Synthesis of calcium oxalate trihydrate: New data by vibrational spectroscopy and synchrotron X-ray diffraction.

Calcium oxalate is found in nature in three different crystalline states determined by the number of H2O in the unit formula (whewellite CaC2O4·H2O, COM; weddellite CaC2O4·(2+x)H2O, COD and caoxite CaC2O4·3H2O, COT). The properties of these materials are relevant in the field of biomedicine, cultural heritage and mineralogy. In two previous papers, we have used X-ray diffraction and vibrational spectroscopy (infrared and Raman) to derive information on crystal and molecular structures of COM and COD. In this paper, we complete the synthesis and analysis on the third form, COT, and present a comparative study of the data collected from the three crystalline states. The experiments clearly highlight the role played by the H2O molecules linked within the structure by different kinds of hydrogen bonds. The vibrational assignment of the infrared and Raman bands are critically proposed. The fact relevant for the work in biomedicine, cultural heritage and crystallography is that a simple examination of the spectra allows quickly to determine the chemical nature of the material in an unknown sample even in a minute quantity or in awkward experimental conditions.

Stable amorphous calcium oxalate: synthesis and potential intermediate in biomineralization.

Amorphous calcium oxalate nanoparticles with sizes of ≈10 nm were synthesized at room temperature by hydrolysis of dimethyl oxalate from ethanolic solution.

In vivo synthesis of calcium oxalate whiskers on CoCrMo alloy surfaces via biomineralization.

Surface treatments using bio-technology are valuable and fascinating in the sense that such treatments are natural and yield good biocompatibility. Calcium oxalate whiskers for biomedical applications were successfully synthesized on the CoCrMo alloy surfaces implanted in Aloe leaves which consist of many active bio-chemical elements. The effect of surface wettability and surface morphology on the formation of whiskers was investigated using four differently treated CoCrMo surfaces: (i) smoothly polished surface, (ii) electrochemical etched surface, (ii) textured surface with dimples, and (iv) parallel orientated-grooved surface. Results showed that the formed whiskers had a length ranging between 100 µm and 600 µm, and a diameter in the range of 2 µm to 5 µm. Electrochemically etched surfaces had better wettability and were favorably for growing whiskers. Surface morphology with (i) dimple textures or (ii) parallel grooves facilitated the effective control of the size and amount of the grown whiskers.

Reversible inhibition of calcium oxalate monohydrate growth by an osteopontin phosphopeptide.

Calcium oxalate, primarily as calcium oxalate monohydrate (COM), is the primary constituent of most kidney stones. Certain proteins, such as osteopontin (OPN), inhibit stone formation. The complexity of stone formation and the effects of urinary proteins at various stages of the process make it hard to predict the exact physiological roles of these proteins in growth inhibition. The inhibition of crystallization due to adsorbed impurities is usually explained in terms of a model proposed in 1958 by Cabrera and Vermilyea. In this model, impurities adsorb to growth faces and pin growth steps, forcing them to curve, thus impeding their progress via the Gibbs-Thomson effect. To determine the role of OPN in the biomineralization of kidney stones, crystal growth on the {010} face of COM was examined in real time with atomic force microscopy in the presence of a synthetic peptide corresponding to amino acids 65-80 (hereafter referred to as pOPAR) of rat bone OPN. We observed clear changes in the morphology of the growth-step structure and a decrease in step velocity upon addition of pOPAR, which suggest adsorption of inhibitors on the {010} growth hillocks. Experiments in which pOPAR was replaced in the growth cell by a supersaturated solution showed that COM hillocks are able to fully recover to their preinhibited state. Our results suggest that recovery occurs through incorporation of the peptide into the growing crystal, rather than by, e.g., desorption from the growth face. This work provides new insights into the mechanism by which crystal growth is inhibited by adsorbants, with important implications for the design of therapeutic agents for kidney stone disease and other forms of pathological calcification.

Cytoprotective role of the aqueous extract of Terminalia chebula on renal epithelial cells.

PURPOSE: Kidney stone is one of the most prevalent diseases worldwide. Calcium oxalate (CaOx) has been shown to be the main component of the majority of stones formed in the urinary system of the patients with urolithiasis. The present study evaluates the antilithiatic properties of Terminalia chebula commonly called as ″harad ″ which is often used in ayurveda to treat various urinary diseases including kidney stones. MATERIALS AND METHODS: The antilithiatic activity of Terminalia chebula was investigated on nucleation and growth of the calcium oxalate crystals. The protective potency of the plant extract was also tested on oxalate induced cell injury of both NRK-52E and MDCK renal epithelial cells. RESULTS: The percentage inhibition of CaOx nucleation was found 95.84 % at 25µg/mL of Terminalia chebula aqueous extract which remained almost constant with the increasing concentration of the plant extract; however, plant extract inhibited CaOx crystal growth in a dose dependent pattern. When MDCK and NRK-52E cells were injured by exposure to oxalate for 48 hours, the aqueous extract prevented the injury in a dose-dependent manner. On treatment with the different concentrations of the plant extract, the cell viability increased and lactate dehydrogenase release decreased in a concentration dependent manner. CONCLUSION: Our study indicates that Terminalia chebula is a potential candidate for phytotherapy against urolithiasis as it not only has a potential to inhibit nucleation and the growth of the CaOx crystals but also has a cytoprotective role.

