bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake of fatty acids by the developing rat brain
Authors: Anderson Gregory J. , Connor William E.
Published: November 2006

Polyunsaturated fatty acids are avidly taken up by the developing rat brain. To explore the specificity of this process, [1‐14C]labeled 16∶0, 18∶2n−6, 18∶3n−3, and 22∶6n−3 each were co‐injected with [3H]18∶1n−9 into the jugular vein of two‐wk‐old functionally hepatectomized and shamoperated control rats. The radioactivities present in the brain, liver and serum were assessed 30 min after injection. Uptake of labeled fatty acids into brain lipids steadily increased with increasing degree of unsaturation, with more than twice as much uptake of 22∶6n−3 compared to 16∶0. Phosphatidylcholine was the principal radioactive species in the brain except for animals injected with [1‐14C]22∶6n−3, in which more of the label was incorporated into phosphatidylethanolamine. Determination of watersoluble oxidation products in the brain and serum revealed that the greater uptake of the more unsatrated fatty acids did not result from differences in rates of degradation.
Mevalonate 5‐pyrophosphate decarboxylase in isolated villus and crypt cells of chick intestine
Authors: Iglesias J. , Gonzalez‐Pacanowska D. , Caamaño G. , Garcia‐Peregrin E.
Published: November 2006

Mevalonate 5‐pyrophosphate decarboxylase was studied in isolated enterocytes obtained from duodenal, jejunal and ileal villi and crypts. In our assay conditions, decarboxylase activity was linear for 60 min and up to 0.3 mg of protein. The subcellular location of decarboxylase in chick enterocytes was investigated. About 94% of the total activity was recovered in the cytosol. The distribution of enzyme activity in epithelial cells also was studied. Maximal specific activity was found in cell fractions from jejunum followed by ileum and duodenum. About 80% of total activity was recovered in the villus cells, indicating an active role of these cells in cholesterogenesis. Ileal cells showed the highest cholesterol content. In all the intestinal epithelial cells assayed, free cholesterol represented about 95% of the total cholesterol.
Analysis of autoxidized fats by gas chromatography‐mass spectrometry: X. Volatile thermal decomposition products of methyl linolenate dimers
Authors: Frankel E. N. , Neff W. E. , Selke E. , Brooks D. D.
Published: November 2006

High‐molecular weight compounds previously were found to be important secondary products from autoxidation of polyunsaturated fatty esters. The contribution of dimers to oxidative deterioration was investigated by analyzing their volatile thermal decomposition products by capillary gas chromatography‐mass spectrometry. Dimers were isolated by gel permeation chromatography from autoxidized linolenate and from the corresponding monohydroperoxides, cyclic peroxides and dihydroperoxides. Major volatile decomposition products identified from these oxidative dimers were similar to those formed from the corresponding monomeric hydroperoxides. However, dimers from linolenate hydroperoxides produced more propanal and methyl 9‐oxononanoate than the corresponding monomers but less methyl octanoate and much less or no 2,4‐heptadienal and 2,4,7‐decatrienal. Significant differences in minor volatile products also were observed between dimeric and monomeric products of methyl linolenate oxidation compounds. Mechanisms are suggested for the formation of volatile decomposition products from different dimeric structures. These dimers are believed to be important sources of volatile compounds contributing to flavor and oxidative deterioration of fats.
The influence of n‐6 and n‐3 fatty acids on kidney phospholipid composition and on eicosanoid production in aging rats
Authors: Barcelli Uno O. , Beach Dorothy C. , Pollak Victor E.
Published: November 2006

Changes in eicosanoid production may contribute to some of the complications of the aging process such as atherosclerosis and glomerular sclerosis. Polyunsaturated fatty acids of the n‐6 and n‐3 series are precursors of eicosanoids. We fed diets containing safflower oil as a source of n‐6 fatty acids, fish oil as a source of n‐3 fatty acids or beef tallow as a source of saturated fats to three groups of normal rats from 2–18 months of age. We demonstrated incorporation of the n‐3 fatty acids, 20:5n‐3 and 22:6n‐3 into kidney phospholipids. Feeding of the diet containing n‐3 fatty acids was associated with a markedly decreased giomerular production of PGE, 6‐keto‐PGF1α and TXB2. It also decreased the aortic production of 6‐keto‐PGF1α and platelet production of TXB2. No significant effect of n‐6 fatty acids on dienoic eicosanoid production was observed. There were no adverse effects on kidney function as measured by urinary protein excretion and serum creatinine levels or on renal morphology by any diet. A diet enriched in n‐3 fatty acids for 18 months remains effective in decreasing dienoic eicosanoids in the aging rat.
Relative inhibitory potencies of flavonoids on 12‐lipoxygenase of fish gill
Authors: Hsieh R. J. , German J. B. , Kinsella J. E.
Published: November 2006

The relative efficacy of 10 flavonoid compounds and some common antioxidants in inhibiting 12‐lipoxygenase of fish gill was determined. Lipoxygenase activity was measured by oxygen consumption with polarography and formation of hydroxy fatty acid using thin layer chromatography with autoradiography. Generally, the inhibition of 12‐lipoxygenase by flavonoids was noncompetitive. The lipoxygenase product pattern did not change in the presence of flavonoids. Fisetin (3,3′,4′,7‐tetrahydroxyflavone) and quercetin (3,3′,4′,5,7‐pentahydroxyflavone) were the most potent inhibitors of 12‐lipoxygenase, with IC50's of 0.25 and 0.4 μM respectively. These were compared with IC50's values of 5, 1000 μM for BHA (t‐butylhydroxyanisole) and BHT (t‐butylhydroxytoluene) respectively. Possible inhibitory mechanisms and relationships between flavonoid structure and inhibitory potencies are discussed.
Inhibition of cytochrome c oxidase and hemolysis caused by lysosphingolipids
Authors: Igisu Hideki , Hamasaki Naotaka , Ito Akio , Ou Weija
Published: November 2006

