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Biomedical subjects

S Nojima

Publications and source records attributed to S Nojima.

At least 145 records · Page 8Linked to original sources
PubMed1981

Incorporation and metabolism of 2-acyl lysophospholipids by Escherichia coli.

The incorporation of 2-acyl lysophospholipids into Escherichia coli, and their metabolism were studied. 2-[14C]Acyl lysophosphatidylethanolamine could penetrate into E. coli cells and was mainly incorporated into phosphatidylethanolamine. 2-Acyl lysophosphatidylethanolamine was partially degraded, but some of it was incorporated into membrane phospholipids by acylation. 2-Acyl lysophosphatidylcholine also entered cells and was acylated to phosphatidylcholine. The acylation of 2-acyl lysophospholipid by the envelope fraction was also studied. Fatty acids were incorporated into 2-acyl lysophospholipids by the envelope fraction in the presence of ATP and Mg2+, and the incorporation was stimulated by acyl carrier protein, but not by coenzyme A. No acylation was observed with acyl coenzyme A as acyl donor. The acylation activities of the inner and outer membranes were examined. Pathways for degradation and modification of membrane phospholipids in E. coli are proposed.

Carbon Radioisotopes↗
PubMed1981

The interactions of lysophosphatidylcholine with protein-containing liposomes.

The effect of exogenous lysophosphatidylcholine on the membranes of liposomes containing protein has been studied. Lysophosphatidylcholine severely damaged liposomes prepared in the presence of membrane proteins such as glycophorin and "band 3" protein of human erythrocytes. Some basic proteins such as cytochrome c, lysozyme and polylysine also could sensitize liposomes to lysophosphatidylcholine. As described in previous papers (Inoue, K., et al. (1974) Biochim. Biophys. Acta 363, 361-372; Utsumi, H., et al. (1978) Biochemistry 17, 1990-1996), large multilamellar liposomes without protein were affected by lysophosphatidylcholine only under certain conditions where a phase boundary could exist. Sonicated liposomes without protein were almost completely insensitive to lysophosphatidylcholine. Liposomes prepared by the cholate dialysis method were also insensitive to lysophosphatidylcholine, irrespective of the incubation temperature. It is known that natural membranes such as membranes of erythrocytes and of other mammalian cells are rather sensitive to lysophosphatidylcholine. The difference observed between natural membrane and liposomal membrane seems to be removed by the introduction of proteins into lipid bilayers. The mode of interaction of lysophosphatidylcholine with membranes of liposomes containing protein is discussed.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1981

Reactivity of human C-reactive protein with positively charged liposomes.

Interaction of CRP with liposomes was studied by agglutination, complement consumption, and the binding assay. Liposomes composed of phosphatidylcholine and stearylamine were agglutinated with CRP. The interaction of CRP and liposomes was further demonstrated by the consumption of hemolytic complement activity. Stearylamine could be substituted by cetyltrimethylammonium bromide, indicating that positively charged molecules were required for the interaction. Agglutination of liposomes caused by CRP was dependent on the fatty acid composition of phosphatidylcholine, cholesterol content and temperature. Differential scanning calorimetry measurement revealed that both the agglutination of liposomes and the consumption of complement caused by CRP required the fluid state of membranes. Particle electrophoresis measurement showed that stearylamine in fluid state membranes was more dispersed than in rigid state membranes indicating that lateral distribution of stearylamine affected the reactivity of liposomes. The mode of complement activation by the interaction of CRP with positively charged liposomes was similar to that observed in the system of protamine and heparin.

Agglutination Tests↗
PubMed1981

Enhancement of the transfer of alpha-tocopherol between liposomes and mitochondria by rat-liver protein(s).

alpha-Tocopherol transfer from liposomes to mitochondria was enhanced by a cytosolic protein in rat liver. This protein was separated from the exchange protein specific for phosphatidylcholine. The stimulation was specific for alpha-tocopherol and the "affinity" order of tocopherols for the cytosolic protein was found to be as follows: alpha-tocopherol greater than gamma-tocopherol much greater than alpha-tocopheryl acetate, alpha-tocopherol quinone. The transfer-stimulating protein may act as a carrier, since an intermediate (alpha-tocopherol)-protein complex could be detected when liposomes containing alpha-tocopherol were incubated with the cytosol. This transfer-stimulating activity was present not only in liver, but also in heart, spleen and lung.

