Effects of some ototoxic agents on endocochlear dc potential (EP) are discussed comparing with histological changes of the inner ear. Arsenicals, sodium bromate and cis-platinum severely decreased the magnitude of EP. The stria vascularis and organ of corti were destroyed. The collapse of cochlear duct was also observed. These findings suggest us that the stria vascularis is the source of the EP and endolymph. Loop diuretics, which affect the ion pump at the loop of Henle in the kidney, transiently decreased the magnitude of EP. This phenomenon implys that same kind of ion pump system may exist in the stria vascularis. This ion pump may have the electrogenic function, which is the source of the EP. Loop diuretics gave us some important informations about the mechanism of the production of EP in the stria vascularis. Nitrogen Mustard-N-Oxide (NMNO) modelately decreased the magnitude of EP. The organ of corti was destroyed, however the stria vascularis appeared normal. The EP in the animal whose organ of corti was already destroyed was not decreased by NMNO. This phenomenon may imply some unknown relationship between EP and organ of corti.

抄録全体を表示

Distribution of gentamicin in the inner ear of guinea pigs was examined by immunofluorescence and immunoperoxidase methods. Transtympanic administration of the drug (10mg/0.25ml) resulted in the presence of the specific fluorescene in the outer hair cells, without significant difference among cochlear turns, inner hair cells, tympanic pannicle and Type I hair cells. Immunoelectronmicroscopy using peroxidase revealed the antigen in the stereocilia, cytoplasmic membrane, lysosome of vestibular hair cells and nerve chalice. In the guinea pigs receiving intraperitoneal daily inoculation (50mg/kg, 7 days), antigens were seen in the subcuticular region of outer hair cells of basal turn, likewise in the vestibular ganglion cells and Type I hair cells. These findings suggest that there is a two step mechanism for the initiation of ototoxicity by aminoglycoside antibiotics; at first the drug attacks the receptors in the stereocilia and successively lysosomes in the cytoplasm.

抄録全体を表示

TPI, triphosphoinositide, a highly polar phospholipids has been demonstrated as a receptor for aminoglycosides. In this study some polyamino compounds were demonstrated to be ototoxic when perilymphatically perfused. They also interfered TPI metabolism of brain slices and K⁺-conductance of lyso-TPI channel. Thus polyamino compounds may share the receptor. This also indicate that amino-residures of these drugs are responsible for their binding with TPI. This notion was confirmed by the analysis using three dimensional computer-graphics.
TPI was localized in the cochlea by protein A-gold technique using antibody against TPI. It was found on stereocilia, cuticular plate, plasma membrane, mitochondria and so on. Aminoglycoside binding sites were localized protein A-gold technique using antibody against gentamicin and by neomycin gold labeling. Binding sites were found on the place where TPI was localized and other place.
In conclusion more evidences to prove TPI to be a receptor for aminoglycosides were provided.

抄録全体を表示

A scanning electron microscopic study was done with guinea pigs for comparing the ototoxic effects of Kanamycin, Cisplatin and Nitromin (nitrogen mustard-N-oxide). The same general degeneration pattern was seen for all three drugs, namely, 1) Outer hair cell degeneration in the lower cochlear turns, with lesion being more pronounced in the inner rows of hair cells. 2) Apical lesion of inner and outer hair cells. Fragility of outer hair cells was more pronounced in the outer rows. 3) Vestibular end organs were more resistant than the cochlea. 4) The ampullary crista was more susceptible than the otolithic maculae. It was concluded that all three drugs have essentially the same invasion and distribution patterns within the inner ear.

抄録全体を表示

Authors performed to clarify the secondary degeneration of auditory nerve in guinea pigs after the treatment of KM 200mg/kg/body weight for 28 days. First the auditory nerve of each animals was removed, and then it was immersed in fixative solution and embedded in epon by routine method. The thin cut transverse surfacespecimen of auditory nerve (0.3μm) was obtained and stained with Toluidine blue solution. Specimens, magnified to 50 times each and all, were photographed. These pictures were used for counting nerve fibers with the image analyzer (LUZEX 500, Toyo Inc.) (Fig. -1). As the results in this moment, degeneration of nerve fibers due to KM after being bred for 6 months appeared in three parts, i. e. nerve of cochlear axis (about 2.0%), nerve at near portion of Scarpa's ganglion (about 10%), and nerve at near portion of Glial-Schwann's junction (about 35%), shown in Table-1. Authors certified the deformation of auditory hairs of cells (Fig. -4, 5) and the decrease of spiral ganglion cells (Fig. -6).

