Springer Online Journal Archives 1860-2000
Summary In 10-day-old Balb/cCrgl mice, the subcutaneous injection of 0.1 μg of estradiol in distilled water per animal per day resulted in the conversion, over a 4 day period, of the original 3 cell layered cuboidal epithelium to a stratified, multilayered, fully keratinized epithelium. By light microscopy, there was development of a prominent stratum germinativum and of a mucinified surface on the 1st day, followed by the sequential formation of a stratum spinosum, a stratum granulosum, and a stratum corneum. By electron microscopy, the principal early modifications consisted of a marked increase in ribosomes, desmosomes, and 70 Å cytoplasmic filaments, the latter being aggregated into approximately 700 Å fibrils. The subsequent establishment of a keratin layer was preceded by the appearance of keratohyaline granules and the disappearance of mitochondria and endoplasmic reticulum in cells immediately above the stratum spinosum and by the development of a transitional cell layer in which there was progressive aggregation of cytoplasmic filaments and disappearance of nuclei, keratohyaline granules, and free ribosomes. In the upper stratum granulosum, transitional cell layer, and stratum corneum there were distinctive modifications in desmosomal structure (composite and modified desmosomes). The morphological and physiological significance of these observations is discussed.
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