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Biomedical subjects

K Fukazawa

Publications and source records attributed to K Fukazawa.

77 records · Page 5Linked to original sources
PubMedDate not supplied

Regeneration of adult budgerigar's hair cells following acoustic trauma.

The functional and structural changes of hair cells of the adult budgerigar following acoustic trauma were examined using auditory brainstem response (ABR), and both scanning and transmission electron microscopy. Just after exposure to a 1,500-Hz pure tone at 120 dBSPL for 98 h, severe damages and disappearance of short hair cells were observed in the middle region of the basilar papilla. Fourteen days after the exposure, the threshold of ABR recovered to the level before the exposure, and normal short hair cells, which have synapses with nerve endings, were rearranged all over the damaged region of the basilar papilla. These results indicate that the hair cells of the adult budgerigar have capability to regenerate, and to restore the auditory perceptive function following acoustic trauma.

Animals↗
PubMedDate not supplied

Development of melanosomes and cytochemical observation of tyrosinase activity in the inner ear.

The ultrastructure and tyrosinase activity of melanocytes in the inner ear of pigmented guinea pigs were observed. Melanocytes/melanocyte-like cells were seen in the stria vascularis, the vestibular dark cell area and the endolymphatic sac. In the stria vascularis, melanosomes in several stages of maturation were seen in the cytoplasm of the intermediate cells and melanin-laden endosomes existed in the basal cells. Only the intermediate cells contained tyrosinase-positive cytoorganelles; Golgi sacs and neighboring small vesicles. Numerous melanocytes containing many melanosomes were observed under the epithelium of the vestibular dark cell area, and they showed tyrosinase activity. Melanocytes were seen in the endolymphatic sac, and they also showed tyrosinase activity. However, the epithelial cells of the endolymphatic sac, which had vacuoles containing melanin, did not show tyrosinase activity. Based on these findings, it can be said that (1) most of the intermediate cells of the stria vascularis must be melanocytes, (2) melanogenesis is vigorous in melanocytes of the inner ear, and (3) melanin in the epithelial cells of the endolymphatic sac is transferred in from melanocytes and is never synthesized in the epithelial cells.

Animals↗