[Limits of several cell nucleus reactions in old age and in the presence of a pathological process]

The number of nucleoli and the structure of nucleolus-associated chromatin (determined by the number of perinucleolar chromocentres) was investigated in two groups of mice. The first group was control, and the second one--experimental, given CCl4 injections once a week, for one year. A gradual increase of the number of nucleoli and chromocentres bound with nucleoli was revealed with ageing in control mice. In the experimental group both indices quickly reached the maximum which was equal or even higher than in old control mice. The subsequent development of the pathological process failed to alter these indices. Possible mechanisms limiting the range of the mentioned changes of the nuclei are discussed.