Nitrogen, balance

For protein synthesis to occur, all 20 amino acids must be present in sufficient quantities. Absence of any one essential amino acid leads to cessation of protein synthesis, catabolism of unused amino acids, increased loss of nitrogen in urine, and reduced growth. Negative nitrogen 

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Donovan, S.M., Atkinson, S.A and Lonnerdal, B. 1986 Total nitrogen and non-protein nitrogen balance in preterm infants fed preterm human milk. In Jensen, R.G. and Neville, M.C., eds.. Human Lactation 2. Maternal and environmental factors. New York, Plenum Press 603-610. 

Protein Requirements Can Be Determined by Measuring Nitrogen Balance... 

Not all proteins are nutritionally equivalent. Mote of some than of others is needed to maintain nittogen balance because different proteins contain different amounts of the various amino acids. The body s requirement is for specific amino acids in the correct proportions to replace the body proteins. The amino acids can be divided into two groups essential and nonessential. There are nine essential or indispensable amino acids, which cannot be synthesized in the body histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. If one of these is lacking or inadequate, then—regardless of the total intake of protein—it will not be possible to maintain nitrogen balance since there will not be enough of that amino acid for protein synthesis. 

Two amino acids—cysteine and tyrosine—can be synthesized in the body, but only from essential amino acid ptecutsots (cysteine from methionine and tyrosine from phenylalanine). The dietary intakes of cysteine and tytosine thus affect the requirements for methionine and phenylalanine. The remaining 11 amino acids in proteins are considered to be nonessential or dispensable, since they can be synthesized as long as there is enough total protein in the diet—ie, if one of these amino acids is omitted from the diet, nitrogen balance can stiU be maintained. Howevet, only three amino acids—alanine, aspartate, and glutamate—can be considered to be truly dispensable they ate synthesized from common metabolic intetmediates (pyruvate, ox-... 

B. Griffiths and D. Robin.son, Root-induced nitrogen mineralisation a nitrogen balance model. Plant Soil 759 253 (1992). 

D. J. Jenkinson, The nitrogen economy of the Broadbalk experiments 1. Nitrogen balance in the experiments. Report of the Rothamstead Experimental Station for... 

O Parenteral nutrition (PN), also called total parenteral nutrition (TPN), is the intravenous administration of fluids, macronutrients, electrolytes, vitamins, and trace elements for the purpose of weight maintenance or gain, to preserve or replete lean body mass and visceral proteins, and to support anabolism and nitrogen balance when the oral/enteral route is not feasible or adequate. 

The answer is c. (Hardman, pp 1129-1131J All tetracyclines can produce negative nitrogen balance and increased blood urea nitrogen... 

Specific nitrogen goals are positive nitrogen balance or nitrogen equilibrium and improvement in serum concentration of protein markers (e.g., transferrin or prealbumin). 

Nitrogen balance Prealbumin or transferrin Serum triglyceride... 

This is in striking contrast to numerous reported studies on the feeding of white potatoes to humans (30). An early study in which the sweet potato was used as the sole source of nitrogen in the diet of humans was that of Adolph and Liu (31.). They reported that nitrogen balance could be maintained with sweet potato nitrogen provided sufficient amounts were consumed. 

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