Epithelial proliferation in explants of mouse palatal mucosa cultured in contact and apart.

Explants of mouse palatal mucosa were cultured on grids either in isolation or with their lateral margins in contact. After 25 h the labelling index (LI) was determined using 3HTdR. At the edge of explants in contact LI was 59% that of explants cultured apart but the mean grain count was similar in the two groups. Metaphase arrest using vinblastine between 24--28 h of culture showed that in the basal cells, the rate of entry into mitosis was 1.1% per hour in explants cultured in contact and 1.9% per hour in explants cultured apart. In both groups the duration of mitosis was 1.0 h. Since in vivo the rate of entry into mitosis in this tissue is 1.2% per hour, the result suggest that an increase in epithelial proliferation does occur near to the edge of cultured mucosal explants and that this is diminished by the proximity of the edge of a second explant.