bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved resolution of31P nuclear magnetic resonance spectra of phospholipids from brain
Authors: Capuani G. , Aureli T. , Miccheli A. , Di Cocco M. E. , Ramacci M. T. , Delfini M. 
Published: November 2006

AbstractA method is described wherein the resolution of31P nuclear magnetic resonance spectra of the lipophilic fraction from a Bligh‐Dyer extract of rat brain can be enhanced. The lipids are dispersed as micelles in aqueous solution with sodium deoxycholate, and spectral resolution is further optimized by adjusting the pH and by removing ions from the solution. The application of the method to the study of aging in rat brain serves as an example.
One‐step synthesis of radioactive acyl‐CoA and acylcarnitines using rat liver mitochondrial outer membrane as enzyme source
Authors: Jalaluddin Bhuiyan A. K. M. , Pande S. V. 
Published: November 2006

AbstractRat liver mitochondrial outer membrane enriched preparations have proven to be a convenient enzyme source for synthesizing coenzyme A (CoA) and carnitine esters of radioactive fatty acids. These membranes are simple to isolate and they retain acyl‐CoA ligase and carnitine palmitoyltransferase activities well upon storage. Enzyme purification is not required. A novel aspect of the present procedure is that the same enzymatic incubation step allows both the acyl‐CoA and the acylcarnitine esters to be obtained simulataneously when carnitine is present, but produces acyl‐CoA ester only when carnitine is not included. Under the conditions described, the conversion of [1‐14C]octanoic acid to the respective esters was about 95%; the corresponding figure for [1‐14C]palmitic acids was over 70%. The procedure seems suitable for synthesizing the labeled CoA and carnitine esters from a variety of radioactive fatty acids.
Adenosine triphosphate (ATP) and other nucleotides stimulate the hydrolysis of phosphatidylethanolamine in intact fibroblasts
Authors: Kiss Zoltan , Crilly Karan S. 
Published: November 2006

AbstractAddition of adenosine triphosphate (ATP) to [14C]ethanolamine‐prelabeled NIH 3T3 fibroblasts resulted in rapid formation of [14C]ethanolamine from the prelabeled cellular phosphatidylethanolamine (PtdEtn) pool. After 2‐min exposure, 10 μM ATP had near maximal effects on PtdEtn hydrolysis. Several other nucleotides, including UTP, ITP, and the stable ATP analog adenosine 5′‐O‐(3‐thiotriphosphate) (ATPγS), also had stimulatory effects on PtdEtn hydrolysis with a potency comparable to that observed with ATP. The same nucleotides which acted on PtdEtn hydrolysis also had similar stimulatory effects on the hydrolysis of phosphatidylcholine (PtdCho) in [14C]choline‐labeled cells. In isolated membranes, Mg2+ greatly enhanced the stimulatory effects of ATP and ATPγS, but not of other nucleotides, on the hydrolysis of PtdEtn and PtdCho. Results indicate that in isolated membranes, both ATP and ATPγS stimulate phospholipid hydrolysis by two different mechanisms, but in intact cells only one of these mechanisms appears to be responsive to externally added nucleotides.
Hypothyroidism and thyroxin substitution affect the n−3 fatty acid composition of rat liver mitochondria
Authors: Raederstorff D. , Meier C. A. , Moser U. , Walter P. 
Published: November 2006

AbstractThe effects of hypothyroidism and of daily treatment for up to 21 days with thyroxin (T4, 0.5 μg/100 g body weight) on the fatty acid composition of total lipid, phosphatidylethanolamine, and phosphatidylcholine of rat liver mitochondria were studied. The fatty acid compositions of hypothyroid and euthyroid (control) rats of similar age were compared. The n−6 and n−3 polyunsaturated fatty acids (PUFA) were affected differently by the hypothyroid state. The levels of linoleic (18∶2n−6), γ‐linolenic (18∶3n−6) and dihomo‐γ‐linolenic acids (20∶3n−6) were higher in hypothyroid rats than in controls, while the level of arachidonic acid (20∶4n−6) was lower, which suggests an impairment of the elongase and desaturase activities. The n−3 polyunsaturated fatty acids, eicosapentaenoic (EPA, 20∶5n−3) and docosapentaenoic (22∶5n−3) acids, were higher in hypothyroid rats, whereas the linolenic acid (18∶3n−3) content remained constant. The level of docosahexaenoic acid (DHA, 22∶6n−3) was dramatically decreased in hypothyroid rats, while the levels of C22n−6 fatty acids were unchanged. The differences were probably due to the competition between n−3 and n−6 PUFA for desaturases, elongases and acyltransferases. When hypothyroid rats were treated with thyroxin, the changes induced by hypothyroidism in the proportions of n−6 fatty acids were rapidly reversed, while the changes in the n−3 fatty acids were only partially reversed. After 21 days of thyroxin treatments, the DHA content was only half as high in hypothyroid rats than in euthyroid rats. These results suggest that the conversion of 18∶2n−6 to 20∶4n−6 is suppressed in the hypothyroid state which favors the transformation of 18∶3n−3 to 20∶5n−3. The marked decrease in DHA content indicates an impairment of the enzymes involved in the DHA metabolism, possibly the n−3 Δ4 desaturase or the acyltransferases. The increased levels of EPA and 22∶5n−3 is consistent with the inhibition of the n−3 pathway at the Δ4 desaturase step. Observed modifications in the fatty acid composition may significantly alter eicosanoid synthesis and membrane functions in hypothyroidism.
Incorporation of n−3 fatty acids into WB‐F344 cell phospholipids inhibits gap junctional intercellular communication
Authors: Hasler Clare M. , Trosko James E. , Bennink Maurice R. 
Published: November 2006

AbstractIn this investigation, we demonstrate that rat liver epithelial (WB‐F344) cells grown in medium supplemented with n−3 fatty acids (FA) results in the inhibition of gap junctional intercellular communication (GJIC). Cells incubated for 48 hr in medium containing 50 μM α‐linolenate (18∶3n−3) resulted in a 60% inhibition of GJIC, compared to control cells, while treatment with γ‐linolenate (18∶3n−6) had no effect. Supplementation with octadecatetraenoate (18∶4n−3), eicosapentaenoate (20∶5n−3), and docosahexaenoate (22∶6n−3), inhibited GJIC by 42%, 28%, and 18%, respectively. Incubation with each of the n−3 FA markedly increased the total n−3 FA content of cellular phospholipids (PL). Growing cells in medium containing 50 μM arachidonate (20∶4n−6) plus 50 μM 18∶3n−3 partially attenuated the inhibition of GJIC induced by 18∶3n−3. The mechanism by which n−3 FA inhibit GJIC remains to be determined.
Rapid three‐step purification of a hepatic neutral cholesteryl ester hydrolase which is not the pancreatic enzyme
Authors: Ghosh Shobha , Grogan W. McLean 
Published: November 2006

AbstractA rat liver cytosolic cholesteryl ester hydrolase (CEH) was purified 12,600‐fold by ammonium sulfate precipitation, cation exchange chromatography and gel permeation high‐performance liquid chromatography, with an overall yield of 20%. Its properties are compared to those of pancreatic CEH, with which it has sometimes been identified. Liver CEH exhibited a single silver stained band following SDS‐polyacrylamide gel electrophoresis (Mr=66 kDa), was activated by 0.5–10 mM taurocholate but was strongly inhibited by higher levels of taurocholate, which activate pancreatic CEH. Whereas bile salts are known to induce formation of a hexamer of pancreatic CEH, in the current study, 0.5 mM taurocholate dissociated a multimeric form of liver CEH to monomer. Liver CEH did not coelute with pancreatic CEH from cation exchange and chromatofocusing columns, exhibited no immunoreactivity with anti‐rat pancreatic CEH IgG in Western blots, was not inhibited by anti‐rat pancreatic CEH IgG and had a different amino acid composition from pancreatic CEH. In contrast to liver CEH, which is known to be activated by protein kinases A and C, pancreatic CEH was unaffected by cofactors for protein kinase A and was inhibited by cofactors for protein kinase C.
Effect of chylomicron remnants on cholesterol metabolism in cultured rabbit hepatocytes: Very low density lipoprotein and bile acid production
Authors: Kosykh Vladimir A. , Novikov Dmitri K. , Trakht Iliya N. , Podrez Eugeni A. , Victorov Alexander V. , Repin Vadim S. , Smirnov Viadimir N. 
Published: November 2006

AbstractThe interrelationship between very low density lipoprotein (VLDL) secretion and bile acid production was studied in primary culture of rabbit hepatocytes. Chylomicron remnants (CR) were added to the cultures to study their effect on VLDL secretion and bile acid production. After 24 hr preincubation of cells with CR (10–50 μg protein/mL), intercellular neutral lipid content was increased 1.5–4‐fold in a dose‐dependent manner. Neutral lipid accumulation was accompanied by a 70–90% reduction of [14C]acetate incorporation into cholesterol, while no stimulation of [14C]oleate incorporation into cholesteryl esters was observed. Incubation of cells with CR increased secretion of free cholesterol, triacylglycerol and apoproteins B and E in VLDL. Stimulation of VLDL cholesterol secretion was accompanied by a reduction of taurocholic acid synthesis. These data demonstrate the existence of an inverse relationship between secretion of VLDL cholesterol and bile acid production under conditions of effective uptake of triacylglycerol‐rich CR by hepatocytes.
Similarities in surface lipids of chylomicrons from glyceryl and alkyl ester feeding: Major components
Authors: Yang Lu‐Ying , Kuksis Arnis , Myher John J. 
Published: November 2006

AbstractThis study tests the hypothesis that the rat chylomicrons are assembled and released into lymph similarly regardless of the site (rough or smooth endoplasmic reticulum) or pathway (phosphatidic acid or monoacylglycerol) of triacylglycerol biosynthesis. For this purpose we determined the lipid class, fatty acid and molecular species composition of the choline, ethanolamine, inositol and serine phospholipids of lymph chylomicrons during absorption of menhaden, mustard‐seed and corn oil (monoacylglycerol pathway) or the corresponding fatty acid methyl or ethyl esters (phosphatidic acid pathway). The dietary fatty acids were found to be incorporated to various extents into different phospholipid classes, the proportions of which were not affected by the nature of the dietary fat. The chylomicron phospholipids contained 80–82% choline, 8% ethanolamine and 2.5% inositol glycerophospholipids, and much smaller amounts of serine and other minor phospholipids. Administration of a meal of each dietary fat resulted in a retention of approximately 50% endogenous fatty acids in the major glycerophospholipids of the chylomicrons. A minimum of 50% of the molecular species of the choline and ethanolamine glycerophospholipids contained at least one exogenous fatty acid. No significant discrepancies were found in the fatty acid and molecular species composition of the glycerophospholipids between chylomicrons from the oil and corresponding ester feeding. It is concluded that the chylomicrons arising from the monoacylglycerol (oil feeding) and the phosphatidic acid (ester feeding) pathways of triacylglycerol biosynthesis become enveloped in surfactant monolayers containing qualitatively and quantitatively identical classes and molecular species of phospholipids.
Compositional changes and apoprotein A‐I metabolism of plasma high density lipoprotein in estrogenized chicks
Authors: Cho B. H. Simon , Park Jeong R. 
Published: November 2006

AbstractThe effect of estrogen on compositional changes, apolipoprotein (apo) A‐I metabolism and the morphology of plasma high density lipoprotein (HDL) were investigated in chicks. The administration of 17β‐estradiol (25 mg/kg body weight) to growing male chicks (8‐week‐old) markedly reduced the concentrations of plasma HDL components, except for triglyceride (TG). At the same time, levels of TG, total cholesterol (TC) and phospholipid (PL) in plasma were greatly elevated. The respective values for TG, TC, PL and protein in HDL were 13.9, 89.3, 154.1 and 231.7 (mg/dL) in the control, and 39.0, 35.1, 113.8 and 160.0 (mg/dL) in chicks upon estrogen treatment for one day.In vivo kinetic studies showed that the fractional catabolic rate of HDL apo A‐I was significantly higher (p<0.05) in estrogen‐treated chicks than in control birds, indicating an increased efficiency of HDL removal in the former. The production rate of HDL apo A‐I also was significantly lower (p<0.05) in estrogen‐treated chicks. Sodium dodecyl sulfate‐acrylamide gel electrophoresis followed by laser scanning densitometry of HDL apolipoproteins in estrogen‐treated chicks revealed a reduction of apo A‐I and the occurrence of new apolipoproteins which had been absent in HDL of untreated birds. The HDL particles showed that the mean particle size of HDL became larger upon estrogen treatment. Particles with diameters between 70 and 123 Å were predominant in HDL of control chicks, while particles with diameters between 97 and 143 Å were most abundant in HDL of estrogen‐treated chicks.
In vivo determination of triglyceride secretion using radioactive glycerol in rats fed different dietary saturated fats
Authors: Lai Hui‐Chuan , Lasekan John B. , Yang Huan , Clayton Murray K. , Ney Denise M. 
Published: November 2006

AbstractOur objective was to determine the relative rates ofin vivo triglyceride (TG) secretion and the composition of very low density lipoproteins (VLDL) in rats fed different dietary saturated fats. Male Sprague‐Dawley rats (150–200 g) were fed diets containing 16% corn oil, or 14% butterfat, 14% beef tallow, 14% olive oil, or 14% coconut oil plus 2% corn oil for 5 wk. Changes in plasma TG specific radioactivity were determined in individual, unanesthetized fasted rats after injection of 100 μCi [2‐3H]glycerol. Nonlinear regression analysis using a 2‐compartment model was used to determine the fractional rate constant for TG turnover in plasma. The plasma TG pool was 33–40% larger with beef tallow than with corn, olive or coconut oil feeding (p<0.05), and 20% larger with beef tallow than with butterfat feeding. The rate of TG secretion into plasma (mg/min/100 g body weight) was 60% higher in animals fed beef tallow than corn or coconut oil (p<0.05) and 26–33% higher in animals fed beef tallow than olive oil or butterfat. Differences in VLDL composition (% wt) were also noted. Our data suggest that greater TG secretion is the primary factor contributing to the larger TG pool with ingestion of beef tallow relative to butterfat, corn or coconut oil. These results suggest that different dietary saturated fats have unique effects on TG metabolism in rats.
Further oxidation products of 2,2,5,7,8‐pentamethyl‐6‐chromanol
Authors: Suarna Cacang , Baca Manuel , Craig Donald C. , Scudder Marcia , Southwell‐Keely Peter T. 
Published: November 2006

AbstractIn order to undertake a quantitative study by high‐performance liquid chromatography of the rate of oxidation of 2,2,5,7,8‐pentamethyl‐6‐chromanol (1), the model compound of α‐tocopherol, a number of potential products were required as standards. Among these compounds were 2,2,7,8‐tetramethylchroman‐5,6‐dione (10) and 2,2,7‐trimethyl‐6‐hydroxychroman‐5,8‐dione (17), the model compounds of tocored and tocopurple, respectively. Attempts to synthesize 10 and 17 led to the isolation of 8‐hydroxymethyl‐2,2,7‐trimethylchroman‐5,6‐dione (14) and 1,2‐bis(2,2,7‐trimethylchroman‐5,6‐dione‐8‐)ethane (19) a dimer of 10. Purification by thin‐layer chromatography of the spirodimer (20) of 1 resulted in an acid‐catalyzed decomposition to 1‐(2,2,7,8‐tetramethyl‐6‐chromanol‐5‐)2‐[2‐(3‐methyl‐3‐hydroxybutyl)‐5,6‐dimethyl‐1,4‐benzoquinone‐3‐]ethane (23), a new chromanol‐quinone dimer.
Lipid hydroperoxide measurement by oxidation of Fe2+ in the presence of xylenol orange. Comparison with the TBA assay and an iodometric method
Authors: Jiang Zhen‐Yue , Woollard Alison C. S. , Wolff Simon P. 
Published: November 2006

