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| Direct Microfabrication of Topographical and Chemical Cues for the Guided Growth of Neural Cell Networks on Polyamidoamine Hydrogels.
May 4, 2010 at 7:30 AM
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| | Direct Microfabrication of Topographical and Chemical Cues for the Guided Growth of Neural Cell Networks on Polyamidoamine Hydrogels. Macromol Biosci. 2010 Apr 30; Authors: Dos Reis G, Fenili F, Gianfelice A, Bongiorno G, Marchesi D, Scopelliti PE, Borgonovo A, Podestà A, Indrieri M, Ranucci E, Ferruti P, Lenardi C, Milani P Cell patterning is an important tool for organizing cells in surfaces and to reproduce in a simple way the tissue hierarchy and complexity of pluri-cellular life. The control of cell growth, proliferation and differentiation on solid surfaces is consequently important for prosthetics, biosensors, cell-based arrays, stem cell therapy and cell-based drug discovery concepts. We present a new electron beam lithography method for the direct and simultaneous fabrication of sub-micron topographical and chemical patterns, on a biocompatible and biodegradable PAA hydrogel. The localized e-beam modification of a hydrogel surface makes the pattern able to adsorb proteins in contrast with the anti-fouling surface. By also exploiting the selective attachment, growth and differentiation of PC12 cells, we fabricated a neural network of single cells connected by neuritis extending along microchannels. E-beam microlithography on PAA hydrogels opens up the opportunity of producing ! multifunctional microdevices incorporating complex topographies, allowing precise control of the growth and organization of individual cells. PMID: 20437406 [PubMed - as supplied by publisher] | | |
| Enzyme-assisted photolithography for spatial functionalization of hydrogels.
May 4, 2010 at 7:05 AM
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| | Enzyme-assisted photolithography for spatial functionalization of hydrogels. Lab Chip. 2010 Apr 30; Authors: Gu Z, Tang Y The ability to form functional polymeric patterning structures has important implications for the studies of cell biology, tissue engineering, and medical diagnostics. We have developed a novel enzyme-assisted photolithography (EAPL) method for spatial functionalization of hydrogels via a high throughput fashion. A bisacrylated peptide crosslinker, containing a protease cleavable amino acid sequence and caged by a photolabile moiety, is used during hydrogel polymerization. A facile two-step process is employed, including UV exposure to decage the peptide crosslinker at a desired area and protease development to specifically digest gels at UV treated regions only. Importantly, proteolysis of the peptide bonds generates free nucleophilic amine groups at the patterned area that can be further functionalized. Using this strategy and caspase-3 as the enzyme developer, we demonstrate the simultaneous generation of topographical and functional patterns into poly(ethylene! glycol) (PEG) hydrogels. We show that 20 mum-wide line arrays functionalized with arginine-glycine-aspartic acid (RGD)-containing peptides can be used to generate cell patterns with individual cell resolution. We also fabricated arrays 20 mum diameter cavities decorated with B lymphocyte specific anti-CD19, which was used to achieve a 600-fold enrichment of B-cells from a 0.1% starting B-cell mixture. The simple fabrication process, straightforward chemistry and an all-aqueous based biocompatible and environmentally friendly approach render EAPL a versatile platform to construct biologically responsive 2D patterns or 3D scaffolds for lab-on-a-chip systems and tissue engineering. PMID: 20436969 [PubMed - as supplied by publisher] | | |
| Finite element modelling of a unilateral fixator for bone reconstruction: Importance of contact settings.
