This content is PDF only. Please click on the PDF icon to access.
Abstract
Keratinization was induced in the corneal epithelium of rats by the extirpation of the lacrimal glands and, for comparison, by vitamin A deficiency. The lacrimal extirpation brought about a condition resembling advanced keratoconjunctivitis sicca of humans. While the deficient epithelium displayed a stratum corneum-like appearance, only the superficial cells of the dry epithelium keratinized; nor did the dry epithelia become edemaious or vascular, as did the deficient ones. In both conditions, cytoplasmic fibrils composed of atypical microtubules occurred below the keratinized region. These were seldom seen in the keratinized cells, which instead contained electron-opaque filaments 90 Å wide. The surface of the keratinizing epithelia showed a drastic reduction in the number of microplicae, often accompanied by the development of fewer, but taller, microvilli. A series of apparently transitional forms suggests that the lipoid vacuoles which are found in the vitamin A-deficient corneas are degenerate mitochondria. In general, keratinization in the dry corneal epithelium was less extensive, and in some ways qualitatively different, than that in the vitamin A-deficient epithelium.