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  • 1
    Electronic Resource
    Electronic Resource
    Urease-induced precipitation of phosphate salts in vitro on indwelling catheters made of different materials (1991)
    Springer
    Urological research 19 (1991), S. 297-300 
    Details
    ISSN: 1434-0879
    Keywords: Indwelling catheters ; Catheter encrustations ; Urease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The urease-induced precipitation of phosphate salts on indwelling catheters was studied in an experimental in vitro model. The precipitation was strongly pH-related and was much higher in synthetic urine than in human urine. In the latter, it was significantly lower on silicone catheters than on latex catheters, including those with a hydrophilic coating. The precipitation on silicone catheters that had been in situ was not increased as compared with that on unused catheters, in contrast to latex catheters with a hydrophilic coating, among which the precipitation on used catheters was higher.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299063
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    How variations in the composition of urine influence urease-induced crystallization (1990)
    Springer
    Urological research 18 (1990), S. 413-417 
    Details
    ISSN: 1434-0879
    Keywords: Urease-induced crystallization ; Urine composition ; Urinary pH ; Urinary calcium ; Urinary magnesium ; Urinary albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To Study how the composition of urine influences urease-induced crystallization, human urine samples were incubated with urease and the subsequent precipitation measured. Beside the pH increase, the urinary content of magnesium and calcium had profound effects on the precipitation of magnesium ammonium phosphate and calcium phosphate, respectively. Urine phosphate, ammonium and osmolarity had no direct effects on the precipitation. Among the urine components with potential inhibitory properties, only albumin was found to be correlated with such an effect. This inhibitory activity was especially influential in urines with high calcium and magnesium levels. These findings suggest that the composition of urine could also influence the formation of stones consisting of magnesium ammonium phosphate and calcium phosphate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297375
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Studies of urease-induced crystallisation in undiluted human urine using the Coulter counter technique (1991)
    Springer
    Urological research 19 (1991), S. 171-175 
    Details
    ISSN: 1434-0879
    Keywords: Urease-induced crystallisation ; Coulter counter ; Undiluted human urine ; Magnesium ammonium phosphate ; Calcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Urease-induced crystallisation was studied in different human urine samples after urease incubation. The studies were performed using the Coulter counter technique, which enables determination of the number and size of particles in a solution and calculation of the total particle volume. The crystallization took place in three consecutive but overlapping steps: (1) nucleation, (2) growth and (3) aggregation. The maximal number of particles obtained in the different samples varied little, but there was a great variation in particle size and total particle volume. The variation in particle size appeared to be mainly due to differences in particle growth, a factor that might be of importance for stone formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303744
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of pH and urine composition on urease enzymatic activity in human urine (1992)
    Springer
    Urological research 20 (1992), S. 35-39 
    Details
    ISSN: 1434-0879
    Keywords: Urease activity ; Urine pH ; Urine crystallisation ; pH-stat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is reasonable to assume that the rate of pH increase in urine induced by urease-producing microorganisms is one of the factors which determine whether crystallisation with subsequent stone formation will occur or not. To evaluate how the time needed to increase urine pH varies between different urine samples and how it depends on urine composition, a standardised amount of urease was added to different human urine samples. The incubations were performed in a pH-stat. This allowed simultaneous study of how urease enzymatic activity depends on urine pH and how it varies between different urines. The enzymatic activity was found to be negatively correlated to urine pH and to vary between different urines. The rate of the pH increase varied markedly between different urines. Small pH increases depended on the native urine pH and urease enzymatic activity. Higher pH increases up to the levels of phosphate crystallisation depended more on urine phosphate, the major urine buffer. The results presented show that urine composition influences the urease-induced pH increase. This might have clinical implications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294332
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of serum, albumin and immunoglobulins on urease-induced crystallization in urine (1990)
    Springer
    Urological research 18 (1990), S. 407-411 
    Details
    ISSN: 1434-0879
    Keywords: Urease-induced crystallization ; Serum ; Albumin ; Gammaglobulin ; Magnesium ammonium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of serum, albumin and gammaglobulins on urease-induced crystallization have been studied in synthetic and in human urine. Serum and the studied proteins increased urease enzymatic activity in synthetic urine. In human urine only serum had this effect. In synthetic urine, the proteins and serum markedly decreased the precipitation attached to glass surfaces, while the intraluminal precipitation was increased. In human urine, similar but weaker effects on the precipitation were found for serum and albumin. These findings suggest that the proteins studied, in the concentrations in which they are present in human urine, have profound effects on urease-induced crystallization and may be physiological crystallization inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297374
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Human urine - Chemical composition and fertilizer use efficiency (1994)
    Springer
    Nutrient cycling in agroecosystems 40 (1994), S. 149-154 
    Details
    ISSN: 1573-0867
    Keywords: heavy metals ; ionic composition ; 15N- and32P-tracer ; plant nutrients ; pot experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Stored human urine had pH values of 8.9 and was composed of eight main ionic species (〉 0.1 meq L−1), the cations Na, K, NH4, Ca and the anions, Cl, SO4, PO4 and HCO3. Nitrogen was mainly (〉 90%) present as ammoniacal N, with ammonium bicarbonate being the dominant compound. Urea and urate decomposed during storage. Heavy metal concentrations in urine samples were low compared with other organic fertilizers, but copper, mercury, nickel and zinc were 10–500 times higher in urine than in precipitation and surface waters. In a pot experiment with15N labelled human urine, higher gaseous losses and lower crop uptake (barley) of urine N than of labelled ammonium nitrate were found. Phosphorus present in urine was utilized at a higher rate than soluble phosphate, showing that urine P is at least as available to crops as soluble P fertilizers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750100
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    Paper (German National Licenses)
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