Bull frogs posterior semicircular canals (psc) were used to simulate the condition of benign paroxysmal positional vertigo (BPPV). The psc was isolated in frog Ringer's solution, and the saccular otoconia were used as a responsible material to stimulate the cupula. When the otoconia were placed on the cupular surface to mimic the condition of cupulolithiasis, the psc ampullary nerve action potentials instantaneously changed according to the direction of the gravity produced by otoconia. When the otoconia were dropped into the canal to mimic the condition of moving otoconia in the canal, the action potentials changed together with the otoconial flow after a latent period. Both cupulolithiasis and moving otoconia are possibly valid mechanisms of BPPV, since they effectively stimulate the cupula. However, moving otoconia with a latent period would better explain clinical features of BPPV.
We have developed a high-frame-rate laryngoscope that can measure the vibration distribution of a human vocal fold in real time at hundreds of hertz. Our laryngoscope can extract a vocal-fold contour at 4000 fps as 20 pairs of its left and right border points from 256 × 512-pixel images to quantify left-right asymmetry of vocal-fold vibrations. Experiments on artificial vocal-fold-like vibrations of a silicon rubber membrane were performed to confirm the laryngoscope's effectiveness, and the vocal folds of human subjects, including patients with laryngeal diseases, were examined under clinical conditions.
Isolated posterior semicircular canals (psc) of bull frogs were used for a model of positional vertigo. Induced ampullary nerve action potentials were recorded. When the cupula was removed and the saccular otoconia were dropped onto the cilia, excitatory, and inhibitory potentials were evoked by changing the psc positions into canal-down and canal-up, respectively. When the otoconia were allowed to stay on the cupular surface, canal-down and canal-up positions also evoked excitatory and inhibitory responses, respectively. When the otoconia were inserted in the canal and were allowed to move, changing the psc positions likewise evoked responses. However, when one end of the canal was closed, these responses disappeared, indicating the efficacy of canal plugging.
D Abstract -Effect of thermal stimulus on the vestibular receptor was studied using the isolated frog semicircular canal. The posterior (PSC) and lateral semicircular canals (LSC) were placed in the horizontal plane in frog Ringer's solution. The ampullary nerve was sucked into a glass suction electrode to record compound potentials. The steel thermal probe was positioned next to the ampul· lary surface to give thermal stimuli. When the PSC ampulla was cooled, the spontaneous dis· charge markedly increased. When the PSC am· pulla was warmed, the discharge decreased. When the LSC ampulla was cooled, the discharge in· creased in the same manner as in the PSC. Also, warming of the LSC decreased the discharge in the same manner as in the PSC. The cupula was removed from the crista in order to eliminate the effect of volume change of the endolymph. The reo suits were comparable to those with intact cupula in both the PSC and LSC. Cooling increased, while warming decreased the discharge. These reo sponses are possibly due to a mechanism other than mechanical volume change, because the PSC and LSC yielded the same type of responses. Di· rect temperature reaction of the vestibular hair cell was suggested.
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