bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma membrane phospholipid, cholesterol and fatty acyl composition of differentiated and undifferentiated L6 myoblasts
Authors: Perkins Roger G. , Scott Robert E.
Published: November 2006

The lipid composition of plasma membranes isolated from differentialted and undifferentiated L6 myoblasts has been compared. In general, the plasma membranes of differentiated L6 myoblasts have a higher cholesterol to phospholipid molar ratio than plasma membranes of undifferentiated cells. Differentiated L6 myoblasts have increased relative amounts of phosphatidylethanolamine and phosphatidylcholine in their plasma membrane and a decreased relative amount of sphingomyelin when compared with the plasma membranes of undifferentiated myoblasts. In addition, preliminary results show that differentiated L6 myoblasts plasma membrane phospholipid shows differences in the fatty acyl composition, specifically there appears to be relatively more 17∶0 and 24∶1 and less 16∶1 and 18∶1 than in plasma membrane phospholipids of undifferentiated L6 myoblasts. These observations indicate that significant changes in plasma membrane lipid composition occur during myoblast differentiation. The role that changes in lipid composition play in control of cellular differentiation, however, remains to be elucidated.
Differences in the phospholipid, cholesterol, and fatty acyl composition of 3T3 and SV3T3 plasma membranes
Authors: Perkins Roger G. , Scott Robert E.
Published: November 2006

An analysis of the phospholipid, cholesterol, and phospholipid fatty acyl composition of isolated plasma membranes of 3T3 and SV3T3 mouse embryo cells has been performed. The results show that the plasma membrane of SV3T3 cells contain relatively less phosphatidylethanolamine and sphingomyelin and more cholesterol than 3T3 plasma membranes. The fatty acyl composition of individual phospholipid classes as determined by gas liquid chromatography also showed differences between 3T3 and SV3T3 plasma membranes. The plasma membranes of SV40 transformed 3T3 cells contain: (a) a higher percentage of 18∶1 and less 20∶3 and 20∶4 in phosphatidylethanolamine; (b) a higher percentage of 18∶1 in phosphatidylserine; and (c) a higher percentage of 18∶2 and 20∶4 in phosphatidylinositol.
The interaction of 1,25‐dihydroxyvitamin D3 with its intestinal mucosa receptor: Kinetic parameters and structural requirements
Authors: Putkey John A. , Wecksler Wayne R. , Norman Anthony W.
Published: November 2006

Vitamin D3 and its metabolites comprise an endocrine system which plays a critical role in calcium homeostasis. The active form of vitamin D3 is 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3]. Chromatin localization of 1,25(OH)2D3 and sucrose density gradient centrifutation have demonstrated the presence of an intestinal mucosa cytosol receptor which specifically binds 1,25(OH)2D3. The kinetic parameters of 1,25(OH)2D3 binding to its receptor have been determined by hydroxylapatite and reconstituted chromatin cytosol assays. Utilization of these assays has also permitted a determination of the precise structural requirements of the vitamin D ligand for the intestinal receptor. Furthermore, it has been possible to propose two receptor‐ligand models which are capable of accommodating the conformationaly modile A ring of the vitamin D seco‐steroids.
Brain mitochondrial incorporation of elongated fatty acids into phospholipids
Authors: Moss S. A. , Yatsu F. M.
Published: November 2006

The characteristics patterns and asymmetric distribution of phospholipid fatty acids suggest precise control mechanisms. Our investigations were designed to assess mitochondrial fatty acid elongation and their pattern of incorporation into complex lipids. Fatty acid chain elongation in the total lipid fraction occurred primarily with the more abundant fatty acids present. Elongation patterns in free fatty acids were similar to the total lipid fraction except C20:4 and C22:4 were formed to slightly greater extent. Choline glycerophosphatide and ethanolamine glycerophosphatide displayed different patterns of elongation. Choline glycerophosphatide contained more elongated longer chain polyunsaturated fatty acids, while ethanolamine glycerophosphatide contained greater amounts of elongated shorter chain saturated and monounsaturated fatty acids. These results suggest that fatty acid elongation may play a specific role in fulfilling mitochondrial phospholipid fatty acid requirements.
Lipids of cultured hepatoma cells: V. Distribution of isomeric monoene fatty acids in individual lipid classes
Authors: Wood Randall , Falch John , Wiegand Rex D.
Published: November 2006

Monoenoic acid fractions were isolated from phosphatidylcholines, phosphatidylethanolamines, triglycerides, and cholesterol esters derived from minimal deviation hepatoma 7288C cells cultured on 11 media containing varying levels of serums and lipids. Hexadecenoate (16∶1), octadecenoate (18∶1), and eicosenoate (20∶1) fractions were subjected to ozonolysis and the isomeric composition of the monoene fractions determined quantitatively by gas liquid chromatography. The 16∶1 fractions consisted of palmitoleic acid, the Δ9 isomer (85–90%), and the Δ11 isomer (10–15%) in most of the cases; growth media and lipid class origin had little effect upon composition. The predominate acids of the 20∶1 fraction were the Δ13 and Δ11 isomers. Generally, the Δ13 isomer was present in the highest concentration, and this isomer was higher in phosphatidylcholines than the other classes. Vaccenic acid represented 33–66% of the 18∶1 fraction, and the balance was oleic acid. Oleic acid concentrations decreased, and vaccenic acid levels increased as the growth medium serum and lipid levels decreased. Lipid classes did not exhibit any distinct preference for either isomer. These data represent the first quantitative isomeric analysis of monoenoic acids derived from individual lipid classes and are the first to show the occurrence of high levels of vaccenic acid in neoplastic cells. This study suggests that the elevated levels of oleic acid, one of the most frequently observed changes in tumor lipids, may, in fact, represent elevated levels of vaccenic acid.
Changes in phospholipid composition in hibernating ground squirrel,Citellis lateralis, and their relationships to membrane function at reduced temperatures
Authors: Aloia Roland C. , Pengelley Eric T. , Bolen James L. , Rouser George
Published: November 2006

