Radioiodine administration in hyperthyroidism--a cytogenetic study

Induction of BCR-ABL fusion genes by in vitro X-irradiation

The Philadelphia chromosome consists of a reciprocal translocation between the ABL oncogene at chromosome 9q34 and the BCR gene at chromosome 22q11, resulting in the expression of chimeric BCR-ABL mRNAs specific to chronic myelogenous leukemia (CML). Presence of the fusion gene can be detected with high specificity and sensitivity by means of reverse transcription and polymerase chain reaction. Using this assay, it was possible to detect BCR-ABL fusion genes induced among HL60 cells after 100 Gy of X-irradiation in vitro. In total, five fusion gene transcripts were obtained among 10(8) cells examined. These fusion genes contained not only CML-specific BCR-ABL rearrangements, but also other forms of BCR-ABL fusions. These latter genes had junctions of BCR exon 4/ABL exon 2 intervened by a segment of DNA of unknown origin, BCR exon 5/ABL exon 2, and BCR exon 4/ABL exon 2. The results appear to be direct evidence for the induction of the BCR-ABL fusion gene by X-irradiation. In terms of leukemogenesis, it appears that only those cells bearing certain CML-related BCR-ABL fusion genes are positively selected by virtue of a growth advantage in vivo.

Changes of the blood lymphocyte population following 131I treatment for nodular goiter

The blood lymphocyte population was examined in 34 patients who were treated with 131I for toxic or atoxic nodular goiter. The patients received one to three doses of 300-550 MBq of 131I administered at 1 week intervals. Lymphocyte counts were significantly reduced both 1 and 6 weeks after treatment. This reduction was accompanied by a changed composition of the lymphocyte population. The frequency of lymphocytes expressing membrane receptors for C'3 (EAC-rosette forming) was significantly reduced 1 and 6 weeks after 131I-administration. At 6 weeks there was a slight but statistically significant increase of the frequency of T-cells as identified by Leu 1 monoclonal antibodies. This was largely caused by an increased proportion of helper/induced T-cells as identified by Leu 3a monoclonals. 131I-treatment also reduced the capacity of lymphocytes to secrete immunoglobulins (Ig) upon PWM-stimulation. The most pronounced effect was observed for IgM. Secretion of IgG and IgA were less reduced. Mitogenic stimulations of lymphocytes with PHA and ConA were not significantly changed. We conclude that these changes observed, with the exception of mitogen reactivity, are essentially similar to those occurring after external radiation therapy for cancer. We speculate that blood lymphocytes passing through the continuously irradiated gland are damaged mainly by emitted beta-particles.

Simultaneous staining of sister chromatid exchanges and Q-bands in human chromosomes after treatment with methyl methane sulphonate, quinacrine mustard, and quinacrine

Human peripheral lymphocyte chromosomes were stained simultaneously for sister chromatid exchanges (SCEs) and Q-banding. No effect of treatment with MMS, QM, and Q on the distribution of SCEs in chromosomes was found compared with controls. The SCEs were distributed between chromosomes roughly according to metaphase length, with the shorter chromosomes underrepresented. The majority of SCEs were located to pale bands, while a few occurred in bright bands and at interfaces between pale and bright bands. A greater frequency than expected of SCEs had occurred at identical sites in homologous chromosomes. This frequency was significantly increased after treatment with MMS.