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Biomedical subjects

B Maggio

Publications and source records attributed to B Maggio.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effect of chemical modifications of myelin basic protein on its interaction with lipid interfaces and cell fusion ability.

The ability of native and chemically modified myelin basic protein to induce fusion of chicken erythrocytes and to interact with lipids in monolayers at the air-water interface and liposomes was studied. Chemical modifications of myelin basic protein were performed by acetylation and succinylation: the positive charges of the native protein were blocked to an extent of about 90-95%. Cellular aggregation and fusion of erythrocytes into multinucleated cells was induced by the native myelin basic protein. This effect was diminished for both acetylated and succinylated myelin basic protein. Native myelin basic protein penetrated appreciably in sulphatide-containing lipid monolayers while lower penetration occurred in monolayers of neutral lipids. Contrary to this, both chemically modified myelin basic proteins did not show any selectivity to penetrate into interfaces of neutral or negatively charged lipids. The intrinsic fluorescence of the native and chemically modified myelin basic proteins upon interacting with liposomes constituted by dipalmitoylphosphatidycholine, glycosphingolipids, egg phosphatidic acid or dipalmitoylphosphatidyl glycerol was studied. The interaction with liposomes of anionic lipids is accompanied by a blue shift of the maximum of the native protein emission fluorescence spectrum from 346 nm to 335 nm; no shift was observed with liposomes containing neutral lipids. The acetylated and succinylated myelin basic proteins did not show changes of their emission spectra upon interacting with any of the lipids studied. The results obtained in monolayers and the fluorescence shifts indicate a lack of correlation between the ability of the modified proteins to penetrate lipid interfaces and the microenvironment sensed by the tryptophan-containing domain.

Acetylation↗
PubMed1985

Molecular parameters and conformation of globoside and asialo-GM1.

Comparative studies of the individual properties and intermolecular organization of asialo-GM1 (Gg4Cer) and globoside (Gb4Cer) were made employing lipid monolayers and high-sensitivity differential scanning calorimetry. The surface pressure-area isotherm of Gb4Cer is more expanded than that of Gg4Cer. This results in greater molecular areas and compressibilities, and lower intermolecular interaction energies, for Gb4Cer compared to Gg4Cer at all surface pressures. This looser intermolecular packing may be responsible for a lower transition temperature (40.5 degrees C) and enthalpy of transition (delta Hcal) (2.0 kcal mol-1) found for the phase transition of Gb4Cer compared to Gg4Cer (54.0 degrees C and 4.2 kcal mol-1). The surface potential per molecule and resultant molecular dipole moment vector values are greater for Gb4Cer than for Gg4Cer at comparable values of surface pressure and molecular area. All these results reflect the existence of a rigid L-shape in the oligosaccharide chain of Gb4Cer that prevents a close intermolecular packing compared to the straight orientation of the polar head group of Gg4Cer. Significant movements of the oligosaccharide chain may occur depending on the lateral surface pressure. At low surface pressures the orientation of the oligosaccharide chain of Gg4Cer may be displaced an angle of up to about 40 degrees compared to the perpendicular position adopted at high surface pressures. In agreement with an enhanced liquid character of the interface, the oligosaccharide chain of Gb4Cer exhibits a greater freedom of movement and the displacement from the position perpendicular to the interface can reach to about 65 degrees.

Chemical Phenomena↗
PubMed1985

Thermotropic behavior of binary mixtures of dipalmitoylphosphatidylcholine and glycosphingolipids in aqueous dispersions.

The thermotropic behavior of mixtures of dipalmitoylphosphatidylcholine (DPPC) with natural glycosphingolipids (galactosylceramide, phrenosine, kerasine, glucosylceramide, lactosylceramide, asialo-GM1, sulfatide, GM3, GM1, GD1a, GT1b) in dilute aqueous dispersions were studied by high sensitivity differential scanning calorimetry over the entire composition range. The pretransition of DPPC is abolished and the cooperativity of the main transition decreases sharply at mole fractions of glycosphingolipids below 0.2. All systems exhibit non-ideal temperature-composition phase diagrams. The mono- and di-hexosylceramides are easily miscible with DPPC when the proportion of glycosphingolipids in the system is high. A limited quantity (1-6 molecules of DPPC per molecule of glycosphingolipid (GSL) can be incorporated into a homogeneously mixed lipid phase. Domains of DPPC, immiscible with the rest of a mixed GSL-DPPC phase that shows no cooperative phase transition, are established as DPPC exceeds a certain proportion in the system. One negative charge (sulfatide) or four neutral carbohydrate residues (asialo-GM1) in the oligosaccharide chain of the glycosphingolipids results in phase diagrams exhibiting coexistence of gel and liquid phases over a broad temperature-composition range. Systems containing gangliosides show complex phase diagrams, with more than one phase transition. However, no evidence for phase-separated domains of pure ganglioside species is found. The thermotropic behavior of systems containing DPPC and glycosphingolipids correlates well with their interactions in mixed monolayers at the air/water interface.

