• Volume 23,Issue 6,2008 Table of Contents
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    • Expression of p-HSP27 in vessel under different frequencies of cyclic tensile strain and its role in the migration of vascular smooth muscle cells

      2008, 23(6):415-419. DOI: 10.3871/j.1004-7220.2008.6.419.

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      Abstract:Objective To investigate the expression of p-HSP27 in vessel and vascular smooth muscle cells(VSMCs) exposed to different frequencies of cyclic tensile strain respectively, and to study its role in the migration of VSMCs.Methods Porcine common carotid arteries were cultured in a blood vessel organ-culture system under pulsatile flow for 24 hours.The frequencies of the flows studied were 0.5 Hz and 1.25 Hz.The mean pressure and flow rate were 15.996 kPa(120 mmHg) and 50 ml/min respectively.Human VSMCs were also subjected to 10 % tensile strain with two different frequencies, 0.5 Hz and 1.25 Hz, using a Flexercell Strain Unit for 12 hours.The expression of p-HSP27 in the vessel and VSMCs under different frequencies of strain was determined by Western blot.The change in VSMC migration after HSP27 RNAi was examined by Transwell under the two different frequencies of mechanical strains.Results The frequency 1.25 Hz activated the phosphatization of protein HSP27 more than the frequency of 0.5 Hz, in turn inhibited the migration of VSMCs.The migration of VSMCs significantly increased after HSP27 RNAi.Conclusion The results demonstrate that the biological frequency, 1.25 Hz, could inhibit the migration of VSMCs by activating phosphatization of protein HSP27 to maintain the biological structure and function of the vessel.

    • Migration and β1 integrin expression of cultured human trophoblast cells exposed to flow-induced shear stress

      2008, 23(6):420-423. DOI: 10.3871/j.1004-7220.2008.6.423.

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      Abstract:Objective During fetal development, trophoblast cells enter endometrial capillaries, migrate against blood stream within the uterine vasculature, and eventually reside within spiral arteries of the human uterus.In this paper, the hypothesis was tested that by regulating the expression of β1 integrin in trophoblast cells, flow-induced shear stress affects the motility of trophoblast cells.Method Early gestation human trophoblast cells were cultured in glass piece and then exposed to steady shear stresses of 0, 75, 150, or 300 Pa for up to 24 h.Then the migration and β1 intergin expression of the cells were measured.Results Result showed that exposure of the cells to shear stress within 24h significantly increased the level of their motility.Shear stress also altered the expression of β1 integrin in trophoblast cell.Conclusion These results suggest that flow-induced shear stress regulates the expression of β1 integrin, in turn affects the motility of trophoblast cells.

    • Estimating compressive strength of hydroxyapatite based on comparison to tested strength of bone,bone without collagens and hydroxyapatite

      2008, 23(6):424-428. DOI: 10.3871/j.1004-7220.2008.6.428.

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      Abstract:Objective To estimate whether the implanted coralline hydroxyapatite(CHA) prepared by hydrothermal conversion of coral can reach the level of compressive strength of bone in vivo, because CHA could be implanted in human body directly and then make the bone tissues grow into their porous structure, which will reinforce their strength.Methods The compressive strengths of CHA, bone with and without collagens are measured respectively to determine the enhancement of collagen to compressive strength of bone.Based on the test results, a typical model for predicting the variation of strength of porous bioceramic with porosity is employed to estimate the compressive strength of CHA with porosity from 0.1 to 0.5.Results The compressive strengths achieved by CHA, bone with and without collagens are 14.1GPa, 207 GPa and 31.7 GPa respectively.Conclusion The compressive strength of bone would decrease 80% after its collagens are eliminated.The strength of CHA may be stronger than that of hydroxyapatite in bone, and its final strength could be able to reach the level of bones with the bone tissue grow up.

    • Study on fabrication and mechanical property of chitosan conduit

      2008, 23(6):429-433. DOI: 10.3871/j.1004-7220.2008.6.433.

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      Abstract:Objective Chitosan has a potential use in tissue engineered blood vessel and nerve regeneration conduit, but it degrades slowly.This research aims at minishing the chitosan conduit wall thickness with its fundamental mechanical property remained so as to shorten its degradation time.Methods Chitosan conduits were manufactured by adding some glycerol and PEG to the original solution and then using immersing-filtering methods.Effects of different molding parameters on chitosan conduit mechanical property were studied.Results Adding appropriate glycerol to original solution was of benefit to improve chitosan conduit's broken stress and broken elongation, but having no apparent effect on its Yang's modulus;the conduit's broken stress, broken elongation and Yang's modulus made of 2% chitosan were higher than that of 2.5% chitosan;with twice immersion-dryness, the conduit's broken stress, broken elongation and Yang's modulus were higher than that of thrice.Conclusion Chitosan conduit's mechanical property could be influenced by the original glycerol, the chitosan content and repeat times, and the best conduit wall thickness could be achieved by optimizing molding parameters.

