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T Kiryu

Publications and source records attributed to T Kiryu.

At least 37 records · Page 2Linked to original sources
PubMed1992

A muscle fatigue index based on the relationship between preceding background activity and myotatic reflex response (MRR).

A new index of muscular fatigue was developed using the myotatic reflex response (MRR). The MRR of masseter muscles is evoked by periodical mechanical chin tapping during clenching. The MRR waveform is composed of somewhat synchronized action potentials of muscle fibers. We estimate the change of the MRR waveform due to fatigue using the instantaneous frequency pattern (IFP) with the Hilbert transform. As a result, the features of IFP were different from the monotonic changes that have been observed by the conventional fatigue indices. That is, a plateau IFP was observed ahead of considerable fatigue, whereas the IFP showed a monopeak pattern during other phase of an exercise. Also, the relationship between the preceding background mean power frequency and the instantaneous frequency around the first part of the MRR waveform was nonlinear during the whole process of fatigue. These features may allow us to estimate the degree of fatigue at each time instant. Although the details have not yet been solved, by using the computer simulations one of them seemed to be the alteration of the dominant frequency components. The dominant frequency components may be related to the active muscle fiber types.

Action Potentials↗
PubMed1992

Investigation on parametric analysis of dynamic EMG signals by a muscle-structured simulation model.

In the analysis of electromyographic (EMG) signals during dynamic movement, we have proposed an estimation algorithm for the time-varying parameters of an autoregressive model. The parameters correspond to less biased time-varying reflection coefficients. We determined the less biased estimation using a locally quasi-stationary model and named these parameters "k parameters." We estimated k parameters up to the fifth order for the surface EMG signals of a masseter muscle during rapid open-close movement of the lower jaw, a ballistic contraction, and fatigue. According to the results, the time courses of the k parameters displayed remarkable properties. In order to study the behavior of k parameters physiologically, we produced a muscle-structured simulation model based on anatomical and physiological data. The simulation results suggested that the behavior of the third parameter is related to the number of active motor units (MU's) at the shallow layer of a muscle. The detailed recruitment mechanism in terms of the MU's types has not yet been solved. Although further study is required, the parametric analysis using k parameters offers a new perspective for evaluation of muscle dynamics during several movements.

Algorithms↗
PubMed1992

[Production of reactive oxygen species by rat alveolar macrophages. Dissociation between the intracellular and extracellular release of hydrogen peroxide].

In order to clarify the features of reactive oxygen species produced by rat alveolar macrophages (AMs), the concentrations of intracellular and extracellular hydrogen peroxide were measured under various experimental conditions. Intracellular hydrogen peroxide was measured by DCFH method using a flow cytometer, while the extracellularly released fraction was measured by scopoletin method using a spectrophotometer. The concentration of intracellular hydrogen peroxide after stimulation with opsonized zymosan (10 micrograms/ml) was significantly higher than that after stimulation with phorbol myristate acetate (PMA; 100 ng/ml). On the other hand, hydrogen peroxide released extracellularly after stimulation with PMA was significantly greater that that after stimulation with opsonized zymosan. These results indicate that the soluble membrane stimulant and the phagocytic particles have different mechanisms in activating the production of hydrogen peroxide in AMs. That is, hydrogen peroxide induced by PMA was mainly released extracellularly, while that induced by zymosan was mainly released into the intracellular environment. At rest, the concentration of intracellular hydrogen peroxide in rat AMs was high. Potassium cyanate, a known mitochondrial inhibitor, suppressed the intracellular hydrogen peroxide in AMs not only at rest but also after stimulations, indicating that most of the reactive oxygen species released into the intracellular environment in AM are produced by mitochondria. From these results, in order to gain a closer insight into the function of AMs, it is very important to distinguish the oxidative metabolites produced intracellularly which are related to bactericidal function from those of the extracellularly released fraction which give rise to lung damage.

Animals↗
PubMed1991

EMG analysis of complete denture wearers using a three-dimensional representation of the time behavior of AR model parameters.

Three-dimensional representation to screen the adaptation process of individual dentures is presented. In the parametric analysis of electromyographic (EMG) signals, we have to deal with the complicated behavior of a lot of parameters in the time domain. We have employed the less-biased time varying AR model parameters estimated by locally quasi-stationary processing. Hence, we propose the time-suppressed representation of the behavior, projecting the time series of less-biased time-varying vectors onto three standard planes. The vector is composed of the k parameters, K(i) for i = 1, 2, 3. Therefore, the mutually perpendicular coordinates are K(1), K(2) and K(3). Significant changes which appear to result from the muscle dynamics are observed in the K(2)-K(3) plane, as the masticatory function is recovered.

Adaptation, Physiological↗
PubMed1990

IgG subclass distributions of anti-horse serum antibodies and natural venom-antibodies produced in response to antivenom injection or snake bite in humans.

