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Country MW, Jonz MG. Goldfish and crucian carp are natural models of anoxia tolerance in the retina. Comp Biochem Physiol A Mol Integr Physiol 2022; 270:111244. [PMID: 35618216 DOI: 10.1016/j.cbpa.2022.111244] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 05/15/2022] [Accepted: 05/16/2022] [Indexed: 10/18/2022]
Abstract
Vertebrates need oxygen to survive. The central nervous system has an especially high energy demand, so brain and retinal neurons quickly die in anoxia. But fish of the genus Carassius are exceptionally anoxia-tolerant: the crucian carp (C. carassius) can survive months without oxygen in ice-covered ponds, and the common goldfish (C. auratus) can withstand hours of anoxia at room temperature. These fish previously offered insights into anoxia tolerance in the brain, heart, and liver. Here, we advance Carassius spp. as models to study anoxia tolerance in the retina. Electroretinogram and evoked potential recordings show that crucian carp reversibly downregulate their visual systems in anoxia, probably to save ATP. Notably, Carassius suppress their visual systems nearly twice as much as anoxia-tolerant turtles, Trachemys and Chrysemys spp., which are often promoted as the champions of anoxia tolerance. We summarize what is known about anoxia tolerance in the goldfish and crucian carp retinas, including cellular pathways which may protect retinal neurons from excitotoxic cell death. We compare the Carassius retina with two relevant models: natural anoxia tolerance in the turtle brain, and ischemic preconditioning in the rat retina. All three models include mitochondria as oxygen sensors: mitochondria depolarize due to mitochondrial ATP-dependent K+ channels, possibly to trigger neuroprotective second messenger cascades. The Carassius retina is an accessible and inexpensive model, with over 70 fruitful years of history in vision research. As a model for anoxia tolerance, it may provide new insights into diseases of the eye (like diabetes, macular degeneration, and eye stroke).
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Affiliation(s)
- Michael W Country
- Department of Biology, University of Ottawa, Canada. https://twitter.com/biologycountry
| | - Michael G Jonz
- Department of Biology, University of Ottawa, Canada; Brain and Mind Research Institute, University of Ottawa, Canada.
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Sparks K, Couturier CS, Buskirk J, Flores A, Hoeferle A, Hoffman J, Stecyk JAW. Gene expression of hypoxia-inducible factor (HIF), HIF regulators, and putative HIF targets in ventricle and telencephalon of Trachemys scripta acclimated to 21 °C or 5 °C and exposed to normoxia, anoxia or reoxygenation. Comp Biochem Physiol A Mol Integr Physiol 2022; 267:111167. [PMID: 35182763 PMCID: PMC8977064 DOI: 10.1016/j.cbpa.2022.111167] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 02/10/2022] [Accepted: 02/10/2022] [Indexed: 12/20/2022]
Abstract
In anoxia-sensitive mammals, hypoxia inducible factor (HIF) promotes cellular survival in hypoxia, but also tumorigenesis. By comparison, anoxia-tolerant vertebrates likely need to circumvent a prolonged upregulation of HIF to survive long-term anoxia, making them attractive biomedical models for investigating HIF regulation. To lend insight into the role of HIF in anoxic Trachemys scripta ventricle and telencephalon, 21 °C- and 5 °C-acclimated turtles were exposed to normoxia, anoxia (24 h at 21 °C; 24 h or 14 d at 5 °C) or anoxia + reoxygenation and the gene expression of HIF-1α (hif1a) and HIF-2α (hif2a), two regulators of HIF, and eleven putative downstream targets of HIF quantified by qPCR. Changes in gene expression with anoxia at 21 °C differentially aligned with a circumvention of HIF activity. Whereas hif1a and hif2a expression was unaffected in ventricle and telencephalon, and BCL2 interacting protein 3 gene expression reduced by 30% in telencephalon, gene expression of vascular endothelial growth factor-A increased in ventricle (4.5-fold) and telencephalon (1.5-fold), and hexokinase 1 (2-fold) and hexokinase 2 (3-fold) gene expression increased in ventricle. At 5 °C, the pattern of gene expression in ventricle or telencephalon was unaltered with oxygenation state. However, cold acclimation in normoxia induced downregulation of HIF-1α, HIF-2α, and HIF target gene expression in telencephalon. Overall, the findings lend support to the postulation that prolonged activation of HIF is counterproductive for long-term anoxia survival. Nevertheless, quantification of the effect of anoxia and acclimation temperature on HIF binding activity and regulation at the protein level are needed to provide a strong scientific framework whereby new strategies for oxygen related pathologies can be developed.
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Affiliation(s)
- Kenneth Sparks
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States
| | - Christine S Couturier
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States
| | - Jacob Buskirk
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States
| | - Alicia Flores
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States
| | - Aurora Hoeferle
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States
| | - Jessica Hoffman
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States
| | - Jonathan A W Stecyk
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, United States.
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Abstract
ABSTRACT
Hypoxia is one of the strongest environmental drivers of cellular and physiological adaptation. Although most mammals are largely intolerant of hypoxia, some specialized species have evolved mitigative strategies to tolerate hypoxic niches. Among the most hypoxia-tolerant mammals are naked mole-rats (Heterocephalus glaber), a eusocial species of subterranean rodent native to eastern Africa. In hypoxia, naked mole-rats maintain consciousness and remain active despite a robust and rapid suppression of metabolic rate, which is mediated by numerous behavioural, physiological and cellular strategies. Conversely, hypoxia-intolerant mammals and most other hypoxia-tolerant mammals cannot achieve the same degree of metabolic savings while staying active in hypoxia and must also increase oxygen supply to tissues, and/or enter torpor. Intriguingly, recent studies suggest that naked mole-rats share many cellular strategies with non-mammalian vertebrate champions of anoxia tolerance, including the use of alternative metabolic end-products and potent pH buffering mechanisms to mitigate cellular acidification due to upregulation of anaerobic metabolic pathways, rapid mitochondrial remodelling to favour increased respiratory efficiency, and systemic shifts in energy prioritization to maintain brain function over that of other tissues. Herein, I discuss what is known regarding adaptations of naked mole-rats to a hypoxic lifestyle, and contrast strategies employed by this species to those of hypoxia-intolerant mammals, closely related African mole-rats, other well-studied hypoxia-tolerant mammals, and non-mammalian vertebrate champions of anoxia tolerance. I also discuss the neotenic theory of hypoxia tolerance – a leading theory that may explain the evolutionary origins of hypoxia tolerance in mammals – and highlight promising but underexplored avenues of hypoxia-related research in this fascinating model organism.
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Affiliation(s)
- Matthew E. Pamenter
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 9A7. University of Ottawa, Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada, K1H 8M5
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Na +/K +-ATPase activity is regionally regulated by acute hypoxia in naked mole-rat brain. Neurosci Lett 2021; 764:136244. [PMID: 34530116 DOI: 10.1016/j.neulet.2021.136244] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 09/09/2021] [Accepted: 09/09/2021] [Indexed: 11/21/2022]
Abstract
Matching ATP supply and demand is key to neuronal hypoxia-tolerance and failure to achieve this balance leads to excitotoxic cell death in most adult mammalian brains. Ion pumping is the most energy-demanding process in the brain and some hypoxia-tolerant vertebrates coordinately down-regulate ion movement across neuronal membranes to reduce the workload of energy-expensive ion pumps, and particularly the Na+/K+-ATPase. Naked mole-rats are among the most hypoxia-tolerant mammals and achieve a hypometabolic state while maintaining brain [ATP] during severe hypoxia; however, whether ionic homeostasis is plastic in naked mole-rat brain is unknown. To examine this question, we exposed animals to 4 h of normoxia or moderate or severe hypoxia (11 or 3% O2, respectively) and measured changes in brain Na+/K+-ATPase activity. We found that 1) whole body metabolic rate decreased ∼25 and 75% in moderate and severe hypoxia, respectively, and 2) Na+/K+-ATPase activity decreased ∼50% in forebrain but increased 2-fold in cerebellum and was unchanged in brainstem. These results indicate that naked mole-rats acutely modulate brain energy demand in a region-specific manner to prioritize energy usage by the cerebellum. This may support exploration, navigation, and escape behaviours, while also enabling ATP savings when encountering hypoxia in nature.
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Ionescu RA, Hepditch SLJ, Wilkie MP. The lampricide 3-trifluoromethyl-4-nitrophenol causes temporary metabolic disturbances in juvenile lake sturgeon ( Acipenser fulvescens): implications for sea lamprey control and fish conservation. CONSERVATION PHYSIOLOGY 2021; 9:coab069. [PMID: 34512991 PMCID: PMC8427354 DOI: 10.1093/conphys/coab069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 07/19/2021] [Accepted: 09/03/2021] [Indexed: 06/13/2023]
Abstract
The pesticide 3-trifluoromethyl-4-nitrophenol (TFM) is applied to rivers and streams draining into the Laurentian Great Lakes to control populations of invasive sea lamprey (Petromyzon marinus), which are ongoing threats to fisheries during the lamprey's hematophagous, parasitic juvenile life stage. While TFM targets larval sea lamprey during treatments, threatened populations of juvenile lake sturgeon (Acipenser fulvescens), particularly young-of-the-year (<100 mm in length), may be adversely affected by TFM when their habitats overlap with larval sea lamprey. Exposure to TFM causes marked reductions in tissue glycogen and high energy phosphagens in lamprey and rainbow trout (Oncorhynchus mykiss) by interfering with oxidative ATP production in the mitochondria. To test that environmentally relevant concentrations of TFM would similarly affect juvenile lake sturgeon, we exposed them to the larval sea lamprey minimum lethal concentration (9-h LC99.9), which mimicked concentrations of a typical lampricide application and quantified energy stores and metabolites in the carcass, liver and brain. Exposure to TFM reduced brain ATP, PCr and glycogen by 50-60%, while lactate increased by 45-50% at 6 and 9 h. A rapid and sustained depletion of liver glucose and glycogen of more than 50% was also observed, whereas the respective concentrations of ATP and glycogen were reduced by 60% and 80% after 9 h, along with higher lactate and a slight metabolic acidosis (~0.1 pH unit). We conclude that exposure to environmentally relevant concentrations of TFM causes metabolic disturbances in lake sturgeon that can lead to impaired physiological performance and, in some cases, mortality. Our observations support practices such as delaying TFM treatments to late summer/fall or using alternative TFM application strategies to mitigate non-target effects in waters where lake sturgeon are present. These actions would help to conserve this historically and culturally significant species in the Great Lakes.
