Glucocorticoids, thyroid hormones, and iodothyronine  deiodinases in embryonic saltwater crocodiles

Shepherdley, Caroline A.; Daniels, Christopher B.; Orgeig, Sandra; Richardson, Samantha; Evans, Barbara K.; Darras, Veerle

doi:10.1152/ajpregu.00015.2002

Cited by 33 publications

(34 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence, at this time point, T 3 does appear to have a specific effect. At day 75, the administration of Dex caused endogenous corticosterone production to be completely abolished (52). Hence, the effect of increased PL content in lavage at this time point is directly mediated by Dex.…”

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 85%

“…At days 60 and 75, both T 3 and Dex ϩ T 3 increased total PL, whereas at day 75, Dex alone also increased total PL. It is possible that the T 3 effect is mediated by corticosterone, because the major effect of T 3 administration at days 60 and 68 was the increase in circulating corticosterone (52). However, at day 75, when endogenous corticosterone levels are already extremely elevated, T 3 did not elevate corticosterone any further.…”

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 98%

“…This implies that the dramatic increase in extracellular surfactant pools seen after hatching in the crocodile (and also birthing in the rat) is due to factors other than the constitutive secretion of surfactant PLs from the type II cells. Given the potent effect of the agonists in the culture medium on PC secretion and that all three hormone pretreatments increased total PL at day 75 of incubation, it is likely that an increase in circulating levels of hormone [predominantly T 3 in the crocodile as this was elevated at hatching (52)] or neurotransmitter provide the stimulus for surfactant secretion before hatching. A change in the response of type II cells to surfactant secretagogues is also seen in the rat (20).…”

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 99%

“…This may be explained by the rapid maturation of the surfactant system in the crocodile between day 75 (94% of total incubation) and hatching, requiring synchronization of signal transduction pathways. It is likely that this rapid maturation and high cellular responsiveness at day 75 is mediated by corticosterone, because circulating levels of this hormone are highest at day 75 (52).…”

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 99%

“…Treatment with T 3 significantly increased free T 3 levels in the plasma on days 68 and 75 of incubation, whereas treatment with Dex alone did not affect the concentration of free T 3 in plasma on days 68 or 75. However, treatment with both Dex ϩ T 3 increased the concentration of plasma free T 3 on day 75 of incubation (52). It is clear, therefore, that exogenous hormone treatment of the egg during the latter stages of development is capable of interacting with the hypothalamo-pituitary axis of the embryo to regulate endogenous hormone treatment.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Control of the development of the pulmonary surfactant system in the saltwater crocodile,Crocodylus porosus

Sullivan

Orgeig

Daniels

2002

American Journal of Physiology-Regulatory, Integrative and Comp

Self Cite

View full text Add to dashboard Cite

. Control of the development of the pulmonary surfactant system in the saltwater crocodile, Crocodylus porosus. Am J Physiol Regul Integr Comp Physiol 283: R1164-R1176, 2002. First published July 25, 2002 10.1152/ ajpregu.00009.2002.-Pulmonary surfactant is a mixture of lipids and proteins that controls the surface tension of the fluid lining the inner lung. Its composition is conserved among the vertebrates. Here we hypothesize that the in ovo administration of glucocorticoids and thyroid hormones during late incubation will accelerate surfactant development in the saltwater crocodile, Crocodylus porosus. We also hypothesize that the increased maturation of the type II cells in response to hormone pretreatment will result in enhanced responsiveness of the cells to surfactant secretagogues. We sampled embryos at days 60, 68, and 75 of incubation and after hatching. We administered dexamethasone (Dex), 3,5,3Ј-triiodothyronine (T3), or a combination of both hormones (Dex ϩ T3), 48 and 24 h before each prehatching time point. Lavage analysis indicated that the maturation of the phospholipids (PL) in the lungs of embryonic crocodiles occurs rapidly. Only T3 and Dex ϩ T3 increased total PL in lavage at embryonic day 60, but Dex, T3, and Dex ϩ T3 increased PL at day 75. The saturation of the PLs was increased by T3 and Dex ϩ T3 at day 68. Swimming exercise did not increase the amount or alter the saturation of the surfactant PLs. Pretreatment of embryos with Dex, T3, or Dex ϩ T3 changed the secretion profiles of the isolated type II cells. Dex ϩ T3 increased the response of the cells to agonists at days 60 and 68. Therefore, glucocorticoids and thyroid hormones regulate surfactant maturation in the crocodile.

