1,721,392 research outputs found
Lipid accumulation. The common feature to photosensitizer-retaining normal and malignant tissues
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Role of hypoxia in Photodynamic Therapy of tumors
No full textThe photodynamic therapy of tumors is based on a photosensitization reaction that produces oxygen-derived cytotoxic species. The availability of oxygen is therefore a necessary condition to obtain the desired effect. However, most tumors develop regions that have outgrown their vascular supply, and therefore present severe hypoxia. In many hypoxic, yet viable areas, oxygen partial pressures almost two orders of magnitude lower that in normal tissues have been measured by other authors. It is here suggested that hypoxic cells are resistant to the therapy and hence are a source of postirradiation recurrence of the tumors. Methods are reviewed and discussed that can be used to: (a) improve the tumor oxygenation status prior to, or during irradiation; (b) destroy hypoxic cells; and, (c) allow the reoxygenation of the tumor by using fractionated irradiation protocols which increase tumor photosensitivity. Hyperthermia, a therapy to which hypoxic cells are particularly sensitive, is discussed. Cellular and vascular parameters that should be considered when discussing the synergism between hyperthermia and photodynamic therapy are listed. The new research field of hypoxia mapping by nondestructive, noninvasive, imaging techniques is briefly discussed
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
Dark effects of Hematoporphyrin Derivative on Lactate Dehydrogenase activity and distribution in HeLa cells: Cytochemical evaluation
No full textThe effects of hematoporphyrin derivative (HpD) in the dark on the activity and subcellular location of lactate dehydrogenase (LDH) in HeLa cells are evaluated with an original quantitative cytochemical technique. The enzyme activity is visually indicated by diffuse patterns ascribed to loosely-bound, cytoplasm-LDH and by granular formations ascribed to tightly bound, mitochondrial-LDH. The granular pattern has a longer formation lag than the diffuse pattern, since mitochondrial loci are less accessible to the reagents. Observations occasionally and unexpectedly found show that the percentage of cells with granular pattern is highly enhanced in suffering cells. This suggests that the mitochondrial-LDH activity increases as a reaction to stress.
In cells that have incorporated HpD for 24 h in the dark, significant changes of LDH activity and distribution occur as many more cells with granular pattern and larger granules are seen, while the diffuse activity significantly decreases. These results point towards: (a) a binding of HpD at the cytoplasm LDH active site or close to it leading to enzyme inactivation; (b) a labilization of the mitochondrial membrane facilitating access to the inner loci by the cytochemical reagents and hence better visualization of the mitochondrial-enzyme; and/or (c) an increased LDH activity ensuing from drug-induced stress
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