Waxes and lipids associated with the external waxy structures of nymphs and pupae of the giant whitefly, Aleurodicus dugesii

The nymphs and pupae of the giant whitefly, Aleurodicus dugesii, produce large quantities of external lipids, both as waxy particles and as waxy filaments. The nymphs and pupae extrude filaments from two dorsal rows of five pores each. Filaments can attain lengths of 5-8 cm. The external lipids of nymphs and pupae consist largely of long-chain aldehydes, alcohols, acetate esters and wax esters. Hydrocarbons are minor components. Soon after hatching, the nymph produced an unidentified waxy fringe extruded laterally from its margin. After molting to the second instar, long, hollow, waxy filaments were produced by the immature stages. The major lipid class associated with the filaments was saturated wax esters (89%), mainly C44, C46 and C60. Associated with formation of the filaments were waxy particles in the shape of curls, which peeled off of the extruding filaments. Similar but more tubular-shaped curls were also produced by numerous lateral pores so that, eventually, the curls completely camouflaged the nymph. The major lipid class of the curls was wax esters (50%), mainly C44 and C46. The cuticular surface lipids of the nymphs were mainly long-chain aldehydes (43%) and wax esters (27%). Unsaturated fatty acid moieties constituted 2 and 19% of the wax esters of curls and nymph cuticular surface lipids, respectively. The major lipid classes of pupae and of their palisade were long-chain aldehydes and alcohols. No unsaturated wax esters were detected in the filaments, but 30% of pupal and 21% of palisade surface wax esters were unsaturated in their fatty acid moieties, 16:1, 18:1 and 20:1.     

Infrared spectroscopic study of stratum corneum model membranes prepared from human ceramides, cholesterol, and fatty acids

The outermost layer of the skin, the stratum corneum, consists of corneocytes surrounded by lipid domains. The main lipid classes in stratum corneum are cholesterol, ceramides (CER), and free fatty acids forming two crystalline lamellar phases. However, only limited information is available on whether the various lipid classes participate in the same crystalline lattices or if separate domains are formed within the lipid lamellae. In this article infrared spectroscopic studies are reported of hydrated mixtures prepared from cholesterol, human CER, and free fatty acids. Evaluation of the methylene stretching vibrations revealed a conformational disordering starting at approximately 60 degrees C for all mixtures. Examination of the rotational ordering (scissoring and rocking vibrations) of mixtures prepared from equimolar cholesterol and CER with a variation in the level of free fatty acids showed that at lower free fatty acid content orthorhombic and hexagonal domains coexist in the lipid lamellae. Increasing the fatty acid level to an equimolar cholesterol/CER/fatty acid mixture reveals the dominant presence of an orthorhombic lattice, confirming x-ray diffraction studies. Replacing the protonated free fatty acid chains by their perdeuterated counterparts demonstrates that free fatty acids and CER participate in the same orthorhombic lattice up to a level of slightly less than 1:1:0.75 cholesterol/CER/free fatty acids molar ratio but that free fatty acids also form separate domains within the lipid lamellae at equimolar ratios at room temperature. However, no evidence for this has been observed at 32 degrees C. Extrapolating these findings to the situation in stratum corneum led us conclude that in stratum corneum, fatty acids and CER participate in the orthorhombic lattice at 32 degrees C, the skin temperature.     

Mechanisms of inhibition of triacylglycerol hydrolysis by human gastric lipase

In the human stomach, gastric lipase hydrolyzes only 10 to 30% of ingested triacylglycerols because of an inhibition process induced by the long chain free fatty acids generated, which are mostly protonated at gastric pH. The aim of this work was to elucidate the mechanisms by which free fatty acids inhibit further hydrolysis. In vitro experiments examined gastric lipolysis of differently sized phospholipid-triolein emulsions by human gastric juice or purified human gastric lipase, under close to physiological conditions. The lipolysis process was further investigated by scanning electron microscopy, and gastric lipase and free fatty acid movement during lipolysis were followed by fluorescence microscopy. The results demonstrate that: 1) free fatty acids generated during lipolysis partition between the surface and core of lipid droplets with a molar phase distribution coefficient of 7.4 at pH 5.40; 2) the long chain free fatty acids have an inhibitory effect only when generated during lipolysis; 3) inhibition of gastric lipolysis can be delayed by the use of lipid emulsions composed of small-size lipid droplets; 4) the release of free fatty acids during lipolysis induces a marked increase in droplet surface area, leading to the formation of novel particles at the lipid droplet surface; and 5) the gastric lipase is trapped in these free fatty acid-rich particles during their formation. In conclusion, we propose a model in which the sequential physicochemical events occurring during gastric lipolysis lead to the inhibition of further triacylglycerol lipolysis.     

