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.     

Effect of hydrochlorothiazide therapy on the crystallization of calcium oxalate in urine

1 We examined the case notes of 82 psychiatric out-patients (aged 21-84 years) receiving lithium prophylaxis and with steady-state plasma lithium levels. 2 The mean weight-related daily dose of lithium prescribed decreased by about 50% between the third and eight decades. 3 The corresponding steady-state plasma lithium levels showed a less marked tendency to decrease, this only being seen in the seventh and eighth decades. 4 In patients aged 50 years or over the daily lithium dose required to give a plasma level of 1 mmol l-1 (0.50 mmol kg-1) was significantly lower than that (0.65 mmol kg-1) in patients aged under 50 years (P less than 0?5, Student's t-test). In patients aged 70-79 years this dose was 31% lower than in patients under 50 years. However, interindividual variation was great and it was estimated that age only contributed about 14% to the total interpatient variation. 5 Of the 36 patients under 50 years of age, 42% had minor lithium side-effects and 17% were not optimally controlled with lithium. The corresponding figures for the 46 'older' patients were 46% and 28%. 6 Generally the 50% dosage reduction seemed necessary to compensate for an age-related decrease in lithium excretion and to reduce lithium side effects to a level comparable to that acceptable in younger patients.     

Effects of citrate on the different phases of calcium oxalate crystallization

Urinary citrate appears to be an important factor in the crystallization process of calcium oxalate and calcium phosphate. The urinary excretion of citrate was found to be significantly lower in patients with calcium oxalate stone disease as compared with normal subjects, and about 30 per cent of the calcium stone formers can be considered as hypocitraturic. The lowest excretion of citrate was recorded in urine collected during the night. Citrate has significant effects on supersaturation with respect to both calcium oxalate and calcium phosphate, it also inhibits the growth of these crystals. In addition, citrate appears to be capable of inhibiting the aggregation of crystals composed of calcium oxalate, brushite, and hydroxyapatite. The heterogenous growth of calcium oxalate on calcium phosphate is also counteracted by citrate. As a consequence of the crucial role of citrate in these processes, stone prevention with alkaline citrate has become an attractive form of treatment in patients with recurrent stone formation. Single evening dose administration of sodium potassium citrate resulted in an of sodium potassium citrate resulted in an increased excretion of citrate, reduced levels of the calcium/citrate ratio as well as supersaturation with respect to calcium oxalate and a decreased rate of stone formation. However, conflicting results of stone preventive treatment with alkaline citrate have been reported by different groups, and long-term follow-up of patients treated in a randomized way is necessary to definitely assess the efficacy of alkaline citrate.     

Circadian variations in the risk of urinary calcium oxalate stone formation

OBJECTIVE: To evaluate the circadian fluctuations in the risk of urinary calcium oxalate stone formation with regard to critical periods of crystallization. PATIENTS AND METHODS: Over a given time period, the Tiselius index depends on urine volume and urinary excretion of oxalate, calcium, citrate and magnesium. This crystallization potential was evaluated during three successive periods spread over 24 h for 25 recurrent stone-formers aged 16-76 years (mean 50) and 25 control subjects aged 27-71 years (mean 44). RESULTS: There was no significant difference in the value of the Tiselius index for all equivalent time periods in both groups of patients. The minimum value was recorded in the afternoon and the circadian pattern of the index illustrated the predominant importance of urinary output in its determination. Morning urinary concentrations and excretions of citrate, and nocturnal levels of magnesium were significantly higher in the stone-formers when compared with the control subjects. CONCLUSION: The lithogenic risk for calcium oxalate stones was maximal at the end of the night or during the early morning, when urinary output was minimal. This circadian study revealed abnormalities that are not apparent from non-fractionated 24 h urine samples, and which were potentially relevant to therapy.     

