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PubMedDate not supplied

Chemiluminescence in the coupled oxidation of lecithin and ascorbate.

Chemiluminescence (CL) that appears during oxidation of lecithin and ascorbate has been studied. A simple system consisting only of purified lecithin, which has one double bond, and ascorbate as a physiological reductant with a low redox potential, was used. The CL spectrum of lecithin contain a strong band lying in the near infrared, and three bands at 20 900 cm-1, 17 700 cm-1 and 15 800 cm-1, being characteristic of singlet molecular oxygen (1O2). The effect of 1O2 quenchers on both autooxidation processes has also been investigated. The obtained results indicate that the main emitter is the 1O2. An addition of ascorbate to the system lecithin plus buffer causes a decrease of CL intensity. That is a result of stronger quenching properties of ascorbate and not due to efficiency of the generation of 1O2.

Ascorbic Acid↗
PubMed1976

Serum lipids and fatty acid composition of serum lecithin in the non-pregnant state in patients with previous cholestasis of pregnancy.

Serum lipids and fatty acid composition of serum lecithin were studied 8-21 months after delivery in 20 non-pregnant women who during their latest pregnancy had presented signs of CP. These women were compared with normal non-pregnant women (n=18) and with patients with cholestasis of pregnancy (CP) (n=28). In the non-pregnant state women with previous cholestasis of pregnancy (CP) showed in serum lecithin a low relative content of palmitic (16:0) and linoleic (18:2) acids and a high portion of stearic acid (18:0). These findings indicate as a basic defect in CP, a reduction in liver lecithin synthesis via pathway I (Kennedy's pathway) in favour of an increased pathway II (Greenberg's pathway). These data further support the hypothesis of increased estrogen activity as an etiological factor in CP. The basic influence by pregnancy on serum lipids and serum lecithin fatty acid composition was the same in women with CP as in women with a normal pregnancy.

Adult↗
PubMed1996

Interfacial properties as stability predictors of lecithin-stabilized perfluorocarbon emulsions.

The purpose of this study was to determine whether the addition of small quantities of minor lecithin components (phosphatidylinositol, phosphatidic acid, lysophosphatidylethanolamine, and cholesterol) and Pluronic F68 to lecithin could improve the stability of lecithin-stabilized perfluorocarbon emulsions. Attempts were made to correlate emulsion stability with interfacial properties (tension and charge). Dynamic interfacial tension was determined using a Teflon Wilhelmy plate method [reported previously (1)]. Emulsions were prepared by microfluidization. Microelectrophoresis was used to measure emulsion droplet charge, and photon correlation spectroscopy and Coulter analysis were used to determine emulsion stability as a function of droplet size. Thermal kinetic accelerated stability testing was conducted. Various droplet size parameters were used to compare emulsion stabilities, and an overall stability ranking, based on these parameters, was obtained for each emulsion. Small quantities of additives altered emulsion stability and these data were correlated with interfacial properties and initial droplet diameters. The addition of cholesterol to lecithin resulted in the most stable perfluorocarbon emulsion.

Chemical Phenomena↗
PubMed1977

Phospholipase C from Bacillus cereus. Action on some artificial lecithins.

The hydrolysis by phospholipase C from B. cereus of several lecithins of different fatty acyl chain length was examined. The enzyme showed significant activity towards mono-molecularly dispersed short chain lecithins and the reaction obeyed normal Michaelis-Menten kinetics. Rate vs. substrate concentration curves obtained with dihexanoyl-, diheptanoyl- and dioctanoyllecithins showed marked discontinuities in the region of the known critical micelle concentrations for these substrates and distinctly higher rates were obtained just above these levels. Using these three lecithins at levels below their respective critical micelle concentrations, rate increases were noted if the reactions were allowed to proceed to a sufficiently great extent. The presence of deoxycholate in the reaction system had little or no effect on the rate of enzyme-catalysed hydrolysis of lecithins of fatty acyl chain length less than or equal to Cbeta, but for fatty acyl chain lengths greater than C10, significant rate increases occurred. The pH profile for the enzyme activity was also examined.

Bacillus cereus↗
PubMed1978

Antimycobacterial activity of lecithin-cholesterol liposomes in the presence of phospholipase A2.

Tubercle bacilli were preincubated with lecithin-cholesterol liposomes to be subsequently exposed to phospholipase A2. After further incubation in the environment of acidic buffer, viable units in the final mixture were enumerated by inoculating the serial dilutions of an aliquot onto Kirchner agar medium containing horse serum in 5%. Another aliquot was used for lipid analyses to confirm hydrolysis of lecithin. In addition to this bactericidal type of experiments, bacteriostatic tests were also conducted with Kirchner semi-solid agar medium, into which liposome-treated bacilli were inoculated with the enzyme at a time. Various natural and synthetic lecithins different in constituent fatty acids were employed. The results indicated that toxic fatty acids released from lecithin acted to kill the bacilli or to inhibit their growth.

