The Relationship between Chromosome Aberrations and Low LET Radiation Dose to Human Lymphocytes

Abstract

In vitro dose-response curves of unstable chromosome aberrations in human lymphocytes have been obtained for 250 kV X-rays and cobalt-60gamma-radiation. The aberration yields have been fitted to the quadratic function Y = alphaD +betaD2, which is consistent with the single-track and two-track model for aberration formation. The values of the coefficients alpha and beta support the hypothesis that the dose-rate effect is limited to the D2 term. The main difference between the coefficients for X- and gamma-radiation is in the alpha values, indicating that X-rays are slightly more efficient, at lower doses, in producing two lesions with a single ionizing track. The lower limits of dose estimate, with 500 cells analysed, are 4 rad for X-rays and 10 rad gamma-radiation. Further evidence is presented confirming that, for cytogenetic dosimetry, in vitro dose-response curves should be prepared by irradiating whole blood maintained at 37 degrees C and prior to PHA stimulation. Curves were plotted showing the variation of the number of cells without aberrations with radiation dose and the shape of these curves were compared with those from human cell survival experiments.

Dicentric chromosome frequency analysis using slit‐scan flow cytometry

“…Rejection of false-positive events was accomplished by adjusting the stringency criterion. In the present study, the stringency criterion was adjusted so that the SSFCM analyses of several training sets produced dicentric frequency dose-response curves that increased with dose in a linear-quadratic manner similar to that described by Lloyd et al (11). The fact a stringency criterion of 0.05 yielded a linear-quadratic doseresponse curve, while 0.15 did not, suggest that many artifacts such as clumps produce profiles that have the same general trimodal shape as dicentric chromosome profiles.…”

“…The frequency of structurally aberrant chromosomes has long been known to increase with increasing radiation-induced genetic damage (2,9,10,11,18). Dicentric chromosomes are easily and reliably scored during analysis of metaphase spreads, even without banding analysis, and are thus routinely scored for estimation of the extent of such damage (5,11,12).…”

“…The training and test data sets analyzed with a stringency criterion of 0.05 are plotted in Figure 5 The dashed curve is a least-squares best-fit of the equation to the dicentric frequency dose response data reported by Lloyd et al (11). A scale factor of 1/300 was required to match the dose-response curve measured by Lloyd et al, using visual analysis of conventionally stained metaphase spreads to the dose-response curve generated by analysis of SSFCM profiles.…”

Radiation Exposure of Leukemia Blood Samples and Its Impacts on the Density of RBC, WBC, and PLT: <i>In Vitro</i>

“…Suspended in the watery plasma are seven types of cells and cell fragment; Red blood cells (RBCs), Platelets (PLT), and five kinds of white blood cells (WBCs) [18,19]. If one takes a sample of blood, treats it with an agent to prevent clotting, and spins it in a centrifuge.…”

How radiation-specific is the dicentric assay?

“…Ž . 1984;Fabry et al, 1985 , and linear energy transfer LET , Ž respectively Scott et al, 1969Scott et al, , 1970Lloyd et al, 1975; . Virsik et al, 1977;Dolphin, 1978 .…”