bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of calcium‐independent cytosolic phospholipase A2 activity in the submucosal regions of rat stomach and small intestine
Authors: Fukushima Takeshi , Serrero Ginette 
Published: November 2006

AbstractThis study was undertaken to compare the calcium‐independent phospholipase A2 (PLA2) activities in the cytosols of twelve rat tissues and to determine whether their activities were distinct. 1‐O‐Alk‐1′‐enyl‐2‐[14C]‐oleoyl‐sn‐glycero‐3‐phosphocho‐line (PlsC) and 1‐O‐Alk‐1′‐enyl‐2‐[14C]oleoyl‐sn‐glycero‐3‐phosphethanolamine (PlsE) were synthesized and used as substrates, instead of phosphatidyl compounds, to exclude hydrolysis by cytosolic PLA1 activity that could be present in some of the cytosolic preparations. For each tissue, we examined substrate specificity, pH optimum, and effect of adenosine triphosphate (ATP) and ATP analogues. PLA2 activity was detected in eleven out of the twelve issues examined. Based on substrate specificity and pH optimum, cytosolic calcium‐independent PLA2 were classified in three groups. The first group, which included PLA2 from small intestine, stomach and spleen, had the highest specific activity with PlsC as substrate (1253, 309 and 75 nmol/mg protein/hour, respectively) and an optimal pH at 6.5. Activity with PlsE as substrate was much lower (20–37%) than with PlsC. The second group of PLA2 activities included the cytosolic activities from thymus, lung, liver and pancreas that showed lower specific activities for both substrates (14–23 nmol/mg protein/hour with PlsC) and had a broader optimal pH range of 6.1 to 7.5. The cytosols from brain, kidney, heart and muscle comprised the third PLA2 group that was found to have a higher specific activity with PlsE (5–20 nmol/mg protein/hour) than PlsC and an optimal pH range from 7.4 to 7.9. Since the highest specific activity was found in the cytosol from small intestine, this PLA2 was examined further. PLA2 activity was found to be equally distributed in the cytosol of the submucosal portion of duodenum, jejunum and ileum with an optimal pH of 6.1 and a 5‐fold higher activity with PlsC than PlsE as substrate. Moreover, this PLA2 activity was inhibited by treatment with detergents. These results indicate the presence in the submucosal portion of the intestine of a calcium‐independent cytosolic PLA2 with a high specific activity toward PlsC and properties distinct from those described for the PLA2 found in the intestinal brush‐border.
Vitamin E isomers in grain amaranths (Amaranthus spp.)
Authors: Lehmann James W. , Putnam Daniel H. , Qureshi Asaf A. 
Published: November 2006

AbstractVitamin E isomers are important antioxidants, but their variation is poorly documented in pseduocereal grains such as amaranths. Using normal‐phase, high‐performance liquid chromatography with fluorescence detection, seeds of thirteen amaranth (Amaranthus cruentus L.,A. hypochondriacus L.) accessions were surveyed for the composition of tocols. The most common tocols found were α‐tocopherol (2.97 to 15.65 mg/kg seed) and β‐tocotrienol (5.92 to 11.47 mg/kg seed) and γ‐tocotrienol (0.95 to 8.69 mg/kg seed), while someA. cruentus accessions contained δ‐tocotrienol (0.01 to 0.42 mg/kg seed). This is the first report of tocotrienols in amaranths.Amaranthus cruentus grain‐types of Mesoamerican origin had significantly (P≤0.01) greater levels of four tocols than didA. cruentus African vegetable‐types. Unlike many cereal grains, amaranths have significant amounts of both β‐ and γ‐tocotrienols; however, β‐tocopherol was not detected in any of the amaranths. Using multiple linear regressions, α‐tocopherol variation of both species and types was consistently explained by variation in tocols other than α‐tocopherol. On the whole, fresh amaranth samples of both species tended to have higher levels of tocotrienols than samples stored for two years. Storage effects on amaranth tocol composition are suspected.
Structure and biosynthesis of novel conjugated polyene fatty acids from the marine green algaAnadyomene stellata
Authors: Mikhailova Marina V. , Bemis Debra L. , Wise Mitchell L. , Gerwick William H. , Norris James N. , Jacobs Robert S. 
Published: November 2006

