bluuebunny/crossref_metadata_2025_split huggingface dataset:
The peroxidizing effect of α‐tocopherol on autoxidation of methyl linoleate in bulk phase
Authors: Terao J. , Matsushita S. 
Published: November 2006

AbstractIn order to understand the effect of α‐tocopherol on the autoxidation mechanism of edible oil under storage conditions, methyl linoleate was allowed to autoxidize at 50 C in bulk phase without any radical initiator. The reaction was monitored by determining the production of four isomeric hydroperoxides (13‐cis,trans; 13‐trans,trans; 9‐cis,trans; 9‐trans,trans) by high performance liquid chromatographic analysis after reduction. In the absence of α‐tocopherol, the rate of autoxidation depended on the sample size, and the duration of the induction period was affected by the initial level of hydroperoxides. However, the distribution of c‐t and t‐t hydroperoxide isomers remained constant during the propagation period regardless of the sample size. The addition of α‐tocopherol at 0.1 and 1.0% caused a linear increase in the amount of hydroperoxides and elevated the distribution of the c‐t isomers. The rate of hydroperoxidation appeared to be governed by the initial concentration of α‐tocopherol rather than the sample size or the initial hydroperoxide level. This peroxidizing effect of α‐tocopherol was suppressed by the presence of ascorbyl palmitate. A mechanism in which chromanoxy radical participates is proposed for the effect of α‐tocopherol on lipid autoxidation in bulk phase. It is therefore suggested that α‐tocopherol at high concentrations influences the mechanism of autoxidation of edible oil.
Enzymic oxidation of linolenic acid to 1,Z‐5‐octadien‐3‐ol, Z‐2,Z‐5‐octadien‐1‐ol and 10‐oxo‐E‐8‐decenoic acid by a protein fraction from mushrooms (Psalliota bispora)
Authors: Wurzenberger Margot , Grosch Werner 
Published: November 2006

AbstractThe pathway for the oxidative cleavage of linolenic acid was investigated using a protein fraction from mushrooms (Psalliota bispora) as the enzyme source. Incubation of the protein fraction with linolenic acid resulted in 1,Z‐5‐octadien‐3(R)‐ol and Z‐2,Z‐5‐octadien‐1‐ol (in a 3∶2 ratio) and 10‐oxo‐E‐8‐decenoic acid (10‐ODA). Experiments with molecular oxygen‐18 indicated that the oxygen in the hydroxy group of both octadienols originates from the gaseous phase and not from water. The protein fraction was incubated with the individual 9‐, 10‐, 12‐, 13‐, 15‐ and 16‐hydroperoxide isomers of linolenic acid. Only the 10‐hydroperoxy‐E‐8,Z‐12,Z‐15‐octadecatrienoic acid (10‐HPOT) served as substrate, and was cleaved into the two octadienols and the 10‐ODA. This result suggests that in the oxidation of linolenic acid by the mushroom fraction the 10‐HPOT is an intermediate cleaved by a hydroperoxide lyase into the octadienols and the 10‐ODA. Model experiments in which the methyl esters of both 10‐hydroperoxy‐E‐8,Z‐12‐octadecadienoic acid (10‐HPOD) and 10‐HPOT were treated with the Lewis acid BF3 yielded only various C9 compounds. It was therefore concluded that the reactions of the mushroom hydroperoxide lyase cannot be explained by the heterolytic rearrangement mechanism, which was proposed for the corresponding plant enzyme. β‐Scission of the 10‐HPOD and the 10‐HPOT explains the reactions of the mushroom hydroperoxide lyase and is discussed in detail.
Calories, fat and cancer
Authors: Kritchevsky David , Weber Maxine M. , Buck Carrie L. , Klurfeld David M. 
Published: November 2006