Galactosylsphingosine, glucosylsphingosine and sphingosine all inhibited cytochrome c oxidase activity in mitochondria from rat liver; more than 50% inhibition was caused by 5 μM lipid (0.1 μmol/mg mitochondrial protein). However, these lysosphingolipids did not suppress the activity of purified cytochrome c oxidase. When the enzyme was “reconstituted” with phosphatidylcholine, the lysosphingolipids clearly inhibited the activity. On the other hand, galactosylsphingosine, glucosylsphingosine and sphingosine all hemolyzed erythrocytes, indicating that lysosphingolipids can disrupt the membrane. Thus, it appears that the inhibition of cytochrome c oxidase, a membrane‐bound enzyme in mitochondria, is due to perturbation of the environment of the enzyme and that the primary attacking site of the lysosphingolipids is the membrane. Because the potency to inhibit cytochrome c oxidase and to hemolyze erythrocytes did not differ among these lysosphingolipids and because galactosylceramide caused neither inhibition of cytochrome c oxidase nor hemolysis, the free amino group in the lysosphingolipids seems to be essential to give the effects. In addition, both inhibition of cytochrome c oxidase and hemolysis caused by lysosphingolipids were completely abolished by albumin, suggesting that toxic effects of lysosphingolipids may not be apparent in blood.
Triterpene alcohols, 4‐methylsterols and 4‐desmethylsterols of eggplant seed oil: A new phytosterol
Authors: Farines Marie , Cocallemen Serge , Soulier Jacques
Published: November 2006

4‐Desmethylsterols, 4‐methylsterols and triterpene alcohols of eggplant seed oil were isolated and characterized by1H nuclear magnetic resonance (NMR) and mass spectrometry. In addition to several compounds that have been shown to be present in eggplant seed oil, one triterpene alcohol and three sterols are described for the first time. One of these sterols, 14α‐methyl‐5α‐cholest‐9(11)‐en‐3β‐ol, never before had been observed in plant lipids.
Separation of α‐tocopherol and its oxidation products by high performance liquid chromatography
Authors: Ha Yeong L. , Scallany A. Saari
Published: November 2006

A very sensitive high performance liquid chromatographic (HPLC) method was developed for the separation of α‐tocopherol (α‐T) and its five oxidation products: α‐tocopheryl quinone (TQ), dimer (D), dihydroxy dimer (DHD), trimer (T) and 9‐methoxy‐α‐tocopherone commonly called α‐tocopheroxide (TO). The separation was achieved on a normal‐phase silica‐based column (Ultrasphere‐Si), using a mobile phase of hexane/chloroform/isopropanol (95∶4.5∶0.5, v/v/v) at a flow rate of 0.4 ml/min, and the eluants were monitored simultaneously at their maximum absorptions using a variable‐wavelength UV detector. The minmum detection limit is 0.01 μg for α‐T, TQ and TO, 0.05 μg for DHD and D, and 0.1 μg for T/injection. This normal‐phase method has the combined advantages of being very sensitive, fast and capable of separating all six compounds at the same time.
Microcomputer‐based system for data acquisition and analysis of oxygen uptake studies
Authors: Schanus E. G. , Caviness G. O. , Kahl J. L. , Herrick I. W.
Published: November 2006

The use of a Warburg Respirometer to study oxidation reactions is tedious and time‐consuming. A microcomputer‐based oxygen uptake device that is more sensitive than a Warburg Respirometer is described. The device consists of stainless steel or Teflon reaction vessels coupled to ultrasensitive pressure transducers. A high speed analog to digital convertor is used to poll the transducers. The direct memory access (DMA) controller of an IBM XT is used to poll the convertor and store the data in memory. Software used to program the DMA controller and IBM XT is described. The reproducibility and utility of the device is demonstrated with a brief study of lipid oxidation.
The use of a microwave oven in the chemical transformation of long chain fatty acid esters
Authors: Lie Ken Jie Marcel S. F. , Yan‐Kit Cheung
Published: November 2006

The use of a microwave oven as an energy source allowed transformation of fatty acid derivatives to be complete in a few minutes. Hydrolysis of triglycerides, esterification of free fatty acids, epoxidation of unsaturated fatty acid esters, cyclization of dioxostearates and oxounsaturated fatty acid esters into furanoid derivatives, conversion of epoxystearate to oxostearate derivatives, and substitution of a tosyl group by an azide all took about five min to complete and were in very high yields. The most sluggish reaction encountered was the acid catalyzed hydrolysis (ring opening) reaction of a furanoid ester to the corresponding 1,4‐dioxo derivative, which required three 10‐min periods of heating. The use of microwaves not only decreased the reaction time considerably but also allowed smaller volumes of solvent and lower quantities of reagents to be used as compared with the conventional methodologies reported.
Malondialdehyde excretion by subjects consuming cod liver oil vs a concentrate of n‐3 fatty acids
Authors: Piche L. A. , Draper H. H. , Cole P. D.
Published: November 2006

Urinary malondialdehyde (MDA), an indicator of lipid peroxidation in the diat and in the tissues, was determined in human adults consuming a supplement of n‐3 fatty acids derived from a pharmaceutical grade of cod liver oil (CLO) without added antioxidants vs a concentrate of n‐3 acids containing dodecyl gallate and vitamin E. MDA excretion increased immediately in the subjects consuming CLO but remained unchanged in those ingesting the concentrate for 50 days. The increase in the subjects taking CLO was attributable to MDA in the oil. The results indicate that consuming unstabilized fish oils as a source of n‐3 fatty acids may entail exposure to potentially toxic products of lipid peroxidation.
Metabolism of 2(RS),3‐epiminosqualene to 24(RS),25‐epiminolanosterol byGibberella fujikuroi
Authors: Nes W. David , Parish Edward J.
Published: November 2006