Animals↗
PubMed1980

Acyl phosphatidylglycerol of Escherichia coli.

Acyl phosphatidylglycerol, isolated from Escherichia coli, has been identified as 3-sn-phosphatidyl-1'-(3'-acyl)-sn-glycerol. The fatty acids of the diacylglycerol moiety of acyl phosphatidylglycerol resemble those of phosphatidylglycerol in composition. However, the monoacylglycerol moiety of this lipid contains more unsaturated fatty acids than the diacylglycerol part of this lipid or other phospholipids in E. coli. Furthermore, the fatty acids present in the monoacylglycerol moiety, were found to contain major amounts of an unsaturated acid identified as 7-tetradecenoic acid by combined gas-liquid chromatography-mass spectrometry. This acid was present only in low concentrations in most phospholipids of E. coli.

Diglycerides↗
PubMed1980

Interaction of dilauroylglycerophosphocholine with erythrocytes: pre-hemolytic events and hemolysis.

The process of interaction of dilauroylglycerophosphocholine with erythrocytes that eventually results in hemolysis was examined. 1. The rate of uptake of dilauroylglycerophosphocholine by human erythrocytes was rather slow, but increased with increasing temperature. 2. The first observable change of human erythrocytes induced by dilauroylglycerophosphocholine was a morphological change from discocytes to spheroechinocytes. This change preceded K+ leakage. 3. Adsorption of dilauroylglycerophosphocholine to human erythrocytes caused K+ leakage. The rate of K+ leakage was also temperature-dependent. The temperature-dependence was due to the temperature-dependence of lipid uptake, because in order to cause K+ leakage a given amount of dilauroylglycerophosphocholine must be bound to the erythrocytes, irrespective of the temperature. 4. The temperature-dependence of hemolysis of human erythrocytes was different from that of pre-hemolytic events (morphological change, adsorption of lipids and K+ leakage). Hemolysis was rapid below 10 and above 37 degrees C, but slow at about 25 degrees C. The hemolysis observed below 10 degrees C seemed to be a 'colloid osmotic lysis', since it occurred immediately after K+ leakage, but the hemolysis above 37 degrees C may not be a colloid osmotic lysis. Above 37 degrees C, additional binding of dilauroylglycerophosphocholine to the erythrocyte membrane may cause hemolysis by a different mechanism from that working below 10 degrees C. 5. Above 25 degrees C, most human erythrocytes are resistant to colloid osmotic lysis induced by dilauroylglycerophosphocholine. It can be concluded that human erythrocytes are composed of two types of population, one resistant, and one sensitive to colloid osmotic lysis. The mechanism of the resistance was sensitive to temperature, pH and various sulfhydryl agents. 6. Pig erythrocytes were hemolysed immediately after K+ leakage even above 25 degrees C, indicating that they were sensitive to a colloid osmotic mechanism over the whole temperature range tested. Pig erythrocytes may lack the 'mechanism' giving resistance to colloid osmotic lysis. The process of hemolysis of erythrocytes by dilauroylglycerophosphocholine is shown schematically.

Absorption↗
PubMed1980

Selective release of non-electrolytes from liposomes upon perturbation of bilayers by temperature change or polyene antibiotics.

