DYNAMICS OF MORPHOFUNCTIONAL ORGANIZATION AND DEVELOPMENTAL POTENTIAL OF MOUSE EMBRYOS IN THE STATE OF
"TWO-CELL BLOCK IN VITRO"
N. A. Bogolyubova, I. O. Bogolyubova
Institute of Cytology RAS, St. Petersburg;
e-mail: ibogol@yahoo.com
Vital observation in combination with electron microscopy and immunocytochemistry was used for studying
structural organization and developmental potential of BALB/c mouse embryos after cleavage cessation at a two cell
stage caused by the "two-cell block in vitro" phenomenon. Modification of structure and viability of embryos
was followed for 2 days from the time of cleavage arrest. Several hours before cleavage arrest, changes in
mitochondrian distribution were noticed in embryos, no other disturbances in structural organization of blastomeres
being obvious. Embryos, whose development was arrested for 24 h, remained viable and demonstrated some morphological
changes similar to those seen in normally developing embryos of the same age. Towards the end of a 48 h block period
some embryos died, the surviving embryos remained morphologically intact and metabolically active. At the same time,
the nuclei of the latter frequently displayed chromatin condensation near the nuclear membrane, which is similar to
the pattern of chromatin reorganization in the nuclei of early apoptotic cells. Our results support a concept on the
"two-cell block in vitro" phenomenon as a specific functional state of embryos, and well compare with data on
a partial realization by blocked embryos of the developmental program.
Key words: mouse embryos, preimplantation development, "two-cell block in vitro",
developmental potential, ultrastructural organization
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