bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of new methods and analytical approaches to research on polyunsaturated fatty acid homeostasis
Authors: Cunnane Stephen C.
Published: November 2006

New methods and analytical approaches are important to challenge and/or validate established beliefs in any field including the metabolism of polyunsaturated fatty acids (PUFA; polyunsaturates). Four methods that have recently been applied toward obtaining a better understanding of the homeostasis of PUFA include the following: whole‐body fatty acid balance analysis, magnetic resonance imaging (MRI), 13C nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS). Whole‐boby balance studies permit the measurement of both the percentage of oxidation of linoleate and α‐linolenate and their conversion to long‐chain PUFA. This method has shown that β‐oxidation to CO2 is normally the predominant metabolic fate of linoleate and α‐linolenate. Furthermore, models of experimental undernutrition in both humans and animals show that β‐oxidation of linoleate and α‐linolenate markedly exceeds their intake, despite theoretically sufficient intake of linoleate or α‐linolenate. Preliminary results suggest that by using MRI to measure body fat content, indirect whole‐body linoleate balance can be done in living humans, 13C NMR spectroscopy provided unexpected evidence that linoleate and α‐linolenate were metabolized into lipids synthesized de novo, an observation later quantified by tracer mass balance done using GC‐C‐IRMS. This latter method showed that within 48 h of dosing with 13C‐α‐linolenate, >80% underwent β‐oxidation to CO2 by suckling rats, whereas 8–9% was converted to newly synthesized lipids and <1% to docosahexaenoate. Further application of these recently developed methods in different models should clarify the emerging importance of β‐oxidation and carbon recycling in PUFA homeostasis in mammals including humans.
A new concept of cellular uptake and intracellular trafficking of long‐chain fatty acids
Authors: Stremmel Wolfgang , Pohl Jürgen , Ring Axel , Herrmann Thomas
Published: November 2006

Fatty acids are the main structural and energy sources of the human body. Within the organism, they are presented to cells as fatty acid: albumin complexes. Dissociation from albumin represents the first step of the cellular uptake process, involving membrane proteins with high affinity for fatty acids, e.g., fatty acid translocase (FAT/CD 36) or the membrane fatty acid‐binding protein (FABPpm). According to the thus created transmembrane concentration gradient, uncharged fatty acids can flip‐flop from the outer leaflet across the phospholipid bilayer. At the cytosolic surface of the plasma membrane, fatty acids can associate with the cytosolic FABP (FABPc) or with caveolin‐1. Caveolins are constituents of caveolae, which are proposed to serve as lipid delivery vehicles for subcellular organelles. It is not known whether protein (FABPc)‐ and lipid (caveolae)‐mediated intracellular trafficking of fatty acids operates in conjunction, or in parallel. Channeling fatty acids to the different metabolic pathways requires activation to acyl‐CoA. For this process, the family of fatty acid transport proteins (FATP 1‐5/6) might be relevant because they have been shown to possess acyl‐CoA synthetase activity. Their variable N‐terminal signaling sequences suggest that they might be targeted to specific organelles by anchoring in the phospholipid bilayer of the different subcellular membranes. At the highly conserved cytosolic AMP‐binding site of FATP, fatty acids are activated to acyl‐CoA for subsequent metabolic disposition by specific organelles. Overall, fatty acid uptake represents a continuous flow involving the following: dissociation from albumin by membrane proteins with high affinity for fatty acids; passive flip‐flop across the phospholipid bilayer; binding to FABPc and caveolin‐1 at the cytosolic plasma membrane; and intracellular trafficking via FABPc and/or caveolae to sites of metabolic disposition. The uptake process is terminated after activation to acyl‐CoA by the members of the FATP family targeted intracellularly to different organelles.
Polyunsaturated fatty acids and T‐cell function: Implications for the neonate
Authors: Field Catherine J. , Clandinin M. Thomas , Van Aerde John E.
Published: November 2006

Infant survival depends on the ability to respond effectively and appropriately to environmental challenges. Infants are born with a degree of immunological immaturity that renders them susceptible to infection and abnormal dietary responses (allergies). T‐lymphocyte function is poorly developed at birth. The reduced ability of infants to respond to mitogens may be the result, of the low number of CD45RO+ (memory/antigen‐primed). T cells in the infant or the limited ability to produce cytokines [particularly interferon‐γ, interleukin (IL)‐4, and IL‐10]. There have been many important changes in optimizing breast milk substitutes for infants; however, few have been directed at replacing factors in breast milk that convey immune benefits. Recent research has been directed at the neurological, retinal, and membrane benefits of adding 20∶4n−6 (arachidonic acid; AA) and 22∶6n−3 (docosahexaenoic acid; DHA) to infant formula. In addults and animals, feeding DHA affects T‐cell function. However, the effect of these lipids on the development and function of the infant's immune system is not known. We recently reported the effect of adding DHA+AA to a standard infant formula on several functional indices of immune development. Compared with standard formula, feeding a formula containing DHA+AA increased the proporition of antigen mature (CD45RO+) CD4+ cells, improved IL‐10 production, and reduced IL‐2 production to levels not different from those of human milk‐fed infants. This review will briefly describe T‐cell development and the potential immune effect of feeding long‐chain polyunsaturated fatty acids to the neonate.
Polyunsaturated n−3 fatty acids and the development of atopic disease
Authors: Duchén Karel , Björkstén Bengt
Published: November 2006

The relationship between polyunsaturated long‐chain fatty acids and atopy has been discussed for decades. Higher levels of the essential fatty acids linoleic acid and α‐linolenic acid and lower levels of their longer metabolites in plasma phospholipids of atopic as compared to nonatopic individuals have been reported by several, but not all, studies. Largely similar findings have been reported in studies of cell membranes from immunological cells from atopics and nonatopics despite differences in methodology, study groups, and definitions of atopy. An imbalance in the metabolism of the n−6 fatty acids, particularly arachidonic acid and dihomo‐γ‐linolenic acid, leading to an inappropriate synthesis of prostaglandin (PG) E2 and PGE1 was hypothesized early on but has not been corroborated. The fatty acid composition of human milk is dependent on the time of lactation not only during a breast meal but also the time of the day and the period of lactation. This explains the discrepancies in reported findings regarding the relationship between milk fatty acids and atopic disease in the mother. Prospective studies show disturbances in both the n−6 and n−3 fatty acid composition between milk from atopic and nonatopic mothers. Only the composition of long‐chain polyunsaturated n−3 fatty acids was related to atopic development in the children, however. A relationship between lower levels of n−3 fatty acids, particularly eicosapentaenoic acid (20∶5 n−3), and early development of atopic disease is hypothesized.
The role of polyunsaturated fatty acid supplementation in intestinal inflammation and neonatal necrotizing enterocolitis
Authors: Caplan Michael S. , Jilling Tamas
Published: November 2006

Dietary polyunsaturated fatty acid (PUFA) supplementation has been shown to reduce the incidence of necrotizing enterocolitis (NEC) in a recent randomized, controlled trial. These compounds are known to modulate the inflammatory cascade and to influence intestinal health in a variety of ways. Although the pathophysiology of NEC is not well understood, recent evidence suggests that platelet‐activating factor (PAF) is a key endogenous mediator of intestinal necrosis in animals. Using a neonatal rat model of NEC that includes the key risk factors of asphyxia and formula feeding, we investigated the role of dietary PUFA supplementation on the incidence and pathophysiology of NEC. Our findings suggest that PUFA reduce the incidence of NEC by modulating PAF metabolism and endotoxin translocation.
Changes in the chemical composition of surfactant‐like particles secreted by rat small intestine in response to different dietary fats
Authors: Kalra Seema , Mahmood Safrun , Nagpaul J. P. , Mahmood Akhtar
Published: November 2006

Consumption of dietary oil, viz., corn, fish, coconut, or olive, induced the secretion of surfactant‐like particles (SLP) in rat intestine. These lipoprotein particles differ in (i) levels of alkaline phosphatase activity, (ii) lipid composition, and (iii) FA composition in response to feeding of different oils. The secreted particles had similar buoyancy (1.07–1.08 g/mL) and cholesterol/phospholipid molar ratios (0.61–0.72) except that feeding coconut oil to rats produced SLP with a low (0.18) cholesterol/phospholipid molar ratio compared to control animals. It is concluded from these observations that feeding different oils induces the secretion of lipoprotein particles in rat intestine with different chemical compositions.
Albumin stimulates lysophosphatidic acid acyltransferase activity in T‐lymphocyte membranes
Authors: Jolly Christopher A. , Kannan Latha
Published: November 2006

Phosphatidic acid (PtdOH) and lysophosphatidic acid (lysoPtdOH) have been shown to enhance T‐lymphocyte function. However, the FA preference and influence of acyl‐CoA binding proteins on lysoPtdOH and PtdOH biosynthesis are not known. Therefore, we determined glycerol‐3‐phosphate acyltransferase (GPAT) and lysophosphatidic acid acyltransferase (LAT) activity in rat T‐lymphocyte and liver membrane preparations in the presence of palmitoyl‐CoA and oleoyl‐CoA with or without BSA. We found two different properties of GPAT and LAT in whole T‐lymphocyte membrane preparations relative to liver. First, T‐lymphocyte basal GPAT and LAT activities were similar, whereas in liver membranes LAT activity was 10‐fold higher than GPAT. Second, T‐lymphocyte LAT, but not GPAT, activity was inducible (fivefold) by the addition of albumin in the presence of palmitoyl‐CoA but not oleoyl‐CoA. In contrast, albumin stimulated GPAT, but not LAT, activity in liver membranes in the presence of palmitoyl‐CoA. These results show, for the first time, that T‐lymphocyte LAT activity can be increased by the presence of an acyl‐CoA binding protein, which may indicate a new important control mechanism for regulating intracellular lysoPtdOH and PtdOH levels in T‐lymphocytes.
Analysis of vitamin E and its oxidation products by HPLC with electrochemical detection
Authors: Yamauchi Ryo , Noro Hiroki , Shimoyamada Makoto , Kato Koji
Published: November 2006

A sensitive HPLC procedure with postcolumn reduction and electrochemical detection was developed for the analysis of vitamin E and its oxidation products, α‐tocopherylquinone, epoxy‐α‐tocopherylquinones, and 8a‐(lipid‐dioxy)‐α‐tocopherones. After the separation on a reversed‐phase column, on‐line zinc‐catalyzed reduction allowed the detection of α‐tocopherylquinone and epoxy‐α‐tocopheryl‐quinones, whereas platinum‐catalyzed reduction allowed the detection of 8a‐(lipid‐dioxy)‐α‐tocopherones. The lowest detectable level of each compound was about 0.2 pmol at the signal‐to‐noise ratio of 3. This method was applied to the detection of α‐tocopherol products in peroxidized human plasma. When the plasma was peroxidized by the addition of a free radical initiator, peaks corresponding to α‐tocopherylquinone, epoxy‐α‐tocopherylquinones, and the addition products of α‐tocopherol with peroxyl radicals derived from cholesteryl ester hydroperoxides and PC hydroperoxides were observed. The amount of these oxidation products in the plasma increased with the depletion of endogenous α‐tocopherol. The results indicate that the method is useful to detect the oxidation products formed by the peroxyl radical‐trapping reactions of α‐tocopherol in biological systems.
Differences in Δ9 desaturase activity between jersey‐and limousin‐sired cattle
Authors: Siebert B. D. , Pitchford W. S. , Kruk Z. A. , Kuchel H. , Deland M. P. B. , Bottema C. D. K.
Published: November 2006

