D-甲硫氨酸对庆大霉素耳毒性保护作用的研究

目的：探讨D－甲硫氨酸对庆大霉素耳毒性的保护作用。方法：30只豚鼠分为生理盐水对照组、庆大霉素组及D－甲硫氨酸加庆大霉素联合用药组。采用听觉脑干诱发电位（ABR）及耳蜗铺片技术，观察研究耳毒性及D－甲硫氨酸的保护作用。结果：联合用药组动物各频率阈移均比单独使用庆大霉素组显著降低,且耳蜗组织学检查显示其毛细胞缺失明显轻于庆大霉素组。结论：使用庆大霉素的同时联合应用D－甲硫氨酸可有效减少庆大霉素的耳毒性。     

单次大剂量水杨酸钠注射所致大鼠耳蜗基因表达谱改变

目的:研究大剂量水杨酸钠耳毒性的作用机制。方法:运用寡核苷酸基因芯片技术分析大剂量水杨酸钠注射对大鼠耳蜗基因表达谱的影响。联用TRIzol和RNA纯化柱分别从13周正常大鼠和水杨酸钠注射后的大鼠耳蜗内容物提取总RNA,将总RNA逆转录为cDNA,再将cDNA体外转录为cRNA,在此过程中同时进行生物素标记,将cRNA片段化后作为探针与质量检测芯片杂交,确定无问题后再与寡核苷酸基因芯片杂交扫描,用Affymetrix Microarray Suite software 5.0分析处理扫描结果,获得两种情况下耳蜗的基因表达谱。结果:表达上调2倍以上的基因和EST有42个,下调2倍以上的有49个。结论:水杨酸钠影响各种离子通道和突触蛋白基因,可能有助于解释水杨酸钠所致的耳聋和耳鸣作用机制,而其他变化基因亦有助于解释水杨酸钠广泛的药理作用。     

Styrene induced alterations in biomarkers of exposure and effects in the cochlea: mechanisms of hearing loss.

It is known that styrene is ototoxic and causes cochlear damage starting from the middle turn. However, the cellular mechanism underlying styrene ototoxicity is still unclear. In this study, rats were exposed to styrene by gavage at different doses once a day for varying periods. Styrene levels in the cochlear tissues, styrene-induced permanent hearing loss, cochlear disruptions, and cell death pathways were determined. Styrene concentration in the cochlea varied along with the basilar membrane with the lowest level in the basal turn being consistent with the lowest styrene-induced threshold shift and hair cell loss in this region. After 3 weeks of exposure (5 days per week), a dose-dependent permanent hearing loss and a hair cell loss, especially in the midfrequency region, were observed. The styrene exposure at a dose of 200 mg/kg, which induced a blood level of 6.0 +/- 1.0 microg/g, caused an average of 4.4 +/- 0.5% OHC (outer hair cell) loss and 2-5 dB threshold shift in the cochlear region of 20-70% from the apex. A significant OHC loss was not observed until 7 days of exposure at a dose of 800 mg/kg. Deiters cells appeared to be the most vulnerable target of styrene. When condensed nuclei were observed in Deiters cells after a few days of styrene exposure (800 mg/kg), other cells were still intact. Apoptotic cell death appeared to be the main cell death pathway in the cochlea after styrene exposure. In the styrene-induced apoptotic OHCs, histochemical staining detected activated caspases-9 and 8, indicating that both mitochondrial-dependent pathway and death receptor-dependent pathway were involved in the styrene-induced cell death.     

