The pH regulation of the outer hair cell (OHC) was investigated using fluorescence imaging microscope. The application of NH₄Cl increased intracellular pH in OHC followed by a slow recovery of pH. The subsequent addition of Na-free solution led to the acidification. Moreover, the application of a standard solution gradually increased pH, which was inhibited by amiloride. CO₂-loaded OHC showed a rapid acidification inhibited by acetazolamide. These finding indicate that Na-H exchange and carbonic anhydrase are involved in acid-base regulation in OHC.

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Anionic sites of the basement membrane of the Reissner's membrane and the capillary wall in the stria vascularis were presented and its variability was studied with the change of pH adoministered. Guinea pigs were systematically 0.15ml/100g B. W. through an axillary vein. Acidosis and alkalosis were produced by hypoxia and injection of 7% NaHCO₃, respectively. Decrease of anionic sites was more remarkable in the basement membrane of the capillary wall than that of the Reissner's membrane.

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Vestibular hair cells were isolated from saccule and ultricle of guinea pig by enzymatic and mechanical dissociation. These hair cells were classified into two types; cells which showed flask shape form and different length of neck are thought to be type I cells and cells which showed rod or round shape form and had no neck might be type II cells. Using these cells, we examined their intracellular distribution of cytoplasmic free Ca²⁺ concentration ([Ca²⁺] i) by the Ca²⁺ sensitive dye fura-2. In the resting state, type I like cell showed high [Ca²⁺] i in nucleus and cuticular plate although type II like cell showed high [Ca²⁺] i only in nucleus. During ionomycin stimulation and depolarization state induced by elevated K⁺, [Ca²⁺] i of both types of cells were markedly increased.

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The DC potential and K⁺ activity in the stria vascularis were simultaneously recovered from normal and Kanamycin-deafened guinea pigs, using K⁺-selective microelectrode. The positive DC potential, possibly the resting potential of marginal cell, was approximately 40-80mV and significantly lower than the endocochlear potential (EP). During anoxia, that DC potential of both groups showed parallel decreases. The K⁺ activity ranged from 20 to 60mEq/1 and was much lower than that of the endolymph before and during anoxia in both groups. These results suggest that K⁺ pumps may exist at the basolateral and luminal membranse of the strial marginal cell.

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The endocochlear potentials (EP) and potassium activities of endolymph were measured in the second turn of the cochlea in normal and kanamycin-deafened guinea pigs after perfusing the scala media with Ringer's solution (5mMKCI) or 50mMKCI. Active K⁺ flux was calculated from the measured K⁺ flux after perfusion and the passive flux derived from Gk and the driving force for potassium ions. The electrogenic potential transport was plotted as a function of active K⁺ transport after perfusion in both groups of animals. It was suggested that the EP consists of positive and negative components, but the negative component is very small (=0) in normal physiological condition, which may be K diffusion potential through the organ of Corti produced by anoxia.

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H-8, an inhibitor of cAMP-dependent protein kinase, eliminated elevation of endocochlear potential (EP) produced by forskolin, an adenylate cyclase stimulant, whereas H-8 had no effect on EP itself. Forskolin elevated EP even if Na⁺-K⁺K pump was completely suppressed by ouabain. Endolymphatic Na⁺ and k⁺ concentrations were not significantly altered during EP elevation produced by forskolin. The results suggest that cochlear adenylate cyclase may be activated and play an important role as a reserve battery without activating Na⁺-K⁺ pump in some pathological conditions.

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Excitatory amino acid-induced responses in isolated guinea-pig cochlear spiral ganglion cells were investigated by a patch-clamp technique. The cells were dissociated by the enzymatic and mechanical treatment. L-glutamate (Glu) and its agonists, quisqualate (QA) and kainate (KA), induced a inward currents. None of cells responded to one of Glu agonists, N-methyl-D-aspartate (NMDA). Kyn, diCl-HQC, CNQX and DNQX suppressed the Glu-, QA-, and KA-induced currents. CNQX blocked the Glu- and QA-induced currents more than the KA-induced one.

