title: Injection of a sperm extract triggers egg activation in the newt Cynops pyrrhogaster.
abstract: Unfertilized eggs of the newt Cynops pyrrhogaster are arrested at the second meiotic metaphase. The primary signal for egg activation is a transient increase in [Ca2+](i), which is triggered by the fertilizing sperm and propagates over the egg cortex as a Ca2+ wave. We injected an extract of Cynops sperm (SE) into unfertilized eggs and induced a wave-like [Ca2+](i) increase which resulted in activation and resumption of meiosis. The SE-injected eggs showed degradation of cyclin B1 and DNA replication. When SE was boiled or treated with proteinase K before injection, it was unable to cause egg activation. Preinjection of Ca2+ -chelator BAPTA before SE injection inhibited egg activation. These results indicate that a heat-labile and proteinaceous factor in the sperm cytoplasm induces a transient increase in [Ca2+](i) which is required for egg activation. Injection of IP3 into unfertilized eggs caused an increase in [Ca2+](i) and egg activation, but injection of cADP-ribose did not. These results support the hypothesis that Ca2+ release at fertilization occurs via IP3 receptors.
authors.affiliation: Department of Biological Science, Faculty of Science, Yamaguchi University, 753-8512 Yamaguchi, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
authors.forename: H Y
authors.initials: HY
authors.lastname: Kubota
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshimoto
authors.forename: Y
authors.initials: Y
authors.lastname: Iwao
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002614:Chelating Agents / Q000494:pharmacology; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D004261:DNA Replication; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D010063:Ovum / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012455:Salamandridae / Q000502:physiology*; D013084:Sperm-Ovum Interactions / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology
chemical_list: D015220:Calcium Channels; D002614:Chelating Agents; D019926:Cyclin B; D056744:Cyclin B1; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D004533:Egtazic Acid; D001973:Bromodeoxyuridine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid