Fatty Acid Distribution in Glycolipids and Phospholipids in Cotyledons of Germinating Soybeans

This investigation was conducted to observe changes in the fatty acid distributions of glycolipids (GL) and phospholipids (PL) in cotyledons of soybean seeds which were germinated either in the dark or the light at 28°C for 8 days. The GL isolated from the total lipids of cotyledons at different germinating stages were : acyl sterylglycoside (ASG), monogalactosyl diglyceride (MGD), digalactosyl diglyceride (DGD) and sulfolipid (SL). The PL isolated from the same total lipids as described above were : diphosphatidyl glycerol (DPG), phosphatidic acid (PA), phosphatidyl ethanolamine (PE), phosphatidyl glycerol (PG), phosphatidyl choline (PC) and phosphatidyl inositol (PI).

During germination of soybean seeds, the content of linoleic and linolenic acids in MGD or DGD was markedly higher than that of the other GL. The positional distribution of fatty acids in PE, PC and PI was shown in all PL, in which saturated fatty acids, especially palmitic acid, were highly concentrated in position 1 and unsaturated fatty acids, especially linoleic acid, mainly occupied position 2. A remarkable difference in the changing patterns of fatty acid composition, which depended on the germinating conditions tested, was observed between GL and PL. The changes in fatty acid composition of GL were more marked in the light-grown seedlings than in the dark-grown, whereas those of PL were more remarkable in the latter than in the former. Therefore, the positional distribution of fatty acids in PL was more evident in the light-grown seedlings than in the dark-grown ones.

These results suggest the metabolic fate of GL and PL in cotyledons of soybean seeds, probably owing to the differences in the two germinating conditions tested.     

Antigen-induced changes in phospholipid metabolism in antigen-binding B lymphocytes

Previous studies have demonstrated a marked change in the metabolism of phospholipids (PL) after activation of resting B lymphocytes with anti-immunoglobulin (anti-Ig). In this study we examined PL metabolism in highly purified trinitrophenyl (TNP)-binding B cells after their activation with various forms of TNP-carrier protein. Such cells show similar changes in PL metabolism when stimulated with either antigen or anti-Ig, i.e., increased incorporation of 32PO4 into phosphatidic acid and phosphatidyl inositol (PI) but not phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl serine. We have demonstrated that these responses to antigen are TNP-specific and dose-related between 1 and 50 micrograms/ml, producing up to a 2.5-fold stimulation of 32PO4 incorporation into PI. The PL response is also directly related to the density of TNP on the carrier and can be augmented by additional cross-linking of the carrier protein. These data suggest that cross-linking of surface Ig by antigen induces a change in PL metabolism as an early event in B cell activation.     

Alterations in L fibroblast lipid metabolism and morphology during choline deprivation.

The growth of L fibroblasts in suspension culture after transfer directly to choline-free medium without a rinse was reduced to zero after 72 h. Monolayer cultures similarly treated multiplied at control rates for 96 h; one rinse of the latter prior to incubation in choline-free medium reduced growth at 48 h to 75% of control cells. A decrease in the size of cells in these rinsed monolayer cultures was apparent within 12 h, and preceded any changes in cell lipid composition; further decreases in cell size were observed at 24 and 48 h. After 24 h in choline-free medium the percent phosphatidyl choline had decreased only slightly and even at 48 h remained at 72 % of the value of control cells. At this time, however, there was a 50% decrease in the total phospholipid (PL) content of the cells, and a coincident 5–10-fold increase in the amount of triglyceride. There was no adaptive increase in the other principal PL classes. Changes in the ultrastructure of mitochondria were observed as early as 24 h; after 48 h without choline there was a decrease in the relative mitochondrial volume to 50% of control values. Alterations in the adhesive properties of choline-deprived cells may be related to altered lipid content or composition of the cell surface.     

Long-term exposure to LPS enhances the rate of stimulated exocytosis and surfactant secretion in alveolar type II cells and upregulates P2Y2 receptor expression

