Effects of X-ray on fibroblast mechanical properties

Concerning the widespread use of X-rays to detect various diseases, such as oral and dental ones, it is essential to study the effects of this radiation on living cells. From the past, genetic effects and cell death because of X-rays have been studied. In addition, the effect of this ionizing radiation on the mechanical properties of the cell and cytoskeleton has been studied, but different results have been obtained based on different models. In this study, post-culture gingival fibroblast cells were classified into two groups of control and radiation with Nano Magnetic Particles functionalized by folic acid. The cells of the radiation group were exposed to X-rays of 3 mGy·cm2 . The specimens were undergone static creep test by a magnetic tweezer. Spring and damper coefficients were obtained based on the viscoelastic solid modeling. The static and dynamic stiffness of the groups was also calculated. The maximum deformation was decreased after radiation from 0.049 ± 0.01 µm to 0.029 ± 0.01 µm and the static stiffness of the model was 1.6 times decreased. Also, the gel point frequency for the control group was 27 Hz and for the radiation group was 7.5 Hz. The results show that the static and dynamic stiffness of the cells decreases after radiation, and less deformation appears in the cells after irradiation. These changes can be due to the breakdown of membrane chemical bonds and activation of actin fibers after radiation

Influence of Whole-Body Vibration on Dynamic Response of Lumbar Spine after Transformal Lumbar Interbody Fusion

Introduction: Occupational whole body vibration (WBV) plays a major role in determining dynamic responses of the lumbar spine. WBV has been shown to cause low-back problems and degenerative disc diseases. Fusion surgery such as trans-formal lumbar inter-body fusion (TLIF) have been widely utilized to treat such disorders. Materials and Methods: In this study, finite element method (FEM) was used to investigate dynamic responses of the lumbar spine due to WBV with the frequency in the range of regular physiologic activities after TLIF. A FE model of the L1-L5 lumbar spine was modeled and cyclic loading with the frequency of 1 Hz and 5 Hz were exerted to the model. Then, the disc bulge and stress distribution on the annual ground substance and vertebral bodies were measured.Results: It was observed that the maximum disc bulge (MDB) and maximum von-Mises stress (MMS) occurred in proportion to the loading frequency; overall, in the 5 Hz model, MDB and MMS were detected to happen 5 times more frequently as compared to the 1 Hz model. However, the magnitude of MDB and MMS were not generally affected by the loading frequency. Conclusions: It can be concluded that different frequency of WBV, although in the physiologic range, can alter dynamic responses of the lumbar spine and, thus, their fatigue behavior. In the results can be of assistance to broaden the understanding regarding the dynamic responses of the lumbar spine during WBV after TLIF

Effects of external loading on lumbar extension moment during squat lifting

Objectives The main objective of this study has been qualitative investigation of the effects of external loading on the lumbar extension moment during squat lifting. Findings of this study may allow to determine the factor with the most considerable effect on the lumbar extension moment and may help determine the lumbar spine risk factors at temporo-spatial coordination during squat lifting. Material and Methods Twelve healthy men volunteered to perform slow and fast squat lifting of a box of varied mass (4 kg, 8 kg and 12 kg). The eight-channel electromyography was applied to detect the activities of abdominal (rectus abdominis and external oblique) and lower back muscles (iliocostalis lumborum and multifidus). The lumbar extension moment was calculated using 3D linked segment model. Ground reaction forces and kinematic data were recorded using a Vicon system with 2 parallel Kistler force-plates. Results Significant increases (both p-values 0.05) were detected between the lumbar angles related to the lower trunk muscles peak activities and lumbar angle related to the peak lumbar extension moment in most of the lifts. Conclusions According to the findings, the inertial force of the lifted box is the most important factor that affects the lumbar extension moment during squat lifting. Moreover, critical lumbar angles are seemingly those ones in which the lifted box reaches the peak acceleration. Int J Occup Med Environ Health 2017;30(4):665–67