To see the other types of publications on this topic, follow the link: Expressive metamorphosis.
Journal articles on the topic 'Expressive metamorphosis'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Expressive metamorphosis.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Kang, Eun-Mi. "Animation Technique and Significances Underlying in Michēle Cournoyner’s Animated Film “Soif” - Focusing on the Expressive Form of Metamorphosis -." Journal of the Korea Entertainment Industry Association 13, no. 8 (December 31, 2019): 255–66. http://dx.doi.org/10.21184/jkeia.2019.12.13.8.255.
Full text
2
Sturm, Bob L. "Composing for an ensemble of atoms: the metamorphosis of scientific experiment into music." Organised Sound 6, no. 2 (August 2001): 131–45. http://dx.doi.org/10.1017/s1355771801002102.
Full textAbstract:
In quantum mechanics a particle can behave like a particle or a wave. Thus, systems of particles can be likened to a superposition of waves. Since sound can be described as a superposition of frequencies, it can also be described in terms of a system of particles manifest as waves. This metaphor between ‘particle physics’ and sound synthesis is quantitatively developed here, suggested initially from some similarities between the two domains. It is applied to a few fundamental physical principles to show how these can be sonified. The author discusses the process of using a simulated ‘atom trap’ to compose a piece that does not require a physicist to appreciate it. This metaphor blurs the distinctions between science and art, where scientific experiment becomes musical composition, and exploring a musical idea involves playing with particle system dynamics. In the future, methods like these could be used with a real system of particles – the particle accelerator will become an expressive musical instrument, and the particle physicist will become the composerscientist.
3
Kanki, Keita, and Masami Wakahara. "Spatio-Temporal Expression of TSHβ and FSHβ Genes in Normally Metamorphosing, Metamorphosed, and Metamorphosis-Arrested Hynobius retardatus." General and Comparative Endocrinology 119, no. 3 (September 2000): 276–86. http://dx.doi.org/10.1006/gcen.2000.7502.
Full text
4
Oliveira, Livia Sprizão de, and Edina Regina Panichi. "Lexical choices along the creative process of coc comparato." Signum: Estudos da Linguagem 22, no. 1 (July 4, 2019): 141. http://dx.doi.org/10.5433/2237-4876.2019v22n1p141.
Full textAbstract:
Lexicographical words represent things – physical or abstracts – and are also plenty of expressive shapes, which are socially built. The grammatical use of words disseminates denotative meanings and metaphorical effects that engage emotions. The context in which words are placed creates a feedback cycle between the sign and the psychic images that it evokes. Through the analysis of the manuscripts of the Brazilian dramatist, Doc Comparato, we shall observe the movements of experimentation and lexical choice along the creative process of his writing of the script Jamais (Never) - also called Calabar or A tribute to the treason. We are going to verify the changes on the effects of meaning by comparing the reviews applied to the text, following the author’s search for the grammatical shape that gives life to the idea. In order to analyze the metamorphosis of the writing process we shall use the fundaments of Genetic Criticism and the Stylistic to evaluate the results reached by the author – considering that a dramaturgical text is made to be staged and, for being so, must predict the impact of the sounds of words and also the actions that follow them.
5
Burrai, Francesco, and Giovanni Salis. "Umanizzazione delle cure: curare con l'arte." Giornale di Clinica Nefrologica e Dialisi 32, no. 1 (June 30, 2020): 92–95. http://dx.doi.org/10.33393/gcnd.2020.2154.
Full textAbstract:
Art can be a way, together with Nature, to intercept that landscape and inner climate characterized by the rhythm of silence. That dimension of iridescent calm imbued with creative and vital energy, which pushes towards a universal, seductive, profound sphere. Man can, with courage, abandon himself in this harmony and melody of thoughts that suggest a vast and visionary possibility. Each person has the inner possibility to be Art, to get out of the continuous distortions of daily life, to produce a metamorphosis of one’s life. Art triggers the unconscious side of seeing, a rhythmic, dynamic principle, on which every gesture of maximum spontaneity depends, not touched by the artificial, by masks of fugacity and by false personalities. Without Art, it seems that part of real life is missing. The deep artistic power is fluid, without space or time, pulsating with new forms and substance and creating a new personal identity, contiguous to the real world, which inspires new desires. Many diseases of today and yesterday are produced by the lack of expressiveness or by the repression of personal creativity. Art produces well-being because it is the transformation of unconscious expressive energies, so life for our health.
6
Eri, R., J. M. Arnold, V. F. Hinman, K. M. Green, M. K. Jones, B. M. Degnan, and M. F. Lavin. "Hemps, a novel EGF-like protein, plays a central role in ascidian metamorphosis." Development 126, no. 24 (December 15, 1999): 5809–18. http://dx.doi.org/10.1242/dev.126.24.5809.
Full textAbstract:
All chordates share several characteristic features including a dorsal hollow neural tube, a notochord, a pharynx and an endostyle. Unlike other chordate taxa, ascidians have a biphasic life-history with two distinct body plans. During metamorphosis, the larval nerve cord and notochord degenerate and the pharyngeal gill slits and endostyle form. While ascidians, like other marine invertebrates, metamorphose in response to specific environmental cues, it remains unclear how these cues trigger metamorphosis. We have identified a novel gene (Hemps) which encodes a protein with a putative secretion signal sequence and four epidermal growth factor (EGF)-like repeats which is a key regulator of metamorphosis in the ascidian Herdmania curvata. Expression of Hemps increases markedly when the swimming tadpole larva becomes competent to undergo metamorphosis and then during the first 24 hours of metamorphosis. The Hemps protein is localised to the larval papillae and anterior epidermis of the larva in the region known to be required for metamorphosis. When the larva contacts an inductive cue the protein is released, spreading posteriorly and into the tunic as metamorphosis progresses. Metamorphosis is blocked by incubating larvae in anti-Hemps antibodies prior to the addition of the cue. Addition of recombinant Hemps protein to competent larvae induces metamorphosis in a concentration-dependent manner. A subgroup of genes are specifically induced during this process. These results demonstrate that the Hemps protein is a key regulator of ascidian metamorphosis and is distinct from previously described inducers of this process in terrestrial arthropods and aquatic vertebrates.
7
Belles, Xavier. "The innovation of the final moult and the origin of insect metamorphosis." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20180415. http://dx.doi.org/10.1098/rstb.2018.0415.
Full textAbstract:
The three modes of insect postembryonic development are ametaboly, hemimetaboly and holometaboly, the latter being considered the only significant metamorphosis mode. However, the emergence of hemimetaboly, with the genuine innovation of the final moult, represents the origin of insect metamorphosis and a necessary step in the evolution of holometaboly. Hemimetaboly derives from ametaboly and might have appeared as a consequence of wing emergence in Pterygota, in the early Devonian. In extant insects, the final moult is mainly achieved through the degeneration of the prothoracic gland (PG), after the formation of the winged and reproductively competent adult stage. Metamorphosis, including the formation of the mature wings and the degeneration of the PG, is regulated by the MEKRE93 pathway, through which juvenile hormone precludes the adult morphogenesis by repressing the expression of transcription factor E93, which triggers this change. The MEKRE93 pathway appears conserved in extant metamorphosing insects, which suggest that this pathway was operative in the Pterygota last common ancestor. We propose that the final moult, and the consequent hemimetabolan metamorphosis, is a monophyletic innovation and that the role of E93 as a promoter of wing formation and the degeneration of the PG was mechanistically crucial for their emergence. This article is part of the theme issue ‘The evolution of complete metamorphosis’.
8
Shikuma, Nicholas J., Igor Antoshechkin, João M. Medeiros, Martin Pilhofer, and Dianne K. Newman. "Stepwise metamorphosis of the tubewormHydroides elegansis mediated by a bacterial inducer and MAPK signaling." Proceedings of the National Academy of Sciences 113, no. 36 (August 22, 2016): 10097–102. http://dx.doi.org/10.1073/pnas.1603142113.
Full textAbstract:
Diverse animal taxa metamorphose between larval and juvenile phases in response to bacteria. Although bacteria-induced metamorphosis is widespread among metazoans, little is known about the molecular changes that occur in the animal upon stimulation by bacteria. Larvae of the tubewormHydroides elegansmetamorphose in response to surface-boundPseudoalteromonas luteoviolaceabacteria, producing ordered arrays of phage tail-like metamorphosis-associated contractile structures (MACs). Sequencing theHydroidesgenome and transcripts during five developmental stages revealed that MACs induce the regulation of groups of genes important for tissue remodeling, innate immunity, and mitogen-activated protein kinase (MAPK) signaling. Using two MAC mutations that blockP. luteoviolaceafrom inducing settlement or metamorphosis and three MAPK inhibitors, we established a sequence of bacteria-induced metamorphic events: MACs induce larval settlement; then, particular properties of MACs encoded by a specific locus inP. luteoviolaceainitiate cilia loss and activate metamorphosis-associated transcription; finally, signaling through p38 and c-Jun N-terminal kinase (JNK) MAPK pathways alters gene expression and leads to morphological changes upon initiation of metamorphosis. Our results reveal that the intricate interaction betweenHydroidesandP. luteoviolaceacan be dissected using genomic, genetic, and pharmacological tools.Hydroides' dependency on bacteria for metamorphosis highlights the importance of external stimuli to orchestrate animal development. The conservation ofHydroidesgenome content with distantly related deuterostomes (urchins, sea squirts, and humans) suggests that mechanisms of bacteria-induced metamorphosis inHydroidesmay have conserved features in diverse animals. As a major biofouling agent, insight into the triggers ofHydroidesmetamorphosis might lead to practical strategies for fouling control.
9
Vasiliu, Laura Otilia. "Ancient Greek Myths in Romanian Opera. Pascal Bentoiu’s Jertfirea Ifigeniei [The Sacrifice of Iphigenia]." Artes. Journal of Musicology 19, no. 1 (March 1, 2019): 108–23. http://dx.doi.org/10.2478/ajm-2019-0006.
