Positional analyses of triacylglycerol fatty acids in the milk fat of the antarctic fur seal (Arctocephalus gazella)

The positional distribution of fatty acids has been determined for the milk triacylglycerols of the Antarctic fur seal,Arctocephalus gazella. Of particular interest was the positional distribution of the polyunsaturated n−3 fatty acids in milk triacylglycerols (TG). In adipocytes of pinnipeds, TG are synthesized with the n−3 fatty acids primarily in thesn-1,3 positions. To determine the positional distribution, extracts of enzymatically digested lipids were separated by thin-layer chromatography, and the constituent fatty acids were separated and quantified by gas-liquid chromatography. Monoenoic and saturated fatty acids comprised over 75% of the total, the ratio of monoenoic to saturated fatty acids being 2∶1. The percent content of the long-chain n−3 fatty acids, 20∶5, 22∶5 and 22∶6, ranged between 15–20%. The positional analyses revealed that at thesn-2 position of milk TG, saturated fatty acids were in excess (57%), and the content of n−3 fatty acids was less than 5%. More than 80% of the n−3 fatty acids in milk were located in thesn-1,3 positions. The data indicate that in pinnipeds TG are synthesized in the mammary gland and adipose tissue with fatty acids having similar positional distributions.     

Metabolism of arachidonate in rat testis: Characterization of 26–30 carbon polyenoic acids

Fatty acid methyl esters of long-chain polyenoic fatty acids (LCPA) from rat testis injected with [1-¹⁴C] arachidonate were analyzed and separated by reversed-phase high performance liquid chromatography (RP-HPLC). Earlier, all previously identified LCPA were prepared in high purity along with 4 previously unidentified fatty acids, which were further characterized by capillary gas chromatography (GC), catalytic hydrogenation and alkaline isomerization. Unidentified fatty acids proved to be 26∶4, 26∶5, 28∶5 and 30∶5. All of these LCPA incorporated¹⁴C from arachidonate (20∶4) to specific activities that were comparable to that of 20∶4 and previously identified metabolites of 20∶4 and much greater than specific activities of 18∶1n−9 or 22∶6n−3. LCPA were analyzed on a capillary GC system capable of resolving knowncis-trans and positional isomers of the n−3, n−6, n−7 and n−9 families of unsaturated fatty acids. Log plots of isothermal retention times and normal plots of temperature programmed retention times were linear (r=0.999) in carbon number when values for known and previously unidentified LCPA of 4 or 5 double bonds, respectively, were coplotted. Thus, the newly identified fatty acids belong to the n−6 family of fatty acids synthesized from arachidonic acid.     

The high content of monoene fatty acids in the lipids of some midwater fishes: Family myctophidae

The total lipids of eleven species of Myctophids caught at depths between 20 and 700 m in the northern Pacific Ocean were analyzed using silicic acid column chromatography (lipid classes) and capillary gas chromatography (fatty acid and fatty alcohol composition). The major components in the lipid classes were triacylglycerols or wax esters; triacylglycerols were the dominant acyl neutral lipids (68.1–96.1%) in eight species, and wax esters were found as the dominant lipid (85.5–87.9%) in three species. The major fatty acids and alcohols contained in the was esters of the three fishes were 18:1n–9, 20:1n–9, 20:1n–11, and 22:1n–11 for fatty acids, and 16:0, 18:1, 20:1, and 22:1 for fatty alcohols. Fatty acids in the triacylglycerols ranging from C₁₄ to C₂₂ were predominantly of even chain length. The major components were 16:0, 16:1n–7, 18:1n–9, 20:1n–11, 22:1n–11, 20:5n–3 (icosapentaenoic acid), and 22:6n–3 (docosahexaenoic acid). In both the triacylglycerols and the wax esters, the major fatty components were monoenoic acids and alcohols. It is suggested from the lipid chemistry of the Myctophids that they may prey on the same organisms as the certain pelagic fishes such as saury and herring, because the large quantities of monoenoic fatty acids are similar to those of saury, herring, and sprats whose lipids originate from their prey organisms such as zooplanktons which are rich in monoenoic wax esters.     

