Electron-microscopic morphometric analysis of mouse liver. II. Effect of ageing and thymus transplantation in old animals.

The influence of age and thymus on liver cells has been investigated by performing a complete morphometric analysis. The age-dependence was tested in three groups of mice aged 2, 12, and 24 months, while the action of the thymus was studied on 24-month-old mice grafted with neonatal thymus 30 days before the analysis was performed. Among the investigated parameters, the most considerable changes were found in the mean nuclear volume, which displayed a significant increase during ageing. The thymus was capable of reversing such an age-dependent increase when grafted into old animals. The volume of single hepatocytes also displayed an age-dependent increase which was not corrected by thymus grafting. The data presented suggest that the thymus influences the mitotic activity of the hepatocytes and further support the hypothesis that the thymus also plays an important role in non-immunological processes of ageing.