Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LYSOLECITHIN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1979

Effect of lysolecithin in solubilizing membrane-bound glycosyltransferases.

Microsomal membranes were solubilized by incubation with lysolecithin which caused considerable release of galactosyl- and N-acetylglucosaminyl-transferase into a high-speed supernatant fraction. With a critical concentration of lysolecithin (2.5 mg/10 mg protein in 1 mL microsome suspension), there was a maximal binding of radioactive lysolecithin to the sediment fraction obtained after high-speed centrifugation. Increase of lysolecithin concentration (above 2.5 mg/mL) in the incubation mixture caused a progressive release of the enzymes into the supernatant fraction. Lysolecithin binding to the membrane was greatly inhibited by 1 M NaCl, and high salt concentration also inactivated galactosyltransferase in the sediment, suggesting an electrostatic interaction between lysolecithin and membrane enzyme. In contrast, high NaCl concentration had no inhibitory effect on the enzyme activity in the sediment when the fraction was prepared by treatment with Triton X-100. Lysolecithin-treated microsomal sediment and supernatant galactosyltransferase was inactivated by oleoyllysophosphatidic acid but not by palmitoyllysophosphatidic acid or egg yold lysophosphatidic acid. Triton X-100 treated microsomal fractions were also similarly affected by different species of lysophosphatidic acid. The results suggested a similarity of interactions of lysophosphatidic fatty acyl species with lysolecithin and Triton-treated galactosyltransferase.

Animals↗
PubMed1976

Enzymatic hydrolysis of 1-monoacyl-SN-glycerol-3-phosphoryl-choline (1-lysolecithin) by phospholipases from peanut seeds.

Hydrolysis of 1-lysolecithin (1-acyl glycerophosphorylcholine [1-acyl GPC]) by preparations of phospholipase D from peanut seeds was investigated. 1-Lysolecithin was hydrolyzed at a much slower rate than phosphatidylcholine (lecithin). Although Ca+2 ions are required for the cleavage of lecithin by the enzyme, their effect on the hydrolysis of lysolecithin depended upon the concentration of the substrate: at 0.2 mM 1-lysolecithin, Ca+2 ions increased the reaction rates, whereas at concentrations of the substrate lower than 0.1 mM, Ca+2 ions were inhibitory. A broad pH activity curve between 5 and 8 was obtained with higher rates in the alkaline range, both in the absence and presence of Ca+2 ions. The increased hydrolysis of lysolecithin due to Ca+2 was noticed over the entire pH range. Upon storage of the enzyme solutions at 4 C, decreased rates of hydrolysis of lecithin were observed, with t 1/2 values of ca. 50 and 100 days depending on the purity of the preparation. During the same period, no reduction occurred in the activity of these preparations on lysolecithin as substrate. The effects of Ca+2 ions and the analysis of the products of 1-acyl GPC cleavage by the enzyme preparations revealed the presence of more than one enzyme and the formation of the following compounds: lysophosphatidic acids (1 acyl glycerophosphoric acids), free fatty acids, glycerophosphorylcholine, and choline. The possible pathways leading to the degradation of lysolecithin and the formation of these products include reactions catalyzed by lysophospholipase A1 (lysophosphatidylcholine 1-acyl hydrolase, E.C. 3.1.1.5) and a phosphodiesterase (L-3-glycerylphosphorylcholine glycerophosphohydrolase, E.C.3.1.4.2), in addition to phospholipase D (phosphatidyl-choline phosphatidohydrolase, E.C. 3.1.4.4).

Arachis↗
PubMed1985

Intestinal cholesterol uptake: comparison between mixed micelles containing lecithin or lysolecithin.

The aim of our study was to define the mechanism by which cholesterol uptake is inhibited by lecithin but not by lysolecithin. The work compared the cholesterol uptake by everted rat jejunal sacs from bile salt-lecithin-cholesterol or bile salt-lysolecithin-cholesterol micelles. The micellar size and the cholesterol saturation were measured. The size or molecular weight increases when the lecithin concentration rises, and the cholesterol uptake decreases and leads to zero when the micelles contain more than 30% lecithin. The size of bile salt-lysolecithin-cholesterol micelles is smaller than that of lecithin micelles in comparable molar ratios. Consistent with this result is the fact that, for a given phospholipid concentration, cholesterol uptake is greater in the presence of lysolecithin than in the presence of lecithin. The diffusion rate of the micelles through the unstirred water layer decreases when micellar size increases. However, the comparison of uptakes from lecithin or lysolecithin micelles similar in size and in cholesterol saturation showed that the cholesterol uptake is still lower for lecithin micelles. This shows that with larger micelles some factor other than micellar size and cholesterol content of the micelles is important. We observe that lysolecithin absorption is 15-fold greater than lecithin absorption. We suggest that lysolecithin absorption results in a rapid supersaturation with cholesterol leading to cholesterol absorption.

