bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential uptake of cholesterol and plant sterols by rat erythrocytes in vitro
Authors: Child P. , Kuksis A. 
Published: December 2006

AbstractThe in vitro uptake of radioactively labeled cholesterol and the plant sterol β‐sitosterol has been examined in rat erythrocytes. From mixed micellar solutions containing egg yolk phospholipid and sodium taurocholate, the erythrocytes showed a nonlinear uptake of the two sterols. The uptake leveled off after about 45 min with the attainment of a 1∶1 total sterol‐to‐phospholipid ratio within the cell membrane, as determined on a mass basis. From soltuions containing egg yolk phospholipid, or purified egg yolk phosphatidylcholine, a preference for cholesterol over the plant sterol was observed, increasing with time from a cholesterol/β‐sitosterol uptake ratio of unity (the media ratio) to a maximum of 2 after a 60‐min incubation. Correction of the data for nonspecifically bound sterol increased the ratio to a maximum of 5 at the 30‐min time point. The increase in the cholesterol/β‐sitosterol uptake ratio with time, following an initial nonspecific association, showed that penetration of the plasma membrane by the sterol was required for the selectivity to be expressed. The presence of lysophosphatidylcholine or bovine serum albumin did not exert any noticeable influence over the extent of selectivity of absorption. Replacement of the egg yolk phospholipid with synthetic dipalmitoyl‐phosphatidylcholine led to a loss of the sterol selectivity. No evidence was found to support a selective extraction of sterol from the erythrocyte membrane to account for the observed effects, nor was there any sign of a mass accumulation of phospholipid during the incubation. It is suggested that the media phospholipid influences the membrane permeability toward cholesterol and β‐sitosterol.
Phospholipids ofRhizobium meliloti andAgrobacterium tumefaciens: Lack of effect of Ti plasmid
Authors: Thompson Emily A. , Kaufman Allan E. , Johnston Norah C. , Goldfine Howard 
Published: December 2006

AbstractWe have studied the phospholipid composition ofRhizobium meliloti strains which do or do not contain the large, tumor‐inducing (Ti) plasmid ofAgrobacterium tumefaciens. The major phospholipids of stationary phase cells were phosphatidylethanolamine (PE) (22%), phosphatidyl‐N‐methylethanolamine (22%), phosphatidylcholine (PC) (27%), phosphatidylglycerol (11.4%), and cardiolipin (11%); as average percent of lipid phosphorus. Phosphatidyl‐N,N‐dimethylethanolamine (3.7%) was also present. The proportions of PE were higher, and PC lower, in logarithmic phase cells. No significant differences were seen in the proportions of phospholipids in strains with or without the Ti plasmid. Qualitative examination of the phospholipids ofA. tumefaciens with or without the Ti plasmid similarly revealed no differences.
Biosynthesis of the novel fatty acid, 17‐methyl‐cis‐9,10‐methyleneoctadecanoic acid, by the parasitic protozoan,Herpetomonas megaseliae
Authors: Holz G. G. , Beach D. H. , Singh B. N. , Fish W. R. 
Published: December 2006

AbstractHerpetomonas megaseliae, a flagellate protozoan parasite of the gut of a dipteran,Megaselia scalaris, is shown by chromatographic, spectrometric and radiotracer methods to synthesize de novo aniso‐branched chain cyclopropane fatty acid, 17‐methyl‐cis‐9,10‐methyleneoctadecanoic acid.
A comparison of the oleaginous yeast,Candida curvata, grown on different carbon sources in continuous and batch culture
Authors: Evans Christopher T. , Ratledge Colin 
Published: December 2006

AbstractThe oleaginous yeast,Candida curvata D, was grown in both batch and continuous culture on 5 different carbon sources to compare the efficiency of fat production from the various substrates. Maximum lipid accumulation occurred in batch culture with xylose as the carbon source on nitrogenlimited medium reaching a level of 49% (w/w) of the biomass, but this was reduced to 37% at the optimum dilution rate (D=0.05/hr) in a chemostat. Both the highest biomass and lipid yields were attained in continuous culture with lactose as the sole carbon source at a dilution rate of D=0.04/hr, giving an efficiency of substrate conversion of 60 g of biomass and 18.6 g lipid per 100 g lactose utilized. The relative proportions of the major fatty acids (16∶0, 18∶0, 18∶1, 18∶2) in the lipid were found to vary considerably in batch culture and in continuous culture under carbon‐limited conditions. However, on nitrogen‐limited media in the chemostat, the fatty acid composition remained relatively constant over the whole range of dilution rates employed. Lipid from xylose‐grown cells contained the greatest percentage of stearic acid (18∶0) 15% and the lowest linoleic acid (18∶2) 4%, whereas lipid from ethanol‐grown cells contained elevated levels of oleic acid (18∶1) 51% and decreased palmitic acid (16∶0) 25%.
Biochemical activities during lipid accumulation inCandida curvata
Authors: Evans Christopher T. , Ratledge Colin 
Published: December 2006

