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The effects of impulse noise (firecrackers at 170 dB SPL, 1, 10, 20 rounds) on auditory cortical response threshold (CRT) and activity of succinic dehydrogenase (SDH) and acetylcholinesterase (AchE) in the inner ear were studied in 37 guinea pigs. The results showed that extent of damage in the cochlea was related to amount of exposure to the noise. Exposure to 10 rounds resulted in temporal threshold shift (TTS); to 20 rounds the result was permanent threshold shift (PTS). For the period when TTS existed, inverse correlation was noticed between enzyme activity change and CRT shift. The correlation could not be established when PTS was induced. The results suggest that the pathomechanism of PTS was more complex than that of TTS. The significance of the results is discussed. [ABSTRACT FROM AUTHOR]

Objective: To investigate the clinical effects of tinnitus retraining therapy (TRT) on tinnitus., Methods: 225 tinnitus patients were divided into two groups. 117 patients in the TRT group were treated with TRT and drugs, and 108 patients in the control group were treated with only tinnitus masking and drugs. The TRT is consisted of four strategies: (1) tinnitus masking with low level and broad band noise; (2) deep relaxation of the whole body; (3) diversion of the attention to other things; and (4) psychological counseling and therapy. Drugs, such as vasodilator, neurotrophic drug, and sedative of the similar dose and duration of pharmacotherapy were administered to the 2 groups. Effect evaluation was conducted thrice 2, 6, and 12 months after the beginning of therapy to see if the tinnitus was attenuated or disappeared and if the patients' emotion, sleep, and work were disturbed by tinnitus., Results: The relief rate was 17.09%, 82.05%, and 88.03% in the TRT group 2, 6, and 12 months after respectively; and 2.78%, 26.85%, and 41.6% in the control group 2, 6, and 12 months after respectively (chi(2) = 12.54, 69.30, and 63.64, all P < 0.01)., Conclusion: TRT is effective in treatment of tinnitus.

Objective: To investigate the clinical features, diagnosis, and treatment of glomus jugulare tumor., Methods: The data of 37 patients of glomus jugulare tumor diagnosed by digital subtraction angiography (DSA) and/or operation and pathology, 14 males (37.8%) and 23 females (62.2%), with an average age of 37.2 (3.5 approximately 66 years) and an average course of 4.3 years (1 month - 19 years), were analyzed., Results: The tumor was located in the left ear in 19 cases, in the right ear in 17 cases, and in both ears in 1 case, totally 38 ears. The tumor was chromaffin in one case with hypertension. One case was complicated by ipsilateral carotid body tumor, and 2 cases were complicated by ipsilateral cholesteatoma. Thirty cases (81.1%) presented pulsatile tinnitus and hearing loss as the main symptoms. Thirteen cases (35.1%) were diagnosed as glomus jugulare tumor at the first visit, and 24 cases (64.9%) were diagnosed as other diseases with an average misdiagnosis period of 4.4 years. Eighteen tumors originated from typanum and 28 tumors from glomus jugulare. According the Fisch classification 1981, the tumors in 11 ears were type A, in 7 ears were type B, in 7 ears type C, in 5 ears type D1, and in 8 ears type D2. All cases, except the one with bilateral lesions, underwent operation. The tumor was completely resected in 30 cases. Postoperatively, facial paralysis was seen in 6 cases, dizziness, hoarseness, and subauricular necrosis was seen in one case respectively. Of the 25 patients followed up with a mean follow-up time of 5.2 years (1.1 - 16.1 years), 3 died of lung cancer, neuroblastoma, or extensive involvement of glomus jugulare tumor respectively, 19 survived without tumor, and 3 survived with the tumor., Conclusion: Glomus jugulare tumor is likely to involve surrounding important tissues, and to be misdiagnosed. Early surgical removal of the lesion is important.

Objective: To probe the relationship between the density of L-type calcium channels on outer hair cells(OHCs) among various turns and the tonotopic map in the guinea pig cochlea., Methods: The L-type calcium channels in outer hair cells of guinea pigs were labeled with DM-BODIPY DHP and RH414 and monitored using a laser scanning confocal microscope. The fluorescence ratio of DM-BODIPY DHP/RH414 revealed the distribution of L-type calcium channels on the cellular membrane., Results: The results showed that the cellular membrane had lesser DM-BODIPY DHP staining when pretreated with nifedipine, indicating that calcium channels on OHCs had the specificity of a L-type calcium channel. The density of L-type calcium channels had a tendency of increasing gradually from low frequency areas to high frequency areas. Variance analysis showed that the difference of the density of L-type calcium channels on OHCs between the fourth turn and the second turn was significant. There were no apparent differences in the distribution of L-type calcium channels among various regions on the cellular membrane of OHCs., Conclusions: The descripency of the distribution of L-type calcium channels on OHCs among various turns of the guinea pig cochlea may be one of the molecular mechanisms of the tonotopic map of the cochlea.