Animals↗
PubMed1976

Selective solubilization of the components of the mitochondrial inner membrane by lysolecithin.

1. Of various phospholipids tested, lysolecithin was the most efficient in the solubilization of the components of beef heart submitochondrial particles. Lysolecithin solubilized selectively nicotinamide nucleotide transhydrogenase, succinate dehydrogenase, NADH dehydrogenase and oligomycin-sensitive ATPase. Various cytochromes other than cytochrome c were only slightly solubilized. 2. The effect of various parameters, e.g. ionic strength, pH, time of centrifugation, and concentrations of lysolecithin and protein was investigated. Increasing times of centrifugation led to a partial sedimentation of NADH dehydrogenase, and a complete sedimentation of oligomycin-sensitive ATPase and cytochrome oxidase. 3. Further fractionation of the lysolecithin extract by centrifugation in the presence of low concentrations of cholate gave a complete separation of NADH dehydrogenase and transhydrogenase, indicating that these enzymes are not related functionally. 4. With the lysolecithin fractionation procedure a more than 10-fold purification of transhydrogenase was achieved. Polyacrylamide gel electrophoresis of the partially purified transhydrogenase in the presence of sodium dodecyl sulphate showed major increases in protein-stained bands corresponding to between 70 000 and 54 000 daltons. 5. A possible mechanism for the detergent action of lysolecithin involving a specific exchange of bound phospholipids for lysolecithin is discussed.

Adenosine Triphosphatases↗
PubMedDate not supplied

Lysolecithin-dependent release of cholesterol from rat plasma.

We studied the effect of lysolecithin on the clearing of plasma cholesterol. The immediate and maximal conversion of plasma lecithin to lysolecithin was produced in rats by intravenous injection of phospholipase A. The changes which took place in the converted lysolecithin and of cholesterol were followed in rats which had previously received [32-P]phosphate and [14-C]cholesterol. We followed simultaneously the in vitro changes in blood removed immediately after the in vivo administration of phospholipase A. The experiments showed that a substantial part of the plasma lecithin was converted to lysolecithin within the first minute after intravenous administration of phospholipase A. In the course of 60 min of blood incubation, the ratio of plasmatic lysolecithin in the closed system continued to increase. At the same time the content of cholesterol also increased. In vivo, the converted lysolecithin was quickly released from the plasma, so that within 10 min the original lecithin content dropped to 15-5% depending on the dose of phospholipase A that had been administered. The content of sphingomyelin and lysolecithin, which increased only temporarily shortly after injection, did not alter during the experiment. The level of plasma cholesterol esters, however, dropped significantly, whereas the free cholesterol content increased. The molar ratio of the drop in lipid phosphorus and cholesterol esters in plasma after the administration of phospholipase A was similar. A significantly higher cholesterol content was found in the liver of animals treated with phospholipase A.

Animals↗
PubMed1984

1-Acyl-lysolecithin acyltransferase and synthesis of biliary lecithins in rat liver.

The role of lysolecithin acyltransferase activities in biliary lecithin formation was investigated, using livers perfused in the presence of labeled palmitoyl-lysolecithin and albumin, overloaded or not with linoleic acid. At the end of liver perfusion, the lecithins extracted from microsomes, mitochondria and plasma membranes displayed the same specific activity. Double-labeled lysolecithin was used to prove that labeled lecithins were synthesized by lysolecithin acylation. In the absence or presence of a linoleic acid overload, the level of lysolecithin incorporation into linoleyl and arachidonyl containing lecithin was identical. Hence fatty acids did not influence phosphatidylcholine synthesis by the acylation pathway. In vitro the rate of linoleyl lecithin synthesis was the same in plasma membranes, mitochondria and microsomes provided the linoleyl-CoA concentration was lower than 30 microM. Taurocholate was essential to the excretion of lecithin synthesized from lysolecithin and stimulated its synthesis. The specific activities of the two lecithin molecular species excreted in bile (linoleyl and arachidonyl) were not significantly different. These results enabled us to evaluate the contribution of the lysolecithin pathway to the synthesis of lecithin in liver and bile: this contribution in bile was less than 2% under the perfusion conditions used.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1988

Dielectric spectroscopy of L-alpha-lysolecithin-packaged gramicidin A.

