Structural alteration of the target plasma membrane affects reception but not expression of the neural inductive signal

We have previously reported that incubation of presumptive neuroectoderm in a solution of lectin (soybean agglutinin or garden pea agglutinin at 50 micrograms ml-1, 30 min) prior to its association with blastoporal lip inhibits neural induction (Duprat et al., 1982). We have also shown that incubation of presumptive ectoderm immediately after its association with blastoporal lip does not prevent neural induction. The same pattern of fluorescence on the ectodermal surface was observed when incubation with lectin was carried out before or after association of ectoderm with blastoporal lip. Although a particular molecular organization of the plasma membrane of the target ectoderm appears to be essential for reception or initiation of neural induction, the subsequent transmission and expression of this neural information does not appear to be affected by structural modifications of the target membrane. Similar studies performed using the inducer Con A indicated that the experimentally induced signal differed from the natural one.