The Effects of Starvation on Photoreactivation in Colpidium colpoda

Abstract

Specimens of Colpidium colpoda starved for 48 hours are much more sensitive to UV radiations and much less susceptible to photoreactivation (recovery from UV damage) than well-fed controls. Refeeding starved animals decreases their sensitivity to UV but only after many hours during which time the food has been incorporated into the protoplasm. Suspension of colpidia in dilute solutions of glutathione reduces their sensitivity to UV. Sensitivity of starved colpidia may therefore be due to lack of reducing substances in the protoplasm, substances normally present in well fed animals. Refeeding after UV but before photoreactivation does not increase the efficiency of the photoreactivation process to a greater degree than an equivalent sojourn in balanced salt medium. To be effective for photoreactivation, the protoplasmic constituents of consequence must-be in situ at the time of UV treatment. The possible significance of the results is discussed.