| Scale-dependent fiber kinematics of elastomeric electrospun scaffolds for soft tissue engineering.
September 16, 2009 at 7:27 am
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| | Scale-dependent fiber kinematics of elastomeric electrospun scaffolds for soft tissue engineering. J Biomed Mater Res A. 2009 Sep 14; Authors: Stella JA, Wagner WR, Sacks MS Electrospun poly(ester urethane)urea (PEUU) scaffolds contain complex multiscale hierarchical structures that work simultaneously to produce unique macrolevel mechanical behaviors. In this study, we focused on quantifying key multiscale scaffold structural features to elucidate the mechanisms by which these scaffolds function to emulate native tissue tensile behavior. Fiber alignment was modulated via increasing rotational velocity of the collecting mandrel, and the resultant specimens were imaged using SEM under controlled biaxial strain. From the SEM images, fiber splay, tortuosity, and diameter were quantified in the unstrained and deformed configurations. Results indicated that not only fiber alignment increased with mandrel velocity but also, paradoxically, tortuosity increased concurrently with mandrel velocity and was highly correlated with fiber orientation. At microlevel scales (1-10 mum), local scaffold deformation behavior was observed to be highly heterogeneous, while increasing the scale resulted in an increasingly homogenous strain field. From our comprehensive measurements, we determined that the transition scale from heterogenous to homogeneous-like behavior to be approximately 1 mm. Moreover, while electrospun PEUU scaffolds exhibit complex deformations at the microscale, the larger scale structural features of the fibrous network allow them to behave as long-fiber composites that deform in an affine-like manner. This study underscores the importance of understanding the structure-function relationships in elastomeric fibrous scaffolds, and in particular allowed us to link microscale deformations with mechanisms that allow them to successfully simulate soft tissue mechanical behavior. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009. PMID: 19753623 [PubMed - as supplied by publisher] |
| Corneal epithelial cell adhesion and growth on EGF-modified aminated PDMS.
September 16, 2009 at 7:27 am
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| | Corneal epithelial cell adhesion and growth on EGF-modified aminated PDMS. J Biomed Mater Res A. 2009 Sep 14; Authors: Klenkler BJ, Dwivedi D, West-Mays JA, Sheardown H Growth factor tethering has significant potential to mediate cellular responses in biomaterials and tissue engineering. We have previously demonstrated that epidermal growth factor (EGF) can be tethered to polydimethylsiloxane (PDMS) substrates and that these surfaces promoted interactions with human corneal epithelial cells in vitro. The goal of the current work was to better understand the specific effects of the tethered growth factor on the cells. The EGF was reacted with a homobifunctional N-hydroxysuccinimide (NHS) polyethylene glycol (PEG) derivative, and then bound to allyamine plasma-modified PDMS. Human corneal epithelial cells were seeded on the surfaces and cultured in serum-free medium for periods of up to 5 days. Cell growth was monitored and quantified by trypsinization and counting with a Coulter counter. Expression of matrix proteins and alpha(6)-integrins was assessed by immunostaining and confocal microscopy. A centrifugation assay was used to determine cell adhesion under an applied detachment force. Binding of EGF was found to significantly increase cell numbers and coverage across the surfaces at 5 days of culture in vitro. Immunofluorescence experiments indicate increased expression of fibronectin, laminin, and alpha(6)-integrins on the EGF-modified surfaces, and expression is localized at the cell-material interface as observed by confocal microscopy. In accordance with these results, the highest quantity of adherent cells is found on the EGF-modified subtrates at 5 days of culture. The results provide initial evidence that binding of EGF may be used to improve the epithelialization of and the adhesion of the cells on a polymeric artificial cornea device. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009. PMID: 19753622 [PubMed - as supplied by publisher] |
| Adipose tissue engineering: state of the art, recent advances and innovative approaches.
