Ingestion Of Melamine Research Articles

Melamine induced changes in histopathology of the main organs and transcriptional levels of MAPK signaling genes in kidneys of female mice.

Melamine is an important chemical raw material used in industries, which has potential health risks to animals and humans. Current research mainly focuses on the toxic effects of high-dose melamine ingestion. However, there are few reports on whether melamine at the current limited standard dose has adverse effects on various tissues and organs, and whether there are sensitive target genes for risk evaluation. For this, 24 female Kunming mice were fed 0, 1.8-, 3.6-, and 7.2- mg/kg/d melamine via drinking water for consecutive 28 days, respectively. The morphological changes of the ovarian, hepatic, and renal tissues were firstly observed. The results demonstrated that the histopathology of ovary, liver, and especially in kidney had been altered by melamine intake in female. And then, the transcriptional levels of MAPK signaling genes including p38, ERK1, ERK2, JNK1, and JNK2 in kidneys were investigated by real-time PCR. The data showed that ERK1 and p38 mRNAs expressions were up-regulated significantly by melamine, suggesting that ERK1 and p38 transcriptional levels in the kidney might to be considered as candidate targets for lower-dose melamine toxicity. This study not only provides potential targets for the diagnosis and prevention of melamine damage, but also helps to assess the health risks of the current minimum allowable levels of melamine in food and environment.

Visual and Optical Absorbance Detection of Melamine in Milk by Melamine-Induced Aggregation of Gold Nanoparticles.

The present study reported a facile method for the determination of melamine in milk powder products based on the aggregation of reactant-free 5 nm gold nanoparticles (AuNPs). The strong electrostatic attraction between the positively charged exocyclic amine groups present in the melamine molecule and the negatively charged ions bound to the AuNPs induced aggregation of the AuNPs, resulting in visible color changes that could be seen with the naked eye and monitored by ultraviolet–visible (UV–Vis) absorbance spectra. The method shows high sensitivity with detection limits of 1 × 10−9 M for visual detection and 1 × 10−11 M for UV–Vis analysis, which is far below the safety limit of melamine ingestion in infant formula (1 ppm = 7.9 × 10−6 M) and the detection limit acquired by most AuNP-based melamine detection methods. Good recoveries were obtained over the range of 94.7–95.5% with a relative standard deviation of mean recovery (RSD) ranging from 1.40 to 5.81. The method provides a simple, feasible, fast and real-time detection of melamine adulterants in infant formula by the naked eye, without the aid of advanced instruments.

Detection of Melamine in Milk Using Nanotechnology

Melamine is a poisonous substance which causes formation of kidney stone, nephrolithiasis, kidney injury in infant as well as in adult human beings by the ingestion of melamine contaminated food items, powder formula, powder milk. Nobel metal may be used to shape a type of nano-particles, known as NMNPs, which are inert (oxidation-resistant/corrosion resistant) and have special physical and optical properties. NMNPs are extremely detailed and responsive visual bio sensors for the analysis of a broad variety of inorganic and organic components and are particularly gold and silver nano-particles (AuNPs and AgNPs). Colorimetric changes result in a specific and sensitive identification of contaminants, heavy metals, nucleic acids, lipeid, protein, antibody, and other molecules through interactions between noble metal nanoparticles (NMNPs) and inorganic/organic molecules. Capping agents can react or transfer, causing cross-connection and non-cross binding, broadening, or modifying local surface plasmone resonance absorption, to the hydrogen bondage, electrostatic interaction, and steric effects of inorganic and organic molecules with surface NMNPs. A collection of independent, fast and low-cost diagnostic products with colorimetric or clear visual reading have been extensively applied to NMNPs-based bio sensors.

