A single column packing for the gas-liquid chromatographic separation of various biologically important compounds.

The use of a single, commercially available column packing, TabsorbR, is described for the g.l.c. separation of a large number of different compounds. The resolution of the homologous members of the following series of compounds was achieved: (1) saturated fatty acids (C1-C18), (2) normal aliphatic saturated dicarboxylic acids (C2-C14), (3) normal aliphatic saturated alcohols (C1-C24), (4) normal aliphatic saturated amines (C1-C12), (5) the common amino acids except arginine, histidine and cysteine, (6) aliphatic hydrocarbons (C10-C20) and (7) monosaccharides. It should be noted that twenty-two monosaccharides including three hexosamines and two anhydrohexoses, could be resolved as alditol acetates in a single run. In addition, galacturonic, glucuronic and iduronic acids could be separated from one another as their 1,4-lactones. The resolution achieved in these series of compounds was found to be consistent and highly reproducible. It is of further interest that certain isomers of the higher fatty acids and hydrocarbons with one double bond could also be separated from the normal and saturated compounds, respectively. The applicability of "Tabsorb" for the g.l.c. separation, although noted above to be considerably broad, is by far not yet exhausted. These procedures which form the basis for the quantitative determinations of the various compounds studied as demonstrated by analysis of glycopeptides for neutral hexoses and proteins for the amino acids, can readily be adapted to preparative methods. From the biochemical point of view "Tabsorb" is an extremely versatile column packing in that it can be used for the identification of many of the common building blocks of natural products.     

Liquid chromatography/mass spectrometry of fatty acids as their anilides

The mass spectra of a series of saturated (C16:0-C30:0) and unsaturated (C16:1, C18:1, C18:2, C18:3) fatty acids have been recorded as their anilides using liquid chromatography/mass spectrometry with the atmospheric-pressure-ionization interface system. The spectra show an intense peak for (molecule + H)+ ion in each case. The liquid chromatographic/mass spectrometric separation was performed on a reverse phase column using a solvent system of methanol alone or methanol + 2-propanol. This method seemed promising for application to both qualitative and quantitative micro-analysis of fatty acids including very long chain fatty acids.     

Structural analysis of a unique hybrid-type ganglioside with isoglobo-, neolacto-, and ganglio-core from the gills of the Pacific salmon (Oncorhynchus keta)

Monosialosyl gangliosides from the gills of the Pacific salmon, Oncorhynchus keta, have been prepared by solvent extraction and DEAE-Sephadex column chromatography. The unknown acidic glycolipids (M14 and M15) with slower mobility than GM1a on thin-layer chromatography were separated by Iatrobeads column chromatography and were characterized by compositional analysis, methylation analysis, chemical, and enzymatic degradation, negative-ion LSIMS, and (1)H nuclear magnetic resonance spectroscopy. Both M14 and M15 contained a same oligosaccharide core with isoglobo-, neolacto-, and ganglio-series as follows: [carbohydrate structure: see text]. The only difference between M14 and M15 was in fatty acid acylation. Analysis of the fatty acids indicated a predominance of C24:1 fatty acid in M14 and shorter chain saturated fatty acids, C14:0 and C16:0, in M15.     

Effect of column and software on gas chromatographic determination of fatty acids

Four capillary columns (A: CP-WAX 52 CB 25 m x 0.25 mm; B: CP WAX 52 CB 30 m x 0.25 mm; C: CP-WAX 58 CB 25 m x 0.25 mm, Chrompack; D: OMEGAWAX 320 30 m x 0.32 mm, Supelco) and two integration software (Mosaic v.5.10, Chrompack and CSW v.1.7, Data Apex5) were compared for analysis of fatty acids. Column A was mounted stepwise in two different instruments. Fatty acids of blood plasma phosphatidylcholine and standard mixture of saturated fatty acids were analysed as methyl esters under identical chromatographic conditions. Both integrating software did not differ significantly in most results; differences were observed only for minor components: 16:1n9 (0.10+/-0.020 vs. 0.17 +/- 0.005 M%, P < 0.0001, column Al; 0.09 +/- 0.011 vs. 0.16 +/- 0.007 M%, P< 0.0001, column A2; 0.09 +/- 0.010 vs. 0.17 +/- 0.003 M%, P < 0.0001, column C; 0.09 +/ -0.008 vs. 0.19 +/- 0.003 M%, P < 0.0001, column D), 20:0 (0.10+0.001 vs. 0.06 +/- 0.005 M%, P < 0.05, column C) and 20:2n6 (0.43 +/- 0.030 vs. 0.91 +/- 0.016 M%, P < 0.0001, column A2). Increased values for 16:1n9 and 20:2n6 integrated by MOSAIC are caused by cointegration of two poorly resolved peaks: fatty acid and impurity from sample matrix. Lower values for 20:0 are caused by incomplete integration of minor peak. Differences between columns were observed mostly for minor fatty acids. The results indicate that CSW is more suitable software for integration of complicated chromatograms. Linear calibration dependences measured with standard mixture of saturated fatty acids (carbon number 10-24) were observed in wide range of concentrations (three orders). Slope close to unity and minimal value of intercept confirmed theoretical relations when analyses are run under optimal conditions. Use of one column is advisable in small intervention or experimental metabolic studies.     