Cholesterol↗
PubMedDate not supplied

Improving emulsification efficacy of lecithin by formulation design. I: Effect of adding a secondary surfactant.

The objective of this study was to seek improvement in the emulsification efficacy of lecithin by formulation design. A Base Emulsion was developed containing lecithin as the primary emulsifier. The lecithin concentration and method of preparation of the Base Emulsion were optimized to obtain minimum particle size and creaming of the emulsion. Selected hydrophilic and hydrophobic synthetic surfactants were evaluated as secondary emulsifiers for their ability to reduce particle size of the Base Emulsion. The selection of type and concentration of the secondary emulsifier was done by application of the HLB method. The hydrophilic emulsifiers selected were Tween 80, Tween 20, Pluronic F68, and Pluronic F127. The hydrophobic surfactants studied included Span 20, Span 80, Pluronic P103, and Pluronic P123. The median droplet size of the Base Emulsion was 2.7 microns. Addition of the hydrophilic emulsifiers caused an increase in particle size and substantial creaming of the emulsions. Addition of three of four hydrophobic surfactants resulted in particle size reduction, but the emulsions showed substantial creaming. Span 20 was found to be the most effective secondary emulsifier. The median particle size of the emulsion was 1.7 microns. These results suggest that supplementing the hydrophilic attributes of lecithin with an appropriate type and amount of hydrophobic surfactant improves the emulsion properties by applying principles of formulation design.

Chemistry, Pharmaceutical↗
PubMed1992

Lecithin increases plasma free choline and decreases hepatic steatosis in long-term total parenteral nutrition patients.

Plasma-free choline levels have previously been found below normal in patients receiving long term parenteral nutrition (TPN). In a group of 15 patients receiving home TPN who had low plasma free choline levels (6.3 +/- 0.8 mmol/L), we found 50% had hepatic steatosis. These patients were given oral lecithin or placebo in a double-blind randomized trial for 6 weeks. Lecithin supplementation led to an increase in plasma free choline of 53.4% +/- 15.4% at 2 weeks (P = 0.04), which continued at 6 weeks. The placebo group had no change in plasma-free choline at 2 weeks, but a significant decrease of 25.4% +/- 7.1% (P = 0.01) at 6 weeks. A significant and progressive decrease in hepatic fat was indicated by increased liver-spleen CT Hounsfield units at 2 and 6 weeks (7.5 +/- 1.7 units, P = 0.02; 13.8 +/- 3.5 units, P = 0.03) in the lecithin supplemental group. Nonsignificant changes were seen in the placebo group. It was concluded that hepatic steatosis in many patients receiving long term TPN is caused by plasma-free choline deficiency and may be reversed with lecithin supplementation. Choline is a conditionally essential nutrient in this population.

Aged↗
PubMedDate not supplied

Effect of exogenous lecithin on ethanol-induced testicular injuries in Wistar rats.

Infertility is well-established harmful effect in chronic alcoholism and so far, there is no effective treatment for this condition. The study was conducted to determine the effects of lecithin, a known hepatoprotective on ethanol induced testicular injuries in male albino rats of Wistar strain. Five groups (n=6) of animals were used. Group I served as control. Group II received daily 1.6 g ethanol/kg body weight/day for 4 weeks orally. Group III received 1.6 g ethanol + 500 mg lecithin/kg body weight/day for four weeks orally. Group IV received 1.6 g ethanol/kg body weight for/day 4 weeks and followed by 500 mg lecithin/kg body weight/ day for four weeks orally. Group V received 1.6 g ethanol/kg body weight/ day orally for 4 weeks, followed by 4 weeks abstinence. Twenty-four hours after the last treatment the rats were sacrificed using anesthetic ether. Testes were removed and used for the estimation of extent of lipid peroxidation and tissue levels of antioxidants and steroidogenic enzymes. Lecithin protected testes from ethanol induced oxidative stress. However, the drug did not show any considerable effect on the activities of testicular delta5, 3beta-HSD and 17beta-HSD. In conclusion, ethanol induced oxidative stress can be reversed by treatment with lecithin. However the effect of lecithin on steroidogenesis was not promising.

Animals↗
PubMedDate not supplied

[Rate of interaction of ferricytochrome c with negatively charged liposomes from natural lecithin: effect of the physicochemical state of the membrane hydrophobic layer].

