Nuclear envelope formation around metaphase chromosomes: chromosome decondensation and nuclear envelope reconstitution during mitosis.

The hypothesis of a possible correlation between reconstitution of the nuclear envelope and decondensation of the chromosomes has been experimentally examined. In the presence of colcemid, which delays C-metaphase chromosome decondensation for several hours, compared to normal mitosis, nuclear envelope formation is also significantly delayed. On the contrary, the treatment of the cells with a hypotonic solution, resulting in some swelling of metaphase chromosomes, induces the establishment of contacts between these chromosomes and membranes and the formation of an envelope around them. A new method, by which micronuclei are formed under hypotonic treatment, is discussed.