[Electron microscope study of chromatin in nuclei of rat hepatocytes during age-related changes in the genome]

On ultrathin liver sections, condensed chromatin of rat hepatocyte nuclei was studied. The animals were 2 days, 6 and 28 months old. It was established that neither maturation nor senescence were accompanied by the change of the relative square of total condensed chromatin. Relative square of perimembrane, nucleoplasmic and perinucleolar condensed chromatin were non changed either. Intensively proliferating hepatocytes of nascent animals were characteristic of maximal values of the following parameters (i) the relative length of the perimembrane condensed chromatin boundary with nucleoplasma. (ii) amount of chromatin clumps, (iii) the relative length of the nuclear membrane without condensed chromatin. For mature animals all these parameters are significantly decreased. For old rats as compared with mature ones the following parameters are significantly diminished: (i) the relative length of the perimembrane chromatin boundary with nucleoplasma, (ii) the relative length of the nuclear membrane without condensed chromatin, (iii) the mean square of the nucleolus. So, the known diminishing of the RNA synthesis at senescence is expressed morphologically in margination of condensed chromatin, in smoothing of the condensed chromatin surface responsible for the hnRNA synthesis and also in diminishing of the nucleolus responsible for the rRNA synthesis.