An experiment examined Δ9 desaturase activity and FA composition in subcutaneous adipose tissue in two differing breeds of cattle. Jersey‐sired cattle had significantly higher rates of desaturase activity than Limousin‐sired cattle (1.55 vs. 0.75 nmol/mg protein/min). This difference was also demonstrated by a lower concentration of individual (e.g. 18∶0) and total saturated FA (38.3 vs. 45.1 wt%), and a higher concentration of individual (e.g., 16∶1) and total monounsaturated FA (58.2 vs. 52.7 wt%) in the Jersey animals. Other indices of desaturation calculated from the FA composition showed this same difference. The slip point of adipose tissue of Jersey cattle (36.8°C) was significantly lower than that of Limousin cattle (39.2°C), but Jersey adipose tissue had a greater content of β‐carotene. The positive relationship between adipose tissue β‐carotene and desaturation opposes the negative relationship between dietary β‐carotene and desaturation determined elsewhere. These results, however, lead to the hypothesis that some cattle have a reduced capacity to metabolize β‐carotene to various forms of vitamin A, a compound that can reduce Δ9 desaturase enzyme activity. In addition, the higher level of intramuscular fat in Jersey cattle (6.97 vs. 3.82%) is possibly related to a lack of inhibition of the adipocyte differentiation genes by vitamin A.
Development of intestinal alkaline sphingomyelinase in rat fetus and newborn rat
Authors: Lillienau Jan , Cheng Yajun , Nilsson Åke , Duan Rui‐Dong
Published: November 2006

Sphingomyelin metabolism is a novel signal transduction pathway related to cell differentiation, proliferation, and apoptosis. Alkaline sphingomyelinase (alk‐SMase) is specifically present in the intestinal tract of many species. The enzyme is important in digestion of dietary sphingomyelin. Milk is the ony exogenous source of sphingomyelin for an infant, and digestion of milk sphingomyelin may be important for development of intestinal mucosa. It is unknown whether alk‐SMase is present before birth and whether it changes after birth and during the suckling period. We studied activities, expression, and distribution of alk‐SMase in rat fetus and newborn. The changes of acid and neutral SMase as well as alkaline phosphatase were analyzed for comparison. Little activity of alk‐SMase was identified up to gestation day 20, but increased 10 times during the following 2 d. After birth, the activity continused to increase during the following 4 wk. Western blot using IgY antibody against rat alk‐SMase failed to identify the enzyme at gestation day 20 but clearly showed the protein at day 22. The distribution pattern of the enzyme along the intestinal tract in fetus was largely the same as in adult animals, but became more pronounced after birth. Short‐term weaning had no effect on alk‐SMase activity. The activities of acid and neutral SMase were high at gestation day 20 and decreased significantly before birth. The changes of alk‐SMase also differed from those of alkaline phosphatase, another brush border enzyme. Thus, we conclude that alk‐SMase is rapidly expressed during the last days of gestation and that the newborn rat acquires the ability to digest milk sphingomyelin early in life.
Occurrence of a novel cis,cis,cis‐octadeca‐3,9,12‐trienoic (Z,Z,Z‐octadeca‐3,9,12‐trienoic) acid in Chrysanthemum (Tanacetum) zawadskii herb. (Compositae) seed oil
Authors: Tsevegsuren Nanzad , Fujimoto Kenshiro , Christie William W. , Endo Yasushi
Published: November 2006

A new octadecatrienoic acid (6.9%), found as a component of Chrysanthemum zawadskii Herb. (Asteraceae) seed oil, was shown to be the hitherto unknown cis,cis,cis‐octadeca‐3,9,12‐trienoic acid. The oil also contained 8.6% of crepenynic acid in addition to the other common FA. The structures of the new unusual FA and other FA were confirmed by chromatographic (TLC, GC), spectroscopic (IR, UV, and NMR), and MS methods by using different chemical derivatizations (preparation of methyl ester, pyrrolidide, picolinyl esters, and dimethyloxazoline derivatives).
Quantitative characterization of phospholipids in milk fat via31P NMR using a monophasic solvent mixture
Authors: Murgia Sergio , Mele Stefania , Monduzzi Maura
Published: November 2006

The phospholipids (PL) occurring in both ewe and cow milk fat globule membrane were identified and quantitatively determined using 31P NMR spectroscopy with inverse gated decoupled sequences, which allowed a rigorous quantitative analysis. A strict relation between amount and distribution of PL and type of feeding was found. The method was calibrated over a mixture of PL standards. A recently introduced solvent constituted by a monophasic dimethylformamide/triethylamine/guanidinium hydrochloride solvent mixture was used. Compared to the traditional chloroform/methanol/water‐EDTA solvent, the new solvent mixture shows very similar accuracy and precision from a quantitative point of view. The monophasic solvent overcomes the partition problems related to a biphasic system, and slightly enlarges the range of 31P NMR chemical shifts, thus improving the resolution. In addition, the new solvent apparently displays a lower chemical shift dependence on the various PL concentrations. The limit of the method is mainly determined by the formation of adducts between triethylamine and some PL, namely, PE, monomethylphosphati‐dylethanolamine, phosphatidylethanolamine plasmalogens, and some lyso‐PL. However, the new 31P NMR signals arising from these adducts could be easily quantified in the determination of PE.
n−3 fatty acid enrichment of edible tissue of poultry: A review
Authors: Rymer C. , Givens D. I.
Published: November 2006

