Can Randall's plug composed of calcium oxalate form via the free particle mechanism?

BACKGROUND: The likelihood of a Randall's plug composed of calcium oxalate monohydrate (COM) forming by the free particle mechanism in a model of kidney with a structure recently described by Robertson was examined at the most favourable conditions for the considered mechanism. METHODS: The Robertson model of the kidney is used in the following development. The classical theory of crystallization was used for calculations. RESULTS: Initial COM nuclei were assumed to form at the beginning of the ascending loop of Henle where the supersaturation with respect to COM has been shown to reach the threshold level for spontaneous nucleation. Nucleation proceeds by a heterogeneous mechanism. The formed particles are transported in the nephron by a laminar flow of liquid with a parabolic velocity profile. Particles travel with a velocity dependent on their position in the cross-section of the nephron assumed to be straight tubule with smooth walls and without any sharp bends and kinks. These particles move faster with time as they grow as a result of being surrounded by the supersaturated liquid. Individual COM particles (crystals) can reach maximum diameter of 5.2 × 10-6 m, i.e. 5.2 µm, at the opening of the CD and would thus always be washed out of the CD into the calyx regardless of the orientation of the CD. Agglomeration of COM crystals forms a fractal object with an apparent density lower than the density of solid COM. The agglomerate that can block the beginning of the CD is composed of more crystals than are available even during crystaluria. Moreover the settling velocity of agglomerate blocking the opening of the CD is lower than the liquid flow and thus such agglomerate would be washed out even from upward-draining CD. CONCLUSIONS: The free particle mechanism may be responsible for the formation of a Randall's plug composed by COM only in specific infrequent cases such as an abnormal structure of kidney. Majority of incidences of Randall's plug development by COM are caused by mechanism different from the free particle mechanism.

The power of desktop scanning electron microscopy with elemental analysis for analyzing urinary stones.

The aim of this paper is to present a protocol for the routine morphocompositional study of kidney stones in a clinical setting, and to demonstrate that it is a simple and useful approach that can reliably determine the etiology of all types of kidney stones. Our routine study of kidney stones consists of a combination of stereoscopic microscopy, scanning electron microscopy, and infrared spectroscopy. The usefulness of such a procedure is demonstrated by its application to several illustrating examples. The protocol applied here is reliable and fast, and does not require multiple infrared spectroscopic analyses for most non-homogeneous samples. It also provides the identification of components that are present in very small proportions, the characteristics of internal and external structures, and information about areas with biological structures, such as renal tubules. It should be noted that results are obtained in a relatively short time and with high reliability. The detailed morphocompositional study of a urinary calculus is essential for establishing the diagnosis and etiology and for initiating the treatment of a patient with renal lithiasis, because there is a relationship between the specific characteristics of a stone and the specific etiology of the disease. The increasing number of treatments available for patients with different types of renal calculi makes improvements in diagnosis and determination of stone etiology, such as the procedure described here, more important now than ever.

A simple and rapid colorimetric method for determination of phytate in urine.

Phytate is a natural product present in urine and biological fluids that is associated with health benefits, such as the prevention of calcium renal stone formation. The available methods for phytate analysis in urine all require elaborate instrumentation and cannot be routinely applied in clinical laboratories. Here, we describe a simple procedure for urinary phytate determination, employing colorimetric detection. Our method requires purification and preconcentration of phytate via solid-phase extraction prior to colorimetric detection employing Fe(III)-thiocyanate. The working linear range of the assay is 0-5 µM phytate. The limit of detection is 0.055 µM. The relative standard deviation obtained upon assay of samples containing 2 µM phytate was 3.5 %. Several urine samples were analyzed using an alternative method based on the detection of phosphorus; the results of the two assays were comparable. Our novel method of phytate analysis in human urine is simple, rapid (3 h for 10 samples), accurate, precise, reliable, and highly sensitive. The assay can be run in most analytical laboratories and does not require sophisticated instrumentation.

Urinary pH and renal lithiasis.