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Affiliation(s)
- R Adrian Ionescu
- Department of Biology and Laurier Institute for Water Science, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | - Scott L J Hepditch
- Department of Biology and Laurier Institute for Water Science, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
- Current Address: Centre Eau Terre Environment, Institut National de la Recherche Scientifique, Québec, Québec City G1K 9A9, Canada
| | - Michael P Wilkie
- Department of Biology and Laurier Institute for Water Science, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
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Hypoxia Tolerance Declines with Age in the Absence of Methionine Sulfoxide Reductase (MSR) in Drosophila melanogaster. Antioxidants (Basel) 2021; 10:antiox10071135. [PMID: 34356368 PMCID: PMC8301005 DOI: 10.3390/antiox10071135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 07/07/2021] [Accepted: 07/13/2021] [Indexed: 11/17/2022] Open
Abstract
Unlike the mammalian brain, Drosophila melanogaster can tolerate several hours of hypoxia without any tissue injury by entering a protective coma known as spreading depression. However, when oxygen is reintroduced, there is an increased production of reactive oxygen species (ROS) that causes oxidative damage. Methionine sulfoxide reductase (MSR) acts to restore functionality to oxidized methionine residues. In the present study, we have characterized in vivo effects of MSR deficiency on hypoxia tolerance throughout the lifespan of Drosophila. Flies subjected to sudden hypoxia that lacked MSR activity exhibited a longer recovery time and a reduced ability to survive hypoxic/re-oxygenation stress as they approached senescence. However, when hypoxia was induced slowly, MSR deficient flies recovered significantly quicker throughout their entire adult lifespan. In addition, the wildtype and MSR deficient flies had nearly 100% survival rates throughout their lifespan. Neuroprotective signaling mediated by decreased apoptotic pathway activation, as well as gene reprogramming and metabolic downregulation are possible reasons for why MSR deficient flies have faster recovery time and a higher survival rate upon slow induction of spreading depression. Our data are the first to suggest important roles of MSR and longevity pathways in hypoxia tolerance exhibited by Drosophila.
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Farhat E, Cheng H, Romestaing C, Pamenter M, Weber JM. Goldfish Response to Chronic Hypoxia: Mitochondrial Respiration, Fuel Preference and Energy Metabolism. Metabolites 2021; 11:187. [PMID: 33809959 PMCID: PMC8004290 DOI: 10.3390/metabo11030187] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 03/10/2021] [Accepted: 03/17/2021] [Indexed: 12/16/2022] Open
Abstract
Hypometabolism is a hallmark strategy of hypoxia tolerance. To identify potential mechanisms of metabolic suppression, we have used the goldfish to quantify the effects of chronically low oxygen (4 weeks; 10% air saturation) on mitochondrial respiration capacity and fuel preference. The responses of key enzymes from glycolysis, β-oxidation and the tricarboxylic acid (TCA) cycle, and Na+/K+-ATPase were also monitored in various tissues of this champion of hypoxia tolerance. Results show that mitochondrial respiration of individual tissues depends on oxygen availability as well as metabolic fuel oxidized. All the respiration parameters measured in this study (LEAK, OXPHOS, Respiratory Control Ratio, CCCP-uncoupled, and COX) are affected by hypoxia, at least for one of the metabolic fuels. However, no common pattern of changes in respiration states is observed across tissues, except for the general downregulation of COX that may help metabolic suppression. Hypoxia causes the brain to switch from carbohydrates to lipids, with no clear fuel preference in other tissues. It also downregulates brain Na+/K+-ATPase (40%) and causes widespread tissue-specific effects on glycolysis and beta-oxidation. This study shows that hypoxia-acclimated goldfish mainly promote metabolic suppression by adjusting the glycolytic supply of pyruvate, reducing brain Na+/K+-ATPase, and downregulating COX, most likely decreasing mitochondrial density.
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Affiliation(s)
- Elie Farhat
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
| | - Hang Cheng
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
| | - Caroline Romestaing
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
- Univ Lyon, Université Claude Bernard Lyon1, CNRS, ENTPE, UMR 5023, LEHNA, F 69622 Villeurbanne, France
| | - Matthew Pamenter
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
- Faculty of Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Jean-Michel Weber
- Biology Department, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (E.F.); (H.C.); (C.R.); (M.P.)
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Petrushanko IY, Mitkevich VA, Makarov AA. Molecular Mechanisms of the Redox Regulation of the Na,K-ATPase. Biophysics (Nagoya-shi) 2020. [DOI: 10.1134/s0006350920050139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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9
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Farhat E, Devereaux MEM, Pamenter ME, Weber JM. Naked mole-rats suppress energy metabolism and modulate membrane cholesterol in chronic hypoxia. Am J Physiol Regul Integr Comp Physiol 2020; 319:R148-R155. [PMID: 32663032 DOI: 10.1152/ajpregu.00057.2020] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Naked mole-rats (NMRs) are mammalian champions of hypoxia tolerance that enter metabolic suppression to survive in low oxygen environments. Common physiological mechanisms used by animals to suppress metabolic rate include downregulating energy metabolism (ATP supply) as well as ion pumps (primary cellular ATP consumers). A recent goldfish study demonstrated that remodeling of membrane lipids may mediate these responses, but it is unknown if NMR employs the same strategies; therefore, we aimed to test the hypotheses that these fossorial mammals 1) downregulate the activity of key enzymes of glycolysis, tricarboxylic acid (TCA) cycle, and β-oxidation, 2) inhibit sodium-potassium-ATPase, and 3) alter membrane lipids in response to chronic hypoxia. We found that NMRs exposed to 11% oxygen for 4 wk had a lower metabolic rate by 34%. This suppression occurs concurrently with tissue-specific 25-99% decreases in metabolic enzymes activities, a 77% decrease in brain sodium/potassium-ATPase activity, and widespread changes in membrane cholesterol abundance. By reducing glycolytic and β-oxidation fluxes, NMRs decrease the supply of acetyl-CoA to the TCA cycle. By contrast, there is a 94% upregulation of citrate synthase in the heart, possibly to support circulation and thus oxygen supply to other organs. Taken together, these responses may reflect a coordinated physiological response to hypoxia, but a clear functional link between changes in membrane composition and enzyme activities could not be established. Nevertheless, this is the first demonstration that hypometabolic NMRs alter the lipid composition of their membranes in response to chronic in vivo exposure to hypoxia.
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Affiliation(s)
- Elie Farhat
- Biology Department, University of Ottawa, Ottawa, Ontario, Canada
| | | | - Matthew E Pamenter
- Biology Department, University of Ottawa, Ottawa, Ontario, Canada.,University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario, Canada
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Otero-Rodiño C, Conde-Sieira M, Comesaña S, Álvarez-Otero R, López-Patiño MA, Míguez JM, Soengas JL. Na +/K +-ATPase is involved in the regulation of food intake in rainbow trout but apparently not through brain glucosensing mechanisms. Physiol Behav 2019; 209:112617. [PMID: 31319109 DOI: 10.1016/j.physbeh.2019.112617] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/20/2019] [Accepted: 07/14/2019] [Indexed: 11/16/2022]
Abstract
To assess the hypothesis that Na+/K+-ATPase (NKA) is involved in the central regulation of food intake in fish, we observed in a first experiment with rainbow trout (Oncorhynchus mykiss) that intracerebroventricular (ICV) treatment with ouabain decreased food intake. We hypothesized that this effect relates to modulation of glucosensing mechanisms in brain areas (hypothalamus, hindbrain, and telencephalon) involved in food intake control. Therefore, we evaluated in a second experiment, the effect of ICV administration of ouabain, in the absence or in the presence of glucose, on NKA activity, mRNA abundance of different NKA subunits, parameters related to glucosensing, transcription factors, and appetite-related neuropeptides in brain areas involved in the control of food intake. NKA activity and mRNA abundance of nkaα1a and nkaα1c in brain were inhibited by ouabain treatment and partially by glucose. The anorectic effect of ouabain is opposed to the orexigenic effect reported in mammals. The difference might relate to the activity of glucosensing as well as downstream mechanisms involved in food intake regulation. Ouabain inhibited glucosensing mechanisms, which were activated by glucose in hypothalamus and telencephalon. Transcription factors and neuropeptides displayed responses comparable to those elicited by glucose when ouabain was administered alone, but not when glucose and ouabain were administered simultaneously. Ouabain might therefore affect other processes, besides glucosensing mechanisms, generating changes in membrane potential and/or intracellular pathways finally modulating transcription factors and neuropeptide mRNA abundance leading to modified food intake.
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Affiliation(s)
- Cristina Otero-Rodiño
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain
| | - Marta Conde-Sieira
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain
| | - Sara Comesaña
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain
| | - Rosa Álvarez-Otero
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain
| | - Marcos A López-Patiño
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain
| | - Jesús M Míguez
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain
| | - José L Soengas
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía and Centro de Investigación Mariña-CIM, Universidade de Vigo, Spain.
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The expression of genes involved in excitatory and inhibitory neurotransmission in turtle (Trachemys scripta) brain during anoxic submergence at 21 °C and 5 °C reveals the importance of cold as a preparatory cue for anoxia survival. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2019; 30:55-70. [DOI: 10.1016/j.cbd.2018.12.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Accepted: 12/27/2018] [Indexed: 11/20/2022]
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Chen N, Wu M, Tang GP, Wang HJ, Huang CX, Wu XJ, He Y, Zhang B, Huang CH, Liu H, Wang WM, Wang HL. Effects of Acute Hypoxia and Reoxygenation on Physiological and Immune Responses and Redox Balance of Wuchang Bream ( Megalobrama amblycephala Yih, 1955). Front Physiol 2017. [PMID: 28642716 PMCID: PMC5462904 DOI: 10.3389/fphys.2017.00375] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
To study Megalobrama amblycephala adaption to water hypoxia, the changes in physiological levels, innate immune responses, redox balance of M.amblycephala during hypoxia were investigated in the present study. When M. amblycephala were exposed to different dissolved oxygen (DO) including control (DO: 5.5 mg/L) and acute hypoxia (DO: 3.5 and 1.0 mg/L, respectively), hemoglobin (Hb), methemoglobin (MetHb), glucose, Na+, succinatedehydrogenase (SDH), lactate, interferon alpha (IFNα), and lysozyme (LYZ), except hepatic glycogen and albumin gradually increased with the decrease of DO level. When M. amblycephala were exposed to different hypoxia time including 0.5 and 6 h (DO: 3.5 mg/L), and then reoxygenation for 24 h after 6 h hypoxia, Hb, MetHb, glucose, lactate, and IFNα, except Na+, SDH, hepatic glycogen, albumin, and LYZ increased with the extension of hypoxia time, while the above investigated indexes (except albumin, IFNα, and LYZ) decreased after reoxygenation. On the other hand, the liver SOD, CAT, hydrogen peroxide (H2O2), and total ROS were all remained at lower levels under hypoxia stress. Finally, Hif-1α protein in the liver, spleen, and gill were increased with the decrease of oxygen concentration and prolongation of hypoxia time. Interestingly, one Hsp70 isoforms mediated by internal ribozyme entry site (IRES) named junior Hsp70 was only detected in liver, spleen and gill. Taken together, these results suggest that hypoxia affects M. amblycephala physiology and reduces liver oxidative stress. Hypoxia-reoxygenation stimulates M. amblycephala immune parameter expressions, while Hsp70 response to hypoxia is tissue-specific.
