ExtractThis paper reports in vitro tests of chromosomal radiosensitivity in five children and three adults with normal karyotypes as control subjects, in seven patients (children) with chromosomal abnormalities, and in six translocation carriers (adults). Peripheral blood samples from each individual and skin fibroblast cultures from four children in the control group, five patients with chromosomal abnormalities, and one translocation carrier were irradiated with 10 and 100 rads. Nonirradiated duplicate cultures were used as controls. Blood cultures were harvested after 52 hr of incubation and fibroblast cultures were harvested 24 hr after irradiation. The frequency of chromosomal breakage caused by irradiation was calculated by subtracting the values for nonirradiated samples from those for irradiated samples. In normal control subjects, the number of chromosome-type breaks per cell per rad was 0.0024 ± 0.0009 and 0.0020 ± 0.0009 in lymphocytes of children and adults, respectively, and 0.0049 ± 0.0021 in fibroblasts of children. The number of breaks per cell per rad was 0.0055 ± 0.0017 in lymphocytes and 0.00:82 ± 0.0013 in fibroblasts of patients, and 0.0040 ± 0.0018 in lymphocytes and 0.0063 ± 0.0017 in fibroblasts of carriers. In comparison with age-matched controls, significantly elevated frequencies of breaks per cell per rad were observed in cultured lymphocytes and fibroblasts of patients, and in cultured lymphocytes of translocation carriers (Table II). After irradiation with 100 rads, the number of dicentrics and rings per cell was significantly greater in both patients and carriers of chromosomal abnormalities than in control subjects (Tables I and III). Therefore, chromosomes of cells of patients with chromosomal abnormalities and of translocation carriers were significantly more radiosensitive in vitro than those of control subjects.
SpeculationPatients with chromosomal abnormalities and carriers with a translocated chromosome show greater chromosomal changes after irradiation in all age groups than do normal control subjects. These individuals, therefore, should be subjected to as little x-ray examination as possible.
514Abnormal karyotypes and chromosomal radiosensitivity 515