Formation of calcium oxalate crystals, either as monohydrate or dihydrate, is apparently unrelated to urinary pH because the solubilities of these salts are practically unaltered at physiologic urinary pH values. However, a urinary pH <5.5 or >6.0 may induce uric acid or calcium phosphate crystals formation, respectively, which under appropriate conditions may induce the development of the calcium oxalate calculi. We assessed the relationship between the urinary pH and the formation of different types of calculi. A retrospective study in 1,478 patients was done. We determined the composition, macrostructure, and microstructure of the calculi and the urinary pH, 50.9% of calcium oxalate monohydrate unattached calculi were present in patients with urinary pH <5.5. We found that 34.1 and 41.5% of calcium oxalate dihydrate calculi were present in patients with urinary pH <5.5 and >6.0, respectively. Infectious calculi were found primarily in patients with urinary pH >6.0 (50.7%). Only calcium oxalate monohydrate papillary calculi were associated with urinary pH between 5.5 and 6.0 (43.1%). Urine of pH <5.5 shows an increased capacity to develop uric acid crystals, which can act as a heterogeneous nuclei of calcium oxalate crystals. In contrast, urine of pH >6.0 has an increased capacity to develop calcium phosphate crystals, which can act as a heterogeneous nuclei of calcium oxalate crystals. Oxalate monohydrate papillary calculi were associated to pH between 5.5 and 6.0 because the injured papilla acts as a heterogeneous nucleant. Consequently, measurement of urinary pH may be used to evaluate the lithogen risk of given urine.

Effects of Mediterranean diets with low and high proportions of phytate-rich foods on the urinary phytate excretion.

BACKGROUND: Important health benefits have been reported recently to phytate intake. This includes the prevention of pathological calcifications such as renal calculi, dental calculi and cardiovascular calcification, due its action as crystallization inhibitor of calcium salts, and as preventive of cancer. AIM OF STUDY: The aim of this study was to establish a relation between the intake of phytate, through consumption of typical components of the Mediterranean diet (including nuts), and its excretion in urine. METHODS: This study recruited participants from subjects included in a larger trial (PREDIMED) of food habits, that were assigned to one of two diet groups: (1) the Mediterranean diet with low proportion of phytate-rich food group, where participants were asked to maintain their usual diet; and (2) the Mediterranean diet with high proportion of phytate-rich food group, where participants were asked to increase phytate-rich foods in their diet. Phytate intake was assessed on the basis of a food frequency questionnaire. Urinary phytate excretion was determined in 2-h urine samples. RESULTS: The overall phytate consumption of the Mediterranean diet with high proportion of phytate-rich food group (672 +/- 50 mg) was significantly higher than the Mediterranean diet with low proportion of phytate-rich food group (422 +/- 34 mg), representing a 59% difference. Urinary phytate excretion was also significantly higher (54%) in the Mediterranean diet with high proportion of phytate-rich food group (1,016 +/- 70 microg/L) than the Mediterranean diet with low proportion of phytate-rich food group (659 +/- 45 microg/L). CONCLUSIONS: Mediterranean diets high in whole cereals, legumes and nuts compared to Mediterranean diets low in these phytate-rich foods increase the urinary phytate excretion in humans.

Anticalculus effect of a triclosan mouthwash containing phytate: a double-blind, randomized, three-period crossover trial.

BACKGROUND AND OBJECTIVE: Dental calculus occurs as a consequence of supersaturation of saliva with respect to calcium phosphates. This mineralization of dental plaque can be delayed by the presence of crystallization inhibitors, such as pyrophosphate or bisphosphonates. Phytate inhibits brushite and hydroxyapatite crystallization and has the potential to prevent dental calculi formation. The aim of the present study was to examine the effects of phytate and zinc, administered in a mouthwash solution, to prevent the formation of dental calculus. MATERIAL AND METHODS: Healthy dental plaque-forming volunteers (n = 25) took part in a randomized, double-blind, three-period crossover clinical study to assess the efficacy of a phytate-containing mouthwash in relation to control and placebo effects. Subjects rinsed their mouths for 1 min, twice each day, with 20 mL of the test solution, without ingestion. Mouthwash efficacy was assessed through quantification of the amounts of calcium, phosphorus and magnesium present in the residues obtained by dental cleaning, performed by a single trained examiner. RESULTS: A good correlation was found among total calcium, magnesium and phosphorus in calcified dental plaque residues, indicating that any of these variables is adequate for evaluating the reduction of plaque crystallization as calcium phosphate. A statistically significant decrease in total calcium, magnesium and phosphorus was found in the phytate-treatment period compared with control and placebo periods, demonstrating the efficacy of the proposed treatment in reducing dental calculus formation. CONCLUSION: The high efficacy of phytate in reducing dental calculus formation suggests that this substance may be an effective treatment for preventing the development of calculus deposits.

