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Biomedical subjects

E Antonini

Publications and source records attributed to E Antonini.

At least 19 recordsLinked to original sources
PubMed1991

Value of combined assessment of physical health and functional status in community-dwelling aged: a prospective study in Florence, Italy.

A survey of the health and social conditions of a representative sample of 967 persons aged 60 years and older from the city of Florence, Italy, was undertaken in 1980. In 1987, a follow-up survey of this cohort was performed. There were 391 documented deaths, 408 survivors, and 168 individuals who could not be located. Functional ability at baseline was assessed using a World Health Organization 14-item scale. Indicators of physical health status included chronic disease status, number of drugs, physician visits, and days of hospitalization. After adjustment for age and sex, both functional ability and indicators of physical health status were found to be independent, statistically significant predictors of mortality. The results of this study further support the view that biomedical and functional assessment are both necessary for a comprehensive evaluation of the older population.

Activities of Daily Living↗
PubMed1987

The effect of saturation with Zn2+ and other metal ions on the antibacterial activity of ovotransferrin.

The antibacterial activity of metal complexes of ovotransferrin was tested "in vitro" against different bacterial species and the Zn2+ saturated ovotransferrin appeared to be the most active by comparison with the apo-protein and other metal complexes. Appropriate controls showed that such an effect was neither due to Zn2+ ions, nor to iron deprivation, but to a specific activity of the Zn-ovotransferrin complex. This antibacterial activity required a direct contact of Zn-ovotransferrin with the bacterial surface. In vivo experiments confirmed the higher antibacterial activity of Zn-ovotransferrin as compared with the apo-form.

Animals↗
PubMed1985

Calorimetric studies of oxyhemoglobin dissociation. II. Erythrocytic oxygen depletion by sodium dithionite.

Dithionite causes the depletion of dioxygen from suspensions of erythrocytes by reduction of the external dioxygen and not by diffusion into the cell. The molar enthalpy for the reduction shows a small difference with respect to the values found for free hemoglobin; and the normal stoichiometry of 2 moles dithionite/mole dioxygen found there is not observed with erythrocytes. At low hematocrit, the stoichiometry is 2.6:1 and decreases to 1.5:1 at high hematocrit. The change is not due to differences in the hemoglobin saturation or to an inability of dithionite to reduce all dioxygen present at the higher hematocrit. Neither catalase nor peroxidase added to the extracellular volume significantly alters the stoichiometry or the enthalpy of dioxygen reduction by dithionite. Addition of superoxide dismutase, however, restores the normal stoichiometry at high hematocrit and further increases the stoichiometry at low hematocrit. The calorimetrical signal of hydrogen peroxide, clearly seen with free dioxygen, is not present with erythrocytes. In all these cases the total heat evolved is the same.

Animals↗
PubMed1984

Effect of bepridil on the activity of cytochrome c oxidase in solution and in proteoliposomes.

The interaction between bepridil and mitochondrial cytochrome c oxidase has been studied using the purified enzyme either in aqueous suspensions in the presence of detergents, or embedded into phospholipid vesicles. The investigation, systematically extended to nonactin and valinomycin for comparison, showed that: (a) valinomycin and nonactin induce similar changes in the visible absorption spectrum of cytochrome oxidase; these changes are quite different from those induced by bepridil. (b) The three compounds have an effect on the functional properties of purified, solubilized oxidase which may be related to binding. In particular, bepridil displays a complex pH-dependent effect which at concentrations below 50 microM results in a stimulation of the activity of approximately 30% starting with the oxidized resting enzyme. At variance with valinomycin and nonactin, the stimulatory effect is the same, within the errors, for the detergent-suspended, the vesicle-embedded and even the Keilin-Hartree particles. (c) In the case of detergent-suspended oxidase, the stimulatory effect of bepridil is also similar whether the enzyme is in the resting or in the pulsed state. If the oxidase is embedded into vesicles, however, the pulsed state is significantly more sensitive to bepridil than the resting one. These results are discussed in the light of the possible role assigned to pulsed oxidase in the regulation of the electron flux through the respiratory chain.

Animals↗
PubMed1983

Transient removal of proflavine inhibition of bovine beta-trypsin by the bovine basic pancreatic trypsin inhibitor (Kunitz). A case for "chronosteric effects".

