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The hypothesis that tumors arising in a particular organ site impose a characteristic plasma free amino acid (PFAA) pattern was tested by analyzing PFAA in fasting venous blood of preoperative patients with breast cancer, gastrointestinal tract cancer, and head and neck cancer. Healthy volunteers served as control subjects. Levels of 28 PFAA were determined in blood samples using an amino acid analyzer, and the data were compared using discriminant analysis and chi‐square testing. Compared with control subjects, the concentrations of seven amino acids (glutamine, threonine, histidine, cysteine, alanine, arginine, and ornithine) in patients with tumors correlated closely with the known diagnoses. By means of discriminant analysis, these seven amino acids had the highest correlation with the specific diagnoses, indicating that PFAA profiles correlate diagnostically with the organ‐site origin of three different kinds of malignant tumors.

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The influence of graded amounts of total parenteral nutrition (TPN) on food intake and feeding indexes was investigated in 90 rats housed in Automated Computerized Rat Eater Meter metabolic cages with free access to water and chow. When food intake was stable after catheter placement, 10 control rats continued with the 3 ml/h normal saline used for catheter patency, whereas study rats were given graded TPN continuously for 3 days, amounting to the equivalent of 26% (TPN-26), 53% (TPN-53), 81% (TPN-81), or 114% (TPN-114) of their daily caloric needs. TPN consisted of glucose, fat, and amino acids in the caloric ratio of 50:30:20. In study rats, the graded TPN depressed food intake, meal number, meal size, and eventually food consumption rate, meal sniffs, and intermeal sniffs in a dose- and time-dependent manner. During graded TPN, rats decreased total food intake by eating fewer, smaller, shorter meals at a decreasing consumption rate; sniffing activities were correspondingly curtailed. Stopping TPN led to normalization of feeding indexes. Blood glucose did not change while plasma insulin rose with graded TPN. A decrease in hepatic glycogen and an increase in hepatic triglycerides occurred. Plasma valine, phenylalanine, and methionine rose in a TPN dose-dependent manner. TPN-26 and TPN-53 significantly decreased whole brain amino acids; with TPN-114 no change occurred. Brain influx of tryptophan remained unchanged, but a progressive decrease in brain influx of tyrosine occurred. Whole brain dopamine and serotonin were depressed with TPN-26 and TPN-81 but were normal with TPN-114.(ABSTRACT TRUNCATED AT 250 WORDS)