Streptomycin-induced apoptosis of rat cochlear hair cell cultured in vitro / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To evaluate if caspase pathway was involved in streptomycin-induced cell apoptosis in cochlear hair cells.</p><p><b>METHODS</b>F344 rats at postnatal day 3 or 4 were used for the study in cochlear organotypic cultures. The cochlear basilar membrane was micro-dissected out and cultured overnight, and then treated with 1 mmol/L streptomycin for 24 hours. Before the termination, the activity of caspase-8, 9 or 6 were detected with FAM-peptide-FMK labeled caspase-8, 9 or 6, respectively. The stereocilia and cuticular plate of hair cells were stained with TRITC conjugated phalloidin, and the nuclei were stained with Topro-3 DNA probe. The specimens were observed and photographed under confocal fluorescent microscope.</p><p><b>RESULTS</b>Streptomycin with 1 mmol/L causes about 80% cochlear hair cells missing in the basal turn and 10% hair cell loss in the apex. After streptomycin treatment, the nuclear shrinkage and fragmentation were found in most cochlear hair cells, and the caspase-8, caspase-9 and caspase-6 were greatly activated.</p><p><b>CONCLUSIONS</b>Apoptosis is involved in the cochlear hair cells death induced by Streptomycin in vitro. The caspase activities in upstream and downstream are maybe the major apoptotic pathway.</p>

Correlation between reduction of distortion product otoacoustic emission and percentage of outer hair cell missing in chinchillas / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To explore the quantitative relationship between the reduction of distortion product otoacoustic emission (DPOAE) and the percentage of outer hair cell loss.</p><p><b>METHODS</b>Coadministration of cisplatin (0.2 mg/kg) and ethacrynic acid (40 mg/kg) were used to establish a cochlear lesion model in chinchillas. DPOAE was measured before and 1 week, 2 weeks, and 3 weeks later respectively after cisplatin and ethacrynic acid treatment. Animals were terminated 3 weeks after the treatment. Cochlear surface preparations were performed, and the cochlear hair cells were counted through entire length of the cochlea. The correlation between DPOAE reduction and outer hair cell missing was analyzed using Pearson correlation analysis.</p><p><b>RESULTS</b>Cisplatin and ethacrynic acid treatment induced cochlear hair cell lesion that the outer hair cell loss in the cochlea developed in a stereotypic pattern; damage began in the base of the cochlea and progressed towards the apex. Reduction of DPOAE was relatively consistent with outer hair cells loss. On the average, 1% outer hair cells loss may result in 0.24 dB reduction in DPOAE levels. Pearson analysis showed a positive correlation between the reduction in DPOAE and missing of outer hair cells (r = 0.796, P < 0.05).</p><p><b>CONCLUSIONS</b>It may be helpful to evaluate missing percentage of outer hair cells from reduction in DPOAE levels.</p>

Ototoxic effects of streptomycin in vestibular organotypic cultures / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the ototoxic effects of streptomycin in vestibular organotypic cultures.</p><p><b>METHODS</b>F344 rats with age at postnatal day three or four were used for this study. The maculae of saccule and utricle were routinely dissected out and cultured with serum-free medium containing various dose of streptomycin for 24 hours. The ciliary turf of vestibular hair cells was stained with fluorescent phalloidin, and its nucleus was stained with to pro-3 DNA probe. The vestibular hair cells were quantitatively counted and photographed under confocal fluorescent microscope.</p><p><b>RESULTS</b>Morphological feature of vestibular hair cells were good in normal control cultures. However, the density of hair cells was decreased in evidence with increase of streptomycin sulfate concentrations. Twenty-four hours after streptomycin cultures, 0.25 mmol/L streptomycin caused a 10% hair cell missing, 50% hair cell loss from 1 mmol/L streptomycin treatment, and more than 75% hair cells gone post-3 mmol/L streptomycin cultures. After streptomycin treatment, the nuclear shrinkage and fragmentation were found in vestibular hair cells, whereas the vestibular supporting cells were normal.</p><p><b>CONCLUSION</b>Streptomycin induced-vestibular hair cells lesion was in a dose dependent manner with nuclear shrinkage and fragmentation. This may suggest that streptomycin leads vestibular hair cell die through apoptosis.</p>

