bluuebunny/crossref_metadata_2025 huggingface dataset:
Isomerization of the double bonds of a conjugated fatty acid during β‐oxidation
Authors: Du Plessis L. M. , Grobbelaar N.
Published: November 2006

The β‐oxidation of an unsaturated fatty acid containing conjugated double bonds at odd‐numbered carbon atoms has not previously been studied. It is, therefore, not clear whether, during the β‐oxidation of such an acid, the double bonds will be isomerized by enoyl‐CoA isomerase (Δ3‐Δ2‐enoyl‐CoA isomerase) with the loss or retention of its conjugated nature. To investigate the problem, (E,E)‐3,5‐octadienoyl‐CoA was synthesized for use as a model substrate, and enoyl‐CoA isomerase was partially purified from bovine liver. The isomerization was followed by spectrophotometric and gas liquid chromatographic methods, and the results suggested that the isomerization of the model substrate proceeded with retention of a conjugated double bond system. It is, therefore, proposed that the β‐oxidation intermediate of α‐eleostearic acid (Δ9,11,13 fatty acid) will also isomerize with retention of the conjugated double bond system.
Extraction and analysis of lipids from immature soybeans
Authors: Phillips F. C. , Privett O. S.
Published: November 2006

A procedure is described for the extraction of lipids from immature soybeans that eliminates artifact formation and provides complete recovery of the lipid, including highly polar glycolipids free of nonlipid substances. The method involves pretreatment and extraction of the beans with hot dilute (0.25%) acetic acid, followed by chloroform‐methanol extraction. Pretreatment and extraction of the tissue with hot dilute acetic acid destroys hydrolytic enzymes and removes organic‐soluble, nonlipid substances that contaminate extracts obtained by chloroform‐methanol extraction. Application of the method to immature soybeans confirmed that phosphatidic acid was largely an artifact of freezing and thawing of the beans, and phosphatidylmethanol was produced via transphosphatidylation of phosphatidylcholine and phosphatidylethanolamine upon extraction with chloroform‐methanol.
Fatty alcohols in capelin, herring and mackerel oils and muscle lipids: II. A comparison of fatty acids from wax esters with those of triglycerides
Authors: Ratnayake W. N. , Ackman R. G.
Published: November 2006

The fatty acids recovered from the triglycerides and wax esters of common northwest Atlantic copepods are compared with the fatty acids of wax esters recovered intact from certain fish skin and body lipid, and from commercial fish oils. The fish species, herring, capelin and mackerel, all feed on copepods, and many resemblances of the copepod lipid fatty acids to those of a previous analysis of similar copepods suggest that the basic dietary fat input for these fish may be quite constant. The two copepod fatty acid analyses differed quantitatively in triglyceride 20∶1 and 22∶1 and also in 20∶5ω3 and 22∶6ω3, confirming the primary role of the wax esters in copepods. Selectivity factors are discussed in comparing the copepod wax ester fatty acids with the fatty acids of the wax esters recovered intact from the fish lipids and oils. The basic role of copepods in supplying all types of fatty acids to fish depot fats is considered to be strongly supported by these findings.
Effects of an essential fatty acid deficiency on serum lipoproteins in the rat
Authors: Sano M. , Privett O. S.
Published: November 2006

Studies are reported on the effect of an essential fatty acid (EFA) deficiency in male Sprague‐Dawley rats and its exacerbation by inclusion oftrans fatty acids in the diet on the level and composition of serum lipoproteins. Weanling male Sprague‐Dawley rats were fed diets containing all essential nutritients and a 5% fat supplement of safflower oil (SAFF) or hydrogenated coconut oil (HCO) in 2 experiments, one for 31 wk and the other for 17 wk. For the final 3 wk of each experiment, animals were switched from each group to a 5% supplement of a concentrate of ethyl linolelaidate (TRANS). In addition, a group of animals fed the HCO diet in the first experiment were also switched to the SAFF Diet. With the development of an EFA deficiency in the HCO group, there was a decrease in the high density lipoprotein (HDL) and an increase in the very low density plus the low density (VL‐LDL) lipoprotein fractions separated by heparin‐manganese precipitation. Switching animals of the HCO group to the TRANS supplement exaggerated this effect and produced a very low ratio of HDL‐to‐VL‐LDL. Analysis of the serum lipoproteins by polyacrylamide disc gel electrophoresis showed that an EFA deficiency produced a marked alternation of the HDL fraction. Changes also appeared to be produced in the VL‐LDL fraction by an EFA deficiency and particularly upon switching EFA‐deficient animals to the TRANS supplemented diet. Switching animals of the SAFF group to the TRANS supplement brough about an immediate reduction in HDL with a corresponding decrease in serum arachidonic acid. The data suggested a general relationship between arachidonic acid and the level and composition of HDL on the one hand, and 18∶1 and VL‐LDL on the other. Accordingly, the ratio of HDL‐to‐VL‐LDL appears to provide a sensitive biochemical index of the EFA status of the rat.
Analysis of oleate, linoleate and linolenate hydroperoxides in oxidized ester mixtures
Authors: Fatemi Seyed H. , Hammond Earl G.
Published: November 2006

The hydroperoxides in oxidized mixtures of methyl oleate, linoleate and linolenate were analyzed by reducing the hydroperoxides to the corresponding hydroxyesters and separating the hydroxyesters from the unoxidized esters by thin layer chromatography (TLC). The hydroxyesters from linolenate were separated from the other hydroxyesters by TLC on silver ion plates. The hydroxyesters were converted to TMS‐hydroxy derivatives. The TMS‐hydroxyoleate and TMS‐hydroxylinoleate were separated by gas chromatography (GC), and all the TMS‐derivatives were quantified by GC. The relative rates of oxidation of methyl oleate, linoleate and linolenate in mixtures were ca. 1∶10.3∶21.6. The hydroperoxides formed in the oxidation of soybean and olive oils were similar before and after randomization and similar to corresponding methyl ester mixtures.
A structural model for the cholesterol‐phosphatidylcholine complexes in bilayer membranes
Authors: Huang Ching‐Hsien
Published: November 2006

