The voltage-dependent channels in outer hair cells dissociated from guinea pig cochlea wereinvestigated using a whole-cell patch-clamp technique. Depolarizing voltage steps to potentials morepositive than-30mV elicited a slowly inactivating outward K+current (IKCa), which is dependent onintracellular Ca2+. Hyperpolarizing voltage steps to more negative than-90mV rapidly inactivatedan inward K+current (Ik, n), which is already activated at resting membrane potential. When both K+currents were suppressed by replacing K+ with other cation of large molecule, depolarizing voltagesteps elicited a slowly-inactivating inward current. The maximum values of current amplitudeincreased in a hyperbolic manner with increasing extracellular Ca2+concentration. Indicating thatouter hair cell possesses L-type Ca2+channel. The effects of inorganic Ca2+channel antagonist, which is usually used as drug against systemic circulatory dysfunction, on Ca2+current in outer haircell were investigated. Inhibitory strength was in the order of flunarizine=nicardipine>=diltiazem.The effects of well-known ototoxic drug, aminoglycoside, on voltage-dependent channels in outerhair cell of guinea pig was examined, because of the easy fragility of outer hair cell to aminoglyocosideantibiotics in the cochlear cells. The aminoglycoside antibiotics selectively suppressed Ca2+current in outer hair cell. The inhibitory strength was in the order of neomycin>gentamycin≥kanamycin=streptomycin.
To further understand the role of immunocompetent cells in the defense mechanism of the innerear, the distribution patterns of those cells were investigated in endolymphatic sac (ELsac) of ICRmice bred in three different conditions: germ-free (GF), specific pathogen-free (SPF), and conventional (CV). In a different experiment, recruitments of lymphocyte subsets were examined in the Elsac of SPF rats undergoing a perilymphatic antigen challenge after systemic immunization, or passivetransfers of antigen-specific serum and/or sensitized lymphocytes. Results obtained from theseexperiments suggest that the ELsac is not originally equipped to possess immunocompetent cells andmount an immune response, but that once it has been activated with the inner ear antigenic stimuli, the ELsac can be the active site of a local immune response of the inner ear.
The effect of cochlear strial circulation due to sound exposure was investrigated immunohistologicallyby using kanamaycin as a tracer of blood flow and the possibility of the occurence offree radical in the cochlea was examined. After intense sound exposure (120-125dB SPL, 3h), theblood flow in the stria vascularis was greatly dimminished. Two hrs. after sound exposure, strialblood flow started to re-circulate and6hrs. after sound exposure blood flow seemed to recover tothe normal level. But the function of strial cell has not yet fully recovered. Sound exposure of60-70dB SPL and cutting or stimulating treatment of superior cervical gaglioncould not produce the remarkable change of strial blood flow. This fact suggested that the cause ofimpairment of strial circulation is not related to the autonomic unballance in the inner ear. In this study there is a possibility that free radical is produced in the cochlea by acoustictrauma.
The present study reviewed the immunocytochemical localization of various neurotransmitters/neuromodulators and cytoskeletal proteins in the inner ear. Three different nervous systems, afferent, efferent, and sympathetic nervous system were characterized by neuroactive substances localizedin each neuron. Excitatory amino acids, such as glutamate and aspartate were enriched in haircells, indicating the possibility that these amino acids may serve as hair cell transmitters. However, quantitative electron microscopic analysis revealed notable differences between cochlear haircells and presumed glutamatergic terminals in the CNS. In the avian inner ear, GABA ergic systemwas found at the level of hair cells. Primary afferent neurons can be devided into several chemicallydistinct subpopulations on the basis of the contents of neuropeptides (substance P: SP) orcytoskeletal protein (neurofilament: NF) present within them. Small vestibular ganglion cells contain SP, suggesting that they may mediate a different modality. The anatomical classification ofcochlear efferents (lateral and medial system) is also compatible with the neurochemical view point, i. e., the lateral system is characterized as dynorphins-, enkephalins-immunoreactive system, whereas SP-like immunoreactivity was found in medial system. Recent advances in immunocytochemistry have also enabled exploration of various cytoskeletalproteins in the inner ear, and findings have revealed fascinating charasteristic distribution patterns, which appear to correlate with specific functions of each cell type in the inner ear. In the presentstudy, neuronal cytoskeletal components, such as NF proteins, were focused. NF 68kD and NF 160kD-like immunoreactivities were predominantly distributed in large vestibular ganglion cells, where as NF 200kD was found in large and small ganglion cells. The differences in NF composition maycontribute to functional differences between cytochemically distinct primary afferent neurons. Indamaged inner ear (streptomycin-treated animal), NF-like immunoreactivities (especially 68kD and 160kD) decreased, whereas immunoreactivities for the other cytoskeletal proteins were not affected.
