Technical report: effect of cryopreservation on chromosomal aberration yield in irradiated lymphocytes.

Cryopreservation is the usual method to store cells before analysis or use, for instance for biological dosimetry purposes. Some investigations have shown that thawing following freezing may induce cell injury but few studies have been made of the effect of cryopreservation on cells containing radiation-induced unstable chromosomal aberrations. In this work, lymphocytes were irradiated with 1 to 4 Gy gamma rays and stored in liquid nitrogen. The dicentric and centric ring yields were analysed after storage periods of 1 week, 1 month and 3 months. No difference in aberration frequency from control, unfrozen samples was observed over this period. Lymphocytes stored at -196 degrees C for up to at least 3 months may therefore be used for chromosome aberration scoring when over-exposure to ionizing radiation is suspected.

The cytogenetic dosimetry of recent accidental overexposure.

When accidental exposure to ionizing radiations is suspected, optimal choice of a treatment strategy requires, in addition to information about the clinical signs and physical dosimetry, a determination by biological parameters of the dose received. The scoring of unstable chromosomal aberrations in peripheral blood lymphocytes is the current reference method. Preparation of these samples depends on the goal sought--an exact assessment of several irradiations or rapid triage in the case of a large-scale accident. Moreover, some adaptation may be necessary if the irradiation is either heterogenous or not recent. Despite the robustness and adaptability of this procedure, conventional cytogenetics remains a tedious and time-consuming technique, and it requires specialized staff. Scoring micronuclei in binucleated lymphocytes may be an easier, simpler altemative to a dicentric assay. This paper, which is based on the experience acquired by the IPSN in recent years in expert assessment of suspected radiations, has as its goal to provide a succinct technical guideline of these different approaches, as they are adapted to suspected recent irradiation and triage.