Based on the structural properties of phospholipid and cholesterol molecules, and making use of the known structural and motional effects of cholesterol and its analogs on phospholipid bilayers, a model for the cholesterol‐phosphatidylcholine complex is proposed. In this model, the 3β‐hydroxyl group of cholesterol is assumed to engage in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids. Some specific configurations of the saturated and unsaturated fatty acyl chains of the phospholipid are suggested to participate in van der Waals attractive interactions with the α and β surface of the steroid nucleus.
Alkyl‐and alkenylresorcinols inRapanea laetevirens seed lipids
Authors: Madrigal R. V. , Spencer G. F. , Plattner R. D. , Smith C. R.
Published: November 2006

The seed lipids ofRapanea laetevirens (Myrsinacea) were found to contain a series of 5‐alkylresorcinols. Some of these alkylresorcinols have been reported previously in other plant families, but never before in the Myrsinaceae. The various homologs were shown by mass spectrometry to have alkyl side chains that included C11 and C13 saturated as well as C11, C13, and C15 monoenoic substituents. This is the first report of the natural occurrence of tridecenylresorcinol, the homolog with the C13 monoenoic side chain. The positions of the double bonds in the side chains were determined by mass spectrometry of their methoxy trimethylsilyloxy derivatives. Also found were embelin and rapanone, benzoquinone pigments which occur commonly in the Myrsinaceae. The fatty acid composition ofRapanea seed triglycerides was not unusual, consisting mainly of 16∶0 (27%), 18∶1 (22%), and 18∶2 (44%).
The effect of protein deficiency on some rat liver lipid metabolic enzymes and CoA
Authors: Gerson T. , Wong M. N.
Published: November 2006

Two groups of male Wistar rats were fed normal (i.e., 18%) and protein‐free diets, respectively, for 7 weeks. In vivo incorporation of [1‐14C] acetate into palmitic, stearic, oleic, and arachidonic acids by the liver was reduced in the protein‐deficient rats. In vitro incubation of liver microsomes with labeled palmitate or linoleate revealed no change in the specific activities of chain elongating or desaturating enzymes. Protein deficiency resulted in a decrease in specific activity of short chain acyl‐CoA synthetase and in total CoA, accompanied by the virtual disappearance of acyl‐CoA and an increase in free CoA. Furthermore, there was less microsomal fatty acid synthetase and mitochondrial β‐hydroxybutyrate dehydrogenase activity. These results are discussed in relation to fatty acid synthesis and the changes in liver fatty acid composition.
Characterization of a prostaglandin‐like metabolite of linolenic acid produced by a flaxseed extract
Authors: Zimmerman D. C. , Feng Paul
Published: November 2006

One of the products formed upon incubation of linolenic acid (cis9,12,15‐octadecatrienoic acid) with an extract of flaxseed acetone powder has been characterized as 8‐[2‐(cis‐pent‐2′‐enyl)‐3‐oxo‐cis‐cyclopent‐4‐enyl]octanoic acid. The cyclopentenone ring structure of this acid is analogous to that of the A‐type prostaglandins produced in mammalian systems.
Biosynthesis of hydrocarbons in insects: Decarboxylation of long chain acids ton‐alkanes inPeriplaneta
Authors: Major Michael A. , Blomquist Gary J.
Published: November 2006

The biosynthetic pathway ofn‐alkanes was investigated in the cockroachesPeriplaneta americana andPeriplaneta fuliginosa. Both sodium [1‐14C] acetate and randomly tritiated long chain fatty acids were incorporated into the cuticular hydrocarbons of both species. The relative incorporation of acetate into each component of the hydrocarbon fraction was about the same as the relative amount of each component in the fraction. In contrast, [R‐3H] hexacosanoic acid was preferentially incorporated inton‐pentacosane inP. americana and [R‐3H] tetracosanoic acid inton‐tricosane inP. fuliginosa. Long chain ketones and secondary alcohols, likely intermediates in the proposed condensation‐reduction pathway forn‐alkane biosynthesis, were not incorporated into hydrocarbon. Results from experiments with dual labeled lauric aicd were also not consistent with the condensation‐reduction pathway. The demonstration of the direct decarboxylation of long chain fatty acids ton‐alkanes one carbon unit shorter and the lack of incorporation of proposed intermediates of a condensation‐reduction pathway constitute the strongest evidence to date that insects utilize an elongation‐decarboxylation pathway forn‐alkane biosynthesis.
Sterol‐polyene antibiotic complexation: Probe of membrane structure
Authors: Bittman Robert
Published: November 2006

Polyene antibiotics are useful tools for studying the role of sterols in biological membranes. The interaction of polyene antibiotics with membrane‐bound sterols in artificial membrane systems, prokaryotic and eukaryotic cells, and lipid‐containing viruses is reviewed. The pentaene macrolide, filipin, is shown to serve as a probe of phosphatidylcholine‐sterol interaction and of the localization of cholesterol in the membrane of mycoplasmas.
Sex hormones of the aquatic fungusAchlya
Authors: McMorris Trevor C.
Published: November 2006

