bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of α‐tocopherol and its oxidation products by high performance liquid chromatography
Authors: Ha Yeong L. , Scallany A. Saari 
Published: November 2006

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractUrinary 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

AbstractThe 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

AbstractPlatypus 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

AbstractThe 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

AbstractTwo 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

AbstractA 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

AbstractLimited 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

AbstractA 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

AbstractPhospholipid (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

AbstractFree 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

AbstractHydrogenation 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

AbstractThe 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

AbstractAcyl 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

AbstractThe 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

AbstractIn 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.