title: Somite cell cycle analysis using somite-staging to measure intrinsic developmental time.
abstract: Somite stages were employed as units of intrinsic developmental time to measure cell doubling rate and other cell cycle parameters of chick forelimb level somites. Somite cell nuclei doubled over an interval corresponding to approximately 7+ somite stages (7+ ss; approximately 11 hr) and approximately 24 new primary myotome cells are born per somite stage ( approximately 16/hr). FACS analysis of DNA content in dissociated paraxial mesoderm cells indicated that slightly more than half are in G1/G0 phase of the cell cycle and that the average combined length of the S phase and G2 phase intervals is approximately 3 ss ( approximately 4.5 hr). A wavefront of increased mitotic nuclei per segment coincident with somite budding potentially reflects a surge in the number of cells entering S phase 3 ss earlier as each PSM segment becomes unresponsive to FGF signaling as it passes through the determination front.
authors.affiliation: Department of Anatomy, UCSF, HSW 1330, San Francisco, California 94143-0452, USA.
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Venters
authors.forename: Michael L
authors.initials: ML
authors.lastname: Hultner
authors.forename: Charles P
authors.initials: CP
authors.lastname: Ordahl
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D001973:Bromodeoxyuridine; D002453:Cell Cycle / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology*; D002642:Chick Embryo; D005434:Flow Cytometry; D018613:Microscopy, Confocal; D024510:Muscle Development / Q000502:physiology*; D019170:Somites; D013997:Time Factors
chemical_list: D001973:Bromodeoxyuridine