A new system for assaying the permeability characteristics of liposomes was established using Amicon cells equipped with a membrane filter (pore size, 0.3 micrometer). In this system, damage of liposomes during the assay procedure was negligible. Changes in permeability to non-electrolytes, such as glucose (Mr 180), sucrose (Mr 342), inulin (Mr 5000) and dextran (Mr 75000), induced by perturbation of the bilayers were examined with this system. The following results were obtained on the barrier properties of multilamellar liposomes modified by various treatments. 1. Amphotericin B and nystatin did not cause any change in permeability to glucose of egg yolk phosphatidylcholine liposomes prepared in physiological saline and containing trace amounts of radioactive markers in their aqueous compartments. Both antibiotics, however, induced nonspecific release of glucose, sucrose, inulin and dextran from liposomes that contained 0.3 M glucose in their aqueous compartments. These antibiotics first seem to form pores through which small ions can permeate; Na+ and Cl- can enter the liposomes through these pores, whereas glucose in the liposomes cannot pass out. As a result, the liposomes become swollen with consequent severe disruption of their membranes. 2. Filipin and digitonin disrupted the membrane structures, resulting in release of large molecules such as dextran even in the absence of an osmotic mechanism. 3. Perturbation of the phase equilibrium by temperature change resulted in formation of 'pores'. The penetration of cations and anions through these 'pores' was apparently much faster than that of glucose, since when liposomes swollen in 0.3 M glucose were incubated in salt solution they were disrupted by an osmotic mechanism releasing not only glucose but also dextran. Most of the 'pores' were not large enough to allow passage of large non-electrolytes, such as inulin and dextran, since no appreciable amounts of these markers were released from liposomes under conditions where there should be no osmotic gradient. 4. At a temperature well above the phase transition temperature, egg yolk phosphatidylcholine liposomes exhibited specific release of glucose. This process did not involve an osmotic gradient, indicating that it was mainly due to diffusion of the solutes through the bilayers.

Amphotericin B↗
PubMed1980

Phosphatidylcholine liposomes containing cholesterol analogues with side chains of various lengths.

The effect of the length of the side chain of sterols on their interaction with phosphatidylcholine was studied by measuring the permeability properties of liposomes constituted with sterol analogues with side chains of various lengths. The sensitivities of liposomes constituted with these sterol analogues toward digitonin and polyene antibiotics were also examined. The effects of sterols on phase transition of phosphatidylcholine were examined by measuring their effects on permeability increase due to perturbation of phase equilibrium and by differential scanning calorimetry. An analogue with a short side chain, isopropyl (C-22), had a very similar effect to cholesterol in suppressing the permeability increase, suggesting that the full length of the side chain is not necessary for this effect. The permeability of egg yolk phosphatidylcholine at 42 degrees C was suppressed as much by the analogue C-22 as by cholesterol. Androstene-3-beta-ol, an analogue without a side chain, however, had little suppressive effect. Thus it is concluded that the condensing effect of sterol requires a side chain, but not the full length of side chain. Liposomes constituted with analogues having a side chain with more than 5 carbon atoms showed maximum reactivity with a polyene antibiotic, amphotericin B, whereas those constituted with analogues having a side chain with less than 4 carbon atoms showed weaker reactivity. These findings indicate that a side chain with more than 5 carbon atoms is essential for the maximum interaction of liposomes with amphotericin B. Unlike amphotericin B, filipin reacted almost equally well with liposomes containing C-22 and with those containing cholesterol. Thus the chain length of the side chain of sterol is less important for interaction of liposomes with filipin than for their interaction with amphotericin B. Liposomes containing analogues having a side chain with more than 6 carbon atoms showed maximum reactivity with digitonin. Thus for the maximum interaction of liposomes with digitonin, the side chain of sterol should be longer than 6 carbon atoms.

Anti-Bacterial Agents↗
PubMed1980

Transfer of steroids and alpha-tocopherol between liposomal membranes.

The transfer of various steroids and alpha-tocopherol between liposomes was examined. The transfer rate of cholest-4-en-3-one and epicholesterol between egg yolk phosphatidylcholine liposomes was much higher than that of cholesterol. Rapid transfer was also noted for coprostanol and 5-cholesten-3 beta-ol-7-one, while the transfer of cholestanol, which has a 3 beta-hydroxyl residue and a planar nucleus structure, was similar to that of cholesterol. These results suggest that the mode of interaction between steroid and phospholipid may be an important factor controlling the rate of transfer. It was found that alpha-tocopherol could also be transferred between liposomes. The transfer rate of alpha-tocopherol was dependent on the temperature and the phospholipid composition.

