title: Biological characteristics of the globular substance in the otoconial membrane of the guinea pig.
abstract: Biological characteristics of the globular substance, which is considered to be a precursor of otoconia, were investigated by means of confocal laser scanning microscopy. The shape of the globular substance was a complete sphere, 3-10 microns in diameter. Its surface stained positively with both rhodamine 123 and DiOC6(3), implying similarity to intracellular organelles, whereas no fluorescence was seen when stained with chlortetracycline, a membrane-associated Ca2+ dye. Meanwhile, this substance showed very little affinity for six kinds of lectins, indicating the lack of a surface structure of carbohydrates. The fluorescence of fluo-3 in the globular substance increased markedly after the application of ionomycin. But this was completely inhibited by the depletion of external Ca2+. This reaction suggests that the surface of the globular substance exhibits characteristics of a biological membrane and that the influx of external Ca2+ occurs through membrane-combined ionomycin. Internal free Ca2+ concentration varied from 1.1 x 10(-9) to 1.6 x 10(-4) M, the geometric mean being 3.3 x 10(-7) M, which is higher than normal resting level of intracellular Ca2+ concentration but lower than the calcium content of the globular substance estimated by X-ray microanalysis in previous studies.
authors.affiliation: Department of Otolaryngology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: T
authors.initials: T
authors.lastname: Takasaka
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002232:Carbocyanines / Q000737:chemistry; D004577:Electron Probe Microanalysis; D005456:Fluorescent Dyes / Q000737:chemistry*; D006168:Guinea Pigs; D015759:Ionomycin / Q000378:metabolism; D037102:Lectins / Q000378:metabolism; D018613:Microscopy, Confocal; D010037:Otolithic Membrane / Q000648:ultrastructure*; D015203:Reproducibility of Results; D020112:Rhodamine 123; D012235:Rhodamines / Q000737:chemistry; D013194:Staining and Labeling
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; D037102:Lectins; D012235:Rhodamines; D020112:Rhodamine 123; C007392:3,3'-dihexyl-2,2'-oxacarbocyanine; D015759:Ionomycin; D002118:Calcium