Calorimetry, Differential Scanning↗
PubMed1985

Geometric and thermodynamic restrictions for the self-assembly of glycosphingolipid-phospholipid systems.

The thermodynamic and geometrical features of possible self-assembled structures of a series of chemically related glycosphingolipids differing in the complexity of their polar headgroup, and of their mixture with phospholipids, have been predicted according to the theory of self-assembly of hydrocarbon amphiphiles of Israelachvili et al. ((1980) Q. Rev. Biophys. 13, 340-357). The type and number of carbohydrate residues in the oligosaccharide chain of the polar headgroup are of paramount importance to determine the characteristics and thermodynamic stability of the possible self-assembled structure. In single component systems, the general prediction of the theory is that smaller aggregates may form as the polar headgroup of the glycosphingolipid is more complex and as the lateral surface pressure is smaller. In noninteracting two-component glycosphingolipid-phospholipid systems, the thermodynamic stability and the overall geometry of the possible aggregate appear to be determined by the proportion and type of glycosphingolipid present. Large and abrupt changes of the possible free energy per molecule, radius of curvature, and predicted asymmetry ratio for a particular glycosphingolipid may be triggered by relatively small changes of the molecular parameters, lipid composition, lateral surface pressure or vice-versa. If intermolecular interactions are taken into account with respect to the predictions for an ideal, noninteracting system, the theory indicates that two-component bilayer vesicles of polysialoganglioside-phosphatidylcholine may be thermodynamically and geometrically more stable. On the other hand, for systems constituted by phosphatidylcholine and neutral glycosphingolipids or monosialogangliosides, the possible bilayer vesicle is predicted to be less stable than in the ideal, noninteracting case. The results emphasize the general validity of the theory as applied to glycosphingolipid-containing systems.

Glycosphingolipids↗
PubMed1985

Thermotropic behavior of glycosphingolipids in aqueous dispersions.

The thermotropic behavior of 20 chemically related glycosphingolipids (GSLs) of high purity, containing neutral and anionic carbohydrate residues in their oligosaccharide chains, was studied by high-sensitivity differential scanning calorimetry. In general, the polar head group of GSLs appears to be one of the major determinants of their phase behavior. Compared to phospholipids, the presence of the carbohydrate rather than the phosphorylcholine moiety in the polar head group and a sphingosine base in the hydrocarbon portion of GSLs reduces the effect on the transition temperature (Tm) brought about by increasing the number of methylene groups in the amide-linked fatty acyl chains. For simple neutral GSLs, the Tm's were 20-40 degrees C higher than those of phospholipids with comparable hydrocarbon chains. As the oligosaccharide chain of GSLs becomes more complex, the excess heat capacity, Tm, enthalpy (delta Hcal), and entropy of the transition decrease proportionally to the number of carbohydrate residues present in the polar head group. The Tm and delta Hcal for anionic GSLs were 16-25 degrees C and 1-3 kcal mol-1 lower than those of neutral GSLs with comparable oligosaccharide chains. A linear dependence of delta Hcal with Tm was found. However, the slopes of these plots were different for neutral and for anionic GSLs, suggesting different types of intermolecular organizations for the two. The Tm and delta Hcal were linearly dependent on the molecular area of both neutral and anionic GSLs; this indicated that the influence of the complexity of the polar head group in GSLs for establishing the thermodynamic behavior may be mediated by the intermolecular spacings.

Calorimetry, Differential Scanning↗
PubMed1985

[Synthesis and pharmacologic activity of new derivatives of salicylic acid].

New 1-phenyl-2-R2-3-methyl-5-salicyloylimmino-3-pyrazolines were synthesized according to a previously described route. The obtained pyrazoline derivatives, together with some others reported in previous papers, were tested for analgesic and antiinflammatory activities. Some derivatives showed analgesic and/or antiinflammatory activity similar to that of acetylsalicylic acid.

Animals↗
PubMed1984

Tryptophan fluorescence properties of cholera toxin upon interacting with ganglioside GD1b.