Full textAbstract:
Abstract Romanian composers’ interest in Greek mythology begins with Enescu’s peerless masterpiece – lyrical tragedy Oedipe (1921-1931). The realist-postromantic artistic concept is materialised in the insoluble link between text and music, in the original synthesis of the most expressive compositional means recorded in the tradition of the genre and the openness towards acutely modern elements of musical language. The Romanian opera composed in the knowledge of George Enescu’s score, which premiered in Bucharest in 1958, reflect an additional interest in mythological subject-matter in the poetic form of the ancient tragedies signed by Euripides, Aeschylus and Sophocles. Significant Romanian musical works written in the avant-garde period of 1960 to 1980 – Doru Popovici’s opera Prometeu, Aurel Stroe’s Oedipus at Colonus, Oresteia I – Agamemnon, Oresteia II – The Choephori, Oresteia III – The Eumenides, Pascal Bentoiu’s The Sacrifice of Iphigenia – to which titles of the contemporary art of the stage are added – Cornel Ţăranu’s Oreste & Oedip – propose new philosophical and artistic interpretations of the original myths. At the same time, the mentioned works represent reference points of the multiple and radical transformation of the opera genre in Romanian culture. Emphasising the epic character, a heightened chamber dimension and the alternative extrapolation of the elements in the syncretic complex, developing new modes of performance, of sonic and video transmission – are features of the new style of opera associated to the powerful and simple subject-matter of ancient tragedy. In this sense, radio opera The Sacrifice of Iphigenia (1968) is a significant step in the metamorphosis of the genre, its novel artistic value being confirmed by an important international distinction offered to composer Pascal Bentoiu – Prix Italia of the Italian Radio and Television Broadcasting Company in Rome. The poetic quality of the text quoted from the masterpiece of ancient theatre, Euripides’ Iphigenia in Aulis, the hymnic-oratory character of the music, the economy and expressive capacity of the compositional means configured in the relationship between voice, organ, percussion, electro-acoustic means – can be associated in interpreting the universal major theme: the necessity of virgin sacrifice in the process of durable construction.
10
Stolow, M. A., D. D. Bauzon, J. Li, T. Sedgwick, V. C. Liang, Q. A. Sang, and Y. B. Shi. "Identification and characterization of a novel collagenase in Xenopus laevis: possible roles during frog development." Molecular Biology of the Cell 7, no. 10 (October 1996): 1471–83. http://dx.doi.org/10.1091/mbc.7.10.1471.
Full textAbstract:
Matrix metalloproteinases (MMPs) participate in extracellular matrix remodeling and degradation and have been implicated in playing important roles during organ development and pathological processes. Although it has been hypothesized for > 30 years that collagenase activities are responsible for collagen degradation during tadpole tail resorption, none of the previously cloned amphibian MMPs have been biochemically demonstrated to be collagenases. Here, we report a novel matrix metalloproteinase gene from metamorphosing Xenopus laevis tadpoles. In vitro biochemical studies demonstrate that this Xenopus enzyme is an interstitial collagenase and has an essentially identical enzymatic activity toward a collagen substrate as the human interstitial collagenase. Sequence comparison of this enzyme to other known MMPs suggests that the Xenopus collagenase is not a homologue of any known collagenases but instead represents a novel collagenase, Xenopus collagenase-4 (xCol4, MMP-18). Interestingly, during development, xCol4 is highly expressed only transiently in whole animals, at approximately the time when tadpole feeding begins, suggesting a role during the maturation of the digestive tract. More importantly, during metamorphosis, xCol4 is regulated in a tissue-dependent manner. High levels of its mRNA are present as the tadpole tail resorbs. Similarly, its expression is elevated during hindlimb morphogenesis and intestinal remodeling. In addition, when premetamorphic tadpoles are treated with thyroid hormone, the causative agent of metamorphosis, xCol4 expression is induced in the tail. These results suggest that xCol4 may facilitate larval tissue degeneration and adult organogenesis during amphibian metamorphosis.
11
Hyodo, S. "Expression of the vasotocin gene in the hypothalamus of intact and osmotically stimulated bullfrogs during metamorphosis." Journal of Molecular Endocrinology 22, no. 3 (June 1, 1999): 305–12. http://dx.doi.org/10.1677/jme.0.0220305.
Full textAbstract:
To study the ontogeny of the vasotocin (VT) system and its contribution to anuran metamorphosis, VT mRNA levels were determined by Northern blot analysis in metamorphosing bullfrog tadpoles. Effects of osmotic stimulation on VT mRNA levels were also analyzed in order to follow the development of osmotic responsiveness of VT neurons. The intensity of hybridization signals for VT mRNA gradually increased during prometamorphic development. The increase became marked thereafter until metamorphic climax. Plasma osmolality and hematocrit remained unchanged before metamorphosis, and increased after metamorphic climax, indicating that climactic tadpoles in a semi-terrestrial environment were in a dehydrated condition. These increases correlated well with the increase in VT mRNA level. Immersion of tadpoles in 30% seawater (approximately 350 mOsmol) for 3 days increased plasma osmolality at all stages. No significant changes were observed in the VT mRNA level in response to this treatment during premetamorphic stages. The VT mRNA levels were significantly higher in the treated tadpoles after preclimax stages. Hyperosmotic treatment also increased hematocrit until early metamorphic climax, but did not alter it in tadpoles at late metamorphic climax. These results suggest that the responsiveness of VT-producing neurons to hyperosmotic or hypovolemic stimulation, or both, is established by the time of the metamorphic climax in bullfrog. The marked increase in VT mRNA levels at metamorphic climax stages of intact individuals is probably induced by dehydration. VT-stimulated water absorption and reabsorption in the target organs probably prevented the increase in hematocrit at late metamorphic climax. Thus VT may contribute importantly to osmoregulatory mechanisms in relation to adaptation to a semi-terrestrial habitat through the metamorphosis.
12
Brzezińska, Anna Maria. "Atmosphere of societal anxiety and representations of the body: The image of man in surrealist works of Vítězslav Nezval in the 20th century interwar period in Bohemia." Journal of Education Culture and Society 9, no. 1 (June 27, 2018): 181–89. http://dx.doi.org/10.15503/jecs20181.181.189.
Full textAbstract:
Aim: The interwar period in Czechoslovakia was a time of societal anxiety. The aim of this paper is to find the central themes of societal fear, as reflected in the surrealist works of Vítězslav Nezval, a czech poet. The analysis will be based primarily on the lyric poetry from the collections: Žena v množném čísle [Woman in Plural] (1936) and Absolutní hrobař [Absolute Gravedigger] (1937).
Methods: The analysis is based on the Josef Vojdovík’s anthropo-phenomenological method of exploring the surrealist perceptions of the body, which is based on vertical and horizontal anthropological dimensions and phenomenological conceptions of fears.
Results: Surrealist poetry and other literary works contain images of the body that are changed by fear: deformations, metamorphoses, fragmentarisations, hybridisations, expressing the body as a collage, a mosaic, an amalgam, a phantom, a grotesque, an inlay, and as lifelessness. It undergoes multiple metamorphoses, not only within its own form, but also with regard to the categories of life and lifelessness.
Conclusions: The analysis leads to the conclusion, that V. Nezval’s works show a clear tendency to portray the body as an object which undergoes a metamorphosis. The body is balanced on the edge between living and dead, organic and inorganic, it is determined by time and space. It is often shown along the narrowing-widening relation, in stupor, petrification, reduced to a flat surface or miniaturised.
13
MIHAIL, Rarița. "THE METAMORPHOSIS OF THE ALIENATION CONCEPT." International Multidisciplinary Scientific Conference on the Dialogue between Sciences & Arts, Religion & Education 4, no. 1 (December 7, 2020): 17–24. http://dx.doi.org/10.26520/mcdsare.2020.4.17-24.
Full textAbstract:
This article touches the notion of alienation from Rousseau’s, Hegel’s and young Marx’s perspective, Althusser’s critique being its offset, which, according to, this concept stems from an abstract, metaphysical view of history and human agents’ activities. According to Althusser, alienation is indeed the humanistic expression of a back-to-origins philosophy and of lost human essence retrieval. Hence, the philosophy of contractual alienation (as a foundation of political community as per Rousseau), the interrogation of historical positivity from young Hegel’s writings and, last but not least, the alienated work critique elaborated by young Marx in Manuscripts of 1844 can be interpreted as variations around the same essential concepts of human history. In the attempt of overcoming such an undifferentiated approach, the study tries to highlight the original and particular reflection that each of these authors develop on the subject and highlights, at the same time, what they have in common, despite their differences on this theme. When we talk about alienation we always relate to a mutilated loss in the relationship with the self, with others and with the social world. Moreover, we also talk about the possibility of overcoming some of the conditions that are considered degrading for humans. In other words, this study aims to prove that not only it is not possible to reduce the alienation to an abstract and naïve humanistic notion, but that it also represents an essential landmark for understanding the impossibility of some social groups of classes to develop on the merits of long-lasting deprivation of the benefits the relationship with the self, the others and the social world can bring.
14
Abū Kishik, Zahirah Taufīq, and Atikah Khattab Al-Ubaidi. "دور استدعاء الشخصيات التراثية في توجيه الدلالة: شعر محمد القيسي أُنموذجاً / The function of recalling traditional characters in implying meanings: The poem of Muḥammad al-Qaisi as case study." مجلة الدراسات اللغوية والأدبية (Journal of Linguistic and Literary Studies) 9, no. 1 (April 29, 2018): 166–86. http://dx.doi.org/10.31436/jlls.v9i1.616.
