bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secretion of hepatic lipase by perfused liver and isolated hepatocytes
Authors: Galan Xavier , Robert Monique Q. , Llobera Miquel , Ramírez Ignasi 
Published: November 2006

AbstractHepatic lipase is found in liver and in adrenal glands and ovaries. Because in adult rats, neither adrenals nor ovaries synthesize this enzyme, it is assumed that the liver is the origin of their hepatic lipase. Our aim was to study the secretion of hepatic lipase by the liver. We observed that plasma of both fed and fasted rats contained hepatic lipase activity. This activity was significantly correlated with that in the liver. Isolated livers, perfused with heparin‐free medium, secreted fully active hepatic lipase to the perfusate. The addition of heparin resulted in a rapid and larger release of hepatic lipase to the perfusate. In isolated hepatocytes, heparin did not affect the secretion of hepatic lipase mass, although it increased the stability of the enzyme activity. To study the degradation of hepatic lipase by hepatocytes, protein synthesis was blocked with cycloheximide, and both secreted and intracellular hepatic lipases were analyzed by Western blotting. We observed that the amount of hepatic lipase secreted equaled the decrease of intracellular mass. The total mass of the enzyme (inside and outside the cells) remained constant, at least for 90 min. In the next experiment, 0.7 nM 125I‐hepatic lipase was added to hepatocyte suspensions, and the appearance of trichloracetic acid‐soluble products was analyzed. Only 12% of the radioactivity added was associated with the cells after 90 min of incubation, and less than 2% of the hepatic lipase added was degraded. Although the association was decreased in the presence of heparin, the amount of 125I‐hepatic lipase degraded was not affected. Taking all these results into account, we propose a model for the continuous secretion of hepatic lipase by the liver.
Study of individual trans‐ and cis‐16∶1 isomers in cow, goat, and ewe cheese fats by gas‐liquid chromatography with emphasis on the trans‐Δ3 isomer
Authors: Destaillats Frédéric , Wolff Robert L. , Precht Dietz , Molkentin Joachim 
Published: November 2006

AbstractLow‐temperature gas‐liquid chromatography (GLC) was applied to study the distribution profiles of isomeric trans‐and cis‐hexadecenoic acids in ruminant (cow, goat, and ewe) milk fat after their fractionation by argentation thin‐layer chromatography (Ag‐TLC). The fat was extracted from cheeses (12 samples of each species), the most common foods made with goat and ewe milks. The predominant trans‐16∶1 isomer is palmitelaidic acid (the Δ9 isomer), but it does not exceed one‐third of the total group, which itself represents 0.17% (cow), 0.16% (goat), and 0.26% (ewe) of the total fatty acids. The trans‐Δ3 16∶1 isomer, which is reported for the first time in ruminant lipids and which likely comes from the animals' feed, is present at a level of ca. 10% of the trans‐16∶1 acid group. Otherwise, all isomers with their ethylenic bond between positions Δ4 and Δ14 are observed in the three species studied, roughly showing the same relative distribution pattern. Quantitatively, the trans‐16∶1 isomers only represent ca. 5% of the sum of the trans‐16∶1 plus trans‐18∶1 isomers, and they appear of little importance in comparison. It is inferred from this and recent studies that some previously reported data that were established for consumption assessments dealt in fact mainly with iso‐17∶0 acid, which was confused with (and added to) trans‐Δ9 (palmitelaidic) acid; consequently, these results were large overestimates. Regarding the cis‐16∶1 acids, the Δ9 isomer is the prominent constituent as expected, but the second‐most important isomer is the Δ13 isomer. It does not appear that trans‐16∶1 isomers are from ruminant milk fats of great nutritional importance as compared with trans‐18∶1 isomeric acids. As for trans‐18∶1 isomers, the combination Ag‐TLC/GLC is a necessary procedure to quantitate trans‐16∶1 acids accurately and reliably. Ag‐TLC allows removal of interfering branched 17∶0 acids and cis‐16∶1 acids, and low‐temperature GLC permits an accurate measurement of all individual isomers most of which with baseline resolution.
Determination of the phospholipid/lipophilic compounds ratio in liposomes by thin‐layer chromatography scanning densitometry
Authors: Rodríguez S. , Cesio M. V. , Heinzen H. , Moyna P. 
Published: November 2006

