Verfahren zur Anreicherung von Stearidonsäure

Preparation of Stearidonic Acid Concentrates Fatty acids of the n-3 series are precursors of the biochemical synthesis of prostaglandins which are known as inhibitors of blood platelet aggregation. The parent compound of this series, α-linolenic acid (ALA), is transformed to stearidonic acid C18:4 δ6.9, 12.15 (SA) by catalysis by the liver enzyme δ6-desaturase. SA is found in few natural materials such as fish oils and blackcurrent seed oil (BCO) and only at low concentrations. In this context the oil extracted from entrails of squids caught in warm-water seas is reported to present an interesting source of arachidonic acid with contents of up to 8%. A two-step procedure was developed for the preparation of SA concentrates with 15% SA was obtained by urea fractionation. Simultaneously the γ-linolenic acid (GLA) concentration was increased to 80%. Subsequent separation of SA from GLA was carried out by preparative HPLC yielding SA concentrates with a purity of ≧ 90%. These SA concentrates were used for a comparative investigation of the inhibiting effects of some polyunsaturated fatty acids such as GLA, ALA or eicosapentaenoic acid on blood platelet aggregation. It was found that, compared with the other fatty acids. SA inhibits more specifically the aggregation stimulated by thrombine.     

Sodium Coordination Environments in Silica Films

The local structure centered on sodium after diffusion in silica (Na-SiO₂ samples) has been determined by means of extended X-ray absorption fine structure (EXAFS) studies. The Na-SiO₂ samples are of particular interest because (i) their sodium content can be varied over a wide range of concentration and (ii) their local structure is representative of that of soda–silica glass. EXAFS analyses reveal the existence of a well-defined local structure involving oxygen, sodium, and silicon neighbors. The Na-O, Na-Na, and Na-Si bonds lengths, which amount to 0.23, 0.30, and 0.38 nm, respectively, do not depend on sodium concentration. This environment closely resembles that found in soda–silica glass. Moreover, it is compatible with the "target site" and "the site memory effect" suggested by recent theories of the ionic conductivity in oxide glasses.     

Sex- and site-dependent variations in the thickness and mechanical properties of human skin in vivo

A new method for the in vivo characterization of the physical properties of skin is presented. This comprises an ultrasound device to measure the vertical displacement of the surface of the skin, as well as its thickness and that of the hypodermis under suction. In combination with this, a mathematical model is used to calculate the following skin parameters: Young's modulus, the initial stress and an index of non-elasticity. These parameters were evaluated from the volar forearm and the forehead of 30 male and 30 females, of similar ages (28 +/- 6-years-old). The sensitivity of the testing procedure, allowing the characterization of the mechanical parameters of the skin, easily differentiated these two sites, and in some cases, differences between women and men were demonstrated. The main results showed for both sexes that the thickness (P = 0.0001), Young's modulus (P = 0.0001), and the index of non-elasticity (P = 0.0001) were greater for the forehead than for the ventral forearm, but that the initial stress was lower (P = 0.0001). The results show that the skin is thicker, stiffer and less tense and elastic on the forehead than on the ventral forearm, suggesting structural differences between these two sites (collagen fibre network, elastic fibres, epidermis, stratum corneum, microvascularization, actinic damage, presence of sebaceous glands, etc.). It is hoped that this device will be useful for the evaluation of certain skin disorders (scleroderma, Ehlers-Danlos syndrome, cutis laxa, oedema, etc.) and their therapy, as well as being a useful tool in skin ageing and cosmetic product assessment.     

Covalent modifications of aminophospholipids by 4-hydroxynonenal

Lipid oxidation is implicated in a wide range of pathophysiological disorders, which leads to reactive compounds such as aldehydes. Among them 4-hydroxynonenal (4-HNE) reacts strongly with the NH2 groups of amino acids and forms mainly Michael adducts and minor Schiff-base adducts. Such reactions occur also with compounds containing thiol groups. No data are available describing 4-HNE interactions with amino-phospholipids. To investigate such a possibility, 4-HNE was incubated with either phosphatidylethanolamine (PE) or phosphatidylserine (PS) in an aqueous-organic biphasic system and the resulting products were identified by liquid chromatography-mass spectrometry (LC-MS). Our study points out the potential capacity of 4-HNE to react with phospholipids containing amino groups and particularly PE. The main resulting compounds found were a Michael adduct plus a minor Schiff base adduct, which was partly cyclized as a pyrrole derivative via a loss of water. Its stabilization as a pyrrole derivative allows to differentiate 4-HNE from the other aldehydes generated via lipid oxidation (e.g., malondialdehyde, 2-nonenal) that lack the 4-hydroxyl group. Their formation seems not to be affected when the pH varies from 6.5 to 8.5. Surprisingly, PS reacted poorly producing only a small amount of Michael adduct, the Schiff-base adduct being nondetectable. We conclude that such adducts, if they are formed in cell membranes, could alter the phospholipase-dependent cell signaling.     