Ratiometric fluorescence detection of melamine in milk by a zirconium-based metal-organic frameworks composite

Melamine has biological toxicity and is forbidden to be used in food processing and food additives. The long-term ingestion of melamine will cause renal malfunction and metabolic problems of the urinary system, so it is of great significance for the rapid and selective detection of melamine. Herein, a zirconium-based metal–organic frameworks (Zr-based MOFs) encapsulated tris(2,2-bipyridyl)ruthenium (II) chloride hexahydrate ([Ru(bpy)3]2+) composite, donated as UiO-66-NH2@Ru, was reported and further studied its sensing performance for melamine based on ratiometric fluorescent method. The UiO-66-NH2@Ru was prepared from ZrCl4, 2-amino-terephthalic acid (TPA-NH2) and [Ru(bpy)3]2+ by one pot reaction through solvothermal method, which exhibited dual emission signals at 445 and 595 nm from single excitation of 350 nm. The corresponding two peaks showed different responses to melamine, that was, the obvious enhancement at 445 nm and the slow decrease at 595 nm, thus achieving the “on–off” ratiometric fluorescence detection. When the concentration of melamine was in the range of 0.27 to 110 μM, the ratio of fluorescence intensity F445/F595 had a good linear relation with the correlation coefficient R2 = 0.995 and the detection limit of 90 nM. The synthetic UiO-66-NH2@Ru probe implemented rapid determination of melamine in real sample of milk powder with high sensitivity and selectivity. Compared with the reported carbon dots, quantum dots, metal nanoclusters, nanocomposites and other fluorescent sensors, MOFs-based sensor have broadened the application of nanomaterials in melamine detection for the first time. This study also demonstrates the Zr-based MOFs as a platform to encapsulate fluorescent dye for constructing ratiometric sensor in the determination of melamine is feasible and exciting.

Melamine Impairs Renal and Vascular Function in Rats.

Melamine incident, linked to nephrotoxicity and kidney stone in infants previously exposed to melamine-contaminated milk products, was unprecedentedly grave in China in 2008 as little was known about the mechanistic process leading to renal dysfunction in affected children. This study investigates whether neonatal ingestion of melamine leads to renal and vascular dysfunction in adulthood; and whether ingestion of melamine in pregnant rats leads to renal dysfunction in their offspring. A combination of approaches employed includes functional studies in rat renal arteries, renal blood flow measurement by functional magnetic resonance imaging, assay for pro-inflammatory and fibrotic biomarkers, immunohistochemistry, and detection of plasma and renal melamine. We provide mechanistic evidence showing for the first time that melamine reduces renal blood flow and impairs renal and vascular function associated with overexpression of inflammatory markers, transforming growth factor-β1, bone morphogenic protein 4 and cyclooxygenase-2 in kidney and renal vasculature. Melamine also induces renal inflammation and fibrosis. More importantly, melamine causes nephropathies in offsprings from pregnant rat exposed to melamine during pregnancy, as well as in neonatal rat exposed to melamine afterbirth, thus supporting the clinical observations of kidney stone and acute renal failure in infants consuming melamine-contaminated milk products.

The effects of melamine on humoral immunity with or without cyanuric acid in mice

Melamine is an industrial chemical with high nitrogen content. When added to the pet food and milk it can falsely elevate the apparent protein concentration readings. Cyanuric acid related structurally to melamine has a strong mutual affinity with melamine. The combined ingestion of melamine and cyanuric acid was considered to be responsible for the crystalluria, kidney stones and subsequent renal failure in animals. In our previous investigation, we demonstrated that melamine alone or its combination with cyanuric acid appears to be toxic to the immune system in mice. The objective of this study was to investigate the potential effects of melamine on humoral immunity with or without cyanuric acid in mice. In comparison to control group, a significantly lower content of plasma cells expressing CD138 were observed in mixture groups of melamine and cyanuric acid with both middle and high doses. The co-administration of melamine and cyanuric acid resulted in a significant decreasing in blimp-1 protein expression and the contents of sIgA, C3, IL-21 and IL-4 compared with the control group. Moreover, our data clearly showed that melamine-related toxicity suppressed the production of IL-6 and IL-10 in a dose-dependent manner. Also, the animals from mixture of melamine and cyanuric acid with high dose group exhibited a significantly lower expression of gata-3 protein, The results from the present study suggested that the exposure to melamine alone or combination with cyanuric acid had certain humoral immunotoxicity in mice, especially when ingested in high dosage.

