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Lisondro-Arosemena AK, Salazar-Nicholls MJ, Warkentin KM. Elevated ammonia cues hatching in red-eyed treefrogs: A mechanism for escape from drying eggs. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2024; 342:406-411. [PMID: 38708813 DOI: 10.1002/jez.b.23253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 02/01/2024] [Accepted: 04/02/2024] [Indexed: 05/07/2024]
Abstract
Egg dehydration can kill terrestrial frog embryos, and this threat is increasing with climate change and deforestation. In several lineages that independently evolved terrestrial eggs, and retained aquatic tadpoles, embryos accelerate hatching to escape from drying eggs, entering the water earlier and less developed. However, the cues that stimulate drying-induced early hatching are unknown. Ammonia is a toxic, water-soluble metabolic waste that accumulates within eggs as embryos develop and concentrates as eggs dehydrate. Thus, increasing ammonia concentration may be a direct threat to embryos in drying eggs. We hypothesized that it could serve as a cue, stimulating embryos to hatch and escape. The embryos of red-eyed treefrogs, Agalychnis callidryas, hatch early to escape from many threats, including dehydration, and are known to use mechanosensory, hypoxia, and light cues. To test if they also use high ammonia as a cue to hatch, we exposed stage-matched pairs of hatching-competent, well-hydrated sibling embryos to ammonia and control solutions in shallow water baths and recorded their behavior. Control embryos remained unhatched while ammonia-exposed embryos showed a rapid, strong hatching response; 95% hatched, on average in under 15 min. This demonstrates that elevated ammonia can serve as a hatching cue for A. callidryas embryos. This finding is a key step in understanding the mechanisms that enable terrestrial frog embryos to escape from egg drying, opening new possibilities for integrative and comparative studies on this growing threat.
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Affiliation(s)
| | | | - Karen M Warkentin
- Gamboa Laboratory, Smithsonian Tropical Research Institute, Panamá, Panamá
- Department of Biology, Boston University, Boston, Massachusetts, USA
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Méndez-Narváez J, Warkentin KM. Early onset of urea synthesis and ammonia detoxification pathways in three terrestrially developing frogs. J Comp Physiol B 2023; 193:523-543. [PMID: 37639061 DOI: 10.1007/s00360-023-01506-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 07/18/2023] [Accepted: 07/19/2023] [Indexed: 08/29/2023]
Abstract
Frogs evolved terrestrial development multiple times, necessitating mechanisms to avoid ammonia toxicity at early stages. Urea synthesis from ammonia is a key adaptation that reduces water dependence after metamorphosis. We tested for early expression and plasticity of enzymatic mechanisms of ammonia detoxification in three terrestrial-breeding frogs: foam-nest-dwelling larvae of Leptodactylus fragilis (Lf) and arboreal embryos of Hyalinobatrachium fleischmanni (Hf) and Agalychnis callidryas (Ac). Activity of two ornithine-urea cycle (OUC) enzymes, arginase and CPSase, and levels of their products urea and CP in tissues were high in Lf regardless of nest hydration, but reduced in experimental low- vs. high-ammonia environments. High OUC activity in wet and dry nests, comparable to that under experimental high ammonia, suggests terrestrial Lf larvae maintain high capacity for urea excretion regardless of their immediate risk of ammonia toxicity. This may aid survival through unpredictably long waiting periods before rain enables their transition to water. Moderate levels of urea and CP were present in Hf and Ac tissues and enzymatic activities were lower than in Lf. In both species, embryos in drying clutches can hatch and enter the water early, behaviorally avoiding ammonia toxicity. Moreover, glutamine synthetase was active in early stages of all three species, condensing ammonia and glutamate to glutamine as another mechanism of detoxification. Enzyme activity appeared highest in Lf, although substrate and product levels were higher in Ac and Lf. Our results reveal that multiple biochemical mechanisms of ammonia detoxification occur in early life stages of anuran lineages that evolved terrestrial development.
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Affiliation(s)
- Javier Méndez-Narváez
- Calima, Fundación para la Investigación de la Biodiversidad y Conservación en el Trópico, Cali, Colombia.
- Department of Biology, Boston University, Boston, MA, USA.
| | - Karen M Warkentin
- Department of Biology, Boston University, Boston, MA, USA
- Smithsonian Tropical Research Institute, Panamá, Republic of Panama
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3
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Méndez‐Narváez J, Warkentin KM. Reproductive colonization of land by frogs: Embryos and larvae excrete urea to avoid ammonia toxicity. Ecol Evol 2022; 12:e8570. [PMID: 35222954 PMCID: PMC8843769 DOI: 10.1002/ece3.8570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 12/30/2021] [Accepted: 01/05/2022] [Indexed: 11/24/2022] Open
Abstract
Vertebrate colonization of land has occurred multiple times, including over 50 origins of terrestrial eggs in frogs. Some environmental factors and phenotypic responses that facilitated these transitions are known, but responses to water constraints and risk of ammonia toxicity during early development are poorly understood. We tested if ammonia accumulation and dehydration risk induce a shift from ammonia to urea excretion during early stages of four anurans, from three origins of terrestrial development. We quantified ammonia and urea concentrations during early development on land, under well-hydrated and dry conditions. Where we found urea excretion, we tested for a plastic increase under dry conditions and with ammonia accumulation in developmental environments. We assessed the potential adaptive role of urea excretion by comparing ammonia tolerance measured in 96h-LC50 tests with ammonia levels in developmental environments. Ammonia accumulated in foam nests and perivitelline fluid, increasing over development and reaching higher concentrations under dry conditions. All four species showed high ammonia tolerance, compared to fishes and aquatic-breeding frogs. Both nest-dwelling larvae of Leptodactylus fragilis and late embryos of Hyalinobatrachium fleischmanni excreted urea, showing a plastic increase under dry conditions. These two species can develop the longest on land and urea excretion appears adaptive, preventing their exposure to potentially lethal levels of ammonia. Neither late embryos of Agalychnis callidryas nor nest-dwelling larvae of Engystomops pustulosus experienced toxic ammonia levels under dry conditions, and neither excreted urea. Our results suggest that an early onset of urea excretion, its increase under dry conditions, and elevated ammonia tolerance can all help prevent ammonia toxicity during terrestrial development. High ammonia represents a general risk for development which may be exacerbated as climate change increases dehydration risk for terrestrial-breeding frogs. It may also be a cue that elicits adaptive physiological responses during early development.
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Affiliation(s)
- Javier Méndez‐Narváez
- Department of BiologyBoston UniversityBostonMassachusettsUSA
- CalimaFundación para la Investigación de la Biodiversidad y Conservación en el TrópicoCaliColombia
| | - Karen M. Warkentin
- Department of BiologyBoston UniversityBostonMassachusettsUSA
- Smithsonian Tropical Research InstitutePanamaRepublic of Panama
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4
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White LJ, Sutton G, Shechonge A, Day JJ, Dasmahapatra KK, Pownall ME. Adaptation of the carbamoyl-phosphate synthetase enzyme in an extremophile fish. ROYAL SOCIETY OPEN SCIENCE 2020; 7:201200. [PMID: 33204476 PMCID: PMC7657897 DOI: 10.1098/rsos.201200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 09/21/2020] [Indexed: 05/03/2023]
Abstract
Tetrapods and fish have adapted distinct carbamoyl-phosphate synthase (CPS) enzymes to initiate the ornithine urea cycle during the detoxification of nitrogenous wastes. We report evidence that in the ureotelic subgenus of extremophile fish Oreochromis Alcolapia, CPS III has undergone convergent evolution and adapted its substrate affinity to ammonia, which is typical of terrestrial vertebrate CPS I. Unusually, unlike in other vertebrates, the expression of CPS III in Alcolapia is localized to the skeletal muscle and is activated in the myogenic lineage during early embryonic development with expression remaining in mature fish. We propose that adaptation in Alcolapia included both convergent evolution of CPS function to that of terrestrial vertebrates, as well as changes in development mechanisms redirecting CPS III gene expression to the skeletal muscle.
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Affiliation(s)
- Lewis J. White
- Biology Department, University of York, York YO10 5DD, UK
- Author for correspondence: Lewis J. White e-mail:
| | - Gemma Sutton
- Biology Department, University of York, York YO10 5DD, UK
| | - Asilatu Shechonge
- Tanzania Fisheries Research Institute, PO BOX 98, Kyela, Mbeya, Tanzania
| | - Julia J. Day
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
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5
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Williams TA, Bernier NJ. Corticotropin-releasing factor protects against ammonia neurotoxicity in isolated larval zebrafish brains. J Exp Biol 2020; 223:jeb211540. [PMID: 31988165 DOI: 10.1242/jeb.211540] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 01/20/2020] [Indexed: 08/26/2023]
Abstract
The physiological roles of corticotropin-releasing factor (CRF) have recently been extended to cytoprotection. Here, to determine whether CRF is neuroprotective in fish, the effects of CRF against high environmental ammonia (HEA)-mediated neurogenic impairment and cell death were investigated in zebrafish. In vivo, exposure of 1 day post-fertilization (dpf) embryos to HEA only reduced the expression of the determined neuron marker neurod1 In contrast, in 5 dpf larvae, HEA increased the expression of nes and sox2, neural progenitor cell markers, and reduced the expression of neurog1, gfap and mbpa, proneuronal cell, radial glia and oligodendrocyte markers, respectively, and neurod1 The N-methyl-d-aspartate (NMDA) receptor inhibitor MK801 rescued the HEA-induced reduction in neurod1 in 5 dpf larvae but did not affect the HEA-induced transcriptional changes in other neural cell types, suggesting that hyperactivation of NMDA receptors specifically contributes to the deleterious effects of HEA in determined neurons. As observed in vivo, HEA exposure elicited marked changes in the expression of cell type-specific markers in isolated 5 dpf larval brains. The addition of CRF reversed the in vitro effects of HEA on neurod1 expression and prevented an HEA-induced increase in cell death. Finally, the protective effects of CRF against HEA-mediated neurogenic impairment and cell death were prevented by the CRF type 1 receptor selective antagonist antalarmin. Together, these results provide novel evidence that HEA has developmental time- and cell type-specific neurotoxic effects, that NMDA receptor hyperactivation contributes to HEA-mediated impairment of determined neurons, and that CRF has neuroprotective properties in the larval zebrafish brain.