May 4, 2010 at 7:05 AM
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| | Finite element modelling of a unilateral fixator for bone reconstruction: Importance of contact settings. Med Eng Phys. 2010 Apr 29; Authors: Karunratanakul K, Schrooten J, Van Oosterwyck H When reconstructing a large segmental bone defect by means of a porous scaffold, a fixator is used to stabilize the reconstruction. The fixator stiffness is an important factor as it will influence the biomechanical environment to which scaffold and regenerating tissues are exposed. A finite element (FE) model can be used to predict the fixator stiffness. The goal of this study was to develop and validate a detailed 3D FE model of a custom-developed unilateral external fixator. In particular, it was hypothesized that the contact interfaces between the different fixator components play a major role for the prediction of the fixator stiffness. In vitro mechanical testing of the entire fixator as well as of separate fixator components was performed in order to measure the stiffness. The mechanical test set-ups were simulated by means of detailed FE models that considered different levels of refinement of the various contact interfaces. The error on predicted fixator ! stiffness in comparison to measured stiffness was reduced from 121% to 16% by refining the contact settings of the FE model. The individual sources of error between the measured and predicted fixator stiffness could be quantitatively assessed as well. In conclusion, this study warrants for a careful modelling of the geometry and contact settings, when using FE models for the prediction of fixator stiffness. PMID: 20434935 [PubMed - as supplied by publisher] | | |
| Future of local bone regeneration - Protein versus gene therapy.
May 4, 2010 at 7:05 AM
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| | Future of local bone regeneration - Protein versus gene therapy. J Craniomaxillofac Surg. 2010 Apr 29; Authors: Fischer J, Kolk A, Wolfart S, Pautke C, Warnke PH, Plank C, Smeets R The most promising attempts to achieve bone regeneration artificially are based on the application of mediators such as bone morphogenetic proteins (BMPs) directly to the deficient tissue site. BMPs, as promoters of the regenerative process, have the ability to induce de novo bone formation in various tissues, and many animal models have demonstrated their high potential for ectopic and orthotopic bone formation. However, the biological activity of the soluble factors that promote bone formation in vivo is limited by diffusion and degradation, leading to a short half-life. Local delivery remains a problem in clinical applications. Several materials, including hydroxyapatite, tricalcium phosphate, demineralised bone matrices, poly-lactic acid homo- and heterodimers, and collagen have been tested as carriers and delivery systems for these factors in a sustained and appropriate manner. Unfortunately these delivery vehicles often have limitations in terms of biodegrad! ability, inflammatory and immunological rejection, disease transmission, and most importantly, an inability to provide a sustained, continuous release of these factors at the region of interest. In coping with these problems, new approaches have been established: genes encoding these growth factor proteins can be delivered to the target cells. In this way the transfected cells serve as local "bioreactors", as they express the exogenous genes and secrete the synthesised proteins into their vicinity. The purpose of this review is to present the different methods of gene versus growth factor delivery in tissue engineering. Our review focuses on these promising and innovative methods that are defined as regional gene therapy and provide an alternative to the direct application of growth factors. Various advantages and disadvantages of non-viral and viral vectors are discussed. This review identifies potential candidate genes and target cells, and in vivo as well as ex vivo appr! oaches for cell transduction and transfection. In explaining t! he biolo gical basis, this paper also refers to current experimental and clinical applications. PMID: 20434921 [PubMed - as supplied by publisher] | | |
| Are ankle chondrocytes from damaged fragments a suitable cell source for cartilage repair?
