The action of steroids and triton X-100 upon phospholipid/cholesterol structures

Weissmann, Gerald; Sessa, Grazia; Weissmann, S.

doi:10.1016/0006-2952(66)90198-5

Cited by 81 publications

(21 citation statements)

References 20 publications

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“…Delivery of cholesterol to depleted membranes was accomplished using cholesterol-loaded m␤cd, saturated cholesterol solutions (Alivisatos et al, 1977), and cholesterol-loaded 2-hydroxypropyl-␤-cyclodextrin (hp␤cd), a related cyclodextrin with a relatively lower affinity for membrane cholesterol. Studies were also carried out with polyene antibiotics, a class of molecules known to bind and effectively sequester sterols in the membrane (Weissmann and Sessa, 1967;Norman et al, 1972a;Norman et al, 1972b;Patterson et al, 1979). Cholesterol oxidase was used to metabolically 'remove' cholesterol from the membranes and effectively disrupt functional microdomains (Xu and London, 2000;Samsonov et al, 2001) The results of these experiments support the role of cholesterol as a pre-fusion organizer (Lang et al, 2001;Salaun et al, 2005), but also indicate that cholesterol functions more directly in the native molecular mechanism of bilayer merger.…”

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confidence: 89%

Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion

Churchward

Rogasevskaia

Höfgen

et al. 2005

Journal of Cell Science

174

312

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The process of regulated exocytosis is defined by the Ca2+-triggered fusion of two apposed membranes, enabling the release of vesicular contents. This fusion step involves a number of energetically complex steps and requires both protein and lipid membrane components. The role of cholesterol has been investigated using isolated release-ready native cortical secretory vesicles to analyze the Ca2+-triggered fusion step of exocytosis. Cholesterol is a major component of vesicle membranes and we show here that selective removal from membranes, selective sequestering within membranes, or enzymatic modification causes a significant inhibition of the extent, Ca2+ sensitivity and kinetics of fusion. Depending upon the amount incorporated, addition of exogenous cholesterol to cholesterol-depleted membranes consistently recovers the extent, but not the Ca2+ sensitivity or kinetics of fusion. Membrane components of comparable negative curvature selectively recover the ability to fuse, but are unable to recover the kinetics and Ca2+ sensitivity of vesicle fusion. This indicates at least two specific positive roles for cholesterol in the process of membrane fusion: as a local membrane organizer contributing to the efficiency of fusion, and, by virtue of its intrinsic negative curvature, as a specific molecule working in concert with protein factors to facilitate the minimal molecular machinery for fast Ca2+-triggered fusion.

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mentioning

confidence: 89%

Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion

Churchward

Rogasevskaia

Höfgen

et al. 2005

Journal of Cell Science

174

312

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“…Synthetic lipid structures with varying ratios of phospholipid to cholesterol can be prepared, the response of which to the several polyenes can be made to resemble that of erythrocytes or of mitochondria. 22 Finally, the lesions produced in the matrix of cartilage alone by the action of filipin deserve attention. Histochemical stains for acid mucopolysaccharides demonstrated that loss of polyanions, accompanied by fibrillation of cartilage and formation of chondrocyte clusters, was evident in areas of articular cartilage which were not in direct apposition to inflammatory pannus.…”

Section: Discussionmentioning

confidence: 99%

Arthritis induced by Filipin in rabbits

Weissmann

Pras

Rosenberg

1967

Arthritis & Rheumatism

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“…Liposomes were prepared under sterile conditions as described by Weissmann et a1 (5)(6)(7). Briefly, for each set of experiments, 60 pmoles of phosphatidylcholine, 17.16 pmoles of dicetyl phosphate, and 8.58 pmoles of cholesterol (molar ratio 7:2: 1) were dissolved in chloroform in a 100-ml round-bottomed flask.…”

Section: Methodsmentioning

confidence: 99%

Liposome‐induced synovitis in rabbits: Light and electron microscopic studies

Clayburne

et al. 1986

Arthritis & Rheumatism

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A solution containing synthetic liposomes was injected into rabbit knee joints. This induced light and electron microscopic findings very similar to those seen in acute or chronic arthritis, not attributable to any mechanism other than to spherulites, in humans. Synovial fluid studies revealed leukocytosis and abundant extracellular, and/or intracellular positively birefringent spherulites, which appeared as Maltese crosses. Histologic studies of synovial membranes showed infiltration with polymorphonuclear neutrophils or mononuclear cells. Examination of the synovial fluids and synovial membranes by electron microscopy revealed intracellular multilayered membranous arrays of varying shapes. These observations suggest that further consideration should be given to a phlogistic role for similar spherulites found in some patients.Intracellular birefringent lipid spherulites, appearing as Maltese crosses, have been reported in the synovial fluid (SF) of several patients with unexplained acute or chronic arthritis (1-3). These spherulites consist of multilayered structures similar to artificially prepared liposomes, smectic mesophases, or hydrated lipid liquid crystals (4). It was suggested that these liposome-like spherulites might have induced inflammation similar to that seen in crystal-induced arthritis (1-3), but there was no proof of phlogistic potential for such spherulites.In this paper, we have shown that synthetic liposomes which have the appearance of a Maltese cross can induce inflammation when injected into rabbit joints. We have also compared the pathologic findings in this experimental model with observations made in arthritis in humans. MATERIALS AND METHODSLipids. L-a-phosphatidylcholine type VII-E and cholesterol were purchased from Sigma Chemical Company (St. Louis, MO). Dicetyl phosphate was obtained from Alfa Products (Danvers, MA).Preparation of liposomes. Liposomes were prepared under sterile conditions as described by . Briefly, for each set of experiments, 60 pmoles of phosphatidylcholine, 17.16 pmoles of dicetyl phosphate, and 8.58 pmoles of cholesterol (molar ratio 7:2: 1) were dissolved in chloroform in a 100-ml round-bottomed flask. After rotary evaporation, a uniformly thin lipid film was formed. Six milliliters of 0.145M KH2P04 (pH 7.4) solution was added to the flask and the lipid film was dispersed by vortexing (10 minutes at 23°C). Thereafter, the suspension (15 pmoles of lipid/ml) was allowed to equilibrate for 2 hours at 23°C.The resulting liposomes were viewed under compensated polarized light and were strongly positive birefringent spherulites (i.e., the 2 blue portions of the Maltese cross

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The action of steroids and triton X-100 upon phospholipid/cholesterol structures

Cited by 81 publications

References 20 publications

Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion

Cholesterol facilitates the native mechanism of Ca2+-triggered membrane fusion

Arthritis induced by Filipin in rabbits

Liposome‐induced synovitis in rabbits: Light and electron microscopic studies

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