bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hepatic zonation of the formation and hydrolysis of cholestery esters in periportal and perivenous parenchymal cells
Authors: Romero José Ramón , Fresnedo Olatz , Isusi Efrén , Barrionuevo Javier , Ochoa Begoña 
Published: November 2006

AbstractThe periportal (PP) and perivenous (PV) zones of the liver acinus differ in enzyme complements and capacities for cholesterol and bile acid synthesis and other metabolic processes. The aim of this investigation was to determine the acinar distribution of the catalytic activity of the enzymes governing the formation and hydrolysis of cholesteryl esters using PP and PV hepatocytes from normal or cholestyramine‐fed rats. The hepatocyte subpopulations were isolated by centrifugal elutriation, characterized according to the distribution pattern of a number of cell parameters and marker enzymes, and assayed for acyl‐CoA: cholesterol acyltransferase (ACAT) and lysosomal, cytosolic and microsomal cholesteryl ester hydrolase (CEH). In normally fed rats, no zonation was found in the activity of lysosomal CEH and ACAT, and the activity of both cytosolic and microsomal CEH zonated toward the PV zone of the acinus. Concentrations of free and esterified cholesterol in homogenates, cytosol, and microsomes of PP and PV cells were, however, similar. Cholestyramine raised significantly the PV/PP ratio of ACAT because of an exclusive PP reduction of activity and abolished the heterogeneity in microsomal CEH because of a greater inhibitory PV response, whereas the PV dominance of cytosolic CEH and the homogeneous distribution of lysosomal CEH were unaffected. These results demonstrated homogeneity within the liver acinus for the enzymatic degradation of endocyted lipoprotein‐derived cholesteryl esters, a structural zonation of the cytosolic CEH and a dynamic zonation of ACAT and the microsomal CEH, with a PV dominance of the enzymatic capacity for the degradation of stored cholesteryl esters in normal livers.
Acyltransferase activities in the yolk sac membrane of the chick embryo
Authors: Murray Alison M. B. , Denis Raphael , Speake Brian K. 
Published: November 2006

AbstractThe activities of some enzymes of glycerolipid synthesis and fatty acid oxidation were measured in subcellular fractions of the yolk sac membrane (YSM), an extra‐embryonic tissue that mediates the transfer of lipid from the yolk to the circulation of the chick embryo. The activities of monoacylglycerol acyltransferase and carnitine palmitoyl transferase‐1 in the YSM (respectively, 284.8±13.2 nmol/min/mg microsomal protein and 145.6±9.1 nmol/min/mg mitochondrial protein; mean ±SE; n=4) at day 12 of development appear to be the highest yet reported for any animal tissue. Also, the carnitine palmitoyl transferase‐1 of the YSM was very insensitive to inhibition by malonyl CoA. The maximal activities of glycerol‐3‐phosphate acyltransferase and diacylglycerol acyltransferase in the YSM (respectively, 26.7±2.2 and 36.1±2.1 nmol/min/mg microsomal protein) were also high compared with the reported values for various animal tissues. The very high enzymic capacity for glycerolipid synthesis supports the hypothesis that the yolk‐derived lipids are subjected to hydrolysis followed by reesterification during transit across the YSM. The monoacylglycerol pathway appears to be the main route for glycerolipid resynthesis in the YSM. The results also suggest that the YSM has the capacity to perform simultaneously β‐oxidation at a high rate in order to provide energy for the lipid transfer process.
Lipid composition of hepatocyte plasma membranes from geese overfed with corn
Authors: Cazeils J. L. , Bouillier‐Oudot M. , Auvergne A. , Candau M. , Babile R. 
Published: November 2006

