Total Cell Lipids Research Articles

A novel lipopeptide, an inhibitor of bacterial adhesion, from the thermophilic and halotolerant subsurface Bacillus licheniformis strain 603

A new Bacillus licheniformis strain, 603, isolated from a mixture of drilling fluid and subsurface thermal water, has been found to produce a cyclic lipopeptide which is released into cultural medium as well as present in cells as the major lipid constituent (57% of the total cell lipids extractable with 2:1 chloroform–methanol). The quantitative ratio of the extracellular and intracellular lipopeptide has been estimated as 23:10. The metabolite represents a heptapeptide, l-Asp→ l-Leu→ l-Leu→ l-Val→ l-Val→ l-Glu→ l-Leu, N-acylated to the N-terminal amino acid, l-Asp, by a 3-hydroxy fatty acid (from 13:0 to 17:0 with n-, iso-, and anteiso-chains), the 3-OH group of which is esterified by the C-terminal amino acid, l-Leu. The chemical structure of the lipopeptide has been established by means of infrared (IR), 1H- and 13C-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionisation (ESI) mass spectrometry (MS), including secondary ion mass spectrometry, along with chemical and enzymatic degradation. Although a diversity of similar metabolites synthesised by various B. licheniformis strains are presently known, such a structure has not been reported thus far. Added to the growth medium of strain 603 at the concentration of 1.6 μg/ml, the lipopeptide prevents adhesion of cells to a glass surface. Also, it exhibits a considerable growth-inhibiting activity against Corynebacterium variabilis and a much lower activity against Acinetobacter sp.

Quantitative ultrastructural changes of hepatocyte constituents in euthermic, hibernating and arousing dormice ( Muscardinus avellanarius)

Hibernating animals represent a suitable model for investigating the structural effects of drastic changes in cell activity under physiological conditions. In this study we investigated by means of electron microscopy and morphometrical analysis the fine structural counterpart of functional rest in hepatocytes of the hibernating dormouse, Muscardinus avellanarius, in comparison with arousing and euthermic dormice. Our observations demonstrate that during hibernation several structural constituents of the hepatocyte undergo modifications. In particular, during deep hibernation, the total cell and cytoplasm area significantly reduced, as well as the total and percent glycogen and residual body area, and the Golgi apparatus almost disappeared. Upon arousal, the amount of glycogen was minimal, whereas total cell and cytoplasm area significantly increased towards the euthermic value as well as total and percent residual body area. In comparison with the euthermic condition, the total and percent cell lipid area significantly increased in early hibernation, reduced in deep hibernation and almost disappeared during arousal. Taken together, our findings give quantitative ultrastructural support to the marked reduction found in hepatocyte functional activities during hibernation. Such a reduced activity involves profound rearrangement of the euthermic cell structure, which is rapidly resumed upon arousal.

Carbon isotope variability in monosaccharides and lipids of aquatic algae and terrestrial plants

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 232:83-92 (2002) - doi:10.3354/meps232083 Carbon isotope variability in monosaccharides and lipids of aquatic algae and terrestrial plants Bart E. van Dongen*, Stefan Schouten, Jaap S. Sinninghe Damsté Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands *E-mail: dongen@nioz.nl ABSTRACT: The stable carbon-isotope compositions of individual monosaccharides and lipids, as well as the bulk stable carbon-isotope composition of total cell material from different aquatic and terrestrial plants were determined. With the exception of a Phaeocystis sp. bloom sample, monosaccharides were generally enriched in 13C by 0 to 9” compared to the total cell material and significantly enriched (1 to 16”) in 13C compared to lipids (fatty acids, phytol, sterols and alkenones) within single organisms. The depletion of 13C in n-alkyl lipids relative to monosaccharides was larger than the depletion of 13C in isoprenoid lipids relative to monosaccharides. In addition, an isotopic enrichment was observed in the 13C content of C5 monosaccharides compared to glucose in some of the organisms studied, indicating isotopic heterogeneity within carbohydrates. The magnitude of the differences between monosaccharides, total cell material and lipids was far greater than previously reported. Thus, selective assimilation of ingested carbohydrates can lead to isotopic enrichments of heterotrophic biomass and zooplankton and subsequent trophic levels. In addition, since dissolved organic carbon (DOC) and particulate organic carbon (POC) has a significant carbohydrate fraction, the δ13CPOC and δ13CDOC signal will be significantly influenced by the relative amounts and the δ13C values of the carbohydrates present. This has significant implications for the isotopic integrity of the organic matter fractions during carbon cycling in food chains of aquatic ecosystems. KEY WORDS: Carbohydrates · 13C · Stable carbon isotope · Food web · Lipids · Aquatic · Terrestrial Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 232. Online publication date: May 03, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Quantified increases of cholesterol, total lipid and globotriaosylceramide in filipin-positive Niemann-Pick type C fibroblasts

