Effects of supplemental RDP and RUP on nutrient digestion, N metabolism, urea kinetics, and muscle protein degradation were evaluated in Nellore heifers () consuming low-quality signal grass hay (5% CP and 80% NDF, DM basis). Five ruminally and abomasally cannulated Nellore heifers (248 ± 9 kg) were used in a 5 × 5 Latin square. Treatments were the control (no supplement) and RDP supplementatio...

Hepatic urea synthesis is the organism's main channel for the disposal of nitrogen and it may be an 'essential' liver function. In six control subjects and five patients with cirrhosis of the liver urea synthesis was studied during continuous infusion for six to 24 hours of about 3 mmol alpha-amino nitrogen/h X kg body weight. The urea synthesis rate was calculated in intervals of two hours as ...

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,...

In mangrove killifish Rivulus marmoratus, urea excretion (J(urea)) follows a distinct diurnal pattern with the highest rates between 12:00 h and 18:00 h. We investigated the regulating mechanisms that underlie temporal rhythms in J(urea) in R. marmoratus. We hypothesized that the daily pattern of J(urea) in R. marmoratus is (1) due to diurnal changes in urea synthesis rates and ultimately metab...

tions a constant (1). If now these conditions are all complied with, but in addition some new factor is introduced, the effect on the rate of urea excretion can be measured by the deviation of the ratio from its constant value. Most of the experiments given in this paper were carried out on the two subjects, Add. and Dru., whose ratios under standard conditions are given in Paper V of this seri...

Lactatingdairy cows (n=177) fed with grass and corn silage ad libitum kept in pasture, were randomly assigned to evaluate how urea nitrogen in plasma and milk can be related to their pregnancy rate. Blood and milk samples were collected on the artificial insemination (AI) day to evaluate plasma urea nitrogen (PUN) and milk urea nitrogen (MUN) as well as progesterone levels, excluding cows with ...

It has been difficult to directly measure the spontaneous hydrolysis rate of urea and, thus, 1,1,3,3-tetramethylurea (Me4U) was used as a model to determine the "experimental" rate constant for urea hydrolysis. The use of Me4U was based on an assumption that the rate of urea hydrolysis should be 2.8 times that of Me4U hydrolysis because the rate of acetamide hydrolysis is 2.8 times that of N,N-...

The myofibril suspension (in 0.16M KCI-40 mm Tris-HCI , pH 7.5 or 0.16tit KCI-40 mm Trismaleate, pH 5.8)of blue shark and tiger shark was kept at a fixed temperature in the range of 20-45°C with various concentrations of urea and measured for its Ca-ATPase activity with a lapse of tme. In the presence of urea, myofibrillar Ca-ATPase of blue shark inactivated in two first order reactions with an...

The evidence that urea is present in high concentration in the cells of the convoluted tubules of the kidney and is passing through these cells has been reviewed. Following the deposition of a large amount of carmine in the cells of the convoluted tubules the rate of urea excretion, as measured by the relation of the rate of urea excretion to the blood urea concentration, is increased. This is ...