Metabolism of saturated 1-14C-labelled fatty acids in the silkworm Bombyx mori L

1. Only a small percentage of 1-(14)C-labelled saturated fatty acids injected in the silkworm is respired as carbon dioxide. 2. The rate of utilization of fatty acids is low both at the larval and pupal stages. 3. The insect has the ability to elongate C(12) and C(16) saturated fatty acids and to desaturate C(18) saturated fatty acids. 4. Much of the administered radioactivity is found in the triglyceride fraction, followed by the phospholipid and diglyceride fractions. 5. Diglycerides seem to be the transport form of fatty acids. 6. The insect seems to metabolize both natural and unnatural fatty acids in the same manner.     

Analysis of fatty acid composition of Candida species by gas-liquid chromatography using a polar column

The fatty acid composition of representative Candida species was examined by gas-liquid chromatography (GLC) using a polar column. The major fatty acids were C14:0, C16:0, C18:0 saturated, C16:1 and C18:1 monoenoic series, with or without C18 polyunsaturated acids (C18:2 and C18:3). In Torulopsis glabrata and Saccharomyces cerevisiae the C18:2 and C18:3 acids were not found, but the C10:0 and C12:0 acids were detected in S. cerevisiae. These results indicated that the Candida genus could be distinguished from Torulopsis and Saccharomyces genera by GLC analysis of fatty acids. Quantitative differences in the fatty acid composition between cells grown at high temperature (37 degrees C) and low temperature (25 degrees C) were found generally in Candida species, and the amounts of C18 polyunsaturated acids (C18:2 and C18:3) increased in the cells grown at 25 degrees C. Each Candida species showed a characteristic profile in fatty acid composition. Determination of the cellular fatty acid composition in Candida species is likely to be useful for the grouping or chemotaxonomy of newer isolates of Candida species.     

Activation of lecithin: cholesterol acyltransferase by human apolipoprotein A-IV

Human plasma apoproteins (apo) A-I and A-IV both activate the enzyme lecithin:cholesterol acyltransferase (EC 2.3.1.43). Lecithin:cholesterol acyltransferase activity was measured by the conversion of [4-14C] cholesterol to [4-14C]cholesteryl ester using artificial phospholipid/cholesterol/[4-14C]cholesterol/apoprotein substrates. The substrate was prepared by the addition of apoprotein to a sonicated aqueous dispersion of phospholipid/cholesterol/[4-14C]cholesterol. The activation of lecithin:cholesterol acyltransferase by apo-A-I and -A-IV differed, depending upon the nature of the hydrocarbon chains of the sn-L-alpha-phosphatidylcholine acyl donor. Apo-A-I was a more potent activator than apo-A-IV with egg yolk lecithin, L-alpha-dioleoylphosphatidylcholine, and L-alpha-phosphatidylcholine substituted with one saturated and one unsaturated fatty acid regardless of the substitution position. When L-alpha-phosphatidylcholine esterified with two saturated fatty acids was used as acyl donor, apo-A-IV was more active than apo-A-I in stimulating the lecithin:cholesterol acyltransferase reaction. Complexes of phosphatidylcholines substituted with two saturated fatty acids served as substrate for lecithin:cholesterol acyltransferase even in the absence of any activator protein. Essentially the same results were obtained when substrate complexes (phospholipid-cholesterol-[4-14C]cholesterol-apoprotein) were prepared by a detergent dialysis procedure. Apo-A-IV-L-alpha-dimyristoylphosphatidylcholine complexes thus prepared were shown to be homogeneous particles by column chromatography and density gradient ultracentrifugation. It is concluded that apo-A-IV is able to facilitate the lecithin:cholesterol acyltransferase reaction in vitro.     

