In heart failure, QT interval and action potential duration (APD) is prolonged and IKs, a slow component of delayed rectifier potassium current, decreases. We have reported that the KCNE1 gene, coding IKs channel, increases and QT interval is prolonged in patients with heart failure. Since it is known that increasing KCNE1 increases the maximum conductance of the IKs channel, the mechanism of APD prolongation is not explained by the over expression of KCNE1. In this study, we construct a cardiac membrane action potential simulation model based on the experimental data from oocytes expression to investigate the relationship between the increase of KCNE1 and APD. In the experiment of oocyte expression, 1 ng and 5 ng of KCNE1 were co-injected with 5 ng of KCNQ1. Expressed currents were recorded 1-2 days after injection by the double-microelectrode voltage clamp method at 35 degrees centigrade. Maximum IKs conductance and relationships between time constants, maximum activation parameter and membrane potential were obtained from fitting functions describing IKs channel properties in the Luo-Rudy model to experimental results with the Nelder-Mead simplex method. In simulations, APD was prolonged by increasing the co-injected amount of KCNE1. APD at 5 ng KCNE1 was 183 ms, which is 3.4% longer than that at 1 ng KCNE1 (APD=177 ms). This study shows that increasing the KCNE1 expression level makes maximum IKs conductance increase and IKs channel open slowly and IKs conductance decrease according to the APD time scale. Therefore increasing the KCNE1 expression level may prolong APD with this mechanism. This method of constructing a simulation model based on experiments helps to explain the relationship between KCNE1 expression ratio and QT interval prolongation.
Flow visualization was conducted in a dialyzer header using particle imaging velocimetry. A full-scale model for visualization and a mixed solution mixed with glycerin and a sodium iodide solution as the working fluid was used. As a result, the jet flow from the inlet collided against the center surface of the end of a hollow fiber, went outside and caused eddies in the one-third radial position from the radial terminal of the inflow header. On the other hand, the uniform flow from the end of the hollow fiber accelerated by the contraction of the outlet header and went to the outlet. It was suggested that the velocity profile near the end of the hollow fiber in the outflow header is the most reliable PIV (particle imaging velocimetry) measurement data to validate the data by the other measurement method in the end of the hollow fiber of a dialyzer.
Magnetic stimulation has been reported to be effective for eliminating urinary incontinence. Magnetic stimulation can be applied as a low invasive technique without requiring the removal of clothes. However clinical applications of this treatment are uncommon because little physiological and technical information is available. Stimulation focused on the target is highly desirable from a safety perspective. The effect of magnetic stimulation for the treatment of urinary incontinence has been explained as a re-activation of lost functions of the pelvic floor muscles. A model study was used to investigate how electric current is distributed in the body during the application of magnetic stimulation. Current distribution induced in a homogeneous model (infinite conductor) is easy to understand. However, current distribution in an in-homogeneous model displays a much more complicated distribution than current distribution using a homogeneous model. This study investigated current distribution in the female abdomen using experimental and computer models of magnetic stimulation for the treatment of urinary incontinence. The influence of tissue in-homogeneity on current distribution was reported. In the region of the pelvic floor muscles, at depths of 20 and 50 mm above the stimulation coil, the analysis of eddy current distribution could not be performed as a homogeneous conductor due to large differences in angles and the summation of currents between inhomogeneous and homogeneous models. Within the region of the bladder and other organs at a depth of 100 mm above the stimulation coil, the pelvis and other tissues exerted little influence on current distribution.
Elderly people have more opportunities to use information technology terminals because of the increasing dissemination of the Internet. Since visual functions are weakened with senescence, website visibility is important; however there is little tangible data regarding visibility provided or considered when sites are created. In this study, the website visibilities of elderly people and young adults are compared. The visibilities of several web-safe color combinations were examined using psychological methodology, a paired comparison. Twenty-one web-safe colors were employed for visual stimuli. Fifteen elderly persons ranging from age 65 to 75 years old (average 67.6) and 12 young adults ranging from age 21 to 29 years old (average 22.9) were recruited. All subjects had normal color sensation. In examining the relationship between the psychological rankings of color combinations and visual sensations, each color combination was first scored for visibility by Thurstone's paired comparisons technique. Secondly, visual sensation was deduced by applying Weber-Fechner's law to the contrast of foreground and background colors. The following results from the comparisons were obtained: (1) The visibilities of the elderly and young adults depended on the contrast of foreground and background colors and the chromaticity of the foreground colors; in particular, elderly people were more strongly influenced by the contrast. (2) The bluish and reddish colors had high visibility in both groups; however, special care in terms of the elderly is necessary when using bluish and blackish colors simultaneously because the white turbidity of crystalline lens with senescence makes it more difficult to distinguish the two colors. (3) High contrasts do not always provide good visibility;, that is, asthenopia accumulation is accelerated when websites use very-high contrast colors.
