FIG. 4.

Stages II–VI are the most susceptible to exogenous RA treatment. A–C) Pictures depicting STRA8 localization in Stages II–VI in vehicle control (A) and RA-treated (B, C) vitamin A-sufficient adult male mice. Black arrows denote STRA8-positive spermatogonia, red arrows denote STRA8-negative spermatogonia, and stages are indicated by roman numerals in the center of the tubules. Bars = 50 μm. D) Graphs depicts quantification of the numbers of STRA8-positive spermatogonia per tubule in four different groups of stages (XII–I, II–VI, VII–VIII, IX–XI) from vehicle control (black bars) and RA-treated (white bars) vitamin A-sufficient adult male mice. The average number (n = 3) of STRA8-positive spermatogonia per tubule is given on the Y axis with the stages listed on the X axis. The error bars represent SEM (***P < 0.0005, **P < 0.01).