AbstractTwelve‐week‐old Landes male geese were overfed with corn for 21 d in order to induce liver steatosis (fatty liver). Lipid composition of hepatocyte plasma membranes from fatty livers was compared to that of lean livers obtained from geese fed a normal diet. The ratio cholesterol/phospholipids was higher in fatty hepatocyte plasma membranes (0.63 vs. 0.47), whereas the phospholipid/protein ratio was less than half. Overfeeding induced changes in fatty acid composition of hepatocyte plasma membranes, including a greater than twofold increase in the percentage of oleic acid (29.7 vs. 13.8%) and a somewhat lesser increase in lauric, palmitic, and palmitoleic acid contents of plasma membrane lipids of fatty livers. A concomitant reduction in the proportion of stearic acid (18.4 vs. 25.1%) was also observed. In fatty livers, the increased ratio of saturated to polyunsaturated fatty acids (PUFA) (1.5 vs. 1.0) was related to a significant decrease in PUFA content. Among all the PUFA, only the eicosatrienoic acid (20∶3n−9) percentage was increased by liver steatosis. Overfeeding with corn appeared to induce competition between de novo synthesized and dietary fatty acids incorporated in hepatocyte plasma membranes. This resulted in an accumulation of de novo synthesized monounsaturated and derived fatty acids in plasma membranes from overfed birds. A defect in the incorporation of linoleic acid and linoleic‐ and linolenic‐derived PUFA was observed despite the high proportion of these essential fatty acids in the diet. It was conclued that in overfed palmipeds, de novo hepatic lipogenesis prevails over dietary lipid intake to modulate lipid composition of the fatty liver plasma membrane.
Metabolism of trideuterated iso‐lignoceric acid in rats in Vivo and in human fibroblasts in culture
Authors: Poulos Alfred , Stockham Peter C. , Johnson David W. , Paton Barbara C. , Beckman Kaye , Singh Harmeet 
Published: November 2006

AbstractSaturated very long chain fatty acids (fatty acids with greater than 22 carbon atoms; VLCFA) accumulate in peroxisomal disorders, but there is little information on their turnover in patients. To determine the suitability of using stable isotope‐labeled VLCFA in patients with these disorders, the metabolism of 22‐methyl[23,23,23‐2H3]tricosanoic (iso‐lignoceric) acid was studied in rats in vivo and in human skin fibroblasts in culture. The deuterated iso‐VLCFA was degraded to the corresponding 16‐ and 18‐carbon iso‐fatty acids by rats in vivo and by normal human skin fibroblasts in culture, but there was little or no degradation in peroxisome‐deficient (Zellweger's syndrome) fibroblasts, indicating that its oxidation was peroxisomal. Neither the 14‐, 20‐, and 22‐carbon iso‐fatty acids nor the corresponding odd‐chain metabolites could be detected. In the rat, the organ containing most of the iso‐lignoceric acid, and its breakdown products, was the liver, whereas negligible amounts were detected in the brain, suggesting that little of the fatty acid crossed the blood‐brain barrier. Our data indicate that VLCFA labeled with deuterium at the ω‐position of the carbon chain are suitable derivatives for the in vivo investigation of patients with defects in peroxisomal β‐oxidation because they are metabolized by the same pathways as the corresponding n‐VLCFA. Moreover, as iso‐VLCFA and their β‐oxidation products are readily separated from the corresponding n‐fatty acids by normal chromatographic procedures, the turnover of VLCFA can be more precisely measured.
Δ9 desaturase activity in bovine subcutaneous adipose tissue of different fatty acid compositiondesaturase activity in bovine subcutaneous adipose tissue of different fatty acid composition
Authors: Yang A. , Larsen T. W. , Smith S. B. , Tume R. K. 
Published: November 2006