Elongation of (n−9) and (n−7)cis-monounsaturated and saturated fatty acids in seeds ofsinapis alba

Lipids in developing seeds ofSinapis alba contain appreciable proportions of (n−7)octadecenoic (vaccenic) acid besides its (n−9) isomer (oleic acid), whereas the constituent very long chain (>C₁₈) monounsaturated fatty acids of these lipids are overwhelmingly composed of the (n−9) isomers. Cotyledons of developingSinapis alba seed use [1-¹⁴C]acetate, [1-¹⁴C]malonate or [1,3-¹⁴C]malonyl-CoA for de novo synthesis of palmitic, stearic and oleic acids and for elongation of preformed oleic, vaccenic and stearic acids to their higher (n−9), (n−7) and saturated homologs, respectively. Moreover, elongation of preformed (n−7)palmitoleic acid to vaccenic acid is observed. Stepwise C₂-additions to preformed oleoyl-CoA by acetyl-CoA or malonyl-CoA yielding (n−9)icosenoyl-CoA, (n−9)docosenoyl-CoA and (n−9)tetracosenoyl-CoA are by far the most predominant reactions catalyzed by the elongase system, which seems to have a preference for oleoyl-CoA over vaccenoyl-CoA as the primer. The pattern of¹⁴C-labeling of the very long chain fatty acids formed from either acetate or malonate shows a close analogy in the mode of elongation of monounsaturated and saturated fatty acids.     

Sponge fatty acids. 3. Occurrence of series of n−7 monoenoic andiso-5,9 dienoic long-chain fatty acids in the phospholipids of the marine spongeCinachyrella aff.schulzei keller

The fatty acid composition of phospholipids from the New Caledonian spongeCinachyrella aff.schulzei Keller was studied. More than 60 fatty acids were identified as methyl esters andN-acyl pyrrolidides by gas chromatography and gas chromatography/mass spectrometry. Two isoprenoid fatty acids also were shown to be present, namely 4,8,12-trimethyltridecanoic and 5,9,13-trimethyltetradecanoic acids. The unusual 6-tetradecenoic, 6-pentadecenoic, 12-nonadecenoic and 26-methylheptacosanoic (iso-28∶0) acids were found for the first time in sponge phospholipids. A series of six n−7 monoenoic long-chain fatty acids (C₂₃ to C₂₈) were identified, including the rare 16-tricosenoic, 18-pentacosenoic and 21-octacosenoic acids. Fifteen fatty acids possessing the typical 5,9 dienoic moiety accounted for 30% of the total fatty acid mixture. Two new fatty acids were identified, namely 5(Z)-octacosenoic and 27-methyl-5(Z),9(Z)-octacosadienoic (iso-5,9-29∶2). Based on gas chromatography/Fourier transform infrared experiments, the double bonds were assigned the (Z) configuration. For part 2 of this series, see Reference 1.     

Fatty acids of unusual double-bond positions and chain lengths found in rat skin surface lipids

The fatty acids of rat skin surface lipids comprise four main skeletal types of chains which occur both as saturates and monoenes and range from C₁₂ to C₃₈: straight even, straight odd, iso and anteiso (the latter two identified by GC retention data only). Two unidentified series of branched monoenes also occur in trace amounts. Reductive ozonolysis of monoenes reveals two characteristic double-bond position patterns, one for the straight even chain series and the other for the straight odd chain series. The straight even chain pattern comprises four series, of which ω7 ≫ω9>ω5>ω11; the straight odd chain series in contrast shows a large number of ω series with irregular distribution. The biosynthesis of the even chain fatty acid monoenes can be thought of as occurring in two stages: synthesis of 14∶Δ9, 16∶Δ9, 18∶Δ9 and 20∶Δ9, with 16∶Δ9 predominating; elongation of these chains mostly by 1, 2, or 3 C₂ units but up to the unusually long lengths by 11 C₂ units. For the formation of the former, two schemes by known pathways are proposed. Iso and anteiso chains which are nearly all saturated comprised 1/3 the total fatty acids. Special terms and abbreviations: Normal even=a straight chain with an even number of carbon atoms, normal odd=a straight chain with an odd number of carbon atoms, ω=terminal carbon atom, iso=a straight chain with a methyl group at the ω−1 position, anteiso=a straight chain with a methyl group at the w−2 position, Δn=a double bond between the n^th and the (n+1)^th carbon atom from the carbonyl group of the fatty acid or ester, ωn=a double bond between the ω∩n^th and the ω-(n−1)^th carbon atom where n is an integer, aldester=aldehyde methyl ester, Me=methyl, GLC=gas-liquid chromatography, TLC=thin-layer chromatography.     

