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Urea

About: Urea is a research topic. Over the lifetime, 21394 publications have been published within this topic receiving 382444 citations. The topic is also known as: carbamide & carbonic acid diamide.


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Journal ArticleDOI
TL;DR: Part of the urea is incorporated into the soil before hydrolysis; the NH3 produced inside the soil is retained by the negative charges of colloidal material and losses are reduced even if no rain or irrigation incorporates urea into the soils.

238 citations

Journal ArticleDOI
TL;DR: It is suggested that highly charged anions and polyanions may have some clinical value as a possible treatment for recurrent calcium oxalate stone-formation in man.

237 citations

Journal ArticleDOI
TL;DR: Excess rumen degradable N in ewe diets elevates urea and ammonia in plasma and in utero, with an associated increase in embryo mortality, Nevertheless, metabolism appears to be up-regulated in some embryos and, among those that survive, fetal growth seems to be enhanced.

237 citations

Journal ArticleDOI
TL;DR: Analysis of inner medullary tissue after water restriction revealed marked depletion of urea in UT-A1/3(-/-) mice, confirming the concept that phloretin-sensitive IMCD urea transporters play a central role in Medullary urea accumulation.
Abstract: To investigate the role of inner medullary collecting duct (IMCD) urea transporters in the renal concentrating mechanism, we deleted 3 kb of the UT-A urea transporter gene containing a single 140-bp exon (exon 10). Deletion of this segment selectively disrupted expression of the two known IMCD isoforms of UT-A, namely UT-A1 and UT-A3, producing UT-A1/3-/- mice. In isolated perfused IMCDs from UT-A1/3-/- mice, there was a complete absence of phloretin-sensitive or vasopressin-stimulated urea transport. On a normal protein intake (20% protein diet), UT-A1/3-/- mice had significantly greater fluid consumption and urine flow and a reduced maximal urinary osmolality relative to wild-type controls. These differences in urinary concentrating capacity were nearly eliminated when urea excretion was decreased by dietary protein restriction (4% by weight), consistent with the 1958 Berliner hypothesis stating that the chief role of IMCD urea transport in the concentrating mechanism is the prevention of urea-induced osmotic diuresis. Analysis of inner medullary tissue after water restriction revealed marked depletion of urea in UT-A1/3-/- mice, confirming the concept that phloretin-sensitive IMCD urea transporters play a central role in medullary urea accumulation. However, there were no significant differences in mean inner medullary Na+ or Cl- concentrations between UT-A1/3-/- mice and wild-type controls, indicating that the processes that concentrate NaCl were intact. Thus, these results do not corroborate the predictions of passive medullary concentrating models stating that NaCl accumulation in the inner medulla depends on rapid vasopressin-regulated urea transport across the IMCD epithelium.

237 citations

Journal ArticleDOI
TL;DR: In this paper, the uptake of nitrate, ammonium, and urea by natural phytoplankton populations in 36 samples collected at nine stations off the coast of southern California was studied.
Abstract: Nitrogen-15 isotopes were used to study the uptake of nitrate, ammonium, and urea by natural phytoplankton populations in 36 samples collected at nine stations off the coast of southern California. The percentage of the total phytoplankton nitrogen productivity accounted for by urea varied from 60% and for the entire study averaged 28%. The percentage of total available nitrogenous nutrient (ambient nitrate, ammonium, and urea plus the 15N additions) utilized per day varied among the stations from a minimum of 5% at station 4 (12 km off San Diego) to a maximum of 46% at station 19 (off White Point). The average C:N uptake ratio was 12.4.

236 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,000
20221,982
2021433
2020502
2019589
2018557