Full textAbstract:
ملخص البحث:
تسعى هذه الدراسة إلى تتبع استدعاء الشخصيات التراثية من دينية وتاريخية في تجربة الشاعر محمد القيسي الشعريّة، وذلك لإظهار دورها في توجيه دلالات النصّ، وتفعيل إيقاعه، بتلك المثيرات البصرية التي تفعّل الدفقة الشعريّة، وتغلفها بالطابع الدراميّ. وقد سارت الدراسة لتوضيح ذلك في ثلاثة مستويات: الأول يبحث في الاندماج الكلي ما بين الشخصية المـُستدعاة والواقع، والثاني في التأثير الجزئي لهذه الشخصيات، أما الثالث فيكون في النفي الكلي أو القلب لما هي عليه الشخصية التراثية؛ ولذلك فقد أسهم هذا الاستدعاء في خلق حركة مراوغة بين الشكل والمضمون في تجربة الشاعر محمد القيسي. توصل البحث إلى أن ظاهرة استدعاء الشخصيات التراثية من أهم الظواهر التي أثْرت القصيدة المعاصرة، وأسهمت في تشكيل رؤيا الشاعر اتجاه قضايا عصره، وحددت مواقفه المعبرة عن واقعه؛ لذا ربطته علاقة قوية وفاعلة بالتراث، تنم عن وعيه بموروثه الإنساني الشامل والزاخر بمصادره؛ لتعزز بذلك دلالات وجماليات متعددة.
الكلمات المفتاحية: الشخصية- التراث- استدعاء- دلالة- الواقع.
Abstract
The study attempts to trace the technique of recalling traditional religious and historical figures in the poem of Muhammad al-Qaisi with respect to its function in implying the textual meaning and activating its rhythm through the visual stimulus that sensitize the poetic aesthetic and embrace it with dramatic feature. The study does this in three stages: first it discusses in the total metamorphosis between the invoked character and the reality, second, in the partial effect of these characters; and thirdly, total denial or the reversal of what used to be the experience of those characters. The recalling of those characters had contributed in circumventing between form and content in the poetic experience of Muhammad al-Qaisi. The study concludes that recalling traditional characters is among the most important phenomenon that has influenced modern poetry and contribute in forming the vision of the poet about the issues of his time and shape his positions that are expressive of his reality. This had helped to forge a strong relation with the tradition derived from his awareness and his human heritage that is comprehensive and rich with resources to consolidate the various aesthetical meanings.
Keywords: Characters, Tradition, Recalling, Meaning, Reality
Abstrak
Kajian ini mencuba untuk mengesan teknik mengenang kembali figura budaya, agama dan sejarah dalam syair nukilan Muhammad al-Qaysi berkaitan fungsinya dalam memberikan bayangan makna tekstual dan menggiatkan iramanya melalui rangsangan visual yang mencetuskan nilai estetika syair dan merangkuminya dengan ciri yang dramatik. Kajian ini dilaksanakan dalam tiga tahap: pertama ia membicarakan tentang metamorphosis total antara watak yang dibayangkan itu dan reality; keduanya, ia membicarakan tentang kesan yang dibawa watak tersebut; ketiga, mengetengahkan penafian menyeluruh atau rekaan semula ciri dan situasi watak tersebut. Penggunaan watak dan figura tersebut telah berjaya mengimbangkan di antara bentuk dan kandungan syair yang dinukilkan Muhammad al-Qaysi. Kajian ini mendapati penampilan watak-watak lama ini merupakan satu teknik yang telah menyumbang dalam mewarnai syair-syair moden dan membantu membentuk persepsi penyair terhadap isu era beliau juga pendirian beliau yang diluahkan berdasarkan realiti yang dialami. In itelah membantu juga dalam mengukuhkan hubungan di antara budaya dan kesedaran beliau serta kahazanah kemanusiaan beliau yang menyeluruh dan kaya dengan sumber-sumber yang dapat menyerlahkan lagi nilai estetika dalam karya-karya yang dinukilkan.
Kata kunci: Watak-watak, Tradisi, Mengenang kembali, Makna, realiti
15
Wray, Gregory A. "Gene expression during echinoderm metamorphosis." Zygote 8, S1 (December 1999): S48—S49. http://dx.doi.org/10.1017/s0967199400130230.
Full textAbstract:
Metamorphosis is a remarkable process in echinoderms, transforming a bilaterally symmetrical planktonic larva into a radially symmetrical benthic adult. This shift in habitat involves functional and anatomical changes in virtually every organ system (Bury, 1895; MacBride, 1914; Okazaki, 1975). Although metamorphosis is a crucial process in echinoderm development, we know relatively little about it. Furthermore, most of what we do know concerns sea urchins, and even less information is available about metamorphosis in other echinoderms. We have examined the expression of regulatory and structural genes during metamorphosis in several different echinoderm species (Lowe & Wray, 1997 and unpublished results). These data, together with those from several recent studies concerning additional genes (reviewed in Wray & Lowe, 2000), are beginning to shed new light on this complex and important process in echinoderm development.The overt transformation from swimming larva to settled juvenile is quite rapid in echinoderms (Cameron & Hinegardner, 1978), requiring less than half an hour in many species. The complete process of metamorphosis takes much longer, however (Okazaki, 1975; Gosselin & Jangoux, 1998). Extensive preparations begin several days to weeks before settlement (MacBride, 1914; Okazaki, 1975), depending upon the species and upon environmental conditions (Strathmann et al., 1992). During this preparatory phase, initially small populations of ectodermal and mesodermal cells fated to become the adult proliferate, differentiate and undergo complex morphogenetic movements to form the imaginal rudiment (MacBride, 1914; Okazaki, 1975). The rudiment is more complex than the larva in several important ways: it contains a greater number of cell types, it is the first place where true tissues form, and it contains the first well-organised nervous system (Okazaki, 1975; Chia & Burke, 1978).
16
Wakahara, Masami, and Masahiro Yamaguchi. "Heterochronic Expression of Several Adult Phenotypes in Normally Metamorphosing and Metamorphosis-Arrested Larvae of a Salamander Hynobius retardatus." Zoological Science 13, no. 3 (June 1996): 483–88. http://dx.doi.org/10.2108/zsj.13.483.
Full text
17
Rollins-Smith, Louise A., Martin F. Flajnik, Patrick J. Blair, A. Tray Davis, and Wayne F. Green. "Involvement of Thyroid Hormones in the Expression of MHC class I Antigens During Ontogeny inXenopus." Developmental Immunology 5, no. 2 (1997): 133–44. http://dx.doi.org/10.1155/1997/38464.
Full textAbstract:
The major histocompatibility complex (MHC) is a cluster of genes encoding products central to all major functions of the vertebrate immune system. Evidence for an MHC can be found in all vertebrate groups that have been examined except the jawless fishes. Expression of MHC class I and class II antigens early in ontogeny is critically important for development of T lymphocytes capable of discriminating self from nonself. Because of this essential role in T-cell development, the ontogeny of MHC expression in the South African clawed frog,Xenopus laevis, was studied. Previous studies of MHC class I expression inXenopus laevissuggested that class I antigens are virtually absent from tadpole tissues until climax of metamorphosis. We therefore examined the possible role of thyroid hormones (TH) in the induction of class I. By flow cytometry, a small amount of class I expression was detectable on splenocytes and erythrocytes in untreated frogs at prometamorphic stages 55-58, and the amount increased significantly at the conclusion of metamorphic climax. Thus, metamorphosis is associated with increased intensity of class I expression. Neither inhibition nor acceleration of metamorphosis altered the timing of onset of class I expression. However, inhibition of metamorphosis prevented the increase in class I expression characteristic of adult cell populations. Because expression was not accelerated in TH-treated frogs or delayed in metamorphosis-inhibited frogs, it is unlikely that TH are the direct developmental cues that induce expression, although they seem to be required for the upregulation of class I expression occurring at metamorphosis. Differences in the pattern of expression in different subpopulations of cells suggest a complex pattern of regulation of expression of class I antigens during ontogeny.
18
Tamura, Kei, Shutaro Takayama, Takako Ishii, Shuuji Mawaribuchi, Nobuhiko Takamatsu, and Michihiko Ito. "Apoptosis and differentiation of Xenopus tail-derived myoblasts by thyroid hormone." Journal of Molecular Endocrinology 54, no. 3 (June 2015): 185–92. http://dx.doi.org/10.1530/jme-14-0327.
Full textAbstract:
The metamorphosis of anuran amphibians is induced by thyroid hormone (TH). To study the molecular mechanisms underlying tail regression during metamorphosis, we established a cell line, XL-B4, from a Xenopus laevis tadpole tail at a premetamorphic stage. The cells expressed myoblast markers and differentiated into myotubes in differentiation medium. XL-B4 cells expressing fluorescent proteins were transplanted into tadpole tails. At 5 days post-transplantation, fluorescence was observed in myotube-like structures, indicating that the myoblastic cells could contribute to skeletal muscle. Exposure of XL-B4 cells to the TH triiodothyronine (T3) for several days significantly induced apoptotic cell death. We then examined an early response of expression of genes involved in apoptosis or myogenesis to T3. Treatment of the cells with T3 increased transcription of genes for matrix metalloproteinase-9 (MMP-9) and thyroid hormone receptor beta. Interestingly, the T3-treatment also increased myoD transcripts, but decreased the amounts of myogenin mRNA and myosin heavy chain. Importantly, we also observed upregulation of myoD expression and downregulation of myogenin expression in tails, but not in hind limbs, when tadpoles at a premetamorphic stage were treated with T3 for 1 day. These results indicated that T3 could not only induce apoptosis, but also attenuate myogenesis in tadpole tails during metamorphosis.
19
Truman, J. W., W. S. Talbot, S. E. Fahrbach, and D. S. Hogness. "Ecdysone receptor expression in the CNS correlates with stage-specific responses to ecdysteroids during Drosophila and Manduca development." Development 120, no. 1 (January 1, 1994): 219–34. http://dx.doi.org/10.1242/dev.120.1.219.
