bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of a neutral triacylglycerol hydrolase from rat heart by phosphatidylethanolamine and lysophosphatidylethanolamine
Authors: Severson David L. , Hurley Brenda 
Published: November 2006

AbstractTriacylglycerol hydrolase activity measured at pH 7.5 in a pH 5.2 precipitate fraction from rat heart was increased two‐to three‐fold by the presence of phosphatidylethanolamine (PE) or lysophosphatidylethanolamine (LPE). This stimulatory effect also could be obtained in assays with particulate and soluble subcellular fractions and was observed with two different methods of preparing triolein substrate emulsions. Ethanolamine and glycerophosphorylethanolamine had no effect on hydrolase activity, whereas phosphatidylcholine (PC) and acidic phospholipids such as cardiolipin were inhibitory. Palmitic acid, palmityl CoA and palmityl carnitine inhibited PE‐stimulated hydrolase activity, but ethyl esters of palmitate had no effect. The preparation of acetone‐ether powders resulted in a marked reduction of triacylglycerol hydrolase activity, but PE and LPE now stimulated hydrolase activity by ten‐fold or greater, suggesting that these phospholipids may have an obligatory role in modulating triacylglycerol hydrolase activity. Triton X‐100 also stimulated hydrolase activity in acetone‐ether powders.
Altered arachidonic acid content in polymorphonuclear and mononuclear cells from patients with allergic rhinitis and/or asthma
Authors: Rocklin Ross E. , Thistle Lori , Gallant Leo , Manku M. S. , Horrobin David 
Published: November 2006

AbstractWe previously have found that monocytes from patients with allergic rhinitis and/or asthma produce less PGE2 than cells from normal subjects in response to a histamine‐induced lymphokine. In order to investigate this observation further, we measured the fatty acid content in the total phospholipids derived from the plasma, red cells, buffy coat cells, neutrophils, monocytes and lymphocytes of 27 allergic patients and 21 normal controls. There were no substantial differences between atopics and normals in the fatty acid analyses carried out for plasma and red cells. However, linoleic acid (18∶2n−6) levels were elevated significantly in the buffy coat fraction, while arachidonic acid (20∶4n−6) levels were reduced. Measurement of fatty acid levels after fractionation of the buffy coat population into neutrophils and monocytes yielded similar elevations in 18∶2n−6 and reduced 20∶4n−6. In contrast, lymphocytes appeared to have the reverse pattern, i.e., significantly reduced 18∶2n−6 and elevated 20∶4n−6 levels. These data suggest that atopic leukocytes may have altered essential fatty acid metabolism.
Measurement of the incorporation of orally administered arachidonic acid into tissue lipids
Authors: Kulmacz Richard J. , Sivarajan Muthumalayan , Lands William E. M. 
Published: November 2006

AbstractThe applicability of a stable isotope method to monitor the mixing of dietary arachidonic acid with endogenous arachidonic acid in tissue lipids was evaluated. Rats were fed octadeuterated arachidonic acid during a 20‐day period, and the entry of the dietary acid into lipid esters of various tissues was examined by gas chromatographymass spectrometric (GC‐MS) analysis of their fatty acids. The rats were maintained on a fat‐free diet from weaning until 63 days old to enhance the ratio of the dietary acid to endogenous arachidonate. Three separate forms of eicosatetraenoic acid in the tissue lipids could be distinguished by GC‐MS: octadeuterated arachidonic acid (recent dietary origin), unlabeled arachidonic acid (maternal origin) and unlabeled, 4,7,10,13‐eicosatetraenoic acid (originating from palmitoleic acid).The total eicosatetraenoic acid in the tissue lipids contained about 90% arachidonate from recent dietary origin in lung, kidney, heart and fat, 70% in muscle and liver and 27% in brain. The n−7 isomer of eicosatetraenoic acid was estimated to make up 6% or less of the total eicosatetraenoic acid in lung, kidney, brain, muscle and heart tissue lipids, but it comprised around 15% of the total eicosatetraenoic acid in liver. The unlabeled arachidonic acid of maternal origin thus comprised only about 10% of the eicosatetraenoic acid in all tissues examined except muscle and brain, where it was 24% and 70% of the eicosatetraenoic acid, respectively.The relative amounts of the three forms of eicosatetraenoic acid are consistent with a limited access of dietary arachidonate to the brain tissue and with a competition between the dietary n−6 isomer and the endogenous n−7 isomer for esterification in the liver. Because most muscle mass would have formed after weaning, the high proportion of maternal arachidonate in the muscle lipids suggested that maternal arachidonate may have been displaced from other tissues to muscle, from which it equilibrated slowly with dietary arachidonate acid. The combination of deuterated arachidonic acid and GC‐MS analysis thus furnished more detailed information about the composition and origin of eicosatetraenoic, acid in tissue lipid esters than that previously available from radiotracer studies or GC‐MS analyses alone.
Oxysterols: Chemical synthesis, biosynthesis and biological activities
Authors: Parish Edward J. , Nanduri Venkata B. B. , Kohl Herbert H. , Taylor Frederick R. 
Published: November 2006