Effects of fatty acid chain length and saturation on gastric inhibitory polypeptide release in obese hyperglycaemic (ob/ob) mice

Plasma gastric inhibitory polypeptide (GIP) responses to equimolar intragastrically administered emulsions of fatty acids (2.62 mmol/7.5 ml/kg) were examined in 18 h fasted obese hyperglycaemic (ob/ob) mice. Propionic acid (C3:0), a saturated short-chain fatty acid, and capric acid (C10:0), a saturated medium chain fatty acid, did not signilicantly stimulate GIP release. However, the saturated long-chain fatty acid stearic acid (C18:0), and especially the unsaturated long-chain fatty acids oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) acids produced a marked GIP response. The results show that chain length and to a lesser extent the degree of saturation are important determinants of fatty acid-stimulated GIP release. The GIP-release action of long-chain, but not short-chain, fatty acids may be r e l a t e d to differences in their intracellular handling.     

A convenient synthesis of phosphatidylcholines: acylation of sn-glycero-3-phosphocholine with fatty acid anhydride and 4-pyrrolidinopyridine.

A high-yield synthesis of saturated, unsaturated, and short chain phosphatidylcholines from sn-glycero-3-phosphocholine is described. The procedure offers advantages over other reported procedures for the synthesis of phosphatidylcholine in that the large-scale synthesis and purification can be achieved in a minimum time. The procedure utilizes 4-pyrrolidinopyridine as a catalyst and moderate amounts of fatty acid anhydride (2 mol eq. of fatty acid anhydride per mol of OH) in a 1:1 mixture of benzene-dimethylsulfoxide (DMSO) at 40 degrees--42 degrees C (oilbath) for 2--5 hr. At the end of the reaction, the phosphatidylcholine can be purified in the usual manner or by using a Waters Prep LC/500 with a radially compressed silica gel column eluted with chloroform-methanol-water 60:30:4. At a flow rate of 200 ml/min, the phospholipid elutes in 10--15 min, depending on the chain length and unsaturation.     

Diet preferences of warblers for specific fatty acids in relation to nutritional requirements and digestive capabilities

During energy-demanding periods of the annual cycle such as migration or during cold days in winter, birds store fat comprised mostly of 16- or 18-carbon unsaturated fatty acids. In such situations, birds may feed selectively on foods with specific fatty acids that enable efficient fat deposition. We offered wild-caught yellow-rumped warblers Dendroica coronata paired choices between semi-synthetic diets that differed only in their fatty acid composition. Warblers strongly preferred diets containing long-chain (18:1; carbon atoms:double bonds) unsaturated, unesterified fatty acids to diets containing long-chain saturated, unesterified fatty acids (18:0) and they preferred diets containing mono-unsaturated fats (18:1) to diets containing poly-unsaturated fats (18:2). The preference for diets containing long-chain unsaturated fatty acids to diets containing long-chain saturated fatty acids was consistent in birds tested one week after capture at 21°C, one month after capture when cold-acclimated (1°C), and six weeks after capture at 21°C. Birds acclimated to a diet with 50% of the fat comprised of unesterified stearic acid (18:0) lost mass and reduced their food intake when we reduced ambient temperature from 21°C to 11°C over three days. We conclude that especially in energy-demanding situations there are limits to the yellow-rumped warblers' ability to assimilate some long-chain saturated fatty acids and that this digestive constraint can explain in part why yellow-rumped warblers prefer diets containing long-chain unsaturated fatty acids to diets containing long-chain saturated fatty acids.     

Isolation and mass spectrometry characterization of molecular species of lactosylceramides using liquid chromatography-electrospray ion trap mass spectrometry

Reverse-phase liquid chromatography/electrospray ion trap mass spectrometry (LC-ESI-MSn) was established for identification of the molecular species of lactosylceramides. Lactosylceramides derived from porcine blood cells were separated on a CapcellPak C8 column using a mixture of methanol and 1 mM ammonium formate from the C16 to C26 fatty acyl chains based on the length of total carbon chains and the nature of sphingoid bases (w') and fatty acyl chains (Y0'-w') was identified by MS3 as their [M+H]+ ions. The same number of fatty acyl moieties appeared in the order of unsaturated, (2-)hydroxylated, and saturated components. The molecular species of lactosylceramides derived from porcine blood cells totaled more than 33 and included mainly C24:0-d18:1, Ch24:0-d18:1, Ch24:1-d18:1, C24:1-d18:1, and C22:0-d18:1 in addition to 28 minor species from C16:0 to C26:0 fatty acyl moieties. The molecular species of lactosylceramides in the membrane microdomain fraction of HL-60 cells (70% were differentiated into macrophage-lineage cells) were identified as C24:0-d18:1, C24:1-d18:1, C22:0-d18:1, C16:0-d18:1, and more than 21 other minor species. Our results suggest that reverse-phase LC-ESI-MSn is a useful and simple method for identification of lactosylceramide molecular species.     