September 16, 2009 at 7:27 am
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| | Adipose tissue engineering: state of the art, recent advances and innovative approaches. Expert Rev Med Devices. 2009 Sep;6(5):533-51 Authors: Tanzi MC, Farè S Adipose tissue is a highly specialized connective tissue found either in white or brown forms, the white form being the most abundant in adult humans. Loss or damage of white adipose tissue due to aging or pathological conditions needs reconstructive approaches. To date, two main strategies are being investigated for generating functional adipose tissue: autologous tissue/cell transplantation and adipose tissue engineering. Free-fat transplantation rarely achieves sufficient tissue augmentation owing to delayed neovascularization, with subsequent cell necrosis and graft volume shrinkage. Tissue engineering approaches represent, instead, a more suitable alternative for adipose tissue regeneration; they can be performed either with in situ or de novo adipogenesis. In situ adipogenesis or transplantation of encapsulated cells can be useful in healing small-volume defects, whereas restoration of large defects, where vascularization and a rapid volumetric gain are strict requirements, needs de novo strategies with 3D scaffold/filling matrix combinations. For adipose tissue engineering, the use of adult mesenchymal stem cells (both adipose- and bone marrow-derived stem cells) or of preadipocytes is preferred to the use of mature adipocytes, which have low expandability and poor ability for volume retention. This review intends to assemble and describe recent work on this topic, critically presenting successes obtained and drawbacks faced to date. PMID: 19751125 [PubMed - in process] |
| New directions in nanofibrous scaffolds for soft tissue engineering and regeneration.
September 16, 2009 at 7:27 am
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| | New directions in nanofibrous scaffolds for soft tissue engineering and regeneration. Expert Rev Med Devices. 2009 Sep;6(5):515-32 Authors: Baker BM, Handorf AM, Ionescu LC, Li WJ, Mauck RL This review focuses on the role of nanostructure and nanoscale materials for tissue engineering applications. We detail a scaffold production method (electrospinning) for the production of nanofiber-based scaffolds that can approximate many critical features of the normal cellular microenvironment, and so foster and direct tissue formation. Further, we describe new and emerging methods to increase the applicability of these scaffolds for in vitro and in vivo application. This discussion includes a focus on methods to further functionalize scaffolds to promote cell infiltration, methods to tune scaffold mechanics to meet in vivo demands and methods to control the release of pharmaceuticals and other biologic agents to modulate the wound environment and foster tissue regeneration. This review provides a perspective on the state-of-the-art production, application and functionalization of these unique nanofibrous structures, and outlines future directions in this growing field. PMID: 19751124 [PubMed - in process] |
| Carbon nanotubes in scaffolds for tissue engineering.
September 16, 2009 at 7:27 am
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| | Carbon nanotubes in scaffolds for tissue engineering. Expert Rev Med Devices. 2009 Sep;6(5):499-505 Authors: Edwards SL, Werkmeister JA, Ramshaw JA Carbon nanotubes are hollow graphitic cylinders of nanoscale dimensions. They are electrically conductive, chemically and thermally stable, and exceptionally strong. Given this unique combination of properties there has been much interest in carbon nanotubes, and finding applications for them. One application where this combination of properties may prove useful is in the area of tissue regeneration, incorporating carbon nanotubes into scaffolds for tissue engineering. It is believed that carbon nanotubes may improve scaffold properties and enhance tissue regeneration. This report aims to discuss the suitability of carbon nanotubes as a biomaterial for scaffold production, and the fabrication, properties and performance of carbon nanotube-based scaffolds. PMID: 19751122 [PubMed - in process] |
| Engineering Embryonic Stem Cell Aggregation Allows an Enhanced Osteogenic Differentiation In Vitro.
