Involvement of phospholipids in polyunsaturated Fatty Acid synthesis in developing soybean cotyledons

Developing soybean (cv. Dare) cotyledons harvested at 30 days after flowering were pulse-labeled with [1-(14)C]oleoyl-CoA. The metabolic interrelation of radiolabeled unsaturated fatty acids between the major glycerolipid classes was determined at various time intervals. At chase time zero, [(14)C]oleic acid accounted for 99.2% of the total glycerolipid radioactivity, and phospholipids contained 92% of the total incorporated radioactivity. With time, phospholipids were metabolized in triacylglycerol biosynthesis and radioactivity was detected in polyunsaturated fatty acids. The hypothesis that phospholipids were metabolic intermediates in polyunsaturated fatty acid biosynthesis was tested by comparing the theoretical and the actual amount of radiolabeled oleic acid that was associated with triacylglycerol as a function of time. The radioactive oleic acid found in triacylglycerol at various intervals was derived from phospholipids via a diacylglycerol intermediate. Assuming no phospholipid desaturation, the potential or theoretical amounts of [(14)C]oleic acid that could be transferred to triacylglycerol from phospholipids was defined by a system of differential equations. The results demonstrated that the decline in [(14)C]oleic acid from phospholipid after long chase intervals was equal to the total amount of radioactive unsaturated fatty acids found in neutral lipids. The difference between the theoretical and actual amounts of [(14)C]oleic acid present in triacylglycerol after long time intervals was equal to the amount of radioactivity present in polyunsaturated fatty acids. Based upon those findings in soybeans, the desaturation of oleic acid associated with phospholipids was highly probable.     

The thrombin-dependent enrichment of alkenylacyl ethanolamine phosphoglyceride with [14C]eicosapentaenoic and [3H]arachidonic acids in prelabelled human platelets

The thrombin-dependent enrichment of alkenylacyl ethanolamine phosphoglyceride in [14C]eicosapentaenoic acid [( 14C]EPA) was demonstrated and compared with [3H]arachidonic acid [( 3H]AA) following the simultaneous prelabelling of individual human platelet phospholipids with these two fatty acids. The alkenylacyl, diacyl, and alkylacyl classes of ethanolamine phosphoglycerides (PE) were separated by thin-layer chromatography as their acetylated derivatives after hydrolysis of the parent phospholipid with phospholipase C. The ratios of [3H]/[14C] for the increased radioactivity appearing in alkenylacyl PE following 60 and 120 s of thrombin stimulation were the same as the corresponding ratio (2.0) found in the choline phosphoglycerides (PC) from control (unstimulated) platelets. These results suggest no significant selectivity between EPA and AA in the thrombin-stimulated transfer of these fatty acids from diacyl PC to alkenylacyl PE. The present findings may possibly bear some relevance to the altered platelet reactivity and (or) decreased thromboxane A2 formation observed in human subjects following the ingestion of marine lipid containing EPA.     

Apparent Role of Phosphatidylcholine in the Metabolism of Petroselinic Acid in Developing Umbelliferae Endosperm