AbstractThe experiments reported are part of our effort to dissociate the tumor‐enhancing effects of dietary fat and high caloric intake. Rats either were fed ad libitum diets containing 4% corn oil or their calories were restricted by 40% and their diets contained 13.1% corn oil. Incidence of 7,12‐dimethylbenz(a)anthracene (DMBA)‐induced mammary tumors was 80% in rats fed ad libitum and 20% in those fed the calorie‐restricted diets. Incidence of 1,2‐dimethylhydrazine (DMH)‐induced colon tumors was 100% in rats fed ad libitum and 53% in those whose caloric intake was restricted by 40%. The tumor yield (tumors per tumor‐bearing rat) was significantly lower in rats on caloric restriction. In another series, rats were fed diets containing 5, 15 or 20% corn oil ad libitum or were fed calorie‐restricted (by 25%) diets which provided 20 or 26.6% corn oil (therefore, the same absolute amount of fat was consumed in each of the pair‐fed groups). Tumor incidence and tumor yield in the two calorie‐restricted groups were similar to those seen in the rats fed 5% fat ad lititum; tumor burden (total g of tumor) was 45–65% lower in the calorie‐restricted rats. The data suggest that caloric intake is a more stringent determinant of tumor growth than fat intake.
Effects of high levels of dietary fats on the growth of azaserine‐induced foci in the rat pancreas
Authors: Roebuck B. D. 
Published: November 2006

AbstractAzaserine induced two phenotypically different populations of foci, namely, acidophilic and basophilic foci. The effects of dietary modification during the post‐initiation phase of carcinogesis were examined. A diet of 20% (w/w) unsaturated fat (unsat) compared to a 20% saturated fat (sat) diet or a control diet (5% unsaturated fat) increased the number of acidophilic foci, as well as the thymidine labeling index (LI) of their nuclei. While the basophilic foci are carcinogen‐induced and at 2.5 mo post‐initiation have a similarly high growth rate to the acidophilic foci, this rate is not sustained as indicated by examination of both the LI and mean size of foci at 4 mo post‐initiation.
Dietary polyunsaturated fat in relation to mammary carcinogenesis in rats
Authors: Braden Laura M. , Carroll Kenneth K. 
Published: November 2006

AbstractHigh fat diets promote the development of mammary tumors induced in rats by 7,12‐dimethylbenz(a)anthracene (DMBA), and polyunsaturated fats are more effective than saturated fats. This difference is related to the linoleic acid content of polyunsaturated vegetable oils, but the amount of linolealte required for maximum tumor promotion appears to be higher than indicated by earlier experiments. Comparison of the effects of a polyunsaturated vegetable oil (corn oil) containing linoleate with a fish oilo (menhaden oil) containing polyunsaturated fatty acids derived from linolenic acid showed that higher dietary mammary tumors, while corresponding levels of menhaden oil had an inhibitory effect. This is further evidence that promotion of mammary tumorigenesis by polyunsaturated vegetable oils may be mediated by prostaglandins or other biologically active eicosanoids derived from n−6 fatty acids.
Ether lipid derivatives: Antineoplastic activity in vitro and the structure‐activity relationship
Authors: Berdel Wolfgang E. , Von Hoff Daniel D. , Unger Clemens , Schick Hans D. , Fink Ulrich , Reichert Anneliese , Eibl Hansjorg , Rastetter Johann 
Published: November 2006