Background: Niemann-Pick disease type C (NPC) is a neurovisceral lysosomal lipidosis caused in most cases by mutations in the NPC1 gene that codes for the cholesterol regulating NPC1 protein. Methods: Cultured skin fibroblasts from 11 NPC patients aged 0.25 to 34 years at diagnosis with different severity of neurologic and visceral involvement, diagnosed by the cytochemical filipin test for lysosomally stored cholesterol, were analyzed for lipid composition. Cholesterol and other lipids were separated on thin-layer chromatography from fibroblast total lipid extracts, quantified by densitometry and compared with the total cell lipid mass. Results: Cholesterol concentration in the patient cells was 1.5 to 5-fold higher than normal and total lipids up to 2.4-fold normal. Cholesterol and total lipids were particularly high in cells from NPC patients aged less than about 6 years, and for the whole patient series the abundance of fibroblast cholesterol was correlated with the tentatively assessed clinical disease severity. The findings in NPC suggested that NPC1 protein has a role not only in the balance of cholesterol but also the distribution of the total cell lipid mass. Another increase found in the NPC cells was that of a minor lipid fraction, globotriaosylceramide (Gb3, known as a cell signalling glycolipid). Gb3, in the average of its very variable individual concentrations, was about 2.5-fold higher in the NPC cell group as compared to normal or pathologic control group, but there was no correlation of Gb3 with the other lipid concentrations studied. Conclusions: For NPC diagnosis, the fibroblast cholesterol and total lipid quantification can be used as an alternative to the usual filipin test for lysosomal cholesterol, but both test methods are prone to equivocal results in cells from a small fraction of atypical NPC patients, where chemical testing in organ biopsies or mutational analysis of the NPC1 gene should be tried.

Effects of zinc on lipids of erythrocytes from carp (Cyprinus carpio L.) acclimated to different temperatures.

We compared the effect of zinc (0.01, 0.1, 0.5 and 1 mM) at two temperatures (5 and 20 degrees C) on erythrocytes from summer and winter acclimatised carp. An increase in temperature from 5 to 20 degrees C increased the unsaturation index (UI) and relative proportion (UI/SFA) of unsaturated to saturated fatty acids in total lipids of the red cells. At 5 degrees C, the unsaturation index of phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) decreased (30-40%) in the presence of 1 mM zinc. The change in unsaturation of phospholipids in the presence of zinc at 5 degrees C is probably responsible for the alteration in structural integrity of erythrocyte membrane as observed by hemolysis and the decreased thiol group content in the erythrocytes. In light of this result, zinc may be considered an environmental hazard for these fish at low temperatures.

