bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synergistic enhancement of the antiproliferative activity ofcis‐diamminedichloroplatinum(II) by the ether lipid analogue BM41440, an inhibitor of protein kinase C
Authors: Hofmann Johann , Ueberall Florian , Posch Lydia , Maly Karl , Herrmann Dieter B. J. , Grunicke Hans 
Published: November 2006

AbstractThe new phospholipid analogue 3‐hexadecylmercapto‐2‐methoxy‐methyl‐propyl‐1‐phosphocholine inhibits the phospholipid‐calcium‐dependent protein kinase, partially purified from Walker carcinoma cells with a Ki value of 0.56 μM. The compound inhibits the phorbol ester stimulated phosphorylation of the ribosomal protein S6 indicating that the depression of Ca2+‐phospholipid‐dependent protein kinase by the alkyl phospholipid also occurs in intact cells. The dose effect curve for the inhibition of cell proliferation by 3‐hexadecylmercapto‐2‐methoxy‐methyl‐propyl‐1‐phosphocholine in Walker cells exhibits a close correlation to the dose effect curve for the depression of Ca2+‐phospholipid‐dependent protein kinase activity. Although alternative mechanisms cannot be excluded, the data suggest that the growth inhibitory activity of 3‐hexadecylmercapto‐2‐methoxy‐methyl‐propyl‐1‐phosphocholine correlates with the inhibition of Ca2+‐phospholipid‐dependent protein kinase. The antiproliferative activity of 3‐hexadecylmercapto‐2‐methoxymethyl‐propyl‐1‐phosphocholine is synergistically enhanced bycis‐diamminedichloroplatinum(II).
Quantification, characterization and fatty acid composition of lysophosphatidic acid in different rat tissues
Authors: Das Arun K. , Hajra Amiya K. 
Published: November 2006

AbstractThe amount and composition of lysophosphatidate present in different rat tissues have been estimated by an internal standard method in which a synthetic unnatural isomer (1‐heptadecanoyl‐rac‐glycerol‐3‐phosphate) was added to the total lipid extracts, and the fatty acid composition of purified lysophosphatidate was determined. Lipids from tissues were extracted under acidic conditions, and the lysophosphatidate was purified by solvent partitions followed by thin‐layer chromatography in multiple solvent systems. The purified lipid was shown to be 1‐acyl‐sn‐glycerol‐3‐phosphate by chromatographic and chemical analysis, by its resistance to hydrolysis when treated with phospholipase A2 and also by its complete conversion to 1‐acyl‐sn‐glycerol when treated with alkaline phosphatase. The fatty acid consituents of this lipid were determined by gas‐liquid chromatography of the derived methyl esters. The concentrations (nmol/g of tissue) of lysophosphatidate in various tissues were: 86.2±4.2 in brain, 60.3±6.3 in liver, 46.4±6.5 in kidney, 30.6±5.0 in testis, 22.3 in heart and 19.3 in lung. Mostly (80%) saturated fatty acids were found to be present in this lyso lipid. A significantly high level of stearic acid was present in this lipid from all the tissues (50–60% in liver, kidney, brain and testis, and about 40% in heart and lung) compared to plamitic acid (10–15% in liver, kidney and brain and 25–30% in testis, heart and lung). The fatty acid compositions of phosphatidic acid, the putative product of lysophosphatidate acylation, from different tissues were also determined and palmitate was found to be the major saturated fatty acid. These results suggest that tissue lysophosphatidic acid is not only formed byde novo biosynthesis but is also generated via the breakdown of phospholipids such as phosphoinositides.
The essential fatty acid requirement for azoxymethane‐induced intestinal carcinogenesis in rats
Authors: Bull Arthur W. , Bronstein Joel C. , Nigro Norman D. 
Published: November 2006