AbstractIntracellular and extracellular concentrations of citrate and the specific activities of ten different enzymes inCandida curvata D were examined in relation to lipid biosynthesis in batch and continuous culture. Citrate was found to accumulate prior to lipid production and declined markedly as lipid accumulated in batch culture. The cells excreted citrate as the culture became nitrogen‐limiting after 30 hr of growth, but little more was expelled after 40 hr when lipid accumulation was more marked. In continuous culture, only low levels of citrate were detected at the lower dilution rates and citrate was completely absent from both the cells and medium above a dilution rate of 0.1/hr. The activity of malic enzyme, malate dehydrogenase and ATP:citrate lyase increased in batch culture on lipid accumulated, and, in continuous culture, both malic enzyme and ATP: citrate lyase varied in parallel with the specific rate of lipid synthesis which increased with increasing dilution rate. Activity of malate dehydrogenase, citrate synthase and glucose‐6‐phosphate dehydrogenase decrease with increasing dilution rate. The regulatory significance of these enzymes in lipid accumulation byC. curvata is discussed.
Effect of age on plasma bile acids and lipid components in the rat
Authors: Suzuki Hiramitsu , Hayakawa Seiichi , Tajima Makoto 
Published: December 2006

AbstractWith increasing age, total plasma bile acid contents increased in rats over a period of 11 months, and also total plasma cholesterol and carcass fat contents increased in the same manner. Plasma showing high bile acid levels at 11 months was found by means of high performance liquid chromatography to contain cholic acid as one of the major components, chenodeoxycholic acid and trace deoxycholic acid. These results suggest that there are close relationships between the plasma bile acids and age‐dependent changes of lipid components in the rat.
Lung lipid synthesis from acetoacetate and glucose in developing rats in vitro
Authors: Sheehan Patricia M. , Yeh Yu‐Yan 
Published: December 2006

AbstractAcetoacetate (AcAc) and glucose were compared as energy sources and as precursors for lipid synthesis in the lungs of developing rats. Minced lung tissue was incubated with [3‐14C]AcAc or [U‐14C]glucose and the oxidation of each substrate to CO2 or its incorporation into tissue lipids was quantified. The highest rates of oxidation were obtained during the first 5 days for AcAc and the first 2 days of life for glucose and oxidation of AcAc was 3–4 times greater than that of glucose at all ages. Throughout postnatal development, the rates of nonsaponifiable lipid, fatty acid and hence total lipid (chloroform/methanol extractable) synthesis from AcAc were 2–3 times those of glucose. The highest rates of total lipid synthesis from AcAc and glucose were observed at birth. Glucose was utilized for glyceride‐glycerol synthesis at a higher rate than AcAc. Similar patterns of incorporation of AcAc and glucose into various lipid classes were noted. Of the total lipids synthesized from AcAc and glucose, respectively, phospholipid plus monoglyceride accounted for 64% and 77%, triglyceride 13% and 13%, diglyceride plus cholesterol 11% and 4% fatty acids 9% and 4%, and cholesteryl esters 3% and 1%. At birth, the specific activities of all lipids except triglyceride derived from AcAc were greater than those from glucose. Rates of synthesis of all complex lipids declined with age. The results of these experiments demonstrate that AcAc is utilized more readily than glucose for energy production and lipid synthesis in developing rat lungs.
Asymmetric distribution of decanoate in triacylglycerol synthesized in vitro by mammary glands of lactating mice
Authors: Rao G. Ananda , Abraham S. 
Published: December 2006

AbstractSlices, prepared from the mammary glands of lactating mice, were incubated with either [1‐14C]acetate, [U‐14C]glucose, or [1‐14C]decanoate. From all 3 substrates, radioactivity in the synthesized lipids was found mainly in triacylglycerols (TG). When acetate or glucose served as substrate, decanoate (C10) accounted for 24% of the fatty acids in TG. Hydrolysis of the TG by pancreatic lipase yielded [14C] fatty acids which had relatively more C10 (38%) than did either of the other hydrolysis products mono‐ or diacylglycerol (14–17%). However, when TG produced by slices from C10 were hydrolyzed, the acid was found to be esterified equally at the C‐1, C‐2 and C‐3 of glycerol. Thus, when fatty acids are synthesized de novo and are converted to TG by gland slices, C10 is predominantly located in the C‐3 position, a finding in accord with the situation in milk TG, although such preferential incorporation does not occur when the free acid is presented to the tissue slices.
Distribution of antithrombin III and glucosylceramide in human plasma lipoproteins and lipoprotein deficient plasma
Authors: Chatterjee Subroto , Bell William R. , Kwiterovich Peter O. 
Published: December 2006

AbstractWe have investigated the distribution of antithrombin‐III and glucosylceramide (Glc‐Cer) in human plasma, plasma lipoproteins and lipoprotein‐deficient plasma. Antithrom bin III activity was measured employing immunochemical and biological assays. Glc‐Cer was quantified by gas liquid chromatography (GLC). Whole plasma contained 145 μg antithrombin III/ml plasma, all of which was associated with the lipoprotein‐deficient plasma (d>1.25 g/ml). Whereas, most if not all the plasma GlcCer was associated with plasma low density lipoproteins (LDL) (d‐1.022–1.055 g/ml) and high density lipoproteins (HDL) (d‐1.063–1.25). GlcCer was not found in the lipoprotein‐deficient plasma. We conclude that GlcCer on lipoproteins does not contribute to antithrombin III activity. Moreover, the absence of GlcCer in lipoprotein‐deficient plasma does not impair antithrombin‐III activity.
Microsomal phosphatidylethanolamine methyltransferase: Inhibition by S‐adenosylhomocysteine
Authors: Hoffman Dennis R. , Haning Judy A. , Cornatzer W. E. 
Published: December 2006

AbstractInhibition by S‐adenosylhomocysteine (AdoHcy) of the three reactions of phosphatidylethanolamine methyltransferase which catalyzes the production of phosphatidylcholine from phosphatidyl‐ethanolamine in guinea pig and rat liver microsomes has been evaluated. Five of the six methylation reactions in these two species exhibit greater affinity for inhibitor, AdoHcy, than for substrate, S‐adenosylmethionine (AdoMet). The Ki values for the rate‐limiting reactions were 3.8 μM and 68 μM in rat and guinea pig livers, respectively. An AdoMet:AdoHcy ratio of 12∶1 in developing liver was found to decline to a constant value in the adult of 5∶1. The concentration of AdoHcy in rat and guinea pig liver increases markedly following death of the animal. A concomitant decrease in the AdoMet level was observed in guinea pig liver. A comparison of phosphatidylethanolamine methyl‐transferase activity with the hepatic concentrations of AdoMet and AdoHcy in mouse, rat, rabbit and guinea pig is presented. Regulation of the methylation pathway is discussed.
Structure of biliary phosphatidylcholine in cholesterol gallstone patients
Authors: Cantafora A. , Angelico M. , Di Biase A. , Pièche U. , Bracci F. , Attili A. F. , Capocaccia L. 
Published: December 2006

AbstractThe fatty acid composition of biliary phosphatidylcholine was analyzed in 13 patients with radiolucent gallstones undergoing elective cholecystectomy, and in 11 normolipemic patients without gallstones undergoing abdominal surgery. The only difference in the percentage fatty acid composition between the two groups was a significantly (p<0.05) higher percentage arachidonic acid in the first group. This acid was exclusively located in thesn‐2 position of phosphatidylcholine (PC), accounting for 13.0±4.9% in the first group and 8.2±4.9% in the second (p<0.05). The percentage arachidonic acid of PC was negatively correlated (p<0.001) with the percentage biliary chenodeoxycholate in gallstone patients, but not in controls. Explanation of these findings is, at present, only speculative.
Utilization of polyunsaturated long‐chain alcohols byClostridium butyricum
Authors: Gilbertson J. R. , Crout R. J. , Gilbertson J. D. 
Published: December 2006

AbstractWhen a trace amount of linolenyl alcohol (cis,cis,cis‐9,12,15‐octadecatriene‐1‐ol) was added to the culture media ofClostridium butyricum, the polyunsaturated alcohol was readily assimilated. After an initial 18‐hr exposure interval, there was a large increase in the amount and a change in the composition of thelong‐chain alcohols present. However, this alteration was temporary. As the duration of the exposure interval increased, the alcohol content and composition of the treated bacteria returned toward control values. This return of the long‐chain alcohol composition toward control values was associated with an increase in the proportion of linolenic acid in the phospholipid fraction. The ether moiety of the alk‐1‐enyl phosphoglycerides was unchanged in amount or composition upon exposure to linolenyl alcohol.
Alkane contamination of lipids extracted fromLagenidium giganteum andLagenidium callinectes
Authors: Warner S. A. , Graham M. S. , Sovocool G. W. , Domnas A. J. 
Published: December 2006

AbstractAlkanes associated with the mycelia of the fungiLagenidium giganteum andL. callinectes were analyzed. Careful studies showed that these substances were contaminats derived from glass ware, media and solvents. No alkane biosynthesis or transformation was detected, indicating little or no alkane metabolism. The importance of using clean techniques, high‐purity solvents and proper media controls was emphasized.
Influence of vitamin E and nitrogen dioxide on lipid peroxidation in rat lung and liver microsomes
Authors: Sevanian Alex , Hacker Allen D. , Elsayed Nabil 
Published: December 2006

AbstractRat lung and liver microsomes were used to examine the effects of dietary vitamin E deficiency on membrane lipid peroxidation. Microsomes from vitamin‐E‐deficient rats displayed increased lipid peroxidation in comparison to microsomes from vitamin‐E‐supplemented controls. The extent of lipid peroxidation, as determined by measurement of thiobarbituric acid reacting materials, was enhanced by addition of reduced iron and ascorbate (or NADPH). Rats fed a vitamin‐E‐supplemented diet and exposed to 3 ppm NO2 for 7 days did not exhibit increases in microsomal lipid peroxidation compared to air‐breathing controls. However, increases were found in microsomes prepared from rats fed a vitamin‐E‐deficient diet and exposed to NO2. Lung microsomes from vitamin‐E‐fed rats contained almost 10 times as much vitamin E as liver microsomes when expressed in terms of polyunsaturated fatty acid content. The extent of lipid peroxidation was, in turn, considerably less in lung than in liver microsomes. Lipid peroxidation in lung microsomes from vitamin‐E‐deficient rats was comparable to liver microsomes from vitamin‐E‐supplemented rats as was the content of vitamin E in these respective microsomal samples. A combination of vitamin E deficiency and NO2 exposure resulted in the greatest increases in lung and liver microsomal lipid peroxidation with the largest relative increases occurring in lung microsomes. An inverse relationship was found between the extent of lipid peroxidation and vitamin E content. Most of the peroxidation in lung microsomes appeared to proceed nonenzymatically whereas peroxidation in liver was largely enzymatic. Vitamin E appears to be assimilated by the lung during oxidant inhalation, but with dietary vitamin E deprivation, the margin for protection in lung may be less than in liver.
Studies on the substrate specificity of purified human milk lipoprotein lipase
Authors: Wang C. ‐S. , Kuksis A. , Manganaro F. 
Published: December 2006

AbstractThe fatty acid specificity of purified human milk lipoprotein lipase was studied using the C18 to C54 (total acyl carbon number) saturated and the C54 mono‐, di‐ and triunsaturated monoacid triacylglycerols. Kinetic determinations indicated that the medium‐chain triacylglycerols were better substrates than long‐ or very short‐chain saturated triacylglycerols. The unsaturated triacylglycerols were hydrolyzed at rates comparable to that of tricaprylin with triolein having the highest rate of hydrolysis of the unsaturated species tested. The enzyme attacked the primary ester bond much more readily than the secondary ester bond. The purified human milk lipoprotein lipase showed a preferential stereospecific lipolysis of thesn‐1‐position of the triacylglycerol molecule.
Prostaglandin and acyl chain effects on glutamate dehydrogenase activity
Authors: Shafer Paul T. , Fiskin A. Max 
Published: December 2006