The hearts of hibernating mammals have the capacity to function at reduced temperatures of 1 C in contrast to hearts of nonhibernating mammals which undergo ventricular fibrillation during deep hypothermia. Thus, all vital membrane functions continue in hibernators. This suggests that there may be special features of their lipid and protein composition. Analysis of the hearts of the hibernating ground squirrel,Citellus lateralis, in the active (37 C) and hibernating state (1–4 C) reveals differences in the percent composition of the phospholipid classes. There is a decrease in the percentage of diacyl choline, ethanolamine, serine phosphoglycerides, and diphosphatidyl glycerol and an increase in the percentage of lysophosphatidyl choline, lysophosphatidyl ethanolamine, lysodiphosphatidyl glycerol, and phosphatidic acid in the hibernating state. There is also an increase in the molar amount of phosphorus/100 g fresh wt of tissue during hibernation. The most striking difference in phospholipid composition between active and hibernating heart tissue is the 3.5‐fold increase in lysoglycerophosphatides. These compounds are implicated as contributing factors controlling membrane fluidity during hibernation and upon which the physiological state of hibernation may be contingent.
New series of fatty acids in Northern Pike (Esox lucius)
Authors: Glass R. L. , Krick Thomas P. , Eckhardt Allen E.
Published: November 2006

The presence in Northern Pike (Esox locius) liver and testes lipids of a group of eight homologous fatty acids of as yet unknown structure is reported. They occur esterified to cholesterol and to glycerol as triglycerides but are absent from the phospholipids. They contain three oxygens and are characterized further by being more resistant to hydrogenation than normal unsaturated fatty acids and by an inability to form urea inclusion compounds. They also have been found to be major constituents of the liver fatty acids of four additional species of fish.
Metabolism of 2,4‐3H‐14α‐methyl‐5α‐ergost‐8‐enol and 2,4‐3H‐5α‐ergosta‐8,14‐dienol inChlorella ellipsoidea
Authors: Tsai L. B. , Patterson G. W. , Cohen C. F. , Klein P. D.
Published: November 2006

5α‐Ergosta‐8,14‐dienol and 14α‐methyl‐5α‐ergost‐8‐enol were synthesized chemically from ergosterol and labeled with tritium at the C‐2 and C‐4 positions. Both labeled sterols, when incubated with growing cultures ofChlorella ellipsoidea, were converted to ergost‐5‐enol but not to C‐27 or C‐29 sterols.Chlorella ellipsoidea, thus, has the capability of removing the C‐14 methyl group and converting the 8(9) and 8,14 double bond systems to the 5(6) position. Brassicasterol produced by this organism is not labeled in these experiments, indicating that it is not derived from a saturated side chain precusor.
Transport of diacylalkylglycerols in chylomicrons and very low density lipoproteins of rat intestinal lymph following intragastric administration of 1,3‐dioctadecenoyl‐2‐hexadecylglycerol
Authors: Pitas R. E. , Hagerty M. M. , Jensen R. G.
Published: November 2006

The triacylglycerol (TG) analog 1,3‐dioctadecenoyl‐2‐hexadecyl glycerol was used in the study of the transport of dietary lipids by lipoprotein fractions of rat intestinal lymph. 1,3‐Diacyl‐2‐alkyl glycerols (DAG) are hydrolyzed by pancreatic lipase to form 2‐alkyl glycerols and free fatty acids. These hydrolysis products are then absorbed, and DAG are resynthesized within the intestinal mucosa. Intestinal lymph of rats was collected following intragastric administration of 1,3‐dioctadecenoyl‐2‐hexadecyl glycerol. The DAG to TG ratios in very low density lipoprotein (VLDL) and chylomicron fractions were determined as a measure of the incorporation of lipid of dietary origin. The ratio of DAG to TG in the VLDL‐2 (Sf 12–100) fraction ranged from0.06 to 0.56 indicating a significant amount of DAG transported relative to TG. The glyceryl ether to TG ratio increased with mean lipoprotein volume from the VLDL‐2 fraction to the chylomicron (Sf>400) fraction. The correlation between glyceryl ether to TG ratio and average volume and between the amount of DAG per ml of original lymph and average volume within the chylomicron fraction was 0.99. Thus, the amount of dietary fat transported was correlated with the size of the chylomicrons produced. The glyceryl ether to TG ratio was positively correlated with the average volume of the lipoprotein fractions isolated (chylomicrons, chylomicron rich (Sf>100), VLDL‐1 (Sf 100–400) and VLDL‐2) (r=0.87). These results suggest that the size of the lipoproteins produced by the intestine is determined by the amount of fat available for transport and that particles of larger diameter are formed by the addition of lipid of dietary origin to existing VLDL.
Distinctive medium chain wax esters, triglycerides, and diacyl glyceryl ethers in the head fats of the pacific beaked whale,Berardius bairdi
Authors: Litchfield Carter , Greenberg Anne J. , Ackman R. G. , Eaton C. A.
Published: November 2006

