bluuebunny/crossref_metadata_2025_split huggingface dataset:
Instability of malondialdehyde in the presence of H2O2: Implications for the thiobarbituric acid test
Authors: Kostka Peter , Kwan Chiu‐Yin 
Published: December 2006

AbstractThe content of thiobarbituric acid‐reactive material (primarily malondialdehyde) is frequently used to estimate the extent of lipid peroxide formation. How‐ever, malondialdehyde is unstable in the presence of millimolar concentrations of hydrogen peroxide. This observation considerably limits the applicability of the thiobarbituric acid test, as hydrogen peroxide is known to be formed in a number of lipid peroxidation‐promoting systems. The instability of malondialdehyde in the presence of hydrogen peroxide seems to account for the inconsistent outcomes in studies relating the manipulations of intermediate H2O2 levels to the initiation of lipid peroxidation.
Essential and nonessential fatty acid oxidation in mice bearing Ehrlich ascites carcinoma
Authors: Ookhtens Murad , Baker Nome 
Published: December 2006

AbstractWe tested the hypothesis that mobilized (essential) free fatty acids (FFA) are spared from oxidation in cancer‐bearing animals. We injected tracers [1‐14C]linoleate, [1‐14C] palmitate and NaH14CO3 intravenously as single rapid doses in separate groups of mice bearing Ehrlich ascites tumor (EAT) and controls, and measured breath14CO2. The data from NaH14CO3 injections were used to develop kinetic, compartmental models of the HCO3−‐CO2 systems. These models were integrated with our earlier model of plasma FFA turnover for control and EAT‐bearing mice. The integrated multicompartmental models were then fitted to breath14CO2 data from mice injected with tracer FFA to compute the rates of FFA oxidation. FFA were not spared from an oxidative fate in our cancer‐bearing vs normal animals; moreover, essential FFA were not preferentially spared from oxidation compared to nonessential FFA in the cancer‐bearing mice.
Hydroperoxides formed by ferrous ion‐catalyzed oxidation of methyl linolenate
Authors: Toyoda I. , Terao J. , Matsushita S. 
Published: December 2006

AbstractAn emulsion of methyl linolenate was allowed to oxidize with a catalyst of ferrous sulfate and ascorbic acid. Three oxidation products were isolated, and their hydrogenated derivatives were characterized as the isomeric mixture of methyl monohydroxyoctadecanoate (monoOH), methyl 9,16‐dihydroxyoctadecanoate (diOH), and the isomeric mixture of methyl trihydroxyoctadecanoate (triOH). The monoOH isomers and diOH apparently were derived from methyl monohydroperoxyoctadecatrienoate (monoHPO) and methyl dihydroperoxyoctadecatrienoate (diHPO), respectively. Two triOH isomers (the 9,10,12‐ and 13,15,16‐isomers) were thought to be derived from the products containing cyclic peroxide‐hydroperoxide structure. 9,16‐diHPO was produced by the incubation of monoHPO with ferrous sulfate and ascorbic acid. Moreover, the experiment using18O2 demonstrated that mono‐HPO yielded 9,16‐diHPO by reacting with oxygen molecule. 9,10,13‐ and/or 9,12,13‐ and 12,13,16‐ and/or 12,15,16‐triOH isomers were also detected in the hydrogenated derivatives of oxidation products from monoHPO.
Herbal remedies of the maritime Indians: Sterols and triterpenes ofTanacetum vulgare L. (Tansy)
Authors: Chandler R. F. , Hooper S. N. , Hooper D. L. , Jamieson W. D. , Lewis E. 
Published: December 2006

