The memory enhancement effect of Kai Xin San on cognitive deficit induced by simulated weightlessness in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: It is vital for astronauts to develop effective countermeasures to prevent their decline of cognitive performance in microgravity to make space-flight missions successful. The traditional Chinese herbal formula Kai Xin San (KXS) has been used to treat amnesia for thousands years. It is a traditional complex prescription comprising of ginseng (Panax ginseng C. A. Meyer), hoelen (Poria cocos (Schw.) Wolf), polygala (Polygala tenaifolia Willd), and acorus (Acorus tatarinowii Schott). Previous study showed KXS could improve CMS-induced memory impairment in rats. MATERIAL AND METHODS: In this paper, a unique environmental factor-microgravity (weightlessness) was simulated as hindlimb suspension (HLS) by tail in rats for two weeks as the HLS animal model. The KXS at the doses of 0.3 or 0.6g/kg p.o. daily was administrated to HLS rats for two weeks at the same time of HLS, the memory behavior tests were investigated with Morris water maze (MWM) and Shuttle Box (SB) test. The levels of ROS, 8-OHdG and 3-nitrotyrosine (3-NT) in the serum, and AChE and ChAT activity in the brain of rats were determined by ELISA or biochemical analysis. RESULTS: After HLS for two weeks, the escape latency and the swimming distance were significantly increased in the MWM test in rats in the HLS group, compared with control group. The percent of swimming distance in target quadrant and the number of target crossing was significantly decreased in rats in the HLS group compared with the control group. Performance in the SB test showed, the numbers and the distance of active avoidance was decreased from day 4 to day 7, the time spent in electric area was increased in rats in the HLS group compared with the control group. Administration of KXS 0.3 or 0.6g/kg to the HLS rats for two weeks significantly reduced the escape latency and the swimming distance, increased the percentage of swimming distance in target quadrant and the number of target crossings (P<0.01, compared with the HLS group) in the MWM test. Similar treatment with KXS increased the numbers and the distance of active avoidance (P<0.01, compared with the HLS group) and reduced the time spent in electric area after training 3 days in the SB test (P<0.01, compared with the HLS group). The HLS induced the increase of the ROS, 8-OHdG and 3-NT in the serum of rats, but has little influence on the AChE, ChAT activity in the brain. Only the AChE activity in the cortex and the ChAT activity in the hippocampus had some changes in rats in the HLS model group. After administration of KXS 0.6g/kg for two weeks, the abnormal levels of ROS, 8-OHdG, 3-NT were found reversed in the serum of rats (P<0.05, compared with HLS model group). And KXS 0.3g/kg was found reversed the increased AChE activity in the cortex. CONCLUSIONS: Experimental results from this study show that KXS may improve memory deficiency induced by HLS, its mechanisms are major related to antioxidant activities, rather than the central cholinergic system.

The effect of mechanical stimuli on numerical simulation of bone remodeling / 医用生物力学

Objective To study the effect of three different kinds of mechanical stimuli (i.e. strain energy density, equivalent stress and equivalent strain) on numerical simulation of bone remodeling. Methods A two-dimensional finite element model of the proximal femur was constructed. Based on the mechanostat theory and finite element method, the inner structure of the proximal femur and its density distributions under the three different stimuli were predicted. Then the simulation results were compared quantitatively with calculation results obtained from CT images. ResultsThe predicted density distributions on the proximal femur under different stimuli were all well matched with the real structure of the proximal femur. By comparing the values and shapes of the calculated bone density curves, the predictions from the model using equivalent stress as mechanical stimuli were mostly consistent with the CT images. ConclusionsThe equivalent stress might play a leading role in mechano-regulation algorithms of bone remodeling. The accurate prediction of bone remodeling process will provide a theoretical basis for clinical practices such as orthopedic surgery, treatment of bone diseases and personalized design and optimization of prosthesis.

Biomechanical effects on sacroiliac fusion for treating low back pain / 医用生物力学

Objective Based on the finite element method, both sacroiliac fusion and sacroiliac contact models were built to compare the biomechanical differences between the two models and to explore the biomechanical mechanism in the treatment of low back pain by sacroiliac fusion. Methods Two pelvic finite element models were constructed, including the pelvic ring, sacrum, part of the femur, ligaments, cartilage and joint contact. The sacroiliac joints were set to be contact in one model and fusion in the other, respectively. Differences in mechanical conduction on the pelvic ring and the stress on the sacroiliac cartilage under 500 N load between the two models were explored. Results For the fusion model, stresses and displacement on the sacroiliac joint were significantly lower than that of the contact model, especially on the sacroiliac cartilage, where the displacement was reduced by 261% from 0.83 mm to 0.23 mm, and the stresses reduced by 32% from 6.6 MPa to 5.0 MPa. However, the transfer of stress on the pelvic ring was relatively more concentrated in the fusion model. Conclusions Sacroiliac fusion may provide better therapeutic effects on the treatment of low back pain, but the risk of disc herniation and femoral head necrosis must be assessed seriously in advance.