Bacterial LPS is a potent proinflammatory molecule. In the lungs, LPS induces alterations in surfactant pool sizes and phospholipid (PL) contents, although direct actions of LPS on the alveolar type II cells (AT II) are not yet clear. For this reason, we studied short- and long-term effects of LPS on basal and agonist-stimulated secretory responses of rat AT II by using Ca(2+) microfluorimetry, a microtiter plate-based exocytosis assay, by quantitating PL and (3)H-labeled choline released into cell supernatants and by using quantitative PCR and Western blot analysis. Long term, but not short term, exposures to LPS led to prolonged ATP-induced Ca(2+) signals and an increased rate in vesicle fusions with an augmented release of surfactant PL. Most notably, the stimulatory effect of LPS was ATP-dependent and may be mediated by the upregulation of the purinergic receptor subtype P2Y(2). Western blot analysis confirmed higher levels of P2Y(2), and suramin, a P2Y receptor antagonist, was more effective in LPS-treated cells. From these observations, we conclude that LPS, probably via Toll-like receptor-4, induces a time-dependent increase in P2Y(2) receptors, which, by yet unknown mechanisms, leads to prolonged agonist-induced Ca(2+) responses that trigger a higher activity in vesicle fusion and secretion. We further conclude that chronic exposure to endotoxin sensitizes AT II to increase the extracellular surfactant pool, which aids in the pulmonary host defense mechanisms.     

Differential induction of oxylipin pathway in potato and tobacco cells by bacterial and oomycete elicitors

Key message

Potato and tobacco cells are differentially suited to study oxylipin pathway and elicitor-induced responses.

Abstract

Synthesis of oxylipins via the lipoxygenase (LOX) pathway provides plant cells with an important class of signaling molecules, related to plant stress responses and innate immunity. The aim of this study was to evaluate the induction of LOX pathway in tobacco and potato cells induced by a concentrated culture filtrate (CCF) from Phytophthora infestans and lipopolysaccharide (LPS) from Pectobacterium atrosepticum. Oxylipin activation was evaluated by the measurement of LOX activity and metabolite quantification. The basal levels of oxylipins and fatty acids showed that potato cells contained higher amounts of linoleic (LA), linolenic (LnA) and stearic acids than tobacco cells. The major oxylipin in potato cells, 9(S),10(S),11(R)-trihydroxy-12(Z),15(Z)-octadecadienoic acid (9,10,11-THOD), was not detected in tobacco cells. CCF induced a sharp increase of LA and LnA at 8 h in tobacco cells. In contrast they decreased in potato cells. In CCF-treated tobacco cells, colneleic acid increased up to 24 h, colnelenic acid and 9(S)-hydroxyoctadecatrienoic acid (9(S)-HOT) increased up to 16 h. In potato cells, only colneleic acid increased slightly until 16 h. A differential induction of LOX activity was measured in both cells treated by CCF. With LPS treatment, only 9,10,11-THOD accumulation was significantly induced at 16 h in potato cells. Fatty acids were constant in tobacco but decreased in potato cells over the studied time period. These results showed that the two elicitors were differently perceived by the two Solanaceae and that oxylipin pathway is strongly induced in tobacco with the CCF. They also revealed that elicitor-induced responses depended on both cell culture and elicitor.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> high-cell-density culture: carbon mass balances and release of outer membrane components

Carbon mass balances were calculated in fed-batch cultures of E. coli W3110, using mineral medium with glucose as the limiting substrate. The carbon recovery, based on biomass, CO(2), and acetate was approximately 90% at the end of the culture (25 h, 27 g L(-1) dw). The missing carbon remained as soluble organic compounds in the medium. Outer membrane (OM) constituents, such as lipopolysaccharides (LPS), phospholipids (PL), and carbohydrates (each at approximately 1 g L(-1)) contributed to 63% of the extracellular carbon. The amount of released LPS and PL equaled the total amount of OM bound to the cells in the culture. Small amounts of DNA and protein detected in the medium indicated that no cell lysis had occurred. Acetate, lactate, ethanol, formate, succinate and amino acids (Glu, Gln, Asp, Asn, Ala, Gly, Ser) were detected in the culture medium, but made up only a few percent of the extracellular carbon mass. The remaining 30% was not identified, but was assumed to constitute complex carbohydrates.     

Changes in Glycolipid and Phospholipid Compositions in Cotyledons of Germinating Soybeans

This investigation was conducted to observe changes in the compositions of fatty acids, glycolipids (GL) and phospholipids (PL) in cotyledons of soybean seeds which were germinated either in the dark or the light at 28°C for 8 days. The patterns of changes in lipid composition depended on the germinating conditions tested. In general, non-polar lipids were metabolized at a faster rate than polar lipids. Changes in lipid contents in cotyledons were also observed more clearly with the polar lipids than with the non-polar ones, especially in the light-grown seedlings. The major component of lipid, GL in chloroplasts, appeared rapidly at an earlier stage in the cotyledons of light-grown seedlings. During germination of soybean seeds, acyl sterylglucoside in cotyledons decreased rapidly, but monogalactosyl diglyceride and digalactosyl diglyceride (DGD) increased in the light-grown seedlings, whereas sterylglucoside and DGD increased in the dark-grown seedlings.

