This study confirms in humans an age-related increase in plasma urea levels (r = 0.62; P < 0.001; y = 0.229x + 18.26) and no correlation between plasma creatinine and age (r = 0.06; NS). Fractional urea excretion (FE urea) decreases with age (r = -0.41; P < 0.001; y = -0.226x + 55). Comparing urea and creatinine clearances, measured in 19 young and in 15 old women, a larger decrease of urea cle...

a fiel experiments was laid out in agricultural research farm, city namin, ardabil province, iran in 2013. experiment was conducted in a randomized complete block with seven treatments and three replication. foliar spray treatments urea solution at a rate of 1, 2 and 3% (in two stages, the first stage a month after transplanting when they had reached 10 cm in height to 20 days after the first s...

Urea is the major nitrogen (N) form supplied as fertilizer in agriculture, but it is also an important N metabolite in plants. Urea transport and assimilation were investigated in Arabidopsis (Arabidopsis thaliana). Uptake studies using (15)N-labeled urea demonstrated the capacity of Arabidopsis to absorb urea and that the urea uptake was regulated by the initial N status of the plants. Urea up...

Urea synthesized commercially and formed naturally as a by-product of cellular metabolism is an important source of nitrogen (N) for primary producers in aquatic ecosystems. Although urea is usually present at ambient concentrations below 1 μM-N, it can contribute 50% or more of the total N used by planktonic communities. Urea may be produced intracellularly via purine catabolism and/or the ure...

Urea production rate (Ra) is commonly measured using a primed continuous tracer urea infusion, but the accuracy of this method has not been clearly established in humans. We used intravenous infusions of unlabeled urea to assess the accuracy of this technique in normal, postabsorptive men under the following four different conditions: 1) tracer [13C]urea was infused under basal conditions for 1...

ROCH-RAMEL, FRANCOISE, J. DI~ZI, FRANGOISE CHOM~TY, PIERRETTE MICHOUD, AND G. PETERS. Disposal of large urea overloads by the rat kidney: a micropuncture study. Am. J. Physiol. 2 1 a(6) : 1524-1532. 1970.-In rats overloaded with urea, at plasma concentrations of 60-80 mM, the proximal fractional reabsorption of urea was not impaired, whereas the cortical tissue-to-plasma urea concentration rati...

Urea degradation was measured during 16 experiments in 13 chronic uremic patients being treated with essential amino acids or their analogues. [(14)C]Urea was injected i.v. and the clearance of labeled urea from its volume of distribution was compared with the simultaneous renal clearance of ordinary urea, which averaged 2.0 liters/day. The difference, extrarenal clearance of urea, averaged 3.1...

Four gilts (average BW 80 kg) were used in the first experiment to study the effect of i.v. infusion of urea on urea kinetics by means of a radioisotope dilution technique. The pigs were fed twice daily 600 g of a cornstarch-based diet formulated to contain 16% CP by supplementation with isolated soy protein. Infusion of urea, compared with saline, increased (P < .05) plasma urea concentration,...