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Affiliation(s)
- Tegan A Williams
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Nicholas J Bernier
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
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6
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Wang Y, Pasparakis C, Mager EM, Stieglitz JD, Benetti D, Grosell M. Ontogeny of urea and ammonia transporters in mahi-mahi (Coryphaena hippurus) early life stages. Comp Biochem Physiol A Mol Integr Physiol 2019; 229:18-24. [PMID: 30503629 DOI: 10.1016/j.cbpa.2018.11.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 11/25/2018] [Indexed: 01/17/2023]
Abstract
The mechanism(s) of ammonia and urea excretion in freshwater fish have received considerable attention; however, parallel investigations of seawater fish, specifically in the early life stages are scarce. The first objective of this study was to evaluate the patterns of ammonia and urea excretion in mahi-mahi (Coryphaena hippurus) up to 102 hours post fertilization (hpf). Similar to other teleosts, mahi embryos are ureotelic before hatch and gradually switch to being ammoniotelic around the time of hatch. The second objective was to characterize mRNA levels of ammonia transporters (Rhag, Rhbg, Rhcg1 and Rhcg2), as well as urea transporter (UT) and sodium hydrogen exchangers (NHE3 and NHE2) during mahi development. As predicted, the mRNA levels of the Rhesus glycoprotein (Rh) genes, especially Rhag, Rhbg and the UT gene were highly consistent with the ontogeny of ammonia and urea excretion rates. Further, the localization of each transporter was examined in larvae collected at 60 and 102 hpf using in situ hybridization. Rhag was expressed in the gills, yolk sac, and operculum. Rhbg was expressed in the gills and upper mouth. Rhcg1 and NHE3 were co-localized in the sub-operculum, and Rhcg2 was expressed in the skin. Together, these results indicate that urea excretion is critical for ammonia detoxification during embryonic development and that Rh proteins are involved in ammonia excretion via gills and yolk sac, possibly facilitated by NHE3.
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Affiliation(s)
- Y Wang
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States.
| | - C Pasparakis
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - E M Mager
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States; Department of Biological Sciences & Advanced Environmental Research Institute, University of North Texas, Denton, TX 76203, United States
| | - J D Stieglitz
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - D Benetti
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - M Grosell
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
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7
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Zimmer AM, Wright PA, Wood CM. Ammonia and urea handling by early life stages of fishes. ACTA ACUST UNITED AC 2018; 220:3843-3855. [PMID: 29093184 DOI: 10.1242/jeb.140210] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nitrogen metabolism in fishes has been a focus of comparative physiologists for nearly a century. In this Review, we focus specifically on early life stages of fishes, which have received considerable attention in more recent work. Nitrogen metabolism and excretion in early life differs fundamentally from that of juvenile and adult fishes because of (1) the presence of a chorion capsule in embryos that imposes a limitation on effective ammonia excretion, (2) an amino acid-based metabolism that generates a substantial ammonia load, and (3) the lack of a functional gill, which is the primary site of nitrogen excretion in juvenile and adult fishes. Recent findings have shed considerable light on the mechanisms by which these constraints are overcome in early life. Perhaps most importantly, the discovery of Rhesus (Rh) glycoproteins as ammonia transporters and their expression in ion-transporting cells on the skin of larval fishes has transformed our understanding of ammonia excretion by fishes in general. The emergence of larval zebrafish as a model species, together with genetic knockdown techniques, has similarly advanced our understanding of ammonia and urea metabolism and excretion by larval fishes. It has also now been demonstrated that ammonia excretion is one of the primary functions of the developing gill in rainbow trout larvae, leading to new hypotheses regarding the physiological demands driving gill development in larval fishes. Here, we highlight and discuss the dramatic changes in nitrogen handling that occur over early life development in fishes.
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Affiliation(s)
- Alex M Zimmer
- Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N57
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Chris M Wood
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.,Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
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8
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Fujimoto M, Lovett B, Angoshtari R, Nirenberg P, Loch TP, Scribner KT, Marsh TL. Antagonistic Interactions and Biofilm Forming Capabilities Among Bacterial Strains Isolated from the Egg Surfaces of Lake Sturgeon (Acipenser fulvescens). MICROBIAL ECOLOGY 2018; 75:22-37. [PMID: 28674774 DOI: 10.1007/s00248-017-1013-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 06/08/2017] [Indexed: 05/25/2023]
Abstract
Characterization of interactions within a host-associated microbiome can help elucidate the mechanisms of microbial community formation on hosts and can be used to identify potential probiotics that protect hosts from pathogens. Microbes employ various modes of antagonism when interacting with other members of the community. The formation of biofilm by some strains can be a defense against antimicrobial compounds produced by other taxa. We characterized the magnitude of antagonistic interactions and biofilm formation of 25 phylogenetically diverse taxa that are representative of isolates obtained from egg surfaces of the threatened fish species lake sturgeon (Acipenser fulvescens) at two ecologically relevant temperature regimes. Eight isolates exhibited aggression to at least one other isolate. Pseudomonas sp. C22 was found to be the most aggressive strain, while Flavobacterium spp. were found to be one of the least aggressive and the most susceptible genera. Temperature affected the prevalence and intensity of antagonism. The aggressive strains identified also inhibited growth of known fish pathogens. Biofilm formations were observed for nine isolates and were dependent on temperature and growth medium. The most aggressive of the isolates disrupted biofilm formation of two well-characterized isolates but enhanced biofilm formation of a fish pathogen. Our results revealed the complex nature of interactions among members of an egg associated microbial community yet underscored the potential of specific microbial populations as host probiotics.
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Affiliation(s)
- M Fujimoto
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - B Lovett
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - R Angoshtari
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - P Nirenberg
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - T P Loch
- Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - K T Scribner
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, 48824, USA
- Department of Zoology, Michigan State University, East Lansing, MI, 48824, USA
| | - T L Marsh
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA.
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9
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Williams TA, Bonham LA, Bernier NJ. High environmental ammonia exposure has developmental-stage specific and long-term consequences on the cortisol stress response in zebrafish. Gen Comp Endocrinol 2017; 254:97-106. [PMID: 28958860 DOI: 10.1016/j.ygcen.2017.09.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/22/2017] [Accepted: 09/24/2017] [Indexed: 12/15/2022]
Abstract
The capacity for early life environmental stressors to induce programming effects on the endocrine stress response in fish is largely unknown. In this study we determined the effects of high environmental ammonia (HEA) exposure on the stress response in larval zebrafish, assessed the tolerance of embryonic and larval stages to HEA, and evaluated whether early life HEA exposure has long-term consequences on the cortisol response to a novel stressor. Exposure to 500-2000μM NH4Cl for 16h did not affect the gene expression of corticotropin-releasing factor (CRF) system components in 1day post-fertilization (dpf) embryos, but differentially increased crfa, crfb and CRF binding protein (crfbp) expression and stimulated both dose- and time-dependent increases in the whole body cortisol of 5dpf larvae. Pre-acclimation to HEA at 1dpf did not affect the cortisol response to a subsequent NH4Cl exposure at 5dpf. In contrast, pre-acclimation to HEA at 5dpf caused a small but significant reduction in the cortisol response to a second NH4Cl exposure at 10dpf. While continuous exposure to 500-2000μM NH4Cl between 0 and 5dpf had a modest effect on mean survival time, exposure to 400-1000μM NH4Cl between 10 and 14dpf decreased mean survival time in a dose-dependent manner. Moreover, pre-acclimation to HEA at 5dpf significantly decreased the risk of mortality to continuous NH4Cl exposure between 10 and 14dpf. Finally, while HEA at 1dpf did not affect the cortisol stress response to a novel vortex stressor at 5dpf, the same HEA treatment at 5dpf abolished vortex stressor-induced increases in whole body cortisol at 10 and 60dpf. Together these results show that the impact of HEA on the cortisol stress response during development is life-stage specific and closely linked to ammonia tolerance. Further, we demonstrate that HEA exposure at the larval stage can have persistent effects on the capacity to respond to stressors in later life.
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Affiliation(s)
- Tegan A Williams
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Luke A Bonham
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Nicholas J Bernier
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
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10
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Pasparakis C, Mager EM, Stieglitz JD, Benetti D, Grosell M. Effects of Deepwater Horizon crude oil exposure, temperature and developmental stage on oxygen consumption of embryonic and larval mahi-mahi (Coryphaena hippurus). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 181:113-123. [PMID: 27829195 DOI: 10.1016/j.aquatox.2016.10.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Revised: 10/23/2016] [Accepted: 10/24/2016] [Indexed: 06/06/2023]
Abstract
The timing and location of the 2010 Deepwater Horizon (DWH) incident within the Gulf of Mexico resulted in crude oil exposure of many commercially and ecologically important fish species, such as mahi-mahi (Coryphaena hippurus), during the sensitive early life stages. Previous research has shown that oil exposure during the embryonic stage of predatory pelagic fish reduces cardiac function - a particularly important trait for fast-swimming predators with high aerobic demands. However, it is unclear whether reductions in cardiac function translate to impacts on oxygen consumption in these developing embryos and larvae. A 24-channel optical-fluorescence oxygen-sensing system for high-throughput respiration measurements was used to investigate the effects of oil exposure, temperature and developmental stage on oxygen consumption rates in embryonic and larval mahi-mahi. Oil-exposed developing mahi-mahi displayed increased oxygen consumption, despite clear cardiac deformities and bradycardia, confirming oxygen uptake and delivery from a source other than the circulatory system. In addition to metabolic rate measurements, nitrogenous waste excretion was measured to test the hypothesis that increased energy demand was fueled by protein catabolism. This is the first study to our knowledge that demonstrates increased energy demand and energy depletion in oil-exposed developing mahi-mahi.
