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Biomedical subjects

K Muramatsu

Publications and source records attributed to K Muramatsu.

At least 127 records · Page 7Linked to original sources
PubMed1984

Self-selection of phenylalanine in the rat.

The regulation of phenylalanine intake in rats was investigated by means of a self-selection feeding method. The relationship between phenylalanine intake and the alteration of phenylalanine and tyrosine concentrations in plasma and brain was also studied. Weanling rats were offered a choice of two diets differing only in phenylalanine content for 2 weeks. Weight gain and food consumption of all the self-selecting rats were not significantly different from each other and were of the same levels as those in rats fed on a 10% casein or 10% casein plus 1.0% phenylalanine diet as a fixed ratio. Phenylalanine intake of the self-selecting rats ranged from 0.31 to 2.29% of the food consumed. The phenylalanine and tyrosine concentrations in plasma and brain of self-selecting rats were within normal levels. It became clear that rats have an ability to regulate phenylalanine intake, and that they select phenylalanine to meet their requirement for the amino acid.

Animals↗
PubMed1982

Regulation of amino acid intake in the rat: self-selection of methionine and lysine.

A study was undertaken to measure the ability of rats to regulate amino acid intake by means of a self-selection method. Weaning rats were simultaneously offered a choice between a 10% casein diet or a 10% amino acid mixture diet lacking methionine or lysine and a 10% casein diet containing different levels of methionine or lysine over 2 weeks. Weight gain and food consumption of rats allowed a choice between the two diets were much greater than those of animals fed on the fixed diets with high levels of methionine or lysine added, and the self-selecting rats had the ability to take in amounts of methionine or lysine appropriate to meet the requirement. Methionine intakes of self-selecting rats were kept to a relatively narrow range (41--100 mg/day), but lysine intakes of self-selecting rats were wide-ranging (86--300 mg/day). It was demonstrated that methionine or lysine intake is closely regulated in rats given a choice of diets containing varied levels of methionine or lysine.

Animals↗
PubMed1977

Effect of supplementation of limiting amino acids on tyrosine toxicity in rats fed wheat gluten diets.

The effect of supplementation of limiting amino acids on rats fed a 10 or 20% wheat gluten diet containing 5% tyrosine has been investigated. Growth-limiting amino acids in a 20% wheat gluten diet were lysine and threonine. When rats were fed a 20% wheat gluten diet containing excess tyrosine, the addition of 1.0% lysine-HCl or 1.0% lysine-HCl and 0.4% threonine completely prevented the development of tyrosine toxicity, and was accompanied by a lowering of free tyrosine concentrations in plasma, liver and muscle. In rats receiving a 10% wheat gluten diet, lysine, threonine and methionine were limiting for growth. The addition of 1.0% lysine-HCl to the 10% wheat gluten plus 5% tyrosine diet failed to alleviate the tyrosine toxicity, but the supplement of 1.0% lysine-HCl and 0.4% threonine could partially alleviate the toxicity. The combined addition of 1.0% lysine-HCl, 0.4% threonine and 0.5% methionine was most effective. The free tyrosine concentrations in plasma, liver and muscle were lowered greatly by the supplementation of three limiting amino acids, but amounts of free tyrosine and phenolic metabolites excreted in the urine did not decrease with addition of these limiting amino acids.

Amino Acids↗
PubMed1976

Effect of individual amino acid supplements on the toxicity of excess tyrosine in rats.

The object of this study was to determine the effects of individual amino acid supplements on the development of tyrosine toxicity in growing rats fed 10% casein containing 5% tyrosine. Each amino acid was added at levels equivalent to its content in 20% casein. Supplement of methionine to the high tyrosine diet partially alleviated both growth depression and pathological lesions. Threonine and cystine had a somewhat beneficial effect, but the single addition of other amino acids was not effective. Besides, some amino acids enhanced the severity of the toxicity even more. The effects of methionine supplementation were highest at 0.66 to 1.32% levels (equivalent to the methionine content in 20 to 40% casein). By the supplement of both 0.66% methionine and 0.90% threonine to the high tyrosine diet, growth was significantly improved and toxic lesions were completely prevented. It was confirmed that the counteracting effects to the toxicity, caused by the extra addition of protein (casein) to rats fed a high tyrosine-low protein diet, were mainly attributed to the effectiveness of the methionine and threonine, i.e., first-and second-limiting amino acids, respectively, contained in it.

Amino Acids↗
PubMed1976

Beneficial effect of methionine and threonine supplements on tyrosine toxicity in rats.

The growth retardation and external pathological lesions that occur in rats fed a 10% casein diet containing 5% tyrosine could be alleviated by the supplementation of extra protein (20% casein) or 0.66% methionine plus 0.90% threonine (equivalent to the contents in a 20% casein, respectively). Liver tyrosine aminotransferase activity is elevated by ingestion of excess tyrosine, but lowered by the supplementation of extra casein of methionine plus threonine. In rats fed a high tyrosine diet supplemented with methionine plus threonine, liver p-hydroxyphenylpyruvate hydroxylase activity was not higher than that of the 10% casein group, but liver homogentisate oxidase activity increased significantly. When excess tyrosine was included in the 10% casein diet, free tyrosine concentrations in plasma, liver, muscle and brain were extremely elevated, but when the high tyrosine diet was supplemented with extra casein or methionine plus threonine, their plasma and tissues tyrosine concentrations lowered significantly. A large increase in total phenols, p-hydroxyphenylpyruvate and free tyrosine excretions in urine was produced in animals fed the high tyrosine-low protein diet, but these were lowered by the supplementation of methionine and threonine to the diet.

4-Hydroxyphenylpyruvate Dioxygenase↗