Evolution of the lumbo-sacral neural crest in the avian embryo: Origin and differentiation of the ganglionated nerve of Remak studied in interspecific quail-chick chimaerae.

Isotopic and isochronic transplantation of fragments of quail neural tube into chick demonstrates that neural and glial cells of the entire ganglion of Remak (RG) arise from the lumbo-sacral level of the neural crest.The ganglioblasts first accumulate in the mesorectum (stage 24 of Hamburger and Hamilton, in the chick and I8 of Zacchei in the quail) and subsequently migrate cranially.Histochemical studies have been carried out on the rectal and cloacal parts of the quail RG at various stages of development. Cholinesterase activity can be detected as soon as the primordium is in place and the intensity of the reaction increases rapidly. During morphogenesis of the cloacal region the RG and the pelvic plexus become intimately associated. Catecholamine-containing cells are found first in the pelvic plexus, then in the cloacal part of the RG. Fluorescent cells are often grouped close to blood vessels and associated with non-fluorescent ganglia. Cranial to the level of the bursa of Fabricius, the RG is composed only of non-fluorescent neurons whatever the developmental stage considered (up to 1 day after hatching).The developmental capabilities of the RG of the 5-day quail have been tested by transplanting various parts of the hind-gut with the dorsal mesentery onto the chorio-allantoic membrane. Catecholamine-containing cells develop only in grafts including the cloacal region.By using quail-chick chimaerae in which the RG belongs to the quail while mesentery and gut are of chick origin, it was possible to show that neurons which develop in the graft (i.e. in the absence of preganglionic innervation), send nerve fibres into the gut wall. Moreover some neuroblasts located in the primordium of the RG migrate into the gut wall and give rise to some enteric ganglion cells. The contribution of the lumbo-sacral neural crest to the enteric ganglia, by this route, is discussed.