Visualization of pores (export sites) correlated with cellulose production in the envelope of the gram-negative bacterium Acetobacter xylinum

The Gram-negative bacterium Acetobacter xylinum assembles a cellulse ribbon composed of a number of microfibrils in the longitudinal axis of its envelope. The zone of ribbon assembly was investigated by freeze-etch electron microscopy. Freeze-etching revealed, beneath the cellulose ribbons, a linear array of pores on the lipopolysaccharide membrane. These pores have a rim diameter of 120--150 A and a central hole or deepening of approximately 35 A. The axes of pore arrays closely coincide with linear arrays of 100 A particles on the E- and P-faces of the fractured lipopolysaccharide membranes. Pores and particles in the lipopolysaccharide membrane are probably congruent. The pores are hypothesized to be the export sites (penetration sites) for cellulose.     

Comparison of the antilipolytic effect of metoprolol,acebutolol, and propranolol in man.

Metoprolol and acebutolol, two supposedly cardioselective beta-adrenoceptor antagonists, were tested in 11 healthy men against propranolol, a non-selective drug, for their effect on plasma free fatty acid concentrations before and after insulin. The fasting concentrations of free fatty acid were significantly reduced after acebutolol and propranolol, and their return to normal after insulin was delayed. Metoprolol had no significant effect on free fatty acid levels either before or after insulin. Although both selective and non-selective beta-blocking drugs should be expected to delay the return of free fatty acid values to normal after insulin, in contrast to propranolol and acebutolol, metoprolol had no such effect. This suggests that metoprolol may not be as effective as the other two drugs in controlling lipid metabolism during long-term treatment with beta-adrenoceptor antagonists.     

Effects of short chain fatty acid producing bacteria on epigenetic regulation of FFAR3 in type 2 diabetes and obesity

The human gut microbiota and microbial influences on lipid and glucose metabolism, satiety, and chronic low-grade inflammation are known to be involved in metabolic syndrome. Fermentation end products, especially short chain fatty acids, are believed to engage the epigenetic regulation of inflammatory reactions via FFARs (free fatty acid receptor) and other short chain fatty acid receptors.     

The transfer of fatty acids across the sheep placenta

Maternal and fetal plasma concentrations of free fatty acids, triacylglycerols and phospholipids and the profile of their fatty acids were measured in three catheterized and unanaesthetized sheep. Fetal concentrations of all three lipid fractions were low and did not correlate with maternal concentrations. There were no measurable umbilical venous-arterial differences. Linoleic acid concentrations were low in both mother and fetus. The fatty acid composition of fetal adipose tissue, liver, lung and cerebellum of five animals was analysed. Again linoleic acid levels were very low, but phospholipids contained 2-8% arachidonic acid. [14C] linoleic acid and [3H] palmitic acid were infused intravenously into three ewes. Only trace amounts of labelled fatty acids were found in fetal plasma and these were confined to the free fatty acids. 14C-label was incorporated into fetal tissue lipids, but most of this probably was due to fetal lipid synthesis from [14C] acetate or other water-soluble products of maternal [14C] linoleic acid catabolism. It is concluded that only trace amounts of fatty acids cross the sheep placenta. They are derived mainly from the maternal plasma free fatty acids and might just be sufficient to be the source of the small amounts of essential fatty acids found in the lamb fetus, but are insignificant in terms of energy supply or lipid storage.     

Isolation and characterization of lipid in phloem sap of canola

Phloem isolated from canola (Brassica napus L.) stems was found to contain phospholipid, diacylglycerol, triacylglycerol, steryl and wax esters, and comparatively high concentrations of unesterified fatty acids. Indeed, the composition of phloem lipid was markedly different from that of microsomal membranes and cytosol isolated from both leaves and stems. Specifically, phloem lipid consisted predominantly of unesterified fatty acids and was enriched in medium-chain fatty acids, in particular, lauric, myristic and pentadecanoic acids. This unique composition also distinguished phloem lipid from that of well-characterized cytosolic lipid particles such as oil bodies found in plant cells. Moreover, levels of medium-chain fatty acids in the phloem increased when canola plants were stressed by exposure to sublethal doses of ultraviolet irradiation. Phloem levels of lauric acid, for example, increased by 11-fold upon treatment with sublethal ultraviolet irradiation. Spherical lipid particles were discernible in isolated phloem sap by electron microscopy, suggesting that the lipid in phloem is in the form of lipid particles. The presence of lipid in phloem may be reflective of long-distance lipid transport in plants, primarily in the form of free fatty acids.     

