bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stearoyl‐coenzyme A desaturase activity in novikoff hepatoma
Authors: Renuka Prasad M. , Joshi Vasudev C. 
Published: November 2006

AbstractThe activities of microsomal stearoyl‐CoA desaturation, NADH‐cytochrome b5 reductase, NADH‐cytochrome c reductase, and the content of cytochrome b5 were similar in livers of normal and host rats. On the other hand, stearoyl‐CoA desaturation activity was absent in Novikoff hepatoma. The activities of NADH‐cytochrome b5 and NADH‐cytochrome c reductases in the hepatoma microsomes were 4.8% and 2.2%, respectively, of those in normal liver. Furthermore, in hepatoma microsomes, cytochrome b5 was absent. An active stearoyl‐CoA desaturation was reconstituted only on addition of both cytochrome b5 and the terminal desaturase enzyme to the hepatoma microsomes. These results indicated that a complete absence of cytochrome b5 and terminal desaturase is responsible for the lack of stearoyl‐CoA desaturation in Novikoff hepatoma microsomes.
Characterization and composition of sterols in the free and esterified sterol fractions ofAspergillus oryzae
Authors: Fujino Yasuhiko , Ohnishi Masao 
Published: November 2006

AbstractFree and esterified sterol fractions were isolated fromAspergillus oryzae, and their components analyzed mainly by gas chromatography‐mass spectrometry. Cholesterol, brassicasterol, episterol (5α‐ergosta‐7,24[28]‐dien‐3β‐ol), 4α‐methyl‐5α‐ergosta‐8[9],24[28]‐dien‐3β‐ol, lanosterol and 24‐methylene‐24‐dihydrolanosterol were well characterized, whereas 5‐dihydroergosterol, sitosterol and 24[28]‐dehydroergosterol were tentatively characterized. The principal sterol of the free sterol fraction was brassicasterol, and that of the esterified sterol fraction was episterol. Ergosterol, which is reported to be widely distributed in the fungi kingdom, was not detected.
Mitochondrial and microsomal phospholipid phosphorus metabolism during postnatal growth in rat heart and liver
Authors: Hallman Mikko , Kankare Paavo 
Published: November 2006

AbstractThe relative specific activities of phospholipids of hearts and livers of newborn and older rats were measured 2 hr after intraperitoneal32P‐orthophosphate. There was a close linear correlation between the specific activity of cardiolipin and the net increase in the amount of this phospholipid. In one‐day‐old animals, the relative specific activities in the heart and liver were highest and exceeded by 7.3‐ and 3‐fold, respectively, the corresponding activities in the adult. The apparent half‐lives of cardiolipins were calculated on the basis of the linear correlation that was found between the net increase in cardiolipin and the rate of incorporation. These half‐lives were 4.7 days in liver and 6.4 days in heart. Though the changes in the phospholipid composition of the organelles during neonatal development were small, the relative specific activities of the individual phospholipids varied considerably. In addition to cardiolipin, there was a good correlation between the specific activity and the net increase in mitochondrial phosphatidylinositol. At birth, the specific activity of mitochondrial phosphatidylcholine in liver was 2.9 times that in microsomes. During the 12 neonatal hours, the specific activity of microsomal phosphatidylcholine increased 6.3‐fold and exceeded the corresponding mitochondrial activity. The relation between the activation of microsomal phosphatidylcholine synthesis and the induction of serum lecithin synthesis in newborn liver is discussed. The finding that at birth the specific activity of mitochondrial phosphatidylcholine unexpectedly was higher than that of microsomal phosphatidylcholine points out the difficulties in interpreting the in vivo evidence for precursor‐product relationship.
In vitro and in vivo effects of exogenous lipids on the enzymatic hydrolysis of rat bile phospholipids
Authors: Reisser D. , Boucrot P. 
Published: November 2006

AbstractThe addition of total phospholipids, phosphatidylcholines, triglycerides, cholesterol or glycerol to incubation media containing rat pancreatic juice and bile labeled with [9,103H2] oleic acid (90% of the radioactivity present as phospholipids) had no effect on the hydrolysis of bile endogenous phospholipids. The introduction of 2 or 10 mg of phosphatidylcholines and 0.5 ml of bile (≈ 1.5 mg of phospholipids)into the rat upper duodenum decreased the rate of absorption of rative bile phospholipids. It was not followed by an increase of free fatty acids released from biliary phospholipids in the intestinal lumen. The introduction of bile (0.5 ml) and small amounts of triolein (1.4–3.5 mg) into the duodenum had little effect on the rate of hydrolysis and absorption of native bile phospholipids, but caused a reduced absorption of the free fatty acids released or those coming from initial nonphosphorus biliary lipids. The introduction of bile (0.5 ml) and large amounts of triolein (30 mg) into the duodenum increased the rates of hydrolysis and absorption of endogenous bile phospholipids. These observations suggest that luminal lipid components can modify the organization of luminal micelles and, consequently, the action of the pancreatic phospholipase A2 and the absorption of bile lipids.
Effect of serum lipoproteins of bile obstructed rats on 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase activity in perfused rat liver
Authors: Barak A. J. , Sorrell M. F. , Tuma D. J. 
Published: November 2006