The complex permittivities of L-alpha-lysolecithin in the absence and presence of the gramicidin A ion channel were measured over the temperature range 0-60 degrees C and over the frequency range 1-1000 MHz. One dielectric relaxation/loss has been observed. It is located at 103.3 MHz (1.54 ns) for a micellar 0.4 M L-alpha-lysolecithin solution at 20 degrees C, whereas it is shifted to 71.7 MHz (2.22 ns) for a lamellar L-alpha-lysolecithin-gramicidin A aqueous solution (0.4 M L-alpha-lysolecithin, 0.0308 M gramicidin A) at 20 degrees C. The dielectric relaxation decreases and the relaxation time increases when gramicidin A is incorporated into L-alpha-lysolecithin. These dielectric changes are related, in part, to the micellar-to-lamellar lipid phase transition induced by the incorporation of gramicidin A into lysolecithin. We suggest that the diffuse rotational motion of the polar head group of L-alpha-lysolecithin contributes to the dielectric relaxation/loss at around 100 MHz.

Electrochemistry↗
PubMed1988

Lysolecithins as endothelium-dependent vascular smooth muscle relaxants that differ from endothelium-derived relaxing factor (nitric oxide)

The effects of lysolecithin (lysophosphatidylcholine) derived from egg yolk as well as of synthetic lysolecithins with different aliphatic chain lengths on tension development of rabbit aortic strips were investigated. Lysolecithins caused slowly progressing, dose-dependent relaxation that was inhibited by hemoglobin, methylene blue, and nordihydroguiaretic acid. Indomethacin caused no inhibition of relaxation. The degree of relaxation was endothelium-dependent and appeared to be related to the activation of guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2]. Superoxide dismutase failed to influence relaxation. Lysolecithins with the longest aliphatic chain were the most potent relaxants of aortic strips. The experiments suggest a role of lysolecithins through their weak detergent action on membrane dynamics of endothelial cells, resulting in the production of cyclic GMP and the relaxation of arterial smooth muscle. Lysolecithins differ in several respects from endothelium-derived relaxing factor. Endothelium-derived relaxing factor is an unstable humoral substance released from endothelium and is identical to nitric oxide, itself a labile substance causing vascular relaxation and cyclic GMP accumulation. Lysolecithins may represent a different type of endothelium-dependent muscle relaxant.

Acetylcholine↗
PubMed1995

Lysolecithin-induced alteration of subendothelial heparan sulfate proteoglycans increases monocyte binding to matrix.

The cause and consequence of altered proteoglycans in atherosclerosis are poorly understood. To determine whether proteoglycans affect monocyte binding, we studied the effects of heparin and proteoglycan degrading enzymes on THP-1 monocyte adhesion to subendothelial matrix (SEM). Monocyte binding increased about 2-fold after SEM was treated with heparinase. In addition, heparin decreased monocyte binding to fibronectin, a known SEM protein, by 60%. These data suggest that SEM heparan sulfate inhibits monocyte binding to SEM proteins. We next examined whether lysolecithin, a constituent of modified lipoproteins, affects endothelial heparan sulfate proteoglycan (HSPG) production and monocyte binding. Lysolecithin (10-200 microM) decreased total 35SO4 in SEM (20-75%). 2-fold more monocytes bound to SEM from lysolecithin treated cells than to control SEM. Heparinase treatment did not further increase monocyte binding to lysolecithin-treated SEM. HSPG degrading activity was found in medium from lysolecithin-treated but not control cells. 35SO4-labeled products obtained from labeled matrix treated with lysolecithin-conditioned medium were similar in size to those generated by heparinase. These data suggest that lysolecithin-treated endothelial cells secrete a heparanase-like activity. We hypothesize that decreased vessel wall HSPG, as occurs in atherogenic conditions, allows increased monocyte retention within the vessel and is due to the actions of an endothelial heparanase.

Animals↗
PubMed1975

[Isolation, identification and quantitative determination of lysolecithin in the human gastric juice].

Lysolecithin was isolated and identified from the gastric contents of 5 patients with gastric ulcer and erosive and atrophic gastritis. The methods used involved methanolic extration, column chromatography on silica gel and sephadex gel filtration, followed by preparative thin layer chromatography. Identification of lysolecithin was verified in one sample by thin layer chromatography and elementary analysis. A method for quantitation of lysolecithin in human gastric fluid for routine clinical analysis is described, based on the procedure used for identification of this phospholipid. Further, a hemolysis test is proposed for screening gastric contents for lysolecithin concentrations above approximately 10 mg/100 ml. With the quantitative method, an average concentration of 66.1 mg of lysolecithin in 100 ml gastric content was found in the group of 5 patients. The screening test was positive in all 5 samples, but was negative with native gastric juice in 25 persons serving as controls. When the gastric fluid of the controls was concentrated, however, 9 samples gave a positive hemolytic reaction. From these 9 specimens, the lysolecithin concentration was found to average 0.9 mg/100 ml. These findings afford evidence that lysolecithin may be involved as a factor in the pathogenesis of gastric ulceration.

