Experimental protein malnutrition in primates: electronmicroscopic observations on the cerebellum of healthy and malnourished squirrel monkeys (Saimiri sciureus).

Eight young adult squirrel monkeys were maintained on a protein deficient (2% calories from proteins) diet for a period of 15 weeks during which the animals lost wieght steadily and developed varying degrees of sensory and motor impairments as evidenced by lack of interest in the surrounding environment and changes in posture and gait. An additional eight animals were maintained on a high protein diet (25% calories from proteins) to serve as controls. Two animals each from the experimental and control groups were sacrificed at 9, 11, 13 and 15 weeks of special feeding schedule. The Purkinje cells of the cerebellum of malnourished animals showed significant changes in the ribosomes, endoplasmic reticulum and Golgi zone indicating greatly disturbed protein metabolism. The granule cells, especially of the pale variety show prominent watery swellings with scant cell organelles. The most prominent change appeared in various types of neurons related to the multiplication of various types of lysosomes, multivesicular lamellar bodies and the lipofuscin pigment bodies. In the animals sacrificed at different intervals, the relatively more malnourished animals showed significantly larger number of lipofuscin pigment in the various types of neurons of the cerebellar cortex. The dendritic changes included honey-comb formation in the lumen. The astrocyte glial fibers were greatly increased. The pericytes of the blood vessels showed irregular outlines and were greatly enlarged with numerous osmiophilic bodies (presumably lipofuscin) in the experimental animals as compared to the controls.