The major PL present immediately after immersion were phosphatidyl ethanolamine (PE), phosphatidyl choline (PC) and phosphatidyl inositol (PI). During germination under both conditions, light and dark, PE in cotyledons decreased with PC or PI, while phosphatidic acid increased rapidly, and phosphatidyl glycerol and diphosphatidyl glycerol also increased slightly. These changes in glycolipid and phospholipid compositions during germination seem to occur from the formation of photosynthetic tissues and the metabolic interconversion of phospholipids.     

Phospholipid Composition and Metabolism of Micrococcus denitrificans

The phospholipid composition of Micrococcus denitrificans was unusual in that phosphatidyl choline (PC) was a major phospholipid (30.9%). Other phospholipids were phosphatidyl glycerol (PG, 52.4%), phosphatidyl ethanolamine (PE, 5.8%), an unknown phospholipid (5.3%), cardiolipin (CL, 3.2%), phosphatidyl dimethylethanolamine (PDME, 0.9%), phosphatidyl monomethylethanolamine (PMME, 0.6%), phosphatidyl serine (PS, 0.5%), and phosphatidic acid (0.4%). Kinetics of ³²P incorporation suggested that PC was formed by the successive methylations of PE. Pulse-chase experiments with pulses of ³²P or acetate-1-¹⁴C to exponentially growing cells showed loss of isotopes from PMME, PDME, PS, and CL with biphasic kinetics suggesting the same type of multiple pools of these lipids as proposed in other bacteria. The major phospholipids, PC, PG, and PE, were metabolically stable under these conditions. The fatty acids isolated from the complex lipids were also unusual in being a simple mixture of seven fatty acids with oleic acid representing 86% of the total. Few free fatty acids and no non-extractable fatty acids associated with the cell wall or membrane were found.     

Die Lipide von Endomycopsis vernalis bei verschiedener Stickstoff-Ernährung

1. Endomycopsis vernalis was cultivated on media with different N supply: series A 1%, series B 0,125% asparagine. Sonified cells were extracted and yielded 14.3% (A) and 65.3 (B) total lipids/non lipid dry matter respectively.
2. Neutral and complex lipids were separated by rubber membrane dialysis. There is no difference in the percentage of complex lipids of both series. The increase of lipids in cells grown on low N level is due to a higher content of neutral lipids.
3. Components of the neutral lipids, analysed by DC, were diglycerides, triglycerides, free and esterified ergosterol. Their percentage is influenced by the nutritional conditions. There is a significant increase of triglycerides and of sterol esters in the high lipid cells of series B.
4. Methyl esters of component fatty acids of glycerides and sterol esters were analyzed by GLC. Saturated acids C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, monoenic acids C₁₆ and C₁₈, linoleic and linolenic acids were found to be present. Major acids were in all cases 18:1 (17–57%), 18:2 (18–50%) and 16:0 (10–18%). Linolenic acid is higher in di-and triglycerides of low lipid cells of series A than in high lipid cells of series B. Both qualitative and quantitative differences of fatty acids were found in sterol esters of series A and B respectively.
5. The major components of complex lipids, identified by DC and isolated by CC, in both series, were phosphatidyl choline (A:36.5, B:41.0%) and phosphatidyl ethanolamine (A:24.9, B:20.5%) in addition to small amounts of lysophosphatidyl choline, lysophosphatidyl ethanolamine, phosphatidyl serine, monophosphoinositide, diphosphatidyl glycerol and, possibly cerebroside like substances.
6. Methyl esters of the fatty acids of phosphatidyl choline and ethanolamine from both series were determined by GLC. In all samples 16:0, 18:0, 18:1, 18:2 and 18:3 acids were present besides of traces of 16:1 and 17:0. In contrast to neutral lipids the major acid of phospholipids is linoleic (53–58%), followed by oleic (8–24%) and linolenic acid (1–18%). The percentages of palmitic (4–8%) and stearic acids (tr.-1%) are small. Low lipid cells of series A differ from high lipid cells of series B by an increase of linolenic, and a decrease of linoleic acids, both in phosphatidyl choline and phosphatidyl ethanolamine.

     

Differential effects of unsaturated fatty acids on modulation of endotoxin-induced tissue factor activation in cultured human leukemia U937 cells.

