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1.
Antibodies to liposomal phosphatidylserine and phosphatidic acid   总被引:1,自引:0,他引:1  
Polyclonal antisera to phosphatidylserine or phosphatidic acid were induced in rabbits by injecting liposomes containing phosphatidylserine or phosphatidic acid and lipid A. Adsorption of antisera with liposomes containing different phospholipids revealed that some degree of reactivity with one or more phospholipids other than the immunizing phospholipid was often observed. However, cross-reactivity with other phospholipids was not a universal phenomenon, and one antiserum to phosphatidylserine failed to cross-react (i.e., was not adsorbed) with liposomes containing other phospholipids. All of the antisera were inhibited by soluble phosphorylated haptens (e.g., phosphocholine but not choline), but one of the antisera to phosphatidylserine was inhibited both by phosphoserine and by serine alone. Liposomal membrane composition influenced the activity of antiserum to phosphatidylserine. Regardless of whether unsaturated (beef brain) or saturated (dimyristoyl) phosphatidylserine was used in the immunizing liposomes, the antisera reacted more vigorously with liposomes containing unsaturated than saturated phosphatidylserine. We conclude that liposomes containing lipid A can serve as vehicles for stimulating polyclonal antisera to phosphatidylserine and phosphatidic acid. Although cross-reactivity with certain other phospholipids can be observed, sera from selected animals apparently can exhibit a high degree of specific activity to the immunizing phospholipid antigen.  相似文献   

2.
Form A of the beta-D-galactoside alpha 2----3 sialyltransferase from porcine submaxillary glands was incorporated into liposomes. Incorporation was achieved by gel filtration of the enzyme in the presence of octylglucoside-phospholipid micelles. As detergent was removed during gel filtration, liposomes (average diameter, 370 A) with bound enzyme were formed and emerged unretarded from the column. The recovery of enzyme activity in the liposomes was about 40% of the initial activity starting with as little as 9 micrograms of transferase. Chromatography on Sepharose CL6B and sucrose density gradient centrifugation confirmed the association of enzyme with liposomes. In contrast to Form A, Form B of the sialyltransferase, which lacks the proposed lipid-binding domain of Form A, cannot be incorporated into liposomes. Form A of the transferase was also incorporated into liposomes composed of phosphatidylcholine, cholesterol, and a mixture of phospholipids from the membranes of the Golgi apparatus from porcine submaxillary glands. Although the transferase was distributed about equally on the internal and external surface of the phosphatidylcholine liposomes, most of the transferase was on the external surface in liposomes containing cholesterol (72%) or in liposomes containing Golgi apparatus phospholipids (88%). The enzyme bound to phosphatidylcholine liposomes was shown by kinetic analysis to have the same activity as that found in the presence of activity-stimulating detergents such as Triton X-100. Enzyme incorporated into cholesterol-containing liposomes had the same activity. In contrast, enzyme bound to liposomes formed from the Golgi apparatus mixed phospholipids had a lower activity, but one similar to that of the transferase in Golgi apparatus membranes. These studies suggest that the composition of a biological membrane may well influence the orientation of the transferase in the membrane as well as modulate its enzymic activity.  相似文献   

3.
A system consisting of liposomes and mitochondria for studying the exchange of specific phospholipids is described. The liposomes were prepared from phosphatidylcholine labelled with 14C-palmitic acid. The transfer of liposomes to the mitochondria is specifically stimulated 2- to 3fold by the pH 5.1 supernatant, and proceeds in a linear fashion for 90 min.  相似文献   

4.
M Kinjo  T Araiso  T Koyama 《Biorheology》1988,25(3):517-525
Membrane fluidity and osmotic sensitivity were examined in DPPC liposomes treated with phospholipase A2 (PL.A2) in the presence of Ca2+ or Mg2+. The amount of liposome phospholipid hydrolyzed differed with the two ions. Embedded DPH, a rod-like fluorescent probe, was employed in the determination of membrane fluidity. Membrane fluidity decreased according to the degree of phospholipid hydrolization in liposomes by PL.A2. The reciprocal value of absorption at 450 nm was measured as the index of osmotic sensitivity of liposomes. Intact sonicated liposomes showed osmotic insensitivity. PL.A2-treated liposomes in which about 40% of total phospholipid was hydrolyzed showed osmotic sensitivity. No change in the membrane fluidity was obtained when PL.A2-treated liposomes were exposed to hypertonic or hypotonic solution. These results suggested that the motion of the acyl-chain of phospholipids and free fatty acids was resisted in PL.A2-treated liposomes. The resistance may be due to a phase separation between phospholipids and free fatty acids. The pore for water permeation might be induced in the border between phase-separated domains in PL.A2-treated liposomes.  相似文献   

