Follicles and related structures in the pars intermedia of the adenohypophysis of the jird (Meriones unguiculatus)

Two types of follicle composed of non-granulated cells are regularly found in the pars intermedia of the mature jird (Meriones unguiculatus). A few (Type I) are large and cystic with a flattened epithelium bearing some microvilli, but most (Type II) are small and irregular in shape with a cuboidal to low columnar epithelium bearing many microvilli. They are apposed to the granulated chief cells, and contain a strongly PAS-positive material, but no cell debris. The Type II follicles also show crystalloid strands or chains. Villous projections sometimes protrude from the pars nervosa into the follicular lumen. The follicular cells show pinocytotic vesicles, complex interdigitations and invaginated nerves.

Effect of long-term treadmill running on gonadal activity in female rats

Histochemical studies of delta5-3beta-HSD and G-6-PD activities in the ovaries of female rats undergoing long term-treadmill running showed a marked reduction. This change was associated with increased concentration of total cholesterol and total ascorbic acid in the same organ. All these results suggest ovarian hypoactivity.

Development and cytodifferentiation of the rabbit pars intermedia. II. Neonatal to adult

Material from pars intermedia obtained from rabbits ranging from the second week post-partum to the adult stage, and including specimens from pregnant animals, was studied. The rate of cell division became greatly reduced early in postnatal) development. The commonest type of cell (the pars intermedia-glandular cell) becomes increasingly PAS-positive during the early stages of development. Although by 35 days differentiation of all the ACT-type cells is complete, the pars intermedia-glandular cells take as long as 53 days to mature. The epithelioid border of the hypophysial cleft persists throughout life, commonly containing dark cells. A ciliary fringe frequently appears in neonates and persists in pregnancy. Possible functions of such cilia are discussed. Throughout development the fine structure of the vasculature was studied. Secretory granules resembling those within the cells were seen in and around the blood vessels, and the mode of endocrine secretion in the pars intermedia tissue is discussed. The pars intermedia-glandular cells of the pregnant rabbits appeared hyperactive. The functional significance of the mammalian pars intermedia is discussed.

Histological and ultrastructural studies of the rabbit pars intermedia in organ culture. I. Adult and young adult tissue

Fuuly differentiated rabbit pars intermedia has been maintained successfully for over six weeks as organ culture. PI-glandular cells are the commonest type throughout the culture. They retain their differential condition for at least five weeks. Autoradiography indicates that cell division occurs in cultures for at least two weeks. Dense granules are seen in the intercellular, perivascular and vascular spaces and are taken to indicate secretory activity under the conditions of culture. Some interstitial cells remain recognisable throughout the culture and ACT-type cells for more than two weeks. Other interstitial cells lose their usual appearance and become peripheral dark cells. Modification of cytoplasmic organelles, including distortion and darkening of mitochondria, increase in intracellular filaments and enlargement and liberation of the content of the PI-vesicles are reported.

Histological and ultrastructural studies of the rabbit pars intermedia in organ culture. II. Developing tissue

Pars intermedia (PI) tissue from fetal, perinatal, neonatal and juvenile rabbits has been maintained in organ culture for up to nine weeks after explantation. Autoradiography showed that DNA synthesis took place for at least 22 days of culturing. PI-glandular cells and interstitial cells remain identifiable throughout this period but ACT-type cells were recognised only up to six weeks. Material from fetal and perinatal animals had a higher proportion of surviving cells than that from adult animals. The degree of differentiation achieved by PI-glandular cells in vitro appears to depend on three factors: i) the stage of development reached before explantation; ii) the original topographic position in the PI tissue before explantation; and iii) the position in the explant in relation to the gas-liquid interphase.

The effect of culture on ultrastructure of dissociated rabbit adenohypophysial cells

Cells from the rabbit pars distalis and pars intermedia have been cultured in several ways. In clump cultures the glandular adenohypophysial cells of the primary clump remain identifiable for long periods. Both acidophil and mucoid cells can be maintained in this way for over 50 days. During this time two different modes of granule extrusion are observed, one being found only in acidophil cells and the other being exclusive to mucoid cells. From this it is concluded that specific release of secretory products from these cells can occur in the absence of hypothalmic control. A special form of collagenous fibre is produced in clump cultures. Monolayer cell cultures are derived either from isolated adenohypophysial cells or from secondarily aggregated clumps, but in either case the predominant cells are fibroblasts, which persist for over 50 days (as isolated cultures) and for over 90 days (as spreads from clumps). Rounded cells can be recognized as a separate type in isolated cell culture.

Development and cytodifferentiation of the rabbit pars intermedia. I. Fetal and perinatal stages

The developing pars intermedia (PI) of rabbits of between 14 days post coitum (PC) and one day post partum (PP) have been studied by light and electron microscopy. Cell division is marked until 4th week PC, after which it is reduced. The (PI) loses its homogeneity by the 5th week PC due to localisation both intrinsic and invading cells and blood vessels. Four groups of parenchyma cells are recognisable: PI-glandular cells, interstitial cells, ACT-type cells and a heterogeneous group of dark cells. The ultrastructure of the ACT-type cells in the rabbit PI are here described for the first time. The differentiation of these cell types has been traced from 14 days PC to 32 days PC, in particular ACT-type cells are shown to develop in situ and the significance of this is discussed. In the PI-glandular cells dense cored granules appear first on the 15th day PC which is one day before any nerve connection is made with the primitive neural lobe and more than a week before vascularisation. Thereafter granularity increases until parturition when there is a phase of degranulation. Relatively electron lucent, larger vesicles are not found until 4th week PC.

Ultrastructural studies on the intranuclear inclusions of the rabbit adenohypophysis in vivo and in vitro

Intranuclear inclusions of three basic types are described in various parts of the rabbit adenohypophysis in vivo and in organ and cell cultures. These inclusions are mostly found in the postnatal tissue but occur in both glandular and non-glandular cells. A comparison is made with similar structures encountered elsewhere. Their significance is not known.

Extracellular banded structures in cultures of the rabbit adenohypophysis

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