Control of the gliding directions of kinesin-driven microtubules (MTs) in vitro has good feasibility for the development of nano-scale transport systems. A requirement for the control of transporters in these systems includes detecting the positions of gliding MTs; however, no studies have reported on the monitoring of the positions of gliding MTs. Here, we suggest an algorithm to detect tip coordinates of gliding MTs by binarization, skeletonization, and filtration of fluorescent images of MTs. The algorithm was first applied to artificially drawn segments with given lengths (10-80 pixels), widths (1-10 pixels), and curvature radii (20-120 pixels) to verify the effect of the sizes of MTs on accuracy of tip coordinates extracted by the algorithm, and error was estimated by referring to the true coordinates. The estimated errors were as small as 2 pixels in the width and were not affected by the length and the curvature radius, indicating that our algorithm is useful to extract the tips of MTs. The algorithm was subsequently applied to images of gliding MTs. Since distances from the trajectories of the MTs to the centers of gravity of the MTs (3.7 ± 2.1 pixels) were significantly larger than those to the tips (1.9 ± 0.5 pixels), the use of the tips as representative points of gliding MTs was verified. A detection method using tips of MTs, as suggested in this study, may be a useful technique for monitoring each MT in nanoscale transport systems.

Keywords

Image Analysis, Tip Detection, Microtubule, Kinesin, Nano-Scale Transport System

Paper information

Shukei SUGITA, Naoya SAKAMOTO, Toshiro OHASHI and Masaaki SATO, “Novel Image Analysis for Trajectory of Microtubules Gliding on Kinesins with Tip Detection”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.404-414 . doi:10.1299/jbse.4.404

Displacement of actin filament and its binding proteins in mouse myoblasts under locally applied deformation was analyzed by manual method or digital image correlation method. Cyotoskeletal components labeled by immunofluorescent technique or green fluorescent protein-fused protein were deformed via the movement of a glass needle which was poked into a cell. First, we confirmed the digital image correlation method is able to use to analyze displacement map by comparison of the manual method. Next, we examined whether the applied deformation isotropically propagates into cell body. At focal adhesions, fluorescent signals from the deformed area unchanged under the application. Mainly, focal adhesions around the poked area were moved to the direction of the movement of the needle. In addition, some adhesions away from the poked area were moved. Similar results were observed in phalloidin-stained cells. Finally, we applied the local deformation to live cells. However, displacement at the locally deformed area was not observed due to the disappearance of fluorescent signals. These results indicate that applied deformation propagated heterogeneously into a cell, and may imply that biochemical signals disrupt actin fibers under local deformation.

Keywords

Mechanical Loading, Digital Image Correlation Method, Cytoskeletal Network, Remodeling

Paper information

Takeomi MIZUTANI, Kenichi DOI, Yasuyuki MORITA, Masakazu UCHINO, Mitsugu TODO, Hisashi HAGA and Kazushige KAWABATA, “Displacement of Actin Filament and Actin Binding Proteins under Local Deformation Processed by Digital Image Correlation Method in a Myoblast”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.415-422 . doi:10.1299/jbse.4.415

Propelling handcart tasks, such as pushing a wheelchair with an occupant or a handcart with heavy objects are well seen and met in our daily life and occupational works. Office workers and attendants in propelling wheelchairs are physically weaker than workers in industries. Also, aged persons propelling wheelchairs for aged spouses increase in recent aged society in advanced industrialized countries around the world. In this paper, we proposed the linear signal model of worker-cart system based on steady propelling state, and produced the experimental device for investigating the propelling activity in daily life. We analyzed the mechanism of the steady propelling behavior at steady state with the model and device. From experimental results with three subjects in his 20s, we found followings; The proposed model is useful in walking speed 1km/h above. Maximum estimated forces by single leg is around 50N against maximum road resistance, and the force decreases proportionally in walking speed 1km/h above against the decrease of the resistance. Also, autonomous natural pushing force in maximum mechanical power 25-40W, are carried out under exercising heart ratio (EHR) 30%, which shows light load activity to be able to continue over 20min.

Keywords

Handcart, Propelling Activity, Worker-Cart Model, Autonomous Propelling, Subjective Exercising Heart Ratio

Paper information

Tatsuto SUZUKI and Hironobu UCHIYAMA, “Investigation of the Light Load in Propelling a Handcart on Various Road Resistances”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.423-433 . doi:10.1299/jbse.4.423

The purpose of this study is to test a hypothesis that involvement of the low-magnitude, high frequency strain components in the walking-induced bone strain is essential to elicit the osteogenic response of osteoblasts to the bone strain. To this end, a strain waveform recorded in vivo on a radius of a walking dog (original strain) was used to stimulate osteoblasts cultured in a porous, hydroxyapatite-deposited collagen matrix. The cells were loaded under three different strain waveforms: the original strain with 0 - 50 Hz components, and low-pass filtered strains limited to either 0-5 Hz components or 0-2 Hz components. We found that the original strain and the 0-5 Hz strain elevated significantly mRNA levels of stress-sensitive or bone-formation related genes such as c-fos, cyclooxygenase 2, egr1 and osteocalcin. There was no significant difference between these two strains in the mRNA levels. The 0-2 Hz strain increased significantly only osteocalcin mRNA level, but the level was about 30% of those in the original and the 0-5 Hz strains. It was concluded that involvement of strains from 2 to 5 Hz is essential, but high-magnitude, lower frequency strains from 0 to 2 Hz and low-magnitude, higher frequency strains from 5 to 50 Hz are not, to elicit the osteoblastic response to the walking-induced bone strain.