The metabolic fate of 2(RS),3‐epiminosqualene (Isq.), a demonstrable inhibitor of the 2,3‐oxidosqualene‐lanosterol cyclase, has been studied inGibberella fujikuroi. The fungus transforms Isq. to a tetracyclic product for which the 24(RS),25‐epiminolanosterol (EL) formulation was indicated by chromatographic and spectral data. The results are consistent with the pathway: Isq.→2,3‐imino‐22, 23‐oxidosqualene→EL.
Fatty acids of the milk and food of the platypus (Ornithorhynchus anatinus)
Authors: Gibson Robert A. , Neumann Mark , Grant T. R. , Griffiths Mervyn
Published: November 2006

Platypus milk fat contains 98.5% triglyceride. Polyunsaturates (C18∶2–C22∶5) account for 29% of the triglyceride fatty acids in the milk fat and 32% of the total fatty acids in the lipid of the food of the platypus. Linoleate and arachidonate are the major ω6 polyunsaturates of both food and milk lipids. However, while the ω3 polyunsaturates linolenate and eicosapentaenoate are present in both food and milk, docosapentaenoate is present in meaningful amounts in milk only. It is suggested that with the exception of 22∶5ω3, the polyunsaturates in platypus milk originate in the diet.
Fatty acid composition of macrophage phospholipids in mice fed fish or borage oil
Authors: Chapkin Robert S. , Somers Scott D. , Schumacher Leslie , Erickson Kent L.
Published: November 2006

The polyunsaturated fatty acid (PUFA) composition of murine peritoneal macrophage phospholipids was dramatically altered in vivo following the four‐wk feeding of specific dietary oils. Fish oil (containing 20∶5n–3 and 22∶6n−3) feeding significantly increased macrophage 20∶5n−3, 22∶5n−3, and 22∶6n−3 (P<0.05), while borage oil (containing 18∶2n−6 and 18∶3n−6) increased (P<0.05) the macrophage 20∶3n−6/20∶4n−6 ratio, relative to safflower oil (containing 18∶2n−6) and hydrogenated coconut oil (containing 12∶0)‐fed animals. The macrophage phospholipid PUFA profiles were compared with those of the liver, lung and spleen. The significance of the PUFA alterations is discussed.
Volatiles from thermal decomposition of isomeric methyl (12S, 13S)‐(E)‐12,13‐epoxy‐9‐hydroperoxy‐10‐octadecenoates
Authors: Gardner H. W. , Selke E.
Published: November 2006

Two epimers of methyl (12S,13S)‐(E)‐12,13‐epoxy‐9‐hydroperoxy‐10‐octadecenoate were isolated after esterification of a mixture of fatty acids obtained from decomposition of (13S)‐(9Z,11E)‐13‐hydroperoxy‐9,11‐octadecadienoic acid by an Fe++‐cysteine catalyst. These epimeric epoxyhydro‐peroxyoctadecenoates were decomposed by heat (210 C) in the injection port of a gas chromatograph, and the cleavage fragments were subsequently separated by gas chromatography (GC) and identified by mass spectrometry (MS). Among the scission products obtained, the most prominent in the GC peak profile were methyl octanoate and methyl 9‐oxononanoate. Other peaks were identified as pentane, 1‐pentanol, hexanal, 2‐heptanone, 2‐pentylfuran, methyl heptanoate, 2‐octenal, 4,5‐epoxy‐2‐decenal, methyl 8‐(2‐furyl)‐octanoate, 11‐oxo‐9‐undecenoate and methyl 13‐oxo‐9,11‐tridecadienoate. In addition, 3,4‐epoxynonanal, methyl 8‐oxooctanoate, 3‐hydroxy‐2‐pentyl‐2,3‐dihydrofuran and methyl 10‐oxodecanoate were tentatively identified. Except for the furan compounds, the formation of the fragmentation products could be explained by conventional free‐radical scission mechanisms.
Differences in polyisoprenoid alcohols of mono‐and dicotyledonous seeds
Authors: Ravi Kothapalli , Rip Jack W. , Carroll Kenneth K.
Published: November 2006

A lipid fraction enriched in polyisoprenoid alcohols was prepared from seeds of a number of crop plants, using Florisil chromatography. Analysis by HPLC of the fraction from soybeans showed a series of peaks corresponding to α‐saturated homologues (dolichols) from 15 to 22 isoprene units in length. Similar results were obtained with seeds of other dicotyledonous species (rapeseed, peanuts, mung beans, navy beans and peas). In contrast, analysis of the seeds of monocotyledonous plants (wheat, rye, barley, rice and corn) by HPLC gave split peaks, indicating the presence of nearly equal amounts of 2 different homologous series of compounds. The polyisoprenoid material isolated from wheat germ was subsequently shown to consist of a mixture of dolichols and α‐unsaturated homologues (polyprenols). Treatment with managanese dioxide selectively oxidized the polyprenols to the corresponding aldehydes, which were separated from the dolichols by TLC. The identity of the components was established by infrared‐nuclear magnetic resonance (IR‐NMR) spectroscopy and by comparison with authentic standards on high performance liquid chromatography (HPLC). The concentration of polyisoprenoid alcohols in seeds varied from 1–16 mg/100 g. Seeds of different species showed some differences in the pattern of homologues present.
Effect of external abdominal irradiation on the dimensions and characteristics of the barriers to passive transport in the rat intestine
Authors: Thomson A. B. R. , Cheeseman C. I. , Walker K.
Published: November 2006

