bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cholesterol synthesis and esterification in isolated enterocytes: Regulation by cholesterol and cholestyramine feeding
Authors: Iglesias José , Gonzalez‐Pacanowska Dolores , Marco Carmen , Garcia‐Peregrin Eduardo 
Published: November 2006

AbstractThe purpose of the present study was to investigate the physiological control of the main regulatory enzymes of cholesterol metabolism in isolated enterocytes obtained from chick duodenum, jejunum and ileum. Cholesterol feeding resulted in an inhibition of 3‐hydroxy‐3‐methylglutaryl‐CoA reductase and mevalonate 5‐pyrophosphate decarboxylase, while cholestyramine feeding increased reductase activity in all the regions studied and decarboxylase activity only in duodenum. Cholesterol feeding markedly increased acyl‐CoA:cholesterol acyltransferase, but the effects of cholestyramine were less clear. The effects on transferase activity cannot be due to differences in the availability of acyl‐CoA as exogenous substrate as no significant differences were found in acyl‐CoA hydrolase activity after any of the dietary treatments. The effects of cholesterol feeding were related to changes in the cholesterol content of epithelial cells, whereas in the case of cholestyramine this relationship was less apparent.
2‐alkenyl‐4,4‐dimethyloxazolines as derivatives for the structural elucidation of iosmeric unsaturated fatty acids
Authors: Luthria Devanand L. , Sprecher Howard 
Published: November 2006

AbstractSeveral types of unsaturated fatty acid methyl esters were converted into 4,4‐dimethyloxazoline (DMOX) derivatives and analyzed by mass spectrometry to further evaluate the feasibility of using this derivative for locating the positions of double bonds in isomeric fatty acids. Five isomeric 20‐carbon tetraenoic acids were analyzed in which the fourcis double bonds were systematically moved from the 4,7,10,13‐ to the 8,11,14,17‐positions. It was possible to locate the positions of all four double bonds in the 7,10,13,16‐ and 8,11,14,17‐isomers by appropriate ions differing by 12 atomic mass units. In a similar way the three terminal double bonds in the 4,7,10,13‐, 5,8,11,14‐ and 6,9,12,15‐isomers could be assigned. Odd‐numbered ions atm/z 139, 153 and 167 which are accompanied by an even mass ion at 138, 152 and 166, respectively, are diagnostic for DMOX derivatives of acids with their first double bond, respectively, at positions 4, 5 and 6. It was thus possible to assign the location of all four double bonds in these three isomers. A comparison of the spectra of the DMOX derivatives of 17,17,18,18‐d4vs. 9,10,12,13‐d4 linoleic acid suggests that double bonds preferentially migrate toward the polar end of the molecule prior to fragmentation. The merit of using DMOX derivatives to locate double‐bond positions in mono‐ and dicarboxylic acids, produced during β‐oxidation of polyunsaturated fatty acids, was evaluated. The spectra of 3‐cis‐ and 4‐cis‐decenoic acids differ as do the spectra of 8‐carbon dicarboxylic acids with their double bonds at positions 3 and 4.
Time response of cholesterol synthesis inhibition by compactin‐related compunds.In vitro quantitation of the “Escape Phenomenon”
Authors: Sviridov Dmitri D. , Endo Akira , Pavlov Michael Y. , Repin Vadim S. 
Published: November 2006

AbstractThe time course of the inhibition of cholesterol synthesis by low and high doses of mevinolin and monacolin X were studied in normal human skin fibroblasts, fibroblasts without low density lipoprotein receptor and HepG2 hepatome cells. Low doses of the inhibitors (0.2 ng/mL) caused a sharp decrease in the rate of cholesterol synthesis during the firt 2–3 h, which gradually increased to about 40% during the next 6 h. Further incubation led to a decrease or stabilization of the cholesterol synthesis rate. High doses of the drugs (100 mg/mL) strongly inhibited cholesterol synthesis during the first 2–3 h, followed by a moderate increase during the next 20 h. No drug or tissue selectivity was observed.
Oxidative modification of triglyceride‐rich lipoproteins in hypertriglyceridemic rats following magnesium deficiency
Authors: Gueux Elyett , Cubizolles Christine , Bussière Laurence , Mazur Andrzej , Rayssiguier Yves 
Published: November 2006