The formation of the bovine beta-trypsin-bovine basic pancreatic trypsin inhibitor (Kunitz) (BPTI) complex was monitored, making use of three different signals: proflavine displacement, optical density changes in the ultraviolet region, and the loss of the catalytic activity. The rates of the reactions indicated by the three different signals were similar at neutral pH, but diverged at low pH. At pH 3.50, proflavine displacement precedes the optical density changes in the ultraviolet and the loss of enzyme activity by several orders of magnitude in time (Antonini, E., Ascenzi, P., Menegatti, E., and Guarneri, M. (1983) Biopolymers 22, 363-375). These data indicated that the bovine beta-trypsin-BPTI complex formation is a multistage process and led to the prediction that, at pH 3.50, BPTI addition to the bovine beta-trypsin-proflavine complex would remove proflavine inhibition and the enzyme would recover transiently its catalytic activity before being irreversibly inhibited by completion of BPTI binding. The kinetic evidences, by completion of BPTI binding. The kinetic evidences, here shown, verified this prediction, indicating that during the bovine beta-trypsin-BPTI complex formation one transient intermediate occurs, which is not able to bind proflavine but may bind and hydrolyze the substrate. Thus, the observed peculiar catalytic behavior is in line with the proposed reaction mechanism for the bovine beta-trypsin-BPTI complex formation, which postulates a sequence of distinct polar and apolar interactions at the contact area.

Acridines↗
PubMed1983

Heterogeneity of the basic pancreatic inhibitor (Kunitz) in various bovine organs.

Four protein protease inhibitors (I, II, III, IV) having low molecular weights (10 600-6500) and basic isoelectric points were isolated by affinity chromatography from bovine spleen. Inhibitor IV was identified as the basic pancreatic trypsin inhibitor (Kunitz inhibitor); the presence and distribution of components I, II and III vary in the different bovine organs. Spleen inhibitors I, II, III and IV were purified by ion-exchange chromatography; they form 1:1 complexes with trypsin and inhibit enzymatic activity of trypsin, chymotrypsin and kallikrein. Inhibitors I, II and III contain carbohydrate moieties (7-4%) covalently bound to the polypeptide chain. Specific basic pancreatic trypsin inhibitor antiserum has shown the complete identity between inhibitor IV and the basic pancreatic trypsin inhibitor, while partial cross-reactivity between the basic pancreatic trypsin inhibitor and inhibitors I, II and III can be seen from a double immunodiffusion test.

Animals↗
PubMed1983

Kinetic studies on cytochrome c oxidase inserted into liposomal vesicles. Effect of ionophores.

Cytochrome c oxidase from ox heart was inserted into artificial liposomal vesicles obtained by sonication of purified soya-bean phospholipids. The cytochrome oxidase vesicles showed a respiratory control ratio of about 2. Spectroscopic properties in the visible and Soret regions and kinetics of CO binding are similar to those of the soluble oxidase. The catalytic efficiency of the cytochrome oxidase vesicles in oxidizing cytochrome c increases as a result of the formation of the 'pulsed' form of the oxidase and of the presence in the reaction mixture of carbonyl cyanide p-trifluoromethoxy-phenylhydrazone and nonactin. Analysis of the experimental results obtained under several conditions supports the conclusions that: (i) the alkalinization of the internal microenvironment in the liposomal vesicle is not by itself responsible for the decrease in catalytic activity; (ii) the electrical potential difference created during turnover by proton consumption and/or pumping through the liposome wall is an important mechanism of control in the chain of events leading to the oxidation of external cytochrome c.

Anti-Bacterial Agents↗
PubMed1983

Studies of the antimicrobial activity of ovotransferrin.

The antibacterial activity of ovotransferrin (conalbumin) against different bacterial species was studied in vitro. The most sensitive species were Pseudomonas sp., E. coli, S. mutans; and the most resistant ones S. aureus, Proteus sp., Klebsiella. The bacteriostatic activity of conalbumin in various conditions was also tested. The presence of bicarbonate ions always increased the activity of conalbumin, while an antagonistic effect of citrate was observed in bacteria with a receptor for the iron-citrate complex. Experiments with conalbumin covalently linked to Sepharose 4B indicated that its antibacterial activity may not be due simply to the removal of iron from the medium, but probably involves other metals and an interaction with the bacterial surface. The in vitro studies carried out with conalbumin and lactoferrin demonstrated that the two proteins produced a similar inhibition of growth of E. coli and S. mutans. The in vivo studies showed that the protective effect of conalbumin in newborn guinea pigs with E. coli by gastrointestinal route was similar to that naturally provided by the lactoferrin present in milk.

