A comparison of the effects of various spindle toxins on metaphase arrest and formation of micronuclei in cell-suspension cultures ofNicotiana plumbaginifolia.

The effects of the spindle toxins colchicine, oryzalin and amiprophos-methyl (APM) on metaphase arrest, chromosome scattering, and on the induction and yield of micronuclei were compared in suspension cells ofNicotiana plumbaginifolia (kanamycin-resistant "Doba" line). The inhibition of spindle formation is stronger with oryzalin and APM than with colchicine, which resulted in a more efficient accumulation of meta-phases with well-scattered chromosomes, allowing the isolation of single chromosomes. Further, APM and oryzalin treatments resulted in a higher frequency of micro-nucleated cells and greater yield of micronuclei than after colchicine treatment. The different actions of the chemicals on the functioning of the spindle, development of nuclear membranes around the chromosomes, formation of micronuclei and fusion of micronuclei, resulting in restitution nuclei, are discussed.