听信息在毛细胞中的转导过程及模型

一、引言外耳接收的声波,经外耳道而达鼓膜,鼓膜的振动借小听骨使镫骨扣击前庭窗,引起前庭阶外淋巴液振动,从而振动前庭膜和蜗管的内淋巴液,于是引起基底膜内听弦的共振;当基膜振动时,毛细胞的纤毛触及盖膜弯曲,使毛细胞受到刺激,引起神经冲动,由位听神经的蜗神经传入脑的听中枢,这是产生听觉的基本过程。在这个过程中,听觉的感受器一毛细胞利用各种机械的、流体力学的、电的方法,     

豚鼠耳蜗毛细胞静纤毛的扫描电镜观察

目的 了解耳蜗毛细胞正常和静纤毛的形态特征。方法 用扫描电镜观察了２５４只豚鼠的耳蜗。结果 豚鼠耳蜗毛细胞静纤毛正常和几种变异的形态特征为：１．外毛细胞行毛排列不规则及静纤毛的自然缺失;２．外毛细胞静纤毛束转位;３．外毛细胞行毛副毛与列外内毛细胞。结论 外毛细胞静纤毛排列不规则和静纤毛的自然缺失不是病理变化。外毛细胞静纤毛束转位,静纤毛副毛与列外内毛细胞是遗传变异引起的。     

基于基底膜响应的圆窗激振性能评估偏差研究

目的研究采用传统基底膜位移评价标准评估圆窗激振式人工中耳听力补偿性能的准确性,为圆窗激振式人工中耳的性能评估提供理论基础。方法基于耳蜗几何结构的实验数据,建立耳蜗感声微观有限元模型,通过对比内听毛细胞、外听毛细胞、盖膜等部位位移响应的实验测量值,验证模型的可靠性。基于该模型,对比分析正向激振、圆窗激振下的基底膜位移与内听毛细胞静纤毛剪切位移;以内听毛细胞静纤毛剪切位移作为感声标准,研究圆窗激振时采用传统人工中耳基底膜评价标准的等效声压级偏差。结果在所研究耳蜗微段对应的5 k Hz特征频率处,相同幅值的声压作用下,圆窗激振的基底膜位移和内听毛细胞静纤毛剪切位移均小于正向激振的对应值。结论正向激振下的内听毛细胞更兴奋,感声效果更强。同时,采用正向激振的基底膜位移评价方法评估圆窗激振的听力补偿效果,会高估圆窗激振的听力补偿性能;但偏差较小,是一种相对可靠的评价方法。     

豚鼠化脓性中耳炎耳蜗Corti氏器组织学及超微结构研究

<正> 以中耳接种金黄色葡萄球菌的方法诱发豚鼠化脓性中耳炎,用光学及电子显微镜观察实验性化脓性中耳炎不同时间耳蜗Corti氏器的病理改变。发现随中耳炎病程的延长,受累耳蜗外毛细胞缺失有增多的趋势,在扫描及透射电镜下,则可见存留的外毛细胞静纤毛改变、线粒体变性、     

蝾螈椭圆囊毛细胞换能、编码和突触传递的形态学基础

本实验研究椭圆囊毛细胞换能、编码和突触传递的形态和显微力学基础。以幼年蝾螈为对象，光镜和电镜观察椭圆囊囊斑的微细和超微结构。实验结果：（１）只有毛细胞的高静纤毛和动纤毛的头部和耳石膜接触，耳石膜的剪切力由直接和间接两种途径传递至静纤毛；（２）耳石膜和表皮板组成纤毛束上下两端的致密板状结构，皮板下微管起固定和支撑下板作用，在两板之间的无定形物质有缓冲和利于上板滑动的功能，这种安排是纤毛受力后偏曲的基础；（３）囊斑上皮存在着动纤毛排列方向不同的四种毛细胞，感受器依靠这些分布不同的毛细胞群进行信号编码；（４）多根传入神经末梢和１～２ 根传出神经末梢与毛细胞构成传入和传出突触，存在于毛细胞底部胞液内和传出神经末梢内的囊泡是突触传递的物质基础。     

外柱细胞软化对Corti器感音影响的生物力学研究

Corti器的感音过程容易受到内部结构属性变化的影响。外柱细胞血管舒张刺激磷蛋白缺失会减缓肌动蛋白丝的形成,从而产生听力延迟。本研究运用COMSOL建立三维有限元模型研究肌动蛋白缺失导致外柱细胞软化时,Corti器感音过程中基底膜和外毛细胞与Deiters细胞结合点的力学行为变化。结果表明,外柱细胞软化会削弱外毛细胞主动力对基底膜位移增益的放大作用,但削弱作用并不会立即产生,Corti器存在维持正常功能的“缓冲”阶段。在100 dB和120 dB之间可能存在一个声压级临界值,在该临界值两侧外柱细胞软化对基底膜应力变化的影响是截然相反的。另外外柱细胞软化对不同外毛细胞与Deiters细胞结合点力学行为的影响也不同,位移增益优先级会因此产生改变。     

