Fatty acids of some cornaceae,hydrangeaceae, aquifoliaceae,hamamelidaceae and styracaceae

Seed, kernel or fruit oils of the Cornaceae (nine species). Hydrangea, Hamamelis, Ilex (Aquifoliaceae) and the Styracaceae (two species) were analysed for fatty acid composition. Special attention was paid to the occurrence of petroselinic acid (18: 1Δ6c). In the species investigated. C₁₈ acids were always present in greater quantities than C₁₆ fatty acids; C₂₀ and C₂₂ acids were only minor components. The Cornaceae show differing fatty acid patterns which correlate well with anatomical, morphological and other chemical data. In Cornus, Curtisia, Mastixia and Corokia linoleic acid predominates, whereas linoleic and linolenic acid form the major components in Davidia and Nyssa. 18 : 1Δ6c, an aralioid type, occurs in large amounts in Aucuba and Griselinia. Hamamelis, Hydrangea and Ilex show a common fatty acid pattern with linoleic acid as the dominant component in all cases. Classification currently based on morphological and anatomical differences between the two species of Styracaceae which were investigated here should include their different fatty acid compositions: in Halesia linoleic acid predominates over oleic acid, whereas in Styrax equal amounts of these two acids are found.     

Biosynthesis of gibberellins A12, A15, A24, A36, and A37 by a cell-free system from Cucurbita maxima

GA₁₂-aldehyde obtained from mevalonate via ent-kaurene, ent-kaurenol, ent-kaurenoic acid and ent-7α-hydroxykaurenoic acid in a cell-free system from immature seeds of Cucurbita maxima was converted to GA₁₂ by the same system. When Mn²⁺ was omitted from the system GA₁₂-aldehyde and GA₁₂ were converted further to several products. Among these GA₁₅, GA₂₄, GA₃₆ and GA₃₇ were conclusively identified by GC-MS. With the exception of GA₃₇ these GAs have not previously been found in higher plants. Another biosynthetic pathway led from ent-7α-hydroxykaurenoic acid to very polar products via what was tentatively identified as ent-6α, 7α-dihydroxykaurenoic acid. An unidentified component with an MS resembling that of a dihydroxykaurenolide was also obtained from incubations with mevalonate.     

Determination of structure and composition of suberin from the roots of carrot, parsnip, rutabaga, turnip, red beet, and sweet potato by combined gas-liquid chromatography and mass spectrometry

Suberin from the roots of carrots (Daucus carota), parsnip (Pastinaca sativa), rutabaga (Brassica napobrassica), turnip (Brassica rapa), red beet (Beta vulgaris), and sweet potato (Ipomoea batatas) was isolated by a combination of chemical and enzymatic techniques. Finely powdered suberin was depolymerized with 14% BF₃ in methanol, and soluble monomers (20-50% of suberin) were fractionated into phenolic (<10%) and aliphatic (13-35%) fractions. The aliphatic fractions consisted mainly of ω-hydroxyacids (29-43%), dicarboxylic acids (16-27%), fatty acids (4-18%), and fatty alcohols (3-6%). Each fraction was subjected to combined gas-liquid chromatography and mass spectrometry. Among the fatty acids very long chain acids (>C₂₀) were the dominant components in all six plants. In the alcohol fraction C₁₈, C₂₀, C₂₂, and C₂₄ saturated primary alcohols were the major components. C₁₆ and C₁₈ dicarboxylic acids were the major dicarboxylic acids of the suberin of all six plants and in all cases octadec-9-ene-1, 18-dioic acid was the major component except in rutabaga where hexadecane-1, 16-dioic acid was the major dicarboxylic acid. The composition of the ω-hydroxyacid fraction was quite similar to that of the dicarboxylic acids; 18-hydroxy-octadec-9-enoic acid was the major component in all plants except rutabaga, where equal quantities of 16-hydroxyhexadecanoic acid and 18-hydroxyoctadec-9-enoic acid (42% each) were found. Compounds which would be derived from 18-hydroxyoctadec-9-enoic acid and octadec-9-ene-1, 18-dioic acid by epoxidation, and epoxidation followed by hydration of the epoxide, were also detected in most of the suberin samples. The monomer composition of the six plants showed general similarities but quite clear taxonomic differences.     