AbstractAs a class of compounds, oxysterols have demonstrated a wide variety of biological properties. Due to the general interest in these compounds, new methods of chemical synthesis have been developed to provide them for biological investigation. The specific inhibition by oxysterols of cholesterol biosynthesis in mammalian cells has been shown to result primarily from a decrease in cellular levels of 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase activity. Recent evidence suggests these cellular responses may be mediated by an oxysterol binding protein found in the cytosol of many lines of cultured cells. In certain instances, oxysterols have been shown to be produced in biological systems. These results support the supposition that oxysterols may regulate sterol biosynthesis at the cellular level. Included herein are the inhibitory effects of 9α, 11α‐epoxycholest‐7‐en‐3β‐ol cholest‐8‐en‐3β‐ol‐7‐one and cholest‐8‐en‐3β‐ol‐11‐one on HMG‐CoA reductase activity and their relative affinities for a cytosolic binding protein.
Sterol composition during the life cycle of the soybean and the squash
Authors: Fenner Gregory P. , Patterson Glenn W. , Koines Penelope M. 
Published: November 2006

AbstractSterol analyses were performed on soybeans and squash at intervals throughout the life cycle from seed to mature seed‐bearing plant. The sterols of the soybean (24‐methyl‐cholesterol, stigmasterol and sitosterol) increased in quantity from that in the seed in each stage examined except for a pause or decrease prior to flowering and a decrease at senescence. Individual sterols remained in the same proportion to each other and changes in content were similar in roots and shoots. In the squash a much more complicated sterol mixture was found, composed primarily of C‐7 unsaturated sterols characteristic of Cucurbitaceae. Sterol composition also increased during the life cycle except for approximately two wk in the preflowering to early flowering period. The data indicate low synthesis or high turnover of sterols (or both) in these plants in the weeks at or just prior to flowering.
Sterol composition and biosynthesis in sorghum: Importance to developmental regulation
Authors: Heupel Rick C. , Sauvaire Y. , Le Phu H. , Parish Edward J. , Nes W. David 
Published: November 2006

AbstractSterol composition and biosynthesis have been examined in seeds, germinating seeds and blades from fally matured leaves ofSorghum bicolor in various stages of development’from seedlings (seven‐day plants) to flowering (66‐day) plants. The profile of the dominant free sterols of seeds was similar to that of leaf blades; both contained cholesterol, 24α‐methylcholesterol (campesterol), 24β‐methylcholesterol (dihydrobrassicasterol), 24α‐ethylcholesterol (sitosterol) and 24α‐ethylcholesta‐5,22‐dienol (stigmasterol). Sufficient sterol intermediates were identified in the plant to indicate separate post‐cycloartenol pathways to sterolic end products. The total free sterol content of the seed (μg/seed) increased somewhat during the 20 hr germination period. However, as the plant developed (seven to 48 days), there was a logarithmic increase in the leaf blade sterol content (μg/leaf blade) which plateaued at the onset of floral differentiation (ca. day 41). Over the next 18 days (48 to 66 days—period of inflorescense development), the sterol content rapidly decreased. In the early stages of plant development, the leaf blade pentacyclic triterpenoid (PT) content was negligible. With the onset of floral differentiation, PT content increased logarithmically, reaching a plateau level that surpassed the sterol content as flowering progressed. These results imply that a critical mass of sterol is associated with sorghum for floral induction. Sterol loss from the leaves of the flowering plants presumably was compensated for by the diversion of 2,3‐oxidosqualene (SO) from sterol synthesis to PT production. Additional feeding and trapping experiments with [2‐14C]mevalonic acid, [2‐3H]cycloartenol, [24‐3H]lanosterol [4‐14C]sitosterol and [4‐14C]cholesterol fed to germinating seeds and leaves from flowering plants demonstrated that sorghum possessed a cycloartenolbased pathway; germinating seeds synthesized 24‐alkylsterols but not cholesterol, although cholesterol was identified in both dry and germinating seeds by gas chromatography‐mass spectroscopy (GC‐MS); and mature leaves synthesized cholesterol and 24α‐alkylsterols but not 24β‐methylcholesterol.
The fate of radiolabeled steroids in ovaries and eggs of the tobacco hornworm,Manduca sexta
Authors: Thompson Malcolm J. , Svoboda James A. , Feldlaufer Mark F. , Lozano Ruben 
Published: November 2006

