Fatty acid variability of plasma lipids and cholesteryl esters in adult male twins and their brothers

Variation in the fatty acid composition of fasting plasma lipids and of cholesteryl esters was studied in 69 sets of adult male twins and 25 of their brothers. Genetic variances were estimated using the twin model. In general, monozygotic (MZ) twins were characterized by the smallest within-pair variance, and brothers of twins by the largest. Variation within dizygotic pairs fell intermediate to that of MZ twins and brothers. The present study did not reveal consistent significant (P<0.05) genetic variation in plasma fatty acids from total plasma lipids or cholesteryl esters.     

Analysis of Phospholipids in Rat Brain Using Liquid Chromatography–Mass Spectrometry

The brain is a lipid-rich organ containing complex polar lipids including phospholipids (PLs) and sphingolipids. These lipids are involved in the structure and function of cell membranes in the brain. We developed a fast and efficient liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to quantify five different classes of PLs [Choline glycerophospholipid (consists of phosphatidyl choline and plasmenyl choline in these samples), ethanolamine glycerophospholipid (consist of phosphatidyl ethanolamine and plasmenyl ethanolamine in these samples), phosphatidyl serine, phosphatidyl inositol, and sphingomyelin] in the brain tissues of 80-day-old Wistar rats. The PLs were extracted from rat brain using chloroform/methanol/water. After separation using a hydrophilic high performance liquid chromatography column, PL-class-specific fragmentation (head group identification) with a tandem mass spectrometer in positive ion mode was utilized to measure changes in the relative concentration of the five PL classes. The advantage of this approach was its improved specificity over previously reported LC–MS methods. The method had good repeatability (coefficient of variation 3–9%, excluding phosphatidyl inositol) and recovery (92–103%) and compared well with more laborious traditional methods.     

Liver lipids during development

The fatty acid composition of the major liver microsomal phospholipids has been studied during pre- and postnatal development of the rabbit. The fatty acid composition of the total lipids, phosphatidyl choline, and phosphatidyl ethanolamine from animals −6, −3, 0, +3, +6, +9, +16, and +112 days of age was determined. Fatty acid composition is similar in phosphatidyl choline and phosphatidyl ethanolamine for oleic acid at +3, +6, +9, and +16 day old animals; palmitoleic acid at +9 day old animals and linoleic acid at −6, −3, and 0 day old animals. Palmitoleic acid demonstrated a uniform decrease during early development in the total lipids and in both phosphatidyl choline and phosphatidyl ethanolamine; however, in the 112 day animal, the amount was just slightly lower than that observed for the earliest prenatal animal studied. Oleic acid decreased considerably during early postnatal development in the total lipids, phosphatidyl choline and phosphatidyl ethanolamine, but an increase in the 112 day animal was observed. Linoleic acid fluctuated considerably throughout postnatal development in the total lipids as well as in the two major phosphatides. Lecithin biosynthesis has been studied by two pathways during development of rabbit liver from −6 days to +110 days. The two pathways of lecithin biosynthesis were evaluated by assaying the activities of the liver enzymes choline phosphotransferase and phosphatidylmethyltransferase at different time intervals during development. The greater enzymatic activity was observed in the cholinephosphotransferase during development.     

A comparative study of the lipids of chylomicron membrane and fat core and of the lymph serum of dogs

Thoracic lymph was collected from 13 dogs fed corn oil and butterfat. The chylomicrons were isolated by centrifugation. The lipid composition of the fat core and the membrane of the chylomicron was compared to that of the surrounding lymph serum. The fat cores contained 90–96% triglyceride, 0.7–1.9% free cholesterol, 0.2–0.5% steryl ester, 0.9–3.5% free fatty acid and 1.4–6.1% diglyceride, but no phospholipid. The lipids of the membranes contained 58–75% phospholipid, 20–35% triglyceride, 2–5% free cholesterol, 1–2% free fatty acid, and 2–3% diglyceride, but little or no steryl ester. The membrane phospholipids were made up of 70–90% lecithin, 5–20% phosphatidyl ethanolamine, and 1–3% each of lysolecithin and sphingomyelin. The lymph serum contained 24–47% of total lipid as phospholipid, of which 70–92% was lecithin; the phosphatidyl ethanolamine, lysolecithin and sphingomyelin also present contributed 1–10% each. The neutral lipids of the lymph serum contained 49–75% triglyceride, 2–15% free cholesterol, 6–23% esterified cholesterol, 10–33% free fatty acid and 1–6% diglyceride. Alterations in dietary fat, or plant sterol supplementation led to lesser changes in the lipids of the chylomicron membranes than in the lipids of any other lymph fraction. The least variation was seen in the phospholipids. Taken in part from a PhD Thesis submitted by T. C. Huang to Queen's University, Kingston, Canada, in April 1965. Presented at the AOCS 56th Spring Meeting, Houston, May 1965.     

