Bacterial Hydrolysis of Urea in the Tissues of Carcharhinid Sharks

1988 ◽  
Vol 45 (2) ◽  
pp. 357-360 ◽  
Author(s):  
Ivor T. Knight ◽  
D. Jay Grimes ◽  
Rita R. Colwell
Keyword(s):  
Urea Hydrolysis ◽  
Shark Species ◽  
Blood Samples ◽  
Negaprion Brevirostris ◽  
Liver Homogenates ◽  
Hydrolysis Of ◽  
Ureolytic Bacteria ◽  
Hydrolysis Of Urea

Ureolytic activity was detected in liver homogenates of two carcharhinid shark species, Galeocerdo cuvieri and Negaprion brevirostris, employing 14C-labeled urea to monitor mineralization over 48 h. Significant (P < 0.05) urea hydrolysis was detected in liver homogenates within 48 h whereas no hydrolysis was detected in homogenates incubated with either ampicillin or the vibriostatic agent O/129, indicating bacterial mediation of the ureolytic activity. Urea hydrolysis could not be detected in blood samples. The autochthonous microflora of sharks has been found to contain ureolytic bacteria, and the present study supports the conclusion that they are present in organ tissues of healthy sharks but are not present in the blood.

EFFECTS OF CATECHOL AND P-BENZOQUINONE ON THE HYDROLYSIS OF UREA AND ENERGY BARRIERS OF UREASE ACTIVITY IN SOILS

1984 ◽  
Vol 64 (1) ◽  
pp. 51-60 ◽  
Author(s):  
J. S. TOMAR ◽  
A. F. MacKENZIE
Keyword(s):  
Activation Energy ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Key Words ◽  
Urease Activity ◽  
Urea Hydrolysis ◽  
Urease Inhibitors ◽  
Soil Urease ◽  
Hydrolysis Of ◽  
Hydrolysis Of Urea

The effects of the urease inhibitors, catechol and p-benzoquinone, and temperature on the hydrolysis of urea in five soils were investigated in a laboratory study. Urea hydrolysis decreased significantly with the amount of inhibitors applied and increased significantly with each 5 °C increase in temperature from 5 to 25 °C. The effectiveness of inhibitors generally decreased with increases in temperature from 5 to 25 °C. The correlation of hydrolysis of urea with organic matter contents of the soils was highly significant (r = 0.67** to 0.86**). Both catechol and p-benzoquinone tended to increase the energies and entropies of activation of soil urease and the effect was enhanced with a decrease in soil organic matter. It is suggested that an increase in the activation energy of the soil urease as a result of inhibitor use was related to an increase in the effectiveness of the inhibitor. Key words: Urease inhibitors, urea hydrolysis, energy of activation

A Coulometric Determination of Urea Nitrogen in Blood and Urine

1965 ◽  
Vol 11 (7) ◽  
pp. 700-707 ◽  
Author(s):  
Gary D Christian ◽  
Edward C Knoblock ◽  
William C Purdy
Keyword(s):  
Urine Samples ◽  
Coulometric Determination ◽  
Urea Nitrogen ◽  
Blood Samples ◽  
End Point ◽  
End Point Detection ◽  
Point Detection ◽  
Hydrolysis Of ◽  
Hydrolysis Of Urea

Abstract To determine urea nitrogen, ammonia resulting from urease hydrolysis of urea is titrated with coulometrically generated hypobromite ion using a direct amperometric end-point detection. In blood samples, the ammonia is first separated by the microdiffusion technic. The ammonia may be titrated directly in urine samples.

The Nitrogen Cycle in the Sea

1937 ◽  
Vol 22 (1) ◽  
pp. 183-204 ◽  
Author(s):  
L. H. N. Cooper
Keyword(s):  
Amino Acids ◽  
Nitrogen Cycle ◽  
Sea Water ◽  
Equilibrium Mixture ◽  
Urea Hydrolysis ◽  
Trimethylamine Oxide ◽  
Hydrolysis Of ◽  
Hydrolysis Of Urea

The nitrogen cycle in the sea is reviewed as a whole in accordance with the scheme set out in Fig. 1. This summary includes only original matter, since the survey of other work does not admit of further condensation. The metabolism has been discussed of the following sources of nitrogen available to plants in sea water: mono, di and trimethylamine, trimethylamine oxide, urea, amino-acids, ammonia, hyponitrite, nitrite and nitrate. The methylamines will interfere in analyses of ammonia by distillation. Thermodynamic methods have been extensively used. The equilibrium between urea and ammonium cyanate at sea-water concentrations favours the cyanate. In sea water containing 28 mg. ammonia N per cu. m., the equilibrium mixture will contain fifteen times as much cyanate as urea. Hydrolysis of urea is probably purely chemical.

Urea hydrolysis and inorganic N in a Luvisol after application of fertiliser containing rare-earth elements

Soil Research ◽  
2003 ◽  
Vol 41 (4) ◽  
pp. 741 ◽  
Author(s):  
Xingkai Xu ◽  
Zijian Wang ◽  
Yuesi Wang ◽  
Kazuyuki Inubushi
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Substantial Reduction ◽  
Application Rate ◽  
Urea Hydrolysis ◽  
High Rate ◽  
Short Term ◽  
N Content ◽  
N Fertilisers ◽  
Hydrolysis Of

In recent decades, Chinese agriculturists have used rare-earth-containing fertilisers as basal fertilisers together with N fertilisers (e.g. urea). We studied urea hydrolysis and its hydrolysis products in a laboratory experiment using urea-N fertiliser with rare earths at rates from 0.5 to 50% (w/w). The results indicated that application of rare earths at a high rate could result in a short-term inhibition of urea hydrolysis and an increase in soil (NH4+ + NO3– + NO2–)-N content. When the application rate of rare earths was higher than 5% of the applied urea-N (corresponding to 10 mg/kg soil), soil exchangeable NH4+-N content increased significantly following the hydrolysis of the applied urea. Increasing the application rate of rare earths appeared to reduce the content of soil urea-derived (NO3– + NO2–)-N. A substantial reduction in soil pH was found immediately after application of rare earths and urea. We conclude that application of rare earths at >10 mg/kg may lead to a substantial increase in the content of urea-derived N in the soil, via the inhibition of urea hydrolysis and nitrification.

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