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PubMed1975

Epitaxial relationships in urolithiasis: the calcium oxalate monohydrate-hydroxyapatite system.

Chemical kinetic data, complemented with scanning electron-microscope observations of the crystalline phase, show that seed crystals of hydroxyapatite have the ability to induce the growth of calcium oxalate monohydrate crystals epitaxially from a metastable supersaturated solution of calcium oxalate. The rate of growth of calcium oxalate crystals is dependent on the surface area of the seed material and follows a second-order rate law. It is suggested that there may be a causal relationship between the occurrence of apatite crystals in the urinary tract and the formation of both 'pure' and mixed urinary stones containing calcium oxalate. Under similar experimental conditions, however, seed crystals of calcium oxalate monohydrate appeared unable to induce epitaxially the growth of calcium phosphate crystals from a supersaturated calcium phosphate solution, indicating the absence of an epitaxial relationship between calcium oxalate monohydrate and the initially precipitating calcium phosphate phase(s).

Calcium↗
PubMed1978

Evidence of increased oxalate absorption in patients with calcium-containing renal stones.

1. The possible roles of the diet and of intestinal absorption in the increased excretion of oxalate by patients with renal calcium stones have been studied. 2. Dietary surveys showed that the mean daily intake of oxalic acid by stone-formers was not significantly different from that of non-stone-formers. 3. The mean urinary excretion of oxalate, expressed as an oxalate/creatinine molar ratio, was significantly reduced by fasting, the change being more marked in the stone-formers than in the normal subjects. Moreover, fasting abolished the difference in mean oxalate/creatinine ratios between stone-formers and control subjects. 4. These results are compatible with the hypothesis that the small increases in urinary oxalate excretion which occur in some idiopathic calcium oxalate stone-formers are due to increased absorption of oxalate from the intestine, which may be due to a reduction in intraluminal calcium concentration.

Adult↗
PubMed1993

Effects of oral and intravenous calcitriol on serum calcium oxalate saturation in dialysis patients.

1. To determine whether the multiple changes in the blood chemistry profile induced by calcitriol may be conducive to secondary systemic oxalosis we have studied nine patients on regular dialysis treatment under three different regimens: (1) oral calcitriol, 0.25 microgram/daily for at least 6 months. (2) off calcitriol, a 1-month withdrawal of the drug, taken as the baseline study period; (3) intravenous calcitriol, 1 microgram three times weekly at the end of dialysis, with tests performed at 1 and 3 months from initiation. 2. Serum concentrations were measured pre- and post-dialysis at the end of each study period. The whole dialysate was used for the determination of the overall calcium and oxalate removal by dialysis. The degree of saturation with calcium oxalate monohydrate was estimated by a computer program. Serum calcitriol concentrations were also assessed. 3. Total and ionized serum calcium did not change on average, although mild hypercalcaemia developed in some patients on intravenous calcitriol. There was an increase in plasma level of oxalate during both oral and intravenous calcitriol treatment, but this was less pronounced during intravenous therapy. Removal of oxalate by dialysis was also greater in patients on oral calcitriol. 4. These increases were probably originated from intestinal absorption and secondary to hyperabsorption of dietary calcium. Consequently, the degree of saturation with calcium oxalate before dialysis rose during calcitriol treatment, irrespective of the route of administration. 5. These results emphasize that, in addition to soft tissue calcification due to calcium phosphates, ectopic calcium oxalate crystallization must also be viewed as a potential risk associated with long-term administration of calcitriol.

Administration, Oral↗
PubMed2002

Detection and identification of oxalate-degrading bacteria in human feces.

BACKGROUND: Oxalate is detoxified (catabolized) via the action of two enzymatic proteins, formyl coenzyme A transferase (encoded by the frc gene) and oxalyl coenzyme A decarboxylase (encoded by the oxc gene), contained in the cytosol of Oxalobacter formigenes that colonizes the human intestinal tract. It is speculated that oxalate-degrading bacteria decrease oxalate absorption from the intestines and their absence in the gastrointestinal tract correlates with the formation of calcium-oxalate urolithiasis. METHODS: Two methods of detection and identification of this bacterial strain were studied in human fecal samples collected from Japanese subjects. Genomic DNA was isolated from bacterial culture, and specific 16S rDNA was amplified by polymerase chain reaction (PCR) followed by sequencing. The oxc gene was amplified directly from human feces by PCR using the specific primers. RESULTS: Oxalate-degrading bacteria were identified by comparing the sequences of 16S rDNA. The oxc gene was directly detected from human feces by PCR. It was ascertained that a combined PCR detection method using both 16S rDNA and the oxc gene allows for identification of O. formigenes in human fecal samples. CONCLUSION: This detection and identification method of oxalate-degrading bacteria using 16S rDNA and oxc gene should be applied in examination of clinical samples.

DNA, Bacterial↗
PubMed1999

Metabolic characteristics of the elderly with recurrent calcium oxalate stones.

OBJECTIVE: To determine the metabolic characteristics of elderly patients with recurrent calcium oxalate stones. PATIENTS AND METHODS: Metabolic abnormalities were investigated in 88 patients with recurrent calcium oxalate stones, including 70 aged <60 years and 18 aged >/=60 years. The frequency of each metabolic abnormality and the value of each urinary constituent were compared among subgroups of age and gender. RESULTS: Hyperoxaluria was the most common abnormality, present in 56% and 67% of patients aged <60 and >/=60 years, respectively. Hyperuricosuria was significantly more common in older than in younger patients. There were no significant differences in the frequencies of hypercalciuria and hypocitraturia between the age groups. The urinary excretion of oxalate and the ratio of oxalate to creatinine were significantly greater in older than in younger men. The frequency of low urine volume was lower in older than in younger patients and the mean urinary volume was also greater in the older group. CONCLUSIONS: Hyperuricosuria and hyperoxaluria seem to be essential risk factors for calcium oxalate stone formation in elderly patients. Urinary oxalate excretion is significantly greater in older than in younger stone formers and is more prominent in men.

Adult↗
PubMed2001

Effect of experimental hyperoxaluria on renal calcium oxalate monohydrate binding proteins in the rat.

OBJECTIVE: To determine the functional role of calcium oxalate binding proteins in the nucleation, aggregation and retention of calcium oxalate crystals under physiological and hyperoxaluric conditions. Materials and methods Hyperoxaluria was induced in rats using 0.75% of ethylene glycol in drinking water. Calcium oxalate binding proteins were isolated and fractionated by cellulose column chromatography. Three major protein peak fractions were obtained (73 kDa in Tris-HCl buffer, 20 kDa in 0.05 mol/L NaCl buffer and 23 kDa in 0.3 mol/L buffer). Oxalate binding and the inhibition of crystal nucleation and aggregation by these fractions were determined. RESULTS: The adsorption of calcium oxalate monohydrate (COM) was ubiquitous in rat tissues and subcellular organelles, but the percentage adsorption varied; maximum absorption occurred in kidneys and pancreas, with microsomes showing maximal adsorption in the kidney. Hyperoxaluric rat tissues showed a greater percentage adsorption. Microsomes were enriched with the 20 kDa protein, while nuclei contained the 23 kDa protein in higher concentrations. COM-binding proteins derived from hyperoxaluric rat kidney had a greater content of 74 kDa and 23 kDa proteins with increased oxalate-binding activities. In the crystal-growth studies, the 74 kDa protein was a promoter, while the other protein fractions inhibited crystallization. In hyperoxaluria, the crystal-growth promoting activity of the 74 kDa protein was further increased, while the inhibition by the 20 and 23 kDa proteins was decreased. The 74 kDa protein derived from control rats formed single COM crystals in a crystal growth system, while the hyperoxaluric rat fraction induced the aggregation of COM crystals. CONCLUSION: COM-binding proteins (the 74 and 23 kDa fractions) were expressed more in hyperoxaluric rats. In hyperoxaluria the 74 kDa protein tended to promote crystal nucleation and aggregation, and the 20 and 23 kDa proteins were less inhibitory, which increases the risk of stone formation.

