Phosphatidyldimethylethanolamine Research Articles

Metabolomic Profiling of Blood Plasma in Females with Hyperplasia and Endometrial Cancer.

Uterine cancer is the most prevalent gynecologic malignancy in women worldwide. Endometrial cancer (EC) has an 81% five-year survival rate, depending on disease stage and time of diagnosis. While endometrial cancer is largely treatable when detected early, no established screening techniques are available in clinical practice. As a result, one of the most significant issues in the medical field is the development of novel ways for early cancer identification, which could boost treatment success rates. Liquid chromatography-high-resolution mass spectrometry (LC-HRMS)-based metabolomics was employed to explore the metabolomic markers and pathways unique to this cancer type and link them to the benign endometrial hyperplasia that may progress to cancer in 5% to 25% of patients. The study involved 59 postmenopausal participants, 20 with EC type 1, 20 with benign hyperplasia, and 19 healthy participants. Metabolite distribution changes were analyzed, and 338 of these features were dysregulated and significant. The first two main components, PC1 and PC2, were responsible for 11.5% and 12.2% of the total metabolites, respectively. Compared with the control group (CO), EC samples had 203 differentially expressed metabolites (180 upregulated and 23 downregulated); in hyperplasia (HP), 157 metabolites were dysregulated (127 upregulated and 30 downregulated) compared to the CO group while 21 metabolites exhibited differential regulation (16 upregulated and 5 downregulated) in EC plasma samples compared to the HP group. Hyperplasia samples exhibited similar metabolic changes to those reported in cancer, except for alterations in triglyceride levels, 7a,12 b-dihydroxy-5b-Cholan-24-oic acid, and Hept-2-enedioyl carnitine levels. The metabolites N-heptanoyl glycine and -(Methylthio)-2,3-isopentyl phosphate and formimino glutamic acid can be specific markers for hyperplasia conditions and dimethyl phosphatidyl ethanolamine and 8-isoprostaglandin E2 can be specific markers for EC conditions. Metabolic activities rely on mitochondrial oxidative phosphorylation for energy generation. The changes in metabolites identified in our study indicate that endometrial cancer cells adopt alternative strategies to increase energy production to meet the energy demand, thereby supporting proliferation.

Sulfurovum mangrovi sp. nov., an obligately chemolithoautotrophic, hydrogen-oxidizing bacterium isolated from coastal marine sediments.

A novel mesophilic, chemolithoautotrophic, hydrogen-oxidizing bacterium, designated strain ST1-3T, was isolated from mud sediment samples collected from mangroves in Jiulong River estuary. The cells were Gram-stain-negative, non-motile and rod-shaped. The temperature, pH and salinity ranges for growth of strain ST1-3T were 4-45 °C (optimum, 35 °C), pH 5.0-8.5 (optimum, pH 7.0) and 0-8.0 % (w/v) NaCl (optimum, 4.0 %). The isolate was an obligate chemolithoautotroph capable of growth using hydrogen as the only energy source, and molecular oxygen, thiosulphate and elemental sulphur as electron acceptors. The major cellular fatty acids of strain ST1-3T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c). The major polar lipids were phosphatidylethanolamine, phosphatidyldimethyl ethanolamine and phosphatidylglycerol. The respiratory quinone was menaquinone-6. The genomic DNA G+C content was 43.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and core genes showed that the novel isolate belonged to the genus Sulfurovum and was most closely related to Sulfurovum lithotrophicum 42BKTT (94.7 % sequence identity). The average nucleotide identity and digital DNA-DNA hybridization values between ST1-3T and S. lithotrophicum 42BKTT were 74.6 and 16.3 %, respectively. On the basis of the phenotypic, phylogenetic and genomic data presented here, strain ST1-3T represents a novel species of the genus Sulfurovum, for which the name Sulfurovum mangrovi sp. nov. is proposed, with the type strain ST1-3T (=MCCC M25234T=KCTC 25639T).

