The uptake of tritiated thymidine by the dorsal epidermis of the fetal and newborn ratThis investigation was supported by U.S.P.H.S. grant DE 01925-07.

0003-276X

Life and Medical Sciences ; Cell & Developmental Biology

Wiley InterScience Backfile Collection 1832-2000

Medicine

The dorsal epidermis of fetal and newborn rats was examined to determine the difference in ability of the basal cells to bind tritiated thymidine during different stages of epidermal morphogenesis. Five rats were examined for each time period from the eleventh day of gestation to the fifth day after birth. The number of labeled cells in 5000 basal cells was counted and expressed as a percentage. The labeling index is ∼ 10% from the eleventh to the fifteenth fetal day. It increases to ∼ 30% by the eighteenth day, decreases to ∼ 10% from the twenty-first day until the first postpartum day and drops to 5% or less from the second to fifth day. These changes in labeling index are accompanied by and apparently correlated with the normal differentiation of rat epidermis. The growth of the epidermis is continuous during the course of the study. Keratohyalin granules begin to form on the eighteenth day and by the twentieth day the first cornified cells appear. The s. corneum becomes progressively thicker each day thereafter. The s. Malpighii, on the other hand, decreases somewhat in thickness after birth. The labeling index curve represents a relationship between basal cell activity and control or influencing mechanisms inherent in the maturational system of skin. The increase and decrease are not related to growth alone, but appear to be related to differentiation.

11 Ill.

Electronic Resource