Possible relation between consumption of different food groups and depression.

BACKGROUND: Diverse studies have investigated the relationship between diet and depression. In fact some cross-sectional studies suggested that a healthy diet reduced the risk for depression. The main objective of this study was to assess the relationship of consumption of different food groups with depression. The food groups were selected based on their content of substances that were precursors to neurotransmitters (tryptophan or inositol) or their effect on oxidative stress. METHODS: This observational retrospective study compared the diets of individuals who were with depressive symptoms (Beck Depression Inventory Questionnaire [BDI] ≥ 10; 53 women, 23 men, age 38+/- 11) and with no depressive levels (BDI < 10; 33 women, 23 men, age 41+/- 13). Dietary data were collected from a questionnaire that asked about consumption of legumes, nuts, whole-grain foods, fruits and vegetables, chocolate, and sweet foods and refined sugars. RESULTS: Depressed individuals consumed significantly lower amounts of legumes, fruits, and vegetables, but higher amounts of sweets and refined sugars (p < 0.05 for all comparisons). After statistical adjustment for age and sex, the consumption of no legumes (adjusted odds ratio [aOR] = 2.60, 95% confidence interval [CI] = 1.19-5.67), low consumption of fruits and vegetables (aOR = 2.69, 95% CI = 1.18-6.13), and high consumption of sweet foods and refined sugars (aOR = 1.91, 95% CI = 1.23-2.99) were significantly associated with depression. The two groups had no significant differences in the consumption of chocolate. DISCUSSION: The results indicate significant relationships of the consumption of certain foods with depression, although the study design precludes any conclusions regarding causality. Further studies are necessary to determine the causal relationships of the consumption of specific foods with depression, and of depression with the consumption of specific foods. CONCLUSION: In spite of the limitations, we find that individuals without depression consumed more legumes, fruits, and vegetables, but fewer sweets and pastries than those with depression.

Intake of myo-inositol hexaphosphate and urinary excretion of inositol phosphates in Wistar rats: Gavage vs. oral administration with sugar.

OBJECTIVE: To evaluate the urinary levels of inositol phosphates (InsPs) in rats that received different salts of myo-inositol hexaphosphate (InsP6) by gavage or by oral administration. METHODS: Thirty rats received AIN-76A diet (in which InsPs are undetectable) for 15 days. Then, 12 rats received InsP6 by gavage as a Na salt or a Ca/Mg salt; after 4 days, the Na or Ca/Mg InsP6 was administered with water containing 15 g/L sucrose and urine samples were collected. The other 18 rats received oral InsP6, in which 0.5 g of sugar was combined with InsP6 as a Na salt, a Ca/Mg salt, or a Na salt with CaCO3; daily urine samples were collected. Urine levels of InsPs were determined using a nonspecific method and a specific method (polyacrylamide gel electrophoresis, PAGE), and different InsPs were identified by mass spectroscopy (MS). RESULTS: After 15 days of the InsP6-free diet, the non-specific method detected no urinary InsPs, and MS detected only InsP2. After administration of Na-InsP6 by gavage, the non-specific method indicated more urinary InsPs than the amount of InsP6 determined by PAGE. MS indicated the presence of urinary InsP2, InsP3, InsP4, InsP5, and InsP6 in these rats, with notable variations among animals. Use of the same treatment to administer Ca/Mg-InsP6 led to a lower overall content of urinary InsPs and a lower level of InsP6. Oral administration of InsP6 as a sugar pill led to lower urinary levels of InsPs than administration of InsP6 by gavage, and administration as a Ca/Mg pill or a Ca/Mg pill with CaCO3 led to lower levels than administration as a Na pill. CONCLUSION: Administration of InsP6 to rats leads to the excretion of a mixture of different InsPs. Rats more effectively absorb InsP6 when supplied without dietary components that interfere with its uptake, such as the Ca ion and sugar.