AbstractThe determination of the ratio of phospholipid/ lipophilic compounds in liposomes was achieved after thin‐layer chromatography (TLC) by measuring the spot intensities of dipalmitoyl phosphatidylcholine and the lipophilic compound. The liposome components under study were separated on one TLC plate, developed in two steps, and detected after charring the plate with specific visualization reagents. The method shows good reproducibility and provides a simple way to quantify the level of lipophilic compound incorporated in the liposome bilayer.
Antioxidant reactions of α‐tocopherolhydroquinone
Authors: Liebler Daniel C. , Burr Jeanne A. 
Published: November 2006

Abstractα‐Tocopherolhydroquinone (TQH2) is a product of α‐tocopherol oxidation/reduction that exerts antioxidant effects in biological systems. TQH2 inhibited autoxidation of methyl linoleate initiated by peroxyl radicals derived from thermolysis of 2,2′‐azobis(2,4‐dimethylvaleronitrile) in acetonitrile. TQH2 oxidation yielded α‐tocopherolquinone (TQ) as a major product and 2,3‐epoxy‐α‐tocopherolquinone and 5,6‐epoxy‐α‐tocopherolquinone as minor products. Each TQH2 consumed approximately two peroxyl radicals in the course of the oxidation. The data suggest that TQH2 scavenges peroxyl radicals primarily by electron transfer to form TQ and secondarily by addition‐elimination to form the epoxyquinones.
Biotransformation of linoleic acid by Clavibacter sp. ALA2: Heterocyclic and heterobicyclic fatty acids
Authors: Gardner Harold W. , Hou Ching T. , Weisleder David , Brown Wanda 
Published: November 2006

AbstractClavibacter sp. ALA2 transformed linoleic acid into a variety of oxylipins. In previous work, three novel fatty acids were identified, (9Z)‐12,13,17‐trihydroxy‐9‐octadecenoic acid and two tetrahydrofuran‐(di)hydroxy fatty acids. In this report, we confirm the structures of the tetrahydrofuran‐(di)hydroxy fatty acids by nuclear magnetic resonance as (9Z)‐12‐hydroxy‐13,16‐epoxy‐9‐octadecenoic acid and (9Z)‐7,12‐dihydroxy‐13,16‐epoxy‐9‐octadecenoic acid. Three other products of the biotransformation were identified as novel heterobicyclic fatty acids, (9Z)‐12,17;13,17‐diepoxy‐9‐octadecenoic acid, (9Z)‐7‐hydroxy‐12,17;13,17‐diepoxy‐9‐octadecenoic acid, and (9Z)‐12,17;13,17‐diepoxy‐16‐hydroxy‐9‐octadecenoic acid. Thus, Clavibacter ALA2 effectively oxidized linoleic acid at C‐7,‐12,‐13,‐16, and/or‐17.
Dietary conjugated linoleic acid did not alter immune status in young healthy women
Authors: Kelley D. S. , Taylor P. C. , Rudolph I. L. , Benito P. , Nelson G. J. , Mackey B. E. , Erickson K. L. 
Published: November 2006

