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Biomedical subjects

M Petrarulo

Publications and source records attributed to M Petrarulo.

49 records · Page 3Linked to original sources
PubMed1990

Primary oxalosis mimicking hyperparathyroidism diagnosed after long-term hemodialysis.

Primary oxalosis is a rare inborn error of oxalate metabolism. Most cases are discovered in children, but occasionally symptoms begin later in life. Since early deaths in the past were from renal failure, prolonged survival obtained with chronic dialysis allows oxalosis to develop. This paper presents a 38-year-old man with an atypical history of type-I primary hyperoxaluria, not diagnosed until after 5 years of dialysis. Bone biopsy was performed because the biochemical and radiologic features did not seem consistent with a putative diagnosis of secondary hyperparathyroidism. This case emphasizes the clinical heterogeneity of this disorder, and the need for its considerations in the spectrum of dialysis-related bone diseases. It also stresses that bone oxalosis may mimic hyperparathyroidism, especially radiologically. Differential diagnosis is therefore mandatory.

Adult↗
PubMed1990

Preventing ascorbate interference in ion-chromatographic determinations of urinary oxalate: four methods compared.

In an attempt to decrease ascorbate interference on the ion-chromatographic determination of urinary oxalate, we compared the effectiveness of four different methods for ascorbate elimination by analyzing a representative urine pool supplemented with successive ascorbate additions. Two of the methods--treatment with ferric ions or boric acid--have been described elsewhere; treatments with nitrites or ascorbate oxidase (EC 1.10.3.3) are investigated here as possible alternatives. Consideration of the main features, advantages, and drawbacks of the four procedures leads us to conclude that boric acid dilution is a good routine method and that pre-incubation with ascorbate oxidase reliably prevents ascorbate interference in assays of urinary oxalate.

Adult↗
PubMed1989

Derivatization and high-performance liquid chromatographic determination of urinary glycolic acid.

A high-performance liquid chromatographic method for the determination of urinary glycolic acid is proposed, based on pre-column derivatization with phenylhydrazine coupled with the enzymatic oxidation of glycolate to glyoxylate. The phenylhydrazone formed is separated by liquid chromatography and detected at 324 nm. The minimum detectable concentration of glycolate was 10.0 mumol/l. The recovery of glycolate added to urine averaged 96.1%. The day-to-day coefficients of variation calculated by analysis of two urine samples with normal and high glycolate contents were 4.6 and 7.5%, respectively. Results of analyses of urine samples from healthy persons, idiopathic calcium stone formers and Type I primary hyperoxaluria patients are reported.

Chromatography, High Pressure Liquid↗
PubMed1989

Effect of animal and vegetable protein intake on oxalate excretion in idiopathic calcium stone disease.

Oxalate excretion was measured in healthy subjects and idiopathic calcium stone-formers on dietary regimens which differed in the type and amount of protein allowed; 24-h urine collections were obtained from 41 practising vegetarians and 40 normal persons on a free, mixed, "mediterranean" diet. Twenty idiopathic calcium stone-formers were also studied while on two low calcium, low oxalate diets which differed in that animal protein was high in one and restricted in the other. Vegetarians had higher urinary oxalate levels than controls and although the calcium levels were markedly lower, urinary saturation with calcium/oxalate was significantly higher. This mild hypercalciuria was interpreted as being secondary to both a higher intake and increased fractional intestinal absorption of oxalate. Changing calcium stone-formers from a high to a low animal protein intake produced a significant decrease in calcium excretion but there was no variation in urinary oxalate. As a result, the decrease in calcium oxalate saturation was only marginal and not significant. It was concluded that dietary animal protein has a minimal effect on oxalate excretion. Mild hyperoxaluria of idiopathic calcium stone disease is likely to be intestinal in origin. Calcium stone-formers should be advised to avoid an excess of animal protein but the risks of a vegetable-rich diet should also be borne in mind.

Adult↗
PubMed1988

High-performance liquid chromatographic determination of glyoxylic acid in urine.

A high-performance liquid chromatographic (HPLC) method for the determination of urinary glyoxylic acid is proposed. The system is based on the precolumn derivatization of alpha-keto acids by means of phenylhydrazine, separation of the phenylhydrazone formed by HPLC and spectrophotometric detection at 324 nm. The method is precise and allows the determination of 0.5 mumol/l glyoxylate. The poor stability of glyoxylate under all conventional preservation conditions requires the analysis to be carried out as soon as possible after urine collection. Results of determinations on urine samples from healthy controls and from patients with idiopathic calcium stone disease and type I primary hyperoxaluria are reported.