AbstractProstaglandins A1 (PGA1), A2, B1, B2, E1, E2, F1α, F2α, and 19 esterified natural fatty acids were tested as effectors of beef liver glutamate dehydrogenase (L‐glutamate: NAD(P)+, oxidoreductase [deaminating], EC 1.4.1.3). All prostaglandins tested are found to activate the enzyme initially, but only PGA2>PGB2≥PGA1 cause a subsequent time‐dependent loss (not inhibition) of NADH oxidation activity. Both PGA1 and PGA2 desensitize glutamate dehydrogenase to allosteric activation by ADP, whereas PGA2 and PGB2 desensitize to allosteric inactivation by GTP. Preincubation of enzyme with diethylstilbestrol prevents the initial activation by the PG. Of the methyl esters, only prostaglandin precursors inactivated the enzyme. Simultaneous desensitization to the ADP and GTP allosteric effects resulted. Multiple esterification to glycerol or phospholipids enhanced the action of linoleoyl and diminished the action of linolenoyl chains. Preincubation of the PGA with glutathione or cysteine prevents the inactivation; i.e., the sulfhydryl binding region of the prostaglandin must be free for enzyme to be inactivated. Sulfhydryl reagents also protect the enzyme from the effects of the unsaturated acyl chains, and pHMB mimics acyl protection against GTP allosteric inactivation. Where the lipid effector is active against sulfhydryl groups, the desensitizations to the ADP and GTP allosteric effectors are reciprocal. The initial activation, subsequent inactivation and desensitization to ADP and GTP are all characteristic of binding in the estrogen‐specific effector site, suggesting this site as the target for PG and acyl action. In the PGA2 activation, the effect is found to be amplified by the cooperativity of the enzyme at 1 PG molecule/6 molecules of GDH. We conclude from the action of the PG and structural analogs that the initial activation of glutamate dehydrogenase is caused by α,β‐unsaturated monoketo cyclopental structures. GTP inhibition is blocked primarily by diketo structures which eventually inactivate the enzyme. ADP activation is blocked by sulfhydryl binding of the unsaturated cyclopental keto structure of the PG. Appearance of a 270 nm absorbance simultaneous to the acyl effects on the enzyme suggests that conjugated unsaturations are responsible for the precursor's qualitatively similar action to that of the PG.
Analysis of autoxidized fats by gas chromatography‐mass spectrometry: VII. Volatile thermal decomposition products of pure hydroperoxides from autoxidized and photosensitized oxidized methyl oleate, linoleate and linolenate
Authors: Frankel Edwin N. , Neff William E. , Selke Edward 
Published: December 2006

AbstractTo clarify the sources of undesirable flavors, pure hydroperoxides from autoxidized and photosensitized oxidized fatty esters were thermally decomposed in the injector port of a gas chromatograph‐mass spectrometer system. Major volatile products were identified from the hydroperoxides of methyl oleate, linoleate and linolenate. Although the hydroperoxides from autoxidized esters are isomerically different in position and concentration than those from photosensitized oxidized esters, the same major volatile products were formed but in different relative amounts. Distinguishing volatiles were, however, produced from each type of hydroperoxide. The 9‐ and 10‐hydroperoxides of photosensitized oxidized methyl oleate were thermally isomerized in the injector port into a mixture of 8‐, 9‐, 10‐ and 11‐hydroperoxides similar to that of autoxidized methyl oleate. Under the same conditions, the hydroperoxides from autoxidized linoleate and linolenate did not undergo significant interconversion with those from the corresponding photosensitized oxidized esters. The compositions of the major volatile decomposition products are explained by the classical scheme involving carboncarbon scission on either side of alkoxy radical intermediates. Secondary reactions of hydroperoxides are also postulated, and the hydroperoxy cyclic peroxides from methyl linoleate (photosensitized oxidized) and methyl linolenate (both autoxidized and photosensitized oxidized) are suggested as important precursors of volatiles.
Effect of 2‐hexadecynoic acid on cultured 7288C hepatoma cells
Authors: Upreti Girish C. , Matocha Martha , Wood Randall 
Published: December 2006

AbstractThe effects of 2‐hexadecynoic acid on the growth and lipid metabolism of cultured 7288 (HTC) cells have been evaluated. Growth was inhibited by the acetylenic acid: the LD50 was 35–85 μM as determined by two methods at low and high cell densities. Reduced growth did not result from damaged plasma membranes as determined by α‐amino isobutyrate leakage. DNA synthesis was unaffected by the acetylenic acid and the effect on RNA and protein synthesis appeared to be secondary to the effects on lipid metabolism. The 2‐hexadecynoic acid inhibited lipid metabolism of the HTC cells at least at two levels. Data from both mass studies and radioactive acetate distributions in cellular and media lipids indicated that fatty acid elongation and acylation, especially triglyceride synthesis, were inhibited.