Fatty acids of pulmonary surfactant phosphatidylcholine from fetal rabbit lung tissue in culture. Biosynthesis of n-10 monoenoic fatty acids

We have previously reported that fetal rabbit lung tissue in organ culture produces a lamellar body material (pulmonary surfactant) with a lower percentage of disaturated phosphatidylcholine than is typically found in rabbit lung in vivo (Longmuir, K.J., C. Resele-Tiden, and L. Sykes. 1985. Biochim. Biophys. Acta. 833: 135-143). This investigation was conducted to identify all fatty acids present in the lamellar body phosphatidylcholine, and to determine whether the low level of disaturated phosphatidylcholine is due to excessive unsaturated fatty acid at position sn-1, sn-2, or both. Fetal rabbit lung tissue, 23 days gestation, was maintained in culture for 7 days in defined (serum-free) medium. Phospholipids were labeled in culture with [1-14C]acetate or [U-14C]glycerol (to follow de novo fatty acid biosynthesis), or with [1-14C]palmitic acid (to follow incorporation of exogenously supplied fatty acid). Radiolabeled fatty acid methyl esters obtained from lamellar body phosphatidylcholine were first separated by reverse-phase thin-layer chromatography (TLC) into two fractions of 1) 14:0 + 16:1 and 2) 16:0 + 18:1. Complete separation of the individual saturated and monoenoic fatty acids was achieved by silver nitrate TLC of the two fractions. Monoenoic fatty acid double bond position was determined by permanganate-periodate oxidation followed by HPLC of the carboxylic acid phenacyl esters. Lamellar body phosphatidylcholine contained four monoenoic fatty acids: 1) palmitoleic acid, 16:1 cis-9; 2) oleic acid, 18:1 cis-9; 3) cis-vaccenic acid, 18:1 cis-11; and 4) 6-hexadecenoic acid, 16:1 cis-6. In addition, 8-octadecenoic acid, 18:1 cis-8, was found in the fatty acids of the tissue homogenate. The abnormally low disaturated phosphatidylcholine content in lamellar body material was the result of abnormally high levels of monoenoic fatty acid (principally 16:1 cis-9) found at position sn-2. Position sn-1 contained normal levels of saturated fatty acid. The biosynthesis of the unusual n-10 fatty acids was observed from the start of culture throughout the entire 7-day culture period, and was observed in incubations of tissue slices of day 23 fetal rabbit lung. This is the first report of the biosynthesis of n-10 fatty acids (16:1 cis-6 and 18:1 cis-8) in a mammalian tissue other than skin, where these fatty acids are found in the secretory product (sebum) of sebaceous glands.     

Significance and taxonomic value of iso and anteiso monoenoic fatty acids and branded beta-hydroxy acids in Desulfovibrio desulfuricans.

The fatty acids obtained from extractable lipids of the anaerobic sulfate bacterium Desulfovibrio desulfuricans were identified. Saturated and monoenoic iso (C15-C19) and anteiso (C15, C17) fatty acids and saturated normal (C14-C18) and monoenoic normal (C16, C18) fatty acids were shown to be shown to be present by capillary gas chromatography-mass spectrometry. Iso and anteiso beta-hydroxy fatty acids were analyzed as trimethylsilyl ethers in the same way. The position of methyl branches in the monoenoic fatty acids was determined from characteristic fragment ions in the mass spectra of their methyl esters. Disilyloxy methyl esters, prepared by derivatization of the mono unsaturated methyl esters and analyzed by capillary gas chromatography-mass spectrometry, provided the position of double bonds. The monoenoic fatty acids identified in this way were normal (delta7-C16:1, delta9-C16:1, delta9-C18:1, delta11-C18:1), iso (delta7-C15:1, delta9-C16:1, delta9-C17:1, delta11-C18:1, delta11-C19:1), and anteiso (delta7-C15:1, delta9-C17:1). Iso delta9-C17:1 fatty acid is present as the major component. The occurrence of these monoenoic fatty acids in this bacterium is of taxonomical importance.     

