity of FD was tested on cell proliferation both in the absence and in the presence of 5%, 10% and 15% fetal bovine serum (FBS). For cells growing in monolayers, the medium was renewed with fresh medium containing FD 24 hours after plating and 3 days after the first exposure. In breast cancer cells only, it was also changed after 6 days. For leukemic cells, which grow in suspension, FD was added directly to the medium the day of the seeding and then after 3 and 6 days.
Results: In normal fibroblasts, when plated at a low density, a strong inhibitory effect on cell growth was seen with the highest FD dose. This effect was observed in the presence of 5% and 10% FBS, while it disappeared with 15% FBS. In endothelial cells, FD, in the presence of 5% or 10% FBS, produced a modest but constant inhibition of cell proliferation, which was evident after a short treatment and with almost every dose of FD. Breast cancer and leukemic cell lines, plated at a standard density, were markedly inhibited by FD, but this effect was reversed in serum-free conditions, at least in mammary cells. In leukemic cells, after an initial stimulatory effect, FD was not able to counterbalance the absence of serum.
Conclusions: Our data seem to suggest that in FD both stimulating and inhibitory growth-factors coexist, the activity of which are greatly influenced by the culture conditions used
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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