Fungi in the order Saprolegniales are known to contain varying proportions of sterols, such as cholesterol and fucosterol. In the caseAchyla, it has been found that fucosterol, the major sterol component, serves as the biosynthetic precursor of the hormones, antheriodiol and the oogoniols. Antheridiol is secreted by female strains ofAchlya and induces the formation of antheridial hyphae in male strains. It also causes the male to secrete the oogoniols which induce the formation of oogonial initials in female strains. Antheriodiol is responsible for the chemotropic growth of the antheridial hyphae to a developing oogonium which results in sexual conjugation. The structures, biosynthesis, and functions of these hormones are discussed in this paper.
Sterols in yeast subcellular fractions
Authors: Parks L. W. , McLean‐Bowen C. , Taylor F. R. , Hough S.
Published: November 2006

Yeast is the most primitive organism synthesizing substantial amounts of sterols. Because of this eucaryotic organism's versatility in growth conditions, ease of culture, well‐defined genetic mechanism, and characteristic subcellar architecture, it is readily applied to studies of the role of sterols in the general economy of the cell. Sterols exist in two major form, as the free sterol, or esterified with long chain fatty acids. The importance of sterols for this organism can be demonstrated using a naturally occurring antimycotic azasterol. This agent inhibits yeast growth. Three effects are seen on sterol synthesis: inhibition of the enzymes Δ14‐reductase, sterol methyltransferase, and methylene reductase. Cells cultured on respiratory substrates are more sensitive to inhibition than are cells growing on glucose. We have demonstrated a relationship between respiratory competency and sterol biosynthesis in this organism. Many mutants altered in sterol synthesis are respirationally defective and must growth fermentatively. One clone has temperature conditional respiration. Experiments with purified mitochondria, perpared from this mutant and its isogenic wildtype, show that the mutant organism is able to respire at the higher temperature but lacks the ability to couple respiration to phosphorylation. No similar loss is seen in the wild‐type clones. Data are given which support the proposal that, for inclusion in mitochondrial structures, yeast cells may discriminate among sterols available from the total sterol pool in favor of ergosterol.
Insect juvenile hormones and pheromones of isopentenoid biogenesis
Authors: Bowers W. S.
Published: November 2006

In their diversity, speciation, and sheer numerical superiority, few should question that insects are the dominant life‐form on earth. Their utilization of the multifunctional isopentenoids to regulate their life processes is equally diverse. To catalog or even summarize the contribution of isopentenoids in the regulatory chemistry of insect feeding, development, reproduction, diaproduction, diapause, and behavior is beyond the scope of this review. However, a topical treatment of the chemistry of insect juvenile hormones and pheromones provides an insight into the dependence of insects upon isopentenoids.
Insect steroid metabolism
Authors: Svoboda J. A. , Thompson M. J. , Robbins W. E. , Kaplanis J. N.
Published: November 2006

Insects are unable to biosynthesize the steroid nucleus and generally require an exogenous source of sterols. Two salient areas of insect steroid metabolism are the dealkylation and conversion of dietary C28 and C29 plant sterols to cholesterol and other C27 sterols, and the biosynthesis and metabolism of the steroidal insect molting hormones. Certain azasteroids and nonsteroidal amines block this conversion of 24‐alkyl sterols to cholesterol and/or disrupt molting and development in insects. These inhibitors have served in charting metabolic pathways for steroids in insects and are serving as models in developing selective pesticidal chemicals and chemotherapeutic agents for use against insects and other invertebrate pests and parasites. The mode of action of some of these inhibitors on molting and development has been investigated in vivo and in vitro. Certain of these inhibitors represent a new class of insect hormonal compounds with a novel mode of action—the disruption of molting hormone metabolism. Research on sterol metabolism in insects provides important information on the comparative biochemistry and physiological functions of steroids in living systems.
The effect of elaidic acid incorporation upon the lipid composition of ehrlich ascites tumor cells and of the host's liver
Authors: Awad Atif B.
Published: November 2006

The incorporation of elaidic acid into Ehrlich ascites tumor cells (EATC) upon feeding the host an elaidic acid‐rich diet has been investigated in the present study. The EATC lipids contained only one‐half the concentration of elaidic acid found in the lipids of either the host livers or of livers from normal mice. On the other hand, elaidic acid incorporation into tumor cells was close to that of ascites fluid. This incorporation was mainly into phospholipids; the highest into choline phospholipids and ethanolamine phospholipids. Some changes in the EATC fatty acid composition were noted due to this incorporation. EATC phospholipids had reduced polyunsaturated fatty acids as compared with oleic acid‐grown cells. The same was true with respect to ascites fluid phospholipids, but neutral lipids were not altered. Tumor development was accompanied by an increase in elaidic acid of the host's liver. Elaidic acid incorporation into tumor cells resulted in a reduction in the amount of all major lipids in the tumor. In contrast, elaidic acid had no effect on lipid composition of livers from normal mice and‐tumor bearing mice, and also had no effect upon the lipids of the ascites fluid that bathes the tumor cells. The incorporation of elaidic acid into the lipids of EATC, normal liver and host liver did not affect the relative composition of phospholipids in these tissues. The development of the tumor did result in decreases in triacylglycerols and esterified cholesterol, and increases in phospholipids and free cholesterol in the livers of host animals.
Esterification of palmitic acid in swine aortic homogenates
Authors: Huang William Y. , Kumerow Fred A.
Published: November 2006

The incorporation of [1‐14C] palmitic acid into tissue lipids of the medial and intimal layers of swine aortic homogenates was investigated. The homogenates obtained were metabolically active as indicated by their ready incorporation of labeled palmitic acid into phospholipids, diglycerides and triglycerides in the presence of α‐glycerophosphate in the incubation medium. Predominantly, labeling of phospholipids and especially of phosphatidylcholine was found when α‐glycerophosphate or lysolecithin served as the fatty acid acceptor. Glycerol and monoolein did not serve as fatty acid acceptors. More than 98% of the radioactivity was recovered as the phosphatidylcholine fraction at the level of 0.64 μmoles/ml of lysolecithin in the incubation medium.
Effects of essential fatty acid deficiency on prostaglandin synthesis and fatty acid composition in rat renal medulla
Authors: Dunham E. W. , Balasingam M. , Privett O. S. , Nickell E. C.
Published: November 2006

