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Biomedical subjects

S Nojima

Publications and source records attributed to S Nojima.

At least 163 records · Page 9Linked to original sources
PubMed1978

Synthesis of acyl phosphatidylglycerol from phosphatidylglycerol in Escherichia coli K-12. Evidence for the participation of detergent-resistant phospholipase A and heat-labile membrane-bound factor(s).

The conversion of phosphatidylglycerol to acyl phosphatidylglycerol by extracts of Escherichia coli K-12 strains was examined under various conditions. The maximum rate of conversion was observed at pH 7.2 in the presence of 50% (v/v) diethyl ether and 10 mM CaCl2. This conversion was found to involve two sequential reactions: (1) The formation of 2-acyl glycerophosphoglycerol and 2-acyl glycerophosphoethanolamine from phosphatidylglycerol and phosphatidylethanolamine, respectively, by detergent-resistant phospholipase A in the presence of Ca2+ and (2) transfer of the acyl group of 2-acyl lysophospholipid to phosphatidylglycerol by a heat-labile factor(s) in the presence of diethyl ether. Neither fatty, acid acyl-CoA nor 1-acyl lysophospholipid could act as an acyl donor for phosphatidylglycerol. The heat-labile factor(s) was found in both the inner membrane and supernatant fractions.

Calcium↗
PubMed1978

Change in permeability of liposomes caused by methylmercury and inorganic mercury.

The effects of two mercurial compounds, methylmercury and inorganic mercury, on lipids were examined by measuring permeability change of lipid bilayer, liposome. Both decrease in the cholesterol content and increase in the content of unsaturated fatty acid moieties in the lipid bilayers, augmented to susceptibility of the liposomes to the mercurial compounds. Inorganic mercury and methylmercury disrupted the lipid membrane to essentially the same extent. The influence on the permeability seems to be specific for mercury compounds. The significant increase in the permeability of some liposomal preparation noted even at the mercurial concentration of 10(-7) M strongly suggests that lipid in biomembrane could be one of the primary targets of these toxic substances.

Animals↗
PubMed1977

Effects of temperature and bovine serum albumin on lysis of erythrocytes induced by dilauroylglycerophosphocholine and didecanoylglycerophosphocholine.

The effects of the incubation temperature and bovine serum albumin on hemolysis induced by short-chain phosphatidylcholine were examined. The rate of hemolysis of human, monkey, rabbit, and rat erythrocytes by dilauroylglycerophosphocholine showed biphasic temperature-dependence: hemolysis was rapid at 5-10 degrees C and above 40 degrees C, but slow at around 25 degrees C. In contrast, the rate of lysis of cow, calf, sheep, pig, cat, and dog erythrocytes did not show biphasic temperature-dependence, but increased progressively with increase in the incubation temperature. Bovine serum albumin increased the hemolysis of human erythrocytes induced by dilauroylglycerophosphocholine or didecanoylglycerophosphocholine: it shortened the lag time of lysis and reduced the amount of phosphatidylcholine required for lysis. A shift-down of the incubation temperature from 40 to below 10 degrees C also shortened the lag time of lysis of human erythrocytes induced by dilauroylglycerophosphocholine and reduced the amount of phosphatidylcholine required for lysis.

Animals↗
PubMed1977

Detergent-resistant phospholipase A of Escherichia coli K-12. Purification and properties.

Detergent-resistant phospholipase A, which is tightly bound to the outer membranes of Escherichia coli K-12 cells, was purified approximately 2000-fold to near homogeneity by solubilization with sodium dodecylsulfate and butan-1-ol, acid precipitation, acetone fractionation and column chromatographies on Sephadex G-100 in the presence of sodium dodecylsulfate and on DEAE-cellulose in the presence of Triton X-100. The final preparation showed a single band in the sodium dodecylsulfate gel system. The enzyme hydrolyzes both the 1-acyl and 2-acyl chains of phosphatidylethanolamine or phosphatidylcholine. It also attacks 1-acyl and 2-acylglycerylphosphorylethanolamine. Thus, this enzyme shows not only phospholipase A1 and lysophospholipase L1 activities but also phospholipase A2 and lysophospholipase L2 activities. The enzyme lost its activity completely on incubation at 80 degrees C for 5 min at either pH 6.4 or pH 8.0. It was stable in 0.5% sodium dodecylsulfate at below 40 degrees C. The enzyme was inactivated on incubation for 5 min at 90 degrees C in 1% sodium dodecylsulfate/1% 2-mercaptoethanol/4 M urea. The native and inactivated enzymes showed different protein bands with RF values corresponding to Mr 21 000 and Mr 28 000 respectively, in a sodium dodecylsulfate gel system. Triton X-100 seemed to protect the enzyme from inactivation. The purified enzyme was fully active on phosphatidylethanolamine in the presence of 0.0002% or 0.05% Triton X-100. The enzyme requires Ca2+. From its properties this enzyme seems to be identical with the enzyme purified from crude extracts of Escherichia coli B by Scandella and Kornberg. However, it differs from the latter in its positional specificity and susceptibility to sodium dodecylsulfate. Possible explanation of the difference of positional specificity of the two preparations is also described.

