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Biomedical subjects

F Grases

Publications and source records attributed to F Grases.

At least 91 records · Page 5Linked to original sources
PubMed1991

The origin and causes of struvite stones.

The aim of this paper is to evaluate the possible causes of the origin of "infection stones". The main differences between the ordinary biochemical parameters of a group of patients with this type of stones was analyzed and compared with a group of oxalocalcic stone-formers and with a group of healthy subjects. The importance of persistent basic urinary pH values is pointed out as possible origin of "infection stones" in some instances. The main urinary citrate concentration in patients with "infection stones" was significantly lower than in healthy subjects, this being an important factor that favours this kind of stone formation.

Calcium Oxalate↗
PubMed1991

Determination of citric acid based on inhibition of the crystal growth of calcium fluoride.

Inhibition of the growth of calcium fluoride crystals in the presence of citrate was followed using a kinetic-potentiometric technique and a calcium ion-selective electrode, and as a consequence, a method for the determination of citrate in the range 0.5-2.4 micrograms ml-1 has been developed. The method was successfully applied to the determination of citrate contained in pharmaceutical products and urine. Urine analysis requires prior separation of phosphate, sulphate and magnesium(II). Elimination of these interferences was studied and accomplished using precipitation processes. Magnesium and phosphate were jointly eliminated in basic media by the addition of ammonium ions. Phosphate and sulphate were eliminated with barium(II). Phosphate was also eliminated as a lithium salt.

Calcium Fluoride↗
PubMed1991

An animal model to study the effects of diet on risk factors of calcium stone formation.

The effects of diet on the formation of calcium oxalate stones were studied in 150-day-old rats by measuring the diuresis, pH, and urinary and blood concentrations of promoting and inhibitory substances. An increase in phosphate (promoting) and magnesium (inhibiting), and a decrease in citrate (inhibiting) and pH were found in the urine of rats fed with a high protein diet. No differences were observed in the plasma concentrations of calcium, magnesium, and phosphate. These results confirm epidemiological and clinical studies in humans that have shown that any diet rich in protein can change the concentrations of these substances in urine.

Animals↗
PubMed1990

[Urochemistry].

Explore the source record for details and available documents.

Humans↗
PubMed1990

Production of calcium oxalate monohydrate, dihydrate or trihydrate. A comparative study.

Procedures to obtain calcium oxalate monohydrate, dihydrate and trihydrate are presented and discussed. The influence of several additives and conditions in the formation of calcium oxalate dihydrate crystals are comparatively evaluated. It seems that the presence of colloidal phosphate favours the formation of calcium oxalate dihydrate crystals through heterogeneous nucleation.

Calcium Oxalate↗
PubMed1990

Can a relationship reflect the risk of calcium oxalate urolithiasis?

Different mathematical expressions have been proposed in the literature with the aim to reflect the risk of calcium oxalate urolithiasis. Such expressions, as well as a number of new relationships proposed by us, have been evaluated in 76 patients and 34 normal subjects. Stone-formers were divided into two groups: patients with normal calcium and oxalate excretion and patients with hypercalciuria and/or hyperoxaluria. The results obtained were comparatively evaluated. Several formulae gave some acceptable results, but none of them were excellent. This can be explained by the fact that these discrimination indexes more or less reflect supersaturation and/or inhibition deficit, but none of them reflect promoting factors such as heterogeneous nucleation and/or aggregation capacity.

Calcium Oxalate↗
PubMed1990

On the relation between citrate and calcium in normal and stone-former subjects.

The aim of this work is to evaluate citrate in a group of patients with calcium oxalate urolithiasis and in a control group for detecting possible differences between the two groups. The mean urinary concentration in the stone-formers was found significantly lower than in the controls. Particularly interesting was the correlation study between citrate and calcium. It was found that patients with hypocitraturia have hypercalciuria. Thus, it is particularly interesting to point out the importance of citrate in preventing the risk of lithiasis in the group of stone-formers studied by us.

Adult↗
PubMed1990

Study of factors affecting calcium oxalate crystalline aggregation.

A study was made of the effects of citrate, pentosan polysulphate (a glycosaminoglycan) and mucin (a mucoprotein) upon crystalline growth and aggregation of calcium oxalate in synthetic urine. It was found that citrate inhibited aggregation. Pentosan polysulphate had no perceptible effect on aggregation but favoured the formation of calcium oxalate dihydrate crystals. Mucin enhanced the formation of large characteristic aggregates and also led to the formation of calcium oxalate dihydrate crystals. Particles of mucin in a solution served as a substrate on which several crystals of calcium oxalate dihydrate were formed by heterogeneous nucleation; the subsequent growth of these crystals resulted in the formation of large agglomerates.

Calcium Oxalate↗
PubMed1990

Relation between calcium oxalate hydrate form found in renal calculi and some urinary parameters.

In calcium oxalate urolithiasis, the monohydrate and dihydrate forms can be found. The aim of this paper is to examine a group of patients with calcium oxalate calculi to determine the calcium oxalate form and the possible relationship with calcium and other urinary biochemical parameters. It was found that calcium oxalate monohydrate is more frequent in the normocalciuric group and also is associated with a lack of inhibitory capacity, while a mixed calculus of calcium oxalate and phosphate or calcium oxalate dihydrate can be related with hypercalciuria.

