TISSUE RESPONSE TO IMPACT LOADING IN SPORTS

The response of biological tissue to impact like mechanical loading in sports is of vital interest in sports biomechanics, athletic training research and especially the development of an injury reduction model. Bone and articular cartilage react differently to mechanical loading in the long term. A strong association to the loading patterns for the response of bone but not for that of cartilage has been be identified. For the short term experimental results provide evidence on two different articular cartilage responses related to loading regimes (high frequent impact vs. low frequent impact). From the reported results the risk of overuse through impact loading was derived as a function of sports related impact loading patterns and subject specific prerequisites

THE CHOICE OF TRAINING FOOlWEAR HAS AN EFFECT ON CHANGES :IN MORPHOLOGY AND FUNCTION OF FOOT AND SHANK MUSCLES

The use of minimal footwear leads to higher muscle activity of the M. flexor hallucis longus and to a higher range of motion in the metatarsophalangeal joints (MPJ). This could lead to training effects of in-and extrinsic foot structures as muscles and tendons. The purpose of the study was to determine whether muscle strength or the anatomical cross sectional area of foot and shank muscles are affected by the use of minimal footwear. In a longitudinal prospective intervention study the effect of the use of a minimal shoe was evaluated. Therefore isometric MPJ f1exion strength, inversion strength and plantar f1exion strength were determined. The effect on the anatomical cross sectional areas (ACSA) of selected foot and shank muscles were measured using MRI. ACSA as well as muscular performance increased significantly using the minimal shoe in comparison to conventional footwear. This should lead to performance enhancement and injury prevention

METHOD EVALUATION TO DETERMINE HYDRATION STATES OF TENDONS BY USING MRI

Due to the fact that water content is a determinant of the material properties of tendons and therefore might affect sports performance and the risk of injury, the purpose of this pilot study was to evaluate the reliabilityand sensitivity of a MRI based method to quantify content of a tendon. For this pilot study twenty porcine digital flexor tendons were chosen. All samples were examined on a MR scanner using three 3D ultra-short echo time sequences. With the applied sequences it was possible to determine a decrease in water content of the tendons. In addition, the methods showed a good inter session reliability. Further investigations are needed to improve the upper and lower limit of resolution regarding the physiological hydration state

Pivotal Role of Tenascin-W (-N) in Postnatal Incisor Growth and Periodontal Ligament Remodeling

The continuously growing mouse incisor provides a fascinating model for studying stem cell regulation and organ renewal. In the incisor, epithelial and mesenchymal stem cells assure lifelong tooth growth. The epithelial stem cells reside in a niche known as the cervical loop. Mesenchymal stem cells are located in the nearby apical neurovascular bundle and in the neural plexus. So far, little is known about extracellular cues that are controlling incisor stem cell renewal and guidance. The extracellular matrix protein tenascin-W, also known as tenascin-N (TNN), is expressed in the mesenchyme of the pulp and of the periodontal ligament of the incisor, and is closely associated with collagen 3 fibers. Here, we report for the first time the phenotype of tenascin-W/TNN deficient mice, which in a C57BL/6N background exhibit a reduced body weight and lifespan. We found major defects in the alveolar bone and periodontal ligament of the growing rodent incisors, whereas molars were not affected. The alveolar bone around the incisor was replaced by a dense scar-like connective tissue, enriched with newly formed nerve fibers likely leading to periodontal pain, less food intake and reduced body weight. Using soft food to reduce mechanical load on the incisor partially rescued the phenotype. In situ hybridization and Gli1 reporter mouse experiments revealed decreased hedgehog signaling in the incisor mesenchymal stem cell compartment, which coordinates the development of mesenchymal stem cell niche. These results indicate that TNN deficiency in mice affects periodontal remodeling and increases nerve fiber branching. Through periodontal pain the food intake is reduced and the incisor renewal and the neurovascular sonic hedgehog secretion rate are reduced. In conclusion, tenascin-W/TNN seems to have a primary function in rapid periodontal tissue remodeling and a secondary function in mechanosensation.Peer reviewe