Duration-tuning of the neurons in the inferior colliculus of guinea pigs and the role of gamma-aminobutyric acid mediated inhibition / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To evaluate duration tuning in the inferior colliculus (IC) of guinea pigs and the role of GABA-mediated inhibition on this tuning.</p><p><b>METHODS</b>Totally 23 healthy albino guinea pigs of either sex were employed in this study. After anesthesia, spikes of neurons in inferior colliculus were recorded using five-barrel glass-pipettes. The characteristic frequency was determined by recording iso-intensity response curves at moderate intensity level (40-70 dB SPL) and duration tuning was measured with signals of fixed intensity and varied durations. GABA-A receptor antagonist, bicuculline, was applied to neurons by means of in vivo micro-iontophoresis through one channel in the five-barrel glass-pipettes.</p><p><b>RESULTS</b>IC neurons of guinea pigs, especially for those who showed sustained temporal response pattern, showed stronger duration tuning in their transient response peak to signal onset. Among 207 neurons recorded, totally 93 neurons were found to show clear duration selectivity. The duration selectivity was eliminated or turned to be weaker in most of the neurons in which the effect of bicuculline was observed successfully.</p><p><b>CONCLUSIONS</b>Unlike what was reported in bats, duration selectivity may be a transient process for most of IC neurons in guinea pigs. Duration selectively of IC neurons in the guinea pig was also largely dependent on the GABAergic inhibition.</p>

Anatomic and spiral computed tomographic study of the genial tubercles for genioglossus advancement / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To study anatomic and computed tomographic measurements of Chinese mandibular genial tubercles and to evaluate the correlations between them.</p><p><b>METHODS</b>The axial images were taken by spiral CT in 40 adult human skulls with 1 mm thick section from infraorbital margin to menton. Sagittal plane reconstruction was produced through mandibular central line. Then the height and width of superior genial tubercles, the distance between menton and inferior margin of genial tubercles, the distance between mandibular incisor apex and superior margin of superior genial tubercles, the thickness of mandible were measured respectively. Thereafter anatomic measurements were taken by the same methods as computed tomographic images. The measured value were showed as means +/- standard deviation, then paired-t test and correlation analysis was made by SPSS 10.0.</p><p><b>RESULTS</b>The genioglossus almost origins from superior genial tubercles, geniohyoideus from inferior genial tubercles. The height of superior genial tubercles which were measured by anatomy and spiral CT were (5.82 +/- 0.71) mm and (6.17 +/- 0.71) mm respectively. The width of superior genial tubercles were (6.98 +/- 1.35) mm and (7.01 +/- 1.13) mm. The distance between menton and inferior margin of superior genial tubercles were (11.08 +/- 2.05) mm and (10.41 +/- 1.55) mm. The distance between mandibular incisor apex and superior margin of superior genial tubercles for male were (15.57 +/- 1.82) mm and (14.34 +/- 2.06)mm, and for female were (9.36 +/- 2.79) mm (8.78 +/- 2.53) mm. The thickness of mandibles at genial tubercles were (11.95 +/- 1.59) mm and (12.19 +/- 1.64) mm. The distance from menton to superior margin of superior genial tubercles were (16.1 +/- 2.30) mm and (15.73 +/- 2.12) mm. The correlations between anatomic measurements and spiral CT measurements of the above mentioned parameters were significant except for height of superior genial tubercles (r = 0.59 - 0.92).</p><p><b>CONCLUSION</b>The anatomic and spiral CT measurements of genial tubercles appear to have significant correlations. Preoperative spiral CT measurements of genial tubercles could be help for the design of osteotomy in genioglossus advancement.</p>