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Responses from the cochlear nucleus neuron of the anesthetized cat were obtained under the condition of short-term adaptation and PST histogram, spike discharge rate and membrane potential were examined. Input-output function was obtained from the pauser and buildup neuron under the following conditions; when the interval was 40ms and the duration of the masker was 100ms. Under such condition dynamic range of input-output function was enlarged by 20dB and threshold became better by from 5 to 10dB> The discharge pattern changed from pauser to sustained type.

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Response of 25 units in cat cochlear nucleus to pure tone and complex tone was investigated. Glass microelectrode was inserted to ventral cochlear nucleus strerotaxically, and rate of action poteneials was counted during sound stimulation at 90dBSPL. Complex tones consist of two pure tones of the same intensity, one of which is a double of the other in frequency. Although most of units showed no change in their response between pure tones and compound tones, some responded more strongly to compound tones, and others responded less than pure tones. Decrease in responsiveness to complex tones may be explained by two-tone suppression in the cochlea or neural inhibition in cochlear nucleus, but increase in responsiveness is thought to be of unknown origin.

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The cochlear efferent neuron response to the sound stimuli was physiologically examined in the cat. The recording electrode was placed in the superior olivary complex (SOC), and the bipolar stimulating electrode was placed in the contralateral round window. A single neuron which responded to the contralateral electrical stimuli with a latency shorter than 1.5 msec was identified as cochlear efferent neuron and its responses to the sound stimuli were observed. Cochlear efferent neurons existed mainly in the medial part of the SOC. The neurons which reacted to the contralateral sound stimuli with a higher characteristic frequency were found in the more dorsal part of the SOC than neurons with lower frequency.

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Fixed malleus syndrome causes mild to moderate hearing losses. Ritter reported that anterior process of malleus fixed to the superior epitympanum in cat. The aim of this experiment is to investigate whether the malleus fixation in cat is able to be a real model of fixed malleus syndrome in man. The round window CM changes before and after the fracture of the anterior process of malleus, and before and after the fixation of the collum mallei by adhesive to the tympanic wall were measured in cat. As the results CM amplitude showed not to increase after the fracture of anterior process, to decrese by the fixation of collum mallei. The rates of decrement in CM were dependent on the frequencies respectively

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The effects of indomethacin upon EP during perilymphatic perfusion were studied with albino guinea pigs. Indomethacin, at 10^-3M, 10^-4 and 10^-5M, was applied. During perilymphatic perfusion with 10^-3M indomethacin, EP decreased significantly, but it recovered gradually after artificial perilymphatic perfusion without indomethacin. When indomethacin concentrations of 10^-4M and 10^-5M were used significant changes in EP were not noted. These findings may help in elucidating the mechanism of indomethacin ototoxicity and the role of prostaglandins in the cochlea.

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The effects of nitrogen mustard-N-Oxide (NMO) on the EP were studied by measuring K⁺ and Na⁺ activity in the scala media in normal and Kanamycin-deafened guinea pigs. The EP was decreased to around 37mV 24 hours after administration of NMO, gradually recovered to the normal level after 2 weeks in normal animals. However the EP remained unchanged in KM animals during the period. The K⁺ was decreased in both groups and the Na⁺ was increased in normal but not in KM animals 24 hours after administration of NMO.
At that time the potassium conductance (Gk) was decreased through the cochlear partition in KM but not in normal animals. The GNa was increased in normal but not in KM animals. The results suggest that the decrease in the EP of normal are mainly the inhibition of the active transport process in the stria vascularis and that no change in the EP of KM animals is because access of NMO to the strial cell is maybe inhibited by Kanamycin.

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The EP responses to anoxia for mature and immature inner ear of guinea pigs were compared. EP decreased much more slowly after anoxia in guinea pig embryos than in neonates. In many embryos, EP didn't reach a negative voltage. The development of the negative component of EP is a function of its positive component.

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The effect of asphyxia on the endolymphatic sac DC potential (ESP) was examined in the guinea pig. Asphyxia was administered for 1.5 min by stopping the respirator. The ESP decreased in amplitude during asphyxia. After the termination of asphyxia the ESP showed a diphasic recovery pattern. When the respiration was resumed, the ESP decreased again following a transient recovery. Thereafter the ESP showed a gradual recovery. β-blocker (propranolol) inhibited a decrease in the ESP after the resumption of respiration, but not a α-blocker (phentolamine).The result indicates that the ESP decrease after the resumption of respiration is induced by-βadrenergic action.

