Some CellTracker™-labeled cells in the niche are also immunoreactive for glutamine synthetase. A. Projections of stacked images from the most ventral region of the neurogenic niche reveal a CTG-labeled cell just below its surface. Ai. Confocal scans taken deeper in the niche expose the CTG-labeled cell. An arrow drawn between A and Ai show the same CTG-labeled cell at different depths within the niche. Aii are the separate channels for GS labeling in the niche (top); PI revealing cell nuclei (middle); and CTG-labeled cell (bottom). B. Other CTG-labeled cells, although not labeled with glutamine synthetase (GS), have interesting morphological characteristics. In B there are labeled cells just outside the niche (arrowheads), one with a long process extending into the niche (arrow), and another CTG-labeled cell that appears to be inserting into the outer margin of the niche. Bi. Top, middle bottom are separate channels: GS labeling the niche (top); PI revealing cell nuclei, arrowheads pointing to the respective CTG-labeled cells in B (middle); and CTG-labeled cells with arrow pointing to the fine process coming from one of these (bottom). Scale bars: A, Ai, Aii and B, 20 μm; Bi, 10 μm.