Studies were conducted to characterize the metabolism of the unusual fatty acid petroselinic acid (18:1cis[delta]6) in developing endosperm of the Umbelliferae species coriander (Coriandrum sativum L.) and carrot (Daucus carota L.). Analyses of fatty acid compositions of glycerolipids of these tissues revealed a dissimilar distribution of petroselinic acid in triacylglycerols (TAG) and the major polar lipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Petroselinic acid comprised 70 to 75 mol% of the fatty acids of TAG but only 9 to 20 mol% of the fatty acids of PC and PE. Although such data appeared to suggest that petroselinic acid is at least partially excluded from polar lipids, results of [1-14C]acetate radiolabeling experiments gave a much different picture of the metabolism of this fatty acid. In time-course labeling of carrot endosperm, [1-14C]acetate was rapidly incorporated into PC in high levels. Through 30 min, radiolabel was most concentrated in PC, and of this, 80 to 85% was in the form of petroselinic acid. One explanation for the large disparity in amounts of petroselinic acid in PC as determined by fatty acid mass analyses and 14C radiolabeling is that turnover of these lipids or the fatty acids of these lipids results in relatively low accumulation of petroselinic acid mass. Consistent with this, the kinetics of [1-14C]acetate time-course labeling of carrot endosperm and "pulse-chase" labeling of coriander endosperm suggested a possible flux of fatty acids from PC into TAG. In time-course experiments, radiolabel initially entered PC at the highest rates but accumulated in TAG at later time points. Similarly, in pulse-chase studies, losses in absolute amounts of radioactivity from PC were accompanied by significant increases of radiolabel in TAG. In addition, stereospecific analyses of unlabeled and [1-14C]acetate-labeled PC of coriander endosperm indicated that petroselinic acid can be readily incorporated into both the sn-1 and sn-2 positions of this lipid. Because petroselinic acid is neither synthesized nor further modified on polar lipids, the apparent metabolism of this fatty acid through PC (and possibly through other polar lipids) may define a function of PC in TAG assembly apart from its involvement in fatty acid modification reactions.     

Culture age and carbamoylcholine increase the incorporation of endogenously synthesized linoleic acid in lipids of Trypanosoma cruzi epimastigotes

Physiological and cellular adaptations to environmental changes are known to be related to modifications in membrane lipids. This work provides metabolic and compositional evidence that Trypanosoma cruzi epimastigotes are able to synthesize and desaturate fatty acids, to incorporate them into their lipids, and to modify this incorporation when carbamoylcholine is present in the medium. The fatty acids formed from [2-(14)C]acetate in the period from 2 to 9 days were mostly (70%) incorporated in phospholipids, the remainder 30% being recovered in neutral lipids, such as triacylglycerols (TAG) and diacylglycerols (DAG). The main fatty acids formed from [2-(14)C]acetate were saturates (16:0, 18:0), monoenes (16:1, 18:1) and dienes (mostly 18:2). The ratios between labelled unsaturated and saturated fatty acids increased continuously with growth, consistent with a precursor-product relationship between the main fatty acids, and with the occurrence in T. cruzi of Delta(9)- and Delta(12)-desaturases. From days 2 to 5, [(14)C]18:2 was the main fatty acid produced. Accordingly, the fatty acid profiles showed a significant increase in the percentage of 18:2 in all lipids in the period under study, especially in the first 2 to 5 days. In the presence of carbamoylcholine, the labelling of DAG and TAG with [(14)C]18:2 augmented. The results indicate that T cruzi is able to synthesize the main types of fatty acids required to form its membrane lipids, and to exchange them actively in response to environmental stimuli.     

Inhibition of conjugation in Tetrahymena pyriformis by cerulenin. Possible requirement for de novo lipid synthesis.

Conjugation in Tetrahymena pyriformis is induced by the mixing of two starved complementary mating types. Addition of the antibiotic cerulenin, a specific inhibitor of de novo lipid synthesis, upon mixing of the mating types inhibited the conjugation process. The inhibition of conjugation was found to be reversible upon washing the cells. Cerulenin inhibited [14C]acetate incorporation into the lipid fraction of the cells, while it did not affect the incorporation of [3H]leucine into proteins. Analysis of the fatty acid composition of the whole cells revealed that during conjugation the ratio of saturated to unsaturated fatty acids is markedly changed. While the ratio of saturated:unsaturated fatty acids is 0.30 in unconjugated cells, it reached a value of 0.45 in conjugated cells.     

