Preparation and characteristics of lipid vesicles

Miyamoto, Vernon K.; Stoeckenius, Walther

doi:10.1007/bf02431974

Cited by 62 publications

(17 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thin sections of lipoproteins were obtained on samples concentrated by membrane filtration (31) using membranes of 0.025-,um pore size (Millipore Corp., Bedford, Mass.). Samples were fixed first in osmium tetroxide for 24-8 h at 4°C, filtered, and then block-stained in 2% aqueous uranyl acetate for 24-48 h at 370C.…”

Section: Methodsmentioning

confidence: 99%

Discoidal bilayer structure of nascent high density lipoproteins from perfused rat liver.

Hamilton¹,

Williams²,

Fielding³

et al. 1976

J. Clin. Invest.

521

136

View full text Add to dashboard Cite

A B S T R A C T Rat livers were perfused for 6 h without added plasma proteins using washed erythrocytes and buffer in a recirculating system. An inhibitor to the enzyme lecithin-cholesterol acyltransferase (5,5'-dithionitrobenzoic acid) was added in some experiments to prevent modification of substrate-lipids contained in secreted lipoproteins. The inhibitor did not detectably alter hepatic ultrastructure or gas exchange, but it inhibited the secreted lecithin-cholesterol acyltransferase by more than 85%. Very low density lipoproteins in perfusate were unaltered but the high density lipoproteins obtained from livers perfused with the inhibitor appeared disk-shaped in negative stain by electron microscopy with a mean edge thickness of 46±5 A and a mean diameter of 190±25 A. The high density lipoproteins were composed predominantly of polar lipids and protein with only small amounts of cholesteryl esters and triglycerides. The major apoprotein of these discoidal fractions had the same electrophoretic mobility as the arginine-rich apoprotein, whereas plasma high density lipoproteins contained mainly the A-I apoprotein. In all these respects the discoidal perfusate high density lipoproteins closely resemble those found in human plasma which is deficient in lecithin-cholesterol acyltransferase. Perfusate high density lipoproteins obtained in the absence of the enzyme inhibitor more closely resembled plasma high density lipoproteins in Portions of this work have appeared in an abstract and in a review (1, 2).Dr. Hamilton is the recipient of a Research Career Development Award. Dr. Williams was the recipient of a Postdoctoral Fellowship from the National Heart and Lung Institute. Dr. Fielding was an Established Investigator of the American Heart Association.Received for publication 30 January 1976 and in revised form 12 April 1976. chemical composition (content of cholesteryl esters and apoproteins) and in electron microscopic appearance. Purified lecithin-cholesterol acyltransferase synthesized cholesteryl esters at a substantially faster rate from substrate lipids of perfusate high density lipoproteins than those from plasma. The discoidal high density lipoproteins were the best substrate for this reaction. Thin sections of plasma high density lipoproteins indicated a spherical particle whereas discoidal high density lipoproteins stained with the characteristic trilaminar image of membranes. These observations suggest that the liver secretes disk-shaped lipid bilayer particles which represent both the nascent form of high density lipoproteins and preferred substrate for lecithin-cholesterol acyltransferase. INTRODUCTIONThe plasma lipoproteins are usually separated into four major physically defined groups although it is recognized that heterogeneity exists within each. This heterogeneity is further complicated by movements of both lipids and apoproteins between particles of the different groups. One approach to obtain a clearer understanding of the physiological significance of the different plasma lipoproteins h...

show abstract

Section: Methodsmentioning

confidence: 99%

Discoidal bilayer structure of nascent high density lipoproteins from perfused rat liver.

Hamilton¹,

Williams²,

Fielding³

et al. 1976

J. Clin. Invest.

521

136

View full text Add to dashboard Cite

show abstract

“…The technique for preparation of purple membrane vesicles is also used essentially as described (Racker, 1973) with the following modifications. The dried lipid is first sonicated alone and lipid vesicle formation is monitored by the light scattering at 500 nm (Miyamoto & Stoeckenius, 1971), Scattering decreases and becomes constant after about 30 min of sonication. The purple membrane is then added and sonication continued for a short time as described in Results.…”

Section: Electron-microscopymentioning

confidence: 99%

Purple membrane vesicles: Morphology and proton translocation

Hwang

Stoeckenius

1977

J. Membrain Biol.

Self Cite

View full text Add to dashboard Cite

Purple membrane vesicles prepared by different techniques differ widely in their morphology and ability to establish a proton gradient in the light. The procedures used to prepare active vesicles do not completely dissociate the purple membrane and thus preserve a preferential orientation of the protein, while most of the lipid is exchanged for added lipid. Responses to illumination are largely determined by the size of the vesicles and the degree to which bacteriorhodopsin is preferentially oriented. Any attempt to compare the interaction of different lipids with bacteriorhodopsin by measuring the pH response must take these factors into account. With an improved technique we have obtained vesicles of rather uniform size and bacteriorhodopsin orientation, which accumulate protons with an initial rate of 160 ng H+ sec-1 mg-1 protein at light intensities of 10(6) erg cm-2 sec-1. The kinetics of the process are complex and at present insufficiently understood.

show abstract

“…As NH 3 concentration increased, disruption increased proportionately until there were no recognizable membrane structures remaining, except remanents of the cellular membrane system. These remains are similar in shape to artificial membranes formed from hydrated phospholipids (5,16). The circular shape is the most energetically favorable conformation for phospholipids to assume in an aqueous environment and therefore it is not surprising that disrupted cellular membranes should assume a similar shape.…”

Section: Resultsmentioning

confidence: 94%

The effects of anhydrous ammonia on membrane stability ofP.hymatotrichum omnivorum

Rush

Lyda

1982

Mycopathologia

View full text Add to dashboard Cite

Sclerotia and mycelium of Phymatotrichum omnivorum were exposed to anhydrous ammonia (NH3) and then observed with an electron microscope in order to determine the effects of the NH 3 treatment on the fungal membranes. Sclerotia were exposed to four rates of NH3: 28, 56, 84, and 112 #g NH3/ml of air for 24 hours. At 28 ~g/ml, the plasmalemma became wavy and the mitochondrial cristae began to swell and disperse. At 56 #g NH3/ml the plasmalemma showed breakage and formation of vesicles, and all other membrane systems within the cell were broken and distorted. All membranes were totally disrupted and no organelles were recognizable at 84 ~g NH3/ml. Mycelium was exposed to 2, 4, 8,20, and 40 #g NH3/ml for one minute. Damage to cell membranes was not observed at NH 3 conc. up to 4 #g/ml. At 8 #g NH3/ml the plasmalemma was broken and the mitochondria were disrupted. At 20 ~g/ml and above, all internal organization was destroyed.

show abstract

Preparation and characteristics of lipid vesicles

Cited by 62 publications

References 24 publications

Discoidal bilayer structure of nascent high density lipoproteins from perfused rat liver.

Discoidal bilayer structure of nascent high density lipoproteins from perfused rat liver.

Purple membrane vesicles: Morphology and proton translocation

The effects of anhydrous ammonia on membrane stability ofP.hymatotrichum omnivorum

Contact Info

Product

Resources

About