The effect of ascorbic acid ingestion on the biochemical and physicochemical risk factors associated with calcium oxalate kidney stone formation

Current information on the pathophysiology, diagnostic process, and treatment of growth hormone deficiency is provided. A case study is provided that shows the positive effects of growth hormone therapy on a patient and his family. Information regarding the intravenous clinician's role in administration of growth hormone and patient teaching also is included.     

The evaluation of some biochemical parameters in pyridoxine-treated calcium oxalate renal stone formers

20-, 40- and 60-day old chicks were infected with E. tenella (100000 oocysts). The nature of changes in cholesterol, general fat and lecithin of chicks' blood is the same as at the infection with a small dose (5000) of oocysts of E. tenella. Changes in the lipoid components differ only quantitatively: they are greater at the infection with a greater dose of oocysts that at the infection with a small one.     

硫酸锌溶液冷却结晶除钙镁生产实践

对几种不同的除钙镁工艺进行了对比分析,研究了冷却沉降法除硫酸锌溶液中的Ca、Mg,实验表明,冷却沉降法是一种节能、高效的工艺方案,控制温度25℃、pH=3.8～4.5、晶种加入量4 g/L、沉降时间100 min,可获得较好的工艺指标。     

Oxalate: its role in lithogenesis and composition of calcium oxalate lithiasis

A prospective study was conducted on 374 patients with urinary lithiasis, aiming to analyze the participation of oxalate in the lithogenesis and composition of the calcium oxalate calculi, alone or associated to other factors. METHODOLOGY: Metabolic urinary study of the patient and analysis of calculi with infrared spectrography and optical microscopy. RESULTS: 26.3% patients had hyperoxaluria and 77.5% of the calculi contain calcium oxalate; these are 167 cases of calcium oxalate, 110 of oxalate and calcium phosphate and 13 cases of mixed calcium oxalate and uric acid lithiasis. 43.4% patients with pure monohydrate calcium oxalate calculi have hypercalciuria, 22.6% hyperoxaluria and 19% hyperuricosuria. Dihydrated calcium oxalate calculi are related to high hypercalciuria in 65% cases and to significant hyperoxaluria in 35% cases. 45% patients present a single lithogenic factor, either hypercalciuria (49.6%), hyperoxaluria (20.6%), hyperuricosuria (13.74%), hypocitraturia (9%), urinary infection (1.5%), A.T.R. (2.25%) or acid oliguria (3%).     

Differential expression of urinary inter-alpha-trypsin inhibitor trimers and dimers in normal compared to active calcium oxalate stone forming men

PURPOSE: We determine if the immunoreactive profile of urinary inter-alpha-trypsin inhibitor can be used to distinguish between normal individuals and individuals with calcium oxalate stone disease. MATERIALS AND METHODS: Urinary proteins were dialyzed against water (15 kDa. molecular weight cutoff), lyophilized and resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (6% acrylamide, reducing conditions) followed by Western blot. Inter-alpha-trypsin immunoreactive proteins were detected by enhanced chemiluminescence. Stone formation was confirmed to be active radiologically or passed as stone or gravel within 12 months of the sample. Stone composition was confirmed crystallographically. Normal individuals had no personal or familial history of urolithiasis and matched stone forming patients regarding race (white) and age (23 to 71 years old). Urine from a total of 101 individuals was analyzed. RESULTS: The intact inter-alpha-trypsin trimer (approximately 220 to 240 kDa.) and heavy chain (HC) 2-bikunin/HC1-bikunin dimers (approximately 115 to 130 kDa.) were detected more often in stone forming men (23 of 26 [89%] and 26 of 26 [100%], respectively) than in normal individuals (6 of 26 [23%] and 5 of 26 [19%], respectively, p < 0.0001). In those normal individuals who expressed inter-alpha-trypsin trimer and HC-bikunins the relative intensities were 5.3+/-1.4% and 16.3+/-17.1% of the stone forming controls, respectively. The identity of high molecular weight-inter-alpha-trypsin immunoreactive bands was confirmed using antibodies against the individual subunits (HC1, HC2, HC3, bikunin). In contrast to men high molecular weight-inter-alpha-trypsin's were readily detected in normal and stone forming women with equal frequency (inter-alpha-trypsin-trimer p=0.1337, HC-bikunins p=0.2836): inter-alpha-trypsin-trimer 17 of 18 [94%] and 9 of 13 [77%]; HC-bikunins 17 of 18 [94%] and 10 of 13 [85%]). Inter-alpha-trypsin-trimer and HC-bikunins, respectively, were detected in 2 and 5 of 10 patients with chronic renal disease. Expression was not related to hematuria or proteinuria. CONCLUSIONS: Immunoreactive profiles of urinary proteins may be able to be developed into a useful diagnostic tool to identify active stone formation, although a separate panel may be required for men and women. It is possible that these differences may provide clues as to why the incidence of stone disease is higher in men than women.     

