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PubMed1979

[Lecithin-sphingomyelin ratio "its prognostic importance to pregnancy" of diabetics (author's transl)].

The lecithin-sphingomyelin ratio was determined by the authors, applying Gluck's technique to 98 amniotic fluid samples of 55 pregnant patients with diabetes, depending on gestational age. Amniocentesis was preceded by ultrasonic placentography. Carbohydrate metabolism of this group was kept under optimum management and regulation. Its L/S ratio (3.1) was twice as much as that recorded from another group of patients (1.5) without adequate management of the carbohydrate metabolism. The rate of complications in the first group was below that in the second. -- It has been emphasised by the authors that variation in the L/S ratio along with gestational age depended not only on the severity of the given course of diabetes but, as well, on the management of the carbohydrate metabolism during pregnancy. They found that in any pregnancy under the conditions of diabetes the L/S ratio was an important criterion for diagnostic assessment of foetal lung maturity.

Amniotic Fluid↗
PubMed1979

Plasma lecithin-cholesterol acyltransferase: lack of induction by phenobarbital in guinea pigs.

Compared with controls, guinea pigs ip injected by phenobarbital for 4 days displayed higher activities of two hepatic microsomial enzymes: aminopyrine N-deme-thylase and benzo(alpha)pyrene hydroxylase. In contrast plasma lecithin-cholesterol acyltransferase (LCAT) activity was not increased by phenobarbital. It then appears that like in humans, plasma LCAT does not seem inducible by phenobarbital.

Aminopyrine N-Demethylase↗
PubMed1970

Comparison of physical models used to explain condensation effects in lecithin-cholesterol mixed films.

The apparent condensation effect observed with mixed monolayers of lecithin and cholesterol has been examined with respect to both molecular interaction and molecular cavity models. For each, model equations are presented which predict the surface areas of the film components as a function of the mole fraction of each component. For mixed monolayers where linearity does not exist in plots of mean surface area vs. mole fraction, and where there are breaks in the curve at mole fraction values other than 0.5, the size of the cavities are not invariant with respect to mole fraction.

Chemical Phenomena↗
PubMed1978

[Evaluation of fetal lung maturity using a modified lecithin-sphingomyelin determination and Clements' foam test].

The modified thin layer chromatographic method for the determination of the phospholipids lecithin and sphingomyelin from amniotic fluid is useful in estimating fetal pulmonary maturity. The foam test of Clements is a simple rapid method for screening of suspicious cases of pregnancies at risk and of great value as bed side test even performing by the doctor. In comparing Clements-Test with thin layer chromatographic for L/S-Ratio determination we found a good correlation of 81,8% of all cases.

Amniocentesis↗
PubMed1982

Interaction between RNAs from different sources and egg lecithin liposomes.

The interaction of RNAs of molecular weight ranging between 15,000 and 30,000 with egg lecithin large and small unilamellar liposomes has been investigated. Torula and tRNA proved to be incorporated to a similar extent but no linear relationship between molecular weight and percent of incorporation was demonstrated. A relationship between percent of secondary structure of RNA and its ability to be trapped in SUV liposomes is suggested.

Animals↗
PubMed1978

Comparison of fetal maturity evaluation with ultrasonic biparietal diameter and amniotic fluid lecithin-sphingomyelin ratio.

Fetal head biparietal (BP) measurements by ultrasonic techniques and amniotic fluid lecithin-sphingomyelin (L/S) ratios were simultaneously determined (within 2 days) on 84 occasions in 72 women. Using the criteria for maturity of an L/S ratio of 2.0 or more or a BP measurement of 9.0 cm or more, there was agreement between these test results in 66.7% of the cases. The BP incorrectly predicted the L/S ratio 33.3% of the time, with a false positive rate of 27.3% and a false negative rate of 6.0%. If an L/S ratio of 1.5 were used as the critical determinant, the BP false positive rate remained high (9.5%). A high false negative error (21.4%) occurred if a BP value of 9.3 cm was used. These results suggest that ultrasonic BP measurements should not be used as the only criteria of fetal maturity in the management of high-risk pregnancies.

Amniotic Fluid↗
PubMed1981

Interaction between synthetic lecithin and various sulfur-containing radioprotectors.

