Checkpoint activation upon low nuclei to cytoplasm ratios in the presence of aphidicolin.

<p>(a) Sperm nuclei (100 nuclei/μl) were added to egg extracts in the presence of aphidicolin, nuclear extracts were prepared and subjected to gel electrophoresis and western blot analysis using an anti- P-Chk1 and XChk1 antibody, (b) For combing experiments sperm nuclei (100 nuclei/μl) were added to egg extracts in the presence of aphidicolin (7.5 μg/ml), biotin-dUTP and in the presence or absence of UCN-01 (1μM) for 90 min, DNA was isolated and combed, mean replication extent of two independent experiments with SEM (t-test, P = 0.049), (c) <i>Xenopus</i> embryos were incubated in aphidicolin (100 μM) for 30 min prior to harvest at stage 8 (pre-MBT) and stage 9 (post-MBT), nuclei extracts were prepared, subjected to gel electrophoresis and western blot analysis using a P-Chk1 antibody and XORC as loading control, LSS (low speed supernatant, extract),* significantly different (P < 0.05).