<i>Xenopus</i> Tadpole Melanophores Are Controlled by Dark and Light and Melatonin Without Influence of Time of Day

Binkley, Sue; Mosher, Karen; Rubin, Frances; White, Benjamin H.

doi:10.1111/j.1600-079x.1988.tb00771.x

Cited by 20 publications

(19 citation statements)

References 30 publications

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“…Thus, the melanosome dispersion observed with long‐term melatonin treatment does not appear to result from direct actions of melatonin on melanophores and pigment localization. These data, together with those showing no role of the pineal gland in skin pigmentation at stage 42, suggest that the pineal gland‐dependent secretion of melatonin that regulates skin pigmentation in the adult (Bagnara, ; Binkley et al., ) is not functional at stage 42. Rather, melatonin functions in some unknown circuit to control melanosome aggregation/dispersion.…”

Section: Resultsmentioning

confidence: 83%

Two light‐activated neuroendocrine circuits arising in the eye trigger physiological and morphological pigmentation

Bertolesi

Hehr

Munn

et al. 2016

Pigment Cell Melanoma Res

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Two biological processes regulate light-induced skin colour change. A fast 'physiological pigmentation change' (i.e. circadian variations or camouflage) involves alterations in the distribution of pigment containing granules in the cytoplasm of chromatophores, while a slower 'morphological pigmentation change' (i.e. seasonal variations) entails changes in the number of pigment cells or pigment type. Although linked processes, the neuroendocrine coordination triggering each response remains largely obscure. By evaluating both events in Xenopus laevis embryos, we show that morphological pigmentation initiates by inhibiting the activity of the classical retinal ganglion cells. Morphological pigmentation is always accompanied by physiological pigmentation, and a melatonin receptor antagonist prevents both responses. Physiological pigmentation also initiates in the eye, but with repression of melanopsin-expressing retinal ganglion cell activity that leads to secretion of alpha-melanocyte-stimulating hormone (α-MSH). Our findings suggest a model in which eye photoperception links physiological and morphological pigmentation by altering α-MSH and melatonin production, respectively.

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Section: Resultsmentioning

confidence: 83%

Two light‐activated neuroendocrine circuits arising in the eye trigger physiological and morphological pigmentation

Bertolesi

Hehr

Munn

et al. 2016

Pigment Cell Melanoma Res

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“…Because we know that melanophores are dynamic in response to light, we chose the first time point at lights on in the morning. We used melatonin 5 ng/mL as a positive control, as it has been well established by prior studies to regulate melanophore behavior in Xenopus , inducing pigment aggregation during night time (Binkley et al 1988). Melatonin significantly decreased the proportion of the brain covered by melanophores at the 15-minute, 30-minute, and 6-hour time points when compared with controls (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Second, photoperiod contributes to changes in melanophore pigment distribution, which largely regulated by changes in circulating levels of melatonin. Initial experiments investigating the role of melatonin in amphibian pigmentation found that changes in melanophore appearance result from changes in environmental illumination, which regulates release of melatonin (Binkley et al 1988). Onset of night induces release of melatonin from the pineal gland, which provides temporal control over physiology and behavior (Hatori and Panda 2010).…”

Section: Introductionmentioning

confidence: 99%

“The flavor enhancer maltol increases pigment aggregation in dermal and neural melanophores in Xenopus laevis tadpoles”

Dahora

Fitzgerald

Emanuel

et al. 2019

Preprint

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Melanophores are pigmented cells that change the distribution of pigmented melanosomes, enabling animals to appear lighter or darker for camouflage, thermoregulation, and UV-protection. A complex series of hormonal and neural mechanisms regulates melanophore pigment distribution, making these cells a valuable tool to screen toxicants as a dynamic cell type that responds rapidly to the environment. We found that maltol, a naturally occurring flavor enhancer and fragrance agent, induces melanophore pigment aggregation in a dose-dependent manner in Xenopus laevis tadpoles. To determine if maltol affects camouflage adaptation, we placed tadpoles into maltol baths situated over either white or black background. Maltol induced pigment aggregation in a similar dose-dependent pattern regardless of background color. We also tested how maltol treatment compares to melatonin treatment and found that the degree of pigment aggregation induced by maltol is similar to treatment with melatonin, but the time course differs significantly. Last, maltol had no effect on mRNA expression of pro-opiomelanocortin or melanin concentrating hormone receptor in the brain, both of which regulate camouflage-related pigment aggregation. Our results suggest that maltol does not exert its effects via the camouflage adaptation mechanism nor via melatonin-based mechanisms. These results are the first to identify a specific toxicological effect of maltol exposure and rules out several mechanisms by which maltol may exert its effects on pigment aggregation.

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“…This molecule has the ability to promote pigment aggregation in ectothermic vertebrate chromatophores (Kavaliers et al 1980;Binkley et al 1987Binkley et al , 1988Binkley 1988;Filadelfi & Castrucci 1994). In crustaceans, the involvement of melatonin in pigment translocation is almost unknown.…”

Section: Introductionmentioning

confidence: 99%

Melatonin does not affect the black pigment migration in the crab Neohelice granulata

et al. 2009

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N-acetyl-5-methoxytryptamine or melatonin is a multifunctional molecule. The main physiological function, at least in vertebrates, is to transduce to the animal the photoperiodic information and regulate rhythmic parameters. But studies have also observed the action of this molecule on pigment migration in ectothermic vertebrates. Thus the aim of this paper was to investigate in vivo and in vitro the influence of melatonin on the pigment migration in melanophores of the crab Neohelice granulata. Injections of melatonin (2 × 10 −9 moles · crab −1 ) at 07:00 h or 19:00 h did not affect (p > 0.05) the circadian pigment migration of the melanophores in constant darkness. Additionally no significant pigment migration (p > 0.05) was verified in normal and eyestalkless crabs injected with melatonin (10 −10 -10 −7 moles · crab −1 ) during the day or night. In the in vitro assay, the response of melanophores to the pigment-dispersing hormone in eyestalkless crabs injected with melatonin (2 × 10 −9 moles · crab −1 ) 1 and 12 hours before the observations did not differ (p > 0.05) from the control group (injected with physiological solution). These results suggest that melatonin does not act as a signaling factor for pigment dispersion or aggregation in the melanophores of N. granulata.

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Xenopus Tadpole Melanophores Are Controlled by Dark and Light and Melatonin Without Influence of Time of Day

Cited by 20 publications

References 30 publications

Two light‐activated neuroendocrine circuits arising in the eye trigger physiological and morphological pigmentation

Two light‐activated neuroendocrine circuits arising in the eye trigger physiological and morphological pigmentation

“The flavor enhancer maltol increases pigment aggregation in dermal and neural melanophores in Xenopus laevis tadpoles”

Melatonin does not affect the black pigment migration in the crab Neohelice granulata

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