Concentrations Of Lysolecithin Research Articles

Effect of sperm treatment with lysolecithin on in vitro outcomes of equine intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) in horses is currently employed for clinical and commercial uses, but the protocol could be optimized to improve its efficiency. We have hypothesized that destabilization of plasma and acrosomal membranes prior to injection would positively impact the developmental potential of equine zygotes generated by ICSI. This study evaluated effects of the sperm treatment with lysolecithin on plasma and acrosomal membranes and on oocyte activation ability, initially following heterologous ICSI on bovine oocytes and subsequently employing equine oocytes. The effects of the lysolecithin -treatment on the efficiency of conventional and piezo-assisted equine ICSI were evaluated. To do this, the equine sperm were treated with different concentrations of lysolecithin and the sperm plasma membrane, acrosome and DNA integrity were evaluated by flow cytometry. The results showed that a lysolecithin concentration of 0.08 % destabilized the membranes of all sperm and affected DNA integrity within the range described for the species (8–30 %). In addition, the heterologous ICSI assay showed that lysolecithin treatment was detrimental to the sperm's ability to activate the oocyte, therefore, chemical oocyte activation was used after equine ICSI after injection with lysolecithin -treated sperm. This group showed similar developmental rate to the control group with and without exogenous activation. In conclusion, lysolecithin pre-treatment is not necessary when using ICSI to produce equine embryos in vitro. The results from the current study provide additional insight regarding the factors impacting ICSI in horses.

Epidemiological, biological and clinical update on exercise-induced hemolysis.

Exercise-induced hemolysis can be conventionally defined as rupture and destruction of erythrocytes during physical exercise. The currently available epidemiologic information attests that a substantial degree of exercise-induced hemolysis is commonplace after short-, medium-, long- and ultra-long distance running, as reflected by significant decrease of serum or plasma haptoglobin and significant increase of plasma concentration (or overall blood content) of free hemoglobin. This paraphysiological intravascular hemolysis is typically mild (average variations of hemolysis biomarkers are usually comprised between 1.2- and 1.8-fold), almost self-limiting (completely resolving within 24-48 hours), with severity depending on athlete population, analytical technique used for detecting intravascular hemolysis, as well as on number, frequency and intensity of ground contacts, but not on running technique. Additional lines of evidence support the notion that both osmotic fragility and membrane structure of erythrocytes are considerably modified during endurance exercise. This fact goes hand in hand with findings that erythrocyte lifespan in runners is approximately 40% shorter than in sedentary controls. Direct mechanical injury caused by forceful ground contacts, repeated muscle contractile activity or vasoconstriction in internal organs are three potential sources of exercise-induced hemolysis, whilst metabolic abnormalities developing while exercising (e.g., hyperthermia, dehydration, hypotonic shock, hypoxia, lactic acidosis, shear stress, oxidative damage, proteolysis, increased concentration of catecholamines and lysolecithin) may actively contribute to trigger, accelerate or amplify this phenomenon. Although no systematic evidence is available, it seems also reasonable to hypothesize that patients bearing erythrocyte disorders may be particularly vulnerable to developing exercise-induced hemolysis.

A novel oil-in-water emulsion as a potential adjuvant for influenza vaccine: Development, characterization, stability and in vivo evaluation

Oil-in-water emulsions consisting of squalene, tween and/or span have shown significant benefits for the prevention and control of influenza, with their adjuvant efficacy enhancing the immunogenicities of influenza vaccines in high-risk groups. However, concerns have been raised following reports that post-immunization reactions associated with these adjuvanted vaccines are more frequent. In this work, a stable and biocompatible oil-in-water emulsion adjuvant containing squalene, egg lecithin and sodium oleate has been developed. Animal studies demonstrated that this adjuvant could induce strong immune responses in BALB/c mice, as measured by hemagglutinin inhibition titers, influenza-specific serum antibody titers and cytokine levels (IFN-γ and IL-4). Different oil compositions, including squalene, medium chain triglyceride and long chain triglyceride, were also evaluated. Furthermore, in contrast to MF59(®) which can only be sterilized by aseptic filtration, this adjuvant remained stable during autoclaving, showing minimal changes in pH, particle size and lysolecithin concentration.

