The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Robert J. Denver - One of the best experts on this subject based on the ideXlab platform.
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genetic accommodation via modified endocrine signalling explains phenotypic divergence among spadefoot toad species
Nature Communications, 2017Co-Authors: Saurabh S Kulkarni, Robert J. Denver, Ivan Gomezmestre, Daniel R BuchholzAbstract:Phenotypic differences among species may evolve through genetic accommodation, but mechanisms accounting for this process are poorly understood. Here we compare hormonal variation underlying differences in the timing of Metamorphosis among three spadefoot toads with different larval periods and responsiveness to pond drying. We find that, in response to pond drying, Pelobates cultripes and Spea multiplicata accelerate Metamorphosis, increase standard metabolic rate (SMR), and elevate whole-body content of thyroid hormone (the primary morphogen controlling Metamorphosis) and corticosterone (a stress hormone acting synergistically with thyroid hormone to accelerate Metamorphosis). In contrast, Scaphiopus couchii has the shortest larval period, highest whole-body thyroid hormone and corticosterone content, and highest SMR, and these trait values are least affected by pond drying among the three species. Our findings support that the atypically rapid and canalized development of S. couchii evolved by genetic accommodation of endocrine pathways controlling Metamorphosis, showing how phenotypic plasticity within species may evolve into trait variation among species.
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developmental expression and hormonal regulation of glucocorticoid and thyroid hormone receptors during Metamorphosis in xenopus laevis
Journal of Endocrinology, 2004Co-Authors: L P Krain, Robert J. DenverAbstract:Corticosteroids, the primary circulating vertebrate stress hormones, are known to potentiate the actions of thyroid hormone in amphibian Metamorphosis. Environmental modulation of the production of stress hormones may be one way that tadpoles respond to variation in their larval habitat, and thus control the timing of Metamorphosis. Thyroid hormone and corticosteroids act through structurally similar nuclear receptors, and interactions at the transcriptional level could lead to regulation of common pathways controlling Metamorphosis. To better understand the roles of corticosteroids in amphibian Metamorphosis we analyzed the developmental and hormonedependent expression of glucocorticoid receptor (GR) mRNA in the brain (diencephalon), intestine and tail of Xenopus laevis tadpoles. We compared the expression patterns of GR with expression of thyroid hormone receptor beta (TR). In an effort to determine the relationship between nuclear hormone receptor expression and levels of ligand, we also analyzed changes in wholebody content of 3,5,3-triiodothyronine (T3), thyroxine, and corticosterone (CORT). GR transcripts of 8, 4 and 2 kb were detected in all tadpole tissues, but only the 4 and 2 kb transcripts could be detected in embryos. The level of GR mRNA was low during preMetamorphosis in the brain but increased significantly during proMetamorphosis, remained at a constant level throughout Metamorphosis, and increased to its highest level in the juvenile frog. GR mRNA level in the intestine remained relatively constant, but increased in the tail throughout Metamorphosis, reaching a maximum at metamorphic climax. The level of GR mRNA was increased by treatment with CORT in the intestine but not in the brain or tail. TR mRNA level increased in the brain, intestine and tail during Metamorphosis and was induced by treatment with T3. Analysis of possible crossregulatory relationships between GRs and TRs showed that GR mRNA was upregulated by exogenous T3 (50 nM) in the tail but downregulated in the brain of premetamorphic tadpoles. Exogenous CORT (100 nM) upregulated TR mRNA in the intestine. Our findings provide evidence for tissuespecific positive, negative and crossregulation of nuclear hormone receptors during Metamorphosis of X. laevis. The synergy of CORT with T3 on tadpole tail resorption may depend on the accelerated accumulation of GR transcripts in this tissue during Metamorphosis, which may be driven by rising plasma thyroid hormone titers.
