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<meta content="Girling, Jane E." name="eprints.creators_name" />
<meta content="Jones, Susan M." name="eprints.creators_name" />
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<meta content="S.M.Jones@utas.edu.au" name="eprints.creators_id" />
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<meta content="Adrenal; Embryo; Gonad; Niveoscincus microlepidotus; Parturition; Reptile;
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<meta content="In some mammalian species, hormones produced by the embryo(s) at the completion of development are involved in the cascade of events that result in parturition. Our overall aim was to determine whether a similar mechanism exists in viviparous reptiles. The alpine skink Niveoscincus microlepidotus provides a useful model for studies of gestation and parturition in viviparous reptiles as the completion of embryonic development and parturition are temporally separated; ovulation occurs in spring, embryonic development is completed by autumn, but parturition does not occur until the following spring. In this study, we determined how in vitro steroid hormone production by embryonic adrenals (progesterone, corticosterone, and testosterone) and mesonephric kidney-gonads (oestradiol and testosterone) varied during the later stages of gestation. We hypothesised that embryonic adrenals and kidney-gonads were capable of producing steroid hormones in vitro, and that the pattern of production would change as parturition approached, would be influenced by temperature, and would increase in the presence of corticotropin (ACTH) or pregnenolone, respectively. Embryonic adrenals and kidney-gonads were incubated with or without ACTH or the steroid precursor pregnenolone, respectively. Tissues were incubated for 3h at either 16 or 24 degrees C (preferred body temperature of pregnant N. microlepidotus). Incubation medium was analysed for steroid hormones using radioimmunoassay. Low levels of progesterone were produced in vitro during the later stages of gestation when embryonic adrenals were incubated with ACTH. In vitro corticosterone production by embryonic adrenals also occurred, with greater production occurring when tissues were incubated at 24 degrees C. Testosterone was produced in vitro by both adrenals and kidney-gonads in March (late autumn when embryonic development was complete, but prior to parturition the following spring), with greater production at 16 degrees C. This peak in testosterone production coincided with differentiation and continuing growth of the hemipenes. Low levels of oestradiol were produced in vitro by embryonic kidney-gonads in March. These results provide some support for the hypothesis that corticosterone production by the embryonic adrenal may have a role in determining the timing of parturition in a viviparous reptilian species. Further research is needed to differentiate the activity of various tissues and steroid hormones in control of embryonic development, sexual differentiation, and the potential regulation of gestation and parturition in N. microlepidotus and other viviparous reptiles." name="eprints.abstract" />
<meta content="2006-01" name="eprints.date" />
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<meta content="General and Comparative Endocrinology" name="eprints.publication" />
<meta content="145" name="eprints.volume" />
<meta content="2" name="eprints.number" />
<meta content="169-176" name="eprints.pagerange" />
<meta content="10.1016/j.ygcen.2005.08.012" name="eprints.id_number" />
<meta content="UNSPECIFIED" name="eprints.thesis_type" />
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<meta content="Bernal, A.L., 2001. Overview of current research in parturition. Exp. Physiol. 86, 213-222.
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Desvages, G. and Pieau, C., 1991. Steroid metabolism in gonads of turtle embryos as a function of the incubation temperature of eggs. J. Steroid Biochem. Mol. Biol. 39, 203-213.
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Wapstra, E., Olsson, M., Shine, R., Edwards, A., Swain, R., Joss, J.M.P., 2004. Maternal basking behaviour determines offspring sex in a viviparous reptile. Proc. R. Soc. Lond. B (Suppl.) 271, S230-S232.
White, R.B., Thomas, P., 1992. Adrenal-kidney and gonadal steroidogenesis during sexual differentiation of a reptile with temperature-dependent sex determination. Gen. Comp. Endocrinol. 88, 10-19.