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Affiliation(s)
- Christina Pasparakis
- Department of Marine Biology and Ecology, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States.
| | - Edward M Mager
- Department of Marine Biology and Ecology, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - John D Stieglitz
- Department of Marine Biology and Ecology, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - Daniel Benetti
- Department of Marine Biology and Ecology, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - Martin Grosell
- Department of Marine Biology and Ecology, University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
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11
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Zimmer AM, Wood CM. Physiological and molecular ontogeny of branchial and extra-branchial urea excretion in posthatch rainbow trout (Oncorhynchus mykiss). Am J Physiol Regul Integr Comp Physiol 2016; 310:R305-12. [PMID: 26608657 PMCID: PMC4796753 DOI: 10.1152/ajpregu.00403.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 11/24/2015] [Indexed: 12/31/2022]
Abstract
All teleost fish produce ammonia as a metabolic waste product. In embryos, ammonia excretion is limited by the chorion, and fish must detoxify ammonia by synthesizing urea via the ornithine urea cycle (OUC). Although urea is produced by embryos and larvae, urea excretion (J(urea)) is typically low until yolk sac absorption, increasing thereafter. The aim of this study was to determine the physiological and molecular characteristics of J(urea) by posthatch rainbow trout (Oncorhynchus mykiss). Following hatch, whole body urea concentration decreased over time, while J(urea) increased following yolk sac absorption. From 12 to 40 days posthatch (dph), extra-branchial routes of excretion accounted for the majority of J(urea), while the gills became the dominant site for J(urea) only after 55 dph. This represents the most delayed branchial ontogeny of any process studied to date. Urea transporter (UT) gene expression in the gills and skin increased over development, consistent with increases in branchial and extra-branchial J(urea). Following exposure to 25 mmol/l urea, the accumulation and subsequent elimination of exogenous urea was much greater at 55 dph than 12 dph, consistent with increased UT expression. Notably, UT gene expression in the gills of 55 dph larvae increased in response to high urea. In summary, there is a clear increase in urea transport capacity over posthatch development, despite a decrease in OUC activity.
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Affiliation(s)
- Alex M Zimmer
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Chris M Wood
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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12
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Wang J, Li J, Xu N, Li J, Li Z, Chen Y, Yang Z. Responses of Takifugu obscurus fertilized eggs and larvae to increased ammonia exposure. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:15976-15984. [PMID: 26054459 DOI: 10.1007/s11356-015-4815-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 05/28/2015] [Indexed: 06/04/2023]
Abstract
Ammonia is a common toxicant in aquatic systems; this substance has become a critical threat to fish, especially in early life stages. This study aimed to evaluate the effects of unionized ammonia (NH3-N: 0, 0.068, 0.138, 0.206, 0.275, 0.343, 0.412, and 0.481 mg L(-1)) on fertilized eggs and larvae of obscure puffer Takifugu obscurus, a fish species with potential economic value. Results showed that hatch time was significantly retarded and hatch rate was significantly decreased as NH3-N concentrations increased; newly hatched larvae exhibited high rate of abnormalities and low viability. The survival rate of larvae also decreased significantly as NH3-N concentrations increased; larvae could tolerate NH3-N to a less extent than embryos. NH3-N also caused a significant decrease in superoxide dismutase (SOD) and Na(+)/K(+) ATPase activities but not in malondialdehyde (MDA) levels of larvae. Two-way ANOVA indicated that there was a statistically significant interaction between NH3-N concentrations and exposure times on SOD activity but not on Na(+)/K(+) ATPase activity. Such responses indicated that an increase in ammonia concentration in surface water may negatively affect the early development of T. obscurus and thus likely impair population recruitment and persistence of this fish species.
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Affiliation(s)
- Jun Wang
- Jiangsu Province Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Jiajia Li
- Jiangsu Institute of Freshwater Fisheries, 79 East Chating Street, Nanjing, 210017, China
| | - Nuo Xu
- Jiangsu Province Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Jing Li
- Jiangsu Province Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Ziheng Li
- Jiangsu Province Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
| | - Yafen Chen
- State Key Laboratory of Lake and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing, 210008, China.
| | - Zhou Yang
- Jiangsu Province Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China
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13
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LeMoine CMR, Walsh PJ. Evolution of urea transporters in vertebrates: adaptation to urea's multiple roles and metabolic sources. J Exp Biol 2015; 218:1936-45. [PMID: 26085670 DOI: 10.1242/jeb.114223] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In the two decades since the first cloning of the mammalian kidney urea transporter (UT-A), UT genes have been identified in a plethora of organisms, ranging from single-celled bacteria to metazoans. In this review, focusing mainly on vertebrates, we first reiterate the multiple catabolic and anabolic pathways that produce urea, then we reconstruct the phylogenetic history of UTs, and finally we examine the tissue distribution of UTs in selected vertebrate species. Our analysis reveals that from an ancestral UT, three homologues evolved in piscine lineages (UT-A, UT-C and UT-D), followed by a subsequent reduction to a single UT-A in lobe-finned fish and amphibians. A later internal tandem duplication of UT-A occurred in the amniote lineage (UT-A1), followed by a second tandem duplication in mammals to give rise to UT-B. While the expected UT expression is evident in excretory and osmoregulatory tissues in ureotelic taxa, UTs are also expressed ubiquitously in non-ureotelic taxa, and in tissues without a complete ornithine-urea cycle (OUC). We posit that non-OUC production of urea from arginine by arginase, an important pathway to generate ornithine for synthesis of molecules such as polyamines for highly proliferative tissues (e.g. testis, embryos), and neurotransmitters such as glutamate for neural tissues, is an important evolutionary driving force for the expression of UTs in these taxa and tissues.
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Affiliation(s)
- Christophe M R LeMoine
- Department of Biology, Centre for Advanced Research in Environmental Genomics, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada, K1N 6N5
| | - Patrick J Walsh
- Department of Biology, Centre for Advanced Research in Environmental Genomics, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada, K1N 6N5
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14
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Brown CA, Green CC. Metabolic and embryonic responses to terrestrial incubation of Fundulus grandis embryos across a temperature gradient. JOURNAL OF FISH BIOLOGY 2014; 84:732-747. [PMID: 24588641 DOI: 10.1111/jfb.12348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 01/16/2014] [Accepted: 01/16/2014] [Indexed: 06/03/2023]
Abstract
This study simulated terrestrial incubation and measured rates of embryogenesis, nitrogen elimination, heart rate, lactate production, maximum length of time a hatch could be delayed and developmental responses of terrestrially incubated Gulf killifish Fundulus grandis embryos at temperatures ranging from 20 to 30° C. Temperature had a positive relationship with rate of embryogenesis, but a negative relationship with extent of extended incubation. The 30° C treatment reached embryonic maturity 6 days before the 20° C treatment. Embryos hatched between intervals of 240 and 336, 144 and 288, 96 and 240 and 96 and 192 h after reaching developmental maturity for the 20, 23, 26 and 30° C treatments. Significantly higher concentrations of total nitrogen, in the form of ammonia and urea, were recorded in the 20 and 30° C treatments. While temperature significantly influenced lactate and ATP concentrations, no significant influence of time of incubation was detected. Terrestrial embryos displayed an ability to develop quickly during embryogenesis and prolong incubation for an extended period of time after reaching embryonic maturity. This adaptation may be a life-history trait used to minimize asynchronous hatching, cannibalism and cohort size heterogeneity.
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Affiliation(s)
- C A Brown
- Louisiana State University Agricultural Center, Aquaculture Research Station, 2410 Ben Hur Road, Baton Rouge, LA 70820, U.S.A
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15
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Fujimoto M, Crossman JA, Scribner KT, Marsh TL. Microbial community assembly and succession on lake sturgeon egg surfaces as a function of simulated spawning stream flow rate. MICROBIAL ECOLOGY 2013; 66:500-511. [PMID: 23857377 DOI: 10.1007/s00248-013-0256-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 06/07/2013] [Indexed: 06/02/2023]
Abstract
We investigated microbial succession on lake sturgeon (Acipenser fulvescens) egg surfaces over the course of their incubation period as a function of simulated stream flow rate. The primary objective was to characterize the microbial community assembly during succession and to examine how simulated stream flow rate affect the successional process. Sturgeon eggs were reared under three flow regimes; high (0.55 m/s), low (0.18 m/s), and variable (0.35 and 0.11 m/s alternating 12 h intervals). Eggs were collected from each flow regime at different egg developmental stages. Microbial community DNA was extracted from egg surface and the communities were examined using 16S rRNA gene-based terminal restriction fragment length polymorphism and 454 pyrosequencing. Analysis of these datasets using principal component analysis revealed that microbial communities were clustered by egg developmental stages (early, middle, and late) regardless of flow regimes. 454 pyrosequencing data suggested that 90-98 % of the microbial communities were composed of the phyla Proteobacteria and Bacteroidetes throughout succession. β-Protebacteria was more dominant in the early stage, Bacteroidetes became more dominant in the middle stage, and α-Proteobacteria became dominant in the late stage. A total of 360 genera and 5,826 OTUs at 97 % similarity cutoff were associated with the eggs. Midway through egg development, the egg-associated communities of the low flow regime had a higher diversity than those communities developed under high or variable flow regimes. Results show that microbial community turnover occurred during embryogenesis, and stream flow rate influenced the microbial succession processes on the sturgeon egg surfaces.