Optimization of lipid nanoparticle formation for beverage applications: Influence of oil type, cosolvents, and cosurfactants on nanoemulsion properties

The influence of flavor oil composition, cosolvents (glycerol and propylene glycol), and cosurfactant (lysolecithin) on the formation and stability of lemon oil nanoemulsions stabilized by sucrose monoesters was examined. At ambient temperature, nanoemulsions containing 1-, 3-, and 5-fold lemon oils were stable to droplet growth, whereas those containing 10-fold lemon oil were unstable. For 10-fold lemon oil nanoemulsions, the droplet growth rate increased with increasing temperature, cosolvent addition, and decreasing lysolecithin concentration, which was attributed to the influence of these factors on the phase inversion temperature. Clear nanoemulsions could be formulated that maintained small mean particle diameters (d≈81nm) during storage at ambient temperature for 1month. The information generated in this study is useful for designing stable flavor nanoemulsions for applications in functional foods and beverages.

Lysolipid exchange with lipid vesicle membranes.

While the aqueous solubility for bilayer phospholipids is less than 10(-10) M--keeping lipid membranes at essentially constant mass, single chain surfactants can have a significant aqueous solubility. Thus, in surfactant solutions, both monomer and micelles can interact with a lipid bilayer, and the mass and composition of the bilayer can be changed in seconds. These changes in composition are expected to have direct consequences on bilayer structure and material properties. We have found that the exchange of surfactants like lysolecithin can be described in terms of a kinetic model in which monomer and micelles are transported to the membrane from bulk solution. Molecular transport is considered at the membrane interfaces and across the midplane between the two monolayers of the bilayer. Using micropipet manipulation, single vesicles were transferred into lysolecithin solutions, and the measurement of vesicle area change gave a direct measure of lysolecithin uptake. Transfer back to lysolecithin-free media resulted in desorption. The rates of uptake and desorption could therefore be measured at controlled levels of membrane stress. With increasing lysolecithin concentration in the bulk phase, the amount of lysolecithin in the membrane reached saturation at approximately 3 mol% for concentrations below the critical micelle concentration (CMC) and at > 30 mol% for concentrations above the CMC. When convective transport was used to deliver lysolecithin, uptake occurred via a double exponential: initial uptake into the outer monolayer was fast (approximately 0.2 sec-1); transfer across the bilayer midplane was much slower (0.0019 sec-1).

Biliary phospholipases in the prairie dog model for cholesterol cholelithiasis

Lysolecithin has been implicated as a contributing factor in the pathogenesis of cholecystitis and cholesterol cholelithiasis. The phospholipases are key enzymes in the generation of a number of metabolites including lysolecithin, but conflicting reports exist concerning the presence of these enzymes in the biliary tract. In this study, measurement of phosphatidylcholine-specific phospholipase activity by means of the hydrolysis of radiolabeled phosphatidylcholine (100 nmol) by 90 micrograms of homogenate protein during a 60-min incubation demonstrated substantial enzyme activities in gastric fundus and distal ileum (90% and 70% hydrolysis, respectively), whereas activity was virtually undetectable in gallbladder mucosa (0.7% hydrolysis). Additional studies were conducted in prairie dogs fed diets high in cholesterol or with trace amounts of cholesterol using homogenates of gallbladder mucosa, seromuscularis and full-thickness tissue, as well as samples of hepatic and gallbladder bile. The only hydrolytic activity in excess of blank values that was detected was a highly variable phospholipase A2 activity in several gallbladder biles from animals given diets with both low levels and high levels of cholesterol, with the enzyme activities of the two dietary groups being similar. These results demonstrate that prairie dog gallbladder contains extremely low levels of phospholipase activity, in marked contrast to other gastrointestinal tissues. However, there was evidence of a phospholipase A2 activity in gallbladder bile. In light of the low activity in gallbladder tissue, the source of this enzyme appears to be the liver and not the gallbladder.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous measurement of two cellular antigens and DNA using fluorescein‐isothiocyanate, R‐phycoerythrin, and propidium iodide on a standard FACScan

