. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. DIFFUSION MODEL 371 Recently much emphasis was placed on the findings that some externally applied chemical agents have biological effects qualitatively similar to those of radiation, particularly as far as inhibition of cell division and production of genetic effects are concerned. Such situations may be also handled similarly to the above treatment, using the diffusion model. The chief difference is in the boundary values of the diffusion. Cell—' '—Poison Nucleus Fig. 7. Diffusion model of the acti
. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. DIFFUSION MODEL 371 Recently much emphasis was placed on the findings that some externally applied chemical agents have biological effects qualitatively similar to those of radiation, particularly as far as inhibition of cell division and production of genetic effects are concerned. Such situations may be also handled similarly to the above treatment, using the diffusion model. The chief difference is in the boundary values of the diffusion. Cell—' '—Poison Nucleus Fig. 7. Diffusion model of the action of a poison on the cell. When the cell is placed in a medium containing a uniform concentration of poison, migration of the poison through the cell wall and cytoplasm begins toward the nucleus. This figure is a graphic representation of the concentration gradient of the poison in the cell. Whether or not the effect is genie, dose-effect relationships may be calculated using the diffusion model wdth the proper boundary conditions. problem. Figure 7 shows a crude representation of this problem. When a cell is placed in a medium containing the external agent, diffusion through the cell membrane into the interior of the cell begins; the density of the blackening in Fig. 7 shows a plausible concentration dis- tribution of the poison in the process of diffusing to the nucleus of the cell. Consideration of the figure shows that, because of the larger volume of the cytoplasm to be crossed by the poison, the shape of the "survival" curve as a function of the amount and duration of poisoning might be different from the radiation survivals, and also that in some cases the cell wall and cytoplasmic constituents might effectively protect the nucleus even at the expense of their own destruction. Some German. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrat
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