May 4, 2010 at 7:05 AM
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| | Are ankle chondrocytes from damaged fragments a suitable cell source for cartilage repair? Osteoarthritis Cartilage. 2010 Apr 28; Authors: Candrian C, Miot S, Wolf F, Bonacina E, Dickinson S, Wirz D, Jakob M, Valderrabano V, Barbero A, Martin I OBJECTIVE: Characterize the post-expansion cartilage-forming capacity of chondrocytes harvested from detached fragments of osteochondral lesions of ankle joints (Damaged Ankle Cartilage Fragments, DACF), with normal ankle cartilage (NAC) as control. DESIGN: DACF were obtained from 6 patients (mean age: 35years) with symptomatic osteochondral lesions of the talus, while NAC were from 10 autopsies (mean age: 55years). Isolated chondrocytes were expanded for two passages and then cultured in pellets for 14 days or onto HYAFF(R)-11 meshes (FAB, Italy) for up to 28 days. Resulting tissues were assessed histologically, biochemically (glycosaminoglycan -GAG-, DNA and type II collagen -CII-) and biomechanically. RESULTS: As compared to NAC, DACF contained significantly lower amounts of DNA (3.0-fold), GAG (5.3-fold) and CII (1.5-fold) and higher amounts of type-I collagen (6.2-fold). Following 14 days of culture in pellets, DACF-chondrocytes generated tissues less intense! ly stained for Safranin-O and CII, with significantly lower GAG contents (2.8-fold). After 28 days of culture onto HYAFF((R))-11, tissues generated by DACF chondrocytes were less intensely stained for Safranin-O and CII, contained significantly lower amounts of GAG (1.9-fold) and CII (1.4-fold) and had lower equilibrium (1.7-fold) and dynamic pulsatile modulus (3.3-fold) than NAC chondrocytes. CONCLUSION: We demonstrated that DACF-chondrocytes have inferior cartilage forming capacity as compared to NAC-chondrocytes, possibly resulting from environmental changes associated with trauma/disease. The study opens some reservations on the use of DACF-derived cells for the repair of ankle cartilage defects, especially in the context of tissue engineering-based approaches. PMID: 20434576 [PubMed - as supplied by publisher] | | |
| Tissue Engineering of Cartilage using Poly-epsilon-Caprolactone Nanofiber Scaffolds Seeded in vivo with Periosteal Cells.
May 4, 2010 at 7:05 AM
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| | Tissue Engineering of Cartilage using Poly-epsilon-Caprolactone Nanofiber Scaffolds Seeded in vivo with Periosteal Cells. Osteoarthritis Cartilage. 2010 Apr 28; Authors: Casper ME, Fitzsimmons JS, Stone JJ, Meza AO, Huang Y, Ruesink TJ, O'Driscoll SW, Reinholz GG OBJECTIVE: To determine the potential of periosteal cells to infiltrate poly-epsilon-caprolactone (PCL) nanofiber scaffolds in vivo and subsequently produce cartilage in vitro. DESIGN: PCL nanofiber scaffolds, with or without chitosan coating were implanted under periosteum in six-month old rabbits. Transforming growth factor-beta1 (TGF-beta1) or vehicle was injected into each implant site. After 1, 3, 5 or 7 days, scaffolds were removed, separated from the periosteum, and the scaffolds and periosteum were cultured separately for six weeks under chondrogenic conditions. Sulfated glycosaminoglycan (GAG), type II collagen and DNA content, cartilage yield, and calcium deposition were then analyzed. RESULTS: Cell infiltration was observed in all the scaffolds. Cartilage formation in the uncoated scaffolds increased with duration of implantation (maximum at 7 days). Cells in the uncoated scaffolds implanted for 7 days produced significantly higher levels of both GAG (5! 60 (95% CI, 107-1013) vs. 228 (95% CI, 177-278) mugGAG/mugDNA) and cartilage yield (9% (95% CI, 3-14%) vs. 0.02% (95% CI, 0-0.22%)) compared to chitosan-coated scaffolds (p=0.006 or less). There was no significant difference in GAG content or cartilage yield between the TGF-beta1-injected and vehicle-injected scaffolds. However, significantly more mineral deposition was detected in TGF-beta1-injected scaffolds compared to vehicle-injected scaffolds (p<0.0001). Cartilage yield from the periosteum, moreover, was significantly increased by subperiosteal TGF-beta1 injections (p<0.001). However, this response was reduced when chitosan-coated scaffolds were implanted. CONCLUSIONS: This study demonstrates that it is possible to seed PCL nanofiber scaffolds with periosteal cells in vivo and subsequently produce engineered cartilage in vitro. PMID: 20434575 [PubMed - as supplied by publisher] | | |
| Cell architecture-cell function dependencies on titanium arrays with regular geometry.
