The observation of mitotic division aberrations in mammalian cells exposed to chemical and radiation treatments.

The fidelity of chromosome segregation and the maintenance of the integrity of the chromosome karyotype of eukaryotic cells is dependent upon the synthesis and functioning of division-related structures such as the nuclear spindle and events such as the attachment of chromosomes to the spindle and their subsequent movement to the poles of the dividing cell. Chemical and physical treatment which modify the synthesis and functioning of division-related events may potentially lead to the production of cells with abnormal chromosome numbers (of both whole chromosome sets and of individual chromosomes). The ability of environmental agents to modify division-related structures in mammalian cells has been assessed by morphological examination of exposed mitotically dividing cells using staining techniques which identify spindle and chromosome structure and by the analysis of the characteristics of microtubule polymerisation in vitro. Such techniques have been used to identify the spindle-modifying effects of chemicals such as the synthetic hormone diethylstilboestrol and modifications of chromosome to spindle attachment in cells exposed to both UV- and X-irradiation. Such modifications of cell-division-related activities may lead to alterations in the fidelity of division events leading to the production of chromosomally abnormal daughter cells with aneuploid or polyploid karyotypes.