Showing papers in "Lipids in 1988"

Rapid separation of neutral lipids, free fatty acids and polar lipids using prepacked silica Sep-Pak columns.

Abstract: A method is described for the separation of neutral lipid, free fatty acid and polar lipid classes using small (600 mg), prepacked silica Sep-Pak columns. Combinations of hexane and methyltertiarybutylether were used to progressively elute cholesteryl ester first then triglyceride from the column. After column acidification, fatty acids were eluted followed by cholesterol. Recoveries of these lipids were 96% or greater. Polar lipids were eluted from the column using combinations of methyltertiarybutylether, methanol and ammonium acetate. Phospholipid classes could not be separated completely from each other. Phosphatidylethanolamine and phosphatidylinositol eluted together, whereas the more polar phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were eluted as a second fraction. Recoveries of each phospholipid was greater than 98%.

Hypocholesterolemic action of chitosans with different viscosity in rats

Abstract: The relationship between hypocholesterolemic efficacy and average molecular weight of chitosan was studied in rats fed a cholesterol-enriched (0.5%) diet. Several chitosan preparations with a comparable degree of deacetylation but differing widely in average molecular weight, as demonstrated by viscosity, almost completely prevented the rise of serum cholesterol at the 5% dietary level. At the 2% level, chitosans with viscosities at both extremes exerted a comparable cholesterol-lowering action. The glucosamine oligomer composed mainly of three to five aminosugar residues was not effective. The results indicate that the hypocholesterolemic action of chitosans is independent of their molecular weight within the tested viscosity range.

Milk fat globules: fatty acid composition, size and in vivo regulation of fat liquidity.

Abstract: Populations of large and small milk fat globules were isolated and analyzed to determine differences in fatty acid composition. Globule samples were obtained by centrifugation from milks of a herd and of individual animals produced under both pasture and barn feeding. Triacylglycerols of total globule lipids were prepared by thin layer chromatography and analyzed for fatty acid composition by gas chromatography. Using content of the acids in large globules as 100%, small globules contained fewer short-chain acids, −5.9%, less stearic acid, −22.7%, and more oleic acids, +4.6%, mean values for five trials. These differences are consistent with alternative use of short-chain acids or oleic acid converted from stearic acid to maintain liquidity at body temperature of milk fat globules and their precursors, intracellular lipid droplets. Stearyl-CoA desaturase (EC 1.14.99.5), which maintains fluidity of cellular endoplasmic reticulum membrane, is suggested to play a key role in regulating globule fat liquidity. Possible origins of differences between individual globules in fatty acid composition of their triacylglycerols are discussed.

Geraniol interferes with membrane functions in strains ofCandida andSaccharomyces

Abstract: Geraniol, an olefinic terpene, was found to inhibit growth ofCandida albicans andSaccharomyces cerevisiae strains. Geraniol was shown to enhance the rate of potassium leakage out of whole cells and also was shown by fluorescence polarization to increaseC. albicans membrane fluidity. Biophysical studies using differential scanning calorimetry, fluorescence polarization and osmotic swelling of phospholipid vesicles demonstrated that geraniol decreased the phase-transition temperature of dipalmitoylphosphatidylcholine vesicles, affected fluidity throughout the bilayer, particularly the central portion of the bilayers, and caused an increase in bilayer permeability to erythritol. Geraniol may have potential use as an antifungal agent.

Rhizomucor miehei triglyceride lipase is synthesized as a precursor.

Abstract: ARhizomucor miehie cDNA library constructed inEscherichia coli was screened with synthetic oligonucleotides designed from knowledge of a partial amino acid sequence of the secreted triglyceride lipase (triacyl-glycerol acylhydrolase EC 3.1.1.3) from this fungus. Lipase-specific recombinants were isolated and their insert sequenced. Unlike characterized bacterial and mammalian triglyceride lipases, the fungal enzyme is synthesized as a precursor, including a 70 amino acid residue propeptide between the 24 amino acid residues of the signal peptide and the 269 residues of the mature enzyme. The precursor processing mechanism, which involves cleavage between a methionine and a serine residue, is unknown. By sequence comparison with other lipases, a serine residue involved in substrate binding was identified in the fungal lipase. The sequence around this residue is well-conserved among characterized lipases. Conservation of an intron in an isolated cDNA recombinant and immunoprecipitation of in vitro synthesizedR. miehei translation products indicates that the expression of the lipase gene might involve inefficient mRNA splicing.

Absorption and transport of fat in mammals with emphasis on n−3 polyunsaturated fatty acids

Abstract: The current state of knowledge concerning the absorption and transport of dietary fat with emphasis on long-chain polyunsaturated n−3 fatty acids in mammals is reviewed. It is apparent that long-chain polyunsaturated n−3 fatty acids, either as free acids or as part of triglycerides, are readily absorbed in the gut and transported by the circulatory system. Indeed, it would appear that long-chain polyunsaturated n−3 fatty acids are digested, absorbed and transported similarly to other long-chain fatty acids with only minor variations, although there is much that is still not understood about these processes. The main unresolved issues in the area of the absorption and transport of long-chain polyunsaturated n−3 fatty acids appear to be: 1) If they, when located in the 2-position of triglycerides, have unique metabolic pathways; and 2) whether the unnatural forms, i.e., methyl or ethyl ester derivatives, are suitable vehicles for administration as dietary supplements. The effect in man of dietary, long-chain polyunsaturated n−3 fatty acids on blood serum lipid and lipoprotein levels, particularly the low density lipoproteins, remains controversial, except for the well-documented reduction in serum triglyceride levels. Also, there is uncertainty regarding their distribution and metabolism in tissues. Finally, if the consumption of long-chain polyunsaturated n−3 fatty acids has beneficial health consequences, what is the appropriate therapeutic dose? In view of these important, unresolved issues and uncertainties, it would seem prudent to direct additional research toward a better understanding of the overall process by which fat is digested, absorbed and transported.

Quantification of oxysterols in Dutch foods: Egg products and mixed diets.

Abstract: A sensitive and specific method is described for quantifying various cholesterol oxidation products in foodstuffs, including 7β-hydroxycholesterol, cholesterol-α-epoxide, cholestane-triol, 7-ketocholesterol and 25-hydroxycholesterol. A chloroform-methanol extract of the food was fractionated over two successive silica columns. Two fractions containing different classes of oxysterols were then analyzed as trimethylsilyl derivatives by capillary gas liquid chromatography, using on-column injection and a temperature gradient from 70 to 200°C. The detection limit was about 0.5 μg/g dry weight for egg yolk powder. Fresh egg yolk contained only 1.2 μg/g of total oxides per g dry weight, showing that artifactual oxidation during the procedure was minimal. Recovery of 5 pure oxysterols added to egg yolk at levels of 6.5 and 10 μg/g was between 93 and 102%. In commercial egg yolk and whole egg powder stored for one year, total amounts of oxysterols ranging from 21 to 137 μg/g dry weight were found. In duplicates of mixed Dutch diets, total amounts ranged from 3.6 to 6.2 μg/g dry weight. Duplicates containing mostly fried and baked foods did not have higher levels than duplicates in which foods had been prepared by boiling or left raw. We conclude that a normal mixed diet provides only minor amounts of cholesterol oxidation products.

Integral lipids of human hair.

Abstract: It has long been recognized that hair is coated with nonpolar lipids originating in the sebaceous glands, and recently it has been shown that hair also contains cholesterol sulfate and small amounts of ceramides, similar to those found in the keratinized portion of the epidermis. In the present study, it is demonstrated that significant amounts of several additional lipids are tightly associated with hair in such a way as to be highly resistant to solvent extraction. These integral hair lipids included cholesterol sulfate (3.3 mg/g of extracted hair), cholesterol (0.6 mg/g), fatty alcohols (0.2 mg/g) and free fatty acids (4.3 mg/g). The principal fatty acid, comprising 40% of the total fatty acids, was identified as 18-methyl-eicosanoic acid by cochromatography with authentic standard on gas-liquid chromatography (GLC) and by mass spectrometry (MS).