Multiparameter flow cytometry is a powerful tool for analyzing the phenotypic, cell kinetic, and ploidy heterogeneity of tumor cell populations. Because of the substantial spectral overlap of propidium iodide (PI) and R-phycoerythrin (PE) fluorescence emission, this combined use of these fluorochromes has been thought not to be feasible on a standard flow cytometer for these kind of studies. Instead of PI, 7-amino-actinomycin D (7-AAD) is used as DNA stain. In this paper however, we show that PI can be used as a DNA stain in combination with fluorescein isothiocyanate (FITC) and R-phycoerythrin (PE) on a standard FACScan. Three established ovarian cancer cell lines (IGROV1, NIH: OVCAR-3, and COV362.c14) were used for these experiments. Cells were fixed with 1.0% paraformaldehyde and permeabilized with various concentrations of lysolecithin for the simultaneous detection of surface antigens by monoclonal antibodies MOv18, BMA180 or OV632, intermediate filament antigens (keratin 18 or vimentin), and DNA. A final concentration of 80 micrograms/ml lysolecithin was found to give optimal results. The emission spectrum overlap from PI into the orange fluorescence channel (FL2) used for PE fluorescence detection could be sufficiently compensated up to a photomultiplier tube potential of about 440 Volts (V) required at the FL2 channel. Using the same instrument settings, 5.10 x 10(4) PE equivalents were detectable. Under these conditions, CVs obtained for the DNA histograms ranged from 3.0-4.1. Application of the method on a mixture of activated peripheral blood lymphocytes and ovarian tumor cells resulted in a clear separation of the two populations both by surface and cytoplasmic antigen expression and DNA content.

Effects of lysolipids and oxidatively modified low density lipoprotein on endothelium-dependent relaxation of rabbit aorta.

Exposure of isolated arteries to oxidatively modified low density lipoprotein (LDL) has been reported to suppress endothelium-dependent relaxation (EDR). To determine whether lipid degradation products in oxidized LDL contribute to impaired relaxation, we have tested the responsiveness of isolated rabbit aortas to endothelium-dependent relaxants (acetylcholine, ATP, and calcium ionophore A23187) and nitroglycerin before and after 2-hour incubations with selected lipids and LDL preparations. Concentrations (10 microM) of lecithin, phosphatidylserine, lysophosphatidylserine, sphingomyelin, phosphatidic acid, palmitate, arachidonate, and auto-oxidized arachidonate had no effect on EDR. Concentrations (10 microM) of lysolecithin, lyso-platelet activating factor, and sphingosine significantly suppressed endothelium-dependent relaxation. Native LDL (100 micrograms/ml incubation buffer) containing only small amounts of lysophosphatidylcholine exerted no effect on EDR. In contrast, LDL preparations oxidatively modified by exposure to cultured endothelial cells or copper inhibited EDR. When modified LDL was depleted of its lysolecithin by treatment with a selective phospholipase B (lysolecithinase), the inhibitory effects were attenuated. In contrast, native LDL accumulating lysolecithin under the influence of a phospholipase A2 (lecithinase) exerted inhibitory effects mimicking those of oxidized LDL. Lipids and lipoproteins had no effect on the responsiveness to nitroglycerin, an endothelium-independent vasodilator. We conclude that lysolecithin in oxidatively modified LDL contributes importantly to its vasomotor effects.

Isolation of high quality mRNA from a discrete cell cycle population identified using a nonvital dye and fluorescence activated sorting.

Flow cytometry (FCM) is useful for measuring DNA content as related to cell cycle position. We have extended this technology by developing a method that measures cellular DNA content using propidium iodide after permeabilization with lysolecithin. This technique maintains cell integrity such that high quality mRNA can be isolated from a sorted population. Unfixed MDA-468 cells, a human breast cancer cell line, were temporarily permeabilized with lysolecithin. A range of lysolecithin concentrations were studied in order to optimize DNA staining but minimize alterations in cell size and integrity. Cells permeabilized with lysolecithin in PBS, were stained with propidium iodide (50 micrograms/ml) in the presence of 1% bovine serum albumin, 1 mM Na2EDTA in PBS. The optimal concentration (4 micrograms lysolecithin/ml) combined staining approximately 90% of the cells for DNA, with minimal effects on cell size. Subsequently, the cells were assayed for DNA content as a measure of cell cycle position. MDA-468 cells identified as being in G1 were sorted and collected. From these, high quality mRNA could be isolated, as judged by its ability to be in vitro translated into protein of a wide range of molecular weights. This technique should be useful for molecular studies requiring discrete cell populations based on DNA content and/or cell cycle position.

Characterization of biotinylated repair regions in reversibly permeabilized human fibroblasts.