A comparative study of the lipids of globule membrane and fat core and of the milk serum of cows

Nine samples of fresh raw cow's milk were separated into fat globules and milk serum by centrifugation. After destabilization by freezing and thawing, the milk fat globules were resolved into membranes and fat cores. The lipid composition of these structures was compared to that of the surrounding milk serum. Of the total milk fat, 95–98% was in the fat cores, 0.5–1% in the globule membranes and the rest (1.5–4%) in the milk serum. The fat cores contained 88–93% triglyceride, 5.2–9.8% diglyceride, 1.5–7.3% free fatty acid and 0.2–0.4% cholesterol, but no phospholipid. The lipids of the membrane contained 21–44% phospholipid, made up of about equal proportions of phosphatidyl ethanolamine, phosphatidyl choline, and sphingomyelin. The other lipids of the membrane (56–79%) consisted of 83–88% triglyceride, 5.1–10.7% diglyceride, 1–5.1% free fatty acid and 0.4–1.9% cholesterol. The milk serum contained 30–45% phospholipid divided about equally among phosphatidyl ethanolamine, phosphatidyl choline and sphingomyelin. The rest (55–70%) of the milk serum lipids was made up of 71–83% triglycerides, 4.3–10.1% diglycerides, 8.7–15.7% free fatty acids, and 1.2–8.4% cholesterol. Corresponding phospholipid classes of milk serum and globule membranes had identical fatty acid compositions. The triglycerides and diglycerides of the globule membranes possessed increased proportions of palmitic and stearic acids in comparison to the glycerides of the fat cores. Taken in part from a PhD thesis submitted by T. C. Huang to Queen's University, Kingston, Canada in April, 1965. Presented in part at the 47th Canadian Chemical Conference and Exhibition held in Kingston, Canada, June 1–3, 1964.     

Composition and structure of phospholipids in chicken muscle tissues

Lipids extracted from breast muscle and thigh muscle of one-year old chickens on a standard MSU-Z-4 diet have been fractionated by silicic acid column chromatography into nonphospholipids, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl choline (lecithin), and sphingomyelins. Phospholipid fractions were identified by thin-layer chromatography and the quantity of each determined by gravimetric analysis, analysis of the phosphorus content, and infrared spectra. The phospholipid content of thigh muscle (dark meat) lipids was higher than that in the breast muscle (white meat). Phosphatidyl choline and phosphatidyl ethanolamine were found in relatively greater amts than phosphatidyl serine and sphingomyelins. Enzymatic hydrolysis followed by gas-liquid chromatographic analysis of the fatty acids liberated and those in the lysocompounds was used to establish the positional specificity of the fatty acids in the phosphoglycerides. The polyunsaturated fatty acids are located primarily at the β-position and the saturated fatty acids at the α′-position. The qualitative and quantiative determination of the plasmalogens was also accomplished. Michigan Agriculture Experiment Station Journal Article No. 3527. Presented at the AOCS Meeting in Chicago, October, 1964.     

Thermophilic fungi: III. The lipids ofHumicola grisea var.thermoidea

The lipids of the thermophilic fungusHumicola grisea var.thermoidea were qualitatively and quantitatively determined. The polar lipids consisted of 38.4–42.3% of the total lipids. The relative per cent phospholipids based upon the total phospholipids were as follows: phosphatidyl choline, 32.3–33.7%; phosphatidic acid, 24.5–31.7%; phosphatidyl ethanolamine, 15.8–20.9%; phosphatidyl inositol, 12.5–13.0%; phosphatidyl serine, 2.3–5.4%; and diphosphatidyl glycerol, 3.9–4.0%. The relatively high concentration of phosphatidic acid may be characteristic of fungi grown at elevated temperatures. Several sterol glycosides (3.1–6.0%) were present in the polar lipids. The neutral lipids consist of triglycerides, 28.6–36.0%; free fatty acids, 5.3–13.5%; sterols, 11.4–13.9%; sterol esters, 1.8–3.0%; and diglycerides, 2.2–3.4%. The sterols and derivatives comprise an unusually large fraction of the total lipids (16.3–22.9%) suggesting a role in thermostability.     

