bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipid composition of the membrane released after an in vitro acrosome reaction of epididymal boar sperm
Authors: Nikolopoulou Maria , Soucek Donald A. , Vary James C. 
Published: November 2006

AbstractPrior to fertilization, mammalian sperm must undergo the acrosome reaction, which involves modifications of the plasma and outer acrosomal membranes followed by vesiculation and release of the membranes. The membrane fraction that was released from caudal boar sperm undergoing an in vitro acrosome‐like reaction was isolated and characterized with respect to density, marker enzymes and lipid composition. This membrane had a lower phospholipid/protein ratio (mg/mg) than the sperm plasma membrane, whereas both membranes had similar molar sterol/phospholipid ratios. The major phospholipid was sphingomyelin, followed by phosphatidylethanolamine and phosphatidylcholine, whereas in the plasma membrane the order was reversed; the two major phosphoglycerides contained alkylacyl and alkenylacyl species in addition to the diacyl species. The released membrane also contained lower amounts of cholesterol sulfate and unsaturated fatty acids than the plasma membranes. These results, in combination with our studies on the changes of the sperm membranes during maturation and acrosome reaction, will allow a better understanding of the mechanism of the sperm acrosome reaction.
Fast atom bombardment and tandem mass spectrometry of phosphatidylserine and phosphatidylcholine
Authors: Jensen Nancy J. , Tomer Kenneth B. , Gross Michael L. 
Published: November 2006

AbstractFast atom bombardment (FAB) desorption of phosphatidylserine and various phosphatidylcholines produces a limited number of very informative negative ions. Especially significant is the formation of (M‐H)− ions for phosphatidylserine, a compound which does not yield informative high mass ions by other ionization methods. Phosphatidylcholines of not yield (M‐H)− ions but instead produce three characteristic high mass ions, (M‐CH3+_−, [M‐HN(CH3)3+]− and [M‐HN(CH33+‐C2H2]−. Both classes of lipids also yield anions attributed to the carboxylate components of these complex lipids. FAB desorption in combination with collisional activation allows for characterization of fragmentation and determination of structural features. Collisional activation of the carboxylate anion fragments from the complex lipids is especially informative. Structural characterization of the fatty acid chain can be achieved as the released saturated carboxylate anions undergo a highly specific 1,4‐elimination of H2, which results in the losses of the elements of CH4, C2H6, C3H8...in a fashion entirely consistent with the chemistry of carboxylate anions desorbed from free fatty acids. These CnH2n+2 losses begin at the alkyl terminus and progress along the entire alkyl chain. Modified fatty acids undergo a similar fragmentation; however, the modification affects the series of CnH2n+2 losses in a manner which permits determining the type of modification and its location on the fatty acid chain.
A relationship between essential fatty acid and vitamin E deficiency
Authors: Subramanian Carole S. , Mead James F. 
Published: November 2006

AbstractTo test whether vitamin E deficiency might influence the course of essential fatty acid (EFA) deficiency, Long Evans rats were fed diets containing a marginal amount (1.5% of calories) of 18∶2ω6 or 18∶3ω3 fatty acid with complete absence of the other and with or without vitamin E. Vitamin E contents decreased continuously in serum and liver in all rats fed the E‐free diets but in the brains of only the rats fed the marginal 18∶3ω3, E‐free diet. It is considered that the vitamin E is cooxidized in the liver with 22∶6ω3, since this fatty acid is very low in livers of the rats fed the marginal 18∶2ω6 diet but much higher in livers of the rats fed the marginal 18∶3ω3 diet. Brain 22∶6ω3 values are comparable for both groups. The source of 22∶6ω3 is evidently in the mother's milk, since following weaning there is a precipitous drop in 22∶6ω3 in serum, liver and carcass of rats on the 18∶2ω6‐containing diet. No significant signs of EFA deficiency were seen in the E‐deficient rats.
Imprints of virus infection: Can paramyxoviruses permanently modify triacylglycerol metabolism?
Authors: Wild T. F. , Bernard A. , Malak N. Abdul , Brichon G. , Zwinglestein G. 
Published: November 2006

AbstractWe have examined whether the passage of a paramyxovirus in a cell (BGM, African green monkey kidney) or animal (Swiss mouse) can permanently modify its metabolism. In an in vitro model in which cells had been cured of a measles virus persistent infection, the cells retained the modifications affecting lipid metabolism and composition induced during the infection. In a canine distemper virus mouse model, the same virus‐induced modifications were observed in mice after the virus had been eliminated.
Metabolism of erucic acid in perfused rat liver: Increased chain shortening after feeding partially hydrogenated marine oil and rapeseed oil
Authors: Christiansen E. N. , Thomassen M. S. , Christiansen R. Z. , Osmundsen H. , Norum K. R. 
Published: November 2006