AbstractNovel polyunsaturated fatty acids with four conjugated double bonds were found in extracts of the green macroalga,Anadyomene stellata. The isolation of five of these with different chain lengths and varying degrees of unsaturation −16∶5, 18∶4, 20∶5, 20∶6, and 22∶7—was accomplished by organic extraction followed by a combination of vaccum and high‐performarce liquid chromatography. One of these that was a novel substance (22∶7) was characterized as 4ZZ,7Z,9E,13Z,16Z,19Z‐docosaheptaenoic acid and assigned the trivial name stellaheptaenoic acid. The structure of this new compound, isolated as its methyl ester derivative, was deduced from detailed nuclear magnetic resonance, gas chromatography/mass spectrometry (GC/MS), and other spectroscopic methods. Incubation of a chloroplast preparation, isolated from a crude algal homogenate by differential centrifugation, with six unsaturated fatty acids (palmitoleic, 6Z,9Z,12Z,15Z‐octadecatetraenoic acid, arachidonic acid, eicosapentaenoic acid, 7Z,10Z,13Z,16Z‐docosatetraenoic acid, and 4Z,7Z,10Z,13Z,16Z,19Z‐docosahexaenoic acid) resulted in substantially increased synthesis of unique tetraene compouds as detected by ultraviolet spectrophotometry and tentatively identified by GC/MS.
Furan fatty acids determined as oxidation products of conjugated octadecadienoic acid
Authors: Yurawecz Martin P. , Hood Jennifer K. , Mossoba Magdi M. , Roach John A. G. , Ku Yuoh 
Published: November 2006

AbstractThe objective of this study was to identify oxidation products of conjugated linoleic acid (CLA), a series of octadecadienoic acids with conjugated double bonds, which have been reported to have antioxidant and anticarcinogenic properties. Reference materials of CLA were oxidized in different concentrations of water/methanol; for example, 0.5 g octadecadienoic acid was dissolved in 50 mL methanol, and 100 mL water was added; this suspension was heated at 50°C and continuously aerated. Aliquots of 5 mL were taken over time, extracted with ether, treated with diazomethane and examined by gas chromatography/mass spectrometry and/or gas chromatography with flame‐ionization detection. Products identified included the following furan fatty acids (FFAs): 8,11‐epoxy‐8,10‐octadecadienoic; 9,12‐epoxy‐9,11‐octadecadienoic; 10,13‐epoxy‐10,12‐octadecadienoic; and 11,14‐epoxy‐11,13‐octadecadienoic. Conjugated dienes should be considered as a possible source of FFAs, and CLA may have products common to furans in their overall oxidative scheme.
Reinvestigation of the antioxidant properties of conjugated linoleic acid
Authors: van den Berg Jeroen J. M. , Cook Nancy E. , Tribble Diane L. 
Published: November 2006

