To investigate the signals that pass from the sperm to the egg to initiate development, the function of G-proteins and G-protein-linked receptors in the egg membrane will be examined. The specific aims are: 1) To identify and characterize G-protein alpha-subunits in eggs and embryos. 2) To investigate how closely G-protein stimulation mimics events at fertilization. 3) To investigate the effects of inhibiting G-protein function in eggs, as well as in oocytes and embryos. 4) To determine if G- proteins are activated at fertilization. 5) To investigate the functions of G-protein-linked receptors in eggs, as well as in oocytes and embryos. The experimental design and methods include immunoblotting of egg membranes with G-protein-specific antibodies, measurements of calcium transients and calcium-mediated ion channel opening, microinjection of antibodies against particular G-proteins, use of azido-anilido-GTP to detect G-protein activation, and expression in eggs of mRNAs encoding G-protein-linked receptors. The significance of this work to the study of human development is that the cell biological principles we discover in our work with echinoderms and amphibians will form a basis for future studies of mammals. This basic science background may ultimately find applications to practical problems such as contraception and infertility.