Abstract:Objective To study the effects of ligustrazine and shear stress on the apoptosis of suspending vascular endothelial cell. Methods Rat cerebral microvascular endothelial cell (rCMEC) cultured in vitro was used. The administration of the drug incorporated with different levels of shear rate introduced by rotational cone plate shear generator. The influences of ligustrazine and shear rate on the apoptosis were determined by the immunofluorescent of Annexin V-FITC/PI with flow cytometer. Results The analysis of variance shows that ligustrazine and shear rate can affect the apoptosis rate of suspending rCMEC significantly. Ligustrazine can restrain apoptosis rate, high shear rates can raise apoptosis rate;however, there is no interaction between ligustrazine and shear rate. The t test shows that ligustrazine(31.5～126μg/ml) has no significant effect on suspending rCMEC apoptosis at zero shear rate. However, high shear rates (6000, 8000s -1 ) can induce apoptosis which can be significantly inhibited by adding ligustrazine. Conclusion The results indicate that a suitable dose of ligustrazine can distinctly restrain vascular endothelial cell apoptosis induced by high shear rates.

Abstract:Objective To investigate the stress relaxation response of bony tissue under constant displacement loading. Methods A modern porous medium model was developed to do the research on the mechanical behavior of fluid saturated living bone tissue based on the mixture theory by using the Laplace transform technique. Results A one dimensional governing equation is derived for the case of a linear poroelastic solid skeleton saturated with viscid bony fluid. The result shows that the bone tissue is provided with certain features similar to those appearing in viscoelastic solids, which means the responses do not only depend on time, but also depend on previous loading history. Conclusion Viscoelastic behavior and energy dissipation of cancellous bone are depended on the flow and diffusion rate of the fluid composition in bone.

Abstract:Objective To repair critical sized meniscal defects in an immunocompetent mammal by tissue engineering approach and to discuss its biomechanical relevance. Methods Fifteen 45 day old Changfeng crossbred pigs were selected as experimental animals. Autologous fibrochondrocytes were obtained from left knee meniscus by modified Klagsbrun's method and were proliferated in vitro to a proper amount. A 1 cm long full layer defect of right medial meniscus was created anterior to the medial collateral ligament. PGA fibrochondrocyte pluronic complex, fibrochondrocyte pluronic complex or PGA only was respectively implanted into the defects. We used intact menisci and untreated meniscal defects as a control group. Samples obtained in 9w, 16w, 25w and 36w respectively were evaluated by macroscopy, histology, biochemistry and biomechanics. Results From the sights of macroscopic morphology, histological structure and Young's modulus (69.5% of normal meniscus at 36w), the PGA cell pluronic complex can form the best quality tissue, which can stabilize the GAG ratio (58.3% of normal cartilage at 36w) in the cartilage of medial femoral condyle. Conclusion Under a favorable mechanical circumstance, autologous tissue engineered fibrocartilage is a promising method to regenerate or reconstruct menisci, thus preventing the knee from degeneration.

Abstract:Objective To study of the dynamic role of both positive and negative feedback reactions in blood coagulation.Methods A kinetic model is developed for the reactions of central blood coagulation. Results The system has positive solution only ifβ≥β 0(which exists, but can not be obtained easily by simulation);The concentration of Xa transmits from oscillating slightly to a positive solution to gradually increasing to a positive solution; If κ 3 is over 8 times of its normal level, the system has periodic solution.Conclusion It is evident that Xase must exceed a threshold value to amplify blood coagulation, and the value increases as the concentration of APC increases. Furthermore, after studying the relation of oscillation and periodicity to APC, we found that oscillation may occurs under pathology. In addition, according to mathematics law, we gave the theory base for haemophilia therapy.

Abstract:Objective The purpose of this paper was to investigate the effects of acyclic exercise and manipulation on the biomechanical properties of patellar ligament of rabbits. Methods The rabbits underwent acyclic exercise for 3 weeks by an electric cage method and received the manipulations to the rear limbs at the same periods.Results Acyclic exercise increases the velocity of stress relaxation, reduces the elastic modulus of rabbit patellar ligament. In addition, the strain in stress-strain curve shifted to right. The manipulation had a beneficial effect for recovery of these biomechanical behaviors. Conclusion The acyclic exercise induces the relaxation of ligament and the manipulation can prevent it.

