Maria Pizzichini

Influence of amalgam fillings on Hg levels and total antioxidant activity in plasma of healthy donors.

In order to evaluate the influence of specific factors on mercury (P-Hg) levels and antioxidant power (P-FRAP) in human plasma, 26 healthy donors were examined by a dentist, their plasma analyzed for Hg by atomic absorption spectrometry and for total antioxidant activity by FRAP method. Hg plasma concentration was found to be correlated with the number of amalgam fillings, suggesting that Hg released from fillings is a source of Hg in non-occupational exposed subjects. P-FRAP correlated negatively with P-Hg suggesting a pro-oxidant role of the Hg released from amalgam fillings. Though age by itself was not significantly correlated with P-FRAP, when considered together with P-Hg in multivariate analysis, it was found to be a major related cofactor. Multivariate analysis showed no influence of fish consumption or cigarette smoking on P-FRAP.

Effects of testosterone on cholesterol levels and fatty acid composition in the rat.

The effects of testosterone treatment on cholesterol levels and its fatty acid components were studied in adult rats. Cholesterol levels increased both in the liver and in the serum of castrated rats. Androgen administration restored the normal values only in the serum. A general decrease in unsaturated and essential fatty acids in cholesterol esters was evident after testosterone administration. In the liver, only the C16:O/C16:1 ratio clearly increased after testosterone administration, which inhibited the delta 9 unsaturation of palmitic acid, but not of stearic acid. In the serum the C16:O/C16:1, C18:O/C18:1, and C18:2/C2O:4 ratios decreased after castration and were restored by testosterone. The results indicate a clear inhibition of delta 9 unsaturation of palmitic and stearic acids, of delta 5 unsaturation and elongation in organs other than the liver. No effect was evident on delta 6 unsaturation. This suggests that fatty acid unsaturations are regulated differently by testosterone in different tissues. For delta 9 unsaturation in the liver, the effect also seems to be substrate-dependent.

Determination and separation of allantoin, uric acid, hypoxanthine, and xanthine by capillary zone electrophoresis.

Hypoxanthine, xanthine, uric acid and allantoin are the main products of purine nucleotide catabolism and they are formed through the sequence: nucleotide→ hypoxanthine → xanthine→ uric acid→ allantoin. Under normal conditions, they represent the balance between synthesis and breakdown of nucleotides. Their levels change, for example, under oxidizing conditions and may be useful for quantifying oxidant generation in human extracts. Uric acid is oxidized to allantoin by variuos reactive oxygen species and is thought to act as an antioxidant in human bodily fluids. Allantoin concentrations may therefore indicate free radical damage in vivo.

Effect of testosterone on purine metabolism and morphometric parameters in the rat liver

The effect of testosterone on the morphology and biochemistry of adult castrated rat liver is described. Castration decreases mean weight and volume of hepatocytes, volume and surface area of sinusoidal lumen, and apparently increases cell number per g of tissue. These variations indicate cell distress. Testosterone administration restored sinusoidal volume and surface area, indicating a true hyperplastic response and improved trophic conditions. Acid soluble nucleotides, RNA and DNA content were lower after castration, being partially restored after testosterone treatment. This restoration, however, was only statistically significant for total guanylate. We concluded that testosterone deficiency and administration exerts a specific effect on the liver in terms of morphological and biochemical changes. Purine nucleotide metabolism is probably the first target of hormonal action, since its changes are the most significant and useful to explain all the other observations.

THE INFLUENCE OF TESTOSTERONE ON PURINE NUCLEOTIDE METABOLISM IN RAT LIVER

Purine nucleotide metabolism was studied in rat liver by following the incorporation of 14C-formate into soluble nucleotides, uric acid and RNA ribonucleotides. After castration, GMP formation was less than that of AMP, and purine nucleotide catabolism and RNA synthesis decreased. Testosterone administration did not modify GMP or AMP synthesis, but restored purine nucleotide catabolism and RNA production to normal values. These results demonstrate the influence of testosterone on purine nucleotide metabolism in a non-reproductive organ.

Separation and determination of liver uric acid and allantoin.

We previously described the only satisfactory procedure yet achieved for separating uric acid and allantoin from rat liver. The procedure was based on trichloroacetic acid (TCA) extraction, acid hydrolysis, treatment with Hg-acetate, and cation- and anion-exchange chromatography. After separation, allantoin was quantified by a colorimetric method, and uric acid enzymatically using uricase. Since this procedure is too time-consuming, we propose an improved version which avoids the need for anion-exchange chromatography and the complex assay of catabolic compounds. The new method consists of a very fast and simple HPLC separation and direct determination of uric acid and allantoin at 220 nm. The method can be used for fresh tissue or after treatment of the tissue with labeled precursor.

