Effects of polyamine limitation on nucleolar development and morphology in early chick embryos.
Inhibition of polyamine synthesis in early chick embryos by in ovo treatment with DL-alpha-difluoromethylornithine (DFMO), injected beneath the blastoderm after 5 h of incubation, permanently blocks post-gastrular development. After the first day of polyamine limitation, the embryos possess a thickened primitive streak. Further morphogenesis is blocked and the ectoderm and mesoderm are condensed around the streak. There is obvious suppression of nucleolar formation in 24 h DFMO-treated embryos. In the mesoderm obliquely in front of Hensen's node the frequency of nucleolus-possessing cells is only a few percent lower in DFMO-treated than in control embryos. However, in the same area the frequency of mesoderm cells possessing multiple nucleoli is about 50% lower in the polyamine-depleted embryos. At the ultrastructural level, mesoderm cells from 24 h DFMO-treated embryos show a reduction of the fibrillar component of the nucleolus with a resulting segregation of the nucleolar material. Our data indicate that stimulation of polyamine synthesis is an obligatory step in the differentiation of epiblast cells into mesoderm cells.
D000818:Animals; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors*; D002466:Cell Nucleolus / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D002642:Chick Embryo; D000518:Eflornithine; D008854:Microscopy, Electron; D008940:Mitotic Index / Q000187:drug effects; D009952:Ornithine / Q000031:analogs & derivatives* / Q000494:pharmacology; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines / Q000096:biosynthesis*
D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D009952:Ornithine; D002262:Carboxy-Lyases; D000518:Eflornithine