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Affiliation(s)
- Nan Chen
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Meng Wu
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Guo-Pan Tang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China.,Laboratory of Freshwater Animal Breeding, College of Animal Science and Technology, Henan University of Animal Husbandry and EconomyZhengzhou, China
| | - Hui-Juan Wang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Chun-Xiao Huang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Xin-Jie Wu
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Yan He
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Bao Zhang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Cui-Hong Huang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Hong Liu
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
| | - Wei-Min Wang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China
| | - Huan-Ling Wang
- Key Lab of Freshwater Animal Breeding, Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural UniversityWuhan, China.,Freshwater Aquaculture Collaborative Innovation Center of Hubei ProvinceWuhan, China
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Na +/K +-ATPase activity in the anoxic turtle (Trachemys scripta) brain at different acclimation temperature. Comp Biochem Physiol A Mol Integr Physiol 2017; 206:11-16. [PMID: 28089857 DOI: 10.1016/j.cbpa.2017.01.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 12/23/2016] [Accepted: 01/04/2017] [Indexed: 11/24/2022]
Abstract
Survival of prolonged anoxia requires a balance between cellular ATP demand and anaerobic ATP supply from glycolysis, especially in critical tissues such as the brain. To add insight into the ATP demand of the brain of the anoxia-tolerant red-eared slider turtle (Trachemys scripta) during prolonged periods of anoxic submergence, we quantified and compared the number of Na+-K+-ATPase units and their molecular activity in brain tissue from turtles acclimated to either 21°C or 5°C and exposed to either normoxia or anoxia (6h 21°C; 14days at 5°C). Na+-K+-ATPase activity and density per g tissue were similar at 21°C and 5°C in normoxic turtles. Likewise, anoxia exposure at 21°C did not induce any change in Na+-K+-ATPase activity or density. In contrast, prolonged anoxia at 5°C significantly reduced Na+-K+-ATPase activity by 55%, which was largely driven by a 50% reduction of the number of Na+-K+-ATPase units without a change in the activity of existing Na+-K+-ATPase pumps or α-subunit composition. These findings are consistent with the "channel arrest" hypothesis to reduce turtle brain Na+-K+-ATPase activity during prolonged, but not short-term anoxia, a change that likely helps them overwinter under low temperature, anoxic conditions.
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Xie L, Wu X, Chen H, Dong W, Cazan AM, Klerks PL. A low level of dietary selenium has both beneficial and toxic effects and is protective against Cd-toxicity in the least killifish Heterandria formosa. CHEMOSPHERE 2016; 161:358-364. [PMID: 27448316 DOI: 10.1016/j.chemosphere.2016.07.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/02/2016] [Accepted: 07/11/2016] [Indexed: 06/06/2023]
Abstract
As an essential element, selenium (Se) is beneficial at low levels yet toxic at high levels. The present study assessed the effects of dietary exposure to Se in the least killifish Heterandria formosa, and investigated how this exposure influences the effects of a subsequent exposure to cadmium (Cd). The fish were pre-exposed to an environmentally relevant concentration (2 μg g(-1) dry wt) of dietary selenite (Se(4+)) or seleno-l-methionine (Se-Met) for 10 d. The same fish were then exposed to 0.5 mg L(-1) of Cd for 5 d. Both Se(IV) and Se-Met rapidly accumulated in H. formosa. Results for the two Se species were generally similar in this study. Fish exposed to Se had lower levels of lipid peroxidation (measured as levels of thiobarbituric acid reactive substances or TBARS) and a higher catalase (CAT) activity. In contrast, their Na(+)/K(+)-ATPase activity was reduced. The Cd exposure resulted in an increase in lipid peroxidation and decreases in the activities of catalase and Na(+)/K(+)-ATPase. The Cd-exposed H. formosa that were pre-exposed to Se had lower Cd body burdens, less lipid peroxidation, and higher catalase activity, than did fish not pre-exposed to Se. The Se exposure did not have a protective effect on the Cd-induced reduction in Na(+)/K(+)-ATPase activity. These results clearly demonstrate that a Se-enriched diet reduces some (but not all) forms of Cd-toxicity and that Se can simultaneously have beneficial and detrimental effects, making it difficult to predict the net outcome of changes in dietary Se levels for fish.
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Affiliation(s)
- Lingtian Xie
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, PR China.
| | - Xing Wu
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, PR China
| | - Hongxing Chen
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, PR China
| | - Wu Dong
- Inner Mongolia University for the Nationalities, Tongliao 028000, PR China.
| | - Alfy Morales Cazan
- Department of Biology, University of Louisiana at Lafayette, P. O. Box 43602, Lafayette, LA 70504-3602, USA
| | - Paul L Klerks
- Department of Biology, University of Louisiana at Lafayette, P. O. Box 43602, Lafayette, LA 70504-3602, USA
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Xie L, Wu X, Chen H, Luo Y, Guo Z, Mu J, Blankson ER, Dong W, Klerks PL. The bioaccumulation and effects of selenium in the oligochaete Lumbriculus variegatus via dissolved and dietary exposure routes. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2016; 178:1-7. [PMID: 27450235 DOI: 10.1016/j.aquatox.2016.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/13/2016] [Accepted: 07/15/2016] [Indexed: 06/06/2023]
Abstract
Aquatic organisms take up selenium from solution and from their diets. Many questions remain regarding the relative importance of selenium accumulation from these sources and resulting effects in benthic invertebrates. The present study addressed the toxicity and accumulation of Se via dissolved and dietary exposures to three different Se species, in the freshwater oligochaete Lumbriculus variegatus. Worms were exposed to 20μg/g dry weight of selenite (Se(IV)), selenate (Se(VI)), or seleno-l-methionine (Se-Met) in their diet (sediment) or to 15μg/L dissolved Se in water-only exposures. While the dissolved and sediment Se levels differed greatly, such levels may co-occur at a Se-contaminated site. Se accumulation, worm population growth, lipid peroxidation (as TBARS), and Na(+)/K(+)-ATPase activity were quantified at the end of the 2-week exposure. The sediment Se-Met exposure caused 100% mortality, while worm densities were reduced by the other exposures except the Se(VI) one. Se bioaccumulation was generally higher for the sediment-Se exposure than the dissolved-Se ones, and was higher for Se(IV) than Se(VI) in the dissolved-Se exposure but not the sediment-Se one. The Se accumulation was highest for Se-Met. The oligochaetes that accumulated Se had higher levels of lipid peroxidation and reduced Na(+)/K(+)-ATPase activity. The present study's findings of differences in Se accumulation and toxicity for the three Se species, with effects generally but not exclusively a function of Se body burdens, underscore the need for research on these issues in invertebrates. Moreover, the results imply that the dietary uptake route is the predominant one for Se accumulation in L. variegatus.
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Affiliation(s)
- Lingtian Xie
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, PR China.
| | - Xing Wu
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, PR China
| | - Hongxing Chen
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, PR China
| | - Yongju Luo
- Guangxi Academy of Fishery Science, Guangxi 530021, PR China.
| | - Zhongbao Guo
- Guangxi Academy of Fishery Science, Guangxi 530021, PR China
| | - Jingli Mu
- Division of Marine Chemistry, National Marine Environmental Monitoring Center, Dalian, Liaoning 116023, PR China
| | - Emmanuel R Blankson
- Department of Biology, University of Louisiana at Lafayette, P. O. Box 43602, Lafayette, LA 70504-3602, USA
| | - Wu Dong
- Inner Mongolia University for the Nationalities, Tongliao 028000, PR China
| | - Paul L Klerks
- Department of Biology, University of Louisiana at Lafayette, P. O. Box 43602, Lafayette, LA 70504-3602, USA
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Bogdanova A, Petrushanko IY, Hernansanz-Agustín P, Martínez-Ruiz A. "Oxygen Sensing" by Na,K-ATPase: These Miraculous Thiols. Front Physiol 2016; 7:314. [PMID: 27531981 PMCID: PMC4970491 DOI: 10.3389/fphys.2016.00314] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 07/12/2016] [Indexed: 12/16/2022] Open
Abstract
Control over the Na,K-ATPase function plays a central role in adaptation of the organisms to hypoxic and anoxic conditions. As the enzyme itself does not possess O2 binding sites its "oxygen-sensitivity" is mediated by a variety of redox-sensitive modifications including S-glutathionylation, S-nitrosylation, and redox-sensitive phosphorylation. This is an overview of the current knowledge on the plethora of molecular mechanisms tuning the activity of the ATP-consuming Na,K-ATPase to the cellular metabolic activity. Recent findings suggest that oxygen-derived free radicals and H2O2, NO, and oxidized glutathione are the signaling messengers that make the Na,K-ATPase "oxygen-sensitive." This very ancient signaling pathway targeting thiols of all three subunits of the Na,K-ATPase as well as redox-sensitive kinases sustains the enzyme activity at the "optimal" level avoiding terminal ATP depletion and maintaining the transmembrane ion gradients in cells of anoxia-tolerant species. We acknowledge the complexity of the underlying processes as we characterize the sources of reactive oxygen and nitrogen species production in hypoxic cells, and identify their targets, the reactive thiol groups which, upon modification, impact the enzyme activity. Structured accordingly, this review presents a summary on (i) the sources of free radical production in hypoxic cells, (ii) localization of regulatory thiols within the Na,K-ATPase and the role reversible thiol modifications play in responses of the enzyme to a variety of stimuli (hypoxia, receptors' activation) (iii) redox-sensitive regulatory phosphorylation, and (iv) the role of fine modulation of the Na,K-ATPase function in survival success under hypoxic conditions. The co-authors attempted to cover all the contradictions and standing hypotheses in the field and propose the possible future developments in this dynamic area of research, the importance of which is hard to overestimate. Better understanding of the processes underlying successful adaptation strategies will make it possible to harness them and use for treatment of patients with stroke and myocardial infarction, sleep apnoea and high altitude pulmonary oedema, and those undergoing surgical interventions associated with the interruption of blood perfusion.