AbstractTwo experiments were conducted to investigate the relationship between Δ9 desaturase (stearoyl‐coenzyme A desaturase) activity and fatty acid composition in subcutaneous adipose tissue from cattle of different backgrounds. In Experiment 1, subcutaneous adipose tissue samples were taken from carcasses of pasture‐fed cattle and feedlot cattle fed for 100, 200, or 300 d. Adipose tissue from pasture‐fed cattle had significantly lower total saturated fatty acids and higher total unsaturated fatty acids than feedlot cattle. Desaturase activity correspondingly was 60–85% higher in pasture‐fed cattle than in feedlot cattle. There was no difference in the fatty acid composition or desaturase activity among samples from the 100‐, 200‐, and 300‐d feedlot cattle. In Experiment 2, adipose tissue samples were collected from carcasses of feedlot cattle fed for 180 d with either a standard feedlot ration (control group), or a ration containing rumen‐protected cottonseed oil (CSO) for the last 70–80 d. Adipose tissue from the CSO‐fed cattle was more saturated than that from the control group, having significantly more 18∶0 and less 16∶1 and 18∶1. Correspondingly, adipose tissue from the CSO group had significantly lower desaturase activity. The elevated 18∶2 in adipose tissue from the CSO group confirmed that unsaturated fatty acids (including cyclopropenoid fatty acids) were protected from biohydrogenation. Further studies are needed to determine whether the repression of desaturase activity results from direct inhibition by cyclopropenoic acids or by higher dietary contents of 18∶2.
Lipase‐catalyzed fractionation of conjugated linoleic acid isomers
Authors: Haas Michael J. , Kramer John K. G. , McNeill Gerald , Scott Karen , Foglia Thomas A. , Sehat Najibulla , Fritsche Jan , Mossoba Magdi M. , Yurawecz Martin P. 
Published: November 2006

AbstractThe abilities of lipases produced by the fungus Geotrichum candidum to selectively fractionate mixtures of conjugated linoleic acid (CLA) isomers during esterification of mixed CLA free fatty acids and during hydrolysis of mixed CLA methyl esters were examined. The enzymes were highly selective for cis‐9,trans‐11–18∶2. A commercial CLA methyl ester preparation, containing at least 12 species representing four positional CLA isomers, was incubated in aqueous solution with either a commercial G. candidum lipase preparation (Amano GC‐4) or lipase produced from a cloned high‐selectivity G. candidum lipase B gene. In both instances selective hydrolysis of the cis‐9,trans‐11–18∶2 methyl ester occurred, with negligible hydrolysis of other CLA isomers. The content of cis‐9,trans‐11–18∶2 in the resulting free fatty acid fraction was between 94 (lipase B reaction) and 77% (GC‐4 reaction). The commercial CLA mixture contained only trace amounts of trans‐9,cis‐11–18∶2, and there was no evidence that this isomer was hydrolyzed by the enzyme. Analogous results were obtained with these enzymes in the esterification in organic solvent of a commercial preparation of CLA free fatty acids containing at least 12 CLA isomers. In this case, G. candidum lipase B generated a methyl ester fraction that contained >98% cis‐9,trans‐11–18∶2. Geotrichum candidum lipases B and GC‐4 also demonstrated high selectivity in the esterification of CLA with ethanol, generating ethyl ester fractions containing 96 and 80%, respectively, of the cis‐9,trans‐11 isomer. In a second set of experiments, CLA synthesized from pure linoleic acid, composed essentially of two isomers, cis‐9,trans‐11 and trans‐10,cis‐12, was utilized. This was subjected to esterification with octanol in an aqueous reaction system using Amano GC‐4 lipase as catalyst. The resulting ester fraction contained up to 97% of the cis‐9,trans‐11 isomer. After adjustment of the reaction conditions, a concentration of 85% trans‐10,cis‐12–18∶2 could be obtained in the unreacted free fatty acid fraction. These lipase‐catalyzed reactions provide a means for the preparative‐scale production of high‐purity cis‐9,trans‐11–18∶2, and a corresponding CLA fraction depleted of this isomer.
Enhancement of both reaction yield and rate of synthesis of structured triacylglycerol containing eicosapentaenoic acid under vacuum with water activity control
Authors: Han Jeong Jun , Yamane Tsuneo 
Published: November 2006