We examined the direct effects of unsaturated fatty acids, oleic (18:1 n-9), linoleic (18:2 n-6), eicosapentaenoic (20:5 n-3) and docosahexaenoic (22:6 n-3) on tissue factor (TF) activity in the human leukemia monocytic U937 cell line. After exposing cells to fatty acids for 16 h, there were no significant effects on either TF activity or its activation induced by bacterial endotoxin (LPS). When the cells were primed with fatty acids for 24 h, 48 h or 72 h, the TF activity remained essentially unchanged. However, the extent of TF-activation induced by LPS depended on the length of priming, and the dose and the degree of unsaturation of the fatty acids to which cells were exposed. After a 72-h priming, 18:1 produced 40-60 per cent elevation in LPS-challenge. In contrast, approximately 20-50 per cent reduction in LPS-challenge was achieved by 18:2, 20:5 and 22:6 at high concentrations. The results suggest that chronic exposure of U937 cells to unsaturated fatty acids leads to modulation of the TF-activation in response to LPS.     

Are polyphosphorylated phospholipids involved in the hormonal control of cholesterol side-chain cleavage activity in tumour Leydig cells?

The possible role of LH or dcAMP induced changes in polyphosphorylated phospholipid metabolism in the regulation of cholesterol side-chain cleavage activity has been studied in tumour Leydig cells. Mitochondria isolated from LH-stimulated Leydig cells were 400% more active in pregnenolone production than mitochondria from control cells. Steroid production in isolated mitochondria from control cells could be stimulated only 25% by cytosol fractions from stimulated cells and 100 microM phosphatidyl inositol-4'-phosphate (PtdIns4P). Other polyphosphorylated phospholipids were either inactive or showed aspecific effects. During a preincubation period tumour cells were labelled with [32P]phosphate and steady-state labelling was obtained for the pholyphosphorylated phospholipids after 40-60 min. [32P]Phosphate incorporation in Ptd Ins4P, phosphatidyl inositol (PtdIns), phosphatidyl choline (PtChl), phosphatidyl ethanolamine (PtdEtn) and cardiolipin (CL) was not affected by treatment of the Leydig cells with LH which stimulated (6-fold), or with cycloheximide which suppressed (4-fold) steroid production. A 25% increase of phosphate incorporation by LH was observed only in phosphatidyl inositol-4',5'-biphosphate (PtdIns4,5P2). 32P Incorporation in PtdIns4,5P2, PtdIns,PtdEtn and CL was stimulated by quinacrine 50 microM. Under these conditions the LH-stimulated pregnenolone production but not the 25-hydroxycholesterol dependent pregnenolone production, was completely inhibited. The results obtained with isolated mitochondria and intact cells indicate that increased levels of polyphosphorylated phospholipids are not consistently correlated with increased mitochondrial pregnenolone production. This argues against an important role of polyphosphorylated phospholipids in the hormonal regulation of cholesterol side-chain cleavage activity in tumour Leydig cells.     

Effect of heat stress on LPS-induced febrile response in D-galactosamine-sensitized rats

We have previously reported that heat conditioning augments lipopolysaccharide (LPS)-induced fever in rats, which is accompanied by an accumulation of heat shock protein (HSP) in the liver and the reduction of the plasma level of tumor necrosis factor (TNF-alpha) (Kluger MJ, Rudolph K, Soszynski D, Conn CA, Leon LR, Kozak W, Wallen ES, and Moseley PL. Am J Physiol Regulatory Integrative Comp Physiol 273: R858-R863, 1997). In the present study we have tested whether inhibition of protein synthesis in the liver can reduce the effect of this heat conditioning on the LPS-induced febrile response in the rat. D-galactosamine (D-gal) was used to selectively inhibit liver protein synthesis. D-gal (500 mg/kg) or PBS as control was administered intraperitoneally 1 h before heat stress. LPS (50 microg/kg ip) was injected 24 h post-heat exposure. Treatment with D-gal blunted the febrile response to LPS. Moreover, heat-conditioned rats treated first with D-gal and subsequently with LPS demonstrated a profound fall in core temperature 10--18 h post-LPS. A significant increase of serum TNF-alpha accompanied this effect of D-gal on fever. Heat-conditioned animals receiving D-gal showed an inhibition in inducible HSP-70 in the liver. These data support the role of hepatic function in modulating the febrile response to LPS.     