Free acetate production by rat hepatocytes during peroxisomal fatty acid and dicarboxylic acid oxidation

The fate of the acetyl-CoA units released during peroxisomal fatty acid oxidation was studied in isolated hepatocytes from normal and peroxisome-proliferated rats. Ketogenesis and hydrogen peroxide generation were employed as indicators of mitochondrial and peroxisomal fatty acid oxidation, respectively. Butyric and hexanoic acids were employed as mitochondrial substrates, 1, omega-dicarboxylic acids as predominantly peroxisomal substrates, and lauric acid as a substrate for both mitochondria and peroxisomes. Ketogenesis from dicarboxylic acids was either absent or very low in normal and peroxisome-proliferated hepatocytes, but free acetate release was detected at rates that could account for all the acetyl-CoA produced in peroxisomes by dicarboxylic and also by monocarboxylic acids. Mitochondrial fatty acid oxidation also led to free acetate generation but at low rates relative to ketogenesis. The origin of the acetate released was confirmed employing [1-14C]dodecanedioic acid. Thus, the activity of peroxisomes might contribute significantly to the free acetate generation known to occur during fatty acid oxidation in rats and possibly also in humans.     

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

Analysis of fatty acid composition of anaerobic rumen fungi

The fatty acid (FA) composition of fresh mycelia of anaerobic rumen fungi was determined. The fatty acids methyl esters (FAME) of six strains belonging to four genera (Neocallimastix, Caecomyces, Orpinomyces, Anaeromyces) and one unknown strain were analyzed by gas chromatography. All studied fungi possess the same FAs but differences were found in their relative concentrations. The FA profile of anaerobic fungi comprises carbon chains of length ranging from 12 to 24; the most common fatty acids were stearic (C(18:0)), arachidic (C(20:0)), heneicosanoic (C(21:0)), behenic (C(22:0)), tricosanoic (C(23:0)) and lignoceric (C(24:0)) with relative amount representing >4% of total FA. Significant differences were determined for heptadecanoic, oleic, behenic and tricosanoic acids. Rumen anaerobic fungi can contain very long chain fatty acids; we found unsaturated fatty acids including cis-11-eicosenoic (C(20:1)), cis-11,14-eicosadienoic (C(20:2)), erucic (C(22:1n9)), cis-13,16-docosadienoic (C(22:2)) and nervonic (C(24:1)) acids in very small amounts but their presence seems to be unique for anaerobic fungi.     

Gas chromatography-mass spectrometry determination of metabolites of conjugated cis-9,trans-11,cis-15 18:3 fatty acid

Structural determination of polyunsaturated fatty acids by gas chromatography-mass spectrometry (GC-MS) requires currently the use of nitrogen containing derivatives such as picolinyl esters, 4,4-dimethyloxazoline or pyrrolidides derivatives. The derivatization is required in most cases to obtain low energy fragmentation that allows accurate location of the double bonds. In the present work, the following metabolites of rumelenic (cis-9,trans-11,cis-15 18:3) acid, from rat livers, were identified: cis-8,cis-11,trans-13,cis-17 20:4, cis-5,cis-8,cis-11,trans-13,cis-17 20:5, cis-7,cis-10,cis-13,trans-15,cis-19 22:5, and cis-4,cis-7,cis-10,cis-13,trans-15,cis-19 22:6 acids by GC-MS as their 4,4-dimethyloxazoline and methyl esters derivatives. Specific fragmentation of the methyl ester derivatives revealed some similarity with their corresponding DMOX derivatives. Indeed, intense ion fragments at m/z=M+-69, corresponding to a cleavage at the center of a bis-methylene interrupted double bond system were observed for all identified metabolites. Moreover, intense ion fragments at m/z=M+-136, corresponding to allylic cleavage of the n-12 double bonds were observed for the C20:5, C22:5, C22:6 acid metabolites. For the long chain polyunsaturated fatty acids from the rumelenic metabolism, we showed that single methyl esters derivatives might be used for both usual quantification by GC-FID and identification by GC-MS.     

Biosynthesis of saturated and unsaturated fatty acids by a T-strain mycoplasma (Ureaplasma).

A human T mycoplasma (Ureaplasma urealyticum) incorporated radioactivity into its lipids from [1-14C]acetate in the growth medium. Methanolysis of the lipids showed the label to be confined almost entirely to the methyl esters of the fatty acids. About 80% of the label was associated with the methyl esters of the saturated fatty acids, and the rest was found in the unsaturated methyl ester fraction. Gas-liquid chromatography of the saturated methyl esters showed the label to be present in the peaks of palmitate, myristate, and stearate, whereas in the unsaturated methyl ester fraction most of the radioactivity emerged in the peak of palmitoleate. The addition of either oleic or palmitic acid to the growth medium markedly decreased the organisms' incorporation of radioactivity from acetate. It is concluded that the T mycoplasma strain is capable of de novo synthesis of both saturated and unsaturated fatty acids, in this respect differing from all of the Mycoplasma and Acholeplasma strains investigated to date.     