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Affiliation(s)
- Anna Bogdanova
- Institute of Veterinary Physiology, Vetsuisse Faculty and the Zurich Center for Integrative Human Physiology (ZIHP), University of ZurichZurich, Switzerland
| | - Irina Y. Petrushanko
- Engelhardt Institute of Molecular Biology, Russian Academy of SciencesMoscow, Russia
| | - Pablo Hernansanz-Agustín
- Servicio de Inmunología, Instituto de Investigación Sanitaria Princesa (IIS-IP), Hospital Universitario de La PrincesaMadrid, Spain
- Departamento de Bioquímica, Universidad Autónoma de MadridMadrid, Spain
| | - Antonio Martínez-Ruiz
- Servicio de Inmunología, Instituto de Investigación Sanitaria Princesa (IIS-IP), Hospital Universitario de La PrincesaMadrid, Spain
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ATP-consuming processes in hepatocytes of river lamprey Lampetra fluviatilis on the course of prespawning starvation. Comp Biochem Physiol A Mol Integr Physiol 2016; 201:95-100. [PMID: 27399971 DOI: 10.1016/j.cbpa.2016.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 07/05/2016] [Accepted: 07/05/2016] [Indexed: 11/24/2022]
Abstract
The work was performed to establish which of the major ATP-consuming processes is the most important for surviving of hepatocytes of female lampreys on the course of prespawning starvation. The requirements of protein synthesis and Na(+)-K(+)-ATPase for ATP in the cells were monitored by the changes in mitochondrial membrane potential (MMP) in the presence of corresponding inhibitors from the peak of metabolic depression (January-February) to the time of recovery from it (March-April) and spawning (May). Integrity of lamprey liver cells was estimated by catalytic activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in blood plasma. In January-February, the share of ATP necessary for protein synthesis was 20-22%, whereas before spawning it decreased to 8-11%. Functioning of Na(+)-K(+)-pump required 22% of cellular ATP at the peak of metabolic depression, but 38% and 62% of ATP in March-April and May, respectively. Progression of prespawning period was accompanied by 3.75- and 1.6-fold rise of ALT and AST activities in blood plasma, respectively, whereas de Ritis coefficient decreased from 2.51±0.34 to 0.81±0.08, what indicates severe damage of hepatocyte membranes. Thus, the adaptive strategy of lamprey hepatocytes to develop metabolic depression under conditions of energy limitation is the selective production of proteins necessary for spawning, most probably vitellogenins. As spawning approaches, the maintenance of transmembrane ion gradients, membrane potential and cell volume to prevent premature cell death becomes the priority cell function.
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Schwarze K, Singh A, Burmester T. The Full Globin Repertoire of Turtles Provides Insights into Vertebrate Globin Evolution and Functions. Genome Biol Evol 2015; 7:1896-913. [PMID: 26078264 PMCID: PMC4524481 DOI: 10.1093/gbe/evv114] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Globins are small heme proteins that play an important role in oxygen supply, but may also have other functions. Globins offer a unique opportunity to study the functional evolution of genes and proteins. We have characterized the globin repertoire of two different turtle species: the Chinese softshell turtle (Pelodiscus sinensis) and the western painted turtle (Chrysemys picta bellii). In the genomes of both species, we have identified eight distinct globin types: hemoglobin (Hb), myoglobin, neuroglobin, cytoglobin, globin E, globin X, globin Y, and androglobin. Therefore, along with the coelacanth, turtles are so far the only known vertebrates with a full globin repertoire. This fact allows for the first time a comparative analysis of the expression of all eight globins in a single species. Phylogenetic analysis showed an early divergence of neuroglobin and globin X before the radiation of vertebrates. Among the other globins, cytoglobin diverged first, and there is a close relationship between myoglobin and globin E; the position of globin Y is not resolved. The globin E gene was selectively lost in the green anole, and the genes coding for globin X and globin Y were deleted in chicken. Quantitative real-time reverse transcription polymerase chain reaction experiments revealed that myoglobin, neuroglobin, and globin E are highly expressed with tissue-specific patterns, which are in line with their roles in the oxidative metabolism of the striated muscles, the brain, and the retina, respectively. Histochemical analyses showed high levels of globin E in the pigment epithelium of the eye. Globin E probably has a myoglobin-like role in transporting O2 across the pigment epithelium to supply in the metabolically highly active retina.
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Affiliation(s)
- Kim Schwarze
- Institute of Zoology, Department of Biology, University of Hamburg, Germany
| | - Abhilasha Singh
- Institute of Zoology, Department of Biology, University of Hamburg, Germany
| | - Thorsten Burmester
- Institute of Zoology, Department of Biology, University of Hamburg, Germany
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Cádiz L, Román-Padilla J, Gozdowska M, Kulczykowska E, Martínez-Rodríguez G, Mancera JM, Martos-Sitcha JA. Cortisol modulates vasotocinergic and isotocinergic pathways in the gilthead sea bream. ACTA ACUST UNITED AC 2014; 218:316-25. [PMID: 25524977 DOI: 10.1242/jeb.113944] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In the present study, we assessed the responses of the vasotocinergic and isotocinergic systems to chronic stress induced by cortisol administration in the gilthead sea bream (Sparus aurata). Pituitary and plasma arginine vasotocin (AVT) and isotocin (IT) levels, as well as hypothalamic pro-vasotocin (pro-VT) and pro-isotocin (pro-IT) mRNA expression levels, were analysed. In addition, the mRNA levels of three receptors, AVTR type V1a2, AVTR type V2 and ITR, were analysed in several target organs associated with the following physiological processes: (i) integration and control (hypothalamus), (ii) metabolism and its control (liver and hypothalamus), (iii) osmoregulation (gills) and (iv) stress response (head kidney). Specimens were injected intraperitoneally with slow-release implants (5 μL g(-1) body mass) containing coconut oil alone (control group) or with cortisol (50 μg g(-1) body mass; cortisol group). Both AVT and IT synthesis and release were correlated with plasma cortisol values, suggesting a potential interaction between both hormonal systems and cortisol administration. Our results suggest that the activation of hepatic metabolism as well as the hypothalamic control of metabolic processes provide the energy necessary to overcome stress, which could be partly mediated by AVTRs and ITR. Upregulation of branchial AVT and IT receptor expression following cortisol treatment suggests an involvement of the vasotocinergic and isotocinergic systems in the regulation of ion channels/transporters during stressful situations. Finally, changes in AVT and IT receptor mRNA expression in the head kidney suggest these nonapeptides participate in feedback mechanisms that regulate the synthesis/release of cortisol. Our results indicate a relationship between cortisol and both the vasotocinergic and isotocinergic systems during simulated chronic stress in S. aurata.
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Affiliation(s)
- Laura Cádiz
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas (ICMAN-CSIC), 11510 Puerto Real, Cádiz, Spain
| | - Javier Román-Padilla
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain
| | - Magdalena Gozdowska
- Department of Genetics and Marine Biotechnology, Institute of Oceanology of the Polish Academy of Sciences, 81-712 Sopot, Poland
| | - Ewa Kulczykowska
- Department of Genetics and Marine Biotechnology, Institute of Oceanology of the Polish Academy of Sciences, 81-712 Sopot, Poland
| | - Gonzalo Martínez-Rodríguez
- Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas (ICMAN-CSIC), 11510 Puerto Real, Cádiz, Spain
| | - Juan M Mancera
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain
| | - Juan A Martos-Sitcha
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas (ICMAN-CSIC), 11510 Puerto Real, Cádiz, Spain
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Tseng YC, Liu ST, Hu MY, Chen RD, Lee JR, Hwang PP. Brain functioning under acute hypothermic stress supported by dynamic monocarboxylate utilization and transport in ectothermic fish. Front Zool 2014. [DOI: 10.1186/s12983-014-0053-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Martos-Sitcha JA, Fuentes J, Mancera JM, Martínez-Rodríguez G. Variations in the expression of vasotocin and isotocin receptor genes in the gilthead sea bream Sparus aurata during different osmotic challenges. Gen Comp Endocrinol 2014; 197:5-17. [PMID: 24332959 DOI: 10.1016/j.ygcen.2013.11.026] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 11/21/2013] [Accepted: 11/27/2013] [Indexed: 11/24/2022]
Abstract
The dynamic changes in mRNA expression levels for vasotocin (AVT) and isotocin (IT) receptor gene levels were assessed in a time-course response study in immature male specimens of the gilthead sea bream (Sparus aurata) submitted to hyper- (55‰ salinity) and hypo-osmotic (5‰ salinity) challenges. Two different cDNAs for the AVT receptor and one for the IT receptor (V1a2-type and V2-type AVTR, and ITR, respectively) were cloned by screening an S. aurata brain cDNA library. Genes for these receptors were expressed differentially and is nearly ubiquitously in 26 of the examined tissues. In the gills, both environmental salinity challenges up-regulated AVTR V1a2-type gene expression concomitantly with mRNA expression protein activity of Na(+), K(+)-ATPase gene expression and protein, whereas the AVTR V2-type and cystic fibrosis transmembrane conductance regulator (CFTR) mRNA levels were associated with mRNAs environmental salinity, indicating a possible connection between AVTRs and these transporters. In kidney, AVTR V1a2-type gene expression peaked rapidly and lasted only a short time (12-24h) in response to both osmotic challenges. In contrast, AVTR V2-type mRNA levels were enhanced in specimens exposed to hyperosmotic conditions, whereas they decreased under hypoosmotic environments, suggesting an antidiuretic role related to the vasoconstriction function. In the hypothalamus, only the expression of the AVTR V2-type gene was enhanced at 7 and 14 days under both experimental conditions. In the liver, both AVTRs had increased mRNA levels, with the upregulation of their AVTR V2-type gene increasing faster than the V1a2-type. The ITR gene was not sensitive to variations of external salinity in any of the analyzed tissues. Our results demonstrate the involvement of the vasotocinergic, but not the isotocinergic, pathway as well as the hypothalamic function, in the adjustments of both osmoregulatory and metabolic processes after osmotic challenges.
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Affiliation(s)
- J A Martos-Sitcha
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain; Centre of Marine Sciences (CCMar), CIMAR - Laboratório Associado, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal; Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas, 11510 Puerto Real, Cádiz, Spain.
| | - J Fuentes
- Centre of Marine Sciences (CCMar), CIMAR - Laboratório Associado, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
| | - J M Mancera
- Department of Biology, Faculty of Marine and Environmental Sciences, University of Cádiz, 11510 Puerto Real, Cádiz, Spain
| | - G Martínez-Rodríguez
- Instituto de Ciencias Marinas de Andalucía, Consejo Superior de Investigaciones Científicas, 11510 Puerto Real, Cádiz, Spain
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Clanton TL, Hogan MC, Gladden LB. Regulation of cellular gas exchange, oxygen sensing, and metabolic control. Compr Physiol 2013; 3:1135-90. [PMID: 23897683 DOI: 10.1002/cphy.c120030] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells must continuously monitor and couple their metabolic requirements for ATP utilization with their ability to take up O2 for mitochondrial respiration. When O2 uptake and delivery move out of homeostasis, cells have elaborate and diverse sensing and response systems to compensate. In this review, we explore the biophysics of O2 and gas diffusion in the cell, how intracellular O2 is regulated, how intracellular O2 levels are sensed and how sensing systems impact mitochondrial respiration and shifts in metabolic pathways. Particular attention is paid to how O2 affects the redox state of the cell, as well as the NO, H2S, and CO concentrations. We also explore how these agents can affect various aspects of gas exchange and activate acute signaling pathways that promote survival. Two kinds of challenges to gas exchange are also discussed in detail: when insufficient O2 is available for respiration (hypoxia) and when metabolic requirements test the limits of gas exchange (exercising skeletal muscle). This review also focuses on responses to acute hypoxia in the context of the original "unifying theory of hypoxia tolerance" as expressed by Hochachka and colleagues. It includes discourse on the regulation of mitochondrial electron transport, metabolic suppression, shifts in metabolic pathways, and recruitment of cell survival pathways preventing collapse of membrane potential and nuclear apoptosis. Regarding exercise, the issues discussed relate to the O2 sensitivity of metabolic rate, O2 kinetics in exercise, and influences of available O2 on glycolysis and lactate production.
