Search PubMed⌕ Search

Biomedical subjects

F Grases

Publications and source records attributed to F Grases.

At least 55 records · Page 3Linked to original sources
PubMed1998

Effects of phytic acid on renal stone formation in rats.

The effects of phytic acid and phytic acid/zinc mixtures on renal urolith development in an animal model of nephrolitiasis were studied. Male rats were divided into four groups of 15, 10, 10 and 12 rats each. The rats of Group I were treated with ethylene glycol; of Group II with ethylene glycol plus zinc; of Group III with ethylene glycol phytic acid; and of Group IV with ethylene glycol plus a mixture of phytic acid/zinc. Urine analysis (24 h) was carried out to determine the levels of calcium, oxalate, citrate, zinc and phytic acid in each group. At the end of the experiment all kidneys were removed and examined macroscopically and microscopically for possible crystal/stone locations and the total calcium amount in the renal papillary tissue was evaluated. In the rats treated with the aqueous phytic acid and phytic acid/zinc mixture, the number of calcifications on the papillary tips and the total calcium amount of the papillary tissue were significantly reduced compared with the controls treated exclusively with ethylene glycol or ethylene glycol plus zinc. Consequently, phytic acid and mixtures of phytic acid/zinc may be a useful agent in the treatment of patients with calcic urolithiasis.

Animals↗
PubMed1998

Development of calcium oxalate crystals on urothelium: effect of free radicals.

The effects of free radicals on the development of crystals attached to the living epithelium have been studied using an experimental model that enables close simulation of the conditions prevailing in the kidney. The results obtained clearly demonstrate that free radical-damaged cells produce a favorable environment for crystal development. At low free radical concentrations, crystals develop on calcium-enriched zones, whereas at higher concentrations, crystals develop on areas with a destroyed monolayer of superficial cells. Evaluation of the action of some products with antioxidant action and/or crystallization-inhibitory capacity is also included. Antioxidants, such as ascorbic acid and mannitol, exerted the most remarkable effects in avoiding calcium oxalate crystal development, whereas crystal inhibitors, such as citric acid, did not produce any remarkable reduction in calcium oxalate crystallization. Phytic acid notably decreased calcium oxalate crystal development. The ability of phytic acid to diminish calcium oxalate crystallization must be attributed to the combination of its inhibitory capacity of calcium oxalate crystallization and its preventive antioxidant action.

Animals↗
PubMed1997

Simple test to evaluate the risk of urinary calcium stone formation.

A simple test to evaluate the capacity of a urine to crystallize calcium salts is presented. The test is based on the fact that if a non-protected non-renewed surface remains in contact with a urine, sooner or later the contained supersaturated substances crystallize on it. Thus, by using an adequate surface, it is possible to derive a period within which a normal urine does not crystallize whereas a lithogenic urine induces the growth of calcium salts. The test was applied to urines of oxalocalcic stone-formers and healthy people and showed an excellent discrimination between clearly abnormal and healthy urines. Semiologic analysis of the data is also included.

Adult↗
PubMed1997

Chronopharmacological studies on potassium citrate treatment of oxalocalcic urolithiasis.

The effect of minimum doses of extradietary potassium citrate ingestion on urolithogenic parameters has been studied. Separate urine fractions were collected in 24-hour periods. Five calcium oxalate stone formers have participated in the study. pH, calcium, citric acid, and the crystallization inhibitory capacity levels in fractional urine samples were determined before and during treatment. The most beneficial effect (increase in citraturia and crystallization inhibitory capacity) was produced by potassium citrate tablets ingested after dinner.

Adult↗
PubMed1997

Structure of uric acid concretion developed around a catheter.

A uric acid concretion formed round a catheter (JJ stent) in the bladder and removed intact from the body together with the catheter was studied using an electron scanning microscope. The concretion was composed of anhydrous uric acid, some uric acid dihydrate (< 5 wt.%) and individual particles of calcium oxalate monohydrate. The stone interior was porous with frequent occurrence of differently sized cavities that were either empty or partially filled with particles of uric acid and/or calcium oxalate monohydrate. Calcium oxalate particles were not of crystalluria origin but developed in the cavity. The succession of processes leading to the stone formation was deduced from its inner structure. The stone was formed due to a crystalline growth with minor, if any, participation of sedimentation. The estimated average rate of the calculus development, 2 x 10(-9) m/s, confirms the predominant role of crystalline growth in stone formation and indicates a relatively low urinary supersaturation with respect to uric acid prevailing during the period of calculogenesis.

Calcium Oxalate↗
PubMed1996

Phosphates precipitating from artificial urine and fine structure of phosphate renal calculi.

Phosphates precipitating from artificial urine in the pH range 6-8 were identified using X-ray diffraction, chemical analysis and scanning electron microscopy. The influence of magnesium and citrate on phases precipitating from urine was established. From urine containing a normal quantity of magnesium (around 70 ppm), brushite accompanied by hydroxyapatite (HAP) precipitated at pH < or = 7.0 and struvite with HAP at pH > 7.0. HAP was formed exclusively from magnesium deficient urine at pH 7.0. Newberyite, octacalcium phosphate and whitlockite were not identified. The chemical and phase composition and inner fine structure of 14 phosphate calculi were studied. Three types of stones were distinguished based on their magnesium content: (i) stones rich in magnesium composed of struvite, hydroxyapatite and abundant organic matter, (ii) stones with low magnesium content constituted by calcium deficient hydroxyapatite, up to 5% of struvite, considerable amount of organic matter and occasionally brushite, and (iii) calculi without magnesium consisting of brushite, hydroxyapatite and little organic matter. Conditions prevaling during stone-formation assessed for each type of stone were confirmed by corresponding urinary biochemical data and corroborate the in vitro studies of phosphates precipitation.

