Biomedical subjects

F Macri

Publications and source records attributed to F Macri.

14 recordsLinked to original sources

PubMed1999

Hydrogen peroxide generation by higher plant mitochondria oxidizing complex I or complex II substrates.

The generation of H2O2 by isolated pea stem mitochondria, oxidizing either malate plus glutamate or succinate, was examined. The level of H2O2 was almost one order of magnitude higher when mitochondria were energized by succinate. The succinate-dependent H2O2 formation was abolished by malonate, but unaffected by rotenone. The lack of effect of the latter suggests that pea mitochondria were working with a proton motive force below the threshold value required for reverse electron transfer. The activation by pyruvate of the alternative oxidase was reflected in an inhibition of H2O2 formation. This effect was stronger when pea mitochondria oxidized malate plus glutamate. Succinate-dependent H2O2 formation was ca. four times lower in Arum sp. mitochondria (known to have a high alternative oxidase) than in pea mitochondria. An uncoupler (FCCP) completely prevented succinate-dependent H2O2 generation, while it only partially (40-50%) inhibited that linked to malate plus glutamate. ADP plus inorganic phosphate (transition from state 4 to state 3) also inhibited the succinate-dependent H2O2 formation. Conversely, that dependent on malate plus glutamate oxidation was unaffected by low and stimulated by high concentrations of ADP. These results show that the main bulk of H2O2 is formed during substrate oxidation at the level of complex II and that this generation may be prevented by either dissipation of the electrochemical proton gradient (uncoupling and transition state 4-state 3), or preventing its formation (alternative oxidase). Conversely, H2O2 production, dependent on oxidation of complex I substrate, is mainly lowered by the activation of the alternative oxidase.

Hydrogen Peroxide↗

PubMed1996

Zearalenone-induced uncoupling in plant mitochondria is sensitive to 6-ketocholestanol.

Zearalenone (F-2) is a mycotoxin which acts as a protonophoric uncoupler in plant mitochondria [Macri, F. and Vianello, A., (1990) J. Plant Physiol. 136, 754-757]. In the present paper, the mechanism of F-2-induced uncoupling in pea mitochondria was studied. The uncoupling by F-2 was partially reversed by 6-ketocholestanol (kCh) under conditions in which kCh completely reversed the FCCP-induced uncoupling and almost did not affect the palmitate-induced uncoupling. Recoupling effects of carboxyatractylate, ADP and cyclosporin A were small and could not essentially decrease the kCh-insensitive part of F-2-induced uncoupling. It is suggested that a protein, mediating kCh-sensitive uncoupling, is involved in the F-2 effect in plant mitochondria.

Atractyloside↗

PubMed1995

Effect of cyclosporin A on energy coupling in pea stem mitochondria.

Effect of cyclosporin A on energy coupling in pea stem mitochondria is studied. It is found that incubation of mitochondria with 100 nM FCCP and/or CAtr, oligomycin, CaCl2, palmitate and ADP results, after some lag phase, in a collapse of delta psi generated by succinate oxidation in the presence of rotenone. Cyclosporin A (0.2-0.8 nmol/mg mitochondrial protein) markedly increases the lag phase. The cyclosporin A effect requires dithioerythritol to be added to the isolated medium. Metabisulphite fails to substitute for dithioerythritol. The relationships between these effects and cyclosporin A-sensitive mitochondrial permeability transition in animal mitochondria are discussed.

Animals↗

PubMed1995

Effect of 6-ketocholestanol on FCCP- and DNP-induced uncoupling in plant mitochondria.

Effect of 6-ketocholestanol on FCCP-induced and DNP-induced uncoupling in beef liver and pea stem mitochondria was studied, under experimental conditions at which this steroid abolished the effect of low concentrations of FCCP and other most potent uncouplers in rat mitochondria [Starkov et al. (1994) FEBS Lett., 355, 305-308]. It is shown that, in both types of mitochondria, 6-ketocholestanol prevents or reverses the uncoupling induced by low concentrations of FCCP, but not that caused by high concentrations of FCCP or by any concentration of DNP. Progesterone and male sex hormones, showing recoupling capability in animal mitochondria, appear to be ineffective in the plant system. Cholesterol does not recouple in both animal and plant mitochondria. Plant steroids, such as beta-sitosterol and stigmasterol, are also without effect.

