Effects of a high alpha-linolenate and high linoleate diet on hemolysis and lipid peroxidation of rat erythrocytes.

alpha-Linolenic acid (18:3n-3) is known to autoxidize several fold faster than linoleic acid (18:2n-6). Feeding a high alpha-linolenate or a high linoleate diet to rats resulted in significant changes in the n-3/n-6 ratios of 20 and 22 carbon highly unsaturated fatty acids in erythrocytes. However, the rates of hemolysis observed in N2- or O2-atmosphere were similar between the two dietary groups. No significant amounts of conjugated dienes were detected and no measurable changes in the fatty acid compositions were observed during the incubations, indicating that the hemolysis occurred without involving significant lipid peroxidation. When stimulated with a free radical initiator, [2,2'-azobis-(2-amidinopropane)dihydrochloride] (AAPH), hemolysis occurred more rapidly, conjugated dienes formed and unsaturated/saturated ratios of phospholipid fatty acids decreased. However, no statistically significant difference was observed in these parameters of the two dietary groups. These results indicate that hemolysis occurs without involving lipid peroxidation but is accelerated by free radicals through lipid peroxidation, and that the difference in autoxidizabilities of alpha-linolenate and linoleate is not reflected in the rates of hemolysis and autoxidation in rat erythrocytes.     

Effect of dietary alpha-linolenate/linoleate balance on collagen-induced platelet aggregation and serotonin release in rats

Male Sprague-Dawley rats at 3 weeks of age were weaned to a diet supplemented either with perilla seed oil [alpha-linolenic acid (alpha-LnA)/linoleic acid (LA) = 3.66] or with safflower seed oil (alpha-LnA/LA less than 0.01) for 5-6 weeks. The eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio in platelet phospholipids was much higher in the perilla oil group than in the safflower oil group. Platelet aggregability determined turbidometrically varied greatly among individual animals, and the difference in platelet aggregability between the two dietary groups was relatively small when higher concentrations (15 and 20 micrograms/ml) of collagen were used. However, when platelet aggregability was determined as an all-or-none phenomenon at lower concentrations (7.5 and 10 micrograms/ml) of collagen, a very distinct difference was observed between the two dietary groups; aggregability was much lower in the perilla oil group than in the safflower oil group. Collagen-induced serotonin release from platelets was significantly reduced in the perilla oil group as compared with the safflower oil group. These results emphasize the importance of estimating aggregability at threshold concentrations of collagen and confirm that dietary manipulation of the essential fatty acid balance could be useful in reducing the thrombotic tendency.     

Determination of alpha-tocopherol and alpha-tocopherol acetate in diets of experimental animals. Study of stability in the diets.

A simple method is described which permits, avoiding saponification, alpha-tocopherol and alpha-tocopheryl acetate measurement in semi-synthetic diets for experimental animals by HPLC, with both UV and fluorescence detection. Phenyldodecane was chosen as internal standard with remarkable performances, and EDTA and BHT were added to prevent oxidation in aqueous and non-aqueous phases respectively. The mobile phase was methanol-water (94:6 v/v) at a flow-rate of 2 ml/min. Samples were homogenized and extracted twice with n-hexane by probe sonication. Extracts were evaporated to dryness and redissolved with chloroform-methanol (1:1, v/v). Validation parameters were studied between 25 ng and 6 micrograms for alpha-tocopherol and between 3 and 24.2 micrograms for alpha-tocopheryl acetate, which corresponds to the range of values in the existing diets. Results had correlation coefficients > 0.99; recoveries > 85%; R.S.D. < 6%, so the method is adequate to control vitamin E intake in animals as well as vitamin E stability in food during storage.     

Examining the collision-induced decomposition spectra of ammoniated triglycerides. III. The linoleate and arachidonate series

A series of positionally pure triglycerides (TAGs) of the form LXL, YLY, AXA, and YAY was synthesized and analyzed by reversed-phase high-performance liquid chromatography/tandem mass spectrometry. L and A represent the linoleate and arachidate moieties, respectively, and X and Y represent large arrays of fatty acid moieties of various chain lengths, degree of unsaturations, double-bond positions, and cis/trans configurations. The abundances of the collision-induced decomposition (CID) products of ammoniated TAGs were examined as a function of these parameters. The major CID products, the diglyceride (DAG) product ions and the MH(+) ions, are plotted as functions of chain length for the saturated and monounsaturated series of X and Y. The following trends are observed in the data. TAGs with higher degrees of unsaturation tend to show greater relative abundances of MH(+) in the CID spectra of their ammoniated precursor ions. The position of the fatty acid constituents along the glycerol backbone also seems to influence the abundances of the MH(+) ion in the CID spectra of the ammoniated precursor ions. A fatty acid constituent with double bonds along the fatty acid chain positioned close to the carbonyl promotes the formation of the DAG product ion that corresponds to its loss upon CID of the ammoniated precursor ion. Linoleic acid substituents also seem to promote the formation of DAG product ions, but to a lesser extent. Data for the YAY TAGs are used to predict the abundances of the product ions in the CID spectra of ammoniated YAX TAGs. These data are discussed in context of a broader project to develop and validate software algorithims to support a platform for comprehensive analysis of complex mixtures of TAGs.     

