bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of side chain mobility with cholesterol retention by phospholipid vesicles
Authors: Jacobsohn Myra K. , Estahani Mojtaba , Jacobsohn Gert M.
Published: November 2006

Multilamellar vesicles were prepared from choline phospholipids with various fatty acyl chains, singly and in mixtures, with and without cholesterol. Mobility of acyl side chains for each type of vesicle was measured by fluorescence polarization with diphenylhexatriene, and the amounts of cholesterol and phospholipid retained by them after extraction with a nonpolar solvent were determined. The data suggest that structures of acyl chains determine the extractability of cholesterol. Phosphatidylcholines with unsaturated or short saturated side chains above transition temperature retain less cholesterol upon extraction with petroleum ether than phosphatidylcholines with saturated side chains below transition temperature. Correlation of cholesterol retention with side chain mobility showed that cholesterol is more easily removed from vesicles with mobile acyl side chains than from vesicles with rigid side chains. The presence of cholesterol also alters extractability of phospholipids from vesicles and suggests that sterol affects the polarity rather than spacing of headgroups on vesicle surfaces.
Effects of dietary linolenate on the fatty acid composition of brain lipids in rats
Authors: Anding Roberta H. , Hwang Daniel H.
Published: November 2006

Weanling male rats were fed hydrogenated coconut oil to induce essential fatty acid (EFA) deficiency. After 15 weeks, the rats were divided into six groups. Five groups were fed graded amounts of purified linolenate (18∶3ω3) with a constant amount of linoleate (18∶2ω6) for six weeks. Fatty acid composition was determined in brain lipids. Increasing dietary 18∶3ω3 resulted in a decrease in arachidonic acid (20∶4ω6), docosatetraenoic acid (22∶4ω6) and docosapentaenoic acid (22∶5ω6), whereas 18∶2ω6 and eicosatrienoic acid (20∶3ω6) were increased both in total lipids and phospholipids. These results suggest that dietary 18∶3ω3 exerts its inhibitory effect mainly on the desaturation of 20∶ω6 to 20∶4ω6 in brain lipids. Linolenate was undetectable in brain lipids from any dietary treatments. The levels of eicosapentaenoic acid (20∶5ω3) in groups receiving dietary 18∶3ω3 were not different from that of the group receiving no 18∶3ω3. These results indicate that, in the brain, 18∶3ω3 is rapidly converted mainly to 22∶6ω3 without being accumulated and imply that dietary 18∶3ω3 can modulate the level of precursor of diene prostaglandins (PG) but not that of triene PG in the rat brain.
Glucosylceramide and the level of the glucosidase‐stimulating proteins
Authors: Datta Subhash C. , Radin Norman S.
Published: November 2006

The concentration of β‐glucosidase‐stimulating proteins (called cohydrolase here) was measured in mouse liver and brain by immunoassay. Factors that might influence the levels of cohydrolase were examined. Injecting mice with an inactivator of glucosidase (conduritol B epoxide) rapidly produced elevations in liver glucosylceramide (the enzyme's substrate) and in liver and brain cohydrolase. Injection of glucosylceramide emulsified with Myrj 52 produced the same two effects in liver but not in brain. The increases in cohydrolase level induced by the enzyme inhibitor persisted in both organs for at least seven days, reaching 61–70% above the normal level. Injection of emulsified galactocerebroside, sphingomyelin and mixed glucosphingolipids but not of ceramide also produced rises in cohydrolase level. An increase in cohydrolase level resulted from injection of phenylhydrazine, which produces hemolysis and consequently an increased workload for the glucosidase of liver. When the enzyme inhibitor and/or larger amounts of glucosylceramide emulsion were injected (750 mg/kg body weight), increases in liver weight of 13 to 37% appeared within one day. The increased weight was characterized by increases in the weights of protein, total lipid and DNA and a very high increase in glucosylceramide level. These procedures have produced a rapidly developing model version of Gaucher disease in mice. Injected glucocerebroside also induced an elevated level of glucosidase activity.
An improved method for the separation of molecular species of cerebrosides
Authors: Hirabayashi Yoshio , Hamaoka Akira , Matsumoto Makoto , Nishimura Kenji
Published: November 2006

A method employing reversed‐phase high performance liquid chromatography (HPLC) has been developed for the analysis of molecular species of underivatized cerebrosides. By using a high carbon (20%) C18‐silica bead column, monohexosylceramides isolated from bovine brain and Japanese quail intestine could each be separated into 42 and 56 peaks, respectively, and could subsequently be recovered. Under our analytical conditions, underivatized cerebrosides with 24∶1 and 22∶0 fatty acids were completely separated by single step HPLC. Each of the molecular species was then analyzed by high performance thin layer chromatography and gas chromatography‐mass spectrometry (or fast atom bombardment mass spectrometry). This analytical method permits the complete identification of molecular species of glycosphingo‐lipids.
Desaturation of fatty acids inTrypanosoma cruzi
Authors: de Lema Mirta G. , Aeberhard Ernesto E.
Published: November 2006

