15N uptake

If 15N ammonium citrate was administered, and glutamate, aspartate, and glycine isolated from liver and intestinal wall protein, all showed 15N uptake. From the results of labeling studies, Schoenheimer finished his Edward K.Dunham lectures in Harvard in 1941 with the phrase— the structural materials [of the body] are in a steady state of flux. The classical picture must thus be replaced by one which takes account of the dynamic state of body structure —an idea which has become an integral part of biochemistry since that time, and which was almost totally dependent on the introduction of isotopes for its discovery. 

The influence of nitrogen concentration and ammonium/nitrate ratio on N-uptake of citrus was studied by Serna et al. (1992). In short-term water culture experiments with 15N labelled NH/ or N03 at various concentrations, citrus seedlings absorbed... 

Lund, B. A. (1987). Mutual interference of ammonium, nitrate, and urea on uptake of 15N sources by the marine diatom Skeletonema costatum (Grev.) Cleve.J. Exp. Mar. Biol. Ecol. 113, 167—180. 

Hristov, A. and G.A. Broderick, 1994. In vitro determination of ruminal protein degradability using [15N]-ammonia to correct for microbial nitrogen uptake. J. Anim. Sci. 72, 1344-1353. 

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