[1] Department of Otorhinolaryngology,
[2] University Hospital Groningen,undefined
[3] PO Box 30.001,undefined
[4] 9700 RB,undefined
[5] Groningen,undefined
[6] The Netherlands e-mail: e.a.dunnebier@kno.azg.nl Tel.: +31-50-3612540,undefined
[7] Fax: +31-50-3611698,undefined
[8] Laboratory for Cell Biology and Electron Microscopy,undefined
[9] University of Groningen,undefined
[10] Groningen,undefined
[11] The Netherlands,undefined