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Dichiera AM, Negrete, Jr B, Ackerly KL, Esbaugh AJ. The role of carbonic anhydrase-mediated tissue oxygen extraction in a marine teleost acclimated to hypoxia. J Exp Biol 2022; 225:281316. [DOI: 10.1242/jeb.244474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 10/12/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT
With the growing prevalence of hypoxia (O2 levels ≤2 mg l−1) in aquatic and marine ecosystems, there is increasing interest in the adaptive mechanisms fish may employ to better their performance in stressful environments. Here, we investigated the contribution of a proposed strategy for enhancing tissue O2 extraction – plasma-accessible carbonic anhydrase (CA-IV) – under hypoxia in a species of estuarine fish (red drum, Sciaenops ocellatus) that thrives in fluctuating habitats. We predicted that hypoxia-acclimated fish would increase the prevalence of CA-IV in aerobically demanding tissues to confer more efficient tissue O2 extraction. Furthermore, we predicted the phenotypic changes to tissue O2 extraction that occur with hypoxia acclimation may improve respiratory and swim performance under 100% O2 conditions (i.e. normoxia) when compared with performance in fish that have not been acclimated to hypoxia. Interestingly, there were no significant differences in relative CA-IV mRNA expression, protein abundance or enzyme activity between the two treatments, suggesting CA-IV function is maintained under hypoxia. Likewise, respiratory performance of hypoxia-acclimated fish was similar to that of control fish when tested in normoxia. Critical swim speed (Ucrit) was significantly higher in hypoxia-acclimated fish but translated to marginal ecological benefits with an increase of ∼0.3 body lengths per second. Instead, hypoxia-acclimated fish may have relied more heavily on anaerobic metabolism during their swim trials, utilizing burst swimming 1.5 times longer than control fish. While the maintenance of CA-IV may still be an important contributor for hypoxia tolerance, our evidence suggests hypoxia-acclimated red drum are using other mechanisms to cope in an O2-depleted environment.
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Affiliation(s)
- Angelina M. Dichiera
- The University of British Columbia 1 Department of Zoology , , Vancouver, BC , Canada V6T 1Z4
| | - Benjamin Negrete, Jr
- Marine Science Institute, The University of Texas at Austin 2 , Port Aransas, TX 78373 , USA
| | - Kerri Lynn Ackerly
- Marine Science Institute, The University of Texas at Austin 2 , Port Aransas, TX 78373 , USA
| | - Andrew J. Esbaugh
- Marine Science Institute, The University of Texas at Austin 2 , Port Aransas, TX 78373 , USA
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2
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Oxygen consumption and acid secretion in isolated gas gland cells of the European eel Anguilla anguilla. J Comp Physiol B 2022; 192:447-457. [PMID: 35289381 PMCID: PMC9197889 DOI: 10.1007/s00360-022-01432-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 02/18/2022] [Accepted: 02/23/2022] [Indexed: 02/06/2023]
Abstract
Swimbladder gas gland cells are known to produce lactic acid required for the acidification of swimbladder blood and decreasing the oxygen carrying capacity of swimbladder blood, i.e., the onset of the Root effect. Gas gland cells have also been shown to metabolize glucose via the pentose phosphate shunt, but the role of the pentose phosphate shunt for acid secretion has not yet been evaluated. Similarly, aerobic metabolism of gas gland cells has been largely neglected so far. In the present study, we therefore simultaneously assessed the role of glycolysis and of the pentose phosphate shunt for acid secretion and recorded oxygen consumption of isolated swimbladder gas gland cells of the European eel. Presence of glucose was essential for acid secretion, and at glucose concentrations of about 1.5 mmol l−1 acid secretion of gas gland cells reached a maximum, indicating that glucose concentrations in swimbladder blood should not be limiting acid production and secretion under physiological conditions. The data revealed that most of the acid was produced in the glycolytic pathway, but a significant fraction was also contributed by the pentose phosphate shunt. Addition of glucose to gas gland cells incubated in a glucose-free medium resulted in a reduction of oxygen uptake. Inhibition of mitochondrial respiration significantly reduced oxygen consumption, but a fraction of mitochondria-independent respiration remained in presence of rotenone and antimycin A. In the presence of glucose, application of either iodo-acetate inhibiting glycolysis or 6-AN inhibiting the pentose phosphate shunt did not significantly affect oxygen uptake, indicating an independent regulation of oxidative phosphorylation and of acid production. Inhibition of the muscarinic acetylcholine receptor caused a slight elevation in acid secretion, while forskolin caused a concentration-dependent reduction in acid secretion, indicating muscarinic and c-AMP-dependent control of acid secretion in gas gland cells.
