1,354,387 research outputs found
Implantation of a novel biologic and hybridized tissue engineered bioimplant in large tendon defect: an in vivo investigation.
No full textSurgical reconstruction of large Achilles tendon defects is technically demanding. There is no standard method, and tissue engineering may be a valuable option. We investigated the effects of 3D collagen and collagen-polydioxanone sheath (PDS) implants on a large tendon defect model in rabbits. Ninety rabbits were divided into three groups: control, collagen, and collagen-PDS. In all groups, 2 cm of the left Achilles tendon were excised and discarded. A modified Kessler suture was applied to all injured tendons to retain the gap length. The control group received no graft, the treated groups were repaired using the collagen only or the collagen-PDS prostheses. The bioelectrical characteristics of the injured areas were measured at weekly intervals. The animals were euthanized at 60 days after the procedure. Gross, histopathological and ultrastructural morphology and biophysical characteristics of the injured and intact tendons were investigated. Another 90 pilot animals were also used to investigate the inflammatory response and mechanism of graft incorporation during tendon healing. The control tendons showed severe hyperemia and peritendinous adhesion, and the gastrocnemius muscle of the control animals showed severe atrophy and fibrosis, with a loose areolar connective tissue filling the injured area. The tendons receiving either collagen or collagen-PDS implants showed lower amounts of peritendinous adhesion, hyperemia and muscle atrophy, and a dense tendon filled the defect area. Compared to the control tendons, application of collagen and collagen-PDS implants significantly improved water uptake, water delivery, direct transitional electrical current and tissue resistance to direct transitional electrical current. Compared to the control tendons, both prostheses showed significantly increased diameter, density and alignment of the collagen fibrils and maturity of the tenoblasts at ultrastructure level. Both prostheses influenced favorably tendon healing compared to the control tendons, with no significant differences between collagen and collagen-PDS groups. Implantation of the 3D collagen and collagen-PDS implants accelerated the production of a new tendon in the defect area, and may become a valuable option in clinical practice
Collagen implants in experimental tendon injury in rabbits: a clinical, ultra-structural and biomechanical investigation.
No full textThis study investigated the effects of hybridized micro and nano structured collagen implants on tendon healing in an experimental tendon injury in rabbits. Fifty mature male New Zealand white rabbits were randomly divided into two groups of treated and control. Two cm of the left Achilles tendon were discarded. In the treated group, a 3-dimensional (3D) collagen implant was engineered and implanted in the defect area. No implant was used in the control group. At day 120 after injury, the Achilles tendon of the animals were ultrasonographically (days 0-120 after injury) and radiographically (day 120 after injury) examined, and the animals were euthanized. The tendons were dissected and used for gross pathological, histopathological, ultra-structural and biomechanical investigations. Application of the collagen implant significantly increased the diameter of the newly regenerated tissue in the defect area compared to the control tendons. Treatment also significantly increased the echogenicity and homogeneity of the injured area, the diameter of the collagen fibrils and fibers, maturity of the tenoblasts, number of tenocytes, collagen density, alignment, ultimate and yield load, stiffness, stress and modulus of elasticity. The collagen implants were almost totally absorbed 120 days after surgery. No inflammatory reaction or tissue degeneration or necrosis was evident in the treated tendons compared to the control ones. 3D collagen implants produced a newly regenerated tendinous tissue at the defect area that was morphologically and biomechanically superior to the control group. This collagen implant was biocompatible and biodegradable with high bio-safety in rabbits
Bone regenerative medicine: classic options, novel strategies, and future directions.
No full textThis review analyzes the literature of bone grafts and introduces tissue engineering as a strategy in this field of orthopedic surgery. We evaluated articles concerning bone grafts; analyzed characteristics, advantages, and limitations of the grafts; and provided explanations about bone-tissue engineering technologies. Many bone grafting materials are available to enhance bone healing and regeneration, from bone autografts to graft substitutes; they can be used alone or in combination. Autografts are the gold standard for this purpose, since they provide osteogenic cells, osteoinductive growth factors, and an osteoconductive scaffold, all essential for new bone growth. Autografts carry the limitations of morbidity at the harvesting site and limited availability. Allografts and xenografts carry the risk of disease transmission and rejection. Tissue engineering is a new and developing option that had been introduced to reduce limitations of bone grafts and improve the healing processes of the bone fractures and defects. The combined use of scaffolds, healing promoting factors, together with gene therapy, and, more recently, three-dimensional printing of tissue-engineered constructs may open new insights in the near future
On the Similarity Group of Forms of Higher Degree
No full textOryan M.