Occurrence of n−5 monounsaturated fatty acids in jujube pulp lipids

The pulp lipids of jujube (Zizyphus jujuba var.inermis) fruit have been shown by chromatographic, spectrometric and chemical analyses to contain a series ofcis-monoenoic fatty acids with n−5 unsaturation as major acyl moieties. The total concentration of these n−5 fatty acids, such as 14∶1n−5, 16∶1n−5 and 18∶1n−5, ranged from 22 to 54% of total fatty acids in the pulp lipids of 11 different sources. The main component of the n−5 homologues was 16∶1n−5 in all cases. Other monoenoic acids with n−7 unsaturation, namely palmitoleic (cis-9-hexadecenoic) acid andcis-vaccenic (cis-11-octadecenoic) acid, as well as with n−9 unsaturation, namely oleic acid, were also identified. In the seed lipids of jujube fruit, none of the n−5 monoenoic acids could be detected. Thus the jujube pulp lipids are characterized by the predominance of n−5 monoenoic acid isomers.     

Occurrence of 22∶3n−9 and 22∶4n−9 in the lipids of the topminnow (Poeciliopsis lucida) hepatic tumor cell line,PLHC-1

The lipids of the hepatic tumor cell line, PLHC-1, from the topminnow (Poeciliopsis lucida), were found to contain considerable amounts of a range of n−9 polyunsaturated fatty acids despite culture in serum containing significant amounts of essential fatty acids. The structural identity of all the n−9 polyunsaturated fatty acids was confirmed by gas chromatography/mass spectrometry. Of particular interest, PLHC-1 cell total lipid contained 1.9% of 22∶3n−9 and 3.3% of 22∶4n−9. As the culture medium contained virtually no n−9 polyunsaturated fatty acids, these fatty acids are all formed by the PLHC-1 cells, presumably form 18∶1n−9. The 22∶3n−9 and 22∶4n−9 are presumably formed by processes of elongation and “Δ4” desaturation of Mead acid, 20∶3n−9, present at over 11% in fatty acids of total lipid. Both 22∶3n−9 and 22∶4n−9 were primarily located in phosphatidylserine (4.1 and 8.5% respectively) and, to a lesser extent, in phosphatidylethanolamine (2.2 and 6.5%, respectively), in common with the C₂₂ derivatives of the n−3 and n−6 series, whereas 20∶3n−9 was preferentially located in phosphatidylinositol (31.2%). The results establish that long-chain polyunsaturated fatty acids of the n−9 series can be formed in vertebrate tissue other than in conditions of classical essential fatty acid deficiency.     

Fatty acid composition of oil in snow crab (Chionoecetes opilio) by gas chromatography/mass spectrometry

The hepatopancreatic fatty acid extract of the snow crab contains a high percentage (26%) of odd-carbon-numbered fatty acids and a substantial quantity (29%) of methyl-branched fatty acids, as indicated by gas chromatography/mass spectrometry (GC/MS) and gas liquid chromatography (GLC). A wide distribution in chain length of the fatty acids (C₁₀ to C₂₆) and in positional isomers of the linear monoenes are also indicated by GC/MS.     

Lipids of the pawpaw fruit: Asimina triloba

The fatty acid composition and structure of pawpaw fruit (Asimina triloba) triglycerides were examined and found to contain fatty acids ranging from C₆ to C₂₀. Octanoate represented 20% of the fatty acids while other medium-chain fatty acids were present in low amounts. Analysis of the intact triglycerides by high-temperature gas-liquid chromatography gave an unusual three-cycle carbon number distribution. Analysis of triglyceride fractions separated according to degree of unsaturation suggested that one octanoate was paired with diglyceride species containing long-chain fatty acids. Determination of the double-bond positions of monoene fatty acids revealed cis Δ9 and cis Δ11 hexadecenoate and cis Δ9, cis Δ11, and cis Δ13 octadecenoate isomers were present in significant quantities. Octanoate and positional monoene fatty acid isomers were found only in the fruit lipids and not in the seed lipids. Phenacyl esters of fatty acids were found to be useful derivatives for structure determination using multiple types of analyses.     