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Affiliation(s)
- Masanori Fujimoto
- Department of Microbiology and Molecular Genetics, Michigan State University, 6171 Biomedical and Physical Sciences, East Lansing, MI, 48824, USA
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16
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Bucking C, Lemoine CMR, Walsh PJ. Waste nitrogen metabolism and excretion in zebrafish embryos: effects of light, ammonia, and nicotinamide. ACTA ACUST UNITED AC 2013; 319:391-403. [PMID: 23754660 DOI: 10.1002/jez.1802] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 01/28/2013] [Accepted: 04/01/2013] [Indexed: 11/08/2022]
Abstract
Bony fish primarily excrete ammonia as adults however the persistence of urea cycle genes may reflect a beneficial role for urea production during embryonic stages in protecting the embryo from toxic effects of ammonia produced from a highly nitrogenous yolk. This study aimed to examine the dynamic scope for changes in rates of urea synthesis and excretion in one such species (zebrafish, Danio rerio) by manipulating the intrinsic developmental rate (by alteration of light:dark cycles), as well as by direct chemical manipulation via ammonia injection (to potentially activate urea production) and nicotinamide exposure (to potentially inhibit urea production). Continuous dark exposure delayed development in embryos as evidenced by delayed appearance of hallmark anatomical features (heartbeat, eye pigmentation, body pigmentation, lateral line, fin buds) at 30 and 48 hr post-fertilization, as well by a lower hatching rate compared to embryos reared in continuous light. Both ammonia and urea excretion were similarly effected and were generally higher in embryos continuously exposed to light. Ammonia injection resulted in significant increases (up to fourfold) of urea N excretion and no changes to ammonia excretion rates along with modest increases in yolk ammonia content during 2-6 hr post-injection. Nicotinamide (an inhibitor of urea synthesis in mammals) reduced the ammonia-induced increase in urea excretion and led to retention of ammonia in the yolk and body of the embryo. Our results indicate that there is a relatively rapid and large scope for increases in urea production/excretion rates in developing embryos. Potential mechanisms for these increases are discussed.
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Affiliation(s)
- Carol Bucking
- Department of Biology, University of Ottawa, Ottawa, ON, Canada.
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17
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LeMoine CMR, Walsh PJ. Ontogeny of ornithine-urea cycle gene expression in zebrafish (Danio rerio). Am J Physiol Regul Integr Comp Physiol 2013; 304:R991-1000. [PMID: 23576614 DOI: 10.1152/ajpregu.00411.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although the majority of adult teleosts excrete most of their nitrogenous wastes as ammonia, several fish species are capable of producing urea early in development. In zebrafish, it is unclear whether this results from a functional ornithine-urea cycle (O-UC) and, if so, how it might be regulated. This study examined the spatiotemporal patterns of gene expression of four major O-UC enzymes: carbamoyl phosphate synthase III (CPSIII), ornithine transcarboxylase, arginosuccinate synthetase, and arginosuccinate lyase, using real-time PCR and whole mount in situ hybridization. In addition, we hypothesized that CPSIII gene expression was epigenetically regulated through methylation of its promoter, a widespread mode of differential gene regulation between tissues and life stages in vertebrates. Furthermore, to assess CPSIII functionality, we used morpholinos to silence CPSIII in zebrafish embryos and assessed their nitrogenous waste handling during development, and in response to ammonia injections. Our results suggest that mRNAs of O-UC enzymes are expressed early in zebrafish development and colocalize to the embryonic endoderm. In addition, the methylation status of CPSIII promoter is not consistent with the patterns of expression observed in developing larvae or adult tissues, suggesting other means of transcriptional regulation of this enzyme. Finally, CPSIII morphants exhibited a transient reduction in CPSIII enzyme activity 24 h postfertilization, which was paralleled by reduced urea production during development and in response to an ammonia challenge. Overall, we conclude that the O-UC is functional in zebrafish embryos, providing further evidence that the capacity to produce urea via the O-UC is widespread in developing teleosts.
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18
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Dhiyebi HA, O'Donnell MJ, Wright PA. Water chemistry in the microenvironment of rainbow trout Oncorhynchus mykiss embryos is affected by development, the egg capsule and crowding. JOURNAL OF FISH BIOLOGY 2013; 82:444-457. [PMID: 23398061 DOI: 10.1111/j.1095-8649.2012.03491.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The hypothesis tested was that embryonic metabolism affects the water chemistry in the boundary layer. In addition, embryo crowding would further compound the metabolic effect on the water chemistry in the boundary layer. As development progressed, the magnitude of the boundary layer gradients for O(2) and pH, but not for NH4(+), increased. The presence of the egg capsule hindered the diffusion of O(2) into and H(+) and NH4(+) out of the embryo. The magnitude of the O(2), pH and NH4(+) boundary layer gradient was significantly increased when embryos were surrounded by either sham embryos or live embryos. The majority of this crowding effect on embryo boundary layers was due to changes in water flow rather than due to metabolism directly. These results clearly show that the microenvironment adjacent to the developing rainbow trout Oncorhynchus mykiss embryo becomes more stagnant as development progresses in the presence of the egg capsule and is further intensified with embryo crowding.
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Affiliation(s)
- H A Dhiyebi
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.
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19
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Vosylienė MZ, Kazlauskienė N. Comparative Studies of Sublethal Effects of Ammonia on Rainbow Trout (Oncorhynchus Mykiss) at Different Stages of its Development. ACTA ACUST UNITED AC 2012. [DOI: 10.1080/13921657.2004.10512568] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Milda Zita Vosylienė
- a Institute of Ecology of Vilnius University , Akademijos 2, LT-08412 , Vilnius-21 , Lithuania E-mail:
| | - Nijolė Kazlauskienė
- a Institute of Ecology of Vilnius University , Akademijos 2, LT-08412 , Vilnius-21 , Lithuania E-mail:
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20
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Glutamine synthetase activity and the expression of three glul paralogues in zebrafish during transport. Comp Biochem Physiol B Biochem Mol Biol 2012; 163:274-84. [PMID: 22750401 DOI: 10.1016/j.cbpb.2012.06.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/18/2012] [Accepted: 06/19/2012] [Indexed: 01/13/2023]
Abstract
The enzyme glutamine synthetase (GS; glutamate-ammonia ligase, EC 6.3.1.2) plays an important role in the nitrogen metabolism of fish. In this study the GS activity and the corresponding genes were examined to understand how they are regulated in zebrafish in response to hyperammonemic stress during a 72 h simulated transport. Whole body ammonia levels, the activity of the enzyme GS and the mRNA expression of the splice variants of three paralogues of glul, glutamine synthetase gene (glula, glulb and glulc) were examined in brain, liver and kidney of zebrafish. Whole body ammonia reached significantly higher levels by 48 h, while brain showed higher levels as early as 24 h, compared to the values at the start of the transport. The GS activities in brain, liver and kidney were significantly higher at the end of 72 h transport than those at the start. However, only the expression of mRNA of glulb-002 and glulb-003 were significantly upregulated during the simulated transport. In silico analysis of the putative promoter regions of glul paralogues revealed glucocorticoid receptor binding sites. However, glucocorticoid response elements of glulb were not different. The up-regulation of GS enzyme activity and hitherto unreported mRNA expression of glul paralogues during zebrafish transport indicate a physiological response of fish to ammonia.
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21
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Sashaw J, Nawata M, Thompson S, Wood CM, Wright PA. Rhesus glycoprotein and urea transporter genes in rainbow trout embryos are upregulated in response to alkaline water (pH 9.7) but not elevated water ammonia. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2010; 96:308-13. [PMID: 20044151 DOI: 10.1016/j.aquatox.2009.11.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 11/18/2009] [Accepted: 11/21/2009] [Indexed: 05/28/2023]
Abstract
Recent studies have shown that genes for the putative ammonia transporter, Rhesus glycoproteins (Rh) and the facilitated urea transporter (UT) are expressed before hatching in rainbow trout (Oncorhychus mykiss Walbaum) embryos. We tested the hypothesis that Rh and UT gene expressions are regulated in response to environmental conditions that inhibit ammonia excretion during early life stages. Eyed-up embryos (22 days post-fertilization (dpf)) were exposed to control (pH 8.3), high ammonia (1.70 mmol l(-1) NH4HCO3) and high pH (pH 9.7) conditions for 48h. With exposure to high water ammonia, ammonia excretion rates were reversed, tissue ammonia concentration was elevated by 9-fold, but there were no significant changes in mRNA expression relative to control embryos. In contrast, exposure to high water pH had a smaller impact on ammonia excretion rates and tissue ammonia concentrations, whereas mRNA levels for the Rhesus glycoprotein Rhcg2 and urea transporter (UT) were elevated by 3.5- and 5.6-fold, respectively. As well, mRNAs of the genes for H+ATPase and Na+/H+ exchanger (NHE2), associated with NH3 excretion, were also upregulated by 7.2- and 13-fold, respectively, in embryos exposed to alkaline water relative to controls. These results indicate that the Rhcg2, UT and associated transport genes are regulated in rainbow trout embryos, but in contrast to adults, there is no effect of high external ammonia at this stage of development.
