Entity

Time filter

Source Type


Kirkegaard M.,University of Southern Denmark | Kirkegaard M.,National Environmental Research Institute of Denmark | Sonne C.,University of Southern Denmark | Sonne C.,National Environmental Research Institute of Denmark | And 5 more authors.
Toxicological and Environmental Chemistry | Year: 2010

This study investigated whether low-level, long-term in utero and post-natal exposure to organohalogen pollutants disrupts male reproductive organ morphology and testosterone production in Greenland sledge dogs (Canis familiaris), as a model of Arctic top predators feeding on marine mammals. Six male dogs were followed for 1 year and testosterone concentrations, testes/baculum morphology and baculum bone mineral density (BMD) was determined. Three males were exposed to organohalogenated contaminants (OHCs) in utero through maternal dietary intake of minke whale blubber (Balaenoptera acutorostrata), with a post-weaning ΣOHC intake of 10.4- 11.7 μg kg-1day-1 resulting in an adipose tissue range of ΣOHC 4518- 5729 ng (g lw) -1 after 1 year. Three control males were exposed to very low concentrations of OHCs through pork fat. No significant differences were seen in plasma testosterone concentrations, baculum weight, BMD, and testicular length in the six male dogs (control, n=3 and exposed, n=3) measured at 3, 5, 7, 9, and 12 months of age. Testicular weights were significantly lower in the exposed group (p=0.015, n=2). Although this study had a limited number of animals, it was observed that in utero and the following 12 months of chronic exposure to a complex mixture of contaminants in the form of naturally accumulated OHCs does not affects testosterone levels, but possibly affects testicular weights in sledge dogs. © 2010 Taylor & Francis. Source


Wong C.,University Hospital of Hvidovre | Rasmussen J.,University of Aalborg | Simonsen E.,Copenhagen University | Hansen L.,Team Danmark | And 2 more authors.
Open Spine Journal | Year: 2011

Introduction: Previous studies of bone stresses in the human lumbar spine have relied on simplified models when modeling the spinal musculature, even though muscle forces are likely major contributors to the stresses in the vertebral bones. Detailed musculoskeletal spine models have recently become available and show good correlation with experimental findings. A combined inverse dynamics and finite element analysis study was conducted in the lumbar spine to investigate the effects of muscle forces on a detailed musculoskeletal finite element model of the 4th lumbar vertebral body. Materials and Methodology: The muscle forces were computed with a detailed and validated inverse dynamics musculoskeletal spine model in a lifting situation, and were then applied to an orthotropic finite element model of the 4th lumbar vertebra. The results were compared with those from a simplified load case without muscles. Results: In general the von Mises stress was larger by 30%, and even higher when looking at the von Mises stress distribution in the superio-anterior and central part of the vertebral body and in the pedicles. Conclusion: The application of spine muscles to a finite element model showed markedly larger von Mises stress responses in the central and anterior part of the vertebral body, which can be tolerated in the young and healthy spine, but it would increase the risk of compression fractures in the elderly, osteoporotic spine. © Wong et al. Source


Wong C.,University Hospital of Hvidovre
Danish medical bulletin | Year: 2010

INTRODUCTION: Fractures of the tibial shaft are relatively common injuries. There are indications that tibial shaft fractures share characteristics in terms of site, type and local fracture mechanisms. In this study, we aimed to set up a mathematical, computer-based model using finite element analysis of the bones of the lower leg to examine if such a model is adequate for prediction of fracture locations and patterns. In future studies, we aim to use these biomechanical results to examine fracture prevention, among others, and to simulate different types of osteosynthesis and the process of bony healing. The biomechanical results are the basis for fracture healing, biomechanical fall analysis and stability analysis of osteosynthesis. MATERIAL AND METHODS: A finite element model of the bony part of the lower leg was generated on the basis of computed tomography data from the Visible Human Project. The data consisted of 21,219 3D elements with a cortical shell and a trabecular core. Three types of load of torsion, a direct lateral load and axial compression were applied. RESULTS: The finite element linear static analysis resulted in relevant fracture localizations and indicated relevant fracture patterns. CONCLUSION: In the present study, we have successfully simulated fracture mechanisms, obtained adequate fracture locations and achieved an indication of the fracture morphology. The method of fracture simulation employed showed good agreement with known clinical data and data from prior mechanical testing. This substantiates the validity of fracture simulation for future studies examining tibial fractures, fracture healing and prevention. Source


