Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LECITHINS”

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 541 records · Page 30Linked to original sources
PubMed1975

[Nutritional needs of adult Drosophila: influence of lecithins and of choline chloride on the fecundity, the fertility and the size of ova].

The lecithin or choline chloride deficiency, in Drosophila, results in an important decrease of the number of eggs produced, hatching and egg size. However, the ovogenesis is not completely stopped, even after 15 days. This effects seem caused by the choline deficiency. When used under the chloride form, choline has no toxic effect even at a rate as high as 3 g/litre. However, the lecithin has toxic effects for amounts up to 4 g/litre. In the adults, the optimal concentration could be about 2 g/litre for the lecithin and 300 mg/litre for the cholin chloride.

Animals↗
PubMed1966

New, partially hydrolyzable synthetic analogues of lecithin, phosphatidyl ethanolamine, and phosphatidic acid.

The synthesis of two new synthetic analogues of lecithin, two of phosphatidyl ethanolamine ("cephalin"), and one new phosphatidic acid analogue is described. They comprise one of each of the following types: the "isosteric" diether lecithin and cephalin analogues ROCH(2)CH(OR)- CH(2)CH(2)P(O) (O(-))OCH(2)CH(2)N(+)R'(3) (R = C(18)H(37); R' = H or CH(3)); and the "hydrocarbon" analogues of phosphatidic acid, lecithin, and cephalin, C(17)H(35)CH(2)CH(C(18)H(37))CH(2)P(O)(R) = (R'); [R = R' = OH; R = O(-), R' = OCH(2)CH(2)N(+)(CH(3))(3); and R = O(-), R' = OCH(2)CH(2)N(+)H(3)]. Infrared spectra and other properties of these compounds are described.

Chemical Phenomena↗
PubMed1982

Quantitative determination of lecithin and sphingomyelin in amniotic fluid.

A quantitative method for lecithin and sphingomyelin is presented. In this method, which may be calibrated with a primary standard phosphate salt or pure phospholipids, 2 mL of amniotic fluid is extracted, and the solvent passed through a column of hydroxyapatite to remove all phospholipids except lecithin and sphingomyelin. After evaporation, the residue is treated with methanolic sodium hydroxide, which hydrolyzes lecithin to inorganic phosphate and a methyl ester. The unreacted sphingomyelin is removed by extraction, and the solvent evaporated. Both fractions are digested and assayed for phosphate by reduced phosphomolybdate. The total time required is 2 h. Analytical recoveries were 91-97%, and excellent agreement was found for controls. Amniotic fluid specimens were assayed to illustrate application of the proposed method. If this method is used for obtaining a lecithin/sphingomyelin ratio, a new ranges must be established, as this method is not equivalent to thin-layer chromatographic ones.

Amniocentesis↗
PubMed1983

Reaction of lecithin:cholesterol acyltransferase with micellar complexes of apolipoprotein A-I and phosphatidylcholine, containing variable amounts of cholesterol.