AbstractThe essential fatty acid requirement for the development of intestinal carcinogenesis was determined and compared to the overall essential fatty acid status of the animals as measured by the triene/tetraene ratio in the plasma, liver and colon. To induce tumors, male Sprague‐Dawley rats were given two weekly injections (20 mg/kg body wt) of azoxymethane. Two weeks after the last injection, the rats were divided into groups of 25 and given one of six diets containing various levels of essential fatty acids (as linoleate). The diets contained 5% total fat and were prepared by mixing safflower oil (high essential fatty acids, beef fat (low essential fatty acids), and medium chain triglyceride oil (no essential fatty acids). One group of rats was fed a 20% beef fat diet. The range of essential fatty acids was from <0.03% to 1.28% (w/w). Twenty‐six weeks after the first azoxymethane injection, the animals were killed and intestinal tumor incidence and multiplicty were determined. Samples of plasma, liver and colon were also taken for measurement of the triene/tetraene ratio by gas chromatography.Large bowel tumor incidence showed a dependence on the essential fatty acid content of the diet. The results were as follows: (percent essential fatty acids: percent tumor incidence) Group A (1.28∶ 72.4), Group B (0.60∶ 73.3), Group C (0.11∶ 55.2), Group D (0.08∶ 39.3), Group E (<0.03∶ 37.9) and Group F, which was fed 20% beef fat, (0.34∶ 88.5). These data suggest the essential fatty acid requirement for colon tumorigenesis is much lower than values previously reported for tumorigenesis in the breast and pancreas. The plasma and liver triene/tetraene ratios showed clear‐cut essential fatty acid deficiency (ratio >0.4) in Groups D and E, although no clinical symptoms were evident. In all dietary groups, the triene/tetraene ratio in the colon was lower than 0.3. In addition in the colon, the percentage of fatty acids present as 20 carbon polyunsaturated fatty acids was lower than in the plasma and liver. These data suggest the colon possesses low levels of the fatty acid desaturase and elongase needed for conversion of linoleate to 20 carbon fatty acids, and therefore, that the colonic requirement for essential fatty acids may be low. Furthermore, in the absence of other clinical symptoms, the reduced tumorigenesis observed in the groups fed low essential fatty acids suggests the essential fatty acid requirement of tumor tissue may be higher than that of normal colon mucosa.
Impact of lemongrass oil, an essential oil, on serum cholesterol
Authors: Elson C. E. , Underbakke G. L. , Hanson P. , Shrago E. , Wainberg R. H. , Qureshi A. A. 
Published: November 2006

AbstractTo test the hypothesis that non‐sterol mevalonate pathway end products lower serum cholesterol levels, we asked 22 hypercholesterolemic subjects (315±9 mg cholesterol/dl) to take a daily capsule containing 140 mg of lemongrass oil, an essential oil rich in geraniol and citral. The paired difference in serum cholesterol levels of subjects completing the 90‐day study approached significance (P<0.06, 2‐tailed t‐test). The subjects segregated into two groups, one consisting of 14 subjects resistant to the protocol and the other consisting of 8 subjects who responded. Paired differences in cholesterol level at 30, 60 and 90 d for resistant subjects were +2±6, +2±7 and −1±6 mg/dl; paired differences for the responding subjects were −25±10 (p<0.05), −33±8 (p<0.01) and −38±10 (p<0.025), respectively. The paired difference (+8±4) in the cholesterol levels of six responders 90 days after the discontinuation of lemongrass oil was not significant.
Suppression of growth in a leukemic T cell line by n−3 and n−6 polyunsaturated fatty acids
Authors: Chow S. C. , Sisfontes L. , Björkhem I. , Jondal M. 
Published: November 2006

AbstractProliferation in a lekemic T cell line (Jurkat) was suppressed in a dose dependent manner by n−6 and n−3 polyunsaturated fatty acids (PUFA) added to the culture medium. At high concentrations, PUFA have a cytotoxic effect on Jurkat cells. The inhibitory effect of the PUFA was not due to production of prostaglandins, and lipid peroxidation was only partly responsible. In addition to production of peroxides and aldehydes, lipid peroxidation also reduced the plasmalogen levels in these cells. The antioxidant α‐tocopherol blocked lipid peroxidation and restored the plasmalogen levels to normal. α‐Tocopherol did not totally restore cell proliferation although the MDA‐like products in these cultures (supplemented with PUFA) were reduced to control level. Cultures supplemented with n−6 PUFA seemed to respond better to α‐tocopherol than n−3 PUFA. This suggests that n−6 PUFA may exert their growth inhibitory effect predominantly via lipid peroxidation while different mechanisms might be operating for the n−3 PUFA.
Effects of cholestyramine and squalene feeding on hepatic and serum plant sterols in the rat
Authors: Strandberg Timo E. , Tilvis Reijo S. , Miettinen Tatu A. 
Published: November 2006

AbstractHepatic and serum phytosterol concentrations were compared in the rat under basal conditions and during activated cholesterol and bile acid production due to squalene and cholestyramine feeding. Both treatments consistently decreased hepatic and serum levels of sitosterol and campesterol and, unlike esterified cholesterol, esterified plant sterols were not increased in liver during squalene feeding. Serum levels of phytosterols were decreased quite proportionately to those in the liver. The hepatic levels of sitosterol and campesterol closely correlated with each other, but not with cholesterol levels. The percentage esterification of both phytosterols was lower than that of cholesterol. The results indicate that activation of hepatic sterol production leads to depletion of hepatic plant sterols. It is suggested that poor esterification of plant sterols may contribute to this decrease.
Effect of hyperpnea on enzymes of the CDPcholine path for phosphatidylcholine synthesis in rat lung
Authors: Barr Heather A. , Nicholas Terence E. , Power John H. T. 
Published: November 2006

AbstractWe have examined the activity of three enzymes in pulmonary surfactant phosphatidylcholine synthesis following the hyperpnea induced by having rats either inspire 5% CO2/13%O2/82% N2 for 24 hr or swim in thermoneutral water for 30 min. Both stimuli markedly increase frequency and tidal volume of breathing and promote the release of surfactant. Lungs were perfused to remove blood, lavaged, and then homogenized in 1 mM Hepes, 0.15M KCl at pH 7.0. The homogenate was centrifuged at 9,000 g (av) for 10 min to sediment the mitochondria and lamellar bodies and at 100,000 g (av) for 60 min to obtain the microsomal and cytosol fractions. Incubations were carried out under determined optimal conditions and zero order kinetics. Choline kinase (CK), cholinephosphate cytidylytransferase (CP‐cyT) and choline phosphotransferase (CPT) were assayed by the incorporation of [methyl‐14C] choline chloride into phosphocholine, [methyl‐14C]phosphocholine into CDPcholine, and [14C]CDPcholine into phosphatidylcholine, respectively. The incubation products were separated by thin‐layer chromatography. Whereas both forms of hyperpnea increased the activity of CP‐cyT in the microsomal fraction, they had no effect on the activity of either cytosolic CP‐cyT and CK, or microsomal CPT. A similar increase in tidal volume in an isolated perfused rat lung had no effect. We conclude that,in vivo, hyperpnea increases the activity of CP‐cyT, the rate‐limiting enzyme in phosphatidylcholine synthesis. Whether this is due to an increase in the amount of enzyme, or of a cofactor, is unknown.
Acyl lipid metabolism in the oleaginous yeastRhodotorula gracilis (CBS 3043)
Authors: Rolph Carole E. , Moreton Rod S. , Harwood John L. 
Published: November 2006

AbstractThe effects of culture conditions on acyl lipid metabolism in the oleaginous yeastRhodotorula gracilis (CBS 3043) have been investigated. Growth ofR. gracilis under conditions of nitrogen‐limitation resulted in the accumulation of large quantities of triacylglycerols. Thin layer and gas chromatographic analysis of total lipid extracts revealed that the majority of this storage lipid was produced by stationary‐phase cells. In contrast, no such increase in triacylglycerol biosynthesis could be detected in carbon‐limited cells. Freeze‐fracture electron microscopy evidence supported these findings. Growth medium composition was found to have little effect on the relative abundance of the primary phospholipid classes present inR. gracilis. The acyl compositions of triacylglycerols were similarly unchanged by alterations in the composition of the growth medium. In contrast, the degree of unsaturation exhibited by the phospholipid fractions appeared to be particularly sensitive to this external parameter. Acyl quality of triacylglycerol pools extracted from nitrogen‐limited cells were observed to become increasingly saturated as cultures increased in age.Growth of nitrogen‐limited cells at a lower growth temperature was observed to have little effect on triacylglycerol accumulation. However, both triacylglycerol and phospholipid fractions extracted from these cultures were found to contain increased proportions of the polyunsaturated fatty acid, α‐linolenate.
Microsomal lipid peroxidation: Effect of vitamin E and its functional interaction with phospholipid hydroperoxide glutathione peroxidase
Authors: Maiorino Matilde , Coassin Mariagrazia , Roveri Antonella , Ursini Fulvio 
Published: November 2006

AbstractThe role of vitamin E in the protection against iron dependent lipid peroxidation was studied in rat liver microsomes and Triton‐dispersed microsomal lipid micelles. In these systems, an antioxidant effect of vitamin E at a physiological ratio to phospholipids could be observed only in the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPX) and glutathione. The rationale of this cooperation is discussed on the basis of the hydroperoxyl radical scavenging capacity of vitamin E and the reduction of membrane hydroperoxides by PHGPX. The scavenging of lipid hydroperoxyl radicals by vitamin E, although inhibiting propagation of the peroxidative chain, produces lipid hydroperoxides from which ferrous iron generates alkoxyl radicals that react with vitamin E almost as fast as with fatty acids. Therefore, only if membrane hydroperoxides are continuously reduced by this specific peroxidase does the scavenging of hydroperoxyl radicals by vitamin E lead to an effective inhibition of lipid peroxidation.
Effect of magnesium deficiency on Δ6 desaturase activity and fatty acid composition of rat liver microsomes
Authors: Mahfouz M. M. , Kummerow F. A. 
Published: November 2006

