We used a perfused gill preparation from dogfish to investigate the origin of low branchial permeability to urea. Urea permeability (14C-urea) was measured simultaneously with diffusional water permeability (3H2O). Permeability coefficients for urea and ammonia in the perfused preparation were almost identical to in vivo values. The permeability coefficient of urea was 0.032 x 10(-6) cm/sec and...

the study was conducted to evaluate the effects of feeding varying levels of ficus sycomorus leaf forages as protein supplements to a basal diet of urea treated maize stover. four yankasa goats averaging one year and weighing 11.7±1.8 kg were used to measure the feed intake, digestibility and nitrogen balance. the basal diet (urea treated maize stover) was supplemented with 0 (t1), 50 (t2), 100...

in order to evaluate the response of quantitative and qualitative characteristics of the isabgol (plantago ovata frosk.) medicinal plant to separate and combined application of urea and biofertilizer an experiment was conducted in a randomized complete block design at the research farm of shahrekord university in 2011. the experimental treatments consisted of control (no urea and biological fer...

Urea transport in the proximal tubule is passive and is dependent on the epithelial permeability. The present study examined the maturation of urea permeability (P(urea)) in in vitro perfused proximal convoluted tubules (PCT) and basolateral membrane vesicles (BLMV) from rabbit renal cortex. Urea transport was lower in neonatal than adult PCT at both 37 and 25 degrees C. The PCT P(urea) was als...

Nitrogenous waste excretion in resting dogfish occurred largely (>90 %) as urea-nitrogen (urea-N) efflux across the gills, with a very small urea efflux via the kidney. Ammonia excretion, almost entirely at the gills, accounted for less than 3 % of total nitrogen excretion. Given the extremely high blood urea levels (approximately 640 mmol-N l-1) 'retained' for osmoregulation, and blood ammonia...

1. Stable urea isotopes can be used to study urea kinetics in humans. The use of stable urea isotopes for studying urea kinetic parameters in humans on a large scale is hampered by the high costs of the labelled material. We devised a urea dilution for measurement of the distribution volume, production rate and clearance of urea in healthy subjects and renal failure patients using the inexpensi...

All teleost fish produce ammonia as a metabolic waste product. In embryos, ammonia excretion is limited by the chorion, and fish must detoxify ammonia by synthesizing urea via the ornithine urea cycle (OUC). Although urea is produced by embryos and larvae, urea excretion (J(urea)) is typically low until yolk sac absorption, increasing thereafter. The aim of this study was to determine the physi...