September 16, 2009 at 7:27 am
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| | Engineering Embryonic Stem Cell Aggregation Allows an Enhanced Osteogenic Differentiation In Vitro. Tissue Eng Part C Methods. 2009 Sep 14; Authors: Gothard D, Roberts SJ, Shakesheff K, Buttery LD Pluripotent embryonic stem (ES) cells hold great promise for the field of tissue engineering, with numerous studies investigating differentiation into various cell types including cardiomyocytes, chondrocytes and osteoblasts. Previous studies have detailed osteogenic differentiation via dissociated embryoid body (EB) culture in osteo-inductive media comprising of ascorbic acid, beta-glycerophosphate and dexamethasone. It is hoped that these osteogenic cultures will have clinical application in bone tissue repair and regeneration and pharmacological testing. However, differentiation remains highly inefficient and generates heterogeneous populations. We have previously reported an engineered 3D culture system for controlled ES cell-ES cell interaction via the avidin-biotin binding complex. Here we investigate the effect of such engineering on ES cell differentiation. Engineered EBs exhibit enhanced osteogenic differentiation assessed by cadherin-11, Runx2 and osteopontin expression, alkaline phosphatase activity and bone nodule formation. Results show that cultures produced from intact EBs aggregated for 3 days generated the greatest levels of osteogenic differentiation when cultured in osteo-inductive media. However, when cultured in control media only engineered samples appeared to exhibit bone nodule formation. In addition, PCR analysis revealed a decrease in endoderm and ectoderm expression within engineered samples. This suggests that engineered ES cell aggregation has increased mesoderm homogeneity contributing to enhanced osteogenic differentiation. PMID: 19751101 [PubMed - as supplied by publisher] |
| Science is the fuel for the engine of technology and clinical practice.
September 16, 2009 at 7:27 am
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| | Science is the fuel for the engine of technology and clinical practice. J Am Dent Assoc. 2009 Sep;140 Suppl 1:17S-24S Authors: Snead ML, Slavkin HC BACKGROUND: The biological, chemical, behavioral and physical sciences provide the fuel for innovation, discovery and technology that continuously improves the quality of the human condition. Computer power derived from the dramatic breakthroughs of the digital revolution has made extraordinary computational capacity available for diagnostic imaging, bioinformatics (the science of information) and numerous aspects of how we practice dentistry in the 21st century. OVERVIEW: The biological revolution was initiated by the identification of the structure for DNA in 1953, a discovery that continues to catalyze improvements in patient care through new and better diagnostics, treatments and biomaterials. Humanity's most basic and recognizable characteristics--including the face--are now better understood through the elucidation of our genome and proteome, the genes and proteins they encode. Health care providers are beginning to use personalized medicine that is based on a person's genetic makeup and predispositions to disease development. CONCLUSIONS: Advances in the fields of genetics, developmental and stem cell biology, and many other disciplines continue to fuel innovative research findings that form the basis for new diagnostic tests, therapeutic interventions and procedures that improve the quality of life for patients. Scientists are on the threshold of applying knowledge in stem cell biology to regenerative medicine and dentistry, heralding an era when clinicians can consider using biological engineering to replace tissues and organs lost to disease or trauma. PMID: 19723927 [PubMed - in process] |
| Surgical pathology to describe the clinical margin of debridement of chronic wounds using a wound electronic medical record.
September 16, 2009 at 7:27 am
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| | Surgical pathology to describe the clinical margin of debridement of chronic wounds using a wound electronic medical record. J Am Coll Surg. 2009 Aug;209(2):254-260.e1 Authors: Golinko MS, Joffe R, de Vinck D, Chandrasekaran E, Stojadinovic O, Barrientos S, Vukelic S, Tomic-Canic M, Brem H BACKGROUND: Chronic wounds, including diabetic foot ulcers (DFU), pressure ulcers (PU), and venous ulcers (VU) result from multiple physiologic impairments. Operative debridement is a mainstay of treatment to remove nonviable tissue and to stimulate wound healing. Unlike tumor resection, however, operative wound specimens are not routinely sent for pathology. The objective of this study was to describe the pathology present in chronic wounds. STUDY DESIGN: Pathology reports of the skin edge and wound base from 397 initial debridements in 336 consecutive patients with chronic wounds were retrospectively reviewed. All data were entered and stored in a Wound Electronic Medical Record. Pathology data were extracted from the Wound Electronic Medical Record, coded, and quantified. RESULTS: Up to 15 distinct histopathologic findings across 7 tissue types were observed after review of pathology reports from chronic wounds. Specifically, the pathology of epidermis revealed hyperkeratosis: 66% in DFUs, 31% in PUs, and 29% in VUs. Dermal pathology revealed fibrosis in 49% of DFUs, 30% of PUs, and 15% of VUs. Wound bed pathology revealed necrosis in the subcutaneous tissue in 67% of DFUs, 55% of PUs, and 19% of VUs. Fibrosis was reported in between 19% and 52% of all wound types. Acute osteomyelitis was present in 39% of DFUs, 33% of PUs, and 29% of VUs. CONCLUSIONS: This observational study of the histopathology of initial surgical debridement of chronic wounds revealed a wide range of findings across multiple tissue levels. Although certain findings such as osteomyelitis and gangrene have been shown to directly relate to impaired wound healing and amputation, other findings require additional investigation. To rigorously define a margin of debridement, a prospective study relating histopathology and clinical outcomes such as healing rates and amputation is needed. PMID: 19632603 [PubMed - indexed for MEDLINE] |
| Differentiation of embryonic stem cells into anterior definitive endoderm.
