161,022 research outputs found
Cellular communication and bystander effects in modelling low-dose radiation action
No full textAvailable data suggesting the occurrence of “bystander effects” (i.e. damage induction in cells not traversed by radiation)
were collected and critically evaluated, in view of the development of low-dose risk models. Although the underlying mechanisms
are largely unknown, cellular communication seems to play a key role. In this context, the main features of cellular
communication were summarised and a few representative studies on bystander effects were reported and discussed. Three
main approaches were identified: (1) conventional irradiation of cell cultures with very low doses of light ions; (2) irradiation
of single cells with microbeam probes; (3) treatment with irradiated conditioned medium (ICM), i.e. feeding of unexposed
cells with medium taken from irradiated cultures. Indication of different types of bystander damage (e.g. cell killing, gene
mutations and modifications in gene expression) has been found in each of the three cases. The interpretations proposed
by the investigators were discussed and possible biases introduced by specific experimental conditions were outlined. New
arguments and experiments were suggested, with the main purpose of obtaining quantitative information to be included in
models of low-dose radiation action. Implications in interpreting low-dose data and modelling low-dose effects at cellular and
supra-cellular level, including cancer induction, were analysed. Possible synergism with other low-dose specific phenomena
such as adaptive response (AR) (i.e. low-dose induced resistance to subsequent irradiation) was discussed
Antioxygenic enzymes as tumor markers: a critical reassessement of the respective roles of superoxide dismutase and glutathione peroxidase
No full textMisura del danno ossidativo radioindotto su matrici lipidiche per mezzo della fluorometria
No full textVariations on the Author
No full text“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
Radiation induced membrane oxidative damage in human cells at low and high dose-rate: production and repair.
No full textHuman cell membrane oxidative damage induced by single and fractionated doses of ionizing radiation: a fluorescence spectroscopy study.
No full textPublisher: Informa Healthcare
Place of Publication: Englan
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Alteration in erytrocyte membrane lipids induced by low doses of ionizing radiation as revealed by 1,6-diphenil-1,3,5-hexatriene fluorescence lifetime
No full textDamage in membrane lipids induced by low doses of ionizing radiation in the presence of oxygen has been detected in rabbit erythrocyte ghosts labelled with 1,6-diphenyl-1,3,5-hexatriene (DPH). Multifrequency phase and modulation fluorometry was used to measure DPH fluorescence lifetime. This technique is particularly suited for the observation of heterogeneous fluorescence decays. DPH decay in erythrocyte membranes is described by a two-component continuous distribution of lifetimes. The value of the distribution width of the long-lived component is found to be affected by radiation-induced membrane lipid damage at doses as low as 0.5 Gy, well within the dose range used to measure cell survival. The width of the DPH lifetime distribution decreases when the ghosts are irradiated in the presence of oxygen. Such a decrease is a linear function of the logarithm of the dose. After a dose of 110 Gy and above, the fractional intensity of the short-lived component of the DPH decay increases linearly, indicating severe membrane damage. Experiments performed in the absence of oxygen do not show any change in the fluorescence parameters up to a dose of 550 Gy. The molecular identification of the produced damage has not been accomplished, but the necessity of oxygen to observe the damage suggests that hydroperoxides and lipids crosslinks are produced
Cholesterol protects the phospholipid bilayer from oxidative damage.
No full textPublisher: New York : Pergamon
Copyright © 1995 Elsevier Science Ltd Printed in the USA
Tecniche di fluorescenza per l’osservazione di danni ossidativi prodotti da basse dosi di radiazioni ionizzanti su lipidi di membrana
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