Immunohistochemical study on the development of the adenohypophysial cells in the lizard Gallotia galloti

Origin of adenohypophysial lobes and cells from Rathke's pouch in Swiss albino mice. Proliferation and expression of Pitx 2 and Calbindin D28K in corticotropic and somatotropic cell differentiation

A developmental study of the adenohypophysis of the mouse was carried out in response to several as yet unanswered questions about its organogenesis and differentiation. The main objectives were to establish the origin of adenohypophysial lobes and cells from the Rathke's pouch (RP) and elucidate the mechanisms of development and functional differentiation of the gland. Using diverse techniques, the morphological development, proliferation and differentiation were studied in order to delimit different proliferative regions in the RP, and provide a satisfactory explanation for the distribution of each cell type in the adult gland. Combining the proliferation and differentiation studies, corticotropic and somatotropic cells appear to mainly originate from undifferentiated precursors located within each of these proliferative regions. The involvement of transcription factor Pitx 2 and calcium-binding protein Calbindin D 28K in the differentiation of corticotropic and somatotropic cells is further clarified.

Immunohistochemical distribution of regulatory peptides in the human fetal adenohypophysis

We have studied here the cellular distribution of several regulatory peptides in hormone-producing cells of the human pituitary during the fetal period. Immunohistochemistry was used to show the expression of several regulatory peptides, namely Angiotensin-II, Neurotensin and Galanin, at successive gestational stages and their co-localization with hormones in the human fetal adenohypophysis. Somatotrophs, gonadotrophs and thyrotrophs were differentiated earliest. At gestational week 9, Angiotensin-II immunoreactivity was co-localized only with growth hormone immunoreactivity in somatotrophs, one of the first hormone-producing cells to differentiate. This co-localization remained until week 37. Neurotensin immunoreactivity was present in gonadotrophs and thyrotrophs in week 23, after FSH and TSH hormone differentiation. Galanin immunoreactivity was present in all hormone-producing cell types except corticotrophs. The different pro-opiomelanocortin-derived peptides were detected at different stages of gestation and adrenocorticotrophic hormone immunoreaction was the last to be detected. Our results show an interesting relationship between regulatory peptides and hormones during human fetal development, which could imply that these peptides play a regulatory role in the development of pituitary function.

Origin of adenohypophysial lobes and cells from Rathke's pouch in chicken (Gallus gallus) and Japanese quail (Coturniz coturniz japonica). Expression of calcium-binding proteins

A histological and immunochemical study of adenohypophysis development in two bird species: chicken (Gallus gallus) and Japanese quail (Coturnix coturnix japonica) was carried out, focussing firstly morphologically on the origin of its different lobes, then secondly on the differentiation of hormone-producing cells from the adenohypophysial anlage and their involvement in the differentiation of three calcium-binding proteins. The results of the morphological development study show how the origin of the adenohypophysis in chicken is totally ectodermic, whilst in Japanese quail the endoderm, in the form of Sessel's pouch, participates in forming the rostral zone of the anterior lobe. After studying the organogenesis and spatio/temporal differentiation of the hormone-producing cells proceeding from the adenohypophysial anlage, a regionalization model is proposed for the origin of the different lobes and cell types as well as time sequence, fundamentally the origin of cell regionalization in the adult adenohypophysis. In this process, at least in the two bird species studied, the results obtained from expressing the calcium-binding proteins, calbindin D 28K, calretinin and parvalbumin show a characteristic distribution pattern for each, suggesting distinct functions.

Role of the adrenal gland in early post-hatching differentiation of alternative male phenotypes in the tree lezard (Urosaurus ornatus)

During development, sex steroids are important in establishing differences between males and females. However, sex steroids also are involved in the development and maintenance of individual differences in morphology and behavior within each sex. As adults, male tree lizards (Urosaurus ornatus) exhibit alternative reproductive tactics correlated with dewlap (throat fan) coloration. Males with orange-blue dewlaps are aggressive and territorial, whereas males with orange dewlaps are less aggressive and employ a satellite strategy. Dewlap coloration develops within the first 90 days after hatching and remains fixed throughout life. Recent work demonstrates that individual males differ in progesterone and testosterone secretion during development, suggesting that these hormones regulate the development of alternative male phenotypes. The current work uses in vitro incubation of adrenal and gonadal tissues to identify the source of progesterone and testosterone during the period of male differentiation and to follow ontogenetic changes in hormone release. The results indicate that, in all developmental stages sampled, adrenal incubations primarily contain progesterone and corticosterone whereas gonadal incubations contain primarily testosterone. These data indicate that the hatchling adrenal is the primary source of progesterone during early post-hatching development. Since progesterone has been demonstrated to play a role in the establishment of individual differences in morphology and behavior in male tree lizards, our results suggest that the hatchling adrenal gland plays an important role in post-hatching development of alternative male phenotypes.

Immunohistochemistry and tinctorial affinity of adenohypophysial cells of the rat snake Ptyas mucosus (Colubridae)

Immunocharacteristics of the adenohypophysial cells of the rat snake Ptyas mucosus (Colubridae) were studied with an unlabeled antibody enzyme technique (PAP method) using rabbit antisera against mammalian/synthetic hypophysial hormones. Adenohypophysial cells were identified on the basis of their specific immunoreactivity with various heterologous antisera. As in other reptiles, there was regional localization of pars distalis (PD) cell types in this snake. The gonadotropic (GTH) cells were identified by their specific immunoreactivity with anti-porcine (p)LH beta serum and were distributed uniformly throughout the PD. The thyrotropic (TSH) cells, recognized by their specific immunoreactivity with anti-human (h)TSH beta serum, were found in the medial PD. The prolactin (PRL) and growth hormone (GH) cells were revealed by their specific immunoreactivity with anti-ovine (o)PRL and anti-hGH sera, respectively; the former were confined to the anterior two-thirds of the PD, and the latter were restricted to the posterior third of the PD. The corticotropic (ACTH) cells, identified by their specific immunoreactivity with the anti-ACTH1-24 serum, were localized in the anterior two-thirds of the PD. Though both ACTH and PRL cells were confined to the same area of the PD, they could be distinguished by their distinctive morphology and distribution pattern. Cells of the pars intermedia were revealed by their immunoreactivity to anti-alpha MSH (melanophore-stimulating hormone) and anti-ACTH1-24 sera. Among each adenohypophysial cell type, there was variation in the intensity of immunoreactivity and morphological features, which may be due to their heterogeneity, reflecting various stages of cellular activity. Unlike most other snake species, the occurrence of a rudimentary pars tuberalis in P. mucosus containing a few immunoreactive GTH and TSH cells appeared to be a novel finding. The occurrence of the PRL-like and TSH-like immunoreactivity seen in certain neuronal perikarya and fibers of the hypothalamus and median eminence conforms with earlier observations in other tetrapods. To resolve certain discrepancies in the literature, the tinctorial affinities of immunohistochemically identified adenohypophysial cell types of P. mucosus were studied using various conventional staining methods and were compared with those of other reptilian species studied earlier, including snakes of the family Colubridae.