[Accessory nuclei of the primary erythroid cells of chick embryos: the kinetics of their formation and the relationship to the synthesis of extra DNA].

Kinetics of formation of accessory nuclei (AN), synthesis and accumulation of DNA in AN and main nuclei (MN) of the chick embryo primary erythroid cells (PEC) (2-7 days of development) and interdependence of these processes were studied using cytomorphology, autoradiography and differential cytophotometry. The earlier data on the existence of AN in primary erythrocytes (EC) were confirmed, and it was shown for the first time that the formation of AN accompanied the primary erythropoiesis from the very beginning of the proerythroblast (PEB) stage. The number of AN-bearing cells increases as erythropoiesis proceeds to reach the value of 50% PEC. The AN are formed in diploid, tetraploid, as well as in binuclear cells. The DNA content in AN may vary from 1-2 to 80% of the 2c value and has a tendency of increasing during erythropoiesis, while that in MN is always 2c or multiple thereof. Formed at early stages of PEC proliferation as pieces of segregated Feulgen-positive material, the AN are preserved during mitosis, taking no part in mitotic rearrangements of the chromosomes and being eventually involved in one of the daughter cells. Clusters of metaphase, anaphase and telophase chromosomes contain strictly 4c or 2c + 2c DNA. DNA synthesis in MN and AN may proceed in parallel and independently. It is frequently observed in AN of terminally differentiated PEC-reticulocytes (RC) and EC, whose MN no longer incorporate 3H-thymidine.(ABSTRACT TRUNCATED AT 250 WORDS)