Uptake and metabolism of saturated (16∶0, 18∶0) and unsaturated [18∶1(n−9), 18∶2(n−6), 18∶3(n−3)] fatty acids by cultured epimastigotes ofTrypanosoma cruzi were studied. Between 17.5 and 33.5% of the total radioactivity of [1‐14C]labeled fatty acids initially added to the culture medium was incorporated into the lipids ofT. cruzi and mostly choline and ethanolamine phospholipids. As demonstrated by argentation thin layer chromatography, gas liquid chromatography and ozonolysis of the fatty acids synthesized, exogenous palmitic acid was elongated to stearic acid, and the latter was desaturated to oleic acid and 18∶2 fatty acid. The 18∶2 fatty acid was tentatively identified as linoleic acid with the first bond in the Δ9 position and the second bond toward the terminal methyl end. Exogenous stearic acid was also desaturated to oleic and 18∶2 fatty acid, while oleic acid was only converted into 18∶2. All of the saturated and unsaturated fatty acids investigated were also converted to a small extent (2–4%) into polyunsaturated fatty acids. No radioactive aldehyde methyl ester fragments of less than nine carbon atoms were detected after ozonolysis of any of the fatty acids studied. These results demonstrate the existence of Δ9 and either Δ12 or Δ15 desaturases, or both, inT. cruzi and suggest that Δ6 desaturase or other desaturases of the animal type are likely absent in cultured forms of this organism.
Effect of malonyl‐CoA on Δ6 desaturation activity of rat liver microsomes
Authors: de Gomez Dumm Irma N. T. , de Alaniz Maria J. T. , Brenner Rodolfo R.
Published: November 2006

The effect of malonyl‐CoA on linoleic acid desaturation and elongation reactions of rat liver microsomes was studied. Under strict desaturation conditions, the in vitro microsomal conversion of linoleic acid to γ‐linolenic acid is time‐dependent. When malonyl‐CoA was added to the aforementioned incubation medium, linoleic acid was desaturated to γ‐linolenic acid and elongated to its higher homologues. Under these conditions, Δ6 desaturation activity, calculated by adding γ‐18∶3, 20∶3 and 20∶4 acids, was neither inhibited nor activated by malonyl‐CoA. These results indicate that the elongation of γ‐linolenyl‐CoA coupled to the desaturation of linoleic acid did not modify Δ6 desaturase activity.
Growth support and metabolism of phytosterols inParamecium tetraurelia
Authors: Whitaker Bruce D. , Nelson David L.
Published: November 2006

The basis of the growth requirement ofParamecium for one of several structurally similar phytosterols is not known. Previous research has indicated that selective esterification of only growth‐promoting sterols may be a key. In this study, it was found that under certain conditions sterols that fail to support growth (e.g., cholesterol) can be esterified in large amounts inParamecium. We found no compelling evidence to support the hypothesis that steryl esters serve a specialized role in the fatty acid metabolism of the cell. Octadecenoic acid, essential for cell growth, was the major fatty acid in both steryl esters and triglycerides. It was also shown thatP. tetraurelia can dehydrogenate Δ0 and Δ7, as well as Δ5‐3β‐hydroxy sterols, to yield the conjugated 5,7‐diene derivative. These results indicate the presence of a Δ5, in addition to a Δ7, desaturase of the sterol nucleus in this ciliate. Two C24 α‐ethyl sterols, Δ22‐stigmasterol (Δ22) and stigmastanol (Δ0), were shown for the first time to promote growth. Finally, we found that non‐growth‐promoting sterols may compose a high percentage of the free sterols of the surface membrane without adversely affecting cell growth or viability. These data support the conclusion that the growth requirement for select phytosterols inParamecium does not involve the structural or functional role of “bulk” sterols in cell membranes.
Lipid peroxidation in erythrocyte membranes: Cholesterol product analysis in photosensitized and xanthine oxidase‐catalyzed reactions
Authors: Girotti Albert W. , Bachowski Gary J. , Jordan John E.
Published: November 2006

The effects of singlet oxygen‐ and oxygen radical‐induced lipid peroxidation on cell membrane integrity were compared, using the human erythrocyte ghost as a model system. Resealed ghosts underwent lipid peroxidation and lysis (release of trapped glucose‐6‐P) when irradiated in the presence of uroporphyrin (UP) or when incubated with xanthine (X), xanthine oxidase (XO) and iron. The UP‐sensitized process was inhibited by azide but not by phenolic antioxidants, consistent with singlet oxygen (nonradical) involvement. This was confirmed by showing that the predominant photoproduct of membrane cholesterol was the 5α‐hydroperoxide. Total hydroperoxide (LOOH) content in UP‐photooxidized ghosts increased linearly during the prelytic lag and throughout the period of rapid lysis. Unlike the photoreaction, X/XO/iron‐dependent peroxidation and lysis was inhibited by catalase, superoxide dismutase and phenolic antioxidants, indicating O2−/H2O2 intermediacy and a free radical mechanism. Correspondingly, only radical reactions products of cholesterol were formed, notably the 7α‐, 7β‐hydroperoxide pair. Membranes lysis had a distinct lag as in photooxidation; however, the LOOH profile was more complex, with an initial lag followed by a sharp increase and then slow decline. X/XO/iron‐induced lysis commenced when LOOH levels were 2–3 times higher than in photosensitized lysis, suggesting that the pathways of membrane lesion formation are different in the two systems. In low concentrations, ascorbate exacerbated the damaging effects of photoperoxidation, switching the reaction from primarily singled oxygen‐ to oxygen radical‐dependence, as indicated by cholesterol product analysis.
Effects of fatty acids on gap junctional communication: Possible role in tumor promotion by dietary fat
Authors: Aylsworth Charles F. , Welsch Clifford W. , Kabara Jon J. , Trosko James E.
Published: November 2006

