ABSTRACT
Abstract Introduction The question as to whether occupational noise exposure causes symmetrical or asymmetrical hearing loss is still controversial and incompletely understood. Objective Two electrophysiological methods (cortical evoked response audiometry: CERA and auditory steady state responses: ASSR) were used to address this issue. Method 156 subjects with a well-documented history of noise exposure, a wide range of noise induced hearing loss (NIHL) and without middle ear pathology underwent both a CERA and an ASSR examination in the context of an exhaustive medicolegal expert assessment intended for possible compensation. Results Whatever the method (CERA or ASSR), the average electrophysiological hearing thresholds (1-2-3 kHz) are significantly worse in the left ear. The right - left differences in CERA and ASSR thresholds are strongly correlated with each other. No significant effect of frequency is found. No correlation is observed between right - left differences in hearing thresholds and either age or degree of hearing loss. Conclusion In NIHL, there is an actual average right - left difference of about 2.23 dB, i.e., 3.2%, the left ear being more impaired.
ABSTRACT
Nous avons etudie les effets du clenbuterol; un agoniste du recepteur ?2-adrenergique entrainant l'hypertrophie musculaire; sur l'expression de l'IGF-1 et des IGFBPs par les myotubes de cellules C2C12 en culture. A la concentration de 10-4 M; le clenbuterol a entraine une augmentation du niveau de l'ARN messager de l'IGF-1; IGFBP-4 et de l'IGFBP-5. L'effet sur l'IGFBP-5 est apparu apres 24h alors que les effets sur l'IGF-1 et l'IGFBP-4; plus tardifs; ont ete observes au bout de 48 heures d'incubation. Ces resultats montrent que le clenbuterol agit directement sur les cellules musculaires pour augmenter de l'expression de l'IGF-1 et des IGFBPs; mediateurs possibles de l'hypertrophie musculaire