抄録全体を表示

Pre and post kanamycin sulfate administration was evaluated in guinea pigs treated with silver nitrate which induces endolymphatic hydrops. Group A animals, which received silver nitrate initially followed by the daily intramuscular administration of 300mg/kg of kanamycin for 10 days, showed collapse in the saccule and lower turns of the cochlea after development of endolymphatic hydrops. Group B animals, which received 300 mg/kg of kanamycin for 10 days followed by silver nitrate treatment on the 10th to induce hydrops, showed small saccule and moderate hydrops in the cochlea. Both groups induced extensive utricular hydrops. In addition to the severe degeneration of the organ of Corti, they showed vacuolated degeneration of the stria vascularis. From these results, it appears that kanamycin might affect the stria vascularis primarily by reducing endolymph production and the degeneration of the organ of Corti would be a secondary event.

抄録全体を表示

The white rabbits (No. 1-5) with electrodes permanently implanted in the round windows were injected intramuscularly with daily doses of 200 mg/kg of kanamycin (KM). The amplitude of cochlear microphonics had been diminished by the administration of KM for a period varing from 8 to 13 days. Then No. 6-10 rabbits without electrodes were injected intramuscularly with same doses of KM for 10 days. The outer hair cells of these rabbits were studied with the block surface preparation technique reported by Spoendlin. After surface observation of the organ of Corti, the outer hair cells which were not damaged light-microscopically were observed with transmission electron microscope. The increase of the secondary lysosomes at the subcuticular zone was considered the ultrastructural primary change of the outer hair cells of the KM administered rabbits.

抄録全体を表示

The hypothesis was tested that gentamicin causes loss of cochlear microphonics by interfering with glucose transport or metabolism in cochlear structures. Gentamicin (3 or 10 mM), applied by perilymphatic perfusion in the guinea pig, reduced cochlear microphonics in a dose-dependent manner. The presence of 5 mM glucose lowered the initial rate but not the final (60 min) loss of cochlear microphonics.
Glucose utilization was measured by introducing radiolabeled deoxyglucose into the perfusate and determining its uptake into inner ear tissues. Concentrations of deoxyglucose-6-phosphate in organ of Corti and in stria vascularis increased linearly with time and remained unaffected by the presence of 3 mM gentamicin. Ten mM gentamicin reduced deoxyglucose uptake by 30% in the lateral wall tissues but not in the organ of Corti preparation. The lack of correlation between loss of microphonics and glucose utilization does not support interference with glucose metabolism as a primary mechanism of aminoglycoside ototoxicity.

抄録全体を表示

Permeability of the round window membrane to neomycin and its pharmacokinetics in the perilymph were studied along with toxicity of neomycin to the organ of Corti. Neomycin was applied directly on the round window membrane of guinea pigs, and after various time intervals, the perilymph was collected and the concentration of neomycin was determined by high-performance liquid chromatography. The results showed that neomycin permeated the round window membrane quickly, and that its concentration in the perilymph became extremely high, reaching a peak after 2 hours of application, and decreased less quickly to a level below detection after 24 hours. However, variations of the results among guinea pigs were high. Light microscopic observations of the organ of Corti revealed that ototoxicity of neomycin was apparent already after 4 hours of application. Damage to the organ of Corti increased its frequency as the time interval became longer, but no consistent relationship was noted between the concentration of neomycin in the perilymph and the appearance of the damage.

抄録全体を表示

Our previous report showed that injection of Lidocaine reduced the spontaneous discharge rate of the cochlear nerve transiently. But the action sites of Lidocaine is not yet clear. To know the effects on the nerve, we recorded the latencies and the thresholds of the cochlear nerve action potentials (spikes) which were evoked by the electrical pulses applied through the round window membrane before and after intravenous injection of Lidocaine. According to Moxon (1971), The electrical pulses excite the unmyelinated nerve directly. Threshold at one min after injection of Lidocaine was about two times of that of preinjection and decreased linearly. It takes 36 min for the nerve to return to the level of preinjection. The mean onset of decrease of of the latencies of the spikes is about 36 sec after onset of injection (n=12). This reveals that intravenous injection of Lidocaine acts directly on the cochlear nerve and decreases the excitability of the nerve transiently.

抄録全体を表示

Cisplatin or cisplatin with steroid was injected in guinea pigs intraperitoneally once a day for 5days in succession to produce an experimental cochlear damage. Histlogical examination was made by a scanning electron microscope. At the same time, comparisons of Pt concentration were made in cochlear emulsion and in blood.
The following interesting findings were obtained:
(1) It was found that the degree of cochlear damage depends on the Pt concentration in cochlear emulsion, not on that in blood.
(2) Pt concentration in blood showed higher value when cisplatin was solely injected (P<0.05).
(3) As for Pt concentration in cochlear emulsion, no differences were observed between single administration of cisplatin and simultaneous administration of cisplatin with steroid.

抄録全体を表示

The electrophysiological and histopathological changes in the cochleas caused by the administration of cis-DDP (cis-diamminedichloroplatinum) were studied in guinea pigs. Hearing function was evaluated by ABR, and morphological studies were conducted by scanning electron microscope. The sensitivity of the cochlea to cis-DDP was dose-dependent. Hearing impairment was stronger in the group given 4 doses of 3mg/kg cis-DDP twice a week than in the group given 12 doses of 1mg/kg. The outer hair cells in the basal turn were mainly damaged and those changes gradually decreased in the upper turn. The inner hair cells were rarely damaged. Vestibular sensory epithelia of the guinea pig given a single dose of 12 mg/kg cis-DDP were investigated by scanning electron microscope, and there was almost no loss of sensory cells.

