Journal of Biomechanical Science and Engineering
Online ISSN : 1880-9863
ISSN-L : 1880-9863
Volume 7, Issue 2
Displaying 1-16 of 16 articles from this issue
Papers
  • Motomu NAKASHIMA, Shun MAEDA, Takahiro MIWA, Hiroshi ICHIKAWA
    2012 Volume 7 Issue 2 Pages 102-117
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    In this study, the optimal arm strokes in crawl swimming which maximize the swimming speed and propulsive efficiency were solved computationally. For this objective, an optimizing method which consisted of the random search and the PSO (Particle Swarm Optimization) algorithm was constructed. In order to consider the muscle strength characteristics of the swimmer as the constraint condition of the optimization, an experiment to measure the maximum joint torques was carried out for various joint angles and angular speeds. Using the measured experimental data as the reference values, a musculoskeletal simulation model was constructed. By the constructed musculoskeletal model, muscle strength characteristics in various conditions were investigated and used to create a database. Using this database, the optimizing calculation was finally conducted and the following results were obtained: In the optimization maximizing the swimming speed, the swimming speed became maximum when the stroke cycle was 0.9 s. A relatively I-shaped stroke was obtained in this case. In the optimization maximizing the propulsive efficiency, the propulsive efficiency became maximum when the stroke cycle was 1.3 s. A relatively S-shaped stroke was obtained in this case. Two strokes which respectively maximized the swimming speed and propulsive efficiency were very similar to each other when the stroke cycles were the same. The swimming speeds and stroke cycles obtained in the optimizing calculation were within reasonable ranges compared to the actual races.
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  • Hiromichi NAKADATE, Eiichi SEKIZUKA, Shigeru AOMURA, Haruyuki MINAMITA ...
    2012 Volume 7 Issue 2 Pages 118-129
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    Endothelial cells (ECs) are constantly subjected to shear stress, a tangential stress generated by blood flow, and hydrostatic pressure, a normal stress generated by blood pressure. Using a perfusion system that enables the independent control of flow volume and pressure, we investigated the effect of this combined stress on adhesion molecule expression in cytokine-stimulated cultured ECs. Human umbilical vein endothelial cells were incubated with 25 ng/ml tumor necrosis factor-alpha (TNF-α) for 6 hours. Activated ECs were then exposed to pulsatile flow (a shear stress of 1.5 ± 0.3 Pa, and a hydrostatic pressure of 100 ± 20 mmHg) for 1—24 hours. After exposure to pulsatile flow, endothelial selectin (E-selectin), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) were stained and observed using fluorescence microscopy. Results showed that E-selectin was expressed in approximately 30% of the total ECs after incubation with TNF-α, however, TNF-α-induced E-selectin expression was decreased after 1 hour of exposure to pulsatile flow resulting in E-selectin expression in under 10% of total ECs at 24 hours. VCAM-1 was expressed in approximately 75% of the total ECs after incubation with TNF-α, however, TNF-α-induced VCAM-1 expression was decreased after 6 hours of exposure to pulsatile flow resulting in VCAM-1 expression in approximately 40% of the total ECs at 24 hours. ICAM-1 was expressed in all ECs after incubation with TNF-α, however, TNF-α-induced ICAM-1 expression was decreased after 12 hours of exposure to pulsatile flow resulting in ICAM-1 expression in approximately 40% of the total ECs at 24 hours. These results suggest that combined stress time-dependently suppresses overexpression of cytokine-induced adhesion molecules in ECs.
