Fetal development of the pituitary gland in the beagle

Abstract

Background:The pituitary gland of the dog is different from all animals and is described as ''typical'' for mammals. How might this complex pituitary gland of the dog be formed in fetal life? The current study examined the fetal development of the complex and unique dog pituitary and the ontogeny of specific cell types in the pars distalis.Methods: Adenohypophysis of the beagle, from 25 to 60 days of gestation and at 2 days of age, was studied by immunocytochemical and histological staining.Results: At 25 days gestation, the primordium (Rathke's pouch) of the adenohypophysis began to form by an upward evagination from the epithelium of the primary oral cavity. At 38 days, the pituitary gland showed the same morphology as in adult dogs, being merely smaller. Five walls of Rathke's pouch (anterior wall [A], lateral walls [L], posterior wall [P], and upper wall [U]) were found at 25 days, and by 38 days they had specialized into specific regions of the adenohypophysis through complex and unique processes. The pars intermedia was derived from the U and the dorsal area of the A. The pars tuberalis was derived from the dorsal area of the A. The pars distalis was formed by more singular processes: the peripheral areas of the pars distalis were first formed by A and P; then the ventral lumen of the extensive Rathke's lumen surrounded by these areas was filled up by proliferation of cells, although the dorsal lumen remains as Rathke's lumen after 38 days. The blood capillaries may play an important role in the development of parencymal cells in the Rathke's pouch during canine fetal life. At 30 days gestation, the first adrenocorticotropic hormone cells were found in the anterior-and posterior-ventral regions (derived from middle and ventral areas of the A and the P) of the pars distalis anlage, and blood capillaries invaded the parenchymal cells from the mesencyme surrounding the anlage. At 38 days, portal vessels without capillary loops in the median eminence had appeared, and growth hormone and luteinizing hormone cells appeared in the ventral areas of A and P in the pars distalis. By 52 days, when capillary loops were seen in the portal vessels in the median eminence, these types of cells spread through the whole pars distalis.

Syndrome of inappropriate antidiuretic hormone secretion in a cat with a putative Rathke’s cleft cyst

“…Cells from the walls of Rathke’s pouch form the pars distalis, pars intermedia and pars tuberalis, and as formation of the pituitary gland is completed, a lumen known as Rathke’s cleft remains between the pars distalis and the pars intermedia. 19,21,22…”

“…Cells from the walls of Rathke's pouch form the pars distalis, pars intermedia and pars tuberalis, and as formation of the pituitary gland is completed, a lumen known as Rathke's cleft remains between the pars distalis and the pars intermedia. 19,21,22 In humans, RCCs are typically incidental findings on autopsy, and rarely cause clinical signs of headaches, visual disturbances and pituitary dysfunction. [5][6][7][8]20,23,24 RCC in dogs has been rarely associated with pituitary dwarfism, nasopharyngeal obstruction and aggressive behavior.…”

A Contracted DNA Repeat in LHX3 Intron 5 Is Associated with Aberrant Splicing and Pituitary Dwarfism in German Shepherd Dogs

“…Normally, the various cell types of the adenohypophysis arise in a distinct temporal order from progenitor cells. The corticotropic cells are the first to differentiate followed by gonadotropes, thyrotropes, lactotropes and somatotropes [1], [2]. Several of the transcription factors involved in the differentiation cascade of the endocrine cells of the pituitary have been identified [3].…”

Immunohistochemical Localization of Certain Inducers Related to the Proliferation of the Pituitary Gland and a Study on Cell Contacts between the Presumptive Neurohypophysis and the Adenohypophysis in the Foetal Mouse

“…For comparison purposes, the NL-IL boundaries were then examined using TEM in an attempt to couple the embryonic NL pituicytes with the IL cells. Sasaki & Nishioka, 1998). In the present study, stage II-IV foetuses were decapitated, and the head portions containing the developing pituitary gland were dissected and trimmed into blocks.…”