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.     

Fatty acid composition and incorporation of arachidonic acid into phospholipids of hemocytes from the tobacco hornworm Manduca sexta

The fatty acid compositions were determined for total lipids, triacylglycerols, phospholipids and four phospholipid fractions, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine/phosphatidylinositol (PS/PI) and cardiolipin (CA) obtained from hemocytes and cell-free serum from second day, fifth instar larvae of the tobacco hornworm Manduca sexta and the standard Manduca rearing medium. The hemocyte fatty acid profiles were considerably different from the profiles of the medium the insects were reared on and from the profiles of the cell-free serum. Hemocyte neutral lipids had lower proportions of polyunsaturated fatty acids than phospholipids. The fatty acid profiles of PC, PE, PS/PI and CA differ from each other and from the total lipid profiles, indicating selective fatty acid incorporation into hemocyte phospholipid species. Studies with radioactive arachidonic acid similarly indicated selective incorporation of polyunsaturated fatty acids into hemocyte lipids. Under our in vitro conditions, >40% of the total radioactivity was incorporated into hemocyte lipids. About 93% of the incorporated radioactivity was found in phospholipids. Within phospholipids. most of the radioactivity was associated with PC (46%), and less with PE (28%) and PS/PI (21%). Very little radioactivity was recovered in CA (0.9%).     

The influence of ionic detergents on the phospholipid fatty acid compositions of Porphyridium purpureum

The phospholipid fatty acid composition of Porphyridium purpureum on a solid medium was studied in the presence of sodium dodecyl sulphate (SDS) and cetyl trimethylammonium bromide (CTAB). The most common fatty acids in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were palmitic (16:0), stearic (18: 0), linoleic (18:2ω 6), arachidonic (20:4ω 6) and eicosapentaenoic (20:5ω 3) acids, 20:4ω 6 being very abundant. In phosphatidyl glycerol (PG) the most common acids were 16:0, trans-hexadecenoic acid (tr 16:1ω 13), oleic acid (18:1) and 20:4ω 6. Both detergents increased the saturation grade of PC and PE by decreasing the relative amount of the polyunsaturated acids, especially 20:4ω 6. A corresponding increase in the amounts of saturated acids was observed in PC and PE. The changes in PG fatty acid composition were not very significant: a slight increase was observed in the amounts of 16:0 and tr 16:1ω 13 , with a corresponding decrease in the amounts of 20:4ω 6 and 20:5ω 3. Both detergents decreased the PC/PE and the (PC + PE)/PG ratios very markedly, most probably as a result of increases in the amounts of PE and PG. In the presence of CTAB the cells seemed to contain much more phospholipids than in the presence of SDS, perhaps as a result of the mucilage-precipitating effect of CTAB. The significance of the findings is discussed.     

The incorporation of monomethylethanolamine and dimethylethanolamine in fetal brain aggregating cell culture

Fetal rat brain aggregating cell cultures were exposed to varying concentrations of [³H]monomethylethanolamine (MME) and [³H] dimethylethanolamine (DME). The rate of labeling of water-soluble compounds was more rapid and the amount of radioactivity present was greater than in the lipids. After a 72 hour incubation in the presence of millimolar concentrations of these nitrogenous bases, the major water-soluble products were the phosphorylated form of the bases. Little label was associated with the free bases or their cytidyl derivate. In the phospholipids, 97% of the radioactivity was recovered in phosphatidylmonomethylethanolamine (PMME) and 3% in phosphatidyldimethylethanolamine (PDME) or 95% in PDME and 5% in phosphatidylcholine (PC) after growth in presence of [³H]MME and [³H]DME respectively. The rate of formation of the radioactive products increased as function of the concentration of the nitrogenous base added up to 4 mM, the highest concentration employed. There was no significant difference in the pattern of labeling with cells grown in media devoid of methionine or choline. The turnover of the water-soluble metabolites was more rapid than in the phospholipids where an apparent half-life of 24 hours was calculated.Abbreviations PMT phospholipid-N-methyltransferase - AdoMet S-adenosyl-L-methionine - EA ethanolamine - MME N-monomethylethanolamine - DME N,N-dimethylethanolamine - CH choline - PE phosphatidylethanolamine - PMME phosphatidylmonomethylethanolamine - PDME phosphatidyldimethylethanolamine - PC phosphatidylcholine - PS phosphatidylserine - CAPS cyclohexylaminopropane sulfonic acid     

