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Biomedical subjects

L R Njaa

Publications and source records attributed to L R Njaa.

10 recordsLinked to original sources
PubMed1983

Absorption of methionine and methionine sulphoxide in rat intestine and the effect of glutathione.

The absorption of methionine and methionine sulphoxide was compared in inverted rings from three sections of rat intestine. In all sections, absorption of unoxidized methionine was 20-40% higher than that of methionine at low physiological substrate concentrations. At higher substrate levels, the difference was not so pronounced. Inhibition studies indicated that absorption of methionine and of methionine sulphoxide took place by different absorption systems. Glutathione increased the absorption of methionine and, to a greater extent, the absorption of methionine sulphoxide.

Animals↗
PubMed1982

The nitrogen-sparing effect of methionine sulphoxide and some other sulphur-containing amino acids.

The nitrogen-sparing effect of methionine, methionine sulphoxide, homocystine, cystine and choline was studied in rats by determining dialy N excretions during 5 d after changing from a high-protein diet to a protein-free diet, L-glutamic acid was used as a negative control. 2. L-, D- and DL-methionine were equally active in sparing N. L-methionine sulphoxide, DL-homocystine and L-cystine were as active as L-methionine. D-methionine sulphoxide was slightly less active than L-methionine sulphoxide. Choline hydrogen tartrate was not different from the negative control. 3. It is concluded that in short-term experiments cystine is the key substance in the N-sparing effect.

Amino Acids↗
PubMed1980

A method for determination of unoxidized and total methionine in protein concentrates, with special reference to fish meals.

1. An automated colorimetric method for determination of methionine using an iodoplatinate reagent is described. Methionine sulphoxide does not react under the chosen conditions. 2. The method may be used to distinguish between unoxidized and total methionine by doing one determination without and one determination with previous reduction of a portion of the sample with titanium trichloride. Methionine sulphoxide is then obtained by difference. 3. The method has been used with protein concentrates, mainly fish meals, after hydrolysis with barium hydroxide. Interference from cysteine-cystine is eliminated by adding a small amount of cadmium acetate to the sample before hydrolysis. 4. Results obtained for total methionine and for methionine sulphoxide by independent methods show good agreement with results obtained with the iodoplatinate method.

Animal Feed↗
PubMed1977

Methionine sulphoxide as a source of sulphur-containing amino acids for the young rat.

1. Young male rats were used in five experiments to study the utilization for growth of methionine sulphoxide, and the relationship between the sulphoxide content in the diet and the level of microbiologically determined methionine activity in blood or blood plasma. In one nitrogen-balance experiment methionine and methionine sulphoxide were compared as supplements to a casein diet and a fish-meal diet. 2. Methionine sulphoxide was poorly utilized for growth when testd as the sole sulphur amino acid in an amino acid diet. Substitution of one-third of the sulphoxide with cystine improved utilization so that it approached that of methionine. 3. Methionine alone and in combination with methionine sulphoxide were added to a soya-bean-meal diet. The sulphoxide showed no adverse effect on growth. 4. Fish meal in which methionine had been oxidized to methionine sulphoxide was tested alone and in combinations with unoxidized fish meal. Only when the oxidized meal was given alone was there an appreciable effect on growth. The fish meal used were low in cystine. 5. Whereas both methionine and methionine sulphoxide improved the N balance when a casein diet was given, there was no effect when a fish-meal diet was given. 6. There was a linear relationship between methionine sulphoxide content in the amino acid diets and the methionine activity in the blood plasma. Methionine sulphoxide added to a soya-bean-meal diet or present in oxidized fish meal gave a curvilinear relationship, and the observed activities were lower than with the amino acid diets. Methionine activity in blood could not be used as an indicator of moderate amounts of methionine sulphoxide in protein-containing diets.

Amino Acids, Sulfur↗