Auditory hair cells in human fetuses: Synaptogenesis and ciliogenesis

This paper brings together the most recent findings concerning the development of human fetus cochlear hair cells, as observed using transmission and scanning electron microscopy (TEM and SEM). Specific attention is drawn to the formation of synapses and the growth of stereocilia. In both types of hair cells, synaptogenesis begins before ciliogenesis (week 10 of gestation versus week 12). In the inner hair cell (IHC), an adultlike stage is seen around week 15 for synapses, but not before week 22 for stereocilia. In the outer hair cell (OHC), both synapses and stereocilia are not yet fully mature at week 22. Classic gradients of maturation are found: a base-to-apex gradient, and an IHC-to-OHC gradient. By comparing these results with the anatomical and functional data on cochlear development in laboratory mammals, the onset of cochlear function in the human fetus can be estimated to occur around week 18. The completion of cochlear maturation based upon the same anatomical criteria should occur about 10 weeks later.     

Serial reconstruction of inner hair cell afferent innervation using semithick sections

The afferent innervation pattern of inner hair cells in the apex of the guinea pig cochlea was studied using serial reconstruction of semithick (0.25–μm) sections and high-voltage electron microscopy (HVEM). This thickness produced a good compromise between the ability to resolve details of the synaptic contacts between the hair cells and sensory neurons and the number of sections required to reconstruct the nerve terminals within the receptor organ. The use of a goniometer allowed the sections to be tilted to angles optimum for viewing either the synaptic membrane specializations or the presynaptic bodies. Reasonably good images of 0.25-μm sections could be obtained using a conventional 120-keV microscope, but the images produced by the HVEM were clearly superior. The sensory nerve terminals and hair cells were reconstructed using a microcomputer-based computer-aided-design system. Nerve terminals with complex shapes could be successfully rendered as surface models viewed as stereo pairs. The advantages and limitations of the techniques used are discussed.     

Organization of microtubules in cochlear hair cells

The organization of microtubules in hair cells of the guinea-pig cochlea has been investigated using transmission electron microscopy and correlated with the location of tubulin-associated immunofluorescence in surface preparations of the organ of Corti. Results from both techniques reveal consistent distributions of microtubules in inner and outer hair cells. In the inner hair cells, microtubules are most concentrated in the apex. Reconstruction from serial sections shows three main groups: firstly, in channels through the cuticular plate and in a discontinuous belt around its upper perimeter; secondly, forming a ring inside a rim extending down from the lower perimeter of the plate; and thirdly, in a meshwork underlying the main body of the plate. In the cell body, microtubules line the inner face of the subsurface cistern and extend longitudinally through a tubulo-vesicular track between the apex and base. In outer hair cells, the pattern of microtubules associated with the cuticular plate is similar, although there are fewer present than in inner hair cells. In outer hair cells from the apex of the cochlea, microtubules occur around an infracuticular protrusion of cuticular plate material. In the cell body, many more microtubules occur in the region below the nucleus compared with inner hair cells. The possible functions of microtubules in hair cells are discussed by comparison with those found in other systems. These include morphogenesis and maintenance of cell shape; intracellular transport, e.g., of neurotransmitter vesicles; providing a possible substrate for motility; mechanical support of structures associated with sensory transduction.     

The morphology of the inner ear from the domestic pig (Sus scrofa)

The morphology of the hair cells of the inner ear end organs from the domestic pig ( Sus scrofa ) have been studied using a combination of Scanning and Transmission Electron Microscopy (SEM and TEM), revealing hair cells from the cochlea and vestibule using a novel surgical and technical approach. This is the first time that the inner ear hair cells from S. scrofa have been studied, thus providing useful anatomical information on the morphology of the hair cells from the cochlea, saccule and utricle from a large mammal. Anatomical information in relation to the morphology of the inner ear is of considerable importance, both in the pathological diagnosis of trauma and in the development of cochlea implants and other biotechnological systems associated with the enhancement of hearing. Standard fixation protocols using cardiac perfusion was not employed in this study as this method cannot always be applied, such as the pathological examination of the human ear, or the study of animals protected by endangered species legislation. With the exception of a very few countries, cetaceans cannot be killed for research purposes, yet physiological information on the inner ear from these species is urgently required for ecological assessment reasons. Supporting the use of S. scrofa as a model for cetacean hearing research is that this animal is a member of the order Artiodactyla, which includes both the hippopotamus and cetaceans. Being of a similar size, the pig is an ideal subject for developing protocols and surgical techniques required to investigate both the human and small cetacean auditory systems.     

