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Biomedical subjects

C Guarnieri

Publications and source records attributed to C Guarnieri.

At least 109 records · Page 6Linked to original sources
PubMed1986

Heart ornithine decarboxylase from control and isoproterenol-treated rats: kinetic properties, multiple forms and subcellular distribution.

Heart ornithine decarboxylase (ODC) from isoproterenol treated rats was compared to heart ODC from control rats. Isoproterenol administration did not significantly change Km for ornithine, but it induced a marked increase of Vmax, X Km for pyridoxal phosphate (PLP) was somewhat reduced. Both Kornm and Vmax were a function of the dithiothreitol (DTT) concentration, in a similar way for control and stimulated enzyme. Two ODC forms were detected by ion exchange chromatography in both control and isoproterenol treated hearts. In control heart, ODC specific activity was high in cytosol and nucleoli. Isoproterenol administration induced a remarkable increase of the cytosolic enzyme only.

Animals↗
PubMed1986

Effect of isoproterenol administration of rat heart glutathione status.

The intraperitoneal administration of 3, 10 and 80 mg/Kg isoproterenol produced in the cardiac muscle a dose dependent increase of GSH content and a slight elevation of GSSG content. In addition, the treatment with the catecholamine at the doses of 3 and 10 mg/Kg produced a slight decrease of the mixed glutathione disulfides level, whilst at the dose of 80 mg/Kg, this effect was more pronounced. These changes were not accompanied by modifications of the activities of the enzymes glutathione peroxidase, glutathione reductase and glutathione S-transferase.

Animals↗
PubMed1985

Inhibition of rat heart ornithine decarboxylase by basic polypeptides.

Purified and partially purified ornithine decarboxylase (ODC) from rat heart was inhibited by basic polypeptides in vitro. Poly-L-arginine, the most effective, was inhibitory at a concentration as low as 0.1 microgram/ml; protamine and histone clearly inhibited ODC at concentrations higher than 2 micrograms/ml, but poly-L-lysine was less effective. The ability to inhibit ODC appeared to correlate with the arginine-residue content of basic polypeptides. The inhibition effect could be decreased by increasing substrate concentration and ionic strength.

Animals↗
PubMed1985

Involvement of superoxide radicals on adrenochrome formation stimulated by arachidonic acid in bovine heart sarcolemmal vesicles.

Highly purified sarcolemmal membranes prepared from bovine heart muscle produced superoxide radicals, especially when incubated with NADPH or NADH, as revealed by the oxidation of adrenaline to adrenochrome. The reaction was inhibited by superoxide dismutase or by heat denaturation of the sarcolemmal vesicles. Less evident was the inhibitory effect shown by catalase, while mannitol, deferoxamine or dicumarol were uneffective. The formation of adrenochrome was an oxygen-dependent reaction with a Km for adrenaline of 8-10 microM. Moreover, the reaction was inhibited by preincubating the sarcolemmal membranes with propranolol, while the alpha-antagonist phentolamine was without effect. Adrenaline oxidation was unaffected by the presence of exogenous linolenic acid or methylarachidonic acid, while arachidonic acid, with a Km for this reaction of 175 microM, showed a marked stimulatory effect. This activation was suppressed by superoxide dismutase, catalase and NaCN, while mannitol was without effect. Moreover, the reaction was blocked by the cyclooxygenase inhibitor indomethacin, differently from the lipooxygenase inhibitor nordihydroguaiaretic acid. Also, the incubation of the sarcolemmal vesicles with phospholipase A2 and calcium produced a stimulation of adrenochrome formation which was partially suppressed by albumin. In the experiments using arachidonic acid or phospholipase A2, the addition of indomethacin blocked the adrenaline oxidation. These results indicate that arachidonic acid accentuated the heart sarcolemmal adrenochrome formation presumably by participating in the cyclooxygenase reaction.

Adrenochrome↗
PubMed1985

Changes in the cardiac glutathione status after ischemia and reperfusion.

In the isolated and perfused rabbit heart ischemia induced a rapid decline of contractility, associated with a reduction of the content of tissue GSH with no significant changes in GSSG. Reperfusion induced a small recovery of contractility, a substantial release of total glutathione and a further decrease in the content of tissue GSH with a significant increase of tissue GSSG. Glutathione reductase and glutathione peroxidase activities were not affected by ischemia and reperfusion. This study suggests a possible role for glutathione in the determination of functional damage induced by myocardial ischemia and reperfusion.

Animals↗
PubMed1985

Oxygen radicals and tissue damage in heart hypertrophy.

