Thyroid development in the marsupial bandicoot, <i>Isoodon macrourus</i>

Johnston, Georgina C. A.; Gemmell, R. T.

doi:10.1002/ar.1092170210

Cited by 13 publications

(7 citation statements)

References 19 publications

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“…Thus there appears to be a correlation between weight of thyroid gland and plasma concentrations of T, and T, in the young possum. This observation on the max- imum ratio of thyroid gland to body weight concurs with that observed for the bandicoot Isoodon macrourus, the maximum ratio being observed at day 50 postpartum (Johnston and Gemmell, 1987). The plasma concentration of T, in the tammar pouch young has been shown to rise from less than 15 nmol/l (10.5 ng/ml) early in pouch life to a peak of about 75 nmoUl(58.3 ng/ml) on about day 160 and then to fall to the adult level of about 12 nmol/l (8.4 ng/ml).…”

Section: Discussionsupporting

confidence: 89%

“…Morphological and biochemical studies have been used to estimate the time at which the thyroid gland of pouch young becomes functional. In the bandicoot, Isoodon macrourus, follicles have been observed at day 12 postpartum, and lysosomes, required for the transfer of thyroglobulin to thyroxine, were first seen at day 30 postpartum, halfway through the lactation period of 60 days (Johnston and Gemmell, 1987). Thyroid secretion rates were similar in adult marsupials and adult eutherians (Setchell, 1974;Hulbert and Augee, 1982;Withers and Hulbert, 1988).…”

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confidence: 97%

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Thyroid gland development in the brushtail possum, Trichosurus vulpecula

Buaboocha

Gemmell

1995

Anat. Rec.

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Background: The onset of thyriod function occurs at different times with respect to birth in different mammals. In most marsupials studied thus far, thyroid function begins during the latter half of pouch life. However, in marsupials, thyroxine can be transported from the mother to the young via milk. In this study the plasma concentration of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3), in the young was correlated with the ultrastructural appearance of the thyroid of the young. Methods: Thyroid glands at 40, 65, 70, 96, 113, 115, and 129 days postpartum and from an adult were examined with the light and electron microscope. Plasma concentrations of both T4 and T3 in young possums were determined by radioimmunoassay. Results: Plasma concentrations of T4 in the young were less than 10 ng/ml prior to day 60 and 12 ng/ml on day 60; they rose to a peak of 45 ng/ml on day 120 postpartum and then diminished to below 10 ng/ml by day 160 postpartum. Plasma T3 concentrations were similar in profile, the peak concentration being 0.25 ng/ml on day 120 postpartum, and, as with T4, T3 concentrations decreased in the latter part of the lactation period. The morphology of the follicular cells of the thyroid gland would suggest that the developing brushtail possum is capable of producing thyroxine at about day 65 postpartum. Densely staining bodies, presumably lysosomes that are required for the conversion of thyroglobulin to thyroxine, were first seen on day 65, and greater quantities were noted in day 96, 113, 115, and 129 thyroid tissue. Conclusions: The plasma concentrations of T4 and T3 of the young are greater than that of the adult by day 60 postpartum, with peak concentrations of thyroid hormones on day 120 postpartum. Ultrastructural examination would suggest that the possum thyroid gland is capable of producing thyroid hormones at about day 65 postpartum. The activation of the thyroid gland precedes the reported increase in growth rate of the young possum on day 96 (Gemmell and Hendrikz, 1993. Aust. J. Zool., 41:141 – 149 ). © 1995 Wiley‐Liss, Inc.

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Section: Discussionsupporting

confidence: 89%

mentioning

confidence: 97%

Thyroid gland development in the brushtail possum, Trichosurus vulpecula

Buaboocha

Gemmell

1995

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“…By day 35, the opossum thyroid has a structure typical of the adult (Krause & Cutts, 1983). Another indication of a peak in thyroid activity is that in both opossum and bandicoot the ratio of thyroid gland weight to body weight is considerably greater during late pouch life than it is in adults (Krause & Cutts, 1983;Johnston & Gemmell, 1987). This pattern of sequential developmental surges in plasma T4 and T3 is also seen in eutherians.…”

Section: Discussionmentioning

confidence: 83%

“…Thyrotrophs are the first cell types to appear in the anterior pituitary of the bandi¬ coot and are present in pouch young on day 7 (Hall & Hughes, 1985). Although a presumptive thyroid gland is present in newborn bandicoots, the first signs of active hormone secretion are not seen until day 30, and a peak in secretory activity is present around day 50 (Johnston & Gemmell, 1987). This peak in thyroid activity is correlated with the development of both hair and thermoregulatory capacity during the last 2 weeks of pouch life (Gemmell & Johnston, 1985).…”

Section: Discussionmentioning

confidence: 99%

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Thyroid hormones during development of a marsupial, the tammar wallaby, Macropus eugenii

Janssens

Grigg²,

Dove³

et al. 1990

Journal of Endocrinology

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The levels of thyroid hormones in the plasma and the activities of 5'-deiodinase activity in liver and kidney were determined in the tammar wallaby, Macropus eugenii, from early pouch life to adulthood. The total concentration of plasma thyroxine (T4) was below 15 nmol/l before day 75 of pouch life, rose to about 75 nmol/l at day 160, and then decreased to about 12 nmol/l in the adult. The total concentration of plasma tri-iodothyronine (T3) was below 0.4 nmol/l before day 120, increased to 3 nmol/l by about day 220 and then decreased to 1.0 nmol/l in adults. Concentrations of free T4 and free T3 followed a similar pattern but peaked at 45 and 160 pmol/l respectively. Concentrations of reverse T3 (rT3) were extremely variable, ranging from 0 to 1 nmol/l at day 100, and from 0 to greater than 2 nmol/l at day 180. After about day 230, rT3 levels fell rapidly and were below 0.3 nmol/l in adults. Liver and kidney 5'-deiodinase activities, which were undetectable before day 80, reached adult levels by day 220. Half-maximal activity of both these enzymes occurred at about day 205, mid-way between the peaks of T4 and T3. These findings suggest that the systems supporting synthesis and release of hormones from the thyroid gland are probably mature by about day 160 of pouch life in the tammar, while peripheral deiodinase activity, which is a major factor in the production of T3 in the plasma, matures by about day 220. These events thus precede the development of physiological independence of the young tammar from its mother.

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Ultrastructure of the olfactory system of three newborn marsupial species

Gemmell¹,

Nelson²

1988

Anat. Rec.

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The ultrastructure of the olfactory apparatus of three newborn marsupial species, the northern native cat, the brushtail possum, and the northern brown bandicoot, were examined. The olfactory epithelium and olfactory bulbs were at a similar stage of development in all three species. Receptor cells with cilia were observed, and although the olfactory system undergoes further differentiation during pouch life and although the olfactory epithelium and bulb of the newborn differs from that of the adult, these facts do not preclude the ability of the newborn to detect smell. The presence of touch receptors around the mouth region and of sensory cells within the olfactory epithelium would suggest that touch and smell are two of the senses allowing the newborn marsupial to reach the pouch.

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Thyroid development in the marsupial bandicoot, Isoodon macrourus

Cited by 13 publications

References 19 publications

Thyroid gland development in the brushtail possum, Trichosurus vulpecula

Thyroid gland development in the brushtail possum, Trichosurus vulpecula

Thyroid hormones during development of a marsupial, the tammar wallaby, Macropus eugenii

Ultrastructure of the olfactory system of three newborn marsupial species

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