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  • Kazuaki NAGAYAMA, Akifumi ADACHI, Takeo MATSUMOTO
    2012 Volume 7 Issue 2 Pages 130-140
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    In order to determine how cells change their traction forces at focal adhesions (FAs) under macroscopic deformation conditions, we investigated the dynamic changes in traction force at FAs by culturing porcine aortic smooth muscle cells (SMCs) on elastic micropillar substrates and giving them macroscopic deformation by stretching the substrates. We patterned adhesion region on the top surface of a polydimethylsiloxane-based micropillar array using our original micropatterning technique to align the cells on the pillar array parallel to the stretch direction. SMCs plated on the micropillars successfully spread in the adhesion region and their actin stress fibers (SFs) aligned in the direction to be stretched. Cells were then stretched and released cyclically with strain rates of 0.3%/15s up to 3—6% strain, and deflection of micropillars at both side regions of cells were measured simultaneously to obtain the traction force at each FA in situ. SMCs aligned in the stretch direction showed two types of responses: almost a half of the SMCs changed their force in phase with the applied strain, and showed gradual active contraction with the stretch cycles (synchronous group); and the rest tended to keep their force constant and became elongated with the cycles (asynchronous group). In the asynchronous group, the force sometimes changed in antiphase with the cell strain as if the cells maintain intracellular traction force at a constant level. These results may indicate that SMCs sometimes exhibit active homeostatic responses to keep their pretension constant during macroscopic stretching, and such tensional homeostatic responses may occur concurrently with cell elongation.
    Editor's pick

    ★Paper of the Year 2012
    ★Graphics of the Year 2012

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  • Keunyoung PARK, Youngwoo KIM, Chikara NAGAI, Goro OBINATA
    2012 Volume 7 Issue 2 Pages 141-155
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    Recently, bilateral movement training based on robot-assisted rehabilitation systems has been attracting a lot of attention as a post-stroke motor rehabilitation protocol. Since humans generate coordinated motions based on their motor and sensory system, investigation of the innate properties of human motor and sensory systems may provide insight into planning of effective bilateral movement training in motion. In this study, therefore, we investigate the effects of proprioception and handedness on the movements of the contra-lateral upper limb, under both active and passive robot guidance conditions of the robot manipulators. Active and passive guidance-reproduction based bimanual tasks were used in this study; in these the subject is asked to hold both right and left knobs installed at the end-effectors of two robot manipulators. The results indicate that better reproducing performance was obtained when the proprioceptive input was acquired from the active guidance condition.
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  • Daisuke ITO, Sota YAMAMOTO, Eiichi TANAKA, Koji MIZUNO, Masahito HITOS ...
    2012 Volume 7 Issue 2 Pages 156-167
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    To discuss the mechanism of muscle strain injury from biomechanical viewpoints, the change of mechanical properties of injured skeletal muscle was evaluated experimentally. We induced strain injury to rabbit tibialis anterior muscle by applying a single tension loading/unloading process under the conditions of various stretch amplitude, stretch rate, and muscle activation in situ. The results showed that isometric contractile force decreased with increasing stretch amplitude during the injury-induction process. Multiple regression analyses were conducted for the results and they showed that the stretch amplitude played a dominant role in the decrease of the contractility. The failure stress decreased significantly with the increasing stretch amplitude and dissipation energy during the injury-induction process. Moreover, the failure stresses of the muscle injured under unstimulated conditions obviously decreased in comparison with those of the muscles in intact and injured under stimulated conditions. On the basis of these results and previous experimental studies, we concluded that muscle activity played a significant roll to prevent the decrease of the failure stress and that the damage mechanism of strain injury depended on the muscle activity during injury-induction process.
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  • Hisashi NAITO, Yasushi AKAZAWA, Ayu MIURA, Takeshi MATSUMOTO, Masao TA ...
    2012 Volume 7 Issue 2 Pages 168-176
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    In this study, we proposed a method for estimating muscle length parameters on an individual basis from measured data based on a musculo-skeletal structure with a Hill-type muscle model. Passive joint moments of the ankle were measured for 4 healthy subjects in two different knee positions, i.e., in knee flexion and extension, using manual measurement apparatus. Estimation of muscle length parameters based on measurement data from each subject was performed using a two-dimensional musculo-skeletal model of the lower limb with a Hill-type muscle model. Predicted passive joint moment properties using the estimated parameters were consistent with measured data. The estimated length parameters of muscles differed between subjects depending on their passive joint moment properties. These observations suggest that the proposed estimation method is available to identify muscle length parameters required for a quantification of ankle joint function and the musclo-skeletal model analyses on an individual basis.
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  • Yo KOBAYASHI, Atsushi KATO, Hiroki WATANABE, Takeharu HOSHI, Kazuya KA ...
