Osteoporosis lowers bone density and is the main cause of falls and fractures. The aim of this study was to clarify the following three points by focusing on bone density and the lower limb muscle strength and to do so with the view to prevent both osteoporosis and falls. (1) The changes in bone density and the lower limb muscle strength brought on by age. (2) The consequences on bone density and the lower limb muscle strength brought on by menopause which affected the changes in bone density. (3) The examination of the prediction factors of the decline of bone density. There were 257 females (34 to 70 years) who had received the medical screening for osteoporosis. The lower limb muscle strength was determined by measuring the abductor muscle strength of the hip joint. To determine bone density was measured the bone density of the lumbar vertebrae by applying the DXA method. Our results indicated the following facts:With age, bone density and the knee gap force declined by approximately 20%. The changes brought on by menopause lowered bone density by 20% within ten years after menopause. The age group who were ten years after menopause indicated that the beginning of the decline of the lower limb muscle strength, which accompanied the decline in bone density, corresponded to age 55 and older. The results of the multiple regression analysis, which was conducted for the purpose of extracting the prediction factors for bone density, identified three such factors:Body weight, the presence or absence of underlying disease and the risk potential of the knee gap force (10 kgf) for falls. Our results further indicated that the abductor muscle strength of the hip joint was related to the bone density of the lumbar vertebrae. The results also indicated that the fact that the lower limb muscle strength was also closely related to falls suggested the possibility that maintaining the abductor muscle strength of the hip joint above 10 kgf would be effective in preventing osteoporosis-related falls and fractures.
We can discriminate objects even if they are seen from different viewing angles. It had been believed that view-invariant object recognition across similar objects develops through the experience of successively viewing different views of each object. However we have found previously that after monkeys learned to discriminate individual views of objects, they were able to recognize objects across rotations up to 60 deg. In the present study, we further investigated responses of neurons in the inferotemporal cortex (IT) of monkeys to the object images with different prior experiences. We created six object sets each of which consisted of four similar objects seen from 4 viewing angles with 30 deg intervals. Each of the two monkeys used in the present study experienced 6 object sets in three different tasks, 2 sets in each task. Same-or-not task was a simple viewing without discrimination within the object set, Image task required discrimination of the images within each object set in the same viewing angles, and Object task required view-invariant object discrimination. We found that the viewing angle tuning of the IT neurons responding to the object images with the prior experience of the Image task was similar to that of the IT neurons responding to the object images with the prior experience of the Object task, and different from that of the IT neurons responding to the object images with the prior experience of the Same-or-not task. The results suggest that view-invariant neuronal representations in the IT developed through the experience of discrimination of similar objects in the same viewing angles.
Visual induced motion sickness (VIMS) due to real videos (passive videos) has been well evaluated by using a set of RR intervals (RRI) on electrocardiograms (ECG). However, in case of the estimation of VIMS for interactive videos suchas video games, it is difficult to obtain a stable VIMS index by using only RRI because of several modulation factors by respiration and personal errors among individual operations. For the evaluation of VIMS on interactive videos we propose VIMS quantification indices that use principal component analysis (PCA) of two time-variant biosignals, RRI and respiration signal (RESP), respectively. As VIMS indices we introduced frequency components of a score (rr) and a score (resp), which are time-variant scores resulting from PCA of the biosignals. The experimental results were estimated by regression analysis between the proposed indices and simulator sickness questionnaire (SSQ) or global motion vectors (GMVs) of videos. The experimental results show that a positive correlation is shown between the index of the score (rr) frequency analysis and SSQ for both passive and interactive videos. Because there are no significant difference between the indices for interactive video and for passive videos, the index does not influence operation factors, and reflects biomedical influence caused by video features such as GMVs. This means that the index calculated by score (rr) is effective for quantifying the VIMS caused by video factors, even though the dispersion of the index caused by the subject's individuality is not sufficiently small. This index also influenced the individuality of the subject's game habituation. On the other hand, there is little correlation between the index of the score (resp) frequency analysis and SSQ for each type of video. As a dependency of the operation and personal errors might be included in this index, we need to study more detail about this component.