Drug Stability↗
PubMed1977

Synthesis and micellar formation of spin-labeled lysolecithin.

A spin-labeled lysolecithin, 1-[12'-(N-oxyl-4",4"-dimethyloxazolidine)-stearoyl]-sn-glycero-3-phosphorylcholine, has been synthesized in which the spin is covalently attached to its fatty acyl chain. The electron spin resonance spectra of this lysolecithin is an aqueous solution generally showed sharp three resonance lines superposed on a broad resonance line. Investigation of changes in the signal intensity of these spectra against the concentration of lysolecithin led to the inference that the sharp lines are due to monomers of lysolecithin while the broad one to micelles. The critical micellar concentration was consistent with that evaluated from the spectral shift of a dye. In the electron spin resonance spectra obtained from spin-labeled lysolecithin solutions with various amounts of dimyristoyllecithin, the line width of broad signal arised from micellar spin-labeled lysolecithin broadened as increase of dimyristoyllecithin. The line-broadening thus observed was briefly discussed.

Colloids↗
PubMed1977

Positional specificity of phospholipase B of Penicillium notatum.

Phospholipase B[EC 3.1.1.5] of Penicillium notatum was shown to catalyze the following two reactions successively: diacylphospholipidlead to 1-monoacylphospholipid+fatty acid; and 1-monoacylphospholipid lead to glycerylphosphoryl-base+fatty acid. 1-Monoacylphospholipid was accumulated measurable in a reaction mixture containing methanol. An attempt to classify phospholipase B according to positional specificity is described.

Kinetics↗
PubMed1977

Morphology of lipid micelles containing lysolecithin.

Mixtures of lysolecithin with various phospholipids were studied by electron microscopy using negative staining. Mixtures of dipalmitoyllecithin and lysolecithin produced disc-shaped structures which were stacked in aggregates with a 6.0--6.4 nm repeat. The disc were 10--50 nm in diameter. The disc-shaped structures were best observed in equimolar mixtures of dipalmitoyllecithin and lysolecithin. When dipalmitoyllecithin was replaced by dimyristoyllecithin, the structures were rather different from those observed in the system containing dipalmitoyllecithin; a cylindrical micellar phase was predominant. Equimolar mixtures of egg lecithin and lysolecithin formed the more usual smectic, concentric lamellae (liposomes) and elongated rod-like micelles which might be bimolecular fragments of spherules. The radius of the rod-like micelles was about 6 nm. Structures of rod-like micelles were observed more frequently in the samples after incubation at room temperature and then further incubation at 0 degrees C. Equimolar mixtures of didecanoyllecithin and lysolecithin produced large amounts of elongated rod-like micelles. Beef brain sphingoymyelin showed disc-shaped structures when mixed with lysolecithin. Incorporation of cholesterol into the mixtures of dipalmitoyllecithin and lysolecithin changed the morphological structure; the size of the disc became larger and eventually liposomes were formed with an increase of cholesterol content. The structures observed in mixtures of dipalmitoyllecithin or sphingomyelin and lysolecithin closely resembled those observed in complexes of apolipoprotein and lipid.

Cholesterol↗
PubMed1976

Properties of liposomal membranes containing lysolecithin.

Liposomes have been prepared with lysolecithin (1-acyl-sn-3-glycerylphosphorylcholine), egg lecithin (3-sn-phosphatidylcholine), dicetyl phosphate, and cholesterol. The ability to function as a barrier to the diffusion of glucose marker and the sensitivities of the liposomes to hypotonic treatment and other reagents which modified the permeability were examined. Generally, lysolecithin incorporation decreased the effectiveness of the membranes as a barrier to glucose and made the membranes more "osmotically fragile." Cholesterol incorporation counteracted the effect of incorporated lysolecithin. The more cholesterol incorporated into liposomes, the more lysolecthin could be incorporated into the membrane without loss of function as a barrier. With more than 50 mole% of colesterol, lysolecithin alone could form membranes which were practically impermeable to glucose. The hemolytic activity of lysolecithin was affected by mixing with various lecithins or cholesterol. Liposomes containing lysolecithin, which have the ability to trap glucose marker, showed poor hemolytic activity, while lipid micelles with lysolecithin (which could trap little glucose) showed almost the same hemolytic activity as lysolecithin itself. There seems to be a close correlation between hemolytic activity and barrier function of lipid micelles.

Binding Sites↗
PubMed1976

Effect of albumin and methylated albumin on the glucose permeability of lipid membranes.

