title: Dependence of the timing system regulating the onset of gastrulation on cytoplasmic, but not nuclear, activities in the Xenopus embryo.
abstract: This study examines the properties of the timer that regulates the onset of gastrulation in the Xenopus embryo. Pre-gastrulation embryos were exposed to aphidicolin, vinblastine, 6-dimethylaminopurine (6-DMAP) or urethane. Embryos exposed to aphidicolin or vinblastine for 0.5-2 h before the presumptive onset of gastrulation, began gastrulation at the same time as control embryos. However, those exposed to 6-DMAP or urethane commenced gastrulation significantly later than controls. In 6-DMAP- and urethane-treated embryos, the onset of gastrulation was retarded by approximately 25% and 120%, respectively. 6-DMAP and urethane, but not vinblastine, also lowered the rate of nuclear doubling by 30% and 120%, respectively, in late-blastula to early-gastrula embryos. 6-DMAP and urethane also lowered the rate of cleavage and cleavage-relevant cytoplasmic cycling by 30% and 80%, respectively, in cleavage-stage embryos. We propose that cytoplasmic activities that can be retarded by 6-DMAP and urethane, but not aphidicolin or vinblastine, may be responsible for regulating the onset of gastrulation in Xenopus embryos.
authors.affiliation: Department of Biology, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-Machi, Yamagata 990-8560, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Takagi
authors.forename: Taiki
authors.initials: T
authors.lastname: Shimoda
authors.forename: Atsunori
authors.initials: A
authors.lastname: Shinagawa
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D002455:Cell Division / Q000502:physiology; D002467:Cell Nucleus / Q000502:physiology; D048749:Cytokinesis / Q000502:physiology*; D003593:Cytoplasm / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D005775:Gastrula / Q000166:cytology / Q000502:physiology*; D013997:Time Factors; D014520:Urethane / Q000494:pharmacology; D014747:Vinblastine / Q000494:pharmacology; D014981:Xenopus / Q000196:embryology*
chemical_list: D016590:Aphidicolin; D014520:Urethane; D014747:Vinblastine; C001020:N(6),N(6)-dimethyladenine; D000225:Adenine