. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. 248 FACTORS INFLUENCING CELL RADIOSENSITIVITY tion (Fig. 5). On chains of giant cells apparently doomed to die, cells of normal appearance often arise from which normal colonies then develop. In yeasts this ability to recover from radiation injury is thus linked to Haploid Diploid Fig. 5. Aspect of colonies and injured cells of S. cerevisiae after x-irradiation. Action of Temperature When temperature influences the production of a lesion, it is difficult to know whether this influence ta
. The basic aspects of radiation effects on living systems. Radiation -- Physiological effect. 248 FACTORS INFLUENCING CELL RADIOSENSITIVITY tion (Fig. 5). On chains of giant cells apparently doomed to die, cells of normal appearance often arise from which normal colonies then develop. In yeasts this ability to recover from radiation injury is thus linked to Haploid Diploid Fig. 5. Aspect of colonies and injured cells of S. cerevisiae after x-irradiation. Action of Temperature When temperature influences the production of a lesion, it is difficult to know whether this influence takes place during the primary effect, or later, during the "dark reactions" (chemical reactions initiated by the primary effect). However, in certain cases, an experiment may answer this question. Radiochemical reactions are usually considered insensitive to tem- perature. Although rather general, this affirmation should not be ac- cepted in all cases. Thus Schreiber (26), in suppressing the motility of Sphaerocarpus donelUi spermatozoa by monochromatic ultraviolet rays (2650 and 3025 A), obtained the following results: with 2650 A, the efficiency of irradiation remains constant between 0 and 15° C, then increases regularly above 15°; with 3025 A, the efficiency increases steadily with temperature from 0° on. The temperature coefficient of the phenomenon therefore depends on the wave length; this proves (a) that temperature acts on the primary effect rather than on the dark reactions; (6) that this primary effect is a photochemical reaction with- out intermediate; (c) that this photochemical reaction is sensitive to temperature. (In this case, a relatively simple experiment informs us of the nature of the primary effect.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Symposium on Radiobiology
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