AbstractThe purpose of this study was to examine whether conjugated linoleic acid (CLA) supplementation in human diets would enhance indices of immune status as reported by others for animal models. Seventeen women, 20–41 yr, participated in a 93‐d study conducted in two cohorts of 9 and 8 women at the Metabolic Research Unit of Western Human Nutrition Research Center. Seven subjects were fed the basal diet (19, 30 and 51% energy from protein, fat, and carbohydrate, respectively) throughout the study. The remaining 10 subjects were fed the basal diet for the first 30 d, followed by 3.9 g CLA (Tonalin)/d for the next 63 d. CLA made up 65% of the fatty acids in the Tonalin capsules, with the following isomeric composition: t10, c12, 22.6%; c11, t13, 23.6%; c9, t11, 17.6%; t8, c10, 16.6%; and other isomers 19.6%. Most indices of immune response were tested at weekly intervals, three times at the end of each period (stabilization/intervention); delayed‐type hypersensitivity (DTH) to a panel of six recall antigens was tested on study day 30 and 90; all subjects were immunized on study day 65 with an influenza vaccine, and antibody titers were examined in the sera collected on day 65 and 92. None of the indices of immune status tested (number of circulating white blood cells, granulocytes, monocytes, lymphocytes, and their subsets, lymphocytes proliferation in response to phytohemagglutinin, and influenza vaccine, serum influenza antibody titers, and DTH response) were altered during the study in either dietary group. Thus, in contrast to the reports with animal models, CLA feeding to young healthy women did not alter any of the indices of immune status tested. These data suggest that short‐term CLA supplementation in healthy volunteers is safe, but it does not have any added benefit to their immune status.
Cu2+‐induced low density lipoprotein peroxidation is dependent on the initial O2 concentration: An O2 consumption study
Authors: Lodge John K. , Traber Maret G. , Sadler Peter J. 
Published: November 2006

AbstractAtherosclerotic plaques form in the arterial intima, where low density lipoprotein (LDL) is thought to be oxidatively modified at sites which may contain catalytic amounts of copper in the presence of low O2 tension. We have investigated O2 consumption during LDL peroxidation induced by Cu2+ ions in vitro and found two phases: a lag phase followed by a phase of rapid O2 consumption. The length of the lag phase was dependent on Cu2+ and on initial O2 concentrations; increasing either decreased the lag time; however, LDL concentration had no effect. LDL‐induced Cu2+ reduction, however, was not affected by low initial O2 concentrations, suggesting that O2 is not required for LDL‐mediated reduction of Cu2+. Following the lag phase O2 consumption was dependent upon LDL or initial O2 concentrations; Cu2+ concentrations had little effect, suggesting that the propagation phase is more dependent on the presence of LDL lipids and O2 as substrates for the reaction. In summary, LDL peroxidation takes place in the presence of Cu2+ at low O2 tension; however, the reaction is dependent upon initial O2 concentrations; increases shorten the lag phase and accelerate O2 consumption.
Further characterization of rat dihydroceramide desaturase: Tissue distribution, subcellular localization, and substrate specificity
Authors: Causeret Catherine , Geeraert Luc , Van der Hoeven Gerd , Mannaerts Guy P. , Van Veldhoven Paul P. 
Published: November 2006

AbstractThe introduction of the double bond in the sphingoid backbone of sphingolipids occurs at the level of dihydroceramide via an NADPH‐dependent desaturase, as discovered in permeabilized rat hepatocytes. In the rat, the enzyme activity, which has now been further characterized, appeared to be mostly enriched in liver and Harderian gland. By means of subcellular fractionation of rat liver homogenates and density gradient separation of microsomal fractions, the desaturase was localized to the endoplasmic reticulum. Various detergents were inhibitory to the enzyme, and maximal activities were obtained in the presence of NADPH and when the substrate was complexed to albumin. In the presence of albumin, the chain length of the fatty acid of the truncated dihydroceramides hardly affected the activity. Finally, in view of a likely evolutionary relationship between desaturases and hydroxylases, the formation of hydroxylated intermediates was analyzed. No evidence for their presence was found under our assay conditions.
Discovery of an 11(R)‐ and 12(S)‐lipoxygenase activity in ovaries of the mussel Mytilus edulis
Authors: Coffa Gianguido , Hill Elizabeth M. 
Published: November 2006

