PCNA positivity in the telencephalic matrix areas in the adult of a newt, Triturus carnifex.

Abstract

The Proliferating Cell Nuclear Antigen (PCNA) is an auxiliary protein of the DNA polymerase delta, belonging to the cyclin family, which attains appreciable levels only in those phases of the cell cycle in which DNA synthesis occurs. Using an immunocytochemical method that exploits this proliferative marker, we observed a certain PCNA positivity in the telencephalon of normal adult individuals of Triturus carnifex. The elements that display this peculiarity occupy an ependymal and/or sub-ependymal site. They are located in the anterior portion of the telencephalon only at the dorsal level and tend to decrease in number until they disappear temporarily as the intermediate portion is approached. In the posterior portion of the telencephalon, the dorsal labelling patterns, the size of which is however smaller than that observed more anteriorly, reappear and in the ventral region a large population of labelled cells appears. Then, again proceeding in a caudal direction, while the PCNA-positive elements lying dorsally diminish and disappear, they persist in the ventral region and gradually taper off until they final disappear where the telencephalic ventricles come together. This immunocytochemical picture supports the findings of other authors in adult Urodeles under both normal and experimental conditions (with classical and autoradiographic histological techniques) concerning the persistence of the telencephalon in dorsal and ventral germinative areas responsible for physiological and plastic neurogenetic events.