Urea in renal medullas is sufficiently high to perturb macromolecules, yet the cells survive and function. The counteracting osmolytes hypothesis holds that methylamines, such as glycine betaine (betaine) and glycerophosphocholine (GPC) in renal medullas, stabilize macromolecules and oppose the effects of urea. Although betaine counteracts effects of urea on macromolecules in vitro and protects...

Urea-induced protein denaturation is widely used to study protein folding and stability; however, the molecular mechanism and driving forces of this process are not yet fully understood. In particular, it is unclear whether either hydrophobic or polar interactions between urea molecules and residues at the protein surface drive denaturation. To address this question, here, many molecular dynami...

The absorption, translocation, and assimilation of urea, nitrate, and ammonium in tomato plants within 24 h after N labeled compounds were applied at four different growth stages: seedling, ̄owering, fruiting, and harvesting. The absorption of urea-N was only 25% of NO3-N at seedling stage, but it was up to about 80% of NO3-N at the subsequent growth stages. The translocation of urea-N was limit...

Urea is the major nitrogen form supplied as fertilizer in agricultural plant production but also an important nitrogen metabolite in plants. We report the cloning and functional characterization of AtDUR3, a high-affinity urea transporter in plants. AtDUR3 contains 14 putative transmembrane-spanning domains and represents an individual member in Arabidopsis that belongs to a superfamily of sodi...

Urea is the principal end-product of nitrogen metabolism in mammals and is excreted almost entirely through the kidney. Studies by Shannon (1, 2) in the dog and by Chasis and Smith (3, 4) in man have shown that the renal clearance of urea is less than the inulin or creatinine clearance at all rates of urine flow, and that the clearance of urea increases as the urine flow rises. These observatio...

To explain the large, opposite effects of urea and glycine betaine (GB) on stability of folded proteins and protein complexes, we quantify and interpret preferential interactions of urea with 45 model compounds displaying protein functional groups and compare with a previous analysis of GB. This information is needed to use urea as a probe of coupled folding in protein processes and to tune mol...

Urea in biological fluids has been determined by a variety of direct and indirect procedures. Some indirect methods depend on the hydrolysis of urea with the enzyme urease to form ammonia, with subsequent quantitation of the ammonia by nesslerization (1-4). Undesirable features of these indirect methods are the use of relatively unstable reagents and loss of ammonia during the procedure. Direct...

TRUNIGER, BRUNO, AND BODIL SCHMIDT-NIELSEN. Intrarenal distribution of urea and related compounds: effects of nitrogen intake. Am. J. Physiol. 207(s) : 971-978. rg64.-Nitrogen and NaCl intake influence the excretion of urea. In rats maintained on a low-protein, high-salt intake the urea-to-inulin clearance ratio decreases to 0.01. In antidiuretic “low-protein” rats the urea concentrations in th...

4. Plasma concentrations and urea entry rates were significantlj and linearly related. 5. The relationship between excretion rate and plasma urea concentration was best described by a cubic equation. 6. Degradation of urea in sheep was found to be extensive in all the animals studied ; as the protein intake increased, the quantity of urea degraded also increased but the percentage of ureaenteri...

to study the effect of urea application in safflower (carthamus tinctorius) and determination of effective traits on its yield, a factorial experiment based on randomized complete block design in three replications was conducted in tabriz, iran, during 2012. studied factors were urea rate levels as 100, 150 and 200 kg/ha and urea application times 100% in sowing time, 50% sowing time + 50% stem...