Metabolism of phospholipids and the characterization of fatty acids in bovine corpus luteum

1. Phosphatidylcholine was the predominant phospholipid in bovine corpora lutea; it accounted for about 50% of the total phospholipid phosphorus. Phosphatidylethanolamine (13%) and ethanolamine plasmalogen (8-9%) were the next two major components. 2. After incubation of the tissue with [(32)P]orthophosphate the total radioactivity and specific radioactivity of phosphatidylinositol were higher than those of any other lipid. 3. Luteinizing hormone failed to increase significantly the incorporation of [(32)P]orthophosphate into total phospholipids from luteal tissue slices, but did stimulate progesterone synthesis and lactate production. 4. The proportion of oleate (18:1) in the neutral lipids and phospholipids was higher than that of any other fatty acid. 5. The proportion of unsaturated fatty acid in the tissue lipids exceeded 60%, and almost half of this was polyunsaturated. Arachidonate (20:4), docosatetraenoate (22:4) and docosapentaenoate (22:5) were the principal polyunsaturated fatty acids. 6. After incubation of luteal tissue with [1-(14)C]acetate, the greatest proportion of radioactivity in the fatty acids isolated from the total lipid fraction was in palmitate (16:0) and docosatetraenoate (22:4). Polyunsaturated fatty acids accounted for almost 50% of the (14)C radioactivity incorporated and this pattern was observed in phospholipids, triglycerides and free fatty acids.     

Inhibition of conjugation in Tetrahymena pyriformis by cerulenin. Possible requirement for de novo lipid synthesis

Conjugation in Tetrahymena pyriformis is induced by the mixing of two starved complementary mating types. Addition of the antibiotic cerulenin, a specific inhibitor of de novo lipid synthesis, upon mixing of the mating types inhibited the conjugation process. The inhibition of conjugation was found to be reversible upon washing the cells.Cerulenin inhibited [¹⁴C]acetate incorporation into the lipid fraction of the cells, while it did not affect the incorporation of [³H]leucine into proteins. Analysis of the fatty acid composition of the whole cells revealed that during conjugation the ratio of saturated to unsaturated fatty acids is markedly changed. While the ratio of saturated:unsaturated fatty acids is 0.30 in unconjugated cells, it reached a value of 0.45 in conjugated cells.     

Reversal of cerulenin-induced inhibition of phospholipids and sterol synthesis by exogenous fatty acids/sterols in Epidermophyton floccosum

Cerulenin, a specific inhibitor of fatty acids and sterol biosynthesis inhibited the growth of Epidermophyton floccosum, which was reversed when growth medium was supplemented with palmitic acid and sterols. Unsaturated fatty acids partially restored the growth. Cerulenin inhibited both phospholipid and sterol biosynthesis (60-70%) at the minimum inhibitory concentration (0.5 microgram/ml) as demonstrated by [32P]orthophosphoric acid and [14C]acetate incorporation into the respective lipids. Cerulenin-induced inhibition of phospholipid and sterol synthesis was dose dependent up to 0.5 microgram/ml. Exogenously supplied fatty acids and sterols restored the biosynthesis of phospholipids in cerulenin-treated cultures, while that of sterols was enhanced. The biosynthesis of both saturated and unsaturated fatty acids was inhibited by cerulenin.     

Temperature-induced changes in fatty acid composition of myelinated and non-myelinated axon phospholipids

The olfactory (non-myelinated) and trigeminal (myelinated) nerve axons of garfish show changes in phospholipid fatty acid composition when these fish are acclimated to temperatures ranging from 11 to 35 degrees C. Myelinated and non-myelinated nerve axons show similar changes in the percent saturated, percent 16-carbon, percent 18-carbon, and percent 20-carbon-and-greater unsaturated fatty acids. The observed changes in phospholipid fatty acid composition fit a linear regression model suggesting a gradual change in axonal phospholipid fatty acid composition with temperature. The temperature-induced changes in garfish nerve phospholipid fatty acid composition are consistent with the general observation of increased saturated fatty acid residues in plasma membrane phospholipids of organisms acclimated to higher environmental temperatures. The garfish data are similar to data previously obtained for goldfish tissues and Tetrahymena.     

Mechanism of the apparent regulation of Escherichia coli unsaturated fatty acid synthesis by exogenous oleic acid.