Kinetic mechanism of phosphatidylethanolamine N-methyltransferase

We have investigated the kinetic mechanism of phosphatidylethanolamine (PE) N-methyltransferase purified from rat liver using PE, phosphatidyl-N-monomethylethanolamine (PMME), and phosphatidyl-N,N-dimethylethanolamine (PDME) as substrates. We previously reported (Ridgway, N. D., and Vance, D. E. (1987) J. Biol. Chem. 262, 17231-17239) that initial velocity curves with PE, PMME, and PDME at a fixed concentration of Triton X-100 were sigmoidal, thus generating nonlinear inverse plots. Comparison with other integral membrane enzymes suggested this response resulted from the enzyme's requirement for a complete boundary layer of phospholipid. Hence, the effect of a nonsubstrate phospholipid on initial velocity patterns for PE, PMME, and PDME was examined. The sigmoidicity of initial velocity curves at constant Triton X-100 concentration and increasing PE, PMME, and PDME were converted to the more familiar hyperbolic response by the addition of egg phosphatidylcholine (PC). Hill coefficients for PE, PMME, and PDME at a fixed Triton concentration were 3.6, 2.5, and 4.7, respectively, but with the addition of 30 or 40 mol % of egg PC, coefficients were close to unity (0.9-1.2). The activation by egg PC of PE, PMME, and PDME methylation indicates that a secondary phospholipid binding site(s) plays a role in catalysis in mixed micelles. This site(s) may represent a transmembrane segment(s) in close association with a boundary layer of phospholipid. Kinetic analysis of initial velocity and product inhibition patterns for PMME and PDME methylation fit an ordered Bi Bi mechanism. Phospholipid substrates and products were the first to bind and the last to dissociate from the active site, respectively. As well, PE, PMME, and PDME compete for a single active site. The overall kinetic scheme for the methylation of PE to PC in mixed micelles involves the initial binding of PE, followed by successive steps where S-adenosyl-L-methionine is bound, the sulfonium methyl group is transferred, and S-adenosyl-L-homocysteine is released.     

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.     

Effect of Modification of Membrane Phospholipid Composition on Phospholipid Methylation in Aggregating Cell Culture

The effect of the presence of nitrogenous bases in the growth medium of fetal rat brain aggregating cell cultures was investigated. The presence of either N-methylethanolamine (MME) or N,N-dimethylethanolamine (DME) in the growth medium resulted in significant increase of the corresponding phospholipid, phosphatidyl-N-monomethylethanolamine (PMME) or phosphatidyl-N,N-dimethylethanolamine (PDME). They represented 28% and 32% of the total phospholipids, respectively. The presence of the new phospholipids was accompanied by a significant decrease of phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Cells grown in the presence of ethanolamine or choline had only barely detectable amounts of PMME and PDME. Intact cells previously grown with the bases were incubated with [methyl-3H]methionine. Incubation of cells previously grown in presence of the bases MME and DME resulted in a marked increase of radioactivity in the corresponding phospholipids possessing one additional methyl group, PDME and PC respectively. The incorporation of S-adenosyl[methyl-3H]methionine (AdoMet) was examined in cell homogenates incubated in presence or absence of either PMME or PDME acceptors. The addition of these exogenous phospholipids caused a three-or fourfold stimulation of radioactivity incorporated into the total phospholipids of cells grown in the absence of nitrogen bases. The cells grown in presence of either MME or DME in the culture medium did not show an increased incorporation of methyl groups from AdoMet into the total phospholipids after addition of exogenous acceptors. This work suggests that MME and DME incorporated into the corresponding phospholipids function as effective substrates for phospholipid-N-methylation.     

Changes in phospholipids and free fatty acids in the brains of mice preconditioned by hypoxia.

Changes in the composition and contents of phospholipids and free fatty acids were observed and compared in three groups: (A) unpreconditoned normal controls, (B) exposure to 1 run of hypoxia and (C) exposure to 4 runs of hypoxia. In group B, the content of phosphatidyl ethanolamine (PE), phosphatidyl serine (PS) and free fatty acids (FFAs) increased significantly and the content of phosphatidyl choline (PC) and sphingomyelin (SM) decreased significantly. While in group C the content of PE, PS, PC and FFAs changed significantly when compared with that of group B, all phospholipid (except SM) and FFA contents tended to decrease to the level of group A. No new FFA was seen in the brain homogenates in any of the three groups. These results suggest that the changes in the content of mouse brain phospholipids and FFAs may be adaptive and involved in the animals' tolerance to hypoxia.     

Composition and metabolism of phospholipids of human leukocytes

Human mononuclear (MN) and polymorphonuclear (PMN) leukocytes were analyzed for their phospholipid, triglyceride, cholesterol and fatty acid content. The phospholipid/cholesterol ratio was 1.24 for both cels. MN cells contain more phosphatidylcholine (PC), but less phosphatidylserine (PS), phosphatidylethanolamine (PE) and sphingomyelin (SPH) than PMN cells when expressed as percent of total phospholipid. When expressed on the basis of lipid content per cell, MN cells contain less PS, PE and SPH but more triglyceride than PMN cells. PMN cells incorporate palmitic, stearic, linoleic and linolenic acids into their phospholipids, triglycerides or cholesterol esters. The incorporation into triglycerides was highest for all fatty acids. Of the phospholipids, the incorporation was highest into PC. Labeled fatty acids also were found in proteins which had been delipidized by exhaustive extraction with organic solvents. These represent tightly or covalently bound fatty acids. The incorporation of [³H]palmitic acid into this protein fraction is stimulated by insulin.     

Changes in phospholipids of Microsporum species in the presence of ethanol

Ethanol supplementation to the growth medium of Microsporum gypseum and Microsporum cookie resulted in changes in phospholipid composition and degree of unsaturation of their fatty acids without affecting the growth rate of the organism. Phosphatidylethanolamine increased with a simultaneous decrease in phosphatidylserine. Unsaturated fatty acids of total phospholipids decreased significantly which was primarily due to the decreased levels of linoleic acid.Abbreviations CL Cardiolipin - LPC Lysophosphatidylcholine - PC Phosphatidylcholine - PE Phosphatidylethanolamine - PI Phosphatidylinositol - PS Phosphatidylserine - UK Unknown phospholipids     

Incorporation of radioiodinated fatty acids into cardiac phospholipids of normoxic canine myocardium

The aim of this study was to assess the phospholipid distribution of radioiodinated 17-iodoheptadecanoic acid (IHDA), 15-(p-iodophenyl)pentadecanoic acid (p-IPPA) and 15-(p-iodophenyl)-3,3-dimethylpentadecanoic acid (DMIPPA) under normoxic conditions and to compare these data with the fatty acid composition of the phospholipid classes. After simultaneous i.v. injection of the radioiodinated fatty acids (1-123-IHDA; 1-131-p-IPPA; 1-125 DMIPPA) in open-chest dogs seven myocardial biopsies were taken over 40 min (n = 26). After lipid extraction of the biopsies the organic phase was analyzed for both neutral and polar lipids by two different TLC systems. The following polar lipid fractions were analyzed: lysophopshatidylcholine (LPC), sphingomyelin (SPH), phosphatidy1choline (PC; lecithin), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG; cardiolipin) and neutral lipids. Fractions were counted in a gamma well counter and corrected for cross-over and recovery. Results of the polar phospholipids analysis showed that IHDA has the highest incorporation into the phospholipids. The IHDA was mainly incorporated into PI (45.6%) followed by PC (30.9%), PE (14.0%) and PS (5.6%). The p-IPPA was predominantly incorporated incorporated into PC (37.2%), followed by PS (20.1%) and PE (13.7%). In contrast to IHDA, incorporation of p-IPPA into PI was small (6.4%). The DMIPPA analogue was incorporated into phopsholipids to only a very small degree, compared to IHDA and p-IPPA. PS (27.4%) was the only considerable phospholipid fraction into which DMIPPA was incorporated.The results clearly demonstrated that these radioiodinated fatty acid analogues have entirely different patterns of phospholipid incorporation. Major resemblances have been found between the incorporation into phospholipids of IHDA and the phospholipid distribution of the natural counterpart: stearic acid. The p—IPPA phospholipid incorporation only partly resembles the phospholipid distribution of palmitic acid. DMIPPA is because of its modified structure, incorporated into phospholipids to a low extent, mainly into PS. (Mol Cell Biochem116: 79–87, 1992)     

