Hand-held aperture-sharing camera for a multiview image set.

A hand-held camera that is capable of acquiring full parallax multiview images is introduced. Since the camera is based on spatial sharing of the aperture stop of a digital camera, it is easy to manufacture. The aperture stop is spatially shared by a 2D high-speed liquid crystal (LC) shutter array that is fixed on the front surface of the camera objective. The shutter array consists of 8×8 LC shutters to acquire 8×8 multiview images. The equivalent optical configuration of the camera is not different from that of a parallel-type multiview camera array. Each of the multiview images has an equal disparity from its neighbors and has the full detector resolution of the camera. The disparity is small enough to be used in light field imaging. The depth resolution and the resolvable number of depth layers calculated from the configuration are not different from those obtained experimentally.

Depth resolution in three-dimensional images.

The depth of field of a camera defines the depth range to be covered by the camera. In 3D images, the resolvable depth range is also determined by the depth of field (DOF). Hence the depth resolution and resolvable number of depth layers obtainable with a given 3D display will be defined within the DOF when the display has the same resolution as the total camera resolution of the array in the horizontal direction. The depth resolution and resolvable number of depth layers are mathematically derived in terms of the circle of confusion. The resolvable number of depth layers is approximately linearly proportional to the camera distance and inversely proportional to the aperture diameter of the camera objective. The accuracies of the derivations are examined experimentally. The results show that the DOF extends slightly and the depth resolution improves up to 20% more than that predicted by theory for the given experimental condition. This means that the depth resolution derived has more than 80% accuracy.

Association of force steadiness of plantar flexor muscles and postural sway during quiet standing by young adults.

This study was conducted to assess the relations of force fluctuations during isometric plantar-flexion and postural sway during quiet standing. Twelve healthy men (M age = 21 yr., SD = 1) performed unilateral plantar flexion measured by a strain gauge force transducer. Participants performed force-matching tasks; sustained plantar flexion for 20 sec. at levels corresponding to 10% and 20% of maximum voluntary contraction with the visual feedback. Also, participants were asked to stand quietly with their eyes open, and then the center of mass displacement and velocity in the anteroposterior were measured. In analysis, postural sway was associated with force fluctuation at only 10% of maximum voluntary contraction. The statistically significant correlation between variables was found only at corresponding contraction intensities for plantar-flexor muscles. From this one may infer neural strategies in plantar-flexor muscles during quiet standing may be characteristics similar to those controlling the plantar-flexion force in young adults.

Asymmetry of force fluctuation during low and moderate intensity isometric knee extensions.

The purpose of this study was to investigate the asymmetry of force fluctuation during isometric knee extension at low and moderate intensities. 11 healthy men (M age = 21 yr., SD = 1) performed unilateral force matching tasks; sustained isometric knee extension at 20% and 30% maximal voluntary contraction (MVC). During the tasks, a mechanomyogram was measured by an accelerometer arrangement placed on the vastus lateralis. Although force fluctuation was not significantly different between the two legs at 20% MVC, it was higher in the left (weaker) leg than in the right (stronger) leg at 30% MVC. A significant difference in mean power frequency of the mechanomyographic signal between the two legs was also observed only at 30% MVC. These results suggest that the asymmetry of force fluctuation during isometric knee extension was not statistically significant at low intensity; however, it was significant at moderate intensity. These differences in force fluctuation between intensities might be influenced by different motor-unit firing rates in active muscle.

Influence of tactile sensitivity in the finger on postural control while using the light touch effect.

