Fig. 1. (A) C. lacteus oocytes treated with 1 µM 5-HT in the presence or absence of 20 µM U0126 and probed for MAPK activity with anti-phospho-ERK1/2 Ab. Note normal levels of GVBD in U0126-treated samples even though MAPK signal is greatly reduced. 'Positive control' was supplied by Cell Signaling as material used to generate antibody. (B) Although 5-HT-treated oocytes mature at high levels without MAPK activity, similar incubations in U0126 or 25 µM PD98059 reduce spontaneous GVBD. Each blot is representative of five replicates. (C) Activity assays of MPF and ERK1/2 MAPK in maturing C. lacteus oocytes. Upper two bands at 66 and 48 kDa represent full-length and truncated Rb fusion protein probed with a phospho-Rb-specific antibody to track MPF activity. Phospho-ELK-1 band at 34 kDa depicts ERK1/2 activity. Note MPF activation continues in the absence of substantial MAPK activity.

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