Conformation of Aortic Elastin Revealed by Scanning Electronmicroscopy of Dissected Surfaces
A scanning electron microscopic study of the elastin residue of normal human aortas has been made. Purification has been achieved by successive salt or guanidine extraction and by autoclaving, sodium hydorxide or collagenase treatment to remove contaminating proteins. Purity has been judged by amino acid analysis. The cleanest specimens have been obtained with NaOH. The elastin residue has been fixed with glutaraldehyde and osmium tetroxide. The specimens were rendered conductive by osmium-thiocarbohydrazide treatment and examined with a Cambridge scanning electronmicroscope without coating.
The three-dimensional form of successive layers of the elastin structure from intima to adventitia has been disclosed by partial dissection of the aortic wall before isolation of the elastin. A mat of randomly oriented, fine, circumferential fibers permeates the intima. A myriad of coarse, branched fibers and septa connect medial laminae with which they are continuous. At the adventitial junction these are continuous with small, tangled, curly fibers of the adventitia. No natural discontinuities were seen between the fibers and laminae. Artificial cleavage of the media produced no smooth laminar surfaces but left a distinctive pattern of broken ends of interlaminar fibers. It is concluded that the normal aortic media contains a continuum of elastin surrounding compartments in which the cells and collagen fibers are enclosed. Strain of this structure is spread throught it accordingly.
KeywordsElastic Tissue Break Fiber Coarse Fiber Circumferential Fiber Medial Lamina
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