Cytoprotective role of the aqueous extract of Terminalia chebula on renal epithelial cells

PURPOSE: Kidney stone is one of the most prevalent diseases worldwide. Calcium oxalate (CaOx) has been shown to be the main component of the majority of stones formed in the urinary system of the patients with urolithiasis. The present study evaluates the antilithiatic properties of Terminalia chebula commonly called as "harad" which is often used in ayurveda to treat various urinary diseases including kidney stones. MATERIALS AND METHODS: The antilithiatic activity of Terminalia chebula was investigated on nucleation and growth of the calcium oxalate crystals. The protective potency of the plant extract was also tested on oxalate induced cell injury of both NRK-52E and MDCK renal epithelial cells. RESULTS: The percentage inhibition of CaOx nucleation was found 95.84% at 25µg/mL of Terminalia chebula aqueous extract which remained almost constant with the increasing concentration of the plant extract; however, plant extract inhibited CaOx crystal growth in a dose dependent pattern. When MDCK and NRK-52E cells were injured by exposure to oxalate for 48 hours, the aqueous extract prevented the injury in a dose-dependent manner. On treatment with the different concentrations of the plant extract, the cell viability increased and lactate dehydrogenase release decreased in a concentration dependent manner. CONCLUSION: Our study indicates that Terminalia chebula is a potential candidate for phytotherapy against urolithiasis as it not only has a potential to inhibit nucleation and the growth of the CaOx crystals but also has a cytoprotective role.

Metal-ligand-coordinated vesicles and vesicle-assisted preparation of calcium oxalate.

A Ca(2+) -ligand-coordinated vesicle phase was prepared from a mixture of tetradecyldimethylamine oxide (C14DMAO) and calcium tetradecylamidomethyl sulfate [(CH3(CH2)13NHCOCH2OSO3)2Ca] in aqueous solution. At the appropriate mixing ratios, Ca(2+) -ligand coordination results in the formation of molecular bilayers because Ca(2+) can firmly bind to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca by complexation which reduces the area of head group. In this system, no counterions in aqueous solution exist because of the Ca(2+) -ligand coordination, and the bilayer membranes are not shielded by salts, i.e., a salt-free but charged molecular bilayer. The structures of the birefringent solutions of (CH3(CH2)13NHCOCH2OSO3)2Ca and C14DMAO mixtures were determined by transmission electron microscopy (TEM) images and rheological measurements, demonstrating that the birefringent sample solutions consist of vesicles. The Ca(2+) -ligand complex vesicle phase was used as a microreactor to prepare calcium oxalate (CaC2O4) crystals. Dimethyl oxalate, as a precursor, can hydrolyze to oxalic acid and methanol. Oxalic acid should precipitate Ca(2+) ions binding to the head groups of C14DMAO and (CH3(CH2)13NHCOCH2OSO3)2Ca to produce CaC2O4 crystals (Ca(2+) + H2C2O4 --> CaC2O4 (downward arrow) + 2H+). The obtained particles were CaC2O4 monohydrate, which were dominated by (020) faces. CaC2O4 precipitates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) analysis. After removal of CaC2O4 precipitates, a new cationic and anionic (catanionic) vesicle phase was constructed through electrostatic interaction between cationic C14DMAOH+ (C14DMAO + H+ --> C14DMAOH+) and anionic CH3(CH12)13 NHCOCH2OSO3-.

Papel de las tiazidas en la profilaxis de la litiasis cálcica recidivante / The role of thiazides in the prophylaxis of recurrent calcium lithiasis

Objetivo: Demostrar la eficacia prolongada de las tiazidas en la profilaxis y tratamiento de las recidivas en pacientes con litiasis cálcica de oxalato y fosfato cálcico. Métodos: Se realiza un estudio prospectivo aleatorizado, con un seguimiento de tres años, en 150 pacientes diagnosticados de litiasis cálcica recidivante. Los pacientes se distribuyen en tres grupos: A) 50 casos sometidos a observación sin tratamiento, B) 50 casos tratados con 50 mg/día de hidroclorotiazida y C) 50 casos tratados con 50 mg de hidroclorotiazida y 20 mlEq de citrato potásico/día. En cada grupo se realiza estudio renal con técnicas de imagen, y estudio metabólico urinario basal, 12, 24 y 36 meses. Resultados: En los pacientes tratados con tiazidas (Grupo B y C) se obtiene una reducción significativa de recidiva litiásica en relación con el grupo control (Grupo A). La alteración más frecuente encontrada en el estudio metabólico fue hipercalciuria, 52% de los casos; el 16% presentan patrón litógeno mixto. El número de recidivas y necesidad de nuevas sesiones de litotricia extracorpórea en los pacientes con hipercalciuria tratados con tiazidas disminuye significativamente con respecto al Grupo A (p=0.003) Conclusiones: Se observa una relación significativa entre patrón litógeno y recidiva litiásica. Las tiazidas nos ayudan a controlar los factores litogénicos y las recidivas en pacientes con litiasis cálcica. Este efecto es prolongado y significativo en pacientes con hipercalciuria