AbstractThe antineoplastic activity of two ether lipid derivatives, the alkyl‐lysophospholipid derivative (ALP) ET‐18‐OCH3 and the ether‐linked lipoidal amine CP‐46,665 was tested in a human tumor clonogenic assay (HTCA) in vitro. CP‐46,665 suppresed the colony formation of various human tumors with a slight dose response relation after 1 hr incubation and with a clear optimum (85% response rate) after continuous exposure in the higher dose range tested (10 μg/ml). ET‐18‐0CH3 did not have substantial activity after 1 hr of incubation. However, when continuous exposure to the compound was used, ET‐18‐OCH3 seemed to have a modest dose response effect and yielded a response in about 60% of the tumor cell samples tested in the higher dose range (10 μg/ml). Thus, both compounds have in vitro antitumor activity in the HTCA within a dose range of 1–10 μg/ml, especially during continuous exposure. The tumor specific type activity was found in breast cancer, ovarian cancer, lung cancer and mesothelioma. Both compounds caused decreases in colony formation down to the 0%, 2% and 4% levels. In a comparison of specimens in which both compounds were used, only one of five times showed a discordance in sensitivity or resistance; therefore the compounds appear similar in their in vitro activity.In a second set of experiments we tested the structure‐activity relationship among a variety of ALP in the [3H]thymidine incorporation assay after incubation with HL‐60 leukemic blasts and other neoplastic cells from human origin. From these studies it can be concluded that in the ALP the alkyl linkage in the sn‐1 position is a necessary prerequisite for cytotoxicity; furthermore, in the majority of tumors tested the substitution of the sn‐2 position to prevent reacylation of the molecule is necessary for cytotoxicity.
The metabolism of malondialdehyde
Authors: Draper H. H. , McGirr L. G. , Hadley M. 
Published: November 2006

AbstractInterest in malondialdehyde (MDA) metabolism stems from its formation as a product of lipid peroxidation in the diet and in the tissues; its reactivity with functional groups of nucleic acid bases, proteins and phospholipids; its mutagenicity in bacteria, and its reported skin and liver carcinogenicity in animals. Administration of the Na enol salt of MDA in the drinking water of mice over a range of 0.1–10.0 μg/g/day for 12 mo produced dose‐dependent hyperplastic and neoplastic changes in liver nuclei and increased mortality at the highest level but produced no gross hepatic tumors. Addition of MDA to the medium of rat skin fibroblasts grown in culture caused nuclear abnormalities at concentrations as low as 10−6M despite an uptake of only 4%. [1,3‐14C]MDA was rapidly oxidized to [14C]acetate in rat liver mitochondria and to14CO2 in vivo: however, ∼10% of the radioactivity was recovered in the urine. Chromatographic analysis of rat urine revealed the presence of several compounds which yield MDA on acid hydrolysis. Total MDA excretion increased in response to conditions which stimulate lipid peroxidation in vivo, including vitamin E deficiency, Fe or CCl4 administration, and enrichment of the tissues with PUFA. N‐acetyl‐e‐(2‐propenal)lysine was identified as a major urinary metabolite of MDA in rat and human urine. This compound is derived primarily from N‐α‐(2‐propenal)lysine released in digestion as a product of reactions between MDA and the ε‐amino groups of N‐terminal lysine residues in food proteins. However, its presence in the urine of animals fasted or fed MDA‐free diets indicates that it is also formed in vivo. Identification of the metabolites of MDA excreted in the urine may provide clues to the mechanisms of cellular damage caused by this compound in the tissues.
Ion‐pair high‐performance liquid chromatography of bile salt conjugates: Application to pig bile
Authors: Legrand‐Defretin Véronique , Juste Catherine , Henry Robert , Corring Tristan 
Published: November 2006

AbstractThe high‐performance liquid chromatographic separation and quantitation of conjugated bile salts from pig bile is reported. Synthetic standards and bile samples were chromatographed on a C18 reversed phase column using acetonitrile/water/tetrabutyl ammonium phosphate as an isocratic mobile phase at a flow rate of 1 mL/min. Detection of the ion‐pairs was at 214 nm. The method permits efficient separation of all conjugated pig biliary bile salts without prior modification or treatment of the samples. Analysis of 12 pig biles showed that 85% of the bile salts are conjugated to glycine. The three main conjugated bile salts were glyco‐3α,6α,7α‐trihydroxy‐5β‐cholanoic acid (GHC), glyco‐3α,7α‐dihydroxy‐5β‐cholanoic acid (GCDC), and glyco‐3α,6α‐dihydroxy‐5β‐cholanoic acid (GHDC). Glyco‐3α‐hydroxy‐6‐oxo‐5β‐cholanoic acid (G3α6oxo), tauro‐3α,7α‐dihydroxy‐5β‐cholanoic acid (TCDC), tauro‐3α,6α,7α‐trihydroxy‐5β‐cholanoic acid (THC), and tauro‐3α,6α‐dihydroxy‐5β‐cholanoic acid (THDC) were found to contribute each for 4 to 5% ot the total. An excellent correlation was found between the sum of conjugated bile salts quantitated by high‐performance liquid chromatography (HPLC) and values obtained by conventional enzymatic assay. Simplicity, efficiency and relative rapidity of the method render it suitable for routine analyses.
Diversity of sterol biosynthetic capacity in the caryophyllidae
Authors: Salt Thomas A. , Xu Sihua , Patterson Glenn W. , Adler John H. 
Published: November 2006

