内耳色素与爆震性听损伤

目的 探讨内耳色素与爆震性听损伤的关系。方法 选用豚鼠４８只，分为：白化豚鼠爆震组，杂色豚鼠爆震组，正常对照组。爆震前及爆震后６小时、１、２、７、１４、２１天测定Ａ、Ｂ组豚鼠ＡＢＲ阈值。处死豚鼠做耳蜗铺片、耳蜗树脂包埋半薄切片、耳蜗扫描电镜制样，观察耳蜗内色素及耳蜗损伤情况。结果 光镜下杂色豚鼠可见耳蜗内色素颗粒，而白化豚鼠未见。爆震后白化豚鼠听力损伤比杂色豚鼠严重，其听力恢复亦较杂色豚鼠慢。爆震     

东菱精纯克栓酶对爆震性听损伤影响的实验研究

目的观察东菱精纯克栓酶(DF-521)对豚鼠爆震性听损伤的影响.方法随机将70只豚鼠分为2组爆震+生理盐水组(A组)35只;爆震+DF-521组(B组)35只.爆震前后于多个时间点测定听觉脑干反应(ABR)阈值与血液流变学各指标,并观察耳蜗微循环.结果A组豚鼠的血液流变学改变,耳蜗微循环改变及听功能损伤均较B组豚鼠重.结论DF-521能减轻爆震所致的听器损伤,对爆震性听损伤有一定的保护作用,为防治爆震性聋提供了新方法.     

爆震对豚鼠内耳损伤的研究

爆震性聋属于感音神经性聋的一种，与耳蜗损伤毛细胞有关，但不同强度噪声致聋及不同类型的神经性聋各有其特点，本研究采用爆震性聋（172dBSPL）豚鼠动物模型，检测爆震对豚鼠造成的听力损伤不同时期昕l螂卤干反应（ABR）阈值的变化，同时采用扫描电镜及光镜观察耳蜗形态学改变，探讨高强度爆震致聋豚鼠内耳损伤的特点，为探讨爆震聋发病机制提供试验依据。     

表皮生长因子及地塞米松对爆震性聋治疗作用的实验研究

为研究爆震后豚鼠耳蜗毛细胞表皮生长因子受体（epidermalgrowthfactorreceptor，EGFR）的表达，以及表皮生长因子（epidermalgrowthfactor，EGF）及地塞米松（dexamethasone，DXM）的治疗效果，采用免疫组织化学ABC技术和听性脑干反应（ABR）检测。结果发现正常豚鼠耳蜗内、外毛细胞有散在的表皮生长因子受体（EGFR）表达，阳性反应位于听毛，呈节段性分布。爆震后24小时EGFR阳性反应分布于内毛细胞胞浆。爆震后72小时内毛细胞听毛和外毛细胞皮板呈阳性反应。震后1周内毛细胞阳性反应明显增多，部分外毛细胞听毛呈阳性反应。EGFR阳性反应至2周有所减少。震后1个月内、外毛细胞听毛均呈EGFR阳性反应。EGF及DXM对爆震性聋均有一定的治疗作用，二者合用可使豚鼠听力明显恢复。结果提示，毛细胞损伤修复可能与EGF有关。     

丹参防治爆震性聋的实验研究

观察了爆震后实验动物的听性脑干反应(ABR)和氧自由基代谢产物丙二醛(MDA)含量变化。结果发现,单纯爆震组ABR阈移和耳蜗MDA含量比丹参防治组和正常对照组明显增高;丹参防治组与正常对照组相比无显著差异。提示丹参能较有效地防治爆震性耳聋,并对其作用机理进行了讨论。     

