title: Induction and disappearance of γH2AX foci and formation of micronuclei after exposure of human lymphocytes to ⁶⁰Co γ-rays and p(66)+ Be(40) neutrons.
abstract: OBJECTIVE
  To investigate both the formation of micronuclei (MN) and the induction and subsequent loss of phosphorylated histone H2AX foci (γH2AX foci) after in vitro exposure of human lymphocytes to either (60)Co γ-rays or p(66)+ Be(40) neutrons.
  
  
  METHODS
  MN dose response (DR) curves were obtained by exposing isolated lymphocytes of 10 different donors to doses ranging from 0-4 Gy γ-rays or 0-2 Gy neutrons. Also, γH2AX foci DR curves were obtained following exposure to doses ranging from 0-0.5 Gy of either γ-rays or neutrons. Foci kinetics for lymphocytes for a single donor exposed to 0.5 Gy γ-rays or neutrons were studied up to 24 hours post-irradiation.
  
  
  RESULTS
  Micronuclei yields following neutron exposure were consistently higher compared to that from (60)Co γ-rays. All MN yields were over-dispersed compared to a Poisson distribution. Over-dispersion was higher after neutron irradiation for all doses > 0.1 Gy. Up to 4 hours post-irradiation lower yields of neutron-induced γH2AX foci were observed. Between 4 and 24 hours the numbers of foci from neutrons were consistently higher than that from γ-rays. The half-live of foci disappearance is only marginally longer for neutrons compared to that from γ-rays. Foci formations were more likely to be over-dispersed for neutron irradiations.
  
  
  CONCLUSIONS
  Although neutrons are more effective to induce MN, the absolute number of induced γH2AX foci are less at first compared to γ-rays. With time neutron-induced foci are more persistent. These findings are helpful for using γH2AX foci in biodosimetry and to understand the repair of neutron-induced cellular damage.
authors.affiliation: NRF iThemba LABS (Laboratory for Accelerated Based Sciences), Somerset West, South Africa and Department of Medical Imaging and Clinical Oncology, University of Stellenbosch , South Africa.
authors.forename: Veerle
authors.initials: V
authors.lastname: Vandersickel
authors.forename: Philip
authors.initials: P
authors.lastname: Beukes
authors.forename: Bram
authors.initials: B
authors.lastname: Van Bockstaele
authors.forename: Julie
authors.initials: J
authors.lastname: Depuydt
authors.forename: Anne
authors.initials: A
authors.lastname: Vral
authors.forename: Jacobus
authors.initials: J
authors.lastname: Slabbert
mesh_terms: D000328:Adult; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D056426:Genetic Loci; D006657:Histones / Q000032:analysis*; D006801:Humans; D008214:Lymphocytes / Q000528:radiation effects* / Q000648:ultrastructure; D008297:Male; D048629:Micronuclei, Chromosome-Defective; D008875:Middle Aged; D009502:Neutrons; D012062:Relative Biological Effectiveness
chemical_list: C468783:H2AX protein, human; D006657:Histones