Relationship between essential fatty acid requirements of aquatic animals and the capacity for bioconversion of linolenic acid to highly unsaturated fatty acids.

1. [1-14C]linolenic acid was injected into the rainbow trout, Salmo gairdnerii, ayu, Plecoglossus altivelis, eel, Anguilla japonica, red sea bream, Chrysophrys major, rockfish, Sebastiscus marmoratus, globefish, Fugu rubripes rubripes and prawn, Penaeus japonicus (molting stage D"1-D2), and the bioconversion of linolenic acid (18:3 omega 3) to highly unsaturated fatty acids such as eicosapentaenoic (20:5 omega 3) and docosahexaenoic (22:6 omega 3) acids was investigated. 2. Linolenic acid was converted to 20:5 omega 3 and 22:6 omega 3 intensively in the rainbow trout, moderately in the ayu, eel and prawn, but slightly in the red sea bream, rockfish and globefish. 3. These results were discussed in relation to the essential fatty acid requirements of the aquatic animals.     

Effects of postnatal age and diet on the fatty acid composition of plasma lipid fractions in preterm infants

Diet and postnatal age effect the fatty acid composition of plasma and tissue lipids. This work was designed as a transversal study to evaluate the changes in the fatty acid composition of plasma phospholipids, cholesteryl esters, triglycerides and free fatty acids in preterm infants (28-35 weeks gestational age), fed human milk (HM) and milk formula (MF) from birth to 1 month of life. Sixteen blood samples were obtained from cord, and 19 at 6-8 h after birth, 14 at 1 week and 9 at 4 weeks from HM-fed infants and 18 at 1 week and 14 at 4 weeks from MF-fed ones. Groups had similar mean birth weight, gestational age and sex ratio. The MF provided 69 kcal/dl and contained 16% of linoleic acid and 1.3% of alpha-linolenic acid on the total fat. Plasma lipid fractions were extracted and separated by thin-layer chromatography and fatty acid methyl esters were quantitated by gas liquid chromatography. In plasma phospholipids, linoleic acid (18:2 omega 6) continuously increased from birth to 1 month of age, but no changes were seen as related to type of diet; polyunsaturated fatty acids greater than 18 carbon atoms of both the omega 6 and omega 3 series (PUFA omega 6 greater than 18 C and omega 3 greater than 18 C) dropped from birth to 1 week and continued to decrease in MF-fed infants until 1 month; eicosatrienoic (20:3 omega 6), arachidonic (20:4 omega 6) and docosahexaenoic (22:6 omega 3) were the fatty acids implicated. In cholesteryl esters palmitoleic (16:1 omega 7) and oleic (18:1 omega 9) acids decreased from birth to 1 month and linoleic acid increased and arachidonic acid dropped, especially in MF fed infants. In triglycerides, palmitic, palmitoleic and stearic acid (18:0) decreased during the first month of life; oleic acid remained constant and linoleic acid increased in all infants, but arachidonic acid decreased only in those fed formula. Free fatty acids showed a similar behavior in fatty acids and in plasma triglycerides. Preterm neonates seem to have special requirements of long-chain PUFA and adapted MF should contain these fatty acids in similar amounts to those of HM to allow the maintenance of an adequate tissue structure and physiology.     

Protein synthesis and degradation in isolated muscle. Effect of omega 3 and omega 6 fatty acids.

The ability of derivatives of the essential fatty acids linoleic acid (C18:2, omega 6) and alpha-linolenic acid (C18:3, omega 3) to stimulate rates of protein synthesis and degradation was investigated in isolated intact muscles from fasted rabbits. Both omega 6 derivatives examined, arachidonic acid (C20:4, omega 6) and dihomo-gamma-linolenic acid (C20:3, omega 6), when added at concentrations up to 1 microM, stimulated the rate of protein synthesis and the release of prostaglandin F2 alpha (PGF2 alpha). Metabolites of the omega 6 series, namely eicosapentaenoic acid (C20:5, omega 3) and docosahexaenoic acid (C22:6, omega 3), were without effect on the rate of protein synthesis and resulted in a decrease in the release of PGF2 alpha. None of the fatty acids had a significant effect on the rate of protein degradation. Although insulin (100 mu units/ml) also stimulated rates of protein synthesis when added alone, none of the omega 3 or omega 6 fatty acids, when added with insulin at concentrations of 0.2 microM, potentiated the effect of the hormone.     

