庆大霉素致豚鼠前庭毛细胞破坏后再生及功能恢复

为探讨哺乳动物前庭毛细胞破坏后能否再生及前庭功能能否恢复，以豚鼠为研究对象。实验组动物每日给予庆大霉素（１５０ｍｇ／ｋｇ）皮下注射，连续１０天，对照组动物给予等量生理盐水。于停药后的第２、４、１２和２４周分别处死动物，扫描电镜观察发现，停药２周椭圆囊和壶腹嵴毛细胞破坏最明显的区域可见到不成熟的毛细胞纤毛丛，至停药２４周后继续存在。与对照组相比，停药１２周毛细胞密度（毛细胞数／１００μｍ基底膜长度）下降明显（Ｐ＜０．０１），停药后２４周时毛细胞密度较１２周明显上升（Ｐ＜０．０５），但仍未达到正常水平（Ｐ＜０．０５）。另取豚鼠按上述方法进行庆大霉素注射，于注射前和停药后４、１２和２４周进行冰水诱发眼震电图检查，可见停药４～１２周平均慢相眼震速度（Ｖｍｅａｎ）明显下降（Ｐ＜０．０１），停药２４周后Ｖｍｅａｎ有明显恢复（Ｐ＜０．０５），但仍未达到正常水平（Ｐ＜０．０１）。提示：豚鼠周围前庭功能破坏后可以部分恢复，前庭毛细胞破坏后可以修复，其功能的恢复可能源于毛细胞再生。     

庆大霉素致豚鼠前庭毛细胞破坏后再生及功能恢复

为探讨哺乳动物前庭毛细胞破坏后能否再生及前庭功能能否恢复，以豚鼠为研究对象。实验组动物每日给予庆大霉素皮下注射，连续１０天，对照组动物给予等量生理盐水。于停药后的第２、４、１２和２４周分别处死动物，扫描电镜观察发现，停药２周椭圆囊和壶腹嵴毛细胞破坏最明显的区域可见到不成熟的毛细胞纤毛丛，至停药２４周后继续存在。与对照组相比，停药１２周毛细胞密度下降明显（Ｐ〈０．０１），停药后２４周时毛细胞密度较１     

庆大霉素损伤后豚鼠前庭感觉上皮细胞凋亡和再生

目的 研究豚鼠前庭毛细胞庆大霉素损伤后前庭感觉上皮细胞凋亡和细胞增殖之间的关系。方法 成年豚鼠肌肉注射庆大霉素１００ｍｇ／ｋｇ／ｄ连续１４ｄ,停用庆大在霉素后１ｄ和１０ｄ。腹腔注射Ｂｒｄｕ ３００ｍｇ／ｋｇ ６ｈ后处死实验动物,免疫组化显色壶腹嵴可见Ｂｒｄｕ标记细胞,同时应用ＴＵＮＥＬ技术原位显示凋亡细胞,观察应用庆大霉素后１ｄ和１０ｄ壶腹嵴毛细胞损伤区域细胞凋亡和细胞增殖状况,结果 损伤后１ｄ,     

Regenerative therapy for vestibular disorders using human induced pluripotent stem cells (iPSCs): neural differentiation of human iPSC-derived neural stem cells after in vitro transplantation into mouse vestibular epithelia

Objectives: Vestibular ganglion cells, which convey sense of motion from vestibular hair cells to the brainstem, are known to degenerate with aging and after vestibular neuritis. Thus, regeneration of vestibular ganglion cells is important to aid in the recovery of balance for associated disorders.

Methods: The present study derived hNSCs from induced pluripotent stem cells (iPSCs) and transplanted these cells into mouse utricle tissues. After a 7-day co-culture period, histological and electrophysiological examinations of transplanted hNSCs were performed.

Results: Injected hNSC-derived cells produced elongated axon-like structures within the utricle tissue that made contact with vestibular hair cells. A proportion of hNSC-derived cells showed spontaneous firing activities, similar to those observed in cultured mouse vestibular ganglion cells. However, hNSC-derived cells around the mouse utricle persisted as immature neurons or occasionally differentiated into putative astrocytes. Moreover, electrophysiological examination showed hNSC-derived cells around utricles did not exhibit any obvious spontaneous firing activities.