Urinary tract infection's etiopathogenic role in nephrolithiasis formation.

Urolithiasis has a high prevalence and recurrence rate, especially in developed countries, and is a major public health issue with a high socioeconomic cost. There are multiple causes of urolithiasis, including urinary tract infection (UTI). Infection stones (mainly composed of struvite) are associated with renal infections by urease-producing bacteria. However, there is limited knowledge about the role of UTIs in the formation of stones that are apparently not related with infection. We hypothesize that UTIs promote the formation of certain urolithiasis that appear to be non-infection stones. Some recent studies have reported the presence of bacterial growth in cultures of stones removed by endourological procedures. These findings have led to the hypothesis that UTIs have a role in the formation of stones that are apparently non-infection stones. It is unknown whether these UTIs promoted stone formation, or if the stones became infected after formation. Several in vitro studies and ultrastructural microscopic analyses of urolithiasis are consistent with our hypothesis. If our hypothesis is correct, it could have a great impact on the treatment of urolithiasis. Especially, early identification and treatment of renal infections could help to prevent septic events, which are frequently life-threatening. It could also help to reduce the recurrence of urolithiasis, and thereby reduce health care costs. In conclusion, some evidence suggests that UTIs have a role in the formation of some apparently non-infection urolithiasis. If this is so, it could have a great impact on the treatment and prevention of this disease.

Evaluation of inositol phosphates in urine after topical administration of myo-inositol hexaphosphate to female Wistar rats.

AIMS: Previous studies demonstrated a remarkable increase of urinary InsP6 by topical administration. However, the methodology used for InsP6 analysis was not specific. The aim of this paper is to measure urinary inositol phosphates InsPs using more advanced methodologies and to compare the results with those obtained by the non-specific method. MATERIALS AND METHODS: We fed 12 female rats with a diet without InsP6 for 16days. Then, we administered a topical InsP6 gel at high doses for 7days (50mgInsP6/day) or at low doses for 28days (20mgInsP6/day). We measured urine levels InsPs using a nonspecific method (based on the ability of InsPs to complex Al3+) and levels of InsP6 by a specific method (using polyacrylamide gel electrophoresis). Identification of different InsPs was performed by MS. KEY FINDINGS: At baseline, after dietary deprivation of InsP6, rats only excreted InsP2 in their urine, and there was no detectable InsP6 or other InsPs. Rats given the high dose treatment for 7days had abundant urinary InsP6, but also had other InsPs in their urine; cessation of InsP6 administration led to decreased levels of urinary InsPs. Rats given the low dose treatment for 28days had increasing levels of urinary InsPs over time. The maximum urinary InsP6 was at 21days, after which InsPs excretion decreased. SIGNIFICANCE: We conclude that the skin can absorb InsP6 from a topical gel, and that InsP6 is excreted in the urine, along with other InsPs (InsP5, InsP4, InsP3, and InsP2).

Structural features of three ureterocele calculi.

Ureterocele calculi are developed in cavities with urinary retention but far from the upper renal cavities. The structural features of three ureterocele calcium oxalate stones were observed by scanning electron microscope coupled with X ray microanalysis. The urinary parameters of the three patients were also determined. The stone A consisted of loose structure of large calcium oxalate dihydrate crystals and small spheres of hydroxyapatite. The interior contains disorganized plate-like calcium oxalate monohydrate crystals. The stone B was formed by a compact outer layer of calcium oxalate monohydrate columnar crystals. The structure of stone interior was similar to the stone A. The stone C was formed by concentric layers composed of either calcium oxalate monohydrate columnar crystals or hydroxyapatite. The core consisted of agglomerated calcium oxalate monohydrate crystals, hydroxyapatite and organic matter. From the urinary biochemical data it was deduced that two ureterocele patients (who formed A and B stones) were hypercalciuric (calcium > 300 mg/24 h), being 6.5 the urinary pH value of the patient that formed the A stone, and 7.0 the urinary pH of the patient that formed the C stone. The rest of urinary parameters for the three patients were normal. Thus, one of the requisite conditions for unattached stone development is the existence of a place inside the urinary tract where the solid particles that act as calculus initiator of the stone can be retained enough time to exert this action.