AbstractTotal lipoproteins as well as fractionated VLDL+LDL and HDL from fasted control rats and bileligated rats were tested in liver perfusion for their effect on 3‐hydroxy‐3‐methylglutaryl CoA reductase to increase 3‐hydroxy‐3‐methylglutaryl CoA reductase activity than that of the control total lipoproteins. When the fractionated lipoproteins were tested from fasted control rats, it was found that the major stimulating activity was in the HDL fraction with minor activity in the VLDL+LDL fraction. When these plasma components isolated from fasted bile‐ligated rats were tested, it was found that the major activity had shifted to the VLDL+LDL fraction with the HDL having only a minor stimulatory role. The possible mechanism of action of the abnormal lipoproteins associated with bile obstruction in regulating 3‐hydroxy‐3‐methylglutaryl CoA reductase activity is discussed.
Isomerization of the double bonds of a conjugated fatty acid during β‐oxidation
Authors: Du Plessis L. M. , Grobbelaar N. 
Published: November 2006

AbstractThe β‐oxidation of an unsaturated fatty acid containing conjugated double bonds at odd‐numbered carbon atoms has not previously been studied. It is, therefore, not clear whether, during the β‐oxidation of such an acid, the double bonds will be isomerized by enoyl‐CoA isomerase (Δ3‐Δ2‐enoyl‐CoA isomerase) with the loss or retention of its conjugated nature. To investigate the problem, (E,E)‐3,5‐octadienoyl‐CoA was synthesized for use as a model substrate, and enoyl‐CoA isomerase was partially purified from bovine liver. The isomerization was followed by spectrophotometric and gas liquid chromatographic methods, and the results suggested that the isomerization of the model substrate proceeded with retention of a conjugated double bond system. It is, therefore, proposed that the β‐oxidation intermediate of α‐eleostearic acid (Δ9,11,13 fatty acid) will also isomerize with retention of the conjugated double bond system.
Extraction and analysis of lipids from immature soybeans
Authors: Phillips F. C. , Privett O. S. 
Published: November 2006

AbstractA procedure is described for the extraction of lipids from immature soybeans that eliminates artifact formation and provides complete recovery of the lipid, including highly polar glycolipids free of nonlipid substances. The method involves pretreatment and extraction of the beans with hot dilute (0.25%) acetic acid, followed by chloroform‐methanol extraction. Pretreatment and extraction of the tissue with hot dilute acetic acid destroys hydrolytic enzymes and removes organic‐soluble, nonlipid substances that contaminate extracts obtained by chloroform‐methanol extraction. Application of the method to immature soybeans confirmed that phosphatidic acid was largely an artifact of freezing and thawing of the beans, and phosphatidylmethanol was produced via transphosphatidylation of phosphatidylcholine and phosphatidylethanolamine upon extraction with chloroform‐methanol.
Fatty alcohols in capelin, herring and mackerel oils and muscle lipids: II. A comparison of fatty acids from wax esters with those of triglycerides
Authors: Ratnayake W. N. , Ackman R. G. 
Published: November 2006

AbstractThe fatty acids recovered from the triglycerides and wax esters of common northwest Atlantic copepods are compared with the fatty acids of wax esters recovered intact from certain fish skin and body lipid, and from commercial fish oils. The fish species, herring, capelin and mackerel, all feed on copepods, and many resemblances of the copepod lipid fatty acids to those of a previous analysis of similar copepods suggest that the basic dietary fat input for these fish may be quite constant. The two copepod fatty acid analyses differed quantitatively in triglyceride 20∶1 and 22∶1 and also in 20∶5ω3 and 22∶6ω3, confirming the primary role of the wax esters in copepods. Selectivity factors are discussed in comparing the copepod wax ester fatty acids with the fatty acids of the wax esters recovered intact from the fish lipids and oils. The basic role of copepods in supplying all types of fatty acids to fish depot fats is considered to be strongly supported by these findings.
Effects of an essential fatty acid deficiency on serum lipoproteins in the rat
Authors: Sano M. , Privett O. S. 
Published: November 2006

