[Early histological changes in the thyroid gland in irradiated rats without a pineal body].

The authors investigated histological characteristics of the thyroid gland in irradiated rats under the conditions of anepiphysia. Pseudo-epiphysectomized rats and epiphysectomized rats were irradiated in toto with a single dose of 8 Gy gamma irradiation. The animals were decapitated on the 121st day of the postoperative period, in other words, on the 6th day following irradiation. The animals with an intact epiphysis showed significant changes in the histological structure of the thyroid, but they were of a considerably lesser intensity when compared to the changes observed in epiphysectomized rats. On the basis of the differences observed in behavioural characteristics as well as the degree of mortality, we propose that pineal gland absence has determined the behaviour of the glandular parenchyma, as well as of the whole organism in the given conditions.