Récentes Connaissances Sur La Structure Submicroscopique Des Organes Du Vestibule

Longitudinal flow of macromolecules in the endolymphatic space of the rat. An autoradiographical study

Secretion and resorption of sulphated glycoproteins by the epithelial lining of the endolymphatic space of the rat were studied autoradiographically with the use of 35SO4 as a selective marker. This isotope was found to be incorporated into the sensory area of cristae and maculae and a small area of epithelial cells adjacent to the sensory epithelium. Thereafter 35S-labelled glycoproteins were secreted into cupulae and otolithic membranes. No such process could be established in the tectorial membrane. From the gradual disappearance of 35S-labelled glycoproteins from cupulae and otolithic membrane coupled with an accumulation of this substance in the lumen of the endolymphatic sac, the existence of a longitudinal flow under physiological conditions could be concluded. Resorption of glycoproteins by the saccus epithelium was found to be very slow. Accumulation of 35S-labelled glycoproteins in the endolymphatic duct after saccus obstruction indicates that, in addition to the endolymphatic sac, also the duct contributes to the mechanism underlying the longitudinal flow of macromolecules.

Formation of the cupula cristae ampullaris: development in vivo and in vitro

The development of the cupula cristae ampullaris in the mouse starts on the 14th gestational day and occurs mainly during the 15th and 16th gestational days. Subsequently the secretory activity of the epithelial cells diminishes. The cupula is formed from the underlying epithelium when there are only a small number of differentiated hair cells present. Secretion of cytoplasmic material occurs mainly from supporting cells. The surface of the epithelium at a location corresponding to the planum semilunatum in the adult organ has a thick layer of microvilli and demonstrates a particularly high secretory activity on the 15th gestational day. After the 16th gestational day there are few morphologic signs of secretion. The cupula also develops in inner ear anlages that have been explanted at the otocyst stage on the 12th or 13th gestational day and cultured for eight days in vitro.