Abstract:Objective To study the circumferential stress strain properties of layered esophagus in vitro.Methods A total of 8 male Wister rats were anesthetized and the esophagus were marked on the surface in vivo, excised and placed into the calcium free Krebs solution with dextran and EGTA added. The middle parts of the esophagi were selected for distention test and were separated into inner (mucosa and submucosa) and outer (muscle) esophagi. In distention tests the intact and layered esophagi were elongated to the in vivo length respectively with the pressures were applied in a ramp way at the rate of 2 cm H 2O per minute. The stresses and strains were computed from the morphometric data obtained from the images using the definitions by Kirchhoff and Green. Zero stress state was used as the initial reference for the stress strain analysis. Results The esophagus shortened axially by 24% after excision. The circumferential stress strain curves in intact and layered esophagus fitted well to mono-exponential function: τ=(τ *+β)e α(ε-ε *) -β(determination coefficients >0.96). Comparing the stress strain curves of intact esophagus, the curves of inner esophagus were shifted to the left ( P<0.05 ); and the curves of outer esophagus were shifted to the right (P >0.05). The differences between the curves of the inner and outer esophagus were also significant (P <0.05).Conclusion The circumferential stress-strain properties of the intact and layered esophagus showed non linearity. The inner esophagus is stiffer than the outer and intact esophagus.

Abstract:Objective Through controlling the liquid capacity and liquid resistance in an apparatus of endothelial cells' shear stress testing to simulate a physiological condition of the body for endothelial cells. Methods Bases on the hydrodynamics and hemodynamics theories, the liquid capacity and liquid resistance were calculated. Results This apparatus can clearly simulate hemodynamic environment coincided with the physiological condition of the body and regulate the values of the shear stress, vertical stress and pulsatile amplitude ,pulsatile frequency of the vertical stress. Conclusion The liquid capacity and liquid resistance in testing apparatus of endothelial cells' shear stress can simulate a fidelity physiological condition of the body for endothelial cells.

Abstract:Objective To assess the efficiency of intra oral comprehensive anchorage on the reinforcement of stability of molar segments. Methods 15 adolescents with Class I severe anterior crowding were included for the trial. The comprehensive anchorage package, which consisted of the transpalatal arch(TPA), banding of second molars and the canine laceback, was adopted simultaneously to maintain the integrity of molar relations. Quantitative cephalometric analysis was conducted for the evaluation of the anchorage efficacy. Results Minimal mesialization of anchorage molars was verified by evaluation measurements of Ptm 6, So 6 AP ; 6 PP,MP FH and ANS Me, indicating a strong consolidation of molar anchorage.Conclusion A comprehensive employment of intra oral anchorage reinforcement comprised by TPA, second molar banding and canine laceback might lead to a sufficient resource for anchorage control.

Abstract:Objective To evaluate the Biomechanical characteristics of the SSRF in the treatment of lumbar spondylolisthesis.Methods Five fresh cadaver specimens were used in the studies. The spinal intensity ,stiffness and stability by using experiment mechanics analysis methods after SSRF interfixation in the treatment of lumbar spondylolisthesis contrast with those after Steffee steel plate interfixation ,MSF interfixation and SF interfixation. Results The spinal average intensity and stiffness after SSRF interfixation in the treatment of lumbar spondylolisthesis is higher than those of normol specimens and those after Steffee steel plate interfixation ,MSF interfixation and SF interfixation. The spinal ultimate stength after SSRF interfixation in the treatment of lumbar spondylolisthesis is higher than those after Steffee steel plate interfixation ,MSF interfixation and SF interfixation.Conclusion The biomechanical characteristics of SSRF device are superior to those of Steffee steel plate ,MSF interfixator and SF interfixator. It is effective and safe for the treatment of lumbar spondylolisthesis .

Abstract:Objective To investigate the biomechanical behavior of human knee meniscus. Methods Human fresh meniscus was obtained from death fresh bodies caused by fulminant trauma. One-dimensional tensile test and stress relaxation test were performed. Results The destructive load?stretchy ratio?Lagrange spreading stress?Lagrange spreading strain were obtained. The data of stress and strain was fitting with polynomial by the least square method. In addition, the equation of stress relaxation was also obtained. Based on Feng YZ's the semi-linear theory G(t) formula, the constitutive equation K(λ,t)=G(t)T (e) (λ) was obtained. Conclusion destructive load in one-directional tensile test is 40±3N, the stretchy ratio is 1.369±0.048, the spreading stress is 7.27±0.59MPa and the strain is 43.8±6.6%; Stress relaxation occurs during the first 1200 second and the stress relaxation curve is the logarithmic relation relative to time.

Abstract:构建组织工程血管是解决临床血管移植物短缺的最好方法。本文概述了组织工程血管的研究简史 ,组织工程血管构建方法。重点讨论了非降解材料和降解材料为支架构建的组织工程血管及全生物化组织工程血管的构建方法和优缺点 ,并初步讨论了组织工程血管构建的力学问题。组织工程血管构建的主要研究方向为在模拟体内力学环境下构建全生物化组织工程血管

Abstract:错 畸形的矫治主要通过矫治器对错位牙施以矫治力 ,使错位牙得到矫正 ,从而恢复和重建平衡的受力关系。作者就目前有关正畸力作用下牙体、牙周组织及牙槽骨的力学反应 ,以及不同类型的矫治力与牙齿移动的关系的研究进展作如下综述。