Biomedical subjects

P G Daniele

Publications and source records attributed to P G Daniele.

6 recordsLinked to original sources

PubMed2001

Characterization of ligand sites on natural sediment particles.

Organic and inorganic ligand sites on sediment particles were alkalimetrically titrated using a glass electrode as indicating device. Data obtained for suspensions containing known masses of sediment were used to calculate the concentration of surface ligand sites and their stability constants for complex formation with proton and copper(II) ion. The relationship between the concentration of ligand sites and the concentrations of metals (Cd, Cr, Cu, Fe, Mn, Pb, and Zn) and of C, N, and S was used to try to discriminate between the contributions of organic and inorganic components to the total ligand capacity of the sediment. The reliability of the chemical model deduced from potentiometric data was checked by comparing calculated values for aqueous copper(II) as a function of pH with values experimentally determined via atomic absorption spectrometry. The procedure proposed might contribute to the modeling of sediment-contaminant interaction, providing information on the nature of the ligands involved.

Journal Article↗

PubMed2000

Speciation and structure of copper(II) complexes with histidine-containing peptides in aqueous medium: a combined potentiometric and spectroscopic study.

The complex formation between copper(II) and some histidine-containing peptides has been investigated by means of potentiometric and spectroscopic measurements. Due to the interesting co-ordination mode towards copper(II), peptides with histidyl residue located in second position from the N-terminal amino group have been chosen. The stability constants evaluation has been performed by both pH-metric and ESR (room temperature) measurements; in this context a suitable computer program for the calculation of both stability constant values and the ESR spectrum for each complex has been written. Visible spectrophotometric and circular dichroism spectra, together with the isotropic ESR parameters, were used in order to propose a structure for each complex having a significant percentage of formation in solution.

Circular Dichroism↗

PubMed1991

Serum calcium oxalate saturation in patients on maintenance haemodialysis for primary hyperoxaluria or oxalosis-unrelated renal diseases.

1. The serum oxalate concentration rises in chronic renal failure and it is only partially eliminated by regular dialysis treatment. However, the recent literature is not conclusive on whether progressive oxalate retention and secondary oxalosis should be expected in patients on regular dialysis treatment. 2. To further investigate this, we have estimated the state of saturation with respect to calcium oxalate monohydrate in plasma ultrafiltrates from 28 patients on maintenance haemodialysis and eight healthy control subjects, matched for sex and age. Five patients had type I primary hyperoxaluria and histologically proven oxalosis, whereas 23 had oxalosis-unrelated renal diseases. Dialysis efficiency was quantified as the KdTd/V of urea. Samples were obtained from each patient before, immediately after and 48 h after a dialysis session. Fasting samples were obtained from the control subjects. Oxalate was determined in both plasma ultrafiltrates and the whole dialysate by ion-exchange chromatography, after a non-delayed and [14C]oxalate-recovery-controlled procedure. The state of saturation with calcium oxalate monohydrate was estimated by means of a computer system which solved the interactions among 45 complex species. 3. The fasting plasma oxalate concentration (means +/- SD) in ultrafiltrates from healthy subjects was 3.8 +/- 1.5 (range 1.4-5.8) mumol/l, and the state of saturation with calcium oxalate monohydrate was 0.096 +/- 0.04.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1985

Urine saturation with calcium salts in normal subjects and idiopathic calcium stone-formers estimated by an improved computer model system.

The state of saturation of urine with calcium salts has been estimated by means of a computer model system whose accuracy has been improved by the use of stability constants of 31 complexes which were re-determined at 37 degrees C and at the actual ionic strength of urine. The experimental determination of the concentration solubility products of calcium oxalate monohydrate (CaOx) and of calcium hydrogen phosphate dihydrate (bsh) allows an expression of the saturation degree as free concentration product ratio beta CaOx and beta bsh. Morning urine samples from 50 healthy controls and 50 idiopathic calcium stone-formers and 24 h urines from 40 normal subjects and 192 stone-formers, taking normal diet were investigated by this technique. From our results urine supersaturation with calcium oxalate salts seems to play an important role in calcium stone disease. Hypercalciuria and hyperoxaluria seem to be the main pathological features in this regard. The data concerning beta bsh values have not confirmed previous reports in which this parameter was found to be increased in stone-formers.

Calcium↗

PubMed1983

Critical evaluation of various forms of therapy for idiopathic calcium stone disease.

The results are presented of the dietary management, alone or in association with thiazides and/or allopurinol, evaluated in 143 idiopathic calcium stone formers after a mean follow-up of 18 months. Diet alone proved to be effective in the prevention of stone relapses. The addition of thiazide and/or allopurinol provided mild improvements of urine environment but seemed to give no further clinical benefits irrespective of underlying metabolic abnormalities.

Allopurinol↗

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↗