130,399 research outputs found
The toxic effect of fluoride on MG-63 osteoblast cells is also dependent on the production of nitric oxide
No full textSome soda-lime-phospho-silicate glasses, such as Hench’s Bioglass® 45S5, form bone-like apatite ontheir surface when bound to living bone. To improve their osteointegration for clinical purposes, thefluoride insertion in their structure has been proposed, but we recently showed that fluoride causesoxidative damage in human MG-63 osteoblasts, via inhibition of pentose phosphate oxidative path-way (PPP) and its key enzyme glucose 6-phosphate dehydrogenase (G6PD). In the same cells we havenow investigated the role of nitric oxide (NO) in these effects. Fluoride-containing bioactive glasses andNaF caused, as expected, release of lactate dehydrogenase in the extracellular medium, accumulation ofintracellular malonyldialdehyde, inhibition of PPP and G6PD: we have now observed that these effectswere significantly reverted not only by superoxide dismutase (SOD) plus catalase (scavengers of reactiveoxygen species), but also by N-monomethyl l-arginine (l-NMMA, a NOS inhibitor) and 2-phenyl-4,4,5,5,-tetramethylimidazoline-1oxyl 3-oxide (PTIO, a NO scavenger). Moreover the two highest concentrationsof both fluoride-containing bioglasses and NaF caused increase of nitrite (a stable derivative of NO) levelsin the culture supernatant, which was inhibited by l-NMMA, erythrocytes, PTIO and SOD/catalase, andincrease of intracellular NO synthase (NOS) activity. The incubation with bioglasses or NaF increasedalso the phosphorylation of Ser1177 in the endothelial NOS isoform. Furthermore, the NO donor spermineNONOate was able to inhibit G6PD activity in vitro, and this effect was partly reverted by PTIO. Thereforeour results suggest that most cytotoxic effects of fluoride are mediated by the production of NO: reactiveoxygen species are important, causing NOS phosphorylation. We also observed, for the first time, thatTempol, but not SOD/catalase, besides inhibiting the oxidative stress induced by fluoride, also scavengesfluoride ions. For this reason it is not a selective inhibitor of the oxidative effects of fluoride
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
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
Fluoride-containing bioactive glasses inhibit pentose phosphate oxidative pathway and glucose 6-phosphate dehydrogenase activity in human osteoblasts
No full textBioactive glasses such as Hench's 45S5 (Bioglass®) have applications to tissue engineering aswell as bone repair, and the insertion of fluoride in their composition has been proposed to enhancetheir bioactivity. In view of a potential clinical application, we investigated whether fluoride-containingglasses exert toxic effects on human MG-63 osteoblasts, and whether and how fluoride, which isreleased in the cell culture medium, might play a role in such cytotoxicity. A 24 h incubation with 50μg/ml (12.5 μg /cm2) of fluoride-containing bioactive glasses termed HCaCaF2 (F content: 5, 10 and15% mol) caused the release of lactate dehydrogenase in the extracellular medium (index ofcytotoxicity), the accumulation of intracellular malonyldialdehyde (index of lipoperoxidation), and theincrease of glutathione consumption. Furthermore, fluoride-containing glasses inhibited the pentosephosphate oxidative pathway and the glucose 6-phosphate dehydrogenase activity. These effects areascribable to the fluoride content/release of glass powders, since they were mimicked by NaF solutionsand were prevented by dimethyl sulfoxide and tempol (two radical scavengers), by superoxidedismutase (a superoxide scavenger), and by glutathione (the most important intracellular antioxidantmolecule), but not by apocynin (an inhibitor of NADPH oxidase). The presence of fluoride-containingglasses and NaF caused also the generation of reactive oxygen species, which was prevented bysuperoxide dismutase and catalase. The data suggest that fluoride released from glasses is the cause ofMG-63 cell oxidative damage and is independent of NADPH oxidase activation. Our data provide a newmechanism to explain F ̅ ions toxicity: fluoride could trigger, at least in part, an oxidative stress viainhibition of the pentose phosphate oxidative pathway and, in particular, through the oxidativeinhibition of glucose 6-phosphate dehydrogenase
Variation of vascular and blood indicators of early endothelial dysfunction after root canal therapy: A clinical and biomolecular study
No full textAim: Apical periodontitis (AP) is correlated with a higher risk of developing cardiovascular disease (CVD). No data currently exist to suggest that endothelial dysfunction (ED) improves after endodontic treatment in patients who have AP, despite a link between chronic AP and ED. This study was designed to investigate the expression of early ED markers in young adults with chronic AP, before and after root canal treatment. Methodology: 41 subjects (20 controls and 21 patients with AP) were examined at enrolment. Patients with AP were also assessed 2 and 12 months after treatment. ENDO-PAT was used to measure endothelial flow reserve (EFR) and ELISAs were used to assess plasma levels of interleukin (IL)-1, IL-6 and TNF-alpha, vasoconstrictor ED endothelin (ET)-1, the circulating endothelial adhesion markers intercellular adhesion molecule-1 (ICAM)-1/ CD54 and soluble vascular cellular adhesion molecule-1 (sVCAM)-1/CD106, soluble CD14, and the endothelial leukocyte adhesion molecule E-selectin. Results: Baseline serum levels of ET-1, ICAM-1, E-selectin, IL-1, and sCD14 were elevated in patients with AP compared to the control group. There was no macroscopic evidence of reduced EFR in either group. Treatment for AP was associated with reduced inflammation and improved early ED, indicated by a lowering of IL-1, sCD14, ET-1, ICAM-1/ CD54 and E-selectin levels to resemble those of control subjects. Conclusions: Early vascular ED may be driven by AP but is reversible with effective endodontic treatment
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Bioactive phospho-silicate glasses containing CaF2: bioactivity test in simulated body fluids and behaviour towards osteoblast cells
No full textIn this work it is reported a study, in vitro (DMEM), of some potentially bioactive glasses based on the composition of Bioglass® 45S5 bioactive glass, in which CaF2 substitutes alternatively CaO and Na2O. Using a multi-techniques investigation, it is possible to explain in detail the glasses degradatation and the mechanism of formation of an apatitic layer between inorganic material and biological medium. The behaviour of doped glasses is differs from that proposed by Hench for Bioglass® 45S5 bioactive glass, however, these doped glasses have capability of developing bio-activity.A preliminary cellular test is also performed in view of a potential clinical applicatio
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
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