Limited information is available on the effect of irradiation on the intestinal absorption of passively transported nutrients. In this study a previously validated in vitro technique was used to measure the uptake of fatty acids (FA), fatty alcohols and cholesterol into the jejunum, ileum and colon of control rats and animals exposed to cesium−137 source irradiation applied to the abdomen. The effective resistance of the intestinal unstirred water layer was measured with lauryl alcohol, and in control rats this resistance was lowest in the ileum, highest in the colon, and of intermediate value in the jejunum. Fourteen days after 600 rads, unstirred layer resistance was reduced by half in the colon when the bulk phase was stirred at 600 rpm, and in the jejunum, ileum and colon when the bulk phase was unstirred (0 rpm). The incremental change in the free energy of transfer (fΔFw→α) was measured with a homologous series of saturated medium‐chain length fatty acids; 14 days after 600 and 900 rads the value offΔFw→α in the jejunum rose significantly, and occurred when light and electron microscopic changes were minimal. Fourteen days after 300 rads, the uptake of FA 6∶0–12∶0 was reduced, but this decline in uptake appeared to be caused by a fall in the functional surface area of the membrane rather than a change infΔFw→α. The uptake of cholesterol into the jejunum, ileum and colon was unaffected by irradiation, suggesting that cholesterol and fatty acids may have different diffusion pathways through the membrane. Thus, external abdominal irradiation influences the dimensions and characteristics of the barriers to passive transport in the intestine of the rat, and thereby modifies the uptake of some but not all passively absorbed nutrients. These functional changes are not closely associated with morphological alterations.
Hydrocarbon transport in chylomicrons and high‐density lipoproteins in rat
Authors: Vost A. , Maclean N.
Published: November 2006

A lipoprotein system is described that transports gut hydrocarbons of low polarity in chylomicrons of intestinal lymph and plasma to plasma high density lipoproteins (HDL) in rat. Four highly lipophilic aryl and alkyl hydrocarbons [benzo(α)pyrene; 1,1,1‐trichloro‐2,2‐bis(p‐chlorophenol)ethane (DDT), hexadecane and octadecane] were selected to give a graded range of polarity. Chylomicrons were labeled doubly with radioisotopes in triacylglycerol and a single hydrocarbon by feeding [3H]‐glycerol and [14C]hydrocarbon. All hydrocarbons were transported in the triacylglycerol oil phase of chylomicrons. Injected chylomicron triacylglycerol and 3 of 4 hydrocarbons were cleared simultaneously from plasma consistent with lipoprotein‐lipase dependent hydrocarbon clearance but DDT was cleared more rapidly. HDL was the major plasma acceptor of all labeled hydrocarbons. Plasma chemical fluxes were measured for octadecane and DDT and both showed net fluxes from chylomicrons to HDL. HDL selectively concentrated chylomicron hydrocarbons from chylomicron triacylglycerol. Lipoprotein lipase stimulation by intravenous heparin significantly increased transfer of alkanes from chylomicrons to HDL. These results indicate that (a) chylomicrons transport gut‐derived hydrocarbons with a wide range of structure and polarity as triacylglycerol solutes; (b) HDL are a major plasma acceptor of all these hydrocarbons, demonstrating both selective solute uptake from triacylglycerol and net chemical uptake for the 2 hydrocarbons studied and (c) efflux of these chylomicron hydrocarbons from plasma and into HDL is regulated partly by hydrolysis of chylomicron triacylglycerol.
Differential response of lipid metabolism and membrane physical state by an actively and passively overwintering planktonic crustacean
Authors: Farkas T. , Nemecz Gy , Csengeri I.
Published: November 2006

Phospholipid (PL) composition, fatty acid (FA) composition of total and major individual PL as well as the physical state of isolated PL were investigated in relation to temperature exposure by freshwater planktonic crustaceans,Cyclops vicinus andDaphnia magna. C. vicinus, adapted to warm water, accumulated appreciable amounts of docosahexaenoic acid in its PL within 3 days when the temperature was decreased from 20 C to 10 C. Docosahexaenoic acid was preferentially esterified to phosphatidylethanolamine (PE). Docosapolyenoic FA were absent in PL ofD. magna and this species did not increase polyenoic acid level under identical temperature treatment. The level of PE was elevated, however, in both species in response to decreased environmental temperature. Two characteristic breaks were observed in ln S vs 1/T plots of 5‐doxyl stearic acid spin probs. These were at 19 C and 13 C forC. vicinus and at 20 C and 7 C forD. magna. C. vicinus shifted both the upper and lower phase‐separation temperatures of its PL to lower temperatures when exposed to cold. Differences between the onset and completion of phase‐separation temperatures equalled that in environmental temperature (10 C). The phase‐separation temperatures ofD. magna were unchanged under identical experimental conditions. Results are interpreted as a complete temperature adaptation of membrane transitional state byC. vicinus but not byD. magna. Researchers have postulated that one of the reasons the latter species cannot overwinter in an active form as doesC. vicinus, but instead overwinters as resting eggs, involves its failure to adapt membrane PL composition and physical state to temperature.
Free and esterified sterols of the marine dinoflagellateGonyaulax polygramma
Authors: Volkman John K. , Gagosian Robert B. , Wakeham Stuart G.
Published: November 2006

Free and esterified sterols of the common marine dinoflagellateGonyaulax polygramma were identified using capillary gas chromatography—mass spectrometry (GC‐MS). Fractions containing free 4α‐methyl and 4‐desmethyl sterols were isolated by column chromatography and shown to consist of at least 20 components. Major sterols included 4α,23,24‐trimethyl‐5α‐cholestan‐3β‐ol (dinostanol), 4α,23,24‐trimethyl‐5α‐cholest‐22E‐en‐3β‐ol (dinosterol), cholest‐5‐en‐3β‐ol (cholesterol), 23,24‐dimethyl‐5α‐cholest‐22E‐en‐3β‐ol and 23,24‐dimethylcholesta‐5,22E‐dien‐3β‐ol. Although the same group of sterols was found in the free and esterified sterol fractions, the proportions of individual sterols were quite different. The complexity of the sterol distributions, together with the predominance of dinostanol, distinguishes the sterol composition of this alga from those of other members of theGonyaulacaceae.
Hydrogenation of unsaturated fatty esters during isobutane chemical ionization mass spectrometry
Authors: Rohwedder William K. , Cox Sandra M.
Published: November 2006

