Biomedical subjects
Publications and source records attributed to I Vyhmeister.
To meet the professional demands of their positions, dietitians must delegate less demanding responsibilities and routine tasks to educationally qualified dietetic technicians. This research was conducted to determine the degree to which A.D.A. qualified dietetic technicians were performing identified tasks.
Chronically uremic rats weighing approximately 180-200 g and sham-operated controls of similar weight were pair fed diets containing 5, 15 or 23% protein for 10-12 wk. At each level of protein intake, uremic animals gained less weight and had lower protein efficiency ratios than controls. In addition, certain plasma amino acid levels were altered in the uremic animals. These included tyrosine and the tyrosine/phenylalanine ratio, which were decreased, and citrulline, glycine, and the methylhistidines, which were increased. In both uremic and control rats, plasma concentrations of certain amino acids, primarily nonessential ones, varied inversely with protein intake; with the 5% protein diet, the ratio of essential to nonessential amino acids was significantly reduced. These observations indicate that both uremia and reduced protein intake may affect growth and amino acid metabolism in rats with chronic renal failure. The finding that uremic rats utilize protein less efficiently may indicate that marked reductions in protein intake may be particularly hazardous to the nutritional status of the uremic patient.
The chronically uremic rat has been used as a model to study amino acid metabolism in uremia. Uremic rats fed low protein diets (6% casein) survived longer than uremic rats receiving either higher levels of dietary protein or a low protein diet supplemented with a mixture of nonessential amino acids. Alterations in plasma amino acid levels were observed in the uremic rats and were similar to those found in patients with renal failure. Plasma concentrations of citrulline, free tryptophan, glycine and the methylhistidines were increased and levels of serine, ornithine, lysine, total tryptophan, tyrosine, and the tyrosine-phenylalanine ratio were reduced. The metabolic basis of the altered tyrosine-phenylalanine ratio in plasma was studied. Tyrosine aminotransferase (TAT) and phenylalanine hydroxylase (PHL) activity were normal in the liver, but renal PHL activity of was decreased as compared to control rats. Tissue concentrations of citrulline were also found to be raised in liver and muscle of uremic rats. The activity of ornithine transcarbamoylase, was reduced in the liver and arginine synthetase activity was decreased in the kidneys of uremic rats. Thus elevated citrulline levels in uremic tissue appear to be caused by a decrease conversion of citrulline to arginine in the kidney. Preliminary studies of tryptophan metabolism in uremic rats have shown elevated brain levels of 5-hydroxyindoleacetic acid and increased hepatic tryptophan oxygenase activity. Increased plasma amine levels were associated with altered activities of monoamine oxidase and diamine oxidase in kidney and other tissues.