Changes in the interior surface of newly mesodermalized ectoderm and its contact activity with competent ectoderm in the newtCynops (Amphibia)

Abstract

The presumptive ectoderm (pE) ofCynops gastrulae was artificially mesodermalized by contact with teleost swimbladder. The newly mesodermalized ectoderm (mE) acquired the capacity for neural induction (Suzuki et al. 1986a). SEM observations revealed that the mE cells altered their cellular profiles immediately after mesodermalization. The characteristics of the cell surface and the cell architecture became similar to those of invaginated mesoderm cells. There were distinct differences in the cellular contact between mE-pE and pE-pE combinations. The mE-pE combinations kept close contact at their interior surfaces, while the pE-pE combinations did not keep contact. Both TEM and SEM observations also indicated that there were tight contacts between mE and pE cells. These findings suggest that neural-inducing activity of the newly mesodermalized ectoderm cells is coupled with acquisition of cellular affinity toward the interior surface of competent ectoderm cells, and probably requires close cell contacts.

Comparative study of sequential expression of the organizer‐related genes in normal Cynops pyrrhogaster embryos and mesodermalized ectoderm

“…It is also well‐known that basic FGF (bFGF) activates bra expression without any expression of gsc in both C. pyrrhogaster and X. laevis animal caps (Takabatake et al 1996; Conlon & Smith 1999); particularly in dispersed animal cells (Smith et al 1991). The isolated and cultured ectodermal cells are also rearranged (Suzuki et al 1991). These observations suggest that Xbra has some connection with the changes in cell shape and mobility during cell differentiation (Yamada 1994; Conlon et al 1996).…”

Expression of a Novel Matrix Metalloproteinase Gene during Cynops Early Embryogenesis

“…When the animal cap was artificially mesodermalized by the swim bladder (15,16), the gene was activated in the FIG. 2.…”

“…There are various shapes of pseudopodia, including blebs, filopodia, and lamellipodia, on the interior (blastocoelic) surface of the early Cynops gastrula (16). The interior surface of the competent ectoderm contains a network of fine fibrous processes, and the mesodermalized ectoderm cells acquires cellular affinity toward the interior surface of competent ectoderm cells concomitant with a change of the cell surface features (16).…”

“…The interior surface of the competent ectoderm contains a network of fine fibrous processes, and the mesodermalized ectoderm cells acquires cellular affinity toward the interior surface of competent ectoderm cells concomitant with a change of the cell surface features (16).…”

“…During gastrulation, the involuted mesodermal cells migrate along the fibril network on the interior surface of the overlying competent ectoderm (16,17). Many studies have indicated that these fibrils contain glycoproteins, fibronectin, laminin and other components (18,19).…”