1,721,059 research outputs found
Oxygen Tension Controls the Expansion and Differentiation of Normal and Tumor-derived Human Neural Stem Cells. Role of oxygen in BMP responsiveness
Full text linkDuring neural development the generation of diverse cell types involves the response of precursor cells to a wide variety of environmental cues, like soluble factors, the extracellular matrix and oxygen tension. Among these, oxygen tension and oxidation state in particular are important biophysical parameters that control neural precursor proliferation, survival and fate determination, so the dynamic control of oxygen availability regulates self renewal and the generation of cell diversity during development and throughout the life of the organism. However, the mechanisms by which oxygen acts in this manner are poorly understood.
Current evidence suggests that oxygen levels in both developing and mature brain are much lower than the 20% oxygen used in standard mammalian cell culture (Erecinska M. et al. 2001).
Previously it has been found that the sensitivity to oxygen tension is greater in mouse than in rat cells. Precursor survival and expansion is greatly improved at an oxygen tension (2-5%) closer to that measured in vivo and far lower than conditions typically used (20%) in culture studies. In the last decade much research has focused on the detrimental effect of anoxia during ischemic episodes and these results indicate that atmospheric oxygenation is incompatible with long-term precursors cell survival. Furthermore, one of the main effort is directed to maximize the culture efficiency of neural precursors for replacement therapies and also in vitro fertilization research has focused on oxygenation in order to optimize viability of the early post-fertilization embryo. It will be very important to understand the signals that control survival, proliferation and fate choice of precursor cells and it will also be necessary to investigate what subtypes of precursors are preferentially selected under normal in vitro condition. Indeed, the addition of antioxidants and other free radical scavengers is likely to be no more than a sub-optimal surrogate for culturing in lowered oxygen.
Moreover, it has been recently shown that hypoxia is a crucial component of the brain tumor niche as it positively correlates with tumor aggressiveness and over-activity of Hypoxia Inducible Factor-1? (HIF-1?) reinforces tumor progression.
Thus, the main aim of the project is to understand the role of oxygen tension in proliferation and lineage determination of Human CNS (Central Nervous System) and brain tumor derived precursor cells. We sought to understand if a lower oxygen tension (2-5%), compared to environmental 20% oxygen, promotes the expansion of a more premature and actively proliferating subtype of precursor cells, affecting cell multipotency, and which could be the molecular pathways modulated by oxygen tension.
Our results indicate that dynamic control of oxygen tension regulates different steps in fate and maturation and may be crucial for treating neurodegenerative diseases (i.e. demyelinating diseases). They also suggest that the maintenance of brain tumors stem-ness, particularly in high Grade Glioma (HGG) tumors, is correlated to a hypoxic microenvironment in which BMP signaling pathway and the pro-differentiating effects mediated by BMP are down-regulated
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
Role of gut microbiota and nutrients in amyloid formation and pathogenesis of Alzheimer disease
No full textIt has been hypothesized that alterations in the composition of the gut microbiota might be associated with the onset of certain human pathologies, such as Alzheimer disease, a neurodegenerative syndrome associated with cerebral accumulation of amyloid-β fibrils. It has been shown that bacteria populating the gut microbiota can release significant amounts of amyloids and lipopolysaccharides, which might play a role in the modulation of signaling pathways and the production of proinflammatory cytokines related to the pathogenesis of Alzheimer disease. Additionally, nutrients have been shown to affect the composition of the gut microbiota as well as the formation and aggregation of cerebral amyloid-β. This suggests that modulating the gut microbiome and amyloidogenesis through specific nutritional interventions might prove to be an effective strategy to prevent or reduce the risk of Alzheimer disease. This review examines the possible role of the gut in the dissemination of amyloids, the role of the gut microbiota in the regulation of the gut-brain axis, the potential amyloidogenic properties of gut bacteria, and the possible impact of nutrients on modulation of microbiota composition and amyloid formation in relation to the pathogenesis of Alzheimer disease
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
The Use of Neuroimaging to Assess Associations Among Diet, Nutrients, Metabolic Syndrome, and Alzheimer's Disease
No full textIn the last decade, specific dietary patterns, mainly characterized by high consumption of vegetables and fruits, have been proven beneficial for the prevention of both metabolic syndrome (MetS)-related dysfunctions and neurodegenerative disorders, such as Alzheimer's disease (AD). Nowadays, neuroimaging readouts can be used to diagnose AD, investigate MetS effects on brain functionality and anatomy, and assess the effects of dietary supplementations and nutritional patterns in relation to neurodegeneration and AD-related features. Here we review scientific literature describing the use of the most recent neuroimaging techniques to detect AD- and MetS-related brain features, and also to investigate associations between consolidated dietary patterns or nutritional interventions and AD, specifically focusing on observational and intervention studies in humans
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
- …
