Normal development of the pituitary in the opossum and its responses to hormonal treatments

The structure of various sense organs and endocrine glands was examined in the stripe-faced dunnart, Sminthopsis macroura. This marsupial has the shortest gestation known for all mammals, 10.5–11 days. The morphology of the anterior pituitary, adrenal gland, olfactory epithelium, Merkel cells around the mouth and the utricle of the vestibular system of S. macroura was similar to that observed in other newborn marsupials. These structures are thought to be required by the newborn to transfer from the uterus to the pouch. The stage of development of the urinary system, the semicircular canals of the vestibular system, eyes and lungs was slightly different to that of other newborn marsupials. These structures are thought to have secondary importance in allowing the newborn to reach the teat. Although marsupials display variation in gestation length and produce newborn of differing body weights, there is little difference in morphology between various newborn marsupial species

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“…In D. virginiana [Wheeler, 1943], D. viverrinus (Hill and Hill, 1955] and M. rufogriseus [Walker and Rose, 1981] as in . S'.…”

Section: Discussionmentioning

confidence: 99%

Structural Development in the Newborn Marsupial, the Stripe-Faced Dunnart, <i>Sminthopsis macroura</i>

Gemmell

Selwood²

1994

Cells Tissues Organs

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“…17 mm), the wombat, Phascolomys mitchelli (G.L. 15.5 mm, 17.5 mm) (Parker, 1917), and the opossum (Wheeler, 1943). Differentiation is in progress in cells of the wallaby M. rufogriseus pars distalis at birth; and although mitoses are occasionally seen, the cells exhibit differential nuclear and cytoplasmic staining, and many contain membrane-bound, electron-dense granules and profiles of rough endoplasmic reticulum.…”

Section: Discussionmentioning

confidence: 96%

“…Cellular differentiation of the marsupial pituitary is reportedly absent in the neonate of the short-tailed wallaby, Set@ nix setosus (syn. S. brachyurus, Hanstrom, 1954) and until 1 1 days after birth in the opossum, Didelphis uirginiana (Wheeler, 1943). The ultrastructure of the pituitary cells of the newborn M. rrtfogriseus will be examined to determine whether the gland is capable of granule synthesis at birth.…”

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confidence: 99%

Organogenesis of the pituitary, adrenal, and lung at birth in the wallaby, Macropus rufogriseus

Walker¹,

Gemmell²

1983

Am. J. Anat.

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The ultrastructure of the pituitary, the adrenal, and the lung was examined in the newborn wallaby, Macropus rufogriseus. Tissue from six wallaby neonates (less than 8 hr of age), two near-term fetuses (26 days after removal of suckling pouch young [RPY]), and a two-day-old pouch young was examined; and tissue levels of cortisol in the adrenal glands of five neonates and a near-term fetus (26 days) were measured by radioimmunoassay. At birth the adenohypophysis comprised the bulk of the pituitary gland. The pars distalis was well vascularized and many cells contained electron-dense, membrane-bound granules. The adrenal glands lacked specific zones but comprised two distinct populations of cells. The cytoplasm of one cell type contained electron-dense, membrane-bound granules, similar to those observed inside catecholamine-secreting cells of the adrenal medulla; the other cell type possessed large amounts of smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae. These features are characteristic of cells which are actively synthesizing steroid hormones. The concentration of cortisol was 0.58 ng/adrenal in the wallaby at birth. The fetal lungs near term were at the glandular stage of development, and epithelial differentiation of type I and type II pneumocytes was imminent although attenuation was not evident. The canalicular neonatal lung did not contain true alveoli, but type II pneumocytes contained osmiophilic lamellar inclusions of surfactant. The fetal pituitary and adrenal are functional at birth and are thus capable of initiating parturition and of influencing lung maturation in the fetus.

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“…Such changes cannot be regarded as being primarily degenerative since they also occur under normal physiological conditions as, for example, in the opossum (Didelphys virginiana) at the time of onset of gonad maturation (Wheeler, 1943).…”

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confidence: 99%

Discussion on the Functional Activities of the Basophil Cells of the Pituitary Gland

Ds³

et al. 1956

Proceedings of the Royal Society of Medicine

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TBE object of this paper is to summarize the present state of knowledge concerning the conditions which give rise to hyalinization of basophil cells and to the formation of basophil cell adenomata in the rat pituitary. The hyalinization and basophil adenomata which are found in the human pituitary in cases of the Cushing syndrome will be discussed in the light of the implications of the observations which have been made in the rat.Three types of basophil cell in the rat.-In the pars distalis of the rat pituitary there are three types of glycoprotein-containing cell, each type containing a specific glycoprotein in the form of cytoplasmic granules which are considered to be the storage form of one or other of the three glycoprotein hormones-thyrotrophin, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). The names "thyrotrophs", "FSH cells", and "LH cells" have been given to these specific cell types, each of which is considered to be concerned exclusively with the secretion of its appropriate hormone (Purves andGriesbach, 1951, 1954). Since the glycoprotein granules of all three types in the rat pituitary stain blue with about the same intensity by trichrome staining methods, they were, in the period before their diversity was recognized, referred to collectively as "the basophil cells".Hyalinization in basophil cells.-In certain mammalian species, including the rat, rabbit, dog and opossum, the occurrence of hyalinization is observed in basophils during states of high secretory activity such as occur particularly after castration or thyroidectomy.Such changes cannot be regarded as being primarily degenerative since they also occur under normal physiological conditions as, for example, in the opossum (Didelphys virginiana) at the time of onset of gonad maturation (Wheeler, 1943).-Electron-micrograph studies.-The electron-micrograph studies of Farquhar and Rinehart (1954a, b) on the rat pituitary show that the basophil cells contain small ovoid vesicles. It is in these vesicles that hyaline accumulation primarily occurs. The large ,hyaline-filled vesicles which are observed in the rat basophils in the later stages of hyalinization are formed by a secondary coalescence of these small vesicles to form large spaces.Hyalinization after thyroidectomy.-Hyalinization occurring in the rat pituitary after thyroidectomy affects only the thyrotrophs. These cells undergo almost complete degranulation in the first forty-eight hours after thyroidectomy, and thereafter enlarge rapidly. Hyalinization is observable as early as six days after thyroidectomy and takes the form of a large number of small hyaline-containing vesicles which subsequently undergo distension and coalescence until three or four large, irregular, thin-walled, hyaline-filled spaces result (Purves and Griesbach, 1956a). Hyalinization of thyrotrophs after exposure of rats to cold.-In rats exposed to a temperature of 4-C. for fourteen days, a small proportion of the thyrotrophs show an annular zone of small hyaline-filled vesicles with retention of ...

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Normal development of the pituitary in the opossum and its responses to hormonal treatments

Cited by 17 publications

References 37 publications

Structural Development in the Newborn Marsupial, the Stripe-Faced Dunnart, <i>Sminthopsis macroura</i>

Structural Development in the Newborn Marsupial, the Stripe-Faced Dunnart, <i>Sminthopsis macroura</i>

Organogenesis of the pituitary, adrenal, and lung at birth in the wallaby, Macropus rufogriseus

Discussion on the Functional Activities of the Basophil Cells of the Pituitary Gland

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