Early Reciprocal Interactions between Ectoderm and Chordamesoderm: Statistical Evaluation of Classical Embryological...

Embryos of the urodele Ambystoma mexicanum were used in time set experiments for the analysis of ectoderm-chrodamesoderm interactions in "primary embryonic induction". The influence of chordamesoderm-age (CM-age), ectoderm-age (CM-age), ectoderm-mass (E-mass) on differentiation processes were investigated. The results revealed that early interactions exist, which, however, seem to be dominated by the ectoderm in various respect: a) the segregations of the CNS is due to the autonomous change in ectoderm competence phases; b) based on the temporal sequence of competence phases, influences are exerted by the ecto-neuroderm which support the chordamesoderm in its self-differentiation capability to chorda and other mesodermal tissues. Consequently, reciprocal impulses from these newly differentiated tissues are warranted (feedback to ectoderm); c) co-ordination of the cranialization effect and corresponding ectodermal competence phase is achieved; d) the inductive efficiency of the chordamesoderm is strongly supported. Three statistical tests (regression, correlation, information analyses) were conducted (dependant variables: quality and quantity of the differentiated structures; independant variables: experimental factors). All three tests equally rendered statistical significance for the following order of decreasing importance the experimental factors play in induction and differentiation processes: E-age, E-mass, CM-age.