[Energy and protein requirements in illness and trauma].
Explore the source record for details and available documents.
Basal Metabolism↗
Biomedical subjects
W J Gerritsen
Publications and source records attributed to W J Gerritsen.
Alkali-extraction of membranes from mouse erythrocytes infected with Plasmodium berghei.
Alkali-extracted membrane material from hypotonically lysed Plasmodium berghei-infected mouse erythrocytes has been analyzed by dodecyl sulphate polyacrylamide gel electrophoresis and fractionated by discontinuous sucrose gradient centrifugation. Components characteristic for the protein pattern associated with P. berghei infection have been recovered in the alkali-extracted material. Parasite components, free of host cell membrane contamination, have been obtained as a high-density fraction from sucrose gradients. This fraction is characterized by polypeptides with apparent molecular weight of 71,000 and 52,000.
Animals↗
Ca2+-induced changes in the barrier properties of cardiolipin/phosphatidylcholine bilayers.
(1) A selective increase in permeability is induced in cardiolipin/phosphatidylcholine bilayers at Ca2+ concentrations of 1--3 mM. At higher concentrations of Ca2+ the permeability barrier is completely destroyed. (2) The selective increase in permeability is correlated with the formation of lipid particles visualized by freeze-fracture electron microscopy and an isotropic signal in 31P-NMR spectra. (3) Lowering the Ca2+ concentration shows reduction in permeability but the formation of the lipid particles is a non-reversible process. (4) At higher Ca2+ concentrations, 31P-NMR spectra and freeze-fracture results indicate the formation of the hexagonal phase, explaining the disappearance of the permeability barrier.
Calcium↗
Lipidic particles.
A new type of lipid organization is observed in mixtures of phosphatidylcholine with cardiolipin in the presence of Ca++, monoglucosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterized by an isotropic 31P NMR signal and is visualized by freeze fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer. It will be shown that such particles and pits appear on the fusion site during fusion of unilamellar vesicles of an equimolar mixture of phosphatidylcholine and cardiolipin in the presence of Ca++.
Calcium↗
The transbilayer movement of phosphatidylcholine in vesicles reconstituted with intrinsic proteins from the human erythrocyte membrane.
Vesicles have been prepared from 18 : 1c/18 : 1c-phosphatidylcholine with or without purified glycophorin or partially purified band 3 (obtained by organomercurial gel chromatography). The vesicles have been characterized by freeze-fracture electron microscopy, binding studies to DEAE-cellulose, 31P-NMR and K+ trap measurements. Pools of phosphatidylcholine available for exchange have been investigated using phosphatidylcholine exchange protein from bovine liver. The protein-containing vesicles both exhibit exchangeable pools larger than the fraction of phosphatidylcholine in the outer monolayer, whereas in the protein-free vesicles the exchangeable pool is consistent with the outer monolayer. The results indicate that both glycophorin and the partially purified band 3 preparation enhance the transbilayer movement of phosphatidylcholine.
Electrophoresis, Polyacrylamide Gel↗
The lipidic particle as an intermediate structure in membrane fusion processes and bilayer to hexagonal HII transitions.
Small unilamellar vesicles comprised of a mixture of phosphatidylethanolamine/phosphatidylcholine/cholesterol (3 : 1 : 2) fuse to form large multilamellar vesicles on increasing the temperature from 0 to 50 degrees C. This event is associated with the appearance of lipidic particles at the fusion sites, consistent with a role as intermediary structures during the fusion process. Further, for phosphatidylcholine/cardiolipin (1 : 1) liposomes in the presence of Mn2+ a direct relationship between lipidic particles and the hexagonal (HII) phase is demonstrated which suggests that lipidic particles can also occur as intermediaries between bilayer and hexagonal (HII) structures.
Cell Fusion↗
Ca2+-induced isotropic motion and phosphatidylcholine flip-flop in phosphatidylcholine-cardiolipin bilayers.
Ca2+ induces a structural change in phosphatidylcholine-cardiolipin bilayers, which is visualised by freeze-fracturing as lipidic particles associated with the bilayer and is detected by 31P-NMR as isotropic motion of the phospholipids. In this structure a rapid transbilayer movement of phosphatidylcholine and a highly increased permeability towards Mn2+ are observed.
Calcium↗
The occurrence of lipidic particles in lipid bilayers as seen by 31P NMR and freeze-fracture electron-microscopy.