Central depressant effects of N3-substituted 6-azauridines in mice.

Central depressant effects in mice of N3-substituted 6-azauridines (6-AzUd) (1) were examined by intracerebroventricular (i.c.v.) injection. Eleven derivatives including alkyl-, benzyl-, xylyl- and phenylethyl-substitution onto the N3-position of 1 were synthesized and their pharmacological effects were evaluated using hypnotic activity, locomotor activity, motor incoordination and pentobarbital-induced sleep prolongation as indices. Six of 12 compounds showed the hypnotic activity. At a dose of 2 mumol/mouse, the mean sleeping time induced by 1, N3-benzyl-6-AzUd (7), N3-o-xylyl-6-AzUd (8), N3-m-xylyl-6-AzUd (9), N3-p-xylyl-6-AzUd (10) and N3-alpha-phenylethyl-6-AzUd (11) was 14, 11, 45, 12, 9 and 16 min, respectively. These derivatives and N3-beta-phenylethyl-6-AzUd (12) (1.5 mumol/mouse) significantly prolonged pentobarbital-induced (40 mg/kg, i.p.) sleeping time, whereas none of the N3-alkylated derivatives (methyl-, ethyl-, n-propyl-, n-butyl- and allyl-substitution) exerted the hypnotic activity or pentobarbital-induced sleep prolongation. Nucleoside 1 and its xylyl-derivatives (1.5 mumol/mouse) significantly decreased locomotor activity of mice, their effects paralleled the hypnotic activity. These compounds (1.5 mumol/mouse) also produced motor incoordination and potentiated the effect of diazepam-induced motor incoordination. These results indicate that 1 and its benzyl-related derivatives, but not alkyl-derivatives have a depressant effect on the central nervous system.     

Steroid Cyclophanes as Artificial Cell-surface Receptors. Molecular Recognition and its Consequence in Signal Transduction Behavior

Steroid cyclophanes, bearing four bile acid moieties covalently placed on a tetraazaparacyclophane skeleton, were designed and synthesized as artificial cell-surface receptors. Guest-binding behavior of the steroid cyclophanes embedded in a bilayer membrane formed with a synthetic peptide lipid was clarified by means of fluorescence and circular dichroism spectroscopy. We found that the steroid cyclophane effectively bound aromatic guests in both bilayer membranes and aqueous solution. In addition, copper(II) ions acted as a guest species for the steroid cyclophane and a competitive inhibitor toward a NADH-dependent lactate dehydrogenase (LDH). On these grounds, we constituted a supramolecular assembly as an artificial signaling system in combination with the steroid cyclophane, a cationic peptide lipid, and LDH. As a consequence, the steroid cyclophane acted as an effective artificial cell-surface receptor being capable of transmitting an external signal to the enzyme in collaboration with copper(II) ions as a signal transmitter.     

Short and long-term effects of Baccharis articulata on glucose homeostasis

In this study, the in vivo effect of the crude extract and n-butanol and aqueous residual fractions of Baccharis articulata (Lam.) Pers. on serum glucose levels, insulin secretion and liver and muscle glycogen content, as well as in vitro action on serum intestinal disaccharidase activity and albumin glycation were investigated. Oral administration of the extract and fractions reduced glycemia in hyperglycemic rats. Additionally, the n-butanol fraction, which has high flavonoids content, stimulated insulin secretion, exhibiting an insulinogenic index similar to that of glipizide. Also, the n-butanol fraction treatment significantly increased glycogen content in both liver and muscle tissue. In vitro incubation with the crude extract and n-butanol and aqueous residual fractions inhibited maltase activity and the formation of advanced glycation end-products (AGEs). Thus, the results demonstrated that B. articulata exhibits a significant antihyperglycemic and insulin-secretagogue role. These effects on the regulation of glucose homeostasis observed for B. articulata indicate potential anti-diabetic properties.     

Stable nitroxyl radicals and hydroxylamines as inhibitors of methyl linoleate oxidation in micelles

Russian Chemical Bulletin - The kinetics of methyl linoleate oxidation in micelles inhibited by nitroxyl radicals and hydroxylamines was studied. The regeneration of nitroxyl radicals in this...     

On the effects of high temperature and high pressure on the hydrogen solubility in rhenium

In situ x-ray diffraction experiments on rhenium hydride compressed up to 46 GPa reveal a hydrogen solubility (x) significantly larger than the previously assumed saturation limit of x ~ 0.38(4). In the layered anti-CdI(2)-type structure of rhenium hydride, the hydrogen solubility was found to increase to x ~ 0.5 at 15 GPa over time. When heated to temperatures above 420 K at pressures above 23 GPa, rhenium hydride undergoes an isomorphous phase transition into the NiAs-type structure accompanied by an increase in hydrogen solubility to x ~ 0.85. The formation of fully stoichiometric rhenium hydride is discussed.     

Glycation of human serum albumin in long-term incubation with low and high concentrations of glucose

Glycated albumin levels of incubation mixtures with high (25.8 mM) and low (8.2 mM) concentrations of glucose when measured by the nitroblue tetrazolium (NBT) reducing method, showed similar values at day 20-25. But when tested by thiobarbituric acid (TBA) colorimetry, the levels with high concentrations of glucose were about twice that with low concentration of glucose.