Dietary lipids, in particular unsaturated fat, promote the development of many experimental tumors. However, no mechanisms to fully explain these effects have been elucidated. Recent reports, which we summarize here, suggest a role for gap junction‐mediated intercellular communication in the process of tumor promotion. We also review tumor‐promoting effects of dietary fat on experimental, particularly mammary, carcinogenesis. Our main focus is to review recent data examining the inhibitory effects of unsaturated fatty acids on metabolic cooperation in Chinese hamster V79 cells. These data suggest that inhibition of junctional communication may be involved mechanistically in the promotion of tumors by high levels of dietary unsaturated fat. Finally, potential mechanisms by which unsaturated fatty acids inhibit metabolic cooperation are examined.
The influence of dietary medium chain triglycerides on rat mammary tumor development
Authors: Cohen L. A. , Thompson D. O.
Published: November 2006

The N‐nitrosomethylurea rat mammary tumor model was used to compare the tumor‐promoting effects of a highfat (HF) diet containing a 3:1 mixture of medium chain triglycerides (MCT) and corn oil with that of a HF and a low‐fat (LF) corn oil diet. The serum and tumor lipid content and fatty acid (FA) composition were also determined in the three dietary groups. It was found that the MCT‐containing diet failed to promote tumor development compared with the HF corn oil group. Tumor incidence in the HF‐MCT group was similar to that of the LF corn oil group (5% fat, w/w), but significantly decreased compared to the HF corn oil group. Total serum cholesterol levels were significantly depressed in the HF corn oil group compared to the HF‐MCT and LF corn oil groups. Analysis of serum and tumor FA profiles indicated that the HF corn oil group exhibited approximately twice the amount of linoleic acid (LA) as the other two treatment groups. Differences among the three groups in the major FA metabolite of LA, arachidonic acid, were minimal. These results are consistent with the hypothesis that tumor promotion by dietary fat is more a function of the type than the amount of fat ingested. In addition, they indicate that MCT, due at least in part to their unique structural and physiological properties, exert markedly different effects on mammary tumor development than conventional long chain unsaturated fatty acids.
In vivo incorporation of labeled fatty acids in rat liver lipids after oral administration
Authors: Leyton J. , Drury P. J. , Crawford M. A.
Published: November 2006

Striking differences were found in the compartmentalization of fatty acids into liver lipid fractions. The saturated fatty acids—lauric, myristic, palmitic and stearic—were incorporated into phosphoglycerides at faster rates with increasing chain lengths, while triglyceride incorporation was almost uniform. The degree of incorporation of the unsaturated fatty acids into phosphoglycerides (structural) compared to triglyceride (storage and energy) was the converse of their oxidation rates. The incorporation of oleic, linoleic and α‐linolenic acids was mainly into triglyceride, whereas dihomo‐γ‐linolenic acid and arachidonic acid were preferentially incorporated into phosphoglycerides. The data suggest that distribution of each fatty acid is different depending on its destination for structural or energy function.
Partial purification and characterization of free and immobilized lipases from Mucor miehei
Authors: Huge‐Jensen Birgitte , Galluzzo Donna Rubano , Jensen Robert G.
Published: November 2006

An extracellular lipase, a glycoprotein, produced by fermentation with a selected strain ofMucor miehei has been partially purified in two forms, A and B. The two forms have a high degree of antigenic identity and have similar pH‐activity profiles with tributyroylglycerol as a substrate with optima at pH 7. They differ as follows: A, in contrast to B, requires activation at alkaline pH before analysis; A binds with concanavalin‐A more completely than B; the net charges are slightly different at pH 8; and the isoelectric points are different. Our results indicate that the B lipase is formed by partial deglycosylation of the A lipase and that this influences the activity toward emulsions.

In addition, the two enzymes have been immobilized by adsorption. These preparations and the soluble forms were highly specific for primary esters of triacylglycerols (TG); they usually hydrolyzed TG of 12∶0, 14∶0, 16∶0, and 18∶1 more rapidly than those of 4∶0, 6∶0, and 8∶0 and 10∶0 in mixtures of monoacid TG (4∶0 to 18∶1); and they were not stereospecific for TG. Immobilization altered the specificity of the preparations somewhat, in that slightly more 14∶0 and 16∶0 were released.
Alteration of hepatic phospholipids in rats and mice by feeding di‐(2‐ethylhexyl)adipate and di‐(2‐ethylhexyl)phthalate
Authors: Yanagita Teruyoshi , Satoh Mikinobu , Nomura Hisashi , Enomoto Noriyuki , Sugano Michihiro
Published: November 2006

Effects of di‐(2‐ethylhexyl)adipate (DOA) and di‐(2‐ethylhexyl)phthalate (DEHP), plasticizers for polyvinylchloride products, on concentrations and compositions of hepatic phospholipids were studied in rats. When administered to rats at a 2% level for 2 wk, both DOA and DEHP caused a hepatomegaly, an increase in hepatic phospholipids and a decrease in the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE). In the comparable study with mice, the alkyl moiety of DOA was found to be responsible for these alterations. DOA and DEHP specifically altered fatty acid compositions of PC and PE: there was an increase in oleic and palmitic acids and a decrease in stearic and docosahexaenoic acids in PC and an increase in arachidonic acid at the expense of docosahexaenoic acid in PE. In addition, DOA caused an increase in the trienoic and tetraenoic molecular species in PC and an increase in the 1‐palmitoyl‐2‐arachidonyl (16∶0//20∶4) species in PE. Thus, the effects of DOA on the lipid dynamics resembled those observed with DEHP, although the magnitude was slightly moderated.
Derivatization of keto fatty acids, X: Synthesis of thiazanones
Authors: Khan Amjadullah , Husain S. Rafat , Ahmad F. , Siddiqui M. S. , Pimlott W.
Published: November 2006