The effect of methylated phosphatidylethanolamine derivatives on the ionization properties of signaling phosphatidic acid

Phosphatidylethanolamine (PE) and Phosphatidylcholine (PC) are the most abundant glycerophospholipids in eukaryotic membranes. The differences in the physicochemical properties of their headgroups have contrasting modulatory effects on their interaction with intracellular macromolecules. As such, their overall impact on membrane structure and function differs significantly. Enzymatic methylation of PE's amine headgroup produces two methylated derivatives namely monomethyl PE (MMPE) and dimethyl PE (DMPE) which have physicochemical properties that generally range between that of PE and PC. Additionally, their influence on membrane properties differs from both PE and PC. Although variations in headgroup methylation have been reported to affect signaling pathways, the direct influence that these differences exert on the ionization properties of signaling phospholipids have not been investigated. Here, we briefly review membrane function and structure that are mediated by the differences in headgroup methylation between PE, MMPE, DMPE and PC. In addition, using 31P MAS NMR, we investigate the effect of these four phospholipids on the ionization properties of the ubiquitous signaling anionic lipid phosphatidic acid (PA). Our results show that PA's ionization properties are differentially affected by changes in phospholipid headgroup methylation. This could have important implications for PA-protein binding and hence physiological functions in cells where signaling events lead to changes in abundance of methylated PE derivatives in the membrane.

Dissecting the relationship between plasma and tissue metabolome in a cohort of women with obesity: Analysis of subcutaneous and visceral adipose, muscle, and liver.

Untargeted metabolomics of blood samples has become widely applied to study metabolic alterations underpinning disease and to identify biomarkers. However, understanding the relevance of a blood metabolite marker can be challenging if it is unknown whether it reflects the concentration in relevant tissues. To explore this field, metabolomic and lipidomic profiles of plasma, four sites of adipose tissues (ATs) from peripheral or central depot, two sites of muscle tissue, and liver tissue from a group of nondiabetic women with obesity who were scheduled to undergo bariatric surgery (n=21) or other upper GI surgery (n=5), were measured by liquid chromatography coupled with mass spectrometry. Relationships between plasma and tissue profiles were examined using Pearson correlation analysis subject to Benjamini-Hochberg correction. Plasma metabolites and lipids showed the highest number of significantly positive correlations with their corresponding concentrations in liver tissue, including lipid species of ceramide, mono- and di-hexosylceramide, sphingomyelin, phosphatidylcholine (PC), phosphatidylethanolamine (PE), lysophosphatidylethanolamine, dimethyl phosphatidylethanolamine, ether-linked PC, ether-linked PE, free fatty acid, cholesteryl ester, diacylglycerol and triacylglycerol, and polar metabolites linked to several metabolic functions and gut microbial metabolism. Plasma also showed significantly positive correlations with muscle for several phospholipid species and polar metabolites linked to metabolic functions and gut microbial metabolism, and with AT for several triacylglycerol species. In conclusion, plasma metabolomic and lipidomic profiles were reflective more of the liver profile than any of the muscle or AT sites examined in the present study. Our findings highlighted the importance of taking into consideration the metabolomic relationship of various tissues with plasma when postulating plasma metabolites marker to underlying mechanisms occurring in a specific tissue.

Roseomonas bella sp. nov., isolated from lake sediment.

A Gram-stain-negative, non-motile, coccus-shaped, catalase- and oxidase-positive, facultatively anaerobic and pink-pigmented bacterium, designated strain CQN31T, was isolated from sediment of Changqiaohai Lake, Yunnan Province, China. Growth occurred at 4-45 °C (optimum, 37 °C), at pH 6.5-9.5 (optimum, pH 8.0) and with 0-1 % (w/v) NaCl (optimum, 0 %). C18 : 1 ω7c/C18 : 1 ω6c and C16 : 0 were the predominant fatty acids. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidyldimethylethanolamine (PME) and one unidentified aminolipid (AL) were the major polar lipids. The G+C content of the genomic DNA was 71.5 %. 16S rRNA gene sequence comparisons indicated that strain CQN31T shared 96.8 % similarity with Roseomonas wooponensis JCM 19527T and 95.9 % with R. terricola EM0302T. Digital DNA-DNA hybridization values between strain CQN31T and Roseomonas stagni DSM 19981T, R. rosea DSM 14916T and R. mucosa NCTC 13291T were 21.0, 19.4 and 19.8 %, respectively. Average amino acid identity and average nucleotide identity values between strain CQN31T and R. stagni DSM 19981T, R. rosea DSM 14916T and R. mucosa NCTC 13291T were 73.7, 63.4 and 61.9 %, and 79.2, 77.1 and 77.5%, respectively. Distinct morphological, physiological and genotypic differences from previously described taxa support the classification of strain CQN31T as a representative of a novel species in the genus Roseomonas, for which the name Roseomonas bella sp. nov. is proposed. The type strain is CQN31T (=KCTC 62447T=MCCC 1H00309T).