We have examined the incorporation of biotinyl-11-deoxyuridine triphosphate (BiodUTP) into excision repair patches of UV-irradiated confluent human fibroblasts. Cells were reversibly permeabilized to BiodUTP with lysolecithin, and biotin was detected in DNA on nylon filters using a streptavidin/alkaline phosphatase colorimetric assay. Following a UV dose of 12 J/m2, maximum incorporation of BioUTP occurred at a lysolecithin concentration (80-100 micrograms/mL) similar to that for incorporation of dTTP. Incorporation of BiodUTP into repair patches increased with UV dose up to 4 and 8 J/m2 in two normal human fibroblast strains, while no incorporation of BiodUTP was observed in xeroderma pigmentosum (group A) human fibroblasts. The repair-incorporated biotin was not removed from the DNA over a 48-h period, and only slowly disappeared after longer times (approximately 30% in 72 h), while little of the biotin remained in cells induced to divide. Furthermore, the stability of the biotin in repaired DNA was unaffected by a second dose of UV radiation several hours after the biotin-labeling period to induce a "second round" of excision repair. Exonuclease III digestion and gap-filling with DNA polymerase I indicate that the majority of biotin-labeled repair patches (approximately 80%) are rapidly ligated in confluent human cells. However, the remaining patches were not ligated after a 24-h chase period, in contrast to dTTP-labeled repair patches. The BiodUMP repair label in both chromatin and DNA is preferentially digested by staphylococcal nuclease, preventing the use of this enzyme for nucleosome mapping in these regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous domain formation of phospholipase A 2 at interfaces: Fluorescence microscopy of the interaction of phospholipase A 2 with mixed monolayers of lecithin, lysolecithin and fatty acid

Fluorescence microscopy has recently been proven to be an ideal tool to investigated the specific interaction of phospholípase A 2 with oriented substrate monolayers. Using a dual labeling technique, it could be shown that phospholipase A 2 can specifically attack and hydrolyze solid analogous l-α-DPPC domains. After a critical extent of monolayer hydrolysis the enzyme itself starts to aggregate forming regular shaped protein domains (Grainger et al. (1990) Biochim. Biophys. Acta 1023. 365–379). In order to confirm that the existence of hydrolysis products in the mononlayer is necessary for the observed aggregation of phospholipase A 2, mixed monolayers of d- and l-α-DPPC, l-α-lysoPPC an palmitic acid in different ratios were examined. The phase behavior and the interaction of these films with phospholipase A 2 were directly visualized with an epifluorescence microscope. Above a certain critical concentration of lysolecithin and palmitic acid in the monolayer, compression of these mixed films leads to phase separation and formation of mixed domains of unknown composition. Their high negative charge density is evidenced by preferential binding of a cationic dye to these phase-separated areas. Introduction of fluorescence-labeled phospholipase A 2 underneath these mixed domains results in rapid binding of the protein to the domains without visible hydrolytic activity, regardless of whether the l-form of the d-form of the DPPC were used In binary mixtures, only those with DPPC/palmitic acid show formation of phase-separated areas which can be specifically targeted by phospholipase A 2 leading to a rapid formation (within 2 min) of protein domains. Experiments with pyrenedecanoic acid containing monolayers give the first direct evidence that acid is located above the enzyme domains. These results show that a locally high negative charge density of the phase-separated domains is one of the prerequisites for the binding of phospholipase A 2. In addition, however, small amounts of d- or l-α-DPPC headgroups within the domains of the monolayer seen to be necessary for recognition followed by fast binding of the protein to the domains. This is confirmed by experiments with mixed monolayers of diacetylene carboxylic acid and d-ga-DPPC. The acid - immiscible with lecithn - forms well defined pure acid domains in the monolayer. While the cationic dye can be docked rapidly to these phase separated areas, no preferential enzyme binding and thus no protein domain formation below these acid domains can be induced.

Serum phospholipase A 2 and lysolecithin changes following myocardial infarction

We have examined changes in the activities of phospholipase A 2 (PLA 2) and the concentrations of total choline-phospholipids and lysolecithin, in serum from patients following a myocardial infarction by comparison with patients suffering from unstable angina. A significant increase in PLA 2 activity was found after myocardial infarction. The peak increase occurred approximately 36 h after infarction. No significant PLA 2 change was found in the patients with unstable angina. Concentrations of lysolecithin, the major metabolite of PLA 2 activity, were high in the admission samples from the infarction patients, followed by an overall fall during the first 24 h: the concentrations in the patients with angina were normal. PLA 2 and lysolecithin changes post-infarction showed they were involved in processes not occurring in angina.