Regional differences in lipid composition and incorporation of saturated and unsaturated fatty acids into microsomal membranes of rat small intestine

Incorporation of [1-14C]palmitic (16:0) and [1-14C]linoleic (18:2 omega 6) acids into microsomal membranes of proximal (jejunum) and distal (ileum) regions of rat small intestine was investigated, and the lipid composition, including fatty acid profiles of membrane phospholipids, was determined. Jejunal microsomes contained significantly higher amounts of total phospholipids, phosphatidylcholine, and phosphatidylinositol, and lower amounts of cholesterol and sphingomyelin when compared with ileal microsomes. Jejunal microsomal phospholipids contained higher levels of stearic (18:0), 18:2 omega 6, and eicosapentaenoic (20:5 omega 3) acids followed by reduced levels of oleic (18:1 omega 9), arachidonic (20:4 omega 6), and docosahexaenoic (22:6 omega 3) acids when compared with those from the ileum, except for phosphatidylinositol where no significant difference between 20:4 omega 6 content of each site was observed. In both jejunal and ileal microsomes, incorporation of [1-14C]18:2 omega 6 was significantly higher than that of [1-14C]16:0. Incorporation of both [1-14C]16:0 and [1-14C]18:2 omega 6 was significantly higher in jejunal microsomal lipid fractions (phospholipids, diacylglycerols, triacylglycerols) when compared with the ileal microsomal fraction. These data suggest that (1) jejunal and ileal microsomal membranes differ from each other in terms of lipid composition and lipid synthesis, (2) site variations in the specificity of acyltransferases for different fatty acids exist, and (3) higher delta 9-, delta 6-, delta 5-, and delta 4-desaturase activities exist in ileal compared with jejunal enterocytes.     

Comparative levels of arachidonic acid and eicosapentaenoic acid in Malaysian fish

Total lipids were extracted from 22 species of Malaysian fish and the constituent fatty acids were analysed by gas chromatography. Malaysian fish generally contained high levels of saturated fatty acids (range 36-55% total fatty acids) and contained variable amounts of monounsaturates, chiefly palmitic and stearic acids, but only trace levels of 20:1 and 22:1. Unlike fish caught in colder northern hemisphere waters, Malaysian fish were found to contain arachidonic acid (20:4 omega 6, range 2-12%) in addition to the expected eicosapentaenoic acid (20:5 omega 3, range 1-13%) and docosahexaenoic acid (22:6 omega 3, range 6.6-40.4%).     

Comparison of 20-, 22-, and 24-carbon n-3 and n-6 polyunsaturated fatty acid utilization in differentiated rat brain astrocytes

Astrocytes convert n-6 fatty acids primarily to arachidonic acid (20:4n-6), whereas n-3 fatty acids are converted to docosapentaenoic (22:5n-3) and docosahexaenoic (22:6n-3) acids. The utilization of 20-, 22- and 24-carbon n-3 and n-6 fatty acids was compared in differentiated rat astrocytes to determine the metabolic basis for this difference. The astrocytes retained 81% of the arachidonic acid ([(3)H]20:4n-6) uptake and retroconverted 57% of the docosatetraenoic acid ([3-(14)C]22:4n-6) uptake to 20:4n-6. By contrast, 68% of the eicosapentaenoic acid ([(3)H]20:5n-3) uptake was elongated, and only 9% of the [3-(14)C]22:5n-3 uptake was retroconverted to 20:5n-3. Both tetracosapentaenoic acid ([3-(14)C]24:5n-3) and tetracosatetraenoic acid ([3-(14)C]24:4n-6) were converted to docosahexaenoic acid (22:6n-3) and 22:5n-6, respectively. Therefore, the difference in the n-3 and n-6 fatty acid products formed is due primarily to differences in the utilization of their 20- and 22-carbon intermediates. This metabolic difference probably contributes to the preferential accumulation of docosahexaenoic acid in the brain.     

Lipogenesis from glucose-2- 14 C and acetate-1- 14 C in aorta

Lipogenesis was measured with glucose-2-(14)C and acetate-1-(14)C in the everted aortas of normal and atherosclerotic rabbits. More glucose-2-(14)C than acetate-1-(14)C was incorporated into lipids in both the normal and the atherosclerotic aorta. Radiocarbon from glucose-2-(14)C appeared mainly in triglycerides and phospholipids with a small amount in cholesteryl esters. Incorporation increased almost threefold with atherosclerosis, most of the radioactivity being in the glycerol moiety; radioactivity was predominantly in carbon 2 of glycerol. About 70% of the acetate-1-(14)C incorporated into phospholipids and triglycerides was in the fatty acids, and the remainder was in glyceride-glycerol; 98% of the radioactivity in cholesteryl esters was in the fatty acid moiety. Incorporation into cholesteryl esters was increased most during the development of atherosclerosis. Fatty acid synthesis was similar from both acetate-1-(14)C and the 2 carbon unit derived from glucose-2-(14)C, viz., predominantly de novo synthesis of fatty acids with 14 and 16 carbon atoms, and elongation for those of 18 carbons and longer.     

