The effect of spaced radiation on tissue cultures in vitro

Abstract

The material used was derived from the choroid and sclerotic of fowl embryos and was grown in fowl plasma and embryo extract by the hanging drop method. Growths of the 2nd subculture were used. Two exposures of 2 1/2 min. each, separated by a time-interval, produced a different effect from a continuous irradiation of 5 min. When the cultures were given 2 irradiations, each of 2\ min., with 100 mgm. Ra (element) at 0.5 cm. (Pt filter 0.5 mm.), diminution in mitosis was more marked when 80 min. elapsed between exposures than when the interval was 160 min. Repeated exposure to 300 mgm. Ra (element) at 0.5 cm. (Pt filter 0.5 mm.) enhanced the effect of radiation. 24 exposures, each of 2 1/2 min., separated by 80-min. intervals (i.e., a total exposure of 1 hr.) produced a delayed lethal effect equivalent to that following a continuous irradiation of 4 1/2 hrs.