Quantum Relations in Photoreactivation of Colpidium

Abstract

The degree of photoreactivation or rever"~al of injurious effects of ultraviolet radiations (UV) by illumination with visible light has been shown to increase with length of exposure of the irradiated organisms to visible light (Dulbecco, 1949; Kelner, 1951). After maximal photoreactivation of phage has been achieved, further illumination with whitelight has no further effect (Dulbecco, 1949), whereas in EsckericMa coli and Streptomyces griseus additional illumination proved to be injurious in some cases (Keiner, 1951). Photoreactivation in Colpidium coIpod~ increases with exposure to monochromatic or mixed visible light to a maximal value. Additional illumination to the extent previously tried was not injurious (Giese, Brandt, Iverson, and Wells, 1952). The question arises as to how many quanta of visible light are necessary to reverse maximally the action of 1 quantum of UV. This information would be interesting for theoretical reasons. The present report records such determinations for Colpidium colpoda, a ciliate protozoan. Metkods and MaterialsAs a criterion of UV injury the retardation of the third division of the irradiated colpidia was determined in much the same way as in previous experiments with paramecia (Giese, 1939). Photoreversal was measured by recovery from such division delay.Fortunately Colpidiura colpoda like Paramecium caudatura (Giese, 1939(Giese, , 1945 does not show a period of cessation of division after UV treatment as does P. aurdia or P. mul~iraicronucleatura (Giese and Reed, 1940;Kimball and Gaither, 1951) or Tarahymena geleii (Christensen, unpublished). Therefore the delay in the third division after irradiation may be determined without this complication. The methods were in general similar to those described in the previous paper . (Giese, Brandt, Iverson, and Wells, 1952).As a source of radiation a quartz mercury arc was used and the radiations were passed through a natural quartz monochromator. The 2654 A line in the short UV was reflected by a fight angle quartz prism upon the horizontally held quartz cell containing the protozoa. For photoreactivation the light from a high pressure Ames

Photoreactivation

“…He found PR the lowest biological organization, there are with wave lengths 4400, 5500, and 6600 A, the several reports of PR of biomolecules in vitro, greatest effect being obtained with 6600 A. although in only one case is the effect unquestion-Only one other investigator has found PR above able. These experiments are discussed in detail 5000 A (Giese et al, (56); 5490 A), and no one in section IV-B. else has found a maximum above 4358 A, which Bacteriophage.…”

“…considerations and available data ugg that (56) showed that C. colpoda division delay in tin the former starved cells can be photoreactivated over a therhates are morecent constant wider range (3130 to 5490 A). Helnke (67) and that the maximum per cent PRns are more constant in the latter case.)…”

The Effect of Nutritional State on Photoreversal of Ultraviolet Injuries in Didinium Nasutum

“…Active metabolism stimulated by intake of food has been seen to favor resistance to UV in other species as well, e.g. Paramecium (Giese and Reed, 1940) and Colpidium (Giese et al, 1953(Giese et al, , 1954. In all three protozoans experiments indicate that physical screening cannot account for the increased resistance of fed animals to UV, since ingestion is not immediately followed by increased resistance to UV, but only after a lapse of time during which, presumably, the nutrient is incorporated into the protoplasm.…”

“…Colpidia fed after UV but before photoreversal were also little affected. However, for photoreversal of UV injuries to starved colpidla eight times as many quanta of blue/quantum UV are required than for fed animals (Giese et al, 1953(Giese et al, , 1954. For both fed and unfed Didinium the same number of quanta are needed to achieve maximal photoreversal (Table III).…”

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Starvation increases the susceptibility of Paramecium and Colpidium to ultraviolet (UV) radiations (Giese and Reed, 1940;Giese et al, 1954). Injury to starved colpidia is found to be less readily photoreversed than that to well fed animals, eight times as many quanta of blue light per quantum UV being required for maximal photoreversal (Giese et a/., 1953). Refeeding them with bacteria after UV but before blue light has little effect upon the degree of photoreversal (Giese eta/., 1954).

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