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.     

Alterations of phospholipid metabolism by phorbol esters and fatty acids occur by different intracellular mechanisms in cultured glioma, neuroblastoma, and hybrid cells

Differences between the influences of phorbol esters (such as 4 beta-12-O-tetradecanoylphorbol 13-acetate) and of fatty acids (such as oleic acid) on the synthesis and turnover of phosphatidylcholine (PtdCho) and other phospholipids have been studied in glioma (C6), neuroblastoma (N1E-115), and hybrid (NG108-15) cells in culture using [methyl-3H]choline, [32P]Pi, [1,2-14C]ethanolamine, or 1-14C-labeled fatty acids as lipid precursors. 100-500 microM oleic acid stimulated PtdCho synthesis 3- to 5-fold in all three cell lines, but had little influence on chase of choline label following a 24-h pulse. Phorbol ester (50-200 nM) stimulated PtdCho synthesis 1.5- to 3-fold in C6 cells, was without effect in N1E-115 cells, and had intermediate effects on NG108-15 cells. Phorbol ester stimulated both uptake of extracellular choline and synthesis of PtdCho, whereas fatty acid stimulated only synthesis. Release of radioactivity from 24-h pulse-labeled PtdCho to the medium was enhanced by phorbol ester in C6 cells. Incorporation of [32P]Pi, primarily into PtdCho, was stimulated, whereas utilization of [1,2-14C]ethanolamine or 1-14C-fatty acid was little altered by phorbol ester. C6 cells "down-regulated" with phorbol ester lost the stimulatory response of subsequent treatment with phorbol esters on PtdCho synthesis, but the response to fatty acid was enhanced. Fatty acid had little influence on the relative binding of phorbol ester or "translocation" of phorbol ester binding sites. Accordingly, metabolism of phospholipids in these cultured cells of neural origin is markedly influenced by cell type, phospholipid class, condition of incubation medium, and nature of stimulator. Phorbol esters and fatty acids appear to enhance phospholipid synthesis and turnover by distinct intracellular mechanisms.     

Metabolic origins of urinary unsaturated dicarboxylic acids

Previously, we [Jin, S.-J., & Tserng, K.-Y. (1989) J. Lipid Res. 30, 1611-1619] reported the structures of urinary octenedioic acids occurring in patients with dicarboxylic aciduria. We proposed that these unsaturated octenedioic acids were derived from the oxidation of oleic and linoleic acids. By comparison with synthetic decenedioic acids, we have further identified the higher homologues of unsaturated dicarboxylic acids in urine as cis-5-decenedioic (c5DC10), cis-4-decenedioic (c4DC10), cis-3-decenedioic (cDC10), trans-4-decenedioic, trans-3-decenedioic, cis-5-dodecenedioic (c5DC12), cis-3-dodecenedioic (c3DC12), and trans-3-dodecenedioic acids. The presence of these isomeric decenedioic and dodecenedioic acids in urine is consistent with the proposed metabolic origins. In vitro studies using synthetic unsaturated fatty acids and rat liver homogenates support the proposed metabolic origins of these acids. The following metabolic sequences are proposed for metabolites derived from oleic acid: (route A) cis-5-tetradecenoic acid----cis-5-tetradecenedioic acid----c5DC12----c5DC10----suberic (DC8)----adipic (DC6); (route B) cis-3-dodecenoic acid----c3DC12----c3DC10----c3DC8 (cis-3-octenedioic)----DC6. A similar route is derived from linoleic acid: cis-4-decenoic acid----c4DC10----c4DC8 (cis-4-octenedioic)----DC6. The presence of a double bond at position 3, 4, or 5 of fatty acid appears to be rate limiting for further beta-oxidation; therefore, metabolic products with cis-3, cis-4, or cis-5 structure accumulate. Urinary DC8 and DC6 are derived partially from the metabolic degradation of these unsaturated dicarboxylic acids.     