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<meta content="In some mammalian species, hormones produced by the embryo(s) at the completion of development are involved in the cascade of events that result in parturition. Our overall aim was to determine whether a similar mechanism exists in viviparous reptiles. The alpine skink Niveoscincus microlepidotus provides a useful model for studies of gestation and parturition in viviparous reptiles as the completion of embryonic development and parturition are temporally separated; ovulation occurs in spring, embryonic development is completed by autumn, but parturition does not occur until the following spring. In this study, we determined how in vitro steroid hormone production by embryonic adrenals (progesterone, corticosterone, and testosterone) and mesonephric kidney-gonads (oestradiol and testosterone) varied during the later stages of gestation. We hypothesised that embryonic adrenals and kidney-gonads were capable of producing steroid hormones in vitro, and that the pattern of production would change as parturition approached, would be influenced by temperature, and would increase in the presence of corticotropin (ACTH) or pregnenolone, respectively. Embryonic adrenals and kidney-gonads were incubated with or without ACTH or the steroid precursor pregnenolone, respectively. Tissues were incubated for 3h at either 16 or 24 degrees C (preferred body temperature of pregnant N. microlepidotus). Incubation medium was analysed for steroid hormones using radioimmunoassay. Low levels of progesterone were produced in vitro during the later stages of gestation when embryonic adrenals were incubated with ACTH. In vitro corticosterone production by embryonic adrenals also occurred, with greater production occurring when tissues were incubated at 24 degrees C. Testosterone was produced in vitro by both adrenals and kidney-gonads in March (late autumn when embryonic development was complete, but prior to parturition the following spring), with greater production at 16 degrees C. This peak in testosterone production coincided with differentiation and continuing growth of the hemipenes. Low levels of oestradiol were produced in vitro by embryonic kidney-gonads in March. These results provide some support for the hypothesis that corticosterone production by the embryonic adrenal may have a role in determining the timing of parturition in a viviparous reptilian species. Further research is needed to differentiate the activity of various tissues and steroid hormones in control of embryonic development, sexual differentiation, and the potential regulation of gestation and parturition in N. microlepidotus and other viviparous reptiles." name="DC.description" />
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<h1 class="ep_tm_pagetitle">In vitro steroid production by adrenals and kidney-gonads from embryonic southern snow skinks (Niveoscincus microlepidotus): Implications for the control of the timing of parturition?</h1>
<p style="margin-bottom: 1em" class="not_ep_block"><span class="person_name">Girling, Jane E.</span> and <span class="person_name">Jones, Susan M.</span> (2006) <xhtml:em>In vitro steroid production by adrenals and kidney-gonads from embryonic southern snow skinks (Niveoscincus microlepidotus): Implications for the control of the timing of parturition?</xhtml:em> General and Comparative Endocrinology, 145 (2). pp. 169-176. ISSN 0016-6480</p><p style="margin-bottom: 1em" class="not_ep_block"></p><table style="margin-bottom: 1em" class="not_ep_block"><tr><td valign="top" style="text-align:center"><a href="http://eprints.utas.edu.au/735/1/Grling_%26_Jones_2006"><img alt="[img]" src="http://eprints.utas.edu.au/style/images/fileicons/application_pdf.png" border="0" class="ep_doc_icon" /></a></td><td valign="top"><a href="http://eprints.utas.edu.au/735/1/Grling_%26_Jones_2006"><span class="ep_document_citation">PDF</span></a> - Full text restricted - Requires a PDF viewer<br />271Kb</td><td><form method="get" accept-charset="utf-8" action="http://eprints.utas.edu.au/cgi/request_doc"><input value="744" name="docid" accept-charset="utf-8" type="hidden" /><div class=""><input value="Request a copy" name="_action_null" class="ep_form_action_button" onclick="return EPJS_button_pushed( '_action_null' )" type="submit" /> </div></form></td></tr></table><p style="margin-bottom: 1em" class="not_ep_block">Official URL: <a href="http://dx.doi.org/10.1016/j.ygcen.2005.08.012">http://dx.doi.org/10.1016/j.ygcen.2005.08.012</a></p><div class="not_ep_block"><h2>Abstract</h2><p style="padding-bottom: 16px; text-align: left; margin: 1em auto 0em auto">In some mammalian species, hormones produced by the embryo(s) at the completion of development are involved in the cascade of events that result in parturition. Our overall aim was to determine whether a similar mechanism exists in viviparous reptiles. The alpine skink Niveoscincus microlepidotus provides a useful model for studies of gestation and parturition in viviparous reptiles as the completion of embryonic development and parturition are temporally separated; ovulation occurs in spring, embryonic development is completed by autumn, but parturition does not occur until the following spring. In this study, we determined how in vitro steroid hormone production by embryonic adrenals (progesterone, corticosterone, and testosterone) and mesonephric kidney-gonads (oestradiol and testosterone) varied during the later stages of gestation. We hypothesised that embryonic adrenals and kidney-gonads were capable of producing steroid hormones in vitro, and that the pattern of production would change as parturition approached, would be influenced by temperature, and would increase in the presence of corticotropin (ACTH) or pregnenolone, respectively. Embryonic adrenals and kidney-gonads were incubated with or without ACTH or the steroid precursor pregnenolone, respectively. Tissues were incubated for 3h at either 16 or 24 degrees C (preferred body temperature of pregnant N. microlepidotus). Incubation medium was analysed for steroid hormones using radioimmunoassay. Low levels of progesterone were produced in vitro during the later stages of gestation when embryonic adrenals were incubated with ACTH. In vitro corticosterone production by embryonic adrenals also occurred, with greater production occurring when tissues were incubated at 24 degrees C. Testosterone was produced in vitro by both adrenals and kidney-gonads in March (late autumn when embryonic development was complete, but prior to parturition the following spring), with greater production at 16 degrees C. This peak in testosterone production coincided with differentiation and continuing growth of the hemipenes. Low levels of oestradiol were produced in vitro by embryonic kidney-gonads in March. These results provide some support for the hypothesis that corticosterone production by the embryonic adrenal may have a role in determining the timing of parturition in a viviparous reptilian species. Further research is needed to differentiate the activity of various tissues and steroid hormones in control of embryonic development, sexual differentiation, and the potential regulation of gestation and parturition in N. microlepidotus and other viviparous reptiles.</p></div><table style="margin-bottom: 1em" border="0" cellpadding="3" class="not_ep_block"><tr><th valign="top" class="ep_row">Item Type:</th><td valign="top" class="ep_row">Article</td></tr><tr><th valign="top" class="ep_row">Additional Information:</th><td valign="top" class="ep_row">http://www.elsevier.com/locate/ygcen</td></tr><tr><th valign="top" class="ep_row">Keywords:</th><td valign="top" class="ep_row">Adrenal; Embryo; Gonad; Niveoscincus microlepidotus; Parturition; Reptile;
steroid</td></tr><tr><th valign="top" class="ep_row">Subjects:</th><td valign="top" class="ep_row"><a href="http://eprints.utas.edu.au/view/subjects/270604.html">270000 Biological Sciences > 270600 Physiology > 270604 Comparative Physiology</a><br /><a href="http://eprints.utas.edu.au/view/subjects/270599.html">270000 Biological Sciences > 270500 Zoology > 270599 Zoology not elsewhere classified</a></td></tr><tr><th valign="top" class="ep_row">Collections:</th><td valign="top" class="ep_row">UNSPECIFIED</td></tr><tr><th valign="top" class="ep_row">ID Code:</th><td valign="top" class="ep_row">735</td></tr><tr><th valign="top" class="ep_row">Deposited By:</th><td valign="top" class="ep_row"><span class="ep_name_citation"><span class="person_name">A/Prof. Susan M. Jones</span></span></td></tr><tr><th valign="top" class="ep_row">Deposited On:</th><td valign="top" class="ep_row">14 Feb 2007</td></tr><tr><th valign="top" class="ep_row">Last Modified:</th><td valign="top" class="ep_row">04 Feb 2008 13:15</td></tr><tr><th valign="top" class="ep_row">ePrint Statistics:</th><td valign="top" class="ep_row"><a target="ePrintStats" href="/es/index.php?action=show_detail_eprint;id=735;">View statistics for this ePrint</a></td></tr></table><p align="right">Repository Staff Only: <a href="http://eprints.utas.edu.au/cgi/users/home?screen=EPrint::View&eprintid=735">item control page</a></p>
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