stearates and 1-2-distearoyllecithin

The fluorescence-labeled closo-dodecaborane lipid (FL-SBL) was synthesized from (S)-(+)-1,2-isopropylideneglycerol as a chiral starting material. FL-SBL was readily accumulated into the PEGylated DSPC liposomes prepared from DSPC, CH, and DSPE-PEG-OMe by the post insertion protocol. The boron concentrations and the fluorescent intensities of the FL-SBL-labeled DSPC liposomes increased with the increase of the additive FL-SBL, and the maximum emission wavelength of the liposomes appeared at 531 nm. A preliminary in vivo imaging study of tumor-bearing mice revealed that the FL-SBL-labeled DSPC liposomes were delivered to the tumor tissue but not distributed to hypoxic regions.

Topics: Animals; Boron; Boron Compounds; Drug Delivery Systems; Female; Fluorescence; Liposomes; Mice; Neoplasms; Oxadiazoles; Phosphatidylcholines; Phosphatidylethanolamines; Polyethylene Glycols; Stearates; Tissue Distribution

Dipalmitoyl phosphatidylcholine is the principal component of lung surfactant, and knowledge of its behavior as a film spread at the air-water interface is essential for understanding how lung surfactant itself works. We therefore studied the collapse rates of very low surface tension air-water monolayers of dipalmitoyl, dimyristoyl, and palmitoyl-myristoyl phosphatidylcholines at different temperatures. In each case we found that the monolayers abruptly became unstable at temperature 3-4 degree C above their bulk lipid-water phase transition temperatures (Tc). This accords with a comparable increase in Tc occurring in bulk systems subjected to high pressure. These findings are also consistent with the behavior of isolated rat lungs, which have been found to require higher transmural pressures to maintain a given volume on deflation when kept at temperature above the Tc of dipalmitoyl phosphatidylcholine.

Topics: Air; Dimyristoylphosphatidylcholine; Phosphatidylcholines; Pulmonary Surfactants; Stearates; Surface Tension; Temperature; Water

The uptake of free and liposome-entrapped 125I-labelled polyvinylpyrrolidone was measured in an intestinal sac preparation from adult rats. At an equal concentration of 125I-labelled polyvinylpyrrolidone, the rate of uptake of the liposome-entrapped macromolecule by the tissue was over 4-times that of the free macromolecule. The quantity of 125I-labelled polyvinylpyrrolidone present in the serosal fluid of gut sacs, cultured for 2 h, was 1.8-times greater when the macromolecule was entrapped in liposomes than when it was free in the culture medium. When gut sacs were cultured with liposome-entrapped macromolecule, approx. 50% of the total 125I-labelled polyvinylpyrrolidone present in the serosal fluid was associated with a 100 000 X g liposomal pellet.

Topics: Animals; Biological Transport; Cholesterol; Intestine, Small; Kinetics; Liposomes; Phosphatidylcholines; Rats; Stearates

Previous observations on serum-induced leakage of liposome contents from egg phosphatidylcholine liposomes (Allen, T.M. and Cleland, L.G. (1980) Biochim. Biophys, Acta 597, 418--426) have been extended in order to examine the role of the phase transition and phospholipid backbone in leakage. The high-density lipoprotein (HDL) fraction has been purified from human serum and the rate of transfer of radioactively labelled phospholipids from sonicated liposomes to high-density lipoproteins has been examined. Results obtained from the calcein dequenching method for serum-induced leakage of liposome contents showed that as the proportion of solid phospholipid (distearoyl phosphatidylcholine, Tc = 56 degrees C) increased, relative to the proportion of egg phosphatidylcholine, the half-time for retention of liposome contents at 37 degrees C in the presence of serum also increased. Including increasing amounts of bovine brain sphingomyelin (Tc = 30 degrees C) in egg phosphatidylcholine liposomes also substantially decreased leakage from liposomes in the presence of serum at 37 degrees C. 14C-labelled egg phosphatidylcholine was found to transfer readily from liposomes to purified HDL, as did 14C-labelled dioleoyl phosphatidylcholine. Including cholesterol in egg phosphatidylcholine liposomes decreased the rate of transfer of phospholipid to HDL. 14C-labelled distearoyl phosphatidylcholine did not exchange readily with HDL. These results are consistent with the interpretation that tightening bilayer packing prevents the apolipoprotein-mediated transfer of phospholipid to HDL and slows the leakage of liposome contents associated with this transfer. [14C]Sphingomyelin also did not exchange readily with HDL. This does not appear to be a phase transition effect as the majority of sphingomyelin is above its phase transition at 37 degrees C. The failure of sphingomyelin to exchange readily with HDL is interpreted as being due to intermolecular hydrogen bonding between the sphingosine backbones of the sphingomyelin molecule.

Topics: Animals; Blood; Cattle; Cholesterol; Lipid Bilayers; Lipoproteins, HDL; Liposomes; Phosphatidylcholines; Phospholipids; Sphingomyelins; Stearates

Vesicles of a variety of types of phosphatidylcholine have been shown to be suitable donors of phosphatidylcholine to intact rat erythrocytes in the presence of a specific phosphatidylcholine exchange protein. Coincident with the progression of phosphatidylcholine exchange is the onset of hemolysis, occurring at degrees of exchange characteristic for the type of phosphatidylcholine employed. During exchange with the dimyristoyl, dipalmitoyl and distearoyl species, hemolysis starts when 27%, 25% and 22% of the native phosphatidylcholine is replaced by these disaturated species, respectively. In the case of dielaidoylglycerophosphocholine and 1-stearoyl-2-oleoylglycerophosphocholine hemolysis starts after the introduction of 30% and 28%, respectively. In contrast, the replacement of native erythrocyte phosphatidylcholine with egg phosphatidylcholine, and the dioleoyl species up to levels of 60% does not result in rapid hemolysis. Despite such functional consequences, overall contents of the individual phospholipids and cholesterol are normal. Accompanying the biochemical events are morphologic changes, including echinocyte an spherocyte formation. The structure-function implications and possible mechanisms of hemolysis are discussed.

Topics: Animals; Cattle; Dimyristoylphosphatidylcholine; Erythrocyte Membrane; Erythrocytes; Hemolysis; Liposomes; Microscopy, Electron, Scanning; Phosphatidylcholines; Pulmonary Surfactants; Rats; Stearates; Structure-Activity Relationship