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Affiliation(s)
- Jessica Sashaw
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G2W1, Canada
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22
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Braun MH, Steele SL, Perry SF. The responses of zebrafish (Danio rerio) to high external ammonia and urea transporter inhibition: nitrogen excretion and expression of rhesus glycoproteins and urea transporter proteins. J Exp Biol 2009; 212:3846-56. [PMID: 19915127 DOI: 10.1242/jeb.034157] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
While adult zebrafish, Danio rerio, possess ammonia and urea transporters (Rh and UT proteins, respectively) in a number of tissues, they are most heavily concentrated within the gills. UT has a diffuse expression pattern within Na+-K+-ATPase (NKA)-type mitochondrion-rich cells and Rh proteins form a network similar to the arrangement seen in pufferfish gills (Nakada et al., 2007b). Rhag expression appeared to be limited to the pillar cells lining the blood spaces of the lamellae while Rhbg was localized to the outer layer of both the lamellae and the filament, upon the pavement cells. Exposure to high external ammonia (HEA) or phloretin increased tissue levels of ammonia and urea, respectively, in adult and juvenile zebrafish; however, the responses to these stressors were age dependent. HEA increased mRNA levels for a number of Rh proteins in embryos and larvae but did not elicit similar effects in adult gills, which appear to compensate for the unfavourable ammonia excretory gradient by increasing expression of V-type H+-ATPase. Phloretin exposure increased UT mRNA levels in embryos and larvae but was without effect in adult gill tissue. Surprisingly, in both adults and juveniles, HEA increased the mRNA expression of UT and phloretin increased the mRNA expression of Rh proteins. These results imply that, in zebrafish, there may be a tighter link between ammonia and urea excretion than is thought to occur in most teleosts.
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Affiliation(s)
- Marvin H Braun
- Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada.
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23
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Wright PA, Wood CM. A new paradigm for ammonia excretion in aquatic animals: role of Rhesus(Rh) glycoproteins. J Exp Biol 2009; 212:2303-12. [DOI: 10.1242/jeb.023085] [Citation(s) in RCA: 283] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
SUMMARY
Ammonia excretion at the gills of fish has been studied for 80 years, but the mechanism(s) involved remain controversial. The relatively recent discovery of the ammonia-transporting function of the Rhesus (Rh) proteins, a family related to the Mep/Amt family of methyl ammonia and ammonia transporters in bacteria, yeast and plants, and the occurrence of these genes and glycosylated proteins in fish gills has opened a new paradigm. We provide background on the evolution and function of the Rh proteins, and review recent studies employing molecular physiology which demonstrate their important contribution to branchial ammonia efflux. Rhag occurs in red blood cells,whereas several isoforms of both Rhbg and Rhcg occur in many tissues. In the branchial epithelium, Rhcg appears to be localized in apical membranes and Rhbg in basolateral membranes. Their gene expression is upregulated during exposure to high environmental ammonia or internal ammonia infusion, and may be sensitive to synergistic stimulation by ammonia and cortisol. Rhcg in particular appears to be coupled to H+ excretion and Na+uptake mechanisms. We propose a new model for ammonia excretion in freshwater fish and its variable linkage to Na+ uptake and acid excretion. In this model, Rhag facilitates NH3 flux out of the erythrocyte, Rhbg moves it across the basolateral membrane of the branchial ionocyte, and an apical “Na+/NH +4 exchange complex” consisting of several membrane transporters (Rhcg, V-type H+-ATPase, Na+/H+ exchanger NHE-2 and/or NHE-3, Na+ channel) working together as a metabolon provides an acid trapping mechanism for apical excretion. Intracellular carbonic anhydrase(CA-2) and basolateral Na+/HCO –3cotransporter (NBC-1) and Na+/K+-ATPase play indirect roles. These mechanisms are normally superimposed on a substantial outward movement of NH3 by simple diffusion, which is probably dependent on acid trapping in boundary layer water by H+ ions created by the catalysed or non-catalysed hydration of expired metabolic CO2. Profitable areas for future investigation of Rh proteins in fish are highlighted: their involvement in the mechanism of ammonia excretion across the gills in seawater fish, their possible importance in ammonia excretion across the skin, their potential dual role as CO2 transporters,their responses to feeding, and their roles in early life stages prior to the full development of gills.
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Affiliation(s)
- Patricia A. Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1,Canada
| | - Chris M. Wood
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1,Canada
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine Atmospheric Science, University of Miami, Miami, FL 33149, USA
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Braun MH, Steele SL, Ekker M, Perry SF. Nitrogen excretion in developing zebrafish (Danio rerio): a role for Rh proteins and urea transporters. Am J Physiol Renal Physiol 2009; 296:F994-F1005. [PMID: 19279128 DOI: 10.1152/ajprenal.90656.2008] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Injection of antisense oligonucleotide morpholinos to elicit selective gene knockdown of ammonia (Rhag, Rhbg, and Rhcg1) or urea transporters (UT) was used as a tool to assess the relative importance of each transporter to nitrogen excretion in developing zebrafish (Danio rerio). Knockdown of UT caused urea excretion to decrease by approximately 90%, whereas each of the Rh protein knockdowns resulted in an approximately 50% reduction in ammonia excretion. Contrary to what has been hypothesized previously for adult fish, each of the Rh proteins appeared to have a similar effect on total ammonia excretion, and thus all are required to facilitate normal ammonia excretion in the zebrafish larva. As demonstrated in other teleosts, zebrafish embryos utilized urea to a much greater extent than adults and were effectively ureotelic until hatching. At that point, ammonia excretion rapidly increased and appeared to be triggered by a large increase in the mRNA expression of Rhag, Rhbg, and Rhcg1. Unlike the situation in the adult pufferfish (35), the various transporters are not specifically localized to the gills of the developing zebrafish, but each protein has a unique expression pattern along the skin, gills, and yolk sac. This disparate pattern of expression would appear to preclude interaction between the Rh proteins in zebrafish embryos. However, this may be a developmental feature of the delayed maturation of the gills, because as the embryos matured, expression of the transporters in and around the gills increased.
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Affiliation(s)
- M H Braun
- Department of Biology and Center for Advanced Research in Environmental Genetics, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
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25
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Hung CC, Nawata CM, Wood CM, Wright PA. Rhesus glycoprotein and urea transporter genes are expressed in early stages of development of rainbow trout (Oncorhynchus mykiss). JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL GENETICS AND PHYSIOLOGY 2008; 309:262-8. [PMID: 18404668 DOI: 10.1002/jez.456] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The objective of this study was to determine if the genes for the putative ammonia transporters, Rhesus glycoproteins (Rh) and the facilitated urea transporter (UT) were expressed during early development of rainbow trout, Oncorhynchus mykiss Walbaum. We predicted that the Rh isoforms Rhbg, Rhcg1 and Rhcg2 would be expressed shortly after fertilization but UT expression would be delayed based on the ontogenic pattern of nitrogen excretion. Embryos were collected 3, 14 and 21 days postfertilization (dpf), whereas yolk sac larvae were sampled at 31 dpf and juveniles at 60 dpf (complete yolk absorption). mRNA levels were quantified using quantitative polymerase chain reaction and expressed relative to the control gene, elongation factor 1alpha. All four genes (Rhbg, Rhcg1, Rhcg2, UT) were detected before hatching (25-30 dpf). As predicted, the mRNA levels of the Rh genes, especially Rhcg2, were relatively high early in embryonic development (14 and 21 dpf), but UT mRNA levels remained low until after hatching (31 and 60 dpf). These findings are consistent with the pattern of nitrogen excretion in early stages of trout development. We propose that early expression of Rh genes is critical for the elimination of potentially toxic ammonia from the encapsulated embryo, whereas retention of the comparatively benign urea molecule until after hatch is less problematic for developing tissues and organ systems.
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Affiliation(s)
- Carrie C Hung
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada
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26
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Monzani PS, Moraes G. Urea cycle enzymes through the development of pacu (Piaractus mesopotamicus): the role of ornithine carbamoyl transferase. FISH PHYSIOLOGY AND BIOCHEMISTRY 2008; 34:139-149. [PMID: 18649031 DOI: 10.1007/s10695-007-9154-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 06/28/2007] [Indexed: 05/26/2023]
Abstract
The present work reports the activities of urea cycle enzymes during the ontogenic development of the teleost pacu (Piaractus mesopotamicus). Urea cycle enzymes from the kidney and liver of adult fish were compared with those from the fish's embryonic phases. Samples were evaluated over all phases of embryonic development, the larval period and alevin. Ammonia and urea concentrations were determined during embryogenesis and in the plasma of adult fish. Except for carbamoyl phosphate synthetase-III (CPS-III), all enzymes of the urea cycle were expressed in the larvae and alevins as well as in the liver and kidney of adult fish. In spite of the low level of activity of the ornithine urea cycle (OUC) enzymes compared to those in mammals, and the low levels of tissue urea concentration compared to ammonia, the ureogenesis was evaluated in pacu. Ammonia seems to be the main nitrogenous waste during embryonic development. In this phase glutamine synthetase (GS) may play a role in ammonia detoxification, and the OUC enzymes can be individually involved in functions other than urea production. The presence of ornithine carbamoyl transferase (OCT) in all developmental phases of pacu and in the adult liver and kidney suggests that this enzyme is performing different metabolic pathways. OCT in the kidney, wherein the activity is less than in the liver, should work in the biosynthesis of polyamines and control the arginine plasma concentration given that renal arginase and argininosuccinate synthetase-argininosuccinate lyase are more active than from the liver. We suppose that OCT during the embryogenesis is a control step regulating the cellular concentration of ornithine for polyamines synthesis.