Invertases in Oat Seedlings: SEPARATION, PROPERTIES, AND CHANGES IN ACTIVITIES IN SEEDLING SEGMENTS

The soluble invertase activity in etiolated Avena seedlings was highest at the apex of the coleoptile and much lower in the primary leaf, mesocotyl, and root. The activity in all parts of the seedling consisted of two invertases (I and II) which were separated by chromatography on diethylaminoethylcellulose. Both enzymes appeared to be acid invertases, but they differed in molecular size, pH optimum, and the kinetic parameters K_m and V_max of their action on sucrose, raffinose, and stachyose. Invertase II had low stability at pH 3.5 and below, and exhibited high sensitivity to Hg²⁺, with complete inhibition by 2 micromolar HgCl₂. Segments of coleoptiles incubated in water lost about two-thirds of the total invertase activity after 16 hours. The loss of activity was due primarily to a decrease in the level of invertase II. The loss of invertase was decreased by indoleacetic acid, 2,4-dichlorophenoxyacetic acid, and α-naphthaleneacetic acid but not by β-naphthaleneacetic acid and p-chlorophenoxyisobutyric acid. Conditions that inhibited auxin-induced growth of the segments (20 millimolar CaCl₂ and 200 millimolar mannitol) also blocked the auxin effect on invertase loss.     

Endogenous Gibberellins from Sporophytes of Two Tree Ferns, Cibotium glaucum and Dicksonia antarctica

Gibberellin A₁ (GA₁), 3-epi-GA₁, GA₄, GA₉, 11α-hydroxyGA₁₂, 12α-hydroxyGA₁₂, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₅, GA₃₇, GA₄₀, GA₅₈, GA₆₉, GA₇₀, and GA₇₁ have been identified from Kovats retention indices and full scan mass spectra by capillary GC-MS analyses of purified extracts from sporophytes of the tree fern, Cibotium glaucum. Abscisic acid, dihydrophaseic acid, an epimer of 4′-dihydrophaseic acid, and the epimeric ent-6α, 7α, 16α, 17-(OH)₄ and ent-6α, 7α, 16β, 17-(OH)₄ derivatives of ent16, 17-dihydrokaurenoic acid, in addition to the epimeric 16α, 17- and 16β, 17-dihydroxy-16, 17-dihydro derivatives of GA₁₂, were also identified in extracts of C. glaucum. An oxodihydrophaseic acid and a hydroxydihydrophaseic acid were also detected. In extracts of sporophytes of Dicksonia antarctica, GA₄, GA₉, 12α- and 12β-hydroxyGA₁₂, GA₁₅, GA₂₅, and GA₃₇ were identified by the same criteria, as well as abscisic acid, phaseic acid, 8′-hydroxymethylabscisic acid and dihydrophaseic acid. This is the first time that GA₄₀ has been identified in a higher plant; it is also the first report of the natural occurrence of the two gibberellins, 11α- and 12β-hydroxyGA₁₂. The total gibberellin (GA) content in C. glaucum (tall) was at least one order of magnitude greater than that of D. antarctica (dwarf) based on total ion current response in GC-MS and bioassay data. Abscisic acid was a major component of D. antarctica and the oxodihydrophaseic acid was a major component of C. glaucum.     

Dexamethasone,a Specific PLA2 Inhibitor,Allows Nonpathogenic Pseudomonas fluorescens to Induce Virulence Against Spodoptera exigua

Phospholipase A₂ (PLA₂) catalyzes phospholipids at sn-2 position to release arachidonic acid (20:4n-6). The arachidonic acid is further oxidized to form different eicosanoids, which play biological mediators to express cellular or humoral immune reactions in response to pathogen infection. Xeno-rahbdus and Photorhabdus, the symbiotic bacteria of entomopathogenic nematodes, have been known to inhibit PLA₂ to express their pathogenicity. This research aimed to test a hypothesis that other entomopathogenic bacteria also inhibit PLA₂ to express their pathogenicity in Spodopera exigua. Two bacterial species of Enterococcus faecalis and Pseudomonas fluorescens presumably different in ento-mopathogenicity were analyzed in their PLA₂ inhibitory activities. A pathogenic E. faecalis induced significantly immunodepression of S. exigua by inhibiting PLA₂ activity because the bacteria-infected S. exigua recovered immune reactions after the addition of arachidonic acid. However, the nonpathogenic P. fluorescens did not induce immunodepression because the addition of arachidonic acid to P. fluorescens-infected S. exigua did not further increase immune capacities while dexamethasone, a PLA₂ inhibitor, could decrease the immune activities. Injection of E. faecalis along with 10 μg of dexamethasone significantly increased pathogenicity in comparison with the bacteria alone. Moreover, the addition of dexamethasone transformed nonpathogenic P. fluorescens into pathogenic bacterium. This study suggests an evidence that PLA₂ is an inhibitory target even for entomopathogenic bacteria not related with entomopathogenic nematodes, and that the inhibition of PLA₂ determines the bacterial virulence in S. exigua.     

