Development of the Adrenal Gland in the Tammar Wallaby, Macropus Eugenii (Desmarest) (Marsupialia: Macropodidae).

Call, R. N.; Catling, P. C.; Janssens, P. A.

doi:10.1071/zo9800249

Cited by 12 publications

(5 citation statements)

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“…A t this stage of development a thin cortex incompletely surrounds a large medulla (Leslie, 1979). A similar finding has been reported for the tammar wallaby since, although some cells display chromaffin reaction on day 7 of pouch life, a distinct medulla is not found until day 60 (Call et al, 1980). After studying the hour of birth in rats, Lincoln and Porter (1976) suggested that the fetus may determine the day of birth in this species through the maturation of the pituitaryadrenal-placental axis, but the mother may hour of birth.…”

Section: Discussionsupporting

confidence: 74%

Ultrastructural evidence for steroid‐hormone production in the adrenal of the marsupial, Isoodon macrourus, at birth

et al. 1982

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To determine whether the adrenal gland of the bandicoot is actively producing steroid hormones at birth, the cellular structure was examined by electron microscopy, and the concentration of cortisol in the gland was determined by radioimmunoassay. Two distinct cell populations were seen in the adrenal gland. One group of cells possessed dark staining granules, normally observed in catecholamine-secreting cells, and the second group contained large amounts of smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae. Both features are characteristic of steroid-secreting cells. A concentration of 0.094 ng of cortisol per adrenal was determined by pooling glands from nine individual newborn bandicoots. This evidence of cortisol secretion from the bandicoot adrenal at birth indicates that, as in many eutherians, the marsupial adrenal may play an important role in determining the length of gestation.

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Section: Discussionsupporting

confidence: 74%

Ultrastructural evidence for steroid‐hormone production in the adrenal of the marsupial, Isoodon macrourus, at birth

et al. 1982

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“…Beyond this time there is a marked increase in milk consumption and body weight, so that by 200 days the average intake of milk is about 50 ml/day (Green, 1984). These changes in milk intake and composition probably reflect the increasing energetic requirements of the young which, between 100 and 200 days, achieves homeostasis; its thermoregulatory and metabolic functions develop (Setchell, 1974;Paton & Janssens, 1981) and the thyroid, adrenal and pituitary glands begin to secrete their respective hormones (Setchell, 1974;Call, Catling & Janssens, 1980;Wilkes, 1984). Furthermore, it is during this period that the incremental growth rate of the young accelerates (W. E. Poole, personal communication), closely paralleling the accelerated growth of the active mammary gland (Stewart, 1984) and the rising level of plasma prolactin.…”

Section: Discussionmentioning

confidence: 99%

Seasonal and circadian patterns of circulating prolactin during lactation and seasonal quiescence in the tammar, Macropus eugenii

Hinds¹,

Tyndale-Biscoe²

1985

Reproduction

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Prolactin was measured in peripheral plasma of female tammars once a week for 14 months and every 2 months it was measured in a subgroup of 7 tammars at hourly intervals for 28 h to determine short-term changes in concentration. During the course of the study 6 females gave birth in January/February and reared their young to weaning in October-November, while another 4 gave birth 1.5-3.0 months later and weaned their young in November-December. Concentrations of prolactin were less than 40 ng/ml in a non-lactating animal and for the first 140 days of lactation in the others. Between 140 and 180 days of lactation the concentrations of prolactin fluctuated between 10 and greater than 100 ng/ml and thereafter remained high until the young vacated the pouch for the last time at about 250 days. After pouch exit the concentrations declined to about 40 ng/ml even though lactation continued for a further 21-35 days. Although the short-term patterns of prolactin concentrations showed no consistent relationship between light-dark phases there was an increase in the magnitude and duration of peaks of plasma prolactin which correlated with the stage of lactation. Removal of pouch young aged between 203 and 242 days for 24 h resulted in a rapid decrease in plasma prolactin concentration which was reversed when the young was returned to the pouch, indicating that the high levels of prolactin in the second half of lactation may be maintained by the sucking stimulus of the pouch young. This period of lactation, therefore, may be equated with lactation in eutherians, but there appears to be no eutherian equivalent to early lactation in the tammar.

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“…Despite their small size and immaturity at birth, the same is true in tammars. The fetal adrenal is morphologically developing from day 21 of gestation (Renfree, 1972;Call et al, 1980) and by day 24 cortisol is easily measurable in fetal blood. Fetal adrenal cortisol production then increases in the last 2 days of gestation (Ingram et al, 1999) before falling post-partum ( Figure 5).…”

Section: The Trigger For Birth -Fetal Cortisolmentioning

confidence: 99%

Parturition and perfect prematurity: birth in marsupials

Shaw

Renfree

2006

Aust. J. Zool.

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Marsupials are distinguished from eutherian mammals in their mode of reproduction. They give birth to a highly altricial young, which completes its development whilst attached to a teat, usually within a pouch. The marsupial neonate has relatively well-developed digestive, respiratory and circulatory systems but retains its fetal excretory system with a fully functional mesonephric kidney and undifferentiated gonads and genitalia. We have investigated birth in the tammar wallaby (Macropus eugenii) and shown that the tiny (400 mg) fetus determines the time of its own delivery. Although plasma progesterone falls, and oestradiol associated with the postpartum oestrus typically rises, around the time of parturition, neither hormone is essential for the timing of birth. However relaxin may loosen the connective tissue of the cervix and vaginae for birth. Labour starts suddenly and is completed within minutes. Both prostaglandins and mesotocin are essential for the contractions that deliver the young. Prostaglandins from the reproductive tract act via the brain to control parturient behaviour. In the last 2 days of gestation fetal adrenal glucocorticoid production increases, promoting lung maturation and surfactant production and ultimately triggering labour. The accessibility of the altricial neonatal marsupial provides a unique opportunity for experimental manipulation of organ development and maturation.

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Development of the Adrenal Gland in the Tammar Wallaby, Macropus Eugenii (Desmarest) (Marsupialia: Macropodidae).

Cited by 12 publications

References 0 publications

Ultrastructural evidence for steroid‐hormone production in the adrenal of the marsupial, Isoodon macrourus, at birth

Ultrastructural evidence for steroid‐hormone production in the adrenal of the marsupial, Isoodon macrourus, at birth

Seasonal and circadian patterns of circulating prolactin during lactation and seasonal quiescence in the tammar, Macropus eugenii

Parturition and perfect prematurity: birth in marsupials

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