Fig. 4. Adenophostin-A treatment prevents mitotic Ca²⁺ oscillations in fertilized embryos. (A) cIns(1,4,5)P₃ was used to test the responsiveness of Ca²⁺ release in one-cell embryos 4 hours after Ad-A injection (2.5 µM). Peak Fura-red ratio change was significantly reduced in Ad-A injected embryos (n=16) compared with controls (uninjected, n=15; vehicle, n=6) in response to 300 millisecond, 1200 millisecond and 3000 millisecond exposures of UV light (^*, P<0.01), indicating that Ad-A treatment inhibits Ins(1,4,5)P₃-mediated Ca²⁺ release. (B) [Ca²⁺]_i was monitored in Ad-A-treated embryos during mitosis using Fura-2/dextran. Mitotic Ca²⁺ oscillations were detected in all controls (Fura-2/dextran only; n=9) but not following Ad-A treatment (n=12). Open arrow, NEBD; closed arrow, cytokinesis. (C) Ad-A treatment had no effect upon the timing of NEBD or cytokinesis as determined using bright-field optics (data from two similar replicates; buffer, n=30; Ad-A, n=34). (D) Subsequent Hoechst labelling revealed chromatin within both blastomeres, indicating that chromosome disjunction at anaphase was uninhibited (two replicates, n=12 for Ad-A; n=19 for control).