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BACKGROUND: Highway accidents increase year by year, and the most vulnerable area is the neck. Finite element analysis can be used to study the mechanical mechanism of cervical injury. Most of researches focus on the optimization of the model and low-speed collision conditions, but the association of neck injury with cervical tension stress is little reported. OBJECTIVE: To explore the mechanical mechanism of neck injuries caused by traffic accidents, and to compare the von Mises and axial stress of the cervical vertebrae. METHODS: A cervical spine model including cervical vertebrae, intervertebral disc, ligament, muscle, facet joint was set up. The model was validated based on the experimental data of the former impact volunteers. The dynamic response of the cervical vertebrae was achieved using the finite element method (80, 120, and 160 km/h). RESULTS AND CONCLUSION: (1) The established upper cervical model had a high biosimulation, which could be used in studies on the cervical injury and each part injury caused by traffic accidents. (2) Under high-speed post-impact condition, the cervical injury became severe with speed increasing, especially C4level. (3) The axial stress was more available to assess the injury of cancellous bone than von Mises. (4) After high-speed post-impact, the vertebrae diaplaced, especially at 120 km/h, thereby causing articular separation and fracture, further inducing nerve root injury.
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Objective To study the characteristics of mouse-desktop and wrist-desktop contact pressure distributions during different mouse operations, and investigate the influence of desktop on the mouse and wrist during mouse operations, so as to obtain biomechanical references for musculoskeletal disorders of the hand and wrist. Methods The laser scanner and TekScan pressure measurement system were employed to measure contact area and contact pressure of the mouse and wrist during different mouse operations. Results The contact pressure, contact area, and contact force varied with time, and the peak contact pressure of the mouse and wrist with desktop were obtained. The peak contact pressure of the mouse in single clicking of left, right key and scrolling of middle key was 62.87, 33.83, 74.66 kPa, respectively, and for the wrist, the minimum contact pressure appeared in key clicking, being 23.25, 11.02, 16.26 kPa, respectively. Conclusions During mouse operations, the thenar, hypothenar as well as the ulnar and radial sides of the wrist are persistently subjected to the continuous pressure, therefore, repetitive and continuous mouse operation can lead to the development of carpal tunnel syndrome of wrist or other MSDs.
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Objective To study the characteristics of mouse-desktop and wrist-desktop contact pressure distributions during different mouse operations,and investigate the influence of desktop on the mouse and wrist during mouse operations,so as to obtain biomechanical references for musculoskeletal disorders of the hand and wrist.Methods The laser scanner and TekScan pressure measurement system were employed to measure contact area and contact pressure of the mouse and wrist during different mouse operations.Results The contact pressure,contact area,and contact force varied with time,and the peak contact pressure of the mouse and wrist with desktop were obtained.The peak contact pressure of the mouse in single clicking of left,right key and scrolling of middle key was 62.87,33.83,74.66 kPa,respectively,and for the wrist,the minimum contact pressure appeared in key clicking,being 23.25,11.02,16.26 kPa,respectively.Conclusions During mouse operations,the thenar,hypothenar as well as the ulnar and radial sides of the wrist are persistently subjected to the continuous pressure,therefore,repetitive and continuous mouse operation can lead to the development of carpal tunnel syndrome of wrist or other MSDs.
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Objective To investigate effects of 3D co-culture of human keratinocytes (HKC) and human fibroblasts (HFB) under pressure on cell proliferation and collagen synthesis. Methods The HKC and HFB were planted on chitosan-gelatin scaffolds, respectively, for 2 d. The HKC-chitosan-gelatin complex (3D HKC) was cultured at air-liquid interface for 1 d to induce differentiation, and then co-cultured with the HFB-chitosan-gelatin complex (3D HFB) for 12 h. 3.4 kPa pressure was applied on the co-culture group for 24 h. The group of single culture with pressure, the group of single culture without pressure and the group of co-culture without pressure were used as control. HE staining was used to observe distribution and growth of HKC and HFB on chitosan-gelatin scaffolds. MTT method was used to test proliferation of HKC and HFB. Hydroxyproline kit was used to observe collagen concentration of the supernatant fluids. Results HE staining showed that HKC and HFB could grow confluently on chitosan-gelatin scaffolds；3.4 kPa pressure or co-culture both could promote the HKC proliferation and collagen synthesis, while restrain the HFB proliferation and collagen synthesis. Conclusions Pressure and co-culture play an important role in HKC and HFB proliferation and collagen synthesis. This research finding provides some reference for exploring the therapeutic mechanism of hyperplastic scar from clinical operation of resecting scar by transplanting tissue-engineered skin to the wound and then combined with pressure treatment.