当归注射液对庆大霉素耳中毒影响的实验研究

目的以脑干听觉诱发电位(BAEP)、酸性磷酸酶(ACP)组织化学检测为指标,研究当归注射液对庆大霉素(GE)耳毒性的防治作用。方法将30只耳廓反射正常的健康杂色豚鼠随机分成正常对照组、GE组、当归组,各组连续用药20天。结果当归组BAEP阈值升高幅度、波峰潜伏期与波间期变化明显低于GE组(P<0.01),ACP染色变化和毛细胞损害程度均低于GE组(P<0.01)。结论当归注射液能降低GE的耳毒性。保护耳蜗毛细胞内溶酶体的完整性,防止毛细胞的自溶性损伤可能是当归的作用机制之一。     

川芎嗪预防顺铂耳毒性效果的实验研究

目的：研究川芎嗪对顺铂耳毒性的防护作用。方法：80只听力正常体重250～350g的豚鼠随机分为4组（每组20只豚鼠）：生理盐水组、顺铂组、川芎嗪组及川芎嗪＋顺铂组。前3组分别腹腔注射生理盐水4ml/（kg·d）、顺铂4mg/（kg·d）、川芎嗪140mg/（kg·d）,连续注射6d;第4组在第1、2天腹腔注射川芎嗪140mg/（kg·d）,第3天注射川芎嗪后30min,再腹腔注射顺铂4mg/（kg·d）,连续注射6d。在给药前及最后1次给药后测定各组豚鼠听觉脑干诱发电位（ABR）阈值的变化。另外,在最后1次给药后测定每组10只豚鼠的耳蜗组织超氧化物歧化酶（SOD）活性及丙二醛（MDA）含量,并用透射电镜观察每组另10只豚鼠的耳蜗毛细胞形态的变化。结果：顺铂组、生理盐水组、川芎嗪组及川芎嗪＋顺铂组的ABR阈值分别为：（55.652±6.562）dB、（40.556±4.532）dB、（42.321±5.362）dB及（45.639±6.069）dB。顺铂组的ABR阈值明显高于其他3组（P〈0.01）。生理盐水组、顺铂组及川芎嗪＋顺铂组的SOD活性分别为（33.30±5.89）U/mg、（21.44±6.42）U/mg及（29.69±4.47）U/mg。顺铂组SOD活性明显低于生理盐水组（P〈0.01）。川芎嗪＋顺铂组SOD活性与生理盐水组比较,差异无统计学意义（P〉0.05）。生理盐水组、顺铂组及川芎嗪＋顺铂组的MDA含量分别为（10.34±1.74）nmol/mg,（15.72±2.04）nmol/mg及（11.07±1.56）nmol/mg。顺铂组MDA含量明显高于生理盐水组（P〈0.01）。川芎嗪＋顺铂组MDA含量与生理盐水组比较,差异无统计学意义（P〉0.05）。川芎嗪＋顺铂组耳蜗毛细胞细胞体及核的形态基本正常;而顺铂组耳蜗毛细胞核染色质固缩、凝集,空泡样变性,组织超微结构损伤明显。结论：川芎嗪对顺铂所致耳毒性有较好的防护作用。     

A Pilot Study of High-Dose Carboplatin and Pulsed Etoposide in the Treatment of Childhood Solid Tumors

Carboplatin was administered at 1,000 mg/m²/course in combination with etoposide at 300 mg/m²/course to 23 patients aged 5 months to 16 years. Five patients were affected by neuroblastoma, four by CNS tumors, three by Ewing's sarcoma, two by rhabdomyosarcoma, two by malignant teratoma, two by Wilms' tumor, two by head and neck carcinoma, one by hepatoblastoma, one by synovial sarcoma, and one by Langerhans-cell histiocytosis. Eleven patients were pretreated, seven of them with high-dose cisplatin. The overall response rate was 7/11 (64%) for pretreated and 10/12 (83%) for previously untreated patients. Myelosuppression was the main side effect, with anemia and thrombocytopenia more pronounced than leukopenia. Gastrointestinal toxicity and ototoxicity were very mild; nephrotoxicity and neurotoxicity other than hearing loss were not observed. In children with malignant tumors, the therapeutic activity of carboplatin at high doses, even in combination chemotherapy, deserves further studies.     

