Fig. 6. ImmunoEM analysis of RP-A foci on restriction-enzyme-treated sperm nuclei. EM micrographs of Epon (A), Lowicryl (B,D,E) and cryo (C) thin sections of EcoRI restriction enzyme-treated Xenopus sperm heads after incubation with HSS. (A) Multiple RP-A/Ku bodies (some bodies are indicated by arrows) in a sample fixed with glutaraldehyde and postfixed with osmium tetroxide. Note the structural distinction between the chromatin and RP-A/Ku bodies. (B) RP-A/Ku bodies (arrows) labeled with purified anti-RP-A70 antibodies followed by 12 nm gold-coupled anti-rabbit antibody. (C) 30 nm chromatin fibrils (arrows) seen around the RP-A/Ku body (r) (RP-A 70 labeled with 12 nm gold adduct). (D) RP-A/Ku body after DNA labeling by TdT reaction (6 nm gold) and RP-A 34 immunolabeling (12 nm gold; two such gold particles are indicated by arrows). (E) RP-A/Ku bodies (arrows) labeled for XKu86 protein (5 nm gold particles). Bar in (A), 1 µm; bars in (B-E), 100 nm.