September 16, 2009 at 7:27 am
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| | Differentiation of embryonic stem cells into anterior definitive endoderm. Curr Protoc Stem Cell Biol. 2009 Jul;Chapter 1:Unit 1G.3 Authors: Livigni A, Villegas SN, Oikonomopoulou I, Rahman A, Morrison GM, Brickman JM Anterior definitive endoderm (ADE) is both an important embryonic signaling center and a unique multipotent precursor of liver, pancreas, and other visceral organs. Here we describe a method for the differentiation of mouse embryonic stem (ES) cells to endoderm with pronounced anterior character. ADE-containing cultures can be produced in vitro by suspension (aggregation or embryoid body) culture and in a serum-free adherent monolayer culture. Purified ES cell-derived ADE cells appear committed to endodermal fates and can undergo further differentiation in vitro towards liver and pancreas with enhanced efficiency. PMID: 19585461 [PubMed - indexed for MEDLINE] |
| Orthopedic coating materials: considerations and applications.
September 16, 2009 at 7:27 am
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| | Orthopedic coating materials: considerations and applications. Expert Rev Med Devices. 2009 Jul;6(4):423-30 Authors: Ramaswamy Y, Wu C, Zreiqat H The host response to titanium and its alloys is not always favorable, as a fibrous layer may form at the skeletal tissue-device interface, causing aseptic loosening. Therefore, a great deal of current orthopedic research is focused on developing implants with improved osseointegration properties in order to increase their clinical success. Promising new studies have been reported regarding coating the currently available implants with various coating materials and techniques so as to improve the long-term stability of implants. This article will discuss various coating materials developed, their advantages and disadvantages as coating materials and their biological performance. PMID: 19572797 [PubMed - indexed for MEDLINE] |
| IL-2 regulates CD103 expression on CD4+ T cells in Scurfy mice that display both CD103-dependent and independent inflammation.
