Phosphorylated Histone H3 is phosphorylated in embryos exposed to brief periods of anoxia. Embryos were exposed to either normoxia (A-D), 30 minutes of anoxia (E-L), or 6 hours of anoxia (M-P), collected, and stained with DAPI (A, E, I, M), PhosH3 recognizes phosphorylated Histone H3 (B, F, J, N), and the mAb414 to recognize nuclear pore complex (C, G, K, O). Merged image for each set is shown (D, H, L, P). PhosH3 is detected in prophase and metaphase blastomeres in embryos exposed to normoxia (B), and embryos exposed to 30 minutes of anoxia (F, J). Embryos exposed to 6 hours of anoxia have detectible PhosH3 in metaphase blastomeres but not prophase blastomeres (N). The letters P or M are near a representative prophase and metaphase blastomeres respectively with arrows pointed to the representative mitotic chromosomes detected by PhosH3. Scale bar equals 5 μM.