Sonne C.,University of Aarhus | Dyck M.,Environment Canada | Riget F.F.,University of Aarhus | Beck Jensen J.-E.,University Hospital of Hvidovre | And 5 more authors.
Environmental Research | Year: 2015

Industrially produced chemicals have been a major environmental concern across our entire Globe since the onset of rapid industrial development around the early 1900. Many of the substances being used are known to be endocrine disrupting chemicals (EDCs) and are also known to be long-range dispersed and to biomagnify to very high concentrations in the tissues of Arctic apex predators such as polar bears (Ursus maritimus). A major concern relating to EDCs is their effects on vital organ-tissues such as bone and it is possible that EDCs represent a more serious challenge to the species' survival than the more conventionally proposed prey reductions linked to climate change. We therefore analyzed penile bone mineral density (BMD) as a key phenotype for reproductive success in 279 polar bear samples born 1990-2000 representing eight polar bear subpopulations. Since EDC concentrations were not available from the same specimens, we compared BMD with published literature information on EDC concentrations. Latitudinal and longitudinal BMD and EDC gradients were clearly observed, with Western Hudson bears having the highest BMD and lowest EDCs, and North East Greenland polar bears carrying the lowest BMD and highest EDCs. A BMD vs. polychlorinated biphenyls (PCB) regression analysis showed that BMD decreased as a function of the eight subpopulations' PCB concentrations and this relationship was close to being significant (p=0.10, R2=0.39). Risk quotient (RQ) estimation demonstrated that PCBs could be in a range that may lead to disruption of normal reproduction and development. It is therefore likely that EDCs directly affect development and bone density in polar bears. Canadian bears had in general the best health and the North East Greenland subpopulation being at the highest risk of having negative health effects. While reductions in BMD is in general unhealthy, reductions in penile BMD could lead to increased risk of species extinction because of mating and subsequent fertilization failure as a result of weak penile bones and risk of fractures. Based on this, future studies should assess how polar bear subpopulations respond upon EDC exposure since information and understanding about their circumpolar reproductive health is vital for future conservation. © 2014 Elsevier Inc. Source


Wong C.,University Hospital of Hvidovre | Mikkelsen P.,Hospital of Glostrup | Hansen L.B.,Copenhagen University | Darvann T.,Copenhagen University | Gebuhr P.,University Hospital of Hvidovre
Danish Medical Bulletin | Year: 2010

INTRODUCTION: Fractures of the tibial shaft are relatively common injuries. There are indications that tibial shaft fractures share characteristics in terms of site, type and local fracture mechanisms. In this study, we aimed to set up a mathematical, computer-based model using finite element analysis of the bones of the lower leg to examine if such a model is adequate for prediction of fracture locations and patterns. In future studies, we aim to use these biomechanical results to examine fracture prevention, among others, and to simulate different types of osteosynthesis and the process of bony healing. The biomechanical results are the basis for fracture healing, biomechanical fall analysis and stability analysis of osteosynthesis. MATERIAL AND METHODS: A finite element model of the bony part of the lower leg was generated on the basis of computed tomography data from the Visible Human Project. The data consisted of 21,219 3D elements with a cortical shell and a trabecular core. Three types of load of torsion, a direct lateral load and axial compression were applied. RESULTS: The finite element linear static analysis resulted in relevant fracture localizations and indicated relevant fracture patterns. CONCLUSION: In the present study, we have successfully simulated fracture mechanisms, obtained adequate fracture locations and achieved an indication of the fracture morphology. The method of fracture simulation employed showed good agreement with known clinical data and data from prior mechanical testing. This substantiates the validity of fracture simulation for future studies examining tibial fractures, fracture healing and prevention. Source

Discover hidden collaborations