Erdogan Bulut

Effects of sleep deprivation on anaerobic exercise-induced changes in auditory brainstem evoked potentials

Background  The present study was designed to assess how anaerobic exercise affects auditory brainstem response (ABR) parameters, and whether one night of sleep deprivation could alter these possible exercise‐induced changes in ABRs.

DNA methylation of the prestin gene and outer hair cell electromotileresponse of the cochlea in salicylate administration

Background/aim: Activity of the prestin gene may have a role in the pathogenesis of salicylate-induced ototoxicity. We investigated DNA methylation for prestin gene exon 1 in salicylate-injected guinea pigs.Materials and methods: Fifteen guinea pigs (30 ears) underwent audiological evaluation including 1000 Hz probe-tone tympanometry and a distortion product otoacoustic emission (DPOAE) test. The animals were randomly divided into three groups. Groups 2 (8 ears) and 3 (14 ears) were injected with intramuscular saline and sodium salicylate (200 mg/kg), respectively twice daily for 2 weeks. Group 1 (8 ears) received no injection. DPOAE measurements were performed at baseline; after 1, 2, 4, and 8 h (acute effect); and after 1 and 2 weeks (chronic effect). After audiological measurements, the animals were sacrificed for DNA isolation.Results: While a significant decrease (P < 0.01) was found for the acute effect in all frequencies in Group 3 according to baseline measurements, there was no difference in terms of chronic effect. DNA methylation increased during the acute phase of salicylate administration, whereas it returned to initial levels during the chronic phase.Conclusion: Salicylate-induced changes in DPOAE responses may be related to prestin-gene methylation. These results may have important implications for salicylate ototoxicity.

Possible Ototoxic Effects of Topical Rifamycin Application: An Electrophysiological and Ultrastructural Study

Objective This study aimed to investigate possible ototoxicity associated with topical rifamycin application via electrophysiological tests and ultrastructural examinations. Methods Electrophysiological assessment was performed with tympanometry, auditory brainstem response (ABR), and distortion product otoacoustic emission (DPOAE) measurements. This study was conducted on 40 ears of 20 guinea pigs that were detected to have normal hearing thresholds. The animals were randomly assigned to three groups: Group 1 (n=12) received 0.1 mL rifamycin, Group 2 (n=8) received 0.1 ml gentamycin, and Group 3 (n=20) received 0.1 mL physiological saline. The antibiotics and saline solutions were administered via intratympanic injections. After five injections every other day, electrophysiological tests were performed again on the 15th day. After electrophysiological measurements, the temporal bones of all guinea pigs were prepared for ultrastructural examinations and the cochlear surface morphology was examined by scanning electron microscopy (SEM). Results The animals in group 3 did not show a statistically significant change in their DPOAE signal/noise ratio (SNR) or ABR thresholds (p>0.05). In groups 1 and 2, the reduction in the DPOAE SNR and the increase in the ABR threshold were statistically significant (p<0.05). Regarding SEM examination results, the animals in groups 1 and 2 showed statistically significant outer hair cell damage and cochlear degeneration due to the ototoxic effect of the drugs (p<0.05), whereas the animals in group 3 showed no significant damage (p>0.05). Conclusion The results indicate that rifamycin application to the middle ears of guinea pigs has mild ototoxic effects on their inner ears.

Assessment of Reduced Tolerance to Sound (Hyperacusis) in University Students

Introduction: Hyperacusis is defined as a reduction in tolerance to ordinary environmental sounds. Hyperacusis can occur in individuals of all age groups, making daily life difficult for the sufferers. Although there is no objective test to accurately diagnose hyperacusis, questionnaires are useful for the assessment of hyperacusis. The aim of this study was to explore the reduced sound tolerance in university students using a hyperacusis questionnaire (HQ). Materials and Methods: A total of 536 university students (300 females and 236 males) aged between 18 and 25 years, with a mean age of 21.34 ± 1.87 years, were assessed using an HQ developed by Khalfa. The mean total score of all the participants was 16.34 ± 7.91, and 5.78% of the participants had total scores indicating hyperacusis, where a majority of them were females. Results: Females had significantly higher scores than men in terms of both the total and the attentional and emotional dimensions. The scores of the participants who reported noise exposure or a decrease in their tolerance to noise were significantly higher than those of the other participants. Even among young adults, there was a group of participants suffering from some problems related to decreased tolerance to everyday sounds. Discussion: Although the Turkish translation of the HQ seems to be a reliable tool for evaluating hyperacusis in young adults, further work with various populations of different age groups is required to establish validity and to assess the psychometric qualities of the Turkish form.