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The effect of catecholamines on the endolymphatic sac DC potential ESP was examined in the guinea pig. Norepinephrine (NE), epinephrine (EPI) and isoproterenol (ISO) were administered intravenously for 4 min. Catecholamines reversibly decreased the ESP with the rank order of potency ISO>EPI>NE. The threshold dose was 0.021 μg/kg/4 min for ISO. The ratio of threshold dose was 1: 13: 92 for ISO: EPI: NE. β-antagonist (propranolol) blocked the action of catecaholamines on the ESP but not α-antagonist (phentolamine). It indicates that the action of catecholamine on the ESP is β-adrenergic.

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Evoked oto-acoustic emissions in 6 cases with spontaneous OAE were mesured in several stimulating conditions. The standard stimulating sound was the tone burst with 1.5kHz (rise-plateau-fall time; 1-1-1ms). The stimulating rate was changed as 5, 9.5 and 15Hz. The rise and fall time was changed as 0.5, 1 and 1.5ms. The plateau time was changed as 0, 1 and 1.5ms. These changes of stimulating condition did not affect on the appearance and phase of the prolonged EOAEs, though the shifts of main peaks of the EOAE were observed when rise, fall and plateau time were changed. When the intenstiy of stimulating tone increased, the each peaks of the response wave slightly delayed in 8 ears of 12.

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Evoked otoacoustic emissions (e-OAE) and spontaneous otoacoustic emissions (s-OAE) probably have their sources inside the inner ear. I outline the theory of these generation using a cochlear model. The computer simulation indicates that e-OAE is reduced in a subject with a basilar-membrane lesion at the characteristic frequency area. And it is assumed that s-OAE is generated at a region on the basilar membrane with too large active feedback (probably most sensitive to sound). A short tone burst can trigger s-OAE, then continuous s-OAE (which seems to be prolonged e-OAE) is detectable at a certain level.

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A new durable acoustic probe for OAE measurement was made, in accordance with the data of our previous probe K-2, by RION Co. Ltd. The material of the double barrelled acoustic tube which was made of plastics in the K-2, was exchanged for that made of stainless steel. Four samples with different tube length were examined for frequency characteristic. The tube set, of which length was 18 mm for stimulation system and 12 mm for recording system revealed the best characteristic curve. The subminor earphone (RION RK63B) and the miniature microphone (RION EUO8) was employed for a driver and a receiver, respectively. We called this new probe with best frequency characteristic as K-3. The K-3 had a flat characteristic between 900Hz and 1500Hz in its application to actual ears.

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Evoked otoacoustic emission (e-OAE) elicited by click sounds was recorded by two testing apparatus (ILO88: A and laboratory-built e-OAE testing system used by probe K-2: B) and parameters in e-OAE recorded by both apparatus were compared. The subjects were 60 ears with type A tympanogram from 30 normal hearing persons. There were high negative correlations between e-OAE pseudothreshold recorded by apparatus B and total echo power (TEP) and highest peak power (HPP) in e-OAE recorded by apparatus A. However, the correlation coefficients between interaural difference of TEP and HPP in A and that of e-OAE pseudothreshold in B showed lower values because of the small interaural difference of parameters in both testing apparatus. Based upon these results, we concluded that the parameters such as TEP and HPP in apparatus A could be the useful clinical tool to investigate the function of cochlear micromechanics.

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The effects of contralateral noise exposure on evoked otoacoustic emission (e-OAE) was investigated in 10 normal hearing subjects and 3 cases with unilateral deafness. The e-OAE was recorded by ILO88 and weighting noise was given to the contralateral ear. The e-OAE power decreased along with the increased noise intensity given by the air conduction in all normal hearing subjects. But no effect was found in unilateral deafness. The mean decrease of e-OAE power was 2.1dB. The bone conduction noise exposure showed no effects on e-OAE power in either normal hearing subjects or unilateral deafness. Based upon these results, it was suggested that the effects of contralateral noise exposure on the function of cochlear micromechanics was minimal, which could be probably via crossed olivocochlear bundle.

