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Biomedical subjects

M Manno

Publications and source records attributed to M Manno.

At least 55 records · Page 3Linked to original sources
PubMed1992

Suicidal inactivation of human cytochrome P-450 by carbon tetrachloride and halothane in vitro.

A significant loss of human cytochrome P-450 was observed during the anaerobic incubation of NADPH-reduced human liver microsomes obtained from surgical samples, in presence of carbon tetrachloride or halothane. In order to prevent any interference in the classical spectrum of cytochrome P-450 with CO, the method of Johannesen & DePierre (1978) was modified to obtain cytochrome P-450 determination. The enzyme inactivation reaction showed pseudo-first order kinetics and was accompanied by destruction of the haem tetrapyrrolic structure, as indicated by a significant loss of its porphyrin fluorescence. Values of about 200 and 700 were calculated for the partition ratio between metabolic turnover of the substrate and enzyme inactivation during reductive incubation of one of these microsomal preparations with limiting concentrations of CCl4 and halothane, respectively. The results indicate that human liver cytochrome P-450 can be inactivated reductively in vitro by CCl4 and halothane reactive metabolites and suggest that a suicide type of mechanism, similar to that which was recently demonstrated to occur, for both substrates, with rat liver microsomes (Manno et al. 1988a & 1991), may also be involved in the inactivation of the human enzyme(s).

Animals↗
PubMed1992

Hepatitis C virus in hemodialysis patients.

Anti-HCV prevalence in 284 hemodialysis patients was assessed using the Abbott HCV-EIA test. Anti-HCV positivity was found in 19.4% of patients, was higher in males than in females and progressively increased with age. A correlation between time of dialysis treatment, transfusions and ALT course was found. These data suggest that HCV infection is a very important risk in dialysis units.

Adolescent↗
PubMed1992

Double fatal inhalation of dichloromethane.

1 Two cases of lethal poisoning following acute inhalation of extremely high concentrations of dichloromethane (DCM) are reported. The concentrations of the solvent found in the blood of the two subjects collected at autopsy and analysed by gas chromatography/mass spectrometry (572 and 601 mg l-1) were compatible with those measured in the air a few hours after the discovery of the bodies (up to 168,000 ppm). 2 Extensive brain and lung oedema and congestion, microhaemorrhagic changes of the stomach and congestion in other organs were observed on macroscopic and microscopic examination of both subjects. In addition, and in both cases, high but not lethal carboxyhaemoglobin (COHb) levels (30%) were found in the blood collected at autopsy. 3 Narcosis and respiratory depression due to the effect of DCM on the central nervous system (CNS) appear to have played a critical role in the death of the two men. However, biotransformation of the solvent to toxic metabolites, including carbon monoxide (via oxidative dehalogenation by the cytochrome P450-dependent mixed function oxidase system) or formaldehyde, formic acid, inorganic chloride and carbon dioxide (via the glutathione-S-transferase pathway) may have also contributed significantly to fatal toxicity.

Administration, Inhalation↗
PubMed1991

The mechanism of the suicidal reductive inactivation of microsomal cytochrome P-450 by halothane.

Anaerobic incubation of NADPH- or sodium dithionite-reduced rat liver microsomes with halothane resulted in a significant inactivation of cytochrome P-450 and parallel loss of the prosthetic group protohaem. When the loss of microsomal haem was measured in the same incubations by two different methods, the pyridine/haemochrome assay and the porphyrin fluorescence technique, halothane was responsible for a loss of haem in both assays, indicating that the tetrapyrrolic structure of haem has been modified by halothane metabolites. Cytochrome P-450 loss by halothane was found to be irreversible, saturable, inhibited by carbon monoxide and showed biphasic, pseudo first-order kinetics, thus fulfilling all the conditions of a typical "suicide" inactivation reaction. Pretreatment of rats with inducers of cytochrome P-450 isoenzymes modified the kinetics of cytochrome P-450 inactivation and the amount of total inactivable enzyme in microsomes. A partition ratio, between metabolic turnover of the substrate and enzyme inactivation, of about 121 was found with microsomes from phenobarbital-treated rats, indicating that halothane is rather efficient as a suicide substrate of cytochrome P-450. A stable complex between reduced cytochrome P-450 and a halothane metabolite is responsible for the 470 nm peak observed in the difference spectrum of reduced liver microsomes obtained on addition of halothane. An extinction coefficient for this complex was calculated from the amount of enzyme involved.

Animals↗
PubMed1989

The degradation of haem by carbon tetrachloride: metabolic activation requires a free axial coordination site on the haem iron and electron donation.

