Various neurotransmitters and neuromodulators involved in cellular signal transduction exerts their biological action at receptors coupled to phospholipase C (PLC). This enzyme catalyzes the hydorlysis of phosphatidylinositol 4, 5-bisphosphate (PtdInsP2) to inositol 1, 4, 5-trisphosphate (InsP3) and 1, 2-diacyl glycerol (DG) which act as second messengers. Such receptor-mediated activation of PLC is expected to be coupled through guanine nucleotide-binding proteins (G proteins). In the present paper, we investigated biochemically the biological characteristic of the InsP3 second messenger system in the cochlear sensory epithelia (CSE) of the rat. In CSE, the InsP3 second messenger system was linked to muscarinic and purinergic P2y receptors. These receptors were coupled to PLC via cholera and pertussis toxin-insensetive G proteins. From these results, we discussed the function of the InsP3 second messenger system in CSE and hypothesized that the motile property of outer hair cells might be regulated by the cochlear efferent nervous system via the InsP3 second messenger system.
Anti-masking effects mediated by the sound-evoked efferent activity were discussed in the present paper. In the cats, masked auditory responses were enhanced by adding the noise to the contralateral ear both in the compound action potential (CAP) and in the responses of single auditory nerve fibers. These anti-masking effects were disappeared when the olivocohlear bundle (OCB) was interrupted. It has been suggested that classic suppressive effects of OCB on the auditory-nerve responses to the back ground masker are an important component of this OC mediated anti-masking phenomenon. Similar anti-masking phenomena were observable in the human subjects as well. Small but significant enhancements of masked CAP in amplitude were seen in some patients with facial palsy, in which acoustic reflexes of middle ear muscles (MEMs) had disappeared or were impaired.
The whole-cell patch clamp modes were developed to investigate the ionic channels of cellular membrane and to elucidate the signal transduction pathways from receptor to effector. The nystatin perforatedpatch mode in particular, can reveal detailed characteristics of intracellular signaling pathways which were involved in GTP binding proteins (G proteins) and second messengers. This review describes the recent studies of intracellular signaling pathways in dissociated outer hair cells (OHCs) of guinea-pig cochlea by using both the conventional whole-cell mode and the nystatin perforated-patch mode. Substance P (SP) response, decreasing the non-selective cation channel conductance, was involved in pertussis toxin (PTX)-insensitive G protein, but not in any second messengers. Acetylcholine (ACh) response, opening the Ca2+-dependent K+ channels, was involved in both PTX- and cholera toxin (CTX)-sensitive G proteins through IP3 pathway and cAMP pathway respectively. The possible intracellular signaling pathways in OHCs of guinea-pig cochlea were discussed in accordance with present results.
Interleukin-2 receptor (IL-2R) is expressed on the membrane of activated T cells, and soluble IL-2R (sIL-2R) is a released extracellular domain of the alpha-chain of IL-2R. Activated T cells also regulate the expression of intercellular adhesion molecule-1 (ICAM-1) on the endothelium, indirectly through such media as tumor necrosis factor alpha (TNF-α) and interferon gamma (INF-γ), and may contribute to the recruitment of inflammatory cells. To examine the pathogenesis of otitis media with effusion (OME), we measured the levels of sIL-2R, TNF-α and soluble ICAM-1 (sICAM-1), a soluble component of ICAM-1, in the effusion and serum of patients with OME. The average level of sIL-2R in the effusion was 12700 [U/ml], but, there was no significant difference between the levels of serous and mucoid types. The average levels of TNF-α and sICAM-1 in the effusion were 165 [pg/ml] and 848 [ng/ml], respectively. There were also significant differences in the levels of TNF-α and sICAM-1 between the serous and mucoid types. Furthermore, these three levels of sIL-2R, TNF-α and sICAM-1 in the effusion were significantly higher than those in serum. These findings indicated that IL-2 and activated T cells were steadily involved in the pathogenesis of OME and that TNF-α and ICAM-1 affected the regulation of the production of two different types of effusion.
