[The effect of formamide on the achromatic apparatus and the chromosomes of dividing pleurodele eggs: an electron microscope study].

Electron microscope studies of blastulae of Pleurodeles waltlii Michah., treated with formamide (0,5 M for 17 hours), show various abnormalities concerning centrospheres, chromosomes and microtubules as well. At the prophase stage, the centrospheres may display at their outer region an accumulation of dense bodies, which shows a temporary blocking of these centrospheres. At metaphase the poles of pluripolar mitoses appear more or less separated from the material which contains the chromosomes of the equatorial region. Each of these poles contains an unique centriole and therefore it is considered as resulting of the subdivision of a normal anaphasic pole. Astral and spindle microtubules are very reduced in number and more or less shortened. The chromosomes are without any recognizable kinetochcre, they show various degrees of condensation. All these electron microscope observations confirm the light microscope ones, and we may conclude that formamide has a double action on microtubules formation and on the ultrastructure of chromosomes, the latter perhaps by a direct action on DNA protein complexes.