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Damsgaard C, Country MW. The Opto-Respiratory Compromise: Balancing Oxygen Supply and Light Transmittance in the Retina. Physiology (Bethesda) 2022; 37:101-113. [PMID: 34843655 PMCID: PMC9159541 DOI: 10.1152/physiol.00027.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The light-absorbing retina has an exceptionally high oxygen demand, which imposes two conflicting needs: high rates of blood perfusion and an unobstructed light path devoid of blood vessels. This review discusses mechanisms and physiological trade-offs underlying retinal oxygen supply in vertebrates and examines how these physiological systems supported the evolution of vision.
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Affiliation(s)
- Christian Damsgaard
- 1Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark,2Zoophysiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Michael W. Country
- 3Retinal Neurophysiology Section, National Eye Institute,
National Institutes of Health, Bethesda, Maryland
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Drechsel V, Schneebauer G, Fiechtner B, Cutler CP, Pelster B. Aquaporin expression and cholesterol content in eel swimbladder tissue. JOURNAL OF FISH BIOLOGY 2022; 100:609-618. [PMID: 34882794 PMCID: PMC9302985 DOI: 10.1111/jfb.14973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 12/01/2021] [Accepted: 12/02/2021] [Indexed: 05/08/2023]
Abstract
Leakiness of the swimbladder wall of teleost fishes must be prevented to avoid diffusional loss of gases out of the swimbladder. Guanine incrustation as well as high concentrations of cholesterol in swimbladder membranes in midwater and deep-sea fish has been connected to a reduced gas permeability of the swimbladder wall. On the contrary, the swimbladder is filled by diffusion of gases, mainly oxygen and CO2 , from the blood and the gas gland cells into the swimbladder lumen. In swimbladder tissue of the zebrafish and the Japanese eel, aquaporin mRNA has been detected, and the aquaporin protein has been considered important for the diffusion of water, which may accidentally be gulped by physostome fish when taking an air breath. In the present study, the expression of two aquaporin 1 genes (Aqp1aa and Aqp1ab) in the swimbladder tissue of the European eel, a functional physoclist fish, was assessed using immunohistochemistry, and the expression of both genes was detected in endothelial cells of swimbladder capillaries as well as in basolateral membranes of gas gland cells. In addition, Aqp1ab was present in apical membranes of swimbladder gas gland cells. The authors also found high concentrations of cholesterol in these membranes, which were several fold higher than in muscle tissue membranes. In yellow eels the cholesterol concentration exceeded the concentration detected in silver eel swimbladder membranes. The authors suggest that aquaporin 1 in swimbladder gas gland cells and endothelial cells facilitates CO2 diffusion into the blood, enhancing the switch-on of the Root effect, which is essential for the secretion of oxygen into the swimbladder. It may also facilitate CO2 diffusion into the swimbladder lumen along the partial gradient established by CO2 production in gas gland cells. Cholesterol has been shown to reduce the gas permeability of membranes and thus could contribute to the gas tightness of swimbladder membranes, which is essential to avoid diffusional loss of gas out of the swimbladder.