The tone-burst and click evoked otoacoustic emissions (e-OAEs) were investigated in normalhearing ears and the ears with sensorineural hearing loss due to various causes. The resultsobtained in persons with bilateral normal hearing and unilateral cochlear deafness indicated that theinteraural difference of various e-OAE parameters could be the most useful objective parameter toinvestigate the cochlear function quantitatively. The current clinical status of e-OAE as the objectiveindicator of cochlear function was discussed.
Persistent secretory otitis media in 20 children at Chiba Children's Hospital was investigated, andcholesterol crystal was found in middle ear fluid. 1. Among total of 20 children, the disease was bilateral in5children and unilateral in 15. 2. Persistent secretory otitis media were mostly diagnosed in children younger than 10 years of age.The period of suffering in the bilateral cases was 18 months on average and the unilateral cases was 31 months. Their tympanic membranes showed dark red, blue, or amber color. Their hearing was worse than that of children with common types of secretory otitis media. Mastoid cells showed poor development on radiographs. 3. Of 25 ears, 23 were treated only with insertion of ventilating tube. Through the tube18ears hadred brown discharge, which continued for about a month and they showed frequent bacterial infection. 4. The prognosis of secretory otitis media with cholesterol crystal was worse than that withoutcholesterol crystal. In addition, it was suggested that some patients with secretory otitis media withcholesterol crystal had cholesterol granuloma. It was also considered that the presence of cholesterolgranuloma is related to the clinical course of secretory otitis media. 5. We conclude that the presence of cholesterol crystal in middle ear fluid indicates prolonged clinicalcourse in secretory otitis media.
Hyperbaric therapy was performed for 34 children (66ears), aged 3to 13 years, who were sufferingfrom otitis media with effusion. As a result, 39ears (59.1%) showed improvement of average hearinglevels within 20dB, and 40 ears (60.6%) showed improvement on tympanogram. Since the infantile eustachian tube is an open pressure type, no patient experienced earache or othertrouble when exposed to high pressure. This therapy is available to all patients with little trouble for thosewho were able to use it. However, the patients who had no improvement with this therapy required aventilation tube insertion or other surgical therapy.
Studies were performed to vertify whether the fluid disappears shortly after birth with completeaeration, or it continuously exists for some period after birth. Sixty-five infants (27 males and 38 females) out of137normally born infants at Ogikubo Hospitalfrom January to March in1992were included in this study. Every infant was examined withimpedance audiometry and otoscopy. Those procedures were carried out shortly after birth (thefirst check) and at discharge from hospital (the second check). At the first check, 127 new-borns' ears showed type A tympanogram with the normal ear drumand3ears with type B. At the second check, 9infants dropped out of the study and111earsrevealed type A tympanogram with the normal ear drum and1ear type C. We concluded from ourstudy as follows: 1) In almost all new-borns, aeration of the middle ear is accomplished in a very short periodafter birth, probably within 2 to 20 hours. 2) There is no continuity from the fetal physiological fluid to pathologic exudate of the middleear.
Clinical features of cholesteatoma in patients over 60 years of age were studied. Tympanoplasty wascarried out in 30 ears of 29 patients, including 13 males and 16 females at our hospital during the periodfrom 1981 to 1990. The mean age was 65 years old, the oldest patient was a 76-year-old female. Chief complaints were as follows; otorrhea in 14 cases, dizziness or vertigo in 9 cases, tinnitus in5cases, and facial palsy in one case. They had no complaints of hearing loss even when their hearing losseswere demonstrated objectively on admission. Episodes of recurrent otitis in childhood were reported by 19 of the patients (66%). Cholesteatomas were classified into four types, namely attic cholesteatoma in 18 ears, PSQ typecholesteatoma in5cases, mixed type (attic and PSQ) in 5 ears, and adhesive type cholesteatoma in 2 ears. The canal up technique was performed in 6 ears, and the canal down technique in 24 ears. Themastoid cavity was simultaneously obliterated using bone chips or hydroxyapatite granules in 20 ears. Atoperation, exposure of the facial nerve was observed in 13 ears, labyrinthine fistula in6ears, and thedura was exposed in5ears. An air-bone gap closure less than 20dB was achieved in 48% of the patients.No recurrence of cholesteatoma occurred during the subsequent 3-year observation period. Based on these observations, cholesteatoma in the elderly generation can be considered as follows;bone destruction is more frequently observed the duration of the illness is increased but the condition of thecholesteatoma itself is mild and no severe inflammation is observed. Thus, the clinical course is favorablepostoperatively due to minimal recurrence of cholesteatoma. It is concluded that cholesteatoma in elderypeople can be treated safely and without difficulty by the surgeons well appraised of the patients condition.