5.
Phospholipase A2 hydrolysis of neutral and negatively charged lipid membranes modified by positively charged proteins has been studied using liposomes composed of either dioleoylphosphatidylcholine (DOPC) or dioleoylphosphatidylglycerol (DOPG) alone or their equimolar mixture in the presence of cytochrome c, histone H1, cytochrome b5, and polylysine. Twenty minutes after the reaction had been initiated, DOPC hydrolysis was 58%, while that in the equimolar mixture with DOPG was 35%. DOPG hydrolysis was more complete in binary mixtures of liposomes. The same was observed for liposomes in the presence of cytochrome c. Hydrolysis of phospholipids in binary liposomes in the presence of histone H1 was 3 times faster than that in protein-free liposomes. In the presence of polylysine the rate of DOPG hydrolysis was decreased. The results obtained are suggestive of electrostatic interactions between hydrophilic proteins and negatively charged phospholipids, the phospholipase A2 catalytic activity being affected by these interactions.  相似文献   

6.
Summary The pattern of fatty acid release from rat synaptic membranes in the presence of phospholipase A2 (Vipera russelli) was compared to that from liposomes comprised of phospholipids. Phospholipase A2 more readily attacked myelin and synaptic membranes than liposomes prepared from total phospholipids derived from myelin. Although hydrolysis of liposomal phospholipids occurred in the absence of added calcium, the presence of 2mm CaCl2 or 2% bovine serum albumin significantly enhanced the phospholipase attack of liposomes, but not synaptic membranes or myelin. Phospholipase exhibited a marked preference for phospholipids containing docosahexaenoic acid (226) in the synaptic membranes, while with liposomes the pattern of released fatty acid reflected the fatty acid composition in the two-position of the phospholipids. Although either calcium or albumin markedly increased the phospholipase hydrolysis of liposomes, neither affected the hydrolysis of synaptic membranes or the pattern of fatty acid release from liposomes. It was concluded that the nonlipid constituents, particularly the proteins, of biomembranes were responsible for the organization of the phospholipids and accounted for the observed differences between liposomes and synaptic membranes with respect to enzymic accessibility.  相似文献   

7.
Antibodies against phospholipids appeared spontaneously during the course of experimental Trypanosoma rhodesiense infections in rabbits. These antibodies were observed in rabbits infected either with a lethal strain or with a strain newly discovered to give a spontaneous self-cure. Serum antibodies reacting with liposomes containing dimyristoyl phosphatidylcholine (DMPC), phosphatidylinositol (Pl), phosphatidylinositol phosphate (PlP), or cardiolipin were detected at 3 to 4 wk by complement-mediated release of trapped marker from liposomes. Antibodies were also detected against a trypanosomal lipid fraction (TrF2) that contained Pl as a major constituent. The antibody activities against DMPC, Pl, or TrF2 all reacted (or cross-reacted) with DMPC, and were removed from the serum by adsorbing with liposomes containing DMPC as the only phospholipid. Phosphocholine inhibited the antibodies reactive with liposomes containing either DMPC or DMPC and Pl as phospholipids. Antibodies against PlP, however, reacted only with liposomes containing PlP and were not removed by adsorbing with liposomes lacking PlP. We conclude that anti-phospholipid antibodies appear during the course of trypanosomal infections that either undergo apparent self-cure or are lethal, and at least two anti-phospholipid antibody specificities can be detected.  相似文献   