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It was investigated by a computer simulation of the cochlea whether latencies of evoked otoacoustic emissions (e-OAE) could be accounted for in terms of reflections of travelling waves on the basilar membrane. One dimensional model of the cochlea was solved by finite difference method and phase velocities were calculated for sinusoidal inputs with four different frequencies to the oval window. Impulse responses at characteristic places of the basilar membrane for the same four frequencies were also calculated using inverse Fourier transform of frequency response at each point. The results revealed that no simple reflection could explain the latency of e-OAE and several mili-seconds of delay should exist somewhere before the reflection showed up as emissions.

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We examined the input-output function of 100Hz narrow-band EOAE. 100Hz narrow-band EOAE consisted of several echoes with different latencies and detection thresholds. These echoes could be grouped to the one with longer latencies and the other with shorter latencies. In general, the input-output function of echoes with longer latencies showed non-linear property, while that of echoes with shorter latencies did not. The detection threshold of echoes with longer latencies was lower than that with shorter latencies.

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Ten male rats were fed 4mg/kg/day of methylmercury chloride (MMC) for 16 days. After the appearance of intoxication signs, cerebellar and inner ear tissues of the intoxicated rats were fixed, decalcificated, and enbedded in paraffin in the usual manner. Deparaffinized sections were cut 6 μm thick and mercury in the inner ears was demonstrated histochemically using an autoradiographic procedure.
Mercury deposits were typically found in the cerebellum and were shown in parts of the vestibular nerves, cochlear nerves, spiral ganglion. There was a little mercury deposition in the acoustic maculae. They also found in the stria vascularis, but no mercury deposit was detected in the organ of Corti.

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The pharmacokinetics of CH₃-Vitamin B₁₂ in the cochlear periphymph and CSF were studied in guinea pigs following intravanous administration of 500 or 1000 μg/kg of CH₃-B₁₂. The concentration of B₁₂ were datermined with microbiologic methods. The peak of B₁₂ concentration in CSF was observed within 1 hr and clearance was observed as late as 8 hr or 24 following injection of 500 or 1000 μg/kg, respectively. The B₁₂, kinetics in the scala tympani (ST) and in the scala vestibuli (SV) were very similar. However, both increase and decline in ST were earlier than those in SV.

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This study was aimed to elucidate the effects of salicylate on the cochlear nerve by recording the spontaneous activity before and after salicylate administration. After guinea pigs were given salicylate (200mg/kg) intravenously, two of four fibers showed the transient reduction in spontaneous activity, and the elevation over the subsequent 10-20 minutes. The mean spontaneous discharge rate after administration of salicylate (400mg/kg) was significantly higher than the control values. The observed changes in spontaneous activity due to salicylate administration may represent the evidence of a tinnituslike phenomenon in guinea pigs.

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The effects of ototopical preparations (Cortisporin^®, Coly-Mycin^®, Aristocort^®, and Bestron^®) upon the permeability of the round window membrane (RWM) in chinchillas were investigated by detecting tetraethylammonium ions using K⁺-selective microelectrodes and observing the thickness using light microscopy. The RWM permeability was reduced significantly in Cortisporin^®- and Coly-Mycin^®-given ears. Moreover, these two drugs showed a marked thickening of the RWM. In contrast, Aristocort^® or Bestron^® resulted in no alteration of the RWM permeability.

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The ototoxicity of Cisplatin (CDDP) and DWA2114R (DWA) was evaluated using an organ culture system. The inner ears of mouse 21-day embryos were cultured for 4days with or without CDDP or DWA, with doses from 0.1 to 10 μg/ml. The damage of crista ampullaris of cultured inner ear was estimated accordihg to the ototoxicity score based on morphological change by a light microscopic observation of serial sections of the samples. Using this system we showed that the effect of both CDDP and DWA was obvious at a concentration of 0.1 μg/ml and that DWA showed almost the same ototoxicity as CDDP at the same concentration. It can be elucidated that in vivo ototoxicity of CDDP is more toxic than that of DWA since CDDP remains in the body fluids for longer time than DWA. The organ culture system revealed the same ototoxic potentiality of DWA as CDDP. Therefore, this result indicates that when DWA is clinically used for patients with renal dysfunction, it should be as ototoxic as CDDP.