There is clear evidence of the nutritional benefits of consuming long‐chain n−3 PUFA, which are found predominantly in oily fish. However, oily fish consumption, particularly in the United Kingdom, is declining, as is the consumption of all meats with the exception of poultry, which has increased in consumption by 73% in the last 30 yr. This pattern, if less marked, is reflected throughout Europe, and therefore one means of increasing long‐chain n−3 PUFA consumption would be to increase the long‐chain n−3 PUFA content in the edible tissues of poultry. This review considers the feasibility of doing this, concentrating particularly on chickens and turkeys. It begins by summarizing the benefits to human health of consuming greater quantities of n−3 FA and the sources of n−3 PUFA in the human diet. The literature on altering the FA composition of poultry meat is then reviewed, and the factors affecting the incorporation of n−3 PUFA into edible tissues of poultry are investigated. The concentration of α‐linolenic acid (ALA) in the edible tissues of poultry is readily increased by increasing the concentration of ALA in the birds' diet (particularly meat with skin, and dark meat to a greater extent than white meat). The concentration of EPA in both white and dark meat is also increased when the birds' diet is supplemented with EPA, although supplementing the diet with the precursor (ALA) does not result in a noticeable increase in EPA content in the edible tissues. Although supplementing the birds' diets with relatively high concentrations of DHA does result in an increased concentration of DHA in the tissues, the relationship between dietary and tissue concentrations of DHA is much weaker than that observed with ALA and EPA. The impact that altering the FA composition of edible poultry tissue may have on the organoleptic and storage qualities of poultry products is also considered.
Triacylglycerol oxidation in pig lipoproteins after a diet rich in oxidized sunflower seed oil
Authors: Suomela Jukka‐Pekka , Ahotupa Markku , Kallio Heikki
Published: November 2006

The effects of two sunflower seed oil diets differing in oxidation levels (PV in oils 1 and 190 mequiv O2/kg) on lipoprotein TAG and total lipid oxidation were investigated in growing pigs. For 2 wk, two groups of 10 pigs were fed either of the diets, after which blood samples were collected. A method based on RP‐HPLC and electrospray ionization‐MS was used for the analysis of oxidized TAG molecules in chylomicrons and VLDL. The baseline diene conjugation method was used for the estimation of in vivo levels of lipoprotein lipid oxidation. TAG molecules with a hydroxy, an epoxy, or a keto group attached to a FA, as well as TAG core aldehydes were detected in the samples. Typically, lipoprotein TAG and total lipids were more oxidized in the pigs fed on the oxidized oil compared with those fed on nonoxidized oil. Oxidation of dietary fat was thus reflected in the lipoprotein oxidation, which confirmed our earlier findings.
Dietary fatty acids regulate cholesterol induction of liver CYP7α1 expression and bile acid production
Authors: Li Yan , Hou Meng Jun , Ma Jing , Tang Zhi Hong , Zhu Hui Lian , Ling Wen Hua
Published: November 2006

In the present study we investigated the effects of dietary fats containing predominantly PUFA, monounsaturated FA (MUFA), or saturated FA (SFA) on lipid profile and liver cholesterol 7α‐hydroxylase (CYP7α1) mRNA expression and bile acid production in C57BL/6J mice. The animals (n=75) were randomly divided into five groups and fed a basic chow diet (AIN‐93G) (BC diet), a chow diet with 1g/100g of cholesterol (Chol diet), a chow diet with 1g/100g of cholesterol and 14g/100g of safflower oil (Chol+PUFA diet), a chow diet with 1g/100g of cholesterol and olive oil (Chol+MUFA diet), or a chow diet with 1g/100g of cholesterol and myristic acid (Chol+SFA diet) for 6 wk. The results showed that the Chol+SFA diet decreased CYP7α1 gene expression and bile acid pool size, resulting in increased blood and liver cholesterol levels. Addition of PUFA and MUFA to a 1% cholesterol diet increased the bile acid pool production or bile acid excretion and simultaneously decreased liver cholesterol accumulation despite decreased CYP7α1 mRNA expression. The results indicate that the decreased bile acid pool size induced by the SFA diet is related to inhibition of the liver CYP7α1 gene expression, but an increased bile acid pool size and improved cholesterol homeostasis are disassociated from the liver CYP7α1 gene expression.
Regulation of palmitoyl‐CoA chain elongation by clofibric acid in the liver of Zucker fa/fa rats
Authors: Toyama Tomoaki , Kudo Naomi , Mitsumoto Atsushi , Kawashima Yoichi
Published: November 2006

The regulation of palmitoyl‐CoA chain elongation (PCE) by clofibric acid [2‐(4‐chlorophenoxy)‐2‐methylpropionic acid] was investigated in comparison with stearoyl‐CoA desaturase (SCD) in the liver of obese Zucker fa/fa rats. The proportion of oleic acid in the hepatic lipids of Zucker obese rats is 2.7 times higher than that of lean littermates. The activities of PCE and SCD in the liver of Zucker obese rats were markedly higher than in lean rats, and the hepatic uptake of 2‐deoxyglucose (2‐DG) was also higher in Zucker obese rats compared with lean rats. The increased activities of SCD and PCE in Zucker obese rats were due to the enhanced expression of mRNA of rELO1. The proportion of oleic acid in the liver was significantly increased by the administration of clofibric acid to Zucker obese rats, and the hepatic PCE activity and rELO2 mRNA expression, but not the SCD activity or SCD1 mRNA expression, were increased in response to clofibric acid treatment. By contrast, the activities of both PCE and SCD and the mRNA expression of SCD1 and rELO2 in the liver were increased by the treatment of Zucker lean rats with clofibric acid. Multiple regression analysis, which was performed to determine the relationships involving PCE activity, SCD activity, and the proportion of oleic acid, revealed that the three parameters were significantly correlated and that the standardized partial regression coefficient of PCE was higher than that of SCD. These results indicate that oleic acid is synthesized by the concerted action of PCE and SCD and that PCE plays a crucial role in the formation of oleic acid when Zucker fa/fa rats are given clofibric acid.
Lymphatic transport in rats of interesterified oils containing conjugated linoleic acids
Authors: Straarup Ellen Marie , Porsgaard Trine , Mu Huiling , Hansen Christina H. , Høy Carl‐Erik
Published: November 2006

