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R Paroni

Publications and source records attributed to R Paroni.

69 records · Page 4Linked to original sources
PubMed1988

Pre-column derivatization of amino acids with N,N-diethyl-2,4-dinitro-5-fluoroaniline and reversed-phase liquid chromatographic separation.

A new method for the separation and quantification of primary and secondary amino acids by reversed-phase high-performance liquid chromatography and spectrophotometric detection is described. The use of the novel derivatizing reagent N,N-diethyl-2,4-dinitro-5-fluoroaniline yields derivatives that are more stable to light and heat in solution than the traditional ones. A simple gradient between acidic acetate buffer and acetonitrile allows the complete separation of 21 amino acids in 80 min at room temperature. The good reproducibility of peak areas and retention times allows the application of this simple and low-priced method to the determination of amino acids in the range 50-500 pmol per residue.

Amino Acids↗
PubMed1988

Modulation of HMG-CoA reductase activity by pantetheine/pantethine.

The ability of pantetheine/pantethine to modulate the activity of HMG-CoA reductase (EC 1.1.1.34) was determined in vitro with rat liver microsomes. The decay of the activity was obtained with pantethine in the 10(-5)-10(-4) M range, whereas stimulation by pantetheine occurred at 10(-3)-10(-2) M, as previously reported for GSSG and GSH, respectively. Inhibition of HMG-CoA by pantethine in isolated liver cells was also investigated by measuring the enzyme activity in microsomes isolated from hepatocytes incubated without or with 1 mM pantethine under conditions previously shown by us to induce inhibition of cholesterol synthesis from acetate. The enzyme amount was not modified by pantethine, but in cells treated with the disulphide, the relative amounts of the thiolic active forms of the enzyme, both phosphorylated and dephosphorylated, were decreased to about half compared to controls.

Animals↗
PubMed1987

Pantethine inhibits cholesterol and fatty acid syntheses and stimulates carbon dioxide formation in isolated rat hepatocytes.

The effects of pantethine on cholesterol and fatty acid metabolism were investigated in isolated rat hepatocytes. Preincubation of the cells with pantethine induced a concentration-dependent decrease of the radioactivity incorporated into carbon dioxide and lipids in incubations with [2-14C]acetate. When pantethine and the labeled substrate were simultaneously added to the cell suspension, there was an enhancement of carbon dioxide radioactivity at short incubation time (5 min) whereas, at longer incubation time, values were comparable to those of controls; lipid radioactivity, instead, was dramatically reduced by pantethine even at short incubation time and decreased further during the incubation, being 23% of that of controls at 60 min. Analysis of the incubation medium showed that pantethine induced a concentration- and time-dependent release of acetate into the medium. Results of the effect of the acetate concentration on the incorporation of [2-14C]acetate radioactivity into CO2 and lipids in control hepatocytes allowed the conclusion that the above-described modifications induced by pantethine are only partially attributable to the dilution of the labeled substrate, and that catabolism of acetate to carbon dioxide is stimulated by the disulphide pantethine, whereas cholesterol and fatty acid syntheses are inhibited.

Animals↗
PubMed1986

Effects of pantethine on cholesterol synthesis from mevalonate in isolated rat hepatocytes.

Results presented here show that when isolated rat hepatocytes are incubated with increasing concentrations of [2-14C]mevalonolactone, incorporation of the substrate into cholesterol is progressively reduced. Correspondingly, an increase of the incorporation of the substrate into precursors of cholesterol (methyl sterols and squalene) occurs. These effects and the observed inhibition of HMGCoA reductase at high mevalonolactone concentration (0.5 mM) are in agreement with those shown by others in cultured hepatocytes. Since pantethine was reported to affect cholesterol biosynthesis from mevalonate in cultured fibroblasts, effects of its addition to hepatocyte incubations at low and high mevalonolactone concentration were studied. Neither the amount of radioactivity incorporated into cholesterol and in its sterol precursors nor sterol levels were modified by pantethine when a mevalonolactone concentration (0.01 mM) that did not alter the levels of intermediates of cholesterol synthesis was used. Pantethine was shown instead to potentiate the decrease of mevalonate incorporation into cholesterol induced by high concentrations of mevalonolactone (0.5 mM). Decrease of 3-hydroxy-3-methylglutaryl CoA reductase activity induced by 1 mM pantethine was twice that caused by mevalonolactone alone. These results may explain the fact that both in laboratory animals and in humans pantethine administration is effective in reducing cholesterol plasma levels in hyperlipidemic conditions.

Animals↗
PubMed1985

Evidence for a different metabolic behaviour of cytidine diphosphate choline after oral and intravenous administration to rats.

Radioactivity plasma decay was studied in rats after intravenous and oral administration of cytidine diphosphate [methyl-14C]choline at doses of 25 and 300 mg/kg. The kinetics fitted well with a two compartment open model and showed a long lasting elimination phase with a half-life ranging from 2.0 to 2.6 days for the two doses and the two administration routes. Absorption of cytidine diphosphate choline radioactivity was complete after oral treatment with the low dose and accounted for 94.5% of the dose when 300 mg/kg of cytidine diphosphate [methyl-14C]choline were administered. However the distribution of radioactivity in tissues, urine and expired air suggest metabolic differences, at least from a quantitative point of view, between the oral and intravenous treatments. In particular, the higher excretion of radioactivity associated with trimethylamine in urine found when cytidine diphosphate [methyl-14C]choline was given orally, suggest that the compound may be metabolized, at least in part, previous to its gastrointestinal absorption.

