The outer hair cell of the mammalian cochlea has a unique motility directly dependent on the membrane potential.Examination of the force generated by the cell is an important step in clarifying the detailed mechanism as well as the biological importance of this motility.We performed a series of experiments to measure force in which an elastic probe was attached to the cell near the cuticular plate and the cell was driven with voltage pulses delivered from a patch pipette under whole-cell voltage clamp.The axial stiffness was also determined with the same cell by moving the patch pipette. The force generated by the cell is around 100pN/mV and the axial stiffness obtained was 510 nN per unit strain. We used Diamide to change the stiffness of the cell.We thus found that the force was approximately proportional to the axial stiffness.Because Diamide affect the cortical lattice, our observations suggest the importance of the cortical lattice in determining the membrane elasticity and force generation. In contrast, Salicylate caused a decrease in force without stiffness change.
It is known that the olivocochlear (OC) efferent fibers innervated to the outer hair cells (OHCs) can modulate the active process in the cochlea which is related to the motile response of the OHCs.The basic known effect of the activation of this OC efferent neurons is suppression of the auditory system. On the other hand, when tones are presented with background noise, the OC activation can enhance the responses of the auditory nerve.In the respect of the effective signal perception in the cochlea, the OC-system should not act during the signal perception in the background quiet, however, should be activated when the signals are perceived in the masking situation.In the present study, the practical role of this system is discussed by observing the effects of the severance as well as the stimulation of the OC-neurons on the auditory responses. The results obtained suggest that the OC system are not activated in the signal (short duration) perception in quiet. That is, in this situation, the benefit from the active mechanism is not disturbed by the OC efferent system. On the other hand, in the condition of the signal perception in the background continuous noise, OC system is activated effectively by the noise and can improve the perception of the newly presented signal in the cochlea.
With an image analysis method we studied humoral control mechanisms of cochlear spiral ganglion cells (SGCs). We used the rapidly dissected SGCs from the guinea-pig cochlea and the cultivated SGCs removed from newborn mice. Intracellular calcium mobilization was analyzed by ARGUS 100 (Hamamatsu Photonics) using a calcium sensitive dye, Fura-2/AM. We measured the change of a membrane potential using ARGUS 50 PDA (Hamamatsu Photonics) with a voltage sensitive dye, NK3041. We examined the effect of the glutamate, ATP and the glucocorticoid to SGCs. Glutamate is thought to be a neurotransmitter of signal transduction from cochlear inner hair cells to SGCs. We suggested that rapidly dissected SGCs with neuronal process mainly have a non-NMDA type glutamate receptor. Extracellularly applied glutamate caused the increase of intracellular calcium concentration by an influx from outside. Magnesium had extremely small blockade to this response. Without neuronal process of SGCs, this response was not occurred. ATP is the neuromodulator in the signal transduction of cochlea. Extracellularly applied ATP made the increase of intracellualr calcium concentration. Both the influx of calcium from outside and the intracellular calcium mobilization caused this increase. With agonists and antagonists to the purinergic receptor, this response might occur through the P2 type purinergic receptor. There are two types of corticosterone, the mineralcorticoid and the glucocorticoid. We examined the dexamethasone, the representative of synthetic glucocorticoid. Dexamethasone alone did not cause the change of intracellular calcium concentration of SGCs. Dexamethasone enhanced the calcium response caused by ATP. This enhancement might occur through the glucocorticoid receptor (type 2) combined with P2 purinergic receptor. From the time course of this response we thought that dexamethasone made this response by non-genomic effect. From above results we thought that SGCs are regulated by the humoral control mechanisms. In both physiological and pathological conditions this humoral control mechanisms might modulate the signal transduction from hair cell to the brain.
The supporting cells of the organ of Corti are divided into 2 cell groups. One group consists of Deiters cells and Pillar cells which have a cytoskeleton within the cell body. Other group consists of the cells that are located to the outside in the organ of Corti, such as Hensen cell and do not have the cytoskeleton. All of the supporting cells are getting involved in the maintenance action of the environment of corti lymph around the hair cell by the recycling of K+. It is thought that Hensen cell is getting involved in the regulation of the endolymphtic potential and ion organization of the endolymph. On the other hand, Deiters cell has a possibility that it inhibitedly controlled of the outer hair cell-Deiters cell vibration complex by changing the flexibility of the cell long axis accompanied with intnacellular Ca2+incnease. However, Pmar cell does not admit such a mechanical adjustment action. It is suggested that extracellular ATP regulates the intracellular Ca2+level by the Ca mobilization from intracellular Ca2+store within the Deiters cell.
