Author: Shireen Hanna Partovi
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Amphibian metamorphosis is facilitated solely by thyroid hormones (THs), L-thyroxine (T4) and 3,5,3'-triiodothyronine (T3). TH modulates the remodeling of many different organs and systems in the body of developing tadpoles, including the immune system. Previous research found evidence of T4 action on direct-response genes in outer ring deiodinase-poor premetamorphic tadpole tail fin and liver without the required conversion to T3 described by current TH dogma. The mechanisms of environmental endocrine disrupting chemicals (EDCs) may be better understood by expanding our understanding of the transcriptomic effects of both forms of THs and how they relate to estrogen signaling. Furthermore, analysis of TH-modulation of the immune system may enable a greater understanding of the devastating effects of amphibian pathogens such as Ranavirus. Premetamorphic Rana (Lithobates) catesbeiana tadpoles were exposed to physiological concentrations of T4, T3, or 17-beta-estradiol (E2) through water bath immersion. qPCR analysis was performed to assess the response of canonical TH-responsive genes thra, thrb, and thibz to these hormones in the liver and tail fin tissues of bullfrog tadpoles. E2 treatment did not elicit a response in these gene transcripts in either tissue. T3 treatment in the tail fin elicited an overall stronger response than T4, while T4 treatment in the liver recapitulated results consistent with non-genomic mechanisms of T4 signaling for thrb and thibz transcripts. Illumina Hiseq2500 was used to sequence RNA isolated from hormone-treated premetamorphic tadpole liver and tail fin tissues to assess differential transcriptomic responses and identify TH-responsive immune system-associated transcripts. The impact of TH-treatment on the general immune system in the liver and tail fin transcriptomes was also analyzed using RNA-seq data. We found that E2 modulates at least some shared TH pathways in the liver, but none in the tail fin and that the tail fin transcriptome is more affected by T3, while the liver transcriptome is more affected by T4. Additionally, evidence of immune system modulation by both THs was found in both the liver and tail fin transcriptomes. Antimicrobial peptides (AMPs) are an important component of the amphibian immune response. Details regarding the regulation, synthesis, and expression of AMPs remain obscure, although evidence of TH-modulation of specific AMPs has been identified, as well as evidence of increased expression of AMPs throughout metamorphosis. Frog skin is a prolific source of AMPs that may prove useful in the quest for alternative antimicrobial agents in the face of antibiotic resistance. Identification of new AMPs is hindered by the practical limitations of classical protein-based discovery approaches. By using known AMP characteristics and common ¬AMP properties, we developed a high throughput bioinformatics approach predicated on the use of R. catesbeiana genome resources. We mined these resources and identified novel and known AMPs that exhibited verified antimicrobial activity against various bacterial organisms. This thesis sought to elucidate the differential and modulatory effects of both forms of TH on a transcriptomic level and in the context of immunity, and to examine the utility of the bullfrog transcriptome and genomics resources in identifying and characterizing novel bullfrog-derived AMPs and elucidating aspects of AMP expression.

Author: Li Zheng
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN: 9780612681187
Category : Actin
Languages : en
Pages : 350

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Book Description
Amphibian metamorphosis involves a complex but coordinate transformation of individual tissues in a tadpole. It is becoming increasingly clear that thyroid hormone controls metamorphosis by regulating a cascade of gene expression in this process. Thus, the overall objective of my thesis was to establish whether or not thyroid hormone induces the expression of one or more of the actin genes in the heart or other tissues/organs of the metamorphosing Rana catesbeiana (American bullfrog) tadpole. In order to accomplish my objective, I isolated and characterized the cDNAs and genomic DNAs encoding various isoforms of actin in this amphibian and, subsequently, evaluated the expression of the genes encoding these actin isoforms.