Animals↗
PubMed2001

Acute oxalate nephropathy after ingestion of star fruit.

Acute oxalate nephropathy associated with ingestion of star fruit (carambola) has not been reported before. We report the first two cases. These patients developed nausea, vomiting, abdominal pain, and backache within hours of ingesting large quantities of sour carambola juice; then acute renal failure followed. Both patients needed hemodialysis for oliguric acute renal failure, and pathologic examinations showed typical changes of acute oxalate nephropathy. The renal function recovered 4 weeks later without specific treatment. Sour carambola juice is a popular beverage in Taiwan. The popularity of star fruit juice is not compatible with the rare discovery of star fruit-associated acute oxalate nephropathy. Commercial carambola juice usually is prepared by pickling and dilution processes that reduce oxalate content markedly, whereas pure fresh juice or mild diluted postpickled juice for traditional remedies, as used in our cases, contain high quantities of oxalate. An empty stomach and dehydrated state may pose an additional risk for development of renal injury. To avoid acute oxalate nephropathy, pure sour carambola juice or mild diluted postpickled juice should not be consumed in large amounts, especially on an empty stomach or in a dehydrated state.

Acute Kidney Injury↗
PubMed2003

Oxalate-degrading enzymes from Oxalobacter formigenes: a novel device coating to reduce urinary tract biomaterial-related encrustation.

BACKGROUND AND PURPOSE: The long-term placement of biomaterials within the urinary tract is limited by the development of encrustation. In a noninfected urinary environment, encrustation often results from the deposition of calcium oxalate on the biomaterial surface. There is an association between the absence of Oxalobacter formigenes, a commensal colonic bacterium capable of degrading oxalate, and calcium oxalate stone formation. This pilot study was designed to evaluate several oxalate-degrading enzymes produced by O. formigenes as a potential biomaterial coating to reduce urinary tract encrustation. MATERIALS AND METHODS: Circular silicone disks of 6-mm diameter were incubated for 48 hours in oxalylcoenzyme A decarboxylase (OXC), formyl-coenzyme A transferase (FRC), and coenzyme A, while control disks were incubated in distilled water. The adsorption of OXC and FRC was assessed using enhanced chemiluminescence (ECL) and atomic force microscopy (AFM). Coated and uncoated disks (20 of each) were implanted in the bladders of 40 female New Zealand White rabbits. After 30 days, the disks were recovered, and the degree of encrustation on the polymer surface was evaluated utilizing dry weight measurement, calcium atomic absorption spectroscopy (AAS), and scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX). RESULTS: Both ECL and AFM demonstrated coating of the silicone disks with OXC and FRC. The mean dry weights of the coated and control disks following explantation were 0.591 +/- 0.438 g and 0.747 +/- 0.428 g, respectively (P = 0.307). The mean weight of calcium on the coated and control disks, as determined by AAS, was 154.1 +/- 96.25 mg and 258 +/- 181.35 mg, respectively (P = 0.008). CONCLUSIONS: The use of oxalate-degrading enzymes from O. formigenes to coat urinary biomaterials represents a novel paradigm to reduce biomaterial-related encrustation. Coating of silicone with oxalate-degrading enzymes from O. formigenes results in a modest reduction in encrustation with no apparent toxicity. Further studies are warranted.

Animals↗
PubMed1977

Effects of oxalic acid on availability of zinc from spinach leaves and zinc sulfate to rats.