Cortical dipole imaging has been proposed as a method to visualize electroencephalogram (EEG) in high spatial resolution. In the present study, we investigated the inverse estimation of the cortical dipole imaging. The truncated total least squares (TTLS) was applied to the inverse estimation to reduce the influence from both the measurement noise and the transfer matrix error caused by the head model distortion. The effect of the regularization parameter was evaluated by the relative error in a computer simulation. The estimation accuracy was improved by the TTLS compared with Tikhonov regularization. The proposed regularization technique was applied to human experimental data of visual evoked potentials. The TTLS improved the spatial resolution similar to the computer simulation.
In the principle model of pulse oximetry, the measured absorbance change occurs by a thickness change of the arterial blood. However, we cannot explain the absorbance change of the tissue only by thickness change of the arterial blood when we consider these three phenomena of circulatory dynamics:1) arterial blood flows into the tissue as pulsatile flow, 2) Oxygen saturation decreases by oxygen consumption in the tissue, and 3) venous blood flows out from the tissue. In this study, we made a new electrical model of pulse oximetry and examined the mechanism of the absorbance change when the height of the hand is changed. We measured absorbance ratio and SpO2 at three vertical hand positions, 1) on the table (middle), 2) rise over the head (up), 3) lowered (down), with six healthy volunteers. The absorbance ratios increased in the lowered hand position and there was an error to underestimate SpO2. The mean ± SD of SpO2 in the 6 subject at the middle, up, and down positions were 98.0 ± 1.28, 98.4 ± 0.84, 96.3 ± 1.69(%), respectively. We simulated pulse oximetry using our new electrical model, and we were able to express a mechanism to increase the absorbance ratio at the lowered hand position.
Polarization-resolved second-harmonic-generation (SHG) microscopy is a powerful tool to visualize distribution of collagen fiber orientation in tissue with little invasion. However, long image acquisition time, resulting from mechanical rotation of a half-wave plate, makes this microscopy easy to suffer from motion artifact of a sample and hence has limited its use to in vivo application. In this paper, we constructed rapid, polarization-resolved SHG microscopy by combination of an electro-optics-modulator-based polarization modulation with improved data acquisition method. The constructed SHG microscopy enables us to visualize orientation mapping of dermal collagen fiber in rat skin in vivo without influence of motion artifact. This microscope will open the door for in vivo measurement of collagen fiber orientation in tissue.
It is said that the worst cause of death by car accident is drowsy driving. Many studies have been devoted to detect drivers' drowsiness from their behavior or biological signals such as electrocardiogram and arterial pulse wave to prevent drowsy driving. However, there has been few research focused on the relation between drivers' head motion and their drowsiness. In this study, we aimed to clarify the relationship between head driver's motion and their drowsiness. Two acceleration sensors were equipped to subject's head and car seat. Subjects were asked to drive a car under two conditions, i.e. in awakening state and drowsy state after over 20 hours sleep deprivation. The difference between the acceleration of head and car seat were calculated, and the results show that head motion decreases according to driver's drowsiness.
Pathology of aortic valve sclerosis is very similar to that of atherosclerosis and it seems to be one of inflammatory changes caused by damage to endothelium of the aortic valve. However, stress factors of the damage have not been clarified yet. This study focused on both aging and hypertension as the highest risk factor of the valve sclerosis and supposed that local mechanical strain on the valvular surface occurred by valve opening and closing behavior with heartbeat is one of the mechanical trigger for inflammatory. So, in order to clarify the pathogenic mechanism, in vitro experiment using a realistic aortic valve model and a cardiovascular flow simulator was conducted and spatial-temporal distribution of the strain on the leaflet was measured by 3D shape measuring technique. As the result, the areas at the centre of the leaflet and the boundary between the leaflet and Valsalva sinus strained locally much larger than the other area during diastole. And tensile strain on the whole leaflet enlarged with increasing pressure load on the valve. On the other hand, the areas in the vicinity of the boundary with the sinus including valve commissures were bent locally during systole and then the bending strain at the area was almost constant. These results indicated that either tensile strain or bending strain is continuously occurred on the valvular surface during a cardiac period. And these high strain areas on the leaflet model were very similar to the place where lipid deposition as a stage prior to sclerosis by the hyper-cholesterol loaded animal experiment using a rabbit of the normal blood pressure. Therefore, this result suggests the local high strain is one of the important mechanical stress for the valve sclerosis occurring.