AbstractDespite repeated suggestions that antioxidant activity of conjugated linoleic acid (CLA), a collective of conjugated dienoic isomers of linoleic acid, underlies its reported anticarcinogenic and antiatherosclerotic effects, the antioxidant properties of CLA remain ill‐defined. Therefore, this study was undertaken to gain more insight into the mechanism of potential CLA antioxidant activity. It was tested whether CLA could protect membranes composed of 1‐palmitoyl‐2‐linoleoyl phosphatidylcholine (PLPC) from oxidative modification under conditions of metal ion‐dependent or‐independent oxidative stress. Progress of oxidation was determined by direct spectrophotometric measurement of conjugated diene formation and by gas chromatographic/mass spectrometric analysis of fatty acids. The oxidative susceptibility of CLA was higher than that of linoleic acid, and comparable to arachidonic acid. When oxidation of PLPC (1.0 mM) was initiated using the lipid‐soluble 2,2′‐azobis(2,4‐dimethylvaleronitrile) or the water‐soluble 2,2′‐azobis(2‐amidinopropane) hydrochloride, the radical scavengers vitamin E and butylated hydroxytoluene (BHT) at 0.75 μM efficiently inhibited PLPC oxidation, as evident from a clear lagphase. In contrast, 0.75 μM CLA did not have any significant effect on PLPC oxidation. Inhibition of PLPC oxidation by higher concentrations of CLA appeared due to competition, not to an antioxidant effect. When oxidation of PLPC was initiated by hydrogen peroxide/Fe2+ (500 μM/0.05–20 μM), both vitamin E (1 μM) and ethylene glycol‐bis(aminoethyl ether) tetraacetic acid (50 μM) efficiently inhibited PLPC oxidation. However, CLA (1–50 μM) did not show a clear protective effect under any of the conditions tested. We conclude that CLA, under these test conditions, does not act as an efficient radical scavenger in any way comparable to vitamin E or BHT. CLA also does not appear to be converted into a metal chelator under metal‐ion dependent oxidative stress, as had previously been suggested. On the basis of our observations, a role for CLA as an antioxidant does not seem plausible.
Studies on the mechanism of the ursodeoxycholic acid‐induced increase in hepatic low‐density lipoprotein binding
Authors: Bouscarel Bernard , Caryak Susan , Robins Sander J. , Fromm Hans 
Published: November 2006

AbstractPreviously, we have shown, in golden Syrian hamsters, that chronic feeding of ursodeoxycholic acid (UDCA), in contrast to that of its 7α‐epimer, chenodeoxycholic acid (CDCA), produced a significant increment in hepatic low‐density lipoprotein (LDL) uptake, despite similar suppression of bile acid synthesis by both bile acids. Evidence for a direct effect of this bile acid on hepatic LDL metabolism was shownin vitro, with isolated hamster hepatocytes, suggesting that this effect was unique to UDCA and specific for receptor‐mediated LDL catabolism. The aim of the present study was to define the cellular mechanism(s) associated with this phenomenon, using male golden Syrian hamsters. Regardless of chronic exposure of the liver to either UDCA or CDCA, acute incubation with UDCA consistently resulted in an increase of LDL binding to isolated hepatocytes by 15 to 40%. Furthermore, chronic treatment with either UDCA or CDCA did not result in alterations in lipoprotein particle composition. Likewise, incubation of hepatocytes with UDCA was not associated with a change of the membrane lipid composition. In isolated liver membrane fractions, UDCA increased both the maximum number of LDL binding sites and the affinity constant for LDL by around 35% suggesting an interaction of UDCA with the LDL receptor, at the plasma membrane level, independent of an effect on receptor cycling. The results of the studies support a role for UDCA in the recruitment of cryptic LDL receptors from a cellular membrane pool, possibly due to the unique localization of UDCA in the plasma membrane lipid bilayer.
Carbohydrate type and amount alter intravascular processing and catabolism of plasma lipoproteins in guinea pigs
Authors: Fernandez Maria Luz , Conde A. Karin , Ruiz Laura R. , Montano Carlos , Ebner John , McNamara Donald J. 
Published: November 2006

AbstractTo test the effects of exchanging dietary complex and simple carbohydrate for fat calories on lipoprotein metabolism, guinea pigs were fed two different fat/carbohydrate ratios: 2.5∶58% (w/w) or 25∶29% (w/w) with either sucrose or starch as the carbohydrate source. Animals fed high‐fat had higher plasma low‐density lipoprotein (LDL) and hepatic cholesterol concentrations than animals fed low‐fat diets (P<0.01). The cholesteryl ester content per particle was higher, and the number of triacylglycerol (TAG) molecules was lower in very low density lipoprotein (VLDL) and LDL from animals fed high‐fat diets. Intake of high‐fat/sucrose resulted in higher plasma LDL concentrations than intake of high‐fat/starch, and animals fed low‐fat/starch had the highest plasma TAG concentrations associated with VLDL particles containing more TAG molecules, as well as a TAG‐enriched LDL. The activity of plasma lecithin cholesteryl:acyl transferase (LCAT) was highest in animals fed high‐fat/sucrose, and heart lipoprotein lipase (LPL) activity was higher in animals fed high‐fat diets. Hepatic apoprotein B/E (apo B/E) receptor number (Bmax) was increased 21% with low‐fat diets (P<0.01). These results suggest that the hypercholesterolemia induced by high‐fat and by sucrose intake are associated with a higher plasma LCAT activity which results in a cholesteryl ester‐enriched VLDL which, by the action of LPL, might be more readily converted to LDL through the delipidation cascade leading to downregulation of hepatic apo B/E receptors. The hypertriglyceridemia associated with low‐fat intake may result from increased production of VLDL TAG, which would explain the increased TAG content and the higher TAG/CE ratio of VLDL from animals fed the low‐fat/starch diet.
Dietary fatty acids, membrane transport, and oxidative sensitivity in human erythrocytes
Authors: Mills David E. , Murthy Mahadev , Galey William R. 
Published: November 2006