In a continued investigation of lecithin:cholesterol acyltransferase reaction with micellar, discoidal complexes of phosphatidylcholine (PC) . cholesterol . apolipoprotein A-I (apo-A-I), we prepared well defined complexes with variable free cholesterol contents and examined their reactivity with purified enzyme. The complexes, prepared by the sodium cholate dialysis method, were fractionated into "small" and "large" classes by gel filtration of the reaction mixtures through a Bio-Gel A-5m column. The small complexes had egg-PC/cholesterol/apo-A-I molar ratios from 68:14:1 to 80:1:1, discoidal shapes with diameters around 114 (+/- 13) A and widths of 42 A by electron microscopy, and Stokes radii from 47 to 49 A corresponding to molecular weights near 2 X 10(5). The corresponding properties of the large complexes, isolated from samples with higher cholesterol contents, were egg-PC/cholesterol/apo-A-I molar ratios from 84:26:1 to 96:17:1, diameters of 161 (+/- 20) A, widths of 43 A, Stokes radii around 80 A, and estimated molecular weights in the vicinity of 5 X 10(5). Both types of complexes, when adjusted to equal apo-A-I concentrations, gave essentially identical initial reaction velocities with purified lecithin:cholesterol acyltransferase over a wide range of cholesterol concentrations (from 2 X 10(-7) to 4 X 10(-4) M), PC/cholesterol molar ratios (from 3:1 to 12:1), and quite different lipid fluidity conditions as detected by diphenylhexatriene fluorescence polarization. When complexes were adjusted to a constant cholesterol concentration, the initial velocities of the lecithin:cholesterol acyltransferase reaction followed Michaelis-Menten kinetics relative to the apo-A-I concentrations. Arrhenius plots of initial reaction rates for various complexes with variable cholesterol content and fluidity, measured at constant apo-A-I concentrations, gave identical temperature dependences with an average activation energy of 18.0 kcal/mol. These results strongly suggest that the cholesterol esterification on high density lipoprotein particles does not depend on their unesterified-cholesterol contents, PC/unesterified-cholesterol molar ratios, nor on the fluidity of their lipid domains.

Apolipoprotein A-I↗
PubMed1984

High density lipoproteins and lecithin dispersions increase the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase by increasing the rate of synthesis and decreasing the rate of degradation of the enzyme.

Incubation of rat hepatocytes, prepared from rats fed a normal diet, with either human high density lipoproteins or lecithin dispersions resulted in a dose-and time-dependent increase in the specific activity of 3-hydroxy-3-methylglutaryl-CoA reductase. Incubation of cells with both high density lipoprotein and lecithin dispersions resulted in an additive stimulation of enzymic activity. We used pulse and pulse-chase experiments, followed by immunoprecipitation of the radiolabeled reductase, to demonstrate that high density lipoproteins and lecithin dispersions resulted in increased rates of synthesis and decreased rates of degradation of the reductase. We also demonstrate, by the use of immunoblots, that the increased enzymic activity was paralleled by an equivalent increase in the mass of the reductase. Addition of human low density lipoprotein to rat hepatocytes resulted in a small decrease in both enzymic activity and enzyme synthesis.

Animals↗
PubMed1982

Reaction of human lecithin cholesterol acyltransferase with synthetic micellar complexes of apolipoprotein A-I, phosphatidylcholine, and cholesterol.

Micellar, discoidal complexes of human apolipoprotein A-I (apo A-I) with phosphatidylcholines and cholesterol, prepared by the method described in the preceding paper (Matz, C. M., and Jonas, A. (1982) J. Biol. Chem. 257, 4535-4540), were used as substrates for human lecithin cholesterol acyltransferase, purified 10,000-fold. The micellar complexes of apo A-I.egg yolk-phosphatidylcholine.cholesterol were compared to commonly used substrates of lecithin cholesterol acyltransferase, consisting of small unilamellar vesicles of egg yolk-phosphatidylcholine and cholesterol in the presence of apo A-I. Under identical reaction conditions, the micellar complexes had 4- to 5-fold higher initial velocities and 3-fold greater capacities for cholesterol esters than did the corresponding vesicular substrates. Micellar complexes, labeled with 5-dimethylamino-naphthalene-1-sulfonyl fluorescent groups in the apolipoprotein, were isolated by density gradient centrifugation. After reaction with lecithin cholesterol acyltransferase, they had a shorter rotational relaxation time (290 ns) and smaller Stokes radius (47 A) than the unreacted complexes (530 ns and 57 A, respectively). The characteristic stacked, discoidal particles observed on electron micrographs of negatively stained micellar, unreacted complexes disappeared after enzymatic reaction and were replaced by structures with spheroidal shapes.

Apolipoprotein A-I↗
PubMed1980

[Pharmacologic influencing of fetal phospholipid synthesis. Part IV: influencing the DPL(dipalmitoyl-lecithin) content of fetal lung by betamethasone (author's transl)].

