Ultrastructural pattern of brain aging in normal rabbit and in pt mutant.

The aim of the study was to compare ultrastructural brain changes in aging normal rabbits and in pt mutants with CNS hypomyelination. The study was performed on material of pt and healthy 3- and 4-year-old rabbits and on the control group of adult rabbits aged up to 2 years. Ultrastructural changes in both aging normal and pt rabbits included lipofuscin accumulation in glial and nerve cells, wide extension of astrocytic processes around vessels and in neuropil, thinning of capillary endothelial and their lumen distension, neuroaxonal dystrophy and incidence of degenerated dendrites and synaptic terminals. These changes, especially degeneration of axons and dendrites were much more frequent in the pt mutants than in normal rabbits. Moreover, myelin sheath abnormalities, similar as in younger pt rabbits were a characteristic feature in the aging mutants, whereas, the myelin in aging normal rabbits was well preserved, probably because the white matter changes are rather a later event in senescence. It is concluded, that with the exception of white matter affection in mutants, the age-related changes do not vary much qualitatively between pt and normal rabbit, although they are distinctly enhanced and develop earlier in mutants. Further studies are needed for evaluation of the influence of the aging process on the white matter changes in association with pt mutation and under normal conditions in animals of more advanced age.