The absorption velocity of ferricytochrome c on the surface of liposomes from egg lecithin containing 10% of lauric acid was studied. Liposomes were prepared from lecithin of three fractions which differed by the composition of fatty acids, unsaturation and the lipid interaction decreased at the temperature below T phi pi for lecithin fractions containing larger quantity of saturated fatty acids. An opposite tendency was observed for the temperature above T phi pi. In the phase transition region of lecithin of refractory fraction the local maximum of protein-lipid interaction was observed. Judging by the character of the changes of the values of energy activation, small additions of cholesterol in the membrane loosen the bilayer at the temperature below T phi pi and condense it at above T phi pi. The data obtained are discussed in terms of the effect of the state of molecule hydrophobic part on the velocity of protein-lipid interaction.

Adsorption↗
PubMed1990

Equilibrium dialysis studies on aqueous taurocholate-lecithin solutions: further validation of the method.

Since the 1980 publication by Mazer, Benedek and Carey on the concept of the simple micelle-mixed micelle coexistence phenomenon in the bile salt-lecithin systems, it became apparent that a reliable method was needed for measuring the coexisting species concentrations. We recently published a method based on membrane dialysis equilibrium, and the purpose of this report is to review and to validate this previous work. In the present studies, two dialysis membranes with molecular weight cut-off of 8,000 and 12,000 to 14,000 Da, respectively, and two sets of solution volume conditions were investigated with the taurocholate-lecithin system. Coexistence data were obtained over a wide range of lecithin concentrations and the results were found to be in good agreement with those from the previous studies. The bile salt/lecithin molar ratios for the mixed micelles were also deduced from the data. The principal conclusion of this study is that although there is a moderate amount of variability (10% to 15%), the method is both satisfactory and useful in studying bile salt-lecithin equilibria and dynamics.

Bile Acids and Salts↗
PubMedDate not supplied

[Lecithin in the amniotic fluid in the determination of fetal lung maturity].

A prospective study involved 90 patients divided into groups of high risk and risk pregnancies, which matched in age, parity and gestational age. Two methods for the amniotic fluid phospholipid analysis were compared. The value of lecithin was measured by the two phase UV enzyme method and the lecithin/sphingomyelin (L/S) ratio was determined by Gluck's method. The correlation of lecithin and the L/S ratio with gestational age did not prove statistically significant. No correlation was found between the lecithin concentration and L/S ratio on the one hand and the occurrence of the respiratory distress syndrome on the other. The increase of RDS in high risk pregnancies was not statistically significant. The lecithin concentration determination appeared to be a more specific method (37%) than the L/S ratio (19%), and the predictive value of the negative test also proved to be higher (94%) in relation to the L/S ratio (89%).

Amniotic Fluid↗
PubMed1987

Lecithin:cholesterol acyltransferase. Functional regions and a structural model of the enzyme.

The amino acid sequence of human lecithin:cholesterol acyltransferase has been determined by degradation and alignment of peptides obtained from tryptic and staphylococcal digestions and the cleavage with cyanogen bromide and consisted of 416 amino acid residues. All of the tryptic peptides of lecithin:cholesterol acyltransferase were isolated and sequenced. Peptides resulting from digestion by staphylococcal protease, cyanogen bromide cleavage, or the combination of the two methods were employed to find overlapping segments. The N terminus of human lecithin:cholesterol acyltransferase was determined to be phenylalanine by sequencing the whole protein up to 40 residues while the C terminus was identified as glutamic acid through carboxypeptidase Y cleavage. Cys50 and Cys74 and Cys313 and Cys356 were identified as the two disulfide bridges while the free sulfhydryl groups were located at positions 31 and 184. The N-glycosylated sites of the protein were assigned to asparagines at positions 20, 84, 272, and 384. The active site of lecithin:cholesterol acyltransferase was identified as serine on position 181 according to its homology with other serine-type esterases which have a common structure of glycine-variable amino acid-active serine-variable amino acid-glycine (Gly-X-Ser-X-Gly) with the variable amino acids disrupting the homology. No long internal repeats or homologies with apolipoproteins were found. The secondary structure is consistent with the results of predictive algorithms. A simple model of the enzyme is proposed on the basis of available chemical data and predictive methods.

Amino Acid Sequence↗
PubMed1985

Activation of lecithin cholesterol acyltransferase by human apolipoprotein E in discoidal complexes with lipids.

In a continued investigation of lecithin cholesterol acyltransferase reaction with micellar discoidal complexes of phosphatidylcholine, cholesterol, and various water soluble apolipoproteins, we prepared complexes containing human apo-E by the cholate dialysis method. These complexes were systematically compared to apo-A-I complexes synthesized under the same reaction conditions. Apo-E complexes (134 A in diameter) were slightly larger than apo-A-I complexes (110 A) but were very similar in terms of their protein and lipid content (2.4:0.10:1.0, egg phosphatidylcholine/cholesterol/apolipoprotein, w/w) and in the percentage of apolipoprotein in alpha-helical structure (72-74%). Concentration and temperature-dependence experiments on the velocity of the lecithin cholesterol acyltransferase reaction revealed differences in apparent Km values and small differences in apparent Vmax but very similar activation energies (18-20 kcal/mol). These observations suggest that differences in lecithin cholesterol acyltransferase activation by apo-A-I and apo-E are primarily a result of different affinities of the enzyme for the particles but that the rate-limiting step of the reaction is comparable for both complexes. Apo-E was found to be 18% as effective as apo-A-I in activating purified human lecithin cholesterol acyltransferase. Addition of free apo-A-I to apo-E complexes resulted in the exchange of bound for free apolipoprotein causing a slight increase in the reactivity with the enzyme when the incubation mixture was assayed. When the unbound apolipoproteins were removed by ultracentrifugation reisolated complexes containing both apo-E and apo-A-I demonstrated an even greater increase in reactivity with the enzyme.

