title: [Morphometric study of nucleolus-organizing regions of chromosomes from swine embryo kidney cells during Go-, G2-period and mitosis].
abstract: Quantitative characteristics of nucleolus-organizing regions of chromosomes (NORs, or fibrillar centers, FCs) and some other nucleolar components have been studied with the aid of complete series of ultrathin sections of PK-cells. It has been found that: 1) the number of FCs per cell in the G0-period, in the G2-period and at metaphase is equal to 7.0, 33.7 and 8.0, respectively; 2) volumes of individual FCs in the G0-period (0.033 micron 3), G2-period (0.014 micron 3) and at metaphase (0.025 micron 3) are different; 3) the total volume of FCs, calculated for a haploid set of chromosomes, do not differ in the G0 (0.105 micron 3) and G2 (0.107 micron 3) periods, but exceed twice the FCs volume at metaphase (0.04-0.05 micron 3). These data show that the activation and inactivation of ribosomal genes in interphase PK-cells are not accompanied by a change in the total volumes of FCs and are probably connected with the "fragmentation" and fusion of FCs. Complete inactivation of ribosomal genes at mitosis leads to a decrease in the total volumes of FCs; 4) the nucleolus volume is proportional to the volume of the dense fibrillar RNP-component; in the G2-period the nucleolus volume also correlates with the number of FCs (r = 0.99); 5) the volume of the dense fibrillar component within individual fibrillar complexes--the structures corresponding to one nucleolus-organizing region--is not constant. This is an indirect evidence for the differences in the functional activity of NORs of different chromosomes.
authors.forename: O V
authors.initials: OV
authors.lastname: Zatsepina
authors.forename: P
authors.initials: P
authors.lastname: Hozak
authors.forename: D P
authors.initials: DP
authors.lastname: Babadzhanian
authors.forename: Iu S
authors.initials: IuS
authors.lastname: Chentsov
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002875:Chromosomes / Q000648:ultrastructure*; D007399:Interphase; D007668:Kidney; D008938:Mitosis; D009697:Nucleolus Organizer Region / Q000648:ultrastructure*; D013552:Swine
vernacular_title: Morfometricheskoe izuchenie iadryshkoobrazuiushchikh raĭonov khromosom kletok SPEV v Go-periode, v G2-periode i v mitoze.