8.
Multilameller liposomes were prepared with various asialoglycolipids, gangliosides, sialic acid, or brain phospholipids in the liposome membrane and with ethylenediaminetetraacetic acid (EDTA) encapsulated in the aqueous compartments. The liposomes containing glycolipids or sialic acid were prepared from a mixture of phosphatidylcholine, cholesterol, and one of the following test substances: galactocerebroside, glucocerebroside, galactocerebroside sulfate, mixed gangliosides, monosialoganglioside GM1, monosialoganglioside GM2, monosialoganglioside GM3, disialoganglioside GD1a, or sialic acid. The liposomes containing brain phospholipids were mixtures of either sphingomyelin and cholesterol or a brain total phospholipid extract and cholesterol. Distributions of 14C-labeled EDTA were determined in mouse tissues from 15 min to 6 h or 12 h after a single injection of liposome preparation. Liver uptake up encapsulated EDTA was lowest from all liposome preparations containing sialic acid or sialogangliosides, regardless of the amount of sialic acid moiety present or the identity of the particular ganglioside; highest uptake of encapsulated EDTA by liver was from liposomes containing galactocerebroside or brain phospholipids. Lungs and brain took up the largest amounts of EDTA from liposomes containing sphingomyelin and lesser amounts from liposomes containing GD1a. Use of mouse brain phospholipid extract to prepare liposomes did not increase uptake of encapsulated EDTA by the brain. EDTA in liposomes containing monosialogangliosides, brain phospholipids, galactocerebroside, or sialic acid was taken up well by spleen and marrow. Highest thymus uptake of encapsulated EDTA was from liposomes containing GD1a. These results demonstrate that inclusion of sialogangliosides in liposome membranes decreases uptake of liposomes by liver, thus making direction of encapsulated drugs to other organs more feasible. Liposomes containing glycolipids also have potential uses as probes of cell surface receptors.  相似文献   

9.
The effect of the bacterial cytolytic toxin, streptolysin S, on liposomes composed of various phospholipids was investigated. Large unilamellar vesicles containing [14C]sucrose were prepared by reverse-phase evaporation, and membrane damage produced by the toxin was measured by following the release of labeled marker. The net charge of the liposomes had little or no effect on their susceptibility to steptolysin S and the toxin was about equally effective on liposomes composed of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylglycerol. Experiments with liposomes composed of synthetic phospholipids showed that the ability of the toxin to produce membrane damage depended on the degree of unsaturation of the fatty acyl chains. The order of sensitivity was C18 : 2 phosphatidylcholine greater than C18: I phosphatidylcholine greater than C18 : 0 phosphatidylcholine = C16 : 0 phosphatidylcholine. Liposomes containing the latter two phospholipids were virtually unaffected by streptolysin S, and experiments with C18 : 0 phosphatidylcholine suggested that toxin activity does not bind to liposomes composed of phospholipids with saturated fatty acyl chains. The inclusion of 40 mol% cholesterol in C16 : 0 phosphatidylcholine and C18 : 0 phosphatidylcholine liposomes made these vesicles sensitive to streptolysin S. Egg phosphatidylcholine liposomes, which were unaffected at 0 degrees C and 4 degrees C became susceptible to the toxin at these temperatures when cholesterol was included. Liposomes composed of C14 : 0 phosphatidylcholine were unaffected by streptolysin S at temperatures below the chain-melting transition temperature (23 degrees C) of this phospholipid, but became increasingly susceptible above this temperature. The results suggest that the fluidity of the phospholipid hydrocarbon chains in the membrane is important in streptolysin S action.  相似文献   

10.
We have investigated the membrane-damaging effect of phallolysin on liposomes varying in phospholipid composition, net charge and physical constitution. Liposomes were prepared from lipids extracted from bovine or human erythrocyte ghosts. The liposomes composed of bovine lipids (the intact cell showing little sensitivity to phallolysin) were found comparably sensitive to those prepared from lipids of human red cells (these cells being of high sensitivity). In addition, artificial mixtures of lipids were used for the preparation of liposomes, consisting of (a) negatively charged phospholipids such as dicetyl phosphate or phosphatidylserine, (b) cholesterol, and (c) either sphingomyelin (as the major component of erythrocytes from ruminants) or phosphatidylcholine (as the major component of erythrocytes from non-ruminants). Again, we found only little difference in the susceptibilities of sphingomyelin- and phosphatidylcholine-containing liposomes. On the other hand, the susceptibility depended on the presence of phospholipids with negative net charges. Omittance of phosphatidylcholine or dicetyl phosphate, or replacement by the positively charged stearylamine, decreased the susceptibility by a factor of more than 20. Finally, we prepared liposomes from dicetyl phosphate, cholesterol and phosphatidylcholine in two physical states: large unilamellar and smaller multilamellar liposomes. The unilamellar liposomes were about 10-times more sensitive to phallolysin. We conclude: (1) Phallolysin damages phospholipid-membranes in the absence of receptor proteins, but high concentrations of the toxin are required. (2) Membrane damage takes place with liposomes containing phosphatidylcholine as well as those containing sphingomyelin. (3) Phallolysin damages only liposomes containing phospholipids with a negative net charge.  相似文献   

