Birth weight and pathogenesis in phenylketonuria.

The birthweights of an ethnically homogeneous sample of infants with phenylketonuria, their unaffected siblings, and control infants were compared after adjusting for the effects of: mother's age, mother's date of birth, mother's height and obstetric history, the length of gestation, the infant's sex, the place and date of birth. There were no significant differences between the infants with phenylketonuria and their unaffected siblings either in adjusted or unadjusted birthweights. Control infants had slightly, but statistically significant, greater adjusted and unadjusted birthweights than the combined phenylketonuria and unaffected sibling groups. This effect of the phenylketonuria gene is a previously unreported finding but unlikely to be related to the pathogenesis of phenylketonuria. Our results do not provide support for the "justification" hypothesis that the mental and neurological defects in phenylketonuria result from prenatal tyrosine deprivation which would be reflected in lower birthweights.

Insulin decreases muscle protein loss after operative trauma in man.

Seventy-two hours after major operative trauma, nine patients receiving a constant infusion of calories (1460 kcal/m2/day) and protein (75 gm of amino acid/m2/day) showed a negative nitrogen balance, increased muscle catabolism, as measured by 3-methylhistidine excretion, increased amino acid efflux from muscle, and decreased circulating levels of insulin. When 5 U of insulin/hr were added to the infusate, arterial insulin levels rose significantly from 39.7 +/- 4.1 microU/ml to approximately the pretrauma levels (74.6 +/- 7.7 microU/ml). Despite this normalization of insulin levels, excretion of nitrogen and 3-methylhistidine and the efflux of amino acids from forearm muscle fell but did not return to pretraumatic levels, suggesting some insulin resistance. Visceral gluconeogenesis from amino acids appeared to decrease, since insulin infusion decreased the efflux of alanine from skeletal muscle with no change in its arterial level. Insulin also significantly reduced the efflux of isoleucine, tyrosine, phenylalanine, glutamine, and total amino acid nitrogen from forearm muscle. These findings, along with the partial reduction in the excretion of 3-methylhistidine and nitrogen, suggest that insulin, in combination with infused calories and protein, decreases the loss of muscle protein after trauma.

Major operative trauma increases peripheral amino acid release during the steady-state infusion of total parenteral nutrition in man.

The effect of major operative trauma on skeletal muscle metabolism was examined in nine patients receiving a constant infusion of calories (1460 kcal/m2/day) and protein (75 gm of amino acids/m2/day) for 5 days before and 4 days after an operation. Compared with the preoperative state, 72 hours after the operation there was a significant rise in arterial levels of glucagon, cortisol, norepinephrine, and inactive triiodothyronine and a drop in concentrations of insulin, active triiodothyronine, and amino acids. Forearm blood flow increased, as well as the efflux from forearm muscle of lactate, taurine, serine, glycine, valine, methionine, isoleucine, leucine, phenylalanine, lysine, arginine, and total amino acid nitrogen (440%). This loss of muscle protein after trauma is associated with increased muscle proteolysis, as measured by increased urinary 3-methylhistidine excretion (83%), and accounts for increased nitrogen loss (54%) from the body. Increased activity of the sympathetic nervous system is manifested by increased levels of epinephrine and norepinephrine, a relative lack of insulin, and increased levels of glucagon. This hormonal milieu plays an important role in the production of hypoaminoacidemia, increased efflux of amino acids and lactate from muscle, and negative nitrogen balance observed in these traumatized patients.

Metabolism of branched-chain amino acids in dogs with Escherichia coli endotoxin shock.

The arterial-femoral venous difference of phenylalanine concentration is proportional to net proteolysis in the leg. In ten fasting dogs receiving Escherichia coli endotoxin (2 mg/kg) intravenously, the mean systolic blood pressure decreased from 141.1 +/- 25 to 71.5 +/- 17 mm Hg. The absolute net release from the leg of valine, isoleucine, and leucine and their net release relative to net proteolysis (arterial-femoral venous difference in concentration of each branched-chain amino acid relative to that of phenylalanine) were decreased, indicating increased transamination of these amino acids in skeletal muscle. However, the net release of the branched-chain alpha-keto acids formed by transamination, relative to net proteolysis (arterial-venous difference in concentration of each alpha-keto acid relative to that of phenylalanine), was not increased. The findings indicate that in dogs with E. coli endotoxin shock, there is increased oxidative decarboxylation in muscle of the alpha-keto acids derived from valine, isoleucine, and leucine.

Estimation of branched-chain alpha-keto acids in blood by gas chromatography.

Plasma or whole blood is treated with o-phenylenediamine dihydrochloride in phosphoric acid under conditions found spectrophotometrically to give maximum yields of the quinoxalinols. The quinoxalinols are extracted and, after removing phosphoric acid, etc., silylated with bis-trimethylsilyltrifluoracetamide in acetonitrile. Other solvents caused instability of the trimethylsilyl(TMS)-quinoxalinols. Gas chromatography on a packed column of trifluoropropyl silicone gave good separation of the TMS-quinoxalinols from one another and from other substances derived from blood. Some representative values for normal arterial and venous human and canine plasma are reported.

