Structure of the pars distalis in pouch-young tammar wallabies (Macropus eugenii)

Abstract

The pars distalis of pouch-young wallabies (Macropus eugenii) aged 1 to 50 days was studied by means of light-microscopic immunohistochemistry and electron microscopy. In the pars distalis of these pouch-young presumptive somatotrops, which constituted up to 70% of the gland, and nongranulated cells were the most numerous cell types. Small numbers (together representing less than 30% of the pars distalis) of immunoreactive mammotrops, thyrotrops, gonadotrops and corticotrops were also found. The presumptive mammotrops, gonadotrops and thyrotrops increased in number and apparent activity between 1 and 50 days postpartum. Presumptive corticotrop cells in 25 to 30 day-old animals were relatively most numerous, and apparently more active than at any other stage of pouch life; these cells decreased in apparent activity and relative number in older animals. The changes in number and activity of cell types in the pars distalis correlated well with major developmental events such as the onset of adrenal activity, the rapid growth phase in the first 100 days postpartum, and the generally low thyroid activity in pouch-young of less than 50 days of age.

Immunohistochemical Identification of Cell Types in the Pars Distalis of Harp Seals, Phoca groenlandica

“…Immunoreactive somatotrop, mammotrop, thyrotrop, gonadotrop and corticotrop cells were present in considerable numbers in neonatal harp seals. This observation is in accord with similar studies in a number of other mammals including rodents, primates and marsupials (Setalo and Nakane 1972, 1976, Watanabe et al 1973, Dupouy and Magre 1973, Dearden and Holmes 1976, Kaplan et al 1976, Forest et al 1976, Thompson and Trimble 1976, Baker and Yu 1977, Matsumura and Daikoku 1977, Chatelain et al 1979, Daikoku et al 1980, Begeot et al 1978, 1981, Currie et al 1981, Goodyer 1981, Leatherland and Renfree 1983. Even within the neonatal period there was a discernible increase in the numbers of mammotropic and somatotropic cells, and there were marked differences in apparent cell activities and cell size (Table 1) between neonates and juvenile and adult animals.…”

Cortisol in Fetal Fluids and the Fetal Adrenal at Parturition in the Tammar Wallaby (Macropus eugenii )1

“…Cortisol synthesis by the fetal adrenal of the tammar is stimulated by PGE 2 in vitro, suggesting an adrenocorticotrophic role for increased placental PGE 2 production during parturition in this marsupial [15,16]. Cortisol synthesis by the fetal adrenal in vitro is also stimulated by ACTH, which suggests that the corticotrophs in the pituitary [11] may stimulate cortisol as in eutherians [28,29].…”