Factors affecting calcium oxalate dihydrate fragmented calculi regrowth.

BACKGROUND: The use of extracorporeal shock wave lithotripsy (ESWL) to treat calcium oxalate dihydrate (COD) renal calculi gives excellent fragmentation results. However, the retention of post-ESWL fragments within the kidney remains an important health problem. This study examined the effect of various urinary conditions and crystallization inhibitors on the regrowth of spontaneously-passed post-ESWL COD calculi fragments. METHODS: Post-ESWL COD calculi fragments were incubated in chambers containing synthetic urine varying in pH and calcium concentration: pH = 5.5 normocalciuria (3.75 mM), pH = 5.5 hypercalciuria (6.25 mM), pH = 6.5 normocalciuria (3.75 mM) or pH = 6.5 hypercalciuria (6.25 mM). Fragment growth was evaluated by measuring increases in weight. Fragment growth was standardized by calculating the relative mass increase. RESULTS: Calcium oxalate monohydrate (COM) crystals formed on COD renal calculi fragments under all conditions. Under pH = 5.5 normocalciuria conditions, only COM crystals formed (growth rate = 0.22 +/- 0.04 microg/mg x h). Under pH = 5.5 hypercalciuria and under pH = 6.5 normocalciuria conditions, COM crystals and a small number of new COD crystals formed (growth rate = 0.32 +/- 0.03 microg/mg x h and 0.35 +/- 0.05 microg/mg x h, respectively). Under pH = 6.5 hypercalciuria conditions, large amounts of COD, COM, hydroxyapatite and brushite crystals formed (growth rate = 3.87 +/- 0. 34 microg/mg x h). A study of three crystallization inhibitors demonstrated that phytate completely inhibited fragment growth (2.27 microM at pH = 5.5 and 4.55 microM at pH = 6.5, both under hypercalciuria conditions), while 69.0 microM pyrophosphate caused an 87% reduction in mass under pH = 6.5 hypercalciuria conditions. In contrast, 5.29 mM citrate did not inhibit fragment mass increase under pH = 6.5 hypercalciuria conditions. CONCLUSION: The growth rate of COD calculi fragments under pH = 6.5 hypercalciuria conditions was approximately ten times that observed under the other three conditions. This observation suggests COD calculi residual fragments in the kidneys together with hypercalciuria and high urinary pH values may be a risk factor for stone growth. The study also showed the effectiveness of specific crystallization inhibitors in slowing calculi fragment growth.

Influence of concomitant food intake on the excretion of orally administered myo-inositol hexaphosphate in humans.

myo-Inositol hexaphosphate (InsP6) widely occurs in plant seeds. At present, some important benefits of InsP6 for human health have been described. The purpose of this study was to find the best condition for the optimum absorption of orally administered InsP6, evaluated by InsP6 urinary excretion. The influence of different stomach conditions (empty, empty with an alkalinizing agent, and full stomach) on the effects of oral administration of InsP6 and its urinary excretion was investigated in six healthy subjects on an InsP6-poor diet, given 400 mg of calcium/magnesium salt of InsP6 as a single dose. The basal urinary excretion of InsP6 on an InsP6-poor diet (50.91 +/- 15.09 microg) was significantly lower than that found when an InsP6-normal diet was consumed (100.09 +/- 26.42 microg) (P < .05). No differences were observed in the areas under the curve of accumulated excretion at 8 hours among the three different stomach conditions studied, suggesting that the overall InsP6 absorption took place independently of the stomach state (full or fasted) and indicating that the InsP6 absorption also takes place during the intestinal transit. Thus, if InsP6 supplements of vegetal origin are consumed to maintain the optimum InsP6 levels needed for a healthy status, these supplements can be consumed either during or between meals with the same efficacy.