Amino acid metabolism in patients with severe burns.

In this study we set out to determine, if relative to net catabolism of skeletal muscle protein as measured by phenylalanine release, the transamination of branched-chain amino acids (valine, isoleucine, and leucine) was greater in nonseptic burn patients than in controls. Arterial and femoral venous amino acid concentrations and circulating liver enzyme levels were measured. When the ratio of the arterial-femoral venous difference in concentration of each branched-chain amino acid to that of phenylalanine was determined, transamination of the branched chain amino acids, relative to net proteolysis, was not occurring at a greater rate in the burn patients. The net release of alanine relative to that of phenylalanine was not significantly greater in the burn patients, consistent with the conclusion that relative to the net rat of proteolysis, transamination of branched-chain amino acids in skeletal muscle is not increased in burn patients. This finding differs from that in septic dogs and septic humans. The mean arterial-femoral venous differences in concentration of alanine, valine, isoleucine, leucine, and phenylalanine were greater in the burn patients (P less than 0.03), indicating increased proteolysis in this group.

Arterial plasma amino acids during the first week following femoral shaft fracture.

In ten patients with a femoral shaft fracture, arterial plasma amino acids and glucagon, blood glucose, and serum insulin were measured after an overnight fast on the third, fifth, and seventh days following injury. Ten normal subjects were controls. On all days, concentrations of the key glucogenic amino acid, alanine, were the same in both groups, but levels of another glucogenic amino acid, glycine, were significantly less in the fracture patients. Other amino acid changes following injury were maximal at 7 days, with significant elevations of phenylalanine, methionine, tyrosine, ornithine, lysine, arginine, valine, isoleucine, and leucine. Increased levels of insulin, glucose, valine, isoleucine, and leucine on the fifth and seventh days after injury implied insulin resistance. Plasma glucagon was elevated on the third (p less than 0.05) and seventh (p less than 0.01) days after injury, but the concentrations measured are insufficient to explain the impaired carbohydrate tolerance following a fracture.

Femoral arteriovenous amino acid differences in septic patients.

Femoral arteriovenous differences and flux of amino acids across the leg were measured in seven septic patients and compared with those of six nonseptic patients on days 1 and 3 following major surgery. The septic patients were seriously ill and judged clinically to be catabolic. The postoperative patients, although not septic, were expected to have a maximal catabolic response to operation during the first 3 days after operation. Both groups had increased release of phenylalanine from the leg, an index of muscle proteolysis. Septic patients had decreased femoral arteriovenous differences (--20 vs --74 and --60 mumoles/liter) and decreased flux (34 vs 169 and 128 nm/100 gm of calf muscle) of the branched-chain amino acids as compared with the nonseptic postoperative patients on days 1 and 3. The arterial plasmal levels of the branched-chain amino acids and alanine were not different, but phenylalanine was elevated in the septic patients (88 vs 49 and 55 mumoles/liter). The insulin:glucagon molar ratio was lower in the septic patients (2.4 vs 4.4 and 5.5). These findings suggest that in the catabolism of sepsis there is greater oxidation of branched-chain amino acids in muscle than in the catabolism associated with uncomplicated surgery.

Amino acid metabolism in dogs with E. coli bacteremic shock.

In 10 fasting dogs receiving 10(9) viable E. coli bacteria per kilogram intravenously, mean systolic blood pressure decreased from 120.6 +/- 15.1 to 82.2 +/- 12.8 mm Hg. The association of hypoglycemia and increased arterial alanine and glycine with elevated plasma glucagon implied impaired gluconeogenesis. A rapid elevation of blood urea concentration, indicating increased ureagenesis, a fall of blood glucose, and an increase of net urea synthesis relative to that of glucose suggested that an increased proportion of the carbon residues derived from glucogenic amino acids is catabolized via pathways other than gluconeogenesis. In the bacteremic dogs the absolute net release from the leg of valine, isoleucine, and leucine and their net release relative to the net rate of proteolysis were decreased, suggesting increased oxidation of these amino acids in skeletal muscle. An increased net release of alanine relative to the net rate of protein catabolism in muscle was in agreement with this contention.

Krabbe's leukodystrophy without globoid cells.

Krabbe's infantile cerebral sclerosis with a prolonged course was present in a boy who became increasingly hypertonic during infancy and had an increased protein level in the spinal fluid. At 4 years he showed significant growth failure, profound mental retardation, spastic quadriplegia, bilateral optic atrophy, and depressed tendon reflexes. Conduction velocity in motor fibers of the median nerve had become progressively impaired. Autopsy at 5 years 10 months showed severe leukodystrophy with demyelination and gliosis. No stored breakdown products or globoid cells were seen in the brain. Galactosyl ceramide beta-galactosidase was virtually absent, and hardly any myelin was demonstrable on chemical and electron microscopic studies. The presence of globoid cells may not be essential for the pathologic diagnosis of Krabbe's leukodystrophy in the presence of appropriate enzyme deficiency.