Effect of Biliary Tract Procedures on Duodenogastric Reflux and the Gastric Mucosa

The effect of alterations in the biliary tract on the gastric milieu was evaluated in gallstone disease and after cholecystectomy or biliary fenestration and compared with a control group. Endoscopic bile reflux was often found in gallstone patients (67%) and almost always after cholecystectomy (89%). Gastric bile acid concentrations were greater in the gallstone patients than in the control patients, were higher still after cholecystectomy, and were highest after biliary fenestration. The pH of the gastric fluid was more alkaline in the cholecystectomized groups. Lysolecithin concentrations were generally low and did not differ between the groups, nor was there any difference in scintigraphic reflux between the groups. Endoscopic erythematous gastritis correlated with the grade of bile reflux and was a common finding after biliary tract procedures. There were no consistent histologic findings associated with duodenogastric reflux. Helicobacter pylori colonization rates were similar in the various patient groups and were not affected by the reflux grade.

Relationship of Campylobacter pylori and duodenogastric reflux.

We have examined the relationship of Campylobacter-like organism (CLO) and duodenogastric reflux (DGR) in 107 patients with unoperated stomachs. Neither the extent of externally measured bile reflux nor the concentrations of bile acids or lysolecithin in the gastric fluid differed significantly in the groups with different numbers of CLO in the gastric mucosa. Our results suggest that DGR, in the quantities commonly present in unoperated stomachs, does not effect the presence of C. pylori in the gastric mucosa.

Simultaneous paired analysis by flow cytometry of surface markers, cytoplasmic antigens, or oncogene expression with DNA content

Flow cytometry is a useful tool for measuring DNA content and differentiation as expressed by cell surface markers. We have extended this technology to measure simultaneously either surface, cytoplasmic, or nuclear antigens (particularly oncoproteins) with DNA content. Mononuclear blood cells isolated from normal subjects and HL60 leukemic cells were permeabilized and fixed in suspension utilizing 40 micrograms/ml lysolecithin and 1% paraformaldehyde. A range of lysolecithin concentrations in 1% paraformaldehyde was studied to optimize permeabilization of the antibodies to the cell interior without destroying cell integrity. The optimal concentration (40 micrograms lysolecithin/ml) resulted in good cell recovery with a high percentage of cells positive for surface and intracellular antigens. Cells are first stained with fluorescein isothiocyanate conjugated (FITC) antimyeloperoxidase (an azurophil granule enzyme), or with an anti-c-myc antibody and FITC goat anti-mouse IgG F(ab')2. Cells are then incubated with RNase and stained for DNA content with propidium iodide. Alternatively, cells were stained for the cell surface markers Leu M3, OKM1, or the transferrin receptor and were then fixed and permeabilized and stained with propidium iodide. Using this method, we correlated cytoplasmic, nuclear, or cell surface antigens with cell cycle kinetics. This technique should be useful for studies of cellular differentiation and proliferation.

Lysolecithin concentration in pancreatic tissue during therapy with phospholipase A2-inhibitors in acute necrotizing pancreatitis

Four hours after hemorrhagic necrotizing pancreatitis was induced in experimental animals the concentration of lysolecithin in pancreatic tissue rose (p = 0.0025). Parenteral administration of unspecific inhibitors of phospholipase A2, such as chlorpromazine, gabexat mesilat and CaNa2 EDTA, can neither inhibit elevation of the enzyme nor influence the course of the disease.

Lyso-phosphatidylcholine is implicated in thioacetamide-induced liver necrosis

Thioacetamide is a weak hepatocarcinogen. To determine whether alterations in lysophosphatidylcholine are implicated in thioacetamide-induced hepatic necrosis, rats were injected i.p. with this agent (50 mg/Kg body weight per day) or diluent for 1, 3, 8 and 30 days. Serum catalytic activities of aminotransferases were determined. Incorporation of ( 32P)-orthophosphate into hepatic lysophosphatidylcholine was also evaluated in animals killed 75 minutes or 13 hours after isotope administration. Results demonstrate that: A significant increase in hepatic lysolecithin concentration occurs when a maximum level of serum aminotransferases is present. An increase of ( 32P)-orthophosphate radioactive incorporation in lysolecithin was observed at the two assayed labelling periods, which suggest an activation of phospholipase A. The radioactivity present in lysolecithin after 13 h isotope injection showed a close correlation with serum level of aminotransferases. From these results it can be deduced that lysolecithin is implicated in TAA-induced necrosis and may be generated by increase in either phospholipase A activity and/or synthesis.

