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J G March

Publications and source records attributed to J G March.

32 records · Page 2Linked to original sources
PubMed1996

Study of the effects of different substances on the early stages of papillary stone formation.

We have studied the early stages of calcium oxalate monohydrate (COM) crystallization, mainly heterogeneous nucleation, on fixed particles. Experiments were performed using a flow system that closely simulates the human renal conditions related to COM heterogeneous nucleation. The effects of citrate, phytate, aescin and glycyrrhinic acid in the COM heterogeneous nucleation on different solid surfaces as calcium phosphate, a mixture of mucin and calcium phosphate and wax were studied. The presence of citrate at normal urinary concentrations (1.85.10(-3) M) totally inhibited the development of COM crystals only on the most hydrophobic assayed material (wax). Saponins (aescin and glycyrrhinic acid) only exhibited important inhibitory effects of COM crystallization on the hydrophobic wax substrate but in no case the formation of COM crystals was totally prevented. Phytate exerted the most remarkable effects on the heterogeneous nucleation of COM crystals, thus, when it was present at 1.43.10(-7) M, it totally prevented the development of COM crystals on the three assayed solid substrates.

Calcium Oxalate↗
PubMed1995

Effect of Herniaria hirsuta and Agropyron repens on calcium oxalate urolithiasis risk in rats.

The effects on the calcium oxalate urolithiasis urinary risk factors of Herniaria hirsuta L. (Carryophyllaceae) and Agropyron repens L. (Gramineae), in herb infusion form, combined with different diets (standard, high glucidic, high protein) have been studied using Wistar rats. From this study it is deduced that the possible effects of the A. repens infusion can not be assigned to any positive effects on the main urolithiasis risk factors. The tentative antilithiasic effects of the H. hirsuta infusion clearly depends on the diet. Thus, a clear increase in the citraturia was only detected when such infusion was administered with the high protein diet.

Animals↗
PubMed1995

Study on calcium oxalate monohydrate renal uroliths. III. Composition and density.

Density and content of mineral constituents were determined for 33 human calcium oxalate monohydrate (hereafter COM) uroliths whose external appearance and inner structure were described in part I and II respectively. Studied stones contained 0.13-0.42 wt.% of struvite, 0.68-4.12 wt.% of hydroxyapatite, 73-96 wt.% of COM and 3-10 wt.% of water unbound in a crystallohydrate 10 to 20 wt.% of calculus mass is not accounted for by chemical analysis. Density of COM calculi varying between 1.67 and 2.06 g cm-3 is not a function of any single stone parameter. Around 30% of stone volume is not occupied by crystalline components. The mulberry stones of sedimentary origin contained higher amount of organic matter than papillar and mulberry stones displaying site of attachment to epithelium.

Calcium Oxalate↗
PubMed1994

Urolithiasis and phytotherapy.

The effects of seven plants with suspected application to prevent and treat stone kidney formation (Verbena officinalis, Lithospermum officinale, Taraxacum officinale, Equisetum arvense, Arctostaphylos uva-ursi, Arctium lappa and Silene saxifraga) have been studied using female Wistar rats. Variations of the main urolithiasis risk factors (citraturia, calciuria, phosphaturia, pH and diuresis) have been evaluated. It can be concluded that beneficial effects caused by these herb infusions on urolithiasis can be attributed to some disinfectant action, and tentatively to the presence of saponins. Specifically, some solvent action can be postulated with respect to uric stones or heterogeneous uric nucleus, due to the basifying capacity of some herb infusions. Nevertheless, for all the mentioned beneficial effects, more effective and equally innocuous substances are well known.

Animals↗
PubMed1994

Epidemiology of urinary stone disease in the Balearic Islands Community.

In a survey conducted on 1500 individuals, an overall prevalence of 14.3% for the year 1990 was found for urinary stone disease in the Balearic Islands. The prevalence showed higher figures for people living in rural areas than for those living in cities, and this could be correlated with traditional living habits such as traditional Balearic diet. Finally, a surprising fact is that only 54% had consulted a urologist as outpatients and the rare occasion at which the calculi were analyzed (15.1%).

Female↗
PubMed1994

Artificial simulation of the early stages of renal stone formation.

OBJECTIVE: To study the initial steps of calcium oxalate monohydrate (COM) stone formation and the influence of the inhibitor substances citrate and phytic acid, using an in vitro model. MATERIALS AND METHODS: Experiments were performed using a device to simulate renal stone formation in conditions similar to those found in humans. RESULTS: COM crystal formation took place directly on the solid substrate in contact with the urine but no previous formation occurs in the liquid with subsequent attachment. The first COM crystals appeared after 3 h, in the presence of citrate at a physiological concentration of 1.7 x 10(-3) M. A decrease in the total amount of COM was observed during the next 9 h. After 24 h the quantity of COM crystals was the same irrespective of the presence or absence of citrate. In the presence of phytic acid (6 x 10(-3) M) the appearance of the first COM crystals was delayed by > 24 h. At 78 h a few small COM crystals were detected. CONCLUSION: A fixed solid surface, irrespective of its composition, in contact with normal urine sooner or later develops stone-forming compounds on its surface. The composition of these compounds depends on the supersaturated salts that are present. Under the experimental conditions citrate had only a limited capacity to inhibit COM crystal development. In contrast, phytic acid exhibited a much higher capacity for inhibition even at a considerably lower concentration than that of citric acid.