AbstractEicosanoid biosynthesis was investigated in mussel gonads by incubation of tissue homogenates with radiolabeled arachidonic acid and analysis of the products by radio‐high‐performance liquid chromatography. No radiolabeled metabolites were formed in homogenates of testes, but two major metabolites were synthesized by ovarian preparations. The radiolabeled metabolites were analyzed by mass spectrometry and chiral chromatography and identified as 11(R)‐hydroxy‐5,8,12,14‐eicosatetraenoic acid and 12(S)‐hydroxy‐5,8,10,14‐eicosatetraenoic acid. In addition, four other nonlabeled metabolites, formed from endogenous substrates, were detected in ovarian extracts. Their structures, determined by mass spectrometric analysis, were the corresponding 11‐ and 12‐hydroxy analogs formed from eicosapentaenoic acid (11‐HEPE and 12‐HEPE) and 9‐hydroxy‐6,10,12,15‐octadecatetraenoic acid (9‐HOTE) and 13‐hydroxy‐6,9,11,15‐octadecatetraenoic acid formed from stearidonic acid. The biosynthesis of the 11‐ and 12‐hydroxy products was calcium dependent, localized to the 100,000×g supernatant cell fraction, and was inhibited by nordihydroguaiaretic acid, but not inhibited by the prostaglandin synthase inhibitors aspirin and indomethacin, or the monoxygenase inhibitor proadifen. Together these data suggested that both the 11(R)‐ and 12(S)‐hydroxy products were formed from lipoxygenase‐type enzymes. Incubation of homogenates of immature ovaries with eicosapentaenoic acid revealed the major product to be 12‐HEPE, whereas in mature ovaries mainly 11‐HEPE was formed. Extraction of spawned eggs with methanol revealed that predominantly 11‐HEPE and 9‐HOTE were formed from endogenous substrates. This study shows that female gonads of the mussel express an 11(R)‐ and 12(S)‐lipoxygenase activity whose expression is dependent on differentiation of the ovary.
Evidence for the mitochondrial biosynthesis of 3R‐hydroxy‐5Z,8Z,11Z,14Z‐eicosatetraenoic acid in the yeast Dipodascopsis uninucleata
Authors: Fox Simon R. , Hamberg Mats , Friend John , Ratledge Colin 
Published: November 2006

AbstractThe biosynthesis of 3R‐hydroxy‐5Z,8Z,11Z,14Z‐eicosatetraenoic acid (3R‐HETE) from arachidonic acid (20∶4n−6) by the hyphal‐forming yeast, Dipodascopsis uninucleata, in cell‐free enzyme extracts required CoASH, ATP, NAD+ and Mg2+; 3R‐HETE was present as the CoA derivative in enzyme extracts and its biosynthesis was associated with mitochondria. Its synthesis was high from arachidonoyl‐CoA (15% conversion of the substrate; 22 nmol mg protein−1·h), but significantly higher from trans‐2‐arachidonoyl‐CoA (53 nmol mg protein−1·min). Aspirin, an inhibitor of prostaglandin endoperoxide synthase synthase (cyclooxygenase), did not significantly inhibit 3R‐HETE biosynthesis in enzyme extracts, as opposed to antimycin A (46% inhibition). The chirality of 3‐HETE was 95% R and 5% S. 3R‐HETE has the same chirality as the products of peroxisomal enoyl‐CoA hydratases of Neurospora crassa and Saccharomyces cerevisiae; the difference appears to be that in D. uninucleata the R‐enantiomers are synthesized in mitochondria. Exogenously supplied eicosapentaenoic acid was converted to 3‐hydroxy 5Z,11Z,14Z,17Z‐eicosapentaenoic acid by cell‐free enzyme extracts though there was no requirement for a 5Z,8Z‐diene structure for the biosynthesis of 3‐hydroxylated fatty acids as 3‐hydroxy‐8Z,11Z,14Z, and 3‐hydroxy‐11Z,14Z,17Z‐eicosatrienoic acids were synthesized from the corresponding fatty acids. We found no evidence for the synthesis of the prostaglandins F2α and F2.
Human, but not bovine, oxidized cerebral spinal fluid lipoproteins disrupt neuronal microtubules
Authors: Neely M. D. , Swift L. L. , Montine T. J. 
Published: November 2006