Some effects of dietary oxalic acid on availability of zinc from organic and inorganic sources were assessed. Male rats fed zinc-deficient diets with and without added sodium oxalate were orally dosed once with either 65Zn-labeled spinach leaves or 65Zn-labeled zinc sulfate. Spinach plants (Spinacia oleracea, var. "Winter Bloomsdale") were grown in 65Zn-labeled nutrient solutions that contained 0.033, 0.131 or 0.262 ppm zinc. Increasing zinc supply to the plants increased zinc concentration in the leaves. Oxalic acid content in all leaves was about 7% dry weight. Dietary oxalate enhanced the availability of 65Zn from zinc sulfate, but had no effect on absorption and retention of 65Zn from spinach leaves. Regardless of dietary oxalate levels, absorption and retention of 65Zn was greater from spinach leaves than from zinc sulfate. We concluded that endogenous zinc in spinach leaves was readily available to zinc-deficient rats, and that dietary oxalate was not deleterious to zinc availability.

Absorption↗
PubMed1979

Interrelationships in rats among dietary vitamin B6, glycine and hydroxyproline. Effects of oxalate, glyoxylate, glycolate, and glycine on liver enzymes.

Urinary endogenous oxalate was increased by feeding vitamin B6-deficient or control rats with 5.2% hydroxyproline, or 3% glycine plus 5.2% hydroxyproline. The activities of liver lactic dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6PD) , malic enzyme (ME), and ATP citrate lyase were decreased in vitamin B6-DEFICIENT RATS, AND THEIR LIVEr G6PD was further decreased by the addition of glycine and hydroxyproline to their diets. Supplementing control diets with the two amino acids decreased the activities of rat liver LDH, G6PD, and ATP citrate lyase. The effects of glycine and hydroxyproline feeding on the enzymes studied did not appear related to alterations in insulin availability. Since in vitamin B6-deficient rats, there are increases in urinary levels of oxalic and glycolic acids, and glycine, and increases in tissue levels of glyoxylic acid and glycine, the effects of these metabolites on the activities of the above mentioned enzymes were measured. Oxalic acid inhibited the activities of LDH, G6PD, and ME. Glyoxylic acid inhibited LDH and ME, but not G6PD. Glycolic acid inhibited G6PD and ME, but not LDH. ATP citrate lyase was not affected by these substances. Glycine had no effect on the enzymes studied. Diets which increased oxalate excretion generally reduced or did not alter liver and kidney levels of oxalate, glycolate, and glyoxylate. However, the feeding of glycine and hydroxyproline increased kidney oxalate, and liver and kidney glyoxylate in vitamin B6-deficient rats.

ATP Citrate (pro-S)-Lyase↗
PubMed1999

Calcium and oxalic acid kinetics differ in rats.

Small molecular weight calcium salts, if absorbed intact, could provide a nutritional source of calcium in subjects with impaired absorption of calcium by the saturable pathway. An understanding of the mechanism of absorption of calcium oxalate (as a representative salt) may be important nutritionally and therapeutically. The aim of the present study was to develop models to study absorption, distribution and retention of calcium and oxalate in rats as a basis for studying calcium oxalate absorption. Labeled compounds (45Ca and [14C]-oxalic acid) were administered to separate groups of rats orally (n = 8-11) or intravenously (n = 3-5) and blood was sampled for up to 240 min. Data were analyzed using SAAM/CONSAM. Calcium kinetics were fitted by a model with three compartments in the body and one absorption pathway from the intestine. By contrast, oxalic acid kinetics were fitted by two pools in the body and two absorption pathways from the intestine. Calcium and oxalic acid, therefore, demonstrate different absorption and distribution kinetics in rats.

Absorption↗
PubMed1990

Urinary supersaturation with respect to brushite in patients suffering calcium oxalate lithiasis.

The urines of 23 stone-formers presenting repeated calcium oxalate lithiasis and 12 control subjects were collected at six different time periods daily. Supersaturations for calcium oxalate and brushite (DCPD) were calculated using ionic and solubility products. Urines of both groups were supersaturated for calcium oxalate but only urines of the stone-formers were supersaturated for brushite, the most simple calcium phosphate which nucleates very easily at the urinary pH. This fact suggests that the core of the calcium oxalate stone could be made of either a calcium oxalate crystallite or a brushite seed onto which hetergeneous nucleation of calcium oxalate can take place.