Starvation of strains of Escherichia coli which are glycerol auxotrophs and are also defective in beta oxidation results in the accumulation of large amounts of free fatty acid (Cronan, J. E., Jr., Weisberg, L. W., and Allen, R. G. (1975) J. Biol. Chem. 250, 5835-5840). We now report that addition of exogenous oleic acid to these cultures results in no decrease in the synthesis of the unsaturated acids of the free fatty acid fraction although a 40 to 60% decrease of [14C]acetate incorporation into phospholipid unsaturated acyl moieties occurs under these conditions. This result indicates that the decreased synthesis of phospholipid unsaturated acyl moieties observed by others during oleic acid supplementation can be attributed to competition between exogenous and endogenously synthesized unsaturated fatty acids rather than a curtailment of unsaturated fatty acid synthesis per se.     

Alterations of the composition and size of the free fatty acid pool of Tetrahymena responding to low-temperature stress

Cells of Tetrahymena mimbres (formerly T. pyriformis NT-1) in midlogarithmic growth under isothermal conditions (at 39 degrees C) contained a very small, compositionally discrete pool of free fatty acids, principally (60.6% of the total free fatty acid mass) palmitic and stearic acids. The composition, degree of unsaturation, and size of this free fatty acid pool were rapidly (15 min or less) altered in response to chilling. During the acclimation period following chilling to 15 degrees C, the size of the free fatty acid pool increased from a mean value of 15.5 nmol free fatty acid/mumol lipid phosphorus in 39 degrees C cells to 24.2 nmol free fatty acid/mumol lipid phosphorus. The degree of free fatty acid saturation rapidly increased over the initial hour following the onset of hypothermal conditions, but by 24 h the unsaturated free fatty acid/saturated free fatty acid ratio was 0.35 (equivalent to a 2.7-fold increase in unsaturation relative to 39 degrees C controls (unsaturated/saturated ratio = 0.13) and 4.4-fold greater than cells acclimated for 1 h (unsaturated/saturated ratio = 0.08)). By 24 h the percentage of palmitic and stearic acids had decreased to 45.6%. Similar, and in some instances more pronounced, changes were observed to occur in triacylglycerol-bound fatty acids. Modulation of steady-state free fatty acid composition could also be achieved by the addition of exogenous fatty acids to the growth medium. The ability to manipulate the level of intracellular free fatty acids should prove to be a valuable experimental tool in determining how specific fatty acids regulate various lipid-modifying enzymes.     

Effect of erythropoietin on the lipid composition of red blood cell membrane

Effect of Ep on [14C]acetate incorporation into different lipid fractions of RBC membranes in starved and phenylhydrazine-treated rats was studied. The incorporation was increased into both neutral and phospholipid fractions on Ep treatment to starved or phenylhydrazine-treated rats. A slight decrease in the ratio of neutral lipid to phospholipid was observed under the influence of Ep in starved rats (23%) or in phenylhydrazine-treated rats (36%). Incorporation of radioactivities into different phospholipid fractions of RBC membrane increased on Ep treatment to starved rats, whereas, the relative percentages of these phospholipids (except LPC) remained more or less unchanged under similar conditions. Phenylhydrazine treatment increased the relative percentage of PC and concomitantly decreased the percentage of Sph. Percentage composition of both these two phospholipids showed a tendency to return to their normal levels on administration of Ep to phenylhydrazine-treated rats. Ep decreased the sigma saturated/sigma unsaturated ratio of fatty acids in PE, PS, and PC of RBC membrane in starved rats. On the other hand, no significant change was observed in this ratio of fatty acids in the phospholipids except Sph of RBC membrane in the presence of phenylhydrazine and Ep. In Sph, the ratio went down under similar conditions.     

