Biomedical subjects

T C Liu

Publications and source records attributed to T C Liu.

150 records · Page 9Linked to original sources

PubMedDate not supplied

Real-Ear to coupler difference in patients with ear drum perforation.

The aim of this study is to investigate the effects of ear drum perforation on real-ear to coupler difference (RECD) in adults. RECD was measured using a probe tube microphone system in 22 patients with ear drum perforations. Twenty-two normal subjects served as controls. For normal subjects, RECD was in good agreement with the values reported in the literature. For the perforated ears, the RECD was up to 8 dB smaller in the frequency range from 0.5 to 1 kHz. There was no significant difference at frequencies below 0.25 kHz and above 1 kHz. A much larger intersubject variability was found in the experimental group. The mean intersubject standard deviation was 4.4 dB in the experimental group as contrasted with 2.2 dB in the control group. Neither the equivalent ear canal volume nor the perforation size appeared to be correlated with the degree of RECD reduction over lower frequencies. These results strongly suggest the need for individual RECD measurements, rather than using the average normal RECD, to appropriately compensate for the reduced transmission of lower-frequency sounds in fitting hearing aids for patients with ear drum perforations.

Acoustic Impedance Tests↗

PubMedDate not supplied

Ultrastructural localization of glutamate and aspartate immunoreactivities in gerbil inner hair cells.

The endogenous neurotransmitter released at the base of cochlear inner hair cells (IHCs) is still not clear. L-Glutamate is the most likely candidate at present. Although it has been demonstrated that IHCs contain high levels of glutamate, the association of glutamate with synaptic release has not yet been established. In this study, presynaptic location of glutamate and aspartate immunoreactivities was examined by using the postembedding immunogold technique. The results show that neither glutamate nor aspartate exhibit immunoreactivities around the synaptic vesicles of IHCs. Although the results do not support the hypothesis that glutamate or aspartate is the endogenous neurotransmitter, the possibility that the real transmitter is a substance with a structure very similar to glutamate or aspartate cannot be excluded.

Animals↗

PubMedDate not supplied

A novel, simple organotypic culture method to study the organ of Corti from the neonatal gerbil.

An original, simple organotypic culture method was developed to grow the organ of Corti from the neonatal gerbil on the bottom of a Petri dish. In comparison with the commonly used Maximov slide assembly method, this method is easier, less time-consuming, and more economic. Our results in this study using fluorescent live/dead viability assay and fluorescein-conjugated antineurofilament antibodies show that the cultured organ of Corti and spiral ganglion cells not only survived for at least 14 days but also maintained their basic organization and normal development in vitro. Therefore, our method can serve as a reliable and easier alternative to the traditional techniques for studying the development as well as other physiological properties of the cultured organ of Corti.

Animals↗

PubMedDate not supplied

Measurement of [Ca2+]i and [Na+]i in outer hair cells isolated from gerbil cochlea.

Outer hair cells (OHCs) become sodium- and calcium-overloaded after being isolated in high-sodium medium. Most of the sodium and calcium leak occurs through 10-15% of the transduction channels that are open at the resting position of the hair bundle. However, [Ca2+]i and [Na+]i in OHCs can vary greatly from cell to cell even though they all appear normal. Different [Ca2+]i and [Na+]i may result from different leak conductance through the transduction channels. The leak was determined by the degree of damage inflicted upon the tip-link of the hair bundle during isolation. Excessive sodium accumulation may explain why OHCs cannot maintain their normal resting membrane potential in some experimental conditions.

Animals↗

PubMedDate not supplied

Tone detection in Mandarin-speaking hearing-impaired subjects.

The ability of native Mandarin-speaking, hearing-impaired subjects to detect Mandarin tones was assessed in this study. Nine subjects with mild sensorineural hearing loss (SNHL) and nine subjects with moderate SNHL participated in the study. Nine normal subjects served as control. All subjects received a tone detection test and Chinese word recognition test. The results show that tone detection was only minimally impaired in the mild SNHL group if audibility of the stimulus is well compensated for. In the moderate SNHL group, the mean score was significantly lower, but the difference was small. This suggests that tone detection is only slightly impaired for subjects with moderate hearing loss. For each individual tone, the mean scores for tones 2 and 3 were lowest and most easily confused by all normal and hearing-impaired subjects. No significant correlation was found between the tone detection score and word recognition score for all subjects. The relatively preserved ability to perceive tones in mild and moderate SNHL subjects may be helpful in their speech recognition.

Adolescent↗

PubMedDate not supplied

Aging and external ear resonance.

External ear resonance was measured in elderly people using a probe-tube microphone system. Resonance frequency, amplitude, and bandwidth as well as ear canal volume were compared across age groups and genders. No significant age group trends were observed in external ear resonant frequency. Also, the amplitude and bandwidth of the resonance peaks across ages were not significantly different. For the gender effect, the mean external ear resonant frequencies are generally higher for females than for males in all age groups, but the differences are not statistically significant. The mean amplitudes of the resonant frequency are larger for men than for women. But the difference is also small. For the ear canal volume, no significant age trend was found. However, the mean ear canal volume was significantly larger for males than for females.

Acoustic Impedance Tests↗