Change in size, number and morphology of the nucleoli in human hearts as a result of hyperfunction.

In the present study we examined light-microscopically the nuclei of 16 hearts (7 normal hearts, 7 hearts with hypertrophy and 2 hearts with atrophy) for the size, number and morphology of their nucleoli. The size of the nucleoli, defined as the total area of all nucleoli per nucleus, was an early and sensitive indication of a beginning hypertrophy of the myocardium. It increased in parallel to the total heart weight and to the total area of the nucleus of the cell, but initially the size of the nucleoli changed earlier than the other parameters. We found an increase of the ratio in the total area of the nucleoli per nucleus to the total area of the nucleus at the beginning of clinical hyperfunction. This ratio normalised during chronic hyperfunction. The number of the nucleoli also increased during hyperfunction, but it did not exceed the number of nucleolus organiser regions (NOR) given by the number of chromosomes. Nevertheless, we found numbers of nucleoli higher than 10 because, the number of NORs increases during polyploidization. Regarding the morphology of the nucleoli in hearts with hypertrophy, we found a predomination of the nucleoli with a highly branched nucleolonemal structure as an indication of an increased RNA synthesis.