Conclusions: Injected human neural stem cells (hNSCs) showed signs of morphological maturation including reconnection to denervated hair cells and partial physiological maturation, suggesting hNSC-derived cells possibly differentiated into neurons.     

Cytochemical and patch-clamp studies of calcium influx through voltage-dependent Ca2+ channels in vestibular supporting cells of guinea pigs

To clarify whether or not vestibular supporting cells have voltage-dependent Ca²⁺ channels, cytochemical and patch-clamp studies were performed using cells isolated from the ampullae of the semicircular canal of the guinea pig. Image analysis used fura-2 as a Ca²⁺-sensitive fluorescence dye and showed that the intracellular Ca²⁺ concentration ([Ca²⁺]_i) increased with bath application of high (150 mM)K⁺, but was unaffected by 80 mM K⁺. The increase in [Ca²⁺]_i induced by high K⁺ was completely blocked by 1 μM nifedipine as an L-type Ca²⁺ channel antagonist. In the patch-clamp whole-cell recording of the isolated supporting cells, the voltage-dependent inward current was induced by a depolarizing pulse lasting 2 s in a high (50 mM) Ca²⁺ and tetraethylammonium-containing external solution replaced by choline chloride and a Cs⁺-containing internal solution. The inward current was obtained when the membrane was depolarized to –50 mV and maximum current was observed at –10 to +10 mV. This inward current was completely blocked by 1 μM nifedipine. These findings strongly suggest that voltage-dependent Ca²⁺ channels exist in the vestibular supporting cells and regulate Ca²⁺ concentration in the vestibular endolymph. Received: 21 August 1997 / Accepted: 19 November 1997     

Effect of platelet-activating factor on secretion of mucous glycoprotein from chinchilla middle ear epithelial cells in vitro

Platelet-activating factor (PAF) is a naturally occurring phospholipid that acts as a pleiotropic mediator and mediates cell-cell reactions under physiological and pathological conditions. Recently, it has been shown that PAF is a strong secretagogue of mucous glycoprotein in the airways, suggesting its role in mucous glycoprotein secretion and the pathogenesis of otitis media with effusion. In the current study, we examined the effect of PAF on mucous glycoprotein secretion in cultured chinchilla middle ear epithelial cells. PAF at 1 M significantly stimulated mucous glycoprotein secretion from cultured chinchilla middle ear epithelial cells. This action was concentration-dependent, with secretions reaching near maximum when the cells were incubated with PAF at 100 M. In a time-dependent study, PAF demonstrated an initial rapid stimulation of mucous glycoprotein secretion, followed by a gradual increase thereafter. A six-fold increase was seen in the first 2 h compared with controls. Cycloheximide, a protein synthesis inhibitor, demonstrated an inhibitory effect on PAF-stimulated mucous glycoprotein secretion in this study. These findings suggest that PAF plays an important role in the pathogenesis of otitis media with effusion by stimulating mucous glycoprotein secretion in vitro.Supported by NIH grant P0I-D000133 from the National Institute on Deafness and Other Communication Disorders.     

Practical model description of peripheral neural excitation in cochlear implant recipients: 1. Growth of loudness and ECAP amplitude with current

This is the first in a series of five papers, presenting the development of a practical mathematical model that describes excitation of the auditory nerve by electrical stimulation from a cochlear implant. Here are presented methods and basic data for the subjects, who were implanted with the Nucleus^® 24 cochlear implant system (three with straight and three with Contour™ electrode arrays), required as background for all papers. The growth of subjective loudness with stimulus current was studied, for low-rate pulse bursts and for single pulses. The growth of the amplitude of the compound action potential (ECAP) was recorded using the Neural Response Telemetry™ (NRT™) system. An approximately linear relationship was demonstrated between ECAP amplitude and burst loudness, although this failed at the lower end of the dynamic range, to an extent that varied with subject and stimulated electrode. Single-pulse stimuli were audible below ECAP threshold, demonstrating that the audibility of burst stimuli at such low currents was not due solely to temporal loudness summation. An approximate function was established relating the curvature of the burst loudness growth function to the maximum comfortable level (MCL). Loudness at threshold was quantified, as a percentage of loudness at MCL. The relationship between loudness and ECAP growth functions, the curvature versus MCL function and the loudness associated with threshold are relevant to the development of a mathematical model of electrically evoked auditory nerve excitation.