Full textAbstract:
In insects, the ecdysteroids act to transform the CNS from its larval to its adult form. A key gene in this response is the ecdysone receptor (EcR), which has been shown in Drosophila to code for 3 protein isoforms. Two of these isoforms, EcR-A and EcR-B1, are prominently expressed in the CNS and we have used isoform-specific antibodies to examine their fluctuations through postembryonic life. EcR expression at the onset of metamorphosis is extremely diverse but specific patterns of EcR expression correlate with distinct patterns of steroid response. Most larval neurons show high levels of EcR-B1 at the start of metamorphosis, a time when they lose larval features in response to ecdysteroids. Earlier, during the larval molts, the same cells have no detectable receptors and show no response to circulating ecdysteroids; later, during the pupal-adult transformation, they switch to EcR-A expression and respond by maturing to their adult form. During the latter period, a subset of the larval neurons hyperexpress EcR-A and these cells are fated to die after the emergence of the adult. The stem cells for the imaginal neurons show prominent EcR-B1 expression during the last larval stage correlated with their main proliferative period. Most imaginal neurons, by contrast, express only EcR-A when they subsequently initiate maturation at the start of metamorphosis. The imaginal neurons of the mushroom bodies are unusual amongst imaginal neurons in expressing the B1 isoform at the start of metamorphosis but they also show regressive changes at this time as they lose their larval axons. Imaginal neurons of the optic lobe show a delayed expression of EcR-B1 through the period when cell-cell interactions are important for establishing connections within this region of the CNS. Overall, the appearance of the two receptor isoforms in cells correlates with different types of steroid responses: EcR-A predominates when cells are undergoing maturational responses whereas EcR-B1 predominates during proliferative activity or regressive responses. The heterogeneity of EcR expression at the start of metamorphosis presumably reflects the diverse origins and requirements of the neurons that nevertheless are all exposed to a common hormonal signal.
20
Paul, Bindu Diana, Liezhen Fu, Daniel R. Buchholz, and Yun-Bo Shi. "Coactivator Recruitment Is Essential for Liganded Thyroid Hormone Receptor To Initiate Amphibian Metamorphosis." Molecular and Cellular Biology 25, no. 13 (July 1, 2005): 5712–24. http://dx.doi.org/10.1128/mcb.25.13.5712-5724.2005.
Full textAbstract:
ABSTRACT Thyroid hormone receptors (TRs) can repress or activate target genes depending on the absence or presence of thyroid hormone (T3), respectively. This hormone-dependent gene regulation is mediated by recruitment of corepressors in the absence of T3 and coactivators in its presence. Many TR-interacting coactivators have been characterized in vitro. In comparison, few studies have addressed the developmental roles of these cofactors in vivo. We have investigated the role of coactivators in transcriptional activation by TR during postembryonic tissue remodeling by using amphibian metamorphosis as a model system. We have previously shown that steroid receptor coactivator 3 (SRC3) is expressed and upregulated during metamorphosis, suggesting a role in gene regulation by liganded TR. Here, we have generated transgenic tadpoles expressing a dominant negative form of SRC3 (F-dnSRC3). The transgenic tadpoles exhibited normal growth and development throughout embryogenesis and premetamorphic stages. However, transgenic expression of F-dnSRC3 inhibits essentially all aspects of T3-induced metamorphosis, as well as natural metamorphosis, leading to delayed or arrested metamorphosis or the formation of tailed frogs. Molecular analysis revealed that F-dnSRC3 functioned by blocking the recruitment of endogenous coactivators to T3 target genes without affecting corepressor release, thereby preventing the T3-dependent gene regulation program responsible for tissue transformations during metamorphosis. Our studies thus demonstrate that coactivator recruitment, aside from corepressor release, is required for T3 function in development and further provide the first example where a specific coactivator-dependent gene regulation pathway by a nuclear receptor has been shown to underlie specific developmental events.
21
BOWMAKER, JAMES K., MA'AYAN SEMO, DAVID M. HUNT, and GLEN JEFFERY. "Eel visual pigments revisited: The fate of retinal cones during metamorphosis." Visual Neuroscience 25, no. 3 (March 6, 2008): 249–55. http://dx.doi.org/10.1017/s0952523808080152.
Full textAbstract:
During their complex life history, anguilliform eels go through a major metamorphosis when developing from a fresh water yellow eel into a deep-sea silver eel. In addition to major changes in body morphology, the visual system also adapts from a fresh water teleost duplex retina with rods and cones, to a specialized deep-sea retina containing only rods. The history of the rods is well documented with an initial switch from a porphyropsin to a rhodopsin (P5232 to P5011) and then a total change in gene expression with the down regulation of a “freshwater” opsin and its concomitant replacement by the expression of a typical “deep-sea” opsin (P5011 to P4821). Yellow eels possess only two spectral classes of single cones, one sensitive in the green presumably expressing an RH2 opsin gene and the second sensitive in the blue expressing an SWS2 opsin gene. In immature glass eels, entering into rivers from the sea, the cones contain mixtures of rhodopsins and porphyropsins, whereas the fully freshwater yellow eels have cone pigments that are almost pure porphyropsins with peak sensitivities at about 540–545 nm and 435–440 nm, respectively. However, during the early stages of metamorphosis, the pigments switch to rhodopsins with the maximum sensitivity of the “green”-sensitive cone shifting to about 525 nm, somewhat paralleling, but preceding the change in rods. During metamorphosis, the cones are almost completely lost.
22
Schubiger, M., A. A. Wade, G. E. Carney, J. W. Truman, and M. Bender. "Drosophila EcR-B ecdysone receptor isoforms are required for larval molting and for neuron remodeling during metamorphosis." Development 125, no. 11 (June 1, 1998): 2053–62. http://dx.doi.org/10.1242/dev.125.11.2053.
Full textAbstract:
During the metamorphic reorganization of the insect central nervous system, the steroid hormone 20-hydroxyecdysone induces a wide spectrum of cellular responses including neuronal proliferation, maturation, cell death and the remodeling of larval neurons into their adult forms. In Drosophila, expression of specific ecdysone receptor (EcR) isoforms has been correlated with particular responses, suggesting that different EcR isoforms may govern distinct steroid-induced responses in these cells. We have used imprecise excision of a P element to create EcR deletion mutants that remove the EcR-B promoter and therefore should lack EcR-B1 and EcR-B2 expression but retain EcR-A expression. Most of these EcR-B mutant animals show defects in larval molting, arresting at the boundaries between the three larval stages, while a smaller percentage of EcR-B mutants survive into the early stages of metamorphosis. Remodeling of larval neurons at metamorphosis begins with the pruning back of larval-specific dendrites and occurs as these cells are expressing high levels of EcR-B1 and little EcR-A. This pruning response is blocked in the EcR-B mutants despite the fact that adult-specific neurons, which normally express only EcR-A, can progress in their development. These observations support the hypothesis that different EcR isoforms control cell-type-specific responses during remodeling of the nervous system at metamorphosis.
23
Navarro-Martín, Laia, Chantal Lanctôt, Christopher Edge, Jeff Houlahan, and Vance L. Trudeau. "Expression profiles of metamorphosis-related genes during natural transformations in tadpoles of wild Wood Frogs (Lithobates sylvaticus)." Canadian Journal of Zoology 90, no. 9 (September 2012): 1059–71. http://dx.doi.org/10.1139/z2012-074.
Full textAbstract:
Numerous studies using laboratory-reared tadpoles have shown the importance of thyroid hormones (TH), thyroid receptors (TR), and deiodinase (Dio) enzymes during anuran metamorphosis. Our study focuses on the analysis of thyroid-related genes in tadpoles of wild Wood Frogs ( Lithobates sylvaticus (LeConte, 1825); also known as Rana sylvatica (Cope, 1889)) during metamorphosis. Results showed that, in concordance with laboratory-reared studies, thyroid receptor beta (trb) gene expression profiles presented the most marked changes. At climax and compared with premetamorphic stages, brains, tails, and gonad–mesonephros complex (GMC) tissues increased trb expression levels 5-, 21-, and 41-fold, respectively (p < 0.05). In addition, gene expression levels of brain deiodinase type II and III showed opposite trends, where 3-fold decrease and 10-fold increase were, respectively, found. This finding supports the idea that thyroid hormone, as it has been demonstrated in laboratory-reared tadpoles, is also involved in natural metamorphosis in wild tadpoles. Interestingly, and contrary to our predictions, we observed that whole brain corticotropin-releasing factor (crf) and crf receptor 1 (crfr1) gene expression levels significantly decrease through metamorphosis in wild L. sylvaticus tadpoles. Further analyses are required to determine if a role of TH in the timing of anuran gonadal development exists, as well as the importance of cell-specific and tissue-specific expression of crf and crfr1 to metamorphosis.
24
Fletcher, J. C., and C. S. Thummel. "The Drosophila E74 gene is required for the proper stage- and tissue-specific transcription of ecdysone-regulated genes at the onset of metamorphosis." Development 121, no. 5 (May 1, 1995): 1411–21. http://dx.doi.org/10.1242/dev.121.5.1411.
Full textAbstract:
The steroid hormone ecdysone directly induces a small set of early genes, visible as puffs in the larval salivary gland polytene chromosomes, as it signals the onset of Drosophila metamorphorsis. The products of these genes appear to function as regulators that both repress their own expression and induce a large set of secondary-response late genes. We have identified recessive loss-of-function mutations in the early gene E74, a member of the ets protooncogene family that encodes two related DNA-binding proteins, E74A and E74B. These mutations cause defects in pupariation and pupation, and result in lethality during metamorphosis. Here we extend our phenotypic characterization of the E74A and E74B mutant alleles to the molecular level by examining their effects on the transcription of over 30 ecdysone-regulated genes. We show that the transcription of most ecdysone primary-response genes during late larval and prepupal development is unaffected by the E74 mutations. Rather, we find that E74 is necessary for the appropriate regulation of many ecdysone secondary-response genes. E74B is required for the maximal induction of glue genes in mid third instar larval salivary glands, while E74A is required in early prepupae for the proper timing and maximal induction of a subset of late genes. E74 activity is also necessary for the correct regulation of genes expressed predominantly in the fat body, epidermis or imaginal discs. These observations confirm that E74 plays a critical role in regulating transcription during the early stages of Drosophila metamorphosis. In addition, the widespread effects of the E74 mutations on transcription indicate that E74 functions in regulatory hierarchies not only in the larval salivary gland, but throughout the entire organism.