Relation between erythropoietin and vitamin B12 in normal and anemic pregnant women.

In this cross-sectional study of 178 pregnant women between the 7th and 42nd week of pregnancy, we analyzed correlations between erythropoietin (EPO) and vitamin B12 (B12) in different stages of pregnancy and in relation to hemoglobin (Hb) levels. Patients with hypertension, fetal growth retardation and severe systemic diseases were excluded. EPO (by ELISA), B12 (by RIA) and Hb were assayed in the same blood sample taken on admission. On the basis of weeks of pregnancy, EPO levels and B12 levels, the 178 subjects were found to fall into two clusters, before and after the 27th week of gestation. The correlation coefficient between EPO and B12 was highly significant in the first group but not in the second (R = -0.33; p < 0.01). When the patients were divided on the basis of Hb levels (< or = or > 11 g/dl), a significant correlation was found only in the 88 patients with Hb > 11 g/dl (R = -0.44; p < 0.001) and not in the 72 anemic subjects. Moreover, in the former group the correlation between EPO and B12 was high before and after the 27th week, unlike in the latter group for which no significant correlation was found. These results suggest that EPO and B12 act together to establish normal erythropoiesis in pregnancy.

Nitrogen metabolism during liver regeneration.

Nitrogen metabolism was investigated in regenerating liver-bearing rats through the following parameters: (1) liver aminoacid content, (2) plasma and urinary urea and creatinine, (3) plasma and urinary oxypurines, uric acid and allantoin. Two groups of aminoacids were considered: (1) the essential aminoacids (phenylalanine, tyrosine, isoleucine, lysine, leucine, valine, arginine, histidine and methionine); (2) the non-essential aminoacids (aspartic acid, asparagine, glutamic acid, glutamine, alanine, glycine, serine, threonine and proline). Some of the first group tended to decrease, and those of the second group to increase, immediately after partial hepatectomy. Few ketogenic aminoacids are probably oxidized to provide energy. The flux of aminoacids for gluconeogenesis is minutely controlled, therefore, those of the second group being spared at first and set aside for protein synthesis, which increases on the second and third days after partial hepatectomy. Plasma and urinary urea, oxypurines, uric acid and allantoin did not show any significant variations after partial hepatectomy. The conclusion emerging from the present research is that, although variations in aminoacid composition and metabolism and in purine nucleotide metabolism have been demonstrated to occur in the regenerating liver, the overall nitrogen catabolism, as reflected by the principal end products, does not undergo substantial variations. The remaining liver is able to fulfil this function.

EFFECT OF ESTRADIOL ON PHOSPHOLIPID LIPOPROTEIN LEVELS AND FATTY ACID COMPOSITION IN THE RAT

Phospholipid content and fatty acid composition in the different serum lipoproteins showed specific variations after castration and estradiol administration. Only the levels of phospholipids in HDL, the principal lipoprotein carrying phospholipids, increased after castration and were further enhanced by estradiol treatment, especially at low doses. Fatty acid composition showed many variations and an irregular pattern. The EFA/NEFA, EFA/ME and SAT/ME ratios were calculated. EFA/ME increased in VLDL after both doses of estradiol, while EFA/NEFA and EFA/ME of LDL enhanced at the low dose and decreased at the high one in a dose-dependent manner. HDL showed higher EFA/ME and SAT/ME ratios after castration and lower values of all ratios after both doses of estradiol. The correlation with diseases more frequent in men is discussed.

The behavior of free purine nucleotides in lymphocytes infected with HIV-1 virus

The purine nucleotide content was examined in various cells before and after HIV-1 virus infection: healthy peripheral blood lymphocytes (PBL) and cultured PBL after infection; the PBL of asymptomatic, ARC and AIDS patients. In all cases, changes in purine nucleotide concentrations were observed. The pattern of purine nucleosides and nucleobases was also evaluated by HPLC in PBL of controls and patients. The analysis was integrated by following the incorporation of a labelled precursor ([14C]formate) into purine nucleotides, which was investigated as an indication of the rate of purine metabolism in these cells. Many interesting variations in the catabolic and of anabolic pathways were observed, demonstrating that the viral penetration affects purine nucleotide metabolism. These results suggest interesting perspectives in AIDS research.