Characterization of polar lipids of oral isolates of Candida, Pichia and Saccharomyces by Fast Atom Bombardment Mass Spectrometry (FAB MS)

AIMS: To characterize fatty acid and phospholipid analogue profiles of oral yeasts. METHODS AND RESULTS: Twenty-seven strains of oral yeasts were cultured on SDA and lipids of freeze-dried cells were extracted and analysed by FAB MS. The most abundant carboxylate anion was m/z 281 (C18 : 1). The most intense phospholipid analogue ions were of PE, PG, PA and PI. Pichia etchellsii contained molecular species of PG and PE, whereas Saccharomyces cerevisiae had PA, PG and PE analogues. Mass spectra revealed that S. cerevisiae and Candida glabrata were distinct from one another and from the other species tested. CONCLUSION: Oral yeasts largely differ with respect to their polar lipids. It is concluded that oral yeast species have distinctive fatty acid and phospholipid analogue anion profiles. SIGNIFICANCE AND IMPACT OF THE STUDY: FAB MS provided novel chemotaxonomic information.     

Influence of dexamethasone on the lipid distribution of newly synthesized fatty acids in fetal rat lung

There is a developmental increase in fatty acid biosynthesis and surfactant production in late-gestation fetal lung and both are accelerated by glucocorticoids. We have examined the distribution of the newly synthesized fatty acids to determine whether they are preferentially incorporated into surfactant. Explants of 18 day fetal rat lung were cultured with and without dexamethasone for 48 h and then with [3H]acetate for 4 h after which labeled fatty acids were measured. Incorporation of radioactivity from acetate was considered a measure of newly synthesized fatty acids. Phospholipids contained 86% of the newly synthesized fatty acids of which approx. 80% were in phosphatidylcholine. Phosphatidylcholine and disaturated phosphatidylcholine contained a much greater percentage of the labeled fatty acids than of the phospholipid mass determined by phosphorus assay while phosphatidylethanolamine, phosphatidylserine and sphingomyelin contained less. Dexamethasone increased the rate of acetate incorporation into total lipid fatty acids but it had little effect on fatty acid distribution, except that it increased the percentages in phosphatidylglycerol and disaturated phosphatidylcholine. The hormone also increased the mass of these two phospholipids to a greater extent than that of the total. These data suggested that the newly synthesized fatty acids are preferentially incorporated into surfactant phospholipids and that this process is accelerated by dexamethasone. However, since phosphatidylcholine and phosphatidylglycerol are not exclusive to surfactant, we compared isolated lamellar bodies with a residual fraction not enriched in surfactant. The rate of acetate incorporation into fatty acids in lamellar body phosphatidylcholine as well as its specific activity (radioactivity per unit phosphorus) were both increased by dexamethasone. Specific activity, however, was no greater in the lamellar bodies than in the residual fraction in both control and dexamethasone-treated cultures. Therefore, there is no preferential incorporation of newly synthesized fatty acids into phospholipids in surfactant as opposed to those in other components of the lung.     

Differential distribution and metabolism of arachidonic acid and docosahexaenoic acid by human placental choriocarcinoma (BeWo) cells

The time course of incorporation of [¹⁴C]arachidonic acid and [³H]docosahexaenoic acid into various lipid fractions in placental choriocarcinoma (BeWo) cells was investigated. BeWo cells were found to rapidly incorporate exogenous [¹⁴C]arachidonic acid and [³H] docosahexaenoic acid into the total cellular lipid pool. The extent of docosahexaenoic acid esterification was more rapid than for arachidonic acid, although this difference abated with time to leave only a small percentage of the fatty acids in their unesterified form. Furthermore, uptake was found to be saturable. In the cellular lipids these fatty acids were mainly esterified into the phospholipid (PL) and the triacyglycerol (TAG) fractions. Smaller amounts were also detected in the diacylglycerol and cholesterol ester fractions. Almost 60% of the total amount of [3H]Docosahexaenoic acid taken up by the cells was esterified into TAG whereas 37% was in PL fractions. For arachidonic acid the reverse was true, 60% of the total uptake was incorporated into PL fractions whereas less than 35% was in TAG. Marked differences were also found in the distribution of the fatty acids into individual phospholipid classes. The higher incorporation of docosahexaenoic acid and arachidonic acid was found in PC and PE, respectively. The greater cellular uptake of docosahexaenoic acid and its preferential incorporation in TAG suggests that both uptake and transport modes of this fatty acid by the placenta to fetus is different from that of arachidonic acid.     