Studies are reported on the capacity of isolated rat renal papilla (inner medulla) to synthesize and release prostaglandin (PG) E from endogenous and exogenous precursor(s) during development of an essential fatty acid (EFA) deficiency in the rat. Weanling (21‐day‐old) male Sprague‐Dawley rats were fed a fat‐free diet supplemented with either 5% hydrogenated coconut oil (HCO) or 5% safflower oil (SO). At approximately 3, 6 and 7 weeks (6, 9 and 10 weeks of age), groups of animals fed each diet were killed for studies of PGE synthesis in the renal papillae. Differences in the fatty acid composition of the papillae lipids of the animals of each group were also determined. The in vitro production of PGE from endogenous precursor(s) was significantly reduced in the papillae from the 6‐week‐old rats fed the HCO diet compared to the control (SO) rats, and appeared to be near maximally depressed in the 10‐week‐old animals compared to that of animals fed an EFA deficient diet for over a year in an accessory experiment. Analyses of the fatty acids of the papillae lipids of the HCO groups showed that the levels of 18∶2 and 20∶4 were markedly reduced, and those of 16∶1, 18∶1 and 20∶3 were elevated compared to the controls even in the 6‐week‐old animals, typical of an EFA deficiency. The papillae lipids of the animals fed the HCO diet were also depleted of their stores of 22∶4ω6. A fatty acid believed to be derived by chain elongation of 20∶3ω9, 22∶3, was found in large concentrations in the papillae triglycerides of the EFA deficient rats. Incubations of exogenous arachidonic acid (20∶4) in homogenates and tissue slices of the papillae of the HCO dietary groups showed that the PG synthetase was not impaired by an EFA deficiency. The rate of PGE synthesis in the papillae of the EFA deficient animals was generally enhanced when exogenous 20∶4 was added, indicating that the concentration of available precursor(s) is a primary factor in the control of PGE synthesis in the papilla of the rat.
Availability of lysophosphatidylcholine in single bilayer vesicles for hydrolysis by lysophospholipase
Authors: de Oliveira Filgueiras O. M. , van den Besselaar A. M. H. P. , van den Bosch H.
Published: November 2006

Single bilayer vesicles were prepared from total rat liver microsomal lipids to which 5 mol% lysophosphatidylcholine had been added. The availability of lysophosphatidylcholine for enzymatic hydrolysis by lysophospholipase (EC 3.1.1.5) was found to be higher in vesicles prepared by the cholate dispersion technique when compared with sonicated vesicles. Sepharose 4 B chromatography showed that the vesicles prepared by the cholate technique were smaller than those prepared by sonication. This is in contrast to previous observations for egg phosphatidylcholine vesicles. Total rat liver microsomal extracts were found to contain proteolipid, which could be removed by ether precipitation. Cholate vesicles prepared from proteolipid‐free extracts were still smaller than sonicated vesicles from this extract. Experiments with [14C] dextran entrapped in the vesicles indicate that there is no loss of the permeability barrier of the vesicles for high molecular weight solutes during vesicle treatment with lysophospholipase. The high availability of lysophosphatidylcholine in cholate vesicles of total rat liver microsomal lipids is discussed in terms of a highly asymmetric distribution of lysophosphatidylcholine over the inner and outer monolayer of the bilayer.
Study of the two pathways for arachidonate oxygenation in blood platelets
Authors: Dutilh C. E. , Haddeman E. , Jouvenaz G. H. , Ten Hoor F. , Nugteren D. H.
Published: November 2006

During collagen‐induced blood platelet aggregation, arachidonic acid is set free from membrane phospholipids and subsequently converted into 12‐hydroxyeicosatetraenoic acid by arachidonate lipoxygenase and into thromboxane A2, 12‐hydroxyheptadecatrienoic acid (HETE) and malondialdehyde by cyclooxygenase and thromboxane synthase. Lipoxygenase and cyclooxygenase have optimal activity at neutral to basic pH, while the thromboxane synthase is pH‐independent between 5 and 9. These enzymes are membrane‐bound. The cyclooxygenase is rapidly inactivated upon membrane disruption by nonionic detergents or phospholipid degradation with phospholipase A2. It was found that platelet phospholipase A2 preferentially splits off fatty acid with four double bonds. Eicosatetraynoic acid was used to investigate the physiological function of the arachidonate lipoxygenase during collagen‐induced aggregation of rat blood platelets. This fatty acid is a more efficient inhibitor of lipoxygenase than of cyclooxygenase. At an inhibitor concentration of 0.6 μg/ml, platelet aggreation, 12‐hydroxyeicosatetraenoic acid production as well as 15‐hydroxytryptamine release are completely inhibited, while there is an apparent stimulation of the cyclooxygenase. These results indicate that arachidonate lipoxygenase is essential for irreversible blood platelet aggregation.
Different metabolism of saturated and unsaturated long chain plasma free fatty acids by intestinal mucosa of rats
Authors: Gangl A. , Kornauth W. , Mlczoch J. , Sulm O. , Klose B.
Published: November 2006