The synthesis of alkyl chain‐substituted thiazanones from oxo fatty esters and a long chain aldehyde is reported. Four oxo compounds—methyl 10‐oxoundecanoate, methyl 9‐oxooctadecanoate, methyl 9,10‐dioxooctadecanoate and octadecanal—were allowed to react with β‐mercaptopropionic acid in the presence of ammonium carbonate in benzene to give the corresponding 4‐m‐thiazanones in high yields. The structures of these compounds were confirmed by combustion and spectral data.
Effect of cold environment on hepatic microsomal Δ6 and Δ9 desaturase activity of male rats
Authors: Losada Ana Ves , Peluffo Raul O.
Published: November 2006

Male rats maintained at 24 C and then shifted to 5 C for 5 days increased food intake and decreased in growth rate and food conversion. No modification was observed in Δ6 desaturase activity, while Δ9 desaturase activity decreased after this period of time. These results were confirmed by liver microsomal and mitochondrial fatty acid composition. The phospholipid composition of liver microsomes was unaltered, whereas in mitochondria, phosphatidylcholine and sphingomyelin decreased and phosphatidylethanolamine increased due to the cold environment. The influence of food intake and weight changes on fatty acid metabolism was studied using (i) rats maintained at 5 C with restricted food intake to match the food intake of those kept at 24 C with food ad libitum and (ii) rats maintained at 24 C whose food intake was also restricted so that their growth rate would be the same as that of rats maintained at 5 C with food ad libitum, respectively. These results indicate that the negative metabolic balance state of these cold conditions is not an active factor modifier of Δ6 desaturase activity, whereas it decreases Δ9 desaturase activity, reflecting the lipogenic characteristics of the latter enzyme.
Rapid separations of diacyl‐ and dialkylglycerol enantiomers by high performance liquid chromatography on a chiral stationary phase
Authors: Takagi Toru , Itabashi Tutaka
Published: November 2006

Rapid and practical separations of 1,2‐and 2,3‐diacyl‐and dialkyl‐sn‐glycerol enantimers as their 3,5‐dinitrophenylurethane derivatives were carried out by normal‐phase high performance liquid chromatography on a chiral stationary phase, N‐(R)‐1‐(α‐naphthyl)ethylaminocarbonyl‐(S)‐valine chemically bonded to γ‐aminopropyl silanized silica. Complete separations of the racemates into enantiomers were achieved for both of the diacyl‐and dialkylglycerols within 10 min using a stainless steel column (25 cm long) packed with the 5‐μ particles, an isocratic elution with a mixture of hexane/ethylene dichloride/ethanol as a mobile phase and a UV detector. Thesn‐1,2‐enantiomers were eluted ahead of the correspondingsn‐2,3‐enantiomers. Satisfactory separation of thesn‐1,3‐diacylglycerols from the corresponding enantiomers and the separation of the homologues differing in acyl and alkyl groups were also observed. The formations of hydrogen bonding and charge transfer complex between the urethane derivatives and the stationary phase may contribute to the enantiomer separations.
Effect of hypothyroidism on the lipid composition of rat plasma and erythrocyte membranes
Authors: Ruggiero F. M. , Gnoni G. V. , Quagliariello E.
Published: November 2006

The effect of hydrothyroidism on plasma and erythrocyte membrane lipid components has been investigated. This pathological state is accompanied by a) a cholesterol increase of about 60% in plasma, and at the same time a 22% reduction in erythroycte membranes; b) 44% and 30% phospholipid level decreases in both plasma and red cell membranes, respectively; and c) almost unaffected phospholipid and fatty acid compositions of both plasma and erythrocyte membranes. All changes were corrected by treatment of the hypothyroid rats with triiodothyronine for two days. These findings suggest that in hypothyroid rats a reduced transfer of cholesterol from plasma to erythrocyte membrane probably takes place. This could explain, at least in part, the increased hematic cholesterol level observed in hypothyroid animals. In red cell membranes, the simultaneous decrease in cholesterol and phospholipid levels does not alter the cholesterol/phospholipid molar ratio, thus avoiding their abnormal function.
Role of the lymphatic system in the transport of absorbed 7,12‐dimethylbenzanthracene in the rat
Authors: Laher J. M. , Barrowman J. A.
Published: November 2006

To determine the role of the intestinal lymphatic system in the absorption of a polycyclic aromatic hydrocarbon, 7,12‐dimethylbenzanthracene, a radiolabeled preparation of the compound was given by intraduodenal infusion to rats in doses of 10 μg, 10 mg and 20 mg in olive oil solution. The hydrocarbon appeared to be absorbed from the intestine in a fractional manner, ca. 20% of the administered radioactivity being recovered totally in bile and intestinal lymph in 24 hr at all three dose levels. Biliary radiolabel accounted for 75–82% of combined recovery of radioactivity in bile and lymph with all three doses. The recovery of significant amounts of radiolabel in bile before the appearance of isotope in lymph, together with the fact that the biliary radiolabel greatly exceeded at all times the lymphatic recovery of isotope, suggests that an alternative pathway, presumably the portal venous route, is of major importance in the transport of the absorbed hydrocarbon.
Nonenzymatic hydrolysis of phosphatidylcholine prepared as liposomes and mixed micelles
Authors: Ho Rodney J. Y. , Schmetz Mark , Deamer David W.
Published: November 2006

