Emissões otoacusticas evocadas por estímulo trasiente em recém-nascidas homozigotos normais e heterozigotos para a mutação 35delg no gene da conexina / Transient Evoked otoacoustic emissions in carriers and non-carriers 35delG neonates

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

ABSTRACT The many areas in public health are becoming more and more united, aiming to provide better quality of life to the patients. For this reason, Audiology and Genetic are working closely, due to research which relates genetic hearing loss to hearing evaluation tests. Mutations in gene GJB2, which encodes conexin protein 26 represent the main cause of genetic hearing loss. The most frequent mutation found in gene GJB2 is called 35delG. There are individuals with this mutation in only one of the alleles. These individuals are carriers for mutation 35delG and, in many cases, do not have hearing loss. GJB2 gene is widely expressed in the inner ear cells. The connexin 26 protein form a cylindrical channel in gap junctions along adjacent cells, allowing intercellular communication, such as transferring small molecules and ions. For a normal hearing, potassium ions that enter hair cells have to be recycled. Mutations in the GJB2 gene comprising the potassium recycling apparatus thus results in hearing impairment. On the other hand, Otoacoustic Emissions evaluate mainly the performance of outer cells. Therefore the purpose of this study was to observe differences in responses to the on Transient-Evoked Otoacoustic Emissions - TEOAE -examination between carriers and non carriers for mutations in GJB2 gene in a sample of neonates. One thousand and seventy one (1071) newborn children were submitted to the genetic test, using genomic DNA extracted from blood marks acquired on filter paper. Results of these genetic tests identified sixteen (16) newborn carriers. However, for the research, two groups were selected: fourteen (14) non carriers and fourteen (14) carriers for the mutation studied. Both groups underwent the TEOAE examination. The study found differences in response to the TEOAE test between the two groups. The carrier group had lower values than the non carrier group for mean, minimum and maximum response. Carriers also had lower mean, minimum and maximum values of general capacity for reproduction. Both groups had similar responses in the frequency bands of 1.6, 2.4 and 3.2 kHz; in the 4 kHz band, the distance between the mean values measured in the two groups was larger; the mean value measured on carriers was less than that found in the non carrier group, in both ears The present study suggests that this difference is related to the performance of the outer hair cells in the espiral organ, for both the TEOAE examinations and the mutation studied are envolved to this performance.

ASSUNTO(S)

transient evoked otoacoustic emissions genetic neonates emissões otoacusticas evocadas por estímulo trasiente audicao fonoaudiologia deficiência auditiva e recem-nascido hearing loss genética

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