    2012 Volume 7 Issue 2 Pages 177-187
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    We present a material model to represent the viscoelastic and material, nonlinear properties of liver tissue for needle insertion simulation. Material properties of liver tissue were measured using a rheometer and modeled from the measured data. The liver viscoelastic characteristics were represented by differential equations, including the fractional derivative term. Next, nonlinearity with respect to the fractional derivative was measured, and the stress-strain relationship using a cubic function was modeled. The material properties of liver tissue were represented by a simple equation with only a few parameters. We evaluated the variety of each stiffness parameter from measurements of 50 samples. The results showed a high degree of variation in each stiffness parameter, especially with respect to nonlinearity. Moreover, each parameter had a low correlation coefficient. We also modeled the probability of variation in material properties from these results to provide a basis for deformation simulations considering individual patient differences.
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  • Yusuke MITSUOKA, Akira TSUKAMOTO, Shunsuke IWAYOSHI, Katsuko S. FURUKA ...
    2012 Volume 7 Issue 2 Pages 188-198
    Published: 2012
    Released on J-STAGE: March 13, 2012
    JOURNAL FREE ACCESS
    Cells under cyclic stretch sense their environments and induce responses such as actin stress fiber (SF) reorientation and morphological changes. These physiological responses are thought to occur when cells sense incompatibility between SF orientation and stretching direction. This hypothesis requires existence of SFs. However, such existence of SFs in cells under cyclic stretch remains unclear since few studies attempted to track the existence of SFs throughout cyclic stretch. In order to track the existence of SFs throughout cyclic stretch, high time resolution time-lapse imaging was improved in two points. First, SFs were clearly imaged with coexpression of DsRed-zyxin and GFP-actin. Second, time resolution was improved so that fluorescence images were obtained every 28 sec. With the improved high time resolution time-lapse imaging, it was revealed, for the first time, that SFs could exist continuously throughout cyclic stretch. Moreover, physiological responses including morphological change as well as SF reorientation occurred during the time when SFs formed incompatibility between SF orientation and stretching direction. These results demonstrated that SFs continuously existed in cells under cyclic stretch and in turn suggested that continuous presence of incompatibility between orientation of long-lasting SFs and the stretching direction might be important for mechanosensing which induces physiological responses.
    Editor's pick

    ★Paper of the Year 2012
    ★Graphics of the Year 2012

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  • Junji IKEDA, Mikio IWAMOTO, Seido YARIMITSU, Teruo MURAKAMI
    2012 Volume 7 Issue 2 Pages 199-210
    Published: 2012
    Released on J-STAGE: March 14, 2012
    JOURNAL FREE ACCESS
    The phase stability of yttria (3 mol%) stabilized tetragonal polycrystalline zirconia (3Y-TZP) has been evaluated by X-ray diffraction and laser microscope. The differences in kinetics of phase transformation in the aging test under hydrothermal environment and during the hip simulator wear test were compared. It was found that the phase transformation during aging test experiences a Mehl-Avrami-Johnson (MAJ) equation and the phase stability of tetragonal phase can be improved by controlling the sintering condition. Hip simulator wear test using zirconia femoral head with 4 different monoclinic fractions was performed against conventional UHMWPE (GUR 1050) acetabular socket up to 6 million cycles. During hip simulator testing, slight increase in monoclinic fraction of some zirconia femoral head was observed. Increasing rate of monoclinic phase depended on initial monoclinic fraction. But, from the result of measurement of UHMWPE wear rate, mutual relationship between the monoclinic fraction on zirconia femoral head and the wear rate of UHMWPE socket was not observed. From the results of laser microscope observation, in the case of phase transformation during hip simulator test, large number of small monoclinic spots were observed in contrast to the phase transformation during aging test. Moreover an increase in monoclinic fraction on the surface alone was observed significantly compared to the progress into the bulk in aging test. These facts indicate that the nucleation of monoclinic phase on the surface was enhanced by the sliding action against UHMWPE cup. Thus, it was suggested that the phase transformation during hip simulator test was affected on tribochemical reaction during sliding condition.