Excision repair of UV damage in human fibroblasts reversibly permeabilized by lysolecithin

We have examined nucleotide excision repair synthesis in confluent human diploid fibroblasts permeabilized with lysolecithin. Following a UV dose of 12 J/m 2, maximal incorporation of [α 35S]dNTPs occurred at a lysolecithin concentration (∼ 80 μg/ml) where slightly more than 90% of the cells were initially permeable to trypan blue. However, autoradiography of cells, permeabilized at this lysolecithin concentration, demonstrated that only about 20% of the tottal cell population incorporated significant levels of 35S into DNA. This result presumably reflected the fact that ∼ 20% of the total cell population remained permeable for much longer periods of time (up to 2 h) than the remaining cell population (< 20 min). The incorporation of dNTPs by UV-irradiated, permeabilized cells appeared to be bona fide excision repair synthesis since: (1) Incorporation was completely absent in unirradiated, permeabilized cells and in irradiated, permeabilized repair-deficient cells. (2) Nucleotides incorporated in the presence of BrdUTP were associated with normal density DNA. (3) The apparent K m for all 4 dNTPs was 50–100 nM, in agreement with past reports on human fibroblasts irreversibly permeabilized by cell lysis. (4) DNA associated with the newly incorporated dNTPs underwent ligation and rearrangements in chromatin structure analogous to what is observed in intact human cells. Repair incorporation of dNTPs was rapid and linear during the first 2 h after UV irradiation and permeabilization. After this time, incorporation ceased or continued at a much slower rate. Cell viability experiments and autoradiography demonstrated that the cells permeabilized to [ 3H]dNTPs were capable of carrying out DNA replication and cell division. Thus, confluent human diploid fibroblasts can be reversibly permeabilized to labeled dNTPs by lysolecithin for the study of excision repair following physiologic doses of UV radiation. However, under these conditions, only a fraction of the cells remain permeable for an extended period of time.

Studies of structural modifications induced by gamma-irradiation in distearoylphosphatidylcholine liposomes.

An investigation of the structural and thermodynamical modifications induced by gamma-irradiation in model membranes is reported. Differential scanning calorimetry and X-ray diffraction were used to study the different phases and associated transitions of distearoylphosphatidylcholine multilamellar liposomes after 60Co gamma-irradiation. Changes were observed in the shape of the calorimetric peaks and in the corresponding phase transition temperatures. In particular a shoulder was observed at about 20 kGy. The three phases characteristic of lecithins with identical acyl chains were detected also for the highest radiation dose. The formation of lysolecithin and stearic acid upon phospholipid degradation was observed. The lysolecithin concentration increases as a function of irradiation dose, until a saturation value is reached at 40 kGy. These results correlate quite well with those obtained for interlayer and interchain distances and for the width of the main phase transition calorimetric peak. At the highest dose (approximately equal to 80 kGy) cross-linked adjacent radicals and other molecular species are also formed. Appreciable differences, and some similarities, in the behaviour of DSPC and DPPC liposomes under gamma-irradiation were observed.

Lecithin: Cholesterol acyltransferase and lysolecithin in coronary atherosclerosis

Of 100 arteriographically examined, hospitalized, male patients, those without myocardial infarctions were divided into the following categories: zero-, one-, two-, and three-vessel disease; patients diagnosed with myocardial infarction were classified separately. The fasting plasma samples from these patients were examined for concentrations of triglycerides and total cholesterol, lipoprotein profile, lecithin: cholesterol acyltransferase (LCAT) activity, and lysolecithin (LPC) concentration. Those parameters in this group which are commonly determined were consistent with the clinical classification of these patients. Of those remaining parameters, the LCAT activity was increased as the severity of coronary atherosclerosis increased and the changes in the activity of this enzyme were appropriately reflected by increases in LPC concentration and decreases in the proportion of the plasma cholesterol unesterified. The results of this study suggest that increased, rather than decreased, plasma LCAT activity and increased LPC concentrations are characteristic of coronary atherogenesis. The plasma concentrations of LPC observed in these atherosclerotic patients are more than sufficient to qualify this substance for its previously proposed roles of mediator of transmembrane diffusion of LDL and as an inhibitor of platelet aggregation.