The Japanese Mamushi (Agkistrodon halys blomhoffi, BOIE) is the most common snake in Japan. Bite victims treated with antivenom (horse serum) can produce antibodies against the horse serum and the snake venom. We studied distributions of the IgG subclasses of both these antibodies produced in response to antivenom injection and snake bite. We found that IgG1 and IgG4 of each antibody in the victims' serum were present for a long period of time.

Animals↗
PubMed1990

Growth of the Cellular Slime Mold, Dictyostelium discoideum, Is Gravity Dependent.

The effect of artificial gravity on the growth of a microorganism, Dictyostelium discoideum, was studied and the following results were obtained: (a) Germination efficiency increased as gravity increased up to 3 gravities. (b) Cell differentiation was influenced by gravity. Retardation of spore formation or reduction in the spore fraction was observed at hypergravity. (c) Fruiting bodies were taller at hypergravity and smaller at simulated microgravity when compared at 1 gravity. It is suggested that modulation of gravity provides useful information on the mechanisms of life.

Journal Article↗
PubMed1990

Improvement of the frequency responses in an ambulatory ECG system by the natural observation method.

The ambulatory ECG system has been used not only in detecting arrhythmia but also in the diagnosis of myocardial ischemia. Therefore, it is necessary to reproduce ECG waveforms as accurately as possible. However, ambulatory ECG waveforms which are in clinical use are apt to be distorted because the frequency responses do not satisfy the AHA (American Heart Association) recommendation which is well accepted as the standard of the conventional ECG system. An improvement of frequency response is reported here using a compensation circuit, whose theory is based on the natural observation method. Since our system is adjusted with square waveforms and composed of a simple analog circuit, it can be compensated easily in real time. In this paper, our newly developed system and various improved ECG signals are presented and compared with conventional ECG signals. As a result, we could obtain less distorted waveforms than from commercially available devices. This new approach enables us to obtain diagnostic information of the distortion-free ST segment in ECG waveforms.

Arrhythmias, Cardiac↗
PubMed1989

[Development of passive telemetry system for intracranial pressure measurement with corrector of errors caused by temperature variation].

A new passive telemeter for the intracranial pressure monitoring have been developed. The completely implantable pressure sensor used in this system consists of a crystal, a coil and a ferrite rod attached on a diaphragm. The pressure on the diaphragm alters the volume of air in the receptacle and then the ferrite rod moves in and out of the coil and alters the resonance frequency of the sensor. Although the sensor doesn't have a battery or other energy storer, for example, a capacitor, the resonance frequency can be measured without contact. Therefore, at any time, we can measure the intracranial pressure with this sensor implanted under the scalp beforehand. However, not only pressure but also temperature alters the resonance frequency of the sensor, because the volume of air alters in proportion to temperature. Hence, we have developed a new passive telemetry pressure sensor which contains a passive telemetry temperature sensor. The temperature sensor consists of a coil and a special crystal whose resonance frequency varies with ambient temperature and its resonance frequency can be measured in the same way that we measure the resonance frequency of pressure sensor from outside of the body. With this system, we can measure the intracranial pressure about 60 times per second and the intracranial temperature every 8 seconds. The measured value of the pressure was automatically corrected by analog temperature correcting electric circuits. In animal experiment, the output of this system was similar to one of the catheter-tip type pressure transducer and we could observe the intracranial pressure altered synchronizing with respiration and with heart beat.

Animals↗
PubMed1987

[A case of three malignant tumors of the duodenal bulb and large intestine].

A 75-year-old woman with anemia admitted to our hospital and was found to have a polyp in the duodenal bulb. The biopsy specimen was histologically diagnosed as an adenoma. A barium enema examination showed an obstruction in the ascending colon and a biopsy done on a specimen of the ascending colon revealed colonic cancer. A histology of the resected specimen of the duodenal bulb revealed a tubular adenocarcinoma in an adenoma, and a similar examination of a colonic resected specimen revealed a mucinous, papillary carcinoma. A primary malignant tumor in the duodenum is an uncommon tumor and our case is first in Japan showing three malignant tumors with an early duodenal cancer.

Adenocarcinoma, Mucinous↗
PubMed1986

Pedoscope studies on neonatal activity and center of gravity after delivery.

Seventeen normal term infants delivered at the Jikei University School of Medicine were placed daily on a pedoscope in the supine and prone position after birth, and the movement of the gravity center and changes in the activities of the extremities were assessed. The results indicated that both the activity of the extremities and the movement of the gravity center were sluggish after birth, that both increased to reach peaks within 1 to 3 days, and that then temporary decreases occurred before they increased again. The probable reason for the temporary decrease in activity may be habituation or a decrement in the infant, and it is also presumed that the increase in activity after the transitory decrease reflects natural development.

Extremities↗