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The guinea pigs were treated with intravenous injections of 254-S and CDDP (12.5mg/kg) respectively. Effect on endocochlear D. C. potential (EP) was examined and morphological changes were observed. There have been only limited frequency ranges elevating threshold of the preyer's reflex in 254-S group, while have been almost no responce in all range in CDDP group. The EP value have no significantly different between two groups. The negative EP value were -12.2±8.9 (CDDP) and -25.9±10.2 (254-S) mV respectively, and have significantly different (P<0.01). There have been observed collapse of the S. V. and degeneration or disappearance of OHC in CDDP group, but have been the slight morphological changes in 254-S group.

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Cisplatin (CDDP) is known to have toxic effects on inner ears. There are numerous reports about hearing disturbances and damage of the cochleas, but there are very few about vestibular disturbances. We discuss this problem in the following SEM study. Guinea pigs were injected peritoneally with 5 mg/kg or 10 mg/kg CDDP. Pathological changes were observed right after CDDP administration. Exfoliation of cilia was eminent at the central part of the ampullae, while II type cells at both ends of the ampullae were rather well preserved. Cilia in the utricles were deranged but not exfoliated. The structure of the saccules were almost normal without derangement or exfoliation of cilia.

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Tuberactinomycin (Tum) is one of the peptide antibiotics with pharmacological character similar to kanamycin. Thirteen derivatives of Tum were prepared by replacing the R1 branch to various amino acids. The degree of ototoxicity of these derivatives was evaluated in comparison with their chemical structure. The isolated posterior semicircular canal of the bull frog was used. The ampullary nerve action potential in response to mechanical endolymphatic flow was recorded in normal Ringer's solution and in solutions with Tum of 2.5 mg/ml or Tum of 5.0 mg/ml. The degree of ototoxicity was determined by the amount of decrease in the maximum spike count. The derivatives of Rim with R1 branch containing acidic or basic groups of amino acid showed greater ototoxicity than those containing aliphatic side chains.

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Utricle of the mongolian gerbil was embedded in Spurr and the thin section was made and labeled with colloidal gold conjugated with hyaluronidase. Normal otolith was labeled with hyaluronidase-gold intensively but degenerated one was labeled less intensively or was unlabeled. In the sensory epithelia, the secretory granules in the supporting cell were labeled strongly. In the dark cell degenerated otolith was observed, which is labeled or unlabeled with hyaluronidase-gold. These data suggest that otolith is secreted from the supporting cell, maturated, degenerated and absorbed in the dark cell. Hyaluronic acid is likely to be involved in these processes, especially in the generation step.

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The presence of glycoconjugates in the otolithic organ was investigated histochemically using lectins. WGA and Con A were applied to detect the localization of N-acethyl-glucosamin and mannose. Transmission electron microscopic observation using colloidal gold labelled WGA revealed the localization of the glycoconjugates on the otoconia, otolithic membrane and the secretory granules in the supporting cells of the sensory epithelium. The two zones, the peripheral electronic dense zone and the central electronic lucent zone, were demonstrated even in the immature otoconia as in the mature otoconia. WGA labelling was more intense on the peripheral electronic dense zone than on the central electronic lucent zone.

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To study neural mechanisms of motion sickness in rabbits, we examined the changes of heart rate (HR) and the coefficient of variation of R-R interval (CV-RR) during two types of vestibulo-visual conflict (VVC) stimulation. One is vestibular stimulation (VS) without visual input, and the other is VS with optokinetic stimulation. After atropine injection or labyrinthectomy, the changes of HR and CV-RR during both VVC stimulations decreased. These results suggested that vestibulo-autonomic nerve reflex plays an important role in body response during VVC stimulation and this reflex reduces as the conflict vanishes.