Polydopamine-assisted partial hydrolyzed poly(2-methyl-2-oxazolinze) as coating for determination of melamine in milk by capillary electrophoresis

Nitrogen-rich melamine (66% by mass) had been found to be illegally adulterated to milk products and animal feed in order to increase the apparent protein content, and ingestion of melamine may lead to the formation of kidney stones. Hence, the development of reliable analytical methods for the monitoring of melamine in milk products is necessary. The common methods for melamine analysis in milk products are performed via GC–MS or HPLC, however, these procedures require a large of organic solvent and several pretreatment steps. In this study, a new and facile approach was developed to modify a fused-silica capillary inner surface based on poly(dopamine) (PDA) and partial hydrolyzed poly(2-methyl-2-oxazoline) (PMOXA-EI) mixed coating, which was used to determine the melamine in milk powder quantitatively by capillary electrophoresis with ultraviolet (CE-UV) detection with simple analytes pretreatment. Firstly, the influences of the molecular mass of poly(2-methyl-2-oxazoline) (PMOXA), the hydrolysis degree of PMOXA, and the concentration ratio of DA to PMOXA-EI on the separation properties of a mixture of four basic proteins (cytochrome c, lysozyme, ribonuclease A, and α-chymotrypsinogen A) were studied in detail. As a consequence, fast and efficient separation of four proteins was obtained using PDA/PMOXA1k-EI0.4 coating (once coating). Then, a modified facile coating workflow was carried out to acquire a novel twice coating (i.e. PDA/PMOXA1k-EI0.4+PMOXA1k-EI0.4 coated capillary) for highly sensitive and stable analysis of melamine. Under the optimal conditions, the linear response of melamine concentration ranged from 6.25 to 100µg/mL with high correlation coefficient of 0.9910, and the limit of detection (LOD) for melamine was 0.097µg/mL. The minimum amount of melamine determined in milk powder with our proposed method was 4mg/kg. The recoveries and relative standard deviations (RSDs) were 92.13–102.47%, 92.22–100.30%, 2.07–4.98%, and 2.43–3.77%, respectively for the intraday and interday analysis. After being used continually for 45 days, the PDA/PMOXA1k-EI0.4+PMOXA1k-EI0.4 coated capillary could be still used to detect the melamine from milk powder, with the recovery from 91.85% to 106.14%. The technique developed in this study provides a simple and relatively sensitive method for determination of melamine in milk powder.

Use of urinary renal biomarkers to evaluate the nephrotoxic effects of melamine or cyanuric acid in non-pregnant and pregnant rats

Although traditional assessments of renal damage detect loss of kidney function, urinary renal biomarkers are proposed to indicate early changes in renal integrity. The recent adulteration of infant formula and other milk-based foods with melamine revealed a link between melamine ingestion and nephropathy. Thus, the effects of melamine and related analogs (e.g., cyanuric acid) should be assessed in other potentially sensitive groups. We evaluated whether urinary Kim-1, clusterin, and osteopontin could detect the effects of high doses of melamine or cyanuric acid in pregnant and non-pregnant female rats gavaged with 1000 mg/kg bw/day for 10 days. We demonstrate that these biomarkers can differentiate the severity of effects induced by melamine or cyanuric acid. All melamine-treated animals experienced adverse effects; however, pregnant rats were most sensitive as indicated by increased SCr, BUN, and kidney weights, decreased body weight, and presence of renal crystals. These effects coincided with elevated urinary biomarker levels as early as day 2 of exposure. One cyanuric acid-treated rat displayed effects similar to melamine, including increased urinary biomarker levels. This work illustrates that these biomarkers can detect early effects of melamine or cyanuric acid crystal-induced nephropathy and further supports the use of urinary protein immunoassays as a powerful, non-invasive method to assess nephrotoxicity.

Liver involvement in melamine-associated nephrolithiasis.

It is currently believed that melamine ingestion can lead to insoluble crystals in an animal's urinary system with subsequent physical obstruction or bladder carcinoma. However, whether melamine can cause injury of other tissues and organs in humans is yet unknown. In this study, we encountered 3 affected children with liver lesions, 2 males and 1 female, and detailed their clinical characterizations. Their ages were respectively 2, 6, and 10 months. Among the 3 patients with liver lesions, only 1 exhibited symptoms of gradual progressive jaundice, abdominal distention, hepatic intumesce, and bilirubin abnormality; the other 2 were asymptomatic. The mechanism associated with liver lesion may, at least in part, be due to physical deposition and blockage of the biliary tract system. Disturbance of the acid-base equilibrium may be another reason that accelerates stone formation in human tissues.