AbstractHypertriglyceridemia observed in magnesium (Mg)‐deficient rats was associated with a significant increase in the very low‐density lipoprotein (VLDL) plus low‐density lipoprotein (LDL) fractions. The results fromin vitro copper‐induced lipid peroxidation, expressed in terms of conjugated dienes and thiobarbituric acid reactive substances content, showed that VLDL+LDL particles from Mg‐deficient rats were more susceptible to oxidative damage than lipoproteins from control rats. These results suggest that the mechanism responsible for the atherogenicity and tissue damage characteristic of Mg deficiency may be mediated by an increased susceptibllity of triglyceride‐rich lipoproteins to peroxidation in hypertriglyceridemic animals.
Trp89 in the lid ofHumicola lanuginosa lipase is important for efficient hydrolysis of tributyrin
Authors: Holmquist Mats , Martinelle Mats , Clausen Ib Groth , Patkar Shamkant , Svendsen Allan , Hult Karl 
Published: November 2006

AbstractTo determine whether Trp89 located in the lid of the lipase (EC 3.1.1.3) fromHumicola lanuginosa is important for the catalytic property of the enzyme, site‐directed mutagenesis at Trp89 was carried out. The kinetic properties of wild type and mutated enzymes were studied with tributyrin as substrate. Lipase variants in which Trp89 was changed to Phe, Leu, Gly or Glu all showed less than 14% of the activity compared to that of the wild type lipase. The Trp89Glu mutant was the least active with only 1% of the activity seen with the wild type enzyme. All Trp mutants had the same binding affinity to the tributyrin substrate interface as did the wild type enzyme. Wild type lipase showed saturation kinetics against tributyrin when activities were measured with mixed emulsions containing different proportions of tributyrin and the nonionic alkyl polyoxyethylene ether surfactant, Triton DF‐16. Wild type enzyme showed a Vmax=6000±300 mmol·min−1·g−1 and an apparent Km=16±2% (vol/vol) for tributyrin in Triton DF‐16, while the mutants did not show saturation kinetics in an identical assay. The apparent Km for tributyrin in Triton DF‐16 was increased as the result of replacing Trp89 with other residues (Phe, Leu, Gly or Glu). The activities of all mutants were more sensitive to the presence of Triton DF‐16 in the tributyrin substrate than was wild type lipase. The activity of the Trp89Glu mutant was decreased to 50% in the presence of 2 vol% Triton DF‐16 compared to the activity seen with pure tributyrin as substrate. Wild type lipase and all mutants except Trp89Glu had the same affinity for the substrate interface formed by 15.6 vol% tributyrin in Triton DF‐16. The Trp89Glu mutant showed a lower affinity than all the other lipase variants for the interface of 15.6 vol% tributyrin in Triton DF‐16. The study showed that Trp89 located in the lid ofH. lanuginosa lipase is important for the efficient hydrolysis of tributyrin and that this residue plays a role in the catalytic steps after adsorption of the lipase to the substrate interface.
Central nervous system demyelinating diseases and increased release of cholesterol into the urinary system of rats
Authors: Nicholas Harold J. , Taylor John 
Published: November 2006

AbstractThe question of what happens to cholesterol in the adult central nervous system during its slow turnover has been addressed using rats with brain and spinal cord labeled with [4‐14C]cholesterol upon intracerebral injection of labeled cholesterol into rats at 10–12 days of age. At six months after injection,14C was found only in the brain and spinal cord and was slowly releasedvia the rat's urine. When labeled rats were given demyelinating agents (triethyl tin chloride, hexachlorophene, sodium cyanide) and when experimental allergic encephalomyelitis was induced, a measurable increase in urinary14C label above control levels was found. It was concluded that there is a direct relationship between the experimental demyelination induced and the increased release of cholesterol metabolites into urine. The study suggests that a clinical method could be developed to determine the rate of central nervous system demyelination by measuring the amount of urinary cholesterol metabolites.
The immunosuppressive substance 2‐chloro‐2‐deoxyadenosine modulates lipoprotein metabolism in a murine macrophage cell line (P388 cells)
Authors: Lechleitner Monika , Auer Bernhard , Zilian Udo , Hoppichler Fritz , Schirmer Michael , Föger Bernhard , Geisen Francoise , Patsch Josef R. , Konwalinka Günther 
Published: November 2006