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  • Keiko AKIYAMA, Motomu NAKASHIMA
    2012 Volume 7 Issue 2 Pages 211-222
    Published: 2012
    Released on J-STAGE: March 23, 2012
    JOURNAL FREE ACCESS
    The objective of this study was to obtain optimal walking form and orthosis during the exercise of walking in water for elderly people in order to prevent falling down. Since it is effective to increase the muscle strength of iliopsoas and tibialis anterior to prevent falling down, the walking form and orthosis, by which these muscles can be trained, was optimally designed by a simulator which can compute body load considering fluid force. The walking form obtained by the simulation was the one in which the shank is quickly and widely moved in the end of the swing phase. Since a large fluid force acted on the lower limbs by this motion, the target muscles were greatly exerted to resist the fluid force. On the other hand, the orthosis obtained by the simulation was one whose width and depth were small, and the density of the foot part was large. Since the large gravity and inertial force acted by the large density of the foot part, the target muscles were greatly exerted to resist these forces. Therefore, both the walking form and orthosis can be effective for the rehabilitation of elderly people.
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  • Kiwamu SAITOU, Norio INOU, Hitoshi KIMURA, Taisei FUJIKAWA, Naoki OGAW ...
    2012 Volume 7 Issue 2 Pages 223-236
    Published: 2012
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    Mandibular movement is performed by many masticatory muscles. It is important to estimate muscular activities in mastication for examining mechanical function of the movement. However, the estimation method has not yet been established. This study proposes a new method to clarify the cooperative change of muscular lengths using our patient-specific 3-D mandibular motion display system. The method reproduces a mandibular movement from several basic motion modes. The motion modes are expressed by periodic functions with different peak times. The proposed method provides comprehensible information even in a complex mandibular movement. Time series of the muscular lengths are also obtained from the 3-D motion display system. This study discusses a relationship between incisor trajectories and muscular lengths in mandibular movements. We succeeded in reproduction of chewing movements by synthesizing the basic motion modes. With the proposed method, dynamic profiles of masticatory movement show a clear relation to characteristics of the incisor trajectories. We also found all masticatory muscles are cooperatively controlled during mandibular movement. Bilateral difference of contractile muscular lengths and the timings obviously affect the trajectory pattern.
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  • Tateki SUMII, Ryosuke FUJITA, Kazuo TANISHITA, Susumu KUDO
    2012 Volume 7 Issue 2 Pages 237-247
    Published: 2012
    Released on J-STAGE: April 06, 2012
    JOURNAL FREE ACCESS
    To date, no study has described the effects of media flow load on a co-culture model of hepatocytes (HC), hepatic stellate cells (HSC) and endothelial cells (EC). Furthermore, no research has been reported regarding the influence of nitric oxide (NO) concentration in such a co-culture model. Therefore, we developed co-culture models that include two or three of these cell types, and assayed their hepatic functions both in static culture and under flow load. We also measured the NO concentration in each models and inhibited NO production of cells. In static culture, the HC+HSC and HC+HSC+EC models demonstrated higher hepatic function than in the model containing HC alone. Under flow load, all models exhibited higher hepatic function than in static culture. The HC+HSC and HC+HSC+EC models under flow demonstrated the highest hepatic function observed under any condition. In almost all models, NO concentration exhibited the same tendency to increase along with hepatic function, and NO improved hepatic function in vitro without in HC+HSC model under flow load. Inhibition of NO production decreased small levels of hepatic function in HC+HSC and HC+HSC+EC models under flow load. We conclude that co-culture and flow load positively impact hepatic function, and that HSC and NO are related to improvements in hepatic function. Furthermore, we consider that the presence of HSC is responsible for other aspects of improvement in hepatic function.
