Abstract
Epithelial cells changing from the granular stage of differentiation to the horny stage are more numerous, and reveal sequential events of transformation in finer detail in the rumen epithelium than in other keratinizing epithelia thus far studied in the electron microscope. Studies of such cells indicate that transformation is initiated by the release of hydrolytic enzymes, as evidenced by the appearance of lysosomes. As lysosomes increase in number, the nucleus, ribosomes, mitochondria, Golgi apparatus, and mucous granules are gradually degraded. Furthermore, marked changes occur in permeability of the plasma membrane as voluminous amounts of the lysed cell components pass through and accumulate in the intercellular space in the form of an amorphous mass. Filaments, keratohyalin granules, and the content of the ER (ER-protein) are not lysed, revealing the action of released enzymes to be specific. During transformation, filaments become displaced toward the cell periphery and keratohyalin granules disperse and mix with the ER-protein in the cell center. Subsequently, the keratohyalin-ER-protein complex infiltrates the filament network whereby a fibrous-amorphous cell content is formed. Loss of fluids through the plasma membrane leads to reduction of cell volume and consolidation of the remaining cell content. The deep interdigitations formed between the cells ultimately interlock the outer part of the epithelium into a cohesive and protective stratum corneum.
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Selected References
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- BRODY I. An ultrastructural study on the role of the keratohyalin granules in the keratinization process. J Ultrastruct Res. 1959 Oct;3:84–104. doi: 10.1016/s0022-5320(59)80018-6. [DOI] [PubMed] [Google Scholar]
- Bonneville M. A., Weinstock M., Wilgram G. F. An electron microscope study of cell adhesion in psoiatic epidermis. J Ultrastruct Res. 1968 Apr;23(1):15–43. doi: 10.1016/s0022-5320(68)80029-2. [DOI] [PubMed] [Google Scholar]
- Farquhar M. G., Palade G. E. Cell junctions in amphibian skin. J Cell Biol. 1965 Jul;26(1):263–291. doi: 10.1083/jcb.26.1.263. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GIROUD A., LEBLOND C. P. The keratinization of epidermis and its derivatives, especially the hair, as shown by x-ray diffraction and histochemical studies. Ann N Y Acad Sci. 1951 Mar;53(3):613–626. doi: 10.1111/j.1749-6632.1951.tb31963.x. [DOI] [PubMed] [Google Scholar]
- LUFT J. H. Improvements in epoxy resin embedding methods. J Biophys Biochem Cytol. 1961 Feb;9:409–414. doi: 10.1083/jcb.9.2.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lavker R. M. Fine structure of mucus granules in rumen epithelium. J Cell Biol. 1969 May;41(2):657–660. doi: 10.1083/jcb.41.2.657. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lavker R., Chalupa W., Dickey J. F. An electron microscopic investigation of rumen mucosa. J Ultrastruct Res. 1969 Jul;28(1):1–15. doi: 10.1016/s0022-5320(69)90002-1. [DOI] [PubMed] [Google Scholar]
- Lavker R., Chalupa W., Opliger P. Histochemical observations on rumen mucosa structure and composition. J Dairy Sci. 1969 Feb;52(2):266–269. doi: 10.3168/jds.S0022-0302(69)86544-6. [DOI] [PubMed] [Google Scholar]
- PALADE G. E. A study of fixation for electron microscopy. J Exp Med. 1952 Mar;95(3):285–298. doi: 10.1084/jem.95.3.285. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Parakkal P. F. An electron microscopic study of esophageal epithelium in the newborn and adult mouse. Am J Anat. 1967 Sep;121(2):175–195. doi: 10.1002/aja.1001210202. [DOI] [PubMed] [Google Scholar]
- Prutkin L. An ultrastructure study of the experimental keratoacanthoma. J Invest Dermatol. 1967 Apr;48(4):326–336. doi: 10.1038/jid.1967.54. [DOI] [PubMed] [Google Scholar]
- Squier C. A. Ultrastructural observations on the keratinization process in rat buccal epithelium. Arch Oral Biol. 1968 Dec;13(12):1445–1451. doi: 10.1016/0003-9969(68)90026-5. [DOI] [PubMed] [Google Scholar]
- VENABLE J. H., COGGESHALL R. A SIMPLIFIED LEAD CITRATE STAIN FOR USE IN ELECTRON MICROSCOPY. J Cell Biol. 1965 May;25:407–408. doi: 10.1083/jcb.25.2.407. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vollmerhaus B., Schnorr B. Elektronenmikroskopische Untersuchungen an Lysosomen im Pansenepithel der Ziege. 3. Mitteilung zur funktionellen Morphologie der Vormägen der Hauswiederkäuer. Zentralbl Veterinarmed A. 1967;14(8):761–773. [PubMed] [Google Scholar]
- Yamada M., Ofuji S. A study of possible proteolytic enzymes in human skin by a silver protein method. J Invest Dermatol. 1968 Mar;50(3):231–237. doi: 10.1038/jid.1968.33. [DOI] [PubMed] [Google Scholar]