Possible occurrence of amitotic cell division during haemopoiesis in the Urodeles

The liver haemopoietic activity of three species of Urodeles (Triturus carnifex, Triturus alpestris and Speleomantes ambrosii) was examined by morphocytochemical approaches (light and electron microanti-BrdU immunocytochemistry, flow cytometry). The proliferation of haemopoietic cells, detected the anti-BrdU labelling index. was accompanied by absence of mitotic cell division and the appearance of cells showing features of amitosis (e.g. nuclear constrictions with bundles of electron-dense chromatin) sometime positive to the anti-BrdU immune-gold reaction. The possible unbalanced segregation of chromatin during the direct division of the nucleus was detected by flow cytometric measurement in terms of heterogeneous relative DNA content in peripheral blood cells. The presence in the bloodstream samples of cells (erythrocytes) with replicating DNA, nuclear constrictions and binucleations is also consistent with a situation of direct nuclear division.