show abstract

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 85%

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 98%

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 99%

Section: Development Of Surfactant Pls In Crocodilesmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Control of the development of the pulmonary surfactant system in the saltwater crocodile,Crocodylus porosus

Sullivan

Orgeig

Daniels

2002

American Journal of Physiology-Regulatory, Integrative and Comp

Self Cite

View full text Add to dashboard Cite

show abstract

Evolution, Development, and Function of the Pulmonary Surfactant System in Normal and Perturbed Environments

Orgeig

Morrison

Daniels

2015

Comprehensive Physiology

View full text Add to dashboard Cite

Surfactant lipids and proteins form a surface active film at the air-liquid interface of internal gas exchange organs, including swim bladders and lungs. The system is uniquely positioned to meet both the physical challenges associated with a dynamically changing internal air-liquid interface, and the environmental challenges associated with the foreign pathogens and particles to which the internal surface is exposed. Lungs range from simple, transparent, bag-like units to complex, multilobed, compartmentalized structures. Despite this anatomical variability, the surfactant system is remarkably conserved. Here, we discuss the evolutionary origin of the surfactant system, which likely predates lungs. We describe the evolution of surfactant structure and function in invertebrates and vertebrates. We focus on changes in lipid and protein composition and surfactant function from its antiadhesive and innate immune to its alveolar stability and structural integrity functions. We discuss the biochemical, hormonal, autonomic, and mechanical factors that regulate normal surfactant secretion in mature animals. We present an analysis of the ontogeny of surfactant development among the vertebrates and the contribution of different regulatory mechanisms that control this development. We also discuss environmental (oxygen), hormonal and biochemical (glucocorticoids and glucose) and pollutant (maternal smoking, alcohol, and common "recreational" drugs) effects that impact surfactant development. On the adult surfactant system, we focus on environmental variables including temperature, pressure, and hypoxia that have shaped its evolution and we discuss the resultant biochemical, biophysical, and cellular adaptations. Finally, we discuss the effect of major modern gaseous and particulate pollutants on the lung and surfactant system.

show abstract

Environmentally induced phenotypic plasticity explains hatching synchrony in the freshwater turtleChrysemys picta

et al. 2018

View full text Add to dashboard Cite

Environmentally cued hatching allows embryos to alter the time of hatching in relation to environment through phenotypic plasticity. Spatially variable temperatures within shallow nests of many freshwater turtles cause asynchronous development of embryos within clutches, yet neonates still hatch synchronously either by hatching early or via metabolic compensation. Metabolic compensation and changes in circadian rhythms presumably enable embryos to adjust their developmental rates to catch up to more advanced embryos within the nest. Hatchlings of the North American freshwater turtle Chrysemys picta usually overwinter within the nest and emerge the following spring, but still hatch synchronously via hatching early. Here, we used rates of oxygen consumption and heart rate profiles to investigate the metabolic rates of clutches of C. picta developing in conditions that result in asynchronous development to determine if compensatory changes in metabolism occur during incubation. Embryos hatched synchronously and displayed circadian rhythms throughout incubation, but exhibited no evidence of metabolic compensation. Phenotypic traits of hatchlings, including body size and righting performance, were also not affected by asynchronous development. We conclude that less developed embryos of C. picta hatch synchronously with their clutch-mates by hatching early, which does not appear to inflict a fitness cost to individuals. The ultimate mechanism for synchronous hatching in C. picta could be for hatchlings to ensure an optimal overwintering position within the center of the nest. Consequently, immediate fitness costs will not hinder hatchling survival. The geographic location, as well as environmental and genetic factors unique to populations, can all influence hatching behavior in turtles through phenotypic plasticity. Hence, synchronous hatching is an adaptive bet-hedging strategy in turtles, but the mechanisms to achieve it are diverse.

show abstract

Glucocorticoids, thyroid hormones, and iodothyronine deiodinases in embryonic saltwater crocodiles

Cited by 33 publications

References 50 publications

Control of the development of the pulmonary surfactant system in the saltwater crocodile,Crocodylus porosus

Control of the development of the pulmonary surfactant system in the saltwater crocodile,Crocodylus porosus

Evolution, Development, and Function of the Pulmonary Surfactant System in Normal and Perturbed Environments

Environmentally induced phenotypic plasticity explains hatching synchrony in the freshwater turtleChrysemys picta

Contact Info

Product

Resources

About