Disc-like Particles Research Articles

5 Dyslipoproteinaemia of liver disease

Hepatic diseases differ from most other causes of secondary dyslipidaemia in that the circulating lipoproteins are not only present in abnormal amounts but they frequently also have abnormal composition, electrophoretic mobility and appearance. Pre-beta and alpha bands can be absent on electrophoresis in all types of liver disease although material in the VLDL and HDL ranges can be isolated in the ultracentrifuge. Cholestatic liver disease has been the most extensively studied and the hyperlipidaemia can be extreme with marked elevations of free cholesterol and phospholipids. This results largely from the presence of LP-X, an abnormal LDL, with a vesicular structure that appears in rouleaux formation under the electron microscope. It is virtually specific for cholestasis and familial LCAT deficiency. The LDL, however, is heterogeneous and may also contain a large triglyceride-rich particle (LP-Y) as well as more normal-looking particles, which are none the less depleted in cholesteryl esters and rich in triglycerides. Indeed, when patients with cholestasis are hypertriglyceridaemic the excess triglyceride is to be found predominantly in these two LDL fractions rather than in VLDL. HDL in cholestasis may contain disc-like particles, similar to those newly secreted by the liver and intestine, as well as more normal-looking spherical particles. In extrahepatic obstruction concentrations of HDL and its major apolipoproteins, apoAI and apoAII, are frequently reduced, although a subfraction rich in apoE is often found. In all but the latest stages of chronic intrahepatic cholestasis due to primary biliary cirrhosis, however, HDL, especially HDL2, concentrations are increased, probably due to the presence of a circulating inhibitor of HL. Many of these lipoprotein changes found in cholestasis resemble those of familial LCAT deficiency, although the hyperlipidaemia is not usually so severe in the latter condition. Indeed, in patients with cholestasis but well-preserved LCAT activity many of the characteristic lipoprotein changes, such as LP-X, LP-Y and discoidal HDL, may not be seen. In acute hepatocellular disease, such as alcoholic or viral hepatitis, it is not unusual for the patient to go through a cholestatic phase and many of the same lipoprotein changes may be seen. In cirrhosis without cholestasis the patients are not usually significantly hyperlipidaemic and in advanced cases cholesterol and apoB levels may be reduced. Although LCAT activity and the proportion of plasma cholesterol esterified may also be markedly reduced, LP-X is not usually seen, possibly because the flux of free cholesterol and phospholipid (lecithin), the LCAT substrates, is relatively low. Discoidal HDLs are often present.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma lipoproteins in infantile visceral Leishmaniasis: deficiency of apolipoproteins A-I and A-II

This study describes the plasma lipoprotein system of young children with visceral Leishmaniasis (Kala-azar disease). In addition to the presence of amastigote forms in the sternal aspirates of bone marrow, the patients exhibited fever, anemia, hepatosplenomegaly, various degrees of pancytopenia and a slight liver cytolysis. Patients had normal total cholesterol levels and increased triglyceride levels in the plasma. The concentrations of HDL and LDL were 30% and 50% of these reported for normolipemic subjects, respectively. In contrast, there was a three-fold increase in the concentration of VLDL. The ratio of free to total cholesterol was high; this was further substantiated by electron microscopy of HDL showing the presence of disc-like particles. Quantitative determination of apolipoproteins revealed a three-and seven-fold decrease of apolipoproteins (Apo) A-I and A-II, respectively, whereas Apo B levels were within the normal range. The presence of LP-A-II particles was demonstrated by two-dimensional immunoelectrophoresis in most of the patients' plasma during the acute phase of disease.

Characterization of rouleau formation of disc-like particle in bile by transmission electron microscopy

Characterization of rouleau formation of disc-like particle in bile by transmission electron microscopy

Growth kinetics of (θ′– and θ-phases in Al–3Cu alloy

AbstractThe precipitation of θ′ and θ in Al–3Cu alloy has been investigated, using a resistivity and a transmission electron microscopy (TEM) method. Both stages of the transformation obey the Avrami equation, ξ = 1− exp (−ktn), where ξ is the precipitated fraction of excess solute. The growth parameters are n = 1·68±0·10 for θ′ precipitation and n = 0·63 ± 0·04 for θ precipitation, and the corresponding activation energies are 85·3 ± 10·9 and 111·1±5·2 kJ, respectively. The n-value for the θ′ precipitation stage corresponds to the model proposed by Ham for diffusion-limited growth of disc-like particles, and is in agreement with the TEM results of this investigation. The activation energy for θ′ precipitation is in the range for θ′ boundary migration reported by Aaronson and Laird. The n-value and activation energy for θ precipitation suggests a growth model in which concurrent dissolution of θ′ supplies solute to θ particles via dislocation paths.MST/480

Colloid deflocculation detection by transient light scattering

Transient changes occur in the light scattered by colloidal sols subjected to pulsed electric fields. These form the basis of a method for the determination of the deflocculation condition of surfactant dosed mineral sols. Preliminary data are given for slurries of disc-like and brick-like particles up to 33% solids content.