    • Numerical simulation of tumor-induced angiogenesis incorporating mechanical effects in matrix

      2008, 23(6):434-440. DOI: 10.3871/j.1004-7220.2008.6.440.

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      Abstract:Objective To investigate tumor-induced angiogenesis influenced by the mechanical environments in and out of tumor, and simulate the capillary network numerically.Methods Considering the effects of both endothelia cell(EC) and extra cellular matrix(ECM), it is assumed that ECM to be linear visco-elastic.The displacement of ECM is obtained from force balance equation consisted of EC traction, ECM visco-elastic force and external force.The capillary network in and out of tumor is simulated numerically by discrete equation of EC movement equation.Results Taking account of the influence from the mechanical environment, a relatively realistic capillary network could be obtained.The mechanical factor resulted in a layered structure:at the edge of tumor, numerous capillaries are generated, while the closer to the tumor center, less capillaries there would be.Conclusion Generated by such computer simulations, this theoretical capillary networks correspond with realistic physiology and provide a premise for further research.

    • Mathematical model of hemodynamics with posture

      2008, 23(6):441-445. DOI: 10.3871/j.1004-7220.2008.6.445.

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      Abstract:Objective To set up a novel hemodynamics distributing-parameter model with posture change and study the effect of gravity on pressure of blood flow in a singular vessel.Method To simulate the effect of gravity on pressure of blood flow with different postures by introducing a volume-related force into the conventional hemodynamics model.Result The procedures that gravity affects pressure of blood flow are different due to discriminating postures.Conclusion The novel model established in this study is capable of simulating the effect of posture on pressure of blood flow, which is helpful for our further investigation into the effect of posture on cardiovascular indexes.

    • Joint-robotics-based design of biomechanics testing device on human spine

      2008, 23(6):446-453. DOI: 10.3871/j.1004-7220.2008.6.453.

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      Abstract:Objective To establish a biomechanical robot-based testing device to carry out biomechanical experiment of human spine.Method Use the solidwork software to design the fixture and adopt the socket programming to realize the network communications between PC and robot controller through Visual C + +6.0 platform, reading the position and rotation of the robot-end implementation.A data acquisition card is inserted inside the PC to read the force(torque) in three-dimensional space.The pose and torque data are put into the control procedures and handled, drawing the force-displacement two-dimensional curves to help analyze the experimental results.Result Develop a biomechanical robot-based testing device and the corresponding control software(force control, displacement control, a mixed force/ displacement control) and various kinds of monitoring program.Conclusion Design a new experimental testing device based on the computer control of the 6-DOF Robot and use hybrid force-displacement control method to load the human spine, which could have the organizational structure and the force state of the FSU well tested, and it is easy to identify the spinal degeneration and the load-bearing impact on the organizational structure of the FSU after various types of surgery.

    • Biomechanics experimental analysis on dental cast under orthodontic forces with invisaligner

      2008, 23(6):454-458. DOI: 10.3871/j.1004-7220.2008.6.458.

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      Abstract:Objective By biomechanical research on dental cast with invisible orthodontic appliances, analyze the features of the orthodontic forces and effect of invisible appliances.Method A three-dimensional FE model of dental cast was set up, which includes teeth£?periodontal membrane and alveolar bone.According to the typical movement of teeth in the course of orthodontic, several simulated cases were designed and analyzed numerically.The dental cast's stress and strain with invisible orthodontic appliances were analyzed.And the comparative study was made between the invisible appliance and the traditional fixed aligner.Result Compared the invisible appliance with the traditional fixed aligner, the maximal stress on the dental cast and the changing tendency of stresses are greatly similar to each other.Conclusion The well orthodontics and satisfying the patient's needs for beauty during the course can be gained with the properly designed invisible appliance.

    • Finite element analysis of changes in proximal femur stress after modular hip resurfacing arthroplasty

      2008, 23(6):459-464. DOI: 10.3871/j.1004-7220.2008.6.464.