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To produce a precise damage of the inner or outer hair-cells in the cochlea of guinea pigs, the Nd-YAG laser was applied. Prior to the animal experiments, following items were examined. 1) The grade of penetration of Nd-YAG laser through bony wall. 2) The temperature of laser irradiation at the forcused portion in aqua. The Nd-YAG laser of the adequate power and time determined by the results of these basic experiments was irradiated to the cochlea. The precisely localized area produced by the laser irradiation was detected on the surface preparation of the organ of Corti. This method may be interested for both physiological experiment and clinical micro surgery in cochlea.

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Great interest has been focussed on the morphological changes of cochlea during the development of endolymphatic hydrops. The morphological changes of the vestibular organs during the development of endolymphatic hydrops however, still remain unclear. This study using scanning electron microscopy reveals the morphological changes of the vestibular organs one or two months after obliteration of the endolymphatic sac and duct. There was no difference in the extent of the hydrops between these two groups. The saccular macula displayed the greatest degree of hydrops. Missing, fusion and/or disarrangement of the sensory hairs as well as the decrease in glycocalyx were noted in the saccular macula. The disarrangement of the cilia and the decrease in glycocalyx was also observed in the utricular macula and the crista ampullaris.

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Fourteen guinea pigs immunized with endotoxin of Escherichia coli were challenged to 50 μg of the same antigen in the right tympanic cavity through the ear drum. The appearance of plasma cells in the endolymphatic sac on both sides was examined by HE-staining and immunohistochemically using the ABC method. A week following the challenge in the middle ear, plasma cells in the sac on both the inoculated and contralateral sides were sufficiently increased in 3 animals. These plasma cells showed positive reactions most strongly to IgG, then to IgA and slightly to IgM. The results suggested that the endolymphatic sac plays an important immunological role in the inner ear.

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We investigated the effects of inner ear immune response to the anionic sites of the charge barrier. Guinea pigs were immunized with Type II collagen, KLH or HRP through the stylomastoid foramen in second immune response. Polyethyleneimine (PEI) were used as a cationic tracer. A decrease of the charge in stria and sac was found in the animals immunized with Type II collagen and HRP. KLH group did not show any of changes because of its high molecular weight and strong negative charge. A decrease of the charge under immunological conditions may induce a hyperpermeability of the vessels and disturb an endolym absorption, consequently may result in endolymphatic hydrops.

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The distribution of 5-hydroxydopamine (5-OHDA) and horseradish peroxidase (HRP) in the cochlea was examined by light and electron microscopy after perilynphatic perfusion. Reaction product of 5-OHDA was observed along the endolymphatic surface of the cochlear duct in 10-minute and 30-minute perfusions, while that of HRP was observed only in 30-minute perfusion. Both tracers were found in pinocytotic vesicles of Reissner's membrane, Claudius' cells and Hensen's cells. These findings suggest that 5-OHDA and HRP can enter the endolymphatic space from the perilymphatic space by pinocytosis and that the degree of transport depends on the size of particles.

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In this study we tried to quantitate the Calmodulin (CAL) levels in organ of Corti (OC) and its substructures for the purpose of estimating a possible role of CAL as a reguratory protein using quantitative two dimensional polyacrylamide gel electropheresis. The CAL level in OC was estimated 2400mg/kg wet weight, the highest among other inner ear structures or brain tissues in guinea pig. Among the substructures in OC of chinchilla it was found that the CAL level was by far the highest in the outer hair cells (OHC), which suggests that the calcium dependent intracellular response is performed actively in OHC. The relative distribution of CAL is very similar to that of glycogen. This circumstantial evidence suggests the activation of the glycogen phosphorylase kinase is an important role of CAL in OHC.

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Single inner hair cell of cochlea and vestibule of guinea pig were isolated and its F-actin filament were investigated. In isolating procedure inner hair cell and vestibular hair cell hardly keep its cell shape intact in comparison with outer hair cell. In outer hair cell F-actin exists at stereocilia, cuticular plate, infracuticular network, lateral membrane and basal portion of cytoplasm. In inner hair cell and vestibular hair cell F-actin was recognized at stereocilia and cuticular plate. These results might indicate that these latter cells have no ability to move except for vestibular hair cell neck portion.

