title: Inactivation of haemopoietic stem cells by slow alpha-particles.
abstract: Inactivation of murine haemopoietic stem cells, assayed as spleen colony-forming units (CFU-S), has been determined after in vitro irradiation under well defined conditions with small numbers (0.15-3) of alpha-particles of incident energy 3.3 MeV (LET 121 ke V microns-1). Exponential survival curves were obtained with inactivation dose coefficients of 1.83 +/- 0.11 and 1.63 +/- 0.06 Gy-1 for 8 and 12-day CFU-S, respectively, corresponding to inactivation cross sections of 35.6 +/- 2.1 and 31.7 +/- 1.2 microns2. The results indicate that these radiosensitive stem cells have a significant probability of surviving the passage of a single alpha-particle track, estimated at 8 and 18% per particle passage, respectively, if the cells have a diameter of 7 microns. However, this estimation is strongly dependent on the assumed diameter. Conversely, it is demonstrated that the cells cannot have mean geometric diameters of less than 6.7 +/- 0.2 and 6.4 +/- 0.1 microns, respectively. Associated experiments have shown that some cells from the irradiated population do survive to form colonies that express delayed non-clonal chromosome aberrations.
authors.affiliation: Medical Research Council Radiobiolgy Unit, Chilton, Didcot, UK.
authors.forename: S A
authors.initials: SA
authors.lastname: Lorimore
authors.forename: D T
authors.initials: DT
authors.lastname: Goodhead
authors.forename: E G
authors.initials: EG
authors.lastname: Wright
mesh_terms: D000512:Alpha Particles; D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006412:Hematopoietic Stem Cells / Q000528:radiation effects*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA