Lateral electrical conduction along a phosphatidylcholine monolayer.

Lateral electrical conduction due to lipid-monolayers spread on the surface of pure water was observed under both d.c. and a.c. electrical fields. An apparent specific electrical conductivity is evaluated as high as approximately equal to 4.10(-2) mho/cm for the monolayer-water system of L-DPPC at 25 degrees C. Arrhenius plots of the apparent conductance show a deflection at a temperature corresponding to a crystalline-to-fluid phase transition of the surface monolayer. From the magnitude and temperature dependence of conductance and a comparison of results with those obtained by use of deuterated water, it is concluded that enhanced protonic conduction mediated by a network consisted of polar head groups of phosphatidylcholines and water molecules may be brought about near the lipid/water interface.

Growth mechanism of myelin figures of phosphatidylcholine.

The initial growth process of myelin figures, rod-like lyotropic liquid-crystalline structures, formed by phosphatidylcholine in water, ethylene glycol or glycerin, is suggested to be diffusion-limited with an apparent diffusion coefficient D of approx. 10(-6) cm2/s. D can be expressed by the sum of two processes. One is considered to describe the diffusion of an aggregate of phosphatidylcholine molecules and the other mainly to describe a lateral diffusion in the bilayer membranes which constitute myelin figures.

Magnetic-field-induced orientation and bending of the myelin figures of phosphatidylcholine.

In a magnetic field of up to 7 kG, myelin figures of the egg-yolk phosphatidylcholine/water system were oriented because of the diamagnetic anisotropy of the molecules through bending at the roots with the long axes parallel to the field. The time interval for an angular change of their axes was nearly in proportion to H-2. From the orientational behaviour, a curvature-elastic modulus K of lipid-bilayer could be roughly evaluated as 4 X 10(-13) erg.

Electron diffraction study on two-dimensional domain structure of L-DPPC monolayer.

A spatial variation in the two-dimensional crystal lattice orientation of L-DPPC monolayer on a hydrophobic substrate was observed by use of an electron microscope with diffraction and dark-field techniques. It is shown that the monolayer has a mosaic structure with domains, each of which consists of a region with a homogeneously oriented lattice of L-DPPC molecules. The domain structure of L-DPPC monolayer on a hydrophilic surface is also discussed.

Development of antibody against epitope of lipoprotein(a) modified by oxidation: evaluation of new enzyme-linked immunosorbent assay for oxidized lipoprotein(a).

BACKGROUND: Recently, the biological effects of oxidized lipoprotein(a) [Lp(a)] have been reported to be more potent than Lp(a), the arteriosclerosis-relevant lipoprotein. Thus, investigations with oxidized Lp(a) are expected to provide viewpoints different from the conventional ones based on Lp(a). METHODS AND RESULTS: An anti-Lp(a) monoclonal antibody (161E2) was produced against synthetic peptide antigen (Arg-Asn-Pro-Asp-Val-Ala-Pro). This epitope was characterized as having various properties because its external exposure was induced as a result of oxidative modification. Using 161E2 antibody, we developed a new enzyme-linked immunosorbent assay to measure Lp(a) modified by oxidative stress. The present data demonstrated that oxidized Lp(a) that contains the epitope of 161E2 antibody was present in the serum of humans. Therefore, we used this new enzyme-linked immunosorbent assay to evaluate the role of oxidized Lp(a) in patients with hypertension, which induces oxidative stress. Interestingly, hypertensive patients with complications showed a significantly higher level of oxidized Lp(a) in serum than did normotensive subjects (P:<0.01), whereas there was no significant difference in native Lp(a) between normotensive and hypertensive subjects. Importantly, positive immunostaining with 161E2 monoclonal antibody was found in the human arteriosclerotic tissue. CONCLUSIONS: We developed a new antibody against an epitope in Lp(a) as a result of oxidation treatment but not in native Lp(a). The present data demonstrated in vivo the presence of oxidized Lp(a) in the atherosclerotic tissue and its elevation in hypertensive patients. The presence of oxidized Lp(a) may be important in understanding the role of Lp(a) in cardiovascular disease.

Polyhedral assembly of a membrane protein in its three-dimensional crystal.

A novel ordered assemblage of bacteriorhodopsin, a transmembrane protein functioning as a light-driven proton pump, is found in its three-dimensional crystal. Atomic force microscope images of the crystal surface reveal that spherical protein clusters with a diameter of approximately 50 nm are hexagonally close-packed. Electron micrographs of mechanically disintegrated crystals show that the inside of the protein cluster is filled with the mother liquor. The crystal is made up of hollow protein clusters. When disintegrated crystals are illuminated in the presence of a lipophilic anion, a significant alkalization of the external medium occurs. This result indicates that the protein cluster contains native lipids and that the cytoplasmic side of the protein faces the external medium. X-ray diffraction patterns and the observed diameter of the spherical shell suggest that approximately 200 bacteriorhodopsin trimers are aligned on a polyhedral surface lattice. Another remarkable feature of the spherical assemblies of bacteriorhodopsin is that they fuse with each other at low ionic strength and occasionally form a tubular or doughnut-like structure. The concept of membrane protein polymorphism is introduced on the basis of these observations, and it is used to describe the dynamic structure of some other biological membranes.

A novel three-dimensional crystal of bacteriorhodopsin obtained by successive fusion of the vesicular assemblies.

When the two-dimensional crystal of bacteriorhodopsin (bR), purple membrane, is incubated at high temperature (32 degreesC) with a small amount of the neutral detergent octylthioglucoside in the presence of the precipitant ammonium sulfate, a large fraction of the membrane fragments is converted into spherical vesicles with a diameter of 50 nm, which are able to assemble into optically isotropic hexagonal crystals when the precipitant concentration is increased. The vesicularization of purple membrane takes place under such a condition that the miscibility of the detergent to the aqueous phase becomes very low, and we suggest that it is initiated by insertion of the detergent molecules into the membrane. At low temperature, the transformation into the vesicular structure is inhibited and no large crystal is produced directly from membrane/detergent/precipitant mixtures. When a suspension of the spherical vesicles produced at the high temperature is cooled and concentrated below 15 degreesC, however, a birefringent hexagonal crystal is produced that diffracts X-rays beyond 2.5 A resolution. This new crystal belongs to the space group P622 with unit cell dimensions of a=b=104.7 A and c=114.1 A, and it is shown to be made up of stacked planar membranes, in each of which the bR trimers are arranged on a honeycomb lattice and the space among the proteins is filled with the detergent molecules and native lipids. These stacked membranes are suggested to be produced by successive fusion of the spherical vesicles. This implies that the crystallization is achieved without any step for complete solubilization of the protein. The present result offers a unique crystallization method that may be applicable to such membrane proteins that are liable to denature in the presence of an excess amount of detergent.

A nation-wide study of atherosclerosis in infants, children and young adults in Japan.

This paper reports the results of a nation-wide cooperative study of atherosclerosis in young, first generation Japanese with ages ranging from 1 month to 39 years, who were autopsied between 1978 and 1982 in hospitals distributed over the entire archipelago of Japan. Atherosclerotic lesions in 2320 aortas, 1620 coronary arteries and 344 cerebral arteries were classified into fatty streaks, fibrous plaques and complicated lesions and were then quantificated with the point-counting method. Atherosclerosis of aortas, coronary arteries and cerebral arteries, determined by surface involvement (SI) of atherosclerotic lesions and atherosclerotic index (AI), increased with age; the severest were seen in aortas, and then, with decreasing severity, in the coronary and cerebral arteries. Fatty streaks preceded the other lesions and accounted for the largest portion of the lesions in aortas and coronary arteries. Fibrous plaques and complicated lesions developed in the later decades of life. The patients with collagen diseases had a greater severity of aortic atherosclerosis in the 2nd and 3rd decades of life, than those without such disorders. Correlation of antemortem clinical data with SI and AI of each artery were analyzed, using simple correlation analysis and multiple regression analysis. Age, serum cholesterol and blood pressure were significantly and positively correlated with SI and AI of aortas and coronary arteries. Serum cholesterol was more strongly correlated with the extent of fatty streaks than was mean blood pressure and vice versa with that of fibrous plaques. Atherosclerosis of cerebral arteries, however, showed a significant correlation only with the factor of mean blood pressure. Therefore the susceptibility to risk factors varies with the artery in cases of early lesions of atherosclerosis in young Japanese.

Second nation-wide study of atherosclerosis in infants, children and young adults in Japan.

This paper reports the results of the second nation-wide cooperative study of atherosclerosis in young Japanese, aged from 1 month to 39 years, who were autopsied between 1991 and 1995. Atherosclerotic lesions in 1066 aortas and 974 coronary arteries were classified into fatty streaks, fibrous plaques and complicated lesions and quantificated with the point-counting method. The results of this study were compared with those of the former study, which was conducted 13 years earlier in almost the same fashion as this study. Atherosclerosis of aorta, which was determined by surface involvement (SI) of atherosclerotic lesions and atherosclerotic index (AI), increased with age in both sexes of the former and the present studies and their tendency for the progression of the extent of atherosclerotic lesions appeared to be similar. In the coronary arteries, the mean values of SI and AI in the males of the present study were greater significantly than those in the male of the former studies and in the female of the both studies in the third and fourth decades. This difference suggests that atherosclerotic lesions are increasing in young Japanese males. It also suggests that these subjects may be increasingly susceptible to atherosclerotic cardiovascular disease with increasing age.

Bacterial Accumulation of Metallic Compounds.

Xanthomonas maltophilia accumulated metals or metallic compounds within the cell in the form of one or a few particles, in a peculiar condition similar to that of an electrolyte solution in an electric cell. The particles consisted of many little granules, most of which were assumed to be composed mainly of a compound of zinc and phosphorus in an amorphous state.