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Affiliation(s)
- T L Clanton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.
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Madsen JG, Wang T, Beedholm K, Madsen PT. Detecting spring after a long winter: coma or slow vigilance in cold, hypoxic turtles? Biol Lett 2013; 9:20130602. [PMID: 24108677 DOI: 10.1098/rsbl.2013.0602] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many freshwater turtle species can spend the winter submerged in ice-covered lakes by lowering their metabolism, and it has been proposed that such severe metabolic depression render these turtles comatose. This raises the question of how they can detect the arrival of spring and respond in a sensible way to sensory information during hibernation. Using evoked potentials from cold or hypoxic turtles exposed to vibration and light, we show that hibernating turtles maintain neural responsiveness to light stimuli during prolonged hypoxia. Furthermore, turtles held under hibernation conditions for 14 days increase their activity when exposed to light or elevated temperatures, but not to vibration or increased oxygen. It is concluded that hibernating turtles are not comatose, but remain vigilant during overwintering in cold hypoxia, allowing them to respond to the coming of spring and to adjust their behaviour to specific sensory inputs.
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Affiliation(s)
- Jesper G Madsen
- Zoophysiology, Department of Bioscience, Aarhus University, , Building 1131, 8000 Aarhus, Denmark
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25
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Adeyemi JA, Klerks PL. Occurrence of copper acclimation in the least killifish Heterandria formosa, and associated biochemical and physiological mechanisms. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2013; 130-131:51-57. [PMID: 23353058 DOI: 10.1016/j.aquatox.2013.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/30/2012] [Accepted: 01/02/2013] [Indexed: 06/01/2023]
Abstract
We investigated the occurrence of copper acclimation in the least killifish, Heterandria formosa using both lethal and sublethal endpoints. We also investigated potential mechanisms underlying the observed acclimation. To assess the occurrence of acclimation, fish were exposed to either a background Cu level or to 15 μg/L Cu for seven days and subsequently exposed to a lethal Cu level (150 μg/L Cu). During the latter exposure, fish were monitored for survival till all fish had died, and (during the first 8h of this exposure) for changes in whole-body Na levels and lipid peroxidation (LPO). During the high-level Cu exposure, fish pre-exposed to copper had a significantly longer time-to-death than did the control fish. Similarly, neither whole-body Na nor LPO changed in the Cu-pre-exposed fish during the 8h of the exposure to 150 μg/L Cu - while both decreased significantly in the control fish. Thus, acclimation was evident for both time-to-death and the sublethal endpoints. These results also indicate that Cu toxicity may involve both Na loss and LPO, and that Cu-acclimation may be brought about by prevention of these effects. Our follow-up study on potential mechanisms underlying this copper acclimation used a similar pre-exposure/exposure design. Fish were subsampled at the end of the 7-day acclimation period - just before the commencement of high-level Cu exposure (T), after 4h of this Cu exposure (T), and again after 8h of this Cu exposure (T). Whole-body Cu accumulation, Na/K-ATPase activity, metallothionein levels, and catalase activity were quantified for these time points. While Cu levels were higher in the Cu-pre-exposed fish than in the control fish at T, net Cu accumulation was faster in the control fish than in the Cu-pre-exposed fish during the subsequent high-level Cu exposure. Consequently, changes in Cu accumulation dynamics may play a role in the resistance. Metallothionein induction may also play a role in the observed acclimation, as Cu-acclimated fish had a significantly higher metallothionein concentration compared to the control fish. There was no evidence of involvement of Na/K-ATPase in the acclimation, as the activity of this enzyme remained lower in the pre-exposed fish than in the control fish throughout both Cu exposure periods. There was limited evidence that a reduced loss of catalase activity plays a role in the acclimation; catalase activity did not differ after the pre-exposure period but was significantly higher in Cu-acclimated fish than in the control fish at T.
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Affiliation(s)
- Joseph A Adeyemi
- Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70504, United States.
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Pamenter ME, Hogg DW, Gu XQ, Buck LT, Haddad GG. Painted turtle cortex is resistant to an in vitro mimic of the ischemic mammalian penumbra. J Cereb Blood Flow Metab 2012; 32:2033-43. [PMID: 22805876 PMCID: PMC3493991 DOI: 10.1038/jcbfm.2012.103] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Anoxia or ischemia causes hyperexcitability and cell death in mammalian neurons. Conversely, in painted turtle brain anoxia increases γ-amino butyric acid (GABA)ergic suppression of spontaneous electrical activity, and cell death is prevented. To examine ischemia tolerance in turtle neurons, we treated cortical sheets with an in vitro mimic of the penumbral region of stroke-afflicted mammalian brain (ischemic solution, IS). We found that during IS perfusion, neuronal membrane potential (V(m)) and the GABA(A) receptor reversal potential depolarized to a similar steady state (-92 ± 2 to -28 ± 3 mV, and -75 ± 1 to -35 ± 3 mV, respectively), and whole-cell conductance (G(w)) increased >3-fold (from 4 ± 0.2 to 15 ± 1 nS). These neurons were electrically quiet and changes reversed after reperfusion. GABA receptor antagonism prevented the IS-mediated increase in G(w) and neurons exhibited enhanced electrical excitability and rapid and irreversible rundown of V(m) during reperfusion. These results suggest that inhibitory GABAergic mechanisms also suppress electrical activity in ischemic cortex. Indeed, after 4 hours of IS treatment neurons did not exhibit any apparent damage; while at 24 hours, only early indicators of apoptosis were present. We conclude that anoxia-tolerant turtle neurons are tolerant of exposure to a mammalian ischemic penumbral mimic solution.
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Affiliation(s)
- Matthew Edward Pamenter
- Division of Respiratory Medicine, Department of Pediatrics, University of California San Diego, La Jolla, California 92093-0735, USA.
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Adeyemi JA, Deaton LE, Pesacreta TC, Klerks PL. Effects of copper on osmoregulation in sheepshead minnow, Cyprinodon variegatus acclimated to different salinities. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2012; 109:111-117. [PMID: 22210499 DOI: 10.1016/j.aquatox.2011.12.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 12/06/2011] [Accepted: 12/06/2011] [Indexed: 05/31/2023]
Abstract
The sheepshead minnow, Cyprinodon variegatus is a euryhaline fish that inhabits estuaries and coastal marshes where it encounters a wide range of salinities. Many of these areas also have elevated levels of contaminants, creating the potential for toxic ions to interfere with the uptake of ions for osmoregulation. To determine whether the effect of copper on osmoregulatory activity is dependent on the osmotic conditions that individuals have been living at, fish were acclimated for 14 days to 2.5, 10.5 or 18.5 ppt seawater and then exposed to a fixed free cupric ion level (14.6 μM Cu2+) for 6 h. Plasma Na, plasma Cl, wet/dry weight ratio, transepithelial potential difference (TEPD) and branchial Na(+)/K(+)-ATPase activity were determined before and after copper exposure. We also computed Na and Cl equilibrium potentials. Following the salinity acclimation (in fish not yet exposed to copper), fish from the low salinity group (2.5 ppt) had lower TEPD, lower plasma Na levels and higher branchial Na(+)/K(+)-ATPase activity compared to the fish acclimated to higher salinities. No differences in plasma Cl and wet/dry weight ratio were detected. Copper exposure caused a significant decrease in plasma Na levels and Na(+)/K(+)-ATPase activity and an increase in wet/dry weight ratio, but these changes were limited to the 2.5 ppt salinity group. No significant changes in plasma Cl were detected. Copper treatment resulted in a small decrease in TEPD for all except the lowest salinity acclimation group. A comparison of equilibrium potentials with TEPD showed evidence of active transport of both Na and Cl in 2.5 ppt acclimated fish but not for the 10.5 or the 18.5 ppt acclimated fish. Our results show that effects of copper on osmoregulation are dependent on the fish' past salinity regime, and that these effects tend to be more pronounced for euryhaline fish that have been living under hyposmotic conditions.
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Affiliation(s)
- Joseph A Adeyemi
- Department of Biology, University of Louisiana at Lafayette, 300 East St. Mary Blvd, Lafayette, LA, USA.
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Richards JG. Metabolic Rate Suppression as a Mechanism for Surviving Environmental Challenge in Fish. AESTIVATION 2010; 49:113-39. [DOI: 10.1007/978-3-642-02421-4_6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Vornanen M, Stecyk JA, Nilsson GE. Chapter 9 The Anoxia-Tolerant Crucian Carp (Carassius Carassius L.). FISH PHYSIOLOGY 2009. [DOI: 10.1016/s1546-5098(08)00009-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Pamenter ME, Buck LT. delta-Opioid receptor antagonism induces NMDA receptor-dependent excitotoxicity in anoxic turtle cortex. ACTA ACUST UNITED AC 2008; 211:3512-7. [PMID: 18931323 DOI: 10.1242/jeb.021949] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
delta-Opioid receptor (DOR) activation is neuroprotective against short-term anoxic insults in the mammalian brain. This protection may be conferred by inhibition of N-methyl-d-aspartate receptors (NMDARs), whose over-activation during anoxia otherwise leads to a deleterious accumulation of cytosolic calcium ([Ca(2+)](c)), severe membrane potential (E(m)) depolarization and excitotoxic cell death (ECD). Conversely, NMDAR activity is decreased by approximately 50% with anoxia in the cortex of the painted turtle, and large elevations in [Ca(2+)](c), severe E(m) depolarization and ECD are avoided. DORs are expressed in high quantity throughout the turtle brain relative to the mammalian brain; however, the role of DORs in anoxic NMDAR regulation has not been investigated in turtles. We examined the effect of DOR blockade with naltrindole (1-10 micromol l(-1)) on E(m), NMDAR activity and [Ca(2+)](c) homeostasis in turtle cortical neurons during normoxia and the transition to anoxia. Naltrindole potentiated normoxic NMDAR currents by 78+/-5% and increased [Ca(2+)](c) by 13+/-4%. Anoxic neurons treated with naltrindole were strongly depolarized, NMDAR currents were potentiated by 70+/-15%, and [Ca(2+)](c) increased 5-fold compared with anoxic controls. Following naltrindole washout, E(m) remained depolarized and [Ca(2+)](c) became further elevated in all neurons. The naltrindole-mediated depolarization and increased [Ca(2+)](c) were prevented by NMDAR antagonism or by perfusion of the G(i) protein agonist mastoparan-7, which also reversed the naltrindole-mediated potentiation of NMDAR currents. Together, these data suggest that DORs mediate NMDAR activity in a G(i)-dependent manner and prevent deleterious NMDAR-mediated [Ca(2+)](c) influx during anoxic insults in the turtle cortex.
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Affiliation(s)
- Matthew E Pamenter
- Department of Pediatrics and Neuroscience, University of California San Diego, La Jolla, CA 92093, USA
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32
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Wilkie MP, Pamenter ME, Alkabie S, Carapic D, Shin DSH, Buck LT. Evidence of anoxia-induced channel arrest in the brain of the goldfish (Carassius auratus). Comp Biochem Physiol C Toxicol Pharmacol 2008; 148:355-62. [PMID: 18620076 DOI: 10.1016/j.cbpc.2008.06.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Revised: 06/15/2008] [Accepted: 06/15/2008] [Indexed: 11/17/2022]
Abstract
The common goldfish (Carassius auratus) is extremely anoxia tolerant and here we provide evidence that "channel arrest" in the brain of these fish contributes to ATP conservation during periods of anoxia. Whole-cell patch-clamp recordings of slices taken from the telencephalon indicated that the N-methyl-d-aspartate (NMDA) receptor, an ionotropic glutamate receptor and Ca(2+)-channel, underwent a 40-50% reduction in activity during 40 min of acute anoxia. This is the first direct evidence of channel arrest in an anoxia-tolerant fish. Because goldfish produce ethanol as a byproduct of anaerobic metabolism we then conducted experiments to determine if the observed reduction in NMDA receptor current amplitude was due to inhibition by ethanol. NMDA receptor currents were not inhibited by ethanol (10 mmol L(-1)), suggesting that channel arrest of the receptor involved other mechanisms. Longer-term (48 h) in vivo exposure of goldfish to anoxic conditions (less than 1% dissolved O(2)) provided indirect evidence that a reduction in Na(+)/K(+)-ATPase activity also contributed to ATP conservation in the brain but not the gills. Anoxia under these conditions was characterized by a decrease in brain Na(+)/K(+)-ATPase activity of 30-40% by 24 h. Despite 90% reductions in the rates of ventilation, no change was observed in gill Na(+)/K(+)-ATPase activity during the 48-h anoxia exposure, suggesting that branchial ion permeability was unaffected. We conclude that rapid "channel arrest" of NMDA receptors likely prevents excitotoxicity in the brain of the goldfish, and that a more slowly developing decrease in Na(+)/K(+)-ATPase activity also contributes to the profound metabolic depression seen in these animals during oxygen starvation.
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Affiliation(s)
- Michael P Wilkie
- Department of Biology, Wilfrid Laurier University, 75 University Avenue West, Waterloo, Ontario, Canada N2L 3C5.
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Uner N, Oruç E, Sevgiler Y. Neurotoxicity Evaluation of the Organofluorine Pesticide Etoxazole in the Brain ofOreochromis niloticus. Drug Chem Toxicol 2008; 29:157-65. [PMID: 16707325 DOI: 10.1080/01480540600561403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Etoxazole is a new organofluorine pesticide that has been used worldwide as acaricide and insecticide since 1998. Almost no previous attempt has been made to evaluate the toxic effects of etoxazole in vertebrates. Using fish (Oreochromis niloticus) as a suitable model organism, the aim of this study was to indicate whether etoxazole affects acetylcholinesterase and sodium potassium-activated adenosine triphosphatase activities in the brain tissue in order to evaluate the impacts on neurotoxicity and ion transportation. Enzyme activities were determined using spectrophotometric methods. At the sublethal concentrations (0.27, 0.54, 0.81, 1.08, 1.35 mg/L) and exposure durations (1, 7, 15 days) tested, etoxazole has no inhibitory effect on the brain acetylcholinesterase and sodium potassium-activated adenosine triphosphatase activities. Our results suggest that etoxazole and/or its metabolites may not reach or penetrate the blood-brain barrier; therefore, they do not essentially alter the functions of these two important enzymes for the brain.
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Affiliation(s)
- Nevin Uner
- Department of Biology, University of Cukurova, Faculty of Science and Letters, Balcali, Adana, Turkey.
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Pamenter ME, Buck LT. Neuronal membrane potential is mildly depolarized in the anoxic turtle cortex. Comp Biochem Physiol A Mol Integr Physiol 2008; 150:410-4. [PMID: 18519169 DOI: 10.1016/j.cbpa.2008.04.605] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2008] [Revised: 04/21/2008] [Accepted: 04/22/2008] [Indexed: 11/17/2022]
Abstract
Neuronal membrane potential (E(m)) regulates the activity of excitatory voltage-sensitive channels. Anoxic insults lead to a severe loss of E(m) and excitotoxic cell death (ECD) in mammalian neurons. Conversely, anoxia-tolerant freshwater turtle neurons depress energy usage during anoxia by altering ionic conductance to reduce neuronal excitability and ECD is avoided. This wholesale alteration of ion channel and pump activity likely has a significant effect on E(m). Using the whole-cell patch clamp technique we recorded changes in E(m) from turtle cortical neurons during a normoxic to anoxic transition in the presence of various ion channel/pump modulators. E(m) did not change with normoxic perfusion but underwent a reversible, mild depolarization of 8.1+/-0.2 mV following anoxic perfusion. This mild anoxic depolarization (MAD) was not prevented by the manipulation of any single ionic conductance, but was partially reduced by pre-treatment with antagonists of GABA(A) receptors (5.7+/-0.5 mV), cellular bicarbonate production (5.3+/-0.2 mV) or K(+) channels (6.0+/-0.2 mV), or by perfusion of reactive oxygen species scavengers (5.2+/-0.3 mV). Furthermore, all of these treatments induced depolarization in normoxic neurons. Together these data suggest that the MAD may be due to the summation of numerous altered ion conductance states during anoxia.
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Tan SL, Mohd-Adnan A, Mohd-Yusof NY, Forstner MRJ, Wan KL. Identification and analysis of a prepro-chicken gonadotropin releasing hormone II (preprocGnRH-II) precursor in the Asian seabass, Lates calcarifer, based on an EST-based assessment of its brain transcriptome. Gene 2008; 411:77-86. [PMID: 18280674 DOI: 10.1016/j.gene.2008.01.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 01/13/2008] [Accepted: 01/16/2008] [Indexed: 11/27/2022]
Abstract
Using a novel library of 5637 expressed sequence tags (ESTs) from the brain tissue of the Asian seabass (Lates calcarifer), we first characterized the brain transcriptome for this economically important species. The ESTs generated from the brain of L. calcarifer yielded 2410 unique transcripts (UTs) which comprise of 982 consensi and 1428 singletons. Based on database similarity, 1005 UTs (41.7%) can be assigned putative functions and were grouped into 12 functional categories related to the brain function. Amongst others, we have identified genes that are putatively involved in energy metabolism, ion pumps and channels, synapse related genes, neurotransmitter and its receptors, stress induced genes and hormone related genes. Subsequently we selected a putative preprocGnRH-II precursor for further characterization. The complete cDNA sequence of the gene obtained was found to code for an 85-amino acid polypeptide that significantly matched preprocGnRH-II precursor sequences from other vertebrates, and possesses structural characteristics that are similar to that of other species, consisting of a signal peptide (23 residues), a GnRH decapeptide (10 residues), an amidation/proteolytic-processing signal (glycine-lysine-argine) and a GnRH associated peptide (GAP) (49 residues). Phylogenetic analysis showed that this putative L. calcarifer preprocGnRH-II sequence is a member of the subcohort Euteleostei and divergent from the sequences of the subcohort Otocephalan. These findings provide compelling evidence that the putative L. calcarifer preprocGnRH-II precursor obtained in this study is orthologous to that of other vertebrates. The functional prediction of this preprocGnRH-II precursor sequence through in silico analyses emphasizes the effectiveness of the EST approach in gene identification in L. calcarifer.
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Affiliation(s)
- Sik-Loo Tan
- Malaysia Genome Institute, Heliks Emas Block, UKM-MTDC Smart Technology Centre, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor DE, Malaysia
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Storey KB, Storey JM. Tribute to P. L. Lutz: putting life on 'pause'--molecular regulation of hypometabolism. ACTA ACUST UNITED AC 2008; 210:1700-14. [PMID: 17488933 DOI: 10.1242/jeb.02716] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Entry into a hypometabolic state is an important survival strategy for many organisms when challenged by environmental stress, including low oxygen, cold temperatures and lack of food or water. The molecular mechanisms that regulate transitions to and from hypometabolic states, and stabilize long-term viability during dormancy, are proving to be highly conserved across phylogenic lines. A number of these mechanisms were identified and explored using anoxia-tolerant turtles as the model system, particularly from the research contributions made by Dr Peter L. Lutz in his explorations of the mechanisms of neuronal suppression in anoxic brain. Here we review some recent advances in understanding the biochemical mechanisms of metabolic arrest with a focus on ideas such as the strategies used to reorganize metabolic priorities for ATP expenditure, molecular controls that suppress cell functions (e.g. ion pumping, transcription, translation, cell cycle arrest), changes in gene expression that support hypometabolism, and enhancement of defense mechanisms (e.g. antioxidants, chaperone proteins, protease inhibitors) that stabilize macromolecules and promote long-term viability in the hypometabolic state.
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Affiliation(s)
- Kenneth B Storey
- Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada.
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Pamenter ME, Shin DSH, Buck LT. AMPA receptors undergo channel arrest in the anoxic turtle cortex. Am J Physiol Regul Integr Comp Physiol 2007; 294:R606-13. [PMID: 18056983 DOI: 10.1152/ajpregu.00433.2007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Without oxygen, all mammals suffer neuronal injury and excitotoxic cell death mediated by overactivation of the glutamatergic N-methyl-D-aspartate receptor (NMDAR). The western painted turtle can survive anoxia for months, and downregulation of NMDAR activity is thought to be neuroprotective during anoxia. NMDAR activity is related to the activity of another glutamate receptor, the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR). AMPAR blockade is neuroprotective against anoxic insult in mammals, but the role of AMPARs in the turtle's anoxia tolerance has not been investigated. To determine whether AMPAR activity changes during hypoxia or anoxia in the turtle cortex, whole cell AMPAR currents, AMPAR-mediated excitatory postsynaptic potentials (EPSPs), and excitatory postsynaptic currents (EPSCs) were measured. The effect of AMPAR blockade on normoxic and anoxic NMDAR currents was also examined. During 60 min of normoxia, evoked peak AMPAR currents and the frequencies and amplitudes of EPSPs and EPSCs did not change. During anoxic perfusion, evoked AMPAR peak currents decreased 59.2 +/- 5.5 and 60.2 +/- 3.5% at 20 and 40 min, respectively. EPSP frequency (EPSP(f)) and amplitude decreased 28.7 +/- 6.4% and 13.2 +/- 1.7%, respectively, and EPSC(f) and amplitude decreased 50.7 +/- 5.1% and 51.3 +/- 4.7%, respectively. In contrast, hypoxic (Po(2) = 5%) AMPAR peak currents were potentiated 56.6 +/- 20.5 and 54.6 +/- 15.8% at 20 and 40 min, respectively. All changes were reversed by reoxygenation. AMPAR currents and EPSPs were abolished by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). In neurons pretreated with CNQX, anoxic NMDAR currents were reversibly depressed by 49.8 +/- 7.9%. These data suggest that AMPARs may undergo channel arrest in the anoxic turtle cortex.
