title: Studies of bystander effects in human fibroblasts using a charged particle microbeam.
abstract: OBJECTIVE
  To determine the role of cell-to-cell mediated effects in the response of cells to different radiations by using a charged particle microbeam capable of targeting individual cells with counted particles.
  
  
  METHODS
  Primary human fibroblasts were irradiated conventionally with X-rays or alpha-particles and scored for the induction of micronucleated or apoptotic cell formation at various times after irradiation. Cells were also individually irradiated with helium-3 particles from a microbeam and the distribution of damaged cells between hit and non-hit cells scored.
  
  
  RESULTS
  Conventionally exposed fibroblasts showed a dose-dependent production of micronucleated and apoptotic cells 3 days after irradiation for both X-rays and alpha-particles, with a high RBE value for alpha-particles at low doses. Targeting individual alpha-particles, using a microbeam, to four cells within a population produced more micronucleated and apoptotic cells than expected on the basis of a direct effect only.
  
  
  CONCLUSIONS
  This study provides direct evidence for the production of transmissible, cell-to-cell effects between hit and non-hit cells individually exposed to charged particles.
authors.affiliation: Gray Laboratory Cancer Research Trust, Mount Vernon Hospital, Northwood, Middlesex, UK. Michael@graylab.ac.uk
authors.forename: K M
authors.initials: KM
authors.lastname: Prise
authors.forename: O V
authors.initials: OV
authors.lastname: Belyakov
authors.forename: M
authors.initials: M
authors.lastname: Folkard
authors.forename: B D
authors.initials: BD
authors.lastname: Michael
mesh_terms: D000512:Alpha Particles / Q000009:adverse effects; D017209:Apoptosis / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000528:radiation effects*; D006801:Humans; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects; D011839:Radiation, Ionizing; D014965:X-Rays / Q000009:adverse effects