In this study we examined the lymphatic transport in rats of FA after administration of interesterified oils containing CLA, with emphasis on the location of CLA and octanoic acid in the TAG. The oils were produced by enzymatic interesterification. Eight oils with different structures or FA profiles were examined in this study: MCM, CMC, OCO, and COC, where M was expected to be octanoic acid and O oleic acid. In group 1, C was CLA as a mixture of the two CLA isomers c9, t11 or t10,c12, and in group 2, C was mainly the isomer t10,c12. Rats were subjected to cannulation of the mesenteric lymph duct, and the following day they were intragastrically administered one of the oils and lymph samples were collected for 24 h. The lymphatic transport of total FA from 0 to 8 h in group 1 was significantly (P<0.05) higher for the OCO‐1 and the COC‐1 oils than for the CMC‐1 oil. Similarly, in group 2 the transport was higher for the OCO‐2 oil than for the CMC‐2 oil. The recovery of both of the CLA isomers examined was similar (50–70%) and independent of the isomer, oil structure, and FA profile, whereas more octanoic acid was recovered from the CMC oils than from the MCM oils. The results indicated that the FA profiles and the position of octanoic acid had only a minor influence on the absorption of CLA.
Changes of the transcriptional and fatty acid profiles in response to n−3 fatty acids in SH‐SY5Y neuroblastoma cells
Authors: Langelier Bénédicte , Alessandri Jean‐Marc , Perruchot Marie‐Hélène , Guesnet Philippe , Lavialle Monique
Published: November 2006

Synthesis of docosahexaenoic acid (DHA) from its metabolic precursors contributes to membrane incorporation of this FA within the central nervous system. Although cultured neural cells are able to produce DHA, the membrane DHA contents resulting from metabolic conversion do not match the high values of those resulting from supplementation with preformed DHA. We have examined whether the DHA precursors downregulate the incorporation of newly formed DHA within human neuroblastoma cells. SH‐SY5Y cells were incubated with gradual doses of α‐linolenic acid (α‐LNA), EPA, or docosapentaenoic acid (DPA), and the incorporation of DHA into ethanolamine glycerophospholipids was analyzed as a reflection of synthesizing activity. The incorporation of EPA, DPA, and preformed DHA followed a dose‐response saturating curve, whereas that of DHA synthesized either from α‐LNA, EPA, or DPA peaked at concentrations of precursors below 15–30 μM and sharply decreased with higher doses. The mRNA encoding for six FA metabolism genes were quantified using real‐time PCR. Two enzymes of the peroxisomal β‐oxidation, L‐bifunctional protein and peroxisomal acyl‐CoA oxidase, were expressed at lower levels than fatty acyl‐CoA ligase 3 (FACL3) and Δ6‐desaturase (Δ6‐D). The Δ6‐D mRNA slightly increased between 16 and 48 h of culture, and this effect was abolished in the presence of 70 μM EPA. In contrast, the EPA treatment resulted in a time‐dependent increase of FACL3 mRNA. The terminal step of DHA synthesis seems to form a “metabolic bottleneck,” resulting in accretion of EPA and DPA when the precursor concentration exceeds a specific threshold value. We conclude that the critical precursor‐concentration window of responsiveness may originate from the low basal expression level of peroxisomal enzymes.
Dietary effect of a symmetrical triacylglycerol, 1,3‐biseicosapentaenoyl‐2‐γ‐linolenoyl glycerol, on fatty acid composition of guinea pigs
Authors: Ohba S. , Akahane N. , Wakabayashi T. , Nakahara T. , Yokochi T. , Yanagi K. , Ohshima N.
Published: November 2006

The dietary effect of 1,3‐biseicosapentaenoyl‐2‐γ‐linolenoyl glycerol (STG) on the fatty acid composition of guinea pigs was examined and compared with that of an eicosapentaenoic acid ethyl ester (EPA‐F) and of a soybean oil (SBO) diet. In terms of content of plasma lipid, EPA‐E had a greater hypolipidemic effect than STG. On the other hand, in terms of EPA incorporation, contents of EPA in liver lipid were almost the same in the STG and EPA‐E groups. Considering that the amount of EPA administered in the EPA‐E group was almost 1.5 times that of the STG group, FPA may be absorbed more effectively as the glycerol ester than as the ethyl ester in guinea pigs. In all the tissue lipids, the STG group had a higher unsaturation index (UI) than the EPA‐E group even though there is a lower UI in the STG diet than the EPA‐E diet. These results suggest that greater amounts of desaturase products as a whole were synthesized in the STG group than in the other two groups. The dihomo‐γ‐linolenic acid/arachidonic acid (DGLA/AA) ratio in plasma total lipids in the STG group was 3.5 times that of SBO group, and the DGLA/AA ratio in the EPA‐E group was half that of the SBO group. In liver lipid, the ratios of DGLA/AA and EPA/AA in the STG group were 0.687 and 0.488 (phosphatidylcholine fraction) and 0.237 and 0.752 (phosphatidylethanolamine fraction), respectively. The ratio of DGLA/AA as well as the high EPA/AA ratio obtained in the present study with the STG diet may lead to physiological alterations, including enhanced synthesis of 1‐and 3‐series eicosanoids.
Sesamol as an inhibitor of growth and lipid metabolism in Mucor circinelloides via its action on malic enzyme
Authors: Wynn James P. , Kendrick Andrew , Ratledge Colin
Published: November 2006