Hydrogenation of double bonds was observed to occur during the isobutane chemical ionization mass spectrometry (MS) of unsaturated fatty esters. Chemical ionization (CI) spectra of a series of methyl esters in the C16–C20 carbon range containing 0–4 double bonds showed a variety of ionization characteristics in the molecular ion cluster, including hydride abstraction, charge exchange, protonation and, for the unsaturated fatty acids (FA), hydrogenation of the double bond followed by protonation.
Cholesteryl sulfate‐phosphatidylcholine interactions
Authors: Le Grimellec C. , Daigneault A. , Bleau G. , Roberts K. D.
Published: November 2006

The effect of cholesteryl sulfate, a natural membrane component, on the physical state of dipalmitoyl phosphatidylcholine multilamellar vesicles was investigated using fluorescence polarization and differential scanning calorimetry techniques. Cholesteryl sulfate increased the order of acyl chains for those temperatures higher than the gel‐to‐liquid crystalline transition temperature while it decreased the order for those temperatures below the phase transition temperature. At equimolar concentrations, cholesteryl sulfate suppressed the crystal liquid‐to‐gel phase transition of dipalmitoyl phosphatidylcholine. These data suggest that sterol sulfates may provide new tools for the elucidation of molecular mechanisms involved in sterollipid interactions.
Effects of bile salts on rat hepatic acyl CoA:Cholesterol acyltransferase
Authors: Erickson Sandra K. , Van Zuiden Paul E. A.
Published: November 2006

Acyl CoA:cholesterol acyltransferase (EC2.3.1.26, ACAT), responsible for intracellular esterification of cholesterol, may play an important role in cholesterol trafficking within the cell, and thus, in maintenance of cellular cholesterol homeostasis. Bile acids are potential regulators of cholesterol trafficking in the liver. Therefore, the effect of bile salts on hepatic ACAT activity was studied in the perfused rat liver. ACAT activity was increased after liver perfusion with either taurocholate or taurochenodeoxycholate. However, addition of these bile salts at physiological concentrationsin vitro had little effect on microsomal ACAT activity. The increase in hepatic ACAT activity due to perfusion with bile salts was accompanied by reduced accumulation of very low density lipoprotein cholesterol in the perfusate, but there was no effect on 3‐hydroxy‐3‐methylglutaryl‐CoA reductase activity. Hepatic ACAT activity was decreased after bile diversion for four hours in the intact animal. This treatment had no statistically significant effect on 3‐hydroxy‐3‐methylglutaryl‐CoA reductase activity. These data suggest that bile salts induce changes in hepatic compartmentation and traffic of cholesterol within the hepatocyte accompanied by response of ACAT activity to maintain cellular cholesterol homeostasis.
The effects of simvastatin and cholestyramine, alone and in combination, on hepatic cholesterol metabolism in the male rat
Authors: Shand John H. , West David W.
Published: November 2006

The influence of dietary simvastatin, cholestyramine, and the combination of simvastatin plus cholestyramine on hepatic cholesterol metabolism has been investigated in male rats. Recovery from the effects of the drugs was also investigated by refeeding normal chow for 24 h. Both drugs, alone and in combination, increased 3‐hydroxy‐3‐methylglutaryl‐CoA (HMG‐CoA) reductase activityin vitro, but activity returned toward control values, after drug withdrawal. Acyl‐CoA:cholesterol acyltransferase (ACAT) was significantly reduced (P<0.001) by simvastatin (−75%), cholestyramine (−71%), and by the drug combination (−81%), due both to a decrease in microsomal cholesterol and to nonsubstrate‐dependent modulation of enzyme activity. Refeeding control diet increased ACAT activity but not to control levels. The enhanced activity arose partly from higher microsomal cholesterol and partly from increases in total enzyme activity. Cytosolic neutral cholesteryl ester hydrolase (CEH) activity was substantially elevated by simvastatin (3‐fold) and by the drug combination (6‐fold), whereas the effect of cholestyramine was smaller (1.5‐fold). Normal chow for 24 h only partially returned cytosolic CEH activity to control values. Microsomal CEH activity was increased by simvastatin, alone and in combination with cholestyramine (1.4 to 1.7‐fold), and was also enhanced, in the cholestyramine‐treated animals, following drug withdrawal. Removal of simvastatin did not allow recovery of this enzyme activity, while withdrawal of the drug combination led to values 29% below controls. The results indicate that in the rat, simvastatin and cholestyramine alter both ACAT and CEH activity, as well as inhibiting HMG‐CoA reductase activity.
Proteolytic susceptibility of platelet low density lipoprotein receptor
Authors: Pedreño Javier , Fernández Rosa
Published: November 2006