Impact of Early Dietary Intake and Blood Lipid Composition of Long‐Chain Polyunsaturated Fatty Acids on Later Visual Development

ABSTRACTBackgroundIn contrast to human milk, current infant formulas in the United States do not contain ω3 and ω6 long‐chain polyunsaturated fatty acids. This may lead to suboptimal blood lipid fatty acid profiles and to a measurable diminution of visual function in developing term infants. The need for docosahexaenoic acid and arachidonic acid supplementation in the infant diet was evaluated in a double‐blind, randomized clinical trial.MethodsHealthy term infants were randomized to diets of (1) commercial formula, (2) docosahexaenoic acid–enriched formula (0.35% of total fatty acids), or (3) docosahexaenoic acid– (0.36%) and arachidonic acid– (0.72%) enriched formula. Eighty‐seven infants completed the 17‐week nutritional trial, and 58 were observed until 52 weeks of life. A reference group was exclusively breast fed for at least 17 weeks (n = 29). Outcome measures included electroretinographic responses, visual evoked potentials, and blood fatty acid analysis in infants at birth and at 6, 17, and 52 weeks of age.ResultsCommercial formula‐fed infants had 30% to 50% lower content of docosahexaenoic acid in total red blood cell lipids during the 17‐week feeding trial compared with breast‐fed infants. Significant differences persisted at the 1‐year follow‐up. Arachidonic acid content was consistently reduced in the commercial formula group by 15% to 20%. Infants fed long‐chain polyunsaturated fatty acid–enriched formulas had docosahexaenoic acid and arachidonic acid blood lipid profiles resembling those of human milk‐fed infants. Infants receiving this enriched formula had more mature electroretinographic responses than commercial formula‐fed infants at 6 weeks of age. Human milk‐fed and docosahexaenoic acid‐enriched formula‐fed infants had better visual acuity than commercial formula‐fed infants at both 17 and 52 weeks of age. Early (17‐week) fatty acid profiles in blood lipids were correlated with later (52‐week) visual function development in study infants.ConclusionsResults from this clinical trial demonstrate that long‐chain polyunsaturated fatty acid supplementation of formula in term infants produces blood lipid fatty acid profiles that are similar to those observed in breast‐fed infants. This supplementation leads to better visual function later in life (i.e., 1 year of age) than that shown by infants fed commercial formula.

Effect of cell lipid composition on the formation of nonspecific antibiotic resistance in alkanotrophic rhodococci

The antibiotic resistance and lipid composition of rhodococci grown in rich organic media with gaseous or liquidn-alkanes were studied. Hydrocarbon-grown rhodococci exhibited an increased resistance to a wide range of antibiotics (aminoglycosides, linkosamides, macrolides, β-lactams, and aromatic compounds). The enhanced antibiotic resistance of rhodococci grown onn-alkanes correlated with an increased content of total cell lipids (up to 14–28%) and saturated straight-chain fatty acids (C16:0, C18:0, C21:0) and was accompanied by the appearance of cardiolipin and phosphatidylglycerol in cells. These lipid compounds are supposed to promote the formation of nonspecific antibiotic resistance in rhodococci by decreasing the permeability of their cell envelope to antibiotics.

Effect of Growth Phase on the Content and Composition of Ceramides of the Hydrocarbon-assimilating Yeast Candida lipolytica

Candida lipolytica yeast was grown batchwise on n-hexadecane as the carbon and energy source. Ceramides were quantitatively isolated from total lipids of exponential and stationary phase cells by a combination of column chromatography and preparative high-performance thin-layer chromatography. After acid methanolysis their composition was analyzed by gas-liquid chromatography. The ceramide content of the exponential phase cells was two times higher than the one of the stationary phase cells. The composition of long-chain base moiety of ceramides did not change significantly during the growth. In both growth phases 19-phytosphingosine was the major long-chain base. However, the fatty acid composition of ceramides changed greatly during the growth. In the exponential growth phase, ceramides contained predominantly fatty acids greater than 20 carbon atoms, while fatty acids shorter than 20 atoms predominated in ceramides of the stationary phase, 16:0 being the main one. In the exponential growth phase fatty acid moiety of ceramides was characterized by unusually high degree of unsaturation and relatively high proportion of odd-numbered fatty acids. However, the proportion of both, unsaturated and odd-numbered fatty acid decreased significantly in ceramides of the stationary phase. The unexpected finding was the absence of fatty acid hydroxylation of ceramides in the exponential phase cells and unusually low degree of hydroxylation in the stationary phase.

Quantitative analysis of phospholipids in functionally important membrane domains from RBL-2H3 mast cells using tandem high-resolution mass spectrometry.