抄録全体を表示

The effects of cisdiamminedichloroplatinum (cisplatin) on cochlear potentials were studied in 13 guinea pigs. Cisplatin was applied in the scala media by iontophoresis or by diffusion. After recording of cochlear potentials, i. e. endochochlear potentials (EP), cochlear microphonics (CM), summating potentials (SP) and action potentials (AP), the cochleae were removed and perfused with nitroblue-tetrazorium.
In animals whose CM reduced abruptly and markedly, -SP and EP were also suppressed with definite time lug. Six of the animals showed no change of cochlear potentials. All of the spiralorgan showed normal NBT reducebility. These results suggested that cisplatin blocked the receptor membrane of hair cells. The reason why the cisplatin injection in the scala media had no effects in almost half of the animals was unclear, however the fixed negative charge of the tectorial membrane could interfere the mobility of cisplatin.

抄録全体を表示

The changes in the inner ear of the mice induced by intravenous injection of M. fortuitum were investigated using SEM.
In the organ of Corti the inner and outer hair cells had degenerated and disappeared. The changes in the lower turn of cochlea were more severe than those of the upper turn and the changes of the outer hair cells were more severe than those of inner hair cells.
In the vestibular organs, disappearance, fusion and balooning of the sensory hairs was observed.

抄録全体を表示

In this study, authors performed to clarify the pharmacological kinetics of CH₃-B₁₂, ATP, and Kallikrein for the depressed reaction of aleviatin, using guinea pigs. Before administration of CH₃-B₁₂, ATP, and Kallikrein, each animal was received aleviatin 100mg/kg i. m. and was done ABR test every 10min. Then, each animal was sacrificed for measurement of SDH activity with spectrophotometer (Gilford, Model 202). One cochlea of each animal was received intravital perfusion staining with Nachlas solution. After the surface treatment of specimen, SDH activity of hair cells was scanned by multipurpose microspectrophotometer (Olympus Co.). The results were as follows; (1) no significant differences were present in pharmacological reaction, (2) no disappearance of ABR waves were seen in each animal.

抄録全体を表示

An attempt was made to protect the inner ear against gentamicin (GM) ototoxicity by chondroitin sulfate (Chs) which was injected around the stylomastoid foramen. Mature guinea pigs with normal pinna reflex were divided into two groups; Gm group (GM 100mg/kg/day, i. m.) and Chs group (GM+Chs 60mg/kg/day, i. m.). They received 13 times injections. The protective effect against ototoxicity was judged by electrococholeography and morphological changes. There were very slight prophylactic effects on the survived cell and N1 threshold, but there was no significant difference because of an individual deviation. One of the reason about no defference is considered that Chs did not reach to the cochlea sufficiently.

抄録全体を表示

Recently, we had been reported the inhibitory effect of vanadate on the EP and CM with micro perfusion system. In this study, it was to define the affect of the inner ear with administration of vanadate via the intraperitoneally. In 20ppm group, each animal died at 2nd or 3rd day after start of injection and the Pryer's reflex threshold did not changes before then. Other groups, they were presented the elevation of the Pryer's reflex threshold after 7th-14th day and maintained for several days. After that, the complete recovery observed the level before the administration started in spite of the continuous injection, and then the magnitude of EP and CM were not significantly different from control. Pathological changes were not observed in the inner ear. On chemical analysis of serum, liver and kidney functions and electrolytes were within normal limits, however, total cholesterol and phospholipids value were three times higher than the control.

抄録全体を表示

The ommastrephes sloanei pacificus belongs to the phylum mollusca, class cephalopoda, order dibranchia, genus loligo (common squid), and lives in the sea surrounding all of Japan. In a common squid, the statocyst can be seen at the base of and dorsal to the siphon.
The aim of this study is getting some good photographs of the statocyst of the common squid under light microscope. Several common squids (ommastrephes sloanei pacificus), which lived at a depth of about eighty meters in the Pacific Ocean around Jogashima Island, were fished with line. While they were alive, they were fixed with 10% folmaldehyde solution diluted with seawater, and dehydrated with ethylalcohol, distilled water and seawater. These specimens were embedded in celloidin. The sections were cut 30μm thick and stained with hematoxylin eosin, then observed with the light microscope.
As the result of this method, several fine pictures of not only the crista statica but also the statoconia in the statocyst were able to be gotten.