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Affiliation(s)
- Matthew Edward Pamenter
- University of Toronto, Department of Cellular and Systems Biology, 25 Harbord Street, Toronto, Ontario, Canada
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Storey KB. Anoxia tolerance in turtles: Metabolic regulation and gene expression. Comp Biochem Physiol A Mol Integr Physiol 2007; 147:263-76. [PMID: 17035057 DOI: 10.1016/j.cbpa.2006.03.019] [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] [Received: 12/24/2005] [Revised: 03/14/2006] [Accepted: 03/24/2006] [Indexed: 01/08/2023]
Abstract
Freshwater turtles of the Trachemys and Chrysemys genera are champion facultative anaerobes able to survive for several months without oxygen during winter hibernation in cold water. They have been widely used as models to identify and understand the molecular mechanisms of natural anoxia tolerance and the molecular basis of the hypoxic/ischemic injuries that occur in oxygen-sensitive systems and underlie medical problems such as heart attack and stroke. Peter L. Lutz spent much of his career investigating turtle anaerobiosis with a particular focus on the mechanisms of brain ion homeostasis and neurotransmitter responses to anoxia exposure and the mechanisms that suppress brain ion channel function and neuronal excitability during anaerobiosis. Our interests intersected over the mechanisms of metabolic rate depression which is key to long term anoxia survival. Studies in my lab have shown that a key mechanism of metabolic arrest is reversible protein phosphorylation which provides coordinated suppression of the rates of multiple ATP-producing, ATP-utilizing and related cellular processes to allow organisms to enter a stable hypometabolic state. Anoxia tolerance is also supported by selective gene expression as revealed by recent studies using cDNA library and DNA array screening. New studies with both adult T. scripta elegans and hatchling C. picta marginata have identified prominent groups of genes that are up-regulated under anoxia in turtle organs, in several cases suggesting aspects of cell function and metabolic regulation that have not previously been associated with anaerobiosis. These groups of anoxia-responsive genes include mitochondrially-encoded subunits of electron transport chain proteins, iron storage proteins, antioxidant enzymes, serine protease inhibitors, transmembrane solute carriers, neurotransmitter receptors and transporters, and shock proteins.
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Affiliation(s)
- Kenneth B Storey
- Institute of Biochemistry, College of Natural Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6.
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Kallenberg K, Bailey DM, Christ S, Mohr A, Roukens R, Menold E, Steiner T, Bärtsch P, Knauth M. Magnetic resonance imaging evidence of cytotoxic cerebral edema in acute mountain sickness. J Cereb Blood Flow Metab 2007; 27:1064-71. [PMID: 17024110 DOI: 10.1038/sj.jcbfm.9600404] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The present study applied T2- and diffusion-weighted magnetic resonance imaging to examine if mild cerebral edema and subsequent brain swelling are implicated in the pathophysiology of acute mountain sickness (AMS). Twenty-two subjects were examined in normoxia (21% O2), after 16 hours passive exposure to normobaric hypoxia (12% O2) corresponding to a simulated altitude of 4,500 m and after 6 hours recovery in normoxia. Clinical AMS was diagnosed in 50% of subjects during hypoxia and corresponding headache scores were markedly elevated (P<0.05 versus non-AMS). Hypoxia was associated with a mild increase in brain volume (+7.0+/-4.8 ml, P<0.05 versus pre-exposure baseline) that resolved during normoxic recovery. Hypoxia was also associated with an increased T2 relaxation time (T2rt) and a general trend toward an increased apparent diffusion coefficient (ADC). During the normoxic recovery, brain volume and T2rt recovered to pre-exposure baseline values, whereas a more marked reduction in ADC in the splenium of the corpus callosum (SCC) was observed (P<0.05). While changes in brain volume and T2rt were not selectively different in AMS, ADC values were consistently lower (P<0.05 versus non-AMS) and associated with the severity of neurologic symptoms. Acute mountain sickness was also characterized by an increased brain to intracranial volume ratio (P<0.05 versus non-AMS). These findings indicate that mild extracellular vasogenic edema contributes to the generalized brain swelling observed at high altitude, independent of AMS. In contrast, intracellular cytotoxic edema combined with an anatomic predisposition to a 'tight-fit' brain may prove of pathophysiologic significance, although the increase in brain volume in hypoxia was only about 0.5% of total brain volume.
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Affiliation(s)
- Kai Kallenberg
- Department of Neuroradiology, Georg August University Medical Centre, University of Göttingen, Göttingen, Germany.
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Richards JG, Wang YS, Brauner CJ, Gonzalez RJ, Patrick ML, Schulte PM, Choppari-Gomes AR, Almeida-Val VM, Val AL. Metabolic and ionoregulatory responses of the Amazonian cichlid, Astronotus ocellatus, to severe hypoxia. J Comp Physiol B 2007; 177:361-74. [PMID: 17219139 DOI: 10.1007/s00360-006-0135-2] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 11/14/2006] [Accepted: 11/24/2006] [Indexed: 11/28/2022]
Abstract
We examined the metabolic and ionoregulatory responses of the Amazonian cichlid, Astronotus ocellatus, to 20 h exposure to severe hypoxia (0.37 +/- 0.19 mg O(2)/l; 4.6% air saturation) or 8 h severe hypoxia followed by 12 h recovery in normoxic water. During 20 h exposure to hypoxia, white muscle [ATP] was maintained at normoxic levels primarily through a 20% decrease in [creatine phosphate] (CrP) and an activation of glycolysis yielding lactate accumulation. Muscle lactate accumulation maintained cytoplasmic redox state ([NAD(+)]/[NADH]) and was associated with an inactivation of the mitochondrial enzyme pyruvate dehydrogenase (PDH). The inactivation of PDH was not associated with significant changes in cytoplasmic allosteric modulators ([ADP(free)], redox state, or [pyruvate]). Hypoxia exposure caused an approximately 65% decrease in gill Na(+)/K(+) ATPase activity, which was not matched by changes in Na(+)/K(+) ATPase alpha-subunit protein abundance indicating post-translational modification of Na(+)/K(+) ATPase was responsible for the decrease in activity. Despite decreases in gill Na(+)/K(+) ATPase activity, plasma [Na(+)] increased, but this increase was possibly due to a significant hemoconcentration and fluid shift out of the extracellular space. Hypoxia caused an increase in Na(+)/K(+) ATPase alpha-subunit mRNA abundance pointing to either reduced mRNA degradation during exposure to hypoxia or enhanced expression of Na(+)/K(+) ATPase alpha-subunit relative to other genes.
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Affiliation(s)
- J G Richards
- Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver, BC, Canada V6T 1Z4.
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Vornanen M, Paajanen V. Seasonal changes in glycogen content and Na+-K+-ATPase activity in the brain of crucian carp. Am J Physiol Regul Integr Comp Physiol 2006; 291:R1482-9. [PMID: 16741142 DOI: 10.1152/ajpregu.00172.2006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Changes in the number of Na+-K+-ATPase α-subunits, Na+-K+-ATPase activity and glycogen content of the crucian carp ( Carassius carassius) brain were examined to elucidate relative roles of energy demand and supply in adaptation to seasonal anoxia. Fish were collected monthly around the year from the wild for immediate laboratory assays. Equilibrium dissociation constant and Hill coefficient of [3H]ouabain binding to brain homogenates were 12.87 ± 2.86 nM and −1.18 ± 0.07 in June and 11.93 ± 2.81 nM and −1.17 ± 0.06 in February ( P > 0.05), respectively, suggesting little changes in Na+-K+-ATPase α-subunit composition of the brain between summer and winter. The number of [3H]ouabain binding sites and Na-K-ATPase activity varied seasonally ( P < 0.001) but did not show clear connection to seasonal changes in oxygen content of the fish habitat. Six weeks’ exposure of fish to anoxia in the laboratory did not affect Na+-K+-ATPase activity ( P > 0.05) confirming the anoxia resistance of the carp brain Na pump. Although anoxia did not suppress the Na pump, direct Q10effect on Na+-K+-ATPase at low temperatures resulted in 10 times lower catalytic activity in winter than in summer. Brain glycogen content showed clear seasonal cycling with the peak value of 203.7 ± 16.1 μM/g in February and a 15 times lower minimum (12.9 ± 1.2) in July. In winter glycogen stores are 15 times larger and ATP requirements of Na+-K+-ATPase at least 10 times less than in summer. Accordingly, brain glycogen stores are sufficient to fuel brain function for about 8 min in summer and 16 h in winter, meaning about 150-fold extension of brain anoxia tolerance by seasonal changes in energy supply-demand ratio.
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Affiliation(s)
- Matti Vornanen
- Univ. of Joensuu, Dept. of Biology, P.O. Box 111, 80101 Joensuu, Finland.
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Ebensperger G, Ebensperger R, Herrera EA, Riquelme RA, Sanhueza EM, Lesage F, Marengo JJ, Tejo RI, Llanos AJ, Reyes RV. Fetal brain hypometabolism during prolonged hypoxaemia in the llama. J Physiol 2005; 567:963-75. [PMID: 16037083 PMCID: PMC1474220 DOI: 10.1113/jphysiol.2005.094524] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
In this study we looked for additional evidence to support the hypothesis that fetal llama reacts to hypoxaemia with adaptive brain hypometabolism. We determined fetal llama brain temperature, Na(+) and K(+) channel density and Na(+)-K(+)-ATPase activity. Additionally, we looked to see whether there were signs of cell death in the brain cortex of llama fetuses submitted to prolonged hypoxaemia. Ten fetal llamas were instrumented under general anaesthesia to measure pH, arterial blood gases, mean arterial pressure, heart rate, and brain and core temperatures. Measurements were made 1 h before and every hour during 24 h of hypoxaemia (n = 5), which was imposed by reducing maternal inspired oxygen fraction to reach a fetal arterial partial pressure of oxygen (P(a,O(2))) of about 12 mmHg. A normoxaemic group was the control (n = 5). After 24 h of hypoxaemia, we determined brain cortex Na(+)-K(+)-ATPase activity, ouabain binding, and the expression of NaV1.1, NaV1.2, NaV1.3, NaV1.6, TREK1, TRAAK and K(ATP) channels. The lack of brain cortex damage was assessed as poly ADP-ribose polymerase (PARP) proteolysis. We found a mean decrease of 0.56 degrees C in brain cortex temperature during prolonged hypoxaemia, which was accompanied by a 51% decrease in brain cortex Na(+)-K(+)-ATPase activity, and by a 44% decrease in protein content of NaV1.1, a voltage-gated Na(+) channel. These changes occurred in absence of changes in PARP protein degradation, suggesting that the cell death of the brain was not enhanced in the fetal llama during hypoxaemia. Taken together, these results provide further evidence to support the hypothesis that the fetal llama responds to prolonged hypoxaemia with adaptive brain hypometabolism, partly mediated by decreases in Na(+)-K(+)-ATPase activity and expression of NaV channels.
