Properties of Aqueous Dispersions of Phospholipid and Cholesterol

Bruckdorfer, K. Richard; Edwards, Peter A.; Green, C.

doi:10.1111/j.1432-1033.1968.tb00241.x

Cited by 134 publications

(33 citation statements)

References 32 publications

(2 reference statements)

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“…lipid extraction and determination of phospholipid and sterols were all carried out as before [5]. The mixture of plant sterols used to prepare the liposomes was a gift from Dr. L.J.…”

Section: North-holland Publishing Company -Amsterdammentioning

confidence: 99%

Incorporation of plant sterols into membranes and its relation to sterol absorption

Edwards

Green

1972

FEBS Letters

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“…lipid extraction and determination of phospholipid and sterols were all carried out as before [5]. The mixture of plant sterols used to prepare the liposomes was a gift from Dr. L.J.…”

Section: North-holland Publishing Company -Amsterdammentioning

confidence: 99%

Incorporation of plant sterols into membranes and its relation to sterol absorption

Edwards

Green

1972

FEBS Letters

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“…P. Hill and W. L. Glen. The preparation of human plasma /%lipoproteins, liver cell plasma membranes, [14C]cholesterol-labelled erythrocyte ghosts and ovolecithin, the general conditions of incubation, the dispersion of lipids in aqueous media, the determination of lecithin and the measurement of [14C]cholesterol specific activity were all as previously described [ 1,3,5]. The erythrocyte ghosts used in this work were obtained by a slight modification of the earlier method [3].…”

Section: Steroidsmentioning

confidence: 99%

The Incorporation of Steroid Molecules into Lecithin Sols, β‐Lipoproteins and Cellular Membranes

Bruckdorfer

Graham²,

Green³

1968

European Journal of Biochemistry

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I . The dispersion of various steroids in aqueous solution with ovolecithin was investigated and the following molar ratios of lecithin to steroid obtained: cholesterol, 1 : 1 ; 7-dehydrocholesterol, 13.3: 1 ; ergosterol, 13.1 : 1 ; sitosterol, 2.0: 1 ; sterophenol 4.2: 1 ; cholesta-4,6-dien-3-one, 2.0: I ; cholest-4-en-3-one, 1.7: 1.2. The cholesterol contents of sterol-depleted cellular membranes can be restored to their original level by incubation with plasma or an equimolar dispersion of cholesterol and ovolecithin, in the presence of I0 O/io dimethylsulphoxide (v/v).3. Cholesta-4,6-dien-3-one, cholest-4-en-3-one, 7-dehydrocholesterol and sterophenol can exchange readily with the cholesterol of erythrocyte ghosts and can replace cholesterol molecules removed from the membrane. Ergosterol can do so only to a very limited extent. 4.7-Deh ydrocholesterol exchanges between rat erythrocyte ghosts and human plasma p-lipoproteins in the same way as cholesterol. Cholesta-4,6-dien-3-one and cholest-4-en-3-one also exchange but, in addition, there is a net uptake of these steroids by B-lipoproteins. The extra steroid entering the lipoproteins is probably dissolved in the hydrophobic core of the latter.5 . The exchange of cholesta-4,6-dien-3-one between erythrocyte ghosts and lecithin/steroid dispersions or B-lipoproteins is much more rapid than that of cholesterol. The rate of exchange of the dienone, like that of cholesterol. is increased by the addition of a small quantity of dimethylsulphoxide to the medium.The previous paper [I] described certain properties of aqueous dispersions of phospholipids and cholesterol and these were compared with plasma lipoproteins and cellular membranes. I n continuation of these studies, the ability of steroid molecules, differing only slightly from the naturally occurring cholesterol, to enter phospholipid sols, lipoproteins and membranes, and their subsequent behaviour, have been investigated. The compounds involved are shown in Fig. I. MATERIALS AND NETHODS SteroidsCholesterol,7-dehydrocholesterol and ergosterol were purified and (determined as previously described [2,3]. Cholesta-4,6-dien-3-one and cholest-4-en-3-one were obtained from British Drug Houses Ltd. Poole, Dorset and sitos terol from the Aldrich Chemical Company Inc. (Milwaukee, Wis., U.S.A.). Sterophenol was prepared and purified according to Wilds and Djerassi [4]. Sitosterol was determined in the same way as cholesterol and the others from their spectra Table 2 . RESULTS Dispersion of Steroids with LecithinOptically clear, aqueous dispersions of the stcroids with ovolecithin were prepared as described before [ 11 and their composition determined. The results are shown in Table 1. It can be seen that cholesterol is best solubilized a t about 1 mole per mole of lecithin while the other naturally occurring animal sterol tested, 7-dehydrocholesterol, is solubilized to only 7.5 of this level. Ergosterol is solubilized to roughly the same extent as 7-dehydrocholesterol whereas the Incorporation of 7-D~,hydrocholestero...

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“…Extraction of native cholesterol from the surface membrane can be performed with lecithin liposomes (23)(24)(25), and in normal lymphocytes from mice or rats this resulted in a decrease in the microviscosity to a value similar to that found in the mouse lymphoma cells (18). The Unesterified cholesterol is believed to be present almost exclusively in the cell surface membrane (9, 32), and to a first approximation the membrane microviscosity depends only on its cholesterol to phospholipid molar ratio (Fig.…”

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“…Introduction of exogenous cholesterol into the surface membrane of intact cells can be performed with (mole/mole) lecithin-cholesterol liposomes (23)(24)(25), and in the malignant lymphoma cells from mice it resulted in an increase in the microviscosity to a value characteristic of mouse or rat normal lymphocytes (18). Extraction of native cholesterol from the surface membrane can be performed with lecithin liposomes (23)(24)(25), and in normal lymphocytes from mice or rats this resulted in a decrease in the microviscosity to a value similar to that found in the mouse lymphoma cells (18).…”

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Cholesterol as a Bioregulator in the Development and Inhibition of Leukemia

Inbar

Shinitzky

1974

Proc. Natl. Acad. Sci. U.S.A.

115

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Leukemia in mice and humans is accompanied by a marked deficiency of unesterified cholesterol in the surface membrane of leukemic cells as compared to normal leukocytes. This deficiency induces a significant reduction in their membrane microviscosity. Since cholesterol in the cell surface membrane is exchangeable with cholesterol in the serum lipoproteins, concomitant to the cellular deficiency of cholesterol, the average level of cholesterol in the blood serum of leukemic patients is substantially below the average normal level. Based on these observations and the effect of membrane microviscosity on biological functions, a working hypothesis that describes the role of cholesterol in the development and inhibition of leukemia is suggested. This hypothesis can also account for the effect of cholesterol and membrane microviscosity on various other cellular activities of leukocytes.

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Properties of Aqueous Dispersions of Phospholipid and Cholesterol

Cited by 134 publications

References 32 publications

Incorporation of plant sterols into membranes and its relation to sterol absorption

Incorporation of plant sterols into membranes and its relation to sterol absorption

The Incorporation of Steroid Molecules into Lecithin Sols, β‐Lipoproteins and Cellular Membranes

Cholesterol as a Bioregulator in the Development and Inhibition of Leukemia

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