Cyanide-resistant respiration in heart homogenates supplemented with 1 mM NADH was greater in hypertrophied homogenates (60 days banding) with respect to control homogenates, particularly when the homogenates were incubated in 100% oxygen. The intermyofibrillar mitochondria from hypertrophied hearts produced more superoxide radicals than sub-sarcolemmal mitochondria, and both values were greater than in the unbanded group. H2O2 formation was more evident in the intact mitochondria prepared from hypertrophied hearts than in those of the control hearts. Moreover, the perfusion of isolated hearts in anoxic and reoxygenated conditions caused a greater lipoperoxidative and functional damage at the mitochondrial level in hypertrophied hearts than in the control hearts. These results, correlate with the reduction in mitochondrial function found in the overloaded hearts, suggest an involvement of the reactive species of oxygen in the formation of cardiac damage induced by prolonged aortic banding.

Adenosine Diphosphate↗
PubMed1985

Oxygen-mediated myocardial damage during ischaemia and reperfusion: role of the cellular defences against oxygen toxicity.

The possibility that myocardial ischaemia alters the defence mechanisms against oxygen toxicity has been investigated. Ischaemia was induced in isolated, perfused rabbit hearts by reducing coronary flow from 25 ml/min to 1 ml/min for 90 min. Two different degrees of ischaemic damage have been achieved using either spontaneously beating or electrically stimulated hearts. The effects of post-ischaemic reperfusion were also followed for 30 min. Tissue activity of superoxide dismutase (SOD), glutathione peroxidase and reductase (GPD and GRD) have been determined together with tissue content of reduced and oxidized glutathione (GSH and GSSG) and of protein SH groups. The changes in myocardial ATP and CP content and release of CPK and of GSH and GSSG were also determined. Systolic and diastolic pressures were continuously monitored. In the spontaneously beating hearts ischaemia induced a reduction of tissue GSH and protein SH groups. On reperfusion there was a recovery of mechanical function, a transient release of GSH into the coronary effluent and an increase of tissue GSH. In the paced hearts, ischaemia resulted in 50% reduction of mitochondrial SOD activity together with a reduction of tissue GSH and protein SH groups. Reperfusion induced a massive release of CPK and of GSH and GSSG, a further reduction of tissue GSH concomitant with an increase of GSSG and no recovery of mechanical function. GPD and GRD activity were not affected by ischaemia and reperfusion. These data indicate that severe ischaemia induces a reduction of the protective mechanisms against oxygen toxicity.

Adenosine Triphosphate↗
PubMed1985

Effect of ischemia on heart submitochondrial superoxide production.

NADH-dependent formation of superoxide anions (O2-) by rabbit cardiac submitochondrial particles (SMP) was stimulated after exposure of the isolated heart to 90 min of ischemic perfusion. This effect was more evident in the rotenone-inhibited region of the respiratory electron chain in comparison to the antimycin-inhibited region. The kinetic study of the NADH-dependent reaction showed that at the level of the rotenone-inhibited region, ischemia reduced Km value for NADH, differently from the antimycin-inhibited region where the kinetic constants remain unchanged. No significant changes of the Vmax values were observed in both SMP-producing O2- sites. The ischemic perfusions also produced a reduction of mitochondrial function, particularly evident when glutamate as substrate was studied.

Animals↗
PubMed1984

Characterization of highly purified ornithine decarboxylase from rat heart.

A highly purified preparation of heart ornithine decarboxylase was obtained from isoproterenol-treated rats. The molecular and catalytic properties of the cardiac enzyme were investigated. The isoelectric point of the enzyme appeared to be 4.9, and the molecular weight was estimated to be 54000 by SDS-polyacrylamide gel electrophoresis. Under nondenaturing conditions, the molecular weight of the partially purified enzyme was 10000-110000 as determined by gel filtration, whereas a significantly lower (Mr approx. 70000) value was obtained for purified ornithine decarboxylase. Both Km for the substrate and Vmax were affected by the dithiothreitol concentration in the assay mixture. In particular, the Km for ornithine was found to be about 0.09 mM in the presence of 2.9 mM dithiothreitol and appeared to decrease at lower dithiothreitol concentrations. The Km for pyridoxal phosphate was about 0.09 microM; putrescine and lysine inhibited the enzyme competitively, with Ki values of 1.3 and 11.7 mM, respectively. The existence of two different forms of ornithine decarboxylase in cardiac tissue was indicated by DEAE-cellulose chromatography.

Animals↗
PubMed1984

Phosphorylation of rat heart ornithine decarboxylase by type-2 casein kinase.