The effect of temperature on unsaturated fatty acid loss in Tetrahymena pyriformis.

Cultures of Tetrahymena pyriformis W incorporate exogenous 3-[14C]-cilienic acid and gamma-[1(-14)C] linolenic acid, terminal products of unsaturated fatty acid synthesis, into glycerophosphatides without randomization of the radiolabel. There was no difference in the rate of loss of each of the two acids at 15 or 28.5 degrees C. Differential turnover of these fatty acids, therefore, does not appear to be the cause of the shift in fatty acid pattern observed with temperature reduction.     

Polar lipid and fatty acid profiles – Re-vitalizing old approaches as a modern tool for the classification of mycoplasmas?

A set of 20 Mollicutes strains representing different lines of descent, including the type species of the genus Mycoplasma, Mycoplasma mycoides, Acholeplasma laidlawii and a strain of Mesoplasma, were subjected to polar lipid and fatty acid analyses in order to evaluate their suitability for classification purposes within members of this group. Complex polar lipid and fatty acid profiles were detected for each examined strain. All strains contained the polar lipids phosphocholine-6'-alpha-glucopyranosyl-(1'-3)-1, 2-diacyl-glycerol (MfGL-I), 1-O-alkyl/alkenyl-2-O-acyl-glycero-3-phosphocholine (MfEL), sphingomyelin (SphM), 1-O-alkyl/alkenyl-glycero-3-phosphocholine (lysoMfEL), the unknown aminophospholipid APL1 and the cholesterol Chol2. A total of 19 strains revealed the presence of phosphatidylethanolamine (PE) and/or phosphatidylglycerol (PG), and the presence of diphosphatidylglycerol (DPG) was detected in 13 strains. The unknown aminolipid AL1 was found in the extracts of 17 strains. Unbranched saturated and unsaturated compounds predominated in the fatty acid profiles. Major fatty acids were usually C16:0, C18:0, C18:1 omega9c and 'Summed feature 5' (C18:2 omega6, 9c/C18:0 anteiso). Our results demonstrated that members of the M. mycoides cluster showed rather homogenous polar lipid and fatty acid profiles. In contrast, each of the other strains was characterized by a unique polar lipid profile and significant quantitative differences in the presence of certain fatty acids. These results indicate that analyses of both polar lipid and fatty acid profiles could be a useful tool for classification of mycoplasmas.     

On the control of long-chain-fatty acid synthesis in isolated intact spinach (Spinacia oleracea) chloroplasts

1. Chloroplasts isolated from spinach leaves by using the low-ionic-strength buffers of Nakatani & Barber [(1977) Biochim. Biophys. Acta.461, 510-512] had higher rates of HCO(3) (-)-dependent oxygen evolution (up to 369mumol/h per mg of chlorophyll) and higher rates of [1-(14)C]acetate incorporation into long-chain fatty acids (up to 1500nmol/h per mg of chlorophyll) than chloroplasts isolated by using alternative procedures. 2. Acetate appeared to be the preferred substrate for fatty acid synthesis by isolated chloroplasts, although high rates of synthesis were also measured from H(14)CO(3) (-) in assays permitting high rats of photosynthesis. Incorporation of H(14)CO(3) (-) into fatty acids was decreased by relatively low concentrations of unlabelled acetate. Acetyl-CoA synthetase activity was present 3-4 times in excess of that required to account for rates of [1-(14)C]acetate incorporation into fatty acids, but pyruvate dehydrogenase was either absent or present in very low activity in spinach chloroplasts. 3. Rates of long-chain-fatty acid synthesis from [1-(14)C]acetate in the highly active chloroplast preparations, compared with those used previously, were less dependent on added cofactors, but showed a greater response to light. The effects of added CoA plus ATP, Triton X-100 and sn-glycerol 3-phosphate on the products of [1-(14)C]acetate incorporation were similar to those reported for less active chloroplast preparations. 4. Endogenous [(14)C]acetyl-CoA plus [(14)C]malonyl-CoA was maintained at a constant low level even when fatty acid synthesis was limited by low HCO(3) (-) concentrations. Endogenous [(14)C]acyl-(acyl-carrier protein) concentrations increased with increasing HCO(3) (-) concentration and higher rates of fatty acid synthesis, but were slightly lower in the presence of Triton X-100. It is proposed that rates of long-chain-fatty acid synthesis in isolated chloroplasts at saturating [1-(14)C]acetate concentrations and optimal HCO(3) (-) concentrations may be primarily controlled by rates of removal of the products of the fatty acid synthetase.     