AbstractStudies are reported on the effect of an essential fatty acid (EFA) deficiency in male Sprague‐Dawley rats and its exacerbation by inclusion oftrans fatty acids in the diet on the level and composition of serum lipoproteins. Weanling male Sprague‐Dawley rats were fed diets containing all essential nutritients and a 5% fat supplement of safflower oil (SAFF) or hydrogenated coconut oil (HCO) in 2 experiments, one for 31 wk and the other for 17 wk. For the final 3 wk of each experiment, animals were switched from each group to a 5% supplement of a concentrate of ethyl linolelaidate (TRANS). In addition, a group of animals fed the HCO diet in the first experiment were also switched to the SAFF Diet. With the development of an EFA deficiency in the HCO group, there was a decrease in the high density lipoprotein (HDL) and an increase in the very low density plus the low density (VL‐LDL) lipoprotein fractions separated by heparin‐manganese precipitation. Switching animals of the HCO group to the TRANS supplement exaggerated this effect and produced a very low ratio of HDL‐to‐VL‐LDL. Analysis of the serum lipoproteins by polyacrylamide disc gel electrophoresis showed that an EFA deficiency produced a marked alternation of the HDL fraction. Changes also appeared to be produced in the VL‐LDL fraction by an EFA deficiency and particularly upon switching EFA‐deficient animals to the TRANS supplemented diet. Switching animals of the SAFF group to the TRANS supplement brough about an immediate reduction in HDL with a corresponding decrease in serum arachidonic acid. The data suggested a general relationship between arachidonic acid and the level and composition of HDL on the one hand, and 18∶1 and VL‐LDL on the other. Accordingly, the ratio of HDL‐to‐VL‐LDL appears to provide a sensitive biochemical index of the EFA status of the rat.
Analysis of oleate, linoleate and linolenate hydroperoxides in oxidized ester mixtures
Authors: Fatemi Seyed H. , Hammond Earl G. 
Published: November 2006

AbstractThe hydroperoxides in oxidized mixtures of methyl oleate, linoleate and linolenate were analyzed by reducing the hydroperoxides to the corresponding hydroxyesters and separating the hydroxyesters from the unoxidized esters by thin layer chromatography (TLC). The hydroxyesters from linolenate were separated from the other hydroxyesters by TLC on silver ion plates. The hydroxyesters were converted to TMS‐hydroxy derivatives. The TMS‐hydroxyoleate and TMS‐hydroxylinoleate were separated by gas chromatography (GC), and all the TMS‐derivatives were quantified by GC. The relative rates of oxidation of methyl oleate, linoleate and linolenate in mixtures were ca. 1∶10.3∶21.6. The hydroperoxides formed in the oxidation of soybean and olive oils were similar before and after randomization and similar to corresponding methyl ester mixtures.
A structural model for the cholesterol‐phosphatidylcholine complexes in bilayer membranes
Authors: Huang Ching‐Hsien 
Published: November 2006

AbstractBased on the structural properties of phospholipid and cholesterol molecules, and making use of the known structural and motional effects of cholesterol and its analogs on phospholipid bilayers, a model for the cholesterol‐phosphatidylcholine complex is proposed. In this model, the 3β‐hydroxyl group of cholesterol is assumed to engage in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids. Some specific configurations of the saturated and unsaturated fatty acyl chains of the phospholipid are suggested to participate in van der Waals attractive interactions with the α and β surface of the steroid nucleus.
Alkyl‐and alkenylresorcinols inRapanea laetevirens seed lipids
Authors: Madrigal R. V. , Spencer G. F. , Plattner R. D. , Smith C. R. 
Published: November 2006

AbstractThe seed lipids ofRapanea laetevirens (Myrsinacea) were found to contain a series of 5‐alkylresorcinols. Some of these alkylresorcinols have been reported previously in other plant families, but never before in the Myrsinaceae. The various homologs were shown by mass spectrometry to have alkyl side chains that included C11 and C13 saturated as well as C11, C13, and C15 monoenoic substituents. This is the first report of the natural occurrence of tridecenylresorcinol, the homolog with the C13 monoenoic side chain. The positions of the double bonds in the side chains were determined by mass spectrometry of their methoxy trimethylsilyloxy derivatives. Also found were embelin and rapanone, benzoquinone pigments which occur commonly in the Myrsinaceae. The fatty acid composition ofRapanea seed triglycerides was not unusual, consisting mainly of 16∶0 (27%), 18∶1 (22%), and 18∶2 (44%).
The effect of protein deficiency on some rat liver lipid metabolic enzymes and CoA
Authors: Gerson T. , Wong M. N. 
Published: November 2006