Lipids of maturing grain of corn (Zea mays L.): I. Changes in lipid classes and fatty acid composition

The total lipids of the grain from three strains of corn were compared throughout the growing season. The Illinois High Oil stock and the two inbreds, H51 and K6, represented high, intermediate and low oil-producing lines. In all three strains lipid synthesis was most active between 15 and 45 days after pollination. The lipids were extracted from the grain with a mixture of chloroform, methanol and water and were separated into classes by silicic acid and thin layer chromatography. Triglycerides constituted 10–17% of the total lipids at 10 days after pollination and increased to 75–92% at 75 days. Polar lipids at 10 days represented 70–72% and at 75 days 4–21%. Fatty acid compositions of the triglycerides and polar lipids changed as the grain matured, but the fatty acids of the polar lipids were more saturated than those of the triglycerides throughout the sampling periods. The major polar lipids were digalactosyl diglyceride, monogalactosyl diglyceride, phosphatidyl choline, phosphatidyl inositol and phosphatidyl ethanolamine. Presented in part at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968.     

Methodology for the separation o plant lipids and application to spinach leaf and chloroplast lamellae

Procedures for separation of complex plant lipids and results obtained are reviewed. Procedures based on DEAE cellulose and silicic acid chromatography, which may be preceded by countercurrent distribution, are presented for separation of the individual glyceroland sphingolipid classes of spinach leaf and chloroplast lamellae. These procedures appear to be generally applicable to photosynthetic tissue of plants and algae. The separation and infrared spectra of mono-and digalactosyl diglycerides, lecithin, phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl inositol, plant sulfolipid, cerebroside, and sterol glycosides from spinach are recorded. Chloroplast lamellae lipids are in the molar ratio monogalactosyl diglyceride (14.0), digalactosyl diglyceride (8.0), phosphatidyl glycerol (5.5), sulfolipid (3.9), lecithin (2.0), phosphatidyl inositol (1.0). Phosphatidyl ethanolamine, cerebrosides, and sterol glycosides were not detected in chloroplast lamellae. Fatty acid composition of individual lamellae lipids have been determined: The galactosyl lipids contain more than 90% trienoic acids.Trans-3- hexadecenoic acid is restricted almost exclusively to phosphatidyl glycerol. In this report techniques which have been applied to the isolation of plant glycero- and sphingolipids are reviewed and a new scheme presented for the separation of several of the plant lipid classes. Results obtained with spinach leaf and its photosynthetic apparatus are presented and discussed. Paper III in the series Plant and Chloroplast Lipids. Presented at the 15th Annual Summer Program, “Symposium on Quantitative Methodology in Lipid Research”, Aug. 3–7, 1964. Literature is reviewed to July 1964.     

The lipid components of white potato tubers (Solanum tuberosum)

Four Canadian varieties of potatoes were examined for their lipid composition. Lipids, extracted with chloroformmethanol, were shown by TLC and column chromatography to consist of 16.5% neutral lipids, 45.5% phospholipids and 38.1% glycolipids. Among the phospholipids and glycolipids, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol, the galactolipids and the sterol glucosides were the major lipids. The predominant fatty acids were palmitic (19.5%), linoleic (44.8%) and linolenic (30.4%, in Kennebec). Analyses of the fatty acids of stored potatoes showed a marked decrease in linoleic acid and an increase in linolenic acid, in the Irish Cobbler and Sebago potatoes. β-sitosterol comprised 85.0% of total sterols. Nearly half of the carotenoids was lutein (xanthophyll), the others being α-carotene, β-carotene, an unidentified pigment and lutein epoxide. Contribution No. 101 of the Food Research Institute, Canada Department of Agriculture.     