Lipids were extracted from the mandibular fat body (jaw), the fatty forehead (melon), and the dorsal blubber of a Pacific beaked whale (Berardius bairdi) and separated into lipid classes by preparative thin layer chromatography. The head fats were mixtures of wax esters and triglycerides with a very small amount of diacyl glyceryl ether. The blubber fat contained 97% was ester and 3% triglyceride. Gas liquid chromatography (GLC) of the intact lipid classes indicated an unusually low C26–C30 range for most of the jaw and melon wax esters compared to the more normal C32–C40 molecules found in the blubber. Distinctive lower molecular weight C24–C40 triglycerides occurred in the head fats vs. the usual C44–C58 range in the blubber. Most diacyl glyceryl ethers were in the C35–C46 range, below the molecular weight of hexadecyldipalmitoyl glyceryl ether (C48). GLC of the derived fatty acid methyl esters showed that the lower molecular weight neutral lipids in the head fats were due to high levels of iso‐10∶0, n−10∶0, iso‐11∶0, iso‐12∶0, n−12∶0, and iso‐13∶0 acids. The wax ester fatty alcohols and the alkoxy chains of the glyceryl ethers were mostly the C14–C20 chain lengths commonly observed in marine organisms. The distinctive medium chain neutral lipids in the jaw and melon fats of this whale may be related to the postulated acoustical role of these tissues in echolocation.
Selective effects of fatty acids upon cell growth and metabolic regulation
Authors: Lands William E. M. , Sacks Roger W. , Sauter John , Gunstone Frank
Published: November 2006

Positional isomers ofcis‐methyleneoctadecanoic acid differed greatly in their efficiency for growth of an unsaturated fatty acid auxotroph ofEscherichia coli upon glucose as a carbon source. The 8, 9, and 11 isomers were more efficient in producing cells (60–70 cells/fmole) than the others (0–7 cells/fmole), although all isomers were found esterified to a similar extent into cellular lipid. WithSaccharomyces cerevisiae mutants, all isomers between 6 and 12 supported some growth of the eukaryotic cells, and the 7 and 9 isomers were slightly more efficient than the 8‐isomer. WhenE. coli were grown with glycerol, all isomers from 5 to 14 supported growth, and those with the substituent near the center of the acyl chain had the greatest efficiency (70 cells/fmole). With the glycerol medium, the pattern of efficiencies for the variouscis‐methylene acyl chains resembled the broad selectivity reported earlier for thecis‐ethylenic isomers in glucose medium, which agreed closely with predictions based upon the physical property of their phospholipid derivatives. Thus, metabolism of glycerol appeared to allow the cyclopropane acyl chains to support cell functions to the limits expected for bulk phase chain‐chain fluidity considerations. This broad specificity was also obtained when cells were grown on glucose with cyclic AMP added to the culture. Therefore, the selective inadequacies of the 5, 6, 7, 10, 12 and 13 isomers in supporting cell growth on glucose may occur through an interaction modified by cAMP and dependent upon reduced cellular levels of cyclic AMP. The highly selective pattern of efficiency of thecis‐methylene acids forE. coli growth on glucose resembles that with the acetylenic acids, but was shifted one carbon atom toward the methyl terminus. This observed selectivity pattern seems due to interactions of the individual acyl chains with cellular protein(s) rather than to chain‐chain interactions in a bulk phase. The ability of certain positional isomers to support cell function equally well in both nutrient conditions suggests that the role of those acyl chain isomers may be independent of metabolite flux or cyclic nucleotide contents of the cell, whereas the actions of other isomeric fatty acids seem closely related to the metabolic status of the cell. A highly selective role for different fatty acids in modulating cellular function seems possible on the basis of the current evidence.
The evidence for the antiatherogenicity of high density lipoprotein in man
Authors: Miller N. E.
Published: November 2006

It has long been recognized that patients with clinical coronary heart disease (CHD) have, on average, higher concentrations of plasma very low density and low density lipoproteins than do healthy subjects. The same, studies clearly demonstrated that coronary victims tend also to have low plasma concentrations of high density lipoprotein (HDL). It is only recently, however, that the possible significance of this second observation has been examined. Direct evidence for an inverse relationship between HDL cholesterol concentration and the prevalence of clinical CHD, independent of other plasma lipoproteins, has been provided by the Honolulu Heart and Cooperative Lipoprotein Phenotyping Studies. The Tromsø Heart and Framingham Studies subsequently demonstrated that this relationship precedes the clinical manifestation of coronary disease. More recently, angiographic studies have confirmed that the severity of existing coronary atherosclerosis is inversely related to HDL cholesterol concentration. Other investigations have shown that coronary victims also have low mean concentrations of apolipoproteins AI and AII (the major protein components of HDL), although the reduction of apoAI concentration may be less marked than that of HDL cholesterol, and preliminary findings from Tromsø have suggested that apolipoprotein AI may be less powerful than HDL cholesterol as a predictor of CHD. Such observations have supported the proposal that HDL may exert a protective effect against coronary atherosclerosis. Final confirmation (or otherwise) of this hypothesis, however, must await the results of carefully controlled animal experiments and of regression studies in patients with angiographically defined atherosclerosis.
Ultrastructure of serum high density lipoproteins: Facts and models
Authors: Scanu Angelo M.
Published: November 2006

The complexity of the structure of plasma high density lipoproteins (HDL) has invited numerous approaches which have been directed at the study of the intact particles, their apolipoproteins and reassembled complexes. Parameters such as flotation and sedimentation coefficients, size and molecular weight have been determined and in addition, through scattering techniques, an understanding has been obtained on the long range organization between core (cholesteryl esters and triglycerides) and surface components (unesterified cholesterol, phospholipids and apoproteins). In the case of the apolipoproteins, the knowledge of their primary structure has facilitated the study of their physicochemical properties in solution and at the air‐water interface and has also permitted realistic predictions of the two dimensional organization, not only of their α‐helical segments but also of the β‐pleated sheets, random coil and β‐turns, all of which have amphipathic properties. When all of the information from the physical and chemical studies is put together, the various HDL can be described as spherical structures having a liquid core of radius, r—20.2 Å, surrounded by a monolayer of cholesterol and phospholipids with closely packed hydrophobic ends on the surface of the core. The organization of the apoproteins at the lipoprotein interface is comparatively less understood. However, reasonable predictions can be made on secondary structure considerations and on their behavior at the air‐water interface. The emerging overall structural information can be translated into a space‐filling model that not only provides a useful visual representation of HDL, but, more importantly, a basis for planning future studies on the elucidation of the structure of these particles on a molecular level.
Quantitation of high density lipoproteins
Authors: Albers John J. , Warnick G. Russell , Chenng Marian C.
Published: November 2006

