Seasonal changes in the nucleoli of Purkinje cells of the hedgehog cerebellum.

A relationship between size and shape of nucleolus and cellular metabolic demands can be seen from measurements of Purkinje cell nucleoli in cerebellar hemispheres during the annual cycle of the hedgehog. During hibernation, nucleoli are smaller than during activity. The extent of the associated heterochromatin increases from activity to the beginning of hibernation. Moreover, during activity it is mostly distributed in small masses all around the nucleolus, while during hibernation it is clumped in a single mass. Data indicating a lesser protein synthesis by neurons during hibernation agree with electrophysiological indications that during hibernation the cerebral cortex, linked to the cerebellar hemispheres via afferent systems, is silent.