Objective: To show the prolonged efficacy of thiazides in the prophylaxis and treatment of recurrences in patients with calcium oxalate and phosphate lithiasis. Methods: A randomised prospective study is conducted, with a three-year follow-up, in 150 patients diagnosed with recurrent calcium lithiasis. The patients are divided into three groups: A) 50 cases subject to observation with no treatment, B) 50 cases treated with 50 mg/day of hydrochlorothiazide, and C) 50 cases treated with 50 mg of hydrochlorothiazide and 20 mlEq of potassium citrate/day. Each group is subject to a renal study with imaging techniques and a urinary metabolic study at baseline, 12, 24 and 36 months. Results: The patients treated with thiazides (Groups B and C) obtain a significant reduction in lithiasis recurrence compared with the control group (Group A). The most common abnormality found in the metabolic study was hypercalciuria, 52% of cases; 16% present a mixed lithogenic pattern. The number of recurrences and need for new sessions of extracorporeal lithotripsy in patients with hypercalciuria treated with thiazides is significantly smaller than in Group A (p=0.003) Conclusions: We observe a significant relation between lithogenic pattern and lithiasis recurrence. Thiazides help us to control lithogenic factors and recurrences in patients with calcium lithiasis. This effect is prolonged and significant in patients with hypercalciuria

[Preparation and analysis by x-ray diffraction of three crystalline forms of calcium oxalate in a mixture]. / Préparation et dosage par diffraction de rayons X des trois formes cristallines de l'oxalate de calcium en mélange.

The present work describes a method for analysing, quantitatively, mixtures of the three calcium oxalate hydrates which are the most important components of human kidney stone. The method consists in measuring and comparing the relative intensities of X-ray diffraction peaks obtained by means of the so-called powder method. We first give the composition of the solutions from which the three hydrates were grown separately. Second, we briefly describe the principle of the X-ray quantitative phase analysis and give the results we obtained by analysing binary and ternary mixtures of the three solid phases of calcium oxalate. We show that the proportion of either phase can be estimated with an accuracy of about 2 or 3 wt%.

[Studies on the crystallization tendency of calcium oxalate in urine--a study of experimental and computer-assisted determination of the risk of urinary calculi formation]. / Untersuchungen zur Kristallisationsneigung von Calciumoxalat in Urinen--eine Studie zur experimentellen und rechnerischen Ermittlung des Harnsteinbildungsrisikos.

In this study a method o the semiquantitative determination of the crystallization tendency for calcium oxalate in urine is described. It is based on the addition of a well-defined amount of ammonium oxalate (31.3 nmol) to a urine sample (30 ml). The so caused clouding of the urine is measured by a photometer 20 min later. The method guarantees an acceptable reproducibility and is simple to be performed in each clinical laboratory. The results of mathematical correlation and discriminant analysis show that the calcium concentration influences the crystallization of calcium oxalate as most of all urinary constituents. Furthermore, evidence of a high specificity of the method is given by a reclassification rate of about 80% in the discriminant analytical computation.

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.

Estimation by infrared spectrophotometer of the calcium oxalate dihydrate to calcium oxalate monohydrate ratio.

According to the theoretical expression for calibration curve as a function of the optical absorption ratio of two peaks and with the analysis of the infrared spectra of the mixture samples of commercial calcium oxalate monohydrate and synthesized calcium oxalate dihydrate, the following quadratic equation was obtained; Y = 1.79 X2 - 30.90 X + 107.04 in which Y is the percentage of the purity of calcium oxalate dihydrate and X is the ratio of the relative optical absorption at 660 cm.-1 (the wave number at a characteristic absorption peak of calcium oxalate monohydrate) to that at 610 cm.-1 (that of calcium oxalate dihydrate) by regarding the line as a base-line that links the absorption valley at around 700 cm.-1 with that at 550 cm.-1 The linear correlation coefficient of the actual purity to the estimated purity obtained from this formula of calcium oxalate dihydrate is 0.995. When this formula is applied to the results derived from the infrared spectra of the mixture samples of commercial calcium oxalate monohydrate and calcium oxalate dihydrate obtained from urinary stones in duplicate in each percentage, the linear correlation coefficient is 0.991. This estimation method by infrared spectrophotometer of the calcium oxalate dihydrate to calcium oxalate monohydrate ratio gave a very close correlation between actual and estimated purity of calcium oxalate dihydrate and seems useful in the study of calcium oxalate urolithiasis.