Modification of the fatty acid composition of individual phospholipids and neutral lipids after infection of the simian erythrocyte by Plasmodium knowlesi

Using capillary gas-liquid chromatography, we have analyzed the alteration in the total fatty acid, phospholipid and neutral lipid compositions of the monkey erythrocyte, after infection by the malarial parasite Plasmodium knowlesi. Data based on fatty acid quantitation show that the phospholipid composition is altered, with particularly large increases in phosphatidylcholine (PC) and phosphatidylethanolamine (PE), the most abundant phospholipids in normal and P. knowlesi-schizont-infected cells. Unesterified fatty acids were found to be less abundant in infected cells. The total fatty acid content of the cell is increased 6-fold during infection, and total fatty acid composition is also changed: the infected cells are richer in palmitate (+23%), oleate (+29%) and linoleate (+89%), but contained less stearate (-27%) and arachidonate (-40%). The determination of the fatty acid composition of individual phospholipids, neutral lipids and unesterified fatty acids showed that choline-containing phospholipids (PC and sphingomyelin) were not as altered in their fatty acid pattern as anionic phospholipids (PE, phosphatidylserine (PS) and phosphatidylinositol (PI) and lysophosphatidylcholine (lysoPC). Specific alterations in the fatty acid compositions of individual phospholipids were detected, whereas the rise in linoleic acid was the only change during infection that was recovered in each phospholipid (except PC), neutral lipid and unesterified fatty acids. The fatty acid composition of the neutral lipids and unesterified fatty acids was particularly modified: the only rise in arachidonic acid level was observed in these lipid classes after infection. The total plasmalogen level of the erythrocyte is decreased in infected cells (-60%), but their level is increased in PI.     

Lipids of Daucus carota cell suspension cultures

In carrot cell suspension cultures greater amounts of phospholipid were detected than in carrot root material, but the major phospholipid classes were the same in both materials, and their fatty acid composition was very similar. In contrast to the cultured cells, no significant amounts of free fatty acids and monoglycerides, as well as diglycerides, could be detected in the carrot root. The fatty acid composition of the major lipid classes from cell cultures is reported for the first time in this report. The degree of unsaturation was higher in triglycerides and phospholipids than in free fatty acids. In a study of phospholipid biosynthesis, [³H]-glycerol was shown to be incorporated into 4-phospholipids (PE, PC, PG, PS⁷) to different extents. The highest specific activity was observed in PC and PG. Five molecular species were isolated from each of the 4 phospholipids and analyzed by GC-MS and LSC.     

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.     

Age-related changes in mitochondrial membrane composition of rainbow trout (Oncorhynchus mykiss) heart and brain

Membrane composition, particularly of mitochondria, could be a critical factor by determining the propagation of reactions involved in mitochondrial function during periods of high oxidative stress such as rapid growth and aging. Considering that phospholipids not only contribute to the structural and physical properties of biological membranes, but also participate actively in cell signaling and apoptosis, changes affecting either class or fatty acid compositions could affect phospholipid properties and, thus, alter mitochondrial function and cell viability. In the present study, heart and brain mitochondrial membrane phospholipid compositions were analyzed in rainbow trout during the four first years of life, a period characterized by rapid growth and a sustained high metabolic rate. Specifically, farmed fish of three ages (1-, 2- and 4-years) were studied, and phospholipid class compositions of heart and brain mitochondria, and fatty acid compositions of individual phospholipid classes were determined. Rainbow trout heart and brain mitochondria showed different phospholipid compositions (class and fatty acid), likely related to tissue-specific functions. Furthermore, changes in phospholipid class and fatty acid compositions with age were also tissue-dependent. Heart mitochondria had lower proportions of cardiolipin (CL), phosphatidylserine (PS) and phosphatidylinositol, and higher levels of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) with age. Heart mitochondrial membranes became more unsaturated with age, with a significative increase of peroxidation index in CL, PS and sphingomyelin (SM). Therefore, heart mitochondria became more susceptible to oxidative damage with age. In contrast, brain mitochondrial PC and PS content decreased in 4-year-old animals while there was an increase in the proportion of SM. The three main phospholipid classes in brain (PC, PE and PS) showed decreased n-3 polyunsaturated fatty acids, docosahexaenoic acid and peroxidation index, which indicate a different response of brain mitochondrial lipids to rapid growth and maturation.     