AbstractProduction of structured triacylglycerols (sTAG) containing eicosapentaenoic acid (EPA) at the sn‐1 (or 3) position using Lipozyme in a solvent‐free system was studied. Optimal water activity (aw) for the synthesis of the sTAG was investigated. Vacuum was applied to shift reaction equilibrium toward the synthesis reaction by removing by‐products. During vacuum application, the water level of the reaction system was controlled at the optimal level by addition of a suitable amount of water at a predetermined interval. Intermittent periodic addition of a suitable amount of water into the reaction mixture made the reaction rate faster than that without adding water. A molar yield of 89.7% of the targeted sTAG was obtained after 16 h reaction with aw control during the vacuum application as compared with the yield of 87.0% after 24 h of reaction without aw control during the vacuum application.
On the specificity of allene oxide cyclase
Authors: Ziegler Jörg , Wasternack Claus , Hamberg Mats 
Published: November 2006

AbstractJasmonic acid is a carbocyclic fatty acid that is biosynthesized from α‐linolenic acid in several steps. The formation of the ring structure of jasmonic acid is catalyzed by the enzyme allene oxide cyclase (EC 5.3.99.6) and involves the cyclization of an unstable allene oxide into the cyclopentenone 12‐oxo‐10,15(Z)‐phytodienoic acid. In this study, a number of allene oxides were generated, and their enzymatic and nonenzymatic cyclization into cyclopentenones was investigated. Nonenzymatic cyclization was observed with allene oxides having one pair of conjugated double bonds and an additional isolated double bond in the β,γ position relative to the epoxide group, i.e., the partial structure 4,5‐epoxy‐1,3,7‐octatriene. Enzymatic cyclization took place provided that this structural element was inserted in the fatty acid chain with its epoxide group in the n−6,7 position and the isolated double bond in the n−3 position. A number of oxygenated fatty acids having structural features in common with the natural allene oxides were tested as inhibitors of allene oxide cyclase. Fatty acids having an allene oxide structure in the n−6,7 position but lacking the double bond in the n−3 position, as well as fatty acids having a saturated epoxide group in the n−6,7 position, served as competitive inhibitors of the enzyme. Data on the substrate specificity of allene oxide synthase (EC 4.2.1.92) from corn seeds indicated that fatty acid hydroperoxides with a double bond at n−3 and with the hydroperoxide function at n−6 exhibit the highest affinity but the slowest reaction velocity.
Influence of diet on fatty acids of three subtropical fish, subfamily caesioninae (Caesio diagramma and C. tile) and family siganidae (Siganus canaliculatus)
Authors: Saito Hiroaki , Yamashiro Rieko , Alasalvar Cesarettin , Konno Toshiya 
Published: November 2006

AbstractThe total lipid and fatty acid compositions of tissues and the stomach contents of three subtropical marine fish species, subfamily Caesioninae, Caesio diagramma and C. tile, and family Siganidae Siganus canaliculatus, were investigated to clarify the differences between these species. Triacylglycerols (TAG) were the dominant depot lipids of the three species, whereas wax esters were found as a minor component. In particular, muscle lipids were found to contain mainly glycerol derivatives such as TAG and phospholipids. The major fatty acids identified in the three species were 16∶0, 18∶0, 18∶1n−9, and 22∶6n−3 (docosahexaenoic acid, DHA). In addition, noticeable levels of 16∶1n−7, 18∶1n−7, 20∶4n−6 (arachidonic acid, AA), and 20∶5n−3 (eicosapentaenoic acid) were found. DHA was the most abundant polyunsaturated fatty acid (PUFA) in the muscle and viscera lipids of the three species. The high DHA levels in the lipids of all the organs were found to be higher than those of the lipid extracted from the stomach contents of the three fishes. In addition, the specimens of S. canaliculatus contained significantly higher levels of AA in its tissues than did the other two species. A high AA content is unusual since such high levels of n−6 PUFA are rarely found in higher marine organisms. These levels may be due to its characteristic feeding pattern, because S. canaliculatus prefer and mainly feed on seaweed, which often contains high amounts of n−6 PUFA, such as linoleic acid (18∶2n−6) and AA.
An epoxy alcohol synthase pathway in higher plants: Biosynthesis of antifungal trihydroxy oxylipins in leaves of potato
Authors: Hamberg Mats 
Published: November 2006