Sesamol, a nonoil component of sesame seed oil, inhibited growth, fatty acid synthesis, and desaturation by Mucor circinelloides in vivo. Although sesamol also inhibited the growth of other fungi and yeasts, its effect on the lipid metabolism of M. circinelloides was exceptional. An enzymological study demonstrated that sesamol affected lipid synthesis primarily by the inhibition of malic enzyme activity, thereby limiting the NADPH supply for fatty acid synthesis and desaturation. Sesamol itself had no inhibitory effect on malic enzyme activity in vitro. A metabolite of sesamol is therefore probably responsible for the in vivo effects of sesamol on lipid metabolism.
Modification of odd‐chain length unsaturated fatty acids by hepatocytes of rainbow trout (Oncorhynchus mykiss) fed diets containing fish oil or olive oil
Authors: Rodríguez C. , Henderson R. J. , Porter A. E. A. , Dick J. R.
Published: November 2006

Hepatocytes isolated from rainbow trout fed on diets containing either fish oil or olive oil were incubated with individual odd‐chain length unsaturated fatty acids (19∶1n−9, 19∶2n−6, 19∶3n−3, 21∶2n−6, 21∶3n−6, 21∶4n−6, 21∶3n−3, and 21∶5n−3) to examine whether these fatty acids were substrates for modification by desaturation and elongation. All odd‐chain length fatty acids were readily assimilated into the lipids of hepatocytes from both dietary groups of fish, but their conversion to longer‐chain, more unsaturated derivatives was more pronounced with cells from trout fed olive oil. Thus, the conversion of 19∶2n−6 and 21∶2n−6 to 21∶3n−6 and 21∶4n−6, and of 19∶3n−3 to 21∶4n−3 and 21∶5n−3, was most obvious in cells from the olive oil group, as was the conversion of 21∶3n−6 and 21∶3n−3 to 21∶4n−6 and 21∶4n−3, respectively. Elongation of 19∶1n−9 to 21∶1n−9 and 23∶1n−9 occurred in cells from both groups. No 23∶6n−3 was detectable as a product of 19∶3n−3 or 21∶3n−3. However, this fatty acid was a major product formed by cells from fish fed olive oil presented with 21∶5n−3. Cells from both groups of fish incorporated 21∶4n−6 and 21∶5n−3 into their lipids largely without modification but chain‐shortened around 40, 23, and 19% of the incorporated 21∶2n−6, 21∶3n−3, and 19∶1n−9, respectively. The results demonstrate that odd‐chain length unsaturated fatty acids can act as substrates for the desaturation, elongation, and chain‐shortening systems of trout hepatocytes.
Noninvasive characterization of neonatal adipose tissue by 13C magnetic resonance spectroscopy
Authors: Thomas E. L. , Hanrahan J. D. , Ala‐Korpela M. , Jenkinson G. , Azzopardi D. , Iles R. A. , Bell J. D.
Published: November 2006

In vivo13C magnetic resonance spectroscopy (MRS) was applied noninvasively to analyze the fatty acid composition of adipose tissue in 21 full‐term newborn infants and 6 mothers. In order to assess the effects of gestational and postnatal age on adipose tissue composition, we studied preterm infants at birth, term infants at the ages of 6 wk and at 6 mon. We also investigated the influence of maternal diet on infant adipose tissue composition by studying the breast‐fed infants of women who maintained either an omnivore or a vegan diet. Significant differences were observed in adipose tissue composition of neonates compared with their mothers. Neonates had more saturated and less unsaturated fatty acids than their mothers (P<0.01). We also observed changes in adipose tissue composition with maturity. From birth to 6 wk of age 13C MR spectra showed a significant increase in the amount of unsaturated fatty acids, particularly polyunsaturated fatty acids (P<0.01). Similarly, differences were seen as a result of gestational age. Preterm infants had relatively fewer unsaturated fatty acids than full‐term infants. A greater proportion of these unsaturated fatty acids were polyunsaturated. Our results demonstrate that 13C MRS can be utilized to assess noninvasively neonatal adipose tissue lipid composition and to monitor the effects of developmental changes due to gestational age and oral feeding.
A new lipid from an australian marine sponge, Callyspongia sp
Authors: Urban Sylvia , Capon Robert J.
Published: November 2006

A specimen of the sponge Callyspongia sp. collected off the coast of New South Wales, Australia, has yielded the novel lipid (6Z,9Z,12Z,15Z)‐1,6,9,12,15‐octadecapenten‐3‐one, together with (4Z,7Z,10Z,13Z)‐4,7,10,13‐hexadecatetraenoic acid.
Gas‐liquid chromatographic properties of positional isomers of methyl thia, selena, and tellura laurate analogs
Authors: Lie Ken Jie Marcel S. F. , Bakare O. , Cheung Y. K. , Chau S. H.
Published: November 2006