杂色和白色豚鼠听反应阈及耳蜗血管纹细胞增殖活性的差异

目的研究杂色和白色成年豚鼠正常听反应阈及耳蜗血管纹细胞增殖活性的差异。方法用听觉诱发电位仪分别测定杂色和白色豚鼠40Hz听觉相关电位(40HzAERP)及听性脑干反应(ABR)阈值;用免疫组化法检测两种豚鼠耳蜗血管纹增殖细胞核抗原(PCNA)表达的差异。结果杂色和白色豚鼠耳蜗血管纹中间细胞PCNA染色均呈阳性,但前者PCNA的表达显著强于后者;两种豚鼠的听反应阈值无显著性差异。结论正常杂色和白色成年豚鼠血管纹中间细胞均具有增殖能力,但前者的增殖能力显著高于后者,不过这种差异并不造成两种豚鼠的正常听反应阈有明显差异。     

用MP3播放器通过耳机播放音乐对豚鼠听觉系统的影响

目的研究用MP3播放器通过耳机播放音乐对豚鼠的听性脑干反应(auditory brainstem response,ABR)阈值及耳蜗形态学的影响,探讨其对听觉系统的损伤作用。方法实验动物分为对照组及实验组,每组动物12只。对照组不给予音乐暴露,其他条件与实验组相同。实验组每天用MP3播放器播放流行音乐5 h,连续14 d。观察对照组、实验组ABR反应阈及耳蜗形态学的变化。结果实验组动物在音乐暴露过程中及暴露后数天均呈现明显ABR反应阈上移,而对照组ABR反应阈无明显变化,两组间差异有统计学意义;基底膜铺片示实验组耳蜗各转外毛细胞均有不同程度的缺失,以耳蜗底转近钩端最为严重,3排外毛细胞以第二、三排损伤较重。结论用MP3播放器通过耳机播放音乐能引起豚鼠听觉系统的损害,表现为ABR反应阈升高及耳蜗外毛细胞形态的改变。     

西地那非对豚鼠噪声性听觉损伤阈移的影响

目的 探讨西地那非(sildenafil)对豚鼠噪声性听觉损伤阈移的影响.方法 将豚鼠按随机数字表法分为对照组、噪声暴露组和西地那非给药组,每组10只.西地那非组及噪声组豚鼠在白噪声(A计权声压级110 dB)暴露1周后分别腹腔注射西地那非10 mg/(kg·d)及生理盐水4mL/(kg·d),连续给药4周.分别测试噪声暴露前1日、噪声暴露后1、2及4周听性脑干反应(ABR)阈值,并通过扫描电镜观察噪声暴露后4周豚鼠耳蜗毛细胞的形态变化.结果 噪声暴露1后,噪声暴露组豚鼠ABR阈值(声压级)平均提高19.1 dB,随着时间推移,阈移逐渐加大,暴露后4周,阈值平均提高22.0 dB;西地那非组噪声暴露后ABR阈值提高19.8 dB,给药后阈移逐渐减小,给药后4周,阈值仅平均提高4.8 dB.西地那非组与噪声暴露组相比,除噪声暴露结束后这一时间点以外,其余给药后各时间点ABR阈值差异均具有统计学意义(P值均＜0.05).扫描电镜显示,噪声组豚鼠耳蜗内、外毛细胞均出现听毛紊乱、融合及缺失;而西地那非组耳蜗病变较轻,听毛仅有轻微倒伏、融合现象.结论 西地那非能够减轻噪声对豚鼠耳蜗毛细胞的损害,降低噪声性听觉损伤引起的ABR阈值升高.     

急性次声波暴露后豚鼠位听功能及内耳超微结构的变化

目的观察次声波对豚鼠位听功能和内耳超微结构的影响。方法将豚鼠置于频率8Hz、声压级135dBSPL的次声声场中连续暴露90min。应用正弦摆动试验(sinusoidalpendulartest,SPT)、听性脑干反应（auditorybrainstemresponse,ABR）和畸变产物耳声发射(distortionproductionotoacousticemission,DPOAE)评价次声波暴露前后豚鼠前庭功能和听功能的变化,扫描电镜观察豚鼠内耳各结构表面超微形态的变化。结果次声波暴露后不同时间正弦摆动诱发的豚鼠前庭性眼震的最大慢相速度(slow-phasevelocity,SPV)和频率较次声暴露前轻微降低,但无显著性意义(P>0.05)。次声波暴露后各组动物ABR阈值较正常时略有升高,亦无统计学差异(P>0.05),各组动物ABR各波潜伏期和波间期与次声暴露前比较差异均无显著性(P>0.05);DPOAE的幅度值在各个频率段均有明显的降低(P<0.01)。扫描电镜下见各实验组动物内耳半规管壶腹嵴两囊斑及Corti器感觉毛细胞纤毛缺失、散乱、倒伏及融合,表皮板等结构均有不同程度的损伤。结论次声波对豚鼠前庭末梢感受器兴奋性可能有一过性的轻微抑制作用,但SPT无有意义改变。次声波可引起豚鼠内耳毛细胞超微结构的损伤,可导致豚鼠耳蜗外毛细胞功能明显减退,这种功能减退尚不足以引起听力的明显改变。     