Animals↗
PubMed1980

Immune reactions of liposomes containing cardiolipin and their relation to membrane fluidity.

The relation between the immune reactions of phosphatidylcholine liposomes containing cardiolipin with or without cholesterol and the physical state of the liposomes was studied. In egg yolk phosphatidylcholine liposomes, both immune agglutination and complementmediated immune damage occurred irrespective of the presence of cholesterol. Immune agglutination also occurred at all temperatures tested (0--40 degrees C). On the other hand, in dipalmitoylphosphatidylcholine liposomes, both reactions depended on the cholesterol content, but immune agglutination occurred even in the absence of cholesterol above the phase transition temperature at which liposomal membranes became fluid. The finding of antibodies to liposomes was found to be independent of the physical state of the liposomal membranes. The requirement of the fluid state of liposomal membranes for immune reactions is discussed.

Agglutination↗
PubMed1980

Purification and properties of a membrane-bound phospholipase A2 from rat ascites hepatoma 108A cells.

A phospholipase A2 bound tightly to the particulate fractions of rat ascites hepatoma cells was purified approximately 13,000-fold with a reasonably high yield (34%) by extraction with sodium cholate, ammonium sulfate fractionation, solubilization with sodium dodecyl sulfate, column chromatographies on Sephadex G-150 in the presence of sodium dodecyl sulfate, and on DEAE-cellulose and CM-cellulose in the presence of Triton X-100. The enzyme has a unique substrate specificity; namely, it preferentially hydrolyzes phosphatidylethanolamine and, to a lesser degree, phosphatidylglycerol. However, it does not attack phosphatidylcholine, phosphatidic acid or cardiolipin in the present experimental conditions. The final preparation shows both phospholipase A2 and lysophospholipase L2 activities, but neither lysophospholipase L1 nor lipase activity. The purified enzyme has a rather broad pH optimum ranging from 7 to 9, requires Ca2+, and is resistant to heat-treatment at 95 degree C for 5 min.

Animals↗
PubMed1980

C-Reactive protein induced agglutination of lipid suspensions prepared in the presence and absence of phosphatidylcholine.

CRP-induced agglutination of lipid suspensions prepared in the presence and absence of phosphatidylcholine was studied by a newly devised quantitative method. CRP caused as much agglutination of suspensions composed of egg yolk phosphatidylcholine, cholesterol, and Span 60 as of those composed of cholesterol and Span 60, suggesting that phosphocholine residues of phosphatidylcholine are not important as binding sites for CRP. Agglutination of suspensions prepared without phosphatidylcholine was inhibited by phosphocholine, indicating that the inhibition by phosphocholine is non-competitive. Although phosphatidylcholine is not an essential component for agglutination of suspensions, it may modify the mode of interaction of CRP with its binding site on lipid suspensions, since the sensitivity of the agglutination to phosphocholine and the Ca2+ requirement were influenced by the presence of phosphatidylcholine in the suspensions.

C-Reactive Protein↗
PubMed1979

Transfer of cholesterol between liposomal membranes.

