RESPONSE OF SWINE SKIN TO ACUTE SINGLE EXPOSURES OF X-RAYS - QUANTIFICATION OF THE EPIDERMAL-CELL CHANGES

Three 10-cm-diameter skin fields on shoulder, chest, and ham of 24 swine were irradiated with acute single exposures of 1700, 2300, and 2700 R. The animals were anesthetized, biopsied, and sacrificed at intervals from 1 to 70 days following irradiation. The observed histologic changes comprised a degenerative and a regenerative phase. The degenerative phase was characterized by progressive cell loss (similar for all fields), an increase in nuclear volume, and a decrease in mitotic index. The regenerative phase was characterized by the appearance of discrete islands of normal-appearing cells. Three types of islands were designated as small, large, and giant based on chord length. These regenerating islands increased progressively in size until the field was reepithelialized; the mitotic index was as high as 6% with a tritiated thymidine labeling index between 30 and 70%. The cell cycle time was estimated to be 15 hr. The number of islands at 17 to 28 days following irradiation was dose-dependent with D0 of 272 R for small islands, 568 R for large, 1620 R for giant islands and 337 R for the combined data. Reepithelialization was attributed to proliferation of cells in giant islands. Cells from small islands contributed little.