Phenylketonuria in Infant Monkeys

Learning in Monkeys Fed Elevated Amino Acid Diets

“…The problems were given in that order except where noted otherwise, and were preceded by weeks of extensive adaptation to the testing apparatus [13]. This adaption consisted of free food from the object-presentation tray and displacement of single objects from under which food rewards could be obtained.…”

“…The neonates were housed in individual cages and offered Similac [11] (Ross Laboratories, Columbus, Ohio), a modified milk diet for human infants, every 4 h. At 1 week of age the experimental diet was initiated [13] by the addition of an excess of one amino acid to the Similac diet. The amount of amino acid added was increased as rapidly as possible so as to obtain the desired dietary intake.…”

“…As these data were not yet available when the report of growth and preliminary learning results were published [8], they provide information on comparable evaluation tests with the other malnourished monkeys. Apparatus and conditions of rearing, housing, and feeding are discussed in greater detail elsewhere [3,9,13]. The apparatus used in behavioral testing was the standard Wisconsin general test apparatus [1,4], This device contains a movable board on which pairs of objects are placed over a receptacle for food rewards.…”

“…A preliminary report of subnormal food-motivated learning perfor mance [13] in six monkeys with experimental PKU and a subsequent report of abnormalities in both shock-motivated learning and social behavior in four other PKU monkeys [2] were the basis for a more exhaustive study of rhesus monkeys (a) fed diets containing elevated levels of phenylalanine for varying periods of time during infancy; (b) raised on a diet containing elevated levels of parachlorophenylalanine which leads to elevated blood levels of phenylalanine through in hibition of the enzyme which metabolizes phenylalanine; (c) reared on diets containing elevated levels of certain other amino acids; and (d) reared from birth on normal diets but whose mothers were fed diets containing excess phenylalanine during pregnancy.…”

Nutrition in relation to phenylketonuria

“…Any amino acid is toxic if given at levels high enough greatly to raise its concentration in the blood ; an example is phenylalanine in phenylketonuria. Waisman, Wang, Palmer & Harlow (1960), by giving very high levels of phenylalanine to monkeys, reproduced not only the metabolic features of phenylketonuria, but also produced psychological disturbances resembling, to some extent, the clinical features of phenylketonuria. At high concentrations, several amino acids interfere with the metabolism of other, unrelated, amino acids, thus in phenylketonuria the metabolism of tryptophan is interfered with, causing the excretion of indolyllactic and indolylacetic acids.…”