AbstractExperimental Mg2+ deficiency was induced in a group of rats by feeding them a Mg2+‐deficient diet for 23 days. They were pair‐fed to compare with a control group of rats fed a Mg2+‐sufficient diet. In the Mg2+‐deficient group the plasma total cholesterol and triglyceride levels were increased while HDL‐cholesterol was decreased. In the Mg2+‐deficient group the plasma level of thiobarbituric acid reacting substances (TBARS) used as a measure for lipid peroxidation was increased. The increase was attributed to the increased cytosolic Ca2+ in Mg2+‐deficiency which can cause: 1) increase of hydro and endoperoxide levels as a consequence of the increase of arachidonic acid release and eicosanoid synthesis in Mg2+‐deficiency, and 2) inhibition of the mitochondrial respiratory activity and activation of Ca2+‐dependent proteases which may activate the conversion of xanthine dehydrogenase to xanthine oxidase which generates active O2 species. In the Mg2+‐deficient group, the fatty acid composition of the liver microsomes indicated a slower rate of conversion of linoleic acid to arachidonic acid which was consistent with the decrease of Δ6 desaturase activity in liver microsomes of Mg2+‐deficient rats as measuredin vitro. The decrease of Δ6 desaturase activity was attributed to the lower concentration of actual enzyme molecules as a result of the decreased rate of protein synthesis in Mg2+‐deficiency. The possible effects of the increased catecholamine release in Mg2+‐deficiency are discussed.
Dietary fish oil augments the function and fluidity of the intestinal brush‐border membrane of the carp
Authors: Behar D. , Cogan U. , Viola S. , Mokady S. 
Published: November 2006

AbstractTwo groups of carps were raised on a commerical nutritionally complete diet: one was the control group, the other was fed the same diet enriched with 7% fish oil. The experiment lasted seven months (July through February), during which time the environmental temperature dropped gradually from 25°C to 13°C. Intestinal microvillus membranes were isolated after four and seven month feeding and examined for fluidity by fluorescence polarization with 1,6‐diphenyl‐1,3,5‐hexatriene. The functionality of the membrane was assessed by the activity of the intrinsic enzyme alkaline phosphatase.The experimental group exhibited increased membrane fluidity and elevated enzyme activity only when the environmental temperature decreased to 13°C. These changes in the membrane properties seemed to correlate with alterations in the fatty acid profile of the membrane phospholipids. Whereas the control group showed some increase in the n−3 C20∶5, C22∶5, and C22∶6 fatty acids most likely due to cold adaptation, the membranes isolated from the group fed fish oil showed a considerably higher level of these fatty acids reflecting the combined effect of the dietary manipulation and cold adaptation.
Thiol esters of 2‐mercaptoethanol and 3‐mercapto‐1,2‐propanediol
Authors: Sonnet Philip E. , Moore Gordon G. 
Published: November 2006

Abstract2‐Mercaptoethanol and 3‐mercapto‐1,2‐propanediol are selectively S‐acylated by fatty acids with dicyclohexylcarbodiimide (DCC) catalyzed by 4‐dimethylaminopyridine. Since reaction of such thiols with acid halides produces mixtures of S‐ and O‐acylated materials, the procedure using DCC is more efficient. Such thiol esters are valuable as substrates in the study of lipase activity, using Ellman's Reagent in a continuous spectrophotometric assay. This selective synthesis will facilitate the study of fatty acid residues that are less available. Rearrangement of S‐ to O‐acylated compounds occurs only slowly under the conditions of the lipase assay and should not significantly affect activity measurements. Using DCC, it is possible to sequentially esterify 2‐mercaptoethanol to form unsymmetrical diesters.
The simultaneous separation and quantitation of human milk lipids
Authors: Collins Sarah E. , Jackson Marjorie B. , Lammi‐Keefe Carol J. , Jensen Robert G. 
Published: November 2006

