Tadashi Masuda

Three-dimensional motion of the upper extremity joints during various activities of daily living.

Highly reliable information on the range of motion (ROM) required to perform activities of daily living (ADL) is important to allow rehabilitation professionals to make appropriate clinical judgments of patients with limited ROM of the upper extremity joints. There are, however, no data available that take full account of corrections for gimbal-lock and soft tissue artifacts, which affect estimation errors for joint angles. We used an electromagnetic three-dimensional tracking system (FASTRAK) to measure the three-dimensional ROM of the upper extremity joints of healthy adults (N=20, age range 18-34) during 16 ADL movement tasks. The ROM required for the performance of each movement was shown in terms of the joint angle at the completion of the task, using a new definition of joint angle and regression analysis to compensate for estimation errors. The results of this study may be useful in setting goals for the treatment of upper extremity joint function.

Cross-cultural differences in the processing of non-verbal affective vocalizations by Japanese and canadian listeners.

The Montreal Affective Voices (MAVs) consist of a database of non-verbal affect bursts portrayed by Canadian actors, and high recognitions accuracies were observed in Canadian listeners. Whether listeners from other cultures would be as accurate is unclear. We tested for cross-cultural differences in perception of the MAVs: Japanese listeners were asked to rate the MAVs on several affective dimensions and ratings were compared to those obtained by Canadian listeners. Significant Groupu2009×u2009Emotion interactions were observed for ratings of Intensity, Valence, and Arousal. Whereas Intensity and Valence ratings did not differ across cultural groups for sad and happy vocalizations, they were significantly less intense and less negative in Japanese listeners for angry, disgusted, and fearful vocalizations. Similarly, pleased vocalizations were rated as less intense and less positive by Japanese listeners. These results demonstrate important cross-cultural differences in affective perception not just of non-verbal vocalizations expressing positive affect (Sauter et al., 2010), but also of vocalizations expressing basic negative emotions.

Analysis of L-glutamic acid fermentation by using a dynamic metabolic simulation model of Escherichia coli.

BackgroundUnderstanding the process of amino acid fermentation as a comprehensive system is a challenging task. Previously, we developed a literature-based dynamic simulation model, which included transcriptional regulation, transcription, translation, and enzymatic reactions related to glycolysis, the pentose phosphate pathway, the tricarboxylic acid (TCA) cycle, and the anaplerotic pathway of Escherichia coli. During simulation, cell growth was defined such as to reproduce the experimental cell growth profile of fed-batch cultivation in jar fermenters. However, to confirm the biological appropriateness of our model, sensitivity analysis and experimental validation were required.ResultsWe constructed an l-glutamic acid fermentation simulation model by removing sucAB, a gene encoding α-ketoglutarate dehydrogenase. We then performed systematic sensitivity analysis for l-glutamic acid production; the results of this process corresponded with previous experimental data regarding l-glutamic acid fermentation. Furthermore, it allowed us to predicted the possibility that accumulation of 3-phosphoglycerate in the cell would regulate the carbon flux into the TCA cycle and lead to an increase in the yield of l-glutamic acid via fermentation. We validated this hypothesis through a fermentation experiment involving a model l-glutamic acid-production strain, E. coli MG1655 ΔsucA in which the phosphoglycerate kinase gene had been amplified to cause accumulation of 3-phosphoglycerate. The observed increase in l-glutamic acid production verified the biologically meaningful predictive power of our dynamic metabolic simulation model.ConclusionsIn this study, dynamic simulation using a literature-based model was shown to be useful for elucidating the precise mechanisms involved in fermentation processes inside the cell. Further exhaustive sensitivity analysis will facilitate identification of novel factors involved in the metabolic regulation of amino acid fermentation.

Correlations between sagittal plane kinematics and landing impact force during single-leg lateral jump-landings.

