A recently developed method for determining the in viva
rate of cellular proliferation uses immunohistochemistry to
localize 5-bromo-2-deoxyuridine (BrdU), which is a thymidine
analog that is incorporated into cellular DNA during
the S-phase of the cell cycle (16-19). Moreover, immunofluorescent
techniques and interactive laser cytometry have(LI),
allowed for rapid quantification of the BrdU labeling index (LI), as described below.