May 4, 2010 at 7:05 AM
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| | Cell architecture-cell function dependencies on titanium arrays with regular geometry. Biomaterials. 2010 Apr 28; Authors: Matschegewski C, Staehlke S, Loeffler R, Lange R, Chai F, Kern DP, Beck U, Nebe BJ Knowledge about biocomplexity of cell behavior in dependence on topographical characteristics is of clinical relevance for the development of implant designs in tissue engineering. The aim of this study was to find out cell architecture-cell function dependencies of human MG-63 osteoblasts on titanium (Ti) arrays with regular geometry. We compared cubic pillar structures (SU-8, dimension 3 x 3 x 5 and 5 x 5 x 5 mum) with planar samples. Electrochemical surface characterization revealed a low amount of surface energy (including polar component) for the pillar-structured surfaces, which correlated with a reduced initial cell adhesion and spreading. Confocal microscopy of cell's actin cytoskeleton revealed no stress fiber organization instead, the actin was concentrated in a surface geometry-dependent manner as local spots around the pillar edges. This altered cell architecture resulted in an impaired MG-63 cell function - the extracellular matrix proteins collagen-I! and bone sialo protein (BSP-2) were synthesized at a significantly lower level on SU-8 pillar structures; this was accompanied by reduced beta3-integrin expression. To find out physicochemical factors pertaining to geometrically microstructured surfaces and their influence on adjoining biosystems is important for the development of biorelevant implant surfaces. PMID: 20434213 [PubMed - as supplied by publisher] | | |
| Gene expression profiling of primary human articular chondrocytes in high-density micromasses reveals pattern of recovery, maintenance, re- and dedifferentiation.
May 4, 2010 at 7:05 AM
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| | Gene expression profiling of primary human articular chondrocytes in high-density micromasses reveals pattern of recovery, maintenance, re- and dedifferentiation. Gene. 2010 Apr 27; Authors: Dehne T, Schenk R, Perka C, Morawietz L, Pruss A, Sittinger M, Kaps C, Ringe J The high-density micromass culture has been widely applied to study chondrocyte cell physiology and pathophysiological mechanisms. Since an integrated image has not been established so far, we analyzed the phenotypic alterations of human articular chondrocytes in this model on the broad molecular level. Freshly isolated chondrocytes were assembled as micromasses and maintained up to six weeks in medium containing human serum. Formation of cartilaginous extracellular matrix (ECM) was evaluated by histological and immunohistochemical staining. At 0, 3 and 6weeks, chondrocyte micromasses were subjected to gene expression analysis using oligonucleotide microarrays and real-time RT-PCR. Micromasses developed a cartilaginous ECM rich in proteoglycans and type II collagen. On gene expression level, time-dependent expression pattern were observed. The induction of genes associated with cartilage-specific ECM (COL2A1, COL11A1) and developmental signaling (GDF5, GDF10, ID1,! ID4, FGFR1-3) indicated re-differentiation within the first three weeks. The repression of genes related to stress response (HSPA1A, HSPA4), apoptotic events (HYOU1, NFKBIA, TRAF1), and degradation (MMP1, MMP10, MMP12) suggested a recovery of chondrocytes. Constant expression of other chondrogenic (ACAN, FN1, MGP) and hypertrophic markers (COL10A1, ALPL, PTHR1, PTHR2) indicated a pattern of phenotypic maintenance. Simultaneously, the expression of chondrogenic growth (BMP6, TGFA, FGF1, FGF2) and transcription factors (SOX9, EGR1, HES1, TGIF1), and other cartilage ECM-related genes (COMP, PRG4) was consistently repressed and expression of collagens related to de-differentiation (COL1A1, COL3A1) was steadily induced indicating a progressing loss of cartilage phenotype. Likewise, a steady increase of genes associated with proliferation (GAS6, SERPINF1, VEGFB, VEGFC) and apoptosis (DRAM, DPAK1, HSPB, GPX1, NGFRAP1, TIA1) was observed. Sequence and interplay of the identified e! xpression pattern suggest, that chondrocyte micromass cultures! maintai n a differentiated phenotype up to three weeks in vitro and might be useful for studying chondrocyte biology, pathophysiology and differentiation. Cultivation longer than six weeks leads to progressing dedifferentiation of chondrocytes that should be considered on long-term evaluations. PMID: 20433912 [PubMed - as supplied by publisher] | | |