Adolescent↗
PubMed2004

Relationships among endo-polygalacturonase, oxalate, pH, and plant polygalacturonase-inhibiting protein (PGIP) in the interaction between Sclerotinia sclerotiorum and soybean.

The necrotrophic fungal pathogen Sclerotinia sclerotiorum secretes oxalic acid and endo-polygalacturonase (endo-PG) in host plants. Oxalic acid acidifies the plant tissue to values more suitable to endo-PG activity. However, we observed that the infected soybean seedlings possessed a pH of 3.8, which is below that optimal for endo-PG activity (4.5 to 5.0). We investigated, therefore, the effects of pH (from 5.0 to 3.6) and oxalate (5 to 20 mM) on the activity of the major basic endo-PG (PGb) and towards an acidic endo-PG (PGa) secreted by S. sclerotiorum during soybean infection. We verified that only PGb activity is stimulated by oxalate, while at the lowest pH levels, PGa escapes the inhibition of a soybean polygalacturonase-inhibiting protein (PGIP). These results, performed on polygalacturonic acid, were apparently consistent with data obtained from studies with soybean hypocotyl segments, in which PGb activity was increased by oxalate and PGa maintained its activity also at pH 3.6, possibly because at this pH the PGIP contained in the plant tissue is inactive. Reverse transcription-polymerase chain reaction analysis showed that, during soybean infection, the expression of the putative pga gene is delayed in comparison to the basic one. The different temporal expressions of the two endo-PGs and their differing responses to pH, oxalate, and PGIP seem to be consistent with a possible maximization of the fungal PG activity in the host tissue.

Amino Acid Sequence↗
PubMed2004

A porcine model of calcium oxalate kidney stone disease.

PURPOSE: The pig has been extensively used in biomedical research because of the similarities in organ structure and function to humans. It is desirable to have an animal model of oxaluria and urolithiasis with physiological, anatomical and nutritional characteristics that more closely resemble those of man. In this study we determined if feeding pigs trans-4-hydroxy-l-proline (HP) increased urine oxalate levels and if it would serve as a model for human hyperoxaluria and stone disease. MATERIALS AND METHODS: Male Yorkshire-Durox cross-bred pigs were fed HP for up to 20 days. Urine was periodically collected and analyzed for oxalate levels and the presence of crystalluria. After 20 days of feeding the kidneys were removed and examined grossly and microscopically for indications of injury, crystal deposition and stone formation. RESULTS: Feeding pigs 10% HP (weight per weight HP/food) produced hyperoxaluria, which reached a maximum and leveled off by day 6. Urine oxalate remained near this level until the study ended at 20 days regardless of the further increase in HP to 20% of the weight of the food. When the kidneys were removed and grossly examined, calcium oxalate encrustations were observed on multiple papillary tips. Histopathological observation of the papillary tissue showed tissue injury and crystal deposition. CONCLUSIONS: Pigs fed HP have hyperoxaluria and calcium oxalate crystalluria, and calcium oxalate papillary deposits form that may be precursors of kidney stones. The use of the pig as a model of human hyperoxaluria and stone formation should prove ideal for studies of these human diseases.

Animals↗
PubMed2006

Medicago truncatula mutants demonstrate the role of plant calcium oxalate crystals as an effective defense against chewing insects.

Calcium oxalate is the most abundant insoluble mineral found in plants and its crystals have been reported in more than 200 plant families. In the barrel medic Medicago truncatula Gaertn., these crystals accumulate predominantly in a sheath surrounding secondary veins of leaves. Mutants of M. truncatula with decreased levels of calcium oxalate crystals were used to assess the defensive role of this mineral against insects. Caterpillar larvae of the beet armyworm Spodoptera exigua Hübner show a clear feeding preference for tissue from calcium oxalate-defective (cod) mutant lines cod5 and cod6 in choice test comparisons with wild-type M. truncatula. Compared to their performance on mutant lines, larvae feeding on wild-type plants with abundant calcium oxalate crystals suffer significantly reduced growth and increased mortality. Induction of wound-responsive genes appears to be normal in cod5 and cod6, indicating that these lines are not deficient in induced insect defenses. Electron micrographs of insect mouthparts indicate that the prismatic crystals in M. truncatula leaves act as physical abrasives during feeding. Food utilization measurements show that, after consumption, calcium oxalate also interferes with the conversion of plant material into insect biomass during digestion. In contrast to their detrimental effects on a chewing insect, calcium oxalate crystals do not negatively affect the performance of the pea aphid Acyrthosiphon pisum Harris, a sap-feeding insect with piercing-sucking mouthparts. The results confirm a long-held hypothesis for the defensive function of these crystals and point to the potential value of genes controlling crystal formation and localization in crop plants.