AbstractPlant sterols and triterpenes exhibit a wide range of pharmacological activities. As part of our ongoing studies of the medicinal aspects of Maritime flora, particularly the herbal remedies of the Micmac and Malecite Indians, we determined the nature of the sterols and triterpenes ofTanacetum vulgare L. (Compositae)—a widely used herbal remedy usually referred to as tansy. By using thin layer and gas chromatographics, nuclear magnetic resonance (NMR) spectroscopy and combined gas chromatography‐mass spectrometry, we were able to identify β‐sitosterol as the major sterol and α‐amyrin as the major triterpene of tansy. We also identified the sterols stigmasterol, campesterol and cholesterol, and the triterpenes β‐amyrin and taraxasterol. A fourth triterpene was tentatively identified as pseudo‐taraxasterol. The successful therapeutic application of this herb may be due partly to the presence of one or more of these compounds. The sterols and triterpenes of tansy have not been previously reported; neither, to our knowledge, have the NMR spectra of the amyrins and the NMR and mass spectra of taraxasterol.
Tissue fatty acid changes and tumor incidence in C3H mice ingesting cottonseed oil
Authors: Tinsley Ian J. , Wilson Glenn , Lowry Robert R. 
Published: December 2006

AbstractThe incidence of spontaneous mammary tumors in C3H mice at 35 wk was higher in mice fed rations containing cottonseed oil than in mice fed fats of comparable fatty acid composition. The time to 50% (T50) incidence was also shorter in the first group. The fatty acid composition of tissue lipids from mice fed the cottonseed oil showed changes indicating the presence of cyclopropene fatty acids‐higher levels of saturates and lower oleate/stearate and palmitoleate/palmitate ratios. A possible association between the development of a spontaneous mammary tumor in the C3H mouse and the presence of cyclopropene fatty acids in the cottonseed oil is indicated.
Sedimentation equilibrium of human low density lipoprotein subfractions
Authors: Kahlon Talwinder S. , Adamson Gerald L. , Shen Mason M. S. , Lindgren Frank T. 
Published: December 2006

AbstractThe molecular weights of low density lipoprotein (LDL) subfractions were determined precisely by meniscus depletion sedimentation equilibrium. Equilibrium speeds ranged from 9743 to 5896 rpm. The average molecular weights of various LDL subfractions of Sfo values 9.49, 7.94, 6.42, 5.17, and 3.71 determined by sedimentation equilibrium were 2.97×106; 3.13×106; 2.89×106; 2.45 ×106; and 2.61×106 daltons, respectively; and their respective densities were 1.0267, 1.0306, 1.0358, 1.0422, and 1.0492 g/ml. Minimal hydrated molecular weights for these fractions determined by flotation velocity at 37,020 rpm were 2.57×106; 2.37×106; 2.09×106; 1.94×106; and 1.81 ×106 daltons; whereas similar molecular weights determined at 52,640 rpm were 2.53×106; 2.27 ×106; 1.99×106; 1.86×106; and 1.74×106 daltons for the respective LDL subfractions. Higher molecular weights of fractions 2 and 5 compared to their adjacent fractions 1 and 4 by sedimentation equilibrium are of great interest. The calculated frictional ratio f/fo from sedimentation equilibrium and flotation velocity data ranges from 1.10 to 1.31, suggesting complexity and asymmetry of LDL subfraction molecules. There is also evidence that compressibility of LDL molecules may be different than that for the salt solution under high g‐force. Assuming that redistributed LDL molecules at equilibrium under low g‐force are spherical, it is possible that the shape of LDL molecules undergoing flotation velocity determinations may be distorted in high g‐force conditions. Such distortion may be consistent with the high f/fo values obtained and may also be a basis for structural rearrangement and/or lipoprotein degradation with prolonged preparative ultracentrifugation at high g‐force and pressure.
Copper(II)‐catalyzed lipid peroxidation in liposomes and erythrocyte membranes
Authors: Chan Phillip C. , Peller Owen G. , Kesner Leo 
Published: December 2006

AbstractCu++ was uniquely capable of catalyzing the peroxidation of rat erythrocyte membrane lipid in the presence of 10 mM H2O2, whereas several other transition metal ions were without significant effect. In contrast, peroxidation of soybean phospholipid liposomes could be catalyzed with decreasing efficiency by Co++, Cu++, Pb++, or Cr+++ also in the presence of H2O2. The effect of imidazole on Cu++‐catalyzed lipid peroxidation was stimulatory in liposomes and inhibitory in membrane preparations, whereas EDTA, histidine, citrate and alanine inhibited peroxidation in both systems. EDTA could stop the peroxidation after initiation, but catalase could not, indicating that Cu++ alone was necessary for the propagation of the chain reaction. Competitive inhibition studies with various scavengers of hydroxyl radicals or singlet oxygen and the absence of significant reaction enhancement by D2O indicated that neither of these reactive oxygen species was a major mediator in the Cu++‐H2O2 oxidative system. A copper‐oxygen complex may be directly involved in the initiation of peroxidation. Normal erythrocyte membranes and phospholipid liposomes also differ in their sensitivities toward external oxidative stress. In the absence of H2O2, Cu++ (0.2 mM) was capable of catalyzing lipid peroxidation in liposomes, aged erythrocyte membranes and membranes from vitamin‐E‐deficient rats; however, freshly prepared membranes from control rats and liposomes containing α‐tocopherol required H2O2 greater than 2 mM for the catalytic effect of Cu++ to be observed.
Interaction of discoidal complexes of dimyristoyl phosphatidylcholine‐cholesterol‐apolipoprotein A‐I with human plasma high density lipoprotein HDL3
Authors: Jackson Richard L. , Cardin Alan D. , Barnhart Roger L. , Ashraf Muhammad , Johnson J. David 
Published: December 2006

AbstractThe interaction of human plasma high density lipoproteins (HDL3) with discoidal complexes of apolipoprotein A‐I (apoA‐I) and dimyristoyl phosphatidylcholine (DMPC) containing 0, 10, 20 or 30 mol % cholesterol was investigated. Discoidal complexes containing various amounts of cholesterol were prepared by incubating apoA‐I and DMPC‐cholesterol liposomes for 12 hr at 25 C; the protein‐lipid complexes were isolated by gel filtration chromatography on Bio‐Gel A15m. Increasing the cholesterol content from 0 to 30 mol % caused a decrease in the fluidity of the discoidal complexes as determined by fluorescence polarization with 1,6‐diphenyl‐1,3,5‐hexatriene; a reduced phase‐transition amplitude; a decrease in the ratio of apoA‐I to DMPC; and an increase in the width of the discoidal complexes as determined by electron microscopy after negative staining. Incubation of the apoA‐I‐lipid complexes with HDL3 resulted in a complete breakdown of the discoidal structures and a transfer of DMPC and cholesterol to HDL3. As a result of lipid transfer, there was an increase in the size of HDL3. These in vitro results may be of significance as they relate to the interconversion of HDL subfractions during lipoprotein‐lipase‐induced lipolysis of triglyceride‐rich lipoproteins.
Tissue culture of cocoa beans (Theobroma cacao L.): Incorporation of acetate and laurate into lipids of cultured cells
Authors: Tsai C. H. , Kinsella J. E. 
Published: December 2006

AbstractSuspension cultures of cocoa bean tissue readily incorporated exogenous acetate into lipids. The distribution of radioactivity from acetate in individual lipid classes after 48 hr was 20, 5, 1, 15, 25, and 35% in triglycerides, diglycerides, free fatty acids, sterol esters, sterols and polar lipids, respectively. The labeled acetate was rapidly incorporated into various fatty acids within 2 hr. The [1‐14C] saturated fatty acids declined slightly after 4 hr, whereas [1‐14C] oleate declined significantly after 2 hr. There was a concomitant increase in [1‐14C] linoleate. The radioactivity associated with linolenate was relatively high up to 4 hr, declined by 24 hr, and then increased again. The kinetics of fatty acid labeling suggested that biosynthesis of linolenic acid in cocoa bean suspension culture may occur via the desaturation of linoleic acid and the chain elongation of dodecatrienoic acid. The patterns of fatty acid radiolabeling following incubation of cells with [1‐14C] laurate was consistent with this mechanism.
Stearoyl‐coenzyme a desaturase activity in the mammary gland and liver of lactating rats
Authors: Calabro Michael A. , Prasad M. Renuka , Wakil Salih J. , Joshi Vasudev C. 
Published: December 2006