Univ Talca, Dept Informat & Matemat Aplicada, Talca, Chile.Let ƒ = ƒ(X) = ƒ(X1,..., Xn,) k[X1,...,Xn] be a non-singular form of degree d ≥ 3 over the field k (where char(k)= 0 or char(k) > d). The similarity group of ƒ, Sk(ƒ) is the subgroup of GLn(k) consisting of all matrices A such that ƒ(AX) = λAƒ(X) for some λA k×. Let Autk(ƒ) denote the automorphism group of ƒ. Identifying k× with the group of scalar matrices in Sk(ƒ), we show using Kummer′s theory of fields that Sk(ƒ)/Autk(ƒ)k× is a finite abelian group of exponent d. We apply this result to give a complete characterization of the similarity group of rational binaries of odd degree
Effectiveness of tissue engineered three-dimensional bioactive graft on bone healing and regeneration: an in vivo study with significant clinical value
No full textSeveral strategies have been used to promote bone repair, with many failing due to the lack of osteoinduction. This report describes an approach for promoting bone healing that attempts to overcome prior shortcomings. First, the role was compared of different concentrations of gelatine (Gel), nanostructured-hydroxyapatite (nHA), simvastatin (Sim) and nHA-Sim particles on healing of small femoral bone defects in rabbits. The effective concentration of each was studied, and then a three-dimensional porous scaffold was designed using Gel, nHA and Sim, which was then cross-linked with genipin. Morphology, degradation profile and Sim delivery properties of the scaffolds were evaluated in vitro. Then, the scaffolds were subcutaneously tested in vivo to determine their biocompatibility, biodegradability and osteogenic properties. Finally, the scaffolds were implanted in a large radial bone defect model in rabbits and their effect on bone regeneration was investigated. The Gel, nHA and Sim with concentrations of 1, 1 and 5 mg/femoral hole were effective during bone healing respectively, and the Sim showed the most osteoinduction and osteoconduction when compared to controls. The Gel-Sim and Gel-nHA-Sim scaffolds continuously and homogenously released Sim into the simulated body fluid in vitro. Subcutaneously, the scaffolds were biocompatible, biodegradable and able to produce ectopic bone after 30 days. Thirty and 60 days after implantation of the scaffolds in radial bone defects, they were completely degraded and replaced with the new bone that had significantly superior morphology, mineral density, bioelectrical, biophysical and micromechanical properties compared with controls. Such bioactive grafts may be a suitable option for bone reconstruction, healing and repair
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
Use of ovine acellular peritoneal matrix combined with honey and ovine fetal skin extract in the healing of full-thickness infected burn wounds in a rat model
No full textTreatment of infected burn wounds remains a challenge in burn units. Silver-sulfadiazine (SSD) is the most commonly used topical antimicrobial agent in managing these wounds. We aimed to accelerate the healing of burn wounds by combined application of ovine acellular peritoneal matrix (OAPM), honey (H), and ovine fetal skin extract (OFSE). Sixty-four standardized burn wounds were created on the dorsum of 16 rats and were subsequently inoculated with Staphyloccocus aureus and Pseudomonas aeruginosa. After 48 hr, the wounds were surgically debrided and received either physiologic saline (control group) or SSD, OAPM+SSD, OAPM+H+SSD, and OAPM+H+OFSE+SSD. The healing wounds were evaluated for size, bacterial counts, histopathology, and biomechanical properties on days 3, 7, 14, 21, and 28 after surgery. All treatments had effectively reduced the level of S. aureus and P. aeruginosa on wounds compared to the control group by day 3 and 7. The wounds treated with combined application of OAPM+H+OFSE+SSD demonstrated considerable inflammation reduction, fibroplasia, complete re-epithelialization, and wound contraction together with significantly lesser scar tissue formation. Treatment with OAPM+H+OFSE+SSD showed superior biomechanical properties of the healing wounds. The findings suggested that the synergistic effect of dressing the wounds with OAPM, H, and OFSE was a very effective approach in accelerating the healing process of the experimentally induced infected full-thickness burn wounds in rats
Variations on the Author
No full text“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
No full textWe 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
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
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