Studies on the isomers of major monoenoic acids in rapeseed and partially hydrogenated rapeseed oil

An analytical procedure is presented for studies on the composition of hydrogenated oils containing C₂₀ and C₂₂ fatty acids. The method involves an initial separation of esters by preparative gas liquid chromatography into fractions of equal chain length. Each fraction is subsequently studied in detail by gas liquid chromatography, argentation thin layer chromatography, IR spectroscopy, and microozonolysis. Results are presented from a study of the isomers of major monoenoic acids in commercial samples of rapeseed and partially hydrogenated rapeseed oils. Part of a paper presented at the AOCS Meeting, Atlantic City, October 1971.     

Isomeric monoethylenic fatty acids in herring oil

Monoethylenic fatty acids from herring oil were concentrated by chromatography by chromatography on silver nitratesilicic acid columns. Examination of consecutive fractions by open tubular gas chromatography confirmed the preferential elution of longer chain length esters and of esters within one chain length with the double bond closer to the terminal methyl group. Isomeric monoethylenic fatty acids with double bonds in the positions closer to the carboxyl group than the approximate midpoint of the even-numbered fatty acid chains could not be adequately separated by gas chromatography and were determined by ozonolysis. The isomers observed are consistent with primary formation from saturated acids through the action of an enzyme specifically removing hydrogen atoms in positions Δ⁹ and Δ¹⁰ relative to the carboxyl group. Chain extension of particular monoethylenic isomers by two carbon atoms in the C₂₀ and longer chain lengths is apparently influenced by the position of the double bond. This work was carried out in partial fulfillment of MSc requirements at Dalhousie University.     

Double-bond patterns of fatty acids and alcohols in steer and human meibomian gland lipids

Ozonolysis studies of the monoenes of the fatty chain types in lipids of steer meibomian gland excreta (meibum) have confirmed earlier structural assignments based on gas liquid chromatography (GLC) retention data and have assisted in assigning complete structures to a group of recently identified ω-hydroxy fatty acids. The ω-hydroxy acids include straight-chain monoenoic acids (85%), saturated anteiso and iso acids (13%), monoenoic acids of the latter group (1%) and, finally, saturates of the normal monoenoic acids (1%). All the fatty chains of meibum can be biosynthesized by a unified process of chain buildup to primary chain lengths of 12∶0–20∶0 for the straight evens, with 16∶0 predominating, 13∶0–21∶0 for the straight odds with 17∶0 predominating, i16∶0 to i28∶0 for the iso and ai17∶0 to ai29∶0 for the anteiso chain types; then Δ9 desaturation of each of these chain types; and finally chain elongation of 1–10 C₂ units. Some chain degradation may also occur. The meibum lipid components involved are unsubstituted fatty acids, α-OH fatty acids, ω-OH fatty acids, fatty alcohols and some other lipid components incompletely characterized. The carbon skeletons are straight even, straight odd, iso and anteiso except that the α-OH fatty acids are only straight even and straight odd and these chains are not elongated. All fatty chains are almost entirely saturated and monoenoic, the polyenes occurring in only trace amounts. Biosynthesis of the fatty chains of human meibum evidently occurs similarly, except that considerably more 18∶0 than 16∶0 fatty acids are built up by the fatty acid synthetase, before desaturation and extension.     

Melting points of synthetic wax esters

Saturated, monoenoic and dienoic wax esters, C₂₆−C₄₀, have been synthesized from even-numbered fatty alcohols and acids. In homologous series of saturated esters, the increments of melting points follow a regular trend except for those esters which have an acid moiety two carbon atoms shorter than the alcohol moiety. These wax esters have melting points higher than interpolation would predict. Monoenoic wax esters with the double bond in the alcohol chain have melting points about 10 C higher than their isomers with the double bond in the acid chain.     

