1,720,973 research outputs found
Three-dimensional cultures of osteogenic and chondrogenic cells: mimicking bone and cartilage in vitro.
No full textTHE DEVELOPMENT OF TISSUE-ENGINEERED BONE OF DIFFERENT ORIGIN THROUGH ENDOCHONDRAL AND INTRAMEMBRANOUS OSSIFICATION FOLLOWING THE IMPLANTATION OF MESENCHYMAL STEM CELLS AND OSTEOBLASTS IN A MURINE MODEL.
No full textThe study of host cell recruitment by implanted exogenous cells is one of the novel challenges in tissue engineering. We previously reported the development of tissue-engineered bone deposited by host cells in porous ceramic scaffolds seeded with murine mesenchymal stem cells (MSC) and implanted in immunocompromised mice. To better highlight the contribution of host cells to the development of the engineered tissue and to investigate whether the capacity to recruit host cells was dependent on the donor cell commitment, we implanted ceramic scaffolds seeded with either murine GFP labeled MSC or GFP labeled osteoblasts (OB) into immunocompromised mice. Although we observed formation of bone in all scaffolds, the origin of bone cells and the ossification type were strictly dependent on the nature and commitment of the seeded cells. MSC implants led to formation of bone of host origin through the activation of an endochondral ossification process while an intramembranous ossification directly performed by the seeded cells was observed in OB implants. Moreover, we observed an increased vascularization in MSC implants due to the higher capacity of MSC to recruit host CD31+ endothelial cells. The relationship between this enhanced vascularization and the type of ossification is discussed.The study of host cell recruitment by implanted exogenous cells is one of the novel challenges in tissue engineering. We previously reported the development of tissue-engineered bone deposited by host cells in porous ceramic scaffolds seeded with murine mesenchymal stem cells (MSC) and implanted in immunocompromised mice. To better highlight the contribution of host cells to the development of the engineered tissue and to investigate whether the capacity to recruit host cells was dependent on the donor cell commitment, we implanted ceramic scaffolds seeded with either murine GFP labeled MSC or GFP labeled osteoblasts (OB) into immunocompromised mice. Although we observed formation of bone in all scaffolds, the origin of bone cells and the ossification type were strictly dependent on the nature and commitment of the seeded cells. MSC implants led to formation of bone of host origin through the activation of an endochondral ossification process while an intramembranous ossification directly performed by the seeded cells was observed in OB implants. Moreover, we observed an increased vascularization in MSC implants due to the higher capacity of MSC to recruit host CD31+ endothelial cells. The relationship between this enhanced vascularization and the type of ossification is discussed. © 2009 Elsevier Ltd. All rights reserved
The recruitment of two consecutive and different waves of host stem/progenitor cells during the development of tissue-engineered bone in a murine model
No full textAngiogenesis plays a central role in bone regeneration, not only for the transport of nutrients, but also for locally directing skeletal stem/progenitor cells. Following ectopic implantation of porous ceramic cubes seeded with mouse GFP-labeled mesenchymal stem cells (MSC) into syngenic mice, we investigated the cascade of events leading to bone formation. Implants harvested at different times were enzymatically digested to generate single-cell suspensions. Recovered cells were sorted to separate GFP+implanted MSC and host recruited GFP- cells. We isolated and characterized two different waves of cells, migrating from the host to the MSC-seeded ceramic. The first migrated cell population, recovered 7 days after implantation, was enriched in CD31+endothelial progenitors, while the second one, recruited at day 11, was enriched in CD146+pericyte-like cells. Both populations were not recruited into the scaffold following implantation of a non-MSC seeded ceramic. Pericyte-like cell mobilization was dependent on the first migrated endothelial cell population. Pericyte-like cells retained properties distinctive of stem cells, such as capacity of performing a high number of in vitro cell divisions and showed an osteogenic potential. Studies on the cross talk between implanted exogenous MSC and resident stem/progenitor cells could open new perspectives for future clinical applications
Extracellular matrix deposition and scaffold biodegradation in an in vitro three-dimensional model of bone by X-ray computed microtomography.
No full text
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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