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Hong Kong, Hong Kong

Lui P.P.Y.,Headquarters | Wong O.T.,Chinese University of Hong Kong | Lee Y.W.,Chinese University of Hong Kong
American Journal of Sports Medicine | Year: 2014

Background: Both osteointegration and remodeling of graft midsubstance (collectively called graft healing) are slow processes after anterior cruciate ligament (ACL) reconstruction. Tendon-derived stem cells (TDSCs) form a cell sheet after treatment with connective tissue growth factor (CTGF) and ascorbic acid, which exhibits higher tenogenic and maintains high chondroosteogenic gene expression of TDSCs. No external scaffold is required for cell delivery. Hypothesis: Wrapping the TDSC sheet around the ACL graft would promote early graft healing in a rat model. Study Design: Controlled laboratory study. Methods: Green fluorescent protein (GFP) rat TDSCs were treated with connective tissue growth factor and ascorbic acid to promote cell sheet formation. Rats undergoing unilateral ACL reconstruction were divided into a control group and a TDSC group. The tendon graft was wrapped with the GFP-TDSC sheet before graft insertion in the TDSC group. At weeks 2, 6, and 12 after reconstruction, the samples were harvested for computed tomography imaging and histologic or biomechanical testing. The fate of the transplanted cell sheet was examined by immunohistochemical staining of GFP. Results: There were significantly higher tunnel bone mineral density (BMD) (42.3% increase, P = .047) and bone volume/total volume (BV/TV) (625% increase, P = .009) at the metaphyseal region of the tibial tunnel at week 2 and at the femoral tunnel at week 6 (BMD: 30.8% increase, P = .014; BV/TV: 100% increase, P = .014) in the TDSC group compared with the control group. Only the TDSC group showed a time-dependent increase in tunnel BMD (overall P = .038) and BV/TV (overall P = .015) at the epiphyseal region of the tibial tunnel. Semiquantitative image analysis showed better graft osteointegration and higher intraarticular graft integrity with lower cellularity and vascularity, better cell alignment, and higher collagen birefringence in the TDSC group. The ultimate load at week 2 (52.5% increase, P = .027) and stiffness at week 6 (62% increase, P = .008) were significantly higher in the TDSC group. Cells positive for GFP were observed in all samples in the TDSC group at week 2 but became reduced with time after reconstruction. Conclusion: The TDSC sheet improved early graft healing after ACL reconstruction in the rat model. © 2013 The Author(s).


Lang G.T.,U.S. Army | Harrigan M.J.,Headquarters
Military Medicine | Year: 2012

Objective: Helicopter pilots are exposed to noise at work and are at risk of developing hearing loss in excess of that which naturally results from aging. We investigated whether Lynx pilots demonstrated changes to hearing thresholds that differed from Apache pilots. Methods: Survey responses were combined with audiometric data from a retrospective cohort of 59 Lynx and 87 Apache pilots. Subjects' audiograms were analyzed for air conduction thresholds with age correction performed in accordance with ISO 7029. Annual changes in low frequencies (0.5-2 kHz) and high frequencies (3-6 kHz) were calculated. Subjects were categorized for time in service and flying hours. Results: Hearing was better than predicted at nearly all frequencies in both ears for Lynx and Apache pilots. There w ere no differences inhearing between groups of pilots. Significant differences in hearing threshold changes existed for pilots with 20 or moreyears of service compared to those in other categories. Discussion: The results suggest that the circumaural earmuffs currently incorporated into the flying helmet mitigate the risk of noise-induced hearing loss in these pilots. © Association of Military Surgeons of the U.S. All rights reserved.