Reduced Granulation Tissue and Wound Strength in the Absence of α11β1 Integrin

Previous wound healing studies have failed to define a role for either α1β1 or α2β1 integrin in fibroblast-mediated wound contraction, suggesting the involvement of another collagen receptor in this process. Our previous work demonstrated that the integrin subunit α11 is highly induced during wound healing both at the mRNA and protein level, prompting us to investigate and dissect the role of the integrin α11β1 during this process. Therefore, we used mice with a global ablation of either α2 or α11 or both integrin subunits and investigated the repair of excisional wounds. Analyses of wounds demonstrated that α11β1 deficiency results in reduced granulation tissue formation and impaired wound contraction, independently of the presence of α2β1. Our combined in vivo and in vitro data further demonstrate that dermal fibroblasts lacking α11β1 are unable to efficiently convert to myofibroblasts, resulting in scar tissue with compromised tensile strength. Moreover, we suggest that the reduced stability of the scar is a consequence of poor collagen remodeling in α11-/- wounds associated with defective transforming growth factor-β–dependent JNK signaling.publishedVersio

Summertime plankton ecology in Fram Strait - a compilation of long- and short-term observations

Between Greenland and Spitsbergen, Fram Strait is a region where cold ice-covered Polar Water exits the Arctic Ocean with the East Greenland Current (EGC) and warm Atlantic Water enters the Arctic Ocean with the West Spitsbergen Current (WSC). In this compilation, we present two different data sets from plankton ecological observations in Fram Strait: (1) long-term measurements of satellite-derived (1998–2012) and in situ chlorophyll a (chl a) measurements (mainly summer cruises, 1991–2012) plus protist compositions (a station in WSC, eight summer cruises, 1998–2011); and (2) short-term measurements of a multidisciplinary approach that includes traditional plankton investigations, remote sensing, zooplankton, microbiological and molecular studies, and biogeochemical analyses carried out during two expeditions in June/July in the years 2010 and 2011. Both summer satellite-derived and in situ chl a concentrations showed slight trends towards higher values in the WSC since 1998 and 1991, respectively. In contrast, no trends were visible in the EGC. The protist composition in the WSC showed differences for the summer months: a dominance of diatoms was replaced by a dominance of Phaeocystis pouchetii and other small pico- and nanoplankton species. The observed differences in eastern Fram Strait were partially due to a warm anomaly in the WSC. Although changes associated with warmer water temperatures were observed, further long-term investigations are needed to distinguish between natural variability and climate change in Fram Strait. Results of two summer studies in 2010 and 2011 revealed the variability in plankton ecology in Fram Strait

Deficiency of annexins A5 and A6 induces complex changes in the transcriptome of growth plate cartilage but does not inhibit the induction of mineralization

Initiation of mineralization during endochondral ossification is a multistep process and has been assumed to correlate with specific interactions of annexins A5 and A6 and collagens. However, skeletal development appears to be normal in mice deficient for either A5 or A6, and the highly conserved structures led to the assumption that A5 and A6 may fulfill redundant functions. We have now generated mice deficient of both proteins. These mice were viable and fertile and showed no obvious abnormalities. Assessment of skeletal elements using histologic, ultrastructural, and peripheral quantitative computed tomographic methods revealed that mineralization and development of the skeleton were not significantly affected in mutant mice. Otherwise, global gene expression analysis showed subtle changes at the transcriptome level of genes involved in cell growth and intermediate metabolism. These results indicate that annexins A5 and A6 may not represent the essential annexins that promote mineralization in vivo

Anisotropic and age-dependent elastic material behavior of the human costal cartilage

Compared to articular cartilage, the biomechanical properties of costal cartilage have not yet been extensively explored. The research presented addresses this problem by studying for the first time the anisotropic elastic behavior of human costal cartilage. Samples were taken from 12 male and female cadavers and unconfined compression and indentation tests were performed in mediolateral and dorsoventral direction to determine Young's Moduli E-C for compression and E-i5%, E-i10% and E-imax at 5%, 10% and maximum strain for indentation. Furthermore, the crack direction of the unconfined compression samples was determined and histological samples of the cartilage tissue were examined with the picrosirius-polarization staining method. The tests revealed mean Young's Moduli of E-C=32.9 +/- 17.9 MPa (N=10), E-i5%=11.1 +/- 5.6 MPa (N=12), E-i10%=13.3 +/- 6.3 MPa (N=12) and E-imax=14.6 +/- 6.6 MPa (N=12). We found that the Young's Moduli in the indentation test are clearly anisotropic with significant higher results in the mediolateral direction (all P=0.002). In addition, a dependence of the crack direction of the compressed specimens on the load orientation was observed. Those findings were supported by the orientation of the structure of the collagen fibers determined in the histological examination. Also, a significant age-related elastic behavior of human costal cartilage could be shown with the unconfined compression test (P=0.009) and the indentation test (P=0.004), but no sex effect could be detected. Those results are helpful in the field of autologous grafts for rhinoplastic surgery and for the refinement of material parameters in Finite Element models e.g., for accident analyses with traumatic impact on the thorax