The demand for high density lipoprotein (HDL) quantitation has dramatically increased with the renewed awareness of the importance of HDL as a negative risk factor for coronary heart disease. HDL is usually estimated by specific precipitation of the non‐HDL apoB‐containing lipoproteins by polyanions and divalent cations followed by measurement of cholesterol in the supernatant. A common procedure involves precipitation with sodium heparin at 1.3 mg/ml and MnCl2 at 0.046 M (final concentrations). This method is appropriate for serum but less than ideal for plasma because of incomplete precipitation and sedimentation of the apoB‐containing lipoproteins. A two‐fold increase in Mn2+ to 0.096 M improves precipitation of the apoB‐associated lipoproteins from plasma without excessive precipitation of HDL. This modified heparin‐Mn2+ procedure gives results nearly identical to the results with the ultracentrifugal reference method (cholesterol in the d>1.063 fraction corrected for losses and the presence of apoB‐associated cholesterol). The dextran sulfate 500‐Mg2+ and the sodium phosphotungstate‐Mg2+ procedures give results consistently 2–4 mg/dl lower than does the reference method. In contrast, a heparin‐Ca2+ method gives results 5–8 mg/dl higher than does the reference method. Immunochemical analysis of apoA‐I in the precipitate and apoB in the supernatant indicates that lower values for the phosphotungstate‐Mg2+ procedure is due to partial precipitation of the A‐I‐containing lipoproteins, while higher values by the heparin‐Ca2+ method are due to incomplete precipitation of the apoB‐containing lipoproteins. Quantitation of the principal apoproteins of HDL, A‐I and A‐II, represent an important additional index of HDL concentrations and composition. Quantitation of plasma A‐I and A‐II concentrations by radial immunodiffusion indicates that women generally have higher HDL concentrations than men (women, A‐I, 135±25, A‐II, 36±6; men, A‐I, 120±20, A‐II, 33±5; mean±S.D., in mg/dl). A‐I and A‐II do not increase with age in men but show a slight increase with age in women. Estrogen increases HDL cholesterol and protein and may in part account for the higher HDL in women. The lighter density HDL subclass has a higher A‐I/A‐II ratio than the denser HDL subclass, with women generally having significantly more of the lighter HDL subclass. Density‐gradient ultracentrifugation in CsCl2 gradients indicates that HDL contains subpopulations of differing hydrated density which vary in the A‐I/A=II ratio. Immunoassay of A‐I and A‐II when used in combination with HDL cholesterol analysis is a powerful tool for studies of HDL structure, epidemiology and metabolism.
Fatty acid biosynthesis in the developing endosperm ofCocos nucifera
Authors: Oo K. C. , Stumpf P. K.
Published: November 2006

Endosperm tissue of developing coconut endosperm incorporated [14C] acetate and [14C]‐malonate into [14C]C8‐C18 fatty acids. The distribution of [14C] label into the various fatty acids mimicked the distribution of endogenous fatty acids at early and middle stages of endosperm development. Although [14C] C8‐C18 fatty acids were taken up rapidly by endosperm tissue slices, no elongation occurred; [14C] stearic acid was not desaturated to oleic. Cell free preparations have also been obtained from this tissue that readily incorporated [14C] malonyl‐CoA into a range of [14C] fatty acids in the presence of ACP and NADH at pH 7.0. Employing this system, a number of experiments were designed to determine the mechanism of chain length termination. In contrast to intact tissue slice experiments, cell‐free extracts yielded as principal products palmitic and stearic acid, although up to 20% were shorter chain acids. A number of possible mechanisms for chain length termination were proposed and tested.
Composition of lipids bound to pure cytochrome P‐450 of cholesterol side‐chain cleavage enzyme from bovine adrenocortical mitochondria
Authors: Hall P. F. , Watanuk M. , Degroot J. , Rouser G.
Published: November 2006

Phospholipids bound to highly purified cytochrome P‐450 from bovine adrenocortical mitochondria, part of the enzyme complex responsible for catalyzing the conversion of cholesterol to pregnenolone, have been examined for comparison with the bulk phospholipids of the mitochondria from the same tissue. In both cases, the major phospholipids are phosphatidylcholine (PC) (37%) and phosphatidylethanolamine (PE) (56%), as well as smaller amounts of sphingomyelin and diphosphatidylglycerol. The fatty acid compositions of the four classes of phospholipids and of the neutral lipids bound to the pure enzyme are indistinguishable from those of the respective mitochondrial lipids. They are also similar to those of mitochondria from other organs except for high levels of arachidonate and low levels of diphosphatidylglycerol.
The effect of 5,8,11,14‐eicosatetraynoic acid on lipid metabolism
Authors: Tobias L. D. , Hamilton J. G.
Published: November 2006

The purpose of this presentation is to review the current state of knowledge regarding 5,8,11,14‐eicosatetraynoic acid (ETYA, Ro 3‐1428) and its effects on lipid metabolism. Accordingly, the topics discussed include hypocholesterolemic and dermatological studies involving ETYA in both animals and man, as well as the effects of ETYA on desaturate enzymes. Metabolic studies involving ETYA are also noted. Primary interest is focused on the effects of ETYA on selected processes of arachidonate metabolism, and the effect of ETYA on inflammation, platelet aggregation and tumor growth are discussed, keeping in mind the relevance of arachidonate metabolism to these processes.
Stereospecificity of linoleic acid hydroperoxide isomerase from corn germ
Authors: Gardner H. W.
Published: November 2006

