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Biomedical subjects

E Bertoli

Publications and source records attributed to E Bertoli.

141 records · Page 8Linked to original sources
PubMedDate not supplied

Fromation and stoichiometry of a lysozyme-phospholipid-mitochondrial protein ternary complex.

Mitochondrial membranes reconstituted from lipid-depleted mitochondria and aqueous phospholipid dispersions still have the phospholipid negative charges available for ionic interaction with the basic protein, lysozyme. The stoichiometry of the binding is of about 6 nmoles of lysozyme per 100 nmoles of phospholipid in membranes reconstituted with Asolectin, and of 10 nmoles of phospholipid phosphorus in membranes reconstituted with cardiolipin. Unextracted submitochondrial particles ETP also bind lysozyme (about 3 nmoles per 100 nmoles of phospholipid). These observations indicate that the phospholipid anionic groups are not completely shielded by the mitochondrial proteins, which might occupy areas between the nonpolar groups of the lipid molecules.

Animals↗
PubMedDate not supplied

Biophysical studies of erythrocyte membranes from patients with duchenne muscular dystrophy.

Lipid-soluble spin labels were used to probe the fluidity of membrane lipids in erythrocyte membranes from patients with Duchenne muscular dystrophy. A greater mobility of spin label motion was noticed at the surface of the Duchenne erythrocyte membranes in comparison with the similary labeled normal human erythrocytes. Changes in the protein conformation and/or protein-lipid organization, as a consequence of an altered membrane lipid fluidity, have been demonstrated by the use of a sulfhydryl group specific protein spin label. Strongly immobilized sulfhydryl groups appear to be located both at the membrane surface and deep within the lipid bilayer. The ratio of the spectral amplitude of the spin label attached to weakly immobilized sulfhydryl groups to that of strongly immobilized SH-groups is significantly greater in Duchenne membranes, compared to those of controls. These studies suggest alterations in lipid-protein organization at the surface of Duchenne erythrocytes, indicating that Duchenne muscular dystrophy may be a disease resulting from a membrane abnormality at the molecular level.

Electron Spin Resonance Spectroscopy↗
PubMedDate not supplied

Duchenne muscular dystrophy. Morphological study of erythrocytes after treatment with L-alpha-lysophosphatidyl-choline in dystrophic patients and in the carrier state.

The percentage of echinocytes in the blood from patients affected by Duchenne muscular dystrophy, in mothers carriers of the dystrophic state, and in Steinert dystrophic patients, has been investigated after addition of low levels of lysolecithin. The echinocyte content was significantly higher in both Duchenne patients and in carriers, and lower in Steinert patients than in controls. The extents of the differences suggest the possibility to use this methodology as a diagnostic test in Duchenne muscular dystrophy.

Adolescent↗
PubMedDate not supplied

A conformational model for the action of general anesthetics at the membrane level. I. Theoretical considerations.

The first paper of this series describes a working hypothesis for the action of general anesthetics. According to such hypothesis, anesthetics, by inducing a labilisation of lipid-protein interactions in biomembranes, affect the conformation, and hence the activity of membrane-bound catalytic proteins. It is conceivable that such changes in ionic channels in neuronal membranes will abolish the transmission of nervous impulses and give rise to anesthesia. The hypothesis is discussed on the basis of previously known experimental data and of theoretical considerations. Thermodynamic considerations are in favour of the idea that a rupture of lipid-protein interactions will expose protein groups to water destabilising helical structures. A large decrease of alpha-helical content after lipid removal had been previously found. Furthermore lipids affect the kinetics of membrane-bound enzymes, suggesting that conformational changes occur in the catalytic site after lipid removal or perturbation.

Anesthesia, General↗
PubMedDate not supplied

A conformational model for the action of general anesthetics at the membrane level. II. Experimental observations on the effects of anesthetics on lipid fluidity and lipid protein interactions.

We have investigated the effect of general anesthetics (the normal alcohol series up to pentanol, halothane, pentrane, ether, chloroform, and ketamine) on lipid fluidity of phospholipid vesicles and mitochondrial and erythrocyte membranes by using spin labels and fluorescent probes. The spin labels used (5- and 16-doxyl stearic acids) show that all anesthetics tested have a slight fluidizing effect on lipid vesicles but induce a very strong increase in mobility of spin labels in mitochondria and lower in erythrocyte ghosts. These results are interpreted as a labilization of lipid protein interactions at all depths in the bilayer. The fluorescent molecules ANS and NPN, which probe the glycerol region and the core of the bilayer respectively, show a decrease of fluorescence induced by alcohols, halothane, ether, chloroform in both lipid vesicles and membranes. The decrease of fluorescence is due to decreased quantum yield as shown by double reciprocal plots of probe fluorescence against membrane concentration. The fluorescence decrease is interpreted mainly as an increase in fluidity of the lipid bilayer and not as an increase of polarity of the probe environment. The effect of ketamine is that of fluidization in the bilayer core (NPN) but of increased rigidity in the glycerol region (ANS) perhaps due to the amphipathic character of this anesthetic, that is supposed to bind in the polar region of the bilayer. Pentrane also induces fluidization in the bilayer core (NPN) but has a peculiar effect near the surface (ANS): in lipid vesicles it induces a fluorescence decrease, whereas an increase is seen in mitochondrial membranes. These complex effects are considered as the result of some specific change in the lipid protein interactions in the region probed by ANS. The effects of anesthetics on maximal NPN fluorescence (Fo) have been usually found to be stronger in mitochondrial membranes than in lipid vesicles, thus confirming the results of the spin label studies, showing a labilization of lipid protein interactions induced by anesthetics. The effects on Fo of ANS, however, appear to be stronger in lipid vesicles than in membranes. These findings indicate that the presence of the proteins counteracts the perturbation induced by anesthetics at the level of the membrane surface, in contrast with the disruption of lipid protein interactions observed in the membrane hydrophobic areas.

Anesthesia, General↗