Chromatography, High Pressure Liquid↗
PubMed1987

High-performance liquid chromatographic determination of glyoxylic acid and other carbonyl compounds in urine.

A high-performance liquid chromatographic method for the determination of carbonyl compounds, namely aldehydes, ketones and keto acids in urine, has been developed. Pre-column derivatization with 2,4-dinitrophenylhydrazine offers sufficient sensitivity for the determination of glyoxylic acid in urine with a detection limit of 0.5 mg/l. The separation is performed on a C18 10-micron column and with an acetonitrile-aqueous buffer mobile phase, which also allows the resolution of the syn and anti geometric isomers. Matrix effects, precision, accuracy, limits of detection and structural selectivity of the method are discussed.

Aldehydes↗
PubMedDate not supplied

Renal stones: from metabolic to physicochemical abnormalities. How useful are inhibitors?

Despite intensive studies in the last decades many aspects of nephrolithiasis still remain to be elucidated. Supersaturation with respect to lithogenic substances explains stones composed of cystine, uric acid, struvite, and calcium stones secondary to systemic diseases. In this subset there is a clear separation between patients and controls, and stone activity is well related to alterations in the physicochemistry of the urine environment. The understanding of the mechanisms of idiopathic calcium nephrolithiasis, on the other hand, is controversial, because we are still unable to establish clear-cut cause-effect relations between metabolic and physicochemical abnormalities and stone formation. Recent studies have been centered on the kidney, not only as the end organ of biochemical derangements due to systemic or environmental factors, but also as a complex laboratory where some events conduct to and others defend from lithogenesis. Many of these phenomena occur in the proximal tubule. Molecular biology has explained some types of hypercalciuria, which are due to genetic mutations altering tubular function, and similar results are expected for hypocitraturia and hyperoxaluria. The latter is conducive to stone formation through several mechanisms including supersaturation, oxidative stress on tubular cells, and interference with some natural inhibitors. The long list of inhibitors includes ionic and macromolecular moieties, some being produced within the nephron in response to lithogenic insults, and some affecting not only crystallization but also crystal cell adherence. Crystal trapping is believed to anticipate a renal stone. However, much has still to be clarified on their actual role in calcium nephrolithiasis, by what mechanisms they act, if patients and controls differ in the excretion and structure of some inhibitors, and whether differences are genetically determined.

Chemical Phenomena↗
PubMedDate not supplied

[LithoRisk: A software for calculating and visualising nephrolithiasis risk profiles].

BACKGROUND: The pathogenesis of nephrolithiasis, based on the anomalies of the urinary environment, demands metabolic and physicochemical assessment for the medical management of patients. Standard metabolic protocols include the measurement of pertinent urine chemistry values and the calculation of the extent of saturation in stone-forming salts. However, patients are often given fragmentary and hard-to-consult reports and so this weakens the strength of the therapeutic recommendations. This paper introduces LithoRisk, a dedicated software which graphically represents risk profiles of stone formation, including the extent of saturation. METHODS: LithoRisk uses the results of 24-h urine chemistry values widely available in hospital laboratories, i.e., sodium, potassium, calcium, magnesium, ammonia, phosphate, sulphate, citrate, oxalate, chloride, pH and urine volume. Uric acid and cystine are optional. The relative supersaturation (beta), estimated according to our own ab initio calculation, is given in a scale whereby beta=1 is saturation, beta < 1 under - and beta > 1 oversaturation. LithoRisk is available as a CD-ROM and can be loaded on Windows 95/98/Millenium/XP. Colour or laser printers are suitable for printed records. RESULTS: LithoRisk is easily loaded on any PC by following video instructions. Once the loading of the program is completed a grey icon LithoRisk appears on the Desktop. The program can be opened by clicking twice on the icon. The patients data page first appears on the screen and is followed by the evaluation page for the input of variables. This generates the graph representing the diagnostic lithorisk profile, which is drawn as a line connecting different values, according to a specific scale and related to an arbitrary normal point. Normal values are shown as green lines, whereas abnormal ones are red. The beta values for calcium oxalate and phosphate, uric acid and cystine are instantaneously calculated and reported on the graph. CONCLUSIONS: LithoRisk produces a complete, unique and easy to understand report that includes all relevant parameters, it therefore expresses the overall risk of stone formation. It requires the results of chemistry tests done on the same 24-h urine collection, and carried out using suitable preservatives. If the tests for unusual parameters, i.e. sulphate and ammonia, are unavailable, one can use default values with minimal alterations on beta calculation. In spite of being arbitrary, the normal thresholds values are based on widely accepted literature data. The risk profile recognises the most relevant abnormalities and enables the establishment of individual targets aimed at reducing the propensity towards stone formation.

