title: Two histospecific enzyme expressions in the same cleavage-arrested one-celled ascidian embryos.
abstract: Fertilized eggs of the ascidian, Ciona intestinalis, were prevented from undergoing cytokinesis but not nuclear division by treatment with cytochalasin B. After appropriate times, such cleavage-arrested multinucleate zygotes developed acetylcholinesterase of larval tail muscle and an alkaline phosphatase ordinarily localized in the larval endoderm tissues. Separate histochemical reactions on one of a pair of samples taken from the eggs of single animals provided examples (6/34) in which the numbers of cytochalasin-treated embryos displaying the respective reaction product overlapped sufficiently (15-29%) to indicate that some of the zygotes had developed both enzymes in the same uncleaved single cell. With an actual dual-staining technique that can be applied to single cleavage-arrested zygotes, 62% of those developing a strong alkaline phosphatase reaction also had a strong acetylcholinesterase reaction. In other experiments, quantitative measurements of enzyme activity in homogenates of 114 single cleavage-arrested zygotes confirm directly that 18% of the zygotes produce both enzymes. There was no obligatory mutual exclusion of the potential for simultaneous expression of two tissue-specific characteristics that would ordinarily be segregated into different lineages during early cleavages. The cytoplasmic determinants believed responsible for these histotypic expressions can apparently function independently in the same cell.
authors.affiliation: Laboratory of Developmental Genetics, Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
authors.forename: J R
authors.initials: JR
authors.lastname: Whittaker
authors.forename: T H
authors.initials: TH
authors.lastname: Meedel
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis*; D000469:Alkaline Phosphatase / Q000032:analysis*; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D006651:Histocytochemistry; D014561:Urochordata / Q000196:embryology* / Q000201:enzymology; D015053:Zygote / Q000201:enzymology
chemical_list: D000110:Acetylcholinesterase; D000469:Alkaline Phosphatase