Fig. 6. The frequencies of spermatogenic cell stages from B6 (white bars) and Rb/+ (black bars) adult mice. Germ cells were isolated as an enriched population from testes of three adult mice, and the number of leptotene/zygotene spermatocytes (L/Z), pachytene spermatocytes (Pach), and round spermatids (RS) were determined in a total of 250 cells per mouse. These cells represented most but not all of the cell types in the population, which also included somatic cells and elongated spermatids. Asterisks represent paired values that differ significantly (Student's t test; P=0.001 for difference in frequency of pachytene spermatocytes and P=0.008 for difference in frequency of round spermatids).