AbstractThe metabolism of [14‐14C] erucic acid was studied in perfused livers from rats fed on diets containing partially hydrogenated marine oil or rapeseed oil for three days or three weeks. Control rats were given groundnut oil. Chain‐shortening of erucic acid, mainly to 18∶1, was found in all dietary groups. In the marine oil and rapeseed oil groups, the percentage of chain‐shortened fatty acids in very low density lipoproteins‐triacylglycerols (VLDL‐TG) exported from the liver increased after prolonged feeding. A similar increase was found in liver TG only with partially hydrogenated marine oil. This oil, rich intrans fatty acids, thus seemed to be more effective in promoting chain‐shortening. The fatty acid composition of the secreted and stored TG differed both with respect to total fatty acids and radioactively labeled fatty acids, indicating that at least 2 different pools of TG exist in the liver. The lack of lipidosis in livers from rats fed dietary oils rich in 22∶1 fatty acids is discussed in relation to these findings. In conclusion, a discussion is presented expressing the view that the reversal of the acute lipidosis in the hearts of rats fed rapeseed oil or partially hydrogenated marine oils is, to a large extent, derived from the increased chain‐shortening capacity of erucic acid in liver.
Fatty acid composition of heart cells exposed to thermally oxidized fats
Authors: Bird R. P. , Alexander J. C. 
Published: November 2006

AbstractCorn oil and olive oil were thermally oxidized, and the free fatty acids from the fresh fats, and from the distillable non‐urea‐adductable (DNUA) fractions of the thermally oxidized fats were prepared. These were added as emulsions to the medium of primary cultures of heart endothelial and muscle cells from neonatal rats. After exposure for 24 hr, the fatty acid composition of the triacylglycerol (TC) and phospholipid (PL) fractions of the cells was determined. Reflecting the nature of the fat used, the corn oil treatment produced relatively higher concentrations of linoleic acid in the TG and PL fractions compared to the olive oil treatment, in which case the oleic acid level was influenced. Treatment of the cultured cells with components derived from oxidized corn oil or oxidized olive oil resulted in lower concentrations of linoleic and arachidonic acids in the PL moieties compared to the fresh fat controls. However, there were marked increases in arachidonic acid in the TG fractions of both the endothelial and muscle cells. These changes due to the DNUA from thermally oxidized fats indicate a distinct metabolic response to the derivatives formed during thermal oxidation of the fats.
Oxidation of 3‐oxygenated Δ4‐ and Δ5‐C27 steroids by soybean lipoxygenase and rat liver microsomessteroids by soybean lipoxygenase and rat liver microsomes
Authors: Aringer Leif 
Published: November 2006

AbstractThe formation of dioxygenated metabolites of cholesterol, epicholesterol (5‐cholesten‐3α‐ol) 4‐cholesten‐3β‐ol, 4‐cholesten‐3α‐ol, 4‐cholesten‐3‐one and 4‐stigmasten‐3‐one was studied after incubations with soybean lipoxygenase and linoleic acid. From cholesterol and epicholesterol were formed the 7α‐hydroxy‐, 7α‐hydroperoxy‐, 7β‐hydroxy‐, 7β‐hydroperoxy‐, 7‐oxo and 5,6‐epoxyderivatives as well as 6β‐hydroxy‐4‐cholesten‐3‐one. All Δ4‐steroids were hydroxylated in the 6α‐ and 6β‐positions. The ratios between the yields of 6β‐ and 6α‐hydroxylated metabolites varied between 3∶1 and 2∶1. Incubations with 4‐cholesten‐3α‐ol and 4‐cholesten‐3β‐ol also afforded the 4,5‐epoxides of these steroids. The ratios between the yields of the 4β,5β‐ and 4α,5α‐epoxides were ca. 4∶1 for 4‐cholesten 3β‐ol and ca. 3∶2 for 4‐cholesten‐3α‐ol. With iron‐supplemented microsomes from rat liver, the compounds formed were qualitatively and quantitatively the same as with soybean lipoxygenase, whereas with 18,000 × g rat liver supernatant fractions the yields of all products formed—except 7α‐hydroxycholesterol and 6β‐hydroxy‐4‐cholesten‐3‐one—were markedly decreased. The results indicate the presence of a rat liver microsomal 6β‐hydroxylase which can use 4‐cholesten‐3‐one as a substrate and extend previous findings of similarities between soybean lipoxygenase and a nonspecific lipoxygenase in rat liver microsomes.
Cuticular lipid constituents of cabbage seedpod weevils and host plant oviposition sites as potential pheromones
Authors: Richter Ingolf , Krain Horst 
Published: November 2006