Effect of spermine on mitochondrial matrix calcium in relation to its enhancement of mitochondrial calcium uptake

The mechanism of spermine-induced enhancement of mitochondrial Ca2+ uptake was explored using the fluorescent Ca2+ indicator Fluo-3/AM to measure the free matrix Ca2+ concentration. Simultaneously, the extramitochondrial Ca2+ concentration was registered by a Ca(2+)-ion selective electrode. Spermine lowered the extramitochondrial steady state Ca2+ concentration and at the same time induced a decrease of the intramitochondrial Ca2+ concentration. However, there is a concentration-dependent reversal of the stimulatory action of spermine, which may be explained by the existence of a second, low-affinity binding site for spermine which mediates an inhibition of uptake in spite of the existence of an inwardly directed Ca2+ gradient.     

Alterations in MDCK and LLC-PK1 cells exposed to oxalate and calcium oxalate monohydrate crystals

Structural analysis of human kidney stones reveals the presence of cellular membranes and other cell fragments. Experimentally, calcium oxalate crystallization is facilitated when an exogenous nephrotoxin is given with ethylene glycol, thus providing cellular degradation products to act as heterogeneous nuclei. In this report, we tested whether oxalate alone could act as a cell toxin capable of producing damaged cells without the presence of an exogenous agent. Cultured LLC-PK1 and MDCK cells, when exposed to 1.0 mmol KOx, a concentration at the limit of metastability for calcium oxalate nucleation, were severely damaged as measured by specific lactate dehydrogenase (LDH) release in the spent media and by trypan blue exclusion. This effect was magnified by the addition of pre-formed calcium oxalate monohydrate crystals; the injury was significantly amplified when compared to exposure to oxalate alone. Scanning electron microscopy studies illustrated attachment of crystals to cells with loss of cell-to-cell and cell-to-substrate contact, as cells were released from the monolayer. In both oxalate and combined crystal-oxalate studies, more cells were released from the monolayer and exhibited considerably more damage when compared to controls. Oxalate, at the limit of metastability for calcium oxalate, is a cell toxin and can produce cellular degradation products. This effect is increased significantly by the addition of calcium oxalate monohydrate crystals.     

Increase in urinary calcium and oxalate after fructose infusion

We have previously shown that an oral glucose load increased both calciuria and oxaluria while the ingestion of fructose induced a rise in calciuria and a decrease in oxaluria. This latter effect remains unclear and might be linked to the reduced intestinal oxalate absorption subsequent to digestive intolerance in some subjects. Such a hypothesis could be enlightened by the study of a parenteral fructose load. Therefore in 7 healthy subjects, we compared the effects of fructose infusion (F) (15 min iv infusion at 0.185 mmol/kg BW/min) to a control glucose infusion (G) on urinary calcium and oxalate. In this study, glycemia and insulinemia increased less after (F) than after (G) (respectively + 21% vs + 216%, p < 0.001 and + 230% vs + 402%, p < 0.05) and phosphatemia decreased less after (F) than after (G) (-7% vs -14%, p < 0.05). Urinary calcium and oxalate increased only after (F) (respectively + 64%, p < 0.01 and + 60%, p < 0.05). Urinary uric acid, another urolithiasis factor, increased after both (F) and (G) (respectively + 45%; p < 0.01 and + 42%; p < 0.01) but uricemia increased only after (F) (+ 25%; p < 0.01). Our results suggest an additional reason to avoid the use of fructose in parenteral nutrition, particularly in individuals with a known history of either calcium oxalate or urate urolithiasis.     

