[Protecting Effects of Jian'erji on Age-related Hearing Loss of C57BL/6J Mice].

Objective To observe decreased hearing in aged C57BL/6J mice, and to study pro- tective effects of Jian' erji ( JEJ ) for age-related hearing loss (AHL) and its possible mechanism. Methods Totally 36 C57BL/6J mice were randomly divided into four groups, i.e., the normal control group (n =6) , the AHL control group (n =12) , the high dose JEJ group (n =12) , the low dose JEJ group (n =6). Mice in the normal control group drank tap water from ablactation till 2 months old. Mice in the AHL control group drank tap water from ablactation till 7 months old. Mice in high and low dose JEJ groups drank JEJ at the daily dose of 3. 65 g/kg and 0. 91 g/kg respectively from ablactation till 7 months old. Six mice were selected from each group for auditory brainstem response (ABR) using brainstem evoked potentiometer on the day of ending the test. The cochlear tissue, auditory cortex, and liver were immediately collected from 6 mice of the high dose JEJ group and 6 of the AHL control group at the same ages. Contents of malondialdehyde (MDA) , end product of lipid peroxidation were detected by UV spectrophotometer using MDA coomassie blue kit. Results ABR thresholds evoked by short-pure tone from 4 to 48 KHz were in the normal range of 2 months old mice in the normal control group. Compared with 2 months old mice in the normal control group, ABR thresholds were significantly elevated in 7 months old mice of the AHL control group (P <0. 05). Significant differences also existed in ABR thresholds from 8 to 48 KHz in the high dose JEJ group (P <0. 05). Compared with 7 months old mice of the AHL control group, MDA contents in cochlear tissue, auditory cortex, and liver were obviously reduced in the high dose JEJ group (P <0. 01). Conclusions C57BL/6J mice showed significant symptoms of AHL in high frequency range at 7 months old. Daily drinking of high dose JEJ could significantly delay the occurrence and progress of AHL. Its protection might be related to antioxidant effects JEJ contained.

Effects of Erlong Zuoci pill and its disassembled prescriptions on gentamicin-induced ototoxicity model in vitro.

OBJECTIVE: To study the effects of Erlong Zuoci Pill (, ELZCP) and its disassembled: prescriptions on gentamicin (GM)-induced ototoxicity model in vitro. METHODS: After the spiral organ of cochleae: of newborn mice (postnatal days: 2-3) cultured for 24 h, GM alone or combined with water extracting-alcohol precipitating solution of ELZCP or with its disassembled prescriptions was added. Hair cells were observed under a fluorescence microscope after TRITC-phalloidin staining, and the cochlear hair cell loss rate was calculated by counting the whole cochlear hair cells and analyzed by whole cochlear hair cells analyzing software. RESULTS: GM induced cochlear outer hair cells (OHCs) and inner hair cells (IHCs) injuries in a dose-dependent manner, and they were significantly different as compared with those in the normal control group (P<0.05, P<0.01). ELZCP at the concentration of 0.003-3 mg/mL could decrease the hair cells loss induced by the 0.3 mmol/L GM (P<0.05, P<0.01), the effects was in a dose-dependent manner, and the concentration of 0.3 mg/mL showed the optimal protective effect. For the ELZCP disassembled prescriptions, Liuwei-Dihuang could decrease OHC loss rate than that in the 0.3 mmol/L GM model group (P<0.05), but the OHC loss rate was still higher than that in the ELZCP group (P<0.01), which indicated that the protective effect of hair cells by Liuwei-Dihuang was not better than that of ELZCP. Poria decreased OHC loss rate from 72.1 % +/-3.7 % to 58.8 %+/- 8.2 % (P<0.05). CONCLUSIONS: ELZCP could play a role in antagonizing the injury of cochlear hair cells induced by GM ototoxicity,: and its disassembled prescriptions, Liuwei-Dihuang was the main component to protect the cochlear hair cells from GM-induced ototoxicity, and Magnetitum combined with Radix Bupleurui could strengthen the action of the whole prescription; Poria could reduce GM-induced OHC loss.

Effects of exposing C57BL/6J mice to high- and low-frequency augmented acoustic environments: auditory brainstem response thresholds, cytocochleograms, anterior cochlear nucleus morphology and the role of gonadal hormones.

Gonadectomized and intact adult C57BL/6J (B6) mice of both sexes were exposed for 12h nightly to an augmented acoustic environment (AAE): repetitive bursts of a 70dB SPL noise band. The high-frequency AAE (HAAE) was a half-octave band centered at 20kHz; the low-frequency AAE (LAAE) was a 2-8kHz band. The effects of sex, gonadectomy, and AAE treatment on genetic progressive hearing loss (a trait of B6 mice) were evaluated by obtaining auditory brainstem response (ABR) thresholds at ages 3-, 6-, and 9-months. At 9-months of age, hair cell counts (cytocochleograms) were obtained, and morphometric measures of the anteroventral cochlear nucleus (AVCN) were obtained. LAAE treatment caused elevation in ABR thresholds (8-24kHz), with the highest thresholds occurring in intact females. LAAE treatment caused some loss of outer hair cells in the basal half of the cochlea (in addition to losses normally occurring in B6 mice), with intact females losing more cells than intact males. The loss of AVCN neurons and shrinkage of tissue volume that typically occur in 9-month-old B6 mice was lessened by LAAE treatment in intact (but not gonadectomized) male mice, whereas the degenerative changes were exacerbated in intact (but not gonadectomized) females. These LAAE effects were prominent in, but not restricted to, the tonotopic low-frequency (ventral) AVCN. HAAE treatment resulted in some loss of neurons in the high-frequency (dorsal) AVCN. In general, LAAE treatment plus male gonadal hormones (intact males) had an ameliorative effect whereas HAAE or LAAE treatment plus ovarian hormones (intact females) had a negative effect on age-related changes in the B6 auditory system.

Gene Expression Changes in Chinchilla Cochlea from Noise-Induced Temporary Threshold Shift.

Acoustic overstimulation produces many anatomical, biochemical and physiological changes in the inner ear. However, the changes in gene expression that underlie these biological changes are poorly understood. Our approach to investigating this problem is to use gene microarrays to measure the changes in gene expression in the chinchilla inner ear following a 3 h or 6 h noise exposure (95 dB SPL, 707-1414 Hz). This noise exposure causes a temporary threshold shift (~40 dB) and a temporary reduction in distortion product otoacoustic emissions (DPOAE), but no permanent hearing loss or hair cell loss. Here, we present data showing (1) the suitability of mouse and human complementary DNA (cDNA) clones for detecting chinchilla cochlear gene transcripts, and (2) the change in cochlear gene transcripts in noise exposed chinchillas. Chinchilla cochlear transcript probes exhibited strong and discrete signals on both mouse and human cDNA filter arrays. Since the strongest hybridization occurred with mouse clones, mouse cDNA microarrays were used to study noise-induced changes in gene expression. Chinchilla cDNA probes were differentially labelled with Cy3 (control) or Cy5 (noise exposed) by random primed synthesis, hybridized to 8750 mouse cDNAs arrayed on microscope slides and analysed by laser fluorescent microscopy. Several classes of genes exhibited time-dependent up regulation of transcription, including those involved in protein synthesis, metabolism, cytoskeletal proteins, and calcium binding proteins. The results are discussed in relationship to previous studies showing noise-induced changes in structural proteins, calcium binding proteins, metabolic enzymes and membrane bound vesicles.