The excretion of oxalic acid in gouty patients.
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Biomedical subjects
Publications and source records attributed to E Marinello.
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The changes occurring in the fatty acid composition of the plasma lipids were studied in gout. The major changes consisted in an increase in oleic acid and a decrease in linoleic and arachidonic acids in most lipid fractions of plasma; linoleic acid is unchanged in plasma cholesteryl esters and in FFA while arachidonic acid does not vary only in FFA. These changes are not related either to diet or to the age of patients and are similar to those reported in atherosclerotic and diabetic patients, as well as those with cardiac ischemia. The variations observed are directly influenced by the ratio essential fatty acids/monoenoic acids and all factors affecting this ratio.
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Plasma levels of follicle-stimulating hormone, luteinizing hormone, testosterone, progesterone, 17 beta-estradiol, and cortisol were examined in normal subjects and gout patients under baseline conditions and after clomiphene stimulation. A significant decrease in follicle-stimulating hormone, luteinizing hormone, and 17 beta-estradiol was observed both in male and female gout patients; in the same patients, the plasma testosterone: 17 beta-estradiol ratio was found to be significantly higher than in control subjects. The changes observed suggest a possible role played by 17 beta-estradiol in the regulation of purine biosynthesis and uric acid metabolism.
A new method of purification of rat liver L-threonine deaminase has been developed, and the results obtained are compared with values obtained by other authors. Some properties of this enzyme (pH optimum, temperature optimum, thermal stability, specificity, etc.) have been examined and we found that the enzyme is inhibited by carbonate ions, that L-cysteine (a competitive inhibitor) is also an inactivator of the enzyme and that it is bound to the enzyme in a ratio of 0.25 mole of cysteine per mole of enzyme, supporting the hypothesis that the enzyme consists of 4 subunits.
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The paper describes the effects of castration on formate-14C incorporation into the acid-soluble purines and into the nucleic acids of skeletal muscles (ELD and G) and perineal muscle (LAM). 20% homogenates were prepared in 1 M HC10(4), centrifuged and the nucleic acid were extracted from the precipitate with 0.7 N PCA (15 min at 90 degrees C). The acid-soluble purines were precipitated with 1 M AgNO3 from the supernatant of the centrifuged homogenate, then extracted with 1 M HC1 and separated by ion exchange chromatography with a scalar gradient of HC1. In the LAM a significant decrease in the specific activity of the purine bases (A, -56%, P less than 0.01; G, -47%, P less than 0.05) and of the nucleic acid (-47%, P less than 0.01) was observed after castration, while no difference was observed in skeletal muscles.
With the present study, the effects of testosterone deficiency on the biosynthesis of purine nucleotides and nucleic acids in rat liver and kidney has been investigated. 20% homogenates were prepared in 1 N HCl04, centrifuged and the nucleic acid were extracted from the precipitate with 0.7 N PCA (15 min at 90 degrees C): the acid-soluble purines were precipitated with 1 M AgNO3 from the supernatant of the centrifuged homogenate, then extracted with 1 M HC1. An increase of the specific activity of the liver (A, +49%; G, +47%) and of the kidney (A, +54%; G, +34%) has been observed (P less than 0.05), while no variation of the specific activity of nucleic acids was evident after castration.
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Forty-seven patients with gout, 28 of whom had not previously been treated with allopurinol, and 25 normal subjects, were examined for 24-h urinary excretion of the most important adrenal steroid derivatives. Results were submitted to statistical analysis and several variables have been taken in consideration. The untreated patients showed significantly higher values of uricemia, urinary uric acid, triglycerides, slightly higher values of androsterone, 11-oxo-androsterone + 11-oxo-etiocholanolone, dehydroepiandrosterone, and slightly lower values of 11-hydroxyandrosterone and pregnanetriol, in comparison to normal subjects. The different hormonal pattern seems to discriminate between patients with gout and normal subjects.
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In order to evaluate if the aminoacid L-threonine and its isomer allothreonine are metabolized by a single protein or by two specific enzymatic proteins, in the rat liver, we have studied the behaviour of L-threonine aldolase activity and allothreonine aldolase activity in rats which are injected with nicotinamide (1 g/ Kg) or have received a special diet containing 91% of casein or that have been starved for several days. The L-threonine aldolase enhances its activity in all three cases, while the allothreonine aldolase does not show significative changes of activity. These different behaviours of the two enzymatic activities, support the hypothesis that in the rat liver two proteins are necessary for the metabolism of the L-threonine and its isomer allothreonine.
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The induction of L-threonine deaminase, following nicotinamide injection has been studied: the effect of fasting and of hyperproteic diet have been also taken in consideration. Maximal induction is observed after 5 days hyperproteic diet, and is additional only with nicotinamide treatment. Results are interpreted assuming a different hepatic content and behavior of multiple forms of the enzyme.
The degree, the mechanism, and the specificity of the inhibition of purified rat-liver L-serine dehydratase (EC 4.2.1.13) by L-cysteine and aminothiols have been investigated. All the aminothiols tested react with free pyridoxal-5'-phosphate (PLP); only L-cysteine reacts with PLP bound to the enzyme giving an absorption spectrum similar to that of the thiazolidinic ring formed in the chemical reaction. The reaction between L-cysteine and PLP bound to the enzyme has a particular behaviour, different from all the other aminothiols. A stereospecific interaction between L-cysteine and PLP bound to the enzyme, forming one of the two possible diastereoisomers, is postulated.
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