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The cochlear outer hair cells possess a lattice structure, called cytoskeletal spring, beneath it's lateral membrane. The lattice structure locates between lateral membrane and the most-outer layer of subsurface cystern and is considered to act as directed force generators within the organ of Corti. We observed this lattice structure using rapid-freeze, deep-etch method and disscussed the functional aspects of “cytoskeletal spring”.

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In order to study the pathology of the intradural portion of the endolymphatic sac (ES) in Meniere's disease, a comparative study was made using the ES of normal control subjects, ES of inner ear deafness, and ES of Kanamycin (KM) produced inner ear lesions of guinea pigs. All normal control subjects showed well-arranged epithelial cells. The ES in Meniere's disease showed various types of degeneration of the epithelial cells of the ES. However, these findings were also found in a case of cochlear deafness and in cochlear lesions produced by KM injection. From the above results, as one of the etiology, it is appropriate to consider that the findings of degenerated epithelial cells of the ES in Meniere's disease might arise from the sequelae of cochlear deafness.

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The histopathological findings of vascular loops of the anterior inferior cerebellar artery or its branch in temporal bones were reported. In the 356 human temporal bones, loops within the internal auditory canal were encountered in 51 temporal bones (14.3%). In 17.6% of 51 bones, loops were located at the orfice, in 45.2% they entered deeply into the internal auditory canal. And in 64.7% they were seen between the facial and vestibulocochlear nerve. It was thought that loops of the anterior inferior cerebellar artery is associated with the neurovascular cross-compression syndrome, which has clinical symptoms, such as facial spasm, dizziness, tinnitus or hearing loss.

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There were more literatures concerning the computer-aided three dimensional reconstruction (CTDR) of the cochlea, including authors'. In this study, authors performed to make CTDR from the used sections. This is because these specimens do not have the standard points and lines, which is needed for CTDR. During the microscopic observation, authors used two marking points at the constant points and lined between them as a micrometer on the lens. After these serial specimens were photographed, the lines are used as standard ones. As a results, the marking points are useful for the observation of partial region of the cochlea to make CTDR.

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The maculae utriculi and sacculi can be approached through the stapedectomized oval window. Animal experiments show that the maculae completely degenerated 2 weeks after argon laser irradiation. Similar changes probably occur in man. The utriculoampullary nerve runs close to the upper margin of the oval window and can be irradiated by argon laser using an angled laser applicator. The posterior ampulla is the area most difficult to irradiate by argon laser through the oval window.
The possibility of laser labyrinthectomy in man is discussed.

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The histopathological findings in the temporal bones from 12-year-old girl with Sanfilippo syndrome (Mucopolysacchridosis IIIB) are reported. The main histopathological finding is the swelling of the connective tissues is the middle cavity, the mastoid cavity and the orfice of fallopian canal. These tissues were strongly stained with Alacian Blue but nonstained with PAS staining. The organ of Corti was depressed and endolymphatic hydrops in the apical turn was formed.

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The blood flow at the stria vascularis of the guinea pig was observed using the fluorescent dye method. After exposing the cochlear bony wall, 5% FITC Albumin was given intravenously and the cochlear lateral wall was illuminated by a light (wave length: 450-490nm). The observation of the fluorescent image by a microscope and a video camera made it possible to observe the microcirculation of the stria vascularis without removing the bony wall. The change in the blood flow was closely correlated with that in the systemic blood pressure.

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We investigated the effect of elevation of cerebrospinal fluid (CSF) pressure on cochlear and cerebral blood flow (CoBF, CBF) in guinea pigs. CoBF and CBF were measured by a Laser Doppler flowmeter and a thermocouple, respectively. The required elevation in CSF pressure for lowering CBF was lower than that required for causing a reduction in CoBF. Based on the results obtained, the relationships between CoBF and CBF are discussed.

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Effect of loud sound exposure on cochlear blood flow was studied in 14 guinea pigs by the laser Doppler method. The experiment was performed with artificial ventilation. A probe of the laser Doppler flowmeter was attatched to the lateral wall of the basal turn of the cochlea after removal of the mucosa. Loud sound was delivered to the ear for 30 minutes. Twelve of the 14 exposed guinea pigs showed a prompt decrease of blood flow at the onset of sound exposure and a prompt recovery after the cessation of the sound exposure. Artifacts are also discussed.

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