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Acceleration of Ambystoma tigrinum Metamorphosis by corticotropin-releasing hormone
The Journal of experimental zoology, 2002Co-Authors: Graham C. Boorse, Robert J. DenverAbstract:Previous work of others and ours has shown that corticotropin-releasing hormone (CRH) is a positive stimulus for thyroid and interrenal hormone secretion in amphibian larvae and that activation of CRH neurons may mediate environmental effects on the timing of Metamorphosis. These studies have investigated CRH actions in anurans (frogs and toads), whereas there is currently no information regarding the actions of CRH on Metamorphosis of urodeles (salamanders and newts). We tested the hypothesis that CRH can accelerate Metamorphosis of tiger salamander (Ambystoma tigrinum) larvae. We injected tiger salamander larvae with ovine CRH (oCRH; 1 microg/day; i.p.) and monitored effects on Metamorphosis by measuring the rate of gill resorption. oCRH-injected larvae completed Metamorphosis earlier than saline-injected larvae. There was no significant difference between uninjected and saline-injected larvae. Mean time to reach 50% reduction in initial gill length was 6.9 days for oCRH-injected animals, 11.9 days for saline-injected animals, and 14.1 days for uninjected controls. At the conclusion of the experiment (day 15), all oCRH-injected animals had completed Metamorphosis, whereas by day 15, only 50% of saline-injected animals and 33% of uninjected animals had metamorphosed. Our results show that exogenous oCRH can accelerate Metamorphosis in urodele larvae as it does in anurans. These findings suggest that the neuroendocrine mechanisms controlling Metamorphosis are evolutionarily conserved across amphibian taxa.
Richard G Manzon - One of the best experts on this subject based on the ideXlab platform.
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thyroid hormone and retinoid x receptor function and expression during sea lamprey petromyzon marinus Metamorphosis
General and Comparative Endocrinology, 2014Co-Authors: Lori A Manzon, John H Youson, Guillaume Holzer, Leopoldo Staiano, Vincent Laudet, Richard G ManzonAbstract:Sea lampreys (Petromyzon marinus) are members of the ancient class Agnatha and undergo a Metamorphosis that transforms blind, sedentary, filter-feeding larvae into free-swimming, parasitic juveniles. Thyroid hormones (THs) appear to be important for lamprey Metamorphosis, however, serum TH concentrations are elevated in the larval phase, decline rapidly during early Metamorphosis and remain low until Metamorphosis is complete; these TH fluctuations are contrary to those of other metamorphosing vertebrates. Moreover, thyroid hormone synthesis inhibitors (goitrogens) induce precocious Metamorphosis and exogenous TH treatments disrupt natural Metamorphosis in P. marinus. Given that THs exert their effects by binding to TH nuclear receptors (TRs) that often act as heterodimers with retinoid X receptors (RXRs), we cloned and characterized these receptors from P. marinus and examined their expression during Metamorphosis. Two TRs (PmTR1 and PmTR2) and three RXRs (PmRXRs) were isolated from P. marinus cDNA. Phylogenetic analyses group the PmTRs together on a branch prior to the gnathostome TRα/β split. The three RXRs also group together, but our data indicated that these transcripts are most likely either allelic variants of the same gene locus, or the products of a lamprey-specific duplication event. Importantly, these P. marinus receptors more closely resemble vertebrate as opposed to invertebrate chordate receptors. Functional analysis revealed that PmTR1 and PmTR2 can activate transcription of TH-responsive genes when treated with nanomolar concentrations of TH and they have distinct pharmacological profiles reminiscent of vertebrate TRβ and TRα, respectively. Also similar to other metamorphosing vertebrates, expression patterns of the PmTRs during lamprey Metamorphosis suggest that PmTR1 has a dynamic, tissue-specific expression pattern that correlates with tissue morphogenesis and biochemical changes and PmTR2 has a more uniform expression pattern. This TR expression data suggests that THs, either directly or via a metabolite, may function to positively modulate changes at the tissue or organ levels during lamprey Metamorphosis. Collectively the results presented herein support the hypothesis that THs have a dual functional role in the lamprey life cycle whereby high levels promote larval feeding, growth and lipogenesis and low levels promote Metamorphosis.
Hiroshi Wada - One of the best experts on this subject based on the ideXlab platform.