11.
Electrophoretic light scattering (ELS) and depolarization of fluorescence have been used to determine the effect of membrane fluidity on the binding of Ca2+ to liposomes. ELS was used to measure the electrophoretic mobilities of the liposomes. Fluorescence depolarization was used to determine membrane fluidity. Zero to 30 mol% phosphatidylserine (PS) was incorporated into liposomes containing, as bulk phospholipids, one of the following: dimyristoyl-phosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), egg phosphatidylcholine (PC), or hydrogenated egg phosphatidylcholine (H egg PC). The binding of Ca2+ to the liposomes appears to be influenced by membrane fluidity. Liposomes containing bulk phospholipids whose phase transition temperature is higher than the experimental temperature exhibit enhanced binding of CA2+.  相似文献   

12.
In vitro synthesized precursors of several mitochondrial proteins, including P-450(SCC), adrenodoxin, and malate dehydrogenase, bound to liposomes prepared from mitochondrial phospholipids, but not to those from microsomal phospholipids. When liposomes were prepared from various pure phospholipids, adrenodoxin precursor was bound only to the liposomes that contained cardiolipin. The liposomes containing other phospholipids did not show the binding affinity for the precursor. The binding was observed only with the precursor peptides of adrenodoxin and malate dehydrogenase, and their mature forms were not bound to the liposomes. The binding of the precursors was dependent on the concentration of cardiolipin in the liposomes. Liposomes containing various cardiolipin derivatives with modified polar head groups showed very different binding affinity for adrenodoxin precursor, suggesting the importance of the structure of the polar head of the cardiolipin molecule. Two or three positively charged amino acid residues in the extension peptide of P-450(SCC) precursor were replaced by neutral amino acid residues by site-directed mutagenesis. The mutated P-450(SCC) precursors did not bind to the liposomes containing cardiolipin. The results indicated that mitochondrial protein precursors have specific affinity for cardiolipin, and the affinity was due to the interaction between the extension peptides of the precursors and the polar head of the cardiolipin molecule.  相似文献   

13.
Unilamellar liposomes composed of phosphatidylcholine with an entrapped self-quenching fluorescent dye, calcein, were immobilized in chromatographic gel beads by avidin-biotin binding. Bee venom phospholipase A(2) (PLA(2)) was applied in a small amount onto the immobilized liposome column. The release of calcein from the immobilized liposomes resulting from the catalyzed hydrolysis of the phospholipids was detected online by immobilized liposome chromatography (ILC) using a flow fluorescent detector. The PLA(2)-catalyzed membrane leakage of the immobilized liposomes as studied with ILC was found to be affected by the gel pore size used for immobilization, by liposome size, and as expected by the concentration of calcium, but was unaffected by the flow rate of ILC. The largest PLA(2)-induced calcein release from the liposome column was detected on large unilamellar liposomes immobilized on TSK G6000PW or Sephacryl S-1000 gel in the presence of 1 mM Ca(2+) in the aqueous mobile phase. Comparison with the PLA(2)-catalyzed membrane leakage in free liposome suspensions, we conclude that the fluorescent leakage from liposomes hydrolyzed by PLA(2) can be rapidly and sensitively detected by ILC runs using large amount of immobilized liposomes with entrapped fluorescent dye.  相似文献   

14.
Secretory phospholipase A2 (sPLA2) represents a family of small water-soluble enzymes that catalyze the hydrolysis of phospholipids in the sn-2 position liberating free fatty acids and lysophospholipids. Herein we report the synthesis of two new phospholipids (1 and 2) with bulky allyl-substituents attached to the sn-1 position of the glycerol backbone. The synthesis of phospholipids 1 and 2 is based upon the construction of a key aldehyde intermediate 3 which locks the stereochemistry in the sn-2 position of the final phospholipids. The aldehyde functionality serves as the site for insertion of the allyl-substituents by a zinc mediated allylation. Small unilamellar liposomes composed of phospholipids 1 and 2 were subjected to sPLA2 activity measurements. Our results show that only phospholipid 1 is hydrolyzed by the enzyme. Molecular dynamics simulations revealed that the lack of hydrolysis of phospholipid 2 is due to steric hindrance caused by the bulky side chain of the substrate allowing only limited access of water molecules to the active site.  相似文献   