We recently showed that ligand-mediated cross-linking of FcepsilonRI, the high-affinity receptor for immunoglobulin E, on RBL-2H3 mast cells results in its co-isolation with detergent-resistant membranes (DRM) and its consequent tyrosine phosphorylation by the co-localized tyrosine kinase Lyn that is a critical early event in signaling by this receptor [Field et al. (1997) J. Biol. Chem. 272, 4276-4280]. As part of efforts to determine the structural bases for these interactions, we examined the phospholipid composition of DRM vesicles isolated from RBL-2H3 cells under conditions that preserve FcepsilonRI association. We used positive and negative mode electrospray Fourier transform ion cyclotron resonance mass spectrometry to compare quantitatively the phospholipid composition of isolated DRM to that of total cell lipids and to a plasma membrane preparation. From these analyses, over 90 different phospholipid species were spectrally resolved and unambiguously identified; more than two-thirds of these were determined with a precision of +/-0.5% (absolute) or less. Quantitative characterization of lipid profiles shows that isolated DRM are substantially enriched in sphingomyelin and in glycerophospholipids with a higher degree of saturation as compared to total cellular lipids. Plasma membrane vesicles isolated from RBL-2H3 cells by chemically induced blebbing exhibit a degree of phospholipid saturation that is intermediate between DRM and total cellular lipids, and significant differences in the headgroup distribution between DRM and plasma membranes vesicles are observed. DRM from cells with cross-linked FcepsilonRI exhibit a larger ratio of polyunsaturated to saturated and monounsaturated phospholipids than those from unstimulated cells. Our results support and strengthen results from previous studies suggesting that DRM have a lipid composition that promotes liquid-ordered structure. Furthermore, they demonstrate the potential of mass spectrometry for examining the role of membrane structure in receptor signaling and other cellular processes.

Oleic acid inhibits endothelial activation : A direct vascular antiatherogenic mechanism of a nutritional component in the mediterranean diet.

Because oleic acid is implicated in the antiatherogenic effects attributed to the Mediterranean diet, we investigated whether this fatty acid can modulate endothelial activation, ie, the concerted expression of gene products involved in leukocyte recruitment and early atherogenesis. We incubated sodium oleate with human umbilical vein endothelial cells for 0 to 72 hours, followed by coincubation of oleate with human recombinant tumor necrosis factor, interleukin (IL)-1alpha, IL-1beta, IL-4, Escherichia coli lipopolysaccharide (LPS), or phorbol 12-myristate 13-acetate for a further 6 to 24 hours. The endothelial expression of vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and intercellular adhesion molecule-1 was monitored by cell surface enzyme immunoassays or flow cytometry, and steady-state levels of VCAM-1 mRNA were assessed by Northern blot analysis. At 10 to 100 micromol/L for >24 hours, oleate inhibited the expression of all adhesion molecules tested. After a 72-hour incubation with oleate and a further 16-hour incubation with oleate plus 1 microg/mL LPS, VCAM-1 expression was reduced by >40% compared with control. Adhesion of monocytoid U937 cells to LPS-treated endothelial cells was reduced concomitantly. Oleate also produced a quantitatively similar reduction of VCAM-1 mRNA levels on Northern blot analysis and inhibited nuclear factor-kappaB activation on electrophoretic mobility shift assays. Incubation of endothelial cells with oleate for 72 hours decreased the relative proportions of saturated (palmitic and stearic) acids in total cell lipids and increased the proportions of oleate in total cell lipids without significantly changing the relative proportions of polyunsaturated fatty acids. Although less potent than polyunsaturated fatty acids in inhibiting endothelial activation, oleic acid may contribute to the prevention of atherogenesis through selective displacement of saturated fatty acids in cell membrane phospholipids and a consequent modulation of gene expression for molecules involved in monocyte recruitment.

The influence of carbon source on the level and composition of ceramides of the Candida lipolytica yeast.

