1,720,971 research outputs found
Bone remodeling, humoral networks and smart biomaterial technology for osteoporosis.
No full textOne of the unfortunate sequelae of increased life expectancy is a growing number of age-related degenerative diseases, a prime example being osteoporosis. This form of metabolic bone disease and related co-morbidities consume tremendous resources and costs from a nation's health care system. Osteoporosis results from genetic, age-related, and hormone-dependent causes as well as a compendium of secondary pathophysiological states. The presence of osteoporosis as a comorbidity confers a significant negative prognostic element following orthopedic procedures. In vitro and in vivo studies of osteoporotic bone implicate microarchitectural bone rarefaction, microenvironmental and functional disturbance of osteoblast-osteoclast coupling, and abnormal tissue and signalling molecule repertoires, each having detrimental effects on the regenerative and osteointegration processes. This review explores the pathophysiology of bone remodeling from a macro- and micro- systems biology standpoint with a focus on cytokine interactions. Furthermore, therapeutic interventions exploiting vulnerable nodes in these physiological networks will be posited. One exciting development in this area is the use of novel biomaterials
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
In vitro and in vivo behaviour of biodegradable and injectable PLA/PGA copolymers related to different matrices.
No full text This study comparatively investigates the in vitro and in vivo behavior of injectable polymeric materials for the treatment of bone defects. The tested materials were three injectable and biodegradable PLA/PGA 50/50 copolymers dispersed in different matrices: Fisograft-gel (GEL) was dispersed in an aqueous matrix of poly-ethyl-glycole (PEG); Slurry2 (SL2) was dispersed in an aqueous matrix of PEG and dextran; and Slurry6 (SL6) was dispersed in a 3% agarose matrix. The biological characterization of these materials was studied by in vitro and in vivo tests: the in vitro test assessed the cellular response in terms of viability, differentiation and synthetic activity, while the in vivo test evaluated the healing capacity of bone defects treated with these biomaterials. GEL and SL2 induced a similar response for viability and differentiation of MG63 osteoblast-like cells after a 7-day culture, while SL6 caused a higher production of both interleukin-6 and type I collagen. Since the results showed that the materials were biocompatible and not cytotoxic in vitro, the in vivo study was carried out: materials were implanted, under general anesthesia, in critical size defects of rabbit femoral condyles; after 4 and 12 weeks, the healing rates and the quality of the regenerated bone were histomorphometrically calculated. The SL2-treated defects healed better at 12 weeks with a more similar microarchitecture of the newly formed bone to normal bone in comparison with other materials, as demonstrated by bone volume fraction and trabecular thickness values. </jats:p
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Chronic alcohol abuse and endosseous implants : linkage of in vitro osteoblast dysfunction to titanium osseointegration rate
No full textChronic alcohol consumption is associated with pathological effects on bone, and it is correlated with the increasing risk of osteoporosis and fractures. The negative effects of alcohol intake also influence bone repair processes and the osseointegration of implants. The aim of the present in vitro study was to investigate the proliferation and synthetic activity of osteoblasts isolated from the trabecular bone of rats previously exposed to 7-week intermittent exposure to ethanol vapour (EE-OB), and sham-aged rats (SA-OB), when cultured on standard commercially pure Ti (cpTi). Osteoblast proliferation (WST-1), alkaline phosphatase (ALP), osteocalcin (OC), collagen type I (CICP), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and transforming growth factor-beta1 (TGF-beta1) were measured at 1, 7, and 14 days of culture. Our results showed a decrease in the cell viability and synthetic activity of osteoblasts exposed to ethanol when cultured on cpTi. Moreover, the release of local regulatory factors from osteoblasts was imbalanced: TGF-beta1 production was reduced and TNF-alpha and IL-6 were up-regulated. These in vitro data suggest that alcohol abuse affects bone repair and decreases the ability to form bone around standard cpTi. Innovative surfaces and adjuvant therapies could be useful when implants are required in alcoholics
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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