1,720,988 research outputs found
Mecanismos de morte celular activados pela terapia fotodinâmica do cancro : efeito do óxido nítrico
No full textTese de doutoramento em Biologia (Biologia Celular) apresentada à Fac. de Ciências e Tecnologia de CoimbraA terapia fotodinâmica (PDT) é uma técnica muito promissora utilizada no tratamento do cancro. Esta técnica baseia-se na acumulação preferencial de compostos fotossensíveis (chamados fotossensibilizadores) nos tecidos tumorais, seguida da irradiação do tumor com luz visível. O óxido nítrico (NO) tem um papel importante no crescimento dos tumores e formação de metástases. Recentemente foi descrito que tumores que produzem maior quantidade de NO são mais resistentes ao tratamento por terapia fotodinâmica, demonstrando que o NO exerce um efeito protector na erradicação de tumores por PDT. O óxido nítrico pode exercer este efeito protector devido a induzir o relaxamento dos vasos sanguíneos dos tumores, permitindo uma recuperação após a irradiação. Além disso, o NO pode ter um efeito directo, inibindo a morte das células tumorais e/ou endoteliais do tumor. Com a finalidade de estudar o possível efeito directo do NO na morte das células tumorais, utilizamos as células CEM em cultura e a ftalocianina bisulfonada de alumínio (AlPcS2), como fotossensibilizador. Para o efeito, as células foram incubadas com AlPcS2 na presença ou na ausência de dadores de NO (DETA/NONOate, hidroxilamina e SNAP) ou arginina. Na ausência de dadores de NO ou arginina, as células morreram rapidamente por apoptose após irradiação. Observou-se processamento e activação da caspase-3 e caspase–9, fragmentação do DNA e condensação da cromatina. Na presença de dadores de NO ou arginina, o número de células apoptóticas diminuiu. Esta inibição não se deveu à S-nitrosilação de caspases e ocorreu antes ou durante o processamento da caspase-9. Ao contrário de outros modelos de morte celular por apoptose, em que os efeitos protectores do NO foram atribuídos ao aumento de expressão de heme oxygenase-1 (HO-1), proteína de choque térmico 70 (HSP70) ou Bcl-2, a estimulação das células CEM com dadores de NO não aumentou a expressão de nenhuma destas proteínas. No entanto, o efeito protector do NO foi revertido quanto as células foram incubadas com ODQ, um inibidor da guanilciclase, ou com KT5823, um inibidor da cinase dependente de cGMP (PKG). A incubação com 8-bromo-cGMP, um análogo do cGMP ao qual a membrana celular é permeável, diminuiu a morte celular induzida por PDT. Estes resultados demonstram que o NO diminui a morte celular induzida por terapia fotodinâmica por um mecanismo dependente da activação da cinase dependente de cGMP, e indicam que o óxido nítrico pode inibir directamente a morte das células tumorais induzida por terapia fotodinâmica
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
Binding and Release of Cations by Sarcoplasmic Reticulum before and after Removal of Lipid
Full text linkThe Ca2+ bound actively in the presence of ATP by sarcoplasmic reticulum isolated from rabbit skeletal muscle is released by Zn2+ (or Cd2+) as well as by phospholipases A or C and by trypsin. Zinc ions also release Mg2+ and are taken up passively by the reticulum membranes, whereas phospholipases A and C and trypsin release only the actively bound Ca2+. Phospholipase A, and to a smaller extent phospholipase C and trypsin, increase the passive cation-binding capacity of reticulum. Thus, concurrently with the loss of selectively bound Ca2+ caused by these agents, there is an increase in the passively bound Mg2+. The increase in the passive cation-binding capacity of reticulum induced by phospholipase depends on the presence of the splitting products of phospholipids, since their removal when digested reticulum is washed with a 2.5% albumin solution decreases the binding capacity to about 50% of the original value. When Ca2+, Mg2+ or Sr2+ is bound passively by reticulum, the ratio of H+ released to either of these divalent cations bound, expressed in terms of nequiv H+ released per nequiv divalent cation bound is about 1.0, but when Zn2+ is taken up, the ratio H+/Zn2+ is only about 0.5, which suggests that some of the Zn2+ is bound at sites that do not release H+ or bind Ca2+. After lipid extraction with 90% acetone, the cation-binding capacity and H+ release are decreased to about 40% of the original values. This effect is particularly evident between pH values of about 6.0 and 8.0. The apparent passive Ca2+-binding affinity is not affected by the lipid removal.http://dx.doi.org/10.1111/j.1432-1033.1972.tb01865.
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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