James A. Ballantine

LIPIDS AND OXIDISED LIPIDS IN HUMAN ATHEROSCLEROTIC LESIONS AT DIFFERENT STAGES OF DEVELOPMENT

Lipids and oxidised lipids were analysed by GC and GC-MS in human necropsy samples of normal artery and individual atherosclerotic lesions, from aorta and common carotid artery, including fatty streaks, intermediate lesions and advanced lesions. Age-related increases were seen for linoleate, oleate and cholesterol in normal artery, but not in lesions. Each category of lesion was much richer than normal artery in all the lipids measured and in oxidised lipids (oxysterols and hydroxyoctadecadienoic acids), although a degree of overlap existed between the compositions of the various categories of lesion. 26-Hydroxycholesterol and 7 beta-hydroxycholesterol levels were extremely low or undetectable in normal artery, but significantly higher in each of the categories of lesions. The generally wide variation in lipid composition of individual lesions within each category, and the fact that a few individual lesions showed no detectable 26-hydroxycholesterol or 7 beta-hydroxycholesterol, suggested that the lipid oxidation in lesions and therefore perhaps the progression of lesions may be intermittent. Fatty streaks showed the highest concentration of 7 beta-hydroxycholesterol relative to cholesterol, and the lowest ratio of linoleate to oleate, suggesting that this type of lesion experiences the greatest concentration of free radical activity. Levels of the enzymatic product 26-hydroxycholesterol were approximately proportional to cholesterol in all the categories of lesions. 26-Hydroxycholesterol was significantly more abundant in advanced lesions than in intermediate lesions or fatty streaks. 26-Hydroxycholesterol levels were higher in macrophage-rich intermediate and advanced lesions than in their fibrous counterparts. This distinction between macrophage-rich and fibrous lesions was also true for most of the other lipid components, consistent with the involvement of macrophages in lipid accumulation, lipid oxidation and lesion development.

Sterols of the phytoplankton—effects of illumination and growth stage

Abstract The sterol compositions of different species of cultured phytoplankton, (two diatoms— Phaeodactylum tricornutum and Skeletonema costatum , two green algae— Danaliella minuta and Tetraselmis tetrathele and a brown alga— Monochrysis lutheri ) were compared with that of a diatom field population ( > 98 % Thalassionema nitzschioides ) using GC-MS techniques. The effect of culture age in the cultured specimen; was examined by harvesting in both the exponential and stationary growth phases and was found to produce considerable differences in the sterol composition in some species. The influence of the intensity and different spectral illumination on a cultured specimen of a green alga ( Danaliella minuta ) was also examined and found to produce changes in the sterol composition.

lipids and oxidised lipids in human atheroma and normal aorta

Lipids and oxidised lipids were analysed by GC and GC-MS in samples of human atheroma (necrotic gruel from the interior of advanced atherosclerotic plaques in the aorta) and human normal aorta (lesion-free intima plus inner media) from necropsy subjects. Cholest-5-en-3 beta,26-diol and cholest-5-en-3 beta,7 beta-diol were detected in all the atheroma samples examined but not in significant amounts in normal aorta. In atheroma, cholest-5-en-3 beta,26-diol was approximately proportional to cholesterol. Several isomeric hydroxy-octadecadienoic acids were detected in atheroma, and, in smaller amounts, in normal aorta. Many of the components of atheroma showed a high degree of cross-correlation on linear regression analysis, whilst cross-correlations were somewhat weaker for normal aorta. Atheroma showed a vast accumulation of lipid, especially cholesterol, in comparison to normal aorta. The atheroma samples contained a larger proportion of linoleate relative to oleate than the normal aorta. Levels of fatty acids relative to cholesterol were lower for atheroma than for normal aorta. The chemical composition of atheroma appeared unrelated to the age of the subject, whereas age-related increases in linoleate, oleate and cholesterol content were seen in the samples of normal aorta.

Organic reactions catalysed by sheet silicates: ether formation by the intermolecular dehydration of alcohols and by addition of alcohols to alkenes

Abstract Ion-exchanged montmorillonites can be used as heterogeneous catalysts for the dehydration of liquid alcohols in pressure vessels at 200 °C. In contrast to the situation with homogeneous, aqueous acid catalysts, primary alcohols undergo preferential intermolecular dehydration to give good yields of di(alk-1-yl) ethers with these sheet silicate catalysts, whereas secondary and tertiary alcohols undergo the expected facile intramolecular dehydration to the corresponding stable alkenes. With the acid clay catalysts, primary diols give either oligomeric or cyclic ether products by intermolecular dehydration, whereas benzyl alcohol undergoes intermolecular dehydration to produce a polymeric material, poly(phenylene methylene), in the presence of ion-exchanged montmorillonites. Primary alcohols can be induced to add onto highly substituted alkenes to produce mixed primary/tertiary ethers in excellent yields. Less highly substituted alkenes give much lower yields of mixed ethers. In general, these catalysts are more selective than concentrated mineral acids and have the distinct advantage of being much easier to separate from the products.