Humans↗
PubMedDate not supplied

[Kinetics of oxalate in hemodialysis].

Regular dialysis treatment (RDT) does not obviate hyperoxalemia of chronic renal failure (CRF). However, there is emerging evidence suggesting that current dialysis prescription is not always associated with progressive oxalate accumulation. In view of the controversy still concerning this issue we have investigated on plasma profiles and dialysis kinetics of oxalate in patients on RDT. Oxalate was determined by ion chromatography on serum ultrafiltrates and on the whole dialysate in 23 stable patients on RDT for end-stage renal failure unrelated to primary hyperoxaluria. Nine patients were on traditional hemodialysis (HD) and 14 on soft hemodiafiltration (HDF). Plasma profiles showed that dialysis patients were virtually always hyperoxalemic. Dialysis reduced plasma oxalate by more than 60%. There was a post-dialysis oxalate rebound averaging 9.6% at 30 minutes from the end of dialysis. Oxalate dialyzer clearances were mildly higher on HDF than on HD, and were lower than both urea and creatinine clearances, irrespective of the dialysis technique. Distribution space of oxalate was 21.5 1, that is 37.3% of dry body weight, and was quite similar to estimates obtained in normal subjects and in patients with CRF by alternative isotope dilution methods. Oxalate appearance rate averaged 337 +/- 69 mumol/24 h and was not different from the daily oxalate excretion assessed in 40 healthy subjects. Oxalate appearance was significantly related to urea generation and protein catabolic rates. From our results we conclude that, unless metabolic generation of oxalate is increased, current dialysis programs should prevent progressive oxalate accumulation in the majority of the patients.

Female↗
PubMedDate not supplied

[Mineral balance during hemodialysis and hemodiafiltration].

Keeping calcium (Ca) balance in equilibrium is one of the main goals in dialysis patients, and the dialysis schedule by itself can affect mineral metabolism. The aim of this paper is to evaluate Ca and magnesium (Mg) balances on different Quf in patients on RDT. Twenty-one patients [7 on hemodialysis (HD), 14 on hemodiafiltration (HDF)] were studied. Ca and Mg balances were assessed by measuring Ca and Mg in whole dialysis fluid. One patients on HDF was observed for three dialysis sessions, on different Quf, and negative values were observed for Quf above 70 ml/min. Mg balance was always negative. We conclude that an accurate survey of Ca balance is mandatory in high-efficiency dialysis, when high fluxes may produce adverse effects on mineral metabolism.

Calcium↗
PubMedDate not supplied

Molecular analysis of the AGXT gene in Italian patients with primary hyperoxaluria type 1 (PH1).

Specimens were collected from 22 Italian patients with primary hyperoxaluria type 1 (PH1). Ten of them had already been analyzed by molecular biology. To clarify the molecular characteristics of the AGXT gene disease responsible for PH1, DNA samples were examined for known mutations by hybridisation of PCR products with Sequence Specific Oligonucleotides (PCR-SSO). We planned to identify new mutations of the AGXT gene by heteroduplex analysis followed by direct sequencing. We had already standardized a) the conditions for the amplification of the 11 exons of AGXT, b) the PCR-SSO technique and c) the heteroduplex analysis of amplified products. Preliminary results demonstrated that the AGXT mutations described in previous studies were found only in 40% of the examined Italian patients with PH1. The remaining 60% of mutations should be characterised in future studies.

Child↗
PubMedDate not supplied

Biochemical approach to diagnosis and differentiation of primary hyperoxalurias: an update.

The hyperoxaluria syndromes can be differentiated by the assessment of associated abnormalities in generation and urine excretion of metabolically related molecules. Based on the experience gained in our laboratory during the last decade, we have developed a comprehensive diagnostic work-up, which includes measurements of oxalate, glycolate and L-glycerate in plasma, urine and dialysis fluids, and an assay for AGT activity on liver biopsy. The availability of reliable assays for each of these parameters is indispensable for the recognition and differentiation of hyperoxalurias. Patients suspected to have abnormalities in oxalate metabolism are first screened by analysing spot urines and serum, and subsequently are subjected to more extensive studies using properly pre-treated blood samples and 24-hour urine collection. AGT activity, in the case of PH1, is assayed on few milligrams liver specimen by using a sensitive chromatographic procedure. Pertinent biochemistries will also assist in the long-term medical follow-up of these patients and in view of the choice of renal replacement or transplantation strategies.

Diagnosis, Differential↗