In surgery, failure of ablation is fatal to patients, and the operation is difficult for residents to learn. Our study aims to provide a VR-based training environment for ablation. This paper presents a FEM-based soft tissue destruction model that behaves according to variable tearing manipulation. The proposed model adopts a new elastic parameter, rupture stress, for the threshold of deformation. Furthermore, the model determines elements to destroy based on the maximum shearing stress hypothesis. A simulated tension test showed that the direction of tear manipulation resulted in tearing points progressing to different degrees. Additionally, a decrease in reaction stress at the manipulation point matched the progress of destruction. This means that the simulator calculates the relation of soft tissue destruction according to the accumulated shearing stress. Therefore, the study indicates that success or failure of manipulation can be determined when using a physics-based simulation.
Hemolysis is a major factor for developing successful blood pumps. A major cause of hemolysis is the mechanical stress acting on the corpuscles passing through the pump. The empirical formula, which expresses the relationship of the shear stress, exposure time, and hemoglobin release serves as a basic model for the estimation of blood damage. We have conducted computational fluid dynamics (CFD)-based assessment for the hemolysis within the blood pump using one of the above mathematical models. Assuming that the red blood cells pass along the streamlines, a blood damage index was calculated based on the changes in shear stress with time along the streamlines starting from entrance of the pump. The feasibility of this method has been confirmed by making comparisons with experimental results. The indices of hemolysis of different pumps should be compared under the same flow rate and pressure head conditions. In the CFD-based estimation of hemolysis, the preliminary analyses for deriving the rotational speed conditions giving a flow rate of 5 L/min and a pressure head of 100 mmHg should be conducted. In this study, the pump performance derived from CFD analysis coincided well with the experimental results. From the results of the CFD analysis, the existence of reverse flows was found in the inflow cannula and passages between the guide vanes. The reverse flows resulted in the reduction of pump performance and hemo-compatibility due to the increase of the red blood cells passing the impeller area repeatedly. In conclusion, pump design can be improved by CFD analysis of the rotary pump and CFD-based estimation of hemolysis.
We have developed a new noninvasive method for measuring hemoglobin concentration called the “near-infrared spectroscopic imaging method.” This method is based on Lambert-Beer's law and on estimating the path length of light transmitted in a blood vessel using the analysis of near-infrared optical images that visualize peripheral blood vessels in the human finger. To investigate the validity of this method, basic studies were conducted using a prototype device, finger phantoms and a human finger. The experimental results of these basic studies were consistent with a theoretical equation derived from a simple light transmission model under the assumption that the cross-sectional shape of a blood vessel is completely circular. As the result, our noninvasive method was shown to be valid. To apply this method to human fingers, reproducibility and correlation tests were conducted on volunteers. Reproducibility (CV %) with five volunteers was less than 3.5%. Good correlation was obtained between predicted hemoglobin concentrations using this method and reference values obtained by the SLS hemoglobin method using an automated blood cell counter (r=0.86, n=54). These results on volunteers suggest that our noninvasive method can be applied to human fingers. As our method has the advantage of not requiring blood sampling, we will evaluate the usefulness of this noninvasive method for anemia screening.
Recently, the construction of 3-dimensional internal structure images of biological samples has been used for vital observation. To construct the image, the sample is sliced into many sections with a machine such as a microtome. Then images of the sections are acquired by the system. By acquisitioning the images, a 3-dimensional internal structure image of the sample can be created. To realize the mentioned observation system, we proposed a new type of micro-slicer image processing system with a direct translation blade and automatic sample feeding mechanism. An image scanner (contact image sensor) was attached in the system to obtain 2-dimensional images from the sliced sample, not from the sliced section. By using an image scanner called a micro-slicer image processing system instead of a CCD camera, which is used in conventional systems, line lighting of the image scanner enables uniform illumination on the cutting planes of the samples. Additionally, the characteristics of an image scanner, such as shallow depth of field, an oblique illuminating system, and one-dimensional array of light-sensitive elements, enable us to display hollow portions of the sample. As a result, the calibration process of the 2-dimensional images obtained from the sample, which was needed in the conventional system, is no longer necessary. So we achieved the automation of constructing high-definition 3-dimensional images. Furthermore, the miniaturization of equipment was realized because the CCD camera and optical systems became unnecessary.