Dietary polyunsaturated fatty acids (C18:2 omega6 and C18:3 omega3) do not suppress hepatic lipogenesis

Omega 3 polyunsaturated fatty acids are promoted as beneficial in the prevention of metabolic and cardiovascular diseases. In general, dietary omega 3 fatty acids are derived from plant sources as linolenic acid (LNA, C18:3 omega3) the precursor to eicosapentaenoic acid (EPA, C20:5 omega3) and docosahexaenoic acid (DHA, C22:6 omega3). However, it remains unclear if the polyunsaturated fatty acid (PUFA) LNA can provide the same health benefits as the very long chain highly unsaturated fatty acids (HUFA) EPA and DHA generally derived from oily fish. In this study, mice were fed synthetic diets containing lard (low in PUFA and HUFA), canola oil (to supply PUFA), or a mixture of menhaden and arasco (fish and fungal) oils (to supply HUFA) for 8 weeks. The diets were neither high in calories nor fat, which was supplied at 6%. The lard and canola oil diets resulted in high levels of hepatic triglycerides and cholesterol and elevation of lipogenic gene expression. By comparison livers from mice fed the fish/fungal oil diet had low levels of lipid accumulation and more closely resembled livers from mice fed standard laboratory chow. SREBP1c and PPARgamma gene and protein expression were high in livers of animals fed diets containing lard or canola oil compared with fish/fungal oil. Hepatic fatty acid analyses indicated that dietary PUFA were efficiently converted to HUFA regardless of source. Therefore, differences in hepatic lipid levels and gene expression between dietary groups were due to exogenous fatty acid supplied rather than endogenous pools. These results have important implications for understanding the regulation of hepatic lipogenesis by dietary fatty acids.     

Lower fetal status of docosahexaenoic acid, arachidonic acid and essential fatty acids is associated with less favorable neonatal neurological condition

Long-chain polyunsaturated fatty acids, notably arachidonic (AA) and docosahexaenoic (DHA) acids are abundant in brain and may be conditionally essential in fetal life. We investigated umbilical artery (UA) and vein (UV) fatty acid compositions and early neonatal neurological condition in 317 term infants. Neurological condition was summarized as a clinical classification and a 'neurological optimality score' (NOS). Neurologically abnormal infants (n=27) had lower UV DHA and essential fatty acid (EFA) status. NOS correlated positively with AA (UV), and EFA (UV) and DHA status (UV and UA) and negatively with 18:2omega6 and omega9 (UV), and 20:3omega9, omega7 and C18 trans fatty acids (UV and UA). UV DHA, AA, saturated fatty acids, gestational age and obstetrical optimality score explained 16.2% of the NOS variance. Early postnatal neurological condition seems negatively influenced by lower fetal DHA, AA and EFA status. C18 trans fatty acids and 18:2omega6 may exert negative effects by impairment of LCP status.     

Changes in myocardial lipid composition during surgery with cold and chemical cardioplegia

The changes of children myocardium lipid composition were studied for the first time during surgical intervention under cold crystalloid cardioplegia. The surgical intervention was performed as a result of congenital heart disease--atrial septal defect. It was shown that the quantity of short chain fatty acids decreased and the amount of long chain fatty acids increased in the content of phospholipid fraction. Simultaneously the amount of linoleic (C18:2 omega 6), of docosahexaenoic (C22:6 omega 3) and of some other fatty acids decreased in the content of cholesterol esthers. The accumulation of free linoleic (C18:2 omega:6), (C18:2 omega:4) and linolenic (C18:3 omega:6) acids was found. Reperfusion caused the additional changes of myocardium lipid composition. The amount of palmitic (C16:0) acid decreased by 30%. The quantity of some other saturated free fatty acids also diminished. Simultaneously the content of free oleic (C18:1 omega 9) also decreased as a consequence of lipid peroxidative processes activation. The ratio of omega 6/omega 3 increased during the few first minutes of reperfusion in the fraction of free fatty acids and cholesterol esthers.     