Gimesia benthica sp. nov., a planctomycete isolated from a deep-sea water sample of the Northwest Indian Ocean.

A Gram-stain-negative, stalked, oval-shaped and budding bacterial strain, designated E7T, was isolated from a deep-sea water sample collected from the Northwest Indian Ocean. The novel strain was strictly aerobic, and catalase- and oxidase-positive. It grew at 6-40 °C (optimum 30 °C) and pH 5.5-8.0 (optimum pH 7.0-7.5). The strain required 0.5-9.0 % (w/v) NaCl (optimum 3.0-5.0 %) for growth. Aesculin, starch, pectin and Tween 20 were hydrolysed. Based on 16S rRNA gene sequence analysis, strain E7T showed the highest similarity with Gimesia maris DSM 8797T (97.5 %). The average nucleotide identity and in silico DNA-DNA hybridization values between strain E7T and G. maris DSM 8797T were 78.0 and 19.3 %, respectively. The predominant cellular fatty acids of strain E7T were C16 : 0 and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c). The major respiratory quinone was menaquinone-6 (MK-6) and the major polar lipids were phosphatidylethanolamine (PE), phosphatidylmonomethylethanolamine (PMME), phosphatidyldimethylethanolamine (PDME), phosphatidylcholine (PC) and diphosphatidylglycerol (DPG). The genomic DNA G+C content of strain E7T was 52.8 mol%. On the basis of phylogenetic inference and phenotypic characteristics, it is proposed that strain E7T represents a novel species of the genus Gimesia, for which the name Gimesia benthica sp. nov. is proposed. The type strain is E7T (=CGMCC 1.16119T=KCTC 72737T).

Microvirga arsenatis sp. nov., an arsenate reduction bacterium isolated from Tibet hot spring sediments.

Two novel Gram-stain negative, moderately thermophilic, aerobic, rod-shaped strains, designated 3D203T and 3D207, were isolated from hot spring sediment samples collected from Tibet, western China. Phylogenetic analyses based on 16S rRNA gene sequence similarities showed that two isolates belonged to the genus Microvirga and were most closely related to Microvirga makkahensis SV1470T (98.5% and 98.4%, respectively) and two strains had 99.8% similarity to each other. The average nucleotide identity (ANI) based on whole genome sequences of two strains and M. makkahensis SV1470T was 80.8% and 80.78%, respectively. Optimum growth was observed at 45°C, pH 7.0 and 0.5% NaCl. They both could tolerate to high concentration arsenic. Ubiquinone 10 (Q10) was their predominant quinone. The differences of strains 3D203T and 3D207 were phosphatidyl dimethyl ethanolamine, phosphatidyl-N-methylethanolamine, phosphatidylglycerol, unidentified glycolipids and unidentified lipids. The major fatty acids (> 5%) were identified C18:1ω7c and/or C18:1ω6c, C18:0 and C16:0. The genomic DNA G + C contents of strain 3D203T and 3D207 based on whole genome sequences were 64.8% and 64.7%, respectively. Phenotypic, chemotaxonomic, phylogenetic and genomic analyses suggested that two strains represent a novel species of the genus Microvirga, for which the name Microvirga arsenatis sp. nov. is proposed. The type strain is 3D203T (= CGMCC 1.17691T = KCTC 72653T).

Microvirga pakistanensis sp. nov., a novel bacterium isolated from desert soil of Cholistan, Pakistan.