In order to further characterize low density lipoprotein (LDL)‐platelet interaction, we investigated the effect of protease pretreatment of human platelets on the subsequent binding of iodinated LDL (125I‐LDL). Our results showed that the platelet LDL receptor had a proteolytic susceptibility different from that of both classical LDL receptors and the fibrinogen receptor. Platelet pretreatment with chymotrypsin, trypsin, and pronase (at 50 μg/mL) had no effect on125I‐LDL binding, whereas fibroblast125I‐LDL binding was markedly reduced. Mild proteolytic digestion, however (up to 1 mg/mL), was helpful in characterizing the platelet LDL receptor. Scatchard analysis showed that chymotrypsin did not modify LDL binding characteristics, whereas trypsin and pronase altered maximal number of binding sites (Bmax) without variation in dissociation constant. Trypsin increased Bmax approximately twofold (2156±327 binding sites on control platelets vs. 5246±296 on treated platelets,P<0.001, mean±SEM, n=5), but pronase decreased Bmax about 50% (2017±275 control vs. 1153±195 treated,P<0.001). A minimum of 30 min preincubation was required to detect significant effects, and apparent equilibrium was reached by 60 min. Maximal increase in platelet LDL binding sites induced by trypsin was observed at a protein concentration of 1 mg/mL at 37°C, whereas at 4°C no effect was found. In contrast, maximal pronase‐inhibitory effect also was observed at 37°C but at higher protein concentration (10 mg/mL). Aprotinin, phenylmethylsulfonylfluoride, and soybean trypsin inhibitor were capable of fully blocking both the stimulation and the inhibition of platelet LDL binding induced by trypsin and pronase, respectively. Platelet pretreatment with both chymotrypsin and pronase (0.5 mg/mL) activated fibrinogen binding sites to a similar extent as ADP (100 μM). Furthermore, LDL (at a protein concentration of 0.3 mg/mL) increased by 81±6% the binding of fibrinogen to both protease‐ and ADP‐stimulated platelets, but was unable to activate fibrinogen binding sites in unstimulated platelets. Over‐all, the results suggest that platelet LDL receptor presents a different proteolytic susceptibility in comparison with both “classical” LDL receptor and fibrinogen receptor.
Dietary fish oil and cytochrome P‐450 monooxygenase activity in rat liver and kidney
Authors: Valdes Eleva , Vega Patricio , Avalos Nicolas , Orellana Myriam
Published: November 2006

Lauric acid hydroxylation and aminopyrineN‐demethylation were studied in kidney and liver microsomes from rats treated with fish oil. Different doses of fish oil containing 20% eicosapentaenoic acid and 10% docosahexaenoic acid were provided daily to the rats for seven days. In all the groups studied, the lauric acid metabolism was higher in kidney microsomes and the aminopyrine metabolism in the liver microsomes. Although no effect on the renal cytochrome P‐450 concentration was detectable, all four fish oil doses increased the hepatic concentration of cytochrome P‐450 by a mean 27%. The higher fish oil doses used increased the renal and hepatic microsomal metabolism of aminopyrine. The lauric acid metabolism was increased by fish oil only in the liver. Fish oil, a known inducer of fatty acid peroxisomal β‐oxidation, also induced microsomal activity. These results show that liver and kidney respond in different ways to dietary factors such as fish oil. In addition, our study would suggest that fish oil increased the activity of two different families of liver cytochrome P‐450. The activity of kidney lauric acid 11‐ and 12‐hydroxylation, however, was not modulated by fish oil.
Effects of peroxidative stress and age on the concentration of a deoxyguanosine‐malondialdehyde adduct in rat DNA
Authors: Draper Harold H. , Agarwal Sanjiv , Voparil Nelson Dagmar E. , Wee Jae Joon , Ghoshal A. K. , Farber Emmanual
Published: November 2006

The effect of age and peroxidative stress on the concentration of a deoxyguanosine malondialdehyde adduct (dG‐MDA) in rat tissues was investigated. Vitamin E deficiency had not effect on the dG‐MDA content of liver DNA in rats fed a diet containing 10% corn oil. When 2% cod liver oil was added to this diet, the dG‐MDA content of liver DNA doubled in the positive controls fed a high level of vitamin E (100 ppm dl‐α‐tocopherol), and there was a further increase when vitamin E was deleted. Neither iron nitrilotriacetate administration nor choline deficiency had any effect on the dG‐MDA content of liver DNA. Carbon tetrachloride had a lowering effect. The failure of iron or carbon tetrachloride administration and of vitamin E deficiency to increase liver dG‐MDA is consistent with their failure in previous experiments to affect the urinary excretion of dG‐MDA. In contrast, these forms of peroxidative stress produce large increments in the urinary excretion of MDA adducts with lysine, reflecting increased formation and degradation of MDA‐modified proteins. DNA appears to be protected from modification by MDA produced at extranuclear sites. The frequency of dG‐MDA in different tissues of 4‐month‐old rats varied markedly: brain ≫ liver > kidneys and testes. Higher concentrations of dG‐MDA were found in the liver and kidneys, but not the testes, of 25‐month‐old rats. The determinants of the concentration of dG‐MDA in DNA merit further investigation.
The relationship between the structure of monoalkyl branched saturated fatty acids and some physical properties
Authors: Svensson Leif , Hansson Ulf , Gronowitz Salo , Klingstedt Tomas
Published: November 2006

The gel point and the refractive index of monoalkyl branched saturated fatty acids were determined and related to the structure of the acids. A three‐factor central composite face‐centered design was constructed where the three variables were the length of the main chain, the branching position and the length of the side chain. Second‐order models were calculated in which the two properties were related to the structure. In order to confirm the validity of the models, two additional fatty acids were analyzed. The gel point was found to be proportional to the length of the main chain and the square of the branching position whereas the refractive index was proportional to the length of both the main and the side chain and also to the square of the main chain.
3‐carboxy‐4‐nitrophenyl‐dithio‐1,1′,2‐trisnorsqualene: A site‐directed inactivator of yeast oxidosqualene cyclase
Authors: Balliano Gianni , Grosa Giorgio , Milla Paola , Viola Franca , Cattel Luigi
Published: November 2006