Since articular cartilage has important mechanical functions, it is important to evaluate the mechanical properties of cultured cartilage in terms of whether those properties are the same as those of natural cartilage. Mechanical tests such as a compression test and a dynamic visco-elastic measurement are useful for measuring mechanical properties of cultured cartilage, but these methods may damage cultured cartilage. Therefore, there is a need to develop an evaluation method to measure the mechanical properties of cultured cartilage without damaging the tissue. The purpose of this study was to evaluate the electrical impedance of cultured cartilage using a two-electrode electrical impedance method during cultivation. Chondrocytes were isolated from the distal femur of 6-month-old pigs. Chondrocytes were embedded in agarose gel (6 mm in diameter, 1.5±0.2 mm in thickness) at a cell concentration of 5.0×106 cells/ml. Electrical impedance measurement, compression test, biochemical analysis and histological observation were carried out before cultivation and after 4, 8, 12 and 16 days of cultivation. The electrical impedance at 5.0×104 Hz measured using a two-electrode electrical impedance method was defined as a passive electrical property of chondrocyte-agarose construct. Compressive stiffness of chondrocyte-agarose construct was calculated from stress-strain curve obtained from compression test. Synthesis of extracellular matrix was observed after 8 days of cultivation, and the amount of glycosaminoglycan increased with cultivation days. The electrical resistivity increased with cultivation days, and it showed a significant correlation with the amount of glycosaminoglycan. The compressive stiffness also increased with cultivation days, and it was significantly correlated with the amount of glycosaminoglycan. The electrical resistivity of chondrocyte-agarose construct was found to be significantly linearly correlated with the compressive stiffness. These results showed that the compressive stiffness of chondrocyte-agarose construct can be estimated by measuring its electrical impedance during cultivation.
Recent artificial respiration therapy has to be accomplished based on the relevant clinical assessment such as the monitoring of intrapulmonary regional ventilation dynamics of the patients. However, almost all respirators and bedside monitoring systems provide insufficient real-time information during artificial respiration. From this point of view, a ventilation dynamics monitoring system was developed for obtaining the intrapulmonary regional information by use of the bioelectrical impedance method. This system was able to measure 4-channel bioelectrical impedance (60 kHz) of divided thoracic areas simultaneously. Furthermore, the differential pressure-type pneumotachograph was also equipped in the system to calibrate the measurement impedance data to the ventilatory volume of the absolute value. Comparing with complicated systems already reported in the past study, the most advantageous performance of this device was the simpler operation and clear graphical display in the clinical use. These were realized by use of the high-performance LSI and microcomputer system. To evaluate the performance and availability of the system, seven healthy adult volunteers were tested during the variety of spontaneous respirations. In this study, reproducibility and linearity of partial ΔZ versus corresponding ventilatory volume change were examined against various electrode arrangements. As the results, the obtained impedance changes ΔZ in the regional pulmonary parts and the sum of them showed clear correlation for the ventilatory volume change which corresponded to the physiological regional ventilation dynamics (coefficient of correlation:r = around 0.9). By calibrating these data (ΔZ and sum of them) with the pneumotachograph, partial absolute ventilatory volumes were able to estimate within around 10% of error range. In conclusion, this system will be useful as a bedside breathing monitor to the simple and easy prehension of regional ventilation dynamics for the respiration therapy.