title: Effects of very low doses of ionizing radiation on the clonal life-span in Paramecium tetraurelia.
abstract: Effects of very low doses of ionizing radiation were investigated on life-span in Paramecium tetraurelia. After autogamy single cell cultures were place (1) in a control chamber with radiopermeable walls; (2) in a shielded device with 10 cm thick lead walls; (3) in a similar shielding device including a 60Co source giving a dose of 760 mrad per year at the culture level. Life-spans, expressed in days and in mean total number of fissions measured from autogamy to the death of all sublines, were about 200 fissions and 55 days in controls. Life-spans of shielded sublines were increased and lower life-spans were observed in both shielded and irradiated sublines. These findings provide new evidence for a biological effect of very low doses of ionizing radiations and show that fission potential of Paramecium tetraurelia can be affected by variations in the background radiation level.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D002999:Clone Cells / Q000528:radiation effects; D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D010247:Paramecium / Q000528:radiation effects*; D013997:Time Factors
chemical_list: D003037:Cobalt Radioisotopes