Linoleic acid hydroperoxide isomerase from corn germ inverted the stereoconfiguration of its substrate. 9‐D(S)‐Hydroperoxy‐trans‐10,cis‐12‐octadecadienoic acid was converted to 10‐oxo‐9‐L(R)‐hydroxy‐cis‐12‐octadecenoic acid. Presumably, the H2O solvent of OH− acted as a nucleophile. In the presence of another nucleophile, linoleate, the 9‐D(S)‐hydroperoxide was transformed into 9‐L(R)‐linoleoyloxy‐10‐oxo‐cis‐12‐octadecenoic acid. The substitution of nucleophiles from the incubation solution and the inversion of stereoconfiguration at carbon‐9 are consistent with a bimolecular nucleophilic substitution (SN2) mechanism.
Oxidative activation of guanylate cyclase by prostaglandin endoperoxides and fatty acid hydroperoxides
Authors: Graff Gustav , Stephenson Janish H. , Winget Rodner R. , Goldberg Nelson D.
Published: November 2006

Purified prostaglandin endoperoxides (PGG2 and PGH2) and hydroperoxides (15‐OOH‐PGE2) as well as fatty acid hydroperoxides (12‐OOH‐20∶4, 15‐OOH‐20∶4, and 13‐OOH‐18∶2) were examined as effectors of soluble splenic cell guanylate cyclase activity. The procedures employed for the preparation and purification of these components circumvented the use of diethyl ether which obscured effects of lipid effectors because of contaminants presumed to be ether peroxides which were stimulatory to the cyclase. Addition of prostaglandin endoperoxides or fatty acid hydroperoxides to the reaction mixture led to a time‐dependent activation of guanylate cyclase activity; 2.5‐to 5‐fold stimulation was seen during the first 6 min. The degree of stimulation and rate of activation were dependent on the concentration of the fatty acid effector; when initial velocities (6 min) were assessed, half maximal stimulation was achieved in the range of 2 to 3 μM. However, by extending the incubation time to 90 min, similar maximal increases in specific activity could be achieved with 3 or 10 μM PGG2 or PGH2. Activation of guanylate cyclase upon addition of prostaglandin endoperoxides or fatty acid hydroperoxides was prevented or reversed by the thiol reductants dithiothreitol (3 to 5 mM) or gluthathione (10 to 15 mM). Na2S2O4, not known as an effective reducing agent of disulfieds, prevented but was relatively ineffective in reversing activation after it had been induced by PGG2. Pretreatment of the enzyme preparation with increasing concentrations of N‐ethyl‐maleimide in the range of 0.01 to 1.0 mM prevented activation by PGG2 without effecting basal guanylate cyclase activity. These observations indicate that fatty acid hydroperoxides and prostaglandin endoperoxides promote activation of the cyclase by oxidation of enzyme‐related thiol functions. In contrast, PGE2, PGF2α, hydroxy fatty acids (13‐OH‐18∶2, 12‐OH‐20∶4) as well as saturated (18∶0), monoenoic (18∶1), dienoic (18∶2), and tetraenoic (20∶4) fatty acids were ineffective in promoting cyclase activation in the range of 1 to 10 μM. Studies to identify the species of the rapidly metabolized prostaglandin endoperoxides that serve as effectors of the cyclase indicated that PGG2 but not 15‐OOH‐PGE2 (the major buffer‐rearrangement product of PGG2) is most likely an activator. In the case of PGH2 a rapidly generated (30 sec) metabolite of PGH2 was found which contained a hydroperoxy or endoperoxy functional group and was equally as effective as PGH2 as an apparent activator of the enzyme. The combined effects of PGG2 and dehydroascorbic acid, another class of activator, exhibited additivity with respect to the rate at which the time‐dependent activation was induced. These results suggest that activation of soluble guanylate cyclase from splenic cells can be achieved by the oxidation of sulfhydryls that may be associated with specific hydrophobic sites of the enzyme or a related regulatory component.
Molecular species of sphingomyelin in sphingomyelinase‐sensitive and sphingomyelinase‐resistant pools of HL‐60 cells
Authors: Fitzgerald Veronica , Blank Merle L. , Snyder Fred
Published: November 2006

This study of sphingomyelin molecular species in undifferentiated and differentiated (granulocytic form) HL‐60 cells demonstrated only minor differences in the distribution of species between the sphingomyelinase‐sensitive and sphingomyelinase‐resistant pools of sphingomyelin in these cells. The two most prominent species of sphingosine present in both the undifferentiated and differentiated cells were those containing 16∶0 (slightly higher in the sphingomyelinase‐resistant membranes) and 24∶1N‐acyl moieties. Cell differentiation exerted little effect on the distribution of molecular species of sphingomyelin between the sphingomyelinase‐sensitive and sphingomyelinase‐resistant pools in HL‐60 cells, although the levels ofN‐palmitoyl sphinganine were significantly lower and theN‐nervonoyl sphingosine higher in both pools from the differentiated cells. Our results indicate the same species of sphingomyelin, available at both the outer layer of the plasma membrane and inner layer of the plasma membrane (plus intracellular membranes) of HL‐60 cells, serve as precursors for generation of the ceramides that participate in signal transduction processes initiated by cell activation.
Lipid changes in HL‐60 cells on differentiation into macrophages by treatment with a phorbol ester
Authors: Manning Ray , Fallani Anna , Ruggieri Salvatore
Published: November 2006

