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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]

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]

BACKGROUND: There are many treatment methods for knee osteoarthritis, among which electroacupuncture, as an important non-drug treatment, is effective in the treatment of knee osteoarthritis, but its exact mechanism is not clear. OBJECTIVE: Effect of electroacupuncture on the expression of p53 and P21 in articular cartilage and subchondral bone of aged rats with knee osteoarthritis. METHODS: Eight 6-month-old male Sprague-Dawley rats were included in the young group and sixteen 24-month-old male Sprague-Dawley rats were randomly divided into old group (n=8) and electroacupuncture group (n=8). The rats in the electroacupuncture group received electroacupuncture stimulation once a day, 5 days a week, for 8 continuous weeks, and the other two groups did not do any treatment. Eight weeks later, the level of type II collagen C-terminal peptide in peripheral blood was detected by ELISA, the morphology of left knee cartilage and subchondral bone was observed by safranin O-fast green staining, the degree of knee cartilage degeneration was evaluated by modified Mankin’s score, the microstructure of left knee cartilage and subchondral bone was detected by micro-CT, and the expression levels of matrix metalloproteinase 13, P53, P21 mRNA and protein were detected by RT-PCR and western blot respectively. RESULTS AND CONCLUSION: Compared with the young group, the level of C-terminal peptide of type II collagen in the peripheral blood was increased in the old group (P < 0.05). The micro-CT results showed that the bone volume fraction, bone mineral density and the number of bone trabeculae were decreased in the old group compared with the young group (P < 0.05), while the trabecular separation increased (P < 0.05). Safranin O-fast green staining showed that in the old group, the surface layer of cartilage was uneven with fissures, the morphology of chondrocytes was irregular and stained unevenly, the boundary between the cartilage and subchondral bone was blurred, and the matrix loss was serious. The Mankin’s score was higher in the old group than the young group (P < 0.05). The expression of matrix metalloproteinase 13, P53, P21 at mRNA and protein levels increased in the old group compared with the young group (P < 0.05). Compared with the old group, electroacupuncture decreased the level of C-terminal peptide of type II collagen (P < 0.05), increased the bone volume fraction, bone mineral density and the number of bone trabeculae (P < 0.05), and decreased the trabecular separation (P < 0.05). Safranin O-fast green staining showed that in the electroacupuncture group, the surface of cartilage was smooth and red staining was uniform, and the cell morphology and structure were between the young group and the old group. Following electroacupuncture treatment, the Mankin’s score (P < 0.05), matrix metalloproteinase 13 and P21 mRNA expression (P < 0.05), and matrix metalloproteinase 13 and P53 protein expression decreased (P < 0.05), while there was a decreasing trend of P53 mRNA and P21 protein expression, but with no statistical significance (P > 0.05). To conclude, electroacupuncture may delay articular cartilage degeneration and subchondral osteoporosis in aged rats by inhibiting the expression of P53 and P21, so as to protect joints and delay joint aging. [ABSTRACT FROM AUTHOR]

BACKGROUND: Exercise training can maintain bone mass and improve bone mineral density. However, its effect on senile osteoporosis and its possible mechanism are not clear. OBJECTIVE: To study the effects of exercise training on senile osteoporosis and to explore its possible molecular mechanism. METHODS: Sixteen Sprague-Dawley rats aged 24 months old were regarded as the model of senile osteoporosis and randomly divided into elderly model group (n=8) and exercise training group (n=8), while eight young Sprague-Dawley rats of 3 months old were randomly selected as young control group. All rats moved freely in their cages and those in the exercise training group underwent exercise training every day for 8 weeks. After 8 weeks of intervention, serum bone-specific alkaline phosphatase, type I procollagen amino-terminal peptide, tartrate-resistant acid phosphatase 5b and type I collagen aminoterminal peptide were detected using ELISA assay. Bone mineral density of the femur and the fourth lumbar vertebra were measured by dual energy X-ray absorptiometry, while bone microstructural parameters of the tibia and the fifth lumbar vertebra were determined by Micro-CT in each group. mRNA and protein expressions of bone morphogenetic protein 2, Runt-related transcription factor 2, Osterix, and peroxisome proliferator-activated receptor γ in bone marrow of the femur were detected by reverse transcriptase polymerase chain reaction and western blot. RESULTS AND CONCLUSION: Compared with the elderly model group, the serum levels of bone-specific alkaline phosphatase and type I procollagen aminoterminal peptide (P < 0.05), bone mineral density of the femur (P < 0.05) but not that of the fourth lumbar vertebra (P > 0.05), bone volume fraction and trabecular number of the tibia (P < 0.05), and the mRNA and protein expression of bone morphogenetic protein 2, Runt-related transcription factor 2, and Osterix in the femur (P < 0.05) were significantly increased in the elderly model group, while the serum levels of tartrate-resistant acid phosphatase 5b and type I collagen amino-terminal peptide (P < 0.05), trabecular separation of the tibia and the fifth lumbar vertebra (P < 0.05), and the mRNA and protein expression of peroxisome proliferator-activated receptor γ were significantly decreased (P < 0.05). In addition, exercise training could improve the bone volume fraction, trabecular number and trabecular thickness of the fifth lumbar vertebra in rats with senile osteoporosis, although the differences in changes were not always statistically significant (P > 0.05). The trabecular thickness of the tibia had no significant changes after exercise training (P > 0.05). To conclude, exercise training can significantly improve bone mineral density and bone microstructure, promote osteogenic differentiation, and inhibit adipogenic differentiation in aged osteoporotic rats. The mechanism may be related to the bone morphogenetic protein 2/Runt-related transcription factor 2/Osterix signaling pathway. [ABSTRACT FROM AUTHOR]