Lipid metabolism of the yellow clam,Mesodesma mactroides: I. Composition of the lipids

The lipid composition of the yellow clam,Mesodesma mactroides, that lives in the northern beaches of the Buenos Aires province of Argentina was studied. The main nonpolar lipids are triglycerides and alkoxyglycerides. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine are the main phospholipids. The predominant fatty acids are 16∶0, 16∶1ω7, 18∶0, 18∶1ω9, 20∶5ω3, and 22∶6ω3. The are mainly provided by the clam's food and stored in the hepatopancreas. The content of polyunsaturated acids increases in summer together with an increase in nonpolar lipids and is correlative with an increase in phytoplankton in the sea water. Sexual maturity modifies the lipid composition of gametes.     

Lipid and fatty acid composition of testes of quaking mice

Testes of quaking mice (sterile mutants) and of controls were analyzed for major lipid classes and fatty acid composition. Of the main lipid classes, only cholesterol esters differed significantly in concentration between the two groups (1.01 for quakers vs 0.69 mg/g wet wt of tissue for controls). The concentration of triglycerides was 4.5–5.0, that of total phosphatides 18–19, and that of free cholesterol 1.9–2.0 mg/g for mutants and controls. The concentrations of phosphatidyl ethanolamine and of sphingomyelin were both lower in quaking than in normal mice, but only the change in the former was statistically significant. Phosphatidyl choline was the major phosphatide (43–45% of total phosphatides) followed by phosphatidyl ethanolamine (24–26%) and sphingomyelin, phosphatidyl serine, and phosphatidyl inositol (all ca. 7% of total phosphatides). Minor differences between the mutants and controls were observed in concentrations of fatty acids of major lipid classes. The mutants, sterile because of faulty spermatid differentiation, had normal quantities of 22∶6 w3 and 22∶5 w6. These data are consistent with the hypothesis that the 22-carbon polyenes are associated with the formation of spermatids, rather than with their final differentiation into spermatozoa.     

Fungi pathogenic to insects: III. Neutral and polar lipids ofEntomophthora coronata

The neutral and polar lipid composition ofEntomophthora coronata was determined qualitatively. The fungus was grown on a chemically nondefined medium (Sabouraud dextrose yeast extract) and a chemically defined medium for a period up to 26 days. The lipids were characterized by thin-layer, column, gas chromatography, and selective sprays,³²P-labeling, and mass spectrometry. The neutral lipids consist of monoglycerides, diglycerides, cholesterol, free fatty acids, triglycerides, and cholesteryl esters. The polar lipids consist of phospholipids (phosphatidyl ethanolamine, phosphatidyl choline, lysophosphatidyl ethanolamine, lysophosphatidyl choline, and spingomyelin), a number of glycolipids including cerebrosides, and many unrecognizable lipids, most of which are present in trace amounts. The cerebrosides and spingomyelin are present in significant amounts, and their concentration increased with age of the culture. The major fatty acids (>10%) of the total, neutral, and polar lipids of the mycelia are 14∶0, 16∶0, 18∶1, 18∶3(γ), and 24∶1. The polar lipids of total culture (unsaturation index 0.88) and of the conidia (unsaturation index 1.48) are considerably more unsaturated than the corresponding neutral lipids (unsaturated index 0.50 and 0.49). The mycelial polar lipids, compared to the neutral lipids, possess less 14∶0 and 18∶1 but contain a greater percentage of 16∶0, 18∶2, 18∶3(γ), 24∶0, and 24∶1. The major fatty acid of the conidia (>10%) are 13∶0, 14∶0, 18∶1, 18∶2, 18∶3(γ), and 20∶4. Their polar lipids have a higher proportion of 18∶2, 18∶3(γ), and 20∶4. The cerebrosides possess 24.1 in high relative proportion (30.1%). Presented at the AOCS Meeting, Atlantic City, October 1971.     

The renal phospholipid composition of choline-deficient rats

The base composition of the phospholipids involved in the N-methylation pathway for the biosynthesis of phosphatidyl choline was determined in normal and severely hemorrhagic rat kidneys. There was a decrease in the proportion of phosphatidyl choline and phosphatidyl ethanolamine in the renal total lipids. The significant decrease of phosphatidyl ethanolamine in the kidney phospholipids appears to implicate this phospholipid to a greater extent than phosphatidyl choline in the etiology of the hemorrhagic syndrome.     