AbstractTo determine the precursors and the fate of 26‐hydroxyecdysone in eggs, the fate of labeled putative ecdysteroid precursors was examined in the tobacco hornworm,Manduca sexta. Following injection of [14C]cholesterol, 22,25[14C]dideoxyecdysome or [3H]ecdysone into female pupae (day 16), only [14C]cholesterol was incorporated and metabolized. It was converted to labeled nonecdysteroid and ecdysteroid conjugates, of which the latter in ovaries and 48‐ to 64‐hr‐old eggs is mainly 26‐hydroxyecdysone 26‐phosphate (>85% in ovaries). Quantitation of the ecdysteroid conjugate by reversed‐phase high performance liquid chromatography (RP‐HPLC) showed that the levels of 26‐hydroxyecdysone 26‐phosphate were 31 μg/g of ovaries from 4‐day‐old females and 25 μg/g and 17 μg/g of 48‐ to 64‐hr‐old and 72‐ to 88‐hr‐old eggs, respectively. The RP‐HPLC of the conjugate fraction of 48‐ to 64‐hr‐old eggs showed an additional peak of radioactive material eluting about three min before the 26‐hydroxyecdysone 26‐phosphate. The quantity of this material increased in the 72‐to 88‐hr‐old eggs, though it was not detected in the analyses of the conjugate fraction from ovaries. Additional peaks of radioactive material eluting before the 26‐hydroxyecdysone 26‐phosphate peak were observed in the chromatogram of the conjugates of 72‐ to 88‐hr‐old eggs. These radioactive materials need to be identified to determine the ultimate fate of ecdysteroids in the developing embryos of the tobacco hornworm. No radioactive free ecdysteroids were detected in either egg age group.
Hydroxymethylglutaryl‐CoA reductase, a key enzyme in phytosterol synthesis?
Authors: Bach Thomas J. 
Published: November 2006

AbstractHydroxymethylglutaryl‐CoA reductase (HMGR) regulates the synthesis of mevalonic acid (MVA), the precursor of the myriad of isoprenoid compounds functional in plant cells, with phytosterols representing one class of major importance. Recently, it has shown possible to solubilize and purify the membrane‐bound enzyme from a heavy membrane fraction (P 16,000×g) isolated from a cell‐free homogenate of etiolated radish seedlings. What is presently known about the molecular and kinetic properties of radish HMGR is reported.Mevinolin, a highly specific competitive inhibitor of HMGR, has been valuable as a research tool in studying the regulatory role of HMGR activity for the growth and development of intact seedlings and cell cultures. The results obtained indicate a primary effect of mevinolin on phytosterol accumulation, whereas other endproducts of the multibranched isoprenoid pathway, such as ubiquinone in the mitochondria or chlorophylls and carotenoids in the plastids, are less or not at all affected. This and other data can be interpreted to mean that the organelles are autonomous in their capacity to synthesize MVA. Since the mevinolin‐induced drop in free sterol accumulation is paralleled by significant plant growth retardation, a rate‐limiting role of HMGR activity for phytosterol synthesis and normal development of plants is suggested.
An essential fungal growth factor derived from ergosterol: A new end product of sterol biosynthesis in fungi?
Authors: Parks Leo W. , Rodriguez Russell J. , Low Christopher 
Published: November 2006

AbstractConcentrations of ergosterol as low as 1.2 mM are effective in satisfying the essential high specificity microrequirement for C5,6 unsaturated sterol in yeast. In a sterol auxotroph supplemented with saturated sterol (cholestanol), aqueous extracts of yeast provide a growth factor that eliminates the ergosterol microrequirement. The factor is easily differentiated from ergosterol by solubility, thermostability, and thin layer and liquid chromatography and is functional at levels equivalent to those of vitamins, hormones and pheromones.
Sterol analysis of the inner and outer mitochondrial membranes in yeast
Authors: Bottema C. K. , Parks L. W. 
Published: November 2006

