... formation. There are two possible hypotheses to account for this failure: (i) a functional infection organiser is not formed and therefore the positional cues are not provided; (ii) the positional cues are produced, but hcl mutants are unable to respond to this positional signalling. Both possibilities...

... CNRS and College de France, 49 bis Avenue de la Belle Gabrielle, 94736 Nogent-Sur-Marne, France 07 08 1997 © 1997 by Company of Biologists 1997 Sonic Hedgehog chick embryo vertebrate limb development bone morphogenetic proteins positional signalling A fundamental...

... with positional signalling in vertebrate development and suggests that int-1 normally operates in some aspect of this. Fig. 7. Development of Xenopus neurulae following injection of mouse int-1 mRNA into the fertilized egg. Fertilized Xenopus eggs were injected with synthetically derived, defective...

...L. Wolpert; Amata Hornbruch ABSTRACT The positional signal model for specification of the cartilaginous elements in limb development has been tested by examining the effect on the humerus of grafting a polarizing region to different positions along the anteroposterior axis of the limb bud at stage...

.... At stage 10 the activity disappears from the node and is found both posterior to the node and in the future wing region of the flank. The ability of Hensen’s node to generate a positional signal suggests that the signal in the limb and early embryo may be similar. The results support the view...

... of an avian limb positional signalling region . J. Embryol. exp. Morph . 71 , 223 – 232 . Honig , L. S. ( 1983a ). Polarising activity of the avian limb examined on a cellular basis . Prog. Clin. biol. Res . 110 , 99 – 108 . Honig , L. S. ( 1983b ). Does anterior (non...