Differential distribution of DHA-phospholipids in rat brain after feeding: A lipidomic approach

On a per-weight basis, the brain is the organ richest in lipids, including a remarkable proportion of polyunsaturated fatty acids (PUFAs) of the omega 3 series, namely eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. The cerebral effects of exogenous DHA likely depend on its degree of incorporation into neuronal phospholipids and on its distribution among the various brain structures, after intake. Hence, because PUFAs are not evenly distributed among the brain phospholipid classes and because the existence of class-specific phospholipases that regulate their turnover, we sought to investigate the incorporation of omega 3 PUFAs in selected brain areas regions and specific phospholipid classes. Rats (n=7) were administered, by oral gavage, 100mg/kg/d of a commercially available fish oil (containing ～84% of long-chain omega 3 fatty acids, of which ～38% of DHA and ～46% of EPA). Control rats (n=7) received liquid paraffin. This treatment was continued for 30 days. Thereafter, we dissected three areas, namely the hippocampus, the striatum, and the cortex. Quantization of individual phospholipid classes and their molecular species was performed by ESI-MS/MS. Principal component analysis was used to examine the variation of the molecular lipid profiles (as percentage) induced by omega 3 supplementation. Our results show that provision of omega 3 fatty acids to rats results in their incorporation into brain phospholipids, the extent of which is lower in the striatum as compared with cortex and hippocampus. These data might in part explain the mixed therapeutic results obtained in neurological disorders, many of which are likely region-specific.     

The role of the collagen tripeptide fragment GER in the adhesion activation and modification of fatty acid composition in membrane phospholipids of CHO-K1 cells

It has been found that multiply repeated tripeptide fragment GER (Gly-Glu-Arg) from different collagen types stimulates nonspecific adhesion of CHO-K1 cells. Activation of cell adhesion is accompanied by modifications in fatty acid composition of cell membrane phospholipids. Cell incubation with the synthetic peptide increases the unsaturation indexes of phosphatidylcholin (PC), phosphatidylethanolamine (PEA) and phosphatidylinositol (PI). Arachidonic (C20:4omega6) acid is mainly contributed to the increased unsaturation index of PI. In the case of PC and PEA not only arachidonic acid but also other unsaturated fatty acids: docosatetraenoic (C22:4omega6), docosapentaenoic (C22:5omega3) and docosahexaenoic (C22:6omega3) acids are implicated in the index increasing. Besides, the elevation of relative content of molecules with polyenoic fatty acids in the group of PI molecules is accompanied by decrease in monoenoic fatty acids caused mainly by decrease in the oleic (C18:1) acid level. The role of the investigated peptide: 1) in the activation of cell adhesion as a regulator of active or non active state of integrin receptors: 2) in the alterations of fatty acid composition in main classes of phospholipids as modulator of fluidity level in annular lipid zones around these adhesive molecules is discussed.     

Fatty acid composition and lipid peroxidation induced by ascorbate-Fe2+ in different organs of goose (Anser anser)

Many reports have demonstrated that birds show a low degree of fatty acid unsaturation and lipid peroxidation compared with mammals of similar body size. The aim of the present study was to examine fatty acid profiles, non-enzymatic lipid peroxidation and vitamin E levels of mitochondria and microsomes obtained from liver, heart and brain of goose (Anser anser). The unsaturated fatty acid content found in mitochondria and microsomes of all tissues examined was approximately 60% with a prevalence of C18:1 n9 + C18:2 n6 = 50%. The 20:4 n6 + C22:6 n3 content was significantly higher in brain organelles (approx. 16%) compared with mitochondria and microsomes of liver and heart (approx. 4%). Whereas these organelles were not affected when subjected to lipid peroxidation, brain mitochondria were highly affected, as indicated by the increase in chemiluminescence and a considerable decrease of arachidonic and docosahexaenoic acids. These changes were not observed during lipid peroxidation of brain microsomes. Vitamin E content was higher in liver and heart than in brain mitochondria (1.77 +/- 0.06 and 1.93 +/- 0.13 vs. 0.91 +/- 0.09 nmol/mg protein). The main conclusion of this paper is that a lower degree of unsaturation of fatty acids in liver and heart mitochondria and a higher vitamin E level than in brain mitochondria protect those tissues against lipid peroxidation.     