Effects of ginkgoneolic acid on the growth, acidogenicity, adherence, and biofilm of Streptococcus mutans in vitro

Ginkgo biloba has long been used in traditional Chinese medicine. In this study, ginkgoneolic acid, a kind of compound extracted from G. biloba, was investigated for its effects on growth, acid production, adherence, biofilm formation, and biofilm morphology of Streptococcus mutans. The results showed that ginkgoneolic acid inhibited not only the growth of S. mutans planktonic cells at minimum inhibitory concentration (MIC) of 4 μg/mL and minimum bactericidal concentration (MBC) of 8 μg/mL but also the acid production and adherence to saliva-coated hydroxyapatite of S. mutans at sub-MIC concentration. In addition, this agent was effective in inhibiting the biofilm formation of S. mutans (MBIC₅₀?=?4 μg/mL), and it reduced 1-day-developed biofilm of S. mutans by 50 % or more at low concentration (MBRC₅₀?=?32 μg/mL). Furthermore, the present study demonstrated that ginkgoneolic acid disrupted biofilm integrity effectively. These findings suggest that ginkgoneolic acid is a natural anticariogenic agent in that it exhibits antimicrobial activity against S. mutans and suppresses the specific virulence factors associated with its cariogenicity.     

Aliphatic Hydrocarbons of Cladosporium resinae Cultured on Glucose,Glutamic Acid,and Hydrocarbons

The carbon source markedly influenced the qualitative and quantitative composition of cellular hydrocarbons in Cladosporium resinae. Total lipid and hydrocarbon content was greater in cells grown on n-alkanes than in cells grown on glucose or glutamic acid. Glucose-grown cells contained a spectrum of aliphatic hydrocarbons from C₇ to C₃₆; pristane and n-hexadecane comprised 98% of the total. Cells grown on glutamic acid contained C₇ to C₂₃ hydrocarbons; n-tridecane, n-tetradecane, n-hexadecane, and pristane made up 74% of the total. n-Decane-grown cells yielded C₈ to C₃₂ compounds, and n-hexadecane (96%) was the major hydrocarbon. Cells grown on individual n-alkanes from C₁₁ to C₁₅ all contained C₁₁ to C₂₈ hydrocarbons, and cells grown on n-hexadecane contained C₁₁ to C₃₂ hydrocarbons. In n-undecane-grown cells, n-hexadecane and pristane made up 92% of the total, but in cells grown on C₁₂ to C₁₆ n-alkanes the major cellular hydrocarbon was the one on which the cells were grown. This suggests that cells cultured on n-alkanes of C₁₂ or longer accumulate n-alkanes prior to oxidizing them.     

Action of tenuazonic acid,a natural phytotoxin,on photosystem II of spinach

Tenuazonic acid (TeA) is a putative phytotoxin obtained from Alternaria alternata, the organism that can cause brown leaf spot disease of Crofton weed (Eupatorium adenophorum). It is demonstrated here that the tenuazonic acid inhibits the activity of photosystem II (PSII); the I₅₀-value is 48 μg mL^?1. Evidences from chlorophyll fluorescence show that tenuazonic acid interrupts electron transport between Q_A and Q_B on the acceptor side of PSII. It does not have an effect on the antenna pigments, the oxygen-evolving complex (OEC) at the donor side of PSII. On the basis of the fluorescence induction kinetics and competition experiments with [¹⁴C]atrazine, it is shown that tenuazonic acid does not share the same binding environment with atrazine despite their common action target: the Q_B-site. It is concluded that tenuazonic acid is a member of a novel class of PSII inhibitors.     

Metabolism of Proline, Glutamate, and Ornithine in Proline Mutant Root Tips of Zea mays (L.)

