title: Shape changes in isolated outer hair cells: measurements with attached microspheres.
abstract: Shape changes can be induced in isolated outer hair cells by various stimuli and quantified from digitized video-images. While overall changes in length between base and apex are easily measured, changes in defined segments of the cell require fixed landmarks on the cell body. The problem of locating such landmarks makes it difficult to assess if a change in length is uniform or largely confined to a particular segment of the cell. This information is important in identifying the location of a contractile apparatus and the elucidation of mechanisms of motility. We demonstrate here that microspheres can serve as reference points for such measurements. By attaching microspheres to cells we determined that, when outer hair cells increased their volume upon K(+)-depolarization, their middle segment shortened more significantly (14 +/- 6%) than either the basal (10 +/- 5%) or apical section (7 +/- 6%; P less than 0.01). In contrast, when cortical contractions were induced by elevating intracellular Ca2+, the elongation of the cells was more pronounced in their basal (8 +/- 2%) than their apical (6 +/- 2%; P = 0.06) or middle region (6 +/- 3%). This study provides further insight into the mechanisms of shape changes in isolated outer hair cells and illustrates a method to analyze localized changes in the absence of internal landmarks.
authors.affiliation: Kresge Hearing Research Institute, University of Michigan, Ann Arbor 48109-0506.
authors.forename: G
authors.initials: G
authors.lastname: Zajic
authors.forename: J
authors.initials: J
authors.lastname: Schacht
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology; D008863:Microspheres; D011188:Potassium / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology
chemical_list: D015759:Ionomycin; D011189:Potassium Chloride; D011188:Potassium; D002118:Calcium