The purpose of the present sturdy is to elucidate the mechanism of the increased vascular permeablity in the facial nerve following Wallerian degeneration. Seven days and 14 days after nerve damage, the distribution of collagen fibers in the facial nerve distal to the lesion site was observed with Van Gieson staining and compared with that of fluorescein injected intravenouslly. In this portion, a collagen accumulation was observed in the endneurium in addition to increased accumulation of fluorescein at both 7 and 14 days after nerve damage. Therefore, the endoneurial fibrosis following Wallerian degeneration seemed to increase the extracellular space and endneurial vascular permeability.
Seven cases of chondroma of the external ear canal are reported. These tumors were of horn shape, 2-3mm long, and lmm in diameter. They were located in the anterior wall of the bony external ear canal, 2-3mm lateral to the eardrum. his location seemed closely related to the tympanosquamous suture. The tympanic menbranes are normal. There were no obvious symptoms concerning the ear. In two cases, the tumors were removed by curet under local anesthesia. On histologic examinaton, the tumor consists of mature hypertrophic cartilagineous tissue. There are no recurrence after curetting, and no enlargemenet of tumors in nonoperated cases.
The present investigation was undertaken in order to evaluate the effectiveness of intravenous injection of immunoglobulin (IVIG) treatment for the otitis-prone children under 2 years old without evident immunodeficiency. Twenty children suffered from at least 5 or more episodes of acute otitis media during the past 6 month-follow-up period were designated as the otitis-prone group, ere subjected to the present study. The otitis-prone children were given 2 to 5 injections of IVIGs (2.5g of Venoglobulin IH®) until they became 24 to 30 months. The serum level of IgG2 and specific antibody to S. pneumonia, the incidence of acute otitis media and tympanogram before and after the treatment were periodically investigated. Before IVIG treatment, total episodes of acute otitis media of the 20 otitis-prone children were 162 times during the total periods of 147 months. After IVIG treatment, the episodes dramatically decreased to 11 times for 162 months. The mean serum level of antibody against S. pneumonia was 1.7μg/ml in otitis-prone group, which was statistically significantly lower than that of the healthy control group of 3.4μg/ml (p=0.002). The serum antibody levels significantly increased up to those of control group after the IVIG treatment. In 14 ears tympanometry showed alternatively type A and B, and in 24 ears it showed persistently type B before IVIG treatment. After IVIG treatment tympanogram normalized in all ears of alternate A between B type group and 15 ears of persistent B type group. The shorter the duration from the initial episode of acute otitis media to the first IVIG treatment, the higher the rate of normalization of tympanogram (x2 test, p=0.016). These results showed that IVIG treatment is very effective for severe recurrent acute otitis media under 2 years of age.
Three cases of post-operative mastoid cyst (51 and 10-year-old females and 10-year-old male) were preserved. They underwent mastoid obliteration operation 1-16 years ago. The symptoms were a swelling of the external meatus, otorrhea and otalgia. The cysts may be developed after mastoid obliteration. Follow up observation by CT was thought to be an essential examination. Differential diagnosis of cholesteatoma was the most important.
Medial meatal fibrosis (MMF) is a disease which causes obstruction in the medial portion of the external auditory canal due to proliferation of fibrous tissue. Otoscopic findings of the MMF were similar to that of the lateralized tympanic membrane, but are different in the presence of thick scar or granulation tissue behind it. Two cases of MMF occurred following revision myringoplasty are reported. Case 1 is a 50-year-old male with a complaint of bilateral hearing loss. He had a history of bilateral tympanoplasty for chronic otitis media 20 years ago. The tympanic membranes were bilaterally lateralized. Hearing levels were 55dB (right) and 55dB (left), with A-B gaps of 30dB and 28.7dB, respectively. Revision myringoplasty was performed on the left ear by placing a temporal fascia using underlay technique and by repositioning the lateralized tympanic membrane using Lore's method. Ear canal packing was removed on the 12th day after the surgery. Follow-up study revealed that the tympanic membrane was thick due to prominent fibrosis behind it. Conservative treatment such as removal of the superficial granulation tissue and scar could not improve his hearing. Re-operation is planned. Case 2 is a 40-year-old female with a history of left tympanoplasty 20 years ago presented with a complaint of left hearing loss. Revision myringoplasty by the same technique as used in case 1 failed to improve her hearing due to formation of MMF. Conservative treatment could not improve the condition. One year later, the third operation was conducted by removing all the fibrous tissues obstructing the ear canal and by repairing the tympanic membrane and the ear canal using free skin graft. She has been well after the operation with hearing improvement of 18.8dB. On these (each) 2 cases there was postoperative lateralized tympanic membrane. We think Medial Meatal Fibrosis was induced in each case, because we performed myringoplasty that lateralized tympanic membrane was preserved. After all we should excise lateralized tympanic membrane and clean granulation on external auditory canal then cover exposed bone face with flap.
