Chromatin activation in peritoneal exudate leukocytes after fusion with L cell cytoplasts.

Cells reconstituted from the L cell cytoplasts and nuclei of mouse peritoneal leukocytes (PL) have been obtained by fusion procedures. The dormant nuclei of leukocytes undergo reactivation after fusion with active L cell cytoplasms. The reactivation is manifested by the swelling of nuclei, the increase of 3H-actinomycin D binding to chromatin in situ and the 3H-uridine incorporation in nuclei in vivo and by the appearance of nucleoli. The data obtained indicate that the process of dormant nuclei reactivation does not require the presence of the nucleus of the active cell partner. Moreover, the process of chromatin reactivation is more rapid in reconstituted cells than in PL + L cell heterokaryons. Some other details of PL chromatin activation in reconstituted cells and heterokaryons are discussed.