Calcium↗
PubMed1990

The role of hyperoxaluria in the formation of calcium oxalate urinary calculi, and its association with other biochemical measurements.

The part played by hyperoxaluria in the formation of calcium oxalate urinary calculi was studied in 153 patients who had each been diagnosed as having calcium oxalate urinary calculi on one or more occasions. Seventy-seven of the patients excreted normal amounts of calcium (less than 6.2 mmol/d), and 76 had hypercalciuria (excretion greater than or equal to 6.2 mmol/d); each group was divided into a further two groups depending on whether the oxalate concentration was above or below 0.16 mmol/l. Pure calcium oxalate stones were more common in patients whose calcium excretion was normal, and mixed calcium oxalate and phosphate stones were more common among hypercalciuric patients. Urinary concentrations/day of magnesium, citrate, and phosphorus were significantly lower in the two groups in which the oxalate concentrations were below 0.16 mmol/l than in a normal control group, and magnesium and phosphorus were significantly lower in the two groups in which oxalate concentrations were less than 0.16 mmol/l than in the two in which they were above that value. The concentration of citrate was also lower, but not significantly so. In addition, the pH of the urine in patients with mixed stones was significantly higher in all groups than when the stones were composed of pure calcium oxalate.

Calcium Oxalate↗
PubMed1989

Urolithiasis inhibitors and calculus nucleation.

The possible inhibitors of heterogeneous nucleation were investigated. The effects of magnesium, pyrophosphate, citrate and Chondroitin Sulphate on calcium phosphate or uric acid heterogeneous nucleation of calcium oxalate were studied. It was found that whereas magnesium, pyrophosphate and citrate acted as effective inhibitors in the presence of calcium phosphate as heterogeneous nucleant, only chondroitin sulphate manifested important inhibitory effects when uric acid was the heterogeneous nucleant.

Calcium Oxalate↗
PubMed1989

The relation between orthophosphate and pyrophosphate in normal subjects and in patients with urolithiasis.

In calcium lithiasis, inhibitors have a significant effect in reducing the crystallization process. This work evaluated orthophosphate in a group of patients with calcium oxalate lithiasis, and in a control group. The study of orthophosphate and pyrophosphate, showed differences between stone formers and the control group. These results could be attributed to a failure in the renal transformation of orthophosphate into pyrophosphate.

Diphosphates↗
PubMed1989

On the relation between citrate and calcium in normal and stone-former subjects.

The aim of this work is to evaluate citrate in a group of patients with calcium oxalate urolithiasis and in a control group for detecting possible differences between the two groups. The mean urinary concentration in groups of stone-formers was found significantly lower than in the control group. Particularly interesting was the correlation study between citrate and calcium. It was found that patients with hypocitraturia have hypercalciuria. Thus, it is particularly interesting to point out the importance of citrate in preventing the risk of lithiasis in stone-formers studied by us.

Adult↗
PubMed1989

Investigation of GAGS on 24-hour and 2-hour urines from calcium oxalate stone formers and healthy subjects.

The role of urinary glycosaminoglycans (GAGS) in calcium oxalate lithiasis is of great interest in urologic research. It has been claimed that GAGS are important inhibitors of calcium oxalate crystal growth and aggregation. The aim of this paper is to evaluate GAGS excretion and concentration in two groups of patients, calcium stone formers (with or without metabolic alteration) and a control group, to detect possible differences. The findings of this study show that significant differences exist not only in the 24-hour average excretion between stone formers without alteration and healthy subjects but also in the mean concentration values between the stone former and control groups. The same results are obtained from the 2-hour urine analysis. It is concluded that 2-h urine analyses of GAGS have the same or more practical value than a 24-h urine analysis and that the results must be expressed in terms of concentration.

Calcium Oxalate↗
PubMed1989

Inhibitory effect of pyrophosphate, citrate, magnesium and chondroitin sulphate in calcium oxalate urolithiasis.

The inhibitory capacity of pyrophosphate, citrate, magnesium and chondroitin sulphate was investigated, using the urine of 21 calcium oxalate stone-forming patients without metabolic alterations. The inhibitory effect of these substances was assessed by a combination of nephelometry (light scattering) and optical microscopy. The results showed that citrate and magnesium had an inhibitory effect in a significant number of cases. Pyrophosphate and chondroitin sulphate had a less marked effect. The main urinary lithogenic biochemical parameters of the patients were also studied to see if there was a relationship between them and the inhibitory capacity of the compounds.

Calcium Oxalate↗
PubMed1989

Uric acid and its relationship with glycosaminoglycans in normal and stone-former subjects.

Uric acid is implicated in calcium oxalate kidney stone formation. Conspicuously so far, two hypotheses have been proposed: direct induction of calcium oxalate precipitation by uric acid, and uric acid as anti-inhibitor by binding urinary glycosaminoglycans (GAGS). The aim of this work is to evaluate uric acid and the relationship with GAGS in a group of patients with calcium oxalate lithiasis, and in a control group for detecting possible differences between the two groups. It was found that the lower concentration of GAGS in stone formers could impede their inhibitory activity on the heterogeneous nucleation of uric acid in calcium stone formation.

Biomarkers↗