A method for the scrutiny of live mammalian cells in culture and for the measurement of their proliferative ability after x-irradiation.

A method is described for the observation of live mammalian cells in culture with an incubated phase-contrast microscope. A sample of plated cells may be watched and their respective capacities to form a colony measured by daily cell counts. The method has first been used to make direct estimations of the plating efficiency of the diploid line of Syrian hamster fibroblasts, BHK 21 C13, and then to observe the response of synchronous samples of these cells to 220 kV X-rays. A dose of 1.4 Gy given in Gl has no immediate detectable effect on cell or unclear morphology, and cell capacity to reach post-irradiation mitosis in unimpaired apart from delay. In contrast, after this mitosis is completed, descendant cells from some mitoses retain a normal form and clonogenic capacity, whereas the cells from other mitoses show varying degrees of abnormality and produce either slow-growth or stop-growth (micro-) colonies.

Observations of radiation-induced chromosome fragment loss in live mammalian cells in culture, and its effect on colony-forming ability.

Our preceding paper (Crote, Joshi, Revell and Shaw 1981) described a method for the direct scrutiny of live cultured mammalian cells with a microscope, and reported that all diploid Syrian hamster cells (BHK 21 C13) of a sample given 1.4 Gy of 220 kV X-rays in Gl reached post-radiation mitosis without discernible abnormality, but then diverged in observed behaviour: descendent cells from some first mitoses continued to proliferate normally while cells from other first mitoses behaved abnormally and produced either slow-growth or stop-growth colonies. This paper completes our study of the same irradiated cell sample, and shows that these post-mitotic differences in clonogenic ability were related to acentric chromosome fragment losses at post-radiation mitosis, which were detected in live daughter-cell pairs as micronuclei. The proportion of live daughter-cell pairs scored as deficient was at least 80 per cent of the proportion of comparable fixed-and-stained mitoses with detected acentric fragments.