During fat absorption, unsaturated long chain fatty acids are esterified at a higher rate than saturated fatty acids of similar chain length. This phenomenon has been attributed to differences in the binding affinity of fatty acids to a cytosolic fatty acid‐binding protein. As intestinal mucosa utilizes plasma free fatty acids as well, we investigated whether long chainplasma free fatty acids of different degree of saturation are metabolized also at different rates.3H‐Palmitic and14C‐linoleic acid complexed to rat serum were injected rapidly into a tail vein of fasting rats. One, 2 and 4 min later there was no difference between3H and14C‐radioactivity in intestinal mucosa, suggesting equal initial uptake of the two labeled fatty acids from plasma. Despite their equal uptake, the incorporation of the isotopes into ester lipids was significantly different, however: at 2 min, 53.1±3.9% of3H and 73.8±4.6% of14C were recovered in ester lipids. Phospholipids and triglycerides accounted for most of the mucosal3H and14C. At 4 min, a similar distribution of isotopes in intestinal mucosal metabolites was found. These data show that despite equal initial uptake by intestinal mucosa unsaturated long chain fatty acids taken up from plasma are esterified to a higher and oxidized to a lower extent than saturated plasma free fatty acids. Unsaturated plasma free fatty acids, therefore, may provide a more important source of fatty acids for endogenous intestinal lipoprotein lipids than saturated plasma free fatty acids. It is speculated that the fatty acid binding protein might be operative not only in the intracellular transport and metabolism of luminal fatty acids but of plasma free fatty acids as well.
Biosynthesis of cholic acid in rat liver: Formation of cholic acid from 3α, 7α, 12α‐trihydroxy‐ and 3α, 7α, 12α, 24‐tetrahydroxy‐5β‐cholestanoic acids
Authors: Gustafsson Jan
Published: November 2006

Conversion of 3α,7α,12α‐trihydroxy‐5β‐cholestanoic acid into 3α,7α,12α24‐tetrahydroxy‐5β‐cholestanoic and cholic acids was catalyzed either by the mitochondrial fraction fortified with coenzyme A, ATP, MgCl2 and NAD or by the combination of microsomal fraction and 100,000 x g supernatant fluid fortified with coenzyme A, ATP and NAD. 24‐Hydroxylation and formation of cholic acid occurred at similar rates with the 25R‐ and the 25S‐forms of 3α,7α,12α‐trihydroxy‐5β‐cholestanoic acid. The 25R‐ and 25S‐forms of 3α,7α,12α‐trihydroxy‐and 3α,7α,12α,24‐tetrahydroxy‐5β‐cholestanoic acids were administered to bile fistula rats. Labeled cholic acid was isolated from the bile. The initial specific radioactivity of cholic acid was higher and the disappearance of radioactivity more rapid after administration of 3α,7α,12α‐trihydroxy‐5β‐cholestanoic acid than of 3α,7α,12α,24‐tetrahydroxy‐5β‐cholestanoic acid. The findings are discussed in relation to the assumed pathway for side chain cleavage in cholic acid biosynthesis.
Substrate specificity of flax hydroperoxide isomerase
Authors: Feng Paul , Zimmerman Don C.
Published: November 2006

Incubations of the 13‐ and 9‐hydroperoxides of linolenic acid with a flax acetone powder extract containing hydroperoxide isomerase resulted in the formation of 13‐hydroxy‐12‐oxo‐cis‐9,15‐octadecadienoic acid and 9‐hydroxy‐10‐oxo‐cis‐12,15‐octadecadienoic acid, respectively. The rate of formation of product from 13‐hydroperoxy linolenic acid was 36 times that from 9‐hydroperoxy linolenic acid. Analogous results were obtained with the 13‐ and 9‐hydroperoxides of linoleic acid. The results demonstrated the substrate specificity of flax hydroperoxide isomerase.
Antioxidant stoichiometry and the oxidative fate of vitamin E in peroxyl radical scavenging reactions
Authors: Liebler Daniel C. , Burr Jeanne A.
Published: November 2006

Oxidation ofR,R,R‐α‐tocopherol (vitamin E; TH) by peroxyl radicals generated from the azo initiator azobis(2,4‐dimethylvaleronitrile) in acetonitrile, hexane, or in phospholipid liposomes yields 8a‐(alkyldioxy)tocopherone adducts, 8a‐(hydroxy)tocopherone, and their hydrolysis product α‐tocopherolquinone TH oxidation also yields 4a,5‐epoxy‐ and 7,8‐epoxy‐8a‐(hydroperoxy)tocopherones and their respective hydrolysis products 2,3‐epoxy‐α‐tocopherolquinone and 5,6‐epoxy‐α‐tocopherolquinone. Previous work indicates that the distribution of TH oxidation products varies with reaction environment. We investigated the dependence of antioxidant stoichiometry on TH oxidation product distribution for reactions in hexane, acetonitrile, and in phosphatidylcholine liposomes. Yields of 8a‐substituted tocopherones were highest in hexane and lowest in phosphatidylcholine liposomes. In contrast, yields of epoxide products were highest in the liposome system and lowest in hexane. Yields of α‐tocopherolquinone were similar in all three systems. Antioxidant stoichiometry, measured by the inhibited autoxidation method, was approximately 2.0 peroxyl radicals trapped per TH consumed in acetonitrile and in liposomes. In hexane, a slightly larger stoichiometric factor of approximately 2.5 was measured. This may, in part, reflect the generation of more reactive alkoxyl radicals in hexane. The reaction environment thus markedly affects the balance between competing TH oxidation pathways but produces comparatively little effect on antioxidant stoichiometry. These results imply that competing reaction pathways contribute similarly to the antioxidant chemistry of TH.
Monohydroperoxides of linoleic acid in endoplasmic lipids of rats exposed to tetrachloromethane
Authors: Frank Hartmut , Wiegand Manfred , Strecker Manfred , Thiel Dietmar
Published: November 2006

An accurate method for the quantitative determination of hydroperoxy and hydroxy fatty acids in liver microsomes is presented which involves the use of18O‐labeled internal standards. The method is employed for the determination of hydroperoxides in rat liver microsomes after aerobic incubation with Fe2+/ADP and in microsomes from animals exposed to 75 mg tetrachloromethane/kg body weight. The amounts found after artificial microsomal “lipid peroxidation” are almost two orders of magnitude larger than those in microsomes from tetrachloromethaneexposed animals.
The differential effect of polymyxin B1 on guinea pig lung mitochondrial and microsomal glycerophosphate acyltransferase
Authors: Das Salil K. , Haldar Dipak
Published: November 2006