Mucoud otitis is known to be caused by mucoid typeStreptococcus pneumoniae, and the most of them are serotype 3. As the result of the development of antibiotics this bacteria has once been regarded as an unimportant pathogen. However recently, there are found severe cases in which this pathogen is responsible. During the period from January 1998 to July 1999, we have treated 25 cases in which the mucoid typeStreptococcus pneumoniaewas isolated. Based on these experiences, we summarized the current status of the mucoid otitis media as follows. 1. The distribution of patients suffering from mucoid otitis medid ranged infants to elderly people. 2. The patients presented with symptomes, such as severe earache, headache, high fever, profuse otorrhea, aggravation of sensorineural hearing. 3. The relief of the symptomes is usually better and earlier when penicillin was selected as a first choice, while when cephem antibiotics were selected, healing of the otitis media tend to be delayed. 4. As 13 out of 14 strains isolated in 1999 were found to be penicillin-insensitiveStreptococcus pneumoniae (PISP) withpbp2xgene, it is conceivable that the resistance of this pathogen against cephem is under a rapid progress, probably due to abuse cephem in the past in this country. 5. The antibiotics of the first choice against mucoid otitis media is penicillin. If the pathogen would acquire penicillin resistance, treatment of mucoid otitis media may become as difficult as it used be in old days of preantibiotics. We should pay enough attention to this disease as an important reemerging infectious disease in the otolaryngologic field.
Eleven adult patients (fourteen ears, four males, seven females) with acute otitis media associated with bone conduction threshold shift were investigated. The patients ranged in age from 27 to 66 years. Four patients presented with anxiety about deterioration of otalgia or hearing loss. They had no recognition of relation ship between acute otitis media and hearing loss. All the patients were treated by iatravenous antibiotics, steroids and vitamins during hospitalization. Tympanotomy was performed in all the patients but one. They showed marked recovery of hearing (twelve ears showed complete recovery).
Chronic otitis media in children is one of the common diseases in Otolaryngology. Between January 1993 and February 1999, we performed type I tympanoplasty for 30 cases of chronic otitis media with a perforation of the tympanic membrane.All patients were younger than 17 years old.The outcome of surgery including post-operative hearing and graft condition was analyzed. Possible contributing factors on success of surgery, such as patients'age, location and size of the perforation, presence of otorrhea, combination of mastoidectomy were analysed.All patients had a follow-up period for at least 6 months after the surgery. The graft was intact in 83.3% and the post-operative air-bone gap was less than 20dB in 93.4% of the cases.Eighty percent of the case was evaluated as “success” according to the definition of “success” that the graft was intact and the post-operative air-bone gap was less than 20dB. The success rate of type I tympanoplasty in children was satisfuctory and almost comparable to that in adult.The outcome of the surgery was not influenced by any of above-mentioned factors.We concluded that type I tympanoplasty can be safely and effectively performed not only in adult but also in children.
Thirty seven male and 20 female elderly volunteers, ranging in age from 70 to 89 years (mean age 76.0 years), with no history of audiological or neurological hearing problems were tested.These subjects were divided into groups of 5 year intervals according to their age.Pure tone audiometry, speech discrimination test and auditory brain stem response (ABR) were performed. The relationships between the inter peak latency (IPL) of ABR and the scores of the speech iscrimination test were investigated.The results showed no significant correlation between the score of the speech discrimination test and IPL of the I-I, I-V, and III-V. But in the group where the speech discrimination test scores were 80% or less, a slight increase in each of the IPL was seen in comparison with those scores of 85% or more.