The oxidation of dicarboxylic acid CoA esters via peroxisomal fatty acyl-CoA oxidase

Evidence supporting a common peroxisomal beta-oxidation pathway for the coenzyme A thioesters of medium-chain-length dicarboxylic acids (DCn-CoA) and monocarboxylic acids (MCn-CoA) has been obtained. Using the mono-CoA esters of dodecanedioic acid (DC12-CoA) and lauroyl-CoA (MC12-CoA) as substrates, parallel inductions of activities and parallel increases in specific activities during purification of peroxisomal fatty acyl-CoA oxidase (EC 1.3.99.3) from rat liver after di(2-ethylhexyl)phthalate treatment were seen. The purified enzyme was used for antiserum production in rabbits; antiserum specificity was verified by immunoblot analysis. Coincident losses of oxidase activities with MC12-CoA and DC12-CoA were found in immunotitration experiments with rat liver homogenates, supporting the hypothesis that peroxisomal fatty acyl-CoA oxidase is solely responsible for the oxidation of medium-chain length dicarboxylic acid substrates. Kinetic studies with purified enzyme using the mono-CoA esters of sebacic (DC10-CoA), suberic (DC8-CoA), and adipic (DC6-CoA) acids along with DC12-CoA revealed substrate inhibition. Although these substrates exhibited similar calculated Vmax values, with decreasing chain length, the combination of increasing Km values and decreasing substrate inhibition constant (Ki) caused the maximum obtainable velocity to decrease. These studies offer an explanation for the previously observed limit of the ability of peroxisomes to chain-shorten dicarboxylates and increased urinary excretion of adipic acid when peroxisomal oxidation of dicarboxylic acids is enhanced.     

Heterologous expression of a fatty acid hydroxylase gene in developing seeds of<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>

Expression of a cDNA encoding the castor bean ( Ricinus communis L.) oleate Delta12-hydroxylase in the developing seeds of Arabidopsis thaliana (L.) Heynh. results in the synthesis of four novel hydroxy fatty acids. These have been previously identified as ricinoleic acid (12-hydroxy-octadec- cis-9-enoic acid: 18:1-OH), densipolic acid (12-hydroxy-octadec- cis-9,15-enoic acid: 18:2-OH), lesquerolic acid (14-hydroxy-eicos- cis-11-enoic acid: 20:1-OH) and auricolic acid (14-hydroxy-eicos- cis-11,17-enoic acid: 20:2-OH). Using mutant lines of Arabidopsis that lack the activity of the FAE1 condensing enzyme or FAD3 ER Delta-15-desaturase, we have shown that these enzymes are required for the synthesis of C20 hydroxy fatty acids and polyunsaturated hydroxy fatty acids, respectively. Analysis of the seed fatty acid composition of transformed plants demonstrated a dramatic increase in oleic acid (18:1) levels and a decrease in linoleic acid (18:2) content correlating to the levels of hydroxy fatty acid present in the seed. Plants in which FAD2 (ER Delta12-desaturase) activity was absent showed a decrease in 18:1 content and a slight increase in 18:2 levels corresponding to hydroxy fatty acid content. Expression of the castor hydroxylase protein in yeast indicates that this enzyme has a low level of fatty acid Delta12-desaturase activity. Lipase catalysed 1,3-specific lipolysis of triacylglycerol from transformed plants demonstrated that ricinoleic acid is not excluded from the sn-2 position of triacylglycerol, but is the only hydroxy fatty acid present at this position.     

Biodegradation and conversion of alkanes and crude oil by a marine Rhodococcus

A hydrocarbon degrader isolated from a chronically oil-polluted marine site was identified as Rhodococcus sp. on the basis of morphology, fatty acid methyl ester pattern, cell wall analysis, biochemical tests and G + C content of DNA. It degraded upto 50% of the aliphatic fraction of Assam crude oil, in seawater supplemented with 35 mM nitrogen as urea and 0.1 mM phosphorus as dipotassium hydrogen orthophosphate, after 72 h at 30 ° and 150 revolutions per minute. The relative percentage of intracellular fatty acid was higher in hydrocarbon-grown cells compared to fructose-grown cells. The fatty acids C₁₆ , C16_{16 :1} C₁₈ and C_{18 : 1} were constitutively present regardless of the growth substrate. In addition to these constitutive acids, other intracellular fatty acids varied in correlation to the hydrocarbon chain length supplied as a substrate. When grown on odd carbon number alkanes, the isolate released only monocarboxylic acids into the growth medium. On even carbon number alkanes only dicarboxylic acids were produced.     

