The widths of excursion on Békésy audiogram are commonly calculated by means of obtaining mean value of widths in dB between each top and bottom of recorded zigzag tracing. But, by this method the calculation is rather time consumptive. The authors devised a calculating method of the width of excursion for the purpose of saving time. Firstly, the widths of excursion of 2.5, 5.0, 7.5, 10.0, 12.5 and 15.0dB were accurately recorded as zigzag tracings on a paper of audiometer. And then, the recording time of drawing 20 of tops and bottoms on each tracing was measured. The recording times and the widths of excursion showed linear function. In the patients, the widths of excursion were practically able to be calculated easily by this function.
On the peripheral hearing mechanism, the authors assumed interaction, feedback effect and incidence probability of impulse that chose the stationary or nonstationary stochastical process in accordance with the ratio of input to output capacity. Under this assumption, the following result were obtained by application of the stochastical model. 1. Universal explanation that applicable to every loudness growth types of the sensory-neural disorder can be obtained. 2. Comparing the slope of the temporal threshold curve on the short tone durations at the sensory-neural disorder to that of equal loudness curves at the different Sensation levels of the normal ear, the authors could not only pick out the localization and the grade of disorder, but also estimate the stage of the disease (reversible type or unreversible type).
The ototoxic effects of kanendomycin and vistamycin on mice were studied by light and electron microscopy. Toxic reaction were mainly observed in the organ of Corti. Degeneration appeared first in the outer hair cells in the basal turn of the cochlea starting with the increasing of lysosomes, proliferation of smooth endoplasmic reticula and degeneration of mitochondria in the subcuticle area and resulting in the complete loss of hair cells, but the stria vascularis and spiral ligament showed little change. Even after the disappearance of the hair cells, some nerve endings were still present in the organ of Corti but they were also disintegrated in a large dose administration. The degeneration of mitochondria and increasing of lysosomes which were observed one day after the final injection of these dregs were much decreased in long term observation. Even in case of total loss of the outer hair cells in the basal turn, some of the outer hair cells in the hook region still existed. Vistamycin was less ototoxic than kanendomycin.
The side effect of lividomycin a new aminoglucoside antibiotics-on the inner ear was studied using the guinea pigs, and the results were discussed and compared with that of kanamycin, lividomycin was injected every day for 40 to 150 days intramuscularly. Preyer's pinna reflex was used for determination of hearing loss. The lowest sound pressure enable to arise the pinna reflex was measured in the pure tone of 125 to 8, 000Hz every 5 days. After physical examination. pathological change of hair cells of the organ of Corti was observed histologically with silverstain surface preparation method. Though the pattern of the side effect of lividomycin on the inner ear was almost same as that of kanamycin, the ototoxity of lividomycin was somewhat milder than that of kanamycin. In its clinical use, it is necessary to take care of the occurence of ototoxity like as other aminoglucoside antibiotics.
Ototoxicity of lividomycin (LVM), recently developed aminoglycoside antibiotic, was functionally as well as histopathologically evaluated in guinea pigs of Hartley strain (300g body weight at the start of the experiment). Sixty three guinea pigs were divided into following 5 groups. Group 1 (10 guinea pigs), each animal received LVM intramuscularly at dosis of 100mg/kg body weight. Group 2 (21 guinea pigs), each received LVM intramuscularly at dosis of 200mg/kg. Group 3 (11 guinea pigs), each received LVM intramuscularly at dosis of 400mg/kg. Group 4 (10 guinea pigs), each received KM intramuscularly at dosis of 100mg/kg. Group 5 (11 guinea pigs), each received KM intramuscularly at dosis of 200mg/kg. The antibiotics were given to the animals for 4 weeks. Pinna reflex test was performed before, during and after the experiment with audiometer. Frequencies of the audiometer ranged from 10, 000Hz to 500Hz. The animals underwent vital fixation with Wittmaack's fixative under general anesthesia after the end of the experiment. The temporal bones were en bloc removed from the skull and further fixed in the same fixative for one week. The temporal bones were embeded in celloidin after decalcification. The horizontally sectioned serial celloidin sections were stained with hematoxylin-eosin. Histopathological examination was performed on the spiral organ of the cochlea and the vestibular organ, with special reference to the extent of hair cell damage in the cochlea. The results obtained were as follows: 1) LVM was ototoxic in guinea pigs at the dosis of 200 and 400mg per kg body weight. The ototoxicity was much prominent in the hair cells of the spiral organ. In the basal turn of the cochlea the outer hair cells were more sensitive to the antibiotic than the inner hair cells, but in the apical and 4th turns the inner hair cells were more vulnerable than the outer ones. The loss of the outer hair cells, that is advanced damage, started from the basal end and indicated a general tendency to spread upwards. 2) LVM showed almost the same ototoxicity as KM at the dosis of 200mg/kg body weight in guinea pigs.