Metabolism of alkyl glyceryl ethers in the rat

The metabolism of¹⁴C- and³H-labeled alkyl glyceryl ethers after intraperitoneal injections was examined in the liver and intestine of the rat. Additionally, in vitro experiments were conducted with intestinal homogenates and intetinal contents. From these investigations it was concluded that the liver and the intestine metabolize the alkyl glyceryl ethers very differently. Intestinal contents can alter α-batyl alcohol, as indicated by preliminary experiments, and intestinal cells contain enzyme systems which convert the alkyl glyceryl ethers to the mono- and di-acyl derivatives. Very little esterified glyceryl ethers were found in the liver lipids. The intestine contains an enzyme system which, although it has a greater specificity for chain length and for isomeric position of the ether than that of the liver system, does cleave the glyceryl ethers. From in vivo studies, of intestinal tissue it was concluded that all of the injected glyceryl ethers were converted intact the ethanolamine, serine, and choline alkyl glyceryl ether phospholipids; with the use of α-batyl alcohol, the phosphatidyl ethanolamine fraction, contained most of the labeled glyceryl ether phospholipid with β-batyl alcohol, α-chimyl, and β-chimyl alcohols, the phosphatidyl, choline fraction contained most of the labeled alkyl glyceryl ether phospholipid. No significant amount (<1%) of labeled alkyl glyceryl ether phospholipids was found in any of the rat-liver lipids. Predoctoral trainee supported by Public Health Service Training Grant 5TI-GM-404-04 from the National Institute of General Medical Sciences, National Institutes of Health. Work done in partial fulfillment of the Ph.D. in the Department of Biochemistry at the University of North Carolina.     

Lipid composition of 30 species of yeast

The detailed composition of cellular lipid of more than 23 species of yeast has been determined quantitatively by thinchrography on quartz rods, a method previously used for estimating cellular lipids of seven species of yeast. That data was fortified by neutral and phospholipid quantitations on 30 species of yeast cells. Most of the test organisms contained 7–15% total lipid and 3–6% total phospholipid per dry cell weight, except for the extremely high accumulation of triglycerides in two species ofLipomyces. Qualitatively, 30 species of yeast cells contained similar neutral lipid constituents (triglyceride, sterol ester, free fatty acid, and free sterol) and polar lipid components (phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol, cardiolipin, and ceramide monohexoside) without minor constituents. Based on the quantitative composition of neutral lipids, the 30 species of yeast were divided into two groups, the triglyceride predominant group and the sterol derivative group. These groupings were fairly well overlapped from the standpoint of the distribution characteristics of fatty acid. The relative polar lipid compositions also grossly resembled each other. Only one exception of polar lipid composition in yeast cells was found inRhodotorula rubra species which contained phosphatidyl ethanolamine as the most abundant phospholipid. Fatty acid distribution patterns in yeast cells consistently coincided with other reports concerning fatty acid composition of yeast cells. Correlation of lipid composition and classification of yeasts are suggested and discussed. A part of this investigation has been reported at the 14th conference of the Japan Oil Chemists' Society, Nagoya, Japan, October 1975.     

Lipid composition of yoshida ascites hepatoma and of livers and blood plasma from host and normal rats

The lipid composition of Yoshida ascites hepatoma cells was analyzed together with that of ascitic plasma and of livers and blood plasma from host and normal rats. In comparison to normal livers, host livers showed no significant differences in the content of the various lipid classes, but contained a higher percentage of palmitic acid and a lower proportion of arachidonic acid in the major phospholipid classes. In addition, tumor growth induced a marked hypertriglyceridemia in host animals; changes in the concentration of other plasma lipid classes were not statistically significant. The ascitic plasma contained small amounts of lipids mainly constituted by cholesteryl esters and phospholipids. Yoshida hepatoma cells contained less phospholipids in comparison to both host and normal liver, while the increased level of triglycerides and the decrease of free fatty acids were not statistically significant. Hepatoma cells showed appreciable amounts of ether-linked lipids associated in part to neutral lipids (as glyceryl ether diesters) and, in part, to ethanolamine and choline phosphoglycerides. The alkyl groups in GEDE as well as in ethanolamine and choline phosphoglycerides were mainly constituted by C_16∶0 and C_18∶0 followed by C_18∶1. The alk-1-enyl groups in ethanolamine and choline phosphoglycerides were C_16∶0 and C_18∶0 with only a minor proportion of C_18∶1. In comparison to both host and normal liver, Yoshida hepatoma cells showed significant changes in the fatty acid composition of neutral lipids and phospholipids. Some of the major changes consisted of an increase of monoenoic acids associated with a decrease of arachidonic and docosahexaenoic acids in phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol.     