The activities of guinea pig lung mitochondrial and microsomal glycerophosphate acyltransferase differed in sensitivity to polymyxin B1. At an antibiotic concentration of 1 mg/ml, the mitochondrial enzyme activity was stimulated twofold, but the microsomal enzyme activity was completely inhibited. Furthermore, the mitochondrial enzyme activity was stimulated by polymyxin B1 without the addition of exogenous acyl‐CoA. Additional experiments ruled out the possibility of polymyxin B1 acting as a substrate for the mitochondrial acyltransferase. These results suggest either that the polymyxin B1 sensitivity of mitochondrial and microsomal glycerophosphate acyltransferase is different or that their accessibility to substrates is different because the two isoenzymes are located differently in the different phospholipid microenvironment of the membranes.
Effect of feeding protected lipids on fatty acid synthesis in ovine tissues
Authors: Hood R. L. , Cook L. J. , Mills S. C. , Scott T. W.
Published: November 2006

The effects of including protected lipid supplements in the sheep diet have been studied by measuring the incorporation of [1‐14C] acetate into tissue fatty acids in vivo and in vitro. Supplementing the diet with protected lipid significantly (P<0.05) depressed lipogenesis in adipose tissue both in vivo and in vitro. However, when protected lipids of different fatty acid composition were given to lambs, the protected safflower oil supplement containing high levels of linoleic acid was the only treatment to cause a significant (P<0.05) depression in fatty acid synthesis in adipose tissue, the major site of lipogenesis in the sheep. Larger adipose cells in the lipid‐supplemented sheep indicate that these sheep were fatter than those receiving the basal diet. Therefore, supplemented wethers deposited more fat than sheep receiving the basal diet and this fat was derived from the supplement rather than from de novo synthesis.
Effect of different fatty acids on triacylglycerol secretion in isolated rat hepatocytes
Authors: Åkesson B.
Published: November 2006

Lipoprotein triacylglycerol secretion was studied in isolated rat hepatocytes incubated with different albumin‐bound fatty acids and labeled glycerol. The release of labeled triacylglycerol was stimulated more by unsaturated fatty acids than by saturated ones. When lipoprotein secretion was related to cell triacylglycerol synthesis, an effect of unsaturation was no longer observed. Instead the secretion rate, expressed in this manner, increased with increasing fatty acid chain length. For the first time, the secretion of molecular species of triacylglycerol has been studied. The distribution of labeled glycerol among different species was the same in the cells and in the secreted product, indicating that different triacylglycerols were secreted without selectivity. It is concluded that the fatty acid structure influences lipoprotein triacylglycerol secretion and it is emphasized that the effects observed depend on the method of quantitation of the secretion rate.
Horse erythrocyte gangliosides: Preparation of the major hematoside NeuNG1‐Lac‐Cer
Authors: Maget‐Dana R. , Michalski J. C.
Published: November 2006

A simple method for the isolation of hematoside NeuNG1‐Lac‐Cer from horse erythrocytes is described. An aliquot of the crude ganglioside fraction was labeled by tritiated sodium borohydride after mild periodate oxidation. The compounds obtained were used as radioactive tracers in column chromatography. Gangliosides were applied onto a silicic acid column and eluted stepwise by solvents of steadily increasing polarity. The major ganglioside, NeuNG1‐Lac‐Cer, was eluted in a high yield by the solvent mixture chloroform/methanol/water (60∶35∶8, v/v/v).
Regulation of lung surfactant cholesterol metabolism by serum lipoproteins
Authors: Hass Michael A. , Longmore William J.
Published: November 2006

The isolated perfused rat lung was used as an experimental model in the study of the lipoprotein regulation of surfactant cholesterol metabolism. Addition of low density lipoproteins (LDL) to the perfusion medium at a cholesterol concentration of 0.5 mM had no inhibitory effect on [1‐14C]‐acetate incorporation into cholesterol of either the surfactant or residual fractions. Increasing the concentration of cholesterol in the medium to 2.5 mM resulted in significant inhibition of incorporation into cholesterol of both fractions. A similar inhibition resulted when lungs were perfused with 2.5 mM cholesterol in the form of high density lipoproteins (HDL). No inhibition of fatty acid synthesis, measured as incorporation into cholesteryl esters, was observed. The rate of uptake by perfused lung of cholesterol from both high and low density lipoproteins was similar. Competitive binding studies with125I‐labeled lipoproteins indicated the existence of lung receptors for both classes of lipoprotein. The rate of uptake of the apoprotein moiety of low density lipoproteins was significantly greater than that of high density lipoproteins. These data suggest that lung cholesterol metabolism may be subject to regulation by both low and high density serum lipoproteins.
Cyclopropene fatty acids in some Malaysian edible seeds and nuts: I. Durian (Durio zibethinus, Murr.)
Authors: Berry Shiv K.
Published: November 2006

The aril and seeds of the fruit Durian (Durio zibethinus, Murr.) were examined for their protein content and fatty acid composition by gas liquid chromatography (GLC). The values (area percentage) for fatty acids as methyl esters were: aril=14∶0 (0.91%); 16∶0 (34.13%); 16∶1 (7.10%); 18∶0 (1.21%); 18∶1 (42.14%); 18∶2 (7.85%) and 18∶3 plus 20∶0 (5.69%), Seeds=14∶0 (0.12%); 16∶0 (12.20%); 16∶1 (1.15%); 18∶0 (1.42%); 18∶1 (8.42%); 18∶2 (6.50%); dihydrosterculic acid (2.52%); 18∶3 plus 20∶0 (11.30%); malvalic acid (15.72%); sterculic acid (38.53%) and 22∶0 (1.21%). The germ oil contained the highest amount of sterculic acid. The cooking temperatures employed reduced the malvalic and sterculic acid contents in seeds only by ca. 22% and 19%, respectively.
Product specificity of rice germ lipoxygenase
Authors: Yamamoto A. , Fujii Y. , Yasumoto K. , Mitsuda H.
Published: November 2006