Protein kinase C activation by cis-fatty acid in the absence of Ca2+ and phospholipids

Protein kinase C has been shown to be a phospholipid/Ca2+-dependent enzyme activated by diacylglycerol (Nishizuka, Y. (1984) Nature 308, 693-697; Nishizuka, Y. (1984) Science 225, 1365-1370). We have reported that unsaturated fatty acids (oleic acid and arachidonic acid) can activate protein kinase C independently of Ca2+ and phospholipid (Murakami, K., and Routtenberg, A. (1985) FEBS Lett. 192, 189-193). This study shows that other cis-fatty acids such as linoleic acid also fully activate protein kinase C in the same manner. None of the saturated fatty acids (C:4 to C:18) nor the detergents (sodium dodecyl sulfate and Triton X-100) tested here were as effective as oleic acid. Unlike oleic acid, these detergents strongly inhibited protein kinase C activity induced by Ca2+/phosphatidylserine (PS) and diacylglycerol. Lowering the critical micelle concentration of oleic acid by increasing ionic strength also strongly inhibited oleic acid activation of protein kinase C activity. Dioleoylphosphatidylserine activated protein kinase C effectively (Ka = 7.2 microM). On the other hand, dimyristoylphosphatidylserine, which contains saturated fatty acids at both acyl positions, failed to activate protein kinase C even in the presence of Ca2+. These observations suggest that: protein kinase C activation by free fatty acid is specific to the cis-form and is not due to their detergent-like action, cis-fatty acid activation is due to the direct interaction of protein kinase C with the monomeric form of cis-fatty acids and not with the micelles of fatty acids, and cis-fatty acids at acyl positions in PS are also important for Ca2+/PS activation of protein kinase C.     

Lipid profiles of Aspergillus niger and its unsaturated fatty acid auxotroph, UFA2

A comparative study of the mycelial lipid composition of a wild strain (V35) and one unsaturated fatty acid auxotroph (UFA2) of Aspergillus niger has been performed. The lipid composition of both strains are qualitatively the same but quantitatively different. All the strains contain the following phospholipids: cardiolipin, phosphatidylethanolamine, phosphatidylcholine, lysophosphatidylethanolamine, lysophosphatidylcholine, and phosphatidylserine; and triglycerides, diglycerides, monoglycerides, ergosterol, and sterol esters as the neutral lipids; mono- and di-galactosyl diglyceride as the major glycolipids along with small amounts of the corresponding mannose analogs. Phosphatidylethanolamine and phosphatidylcholine constitute the bulk of the phospholipids. The mutant (UFA2) contains a higher level of glycerides and lower levels of sterol (both free and esterified form), phospholipids, and glycolipids than the wild type. Aspergillus niger contains C16 to C18 saturated and unsaturated fatty acids. Small amounts of long-chain (C20 to C24) and short-chain (C10 to C14) saturated and unsaturated acids are also present. Linoleic, oleic, and palmitic are the major acids, stearic and linolenic acids being minor ones. UFA2 grows only in the presence of unsaturated fatty acid (C16 or C18) and accumulates a higher concentration of supplemented acid which influences its fatty acid profile.     

Inhibitors of fatty acid biosynthesis in sunflower seeds

During de novo fatty acid synthesis in sunflower seeds, saturated fatty acid production is influenced by the competition between the enzymes of the principal pathways and the saturated acyl-ACP thioesterases. Genetic backgrounds with more efficient saturated acyl-ACP thioesterase alleles only express their phenotypic effects when the alleles for the enzymes in the main pathway are less efficient. For this reason, we studied the incorporation of [2-(14)C]acetate into the lipids of developing sunflower seeds (Helianthus annuus L.) from several mutant lines in vivo. The labelling of different triacylglycerol fatty acids in different oilseed mutants reflects the fatty acid composition of the seed and supports the channelling theory of fatty acid biosynthesis. Incubation with methyl viologen diminished the conversion of stearoyl-ACP to oleoyl-ACP in vivo through a decrease in the available reductant power. In turn, this led to the accumulation of stearoyl-ACP to the levels detected in seeds from high stearic acid mutants. The concomitant reduction of oleoyl-ACP content inside the plastid allowed us to study the activity of acyl-ACP thioesterases on saturated fatty acids. In these mutants, we verified that the accumulation of saturated fatty acids requires efficient thioesterase activity on saturated-ACPs. By studying the effects of cerulenin on the in vivo incorporation of [2-(14)C]acetate into lipids and on the in vitro activity of beta-ketoacyl-ACP synthase II, we found that elongation to very long chain fatty acids can occur both inside and outside of the plastid in sunflower seeds.     