AbstractA recently developed immunosuppressive substance, 2‐chloro‐2‐deoxyadenosine (2‐CdA), was reported to inhibit monocyte functions at low concentration. Because macrophages play a key role in the formation of atherosclerotic plaques, it was of interest to study the effect of 2‐CdA on cellular lipid metabolism. For this purpose we have used a macrophage cell line (P388) to perform incubation studies in the presence of acetylated low density lipoprotein (Ac‐LDL) and 2‐CdA. The addition of 2‐CdA, in concentrations ranging from 5–20 nM, induced a dose‐dependent decrease in cellular cholesterol content and in the amount of extracellular [14C]oleic acid (OA) incorporated into the cholesteryl ester (CE) fraction. The effect was maximized at 20 nM 2‐CdA with an 86% reduction in cholesterol esterification compared to controls (P<0.008). To evaluate the mechanism of interaction of 2‐CdA with cellular lipid metabolism, deoxycytidine (dCyt) and 3‐methoxybenzamide (3‐MOB), substances known to antagonize the effect of 2‐CdA in different ways, were co‐administered with 2‐CdA. dCyt, a competitive inhibitor of dCyt kinase, which catalyzes phosphorylation to the active metabolite, antagonized the effects of 20 nM 2‐CdA, producing significantly greater incorporation of extracellular [14C]OA into the CE fraction than in the presence of 2‐CdA alone (P<0.0086). Co‐incubation with 2‐CdA and the poly‐ADP‐ribose synthetase inhibitor 3‐MOB, which is known to render cells resistant to 2‐CdA toxicity by preventing cellular nicotinamide adenine dinucleotide (NAD)‐ and adenosine triphosphase‐depletion, also reversed the effect of 2‐CdA on lipid accumulation. However, incubation of P388 cells with 20 nM 2‐CdA did not result in a decrease in cellular NAD content. As 20 nM 2‐CdA showed no effect on intracellular cholesterol synthesis based on measurement by 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase activity, the decrease in cellular cholesterol content and in [14C]OA incorporation seems to be primarily due to an interference with Ac‐LDL metabolism.
Dietary polyunsaturated fat decreases interaction between low density lipoproteins and arterial proteoglycans
Authors: Manning James M. , Gebre Abraham K. , Edwards Iris J. , Wagner Williams D. , Rudel Lawrence L. , Parks John S. 
Published: November 2006

