Protein-calorie malnutrition in young miniature swine: serum free amino acids

Free amino acid levels in undernourished developing rat brain

Free amino acid levels in the brains of young ones born to mothers fed a 20% protein diet ad libitum (well nourished), 7.5% protein diet ad libitum (protein restricted) and a 20% protein diet in restricted amounts (pair-fed) were investigated during brain development in the present study. The dietary protein was obtained from a cereal-legume mixture. Protein restricted animals showed increases in the levels of taurine, glycine and glutamic acid and decreases in the concentrations of methionine, leucine, isoleucine, and GABA. The pair-fed animal showed increases only in glutamic acid and glycine and a decrease only in the levels of GABA. The significance of these observations is discussed.

The inadequacy of urinary N tau-methyl histidine excretion in the pig as a measure of muscle protein breakdown

1. The validity of the urinary excretion of N tau-methyl histidine (N tau-MH) by pigs as an index of muscle protein breakdown in vivo was tested using the criterion of the rate of recovery of radioactivity in urine following an intravenous dose of N tau-[14CH3]methyl histidine. 2. Urinary recoveries of radioactivity from five animals were less than 21% of dose in 7 d after which the daily recovery was less than 0 . 3% per day. 3. The incomplete recoveries of radioactivity were associated with the presence in muscle of a large pool of non-protein-bound N tau-MH, the concentration of which increased with age. 4. The N tau-MH in this pool was present as free N tau-MH and in a dipeptide which constituted more than 90% of the total non-protein-bound N tau-MH. The contribution of the peptide increased with age, reaching 99. 8% in older animals. 5. The pool of non-protein-bound N tau-MH was maintained and increased in both established and newly accreted tissue by retention of some of the N tau-MH released by muscle protein breakdown, only a proportion of which was therefore available for excretion. Hence, the urinary excretion of N tau-MH is not a valid index of muscle protein breakdown in pigs.

Utilization of 14C-tyrosine in brain and peripheral tissues of developmentally protein malnourished rats

Prior studies of developmentally protein malnourished rats have reported substantial changes in brain and peripheral utilization of 14C-leucine, 14C-phenylalanine, and 14C-tryptophan. In the present study rats born to dams fed a low protein diet (8% casein) compared to the offspring of control rats fed a normal diet (25% casein) showed few significant differences in the uptake and incorporation of 14C-tyrosine into brain and peripheral tissues from birth to age 21 days. At birth, the 8% casein pups exhibited significant decreases in brain and peripheral tissue incorporation of tracer only at short post-injection times (10 and 20 min), but not at longer intervals (90 and 180 min). During ontogenetic development (Days 5-21), the 8% casein rats showed significant increases in uptake of 14C-tyrosine into the brain and peripheral tissues on Day 11 and a significantly higher percent incorporation of tracer into brain protein on Day 21 as compared to the 25% casein rats. For the most part, there were no significant changes in incorporation of radioactivity in peripheral tissues for the 2 diet groups on these post-birth days. Overall, the data indicates that developmental protein malnutrition causes relatively fewer changes in brain and peripheral utilization of the semi-essential amino acid tyrosine than those observed in previous studies with essential amino acids.