Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

Thesis (M.S.)--Northern Michigan University, 2007. / Bibliography: leaves 57-62.

As investigações sobre os efeitos da oxigenoterapia hiperbárica (OHB) em lesão por ruído são escassas e apontam para diferentes efeitos em função do momento de intervenção. Dentre os trabalhos já descritos foi observado efeito lesivo da OHB quando aplicada imediatamente ao trauma acústico, contudo, efeito positivo foi observado quando aplicada após 2 e 6 horas. Com relação aos tratamentos usados para trauma acústico, alguns estudos descrevem o uso de corticoides como melhor alternativa, mas recentemente estudos apontam para a sua combinação com OHB como a terapêutica com maior beneficio nas lesões por ruído. O presente estudo teve como objetivos avaliar o momento da intervenção pela OHB após 2, 4 e 6 horas de repouso auditivo após exposição ao ruído e avaliar a associação terapêutica entre a OHB e corticoterapia (CT). Cobaias albinas foram expostas a um ruído branco na faixa de 4 kHz com intensidade igual a 110dB NPS por 72h e divididas em cinco grupos terapêuticos: OHB com início após 2, 4 e 6h de repouso auditivo após exposição ao ruído, CT isolada e OHB após 6 horas de repouso associada a CT. O tratamento durou 5 dias, sendo uma sessão terapêutica por dia. Todos os animais tiveram a função auditiva avaliada pelo Potencial Evocado Auditivo de Tronco Encefálico (PEATE) e pelas Emissões Otoacústicas Produtos de Distorção (EOAPD) em três momentos: pré-ruído, pós-ruído e pós-tratamento. Após a eutanásia dos animais e preparação dos espécimes cocleares, todas as cócleas foram analisadas através de Microscopia Eletrônica de Varredura (MEV). Não houve diferença estatística significativa entre os momentos de intervenção pela OHB após 2, 4 e 6 horas, contudo, os dados de MEV demonstraram que uma maior otoproteção ocorreu quando a intervenção foi realizada após um maior repouso auditivo. Apesar da não diferença estatística significativa, os achados anatômicos e funcionais permitiram concluir que a associação terapêutica entre a OHB e a corticoterapia desempenhou um melhor efeito otoprotetor e terapêutico se comparada a essas mesmas terapias isoladas. / Investigations on the effects of hyperbaric oxygen therapy (HBOT) in noise injury are scarce and point to different effects depending on the time of intervention. Among the work already described has been observed damaging effect of HBOT when applied immediately after the acoustic trauma, however, positive effect was observed when applied after 2 and 6 hours of rest after the trauma. Studies describe the use of corticosteroids as the best alternative to treat acoustic trauma, but recent studies point to their combination with HBOT as the major benefit in lesions by noise. This study aimed to evaluate the time of intervention by HBOT after 2, 4 and 6 hours of rest after hearing noise exposure and to evaluate the association between HBOT and corticoid. Female guinea pigs were exposed to a white noise on 4kHz at 110dB SPL during 72 hours and divided into five treatment groups: HBOT after 2, 4 and 6 hours of rest after the noise exposure, corticosteroid therapy and HBOT combined with corticoid. The treatment lasted five days, being a therapy session per day. All animals were exposed to Distortion Product Otoacoustic Emissions (DPOAE) and Auditory Brainstem evoked Response (ABR) in three moments: before and after exposure to the noise and after the treatment. All cochleae were examined by scanning electron microscopy (SEM). There was no statistically significant difference between the moments of intervention by HBOT after 2, 4 and 6 hours, however, the SEM data showed that a greater otoprotection occurred when the intervention was performed after a higher auditory rest. Although not statistically significant, the anatomical and functional findings concluded that the association between HBOT and corticosteroid therapy played a better otoprotective and therapeutic effect compared to those same therapies alone.