A blue shift of the tryptophan fluorescence emission spectra of cholera toxin or the B protomer is induced by disialoganglioside GD1b with a capacity similar to that of monosialoganglioside GM1. Both gangliosides were also capable of decreasing or reversing the fluorescence quenching by iodide ion of the toxin. The quenching constants (Ksv) for the toxin fluorescence in absence of gangliosides was 2.8 M-1; in presence of GM1 or GD1b, Ksv was 0.8 M-1 and 0.7 M-1, respectively. Gangliosides GD1a and GT1b were unable to decrease the quenching effect. The results suggest that GD1b induces a perturbation in the tryptophan environment of the toxin molecule similar to that induced by GM1.

Animals↗
PubMed1984

Interaction of myelin basic protein, melittin and bovine serum albumin with gangliosides, sulphatide and neutral glycosphingolipids in mixed monolayers.

Some parameters that may regulate the miscibility and stability of mixed lipid-protein monolayers at the air-145 mM NaCl interface were studied employing six glycosphingolipids (acidic or neutral), three different types of proteins (soluble, extrinsic or highly amphipathic) and some phospholipids. The results obtained show that the percentage of the total area occupied by the protein at the interface is an important parameter leading to lateral phase separations; the amount and area contribution of the protein accepted in the film before the components become immiscible increase with the complexity of the polar head group of the glycosphingolipids. The interactions occur with progressive reductions of the intermolecular packing as the polar head group of the glycosphingolipid becomes more complex and this is accompanied by more negative values of the excess free energy of mixing. The lipid component seems to be the major responsible for the reduction in mean molecular area.

Animals↗
PubMed1982

Ganglioside-cholera toxin interactions: a binding and lipid monolayer study.

On t.l.c. plates 125I-cholera toxin binds to a disialoganglioside tentatively identified as GD1b with about 10 times less capacity then to ganglioside GM1. Binding of labeled toxin to both gangliosides was abolished in presence of excess amounts of unlabeled B subunit. Ganglioside extracts from human or pig intestinal mucosa showed toxin binding to gangliosides GM1 and GD1b. In ganglioside-containing lipid monolayers the penetration of the toxin was independent of the ganglioside binding capacity.

Animals↗
PubMed1982

Interaction of soluble and membrane proteins with monolayers of glycosphingolipids.

1. The interactions of four proteins (albumin, myelin basic protein, melittin and glycophorin) with eight neutral or acidic glycosphingolipids, including sulphatides and gangliosides, five zwitterionic or anionic phospholipids and some of their mixtures, were studied in lipid monolayers at the air/145 mM-NaCl interface. 2. In lipid-free interfaces, the surface pressure and surface potential reached by either soluble or integral membrane proteins did not reveal marked differences. 3. All the proteins studied showed interactions with each of the lipids but the maximal interactions were found for basic proteins with acidic glycosphingolipids. 4. Surface-potential measurements indicated that different dipolar organizations at the interface can be adopted by lipid-protein interactions showing the same value for surface free energy. 5. The individual surface properties of either the lipid of protein component are modified as a consequence of the lipid-protein interaction. 6. In mixed-lipid monolayers, the composition of the interface may affect the lipid-protein interactions in a non-proportional manner with respect to the relative amount of the individual lipid components.

Albumins↗
PubMed1982

Central nervous system lipid alterations in rats with experimental allergic encephalomyelitis and its suppression by immunosuppressive drugs.

Rats with experimental allergic encephalomyelitis (EAE) induced with myelin or spinal cord show decreases in the content of sulphatides and cerebrosides and increases in the level of esterified cholesterol in the CNS. In this work it is shown that brain sulphatide changes can be obtained by injection of mixtures containing glycosphingolipids. Alterations in the content of cerebrosides occur when the injection mixture contains cerebrosides. The alterations of sulphatides and cholesterol ester induced by injection of spinal cord could be suppressed by treatment with immunosuppressive drugs (dexamethasone, cyclophosphamide and 6-mercaptopurine) able to prevent clinical signs of EAE.

Animals↗
PubMed1980

Configuration and interaction of the polar head group in gangliosides.

