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F Grases

Publications and source records attributed to F Grases.

100 records · Page 6Linked to original sources
PubMed1989

[Introduction of an enzyme method for determining pyrophosphate in urine--a comparative study between patients with calculi and normal probands].

Interest aroused towards pyrophosphate as a possible inhibitor in calcium oxalate and phosphate lithiasis. A procedure for the quantitative determination of pyrophosphate in urine suitable for use in clinical laboratories is described. The reproducibility of the method was assessed by within-run and between-run reproducibility studies and the accuracy of the method was obtained by determining the amount of pyrophosphate recovered in urine samples. The present study compares the pyrophosphate excretion and concentration between a control group and a calcium oxalate stone former group.

Calcium Oxalate↗
PubMed1988

Variations in the activity of urinary inhibitors in calcium oxalate urolithiasis.

Opinions vary on the effects produced by urinary inhibitors of crystallisation. We describe a simple method for studying inhibitory effects in urine based on nephelometry and optical microscopy. It was concluded that the inhibitory effect of a given substance on calcium oxalate crystallisation depends on the particular sample of urine being examined and that the most effective inhibitor can be determined only by studying the urine of each patient individually.

Calcium Oxalate↗
PubMed1988

Simple method for the study of heterogeneous nucleation in calcium oxalate urolithiasis.

A simple method, based on optic microscopy and a counting chamber, has been devised for the study of heterogeneous nucleation in calcium oxalate urolithiasis. Calcium phosphate, uric acid, silica and macromolecular mucoprotein are proposed as possible nucleants. The importance of heterogeneous nucleation as a fundamental step in the formation of calcium oxalate calculi is demonstrated.

Calcium Oxalate↗
PubMed1984

Spectrofluorimetric determination of desoxycholic acid in the presence of cholic and chenodesoxycholic acids by use of Ce(IV) and concentrated sulphuric acid.

A method for the quantitative estimation of desoxycholic acid (200-700 micrograms/ml) in the presence of cholic and chenodesoxycholic acids is described. The method is based on the transformation of desoxycholic acid in fluorescent products (lambda ex = 350 nm, lambda em = 458 nm) by the action of concentrated sulphuric acid, this being enhanced by the presence of Ce(IV). The sample is mixed with a solution of Ce(IV) and concentrated sulphuric acid under standard conditions. Fluorescence is measured in relation to a reference containing the same components except Ce(IV). Cholic and chenodesoxycholic acids do not produce a reaction under adequate conditions. Synthetic samples of bile acids were tested for validation of the method.

Cerium↗
PubMedDate not supplied

Experimental model to study sedimentary kidney stones.

An experimental model to reproduce, to some extent, the conditions prevailing during the formation of the so-called sedimentary urinary stones, was developed. The results obtained demonstrated that in the absence of organic matter no calcium phosphate crystals were deposited in cavities with scarce liquid renovation. Nevertheless, in such case a regular hydroxyapatite layer was developed on the walls around the cavity. The presence of crystallization inhibitors cannot stop indefinitely the crystal development. Therefore, phytate manifested important inhibitory effects in concentrations normally found in urine (0.77-1.54 x 10(-6) mol/l), whereas citrate only manifested important inhibitory effects when found at high urinary concentrations (2.64 x 10(-3) mol/l). When mucin (a glycoprotein) was present in the urine, a clear deposit of calcified organic material was formed. The organic matter appeared mixed with the spherulites of hydroxyapatite, this demonstrating the capacity of the glycoprotein agglomerates to act as heterogeneous nucleants of calcium salts and their important role in the formation of sedimentary stones. The structural features of the obtained in vitro deposits were compared with the fine structure of human sedimentary phosphate calculi. Scanning electron microscopy images demonstrated a good correspondence between in vitro experiments and in vivo observations.

Calcium Phosphates↗
PubMedDate not supplied

Phytate (IP6) is a powerful agent for preventing calcifications in biological fluids: usefulness in renal lithiasis treatment.

The extraordinary capacity of phytate (myo-inositol hexaphosphate), a substance present in blood, urine, interstitial and intracellular fluids, to inhibit crystallization of calcium salts (oxalate and phosphate) is discussed. Its role in preventing calcium renal stone formation is specifically presented and discussed. "In vitro" and "in vivo" experiments, as well as clinical studies clearly demonstrated that phytate plays an important role as a crystallization inhibitor of calcium salts in biological fluids and becomes a clear alternative in the treatment of calcium oxalate renal lithiasis.

Animals↗
PubMedDate not supplied

Intracellular and extracellular myo-inositol hexakisphosphate (InsP6), from rats to humans.

The presence of myo-inositol hexakisphosphate (InsP6) in biological fluids (blood, urine, saliva, interstitial fluid) of mammalians has been clearly demonstrated. The existence of intracellular InsP6 in mammalian cells has also been established. Further, significant extracellular and intracellular functions of this molecule have been found. The relationship between InsP6 ingestion and the InsP6 distribution in various tissues of mammalians is discussed. It was found that the majority of the extracellular InsP6 found in organs, tissues and biological fluids of mammalians has a dietary origin and is not a consequence of endogenous synthesis, whereas the intracellular InsP6 probably originates in the cell. Little absorption of dietary InsP6 takes place during intestinal transit and depletion of extracellular InsP6 occurs at high rates when InsP6-poor diets are consumed. From these results, it can be deduced that health benefits linked to extracellular InsP6 must be related to dietary InsP6.

Animals↗