Interaction of the synthetic lecithin dipalmitoylphosphatidylcholine (DPPC) smectic mesophases with sulfur-containing radioprotectors was investigated by means of spectrophotometric and dielectric measurements. Electrical conductivity behavior indicated in all cases that an electrostatic interaction occurs between DPPC and the antiradiation drugs. This interaction is very strong in the case of the WR 2721 molecule. Thermal transitions of DPPC studied by spectrophotometry and conductivity Arrhenius diagrams showed that although the radio-protectors investigated (except WR 2721) delete the pretransition of the lipid phase, the principal transition is not modified. The observed electrostatic interactions are discussed with regard to ionized sites of the phosphatidylcholine lipid head and those of the radioprotectors. The special cases of WR 2721 and its metabolite, WR 1065, are examined.

Amifostine↗
PubMed1983

Effect of renal transplantation on lecithin cholesterol acetyltransferase (LCAT) activity and plasma lipids.

The rate of free cholesterol esterification, assessed as lecithin cholesterol acyltransferase (LCAT E.C. 2.3.1.43) activity, and cholesterol as well as triglycerides plasma levels, were determined in 45 patients who had been operated for kidney transplantation. An increased concentration of cholesterol and triglycerides was found in 25% and 31% of tests, respectively, whereas subnormal molar esterification rate (MER) could be detected in 74%, and a reduced cholesterol turnover in the endogenous pool (fractional esterification rate - FER) in as many as 95% of cases. Examination of different time intervals after transplantation surgery revealed that the lowest rate of esterification, as well as the lowest concentration of cholesterol was consistently found early after transplantation (within 10--15 days). The values subsequently rose but even 6--24 months after a successful kidney transplantation the molar and fractional esterification rates of cholesterol in most of the patients did not attain the levels of the healthy control subjects. If the function of the grafted kidney failed and the patient had to be returned to the haemodialysis treatment programme, all examined parameters remained permanently low. These results suggest that a disturbance in cholesterol metabolism accompanies an apparently satisfactory functioning of the transplanted kidney, even though it need not necessarily be reflected in increased plasma cholesterol concentrations.

Adolescent↗
PubMed1984

Discoidal complexes of A and C apolipoproteins with lipids and their reactions with lecithin: cholesterol acyltransferase.

Micellar, discoidal complexes of human apolipoproteins A-I, A-II, C-I, C-II, C-III-1, and C-III-2 with egg phosphatidylcholine (egg-PC) and cholesterol were prepared by the cholate dialysis method. The complexes, isolated by gel filtration, had similar lipid and protein contents by weight, on the average: 1.77:0.083:1.0, egg-PC/cholesterol/apolipoprotein (w/w). The diameters of the discs, visualized by electron microscopy and estimated by gel filtration, ranged from 100 to 200 A. The alpha-helix content of the apolipoproteins in the complexes was from 50-72%, and their fluorescence properties indicated nonpolar, but quite varied environments for the tryptophan residues in the various complexes. Initial reactions of purified human lecithin: cholesterol acyltransferase with the complexes, adjusted to equal egg-PC concentrations, indicated that all the apolipoproteins activate the enzyme from 6-fold to 400-fold over control vesicles of egg-PC and cholesterol. In decreasing order of reactivity were the complexes with A-I, C-I, C-III-1, C-III-2, C-II, and A-II. These results indicate that aside from lipid-binding capacity and high amphipathic alpha-helix content, other structural features are required for optimal enzyme activation by apolipoproteins. Concentration and temperature dependence experiments gave similar apparent Km values, markedly different apparent Vmax, and very similar activation energies (about 19 kcal/mol), for the various complexes. These observations suggest that the rate-limiting enzymatic step of the reaction is common to all the complexes but that the activated enzyme levels differ from complex to complex. We propose that enzyme activation occurs upon binding to complexes via apolipoproteins. Addition of excess (5-fold) free apolipoprotein A-I or A-II to complexes resulted in the exchange of bound for free apolipoproteins and in loss of reactivity with the enzyme.

Apolipoprotein A-I↗
PubMed1984

Lecithin:cholesterol acyltransferase and cholesteryl ester transfer activity from the isolated perfused rabbit liver.

Lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester (CE) transfer activity accumulate linearly in the recirculated medium of the isolated perfused rabbit liver. The appearance of both activities in the perfusate was blocked by the addition of 10 microM colchicine, indicating that these two proteins are synthesized and secreted by the liver. CE transfer activity catalyzed the net transport of cholesteryl ester from high density lipoprotein (donor) to very low and low density lipoproteins (acceptor), both in the perfusate medium and in whole rabbit blood plasma. The activity of LCAT in the perfusate was dependent on the presence of the major protein of the high density lipoprotein class, apoA-I. The similar properties of LCAT and CE transfer activity in rabbit liver perfusate and plasma, compared to these same activities in human blood, suggest that the rabbit is an appropriate model for the study of the cholesterol transport system in man.