Providing additional tactile sensory input, such as light finger touch, improves postural control while standing. This phenomenon is called light touch (LT) effect. The present study investigated influences of tactile sensitivity in a finger on the magnitude of improvement in postural sway owing to LT. The participants were 16 healthy men (20-33 years). They performed two upright postures with their eyes closed; their feet 1) comfortably apart (normal stance) and 2) together in a side-by-side stance (Romberg stance). These tasks were performed both with and without LT. The participants let their right index finger lightly touch a fixed surface. The tactile sensitivity in the finger was evaluated using a two-point discrimination test. Although postural sway decreased owing to the LT, the association between tactile sensitivity in the finger and the percentage change in postural sway was not statistically significant, regardless of the difficulty of the upright tasks. These results suggested that the person might not be able to perceive a change in direction in their posture through LT; however, the LT might be recognized as a reference point to detect relative changes in the alignment of the body. Therefore, tactile sensitivity in the finger might not be necessary to achieve the LT effect.

Effect of haptic sensory input through a fluttering cloth on tandem gait performance.

This study investigated the effects of haptic sensory input through a fluttering cloth on balance control during locomotion. Twenty-one healthy men performed a tandem gait test for 4m with their eyes closed under two different conditions: (1) wearing only half or short tights (HT-condition), or (2) wearing a fluttering cloth that was wrapped around the waist and extended to the lower leg (CLOTH-condition). Participants performed two trials with a 3-min rest period. The first trial involved the HT-condition, whereas the second trial involved either the CLOTH-condition (n=11), or the HT-condition again (n=10). The gait time and double support phase were significantly lower in the CLOTH-condition than in the HT-condition, and the relationship between the change in these two parameters was significant (r=0.74, P<0.01). Further, the relationship between the change in gait time and subjective walking sensation (evaluated through a visual-analogue scale) was significant in the CLOTH-condition (r=0.82, P<0.01). Therefore, if the participant demonstrated improved gait performance while wearing a fluttering cloth, it was accompanied by an improvement in subjective walking sensation. These results suggest that wearing a fluttering cloth can provide a haptic sensory cue to enhance the individuals' perception of their body orientation, which contributes to better balance control during locomotion. Therefore, locomotive ability may improve depending on the shape of the garment.

Influence of light finger touch on postural stability during upright stance with cold-induced plantar hypoesthesia.

The present study investigated the influence of light finger touch on postural stability during an upright stance with or without cold-induced plantar hypoesthesia. Participants were 21 healthy right-handed men (20-33 years), randomly assigned to a normal temperature group (NML-group; n = 11) or cold-induced plantar hypoesthesia group (COLD-group; n = 10). Participants performed two standing tasks with their eyes closed: 1) stand upright with the feet comfortably apart (normal standing); and 2) with the feet together in a side-by-side stance (Romberg standing). The order of the tasks was randomized across participants. After a rest period, they were asked to perform each standing task and let their right index finger lightly touch the fixed surface. Before the each task, participants in the COLD group were conducted a plantar intermediate hypothermic exposure. Postural sway was decreased by providing additional haptic sensory input through the light touching regardless of standing task difficulty with a normal plantar temperature. Although postural sway under plantar hypoesthesia is decreased by light touching, the effect was greater during the difficult posture task. These results suggest that, when the sensory information from the plantar surface is decreased, additional haptic input from the hand or finger might provide supplementary information about the relative changes in one's own body orientation. Therefore, sensory information provided by touching became relatively more important to maintaining postural control during the relatively difficult postural task performed under the reduced plantar sensitivity condition.

Effect and immediate after-effect of lightly gripping the cane on postural sway.

BACKGROUND: This study investigated the effect and after-effect of lightly touching a real cane on postural sway and ankle muscle activity. METHOD: Participants performed a single-leg stance (SLS) task with their eyes closed for 30 s under three tasks. In the first and third tasks, the participants performed a normal SLS. In the second task, the participants in light-grip group (n = 11) were asked to perform SLS while lightly gripping a cane with their hand. The participants in depend-on-cane group (n = 11) were asked to support their own body with a cane. RESULTS: Postural sway during a single-leg stance is decreased by light gripping and is accompanied by decreased co-contraction of the ankle-joint muscles. If a participant lightly gripped a cane, postural sway decreased not only during the light gripping but also immediately after the withdrawal of the cane. Although postural sway and co-contraction in the depend-on-cane group were significantly decreased during the second task compared to the first task, they were not significantly changed between the first and third tasks. CONCLUSION: These results suggest that lightly gripped cane provides a haptic sensory cue that can be used to assist postural control mechanisms due to enhanced perception of self-motion through sensory interaction with the environment through the cane. Further, the haptic sensory cue during postural maintenance might be promoted as a practice effect of postural control.