Otoacoustic Emissions in Young Children with Autism

OBJECTIVE The aim of this study is to investigate otoacoustic emissions (OAEs) in young children with autism compared with those in an age-matched control group. MATERIALS AND METHODS Thirty-eight children with autism aged 3-6 years and 27 typically developing (normally developing) control subjects participated in this study. All the participants had normal hearing and middle-ear function. Auditory brainstem responses were used to determine the hearing status in the autism group. Transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs) were measured in the two groups. RESULTS The TEOAE response level was higher in the autism group. Analysis of the DPOAE response showed that the mean emission levels at 1.5, 2 , 3, and 6 kHz and signal/noise ratios at 2, 4, 6, and 8 kHz were higher in the autism group (p<0.05). The greatest between-group differences were observed in the DPOAE signal levels at 2, 3, and 6 kHz (p=0.000). No statistically significant difference was found between the noise levels in the autism and control groups (p>0.05). CONCLUSION The emission responses in the autism group were higher than those in the control group. The increase in DPOAEs at high frequencies may be related to the higher outer cell activation in the autism group. Further studies with larger sample sizes comprising younger children are needed to confirm the result and investigate the possible association between the increased OAEs and auditory sensitivity reported in autism.

A New Hypothesis on the Frequency Discrimination of the Cochlea

OBJECTIVE Medial olivocochlear efferent (MOCE) neurons innervate outer hair cells (OHCs) of the cochlea, which in turn leads to basilar membrane motion. We hypothesized that MOCE-induced alterations in basilar membrane motion, independent of traveling waves, is responsible for the cochlear frequency discrimination of sound. MATERIALS AND METHODS Eleven guinea pigs underwent bilateral otoscopic and audiologic evaluations under general anesthesia. The study comprised two parts. Part I (n=11) included spontaneous otoacoustic emission (SOAE) recordings with or without contralateral pure-tone acoustic stimuli (1 and 8 kHz) at 60 dB sound pressure level (SPL). Part II involved pure-tone (1 or 8 kHz) acoustic trauma in the right ears of two randomly selected subgroups (G1: 1 kHz; n=4 and G8: 8 kHz; n=4). The remaining three animals served as controls. After frequency-specific deafness was confirmed by distortion product otoacoustic emission (DPOAE), SOAEs were recorded in the left ears in the presence of a contralateral pure-tone (1 and 8 kHz) stimulus of 60 dB SPL. Furthermore, the surface of the organ of Corti was examined by scanning electron microscopy (SEM). RESULTS The contralateral pure tone led to frequency-specific activation in SOAEs in part I (without trauma) and part II (with trauma) measurements. SEM showed heterogeneous OHC damage along the cochlea in traumatized ears with pure tone. CONCLUSION We suggest that MOCEs convey acoustic information from traumatized ears to intact ears. Traumatized ears can show frequency-specific activation in the presence of diffuse damage in OHCs that excludes the passive transmission of the pressure wave from the perilymph to the basilar membrane.

The Effects of Experimental Intratympanic Steroid Administration on Organ of Corti Type 1 Spiral Ganglion

Introduction  It is unclear how effective is the intratympanic (IT) steroid treatment on organ of Corti type 1 spiral ganglion, its optimal dosage and frequency of administration. The effect of dexamethasone on cochlear functions in individuals with a normal hearing ability is also unknown. Objective  The aim of this study was to evaluate, at the electrophysiological and ultrastructural levels, the effect of IT dexamethasone administration in guinea pigs with normal hearing on organ of Corti type 1 spiral ganglion. Methods  A total of 20 guinea pigs ( n  = 40 ears) whose hearing was detected to be normal by electrophysiological tests were included in the study and randomly divided into 6 groups. Four groups were considered study groups, while 2 groups were considered control groups. Dexamethasone was administered intratympanically in doses of 2 mg/mL and 4 mg/mL in the guinea pigs in the study groups. The animals in the control groups received physiological saline in equal doses as the study groups. All interventions were performed under general anesthesia, and the electrophysiological tests were repeated following the IT injections. Results  No statistically significant differences were found among the groups when the IT injections were evaluated in terms of the electrophysiological measurements ( p  > 0.05). The ultrastructural evaluation showed a cellular mitochondrial increase in the spiral ganglions of the cochlea in the groups in which dexamethasone was administered in a dose of 4 mg/mL. Conclusion  According to the findings of this study, it can be suggested that the IT injection of dexamethasone is safe, and when applied in a dose of 4 mg/mL, it increases metabolic activity at the cellular level.