bluuebunny/crossref_metadata_2025_split huggingface dataset:
An improved spectrophotometric triiodide assay for lipid hydroperoxides
Authors: Darrow Robert A. , Organisciak Daniel T. 
Published: November 2006

AbstractA spectrophotometric method is described for the measurement of lipid hydroperoxides, to a lower limit of 0.5 nmoles, based on the formation of triiodide ions measured at the absorbance maximum of 365 nm. The assay mixture, which was modified from an earlier published procedure [El‐Saadani, M., Esterbauer, H., El‐Sayed, M., Goher, M., Nassar, A.Y., and Jürgens, G. (1989)J. Lipid Res. 30, 627–630], contains 18% methanol together with nonionic and cationic detergents, and is designed so that the hydroperoxides to be measured can be added in either water or methanol. By incubating the reaction mixture at 50°C for 30 min, less‐reactive hydroperoxides can be measured with the same fidelity as more‐reactive ones. Under these conditions, the assay can be carried out under ordinary room lighting and without special protection from ambient oxygen with absorbance values being stable up to 15 h. Enzymatic standardizations showed that the triiodide method gave comparable results for H2O2, cumene hydroperoxide, linoleic acid hydroperoxide, phosphatidylcholine hydroperoxide, and a photooxidized tissue extract containing a mixture of hydroperoxides. The triiodide assay is recommended primarily for measuring purified hydroperoxides.
Antagonism of [3H]fatty acid incorporation into vimentin by sodium pyruvate: Pitfalls of protein acylation
Authors: Cenedella Richard J. , Mitchell Jeanne 
Published: November 2006

AbstractIn the course of studying possible fatty acid acylation of vimentin by cultured bovine lens epithelial cells, several potential pitfalls of protein‐fatty acid acylation were recognized. Even exhaustive delipidation of vimentin with organic solvents failed to remove all noncovalently associated [3H]palmitate and [3H]myristate. Hydroxylamine treatment of vimentin, separated by sodium dodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), failed to remove either palmitate or myristate derived radiolabel. Hydroxylamine treatment did remove palmitate label from a group of lower molecular weight proteins. The myristate radiolabel associated with vimentin recovered after SDS‐PAGE and subjected to acid hydrolysis was shown due to incorporated [3H]amino acids, mainly glutamic acid, generated from the fatty acid. Adding excess sodium pyruvate to labeling media has been used by others to reduce the metabolic conversion of fatty acids to amino acids; however, no direct evidence in support of this antagonism was presented. We observed that inclusion of sodium pyruvate at between 5 and 20 mM in the labeling medium produced a dramatic decrease in incorporation of myristic acid radiolabel into vimentin. However, inclusion of even 20 mM pyruvate did not completely antagonize the metabolic conversion of fatty acid label to amino acids. Furthermore, the sodium pyruvate antagonism could be totally obscured if the exposure of X‐ray film by fluorography was even slightly prolonged. The results illustrate the danger in assuming that solvent extraction totally delipidates proteins and that adding sodium pyruvate to labeling media prevents the transfer of fatty acid label to amino acids. Caution is necessary to conclude that radiolabel associated with specific proteins following incubation of cells with labeled fatty acid is due to covalent attachment of the fatty acid to the protein.
Alteration in membrane lipid order and composition in metabolically hyperactive fatty rat adipocytes
Authors: Guerre‐Millo Michèle , Guesnet Phillipe , Guichard Colette , Durand Georges , Lavau Marcelle 
Published: November 2006

AbstractWe have previously shown that adipose cells from young genetically obese Zucker rats are characterized by very high metabolic activity together with an increase in a wide range of membrane‐mediated functions. The aim of the present study was to examine whether the physical properties of the membranes and the composition of the membrane lipids were altered in these cells. Plasma membranes and two intracellular membrane fractions were prepared by differential ultracentrifugation from inguinal adipose cells of 30‐day‐old obese (fa/fa) and lean (Fa/fa) littermates. The lipid order as measured by steady‐state fluorescence polarization of diphenylhexatriene used as probe was markedly decreased in the plasma membranes of obese rat adipose cells. Consistent with this, the cholesterol‐to‐phospholipid ratio was significantly decreased, and the degree of unsaturation of the phospholipid fatty acids was significantly increased. In intracellular membranes, none of these parameters were altered by the different genotype. In fat cells from obese rats, both plasma and intracellular membranes exhibited a 2‐fold decrease in the ratios of n−6/n−3 fatty acids mainly due to an enrichment in docosahexaenoic acid (22∶6n−3). The data show that the fatty genotype is a determinant of membrane lipid order and composition in adipose cells. The alterations reported here for young obese Zucker rat adipocytes might be related to the metabolic hyperactivity of these cells.
Synthesis and structural analysis of stereospecific 3,4,5‐trisubstituted γ‐butyrolactone phospholipids
Authors: Li Xun , Rotella David P. 
Published: November 2006

AbstractThe first synthesis of stereospecific 3,4,5‐trisubstituted γ‐butyrolactone phospholipids has been achieved by a ten‐step sequence starting fromN,N‐dimethylacetamide (9). Alkylation of 9 with 1‐bromohexane gaveN,N‐dimethyloctanamide (11), which was subjected to aldol condensation with acrolein and afforded theerythro‐N,N‐dimethyl‐3‐hydroxy‐2‐hexyl‐4‐pentenamide (6) and itsthreo isomer 7, both of which were subsequently converted to the corresponding 3‐oxy(hexanoyl) esters 15 and 16. Stereospecific cyclization of diastereomeric allylic amides (6,7,15 and 16)via iodolactonization gave 3,4,5‐trisubstituted γ‐butyrolactones (19–25) in satisfactory yields (68–89%) and with high stereoselectivity (at least 6∶1), except for thethreo amide 16 (2∶1). Conversion of the 6‐iodo‐group of the major iodolactones 23 and 24 to the corresponding 6‐hydroxy lactones 31 and 32 through a wet Prévost reaction also resulted in 4‐hydroxy lactones 30 and 33, and a mechanism for this reaction is proposed. Further phosphorylation of 4‐ or 6‐hydroxy lactones 30, 31 and 32 with diphenyl chlorophosphate gave the corresponding diphenyl phosphoric acid lactone esters 34, 35 and 36, whereas 33 underwent an elimination reaction under formation of a C(3)−C(4) double bond. Hydrogenolysis of the diphenyl groups of esters 34, 35 and 36 over Adams' catalyst [platinum(IV) oxide] yielded the corresponding phosphoric acid lactone esters 38, 39 and 40, which were finally treated with choline tetraphenylborate to afford the desired lactone phospholipids 41, 42 and 43 in overall yields of 9, 30 and 18%, respectively. The structures of all new compounds were unambiguously assigned by analysis of their1H and13C one‐dimensional and two‐dimensional nuclear magnetic resonance (NMR) spectra obtained on a 300 MHz NMR spectrometer, and the structures were confirmed by low or high resolution mass spectrometry as well as elemental analysis. The stereoisomeric purity of the final products (98.2, 99.0 and 98.5% for 41, 42 and 43, respectively) was determined by high‐performance liquid chromatography.
Comparison of the fatty acids of the tunicateBotryllus schlosseri from the Black Sea with two associated bacterial strains
Authors: Carballeira Néstor M. , Shalabi Fathi , Stefanov Kamen , Dimitrov Krassimir , Popov Simeon , Kujumgiev Athanas , Andreev Stoitze 
Published: November 2006

AbstractThe fatty acid composition of the tunicateBotryllus schlosseri and of two bacterial strains found within the tunicate, namelyVibrio parahaemolyticus and of an associated but previously unreported gram positive cocci were studied. The polyunsaturated fatty acids 6,9,12‐octadecatrienoic acid, 5,8,11,14,17‐eicosapentaenoic acid, and 4,7,10,13,16,19‐docosahexaenoic acid were particularly abundant inB. schlosseri and were not detected in the two bacterial strains found in the tunicate. Theiso/anteiso pair, 13‐methyltetradecanoic acid and 12‐methyltetradecanoic acid, were the principal fatty acids in the gram positive cocci, and the 9‐ and 11‐hexadecenoic acids were particulary abundant inV. parahaemolyticus. The diunsaturated fatty acid 9,12‐octadecadienoic acid was also shown to be present inV. parahaemolyticus. The fatty acid composition of a third bacterial strain, characterized as either aPseudomonas or anAlteromonas species, and shown to be present only in the sea water from the Black Sea and not inB. schlosseri, is also reported. This is the first investigation on fatty acids from Black Sea bacteria.
The glycosylceramides of the nematodeCaenorhabditis elegans contain an unusual, branched‐chain sphingoid base
Authors: Chitwood David J. , Lusby William R. , Thompson Malcolm J. , Kochansky Jan P. , Howarth Oliver W. 
Published: November 2006

AbstractCaenorhabditis elegans was cultured in semi‐defined medium containing yeast extract, soy peptone, glucose, hemoglobin, Tween 80, and sitosterol. Monoglycosylceramides were chromatographically purified from nematode extracts. Their structures were elucidated with mass spectrometry, nuclear magnetic resonance spectroscopy, and analysis of methanolysis products of the parent cerebrosides. The glycosylceramides were unusual in that the only long‐chain sphingoid base detected was aniso‐branched compound with a C‐4 double bond (i.e., 15‐methyl‐2‐aminohexadec‐4‐en‐1,3‐diol). Glucose was the only sugar moiety detected. The fatty acids consisted of a series of primarily straint‐chain, saturated, 2‐hydroxylated C20–C26 acids; someiso‐branched analogs also occurred. The sphingomyelins ofC. elegans were also hydrolyzed, and the sameiso‐branched C17 compound was the only sphingoid base detected. This is the first structural analysis of a nematode glycosphingolipid and the first report of an organism in which the long‐chain sphingoid bases are entirelyiso‐branched.
Studies on linoleic acid 8R‐dioxygenase and hydroperoxide isomerase of the fungusGaeumannomyces graminis
Authors: Su Chao , Brodowsky Irene D. , Oliw Ernst H. 
Published: November 2006

AbstractLinoleic acid is sequentially converted to7S,8S‐dihydroxy‐9Z,12Z‐octadecadienoic acid by the 8R‐dioxygenase and hydroperoxide isomerase of the fungusGaeumannomyces graminis, which is a common pathogen of wheat. The objective of this study was to separate and characterize the two enzyme activities. The isomerase activity was found mainly in the microsomal fraction of the mycelia and the 8R‐dioxygenase in the cytosol. The 8R‐dioxygenase could be partially purified by ammonium sulfate precipitation, gel filtration, ion exchange chromatography or isoelectric focusing. The 8R‐dioxygenase was unstable during purification, but it could be stabilized by glutathione, glutathione peroxidase and ethylenediaminetetraacetic acid. Several protease inhibitors reduced the enzyme activity. Gel filtration with Sephacryl S‐300 showed that most 8R‐dioxygenase activity was eluted with the front with little retention. Isoelectric focusing in the presence of ethylene glycol (20%) indicated an isoelectric point of pl 6.1–6.3. The enzyme was retained on strong anion exchange columns at pH 7.4 and could be eluted with 0.3–0.5 M NaCl. Incubation of the enzyme with 0.1 mM linoleic acid led to partial inactivation, which may indicate product inhibition. Paracetamol and the lipoxygenase inhibitor ICI 230,487 at 30 μM inhibited the 8R‐dioxygenase by 44 and 58%, respectively. 8R‐hydroperoxy‐9Z,12Z‐octadecadienoic acid was isolated from incubations of linoleic acid with the partially purified enzyme or with the cytosol in the presence ofp‐hydroxymercuribenzoate. The hydroperoxide was rapidly converted by the hydroperoxide isomerase in the microsomal fractions to7S,8S‐dihydroxy‐9Z,12Z‐octadecadienoic acid. The isomerase was neither inhibited by carbon monoxide nor by ketoconazole (100 μM). The isomerase was active over a broad pH range. It could be separated from the 8R‐dioxygenase by differential centrifugation, by ammonium sulfate precipitation and by gel filtration. We conclude that the linoleic acid 8R‐dioxygenase and the hydroperoxide isomerase are two separate enzymes.
Nitric oxide, an inhibitor of lipid oxidation by lipoxygenase, cyclooxygenase and hemoglobin
Authors: Kanner Joseph , Harel Stela , Granit Rina 
Published: November 2006

AbstractThe present study demonstrated that nitric oxide, which is an important mammalian metabolite, can inhibit oxidation by lipoxygenase, cyclooxygenase and hemoglobin. The inhibition is manifested as a lag‐phase that is reversible. The inhibitory effect of nitric oxide on lipoxygenase and cyclooxygenase seems to derive from i) the capability of ·NO to reduce the ferric enzyme to the ferrous form, which is inactive; ii) competition for the iron site available for exogenous ligands; and iii) the radical scavenging ability of the nitroxide radical. Nitric oxide may act as a modulator of the arachidonic acid cascade and in the generation of oxygen‐active species.
Effect of propylthiouracil‐induced hypothyroidism on membranes of adult rat brain
Authors: Salvati S. , Campeggi L. Malvezzi , Sorcini M. , Olivieri A. , Di Biase A. 
Published: November 2006

AbstractThe effect of hypothyroidism on the lipid composition of myelin and synaptosomes isolated from adult rat brain was investigated. The animals were made hypothyroid by adding 0.05% propyl‐2‐thiouracil to their drinking water for four weeks. This pathological state resulted in a significant increase in the relative percentage of choline glycerophospholipids in synaptosomes with a concomitant decrease in ethanolamine glycerophospholipids as compared to controls. In myelin, hypothyroidism significantly influenced only the relative percentage of sulfatides. The effect of the hypothyroid state on mature brain was also reflected in changes in the membrane fatty acid composition. Myelin and synaptosomes showed an increase in arachidonic (20∶4) and eicosatrienoic (20∶3) acids and an increase in the fatty acid unsaturation index. Furthermore, the 20∶4/20∶3 and 20∶3/18∶2 ratios were lower and higher, respectively, in treated animals. The data indicate that hypothyroidism affects the lipid composition of synaptosomes and myelin even though the effects were less pronounced in myelin. The lipid changes observed in hypothyroidism may be of physiological significance, as it is well known that lipid composition modulates various membrane‐bound enzymes, transporters and receptors.
Action of the new hypolipidemic agent lifibrol (K12.148) on lipid homeostasis in normal rats: Plasma lipids, hepatic sterologenesis, and the fate of injected [14C] acetate
Authors: Bell Frank P. , St. John Lori C. 
Published: November 2006