AbstractThe membranes of yeast mitochondria were separated and analyzed for lipid content. The sterolto‐phospholipid molar ratio was found to be very similar between the inner and outer membranes (1∶30). These observed ratios could be substantially altered by using a crude mitochondrial pellet contaminated with a “floating lipid layer”. In this case, the sterol‐to‐phospholipid molar ratios were 1∶8 to 1∶26 for the outer and inner mitochondrial membranes, respectively.
Influence of lecithin on the chromatography of steroidal glucosiduronates in chloroform/formamide
Authors: Mattox Vernon R. , Litwiller Robert D. 
Published: November 2006

AbstractThe interaction between lecithin and steroidal glucosiduronates was investigated by use of partition chromatography in chloroform/formamide and infrared spectroscopy. It was observed that lecithin increases the solubility of both glucosiduronic acids and esters in chloroform and concluded that this phenomenon occurs because of the formation of hydrogen bonds between the phosphodiester group of lecithin and hydroxyl groups of the steroid conjugates.
Cholesteryl ester hydrolase activity in human symptomatic atherosclerosis
Authors: Yatsu F. M. , Hagemenas F. C. , Manaugh L. C. , Galambos T. 
Published: November 2006

AbstractAcid cholesteryl ester hydrolase (CEH) activity was assayed in mononuclear cells of patients with symptomatic atherosclerosis (transient ischemic attacks, TIA) and in age‐matched controls showing no evidence of atherosclerosis. The acid CEH level of TIA patients was significantly lower than that of controls (1074±128 vs 2113±255 pmol/mg P/hr, mean±SE). Neither mononuclear cell nor plasma cholesterol and cholesteryl ester concentrations differed significantly between atherosclerotic and control groups. TIA women had lower mononuclear cell concentrations of free sholesterol than men.
Effect of epinephrine and dibutyryl cyclic AMP on Δ5‐desaturation activity of rat liver microsomes
Authors: de Gomez Dumm I. N. T. , de Alaniz M. J. T. , Brenner R. R. 
Published: November 2006

AbstractThe effect of epinephrine and dibutyryl cyclic AMP on the oxidative desaturation of [1‐14C]‐eicosatrienoic acid to arachidonic acid of rat liver microsomes has been studied. Epinephrine, at a dose of 1 mg/kg/body weight, produced a significant decrease on Δ5‐desaturation activity 3 hr after the injection. This effect was maintained up to 12 hr and reached the control values 48 hr after the hormone administration. Dibutyryl cyclic AMP treatment for 24 hr (5 mg/8 hr/100 g body weight) also produced a significant decrease of the conversion of eicosatrienoic acid to arachidonic acid in rat liver microsomes. The effect of epinephrine on Δ5‐desaturation activity was postulated to be evoked through an increase of the intracellular concentration of cyclic AMP.
Esterified lipids of the freshwater dinoflagellatePeridinium lomnickii
Authors: Cranwell P. A. , Robinson N. , Eglinton G. 
Published: November 2006

AbstractSteryl esters, phytyl esters and triacylglycerols of a naturally occurring freshwater dinoflagellate,Peridinium lomnickii, were identified using capillary gas chromatography‐mass spectrometry (GC‐MS). Steryl esters differing in degree of unsaturation were separated, prior to analysis, by argentation thin layer chromatography. 5α(H)‐Cholestanol was more dominant, relative to 4α‐methylstanols, in steryl esters than in the free sterols, but the same sterol moieties occurred in both fractions. Monoenoic fatty acids were enriched in the steryl esters relative to the free fatty acids. Major acyl groups in steryl esters were 16∶0 or 20∶1, with smaller amounts of 14∶0 and 18∶1. In triacylglycerols the acyl moieties were 14∶0, 16∶0, 18∶1, 16∶1 and 12∶0, in order of decreasing abundance. Phytyl esters, previously inferred to occur in a marine dinoflagellate only by analysis of transesterified products, were identified by GC‐MS comparison with authentic compounds. Direct analysis of these esterified lipids has not been reported for freshwater phytoplankton. The 4α‐methylstanyl esters, 5α(H)‐cholestan‐3β‐yl esters and phytyl esters occurring inP. lomnickii are further features in common with marine dinoflagellates, additional to the 4α‐methylsterols reported previously.
Fatty acids and fatty alcohols of wax esters in the orange roughy: Specific textures of minor polyunsaturated and branched‐chain components
Authors: Takagi Toru , Itabashi Yutaka , Aso Shingo 
Published: November 2006