Calcium Oxalate↗
PubMed1994

Glycosaminoglycans and oxalocalcic urolithiasis.

A very simple analytical procedure with dimethylmethylene blue as photometric reagent was applied for the evaluation of glycosaminoglycan (GAG) urinary excretions and concentrations in both sexes, calcium oxalate stone formers, and a control group. The GAG concentrations varied significantly in stone formers (males and females) and in the control group; moreover, in some individual cases, a deficit of urinary GAGs was clearly detected. Apart from important inhibitory effects of GAGs on heterogenous calcium oxalate nucleation, the low urinary GAG content could be the cause of a pathological epithelium, favoring stone formation. The dimethylmethylene blue method is recommended as a quick screening procedure to determine a GAG deficit.

Calcium Oxalate↗
PubMed1993

Experimental technique simulating oxalocalcic renal stone generation.

A new technique simulating some of the conditions experienced by papillar and caliceal oxalocalcic stones during the early stages of their generation was developed. This technique enables the study of how conditions prevailing at calculogenesis, such as pH, composition of urine and presence of admixtures, influence the rate of formation and development, the crystalline texture and the composition of the concretion formed. Results achieved with this technique demonstrate that: (1) an appropriate substrate always gives rise to a crystalline concretion if it is in contact with supersaturated urine; (2) primary agglomeration plays a significant role in concretion development whereas secondary agglomeration is of minor importance; and (3) citrate and pyrophosphate exert a considerable influence on the shape and composition of particles constituting the concretion.

Calcium Oxalate↗
PubMed1993

Artificial simulation of renal stone formation. Influence of some urinary components.

The effect of natural admixtures occurring in human urine (citrate, pyrophosphate and glycosaminoglycans) on the precipitation of stone-forming compounds was studied. Experiments were carried out under conditions closely simulating the early stages of renal stone formation. Among the studied admixtures, citrate was determined as the most effective substance preventing the phosphate particle formation. Indeed, in the presence of citrate, some calcium oxalate monohydrate crystals were found. Pyrophosphate induced the formation of calcium oxalate dihydrate crystals. Phosphate crystals appeared at pH 6 and never at pH 5. The easy formation of phosphate particles supports the hypothesis that these crystals represent a very important heterogeneous nucleus-initiating oxalocalcic calculus formation in the kidney. Reported results also indicated uric acid as a significant heterogeneous nucleus of calcium oxalate monohydrate crystals at urinary pH equal or lower than 5 and the important role of bacteria in increasing the organic detritus deposited on the solid surfaces.

Calcium Oxalate↗
PubMed1993

New aspects on the composition, structure and origin of calcium oxalate monohydrate calculi.

In this paper a thorough study on the composition and structure of calcium oxalate monohydrate (COM) papillary calculi is presented. In 86.4% of these calculi, small amounts of phosphates were detected and generally located at the calculi core. This demonstrates the importance of phosphates as the heterogeneous nucleus of 'pure' COM calculi. Study of the main biochemical parameters of these patients showed that the most frequent biochemical alteration was associated with hypocitraturia (25%), whereas hypercalciuria and/or hyperoxaluria were detected in very few cases. With respect to the urinary pH values, 70% of the patients presented values lower than 6 and 30% higher than 6. These facts indicate that in a number of cases the formation of phosphates is not the result of persistent high urinary pH values, and the presence of occasional papillary microinfections must be suspected. It is clear that, by avoiding the formation of heterogeneous phosphate nuclei, 'pure' COM calculi would not develop, and consequently therapies for these individuals under these conditions must take this into account.

Calcium↗
PubMed1992

Effect of "Rosa Canina" infusion and magnesium on the urinary risk factors of calcium oxalate urolithiasis.

The effects on the calcium oxalate urolithiasis urinary risk factors of "Rosa Canina", in herb infusion form, and magnesium chloride have been studied using female Wistar rats under balanced dietary conditions. No significant effects on the volume of liquids drunk or on creatinine, phosphate, and oxalate urinary concentrations and excretions were observed. The herb infusion did not cause any diuretic effect. Calciuria decreased and citraturia increased when taking the herb infusion, and vice versa when taking magnesium chloride. Magnesium chloride decreased the urinary pH value, but this effect was not observed when magnesium chloride was administered with herb infusion. In conclusion, the same beneficial effects of the studied infusion herb on calcium oxalate urolithiasis urinary risk factors can be clearly detected. An interesting fact is that it seems that some possible effects depend on dietary components, thus, i.e., an increase in the urinary pH was only detected when the intake of the herb infusion was studied in a magnesium chloride-supplemented diet.

Animals↗
PubMed1991

Glycosaminoglycans, uric acid and calcium oxalate urolithiasis.

The interaction between calcium and glycosaminoglycans (GAGs) was studied using a calcium ion-selective electrode. The Ca-binding capacity of GAGs involved 16% of total calcium in the presence of chondroitin sulphate and 28% in the presence of pentosan polysulphate. The action of GAGs on the nucleation of uric acid and sodium urate was examined and inhibitory effects were observed. The action of uric acid as a heterogeneous nucleant of calcium oxalate was studied, and considerable promotion of the heterogeneous nucleation of calcium oxalate by uric acid was found, which could be inhibited by the action of GAGs. From these summarised in vitro results, we conclude that uric can constitute an important risk factor for calcium oxalate urolithiasis through heterogeneous nucleation and the GAGs can play an important role as preventive agents.

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↗