Lipid labeling with32P-orthophosphate and14C-acetate in marine copepods

Freshly collectedCalanus pacificus were maintained in sea water containing 25 μCi/ml [³²P]orthophosphate or 1 μCi/ml [¹⁴C]acetate at 10 C for 24 hr. The animals took up label from the environment and incorporated it into various lipid fractions. After incubation with [¹⁴C]acetate the order of specific activity of the different lipid classes was: phospholipids > free fatty acids > wax esters > triglycerides. Argentation thin layer chromatography of the fatty acid methyl esters showed that ca. 50% of the activity was in saturated fatty acids and 34% in polyunsaturated acids. When the animals were exposed to [³²P]orthophosphate, lysophosphatidyl choline became most heavily labeled, followed by lysophosphatidyl ethanolamine, sphingomyelin, phosphatidyl ethanolamine, and phosphatidyl choline. Comparison of the data obtained with those available for decapods and mammals revealed striking similarities between these phylogenetically distant groups. It is believed that labeling the lipids of marine and freshwater planktonic crustaceans in this way will provide much information about the metabolism of lipids in these organisms.     

Lipid composition and endogenous respiration of pig heart mitochondria

Lipid composition and endogenous respiration of pig heart mitochondria were studied in parallel, since the level of endogenous respiration affects the oxidation of added substrates and therefore the regulation of oxidative phosphorylation; mitochondrial lipids can interfere either as substrates or as partner in the energy conservation mechanism. O₂ uptake kinetics were measured in presence of different additives: ATP, ADP, NAD⁺ and hexokinase + glucose. The lipid composition of pig heart mitochondria was determined by chromatographic and spectrophotometric methods. Total lipids were 90% phospholipids; the main phosphatides were cardiolipin, phosphatidyl choline and phosphatidyl ethanolamine; the two latter were rich in plasmalogens. The main nonpolar lipids were triglycerides and free fatty acids. The fatty acid composition of total lipids, phospholipids, free fatty acids and triglycerides was determined by gas liquid chromatography. Mitochondrial lipids were characterized by a high content of unsaturation. Part of this work is included in “Thèse de Doctorat de Spècialitè en Biochimie” de J. Comte, Lyon, June 26, 1970.     

Lipids of some thermophilic fungi

Total lipid content in the thermophilic fungi—Thermoascus aurantiacus, Humicola lanuginosa, Malbranchea pulchella var.sulfurea, andAbsidia ramosa—varied from 5.3 to 19.1% of mycelial dry weight. The neutral and polar lipid fractions accounted for 56.4 to 80.2% and 19.8 to 43.6%, respectively. All the fungi contained monoglycerides, diglycerides, triglycerides, free fatty acids, and sterols in variable amounts. Sterol ester was detected only inA. ramosa. Phosphatide composition was: phosphatidyl choline (15.9–47%), phosphatidyl ethanolamine (23.4–67%), phosphatidyl serine (9.3–17.6%), and phosphatidyl inositol (1.9–11.9%). Diphosphatidyl glycerol occurred in considerable quantity only inH. lanuginosa andM. pulchella var.sulfurea. Phosphatidic acid, detected as a minor component only inM. pulchella var.sulfurea andA. ramosa, does not appear to be a characteristic phosphatide of thermophilic fungi as suggested earlier. The 16∶0, 16∶1, 18∶0, 18∶1, and 18∶2 acids were the main fatty acid components. In addition,A. ramosa contained 18∶3 acid. Total lipids contained an average of 0.93 double bonds per mole of fatty acids, and neutral lipids tend to be more unsaturated than phospholipids.