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Liposomes of defined size and homogeneity have been prepared by sequential extrusion of the usual multilamellar vesicles through polycarbonate membranes. The process is easy, reproducible, produces no detectable degradation of the phospholipids, and can double the encapsulation efficiency of the liposome preparation. Multilamellar vesicles extruded by this(More)
Liposomes can be prepared by a combination of reverse phase evaporation and sequential extrusion through polycarbonate membranes. The vesicles have diameters in the range 0.05-0.5 micron and are mostly unilamellar as indicated by electon microscopy, capture volume, and availability of reactive groups to periodate oxidation. Sequential extrusion leads to a(More)
The interaction of phosphatidylserine vesicles with Ca2+ and Mg2+ has been examined by several techniques to study the mechanism of membrane fusion. Data are presented on the effects of Ca2+ and Mg2+ on vesicle permeability, thermotropic phase transitions and morphology determined by differential scanning calorimetry, X-ray diffraction, and freeze-fracture(More)
The effect of divalent metals on the interaction and mixing of membrane components in vesicles prepared from acidic phospholipids has been examined using freeze-fracture electron microscopy and differential scanning calorimetry. Ca2+, and to a certain extent Mg2+, induce extensive mixing of vesicle membrane components and drastic structural rearrangements(More)
Freeze-fracture electron microscopy was used to study the morphological changes occurring following the addition of Ca-2+ to sonicated preparations of phosphatidylserine in aqueous NaCl buffer. Before the addition of Ca-2+, preparations contained only small (200-500 A diameter) spheroidal vesicles. After the addition of Ca-2+ (10 mM) and incubation for 1 h(More)
The membrane stabilization effect of cholesteryl hemisuccinate (CHEMS) and the sensitivity of the CHEMS-phosphatidylethanolamine membranes to protons and calcium ions were studied by differential scanning calorimetry, freeze-fracture electron microscopy, and 31P NMR. (1) At neutral pH, the addition of 8 mol % CHEMS to transesterified egg(More)
The toxicity and therapeutic efficacy of free adriamycin (AM) and AM entrapped in standardized liposomes (AM-MLV) were evaluated in normal mice and in mice bearing M 5076 murine tumor, which metastasizes to the liver after i.v. and s.c. transplants of tumor cell suspensions. Acute and chronic toxicity to AM could be reduced by drug encapsulation in(More)
The interaction and mixing of membrane components in sonicated unilamellar vesicles and also non-sonicated multilamellar vesicles prepared from highly purified phospholipids suspended in NaCl solutions has been examined. Electron microscopy and differential scanning calorimetry were used to characterize the extent and kinetics of mixing of membrane(More)