Oxidation of cholesteryl linoleate by human monocyte-macrophages in vitro

The amount of cholest-5-en-3 beta,7 beta-diol (CD) was significantly higher in cultures of human monocytes incubated with cholesteryl linoleate-bovine serum albumin (CL/BSA) artificial lipoproteins than in no-cell control incubations of CL/BSA. CD production by monocytes was almost completely inhibited by the radical scavengers butylated hydroxytoluene (BHT), probucol, and alpha-tocopherol, and was partially inhibited by the metal chelator EDTA. The production of CD was accompanied by decrease in linoleic acid. CD amounts were negligible in incubations of monocytes with cholesteryl oleate/BSA (CO/BSA) or cholesterol/BSA (C/BSA). Ability to produce CD from CL/BSA appeared to increase with age in culture of human monocyte-macrophages. Considerable variations were observed in the CD production from CL/BSA by monocytes from different blood donations. Higher levels of CD production appeared more common with monocytes from men than from women. The significance of these results in the context of human atherosclerosis is discussed.

Organic reactions catalysed by sheet silicates: ester production by the direct addition of carboxylic acids to alkenes

Abstract The addition of aliphatic acids to a wide Variety of alkenes to form esters is heterogeneously catalysed by ion-exchanged sheet silicates. Cation exchange of the silicate is a prerequisite since natural montmorillonite is a poor catalyst for these reactions. Exchange with almost any multivalent ion induces some degree of catalytic activity but Al 3+ , Cr 3+ and H + ion-exchanged clays proved the most efficient catalysts in the present context. The reactions were carried out in pressure vessels, the reaction temperature range depending on the nature of the alkene employed. Esterification is in competition with alkene oligomerisation, and the synthesis of t-alkyi esters failed at temperatures much above room temperature due to the rapidity of the competing process. All other ester types, however, could be synthesised at temperatures up to 200 °C, and only above this temperature does the competitive process become significant. Initial reaction rates of esterification increase rapidly with temperature although, as would be expected, final equilibrium yields diminish. The number of ester products which may be obtained in a given reaction is determined by the number of stable carbocation intermediates which each alkene can produce. In those reactions where single carbocation intermediates are to be expected, excellent yields of a single ester are often obtained. For example ethyl ethanoate was prepared in 92% yield (based on ethanoic acid) with 96% selectivity, from ethanoic acid and excess ethene using Al 3+ ion-exchanged montmorillonite as the catalyst in a 40 h reaction at 200°C.

Triplet-state energy levels of CO2+2, COS2+ and CS2+2

Abstract Double-charge-transfer spectroscopy has been used to measure the energies of triplet states of CO2+2, COS2+ and CS2+2 up to approximately 15, 13 and 9 eV, respectively, above the ground-state energies. In addition, the double-ionization energies have been calculated using Moller-Plesset perturbation theory with split-valence basis sets and are in excellent agreement with the measured values. The excited triplet state energies correlate well with values calculated in a previous investigation, and an assignment of these states is reported. Other experimental data on these dications have been reviewed and an assignment of these data is also described.

Marine sterols. V. sterols of some tunicata. The occurrence of saturated ring sterols in these filter-feeding organisms

Abstract The sterols present in one oceanic and two coastal tunicates have been determined by combined gas chromatography-mass spectrometry techniques. Very complex sterol profiles were found in a Pyrosoma sp. and Ascidia mentula O. F. Muller, with 25 and 27 sterols, respectively, in which a high proportion of the sterols were identified as saturated ring compounds. The analyses established the presence of related pairs of 5α-stanols and Δ5-sterols with identical sidechains, whereas Δ7-sterols were almost absent in these extracts. A number of the 5α-stanols found are very uncommon in the marine environment and the presence of new C31 and C32 sterols with long sidechains indicated in the Ascidia mentula extracts is notable. Extracts of the coastal species, Ciona intestinalis L., were much simpler and contained only 13 sterols, some of which were saturated ring compounds.

Synthesis, characterization, and catalytic activity of beidellite–montmorillonite layered sillcates and their pillared analogues

A Synthetic beidellite-smectite, characterized by a range of techniques, including high-resolution 27Al ans 29Si solid-state n.m.r. spectroscopy, shows interesting catalytic activity (in secondary amine formation from cyclohexylamine, in ester production from hex-1-ene and acetic acid, and in ether synthesis from pentanol): the selectivities differ significantly from those of montmorillonite-smectites.

Charge inversion of ground-state and metastable-state C2+ cations formed from electroionised C2H2 and C2N2, and a re-evaluation of the carbon dimer's ionisation energy

Abstract Charge-inversion, translational-energy spectrometry has been used to probe the electronic-state compositions of C2+ ion beams formed from electroionised acetylene and cyanogen, and to determine state-specific ionisation energies for C2. It was found that C2+ ions were formed predominantly in the 4Σg− ground state when electrons of about 23 eV energy were used to ionise acetylene. Below this threshold, and down to about 19 eV electron energy, the C2+ ions formed from C2H2 were found to be in the metastable 2Πu state, while above 23 eV the beams were of mixed-state composition. In contrast, ionisation of cyanogen by electrons with energies from about 18 to 100 eV apparently produced beams containing only C2+ (2Πu) ions. From the energy-loss positions of observed spectral peaks, the energies for ionisation of C 2 ( X 1 Σ g + ) into the 4Σg− and 2Σu states were deduced to be 11.4(1) ± 0.30 and 12.3(3) ± 0.30 eV, respectively.