25
Krain, LP, and RJ Denver. "Developmental expression and hormonal regulation of glucocorticoid and thyroid hormone receptors during metamorphosis in Xenopus laevis." Journal of Endocrinology 181, no. 1 (April 1, 2004): 91–104. http://dx.doi.org/10.1677/joe.0.1810091.
Full textAbstract:
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 hormone-dependent 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 (TRbeta). In an effort to determine the relationship between nuclear hormone receptor expression and levels of ligand, we also analyzed changes in whole-body content of 3,5,3'-triiodothyronine (T(3)), 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. TRbeta mRNA level increased in the brain, intestine and tail during metamorphosis and was induced by treatment with T(3). Analysis of possible crossregulatory relationships between GRs and TRs showed that GR mRNA was upregulated by exogenous T(3) (50 nM) in the tail but downregulated in the brain of premetamorphic tadpoles. Exogenous CORT (100 nM) upregulated TRbeta mRNA in the intestine. Our findings provide evidence for tissue-specific positive, negative and crossregulation of nuclear hormone receptors during metamorphosis of X. laevis. The synergy of CORT with T(3) 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.
26
Lozano, Jesus, Raúl Montañez, and Xavier Belles. "MiR-2 family regulates insect metamorphosis by controlling the juvenile hormone signaling pathway." Proceedings of the National Academy of Sciences 112, no. 12 (March 9, 2015): 3740–45. http://dx.doi.org/10.1073/pnas.1418522112.
Full textAbstract:
In 2009 we reported that depletion of Dicer-1, the enzyme that catalyzes the final step of miRNA biosynthesis, prevents metamorphosis inBlattella germanica. However, the precise regulatory roles of miRNAs in the process have remained elusive. In the present work, we have observed that Dicer-1 depletion results in an increase of mRNA levels of Krüppel homolog 1 (Kr-h1), a juvenile hormone-dependent transcription factor that represses metamorphosis, and that depletion of Kr-h1 expression in Dicer-1 knockdown individuals rescues metamorphosis. We have also found that the 3′UTR of Kr-h1 mRNA contains a functional binding site for miR-2 family miRNAs (for miR-2, miR-13a, and miR-13b). These data suggest that metamorphosis impairment caused by Dicer-1 and miRNA depletion is due to a deregulation of Kr-h1 expression and that this deregulation is derived from a deficiency of miR-2 miRNAs. We corroborated this by treating the last nymphal instar ofB. germanicawith an miR-2 inhibitor, which impaired metamorphosis, and by treating Dicer-1-depleted individuals with an miR-2 mimic to allow nymphal-to-adult metamorphosis to proceed. Taken together, the data indicate that miR-2 miRNAs scavenge Kr-h1 transcripts when the transition from nymph to adult should be taking place, thus crucially contributing to the correct culmination of metamorphosis.
27
Tata, Jamshed R. "Hormonal regulation of programmed cell death during amphibian metamorphosis." Biochemistry and Cell Biology 72, no. 11-12 (November 1, 1994): 581–88. http://dx.doi.org/10.1139/o94-077.
Full textAbstract:
Extensive programmed cell death (PCD) is initiated at the onset of amphibian metamorphosis, resulting in 100% of cells dying in some larval tissues, as during total regression of tail and gills. All cell death during metamorphosis is under the control of thyroid hormone (TH), which can initiate the process precociously in whole tadpoles or in individual tissues in culture. The hormone prolactin (PRL), given exogenously, prevents natural and TH-induced metamorphosis. We have exploited this dual hormonal regulation in premetamorphic Xenopus tails in organ culture to identify and characterize early genes that are TH-induced and considered important for initiating cell death. Among the earliest genes activated by TH are those encoding the two thyroid hormone receptors TRα and TRβ. This autoinduction of TR genes is considered important since, in blocking this process, PRL also inhibited the expression of other TH-inducible genes and prevented cell death. The expression of early genes other than TR genes, which are known to promote cell death or survival, is also considered to be important for the initiation of PCD during amphibian metamorphosis. We are, therefore, working on the identification, characterization, and expression of members of the Xenopus bcl-2-like gene family, as well as other genes, such as nur-77 and ICE, which may act as early genes during tadpole tail regression.Key words: cell death, thyroid hormones, Xenopus, metamorphosis, gene expression.
28
Okada, Morihiro, Thomas C. Miller, Liezhen Fu, and Yun-Bo Shi. "Direct Activation of Amidohydrolase Domain-Containing 1 Gene by Thyroid Hormone Implicates a Role in the Formation of Adult Intestinal Stem Cells During Xenopus Metamorphosis." Endocrinology 156, no. 9 (June 18, 2015): 3381–93. http://dx.doi.org/10.1210/en.2015-1190.
Full textAbstract:
The T3-dependent anuran metamorphosis resembles postembryonic development in mammals, the period around birth when plasma T3 levels peak. In particular, the remodeling of the intestine during metamorphosis mimics neonatal intestinal maturation in mammals when the adult intestinal epithelial self-renewing system is established. We have been using intestinal metamorphosis to investigate how the organ-specific adult stem cells are formed during vertebrate development. Early studies in Xenopus laevis have shown that this process involves complete degeneration of the larval epithelium and de novo formation of adult stem cells. A tissue-specific microarray analysis of intestinal gene expression during Xenopus laevis metamorphosis has identified a number of candidate stem cell genes. Here we have carried out detailed analyses of one such gene, amidohydrolase domain containing 1 (AMDHD1) gene, which encodes an enzyme in the histidine catabolic pathway. We show that AMDHD1 is exclusively expressed in the proliferating adult epithelial stem cells during metamorphosis with little expression in other intestinal tissues. We further provide evidence that T3 activates AMDHD1 gene expression directly at the transcription level through T3 receptor binding to the AMDHD1 gene in the intestine. In addition, we have reported earlier that histidine ammonia-lyase gene, another gene in histidine catabolic pathway, is similarly regulated by T3 in the intestine. These results together suggest that histidine catabolism plays a critical role in the formation and/or proliferation of adult intestinal stem cells during metamorphosis.
29
Critchlow, Justin T., Adriana Norris, and Ann T. Tate. "The legacy of larval infection on immunological dynamics over metamorphosis." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190066. http://dx.doi.org/10.1098/rstb.2019.0066.
Full textAbstract:
Insect metamorphosis promotes the exploration of different ecological niches, as well as exposure to different parasites, across life stages. Adaptation should favour immune responses that are tailored to specific microbial threats, with the potential for metamorphosis to decouple the underlying genetic or physiological basis of immune responses in each stage. However, we do not have a good understanding of how early-life exposure to parasites influences immune responses in subsequent life stages. Is there a developmental legacy of larval infection in holometabolous insect hosts? To address this question, we exposed flour beetle ( Tribolium castaneum ) larvae to a protozoan parasite that inhabits the midgut of larvae and adults despite clearance during metamorphosis. We quantified the expression of relevant immune genes in the gut and whole body of exposed and unexposed individuals during the larval, pupal and adult stages. Our results suggest that parasite exposure induces the differential expression of several immune genes in the larval stage that persist into subsequent stages. We also demonstrate that immune gene expression covariance is partially decoupled among tissues and life stages. These results suggest that larval infection can leave a lasting imprint on immune phenotypes, with implications for the evolution of metamorphosis and immune systems. This article is part of the theme issue ‘The evolution of complete metamorphosis'.
30
Johnston, Paul R., Véronique Paris, and Jens Rolff. "Immune gene regulation in the gut during metamorphosis in a holo- versus a hemimetabolous insect." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190073. http://dx.doi.org/10.1098/rstb.2019.0073.
Full textAbstract:
During metamorphosis, holometabolous insects completely replace the larval gut and must control the microbiota to avoid septicaemia. Rapid induction of bactericidal activity in the insect gut at the onset of pupation has been described in numerous orders of the Holometabola and is best-studied in the Lepidoptera where it is under control of the 20-hydroxyecdysone (20E) moulting pathway. Here, using RNAseq, we compare the expression of immune effector genes in the gut during metamorphosis in a holometabolous ( Galleria mellonella ) and a hemimetabolous insect ( Gryllus bimaculatus ). We find that in G. mellonella , the expression of numerous immune effectors and the transcription factor GmEts are upregulated, with peak expression of three antimicrobial peptides (AMPs) and a lysozyme coinciding with delamination of the larval gut. By contrast, no such upregulation was detectable in the hemimetabolous Gr. bimaculatus . These findings support the idea that the upregulation of immune effectors at the onset of complete metamorphosis is an adaptive response, which controls the microbiota during gut replacement. This article is part of the theme issue ‘The evolution of complete metamorphosis’.
31
Buchholz, Daniel R., Shao-Chung Victor Hsia, Liezhen Fu, and Yun-Bo Shi. "A Dominant-Negative Thyroid Hormone Receptor Blocks Amphibian Metamorphosis by Retaining Corepressors at Target Genes." Molecular and Cellular Biology 23, no. 19 (October 1, 2003): 6750–58. http://dx.doi.org/10.1128/mcb.23.19.6750-6758.2003.
Full textAbstract:
ABSTRACT The total dependence of amphibian metamorphosis on thyroid hormone (T3) provides a unique vertebrate model for studying the molecular mechanism of T3 receptor (TR) function in vivo. In vitro transcription and developmental expression studies have led to a dual function model for TR in amphibian development, i.e., TRs act as transcriptional repressors in premetamorphic tadpoles and as activators during metamorphosis. We examined molecular mechanisms of TR action in T3-induced metamorphosis by using dominant-negative receptors (dnTR) ubiquitously expressed in transgenic Xenopus laevis. We showed that T3-induced activation of T3 target genes and morphological changes are blocked in dnTR transgenic animals. By using chromatin immunoprecipitation, we show that dnTR bound to target promoters, which led to retention of corepressors and continued histone deacetylation in the presence of T3. These results thus provide direct in vivo evidence for the first time for a molecular mechanism of altering gene expression by a dnTR. The correlation between dnTR-mediated gene repression and inhibition of metamorphosis also supports a key aspect of the dual function model for TR in development: during T3-induced metamorphosis, TR functions as an activator via release of corepressors and promotion of histone acetylation and gene activation.