Positional isomers of unsaturated fatty acids in rat liver lipids

The fatty acids of liver lipids from rats raised on a fat free diet from the 30th to the 90th day after birth were analyzed with special regard to the detection of positional isomers of mono-, di-, tri-, and tetraenoic fatty acids. The methyl esters obtained after transesterification of total lipids were separated by argentation chromatography into five fractions: I saturated, II monoenoic, III dienoic, IV dienoic nonmethylene interrupted, V triand tetraenoic fatty acid esters. After hydroxylation of the double bonds with osmium tetroxide, the analysis of the poly-O-trimethylsilyl derivatives by gas liquid chromatography on S.C.O.T. columns combined with mass spectrometry revealed the presence of 19 monoenoic, 15 dienoic, and 9 trienoic as well as 3 tetraenoic fatty acid isomers including the normally occurring representatives of the (n−3), (n−6), (n−7), and (n−9) fatty acid families. The majority of the identified isomers can be coordinated to one of these families like 7–16∶1; 11–20∶1; 6,9–18∶2; 8,11–20∶2; 5,11–20∶2; 5,8,11–20∶3; 7,10,13–22∶3 to the (n−9) family, 11–18∶1; 13–20∶1; 5,11–18∶2; 7,13–20∶2; 6,11–18∶2; 6,9–16∶2; 8, 11–18∶2; 10,13–20∶2; 5,8,11–18∶3; 7,10,13–20∶3; 4,7,10,13–20∶4 to the (n−7) family and 11,14–20∶2; 5,11,14–20∶3; 6,9,12–18∶3; 8,11,14–20∶3; 5,8,11,14–20∶4; 7,10,13,16–22∶4 to the (n−6) family. All these naturally occuring isomers can be placed into a network of desaturation and chain elongation steps which allows certain conclusions about the substrate specificity of the Δ6-, Δ5-and Δ4-desaturase systems. The great number of isomers found in the (n−7) family indicates that the members of this family are actively metabolized in partial essential fatty acid deficiency.     

Trace constituents in milk fat: Isolation and identification of oxofatty acids

Ca. 1% of the glycerides of milk fat contain oxofatty acids. The isolation, fractionation, and characterization of oxofatty acids were accomplished using the following sequence of steps: (A) transmethylation, (B) conversion into 2,4-dinitrophenylhydrazones, (C) adsorption of the 2,4-dinitrophenylhydrazones on magnesium oxide to eliminate the colorless lipid, (D) fractionation of the 2,4-dinitrophenylhydrazones into non-oxofatty acid and oxofatty acid fractions on alumina, (E) separation of the oxofatty acid 2,4-dinitrophenylhydrazones into saturated and unsaturated classes by argentation column chromatography, (F) separation of these classes by chain length using liquid-liquid column and thin layer partition chromatography, (G) resolution of positional isomers by thin layer chromatography, (H) regeneration of the positional isomer 2,4-dinitrophenylhydrazones, and (I) analysis of the parent oxofatty acids by gas liquid chromatographymass spectrometry. In this manner, 36 saturated and 11 unsaturated oxofatty acids were identified tentatively or positively. The saturated oxofatty acids ranged in chain length from C₁₀–C₂₄, predominantly C₁₈ and C₁₆, and generally contained an even number of carbon atoms. The unsaturated oxofatty acids ranged from C₁₄–C₁₈, with C₁₈ predominating.     

Characterization of skin-surface lipids from the monkey (Macaca fascicularis)

Skin-surface lipids from the monkeyMacaca fascicularis are composed of sterol esters (38%), cholesterol (4%) and two types of wax diesters, identified as Type II (IIa and IIb, 17% and 40%, respectively). Type IIa contained diesters of 1,2-alkanediols esterified with two molecules of long-chain (C₁₄−C₃₄) fatty acids having straight and branched chains. In the diesters IIa, fatty acids shorter than C₁₉ predominated in position 1, and fatty acids longer than C₂₀ predominated in position 2. Type IIb contained diesters of 1,2-alkanediols esterified with C₄ and C₅ branched-chain fatty acids (predominantly isovaleric acid) at position 1 and long-chain (C₁₄−C₂₇) acids, having straight and branched chains, at position 2. The shortchain acids were converted to 2-nitrophenylhydrazides and analyzed by high-performance liquid chromatography (HPLC). Ammonia chemical ionization (CI)-gas chromatography (GC)-mass spectrometry (MS) resolved the intact diesters IIb into 12 peaks corresponding to molecular weights ranging from 597 to 748, and showed that the molecular species, such as C₂₁−C₁₆−C₅ (diol, fatty acid in position 2, fatty acid in position 1), C₂₂−C₁₆−C₅ and C₂₃−C₁₆−C₅, were prevalent. The fatty acids from both diesters were mostly (>98%) saturated. The 1,2-alkanediols from both diesters consisted of C₁₆−C₂₆ saturated straight- and branched-chain components. The acyl groups of sterol esters contained 86% C₁₄−C₃₄ branched-chain acids. The unsaturated fatty acids (5.4%) belonged to a straight-chain monoenoic series having extremely long chains (C₁₈−C₃₄). The branched-chain structures in the fatty acids and diols were iso and anteiso. These results show the species-specific profile for the skin-surface lipid synthesis.     