1. The ability of haem to catalyse the reductive activation of carbon tetrachloride (CCl4) in vitro has been investigated under anaerobic conditions, using methaemalbumin (MHA) and either sodium dithionite or NADPH together with NADPH-cytochrome P-450 reductase (EC 1.6.2.4) as the reducing agents. 2. In the non-enzymic system protohaem and other non-physiological haem analogues underwent rapid and extensive CCl4-dependent degradation, due to irreversible modification of their porphyrin tetrapyrrolic structure. 3. This mechanism of non-enzymic activation of CCl4 by protohaem mimics that catalyzed by cytochrome P-450 in that it requires a free, reduced haem iron and electron donation and it is largely prevented by carbon monoxide. 4. H.p.l.c. analysis of 14C-haem after anaerobic incubation with CCl4 and sodium dithionite gave radioactive products which eluted before and after haem, and exhibited significantly lower absorbance at 400 nm compared with authentic haem. When the products of CCl4-dependent haem degradation were methylated and applied to silica for t.l.c., two non-fluorescent pigments were isolated, purified and partially characterized. 5. On incubation of haem with 14CCl4 and sodium dithionite a 1:1 stoichiometry could be calculated for haem loss and 14CCl4-derived adduct formation, indicating that, as with microsomes, the loss of haem may be the result of a typical 'suicidal' inactivation reaction where the same haem moiety is both the site of CCl4 activation and the target of CCl4 reactive metabolites.

Animals↗
PubMed1989

Possible involvement of endogenous opioids in beta-cell hyperresponsiveness in human obesity.

Since increased opiate production in obesity has been reported, the effects of naloxone in obese subjects were studied in order to ascertain whether endogenous opioid peptides play a role in the abundant insulin secretion of obesity. The results obtained showed that intravenous administration of naloxone considerably reduced insulin of obese subjects to a mixed meal, whereas it did not modify the blood insulin response to arginine or glucose infusion. Glucagon secretion to ingestion of a mixed meal and to arginine infusion was not modified by the opioid receptor blocking agent. This study seems to indicate that hyperproduction of endogenous opioid peptides in obesity increases insulin secretion stimulated by food intake, whereas it does not appreciably affect insulin production stimulated by circulating glucose or aminoacids.

Adolescent↗
PubMed1988

The mechanism of the suicidal, reductive inactivation of microsomal cytochrome P-450 by carbon tetrachloride.

1. Stoichiometric losses of microsomal haem and cytochrome P-450 were observed when carbon tetrachloride (CCl4) was incubated anaerobically with rat liver microsomes using NADPH or sodium dithionite as a reducing agent. A rapid destruction of haem was also observed during the non-enzymatic reductive incubation of CCl4 with soluble haem preparations (methaemalbumin) in presence of sodium dithionite. The results indicate that haem is both the site and the target of the suicidal activation of CCl4 by cytochrome P-450. 2. When an additional, fluorimetric assay for haem determination was used, an equimolar loss of protoporphyrin IX fluorescence was also observed in both the enzymatic and non-enzymatic system, indicating that the haem moiety of cytochrome P-450 has undergone a structural change, involving either loss or labilization of the porphyrin tetrapyrrolic structure. In both systems the loss of porphyrin was prevented by carbon monoxide (CO). 3. A dichlorocarbene-cytochrome P-450 ligand complex is partially responsible for the difference spectrum obtained on addition of CCl4 to anaerobically reduced rat liver microsomes. A molar extinction coefficient for this complex has been calculated. The carbene trapping agent 2,3-dimethyl-2-butene (DMB) strongly inhibited (greater than 95%) the formation of this spectrum but did not modify the loss of haem in reduced CCl4-supplemented microsomal incubations. The results suggest that dichlorocarbene (:CCl2) is not significantly involved in CCl4-dependent haem destruction. 4. Pretreatment of rats with different microsomal enzyme inducers was responsible for similar but not identical patterns of :CCl2 and CO formation and haem loss during incubation of CCl4 with reduced microsomes. This indicates a critical role of CCl4 metabolism in the suicidal destruction of cytochrome P-450 haem and suggests that the apoprotein of cytochrome P-450 is capable of modulating not only the metabolism of CCl4 to :CCl2 but also the hydrolysis of :CCl2 to CO. 5. Inactivation of cytochrome P-450 by CCl4 with reduced microsomes from Aroclor-pretreated rats was saturable and followed pseudo first-order kinetics. This provides further evidence to conclude that CCl4 activation is a suicidal process where the reactive metabolite(s) formed bind to haem, we predict, in a one to one stoichiometry. 6. The partition ratio between loss of cytochrome P-450 haem and CCl4 metabolism by liver microsomes from Aroclor pretreated rats has been investigated using limiting concentrations of CCl4. It was calculated that approximately 26 molecules of CCl4 had to be metabolised to achieve the loss of one molecule of haem.

Animals↗
PubMed1988

Increased plasma levels of immunoreactive human atrial natriuretic factor in primary IgA nephropathy.

