Fig. 1. Template showing a coronal half-section of the tree shrew brain at level A 3.0 (see Tigges and Shantha, 1969), demonstrating that the number and distribution of BrdU-labeled cells (open circles) change with increased survival time after BrdU injection. Two hours after BrdU injection, most labeled cells are located in the sgz, on the border of the gcl and hilus. Twenty-four hours after BrdU injection, more than twice as many BrdU-labeled cells are observed in the dentate gyrus, predominantly in the sgz. By 3 weeks after BrdU injection, most BrdU-labeled cells are located in the gcl and express NSE (solid dots). cc, Corpus callosum; lv, lateral ventricle; 3V, third ventricle;h, hilus; CA1, CA1 region;CA3, CA3 region.