September 16, 2009 at 7:27 am
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| | IL-2 regulates CD103 expression on CD4+ T cells in Scurfy mice that display both CD103-dependent and independent inflammation. J Immunol. 2009 Jul 15;183(2):1065-73 Authors: Sharma R, Sung SS, Abaya CE, Ju AC, Fu SM, Ju ST Scurfy (Sf) mice lack CD4(+)Foxp3(+) regulatory T cells and develop fatal multiorgan inflammation (MOI) mediated by CD4(+) T cells. Introducing Il2(-/-) gene into Sf mice (Sf.Il2(-/-)) inhibited inflammation in skin and lung. As a major integrin receptor for the organs, we compared CD103 expression on the CD4(+) T cells of B6, Il2(-/-), Sf, and Sf.Il2(-/-) mice. CD103(+)CD4(+) T cells, but not CD8(+) T cells or CD11c(+) dendritic cells, were significantly up-regulated only in Sf mice, indicating Il2(-/-) dominantly and specifically inhibited CD103 up-regulation in Sf CD4(+) T cells. In addition, CD4(+)Foxp3(+) regulatory T cell CD103 expression was not reduced in Il2(-/-) mice. Introducing CD103(-/-) into Sf mice inhibited inflammation in skin and lung as compared with age-matched Sf mice, but they died at approximately 7 wk old with inflammation developed in skin, lungs, and colon, demonstrating fatal MOI induced by CD103-independent mechanism. Transfer of Sf CD4(+) T cells induced MOI more rapidly than CD103(-)CD4(+) T cells, indicating the presence of CD103-dependent mechanism for inflammation. In vitro stimulation with anti-CD3 plus anti-CD28 beads confirmed that CD103 induction in the CD4(+)Foxp3(-) T cells in Il2(-/-) and Sf.Il2(-/-) is defective and cannot be restored by rIL-2 or rIL-15. The data indicate that IL-2 is required for optimal CD103 induction on CD4(+) T cells in Sf mice and this effect contributes to inflammation in an organ-specific manner. IL-2 also has additional roles because the protection of skin and lung inflammation in Sf.Il2(-/-), but not Sf.CD103(-/-) mice is lifelong and Sf.Il2(-/-) mice have longer lifespan than Sf.CD103(-/-) mice. PMID: 19553521 [PubMed - indexed for MEDLINE] |
| American Association of Endodontists.
September 16, 2009 at 7:27 am
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| | American Association of Endodontists. J Am Coll Dent. 2009;76(1):4-8 Authors: Rossman LE Endodontics was recognized as a specialty in the mid-1960s, following decades of developing a body of scientific knowledge and proven techniques for managing the etiology, diagnosis, prevention, and treatment of diseases and injuries of the pulp and associated periradicular conditions. There are now 7000 members of the American Association of Endodontists, about a quarter of whom are board certified. The American Association of Endodontists has identified and is at work addressing the following strategic issues: (a) recruitment and retention of endodontics educators; (b) development and dissemination of educational material to both specialists and general dentists; (c) enhanced biological foundations of therapy, including regenerative endodontics; and (d) advances in technology such as digital radiology, new delivery instrumentation, implants, and enhanced visualization through microscopes. The American Association of Endodontists is working to strengthen relationships with general dentists through education and associate membership, and it is promoting its members' participation in professional and community projects through its Step-Up! program. PMID: 19537475 [PubMed - indexed for MEDLINE] |
| Enrichment and clonal culture of progenitor cells during mouse postnatal liver development in mice.
September 16, 2009 at 7:27 am
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| | Enrichment and clonal culture of progenitor cells during mouse postnatal liver development in mice. Gastroenterology. 2009 Sep;137(3):1114-26, 1126.e1-14 Authors: Kamiya A, Kakinuma S, Yamazaki Y, Nakauchi H BACKGROUND & AIMS: Stem and progenitor cells exist in normal postnatal livers. However, it has not been possible to clonally isolate or analyze postnatal liver stem/progenitor-like cells (PLSCs) derived from noninjured livers because of a lack of specific surface markers. This study aimed to establish a primary culture system for clone-sorted PLSCs. METHODS: To investigate proliferation and differentiation of PLSCs, subpopulations of nonparenchymal cells derived from noninjured livers were purified and cultured using a single-cell culture system. Cells were grown in fetal liver cell-derived conditioned medium in the presence of the Rho-associated kinase (ROCK) inhibitor Y-27632. RESULTS: We identified CD13 and CD133 as markers expressed on the PLSC-containing population in noninjured livers and established an efficient single-cell culture system to clonally analyze PLSCs. Culture of PLSCs is difficult, even using conditioned medium, but the addition of Y-27632 increased PLSC cell proliferation. The proportion of progenitor cells among nonparenchymal cells decreased during postnatal liver development; however, a PLSC population was still preserved in 3-month-old mice. Long-term cultivated cells derived from clone-sorted cells in normal livers were established and were called normal-liver-derived stem-like cells (NLS cells). NLS cells could differentiate into hepatocyte-like and cholangiocyte-like cells under appropriate culture conditions and underwent self-renewal-like activity in serial reclone-sorted culture. CD13 and CD133 were expressed on progenitor cells derived from fetal and postnatal liver, whereas CD49f (integrin alpha6 subunit) was strongly expressed only on PLSCs. CONCLUSIONS: These results demonstrate the presence of progenitor cells in the CD13(+)CD49f(+)CD133(+) subpopulation of nonhematopoietic cells derived from noninjured postnatal livers. PMID: 19524574 [PubMed - indexed for MEDLINE] |
| Induction of cementogenesis and periodontal ligament regeneration by recombinant human transforming growth factor-beta3 in Matrigel with rectus abdominis responding cells.