AbstractTwo groups of male Wistar rats were fed normal (i.e., 18%) and protein‐free diets, respectively, for 7 weeks. In vivo incorporation of [1‐14C] acetate into palmitic, stearic, oleic, and arachidonic acids by the liver was reduced in the protein‐deficient rats. In vitro incubation of liver microsomes with labeled palmitate or linoleate revealed no change in the specific activities of chain elongating or desaturating enzymes. Protein deficiency resulted in a decrease in specific activity of short chain acyl‐CoA synthetase and in total CoA, accompanied by the virtual disappearance of acyl‐CoA and an increase in free CoA. Furthermore, there was less microsomal fatty acid synthetase and mitochondrial β‐hydroxybutyrate dehydrogenase activity. These results are discussed in relation to fatty acid synthesis and the changes in liver fatty acid composition.
Characterization of a prostaglandin‐like metabolite of linolenic acid produced by a flaxseed extract
Authors: Zimmerman D. C. , Feng Paul 
Published: November 2006

AbstractOne of the products formed upon incubation of linolenic acid (cis9,12,15‐octadecatrienoic acid) with an extract of flaxseed acetone powder has been characterized as 8‐[2‐(cis‐pent‐2′‐enyl)‐3‐oxo‐cis‐cyclopent‐4‐enyl]octanoic acid. The cyclopentenone ring structure of this acid is analogous to that of the A‐type prostaglandins produced in mammalian systems.
Biosynthesis of hydrocarbons in insects: Decarboxylation of long chain acids ton‐alkanes inPeriplaneta
Authors: Major Michael A. , Blomquist Gary J. 
Published: November 2006

AbstractThe biosynthetic pathway ofn‐alkanes was investigated in the cockroachesPeriplaneta americana andPeriplaneta fuliginosa. Both sodium [1‐14C] acetate and randomly tritiated long chain fatty acids were incorporated into the cuticular hydrocarbons of both species. The relative incorporation of acetate into each component of the hydrocarbon fraction was about the same as the relative amount of each component in the fraction. In contrast, [R‐3H] hexacosanoic acid was preferentially incorporated inton‐pentacosane inP. americana and [R‐3H] tetracosanoic acid inton‐tricosane inP. fuliginosa. Long chain ketones and secondary alcohols, likely intermediates in the proposed condensation‐reduction pathway forn‐alkane biosynthesis, were not incorporated into hydrocarbon. Results from experiments with dual labeled lauric aicd were also not consistent with the condensation‐reduction pathway. The demonstration of the direct decarboxylation of long chain fatty acids ton‐alkanes one carbon unit shorter and the lack of incorporation of proposed intermediates of a condensation‐reduction pathway constitute the strongest evidence to date that insects utilize an elongation‐decarboxylation pathway forn‐alkane biosynthesis.
Sterol‐polyene antibiotic complexation: Probe of membrane structure
Authors: Bittman Robert 
Published: November 2006

AbstractPolyene antibiotics are useful tools for studying the role of sterols in biological membranes. The interaction of polyene antibiotics with membrane‐bound sterols in artificial membrane systems, prokaryotic and eukaryotic cells, and lipid‐containing viruses is reviewed. The pentaene macrolide, filipin, is shown to serve as a probe of phosphatidylcholine‐sterol interaction and of the localization of cholesterol in the membrane of mycoplasmas.
Sex hormones of the aquatic fungusAchlya
Authors: McMorris Trevor C. 
Published: November 2006

AbstractFungi in the order Saprolegniales are known to contain varying proportions of sterols, such as cholesterol and fucosterol. In the caseAchyla, it has been found that fucosterol, the major sterol component, serves as the biosynthetic precursor of the hormones, antheriodiol and the oogoniols. Antheridiol is secreted by female strains ofAchlya and induces the formation of antheridial hyphae in male strains. It also causes the male to secrete the oogoniols which induce the formation of oogonial initials in female strains. Antheriodiol is responsible for the chemotropic growth of the antheridial hyphae to a developing oogonium which results in sexual conjugation. The structures, biosynthesis, and functions of these hormones are discussed in this paper.
Sterols in yeast subcellular fractions
Authors: Parks L. W. , McLean‐Bowen C. , Taylor F. R. , Hough S. 
Published: November 2006