角蜡蚧和日本龟蜡蚧蜡泌物的超微结构及化学成分分析

采用扫描电镜和气相色谱/质谱联用技术研究了角蜡Ceroplastes ceriferus (Fabricius) 和日本龟蜡蚧C. japonicus Green蜡泌物的超微结构及化学成分。结果表明,这2种蜡蚧分泌蜡质和形成蜡壳的过程基本相似。在1、2龄期分泌的蜡质为“干蜡”,蜡壳为星芒状,虫体周缘的蜡芒均为2大节,与其2个龄期发育相对应,每一个大节又分为若干小节。同时,虫体背面中央蜡质堆积成帽状,也分为均匀的多层。由此说明泌蜡过程具有节律性。虫体周缘与蜡芒对应的突起区上分布着密集的刻点状腺孔,每一个腺孔分泌1根蜡丝,这在以往玻片标本中是观察不到的。雌性第3龄幼虫和成虫期,虫体分泌“湿蜡”,形成龟背状蜡壳,泌蜡腺孔主要为三格腺和四格腺。在肛突区发现了密集的泌蜡腺孔,排列为纵条纹状。从角蜡蚧蜡泌物甲酯化处理样品中检测到14个组分,从直接测试 (未经甲酯化处理) 样品中检测到14个组分;而从日本龟蜡蚧则分别检测到10个组分和25个组分。它们的主要成分是一系列高级的长链饱和与不饱和的烃、脂肪酸、脂肪醇、酯类、醛类以及杂环、多环或大环状化合物。对它们可能的生物生态学功能进行了讨论。     

Lipids of Daucus carota cell suspension cultures

In carrot cell suspension cultures greater amounts of phospholipid were detected than in carrot root material, but the major phospholipid classes were the same in both materials, and their fatty acid composition was very similar. In contrast to the cultured cells, no significant amounts of free fatty acids and monoglycerides, as well as diglycerides, could be detected in the carrot root. The fatty acid composition of the major lipid classes from cell cultures is reported for the first time in this report. The degree of unsaturation was higher in triglycerides and phospholipids than in free fatty acids. In a study of phospholipid biosynthesis, [³H]-glycerol was shown to be incorporated into 4-phospholipids (PE, PC, PG, PS⁷) to different extents. The highest specific activity was observed in PC and PG. Five molecular species were isolated from each of the 4 phospholipids and analyzed by GC-MS and LSC.     

Isolation of nonsedimentable lipid-protein particles from insect intestine

Nonsedimentable lipid-protein particles have been isolated from intestinal tissue of the American cockroach, Periplaneta americana. Most of the particles were within the range 30–50 nm in diameter and appear to originate from larger structures. Lipid analysis of the particles showed them to be enriched in neutral lipid components relative to microsomal membranes. Specifically, there is a decline in the amounts of phosphatidylcholine and phosphatidylethanolamine in the nonsedimentable particles compared with the microsomal membranes. Also, in contrast to microsomal membranes, the particles have a higher content of phosphatidic acid along with 1,2- and 1,3-diacyglycerols, free fatty acids and an unidentified lipid that co-migrates with sterol ester, wax ester and hydrocarbon standards in thin layer chromatograms. The cytosol, separated from the particles by ultrafiltration, contained phosphatidic acid, free fatty acids and the unidentified lipid. By contrast, the composition of neutral lipids in the cytosol resembles that of the particles. SDS—PAGE analysis of microsomal membranes, the particles and particle free cytosol shows an enrichment of low molecular weight proteins in the particles and cytosol. The particles and cytosol appear to possess proteolytic activity that is distinguishable from that of corresponding microsomal membranes since the incubation of these components with BSA resulted in the formation of distinct polypeptides. Many characteristics of these particles resemble those of the deteriosomes that have been isolated from plant tissue. © 1995 Wiley-Liss, Inc.     

On remembrance of the abdominal pores in rainbow trout, Salmo gairdneri Richardson, and some other salmonid spp.

