title: On the late seeding of CFU-S to the spleen: 8- vs 12-day CFU-S.
abstract: Marrow from 5-fluorouracil- or cyclophosphamide-treated mice, injected into lethally irradiated recipients, gives an increasing number of spleen colonies between days 7 and 14. It has been suggested that the later-forming colonies result from the more primitive spleen colony-forming units (CFU-S), which first seed into the marrow, only later to be recirculated and form colonies in the spleen. Strontium 89 (89Sr), a bone-seeking radionuclide, was injected into recipient mice to block such putative recirculation. A dose of 89Sr, which killed at least 99.8% of CFU-S in, or entering, the bone cavities, was incapable of preventing the increase in spleen colony numbers. Similarly, the splenic environment, modified by the presence of spleen colonies and able to provide a better bed for trapping CFU-S from the peripheral circulation, yielded the same number of further CFU-S, whether or not the animal had received 89Sr. Thus, it was concluded that the 12-day CFU-S does not seed initially into the marrow spaces. Direct observation of the quality of CFU-S initially seeding into the bone marrow and spleen showed, by retransplantation into secondary irradiated mice, that a similar spectrum of CFU-S types had seeded both organs.
authors.affiliation: Paterson Institute for Cancer Research, Christie Hospital, Manchester, UK.
authors.forename: B I
authors.initials: BI
authors.lastname: Lord
authors.forename: G
authors.initials: G
authors.lastname: Molineux
authors.forename: R
authors.initials: R
authors.lastname: Schofield
authors.forename: E R
authors.initials: ER
authors.lastname: Humphreys
authors.forename: V A
authors.initials: VA
authors.lastname: Stones
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells; D016026:Bone Marrow Transplantation; D002465:Cell Movement; D003114:Colony-Forming Units Assay; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D051379:Mice; D013154:Spleen / Q000166:cytology*; D013326:Strontium Radioisotopes / Q000633:toxicity; D013997:Time Factors
chemical_list: D013326:Strontium Radioisotopes