In vitro experiments have shown that fermentation of carbohydrates prevents accumulation of nitrogen in the colon. Variable results have been obtained on modulation of dietary intakes in vivo. Lactose[15N,15N]-labeled ureide has been proposed as a tool to study colonic nitrogen metabolism. However, on oral administration of the marker, different urinary excretion patterns of the 15N label have ...

Profound changes in protein metabolism noted in diabetes mellitus are grossly reflected in a negative nitrogen balance. It is not clear whether this is due to depressed protein synthesis or to increased protein catabolism. Turnover studies with N15glycine have been interpreted to favor an effect on synthesis (1). Krahl (2) has demonstrated that liver slices from diabetic rats have a decreased c...

Soil microorganisms mediate many nutrient transformations that are central in terrestrial cycling of carbon and nitrogen. However, uptake of organic nutrients by microorganisms is difficult to study in natural systems. We assessed quantum dots (fluorescent nanoscale semiconductors) as a new tool to observe uptake and translocation of organic nitrogen by fungi and plants. We conjugated quantum d...

Labeled plasma proteins are produced by administering to dogs the amino acid lysine synthesized with heavy nitrogen. Such labeled proteins are apparently indistinguishable biologically from proteins of normal isotope concentration. Labeled plasma proteins, as plasma, injected into normal dogs pass out of the blood stream at an initially rapid but constantly decreasing non-logarithmic rate. This...

Amino acid metabolism and transport was investigated in the leaves of 3-week-old nonnodulated seedlings of Pisum sativum L. Xylem sap entering the shoot contained nitrate (about 5 millimolar), and amino compounds (11 millimolar) of which 70% was asparagine plus glutamine; aspartate and homoserine were also present. Mature leaves showed stable nitrogen levels and incoming nitrogen was redistribu...

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 RNA based stable isotope probing (SIP) facilitates the detection and identification of active members of microbial populations that are involved in the assimilation of an isotopically labeled compound. N-RNA-SIP is a new method that has been discussed in recent literature but has not yet been tested. Herein, we define the limitation...

A study was conducted to evaluate a net value of exogenous (dietary) protein nutrition in rats fed a [15N]-labeled soy protein isolate (SPI). Although [15N]-SPI-derived nitrogen reached a plateau 2 hr after feeding, it accounted for only a half of the total nitrogen in the small intestine. 15N was confirmed that was normally transported to liver, kidney, spleen, and brain. The present study rev...