NaCl-induced changes in plasma membrane lipids and proteins of <Emphasis Type="Italic">Zea mays</Emphasis> L. cultivars differing in their response to salinity

Two contrasting maize (Zea mays L.) cultivars, i.e., Giza 2 (salt tolerant) and Trihybrid 321 (salt sensitive), were grown hydroponically to study NaCl effect (100 mM) on root plasma membrane (PM) lipid and protein alterations. The PM total sterols of Trihybrid 321 were decreased while that of Giza 2 was increased in response to salt. Salt imposition had no significant effect on PM total glycolipids and proteins of both cultivars. The PM total phospholipids were increased in Trihybrid 321 but it did not change significantly in Giza 2 after salinity stress. Molecular percentage of PM phospholipids and fatty acids of both cultivars was different in absence (0 mM) and presence (100 mM) of salt. The most abundant phospholipids in untreated Trihybrid 321 PM were phosphatidylglycerol (PG), phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS), which changed into PG, PS, phosphatidylinositol (PI) and PC after salt treatment. However, the dominant phospholipids of the control PM of Giza 2 were PC, PE, PS and PG, which changed into PG, PE, PS and diphosphatidylglycerol (DPG) after salt imposition. Over 60% of the total fatty acids were saturated in control and salinized PM of both cultivars, which was increased after salt stress. The predominant fatty acid in the control and salinized PM of Trihybrid 321 was C18:1 and C17:0, respectively. However, in control and treated PM of Giza 2, the predominant fatty acid was C17:0 and C20:0, respectively. Qualitative and quantitative differences in PM protein patterns were found in both cultivars with and without salt. PM lipid changes enhanced membrane integrity, reflected in different ion accumulation (Mansour et al. 2005), and hence salt tolerance of Giza 2.     

Enhanced phospholipase B activity and alteration of phospholipids and neutral lipids in Saccharomyces cerevisiae exposed to N-nitrosonornicotine

A tobacco-specific nitrosamine (TSNA), N-nitrosonornicotine (NNN), is a potent carcinogen present in cigarette smoke, and chronic exposure to it can lead to pulmonary cancer. NNN causes changes in phospholipid metabolism and the mechanism is yet to be elucidated. Exposure of Saccharomyces cerevisiae to 50 μM NNN leads to a substantial decrease in phosphatidylserine (PS) by 63%, phosphatidylcholine (PC) by 42% and phosphatidylethanolamine (PE) by 36% with a concomitant increase in lysophospholipids (LPL) by 25%. The alteration in phospholipid content was dependent on increasing NNN concentration. Reduced phospholipids were accompanied with increased neutral lipid content. Here we report for the first time that NNN exposure, significantly increases phospholipase B (PLB) activity and the preferred substrate is PC, a major phospholipid responsible for a series of metabolic functions. Furthermore, NNN also promotes the alteration of fatty acid (FA) composition; it increases the long chain fatty acid (C18 series) in phospholipids specifically phosphatidylethanolamine (PE) and PS; while on the contrary it increases short chain fatty acids in cardiolipin (CL). NNN mediated degradation of phospholipids is associated with enhanced PLB activity and alteration of phospholipid composition is accompanied with acyl chain remodelling. Understanding the altered phospholipid metabolism produced by NNN exposure is a worthwhile pursuit because it will help to understand the toxicity of tobacco smoke.     

Microbial Assimilation of Hydrocarbons: Phospholipid Metabolism

An analysis of the turnover of the major phospholipids of Micrococcus cerificans growing or nongrowing cultures. The turnover rates of (14)C-PE and (14)C-PE were 61.5% of the total phospholipid, exhibited no significant rate of turnover in either growing or nongrowing cultures. The turnover rates of PE-(14)C and PE-(32)P were 3.2% per hr and 1.2% per hr, respectively. Phosphatidylglycerol (PG) exhibited a turnover rate of 11% and 7.7% per hr for (14)C and (32)P, respectively, indicating an extremely slow metabolism. PG metabolism was examined in greater detail, and the data indicated a preferential 75% incorporation of glycerol-1,3-(14)C into the unacylated portion of the PG molecule. The turnover of cardiolipin (CL) was extremely slow in growing cells whereas nongrowing cells exhibited a 30% and 36% increase per hr for (14)C-Cl and (14)C-CL, respectively. Glycerol-1,3-(14)C was not converted to phospholipid fatty acid carbon; all radioactivity appeared only in the water-soluble backbone of the phospholipids. The kinetics of assimilation of hexadecane-1-(14)C into cellular lipids is presented. Radioactivity in neutral lipid increased approximately sevenfold over the growth cycle, whereas radioactivity in phospholipid increased 50-fold during the same time period. The incorporation of radioactive fatty acids derived from the direct oxidation of hexadecane-1-(14)C demonstrated differential kinetics of assimilation into PE, PG, and CL. The results indicated a rapid turnover of phospholipid fatty acids in M. cerificans growing at the expense of hexadecane.     