AbstractPolyunsaturated dietary fat (n−3 and n−6) results in less atherosclerosis in monkeys compared to lard (Parks, J.S., Kaduck‐Sawyer, J., Bullock, B.C., and Rudel, L.L.,Arteriosclerosis 10, 1102–1112; Rudel, L.L., Parks, J.S., Johnson, F.L., and Babiak, J.,J. Lipid Res. 27, 465–474, 1986). We hypothesized that this was due, in part, to a decreased reactivity of low density lipoproteins (LDL) with arterial proteoglycans (PG). To test this hypothesis, cynomolgus monkeys were fed diets containing lard, safflower oil (n−6 polyunsaturated; Poly), menhanden fish oil (FO), or oleic acid‐rich safflower oil (oleinate; Mono) for 14 mon, and plasma LDL were isolated and characterized. Several properties of LDL thought to be important in the interaction of LDL with arterial PG were measured including LDL particle size, chemical composition, sialic acid content, density distribution, apolipoprotein E (apoE) content and cholesteryl ester transition temperature. Plasma LDL cholesterol concentrations (mg/dL) after 14 mon of diet consumption averaged (mean±SEM): FO (366±45), Lard (352±27), Poly (279±24), and Mono (230±43). The composition of LDL was similar among diet groups except that FO LDL were relatively depleted of cholesteryl ester and enriched in protein and were smaller in size. LDL sialic acid content was similar among diet groups (4.5–5.0 μg/mg LDL protein). The LDL apoE/B molar ratio, a measure of the apoE content per LDL particle averaged: Mono (3.0±1.0), Poly (2.0±0.1), Lard (1.8±0.5), and FO (1.0±0.2). The FO group had a lower proportion (13%) of the apoE enriched d=1.015–1.025 g/mL subfraction of LDL than did the other diet groups (31–45%). The transition temperature of the LDL cholesteryl esters was below body temperature for the FO and Poly groups (36°C) and above for the Lard and Mono groups (40–44°C). The percentage of LDL cholesterol that formed insoluble complexes with arterial chondroitin sulfate PG averaged: Mono (29±4%), Lard (18±3%), Poly (14±3%), and FO (7±2%). Among all diet groups, there was a significant positive correlation (r=0.54) between LDL‐PG complex formation and LDL apoE/B molar ratio. We conclude that dietary FO and Poly result in LDL that are less reactive with arterial PG compared to Lard or Mono fats. While FO appears to decrease PG binding by decreasing the apoE content and amount of the largest LDL subfraction, Poly fat appears to affect LDL‐PG interactions by other mechanisms. Decreased LDL‐PG interactions may lead to decreased atherosclerosis in animals fed polyunsaturated dietary fat.
Effect of dietary linseed oil on tumoricidal activity and eicosanoid production in murine macrophages
Authors: Hubbard Neil E. , Chapkin Robert S. , Erickson Kent L. 
Published: November 2006

AbstractDiets that contain high levels of n−3 fatty acids from fish oil have been shown to significantly effect macrophage cytolytic capacity, tumor necrosis factor alpha production and eicosanoid production. The present study was undertaken to determine whether n−3 fatty acids from vegetable origin [linseed oil (LIN)] would have the same effects on murine macrophage tumoricidal capacity and eicosanoid production as would fish oil. Mice were fed for three weeks diets that contained 10% (wt/wt) of either LIN, which is high in linolenic acid (18∶3n−3), menhaden fish oil (MFO), which is high in eicosapentaenoic (20∶5n−3) and docosahexaenoic (22∶6n−3) acids, or safflower oil (SAF), which is high in linoleic acid (18∶2n−6).In vivo‐ orin vitro‐activated macrophages were assessed for select functions. As expected, macrophages from mice fed LIN and MFO produced significantly lower levels of both prostaglandins and leukotriene C4 when compared with macrophages from mice fed SAF. In addition, LIN and MFO macrophages were able to synthesize leuko‐triene C5, which could not be produced by macrophages from mice fed SAF. The effects of LIN, however, were not as pronounced as those of MFO. With respect to specific functions, macrophages from mice fed LIN did not have altered cytolytic capacity when compared with macrophages from mice fed SAF and activatedin vitro with either lipopolysaccharide (LPS) alone for 24 h or with LPS plus interferon gamma (IFNγ) for 5 h. Diet did not significantly alter tumoricidal capacity of macrophages activated completelyin vivo either. Specific binding of macrophages to tumor targets, nitric oxide production and the production of tumor necrosis factor alpha were found to be unaltered by LIN when compared with SAF. The results are not consistent with a general n−3 effect, as LIN could not effect the functions comparable to MFO. The results also suggest that a change in eicosanoid production may not be sufficient to modulate tumoricidal activity in macrophages.
Inhibition of cytolytic T lymphocyte activity by oxysterols
Authors: Küçük Ömer , Stoner‐Picking Jeanette , Yachnin Stanley , Gordon Leo I. , Williams R. Michael , Lis Leonard J. , Westerman Maxwell P. 
Published: November 2006