Nonenzymatic hydrolysis of phosphatidylcholine was investigated at several pH ranges in liposomes and mixed micelles. Phosphatidylcholine was stable to hydrolysis for 140 hr at pH 4, 7 and 10, but slowly hydrolyzed at pH 1 with a half‐time of 50 hr. We conclude that phosphatidylcholine is not significantly degraded by hydrolysis under conditions typical for liposome preparation methods.
Membrane fatty acid modification in tumor cells: A potential therapeutic adjunct
Authors: Burns C. Patrick , Spector Arthur A.
Published: November 2006

The fatty acid compositions of several tumors have been modified sufficiently to alter some of their properties and functions. These modifications were produced in culture by adding specific fatty acids to the growth medium or by feeding fat‐supplemented diets to tumor‐bearing mice. The phospholipid fatty acid composition of the plasma membrane was modified, but there were no changes in membrane phospholipid or cholesterol content or in phospholipid head group composition. Each of the most abundant membrane phosphoglyceride fractions exhibited some degree of fatty acid modification. Electron spin resonance measurements with nitroxystearate spin probes indicated that the fatty acid modifications were sufficient to alter the physical properties of the plasma membrane. The Km′ for methotrexate uptake was reduced when the L1210 leukemia cells were enriched in linoleic acid. Even when the kinetics of uptake at 37 C were not altered, such as for melphalan and phenylalanine uptake, the temperature transition of transport was modified, indicating that these transport systems also are responsive to the membrane fatty acid modifications. Enrichment with highly polyunsaturated fatty acid did not affect either the growth rate or radiosensitivity of the L1210 leukemia. However, the sensitivity of the L1210 cells to the cytotoxic effects of Adriamycin and hyperthermia was increased. These findings suggest the possibility that fatty acid modification of tumors may be a useful adjunct to certain currently available therapeutic modalities.
Biochemical characterization of acetyl‐CoA:1‐alkyl‐2‐lyso‐sn‐glycero‐3‐phosphocholine acetyltransferase in rat spleen microsomes
Authors: Seyama Kuniaki , Ishibashi Teruo
Published: November 2006

Acetyl‐CoA:1‐alkyl‐2‐lyso‐sn‐glycero‐3‐phosphocholine (lyso‐PAF) ultrasonic disruption in the presence of 25% glycerol from rat spleen microsomes. About 26% of the enzymatic activity was recovered in the 225,000×g supernatant by this treatment, although the specific activity was slightly decreased compared with the original microsomes. The solubilized enzyme was remarkably susceptible to various kinds of metal ions. Sulfhydryl reagents such as p‐chloromercuribenzoate and N‐ethyl‐maleimide significantly inhibited the enzyme reaction, suggesting that the enzyme is an SH enzyme. Based on the sedimentation pattern in sucrose density centrifugation, the isoelectric point, the kinetic characteristics and the sensitivity to tryptic digestion of microsomes, it appears that acetyl‐CoA:lyso‐PAF acetyltransferase does not differ from the acetyltransferase responsible for the transfer of acetate from acetyl‐CoA to 1‐acyl‐2‐lyso‐sn‐glycero‐3‐phosphocholine.
Two new icosapentaenoic acids from the temperate red seaweedPtilota filicina J. Agardh
Authors: Lopez Albert , Gerwick William H.
Published: November 2006

Two new fatty acid metabolites, 5(Z),7(E),9(E),14(Z),17(Z)‐icosapentaenoic acid and 5(E),7(E),9(E),14(Z),17(Z)‐icosapentaenoic acid, have been isolated from the temperate red marine alga,Ptilota filicina (Ceramiales, Rhodophyta). The structures of these new compounds, isolated as their methyl ester derivatives, have been deduced from detailed1H nuclear magnetic resonance (NMR),13C NMR and 2D‐NMR analyses as well as comparisons to known compounds.
Measurement of lipid peroxidation in vivo: A comparison of different procedures
Authors: Pompella Alfonso , Maellaro Emilia , Casini Alessandro F. , Ferrali Marco , Ciccoli Lucia , Comporti Mario
Published: November 2006

A study was undertaken to investigate whether some of the methods commonly used to detect lipid peroxidation of cellular membranes in vivo correlate with each other. The study was performed with the livers of bromobenzene‐intoxicated mice, in which lipid peroxidation develops when the depletion of glutathione (GSH) reaches a threshold value. The methods tested and compared were the following: i) measurement of the malondialdehyde (MDA) content of the liver; ii) detection of diene conjugation absorption in liver phospholipids; iii) measurement of the loss of polyunsaturated fatty acids in liver phospholipids; and iv) determination of carbonyl functions formed in acyl residues of membrane phospholipids as a result of the peroxidative breakdown of phospholipid fatty acids. Correlations among the values obtained with these methods showed high statistical significances, indicating that the procedures measure lipid peroxidation in vivo with comparable reliability. Analogously, the four methods appeared also to correlate when applied to in vitro microsomal lipid peroxidation.
Alteration of chain length selectivity of aRhizopus delemar lipase through site‐directed mutagenesis
Authors: Joerger Rolf D. , Haas Michael J.
Published: November 2006