The Effect of Lightly Gripping a Cane on the Dynamic Balance Control.

The purpose of the current study was to investigate the effect of lightly gripping a cane on the Functional Reach Test (FRT) to evaluate dynamic balance. 21 healthy men (19±1 years) were asked to perform the FRT three times. The standard FRT was performed in the first and third trials. In the second trial, participants in a light-grip group (n = 11) were told to lightly grip (but to not apply force for mechanical support) the cane during the FRT. Participants in a depend-on-cane group (n = 10) were told to perform the FRT while supporting their weight with the cane. FRT is improved by not only supporting a person's own weight with a cane but also just lightly gripping the cane. These findings would be helpful in the development of a useful application to improve the human movement using a haptic sensory supplementation for activities of daily living.

SHP2 binds catalase and acquires a hydrogen peroxide-resistant phosphatase activity via integrin-signaling.

Here, we examined whether catalase binds SHP2 and alters SHP2 susceptibility to H2O2. Our results indicated that serum and fibrinogen commonly evoked catalase binding to SHP2 in HeLa and A549 cells in a herbimycin-A and TNFalpha sensitive manner. Expression of active catalase nearly 15-fold over control levels in tet-off HeLa cells substantially increased the SHP2 binding, and the catalase-associated SHP2 displayed significantly high phosphatase activities with a H2O2-resistance compared to those with little catalase. Site-directed mutagenesis at 280 abolished the binding capability of catalase to SHP2-SH2 in vitro. These results suggest that catalase-280pYIQV binds SHP2 via integrin-signaling to increase a H2O2-resistant SHP2 activity.

Catalase binds Grb2 in tumor cells when stimulated with serum or ligands for integrin receptors.

Recent studies have demonstrated that H(2)O(2) acts as a second messenger of mitogenic signaling and that catalase is under the regulation of PKA and PKC signaling. Here we examined whether catalase binds any mitogenic signaling molecules. Our results indicated that serum stimulation of HeLa, Caco-2, and LiSa-2 cells, but not BJ-1 and primary human bronchial epithelial cells, resulted in catalase binding to Grb2. Whereas serum deprivation, butyrate, and herbimycin-A negatively regulated the binding, an extended culture of confluent Caco-2 cells resulted in binding of an additional but as yet unidentified molecule to the Grb2-catalase complex. Expression of active catalase nearly 15-fold over control level in Tet-off HeLa cells substantially increased binding to Grb2, and this was sensitive to 3-aminotriazole, a specific catalase inhibitor. Furthermore, fibrinogen, fibronectin, and laminin, but not collagen types I to V, hyaluronic acid, elastin, insulin, EGF, IGF-I, PDGF, or NGF, resulted in binding similar to that of serum. A mutation of tyrosine to phenylalanine at 447 abolished the binding capability of catalase to Grb2 in vitro. These results support the view that catalase (447)Tyr-Val-Asn-Val binds Grb2 upon phosphorylation in tumor cells when stimulated with serum or ligands for integrin receptors. This is the first report demonstrating that catalase binds a SH2 domain of the molecule and participates in integrin signaling.

Effects of light finger touch to the upper legs on postural sway and muscle activity during quiet standing.

