1,720,987 research outputs found
Cellular protection from oxidative stress by the blood orange pigment cyanidin-3-O-beta-glucopyranoside
No full textThe cyanidin-3-O--glucopyranoside (C-3-G) antioxidant effects were assessed in two models of increased oxidative stress. Isolated post-ischemic rat heart reperfused with C-3-G showed inhibition of malondialdehyde (MDA) formation (-67% and -94% in 10 and 30 M C-3-G-reperfused hearts, respectively) and improved energy metabolism. Normoxic hearts perfused in the recirculating Langendorff mode with 10 and 30 M C-3-G indicated that C-3-G can permeate within myocardial cells. Dose-dependent decrease of MDA generation by C-3-G was observed in 2 mM H2O2-treated human erythrocytes (apparent IC50 of 5.12 M and 38.43 M were calculated for C-3-G and resveratrol, respectively). In conclusion, C-3-G (largely present also in pigmented oranges) may have beneficial effects in case of increased oxidative stress
Hypothesis of the postconcussive vulnerable brain: experimental evidence of its metabolic occurrence
No full textOBJECTIVE: We evaluated the effects of two consecutive concussive injuries on brain energy metabolism and N-acetylaspartate (NAA) to investigate how the temporal interval between traumatic events influences overall injury severity. METHODS: Rats were injured to induce diffuse traumatic brain injury (TBI) (mild, 450 g/1 m; severe, 450 g/2 m). In two groups, two mild TBIs were delivered in 3- or 5-day intervals. Three additional animal groups were used: single mild TBI, single severe TBI, and sham. All animals were killed 48 hours postinjury. Adenosine 5'-triphosphate (ATP), adenosine diphosphate, and NAA concentrations were analyzed with high-performance liquid chromatography on deproteinized whole brain extracts. RESULTS: In control animals, the NAA concentration was 9.17 +/- 0.38 micromol/g wet weight, the ATP concentration was 2.25 +/- 0.21 micromol/g wet weight, and the ATP-to-adenosine diphosphate ratio was 9.38 +/- 1.23. These concentrations decreased to 6.68 +/- 1.12 micromol/g wet weight, 1.68 +/- 0.24 micromol/g wet weight, and 6.10 +/- 1.21 micromol/g wet weight, respectively, in rats that received two mild TBIs at a 5-day interval (P 0.01; not different from results in rats with single mild TBI). When a second TBI was delivered after 3 days, the NAA concentration was 3.86 +/- 0.53 micromol/g wet weight, the ATP concentration was 1.11 +/- 0.18 micromol/g wet weight, and the ATP-to-adenosine diphosphate ratio was 2.64 +/- 0.43 (P 0.001 versus both controls and 3-day interval; not different from rats receiving a single severe TBI). CONCLUSION: The biochemical modification severity in double TBI is dependent on the interval between traumatic events, which demonstrates the metabolic state of the vulnerable brain after mild TBI. These data support the hypothesis of the application of proton magnetic resonance spectroscopy to measure NAA as a possible tool to monitor the full recovery of brain metabolic functions in the clinical setting, particularly in sports medicine
Cerebral oxidative stress and depression of energy metabolism correlate with severity of diffuse brain injury in rats.
No full textOBJECTIVE:
The combined effect of traumatic brain injury (TBI) and secondary insult on biochemical changes of cerebral tissue is not well known. For this purpose, we studied the time-course changes of parameters reflecting ROS-mediated oxidative stress and modifications of cell energy metabolism determined in rats subjected to cerebral insult of increasing severity.
METHODS:
Rats were divided into four groups: 1) sham-operated, 2) subjected to 10 minutes of hypoxia and hypotension (HH), 3) subjected to severe diffuse TBI, and 4) subjected to severe diffuse TBI + HH. Rats were killed at different times after injury, and analyses of malondialdehyde, ascorbate, high-energy phosphates, nicotinic coenzymes, oxypurines, nucleosides, and N-acetylaspartate (NAA) were made by high-performance liquid chromatography on whole-brain tissue extracts.
RESULTS:
Data indicated a close relationship between degree of oxidative stress and severity of brain insult, as evidenced by the highest malondialdehyde values and lowest ascorbate levels in rats subjected to TBI + HH. Similarly, modifications of parameters related to cell energy metabolism were modulated by increasing severity of brain injury, as demonstrated by the lowest values of energy charge potential, nicotinic coenzymes, and NAA and the highest levels of oxypurines and nucleosides recorded in TBI + HH rats. Both the intensity of oxidative stress-mediated cerebral damage and perturbation of energy metabolism were minimally affected in rats subjected to HH only.
CONCLUSION:
These results showed that the severity of brain insult can be graded by measuring biochemical modifications, specifically, reactive oxygen species-mediated damage, energy metabolism depression, and NAA, thereby validating the rodent model of closed-head diffuse TBI coupled with HH and proposing NAA as a marker with diagnostic relevance to monitor the metabolic state of postinjured brain
Chromosomal 17p13.3 microdeletion unmasking recessive Canavan disease mutation
No full textUnmasking a recessive allele on one chromosome by a deletion on the other is a disease causing mechanism often invoked but rarely proven. We report on an Italian female patient with Canavan disease (OMIM# 271900) due to a missense mutation of the aspartoacylase (ASPA) gene and a 17p13.3 chromosomal microdeletion
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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