The coding sequences of theRhizopus delemar lipase and prolipase were altered by oligonucleotide‐directed mutagenesis to introduce amino acid substitutions. The resulting mutant enzymes, synthesized by the bacterial hostEscherichia coli BL21 (DE3), were tested for their ability to hydrolyze the triglycerides triolein (TO), tricaprylin (TC) and tributyrin (TB). Mutagenesis and lipase gene expression were carried out using plasmid vectors derived from previously described recombinant plasmids [Joerger and Haas (1993)Lipids 28, 81–88] by introduction of the origin of replication of bacteriophage fl. Substitution of threonine 83 (thr83), a residue thought to be involved in oxyanion binding, by alanine essentially eliminated lipolytic activity toward all substrates examined (TB, TO and TC). Replacement of thr83 with serine caused from two‐ to sevenfold reductions in the activity toward these substrates. Introduction of tryptophan (trp) at position 89, where such a residue is found in closely related fungal lipases, reduced the specific activity toward the three triglyceride substrates. For the mutagenesis of residues in the predicted acyl chain binding groove, mutagenic primers were designed to cause the replacement of a specific codon within the prolipase gene with codons for all other amino acids. Phenylalanine 95 (phe95), phe112, valine 206 (val206) and val209, were targeted. A phenotypic screen was successfully employed to identify cells producing prolipase with altered preference for olive oil, TC or TB. In assays involving equimolar mixtures of the three triglycerides, a prolipase with a phe95→asparatate mutation showed an almost twofold increase in the relative activity toward TC. Substitution of trp for phe112 caused an almost threefold decrease in the relative preference for TC, but elevated relative TB hydrolysis. Replacement of val209 with trp resulted in an enzyme with a two‐ and fourfold enhanced perference for TC and TB, respectively.
Effects of soybean lipoxygenase‐1 on phosphatidylcholines containing furan fatty acids
Authors: Batna Andreas , Spiteller Gerhard
Published: November 2006

Naturally occurring tetraalkylsubstituted furan fatty acids (F‐acids) were tested as potential substrates for soybean lipoxygenase‐1. For this purpose, F‐acid methyl ester and phosphatidylcholines containing F‐acids at thesn‐2 position of the glycerol residue wer incubated with the enzyme. Oxidation of F‐acids only occurs in the presence of linoleic acid as co‐substrate. Linoleic acid is converted by lipoxygenase to the corresponding hydroperoxide that oxidizes the F‐acid, probably in a radical reaction, to form an unstable dioxoene compound. This intermediate the forms, dependent on pH, unsaturated furanoid acids or isomers with cyclopentenolone structure that can be detected by gas chromatography/mass spectrometry (GC/MS). F‐acids located at thesn‐2 position of a synthetic phosphadidylcholine (PC), containing linoleic acid in thesn‐1 position, are co‐oxidized to a greater extent by incubation with soybean lipoxygenase‐1 than are F‐acids bound to PC with myristic acid in thesn‐1 position when subjected to the enzyme in the presence of a great excess of linoleic acid. The results suggest that F‐acids may play a strategic role in antioxidative processes in plant cells.
Cholesterol secretion from hepatocytes induced by triacylglycerol and apolipoprotein E
Authors: Quarfordt Steven H. , Landis Barry A. , Farouk Marwan O. , Oswald Brian S.
Published: November 2006

The mechanism for the increase in plasma cholesterol levels in cholesterol‐fed rats following chylomicron transport was investigated in intact animals, in isolated perfused liver, and in hepatocytes in monolayer cultures. Intravenous administration of egg phosphatidylcholine in amounts greater than those required to cause a plasma cholesterol response when given as chylomicrons was without effect. This makes it unlikely that increased plasma cholesterol levels resulted from the recruitment of tissue cholesterol by the plasma chylomicron phospholipids that persisted in the plasma after triacylglycerol clearance. The hepatic origin of the increased plasma cholesterol levels was directly confirmed by two hepatic perfusion experiments. When cholesterol‐fed rats received intravenous chylomicrons prior to isolated hepatic perfusion, more cholesterol was secreted by the liver than when the rats were injected intravenously with buffer. Perfusion of apolipoprotein E (apo E)‐rich triacylglycerol emulsions through the livers also enhanced cholesterol secretion. The increase in hepatocyte cholesterol secretion seen with cholesterol‐fed rats was also noted in monolayer cultures following incubation with apo E rich‐triacylglycerol emulsions. The apolipoprotein or the emulsion alone, or apo E‐rich phosphatidylcholine liposomes, had no effect. The data confirm previous indirect observations that the liver is the source of cholesterol that appears in plasma following transport of chylomicrons or following a lipid‐rich meal in cholesterol‐fed rats. The data also re‐emphasize the importance of providing apo E with triacylglycerol emulsions to initiate secretion of lower density lipoproteins by the liver.
A cross‐species comparison of neutral lipid composition of milk fat of prosimian primates
Authors: Myher J. J. , Kuksis A. , Tilden C. , Oftedal O. T.
Published: November 2006

The fatty acid composition of milk fat is known to be affected by dietary and genetic differences, while the milk triacylglycerol structure is believed to be attuned to the needs of the subsequent lipolysis during gastrointestinal passage. The availability of milk samples from eight species of prosimian primates, whose milk triacylglycerol structure had not been analyzed, offered an opportunity to further assess these ideas. The milk samples were collected by manual expression and the lipids extracted with chloroform/methanol (2∶1, vol/vol). The lipid classes were resolved by thin‐layer chromatography, and the neutral lipids subjected to detailed analyses by capillary gas‐liquid chromatography of fatty acids and molecular species of triacylglycerols using nonpolar and polarizable liquid phases. The milk samples were found to differ greatly in total fat content (4–73%) and in the composition of the neutral liqid classes and molecular species. The concentration of triacylglycerols ranged from 88–95%, free fatty acids from 0.5–10%, alkyldiacylglycerols from 0.5–5.0%, and diacylglycerols, monoacylglycerols and free and esterified cholesterol made up the remainder. The fatty acid chain length ranged from C8−C24, with palmitic (16–31%) and oleic (13–40%) acids being the major components in most of the species. In all instances, the molecular association of the fatty acids differed from random distribution by a higher proportion of the monoacid (trioleoyl) and diacid (dipalmitoyloleoyl) glycerols. The phylogenetic influences on neutral milk lipid composition, however, remained unclear, as some of the differences between closely related species were greater than those between more distantly related ones.
Sterol and fatty acid composition of neutral lipids ofParatenuisentis ambiguus and its host eel
Authors: Weber Nikolaus , Vosmann Klaus , Aitzetmüller Kurt , Filipponi Christin , Taraschewski Horst
Published: November 2006