2,4-Dinitrophenol↗

PubMed1994

Effect of carboxyatractylate on transmembrane electrical potential of plant mitochondria in different metabolic states.

The effects of carboxyatractylate (CAtr) on delta psi in sunflower hypocotyl and pea stem mitochondria were compared. In sunflower mitochondria, (1) CAtr at higher concentration increased delta psi in the presence of palmitate and delta psi in metabolic state 3; (2) ]1 microM CAtr did not prevent delta psi decrease, induced by ADP addition (in contrast to pea mitochondria); (3) The ATP-generated delta psi was small and was insensitive to 40 microM CAtr. Under the same conditions, in pea mitochondria generation of delta psi by ATP was inhibited by 1 microM CAtr.

Adenosine Diphosphate↗

PubMed1992

Electrical potential dissipation induced by free fatty acids in pea stem mitochondria.

Linolenic, linoleic, oleic, palmitic and stearic acids (FFA) collapse the electrical potential of pea stem mitochondria in the absence or in the presence of 0.5 mM Mg2+. Higher concentrations of this cation (5 mM) lower the rate of dissipation caused by linoleic, oleic and palmitic acids, while abolishing that induced by stearic acid. Carboxyatractyloside and ADP do not reverse the FFA-induced collapse both in the presence or absence of Mg2+. EDTA, EGTA or BHT do not influence the dissipation caused by FFA that, in addition, is not linked to lipid peroxidation evaluated as malondialdehyde or conjugated diene formation. Only linolenic acid sustains a peroxidation which, however, appears to be caused by its own oxidation catalysed by lipoxygenases rather than by membrane lipoperoxidation induced by this free fatty acid. These results suggest that neither the ATP/ADP exchanger nor lipid peroxidation appear to be involved in FFA-induced uncoupling in pea stem mitochondria.

Cations, Divalent↗

PubMed1990

Increased serum IgE and increased prevalence of eosinophilia in 9-year-old children of smoking parents.

We studied the relationship of serum IgE levels and eosinophil counts with passive smoking in 9-year-old, nonselected children from three Italian towns near Rome. Male children of smoking parents had a significantly higher total count and percentage of eosinophils (p = 0.008) and higher IgE levels (p = 0.01) than male children of nonsmoking parents. Prevalence of eosinophilia (defined as greater than or equal to 4% of total white blood cell count) was significantly correlated with the number of cigarettes smoked by parents among boys (p = 0.003) but not among girls (p = 0.20). There was a significant trend (p = 0.008) for prevalence of eosinophilia to increase with increasing levels of serum IgE. For any given level of serum IgE, the frequency of eosinophilia was higher among children of smoking parents than among children of nonsmoking parents. When parental smoking was studied in a multivariable analysis and after controlling for the other variable, it was still significantly associated with eosinophilia in the children of these smoking parents but not with serum IgE levels. We conclude that parental smoking is associated with a significant enhancement of the expression of the most important markers of allergic sensitization in the children of smoking parents. This is particularly evident for boys and may explain, at least in part, the increased frequency of respiratory symptoms in children of smoking parents.

Child↗

PubMed1988

Parental smoking enhances bronchial responsiveness in nine-year-old children.

We studied the relationship between parental smoking habits and atopy and bronchial responsiveness (BR) in 9-year-old, non-selected schoolchildren. A questionnaire on respiratory disease and maternal and paternal smoking habits was administered to one parent. Skin prick tests using the most common allergens present in central Italy, a flow-volume spirometric test, and a bronchial provocation test using carbachol in increasing doses were performed. Male children with smoking parents had significantly increased BR when compared to those whose parents did not smoke (Odds Ratio (OR) = 4.3, p = 0.009). No such significant increase in BR was found in female children of smoking parents (OR = 1.5, p = 0.4). The relationship between BR in children and smoking in parents was stronger in asthmatics (p = 0.02), but was still significant after controlling for asthma and atopy. Bronchial responsiveness was significantly correlated with atopy (p = 0.001). This was also true for nonasthmatic children and for both males and females separately. Male children of smoking parents had increased reactivity to allergens as assessed by the skin prick test index (p = 0.001). It is hypothesized that passive smoking, by increasing the frequency of BR and of atopy, may increase the risk of asthma in childhood and particularly in boys.

Adult↗

PubMed1979