| [Repair of calvarial defects with human umbilical cord blood derived mesenchymal stem cells and demineralized bone matrix in athymic rats]
May 4, 2010 at 7:05 AM
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| | [Repair of calvarial defects with human umbilical cord blood derived mesenchymal stem cells and demineralized bone matrix in athymic rats] Zhonghua Zheng Xing Wai Ke Za Zhi. 2010 Jan;26(1):34-8 Authors: Liu GP, Li YL, Sun J, Cui L, Zhang WJ, Cao YL OBJECTIVE: To investigate the feasibility of using human umbilical cord blood derived mesenchymal stem cells (UCB-MSCs) and demineralized bone matrix (DBM) scaffolds to repair critical-sized calvarial defects in athymic rats. METHODS: Human UCB-MSCs were isolated, expanded and osteogenically induced in vitro. Osteogenic differentiation of UCB-MSCs was evaluated by Alizarin Red staining and measurement of calcium content respectively, and then the cells were seeded onto DBM scaffolds. Bilateral full-thickness defects (5 mm in diameter) of parietal bone were created in an athymic rat model. The defects were either repaired with UCB-MSC/DBM constructs (experimental group) or with DBM scaffolds alone (control group). Animals were harvested at 6 and 12 weeks post-implantation respectively, and defect repair was evaluated with gross observation, micro-CT measurement and histological analysis. RESULTS: Micro-CT showed that new bone was formed in the experimental group at! 6 weeks post-implantation, while no sign of new bone formation was observed in the control group. At 12 weeks post-transplantation, scaffolds had been degraded almost completely in both sides. It was shown that an average of (78.19 +/- 6.45)% of each defect volume had been repaired in experimental side; while in the control side, only limited bone formed at the periphery of the defect. Histological examination revealed that the defect was repaired by trabecular bone tissue in experimental side at 12 weeks, while only fibrous connection was observed in the control group. CONCLUSIONS: Tissue-engineered bone composed of osteogenically-induced human UCB-MSCs on DBM scaffolds could successfully repair the critical-sized calvarial defects in athymic rat models. PMID: 20432924 [PubMed - in process] | | |
| Management of articular cartilage defects of the knee.
May 4, 2010 at 7:05 AM
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| | Management of articular cartilage defects of the knee. J Bone Joint Surg Am. 2010 Apr;92(4):994-1009 Authors: Bedi A, Feeley BT, Williams RJ Articular cartilage has a poor intrinsic capacity for healing. The goal of surgical techniques to repair articular cartilage injuries is to achieve the regeneration of organized hyaline cartilage. Microfracture and other bone marrow stimulation techniques involve penetration of the subchondral plate in order to recruit mesenchymal stem cells into the chondral defect. The formation of a stable clot that fills the lesion is of paramount importance to achieve a successful outcome. Mosaicplasty is a viable option with which to address osteochondral lesions of the knee and offers the advantage of transplanting hyaline cartilage. However, limited graft availability and donor site morbidity are concerns. Transplantation of an osteochondral allograft consisting of intact, viable articular cartilage and its underlying subchondral bone offers the ability to address large osteochondral defects of the knee, including those involving an entire compartment. The primary theoreti! cal advantage of autologous chondrocyte implantation is the development of hyaline-like cartilage rather than fibrocartilage in the defect, which presumably leads to better long-term outcomes and longevity of the healing tissue. Use of synthetic scaffolds is a potentially attractive alternative to traditional cartilage procedures as they are readily available and, unlike allogeneic tissue transplants, are associated with no risk of disease transmission. Their efficacy, however, has not been proven clinically. PMID: 20360528 [PubMed - indexed for MEDLINE] | | |
| Radiation effects on bone healing and reconstruction: interpretation of the literature.
