CHAPTER 3 



INTRACELLULAR CHANGES 

 CYTOPLASMIC CHANGES 



Lopriore (1897) observed that X rays accel- 

 erate the flow of cytoplasm in the cells of 

 Vallisneria spiralis . When the source of radia- 

 tion is removed, the protoplasm of the cells 

 regains its normal state. But if the irradiation 

 was of an hour's duration, harmful effects of 

 X rays manifested themselves. The protoplasm 

 still continued to move, but it became granular, 

 numerous vacuoles appeared in it, and it ac- 

 quired a yellow tinge. Several years later Seckt 

 (1902) repeated the experiments of Lopriore on 

 the stem hairs of Cucurbita pepo, and also on 

 the stamen hairs of Tradescantia virginiana and 

 and on the leaf hairs of JT. selloi . The hairs 

 were irradiated in a humid chamber after being 

 separated from the organs on which they ap- 

 peared. Observing the movement of the cyto- 

 plasm in the irradiated hairs, Seckt determined 

 that not only is the movement accelerated due 

 to the action of X rays, but the movement is 

 retained for a longer period of time than in the 

 control hairs. Irradiation for a period of 1. 5 

 hours, however, caused dying off, the beginning 

 of plasmolysis, and sometimes deformation of 

 the entire cell. The cell could be returned to 

 its normal condition by placing it in fresh water. 

 Plasmolysis set in much more readily when the 

 distance from the [X-ray] tube was reduced. 

 This caused Seckt to assume that in these cases 

 some other rays also affect the cells. He be- 

 came convinced of this when he set up experi- 

 ments with Spirogyra cells which, in general, 

 are characterized by acute sensitivity to electric 

 currents. When the distance from the tube is 

 great, Spirogyra does not react to the rays, but 

 when the distance is shortened to 10 to 20 centi- 

 meters, plasmolysis takes place within the cells 

 in 5 to 10 minutes. After an hour or two the 

 threads of Spirogyra die. Seckt also set up 

 interesting experiments with irradiation of Mi- 

 mosa pudica and Oxalis corniculata . At a dis- 

 tance of 25 to 30 centimeters from the tube the 

 leaves were observed to begin folding after only 

 10 minutes. After 45 minutes all the leaflets 

 folded and the petioles arched. If the source of 

 radiation was removed, the leaves resumed 

 their normal position in 20 to 25 minutes. Seckt 

 explains this phenomenon by a lowering of the 

 turgor which, in turn, depends on the specific 

 effect of X rays on the protoplasm of the cells. 



After a considerable interval, Schmidt (1910) 

 investigated the irradiation of young sprouts, 

 but not cells as such. 



Williams' experiments (1923) are very 

 interesting. They point up the significance of 

 selection of the proper objects for X irradia- 

 tion. In order to obtain quantitative data for 

 this action, it is essential to have identical 

 materials, to irradiate cells at the same stage 

 of development, to perform the experiments 

 under conditions as identical as possible, and 

 to use homogeneous rays. As material for her 

 experiments, Williams used the epidermis from 

 the upper surface of petioles of Saxifraga um - 

 brosa where, as she knew from previous experi- 

 ments, cells are in a mature state and equal 

 in size. Moreover, these cells are completely 

 transparent and the streaming of the cytoplasm 

 is retained for a long time (48 hours in distilled 

 water). Williams used special doses of X rays 

 in her experiments, and filtered them through 

 an aluminum plate in order to obtain more 

 homogeneous rays. In order to assure identical 

 external conditions, she conducted experiments 

 in darkness and at identical temperatures. The 

 epidermis was examined microscopically at 

 definite intervals after irradiation. The exam- 

 inations were carried out under high magnifica- 

 tions of ordinary microscopes and also with the 

 aid of ultramicroscopes. The first change 

 brought about by X rays was an increase in 

 speed of cytoplasmic streaming, as shown by 

 the accelerated movements of reflecting parti- 

 cles. If the time of exposure was increased, 

 the Brownian movement of the particles in- 

 creased. Since the temperature during the ex- 

 periment was held constant and since the size 

 and optical properties of the particles remained 

 the same, the increase in speed of movement of 

 the latter indicated a change in viscosity of the 

 protoplasm. Still longer periods of irradiation 

 cause a decrease in the speed of the movement 

 and finally its complete stoppage. If the action 

 of X rays is extended beyond the time required 

 to accelerate movement, other changes in the 

 protoplasm take place. The protoplasm begins 

 to withdraw from the walls and, in addition, its 

 pink color becomes less intense. It was possi- 

 ble to assume that the pigment was being broken 



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