Direct connections (abdominal pores) between the peritoneal cavity and the external environment of elasmobranch fishes and some teleost species including the Salmonidae were recognized almost 100 years ago but over this period their existence in these teleost species has been omitted from anatomical texts. In this report, the abdominal pores of rainbow trout, Salmo gairdneri , Atlantic salmon, Salmo salar , and the cisco, Coregonus artedii , were examined in relationship to ip injected particulate material. Both carbon particles and suspensions of the bacterial kidney disease organism were found to be extruded within masses of macrophages and as free particles through the abdominal pores in fish injected ip 72 h previously. The pores were patent in male and female, mature and immature fish. The role and significance of the abdominal pores in rainbow trout in the clearance from the body of material, including material likely to be used for vaccinating fish, is discussed.     

Specific secretion of wax by the follicular cells of Drosophila melanogaster

The follicle cells of Drosophila melanogaster eggs secrete a waxy (hydrophobic) material in the form of lipid vesicles in a special way of secretion. The lipid vesicles maintain their shape after their exit from the epithelial cells, and the accumulation of that material on the extracellular region takes the form of wax plaques creating a hydrophobic layer sealing the oocyte.     

17beta-estradiol affects in vivo the low density lipoprotein composition, particle size, and oxidizability.

The aim of this study was to explore the possible modifications induced by 17beta-estradiol (E(2)) in vivo on low-density lipoprotein (LDL) lipid composition, particle size, and oxidizability. For this purpose, women were recruited from an in vitro fertilization program, ranging their plasma E(2) levels from less than 12 pg/ml to more than 2000 pg/ml at the end of the treatment. The LDL lipid constituents were analyzed by thin layer chromatography and image analysis, and the LDL diameter was calculated from the lipid data. The results showed that high plasma E(2) levels were associated with smaller LDL particles, with lower amounts of free and esterified cholesterol and an increased relative content of alpha-tocopherol. The hormonal treatment produced a remodelation of the LDL acyl composition, rendering a lipoprotein enriched in saturated fatty acids, with a poorer polyunsaturated fatty acid content. These alterations in the physicochemical properties of LDL paralleled changes in the susceptibility of LDL to in vitro oxidation induced by both Cu(2+) and the peroxyl radical generator, 2,2'-azobis (2-amidinopropane), these changes being mainly reflected in a reduced maximum oxidation rate. The in vivo changes in the physicochemical properties of LDL induced by E(2) could explain some of the antiatherogenic actions of estrogens.     

Lipids of Leaves and Seeds

The lipid components of the chlorophyll lipoproteins isolated from the leaves of Cayratia japonica, Vicia sativa, and Artemisia princeps were separated and identified by column, thin-layer, and paper chromatographies. The lipids were mainly composed of carotenoids, quinones including plastoquinone, sterols and their esters, di- and monoglycerides, free fatty acids, chlorophylls and their degradation products, glycolipids including plant sulfolipids, and phospholipids, in which the glycolipids were predominant. The fatty acid composition was characteristic depending on each separated lipid component. Comparison of the lipid distributions was made between whole leaf and chlorophyll lipoprotein, and also between chlorophyll lipoproteins from young leaves and from full-grown leaves.     

Seasonal variation of neutral lipids in Pinus sylvestris L. sapwood and heartwood

Summary The lipid levels and fatty acid composition of three fractions (free fatty acids, triacylglycerols and sterol/triterpenoid esters) extracted from the sapwood and heartwood of three stems of Pinus sylvestris were determined to investigate both seasonal changes in sapwood and possible metabolic changes related to heartwood formation. Seasonal changes were observed only in the amount of the free fatty acids in the sapwood: the level of free fatty acids was greatest at the beginning and end of the growing season. In the January and March samples the amount of the free fatty acid fraction in the sapwood was very small. The amount of the other fractions remained at the same level throughout the study. Marked seasonal changes in the fatty acid composition occurred only in the free fatty acid fraction of the sapwood: the saturation grade increased during the winter.     

Alteration of the specificity and regulation of fatty acid synthesis of Escherichia coli by expression of a plant medium-chain acyl-acyl carrier protein thioesterase.