The transfer of cholesterol between liposomal membranes was examined. On incubation of liposomes compsoed of egg yolk phosphatidylcholine, phosphatidic acid and cholesterol (molar percentage, 65.8 : 1.3 : 32.9 or 65.5 : 6.3 : 31.2), almost complete equilibration of the cholesterol pools was achieved within 6 to 8 h at 37 degrees C. The rate of transfer of cholesterol from the liposomes, in which cholesterol was introduced by 'the exchange reaction', was not significantly different from that from liposomes prepared in the presence of cholesterol, in which the cholesterol was distributed homogenously. These findings indicate that half life for 'flip-flop' of cholesterol molecules in egg yolk phosphatidylcholine liposomes is less than 6 h at 37 degrees C. The transfer of cholesterol between liposomes was strongly dependent on temperature and was affected by the fatty acid composition of the phospholipid, suggesting that the 'fluidity' of the membranes strongly influences the transfer rate. A preferential distribution of cholesterol molecules was observed in heterogeneous liposomes with different classes of phospholipids. The 'affinity order' of cholesterol for phospholipid deduced from the present experiments is as follows: beef brain sphingomyelin greater than dipalmitoylglycerophosphocholine = dimyristoylglycerophosphocholine greater than egg yolk phosphatidylcholine.

Cholesterol↗
PubMed1979

Transfer of cholestane spin label between lipid bilayer membranes and its molecular motion in membranes.

The relation between the molecular motion of a steroid in lipid membranes and the transfer rate between membranes was examined using radioactive cholestane spin label. Order parameters of the molecule were determined in bilayers composedof dipalmitoylglycerophosphocholine or egg yolk phosphatidylcholine at various temperatures. The line widths of the ESR signal of the cholestane spin label in membranes, which depend upon the rate of molecular axial rotation in the membranes, were also measured. The temperature dependences of these two parameters and of the transfer rate suggest a close correlation between the rate of molecular axial rotation and the transfer rate.

Cholestanes↗
PubMed1979

Properties of purified detergent-resistant phospholipase A of Escherichia coli K-12. Inactivation, and protection with detergents and phospholipids.

A crude preparation of membrane-bound phospholipase A (detergent-resistant) in Escherichia coli K-12 cells was found to be quite stable or even apparently activated on incubation at 100 degrees C, but became strikingly thermolabile when it was highly purified and Triton X-100 was removed from the purified enzyme preparation. The rate of inactivation showed a biphasic temperature dependence: inactivation was rapid at 37 degrees C and also above 70 degrees C. Inactivation above 70 degrees C changed the mobility of the enzyme on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, but inactivation at 37 degrees C did not affect the electrophoretic mobility. Triton X-100 effectively protected the enzyme against inactivation at 37 degrees C. The concentration required for the protection of the enzyme was more than its critical micelle concentration. Phospholipids, such as phosphatidylethanolamine, phosphatidylglycerol, cardiolipin, phosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylcholine, also protected the enzyme against inactivation at 37 degrees C. These results suggest that the binding of hydrophobic compounds stabilizes the enzyme.

Cell Membrane↗
PubMed1979

Resealing of erythrocyte membranes after hypotonic hemolysis.

A new quantitative method to study kinetics of resealing of erythrocyte membrane, defined as the recovery of impermeability to dextran, was established. Erythrocyte membrane pre-labelled with 125I were incubated under various conditions. Sealed and unsealed membranes were separated using dextran density gradient centrifugation. Sealed membranes which are impermeable to dextran were recovered from the top of the centrifuge tube, while unsealed membranes were recovered from the bottom of the tube. Degree of resealing was calculated from the counts of 125I recovered from sealed membrane fraction. The resealing of membrane from human erythrocyte after hypotonic hemolysis was dependent on the incubation temperature. Resealing was rapid above 30 degrees C, while it was not observed below 20 degrees C. The process completed within 1 hr at 37 degrees C. Ionic strength of the medium is also an important factor which controls the resealing process. The effect of NaCl in the medium on resealing was biphasic. In the lower range of NaCl (0-50 mM) there was gradual decrease of resealing capacity. Above 50 mM, the capacity was again increased. The mode of resealing of sheep and rabbit erythrocyte membranes was rather different from that observed in human erythrocyte. Under the present experimental condition, these erythrocyte membranes did not reseal well. The immediate resealing, which is observed in human erythrocyte upon hemolysis in the presence of Mg++ or Ca++ ions, was observed neither in sheep erythrocyte membranes nor rabbit ones.

Animals↗