Chromatography, Thin Layer↗
PubMed1983

In vitro studies on the aggregation of isolated lipoprotein(a) upon addition of lysolecithin.

A precipitating effect of lysolecithin on isolated and purified lipoprotein (a) [Lp (a)] was detected and investigated in vitro. After addition of external lysolecithin at an initial concentration of 100 mu mol/l (which is about the concentration of lysolecithin produced per hour in human serum), the lipoprotein solution started to get turbid; turbidity was monitored at 450 nm. This effect was studied in dependence on the ionic strength of the buffer, revealing maximum precipitation in isotonic solutions. Limited trypsinisation or treatment of Lp(a) with neuraminidase changed the surface of that lipoprotein so that no precipitation could be caused by lysolecithin, indicating the role of the protein-carbohydrate part for the aggregation. A difference between L-alpha and DL-alpha lysolecithin could also be established. A weaker precipitating reaction was found for the latter. The presence of serum albumin at physiological serum concentrations weakened the precipitating power of lysolecithin to a certain degree, but could not stop the process. The aggregates were investigated by means of the electron microscope using negative staining for fixation. The individual Lp(a)-particles could still be distinguished but they stuck together in a bulky conformation. Low density lipoprotein (LDL) used as a reference did not show any precipitation by lysolecithin.

Apolipoproteins↗
PubMed1980

Membrane stabilizing effect of lysolecithin in calf red blood cells.

Lysolecithin sensitivity of red blood cells of 4--6 weeks old calves and 5--10 years old cattles was compared in the presence of 1 and 10 microM lysolecithin. When the incubation temperature of red blood cell suspension was increased from 0 or 22 degrees C to 37 degrees C, the addition of 1 microM lysolecithin resulted in reduction of haemolysis and relative stabilization of the membrane as compared to that observed in lysolecithin-free medium. This stabilizing effect was found first of all in calf red blood cells. This effect is hardly detectable in adult cattle red blood cells. ATP depletion resulted in reduction of the stabilizing effect of lysolecithin in calf red blood cells as well. In the presence of 10 microM lysolecithin elevation of the incubation temperature from 22 degrees C to 37 degrees C enhanced the haemolysis of calf red blood cells, while the haemolysis of adult cattle red blood cells was practically not affected. The present results indicate that lysolecithin sensitivity of red blood cells is remarkably different in new-born and adult animals.

Adenosine Triphosphate↗
PubMed1978

The effect of dbcAMP on the lysolecithin induced hemolysis of calf and adult cattle erythrocytes.

The calf erythrocytes have an increased sensitivity against lysolecithin as compared to their adult counterparts. 10(-3)M dbcAMP increases the hemolysis induced by 5 microgram of lysolecithin in 0.15 M NaCl containing 10 mM phosphate buffer (pH 7.4). By increasing the level of phosphate buffer (75 mM) in the incubation mixture, 10(-3)M dbcAMP decreases the hemolysis induced by 5 microgram of lysolecithin. These data suggest a dual effect exerted by dcbAMP: the relatively labilizing or stabilizing effect prevails as a function of exogenous inorganic phosphate level. 10(-6)M dcbAMP also has a relative protective effect against lysolecithin. The combined addition of cAMP (10(-3)) and theophyllin (10(-4)M) does not stabilize the membrane. By increasing the level of lysolecithin to 20 microgram/ml the stabilizing effect of dcbAMP disappears. DbcAMP (10(-3)) as well as cAMP (10(-3)M) and theophyllin (10(-4)M) have a minimum increasing effect on hemolysis in the absence of lysolecithin, too.

Age Factors↗
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↗
PubMed1987

Morphology of lysolecithin-induced damage on esophageal mucosa. An experimental light and scanning electron microscopical study.

The morphology of the esophageal mucosal damage induced by lysolecithin was investigated in an experimental model, where an isolated segment of rabbit esophagus was purfused in situ with lysolecithin, alone or in combination with HCl. The results indicate that lysolecithin alone causes no morphological damage to the esophageal mucosa. However, when combined with HCl, lysolecithin causes widening of intercellular spaces and detachment of superficial cells leading ultimately to disclosure of denuded submucosal collagen bundles. This suggests that, in clinical situations lysolecithin refluxed from the duodenum into the stomach and further to esophagus may have importance in the pathogenesis of reflux esophagitis when gastric acid is present, too. In contrast, under unacidic conditions (i.e., in the pathogenesis of alkaline reflux esophagitis) lysolecithin seems to be of minor importance.