Lipopolysaccharide induces functional ICAM-1 expression in rat alveolar epithelial cells in vitro

Lipopolysaccharide (LPS)-induced lung inflammation is known to increase pulmonary intercellular adhesion molecule-1 (ICAM-1) expression. In the present study, L2 cells, a cell line of alveolar epithelial cells, were stimulated with LPS, and ICAM-1 expression was studied. ICAM-1 protein on L2 cells peaked at 6 (38% increase; P < 0.01) and 10 (48% increase; P < 0.001) h after stimulation with Escherichia coli and Pseudomonas aeruginosa LPS, respectively. ICAM-1 mRNA expression was markedly increased, with a peak at 2-4 (E. coli) and 4-6 (P. aeruginosa) h. Adherence assays of neutrophils to LPS-stimulated L2 cells showed a threefold increase in adherence (P < 0.001). Pretreatment of the neutrophils with anti-lymphocyte function-associated antigen-1 and anti-Mac-1 antibodies reduced adherence by 54% (P < 0.001). Analysis of immunofluorescence staining for ICAM-1 showed an exclusive apical expression of ICAM-1. These results indicate that LPS upregulates functional active ICAM-1 on the apical part of the membrane in rat pneumocytes.     

Lipids of Chlamydomonas reinhardi under different growth conditions

Photo-, mixo- and heterotrophically grown cultures of Chlamydomonas reinhardi (wild type ss and 2 streptomycin-resistant mutants sr₃ and sr₃₅) have been analyzed for lipids and fatty acids. Ether-soluble lipids, chlorophyll, monogalactosyl diglyceride, digalactosyl diglyceride, sulfolipid, phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl glycerol and the relative amounts of fatty acids in total and individual lipids have been determined. The lipid and fatty acid compositions are very similar in the 3 strains and are not affected by the mutations. Fatty acids belong exclusively to the C₁₆ and C₁₈ series, 16:0, 16:4, 18:1, 18:2, 18:3 (6,9,12) and 18:3 (9,12,15) comprising about 90% of the total. 18:3 (6,9,12) is concentrated in phosphatidyl ethanolamine. In streptomycin-bleached sr₃ cells, ether-soluble lipids increase from 7 to 11% of dry weight on greening, mostly due to synthesis of monogalactosyl diglyceride and chlorophyll. Monogalactosyl diglyceride of bleached cells exhibits the same fatty acid pattern before and after greening.     

Two unusual glycerophospholipids from a filamentous fungus, Absidia corymbifera

The chloroform-methanol extractable lipids of the soil filamentous fungus Absidia corymbifera VKMF-965 account for about 20% by weight of dry cells and are composed of low-polarity constituents (about 75% of the total lipids), such as triacylglycerols (mainly), diacylglycerols, sterols and free fatty acids, as well as of glycolipids (about 3%) and phospholipids. The last consist largely of components common to the fungal lipids, namely, phosphatidylethanolamine (38% of the total phospholipids), phosphatidyl-myo-inositol (16%), diphosphatidylglycerol (12%), phosphatidylcholine (7%), phosphatidic acid (6%) and phosphatidylglycerol (3%), and two unusual phospholipids, PL1 (6%) and PL2 (9%). Based on the infrared (IR), (1)H-nuclear magnetic resonance (NMR), (13)C-NMR and mass spectra along with the results of degradation experiment, these two phospholipids have been established to be 1,2-diacyl-sn-glycero-3-phospho(N-acetylethanolamine), or N-acetyl phosphatidylethanolamine, and 1,2-diacyl-sn-glycero-3-phospho(N-ethoxycarbonyl-ethanolamine), respectively. These structures have been confirmed by preparing similar phospholipids from the phosphatidylethanolamine isolated from the same fungus and correlating their chromatographic behaviour, IR and (1)H-NMR spectra with those of PL1 and PL2. So far N-acetyl phosphatidylethanolamine has been detected only in cattle and human brains and a human placenta but its structure was not rigorously proved. PL2 is a novel lipid; to our knowledge no natural phospholipid with an urethane group has yet been found. The main fatty acids of both the phospholipids are n-hexadecanoic, octadecanoic and octadecadienoic ones; PL2 contains in addition a considerable amount of octadecatrienoic acid with its greater portion located at the sn-1 position.     