Animals↗
PubMed1982

Studies on Scapharca hemoglobins. Properties of the dimeric protein reconstituted with Fe- or Co-porphyrin.

A native globin from the dimeric hemoglobin, hemoglobin I, of the mollusc Scapharca inaequivalvis has been obtained with the acid-acetone method. The globin has a lower sedimentation coefficient than the native protein at neutral pH; its reconstitution product with natural heme has the same physicochemical and functional properties as the native protein. proto- and meso-cobalt hemoglobin I have been prepared and characterized. proto-Cobalt hemoglobin I binds oxygen reversibly with a lower affinity and a lower cooperativity than native hemoglobin I; thus, the changes in the functional properties brought about by substitution of iron with cobalt are similar to those observed in human hemoglobin A. The EPR spectra of deoxy-proto-cobalt hemoglobin I and of the photolysis product of oxy-meso-cobalt hemoglobin I indicate that two histidine residues are the apical heme ligands. The broad signal at g = 2.38 in deoxy-proto-cobalt hemoglobin I points to a constrained structure of the heme site in this derivative which results from a distorted coordination of the hindered proximal histidine. A similar structure has been proposed previously for the alpha chains in deoxy-cobalt hemoglobin A.

Apoproteins↗
PubMed1982

The kinetics of electron transfer between pseudomonas aeruginosa cytochrome c-551 and its oxidase.

The redox reaction between cytochrome c-551 and its oxidase from the respiratory chain of pseudomonas aeruginosa was studied by rapid-mixing techniques at both pH7 and 9.1. The electron transfer in the direction of cytochrome c-551 reduction, starting with the oxidase in the reduced and CO-bound form, is monophasic, and the governing bimolecular rate constants are 1.3(+/- 0.2) x 10(7) M-1 . s-1 at pH 9.1 and 4 (+/- 1) x 10(6) M-1 . s-1 at pH 7.0. In the opposite direction, i.e. mixing the oxidized oxidase with the reduced cytochrome c-551 in the absence of O2, both a lower absorbance change and a more complex kinetic pattern were observed. With oxidized azurin instead of oxidized cytochrome c-551 the oxidation of the c haem in the CO-bound oxidase is also monophasic, and the second-order rate constant is 2 (+/- 0.7) x 10(6) M-1 . s-1 at pH 9.1. The redox potential of the c haem in the oxidase, as obtained from kinetic titrations of the completely oxidized enzyme with reduced azurin as the variable substrate, is 288 mV at pH 7.0 and 255 mV at pH 9.1. This is in contrast with the very high affinity observed in similar titrations performed with both oxidized azurin and oxidized cytochrome c-551 starting from the CO derivative of the reduced oxidase. It is concluded that: (i) azurin and cytochrome c-551 are not equally efficient in vitro as reducing substrates of the oxidase in the respiratory chain of Pseudomonas aeruginosa; (ii) CO ligation to the d1 haem in the oxidase induces a large decrease (at least 80 mV) in the redox potential of the c-haem moiety.

Azurin↗
PubMed1981

Equilibrium and kinetic evidence for a transition between six- and five-coordinate ferrous heme in the nitric oxide derivative of Aplysia myoglobin.

The pH dependence in the range 3--7 of the optical absorption and electron paramagnetic resonance of the nitric oxide adduct of ferrous Aplysia myoglobin is reported. Optical spectra in the Soret region show a transition between two conformers with an apparent pK in the range 3.5--5 depending on the presence of carboxylic anions as third component. In the same pH range, the EPR spectrum undergoes a change from a 9-line to a 3-line hyperfine pattern in the g. region, similar to that reported for synthetic heme derivatives and for other hemoproteins. The structural interpretation of the pH-induced transition experienced by Aplysia myoglobin nitric oxide is that of a proton-linked cleavage of the proximal bond as suggested by several lines of evidence. Temperature-jump measurements allowed an estimation of the relaxation time for the process, which is of the order of 0.3 ms at 25 degrees C.

Animals↗
PubMed1981

A plausible two-state model for cytochrome c oxidase.

The catalytic properties of pulsed and resting cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.1), expressed in terms of a minimal kinetic scheme and simulated by numerical computations, were successfully described. A two-state model, in which the relative amounts of the enzyme present in each conformation are regulated by the rates of electron flux and O2 binding on one side and the interconversion rates on the other, accounts for the activation of cytochrome c oxidase during turnover.

Electron Transport Complex IV↗