The sterol composition of free sterol and steryl ester fractions of the fish parasiteParatenuisentis ambiguus was determined. In addition, the fatty acid composition of various neutral lipid classes, i.e., wax esters, steryl esters, triacylglycerols and free fatty acids, as well as the composition of the 1‐O‐alkyl moieties of total ether glycerolipids of the parasite, were investigated. The results of these studies were compared with those obtained on the intestinal tract tissue of its host, the eel (Anguilla anguilla). Cholesterol is the major sterol in bothP. ambiguus andA. anguilla. However, the sterols ofP. ambiguus contain high proportions (>20%) of other sterols, such as campesterol and various dehydrosterols. [e.g., 7‐dehydrocholesterol and cholesta‐5,22(E)‐dienol]. The presence of these minor sterols agrees with the known biotransformations of exogenous sterols in various helminths. Considerable differences are found in the fatty acid composition of neutral lipid fractions, as well as the total lipid extract from the endoparasite as compared to the host tissue. In particular, eicosapentaenoic acid (20∶5n−3), other polyunsaturated fatty acids, such as 20∶4n−6, 22∶5n−3 and 22∶6n−3, as well as long‐chain saturated fatty acids, such as 20∶0, are generally enriched in the neutral lipid fractions of the parasite as compared to those of infected eel intestine. The analysis of ether glycerolipids revealed that 1‐O‐hexadecyl (16∶0) and 1‐O‐hexadecenyl (16∶1) moieties were present in similar proportions in the ether lipids of bothP. ambiguus and eel intestine, whereas 1‐O‐octadecyl (18∶0) moieties are more prominent in the parasite and 1‐O‐octadecenyl (18∶1) moieties in the eel. The results of these studies show thatP. ambiguus has specific mechanisms for the regulation of the sterol and fatty acid composition of its neutral lipids.
Identification of a deoxyguanosine‐malondialdehyde adduct in rat and human urine
Authors: Agarwal Sanjiv , Wee Jae Joon , Hadley Mary , Draper Harold H.
Published: November 2006

In an ongoing study, rat and human urine have been examined for the presence of malondialdehyde (MDA) derivatives as indicators of the nature of lipid peroxidative damage caused by this compoundin vivo. MDA in urine was found to be present mainly in the form of two lysine adducts, one acetylated and the other unacetylated, reflectingin vivo reactions with tissue proteins. Two minor metabolites were identified as adducts with the phospholipid bases serine and ethanolamine and a third one as an adduct with the nucleic acid base guanine. The identification of an MDA adduct with deoxyguanosine (dG‐MDA) among the products of hydrolysis of rat liver DNA suggested the possible occurrence of this compound in urine. In the present study dG‐MDA was identified in rat and in human urine, and a high‐performance liquid chromatographic method utilizing fluorescence detection was developed for its estimation. The method is sensitive to 1 pmol of dG‐MDA and requires a minimum of 1 mL of rat urine or 5 mL of human urine. Its rate of excretion by five‐week‐old rats (28.54±2.28 nmol/kg/24 h) (mean±SEM) was higher than that for nine‐week‐old rats (6.29±1.02) and much higher than that for adult humans (0.40±0.05). The results indicate that, as reported for 8‐hydroxy‐deoxyguanosine, dG‐MDA excretion is related to metabolic rate. Excretion of dG‐MDA by the rat, like the excretion of total MDA, declines during growth on a body weight basis at a rate similar to the decrease in resting energy metabolism. In contrast to other MDA derivatives excreted in rat urine, vitamin E deficiency had no effect on the excretion of dG‐MDA. Together with evidence that the dG‐MDA content of rat liver DNA likewise is unaffected by vitamin E depletion or by administration of catalysts ofin vivo lipid peroxidation, these findings indicate that DNA is protected from lipid peroxidative damage, possibly through conservation of the vitamin E associated with the lipids of the nuclear membrane.
Fatty acid and positional selectivities of gastric lipase from premature human infants:in vitro studies
Authors: Jensen Robert G. , deJong Felice A. , Lambert‐Davis Lisa G. , Hamosh Margit
Published: November 2006

Gastric lipase activity in aspirates from premature human infants was tested for fatty acid and positional selectivity using racemic diacid triacylglycerols (TG) as substrates. The resulting free fatty acids and monoacylglycerols (MG) were recovered and analyzed. Octanoic acid (8∶0) and decanoic acid (10∶0) were hydrolyzed with a preference of 61.5∶1 and 2.4∶1 compared to palmitic acid (16∶0) fromrac‐16∶0–8∶8∶0 andrac‐16∶0–10∶0–10∶0, respectively. The ratio of lauric acid (12∶0) to oleic acid (18∶1) hydrolyzed fromrac‐18∶1–12∶0 was 13∶1. Myristic acid (14∶0), 18∶1 and linoleic acid (18∶2) were released at similar rates. These data and the composition of the MG suggest that,in vitro, the lipase is selective for shorter chain fatty acids and for fatty acids on the primary positions of the TG backbone.
Lymphatic fatty acids from rats fed human milk and formula containing coconut oil
Authors: Roche Matthew E. , Clark Richard M.
Published: November 2006