The role and location of essential thiol groups in 2,3‐oxidosqualene cyclase fromSaccharomyces cerevisiae was examined (i) by comparing inactivation properties of two known thiol reagents, 5,5′‐dithiobis(2‐nitrobenzoic acid) (DTNB) and 2‐nitro‐5‐thiocyanobenzoic acid (NTCB), with 3‐carboxy‐4‐nitrophenyl‐dithio‐1,1′,2‐trisnorsqualene (CNDT‐squalene), a new thiol reagent designed as a sitedirected inactivator of oxidosqualene cyclase and (ii) by testing the ability of the substrate to protect the enzyme against inactivation by the reagents. All reagents gave a time‐dependent inactivation following pseudo‐first order kinetics. DTNB and CNDT‐squalene showed comparable inactivation ability (Ki=0.67 and 1.21 mM), whereas NTCB was less effective (Ki=15.6 mM). Strong differences between the two most active inhibitors, DTNB and CNDT‐squalene, were observed when the enzyme was saturated with substrate prior to incubation with the thiol reagent. While substrate did not protect the enzyme against the inactivation caused by DTNB, a reduction in the inactivation ability of CNDT‐squalene was observed under protection conditions. The data suggest that the squalene‐like inactivator modifies a thiol group located at the active site of the enzyme.
General resistance to sterol biosynthesis inhibitors inSaccharomyces cerevisiae
Authors: Ladevèze Véronique , Marcireau Christophe , Delourme Didier , Karst Francis
Published: November 2006

Screening for resistance to fenpropimorph was undertaken in order to isolate yeast mutants affected in the regulation of the ergosterol pathway. Among the mutants isolated, one bearing the recessivefen1‐1 mutation was characterized by a 1.5‐fold increase in the ergosterol level and a general resistance to sterol biosynthesis inhibitors. Thefen1‐1 mutation was linked toMAT locus on chromosome III. The measurement of enzyme activities involved in the ergosterol pathway revealed that isopentenyl diphosphate (IPP) isomerase activity was specifically increased 1.5‐fold as compared to the wild type strain. However, overexpression of IPP isomerase in the wild type strain was not by itself sufficient to lead to sterol increase or resistance to sterol biosynthesis inhibitors, showing that IPP isomerase is not a limiting step in the pathway. Thefen1‐1 mutation permits viability in aerobiosis of yeast disrupted for sterol‐14 reductase in absence of exogenous ergosterol supplementation, whereas the corresponding strain bearing the wild typeFEN1 allele grows only in anaerobiosis. This result shows that ignosterol is able to efficiently replace ergosterol as bulk membrane component and that thefen1‐1 mutation eliminates the specific ergosterol requirement in yeast.
Parameters influencing cholesterol oxidation
Authors: Kim S. K. , Nawar W. W.
Published: November 2006

The purpose of this study was to investigate the effects of temperature, oxidation time, presence of water, pH, type of buffer and form of substrate used on cholesterol oxidation. Microcrystalline cholesterol films, both solid and melted, and aqueous suspensions of film fragments were used as substrates. Use of dispersing agents was avoided. Quantitative analysis of the unaltered substrate and the products of its autoxidation was carried out by gas chromatography over the course of oxidation. Solid cholesterol films were found to be resistant to autoxidation in the dry state. However, when heated at 125°C, a sudden increase in oxidation rate occurred at a point coinciding with the visible melting followed by a plateau of the oxidation rate. All of the autoxidation products formed underwent further decomposition. Film fragments of cholesterol oxidized at a faster rate in aqueous suspensions than when oxidized in the dry state. In aqueous suspensions, the differences in the resistance of cholesterol to oxidation were not significant within the pH range 6.0–7.4, except for the early stages of oxidation. The 7‐ketocholesterol/7‐hydroxycholesterol ratio dropped significantly with increasing pH. However, at all pH levels tested, this ratio remained relatively constant during the 6 h of heating. While the 7β‐hydroxycholesterol/7α‐hydroxycholesterol ratio was not affected by pH in the range of 6.0–7.4, at pH 7.4 a high preference was observed for the cholesterol β‐epoxide over its α‐isomer. The β/α‐epoxide ratio decreased with time of heating and with decreasing pH. The data show that the physical state of the substrate exerts a major influence on the oxidative behavior of cholesterol.
Cholesterol and 25‐hydroxycholesterol retention in specimens of liver and aorta prepared for electron microscopy. II. Effect of filipin, osmium, digitonin and saponin
Authors: Fornas E. , Renau‐Piqueras J. , Fortea A. , Mayordomo F. , Alborch E.
Published: November 2006

Sprague‐Dawley rats were injected intraperitoneally with [1α,2α(n)‐3H]cholesterol or 25‐hydroxy‐[26,27‐3H]cholesterol, and one and five days later liver and aortic tissues were fixed. The extent to which these sterols were lost from the tissues during preparation for electron microscopy (EM) was examined utilizing different fixation procedures and various protective agents. Radioactive tracers, scintillation counting and standard EM techniques were used. Although most of the procedures examined caused major lipid losses, useful fixation procedures that allow retention of cholesterol or 25‐hydroxycholesterol in liver and aortic tissues were found and are described here.
Microwave‐mediated methanolysis of lipids and activation of thin‐layer chromatographic plates
Authors: Khan Mobashsher U. , Williams John P.
Published: November 2006

A technique is described for the methanolysis of fatty acids from acylglycerols with HCl/CH3OH or NaOH/CH3OH using a microwave oven. The esterification is rapid and complete and does not result in significant degradation of polyunsaturated fatty acids, even in the presence of oxygen. The fatty acid compositions of intact tissues were also determined using this technique. The microwave oven has also been used to condition normal silica gel and argentation thin‐layer chromatographic plates in a fraction of the time normally required.
Enteral feeding a structured lipid emulsion containing fish oil prevents the fatty liver of sepsis
Authors: Lanza‐Jacoby Susan , Phetteplace Hope , Tripp Robert
Published: November 2006