As investigações sobre os efeitos da oxigenoterapia hiperbárica (OHB) em lesão por ruído são escassas e apontam para diferentes efeitos em função do momento de intervenção. Dentre os trabalhos já descritos foi observado efeito lesivo da OHB quando aplicada imediatamente ao trauma acústico, contudo, efeito positivo foi observado quando aplicada após 2 e 6 horas. Com relação aos tratamentos usados para trauma acústico, alguns estudos descrevem o uso de corticoides como melhor alternativa, mas recentemente estudos apontam para a sua combinação com OHB como a terapêutica com maior beneficio nas lesões por ruído. O presente estudo teve como objetivos avaliar o momento da intervenção pela OHB após 2, 4 e 6 horas de repouso auditivo após exposição ao ruído e avaliar a associação terapêutica entre a OHB e corticoterapia (CT). Cobaias albinas foram expostas a um ruído branco na faixa de 4 kHz com intensidade igual a 110dB NPS por 72h e divididas em cinco grupos terapêuticos: OHB com início após 2, 4 e 6h de repouso auditivo após exposição ao ruído, CT isolada e OHB após 6 horas de repouso associada a CT. O tratamento durou 5 dias, sendo uma sessão terapêutica por dia. Todos os animais tiveram a função auditiva avaliada pelo Potencial Evocado Auditivo de Tronco Encefálico (PEATE) e pelas Emissões Otoacústicas Produtos de Distorção (EOAPD) em três momentos: pré-ruído, pós-ruído e pós-tratamento. Após a eutanásia dos animais e preparação dos espécimes cocleares, todas as cócleas foram analisadas através de Microscopia Eletrônica de Varredura (MEV). Não houve diferença estatística significativa entre os momentos de intervenção pela OHB após 2, 4 e 6 horas, contudo, os dados de MEV demonstraram que uma maior otoproteção ocorreu quando a intervenção foi realizada após um maior repouso auditivo. Apesar da não diferença estatística significativa, os achados anatômicos e funcionais permitiram concluir que a associação terapêutica entre a OHB e a corticoterapia desempenhou um melhor efeito otoprotetor e terapêutico se comparada a essas mesmas terapias isoladas. / Investigations on the effects of hyperbaric oxygen therapy (HBOT) in noise injury are scarce and point to different effects depending on the time of intervention. Among the work already described has been observed damaging effect of HBOT when applied immediately after the acoustic trauma, however, positive effect was observed when applied after 2 and 6 hours of rest after the trauma. Studies describe the use of corticosteroids as the best alternative to treat acoustic trauma, but recent studies point to their combination with HBOT as the major benefit in lesions by noise. This study aimed to evaluate the time of intervention by HBOT after 2, 4 and 6 hours of rest after hearing noise exposure and to evaluate the association between HBOT and corticoid. Female guinea pigs were exposed to a white noise on 4kHz at 110dB SPL during 72 hours and divided into five treatment groups: HBOT after 2, 4 and 6 hours of rest after the noise exposure, corticosteroid therapy and HBOT combined with corticoid. The treatment lasted five days, being a therapy session per day. All animals were exposed to Distortion Product Otoacoustic Emissions (DPOAE) and Auditory Brainstem evoked Response (ABR) in three moments: before and after exposure to the noise and after the treatment. All cochleae were examined by scanning electron microscopy (SEM). There was no statistically significant difference between the moments of intervention by HBOT after 2, 4 and 6 hours, however, the SEM data showed that a greater otoprotection occurred when the intervention was performed after a higher auditory rest. Although not statistically significant, the anatomical and functional findings concluded that the association between HBOT and corticosteroid therapy played a better otoprotective and therapeutic effect compared to those same therapies alone.