AbstractStearoyl‐CoA desaturase activity in microsomes from lactating rat mammary gland is very low (0.05–0.15 nmol/min/mg of protein) regardless of lactating time. In such microsomes, reductase activities and content of cytochrome b5 are several‐fold lower than in normal rat liver microsomes. Preincubation of the mammary microsomes with purified terminal desaturase gives a 55‐fold stimulation of stearoyl‐CoA desaturase activity, whereas preincubation with cytochrome b5 has no effect. However, preincubation of mammary microsomes with both cytochrome b5 and terminal desaturase results in a 200‐fold stimulation of overall desaturation. These observations suggest that negligible stearoyl‐CoA desaturase activity in lactating rat mammary microsomes is due to a low cytochrome b5 content and the absence of terminal enzyme. The hepatic stearoyl‐CoA desaturase activity increases 9‐fold during lactation. There is little or no change in the NADH‐cytochrome c reductase activity or in the concentration of cytochrome b5 during this period, but the activity of the terminal desaturase increases with the increase of overall desaturation. These results suggest that liver is one of the more important sources of oleic acid for milk triglycerides.
Autoxidation of phosphatidylcholine liposomes
Authors: Wu Guey‐Shuang , Stein Robert A. , Mead James F. 
Published: December 2006

AbstractAutoxidation of pure soybean phosphatidylcholine liposomes at 40 C was found to proceed without an observed induction period, but otherwise, the rates of disappearance of the linoleic acid (70% of total) and linolenic acid (6% of total) followed typical autocatalytic kinetics. Incorporation of 0.05 mol % of tocopherol into the liposomes produced an induction period of about 7 hr under the condition used for the incubation. The produts formed from the autoxidation of pure soybean phosphatidylcholine liposomes were mostly 9‐ and 13‐hydroperoxyoctadecadienoates (isolated as hydroxy esters). The yield of hydroperoxides withcis,trans configuration was about the same as those withtrans,trans configuration throughout incubation period. After extensive autoxidation, a large quantity of trihy droxyoctadecenoate was also produced. When a large quantity of dipalmitoyl phosphatidylcholine was incorporated into soybean phosphatidylcholine liposomes, the rate of autoxidation decreased and was found to conform to apparent first‐order kinetics. In this system, the yield oftrans, trans hydroperoxides was much greater than that ofcis,trans isomers at all stages of autoxidation. Late in the autoxidation of the mixed liposomes, both trihydroxyoctadecenoate and hydroxyepoxyoctadecenoate were produced in substantial quantities.
Development of the diurnal rhythm of chick 3‐hydroxy‐3‐methylglutaryl‐CoA reductase
Authors: Ramirez H. , Alejandre M. J. , Garcia‐Peregrin E. 
Published: December 2006

AbstractChick liver and intestine 3‐hydroxy‐3‐methylglutaryl‐CoA reductase did not show diurnal rhythm at hatching. Differences in activity between light and dark periods appeared during the first week and remained more or less constant between 10–14 days after hatching. Hepatic and intestinal reductase activities were maximal during the light period and minimal during the dark period. Amplitude of the rhythm was practically similar in both tissues (about 3‐fold) although specific activities and differences between peak and nadir values were always higher in liver. Chick brain reductase did not show significant diurnal variations in the age range assayed.
Positional distribution of fatty acids in triglycerides from milk of several species of mammals
Authors: Parodi Peter W. 
Published: December 2006