Effect of fatty acid supplementation on thermotropic behavior of membrane lipids and leucine transport in Saccharomyces cerevisiae

An unsaturated fatty acid-requiring mutant (KD 115) of Saccharomyces cerevisiae shows altered phospholipid composition, transport behavior, and physical properties of membrane lipids when grown in the presence of different cis- and trans-unsaturated fatty acids. There is an increase in phosphatidyl ethanolamine content and a concomitant decrease in phosphatidyl choline content in the cells supplemented with trans-unsaturated fatty acids. The affinity for uptake of L-leucine is higher in the cis-unsaturated fatty acid-supplemented cells compared with the trans-unsaturated fatty acid-supplemented cells. The temperature-dependence of L-leucine uptake bears a reasonably good correlation with the thermotropic behavior of the membrane lipids as studied by the steady-state fluorescence polarization technique. The present findings are discussed in light of the importance of the lipid environment in modulating membrane-associated functions.     

Changes in the ascorbic acid levels of peritoneal lymphocytes and macrophages of mice with endotoxin-induced oxidative stress.

Ascorbic acid (AA) is an important cytoplasmic antioxidant that mice synthesize in the liver, the intracellular levels of which decrease in an oxidative stress situation such as endotoxic shock. The present work deals with the changes in AA levels, that modulate the immune function, in the two main immune cells, namely macrophages and lymphocytes, from female BALB/c mice suffering endotoxic shock caused by intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS) (100 mg/kg). The intake by cells of this antioxidant present in vitro at different concentrations was also studied. The animals show an oxidative stress, standardized in previous studies, that causes mortality at 30 h after LPS injection. The cells were obtained from the peritoneum at 2, 4, 12 and 24 h after LPS or PBS (control) injections and were incubated without or with AA at 0.01, 0.1 and 1 mM for 10, 30, 60, 120 or 180 min. The hepatic AA levels were also studied at 0, 2, 4, 12 and 24 h after LPS injection. The peritoneal cells obtained from animals injected with LPS showed increased AA levels in relation to the control cells at all times after LPS injection, with maximal effect at 12h. The AA levels decreased after this time, in agreement with changes in the AA hepatic levels. The increase was due to the AA of lymphocytes since macrophages showed a decrease in AA at different times after LPS injection. Both cells showed an increase in the intracellular levels of AA when this antioxidant was added in vitro. This takes place mainly at 30-60 min of incubation in cells from controls and at 10 min in cells from treated mice 12-24 h after LPS injection. The incorporation decreased at these times of endotoxic shock, a few hours before death. In all cases AA levels were higher in lymphocytes than in macrophages, and 1 mM was the most effective concentration. These results suggest that the immune cells need appropriate levels of antioxidants, such as AA, under oxidative stress conditions, and that while lymphocytes take and accumulate AA, macrophages use it.     

Lipid utilization in adult Pieris brassicae with special reference to the rôle of linolenic acid

Fatty acids of adult Pieris brassicae and the incorporation of dietary linolenic acid-1-¹⁴C into adult (and egg) lipids were analysed 1 and 9 days after ecdysis. Females grown on a leaf diet retained palmitic, palmitoleic, and oleic acids but lost linoleic and linolenic acids during adult life, while males utilized their fatty acids more evenly. On an artificial diet both sexes retained palmitic acid but utilized palmitoleic and oleic acids. In both cases females laid eggs with a high palmitic and oleic acid content.Analysis of thorax flight muscles (artificial diet) revealed that 67·9% of the lipids in 1-day females and 83·6% in 9-day females was phospholipid (PL). During adult life linolenic acid increased in thorax neutral lipids (NL) from 14·6 to 20·0% in females and from 18·5 to 30·0% in males. Males incorporated more linolenic acid-1-¹⁴C especially in fat body and flight muscle PL than females. The majority of this was recovered from phosphatidyl cholines (PTC) in 1-day adults whereas in 9-day adults phosphatidyl ethanolamines (PTE) and another compound, most likely cardiolipin, contained more label (29·0% in PTC, 33·1% in PTE, 34·9% in cardiolipin, and 2·0% in sphingomyelin in the thorax of females). The females also incorporated the label into egg lipids (42·2% in PL, 57·8% in NL). There was recovered from PTC 54·5% of the label in egg PL.Most of the label in thorax NL was found to be in free fatty acids (FFA). The label disappeared from triglycerides during adult life and tended to accumulate in FFA (82·7% in 9-day females) while in diglycerides the label did not vary during adult life (17·2% in 9-day post-emergence females). PTC apparently is a fairly labile PL type which is utilized in muscle whereas PTE and cardiolipin may be more structural in function and accumulated more label from linolenic acid with increasing adult age. Linolenic acid, then, essentially is a structural fatty acid and its rôle appears to be mainly in the structures of flight muscle membranes and organelles.