Incubation of linoleic acid with partially purified lipoxygenase from rice germ yielded a ratio of 9‐to 13‐hydroperoxides of linoleic acid of 97∶3 as measured by high performance liquid chromatography. Under similar conditions, hematin gave the 9‐ to 13‐hydroperoxides at a ratio of 51∶49, and soybean lipoxygenase‐a at 9∶91. Infrared spectral analysis revealedcis‐trans configuration to predominate in the reaction products with the rice germ enzyme as was with the soybean enzyme.
Interaction of porcine pancreatic colipase with a nonionic detergent, triton X‐100: Spectrophotometric studies
Authors: Canioni Paul , Julien Robert , Rathelot Joëlle , Sarda Louis
Published: November 2006

Strong perturbation of the ultraviolet spectrum of the tyrosines of porcine pancreatic colipase A is observed in the presence of Triton X‐100 at concentration above the critical micellar concentration. Spectrophotometric titration of the phenolic groups of the protein shows that the apparent pKa value for two tyrosines is about 10.3, while the third tyrosine has a higher pKa value above 11.6. This residue is still protonated at pH 13 in the presence of Triton X‐100. All perturbations induced by the nonionic detergent can be interpreted as resulting from interactions between colipase and Triton X‐100 molecules at a hydrophobic site of the protein that includes the tyrosine residues. Results obtained in studies with Triton X‐100 are similar to those already reported by Sari et al. (Eur. J. Biochem. 58∶561 (1975) on the interaction of colipase with taurodeoxycholate. It is likely that the binding of both types of detergent occurs at the same specific site on the protein molecule. Data presented in this communication give further support to the hypothesis that a hydrophobic domain (residues 49–57), including all three tyrosines of the colipase molecule, participate to the well characterized interaction of the lipase cofactor with triglycerides at lipid‐water interfaces.
Occurrence of 24(E)‐ethylidene sterols in two solanaceae seed oils and rice bran oil
Authors: Itoh Toshihiro , Sakurai Suguru , Tamura Toshitake , Matsumoto Taro
Published: November 2006

The occurrence of two 24 (E)‐ethylidene sterols, fucosterol and 28‐isocitrostadienol, in the unsaponifiable matters of two Solanaceae seed oils fromDatura stramonium andCapsicum annuum, and rice bran oil from the seeds ofOryza sativa (Gramineae) was demonstrated by their isolation or by gas liquid chromatography. AlthoughZ‐isomers of the above two 24‐ethylidene sterols, 28‐isofucosterol and citrostadienol, are a frequent occurrence in higher plant materials including some Solanaceae seed oils and rice bran oil, the report might be the second instance of the unambiguous demonstration of the occurrence of the 24(E)‐ethylidene sterols in higher plants.
Desaturation of isomericcis 18∶1 acids
Authors: Mahfouz M. , Holman R. T.
Published: November 2006

The desaturation of positionalcis 18∶1 isomers (Δ4 through Δ11) was studied, using essential fatty acid deficient rat liver microsomes. Thecis Δ4, Δ5, Δ6 and Δ7 isomers were not desaturated. Thecis Δ10 and Δ11 isomers were desaturated at a very low rate. The maximum desaturation was obtained for Δ8 and Δ9 isomers. Thecis Δ8 and Δ11 isomers were desaturated by Δ5 desaturase; thecis Δ9 isomer was desaturated by Δ6 desaturase; and thecis Δ10 isomer was desaturated to Δ7,10 and 5,10–18∶2 acids.
Relationship between lipids in plasma and skin secretions of neonatal calf with particular reference to linoleic acid
Authors: Noble R. C. , Crouchman M. L. , Jenkinson D. Mcewan , Moore J. H.
Published: November 2006

A study has been made on the lipid composition of the skin secretions and plasma of the neonatal calf. A significant proportion of the skin surface lipids was comprised of triglycerides. Saturated fatty acids comprised the major proportion of the fatty acids of the skin surface triglycerides at birth. Immediately after birth, the pooportion of the saturated fatty acids decreased, and there was a concomittant increase in the proportion of 18∶1. Some 3–4 weeks after birth, the proportion of 18∶2 Δcis‐9, cis‐12 in the skin surface triglycerides increased to ca. 14%, and there was a decrease in the proportion of 18∶1. The 18∶2 was shown to be confined almost entirely to the 2 position of the triglycerides. During the first 5 weeks after birth, the concentrations of the cholesteryl esters and phospholipids in the plasma increased markedly and were accompanied by a rapid increase in the proportion of 18∶2 within these 2 fractions. The results are discussed in relation to the known role of 18∶2 in the metabolism of biological systems.
Incorporation of radioactive polyunsaturated fatty acids into liver and brain of developing rat
Authors: Sinclair A. J.
Published: November 2006

