The rate of unidirectional [14C]urea efflux from human red cells was determined in the self-exchange and net efflux modes with the continuous flow tube method. Self-exchange flux was saturable and followed simple Michaelis-Menten kinetics. At 38 degrees C the maximal self-exchange flux was 1.3 X 10(-7) mol cm-2 s-1, and the urea concentration for half-maximal flux, K1/2, was 396 mM. At 25 degre...

The branchial mechanism of urea retention in elasmobranchs was investigated using an in vitro isolated-perfused head preparation, as well as in vivo samples, in the spiny dogfish shark. Both in vivo and in control saline perfusions containing 350 mmol L(-1) urea, calculated intracellular urea concentrations in gill epithelial cells were close to extracellular concentrations. Urea efflux to the ...

Foliar fertilization with nitrogen (N) is used to supplement soil N application in order to meet the high N requirements of crops (Oosterhuis and Weir, 2010). Urea is the most common foliar N source in cotton, due to its relatively low toxicity, quick absorption, and low cost (Maples and Baker, 1993; McConnell et al., 1998; Oosterhuis and Bondada, 2001). However, in the literature reports of yi...

Nitrification inhibitors may be potential management strategy to reduce N2O emissions in irrigated rice (Oryza sativa L.). A field experiment was conducted to evaluate chemically synthesized as well as locally available neem plant products on N2O emissions, from an irrigated rice at New Delhi, India. Emission of nitrous oxide (N2O) was monitored during 70 days by closed chamber method in rice (...

Nitrogen fertilization is essential for optimizing crop yields and economic returns in irrigated cropping systems in the Central Great Plains area of the USA. However, N application generally increases the emissions of the potent greenhouse gas, N 2 O, from these systems. Nitrous oxide is produced through nitrifi cation and denitrifi cation processes in the soil. Agriculture contributes approxi...

The synthesis of modified carbon dots (N-CDs) from nanocrystalline cellulose, as the source, with combination urea and ethylenediamine, nitrogen dopant agents, was successfully carried out by pyrolysis at 300°C. N-CDs

Urea, in concentrations unique to the renal medulla, increases transcription and protein expression of several immediate-early genes (IEGs) including the zinc finger-containing transcription factor, Egr-1. In the present study, the proximal 1.2 kb of the murine Egr-1 5' -flanking sequence conferred urea-responsiveness to a heterologous luciferase reporter gene when transiently transfected into ...

In the course of some work on protein metabolism it became advisable to estimate urea in animal tissues. Although we were drawn somewhat to the urease method we felt compelled for two reasons to employ other technique. In the first place, it was quite apparent that owing to the relatively large amount of ammonia in the tissue samples, the urea estimations would have to be accompanied by determi...

in order to evaluate the effect of different sources and rates of nitrogen the growth and biomass production of purslane, a randomized complete block design was conducted with three replications at the agricultural research farm of shahrekord university in 2012. fertilization treatments were consisted of control (no n amendment), 30 and 90 kg n ha-1in the form of urea fertilizer, 30 and 90 kg n...