Influence of particle and electrolyte concentration on the electro-optical effect of Na-bentonite

Electro-optical investigations carried out with fractionated Na-bentonite showed an increase of the electro-optical effect with decreasing particle concentration at constant electrolyte concentration (10 −4 mol dm −3) and particle dimensions. Electric polarizability dependence on the electrolyte concentration is observed. The investigations are carried out in the concentration range 0.005–0.1 g dm −3 Na-bentonite where multiple scattering is negligible. The dependence of the electro-optical effect on the Na-bentonite concentration is not connected with the optics of the system (particles' optical anisotropy, oscillation of the optical functions) or with polarization interaction. The results obtained indicated that the interactions among the particles could be responsible for the observed concentration dependence of the electro-optical effect with disc-like particles in aqueous solutions.

23. An endogenous inhibitor of 3H-estradiol binding in rat uterine nuclei

Delamination of layered zinc hydroxide salts (LZH) into hydroxide layers provides nanobuilding blocs of a two-dimensional anisotropy. The methodology, extent of delamination, the size and stability of hydroxide lamellae are described in detail. The ability of lamellae to restack to form oriented hydroxide films depends on the solvent, original LZH salt, and conditions used for delamination. The most interesting results were obtained using LZH intercalated with dodecyl sulfate anions and LZH nitrate delaminated in butanol at 60 °C and in formamide at room temperature, respectively. The former method produces hydroxide lamellae of a lateral size of ca. 10–20 nm. The inner structure of the hydroxide layers is conserved and separated lamellae restack to the original layered structure of LZH dodecyl sulfate. The latter method yields lamellae with a size decreasing from 73.3 nm to 10 nm after a 2-week aging, while their thickness is nearly constant (2.6–3.8 nm). However, the use of formamide is complicated by the formation of Zn(II) formate. The major part of LZH intercalated with dodecyl sulfate anions is transformed during the delamination procedure to anisotropic ZnO nanoparticles, either needle-like particles prolonged in the [0 0 1] direction or disc-like particles flattened along the (0 0 1) plane.

Relation between the initial slope of some electro-optic decays and the moments of the distribution of size

Several well defined average values of the rotatory diffusion constant D of a polydisperse system can be obtained using the initial slope of the free decay of different electro-optical phenomena and different degrees of orientation. The type of average depends also on the orientation mechanism. The type of average and its relation to the corresponding moments of the size distribution, which have been previously misused, are derived for rod-like and disc-like particles, different mechanisms of orientation, and two types of electro-optical effect: birefringence (or dichroism) and light scattering in an electric field. Re-examination of the agreement claimed by previous authors between averages of D measured by this technique and calculated from a distribution of size derived from electron micrographs illustrate the difficulties of the measurements at saturation of orientation, and the role of an exact knowledge of the orientation mechanism. Possible experiments are discussed. Two parameters analytical distribution functions, well suited for the expression of the differen moments appearing in the theory, are indicated.

Electron microscopy of the toxin and hemagglutinin of type A Clostridium botulinum.

Electron micrographs of the toxin and the hemagglutinin of type A Clostridium botulinum showed the toxin to be either round or disclike particles of 4 to 4.5 nm. These particles could also be seen as arranged in long strands or tubules of 9 nm in width. The hemagglutinin appeared as a crystalloid monolayer of stacked particles of 9 nm forming regularly arranged structures of 20 nm. Seen in cross section, these structures appeared as tubules with a lumen of 9 nm. The regularity of the angle of 83 degrees to the long axis of the structure in which the individual particles were arranged suggested that the hemagglutinins formed a helix with sufficient space within its coil to admit the strands of the toxins. A model of the possible arrangement of the toxin and the hemagglutinin in the native state is proposed.

Molecular weight, size and shape of thylakoid-membrane proteins

Chloroplasten, Membranproteine, Molekulargewicht, Konformation The lamellar system of chloroplasts, dissolved in concentrated formic acid, may be freed from lipids by dialysis or gel filtration. The structural protein on both sides of the isoelectric region is water-soluble. The molecular weight was determined to be 470 000 at pH 3.0 - 3.4. Electron micrographs reveal disc-like particles of variable diameter but constant thickness. Particles of 100 Å diameter and 50 Å thickness are mainly observed. The limiting viscosity number [η] = 12 (ml/g) demonstrated that the particles are also anisodiametric in solution. It follows from changes in circular dichroism and infrared absorption that the conformation of the polypeptides is altered by the formic acid treatment. The structural protein can be separated into polypeptides in buffers containing dodecylsulphate, yielding a major component of molecular weight 25 000. From these experiments it may be concluded that one protein layer is contained in the thylakoid membrane which is composed of supra-molecular structural elements.

Precipitation in gold—cobalt alloys

Abstract If cobalt is precipitated from dilute solution in a gold matrix the material can attain high magnetic hardness. Previous electron microscope studies showed that the precipitate was formed in discs on {100} planes of the gold matrix. Disc-like particles are incompatible with the observed magnetic properties. It is shown that in 9·8 wt. % and 1·5 wt. % cobalt alloys the precipitate is face-centred cubic. The disc-like precipitates are found to be clusters of smaller cobalt particles and this observation is compatible with the observed magnetic properties.