Biomedical subjects

Toshiaki Ueno

Publications and source records attributed to Toshiaki Ueno.

9 recordsLinked to original sources

PubMed2006

Effect of wearing a mouthguard on the vestibulocollic reflex.

It has been speculated that the use of a mouthguard improves athletic ability such as muscular strength and equilibrium. The postural system is equipped with response patterns that correct for unexpected perturbations. These responses are driven by immediate feedback from visual, vestibular, and somatosensory information. These are integrated by the central nervous system. We analysed the possibility that wearing a mouthguard influences vestibular information via the vestibulocollic reflex (VCR) in the sagittal plane. The input of the VCR is vestibular afferent activity and its output is neck muscle activation. With the subject in the supine position, the apparatus used in this study induces the VCR by subjecting the head to abrupt vertical acceleration by sudden free fall under the head's own weight. Surface electromyographic (EMG) recordings in the sternocleidomastoid muscles (SCM) of 14 participants were analysed. There were no significant differences in the amplitude of the VCR within the left and right SCM whether subjects were or were not wearing a mouthguard (P=0.3227 within left SCM; P=0.9686 within right SCM). These results suggest that wearing a mouthguard has no effect on the VCR in the sagittal plane when supine, and so that vestibular sensory information is unaffected by wearing a mouthguard, in this context. Further research is required to examine whether this also holds true in more functional, upright and dynamic body positions.

Adult↗

PubMed2006

Noninvasive measurements of intramuscular pressure using pulsed phase-locked loop ultrasound for detecting compartment syndromes: a preliminary report.

OBJECTIVES: To develop a human model for compartment tamponade and test the efficacy of ultrasonic pulsed phase-locked loop (PPLL) fascial displacement waveform analysis for noninvasive measurement of intramuscular pressure (IMP). DESIGN: Human subject experiment. SETTING: University Level 1 trauma center. PARTICIPANTS: Nine male and 1 female volunteers (age 20 to 59),3 male acute compartment syndrome (ACS) patients (age 31 to 38). INTERVENTION: Thigh tourniquet was inflated in a stepwise fashion from 40 to 100 mm Hg to increase IMP transiently in volunteers. MAIN OUTCOME MEASUREMENTS: Invasive IMP by slit catheter and PPLL fascial displacement waveform in volunteers with model ACS and patients with ACS. RESULTS: In the model compartment tamponade group, thigh cuff occlusion increased IMP in the anterior compartment from a mean of 12.1 mm Hg (SE = 1.5) to a mean of 27.4 mm Hg (SE = 2.4, N = 8, P < 0.0001). By fast Fourier transform, the ratio of the amplitude of the fundamental frequency to the amplitude of the second harmonic frequency of the fascial displacement waveform as measured by PPLL increased from a resting mean of 1.12 (SE = 0.07) to a mean of 1.85 (SE = 0.18) under the same protocol (N = 6, P = 0.001). Combined data with compartment syndrome patients revealed linear correlation between IMP and PPLL with an R value of 0.8887. CONCLUSIONS: Subarterial thigh cuff pressure causes a significant and transient increase in IMP, serving as a model for anterior compartment tamponade. PPLL is able to detect fascial displacement waveforms corresponding to arterial pulsation and furthermore distinguishes between normal and elevated IMP. There is a linear correlation between PPLL measurements and invasive IMP. The PPLL shows potential utility as a device for noninvasive measurement of IMP for detecting compartment syndromes.

Adult↗

PubMed2005

Exercise within lower body negative pressure partially counteracts lumbar spine deconditioning associated with 28-day bed rest.

