Fig. 1 The oocytes on the left are arrested in meiotic prophase. Upon stimulation by progesterone (right), meiosis resumes and arrests again at metaphase II. The nucleus (GV) migrates to the top of the oocyte and displaces the pigment granules producing a white spot.

Fig. 2 The increase in oocyte pHi appears to be due to the phosphorylation of the Na+/H+ antiporters located in the oocyte plasma membrane. Upon phosphorylation, the exchange rate of the antiport increases resulting in an increased efflux of H+ ions from the oocyte cytoplasm.

Fig. 3 The proto-oncogene product, c-mos kinase, rapidly induces an increase in oocyte pHi when injected into Xenopus oocytes. C-mos also induces GVBD much later.

Fig. 4 DNA plasmids coding for three forms of Raf-1 were obtained. One coded for Wild-type Raf-1 [WT-Raf-1], one coded for a kinase-deficient Raf-1 [KD-Raf-1] and one coded for a constitutively active form of Raf-1 [deltaN-Raf-1].

Fig. 5 Oocytes were injected with RNAse-free water (lane 2), WT-Raf-1 mRNA (lane 3), delta-N-Raf-1 mRNA (lane 4) or KD-Raf-1 mRNA (lane 5) and monitored for protein synthesis and pHi. Only constitutively active delta-N-Raf-1 Kinase induced an increase in pHi.