Hiromasa Cho

Imprints of the tectorial membrane following acoustic overstimulation and kanamycin treatment.

Normal imprints in guinea pigs were examined mainly using a scanning electron microscope (SEM). Morphological changes in imprints after loading of the conditions mentioned below were also investigated. Imprints observed on the normal tectorial membrane were composed of small concavities lined on a W-shaped line and the W-type was of a V-type in proportion to ascend to the upper turn. The imprints occurred at the rate of one for every outer hair cell and in 3-4 lines corresponding to the outer hair cell hairs. With exposure to a high intensity of sound, small concavities of the imprints were deformed and remnant sensory hairs were observed, sporadically. Another line of new imprints was sometimes evident in the lower turn of the cochlea, in addition to the original imprints. In case of inner ear disturbances due to kanamycin (KM) loading, the imprints were little deformed, but the remnant sensory hairs were numerous and their time-course revealed a gradual decrease and the disposal required a longer time than seen in the degenerated cell fractions on the reticular membrane. With exposure to high intensity sound after KM loading, KM-type changes or high intensity sound-type changes were observed and depended on severity of the KM-induced disturbance. The imprints existed for a considerably long time even when the lower region sensory cells degenerated or disappeared in the presence of various conditions.

Light and electron microscopic studies of a case with simultaneous Mondini and Michel deformities of the inner ears

SummaryWe performed light and electron microscopic studies on the temporal bones of a patient with genetic aplastic deafness, in which the right ear had a Mondini-type defect and the left ear a Michel-type anomaly. The round window of each ear was absent. The stapedial foot plate of the right ear was depressed at its central part and was covered by thin membrane. The course of the internal auditory meatus of the left ear was deviated ventrally. There was total aplasia of the cochlea in the left ear, while that of the right ear showed only three-quarters of a turn. In this ear, three sites of spherical bulging were found and were believed to represent outer hair cells. Other structures of the normal cochlear duct were not present. The modiolus of the left ear was round and dome-shaped, contained sparse nerve fibers and a primitive spiral ganglion. The saccule, utricle and semicircular canals of each ear were missing, so that a common cavity of the vestibular system was present. Several otoliths could be seen under the surface of the membrane covering the common cavity. No sensory cells or their related tissues could be found in either ear.

Epithelial linings of the human semicircular canal

SummaryWe have used scanning and transmission electron microscopy to examine adult human semicircular canals taken at autopsy and at operation. Our findings can be summarized as follows. In the semicircular canals obtained at autopsy from a 30-yearold male, non-sensory ciliated cells having 50–60 cilia were seen sporadically in the canal side of the ampulla of the horizontal canal. A labyrinthine specimen taken at operation demonstrated folding of the cell membrane at the base of columnar cells lining the wall of that part of the canal close to the ampulla. Distal to this site, canal wall cells became progressively flattened and their intracytoplasmic organelles were seen to be progressively less abundant. These cells were found to be layered, facing the endolymphatic space. Dense filaments and fibrocytes were present outside these cells, between which were interposed single-layered basement membranes. Since the capillary network present was found to be sparse, we believe that the portion of the canal studied does not produce endolymph but plays a role in the maintenance of the composition of endolymph and perilymph.

Electron Microscopic Observation of Communication between Inner Ear Stereocilia under Normal and Noise stimulated Conditions

The ultrastructure of communication between inner ear stereocilia under normal and noise stimulated conditions was studied in the guinea pig. With ruthenium red added to the pre- and post fixation solutions, the connections between the stereocilia could be observed in more detail than with ordinary fixation. After exposure to 1,000 Hz 110 dBSPL sound for 3 h, parts of the connections between the stereocilia had disappeared, and adherence between the adjoining stereocilia was observed. The results of our study lend support to the fact that the congregation of stereocilia after noise stimulation is due to the sticky adjoining stereocilia membrane.