Reversibility of lipofuscin accumulation caused by protein malnutrition in the motor cortex of squirrel monkeys, Saimiri scireus.

Lipofuscin pigment has been demonstrated histochemically in the motor cortex by the use of several histochemical and cytochemical methods in the healthy (maintained on a diet with 25% protein content) and protein malnourished (maintained on a diet with 2% protein content) adult animals. 4 animals in the latter category were rehabilitated over a period of 11 months and various histochemical techniques were repeated on the motor cortex of these animals. The healthy animals showed a somewhat uniform distribution of lipofuscin pigment in the neuronal perikarya with the perineuronal glia showing only slight occurrence of pigment bodies. The malnourished animals exhibited a significantly larger number of lipofuscin bodies in the neuronal as well as glial perikarya. The neurons, especially, showed aggregations of lipofuscin bodies characterized by a large increase in the activity of acid phosphatase and simple esterases. The rehabilitated animals, however, showed a decrease of lipofuscin pigment in the neuronal perikarya with a concomitant loss of lysosomal enzymes, while a significant increase of these bodies was observed in the perineuronal glial cells. It is evident that the formation of lipofuscin pigment gets accelerated under the extrinsic influence of dietary protein deprivation in the adult animals, but the process is reversed at least to some extent by halting the dietary deficiency or its correction by rehabilitation. The perineuronal glial cells appear to play a significant role in the removal of lipofuscin bodies from the neuronal perikarya. The significance of these observations has been discussed.