Melamine-Induced Urolithiasis in a Drosophila Model

Melamine-tainted food can induce renal stones in both humans and animals. We have previously reported a novel Drosophila model for the study of renal stone disease. In addition to hyperoxaluria-causing agents, we also tested herein the effect of melamine on crystal formation in Drosophila . The results indicate that administration of melamine alone caused crystal formation in a dose-dependent manner. The crystals also appeared after ingestion of melamine for 3 weeks in the Malpighian tubules of Drosophila when viewed with polarized light. Administration of potassium citrate (K citrate) was found to significantly ameliorate the melamine-induced reduction of lifespan. However, administration of K citrate failed to reduce the quantity of crystals. Because calcium oxalate is not the major crystal induced by melamine, the predominant components of melamine-induced crystals and the potential crystal inhibitors warrant further investigation.

Melamine in eggs, plasma and tissues of hens fed contaminated diets

A study was conducted to evaluate the excretion pattern of melamine from feed into eggs, plasma, kidney, liver and muscle of laying hens. In particular, 90 laying hens were randomly allocated to three dietary treatments and fed diets contaminated with melamine at a level of 2.5, 25 and 250 mg of melamine/kg of diet for T1, T2 and T3 groups, respectively. The diets were offered in six replicate boxes (five hens each) for 13 days. Eggs were collected from each group for melamine quantification on days 0, 1, 3, 6, 9 and 13. At the end of the experimental period, one hen per box was randomly selected and slaughtered to collect plasma, liver, kidney and muscle samples. During the experiment, feeding diets with increasing levels of melamine had no effect (P > 0.05) on weight gain, feed intake, egg production, egg weight and mortality of laying hens. The melamine in eggs increased from day 1 after melamine ingestion and reached a plateau between days 6 and 13 of melamine ingestion. At steady-state condition, the melamine egg concentrations increased (P < 0.01) with treatments, being 0.026, 0.352 and 4.631 mg/kg for T1, T2 and T3, respectively. Similarly, the carryover of melamine from feed to egg increased (P < 0.05) with the levels of melamine in the diets, varying from 0.50 to 0.70 and 0.84 for T1, T2 and T3, respectively. The melamine was detected in plasma of all tested groups, increasing (P < 0.01) with levels of melamine in the diets (0.030, 0.266 and 4.102 mg/l in T1, T2 and T3, respectively). Melamine was not detected in kidney, liver and muscle of hens fed T1. Except for kidney sampled in the T3, no melamine concentration higher than 2.5 mg/kg, representing the maximum allowable limit set by the US Food and Drug Administration and European Union for food and feeds, was measured. The melamine resulted higher in plasma and kidneys than in the liver and muscle both in T2 and T3. The results confirmed the presence of an excretion pattern of melamine from feed to eggs and tissues in laying hens.

Toxicokinetic study of melamine in the presence and absence of cyanuric acid in rats

Several lines of evidence show that the nephrotoxic effect of melamine (MEL) in animals is consistent with combined ingestion of MEL and cyanuric acid (CYA). The aim of the present study was to compare the toxicokinetics of MEL in the presence and absence of CYA, and to elucidate the correlation between toxicity and kinetic properties of MEL. Sprague-Dawley rats were administered a single oral dose of MEL (100 mg kg(-1) ) with or without CYA (100 mg kg(-1) ). Plasma and tissue samples were analyzed by liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay. Significant changes in toxicokinetic parameters of MEL such as lower maximum concentration (7.4 ± 3.5 vs 78.0 ± 11.0 µg ml(-1) ) and area under curve (94.9 ± 53.5 vs 295.1 ± 93.7 µg h ml(-1) ), higher plasma elimination half-life (7.0 ± 3.3 vs 2.5 ± 0.3 h) and volume of distribution (11 505.5 ± 5030.3 vs 1312.7 ± 337.7 ml kg(-1) ), as well as significantly higher concentration of MEL in rat kidney (2.96-274.15 vs < 1 µg g(-1) ) were detected in the CYA co-administration group when compared with MEL alone group (P < 0.05). The differences in kinetic parameters between the two groups meant that CYA co-administration could lower absorption, slow excretion and induce tissue accumulation of MEL, which correlated well with the generation and development of renal toxicity. In conclusion, co-administration with CYA leads to the alteration of the kinetic characteristics of MEL, which provides an additional explanation for renal toxicity.

