Effects of gamma radiation on the shark brain

A comparison was made between the effects of gamma radiation on the elasmobranch and the mammalian brain. Thirty-seven nurse sharks (ginglymostoma cirratum) received a single exposure, in a range of 1 000 to 30 000 rads, to the brain. The animals remained seemingly unaffected in their behavior and at their sacrifice, between one day and 28 months after irradiation, no histological changes could be detected with the exception of one shark (exposed to 30 000 and sacrificed after 12 months) which showed two small necrotic lesions in the tegmentum. No detectable difference in amount and distribution of glycogen in the brain could be demonstrated between irradiated and non-irradiated sharks. Also, the irradiated sharks showed no changes of the blood-brain barrier to protein tracer. Rats irradiated with 25 000 to 30 000 rads to the brain from the same source died shortly after exposure or showed extensive necrotic lesions in the brain. These was also an intense accumulation of glycogen mostly in the astrocytes and a widespread disturbance of the bloodbrain barrier to Evans Blue-albumin tracer.