Dipalmitoyllecithinic (DPL) is the quantitatively largest and most active portion of the surfactant system. Hence only a quantitative DPL determination allows a relevant statement of fetal lung maturity. The antenatal prophylaxis of RDS should result in an increase of the DPL-level in a fetal lung. A new gaschromatographical method for determination of DPL was developed. The results were secured by gaschromatography-mass-spectrometry-couplings. After treatment with betamethasone an increase of the relative DPL-amount in fetal rat lung lecithin species was found, but not an increase of the lecithin-level in the lung-tissue. Corticosteroids probably induce transesterification of the lecithins.

Animals↗
PubMed1982

The relative fatty acid composition of serum lecithin in preeclampsia.

Fasting vein blood samples were drawn from 12 women with an early, and from 14 women with a late, onset of preeclampsia and, in addition, from 21 normal pregnant women at comparable gestational length. The relative fatty acid composition of serum lecithin was an analyzed by gas-liquid chromatography. There seemed to be more pronounced fatty acid changes between early and late start of preeclampsia than between severe and mild preeclampsia as defined in terms of maternal symptoms. In the preeclamptic groups, palmitic acid increased and stearic acid decreased as among the normal pregnant women, suggesting a similar amount of lecithin synthesized along pathway. 1. Linoleic acid was reduced in preeclamptic patients as compared to normal pregnant women. This finding seems to be associated partly with the increased incorporation of longer polyunsaturated fatty acids and partly with the increased incorporation of nonessential monoenoic fatty acids. The increased content of longer polyunsaturated fatty acids in serum lecithin might indicate a further reinforcement of the deacylation-reacylation cycle in preeclampsia. Linoleic acid reduction may be associated with intrauterine growth retardation.

Fatty Acids↗
PubMed1981

Regulation of human plasma lecithin:cholesterol acyltransferase activity by lipoprotein acceptor cholesteryl ester content.

Very low density lipoproteins and low density lipoproteins attain maximal cholesteryl ester contents during the incubation of human plasma and, under these conditions, both lecithin:cholesterol acyltransferase and transfer proteins are inhibited. These lipoproteins provide the major part of free cholesterol for the lecithin:cholesterol acyltransferase reaction, and are the major acceptors of cholesteryl ester generated by lecithin:cholesterol acyltransferase and transported to the lipoprotein acceptors by the transfer protein. The results obtained indicate that the concentration of acceptor limits esterification and transfer in plasma, and that in vivo these acceptors contain close to their maximal cholesteryl ester content. Human plasma end product acceptor lipoproteins have a composition similar to that of the ester-rich large low density lipoprotein characteristic of primate models of experimental atherosclerosis.

Cholesterol Esters↗
PubMed1994

Identification of specific amphipathic alpha-helical sequence of human apolipoprotein A-IV involved in lecithin:cholesterol acyltransferase activation.

To investigate the structure-function relationship of human apolipoprotein A-IV (apoA-IV), several deletion mutants of this protein were constructed by sequentially removing pairs of 22-residue repeats, potentially having an amphipathic alpha-helical conformation. The mutants, produced as recombinant poly-histidine-tagged apolipoproteins (t-apo) in Escherichia coli, assembled with phosphatidylcholine (i.e. dimyristoylphosphatidylcholine, palmitoyloleoylphosphatidylcholine, or egg lecithin) as did native apoA-IV. Lecithin:cholesterol acyltransferase (LCAT) cofactor function, measured as cholesterol esterification occurring when t-apo-phosphatidylcholine-cholesterol complexes were incubated with purified enzyme, decreased significantly when pairs of repeats between residues 117 and 248 were deleted and most markedly when residues 117-160 were deleted. LCAT cofactor activity decreased by 90 and 75%, respectively, when egg lecithin or palmitoyloleoylphosphatidylcholine was used to form the particles with the delta aa 117-160 mutant. Thus, on the basis of deletion scanning of t-apo, residues 117-160 seem to be involved in the LCAT cofactor function of apoA-IV.