Differential analysis of human kidney stone samples using electrospray ionization mass spectrometry

Kidney stones may be caused by many factors, including ingestion of melamine for a relatively long time. The diagnosis of melamine-induced kidney stones and the understanding of how the melamine is involved in the formation of kidney stones are of practical importance. To establish a sensitive method based on widely used electrospray ionization mass spectrometry (ESI-MS) for diagnosis of melamine-induced kidney stones and to probe the differential formation of melamine-induced kidney stones at molecular levels. Human kidney stones were collected in hospital from 6 groups of patients at different ages. ESI-MS was employed as the main technique with the principal component analysis for data processing. Using principal component analysis (PCA) of the ESI-MS fingerprints, a set of 21 melamine-induced kidneystone samples and 21 uric acid derived kidney stone samples were successfully differentiated from the other groups, rendering ESI-MS method a potential platform for differential analysis of the human kidney stones of various causes at molecular levels. The experimental results also indicate that in addition to the melamine, the chemical compounds enwrapped in the melamine-induced kidney stone samples are different from other kidney stone samples. These findings suggest that ESI-MS is a useful tool for diagnosis of melamine-induced kidney stone samples and the melamine-induced kidney stone could be formed by different mechanisms. Key words: Toxicity of melamine, chemical profiling, uric acid, electrospray ionization-mass spectrometry (ESI-MS), kidney stone, melamine, principal component analysis.

Effects of water uptake on melamine renal stone formation in mice

Melamine-tainted food can induce kidney stones both in humans and animals and in domestic animals, severe cases caused acute kidney failure and death. Although increasing water intake can ameliorate kidney stone formation, its effect on melamine (Mel)-induced kidney stones has not been studied. We have analysed the effect of restricted ingestion of drinking water on melamine stone formation in mice. They were given melamine and cyanuric acid orally and received drinking water either freely or for a restricted time. Kidney stone formation and renal function were monitored. Mice receiving drinking water for a restricted 10-h period initially lost body weight, which returned to normal within 2 days. No other abnormalities were observed. Ingestion of melamine alone failed to induce kidney stones even under conditions of restricted drinking water. In mice treated with melamine together with cyanuric acid for 3 days, no renal stones were formed when the supply of drinking was normal. However, when drinking water was limited, stone formation was observed and accompanied by high levels of serum urea and creatinine. An increase in urine haemoglobin and glucose levels was also found. The administration resulted in up-regulated tissue osteopontin, kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin messenger RNA expression and macrophage infiltration. Our results indicate the importance of water intake in the formation of melamine-induced renal stone formation in the mouse and provide new information on the mechanisms of melamine stone formation.

TOF‐SIMS analysis of kidney stones possibly induced by the ingestion of melamine‐ containing milk products

AbstractIngestion of melamine contaminated food likely product kidney stones and may leads to acute kidney failure in mammals. In this study, ToF‐SIMS has been applied to imaging the micro structure of kidney stone samples, revealing information of the micro structure of different stone samples. Our data indicate that the melamine‐induce stones were formed by different mechanisms. However, information obtained using other techniques is also required to correlate the detailed differences in the microstructure of the stone samples with the formation mechanism. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Transfer of melamine from feed to milk and from milk to cheese and whey in lactating dairy cows fed single oral doses

