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S Leoni

Publications and source records attributed to S Leoni.

At least 73 records · Page 4Linked to original sources
PubMed1986

Regulation of acyl CoA: cholesterol acyl transferase (ACAT) activity by mevalonate and cholesterol in isolated rat hepatocytes during perinatal development.

Acyl CoA: cholesterol acyl transferase (ACAT) activity presents marked oscillations and differential sensitivity to the "in vitro" stimulation of the kinase-phosphatase modulatory system in the perinatal rat liver. The regulation of this enzyme activity by some modulators generally active in adulthood, such as cholesterol, lipoproteins and mevalonate, has been studied in hepatocytes isolated at different developmental stages. A lack of effect of mevalonate and a positive effort of lipoprotein cholesterol have been observed at the fetal and neonatal stages. A differential prevalence is suggested of one of the two modulatory mechanisms (phosphorylation-dephosphorylation system, or substrate effect) at each developmental stage.

Age Factors↗
PubMed1985

Hormonal control of cholesterogenesis and related enzymes in isolated rat hepatocytes during pre- and postnatal development.

The effect of glucagon and insulin on the incorporation of 1-14C-acetate into cholesterol and fatty acids and on the enzymes involved in the first steps of cholesterol synthesis (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, 3-hydroxy-3-methyl-glutaryl-coenzyme A synthase, and acetoacetyl-coenzyme A thiolase) was investigated. Isolated rat hepatocytes at different stages of fetal and postnatal development were employed. Data obtained show the appearance of hormonal control on the 18th day of fetal life, indicating the same pattern, as regards acetate incorporation and HMGCoA reductase prepared and assayed in the presence of NaF. On the contrary, HMGCoA reductase, prepared without NaF, HMGCoA synthase, and acetoacetyl CoA thiolase, does not appear to respond to hormonal stimulation. In the perinatal period, the hormonal effect is no longer detectable, probably because of a hormone resistance of this metabolic pathway.

Acetates↗
PubMed1985

Short term regulation of acyl CoA: cholesterol acyl transferase (ACAT) activity in the regenerating and perinatal liver.

Acyl coenzyme A : cholesterol acyltransferase (ACAT), the enzyme catalyzing the hepatic cholesterol esterification, could be involved in the modified availability of cholesterol detectable in proliferating systems. While no significant variations are detectable in the regenerating liver, the modified ACAT activity during liver development and its differential sensitivity to the in vitro stimulation of modulatory systems suggest an involvement of the enzyme in this proliferating process.

Animals↗
PubMed1984

[Electrophoresis of liver proteins from the rat under various physiological conditions].

The total protein and glycoprotein in electrophoretic patterns of rat liver endoplasmic reticulum we studied in peculiar physiological conditions as perinatal development, pregnancy and liver rigeneration. Previous work in these experimental systems showed a changed microsome lipid composition and modified activities of some ER membrane bound enzymes. The microsomes obtained from foetal and neonatal liver show a modified electrophoretic pattern of both total protein and glycoprotein of low weight with respect to the adult animal. As to the microsomes of 8h and 12h regenerating liver modifications are observed only in the pattern of glycoprotein in the molecular weight range.

Animals↗
PubMed1984

Cholesterol synthesis and related enzymes in rat liver during pregnancy.

During pregnancy the synthesis of cholesterol and the activity of 3-hydroxy 3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase fell markedly before parturition; HMGCoA synthase activity was low during pregnancy and fell again immediately before delivery while acetoacetyl-CoA-thiolase was always low and constant.

Acetyl-CoA C-Acetyltransferase↗
PubMed1984

Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and cholesterol synthesis and esterification during the first cell cycle of liver regeneration.

