PCNA indexes in lactiferous sinuses.

Longitudinal sections of L3 nipples were stained for PCNA detection and the number of PCNA-positive nuclei over the total number of nuclei in the lactiferous sinus was counted in at least 4 fields for 3 to 5 independent nipples in each group (except for the Nm23-M1-/- feeding group, n = 2). Results are expressed as means ±SD. The number of total counted nuclei is indicated in parenthesis. P values were obtained by unpaired student t tests against the wild type feeding values. NA: not applicable.