A study was conducted to evaluate the excretion pattern, after a single oral dose, of melamine from feed into milk, and the subsequent transfer to cheese and whey. The transfer of cyanuric acid was also investigated. Twenty-four lactating Holstein cows were randomly allocated to 4 treatments and received single doses of melamine as follows: 0.05, 0.50, 5.00, and 50.00 g/cow for groups D1, D2, D3, and D4, respectively. Individual milk samples were collected for melamine and cyanuric acid analyses on d 1, 2, 3, 4, 5, and 7. Milk collected individually from the second milking after melamine ingestion was used to make cheese on a laboratory scale. Melamine and cyanuric acid were extracted using a solid-phase extraction cartridge, and analyses were carried out by liquid chromatography–mass spectrometry/mass spectrometry. Maximal melamine concentrations occurred between 6 and 18h after treatment and increased with log dose (linear and quadratic), ranging from 0.019 to 35.105 mg/kg. More than 60% of the melamine that was transferred to the milk was observed within 30h after melamine ingestion. Melamine was not detected (limit of detection was 0.002 mg/kg) in milk 5 d after treatment in group D1, and 7 d after treatment in groups D2, D3, and D4. Blood urea nitrogen was not influenced by melamine ingestion. During cheese making, melamine was transferred mainly to the whey fraction. Cyanuric acid was not detected in any of the samples (milk, cheese, or whey). The excretion pattern of melamine in milk and whey may represent a health concern when cows ingest more than 0.50g of melamine/d. However, only at intake levels of 5 and 50 g/d did cheese exceed the limits as set forth by the European Union. The results confirmed that melamine contamination of milk and milk products may be related not only to direct contamination, but also to adulteration of animal feeds.

Derivation of a Melamine Oral Reference Dose (RfD) and Drinking-Water Total Allowable Concentration

Due to its high nitrogen content, melamine has been used to adulterate food to increase apparent protein content. In 2008, thousands of Chinese infants consumed reconstituted formula derived from melamine-adulterated milk. Urinary-tract stones (comprised of melamine and uric acid) accumulated in some victims and lead to acute renal failure or death. Premature infants and children (<2 yr) have an increased susceptibility to ingested melamine. Due to incomplete reporting, the human data were inadequate to identify a no-observed-adverse-effect level (NOAEL) for melamine-induced pediatric urolithiasis. Urolithiasis, urinary bladder cystitis, and ulcerations were observed in F344 rats after subchronic or chronic ingestion of melamine at ≥72 mg/kg-d. Bladder epithelial damage was followed by epithelial hyperplasia that progressed to bladder papillomas and carcinomas in male but not female F344 rats or male or female B6C3F1 mice. Short-term assays suggest, at best, weak genotoxic activity, and kinetic data show that melamine is not metabolized. Since reliable exposure information was lacking from the clinical reports, an oral reference dose (RfD) based on urolithiasis in male rats after 13 wk of continuous melamine ingestion was calculated as a 10% benchmark dose (38 mg/kg-d). Incorporation of 10-fold interspecies and intraspecies (for the increased susceptibility of infants) uncertainty factors and a threefold database uncertainty factor (for the lack of immunological, neurological and reproduction toxicity data) yields an oral RfD of 0.13 mg/kg-d. Assuming the 70-kg adult consumes 2 L of drinking water daily, a total allowable concentration of 0.9 mg/L (900 μg/L) was calculated for melamine in drinking water.

Melamine Toxicity

Melamine contamination of infant formula in China and its health effects highlight the safety of the global food supply especially as it relates to formula-fed infants. Melamine is a widely used industrial chemical not considered acutely toxic with a high LD(50) in animals. The data available on acute and chronic human exposure to melamine have been limited and extrapolated from animal data. Pet food contamination in 2004 and 2007 showed stone formation and illness in animals when melamine was co-ingested with cyanuric acid. The recent outbreak in infants showed that melamine ingested in large doses may cause stones and illness without significant ingestion of cyanuric acid or other melamine-related chemicals. This may be due to increased uric acid excretion in infants and formation of melamine-uric acid stones. Diagnosis and treatment of infants exposed to melamine requires further study. Clinical signs and symptoms in infants are nonspecific. The stones may be radiolucent and are not consistently seen on ultrasound. The use of alkalinization of the urine for treatment has been proposed, but is of unproven benefit. The FDA and other regulatory agencies have recommended acceptable levels of melamine in foods for consumption. Melamine ingestion has been implicated in stone formation when co-ingested with cyanuric acid, but will cause urinary stones in infants when large amounts of melamine alone are ingested.