AbstractThe order Caryophyllales, along with its two associated orders, the Polygonales and Plumbaginales, comprise the angiosperm subclass Caryophyllidae. We have now characterized the sterol compositon of 231 members of this subclass. This includes 210 species and 21 cultivars in 108 genera within the 14 families of these three orders. From these data, clear differences in biosynthetic capability and putative relationships between taxa have been established. Members of the two monofamilial orders (Polygonales and Plumbaginales) contain Δ5‐sterols in ratios typical of “main line” angiosperms. Members of families in the Caryophyllales contain Δ5‐sterols, or Δ7‐sterols or mixtures of Δ5‐ and Δ7‐sterols. In the majority of species where Δ7‐sterols are the dominant sterols produced, trace amounts to almost equal amounts of Δ5‐sterols are also present. Replicate samples of many of these species have shown that the ratio of Δ5‐sterols to Δ7‐sterols in these species is stable over time and/or location. From these data, it appears that the conversion of Δ7‐sterols to Δ5‐sterols is highly regulated in the majority of species within this order. In these families, similarities in sterol composition correlate well with taxonomic relatedness. Relationships between these taxa with respect to biosynthetic capability can now be postulated.
Neutral sterol metabolism in insects
Authors: Svoboda James A. , Feldlaufer Mark F. 
Published: November 2006

AbstractSince they are unable to biosynthesize sterols, many phytophagous and omnivorous insects satisfy their cholesterol requirement by side chain dealkylation of the C‐24 alkyl group of dietary C28 and C29 phytosterols. However, not all insects that can dealkylate the phytosterol side chain produce cholesterol. In addition, certain insects,e.g., some Hymenoptera, Hemiptera, and Diptera, are unable to dealkylate the sterol side chain. Although C27 ecdysteroids (molting hormones), which are biosynthesized from cholesterol, are the major ecdysteroids in most insects, many of those species that are unable to dealkylate phytosterols utilize campesterol as a precursor for the C28 ecdysteroid makisterone A. The considerable diversity of steroid utilization between certain insect species makes it difficult to generalize about insect steroid biochemistry. The ability to disrupt certain unique aspects of steroid utilization and metabolism in insects might be exploited for developing new insect control technology.
Metabolism of plant sterols by nematodes
Authors: Chitwood David J. , Lusby William R. 
Published: November 2006

AbstractParasitic nematodes do not biosynthesize sterolsde novo and therefore possess a nutritional requirement for sterol, which must be obtained from their hosts. Consequently, the metabolism of phytosterols by plant‐parasitic nematodes is an important process with potential for selective exploitation. The sterol compositions of several species of plant‐parasitic nematodes were determined by capillary gas chromatography‐mass spectrometry and compared with the sterol compositions of their hosts. Saturation of the phytosterol nucleus was the major metabolic transformation performed by the root‐knot nematodesMeloidogyne arenaria andM. incognita and the corn root lesion nematode,Prytalenchus agilis. In addition to saturation, the corn cyst nematode,Heterodera zeae, dealkylated its host sterols at C‐24. Because free‐living nematodes can be cultured in sterol‐defined artificial medium, they have been successfully used as model organisms for investigation of sterol metabolism in plant‐parasitic nematodes. Major pathways of phytosterol metabolism inCaenorhabditis elegans, Turbatrix aceti andPanagrellus redivivus incleded C‐24 dealkylation and 4α‐methylation (a pathway unique to nematodes).C. elegans andT. aceti introduced double bonds at C‐7, andT. aceti andP. redivivus saturated the sterol nucleus similarly to the plant‐parasitic species examined. Several azasteroids and long‐chain dimethylalkylamines inhibited growth and development ofC. elegans and also the Δ24‐sterol reductase enzyme system involved in the nematode C‐24 dealkylation pathway.
Cloning and disruption of the yeast C‐8 sterol isomerase gene
Authors: Ashman William H. , Barbuch Robert J. , Ulbright Corinne E. , Jarrett Harry W. , Bard Martin 
Published: November 2006