Loss of hair cells due to acoustic trauma results in the loss of hearing. In humans, unlike other vertebrates, the mechanism of hair cell regeneration is not possible. The molecular mechanisms that underlie this regeneration in nonmammalian vertebrates remain elusive. To understand the gene regulation during hair cell regeneration, our previous microarray study on zebrafish inner ears found that growth hormone (GH) was significantly upregulated after noise exposure. In this current study, we utilized Next Generation Sequencing (NGS) to examine the genes and pathways that are significantly regulated in the zebrafish inner ear following sound exposure and GH injection. Four groups of 20 zebrafish each were exposed to a 150 Hz tone at 179 dB re 1μPa RMS for 40 h. Zebrafish were injected with either salmon GH, phosphate buffer or zebrafish GH antagonist following acoustic exposure, and one baseline group received no acoustic stimulus or injection. RNA was extracted from ear tissues at 1 and 2 days post-trauma, and cDNA was synthesized for NGS. The reads from Illumina Pipeline version SCS 2.8.0 were aligned using TopHat and annotated using Cufflinks. The statistically significant differentially expressed transcripts were identified using Cuffdiff for six different pairwise comparisons and were analyzed using Ingenuity Pathway Analysis. I found significant regulation of growth factors such as GH, prolactin and fibroblast growth factor receptor 2, different families of solute carrier molecules, cell adhesion molecules such as CDH17 and CDH23, and other transcription factors such as Fos, FosB, Jun that regulate apoptosis. Analysis of the cell proliferation network in the GH-injected condition compared to buffer-injected day 1 showed significant up-regulation of GH while downregulation of apoptotic transcription factors was found. In contrast, the antagonist-injected condition compared to the GH-injected condition showed an opposite pattern in which up-regulation of apoptotic transcription factors were found while GH was down-regulated. A number of other transcripts (e.g., POMC, SLC6A12, TMEM27, HNF4A, CDH17 and FGFR2) that showed up-regulation in GH-injected condition showed down-regulation in antagonist-injected condition. These results strongly suggest that injection of exogenous GH potentially has a protective role in the zebrafish inner ear following acoustic trauma.

The axolotl (Ambystoma mexicanum) has been used as a model organism for studying development, genetics, and regeneration. Although the sensory hair cells of the lateral line of this species have been shown to be able to regenerate, it is not known whether this also occurs in the inner ear. In fact, little is known about the hearing capabilities of the axolotl or other salamander species. I recorded auditory evoked potentials (AEPs) of six axolotls at eleven frequencies (0.1, 0.25, 0.4, 0.6, 0.8, 1, 1.5, 2, 3, 4, and 6 kHz) in order to produce baseline audiograms of underwater pressure sensitivity. Individuals were then subjected to a 48-hour, 150 Hz sound exposure at approximately 170 dB (re 1 μPa). AEPs were then performed to measure hearing thresholds immediately after sound exposure and at 2, 4, and 8 days post-sound exposure (DPSE). In the baseline audiogram, axolotls were most sensitive at 600 Hz, with an additional peak of sensitivity at 3 kHz. Following sound exposure, axolotls experienced a 6 to 12 dB temporary threshold shift (TTS) after sound exposure, with TTS being greatest at low frequencies near the 150 Hz stimulus frequency (i.e., 100 and 250 Hz). Hearing sensitivity returned to control levels within 8 DPSE. This indicates that axolotls do possess the ability to recover hearing sensitivity after damage following acoustical trauma. This study is the first to document hearing loss in the axolotl. Future studies are needed to correlate this hearing loss and recovery to sensory hair cell loss and regeneration in the axolotl inner ear.