Metabolism of cis-12-octadecenoic acid and trans-9,trans-12-octadecadienoic acid and their influence on lipogenic enzyme activities in mouse liver

High carbohydrate (65% glucose) diets containing cis-12-octadecenoic acid (12c-18:1) or trans-9,trans-12-octadecadienoic acid (9t,12t-18:2) were fed to weanling mice to investigate the influence of fatty acid structure on six hepatic enzyme activities involved in lipid metabolism. Results with these diets were compared to those with diets containing no fatty acids, saturated fatty acids; cis-9-octadecenoic acid (9c-18:1) and cis-9,cis-12-octadecadienoic acid (9c,12c-18:2). These comparisons show saturated fatty acids, 9c-18:1, 12c-18:1, and 9t,12t-18:2, had little or no influence on the activity levels of fatty acid synthetase, malic enzyme (EC 1.1.1.40)citrate cleavage enzyme (EC 4.1.3.8), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and acetyl-CoA carboxylase (EC 6.4.1.2). Neither 12c-18:1 nor 9t,12t-18:2 produced the dramatic enzyme-lowering effect exhibited by the diet containing 9c,12c-18:2 when compared to the diet devoid of fat. Thus, both the 9 and 12 bonds must be present in the same molecule. Also, at least one and probably both bonds must be in the cis configuration to depress liver enzyme activities. Capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were both used for analysis of the methyl esters derived from the hepatic lipids. The GC and GC-MS data provided (a) direct evidence for incorporation of both isomers into hepatic lipids and (b) indirect evidence that 9t,12t-18:2 lowered liver delta 9-desaturase activity. In addition, since these products were found in the complex liver lipids, there is no doubt that the various enzymes concerned with activation and acylation utilize both of these isomeric fatty acids as substrates.     

Fatty acid utilisation and metabolism in caecal enterocytes of rainbow trout (Oncorhynchus mykiss) fed dietary fish or copepod oil

A combined fatty acid metabolism assay was employed to determine fatty acid uptake and relative utilisation in enterocytes isolated from the pyloric caeca of rainbow trout. In addition, the effect of a diet high in long-chain monoenoic fatty alcohols present as wax esters in oil derived from Calanus finmarchicus, compared to a standard fish oil diet, on caecal enterocyte fatty acid metabolism was investigated. The diets were fed for 8 weeks before caecal enterocytes from each dietary group were isolated and incubated with [1-14C]fatty acids: 16:0, 18:1n-9, 18:2n-6, 18:3n-3, 20:1n-9, 20:4n-6, 20:5n-3, and 22:6n-3. Uptake was measured over 2 h with relative utilisation of different [1-14C]fatty acids calculated as a percentage of uptake. Differences in uptake were observed, with 18:1n-9 and 18:2n-6 showing the highest rates. Esterification into cellular lipids was highest with 16:0 and C18 fatty acids, accounting for over one-third of total uptake, through predominant incorporation in triacylglycerol (TAG). The overall utilisation of fatty acids in phospholipid synthesis was low, but highest with 16:0, the most prevalent fatty acid recovered in intracellular phosphatidylcholine (PC) and phosphatidylinositol (PI), although exported PC exhibited higher proportions of C20/C22 polyunsaturated fatty acids (PUFA). Other than 16:0, incorporation into PC and PI was highest with C20/C22 PUFA and 20:4n-6 respectively. Recovery of labelled 18:1n-9 in exported TAG was 3-fold greater than any other fatty acid which could be due to multiple esterification on the glycerol 'backbone' and/or increased export. Approximately 20-40% of fatty acids taken up were beta-oxidised, and was highest with 20:4n-6. Oxidation of 20:5n-3 and 22:6n-3 was also surprisingly high, although 22:6n-3 oxidation was mainly attributed to retroconversion to 20:5n-3. Metabolic modification of fatty acids by elongation-desaturation was generally low at <10% of [1-14C]fatty acid uptake. Dietary copepod oil had generally little effect on fatty acid metabolism in enterocytes, although it stimulated the elongation and desaturation of 16:0 and elongation of 18:1n-9, with radioactivity recovered in longer n-9 monoenes. The monoenoic fatty acid, 20:1n-9, abundant in copepod oil as the homologous alcohol, was poorly utilised with 80% of uptake remaining unesterified in the enterocyte. However, the fatty acid composition of pyloric caeca was not influenced by dietary copepod oil.     

