Late ultrastructural effects of heavy ions and gamma irradiation in the gastrointestinal tract of the mouse

The irradiated gastrointestinal tract of LAF₁ mice was examined one year following a single dose (1000 rad) of either¹²C heavy ions or⁶⁰Co γ rays. Qualitative ultrastructural analysis of the gastrointestinal tract of mice exposed to heavy ions or γ irradiation did not show any discernible differences. In the stomach of irradiated mice, parietal cells contained numerous lysosomes ; the gastric chief cells occasionally contained myelin figures. The epithelial cells of the small intestine, especially jejunum and ileum, showed several changes: (1) increased vacuolation was seen both inter-and intra-cellularly, (2) epithelial cell projections penetrated the basal lamina and were in contact with underlying mesenchymal cells, (3) occasional Paneth cells contained intracellular vacuoles consisting of fibrillar and granular material. In the large intestine occasional signs of degeneration were observed. Qualitative analysis of stromal elements of the gut in irradiated mice indicated the presence of damage to capillary endothelial cells, smooth muscle cells and some nerve processes. The amount of basement membrane (BM) around capillaries and small vessels was increased; the same phenomenon was observed to affect the nerve processes, but with less severity. Quantitative analysis of the basement membrane thickness around capillaries in irradiated vs. control mice showed significant differences. Basement membrane thickness around capillaries in the gastric mucosa and duodenum did not differ significantly in any of the treatment groups. In jejunum, the γ treated animals exhibited significantly higher BM thickness when compared to unirradiated controls. In ileum, only¹²C-heavy ion treated animals showed thicker BM when compared to their respective controls. In colon, both¹²C-and⁶⁰Co-treated animals showed increased BM thickness when compared to controls.