AbstractThe objective of this study was to investigate the effects of oxysterols (OS), namely 5α‐hydroxy‐6‐ketocholestanol, 6‐ketocholestanol and 25‐hydroxycholesterol, on specific cell‐mediated cytotoxicity by C57BL/6 spleen cells against P815‐X2 (a DBA/2 mastocytoma) target cells. Cytolytic T lymphocytes (CTL) were generated by intraperitoneally injecting C57BL/6 mice with P815‐X2 tumor cells 10 d prior to the cytotoxicity experiments. Preincubation of CTL with 10−5 M 5α‐hydroxy‐6‐ketocholestanol and 6‐ketocholestanol for 45 min in lipoprotein‐depleted medium resulted in an inhibition of cytolytic activity (73 and 43%, respectively) as measured by 4‐h51Cr release. At a concentration of 5×10−6 M, 5α‐hydroxy‐6‐ketocholestanol inhibited CTL activity by 65%, whereas 6‐ketocholestanol did not elicit any inhibition. By contrast, 25‐hydroxycholesterol did not inhibit CTL at either concentration, although it is known to be a potent inhibitor of 3‐hydroxy‐3‐methyl‐glutaryl‐coenzyme A reductase, the rate‐limiting enzyme in the cholesterol biosynthetic pathway. When CTL were preincubated with OS in lipoprotein‐replete medium, there was no inhibition of CTL activity at the respective concentrations. The results suggest that the inhibition of CTL activity upon short‐term incubation with OS is not due to the inhibition of cholesterol synthesis, but may be due to the insertion of OS into the plasma membrane to replace cholesterol and alteration of membrane physical properties.
Reversible or irreversible modification of [3H]PAF binding on rabbit platelet membranes differentiates various PAF receptor antagonists
Authors: Domingo M. T. , Piro F. , Broquet C. , Auclair E. , Chabrier P. E. , Braquet P. 
Published: November 2006

Abstract[3H]Platelet‐activating factor (PAF) binding to rabbit platelet membranes was examined before and after 20 min preincubation at 25°C in the presence of PAF, lysoPAF, or of five different PAF receptor antagonists (L 652731, BN 52021, WEB 2086, BN 52111 and BN 52115). When platelet membranes were not washed after preincubation with PAF or PAF antagonists, no significant specific binding of [3H]PAF was observed, which suggests full occupancy of the binding sites. When membranes were extensively washed, full recovery of specific [3H]PAF binding was attained with L 652731 and partial recoveries (60%, 55% and 30%) were reached with BN52021, WEB 2086 and PAF, respectively; no recovery was seen with the dioxolanes BN 52111 and BN 52115. Scatchard analysis of the binding data indicated that no significant change in the dissociation constant (Kd) and maximum number of binding sites (Bmax) occurred after preincubation of platelet membrane with L 652731, whereas a reduction of Bmax was observed when PAF and BN 52021 were measured. When platelet membranes were preincubated with WEB 2086, Bmax and Kd significantly increased. The data suggest differing binding properties for PAF and the PAF antagonists. Some of the PAF antagonists may tightly bind to the PAF receptor site(s) and/or irreversibly modify or downregulate PAF recognition sites. Our results also suggest that the interaction of PAF receptor antagonists with PAF receptor can be divided into at least two components, namely a reversible component and an irreversible one.
The origin of palmitic acid in brain of the developing rat
Authors: Marbois B. Noelle , Ajie Henry O. , Korsak Rose A. , Sensharma Dilip K. , Edmond John 
Published: November 2006