AbstractMilk triglycerides from the echidna, koala, Tammar wallaby, guinea pig, dog, cat, Weddell seal, horse, pig and cow were subjected to fatty acid and stereospecific analysis to determine the positional distribution of the fatty acids in the triglycerides. The samples presented a wide range of fatty acids, most of which varied in content among species. The compositions of the acids at the 3 positions also varied among species, reflecting the content of these acids in the triglycerides. However, there was a general similarity in fatty acid positional distribution patterns for all the species with the exception of the echidna. The echidna exhibited a completely different fatty acid positional distribution pattern. The saturated acids were preferentially esterified at thesn‐1‐position whereas the unsaturated acids were selectively esterified at thesn‐2‐position. The triglyceride carbon number distribution of milk from the above species (with the exception of the Weddell seal) was determined by gas liquid chromatography and compared to that predicted by the 1‐random‐2‐random‐3‐random fatty acid distribution hypothesis. Agreement was excellent between observed and predicted composition for echidna, koala, Tammar wallaby, guinea pig and pig milk, and agreement was reasonable for dog, cat, horse and cow milk. Results are discussed in relation to biochemical mechanisms.
Digitonide precipitable sterols: A reevaluation with special attention to lanosterol
Authors: Cenedella Richard J. 
Published: December 2006

AbstractThe ability of digitonin to precipitate lanosterol from prepared mixtures and biological sources was evaluated. Commercially available lanosterol was determined to be composed of about 60% lanosterol and 40% dihydrolanosterol. Both sterols were only partially precipitated by digitonin under all conditions examined. The presence of cholesterol increased the precipitation of lanosterol, but never to completion. About 40% of the lanosterols from saponified sheep's‐wool fat was not precipitated by digitonin. Also14C‐labeled lanosterol recovered from rat brain following intracerebral injection of 2‐[14C] mevalonate was only 70% precipitated by digitonin. Steric hinderance by the methyl groups at carbon −4 is suggested to explain the poor precipitability of this sterol. In conclusion, lanosterol can not be considered to be a digitonide‐precipitable sterol equivalent to cholesterol. Caution should be exercised in situations where digitonin‐precipitable sterols are being prepared from sources containing significant concentrations of lanosterol (i.e., mass and/or radiolabel).
Determination of cholesteryl esters and of cholesteryl and epicholesteryl silyl ethers by capillary gas chromatography
Authors: Smith Norman B. 
Published: December 2006

AbstractThe capillary gas chromatography of cholesteryl esters after splitless injection into a 25‐m, OV‐1‐coated, fused silica WCOT column and a 7‐m Silar 10C‐coated glass WCOT column is reported. The nonpolar OV‐1 column separated the cholesteryl esters principally on the basis of carbon number, but separation of the saturated esters from the unsaturated esters was also achieved. The polar Silar 10C column separated the esters mainly according to the degree of unsaturation. Thus, the 2 column types complement each other in the analysis of nanogram quantities of cholesteryl esters from small samples, such as those from plasma or single arterial atherosclerosis lesions. This technique therefore obviates some of the difficulties of analyzing such cholesteryl ester samples in the form of methyl esters (incomplete transmethylation, and contamination by solvent impurities and/or plasticizer esters). Both columns were also found to be useful for the separation and quantitaiton of thet‐BDMS ethers of cholesterol and epicholesterol in mixtures containing various proportions of these epimers.
Saturated fatty acids >C20 are not activated by acid:CoA ligase in rat brain or liver?
Authors: Murphy Mary G. , Spence Matthew W. 
Published: December 2006

AbstractThe formation of long‐chain saturated acyl‐[3H]CoA and [1‐14C] acyl‐[3H]CoA by rat brain microsomes and rat liver was examined. Acyl‐CoA formation was markedly decreased as fatty‐acid chain length increased from C16 to C20. No biosynthesis of behenyl‐[3H] CoA or [1‐14C] lignoceryl‐[3H] CoA was observed. The results suggest that long‐chain saturated fatty acids >20 carbons in length are not activated by acid:CoA ligase to form acyl‐CoA.
ω‐ and (ω‐1)‐hydroxylation of 1‐dodecanol by frog liver microsomes
Authors: Miura Yoshiro 
Published: December 2006