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Affiliation(s)
- Paulo Sérgio Monzani
- Laboratory of Adaptive Biochemistry, Department of Genetics and Evolution, Federal University of Sao Carlos, Rod Washington Luiz Km 235, CP 676, CEP 13565-905, Sao Carlos, SP, Brazil
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27
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Wright PA, Steele SL, Huitema A, Bernier NJ. Induction of four glutamine synthetase genes in brain of rainbow trout in response to elevated environmental ammonia. ACTA ACUST UNITED AC 2007; 210:2905-11. [PMID: 17690239 DOI: 10.1242/jeb.003905] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The key strategy for coping with elevated brain ammonia levels in vertebrates is the synthesis of glutamine from ammonia and glutamate, catalyzed by glutamine synthetase (GSase). We hypothesized that all four GSase isoforms (Onmy-GS01-GS04) are expressed in the brain of the ammonia-intolerant rainbow trout Oncorhynchus mykiss and that cerebral GSase is induced during ammonia stress. We measured GSase activity and the mRNA expression of Onmy-GS01-GS04 in fore-, mid- and hindbrain and liver, as well as ammonia concentrations in plasma, liver and brain of fish exposed to 9 or 48 h of 0 (control) or 670 micromol l(-1) NH(4)Cl (75% of the 96 h-LC(50) value). The mRNA of all four GSase isoforms were detected in brain (not liver). After 9 h of NH(4)Cl exposure, brain, liver and plasma ammonia content were elevated by two- to fourfold over control values. Midbrain, hindbrain and liver GSase activities were 1.3- to 1.5-fold higher in ammonia-exposed fish relative to control fish. Onmy-GS01-GS04 mRNA levels in brain (not liver) of ammonia-exposed fish (9 h) were significantly elevated by two- to fourfold over control values. After 48 h of the NH(4)Cl treatment, ammonia content and GSase activity, but not mRNA levels, in all tissues examined remained elevated compared to control fish. Taken together, these findings indicate that all four GSase isoforms are constitutively expressed in trout brain and are inducible under high external ammonia conditions. Moreover, elevation of GSase activities in fore-, mid- and hindbrain in response to environmental ammonia underlines the importance of brain GSase in the ammonia-stress response.
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Affiliation(s)
- P A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1 Canada.
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28
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Hung CYC, Tsui KNT, Wilson JM, Nawata CM, Wood CM, Wright PA. Rhesus glycoprotein gene expression in the mangrove killifish Kryptolebias marmoratus exposed to elevated environmental ammonia levels and air. J Exp Biol 2007; 210:2419-29. [PMID: 17601945 DOI: 10.1242/jeb.002568] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
SUMMARY
The mechanism(s) of ammonia excretion in the presence of elevated external ammonia are not well understood in fish. Recent studies in other organisms have revealed a new class of ammonia transporters, Rhesus glycoprotein genes(Rh genes), which may also play a role in ammonia excretion in fish. The first objective of this study was to clone and characterize Rhgenes in a fish species with a relatively high tolerance to environmental ammonia, the mangrove killifish Kryptolebias marmoratus (formerly Rivulus marmoratus). We obtained full-length cDNAs of three Rh genes in K. marmoratus: RhBG (1736 bp), RhCG1 (1920 bp) and RhCG2 (2021 bp), which are highly homologous with other known Rh gene sequences. Hydropathy analysis revealed that all three Rh genes encode membrane proteins with 10–12 predicted transmembrane domains. RhBG, RhCG1 and RhCG2 are highly expressed in gill tissue, with RhBG also present in skin of K. marmoratus. Exposure to elevated environmental ammonia (2 mmol l–1 NH4HCO3) for 5 days resulted in a modest (+37%) increase in whole-body ammonia levels, whereas gill RhCG2 and skin RhCG1 mRNA levels were upregulated by 5.8- and 7.7-fold, respectively. RhBG mRNA levels were also increased in various tissues, with 3- to 7-fold increases in the liver and skeletal muscle. In a separate group of killifish exposed to air for 24 h, RhCG1 and RhCG2 mRNA levels were elevated by 4- to 6-fold in the skin. Thus, the multifold induction of Rh mRNA levels in excretory tissues (gills and skin) and internal tissues in response to conditions that perturb normal ammonia excretion suggests that RhBG, RhCG1 and RhCG2 may be involved in facilitating ammonia transport in this species. Furthermore, the findings support earlier studies demonstrating that the skin is an important site of ammonia excretion in K. marmoratus.
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Affiliation(s)
- C Y C Hung
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Finn RN. The physiology and toxicology of salmonid eggs and larvae in relation to water quality criteria. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2007; 81:337-54. [PMID: 17316838 DOI: 10.1016/j.aquatox.2006.12.021] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2005] [Revised: 09/08/2006] [Accepted: 12/28/2006] [Indexed: 05/14/2023]
Abstract
The purpose of this review is to collate physiological knowledge on salmonid eggs and larvae in relation to water quality criteria. Salmonid genera reviewed include Coregonus, Thymallus, Salvelinus, Salmo, and Oncorhynchus spp. When physiological data for salmonids are lacking, the zebrafish and medaka models are included. The primary focus is on the underlying mechanisms involved in the hydro-mineral, thermal, and respiratory biology with an extended section on the xenobiotic toxicology of the early stages. Past and present data reveal that the eggs of salmonids are among the largest shed by any broadcast spawning teleost. Once ovulated, the physicochemical properties of the ovarian fluid provide temporary protection from external perturbations and maintain the eggs in good physiological condition until spawning. Following fertilisation and during early development the major structures protecting the embryo from poor water quality are the vitelline membrane, the enveloping layer and the chorion. The vitelline membrane is one of the least permeable membranes known, while the semi-permeable chorion provides both physical and chemical defense against metals, pathogens, and xenobiotic chemicals. In part these structures explain the lower sensitivity of the eggs to chemical imbalance compared to the larvae, however the lower metabolic rate and the chronology of gene expression and translational control suggest that developmental competence also plays a decisive role. In addition, maternal effect genes provide a defense potential until the mid-blastula transition. The transition between maternal effect genes and zygotic genes is a critical period for the embryo. The perivitelline fluids are an important trap for cations, but are also the major barrier to diffusion of gases and solutes. Acidic environmental pH interferes with acid-base and hydromineral balance but also increases the risk of aluminium and heavy metal intoxication. These risks are ameliorated somewhat by the presence of ambient humic acid. High temperatures during development may be teratogenic, cause sexual bias, or long-term effects on muscle cellularity. Xenobiotics cause inhibition of neural acetylcholine esterase and carboxylases and disrupt the normal signalling pathways of hormones by binding to relevant receptors and mimicking their actions. A complex suite of genes is activated in response to environmental or parentally transmitted xenobiotics. The primary defense mechanism in embryos involves resistance to uptake but later biotransformation via the aryl hydrocarbon receptor (AHR)-mediated activation of members of the cytochrome mixed-function mono-oxygenase superfamily (CYP1A, CYP2B, and CYP3A) and subsequent glucuronidation or glutathionation. Due to the number of duplicate or triplicate genes coding for intermediates in the signalling pathways, and cross-talk between nuclear orphan receptors and steroid hormone receptors, a large number of complications arise in response to xenobiotic intoxicaton. One such syndrome, known as blue-sac disease causes an anaphylactoid response in hatched larvae due to increased permeability in the vascular endothelium that coincides with AHR-mediated CYP induction. Early embryos also respond to such xenobiotic insults, but apparently have an immature translational control for expression of CYP proteins, which coincides with a lack of excretory organs necessary for the end-point of biotransformation. Other syndromes (M74 and Cayuga) are now associated with thiamine deficiency. Where possible guidelines for water quality criteria are suggested.
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Affiliation(s)
- Roderick Nigel Finn
- Department of Biology, University of Bergen, Allégaten 41, N-5020 Bergen, Norway.
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Wilkie MP, Claude JF, Cockshutt A, Holmes JA, Wang YS, Youson JH, Walsh PJ. Shifting Patterns of Nitrogen Excretion and Amino Acid Catabolism Capacity during the Life Cycle of the Sea Lamprey (Petromyzon marinus). Physiol Biochem Zool 2006; 79:885-98. [PMID: 16927235 DOI: 10.1086/505998] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2006] [Indexed: 11/04/2022]
Abstract
The jawless fish, the sea lamprey (Petromyzon marinus), spends part of its life as a burrow-dwelling, suspension-feeding larva (ammocoete) before undergoing a metamorphosis into a free swimming, parasitic juvenile that feeds on the blood of fishes. We predicted that animals in this juvenile, parasitic stage have a great capacity for catabolizing amino acids when large quantities of protein-rich blood are ingested. The sixfold to 20-fold greater ammonia excretion rates (J(Amm)) in postmetamorphic (nonfeeding) and parasitic lampreys compared with ammocoetes suggested that basal rates of amino acid catabolism increased following metamorphosis. This was likely due to a greater basal amino acid catabolizing capacity in which there was a sixfold higher hepatic glutamate dehydrogenase (GDH) activity in parasitic lampreys compared with ammocoetes. Immunoblotting also revealed that GDH quantity was 10-fold and threefold greater in parasitic lampreys than in ammocoetes and upstream migrant lampreys, respectively. Higher hepatic alanine and aspartate aminotransferase activities in the parasitic lampreys also suggested an enhanced amino acid catabolizing capacity in this life stage. In contrast to parasitic lampreys, the twofold larger free amino acid pool in the muscle of upstream migrant lampreys confirmed that this period of natural starvation is accompanied by a prominent proteolysis. Carbamoyl phosphate synthetase III was detected at low levels in the liver of parasitic and upstream migrant lampreys, but there was no evidence of extrahepatic (muscle, intestine) urea production via the ornithine urea cycle. However, detection of arginase activity and high concentrations of arginine in the liver at all life stages examined infers that arginine hydrolysis is an important source of urea. We conclude that metamorphosis is accompanied by a metabolic reorganization that increases the capacity of parasitic sea lampreys to catabolize intermittently large amino acid loads arising from the ingestion of protein rich blood from their prey/hosts. The subsequent generation of energy-rich carbon skeletons can then be oxidized or retained for glycogen and fatty acid synthesis, which are essential fuels for the upstream migratory and spawning phases of the sea lamprey's life cycle.
