1,720,959 research outputs found
Up-regulation of pro-angiogenic pathways and induction of neovascularization by an acute retinal light damage.
Full text linkThe light damage (LD) model was mainly used to study some of the main aspects of age related macular degeneration (AMD), such as oxidative stress and photoreceptor death. Several protocols of light-induced retinal degeneration exist. Acute light damage is characterized by a brief exposure (24 hours) to high intensity light (1000 lux) and leads to focal degeneration of the retina which progresses over time. To date there are not experimental data that relate this model to neovascular events. Therefore, the purpose of this study was to characterize the retina after an acute light damage to assess whether the vascularization was affected. Functional, molecular and morphological investigations were carried out. The electroretinographic response was assessed at all recovery times (7, 60, 120 days after LD). Starting from 7 days after light damage there was a significant decrease in the functional response, which remained low up to 120 days of recovery. At 7 days after light exposure, neo-vessels invaded the photoreceptor layer and retinal neovascularization occurred. Remarkably, neoangiogenesis was associated to the up-regulation of VEGF, bFGF and their respective receptors (VEGFR2 and FGFR1) with the progression of degeneration. These important results indicate that a brief exposure to bright light induces the up-regulation of pro-angiogenic pathways with subsequent neovascularization
Nanoceria protect retinal pigment epithelium in the light damaged retina
No full textPurpose : Dry age-related macular degeneration (AMD) is the most common form of AMD, characterized by retinal pigment epithelium (RPE) dysfunction and death, associated to lipofuscin accumulation, photoreceptors death, autophagy alterations and vision loss. Despite its frequency, only palliative therapies are available. In order to search for improvements we investigated the development of the dry AMD in the light damaged (LD) model and tested the protective effects of cerium oxide nanoparticles (nanoceria).
Methods : The dry features of AMD were investigated on Sprague Dawley albino rats exposed to bright light (1000 lux) for 3h, 6h, 9h, 12h, 24h and for 24h followed by 3 and 7 days of recovery, then compared to the healthy controls. The treatment was performed by nanoceria intravitreal injection (2 μl [1mM]) in both eyes 3 days before light exposure (for 24h). After 7 days from injury treated and untreated animals were compared. Oxidative stress was evaluated by acrolein fluorescence intensity on immunolabeled retinal cryosections and RPE was pointed out by anti-RPE65 immunofluorescence. Lipofuscin quantitation was performed by ImageJ software on retinal whole mounts images acquired by confocal microscopy. Autophagy was analysed by LC3B-II western blot.
Results : The RPE was disrupted in the dorsal retina of LD rats starting 3 days after injury. LCB3-II was significantly increased after 24h of light exposure (p<0,05) and remained up-regulated after 7 days of recovery (p<0,05). We also observed lipofuscin accumulation over time and increased oxidative stress already detectable after 7 days of recovery. By nanoceria treatment oxidative stress was significantly reduced in the outer nuclear layer (p<0,01) and in the RPE (p<0,05) of the treated group. Accordingly the blood-retinal barrier was intact since the RPE was not affected and lipofuscin was significantly reduced in terms of number of granules (p<0,001) and percentage of occupied area (p<0,001). LCB3-II was down-regulated in the nanoceria-treated animals compared to the untreated ones (p<0,001).
Conclusions : Our study demonstrates that cerium oxide nanoparticles protect the RPE and limit the dry features of AMD in the light-damaged model. On this basis we propose nanoceria as a new potential therapeutic agent for the dry form of AMD
Evaluating flow regime alterations due to point sources in intermittent rivers: A modelling approach
Full text linkHydrological regime alterations may strongly influence river morphology, water quality, and river ecosystem. The present paper aimed to define an integrated modelling framework for analysing the hydrological regime alterations induced by point sources (PSs) discharges in data-limited regions through two case studies: the Canale d'Aiedda (Italy) and Nil wadi (Algeria). Long time series of daily streamflow in un-impacted and impacted (PSs discharges) conditions were generated by applying the Soil and Water Assessment Tool model and the hydrological regime was characterised by using several hydrological indicators. Flow regime alterations due to PSs were assessed with the range of variability approach. Results showed that the PSs induced alterations of some flow regime components (magnitude, duration, and timing). Hydrological regime classification of the river reaches receiving wastewaters from PSs shifted from intermittent to perennial. All the components of the low flow (1-, 3-, 7-, 30-, and 90-day minimum flow, zero-days) and the monthly flow recorded in summer were severely altered. Minor hydrological alterations were assessed for high flow components (1-, 3-, 7-, 30-, and 90-day maximum flow) and mean monthly flow in the wet period. The tuning of minimum flow was found to shift later in the year. This study may support river ecologists in the ecological status evaluation
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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