15.
Pleckstrin homology (PH) domains may act as membrane localization modules through specific interactions with phosphoinositide phospholipids. These interactions could represent responses to second messengers, with scope for regulation by soluble inositol polyphosphates. A biosensor-based assay was used here to probe interactions between PH domains and unilamellar liposomes containing different phospholipids and to demonstrate specificity for distinct phosphoinositides. The dynamin PH domain specifically interacted with liposomes containing phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] and, more weakly, with liposomes containing phosphatidylinositol-4-phosphate [PI(4)P]. This correlates with phosphoinositide activation of the dynamin GTPase. The functional GTPase of a dynamin mutant lacking the PH domain, however, cannot be activated by PI(4,5)P2. The phosphoinositide-PH domain interaction can be abolished selectively by point mutations in the putative binding pocket predicted by molecular modelling and NMR spectroscopy. In contrast, the Bruton's tyrosine kinase (Btk)PH domain specifically bound liposomes containing phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P3]: an interaction requiring Arg28, a residue found to be mutated in some X-linked agammaglobulinaemia patients. A rational explanation for these different specificities is proposed through modelling of candidate binding pockets and is supported by NMR spectroscopy.  相似文献   

16.
The peripheral membrane ATPase MinD is a component of the Min system responsible for correct placement of the division site in Escherichia coli cells. By rapidly migrating from one cell pole to the other, MinD helps to block unwanted septation events at the poles. MinD is an amphitropic protein that is localized to the membrane in its ATP-bound form. A C-terminal domain essential for membrane localization is predicted to be an amphipathic alpha-helix with hydrophobic residues interacting with lipid acyl chains and cationic residues on the opposite face of the helix interacting with the head groups of anionic phospholipids (Szeto, T. H., Rowland, S. L., Rothfield, L. I., and King, G. F. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 15693-15698). To investigate whether E. coli MinD displays a preference for anionic phospholipids, we first examined the localization dynamics of a green fluorescent protein-tagged derivative of MinD expressed in a mutant of E. coli that lacks phosphatidylethanolamine. In these cells, which contain only anionic phospholipids (phosphatidylglycerol and cardiolipin), green fluorescent protein-MinD assembled into dynamic focal clusters instead of the broad zones typical of cells with normal phospholipid content. In experiments with liposomes composed of only zwitterionic, only anionic, or a mixture of anionic and zwitterionic phospholipids, purified MinD bound to these liposomes in the presence of ATP with positive cooperativity with respect to the protein concentration and exhibited Hill coefficients of about 2. Oligomerization of MinD on the liposome surface also was detected by fluorescence resonance energy transfer between MinD molecules labeled with different fluorescent probes. The affinity of MinD-ATP for anionic liposomes as well as liposomes composed of both anionic and zwitterionic phospholipids increased 9- and 2-fold, respectively, relative to zwitterionic liposomes. The degree of acyl chain unsaturation contributed positively to binding strength. These results suggest that MinD has a preference for anionic phospholipids and that MinD oscillation behavior, and therefore cell division site selection, may be regulated by membrane phospholipid composition.  相似文献   

17.
Studies were made of the ability of alpha-tocopherol, incorporated into unilamellar liposomes from saturated or unsaturated phospholipids (donor liposomes) to inhibit the accumulation of lipid peroxidation (LPO) products in unilamellar liposomes from rat cerebral cortex lipids (acceptor liposomes) in the presence of LPO inducer (Fe + ascorbate). With the molar alpha-tocopherol: phospholipids rations from 1:1000 to 1:100 in donor liposomes, obtained through sonication of lipid dispersions, alpha-tocopherol was incorporated into both monolayers of liposomes and was distributed in monomeric form without forming clusters. Based on the dependencies of LPO inhibition on the alpha-tocopherol concentrations, we chose the ones that completely prevented the accumulation of LPO products in donor liposomes. Under these conditions LPO inhibition in mixtures of donor and acceptors liposomes was fully determined by the antioxidant effect of alpha-tocopherol in acceptor liposomes due to its intermembrane transfer. The efficiency of the "intermembrane" antioxidant action of alpha-tocopherol increased in the course of preincubation of donor and acceptor liposomes (up to 60 min) and this increase was more pronounced when the donor liposomes contained unsaturated phospholipids. Evidence was obtained that the intermembrane transfer of alpha-tocopherol did not result from the fusion of donor and acceptor liposomes during preincubation.  相似文献   