AbstractLifibrol, a new hypocholesterolemic agent with activity in humans, was examined in normal rats for its short‐term and long‐term effects on lipid homeostasis. Cholesterol (Chol) synthesis inhibition by lifibrol was demonstratedin vitro in liver minces from normal rats by following [1‐14C]acetate ([14C]Ac) and DL‐[2‐14C]mevalonate ([14C]‐MVA) incorporation into [14C]Chol. When administered at 50 mg/kg/d, lifibrol reduced plasma total Chol and triglycerides (TG) (P<0.001) within 24 h. The Chol reduction was largely a result of reduction of low density and very low density lipoprotein cholesterol (LDL+VLDL‐chol) and a smaller decrease in high density lipoprotein cholesterol (HDL‐chol). After 10 d, however, a rebound effect emerged, and after 41 d, plasma Chol, LDL+VLDL‐chol, and HDL‐chol were restored. In contrast, plasma TG remained at reduced levels (P<0.01). The rebound is attributed to counter‐regulation of hepatic sterologenesis that was assessed bothex vivo andin vivo. Theex vivo incorporation of [14C]MVA and [14C]octanoate into [14C]Chol and total digitonin‐precipitable [14C]sterols ([14C]DPS) in liver minces was increased 2‐and 6‐fold, respectively, in rats treated 6 d at 50 mg/kg. Similarly,in vivo incorporation of intraperitoneally injected [14C]Ac into hepatic [14C]DPS (2 h post‐injection) was increased 2‐ to 5‐fold at 50 mg/kg, and evidence for increased sterologenesis in nonhepatic tissue was also obtained. The increased hepatic sterologenesis, evident within 48 h, persisted out to 41 d of treatment by which time increases (P<0.002) in hepatic Chol and carcass total sterols were observed. Additionally, incorporation of injected [14C]Ac into hepatic [14C]TG was inhibited 60% by lifibrol (P<0.001), and the appearance of [14C]TG in plasma was reduced. Circulating free [14C]fatty acids ([14C]FFA) were also reduced, but hepatic [14C]FFA synthesis was unaffected, thus suggesting either a lesser release of newly formed FFA from liver or an enhanced removal from plasma.
Leukotriene B4 promotes phospholipid acylation in human neutrophils
Authors: Tou Jen‐sie , Healey Sean 
Published: November 2006

AbstractThe present study was undertaken to test the hypothesis that leukotriene B4 (LTB4) may promote extracellular fatty acid incorporation into neutrophil choline glycerophospholipids (PC) to replenish phospholipids after deacylation. Incubation of human neutrophils with LTB4 (1.5 to 150 nM) for 1 for 5 min resulted in increased fatty acid incorporation into phosphatidylinositol (PI), diacyl‐sn‐glycero‐3‐phosphocholine (diacyl‐GPC) and alkylacyl‐GPC. The magnitude of stimulation (percentage of control) of fatty acid incorporation appears to reflect increased activity of the acyltransferases catalyzing acylation of the respective lysophospholipids. LTB4 stimulation of arachidonic acid incorporation into PI was greater than into PC, whereas the stimulation of palmitic acid but not by arachidonic acid. LTB4 and 1‐O‐alkyl‐2‐N‐methylcarbamyl‐sn‐glycero‐3‐phosphocholine (cPAF) exhibited a similar stimulatory effect on fatty acid incorporation into the PC fraction. Phosphate analysis could not detect changes in the mass of PI or of PC in neutrophils exposed to LTB4 or cPAF. The results suggest that increased fatty acid incorporation into phospholipids in LTB4‐activated neutrophils reflects activation of phospholipase A2 and acyltransferases as well as ofde novo phospholipid synthesis.
Transfer of arachidonate from phosphatidylcholine to phosphatidylethanolamine and triacylglycerol in guinea pig alveolar macrophages
Authors: Nijssen J. G. , Oosting R. S. , Nÿkamp F. P. , van den Bosch H. 
Published: November 2006