32
Manzon, RG, and RJ Denver. "Regulation of pituitary thyrotropin gene expression during Xenopus metamorphosis: negative feedback is functional throughout metamorphosis." Journal of Endocrinology 182, no. 2 (August 1, 2004): 273–85. http://dx.doi.org/10.1677/joe.0.1820273.
Full textAbstract:
Several hypotheses have been proposed to explain the increase and sustained expression of pituitary thyrotropin (TSH) in the presence of elevated plasma thyroid hormone (TH) concentrations at metamorphic climax in amphibians. It has been proposed that the negative feedback of TH on TSH is inoperative until metamorphic climax, and that it is established at this time by the upregulation of pituitary deiodinase type II (DII); DII converts thyroxine (T(4)) to 3,5,3'-triiodothyronine (T(3)). However, earlier investigators, using indirect measures of TSH, reported that TH negative feedback on TSH was functional in premetamorphic tadpoles. In an effort to understand pituitary TSH regulation during amphibian metamorphosis, we analyzed multiple pituitary genes known or hypothesized to be involved in TSH regulation in tadpoles of Xenopus laevis. Tadpole pituitary explant cultures were used to examine direct negative feedback on TSH mRNA expression. Negative feedback is operative in the early prometamorphic tadpole pituitary and both T(3) and T(4) can downregulate TSH mRNA expression throughout metamorphosis. The expression of both DII and TH receptor betaA mRNAs increased during development and peaked at climax; however, these increases coincided with similar increases in deiodinase type III, which inactivates TH. Moreover, corticotropin-releasing factor (CRF) receptors, CRF binding protein and thyrotropin-releasing hormone receptor type 2 mRNA expression also peaked at climax. Our data suggest that the regulation of TSH is more complex than the timing of DII expression, and likely involves a balance between stimulation of TSH synthesis and secretion by neuropeptides (e.g. CRF) of hypothalamic or pituitary origin, increased pituitary sensitivity to neuropeptides through upregulation of their receptors, and intrapituitary TH levels.
33
Simmons, Andrea M., Seth S. Horowitz, and Judith A. Chapman. "Developmental changes in GABA expression across metamorphosis." Journal of the Acoustical Society of America 109, no. 5 (May 2001): 2357. http://dx.doi.org/10.1121/1.4744289.
Full text
34
Not Available, Not Available, Not Available Not Available, and Not Available Not Available. "Changes in gelsolin expression during ascidian metamorphosis." Development Genes and Evolution 211, no. 5 (June 1, 2001): 252–56. http://dx.doi.org/10.1007/s004270100134.
Full text
35
Rollins-Smith, Louise A., and Patrick Blair. "Expression of Class II Major Histocompatibility Complex Antigens on Adult T Cells inXenopusis Metamorphosis- Dependent." Developmental Immunology 1, no. 2 (1990): 97–104. http://dx.doi.org/10.1155/1990/25197.
Full textAbstract:
Class II major histocompatibility complex (MHC) antigens are expressed predominantly on B lymphocytes and macrophages of tadpoles of the South African clawed frog,Xenopus laevis, as is the pattern in lymphocyte populations of most mammals. However, unlike most mammals, young postmetamorphic frogs show expression of class II MHC antigens on a high proportion of thymocytes and most peripheral T and B lymphocytes. Using the J-strain ofXenopusand the anticlass II monoclonal antibody, 14A2, we have studied, by indirect immunofluorescence, whether inhibition of metamorphosis would alter the pattern of expression of class II antigens during ontogeny. In control animals, class II antigens were virtually absent from thymic lymphocytes and peripheral T cells of normal untreated larvae, but could be found in increasing numbers in both populations after metamorphosis (10-12 weeks of age). In contrast, larvae, whose metamorphosis was inhibited by treatment with sodium perchlorate, had relatively few class II+thymic lymphocytes throughout the 6-month period of study, and the proportion of class II+splenic lymphocytes was approximately equal to that of IgM+B lymphocytes. Thus, perchlorate-treated animals retained the larval pattern of class II epression, suggesting that emergence of class II+T cells is dependent on metamorphosis.
36
Izaguirre, MF, MN García-Sancho, LA Miranda, J. Tomas, and VH Casco. "Expression of cell adhesion molecules in the normal and T3 blocked development of the tadpole's kidney of Bufo arenarum (Amphibian, Anuran, Bufonidae)." Brazilian Journal of Biology 68, no. 3 (August 2008): 561–69. http://dx.doi.org/10.1590/s1519-69842008000300014.
Full textAbstract:
Cell adhesion molecules act as signal transducers from the extracellular environment to the cytoskeleton and the nucleus and consequently induce changes in the expression pattern of structural proteins. In this study, we showed the effect of thyroid hormone (TH) inhibition and arrest of metamorphosis on the expression of E-cadherin, β-and α-catenin in the developing kidney of Bufo arenarum. Cell adhesion molecules have selective temporal and spatial expression during development suggesting a specific role in nephrogenesis. In order to study mechanisms controlling the expression of adhesion molecules during renal development, we blocked the B. arenarum metamorphosis with a goitrogenic substance that blocks TH synthesis. E-cadherin expression in the proximal tubules is independent of thyroid control. However, the blockage of TH synthesis causes up-regulation of E-cadherin in the collecting ducts, the distal tubules and the glomeruli. The expression of β-and α-catenin in the collecting ducts, the distal tubules, the glomeruli and the mesonephric mesenchyme is independent of TH. TH blockage causes up-regulation of β-and α-catenin in the proximal tubules. In contrast to E-cadherin, the expression of the desmosomal cadherin desmoglein 1 (Dsg-1) is absent in the control of the larvae kidney during metamorphosis and is expressed in some interstitial cells in the KClO4 treated larvae. According to this work, the Dsg-1 expression is down-regulated by TH. We demonstrated that the expression of E-cadherin, Dsg-1, β-catenin and α-catenin are differentially affected by TH levels, suggesting a hormone-dependent role of these proteins in the B. arenarum renal metamorphosis.
37
Li, T., and M. Bender. "A conditional rescue system reveals essential functions for the ecdysone receptor (EcR) gene during molting and metamorphosis in Drosophila." Development 127, no. 13 (July 1, 2000): 2897–905. http://dx.doi.org/10.1242/dev.127.13.2897.
Full textAbstract:
In Drosophila, pulses of the steroid hormone ecdysone trigger larval molting and metamorphosis and coordinate aspects of embryonic development and adult reproduction. At each of these developmental stages, the ecdysone signal is thought to act through a heteromeric receptor composed of the EcR and USP nuclear receptor proteins. Mutations that inactivate all EcR protein isoforms (EcR-A, EcR-B1, and EcR-B2) are embryonic lethal, hindering analysis of EcR function during later development. Using transgenes in which a heat shock promoter drives expression of an EcR cDNA, we have employed temperature-dependent rescue of EcR null mutants to determine EcR requirements at later stages of development. Our results show that EcR is required for hatching, at each larval molt, and for the initiation of metamorphosis. In EcR mutants arrested prior to metamorphosis, expression of ecdysone-responsive genes is blocked and normal ecdysone responses of both imaginal and larval tissues are blocked at an early stage. These results show that EcR mediates ecdysone signaling at multiple developmental stages and implicate EcR in the reorganization of imaginal and larval tissues at the onset of metamorphosis.
38
Levi, G., F. Broders, D. Dunon, G. M. Edelman, and J. P. Thiery. "Thyroxine-dependent modulations of the expression of the neural cell adhesion molecule N-CAM during Xenopus laevis metamorphosis." Development 108, no. 4 (April 1, 1990): 681–92. http://dx.doi.org/10.1242/dev.108.4.681.
Full textAbstract:
During amphibian metamorphosis, a complete remodeling of the phenotype takes place under complex hormonal control whose final effectors are thyroid hormones. This process implies the activation of coordinated programs of cell death, proliferation, migration, adhesion and differentiation. Inasmuch as the neural cell adhesion molecule N-CAM is thought to play a central role in the control of morphogenetic processes, we have studied by immunohistofluorescence and immunoblots the patterns of expression of N-CAM at different stages of Xenopus laevis metamorphosis. A scan was made of all major organs and appendages. Before the metamorphic climax, all neuronal cell bodies and processes express high levels of N-CAM. During the metamorphic climax, N-CAM expression decreases sharply on the cell bodies and processes of the peripheral nervous system (PNS) but remains high in the central nervous system (CNS). Towards the end of metamorphosis, the PNS and spinal nerves are virtually negative for N-CAM while the CNS is still positive. The optic and olfactory nerves, although myelinated, are still strongly positive for N-CAM. The lens and olfactory epithelia express N-CAM throughout metamorphosis. In the brain. N-CAM is present at all times as three polypeptides of 180, 140, and 120 X 10(3) Mr; before metamorphosis some of the N-CAM is in its polysialylated form. During metamorphosis and the subsequent growth of the animal, the amount of N-CAM decreases gradually. In all polypeptides, the polysialylated form is the first to disappear. Cardiac muscle expresses high level of N-CAM from its first formation throughout metamorphosis; in contrast, the level of N-CAM in skeletal muscle is high in newly formed muscles, but decreases rapidly after myoblast fusion. The liver of adult Xenopus contains large amounts of a 160 X 10(3) polypeptide that is recognized by polyclonal and monoclonal antibodies against N-CAM. cDNA probes of Xenopus brain N-CAM recognize major transcripts of 9.2, 3.8 and 3.3 kb in Xenopus liver mRNA; these bands are different in size from those recognized in brain mRNA (9.5, 4.2 and 2.2 kb). Premetamorphic liver does not express the 160 X 10(3) form of N-CAM, which can be first detected at stage 59 and persists then through all the life of the animal. Expression of N-CAM in the liver can be induced in premetamorphic animals (stage 51–52) by a 48 h treatment with thyroxine. All hepatocytes are responsive.(ABSTRACT TRUNCATED AT 400 WORDS)
39
Xie, Caixia, Shanliang Xu, Linlin Yang, Zhonghe Ke, Jubin Xing, Junwei Gai, Xiaoling Gong, Liuxiong Xu, and Baolong Bao. "mRNA/microRNA Profile at the Metamorphic Stage of Olive Flounder (Paralichthys olivaceus)." Comparative and Functional Genomics 2011 (2011): 1–12. http://dx.doi.org/10.1155/2011/256038.
