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  • 1
    ISSN: 1434-0879
    Keywords: Calculogenesis ; Calcium oxalate ; Calcium phosphates ; Crystallization inhibitors ; Stone development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An experimental model that enables the close simulation of conditions prevailing in the kidney during the formation of stones, using living tissue of pig urinary bladder, was developed. The results obtained clearly confirmed the importance of the antiadherent glycosaminoglycan (GAG) layer in preventing the development of solid concretions on the urothelium. Of importance was the capacity of the necrosed urothelium to act as a heterogeneous nucleant of calcium oxalate monohydrate (COM) and dihydrate (COD) crystals, demonstrating the major urolithiasic risk factor that alterations of the healthy epithelium covering the renal papilla may pose in humans. The significant increase in brushite and hydroxyapatite crystals detected on the urothelium when the pH of the artificial urine was 6.5, and the protective GAG layer was reduced or the tissue was necrosed, was also notable. The crystallization inhibitory effects caused by citrate and phytate were also studied. It was found that whereas citrate, at normal urinary concentrations, caused a slight reduction in crystallization, with phytate there was total elimination of crystallization-when it was present at very low concentrations such as 1.0 μg/ml.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Urological research 28 (2000), S. 136-140 
    ISSN: 1434-0879
    Keywords: Key words Phytic acid ; Pyrophosphate ; Diphosphonates ; Crystallization inhibitors ; Hydroxyapatite ; Brushite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This is a comparative study of the effects of phytate and pyrophosphate and other polyphosphates on the crystallization of hydroxyapatite and brushite, the most frequent calcium phosphates involved in calcium oxalate urolithiasis. Brushite and hydroxyapatite crystal formation was studied in synthetic urine, through kinetic-turbidimetric measurements that allowed evaluation of the inhibitory effects on crystallization of insoluble salts. The effectiveness in preventing brushite crystallization decreases in the sequence phytate 〉 polyphosphate 〉 EDTPO 〉 etidronate 〉 pyrophosphate 〉 triphosphate 〉 medronate; whereas the order of effectiveness in preventing hydroxyapatite crystallization was EDTPO 〉 etidronate=pyrophosphate 〉 triphosphate 〉 medronate 〉 polyphosphate 〉 phytate. Phytate, a natural inhibitor in urine, most effectively blocked brushite precipitation (1.21·10−5 M prevented crystallization during time periods of at least 1 h), and pyrophosphate was the natural inhibitor that most effectively blocked hydroxyapatite precipitation (2.87·10−6 M prevented crystallization during time periods of at least 1 h). This demonstrates that low excretion of these substances would pose a risk of renal lithiasis.
    Type of Medium: Electronic Resource
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