New cell formation in human sebaceous glands.

Intradermal injection of thymidine-H3 fol- lowed by biopsy removal 40 minutes to 36 days later revealed a characteristic pattern of human sebaceous gland activity. Cells lying on or near the basement membrane divide, and daughter cells move centrally, produce lipid, and undergo nuclear degeneration. The steady state replenishment from the periphery con- tinues for at least 2 to 4 weeks. The average renewal time for the human sebaceous gland in the 4 specimens examined is 7.4 days.