A new type of lipid organization is observed in mixtures of phosphatidyl-choline with cardiolipin (in the presence of Ca2+), monoglycosyldiglyceride and phosphatidylethanolamine (in the presence of cholesterol). This phase is characterised by an isotropic 31P NMR signal and is visualised by freeze-fracturing as particles and pits on the fracture faces of the lipid bilayer. As the most favourable model for this phase we propose the inverted micelle sandwiched in between the two monolayers of the lipid bilayer.
Calcium↗
Fusion of phospholipid vesicles in association with the appearance of lipidic particles as visualized by freeze fracturing.
The addition of Ca2+ to small unilamellar vesicles of an equimolar mixture of egg phosphatidylcholine and cardiolipin induces fusion of these vesicles in association with the appearance of lipidic particles on the fusion sites.
Animals↗
The lateral distribution of intramembrane particles in the erythrocyte membrane and recombinant vesicles.
Triton X-100 (in concentrations which did not cause a significant solubilization of membrane material) caused aggregation of the intramembrane particles of human erythrocyte ghosts. Ghosts from which the extrinsic proteins had been removed by alkali treatment showed a temperature-induced aggregation of the particles. With virtually no spectrin present, the particles in these stripped ghosts could still be aggregated by manipulations with ionic strength and pH, or by the addition of calcium. Recombinant vesicles were made from a Triton X-100 extract and a mixture of phospholipids with a composition which resembled that of the inner monolayer of erythrocyte membrane. In these recombinants the same manipulations with ionic strength and pH and the addition of calcium caused a rearrangement of the particles, resulting in the appearance of particle-free areas. In recombinants prepared from a Triton X-100 extract and egg phosphatidylcholine the lateral distribution of the particles was not altered by these manipulations. It is concluded that in the erythrocyte membrane the intramembrane particles can be aggregated by effects of external agents on lipid components. In this light the role of spectrin in stabilizing the membrane by interactions with lipids in the inner monolayer is discussed.
Erythrocyte Membrane↗
A 13C NMR method for determination of the transbilayer distribution of phosphatidylcholine in large, unilamellar, protein-free and protein-containing vesicles.
(1) Large unilamellar vesicles have been prepared from N-[Ne3-13C]-18 : 1c/18 : 1c-phosphatidylcholine, both with and without the major intrinsic proteins from the human erythrocyte membrane incorporated in the bilayer. (2) It is shown that the inside-outside distribution of the lipid molecules in these large unilamellar structures can be determined using 13C NMR. (3) Large vesicles of 18 : 1c/18 : 1c-phosphatidylcholine containing glycophorin show an enhanced permeability to Dy3+. It is shown that the permeability barrier of these vesicles can be restored by addition of 10 mol% 18 : 1c/18 : 1c-phosphatidylethanolamine or 1-18 : 1c-lysophosphatidylcholine.
Animals↗
Freeze-fracture appearance and disposition of band 3 protein from the human erythrocyte membrane in lipid vesicles.
Single bilayer lipid vesicles were formed by removal of Triton X-100 with Bio Beads SM-2 from a mixture of egg lecithin and a Triton X-100 extract of human erythrocyte ghosts. Upon freeze-fracturing, these vesicles showed intramembrane particles, similar to those seen in the erythrocyte membrane. Similar particles were also observed when a partially purified band 3 preparation was used instead of the crude Triton X-100 extract. In the reconstituted vesicles an equal distribution of the intramembrane particles between the two fracture faces was observed. This is in contrast to the unequal distribution of the particles in the erythrocyte membrane, which did not seem to be altered by removal of the extrinsic proteins. From digestion studies with trypsin and chymotrypsin of vesicles, reconstituted from the crude X-100 extract, it is concluded that band 3 protein in the vesicle bilayer has a similar orientation as in the native membrane.
Blood Proteins↗
Polyene antibiotic-sterol interactions in membranes of Acholeplasma laidlawii cells and lecithin liposomes. I. Specificity of the membrane permeability changes induced by the polyene antibiotics.
Explore the source record for details and available documents.
Acholeplasma laidlawii↗
Polyene antibiotic-sterol interactions in membranes of Acholesplasma laidlawii cells and lecithin liposomes. II. Temperature dependence of the polyene antibiotic-sterol complex formation.
Explore the source record for details and available documents.
Acholeplasma laidlawii↗