Effect of Ethrel and Ceratocystis fimbriata on the Synthesis of Fatty Acids and 6-Methoxy Mellein in Carrot Root

The rate of incorporation of ¹⁴C from acetate-1-¹⁴C into fatty acids by carrot root discs, 18 hours after inoculation with Ceratocystis fimbriata, was 9-fold greater than that in freshly cut discs. The rate in discs treated with water or Ethrel was 3-fold greater. The rate of incorporation of ¹⁴C from glucose-U-¹³C into fatty acids was 3-fold greater 18 hours after any of the above treatments. The rate of ¹⁴C incorporation from malonate-2-¹⁴C into fatty acids 24 hours after inoculation with C. fimbriata or treatment with water was 25 and 60%, respectively, of that in freshly cut discs. Linoleic acid was the principal fatty acid in carrot root, but incorporation of ¹⁴C from acetate-1-¹⁴C into the acid was low until 18 hours after inoculation with C. fimbriata or treatment with Ethrel. Turnover rates of the fatty acids appeared low and were similar for all treatments.     

Effect of omega 3 fatty acids on oxidative stress in humans: GC-MS measurement of urinary F2-isoprostane excretion

Despite the reported benefits associated with omega3 fatty acids for cardiovascular disease, there remains concern that increased intake may lead to increased lipid peroxidation. To date, however, the data, particularly in vivo, are inconclusive. This report describes two interventions, one providing daily fish meals and the other eicosapentaenoic acid (EPA, 20:5 omega3) or docosahexaenoic acid (DHA, 22:6 omega3), the two principal omega3 fatty acids in marine oils, in which in vivo lipid peroxidation was assessed by measurement of urinary excretion of F2-isoprostanes. In both trials, urinary F2-isoprostanes were significantly reduced by 20-27%. Therefore, in contrast with previous reports in the literature, these results demonstrate that omega3 fatty acids reduce in vivo oxidant stress in humans.     

Formula alpha-linolenic (18:3(n - 3)) and linoleic (18:2(n - 6)) acid influence neonatal piglet liver and brain saturated fatty acids, as well as docosahexaenoic acid (22:6(n - 3)).

Saturated fatty acids can be synthesized de novo and play a role in determining properties of structural membranes. The effect of dietary essential fatty acids, linoleic acid (18:2(n - 6)) and alpha-linolenic acid (18:3(n - 3)), on the saturated fatty acid content of membrane phospholipid has not previously been considered in newborn nutrition. The studies report the effect of low (1% fatty acids) or high (4%) formula 18:3(n - 3) with low (16%) or high (30-35%) formula 18:2(n - 6) on the saturated and unsaturated fatty acid composition of liver and brain structural lipid of piglets fed formula from birth for 15 days. A significant inverse relationship between the formula % 18:3(n - 3), but not 18:2(n - 6), and the liver phospholipid palmitic acid (16:0) was found. This may indicate a possible effect of dietary 18:3(n - 3) on de novo synthesis of 16:0 and requires further investigation. Monounsaturated fatty acids in both liver and brain were significantly lower in response to high 18:3(n - 3) and to high 18:2(n - 6) plus low 18:1(n - 9) in the formula. Liver phospholipid and brain total lipid % docosahexaenoic acid (22:6(n - 3)) were significantly higher when formula containing 4% rather than 1% 18:3(n - 3) was fed, suggesting that 1% 18:3(n - 3) may limit tissue (n - 3) fatty acid accretion. These results suggest that future studies of essential fatty acid requirements, specifically 18:3(n - 3), should consider possible influences on the saturated fatty acids which also play a functional role in tissue structural lipids.     

Crystal structure and thermodynamic analysis of human brain fatty acid-binding protein

Expression of brain fatty acid-binding protein (B-FABP) is spatially and temporally correlated with neuronal differentiation during brain development. Isothermal titration calorimetry demonstrates that recombinant human B-FABP clearly exhibits high affinity for the polyunsaturated n-3 fatty acids alpha-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, and for monounsaturated n-9 oleic acid (K(d) from 28 to 53 nm) over polyunsaturated n-6 fatty acids, linoleic acid, and arachidonic acid (K(d) from 115 to 206 nm). B-FABP has low binding affinity for saturated long chain fatty acids. The three-dimensional structure of recombinant human B-FABP in complex with oleic acid shows that the oleic acid hydrocarbon tail assumes a "U-shaped" conformation, whereas in the complex with docosahexaenoic acid the hydrocarbon tail adopts a helical conformation. A comparison of the three-dimensional structures and binding properties of human B-FABP with other homologous FABPs, indicates that the binding specificity is in part the result of nonconserved amino acid Phe(104), which interacts with double bonds present in the lipid hydrocarbon tail. In this context, analysis of the primary and tertiary structures of human B-FABP provides a rationale for its high affinity and specificity for polyunsaturated fatty acids. The expression of B-FABP in glial cells and its high affinity for docosahexaenoic acid, which is known to be an important component of neuronal membranes, points toward a role for B-FABP in supplying brain abundant fatty acids to the developing neuron.     