AbstractThe yeastERG2 gene codes for the C‐8 sterol isomerase, an enzyme required for the isomerization of the δ8 double bond to the δ7 position in ergosterol biosynthesis. TheERG2 gene was cloned by complementation of a C‐8 sterol isomerase mutant strain (erg2). The complementing region of DNA required to restore ergosterol synthesis toerg2 was limited to a 1.0 kbStuI‐BglII fragment. In order to determine whether theERG2 gene was essential for yeast viability, aLEU2 gene was inserted into theNdeI site (made blunt) of this 1.0 kb fragment. Transformation of a wild type diploid strain with theERG2 substituted DNA resulted in the generation of viable haploids containing theerg2 null allele (erg2–4∶∶Leu2). These results suggest that the C‐8 sterol isomerase activity is not essential for yeast cell viability. This disruption represents the second ergosterol biosynthetic gene in the distal portion of the pathway to be disrupted without adversely affecting cell viability.
Aspects related to mevalonate biosynthesis in plants
Authors: Bach Thomas J. , Boronat Albert , Caelles Carmé , Ferrer Albert , Weber Thomas , Wettstein Annette 
Published: November 2006

AbstractWe purified and characterized a membrane‐associated enzyme system from radish (Raphanus sativus L.) that is capable of converting acetyl‐CoA into 3‐hydroxy‐3‐methylglutaryl‐coenzyme A (HMG‐CoA). The enzyme system apparently comprises acetoacetyl‐CoA thiolase (EC 2.3.1.9) and HMG‐CoA synthase (EC 4.1.3.5). Its activityin vitro can be strongly stimulated by FeII. When ferrous ions are applied chelated with ethylenediaminetetraacetate, citrate or adenosine 5′‐triphosphate (ATP), the stimulation is further increased. Stimulation is due to a higher catalytic efficiency as indicated by an increase in Vmax, whereas the affinity of the enzyme towards acetyl‐CoA remains constant (Km=6 μM). A considerable portion of HMG‐CoA lyase activity is associated with the same membranes. HMG‐CoA lyase (EC 4.1.3.4) is also solubilized and partially co‐purified. Its activity requires comparatively high concentrations of Mg2+. The conversion of HMG‐CoA to mevalonic acid is catalyzed by HMG‐CoA reductase (EC 1.1.1.34) that is associated with the same membranes. By cDNA encoding theArabidopsis HMG‐CoA reductase, we isolated a corresponding gene from a cDNA library newly established from etiolated radish seedlings. This full‐length cDNA, referred to as λcRS3, encodes a polypeptide of 583 amino acids with a molecular mass of about 63 kDa. The hydropathy profile suggests the presence of two hydrophobic membrane‐spanning domains within the N‐terminal 165 amino acids. The carboxy‐terminal part, where the catalytic site resides, is highly conserved in all eukaryotic HMG‐CoA reductase genes sequenced so far.
On the structure, biosynthesis, function and phylogeny of isoarborinol and motiol
Authors: Nes W. David , Wong Rosalind Y. , Griffin Jane F. , Duax William L. 
Published: November 2006