Enhanced survival to endotoxin in guinea pigs fed IV fish oil emulsion

Abstract: Improved survival to endotoxin has been demonstrated in rats pretreated with cyclooxygenase inhibitors or made essential fatty acid deficient, implying that excessive ω6 fatty acids, possibly through their eicosanoid products, contribute to mortality. Following endotoxin administration, we also have shown improvement in survival with oral diets supplemented with fish oil. This study sought to explore whether parenteral fish oil ameliorates the adverse impact of endotoxin.

Recent advances in the purification, characterization and structure determination of lipases.

Abstract: Recently, lipases have been purified from mammalian, bacterial, fungal and plant sources by different methodologies. Purified lipases subsequently have been characterized for molecular size, metal binding capabilities, glycoside and phosphorus contents, and substrate specificities. Primary structures of several lipases have been determined either from amino acid or nucleic acid sequences. Lipases sequenced to date share sequence homologies including a significant region, Gly-X-Ser-X-Gly, that is conserved in all. The Ser residue is suspected to be essential for binding to lipid substrates.

Uptake of fatty acids by the developing rat brain

Abstract: Polyunsaturated fatty acids are avidly taken up by the developing rat brain To explore the specificity of this process, [1-14C]labeled 16∶0, 18∶2n−6, 18∶3n−3, and 22∶6n−3 each were co-injected with [3H]18∶1n−9 into the jugular vein of two-wk-old functionally hepatectomized and shamoperated control rats The radioactivities present in the brain, liver and serum were assessed 30 min after injection Uptake of labeled fatty acids into brain lipids steadily increased with increasing degree of unsaturation, with more than twice as much uptake of 22∶6n−3 compared to 16∶0 Phosphatidylcholine was the principal radioactive species in the brain except for animals injected with [1-14C]22∶6n−3, in which more of the label was incorporated into phosphatidylethanolamine Determination of watersoluble oxidation products in the brain and serum revealed that the greater uptake of the more unsatrated fatty acids did not result from differences in rates of degradation

Triacylglycerol structure of plant and fungal oils containing ψ-linolenic acid.

Abstract: 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.

Differential effects of dietary linoleic and α-linolenic acid on lipid metabolism in rat tissues

Abstract: Comparative effects of feeding dietary linoleic (safflower oil) and α-linolenic (linseed oil) acids on the cholesterol content and fatty acid composition of plasma, liver, heart and epididymal fat pads of rats were examined. Animals fed hydrogenated beef tallow were used as isocaloric controls. Plasma cholesterol concentration was lower and the cholesterol level in liver increased in animals fed the safflower oil diet. Feeding the linseed oil diet was more effective in lowering plasma cholesterol content and did not result in cholesterol accumulation in the liver. The cholesterol concentration in heart and the epididymal fat pad was not affected by the type of dietary fatty acid fed. Arachidonic acid content of plasma lipids was significantly elevated in animals fed the safflower oil diet and remained unchanged by feeding the linseed oil diet, when compared with the isocaloric control animals fed hydrogenated beef tallow. Arachidonic acid content of liver and heart lipids was lower in animals fed diets containing safflower oil or linseed oil. Replacement of 50% of the safflower oil in the diet with linseed oil increased α-linolenic, docosapentaenoic and docosahexaenoic acids in plasma, liver, heart and epididymal fat pad lipids. These results suggest that dietary 18∶2ω6 shifts cholesterol from plasma to liver pools followed by redistribution of 20∶4ω6 from tissue to plasma pools. This redistribution pattern was not apparent when 18∶3ω3 was included in the diet.