Calcium Phosphates↗
PubMed1996

Study of the early stages of renal stone formation: experimental model using urothelium of pig urinary bladder.

An experimental model that enables the close simulation of conditions prevailing in the kidney during the formation of stones, using living tissue of pig urinary bladder, was developed. The results obtained clearly confirmed the importance of the antiadherent glycosaminoglycan (GAG) layer in preventing the development of solid concretions on the urothelium. Of importance was the capacity of the necrosed urothelium to act as a heterogeneous nucleant of calcium oxalate monohydrate (COM) and dihydrate (COD) crystals, demonstrating the major urolithiasic risk factor that alterations of the healthy epithelium covering the renal papilla may pose in humans. The significant increase in brushite and hydroxyapatite crystals detected on the urothelium when the pH of the artificial urine was 6.5, and the protective GAG layer was reduced or the tissue was necrosed, was also notable. The crystallization inhibitory effects caused by citrate and phytate were also studied. It was found that whereas citrate, at normal urinary concentrations, caused a slight reduction in crystallization, with phytate there was total elimination of crystallization-when it was present at very low concentrations such as 1.0 microgram/ml.

Animals↗
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↗
PubMed1996

A comparative study between etiological factors of calcium oxalate monohydrate and calcium oxalate dihydrate urolithiasis.

A comparative study between different etiological factors of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) is presented. The most frequent alteration in COD urolithiasis was associated with hypercalciuria, whereas in COM urolithiasis was associated with urinary pH. A comparison between COM and COD groups of stone formers that exhibited 1, 2 or 3 alterations was performed. Thus, in individuals with two simultaneous alterations, the association between altered urinary pH and hypomagnesiuria was the most frequent in the COM group, whereas the association between hypercalciuria and altered urinary pH was most frequent in the COD group. In individuals with three simultaneous alterations, the association between hypercalciuria, hyperphosphaturia and hyperuricuria was most frequent in both COM and COD stone formers.

Analysis of Variance↗
PubMed1995

Calcium oxalate monohydrate renal calculi. Formation and development mechanism.

Available information relevant to stone genesis on both calcium oxalate monohydrate crystallization and fine inner structure of papillary calculi is reviewed. Integration of attained facts facilitated formulating a feasible mechanism of papillary calculi formation and development. Medical implications of this mechanism are assessed.

Calcium Oxalate↗
PubMed1995

A new procedure to evaluate the inhibitory capacity of calcium oxalate crystallization in whole urine.

A procedure to evaluate the global inhibitory capacity of heterogeneous nucleation for a given urine without any modification of its composition was developed. The procedure is based on the use of flat solid substrates that are submerged in urine. The quantification of the amount of formed crystals on the substrate permits to evaluate the crystallization inhibitory capacity for a whole urine. The proposed method was applied to study the inhibitory capacity of urines belonging to stone-formers and healthy people, before and after the ingestion of a dietary complement containing phytate in order to prove its reliability. A clear increase of the inhibitory capacity of the urine was detected in most cases when the dietary complement was consumed. Moreover, lack of crystallization inhibitory capacity was more frequent in stone-formers than in healthy people.

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. I. Qualitative properties.

Shape, colour, surface features and external appearance were determined from 33 human uroliths composed predominantly of calcium oxalate monohydrate (COM). Based on these properties COM renal stones were classified into mulberry (M) and spheroid (S) type, each of which was further divided into two well defined subtypes, M1-fused globules, M2-loose globules, S1-corrugated surface and S2-even surface. This classification indicates that only specific combinations of external characteristics could occur on COM renal uroliths. No apparent correlation between the stone type and respective biochemical urinary data transpired from available information.

Calcium Oxalate↗
PubMed1995

A study on calcium oxalate monohydrate renal uroliths. II. Fine inner structure.

The inner fine structure of 30 human uroliths composed predominantly of calcium oxalate monohydrate was studied in detail. Each type of stone distinguished on the basis of qualitative parameters, viz. M1, M2, S1 and S2 (see Part I), exhibited a specific and characteristic inner structure different in several well-defined aspects from the other types. The inner structure suggests a sedimentary origin of the M1 type stone whereas the fixed particle origin of the M2, S1 and S2 stones, 3 types of core on which M2, S1 and S2 calculi developed were identified. The A type was represented by a void cavity with walls covered by an organic matter, the B type was formed by loosely arranged COM crystals and the C type was represented by a layer of an organic matter. Clinical observations lend support to the sedimentary origin of the M1 stones.

Calcium Oxalate↗
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

Studies on calcium oxalate monohydrate crystallization: influence of inhibitors.

A simple model to study calcium oxalate monohydrate (COM) crystallization on different substrates is presented and the action of different potential inhibitors is evaluated and discussed. COM heterogeneous nucleation was assayed on solid surfaces as calcium phosphate, mixtures of mucin with calcium phosphate, and wax. In the presence of a non-protected non-renewed solid surface in contact with normal urine, COM crystal formation could be detected at short intervals (3 h). The most active heterogeneous nucleation capacity corresponded to calcium phosphate. In the presence of 10% mucin, owing to the renewal of the surface layer no COM crystal were detected on the pellet's surface. The study of citrate and pentosan polysulphate (a semisynthetic polysaccharide) on COM heterogeneous nucleation demonstrated some important inhibitory effects when concentration increased and time decreased. Maximum effects were selectively manifested on calcium phosphate surfaces. Only phytic acid at adequate concentration exhibited a total inhibitory capacity of COM formation, even during longer intervals (15 h).

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↗