Objectives: To study the status of cochlear mitochondrial DNA (mtDNA) and to determine the location of mtDNA deletion in aged mice., Methods: We detected cochlear mtDNA in 2, 7 - 10 and 17 - 19 month old mice by nested polymerase chain reaction (PCR) and DNA sequencing., Results: mtDNA3867bp deletions were found in the cochleae of aged mice. The deletion occurred within nt9103-nt12970 and were flanked by 15 base pair direct repeats. Comparing the incidence of mtDNA3867bp deletions, 17 - 19 month old mice (7/8) were significantly higher than 7 - 10 month old mice (4/16). The deletion was not observed in 2 month old mice (0/7). The ratio of deleted mtDNA/total mtDNA in 17 - 19 month old mice was higher than in 7 - 10 month old mice (P < 0.001)., Conclusion: Cochlear mtDNA 3867bp deletion in aged mice may be related to presbycusis.

Objective: To investigate the genetic mechanism of maternal nonsyndromic inherited sensorineural hearing loss(SNHL), to identify the incidence of the 7445(G) mutation in such pedigrees and sporadic patients with SNHL, and to provide the theoretical evidence for the diagnosis of this disease., Methods: Blood samples were obtained from 2 pedigrees and 14 sporadic patients with SNHL. DNA was extracted from the isolated leukocytes. The mitochondrial DNA (mtDNA) fragments were amplified by PCR. The 1555(G), 3243(G) and 7445(G) mutation was detected by Alw 26 I, Apa I and Xba I restriction endonuclease digestion respectively. The sequence of 12S rRNA, tRNA(Leu(UUR)) and tRNA(Ser(UCN)) was examined., Results: Restriction endonuclease digestion analysis showed that 12 individuals from 2 pedigrees carried homoplasmic 7445(G) mutation, which was of maternal inheritance. Six individuals from 2 pedigrees and 14 sporadic patients did not have 7445(G) mutation. All individuals did not have 1555(G) and 3243(G) mutation. The sequence analysis further showed that none of them carried homoplasmic 1555(G) and 3243(G) mutation, 12 individuals had (nt)7445 A--> G substitution in tRNA(Ser(UCN)) gene., Conclusion: The incidence of 7445(G) mutation in such pedigrees is higher than that in sporadic patients. Screening for mtDNA 7445(G) mutation combined with 1555(G) examination is of much value to clinical use.

Objectives: To investigate the tissue specificity of reactive oxygen species (ROS) damage to mitochondrial DNA (mtDNA) and to determine whether cochlear mtDNA is a sensitive target for ROS damage., Methods: 10 Cu/ZnSOD gene (Cu/Zn superoxide dismutase gene, Sod1) knockout mice and 16 wild-type mice were analyzed by nested polymerase chain reaction (PCR)., Results: Three deletions were detected in various tissues of Sod1 knockout mice. MtDNA3867bp and mtDNA3726bp deletions were the most visible, and mtDNA4236bp deletion was barely detected in these tissues. There were obvious differences in the ratio of deleted mtDNA/total mtDNA in different tissue. Deleted mtDNA was most abundant in the liver and kidney and less in cochlea, heart and brain. The lowest was in spleen and skin. The ratio in various tissues was 3 - 20 times in Sod1 knockout mice over wild-type mice. In cochlea, the ratio was about 15., Conclusions: Without the protection of Sod1, ROS can lead to mtDNA deletions in various tissues with significant tissue specificity. Cochlear mtDNA is a sensitive target for ROS damage.

Objective: To investigate the effect of D-AP5 (D-2-amino-5-phosphonopentanoate, a specific NMDA-antagonist) on the increase of intracellular free Ca2+ concentration ([Ca2+]i) induced by glutamate in isolated cochlear inner hair cells (IHCs), and to detect the autoreceptors of the IHC membrane., Methods: When a laser scanning confocal microscope (LSCM) was used, the exogenous glutamate (Glu)-induced changes in [Ca2+]i of isolated IHCs and OHCs of guinea pig cochlea were observed with fluo-3, a fluorescent probe for [Ca2+]i. After D-AP5 or CNQX (6--cyano--7--nitroguinoxaline--2, 3--dione, a specific AMPA- antagonist) was administered, the exogenous glutamate (Glu)-induced changes in [Ca2+]i of isolated IHCs were recorded., Results: In the presence of a low concentration Glu (3.85 mumol/L), there was an increase of [Ca2+]i in IHCs, whereas there was no change in OHCs. When 50 mumol/L of D-AP5 was administrated in advance, Glu did not induce a corresponding increase in [Ca2+]i in IHCs, and 50 mumol/L of CNQX did not completely block the increase of [Ca2+]i in IHCs., Conclusions: These results suggest that the autoreceptors existing in the IHC membrane are mainly of NMDA type, while there are relatively few AMPA receptors. Exogenous Glu is capable of increasing [Ca2+]i in IHCs by acting on the NMDA autoreceptor of IHCs in a positive feedback manner.