The regenerating rat liver provides a unique in vivo synchronized system for study of the interrelationships between mevalonate and sterol metabolism during the cell cycle. The regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, cholesterol synthesis and acyl coenzyme A: cholesterol acyltransferase during the first cell cycle was investigated. At 8 h postoperative and prior to onset of DNA synthesis or S phase, cholesterol synthesis was depressed in the regenerating liver relative to that in sham-operated controls. This suppression was observed whether assayed in vitro with liver homogenates utilizing radiolabeled acetate, mevalonate or water or in vivo with tritium water. In contrast, at this time point, 3-hydroxy-3-methylglutaryl-CoA reductase activity was increased in microsomes prepared both in the presence and absence of NaF. By 24 h, well into S phase and approaching mitosis, reductase activity and cholesterol synthesis both approached levels observed in the sham-operated control animals. There were no detectable changes in acyl-CoA: cholesterol acyltransferase activity at any time point. Thus, at the 8 h time point, the regulation of the three processes appeared uncoupled. The increased levels of in vitro expressed 3-hydroxy-3-methylglutaryl-CoA reductase activity compared with the decrease in the rate of both cholesterol and squalene biosynthesis suggested diversion of mevalonate into products other than squalene or sterols. We propose that this may reflect the needs of the cell for a nonsterol metabolite of mevalonate necessary for entry of cells into S phase.

Animals↗
PubMed1984

Cholesterogenesis and related enzymes in isolated rat hepatocytes during pre- and postnatal life.

Cholesterogenesis pathway during pre- and postnatal development was studied in isolated rat hepatocytes. No modified activity of cytosol acetoacetyl coenzyme A (CoA), thiolase, or 3-hydroxy-3-methylglutaryl CoA (HMGCoA) synthase was detectable at the different stages examined. Minimal levels of 1(14)C-acetate incorporation into cholesterol and HMGCoA reductase activity were present at 16 days of fetal development in newborn and suckling rats, whereas both parameters increased rapidly before birth. The pattern of NaF nonsuppressible reductase activity showed a different activation state of the enzyme, suggesting the appearance of a modulation state, probably related to the development of some short-term regulatory mechanisms.

Acetates↗
PubMed1984

Os penis.

The presence of os penis in man is very rare. To date only 11 cases have been published. A close study of these cases shows their extreme heterogeneity. We think that the os penis should be considered as a heterotopic bone structure similar to that found in the animal world. To confirm this we present our personal case study.

Adult↗
PubMed1983

[Neutral protease activity in the rat liver during regeneration].

The aim of the present paper is to evidence whether a variation of activity of neutral proteases occurs during regeneration and neonatal growth in rat liver. Protease activity is assayed with a spectrophotometric method in total liver and hepatocyte homogenates using casein as substrate. Results show that the protease activity is Ca++-dependent; it is lower either in neonatal liver or in regenerating liver 4 hours after partial hepatectomy with respect to controls.

Animals↗
PubMed1983

[Lipid composition of rat liver microsomes under various experimental conditions].

Cholesterol and phospholipid content, and phospholipid composition (sphingomyelin, phosphatidylcholine, phosphatidylserine, phosphatidylinositol, phosphatidylethaolamine) were assayed in rat liver microsomes during regeneration, foetal development and pregnancy. Cholesterol was assayed using Liebermann-Buchard reagent; the phospholipid extract was separated by thin-layer chromatography. While in pregnancy no changes were observed, during foetal development and liver regeneration there was a significative decrease of cholesterol/phospholipid ratio, and of phosphatidylcholine content. Moreover, in developing liver microsomes, there is also a significative increase of sphingomyelin and phosphatidylserine + phosphatidylinositol.

Animals↗
PubMed1982

Effect of free fatty acids and cholesterol in vitro on liver plasma membrane-bound enzymes.

The effect of cholesterol and fatty acid treatment in vitro was tested on rat liver plasma membrane-bound enzymes and lipid fluidity. The observed alterations of membrane fluidity affect both (Na+-K+)-ATPase and Mg2+-ATPase activities but not 5'-nucleotidase; basal adenylate cyclase as well as its hormonal sensitivity were differentially affected by changes of membrane microenvironment.

5'-Nucleotidase↗