Gas‐liquid chromatographic analyses of three complete series of synthetic positional isomers of methyl thia, selena, and tellura laurate analogs were carried on a nonpolar (SE‐30) and a polar (SP‐2330) stationary phase. The average ECL (equivalent chain length) values of the thia, selena, and tellura laurate on SE‐30 stationary phase were 13.8, 14,8, and 15.7, respectively, while on SP‐2330 the average values for the same series were 17.1, 19.0, and 19.1, respectively. Positional isomers with the heteroatom at the 2‐position exhibited the lowest ECL values, while those with the heteroatom at the ω‐1 position gave the highes ECL values and were readily separated from the other positional isomers of the same series of analogs by this technique.
Mitochondrial thioredoxin in regulation of oxidant‐induced cell death
Authors: Chen Yan , Cai Jiyang , Jones Dean P
Published: November 2006

Mitochondrial thioredoxin (mtTrx) can be oxidized in response to inducers of oxidative stress; yet the functional consequences of the oxidation have not been determined. This study evaluated the redox status of mtTrx and its association to oxidant‐induced apoptosis. Results showed that mtTrx was oxidized after exposure to peroxides and diamide. Overexpression of mtTrx protected against diamide‐induced oxidation and cytotoxicity. Oxidation of mtTrx was also achieved by knocking down its reductase; and lead to increased susceptibility to cell death. The data indicate that the redox status of mtTrx is a regulatory mechanism underlying the vulnerability of mitochondria to oxidative injury.
Biomimetic Catalysis for Hemicellulose Hydrolysis in Corn Stover
Authors: Lu Yulin , Mosier Nathan S.
Published: November 2006

Efficient and economical hydrolysis of plant cell wall polysaccharides into monomeric sugars is a significant technical hurdle in biomass processing for renewable fuels and chemicals. One possible approach to overcoming this hurdle is a biomimetic approach with dicarboxylic acid catalyst mimicking the catalytic core microenvironment in natural enzymes. This paper reports developments in the use of a dicarboxylic acid catalyst, maleic acid, for hemicellulose hydrolysis in corn stover. Hemicellulose hydrolysis and xylose degradation kinetics in the presence of maleic acid was compared to sulfuric acid. At optimized reaction conditions for each acid, maleic acid hydrolysis results in minimal xylose degradation, whereas sulfuric acid causes 3–10 times more xylose degradation. These results formed the basis for optimizing the hydrolysis of hemicellulose from corn stover using maleic acid. At 40 g/L dry corn stover solid‐loading, both acid catalysts can achieve near‐quantitative monomeric xylose yield. At higher solids loadings (150–200 g dry stover per liter), sulfuric acid catalyzed hydrolysis results in more than 30% degradation of the xylose, even under the previously reported optimal condition. However, as a result of minimized xylose degradation, optimized biomimetic hydrolysis of hemicellulose by maleic acid can reach ∼95% monomeric xylose yields with trace amounts of furfural. Fermentation of the resulting unconditioned hydrolysate by recombinant S. cerevisiae results in 87% of theoretical ethanol yield. Enzyme digestibility experiments on the residual corn stover solids show that >90% yields of glucose can be produced in 160 h from the remaining cellulose with cellulases (15 FPU/g‐glucan).
Characterization and evaluation of boron carbide for plate-impact conditions
Authors: Holmquist T. J. , Johnson G. R.
Published: November 2006

This article addresses the response of boron carbide (B4C) to high-velocity impact. The authors previously characterized this material in 1999, using the Johnson-Holmquist [AIP Conf. Proc. 309, 981 (1994)] (JH-2) model. Since then, there have been additional experimental data presented in the literature that better describe the hydrostatic pressure (including a phase change). In addition, a series of plate-impact experiments (one-dimensional, uniaxial strain) that used configurations that produced either a shock, a shock release, or a shock reshock was performed. These experiments provide material behavior regarding the damage, failed strength, and hydrostat for which previously there has been little or no data. Constitutive model constants were obtained for the Johnson-Holmquist-Beissel [J. Appl. Phys. 94, 1639 (2003)] model using some of these plate-impact experiments. Computations of all the experiments were performed and analyzed to better understand the material response. The analysis provided the following findings: (1) The material fails and loses strength when the Hugoniot elastic limit (HEL) is exceeded. (2) The material has significant strength after failure and gradually increases as the pressure increases. (3) The shear modulus does not degrade when the material fails (as has been postulated), but rather increases. (4) When the material is reloaded from an initial shocked (failed) state, the loading appears to be elastic, indicating the material is not on the yield surface after failure. To provide more insight into the behavior of B4C, the strength versus pressure response was compared to that of silicon carbide (SiC). The strength of SiC increases as the pressure increases beyond the HEL, probably due to pressure hardening or strain hardening. It appears that B4C does not experience any hardening effects and fails at the HEL. Although the HEL for B4C is higher than that of SiC, the hardening ability of SiC produces a similar maximum strength with more ductility. Another important issue with B4C is that there are significant differences between plate-impact data reported by different researchers. These differences are due to one or more of the following possibilities: errors in obtaining the test data, errors in analyzing the test data, a high degree of scatter due to failure of the material, and/or the different manufactured forms of B4C simply behave as different materials. These differences also make it difficult to validate the model (constants) determined from one set of data by applying it to other data reported in the literature. Lastly, the model was used to simulate ballistic impact experiments over a large range of impact velocities (1500–4500m∕s). The computed results overpredict the penetration at low velocities and underpredict the penetration at high velocities. Future work will address this inconsistency, but until this issue is resolved, the current model and constants should be used with caution when applied to ballistic impact and penetration.
Three-particle correlation functions of quasi-two-dimensional one-component and binary colloid suspensions
Authors: Ho Hau My , Lin Binhua , Rice Stuart A.
Published: November 2006