Amino Acid Sequence↗
PubMed1975

[Role of phosphorylcholine group on inhibiting capacity of lecithin-cholesterol liposomes on streptolysin O].

Cholesterol inhibition of the hemolytic activity of streptolysin O was used for testing the presence of cholesterol on the surface of lecithin-cholesterol liposomes. Cholesterol as a liposome component is not available for streptolysin inhibition when the molar ratio lecithin-cholesterol greater than 1,25. Incubation of such liposomes with phospholipase C, which converts the phosphadylcholine group into neutral diglycerides, restores an inhibiting activity of cholesterol parallel to the phosphatid degradation. Incubation of the liposomes with phospholipase D, which converts the phosphatidylcholine group into phosphatidic acid, also restores the inhibiting capacity of cholesterol on the hemolysin. The accessibility of liposome cholesterol to streptolysin O appears to mainly depend upon the cholin group of lecithin.

Cholesterol↗
PubMed1996

Adsorption of mixtures of bile salt taurine conjugates to lecithin-cholesterol membranes: implications for bile salt toxicity and cytoprotection.

Tauroursodeoxycholate (TUDC), a relatively hydrophilic bile salt, reduces disruption of cholesterol-rich membranes by more hydrophobic bile salts such as taurocholate (TC), taurochenodeoxycholate (TCDC), or taurodeoxycholate (TDC). We examined the interactions of these bile salts in adsorption to large unilamellar vesicles to determine whether TUDC may stabilize membranes by preventing adsorption of more toxic bile salts. Fractional adsorption was quantified by rapid ultrafiltration. Adsorption coefficient Ai was defined for each bile salt i as ([bound i]/[free i])/[lecithin]. Affinity of different bile salts for lecithin vesicles varied with their relative hydrophobicity, increasing in the order TUDC < TC << TCDC < or = TDC. Ai of each bile salt fell with its accumulation on membranes, reaching a minimum at bound bile salt/lecithin mole ratio (B:L) between 0.05 and 0.1, then increasing with formation of higher-affinity mixed micelles. Inclusion of cholesterol in vesicles reduced Ai of all bile salts. In heterologous binding studies at submicellar concentrations, Ai of each bile salt varied with total B:L but was independent of the specific bile salts present on the membrane. Addition of TUDC to TDC reduced binding of TDC to membranes only slightly and lowered the threshold TDC concentration associated with transition to mixed micelles. However, above this threshold, TUDC markedly altered the adsorption of TDC to lecithin-containing phases. We conclude that TUDC does not directly stabilize membranes; rather, reduced permeabilization and dissolution of cholesterol-rich membranes after addition of TUDC to TDC may result from effects on the formation and structure of simple and mixed micelles.

Adsorption↗
PubMed1977

Molecular interactions between lecithin and sphingomyelin. Temperature- and composition-dependent phase separation.

X-ray diffraction, scanning calorimetry, and polarizing light microscopy have used to determine the complete ternary phase diagram egg yolk lecithin/bovine brain sphingomyelin/water over the temperature range 10-44 degrees. The phase diagram shows that lateral separation of phospholipid bilayer phases can arise from variations in both composition and temperature. At 44 degrees in excess water, lecithin and sphingomyelin are miscible at all ratios in a lamellar liquid crystal bilayer phase. For samples containing greater than 33 mol % sphingomyelin, colling to 20 degrees results in the progressive lateral separation of an ordered chain sphingomyelin lamellar gel phase from the lecithin/sphingomyelin liquid crystal bilayer phase. At 20 degrees and below, the spingomyelin gel phase co-exists with an ordered bilayer phase, a stoichiometric peritectic molecular compound (66 mol % lecithin, 33 mol % sphingomyelin). Cooling mixtures containing less than 33 mol % sphingomyelin ultimately separates the compound from a lecithin liquid crystal bilayer phase containing small amounts of sphingomyelin. Although singificant variations in the lecithin/sphingomyelin ratio occur in normal and pathological membranes, at 37 degrees our results would suggest complete bilayer phase and lateral phase separation of the "ordered" sphingomyelin gel phase appears uplikely.

