Alteration in ACL loading after total and partial medial meniscectomy.

Anterior cruciate ligament (ACL) injuries are often caused by high impact loadings during competitive sports but may also happen during regular daily activities due to tissue degeneration or altered mechanics after a previous knee injury or surgery such as meniscectomy. Most existing research on ACL injury has focused on impact loading scenarios or the consequence of ACL injury on meniscus. The objective of the present study was to investigate the effects of varying degrees of medial meniscectomy on the mechanics of intact ACL by performing a poromechanical finite element analysis under moderate creep loadings. Four clinical scenarios with 25%, 50%, 75% and total medial meniscectomy were compared with the intact knee finite element model. Our results suggested that different medial meniscal resections may increase, at different extents, the knee laxity and peak tensile stress in the ACL, potentially leading to collagen fiber fatigue tearing and altered mechanobiology under normal joint loadings. Interestingly, the ACL stress actually increased during early knee creep (~ 3 min) before it reached an equilibrium. In addition, meniscectomy accelerated ACL stress reduction during knee creep, transferred more loading to tibial cartilage, increased contact pressure, and shifted the contact center posteriorly. This study may contribute to a better understanding of the interaction of meniscectomy and ACL integrity during daily loadings.

Creep behavior of human knee joint determined with high-speed biplanar video-radiography and finite element simulation.

Creep and relaxation of knee cartilage and meniscus have been extensively studied at the tissue level with constitutive laws well established. At the joint level, however, both experimental and model studies have been focused on either elastic or kinematic responses of the knee, where the time-dependent response is typically neglected for simplicity. The objectives of this study were to quantify the in-vivo creep behavior of human knee joints produced by the cartilaginous tissues and to use the relevant data to validate a previously proposed poromechanical model. Two participants with no history of leg injury volunteered for 3T magnetic resonance imaging (MRI) of their unloaded right knees and for biplanar video-radiography (BVR) of the same knees during standing on an instrumented treadmill for 10 min. Approximately 550 temporal data points were obtained for the in-vivo displacement of the right femur relative to the tibia of the knee. Models of the bones and soft tissues were derived from the MRI. The bone models were used to reconstruct the 3D bone kinematics measured using BVR. Ground reaction forces were simultaneously recorded for the right leg, which were used as input for the subject-specific finite element knee models. Cartilaginous tissues were modeled as fluid-saturated fibril-reinforced materials. In-vivo creep of the knee was experimentally observed for both participants, i.e., the joint displacement increased with time while the reaction forces at the foot were approximately constant. The creep displacements obtained from the finite element models compared well with the experimental data when the tissue properties were calibrated (Pearson correlation coefficient = 0.99). The results showed the capacity of the poromechanical knee model to capture the creep response of the joint. The combined experimental and model study may be used to understand the fluid-pressure load support and contact mechanics of the joint using material properties calibrated from the displacement data, which enhance the fidelity of model results.

Identification of Schizosaccharomyces pombe ird Mutants Resistant to Glucose Suppression and Oxidative Stress.

Glucose is both the favourite carbon and energy source and acts as a hormone that plays a regulating role in many biological processes. Calorie restriction extends the lifespan in many organisms, including Schizosaccharomyces pombe, while uptake of high glucose leads to undesired results, such as diabetes and aging. In this study, sequence analysis of Schizosaccharomyces pombe ird5 and ird11 mutants was performed using next-generation sequencing techniques and a total of 20 different mutations were detected. ird11 is resistant to oxidative stress without calorie restriction, whereas ird5 displays an adaptive response against oxidative stress. We selected nine candidate mutations located in the non-coding (6) and coding (3) region among a total of 20 different mutations. The nine candidate mutations, which are thought to be responsible for ird5 and ird11 mutant phenotypes, were investigated via forward and backward mutations by using various cloning techniques. The results of this study provide report-like information that will contribute to understanding the relationship between glucose sensing/ signalling and oxidative stress response components.

Bone mineral density and associated parameters in pre-pubertal children with asthma treated with long-term fluticasone propionate.

AIMS: The primary aim of the objective of the study was to determine the effects of long-term treatment with the recommended dose of inhaled fluticasone propionate spray usage on bone mineral status in children with asthma. METHODS: This cross-sectional, case-control study was of 270 pre-pubertal children with asthma, who had used inhaled fluticasone propionate at a mean daily dose of 200 µg (range: 200-350 µg) for at least 5 years. The bone mineral density (BMD) of the lumbar spine was measured by dual-energy X-ray absorptiometry (DEXA). The results were compared to untreated controls (n=200), who were newly diagnosed children with asthma without any corticosteroid treatment. RESULTS: The 270 study patients (175 males) were aged between 6 and 13 years. The average age (±SEM) was 9.2±0.6 years, and the mean (±SEM) steroid dosage used was 183.3±57.0 µg daily, with 236.5±17.2 g total steroid use during treatment. Between the study and the control groups, no significant difference was observed in BMD (p>0.05). CONCLUSION: The findings suggest that long-term periodical treatment for 5 years with inhaled fluticasone propionate, 100 µg twice daily, in children with asthma revealed no negative effect on bone mineral density by using DEXA.