Animals↗
PubMed1984

Lithium and lecithin treatment in Alzheimer's disease: a pilot study.

Ten patients with presumed Alzheimer's disease were entered into a pilot study to evaluate the combined effects of lithium and lecithin on cognitive and behavioral parameters. The loss of patients from the study because of toxic effects of lithium was high (30%), and one patient was dropped because of an intervening illness. Of the six remaining patients who completed the study, only two showed behavioral improvement; none showed improvement on measures of cognitive functioning. The possible mechanisms of action are discussed.

Aged↗
PubMed1984

Mechanism of fluorescent response of the probe diS-C3-(5) to transmembrane potential changes in a lecithin vesicle suspension.

The dependence of both the magnitude and the sign of fluorescent responses of the probe diS-C3-(5) in egg lecithin vesicle suspensions on the magnitude of the inside-negative transmembrane potential and on the total probe concentration in the sample volume has been studied. Results were compared with theoretical calculations made on the basis of the equilibrium thermodynamic model suggested earlier as well as on the observed concentration dependence of the probe fluorescence in aqueous media and membranes. It was shown that transmembrane potential results in a redistribution of the probe between the aqueous and the membrane phases and in the membrane interior. The model calculations showed that the probe concentrations in the external aqueous medium and in the outer lipid monolayer of a vesicle significantly decrease. At the same time, the dye concentration in the inner membrane monolayer increases significantly, which should lead to a marked quenching of the dye fluorescence. The changes in the fluorescence and absorption spectra are well explained in terms of the proposed mechanism. The highest responses of diS-C3-(5) to changes of the transmembrane potential were observed in a shorter wavelength region of the fluorescence spectrum at the probe to lipid ratios in membrane of 15-20 moles of probe per 1000 moles of lipid. In the longwave region, the increase in fluorescence is not an obligatory indication of a decrease in the transmembrane potential and, under certain conditions, this process can take place when the transmembrane potential increases. The generation of a quasi-equilibrium diffusion transmembrane potential results in an increase in the average probe concentration in membranes if the signs of the probe charge and the potential inside the vesicles are opposite. Thus, the "on-off" mechanism, working under conditions of steady-state processes, is not valid under equilibrium conditions.

Benzothiazoles↗
PubMed1984

[Incorporation of 1-0-alkyl-2-acetyl-sn-glycerol-3-phosphocholine into human plasma lipoproteins in vitro. Effect of the lecithin:cholesterol acyltransferase activity of plasma].

The binding of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, a platelet activating factor (PAF), to individual classes of human plasma lipoproteins was studied. It was found that PAF is rapidly incorporated into plasma lipoproteins. The degree of PAF binding to the lipoproteins depends on their type. Analysis of PAF binding in Scatchard plots revealed that HDL2 contain high affinity binding sites for PAF. On the other hand, LDL bind PAF in a nonspecific manner. Incubation of PAF with human plasma results in inhibition of lecithin: cholesterol acyltransferase (LCAT)-catalyzed cholesterol esterification. On the contrary, prostaglandin E1 stimulates LCAT activity in human plasma. PAF and prostaglandin E1 do not compete with each other for the binding sites in HDL2. It is concluded that incorporation of PAF into plasma lipoproteins may influence the LCAT activity in vivo.

Alprostadil↗
PubMed1984

Comparison of lecithin: sphingomyelin ratio, fluorescence polarization, and phosphatidylglycerol in the amniotic fluid in the prediction of respiratory distress syndrome.

