Detection of incomplete exchanges and interstitial fragments in X-irradiated human lymphocytes using a telomeric PNA probe.

PURPOSE

The detection of incomplete exchanges and interstitial fragments by fluorescence in situ hybridization using a telomeric peptide nucleic acid (PNA) probe.

MATERIALS AND METHODS

Isolated human lymphocytes were exposed in vitro to X-rays at a dose of 3 Gy. Aberrations were analysed in the first mitosis after irradiation using a telomeric PNA probe.

RESULTS

After an acute dose of 3 Gy, only about 16% of the cells contained a pair of incomplete chromosome elements with telomeric signals at only one terminal end. Acentric interstitial fragments, lacking telomeric signals, were observed with a frequency of 0.56 per cell, which was very similar to the dicentric frequency (0.61 per cell).

CONCLUSIONS

The low frequency of incompleteness suggests that most of the non-reciprocal interchanges observed using chromosome painting must originate from terminal exchanges rather than from incomplete exchanges. Furthermore, it was estimated that about 78% of excess acentric fragments originate from interstitial fragments and only 22% from terminal fragments.