压力波对豚鼠耳蜗外侧壁微循环及听阈的影响

本研究应用生物微球技术、ＨＲＰ示踪显色法，结合光学显微镜，分别将对照组及爆震后２、６、２４ｈ组豚鼠耳蜗外侧壁血流量、微血管数量进行测量，并测试听性脑子反应。结果：爆震前、后各组ＡＢＲ平均阈值，组间差异显著（Ｐ＝０．０００４），６ｈ组阈移最大，其次为２４ｈ组，２ｈ组最小。爆震后豚鼠耳蜗侧壁血流量，无显著差异（Ｐ＞０．０５），而各回血流量有波动；爆震后耳蜗外侧壁血流量与阈移呈负相关（ｒ＝－０．５９３，Ｐ＜０．０５），外侧壁微血管的数量，因时间而变化，与血流量变化相吻合。讨论了爆震后耳蜗外侧壁血流量变化与听力损失、外侧微血管数量变化之间的关系。     

Susceptibility of organ of Corti with or without melanin to acoustic overstimulation]

Albino and pigmented guinea pigs were compared in terms of susceptibility to acoustic trauma. The animals were exposed to a 4 kHz pure tone of 120 dB for 60 min. N1 thresholds of CAP were measured before and after the acoustic exposure. Changes in the outer hair cell and stria vascularis were studied using SEM and TEM. After acoustic trauma, N1 thresholds were more elevated in the albino than in the pigmented guinea pigs. Also, pathological changes in the outer hair cell and stria vascularis were more severe in the albino animals. A noteworthy finding in the stria vascularis was that the melanin in intermediate cells had moved into marginal cells. This melanin migration may be possibly involved in mechanisms underlying prevention of acoustic trauma.     

Toxic effects of cisplatin alone and in combination with gentamicin in stria vascularis of guinea pigs

The toxic effects on the stria vascularis of treatment with cisplatin alone and combined with the aminoglycoside antibiotic, gentamicin, were studied in guinea pigs. The toxicity induced in albino and pigmented guinea pigs was investigated morphologically with light and transmission electron microscopy, and functionally by brainstem-evoked response audiometry. The results of hearing thresholds were variable, ranging from no change in one ear in some of the animals to a hearing loss of 20 dB in one or both ears when treated with low-dose cisplatin alone or in combination with gentamicin. Bilateral deafness resulted from high-dose cisplatin combined with gentamicin. The combined treatment produced prominent structural damage in the stria vascularis. The results should be considered when aminoglycoside therapy is required in conjunction with cisplatin.     

Differential susceptibility to noise-induced permanent threshold shift between albino and pigmented guinea pigs

