Deficiency of a naturally occurring protein inhibitor in brain of clinically 'brain damaged' newborn human infants - a possible cause of mental retardation?

The presence of an inhibitor of guanine deaminase in the 'heavy' mito-chondrial fractions of rat brain homogenates has been reported. The results of the present study, using brain homogenates from normal infants who died between ages 1-6 months, low birth weight infants who were brain damaged and died between ages 2 days-4 months and premature (7-8 months pregnancy) infants, who were considered clinical cases with acute brain damage and died 1-3 days after birth, indicate that while normal human brain contains the inhibitory material, it is conspicuously absent from the particulate fractions of brain damaged low birth weight and premature infants. Since brain damage at birth in an infant could result in mental retardation of some kind on development, a possible relationship between deficiency or absence of the inhibitory material of guanine deaminase in human brain and mental retardation is suggested.