Comparison of free α-tocopherol and α-tocopheryl acetate as sources of vitamin E in rats and humans

Abstract: The uptake of alpha-tocopherol from 2R,4'R,8'R-alpha-tocopherol and 2R, 4'R, 8'R-alpha-tocopheryl acetate has been compared in rats and humans. The two forms of vitamin E were compared simultaneously in each subject (rat and human) by using a combination of deuterium-substitution and gas chromatography-mass spectrometry (GC-MS) to distinguish and measure the competitive uptake of alpha-tocopherol from an orally ingested mixture of the acetate and the free phenol forms. When rats were dosed in a manner analogous to that used in traditional bioassays, i.e., providing the two forms of vitamin E once daily in tocopherol-stripped corn oil for four successive days immediately prior to sacrifice, the net uptake of alpha-tocopherol from the free phenol form was only half that from the acetate. This result is consistent with the greater activity of the acetate that had been observed previously in bioassays. However, when the two forms of tocopherol were intubated into rats as a single dose mixed in with an aqueous bolus of standard laboratory diet, the amount of alpha-tocopherol taken up from the free form after 24 hr was very similar to that derived from the acetate. In five adult humans, competitive uptake studies of the two forms after a single dose taken with a meal showed that the amount of alpha-tocopherol from the free phenol form was equal to that from the acetate in plasma and red blood cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Eicosanoid synthesis in 7,12-dimethylbenz(a) anthracene-induced mammary carcinomas in Sprague-Dawley rats fed primrose oil, menhaden oil or corn oil diet

Abstract: The comparative effects of high-fat diets (20%, w/w) on eicosanoid synthesis during mammary tumor promotion in 7,12-dimethylbenz(a)anthracene (DMBA)-induced rats were studied using diets containing 20% primrose oil (PO), 20% menhaden oil (MO) or 20% corn oil (CO). Sprague-Dawley rats fed the PO or MO diet had 21% or 24% fewer adenocarcinomas, respectively, than rats fed the CO diet. Histologically (i.e., mitotic figures, inflammatory cell infiltration and necrosis), the CO-fed rats exhibited the highest frequency of changes within tumors. Plasma fatty acid composition was significantly altered by diet, reflecting the composition of the oils which were being fed. Only the plasma of PO-fed rats contained detectable levels of gamma-linolenic acid (GLA). Arachidonic acid (AA) levels were significantly higher (p<0.05) in PO-fed than in CO- or MO-fed rats. MO-fed rats had significantly higher levels of plasma palmitic acid, while palmitoleic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were detected only in MO-fed rats. As expected, linoleic acid (LA) and AA levels were lower (p<0.05) in the MO-fed rats than in PO- or CO-fed groups. The plasma of the CO-fed rats contained significantly higher levels of oleic acid. Eicosanoid synthesis in mammary carcinomas of rats fed the 20%-fat diets was 2–10 times higher than in mammary fat pads of control rats. The synthesis of PGE1 and LTB4 was significantly (p<0.05) higher in PO-fed rats than in CO-fed or MO-fed rats, although PGE values were significantly (p<0.05) higher in CO-fed rats than in Mo or PO groups. The synthesis of eicosanoids in both mammary fat pads and mammary carcinomas of MO-fed rats was lower (p<0.05) than in tissues of rats fed either CO or PO diets due to less AA precursor being fed and/or to competition between n−6 and n−3 fatty acids for cyclooxygenase and lipoxygenase. The ratios of monoenoic to dienoic eicosanoids in both mammary fat pads and mammary carcinomas were higher in the PO group than in the MO or CO groups. These results suggest that inclusion of GLA (PO feeding) or EPA and DHA (MO feeding) in the diet may decrease malignancy by altering eicosanoid profiles.

Fatty acids as biological markers for bacterial symbionts in sponges.

Abstract: Analyses of fatty acids with carbon numbers between C12 and C22 are reported for five Great Barrier Reef sponges. These analyses indicate that phototrophic cyanobacterial symbionts (blue-green algae) present in three of the sponges are chemically distinct, whereas the other two sponges do not contain cyanobacterial symbionts. All the sponges contain other, nonphototrophic bacteria. The fatty acid analyses indicate that the non-phototrophic bacterial populations present in the different sponges are distinct in both their chemical compositions and their abundances. Nonphototrophic bacteria are estimated to account for between 60 and 350 micrograms/g (extractable fatty acids:tissue wet weight), whereas cyanobacteria account for between 10 and 910 micrograms/g. One sponge (Pseudaxinyssa sp.) contains a relatively large amount of the isoprenoid acid, 4, 8, 12-trimethyltridecanoic acid; this acid is presumed to be derived from phytol, a degradation product of chlorophyll. This sponge also contains relatively large amounts of the nonmethylene interrupted fatty acid, octadeca-5,9-dienoic acid. Analyses of interior and cyanobacteria-rich surface tissues of this sponge indicate that these two acids are probably not associated with the symbiotic cyanobacteria.