Candida lipolytica yeast was grown batchwise on two different carbon sources, glucose and n-hexadecane. Free ceramides were quantitatively isolated from sphingolipid fractions of total lipids by a combination of column chromatography and preparative thin-layer chromatography. Their composition, after acid methanolysis, was analysed by gas-liquid chromatography. The ceramide content accounted for 2.6% of the total cell lipids in hexadecane-grown cells, which was 1.5 times higher than in glucose-grown cells. The fatty acid composition of ceramides was characterized by the predominance of fatty acids shorter than 20 carbon atoms and by high concentrations of fatty acids with 16 carbon atoms after growth on both carbon sources. The dominant fatty acid was hydroxylated 16:0 in the glucose-grown cells and 16:0 in the hexadecane-grown cells. The striking finding was the low degree of fatty acid hydroxylation and relatively high proportion of odd-numbered fatty acids in ceramide of the n-hexadecane-grown cells. The ceramides contained an unusual long-chain base composition. In hexadecane-grown cells more than 60% of the long-chain bases were C19 phytosphingosine. In glucose-grown cells more than one-half of the total long-chain bases were tetrahydroxy bases, 4,5-dihydroxysphinganine and 4,5-dihydroxyeicosasphinganine.

In vitro metabolism of 14C-polyunsaturated fatty acids in midgut gland and ovary cells from Penaeus kerathurus Forskâl at the beginning of sexual maturation

The incorporation and metabolism via the desaturase/elongase pathway of [1- 14C]18:2(n-6) linoleic acid (LA), [1- 14C]18:3(n-3) linolenic acid (LNA), [1- 14C]20:4(n-6) arachidonic acid (AA) and [1- 14C]20: 5(n-3) eicosapentaenoic acid (EPA) were studied in midgut gland and ovary cell suspensions from wild-caught adult females of Penaeus kerathurus Forskål at the beginning of sexual maturation. The incorporation and recovery of radioactivity in total lipids of midgut gland cells was greater for [1- 14C]LA and [1- 14C]LNA than for [1- 14C]AA or [1- 14C]EPA, indicating a preferential retention of C 18-polyunsaturated fatty acids (PUFAs) in this organ. The recovery of radioactivity from all PUFA decreased during the time course. The incorporation of [1- 14C]PUFAs into total polar lipids in midgut gland cells increased during the time course (from 33.4% to 65.2%) with a concomitant decrease into total neutral lipids. These changes were due to significantly increased incorporation into phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), with significantly decreased incorporation into triacylglycerol (TAG). [1- 14C]AA and [1- 14C]EPA were preferentially incorporated into PI, and [1- 14C]EPA was more important in phospholipid synthesis in midgut gland cells than [1- 14C]-labeled LA, LNA or AA. The incorporation and recovery of radioactivity in total lipids from ovary cells was significantly lower than in midgut gland cells but significantly increased during the time course with all the [1- 14C]PUFAs. The distribution of radioactivity from [1- 14C]AA and [1- 14C]EPA in ovary cells showed preferential retention into polar lipid classes compared with [1- 14C]LA or [1- 14C]LNA, and the general pattern was of net synthesis of PC at the expense of PE, free fatty acid and TAG. The results indicated that midgut gland and ovary cells have only a limited ability to convert C 18-PUFA to C 20- and C 22-highly unsaturated fatty acid. The recovery of radioactivity in 22:6(n-3) was ∼10-fold greater with [1- 14C]EPA than with [1- 14C]LNA as precursor. Substantial amounts of radioactivity were recovered in 24:5(n-6), 24:5(n-3) and 24:6(n-3), particularly in cells incubated with [1- 14C]EPA, indicating that the conversion of EPA to DHA in both organs may occur by a pathway using Δ 6-desaturase activity rather than by a Δ 4-desaturation

The pel1 mutant of Saccharomyces cerevisiae is deficient in cardiolipin and does not survive the disruption of the CHO1 gene encoding phosphatidylserine synthase

Cells of the pel1 mutant of Saccharomyces cerevisiae were found to contain an extremely low content of cardiolipin, a decreased level of phosphatidylcholine and an increased level of phosphatidylinositol. Disruption of the PEL1 gene in cells containing a null mutation in the CHO1 gene was lethal. Despite its putative functional homology with CHO1, the overexpression of the PEL1 gene in the chol null mutant did not restore the wild-type properties of the transformed cells and failed to stimulate the incorporation of l-[3- 3H]serine into total lipids of the intact yeast cells.

