title: Evidence for a chalone control mechanism in the limb regeneration blastema of the newt, Notophthalmus viridescens.
abstract: The objective of this study was to investigate the possible involvement of chalones in the control of limb regeneration. Saline extracts of whole limb, skinned limb, kidney and liver were injected intraperitoneally, followed by 5 x 0 micrograms colchicine per g body weight into newts, Notophthalmus viridescens, bearing cone stage limb regenerates on both forelimbs. Forty-eight hours post-injection, tissues were fixed and mitotic figures and pyknotic nuclei were counted in limb blastemata, liver and kidney. Animals injected with limb extracts had significantly fewer mitotic figures in their blastemata than animals injected with other extracts. Counts of mitotic figures from kidneys and livers of animals receiving homologous extract injections were significantly lower than counts of mitotic figures from kidneys and livers of animals receiving other extract injections. This indicates that the extracts were causing tissue specific mitotic inhibition. Pyknotic nuclei were not increased by extract injection, suggesting that the extracts were not cytotoxic. It is proposed that a chalone control mechanism is present in the tissues of the regenerating newt limb.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000502:physiology; D005552:Forelimb / Q000502:physiology; D006131:Growth Inhibitors / Q000494:pharmacology*; D007668:Kidney / Q000502:physiology; D008099:Liver / Q000502:physiology; D008938:Mitosis; D012038:Regeneration / Q000187:drug effects; D012455:Salamandridae / Q000502:physiology*; D014020:Tissue Extracts / Q000494:pharmacology*
chemical_list: D006131:Growth Inhibitors; D014020:Tissue Extracts