Analysis of cardiac membrane phospholipid peroxidation kinetics as malondialdehyde: Nonspecificity of thiobarbituric acid-reactivity

Abstract: When exposed to xanthine oxidase (superoxide)-dependent, iron-promoted Fenton chemistry, purified cardiac membranes evidenced, by the thiobarbituric acid (TBA) test, a virtually instantaneous peroxidative response with a maximal linear rate of 5.8 nmol malondialdehyde (MDA)-equivalents/mEquivalents lipid ester reacted/min. Yet when the lipids purified from these same membranes and reconstituted into liposomes were peroxidized under identical reaction conditions, the TBA test indicated that a pronounced (∼20-min) lag period preceded a maximal peroxidation rate of only 2.1 nmol MDA-equivalents/ mEquivalents lipid ester reacted/min. After 120 min of peroxidation, the cardiac membranes yielded some 300 nmol TBA-reactive MDA-equivalents/mEquivalent ester, whereas the isolated membrane lipids evidenced ∼40% less TBA-reactivity. To verify that these quantitative and kinetic differences in membrane (phospho)-lipid peroxidation occurred with removal of the lipids from their membrane milieu, the MDA produced during both cardiac membrane peroxidation and the peroxidation of the lipids derived therefrom was isolated as its free anion by ion-pair high-pressure liquid chromatography. As quantified spectrophotometrically, true MDA production during myocardial membrane peroxidation was identical in kinetics and in amount to the production of TBA-reactive substance from the peroxidized isolated membrane lipids. These results demonstrate that significant non-MDA. TBA-reactive species are generated during the peroxidation of cardiac membranes, especially before the maximal rates of bona fide MDA production. As a direct consequence, artifactual levels and kinetics of membrane lipid peroxidation do result.

Malondialdehyde excretion by subjects consuming cod liver oil vs a concentrate of n-3 fatty acids.

Abstract: Urinary malondialdehyde (MDA), an indicator of lipid peroxidation in the diat and in the tissues, was determined in human adults consuming a supplement of n-3 fatty acids derived from a pharmaceutical grade of cod liver oil (CLO) without added antioxidants vs a concentrate of n-3 acids containing dodecyl gallate and vitamin E. MDA excretion increased immediately in the subjects consuming CLO but remained unchanged in those ingesting the concentrate for 50 days. The increase in the subjects taking CLO was attributable to MDA in the oil. The results indicate that consuming unstabilized fish oils as a source of n-3 fatty acids may entail exposure to potentially toxic products of lipid peroxidation.

Absorption and transport of deuterium-substituted 2R,4′R,8′R-α-tocopherol in human lipoproteins

Abstract: Oral administration of a single dose of tri- or hexadeuterium substituted 2R,4′R,8′R-α-tocopheryl acetate (d3- or d6-α-T-Ac) to humans was used to follow the absorption and transport of vitamin E in plasma lipoproteins. Three hr after oral administration of d3-α-T-Ac (15 mg) to 2 subjects, plasma levels of d3-α-T were detectable; these increased up to 10 hr, reached a plateau at 24 hr, then decreased. Following administration of d6-α-T-Ac (15–16 mg) to 2 subjects, the percentage of deuterated tocopherol relative to the total tocopherol in chylomicrons increased more rapidly than the corresponding percentage in whole plasma. Chylomicrons and plasma lipoproteins were isolated from 2 additional subjects following administration of d3-α-T-Ac (140 or 60 mg). The percentage of deuterated tocopherol relative to the total tocopherol increased most rapidly in chylomicrons, then in very low density lipoproteins (VLDL), followed by essentially identical increases in low and high density lipoproteins (LDL and HDL, respectively) and lastly, in the red blood cells. This pattern of appearance of deuterated tocopherol is consistent with the concept that newly absorbed vitamin E is secreted by the intestine into chylomicrons; subsequently, chylomicron remnants are taken up by the liver from which the vitamin E is secreted in VLDL. The metabolism of VLDL in the circulation results in the simultaneous delivery of vitamin E into LDL and HDL.