AbstractGuinea pig alveolar macrophages were labeled by incubation with either arachidonate or linoleate. Arachidonate labeled phosphatidylcholine (PC), phosphatidylethanolamine (PE) and triglycerides (TG) equally well, with each lipid containing about 30% of total cellular radioactivity. In comparison to arachidonate, linoleate was recovered significantly less in PE (7%) and more in TG (47%). To investigate whether redistributions of acyl chains among lipid classes took place, the macrophages were incubated with 1‐acyl‐2‐[1‐14C]arachidonoyl PC or 1‐acyl‐2‐[1‐14C]linoleoyl PC. After harvesting, the cells incubated with 1‐acyl‐2‐[1‐14C]linoleoyl PC contained 86% of the recovered cellular radioactivity in PC, with only small amounts of label being transferred to PE and TG (3 and 6%, respectively). More extensive redistributions were observed with arachidonate‐labeled PC. In this case, only 60% of cellular radioactivity was still associated with PC, while 22 and 12%, respectively, had been transferred to PE and TG. Arachidonate transfer from PC to PE was unaffected by an excess of free arachidonate which inhibited this transfer to TG for over 90%, indicating that different mechanisms or arachidonoyl CoA pools were involved in the transfer of arachidonate from PC to PE and TG. Cells prelabeled with 1‐acyl‐2‐[1‐14C]arachidonoyl PC released14C‐label into the medium upon further incubation. This release was slightly stimulated by zymosan and threefold higher in the presence of the Ca2+‐ionophore A23187. Labeling of macrophages with intact phospholipid molecules appears to be a suitable method for studying acyl chain redistribution and release reactions.
Phosphorylation of lipids in rat primary glial cells and immortalized astrocytes (DITNC)
Authors: Tong Wei , Sun Grace Y. 
Published: November 2006

AbstractPhosphatidylinositol 4,5‐bisphosphate, a substrate in the signal transduction pathway involving phospholipase C, is synthesized in cell membranes by phosphorylation of phosphatidylinositol (PI) and phosphatidylinositol 4‐phosphate (PI‐4‐P). Incubation with [γ‐32P]adenosine triphosphate of membranes isolated from primary glial cells in culture and from an immortalized astrocyte cell line (DITNC) and subsequent separation of the lipids by high‐performance thin‐layer chromatography revealed a number of labeled lipid bands. Further analysis of the deacylated products by high‐performance liquid chromatography indicated the presence of two PI‐4‐P bands and a band corresponding to lysoPIP (PIP, PI phosphate). The two PI‐4‐P bands were more prominent in the samples from astrocyte cell membranes than from synaptic plasma membranes and plasma membranes. Analysis of the fatty acid composition of PI by gas‐liquid chromatography revealed that both 20∶3n−9 and 20∶4n−6 were present in PI of cultured cell membranes, whereas the brain membranes contained exclusively 20∶4n−6. The two PI‐4‐P bands in these membranes can be attributed to the presence of different molecular species of PI. Assignment of the fraction corresponding to lysoPIP was consistent with the observation that an increase in label in this lipid band occurred upon incubation of DITNC cell supernatant with lysoPI (1‐stearoyl PI). This suggests that endogenous lysoPI present in the cell membranes can be phosphorylated to form lysoPIP.
The effect of lidocaine onde novo phospholipid biosynthesis in the isolated hamster heart
Authors: Wong Jason T. , Man Ricky Y. K. , Choy Patric C. 
Published: November 2006

AbstractLidocaine is used clinically as an antiarrhythmic agent, but its effect on cardiac phospholipid metabolism has not been defined. In this study, hamster hearts were perfused with [1,3‐3H]glycerol in the presence of 0.5 mg/mL lidocaine. The incorporation of radioactivities into lysophosphatidic acid, phosphatidic acid, phosphatidylethanolamine, cytidine diphosphate diacylglycerol, phosphatidylinositol, phosphatidylserine, diacylglycerol and triacylglycerol were enhanced by lidocaine treatment, whereas the labelling of phosphatidylcholine was reduced. Analyses of enzyme activities in the heart after perfusion with lidocaine revealed that the activities of phosphatidate phosphatase and acyl‐coenzyme A (CoA):1,2‐diacylglycerol acyltransferase were enhanced. The presence of lidocaine in the assay did not directly stimulate these enzymes. However, the activity of acyl‐CoA:glycerol‐3‐phosphate acyltransferase was stimulated by lidocaine whereas the activity of cytidine diphosphocholine:1,2‐diacylglycerol cholinephosphotransferase was inhibited by lidocaine. We conclude that lidocaine affects the regulation of phospholipid biosynthesis in the heart by both direct and indirect modulation of phospholipid biosynthetic enzymes.