[Purpose] The correlations of peak vertical ground reaction force and sagittal angles during single-leg lateral jump-landing with noncontact anterior cruciate ligament injury remain unknown. This study aimed to clarify the correlations between kinematics and impact force during lateral jump-landing. [Subjects and Methods] Twenty active males were included in the analysis. A sagittal-view movie camera and force plate were time synchronized. Trunk and lower extremity sagittal angles were measured 100u2005ms before initial contact and at peak vertical ground reaction force. Peak vertical ground reaction force, time between initial contact and peak vertical ground reaction force, and loading rate were calculated. [Results] The mean sagittal angle was 40.7° ± 7.7° for knee flexion during the flight phase and 16.4° ± 6.3° for pelvic anterior inclination during the landing phase. The mean peak vertical ground reaction force was four times the body weight. The median time to peak vertical ground reaction force was 63.8u2005ms. The knee flexion during the flight phase and pelvic anterior inclination angles during the landing phase were related to the peak vertical ground reaction force. [Conclusion] Increasing knee flexion and decreasing pelvic anterior inclination might reduce the impact during single-leg lateral jump-landing.

Incidence of floating toe and its association with the physique and foot morphology of Japanese children

[Purpose] Physical development, foot morphology, and toe contact of children aged 3 to 5u2005years were assessed in order to investigate the relationships between body and foot morphology and the incidence of the condition known as “floating toe”. [Subjects] A total of 198 children, aged 3 to 5u2005years old, participated in this study. [Methods] Height and weight were measured for body morphology, and foot length and width were measured for foot morphology. Footprint images were taken to calculate the number of floating toes. Information about the children’s height and weight at birth, and the time of starting to walk was obtained from their guardians. [Results] At least one floating toe was observed in 87.7–98.7% of the children depending on their ages. The fifth toe was most commonly affected, occurring in 74.2% of the study population. Among the body and foot morphology parameters, only weight at birth showed a significant but very weak correlation with the number of floating toes. [Conclusion] There was a high incidence of floating toe among the children, with the fifth toe most commonly affected. Floating toe weakly but significantly correlated with weight at birth, but did not correlated with other measures of physique at birth, physical development, or the time of starting to walk.

Ranges of active joint motion for the shoulder, elbow, and wrist in healthy adults

Purpose: The aim of this study was to show highly reliable normal values and three-dimensional characteristics for final range of motion during active movements of the upper extremity joints, and to develop a database from healthy participants, with the advantage of this database lying in the methods of defining shoulder axial rotation angle and of compensating for soft tissue artifacts. Methods: We used an electromagnetic tracking system (FASTRAK) to measure three-dimensional motions of the shoulder (thoracohumeral), elbow/forearm, and wrist in 20 healthy adults (age range: 18–34 years) during active joint motion tasks of the upper extremity. Results: Joint angles of the upper extremity at the final position of joint motion tasks were determined. Highly reliable data for shoulder axial rotation angle were obtained, using a new definition of joint angle and regression analysis to compensate for estimation errors. Conclusions: These results should be useful in setting goals for the treatment of upper extremity joint functions in the fields of rehabilitation, orthopedics, and sports medicine. Implications for Rehabilitation Complex joint motions that occur naturally (unconsciously) about some axes should be taken into account in interventions for range of joint motion (ROM). The data obtained through this study simultaneously indicating multiple interrelated angles can be used as reference values for maximum active ROM. ROM in the directions of motion involved in the various tasks (for example, elevation angle during shoulder flexion) may have a role to play in evaluating and setting goals for patients with impaired ROM of the arm joints.

Molecular dynamics simulation of a myosin subfragment-1 docking with an actin filament.

