Biomedical subjects

F Grases

Publications and source records attributed to F Grases.

At least 73 records · Page 4Linked to original sources

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↗

PubMed1994

Role of agglomeration in the early stages of papillar stone formation.

Possible effects of crystal agglomeration on the early stages of calcium oxalate papillar stone formation are evaluated. The collecting ducts are filled with liquid that flows laminarly as established through hydrodynamical and physicochemical considerations. Under such conditions, agglomeration due to laminar shear forces proceeds. Agglomeration of calcium oxalate monohydrate crystals present in urine at a concentration typical for clinically observed crystalluria cannot result in the formation of a particle sufficiently large enough to be retained in the Bellini's duct and become a papillar stone nidus (nucleus). Formation of such an aggregate during the passage time of urine through the duct requires an unrealistically high concentration of crystals in urine, one that exceeds the normal content of urinary oxalate by several orders of magnitude. Aggregates obstructing the Bellini's duct as assumed in the free particle theory cannot represent a major factor in stone formation. This conclusion is corroborated by experimental results and other observations.

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

Fine structure of calcium oxalate monohydrate renal calculi.

Fine structure, location and size of the core of 12 calcium oxalate monohydrate (COM) papillar calculi from different 'idiopathic' stone-formers were studied by an optical and scanning electron microscope equipped with the EDAX analytical device. Each individual core exhibited a unique overall structure composed of loosely arranged twined and intergrown crystals of plate-like and/or columnar shape and particles of 'rosette' structure with considerable void space among crystals in some cases or compact structure in others. Crystals were covered by a thin layer or organic material mostly invisible to the microscope. Sometimes debris of organic origin in a core was observed. A substantial amount of organic matrix appeared at the core boundary, often in the form of amorphous plates. The outer striated layer of COM stone consisting of tightly packed columnar crystals originated on this matrix. The stone core was located near the stone surface that was attached to the kidney wall and contained foreign particles that act as heterogeneous nucleants of calcium oxalate crystals.

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

Zinc, copper and oxalocalcic urolithiasis.

The possible effects of Zn and Cu in oxalocalcic urolithiasis were investigated. The formation of calcium oxalate crystals in the presence of Zn and Cu demonstrated that their morphology is clearly affected by these ions. Thus, when such ions were present in a number of higher concentrations, a notable increase in the primary aggregation was clearly detected. On the other hand, Zn and Cu urinary levels were determined in groups of stone-formers and healthy people. Zinc urinary concentration was significantly lower for lithiasic than for healthy people and the copper urinary concentration was lower for lithiasic than healthy males, but both female groups had a similar copper urinary concentration. The mentioned differences disappeared when serum levels were considered. These obtained results have been comparatively evaluated with those obtained by other authors. When considering all the commented aspects, it is concluded that no important direct action of zinc and copper on oxalocalcic calculi genesis takes place.

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↗

PubMed1993

Studies on structure of calcium oxalate monohydrate renal papillary calculi. Mechanism of formation.

A scanning electron microscopy study of the ultrastructure of 18 calcium oxalate monohydrate papillary calculi was performed with the purpose of establishing the main steps in calculus formation. It is concluded that these calculi originate in a "core" located near the central part of the calculus. Significant quantities of organic matter as well as calcium phosphates can be found in the "core" and at the surface of adhesion to the papilla and, in some cases, fibers and calcified tubules can also be found in the contact zone. In no case did this material affect the crystalline structure of the calculi, indicating that its formation follows the calculus genesis. The study of the compact columnar zone revealed that its formation starts in a practically continuous surface formed by organic matter and crystals that surround the core. This layer favors the growth of oriented calcium oxalate monohydrate crystals upon it. Based on these observations, a feasible mechanism of papillary calcium oxalate monohydrate calculus formation is proposed.

Adolescent↗

PubMed1993

Mechanism of oxalocalcic renal calculi generation.

Based on reconsideration of the contemporary knowledge on calcium oxalate urolithiasis a feasible mechanism of calculi generation is suggested. Experimental findings and clinical aspects supporting the suggested mechanism are presented. The ways of urolithiasis treatment and areas of future research are indicated.

Antacids↗

PubMed1992

Urolithiasis, inhibitors and promoters.

The aim of this work is to evaluate the role and importance of inhibitors and promoters in urolithiasis. Carrying in mind theoretical considerations, we conclude that in urolithogenic processes, inhibitors and promoters could only play a decisive role in the "idiopathic" oxalocalcic urolithiasis. We classify the "idiopathic" oxalocalcic stone-formers into three main groups, considering inhibitory and promoting factors. It is shown that such classification is in good agreement with the clinical results observed in a group of 88 "idiopathic" oxalocalcic stone-formers.

Adult↗

PubMed1992

Dietary effects upon calcium oxalate urolithiasis risk.

An animal model involving rats fed with different diets (high protein, high carbohydrate, high lipid, high fiber and control balanced diet) was used to evaluate the dietary effects on the main oxalocalcic urolithogenic parameters. It was found that the inhibitory factors that prevent calcium oxalate stone formation (citrate and magnesium) were clearly more favorable in the group of rats fed with a balanced diet. However, factors favouring the heterogeneous calcium phosphate nucleation were also found in the balanced diet. On the other hand, factors facilitating the heterogeneous uric acid nucleation were found in rats treated with high protein, high lipid, high carbohydrate and high fiber diets. In conclusion it seems that the balanced diet appears to be the less lithogenic one.

Animals↗

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↗

PubMed1992

Agglomeration of calcium oxalate monohydrate in synthetic urine.

The development of agglomerated particles of calcium oxalate monohydrate (COM) on the semi-batch precipitation from a synthetic urine carried out at physiological conditions (37 degrees C, pH = 5.5) was studied by optical and electron scanning microscopy. COM agglomerates develop by primary and secondary agglomeration proceeding simultaneously; the latter mechanism is, however, less important than the former. Citrate ions modify slightly the COM crystal shape and inhibit primary agglomeration. Mucin particles serve as a substrate for preferential formation (nucleation) of new COM crystals. The structure of formed agglomerates closely resembles that of a certain type of COM renal calculi. A combination of primary agglomeration of crystals forming stones and nucleation of new crystals on a mucoprotein layer partially covering their surface constitutes the possible mechanism of such stone development. Experimental data support this mechanism.

Calcium Oxalate↗

PubMed1992

Role of agglomeration in calcium oxalate monohydrate urolith development.

Formation of agglomerates of calcium oxalate monohydrate (COM) crystals on semi-batch precipitation performed at conditions relevant to urolithiasis (37 degrees C, pH = 6, initial ratio [Ca]/[Ox] = 10), but without any specific admixture, was followed by both optical and electron microscopy. COM crystals formed on precipitation developed into large agglomerates consisting of intergrown crystals by a mechanism of primary agglomeration. Primary agglomeration of COM crystals represents an important mechanism of COM renal calculi growth.

Calcium Oxalate↗

PubMed1992

Inhibitors of calcium oxalate crystallization and urolithiasis.

In urolithogenic processes both, promoters and deficit of inhibitors, play an important role. The inhibitory action of added inhibitors (magnesium, citrate, pyrophosphate and chondroitin sulphate) was investigated using the urine of 72 patients with calcium urolithiasis. It was concluded that the deficit of inhibitors seems to be an important cause of stone formation in idiopathic oxalocalcic urolithiasis. Nevertheless, when that specific heterogeneous nucleation takes place it becomes an important factor and the inhibitor plays a complementary role in calcium oxalate urolithiasis.

Calcium Oxalate↗

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↗