AbstractFrog liver microsomes catalyzed the hydroxylation of 1‐dodecanol into the corresponding ω‐ and (ω‐1)‐hydroxy derivatives. The hydroxylation rate for 1‐dodecanol was much lower than that for lauric acid. Both NADPH and O2 were required for hydroxylation activity. NADH had no effect on the hydroxylation. The hydroxylating system was inhibited 49% by CO at a CO∶O2 ratio of 4.0. The formation of ω‐hydroxydodecanol was more sharply inhibited by CO than was the formation of (ω‐1)‐hydroxydodecanol, implying that more than one cytochrome P‐450 was involved in the hydroxylation of 1‐dodecanol and that CO has a higher affinity for the P‐450 catalyzing the ω‐hydroxylation. The formation of laurate during the incubation of 1‐dodecanol with frog liver microsomes suggests that a fatty alcohol oxidation system is also present in the microsomes. NAD+ was the most effective cofactor for the oxidation of 1‐dodecanol and NADP+ had a little effect. Pyrazole (an inhibitor of alcohol dehydrogenase) had a slight inhibitory effect on the oxidation and sodium azide (an inhibitor of catalase) had no effect.
Desaturation of endogenous and exogenous palmitate in lung tissue in vitro
Authors: Balint John A. , Kyriakides Emilios C. , Beeler Donald A. 
Published: December 2006

AbstractLung slices from rats fed a fat‐free diet supplemented with safflower oil (control) or tripalmitoyl‐glycerol (essential fatty acid [EFA]‐deficient) were incubated with [14C] acetate, [14C] palmitate, or [14C] stearate. Of the14C recovered in phospholipids after incubation with [14C] acetate, more than 87% was in 16‐carbon fatty acids. Desaturation, as assayed by the percentage of radioactivity in monoenoates in phospholipid fatty acids, was generally double in EFA‐deficient slices compared to control slices, regardless of substrate. Desaturation was significantly greater in slices incubated with acetate or octanoate compared to palmitate, indicating that endogenously synthesized palmitate was desaturated more actively than that derived from an exogenous source.
Zinc deficiency increases the rate of Δ6 desaturation of linoleic acid in rat mammary tissue
Authors: Cunnane S. C. , Wahle K. W. J. 
Published: December 2006

AbstractThe effect of zinc deficiency on the Δ6‐desaturation of [1‐14C] linoleic acid was studied in mammary tissue microsomes from lactating rats. The rats were maintained on zinc‐adequate (20 ppm zinc) or zinc‐deficient (10 ppm zinc changing to 0.5 ppm zinc during last trimester) diets throughout gestation and for the first 3 days of lactation. Mammary tissue microsomes were incubated with [1‐14C] linoleic acid and other samples of mammary tissue, mammary milk and the milk in the stomachs of the pups were analyzed for total fatty acid composition. In mammary microsomes from zinc‐deficient rats, Δ6‐desaturation of linoleic acid was 3.4 times greater than in microsomes from zinc‐adequate rats. This change in metabolism of linoleic acid was reflected by comparable changes in the relative tissue and milk composition of linoleic and arachidonic acids and in the ratios of palmitic to palmitoleic acid, stearic to oleic acid and linoleic and arachidonic acid.
Anatomical distribution of sterols in oysters (Crassostrea gigas)
Authors: Gordon Dennis T. , Collins Nancy 
Published: December 2006

AbstractOysters (Crassostrea gigas) contain at least 8 predominant sterols as determined by gas liquid chromatography and a modified Liebermann‐Burchard reaction. These sterols and the average amount found in mg/100 are: C26‐sterol (22‐trans‐24‐norcholesta‐5, 22‐diene‐3β‐ol), 19.1; 22‐dehydrocholesterol, 15.1; cholesterol, 46.8; brassicasterol, 27.2; Δ5,7‐sterols (i.e., 7‐dehydrocholesterol) 22.5; 24‐methylenecholesterol 29.1; 24‐ethylcholesta‐5,22‐diene‐3β‐ol, 1.2; and 24‐ethylcholesta‐5‐en‐3β‐ol, 12.7. The distribution of these sterols appears uniform (r2=0.938) between 5 major organs of the oyster. The percent body mass vs percent total sterols in these 5 organs are: mantle 44.1–41.4; visceral mass 30.3–36.7; gills 13.2–11.7; adductor muscle 8.3–3.7; and labial palps 4.2–6.5. The possible sources of these sterols are discussed.