title: Pituitary melanotrope cells of Xenopus laevis are of neural ridge origin and do not require induction by the infundibulum.
abstract: Classical studies in amphibians have concluded that the endocrine pituitary and pars intermedia are derived from epithelial buccal epidermis and do not require the infundibulum for their induction. These studies also assumed that the pituitary is not subsequently determined by infundibular induction. Our extirpation, auto-transplantation and immunohistochemical studies with Xenopus laevis were initiated to investigate early presumptive pituitary development. These studies were conducted especially with reference to the pars intermedia melanotrope cell's induction, and its production and release of α-melanophore stimulating hormone (α-MSH) from the precursor protein proopiomelanocortin (POMC). Auto-transplantation studies demonstrated that the pituitary POMC-producing cells are determined at a stage prior to pituitary-infundibular contact. The results of experiments involving the extirpation of the presumptive infundibulum also indicated that the infundibulum is not essential for the differentiation of POMC-producing cells. We also demonstrated that early pituitary development involves adherence to the prechiasmatic area of the diencephalon with the pituitary placode growing in a posterior direction toward the infundibulum where contact occurs at Xenopus stage 39/40. Overall, our studies provide a model for early tissue relations among presumptive pituitary, suprachiasmatic nucleus, pars tuberalis and infundibulum during neurulation and later neural tube stages of development. It is hypothesized that the overlying chiasmatic area suppresses pituitary differentiation.
authors.affiliation: Dept. Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Faculty of Science, Heyendaalseweg 135, Nijmegen, The Netherlands. gerald.eagleson@loras.edu
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Eagleson
authors.forename: Martijn M
authors.initials: MM
authors.lastname: Selten
authors.forename: Eric W
authors.initials: EW
authors.lastname: Roubos
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Jenks
mesh_terms: D000818:Animals; D052717:Melanotrophs / Q000166:cytology*; D010904:Pituitary Gland, Posterior / Q000166:cytology / Q000196:embryology / Q000254:growth & development*; D014982:Xenopus laevis / Q000196:embryology / Q000254:growth & development*