Animals↗
PubMed1995

Influence of nonesterified fatty acids and lysolecithins on thyroxine binding to thyroxine-binding globulin and transthyretin.

The hydrolysis of lecithin by phospholipase produces equimolar amounts of nonesterified fatty acids (NEFAs) and lysolecithin. In this study, we have evaluated the effect of lysolecithins and NEFAs on thyroid hormone binding by examining their interactions with thyroxine-binding globulin (TBG)(serum 1:10,000 dilution) and purified transthyretin (TTR). Unsaturated NEFAs (palmitoleic, oleic, linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acid) inhibited [125I]T4 binding to TBG. Their affinities, relative to unlabeled T4, ranged from 0.005 to 0.0016%, except for oleic acid with relative affinity of < 0.0005%. Saturated NEFAs, lauric, myristic, palmitic, and stearic acid were inactive. After purification by high-performance liquid chromatography, 1-oleoyl and 2-oleoyl lysolecithin displaced [125I]T4 from TBG with an affinity of 0.0006 and 0.0005%, respectively. On a molar basis, this affinity was approximately 10-fold lower than arachidonic acid, the most potent NEFA in inhibiting T4 binding to TBG in this assay system. Of all the NEFAs tested, only arachidonic acid inhibited [125I]T4 binding to TTR, with an affinity relative to unlabeled T4 of 0.49%. 1-Oleoyl, 1-palmitoyl, and 1-stearoyl lysolecithin were without effect on TTR binding. The T4-displacing effects of NEFAs are markedly attenuated by their extensive binding to albumin. Using purified [14C]NEFA preparations and heptane partitioning, the mean unbound percentages of linoleic, eicosapentaenoic, and docosahexaenoic acid in undiluted normal human serum were 0.00099, 0.0050, and 0.0042%, respectively (n = 3). In view of the very high degree of albumin binding of NEFAs, studies in diluted serum will grossly overestimate their competitor potency. The affinities of lysolecithins for the T4 binding sites of TBG and TTR are lower than those of NEFAs and depend on the fatty acid component. Lysolecithins are unlikely to influence plasma protein binding of T4 during critical illness.

Arachidonic Acid↗
PubMed1981

Passage of molecules through the wall of the gastrointestinal tract. Increased passive permeability in rat ileum after exposure to lysolecithin.

The interaction between lysolecithin and mucosal cells in the distal ileum has been studied. Using a rat experimental model, we determined the intestinal permeability to fluorescent dextran 3000 after exposure to different amounts of lysolecithin. At pH 7.3, lysolecithin, 10 mg/ml, significantly enhanced the transmural passage, and at pH 3.5, even 1 mg/ml markedly increased the permeability. However, when lysolecithin was incubated with homogenized mucosal cells, a rapid disappearance of the compound occurred; this was accompanied by formation of free fatty acids and minor formation of lecithin. It appears, therefore, that high concentrations of lysolecithin can impair the intestinal barrier function in the distal part of ileum but that the mucosal cells are well equipped with activities for the rapid removal of such high concentrations. This could be physiologically significant, since the mucosal cells could otherwise be faced with large amounts of lysolecithin that might facilitate the absorption of potentially antigenic and toxic compounds.

Animals↗
PubMed1986

Lysolecithin affects the viscosity, permeability, and peptic susceptibility of gastric mucin.

The effect of lysolecithin and lecithin on gastric mucin viscosity, permeability to hydrogen ion, and degradation by pepsin was investigated. Preincubation with lysolecithin produced a marked decrease in the glycoprotein viscosity. This decrease was concentration-dependent and at 10 mM lysolecithin reached a value of 74%. A 25% increase in mucin viscosity was obtained with 10 mM lecithin. Permeability measurements showed that 10 mM lecithin increased the retardation ability of the glycoprotein to hydrogen ion by 11%, whereas a 12% decrease in the retardation capacity of the glycoprotein was obtained with 10 mM lysolecithin. The results of peptic activity assay indicated that whereas lecithin had no effect on the rate of mucin proteolysis, the lysolecithin exerted significant (75%) stimulatory effect. The results suggest that lysolecithin in the stomach weakens the integrity of the protective mucus layer by promoting peptic degradation, reducing the ability to resist acid penetration, and decreasing viscosity of its mucin component.

Animals↗