Erland Nelson

Scanning Electron Microscopic Observations on the Luminal Surface of the Rabbit Common Carotid Artery Sublected to lschemia by Arterial Occlusion

The scanning electron microscope (SEM) has been employed to study the effects of ischemia on the luminal surface of the common carotid artery. Fifteen adult rabbits were lightly anesthetized and the common carotid arteries surgically exposed. The right carotid artery was occluded with a single Heifetz clip for five minutes (five animals), 15 minutes (five animals), and 30 minutes (five animals). Following removal of the clip, the animals were immediately perfused with glutaraldehyde and the arteries excised and prepared for critical point drying. Four additional rabbits were perfused following the same method with no surgical procedures performed in the neck. Normal aortas were also examined. The nature and frequency of endothelial cell alterations were determined by analysis of ten randomly selected SEM fields. Examination of the endothelial surface of arterial segments distal to the occluding clip revealed the presence of numerous “crater-like” defects as well as outpouchings or “balloons.” The numbers of craters and balloons were significantly increased in the ischemic (distal) arterial segment as compared to either proximal or sham-operated control segments (P < 0.001). These endothelial cell alterations were never observed in random micrographs of arterial segments taken from unoperated control animals, but were seen at the ostia of some intercostal arteries of the aorta. It is suggested that these craters and balloons could cause interference with blood flow and the for mation of platelet thrombi by their protrusion into the lumen, as well as alteration of the permeability of the arterial intima.

Caveolar systems and sarcoplasmic reticulum in coronary smooth muscle cells of the mouse.

Vascular smooth muscle cells in mouse heart contain prominent membrane systems (“sarcotubules”). One of these systems consists of vesicular structures whose unit membranes are continuous with the sarcolemma and which occur either as single caveolae, more complex tubules, or branched chains of fused caveolae. Such caveolar systems are both analogous to, and homologous with, the T or T-axial tubular systems of striated muscle cells. A second system of membranes, the sarcoplasmic reticulum (SR), comprises tubules and saccules that often come into close association with the sarcolemma but apparently are not open to the extracellular space. In addition to forming “couplings” with the sarcolemma, the SR often comes into close contact with mitochondria and caveolae. The ultrastructural complexity of these membrane systems in coronary vascular smooth muscle equals or surpasses that of smooth muscle cells in the large blood vessels that have been extensively studied by other investigators.

Preparation of vascular endothelium for scanning electron microscopy: a comparison of the effects of perfusion and immersion fixation

A comparison of currently used methods of tissue fixation for scanning electron microscopic study of vascular endothelium revealed that in situ fixation by intravascular perfusion is superior to immersion for the preservation of endothelial surface morphology.

Endothelial Cell Ischemic Injury: Protective Effect of Heparin or Aspirin Assessed by Scanning Electron Microscopy

Scanning electron microscopic observations of the luminal surface of the rabbit common carotid artery subjected to occlusion for 30 minutes or two hours revealed crater-like and balloon-like defects in the endothelial surface. The frequency of occurrence of these abnormalities was significantly decreased by pretreatment with heparin or aspirin in doses considered to have antiplatelet aggregating activity.