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retinoic acid signaling regulates the Metamorphosis of feather stars crinoidea echinodermata insight into the evolution of the animal life cycle
Biomolecules, 2019Co-Authors: Shumpei Yamakawa, Yoshiaki Morino, Hisanori Kohtsuka, Hiroshi WadaAbstract:Many marine invertebrates have a life cycle with planktonic larvae, although the evolution of this type of life cycle remains enigmatic. We recently proposed that the regulatory mechanism of life cycle transition is conserved between jellyfish (Cnidaria) and starfish (Echinoderm); retinoic acid (RA) signaling regulates strobilation and Metamorphosis, respectively. However, the function of RA signaling in other animal groups is poorly understood in this context. Here, to determine the ancestral function of RA signaling in echinoderms, we investigated the role of RA signaling during the Metamorphosis of the feather star, Antedon serrata (Crinoidea, Echinodermata). Although feather stars have different larval forms from starfish, we found that exogenous RA treatment on doliolaria larvae induced Metamorphosis, like in starfish. Furthermore, blocking RA synthesis or binding to the RA receptor suppressed Metamorphosis. These results suggested that RA signaling functions as a regulator of Metamorphosis in the ancestor of echinoderms. Our data provides insight into the evolution of the animal life cycle from the viewpoint of RA signaling.
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The role of retinoic acid signaling in starfish Metamorphosis
BMC, 2018Co-Authors: Shumpei Yamakawa, Yoshiaki Morino, Masanao Honda, Hiroshi WadaAbstract:Abstract Background Although retinoic acid (RA) signaling plays a crucial role in the body patterning of chordates, its function in non-chordate invertebrates, other than its mediation of environmental cues triggering Metamorphosis in cnidarians, is largely unknown. We investigated the role of RA signaling in the Metamorphosis of starfish (Echinodermata). Results We found that exogenous RA treatment induced Metamorphosis in starfish larvae. In contrast, inhibitors of RA synthesis and RA receptors suppressed Metamorphosis triggered by attachment to a substrate. Gene expressions of the RA signaling component were detected in competent larvae. Conclusions This study provides insight into the ancestral function of RA signaling, which is conserved in the Metamorphosis of cnidarians and starfish
Polivanov Lexy - One of the best experts on this subject based on the ideXlab platform.
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The Effects of Phosphate on the Metamorphosis of Larval Western Barred Tiger Salamanders (Ambystoma mavortium)
DigitalCommons@University of Nebraska - Lincoln, 2020Co-Authors: Polivanov LexyAbstract:This investigation will collect data to assist in determining if elevated aquatic phosphate levels affects the Metamorphosis rate of larval western barred tiger salamanders (Ambystoma mavortium). Monoammonium phosphate fertilizers are being used on crops in Nebraska (NDA, 2017). This area lines up with the area the western barred tiger salamanders are disappearing from (Damme, 2018). Monoammonium phosphate is made up of nitrogen and phosphate. There have been several studies showing how nitrogen is harmful to amphibians such as this salamander (Griffis-Kyle, 2007) (Griffis-Kyle & Richtie, 2007), but there have not been many showing how phosphate affects amphibian’s Metamorphosis in the aquatic environment. Therefore, this investigation will look at how elevated levels of phosphates affects the Metamorphosis of larval salamanders. This study will incorporate a control and treatment group of salamanders that will be followed through their Metamorphosis. The data was statistically analyzed. After analyzing the data, it was found that only one of the two treatment salamanders showed a correlation between the phosphate level and its Metamorphosis. Data obtained did not significantly indicate the effects of elevated phosphate levels on Western salamander Metamorphosis
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The Effects of Phosphate on Larval Western Barred Tiger Salamanders (\u3ci\u3eAmbystoma mavortium\u3c/i\u3e)
DigitalCommons@University of Nebraska - Lincoln, 2020Co-Authors: Polivanov Lexy, Ferraro DennisAbstract:This study seeks examine the effects of elevated phosphate levels on the larval stage of the Western Barred Tiger Salamander (Ambystoma mavortium). Hypothesis: Additional phosphate in the water will cause the larval salamanders to have a slower Metamorphosis rate than the control group with no additional phosphates. This hypothesis is based off of research that showed that additional nitrogen in the water caused a slower growth rate in the Western Barred Tiger Salamander (Ambystoma mavortium) (Griffis-Kyle, 2007). The hypothesis was rejected. The dates the larvae morphed alternated between treatment and control. The treatment Metamorphosis was not slowed. Temperature was found to not be significantly correlated to morphing. Further studies are needed to determine the effects of phosphate on larval salamanders. There is some data suggesting increased phosphate levels may influence Metamorphosis of the larvae. However, contrary to the hypothesis this data suggests that the increase in phosphate may have caused Metamorphosis to occur. Despite this only one salamander suggests this data which is not significant enough to say that the phosphate levels influenced Metamorphosis
Andrew P Negri - One of the best experts on this subject based on the ideXlab platform.