We studied changes in lipid composition of human promyelocytic leukemia cells (HL‐60) on differentiation to the macrophage/monocytic lineage by treatment with the phorbol ester, 12‐O‐tetradecanoyl‐phorbol‐13‐acetate. Differentiation was accompanied by: (i) a decrease in the level of phospholipids; (ii) a greater amount of triacylglycerols; (iii) an increase in 1‐alk‐1′‐enyl‐2‐acyl‐ and 1‐alkyl‐2‐acyl‐sn‐glycero‐3‐phosphoethanolamine and a decrease in 1‐alkyl‐2‐acyl‐sn‐glycero‐3‐phosphocholine; and (iv) an increase in the level of arachidonic acid in ethanolamine phospholipids. The increased levels of ether‐linked lipids and of arachidonic acid in ethanolamine phospholipids are consistent with an enhanced biosynthesis of platelet‐activating factor and eicosanoids, which are particularly important in the macrophage function.
Pathogenesis of oleic acid‐induced lung injury in the rat: Distribution of oleic acid during injury and early endothelial cell changes
Authors: Beilman Greg
Published: November 2006

Oleic acid‐induced lung injury, a well‐described laboratory model for acute pulmonary injury in the rat and other species, causes morphologic and cellular changes similar to human adult respiratory distress syndrome (ARDS). Experiments were performed to test the hypothesis that the initial event of oleic acid lung injury is damage of the pulmonary vascular endothelium by oleic acid, with subsequent pulmonary damage and inflammation. Oleic acid levels were followed in the lung and other tissues by measuring accumulation of14C‐oleic acid; the direct effects of oleic acid and other fatty acids on rat endothelial cells, alveolar type II cells, and hepatocytes in culture were determined. Lung tissue from treated rats was also examined by light and electron microscopy for evidence of endothelial cell damage. At 30 min after injury, oleic acid reached high concentrations in lung tissue as demonstrated by presence of radiolabel (3.24×10−6 moles per gram of tissue), with counts in the lung nearly an order of magnitude greater than in any other organ measured. Oleic acid was present in the lung mostly as free fatty acid (85%), and was also present in the alveolar fluid supernatans, rather than being cell‐associated (1.7×10−7 moles vs. 1.1×10−8 moles at 30 min). Oleic acid was toxic to endothelial cells after one minute of exposure at concentrations of 5×10−4M and above. Electron microscopy showed endothelial cell changes as early as 10 min after induction of injuryin vivo, including the presence of endothelial cell blebbing. The results of these studies suggest that the initial event in oleic acid lung injury is damage to the pulmonary vascular endothelial cell.
Thyroid hormone is required for dietary fish oil to induce hypersecretion of biliary cholesterol in the rat
Authors: Prigge William F. , Ketover Scott R. , Gebhard Roger L.
Published: November 2006

In the rat, both fish oil diet and thyroid hormone replacement are reported to augment bile cholesterol secretion out of proportion to bile flow or secretion of other bile lipids. We sought common mechanisms for these effects and evaluated the role of phospholipid fatty acid composition in the process. Methimazole‐treated hypothyroid rats were fed low‐fat chow or chow supplemented with 10% corn oil or fish oil, and were studied before and after thyroid hormone treatment. Serum, hepatic, and bile lipids were measured, phospholipid fatty acid composition determined, and hepatic 3‐hydroxy‐3‐methylglutaryl CoA reductase activity assayed. Fish oil diet stimulated cholesterol secretion into bile only after thyroid hormone was given, and this action was synergistic with that of thyroid hormone. Reduced serum cholesterol in fish oil‐treated rats was associated with increased biliary cholesterol secretion and diminished hepatic cholesterol content. This suggests that augmented biliary cholesterol secretion may contribute to the fish oil‐induced reduction of serum cholesterol. No definite relationship between hepatic or biliary phospholipid fatty acid composition and biliary secretion was apparent, although high bile cholesterol secretion was associated with a low percentage of hepatic and bile phospholipid linoleic acid.
Enteral absorption in man of eicosapentaenoic acid in different chemical forms
Authors: Boustani S. El , Colette C. , Monnier L. , Descomps B. , Crastes de Paulet A. , Mendy F.
Published: November 2006

After administering the equivalent of 1 g of eicosapentaenoic acid (EPA) in four different chemical forms, the kinetics of EPA incorporation into plasma triglycerides (TG) were compared by gas liquid chromatography on a capillary column following separation of the lipid fraction by thin layer chromatography.

EPA incorporation into plasma TG was markedly smaller and later when EPA was administered as an ethyl ester rather than as EPA free fatty acid, EPA arginine salt or 1,3‐dioctanoyl‐2‐eicosapentaenoyl glycerol (2‐EPA). Our results and the data in the literature are compatible with the hypothesis that 2‐EPA is absorbed with minimum hydrolysis and escapes random distribution between the other positions of the glycerol molecule during the absorption process.
Short‐term biological reproducibility of serum fatty acid composition in children
Authors: Moilanen Teemu
Published: November 2006

To assess the biological day‐to‐day reproducibility of the fatty acid composition in serum lipid fractions in children on their habitual diets, fasting serum specimens were collected from healthy 8‐ to 9‐year‐old boys at 2‐day (n=21) or 7‐day (n=19) intervals. Percentage compositions of fatty acids in serum cholesteryl esters (CE), triglycerides (TG), free fatty acids (FFA) and phospholipids (PL) were analyzed by gas chromatography. The reproducibility was estimated by calculating linear correlation coefficients between the values obtained at the two time‐points. Generally the correlations were higher in CE and PL than in TG and FFA. In CE the 7‐day correlations of major fatty acids were only slightly lower than the 2‐day ones. In PL the impairment of correlations was somewhat greater than in CE, but in TG and FFA there was a marked drop in reproducibility from 2‐ to 7‐day intervals. The 2‐day correlation coefficients of the percentages of linoleate, dihomo‐γ‐linolenate, arachidonate and eicosapentaenoate in CE were 0.95, 0.84, 0.91 and 0.92, respectively. In PL, the respective values were 0.86, 0.82, 0.95 and 0.90. The persent results indicate high short‐term biological reproducibility of fatty acid composition in serum CE and PL and clearly lower in those of TG and FFA.
Calmodulin antagonists suppress cholesterol synthesis by inhibiting sterol Δ24 reductasereductase
Authors: Filipovic Ivan , Buddecke Eckhart
Published: November 2006