A Gram-negative, non-spore-forming, non-pigmented, strictly aerobic and non-motile short rod bacterium, designated NCCP-1258T, was isolated from Cholistan desert soil, Bahawalpur, Pakistan. Growth of strain NCCP-1258T was observed at pH range 6.5-9.5 (optimum 7.5-8.5) and temperature range 20-45°C (optimum 40°C), and it tolerated 0-2% NaCl (optimum 0.5%, w/v). Phylogenetic analysis based on 16S rRNA gene sequence comparison revealed that strain NCCP-1258T belongs to genus Microvirga and is most closely related to Microvirga lotononidis (98.0%), Microvirga vignae (97.4%), Microvirga lupini (97.2%), Microvirga zambiensis (97.2%) and Microvirga flocculans (97.1%). Analysis of the concatenated sequences of four housekeeping gene loci (dnaK, gyrB, recA and rpoB) also confirmed the placement of strain NCCP-1258T within the genus Microvirga. DNA-DNA relatedness values of NCCP-1258T with above-mentioned type strains were less than 42%. The DNA G+C content of strain NCCP-1258T was 64.3mol%. Chemotaxonomic data (predominant menaquinone system was Q-10; major fatty acids were C16:0, C18:1 ω7c and C19:0 cyclo ω8c; the polar lipid profile contained diphosphatidylglycerol, phosphatidylcholine, phosphatidyl dimethyl ethanolamine and phosphatidyl ethanolamine) also supported the affiliation of strain NCCP-1258T to the genus Microvirga. On the basis of physiological and biochemical characteristics, phylogenetic analyses and DNA-DNA relatedness, strain NCCP-1258T can be distinguished from the closely related taxa and thus represents a novel species of the genus Microvirga, for which the name Microvirga pakistanensis sp. nov. is proposed with the type strain NCCP-1258T (=CGMCC 1.15074T=KCTC 42496T).

Sphingomonas chloroacetimidivorans sp. nov., a chloroacetamide herbicide-degrading bacterium isolated from activated sludge.

Strain Y1(T), a Gram-negative, non-spore-forming, rod-shaped bacterium, was isolated from activated sludge. This strain is able to degrade several commonly used chloroacetamide herbicides, such as butachlor, acetochlor and alachlor. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Y1(T) is a member of the genus Sphingomonas and shows high sequence similarities with S. starnbergensis 382(T) (95.7 %), S. sanxanigenens NX02(T) (95.7 %) and S. haloaromaticamans A175(T) (95.3 %), and shows low (<95 %) sequence similarities to all other Sphingomonas species. Chemotaxonomic analysis revealed that strain Y1(T) possesses Q-10 as the predominant ubiquinone, C14:0 2-OH as the major 2-hydroxy fatty acid and sym-homospermidine as the major polyamine. The main cellular fatty acids of strain Y1(T) were found to be C18:1 ω7c (38.2 %), C16:1 ω6c/C16:1 ω7c (28.5 %), C16: 0 (10.7 %) and C14:0 2-OH (14.3 %). The main polar lipids were determined to be diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipids (SGL1-SGL3), phosphatidyl dimethylethanolamine and aminophospholipid. The DNA G+C content was found to be 66 ± 0.4 mol%. Based on phylogenetic analysis, phenotypic characteristics and chemotaxonomic data, strain Y1(T) is considered to represent a novel species of the genus Sphingomonas, for which the name Sphingomonas chloroacetimidivorans sp. nov. is proposed. The type strain is Y1(T) (=CCTCC AB 2011178(T) = KACC 16607(T)).

Quantitative profiling of PE, MMPE, DMPE, and PC lipid species by multiple precursor ion scanning: A tool for monitoring PE metabolism

We report a method for the simultaneous identification and quantification of phosphatidylethanolamine (PE), monomethyl-phosphatidylethanolamine (MMPE), dimethyl-phosphatidylethanolamine (DMPE), and phosphatidylcholine (PC) species in lipid extracts. The method employs a specific “mass-tag” strategy where DMPE, MMPE, and PE species are chemically methylated with deuterated methyliodide (CD3I) to produce PC molecules having class-specific mass offsets of 3, 6 and 9Da, respectively. The derivatized aminoglycerophospholipids release characteristic phosphorylcholine-like fragment ions having specific mass offsets that powers sensitive and quantitative analysis by multiple precursor ion scanning on a hybrid quadrupole time-of-flight mass spectrometer. Using the mass-tag strategy, we could for the first time determine the stoichiometric relationship between the biosynthetic intermediates MMPE and DMPE, and abundant PE and PC species in a single mass spectrometric analysis. We demonstrated the efficacy of the methodology by conducting a series of biochemical experiments using stable isotope labeled ethanolamine to survey the activities and substrate specificities of enzymes involved in PE metabolism in Saccharomyces cerevisiae. Finally, we benchmarked the mass-tag strategy by specific and sensitive profiling of intermediate MMPE and DMPE species in liver.