Full textAbstract:
Flatfish is famous for the asymmetric transformation during metamorphosis. The molecular mechanism behind the asymmetric development has been speculated over a century and is still not well understood. To date, none of the metamorphosis-related genes has been identified in flatfish. As the first step to screen metamorphosis-related gene, we constructed a whole-body cDNA library and a whole-body miRNA library in this study and identified 1051 unique ESTs, 23 unique miRNAs, and 4 snoRNAs in premetamorphosing and prometamorphosingParalichthys olivaceus. 1005 of the ESTs were novel, suggesting that there was a special gene expression profile at metamorphic stage. Four miRNAs (pol-miR-20c,pol-miR-23c,pol-miR-130d, andpol-miR-181e) were novel toP. olivaceus; they were characterized as highly preserved homologies of published miRNAs but with at least one nucleotide differed. Representative 24 mRNAs and 23 miRNAs were quantified during metamorphosis ofP. olivaceusby using quantitative RT PCR or stem-loop qRT PCR. Our results showed that 20 of mRNAs might be associated with early metamorphic events, 10 of mRNAs might be related with later metamorphic events, and 16 of miRNAs might be involved in the regulation of metamorphosis. The data provided in this study would be helpful for further identifying metamorphosis-related gene inP. olivaceus.
40
Kawahara, A., B. S. Baker, and J. R. Tata. "Developmental and regional expression of thyroid hormone receptor genes during Xenopus metamorphosis." Development 112, no. 4 (August 1, 1991): 933–43. http://dx.doi.org/10.1242/dev.112.4.933.
Full textAbstract:
A characteristic feature of the obligatory control of amphibian metamorphosis by thyroid hormones is the early acquisition of response of tadpole tissues to these hormones well before the latter are secreted, with ‘exponentially’ increasing hormonal sensitivity upon the onset of metamorphosis. We have therefore analyzed the expression of the two thyroid hormone receptor genes (TR alpha and beta) before, during and after metamorphosis in Xenopus tadpoles and froglets. Using non-cross-hybridizing cRNA probes for 5′ and 3′ sequences of Xenopus TR alpha and beta transcripts for RNAase protection assays, the two mRNAs can be detected in tadpoles as early as stage 39. Their concentration increases abruptly at stage 44 and continues to increase differentially at the onset of metamorphosis (stage 55) and through metamorphic climax at stages 58–62, after which they decline upon completion of metamorphosis at stage 66. Quantitative densitometric scanning of autoradiograms showed that, although the concentration of TR beta transcripts is about 1/30th of that of TR alpha mRNA at stages 44–48, depending on the region, it accumulates 3–10 times more rapidly than does the alpha isoform during further development. A substantial proportion of the increase in TR beta mRNA is localized to the head region of tadpoles. Using the hormone-binding domain (HBD) and 3′ end of Xenopus TR alpha cRNA as probe for in situ hybridization, the highest concentration of TR transcripts in stage 44 tadpoles is seen in the brain and spinal cord. High concentrations of mRNA are also present in the intestinal epithelium and tail tip, tissues programmed for regression. At later stages (55 onwards), strong hybridization signals are also exhibited by hindlimb buds. This pattern persists through metamorphic climax, after which TR mRNAs decline in all tissues to low levels in froglets at stage 66. In developing froglets, TR transcripts were detected in large amounts in the cytoplasm of stage 1 and 2 oocytes but the rate of their accumulation did not increase with further oocyte growth. This observation raises the possibility that the response to thyroid hormones at early stages of tadpoles (42–44) may be due to TR synthesized on maternally derived mRNA. Exposure of tadpoles at premetamorphic stages (48–52) to exogenous thyroid hormone (T3) substantially enhanced the accumulation of TR mRNA, especially that of TR beta message, which could explain the accelerated increase in sensitivity of tadpoles to thyroid hormones at the onset of natural metamorphosis.(ABSTRACT TRUNCATED AT 400 WORDS)
41
Matsuda, Hiroki, Bindu D. Paul, Cheol Young Choi, Takashi Hasebe, and Yun-Bo Shi. "Novel Functions of Protein Arginine Methyltransferase 1 in Thyroid Hormone Receptor-Mediated Transcription and in the Regulation of Metamorphic Rate in Xenopus laevis." Molecular and Cellular Biology 29, no. 3 (December 1, 2008): 745–57. http://dx.doi.org/10.1128/mcb.00827-08.
Full textAbstract:
ABSTRACT Protein arginine methyltransferase 1 (PRMT1) acts as a transcription coactivator for nuclear receptors through histone H4 R3 methylation. The in vivo function of PRMT1 is largely unknown. Here we investigated the role of PRMT1 in thyroid hormone (T3) receptor (TR)-mediated transcription in vivo during vertebrate development. By using intestinal remodeling during T3-dependent Xenopus laevis metamorphosis for in vivo molecular analysis, we first showed that PRMT1 expression was upregulated during metamorphosis when both TR and T3 were present. We then demonstrated a role for PRMT1 in TR-mediated transcription by showing that PRMT1 enhanced transcriptional activation by liganded TR in the frog oocyte transcription system and was recruited to the T3 response element (TRE) of the target promoter in the oocyte, as well as to endogenous TREs during frog metamorphosis. Surprisingly, we found that PRMT1 was only transiently recruited to the TREs in the target during metamorphosis and observed no PRMT1 recruitment to TREs at the climax of intestinal remodeling when both PRMT1 and T3 were at peak levels. Mechanistically, we showed that overexpression of PRMT1 enhanced TR binding to TREs both in the frog oocyte model system and during metamorphosis. More importantly, transgenic overexpression of PRMT1 enhanced gene activation in vivo and accelerated both natural and T3-induced metamorphosis. These results thus indicate that PRMT1 functions transiently as a coactivator in TR-mediated transcription by enhancing TR-TRE binding and further suggest that PRMT1 has tissue-specific roles in regulating the rate of metamorphosis.
42
Franco, Marie-Dominique, Michael P. Pape, Jennifer J. Swiergiel, and Gail D. Burd. "Differential and overlapping expression patterns of X-dll3 and Pax-6 genes suggest distinct roles in olfactory system development of the African clawed frog Xenopus laevis." Journal of Experimental Biology 204, no. 12 (June 15, 2001): 2049–61. http://dx.doi.org/10.1242/jeb.204.12.2049.
Full textAbstract:
SUMMARY In Xenopus laevis, the formation of the adult olfactory epithelium involves embryonic, larval and metamorphic phases. The olfactory epithelium in the principal cavity (PC) develops during embryogenesis from the olfactory placode and is thought to respond to water-borne odorants throughout larval life. During metamorphosis, the PC undergoes major transformations and is exposed to air-borne odorants. Also during metamorphosis, the middle cavity (MC) develops de novo. The olfactory epithelium in the MC has the same characteristics as that in the larval PC and is thought to respond to water-borne odorants. Using in situ hybridization, we analyzed the expression pattern of the homeobox genes X-dll3 and Pax-6 within the developing olfactory system. Early in development, X-dll3 is expressed in both the neuronal and non-neuronal ectoderm of the sense plate and in all cell layers of the olfactory placode and larval PC. Expression becomes restricted to the neurons and basal cells of the PC by mid-metamorphosis. During metamorphosis, X-dll3 is also expressed throughout the developing MC epithelium and becomes restricted to neurons and basal cells at metamorphic climax. This expression pattern suggests that X-dll3 is first involved in the patterning and genesis of all cells forming the olfactory tissue and is then involved in neurogenesis or neuronal maturation in putative water- and air-sensing epithelia. In contrast, Pax-6 expression is restricted to the olfactory placode, larval PC and metamorphic MC, suggesting that Pax-6 is specifically involved in the formation of water-sensing epithelium. The expression patterns suggest that X-dll3 and Pax-6 are both involved in establishing the olfactory placode during embryonic development, but subtle differences in cellular and temporal expression patterns suggest that these genes have distinct functions.
43
Das, B., and D. D. Brown. "Controlling transgene expression to study Xenopus laevis metamorphosis." Proceedings of the National Academy of Sciences 101, no. 14 (March 26, 2004): 4839–42. http://dx.doi.org/10.1073/pnas.0401011101.
Full text
44
Li, Zhiqian, Lang You, Baosheng Zeng, Lin Ling, Jun Xu, Xu Chen, Zhongjie Zhang, Subba Reddy Palli, Yongping Huang, and Anjiang Tan. "Ectopic expression of ecdysone oxidase impairs tissue degeneration in Bombyx mori." Proceedings of the Royal Society B: Biological Sciences 282, no. 1809 (June 22, 2015): 20150513. http://dx.doi.org/10.1098/rspb.2015.0513.
Full textAbstract:
Metamorphosis in insects includes a series of programmed tissue histolysis and remolding processes that are controlled by two major classes of hormones, juvenile hormones and ecdysteroids. Precise pulses of ecdysteroids (the most active ecdysteroid is 20-hydroxyecdysone, 20E), are regulated by both biosynthesis and metabolism. In this study, we show that ecdysone oxidase (EO), a 20E inactivation enzyme, expresses predominantly in the midgut during the early pupal stage in the lepidopteran model insect, Bombyx mori . Depletion of BmEO using the transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA-guided Cas9 nucleases) system extended the duration of the final instar larval stage. Ubiquitous transgenic overexpression of BmEO using the Gal4/UAS system induced lethality during the larval–pupal transition. When BmEO was specifically overexpressed in the middle silk gland (MSG), degeneration of MSG at the onset of metamorphosis was blocked. Transmission electron microscope and LysoTracker analyses showed that the autophagy pathway in MSG is inhibited by BmEO ectopic expression. Furthermore, RNA-seq analysis revealed that the genes involved in autophagic cell death and the mTOR signal pathway are affected by overexpression of BmEO . Taken together, BmEO functional studies reported here provide insights into ecdysone regulation of tissue degeneration during metamorphosis.