Preincubation of hepatoma cells and human skin fibroblasts in the presence of the calmodulin antagonists trifluoperazine and N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalene sulfonamide resulted in a dose‐dependent suppression of [14C] mevalonolactone incorporation into cholesterol. At a calmodulin antagonist concentration of 25 μmol, the incorporation of [14C] mevalonolactone into cellular cholesterol was suppressed to about 30% (hepatoma cells) and 10% (human skin fibroblasts) of control values. When the total nonsaponifiable [14C] lipids were separated and analyzed by two‐dimensional thin layer chromatography, an accumulation of [14C] desmosterol was observed along with reduced formation of [14C] cholesterol. However, when cells were preincubated in the presence of [14C] dihydrolanosterol, [14C] cholesterol formation was not inhibited by the calmodulin antagonists. About 25% of the cell‐associated dihydrolanosterol radioactivity was converted to cholesterol in both control and calmodulin antagonist‐pretreated cells. The data suggest that calmodulin antagonists prevent the conversion of desmosterol into cholesterol by inhibiting sterol Δ24 reductase and that the enzymes catalyzing sterol ring modifications are not affected by the inhibitors.
Effect of environmental temperature changes on liver Δ6 and Δ5 fatty acid desaturases depressed by hyperglycidic diet on male rats
Authors: Losada Ana Ves , Peluffo Raúl O.
Published: November 2006

Male rats maintained on a control diet at 24 C and shifted to 12 C for five days showed no modification in Δ6 or Δ5 desaturase activity. When Δ6 and Δ5 desaturase activities were diminished by a hyperglycidic diet, shifting to cold increased both enzymatic activities. In general, modifications observed in liver microsomal fatty acid composition are consistent with those associated with the enzymatic desaturation activity.
Acyltransferases in subcellular fractions of developing seeds of rape (Brassica napus L.)
Authors: Murphy Denis J. , Mukherjee Kumar D.
Published: November 2006

Acyltransferase activities responsible for the transfer of oleoyl moieties from oleoyl‐CoA to various lipids have been examined in subcellular fractions of developing seeds of rape,Brassica napus L. In the absence of exogenous acyl acceptors, the microsomal and oil body fractions transferred oleoyl moieties mostly to phosphatidylcholines and phosphatidic acids, although there was substantial incorporation of the oleoyl moieties into monoacylglycerols, diacylglycerols and triacylglycerols. The soluble (150,000‐g supernatant) fraction incorporated oleoyl moieties mainly into the neutral lipids (monoacylglycerols and diacylglycerols) and also exhibited a relatively high acyl‐CoA hydrolase activity. In the presence of the exogenous acyl acceptors, lysophosphatidylcholine and lysophosphatidic acid, both microsomal and oil body fractions transferred most of the oleoyl moieties to phosphatidylcholines and phosphatidic acids, respectively. Other lysophospholipids, such as lysophosphatidylethanolamine and lysophosphatidylonositol, were not very effective as acyl acceptors, nor were glycerol‐3‐phosphate, monoacylglycerols or diacylglycerols. In contrast, the soluble fraction showed little or no stimulation of acyltransfer in the presence of exogenous lysophospholipids but was able to utilize, to some extent, exogenous monoacylglycerols and diacylglycerols as acyl acceptors.
The kinetics of the autoxidation of polyunsaturated fatty acids
Authors: Cosgrove John P. , Church Daniel F. , Pryor William A.
Published: November 2006

The kinetics of the autoxidation of a series of polyunsaturated fatty acids (PUFA) with increasing degrees of unsaturation and the mono‐, di‐and triglycerides of linoleate have been studied in homogeneous chlorobenzene solution at 37 C under 760 torr of oxygen. The autoxidations were initiated by thermal decomposition of azo initiators and followed by measuring the rate of oxygen uptake. The rate of chain initiation was determined by the induction period method using α‐tocopherol as the chainbreaking antioxidant. The measured oxidizabilities of the PUFA are linearly dependent on the number of doubly allylic positions present in the molecule. Thus, the oxidizability of linoleate is 2.03×10−2 M−1/2 sec−1/2, and the value for docosahexaenoate is five times greater, 10.15×10−2 M−1/2 sec−1/2. The rate of autoxidation for all PUFA studied and for the mono‐ and diglyceride is proportional to the substrate concentration and to the square root of the rate of chain initiation, implying that the autoxidation of these compounds follows the usual kinetic rate law. The autoxidation of the triglyceride is more complex and does not appear to follow the same rate law at all substrate concentrations. This deviation from the usual kinetic rate expression may be due to lipid aggregation at low concentrations of the triglyceride.
Comparison of the clearances of serum chylomicron triglycerides enriched with eicosapentaenoic acid or oleic acid
Authors: Chen Isabel S. , Le Truc , Subramanian Satchithanandam , Cassidy Marie M. , Sheppard Alan J. , Vahouny George V.
Published: November 2006