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Affiliation(s)
- Michael P Wilkie
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, N2L 3C5, Canada.
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Barimo JF, Walsh PJ. The effects of acute and chronic ammonia exposure during early life stages of the gulf toadfish, Opsanus beta. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2005; 75:225-37. [PMID: 16171879 DOI: 10.1016/j.aquatox.2005.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/11/2005] [Accepted: 08/13/2005] [Indexed: 05/04/2023]
Abstract
The gulf toadfish (Opsanus beta) is unusual among teleosts in that it is facultatively ureotelic and adults and juveniles have a particularly high tolerance to environmental ammonia. Male toadfish brood their offspring in confined nests. It has been hypothesized that the potential accumulation of ammonia in nests from the male and the offspring, coupled with suspected low ammonia tolerance in offspring would provide the selective pressure necessary for excretion of the less toxic urea by adult toadfish. This study examines this so-called 'nest-fouling' hypothesis through acute and chronic ammonia toxicity testing on early life stages of O. beta. In addition, nitrogen elimination was examined among embryos, yolk-sac larvae and juveniles where we found an ontogenic shift from ammonotely to ureotely with advancing life history stages. The acute ammonia 96 h LC50 values for embryos and larvae were 63.6 and 5.45 mmol-Nl(-1) total ammonia (TAmm), respectively. Thus, these early life stages are more tolerant to ammonia than either juveniles or adults and LC50 values are at least 2 orders of magnitude greater than concentrations naturally occurring at nest sites. Furthermore, 40 days exposures at mean and maximum NH3 concentrations normally found within nests revealed no observable detrimental effects. In fact, growth in terms of wet or dry weight was greatest at the maximum NH3 concentration. We therefore conclude that the nest-fouling hypothesis is not a viable explanation for ureotely in the gulf toadfish.
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Affiliation(s)
- John F Barimo
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA.
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Kharbuli ZY, Datta S, Biswas K, Sarma D, Saha N. Expression of ornithine-urea cycle enzymes in early life stages of air-breathing walking catfish Clarias batrachus and induction of ureogenesis under hyper-ammonia stress. Comp Biochem Physiol B Biochem Mol Biol 2005; 143:44-53. [PMID: 16271487 DOI: 10.1016/j.cbpb.2005.09.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2005] [Revised: 07/05/2005] [Accepted: 09/29/2005] [Indexed: 11/16/2022]
Abstract
The air-breathing walking catfish Clarias batrachus is a potential ureogenic teleost with having a full complement of ornithine-urea cycle (OUC) enzymes expressed in various tissues. The present study was aimed at determining the pattern of nitrogenous waste excretion in the form of ammonia-N and urea-N along with the changes of tissue ammonia and urea levels, and the expression of OUC enzymes and glutamine synthetase (GSase) in early life stages of this teleost, and further, to study the possible induction of ureogenesis in 15-day old fry under hyper-ammonia stress. The ammonia and urea excretion was visible within 12 h post-fertilization (hpf), which increased several-fold until the yolk was completely absorbed by the embryo. Although all the early developing stages were primarily ammoniotelic, they also excreted significant amount of nitrogen (N) in the form of urea-N (about 35-40% of total N). Tissue levels of ammonia and urea also increased along with subsequent developmental stages at least until the yolk absorption stage. All the OUC enzymes and GSase were expressed within 4-12 hpf showing an increasing trend of activity for all the enzymes until 350 hpf. There was a significant increase of activity of GSase, carbamyl phosphate synthetase III (CPSase III) and argininosuccinate lyase enzymes (ASL), accompanied with significant increase of enzyme protein concentration of at least two enzymes (GSase and CPSase III) in the 15-day old fry following exposure to 10 mM NH4Cl as compared to respective controls kept in water over a period of 72 h. Thus, it appears that the OUC enzymes are expressed in early life stages of walking catfish like other teleosts, but at relatively high levels and remain expressed all through the life stages with a potential of stimulation of ureogenesis throughout the life cycle as a sort of physiological adaptation to survive and breed successfully under hyper-ammonia and various other environmental-related stresses.
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Affiliation(s)
- Zaiba Y Kharbuli
- Biochemical Adaptation Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793 022, India
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Essex-Fraser PA, Steele SL, Bernier NJ, Murray BW, Stevens ED, Wright PA. Expression of Four Glutamine Synthetase Genes in the Early Stages of Development of Rainbow Trout (Oncorhynchus mykiss) in Relationship to Nitrogen Excretion. J Biol Chem 2005; 280:20268-73. [PMID: 15781468 DOI: 10.1074/jbc.m412338200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The incorporation of ammonia into glutamine, catalyzed by glutamine synthetase, is thought to be important in the detoxification of ammonia in animals. During early fish development, ammonia is continuously formed as yolk proteins and amino acids are catabolized. We followed the changes in ammonia and urea-nitrogen content, ammonia and urea-nitrogen excretion, glutamine synthetase activity, and mRNA expression of four genes coding for glutamine synthetase (Onmy-GS01-GS04) over 3-80 days post fertilization and in adult liver and skeletal muscle of the rainbow trout (Oncorhynchus mykiss). Both ammonia and urea-nitrogen accumulate before hatching, although the rate of ammonia excretion is considerably higher relative to urea-nitrogen excretion. All four genes were expressed during early development, but only Onmy-GS01 and -GS02 were expressed at appreciable levels in adult liver, and expression was very low in muscle tissue. The high level of expression of Onmy-GS01 and -GS03 prior to hatching corresponded to a linear increase in glutamine synthetase activity. We propose that the induction of glutamine synthetase genes early in development and the subsequent formation of the active protein are preparatory for the increased capacity of the embryo to convert the toxic nitrogen end product, ammonia, into glutamine, which may then be utilized in the ornithine-urea cycle or other pathways.
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Steele SL, Yancey PH, Wright PA. The little skate Raja erinacea exhibits an extrahepatic ornithine urea cycle in the muscle and modulates nitrogen metabolism during low-salinity challenge. Physiol Biochem Zool 2005; 78:216-26. [PMID: 15778941 DOI: 10.1086/427052] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2004] [Indexed: 11/03/2022]
Abstract
Urea synthesis via the hepatic ornithine urea cycle (OUC) has been well described in elasmobranchs, but it is unknown whether OUC enzymes are also present in extrahepatic tissues. Muscle and liver urea, trimethylamine oxide (TMAO), and other organic osmolytes, as well as selected OUC enzymes (carbamoyl phosphate synthetase III, ornithine transcarbamoylase, arginase, and the accessory enzyme glutamine synthetase), were measured in adult little skates (Raja erinacea) exposed to 100% or 75% seawater for 5 d. Activities of all four OUC enzymes were detected in the muscle. There were no changes in muscle OUC activities in skates exposed to 75% seawater; however, arginase activity was significantly lower in the liver, compared to controls. Urea, TMAO, and several other osmolytes were significantly lower in the muscle of little skates exposed to 75% seawater, whereas only glycerophosphorylcholine was significantly lower in the liver. Urea excretion rates were twofold higher in skates exposed to 75% seawater. Taken together, these data suggest that a functional OUC may be present in the skeletal muscle tissues of R. erinacea. As well, enhanced urea excretion rates and the downregulation of the anchor OUC enzyme, arginase, in the liver may be critical in regulating tissue urea content under dilute-seawater stress.
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Affiliation(s)
- Shelby L Steele
- Department of Zoology, University of Guelph, Ontario, Canada
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Barimo JF, Steele SL, Wright PA, Walsh PJ. Dogmas and controversies in the handling of nitrogenous wastes: ureotely and ammonia tolerance in early life stages of the gulf toadfish, Opsanus beta. ACTA ACUST UNITED AC 2004; 207:2011-20. [PMID: 15143135 DOI: 10.1242/jeb.00956] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The marine gulf toadfish (Opsanus beta) is an unusual teleost fish as it is able to switch between ammoniotelism and ureotelism in response to a variety of laboratory conditions. The present study integrates field work conducted in Biscayne and Florida Bays, USA with laboratory studies to examine ureotelism during the early life history stages of O. beta. Adult toadfish voluntarily nested in artificial shelters placed amongst seagrass beds and were found to be predominantly ureotelic under natural conditions as the internal shelter water had mean urea and ammonia concentrations (N=51) of 14.2+/-1.6 micro mol N l(-1) and 8.9+/-0.9 micro mol N l(-1), respectively. Toadfish successfully spawned in shelters, providing eggs, larvae and juvenile toadfish for laboratory study. In the lab, juvenile toadfish were also ureotelic and urea was excreted in pulsatile events that accounted for 62.0+/-5.9% of total urea-N excreted. Excretion rates of urea-N and ammonia-N were 1.018+/-0.084 micro mol N h(-1) g(-1) and 0.235+/-0.095 micro mol N h(-1) g(-1), respectively. Field-collected eggs, larvae and juveniles expressed significant levels of the ornithine-urea cycle enzymes carbamoyl-phosphate synthetase III, ornithine transcarbamylase and arginase and the accessory enzyme glutamine synthetase, all of which increased in activity as toadfish developed through early life stages. In juveniles, the ammonia 96-h LC(50) value was 875 micro mol N l(-1) and there was a 3-fold increase in ornithine transcarbamylase activity in the 1000 micro mol N l(-1) NH(4)Cl treatment. The results are discussed in the context of the causal factor(s) for ureotelism in toadfish. Furthermore, the results of this study suggest it is unlikely that the adaptive significance of ureotelism in toadfish is a means to prevent fouling nests with ammonia and in turn poisoning offspring; however, additional study is warranted.
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Affiliation(s)
- John F Barimo
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA.