Urinary calcium oxalate saturation in healthy infants and children

PURPOSE: A number of factors influence the development of renal calculi, the most essential of which is the supersaturation of urine with lithogenic substances. Calcium oxalate stones occur most frequently in adult and pediatric patients with urolithiasis. Therefore, we established normal age and sex related data for urinary calcium oxalate saturation in infancy and childhood to allow a more specific prediction of the risk of (recurrent) stone disease. MATERIALS AND METHODS: We collected 24-hour urine samples from 473 healthy infants and children without a history of renal stones. Urinary lithogenic and stone inhibitory substances were measured, and the urinary calcium oxalate saturation was calculated using a computer program. RESULTS: Mean urinary calcium oxalate saturation was always higher in boys than in girls, which was significant in infancy (5.22 versus 2.03, p < 0.05) and at ages 7 to 9 years (8.84 versus 5.47, p < 0.05). The saturation first increased (p < 0.05) until age 7 to 9 years in boys and girls, and remained at high levels at ages 10 to 12 years (7.03 versus 5.49, p < 0.05 compared to infancy). Calcium oxalate saturation then decreased until adolescence when values were comparable to those of infancy (5.29 versus 3.35). CONCLUSIONS: We recommend calculating urinary calcium oxalate saturation for diagnostic purposes as well as for therapy control. Normal age and sex related values must be considered.     

Periodontal repair in intrabony defects treated with a calcium sulfate implant and calcium sulfate barrier

THIS RANDOMIZED, CONTROLLED, CLINICAL STUDY was designed to evaluate outcome following surgical implantation of an allogeneic, freeze-dried, demineralized bone matrix-calcium sulfate (DBM+CS) composite with a CS barrier in intrabony periodontal defects. Twenty-six patients contributing 26 deep intrabony defects completed the study. Thirteen patients received the DBM+CS implant. Thirteen patients received gingival flap surgery alone (GFS; control). Clinical outcome was assessed at 6 and 12 months postsurgery. At 12 months postsurgery, probing depth (PD) reduction (mean +/-SD) for the DBM+CS and GFS group was to 4.3+/-0.5 and 3.0+/-1.3 mm; clinical attachment gain was to 2.9+/-0.8 and 1.7+/-1.5 mm; and probing bone level gain was to 2.9+/-1.4 and 1.2+/-1.2 mm, respectively. There were no apparent differences between evaluations at 6 and 12 months postsurgery. Clinical improvements were significantly different from presurgery for both groups at both observation intervals (P < 0.01). There were no significant differences between groups in PD reduction and clinical attachment gain. Probing bone level gain was significantly greater in the DBM+CS group compared to controls (P < 0.05). In summary, surgical implantation of DBM+CS with a CS barrier resulted in reduced PD and improved attachment levels comparable to that achieved by gingival flap surgery alone. However, gain in probing bone levels in deep intrabony periodontal pockets assessed by clinical parameters was greater than that observed by gingival flap surgery alone. These changes were noted at both 6 and 12 months after surgery. This regenerative technique needs further biologic evaluation before being generally accepted.     

