HISTOLOGICAL CHANGES AFTER IRRADIATION 1095 



authors' opinion, is that of cells observed in tissue culture after enormous 

 dosages of irradiation. Here it has been seen that vesicles may form at 

 the edge of the cell and that changes in form of the membrane, as in 

 ameboid motion, may cease. In all such cases the changes in the cell 

 membrane have followed severe, irreversible damage to the nucleus. It 

 has been reported that both nucleated and nonnucleated red cells swell 

 after irradiation, and this has been interpreted as being due to injury to 

 the cell membrane. However, the swelling may be simply a result of 

 passage of water through the membrane because of an increased number 

 of ions in the cell. Loss of stainability of the membrane has also been 

 reported. The few instances in which this occurs probably are late 

 stages after high dosage. Certainly it may be accepted that in the great 

 mass of irradiated cells exposed to 1000 to 3000 r, the cell membrane does 

 not lose its stainability. Early swelling of cells as a whole occurs more 

 strikingly in some cell types than in others. It may also appear late, as 

 in the fibroblasts of inflammatory tissue. 



There is evidence in certain plants and in some cells in tissue culture of 

 an immediate decrease in viscosity of the cytoplasm after intense 

 irradiation. Some cells in culture have been observed to slow down, 

 others to move faster, at least for a time. Cytoplasmic movements 

 may proceed for many hours after the nucleus is obviously coagulated as 

 a result of intensive irradiation. 



Organelles. It has been postulated that destruction of the centrosome 

 with its diplosome will prevent the cell from dividing. The proof for this 

 is absent, although it is presumably correct. Ciliary motion stops after 

 irradiation. It has been claimed that changes in the mitochondria are the 

 first morphological evidences of radiation effects. This conclusion has 

 been denied by others on the basis of sectioned material (W. Bloom, 

 1948b; Fogg and Shields Warren, 1937) and on observations of living 

 cells irradiated in tissue culture (W. Bloom, unpublished observations). 

 We have found no evidence that mitochondria degenerate early; on the 

 contrary, they may persist unchanged long after the cells are obviously 

 undergoing irreversible degenerative changes. 



Minor changes in the Golgi net after irradiation of tumor cells have 

 been described (Fogg and Shields Warren, 1937). This subject should 

 be investigated further. 



Neurofibrils and myofibrils occur in cells that are among the most 

 radioresistant in the adult animal. We have found no reports on changes 

 in these fibrils as a result of irradiation with therapeutic dosages or 

 with small multiples thereof. Also, no characteristic changes have been 

 described in cellular inclusions (fat, carbohydrates, chromophil substance, 

 pigment granules). However, it has been noted that, in many types of 

 cells after irradiation, there may be an increase in fat content, and there 

 are also reports on purported changes in the glycogen in liver cells. Such 