1. The interactions of gangliosides with Ca(2+) and some polar-head-group requirements for establishment of particular interactions with phosphatidylcholine were studied in monolayers at the air/145mm-NaCl interface. 2. Ganglioside-Ca(2+) interactions, as revealed by surface-potential measurements, depended on the position occupied by sialosyl residues in the oligosaccharide chain. The interactions with Ca(2+) of the single sialosyl residue of monosialogangliosides occurred above 0.1mm-CaCl(2), whereas the interaction of the cation with additional sialosyl groups in di- or tri-sialogangliosides depended on the carbohydrate residue to which the sialosyl moiety was attached. The sialosyl residue bound in sialosyl-sialosyl linkage interacted very little with Ca(2+). The sialosyl residue attached to the terminal galactose of the neutral tetrasaccharide chain interacted with Ca(2+) above 1mum-CaCl(2). 3. Experiments with mixed monolayers containing dihexadecyl phosphate and hexadecyltrimethylammonium indicated that for the occurrence of interactions of polysialogangliosides with phosphatidylcholine characterized by reductions in molecular packing and surface potential both charged groups of the phospholipid and sialosyl residues with particular dipolar properties in the ganglioside are participating. 4. Possible configurations that can explain the behaviour in monolayers were inspected with space-filling molecular models. The position of the carboxylate group of sialosyl residues with respect to the interface and to the sialosyl molecular plane can explain the different orientation of the dipole-moment vector of this residue, which depends on the position to which it is linked in the oligosaccharide chain. Favoured interactions of polysialogangliosides with phosphatidylcholine may result from a configuration allowing a partial matching of two oppositely oriented electrical vectors contributed by the zwitterionic phosphocholine group and particular sialosyl groups.

Calcium↗
PubMed1980

Neurotransmitter movements in nerve endings. Influence of substances that modify the interfacial potential.

Polysialogangliosides, sulphatides, glycerylmonooleate, unsaturated fatty acids, myelin basic protein and sucrose inhibit the Na+-coupled uptake and induce a Ca2+-dependent release of dopamine from nerve endings. Substances chemically related to those referred to above, such as monosialogangliosides, neutral glycosphingolipids, glycerylmonostearate, saturated fatty acids and albumin, do not show these effects. Mixtures of polysialogangliosides or sulphatides with myelin basic protein or albumin inhibit, to different degrees, the effects of the individual components. The decreased uptake induced by sucrose reverted to control levels upon reduction of the concentration of the perturbing agent. The restoration of the uptake was probably mediated by the Na+-pump reconstituting the transmembrane Na+-gradient necessary for the Na+-coupled cotransport of dopamine. It is suggested that the effects of uptake inhibitor or release inducer agents derive from their ability to decrease the surface potential and modify the molecular organization of phospholipid interfaces which can result in changes of the membrane ionic permeability.

Animals↗
PubMed1979

Membrane instability induced by purified myelin components. Its possible relevance to experimental allergic encephalomyelitis.

The fusogenic properties of purified myelin components in a system employing chicken erythrocytes were studied. Sulphatides, myelin basic protein and the apoprotein of Folch-Lees proteolipid were capable of individually inducing membrane fusion in the presence of Ca2+. By contrast, cerebrosides or a mixture of sulphatides and myelin basic protein (molar ratio 19 : 1) did not show such effect. The fusogenic ability of sulphatide was correlated to its behaviour in mixed monolayers with phospholipids at the air-water interface. Mixed films of sulphatides with phosphatidylcholine or sphingomyelin but not with phosphatidylethanolamine showed reductions of molecular packing and surface potential similar to those found for other fusogenic compounds. The effects of myelin components described could be of importance in the membrane instability and vesicular disruption of myelin occurring in demyelinative disorders.

Animals↗
PubMed1978

Interactions of gangliosides with phospholipids and glycosphingolipids in mixed monolayers.

1. The interactions among five different gangliosides and three chemically related glycosphingolipids and their behaviour in mixed monolayers with six different phospholipids were investigated at the air/145 mM-NaCl interface at pH 5.6. 2. The mixed monolayers of any of the different gangliosides showed an immiscible behaviour at high surface pressures, with absence of interactions among them revealed by an ideal behaviour for mean molecular area and surface potential per molecule. 3. This behaviour was probably the consequence of steric hindrance and electrostatic repulsions between their polar head groups. 4. Di- and tri-sialogangliosides could be differentiated from neutral sphingolipids and monosialogangliosides on the basis of their interactions with phospholipids, which were correlated to the perpendicular electric field at the interface contributed by the carbohydrate residues. 5. The presence of the phosphocholine polar head group in phosphatidylcholine was important to establish interactions with di- and tri-sialogangliosides revealed by negative deviations from the ideal behaviour for mean molecular areas and mean surface potential per molecule. 6. The possible significance of these observations is discussed in relation to the participation of gangliosides in the organization of membranes and to their capability of inducing membrane fusion.

Chemical Phenomena↗