We report the results of experimental determinations of the triplet correlation functions of quasi-two-dimensional one-component and binary colloid suspensions in which the colloid-colloid interaction is short ranged. The suspensions studied range in density from modestly dilute to solid. The triplet correlation function of the one-component colloid system reveals extensive ordering deep in the liquid phase. At the same density the ordering of the larger diameter component in a binary colloid system is greatly diminished by a very small amount of the smaller diameter component. The possible utilization of information contained in the triplet correlation function in the theory of melting of a quasi-two-dimensional system is briefly discussed.
Effect of particle size on the structure and magnetic properties of La0.6Pb0.4MnO3 nanoparticles
Authors: Zhang T. , Li G. , Qian T. , Qu J. F. , Xiang X. Q. , Li X. G.
Published: November 2006

We studied the effect of particle size on the structure and magnetic properties of La0.6Pb0.4MnO3 compounds with particle diameters varying from 5to100nm. With decreasing particle size, the increase of the rhombohedral distortion narrows the bandwidth WO2p and hence results in the decrease of ferromagnetic transition temperature. At the same time, the magnetic domain structure evolves from multidomain to single domain, and finally a superparamagnetic behavior is detected. The critical single domain size determined by experiment is about 25nm, and the critical superparamagnetic behavior size obtained by calculation is 5.8nm. It is found that the variation of coercivity is related to the evolution of magnetic domain states with particle size, and the saturation magnetization decreases significantly due to the increasing contribution of the surface effect with decreasing particle size.
Differential absorption measurements of carbon dioxide using a temperature tunable distributed feedback diode laser
Authors: Repasky Kevin S. , Humphries Seth , Carlsten John L.
Published: November 2006

The design and performance of an absorption measurement instrument for monitoring carbon dioxide are presented. The instrument is based on a temperature tunable distributed feedback diode laser capable of tuning between 2.001 and 2.005μm. Within this wavelength range are 12 absorption lines for carbon dioxide and 9 absorption lines for water vapor. Initial measurements of laser transmission as a function of carbon dioxide concentration are made using a 2m long absorption cell. The measured values compare well with the expected values using the known line strength of the carbon dioxide absorption feature. Carbon dioxide measurements over a 77.5m path length made outside the laboratory show the potential for carbon dioxide concentration monitoring.
Molecular dynamics simulations of surface-initiated melting of nitromethane
Authors: Siavosh-Haghighi Ali , Thompson Donald L.
Published: November 2006

The melting of nitromethane initiated at solid-vacuum interfaces has been investigated using molecular dynamics nvt simulations with a realistic force field [D. C. Sorescu et al., J. Phys. Chem. B 104, 8406 (2000)]. The calculated melting point (251±5K) is in good agreement with experiment (244.73K) and values obtained previously (∼255.5 and 266.5±8K) using other simulation methods [P. M. Agrawal et al., J. Chem. Phys. 119, 9617 (2003)]. Analyses of the molecular orientations and diffusion during the simulations as functions of the distance from the exposed surfaces show that the melting is a direct crystal-to-liquid transition, in which the molecules first gain rotational freedom, then mobility. There is a slight dependence of the melting temperature on the exposed crystallographic face.
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atom formation dynamics in ultraviolet photodissociation of tert-butyl bromide and iso-butyl bromide
Authors: Wang Yanmei , Zhang Song , Wei Zhengrong , Zheng Qiusha , Zhang Bing
Published: November 2006

The photodissociation dynamics of tert-C4H9Br and iso-C4H9Br has been studied at 234 and 265nm using two-dimensional velocity map imaging technique. The translational energy and angular distributions have been analyzed for Br, Br*, and tert-C4H9 radical. The energy distribution of Br atom in the photodissociation of tert-C4H9Br is found to consist of two Gaussian components. The two components are correlated to two independent reaction paths on the excited potential energy surfaces: (1) the high-energy component from the prompt dissociation along the C–Br stretching mode and (2) the low-energy component from the repulsive mode along the C–Br stretching, coupled with some bending motions. For the energy distribution of Br* atom in the photodissociation of tert-C4H9Br, a third multiphoton dissociative ionization channel is observed at 265nm in addition to the two energy components corresponding to channels (1) and (2). The energy distributions of Br and Br* atoms in the photodissociation of iso-C4H9Br can be fitted using only one Gaussian function indicating a single formation channel. Relative quantum yields for Br(P3∕22) at 234 and 265nm in the photodissociation of tert-C4H9Br are measured to be 0.76 and 0.65, respectively. For iso-C4H9Br, the measured value is Φ234nm(Br)=0.81. The contribution of bending modes to Br and Br* is much more obvious in the photodissociation of tert-C4H9Br than in iso-C4H9Br.
Phase retrieval diagnostic for single pulse x-ray characterization of high density plasmas
Authors: Baker K. L. , Carrano C. J.
Published: November 2006

This article presents designs for a single-shot x-ray compatible wave-front sensor and visible light demonstrations of such a wave-front sensor based on a novel implementation of the method of phase retrieval. This wave-front sensor may be used with a soft x-ray laser, as well as with incoherent line emission at multikilovolt x-ray energies. This approach could be used to characterize line-integrated electron density gradients formed in laser-produced and Z-pinch plasma experiments, as well as for at wavelength testing of extreme ultraviolet lithography components and x-ray phase imaging of biological specimens. The phase retrieval diagnostic is experimentally demonstrated in the visible region using a liquid-crystal spatial light modulator to provide a simulated phase profile, representing the phase that would be incurred by an x-ray probe passing through an exploding foil plasma. The visible light phase retrieval diagnostic represents the first experimental test of this phase retrieval algorithm, and the results are compared with an interferometric measurement and shown to be in close agreement. The merits of this diagnostic include a wide dynamic range, broadband or low coherence length light capability, high x-ray efficiency, two-dimensional gradient determination, and experimental simplicity.