The incorporation of radioactivity from orally administered linoleic acid‐1‐14C, linolenic acid‐1‐14C, arachidonic acid‐3Hg, and docosahexaenoic acid‐14C into the liver and brain lipids of suckling rats was studied. In both tissues, 22 hr after dosing, 2 distinct levels of incorporation were observed: a low uptake (from 18∶2‐1‐14C and 18∶3‐1‐14C) and a high uptake (from 20∶4‐3H8 and 22∶6‐14C). In adult rats, the incorporation of radioactivity into brain lipids from 18∶2‐1‐14C and 20∶4‐3H was considerably lower than the incorporation into the brains of the young rats. In the livers of the suckling rats, the activity from the 18 carbon acids was associated mostly with the triglyceride fraction, whereas the activity from the 20∶4‐3H8 and 22∶6‐14C was concentrated in the phospholipid fraction. In the brain lipids, the activity from the different fatty acids was associated predominantly with the phospholipids. In the liver and brain phospholipid fatty acids, some of the activity in the 18∶2‐1‐14C and 18∶3‐1‐14C experiments was associated with 20 and 22 carbon polyunsaturated fatty acids; however, radioactivity from orally administered 20∶4‐3H8 and 22∶6‐14C was incorporated intact into the tissue phospholipid to a much greater extent compared with the incorporation of radioactivity into 20∶4 and 22∶6 in the experiments where 18∶2‐1‐14C and 18∶3‐1‐14C, respectively, were administered. Possible reasons for these differences are discussed. Rat milk contains a wide spectrum of polyunsaturated fatty acids, including linoleate, linolenate, arachidonate, and docosahexaenoate. During the suckling period in the rat, there is a rapid deposition of 20∶4 and 22∶6 in the brain. The results of the present experiments suggested that dietary 20∶4 and 22∶6 were important sources of brain 20∶4 and 22∶6 in the developing rat.
Evidence for distinct precursor pools for biliary cholesterol and primary bile acids in cebus and cynomolgus monkeys
Authors: Stephan Zouhair F. , Hayes K. C.
Published: November 2006

The abnormal metabolism and distribution of plasma lipoproteins have been associated with atherosclerosis and gallstones. To better understand the process of cholesterol excretion, a study was designed to determine whether the contribution of lipoprotein free14C‐cholesterol (as LDL or HDL) to biliary cholesterol or primary bile acids differs in two species of nonhuman primates, cebus and cynomolgus monkeys, having opposite plasma LDL/HDL ratios. Since amino acid conjugation might influence bile acid synthesis or secretion, the taurine and glycine conjugates of newly synthesized primary bile acids, cholic acid (CA) and chenodeoxycholic acid (CDCA), were measured in the species capable of conjugating with taurine or glycine (cynomolgus). After total bile acid pool washout, monkeys were infused with human LDL or HDL labeled with free14C‐cholesterol, and the specific activities (SA) of biliary cholesterol and primary bile acid conjugates were determined. In both species, regardless of the lipoprotein infused, the SA of biliary cholesterol and CA were greater than those for total bile acids and CDCA, respectively. In cynomolgus, the SA of glycine conjugates was higher for CA than CDCA, while the SA of taurine conjugates was greater for CDCA than CA. Under these conditions, (i) infused lipoprotein free cholesterol (as either LDL or HDL) contributed more to biliary cholesterol than to bile acids and more to CA than to CDCA; (ii) glycine conjugated preferentially with CA rather than CDCA, while taurine was the preferred conjugate for CDCA. Further, whereas the two primary bile acids had similar rates of synthesis and turnover in cynomolgus, basal bile acid synthesis was much greater in cebus and the CDCA turnover appeared disproportionately large.
Fatty acid composition of phospholipids and neutral lipids during embryonic and early larval development in Atlantic herring (Clupea harengus, L.)
Authors: Tocher D. R. , Fraser A. J. , Sargent J. R. , Gamble J. C.
Published: November 2006

The fatty acid compositions of total polar and total neutral lipids of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Within 3 hr after fertilization the percentage of total PUFA in neutral lipid decreased from 33% to 20%, with a reciprocal increase in monoenes. Thereafter the percentage of PUFA in the neutral lipids increased progressively, attaining the original level in ripe eggs by the time of yolk sac absorption. During the larval stages the percentage of PUFA continued to increase in the neutral lipid, reaching almost 44% of the total by day 32 after fertilization, although it was reduced to 32% by day 36. The percentage of monoenes in the neutral lipid displayed a progressive decrease during the whole period of development from 3 hr after fertilization. Throughout all the developmental periods the fatty acid composition of total polar lipids remained essentially constant. The polar lipids of the yolk sac displayed virtually the same fatty acid composition as the larval bodies, but the neutral lipids of the yolk sac were low in PUFA compared to the larval bodies. The results are discussed with reference to changes in lipid class composition during development. The conservation of high levels of PUFA in lipids during embryogenesis and early larval development reflects the importance of these fatty acids during development.
Lipid class composition during embryonic and early larval development in Atlantic herring (Clupea harengus, L.)
Authors: Tocher D. R. , Fraser A. J. , Sargent J. R. , Gamble J. C.
Published: November 2006

The lipid class compositions of Atlantic herring eggs and larvae were determined immediately before fertilization, after fertilization and at various times during subsequent embryonic and early larval development. Total lipid constituted 15% of the dry wt of ripe eggs, 70% of the total lipid being polar lipid with phosphatidylcholine (PC) accounting for almost 90% of the polar lipid. In general, the total lipid content decreased gradually during embryogenesis and in particular during larval development. Within 3 hr after fertilization the relative percentage of neutral lipid decreased slightly. This was followed by a general decrease in polar lipid which, by the stage of yolk sac absorption, was reduced to 52% of the total lipid. The decreased percentage of polar lipid was due entirely to a decrease in PC, which was reduced to 66% of the polar lipids at the stage of yolk sac absorption. The accompanying increase in the percentage of neutral lipids was mainly due to increased percentages of triacylglycerols (TAG) up to yolk sac absorption and cholesterol esters in the larval stages. During the first 4 days after hatching, phospholipids and to a lesser extent cholesterol were preferentially depleted in the yolk sacs, which also had higher levels of free fatty acids. The results are discussed in relation to possible roles of different lipids during embryonic and early larval development.