Fig. 1. Tyrosine phosphorylation of mouse spermatozoa. Cauda epididymal sperm were capacitated in BWW for 1 hour followed by 30 minutes with zona pellucidae. Sperm from the free-swimming population and recovered from the zona were fixed, permeabilised and labelled with anti-phosphotyrosine. (A) Cells displayed either partial flagellum (principal piece only) or complete flagellum labelling (midpiece and principal piece). Corresponding phase-contrast images are included. Scale bar, 10 µm. (B) Comparison of percentages of spermatozoa displaying partial (white bar) and complete (black bars) flagellum labelling in free-swimming and zona pellucida (ZP)-bound populations. The experiment was repeated four times and a minimum of 100 cells were scored for each experiment. ^**, P<0.005.