May 4, 2010 at 7:05 AM
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| | Radiation effects on bone healing and reconstruction: interpretation of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010 Feb;109(2):173-84 Authors: Jegoux F, Malard O, Goyenvalle E, Aguado E, Daculsi G OBJECTIVE: Reconstructing irradiated mandibles with biomaterials is still a challenge but little investigated. We collected data that could help us understand studies in the field of regeneration with biomaterials and irradiated bone. STUDY DESIGN: Systematic review of the literature. RESULTS: Delay and duration of radiation delivery and total equivalent dose are the most variable parameters in the various studies, resulting in confusion when interpreting the literature. Most reproducible experiments show that radiation reduces osteogenic cell numbers, alters cytokine capacity, and delays and damages bone remodeling. Interindividual variations and how such changes become irreversible lesions are still uncertain. In the case of regeneration using biomaterials, most studies have addressed the question of reconstruction in previously irradiated bone. The results show that osseointegration is often possible, although the failure rate is higher. The sooner the implanta! tion takes place after the end of the radiation, the higher the likelihood of failure. Few studies have focused on primary reconstruction followed by early irradiation, and most of the currently available engineering models would be altered by radiation. Good outcomes have been obtained with bone morphogenetic protein and with total bone marrow transplanation. CONCLUSION: This review points out the difficulties in achieving reproducible experiments and interpreting literature in this underinvestigated field. PMID: 20123406 [PubMed - indexed for MEDLINE] | | |
| Technical note: a new three-dimensional technique for high resolution quantitative recording of perikymata.
May 4, 2010 at 7:05 AM
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| | Technical note: a new three-dimensional technique for high resolution quantitative recording of perikymata. Am J Phys Anthropol. 2010 Mar;141(3):498-503 Authors: Bocaege E, Humphrey LT, Hillson S The number and spacing of incremental markings at the enamel surface, known as perikymata, are considered important indicators of dental growth patterns, as they provide information on crown formation times and the underlying developmental processes. This study explores the potential of a new three-dimensional technique for the reconstruction of dental growth profiles, using teeth from a medieval child from Abingdon, Oxfordshire. The crowns of three anterior teeth were imaged and analyzed using the Alicona 3D InfiniteFocus imaging microscope. Individual perikyma grooves can be unambiguously identified on a profile of the reconstructed enamel surface and direct distances between successive pairs of perikyma grooves can be calculated from coordinate data. This quantitative approach constitutes a more objective way to record perikymata spacing than current methods. PMID: 19953528 [PubMed - indexed for MEDLINE] | | |
| Microsphere-based drug releasing scaffolds for inducing osteogenesis of human mesenchymal stem cells in vitro.