AbstractYeast is the most primitive organism synthesizing substantial amounts of sterols. Because of this eucaryotic organism's versatility in growth conditions, ease of culture, well‐defined genetic mechanism, and characteristic subcellar architecture, it is readily applied to studies of the role of sterols in the general economy of the cell. Sterols exist in two major form, as the free sterol, or esterified with long chain fatty acids. The importance of sterols for this organism can be demonstrated using a naturally occurring antimycotic azasterol. This agent inhibits yeast growth. Three effects are seen on sterol synthesis: inhibition of the enzymes Δ14‐reductase, sterol methyltransferase, and methylene reductase. Cells cultured on respiratory substrates are more sensitive to inhibition than are cells growing on glucose. We have demonstrated a relationship between respiratory competency and sterol biosynthesis in this organism. Many mutants altered in sterol synthesis are respirationally defective and must growth fermentatively. One clone has temperature conditional respiration. Experiments with purified mitochondria, perpared from this mutant and its isogenic wildtype, show that the mutant organism is able to respire at the higher temperature but lacks the ability to couple respiration to phosphorylation. No similar loss is seen in the wild‐type clones. Data are given which support the proposal that, for inclusion in mitochondrial structures, yeast cells may discriminate among sterols available from the total sterol pool in favor of ergosterol.
Insect juvenile hormones and pheromones of isopentenoid biogenesis
Authors: Bowers W. S. 
Published: November 2006

AbstractIn their diversity, speciation, and sheer numerical superiority, few should question that insects are the dominant life‐form on earth. Their utilization of the multifunctional isopentenoids to regulate their life processes is equally diverse. To catalog or even summarize the contribution of isopentenoids in the regulatory chemistry of insect feeding, development, reproduction, diaproduction, diapause, and behavior is beyond the scope of this review. However, a topical treatment of the chemistry of insect juvenile hormones and pheromones provides an insight into the dependence of insects upon isopentenoids.
Insect steroid metabolism
Authors: Svoboda J. A. , Thompson M. J. , Robbins W. E. , Kaplanis J. N. 
Published: November 2006

AbstractInsects are unable to biosynthesize the steroid nucleus and generally require an exogenous source of sterols. Two salient areas of insect steroid metabolism are the dealkylation and conversion of dietary C28 and C29 plant sterols to cholesterol and other C27 sterols, and the biosynthesis and metabolism of the steroidal insect molting hormones. Certain azasteroids and nonsteroidal amines block this conversion of 24‐alkyl sterols to cholesterol and/or disrupt molting and development in insects. These inhibitors have served in charting metabolic pathways for steroids in insects and are serving as models in developing selective pesticidal chemicals and chemotherapeutic agents for use against insects and other invertebrate pests and parasites. The mode of action of some of these inhibitors on molting and development has been investigated in vivo and in vitro. Certain of these inhibitors represent a new class of insect hormonal compounds with a novel mode of action—the disruption of molting hormone metabolism. Research on sterol metabolism in insects provides important information on the comparative biochemistry and physiological functions of steroids in living systems.
The effect of elaidic acid incorporation upon the lipid composition of ehrlich ascites tumor cells and of the host's liver
Authors: Awad Atif B. 
Published: November 2006

AbstractThe incorporation of elaidic acid into Ehrlich ascites tumor cells (EATC) upon feeding the host an elaidic acid‐rich diet has been investigated in the present study. The EATC lipids contained only one‐half the concentration of elaidic acid found in the lipids of either the host livers or of livers from normal mice. On the other hand, elaidic acid incorporation into tumor cells was close to that of ascites fluid. This incorporation was mainly into phospholipids; the highest into choline phospholipids and ethanolamine phospholipids. Some changes in the EATC fatty acid composition were noted due to this incorporation. EATC phospholipids had reduced polyunsaturated fatty acids as compared with oleic acid‐grown cells. The same was true with respect to ascites fluid phospholipids, but neutral lipids were not altered. Tumor development was accompanied by an increase in elaidic acid of the host's liver. Elaidic acid incorporation into tumor cells resulted in a reduction in the amount of all major lipids in the tumor. In contrast, elaidic acid had no effect on lipid composition of livers from normal mice and‐tumor bearing mice, and also had no effect upon the lipids of the ascites fluid that bathes the tumor cells. The incorporation of elaidic acid into the lipids of EATC, normal liver and host liver did not affect the relative composition of phospholipids in these tissues. The development of the tumor did result in decreases in triacylglycerols and esterified cholesterol, and increases in phospholipids and free cholesterol in the livers of host animals.