Freeze-fracture organization of hair cell synapses in the sensory epithelium of guinea pig organ of Corti

The fine structure of both the afferent and efferent hair cell synapses in the sensory epithelium of guinea pig organ of Corti was examined by freeze-fracture electron microscopy. In the afferent synapse, barlike aggregates of intramembrane particles (IMPs) of about 10 nm in diameter were seen on the P-face of the afferent presynaptic membrane directly beneath the presynaptic dense projection which is located in the active zone of the presynaptic membrane. Small and large depressions have been seen on the presynaptic membrane. The former were observed in the proximity of the barlike aggregates, while the latter were observed some distance from the aggregate. In outer hair cells, IMPs of about 10 nm in diameter were seen on the P-face of the afferent postsynaptic membrane at a density of 3,000/μm². In the efferent synapse, many aggregates composed of from several to tens of large IMPs of 13 nm in diameter were observed on the presynaptic membrane. These aggregates were localized to small membrane depressions, which tended to be deeper as particle number per aggregate increased. Dense populations of IMPs of about 9 nm in diameter were observed on the P-face of the efferent postsynaptic membrane at a density of 4,000/μm². A fenestrated subsynaptic cistern completely covers the efferent postsynaptic membrane. Moreover, the subsynaptic cistern spans several efferent postsynaptic membranes when efferent synapses are gathered in a group. In the afferent and efferent synapses of hair cells, specializations of the synaptic membranes were represented by marked aggregates characteristic of IMPs. In the efferent synapse, IMP movement inside the synaptic membrane was proposed in relationship to retrival of synaptic vesicle membrane. Structural relationship between the subsynaptic cistern and efferent postsynaptic membrane was revealed.     

High-resolution X-ray tomography of the human inner ear: synchrotron radiation-based study of nerve fibre bundles, membranes and ganglion cells

The combination of osmium tetroxide staining and high-resolution tomographic imaging using monochromatic X rays allows visualizing cellular structures of the human inner ear, that is, the organ of Corti, the stria vascularis and further soft tissues of the membranous labyrinth, in three-dimensional space with isotropic micrometre resolution. This approach permits to follow the course of nerve fibre bundles in a major part of the specimen and reveals the detailed three-dimensional arrangement of individual ganglion cells with distinct nuclei by means of X-ray tomography for the first time. The non-destructive neuron cell counting in a selected volume of 125 μm × 800 μm × 600 μm = 0.06 mm³ gives rise to the estimate that 2000 ganglion cells are present along 1 mm organ of Corti.     

Scanning electron microscopy of nerve fibers in human fetal cochlea

The cochleas of four human fetuses ranging 22–25 weeks gestation were studied by scanning electron microscopy (SEM) for the purpose of obtaining a better understanding of the nerve fiber arrangement in the human ear. After critical point drying, the specimens were dissected and the floor of the tunnel of Corti and the outer wall of Nuel's space were exposed for observation. Upper cochlear turns, especially the apical turn, seemed to be still immature. Observed nerve fibers were classified into three types:

• 1 Spiral fibers: Fibers traveling basalward and following the shape of the cochlea were found in both the tunnel of Corti and Nuel's space and believed to be the afferent nerves responsible for innervating the outer hair cells
• 2 Radial fibers: radiating outward from the osseous spiral lamina—one such radial fiber transversing high in the tunnel space (supposedly the efferent nerve servicing the outer hair cells), and another sort of radial fiber (found crossing the tunnel floor), the nature of which was uncertain.
• 3 Irregular fibers: Consisting of thin, randomly running fibers within the cochlea. The destination of these fibers was not determined, but possibly they represent transitory nerve branchings of afferent or more probably efferent nerves, which would later regress during maturation.

     

Atypical cells in the normal guinea pig organ of Corti as revealed by micromanipulation in SEM.