WR-2721 (Amifostine) Ameliorates Cisplatin-Induced Hearing Loss But Causes Neurotoxicity In Hamsters: Dose-Dependent Effects

Chemoprotective agents reduce the toxic side effects of chemotherapy agents such as cisplatin. The conventional belief is that the chemoprotective agent WR-2721 (Amifostine), while protecting against most cisplatin-induced side effects, does not protect against cisplatin-induced ototoxicity (i.e., hearing loss). There is no knowledge, however, about the efficacy of high doses of WR-2721 (WR) in possibly protecting against cisplatin-induced ototoxicity. Thus, the dose-dependent effects of WR in possibly ameliorating cisplatin-induced ototoxicity were investigated. Hamsters were given a series of 5 cisplatin injections (3 mg/kg/injection once every other day, i.p.) either alone or in combination with 18, 40, 80, or 400 mg/kg/injection of the rescue agent WR (n = 5 or 10/group). Other groups received either 80 mg/kg/injection WR alone (n = 5) or were untreated (n = 14). Ototoxicity was assessed by auditory brain stem responses (ABR). WR provided dose-dependent rescue from cisplatins ototoxicity with no protection at the low dose of 18 mg/kg, moderate protection at 40 mg/kg, and nearly complete protection at 80 and 400 mg/kg. However, WR doses of 40 mg/kg or higher caused neurotoxicity as evidenced by prolongations in the ABRs interpeak latencies. Thus, high doses of WR provided the beneficial effect of protecting against cisplatin-induced ototoxicity, but had the harmful side effect of neurotoxicity. Previous failures to find chemoprotection from cisplatin-induced ototoxicity were likely due to the use of WR doses that were too small. The clinical implications of the beneficial and harmful effects of high doses of WR are discussed.     

Acrylonitrile Potentiates Noise-Induced Hearing Loss in Rat

Acrylonitrile, one of the 50 most commonly produced industrial chemicals, has recently been identified as a promoter of noise-induced hearing loss (NIHL). This agent has the potential to produce oxidative stress through multiple pathways. We hypothesize that acrylonitrile potentiates NIHL as a consequence of oxidative stress. The objectives of this study were to characterize acrylonitrile exposure conditions that promote permanent NIHL in rats and determine the ability of this nitrile to produce auditory dysfunction by itself. Additionally, we sought to determine whether a spin-trap agent that can form adducts with ROS would protect against the effects of acrylonitrile. Acrylonitrile administration produced significant elevation in NIHL detected as a loss in compound action potential sensitivity. The effect was particularly robust for high-frequency tones and particularly when acrylonitrile and noise were given on repeated occasions. Acrylonitrile by itself did not disrupt threshold sensitivity. Administration of the spin-trap agent phenyl-N-tert-butylnitrone (PBN), given to rats prior to acrylonitrile and noise, did block the elevation of NIHL by acrylonitrile. However, PBN at the dose and time interval given was ineffective in protecting auditory function in subjects exposed to noise alone. The results suggest that oxidative stress may play a role in the promotion of NIHL by acrylonitrile.     

Calpain activity in the amikacin-damaged rat cochlea

The principal aim of this study was to investigate the involvement of calpain in the degeneration of hair cells and ganglion neurons in the amikacin-poisoned rat cochlea. An antibody designed against fodrin-breakdown products (FBDP), which result exclusively from cleavage by calpain, was used. In addition, the involvement of both caspases and protein kinase C (PKC) was studied using, respectively, antibodies against activated caspase 3 and PKCgamma. The results demonstrate the accumulation of FBDP in the degenerating hair cells, in some supporting cells such as Deiters cells, and, later, in the affected ganglion neurons that had been deprived of their sensory targets. Activated caspase 3 was evidenced in a few dying hair cells and ganglion neurons. PKCgamma was highly expressed in all ganglion neurons, sometimes after the loss of hair cells. We conclude that calpain plays a role in the degradation of both the sensory cells and neurons after amikacin ototoxicity. In the poisoned hair cells, calpain and caspase 3 may have synergistic effects in the process of apoptosis. In the ganglion neurons deprived of their sensory elements, calpain may have a prominent role in cell degradation. By contrast, in these ganglion neurons PKCgamma may be implicated in a survival process. Finally, we suggest that calpain is involved in the remodeling of Deiters cells during the scarring process that follows hair cell loss.