Author: Huimin Hu
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN: 9780612212916
Category : Gene expression
Languages : en
Pages : 232

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Book Description
The complete regression of a tadpole's tail during its transition to a frog is dramatic and a morphological hallmark of amphibian metamorphosis. Studies of tail regression indicate that the destruction of this organ involves a genetic program which is initiated by thyroid hormone and consists of several phases, all of which are thought to involve changes in gene expression. Previous studies, focused on the initial phase of tail regression in the Rana catesbeiana tadpole, have shown that a decrease in the rate of synthesis of some myofibrillar proteins, such as the myosin heavy chains, is an early, thyroid hormone-mediated event. However, the question of whether this event results from regulatory mechanisms operating at the level of transcription and/or translation has not been addressed. Thus, the overall objective of my studies was to establish what effect thyroid hormone has on the expression of mRNAs encoding the heavy chains of myosin in the tail muscle of hormone-treated tadpoles, and, to accomplish my objective, I first had to isolate and characterize cDNAs encoding the myosin heavy chains found in the tail muscle of this tadpole. The results of my investigations demonstrate (1) that the genes which encode at least five of the myosin heavy chains expressed in the tadpole tail muscle are also expressed in the hindlimb muscles of tadpoles at metamorphic climax and in the limb muscles of adult frogs, (2) that thyroid hormone treatment of the tadpole does not repress the level of these mRNAs in its tail, but, instead, appears to promote an accumulation in the level of at least four of the mRNAs encoding these myosin heavy chains, and (3) that the thyroid hormone-induced up-regulation in the levels of the myosin heavy chain mRNAs is early and coincidental with an up-regulation in the levels of mRNAs encoding TR$\alpha,$ TR$\beta$ and the Rana homologue of a mammalian C/EBP-$\delta.$ These results suggest that the thyroid hormone-induced decrease in the rate of myosin heavy chain synthesis in the tadpole tail muscle is not related to a depression in the amount of mRNAs encoding the tadpole (stage-specific) isoforms of the myosin heavy chains.

Author: OECD
Publisher: OECD Publishing
ISBN: 9264076247
Category :
Languages : en
Pages : 33

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Book Description
This Test Guideline describes an amphibian metamorphosis assay intended to screen substances which may interfere with the normal functioning of the hypothalamo-pituitary-thyroid axis. The assay was validated with the species Xenopus laevis, which is ...

Author: Georg Hennemann
Publisher: Marcel Dekker
ISBN:
Category : Medical
Languages : en
Pages : 656

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Book Description

Author: Leobardo Manuel Gómez-Oliván
Publisher: Springer Nature
ISBN: 3030562948
Category : Science
Languages : en
Pages : 338

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Book Description
This book gathers the main international research findings on non-steroidal anti-inflammatory drugs (NSAIDs) as emerging contaminants in water. It focuses on the major routes of exposure, and the destinations and life cycles of NSAIDs in water, as well as the manifestations of toxicity in different organisms. It also reviews the methods used in the detection, analysis and quantification of NSAIDs in water as well as the biological and chemical methods of removing them. Lastly, the book offers an overview of the legal frameworks in place and provides conclusions and recommendations for the future. Given its scope, the book is an indispensable resource for scientists in academia and industry, as well as for decision-makers involved in contamination assessment and environmental analysis and NGOs interested in the problem of water contamination by NSAIDs.

Author: Seyedmojtaba Seyedmousavi
Publisher: Springer
ISBN: 9783319720913
Category : Medical
Languages : en
Pages : 412

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Book Description
This book provides in-depth insights into epidemic and emerging mycoses in various animal groups. The different categories of pathogens and outbreak fungi are discussed. In an introductory chapter, the reader will be provided basic information on fungal infections that are non-transmissible, infections from a common environmental source known as sapronoses, and zoophilic fungal pathogens in various animal species and populations, worldwide Chapter 2 details the vocabulary and terminology that is required in the scientific literature in order to maintain clarity of expression to the field of Mycology. Chapters 3 to 9 discuss epidemic mycoses with a reservoir in animals and occasional outbreaks, including dermatophytoses, coccidioidomycosis, histoplasmosis, paracoccidioidomycosis, adiaspiromycosis and similar diseases, blastomycosis, and paracoccidioidomycosis ceti (lacaziosis/lobomycosis). Chapters 10 to 15 comprise emerging mycoses in animals that include feline sporotrichosis, lethargic crab disease, emergence of C. gattii in animals and zoonotic potential, white-nose syndrome in hibernating bats, chytridiomycosis in frogs and salamanders and aspergillosis in cats. The last chapter is about treatment possibilities, antifungal use in veterinary practice, and emergence of resistance. The book will address medical and veterinary mycologists, microbiologists, veterinarians, infectious disease specialists, epidemiologists, ecologists, public health scientists from academia and industry as well as graduate students, PhD students and postdocs in the field.