外柱细胞软化对Corti器感音影响的生物力学研究

Corti器的感音过程容易受到内部结构属性变化的影响。外柱细胞血管舒张刺激磷蛋白缺失会减缓肌动蛋白丝的形成,从而产生听力延迟。本研究运用COMSOL建立三维有限元模型研究肌动蛋白缺失导致外柱细胞软化时,Corti器感音过程中基底膜和外毛细胞与Deiters细胞结合点的力学行为变化。结果表明,外柱细胞软化会削弱外毛细胞主动力对基底膜位移增益的放大作用,但削弱作用并不会立即产生,Corti器存在维持正常功能的"缓冲"阶段。在100 dB和120 dB之间可能存在一个声压级临界值,在该临界值两侧外柱细胞软化对基底膜应力变化的影响是截然相反的。另外外柱细胞软化对不同外毛细胞与Deiters细胞结合点力学行为的影响也不同,位移增益优先级会因此产生改变。     

DBA/2J小鼠耳蜗毛细胞静纤毛早期的形态结构变化

目的:观察低周龄DBA/2J小鼠耳蜗毛细胞静纤毛形态结构的变化,探讨DBA/2J小鼠早期听力受损的原因。方法:检测DBA/2J小鼠2、4周龄和8周龄听觉脑干反应,扫描电镜下观察耳蜗底回毛细胞静纤毛的形态结构特征。结果:听觉脑干反应显示DBA/2J小鼠在4周龄后表现为渐进性的听力受损。扫描电镜可见2周龄时高倍镜下纤毛束融合并伴有纤毛束软化,4周龄时纤毛束融合、软化和倒伏更为严重,8周龄低倍镜下纤毛束缺失数目较多,尚存纤毛融合倒伏更为严重。结论:DBA/2J小鼠耳蜗毛细胞静纤毛出现纤毛束融合、软化、弯曲、倒伏甚至缺失,可能是导致其早发性听力受损的主要原因。     

盖膜基因与耳聋

盖膜是耳蜗的 Corti器表面的细胞外基质成分 ,在早期的耳聋研究中它是一个被忽略的因素 ,但是许多的研究发现盖膜的组成成分盖膜蛋白、 型胶原、 型胶原、Otogelin糖蛋白与综合征型耳聋和非综合征型耳聋都有关系。本文就盖膜基因的克隆、结构、功能、表达和致病情况作一综述     

盖膜基因与耳聋

盖膜是耳蜗的Corti器表面的细胞外基质成分。在早期的耳聋研究中它是一个被忽略的因素。但是许多的研究发现盖膜的组成成分盖膜蛋白，Ⅱ型胶原，Ⅺ型胶原，Otogelin糖蛋白与综合征型耳聋和非综合征型耳聋都有关系。本就盖膜基因的克隆。结构，功能，表达和致病情况作一综述。     

Tectorial membrane-organ of Corti relationship during cochlear development

The development of stereociliary attachment to the tectorial membrane was investigated in the mouse cochlea using transmission and scanning electron microscopy. At the 18th gestational day, only the major tectorial membrane can be identified covering the greater epithelial ridge and the inner hair cells in all turns. At the 19th gestational day, the minor tectorial membrane was first seen in the basal turn, over the outer hair cells. During early stages of development, the stereocilia of hair cells were surrounded by a loose fibrillar material underneath the tectorial membrane. After the 10th postnatal day, the outer hair cells' stereocilia were attached to Kimura's (or Hardesty's) membrane, while inner hair cells' stereociliary bundles were attached to the undersurface of the tectorial membrane near the Hensen's stripe. Between the 10th and the 14th postnatal days, the space between the inner hair cells and the first row of outer hair cells widened by virtue of the growth of the heads of pillar cells, and the inner hair cells' stereocilia were displaced towards the Hensen's stripe. After the 14th postnatal day, the inner hair cells' stereociliary bundles detached from the tectorial membrane, while the outer hair cells' stereocilia remained attached to it. The tip-link system, which connects the tips of the stereocilia to the next tallest stereocilia, is present at birth in the outer hair cells. The marginal pillar, that anchored the tectorial membrane to the underlying organ of Corti during development, first appeared on the 6th postnatal day and disappeared on the 14th–15th postnatal day. The present data together with other reports support the idea that although some structures, such as hair cells' stereocilia and innervation, are already formed early during development, the cochlear microarchitecture is not fully developed morphologically and ready to function normally until the end of the second postnatal week in the mouse.     