Administration, Oral↗
PubMedDate not supplied

Efficient production of the cyclosporin metabolite AM1 by rabbit hepatic enzymes.

We describe here conditions for the in vitro preparation of the main metabolite of cyclosporin A, namely AM1, with rabbit liver enzymes. The compound was purified and was identified by comparison with the metabolite isolated from urine of rats treated with [3H]CsA and by its Mass-Spectrometry Fast Ion Bombardment (MS-FIB) and 1HNMR spectra. The procedure is simple and with the enzyme fraction derived from one rabbit liver 3-4 mg of the pure metabolite can be obtained.

Animals↗
PubMedDate not supplied

No documentable role for xanthine oxidase in the pathogenesis of hepatic in vivo ischaemia/reperfusion injury.

An investigation was made into the possible involvement of the enzyme xanthine oxidase (XO) (EC 1.1.3.22), both reversible (XOrev) and irreversible (XOirr), in damage observed after short-term in vivo hepatic ischaemia/reperfusion (60 or 120 min I and 15 min R) in fasted rats with: (i) a physiological content of XO (25%); and (ii) higher XO percentage (45%). In the latter the hepatic XO physiological percentage was increased by diethylmaleate treatment (300 mg kg-1) that depleted the cytosolic glutathione (GSH) to 14% of the controls. It was shown that, in animals with physiological content of XO, 60 and 120 min of hepatic ischaemia followed by 15 min reperfusion results in decreased GSH levels, and significantly increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) serum levels, without any modification of either the percentages of XO (XOirr and XOrev) or the hepatic thiobarbituric acid reactive substances (TBARS). Sixty minutes of ischaemia/reperfusion in rats with the higher XO level and lower hepatic GSH content led to further conversion of XDH to XOrev, with no increase in XOirr. In addition, the ALT and AST serum levels in these animals rose to the same extent as in normal rats after 120 min ischaemia and 15 min reperfusion, this extent being observed to be associated with a moderate increase in thiobarbituric acid reactive substances (TBARS). However, the administration of allopurinol, at a dose of 50 mg kg-1, which almost completely inhibits XO activity, did not lead to any decrease in liver damage or TBARS.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMedDate not supplied

Development and characterization of pituitary GH3 cell clones stably transfected with a human proinsulin cDNA.

Successful beta-cell replacement therapy in insulin-dependent (type I) diabetes is hindered by the scarcity of human donor tissue and by the recurrence of autoimmune destruction of transplanted beta cells. Availability of non-beta cells, capable of releasing insulin and escaping autoimmune recognition, would therefore be important for diabetes cell therapy. We developed rat pituitary GH3 cells stably transfected with a furin-cleavable human proinsulin cDNA linked to the rat PRL promoter. Two clones (InsGH3/clone 1 and 7) were characterized in vitro with regard to basal and stimulated insulin release and proinsulin transgene expression. Mature insulin secretion was obtained in both clones, accounting for about 40% of total released (pro)insulin-like products. Immunocytochemistry of InsGH3 cells showed a cytoplasmic granular insulin staining that colocalized with secretogranin II (SGII) immunoreactivity. InsGH3 cells/clone 7 contained and released in vitro significantly more insulin than clone 1. Secretagogue-stimulated insulin secretion was observed in both InsGH3 clones either under static or dynamic conditions, indicating that insulin was targeted also to the regulated secretory pathway. Proinsulin mRNA levels were elevated in InsGH3 cells, being significantly higher than in betaTC3 cells. Moreover, proinsulin gene expression increased in response to various stimuli, thereby showing the regulation of the transfected gene at the transcriptional level. In conclusion, these data point to InsGH3 cells as a potential beta-cell surrogate even though additional engineering is required to instruct them to release insulin in response to physiologic stimulations.

Animals↗
PubMedDate not supplied

Abdominal aortic coarctation inducing aortic occlusion and renovascular hypertension.

Abdominal aortic coarctation is a rare, non-atherosclerotic disease. It is a functionally significant at an early age when associated with aortic branch stenosis and renovascular hypertension. The pathogenesis of aortic constrictive lesions remains unknown, but may be related to developmental error or aortic growth arrest and various hypotheses have been reported. When the renal arteries are involved by the coarctation, severe hypertension is common at an early age and in untreated patients, life-threatening complications commonly occur. Patients who reach the age of 40 years generally have the coarctation below the renal arteries but even when the renal arteries are not involved by the coarctation, renovascular disease may still occur due to secondary atherosclerosis. Aortic thrombosis secondary to abdominal aortic coarctation with renovascular disease and lower limb ischemia, occurring in a 63-year old woman, is reported.

Aorta, Abdominal↗