EFFECTS OF NEIGHBOURING TISSUES ON DETERMINATION AND DIFFERENTIATION OF NOTOCHORD CELLS IN XENOPUS LAEVIS
Zeng Mi-bai (Tseng Mi-pai) Wu Zhi-li (Shanghai Institute of Cell Biology, Academia Sinica, Shanghai, 200031
By using in vitro coculture technique, the effects of presumptive somites and neuroepithelium on the determination and differentiation of notochord have been studied. Fig. 1 is the schematic diagram showing tissues explanted and cocultured. In the control series, presumptive notochord was explanted and differentiated mainly into muscle with few notochord cells. In the series of coculture with somites of two sides, it has been found that the later provided sufficient condition for the determination and differentiation of notochord which displayed the typical vacuo-lated appearance (Plate I, Fig. 2). If only somite of one side was cocultured, its effect was insufficient. When the presumptive notochord was in direct contact with neuroepithelium alone, not only the notochord became reduced in size but also, in some cases, it remained at early stages of development (stage of a pile of coins or stage of the beginning of vacuolation) (Plate I, Figs. 6,7,9 and 10): but in the presence of neuroepithelium when it was in association of muscle, the notochord became well differentiated (Plate Ⅱ Fig. 8). The complicated relationships during the early development of the axial organs have been discussed.