Comparison of free amino acids in capillary and venous blood serum of children and adolescents with phenylketonuria and leucinosis]

Concentrations of free amino acids were determined quantitatively by ion exchange column chromatography in serum from capillary and venous blood of children and adolescents with phenylketonuria (n = 38) and leucinosis (n = 3). Serum was deproteinised by 5% sulphosalicylic acid (1:1, v/v). The results showed with exception of aspartic acid, glutamine and glutamic acid a very close correlation. The correlation coefficients ranged from 0.849 to 0.996. It is concluded that serum from capillary blood can be used for screening of amino acid metabolism.     

Plasma amino acids in phenylketonuric children treated either with phenylalanine-free amino acids or a protein hydrolysate

The plasma amino acid concentrations were measured in 10 children with phenylketonuria (PKU) on the phenylalanine-free amino acid mixture Phenyldon and 9 PKU children on the phenylalanine-free protein hydrolysate Albumaid. The blood samples were taken fasting and two hours after the meal. The individual amino acid concentrations, the glycine/valine ratios, and the total amino acid concentrations were mutually compared and also compared to reference intervals. No differences of the concentration of phenylalanine on the two diet formulas were observed. Children on Phenyldon showed fasting and postprandial isoleucine higher than the reference intervals. Furthermore, a postprandial increase of several amino acids was observed on both diet formulas. This response was statistically significant in children on Phenyldon.     

Renal transport of amino acids in children with oculocerebrorenal syndrome

Inulin and amino acid clearance studies were made in 6 boys with oculocerebrorenal syndrome (Lowe) aged 11 months to 5 years. Glomerular filtration rate ranged between 50 and 112 ml/min/1.73 m2. Clearance values of all amino acids were increased. Tubular reabsorption of cystine, ornithine, lysine and arginine was relatively more reduced than that of the other amino acids. In Lowe's syndrome the transport system of the basic amino acids and cystine appears to be more impaired than that of other amino acids.     

Excretion of urinary amino acids in children with postural proteinuria

The urinary excretion of free amino acids was studied in urine specimens from 12 subjects with postural proteinuria in recumbent posture and after a period of upright lordotic posture. The lordotic posture produced an increased urinary excretion of total amino acid and 12 amino acids, particularly of taurine, glutamic acid, a-amino adipic acid, valine, leucine, ethanolamine and arginine. However, 90 min after the lordotic posture, all amino acids returned to the initial values. Although, many factors must be considered in the evaluation of the urinary excretion of amino acids, an increased urinary excretion of amino acids occurring after the lordotic posture may be the result of reabsorption disturbance of the renal tubules.     

Visual event-related potentials in children with phenylketonuria

Visual event-related potentials (ERPs) were examined in 16 children (aged 5-14 y) with phenylketonuria (PKU) and 16 age- and sex-matched controls. Lifetime median measures of phenylalanine (Phe) were 230-460 μmol/l. The most recent Phe levels were 56-624 μmol/l. ERPs were recorded whilst the children performed a discrimination task. All stimuli were square wave gratings degree, which appeared for 33 ms. A response to an infrequent grating that differed in orientation or spatial frequency was required. The older children with PKU had a delay in the first peak (P1) of the ERP, and age-related changes in the amplitude of P1. There was attenuation of the second peak across age groups in PKU. There was no evidence of reduced response accuracy or longer reaction times in children with PKU. Latencies of the cognitive P3 were not delayed in PKU. The delayed early peaks are consistent with previous studies that have shown delayed visual evoked potentials in PKU. The lack of differences in reaction time and P3 may be due to relatively good Phe control in children with PKU, or to the simplicity of the task. Suggestions are made for future ERP studies of PKU.     

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.