Potentiating effect of 5,8,11-eicosatrienoic acid on human platelet aggregation

5,8,11-Eicosatrienoic acid (20∶3ω9), a fatty acid increased in the platelet phospholipids of man and animals fed saturated fats, was either added to human platelets simultaneously with the aggregating agents, or incorporated into the platelet phospholipids by preincubation. 20∶3ω9 markedly increased the response of platelets to all aggregating agents tested when added simultaneously with the agent, but solely to thrombin and ionophore, after incorporation into the platelet phospholipids. The potentiating effects of 20∶3ω9 on thrombin aggregation do not appear to be related to prostaglandin formation, but rather to the production of a monohydroxy derivative through the lipoxygenase pathway.     

Study of Nicalon-based ceramic fibres and powders by EXAFS spectrometry,X-ray diffractometry and some additional methods

The Nicalon SiC-based ceramic fibres and their precursors have been investigated by complementary techniques: EXAFS, WAXS, ESCA and NMR. For SiC-Nicalon fibres, an alternative model is proposed based on a microcrystalline structure where pureβ-SiC is embedded in a continuum of tetrahedral SiC_xO_y(x+y=4). We have found that the inorganic material skeleton is already contained in the carbon and silicon structure of the polymer precursor.     

Conductometric biosensor based on glucose oxidase and beta-galactosidase for specific lactose determination in milk

This paper investigates the development of a biosensor associating two distinct enzymatic activities, that of the beta-galactosidase and that of the glucose oxidase, in order to apply it for the quantitative detection of lactose in milk. To eliminate interferences with glucose, a differential mode of measurement was used. Results show a linear calibration curve for lactose concentration between 60 and 800 μM (0.03 to 0.3 g/L). Tests with real commercial milk samples were carried out to validate the conductometric biosensor.     

Human plasma albumin transports [13C]docosahexaenoic acid in two lipid forms to blood cells

Docosahexaenoic acid (22:6) decreases blood platelet function and is highly concentrated in the brain where its depletion leads to functional impairments. Because the platelets and blood brain barrier capillary endothelium cannot hydrolyze the complex lipids for fatty acid (FA) uptake, nonesterified FA (NEFA) bound to albumin are assumed to be the delivery route of FA to these cells. The supply of 13C-labeled 22:6 to blood cells by plasma albumin was studied in humans after a single ingestion of this FA esterified in a triglyceride (TG). The 22:6 13C/12C ratio, measured by gas chromatography combustion-isotope ratio mass spectrometry was measured in lipid classes from albumin, platelets, leukocytes, and erythrocytes (taken as a tentative index of the brain uptake). Nonesterified [13C]22:6 bound to albumin was rapidly produced after ingestion, as a result of the hydrolysis of very low density lipoprotein (VLDL) plus chylomicron TG. We found that albumin carried another source of 22:6, lyso-phosphatidylcholines (lyso-PC), in which [13C]22:6 accumulated while the nonesterified [13C]22:6 reached its minimal plasma concentrations. Computation of the relative contribution of NEFA and lyso-PC for the [13C]22:6 delivery to platelets and erythrocytes showed that the [13C]22:6 supply to platelets occurred uniquely through NEFA, whereas this pool was weakly involved in the delivery to erythrocytes. In contrast, lyso-PC was uniquely concerned with the 22:6 delivery to erythrocytes and represented the major part of this supply. We conclude that plasma albumin carries 22:6 in two lipid forms that are involved differently in the delivery of this FA to target cells.     

Enhancement of eicosaenoic acid lipoxygenation in human platelets by 12-hydroperoxy derivative of arachidonic acid

Human platelet lipoxygenase activity toward several eicosaenoic acids was measured in intact cells as well as in subcellular fractions (cytosol and membranes). In whole platelets, the lipoxygenation of eicosaenoic acids was enhanced greatly by high concentrations of aspirin, which partially inhibit the peroxidase activity associated with the pathway. The lipoxygenation also was increased by arachidonic acid (AA) or its lipoxygenase product, 12-hydroxyperoxy-eicosatetraenoic acid (12-HPETE). Similarly, prostanoid precursors, dihomogammalinolenic (DHLA) and eicosapentaenoic (EPA) acids also were better converted by cyclooxygenase in the presence of AA or 12-HPETE. Among the eicosaenoic acids tested, EPA oxygenation was affected most. Using cytosol or membranes as the lipoxygenase source instead of whole cells led to completely different results. AA exerted a competitive inhibition upon the other eicosaenoic acid oxygenation except that of EPA, for which a dual effect of AA was observed. This makes questionable the use of platelet subfractions for investigating lipoxygenase activity. We conclude that platelet lipoxygenation of eicosaenoic acids appears peroxide-dependent, especially for apparent poor substrates like EPA. This might be relevant in respect to 12-HPETE, which is the main hydroperoxy derivative to be produced during platelet activation.