Propylene glycol (PG), a solvent commonly used in topical ear preparations, to the middle earcavity of laboratory animals can produce severe inflammation and cholesteatoma. We found that cholesteatoma could be produced consistently by the application of high concentrationof PG to chinchilla middle ears and the histopathological results obtained were described inour previous report. In this paper, we further carried out a more detailed histopathological observation on chinchillatemporal bones which were obtained at various time intervals after instillation of PG into the middleear cavity, and otoscopic and tympanometric examinations of these animals were also included inthis study. Our present study indicated that there might be two different morphological patterns inthe development. of cholesteatoma following application of PG to the tympanic cavity. The formerpathological pattern of cholesteatoma development was usually associated with a tympanic membraneperforation, presumably as a result of invasion of hyperplastic keratinized epithelium to the fibrouslayer of the tympanic membrane. The latter morphological pattern of cholesteatoma formation hadthe features characterized by severe middle ear atelectasis and a large amount of keratin debrisaccumulation in the external auditory meatus and the retracted tympanic membrane surface. In ourimpression, it may be reasonable to regard the former pattern of cholesteatoma formation as “immigration type cholesteatoma” and the latter as “retraction type cholesteatoma”.
Acute low-tone sensorineural hearing loss (ALHL) appears to be one of more common otologicdisorders than previously thought and is characterized clinically by the features that: 1) the onset isacute or sudden, 2) the etiology remains obscure, and 3) the hearing loss is mild to moderate andusually unilateral. Although it is generally known that complete recovery of the hearing losses within a few weekscan be expected in majority of the patients, it has been also known that recurrence or even aggravationof this condition can occur, or clinical signs characteristic of Meniere's disease may developin selected patients. We retrospectively studied 137 patients with this disorder since late 1983 over a period of 8 years and could observe similar results with regard to the clinical symptoms and the prognoses tothose reported by other investigators in Japan. In addition, our clinical observations on ALHL further indicated following two clinical findings: Firstly, in patients with unilateral involvement the sum of the hearing level in the lower frequencyrange (500, 250 and 125Hz) was worse than that in the higher frequency range (2, 4 and 8KHz) even inthe unaffected ear and the difference was statistically significant. In other words, even when anear was unaffected (better hearing ear), the lower frequency range of the unaffected ear was alsosomewhat impaired, although the sum of the hearing losses did not reach the value of the lossesdetermined by our diagnostic critera. Thus, the tendency toward bilateral involvement or bilater -ality of the disease may be of some significance to explain its possible pathogenesis or etiology. Secondly, the positive Schellong test results which were thought to be indicative of orthostaticdysfunction were found in 46.3% of the patients with this disorder, and patients with hypotensionwere also found in 37.6%. These percentages were significantly higher than those of the controlgroup. More than one-third of the patients with ALHL seemed to have a systemic condition suggestiveof autonomic imballance or insufficient blood circulation.
It is known that the prognosis of hearing impairment in patients with idiopathic sensory neural suddendeafness with profound hearing loss is usually poor. The prognosis of hearing in 85 patients of suddendeafness with total deafness, who had visited our hospital from July, 1971 to January, 1991, were assessedby the follow-up study. The treatment by OHP had started in 17 cases and other therapeutic methodswere applied in59cases soon after the onset of the disease. Audiological studies befote and after thetreatments revealed that improvement of hearing was greater in the group treated with OHP than in thegroup with the other methods. The hearing in those with sudden deafness with profound hearing losstreated by OHP showed the tendency of much greater improvement when the therapy had started at theearly stage.
Cerebrospinal fluid (CSF) from34patients with sudden deafness, was analyzed for protein concentration, cells, immunoglobulins (IgG, IgA and IgM), and IgG antibodies to herpesvirus family andrubella. None of the patients had increased cells and only3patients had slightly increased protein concentration.Six patients had positive IgG antibodies to viruses studied by enzyme immunoassay, but none of them hadpositive antibodies by complement fixation test. Two patients were positive for herpes simplex virus type1 (HSV-1), two patients for HSV-1and others of herpesvirus family, one patient for HSV-1and rubella, and one patient only for rubella. These 6 patients with IgG antibodies to the viruses showed no significantdifference of titers between the first and the second examination afer 10 to 14 days, and they showed goodhearing recovery. The patients with increased IgG concentration in the CSF had ordinary hearing improvement. Therewas no correlation between patients with increased IgG concentration in the CSF and patients with positiveIgG antibodies to viruses, probably because the number of patients was too small. There were no significant differences of IgG antibodies to HSV-1 and rubella between the suddendeafness patients and control patients without brain or ear disease, because some of the control patientsalso had IgG antibodies. However, a ratio of serum/CSF antibody titers less than 20 was observed in atleast one sudden deafness patient, suggesting that antibody to HSV-1was produced in the CSF.
For investigation of changes in auditory function in animals requiring surgery through the middleear, a method for bone conduction auditory brainstem responses (ABR) was developed. Results wereas follows; 1. Bone conduction stimulation could be used for auditory brainstem responses in chronic experimentalanimal models of the cat. 2. Bone conduction ABRs were stable for6weeks at most. 3. Bone conduction ABRs were stable with changes in bone oscillator positions as large as 1.0cm. 4. This study might not clarify the possible pseudo-bone conduction ABR changes due to middleear impedance changes. 5. Bone conduction ABR might be useful in the cat for evaluating auditory function central tothe middle ear.