[Actin localization in the nuclei of two-cell mouse embryos].

In this study, preimplantation mouse embryos were used as a new model for investigation of actin distribution in the nuclei and identification of functional forms of intranuclear actin. Combination of direct detection of actin by fluorescent-conjugated falloidin and DNase I with the method of indirect immunofluorescence was applied as an integrated approach to study localization of actin in the nuclei of two-cell mouse embryos. Monomeric actin and two oligomeric forms of actin were detected in the nuclei, and each of these forms demonstrated its own pattern of distribution.

Nuclear structure in early mouse embryos: A comparative ultrastructural and immunocytochemical study with special emphasis on the "2-cell block in vitro".

The embryos from many outbred and inbred strains of mice are arrested at the late 2-cell stage when cultured in vitro in simple culture media. This phenomenon is referred to as the "2-cell block in vitro". The ultrastructural morphology of the nuclei of the blocked embryos is not yet well described.

[Dynamics of morphofunctional organization and developmental potential of mouse embryos in the state of "two-cell block in vitro"].

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.

[Changes in the distribution of mitochondria in mouse embryos blocked at the two-cell stage].

Changes in the distribution of mitochondria in the two-cell mouse embryos preceding the developmental arrest in vitro, caused by a genetically determined "two-cell block in vitro" or genisteine treatment, were examined vitally using the mitochondrial-specific probe rhodamine 123 and conventional fluorescence microscopy. In the former case, serious disturbances in the localization of mitochondria appeared already from the middle of two-cell stage, long before the time corresponding to the 2nd cleavage division. Comparison of the behavior of mitochondria in the embryos successfully developing between the one- and two-cell stages and that in the embryos that ceased to cleave suggests that the developmental arrest was accompanied by aggregation of the mitochondria into clusters.

[Characteristic of structural and functional organization of two-cell mouse embryos exposed to inhibitors of cell proliferation].

Within the framework of studying the "2-cell block in vitro" phenomenon, two variants of inhibitory-induced stoppage of development at a two-cell stage were produced and analysed. Mimosine arrested the cleavage on the G1/S interface, and genistein at G2 stage of the second cell cycle. In the experimentally blocked embryos a detailed study was made of the ultrastructural organization of blastomeres and intracellular localization of mitochondria vitally stained with rhodamine 123.