In Vitro Characterization of the Enzyme Properties of the Phospholipid N -Methyltransferase PmtA from Agrobacterium tumefaciens

Agrobacterium tumefaciens requires phosphatidylcholine (PC) in its membranes for plant infection. The phospholipid N-methyltransferase PmtA catalyzes all three transmethylation reactions of phosphatidylethanolamine (PE) to PC via the intermediates monomethylphosphatidylethanolamine (MMPE) and dimethylphosphatidylethanolamine (DMPE). The enzyme uses S-adenosylmethionine (SAM) as the methyl donor, converting it to S-adenosylhomocysteine (SAH). Little is known about the activity of bacterial Pmt enzymes, since PC biosynthesis in prokaryotes is rare. In this article, we present the purification and in vitro characterization of A. tumefaciens PmtA, which is a monomeric protein. It binds to PE, the intermediates MMPE and DMPE, the end product PC, and phosphatidylglycerol (PG) and phosphatidylinositol. Binding of the phospholipid substrates precedes binding of SAM. We used a coupled in vitro assay system to demonstrate the enzymatic activity of PmtA and to show that PmtA is inhibited by the end products PC and SAH and the antibiotic sinefungin. The presence of PG stimulates PmtA activity. Our study provides insights into the catalysis and control of a bacterial phospholipid N-methyltransferase.

Effect of Average Phospholipid Curvature on Supported Bilayer Formation on Glass by Vesicle Fusion

The adsorption of large unilamellar vesicles composed of various combinations of phosphatidylcholine, phosphatidylethanolamine (PE), monomethyl PE, and dimethyl PE (PE-Me 2) onto a glass surface was studied using fluorescence microscopy. The average lipid geometry within the vesicles, described mathematically by the average intrinsic curvature, C 0,ave, was methodically altered by changing the lipid ratios to determine the effect of intrinsic curvature on the ability of vesicles to rupture and form a supported lipid bilayer. We show that the ability of vesicles to create fluid planar bilayers is dependent on C 0,ave and independent of the identity of the component lipids. When the C 0,ave was ∼−0.1 nm −1, the vesicles readily formed supported lipid bilayers with almost full mobility. In contrast, when the C 0,ave ranged from ∼−0.2 to ∼−0.3 nm −1, the adsorbed vesicles remained intact upon the surface. The results indicate that the average shape of lipid molecules within a vesicle ( C 0,ave) is essential for determining kinetically viable reactions that are responsible for global geometric changes.

Rhodovarius lipocyclicus gen. nov. sp. nov., a New Genus of the α-1 Subclass of the Proteobacteria

A bacterial strain (CCUG 44693T) was recovered during an industrial hygiene control. Phylogenetic analyses using the 16S rRNA gene sequence of the isolate indicated that it represents a new lineage in the alpha-1 subclass of the Proteobacteria, with the highest sequence similarity of 93.3% to the type strain of Muricoccus roseus. In the polyamine pattern spermidine was the predominant compound. The polar lipid profile consisted of the major lipids phosphatidyl ethanolamine, phosphatidyl dimethylethanolamine, phosphatidyl glycerol, phosphatidyl cholin and an unknown amino lipid. The major respiratory quinone was a ubiquinone Q-10 and the major whole cell fatty acids were 19:0 cyclo omega8c and 18:1 omega7c. The isolate also contained 18:1 2-OH and other fatty acids typical for members of the alpha-1 subclass of the Proteobacteria in addition to 10:0 2-OH in low amounts, not detected in members of closely related genera. The strain grew heterotrophically and strictly aerobically and formed red-colored colonies on tryptone soy agar. Bacteriochlorophyll a could not be detected by direct spectrophotometric analyses of aerobically grown cells. On the basis of the phylogenetic analyses, chemotaxonomic and biochemical characteristics, we propose that strain CCUG 44693T (CIP 108310T) represents a new genus of the alpha-1 subclass of the Proteobacteria for which we propose the name Rhodovarius lipocyclicus gen. nov. sp. nov.

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 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.