Fenton reactions in lipid phases.

Abstract: Metal catalysis of membrane lipid oxidation has been thought to occur only at cell surfaces. However, conflicting observations of the pro-oxidant activity of ferric (Fe3+) vs ferrous (Fe2+) forms of various chelates have raised questions regarding this dogma. This paper suggests that the solubilities of iron complexes in lipid phases and the corresponding abilities to initiate lipid oxidation there, either directly or via Fenton-like production of reactive hydroxyl radicals, are critical determinants of initial catalytic effectiveness.

Location of methyl branchings in fatty acids: Fatty acids in uropygial secretion of shanghai duck by GC‐MS of 4,4‐dimethyloxazoline derivatives

Abstract: 2-Substituted 4,4-dimethyloxazolines (DMOX) have been found to be a useful alternative to the commonly used methyl esters for the localization of unsaturated bonds and other substituents in the fatty chain by mass spectrometry. The powerful directed fragmentation coupled with good gas chromatographic ability enables the structure elucidation of modified fatty acids in complex mixtures. Continuing our previous study, 76 out of a total of 86 fatty acids obtained from the preen gland wax of Shanghai duck now have been identified by gas chromatography-mass spectrometry (GC-MS) of their oxazoline derivatives. The identification was based on the interpretation of the mass spectra and comparison with the spectra and equivalent chain lengths (ECL) of the corresponding methyl esters. Main components of this lipid mixture are straight chain fatty acids (8.22%), and 2-, 4- or 6-monomethyl branched acids (53.69%), amounting to 61.91% of the total acid fraction. In addition, a large number of dimethyl-substituted fatty acids (31.4%) also have been found. Typical mass spectra, which are easily recognizable and highly specific for fatty acids substituted at various positions, are presented and classified according to the structural feature of the chain.

Docosahexaenoic acid and other dietary polyunsaturated fatty acids suppress leukotriene synthesis by mouse peritoneal macrophages.

Abstract: The efficacy of individual ω-t-3 polyunsaturated fatty acids (PUFA) in altering eicosanoid synthesis in peritoneal macrophages was studied by feeding mice for 10 days a diet containing 2 wt% fat, which included 0.5 wt% ethyl esters of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or linolenic acid (LNA). Upon stimulation with calcium ionophore A23187, macrophages from these animals produced significantly lower amounts of leukotriene C4, leukotriene B4 and 12-hydroxyeicosatetraenoic acid, prostaglandin E2 and 6-keto prostaglandin F1α compared with those obtained from animals on the diets containing olive oil or safflower oil. The decrease in leukotriene synthesis was similar in the animals fed DHA, EPA or LNA diets. This depression of eicosanoids by DHA and EPA was associated with decreased levels of arachidonic acid (AA); however, LA that altered eicosanoids did not have the same effect on AA levels.

Analysis of free malondialdehyde in photoirradiated corn oil and beef fat via a pyrazole derivative

Abstract: Malondialdehyde (MA) formed in linolenic acid, linoleic acid, corn oil and beef fat upon photoirradiation was determined by gas chromatography (GC). The MA produced was reacted with methylhydrazine to give 1-methyl-pyrazole and was subsequently analyzed on a GC equipped with a nitrogen-phosphorus specific detector and a fused silica capillary column. MA values determined by this method correspond to free or unbound MA levels. Linolenic and linoleic acids produced 867 μg MA/g and 106 μg MA/g, respectively. Oleic and stearic acids did not produce detectable levels of MA upon photoirradiation. Amounts of MA produced after eight hour irradiations of corn oil and beef fat were 56.24 μg/g and 25.01 μg/g, respectively. Some photoreaction products in irradiated corn oil also were identified as methylhydrazine derivatives.