Author: Eria A. Rebollar
Publisher: Frontiers Media SA
ISBN: 2889459055
Category :
Languages : en
Pages : 275

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Book Description
The field of amphibian microbial ecology has greatly advanced in recent years. The work published to date has shown that amphibian skin bacterial communities can be influenced by host species, host life-history stage, environmental conditions, surrounding bacterial communities that serve as reservoirs and external biotic agents such as pathogens. As the ecology of amphibian-microbial symbiosis is a relatively new field, there are still many unanswered questions. The aim of this Research Topic is to highlight recent research on amphibian microbiomes that addresses relevant questions on the ecology of amphibian-microbe interactions. The publications gathered in this Research Topic have expanded our knowledge on the role of microbial symbionts of amphibians and have revealed novel insights that can direct the next set of research questions. We suggest that soon the field will move from the basic (and necessary) descriptions of microbial communities to more experimental approaches that include the use of omics methods and a variety of novel analytic and multivariate approaches. In addition to providing more insights into the microbial and disease ecology of amphibians, these studies may lead to effective ways to manipulate the microbiome to achieve protection from diseases, such as chytridiomycosis.

Author: Matthew J. Gray
Publisher: Springer
ISBN: 9783319137568
Category : Science
Languages : en
Pages : 246

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Book Description
This is the first book on ranaviruses. Ranaviruses are double-stranded DNA viruses that cause hemorrhagic disease in amphibians, reptiles, and fish. They have caused mass die-offs of ectothermic vertebrates in wild and captive populations around the globe. There is evidence that this pathogen is emerging and responsible for population declines in certain locations. Considering that amphibians and freshwater turtles are suitable hosts and the most imperiled vertebrate taxa in the world, ranaviruses can have significant impacts on biodiversity and ecosystem function. Additionally, many fish that are raised in aquaculture facilities and traded internationally are suitable hosts; thus, the potential economic impact of ranaviruses is significant. Ranaviruses also serve as a model for replication and gene function of large double-stranded DNA viruses. There is an urgent need to assemble the contemporary information on ranaviruses and provide guidance on how to assess their threats in populations. Through the Global Ranavirus Consortium, 24 experts from six countries were organize to write this volume, the first book on ranaviruses. The book begins with a discussion on the global extent of ranaviruses, case histories of infection and disease in ectothermic vertebrates, and current phylogeny. Basic principles of ranavirus ecology and evolution are covered next, with a focus on host-pathogen interactions and how the virus emerges in its environment. There are two chapters that will discuss the molecular biology of ranaviruses, host response to infection, and the genes responsible for immune system evasion. One chapter establishes standards for testing for infection and diagnosing ranaviral disease. The book ends by providing guidance on how to design ranavirus surveillance studies and analyze data to determine risk, and discussing the role of the Global Ranavirus Consortium in organizing research and outreach activities.

Author: Andrew P. Hendry
Publisher: Princeton University Press
ISBN: 0691204179
Category : Science
Languages : en
Pages : 410

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Book Description
In recent years, scientists have realized that evolution can occur on timescales much shorter than the 'long lapse of ages' emphasized by Darwin - in fact, evolutionary change is occurring all around us all the time. This work provides an authoritative and accessible introduction to eco-evolutionary dynamics, a cutting-edge new field that seeks to unify evolution and ecology into a common conceptual framework focusing on rapid and dynamic environmental and evolutionary change.