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Objectives/Hypothesis: To explore the possible determinants of bilateral audiometric notches in noise-induced hearing loss (NIHL). Study Design: Prospectively enrolled cohort with cross-sectional analysis. Methods: Male workers (n = 412) with exposure to continuous loud noise (noise exposure level normalized to a nominal 8-hour working day >75 dBA) during work were included in this cohort study. The relationship between the presence of bilateral audiometric notches and age, noise exposure duration, noise exposure level, and shift from the predicted thresholds over different frequencies were determined by regression model analysis, receiver operating characteristic analysis, and area under the curve analysis. Results: The presence of bilateral audiometric notches was closely associated with the shifts from the predicted thresholds over 1, 2, 3, 4, and 6 kHz. The shift pattern was somewhat different between those who used hearing protection devices and those who did not. The shifts from the predicted thresholds demonstrated a stronger association with bilateral audiometric notches than did age, gender, noise exposure level, or noise exposure duration. Conclusions: The bilateral audiometric notches in NIHL could not be determined only on the basis of age, gender, noise exposure level, or noise exposure duration. The importance of other factors associated with bilateral audiometric notches should be recognized. Elucidation of the factors of formation of bilateral audiometric notches would help us to develop a more comprehensive protection strategy to prevent further NIHL.

To explore the possible determinants of bilateral audiometric notches in noise-induced hearing loss (NIHL).Prospectively enrolled cohort with cross-sectional analysis.Male workers (n = 412) with exposure to continuous loud noise (noise exposure level normalized to a nominal 8-hour working day75 dBA) during work were included in this cohort study. The relationship between the presence of bilateral audiometric notches and age, noise exposure duration, noise exposure level, and shift from the predicted thresholds over different frequencies were determined by regression model analysis, receiver operating characteristic analysis, and area under the curve analysis.The presence of bilateral audiometric notches was closely associated with the shifts from the predicted thresholds over 1, 2, 3, 4, and 6 kHz. The shift pattern was somewhat different between those who used hearing protection devices and those who did not. The shifts from the predicted thresholds demonstrated a stronger association with bilateral audiometric notches than did age, gender, noise exposure level, or noise exposure duration.The bilateral audiometric notches in NIHL could not be determined only on the basis of age, gender, noise exposure level, or noise exposure duration. The importance of other factors associated with bilateral audiometric notches should be recognized. Elucidation of the factors of formation of bilateral audiometric notches would help us to develop a more comprehensive protection strategy to prevent further NIHL.

Objective/Hypothesis: The retinoid acid (RA) sufficient air-liquid interface interface (ALI) cell culture model, but not the classical submerged single layer (SSL) cell culture model, can achieve ciliary differentiation of nasal epithelial cells. Because gap junction mediated intercellular communication (GJIC) may contribute to differentiation in numerous cell types, this study compared the extent of GJIC and the expression of Connexin 43 (Cx43) in nasal epithelial cells in both SSL and ALI cultures. Methods: Cell morphology was examined via optical and scanning electron microscope, and the number of cells with ciliary beating were counted. Lucifer Yellow dye transfer test using the scrape loading method was performed to assess the GJIC. Cx43 expression was measured with reverse-transcription polymerase chain reaction (RT-PCR) and quantitative (Q)-PCR. Results: Nasal epithelial cells in ALI culture exhibited increased numbers of ciliated cells compared with SSL culture during the 3-week culture period. On day 20, GJIC was increased in ALI culture (ALI % - SSL % = 9.6 ± 1.2%, n = 5). Accordingly, Cx43 expression was increased via RT-FCR (4.22-fold) and Q-PCR (5.3 ± 1.1-fold, n = 5) examination. Conclusions: RA sufficient ALI culture manifested more differentiated nasal epithelial cell status with ciliogenesis. Cx43, being the responsible molecule for GJIC, increased in parallel. Consequently, as in primary cultured limbal epithelial cells, Cx43 expression and extent of GJIC may serve as markers for the differentiation status of nasal epithelial cells.