Morphometry of nuclei, nuclear envelopes and nucleoli in aging hamster cerebrum.

The neuronal nucleus and nucleolus undergo extensive dimensional and configurational changes during maturation and aging, as shown in this study of pyramidal cells of the hamster motor cortex. With maturation, the increase in nuclear perimeter length per unit nuclear area was associated with an increased amount of nuclear invaginations. With maturation and aging, there was a change in nuclear caliper shape, from spherical to very nonspherical. The number of nucleoli containing microbodies peaked first at 15 days and again at 600 days. It is concluded that area, perimeter and form factor relate to nuclear caliper shape and the presence of nucleolar microbodies. The correlated changes in these parameters appear to differentially reflect stage-specific metabolic conditions related to two critical phases: (1) an early phase (10-15 days) at the inception of configurational changes leading to maturity, and (2) a late phase (600-700 days) at the inception of configurational changes leading to old age.