Erik Teig

Actomyosin ATPase activity of middle ear muscles in the cat

SummaryWhen incubated for histochemical demonstration of actomyosin ATPase both the tensor tympani and the stapedius were found to contain two types of muscle fibres, one with high actomyosin ATPase activity, indicating a high speed of contraction, and one with low actomyosin ATPase activity, indicating a low speed of contraction. In the tensor tympani 59% and 41% of the muscle fibres had a high and low ATPase activity, respectively. The corresponding numbers in the stapedius muscle were 82% and 18%. These findings are discussed with reference to previous physiological and morphological studies.

A novel missense mutation in ACTG1 causes dominant deafness in a Norwegian DFNA20/26 family, but ACTG1 mutations are not frequent among families with hereditary hearing impairment

The γ-actin gene (ACTG1) encodes a major cytoskeletal protein of the sensory hair cells of the cochlea. Recently, mutations in ACTG1 were found to cause autosomal dominant, progressive, sensorineural hearing impairment linked to the DFNA20/26 locus on chromosome 17q25.3 in four American families and in one Dutch family. We report here the linkage of autosomal dominant, progressive, sensorineural hearing impairment in a large Norwegian family to the DFNA20/26 locus. Sequencing of ACTG1 identified a novel missense mutation (c.1109T>C; p.V370A) segregating with the hearing loss. Functional analysis in yeast showed that the p.V370A mutation restricts cell growth at elevated temperature or under hyperosmolar stress. Molecular modelling suggested that the p.V370A mutation modestly alters a site for protein–protein interaction in γ-actin and thereby modestly alters γ-actin-based cytoskeletal structures. Nineteen Norwegian and Danish families with autosomal, dominant hearing impairment were analyzed for mutations in ACTG1 by sequencing, but no disease-associated mutations were identified. Finally, a long-term follow-up of the hearing loss progression associated with the p.V370A mutation in ACTG1 is provided. The present study expands our understanding of the genotype–phenotype relationship of this deafness gene and provides a sensitive and simple functional assay for missense mutations in this gene, which may assist future molecular diagnosis of autosomal-dominant hearing impairment. Finally, the present results do not indicate that mutations in ACTG1 are a frequent cause of autosomal-dominant postlingual sensorineural hearing impairment in Norway nor Denmark.

Stapedotomy Piston Diameter – Is Bigger Better?

Introduction: An important question, which confronts every otosclerosis surgeon, is which type of stapes prosthesis should be chosen. A wide variety of prostheses with different shapes, material and shaft diameters is commercially available. This paper addresses the importance of the piston shaft diameter. Patients and Material: In this retrospective study of 225 consecutive stapedotomies performed in the period 1981–1998, prostheses with a diameter of 0.4, 0.6 and 0.8 mm have been compared. Results: Bigger pistons give better hearing results for frequencies up to and including 2 kHz.

Onkologie des Kopf-Hals-Bereiches: (Konsensusbericht)1

Mitglieder der Konsensuskonferenz: F. Bootz, Leipzig (Vorsitz) (HNO) H. Breuninger, Tübingen (Dermatologie) W. Draf, Fulda (HNO) U. Ganzer, Düsseldorf (HNO) H. Glanz, Giessen (HNO) R. Hagen, Stuttgart (HNO) H.-P. Howaldt, Giessen (MKG) D. von Ilberg, Frankfurt am Main (HNO) H. Iro, Homburg (HNO) H. Maier, Ulm (HNO) R.-P. Müller, Köln (Radioonkologie) H.-G. Mergenthaler, Stuttgart (Internistische Onkologie) T.G. Wendt, Jena (Radioonkologie) J.A. Werner, Marburg (HNO)