Rat mesenteric lymph chylomicrons containing triglycerides enriched with either [14C]oleic acid (OA) or [14C]‐eicosapentaenoic acid (EPA) were prepared by ultracentrifugation of lymph samples collected for 6 hr after a single duodenal infusion of an emulsion containing either fatty acid. These chylomicrons were injected into the jugular vein of recipient rats and, at various time intervals, blood was drawn and serum was assayed for radioactivity. In separate animals, serum lipoprotein fractions were separated by ultracentrifugation, and the redistribution of labeled fatty acid among circulating lipoproteins was determined by liquid scintillation spectrometry. When the early disappearance rates (10 min) of either total serum radioactivity or specifically the chylomicron fraction were compared, there were no differences between the groups receiving OA‐or EPA‐enriched chylomicrons. However, disappearance rates of EPA‐enriched chylomicrons were slower than those of OA‐enriched chylomicrons from 25 to 90 min. The small but significant differences in the disappearance rates for the longer time periods cannot be ascertained without further studies. At 5 min after injection of either type of chylomicron, the d<1.006 g/ml lipoprotein fraction of serum chylomicrons and very low density lipoproteins contained almost 90% of the original radioactivity. By 240 min, when less than 2% of the radioactivity remained, this radioactivity in the d<1.006 g/ml fraction was 43–46%, with concomitant increases in the low and high density lipoprotein fractions and in the lipoprotein‐free serum.
Thermal and metal‐catalyzed decomposition of methyl linolenate hydroperoxides
Authors: Frankel E. N. , Neff W. E. , Selke E. , Brooks D. D.
Published: November 2006

Much work has been reported on the volatile oxidative products of fats and their impact on flavor deterioration, cellular damage and the decrease in safety of fatcontaining foods. However, relatively little information is available on the mechanism of hydroperoxide decomposition. Pure methyl linolenate hydroperoxides were decomposed thermally at 150 C and catalytically with ferric chloride‐ascorbic acid at room temperature. The volatile decomposition products were collected on porous polymer (Tenax) traps and concentrated by gel permeation chromatography. The total volatile products showed significant differences in composition by capillary gas chromatography‐mass spectrometry (GC‐MS). Thermal decomposition produced much more methyl octanoate (60.1%) and less 2,4‐heptadienal (0.5%) than catalytic decomposition (13.2 and 60.8%, respectively). The volatiles from the ferric chloride‐ascorbic acid system also contained unique products tentatively identified by GC‐MS as isomers of chloromethyl butene. These results may have important implications in evaluating precursors of flavor deterioration in vegetable oils containing linolenate and in understanding better the biological significance of lipid peroxidation.
Platelet‐activating factor modulates phospholipid acylation in human neutrophils
Authors: Tou Jen‐sie
Published: November 2006

The present study showed that platelet‐activating factor (1‐O‐hexadecyl‐2‐acetyl‐sn‐glycero‐3‐phosphocholine, PAF), but not lysoPAF (1‐O‐hexadecyl‐sn‐glycero‐3‐phosphocholine) rapidly (within 15 sec) stimulated the incorporation of both [1‐14C]arachidonate and [1‐14C]docosahexaenoate into phosphatidylinositol (PI) and phosphatidylcholine (PC) in human neutrophils. Concomitantly, it inhibited the formation of labeled phosphatidic acid from both fatty acids. The magnitude of stimulation (percentage of control) was greater in PI than in PC for the incorporation of arachidonate and vice versa for the incorporation of docosahexaenoate. It reached a maximum at 10−7 M and started to decline at 10−6 M. Extracellular Ca2+ was not essential for the action of PAF on phospholipid acylation. The distribution of labeled arachidonate in the molecular species of PC was not altered by PAF after 1 min incubation, suggesting that the increased formation of arachidonyl‐PC during the early stage of neutrophil‐PAF interaction was not originated from the added PAF. No measurable changes in the mass of each phospholipid were detected in neutrophils challenged by PAF from 15 sec to 2 min. The data suggest that the increased incorporated of extracellular fatty acids into PI and PC elicited by PAF may be secondary to increased deacylation of these phospholipids, and the magnitude of stimulation reflects the specificity of acyltransferase catalyzing the acylation of lysoPI and lysoPC by fatty acyl‐CoA.
High performance liquid chromatographic analysis of 1‐alkyl‐2‐acyl‐ and 1‐alkyl‐3‐acyl‐sn‐glycerols
Authors: Foglia Thomas A. , Vail P. D. , Iwama Takashi
Published: November 2006

A high performance liquid chromatographic (HPLC) method is described for separation and quantitation of 1‐alkyl‐3‐acyl‐ and 1‐alkyl‐2‐acyl‐sn‐glycerol, products of the detritylation reaction of 1‐alkyl‐2‐acyl‐3‐trityl‐sn‐glycerol. The alkyl glycerides were separated on a 25 cm×4.6 mm ID column packed with ∼5–6 μm silica and eluted isocratically with isooctane/isopropanol (98∶2, v/v) as mobile phase. The good separation and linear refractive index (RI) detector responses using cholesterol as an internal standard indicated the applicability of the method not only for the quantitative determination of the alkylglycerols but also for their semipreparative isolation. This HPLC method shows excellent reproducibility and accuracy and is applicable to other types of glycerides such as mono‐ and diacylglycerols.
The determination of steroids with and without natural electrophores by gas chromatography and electron‐capture detection
Authors: Poole C. F. , Zlatkis A. , Sye W. ‐F. , Singhawangcha S. , Morgan E. D.
Published: November 2006

The response of the electron‐capture detector to organic compounds is poorly defined, and the steroids are no exception to this observation. For those steroids which are naturally electron‐capturing, the structures of the electrophores will be defined. Other steroids can be made electron‐capturing by the formation of appropriate derivatives. Some new or infrequently used reagents for this purpose (flophemesyl ethers,t‐buflophemesyl ethers, pentafluorophenylhydrazone derivatives and halogensubstituted aromatic boronic acids) are described.