Methods for the rapid separation and estimation of the major lipids of arteries and other tissues by thin-layer chromatography on small plates followed by microchemical assays

Methods are described for the rapid separation of the major individual phospholipids and neutral lipids of tissues by thin-layer chromatography on small glass plates (75 X 75 mm), and for the specific microchemical estimation of separated lipids and for determination of fatty acid composition and radioactivity. The overall method, involving tissues extraction, thin-layer chromatographic separation and assay has been evaluated using pure standards and biological samples and gives good reproducibility and almost complete recovery of lipids.

Scanning electron microscopy: morphology of aortic endothelium following injury by endotoxin and during subsequent repair

A single injection of endotoxin P45 Poly Serratia marcescens was used to induce endothelial injury in rabbits. The aortic endothelium was examined by Scanning Electron Microscopy (SEM), at various times after administration of endotoxin, using the technique of silver staining and pressure fixation. Within one hour after injection, some endothelial cells were curled-up and spindle-shaped in appearance. Areas of aorta devoid of endothelial cover were occasionally observed and platelets were sometimes found adhering to these sites. Two and four weeks after initial injury no spindle-shaped cells were found. Instead, some endothelial cells were heavily stained with silver. Small denuded zones were still found and these were surrounded by brightly silver-stained cells. This study confirms that endotoxin rapidly causes endothelial injury and suggests that regenerating endothelial cells which were formed following injury are avidly stained by silver salts and appear as bright cells by SEM.

Variation in the volume of coated vesicles isoalted from human placenta

Electron microscopic analysis of 500 negatively stained coated vesicles isolated from human placenta showed that they exist within limits in a continuous range of volumes with an unimodal distribution. Some vesicles were larger than the frequently quoted maximum size of these organelles (diameter 100nm). The ratio of hexagonal to pentagonal facets in the clathrin lattice of the vesicle wall appears to be variable. This feature may be important in morphogenesis since the mean volume of prolate vesicles is larger than that of spherical vesicles. Empty lattices had a mean volume smaller than that of lattices containing phospholipid bilayers.

Scanning electron microscopy of arteries. The morphology of aortic endothelium in haemodynamically stressed areas associated with branches

The endothelial surface around branches of the normal rabbit aorta was examined by scanning electron microscopy (SEM). Focal endothelial damage was consistently found both on, and distal to, aortic flow dividers. In some case small areas were denuded of endothelial cover. Similar injury to endothelal cells was also occasionally observed proximal to the ostium of a branch. Haemodynamic forces, expecially high shear stress, may be responsible for these morphological changes. This altered endothelial integrity probably underlies the susceptibility of these sites to the formation of induced atherosclerotic lesions.

A simple technique for the frequent intravenous infusion of fluid without heparin into the rabbit

A technique is described for the daily intravenous injection over 16 weeks in the rabbit. The system consists of a Teflon cannula passed down the external jugular vein with the tip in the superior vena cava. The cannula is joined at the point of entry to the jugular vein to a length of silicon rubber tubing, which is then passed subcutaneously to the forehead. The silicon tubing is terminated on a Luer needle hub, which is held in a simple Perspex plate secured subcutaneously between the rabbit's ears. The Luer hub is covered with a replaceable rubber cap through which injections may be made. With this system cannulae were maintained patent for 16 weeks by flushing once a day with Hanks' balanced salt solution, pH 7-4.

Scanning electron microscopy in the evaluation of endothelial integrity of the fatty lesion in atherosclerosis

The luminal surface of fatty lesions of atherosclerosis was viewed by scanning electron microscopy (SEM). Endothelial cells were outlined by staining intercellular junctions with silver and the aortas were fixed in situ at physiological pressure. When aortas were dehydrated by passage through organic solvents followed by critical point drying from liquid CO2, there was considerable disruption of the luminal surface and it was not possible to correctly interpret the morphological integrity of the endothelium. In contrast, simple air-drying of aortas, without solvent dehydration after fixation, allowed the integrity of the cell layer overlying the lesion to be evaluated. The success of this technique was attributed to the retention of arterial lipids during dehydration of the tissue.

Scanning electron microscopy: arterial endothelial integrity after fixation at physiological pressure

The luminal surface of normal rabbit aorta was examined by scanning electron microscopy (SEM) after outlining endothelial cells by staining intercellular junctions with silver. When aortas were fixed in situ at physiological pressure before processing for SEM, a reliable assessment of the morphological integrity of the endothelium was possible. In contrast, when aortas were excised and placed in fixative, contraction of the sub-endothelial structures made interpretation of endothelial integrity difficult.

Human platelet reactivity during stressful diagnostic procedures

Conscious subjects undergoing cardiac catheterization and other diagnostic procedures showed a rise in platelet-aggregation response to adenosine diphosphate (ADP) one hour before and during the procedure. The responses returned towards normal one hour afterwards. The response to glass beads was decreased one hour before the procedure, but was unchanged in subsequent samples. Plasma-free fatty acid (FFA) levels were increased during the procedure, and one hour afterwards, but had returned to normal by the following day. Platelet counts were slightly reduced on the day after the procedure. It is suggested that catecholamines released due to emotional stress may be responsible for the increased platelet responses to ADP and that this could influence the development of thrombosis and atherosclerosis.

Studies on the terminal stages of complement lysis

Experiments are described using the reactive lysis system on phospholipid dispersions to study the terminal phases of complement lysis. It has been found that, both on lecithin and on sphingomyelin-cholesterol liposomes, marker release and characteristic EM lesions can be found upon the sequential activity of C567 and C8 and C9 and that for both these parameters of lysis the action of C8 and C9 as well as of C567, are required.

Lysis of liposomes is accompanied by the appearance of traces of the products of phospholipase activity in the supernate but it is believed that these represent the activity of contaminating enzymes and are the consequence and not the cause of lysis. However the possibility that lysis could be due to lipolytic activity cannot be totally excluded because of the negligible hydrolysis theoretically needed to form lesions.