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Morphologic changes in cerebellar mitochondria during aging.

OBJECTIVE
To seek age-dependent morphofunctional changes in mitochondrial metabolic competence in the rat cerebellum.


STUDY DESIGN
Three-, 12- and 24-month-old female Wistar rats were used for the present study. Each group consisted of five animals. The cytoplasmic fraction occupied by mitochondria (volume density, Vu), number of organelles per cubic micrometer (numerical density, Nu) and mitochondrial average volume (V) were measured in Purkinje cell perikaryal organelles histochemically stained to reveal succinic dehydrogenase activity in the three groups analyzed.


RESULTS
Vu did not show significant differences due to age. Nu was constant between 3 and 12 months of age but decreased significantly in old rats. V did not show significant age-dependent differences.


CONCLUSION
The present findings further extend the results of our previous studies on the ultrastructure of synaptic mitochondria and support the concept of marked metabolic impairment as a basal detrimental condition in the process of brain aging. As a marker of metabolically active mitochondria at high rates of cellular respiration, our present data document that with advancing age the number of efficient organelles decreases and that this may be of critical importance for the proper function of nerve cells when the energy demand is high.