May 4, 2010 at 7:05 AM
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| | Microsphere-based drug releasing scaffolds for inducing osteogenesis of human mesenchymal stem cells in vitro. Eur J Pharm Sci. 2010 Jan 31;39(1-3):59-67 Authors: Shi X, Wang Y, Varshney RR, Ren L, Gong Y, Wang DA In this study, in vitro osteogenesis was successfully achieved in human mesenchymal stem cells (hMSCs) by controlled release of the osteogenesis-inducing drugs dexamethasone, ascorbic acid (AA) and beta-glycerophosphate (GP) from poly(lactic-co-glycolic acid) (PLGA) sintered microsphere scaffolds (SMS). We investigated the osteogenesis of human MSCs (hMSCs) on dexamethasone laden PLGA-SMS (PLGA-Dex-SMS), and dexamethasone, AA and GP laden PLGA-SMS (PLGA-Com-SMS). hMSCs cultured on the microsphere systems, which act as drug release vehicles and also promote cell growth/tissue formation-displayed a strong osteogenic commitment locally. The osteogenic commitment of hMSCs on the scaffolds were verified by alkaline phosphatase (ALP) activity assay, calcium secretion assay, real-time PCR and immunohistochemistry analysis. The results indicated hMSCs cultured on PLGA-Com-SMS exhibited superior osteogenic differentiation owing to significantly high phenotypic expression o! f typical osteogenic genes-osteocalcin (OC), type I collagen, alkaline phosphatase (ALP), and Runx-2/Cbfa-1, and protein secretion of bone-relevant markers such as osteoclast and type I collagen when compared with PLGA-Dex-SMS. In conclusion, by promoting osteogenic development of hMSCs in vitro, this newly designed controlled release system opens a new door to bone reparation and regeneration. PMID: 19895885 [PubMed - indexed for MEDLINE] | | |
| [The telomerase activity of human adipose derived stem cells during proliferation and differentiation in vitro]
May 4, 2010 at 6:30 AM
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| | [The telomerase activity of human adipose derived stem cells during proliferation and differentiation in vitro] Zhonghua Zheng Xing Wai Ke Za Zhi. 2010 Jan;26(1):48-52 Authors: Chen GP, Luo SK, Wang HB, Sun ZS, Xu X OBJECTIVE: To investigate the telomerase activity of human adipose derived stem cells (ADSCs) during proliferation and differentiation in vitro. METHODS: ADSCs were highly purified and cultured in vitro. The morphology, phenotype and biological properties of the cultured ADSCs were observed by flow cytometer. Then ADSCs were induced to differentiate into adipocytes and osteoblast. The telomerase activity was detected by TRAP. RESULTS: ADSCs had the ability of multi-directed differentiation, like adipocytes and osteoblast. It could also express the stem cell-related surface markers. The telomerase activity was negative or lowly expressed in ADSCs in vitro within 12 generations. The telomerase activity was up-regulated when ADSCs was adipogenic differentiated, but deceased 3-6 days later. CONCLUSIONS: The telomerase activity of ADSCs is not changed during culture in vitro. It is up-regulated when ADSCs are induced to adipogenic differentiation, but decreased later. PMID: 20432927 [PubMed - in process] | | |
| What are the limits to cell plasticity?
May 4, 2010 at 6:13 AM
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| | What are the limits to cell plasticity? Cell Res. 2010 May;20(5):502-3 Authors: Taylor J, Wilmut I, Sullivan G PMID: 20436508 [PubMed - in process] | | |
| A three-dimensional model of the yeast genome.
May 4, 2010 at 6:13 AM
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| | A three-dimensional model of the yeast genome. Nature. 2010 May 2; Authors: Duan Z, Andronescu M, Schutz K, McIlwain S, Kim YJ, Lee C, Shendure J, Fields S, Blau CA, Noble WS Layered on top of information conveyed by DNA sequence and chromatin are higher order structures that encompass portions of chromosomes, entire chromosomes, and even whole genomes. Interphase chromosomes are not positioned randomly within the nucleus, but instead adopt preferred conformations. Disparate DNA elements co-localize into functionally defined aggregates or 'factories' for transcription and DNA replication. In budding yeast, Drosophila and many other eukaryotes, chromosomes adopt a Rabl configuration, with arms extending from centromeres adjacent to the spindle pole body to telomeres that abut the nuclear envelope. Nonetheless, the topologies and spatial relationships of chromosomes remain poorly understood. Here we developed a method to globally capture intra- and inter-chromosomal interactions, and applied it to generate a map at kilobase resolution of the haploid genome of Saccharomyces cerevisiae. The map recapitulates known features of genome organi! zation, thereby validating the method, and identifies new features. Extensive regional and higher order folding of individual chromosomes is observed. Chromosome XII exhibits a striking conformation that implicates the nucleolus as a formidable barrier to interaction between DNA sequences at either end. Inter-chromosomal contacts are anchored by centromeres and include interactions among transfer RNA genes, among origins of early DNA replication and among sites where chromosomal breakpoints occur. Finally, we constructed a three-dimensional model of the yeast genome. Our findings provide a glimpse of the interface between the form and function of a eukaryotic genome. PMID: 20436457 [PubMed - as supplied by publisher] | | |
| The potential role of metal ion release as a marker of loosening in patients with total knee replacement: a cohort study.
