Hironori Miyawaki

Cytoskeletal Organization of the Vestibular Sensory Epithelia

The cytoskeletal organization of the guinea pig vestibular sensory epithelium was investigated by employing the saponin perfusion method and scanning electron microscopy. The skeletal framework of a a cell was found to consist of actin, intermediate filaments and microtubules. The membrane-bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well documented. This made it possible to investigate the three-dimensional organization of cytoskeletons as well as their complex interaction with various membrane-bound organelles. The intermediate filaments were demonstrated not only in the supporting cells but also in the sensory cells. They are usually seen surrounding the nucleus and extending through the cytoplasm which connects the nuclear membrane to the plasma membrane, cuticular plate, reticular lamina or other cyto-organelles. The intermediate filaments are also closely related to the desmosomes. These findings suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. In the sensory cells, microtubules are found mainly in the supranuclear portion of the cells, running parallel to the main axis of the cell body, which is directly connected to the cuticular plate. These findings suggest that the microtubules provide the cell with mechanical support and may be closely related to the sensory cell transduction system. Inside the supporting cells, the microtubules are closely related to the secretory granules, Golgi apparatus and intermediate filaments, which supports the idea that the microtubules may control the distribution of intermediate filaments, and also play an important role for transport of the secretory granules.

Isolated Vestibular Sensory Cells in the Guinea Pig

Vestibular sensory cells were isolated from the utricular macula or cristae ampullares of the guinea pig by enzymatic and mechanical dissociation. The isolated cells were classified into three types: flask-shaped type I sensory cells, rod-shaped type II sensory cells and round-shaped supporting cells. The cilia of type I sensory cells in the crista ampullaris were longer than those in the corresponding cell type in the utricular macula, while no morphological differences of the cell bodies were noted between crista ampullaris and utricular macula. Isolated living vestibular cells have a motile capacity. After exposure to a hypo-osmotic medium, the type I sensory cells showed tilting of the hair bundle. This change in shape may be closely related to the active mechanical transduction control.

Three-dimensional organization of cytoskeletons in the vestibular sensory cells

The cytoskeletal organization of the guinea pig vestibular sensory cells was investigated employing the saponin perfusion method using scanning electron microscopy as well as immunohistochemical technique. The intermediate filaments were demonstrated in the sensory cells. They were usually seen surrounding the nucleus and extending through the cytoplasm which connected the nuclear membrane to the plasma membrane, cuticular plate or other cytoorganelles. These findings may suggest that the intermediate filaments provide mechanical support to the cell and its nucleus. Microtubules were found mainly in the supranuclear portion of the cells and run parallel to the main axis of the cell body, which is directly connected to the cuticular plate. These findings may suggest that the microtubules provide mechanical support to the cell and may be closely related to the sensory cell transduction system. The actin filaments were densely packed in the site of the cuticular plate. They also distributed throughout the cytoplasm, which appeared as a dense network in the periphery region. These findings support the idea that the actin filaments could be responsible for sensory cell transduction as well as to give mechanical strength to the surface of the cell and enable the cell to change its shape and move.

Motile responses of isolated vestibular hair cells.

Vestibular sensory cells were isolated from the utricular macula or crista ampullaris of the guinea pig by enzymatic and mechanical dissociation. Isolated vestibular hair cells, especially type I hair cells, showed an active motile capacity. After exposure to a medium containing high concentration of potassium, or to a hypoosmotic medium, the type I hair cells showed tilting of their hair bundle to about 15 degrees. Given the tight and dense structure of the vestibular epithelium, the changes in shape of the isolated vestibular hair cells may in vivo lead to an influence of the mechano-sensitive stereocilia and modulate stiffness and compliance of the receptor structure as a whole including its cupular or macular relationship. This active mechanical events could be closely related to an active adaptation process.

Cytoskeletal Organization of the Vestibular Sensory Epithelia: Saponin Perfusion Method for Observing Intracellular Structures by Scanning Electron Microscopy

The cytoskeletal organization of the guinea pig vestibular sensory epithelial cells were investigated by the use of saponin perfusion method using scanning electron microscopy. The skeletal framework of a cell is composed of thin (actin or intermediate filaments) and thick filaments (microtubules). The membrane bound organelles such as nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc. were also well demonstrated. This made it possible to investigate the three-dimensional structures of cytoskeletons as well as their complex interactions with various membranes bound organelles. It is therefore suspected that this technique may provide us further information about distribution, topographic relationships, and the functional role of cytoskeletons.

A Case of Primary Nasopharyngeal Tuberculosis

We report a case of primary nasopharyngeal tuberculosis in a 27-year-old woman who had immigrated to Japan from Vietnam. She initially complained of right cervical swelling. A red granular mass with ulcer was observed in the nasopharyx. A biopsy from the nasopharynx showed tuberculous changes. Tubercle bacilli were detected in a smear of pharyngeal discharge. Since there were no apparent pulmonary tuberculous lesions, we diagnosed the case as primary nasopharyngeal tuberculosis with tuberculous cervical lymphadenitis.The nasopharyngeal lesion disappeared after three weeks anti-tuberculosis chemotherapy. Tuberculous cervical lymphadenitis increased despite chemotherapy, and required dissection and drainage.Anti-tuberculosis chemotherapy was administered by a short course of carefully monitored treatment.