Calorimetry, Differential Scanning↗
PubMed1976

Transfer of cholesterol and lecithin between erythrocytes and serum in vitro.

1. In human blood incubated in vitro, the transfer of free cholesterol and lecithin from erythrocytes to serum was not related to glycolytic activity in erythrocytes or esterification of cholesterol in serum. 2. The stability of free cholesterol concentration in serum was dependent on the activity of lecithin:cholesterol acyltransferase (EC 2.3.1.43), and the stability of lecithin concentration in erythrocytes, on glycolytic activity.

Acyltransferases↗
PubMed1998

Lecithin can be detected by volume-selected proton MR spectroscopy using a 1.5 T whole body scanner: a potentially non-invasive method for the prenatal assessment of fetal lung maturity.

The prenatal determination of fetal lung maturity is currently assessed by chemical analysis of surfactant associated lipids from aminotic fluid obtained by amniocentesis. This is an invasive procedure with rare but occasionally serious morbidity. Magnetic resonance spectroscopy (MRS) is a non-invasive method for the in vivo localization and identification of molecules with known resonance peaks at specified chemical shifts. In this report we examine the in vitro MRS of a lecithin/saline solution as well as term and preterm amniotic fluid samples with the use of a 1.5 T whole body scanner and a flexible surface coil. We found that amniotic fluid at term demonstrates a resonance peak at 3.2 ppm which was the same as the chemical shift of lecithin in saline. The lecithin peak is not observed in preterm amniotic fluid. This demonstrates the feasibility of using MRS with a whole body scanner to detect lecithin, one of the markers for fetal lung maturity.

Adult↗
PubMed1961

The Third International Reference Preparation of Egg Lecithin.

The Third International Reference Preparation of Egg Lecithin was produced (in a quantity of 5000 ml) at the WHO Serological Reference Centre, Copenhagen, and assayed in 1958 against the Second International Reference Preparation by four laboratories in three countries. Complement-fixation and slide-flocculation tests were used. The new preparation was found acceptable, and its establishment was authorized by the WHO Expert Committee on Biological Standardization.The average log(10) titres and results of analyses of variances are shown. The variances were of the usual order of magnitude, and the differences in titre between antigens containing the Second and the Third International Reference Preparations varied from -0.011 to 0.116; only one of the differences exceeded the 5% limit of significance.The use of the Third International Reference Preparation in tests for the acceptability of lecithin preparations is described.

Biological Assay↗
PubMed1964

MICROAEROSOL ADMINISTRATION OF SYNTHETIC BETA-GAMMA-DIPALMITOYL-L-ALPHA-LECITHIN IN THE RESPIRATORY DISTRESS SYNDOME: A PRELIMINARY REPORT.

Synthetic L-alpha-lecithin was administered by inhalation to 11 infants suffering from respiratory distress. The L-alpha-lecithin was delivered by microaerosolization, at a concentration of 0.25% in a mixture of equal volumes of propylene glycol and water. This was done with the aim of decreasing the alveolar surface tension. In eight of the treated infants who survived, the respiratory distress was alleviated. The results are inconclusive but they justify further investigation.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Lecithin cholesterol acyl transferase deficiency: molecular analysis of a mutated allele.

The enzyme, lecithin cholesterol acyltransferase (LCAT), is responsible for the esterification of plasma cholesterol mediating the transfer of an acyl group from lecithin to the 3-hydroxy group of cholesterol. Deficiency of the enzyme is a well-known syndrome with a widespread geographic occurrence. We have cloned an allele from a patient homozygous for the LCAT deficiency. The only change that we could detect is a C to T transition in the fourth exon of the gene; this causes a substitution of Arg for Trp at position 147 of the mature protein. The functional significance of such a substitution with respect to the enzyme defect was demonstrated by transfecting the mutated LCAT gene in the cell line COS-1.

Alleles↗