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Biomedical subjects

J L Rigaud

Publications and source records attributed to J L Rigaud.

At least 73 records · Page 4Linked to original sources
PubMed1980

Effect of membrane cholesterol on action of phospholipase A2 in Mycoplasma mycoides var. Capri. Evidence for lysophospholipase activity.

Cells of Mycoplasma mycoides var. Capri grown in a medium containing 10 micrograms/ml cholesterol (native organisms) or in cholesterol-free medium (adapted organisms) were treated with phospholipase A2. Hydrolysis of polar lipids (phosphatidylglycerol and diphosphatidylglycerol) only occurred in the adapted cells. Cholesterol replenishment of the membranes of these adapted cells in vitro which involves an increase from 7 micrograms to 66 micrograms cholesterol/mg membrane protein, completely abolished hydrolysis of polar lipid pools by phospholipase A2. This suggests that cholesterol incorporated either during growth or under conditions in vitro has an identical disposition and function in the membrane. This observation further indicates that cholesterol incorporation in M. mycoides var. Capri can be explained in terms of a simple physical adsorption process. Polar-lipid breakdown products resulting from phospholipase A2 action on intact cells, isolated membranes and lipids extracted from adapted organisms were analyzed. In experiments with intact cells [14C]oleic lysoderivatives but not [3H]palmitic lysoderivatives are accumulated within the membranes. In membrane preparations, again only [14C]oleic lysoderivatives are accumulated but transiently. Finally, both [14C]oleic and [3H]palmitic lysoderivatives were produced in phosphatidylglycerol-diphosphatidylglycerol liposomal preparations. From these results it can be concluded that: (a) 80% of the phosphatidylglycerol and diphosphatidylglycerol have an unusual positional distribution of their fatty acid (unsaturated oleic acid in position 1) and (b) membranes of M. mycoides var. Capri contain an active lysophospholipase which more efficiently hydrolyzes palmitic-acid-containing lysoderivatives.

Cardiolipins↗
PubMed1978

Anion diffusion selectivity in a pore model. The phosphatidylcholine-water lamellar phase.

The diffusion coefficients D(cm2.s-1) of the sodium salts of a series of hydrophilic mono- and dicarboxylic acids, have been measured in the hydrophilic layers of phosphatidylcholine-water lamellar phases, as a function of phase hydration. At pH 9.0, the diffusion rates of the anionic (RCOO-) form of the acid exhibit a prominent increase within a narrow range of water content, specific to each anion. This high diffusion rate seems to occur when the Stokes diameter of an anion is equal to the thickness of the aqueous layer between the two planes formed by the quaternary ammonium groups of the choline phosphate dipoles of two facing layers of phosphatidylcholine molecules. This phenomenon demonstrates the importance of the spatial organization of successive binding sites in the rate constant of diffusional processes in hydrophilic channels.

Anions↗
PubMed1977

Cation diffusion selectivity in a pore model. The phosphatidylcholine/water lamellar phase.

The diffusion coefficients D (cm2/s), of four monovalent cations K+, Na+, Rb+ and Cs+ and of Ca2+ have been measured in phosphatidylcholine/water lamellar phase as a function of phase hydration and temperature and in the presence of divalent cations. Diffusion rates vary strongly with phase hydration, between 10(-7) and 10(-6) cm2/s for monovalent and 10(-8) and 10(-7) for Ca2+. The activation energies obtained are relatively small (5--10 kcal/mol). As the phase water content increases, a series of diffusion sequences is obtained, corresponding to the sequences predicted by Eisenman's theory of alkali ion equilibrium selectivity. This diffusional selectivity, which depends exclusively upon non-equilibrium parameters (mobility) within the hydrophilic path is discussed in respect to current theories of pore selectivity.

Cations↗
PubMed1977

Fatty acids diffusion in lecithin multilayers: hydration and PH effects.

The diffusion of the sodium salt of monocarboxylic fatty acids, from formate to stearate, has been studied as a function of water content and pH in lecithin--water lamellar phases. Evolution of the diffusion coefficients with increasing chain length reflects the different localizations of fatty acids in the system. From formate to butyrate, which are mainly restricted to the hydrophilic layer of the phase, diffusion rates decrease rapidly. From butyrate to stearate, fatty acids (anchored at the hydrophilic--lipophilic interface) undergo lateral diffusion and then the decrease of D with increasing chain length is much slower. The diffusion of stereate is already comparable to the diffusion of the lecithin molecule itself. The diffusion rates strongly depend upon phase hydration and pH: it is shown that both parameters control the fatty acid ionization. The variations in diffusion rates observed may be ascribed to the fact that, depending upon their state of ionization, fatty acids assume a different localization and therefore experience different interactions in the lamellar system.

Biological Transport↗
PubMed1977

[Rickettsial arteritis due to Coxiella Burnetii].

Case of an 48 year old man who has presented from 1968 to 1973 a lot of diseases such as: --mitral incompletence discovered in 1968 in Madagascar island in spite of many previous clinical examinations; --acute pneumonia and heart failure in January 1973. Serological reactions of Ricketsia were quite positive; --acute thrombosis of right humeral artery in May 1973. It has been treated by surgical way, bay "desobstruction" and by pass and medical treatment chloramphenicol). Pathologic endartery has been inoculated to an hamster, cobaye. These animal became feverish, and presented an inflammation of testis. A least serological reaction of Ricketsia became positive for all of them; --few weeks, thrombosis of left femoral and posterior tibial arteries treated by surgical and medical ways. Some commens are exposed about evolution of Coxiella Burneti infections, about the frequency of arterial and cardiac lesions, and about the effect of tifomycine which seems to be decreasing and the action of cycline (doxicycline).

