Immuno-electron microscopic study of keratin distribution in the cochlea using monoclonal antibody

Keratin filament deployment and cytoskeletal networking in a sensory epithelium that vibrates during hearing

The intricate and spatially precise ways in which keratin intermediate filaments are deployed in certain cochlear epithelial cells, called supporting cells, suggests that these filaments make a micromechanically important contribution to the functional design of the guinea pig organ of Corti. Filament arrays that include keratins 8, 18, and 19 are confined mainly to regions close to the ends of large transcellular microtubule bundles in supporting cells. These cells and their microtubule bundles link sensory hair cells to a specialized basement membrane that vibrates during hearing. The keratin filament arrays apparently help anchor the ends of the microtubule bundles to cell surfaces. Filaments are concentrated at the apices and bases of most cells that contact hair cells. Substantial arrays of adherens junctions link the apices of these cells. Hence, keratin filaments may contribute to a cytoskeletal network that distributes mechanical forces from cell to cell and that coordinates the displacement of neighboring hair cells. However, high concentrations of keratin filaments have not been detected at the apices of one of the supporting cell types, which apparently has a mechanical role that is different from that of the others. Transmission electron microscopy has revealed previously undescribed filament networks at all the locations where the binding of antibodies to keratins is most marked. There is evidence that intercellular linkage of the keratin networks via their association with actin-containing meshworks and adherens junctions is more extensive than linkage provided by desmosomes.

Antigen retrieval immunohistochemistry used for routinely processed celloidin-embedded human temporal bone sections: standardization and development

The use of immunohistochemistry (IHC) in routinely processed celloidin-embedded human temporal bone section has created a fruitful field in understanding the pathogenesis and pathophysiology of the human inner ear at a molecular level since the early 1990s when the antigen retrieval (AR) technique was developed. This review article focuses on several critical technical issues of AR technique based predominantly on our experiences and suggestions concerning further development and standardization of AR-IHC for IHC study of human temporal bone section, as well as other tissues embedded in celloidin. Examples of using AR-IHC in human temporal bone sections collected include our unpublished data in order to indicate the potential utility of this novel method. Suggestions of further development of AR techniques are proposed for references and comments.

Distribution of cytokeratins in the vestibular epithelium of the guinea pig

Cytokeratin expression in the vestibular labyrinth of the guinea pig was investigated with immunofluorescence and immunoperoxidase staining on surface preparations of the vestibular epithelium. Phalloidin, an F-actin-specific probe, was used to distinguish between hair cells and supporting cells. Cytokeratin expression was not found in the cytoplasmic domain of hair cells of the crista ampullaris, utricle, or saccule. Cytokeratin expression was abundant in supporting cells of the vestibular sensory epithelium. Electron microscopy revealed the presence of desmosomes, which are associated with cytokeratins, within type 2 hair cells of the vestibular epithelium. It appears that cytokeratins are absent within the cytoplasmic domain of hair cells, but are present in association with intercellular junctions. The functional significance of this unique pattern of cytokeratin expression within the vestibular epithelium is discussed.

Cytoskeletal polypeptides: cell-type specific markers useful in investigative otorhinolaryngology

In the last decade, it has been established that eukaryotic cells possess a cytoskeleton, i.e. an integrated cytoplasmic network of microfilaments (MFs), microtubules (MTs) and intermediate filaments (IFs). Moreover, certain cell membrane specializations as well as the inner lamina of the nuclear membrane also participate in the cytoskeletal structure. Although this definition of the cytoskeleton is up to date it is obvious that the future course of cell biology will be reflected in a revised definition. While the bulk of structural polypeptides involved were characterized at regular intervals, surprisingly, the function of the cytoskeleton remained largely speculative and is still less precisely defined. The most widely postulated function concerns mechanical support and integration of diverse cellular activities and thus refers to cellular architecture. Briefly, the mechanical function is thought to involve cell movement, adhesive interaction with the extracellular matrix and neighbouring cells, as well as the stabilization of cell shape. The integrative function refers to intracellular movement, i.e. transport and positioning to the appropriate locations of organelles, intracellular particles, RNA and proteins. It has been established from numerous investigations that (certain) cytoskeletal polypeptides provide significant information about the cellular origin and differentiation state. This consideration constitutes the most prominent reflection underlying this review. Furthermore, this appreciation encourages additional efforts to explore these markers in normal and pathological conditions. The first purpose of this review is briefly to summarize our present comprehension of the molecular components of the cytoskeleton, restricted to the filamentous trinity for practical reasons. The second and main aim is to survey the field with respect to otorhinolaryngology-related issues. To the author's knowledge, this has not been dealt with in the past. In bridging this gap in the literature, I hope to provoke additional interest in one of the fastest moving areas of cell biology. A comprehensive review covering the whole cytoskeleton has been covered by Preston et al. (The Cytoskeleton and Cell Motility. Blackie, Glasgow and London, 1990, pp. 7-69, 188-191). Additional information on the participating substructures is provided in the text, inclusive of last year's reviews.

Immunohistochemical study of intermediate filament proteins on routinely processed, celloidin-embedded human temporal bone sections by using a new technique for antigen retrieval

Although immunohistochemical studies of intermediate filament proteins have been carried out on temporal bone sections by using modified fixation/embedding techniques to preserve antigenicity, there have been no light microscopic studies concerning immunohistochemical staining on routinely formalin-fixed celloidin-embedded human temporal bone sections. A method for immunostaining routinely processed celloidin-embedded tissues would be extremely valuable in that it would permit study of the extensive collections of formalin-celloidin temporal bone specimens that exist in major centers of otopathologic research. Recently, we have developed a new technique which can be used to retrieve the antigenicity masked by formalin fixation and decalcification. This method requires immersing slides for 30 min at room temperature in a solution of saturated sodium hydroxide in methanol before immunostaining. Using this method, 45 celloidin-embedded human temporal bone sections were stained with monoclonal antibodies to keratin, vimentin, neurofilament, glial fibrillary acidic protein and desmin as primary antibodies using a sensitive streptavidin-biotin procedure. The results obtained by using this technique are at least equivalent to those obtained with modified fixatives, cryosections or immuno-electron microscopy. This new method may provide a useful approach for studying routinely processed, celloidin-embedded human temporal bone sections and open a new field in immuno-otopathology.