1. Cytokine production in vitro was assessed in 16 malnourished children, before and after nutritional recovery. 2. Tumour necrosis factor-α and interleukin-6 were measured in whole blood after lipopolysaccharide stimulation. 3. The total amount of both cytokines was significantly less after 24 h incubation among malnourished children when compared with the same children after nutritional rehabilitation. 4. Cytokine production in vitro is impaired in severely malnourished children.

1. The responses of plasma levels of C-reactive protein and serum amyloid A were assessed in two groups of malnourished children. 2. Sixty-six severely malnourished children were studied at admission. Fifty of these had clinical and/or laboratory evidence of infection. C-reactive protein was not elevated in 23 (46%) and serum amyloid A was not raised in 29 (58%) of these 50 children. 3. Surviving children ( n = 62) received two doses of diphtheria-pertussis-tetanus vaccine, to which the C-reactive protein and serum amyloid A responses were measured. The first was given early in recovery, the second after nutritional rehabilitation. Ten mildly malnourished children acted as controls, receiving a single dose of diphtheria-pertussis-tetanus vaccine. 4. The responses of both C-reactive protein and serum amyloid A to diphtheria-pertussis-tetanus vaccine were significantly less in early recovery than after nutritional recovery. The response of the mildly malnourished group was no different from that of the severely malnourished group in early recovery, but was less than their response on discharge. 5. The acute-phase protein response of malnourished children is impaired. This may have prognostic implications as the response plays a central role in promoting healing.

1. Glutamine [ 15 N]amide was infused at a steady rate of 33.34 μmol/h into seven male adult volunteers who were in the fed state and normal acid-base status. 2. Plasma glutamine amide N enrichment and urinary ammonia N enrichment rose to a constant value within 3 h. 3. The glutamine production rate was 51.8 ± 7.9 mmol/h. 4. The total ammonia excretion rate was 0.87 mmol/h. Of this excreted ammonia 62.6 ± 9% was derived from the amide N atom of glutamine. 5. The excreted glutamine amide N (0.53 mmol/h) was only 1% of the glutamine production. If half the ammonia formed by the kidney is excreted in urine and half liberated into the renal vein in subjects with normal acid-base status [E. E. Owen & R. R. Robinson (1963) Journal of Clinical Investigation , 42 , 263–276], then the kidney accounts for only 2% of glutamine disposal. 6. Whole body protein turnover, measured from the urinary [ 15 N]ammonia enrichment, was 30.3 ± 7.7 g of N/day (2.8 g of protein day −1 kg −1 ).

1. [ 15 N]Glycine was infused into fed, fasted or acidotic humans. 2. In all metabolic states there was considerable transfer of labelled nitrogen to urea and ammonia, but alanine and glutamate did not become enriched. 3. The findings show that free exchange of nitrogen between all amino acids does not take place. Glycine, serine, threonine, lysine and histidine cannot be considered part of the α-aminonitrogen pool as classically conceived, although they form up to one-half of that pool.

1. Whole-body protein turnover was measured in rats by constant infusion of 15 N-labelled glycine, aspartate, valine and leucine and measuring the enrichment of hepatic and renal urea and ammonia nitrogen. 2. The values obtained with [ 15 N]glycine were comparable with values reported with methods based on different assumptions. 3. [ 15 N]Aspartate gave rise to an increased enrichment of urea and ammonia and hence to lower protein-turnover rates. 4. [ 15 N]Valine and [ 15 N]leucine gave low enrichments of nitrogenous end products and hence to high protein-turnover rates. 5. All 15 N-labelled amino acids are not equally suitable for measuring whole-body protein turnover by the end-product method. The relative amounts of 15 N going to the end products can be predicted from the known individual metabolism of aspartate and the branched-chain amino acids.

1. Rates of total protein turnover, synthesis and breakdown were measured in five children before and after recovery from severe protein-energy malnutrition and while receiving 0·6 g of protein and 397 kJ day −1 kg −1 . 2. These rates were calculated after giving doses of [ 15 N]glycine every 2 h along with the feeds and measuring the rate of excretion of [ 15 N]urea in urine. 3. Malnourished children had significantly lower rates of protein turnover, synthesis and breakdown than after they had recovered. 4. During recovery from protein-energy malnutrition, two children on a daily intake of 1·2 g of protein and 605 J/kg body weight, had rates of protein turnover, synthesis and breakdown that were twice as great as those found on admission and higher than after recovery. 5. On the study diet the malnourished children maintained their weight while the recovered children lost weight; the apparent nitrogen balance was more positive in the malnourished children. 6. In recovered children, the rate of protein synthesis was unchanged over a wide range of protein intake, whereas the rate of protein breakdown appeared to rise with a reduction in protein intake.

1. Total body protein turnover was studied in six elderly patients. 2. During the study they were fed by continuous infusion of a liquid formula through a nasogastric tube. l-[1- 14 C]Leucine and [ 15 N]glycine were infused at a constant rate for 30 h. The labelled glycine was infused into the intragastric line; the labelled leucine was given either by this route or intravenously. 3. The specific radioactivity of free leucine in plasma and the rate of output of 14 CO 2 in expired air both reached a plateau at 10 h, and remained constant until the end of the infusion at 30 h. 4. The 15 N abundance in urinary urea and total N was very similar. In neither was a plateau reached by 30 h but in four out of the six patients the abundance in urinary NH 4 + had attained a plateau by the end of the infusion. 5. Flux rates and rates of protein synthesis were calculated in four ways: (A) from the specific radioactivity of plasma leucine at plateau; (B) from the proportion of dose excreted as 14 CO 2 at plateau; (C) from the final rates of 15 N excretion in urea or total urinary N; (D) from the final or plateau rates of 15 N excretion in urinary NH 4 + . 6. On average, the estimates of synthesis rate obtained by methods B and C agreed closely; those given by methods A and D were lower. Methods A, B and D ranked the individual patients in almost identical order. 7. The comparison of methods makes it possible to examine the validity of the assumptions on which the different methods depend. Method B is probably theoretically the most satisfactory and, of the methods used in this work, probably gives the best estimate of the absolute turnover rate. The other methods can be used for comparative purposes. 8. The results suggest that the rate of protein turnover is reduced in the elderly, compared with younger subjects.