September 16, 2009 at 7:27 am
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| | Induction of cementogenesis and periodontal ligament regeneration by recombinant human transforming growth factor-beta3 in Matrigel with rectus abdominis responding cells. J Periodontal Res. 2009 Feb;44(1):81-7 Authors: Ripamonti U, Parak R, Petit JC BACKGROUND AND OBJECTIVE: In primates and in primates only, the transforming growth factor-b proteins induce endochondral bone formation. Transforming growth factor-b3 also induces periodontal tissue regeneration. Two regenerative treatments using human recombinant transforming growth factor-b3 were examined after implantation in mandibular furcation defects of the nonhuman primate, Papio ursinus. MATERIAL AND METHODS: Class III furcation defects were surgically created bilaterally in the mandibular first and second molars of two adult Chacma baboons (P. ursinus). Different doses of recombinant transforming growth factor-beta3 reconstituted with Matrigel matrix were implanted in the rectus abdominis muscle to induce heterotopic ossicles for subsequent transplantation to selected furcation defects. Twenty days after heterotopic implantation, periodontal defects were re-exposed, further debrided and implanted with minced fragments of induced heterotopic ossicles. Contralateral class III furcation defects were implanted directly with recombinant transforming growth factor-beta3 in Matrigel matrix with the addition of minced fragments of autogenous rectus abdominis muscle. Treated quadrants were not subjected to oral hygiene procedures so as to study the effect of the direct application of the recombinant morphogen in Matrigel on periodontal healing. Histomorphometric analyses on undecalcified sections cut from specimen blocks harvested on day 60 measured the area of newly formed alveolar bone and the coronal extension of the newly formed cementum along the exposed root surfaces. RESULTS: Morphometric analyses showed greater alveolar bone regeneration and cementogenesis in furcation defects implanted directly with 75 microg of transforming growth factor-beta3 in Matrigel matrix with the addition of minced muscle tissue. CONCLUSION: Matrigel matrix is an optimal delivery system for the osteogenic proteins of the transforming growth factor-beta superfamily, including the mammalian transforming growth factor-beta3 isoform. The addition of minced fragments of rectus abdominis muscle provides responding stem cells for further tissue induction and morphogenesis by the transforming growth factor-beta3 protein. PMID: 18973524 [PubMed - indexed for MEDLINE] |
| Three-dimensional organization of dermal fibroblasts by macromass culture.
September 16, 2009 at 7:27 am
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| | Three-dimensional organization of dermal fibroblasts by macromass culture. Biotechnol Appl Biochem. 2008 Jan;49(Pt 1):65-72 Authors: Deshpande M The three-dimensional organization of cells by high-cell-seeding-density culture, termed 'macromass culture', is described. By macromass culture, dermal fibroblasts can be made to organize themselves into a unified three-dimensional form without the aid of a scaffold, and macroscopic constructs, named macromasses, can be made wholly from cells. The sole factor causing three-dimensional organization is culture of cells at high cell seeding density per unit area. No scaffold or extraneous matrix is used for the generation of macromasses; they are of completely cellular origin. No other agents or external influences such as tissue-inducing chemicals, tissue-inducing growth factors, substratum with special properties, rotational culture, centrifugation etc. are employed for macromass formation, and all seeded cells become part of the cohesive construct. These three-dimensional constructs have the potential for use as in vitro tissue analogues, and a possible application for in vitro cytotoxicity testing is demonstrated. PMID: 17623015 [PubMed - indexed for MEDLINE] | | | 
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