18.
Multilamellar liposomes were prepared with various asialoglycolipids, gangliosides, sialic acid, or brain phospholipids in the liposome membrane and with ethylenediaminetetraacetic acid (EDTA) encapsulated in the aqueous compartments. The liposomes containing glycolipids or sialic acid were prepared from a mixture of phosphatidylcholine, cholesterol, and one of the following test substances: galactocerebroside, glucocerebroside, galactocerebroside sulfate, mixed gangliosides, monosialoganglioside GM1, monosialoganglioside GM2, monosialoganglioside GM3, disialoganglioside GD1a, or sialic acid. The liposomes containing brain phospholipids were mixtures of either sphingomyelin and cholesterol or a brain total phospholipid extract and cholesterol. Distribution of 14C-labeled EDTA were determined in mouse tissues from 15 min to 6 h or 12 h after a single injection of liposome prepartion. Liver uptake of encapsulated EDTA was lowest from all liposome preparations containing sialic acid or sialogangliosides regardless of the amount of sialic acid moiety present or the identity of the particular ganglioside; highest uptake of encapsulated EDTA by liver was from the liposomes containing galactocerebroside or brain phospholipids. Lungs and brain took up the largest amounts of EDTA from liposomes containing sphingomyelin and lesser amounts from liposomes containing GD1a. Use of mouse brain phospholipid extract to prepare liposomes did not increase uptake of encapsulated EDTA by the brain. EDTA in liposomes containing monosialogangliosides, brain phospholipids, galactocerebroside, or sialic acid was taken up well by spleen and marrow. Highest thymus uptake of encapsulated EDTA was from liposomes containing GD1a. These results demonstrate that inclusion of sialogangliosides in liposome membranes decreases uptake of liposomes by liver, thus making direction of encapsulated drugs to other organs more feasible. Liposomes containing glycolipids also have potential uses as probes of cell surface receptors.  相似文献   

19.
Letters     
Abstract

Long-term effects of life-long (>2 year) repeated intravenous injections (up to 17) of high doses of liposomes, lipid A, or liposomes containing lipid A were assessed in BALB/c mice. the liposomes contained dipalmitoylphosphatidylcholine, and cholesterol (1/0.75). When compared with mice injected only with normal saline, there were no statistical differences in life spans observed between the different groups. Animals injected with liposomes or liposomes containing lipid A gradually developed “ruffled” fur, but the animals did not appear sick otherwise, and no differences were observed in the mean weights of the animals in the different groups. All of the animals that were tested in each group, including those injected with normal saline, developed IgG antibodies against one or more of nine lipid antigens. the antibodies were detected by a solid-phase enzyme-linked immunosorbent assay (ELisA) and the antigens consisted of either lipid A or one of eight different phospholipids. After 765 days, when approximately half of the animals had died spontaneously, the surviving animals were sacrificed and subjected to extensive histopathological analysis. In each group (including the normal saline group) certain animals exhibited pathological changes in liver, spleen, or lung that might be expected to occur in highly aged animals. Approximately half of the animals in each group had lymphoproliferative disorders (hyperplasia and/or lymphoma). However, there were no bone marrow abnormalities, and no hepatic or splenic granulomatous reactions were found in any of the animals. From a pathological standpoint the groups were indistinguishable from each other. We conclude that life-long repeated injection of liposomes, lipid A, or liposomes containing lipid A does not alter longevity or cause any overt pathological changes in mice. We also conclude that antibodies to lipid A and a variety of phospholipids occur spontaneously in aged mice that have been injected only with normal saline.  相似文献   

20.
The permeability of liposomes prepared from beef heart mitochondrial phospholipids was studied after treatment with phospholipase A2. The permeability to H+ ions was measured by recording the rate of change of pH in the external medium following an addition of an aliquot of alkali to liposomes with a highly buffered inner medium, while the penetration of Ca2+ ions into liposomes was measured in liposomes loaded with arsenazo III. There was a doubling of H+ permeability when the lysophospholipid content was increased to 2% by treatment with phospholipase A2, and a tripling at 4%. Entrapped sucrose leakage from liposomes became apparent at above 6% lysophospholipid. Treatment with phospholipase A2 stimulated Ca2+ penetration into liposomes driven by a valinomycin-induced diffusion potential or a nigericin-induced H+ gradient. The data are discussed in relation to the mechanism of damage to mitochondria occurring in Ca2+ overload as well as in phospholipase A2-induced cellular damage.  相似文献   

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