AbstractThis study examined effects of dietary n−3 fatty acids on age‐related changes in erythrocyte anion transport and susceptibility to oxidation. Blood was drawn from healthy adult volunteers before and after six weeks' supplementation (nine/group) with 4.0 g/day of safflower oil (containing 2.9 g n−6 fatty acids) or fish oil (containing 1.2 g long‐chain n−3 fatty acids). Following density separation of young and old erythrocytes, membrane anion transport and cell membrane lipid composition were measured. Oxidative damage was measured in erythrocyte ghosts exposed to a free radical generator. Fish oil significantly increased 16∶0 and 20∶5n−3 in ghosts of both young and old cells, and 22∶5n−3 and 22∶6n−3 in old cells alone. Safflower oil increased 16∶0, 18∶0, 18∶1n−9, and 22∶5n−6 in ghosts of young cells only. The age‐dependent increase in membrane anion transport (P<0.01) was decreased by dietary fish oil supplementation, but not by safflower oil supplementation. Safflower oil and fish oil increased the susceptibility of both young and old erythrocytes to oxidative damage by free radical generation (P<0.001).
Separation of γ‐ and α‐linolenic acid containing triacylglycerols by capillary supercritical fluid chromatography
Authors: Manninen Pekka , Laakso Päivi , Kallio Heikki 
Published: November 2006

AbstractThe separation of γ‐ and α‐linolenic acid containing triacylglycerols with an identical acyl carbon number and degree of unsaturation was obtained on capillary supercritical fluid chromatography using a 25% cyanopropyl−75% methylpolysiloxane stationary phase. The resolution of 1,3‐dioleoyl‐2‐γ‐linolenoyl‐sn‐glycerol and 1,3‐dioleoyl‐2α‐linolenoyl‐sn‐glycerol was 1.35 on a 10 m×50 μm i.d. column, whereas the resolution was enhanced to 1.66 by combining two 10‐meter columns in series. The difference in the position of double bonds in one linolenic acid residue of triacylglycerols resulted in two series of peaks in the separation of alpine currant (Ribes alpinum) and black currant (R. nigrum) seed oils. The use of the 10‐meter column was found to be appropriate for the screening of the triacylglycerol profile in both seed oils studied.
Lymphatic fatty acids from rats fed human milk and formula supplemented with fish oil
Authors: Clark Richard M. , She Li 
Published: November 2006

AbstractAbsorption of long‐chain polyunsaturated fatty acids from human milk and formula supplemented with fish oil was studied to determine if the distribution route into lymphatic triacylglycerol (TAG) and phospholipid (PL) varies with the dietary source. Rats were intraduodenally infused with human milk or formula containing graded amounts of fish oil (0, 0.5, or 1.0 g/100 mL), and the mesenteric lymph was collected. Arachidonic acid (20∶4n−6) levels in lymphatic TAG and PL were highest from animals fed human milk. In the animals infused with formula containing fish oil, as the amount of eicosapentaenoic acid (EPA, 20∶5n−3) infused increased, there was essentially an equal increase of EPA associated with both lymphatic TAG and PL. Animals intraduodenally infused with human milk or formula without fish oil had only minor levels (less than 1%) of EPA in the lymph. In the fish oil‐treated animals, as the amount of docosahexaenoic acid (DHA, 22∶6n−3) infused increased, there was a 16‐fold increase in DHA associated with lymphatic TAG, but only a 3‐fold increase in DHA associated with lymphatic PL. The highest level of DHA in rats infused with human milk was observed in lymphatic PL. Hence, fish oil can be added to formula as a source of long‐chain polyunsaturated fatty acids, but the distribution of fatty acids into lymphatic TAG and PL is not the same as that observed with human milk.
9‐cis β‐carotene in human plasma and blood cells after ingestion of β‐carotene
Authors: Tamai Hiroshi , Morinobu Takao , Murata Takuji , Manago Mitsuhiro , Mino Makoto 
Published: November 2006

