Reversible contraction of isolated mammalian cochlear hair cells

AbstractOuter hair cells were isolated from the guinea pig cochlea using a micromechanical non-enzymatic procedure. Depolarization of outer hair cells in the presence of 25–125 mM K+ was accompanied by a longitudinal contraction of the isolated cells. A decrease of [K+] to 5.4 mM interrupted contraction and induced a relaxation. Individual hair cells were able to undergo as many as 5 cycles of contraction and relaxation. External Ca2+ was required for relaxation of the contracted hair cells. The contractile event led to the production of a visible cytoplasmic network between the supranuclear area and the cuticular plate

Molecular characterization of anion exchangers in the cochlea

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Waardenburg syndrome. A heterogenic disorder with variable penetrance [Waardenburg-syndrom. Eine heterogene erkrankung mit variabler penetranz]

PubMed ID: 15029423Background. Waardenburg syndrome (WS) is an autosomal dominant disorder characterised by pigmentary anomalies of the skin, hairs, eyes and various defects of other neural crest derived tissues. It accounts for over 2% of congenital hearing impairment. At least four types are recognized on the basis of clinical and genetic criteria. Patients and methods. Based on a screening of congenitally hearing impaired children, 12 families with WS type II were detected. Of special interest was the phenotype of these families, in particular the reduced penetrance of hearing impairment within the families. Results and conclusion. In all cases a high variability of the disease phenotype was detected and the penetrance of the clinical traits varied accordingly. Therefore, it is not possible to predict the clinical phenotype even in a single family. Based on these studies, we plan to identify the pathogenetic cause of the disease in order to perform a detailed genotype/phenotype analysis