抄録全体を表示

The fine structure of the neuromast of the lateral line organ was observed by using the electron microscope. The neuromast is composed of receptor cells, supporting cells and mantle cells. Each receptor cell is surrounded by several supporting cells. The apical surface of the receptor cell is studded with sensory hairs composed of a single kinocilium and approximately 20 stereocilia. The kinocilium is similar to the usual motile cilia in possesing 9+2 type tubules. The streocilia sends filamentous rootlets into the cuticular plate. The nerve fibers terminate at the basal portion of the receptor cells. Two kinds of nerve endings are distinguishable. One type contains a small number of synaptic vesicles and the other many vesicles. The supporting cell is cylindrical in appearance. Its cytoplasm contains numerous mitochondria, abundant filaments and some melanin-like granules. The lateral wall of the neuromast is covered by a few layers of the mantle cells.

抄録全体を表示

In order to determine the melanin of inner ear, the authors collected tissue samples from the utricles and posterior ampullae of 8 colored guinea pigs and 5 albino guinea pigs, using microanalysis developed by Ito, and measured the levels of pyrrol-2, 3, 5-trycarboxylic acid (PTCA) as an indicator of eumelanin and of aminohydroxyphenylalanin (AHP) that serves an indicator of pheomelanin. The results indicated that in the colored guinea pigs PTCA averaged 10.1 ng/ear and AHP 1.8 ng/ear and that in the albino guinea pigs the former averaged 0.3 ng/ear and the latter 4.6 ng/ear. In the colored guinea pig, eumelanin was dominant with levels higher than those in the black hairs of the Japanese. This suggests that melanin in the inner ear of at least guinea pigs belongs to the same type in composition as that in hairs and eyes, though its function in the inner ear remains unknown.

抄録全体を表示

Spiral ganglion cells of adult Guinea pigs and young rats were studied under electron microscopy and following results were obtained.
1) adult Guinea pigs Two types of cytoplasm in myelinated nerve cells were observed; the one included a number of mitochondria, lysosomes and rough surfaced endoplasmic reticulums, and another contained numerous pigmented granules and a little of them described above. Cytoplasm in both types were surrounded by approximate 10 layers of myelin sheath. On the other hand, there were a little of mitochondria, lysosomes and rough surfaced endoplasmic reticulums in cytoplasm of non-myelinated cells, but markedly numerous neurofilaments were detected.
2) young rats: Myelination is scarcely observed at 1 day after birth, but a few layers of myelin were confirmed at 10 days after birth, compared with about 10 layers of myelin in adult rats. Salient growth of mitochondria in cytoplasm was observed, compared with that in adult rats. Many invaginations of nuclear membranes were observed in adult rats, but were not in young rats. Myelination of neurons was proceded rather than that of ganglion cells.

抄録全体を表示

Dark cells of the guinea pig vestibular apparatus were studied using transmission electron microscope. They were located around the macula utriculi and peripheral portion of the semicircular canal cristae except for the planum semilunatum. Most dark cells were located facing the endolymphatic lumen, but some of them were found beneath the transitional cells or were embedded in the connective tissue. On the apical surface of dark cells, otoconia of various shape were occasionally found. Furthermore, cell membrane of the apical portion was invaginated, showing network structure. Fusion of the vesicles and/or tubules possibly formed this network. In the cytoplasm of the dark cells, numerous free ribosomes, vacuoles of various size, and well developed basal infolding with numerous fenestrations were seen. Presence of the vacuoles and basal infolding strongly suggests that fluid transport is one of the main functions of the dark cells.

抄録全体を表示

The nests of neuroglial tissues have been observed beyond the Schwann-glial junction of the eighth nerve specimens from patients with known vestibular disorders. The inner ears of a 71-year-old male who died of lung carcinoma were fixed with 2% paraformaldehyde and 2% glutaraldehyde one and one-half hours after death. He was reported to have no auditory or vestibular complaints. The tissue was postfixed in 2% osmium tetroxide. The superior vestibular nerve was removed intact and studied with an electron microscope. The neuroglial tissues were observed among the myelinated vestibular nerve fibers in the distal part close to the cribriform area. They consisted of bundles of numerous cytoplasmic processes of fibrous astrocytes. The process contained bundles of abundant filaments, endoplasmic reticulum and mitochondria. These glial processes were joined by a double membrane and numerous tight junctions were observed. The filaments extended as parallel arrays in the processes. It has been suggested that neuroglial tissues are focus of the eighth nerve tumor or causes of various vestibular disorders including Meniere's disease. However, this study exhibits that neuroglia in the vestibular nerve could be normal histological characteristics.

抄録全体を表示

The residue of tectorial membrane insertion of cochlear sensory cell hairs of the guinea pig and the rat was studied by means of a scanning electron microscope. Imprints of the inner sensory cell hairs were found on the under surface of the lateral portion of Hensen's stripe. The relative position of these imprints corresponded to the location and the size of the inner hair cells. Such imprints were noted only in the 1st and 2nd half turn of the cochlea. On the other hand, imprints of the outer sensory cell hairs were observed on the under surface of the middle zone of the tectorial membrane in all cochlear turns. However, imprints corresponding to the sensory hairs of the 3rd row of the outer sensory cells near the apical end of the cochlear turn were not detectable infrequently in both animals. The mode of the attachment of the sensory cell hairs to the under surface of the tectorial membrane may possibly differ in each cochlear turn of these two animals.