Isolation and characterization of the monounsaturated long chain fatty acids ofMycobacterium tuberculosis

The positions of double bond in the monounsaturated C₁₅−C₃₂ fatty acids ofMycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives. The monounsaturated C₁₅−C₂₁ fatty acids had the double bond primarily at the Δ⁹ position while the monounsaturated longer chain fatty acids (C₂₂−C₃₂) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follow: C₂₂, Δ⁴; C₂₄, Δ⁵; C₂₆, Δ⁷ and Δ⁹; C₂₈, Δ⁹; C₃₀, Δ¹¹ and Δ¹³; C₃₂, Δ¹³ and Δ¹⁵.     

Fatty acids and fatty alcohols of wax esters in the orange roughy: Specific textures of minor polyunsaturated and branched-chain components

Open-tubular gas chromatography was carried out on fatty acids and alcohols obtained from wax esters of the orange roughy,Hoplostethus atlanticus, caught at sea off New Zealand. The major (above 5%) components were 16∶1(n−7), 18∶1(n−9) and (n−7), 20∶1(n−9) and (n−7), and 22∶1(n−11, n−13) as fatty acids, and 16∶0, 18∶0, 18∶1(n−9), 20∶1(n−9) and (n−7), and 22∶1(n−11, n−13) as fatty alcohols. The total percentages of the minor components were 10% in the acids and 26% in the alcohols. The 22∶1/20∶1 ratio of the fatty alcohols obtained in this study was less than 1.0, although the ratio for the Atlantic orange roughy has been reported as being greater than 1.0. The contents of polyenes were as low as 2.48% in the acids and 0.95% in the alcohols, but their compositions showed some specific features. The percentages of the C₁₆−C₂₂ dienes in the total polyenes were remarkably high, 57.7% of these acids and 53.1% of these alcohols. The most important dienes were 18∶2(n−6) in the acids and 20∶2(n−6) in the alcohols.     

Dietary n−3 long-chain polyunsaturated fatty acid deprivation, tissue lipid composition, ex vivo prostaglandin production, and stress tolerance in juvenile dover sole (Solea solea L.)

Larval Dover sole fed an Artemia diet supplemented with n−3 long-chain (C₂₀+C₂₂) polyunsaturated fatty acids (PUFA) are known to be more resistant to low-temperature injury. Here we explore the relationship between tissue fatty acid composition and tolerance of stressful environmental conditions over the larval and early juvenile periods. Artemia nauplii supplemented with n−3 long-chain PUFA-deficient and PUFA-enriched oil emulsions were fed to two groups of larvae. Whole body tissue samples from the resulting PUFA-deficient and-enriched juveniles possessed 12.1 and 21.9% n−3 long-chain PUFA, respectively. These differences were at the expense of C₁₈ PUFA, while proportions of saturated fatty acids, monousaturated fatty acids, and total PUFA were unaffected. Brain and eye tissues from the PUFA-deficient fish contained lower levels of 22∶6n−3, known to be important for optimal nervous system function, incorporation instead a range of fatty acids of lower unsaturation. PUFA-deprived juveniles showed substantially greater mortality when exposed to a combination of low temperature and low salinity, as well as to high temperature and to hypoxia. After adaptation to the different diets, both dietary groups were fed a common formulated feed high in n−3 long-chain PUFA. Tissue PUFA in both groups progressively increased to the same high value, with a consequent loss of the differences in cold-susceptibility. These correlated changes support a link between dietary manipulation of n−3 long-chain PUFA and development of a stress-sensitive phenotype. PUFA deprivation had no detectable effect upon static hydrocarbon order of purified brain membranes (as assessed by fluorescence polarization) but was associated with an increase in the whole-body content of prostaglandins. We conclude that susceptibility to environmental stress is responsive to dietary n−3 long-chain PUFA manipulation, possibly due to altered tissue development or the overproduction of eicosanoids.