Prematurely condensed chromosome fragments in human lymphocytes induced by high doses of high-linear-energy-transfer irradiation

Abstract: This study provides a useful biodosimetry protocol for radiation accidents that involve high doses of heavy particle radiation. Human peripheral blood lymphocytes (PBLs) were irradiated in vitro with high doses (5–50Gy) of charged heavy-ion particles (carbon ions, at an effective linear-energy-transfer (LET) of 34.6keV/μm), and were then stimulated to obtain dividing cells. PBLs were treated with 100nM calyculin A to force chromosomes to condense prematurely, and chromosome spreads were obtained and stained with Giemsa. The G2 prematurely condensed chromosome (G2-PCC) index and the number of G2-PCC including fragments (G2-PCC-Fs) per cell for each radiation dose point were scored. Dose-effect relationships were obtained by plotting the G2-PCC indices or G2-PCC-Fs numbers against radiation doses. The G2-PCC index was greater than 5% up to doses of 15Gy; even after a 30Gy radiation dose, the index was 1 to 2%. At doses higher than 30Gy, however, the G2-PCC indices were close to zero. The number of G2-PCC-Fs increased steeply for radiation doses up to 30Gy at a rate of 1.07Gy−1. At doses higher than 30Gy, the numbers of G2-PCC-Fs could not be accurately indexed because of the limited numbers of cells for analysis. Therefore, the number of G2-PCC-Fs could be used to estimate radiation doses up to 30Gy. In addition, a G2-PCC index close to zero could be used as an indicator for radiation doses greater than 40Gy. [Copyright &y& Elsevier]