抄録全体を表示

The distribution of the tectal cells of the outer tunnel which was reported by Henson et al in 1983 was studied in golden hamster by scanning electron microscope. And the following conclusions were obtained as a result. 1) Between the third row of Deiters' cells and the most medial row of Hensen's cells, there is the area which has the different surface structure from two other cells and it is suggested to be tectal expansion. 2) This part shows a thin plate-like structure and forms the roof of the outer tunnel of the organ of Corti. 3) Tectal expansion is absent in the upper turn and begins to be recognized in the lower middle turn. In the basal turn, it shows a larger cell surface.

抄録全体を表示

The structural features of the basal lamina in Reissner's membrane were examined electron microscopically using tannic acid fixation, poly-cationic staining (ruthenium red), and mono-cationic staining (safranin O). Tannic acid fixation revealed 5-10 nm filaments which ran perpendicularly between the lamina densa and the cytoplasmic surface of squamous epithelial cells. Ruthenium red staining showed a lattice-like arrangement of anionic sites on both sides of the lamina densa. Safranin O staining revealed filamentous networks, at the same sites. These structural features of the basal lamina in the reissner's membrane were very similar to those of the glomerular and the alveolar basement membrane. Therefor, the possibility that anionic sites of Reissner's membrane may play a role of size and charge-selective barrier between the scala media and the scala vestibuli, much in the same way that the glomerular basement membrane plays the same role of barrier, have to be given attention.

抄録全体を表示

To reconstruct the entire arrangements of neural terminals on outer hair cells (OHC), serial sectioning technique was employed. Specimens collected on single hole grids were examined under both conventional electron microscope (JEM-100C) and highvoltage electron microscope (JEOL-1000) with accelerating voltages of 80kV and 1000kV.
It was confirmed that OHC1 from upper basal turn (about 8mm from basal end) were innervated by 13 to 17 nerve endings. OHC2 and OHC3 were also terminated by 10 to 11 and 8 to 16 endings respectively. Every OHC, regardless of which row they are belonging to, possessed both efferent and afferent terminals, although average ratio between efferent and afferent terminals were quite variable from one row to another. OHC1 and OHC2 in the upper basal turn were innervated by almost equal number of both kinds of terminals, but OHC3 showed average ratios of approximately 3 to 9.

抄録全体を表示

In order to elucidate the cell kinetics of the component cells of human cochlea, we have carried out the Feulgen-DNA cytofluorometry using serial section method (ref. Report I-III). The data obtained from 20 cases (0-87 years old) demonstrated that the hair cells have diploid G1 pattern in DNA distribution without any exception. The supporting cells, however, had polyploid cells in some cases; we found 29 tetraploid and one octaploid cell in Hensen's cells of 7 cases and two tetraplod cells in Deiters' cells of two cases. Interestingly, these Hensen's cells were found almost always in the neighborhood of the damaged or missing outer hair cells, while Deiters' cells in these area was swollen but remained to be diploid. Although both supporting cells seems to have the ability to repair the damaged organ of Corti by replacing the damaged or missing outer hair cells, the way to do so was quite diffrent; Hensen's cells seemed to involve nucleus (polyploidization) and Deiters' cells cytoplasma (swelling).

抄録全体を表示

We have previously demonstrated the localization of the Na⁺/K⁺ pump in the cochlea by an autoradiographic method using ³H-ouabain (Ear Res Jpn 14, 126-132, 1983; 15, 339-342, 1984). In this study we attemted to localize the pump by demonstrating the ouabain sensitive Na⁺-K⁺ATPase (NPPase) by an recently developed cytochemical method.
The reaction products were mainly observed on the plasma membrane of the basal infoldings of the marginal cell and epithelial cell (basolateral side) or stromal cell of the spiral prominence. These locations were well compatible with the ouabain binding sites. Therefore, it is likely that Na⁺/K⁺ pump works in the spiral prominence especially in its deep region as well as in the vascular stria.

抄録全体を表示

The effect of acute hypertension and hypotension on blood vessels of the vestibular organs were studied electron microscopically with the tracer method of horseradish peroxidase (HRP). Acute hypertension was induced by i. v. infusion of methoxamine chloride (Mexan), and acute hypotension by i. v. infusion of trimetaphan camsilate (Arfonad). In both acute hyper- and hypotensive experiments, there was no extravasation of HRP from capillaries in sacculus, utriculus and semicircular canals, despite the presence of some labelled pinocytotic vesicles. The endothelial cells were intact, and no HRP penetration occured through endothelial tight junctions. These findings suggest that the capillary of the vestibularorgans is of the ordinary brain capillary type. And, moreover, comparison between capillary permeability of vestibular organs and that of cochlea will be discussed.

