A STUDY OF DEPOLYPLOIDIZATION AND DEPOLYTENIZATION OF SECONDARY GIANT TROPHOBLAST CELLS OF THE FIELD VOLE
MICROTUS ROSSIAEMERIDIONALIS BY CYTOPHOTOMETRIC MEASUREMENT OF THE HETEROCHROMATIZED GONOSOMAL CHROMATIN
BODIES
E. V. Zybina, M. S. Bogdanova, T. G. Zybina, G. I. Stein
Institute of Cytology, RAS, St. Petersburg, Russia;
e-mail: zybina@mail.cytspb.rssi.ru
A study was made of the distribution of the heterochromatized gonosomal chromatin bodies (GCB) material in the
course of nuclear fragmentation of secondary giant trophoblast cells resulting in polykaryocyte formation at the late stage of
their differentiation. A simultaneous DNA cytophotometry in GCBs and nuclear fragments showed a progressive GCB DNA content
decrease proportional to that of DNA content in nuclear fragments. DNA contents in the nuclear fragments corresponded to
2ñ, 4ñ and 8ñ. In most cases 1-2 GCBs were found in the nuclear fragments of different ploidy levels. Both
the total DNA content in GCBs and the DNA content in separate GCBs well correlated with the ploidy levels of fragments. The data
obtained demonstrate a regular, whole-genome distribution of chromosomal materials into the nuclear fragments exemplified by sex
chromosome distribution in compliance with the ploidy of nuclear fragments. We discuss a possible mechanism of nuclear
fragmentation that may ensure substantially a balanced genome of nuclear fragments without leading to mitotic cycle renewal in
the giant trophoblast cell population.
Key words: heterochromatin, sex chromosomes, endoreduplication, depolyploidization, nuclear fragmentation,
trophoblast, mammals
Back
Contents
Main
