Electroencephalographic findings in children with phenylketonuria

The electroencephalographic findings of 90 patients with phenylketonuria (PKU) who were observed in one clinic were critically reviewed. Seventy-three percent of patients with classical PKU that was diagnosed and treated early (group 1) were found to have normal EEGs, 23% had mild background abnormalities, and 4% had paroxysmal discharges. Only 31% of the patients in whom PKU was diagnosed after 6 months of age (group 2) had normal EEGs, while 24% had background abnormalities and 45% had paroxysmal discharges. Of the patients with atypical PKU (group 3), 62% had normal EEGs and 38% showed background abnormalities. No major changes in EEG patterns were noted with initiation or termination of the low phenylalanine diet. There was no correlation between the degree of dietary control, EEG findings, and intellectual performance in group 1.

An abnormality in sebaceous function in phenylketonuria

The sebum excretion rate has been found to be increased in female patients with phenylketonuria. This may be related to a depletion of midbrain dopamine and release of the sebotrophic hormone.

The isolation and properties of phenylalanine hydroxylase from human liver

Phenylalanine hydroxylase was prepared from human foetal liver and purified 800-fold; it appeared to be essentially pure. The phenylalanine hydroxylase activity of the liver was confined to a single protein of mol.wt. approx. 108000, but omission of a preliminary filtration step resulted in partial conversion into a second enzymically active protein of mol.wt. approx. 250000. Human adult and full-term infant liver also contained a single phenylalanine hydroxylase with molecular weights and kinetic parameters the same as those of the foetal enzyme; foetal, newborn and adult phenylalanine hydroxylase are probably identical. The K(m) values for phenylalanine and cofactor were respectively one-quarter and twice those found for rat liver phenylalanine hydroxylase. As with the rat enzyme, human phenylalanine hydroxylase acted also on p-fluorophenylalanine, which was inhibitory at high concentrations, and p-chlorophenylalanine acted as an inhibitor competing with phenylalanine. Iron-chelating and copper-chelating agents inhibited human phenylalanine hydroxylase. Thiol-binding reagents inhibited the enzyme but, as with the rat enzyme, phenylalanine both stabilized the human enzyme and offered some protection against these inhibitors. It is hoped that isolation of the normal enzyme will further the study of phenylketonuria.

Effects of totally synthetic, low phenylalanine diet on adolescent phenylketonuric patients

The long-term responses of 5 adolescent phenylketonuric patients to chemically-defined, synthetic diets with normal and low phenylalanine content were determined. The synthetic preparations were found capable of sustaining good health and rapid growth in this group of profoundly retarded, behaviourally disturbed patients over a 3½-year period without clinical or biochemical evidence of nutritional inadequacy. 4 of these patients who were treated for 6 months on a comparable diet, in which 80% of the phenylalanine was replaced by tyrosine, continued to show weight maintenance and height increases. There was no evidence of poor acceptability of the imbalanced diet, whether the blood phenylalanine concentrations were at phenylketonuric or treatment levels. The phenylalanine intake required to maintain blood phenylalanine concentrations of 3-5 mg/100 ml in these 4 patients was well below normal requirements, and ranged between 6·8 and 20·1 mg/kg per day. Predictably, the phenylalanine requirement varied with individual growth rates. All 4 treated patients had objective signs of improved central nervous system function during the six-month period on the phenylalanine-restricted diet. These electrophysiological and behavioural improvements were manifest after blood phenylalanine concentrations fell below 12 mg/100 ml in 3 cases and below 5 mg/100 ml in the fourth.

Eye movement ativity during sleep and intellectual function in mental retardation

A positive relation was found between the amount of eye movement during rapid-eye-movement or paradoxical sleep and estimates of intellectual level in a group of retarded adults. This result supports the hypothesis that during sleep the brain carries out processes important for cognitive function.