Molecular and Functional Analysis of Three Fatty Acyl-CoA Reductases with Distinct Substrate Specificities in Copepod Calanus finmarchicus

The marine copepod Calanus finmarchicus constitutes the substantial amount of biomass in the Arctic and Northern seas. It is unique in that this small crustacean accumulates a high level of wax esters as carbon storage which is mainly comprised of 20:1n−9 and 22:1n−11 alcohols (Alc) linked with various kinds of fatty acids, including n−3 polyunsaturated fatty acids. The absence of 20:1n−9 Alc and 22:1n−11 Alc in diatoms and dinoflagellates, the primary food sources of copepods, suggests the existence of de novo biosynthesis of fatty alcohols in C. finmarchinus. Here, we report identification of three genes, CfFAR1, CfFAR2, and CfFAR3, coding for fatty acyl-CoA reductases involved in the conversion of various fatty acyl-CoAs to their corresponding alcohols. Functional characterization of these genes in yeast indicated that CfFAR1 could use a wide range of saturated fatty acids from C18 to C26 as substrates, CfFAR2 had a narrow range of substrates with only very-long-chain saturated fatty acid 24:0 and 26:0, while CfFAR3 was active towards both saturated (16:0 and 18:0) and unsaturated (18:1 and 20:1) fatty acids producing corresponding alcohols. This finding suggested that these three fatty acyl-CoA reductases are likely responsible for de novo synthesis of a series of fatty alcohol moieties of wax esters in C. finmarchicus.     

Metabolism of saturated and polyunsaturated very-long-chain fatty acids in fibroblasts from patients with defects in peroxisomal beta-oxidation.

The metabolism of [1-14C]lignoceric acid (C24:0) and [1-14C]tetracosatetraenoic acid (C24:4, n-6) was studied in normal skin fibroblast cultures and in cultures from patients with defects in peroxisomal beta-oxidation (but normal peroxisomal numbers). Cells from X-linked adrenoleukodystrophy (ALD) patients with a presumed defect in a peroxisomal acyl-CoA synthetase, specific for fatty acids of carbon chain lengths greater than 22 (very-long-chain fatty acids; VLCFA), showed a relatively normal production of radiolabelled CO2 and water-soluble metabolites from [1-14C]C24:0. However, the products of synthesis from acetate de novo (released by beta-oxidation), i.e. C16 and C18 fatty acids, were decreased, and carbon chain elongation of the fatty acid was increased. In contrast, cell lines from two patients with an unidentified lesion in peroxisomal beta-oxidation (peroxisomal disease, PD) showed a marked deficiency in CO2 and water-soluble metabolite production, a decreased synthesis of C16 and C18 fatty acids and an increase in carbon chain elongation. The relatively normal beta-oxidation activity of ALD cells appears to be related to low uptake of substrate, as a defect in beta-oxidation is apparent when measurements are performed on cell suspensions under high uptake conditions. Oxidation of [1-14C]C24:4 was relatively normal in ALD cells and in the cells from one PD patient but abnormal in those from the other. Our data suggest that, despite the deficiency in VLCFA CoA synthetase, ALD cells retain a near normal ability to oxidize both saturated and polyunsaturated VLCFA under some culture conditions. However, acetate released by beta-oxidation of the saturated VLCFA and, to a much lesser degree, the polyunsaturated VLCFA, appears to be used preferentially for the production of CO2 and water-soluble products, and acetate availability for fatty acid synthesis in other subcellular compartments is markedly decreased. It is likely that the increased carbon chain elongation of the saturated VLCFA which is also observed reflects the increased availability of substrate (C24:0) and/or an increase in microsomal elongation activity in ALD cells.     