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  • Taira OGITA, Masaru KANAOKA, Masahiro TODOH, Shigeru TADANO
    2012 Volume 7 Issue 2 Pages 248-258
    Published: 2012
    Released on J-STAGE: April 20, 2012
    JOURNAL FREE ACCESS
    Orthopedic implants are widely used to fix a bone or to replace the articulating surface of a joint. Implant surgeries are performed only by highly specialized and trained surgeons. It is quite important to develop a technique that can bond bone and implant materials directly. Laser processing with high energy density is an effective tool for bonding different materials in a very short time with a high positional accuracy. In this study, to investigate the possibility of laser bonding living bones and bioceramics, an in-vitro laser processing technique was developed for bonding a bovine cortical bone specimen with a ceramics composed of synthetic tricalcium phosphate (TCP) and MgO-Al2O3-SiO2-glass (TG ceramics). By irradiating the surface of the bone specimen with a laser beam, a microporous foam-like substance was generated that bonded the bone specimen with the TG ceramics in a manner similar to spot welding. The bonding strength was defined as the shear stress between the interface of the bone specimen and the ceramics specimen. It was found that the strength of the bond increased with an increase in the duration of laser irradiation.
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  • Youngwoo KIM, Keiichi ONISH, Goro OBINATA, Kazunori HASE
    2012 Volume 7 Issue 2 Pages 259-274
    Published: 2012
    Released on J-STAGE: April 20, 2012
    JOURNAL FREE ACCESS
    In this paper, we analyze the influence of dynamical characteristics of man-machine interfaces on both impedance perception levels and motor control characteristics of humans. In order to estimate dynamical characteristics of man-machine interfaces, humans make use of the coupling characteristics between sensory systems and motor systems in their bodies. In this study, we propose a new model-based estimation method of impedance perception level of related with motor control characteristics of the body. For the experiment, we used a 6 degree-of-freedom manipulator to simulate different impedances. A dual task was imposed on the subjects along with measuring dynamic characteristics of human who are operating the manipulator, where subjects were asked to perform simultaneously an upper limb tracking task and an impedance perception task. Based on the experimental results that show proportional relation between the differences of impedance perception levels and changes of the gain characteristics of the motor control transfer function model, the power spectrum density of the developed human model can be applied for on-line estimation of the impedance perception level of human in man-machine interface. The effectiveness of the proposed method is verified through comparison with subjective evaluation results.
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  • Seiji SHIOZAKI, Kenichi L. ISHIKAWA, Shu TAKAGI
    2012 Volume 7 Issue 2 Pages 275-283
    Published: 2012
    Released on J-STAGE: April 20, 2012
    JOURNAL FREE ACCESS
    The interaction between platelets and vessel walls in the primary aggregation of platelets was investigated using kinetic Monte Carlo simulation for the multiscale simulation of thrombus formation. The kinetic Monte Carlo lattice model of a platelet surface with glycoprotein Ibα (GPIbα) localization region was simulated by considering 3 types of events: GPIbα diffusion, GPIbα-von Willebrand factor (vWF) bond formation, and breakage. The formation and breakage model of GPIbα-vWF bonds were constructed to reproduce experimental results. Next, the adhesion force between a platelet and vessel wall was evaluated, and the contribution of GPIbα localization in platelet adhesion was investigated. The adhesion force curves with respect to the distance between the platelet and vessel wall were convex upward. The results showed that when the bond formation probability between GPIbα and vWF was small, the localization of GPIbα had a large effect on the adhesion force between the platelet and the vessel wall.
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  • - Experiment Using a Developed Patient Dummy -
    Hiroko KOBAYASHI, Yutaka FUKUI, Yusuke TANAKA, Tsuneo KAWANO
    2012 Volume 7 Issue 2 Pages 284-291
    Published: 2012
    Released on J-STAGE: April 24, 2012
    JOURNAL FREE ACCESS
    The purpose of this study is to propose a lying location on a gatch bed for bedridden elderly people or patients, in order to decrease pressures around the abdominal region during backrest lifting. A proposed lying location is defined as the location where an ischial tuberosity of the patient is positioned right above the rotational axis of the backrest. A patient dummy has been developed to directly measure the abdominal pressures. Experiments were carried out to verify the effects of the proposed lying location during the backrest lifting and lowering. The pressures and slipping displacements were measured using the developed patient dummy in the conventional and proposed lying location. As a result the pressures and slipping displacements were decreased in the proposed lying location.
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