Fish oils (FO) have been shown to reduce plasma triglycerides (TG). In this study we evaluated whether enteral feeding with a structured lipid emulsion (SLE) containing FO and medium‐chain triglycerides (MCT) would prevent the hypertriglyceridemia and fatty infiltration of the liver that develops during sepsis. For five days, male Lewis rats (275–300 g) were fed intragastrically a nutritionally complete diet containing a SLE or a similar diet with a soybean oil emulsion (SOE) in place of the SLE. On the fifth day, sepsis was induced by intravenously injecting 8×107 liveEscherichia coli colonies/100 g b.w.; 24 h later the control SLE, septic SLE, control SOE, and septic SOE rats were sacrificed. Diet, but not treatment, had a significant effect on serum TG and free fatty acids (FFA). Feeding the SLE reduced the plasma FFA of the control and septic rats by more than 50% in comparison to both control and septic rats fed the SOE. Soleus muscle activity of lipoprotein lipase from the septic SLE rats was 44% higher than the control SLE rats. Soleus muscle from the septic SLE rats also had a twofold greater activity of lipoprotein lipase than the septic SOE rats. TG did not accumulate in the livers of the septic rats fed SLE when compared to the control SLE rats and the rats fed the SOE. Livers from the septic rats fed the SLE had a third of the TG that were present in the livers from the septic rats fed the SOE. The rate of incorporation of [14C]oleate into liver lipids was significantly lower in septic rats fed SLE than in those fed the SOE. TG esterification was 70% lower in the septic rats fed SLE rather than the SOE. Our findings suggest that the SLE with FO and MCT has a role in the prevention of the sepsis‐associated fatty liver by reducing the biosynthesis of liver TG.
Effect of tumor necrosis factor‐α on triglyceride and phospholipid content and fatty acid composition of liver and carcass in rats
Authors: Raina Nilima , Matsui Junichi , Cunnane Stephen C. , Jeejeebhoy Khursheed N.
Published: November 2006

We have previously shown that a continuous infusion of tumor necrosis factor‐α (TNF‐α) in rats results in an increase in plasma triglyceride (TG), liver protein and DNA, and at the same time a reduction in muscle protein. However, there is no information on the associated effects of TNF‐α on liver and muscle lipids. The present study, therefore, determined the effect of TNF‐α on the TG and phospholipid (PL) content and their fatty acid composition, in the liver and carcass of rats and correlated with the plasma levels of insulin, corticosterone, and catecholamaines. Total parenteral nutrition that met the daily nutrient requirements was continuously infused for 10 d through a central vein catheter in two groups of rats, one receiving infused TNF‐α (100 μg/kg/d) and a control group. Hepatic TG and PL, expressed either as mg/g dry weight or total organ content, were significantly increased in the TNF‐α‐infused group compared with controls. Livers of TNF‐α infused rats contained significantly less saturated and monounsaturated fatty acids and significantly more polyunsaturated fatty acids (PUFA) of the ω3 and ω6 series than controls. The carcass, on the other hand, contained significantly more monounsaturated and significantly less polyunsaturated fatty acids of the ω6 series than controls. There were no changes in corticosterone level. Although plasma glucose levels were comparable between control and TNF‐α infused rats, the latter had a marked increase in insulin levels, demonstrating insulin resistance. In addition TNF‐α infused rats had raised norepinephrine levels. The fall in carcass and rise in liver TG and PL are consistent with the presence of insulin resistance and raised norepinephrine levels. However, the increase in PUFA content of the liver, especially the increase in 20∶4ω6 levels in liver PL and TG, is likely to be the effect of TNF‐α and suggests increased activity of Δ5‐desaturase.
Critical analysis of phospholipid hydrolyzing activities in ripening tomato fruits. Study by spectrofluorimetry and high‐performance liquid chromatography
Authors: Rouet‐Mayer Marie‐Aude , Valentova Olga , Simond‐Côte Elizabeth , Daussant Jean , Thévenot Claudine
Published: November 2006

Using the spectrofluorimetric method described by Wittenaueret al. [Wittenauer, L.A., Shirai, K., Jackson, R.L., and Johnson, J.D. (1984)Biochem. Biophys. Res. Commun. 118, 894–901] for phospholipase A2 (PLA2) measurement, we have detected a phospholipase activity in Ailsa Craig and in mutantrin tomatoes at their normal harvest time (mature green stage). This activity in Ailsa Craig tomatoes increased at the beginning of fruit ripening (green‐orange stage) and then decreased slowly. The decrease in activity, however, was greater when ripening occurred after tomato picking at normal harvest time than when ripening occurred on tomato plants. This phospholipase activity was always higher inrin tomatoes than in normal ones. Thin‐layer chromatography of compounds obtained after incubation of tomato extract demonstrated a decrease in the substrate 1‐acyl‐2‐{6[(7‐nitro‐2,1,3, benzoxadiazol‐4‐yl)amino]‐caproyl}‐sn‐glycero‐3‐phosphocholine (C6‐NBD‐PC), and an increase in one product (NBD‐aminohexanoic acid), but failed to detect the second product (1‐acyl‐sn‐glycero‐3‐phosphocholine). We, therefore, developed a new one‐step method for separation and quantification of a mixture of phospholipids and other lipids, using straight‐phase‐high‐performance liquid chromatography with light‐scattering detection. This method detected another fatty acid‐releasing activity in enzyme extract from green‐orange tomatoes. This lipolytic enzyme (or family of enzymes) slowly produced free fatty acids when 1‐oleoyl‐sn‐glycero‐3‐phosphocholine was added as substrate. The production of fatty acids was stoichiometric and more rapid when 1‐oleoyl‐sn‐glycero‐3‐phosphate and 1‐oleoyl‐sn‐glycerol were used as substrates. On the other hand, the same tomato extract was unable to hydrolyze 1,2‐dioleoyl‐sn‐glycero‐3‐phosphate and 1,2‐dioleoyl‐sn‐glycerol. Crude tomato extract exhibited lipid acyl hydrolase activity according to the definition of Galliard [Galliard, T. (1979), inAdvances in the Biochemistry and Physiology of Plant Lipids (Appelqvist, L.A., and Liljenberg, C. eds.), pp. 121–132, Elsevier, Amsterdam]. But in order to demonstrate whether tomato extract contains PLA2 activity and/or lysophospholipase activity, further work on purified tomato extract will be necessary.