In excised pro_1-1 mutant and corresponding normal type roots of Zea mays L. the uptake and interconversion of [¹⁴C]proline, [¹⁴C]glutamic acid, [¹⁴C]glutamine, and [¹⁴C]ornithine and their utilization for protein synthesis was measured with the intention of finding an explanation for the proline requirement of the mutant. Uptake of these four amino acids, with the exception of proline, was the same in mutant and normal roots, but utilization differed. Higher than normal utilization rates for proline and glutamic acid were noted in mutant roots leading to increased CO₂ production, free amino acid interconversion, and protein synthesis. Proline was synthesized from either glutamic acid (or glutamine) or ornithine in both mutant and normal roots; it did not accumulate but rather was used for protein synthesis. Ornithine was not a good precursor for proline in either system, but was preferentially converted to arginine and glutamine, particularly in mutant roots. The pro_1-1 mutant was thus not deficient in its ability to make proline. Based on these findings, and on the fact that ornithine, arginine, glutamic acid and aspartic acid are elevated as free amino acids in mutant roots, it is suggested that in the pro_1-1 mutant proline catabolism prevails over proline synthesis.     

Cultivation of a new microalga,Micractinium reisseri,in municipal wastewater for nutrient removal,biomass, lipid,and fatty acid production

Coupling of advanced wastewater treatment with microalgae cultivation for low-cost lipid production was demonstrated in this study. The microalgal species Micractinium reisseri and Scenedesmus obliquus were isolated from municipal wastewater mixed with agricultural drainage. M. reisseri was selected based on the growth rate and cultivated in municipal wastewater (influent, secondary and tertiary effluents) which varied in nutrient concentration. M. reisseri showed an optimal specific growth rate (μ_opt) of 1.15, 1.04, and 1.01 1/day for the influent and the secondary and tertiary effluents, respectively. Secondary effluent supported the highest phosphorus removal (94%) and saturated fatty acid content (40%). The highest lipid content (40%), unsaturated fatty acid content, including monounsaturated and polyunsaturated fatty acids (66%), and nitrogen removal (80%) were observed for tertiary effluent. Fatty acids accumulating in the microalgal biomass (M. reisseri) were mainly composed of palmitic acid, oleic acid, linoleic acid, and a-linolenic acid. Cultivation of M. reisseri using municipal wastewater served a dual function of nutrient removal and biofuel feedstock generation.     

Diterpene acids from Helianthus species and their microbiological conversion by Gibberella fujikuroi, mutant B1-41a

The diterpene acid content in 10 species of Helianthus has been investigated. Ent-12,16-cyclokauranoic acid, isolated from H. annuus, is converted into a series of 12,16-cyclogibberellins by cultures of Gibberella fujikuroi, mutant B1-41a, and 12,16-cyclogibberellins A₉, and A₁₂ have been isolated. Ent-12β-acetoxykaurenoic acid and ent-13(S)-angeloxyatisenoic acid have been isolated from H. decapetalus; the metabolism of ent-13(S)-hydroxyatisenoic acid and atisenoic acid by B1-41a is also described.     

Synthesis, characterizations, and crystal structures of triorganotin(IV) derivatives with areneseleninic acids

Six new triorganotin(IV) complexes, [R₃Sn(O₂SeC₆H₄Cl)]_n (R = Me 1; Ph 2), [R₃Sn(O₂SeC₆H₄Me)]_n (R = Me 3; Ph 4), [R₃Sn(O₂SeC₆H₄Bu)]_n (R = Me 5; Ph 6) have been synthesized by the reaction of 4-chlorobenzeneseleninic acid, p-Tolueneseleninic acid, and 4-tert-butylbenzeneseleninic acid with triorganotin(IV) chloride in the presence of sodium ethoxide. All of the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy, and X-ray crystallography. Crystal structures show that all of the complexes exhibit 1D infinite chain structures which are generated by the bidentate oxygen atoms and the five-coordinated tin centers.     