Differential effects of cis and trans fatty acid isomers, oleic and elaidic acids, on the cholesteryl ester transfer protein activity.

In a previous publication (Lagrost, L. and Barter, P.J. (1991) Biochim. Biophys. Acta 1085, 209-216), saturated and cis unsaturated non-esterified fatty acids have been shown to modulate the rate at which cholesteryl esters are transferred from high-density lipoproteins (HDL) to low-density lipoproteins (LDL) in the presence of the human cholesteryl ester transfer protein (CETP). In the present report, the effects of cis (oleic acid) and trans (elaidic acid) monounsaturated isomers on the CETP-mediated transfer of cholesteryl esters between HDL and LDL were compared. Mixtures of human LDL and HDL3, containing or not radiolabelled cholesteryl esters, were incubated at 37 degrees C with CETP in the presence or in the absence of either stearic (18:0), oleic (18:1 cis) or elaidic (18:1 trans) acids. It was observed that oleic acid and elaidic acid had different effects on the CETP-mediated redistribution of radiolabelled cholesteryl esters as well as on the net mass transfer of cholesterol from HDL3 to LDL. In particular, at high non-esterified fatty acid/lipoprotein ratio, the transfer of cholesteryl esters was significantly inhibited by the cis isomer and increased by the trans isomer.     

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.     

Feeding stimulants eliciting the probing behavior for Peregrinator blannulipes Montrouzier et Signore (Hemiptera: Ruduviidae) from Tribolium confusum (Jacquelin du Val)

Four fatty acid methyl esters identified in the solvent extract of Tribolium confusum (Jacquelin du Val) larvae as kairomones were individually and collectively tested for probing behavior of Peregrinator biannulipes Montrouzier et Signoret. All identified fatty acid methyl eaters, methyl palmitate, methyl linolate, methyl oleate and methyl stearate, exhibited characterisitic kairomonal probing behavior of P. biannulipe toward the lure. These fatty acid methyl ester were active at 0.2 microg/lure but a synergistic effect was not observed among them. Commercially available C8-C14 even-numbered fatty acid methyl esters that were not detected in the extract of T. confusum larvae also elicited a probing behavior but their activities were weaker than those of four fatty acid methyl ester (C16:0, C18:0, C18:1 and C18:2) identified in the extract. On the other hand, C17 and C19 odd-numbered fatty acid methyl esters did not show any activity at all.     

Acyl-CoA Synthetase in Oilseeds: Fatty Acid Structural Requirements for Activity and Selectivity

The substrate specificities and selectivities of acyl-CoA synthetasesfrom maturing oilseeds were investigated to reveal fatty acidstructures that the enzymes recognize. The synthetases fromrapeseed (Brassica nap us) and castor bean (Ricinus communis)activated palmitic acid 16:0 most rapidly among the saturatedfatty acids tested. Native unsat-urated fatty acids, oleic 18:1cis-9, linoleic 18:2 cis-9,12 and linolenic acid 18:3 m-9,12,15,were all effectively utilized. Palmitoleic acid 16:1 cis-9 wasalso a good substrate, while myristoleic acid 14:1 cis-9 wasa poor substrate. The activation of erucic acid 22:1 cis-13was very slow. Elaidic acid 18:1 trans-9 was utilized at ratessimilar to those of the cis isomer. The efficiencies of petroselinicacid 18:1 cis-6 were half the efficiencies of oleic acid, whilethe rates of activation of m-vaccenic acid 18:1 cw-11 were comparableto those for oleic acid. These findings suggest that acyl-CoAsynthetases of oilseeds producing long-chain fatty acids strictlyrecognize the molecular structures of fatty acids, i.e., thecarbon-chain length between C¹⁶-C¹⁸ and the position of thefirst double bond (     

Stimulation of pollen tube growthin vitro by dicarboxylic acids

Summary Effect of eight dicarboxylic acids and three monocarboxylic acids on pollen growth ofCamellia japonica was tested. While monocarboxylic acids inhibited pollen germination and pollen tube elongation, dicarboxylic acids, namely oxalic, succinic, suberic, adipic, sebacic, traumatic cis-1,2-cyclohexane dicarboxylic, and 3,3-diethyl glutaric acids stimulated pollen tube elongation stronger than indoleacetic acid.