Summary
Keratohyalin in the cavy back and plantar epidermis was examined by transmission electron microscopy. These cytoplasmic aggregates are made up of numerous fine particles uniformly stained by osmium, probably the protein component. Phospholipid in the interstices is removable in lipid solvents before osmium post-fixation. After glutaraldehyde fixation without osmium, tissue stained in uranyl acetate showed keratohyalin aggregates composed of mixtures of darkly stained and weakly stained groups of fine particles which indicate heterogeneity in composition. More weakly stained aggregates of keratohyalin composed of these particles were found in the interiors of keratinized cells in the lower part of the stratum corneum not previously demonstrated at this level. Oxidation in peracetic acid followed by staining in uranyl acetate showed dark areas in keratohyalin aggregates, which it is thought contain cystine. Keratohyalin aggregates are not surrounded by a membrane and they are not organelles. Their heterogeneous composition suggests different derivations and destinies of component substances, some of which may be synthetic and others autolytic products. It is suggested that keratohyalin is a cytoplasmic coacervate of protein, phospholipid, and bound calcium precipitated under unstable physiochemical conditions associated with keratinization involving extensive cytolysis.
Zusammenfassung
Das Keratohyalin der Meerschweinchenrücken- und Sohlenepidermis wurde transmissionselektronenmikroskopisch untersucht. Die cytoplasmatischen Komplexe bestehen aus zahlreichen feinen Partikeln, die, wahrscheinlich Proteinanteile, sich mit Osmium homogen färben lassen. In den Spalträumen gelagerte Phospholipide können mit fettlösenden Substanzen entfernt werden. Glutaraldehydfixierung ohne Osmium und anschließende Färbung mit Uranylacetat zeigte, daß Keratohyalin aus einer Mischung von dunkel gefärbten und schwach gefärbten Gruppen feiner Partikel bestehen, die auf die Heterogenität dieser Komplexe hinweisen. Schwächer gefärbte Keratohyalinkomplexe wurden in den verhornten Zellen der unteren Stratum corneum-Abschnitte erstmals nachgewiesen. Essigsäureoxydation mit nachfolgender Uranylacetatfärbung zeigte innerhalb der Keratohyalinkomplexe dunkle Areale, die vermutlich Cystin enthalten.
Keratohyalinkomplexe sind nicht membrangebunden und stellen keine Organellen dar. Ihre heterogene Zusammensetzung läßt unterschiedliche Herkunft der Einzelsubstanzen vermuten, von denen einige neu synthetisiert werden, andere als Folge von Autolyse entstehen. Es wird angenommen, daß Karatohyalin ein Komplex von Proteinphospholipid und gebundenem Calcium darstellt, das unter unstabilen physikochemischen Bedingungen im Verlaufe der Keratinisation und Cytolyse präcipitiert wird.
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Spearman, R.I.C., Hardy, J.A. Some ultrastructural observations on keratohyalin granules of guinea pig epidermis. Arch. Derm. Res. 250, 149–158 (1974). https://doi.org/10.1007/BF00582769
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DOI: https://doi.org/10.1007/BF00582769