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      Abstract:Objective To study the biomechanical variation in proximal femoral stress pattern and periprosthetic femoral stresses distribution after modular hip resurfacing arthroplasty.Methods Three-dimensional finite element model of intact femur, traditional prostheses and modular hip resurfacing arthroplasty were developed.Applied with physiological loading and related muscles forces, the stresses changes in proximal femur with implants were analyzed.Results Compared with intact femur, Stress concentrations were located around the stem in traditional model, high stresses occurred in the inferior of femoral neck(sections 4,10), stress shielding were found in the proximal sections(sections 1, 7).While in modular hip resurfacing arthroplasty model, stress concentrations were also located around the stem but lower, stress distribution in sections of 4,10 were closer to the intact condition.Conclusion The modular hip resurfacing arthroplasty may loaded the proximal femur in a more physiological manner and decreased the risk of femoral neck fracture compared with traditional prostheses.

    • Comparative study of stresses on acetabulum after implanted hemisphere and ellipse cup

      2008, 23(6):465-470. DOI: 10.3871/j.1004-7220.2008.6.470.

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      Abstract:Objective To investigate the influence on acetabular stresses after hemisphere and ellipse cup implanted.Methods The same loads are applied on the three-dimensional model of hemisphere cup, ellipse cup and acetabulum respectively to analyze the stresses distribution and then validated it by photoelastic experiment.Results Under the same load conditions, the maximum stress of hemisphere cup was similar with that of ellipse cup, but the later had more uniform stress distribution.Acetabular stresses produced by hemisphere cup were higher than ellipse's, with the similar stresses distribution at the base of acetabulum.Both the concentration stresses were located in the post-lateral region of acetabulum, but there appears an obvious stress concentrative point in hemisphere cup.Conclusion Our findings suggest that acetabular stresses distribution produced by ellipse cup appears more similar as normal actabulum after total hip arthroplasty.

    • Biomechanical analysis of the mandibular osteotomy on the function of mandibular bone and joint

      2008, 23(6):471-474. DOI: 10.3871/j.1004-7220.2008.6.474.

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      Abstract:Objective To analyze the effects of mandibular Osteotomy based on the Orient Classical Beauty Analysis Mask on the functions of mandibular bone and joint.Meanwhile a precise and quick method of the finite element(FE) modeling before the mandibular osteotomy was developed.Methods The CT data from the same patient pre-and post-mandibular osteotomy were obtained and imported into the ScanIP Module(Simpleware, Simpleware LTD., Exeter, UK).And after the segmentation of the interest regions, the two 3D geometrical models were built up, respectively.Then high-quality meshing was performed in the ScanFE module and the two corresponding FE models were solved in the ANSYS to obtain each stress status under the same loading.Results the 3D FE models including mandible and mandibular joint were created successfully, which kept the accurate anatomical shape.By the configuring material properties, setting the boundary conditions and loading the forces on the different areas, the mechanical status of the models under different loading conditions were simulated and shown to be un-similar.Conclusion There were obvious changes on the patient's joint functions after the mandibular Osteotomy based on Orient Classical Beauty Analysis Mask.The 3D FE modeling software Simpleware and other FE analysis solvers could be integrated to make the biomechanical analysis and the pre-operation plan.

    • Musculoskeletal model based method for predicting muscle force and related issues

      2008, 23(6):475-479. DOI: 10.3871/j.1004-7220.2008.6.479.

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      Abstract:The estimation of individual muscle force during movement has been integral to many researches such as musculoskeletal injury prevention and the design of joint prostheses.Static optimization, dynamic optimization and the EMG-to-force are the three model-based methods widely used in literatures.This paper reviews the three methods and the musculoskeletal modeling and the related issues, pointing out that personal musculoskeletal modeling, new algorithms for estimating muscle force and validation of calculated muscle force would be the emphases for the further research.

    • Advances in cortical ingression during early cytokinesis

      2008, 23(6):480-485. DOI: 10.3871/j.1004-7220.2008.6.485.

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      Abstract:Among mechanisms of cortical ingression regarding cytokinesis, contractile ring hypothesis is the most important one.But it is nohow the conclusive one.Some alternative models have been proposed recently and found to be consistent with experimental observations or to be better to interpret biological processes, while some others are still inconsistent with observations.Cytokinesis, as a complicated biological process, appears the nature of biological conservatism and cell-specific diversity.In this article, cortical ingression during early cytokinesis will be discussed.

    • Bone microdamage and associated bone mechanical properties

      2008, 23(6):486-489. DOI: 10.3871/j.1004-7220.2008.6.489.

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      Abstract:Bone microdamage usually appearing in different type of microcracks in the bone matrix as a result of repetitive mechanical loading and can only be identified by microscopy.Histologic observation and quantitative analysis could be done based on the specific staining and labeling.The microdamage could be classified by their morphology and position related to the osteon.Bone microdamage is often accompanied with the decrease of bone strength and the increase of bone fragility.The length and location of the microcracks are the main factors to affect the biomechanical performance of bone.Microdamage accumulation will finally lead to bone fatigue fracture.

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