Quantitative aspects of proliferation in the nasal epithelium of the rhesus monkey embryo.

Proliferation was studied in the nasal epithelium of rhesus monkey embryos ranging in age from 26 through 41 days of gestation (stages 13-20). Labeling indices were tabulated 1 h after an intrachorionic injection with [3H]thymidine, and the distribution of labeled cells was determined at intervals ranging from 1h to 11h after injection. The labeling index showed a chronological decrease from 69-4% in the nasal placode at stage 13 to 31-6% in the nasal pit at stage 20. The vomeronasal epithelium was distinctive in that the basal cells lost their ability to incorporate [3H]thymidine as early as stage 18. In the remainder of the nasal epithelium, mitotic figures were initially confined to apical regions but later occurred in basal regions as the embryonic pattern of proliferation became converted to the adult type.