Studies on Developing Retinal Vessels: Ix. Reaction of Endothelial Cells to Oxygen

IN reviewing the mechanisms which might be involved in the phenomenon of oxygen vaso-obliteration in the immature retina, it was recently suggested that swelling of the retinal tissue around the vessels could be the primary factor concerned. The detailed evidence upon which this suggestion was based has already been reported (Ashton, 1957; Ashton, Graymore, and Pedler, 1957) and further supporting data have since been published (Gray- more, 1958; Pedler, 1959a, b). It was pointed out, however, that a more direct action of oxygen on the vessel wall could not be excluded by the negative evidence then obtained, because the techniques available at that time were not entirely satisfactory. With the development of the new digest method of Kuwabara and Cogan (1960), it has been possible to isolate the affected capillaries, and with the icquisition of an electron microscope at this Institute a detailed study of the changes in the internal structure of the endothelial cell has become feasible. The findings obtained are presented and discussed in this paper.