The purpose of this study is to investigate the effect of speech rate to speech recognition in 11 cochlear implant users and 13 hearing-impaired elderly adults. The cochlear implant users were postlingually deafened adults (4 males and 7 females) ranging from 18 to 64 years of age, with a mean age of 50.9, who use Nucleus 22 channel cochlear implant system with SPEAK coding strategy. The elderly adults (4 males and 9 females) ranging from 56 to 80 years of age, with a mean age of 64.0 participated in the study. Three speech rate variations were created for each sentence: fast (11 molar per second), middle (9 molar/s), and slow (6 molar/s). The speech recognition performance was evaluated for the percentage score of syllables that were correctly recalled in a sentence composed of 5 syllables. Percentage scores in the fast, middle, and slow speech rate were 15.6%, 38.8%, and 57.1% respectively in cochlear implant users and 59.2%, 67.4%, 81.4% respectively in elderly adults. This result revealed a significant effect of speech rate slowing (p<0.0001) in both groups. However, variation to the effect of speech rate slowing was observed in the cochlear implant users, compared with the older adults. The effect of speech rate slowing was high in cochlear implant users who achieved good recognition score at fast speech rate. Although the recall scores were higher for the first syllable of the sentence than for the syllables in mid-sentence at the fast rate, slowing the rate of speech increased the scores of syllables in every position. Speech rate is important factor for improvement of speech recognition in cochlear implant users and elderly adults.
Case 1 is a 47-year-old female who developed tinnitus and severe hearing loss in her right ear. Case 2 is a 64-year-old male with severe hearing loss and tinnitus of the right ear and mild dizziness. Case 3 is a 35-year-old male with moderate right hearing loss and tinnitus. In all of these three cases, hearing loss occurred suddenly in one ear when the patients were not undergoing actual hemodialysis procedures. All cases were treated with steroids and other drugs. In Case 1, hearing loss showed a significant improvement, but soon after the recovery, about the same degree of hearing loss recurred to the same ear. She was treated again with the same drugs, and her hearing eventually returned to the same level as the other ear. After the second recovery, her hearing did not change. In Case 2, hearing loss showed a slight to moderate improvement mainly at low and middle frequencies, but did not change thereafter. In Case 3, his hearing once returned to normal, but soon after, a moderate hearing loss at low frequencies occurred in the opposite ear and then returned to normal again. In the literature, there were 39 reported cases of sensorineural hearing loss of sudden onset which occurred in hemodialysis and peritoneal dialysis patients in our country, including our three cases. There appear to be many other unreported cases of the same kind, and the incidence of such acute sensorineural hearing loss in dialysis patients would be much higher than that of idiopathic sudden sensorineural hearing loss. A close observation at the clinical courses of these cases, including ours, indicated that this type of acute sensorineural hearing loss in dialysis patients would present diverse clinical pictures which are somewhat different from those of usual idiopathic type, and thus, should be considered as a different group of cases. Also, the possible underlying mechanism in this type of hearing loss was reviewed and discussed.
Electrocochleography (EcochG) was performed in contralateral ears in 27 cases of unilateral acoustic neurinoma, and the relationships between the EcochG findings, tumor size and pure tone thresholds were investigated. As to EcochG findings, negative summating potential to compound action potential ratio (-SP/AP ratio) was examined. The tumor size was assessed by magnetic resonance imaging (MRI). Pure tone audiometry was performed just before EcochG recording. Abnormal-SP/AP ratio exceeding 0.40 of upper limit of normal range was found in 7 (25.9%) of 27 ears. Pure tone thresholds elevated at the low and high frequencies. However, these pure tone threshold shifts had no correlation to abnormal-SP/APratio. Incidence of abnormal-SP/APratiowas 30.0%in cases with a large tumor (n=10), 33.3% in cases with a medium-sized tumor (n=6) and 18.2% in cases with a small tumor (n=11). There was no correlation between incidence of abnormal-SP/AP ratio and tumor size. Averages of-SP/AP ratios were 0.242±0.138, 0.327±0.124 and 0.30±0.130 in cases with large, medium-sized and small tumors respectively. The average of -SP/AP ratio has no statistical difference among the three groups. Moreover, there was no correlation between-SP/AP ratio and pure tone threshold at the EcochG recording. These results suggest that any size of acoustic neurinoma may affect on the contralateral electrocochleographic findings. One of possible causes may be dysfunction of olivocochlear efferent system. The other may be delayed endolymphatic hydrops at present, however, the causes of-SP/AP ratio increase are still unknown. Further investigation on this matter will be needed.