Effects of gamma-irradiation on embryonic development and nucleic acids in trigeminal neurons.

Pregnant rats were exposed to absorbed doses of 0.5, 1, 2, and 4 Gy of 60Co-gamma rays either on day 8 or on day 12 p.c.. The embryos were collected on day 18 p.c.. Irradiations both on day 8 and 12 p.c. result in a dose dependent decrement of weight. The effect is larger for irradiation on day 8 p.c.. Caryometric studies of the neurons in the trigeminal ganglion show, on the other hand, that the reduction of nuclear sizes in this tissue is more substantial for an irradiation on day 12 p.c. when the ganglion is in a stage of formation. Cytophotometric determinations of the Feulgen-DNA content and determination of the RNA content by staining and chromic gallocyanin in combination with ribinuclease digestion lead to the conclusion that the irradiation induces no significant hyperploidy and that the irradiated neurons have the nuclear RNA content that is normal at this stage of gestation. This applies both to the irradiations on day 8 and on day 12 p.c.