AbstractThe solid‐state conformations of the C‐3 acetates of two isomeric hopanoids—1, isoarborinol (D∶C‐friedo‐B1∶A1‐3β,5α,8α,10β,13β,14α,17β,18α,21β) and 2, motion (D∶C‐friedo‐B1∶A1‐neogammacer‐7(8)‐en‐3β‐ol[3β,5α,9α,10β,13α,14β,17α,18β,21α])—have been determined by X‐ray crystallography. The data show that whereas both molecules are planar, 1 orients into a chair‐halfchair‐chair‐chair‐halfchair conformation while 2 orients into a chair‐sofa‐twist‐halfchair‐halfchair conformation. To explain the biogenesis of 1 and 2 from squalene oxide, a step‐wise mechanism is proposed which proceeds through the protosteroid cation (for 1) and dammarenyl cation (for 2). After ring enlargement from the corresponding 13(17)bond followed by concerted 1,2‐migrations and loss of the 11β‐H and 7β‐H as protons, respectively, a 9,11‐double bond (in 1) and a 7,8‐double bond (in 2) is introduced into the nucleus. The mechanism is discussed in relation to the classical view of a non‐stop cyclization process where, for example, squalene oxide folds in a chair‐chair‐chair‐chair‐boat conformation to give a cyclized product (motiol) presumably with the same conformational disposition as the cyclizing material. The three‐dimensional geometry of 1 and 2 was found to be structurally dissimilar from sterols. For instance, 1 and 2 are shorter and volumetrically smaller molecules than cholesterol, and this may explain their diminished importance as membrane inserts compared with sterols in eukaryote evolution.
Fatty acid metabolism inTaphrina deformans treated with sterol biosynthesis inhibitors
Authors: Weete J. D. , Sancholle M. , Patterson K. A. , Miller K. S. , Huang M. Q. , Campbell F. , Van den Reek M. 
Published: November 2006

AbstractChanges in the unsaturated fatty acid content of the fungusTaphrina deformans as a function of growth, temperature, and sterol content were investigated. It was found that the highest growth rate was accompanied by a relatively high degree of fatty acid unsaturation (18∶1<18∶2+18∶3) and low sterol (brassicasterol) content. Also, a substantial shift in the degree of unsaturation from mainly 18∶2+18∶3 to 18∶1 occurred in the later stages (mid‐linear) of culture development. Cells readily adapted from 18°C to 13°C, and exhibited a higher growth rate at the lower temperature after a period of acclimation. Growth was readily inhibited by the sterol biosynthesis inhibitors propiconazole and naftifine, which blocked brassicasterol biosynthesis at C‐14 demethylation and squalene epoxidation, respectively. Growth was also inhibited by tunicamycin which did so without affecting sterol content. The shift in degree of fatty acid unsaturation did not occur in cells from cultures at reduced temperature or treated with any of the inhibitors. Since tunicamycin did not affect the sterol content, delay in the shift in the degree of fatty acid unsaturation was attributed to factors other than a reduction in sterol content.
A facile chemical synthesis of cholest‐4‐en‐3‐one. Carbon‐13 nuclear magnetic resonance spectral properties of cholest‐4‐en‐3‐one and cholest‐5‐en‐3‐one
Authors: Parish Edward J. , Honda Hiroshi , Chitrakorn Sarawanee , Livant Peter 
Published: November 2006

AbstractThis paper presents a simplified method for the chemical synthesis of cholest‐4‐en‐3‐one, which is a naturally occurring steroid and a salient intermediate in steroid chemistry. Pyridinium chlorochromate (PCC) in refluxing benzene has been found to be an effective and convenient reagent for the oxidation and concomitant isomerization of cholest‐5‐en‐3β‐ol (cholesterol) to cholest‐4‐en‐3‐one in high yield. Also described are the carbon‐13 nuclear magnetic resonance spectral properties of cholest‐4‐en‐3‐one and of the isolated reaction intermediate cholest‐5‐en‐3‐one.