Melamine exposure assessment in children with nephrolithiasis

Sirs, We describe here the estimated melamine intake in 49 infant patients treated at the Linyi People's Hospital in Linyi, Shandong Province, China. Our aim is to draw attention to the fact that low levels of melamine exposure may also represent a health risk to young children. Between September 17 and 29, 2008, an ultrasonographic screening of infants was carried out at the Linyi People's Hospital. In all, 63 cases of nephrolithiasis and/or hydronephrosis were identified among the 3976 infants screened who had ingested melamine-tainted formula milk, and one case was identified among the 358 infants screened who had not ingested melamine-tainted formula. Melamine-tainted formula was defined as that formula known to be contaminated with melamine based on test results posted by China’s General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) [1]. In December 2008, we reinvestigated 49 stone-formers with a history of melamine ingestion who were among those screened in September 2008 and identified 36 cases of nephrolithiasis and 16 cases of hydronephrosis (Table 1). It was assumed—but not proven—that the hydronephrosis was due to the nephrolithiasis. Most of the patients were asymptomatic, and their prognosis was good based on the results of our reinvestigation in December. None of the patients presented with common risk factors for nephrolithiasis, such as hypercalciuria, prematurity and acidosis, or with a history of low birth weight, loop-diuretic exposure, hypercalcemia, hypervitaminoses D or hyperparathyroidism. Hematuria is an expected clinical sign of nephrolithiasis in 30–55% of cases [2], but we identified hematuria in only one of 19 patients (among the 49 reinvestigated) with unrecovered nephrolithiasis or hydronephrosis. This incidence did not differ from the number of hematuria cases identified among recovered patients (2/30). These findings are similar to those found in reports published in Beijing [3] and Taiwang [4] on the melamine scandal. We estimated the daily melamine intake in these 49 patients by multiplying formula intake by the highest reported melamine level in each of the products, as reported by AQSIQ. Seven families of the children provided samples of the different formulas that the patients had consumed. The melamine concentrations in these samples were far lower than those reported from AQSIQ. No cyanuric acid (melamine analog) was found in any of these samples. Both of these findings suggest that our estimation based on the reported values from AQSIQ may have been on the high side. It is also very possible that not all of the formula products consumed by the patients were contaminated. The estimated length of exposure to powered formula was 17 months (geometric mean). Thirty-five patients had ingested pure milk, yogurt, biscuits, candy or eggs in addition to the formula; another 14 had excessive exposure to melamine only from formula feeding. These 14 patients had never consumed other market-sourced protein-containing foods suspected to be tainted with melamine. As young infants are mostly fed breast milk or powered formula, we Pediatr Nephrol (2009) 24:2065–2067 DOI 10.1007/s00467-009-1225-7

Hot topic: Pathway confirmed for the transmission of melamine from feed to cow's milk

Eight lactating Holstein cows were randomly allotted to 2 groups in a trial to establish whether a pathway exists for the transmission of melamine from feed to milk. All cows received oat hay ad libitum and 15kg of concentrate pellets per cow daily. The concentrate pellets contained either melamine-contaminated corn gluten meal of Chinese origin (melamine treatment) or locally produced melamine-free corn gluten meal (control treatment). Cows in the melamine treatment ingested 17.1g of melamine per day. Cows were milked twice daily, and milk samples were taken once daily during the afternoon milking for melamine and milk component analyses. Melamine appeared in the milk within 8h after first ingestion of the melamine containing pellets. Melamine concentration reached a maximum of 15.7mg/kg within 56h after first ingestion, with an excretion efficiency of approximately 2%. Milk solids and milk urea nitrogen were not affected by treatment. The melamine concentration dropped rapidly after changing all cows back to the control pellets, but melamine only declined to undetectable levels in the milk more than 6 d (152h) after last ingestion of melamine. Results from the current trial are important to the feed and dairy industries because, until now, any melamine found in milk and milk products was attributed only to the deliberate external addition of melamine to these products, not to adulterated ingredients in animal feeds.