Makoto Shirane

The Effects of Deferoxamine Mesylate and Hypoxia on the Cochlea

Deferoxamine mesylate (DF) is a chelating agent used for the treatment of iron overload. Recently audiological testing of patients on long-term treatment with this drug indicated the possibility of an ototoxic side effect (1). We administered DF to chinchillas with both acute and chronic regimes. Functional and histological damage to the cochlea was detected only in the acute experiment. This was assumed to come not from the direct effect of DF on the cochlea but from the hypoxia as a result of respiratory suppression due to DF toxicity. To confirm this, animals were exposed to hypoxia during the same time course as for the DF experiment. Histological and physiological consequences of this hypoxia alone revealed very similar results to that observed in the acute DF experiment. This implies that DF has little direct toxic effect on the cochlea and, more importantly that considerable attention to hypoxia should be paid when assessing the cochlear pathology of animals which have been subjected to general anesthesia for long periods.

Action Potential of Isolated Frog Utricle

The action potential of an isolated frog utricle was recorded using a suction electrode. The utricle was stimulated with iron sand which were spread evenly on the macula. A magnetic force was employed to induce the iron sand to depress the macula lightly. Integration of the action potential resulted in a phasic component, just as observed in the isolated semicircular canal potential (Harada et al., 1969). The amplitude of the utricular phasic component was liner to the logarithm of the stimulus intensity. Similar relationship was observed between the semicircular canal action potential and the stimulus (Harada & Hirata, 1981). Phasic on-response was invaliably accompanied by an off-response. This suggests functional polarization of the utricle. It is already known that the macula is divided by the striola into two hair-cell groups having differing polarity. Since iron sand is spread evenly on the macula, all sensory cilia bend in one direction at the onset of the stimulus and one of the two cell groups ev...

A Clinical Study of Conductive Hearing Loss with Normal Tympanic Membrane

Seventeen cases (nineteen ears) of conductive hearing loss with normal tympanic membrane treated were studied. Seventeen cases were as follows: 5 cases (5 ears), incudostapedial joint dislocation; 5 cases (7 ears), congenital ossicular malformation; 6 cases (7 ears) otosclerosis. The postoperative hearing-gain was 23.8 dB for incudostapedial joint dislocation and 21.4 dB for congenital ossicular malformation and 22.9 dB for otosclerosis.