14 research outputs found
Small Tympanic Membrane Perforations in the Inferior Quadrants Do Not Impact the Manubrium Vibration in Guinea Pigs
BACKGROUND: It has been believed that location of the perforation has a significant impact on hearing loss. However, recent studies have demonstrated that the perforation sites had no impact on hearing loss. We measured the velocity and pattern of the manubrium vibration in guinea pigs with intact and perforated eardrum using a laser Doppler vibrometer in order to determine the effects of different location perforations on the middle ear transfer functions. METHODS: Two bullas from 2 guinea pigs were used to determine stability of the umbo velocities, and 12 bullas from six guinea pigs to determine the effects of different location perforations on sound transmission. The manubrium velocity was measured at three points on the manubrium in the frequencies of 0.5-8 kHz before and after a perforation was made. The sites of perforations were in anterior-inferior (AI) quadrants of left ears and posterior-inferior (PI) quadrants of right ears. RESULTS: The manubrium vibration velocity losses were noticed in the perforated ears only below 1.5 kHz. The maximum velocity loss was about 7 dB at 500 Hz with the PI perforation. No significant difference in the velocity loss was found between AI and PI perforations. The average ratio of short process velocity to the umbo velocity was approximately 0.5 at all frequencies. No significant differences were found before and after perforation at all frequencies (p>0.05) except 7 kHz (p = 0.004) for both AI and PI perforations. CONCLUSIONS: The manubrium vibration velocity losses from eardrum perforation were frequency-dependent and the largest losses occur at low frequencies. Manubrium velocity losses caused by small acute inferior perforations in guinea pigs have no significant impact on middle ear sound transmission at any frequency tested. The manubrium vibration axis may be perpendicular to the manubrium below 8 kHz in guinea pigs
Response of Glucocorticoid Receptor Alpha and Histone Deacetylase 2 to Glucocorticoid Treatment Predicts the Prognosis of Sudden Sensorineural Hearing Loss
Relationship of glucocorticoid receptor expression in peripheral blood mononuclear cells and the cochlea of guinea pigs and effects of dexamethasone administration.
BACKGROUND: Glucocorticoids (GCs) are widely used to treat sudden sensorineural hearing loss (SSNHL) and significantly improve hearing. However, GC insensitivity has been observed in some patients of SSNHL. OBJECTIVE: To study the correlation between GR expression in peripheral blood mononuclear cells (PBMCs) and in the cochlea of guinea pigs at mRNA and protein levels. METHODS: One group of guinea pigs received dexamethasone (10 mg/kg/day) intraperitoneally for 7 consecutive days (dexamethasone group), and another group of guinea pigs received normal saline (control group). Real time PCR and Western blotting were used to detect the expression of GR mRNA and GR protein in PBMCs and the cochleae. RESULTS: The GR mRNA and GR protein were detected in both PBMCs and the cochlear tissue of guinea pigs. GR mRNA and GR protein levels in PBMCs were positively correlated with those in the cochlea. The expression of GR mRNA and GR protein was significantly increased in the dexamethasone group compared to the control group. CONCLUSIONS: Levels of GR mRNA and GR protein in the PBMCs were positively correlated with those in the cochlea of guinea pigs. Systemic dexamethasone treatment can significantly up-regulate GR expression in PBMCs and in the cochlea. Measurement of the GR level in PBMCs could be used as an indicator of GR level in the cochlea
Average velocity responses recorded from 3 points on the manubrium of the intact TM (upper panel) and the AI quadrant perforated TM (lower panel).
<p>Shapes of the frequency responses were quite similar at all three points on the manubrium while the highest velocities were recorded at the umbo. The average ratio of the short process velocities to the umbo velocities was approximately 0.5 at all frequencies.</p
The average velocity responses recorded from 3 points on the manubrium of the intact TM (upper panel) and the PI quadrant perforated TM (lower panel).
<p>A similar pattern was found in the PI perforations compared to the AI perforations.</p
Mean velocities at the umbo from 12 bullas before and after perforation are presented.
<p>The upper and lower panels are mean velocities record from the perforations in the anterior-inferior quadrants of left ears (a) and in the posterior-inferior quadrants of right ears (b). Velocity losses were noticed below 1.5 kHz and negative losses at higher frequencies (2–8 kHz).</p
Frequency responses were measured at 3 points on the manubrium of intact and perforated TM.
<p>The perforations were made in the anterior-inferior quadrant of left ear and posterior-inferior quadrant of right ear. 1, 2, and 3 on the manubrium represent umbo, middle point of manubrium, and short process of manubrium respectively, and two circlets represent the perforation locations.</p
The umbo velocities recorded from 12 bullas with intact tympanic membrane are plotted.
<p>The individual measurements were drawn in gray. The thick black solid line represents the mean velocities at each of fourteen frequencies (the filled circles) while the thick black dashed lines represent one standard deviations from the means. The range of velocities was approximately 20 dB throughout the frequency range with two peaks at 2 and 4.5 kHz.</p
The umbo velocities throughout the frequency range within a time window and the umbo velocities of selected frequencies.
<p>These results demonstrate that measurement of the umbo velocity was repeatable over a period of 79- (a) or 83-minutes (b) at selected frequencies (2, 5, 8 kHz).</p
Examples of the GR protein band in PBMCs and cochleae of representative guinea pigs from both the control group (Fig. 2A, C1, C2 and C3) and the dexamethasone group (Fig. 2B, D1, D2 and D3).
<p>GAPDH was used as an endogenous control.</p