Inner ear tissue of the normal guinea pig was conductively stained (OTOTO-method) for SEM investigations. The Hensen's cells of the organ of Corti were removed using a micromanipulator inside the SEM. By this method atypical bodies of sensory and supporting cells were revealed in the apical turns of the cochlea. Atypical sensory cells showed great variations in size and shape. Several had no contact to Deiter's cells and no or only one nerve supply at their basal end. Atypical Deiter's cells showed alterations in shape and in the form of their phalangeal processes. Additionally altered parts of the organ of Corti were isolated by micromanipulation and embedded for correlative TEM-investigations.     

A quantitative method for analysing AFM images of the outer surfaces of human hair

Cuticle step height is an important parameter for the quantitative assessment of human hair. This paper describes a novel, computational method for the rapid calculation of step heights from atomic force microscope images obtained from large numbers of specimens. Such an approach is necessary to allow a statistical analysis of the inherently wide distribution of cuticle step heights characteristic of a single hair sample. The method described will be of use to cosmetic formulation chemists and forensic scientists and also to dermatologists in the field of disease diagnosis.     

Ultrastructure of the intercalated body,a novel organelle associated with fluid forming cells in the organ of Corti

The intercalated body is a newly discovered organelle in the inner and outer spiral sulcus cells of the mouse organ of Corti. The organelle was found in the cochleas of 14-day and older intact mice and in organs in culture of corresponding ages. The organelle consists of a stack of interconnected cisternae of endoplasmic reticulum and of membrane bound rodlets that are intercalated between, and run parallel to, the cisternae. The cisternal membranes are predominantly smooth, but some may display ribosomes. Most rodlets are from 1 to 2 μm long, about 0.1 μm wide, and contain electron dense material. Mitochondria are commonly associated with or incorporated into the organelle. Some electron micrographs suggest that the rodlets may originate from modified mitochondria. It is our impression that the formation of the organelle begins with the apposition of cisternae and mitochondria. Cisternal-associated mitochondria appear to constrict, elongate, and lose their inner membranes. In both the intact animal and in culture, the cells of the inner and outer spiral sulci display microvilli, apical junctional complexes, lateral intercellular spaces containing interdigitating cell processes, and appear to be involved in fluid formation. Moreover, in culture, the cells of inner and outer spiral sulci as well as some cells proliferating in the outgrowth zone participate in fluid formation, producing large fluid pockets. All these cells commonly contain intercalated bodies. It is possible that in the intact animal, as in culture, intercalated bodies may play a role in fluid regulation in the immediate vicinity of the hair cells.     

Three-dimensional reconstruction of the guinea pig inner ear, comparison of OPFOS and light microscopy, applications of 3D reconstruction

Three-dimensional (3D) reconstruction of anatomical structures can give additional insight into the morphology and function of these structures. We compare 3D reconstructions of the guinea pig inner ear, using light microscopy and orthogonal plane fluorescence optical sectioning microscopy. Applications of 3D reconstruction of the inner ear are further explored. For each method two bullas were prepared for 3D reconstruction. Both methods are explained. In general, the 3D reconstructions using orthogonal plane fluorescence optical sectioning microscopy are superior to light microscopy. The exact spiral shape of the cochlea could be reconstructed using orthogonal plane fluorescence optical sectioning microscopy and the length of the basilar membrane measured. When a resolution of 20 μm is sufficient, orthogonal plane fluorescence optical sectioning microscopy is a superior technique for 3D reconstruction of inner ear structures in animals.     

工件内、外浅止口直径的测量方法

针对浅止口类工件的直径检测,存在一般量具无法顺利与工件接触的现象,分别介绍了4种用于测量内、外浅止口直径的方法.其中使用自行研制的内、外带表卡规测量止口直径,具有操作方便、成本低、测量范围广、示值准确、检测精度高等特点,填补了浅止口类工件直径测量的技术空白.     

