1,721,202 research outputs found
Dose- and time-dependent effects of recombinant human bone morphogenetic protein-2 on the osteogenic and adipogenic potentials of alveolar bone-derived stromal cells
No full textPark J-C, Kim J.C, Kim B-K, Cho K-S, Im G-I, Kim B-S, Kim C-S. Dose- and time-dependent effects of recombinant human bone morphogenetic protein-2 on the osteogenic and adipogenic potentials of alveolar bone-derived stromal cells. J Periodont Res 2012; 47: 645654. (C) 2012 John Wiley & Sons A/S Background and Objective: Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a well-known growth factor that can induce robust bone formation, and recent studies have shown that rhBMP-2-induced osteogenesis is closely related to adipogenesis. The aim of the present study was to determine the dose- and time-dependent effects of rhBMP-2 on the osteogenic and adipogenic differentiation of human alveolar bone-derived stromal cells (hABCs) in vivo and in vitro. Material and Methods: hABCs were isolated and cultured, and then transplanted using a carrier treated either with or without rhBMP-2 (100 mu g/mL) into an ectopic subcutaneous mouse model. Comprehensive histologic and histometric analyses were performed after an 8-wk healing period. To further understand the dose-dependent (0, 10, 50, 200, 500 and 1000 ng/mL) and time-dependent (0, 3, 5, 7 and 14 d) effects of rhBMP-2 on osteogenic and adipogenic differentiation, in vitro osteogenic and adipogenic differentiation of hABCs were evaluated, and the expression of related mRNAs, including those for alkaline phosphatase, osteocalcin, bone sialoprotein, peroxisome-proliferator-activated receptor gamma-2 and lipoprotein lipase, were assessed using quantitative RT-PCR. Results: rhBMP-2 significantly promoted the osteogenic and adipogenic differentiation of hABCs in vivo, and gradually increased both the osteogenic and adipogenic potential in a dose- and time-dependent manner with minimal deviation in vitro. The expression of osteogenesis- and adipogenesis-associated mRNAs were concomitantly up-regulated by rhBMP-2. Conclusion: The findings of the present study showed that rhBMP-2 significantly enhanced the adipogenic as well as the osteogenic potential of hABCs in dose- and time-dependent manner. The control of adipogenic differentiation of hABCs should be considered when regenerating the alveolar bone using rhBMP-2.N
The dynamic healing profile of human periodontal ligament stem cells: histological and immunohistochemical analysis using an ectopic transplantation model
No full textKim Y-T, Park J-C, Choi S-H, Cho K-S, Im G-I, Kim B-S, Kim C-S. The dynamic healing profile of human periodontal ligament stem cells: histological and immunohistochemical analysis using an ectopic transplantation model. J Periodont Res 2012; 47: 514524. (c) 2012 John Wiley & Sons A/S Background and Objective: Human periodontal ligament stem cells (hPDLSCs) have been reported to play the pivotal role in periodontal regeneration. However, the dynamic cellular healing process initiated by hPDLSCs still remains to be elucidated. In the present study, the sequence of regeneration by hPDLSCs was assessed using histological and immunohistochemical observation in an ectopic transplantation model, which is a well-standardized assessment tool that excludes the innate healing factors from the animals. Material and Methods: Human periodontal ligament stem cells that were isolated and characterized from teeth (n = 12) extracted for the purpose of orthodontic treatment were transplanted with carriers into ectopic subcutaneous pouches in immunocompromised mice (n = 20). Animals were killed after several different healing periods: 3 d (n = 4), 1 (n = 4), 2 (n = 4), 4 (n = 4) and 8 wk (n = 4). Histological analysis for regenerated tissues formed by hPDLSCs was conducted using hematoxylin and eosin, Massons trichrome and picrosirius red staining. In addition, immunohistochemical staining was performed to observe the sequential expression of osteogenic/cementogenic and periodontal ligament tissue-specific markers associated with periodontal regeneration. Results: The whole healing process by transplanted hPDLSCs could be broadly divided into four distinctive phases. In the first phase, proliferated hPDLSCs migrated evenly all over the carrier, and collagenous tissues appeared in the form of amorphous collagen matrices. In the second phase, collagen fibers were well arranged among the carriers, and cementoid-like tissues were observed. In the third phase, the formation of mature collagen fibers, resembling Sharpeys fibers, was associated with active mineralization of cementum-like tissues, and in the fourth phase, the maturation of cementum-like tissues was observed on carrier surfaces. Various osteogenic/cementogenic markers related to the regeneration processes were expressed in a well-orchestrated time order. Interestingly, well-organized cementum-like and periodontal ligament fiber-like tissues and cells with early and late osteogenic/cementogenic markers were frequently observed in the secluded area of carrier surfaces. We termed this area the cell-rich zone. Conclusion: The results from this study clearly demonstrated the sequential histological changes during periodontal tissue regeneration by hPDLSCs. Understanding of this process would potentially enable us to develop better cell-based treatment techniques.N
Comparison of mammalian cell suspension culture methods using poly(lactic-co-glycolic acid) nanospheres and dextran microcarriers
No full textPreviously, we have developed a novel method for suspension culture of anchoragedependent animal cells using biodegradable polymer nanospheres. In this study, we compared the polymer nanosphere culture method to dextran microcarrier culture method, which is a conventional suspension culture method. Most of human dermal fibroblasts (91 ± 5%) cultured with polymer nanospheres formed aggregates on day 2. Most of cells (92 ± 7%) attached onto microcarriers by 4 h. Microcarrier culture method had a lower apoptotic activity (3.4 folds on day 4), compared to the nanosphere culture. The microcarrier culture method had a higher cell growth (2.4-fold versus 1.7-fold growth on day 4) than the nanosphere culture. Although the polymer nanosphere culture method did not yield better outcomes than the microcarrier culture, the polymer nanosphere culture method may offer advantages over the microcarrier culture method with respect to cell protection from the shear stress during agitation at high speed and cell transplantation without enzyme digestion process to harvest cultured cells.N
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
Stimulation of chondrogenic differentiation of mesenchymal stem cells
No full textThe methods for cartilage repair have been studied so far, yet many of them seem to have limitations due to the low regenerative capacity of articular cartilage. Mesenchymal stem cell (MSC) has been suggested as an alternative solution to remedy this challenging problem. MSCs, which have extensive differentiation capacity, can be induced to differentiate into chondrocytes under specific conditions. Particularly, this review focused on the effects of growth factors, cell-to-cell interactions and biomaterials in chondrogenesis of MSCs. Appropriate stimulations through these factors are crucial in differentiation and proliferation of MSCs. However, use of MSCs for cartilage repair has some drawbacks and risks, such as expression of hypertrophy-related genes in MSCs-derived chondrocytes and consequent calcification or cell death. Nevertheless, the clinical application of MSCs is expected in the future with advanced technology.Y
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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