Evidence that reduced levels of cochlear melanin are associated with increased auditory sensitivity, increased levels of auditory fatigue and an increased susceptibility to noise-induced hearing loss led us to investigate the effects of noise exposure on the cochlear microphonic (CM) in albino and pigmented English shorthair guinea pigs. CMs were recorded from the round window prior to and at 90 min and 7 days after exposure to 45 min of 126 dB noise. Thresholds for the first detectable elicitation of the CM for four pure tones were determined and the output voltage of each cochlea was measured in 10 dB steps through intensity levels which produced a maximum voltage amplitude in the CM and voltage rollover. This analysis demonstrated that: albino guinea pigs displayed significantly lower auditory thresholds than did pigmented animals before exposure to noise; thresholds were elevated to comparable levels in both groups 90 min after noise exposure; pigmented guinea pigs showed a reliable recovery in CM thresholds 7 days after exposure to noise while thresholds in the albinos remained elevated to the same degree at both 90 min and 7 days after noise; 90 min after noise exposure, the maximum voltage output of albino cochleas was significantly less than that recorded from the cochleas of the pigmented guinea pigs. These results demonstrate that albino guinea pigs are more susceptible to the ototoxic effects of high intensity noise than pigmented guinea pigs. Converging evidence indicates that some aspects of cochlear function involve melanin pigment and that its absence may produce auditory abnormalities. Reduced melanin pigmentation may also contribute to such phenomena as noise-induced threshold shifts and individual differences in noise-induced hearing loss.     

Comparative anatomy of melanin pigment in the stria vascularis. Evidence for a distinction between melanocytes and intermediate cells in the cat

Although Corti in 1851 first described the presence of cochlear pigmentation in the stria vascularis (SV) of "very old" cats, modern studies have failed to find pigment consistently in the feline stria. While the variable presence of pigment in the feline SV would appear to contrast with this structure's uniform pigmentation in other mammalian species, variability in both the distribution and abundance of inner ear pigment has rarely been studied in any species. In the present study, the SV was examined light microscopically in sectioned material or whole-mounts from pigmented and albino animals of 5 species, including the cat, guinea pig, rabbit, ferret and mouse. In these species, the SV of each pigmented animal contained varying amounts of melanin pigment and none was found in the albino inner ear. Pigmented guinea pigs contained the most uniformly dense and least variable distribution of strial melanin, followed by the rabbit, mouse, ferret and cat. Several species also displayed more strial pigment apically and less basally. In cats, pigmented cells were principally located adjacent to the strial capillaries. Ultrastructural studies of the stria in pigmented cats revealed that these perivascular cells frequently contained an abundance of pigmented organelles and other structural features which allowed them to be distinguished from intermediate cells.     

Turn-specific and pigment-dependent differences in the stria vascularis of normal and gentamicin-treated albino and pigmented guinea pigs.

The aims of the present study were to determine which structures in the stria vascularis (SV) may depend upon the presence of pigmented melanocytes both for normal morphology and for the expression of gentamicin ototoxicity in the inner ear. These pigment-dependent influences were inferred through comparisons of the SV in pigmented guinea pigs and in albinos containing nonpigmented melanocytes. Results were obtained from 6 albino and 8 pigmented guinea pigs given gentamicin, and from 3 albino and 3 pigmented control animals not receiving the drug. One-month old animals received gentamicin daily (100 mg/kg) for 14 days and recovered for an additional 14 days before being prepared for electron microscopy. The SV from each of the 4 cochlear turns was analyzed using stereological point counting procedures. In control animals, differences were found in the higher cochlear turns, where volume density for the marginal cells in albinos was abnormally large (turns 3 and 4), while the volume density for intermediate cells (melanocytes) was abnormally small (turn 3). Cell volume estimates for the intermediate cells were significantly smaller in the albino than pigmented control animals in the higher cochlear turns, indicating that functional abnormalities may be found in the albino cochlea. In animals exposed to gentamicin, marginal cell volume density was reduced significantly in turn 4 of albinos, but not in any region of the pigmented inner ears. Radial area of SV and estimates of the absolute volumes for marginal cells in albinos given gentamicin also were significantly reduced in turn 1 compared to their controls; such differences were not observed in the pigmented animals. The results indicate that marginal cell size is significantly reduced in albino but not pigmented animals 14 days after gentamicin exposure, and further suggest a role of pigmented melanocytes in ameliorating gentamicin-induced cochlear damage.     

