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Objective To investigate the distribution of streaming potential generated by interstitial fluid flow in articular cartilage and obtain electrical characteristics of articular cartilage. Methods The governing equation of fluid and electrostatic theory were combined to establish a two-dimensional (2D) micro-element model of cartilage, and the steady streaming potential generated in microelement under certain pressure was calculated by finite element method. Results The streaming potential in micro-pore model of articular cartilage with the length of 5 μm was about 38.4 μV. The effect of external pressure and Zeta potential on streaming potential of articular cartilage model was significant and showed a linear increase relationship. The streaming potential decreased with the increase of ion number concentration, but the concentration had different effects on streaming potential of articular cartilage. When the ion number concentration was low, streaming potential was more dependent on ion number concentration. When ion number concentration was high, the effect of ion number concentration on streaming potential was very small. Conclusions The results of this study provide important theoretical basis for differentiation and proliferation of chondrocytes, prevention and treatment of articular cartilage diseases, development of tissue-engineered cartilage and repair of articular cartilage injury by means of electric current, electric field and electromagnetic field stimulation.
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BACKGROUND: Resistance training has been shown to help improve bone mineral density in postmenopausal women with osteoporosis. However, it remains to be studied whether the exercise mode, training intensity, training time, and training frequency of resistance training, and the combination with different modes (such as aerobic exercise) is better. OBJECTIVE: To evaluate the effect of resistance training on bone mineral density in postmenopausal women with osteoporosis. METHODS: Randomized controlled trials related to resistance training intervention on bone mineral density in postmenopausal women with osteoporosis were collected. Subjects were divided into resistance training group and blank control group. PubMed, EMBASE, Web of Science, CNKI and Wanfang database were retrieved from inception to December 2019, and relevant references of included literatures were searched. Two researchers screened the literature according to inclusion and exclusion criteria and valid data were extracted for quality evaluation. The included literature data were meta-analyzed by RevMan5.3 software. RESULTS AND CONCLUSION: (1) Finally, 23 randomized controlled trials were included. The risk bias evaluation results of the included literatures showed that the overall literature quality was above medium. (2) The results of meta-analysis showed that compared with the blank control group, the resistance training group had significant effect on the improvement of bone mineral density of lumbar spine [SMD=0.02, 95%CI (0.01,0.03), P < 0.000 1], bone mineral density of total hip [SMD=0.25, 95%CI (0.06, 0.44), P=0.03], bone mineral density of femoral neck [SMD=0.28, 95%CI (0.12,0.04), P=0.000 5], and bone mineral density of greater trochanter [SMD=0.02, 95%CI (0.00, 0.03), P=0.02]. (3) Resistance training is beneficial to maintain the bone mineral density level of postmenopausal women with osteoporosis, and can be an important part of exercise therapy for postmenopausal women with osteoporosis.
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Objective To study the effects of collagen fiber bundle on mechanical properties of articular cartilage, so as to provide references for clinicians to guide the rehabilitation of patients with early cartilage injury. Methods The two-dimensional (2D) numerical model of fiber-reinforced porous viscoelasticity was established, with consideration of the relationship of fiber distribution, elastic modulus, porosity and permeability with cartilage depth. The influences from local fracture of the fiber bundle, the progressive fracture from the surface and the fiber bundle size on mechanical properties of the cartilage were studied, and the maximum principle strain of cartilage matrix was obtained. Results The maximum principal strain of the matrix occurred at a position in middle layer of the cartilage, about upper 1/3 of the cartilage, which was not affected by fiber breakage mode and fiber bundle size. The strain of the cartilage with thicker fiber bundles decreased. Conclusions The middle layer of the cartilage was prone to mechanical damage. The thicker fiber bundle could reduce the maximum principal strain of the matrix. Once the fiber bundle broke, the maximum principal strain of the cartilage matrix with thicker fiber bundle became larger, leading to an easier evolution of the cartilage damage.
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BACKGROUND:Angiotensin II receptor antagonists have been found to exerct a stronger protective effect on bone than angiotensin converting enzyme inhibitors. OBJECTIVE:To investigate the effect of different concentrations of irbesartan (angiotensin II receptor antagonist) on the differentiation and mineralization of mouse preosteoblasts. METHODS:Mouse preosteoblast cel lines MC3T3-E1 in logarithmic phase were selected and cultured in the osteogenic induction medium containing 0 (control group), 0.001, 0.01, 0.1 mmol/L irbesartan, respectively. Ten days later, the cel differentiation was observed by alkaline phosphatase staining. The mineralization was observed by alizarin red staining after 21 days of culture. mRNA expressions of osteocalcin, alkaline phosphatase and Runt-associated transcription factor 2 in osteoblasts were detected by real-time PCR at 1, 4, 7, 14 and 21 days of culture. RESULTS AND CONCLUSION:The activity of alkaline phosphatase in al the irbesartan groups (0, 0.001, 0.01, 0.1) was higher than that in the control group (P<0.05), which was the most obvious in 0.01 mmol/L. The number and area of calcium nodules in each irbesartan group were significantly higher than those in the control group (P<0.05), especial y in 0.01 mmol/L. Compared with the control group, 0.01 mmol/L irbesartan significantly upregulated the mRNA expressions of osteocalcin, alkaline phosphatase and Runt-associated transcription factor 2 (P<0.05). These results suggest that 0.01 mmol/L irbesartan significantly promotes the differentiation and mineralization of osteoblasts.
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Objective To discuss clinical factors associated with high serum bilirubin level postoperatively in patients with liver cancer. Methods In this study,130 postoperative cases of primary liver cancer were divided into two groups of high serum bilirubin and of normal bilirubin according to serum bilirubin level during two weeks of postoperation. Results Preoperative serum bilirubin、 Child grade、 operation time、 blood loss and types of hepatic vascular exclusion were correlated with the level of postoperative serum bilirubin. Types of hepatic vascular exclusion was a independent factor predicting postoperative elevation of serum bilirubin level. Conclusions Preoperative liver function, operation time, types of hepatic vascular exclusion and blood loss are all among factors influencing postoperative serum bilirubin level.