The expression of a plant (Umbellularia californica) medium-chain acyl-acyl carrier protein (ACP) thioesterase (BTE) cDNA in Escherichia coli results in a very high level of extractable medium-chain-specific hydrolytic activity but causes only a minor accumulation of medium-chain fatty acids. BTE's full impact on the bacterial fatty acid synthase is apparent only after expression in a strain deficient in fatty acid degradation, in which BTE increases the total fatty acid output of the bacterial cultures fourfold. Laurate (12:0), normally a minor fatty acid component of E. coli, becomes predominant, is secreted into the medium, and can accumulate to a level comparable to the total dry weight of the bacteria. Also, large quantities of 12:1, 14:0, and 14:1 are made. At the end of exponential growth, the pathway of saturated fatty acids is almost 100% diverted by BTE to the production of free medium-chain fatty acids, starving the cells for saturated acyl-ACP substrates for lipid biosynthesis. This results in drastic changes in membrane lipid composition from predominantly 16:0 to 18:1. The continued hydrolysis of medium-chain ACPs by the BTE causes the bacterial fatty acid synthase to produce fatty acids even when membrane production has ceased in stationary phase, which shows that the fatty acid synthesis rate can be uncoupled from phospholipid biosynthesis and suggests that acyl-ACP intermediates might normally act as feedback inhibitors for fatty acid synthase. As the fatty acid synthesis is increasingly diverted to medium chains with the onset of stationary phase, the rate of C12 production increases relative to C14 production. This observation is consistent with activity of the BTE on free acyl-ACP pools, as opposed to its interaction with fatty acid synthase-bound substrates.     

Quantitative aspects of free fatty acid metabolism in the fasted rat

Palmitate-1-(14)C was injected intravenously into unanesthetized, fasted rats. Disappearance of tracer from plasma free fatty acids was studied. A large component of free fatty acid (FFA) recycling was directly demonstrated by reinjection experiments. The latter studies also indicated the existence of an unidentified, rapidly turning over polar lipid in plasma which was synthesized from palmitate-(14)C. The appearance of (14)C in hepatic and extrahepatic triglycerides, in other esters, and in respired CO(2) was also followed. The data were analyzed using a multicompartmental model and a digital computer. Only a small fraction of the triglycerides formed in liver was derived directly from plasma free fatty acids. The major portion of net triglyceride formation appeared to be by way of an intermediate nontriglyceride ester pool which turned over relatively slowly compared to plasma free fatty acids. Initial approximations are as follows ( micromoles of fatty acid per min per 100 g body weight): net free fatty acid mobilization (irreversible disposal) = 2.4; hepatic triglyceride formation directly from plasma free fatty acid = 0.1; total hepatic lipid formation from plasma free fatty acids = 0.5; oxidation of free fatty acids to CO(2) = 0.8; percentage of respired CO(2) from direct oxidation of fatty acids = 12%; extrahepatic triglyceride formation directly from fatty acids = 0.4; total extrahepatic lipid formed directly from fatty acids = 1.2.     

Role of phospholipids in the lipophorin particles of Rhodnius prolixus.

The lipophorin of Rhodnius prolixus metabolically labelled with 32P exclusively in the phospholipid moiety was purified on a potassium bromide gradient and treated with phospholipase A2 in the presence of an excess of fatty acid-free albumin. The treatment completely removed the phospholipids from the particles and generated [32P]-lysophosphatidylcholine, [32P]-lysophosphatidylethanolamine, and free fatty acids that remained bound to albumin. The phospholipid-depleted lipophorin particles remained soluble, indicating that phospholipids are not essential in maintaining the stability of the particles in aqueous solution. Complete removal of phospholipids did not affect the association of apolipophorin III with lipophorin particles. Lipophorin density increased slightly from 1.120 to 1.134 g/ml after treatment. The phospholipid-depleted particles also retained their ability to be recognized and loaded in vitro with phospholipids delivered by the fat body, thus supporting the concept of lipophorin's role as a reusable lipid shuttle for phospholipids.     

The role of pore structures in the selective permeability of antennal sensilla of the desert burrowing cockroach, Arenivaga sp

To obtain information about the chemical composition of pore structures in antennal sensilla, the antennae were exposed to lipid solvents, or they were prepared to show negative-contrast images in electron micrographs. A heavy-metal tracer, lanthanum nitrate, was also used to indicate the permeability of the receptors to water. The grooves of the large grooved peg open into tubular cavities containing electronopaque material, through which stimulatory molecules must pass to reach the sensory dendrites at the center of the sensillum. The material in these cavities was removed by chloroform or acetone, suggesting a lipid composition. Lanthanum penetrated this receptor only after it had been exposed to acetone or chloroform. Strands at pores of the thin-walled pegs were also removed by the lipid solvents, and the water-soluble tracer failed to penetrate these receptors unless they had been previously exposed to chloroform or acetone. The pore structures appear to be hydrophobic, allowing entry of lipid-soluble substances, while preventing passage of water. The differential action of the solvents on the various types of sensilla suggests that receptor discrimination among different classes of chemical stimuli may be partially determined by the chemical properties of structures at the sensillar pores.