Effect of feeding water washed neem (Azadirachta indica) seed kernel cake on the quality,lipid profile and fatty acid composition of goat meat

Three groups of five indigenous male goats 5–6 months of age, were offered control concentrate mixture (Group I) and those of Groups II and III were fed experimental concentrates containing 15 and 25% of water washed neem (Azadirachta indica) seed kernel cake (NKC). After 180 days of feeding the goats were slaughtered. Longissimus dorsi (LD) muscle from lumbar region was analysed for certain physico-chemical characteristics, organoleptic quality, detailed lipid profile and fatty acid composition; phosopholipids were fractionated into phosphatidyl inositide (PI), phosphatidyl serine (PS), lysophosphatidyl choline (LPC), lysophosphatidyl ethanolamine (LPE), sphingomyelin (SPH), phosphatidyl choline (PC) phosphatidyl ethanolamine (PE) and phosphatidic acid (PA). Fatty acids; capric, lauric, myristic, myristoleic, palmitic, palmitoleic, heptadecanoic, stearic, oleic, linoleic acid were also identified. Feeding of NKC did not affect slaughter weight and dressing out yield. The dressing percentage ranged between 42.2 and 43.8%. The pH, colour, moisture, total crude protein, different protein fractions; water extractable, salt extractable and content of NPN did not differ among the groups. There was a significant decrease in the total lipid content of LD of experimental groups. PC and PE were the major fractions accounting for 60% of total phospholipids. There was a significant increase in PC and LPC fractions while LPE+SPH, PE and PA fractions decreased in goats fed NKC. A significant increase was noticed in unsaturated fatty acid content and decrease in total saturates. It is concluded that NKC feeding has the ability of reducing lipid content and increasing the unsaturated fatty acids, which are considered to be beneficial in reducing the cholesterol level. It may be used beneficially as an alternative for costly conventional oil cakes for economic lean chevon production without affecting the quality of goat meat.     

Low-salt diet alters the phospholipid composition of rat colonocytes

The effect of low-salt diet on phospholipid composition and remodeling was examined in rat colon which represents a mineralocorticoid target tissue. To elucidate this question, male Wistar rats were fed a low-salt diet and drank distilled water (LS, low-salt group) or saline instead of water (HS, high-salt group) for 12 days before the phospholipid concentration and fatty acid composition of isolated colonocytes were examined. The dietary regimens significantly influenced the plasma concentration of aldosterone which was high in LS group and almost zero in HS group. Plasma concentration of corticosterone was unchanged. When expressed in terms of cellular protein content, a significantly higher concentration of phospholipids was found in LS group, with the exception of sphingomyelin (SM) and phosphatidylserine (PS). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) accounted for more than 70% of total phospholipids in both groups. A comparison of phospholipid distribution in LS and HS groups demonstrated a higher percentage of PE and a small, but significant, decrease of PC and SM in LS group. The percentage of phosphatidylinositol (PI), PS and cardiolipin (CL) were not affected by mineralocorticoid treatment. With respect to the major phospholipids (PE, PC), a higher level of n-6 polyunsaturated fatty acids (PUFA) and lower levels of monounsaturated fatty acids were detected in PC of LS group. The increase of PUFA predominantly reflected an increase in arachidonic acid by 53%. In comparison to the HS group, oleic acid content was decreased in PC and PE isolated from colonocytes of the LS group. Our data indicate that alterations in phospholipid concentration and metabolism can be detected in rats with secondary hyperaldosteronism. The changes in phospholipid concentration and their fatty acid composition during fully developed effect of low dietary Na+ intake may reflect a physiologically important phenomenon with long-term consequences for membrane structure and function.