The purpose of the present study was to investigate the effects of light finger touch (LT) to one's own body on postural sway and ankle muscle activity during quiet standing. In the first part of the present study, 24 healthy men (19 ± 1 years) stood upright with their eyes closed on a pneumatic balance disk under 3 different conditions. In the first condition, the participants kept their hands in loose fists, and contact between the fingers/palms and the legs was avoided. In the second condition, the participants touched the lateral sides of upper legs lightly (without applying force for mechanical support) with all fingers. In the third condition, the participants again held their hands in loose fists. Postural sway was significantly decreased during second condition compared to first condition. Further, it also tended to decrease in third condition (P = 0.08). The second part of the present study was designed to investigate the mechanisms underlying the association between postural sway and LT by analyzing electromyographic data. Data were obtained from 12 healthy men (20 ± 1 years). During quiet stance on the stable surface, soleus activity did not significantly change by LT. However, tibialis-anterior activity significantly decreased with LT. These results suggest that LT to the upper part of one's own legs decreases postural sway (during and after touching) during a still stance by decreasing co-activation of the ankle muscles.

Gender difference of aerobic contribution to surface performances in finswimming: analysis using the critical velocity method.

PURPOSE: Finswimming is a speed competition sport practiced on the surface or underwater, by using monofins or two fins. In surface events (SF), competitors should surface within 15 m after the start and any turns. The aim of this study was to investigate the gender differences in the aerobic contribution to SF performances in finswimming, using the critical velocity (CV) concept in the analysis. METHODS: The participants were sixteen monofin swimmers (eight males and eight females; 24±6 years). During a two-day period, participants performed maximal effort swimming at five test distances (100 m, 200 m, 400 m, 800 m and 1500 m), and mean swimming velocity (V) of each distance was calculated. CV was calculated as the slope of the regression line between time and distance in the 400 and 800 m SF tests. RESULTS: Although CV was significantly correlated with V800 m and V1500 m for males, it was significantly correlated with V200 m, V400 m, V800 m and V1500 m for females. CONCLUSION: The present results suggest that although the aerobic performance might contribute to SF performance for events from medium distance (i.e. 200m) to long distance (i.e. 1500m) in female participants, it might contribute to the long distance SF performances in male participants.

Low-frequency force steadiness practice in plantar flexor muscle reduces postural sway during quiet standing.

The purpose of this study was to assess the effect of low-frequency force steadiness practice in the plantar flexor muscles on postural sway during quiet standing. Healthy young 21 men (21±1 yrs) were randomly assigned to a practice group (n=14) and a nonexercising control group (n=7). Practice groups were divided by frequency of practice: 7 participants practiced once a week, and the other 7 twice a week, for 4 weeks. Steadiness practice required practice group to 5 sets of 60-s contraction at levels corresponding to 10% and 20% maximal voluntary contraction (MVC) in the plantar flexor muscles. The 4-week-long practice period reduced the force fluctuations (assessed as the standard deviation (SD) of the outputted force during steady isometric plantar flexion) and postural sway (assessed as SD of the center of mass velocity during quiet standing). However, these practice effects were not significantly affected by the practice frequencies (1 vs. 2 sessions per week) examined in this study. Further, a linear regression analysis revealed the association between prepractice postural sway and the relative change in postural sway by the practice (r=-0.904) in the practice group. These results suggest that the steadiness practice in plantar flexor muscles improves postural stability during quiet standing, even though the practice is low-frequency (once a week) and low-intensity (within 20% MVC). These practice effects are dependent on prepractice postural stability. Further, the present results have provided the functional significance of force fluctuation in lower limb muscles.

Asymmetry of Force Fluctuation During Low Intensity Isometric Contraction in Leg Muscle.