Abstract[1‐14C]Linoleic acid was incubated with a whole homogenate preparation of potato leaves (Solanum tuberosum 1., var. Bintje). The methyl‐esterified product was subjected to straight‐phase high‐performance liquid chromatography and was found to contain four major radioactive oxidation products, i.e., the epoxy alcohols methyl 10(S), 11(S)‐epoxy‐9(S)‐hydroxy‐12(Z)‐octadecenoate (14% of the recovered radioactivity) and methyl 12(R), 13(S)‐epoxy‐9(S)‐hydroxy‐10(E)‐octadecenoate (14%), and the trihydroxy derivatives methyl 9(S), 10(S), 11(R)‐trihydroxy‐12(Z)‐octadecenoate (18%) and methyl 9(S), 12(S), 13(S)‐trihydroxy‐10(E)‐octadecenoate (30%). The structures and stereochemical configurations of these oxylipins were determined by chemical and spectral methods using the authentic compounds as references. Incubations performed in the presence of glutathione peroxidase revealed that lipoxygenase activity of potato leaves generated the 9‐ and 13‐hydroperoxides of linoleic acid in a ratio of 95∶5. Separate incubations of these hydroperoxides showed that linoleic acid 9(S)‐hydroperoxide was metabolized into epoxy alcohols by particle‐bound epoxy alcohol synthase activity, whereas the 13‐hydroperoxide was metabolized into α‐ and γ‐ketols by a particle‐bound allene oxide synthase. It was concluded that the main pathway of linoleic acid metabolism in potato leaves involved 9‐lipoxygenase‐catalyzed oxygenation into linoleic acid 9(S)‐hydroperoxide followed by rapid conversion of this hydroperoxide into epoxy alcohols and a slower, epoxide hydrolase‐catalyzed conversion of the epoxy alcohols into trihydroxyoctadecenoates. Trihydroxy derivatives of linoleic and linolenic acids have previously been reported to be growth‐inhibitory to plant‐pathogenic fungi, and a role of the new pathway of linoleic acid oxidation in defense reactions against pathogens is conceivable.
Factors enhancing diacylglycerol acyltransferase activity in microsomes from cell‐suspension cultures of oilseed rape
Authors: Byers Susan D. , Laroche André , Smith Kevin C. , Weselake Randall J. 
Published: November 2006

AbstractSeveral factors, including an unidentified endogenous component, were found to stimulate microsomal diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) from a microspore‐derived cell‐suspension culture of oilseed rape (Brassica napus L. cv. Jet Neuf). At a concentration of 25mM, MgSO4 and MgCl2 stimulated microsomal DGAT 25‐ and 10‐fold, respectively. AIP and CoA at concentrations of 2 and 1 mM stimulated the enzyme 2.4‐ and 12‐fold, respectively, although the effects were lessened in the presence of higher Mg2+ concentrations. Although microsomal DGAT activity was increased only slightly by the addition of exogenous sn‐1,2‐diacylglycerol to the reaction mixture, it was increased substantially by the addition of exogenous phosphatidate. sn‐Glycerol‐3‐phosphate and other phospholipids tested did not have this stimulatory effect. DGAT activity did not decrease when microsomes were incubated with ATP in the presence of the cytosolic fraction. This fraction, however, contained a small organic compound(s) that stimulated microsomal DGAT activity.
Effects of postnatal ethanol exposure on brain growth and lipid composition in n−3 fatty acid‐deficient and‐adequate rats
Authors: Ward G. R. , Xing H. ‐C. , Wainwright P. E. 
Published: November 2006