Myosins are typical molecular motor proteins, which convert the chemical energy of ATP into mechanical work. The fundamental mechanism of this energy conversion is still unknown. To explain the experimental results observed in molecular motors, Masuda has proposed a theory called the Driven by Detachment (DbD) mechanism for the working principle of myosins. Based on this theory, the energy used during the power stroke of the myosins originates from the attractive force between a detached myosin head and an actin filament, and does not directly arise from the energy of ATP. According to this theory, every step in the myosin working process may be reproduced by molecular dynamics (MD) simulations, except for the ATP hydrolysis step. Therefore, MD simulations were conducted to reproduce the docking process of a myosin subfragment-1 (S1) against an actin filament. A myosin S1 directed toward the barbed end of an actin filament was placed at three different positions by shifting it away from the filament axis. After 30 ns of MD simulations, in three cases out of ten trials on average, the myosin made a close contact with two actin monomers by changing the positions and the orientation of both the myosin and the actin as predicted in previous studies. Once the docking was achieved, the distance between the myosin and the actin showed smaller fluctuations, indicating that the docking is stable over time. If the docking was not achieved, the myosin moved randomly around the initial position or moved away from the actin filament. MD simulations thus successfully reproduced the docking of a myosin S1 with an actin filament. By extending the similar MD simulations to the other steps of the myosin working process, the validity of the DbD theory may be computationally demonstrated.

Effect of exercise therapy combined with branched-chain amino acid supplementation on muscle strengthening in persons with osteoarthritis

Background: Improving lower limb muscle strength is important in preventing progression of osteoarthritis (OA) and its symptoms. Exercise with branched-chain amino acid (BCAA) supplementation has been reported to affect protein anabolism in young and elderly persons. However, few studies provided daily BCAAs for patients with OA. Objective: This study examined the effects of combined BCAAs and exercise therapy on physical function improvement in women with hip OA scheduled for total hip arthroplasty. Methods: The subjects were 43 women with OA (age: 64.2 ± 9.4). The participants were randomly divided into two groups: BCAA (n=21) and control (n=22). The combined therapy was carried out for one month. Exercise intervention involved hip abductor muscle exercise in both groups. For the nutritional intervention, 6 g of BCAAs or 1.2 g of starch were consumed within 10 min before starting the exercise. Results: There was a marginally significant difference in the main effect between the groups in 10-m timed gait time. The improvement rate in hip abductor muscle strength of the contralateral side was significantly greater in the BCAA group. Conclusion: By combining BCAA intake and exercise therapy, a significant improvement in hip abductor muscle strength of the contralateral side was achieved in women with OA.

Molecular dynamics simulation for the reversed power stroke motion of a myosin subfragment-1

Myosins are typical molecular motor proteins that convert the chemical energy from the ATP hydrolysis into mechanical work. The fundamental mechanism of this energy conversion is still unknown. To explain the experimental results already obtained, Masuda has proposed a hypothesis called the Driven by Detachment theory for the working principle of the myosins. This theory insists that the energy used during the power stroke of the myosins does not directly originate from the chemical energy of ATP, but is converted from the elastic energy within the molecule at the joint between the head and neck domains. One method for demonstrating the validity of this theory is a computational simulation using the molecular dynamics (MD) method. The MD software used was GROMACS. The target of the MD simulations was myosin subfragment-1 (S1), for which the initial structure was obtained from the Protein Data Bank entry 1M8Q. The AFM pull code of GROMACS was used to apply an external force of 17 pN at the end of the neck domain in the direction opposite to the power stroke to observe whether the myosin S1 takes the pre-power stroke conformation. The residues assumed to be engaged in the docking with an actin filament were fixed to the space. Starting from exactly the same initial position, 10 simulations were repeated by varying the random seeds for generating the initial velocities of the atoms. After 64ns of calculations, the myosin S1 took the conformation of the pre-power stroke state in which the neck domain was bent around the joint between the head and the neck domains. This result agrees with the prediction expected by the DbD theory, the validity of which may be established by conducting similar simulations for the other steps of the myosin working processes.

Hip, knee, and ankle kinematics during activities of daily living: a cross-sectional study

Highlights • Several ADLs in healthy individuals had larger joint angles than walking, climbing stairs, and standing up.• Large joint angles in healthy individuals occurred at the hip and knee joints during trunk rotation, during crouching, and getting out of the bath.• Adduction and internal rotation occurred simultaneously in few healthy individuals during maximum flexion of the hip in the measured tasks.