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Objective To explore the combined effects of mechanical stretch and interleukin-1β (IL-1β) on gene expression of extracellular matrix in rabbit corneal fibroblasts. Methods Isolated rabbit corneal fibroblasts were subjected to 15% equibiaxial stretch at frequency of 0.1 Hz for 12 h, 24 h and 36 h, respectively, in presence of IL-1β. The gene expressions of matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases 1 (TIMP-1) and collagen type I alpha 1 (Collagen Iα1) were detected by real-time quantitative PCR. Results The mRNA levels of MMP-1, MMP-3 and MMP-9 could be up-regulated by IL-1β alone. However, MMP-1 and MMP-3 mRNA levels decreased with time, while MMP-9, TIMP-1 and collagen Iα1 increased with time. Compared with corresponding IL-1β treatment with mechanical stretch groups, the mRNA levels of MMP-1, MMP-3 and MMP-9 were increased and the mRNA levels of TIMP-1 and collagen Iα1 were decreased in a time-dependent manner. The mRNA level of Collagen Iα1 was decreased by loading mechanical stretch alone, and would further decrease time-dependently in combination with IL-1β treatment. Conclusions Mechanical stretch combined with IL-1β may facilitate the corneal tissue damage, thereby contribute to the development of keratectasia.
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Cytoskeleton can cause active deformations and resist passive deformations which related to some active deformations of cells known as mitosis. Mitosis occurs through a series of stereotypical shape changes resulted in the mechanical separation of a mother cell into two daugther cells, accompanied by mechanical phenomena throughout the whole course. As a molecular motor of cytoskeleton, myosin II is a kind of multifunctional protein that can participate in mitosis. To make deep study on the roles of myosin II in mitosis could get important theoretical and application value. This paper will sum up the recent research achievements on roles of myosin II in mitosis.
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Objective To determine whether the alteration of cytoskeleton interfere with the mechanical properties of normal rat kidney cells (NRKCs).Method NRKCs were treated with cytochalasin D, colchicine and blebbistatin using micropipette aspiration technique, and the changes in Young’s modulus and viscoelasticity of NRKCs were assessed. Results The Young's modulus of is significantly decreased after treated with all cytoskeleton inhibitors. Compared to the control, the viscoelasticity is significantly decreased in NRKCs treated with cytochalasin D and blebbistatin, but in not in colchicines treated cells. Conclusions The effect of blebbistatin on NRKCs mechanical properties is independent of cytoskeleton. Inhibition of assembling of actin meshwork or the activity of myosin II ATPase will reduce cell's Young's modulus and viscoelasticity. In addition, microtubule assembling is correlated with Young's modulus rather than viscoelasticity.
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A lot of experimental findings have confirmed that: Animal cells acquire a spherical shape just before the division; Under biochemical stimulus of mitotic apparatus aster the cells form a contractile ring in equator plane, and the mother cell divides into two daughter cells; meanwhile the total volume keeps constant. In Zinemanas and Nir's model the reorientation of microfilament and the visco-elasticity of cortex have been took into consideration. In our present work, the effective coefficient m due to biochemical stimulus was incorporated into the model, and the local distribution C was modified to diffuse with the plasma membrane motion. The numerical results showed that the formation of a contractile ring and parameters such as the surface tension in the furrow and internal pressure can be predicted successfully. Compared with Zinemanas and Nir's model, the results of our model are more correspondent with the experimental results. It can be concluded that the effective coefficient m has limited effects on the process control of cytokinesis.