应用内外定标修正实现红外测量系统辐射定标

由于现有的大口径短波红外测量系统的辐射定标需要制备大口径红外平行光管,不仅机动性差且成本较高,故提出了一种基于内、外定标修正的辐射定标新方法。该方法将一个中、高温腔型黑体置于红外系统内部,通过切换反射镜,将中、高温腔型黑体辐射引入红外光学系统,并对部分光路进行中、高温段的内定标。然后,使用大面源黑体对全系统进行中温段的外定标;提取并处理公共温度范围的内、外定标数据以获取内、外定标之间的修正系数。最后,对中、高温段的内定标数据进行修正从而获取全系统的辐射定标数据。使用该方法对某Φ400mm口径的红外测量系统进行了辐射定标,并根据定标结果反演了黑体的辐射亮度和温度。结果显示:辐射亮度反演的最大误差为1.67%,温度反演的最大误差为1.02℃。实验结果证明了该方法可以准确、有效地对大口径短波红外测量系统进行辐射定标。     

轴承内、外圈裂纹与折叠的产生与判断

对轴承外观常见的裂纹与折叠缺陷的含意、产生原因,以及如何判断等问题作了较详细的叙述。     

Effects of atopic dermatitis on the morphology and water content of scalp hair

The effects of atopic dermatitis (AD) on scalp hair properties, such as morphology and water content, were investigated using atomic force microscopy (AFM) and thermogravimetric analyzer. Hairs from lesional and nonlesional scalp regions of eight patients with AD were investigated. The severity of the disease, which was evaluated using the SCORing Atopic Dermatitis index, was 48.75 (range, 40-80). Hairs from 15 normal adults were also examined as controls. The surface images were taken in an area of 20 × 20 μm(2) with 512 × 512 pixels and a scan speed of 0.8 line/s. AD affected the cuticle structures and scales of scalp hair. The edges of cuticles were torn and collapsed, and the scales were very thick. The water contents of both types of AD hair were less than the control: 12% ± 0.7%, 11.7% ± 0.4%, and 13% ± 0.8% for lesional AD hair, nonlesional AD hair, and control hair, respectively. The scalp hair of patients with AD can be characterized by thick and globular scale patterns. The hair of patients with AD has less water content than normal hair showing a good agreement with the property of skin having AD.     

调心球轴承内外圈磨加工工艺分析

针对调心球轴承的内圈、外圈磨加工工艺进行分析，找出影响轴承产品旋旋灵活性和调心性能的关键因素，采取正确的改进措施，以高质量的零配件来保证轴承产品质量的持续提高。     

耐磨涂料复合套代替高压泵上铜制内外导套

耐磨复合套以其良好的性能成功地替代铜导套，既降低了成本，又解决了生产急需，代表了未来的发展方向。     

基于工业CT的零件内外曲面形位误差分析

针对具有复杂内腔结构零件的内部曲面形位误差分析困难的问题,提出了一种基于工业CT技术的零件复杂内腔的形位误差分析方法.首先,使用工业CT对零件进行扫描并重建为测量STL模型.然后将设计IGES模型离散为STL模型与测量STL模型进行配准.其次,利用设计IGES模型作为引导,判定测量STL模型中的点和IGES模型各曲面的...     

Multifractal characterization of morphology of human red blood cells membrane skeleton

The purpose of this paper is to show applicability of multifractal analysis in investigations of the morphological changes of ultra‐structures of red blood cells (RBCs) membrane skeleton measured using atomic force microscopy (AFM). Human RBCs obtained from healthy and hypertensive donors as well as healthy erythrocytes irradiated with neutrons (45 μGy) were studied. The membrane skeleton of the cells was imaged using AFM in a contact mode. Morphological characterization of the three‐dimensional RBC surfaces was realized by a multifractal method. The nanometre scale study of human RBCs surface morphology revealed a multifractal geometry. The generalized dimensions D_q and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of their membrane skeleton organization. Surface characterization was made using areal ISO 25178‐2: 2012 topography parameters in combination with AFM topography measurement. The surface structure of human RBCs is complex with hierarchical substructures resulting from the organization of the erythrocyte membrane skeleton. The analysed AFM images confirm a multifractal nature of the surface that could be useful in histology to quantify human RBC architectural changes associated with different disease states. In case of very precise measurements when the red cell surface is not wrinkled even very fine differences can be uncovered as was shown for the erythrocytes treated with a very low dose of ionizing radiation.     

某变速箱用轴承内外圈装反问题的解决方法

针对某变速箱用轴承在成品内外圈装配过程中存在的装反问题,设计了手动检查装置,解决了靠人工目测检查方法无法杜绝的装反问题,保证了产品质量。