The diffusion of glucose from phospholipid membranes has been measured in the presence of serum albumin or methylated serum albumin. At neutral pH, serum albumin enhanced the rate at which glucose diffused from liposomes containing more than a certain amount of lysolecithin. Net charge of the membrane is not important for the reaction, since positively charged membranes containing stearylamine showed almost the same reactivity as negatively charged liposomes containing dicetyl phosphate. Carboxylmethylated albumin showed enhancement of the diffusion rate of glucose from negatively but not from positively charged liposomes. The amount of methylated albumin required to affect liposomes was much smaller than the amount of albumin required to damage liposomes containing lysolecithin. Cholesterol incorporation suppressed the sensitivity of liposomes to both proteins, albumin and methylated albumin. The effect of temperature and fatty acid composition of phospholipids on the sensitivity of liposomes to proteins suggests the importance of the fluidity of the membrane, especially in the case of methylated albumin.

Binding Sites↗
PubMed1976

Properties of liposomal membranes composed of short-chain lecithins.

Permeability properties of multilamellar liposomes prepared from synthetic, saturated short-chain (C8, C10, C12) lecithins (3-sn-phosphatidyl choline) were studied. Dioctanoyllecithin, didecanoyllecithin, and dilauroyllecithin form "stable" bilayers which are practically impermeable to glucose when prepared with proportions of more than 1.2, 0.75, and 0.6 of cholesterol (molar ratio to phospholipid), respectively. Dioctanoyllecithin liposomes were rather leaky above 30 degrees, even when a proportion of 1.5 of cholesterol (molar ratio to lecithin) was incorporated. Judging from their sensitivities to temperature, Triton X-100, serum albumin, and other reagents, short-chain lecithin bilayers show characteristic properties, different from those of both saturated long-chain lecithins (dipalmitoyllecithin and dimyristoyllecithin) and lecithins having unsaturated fatty acid residues (egg lecithin and dioleoyllecithin).

Anti-Bacterial Agents↗
PubMed1976

Nature of Escherichia coli mutants deficient in detergent-resistant and/or detergent-sensitive phospholipase A.

1. Escherichia coli K-12 mutants deficient in detergent-resistant (DR) and detergent-sensitive (DS) phospholipases A and deficient in DS phospholipase A were isolated. 2. The growth, compositions of phospholipids and fatty acids and turnover of phospholipids of three mutants (DR-, DS-, DR-DS-) were compared with those of their parent (DR- was isolated in a previous study). 3. Autodegradations of membrane phospholipids of 18,000 X g supernatants and precipitates of the homogenates of these three mutants were also compared with those of the parent, and the effects of various detergents and organic solvents on these activities were examined. 4. We could not identify any significant physiological role for DR or DS phospholipase A.

Detergents↗
PubMed1975

Lysophospholipase of Escherichia coli.

A lysophospholipase from Escherichia coli cells was purified about 1,500-fold to near homogeneity by extraction with Tris-HCl buffer, streptomycin treatment, (NH4)2SO4 fractionation, column chromatographies on Sephadex G-200, DEAE-cellulose and hydroxylapatite-cellulose, and polyacrylamide gel electrophoresis. The final preparation had a molecular weight of 39,500 plus or minus 500. The enzyme hydrolyzes 1-acylglycerylphosphorylethanolamine, 2-acylglycerylphosphorylethanoiamine, and 1-acylglycerylphosphorylglycerol, but does not attack diacylphospholipids with long chain fatty acids, such as phosphatidylethanolamine and phosphatidylglycerol. The enzyme does not show any esterase activity against p-nitrophenyl acetate or palmitate. Although it does not hydrolyze triacylglycerol or diacylglycerol, it hydrolyzes 1-acylglycerol at almost the same rate as 1-acyl-sn-glycerol-3-phosphorylethanolamine. Results indicated that the acyl-hydrolyzing activities toward monoacyl-glycerylphosphorylethanolamine and monoacylglycerol belong to the same enzyme. In general, acidic and nonionic detergents inhibited the reaction. This lysophospholipase preparation hydrolyzes the monomolecular and micellar forms of lysophospholipids as well as of monoacylglycerol. The monomolecular and micellar forms of Triton X-100 both inhibited the hydrolyses of lysophospholipids and monoacylglycerol.

Carbon Radioisotopes↗
PubMed1975

Effect of polymyxin B on liposomal membranes derived from Escherichia coli lipids.

The specificity of the action of polymyxin B was studied using liposomes as a model membrane system. Liposomes prepared from total lipids of Gram-negative bacteria Escherichia coli, a mixture of purified E. coli phosphatidylethanolamine and cardiolipin and a mixture of phosphatidylethanolamine and phosphatidylglycerol, were extemely sensitive to polymyxin while those prepared from lipids of Gram-positive bacteria Streptococcus sanguis, lipids of sheep erythrocyte membranes, mixtures of egg lecithin and negatively charged amphiphatic molecules, were less sensitive to the action of the antibiotic. Cholesterol was shown to suppress the polymyxin-induced response in liposomes.

Cardiolipins↗