Biomedical subjects

K Ishioka

Publications and source records attributed to K Ishioka.

At least 19 recordsLinked to original sources

PubMed1992

The effects of hyperthermia on the spinal cord.

This study was conducted to obtain information about the critical temperature of the spinal cord in hyperthermia produced by radiofrequency waves applied to the spine. The first component of the spinal cord evoked potential was analyzed as an indicator of spinal cord function. The spinal cords were heated by radiofrequency waves to a maximum of 47 degrees C momentarily or for 30 minutes. The temperatures were measured with a thermosensor in the epidural space. In momentary heating, the reductions in amplitude were almost parallel with the increases in temperature. In maintained heating for 30 minutes, at 44 degrees C and below, the amplitudes decreased by one-quarter to three-quarters of the control value in the first 5 minutes and recovered to over three-quarters of the control value in 30 minutes. The amplitudes returned to almost the control value after restoration of normal spinal cord temperatures. At 45 degrees C and above, however, the amplitudes were prominently reduced or disappeared in the first 5 minutes and remained depressed during the remainder of the heating. On normalizing the temperature, the amplitudes did not return to the control value. These results suggest that 44 degrees C in the epidural space is the highest tolerable temperature for normal spinal cord function.

Animals↗

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↗

PubMed1991

A three-dimensional measurement system for human jaw movements using a photoelectric camera.

A practical measurement system for human jaw movements has been developed and tested. It consisted of LEDs fixed on the upper and lower jaws, and photoelectric cameras. Although the system was constructed simply, it was accurate and could measure jaw movements regardless of the head movements.

Humans↗

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

[The development of a device for condylar movement by electro-magnetic field. 1. Outline and characteristics of the device].

It is very important for clinical diagnosis to record and analyze condylar movement in cranio-mandibular disorders. Recently, many devices have been developed for this purpose. These devices can measure precisely condylar movements, but are difficult to manipulate. We have developed a simple device which substitute a palpation of the posterior aspect of the TMJ. We modified the Cardiokymograph which use electro-magnetic field. The characteristics of this device are the use of a frequency-variable crystal-controlled oscillator, and the application of the coil itself which is a part of the oscillator as a probe. We tested many electrical characteristics of this device and assured the effectiveness, that is, sensitivity, directivity, frequency response characteristic, transient response characteristic, and temperature response characteristic. We tried to insert a probe into the external auditory meatus, and record condylar movement as a positional change of the skin. It seems to suggest that our device can record a feature of condylar movement.

Electromagnetic Fields↗

PubMed1989

[The effects of angiographic contrast media on the aggregation and morphology of red cells in vitro].

The effects of four angiographic contrast media on the aggregation and morphology of human red cells in vitro, using microscopic observations were studied. The media included an ionic contrast medium, sodium meglumine amidotrizoate (amidotrizoate); non-ionic low-osmolal contrast media, iopamidol and iohexol; and an ionic low-osmolal contrast medium, sodium meglumine ioxaglate (ioxaglate). Strong, large aggregates formed in the control blood, without media, where aggregation of red cells was inhibited by contrast media mixed with the blood in a ratio of 2:1. Almost no aggregates were observed for amidotrizoate, an ionic contrast medium, while there were a few rouleaux formed in the presence of ioxaglate. Nearly all of the red cells aggregated in the presence of iopamidol and iohexol; iohexol produced the greater aggregation of the two. Besides rouleaux, irregular aggregates were formed with iohexol. When the contrast media were mixed with blood in a ratio of 1:2, their inhibitory effects on aggregation declined. These results clearly indicate that contrast media inhibit the in vitro aggregation of red cells, and ionic-contrast media produced more potent inhibitory effects than non-ionic media. With added NaCl and meglumine, iohexol did not induce red cell aggregation. This suggests that ionic-contrast media have greater inhibitory effects on aggregation than non-ionic media, a result of their ionic properties. Red cells were morphologically quite normal in the presence of ioxaglate, where most red cells were crenated in the presence of iopamidol and iohexol, and shrank in the presence of amidotrizoate. In the presence of iopamidol and iohexol with the osmolality adjusted to that of a saline solution, both normal red cells and crenation were observed. This suggests that non-ionic contrast media may directly effect morphological changes in red blood cells. These results revealed that ioxaglate, an ionic contrast medium, was the best in vitro medium, to prevent aggregation of red cells and crenation deformity of erythrocytes.

Contrast Media↗

PubMed1989

[Application of nitrides to dental casting. 2. Feasibility as coating materials for Co-Cr alloy].

Nitrides used in this experiment are hBN, A1N and Si3N4. We studied feasibility of nitrides as wax pattern coating materials for Co-Cr alloy in an atmosphere of argon. Wax patterns were painted with coating material of nitrides (first investing), then a mixture of phosphate bonded investment and water was used in outer investing (second investing). The temperature of mold was 800 degrees C, and an argon arc vacuum-pressure casting machine was used. We cast the thin specimens in Co-Cr alloy (composition Co: 63 wt%, Cr: 27 wt%, Mo: 5 wt%, Bal.: 5 wt%; melting point: 1,380 degrees C). Surfaces of cast specimens were investigated using the unaided eye, a scanning electron microscope and a surface roughness analyzer. Furthermore, the thick specimens (globular form: phi 6.5 mm) using coating material of hBN were investigated using the unaided eye. Results were summarized as follows; 1. The nitrides controlled remarkably the reaction between cast specimen and investment. 2. The nitrides had the good effect of separation. 3. The cast surface coated the nitrides had less clinging than uncoated one, and this indicated that its cleansability was improved. 4. The nitrides decreased the surface roughness (Rz) of the cast to about 1/3. 5. hBN had the best effect in nitrides. 6. hBN also had the effect in a thick globular specimen.

Ammonia↗

PubMed1989

Myogenic expression in esophageal polypoid tumors.

Four cases of esophageal polypoid tumors composed of squamous cell carcinoma and spindle cell sarcomatous components were investigated. Squamous cell carcinoma was consistently present in the base of the polypoid lesions in all four cases and was also intermingled with spindle-shaped sarcomatous cells in two cases. Metastases in the lymph nodes were observed in two cases: one was squamous cell carcinoma with a sarcomatous component and the other consisted of a pure sarcomatous component. All tumors involved at least the muscularis mucosae. In the sarcomatous region, the tumor was composed of highly anaplastic cells with or without forming interlacing fascicles. Pleomorphism was marked and bizarre giant cell forms were frequent. Mitoses were frequently present. Immunohistochemical study revealed that the anaplastic cells in the sarcomatous component in all cases were immunoreactive to desmin, muscle actin, vimentin, and alpha 1-antichymotrypsin, but were negative for cytokeratin, even in the metastatic tumors of the lymph nodes. The immunohistochemical results favor myogenic differentiation of the anaplastic cells, and these tumors were considered to be true carcinosarcomas composed of squamous cell carcinoma and leiomyosarcoma.

Aged↗

PubMed1988