Experimental protein malnutrition in primates: Cytochemical studies on the cerebellum of the squirrel monkey,Saimiri Sciureus

Synopsis The cerebellum of healthy and malnourished squirrel monkeys was studied histopathologically and cytochemically for a number of important enzymes such as phosphatases (acid and alkaline phosphatase, ATPase, thiamine pyrophosphatase), esterases (simple esterase and acetylcholinesterase), dehydrogenases (succinate, malate and isocitrate dehydrogenase, lactate dehydrogenase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase), monoamine oxidase and phosphorylase. The Purkinje cells, stellate and basket cells were found to be more sensitive to protein malnutrition compared to the other types of cells in the cerebellum. An increase in the number of dark cells with large amounts of ribonucleoprotein complex in the Purkinje cell layer of the extremely malnourished animals sacrificed after 15 weeks on a low protein diet may be significant and may reflect either an abnormal metabolic process or an interruption in the axonal transport of RNA complex. This may also be directly related to a significant reduction in the level of oxidative enzymes, especially those of the tricarboxylic acid cycle, these being the main source of energy stored in ATP. At the same time the level of lysosomal enzymes, which are responsible for the catalysis of the different degradation reactions, is greatly increased and indicates cellular catabolism. The present investigations point to the probability that the neurons adapt to the changed environment by beginning to utilize structural proteins for their basic metabolism.