Agglutination Tests↗
PubMed1976

An ESR study of the anchoring of spin-labeled stearic acid in lecithin multilayers.

In egg lecithin-water lamellar phases, spin-labeled stearic acid gives two superimposed ESR spectra which are only well resolved when the temperature is greater than 30 degrees C. These two spectral components are attributed to the dissociated and non-dissociated forms of the fatty acid carboxylic group, anchored at two different positions in the polar interface constituted by the hydrated lipid polar heads. Results on such interactions of other functional groups (spin-labeled fatty ester and fatty alcohol) are also presented.

Binding Sites↗
PubMed1976

An ESR study of the hydration steps of lecithin multilayers.

A spin-labeled stearic acid and other spin-labeled molecules have been used for an ESR study of the hydration process of the egg lecithin lamellar phase for water concentrations, CW greater than 10%. Two hydration steps are found for CW approximately 20% and CW congruent to 30%, in good agreement with results of the literature. To explain discontinuities in the behavior of three spin-labeled molecules at CW congruent to 20%, a conformational change of the phosphatidylcholine polar head and a phase transition in the polar interface are proposed.

Binding Sites↗
PubMedDate not supplied

Sterically stabilized BGTC-based lipoplexes: structural features and gene transfection into the mouse airways in vivo.

BACKGROUND: Colloidal stability of lipid/DNA aggregates is a major requirement for cationic lipid-mediated transfection which is particularly difficult to fulfil at the high DNA concentrations used for in vivo gene delivery. Thus, we have investigated the potential of poly(ethyleneglycol) (PEG) conjugates for steric stabilization of lipoplexes formed by bis(guanidinium)-tren-cholesterol/dioleoyl phosphatidylethanolamine (BGTC/DOPE) liposomes, a class of cationic liposomes we have developed over the past few years. METHODS AND RESULTS: We demonstrate that adequate lipophilic PEG derivatives can stabilize BGTC/DOPE lipoplexes formed at high DNA concentration. We also report the results of cryotransmission electron microscopy studies indicating that PEG-stabilized lipoplexes form DNA-coated structures which assemble into clusters exhibiting various complex morphologies. Finally, we report data from in vivo transfection experiments suggesting that PEG-mediated colloidal stabilization of concentrated lipoplex solutions may allow enhanced transfection of the mouse airways via intranasal administration. CONCLUSION: Our results represent an important step towards the design of multimodular BGTC-based systems for improved in vivo gene transfection.

Animals↗
PubMedDate not supplied

FhuA, an Escherichia coli outer membrane protein with a dual function of transporter and channel which mediates the transport of phage DNA.

FhuA (M(r) = 78,900) is an Escherichia coli outer membrane protein which transports the ferric siderophore ferrichrome and is the receptor for phage T5, phi 80 and T1 and for colicin M. FhuA was purified chromatographically in non-ionic detergent (octyl glucoside). The circular dichroism spectrum indicates that FhuA is essentially organized in beta-strands like the majority of proteins of the outer membrane of Gram-negative bacteria. The structural parameters of FhuA were assessed from size exclusion chromatography, sedimention equilibrium and velocity experiments. FhuA is monomeric in solution and functional since binding of phage T5 causes the release of the phage genome, a double-stranded DNA of 121,000 base pairs, into the surrounding medium. Planar lipid bilayer experiments showed that the FhuA transporter is converted into a high conductance channel upon binding of phage T5. FhuA was reconstituted into large unilamellar vesicles (mean diameter 125 nm). Cryo-electron microscopy and fluorescence experiments, using a DNA intercalant YO-PRO 1, showed that binding of T5 to FhuA triggers the transfer of the phage genome into the proteoliposomes without altering their morphology. Two models can account for these observations, which apply both to in vitro and in vivo DNA transport. The simplest model supposes that the naked DNA is transported through the FhuA channel. Alternatively transfer of DNA might be mediated by pb2, the protein forming the phage straight fiber. pb2 would insert either directly in the membrane or inside the FhuA channel.

Bacterial Outer Membrane Proteins↗
PubMedDate not supplied

Fluorescence energy transfer between ATPase monomers in sarcoplasmic reticulum reconstituted vesicles, in the presence of low concentrations of a nonionic detergent.

We measured fluorescence energy transfer between ATPase monomers labeled with either a donor or an acceptor fluorophore, in order to test the hypothesis that the presumably oligomeric sarcoplasmic reticulum ATPase would dissociate into monomers within the membrane on the addition of low nonsolubilizing amounts of a nonionic detergent, C12E18. We found that at low nonsolubilizing detergent concentrations below the critical micellar concentration (c.m.c.), there was indeed direct interaction between the detergent and the protein; however, only solubilizing detergent concentrations reduced fluorescence transfer to a minimum. Considering the current literature, fluorescence energy transfer proved insufficient, at the present time, to confirm or reject the hypothesis.

Adenosine Triphosphatases↗