title: Evidence for S stage quiescence in regeneration blastema cells.
abstract: Working on the temporal structure of the S stage of regeneration blastema cells we have discovered that some blastema cells, containing a 3C quantity of DNA, do not incorporate radioactive thymidine, or that they proceed through the synthetic phase with a speed undetectable by a radioactive pulse. We report the identification of several short-term periods of quiescence for regeneration blastema cells in vivo, operating during the S stage of the cell cycle. Blastema cell smears from regenerating urodele forelimbs were used in this study. Combined microdensitometric scanning of Feulgen-stained nuclei and microradioautographic labelling of the same nuclei have been exploited to assess DNA replication. A total of 3,600 blastema cell nuclei were scanned, mapped on photographic film and subsequently processed for radioautography. It was found that 49.7% of the cells with a DNA content ranging between 2C and 4C were unlabelled after 1 h exposure to tritiated thymidine.
authors.affiliation: Zoological Institute, University of Cologne, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Koussoulakos
authors.forename: H J
authors.initials: HJ
authors.lastname: Anton
mesh_terms: D000671:Amputation, Surgical; D000818:Animals; D002452:Cell Count; D002467:Cell Nucleus / Q000235:genetics; D004247:DNA / Q000032:analysis; D005552:Forelimb / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology* / Q000502:physiology; D012038:Regeneration / Q000502:physiology*; D016196:S Phase / Q000502:physiology*; D014319:Triturus
chemical_list: D004247:DNA