AbstractStudy of the role of hydroperoxides and lipid peroxidation in disease requires simple and sensitive methods for direct hydroperoxide measurement. We report on a technique for measuring hydroperoxide which relies upon the rapid hydroperoxide‐mediated oxidation of Fe2+ under acidic conditions. Fe3+ forms a chromophore with xylenol orange which absorbs strongly at 560 nm, yielding an apparent E560 (for H2O2, butyl hydroperoxide and cumene hydroperoxide) of 4.3×104 M−1 cm−1. The assay was validated in a study of liposomal lipid peroxidation and shown to give results comparable with those obtained by an iodometric method or by measuring conjugated dienes. The assay involving thiobarbituric acid, by comparison, underestimates lipid peroxidation and does not measure hydroperoxideper se.
Effects of perfluorodecanoic acid onde novo fatty acid and cholesterol synthesis in the rat
Authors: Davis John W. , Vanden Heuvel John P. , Peterson Richard E. 
Published: November 2006

AbstractPerfluorodecanoic acid (PFDA) is a peroxisome proliferator that causes a dose‐dependent (20–80 mg/kg) increase in hepatic triacylglycerol and cholesteryl ester levels in the rat. We hypothesized that PFDA may cause an increase in thede novo synthesis of fatty acids and cholesterol in this species, which would explain observed effects. The incorporation of3H2O into tissue lipids was examined 7 days after rats received vehicle or 20 or 80 mg/kg of PFDA. PFDA treatment decreased the rate of synthesis of cholesterol and fatty acids in the liver and in epididymal fat pad. At a PFDA dose (20 mg/kg) that decreasedde novo synthesis of fatty acids and cholesterol, there was no effect on the concentration of fatty acids and cholesterol in the liver, epididymal fat pads, and plasma. We conclude that PFDA induced fatty liver is due to either a decrease in the oxidation of fatty acids in the liver, or an impairment of triacylglycerol catabolism and/or export from the liver, and is not the result of an increase inde novo synthesis of fatty acids and cholesterol.
Inhibition of cholesterol synthesis by cyclopropylamine derivatives of squalene in human hepatoblastoma cells in culture
Authors: Van Sickle W. A. , Angelastro M. R. , Wilson P. , Cooper J. R. , Marquart A. , Flanagan M. A. 
Published: November 2006

AbstractTwo squalene derivatives, trisnorsqualene cyclopropylamine and trisnorsqualeneN‐methylcyclopropylamine, were synthesized and tested for inhibition of lanosterol and squalene epoxide formation from squalene in rat hepatic microsomes, and for the inhibition of cholesterol syntheses in human cultured hepatoblastoma (HepG2) cells. Trisnorsqualene cyclopropylamine inhibited [3H]‐squalene conversion to [3H]squalene epoxide in microsomes (IC50=5.0 μM), indicating that this derivative inhibited squalene mono‐oxygenase. Trisnorsqualenen‐methylcyclopropylamine inhibited [3H]squalene conversion to [3H]lanosterol (IC50=12.0 μM) and caused [3H]‐squalene epoxide to accumulate in microsomes, indicating that this derivative inhibited 2,3‐oxidosqualene cyclase. Cholesterol biosynthesis from [14C]acetate in HepG2 cells was inhibited by both derivatives (IC50=1.0 μM for trisnorsqualene cyclopropylamine; IC50=0.5 μM for trisnorsqualeneN‐methylcyclopropylamine). Cells incubated with trisnorsqualene cyclopropylamine accumulated [14C]squalene, while cells incubated with trisnorsqualeneN‐methylcyclopropylamine accumulated [14C]squalene epoxide and [14C]squalene diepoxide. The concentration range of inhibitor which caused these intermediates to accumulate coincided with that which inhibited cholesterol synthesis. The results indicate that cyclopropylamine derivatives of squalene are effective inhibitors of cholesterol synthesis, and that substitutions at the nitrogen affect enzyme selectivity and thus the mechanism of action of the compounds.
Effects of n−3 and n−6 fatty acids on tumor necrosis factor cytotoxicity in WEHI fibrosarcoma cells
Authors: Brekke Ole‐L. , Espevik Terje , Bardal Tora , Bjerve Kristian S. 
Published: November 2006