The function of very long chain polyunsaturated fatty acids in the pineal gland

The mammalian pineal gland is a prominent secretory organ with a high metabolic activity. Melatonin (N-acetyl-5-methoxytryptamine), the main secretory product of the pineal gland, efficiently scavenges both the hydroxyl and peroxyl radicals counteracting lipid peroxidation in biological membranes. Approximately 25% of the total fatty acids present in the rat pineal lipids are represented by arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3). These very long chain polyunsaturated fatty acids play important roles in the pineal gland. In addition to the production of melatonin, the mammalian pineal gland is able of convert these polyunsaturated fatty acids into bioactive lipid mediators. Lipoxygenation is the principal lipoxygenase (LOX) activity observed in the rat pineal gland. Lipoxygenation in the pineal gland is exceptional because no other brain regions express significant LOX activities under normal physiological conditions. The rat pineal gland expresses both 12- and 15-lipoxygenase (LOX) activities, producing 12- and 15-hydroperoxyeicosatetraenoic acid (12- and 15-HpETE) from arachidonic acid and 14- and 17-hydroxydocosahexaenoic acid (14- and 17-HdoHE) from docosahexaenoic acid, respectively. The rat pineal also produces hepoxilins via LOX pathways. The hepoxilins are bioactive epoxy-hydroxy products of the arachidonic acid metabolism via the 12S-lipoxygenase (12S-LOX) pathway. The two key pineal biochemical functions, lipoxygenation and melatonin synthesis, may be synergistically regulated by the status of n-3 essential fatty acids.     

Lipids and fatty acids in muscle, liver and skin of three edible fish from the Senegalese coast: Sardinella maderensis, Sardinella aurita and Cephalopholis taeniops

Lipid content and fatty acid composition were determined in three species of edible fish caught in Senegalese waters during the upwelling season (January, 1993). Sardinella maderensis and Sardinella aurita are fat fish containing more than 5% (fresh wt.) of lipids, whereas Cephalopholis taeniops is a lean fish with approximately 1% of lipids. Skin, liver and muscle were studied for each fish species. About 40 fatty acids were identified by GC and GC/MS as methyl esters and N-acyl pyrrolidides. Palmitic acid was the main acid in the muscle and skin of all samples studied (20-33% of total fatty acids). Oleic acid was the main fatty acid in the liver of S. maderensis (27.2%+/-0.1) and S. aurita (44.7%+/-0.1). Arachidonic acid was a minor component in all samples. The flesh (muscle) of the three fish species contained high concentrations of omega3 polyunsaturated fatty acids (PUFA), ranging from 16.0 to 29.1% and including 20:5 omega3 (eicosapentaenoic acid, EPA) and 22:6 omega3 (docosahexaenoic acid, DHA) acids as major components. These two acids together accounted for 24.7%+/-0.1 and 12.9%+/-0.1 of total acids in the skin of S. maderensis and S. aurita, respectively. The percentages of PUFA found in the fish studied were very similar to those in fish used commercially as sources of PUFA. Muscle sterols, which accounted for 9-11% of total lipids, consisted mainly of cholesterol (up to 97% of total sterols).     

Analysis of polyunsaturated fatty acid composition of Strongyloides ratti in relation to development

The effect of linolenic acid (C18:3 omega 3) on the development of Strongyloides ratti first-stage larvae (L1) in culture was studied. The fatty acid composition of S. ratti free-living generations was analyzed by gas chromatography. L1 had abundant linoleic acid (C18:2 omega 6) but its proportion decreased with development. On the contrary, eicosapentaenoic acid (C20:5 omega 3) and C20:4 omega 3 were prominent in the filariform larva (L3). Because C20:5 omega 3 is generally synthesized from C18:3 omega 3 via C20:4 omega 3, the high ratio of C20:5 omega 3/C18:3 omega 3 of L3 in all the free-living generations suggested that polyunsaturated fatty acid metabolism, particularly the omega-3 series, and eicosanoids produced had important roles in the development of S. ratti L1.