Growth hormone is a weaker candidate than prolactin for the hormone responsible for the development of a larval-type feature in cultured bullfrog skin

Takada, Makoto; Kasai, Miyoko

doi:10.1242/jeb.00231

Cited by 10 publications

(2 citation statements)

References 25 publications

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“…PRL has been considered a ''juvenile hormone'', opposing the actions of the THs and, thereby, delaying the time set for metamorphosis (Forsyth and Wallis 2002). This is based on in vivo (Dodd and Dodd 1976) and in vitro (Derby and Etkin 1968;Tata et al 1991;Takada and Kasai 2003) studies with mammalian PRL. However, this is in contrast with data showing that endogenous PRL plasma levels are low at pre-and prometamorphic stages, rising at the metamorphic climax (Clemons and Nicoll 1977;Yamamoto and Kikuyama 1982).…”

Section: Discussionmentioning

confidence: 99%

“…In Xenopus, the GH mRNA expression is higher in larval stages than during the metamorphic climax (Buckbinder and Brown 1993) and the overexpression of GH stimulates growth in Xenopus tadpoles (Huang and Brown 2000b). However, GH stimulates the development of certain larval-type skin related features, in bullfrog skin (Rana catesbeiana) in vitro, but to a lesser extent than PRL (Takada and Kasai 2003).…”

Section: Discussionmentioning

confidence: 99%

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Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut

et al. 2005

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Fish larval development, not least the spectacular process of flatfish metamorphosis, appears to be under complex endocrine control, many aspects of which are still not fully elucidated. In order to obtain data on the functional development of two major endocrine glands, the pituitary and the thyroid, during flatfish metamorphosis, histology, immunohistochemistry and in situ hybridization techniques were applied on larvae of the Atlantic halibut (Hippoglossus hippoglossus), a large, marine flatfish species, from hatching through metamorphosis. The material was obtained from a commercial hatchery. Larval age is defined as day-degrees (D°=accumulated daily temperature from hatching). Sporadic thyroid follicles are first detected in larvae at 142 D°(27 days post-hatch), prior to the completion of yolk sack absorption. Both the number and activity of the follicles increase markedly after yolk sack absorption and continue to do so during subsequent development. The larval triiodothyronine (T 3 ) and thyroxine (T 4 ) content increases, subsequent to yolk absorption, and coincides with the proliferation of thyroid follicles. A second increase of both T 3 and T 4 occurs around the start of metamorphosis and the T 3 content further increases at the metamorphic climax. Overall, the T 3 content is lower than T 4 . The pituitary gland can first be distinguished as a separate organ at the yolk sack stage. During subsequent development, the gland becomes more elongated and differentiates into neurohypophysis (NH), pars distalis (PD) and pars intermedia (PI). The first sporadic endocrine pituitary cells are observed at the yolk sack stage, somatotrophs (growth hormone producing cells) and somatolactotrophs (somatolactin producing cells) are first observed at 121 D°( 23 days post-hatch), and lactotrophs (prolactin producing cells) at 134 D°(25 days post-hatch). Scarce thyrotrophs are evident after detection of the first thyroid follicles (142 D°), but coincident with a phase in which follicle number and activity increase (260 D°). The somatotrophs are clustered in the medium ventral region of the PD, lactotrophs in the anterior part of the PD and somatolactotrophs are scattered in the mid and posterior region of the pituitary. At around 600 D°, coinciding with the start of metamorphosis, somatolactotrophs are restricted to the interdigitating tissue of the NH. During larval development, the pituitary endocrine cells become more numerous. The present data on thyroid development support the notion that thyroid hormones may play a significant role in Atlantic halibut metamorphosis. The time of appearance and the subsequent proliferation of pituitary somatotrophs, lactotrophs, somatolactotrophs and thyrotrophs indicate at which stages of larval development and metamorphosis these endocrine cells may start to play active regulatory roles.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut

et al. 2005

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Ontogeny of central melatonin receptors in tadpoles of the anuran Rana perezi: modulation of dopamine release

et al. 2005

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The objective of this work was to study melatonin receptors in the eye and the brain and their possible functionality in the ontogeny of Rana perezi. The binding of 2-[(125)I]melatonin increases throughout embryonic larval development in both tissues. The most pronounced increase takes place at the end of premetamorphosis and during early prometamorphosis. This rise coincides temporarily with the appearance of the rhythmic melatonin-synthesizing capacity in the retina. In the three studied developmental stages (32G, 40G and 49-50G), melatonin-binding sites are coupled to G proteins and become functional. Moreover, melatonin inhibits dopamine (DA) release by the eyecups and brain of R. perezi tadpoles in vitro (stage 40G). Thus, the modulation of DA release could be one mechanism by which melatonin interacts with hormones, like prolactin and thyroxine that are involved in the regulation of anuran development and metamorphosis. Finally, we show that melatonin decreases K(+)-evoked cAMP content in the frog retina in vitro, suggesting that the effect of melatonin on DA release in the frog retina is mediated by the inhibition of this intracellular messenger.

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Larval bullfrog skin expresses ENaC despite having no amiloride-blockable transepithelial Na+ transport

et al. 2005

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Amiloride-blockable Na(+) transport, measured as an amiloride-blockable short-circuit current (Am-SCC), is mediated by the epithelial Na(+) channel (ENaC). Am-SCC is not normally present in bullfrog tadpole skin, but when such skin is cultured with corticoids an amiloride-blockable Na transport appears. Prolactin (PRL) inhibits its corticoid-induced development. Using specific PCR primers for adult frog ENaC and RT-PCR, we investigated whether corticoids can induce all three ENaC subunits, and whether this expression of ENaC subunit(s) can be blocked by adding PRL with the corticoids. We found that (1) the sequences of the RT-PCR products obtained using primers for alpha-ENaC were identical between larval and adult skins, (2) the mRNAs for all three ENaC subunits were expressed in larval skin under normal conditions despite no amiloride-blockable Na(+) transport being detectable, (3) all three subunits were expressed in larval skins whether they were cultured with corticoids (amiloride-blockable Na transport present) or with corticoids supplemented with PRL (no amiloride-blockable Na transport present). An antibody against a peptide from the alpha-ENaC of adult bullfrog was localized to the apical cells of both larval and adult skins. Since no amiloride-blockable Na transport exists across larval skin under these conditions, these results suggest that ENaC protein was expressed prior to the onset of transport. ENaC may be in the plasma membrane in an inactivated form or, alternatively, within vesicles waiting to be inserted.

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Growth hormone is a weaker candidate than prolactin for the hormone responsible for the development of a larval-type feature in cultured bullfrog skin

Cited by 10 publications

References 25 publications

Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut

Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut

Ontogeny of central melatonin receptors in tadpoles of the anuran Rana perezi: modulation of dopamine release

Larval bullfrog skin expresses ENaC despite having no amiloride-blockable transepithelial Na+ transport

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