Animals↗
PubMed2006

Bis(glycinium) oxalate: evidence of strong hydrogen bonding.

In the title 2:1 salt, 2C2H6NO2+.C2O4(2-), the glycine molecule is in the cationic form with a positively charged amino group and an uncharged carboxylic acid group. The doubly charged oxalate anion lies across a crystallographic inversion centre. One of the reasons why the 1:1 glycinium oxalate salt has a higher melting point than the title compound may be the difference in their hydrogen-bonding patterns. A database search for salts formed between amino acids or substituted amino acids and oxalic acid revealed that, in most of the structures, the conformation about the O=C-OH bond is synplanar. D-Tryptophan oxalate is the only example where the OH group of a semi-oxalate adopts an antiplanar conformation. The 2:1 stoichiometry seen in the present salt is observed only in the salts of DL-serine, DL-aspartic acid and betaine with oxalic acid.

Crystallography, X-Ray↗
PubMed1980

Intrarenal distribution of oxalic acid, calcium, sodium, and potassium in man.

The renal papilla in man has been shown to contain a high concentration of oxalate (5 . 5 +/- 0 . 8 mmole/kg wet weight, mean +/- SEM, n = 7 kidneys), and that there is a significant concentration gradient between oxalate in the papilla and that of the medulla (0 . 4 +/- 0 . 08, P < 0 . 05) and the cortex (0 . 3 +/- 0 . 06, P < 0 . 05). Significant calcium and sodium gradients between renal papilla and medulla and cortex were confirmed and parallel that of oxalate. Potassium showed a significant decrease in the papilla (33 . 1 +/- 0 . 9) as compared to the medulla (42 . 1 +/- 1 . 9 P < 0 . 05). The concentrations of oxalate and calcium in the papilla were respectively 25-fold and 6-fold higher than the urinary concentration of oxalate and calcium. It is concluded that these high concentrations of oxalate and calcium in the renal papilla are related to the formation of Randall's plaques and may be an essential factor in the pathogenesis of renal stones which is still far from clear.

Calcium↗
PubMed1994

Urinary calcium oxalate saturation in 'stone formers' and normal subjects: an application of the EQUIL2 program.

OBJECTIVE: To produce an index of lithogenic risk which identifies patients at risk of stone recurrence and facilitates the monitoring of prophylactic treatments. PATIENTS AND METHODS: The EQUIL2 program provides an evaluation of the state of urinary saturation, particularly of calcium oxalate, based on the pH and total concentrations (mmol/l) of sodium, potassium, calcium, magnesium, uric acid, chloride, ammonium, citrate, phosphate, sulphate, oxalate, pyrophosphate and carbon dioxide. The morning urinary calcium oxalate saturation coefficient was thus calculated for 30 stone-formers (Group 1) and 30 normal control subjects (Group 2). RESULTS: Urine from the majority of individuals was saturated, with no significant difference between the two groups. There appeared to be a correlation between the state of saturation and the urinary calcium oxalate molar product in both stone-formers (r = 0.931) and controls (r = 0.914). CONCLUSION: In future studies on urinary calcium oxalate saturation, it should be possible to supplement the sophisticated coefficient determined by the EQUIL2 program with the molar product, except in cases where monitoring therapies have little or no effect on urinary oxalate or urinary calcium levels.

Adult↗