AbstractFor 44 wk, thirty male volunteers were given daily either 60 mg of synthesized all‐trans β‐carotene, a naturally‐occurring β‐carotene derived fromDunaliella bardawil, or a placebo. Basal levels of 9‐cis β‐carotene in plasma, platelets, and mononuclear cells were 10, 20 and 25% of those of the all‐trans form, respectively. The plasma levels reached a maximum after two weeks of administration and plateaued thereafter in the subjects who took the β‐carotene preparations. The all‐trans β‐carotene level in the subjects given the synthesized all‐trans form was almost twice that for theDunaliella preparation. The plasma 9‐cis level was found to be higher in the all‐trans β‐carotene group than in theDunaliella group, despite no intake of the 9‐cis form in the all‐trans group and the higher intake of the 9‐cis form in theDunaliella group. This finding suggests that isomerization of the all‐trans form to the 9‐cis form may occur in the body either during or after absorption.
Sesamin (a compound from sesame oil) increases tocopherol levels in rats fedad libitum
Authors: Kamal‐Eldin Afaf , Pettersson Dan , Appelqvist Lars‐Åke 
Published: November 2006

AbstractSix groups of rats were fed diets low, but adequate, in α‐tocopherol but high in γ‐tocopherol. The six diets differed only in their contents (0, 0.25, 0.5, 1.0, 2.0, and 4.0 g/kg, respectively) of sesamin, a lignan from sesame oil. After four weeks ofad libitum feeding, the rats were sacrificed and the concentrations of α‐ and γ‐tocopherols were measured in the plasma, livers, and lungs. Sesamin‐feeding increased γ‐tocopherol and γ‐/α‐tocopherol ratios in the plasma (P<0.05), liver (P<0.001), and lungs (P<0.001). The increase was non‐significant for α‐tocopherol. Thus, sesamin appears to spare γ‐tocopherol in rat plasma and tissues, and this effect persists in the presence of α‐tocopherol, a known competitor to γ‐tocopherol. This suggests that the bioavailability of γ‐tocopherol is enhanced in phenol‐containing diets as compared with purified diets.
Inhibition of cardiolipin biosynthesis in the hypoxic rat heart
Authors: Cheng Philip , Hatch Grant M. 
Published: November 2006

AbstractCardiolipin is the principal polyglycerophospholipid in the heart. The effect of hypoxia on cardiolipin biosynthesis was investigated in isolated rat hearts perfused in the Langendorff mode. Hearts were pulsed‐labeled for 60 min with 0.1 mM [1,(3)‐3H]glycerol in Krebs Henseleit buffer saturated with either 95% O2/5% CO2 (control) or 95% N2/5% CO2 (hypoxic). Radioactivity incorporated into phosphatidylglycerol and cardiolipin were reduced 88% (P<.05) and 79% (P<.05), respectively, in hypoxic hearts compared to controls. In other experiments, hearts were pulse‐labeled for 15 min with 1.4 mM [32P]Pi in Krebs Henseleit buffer saturated with 95% O2/5% CO2 and subsequently perfused for 60 min under control or hypoxic conditions. The radioactivity incorporated into CDP‐1,2‐diacyl‐sn‐glycerol, phosphatidylglycerol, and cardiolipin were reduced 61% (P<.05), 71% (P<.05), and 70% (P<.05), respectively, in the hypoxic hearts compared to controls, indicating a decreased formation of CDP‐1,2‐diacyl‐sn‐glycerol in the hypoxic heart. The activities of the enzymes involved in cardiolipin biosynthesis and the cardiac pool sizes of cardiolipin, phosphatidylglycerol, and CDP‐1,2‐diacyl‐1,2‐diacyl‐sn‐glycerol were unaltered between hypoxic and control hearts. In contrast, cardiac adenosine‐5′‐triphosphate and CPT levels were decreased 94% (P<.05) and 92% (P<.05), respectively, in hypoxic hearts compared to controls. We postulate that the biosynthesis of the cardiac polyglycerophospholipid cardiolipin may be inhibited by a decreased adenosine‐5′‐triphosphate and cytidine‐5′‐triphosphate level in the heart.
Absorption of triglycerides with defined or random structure by rats with biliary and pancreatic diversion
Authors: Christensen Michael Søberg , Müllertz Anette , Høy Carl‐Erik 
Published: November 2006

