実験動物における心内膜, 大動脈および二三の動脈内膜の走査電子顕微鏡による研究

Abstract

In order to study the fine surface structure of endocardial and endoarterial endothelium in mature rabbit, dog and rat and neonatal rabbit and dog, a new perfusion and fixation methods were devised, and the heart, aorta and some other arteries were observed with scanning and transmission electron microscopes. The main findings are summarized as follows : 1. As the surface of the endocardial and endoarterial endothelium in each animal were essentially similar in fine structure, the observation of each animal will be described together. Microvillous projections presented various distributions frequently occurred on the surface of endothelial cells, in all animals irrespectively mature or neonatal. Especially, in the sinus aortae and sinus trunci pulmonalis, the endothelial surface tended to show numerous and long projections. Endothelial cells with only a few or no projections were also mingled. In the interior of the microvillus, thin straight filaments (50∿70 Å in diameter) run parallel to the long axis were distinguished. These filaments were closely resembled to myofilaments in smooth muscle cells. The possibility that the microvillous projections are contractile is discussed. 2. Craters are found on the endothelial cell surface in the aorta ascendens, arcus aortae and aa. intercostales branching point. They may possibly reflect physiological damages to endothelial cells in respons to the rheological peculiarities that occur at the site of branching or bending of vessels. 3. In both endocardium and endoarteries, there are endothelial cells with a process probably corresponding to single cilium. In the rabbit and dog a single cilium was identified on each cell, though in the rat its occurrence wes equivocal. A single cilium with its typical microtubular structure was demonstrated in ultrathin sections. In the neonatal rabbits, cilium was sometimes extended downward from the base of endothelial cells. Frequently, most of distal part of the cilium showed edematous swelling, indistinctly microtubular structure and/or dropping. These findings suggest a cause for which the cilia is only rarely observed on the endothelial surface. 4. In the neonatal animals, the endothelial cells of immature type are characterized by the presence of numerous microvillous projections which interlace with similar structures from adjacent cells to form intercellular gaps which overlie a subendothelial tissue. The endothelial cells of sinus aortae, sinus trunci pulmonalis, aa. intercostales branching point and right and left auricle, tended to show relatively immature type.