Astronauts experience spine deconditioning during exposure to microgravity due to the lack of axial loads on the spine. Treadmill exercise in a lower body negative pressure (LBNP) chamber provides axial loads on the lumbar spine. We hypothesize that daily supine LBNP exercise helps counteract lumbar spine deconditioning during 28 days of microgravity simulated by bed rest. Twelve sets of healthy, identical twins underwent 6 degrees head-down-tilt bed rest for 28 days. One subject from each set of twins was randomly assigned to the exercise (Ex) group, whereas their sibling served as a nonexercise control (Con). The Ex group exercised in supine posture within a LBNP chamber for 45 min/day, 6 days/wk. All subjects underwent magnetic resonance imaging of their lumbar spine before and at the end of bed rest. Lumbar spinal length increased 3.7 +/- 0.5 mm in the Con group over 28-day bed rest, whereas, in the Ex group, lumbar spinal length increased significantly less (2.3 +/- 0.4 mm, P = 0.01). All lumbar intervertebral disk heights (L5-S1, L4-5, L3-4, L2-3, and L1-2) in the Con group increased significantly over the 28-day bed rest (P < 0.05). In the Ex group, there were no significant increases in L5-S1 and L4-5 disk heights. Lumbar lordosis decreased significantly by 3.3 +/- 1.2 degrees during bed rest in the Con group (P = 0.02), but it did not decrease significantly in the Ex group. Our results suggest that supine LBNP treadmill exercise partially counteracts lumbar spine lengthening and deconditioning associated with simulated microgravity.

Adaptation, Physiological↗

PubMed2005

System for determination of ultrasonic wave speeds and their temperature dependence in liquids and in vitro tissues.

An interferometric technique capable of accurately measuring wave speed in liquids is reported. The hardware is adapted from a design to measure nonlinear responses of biological tissues to pressure changes (pressure derivatives) and temperature changes (temperature derivatives). It is used with the highly sensitive variable frequency pulsed phase-locked loop (VFPPLL) instrument. The system uses well-understood and well-characterized components and systems. The apparatus covers a temperature range from below 5 degrees C to above 45 degrees C. The system with the high-sensitivity VFPPLL is capable of measurement of wave speed to an uncertainty of less than 0.1%, and changes in wave speed to better than 0.001%. The transducer is an undamped temperature-characterized PZT-5A 500-kHz plate, whose output is corrected for off-resonance operation and for diffraction effects. To test the accuracy of the technique, measurement of ultrasonic compressional wave speed in water at temperatures from 10 degrees C to 45 degrees C are reported, with an estimated uncertainty of 0.07% and a temperature uncertainty of 0.15 degrees C. The agreement between mean values and literature values is better than 0.05%.

Acoustics↗

PubMed2005

Noninvasive assessment of intracranial pressure waveforms by using pulsed phase lock loop technology. Technical note.

Elevated intracranial pressure (ICP) is a major factor associated with incidences of morbidity and mortality in patients with neurological disorders. The use of conventional methods for ICP monitoring is currently limited to patients with severe neurological conditions because of the methods' invasive nature. The authors have developed an ultrasonic device capable of monitoring ICP waveforms noninvasively by using a pulsed phase lock loop (PPLL) technique. The PPLL device records skull movement (several meters) associated with ICP pulsations. The purpose of this study was to correlate PPLL waveforms with invasively measured ICP waveforms in patients at the University of California San Diego Medical Center (13 patients). A linear regression analysis revealed a high correlation between PPLL waveforms and invasively measured ICP waveforms during the same time domain (r2 = 0.88). A coherence function analysis, which provides the fractional portion of the mean square value at the output that is contributed by the input at a certain frequency, showed medium to high correlations (r2 = 0.50-0.90) between PPLL waveforms and invasively measured ICP waveforms at each harmonic wave components. Furthermore, there was a significant correlation (r2 = 0.680, p < 0.01) in the harmonic distortion ratio (an index representing how much a given waveform is distorted from a pure sine wave) between PPLL waveforms and invasively measured ICP waveforms. In conclusion, PPLL technology enables the noninvasive evaluation of ICP dynamics in clinical settings.

Adolescent↗

PubMed2004

Fabrication of a custom diving mouthpiece using a thermoforming material.

