Fig. 4.

Incorporation of BrdU into the DNA of aging nematodes. N2 nematodes at 9 days of age (a,b,c) or 11 days of age (d,e,f) were exposed for 24 h to BrdU. BrdU was detected immunohistochemically using a monoclonal antibody to BrdU, and a fluorescent secondary antibody. In younger worms, incorporation of BrdU is apparent in the gonad, near the distal tips (a), and at higher magnification in (b) and (c). As worms age, label is still apparent in the gonad, although fewer nuclei are labeled, and the gonad appears disordered (d), and at higher magnification in (e) and (f) (see arrows). Also, label begins to appear in amorphous regions that are similar in appearance to those detected by DAPI staining [arrowheads in (e) and (f)]. Five of five 11-day-old animals examined displayed nongonad staining, whereas such staining was not seen in 7- or 9-day-old animals.