Pathological and immunocytochemical changes in chronic calcium oxalate nephrolithiasis in the rat

In the present study, we exposed rats to a crystal-inducing diet (CID) consisting of vitamin D3 and 0.5% ethylene glycol (EG), and we investigated histologically the kidney damage induced by the deposition of calcium oxalate (CaOx) crystals. After 28 days, 50% of the animals had renal CaOx crystals, of which 60% also had small papillary stones. Most crystals were present in the cortex. The occurrence of these crystals coincided with morphological and cytochemical changes: glomerular damage, tubular dilatation and necrosis, and an enlargement of the interstitium. The number of epithelial and interstitial cells positive for the proliferating cell nuclear antigen (PCNA) was increased. Tamm-Horsfall protein (THP) was not only demonstrable in the thick ascending limb of the loop of Henle (TAL), but also frequently in glomeruli, in the proximal tubular epithelium, and in the papilla. In the lumen of the tubular system, it was associated with urinary casts. Reflection contrast microscopy (RCM) showed that the crystals were coated with a thin layer of THP. In spite of the high urinary oxalate concentrations, the above described cellular changes were not observed in CID-fed rats without renal crystals. We conclude, therefore, that in the kidney, the retained CaOx crystals rather than the urinary oxalate ions are responsible for the observed morphological and immunocytochemical changes.     

Experimental nephrolithiasis in rats: the effect of ethylene glycol and vitamin D3 on the induction of renal calcium oxalate crystals

Using ethylene glycol (EG) and vitamin D3 as crystal-inducing diet (CID) in rats, we investigated the effect of the dosage of EG on the generation of chronic calcium oxalate (CaOx) nephrolithiasis. We collected weekly 24 hour urines and measured herein the amount of oxalate, calcium, glycosaminoglycans (GAG's), creatinine, protein, alkaline phosphatase (AP), gamma-glutamyl transpeptidase (gamma-GT), and N-acetyl-beta-glucosaminidase (NAG). The potential of these urines to inhibit crystal growth and agglomeration was also evaluated. After four weeks, the kidneys were screened by histology and radiography for the presence of CaOx crystals and the amount of kidney-associated oxalate was biochemically measured. Using 0.5 vol.% EG, only a part of the rats showed CaOx deposition in the renal cortex and/or medulla, without obvious differences between Wistar and Sprague-Dawley (SD) rats. If a dietary EG concentration of 0.75, 1.0, or 1.5 vol.% was used, the amount of kidney-associated oxalate was proportionally higher and CaOx crystal formation was consistently found in all rats. Most crystals were encountered in the cortex, whereas in the medulla and the papillary region, crystals were only occasionally detected. From these data, we conclude that in the chronic rat model, based on EG and vitamin D3, a consistent deposition of CaOx crystals is obtained using a EG concentration of at least 0.75%.     

Adhesion and endocytosis of calcium oxalate crystals on renal tubular cells

The present investigation was designed to study interactions between Madin-Darby canine kidney (MDCK) cells and calcium oxalate monohydrate (COM) crystals and to clarify the significance of these crystal-cell interactions in stone pathogenesis. MDCK cells cultured in the presence of COM crystals showed a time-dependent uptake of crystals; this was specific for COM crystals. In the dynamic model system designed to study these phenomena under more physiological conditions, COM crystals adhered to the cell surface and were subsequently internalized. In this endocytotic process, the microvilli of the cell appeared to play an important role. The observation by scanning electron microscopy of complexes consisting of aggregated COM crystals and cell debris led us to speculate that adhesion and endocytosis of crystals might provide the calculus nidus for aggregation and retention of crystals in the renal tubule. Furthermore, glycosaminoglycans and the macromolecular fraction of human urine were shown to have the ability to inhibit the cellular uptake of crystals. Evidence that similar processes may also occur in vivo was obtained using an experimental stone model in rats. Our experiments revealed that most of the COM crystals adhered to the tubular cells and some crystals were endocytosed by the cell. Thus, these crystal-cell interactions might be one of the earliest processes in the formation of kidney stones. Further elucidation of the mechanism and the regulatory factors involved in this process may provide new insight into stone pathogenesis.