Formation of red pigment by a two-step 2-thiobarbituric acid reaction of alka-2,4-dienals. Potential products of lipid oxidation

Abstract: Reaction of 2,4-hexadienal, 2,4-nonadienal and 2,4-decadienal with 2-thiobarbituric acid (TBA) in aqueous acetic acid produced a 532-nm absorbing red pigment. While the 1∶1 reaction of the aldehyde and TBA produced little pigment, reaction of the aldehyde with an excess amount of TBA produced significant amounts. Instant heating of the reaction mixture did not produce the pigment. However, initial reaction at 5°C and subsequent heating to 100°C produced the pigment efficiently (two-step reaction). Pigment formation required water and dissolved oxygen. The yield of the pigment from the alka-2,4-dienals was 1/10–1/20 of that from malonaldehyde. In the first step of the reaction at 5°C, the 1∶1 adducts of the aldehydes at the5-position of TBA and several other uniden-tified adducts were formed. In the second step, these adducts were converted at 100°C, in the presence of water and oxygen, into the red pigment. The structure of the red pigment from 2,4-hexadienal was elucidated to be the 1∶2 adduct of malonaldehyde and TBA. 2-Hexenal andt-butylhydroperoxide showed marked synergistic effects on the pigment formation from the alka-2,4-dienals. Red pigment formation due to the alka-2,4-dienals may be enhanced by the presence of other aldehydes and hydro-peroxides.

Long-chain alkanediols: biological markers for cyanobacterial contributions to sediments.

Abstract: One significant family of sedimentary lipids of widespread occurrence are series of C28–C32 alkanediols and hydroxyketones. The recognition of the same series of alkanediols as major lipid components of a field population of the cyanobacteriumAphanizomenon flos-aquae leads us to propose that these lipids are markers for cyanobacterial inputs to sediments. The frequency of occurrence of the alkanediols in sedimentary environments supports the recent finding that cyanobacteria are major contributors to the aquatic biomass.

Biopsy method for human adipose with vitamin E and lipid measurements

Abstract: An adaptation of the needle biopsy procedure of Beynen and Katan for human adipose tissue, which yields 2–10 mg adipose samples, is described and evaluated. Micromethods are presented for the analysis of α-tocopherol, cholesterol and fatty acids in each adipose specimen. The needle biopsy procedure, which uses a Vacutainer to create suction, is compared with a punch biopsy method. The needle biopsy is rapid (6 samples/hr), simple and unobjectionable to the subjects, and provides samples with reproducible ratios of cholesterol and α-tocopherol. Unlike the punch biopsy, the needle biopsy reliably obtains specimens with a lipid composition typical of adipocytes. The needle biopsy method is adaptable to nutritional studies of tocopherol and fatty acid metabolism in adipose, and to studies of hazardous compounds stored in adipose. The linoleic acid content of adipose from residents of the West Coast was found to be considerably higher than values reported earlier. The adipose fatty acid data indicate an increase in human adipose linoleate when compared with earlier reports and suggest a trend toward increasing linoleic acid in the American diet.

Separation of neutral lipid free fatty acid and phospholipid classes by normal phase hplc

Abstract: Normal phase high performance liquid chromatography methods are described for the separation of neutral lipid, fatty acid and five phospholipid classes using spectrophotometric detection at 206 nm. Separations were accomplished in less than 10 min for each lipid class. A mobile phase consisting of hexane/methyltertiarybutylether/acetic acid (100∶5∶0.02) proved effective in separating cholesteryl ester and triglyceride with recoveries of 100% for radiolabeled cholesteryl oleate and 98% for radiolabeled triolein. Free fatty acid and cholesterol were separated by two different mobile phases. The first, hexane/methyltertiarybutylether/acetic acid (70∶30∶0.02) effectively separated free fatty acids and cholesterol, but did not separate cholesterol from 1,2-diglyceride. A mobile phase consisting of hexane/isopropanol/acetic acid (100∶2∶0.02) effectively separated free fatty acid, cholesterol, 1,2-diglyceride and 1,3-diglyceride. Recoveries of oleic acid and cholesterol were 100% and 97%, respectively. Five phospholipid classes were separated using methylteriarybutylether/methanol/aqueous ammonium acetate (pH 8.6) (5∶8∶2) as the mobile phase. The recoveries of phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were each greater than 96%.