AbstractA protocol using a dry column method was modified for the extraction of total lipids and the simultaneous separation and quantitation of neutral and polar lipids in human milk. The triacylglycerol, cholesterol, phospholipid and vitamin E contents of the lipid extracts were determined and compared with lipids extracted using a modified Folch procedure. Good precision for the extraction of neutral, polar and total lipids, as well as the different lipid classes, was demonstrated. No significant differences were found between the two methods with respect to the amount of cholesterol, phospholipid, total lipid or vitamin E extracted, thus validating the method as an extraction technique. We discuss the relationship between vitamin E and the three major milk lipids as an indicator of the vitamin's place of origin in the mammary gland. Our findings do not support the idea that vitamin E in mature milk has its original location in the apical membrane.
Effects of dietary casein and soy protein on metabolism of radiolabelled low density apolipoprotein B in rabbits
Authors: Samman Samir , Khosia Pramod , Carroll Kenneth K. 
Published: November 2006

AbstractRabbits fed semipurified diets containing casein have elevated plasma cholesterol levels compared to those fed soy protein. As part of continuing studies on the mechanism of casein‐induced hypercholesterolemia, two groups of six rabbits were fed these diets for 14 to 16 weeks. Animals fed the casein diet were found to have significantly higher plasma concentrations of protein, cholesterol, triacylglycerol, phospholipid and apolipoprotein B (apo B) associated with low density lipoprotein (LDL) than those fed the soy protein diet. Kinetic studies showed that the fractional catabolic rate of LDL‐apo B was significantly lower in animals fed casein than in those fed soy protein regardless of whether the tracer LDL was obtained from donors fed casein or soy protein. The production rate of LDL‐apo B was higher in casein‐fed animals but this was not statistically significant. These results show that the efficiency of removal of LDL is significantly reduced in animals fed casein compared to those fed soy protein, and that the source of LDL did not affect the efficiency of its subsequent removal. The acumulation of LDL in casein‐fed animals is consistent with down‐regulation of the LDL receptor.
In vivo incorporation of lauric acid into rat adipose tissue triacylglycerols
Authors: Bugaut Maurice 
Published: November 2006

AbstractAn in vivo approach was taken to examine fatty acid esterification in adipose tissue using a coconut oilenriched diet. Rats were fed a diet containing cocounut oil (50% lauric acid) for six weeks. Triacylglycerols from perirenal adipose tissue were fractionated by silver nitrate‐thin layer chromatography and, then, preparative gas chromatography. The distribution of 169 triacylglycerol types accounting for 97% of total triacylglycerols was determined. There was evidence for a very high content of mixed triacylglycerols composed of intermediate (12∶0 and 14∶0) and long acyl moieties. No significant differences were observed between the experimental distribution of triacylglycerol types and the random distribution, calculated from the total fatty acid composition. This indicated that most long chain triacylglycerols stored before coconut oil feeding would have been rearranged after the six weeks of coconut oil feeding. The experimental proportion of trilauroylglycerol reached 2%, as expected from its random proportion, and the proportions of dilauroylacylglycerols were slightly higher than the random values. Present results were compared with those previously obtained from triacylglycerols of adipose tissue of rats fed a low‐fat standard diet (1,2). From our results and those of other authors, it is suggested that lauric acid is a good substrate forsn‐glycero‐3‐phosphate acyltransferase and diacylglycerol acyltransferase in rat adipose tissue.
Effects of cholesterol oxidation derivatives on cholesterol esterifying and cholesteryl ester hydrolytic enzyme activity of cultured rabbit aortic smooth muscle cells
Authors: Morin Robert J. , Peng Shi‐Kaung 
Published: November 2006

AbstractThe effects of 5 μg/ml of 25‐hydroxycholesterol; cholestane‐3β, 5α,6β‐triol; and cholesterol on acyl CoA cholesterol acyltransferase, acid cholesteryl ester hydrolase and neutral cholesteryl ester hydrolase was studied in cultured rabbit aortic smooth muscle cells. After 1 hour incubation, 25‐hydroxycholesterol resulted in a fourfold stimulation of acyl CoA cholesterol acyltrans‐ferase activity. No stimulation by 25‐hydroxycholesterol was noted before 15 minutes or after 5 hours of incubation. Neither cholestane‐3β,5α,6β‐triol nor cholesterol influenced acyl CoA cholesterol acyltransferase activity at any time interval. No significant effects of any of the sterols were noted on acid cholesteryl ester hydrolase or neutral cholesteryl ester hydrolase activity. The imbalance between acyl CoA cholesterol acyl trans‐ferase and hydrolase activities induced by 25‐hydroxycholesterol could result in cholesteryl ester accumulation by arterial smooth muscle cells, which may be associated with atherosclerosis.