Keywords

Osteoblasts, Mechanical Loading, 3D Culture, in Vivo Bone Strain, High Frequency Strain, Fluid Flow

Paper information

Shigeo M. TANAKA and Hui B. SUN, “Walking-Induced Bone Strain Stimulates Cultured Osteoblasts Accompanied by the Low-Magnitude, High Frequency Components”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.434-442 . doi:10.1299/jbse.4.434

Hip protectors can reduce the incidence of hip fractures. However, low user acceptance and compliance in use remain a major obstacle in the effective use of hip protectors, due to its discomfort and extra effort needed to wear it, etc. A leak-allowed air cushion is an air-bubble cushion designed to have one or some orifices on the side. In this cushion, an impact load is shunted to open air with airflow through orifice(s), and the energy is dissipated by the friction of the airflow. With the lightness, the flexibility, and the inexpensiveness, this cushion has a potential to be accepted by the target users at high levels of compliance. The purpose of this study was to evaluate a potential of the cushion as a hip-protector material by comparing with other three commercially-variable impact attenuation materials: polyethylene elastmer; silicon gel; and porous polyurethane. To this end, we performed impact tests for pads made of the materials using a falling-mass impact loader. The pad made of leak-allowed air cushions reduced the peak impact force from 7700N (recorded with no pad) to 1213 N, which was 38―64 % lower than the attenuated peak forces recorded in the other material pads. We concluded that the leak-allowed air cushion could be a novel hip protector material with high capacity of impact-force attenuation.

Keywords

Hip Protector, Air Cushion, Impact Attenuation, Hip Fracture, Osteoporosis

Paper information

Shigeo M. TANAKA, Shinobu TANAKA, Takehiro YAMAKOSHI, Masamichi NOGAWA and Ken-ichi YAMAKOSHI, “A Novel Hip Protector Material With High Impact Force Attenuation: Leak-Allowed Air Cushion”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.443-455 . doi:10.1299/jbse.4.443

To get a deeper insight into the factors affecting the vascular hemodynamic, the propagation coefficient (γ) should be calculated. However, results from estimated method of this quantity are conflicting. Using numerical tools, three methods permitting an estimation of this complex number were investigated. We studied the influence of peripheral resistance, fluid and wall viscosities, stiffness, cross-sectional area, vessel length and measurements errors on the accuracy of these methods. Results obtained from this analysis demonstrated that the three methods provide exact value of propagation coefficient when analysing accurate flow velocity and diameter data. Conversely, in realistic condition (i.e. inaccurate data) significant errors related to the degrees of inaccuracy within the data arise. These errors are systematically larger on the values of propagation coefficient obtained by the three-point method than the error on the values calculated by two-point methods. Hence, we believe that difference in sensitivity of each method to the measurements errors may be the main source of the disparity of results reported in literature. In addition, the small value of attenuation and time lag seem to be the sources of the large difference between calculated and theoretical values of this parameter. Our finding doesn't support previous works which attributed the disparity of results to the high reflection or/and to the failure of the methods themselves. In realistic condition, it seems that two-point methods are more reliable than the three-point method for the estimation of the true propagation coefficient.

Keywords

Propagation Coefficient, Numerical Simulation, Phase Velocity, Attenuation

Paper information

Khaled BEN ABDESSALEM, Saber BEN ABDESSALEM and Wasila SAHTOUT, “Comparison of Linear Methods for the Determination of Propagation Coefficient in Arterials Systems: Numerical Investigation”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.456-467 . doi:10.1299/jbse.4.456

The maximum peak value of traction coefficient between a shoe sole and a floor at heel-strike period |Fh/Fn|h and that at toe-off period |Fh/Fn|t for normal-style and Nanba-style walking were investigated in this paper. The Nanba-style walking is known as Japanese traditional walking style. The characteristics of the Nanba-style walking different from the normal-style walking are knee flexion, anteversion of the upper body and small swing of the arms. Gait experiments were carried out on a dry level walkway. Four healthy male adults participated in the gait experiments, and they were asked to walk in the normal-style and the Nanba-style walking under a wide range of step length and walking speed. Ground reaction forces and full body kinematics were captured. The results indicated that |Fh/Fn|h of the Nanba-style walking was significantly (p<0.05) smaller than that of the normal-style walking under a wide range of walking conditions. Kinematic analysis of the Nanba-style walking indicated that reduction in friction requirement for such walking style would be due to anteriorly displacing the whole body COM as compared with that of the normal-style walking, resulting in decrease of the distance between the whole body COM and the COP in horizontal-plane. While a statistically significant difference of |Fh/Fn|t between these two walking styles were not observed, mean |Fh/Fn|t of the Nanba-style walking was smaller than that of the normal-style walking under a wide range of walking conditions.

Keywords

Biomechanics, Slip, Body Center of Mass, Center of Pressure, Fall, Gait, Nanba-Style Walking, Normal-Style Walking, Traction Coefficient, Tribology

Paper information

Takeshi YAMAGUCHI and Kazuo HOKKIRIGAWA, “Experimental Analysis of Slip Potential in Normal-Style Walking and Nanba-Style Walking”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.468-479 . doi:10.1299/jbse.4.468