Highly purified preparations of rat heart ornithine decarboxylase are readily phosphorylated by rat liver type-2 casein kinase-TS at the same 54 KDa protein band which is also radiolabeled by 3H-DFMO. The reaction, which is stimulated by polylysine leads to the incorporation of up to 0.8 mol P/mol ornithine decarboxylase at seryl residue(s) included in a single 8.6 KDa CNBr fragment. Partially purified preparations of ornithine decarboxylase contain a type-2 casein kinase which promotes the phosphorylation of ornithine decarboxylase at the same CNBr fragment affected by rat liver casein kinase-TS.

Animals↗
PubMed1984

Formation of adrenochrome by bovine cardiac sarcolemma.

A sarcolemma preparation from bovine heart was able to promote adrenaline oxidation especially when NADH and NADPH were added. The superoxide anion O(2) was demonstrated to be involved in the activation of adrenochrome production.

Adrenochrome↗
PubMed1983

Involvement of calcium ions in the activation of ornithine decarboxylase by isoprenaline evaluated 'in situ' in the perfused rat heart.

Ornithine decarboxylase activity evaluated during the perfusion of isolated rat hearts by a method 'in situ' was rapidly increased when the hearts were infused with isoprenaline (isoproterenol). Omission of Ca2+ from the perfusion medium or the administration of verapamil to the perfused hearts decreased the isoprenaline-stimulated ornithine decarboxylase activity, whereas a marked stimulatory effect was registered when the hearts were perfused with the Ca2+ ionophore A23187.

Animals↗
PubMed1983

Effect of superoxide generation on rat heart mitochondrial pyruvate utilization.

Previous research has shown that heart mitochondria are able to produce reactive species of oxygen such as superoxide radicals, hydrogen peroxide and hydroxyl radicals [10, 11]. When these compounds are formed beyond a certain level they are not completely removed by the enzymatic and metabolic processes which neutralize their toxicity, and as a result they are able to produce structural and functional damages that impair mitochondrial function [5, 10]. In order to study the molecular mechanism/s by which the oxygen radicals may function as mediators of cellular injury a flow of these radicals by chemical, enzymatic or photochemical methods has been generated in vitro in the presence of cellular preparations. For example, the exposure of isolated subcellular particles to the enzymatic flow of oxygen radicals produced by the reaction of xanthine oxidase upon xanthine reduced both calcium uptake velocity and Ca2+-ATPase activity in sarcoplasmic reticulum [7], while it reduced Ca2+-stimulated ATPase activity in myofibrillar preparations [4]. In addition, incubation with the xanthine oxidase reaction produced an impairment of the respiratory functions associated with an increased lipid peroxidation in the isolated mitochondria [5, 10]. These negative effects were augmented in alpha-tocopherol-deficient mitochondria [3], but were opposed by the exogenous addition of superoxide dismutase [10]. This report shows that the superoxide radicals generated by the xanthine oxidase reaction reduced rat heart mitochondrial respiration induced by pyruvate. This negative effect was partially prevented by superoxide dismutase and catalase and by thiol protecting agents. Moreover, the generation of free radicals caused a significant reduction in the rate of (1-14C) -pyruvate decarboxylation, while it did not change the transport of pyruvate into mitochondria.

Animals↗
PubMed1983

Vitamin E and the heart: possible role as antioxidant.

When cardiac muscle becomes hypoxic the cells become oedematous and the fine ultrastructure is altered. Developed tension declines and resting tension increases. The cellular stores of ATP and CP are depleted and the mitochondria exhibit an altered respiration, characterized by a reduced state III respiration and a lowered respiratory control index. Reoxygenation results in a further increase of the hypoxic damage. Using these changes in function as indices of the severity of the damage caused by hypoxia and reoxygenation, we have investigated whether the administration of alfa-tocopherol provides protection. Adult male New Zealand white rabbits were used. The hearts were isolated, Langendorff perfused and then made hypoxic. Alfa-tocopherol acetate was infused directly into the aorta inflow cannula, 20 minutes before the onset of hypoxia and was continued for the remainder of the perfusion. Hypoxia was established by substituting 95% N2 and 5% CO2 + CO2 in the gas mixture. The alfa-tocopherol-treated rabbits hearts were protected in that during hypoxia and particularly during reoxygenation had a lower rate or rise of resting tensions and of ATP and CP depletion. This treatment also maintained mitochondrial function after hypoxia and reoxygenation and it resulted in the preservation of the fine ultrastructure of the myocardium as electronmicroscopic examination of the hearts revealed a marked reduction in oedema, contracture-band formation and mitochondria alterations.

Aerobiosis↗