Stereocilia and tectorial membrane development in the rat cochlea

Summary Maturation of the rat cochlea, from postnatal days 2 to 60, was studied using scanning electron microscopyt (SEM), with emphasis on stereocilia and tectorial membrane (TM). Two days after birth, the organ of Corti was very immature. An adult appearance of its surface was observed by day 16 in the basal turn, and by the end of the 3rd postnatal week in the apex. Stereocilia started their development first on inner hair cells. By contrast, the apical pole of outer hair cells ended its maturation before that of inner hair cells. Top-links were detected very early in inner hair cell stereociliary development (postnatal day 2). Marginal pillars temporarily attached the TM to the organ of Corti; they disappeared first in the apical region. This transient attachment seems to play a role in the coupling of outer hair cells to the TM, as prints of their longest stereocilia appeared at the undersurface of the TM by the same time. Moreover, these prints were more clear and regular at the base than at the apex of the cochlea. Results are discussed in relation to ultrastructural and functional data on rat cochlea maturation.     

Selective and transient expression of a native chondroitin sulfate epitope in Deiters' cells, pillar cells, and the developing tectorial membrane.

The tectorial membrane (TM) is an acellular connective tissue overlying the sensory hair cells of the organ of Corti. Association of the tectorial membrane with the stereocilia of the sensory hair cells is necessary for proper auditory function. During development, the mature tectorial membrane is thought to arise by fusion of a "major" and "minor" tectorial membrane (Lim, Hear Res 1986;22:117-146). Several proteins and glycoconjugates have been detected in the developing TM; however, the specific molecules which mediate fusion of the two components of the TM have not been identified. In the present study, a novel monoclonal antibody (TC2) that recognizes a native epitope on glycosaminoglycans enriched in chondroitin-4-sulfate revealed a transient and restricted expression in the developing gerbil TM. The localization patterns suggest that Deiters' and pillar cells secrete a TC2-positive matrix prior to birth that later becomes incorporated into the marginal band and superior layer (cover net) of the TM. The developmental timecourse and patterns of TC2 reactivity suggest that this molecule may play a critical role in the fusion of the minor TM with the major TM.     

Postnatal development of the rat organ of Corti

Summary The development of the rat organ of Corti was studied during the first postnatal weeks. The temporal and the spatial patterns of cochlear development were investigated between 4 and 24 days after birth by means of semi-thin sections at approx. ten equidistant positions along the entire cochlear duct. At all examined positions width, thickness and cross sectional area of basilar membrane, cross-sectional area of tectorial membrane, of cells of Hensen, Claudius and Boettcher and of the organ of Corti were quantitatively analyzed. The most conspicuous maturational changes occur between 8 and 12 days after birth. These are the detachment of the tectorial membrane, the first appearance of filaments within the basilar membrane, the formation of the tunnel of Corti and the opening of the inner spiral sulcus. Quantitative analysis revealed that structures of a given position along the cochlear duct do not develop synchronously. Width of the basilar membrane and cross-sectional area of the tectorial membrane are already mature at the onset of hearing (10–12 days after birth). Length, thickness and cross-sectional area of the basilar membrane as well as cross-sectional area of the organ of Corti and of the cells of Hensen, Claudius and Boettcher still develop after the onset of hearing (up to 20–24 days after birth). We suggest that basic cochlear function is established by structures which are mature before the onset of hearing. Cochlear structures which develop after the onset of hearing might be involved in this improvement during this period.     

The sensory hairs and tectorial membrane of the basilar papilla in the lizardCalotes versicolor

Summary The hearing organ in the lizard, the basilar papilla, is an oblong organ situated in the central opening of the surrounding limbus. The hair cells of the basilar papilla inCalotes versicolor consist of two different types. The type A sensory cells have short hair bundles whose arrangement resembles that of organ pipes, and are situated in the ventral part of the organ. The type B sensory cells have tall, whisk-like hair bundles and are situated in the dorsal part of the basilar papilla. The type A sensory cells are unidirectionally orientated, whereas the type B cells are orientated towards the central sulcus in the papilla. Between the stereocilia, quite close to their base, there is a thin network of interconnecting fibres. Another type of connection is found between the kinocilium and the five adjacent stereocilia. These fibres, however, are situated close to the tips of the relevant cilia. The ventral part of the basilar papilla, i.e., the type A cell population, is covered by a tectorial membrane. Between the microvilli of the supporting cells and the tectorial membrane a network of thin interconnecting filaments is seen. This totally encloses the hair bundles, thus causing them to stand in tubular formations between the sensory epithelium and the tectorial membrane.     