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Metamorphosis of a scleractinian coral in response to microbial biofilms
Applied and Environmental Microbiology, 2004Co-Authors: Nicole S Webster, Linda L. Blackall, Luke Smith, Andrew Heyward, Joy E M Watts, Richard I Webb, Andrew P NegriAbstract:Microorganisms have been reported to induce settlement and Metamorphosis in a wide range of marine invertebrate species. However, the primary cue reported for Metamorphosis of coral larvae is calcareous coralline algae (CCA). Herein we report the community structure of developing coral reef biofilms and the potential role they play in triggering the Metamorphosis of a scleractinian coral. Two-week-old biofilms induced Metamorphosis in less than 10% of larvae, whereas Metamorphosis increased significantly on older biofilms, with a maximum of 41% occurring on 8-week-old microbial films. There was a significant influence of depth in 4- and 8-week biofilms, with greater levels of Metamorphosis occurring in response to shallow-water communities. Importantly, larvae were found to settle and metamorphose in response to microbial biofilms lacking CCA from both shallow and deep treatments, indicating that microorganisms not associated with CCA may play a significant role in coral Metamorphosis. A polyphasic approach consisting of scanning electron microscopy, fluorescence in situ hybridization (FISH), and denaturing gradient gel electrophoresis (DGGE) revealed that coral reef biofilms were comprised of complex bacterial and microalgal communities which were distinct at each depth and time. Principal-component analysis of FISH data showed that the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Cytophaga-Flavobacterium of Bacteroidetes had the largest influence on overall community composition. A low abundance of Archaea was detected in almost all biofilms, providing the first report of Archaea associated with coral reef biofilms. No differences in the relative densities of each subdivision of Proteobacteria were observed between slides that induced larval Metamorphosis and those that did not. Comparative cluster analysis of bacterial DGGE patterns also revealed that there were clear age and depth distinctions in biofilm community structure; however, no difference was detected in banding profiles between biofilms which induced larval Metamorphosis and those where no Metamorphosis occurred. This investigation demonstrates that complex microbial communities can induce coral Metamorphosis in the absence of CCA.
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natural inducers for coral larval Metamorphosis
Coral Reefs, 1999Co-Authors: Andrew Heyward, Andrew P NegriAbstract:Coral gametes from Acropora millepora (Ehrenberg, 1834) and from multi-species spawning slicks provided larvae for use in Metamorphosis assays with a selection of naturally occurring inducer chemicals. Four species of crustose coralline algae, one non-coralline crustose alga and two branching coralline algae induced larval Metamorphosis. However, one additional species of branching coralline algae did not produce a larval response. Metamorphosis was also observed when larvae were exposed to skeleton from the massive coral Goniastrea retiformis (Lamarck, 1816) and to calcified reef rubble, demonstrating Metamorphosis is possible in the absence of encrusting algae. Chemical extracts from these algae and the coral skeleton, obtained using either decalcification or simple methanol extraction procedures, also contained active inducers. These results extend the number of crustose algal species known to induce coral Metamorphosis, suggest that some inducers may not necessarily be strongly associated with the calcified algal cell walls, and indicate that inducer sources in reef habitats may be more diverse than previously reported.
