Gravitational effects on apoptosis of presumptive ectodermal cells of amphibian embryo

The effects of simulated microgravity (clinostat rotation at 6 rpm) on the presumptive ectodermal cells of amphibian embryos were examined. When morulae of Cynops pyrrhogaster developed under the influence of simulated microgravity, the thickness of the presumptive ectoderm was greater significantly. Embryonic cells isolated from the presumptive ectoderm of morulae were cultured for one day under the influence of simulated microgravity. The number of cells was greater after such clinostat rotation than in the control culture. TUNEL staining and electron microscopy revealed apoptotic cells both in embryos and among cultured cells, but the number of apoptotic cells was smaller in clinostat-treated embryos and cultured cells than in their controls. These results suggest that simulated microgravity suppresses apoptosis in the amphibian embryo, and as a result, affects the thickness of the presumptive ectoderm.