Patients with acoustic neurinoma present sudden hearing loss as a initial symptom are increasing. However, specific type of audiogram for acoustic neurinoma has not yet been described. In our institutes between 1981 and 1993, there were 81 cases of acoustic neurinoma, in whitch 33 cases complained chiefly of a sudden hearing loss. But the other 48 cases complained of a slowly progressive hearing loss (nonSD-AT). Pure tone audiograms of 17 in 33 cases before treatment as sudden deafness (SD-AT) were analyzed. The medio-cochlear type audiogram was observed in 11 patients out of 17 with SD-AT, on the other hand this type was not obserbed in non SD-AT group. The hearing loss in high (8kHz) and low (125Hz, 250Hz) frequencies of SD-AT was significantly smaller than that of nonSD-AT. From these results, it was emphasized that any patients with sudden hearing loss of “medio-cochlear type” must be carefully studied for possible acoustic neurinoma.
Prostaglandin I2 (PGI2), which exerts a vasodilating action and inhibits platelet functions has storonger effects than that of PGE1. In this study, we administered beraprost sodium, an oral drug of a stable analog of PGI2, in a dose of 60μg a day to 49 cases with sudden sensorineural hearing loss as outpatient therapy. The results were compared retrospectively with those of 43 patients who received PGE1 therapy and of 50 cases treated with conventional therapy. These was a statistically significant difference in percent of improvement between patients treated with beraprost sodium therapy and those treated with PGE1 therapy and conventional treatment. It was concluded that oral beraprost sodium may be a useful drug for patients with idiopathic sudden sensorineural hearing loss.
A 17-year-old girl riding on a bicycle, was struck by lightning through a headphone type stereo-cassette. After recovery from unconsciousness, she noticed bilateral hearing loss and vertigo. The 1st grade burning on skin was observed on her anterior chest and the external auditory canal in both sides. The drumhead in each side was ruptured due to barotrauma. On pure tone audiogram, the right hearing was 65dB with 49dB of air-bone gap, and the left was averaged 46dB with 45dB of air-bone gap. Vertigo disappeared spontaneously on the 4th day after lightning, and vestibular dysfunction was not recognized. Perforation of both drumheads was conservatively followed up for 60days, but a spontaneous healing was not expected. Myringoplasty was performed on both sides on the 65th day and the postoperative improvement was satisfactory. The clinical course, lightning-induced auditory trauma and treatment of traumatic drumhead perforations were discussed.
Screening of hearing disorders was performed in 1243 of 3-year-old and 1578 of 4-year-old children by using questionnaire, whispered voice test, finger friction test, pure tone audiometry and tympanometry. The results obtained were as follows. 1) The incidence of sensori-neural hearing loss was 0.08% in 3-year-old and 0.06% in 4-year-old children. 2) The incidence of otitis media with effusion (OME) with a mean hearing level more than 40dB was 1.0% in 3-year-old and 1.3% in 4-year-old children. 3) Questionnaire, whispered voice test and finger friction test were not useful at least for the screening of OME with hearing loss (≥40dB). The children with sensori-neural hearing loss were detected by questionnaire. 4) Pure tone audiometry for screening was desirable even though it has limitations. 5) Screening tests for only 3-year-old children was thought not enough for detetion of chronic persistent OME.