Human milk and infant formula containing coconut/soy oil were infused into the duodenum of rats to determine the incorporation of capric, lauric, myristic and palmitic acids into lymphatic triacylglycerol (TAG). The proportion of capric and lauric acids in the lymphatic TAG reflected the fatty acid composition of the diet. Based on positional analysis, it appears that more than 50% of the capric and lauric acids could have been absorbed from the intestine assn‐2 monoacylglycerols. In the rats fed human milk, 50% of palmitic acid in lymphatic TAG was in thesn‐2 position. Because of the nonrandom distribution of palmitic acid in the lymphatic TAG, the nonspecific lipase in human milk, i.e., bile salt‐stimulated lipase, did not appear to be a factor in milk lipid digestion.
Confirmation by gas chromatography/mass spectrometry of two unusualrans‐3‐monoethylenic fatty acids from the nova scotian seaweedsPalmaria palmata andChondrus crispus
Authors: Lamberto M. , Ackman R. G.
Published: November 2006

The structures of two unusual fatty acids, the knownrans‐3‐hexadecenoic acid and a noveltrans‐3‐tetradecenoic acid, both isolated from the Nova Scotian sea‐weedsPalmaria palmata andChondrus crispus, were positively identified. After the extraction of the total fatty acids by saponification, followed by methylation, the monoenoictrans fractions were isolated by thin‐layer chromatography on silica gel impregnated with silver nitrate. The monoenoictrans fractions were derivatized with 2‐amino‐2‐methyl‐propanol prior to analysis by gas chromatography/mass spectrometry. The mass spectra showed prominent [M+1]+ ions but lacked the 12 amu interval useful for identifying the double bond position. Hence, alternative diagnostic peaks were used to confirm the position of the double bond in these two fatty acids. As thetrans‐3‐hexadecenoic acid is found in the photosynthetic tissue of all plants, it may also be present in ruminant fats and, presumably, in human adipose tissue.
Fluorescent substances derived from the reaction of 13‐monohydroperoxylinoleic acid and methylamine
Authors: Kikugawa Kiyomi , Watanabe Shigenobu
Published: November 2006

Reaction of 13‐monohydroperoxy linoleic acid and methylamine in the presence of ferric ions produced at least four fluorescent substances. They were separated by high performance liquid chromatography with a reverse phase column, and major fluorescent substances 1 and 3 were isolated. Fluorescent substances 1 and 3 showed the same fluorescence spectra with excitation maxima at 360 nm and emission maxima at 430 nm, and the same ultraviolet spectra with absorption maxima at 275 and 360 nm. Fluorescence of 1 and 3 was lost in alkaline media owing to the instability of the fluorophores. The fluorophores of 1 and 3 were destroyed on treatment with borohydride. The fluorescence characteristics of 1 and 3 were similar to those of the age‐related fluorescent substances produced in tissues. They were different from those of the fluorescent substances derived from malonaldehyde and resembled those of the fluorescent substances derived from monofunctional aldehydes.
Adenylate cyclase and β‐receptors in salivary glands of rats fed diets containingtrans fatty acids
Authors: Ren Y‐F. , Alam S. Q. , Alam B. S. , Keefer L. M.
Published: November 2006

The effects oftrans fatty acids on adenylate cyclase were determined in the submandibular salivary glands (SMSG) of rats fed diets containing 20% corn oil, 20% partially hydrogenated soybean oil (PHSBO) or 18% PHSBO + 2% corn oil. The fluoride‐and isoproterenol‐stimulated adenylate cyclase activities were higher in the SMSG from rats fed 20% PHSBO than in the control group fed 20% corn oil. The feeding of 2% corn oil with the diet containing 18% PHSBO resulted in a complete restoration of isoproterenol‐stimulated and a partial restoration of fluoride‐stimulated adenylate cyclase activity. There was no significant difference in the concentration of the β‐adrenergic receptor or in the receptor‐binding affinity constants among the three dietary groups as measured by [3H]dihydroalprenolol (DHA)‐binding. Higher fluorescence polarization of diphenyl hexatriene (DPH) was observed in SMSG membranes of rats fed diet containing 20% PHSBO than in the other two oils, suggesting that membrane fluidity may play a role in adenylate cyclase activity.
Triacylglycerol structure of plant and fungal oils containing ψ‐linolenic acid
Authors: Lawson Larry D. , Hughes Bronwyn G.
Published: November 2006

The triacylglycerol stereospecific structure was determined for the major plant oils containing ψ‐linolenic acid (GLA): evening primrose oil (EPO), black currant oil (BCO), borage oil (BO), andMucor javanicus fungal oil (MJO). It was found that GLA, although not α‐linolenic acid, resisted pancreatic lipase hydrolysis. Therefore, the 2‐position analysis was determined using phospholipase C‐generated 1,2‐diacylglycerol and phospholipase A2‐generated lysophosphatidylcholine. GLA was found to be concentrated in the 3‐position of EPO and BCO, the 2‐position of BO, and the 2‐ and 3‐positions of MJO. In BCO, octadecatetraenoic acid (n−3), also a †‐6 fatty acid, was distributed similarly to GLA, but α‐linolenic acid was found predominantly in the 1‐position. Linoleic acid was nearly evenly distributed in all positions of EPO and BCO but was concentrated in the 1‐position of BO and the 2‐position of MJO. Both palmitic and stearic acids were found predominantly in the 1‐position of all of the oils. The results demonstrate similarities and differences in the positional distribution of fatty acids in GLA‐containing oils.