Cholesteryl ester-rich inclusions from human aortic fatty streak and fibrous plaque lesions of atherosclerosis. I. Crystalline properties, size and internal structure

Cholesteryl esters, the major lipid in the lesions of human atherosclerosis, occurred in fatty streaks and fibrous plaques from 42 adults as spherical inclusions whose diameters averaged 1.99 +/- 0.48 and 2.16 +/- 0.62 mu, respectively, and which with polarizing light microscopy resolved into a mixture of various proportions of anisotropic and isotropic forms. Anisotropic forms had diameters of 1.9 +/- 0.4 mu, uniaxial-like symmetry with a formée cross image, a whitish gray interference color under cross polarizer and analyzer, second order blue and first order yellow interference colors with a tint plate, a birefringence of 0.0412 +/- 0.0054 and a refractive index of 1.559 +/- 0.0014. Their probable structural organization is primarily a lyotropic smectic mesophase (liquid crystal) of cholesteryl esters secondarily organized into multiple concentric lamellae. Isotropic forms had diameters of 2.3 +/- 0.6 mu and were optically inactive irrespective of their orientation. At 23 C, fatty streak inclusions from 21 subjects averaged significantly higher in the proportion of anisotropic forms, 85.5 +/- 9.3%, than did fibrous plaque inclusions from 21 subjects, which had 32.4 +/- 16.3% anisotropic forms (P < 0.01).

N.M.R. STUDIES OF BRIDGED RING SYSTEMS: II. UNUSUAL MAGNETIC DESHIELDING EFFECT ON THE BRIDGE METHYLENES OF NORBORNADIENE AND BENZONORBORNADIENE

Proton magnetic resonance spectra of some norbornane derivatives having double bonds and (or) a benzene ring in the skeleton were studied. Differences in the chemical shifts between the bridge methylenes of norbornene and benzonorbornene and that of norbornane result from the diamagnetic anisotropy effect of a double bond or a benzene ring being in good agreement with the values calculated theoretically. However, in the norbornadiene derivatives which have two double bonds or one olefinic double bond with a benzene ring in a part of the skeleton, the signals of their bridge methylenes show extraordinarily larger downfield shifts by about 0.8 p.p.m. than those expected from the additive shielding due to each π-electron system. This anomaly is not observed in bicyclo[2.2.2]octane ring series. A large transannular interaction between two π-electron systems in that system would be a major contribution to the above anomaly.