We have developed a new system for measuring the viscoelastic property of the skin that involves no direct contact with the body surface. Traditional methods for measuring the elastic property of the skin required direct contact with the skin surface and involved many inconveniences in regard to clinical application such as pain and infection during measurement. In this study, we investigate the fundamental validity of this system. This method employs compressed air pressure to apply pressure to an area (6 mm in diameter) on the body surface. The deformation of the central part of this area is then precisely measured with a laser displacement meter. Tissue elasticity and viscosity is calculated from variation in time of displacement and load. The elastic modulus was calculated based on the Boussinesq equation. Because the dermal measuring result proved to be comparatively similar to the Maxwell model, the coefficient of viscosity modulus prescribed in the model can be calculated with this method. Using the system developed in our research, the elastic modulus and coefficient of viscosity were measured for the male and female skin surfaces of the forearm and heal of the foot. In both cases, the elastic modulus of the male forearm was larger than that of the female, while the coefficient of viscosity obtained for the male weas smaller than that of the female. Thus, we confirmed precision and repeatability by measuring the viscoelastic properties of the skin, and in particular, usability in terms of its ability to quantitatively calculate elastic modulus and viscosity.
We have developed a method and a system to quantitatively evaluate human pain without relying on subjective criteria. The concept of pain quantification is to compare the magnitude of the subject's pain to the magnitude of a painless electric stimulus that is comparable to actual pain. We quantified degree of pain as the pain ratio, based on the ratio between pain equivalent current and minimum perceived current. In the system developed as the objective of this study, a gradually increasing pulsed current (frequency was 50 Hz, and the pulse width was 0.3 ms) was applied to the subject's medial forearms, and the subjects compared the magnitude of this sensation to electrical stimulation produced by an electrical current. Using test equipment, we conducted basic evaluations of measurement principles. We induced two types of experimental pain, by applying weight load to the upper arm and the lower leg, and by pinching the skin using clips. We examined whether changes in the degree of sensation with respect to electrical stimulation used in this method could be accurately observed, and whether or not it was possible to accurately and with high reproducibility measure minimum perceived current and pain equivalent current. As a result, we were able to make a clear comparison between pain and the degree of stimulation by electrical current, which was a sensation differing from pain. Although there were individual differences in the measured values, the reproducibility of the pain equivalent current as measured was favorable, and the measured values for pain ratio were also reproducible. We confirmed in the present study that the degree of experimental pain can be expressed as quantitative numerical values using an index defined as pain ratio.
We have been developing a gait simulator that enables a wide range of walking actions. In addition to walking in a straight line, this gait simulator is capable of several kinds of walking performance including going up and down stairs, and changing directions. The gait simulator consists of two footplates that follow the foot during the swing phase and pull it back during the stance phase when the user is walking straight. This gait simulator, however, was unable to perform gait mode transitions when the user changed walking direction. We made efforts to measure the angle of the turn in the foot and to differentiate the change in direction based on that angle, but a turn in the foot did not necessarily indicate a change in direction, so the result was an action that went against the user's intent, creating a feeling of discomfort for the user. In this paper, we first obtained kinematical data in changing direction of walking and examined the characteristics of these actions. Five healthy males between 22 and 28 years of age joined the experiment. Results revealed that the subjects changed their waist angle before the foot angle when changing the direction of walking. The angle of direction of bending the upper trunk could derive the prediction of the starting point and ending point of the directional change. Based on the results, we conducted verification tests of the concerned parameters while controlling the gait simulator. The gait simulator was able to correctly predict the user's directional change action and achieve appropriate directional change.
The purpose of this study was to formulate the dynamic properties of the human flexor pollicis longus muscle (FPL), including short-latency stretch reflex, for a prosthetic hand controller. First, we measured the tension responses of the FPL during isometric contraction. The subjects were four healthy men. While the subject maintained constant isometric force (Fc) in the FPL, we applied a small ramp stretch to the thumb. We measured stretch length X(t), force F(t) and IEMGs (rectified and smoothed EMGs) of the FPL and the extensor pollicis longus (EPL) muscles. Experiments were repeated with various stretch lengths (35 ms, 4 mm ; 50 ms, 4 mm ; 50 ms, 7 mm) and various levels of isometric force (2, 7.5, 15, 22.5, 30% of maximum voluntary contraction (MVC)). Next, we isolated the stretch length perturbation-evoked force attributed to the muscle and short latency stretch reflex Fv(t). We then identified the dynamics by using the Auto-Regressive eXogeneous (ARX) model, the input of which was X(t) and the output of which was Fv(t). We created a third-order ARX model by calculating AIC values. Parameters of the decided ARX model were estimated using a least squares approach. Finally, parameters (K, t1, t2) of the transfer function G(s), which were obtained from the ARX model, were calculated. An almost linear relationship was obtained between the gain K of G(s) and the constant isometric force (Fc). The range of t1 and t2 was determined by calculating the differences between the isolated forces Fv(t) and the calculated forces with the model Fv*(t).