AbstractThe cuticular lipids of cabbage seedpod weevils (Ceutorrhynchus assimilis Payk.) and those at their oviposition site, i.e., the seed pods of the host plant (Brassica napus L.), were analyzed by chromatographic techniques in conjunction with mass spectrometry (MS). Long chain hydrocarbons were most abundant in both lipids; however, the seed pods ofB. napus containedn‐alkanes only, whereasC. assimilis showed a predominance of dimethylalkanes over internally branched methylalkanes as well as iso‐ andn‐alkanes. The amounts of ketones, secondary alcohols and aldehydes, the usual plant components that are unique in insects, occurred in cuticular lipids of both organisms in approximately the same ratio. The composition ofn‐alkanes,n‐ketones, secondaryn‐alcohols, iso‐ and anteisoaldehydes and esterified primary anteiso‐alcohols of wax esters was similar betweenC. assimilis andB. napus. In both sources, qualitative but not quantitative similarities were observed in the composition ofn‐aldehydes and esterified primaryn‐ and iso‐alcohols, respectively. The esterified fatty acids of wax esters fromB. napus were composed of roughly equal proportions of saturated branched and unbranched components. The esterified fatty acids of wax esters and steryl esters fromC. assimilis consisted of major proportions of saturated as well as unsaturatedn‐compounds, whereas iso‐ and anteiso structures were present in minor proportions only. Free fatty acids and traces of ethyl esters of fatty acids found inC. assimilis were mainly composed of unsaturatedn‐compounds.
Free fatty acid content of human milk: Physiologic significance and artifactual determinants
Authors: Chappell Janet E. , Clandinin Michael T. , McVey Muriel A. , Chance Graham W. 
Published: November 2006

AbstractAnalysis of human milk was conducted to determine if free fatty acids occur naturally or as a consequence of artifactual lipolysis after milk expression. Five mothers provided triplicate early morning milk samples on day 43 of lactation. Following extraction, lipid classes were separated by preparative thin layer chromatography and quantified by capillary gas liquid chromatography. Fresh milk samples collected with 20 volumes chloroform‐methanol (1∶1, v/v) were analogous in total free fatty acid level and profile of fatty acids to a duplicate sample collected with 0.4M EDTA and immediately frozen at −10 C. Low milk levels of free fatty acids appear to exist naturally. During days 4–37 of lactation, four serial milk samples from 15 mothers were collected and frozen with 0.4M EDTA. The concentration of free fatty acids in colostrum (0.03–0.5%, w/w) was lower than for subsequent days (0.3–2.5%, w/w). Additional samples were collected with and without a lipase inhibitor (0.4M EDTA) and subjected to routine collection and storage procedures. Significantly different fatty acid profile and higher levels of free fatty acids in milk collected without a lipase inhibitor added indicate that domestic freezing and/or thawing ruptures the fat globule membrane, allowing sn‐1‐stereospecific serum stimulated lipoprotein lipase contact with its triglyceride substrate. Standard procedures for collection of human milk for gavage fed infants appear to stimulate artifactual lipolysis of milk triglyceride and subsequent release of free fatty acids. The proposed relationship between dietary free fatty acids and prolonged, unconjugated hyperbilirubinemia in the newborn is discussed with regard to the significance of preintestinal lipolysis.
The squalene‐2,3‐epoxide cyclase as a model for the development of new drugs
Authors: Cattel L. , Ceruti M. , Viola F. , Delprino L. , Balliano G. , Duriatti A. , Bouvier‐Navé P. 
Published: November 2006

AbstractThe 2,3‐oxido squalene (SO) cyclases represent a group of enzymes which convert SO into polycyclic triterpenoids such as lanosterol, cycloartenol, cucurbitadienol and β‐amyrin. Taking into account the postulated model of the enzymatic cyclization of SO, we have investigated the possibility of designing compounds that would be selective and potent inhibitors of SO cyclases. Due to the fundamental role of sterols in animal, higher plant and fungal tissues, these inhibitors might behave as very selective (ipocholesterolemic, antifungal or phytotoxic) drugs.Our first approach was the synthesis and biological evaluation of 2‐aza‐2,3‐dihydrosqualene and its derivatives which, being protonated at physiological pH, would present some similarities to the C‐2 carbon ion generated by the opening of the oxirane ring of SO. Microsomes from different sources (germinated pea cotyledons, maize seedlings, rat liver and yeasts) were utilized to determine the inhibition values (I50: concentration of inhibitor producing 50% inhibition at a given substrate concentration).From the results obtained so far we conclude that 2‐aza‐2‐dihydrosqualene and its derivatives strongly inhibited the cyclases, the site of the enzyme responsible for binding to the inhibitor is quite sensitive to the steric hindrance, and the degree of the inhibitory activity is greater in higher plants than in rat liver or fungi.
Sterols of cucurbitaceae: The configurations at C‐24 of 24‐Alkyl‐Δ5‐,Δ7‐ and Δ8‐sterols
Authors: Akihisa Toshihiro , Thakur Swapnadip , Rosenstein Fumiko U. , Matsumoto Taro 
Published: November 2006