Membrane lipid alteration: Effect on cellular uptake of mitoxantrone

Abstract: We have studied the effect of membrane structural alteration on the cellular association of the anticancer drug mitoxantrone whose uptake is not carrier-mediated. Membrane fatty acids of L1210 cells were modified by incubating the cells with the highly unsaturated docosahexaenoic acid (22:6), which results in isolated plasma membranes with 37% of the fatty acids as 22:6, or with the monounsaturated oleic acid (18:1), which results in 58% of the fatty acids as 18:1. The rate of uptake by 22:6-enriched cells during the first min was 62% greater than by those enriched with 18:1. The higher rate was recorded at 0.5-16 microM, pH 6.6-7.6 and temperatures 10-40 C. The difference in cell-associated drug apparently was not due simply to a change in mitoxantrone solubility as measured by partitioning of the drug in lipophilic-hydrophilic systems containing lipids from the fatty-acid altered cells. We conclude that the type of fatty acids contained in L1210 cell membranes can affect the cell association of mitoxantrone. This effect could be on transmembrane flux or be due to differences in binding of the drug to intracellular structures.

Effect of dietary vitamin E and selenium on susceptibility of brain regions to lipid peroxidation

Abstract: The effect of dietary vitamin E and/or selenium (Se) supplementation (200 IU and/or 0.2 ppm, respectively) or deficiency for two months on lipid peroxidation in cerebrum, cerebellum, mid-brain, and brain stem of one-month-old male F344 rats was investigated. Dietary treatment had a minimal effect on weight gain of rats for the period tested. Plasma α-tocopherol (α-T) concentration and glutathione peroxidase (GSH-Px) activity were reflective of dietary treatments. Supplementation of diets with vitamin E and/or Se increased plasma α-T and/or GSH-Px activity, while diets devoid of these nutrients reduced them significantly. Increased GSH-Px activity in Sesupplemented rats was further enhanced by vitamin E supplementation. Differential concentrations of α-T among brain regions were affected by dietary vitamin E but not by Se. In vitro lipid peroxidation of brain homogenates was inhibited by dietary vitamin E supplementation and increased by deficiency. Addition of 0.25 mM ascorbic acid or 0.1 mM of Fe2+ to brain homogenates markedly increased in vitro lipid peroxidation. Ascorbic acid-induced lipid peroxidation was inversely correlated with dietary vitamin E and Se in cerebrum. In vitro Fe2+-addition induced the greatest stimulation of lipid peroxidation, with cerebellum and brain stem of vitamin E-deficient rats showing the highest response to Fe2+ challenge. These findings indicate that concentrations of α-T among the brain regions are different and can be altered by dietary vitamin E treatments, cerebellum and brain stem are more susceptible to in vitro challenge by peroxidative agents than other regions, and the degree of lipid peroxidation of brain regions is partially affected by dietary vitamin E but not by Se in the levels tested.

Characterization of HETEs and related conjugated dienes by UV spectroscopy.

Abstract: Three distinct pairs of HETEs can be distinguished on the basis of their UV spectra. We used hydroxy-linoleates (hydroxy-octadeca-cis-trans-dienoates) as a base for comparisons; both the 9- and 13-hydroxy isomers have identical chromophores with λmax near 234 nm. The presence of a double bond three carbons removed from the conjugated diene (the chromophore of 9- and 11-HETE) causes a shift in the observed λmax to near 235 nm. A double bond β to the chromophore (5- and 15-HETE) gives a further shift of 1.5 nm, giving a λmax between 236–236.5 nm. With double bonds in both these positions (8- and 12-HETE), the λmax is observed near 237 nm. It is apparent that the exact λmax of thecis-trans diene chromophore is influenced in a consistent way by the adjacent methylene interruptedcis double bonds.