Cell-cycle-dependent three-dimensional redistribution of nuclear proteins, P 120, pKi-67, and SC 35 splicing factor, in the presence of the topoisomerase I inhibitor camptothecin.

Topoisomerase I (Topo I) is mostly known for its role in DNA relaxation, which is required for duplication and transcription. Topo I acts as a protein kinase mainly directed to the mRNA splicing factor SC35. Camptothecin is one of the specific Topo I inhibitors and is effective on the two functions of the enzyme.

Increased functional load on mouse kidney proximal tubule epithelial cells causes changes in nucleolar 3-D architecture.

Ultrastructural 3-D analysis of nucleolar architecture and Ag-NOR protein distribution in mouse kidney-cortex proximal-tubule epithelium has been performed. A principal scheme of structural changes of the nucleolus and organization of its components during the intensification of pre-rRNA synthesis (dynamic model of a nucleolus) based on computer spatial modelling has been advanced. According to the nucleolar composition, three groups of cells, which differ from each other by rRNA synthesis, are defined in normal kidney.

[The dependence of the 3-dimensional organization and length of the nucleolonema in the hepatocyte nucleoli of normal and regenerating rat livers on the nucleosome structure of the intranucleolar chromatin].

A biochemical and ultrastructural stereo-morphological analysis, with special reference to spatial organization and length of nucleonema and Ag-positive zones, was performed for various modifications of nucleolonemal type nucleoli in normal and regenerating (6 and 22 hours after partial hepatectomy) rat hepatocytes. To determine possible disorders on nucleosomal and supranucleosomal levels, chromatin DNA degradation was carried out during micrococcal nuclease hydrolysis, followed by analysis of electrophoretically separated particles. Functional characterization of intranucleolar chromatin was performed by testing the rate of DNA degradation after DNAase I treatment as well as by detection of free G-C pairs during titration with actinomycin D.

Transcriptional activity and ultrastructure of morphologically different types of nucleoli isolated from hepatocytes of normal and hepatectomized rats.

Morphologically different types of nucleoli were isolated from liver of normal and partially hepatectomized rats, to allow their ultrastructure and transcriptional activity to be precisely correlated. Transcriptional activity was estimated from the intensity of incorporation of [14C]-UTP during periods of maximal RNA-polymerase I activity. RNA synthesis in hepatocyte nucleoli was maximal at 6 and 22 h after partial hepatectomy.

[The 3-dimensional organization of the nucleolus and nucleolus-organizer regions of differentiated cells. IV. The structural and functional heterogeneity of the nucleoli in the epithelium of the proximal nephron in the mouse].

By means of stereological and morphometrical analysis, the ultrastructure of nucleoli in epitheliocytes of mouse kidney cortex proximal tubuli has been studied. In accordance to the nucleolar composition, three main groups of nephrocytes with different levels of rRNA and protein synthesis were defined. Functional heterogeneity of proximal tubuli epithelium was established by correlation between different variants of ultrastructural organization of nucleoli and the total RNA synthesis activity, determined by 3H-uridine incorporation intensity.