Mitotic division of differentiated neurosecretory cells in the hypothalamus of adult amphibians

By means of multiple 3H-thymidine administration to adult frogs, a direct electron microscopic radioautographic evidence is first by presented regarding the possibility of an in vivo mitotic division of differentiated hypothalamic peptidergic neurosecretory cells. The absence of any signs of cytoplasmic dedifferentiation, as well as a poor development of spindle microtubules in this cell may be suggestive of a polyploidizing, possibly acytokinetic mitotic process occurring in such kind of cells.