May 4, 2010 at 6:13 AM
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| | The potential role of metal ion release as a marker of loosening in patients with total knee replacement: a cohort study. J Bone Joint Surg Br. 2010 May;92(5):634-8 Authors: Savarino L, Tigani D, Greco M, Baldini N, Giunti A We investigated the role of ion release in the assessment of fixation of the implant after total knee replacement and hypothesised that ion monitoring could be a useful parameter in the diagnosis of prosthetic loosening. We enrolled 59 patients with unilateral procedures and measured their serum aluminium, titanium, chromium and cobalt ion levels, blinded to the clinical and radiological outcome which was considered to be the reference standard. The cut-off levels for detection of the ions were obtained by measuring the levels in 41 healthy blood donors who had no implants. Based on the clinical and radiological evaluation the patients were divided into two groups with either stable (n = 24) or loosened (n = 35) implants. A significant increase in the mean level of Cr ions was seen in the group with failed implants (p = 0.001). The diagnostic accuracy was 71% providing strong evidence of failure when the level of Cr ions exceeded the cut-off value. The possibility! of distinguishing loosening from other causes of failure was demonstrated by the higher diagnostic accuracy of 83%, when considering only patients with failure attributable to loosening. Measurement of the serum level of Cr ions may be of value for detecting failure due to loosening when the diagnosis is in doubt. The other metal ions studies did not have any diagnostic value. PMID: 20435998 [PubMed - in process] | | |
| Too friable to treat?
May 4, 2010 at 6:13 AM
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| | Too friable to treat? Lancet. 2010 May 1;375(9725):1578 Authors: Kimura K, Sakai-Kimura M, Takahashi R, Watanabe A, Mukai M, Noma S, Fukuda K PMID: 20435230 [PubMed - in process] | | |
| Curing hearing loss: Patient expectations, health care practitioners, and basic science.
May 4, 2010 at 6:13 AM
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| | Curing hearing loss: Patient expectations, health care practitioners, and basic science. J Commun Disord. 2010 Apr 7; Authors: Oshima K, Suchert S, Blevins NH, Heller S Millions of patients are debilitated by hearing loss, mainly caused by degeneration of sensory hair cells in the cochlea. The underlying reasons for hair cell loss are highly diverse, ranging from genetic disposition, drug side effects, traumatic noise exposure, to the effects of aging. Whereas modern hearing aids offer some relief of the symptoms of mild hearing loss, the only viable option for patients suffering from profound hearing loss is the cochlear implant. Despite their successes, hearing aids and cochlear implants are not perfect. Particularly frequency discrimination and performance in noisy environments and general efficacy of the devises vary among individual patients. The advent of regenerative medicine, the publicity of stem cells and gene therapy, and recent scientific achievements in inner ear cell regeneration have generated an emerging spirit of optimism among scientists, health care practitioners, and patients. In this review, we place the diff! erent points of view of these three groups in perspective with the goal of providing an assessment of patient expectations, health care reality, and potential future treatment options for hearing disorders. Learning outcomes: (1) Readers will be encouraged to put themselves in the position of a hearing impaired patient or family member of a hearing impaired person. (2) Readers will be able to explain why diagnosis of the underlying pathology of hearing loss is difficult. (3) Readers will be able to list the main directions of current research aimed to cure hearing loss. (4) Readers will be able to understand the different viewpoints of patients and their relatives, health care providers, and scientists with respect to finding novel treatments for hearing loss. PMID: 20434163 [PubMed - as supplied by publisher] | | | | 
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