The pel1 mutant of Saccharomyces cerevisiae is deficient in cardiolipin and does not survive the disruption of the CHO1 gene encoding phosphatidylserine synthase.

Cells of the pel1 mutant of Saccharomyces cerevisiae were found to contain an extremely low content of cardiolipin, a decreased level of phosphatidylcholine and an increased level of phosphatidylinositol. Disruption of the PEL1 gene in cells containing a null mutation in the CHO1 gene was lethal. Despite its putative functional homology with CHO1, the overexpression of the PEL1 gene in the cho1 null mutant did not restore the wild-type properties of the transformed cells and failed to stimulate the incorporation of L-[3-3H]serine into total lipids of the intact yeast cells.

Regulatory effect of various steroid hormones on the incorporation and metabolism of [14C]stearate in rat hepatoma cells in culture.

We have examined the incorporation and metabolism of [14C] stearic acid within the total lipids of HTC rat-hepatoma cells in suspension culture in presence and in absence of steroidal hormone stimulation. Both, glucocorticoids (dexamethasone, cortisol and corticosterone) and mineralocorticoids (deoxycorticosterone and aldosterone) as well as the estrogen beta-estradiol and the androgen testosterone enhanced the extent of delta 9 desaturation to oleic acid of the saturated precursors, whereas only the two mineralocorticoids affected the incorporation rate of the exogenous acid into total cellular lipids, thus promoting a little stimulation. Furthermore, all the hormones tested increased the radiolabelling of the total cellular phospholipids except deoxycorticosterone and testosterone, the former having no effect and the latter exerting a moderate inhibition. On the other hand, the incorporation of 14C into neutral lipids was stimulated by testosterone, in contrast to the inhibition of this parameter observed exclusively with either the mineralocorticoids or the estrogen. Within the phospholipid subclasses, the radiolabelling of phosphatidylcholine was augmented by means of all the steroids tested save deoxycorticosterone and testosterone, whereas phosphatidylethanolamine exhibited a decrease only in the presence of testosterone. In a similar fashion, within the neutral lipids, the predominating triglyceride fraction was preferentially labelled--at the expense of other subclasses of lesser abundance--upon treatment with the steroids except aldosterone, which exerted no effect. The results obtained were correlated with those changes observed in the mass distribution of the different lipid subclasses either with or without prior hormonal stimulation.

Factors affecting the normal and branched-chain acyl moieties of teicoplanin components produced by Actinoplanes teichomyceticus

Teicoplanin, a glycopeptide antibiotic produced by Actinoplanes teichomyceticus, comprises five main components, denoted T-A2-1 to T-A2-5, differing in the structure of their acyl side chain, which is linear in T-A2-1 and T-A2-3 and branched in the other components. Production of T-A2-1, characterized by a linear C10:1 acyl moiety, is entirely dependent on the presence of linoleate in the fermentation medium. Addition to the medium of oleic acid esters at 2 g l-1 increases the yields of T-A2-3, characterized by a linear C10:0 acyl chain, about threefold. The antibiotic linear side chains thus appear to originate from C18 unsaturated acid by beta-oxidation degradation. The percentage of T-A2-2, T-A2-4 and T-A2-5, bearing the iso-C10:0, anteiso-C11:0 and iso-C11:0 acyl moieties, respectively, is strongly influenced by the presence in the medium of the amino acids known to be precursors of branched-chain fatty acids. Thus, valine increases the production of T-A2-2 whereas isoleucine or leucine increase the relative yields of T-A2-4 or T-A2-5, respectively. Analysis of the total cell lipids upon addition of the same amino acid shows corresponding increases in the proportion of the iso-C16:0, iso-C15:0 or anteiso-C17:0. A mutant A. teichomyceticus strain, which produces a novel teicoplanin with a linear C9:0 chain, differs from the wild strain in the presence of the linear C17:1 acid in its lipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriohopanetetrol: Abundant Lipid in Frankia Cells and in Nitrogen-Fixing Nodule Tissue