抄録全体を表示

The purpose of the report is to reveal the fine structure of the vascular system of the endolymphatic duct and sac of the experimental animals. The corrosion casting of the blood vessels of the temporal bone was obtained with the use of fluid resin, and was observed with SEM.
Fine construction of the following vessels was elucidated.
1. The vein running along the vestibular aqueduct.
2. The arterial twigs of the posterior branch of the occipital artery running into the endolymphatic sac.
3. The capillary network surrounding the endolymphatic sac.

抄録全体を表示

The vein of the cochlear aqueduct (VCAQ) is the main draining vein of the cochlea. Collecting venules from the stria vascularis and from the spiral lamina drain into the spiral modiolar vein (SMV) in the basal turn. But in the basal end, some of collecting venules drain into the vein of the round window (VRW) and into the vestibulo-cochlear vein (VCV). After the confluence of SMV, VRW and VCV, VCAQ empties into the jugular vein or into the dural sinus. In some cases, well developed vessels from mucoperiosteum of the middle ear made some connections with VCAQ. It would be suggested that these connections were available for the collateral circulation on acute obstruction of VCAQ.

抄録全体を表示

The function of pericytes, one of the ubiquitous components in microcirculatory beds, remains uncertain. Recent technical advances in scanning electron microscopy (SEM) allow us to visualize the three dimensional structure of pericytes. These structures have been reported in several body organs. The purpose of this paper is to demonstrate SEM observations of pericytes in several different capillary areas in guinea pig cochlea.
Pericytes composed of a bulged cell body and elongated cytoplasmic processes are scattered along the capillaries. These structures vary from cell to cell, suggesting that they play different roles depending on location. A characteristic feature of cochlear pericytes is the coral. like branching of cytoplasmic processes. These processes are prominent in the spiral capillary and the strial capillary. Such structures seem advantageous for the maintenance of constant blood flow of these capillaries even in the presence of mechanical vibration.

抄録全体を表示

Capillaries entering and leaving the stria vascularis were surrounded by layers of basal cells and fibrocytes. Between entering and leaving, the layers changed. Although entering capillaries were surrounded by one or two thin basal cells, leaving capillaries were surrounded by four or five thicker and interdigitated basal cell layers. Moreover the layers surrounding the leaving capillaries persisted further into the spiral ligament.
Leakage of horseradish peroxidase (HRP) out of the capillary was observed before entering and after leaving the stria vascularis. Although the reaction product of HRP was observed in all perivascular spaces of leaving capillaries, a very weak or no reaction product was observed around some entering capillaries. Blood sludging and no plasma space was observed in all leaving capillaries, but plasma space could be observed in some entering capillaries. It is speculated that the layers of basal cells and fibrocytes around entering and leaving capillaries control the vascular flow out of stria vascularis.

抄録全体を表示

Effects of artificial perilymph with pH ranged from 4 to 10 on endocochlear potential (EP) were investigated in the guinea pig. The mean and standard error of the mean before the perilymphatic perfusion was 75.8±0.8 mV (n=29). The artificial perilymph with pH ranged from 5 to 9 could maintain the EP well at least for one hour perfusion period. After the start of perfusion with pH less than 4, the EP decreased gradually, but recovered to the pre-perfusion level rapidly when the perfusion was stopped. The artificial perilymph with pH over 10 also decreased the EP considerably but showed no recovery even after a cessation of the perfusion. Cochlear microphonics (CM) was maintained within normal range during the perfusion with pH ranged from 5 to 9 for one hour.

抄録全体を表示

In the previous study we reported electrophysiological phenomenon of the guinea pig cochlea induced by hypothermia. The most interesting finding was a change of AP amplitude evoked by a click which showed a transient increase up to 28°C, followed by gradual decrease with the further temperature decline. The studies on narrow band AP, AP tuning curve, threshold of AP and CM revealed the differences in sensitivity and response to hypothermia between the basal turn and second turn, and the transient increase in AP amplitude was due to increased response originating from the basal turn. Then the temperature and EP of the first and the second turn were determined using 15 normal guinea pigs. There was no difference in the change of EP magnitude, the EP response to anoxia and temperature between two turns. These findings suggest that the transient increase in AP amplitude observed in the basal turn during hypothermia is not due to the differnces of EP and temperature change between two turns, but some central factors are likely to be involved.

抄録全体を表示

The effect of NaBrO₃ applied in the perilymph on the inner ear was studied. The changes of K and Cl concentrations in the endolymph as well as the cochlear potentials were observed during and after the perilymphatic perfusion of modified Ringer's solution containing 1 mM NaBrO₃. Following the onset of perfusion, the cochlear microphonics declined gradually and the amplitude of the action potential decreased about 40% in ten minutes. The endocochlear potential fell down to half of its pre-perfusion level for two hours. The decrease of ionic concentrations in the endolymph were 10.5 mEq/L for K and 7.4 mEq/L for Cl one hour after the end of perfusion. Our data demonstrated the direct ototoxic action of bromate.