AbstractFat absorption may be compromised by pancreatic or bile insufficiency, resulting in low uptake of essential fatty acid and energy. Using a rat model of malabsorption, we examined the absorption of defined triglycerides with medium‐chain fatty acids (MCFA) in thesn‐1,3 positions and essential fatty acids in thesn‐2 position (MLM) compared to other fats. The thoracic duct was cannulated for collection of lymph, and the common bile and pancreatic duct was cannulated to divert both the pancreatic juice and bile. The rats were given a single bolus of triglyceride as a taurocholate emulsion. Fat absorption was measured from collected lymph samples. The triglycerides administered were a defined triglyceride, MLM [mainly (8∶0/10∶0)‐(18∶2n−6)‐(8∶0/10∶0)], a similar triglyceride subjected to chemical randomization, a mixture of medium‐chain triglycerides and soybean oil, and soybean oil, respectively. The first three triglycerides had approximately 36 wt% linoleic acid (18∶2n−6) content. Administration of defined triglyceride was followed by significantly higher lymphatic level (wt%) of 18∶2n−6 (P<0.01) as well as a relative enhancement in mol% of 18∶2n−6 (P<0.05) compared to the other triglycerides. Lymphatic absorption of MCFA was similar in the three first groups but not as efficient as for long‐chain fatty acids. Our results indicate that defined triglycerides thus may provide a means to increase absorption of essential fatty acids in fat malabsorption, such as that seen in cystic fibrosis, or for pre‐term infants.
Sources of triacylglycerol accumulation in livers of rats fed a cholesterol‐supplemented diet
Authors: Liu Chuan‐Hsiu , Huang Ming‐ta , Huang Po‐Chao 
Published: November 2006

AbstractThe source of free fatty acids (FFA) and the pathways contributing to the accumulation of neutral fats in livers of rats fed a cholesterol‐enriched diet were investigated in this report. Supplementation with 1% cholesterol in the diet for four weeks resulted in hepatomegaly in the rats. The contents of cholesterol and triacylglycerols (TG) per gram liver measured in rats fasted overnight increased by 48 mg (∼tenfold) and 66 mg (∼fourfold), respectively. The activities of glycerophosphate acyltransferase and diacylglycerol acyltransferase, the two key enzymes for TG synthesis in liver microsomes, were found to increase by 23 and 19%, respectively, in the cholesterol‐fed rats. The secretion of plasma TG present predominantly in very low density lipoprotein was found to decrease by ∼30%. The incorporation of tritium from tritiated water in liver FFA increased by twofold in rats fed the cholesterol‐supplemented diet, whereas the activity of CPT I in liver mitochondria decreased by 23%. The uptake of plasma FFAin vivo in livers of fasted rats maintained on the cholesterol‐supplemented diet decreased by 60%. Our data thus indicate that the excess TG accumulated in livers of rats fed the cholesterol‐enriched diet resulted from increased synthesis and decreased secretion of TG. To meet the demand of fatty acids for this purpose,de novo lipogenesis increased, whereas β‐oxidation decreased. Although difference in the uptake of extrahepatic FFA may be discounted, a difference in the uptake of chylomicron remnants between the control and cholesterol‐fed rats may not be ruled out.