FIG. 4.

TUNEL staining of testes cross-sections obtained from 10-day-old and young adult wild-type control mice. A) TUNEL-stained cross-section from a 10-day-old mouse. B) An H&E-stained testis from a 10-day-old mouse. C) TUNEL-stained young adult testis. D) An H&E-stained young adult testis. Brown precipitate on TUNEL-stained slides indicates TUNEL-positive nuclei, indicative of cells scored positive for apoptosis. Prevalence of apoptosis among the testis decreases approximately by half as the animal ages from 10 days to adulthood in wild-type controls and in Polb+/− mice. Examples of apoptotic nuclei are designated by black arrows. Original magnification A and B ×16; C and D ×6.3.