Teyhen D.S.,U.S. Army | Christ T.R.,U.S. Army | Ballas E.R.,U.S. Air force | Hoppes C.W.,U.S. Army | And 4 more authors.
Journal of Biomechanics | Year: 2010

The purpose was to compare glenohumeral (GH) migration, during dynamic shoulder elevation and statically held positions using digital fluoroscopic videos (DFV). Thirty male volunteers (25±4 years) without right shoulder pathology were analyzed using DFV (30. Hz) during arm elevation in the scapular plane. DFV were obtained at the arm at side position, 45°, 90°, and 135° for static and dynamic conditions. GH migration was measured as the distance from the center of the humeral head migrated superiorly or inferiorly relative to the center of the glenoid fossa. Inter-rater reliability was considered good; ICC (2,3) ranged from 0.83 to 0.92. A main effect was revealed for contraction type (p=0.031), in which . post-hoc t-tests revealed that humeral head was significantly more superior on the glenoid fossa during dynamic contraction. A main effect was also revealed for arm angle (p<0.001), in which . post-hoc t-tests revealed significantly more superior humeral head positioning at 45°, 90°, and 135° when compared to arm at side (p<0.001), as well as at 90° compared to 45° (p=0.024). There was no interaction effect between angle and contraction type (p=0.400). Research utilizing static imaging may underestimate the amount of superior GH migration that occurs dynamically. © 2010.


Wang P.,National University of Defense Technology | Wu Y.,National University of Defense Technology | Hu X.,National University of Defense Technology | Ruan Q.,National University of Defense Technology | Yuan H.,Headquarters
Proceedings of the 2012 International Conference on Industrial Control and Electronics Engineering, ICICEE 2012 | Year: 2012

The analysis of geomagnetic map suitability is one of the key techniques in geomagnetic aided navigation system. Suitability evaluation using the single feature parameter may lead to misjudgment. By considering a group of geomagnetic map feature parameters such as standard deviation, roughness, gradient deviation, information entropy, and fisher information content, the principal component analysis method is used to achieve synthetical evaluation value of candidate matching areas by endogenetic weight. The experiment results indicate well consistency between the synthetical evaluation value and the matching probability. The synthetical evaluation value may be regarded as a quantitative index of suitability to select appropriate geomagnetic aided navigation matching areas. © 2012 IEEE.


Thomas E.,Regional Office for the Americas | van Zonneveld M.,Regional Office for the Americas | van Zonneveld M.,Ghent University | Loo J.,Headquarters | And 3 more authors.
PLoS ONE | Year: 2012

Cacao (Theobroma cacao L.) is indigenous to the Amazon basin, but is generally believed to have been domesticated in Mesoamerica for the production of chocolate beverage. However, cacao's distribution of genetic diversity in South America is also likely to reflect pre-Columbian human influences that were superimposed on natural processes of genetic differentiation. Here we present the results of a spatial analysis of the intra-specific diversity of cacao in Latin America, drawing on a dataset of 939 cacao trees genotypically characterized by means of 96 SSR markers. To assess continental diversity patterns we performed grid-based calculations of allelic richness, Shannon diversity and Nei gene diversity, and distinguished different spatially coherent genetic groups by means of cluster analysis. The highest levels of genetic diversity were observed in the Upper Amazon areas from southern Peru to the Ecuadorian Amazon and the border areas between Colombia, Peru and Brazil. On the assumption that the last glaciation (22,000-13,000 BP) had the greatest pre-human impact on the current distribution and diversity of cacao, we modeled the species' Pleistocene niche suitability and overlaid this with present-day diversity maps. The results suggest that cacao was already widely distributed in the Western Amazon before the onset of glaciation. During glaciations, cacao populations were likely to have been restricted to several refugia where they probably underwent genetic differentiation, resulting in a number of genetic clusters which are representative for, or closest related to, the original wild cacao populations. The analyses also suggested that genetic differentiation and geographical distribution of a number of other clusters seem to have been significantly affected by processes of human management and accompanying genetic bottlenecks. We discuss the implications of these results for future germplasm collection and in situ, on farm and ex situ conservation of cacao. © 2012 Thomas et al.

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