Ken Kitamura

Morphological Changes of Cochlea in a Strain of New-mutant Mice

The hearing ability and histological characteristics of the cochlea of a strain of new-mutant mice were analyzed. This new mutant arose as a spontaneous mutation in the C3H/He stock. The genetic mode is autosomal recessive and the animals show abnormal behavior such as circling, head-tossing and hyperactivity. The audiological findings exhibited no recordable auditory brain stem response (ABR) in any homozygotes at ages ranging from 11 days to 117 days. For morphological examination, we used 36 homozygote with ages ranging from 10 days to 18 months. The primary morphological abnormalities were observed in the organ of Corti. The stereocilia of the outer hair cells showed disarray throughout the whole cochlea, although outer hair cell cytoplasm became fully developed, including the nerve terminals. Age-dependent degeneration of the outer hair cells subsequently occurred from the basal to the apical part of the cochlea. The earliest change demonstrated in the outer hair cells was cuticular degeneration. Although the abnormalities of the inner hair cells occurred late, a complete loss of inner and outer hair cells was demonstrated. The stria vascularis was well preserved at a later age as were spiral ganglion cells. These histological findings confirm that this mouse is classified as a neuroepithelial-type mutant. As this animal was expected to have a single gene abnormality, molecular genetic studies on this animal can provide important information on the nature of histological changes of the hair cell from a mode of gene action.

Fluctuating Hearing Loss in Lipoma of the Cerebellopontine Angle

Two cases of lipoma of the cerebellopontine angle are presented. Both of them showed fluctuating hearing loss, and one case exhibited Menière-like symptoms. In one of the cases, continued clinical surveillance is considered in view of a high chance of postoperative morbidity.

Anionic Sites of the Basement Membrane of the Labyrinth

The presence of anionic sites in the labyrinth is demonstrated in this study, using polyethyleneimine as a cationic probe. Hartley-strain guinea pigs (200-300 g) with a normal Preyers reflex were used. A 0.5% polyethyleneimine (PEI, MW 1,800) solution adjusted to pH 7.3 with HCl following Schurers method was systemically administered through an axillary vein. In the cochlea, the presence of anionic sites was demonstrated on the basement membrane of the capillary wall in the stria vascularis. The presence of anionic sites was also confirmed on the basement membrane in Reissners membrane but its density was much lower than that in the stria vascularis. In the ampulla and macula, the anionic sites were present on the basement membrane of the capillary wall and sensory epithelium.

Abrupt (Sharp Cut) Type Sensorineural Hearing Loss: —A Human Temporal Bone Study—

Histopathology of a case of bilateral sensorineural hearing loss of abrupt (sharp cut) type is reported. While there was a 45 dB gap in threshold between 1,000 Hz and 2,000 Hz bilaterally, the patient had a good hearing at 1,000 Hz and lower frequencies. The patient was suffering from Takayasus arteritis. Major histopathological findings were as follows: Almost complete loss of the outer hair cells from the basal end to 12 mm area in the left cochlea (length: 30.5 mm) and 13 mm in the right (length: 31.5 mm). The inner hair cell of the same region was also missing in the left cochlea, and to a lesser degree in the right. There was a clear separation between the normal and the pathological organ of Corti. Marked loss of the cochlear neuron was noted in the same region. Blood vessels within the cochlea and the internal auditory meatus were normal. Bilateral abrupt (sharp cut) type sensorineural hearing loss with unknown etiology is a group of inner ear disease due to abiotrophy of the organ of Corti and cochlear neuron. Disposition or hereditary factor possibly plays an important role in the development of hearing loss.

An Ultrastructural Study on Vestibular Sensory Cells in a New-Mutant Mouse

The ultrastructural characteristics of the vestibular epithelium and light microscopical study of the central nervous system of a strain of new-mutant mice were analyzed. For the vestibular study, we used 72 homozygotes with ages ranging from 10 days to 18 months. The most striking findings observed in these mice were the disarray of the stereocilia of the utricular and saccular maculae and disintegration of the saccular otoconia. Many hair cells displayed abnormality of the stereocilia such as reduced number, disorganized distribution, and giant cilia, although the hair cell cytoplasm, including the nerve terminals, became fully developed. Demineralization of the saccular otoconia was age dependent, and a complete loss of the saccular hair cells was demonstrated. In conjunction with the disarray of the outer hair cells of the cochlea, morphological manifestation of the gene abnormality of these mice was related to immaturation of the stereociliary tufts. Because no morphological abnormality was observed in the central nervous system, the abnormal behavior in these mice was primarily correlated with morphological abnormalities of the vestibule.

Ultrastructural findings of the macaque monkey vestibular ganglion cells

The fine structure of macaque monkey vestibular ganglion cell was studied under the electron microscope. Over 400 serial sections enabled us to observe the entire surface of 114 ganglion cells. Eight ganglion cells were characterized by loose myelin layers. The compact myelin sheath was not demonstrated around any area of the perikaryon in these eight cells. The rest of the cells exhibited both compact and loose myelin layers around one perikaryon. All ganglion cells were bipolar in this study. The initial dendritic process was generally thinner and shorter than the initial axonal process. Both compact and loose myelin sheaths were demonstrated around the initial axonal and dendritic segment as far as the first node of Ranvier, after which all processes became thickly myelinated. This study demonstrated two types of cells: myelinated and unmyelinated. However, there is no obvious size or histological difference between the perikarya of different types of ganglion cells.

Short-term effects of iontophoresis on the structure of the guinea pig tympanic membrane.

Guinea pig tympanic membrane was anesthetized iontophoretically. The animals were sacrificed between 2 h and 4 days after the anesthesia and the tympanic membrane was studied histologically by light microscopy and transmission electron microscopy. Edema in the subepidermal connective tissue layer and detachment of the basement membrane from the basal cell layer were observed 2 h after iontophoresis. Eight and 12 h later, the epidermal layer between the handle of the malleus and the bony annulus peeled and retracted towards the bony annulus, leaving only hornified outer epidermis on the fibrous layer. Four days after iontophoresis, the retracted margin of the epidermal layer became greatly thickened and evidence of hyperplasia and migration was observed. This study has demonstrated that iontophoresis of the tympanic membrane produces remarkable histological changes. However, no perforation was observed.

Benign Recurrent Vertigo in Japanese

Twenty-one cases of Japanese patients exhibiting recurrent attacks of vertigo are reported. Fifteen of the cases are females. The mean age of onset of the vertigo is 30.8 years. In 11 patients, the duration of attacks is less than 10 min. Caloric responses are normal in all patients. Although two patients demonstrate hearing loss, the rest of the patients exhibit no hearing loss. Headaches have been reported in all patients. Eighteen of the patients experience headaches associated with the vertiginous attacks. The clinical features observed in our cases are consistent with a diagnosis of benign recurrent vertigo. Four patients exhibit cranial nerve symptoms which are features of basilar artery migraine. Basilar artery migraine is attributed to a migrainous disturbance of the basilar artery. Benign recurrent vertigo is also ascribed to a migrainous disorder affecting the vestibular system, thus it is a localized clinical manifestation of basilar artery migraine.