抄録全体を表示

Endocochlear potential (EP) and electrical resistance of the cochlear partition were measured in embryos and neonates of guinea pigs. In the guinea pig embryo which takes 67 gestation days in average for birth, EP increased sharply in the period from 59th to 64th gestation day to the same level as that of the adult at 64th gestation day.
The electrical resistance of the cochlear partition was formed to rise in accordance with the increase of EP. Since there exists the correlation between the maturation of EP and the increase of the electrical resistance of cochlear partition, this increase of resistance could be considered to be one of contributory factor of the rapid maturation of EP.

抄録全体を表示

The effect of perilymphatic perfusion of vasopressin upon the endocochlear potential (EP), the cochlear microphonics (CM), the summating potential (SP) and action potential (AP) was examined in the pigmented guinea pig. Perilymphatic perfusion of vasopressin decreased the EP in the concentration of more than 1 ×10^-5M. The change in the EP was reversible. The extent of the EP decline was dependent upon the concentration of vasopressin. The EP decreased by vasopressin recovered rapidly to the preperfusion level after the termination of two-minute asphyxia. During the perilymphatic perfusion of vasopressin the CM and AP were suppressed accompanying the EP decline, whereas the SP (DIF component) at high frequencies increased in negative amplitude and the SP at low frequencies was changed in polarity from the positive to the negative.

抄録全体を表示

Clinical studies on the possible involvement of hypertension on hearing function still could not draw defenite answer. We have had some sucess to approach this problem by applying spontaneously hypertensive rat (SHR) as an animal model. In this study, endocochler potential (EP) of SHR was examined comparing with that of Wistar rat Kyoto (WKY).
The followng resuts were obtained and briefly discussed.
1) There was no statistically significant diferrence in the steady EP values or minimal EP values of SHR and WKY during anoxia.
2) The attitude of EP during anoxia showed prominent difference between SHR and WKY. EP of SHR decreased slowly and smmothly, while decreasing slope of WKY's EP showed rapid and slow phases.
3) The speed for reaching 0 value from negative value during permanent anoxia also differed in two species. It was statistically longer in SHR.

抄録全体を表示

It is known that the sensorineural hearing loss frequently occurred in the patients with renal failure. To investigate the cause of hearing loss, the attention was given to the impaired metabolism of Vitamin D and calicum induced by renal failure. Therefore, the cochlear potentials were examined in rats with Vitamin D deficiency diet. The experimental results revealed abnormal findings such as the augmentation of CAP amplitude, the prolongation of CAP latency, the depression of CM amplitude and the elevation of CM threshold. These changes in cochlear potentials are supposed to arise from the change of calcium ion in inner ear fluids or the direct influence of Vitamin D deficiency and secondary hyperparathyroidism on the inner ear. But the degree of the hearing loss in the animals was not so great as what we observe in the patients with renal failure.

抄録全体を表示

Fifteen normal rabbits were implanted with electrodes on the round window. They were exposed to noise (90 or 100 dB SPL of pure tones at 2 KHz) for two hours everyday. CM were measured immediately after each exposure and twenty-two hours later. The following results were obtained. (1) Three patterns of the change of maximum CM amplitude were recognized. these patterns were found to be dependent on the intensity and sensitivity of the tone stimulus. (2) It was useful for the estimation of the phase and the prognosis of noise induced deafness to examine the CM intensity function curve. Because the CM intensity function curve had the charictaristic patterns according to the advance of deafness.

抄録全体を表示

We discussed two experiments examinig the influence of temporal variables on suppression effect in forward masking. The two narrow band maskers of 40dB spectrum level, 200Hz wide, centered at the signal frequency 3.0kHz or 2.1kHz respectively. The suppression were examined as a function of the duration and delay of the signal. For most subjects, the effects of signal duration almost disappeared up to 30ms. Only subject did not show suppression up to 20ms, the data of this subject, however, showed maximal suppression at 30-40ms and the effect of increasing the signal duration almost disappeared up to 70ms. For most subjects, the effects of signal delay showed significant suppression up to 30ms. However, one subject showed up to 50ms. The amount of suppression depended on both duration and delay of signal in a way not accounted for by the current the of suppression. The amount of suppression a given condition depended strongly on the signal duration in the intersubjects.

抄録全体を表示

Stimulated oto-acoustic emission (OAE) was investigated in 17 normal hearing subjects (male: 9, female: 8). OAE was recorded in 93.9% of total ears. Most clear responses against 45dBnHL stimulation existed between 1.0kHz and 2.0kHz. Their maximum responses were between 1.4kHz and 1.8kHz. Pseudothreshold of OAE showed relatively wide intersubject variations and existed between - 5dB and 40dB. However, the interaural difference of pseudothreshold was small and in 86.7% of total ears it was less than 10dB. The input-output function of 17 ears was nonlinear and the mean value of pseudothreshold was 12.7dB. The input-output function of 14 ears was nearly linear and the mean value of pseudothreshold was 30.0dB. The near linear input-output function of the latter could be caused by mixing in resonance of the prove tube and the external and middle ear cavities against intense sound applications. The interaural difference of pseudothreshold in OAE can be instrumental in examining cochlear functions.