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Affiliation(s)
- Victoria Drechsel
- Institute of ZoologyUniversity of InnsbruckInnsbruckAustria
- Center for Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
| | - Gabriel Schneebauer
- Institute of ZoologyUniversity of InnsbruckInnsbruckAustria
- Center for Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
| | - Birgit Fiechtner
- Institute of ZoologyUniversity of InnsbruckInnsbruckAustria
- Center for Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
| | | | - Bernd Pelster
- Institute of ZoologyUniversity of InnsbruckInnsbruckAustria
- Center for Molecular BiosciencesUniversity of InnsbruckInnsbruckAustria
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Schneebauer G, Drechsel V, Dirks R, Faserl K, Sarg B, Pelster B. Expression of transport proteins in the rete mirabile of european silver and yellow eel. BMC Genomics 2021; 22:866. [PMID: 34856920 PMCID: PMC8638102 DOI: 10.1186/s12864-021-08180-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 11/16/2021] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND In physoclist fishes filling of the swimbladder requires acid secretion of gas gland cells to switch on the Root effect and subsequent countercurrent concentration of the initial gas partial pressure increase by back-diffusion of gas molecules in the rete mirabile. It is generally assumed that the rete mirabile functions as a passive exchanger, but a detailed analysis of lactate and water movements in the rete mirabile of the eel revealed that lactate is diffusing back in the rete. In the present study we therefore test the hypothesis that expression of transport proteins in rete capillaries allows for back-diffusion of ions and metabolites, which would support the countercurrent concentrating capacity of the rete mirabile. It is also assumed that in silver eels, the migratory stage of the eel, the expression of transport proteins would be enhanced. RESULTS Analysis of the transcriptome and of the proteome of rete mirabile tissue of the European eel revealed the expression of a large number of membrane ion and metabolite transport proteins, including monocarboxylate and glucose transport proteins. In addition, ion channel proteins, Ca2+-ATPase, Na+/K+-ATPase and also F1F0-ATP synthase were detected. In contrast to our expectation in silver eels the expression of these transport proteins was not elevated as compared to yellow eels. A remarkable number of enzymes degrading reactive oxygen species (ROS) was detected in rete capillaries. CONCLUSIONS Our results reveal the expression of a large number of transport proteins in rete capillaries, so that the back diffusion of ions and metabolites, in particular lactate, may significantly enhance the countercurrent concentrating ability of the rete. Metabolic pathways allowing for aerobic generation of ATP supporting secondary active transport mechanisms are established. Rete tissue appears to be equipped with a high ROS defense capacity, preventing damage of the tissue due to the high oxygen partial pressures generated in the countercurrent system.
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Affiliation(s)
- Gabriel Schneebauer
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria
| | - Victoria Drechsel
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria
| | - Ron Dirks
- Future Genomics Technologies, Leiden, The Netherlands
| | - Klaus Faserl
- Institute of Medical Biochemistry, Protein Core Facility, Medical University Innsbruck, Innsbruck, Austria
| | - Bettina Sarg
- Institute of Medical Biochemistry, Protein Core Facility, Medical University Innsbruck, Innsbruck, Austria
| | - Bernd Pelster
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria.
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria.
- Institut für Zoologie Leopold-Franzens-Universität Innsbruck, Technikerstr. 25, A-6020, Innsbruck, Austria.
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Pelster B. Using the swimbladder as a respiratory organ and/or a buoyancy structure-Benefits and consequences. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2021; 335:831-842. [PMID: 33830682 DOI: 10.1002/jez.2460] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/16/2021] [Accepted: 03/22/2021] [Indexed: 11/07/2022]
Abstract
A swimbladder is a special organ present in several orders of Actinopterygians. As a gas-filled cavity it contributes to a reduction in overall density, but on descend from the water surface its contribution as a buoyancy device is very limited because the swimbladder is compressed by increasing hydrostatic pressure. It serves, however, as a very efficient organ for aerial gas exchange. To avoid the loss of oxygen to hypoxic water at the gills many air-breathing fish show a reduced gill surface area. This, in turn, also reduces surface area available for other functions, so that breathing air is connected to a number of physiological adjustments with respect to ion homeostasis, acid-base regulation and nitrogen excretion. Using the swimbladder as a buoyancy structure resulted in the loss of its function as an air-breathing organ and required the development of a gas secreting mechanism. This was achieved via the Root effect and a countercurrent arrangement of the blood supply to the swimbladder. In addition, a detachable air space with separated blood supply was necessary to allow the resorption of gas from the swimbladder. Gas secretion as well as gas resorption are slow phenomena, so that rapid changes in depth cannot instantaneously be compensated by appropriate volume changes. As gas-filled cavities the respiratory swimbladder and the buoyancy device require surfactant. Due to high oxygen partial pressures inside the bladder air-exposed tissues need an effective reactive oxygen species defense system, which is particularly important for a swimbladder at depth.