Scuba divers may suffer from temporomandibular joint dysfunction and related problems associated with the use of commercially available diving mouthpieces. Several authors have recommended that custom diving mouthpieces be fabricated for relieving the symptoms of diver's mouth syndrome. The lost wax technique is commonly used for this purpose but may be time-consuming and is technically complicated. This article describes a simplified technique using thermoforming material for fabricating a custom diving mouthpiece.

Diving↗

PubMed2003

Modulation of H reflexes in the forearm during voluntary teeth clenching in humans.

We investigated whether there is any modulation of the H reflex in the forearm during teeth clenching and how any correlation that may be found is modulated. The H reflexes of the flexor carpi radialis (FCR) and the extensor carpi radialis (ECR) muscles were evoked on the right side in five healthy adult volunteers. The H reflexes of the FCR and ECR muscles were facilitated in association with voluntary teeth clenching in a force-dependent manner ( r=0.46-0.663, P<0.05). The increase in amplitude of the H reflex of the FCR muscle associated with teeth clenching started before the onset of the EMG activity of the masseter muscle. The results of the present study demonstrate that oral motor activity exerts strong influences on the motor activity of the forearm.

Adult↗

PubMed2003

Cranial diameter pulsations measured by non-invasive ultrasound decrease with tilt.

INTRODUCTION: Intracranial pressure (ICP) may play a significant role in physiological responses to microgravity by contributing to the nausea associated with microgravity exposure. However, effects of altered gravity on ICP in astronauts have not been investigated, primarily due to the invasiveness of currently available techniques. We have developed an ultrasonic device that monitors changes in cranial diameter pulsation non-invasively so that we can evaluate ICP dynamics in astronauts during spaceflight. This study was designed to demonstrate the feasibility of our ultrasound technique under the physiological condition in which ICP dynamics are changed due to altered gravitational force. METHODS: Six healthy volunteers were placed at 60 degrees head-up, 30 degrees headup, supine, and 15 degrees head-down positions for 3 min at each angle. We measured arterial blood pressure (ABP) with a finger pressure cuff, and cranial diameter pulsation with a pulsed phase lock loop device (PPLL). RESULTS: Analysis of covariance demonstrated that amplitudes of cranial diameter pulsations were significantly altered with the angle of tilt (p < 0.001). The 95% confidence interval for linear regression coefficients of the cranial diameter pulsation amplitudes with tilt angle was 0.862 to 0.968. However, ABP amplitudes did not show this relationship. DISCUSSION: Our noninvasive ultrasonic technique reveals that the amplitude of cranial diameter pulsation decreases as a function of tilt angle, suggesting that ICP pulsation follows the same relationship. It is demonstrated that the PPLL device has a sufficient sensitivity to detect changes non-invasively in ICP pulsation caused by altered gravity.

Adult↗

PubMed2002

Study on the effects of shortening the distal end of a mouthguard using modal analysis.

Using a modal analysis system, we carried out a comparative assessment of the vibratory properties of the maxillary dentition of a human dry skull with a different distal end of a mouthguard. Mouthguards used in this study were: 1. a mouthguard covering up to the third molar (8MG), 2. the second molar (7MG), 3. the first molar (6MG), and 4. the second premolar (5MG). To identify the modal shape, the frequency response functions were recorded on a fast Fourier transform analyzer from the force signal impacted with a vibration generator and the response signal picked up using a laser-doppler vibrometer. The transient response waves were obtained throughout the transient response simulation procedures after curve-fitting procedures. Mean decay rates (sec(-1)) of the transient response waves were calculated for the anteriors, premolars and molars, and compared among different sets of experimental conditions. The decay rates became lower as the distal end of a mouthguard was short. The decay rates with 8MG, 7MG and 6MG (anteriors) exceeded the no mouthguard's decay rate + 2S.D. values. These results imply that a mouthguard should distally cover up to the second molar at least to ensure efficient absorption and/or dispersion of a traumatic force.

Adult↗