In this study, a handy gait assessment system with a tri-axial accelerometer has been developed and its application for quantitatively assessing the gait of elderly people was examined. This assessment system consists of a portable acceleration monitor device and analytical software capable of running on a personal computer. The portable device was fixed low on the front of the hip of the subject, and the subject was asked to walk around a test course at a voluntary speed. The activities performed on the test course included standing up, normal walking, fast walking, and walking over a barrier. The gaits of 402 elderly people were measured three times at three-month intervals. The subjects were participating in nursing health services, such as day service, ex-stroke patients, rehabilitation, fall prevention training, and pool training. The measured acceleration was converted into relative velocity and relative displacement of the center of gravity of the subject. Four evaluation indices (i. e. physical activity, stability, symmetry, and average speed) were calculated. The results reveal that both the physical activity and average speed decreased after six months of participating in nursing services.
We describe a novel artificial tactile system for transmitting a few words (verbal information) in which two-channel electrotactile stimulation capable of generating apparent movements is applied to the dorsal carpal area of the left hand via surface concentric electrodes. The utility of the system was demonstrated in psycophysical experiments using 15 healthy subjects. Verbal information was provided regarding the direction in which an object was located, with directions selected from “forward”, “left” and “right” and objects selected from “human”, “car” and “obstruction.” Consequently, nine kinds of verbal information could be sent. We therefore designed six stimulation patterns (duration, 600-900 ms) comprising several burst profiles in which each burst was composed of several pulses (interval of biphasic pulses, 2.85 μs) modulated in amplitude. The recognition experiment showed that the mean (±SD) percentage of correct answers was about 92 ± 4.2% and the mean reaction time was about 2.9 ± 0.1 s. The recognition percentage improved with experience, prior explanation about each stimulation pattern, and by increasing the range of stimulus intensity. These basic findings suggest the possible applicability of the proposed verbal information transmission method to assist auditory impaired persons and prosthetic hand users.
This paper describes the development of a sensor incorporating an algorithm that estimates the quality of comfortableness by measuring peripheral skin temperature, pulse, and galvanic skin response (GSR) that reflect autonomic nervous system activity. A correct answer rate of 83% was obtained between the subjective comfortableness and the estimated comfortableness by the developed sensor. For the application of this human feeling sensor, we used it to estimate the comfortableness of subjects receiving massages, then developed two alternative adaptive massage control procedures based on the sensor's estimate, and verified the effectiveness of the results through testing the subjects. We observed that in course A (dynamic comfortableness) the peripheral skin temperature dropped and the GSR and pulse rate increased, while in course B (static comfortableness) the peripheral skin temperature rose and the GSR and pulse rate dropped. By the end of the control sequence, there was a statistically significant difference in the amounts of change in both the peripheral skin temperature and the GSR between the two sequences (p < 0.05). To examine the effects of each course more closely, we mapped the trajectories of physiological change during the control sequences of each course at twentysecond intervals, and the results correlated closely with the subjective assessments. These results suggest that bio-control adapted to comfortableness is feasible.
This paper describes an communication tool that utilizes eye movements. Amyotrophic lateral sclerosis (ALS) attacks the motor neurons, nerve cells in the brain and spinal cord that control the body's voluntary muscles. As the disease progresses, ALS patients gradually lose the use of their hands, arms, legs, and neck muscles, ultimately becoming paralyzed. Once paralyzed, it is difficult to convey intentions or desires to other. However, thought process, personality, intelligence, and memory are not affected. ALS patients usually maintain control of their eye muscles, and can therefore use eye movement for communication. Communication tools that use EOG have the problems of incorrect input and malfunctioning. In our research, we have successfully developed an input operation that resolves these problems. The input operation results show a high success ratio. Incorrect input and malfunctioning are improved by the new input operation.
Conventional visual field tests for the early detection of visual loss lack reliability because fatigue or lack of attention leads to false results. To overcome such defects, several methods have been proposed. The method utilizing pupillary light reflex is a promising candidate. However, sufficient clinical sensitivity has not yet been achieved because of inflexible and rough light stimulus. The authors have developed a new flexible experimental pupillographic perimetry method which enables detailed light stimulus by using a flat panel display in addition to simultaneously measuring pupillary diameter in real-time with an infrared CCD camera. Preliminary evaluation experiments for a healthy normal individual demonstrated a decline in pupillary response at Mariotte blind spot where no retinal cells exist. This result indicates that the method can be a useful tool for the early detection of visual loss due to diseases such as glaucoma.