Biochemical implications and geochemical significance of novel phospholipids of the extremely barophilic bacteria from the Marianas Trench at 11,000 m

The membrane phospholipids of two barophilic bacteria, DB21MT-2 and DB21MT-5, isolated from sediments from the Marianas Trench at 11,000 m were structurally characterized and quantitatively determined by liquid chromatography/electrospray ionization/mass spectrometry (LC/ESI/MS). Phospholipids detected in the barophiles were distributed in five different classes: phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylcholine (PC), diphosphatidylglycerol (DPG), and phosphatidylethanolamine (PE) and its methylated forms phosphatidylmethylethanolamine (PME) and phosphatidyldimethylethanolamine (PDME). Concentrations of phospholipids/phospholipid groups range from 5.3 to 4.583 μg/g (dry weight). A unique aspect of the phospholipid profiles of the barophilic bacteria was the wide distribution of polyunsaturated fatty acids 20 : 5 (in DB21MT-2) and 22 : 6 (in both DB21MT-5 and DB1MT-2) on the sn-1 and mostly on the sn-2 position of the phospholipids. The results suggest that the adaptation of the barophiles to low temperature and high hydrostatic pressure influenced the synthesis of phospholipids containing polyunsaturated fatty acids. It was also observed that the polyunsaturated fatty acids were associated with almost every phosphatidylglycerol (PG) molecule. Presumably, the larger head group of PG would be expected to cause greater disruption in acyl chain packing within the membrane bilayer and thereby lower the transition temperature in response to the additive effects of low temperature and high pressure. The detection of phospholipids with polyunsaturated fatty acids also has important geochemical implications for paleoenvironment reconstruction and for determining the surface water biological productivity of the ocean. It seems that psychrophilic and barophilic bacteria may be major sources of polyunsaturated fatty acids to the deep-sea sediments, given the fact that the vertical flux of polyunsaturated fatty acids from surface water plankton decreased rapidly with depth.

Cell lipid alterations resulting from prolonged exposure to dimethylaminoethylmethacrylate.

Dimethylaminoethylmethacrylate (DMAEMA), a commonly-used component of visible-light polymerized dental resins, has the potential to elute and interact with tissue cells to cause cytotoxicity or sublethal metabolic changes. Short-term exposure of cultured oral epithelial cells to sublethal DMAEMA concentrations has been shown previously to affect cell neutral lipid and phospholipid metabolism, resulting in accumulation of significant quantities of dimethylphosphatidylethanolamine (DMPE). In non-treated cells, DMPE is a transient intermediate in phospholipid metabolism and is not detectable by standard methods. In the current study, the effects of prolonged exposure of cells to DMAEMA, and the mechanisms for formation of DMPE in the presence of DMAEMA were examined. Exposure of a keratinizing hamster buccal cheek pouch cell line (HCP cells) to 0.8 mM DMAEMA for 2, 3, 7, and 14 days resulted in reduced incorporation of [14C]acetate into several classes of phospholipids. DMPE was detectable at all time points in DMAEMA-exposed cultures and comprised between 12.48% and 18.33% of the total radiolabeled phospholipids. The results of short-term exchange experiments indicated that headgroup exchange was not the major reaction responsible for formation of DMPE in DMAEMA-treated cells; rather the formation appeared to occur through typical phospholipid metabolic pathways. The cells appeared able to re-establish and maintain homeostasis in the presence of this altered cell lipid composition.

Effects of an aminomethacrylate on epithelial cell lipid metabolism

Methacrylates can affect cell functions by surfactant-like effects or by altering cell lipid composition. Dimethylaminoethyl methacrylate (DMAEMA), an activator widely used in visible-light polymerized dental resins has been shown to elute readily into aqueous environments. The current study examined the metabolism of this material by oral epithelial cells (HCP) and its subsequent effects on cell lipids. Cells were plated in culture medium, then exposed to DMAEMA in the presence of 14C-acetate, a precursor which labeled the cell lipids. Other cultures were prelabeled with radioisotope, then exposed to DMAEMA. After incubation, the cell lipids were extracted and separated by TLC. Radioactive lipids were located and quantitated. Exposure of the cells to DMAEMA resulted in decreased synthesis of cholesterol with a concomitant increase in sterol precursors. Cholesterol esters and triacylglycerides also increased. Among the polar lipids, phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) decreased in response to DMAEMA. However, dimethylphosphatidyl ethanolamine (DMPE), a precursor of PC not detectable in control cultures, accumulated to a significant extent in cells exposed to DMAEMA. Furthermore, changes in PC and DMPE levels persisted in the cells for at least 48 h after removal of the DMAEMA. The results indicate that DMAEMA produces alterations in the relative amounts of several cellular neutral and polar lipids. Such alterations, especially of the normal phospholipid composition, along with an alteration in cellular cholesterol, could result in altered membrane-associated cell functions.