AbstractThe major sterols of the seeds ofBenincasa cerifera, Cucumis sativus, Cucurbita maxima, C. pepo andTrichosanthes japonica and of the mature plant tissues (leaves and stems) ofCitrullus battich, Cucumis sativus andGynostemma pentaphyllum of the family Cucurbitaceae were 24‐ethyl‐Δ7‐sterols which were accompanied by small amounts of saturated and Δ5‐and Δ8‐sterols. The 24‐ethyl‐Δ7,22,Δ7,25(27) and Δ7,22,25(27)‐sterols constituted the predominant sterols for the seed materials, whereas the 24‐ethyl‐Δ7 and Δ7,22‐sterols were the major ones for the mature plant tissues. The configurations of C‐24 of the alkylsterols were examined by high resolution1H NMR and13C NMR spectroscopy. Most of the 24‐methyl‐ and 24‐ethylsterols examined which lack a Δ25(27)‐bond (i.e., 24‐methyl‐, 24‐methyl‐Δ22‐, 24‐ethyl‐ and 24‐ethyl‐Δ22 sterols) were shown to occur as the C‐24 epimeric mixtures in which the 24α‐epimers predominated in most cases. The 24‐ethylsterols which possess a Δ25(27) (i.e., 24‐ethyl‐Δ25(27)‐and 24‐ethyl‐Δ7,22,25(27)‐sterols) were, on the other hand, composed of only 24β‐epimers. The Δ8‐sterols identified and characterized were four 24‐ethyl‐sterols: 24α‐and 24β‐ethyl‐5α‐cholesta‐8,22‐dien‐3β‐ol, 24β‐ethyl‐5α‐cholesta‐8,25(27)‐dien‐3β‐ol and 24β‐ethyl‐5α‐cholesta‐8,22,25(27)‐trien‐3β‐ol. This seems to be the first case of the detection of Δ8‐sterols lacking a 4‐methyl group in higher plants, and among the four Δ8‐sterols the latter two are considered to be new sterols. The probable biogenetic role of the Δ8‐sterols and the possible biosynthetic pathways leading to the 24α‐ and 24β‐alkylsterols in Cucurbitaceae are discussed.
Biosynthesis of 24‐methylcholest‐5‐en‐3β‐ol and 24‐ethylcholest‐5‐en‐3β‐ol inZea mays
Authors: Rendeli Nigel , Misso Neil L. A. , Goad L. John 
Published: November 2006

AbstractThe relative rates of synthesis of 24‐methylcholest‐5‐en‐3β‐ol and 24‐ethylcholest‐5‐en‐3β‐ol inZea mays shoots were determined using [2‐14C]mevalonic acid and [methyl‐14C]methionine as substrates. The 24‐ethylsterol had a higher specific activity and it apparently was synthesized at about 3–4 times the rate of the 24‐methylsterol.1H NMR spectroscopy showed that the 24‐ethylsterol was predominantly the 24α‐epimer but the 24‐methylsterol was a mixture of the 24α‐epimer (30–40%) and the 24β‐epimer (60–70%). The results are discussed in relation to the involvement of Δ24(28)‐, Δ23, Δ25‐ and Δ24(25)‐sterol intermediates in 24‐methyl‐ and 24‐ethylsterol production.
Selective sterol transfer in the honey bee: Its significance and relationship to other hymenoptera
Authors: Svoboda James A. , Herbert Elton W. , Thompson Malcolm J. , Feldlaufer Mark F. 
Published: November 2006