抄録全体を表示

Motoneurons innervating the tensor tympani muscle in the monkey were examined using the method of retrograde axonal transport of horseradish peroxidase (HRP).
Injections of HRP into the tensor tympani muscle produced retrograde labeling of cells ipsilaterally. These labeled cells are clustered well in the region lateral or ventrolateral to the trigeminal motor nucleus at its rostral two-thirds levels. A few labeled cells are seen extending in the portion of rostral of the nucleus. No labeled cells are observed within the trigeminal motor nucleus which is traditionally thought to innervate the tensor tympani muscle in the monkey. The labeled cells are multipolar in shape and are smaller than cells in the trigeminal motor nucleus.
From these results, it can be concluded that the cells innervating the tensor tympani muscle in the monkey may arise from the reticular region lateral or ventrolateral to the trigeminal motor nucleus proper.

抄録全体を表示

Neural discharges of the cochlear nucleus neurons of the cats were obtained under the following conditions; before, during and after asphyxia. In this study indium micro-electrode was used and inserted into the left cochlear nucleus of anesthetized cats under visual control. Tonal stimuli were delivered to the left ear with closed system. The intensity of the stimulus tones was measured by the tympanic membrane and indicated by the sound pressure level. After application of muscle relaxant asphyxia was controlled by stopage of the respirator. The results showed that spontaneous discharges became markedly increased and neural responses decreased and threshold of the neuron became higher after asphyxia.

抄録全体を表示

The distribution of substance P containing structure in the vestibular nuclei was investigated by mean of an indirect immunofluorescent method using specific antisera to substance P. Numerous substance P immunoreactive (SP-ir) neurons and fibers were found in the medial vestibular nucleus (VM). Most of them were situated in the caudal part of the nucleus and those in the rostral part were concentrated dorsally. In the descending vestibular nucleus a large number of substance P containing neurons and fibers were evenly distributed. However, in the lateral and superior vestibular nuclei SP-ir fibers were rather poorly distributed. Electron microscopic examination of SP-ir terminals in the VM revealed that the predominant type of synaptic contact of SP-ir terminals were axo-dendritic contact (92%). These dendrites were relatively large and rich in cytoplasmic organella, suggesting that they belong to the proxismal segment of the dendrites. A small number of SP-ir terminals was found to make synaptic contact with neuronal perikarya (7%).

抄録全体を表示

It was reported that the ampullar endolymphatic potential (AEP) was reduced by intravenous administration of ethacrynic acid (ETA) and that saccular endolymphatic potential (SEP) was reduced by ETA and Furosemide. Albino guinea pigs (normal and unilateral labyrinthectomy) were fixed on the tilt table and the counterrolling (CR) of the eyes were measured by photographic method. ETA (50, 100, 150 mg/kg) and furosemide (100 mg/kg) was given intravenously and the measurement was made over the period of 30-150 minutes after administration. Although there was no significantly effect in case of 50 mg/kg ETA and furosemide, 100 and 150 mg/kg ETA significantly reduced the CR of the eyes and the time course of the reduction in CR was quite similar to that in AEP. It is concluded that the function of the otolith organ is inhibited the reduction of endolymphatic potential.

抄録全体を表示

Bullfrog's posterior semicircular canal (psc) was isolated and the ampullary wall was cut and the cupula removed with glass micropipettes. The cupula was replaced on the crista, and the psc ampullary action potential was recorded. The cupula was again removed and cut in half either in the plane vertical to the crista (vertical sectioning) or in the plane parallel to the crista (horizontal sectioning). Then, the sectioned half of the cupula was replaced on the crista. After vertical sectioning, the action potentials were markedly reduced to 50.3% of the replaced entire cupula for weak stimuli, and 79.1% for strong stimuli. After horizontal sectioning, the action potentials were 64.5% for weak stimuli and 108.2% for strong stimuli. These results indicate that the responses are related to the base area and height of the cupula.

抄録全体を表示

Twenty guinea pigs were used to investigate the influence of rotatostimulation on the lateral crista ampullaris. In the subjects investigated immediately after repeating the turning stimuli of cupulometric mode (terminal turning velocity: 450°/ sec) for 48 hours, the morphological change of crista ampullaris on the ampullopetal flow side was more remarkable than that on the ampullofugal flow side. In the other subjects observed two weeks after the same rotatostimulation, the progressive degeneration of sensory cells was noted and Caloric response declined in line with the degenerative progression of sensory cells. However, Directional preponderance revealed by the rotation test immediately after the rotatostimulation decreased by the central compensation.

抄録全体を表示