[Cytophotometric study of the DNA content in the cells of the preoptic area of the hypothalamus in hibernating common frogs].

The DNA content in the squashed Feulgen stained cells of the hypothalamic preoptic region in wintering adult and juvenile frogs was measured cytophotometrically. The vast majority of hypothalamic cells studied showed diploid DNA contents. Only 0.9% of tetraploid cells (4c and 2c X 2 cells) was found in this region, both in adult and juvenile frogs. The incidence of tetraploid hypothalamic cells varied among the individuals studied. In some adult frogs as well as in some juveniles no tetraploid cells were detected. The data obtained do not confirm the age related increase in the mean DNA content in frog's hypothalamic cells population.