The plasma concentration of the immunoreactive (IR) human atrial natriuretic factor (hANF) was measured in 17 patients with primary IgA nephropathy (IgAN) (9 normotensive and 8 hypertensive subjects without impairment of renal function). Furthermore, correlations with the renin-angiotensin II-aldosterone system and hemodynamic alterations were studied. The mean value of IR-hANF was significantly (p less than 0.002) higher in normotensive IgAN patients (68.2 +/- 14.6 pg/ml) than in controls (48.8 +/- 11.5 pg/ml), while it was slightly and not significantly elevated in hypertensive IgAN patients (58.5 +/- 8.4 pg/ml). In the latter the mean plasma renin activity (PRA) was significantly increased (0.92 +/- 0.30 ng/ml/h; p less than 0.002), while in normotensive IgAN patients (0.68 +/- 0.58 ng/ml/h) no difference was observed. Plasma aldosterone levels showed the same behavior pattern as those of PRA. Hemodynamic studies showed that the mean values of the cardiac index (CI) were significantly (p less than 0.002) high in both normotensive (3.55 +/- 0.5 l/min/m2) and hypertensive (3.32 +/- 0.47 l/min/m2) patients, while a significant reduction in the total peripheral resistance index (TPRI) in normotensive (2171 +/- 349 dyn/s/cm-5/m2; p less than 0.02) and a significant increase in hypertensive (2959 +/- 440 dyn/s/cm-5/m2; p less than 0.05) patients were observed. The mean arterial pressure (MAP) had a positive correlation with the TPRI and an inverse correlation with the IR-hANF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

The modulation by arylamines of the in vitro formation of superoxide anion radicals and hydrogen peroxide by rat liver microsomes.

A concentration-dependent increase in the generation of the superoxide anion radical (O-2), was observed during the incubation of benzidine (0.1-5 mM), but not of the structurally related compounds 4-aminobiphenyl, 2-aminobiphenyl or 4-fluoro-4'-aminobiphenyl, with NADPH-supplemented rat liver microsomes. This increase was partially inhibited by carbon monoxide and catalase but unaffected by 4-aminobiphenyl, a substrate of the cytochrome P-450 system. Microsomes from benzo(a)pyrene-treated, but not microsomes from phenobarbitone-pretreated rats, were responsible for a larger benzidine-dependent effect compared to microsomes from control animals. In contrast to the above observations, benzidine decreased the formation of hydrogen peroxide by NADPH-supplemented microsomal preparations from untreated rats. These results indicate that free radicals of oxygen are generated during the metabolism of some arylamines.

Amines↗
PubMed1985

Interaction of low doses of ionizing radiation and carbon tetrachloride on liver superoxide dismutase and glutathione peroxidase in mice.

Male BALB/c mice were treated with intraperitoneal injections of carbon tetrachloride (CCl4) (0.2 g/kg body weight) and/or 50 R of whole-body gamma irradiation, three times per week, for 4 weeks. The effects of the treatments on superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in liver extracts and homogenates, and on alkaline phosphatase (ALP) in serum were investigated. A significant decrease in the SOD and GSH-Px activities in liver extracts and an increase of serum ALP of hepatic origin were found in CCl4-treated animals. In contrast, only an increase in SOD activity was observed in liver homogenates after the combined treatment.

Alkaline Phosphatase↗
PubMed1984

Demonstration and characterization of immunoreactive methionine-enkephalin, leucine-enkephalin, methionine-enkephalin-Arg6-Gly7-Leu8 and methionine-enkephalin-Arg6-Phe7 in human phaeochromocytoma.

To elucidate whether or not human phaeochromocytoma contains methionine-enkephalin-Arg6-Gly7-Leu8 (Met-enkephalin-Arg-Gly-Leu) and methionine-enkephalin-Arg6-Phe7 (Met-enkephalin-Arg-Phe) together with methionine-enkephalin (Met-enkephalin) and leucine-enkephalin (Leu-enkephalin), all of which are known to exist in the same precursor molecule (preproenkephalin A), we examined extracts from 16 phaeochromocytomas using high performance liquid chromatography (HPLC) and gel exclusion chromatography coupled with radioimmunoassays (RIAs) for these four opioid peptides. Met-enkephalin-Arg-Gly-Leu-like immunoreactivity (-LI) and Met-enkephalin-Arg-Phe-LI existed together with Met-enkephalin-LI and Leu-enkephalin-LI in 16 phaeochromocytomas. There was a wide variation in contents of Met-enkephalin-LI, Leu-enkephalin-LI, Met-enkephalin-Arg-Gly-Leu-LI and Met-enkephalin-Arg-Phe-LI. Significant positive correlations were observed among the contents of these four opioid peptides in 16 phaeochromocytomas. HPLC and gel exclusion chromatography followed by the RIAs showed the presence of Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Gly-Leu and Met-enkephalin-Arg-Phe together with their high molecular weight forms, which existed in variable amounts. Molar ratios of the contents of these four opioid peptides determined after HPLC varies from case to case. These results indicate the co-existence of Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Gly-Leu and Met-enkephalin-Arg-Phe in human phaeochromocytomas, suggesting the preservation of amino acid sequences of these four opioid peptides even in neoplastic tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