45
Jindra, Marek. "Where did the pupa come from? The timing of juvenile hormone signalling supports homology between stages of hemimetabolous and holometabolous insects." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1783 (August 26, 2019): 20190064. http://dx.doi.org/10.1098/rstb.2019.0064.
Full textAbstract:
Insect metamorphosis boasts spectacular cases of postembryonic development when juveniles undergo massive morphogenesis before attaining the adult form and function; in moths or flies the larvae do not even remotely resemble their adult parents. A selective advantage of complete metamorphosis (holometaboly) is that within one species the two forms with different lifestyles can exploit diverse habitats. It was the environmental adaptation and specialization of larvae, primarily the delay and internalization of wing development, that eventually required an intermediate stage that we call a pupa. It is a long-held and parsimonious hypothesis that the holometabolous pupa evolved through modification of a final juvenile stage of an ancestor developing through incomplete metamorphosis (hemimetaboly). Alternative hypotheses see the pupa as an equivalent of all hemimetabolous moulting cycles (instars) collapsed into one, and consider any preceding holometabolous larval instars free-living embryos stalled in development. Discoveries on juvenile hormone signalling that controls metamorphosis grant new support to the former hypothesis deriving the pupa from a final pre-adult stage. The timing of expression of genes that repress and promote adult development downstream of hormonal signals supports homology between postembryonic stages of hemimetabolous and holometabolous insects. This article is part of the theme issue ‘The evolution of complete metamorphosis’.
46
Currie, D. A., and M. Bate. "The development of adult abdominal muscles in Drosophila: myoblasts express twist and are associated with nerves." Development 113, no. 1 (September 1, 1991): 91–102. http://dx.doi.org/10.1242/dev.113.1.91.
Full textAbstract:
During metamorphosis, the adult muscles of the Drosophila abdomen develop from pools of myoblasts that are present in the larva. The adult myoblasts express twist in the third larval instar and the early pupa and are closely associated with nerves. Growing adult nerves and the twist-expressing cells migrate out across the developing abdominal epidermis, and as twist expression declines, the myoblasts begin to synthesize beta 3 tubulin. There follows a process involving cell fusion and segregation into cell groups to form multinucleate muscle precursors. These bipolar precursors migrate at both ends to find their correct attachment points. beta 3 tubulin expression continues at least until 51 h APF by which time the adult muscle pattern has been established.
47
Mawaribuchi, Shuuji, Kei Tamura, Saori Okano, Shutaro Takayama, Yoshio Yaoita, Tadayoshi Shiba, Nobuhiko Takamatsu, and Michihiko Ito. "Tumor Necrosis Factor-α Attenuates Thyroid Hormone-Induced Apoptosis in Vascular Endothelial Cell Line XLgoo Established from Xenopus Tadpole Tails." Endocrinology 149, no. 7 (April 10, 2008): 3379–89. http://dx.doi.org/10.1210/en.2007-1591.
Full textAbstract:
Amphibian metamorphosis induced by T3 involves programmed cell death and the differentiation of various types of cells in degenerated and reconstructed tissues. However, the signaling pathway that directs the T3-dependent cell-fate determinations remains unclear. TNF-α is a pleiotropic cytokine that affects diverse cellular responses. Engagement of TNF-α with its receptor (TNFR1) causes intracellular apoptotic and/or survival signaling. To investigate TNF signaling functions during anuran metamorphosis, we first identified Xenopus laevis orthologs of TNF (xTNF)-α and its receptor. We found that xTNF-α activated nuclear factor-κB in X. laevis A6 cells through the Fas-associated death domain and receptor-interacting protein 1. Interestingly, xTNF-α mRNA in blood cells showed prominent expression at prometamorphosis during metamorphosis. Next, to elucidate the apoptotic and/or survival signaling induced by xTNF-α in an in vitro model of metamorphosis, we established a vascular endothelial cell line, XLgoo, from X. laevis tadpole tail. XLgoo cells formed actin stress fibers and elongated in response to xTNF-α. T3 induced apoptosis in these cells, but the addition of xTNF-α blocked the T3-induced apoptosis. In addition, treatment of the cells with T3 for 2 d induced the expression of thyroid hormone receptor-β and caspase-3, and this thyroid hormone receptor-β induction was drastically repressed by xTNF-α. Furthermore, in organ culture of the tail, xTNF-α significantly attenuated the tail degeneration induced by T3. These findings suggested that xTNF-α could protect vascular endothelial cells from apoptotic cell death induced by T3 during metamorphosis and thereby participate in the regulation of cell fate.
48
Fletcher, J. C., K. C. Burtis, D. S. Hogness, and C. S. Thummel. "The Drosophila E74 gene is required for metamorphosis and plays a role in the polytene chromosome puffing response to ecdysone." Development 121, no. 5 (May 1, 1995): 1455–65. http://dx.doi.org/10.1242/dev.121.5.1455.
Full textAbstract:
The steroid hormone ecdysone initiates Drosophila metamorphosis by reprogramming gene expression during late larval and prepupal development. The ecdysone-inducible gene E74, a member of the ets proto-oncogene family, has been proposed to play a key role in this process. E74 is encoded within the 74EF early puff and consists of two overlapping transcription units, E74A and E74B. To assess the function(s) of E74 during metamorphosis, we have isolated and characterized recessive loss-of-function mutations specific to each transcription unit. We find that mutations in E74A and E74B are predominantly lethal during prepupal and pupal development, consistent with a critical role for their gene products in metamorphosis. Phenotypic analysis reveals that E74 function is required for both pupariation and pupation, and for the metamorphosis of both larval and imaginal tissues. E74B mutants are defective in puparium formation and head eversion and die as prepupae or cryptocephalic pupae, while E74A mutants pupariate normally and die either as prepupae or pharate adults. We have also investigated the effects of the E74 mutations on gene expression by examining the puffing pattern of the salivary gland polytene chromosomes in newly formed mutant prepupae. Most puffs are only modestly affected by the E74B mutation, whereas a subset of late puffs are sub-maximally induced in E74A mutant prepupae. These observations are consistent with Ashburner's proposal that early puff proteins induce the formation of late puffs, and define E74A as a regulator of late puff activity. They also demonstrate that E74 plays a wide role in reshaping the insect during metamorphosis, affecting tissues other than the salivary gland in which it was originally identified.
49
Fujimoto, Kenta, Kazuo Matsuura, Biswajit Das, Liezhen Fu, and Yun-Bo Shi. "Direct Activation of Xenopus Iodotyrosine Deiodinase by Thyroid Hormone Receptor in the Remodeling Intestine during Amphibian Metamorphosis." Endocrinology 153, no. 10 (October 1, 2012): 5082–89. http://dx.doi.org/10.1210/en.2012-1308.
Full textAbstract:
Abstract Thyroid hormone (TH) plays critical roles during vertebrate postembryonic development. TH production in the thyroid involves incorporating inorganic iodide into thyroglobulin. The expression of iodotyrosine deiodinase (IYD; also known as iodotyrosine dehalogenase 1) in the thyroid gland ensures efficient recycling of iodine from the byproducts of TH biosynthesis: 3′-monoiodotyrosine and 3′, 5′-diiodotyrosine. Interestingly, IYD is known to be expressed in other organs in adult mammals, suggesting iodine recycling outside the thyroid. On the other hand, the developmental role of iodine recycling has yet to be investigated. Here, using intestinal metamorphosis as a model, we discovered that the Xenopus tropicalis IYD gene is strongly up-regulated by TH during metamorphosis in the intestine but not the tail. We further demonstrated that this induction was one of the earliest events during intestinal metamorphosis, with IYD being activated directly through the binding of liganded TH receptors to a TH response element in the IYD promoter region. Because iodide is mainly taken up from the diet in the intestine and the tadpole stops feeding during metamorphosis when the intestine is being remodeled, our findings suggest that IYD transcription is activated by liganded TH receptors early during intestinal remodeling to ensure efficient iodine recycling at the climax of metamorphosis when highest levels of TH are needed for the proper transformations of different organs.
50
Buchholz, Daniel R., Akihiro Tomita, Liezhen Fu, Bindu D. Paul, and Yun-Bo Shi. "Transgenic Analysis Reveals that Thyroid Hormone Receptor Is Sufficient To Mediate the Thyroid Hormone Signal in Frog Metamorphosis." Molecular and Cellular Biology 24, no. 20 (October 15, 2004): 9026–37. http://dx.doi.org/10.1128/mcb.24.20.9026-9037.2004.
Full textAbstract:
ABSTRACT Thyroid hormone (T3) has long been known to be important for vertebrate development and adult organ function. Whereas thyroid hormone receptor (TR) knockout and transgenic studies of mice have implicated TR involvement in mammalian development, the underlying molecular bases for the resulting phenotypes remain to be determined in vivo, especially considering that T3 is known to have both genomic, i.e., through TRs, and nongenomic effects on cells. Amphibian metamorphosis is an excellent model for studying the role of TR in vertebrate development because of its total dependence on T3. Here we investigated the role of TR in metamorphosis by developing a dominant positive mutant thyroid hormone receptor (dpTR). In the frog oocyte transcription system, dpTR bound a T3-responsive promoter and activated the promoter independently of T3. Transgenic expression of dpTR under the control of a heat shock-inducible promoter in premetamorphic tadpoles led to precocious metamorphic transformations. Molecular analyses showed that dpTR induced metamorphosis by specifically binding to known T3 target genes, leading to increased local histone acetylation and gene activation, similar to T3-bound TR during natural metamorphosis. Our experiments indicated that the metamorphic role of T3 is through genomic action of the hormone, at least on the developmental parameters tested. They further provide the first example where TR is shown to mediate directly and sufficiently these developmental effects of T3 in individual organs by regulating target gene expression in these organs.