Progesterone-induced phospholipid N-methylation and sphingomyelin synthesis in the amphibian oocyte plasma membrane: a second source of the 1,2-diacylglycerol second messenger associated with the G 2/M transition

The effects of progesterone and GTPγS on phospholipid N-methylation and sphingomyelin synthesis were studied in plasma-vitelline membranes isolated from amphibian ( Rana pipiens) oocytes. Plasma-vitelline membranes were preincubated with S- adenosyl- l [methyl- 3 H] methionine for w min at 20°C and total phospholipids extracted at 0, 15, 30 and 60 s after addition of progesterone and/or GTPγS. Progesterone levels (3 μM) that induce meiosis in the intact oocyte stimulated [ 3H-methyl]incorporation into phosphatidylmonomethylethanolamine (PME) 9–10-folrd over the first 6 s with smaller increases in phosphatidyldimethylethanolamine (PDE) and phosphatidylcholine (PC). [ methyl- 3H] labeling of sphingomyelin (SM) rises after 30 s, approaching that of [ methyl- 3H]PME by 60 s. 17β-Estradiol, a noninducer of meiosis, was inactive. When oocytes were prelabeled with [ 3H]palmitic acid, it was found that a fall in [ 3H]ceramide coincides with the transient increase in [ 3H]SM, indicating that the end product of N-methylation (PC) undergoes a transfer reaction with ceramide to form SM and 1,2-DG. GTPγS levels previously reported to stimulate PC-specific phospholipase C activity in oocyte plasma membranes (5 μM) also stimulated both [ methyl- 3H]PME and [ methyl- 3H]SM formation. An inhibitor of phospholipid N-methylation, 2-(methyl-amino)ethanol, blocked stimulation of [ methyl- 3H]SM synthesis by both progesterone and GTPγS as well as induction of meiosis by progesterone. Progesterone thus acts at the oocyte plasma membrane to stimulate PE N-methyltransferase and SM synthase. The finding that GTPγS mimics progesterone suggests that N-methyltransferase is mediated by G-protein(s). The transient increase in 1,2-DG which we had previously reported to occur within 1–2 min following progesterone stimulation of the Rana oocyte appears to arise from PC by two different pathways: SM synthesis and hydrolysis of PC by phospholipase C.

Head group precursors modify phospholipid synthesis in Schistosoma mansoni

The two predominant phospholipids in schistosomula of Schistosoma mansoni are phosphatidylcholine (PC) and phosphatidylethanolamine (PE) which are found in a molar ratio of 0.52 (PE/PC). The incorporation of four fatty acids (arachidonic, myristic, oleic, and palmitic) and glycerol into phospholipids of schistosomula was measured. In two different media (one containing ethanolamine, the other without), all four fatty acids were predominantly incorporated into PC with a PE/PC ratio of approximately 0.1 in a 90-min label. After a 24-h chase, PC remained the predominant labeled phospholipid but the fatty acid-labeled PE/PC ratio increased slightly, the specific activity of labeled neutral lipids decreased, and the specific activity of labeled PE increased. Glycerol was incorporated with a ratio of 0.55 in the presence of ethanolamine but only 0.19 in its absence. Schistosomula also incorporate fatty acids into phosphatidylmonomethylethanolamine (PMME) and phosphatidyldimethylethanolamine (PDME) at rates intermediate to that into PE and PC in the presence of the respective head group precursor; this incorporation was inhibited by choline. Relative to PC, oleic acid is incorporated into PE, PMME, and PDME at rates higher than for palmitic acid. These results suggest that schistosomula possess acyltransferase(s) with head group specificity and that acyl chains are transferred from neutral lipids to phospholipids over time.