AbstractThe honey bee,Apis mellifera, is one of only a few species of phytophagous insects known to be unable to convert C‐24 alkyl phytosterols to cholesterol. Regardless of the dietary sterols available to worker bees, the major tissue sterol of brood reared by the workers is always 24‐methylenecholesterol, followed by sitosterol and isofucosterol. Normally, little or no cholesterol is present in honey bee sterols. The maintenance of high levels of certain sterols is accomplished through a selective transfer of sterols from the endogenous sterol pools of the workers to the developing larvae through the brood food material secreted from the hypopharyngeal and mandibular glands and/or the honey stomach of the workers. The selective uptake and transfer of radiolabeled C27, C28 and C29 sterols have been studied to correlate these aspects of sterol utilization with the discovery of an unusual molting hormone (ecdysteroid) in honey bee pupae as the major ecdysteroid of this stage of development. The phylogenetic implications of this selective transfer phenomenon in the honey bee and comparison with sterol metabolism in certain other hymenopteran species emphasize the diversity of steroid biochemistry in insects.
Evidence for facilitated transport in the absorption of sterols bySaccharomyces cerevisiae
Authors: Nes William R. , Dhanuka Inder C. , Pinto William J. 
Published: November 2006

AbstractSaccharomyces cerevisiae is known to absorb sterols readily in the absence of air. As shown in this paper yeast cells also will absorb sterols with and without various double bonds or an alkyl group at C‐24 in the presence of air at a concentration (ca. 10% of the gas phase) which is growth‐limiting due to limited sterol synthesis. However, if the growth conditions are changed to be fully aerobic, sterol is no longer absorbed to any significant extent even when the sterol in the medium (ergosterol) is the same as that present in the cells. This implies that sterol in the medium does not equilibrate passively with sterol in the plasma membrane and that some sort of facilitated transport, which can be turned on and off, is responsible for the entry of sterol when it occurs as a response to an inadequate endogenous supply of sterol. In agreement with facilitated transport mediated by protein binding, yeast cells in an auxotrophic state for sterol exhibit a high degree of stereoselectivity with respect to the orientation of the side chain around the C‐17(20)‐bond. For instance, E‐17(20)‐ but not Z‐17(20)‐dehydrocholesterol is absorbed by cells undergoing limited growth with 10% air.
Sterols of the oyster,Crassostrea virginica
Authors: Teshima Shin‐Ichi , Patterson Glenn W. , Dutky Samson R. 
Published: November 2006

AbstractA commericial sample of the oyster,Crassostrea virginica, obtained from Maryland waters of the Chesapeake Bay, contained 31 desmethylesterols and at least eight 4‐monomethylsterols. The combined gas liquid chromatography‐mass spectra of the minor components showed the presence of 6 unusual sterols, 24‐ethylcholest‐22‐en‐3β ol, 4α‐methyl‐24‐ethylcholestan‐3β‐ol, occelasterol, (24E)‐24‐propylidene‐cholest‐5‐en‐3β‐ol, (24ZO‐24‐propylidene‐cholest‐5‐en‐3β‐ol, and 24‐methylene‐cholestanol. The C‐24 configuration of 24‐ethylcholest‐5‐enol, 24‐methyl‐cholesta‐5,22‐dienol, and 24‐ethylcholesta‐5,22 dienol were elucidated by 220 MHz nuclear magnetic resonance spectrometry.
Dietary fibers: V. Binding of bile salts, phospholipids and cholesterol from mixed micelles by bile acid sequestrants and dietary fibers
Authors: Vahouny George V. , Tombes Robert , Cassidy Marie M. , Kritchevsky David , Gallo Linda L. 
Published: November 2006

AbstractMixed micelles were prepared containing combinations of either taurocholate or taurochenodeoxycholate, monoolein, oleic acid, dioleylphosphatidylcholine (lecithin) and cholesterol. These were incubated with commercial bile‐acid‐sequestering resins, cholestyramine and DEAE‐Sephadex, or various dietary fibers and fiber components including wheat bran, cellulose, alfalfa, lignin and 2 viscosity grades of guar gum. Binding was determined as the difference between the radioactivity of each micellar component added and that recovered in the centrifugal supernatant after incubation. In general, the extent of bile salt sequestration was characteristic and reproducible for each bile salt, and was largely unaffected by the presence of one or more additional components of the micellar mixture, including the other bile salt. Cholestyramine bound 81–92% of the bile salts and 86–99% of the phospholipid and cholesterol present in micelles. DEAE‐Sephadex sequestered only 49% of the taurocholate and 84% of the taurochenodeoxycholate, but completely removed all of the phospholipid and cholesterol from micelles containing either bile salt. Among the dietary fibers, guar gum of either viscosity bound between 20–38% of each micellar component, whereas lignin, alfalfa, wheat bran and cellulose were progressively less effective in sequestratin of individual components of mixed micelles. The extent of sequestration of micellar components by these resins and fibers is reasonably correlated with the effects of these same materials on lymphatic absorption of lipids and to their suggested hypocholesteremic properties.