Trifluoperazine-Sensitive Step during Sea Urchin, Echiuroid and Pelecypod Egg Activation: (trifluoperazine/calmodulin/calcium/maturation/fertilization).

Trifluoperazine, a calmodulin-antagonist, is shown to inhibit egg activation by ionophore A 23187 in sea urchin (I : 43 μM), by trypsin in echiufoids (I : 22 μM) and by KCl in bivalves (I : 34 μM). In each case the inhibition could be reversed by washing the eggs and the trifluoperazine-sensitive period was clearly limited. In Barnea and Urechis, trifluoperazine inhibits calcium uptake.

Acid Release during Activation of Barnea candida (Mollusca, Pelecypoda) Oocytes: (acid release/oocyte activation/Barnea candida).

Barnea caridida oocytes release acid (1.35 pmole H /oocyte) upon fertilization. After artificial activation by an excess of KCl, germinal vesicle breakdown (GVBD) occurs normally and a quite similar, but not identical, acid release is recorded (1.

UNCOUPLING OF OOCYTE-FOLLICLE CELLS TRIGGERS REINITIATION OF MEIOSIS IN AMPHIBIAN OOCYTES.

Reinitiation of meiosis has been triggered in vitro in oocytes of the anouran Xenopus laevis and the urodeles Pleurodeles waltlii and Ambystoma mexicanum by enzymatic, mechanical or manual defolliculation, without addition of hormone. By measuring changes in the membrane resistance and time constants, we also demonstrate the existence of an electrical polarized coupling between the oocyte and its follicle and show that progesterone breaks it definitively within the first two hours. These results are discussed in relation to mammalian maturation.

PROPIONATE AND CYCLOHEXIMIDE REVERSIBLY BLOCK PROGESTERONE INDUCED CALCIUM SURGE IN AMBYSTOMA MEXICANUM OOCYTES.

The protoprotein aequorin was used in order to monitor Ca transients in conditions where progesterone induced maturation was reversibly inhibited. Propionate but not isethionate Cl-free medium impaired both meiosis reinitiation and the Ca transient, unless oocytes were returned to normal Cl-containing medium. Similar results were obtained with the protein synthesis inhibitor cycloheximide.