AbstractModulation by fatty acids of the cytotoxic effect of recombinant tumor necrosis factor alpha (TNF) toward WEHI 164 mouse fibrosarcoma cells has been examined. Preincubating the highly TNF‐sensitive WEHI clone 13 cells for 44 hr with 50 μmol/L of 20∶5n−3, 22∶6n−3, 18∶3n−6, 20∶3n−6 or 20∶4n−6 reduced cell survival 22 hr after challenge with TNF (40 ng/L) by 65%, 72%, 60%, 98% and 85%, respectively. In comparison, 18∶3n−3, 18∶2n−6 and 18∶1n−9 had only negligible effects on TNF‐induced toxicity. Different extent of fatty acid incorporation into cell total phospholipids or triglycerides could not explain the observed effects on TNF cytotoxicity, and the enhanced cytotoxicity could therefore not be explained merely by an increased unsaturation of the cell membranes. In addition to the fatty acid supplied, preincubation with 18∶2n−6, 18∶3n−6 or 18∶3n−3 also enriched the cells with 20∶2n−6, 20∶3n−6 and 20∶3n−3, respectively, most likely due to chain elongation. The results suggest that the WEHI cells have a low Δ6 desaturase activity, and that n−6 and n−3 acids must have at least 3 or 4 double bonds, respectively, to enhance TNF cytotoxicity in WEHI cells. Dexamethasone partly inhibited TNF‐induced cytotoxicity, while cyclooxygenase, thromboxane synthetase or lipoxygenase inhibitors had no or negligible effects. The antioxidant butylated hydroxyanisole (BHA) completely inhibited TNF‐induced cytotoxicity, while the structurally and functionally similar antioxidant butylated hydroxy‐toluene had no such effect, indicating that BHA does not block TNF cytotoxicity through its antioxidant effect. The results suggest that TNF cytotoxicity involves, directly or indirectly, metabolism of long‐chain polyun‐saturated fatty acids, and we speculate that fatty acid metabolites are involved.
The effect of dietary supplementation with eicosapentaenoic acid on the phospholipid and fatty acid composition of erythrocytes of marmoset
Authors: Gibson Robert A. , Neumann Mark A. , Burnard Sharon L. , Rinaldi Josephine A. , Patten Glen S. , McMurchie Edward J. 
Published: November 2006

AbstractAdult male marmoset monkeys were fed eicosapentaenoic acid (20∶5n−3) as the ethyl ester in diets containing either 32% (reference diet, no added cholesterol) or 7% (atherogenic diet with 0.2% added cholesterol) linoleic acid (18∶2n−6) for 30 wk. No changes were seen in the level of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) but minor changes were observed in both the sphingomyelin (SPM) and phosphatidylinositol plus phosphatidylserine (PI+PS) fractions of erythrocyte lipids. The extent of total n−3 fatty acid incorporation into membrane lipids was higher in atherogenic diets (polyunsaturated/monounsaturated/saturated (P/M/S) ratio 0.2∶0.6∶1.0) than reference diets (P/M/S ratio 1∶1∶1) and this was true for both PE (33.4±1.0%vs 24.3±1.1%) and PC (9.3±0.5%vs 4.9±0.3%). Although suitable controls for cholesterol effects were not included in the study, earlier results obtained with marmosets lead us to believe such effects were probably small. Regardless of basic diet (atherogenic, reference), 20∶5n−3 was preferentially incorporated into PE (10.8±0.2%, 6.0±0.02%) while smaller amounts were incorporated into PC (6.9±0.4%, 3.2±0.2%). The major n−3 polyunsaturated fatty acid found in PE in response to dietary 20∶5n−3 was the elongation metabolite 22∶5n−3 in both the atherogenic (17.7±0.7%) and reference (14.3±1.0%) dietary groups; 22∶6n−3 levels were less affected by diet (4.7±0.3% and 3.9±0.2%, respectively). The results can be interpreted to indicate an inverse relationship between the amount of dietary 18∶2n−6 and incorporation of 20∶5n−3 into erythrocyte membrane phospholipids regardless of whether the major dietary n−3 fatty acid was α‐linolenate (18∶3n−3) or 20∶5n−3. This interpretation is supported by theoretical calculations.