Differential susceptibility to gentamicin ototoxicity between albino and pigmented guinea pigs

The known chemical affinity of melanin pigment for aminoglycoside antibiotics has led to the suggestion that higher concentrations of these drugs will bind to the pigmented inner ear and produce greater ototoxicity compared to the nonpigmented albino cochlea. Although this has provided a compelling hypothesis, results from the few investigations to address this question have been equivocal. In the present study, cochlear microphonic (CM) thresholds were recorded from albino and pigmented guinea pigs both before and two weeks after exposure for 14 consecutive days to 100 mg/Kg gentamicin. Cochleae were dissected and half-turn segments prepared for surface examination of the organ of Corti. After gentamicin exposure, threshold shifts averaged a statistically reliable 33 dB in albinos and 19 dB for the pigmented animals. Anatomical studies revealed a significant 44% mean outer hair cell loss in albinos compared to a 21% loss in the pigmented inner ears. The results showed that albinos display greater ototoxicity from gentamicin than do pigmented guinea pigs. Aminoglycosides are known to exert toxicity through interaction with polyphosphoinositides found in high concentrations in the inner ear. Cochleae in both albino and pigmented animals appear to possess significant phospholipid concentrations and bind toxic levels of these drugs independent of inner ear pigment content. However, evidence showing that melanin can inhibit aminoglycoside activity in vitro suggests that, once these drugs bind to pigmented tissue, they may undergo inactivation in a manner unavailable to the nonpigmented albino cochlea. The present results are consistent with the possibility that cochlear melanin may inhibit gentamicin activity in vivo and decrease the severity of aminoglycoside ototoxicity in the pigmented inner ear.     

庆大霉素对豚鼠血管纹黑色素的影响及其机制

OBJECTIVE: To investigate the effect and its mechanism of gentamicin(GM) on melanin in stria vascularis of guinea pig. METHODS: The differences of auditory thresholds between pigmented and albino guinea pigs, given GM of 150 mg/kg for 7 days, were studied. Moreover, the content of melanosomes, activity of tyrosinase and expression of proliferating cell nuclear antigen(PCNA) in intermediate cells of stria vascularis in gentamicin-treated pigmented guinea pigs were compared with those in control animals by electron microscope and immunohistochemistry, respectively. RESULTS: After gentamicin exposure, the auditory thresholds of all animals increased significantly (P < 0.001), whereas threshold shifts averaged across all frequencies of pigmented animals were much less than those of the albinos(P < 0.001). The number of melanosomes of each examined area (300 microns 2) in intermediate cells was obviously increased from 19.83 +/- 2.74 to 58.33 +/- 16.22. The ratio of tyrosinase reaction products area to the total measured area was significantly increased from 1.65% +/- 0.40% to 3.45% +/- 0.41% after gentamicin exposure. However, the numbers of positive intermediate cells expressing PCNA were 14.08 +/- 2.76 and 13.58 +/- 2.09 before and after gentamicin treatment, respectively. But there was no statistically significant difference between them (P > 0.05). CONCLUSION: The increase of content of melanin in stria vascularis after GM exposure does not result from the change of proliferating activity of melanocytes, but from the enhanced tyrosinase activity. Melanins in stria vascularis may possess the ability to protect the inner ear from ototoxicity of gentamicin.     

Effects of aging on normal hearing loss and noise-induced threshold shift in albino and pigmented guinea pigs

In a previous investigation into noise-induced hearing loss by comparing 2-month-old albino with pigmented guinea pigs, albinos displayed significantly greater shifts in cochlear microphonic (CM) threshold and less recovery than the pigmented animals 7 days after noise exposure. The present study compared the responses of 14-month-old albino and pigmented guinea pigs to the same noise parameters used previously. Thresholds for the first detectable elicitation of CM for three pure tones were recorded prior to, at 90 min and at 7 days after a 45-min exposure to 126 dB broadband noise. Before exposure to noise, thresholds for pigmented guinea pigs were 24 dB higher than those in the albinos. Following noise exposure, the pigmented animals showed less than half the amount of threshold shift displayed by the albinos. This change ws attributed to the higher pre-exposure thresholds in the pigmented guinea pigs. Converging lines of evidence suggest that cochlear pigmentation may have both protective and toxic influences on the inner ear.