The purpose of this study was to investigate the asymmetry of force fluctuation in the leg muscles during isometric knee extension and flexion. Twenty healthy males (21±2 years) performed the maximal voluntary isometric contraction (MVC) in knee extensor and flexor. On the basis of MVC measurement, the subjects performed sustained isometric knee extension and flexion for 15s at levels corresponding to 10%, 20% and 30% MVC. The main findings of this study were: (1) a greater force fluctuation was found in the stronger MVC limb than in the weaker MVC limb at 30% MVC; (2) no difference was found in the force fluctuation between the stronger and weaker MVC limbs at 10% and 20% MVC; and (3) significant positive correlations were found between the target force values and the force fluctuation at each contraction intensity. These results suggest that: (1) asymmetry of force fluctuation increases with load, (2) asymmetry of the force fluctuation is observed at more than 30% MVC intensity; and (3) if the contraction intensity is same relatively loads (% MVC), force fluctuation is increase with absolute load (target force value). Force fluctuation influence the functional ability of an individual in controlling finger or limb movements in daily life. Further, asymmetry of force fluctuation might influence for more than 30% MVC of daily activities.

Relationship between force fluctuation in the plantar flexor and sustainable time for single-leg standing.

The purpose of this study was to investigate the relationships between force fluctuation during isometric plantar flexion and the sustainable time for single-leg standing. Fourteen healthy males (21+/-1 years) performed unilateral (preferred leg) force matching tasks and single-leg quiet standing. Force matching tasks were performed to maintain isometric plantar flexion for 15 s at levels corresponding to 10% and 20% maximal voluntary contraction (MVC) with the visual feedback of force. Force fluctuation during force matching tasks was quantified as the standard deviation of force. Sustainable time for single-leg quiet standing was performed to maintain a single-leg quiet standing barefoot on a platform using the preferred leg with their eyes closed. Force fluctuation was significantly greater in 20% MVC task compared to 10% MVC task. The sustainable time for single-leg quiet standing was strongly correlated with force fluctuation in 20% MVC task (r=-0.56, p=0.04). However, it was not related to force fluctuation in 10% MVC task (r=0.19, p=0.52) or MVC value (r=0.13, p=0.65). These results suggest that a specificity of contraction intensity is observed between force steadiness and the posture stability during single-leg quiet standing; force steadiness during 20% MVC plantar flexion is one of the important components for posture stability during single-leg quiet standing.

Regulation of catalase enzyme activity by cell signaling molecules.

Mitogenic cell proliferation requires a rapid and transient H2O2 generation, which is blocked by catalase or PKA activators. Previously, we observed that anemic HIV(+) individuals expressed acidic pIs of catalase in RBC with significantly high activities [Mol Cell Biochem 165: 77-81, 1996]. These findings led us to hypothesize that cell signaling molecules regulate catalase to control cell mitogenesis. To test the hypothesis, we determined (i) whether RBC counts correlate with their catalase activities, (ii) whether protein kinases and phosphatases alter catalase activity in vitro, and (iii) whether protein kinase activators increase catalase activity to suppress proliferation of cultured cells. The results indicated that RBC counts inversely correlated with RBC catalase activities in both HIV(+) (r: -0.6769, r2: 0.4582, n: 69 male, p < 0.0001) and HIV(-) (r: -0.3827, r2: 0.1464, n: 177 male, p < 0.0001) populations. Catalytic PKA, PKC and Casein Kinase II, but none of PKG, Ca2+/calmodulin kinase II and p34cdc/cyclinB, rapidly elevated catalase activity in vitro by up to 2-fold. Whereas a major CAT subunit (60 kDa) showed immunoreactive phosphoserine and phosphothreonine, the kinases- and gamma-32P-ATP-dependent phosphorylation occurred with a minor component (110 kDa). Among PKC isozymes examined, PKCzeta was the most effective modulator followed by PKCgamma, and protein phosphatase 1gamma and 2A decreased the catalase activity. PKA and PKCzeta activators of forskolin and okadaic acid increased catalase activity and 110 kDa expression in NIH3T3 cells up to 2.4-fold and suppressed the cell growth, showing an inverse correlation of the indices (r: -0.9286, r2: 0.8622, n: 18, p < 0.0001). Taken together, these results suggest for the first time that catalase is under the regulation of cell signaling molecules and capable of modulating mitogenic cell proliferation.