Abstract This research on military aviation noise was conducted because the personnel working with military aircraft were concerned about noise induced hearing damage. In addition, comprehensive data on hearing impairments and occupational exposure of military pilots in the Finnish Air Force was not available. Moreover, data on the effects of overflight noise of military jets was necessary for the evaluation of noise induced hearing deteriorations of members of the public who might be exposured accidentally for the low-level jets' overflights. The averaged noise exposure levels of pilots varied during a flight from 97 dB(A) to 106 dB(A) in the cockpit and from 83 dB(A) to 100 dB(A) at the entrance of the ear canal. Radio noise was 4–10 dB higher than background noise inside the helmet. The attenuation provided by air crew helmets varied from10 to 21 dB(A) in the laboratory, and was at the same level during real flights. The attenuation measured in the laboratory and in working conditions was about 30 dB(A) for earmuffs. An active noise cancellation (ANC) device decreased averaged noise exposure (LAeq8min) 4–8 dB over the noise attenuation of the same helmets when the ANC system was off. The noise of overflights by military jets were measured and the noise levels were lower than those known to cause the permanent threshold shifts. However, noise induced hearing damages might be possible in certain conditions. In order to assess the hearing loss risk of pilots, hearing thresholds were measured before and after one flight using both conventional and extended high frequency (EHF) audiometry. Minor temporary threshold shifts (TTS) were revealed. The risk of noise-induced damage at the studied exposure levels is, in all probability, rather small. A novel NoiseScan data management system proved to be an interesting tool in assessment of the risk of developing hearing impairment on the basis of known risk factors. Due to the small number of risk factors, the hearing of pilots was shown to be at considerably less risk than that of industrial workers in Finland.

Le système auditif ascendant est constitué d’étages multiples procédant chacun à un traitement complexe du signal, traitement qui est modulé par un système descendant, formant de multiples boucles corticales et sous-corticales de rétroaction : le système efférent auditif. La boucle la plus longue de ce système serait capable de moduler directement le fonctionnement des cellules sensorielles de l’organe périphérique de l’audition. Le but de ce travail était d’étudier pour la première fois chez le sujet sain, l’effet d’une modulation corticale expérimentale sur le fonctionnement périphérique auditif. Nous avons donc recueilli, dans le cadre d’un protocole en double aveugle contre placebo, chez 34 sujets sains, l’activité des cellules ciliées externes de l’organe de Corti (cellules sensorielles directement en contact avec les fibres nerveuses efférentes), par le recueil d’otoémissions acoustiques (OEAs), avant et après stimulation du cortex auditif par une stimulation magnétique transcrânienne répétitive (SMTr). Une diminution de l’amplitude d’un type d’OEA a été obtenue du côté controlatéral à une stimulation du cortex auditif par SMTr à 10 Hz, effet qui ne peut être expliqué seulement par une action non-spécifique liée au bruit de la SMTr mais qui reste extrêmement variable d’un sujet à un autre. De plus, nous avons montré, du côté ipsilatéral à la SMTr, une diminution de l’amplitude des OEAs immédiatement après la SMTr, et uniquement pour les fortes intensités d’utilisation de la SMTr (donc, pour des niveaux de bruit plus importants), reflétant un effet direct du bruit de la SMTr sur les mécanismes cochléaires actifs, effet présent chez nos sujets même en cas de protections auditives de bonne qualité / The ascending auditory system involves multiples stages where the auditory information is processed and modulated by a top-down influence involving multiple cortico sub-cortical loops: the efferent auditory system. It is hypothesized that the longest loop of this efferent system is able to modulate directly the sensory cells of the peripheral auditory organ. The aim of this work was to study this system, to our knowledge for the first time in healthy humans, and to show a direct cortical influence on the auditory periphery. In a double blind randomized procedure, we recorded, in 34 healthy subjects, the activity of outer hair cells of the organ of Corti (sensory cells, that are in direct synaptic contact with medial efferent fibers), by means of evoked otoacoustic emissions (OAEs), before and after auditory cortex stimulation by repetitive transcranial magnetic stimulation (rTMS). We showed an inhibitory influence of the auditory cortical stimulation by 10 Hz rTMS on OAE amplitudes, predominantly in the ear contralateral to the rTMS, effect that cannot be attributed to a non-specific effect linked to the impulse noise associated with the rTMS technique, but that remains highly variable across subjects. In addition, we showed a decrease in OAE amplitude on the ipsilateral side, immediately after the rTMS session and only for high rTMS intensities (and hence, higher noise levels), that reflect a direct influence of the rTMS noise on the auditory periphery, effect that is present even in well ear-protected subjects