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BACKGROUND: Pulsed electromagnetic fields, as an important physical therapy, are exactly effective in the treatment of osteoarthritis, but the mechanism has not been fully clarified. OBJECTIVE: To observe the effect of pulsed electromagnetic field on the degeneration of knee joint cartilage in aged rats. METHODS: Eight 6-month-old Sprague-Dawley rats were selected as the young group and were subjected to normal diet with no treatment. Sixteen 22-monthold Sprague-Dawley rats were randomly divided into old group (n=8) and pulsed electromagnetic field group (n=8). The rats in the pulsed electromagnetic field group were subjected to a pulsed electromagnetic field intervention, once a day, 5 days per week for continuous 8 weeks. The rats in the old group were given no treatment. All rats were anesthetized and executed after 8 weeks for the detection of relevant indexes. RESULTS AND CONCLUSION: Compared with the young group, serum type II collagen C-terminal peptide level was increased in the old group (P < 0.05); compared with the old group, serum type II collagen C-terminal peptide level was decreased in the pulsed electromagnetic field group (P < 0.05). Micro-CT showed that the bone volume fraction, bone mineral density, and number of bone trabeculae decreased (P < 0.05) and the trabecular separation increased (P < 0.05) in the tibia of rats in the aged group compared with the young group; and the bone volume fraction, bone density, and number of trabeculae increased (P < 0.05) and the trabecular separation decreased (P < 0.05) in the tibia of rats in the pulsed electromagnetic field group compared with the aged group. The tibial plateau Safranin O-fast green staining showed that the articular cartilage structure of rats in the aged group was disorganized, and the number of chondrocytes was obviously reduced, and the tidal line could not be distinguished. The above results were improved in the pulsed electromagnetic field group. RT-qPCR and western blot assay showed that the mRNA and protein expression levels of matrix metalloproteinase 1, matrix metalloproteinase 13, P53 and P21 in the articular cartilage and subchondral bone of rats were elevated in the aged group compared with the young group (P < 0.05) and decreased in the pulsed electromagnetic field group compared with the old group (P < 0.05). To conclude, pulsed electromagnetic fields may improve osteoarthritis in aged rats by inhibiting chondrocyte senescence, alleviating articular cartilage degradation and inhibiting subchondral bone osteoporosis through suppressing the expression of P53/P21. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Tissue Engineering Research / Zhongguo Zuzhi Gongcheng Yanjiu is the property of Chinese Journal of Tissue Engineering Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Tissue Engineering Research / Zhongguo Zuzhi Gongcheng Yanjiu is the property of Chinese Journal of Tissue Engineering Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the improvement of agricultural equipment level in China, agricultural machinery is developing towards large, wide and efficient trend. Large and medium-sized no-tillage sowing equipment can not only reduce production cost, but also meet the agronomic requirements of no-tillage operation in northern China, and can increase crop yield. However, its wide width and heavy weight lead to the problems of difficult transportation and operation transfer. This study is aimed at the practical application of the medium-sized no-tillage mulch and ridge planting corn seeder as the research object. The medium-sized seeder is connected with seven groups of seeding units with row spacing of 650 mm. On the basis of theoretical analysis, the use of digital prototype, virtual simulation technology to determine the right drill transport platform, through the wheel mechanism and traction mechanism to lateral suspension operation, longitudinal traction transportation, land wheel deformation parameters, arrangement of hydraulic, traction mechanism and transmission ratio adjustment, etc. The transmission system can transfer power to fertilizer shaft and seed shaft according to the specified transmission ratio. The hydraulic electric control system is composed of pressure relay and electromagnetic directional valve to reduce the number of oil inlet and outlet and simplify the operation steps. The simulation results show that the synchronization accuracy of the hydraulic cylinder of the ground wheel mechanism is less than 3.6%. The hydraulic electronic control system is easy to operate and can accurately reach the sequence action position, and the synchronization performance is good. The finite element analysis module of CATIA software was used to analyze the stress and strain of the frame and the ground wheel mechanism. The strength of the frame under the braking state during transportation met the requirements. The stress analysis of the ground wheel mechanism showed that it had good strength and stiffness, and there was a large space for optimization. The total mass of the high mobility frame platform is reduced from 244.0 kg to 178.8 kg, and the mass reduction ratio of the auxiliary ground-wheel mechanism is 26.72%, and the mass reduction ratio of the dual ground-wheel mechanism is 10.96%, which can meet the strength and stiffness requirements of the ground-wheel mechanism, and the optimization effect is significant, and can meet the requirements of transportation and operation. The hydraulic electronic control system test and road transportation vibration test show that the whole machine meets the requirements of various indicators, meet the requirements of mid-sized no-tillage mulch and furrow seeder operation transfer, hydraulic electronic control system can control the hydraulic cylinder to complete the sequence of action, the operation state conversion time of 5min, saving the operation transfer time. Through analyzing the vertical acceleration of the road transportation test vibration, the natural frequency of the vertical vibration at the center of mass of the frame increases with the increase of the vehicle speed, and the increase amplitude decreases gradually. When the driving speed is 10, 15 and 20 km/h, the natural frequency of vertical vibration acceleration at the center of mass is concentrated within 0-3 Hz, and the natural frequency of vertical vibration increases with the increase of driving speed, and the vibration intensity increases rapidly. When the driving speed is 25 km/h, the maximum vertical displacement of the vehicle's center of mass is the largest, which meets the requirement of radial pendulum momentum, and the transportation is safe and stable. In this study, the high maneuvering platform technology was applied reasonably to the compact medium no-tillage mulch and ridge corn seeder, which solved the difficult problem of operation transfer and provided reference for the design of transfer platform of wide range agricultural machinery equipment. [ABSTRACT FROM AUTHOR]