Metamorphic rate in Rana pipiens larvae treated with thyroxine or prolactin at different times in the light/dark cycle

Wright, Mary L.; Frim, Elizabeth K.; Bonak, Valerie A.; Baril, Claire

doi:10.1016/0016-6480(86)90181-4

Cited by 15 publications

(6 citation statements)

References 23 publications

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“…Triiodothyronine and thyroxine day/night fluctuations do not appear until premetamorphosis. How ever, there were diel changes in the T 3 /T 4 ratio prior to this, suggesting possible daily changes in TH utilization and/or degradation, as suggested in R. pipiens (Wright et al, 1986). Similarly, day/night changes in the T 3 /T 4 ratio in larval stages could indicate daily changes in the peripheral 58-deiodinase activity.…”

Section: Discussionmentioning

confidence: 75%

“…Similarly, day/night changes in the T 3 /T 4 ratio in larval stages could indicate daily changes in the peripheral 58-deiodinase activity. Wright et al (1986) found that T 4 -induced metamorphosis in premetamorphic R. pipiens larvae was faster when this hormone was administered either by the end of the dark phase of daily photocycle or during the first half of the light phase, indicating circadian changes in the T 4 target tissue responsiveness, suggesting a rhythmic production of the endogenous hormone and/or changes in the TH receptor availability. Similar results have been described in X. laevis (Burns et al, 1987).…”

Section: Discussionmentioning

confidence: 94%

“…Unfortunately, most of the previous studies on TH during amphibian ontogeny do not specify either the sampling schedule or the photoperiod. Moreover, exogenous T 4 in anuran tadpoles at different times in the light:dark cycle shows circadian variations in target tissue responsiveness (Rana pipiens: Wright et al, 1986Wright et al, , 1990X. laevis: Burns et al, 1987), suggesting rhythmicity in the secretion of endogenous T 4 and/or in the receptor availability or even in peripheral deiodination since it is generally agreed that T 3 is the main bioactive hormone (Buscaglia et al, 1985).…”

mentioning

confidence: 99%

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Changes in Thyroid Hormone Concentrations and Total Contents through Ontogeny in Three Anuran Species: Evidence for Daily Cycles

Gancedo

Alonso-Gómez

Pedro

et al. 1997

General and Comparative Endocrinology

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 99%

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Changes in Thyroid Hormone Concentrations and Total Contents through Ontogeny in Three Anuran Species: Evidence for Daily Cycles

Gancedo

Alonso-Gómez

Pedro

et al. 1997

General and Comparative Endocrinology

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“…Since the duration of the melatonin peak was proportional to the length of the scotophase (7), retardation of development could have occurred because of greater melatonin antagonism of T4 on LD cycles with long dark phases. Such antagonism might also explain why T4 was more effective when given in the light in vivo in both Rana pipiens (27) and Xenopus laevis (4). in vitro, melatonin retarded tail tip regression to the same extent on both short (6L : 18D) and long (1 8L : 6D) photophase cycles.…”

Section: Rana Temporaria (15) Rana Ridibunda (5) Andmentioning

confidence: 99%

“…and thyroid hormone. Antagonism of thyroid hormone action by melatonin is suggested by the finding that T4 was more effective when given in the light (4,27) and that a 1 hr light pulse during the early dark of a 12L : 12D cycle partially counteracted the negative effect of administering T4 at that time (28). In rats, the pineal inhibited the neuroendocrine-thyroid axis (20,24).…”

Section: Introductionmentioning

confidence: 99%

Influence of Melatonin on the Rate of Rana pipiens Tadpole Metamorphosis In Vivo and Regression of Thyroxine‐Treated Tail Tips In Vitro

Wright¹,

Cykowski²,

Mayrand³

et al. 1991

Dev Growth Differ

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Metamorphosis of Rana pipiens tadpoles may be retarded when the light phase of the light/dark (LD) cycle is shortened or when thyroxine (T4) is given in the dark because melatonin peaks during the dark. Injection of premetamorphic tadpoles in spontaneous metamorphosis with melatonin (1 5 pg) retarded tail growth and hindlimb development on 18L:6D but had no significant effect on 6L: 18D. During induced metamorphosis (30 pg/liter T4), melatonin injections retarded tail resorption on 18L : 6D and accelerated it on 6L : 18D, but did not affect the hindlimb. When melatonin was injected during T4 immersion at different times in the photophase on 18L : 6D (L onset 0800 hr), tail regression was retarded by melatonin at 1430 or 2030 hr. At 0830 hr, shrinkage of tail length was accelerated whereas tail height was not affected. Tail tips in vifro induced to resorb by 0.2 pg/ml T4 in Niu-Twitty solution regressed more slowly in the presence of melatonin (10 or 15pg/ml) than with T4 alone on both 6L: 18D and 18L:6D. The findings implicate melatonin in LD cycle effects on tadpole metamorphic rate in vivo, show the importance of the time of melatonin injections, and indicate that melatonin antagonizes the metamorphic action of T4 at the tissue level.

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Effect of a light pulse during the dark on photoperiodic regulation of the rate of thyroxine‐induced, spontaneous, and prolactin‐inhibited metamorphosis in Rana pipiens tadpoles

et al. 1988

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Since Rana pipiens tadpoles injected with thyroxine (T4) early in the dark develop more slowly than those injected in the light, we studied the effect of giving a light pulse of 1 hr early in the dark. Tadpoles injected under a 7.5-W red light bulb in a darkened room with 0.2 microgram T4 daily at 2200 hr went through metamorphosis faster on a 12L:3D:1L:8D cycle with a light pulse after injection than on a 12L:12D cycle without a light pulse, and even faster on a 12L:1.5D:1L:9.5D cycle with a light pulse before the injection. Thus a 1-hr light pulse counteracted the metamorphic delay resulting from administration of T4 in the dark, and set in motion the conditions that resulted in a more rapid response to an injection of T4. However, a 1-hr light pulse in the early dark had no effect on growth and development of older or younger untreated tadpoles or those constantly immersed in 30 micrograms/liter T4. Larvae on 21L:3D with T4 injection in the dark and on 12L:3D:1L:8D with T4 injection at 0700 hr just before the start of the main light phase progressed faster than 12L:3D:1L:8D with injection at 2200 hr in the dark before only a 1-hr light pulse. Thus the length of the light phase immediately after T4 injection was significant. There was no difference on 12L:12D and 12L:3D:1L:8D cycles in the effectiveness of daily injections of 10 micrograms prolactin (PRL) in the early dark at 2200 hr in promoting tail growth or antagonizing tail resorption induced by T4 immersion. Under these conditions, PRL utilization did not appear to be inhibited by the light pulse.

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Metamorphic rate in Rana pipiens larvae treated with thyroxine or prolactin at different times in the light/dark cycle

Cited by 15 publications

References 23 publications

Changes in Thyroid Hormone Concentrations and Total Contents through Ontogeny in Three Anuran Species: Evidence for Daily Cycles

Changes in Thyroid Hormone Concentrations and Total Contents through Ontogeny in Three Anuran Species: Evidence for Daily Cycles

Influence of Melatonin on the Rate of Rana pipiens Tadpole Metamorphosis In Vivo and Regression of Thyroxine‐Treated Tail Tips In Vitro

Effect of a light pulse during the dark on photoperiodic regulation of the rate of thyroxine‐induced, spontaneous, and prolactin‐inhibited metamorphosis in Rana pipiens tadpoles

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