Effect of fermentable fructo-oligosaccharides on mineral, nitrogen and energy digestive balance in the rat.

In the present study, we have assessed the apparent retention of gross energy, nitrogen and Ca, Mg, Fe, Zn and Cu in rats receiving a diet supplemented with fermentable fructo-oligosaccharides with high and low degree of polymerization. Feeding 10% Raftilose (degree of polymerization: 4.8) or 10% Raftiline (degree of polymerization: 10) decreased to the same extent (a) the fecal excretion of all the minerals, despite an increase in total fecal mass excretion leading to an improvement of the absorption of Ca, Mg, Fe and Zn; (b) total gross energy absorption; and (c) led to an increase in the faecal excretion and to a decreased urinary excretion of nitrogen, suggesting a displacement of part of nitrogen excretion towards the large intestine. Feeding fermentable fructo-oligosaccharides may thus constitute a good way to counteract syndromes resulting from hyperammonemia or disturbed Fe, Ca, Mg and Zn homeostasis.

Toxicity of litholytic ethylenediaminetetraacetic acid solutions to the urothelium of the rat and dog.

The toxicity to the urothelium of bipotassium ethylene-diaminetetraacetic acid (K2-EDTA) buffered with 0.2 M triethanolamine (TEA) at pH 8 and 8.5 was tested in rats and dogs. Even at a low concentration of 3.125 mM, K2-EDTA is very noxious to the bladder mucosa. This toxicity is not due to the buffer TEA, which is well tolerated. Although buffered K2-EDTA, at pH 8.5 is an excellent chemolytic agent for calcium-containing stones, its clinical use is limited by this toxicity.

Solubility of calcium oxalate monohydrate and hydroxyapatite in EDTA solutions.

The effect of the addition of a buffer to an ethylenediaminetetracetic acid (EDTA) litholytic solution on the solubility of calcium oxalate monohydrate and hydroxyapatite is investigated. The experiments show that the addition of triethanolamine as a buffer to EDTA solutions at pH 8 and 8.5 enhances the solubility of these salts, confirming theoretical predictions. The solubility of calcium oxalate monohydrate at 25C in solutions with varying ratios of buffer to EDTA concentrations and an osmolality of 0.9 was determined. The solutions resulting in the highest solubility were finally tested for their litholytic ability at 37C. At pH 8 solubilities of 22.5 g X l-1 for calcium oxalate monohydrate and 20.2 g X l-1 for hydroxyapatite were obtained. The corresponding solubilities at pH 8.5 were respectively 24.5 g X l-1 and 19.2 g X l-1.

Screening of chelating agents for chemolysis.

The solubility of calcium oxalate monohydrate and calcium hydroxyapatite was calculated as a function of pH in the presence of different chelating agents and was compared with the solubilities in EDTA- or CDTA-containing solutions. An analysis of the solubility curves for 19 chelating agents showed that 5 of the complexing agents considered result in a high solubility for calcium phosphate and oxalate at pH 8 or higher. For these complexing agents the solubility curves of struvite were also calculated. EGTA and HEDTA showed rather low solubilities for struvite due to their low tendency to form complexes with magnesium. On the basis of the calculated solubility curves, the expected litholytic effectiveness for the inorganic kidney stone compounds could be classified in the following decreasing order: CDTA approximately equal to EDTA approximately equal to EGTA greater than EEDTA greater than DTPA greater than UDA approximately equal to HEDTA. With the exception of EGTA and HEDTA for struvite stones, solutions based on these compounds show high solubilities for all the inorganic kidney stone compounds at a solution pH of 8 or higher and therefore have good prospects as litholytic agents.

Solubility of inorganic kidney stone components in the presence of acid-base sensitive complexing agents.

Computation methods used to calculate the solubilities of the main inorganic kidney stone components in the absence or presence of acid-base-sensitive complexants as a function of pH are described. The solubilities of whewellite, brushite, whitlockite, octocalcium phosphate, hydroxyapatite and struvite were calculated in the presence of ethylenediaminetetraacetate (EDTA), trans-cyclohexane-1,2-diaminetetraacetate (CDTA), citrate, tripolyphosphate and alpha-hydroxyisobutyrate. The results explain why kidney irrigations with citrate give extremely variable results. The calculated solubility curves show that only EDTA and CDTA solutions with a pH of 8 or higher will have good litholytic properties for all compounds concerned. The computation methods presented in this paper can be used to calculate the solubility of a large number of salts. These salts may contain non-acid-base-sensitive cations capable of forming complexes, acid-base-sensitive anions, hydroxyl ions, hydrogen ions or other acid-base-sensitive cations (e.g. NH4+), and the solubilities can be calculated in the presence or absence of acid-base-sensitive complexing agents.

Catalytic influence of Cl(-), Br(-), I(-) and SCN(-) on the cyclic voltammetric behaviour of Sb(III).

The electrocatalysis of the reduction of Sb(III) ions at a mercury electrode by Cl(-), Br(-), I(-) and SCN(-) ions and its dependence on the hydrogen-ion concentration has been studied in 4M (H, Na)ClO(4) solutions by cyclic voltammetry. The electrocatalytic capacity increases considerably in the order Cl(-) < SCN(-) < Br(-) < I(-) and a ligand-bridging mechanism is probably involved. Increasing the acidity at constant bridging-ligand concentration enhances the reaction rate. This can be explained by assuming that the influence of the hydrogen-ion concentration on the bridged activated complex is the same as on the Sb(III) complexes present in the bulk of the solution. From an analytical point of view it is important that the reduction of Sb(III) ions at a mercury electrode proceeds reversibly in the presence of Cl(-), Br(-), I(-) or SCN(-) ions.

Electrochemical study of the oxidation of tin(II) at glassy carbon electrodes.

The voltammetric characteristics of the Sn(IV)/Sn(II) system have been studied at a glassy carbon rotating disk electrode in 4M hydrochloric acid. Anodic oxidation of Sn(II) produces a single well-defined wave, which has been examined in the temperature range 20-50 degrees , and shows distinct irreversibility. The kinetic parameters of the oxidation reaction have been calculated. Kinetic features of the reduction of Sn(IV) to Sn(II) were not evaluated because the reduction proceeds directly to tin metal.