AbstractCerebral spinal fluid (CSF) lipoproteins have become a focus of research since the observation that inheritance of particular alleles of the apolipoprotein E gene affects the risk of Alzheimer's disease (AD). There is evidence of increased lipid peroxidation in CSF lipoproteins from patients with AD, but the biological significance of this observation is not known. A characteristic of the AD brain is a disturbance of the neuronal microtubule organization. We have shown previously that 4‐hydroxy‐2(E)‐nonenal, a major product of lipid peroxidation, causes disruption of neuronal microtubules and therefore tested whether oxidized CSF lipoproteins had the same effect. We exposed Neuro 2A cells to human CSF lipoproteins and analyzed the microtubule organization by immunofluorescence. In vitro oxidized human CSF lipoproteins caused disruption of the microtubule network, while their native (nonoxidized) counterparts did not. Microtubule disruption was observed after short exposures (1 h) and lipoprotein concentrations were present in CSF (20 μg/mL), conditions that did not result in loss of cell viability. Importantly, adult bovine CSF lipoproteins, oxidized under identical conditions, had no effect on the microtubule organization of Neuro 2A cells. Comparison of human and bovine CSF lipoproteins revealed similar oxidation‐induced modifications of apolipoproteins E and A‐I as analyzed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and Western blotting. Fatty acid analysis revealed substantially lower amounts of unsaturated fatty acids in bovine CSF lipoproteins, when compared to their human counterparts. Our data therefore indicate that oxidized human CSF lipoproteins are detrimental to neuronal microtubules. This effect is species‐specific, since equally oxidized bovine CSF lipoproteins left the neuronal microtubule organization unchanged.
Involvement of the ceramide signaling pathway in modulating the differentiated state of porcine thyroid cells
Authors: Schneider C. , Delorme N. , Buisson‐Legendre N. , Bellon G. , Emonard H. , El Btaouri H. , Hornebeck W. , Haye B. , Martiny L. 
Published: November 2006

AbstractNeutral sphingomyelinase (Smase) is a cell membrane‐associated phospholipase that hydrolyzes sphingomyelin to phosphocholine and ceramide, a lipid second messenger involved in cell differentiation and/or apoptosis. We first evidenced that porcine cultured thyroid cells could express neutral Smase activity even if thyrotropin (TSH), an essential hormone in thyroid cell differentiation, was found to induce a 1.7‐fold decrease in Smase activity. Triggering the ceramide pathway by exogenous addition of neutral bacterial Smase (0.1 U/mL for 48 h), which transiently increased ceramide level by fourfold, drastically modified thyroid cell morphology. The follicle‐like structures generated by TSH were disrupted, and the Smase‐induced cell spreading was accompanied by a parallel loss of cell ability to iodinate proteins as well as a decrease of the adenylate cyclase system response. These inhibitory effects have been reproduced using short‐chain exogenous ceramide analogs (C2‐ceramides). Overall these data showed that ceramides emerged as potential mediators of dedifferentiation in thyroid cells.
Modulation of arachidonate and docosahexaenoate in Morone chrysops larval tissues and the effect on growth and survival
Authors: Harel Moti , Lund Eric , Gavasso Sonja , Herbert Ryan , Place Allen R. 
Published: November 2006

