Masahiro Takayama

Appearance of free radicals in the guinea pig inner ear after noise-induced acoustic trauma

The emergence of superoxide anion radicals (O2-) in the guinea pig inner ear following acoustic trauma was investigated by histochemical methods. Five minutes after exposure to sound at 120–125 dB SPL for 3 h, an O2- reaction product was detected in the cochlea along the luminal membrane of the marginal cells of the stria vascularis. This reaction product could not be found at 30 min, but reappeared at 2 h. The first appearance of O2- is not explainable by our studies, but the second appearance may be related to recirculation of strial blood flow after blood flow stasis. The present observations raise the possibility that free radicals are produced in the inner ear after acoustic trauma and lead to inner ear damage.

The Emergence of Free Radicals after Acoustic Trauma and Strial Blood Flow

The effect of acoustic trauma on cochlear strial circulation was investigated immunohistologically in the guinea pig. Kanamycin was used as a tracer of blood flow. Moreover, histochemical examinations were made to reveal the emergence of free radicals in the cochlea following acoustic trauma. At 5 min (5 min after intense sound exposure 120-125 dB SPL, 3 h) the blood flow in the stria vascularis was greatly diminished. At 2 h the strial blood flow started to recirculate and at 6 h it appeared to have returned to normal. Superoxide anion radicals (O2-) emerged along the luminal membrane of the marginal cells of the stria vascularis at 5 min. O2- disappeared at 30 min, but reappeared at 2 h. The cause of its emergence at 5 min was obscure. However, the strange phenomenon that O2- emerged again at 2 h seemed ascribable to the re-circulation of strial blood flow after sound exposure.

Apoptosis of guinea pig cochlear hair cells following chronic aminoglycoside treatment

Abstract Although aminoglycosides have been investigated for their cochleotoxicity, it has still not been determined whether apoptosis or necrosis results in cochlear hair cell death following aminoglycoside treatment. To study possible mechanisms of cell death, we used in situ DNA break-labeling to examine guinea pig cochleae affected by kanamycin ototoxicity. Chronic kanamycin treatment induced DNA fragmentation that was detectable in both outer and inner hair cells, suggesting the occurrence of apoptosis. These findings suggest that apoptosis achieves deletion of affected hair cells without disrupting tissue architecture in the organ of Corti.

Two Modes of Auditory Hair Cell Loss following Acoustic Overstimulation in the Avian Inner Ear

To determine the type of cell death occurring and how the removal of damaged cells proceeds following overstimulation, we examined chick basilar papillae using an in situ DNA nick end labeling method and transmission electron microscopy. Two distinct modes of hair cell loss were identified. First, hair cells which had not progressed into typical cell death processes, apoptosis or necrosis, were deleted by extrusion from the epithelium just after sound exposure. Second, hair cells manifested degeneration through the process of apoptosis, then further deterioration within the epithelium after the beginning of the process of hair cell regeneration. The latter mode may contribute to the following repair processes.

Nitric oxide synthase and contractile protein in the rat cochlear lateral wall: possible role of nitric oxide in regulation of strial blood flow

The present study demonstrated by histochemical and immunohistochemical methods that NADPH diaphorase reactivity, endothelial nitric oxide synthase (eNOS)-like immunoreactivity, and tropomyosin-like immunoreactivity, were located within the rat cochlear lateral wall. Both NADPH diaphorase reactivity and eNOS-like immunoreactivity were found mainly in the endothelium of the strial capillaries (ESC) and that of the vessels of the spiral ligament (ESL). These reaction products appeared to be somewhat more common in the ESC than in the ESL. On the other hand, tropomyosin-like immunoreactivity was localized in tissues outside the endothelium and its intensity was greater in the ESL than in the ESC. These findings suggest that nitric oxide (NO) produced by eNOS may play a role in regulating the blood flow of the cochlear lateral wall. In addition, NADPH diaphorase reactivity, eNOS-like immunoreactivity, and tropomyosin-like immunoreactivity showed different patterns of distribution between ESC and ESL. This suggests that in these two sites blood circulation is controlled by NO through two different mechanisms that are suitable for regulating strial blood flow.