An unusual class of lipid with amphiphilic properties has been detected in nodule tissue of Alnus and Ceanothus. High levels of the same lipid (20-50% of total cell lipids) were detected in solvent extracts of Frankia spp. cells. However, the lipid was absent in host roots. The lipid was purified and quantified by high-performance liquid chromatography/flame ionization detector. Phenol-sulfuric acid determinations and proton nuclear magnetic resonance indicated that the purified lipid is not a glycolipid. Mass spectra of the predominant species are consistent with published spectra for bacteriohopanetetrol (C(35)H(62)O(4)), a pentacyclic triterpenoid, or hopanoid.

Characterization of lipid composition in stimulated human lymphocytes by 1H-NMR

Recent in vivo NMR studies have raised interest in the structural changes of cellular lipids during proliferative activity. We investigated the changes in plasma membrane lipid and total cell lipid during mitogenically-stimulated proliferation of human peripheral blood lymphocytes by extraction of lipids and assay by 500 MHz 1H-NMR. Resonances were assigned using one- and two-dimensional spectroscopic techniques, and signals unique to certain species of lipid were identified. Choline and ethanolamine-containing lipids, glycerophospholipid backbones, sphingolipids, cholesterol, plasmalogens and triacylglycerols were readily detected. Resolution of a number of lipid species was not possible, despite the use of high-resolution techniques. NMR values for proliferation-induced changes in the most easily determined parameters, namely the total cholesterol to total phospholipid molar ratio, and phosphatidylcholine, phosphatidylethanolamine and sphingolipid composition, were found to agree with traditional methods. Differences in phospholipid and fatty acid profiles were found between plasma membranes and total cell lipid for resting values and for response to mitogen.

Effect of salinity on the lipid and fatty acid composition of the halophyteNavicula sp.: potential in mariculture

Navicula sp. (cf.N. tenelloides) was isolated from a salt marsh in Kuwait. The alga grew best with 0.5M NaCl, but abundant growth still occurred up to 2.5M NaCl. The total lipid content and the carotene to chlorophyll ratio of the cells increased with increasing salinity of the medium from 0.5 to 1.7M NaCl, but declined with 2.5M NaCl. Irrespective of the medium salinity, the major lipid class was that of triacylglycerols. The predominant fatty acids in the total lipids of cells grown at different NaCl concentrations were palmitic (16:0) and palmitoleic (16:1) acids; eicosapentaenoic acid (20:5) made up 8–9% of the total fatty acids. The fatty acid composition of the individual lipid classes of cells grown at different salinities is described. The highest concentration of 20:5 occurred in monogalactosyldiacylglycerols and digalactosyldiacylglycerols. In view of the rather small size of this diatom, its halotolerance and its fair content of 20:5, it is suggested as a potential food source for the mariculture industry.

Pregnancy duration and the ratio of long-chain n-3 fatty acids to arachidonic acid in erythrocytes from Faroese women.

Dietary long-chain n-3 fatty acids (FA) may prolong gestation by inhibiting formation of prostaglandins from arachidonic acid. FA were quantified in phosphatidylcholine (PC), phosphatidylethanolamine (PE), and total lipids (TL) of red cells sampled during pregnancy from 29 Faroese women. The ratio of long-chain n-3 FA to arachidonic acid (the (3/6) ratio) was used as the most relevant single measure of exposure. In 18 women with certain gestational age and with spontaneous onset of delivery, gestational age was significantly associated with the (3/6) ratio quantified in PC (correlation coefficient 0.50, P = 0.035), but not with the (3/6) ratio in PE (correlation coefficient 0.21, P = 0.40) or TL (correlation coefficient 0.29, P = 0.26). The association with the (3/6) ratio in PC could not be attributed to confounding by maternal age, weight, marital status or smoking.