Apolipoprotein A-I↗
PubMed1979

[Amniotic fluid concentrations of thyroxine, reverse triiodothyronine and lecithins].

In the present study we tried to find out relationships between lung maturation-assessable by aid of lecithin concentrations in amniotic fluid-and fetal thyreoid gland function. In 256 pregnant women amniocentesis was done after 31/0 weeks of gestation, and concentrations of thyroxin, of reverse triiodothyronine and lecithins were measured. While thyroxin and lecithin concentrations proved not to be correlated, the rT3 and lecithin concentrations showed significant correlation (2 p less than 0.001). The curves measured were interpreted as signs of maturity of various organs (lung, thyreoid gland). We found out, that clinical value of measuring thyreoid gland hormones in relation to diagnosis of fetal maturation is of less importance.

Amniotic Fluid↗
PubMed1969

Molecular species of lecithins of rat heart, kidney, and plasma.

The lecithins of the heart, kidney, and plasma of the rat were isolated, and the major molecular species identified and quantitatively estimated by combined thin-layer and gas-liquid chromatographic analyses and specific enzymic hydrolyses. The lecithins of the three tissues differed significantly in the composition, positional distribution, and pairing of the fatty acids. No preferential pairing of any one saturated with any other unsaturated fatty acids was observed. The three tissues contained qualitatively the same molecular species of lecithins. The lecithin profiles of the rat heart and kidney appeared to be unrelated to that of the plasma.

Acetates↗
PubMed1977

[Intraamniotic application of lecithin in pregnant rabbits (author's transl)].

In order to find possibilities to influence therapeutically the respiratory distress syndrom at the premature infant animal experiences were carried out with 14C-lecithine. High pregnant rabbits got 14C-lecithine by intraamnial application. Investigation of the distribution of lecithine in the amniotic fluid and in the fetal organism showed an accumulation of lecithine metabolits in lung and lever tissue.

Amnion↗
PubMedDate not supplied

[A spectroscopic examination on intermolecular interaction of ergosterol with lecithin].

The ergosterol and lecithin absorption IR-spectra were studied in a nonpolar anhydrous medium. The thermodynamical and spectral characteristics of dimeric associates and the enthalpy value for trimeric associates of this sterol are determined. Thermodynamical and spectral parameters of ergosterol intermolecular associates with lecithin in a nonpolar anhydrous medium are found. It is established that the intermolecular interaction of lecithin with ergosterol occurs according to the mechanism of hydrogen bond. A conclusion is drawn that the presence of binary bonds and methyl groups in the cyclic and aliphatic parts of the sterol molecule affects greatly the structure of the model membrane and its strength. It is shown that under conditions of the experiment the oxygen of the phosphate group contributes to formation of the molecular associates of lecithin with sterols and not that of the carbonyl group. The obtained experimental data may be at use when studying structural disturbances of native membranes in norm and with different pathologies.

Chemical Phenomena↗
PubMed1978

The interaction of apolipoproteins with lecithin:cholesterol acyltransferase.

The rate of lecithin:cholesterole acyltransferase reaction was measured in a cholesterol-containing single bilayer lecithin vesicle system. ApolipoproteinA-I (apoA-I) activated the enzyme by itself; the other components of apolipoproteins of high density lipoproteins (HDL) (rho = 1.08--1.2 g/cm3), or rabbit serum gamma globulin inhibited the reaction. The reaction which was activated by pure apoA-I was strongly inhibited by anti-apoA-I antibody. Quantitative analysis of the results showed that the lecithin:cholesterol acyltransferase reaction was activated by the binding of apoA-I to the surface of lipid substrates. The rate of the lecithin:cholesterol acyltransferase-catalyzed reaction was strictly proportional to the surface density of apoA-I. The inhibition was due to the decrease of the amount of apoA-I on the lipid surface, either through competitive exclusion by apoA-II or by other proteins, or through specific extraction with antibody. The presence of components of apoHDL, other than apoA-I, prevented the inhibitory action of anti-apoA-I antibody.

Antigen-Antibody Reactions↗