Apoptotic cell death in Kikuchi's disease : A TEM study

The pathogenesis of Kikuchis disease (Kikuchi-Fujimoto disease, histiocytic necrotizing lymphadenitis) remains unclear. However, some previous studies have suggested that a disorder in cellular immunity is responsible for this disease, and apoptotic cell death appears to be the principal finding in the histogenesis of this disease. In the present study, a lymph node from a female patient with Kikuchis disease was examined by transmission electron microscopy (TEM). TEM revealed specific morphological features of apoptotic cells, such as nuclear chromatin condensation and fragmentation along the nuclear membrane with intact organelles, and the presence of histiocytes phagocytosing karyorrhectic debris (apoptotic bodies) in areas affected by Kikuchis disease. Although neither the role nor the trigger of apoptosis in Kikuchis disease has been clearly determined, our findings show that apoptotic cell death clearly plays a role in the pathogenesis of Kikuchis disease.

Involvement of nitric oxide in aminoglycoside vestibulotoxicity in guinea pigs

Involvement of nitric oxide (NO) has been reported in physiological and pathological conditions in the inner ear. Recently, the presence of nitric oxide synthase (NOS) was demonstrated in the vestibular epithelium. In this study we used nicotinamide adenine dinucleotide phosphate-diapholase staining to monitor NOS activity during degeneration of guinea pig vestibular epithelia affected by streptomycin. Increased NOS activity was observed in affected epithelia in a dose- and time-dependent manner and a NOS inhibitor could protect hair cells from apoptosis. Additionally, cycloheximide significantly reduced NOS activity and the occurrence of apoptosis. These findings suggest that NO is involved in the degenerative process of vestibular epithelia caused by aminoglycosides.

Study of tuberculosis in the field of otorhinolaryngology in the past 10 years.

Over the 10 years from 1988 to 1997, a total of 18 cases of tuberculosis of the head and neck (8 of the cervical lymph node, 5 of the larynx, 2 of the salivary glands, and 1 each of the hypopharynx, tongue and middle ear) were diagnosed in our department. Four cases were diagnosed in 1996 and 8 in 1997, indicating a rapid increase over these 2 years. Definitive diagnosis was based on histopathological examination in 14 cases, detection of M. tuberculosis in 1 case and exclusion diagnosis, mainly using the tuberculin skin test, in 3 cases. The length of time from the first examination to obtaining a definitive diagnosis was 14.2 +/- 6.5 days in five subjects in whom tuberculosis was suspected from the beginning or in whom tuberculosis was suggested by the physician in making a differential diagnosis, 25.3 +/- 17.2 days in the group in whom malignant tumour was suspected and 64.3 +/- 57.3 days in other cases. Although no significant difference was found (p = 0.077), the length of time until diagnosis tended to be shorter in the cases that were suspected of having tuberculosis from the beginning. Family history and past history of tuberculosis, contact with a tuberculous patient and abnormal findings at chest X-ray were examined as background factors, and some of these were present in nine out of the 18 cases. In the five cases diagnosed in the early stage, some of the background factors were found in four cases. However, no significant difference in the time until definitive diagnosis was found between the groups with or without background factors in all cases (p = 0.675). These results suggest the importance of considering tuberculosis when performing differential diagnoses.

In vivo Regeneration of Vestibular Hair Cells of Guinea Pig

Recent studies have shown that inner ear sensory cells may regenerate in mammals as well as in birds. In this in vivo study we investigated the regeneration of vestibular hair cells in guinea pigs after gentamycin intoxication, and found that the vestibular sensory epithelia reproduced new hair cells 30 days after degeneration, due to 30 consecutive days of gentamycin treatment. From the regeneration pattern of sensory epithelia, the supporting cells were identified as the progenitors of hair cells.

Blockage of reuniting duct in Meniere's disease

Conclusion: The bony saccular orifice to the bony groove of the ductus reuniens (reuniting duct) could not be visualized in the Menieres ear with significantly greater frequency compared with normal subjects, which suggests that the reuniting duct is affected by radio-opaque substances in CT findings. Objective: This study investigated a more specific, objective, and simpler strategy to diagnose Menieres disease by assessing the reuniting duct. Subjects and methods: We examined the ears of 12 patients with definitely diagnosed unilateral Menieres disease in stage 3 based on Menieres disease criteria proposed by the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), and the ears of 12 normal control subjects using three-dimensional (3D) cone beam CT. Results: The bony groove of the reuniting duct between the saccule and cochlea was visualized in all control subjects. However, the bony saccular orifice to the bony groove could not be visualized in the lesional ear of Menieres patients with significantly greater frequency compared with those of the contralateral non-lesional ears and control ears (p < 0.01). This orifice was not patent in 66.7% (8 of 12 ears) on the lesional side but all contralateral non-lesional ears of the patients and normal control ears were patent.