Characterization of methanotrophic bacteria on the basis of intact phospholipid profiles

The intact phospholipid profiles (IPPs) of seven species of methanotrophs from all three physiological groups, type I, II and X, were determined using liquid chromatography/electrospray ionization/mass spectrometry. In these methanotrophs, two major classes of phospholipids were found, phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) as well as its derivatives phosphatidylmethylethanolamine (PME) and phosphatidyldimethylethanolamine (PDME). Specifically, the type I methanotrophs, Methylomonas methanica, Methylomonas rubra and Methylomicrobium album BG8 were characterized by PE and PG phospholipids with predominantly C16:1 fatty acids. The type II methanotrophs, Methylosinus trichosporium OB3b and CSC1 were characterized by phospholipids of PG, PME and PDME with predominantly C18:1 fatty acids. Methylococcus capsulatus Bath, a representative of type X methanotrophs, contained mostly PE (89% of the total phospholipids). Finally, the IPPs of a recently isolated acidophilic methanotroph, Methylocella palustris, showed it had a preponderance of PME phospholipids with 18:1 fatty acids (94% of total). Principal component analysis showed these methanotrophs could be clearly distinguished based on phospholipid profiles. Results from this study suggest that IPP can be very useful in bacterial chemotaxonomy.     

Characterization and metabolism of ovine foetal lipids

1. Total phospholipid concentrations in liver, kidney and brain of the 140-day ovine foetus were only half of those in comparable maternal tissues. 2. Phosphatidylcholine was the predominant phospholipid in all foetal tissues examined. The most striking difference between foetal and maternal tissues in individual phospholipids was in the heart; foetal heart contained more ethanolamine plasmalogen than choline plasmalogen, whereas in adult tissue the concentration of these was reversed. Sphingomyelin content of foetal brain was only one-sixth of that of maternal brain tissue. 3. Oleic acid (18:1) was the predominant acid in the phospholipid extracted from foetal tissues, except in brain where palmitic acid (16:0) was slightly higher. In phospholipids from adult tissues there was a higher proportion of unsaturated fatty acids (linoleic acid, 18:2, and linolenic acid, 18:3) and a correspondingly lower proportion of oleic acid (18:1). The distribution of fatty acids in the neutral lipid fraction of foetal and maternal tissues was very similar; oleic acid (18:1) was generally the principal component. 4. (14)C derived from [U-(14)C]-glucose and [U-(14)C]fructose infused into the foetal circulation in utero was incorporated into the neutral lipids and phospholipids of heart, liver, kidney, brain and adipose tissue. 5. Phospholipid analysis revealed that the specific activity of phosphatidic acid was higher in liver than in other tissues. The specific activity of phosphatidylethanolamine was less than that of phosphatidylcholine in heart, but in other tissues they were about the same. The specific activities of phosphatidylinositol and phosphatidic acid in brain were very similar and were higher than the other components. The specific activity of phosphatidylserine was highest in liver and brown fat. 6. The pattern of incorporation of (14)C derived from [(14)C]glucose and [(14)C]fructose into foetal neutral lipids was similar. Diglyceride accounted for most of the radioactivity in brain, whereas triglyceride had more label in heart, liver, kidney and fat.