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Affiliation(s)
- Germán Ebensperger
- Programa de Fisiopatología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago
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Pörtner HO. Synergistic effects of temperature extremes, hypoxia, and increases in CO2on marine animals: From Earth history to global change. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004jc002561] [Citation(s) in RCA: 296] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Hicks JW, Wang T. Hypometabolism in reptiles: behavioural and physiological mechanisms that reduce aerobic demands. Respir Physiol Neurobiol 2004; 141:261-71. [PMID: 15288598 DOI: 10.1016/j.resp.2004.03.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2004] [Indexed: 10/26/2022]
Abstract
During exposure to hypoxia all vertebrates utilize a suite of cardiovascular and ventilatory responses that, in combination, strive to maintain adequate delivery of oxygen to the metabolizing tissues. In addition to maintaining oxygen delivery through cardio-respiratory responses, oxygen demands in the tissues can also be reduced. Reptiles use this alternative strategy during periods of moderate to severe hypoxia by behavioural reductions in preferred body temperature and by active down-regulation of aerobic metabolism. Below we review these two different strategies and discuss their possible mechanisms and physiological significance.
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Affiliation(s)
- James W Hicks
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
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Prentice HM, Milton SL, Scheurle D, Lutz PL. Gene transcription of brain voltage-gated potassium channels is reversibly regulated by oxygen supply. Am J Physiol Regul Integr Comp Physiol 2004; 285:R1317-21. [PMID: 14615400 DOI: 10.1152/ajpregu.00261.2003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Voltage-dependent potassium channels (Kv channels) are important determinants of brain electrical activity. Hypoxia may be an important modifier, because several voltage-gated K+ channels are reversibly blocked by acute hypoxia and are thought to act as oxygen sensors. Here we show, using the anoxia-tolerant turtle brain (Trachemys scripta) as a model, that brain Kv1 channel transcription is reversibly regulated by oxygen supply. We found that in turtle brains exposed to 4-h anoxia Kv1 transcripts were reduced to 18.5% of normoxic levels. Kv1 channel mRNA levels were restored to normal within 4 h of subsequent reoxygenation. Our results provide clear evidence that brain Kv channel expression is sensitive to oxygen supply and indicate an important mechanism that matches brain activity to oxygen supply.
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Affiliation(s)
- Howard M Prentice
- Department of Biomedical Sciences, Florida Atlantic University, Boca Raton 33431, USA.
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Berntssen MHG, Aatland A, Handy RD. Chronic dietary mercury exposure causes oxidative stress, brain lesions, and altered behaviour in Atlantic salmon (Salmo salar) parr. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2003; 65:55-72. [PMID: 12932701 DOI: 10.1016/s0166-445x(03)00104-8] [Citation(s) in RCA: 194] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Atlantic salmon (Salmo salar L.) parr were fed for 4 months on fish meal based diets supplemented with mercuric chloride (0, 10, or 100 mg Hg kg(-1) DW) or methylmercury chloride (0, 5, or 10 mg Hg kg(-1) DW) to assess the effects of inorganic (Hg) and organic dietary mercury on brain lipid peroxidation and neurotoxicity. Lipid peroxidative products, endogenous anti oxidant enzymes, brain histopathology, and overall behaviour were measured. Methylmercury accumulated significantly in the brain of fish fed 5 or 10 mg kg(-1) by the end of the experiment, and inorganic mercury accumulated significantly in the brain only at 100 mg kg(-1) exposure levels. No mortality or growth reduction was observed in any of the exposure groups. Fish fed 5 mg kg(-1) methylmercury had a significant increase (2-fold) in the antioxidant enzyme super oxide dismutase (SOD) in the brain. At dietary levels of 10 mg kg(-1) methylmercury, a significant increase (7-fold) was observed in lipid peroxidative products (thiobarbituric acid reactive substances, TBARS) and a subsequently decrease (1.5-fold) in anti oxidant enzyme activity (SOD and glutathione peroxidase, GSH-Px). Fish fed 10 mg kg(-1) methylmercury also had pathological damage (vacoulation and necrosis), significantly reduced neural enzyme activity (5-fold reduced monoamine oxidase, MAO, activity), and reduced overall post-feeding activity behaviour. Pathological injury started in the brain stem and became more widespread in other areas of the brain at higher exposure levels. Fish fed 100 mg Hg kg(-1) inorganic mercury had significant reduced neural MAO activity and pathological changes (astrocyte proliferation) in the brain, however, neural SOD and GSH-Px enzyme activity, lipid peroxidative products (TBARS), and post feeding behaviour did not differ from controls. Compared with other organs, the brain is particular susceptible for dietary methylmercury induced lipid peroxidative stress at relative low exposure concentrations. Doses of dietary methylmercury in the range of 5 mg kg(-1) induces protective redox defences in the brain as seen from the induction of anti-oxidant enzyme SOD activity. However, above a threshold of 10 mg kg(-1) methylmercury these defences are overcome and lipid peroxidative injury (TBARS) as well as severe pathological damage and adverse behaviour become apparent.
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Affiliation(s)
- Marc H G Berntssen
- National Institute for Nutrition and Seafood Research, P.O. Box 176, N-5804 Bergen, Norway.
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Abstract
This review focuses on recent research on the metabolic function of fish brain. Fish brain is isolated from the systemic circulation by a blood-brain barrier that allows the transport of glucose, monocarboxylates and amino acids. The limited information available in fishes suggests that oxidation of exogenous glucose and oxidative phosphorylation provide most of the ATP required for brain function in teleosts, whereas oxidation of ketones and amino acids occurs preferentially in elasmobranchs. In several agnathans and benthic teleosts brain glycogen levels rather than exogenous glucose may be the proximate glucose source for oxidation. In situations when glucose is in limited supply, teleost brains utilize other fuels such as lactate or ketones. Information on use of lipids and amino acids as fuels in fish brain is scarce. The main pathways of brain energy metabolism are changed by several effectors. Thus, several parameters of brain energy metabolism have been demonstrated to change post-prandially in teleostean fishes. The absence of food in teleosts elicits profound changes in brain energy metabolism (increased glycogenolysis and use of ketones) in a way similar to that demonstrated in mammals though delayed in time. Environmental factors induce changes in brain energy parameters in teleosts such as the enhancement of glycogenolysis elicited by pollutants, increased capacity for anaerobic glycolysis under hypoxia/anoxia or changes in substrate utilization elicited by adaptation to cold. Furthermore, several studies demonstrate effects of melatonin, insulin, glucagon, GLP-1, cortisol or catecholamines on energy parameters of teleost brain, although in most cases the results are quite preliminary being difficult to relate the effects of those hormones to physiological situations. The few studies performed with the different cell types available in the nervous system of fish allow us to hypothesize few functional relationships among those cells. Future research perspectives are also outlined.
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Affiliation(s)
- José L Soengas
- Laboratorio de Fisioloxía Animal, Facultade de Ciencias, Universidade de Vigo, E-36200, Vigo, Spain.
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Kumosani TA. Kinetics Parameters of Na+, K+-ATPase from Different Mice Brain Lobes. JOURNAL OF MEDICAL SCIENCES 2001. [DOI: 10.3923/jms.2002.29.31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Hochachka PW, Lutz PL. Mechanism, origin, and evolution of anoxia tolerance in animals. Comp Biochem Physiol B Biochem Mol Biol 2001; 130:435-59. [PMID: 11691622 DOI: 10.1016/s1096-4959(01)00408-0] [Citation(s) in RCA: 301] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Organisms vary widely in their tolerance to conditions of limiting oxygen supply to their cells and tissues. A unifying framework of hypoxia tolerance is now available that is based on information from cell-level models from highly anoxia-tolerant species, such as the aquatic turtle, and from other more hypoxia-sensitive systems. The response of hypoxia-tolerant systems to oxygen lack occurs in two (defense and rescue) phases. The first lines of defense against hypoxia include a drastic, if balanced, suppression of ATP demand and supply pathways; this regulation allows ATP levels to remain constant, even while ATP turnover rates greatly decline. The ATP requirements of ion pumping are down-regulated by generalized 'channel' arrest in hepatocytes and by the arrest of specific ion channels in neurons. In hepatocytes, the ATP demands of protein synthesis are down-regulated on exposure to hypoxia by an immediate global blockade of the process (probably through translational arrest caused by complexing between polysomes and elongation factors). In hypoxia-sensitive cells, this translational arrest seems irreversible, but hypoxia-tolerant systems activate 'rescue' mechanisms if the period of oxygen lack is extended by preferentially regulating the expression of several proteins. In these cells, a cascade of processes underpinning hypoxia rescue and defense begins with an oxygen sensor (a heme protein) and a signal transduction pathway that leads to the specific activation of some genes (increased expression of several proteins) and to specific down-regulation of other genes (decreased expression of several other proteins). The functional roles of the oxygen-sensing and signal-transduction system include significant gene-based metabolic reprogramming - the rescue process - with maintained down-regulation of energy demand and supply pathways in metabolism throughout the hypoxic period. We consider that, through this recent work, it is becoming evident how normoxic-maintenance ATP turnover rates can be down-regulated by an order of magnitude or more - to a new hypometabolic steady state, which is prerequisite for surviving prolonged hypoxia or anoxia. Because the phylogenies of the turtles and of fishes are well known, we are now in an excellent position to assess conservative vs. adaptable features in the evolution of the above hypoxia-response physiology in these two specific animal lineages.
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Affiliation(s)
- P W Hochachka
- Department of Zoology, University of British Columbia, Vancouver, Canada V6T 1Z4
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Reglödi D, Somogyvári-Vigh A, Vígh J, Li M, Lengvári I, Arimura A. Pituitary adenylate cyclase activating polypeptide is highly abundant in the nervous system of anoxia-tolerant turtle, Pseudemys scripta elegans. Peptides 2001; 22:873-8. [PMID: 11390016 DOI: 10.1016/s0196-9781(01)00412-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The levels of the pituitary adenylate cyclase activating polypeptide (PACAP) were measured in the central nervous system and in peripheral organs of the anoxia-tolerant freshwater turtle, Pseudemys scripta elegans by radioimmunoassay. The concentration of PACAP38 was strikingly high in the central nervous system and lower but considerable immunoreactivity was detected in the peripheral organs. Levels of PACAP38 in the turtle brain exceed those measured in rat and human brain areas by 10-100-fold. Based on these exceptionally high levels of PACAP and the known neuroprotective role of the peptide, it can be suggested that PACAP38 plays a role in the extraordinary resistance of the turtle brain from anoxia-induced neuronal damage.
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Affiliation(s)
- D Reglödi
- Department of Anatomy, University of Pécs, Hungary
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