CLOCK MECHANISM DETERMINING THE TIME OF TISSUE-SPECIFIC ENZYME DEVELOPMENT DURING ASCIDIAN EMBRYOGENESIS .1. ACETYLCHOLINESTERASE DEVELOPMENT IN CLEAVAGE-ARRESTED EMBRYOS

Abstract

Embryos permanently cleavage-arrested at the early cleavage stages with cytochalasin B were able to differentiate a histochemically detectable enzyme-muscle acetylcholinesterase (AChE). The early gastrulae arrested with colchicine or with colcemid could develop AChE. The clock which must be determining the time when AChE first appears is not apparently regulated by the events of cytokinesis nor does it seem to be controlled by the mitotic cycles of nucleus. DNA replication cycles may be the clock mechanism.