title: Letter: Ageing cell cultures.
mesh_terms: D003585:Cell Biology; D002455:Cell Division; D002470:Cell Survival; D002478:Cells, Cultured; D005347:Fibroblasts; D006801:Humans; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
chemical_list: D014316:Tritium; D013936:Thymidine