Biochemical effects of the hypoglycaemic compound pent-4-enoic acid and related non-hypoglycaemic fatty acids. Fatty acid oxidation

1. The effects of the hypoglycaemic compound, pent-4-enoic acid, and of four structurally related non-hypoglycaemic compounds (pentanoic acid, pent-2-enoic acid, cyclopropanecarboxylic acid and cyclobutanecarboxylic acid), on the oxidation of saturated fatty acids by rat liver mitochondria were determined. 2. The formation of (14)CO(2) from [1-(14)C]palmitate was strongly inhibited by 0.01mm-pent-4-enoic acid. 3. The inhibition of oxygen uptake was less than that of (14)CO(2) formation, presumably because fumarate was used as a sparker. 4. The oxidation of [1-(14)C]-butyrate, -octanoate or -laurate was not strongly inhibited by 0.01mm-pent-4-enoic acid. 5. The other four non-hypoglycaemic compounds did not inhibit the oxidation of any saturated fatty acid when tested at 0.01mm concentration, though they all inhibited strongly at 10mm. 6. The oxidation of [1-(14)C]-myristate and -stearate, but not of [1-(14)C]decanoate, was strongly inhibited by 0.01mm-pent-4-enoic acid. 7. The oxidation of [1-(14)C]palmitate was about 50% carnitine-dependent under the experimental conditions used. 8. The percentage inhibition of [1-(14)C]palmitate oxidation by pent-4-enoic acid was the same whether carnitine was present or not. 9. Acetoacetate formation from saturated fatty acids was inhibited by 0.1mm-cyclopropanecarboxylic acid to a greater extent than their oxidation. 10. The other compounds tested inhibited acetoacetate formation from saturated fatty acids proportionately to the inhibition of oxidation. 11. Possible mechanisms for the inhibition of long-chain fatty acid oxidation by pent-4-enoic acid are discussed. 12. There was a correlation between the ability to inhibit long-chain fatty acid oxidation and hypoglycaemic activity in this series of compounds.     

Rapid quantitation of free fatty acids in human plasma by high-performance liquid chromatography

We report a rapid and sensitive method for separation and quantitation of free fatty acids (FFAs) in human plasma using high-performance liquid chromatography (HPLC). Two established techniques of lipid extraction were investigated and modified to achieve maximal FFA recovery in a reasonably short time period. A modified Dole extraction method exhibited greater recovery (90%) and short processing times (30 min) compared to the method of Miles et al. Reversed-phase HPLC using UV detection was used for plasma FFA separation and quantitation. Two phenacyl ester derivatives, phenacyl bromide and p-bromophenacyl bromide, were investigated in order to achieve optimal separation of individual plasma FFAs (saturated and unsaturated) with desirable detection limits. Different chromatographic parameters including column temperature, column type and elution profiles (isocratic and gradient) were tested to achieve optimal separation and recovery of fatty acids. Phenacyl bromide esters of plasma fatty acids were best resolved using an octadecylsilyl column with endcapped silanol groups. An isocratic elution method using acetonitrile–water (83:17) at 2 ml/min with UV detection at 242 nm and a column temperature of 45°C was found to optimally resolve the six major free fatty acids present in human plasma (myristic [14:0], palmitic [16:0], palmitoleic [16:1], stearic [18:0], oleic [18:1] and linoleic [18:2]), with a run time of less than 35 min and detection limits in the nmol range. The entire process including plasma extraction, pre-column derivatization, and HPLC quantitation can be completed in 90 min with plasma samples as small as 50 μl. Over a wide physiological range, plasma FFA concentrations determined using our HPLC method agree closely with measurements using established TLC–GC methods (r²≥0.95). In addition, by measuring [¹⁴C] or [³H] radioactivity in eluent fractions following HPLC separation of plasma FFA, this method can also quantitate rates of FFA turnover in vivo in human metabolic studies employing isotopic tracers of one or more fatty acids.     

Significant year-to-year variation of the response to radiation-induced stress shown by gill fatty acid metabolism in eels (Anguilla anguilla) captured from the wild.

1. In eels captured in Roskilde Fjord in 1972 and 1975, a specifically enhanced synthesis was found from 14C-acetate of 14C-labelled mono-unsaturated fatty acids (C16:1 and C18:1) relative to saturated fatty acids (C16:0 and C18:0) in sea water 4 days after irradiation (10 Gy, 60Co). 2. Corresponding experiments in 1976 and 1982 showed rather the opposite: irradiation resulted in more 14C-labelled saturated fatty acids relative to unsaturated fatty acids, both in fresh and sea water. 3. The latter effect was less marked than that in 1972 and 1975, but still statistically clearly significant.