AbstractThe artificial rearing model was used to investigate the effects of short‐term exposure to ethanol on growth and fatty acid composition of forebrain (FB) and cerebellum (CB) during the brain growth spurt in either n−3 fatty acid‐adequate (AD) or n−3 deficient (DEF) rat pups. On postnatal day 5, offspring of female rats that had been fed AD or DEF diets from day 5 of life were assigned to three groups: members of two groups were gastrostomized and artificially fed formulas appropriate for their maternal history, and the third group (suckled control) was fostered to lactating dams of a similar dietary history. Half of the artificially reared pups in each dietary condition were fed ethanol in their formula (7% vol/vol) in one‐quarter of their daily feedings, while the others received maltose‐dextrin substituted isocalorically for ethanol. Blood alcohol concentrations did not differ betwen the dietary groups. FB weight on postnatal day 9 was lower in ethanol‐exposed offspring in both dietary conditions. Brain fatty acid composition reflected dietary history in that, compared with AD pups, DEF pups had lower percentages of docosahexaenoic acid, higher percentages of 22∶5n−6, and a higher n−6/n−3 fatty acid ratio. However, the effects of ethanol exposure were inconsistent, lowering the n−6/n−3 ratio in the phosphatidylethanolamine (PF) fraction in FB but not in CB, while increasing this ratio in the phosphatidylcholine (PC) fraction in FB of the DEF pups only. Thus, while ethanol had some effects on lipid composition, there was no difference between the dietary groups in their vulnerability to the effects of early short‐term ethanol exposure on brain growth.
Column and high‐performance size exclusion chromatography applications to the in vivo digestibility study of a thermoxidized and polymerized olive oil
Authors: Sánchez‐Muniz Francisco J. , Bastida Sara , González‐Muñoz M. José 
Published: November 2006

AbstractThis study aimed (i) to design an in vivo model to study fat digestibility, and (ii) to apply this design to test the in vivo digestibility of a highly thermoxidized olive oil. True digestibility of unheated olive oil was tested 2, 4, 6, and 7 h after administering 1 g of olive oil/100 g body weight to young adult Wistar rats by means of esophageal probes. Remaining gastrointestinal lumen fat showed an inversely linear relationship (t=−0.9932; P<0.001) with the length of the experiment. A 4‐h test was considered adequate because after this period, half of the oil administer still temains in the lumen, making it possible to accurately measure the different nondigested, nonabsorbed themoxidized compounds. In a second experiment, fresh olive oil (3.6 mg polar content/100 mg oil) was heated at 180°C for 50 h in the presence of air; the polar content in this oil rose to 46.0 mg/100 mg oil. After 4 h, the true digestibility coefficient of 50‐h heated olive oil did not significantly change, although it tended to decrease (24%) with respect to the unheated oil. Silica gel column chromatography and high‐performance size exclusion chromatography were used to quantify nonthermoxidized and thermoxidized products present in the oils and in the gastrointestinal lumen after these test periods. True digestibility of the different thermoxidized compounds from the heated oil was 30–40%, whereas that of thermoxidized compounds from the fresh oil was much higher (∼80%). Nonoxidized triacylglycerol hydrolysis was negatively affected by the presence of large amounts of thermoxidized compounds. The present proposed model seems to be a useful tool for the study of thermoxidized oils. Data also show that thermoxidized compounds from abused olive oil are poorly but actively hydrolyzed and absorbed in vivo.
Fullerene lipids: Synthesis of C60 fullerence derivatives bearing a long‐chain saturated or unsaturated triester system
Authors: Lie Ken Jie Marcel S. F. , Cheung Sunny Wai‐Hung 
Published: November 2006

AbstractTris(hydroxymethyl)aminomethane was successfully esterified with saturated and unsaturated long‐chain fatty acids. The resulting amino‐triester intermediates were successively reacted with chloroacetyl chloride, sodium azide, and C60 fullerene. Spectral evidence showed that the aziridine ring is joined to the junction of [6,6]‐fused rings of the fullerene. The structures of the various C60 fullerene derivatives bearing a long‐chain saturated or unsaturated triester system were characterized by spectroscopic and spectrometric methods.