Absorption of myo-inositol hexakisphosphate (InsP6) through the skin in humans.

In this paper, we present a pilot study of the absorption of myo-inositol hexakisphosphate (InsP6) through the skin in humans. We found that, after topical treatment with a 4% InsP6 rich gel, InsP6 urinary excretion increased 54% compared to the control situation (participants submitted to an InsP6-poor diet for 15 days, n = 6), clearly demonstrating that InsP6 is absorbed through the skin of humans. These results demonstrate the topical application as a suitable administration route of InsP6 in humans.

Anxiety and stress among science students. Study of calcium and magnesium alterations.

Stress and anxiety of university science students (Chemistry) was evaluated in basal conditions and during exams using validated stress and anxiety questionnaires. The relations between the data obtained and various biochemical markers were established. Results showed that the evaluated students did not experience stress increase as a consequence of exams but suffered a significant increase in anxiety. The psychological findings agree with the urinary biomarkers studied. It is known that anxiety is related to partial magnesium reduction associated with a urinary magnesium excretion increase, as observed in the present data. Nevertheless, stress also correlates with a urinary calcium increase which was not detected in the present study.

Intracellular and extracellular myo-inositol hexakisphosphate (InsP6), from rats to humans.

The presence of myo-inositol hexakisphosphate (InsP6) in biological fluids (blood, urine, saliva, interstitial fluid) of mammalians has been clearly demonstrated. The existence of intracellular InsP6 in mammalian cells has also been established. Further, significant extracellular and intracellular functions of this molecule have been found. The relationship between InsP6 ingestion and the InsP6 distribution in various tissues of mammalians is discussed. It was found that the majority of the extracellular InsP6 found in organs, tissues and biological fluids of mammalians has a dietary origin and is not a consequence of endogenous synthesis, whereas the intracellular InsP6 probably originates in the cell. Little absorption of dietary InsP6 takes place during intestinal transit and depletion of extracellular InsP6 occurs at high rates when InsP6-poor diets are consumed. From these results, it can be deduced that health benefits linked to extracellular InsP6 must be related to dietary InsP6.

[Chronic idiopathic lithoptysis]. / Litoptisis crónica idiopática.

Broncholiths, which usually arise from calcified peribronchial lymph nodes, can be found by radiography or bronchoscopy. We describe the case of a 19-year-old man who had experienced lithoptysis of bronchial hydroxyapatite calculi for over 6 months and who reported having sandy expectoration since childhood. Exhaustive clinical, radiographic, and endoscopic diagnostic studies detected no calcified lesions in the thorax that could explain the origin of the broncholiths. Therefore, we propose that broncholiths may form by mechanisms similar to those involved in calculi formation in other locations.

Relationships between Serum Levels of Atazanavir and Renal Toxicity or Lithiasis.

The main aim of this study is to describe the relationship between serum levels of atazanavir, renal toxicity, and lithiasis. This is a prospective observational study of patients being treated with atazanavir (ATV) at Son Espases Teaching Hospital, Palma de Mallorca, between 2011 and 2013. The study includes 98 patients. Sixteen were found to have a history of urolithiasis. During a median monitoring period of 23 months, nine patients suffered renal colic, in three of whom ATV crystals were evidenced in urine. Cumulative incidence of renal colic was 9.2 per 100 patients. The variables related to having renal colic were the presence of alkaline urine pH and lower basal creatinine clearance. The mean serum level of ATV was slightly higher in patients with renal colic-1,303 µg/L versus 1,161 µg/L-but did not reach statistical significance. Neither were any significant differences detected by analysing the levels according to the timetable for ATV dosage. Cumulative incidence of renal colic was high in patients being treated with ATV, in 33% of whom the presence of ATV crystals was evidenced in urine. We were unable to demonstrate a relationship between ATV serum levels and renal colic or progression towards renal failure.