The structure of rooster-comb dermatan sulfate. Fragmentation of the polysaccharide chains by chondroitinase AC-II digestion,and by periodate oxidation,followed by alkali cleavage

The polysaccharide-chain fragments of rooster-comb dermatan sulfates (RC-20 and RC-30) were obtained by chondroitinase AC-II digestion and by periodate oxidation, followed by alkaline cleavage, and their structures analyzed both quantitatively and qualitatively. RC-20 having a lower d-glucuronic acid content (22.6%) is composed preponderantly of large clusters of N-acetyldermosine sulfate (M_r～17 600–41 000) at the nonreducing terminal, whereas RC-30, having a higher d-glucuronic acid content, (41.4%) is poor in this cluster. Both RC-20 and RC-30 have an N-acetyldermosine sulfate cluster (M_r 6500–7300) within the polysaccharide chains. Most N-acetylchondrosine sulfate units of RC-20 and RC-30 exist as clusters, the large clusters (M_r～17 600) being preponderant in RC-30; both RC-20 and RC-30 contain a large proportion of N-acetylchondrosine sulfate clusters (M_r 3500 and 9000) that corresponds to the uronic acid content. In RC-30, most N-acetyldermosine disulfate units (13.4%) are linked to N-acetylchondrosine sulfate units or clusters.     

Regulatory sulfhydryl groups, conformational change, and allosteric inhibition in rabbit muscle fructose diphosphatase

The 16 sulfhydryl groups of native, homogeneous rabbit muscle fructose diphosphatase can all react with 5,5′-dithiobis-(2-nitrobenzoic acid). High concentrations of substrate (1–2 mm) decrease the reaction rate of the sulfhydryl groups, while concentrations up to 70 μm have no effect. After titration of the four most rapidly reacting sulfhydryl groups there is a marked desensitization toward the allosteric inhibitor AMP. In the presence of 30 μm AMP only 4–5 sulfhydryl groups/tetramer react with 5,5′-dithiobis-(2-nitrobenzoic acid), and the enzyme again becomes desensitized toward AMP inhibition. Together with a 3.5-fold increase in the I₅₀ for AMP inhibition, the K_m for Mg²⁺ or Mn²⁺ ions is also increased. In the presence of 7 mm MgCl₂ or 0.28 mm MnCl₂ only 6–8 sulfhydryl groups are modified. The rapid reaction of 4 sulfhydryl groups again results in desensitization. There is neither a protection by the substrate against inactivation, nor a protection by the allosteric inhibitor against desensitization. It is concluded that AMP and the divalent cations induce conformational changes in the protein molecule making 11–12 or 8–10 sulfhydryl groups inert for 5,5′-dithiobis-(2-nitrobenzoic acid), respectively. The K_m for fructose-1,6-diphosphate is not changed after the modification of 4–5 sulfhydryl groups.     

Fatty acids in the genus Bacillus. II. Similarity in the fatty acid compositions of Bacillus thuringiensis, Bacillus anthracis, and Bacillus cereus

The nature and relative abundance of fatty acids produced by two strains each of Bacillus thuringiensis and of B. anthracis were studied by gas-liquid chromatography on a 12,000 theoretical plate polyester column capable of partially resolving iso- and anteiso-fatty acids with the same number of carbon atoms. Unsaturated fatty acids as the bromo derivatives were separated from the saturated acids and resolved in a short SE-30 column by use of programmed-temperature gas chromatography. All four strains produced 16 major fatty acids: 9 branched (i-C₁₂, i-C₁₃, i-C₁₄, i-C₁₅, i-C₁₆, i-C₁₇, a-C₁₃, a-C₁₅, and a-C₁₇), 3 normal (n-C₁₄, n-C₁₅, and n-C₁₆), and 4 monounsaturated (i-C₁₆¹⁼, i-C₁₇¹⁼, a-C₁₇¹⁼, and n-C₁₆¹⁼), in addition to some minor fatty acids. In all cases, 12 branched acids, including saturated and monounsaturated, made up over 70% of the total fatty acids, and iso-C₁₅ acid was most abundant. These fatty acid distribution patterns were very similar to those of B. cereus and B. cereus var. mycoides. There were, however, minor but clear differences between the fatty acid distribution patterns of B. thuringiensis and B. anthracis. B. thuringiensis, like B. cereus, produced higher proportions of i-C₁₃, a-C₁₃, and i-C₁₄ fatty acids than did B. anthracis. This difference between these two species could be useful as a supplemental criterion in their differentiation. Indications are that the enzyme systems for monounsaturated fatty acid synthesis in B. thuringiensis and B. anthracis prefer normal fatty acids as substrates rather than branched-chain fatty acids.     