The significance of the lecithin sphingomyelin (L:S) ratio as a determining factor in fetal lung maturity is well established. An L:S ratio of greater than 2.0 to 2.5 is indicative of fetal lung maturity in most assays. The fluorescence polarization method (fluorescence polarization less than 0.320) has been associated with fetal lung maturity. The presence of phosphatidylglycerol in amniotic fluid has been related to fetal lung maturity and the absence of respiratory distress syndrome. Amniotic fluid samples from 235 amniocentesis procedures and vaginal pool collection at varying gestational ages were analyzed for L:S ratio, fluorescence polarization, and phosphatidylglycerol. All samples with meconium or hemolyzed blood contamination and selected complications of pregnancy were removed from the study. A positive result will predict the absence of respiratory distress syndrome, and a negative result will predict the presence of respiratory distress syndrome. Correlation of L:S ratio, fluorescence polarization, and phosphatidylglycerol were favorable. False-positive results in three (3.3%) fluorescence polarization samples were noted, whereas there were none (0%) in the L:S ratio sample and one (1%) in the phosphatidylglycerol sample. Twenty-four (77.4%), 28 (73.7%), and 37 (77%) were the number of false-negatives in the fluorescent polarization, L:S ratio, and phosphatidylglycerol samples. Fluorescence polarization, L:S ratio, and presence of phosphatidylglycerol compare favorably as fetal lung maturity tests. The prediction of respiratory distress syndrome is as sensitive with the three modalities. The specificity and the predictive value of a positive test is more favorable with L:S ratio and phosphatidylglycerol.

Amniocentesis↗
PubMed1984

Comparison of the Lumadex-foam stability index test, lecithin: sphingomyelin ratio, and simple shake test for fetal lung maturity.

Amniotic fluid was obtained from 269 patients within 72 hours of delivery. The sensitivity, specificity, and predictive value of the Lumadex-foam stability index test, lecithin: sphingomyelin (L:S) ratio, and simple shake test were assessed in the diagnosis of respiratory distress syndrome (RDS), as well as the accuracy in identification of functional lung maturity in the growth-retarded fetus. The Lumadex-foam stability index test was found to be an accurate, quantitative, simple, and rapid measure of fetal lung maturity in the normal as well as abnormal pregnancy. The L:S ratio was accurate in the normal pregnancy, but became inaccurate in the small growth-retarded fetus. The nonquantitative simple shake test was accurate when it indicated fetal lung maturity, but an immature result was meaningless because of the large false-negative rate.

Amniotic Fluid↗
PubMed1983

[Lipoproteins, apolipoproteins, lipoprotein lipase, hepatic triglyceride lipase and lecithin cholesterol acyltransferase in patients with nephrotic syndrome].

Chronic renal disease with secondary hyperlipidemia is highly atherogenic. In uremia and patients on chronic hemodialysis there is a high incidence of atherosclerotic complications whereas the incidence of atherosclerotic disease is relatively low in the nephrotic syndrome. This is surprising, as nephrosis produces type-II hyperlipidemia, which is usually highly atherogenic. In this study 10 patients (5 male, 5 female) with a newly diagnosed nephrotic syndrome were compared to 10 controls (5 male, 5 female). As laboratory parameters, lipids, lipoproteins (VLDL, IDL, LDL, HDL2 and HDL3 by rate zonal centrifugation) and the percentage composition of the major apolipoproteins in VLDL, HDL2 and HDL3, as well as lipoprotein lipase (LPL), hepatic lipase (HTGL) and lecithin-cholesterol-acyl-transferase (LCAT) were measured. In nephrotic patients significantly higher plasma levels of cholesterol, triglycerides, phospholipids, VLDL, IDL and LDL were found, whereas HDL-chol, HDL2 and HDL3 were unchanged. LPL and HTGL were both significantly impaired, whereas LCAT was distinctly increased. The percentage composition of apolipoproteins in HDL2 and HDL3 was normal. In nephrotic VLDL, apo-AI was distinctly increased at the expense of a decrease in apo-CII, and increased LCAT was explained by the relative rise of apo-AI in nephrotic VLDL. The increase in apo-AI in VLDL is discussed as a possible reason for the low atherogenic risk of secondary hyperlipidemia in nephrotic syndrome.

Adolescent↗
PubMedDate not supplied

[Cholesterol esters increase the permeability of lecithin bilayer membranes].

Conductivity of lecithin bilayers containing cholesterol and its esters was studied. It was shown that cholesterol causes a considerable decrease of conductivity, the original conductivity of bilayers being (5.8 +/- 0.9) . 10(-8) Ohm-1 cm-2. Maximal effect was observed when concentration of cholesterol was about 30 mol%. Further increase of cholesterol content does not change the conductivity of bilayers. It was found that cholesterol esters in contrast to cholesterol cause the increase of ion permeability of bilayers. The same effect was also observed at high membrane cholesterol content. The obtained results were discussed in relation to cell membrane destructions at atherosclerosis.

Cholesterol Esters↗