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Steele SL, Yancey PH, Wright PA. Dogmas and controversies in the handling of nitrogenous wastes: osmoregulation during early embryonic development in the marine little skate Raja erinacea; response to changes in external salinity. ACTA ACUST UNITED AC 2004; 207:2021-31. [PMID: 15143136 DOI: 10.1242/jeb.00959] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Marine elasmobranchs retain relatively high levels of urea to counterbalance the osmotic strength of seawater. Oviparous species, such as the little skate Raja erinacea, release encapsulated embryos that hatch after about 9 months on the seafloor. To study the ureosmotic capability of skate embryos, we measured a variety of possible osmolytes and ornithine-urea cycle (OUC) enzyme activities in little skate embryos, and determined their physiological response to dilute seawater (75% SW) exposure relative to controls (100% SW). The urea:trimethylamine oxide (TMAO) + other osmolytes ratio was 2.3-2.7:1. At the earliest stage of development investigated (4 months), there were significant levels of the key OUC enzyme, carbamoyl phosphate synthetase III, as well as ornithine transcarbamoylase, arginase and glutamine synthetase, providing evidence for a functional OUC. Embryos (4 and 8 months) survived and recovered from exposure to 5 days of 75% SW. There was a significant increase in the rate of urea excretion (five- to tenfold), no change in OUC enzyme activities, and significant decreases in the tissue content of urea, TMAO and other osmolytes in embryos exposed to 75% SW compared to 100% SW. Taken together, the data indicate that little skate embryos synthesize and retain urea, as well as a suite of other osmolytes, in order to regulate osmotic balance with the external environment. Interestingly, these ureosmotic mechanisms are in place as early as 4 months, around the time at which the egg capsule opens and the embryo is in more direct contact with the external environment.
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Affiliation(s)
- S L Steele
- Department of Zoology, University of Guelph, Guelph, ON N1G 2W1, Canada
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Wright PA, Campbell A, Morgan RL, Rosenberger AG, Murray BW. Dogmas and controversies in the handling of nitrogenous wastes: expression of arginase Type I and II genes in rainbow trout: influence of fasting on liver enzyme activity and mRNA levels in juveniles. ACTA ACUST UNITED AC 2004; 207:2033-42. [PMID: 15143137 DOI: 10.1242/jeb.00958] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Through analysis of a cDNA library and third-party annotation of available database sequences, we characterized the full-length coding regions of rainbow trout (Oncorhynchus mykiss) Type I, Onmy-ARG01, and Type II, Onmy-ARG02, arginase genes. Two partial related arginase sequences, Onmy-ARG01b and Onmy-ARG02b, and a full-length zebrafish arginase coding region (Danio rerio), Dare-ARG02, are also reported. Comparison of vertebrate arginase sequences shows that both Type I and Type II genes in bony fishes contain a mitochondrial targeting N-terminal domain. This suggests that the cytosolic Type I arginase found in ureotelic vertebrates arose in the common ancestor of amphibia and mammals. Onmy-ARG01 and Onmy-ARG02 mRNA was detected in liver, kidney, gill, intestine, red muscle and heart tissues. Onmy-ARG01 was expressed at a significantly higher level relative to Onmy-ARG02 in liver and red muscle tissue. To investigate whether there was differential regulation of Onmy-ARG01 and Onmy-ARG02, juvenile trout were fasted for 6 weeks and hepatic enzyme activities and mRNA levels were compared with those of fed control fish. There was a 3-fold increase in liver arginase activity and a 2-fold increase in Onmy-ARG02 mRNA levels but no change in Onmy-ARG01 mRNA levels in fasted fish relative to fed fish. These findings indicate that both types of arginase genes are present and expressed in rainbow trout and that the pattern of expression varies between tissues. The increase in liver arginase activity after a 6-week fast is due, in part, to an increase in the expression of Onmy-ARG02 mRNA levels.
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Affiliation(s)
- Patricia A Wright
- Department of Zoology, University of Guelph, Guelph, ON, Canada N1G 2W1.
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McDonald MD, Wood CM. Differential Handling of Urea and Its Analogues Suggests Carrier‐Mediated Urea Excretion in Freshwater Rainbow Trout. Physiol Biochem Zool 2003; 76:791-802. [PMID: 14988794 DOI: 10.1086/378919] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/03/2003] [Indexed: 11/04/2022]
Abstract
The possible presence of urea transport mechanisms in the gill and kidney of the freshwater rainbow trout (Oncorhynchus mykiss) was investigated in vivo by comparing the branchial and renal handling of analogues acetamide and thiourea with the handling of urea. Trout were fitted with indwelling dorsal aortic catheters and urinary catheters and injected with an isosmotic dose of [(14)C]-labeled urea analogue (acetamide or thiourea) calculated to bring plasma analogue concentrations close to plasma urea concentrations. Urea and analogue concentrations were significantly greater in the urine than in the plasma. Branchial clearance rate of acetamide was only 48% of urea clearance, whereas the clearance of thiourea was only 22%, a pattern that was also observed in branchial uptake of these substances and was similar to our previous observations in toadfish and midshipmen. The renal secretion clearance rates of urea and acetamide were similar, and on average, both substances were secreted on a net basis, although reabsorption did occur in some cases. In contrast, thiourea was neither reabsorbed nor secreted by the kidney tubule. The secretion clearance rates of both acetamide and urea were well correlated with the secretion clearance rates of Na(+), Cl(-), and water, whereas there was no relationship between thiourea and these substances. The pattern of acetamide, thiourea, and urea handling by the gill of the trout is similar to that found in the gills of the midshipman and the gulf toadfish and strongly suggests the presence of a UT-type facilitated diffusion urea transport mechanism. The pattern of differential handling in the kidney is unlike that in the gill and also unlike that in the kidney of the midshipman and the gulf toadfish, suggesting a different mechanism. In addition, renal urea secretion occurs against a concentration gradient, suggesting the involvement of an active transport mechanism.
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Affiliation(s)
- M Danielle McDonald
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
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Murray BW, Busby ER, Mommsen TP, Wright PA. Evolution of glutamine synthetase in vertebrates: multiple glutamine synthetase genes expressed in rainbow trout (Oncorhynchus mykiss). J Exp Biol 2003; 206:1511-21. [PMID: 12654890 DOI: 10.1242/jeb.00283] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutamine synthetase (GSase) is a key enzyme in nitrogen metabolism and encoded by a single gene in mammals. Using PCR cloning techniques, including RT-PCR from total RNA and PCR from a cDNA library, we find evidence of four expressed GSase mRNAs for the tetraploid rainbow trout. For two of these mRNAs (Onmy-GS01, -GS02) we characterize the full-length coding regions, and for two others (Onmy-GS03, -GS04), we describe partial sequences. Northern analysis of Onmy-GS01, -GS02, -GS03 and -GS04 indicates that (1) Onmy-GS02 is expressed at higher levels relative to the other transcripts in most adult tissues, with the exception of brain and gill, where Onmy-GS01 is at the highest level, and (2) the tissue with the highest level of expression of all four transcripts is the brain, with decreasing levels in the intestine, liver, red muscle, gill/kidney, white muscle and heart. Clearly, rainbow trout possess multiple GSase genes with differing levels of tissue expression, implying manifold potential routes of regulation for this octameric enzyme. Our data also indicate that caution should be taken when interpreting mRNA expression data of a single gene, unless multiple genes have been ruled out. Consistent with a southern blot, phylogenetic and intron sequence analyses imply that the trout genes are encoded by at least four separate loci, belonging to two distinct evolutionary branches. Our data on rainbow trout, together with those from two full-length zebrafish Danio rerio GSase genes compiled from GenBank ESTs, support the idea that fish GSases are polyphyletic and that gene duplications have occurred at multiple points and in independent lineages throughout the evolution of bony fishes.
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Affiliation(s)
- Brent W Murray
- Department of Zoology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Terjesen BF, Finn RN, Norberg B, Rønnestad I. Kinetics and fates of ammonia, urea, and uric acid during oocyte maturation and ontogeny of the Atlantic halibut (Hippoglossus hippoglossus L.). Comp Biochem Physiol A Mol Integr Physiol 2002; 131:443-55. [PMID: 11818232 DOI: 10.1016/s1095-6433(01)00496-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Considering that amino acids constitute an important energy fuel during early life of the Atlantic halibut (Hippoglossus hippoglossus L.), it is of interest to understand how the nitrogenous end products are handled. In this study we focused on the kinetics and fates of ammonia, urea and uric acid. The results showed that ammonia (T(Amm): NH(3)+NH(4)(+)), and urea-N contents increased during final oocyte maturation. Urea-N excretion dominated the total nitrogenous end product formation in early embryos. Later, yolk T(Amm) levels increased in embryos and ammonia excretion was low. In the last part of the embryonic stage T(Amm) accumulation dominated, and was apparently due to yolk storage. Around hatching, the larval body tissues (larva with yolk-sac removed) accounted for 68% of whole animal urea-N accumulation, while T(Amm) levels increased predominately by yolk accumulation. Afterwards, ammonia excretion dominated and uric acid accumulation accounted for less than 1%. Urea, synthesised either through the ornithine-urea cycle, argininolysis or uricolysis, accounted for approximately 8% of total nitrogenous end product formation in yolk-sac larvae. The results suggested that a sequence occurred regarding which nitrogenous end products dominated and how they were handled. Urea excretion dominated in early embryos (<7 dPF), followed by yolk ammonia accumulation (7-12 dPF), and finally, ammonia excretion dominated in later embryonic and yolk-sac larval stages (>12 dPF).
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Affiliation(s)
- B F Terjesen
- Department of Zoology, University of Bergen, Allègt. 41, N-5007 Bergen, Norway.
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