The Regulation of Nitrate Reductase,Nitrite Reductase,and Glutamate Dehydrogenase in Excised Pea Roots by Some Exogenous Amino Acids

The effect of growth retarding amino acids (L-aspartic acid,L-leucine,L-methionine, andL-threonine) on nitrate reductase (NO₃R), nitrite reductase (NO₂R), and NADH₂ dependent glutamate dehydrogenase (GDH) in excised pea roots was followed,L-methionine andL-threonine slightly depressed NO₃R activity,L-aspartic acid enhanced NO₂R and GDH activities.L-methionine andL-threonine also slightly decreased nitrate uptake. The results obtained are discussed in connection with the growth effects of the amino acids investigated.     

Screening survey of co-production of fusaric acid,fusarin C,and fumonisins B1, B2 and B3 by Fusarium strains grown in maize grains

Fusarium species isolated from Belgian maize were screened for their ability to produce fusarin C, fusaric acid, fumonisins B₁ (FB₁), FB₂ and FB₃ in maize grains. First, cultivation of Fusarium species in Myro liquid medium allowed overcoming the shortage of the standard of fusarin C on the market. All Fusarium verticillioides produced much higher contents of mycotoxins in Myro compared to Fusarium graminearum or Fusarium venenatum. The optimization of the LC-MS/MS method resulted in low limits of detection and quantification for fusarin C, fusaric acid, FB₁, FB₂ and FB₃ determination in maize grains. Its application for screening the potential toxin production ability evidenced that the concentrations of the analytes were significantly increased at various levels when F. verticillioides strains were cultivated in maize grains and reached 441 mg kg^?1 for fusaric acid, 74 mg kg^?1 for fusarin C, 1,301 mg kg^?1 for FB₁, 367 mg kg^?1 for FB₂ and 753 mg kg^?1 for FB₃.     

Inhibition of the Fermentation of Propionate to Methane by Hydrogen, Acetate, and Propionate

Inhibition of the fermentation of propionate to methane and carbon dioxide by hydrogen, acetate, and propionate was analyzed with a mesophilic propionate-acclimatized sludge that consisted of numerous flocs (size, 150 to 300 μm). The acclimatized sludge could convert propionate to methane and carbon dioxide stoichiometrically without accumulating hydrogen and acetate in a propionate-minimal medium. Inhibition of propionate utilization by propionate could be analyzed by a second-order substrate inhibition model (shown below) given that the substrate saturation constant, K_s, was 15.9 μM; the substrate inhibition constant, K_i, was 0.79 mM; and the maximum specific rate of propionate utilization, q_m, was 2.15 mmol/g of mixed-liquor volatile suspended solids (MLVSS) per day: q_s = q_mS/[K_s + S + (S²/K_i)], where q_s is the specific rate of propionate utilization and S is the initial concentration of undissociated propionic acid. For inhibition by hydrogen and acetate to propionate utilization, a noncompetitive product inhibition model was used: q_s = q_m/[1 + (P/K_p)ⁿ], where P is the initial concentration of hydrogen or undissociated acetic acid and K_p is the inhibition constant. Kinetic analysis gave, for hydrogen inhibition, K_p(H2) = 0.11 atm (= 11.1 kPa, 71.5 μM), q_m = 2.40 mmol/g of MLVSS per day, and n = 1.51 and, for acetate inhibition, K_p(HAc) = 48.6 μM, q_m = 1.85 mmol/g of MLVSS per day, and n = 0.96. It could be concluded that the increase in undissociated propionic acid concentration was a key factor in inhibition of propionate utilization and that hydrogen and acetate cooperatively inhibited propionate degradation, suggesting that hydrogenotrophic and acetoclastic methanogens might play an important role in enhancing propionate degradation to methane and carbon dioxide.     

Human umbilical blood vessel converts all cis-5, 8, 11, 14, 17 eicosapentaenoic acid to prostaglandin I3

All cis-5, 8, 11, 14, 17 eicosapentaenoic acid (EPA) is presented being evaluated for dietary prophylactic use in thrombo-embolic disorders. EPA inhibits the production of TXA₂ and platelet aggregation. We here present results demonstrating that human umbilical arteries convert ¹⁴C- EPA to a substance that in aqueous solutions decomposes to 14C-δ¹⁷-6-keto-PGF_1α. The conversion rate in rat aortic tissue was found substantially lower. These results in combination with earlier data indicating that EPA does not influence the conversion of arachidonic acid (AA) into PGI₂ in human vascular tissue, encourage further research along the lines initiated by the findings of high EPA/AA ratio and low incidence of myocardial infarction in Greenland Eskimos.