AbstractOpen‐tubular gas chromatography was carried out on fatty acids and alcohols obtained from wax esters of the orange roughy,Hoplostethus atlanticus, caught at sea off New Zealand. The major (above 5%) components were 16∶1(n−7), 18∶1(n−9) and (n−7), 20∶1(n−9) and (n−7), and 22∶1(n−11, n−13) as fatty acids, and 16∶0, 18∶0, 18∶1(n−9), 20∶1(n−9) and (n−7), and 22∶1(n−11, n−13) as fatty alcohols. The total percentages of the minor components were 10% in the acids and 26% in the alcohols. The 22∶1/20∶1 ratio of the fatty alcohols obtained in this study was less than 1.0, although the ratio for the Atlantic orange roughy has been reported as being greater than 1.0. The contents of polyenes were as low as 2.48% in the acids and 0.95% in the alcohols, but their compositions showed some specific features. The percentages of the C16−C22 dienes in the total polyenes were remarkably high, 57.7% of these acids and 53.1% of these alcohols. The most important dienes were 18∶2(n−6) in the acids and 20∶2(n−6) in the alcohols.
The monounsaturated acyl‐ and alkyl‐moieties of wax esters and their distribution in commercial orange roughy (Hoplostethus atlanticus) oil
Authors: Body Denis R. , Johnson Cecil B. , Shaw G. John 
Published: November 2006

AbstractWax esters were isolated from commercial orange roughy (Hoplostethus atlanticus) oil by column chromatography and fractionated by argentation thin layer chromatography. Following transesterification, the resultant fatty acid methyl esters and fatty alcohols were analyzed by gas chromatography. both acyl‐ and alkyl‐moieties were mainly of the monoene structure within the 16∶1–22∶1 range. After derivatization, the positions of the double bonds of even numbered fatty acid and fatty alcohol isomers were located by chromatography‐mass spectrometry and compared.Results of these positional analyses indicate that the primary desaturation reactions takes place in the Δ9 position of pre‐existing (C14 to C24) acyl chains. It is proposed that acyl components from 18∶1 are subjected to chain elongation to form a mixture of 24∶1 isomers as the final product. Apart from the 24∶1 acyl moiety of the wax esters, in which the double bond was almost exclusively in the Δ15 position, de novo biosynthetic reactions on acids and alcohols appear to yield related acyl‐ and alkyl‐moieties of resynthesized wax esters.
GSH‐dependent inhibition of lipid peroxidation: Properties of a potent cytosolic system which protects cell membranes
Authors: Gibson Donald D. , Hawrylko Josephine , McCay Paul B. 
Published: November 2006

AbstractProperties of a heat labile, nondialyzable cytosolic factor which prevents lipid peroxidation in membranous organelles are described. The factor is present in liver and other animal tissues, and its capacity to inhibit lipid peroxidation in membranes subjected to oxidative stress is greatly potentiated by glutathione (GSH), although GSH by itself has no inhibitory effect on lipid peroxidation. The data obtained thus far indicate that one or more sulfhydryl groups associated with the factor is required for the inhibition. The mechanism by which lipid peroxidation is inhibited must involve prevention of initiation of peroxidation in the membranes, presumably by a process requiring one or more sulfhydryl groups associated with the heat labile factor. The latter appears to be protected by GSH while the factor is exerting its inhibitory effect on lipid peroxidation. The factor is not one of the known GSH‐dependent enzymes, and appears to be a potent and ubiquitous system for stabilizing cell membranes against oxidative damage.
An improved assay for cholesterol 7α‐hydroxylase activity using phospholipid liposome solubilized substrate
Authors: Junker Louis H. , Story Jon A. 
Published: November 2006

AbstractA persistent problem in measurement of cholesterol 7α‐hydroxylase (7α‐OHase) activity by isotope incorporation has been solubilization of cholesterol substrate. Solubilization with Tween 20, for example, resulted in a 75% reduction in 7α‐OHase activity after a 60 min incubation of substrate with microsomes. Incorporation of cholesterol substrate into small, unilamellar phospholipid vesicles (liposomes) prevented this effect, resulting in a 50% increase in activity over the same 60 min incubation at optimal concentrations. Using cholesterol in liposomes as substrate, standard assay conditions were determined to be: preparation of liposomes with 180 μM cholesterol substrate and 0.5 mg phospholipid/assay; incubation of these liposomes with 0.5 mg microsomal protein at 37 C for 60 min; addition of a NADPH generating system to start the reaction, and incubation at 37 C for 30 min before stopping the reaction and determining the amount of 7α‐hydroxycholesterol formed. In addition to preventing the detergent‐related inhibition of the enzyme, liposome‐solubilized substrate also reduced the variation among replicates from a coefficient of 45% with Tween 20 to 4.2% with phospholipid. This method provides a sensitive and reliable alternative to methods which require more sophisticated equipment and allows total control of substrate concentration in a form readily accessible to the enzyme.