AbstractA rat milk substitute containing lower amounts of palmitic and oleic acid in the triacylglycerols in comparison to natural rat milk was fed to artificially reared rat pups from day 7 after birth to day 14. Pups reared by their mother served as controls. Free trideuterated (D3) palmitic acid [(C2H3)(CH2)14COOH, 98 atom % D] and free perdeuterated (D31) palmitic acid [C152H31COOH, 99 atom % D] in equal quantity were mixed into the triacylglycerols of the milk substitute in an amount equal to 100% of the palmitic acid in the triacylglycerols. A control milk substitute contained unlabeled free palmitic acid in an amount equal to 100% of the palmitic acid in the triacylglycerols of the milk substitute. The objective was to determine if palmitic acid in the diet contributed significantly to the palmitic acid content of developing brain and other organs. The methyl esters of the fatty acids were analyzed by gas chromatography and the palmitic acid methyl ester was examined by fast atom bombardment mass spectrometry. The proportion of deuterated methyl palmitate as a percentage of total palmitate was determined; 32% of the palmitic acid in liver and 12% of the palmitic acid in lung were trideuterated and perdeuterated palmitic acid in approximately equal amounts. The brain, by contrast, did not contain the deuterated palmitic acid moiety. Quantitation of palmitic acid and total fatty acids revealed a significant accumulation in organs in the interval from 7 to 14 days of age. Under our experimental conditions, labeled palmitic acid does not enter the brain. Consequently, we conclude that the developing brain produces all required palmitic acid byde novo synthesis.
Arachidonic acid biosynthesis in non‐stimulated and adrenocorticotropin‐stimulated sertoli and leydig cells
Authors: Hurtado de Catalfo Graciela E. , Mandon Elisabet C. , de Gómez Dumm Irma N. T. 
Published: November 2006

AbstractThe biosynthesis of arachidonic acid in Sertoli and Leydig cells isolated from the testes of mature rats has been investigated. Both types of cells incorporated [2‐14C]eicosatrienoic acid from the incubation medium and transformed it into arachidonic acid. The administration of adrenocorticotropin (ACTH) to the rats decreased the Δ5 desaturating activity in the isolated testicular cells, while ACTH produced no changes in the uptake of the substrate. Similar results were obtained when ACTH was added to the incubation medium of cells isolated from non‐hormone treated rats. The total fatty acid composition of the Sertoli cells isolated from ACTH‐treated rats showed a significant increase in the relative percentage of 18∶2n−6 and a decrease in the C20 and C22 polyenes. This may indicate that ACTH exerts an inhibitory effect on Δ6, Δ5 and Δ4 desaturase activities. Addition of corticosterone to the incubation medium also produced a significant decrease in arachidonic acid biosynthesis. Because ACTH is known to stimulate the release of corticosteronein vivo, both hormones may act cumulatively in the regulation of arachidonic acid metabolism in Sertoli and Leydig cells.
Effects of various dietary fats on cardiolipin acyl composition during ontogeny of mice
Authors: Berger Alvin , Gershwin M. E. , German J. Bruce 
Published: November 2006

AbstractCardiolipin (CL) is a unique mitochondrial phospholipid, containing up to 85 wt% 18∶2n−6 in mammals. The influence of maternal dietary fatty acids on the acyl composition of offspring CL has not been examined previously. Adult female mice were thus fed diets rich in 18∶1n−9 (olive oil), 18∶2n−6 (safflower oil), 18∶3n−3 (linseed oil) or 20∶5n−3 and 22∶6n−3 (fish oil/safflower, 9∶1, w/w), for a five month period, encompassing two breeding cycles. Offspring from the second breeding cycle were then fed these diets. The acyl composition of CL, phosphatidylcholine and phosphatidylethanolamine from liver and heart was evaluated from mice killed 3, 18 and 42 days after parturition. The primary nutrient sources at these three time points were transplacental nutrients, breast milk and the diet, respectively. Maternal diet was found to influence the acyl composition of CLvia both placental transfer of fatty acids and breast milk. Fish oil feeding resulted in replacement of a substantial portion of 18∶2n−6 with 22∶6n−3; after 42 days, the area% of 18∶2n−6 in heart CL was reduced from 62% in safflower oil fed mice to 12%. In comparison to fish oil feeding, linseed oil feeding resulted in a much lower accumulation of 22∶6n−3. Olive oil feeding resulted in substantial replacement of 18∶2n−6 with 18∶1n−9 (18∶2n−6 was reduced from 62% to 31%). Physiologically, these findings are relevant because changes in CL acyl composition may influence the activity of associated inner mitochondrial membrane enzymes.