Type IX collagen knock-out mouse shows progressive hearing loss

Type IX collagen is one of the important components, together with type II, V, and XI collagens, in the tectorial membrane of the organ of Corti. To confirm the significance of type IX collagen for normal hearing, we assessed the detailed morphological and electrophysiological features of type IX collagen knock-out mice, which have recently been reported as a deafness model. Through assessment by auditory brainstem response (ABR), knock-out mice were shown to have progressive hearing loss. At the light microscopic level, the tectorial membrane of knock-out mice was found to be abnormal in shape. These morphological changes started in the basal turn and were progressive toward the apical turn. Electron microscopy confirmed disturbance of organization of the collagen fibrils. These results suggest that mutations in type IX collagen genes may lead to abnormal integrity of collagen fibers in the tectorial membrane.     

Electrical potentials of the subtectorial space in the guinea pig cochlea

Precipitation of cobalt ions and iontophoretic marking by Alcian Blue were utilized in examination of physiological properties of the subtectorial space in the guinea pig cochlea. Cobalt ions injected into the scala media were sulfurated and observed as a black precipitation in cross sections. Precipitation was seen on the upper and the lower surface of the tectorial membrane, and on the reticular membrane. Alcian Blue was the most suitable dye for marking in the organ of Corti. Recording sites of potentials in the subtectorial space were identified by Alcian Blue marking. The potentials were similar to those measured in the scala media. These facts verify that the subtectorial space communicates with the scala media through the outermost margin of the tectorial membrane. Thus the sensory hairs of hair cells are bathed in the endolymph of high potassium concentration, and the condition for optimum sensitivity of their receptor function is maintained.     

In vivo imaging and low-coherence interferometry of organ of Corti vibration

An optical coherence tomography (OCT) system is built to acquire in vivo both images and vibration measurements of the organ of Corti of the guinea pig. The organ of Corti is viewed through a approximately 300-microm-diam hole in the bony wall of the cochlea at the scala tympani of the first cochlear turn. In imaging mode, the image is acquired as reflectance R(x,z). In vibration mode, the basilar membrane (BM) or reticular lamina (RL) are selected by the investigator interactively from the R(x,z) image. Under software control, the system moves the scanning mirrors to bring the sensing volume of the measurement to the desired membrane location. In vivo images of the organ of Corti are presented, indicating reflectance signals from the BM, RL, tectorial membrane, and Reissner's membrane. The tunnel of Corti and the inner sulcus are also visible in the images. Vibrations of +/-2 and +/-22 nm are recorded in the BM in response to low and high sound levels at 14 kHz above a noise floor of 0.2 nm.     

Assessment of ultrastructure in isolated cochlear hair cells using a procedure for rapid freezing before freeze-fracture and deep-etching

Summary Separated cochlear outer hair cells and isolated strips of organ of Corti containing hair cells and supporting cells have been rapidly frozen before freeze-fracture and deep-etching by immersion of samples sandwiched between two copper plates into liquid nitrogen-cooled propane: isopentane. Assessment of this procedure has shown that no significant freezing damage occurs. The ultrastructure of the hair cells revealed by freeze-fracture of these non-chemically fixed preparations was generally very similar to that seen in fixed material. This indicates that the processing of cochlear tissue normally used for electron microscopy produces few obvious structural artefacts. It also demonstrated that procedures for isolating cochlear hair cells generally do not affect cell structure significantly. However, some isolated hair cells did show abnormalities within the membranes of the lateral cisternae. Such membrane alterations, which would not be identified by light microscopy, occurred to a variable extent but were more commonly present after prolonged periods in maintenance medium. Deep-etching of the preparations to examine extracellular features around stereocilia revealed clearly lateral cross-links between stereocilia. However, tip-links could not be positively identified in either unfixed or prefixed preparations.     

Development of the tectal cells in the mouse cochlea

Tectal cells appear at birth in the outer part of the developing organ of Corti. At first they are attached to the basilar membrane, but later they ascend through the auditory epithelium. During the 1st postnatal week (coinciding with the development of the minor tectorial membrane), the newly formed tectal cells show several cytological characteristics suggesting increased metabolic and secretory activities, which include: (1) a large Golgi complex, (2) abundant amorphous material inside the cisterns of rough endoplasmic reticulum, and (3) dense granules inside the mitochondrial matrix. All these features gradually disappear, and by the 14th postnatal day the tectal cells show a dark cytoplasm and few and short microvilli. In addition, tectal cells were stained selectively by some lectins. These findings suggest that tectal cells may participate in the secretion of some components of the minor tectorial membrane, different from those produced by Deiters' cells, Hensen's cells and pillar cells.