AbstractThe extent to which extreme dietary levels of arachidonate (AA) and/pr docosahexaenoate (DHA) modulate lipid composition in the body tissues and consequently affect growth and survival in freshwater Morone larvae species was examined. White bass, M. chrysops, larvae (day 24–46) were fed Artemia nauplii enriched with algal oils containing varying proportions of AA and DHA (from 0 to over 20% the total fatty acids). Growth was significantly reduced (P<0.05) in larvae fed a DHA‐deficient Artemia diet. Increases in dietary levels of AA also were associated with a significant growth reduction. However, the inhibitory effect of AA on larvae growth could be suppressed by the dietary addition of DHA (at a level of 21.6% of the total fatty acids in enrichment lipids). Larval brain+eyes tissue accumulated over 10 times more DHA than AA in its structural lipids (phosphatidylcholine, phosphatidylethanolamine) at any dietary ratio. In contrast, DHA accumulation, as compared to AA, in gill lipids declined considerably at higher than 10∶1 DHA/AA tissue ratios. DHA and eicosapentaenoic acid (EPA) contents in brain+eyes tissue were most sensitive to competition from dietary AA, being displaced from the tissue at rates of 0.36±0.07 mg DHA and 0.46±0.11 mg EPA per mg increase in tissue AA, and 0.55±0.14 mg AA per mg increase in tissue DHA. On the other hand, AA and EPA levels in gill tissue were most sensitive to dietary changes in DHA levels; AA was displaced at rates of 0.37±0.11 mg, whereas EPA increased at rates of 0.68±0.28 mg per mg increase in tissue DHA. Results suggest that balanced dietary DHA/AA ratios (that allow DHA/AA ratios of 2.5∶1 in brain+eyes tissue) promote a high larval growth rate, which also correlates with maximal regulatory response in tissue essential fatty acids.
Effects of fructose and troglitazone on phospholipid fatty acid composition in rat skeletal muscle
Authors: Clore John N. , Li Jing , Rizzo William B. 
Published: November 2006

AbstractSkeletal muscle phospholipid fatty acid (PLFA) composition is associated with insulin sensitivity in animal models and in man. However, it is not clear whether changes in insulin sensitivity cause a change in PLFA composition or vice versa. The present studies have examined the effects of agents known to increase or decrease insulin sensitivity on PLFA composition of the major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), in soleus and extensor digitorum longus muscle. Four groups of Sprague‐Dawley rats— control, 0.2% troglitazone (Tgz), 60% fructose fed, and fructose + Tgz—were treated for 3 wk. Fructose feeding was associated with a decrease in muscle membrane polyunsaturated fatty acids (PUFA) and n‐3 fatty acids in both PC and PE. Administration of Igz alone resulted in an increase in liver (3.75±0.93 to 6.93±1.00 μmol/min/mg tissue, P<0.05) and soleus muscle (0.34±0.03 to 0.67±0.09 μmol/min/mg, P<0.01) elongase activity, which would be expected to increase membrane PUFA. However, Tgz decreased PLFA associated with greater insulin sensitivity (e.g., PUFA and n‐3 fatty acids) and increased PLFA associated with decreased insulin sensitivity (16∶0 and n‐6 fatty acids) in both PC and PE. Co‐administration of fructose and Tgz did not reverse the decrease in PUFA observed with fructose alone. We conclude that the improvement in insulin sensitivity reported with Tgz is associated with an apparently paradoxical effect to decrease PUFA and n‐3 PLFA composition in rat skeletal muscle. These studies suggest that Tgz‐mediated increases in insulin sensitivity do not result in improved PLFA composition.
Phospholipid identification and quantification of membrane vesicle subfractions by31P−1H two‐dimensional nuclear magnetic resonance
Authors: Larijani B. , Poccia D. L. , Dickinson L. Charles 
Published: November 2006

AbstractAn approach to the direct quantification of phospholipids from two‐dimensional31P−1H nuclear magnetic resonance (NMR) spectroscopy with isotropic proton mixing has been developed as a general method for phospholipid analysis of minor membrane vesicle subfractions. Membrane vesicles were subfractionated by sedimentation to density equilibrium in a sucrose gradient, and a modified Folch method was employed to extract their phospholipids. The coefficient for the NMR detection efficiency of each phospholipid and the relative mole percentage of the phospholipids present in the membrane vesicles were calculated. We demonstrate low detection limits such that relative concentrations of phospholipids in membrane subfractions may be determined even in the submicromolar range.