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Affiliation(s)
- Bernd Pelster
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria
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7
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Dichiera AM, Esbaugh AJ. Red blood cell carbonic anhydrase mediates oxygen delivery via the Root effect in red drum. ACTA ACUST UNITED AC 2020; 223:223/22/jeb232991. [PMID: 33243926 DOI: 10.1242/jeb.232991] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 10/08/2020] [Indexed: 12/15/2022]
Abstract
Oxygen (O2) and carbon dioxide (CO2) transport are tightly coupled in many fishes as a result of the presence of Root effect hemoglobins (Hb), whereby reduced pH reduces O2 binding even at high O2 tensions. Red blood cell carbonic anhydrase (RBC CA) activity limits the rate of intracellular acidification, yet its role in O2 delivery has been downplayed. We developed an in vitro assay to manipulate RBC CA activity while measuring Hb-O2 offloading following a physiologically relevant CO2-induced acidification. RBC CA activity in red drum (Sciaenops ocellatus) was inhibited with ethoxzolamide by 53.7±0.5%, which prompted a significant reduction in O2 offloading rate by 54.3±5.4% (P=0.0206, two-tailed paired t-test; n=7). Conversely, a 2.03-fold increase in RBC CA activity prompted a 2.14-fold increase in O2 offloading rate (P<0.001, two-tailed paired t-test; n=8). This approximately 1:1 relationship between RBC CA activity and Hb-O2 offloading rate coincided with a similar allometric scaling exponent for RBC CA activity and maximum metabolic rate. Together, our data suggest that RBC CA is rate limiting for O2 delivery in red drum.
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Affiliation(s)
- Angelina M Dichiera
- The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, USA
| | - Andrew J Esbaugh
- The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, USA
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8
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Schneebauer G, Lindemann C, Drechsel V, Marohn L, Wysujack K, Santidrian E, Dirks R, Hanel R, Pelster B. Swimming under elevated hydrostatic pressure increases glycolytic activity in gas gland cells of the European eel. PLoS One 2020; 15:e0239627. [PMID: 32997701 PMCID: PMC7526912 DOI: 10.1371/journal.pone.0239627] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 09/09/2020] [Indexed: 02/08/2023] Open
Abstract
In spite of many decades of research, the spawning migration of the European eel Anguilla anguilla from the European coast to the Sargasso Sea remains a mystery. In particular, the role of the swimbladder as a buoyancy regulating structure is not yet understood. In this study, we exercised silver eels in a swim tunnel under elevated hydrostatic pressure. The transcriptome of gas gland tissue of these exercised eels was then compared to the known transcriptome of not exercised (control) silver eel gas gland cells. Due to the high infection rate of the eel population with the swimbladder parasite Anguillicola crassus, the comparison also included an exercised group of silver eels with a heavily damaged swimbladder, and we compared the previously published transcriptome of not exercised silver eels with a highly damaged swimbladder with the exercised group of silver eels with a heavily damaged swimbladder. The comparisons of unexercised (control) silver eels with exercised silver eels with functional swimbladder (EF), as well as with exercised silver eels with damaged swimbladder (ED), both showed a significant elevation in transcripts related to glycolytic enzymes. This could also be observed within the comparison of unexercised silver eels with a highly infected swimbladder with exercised eels with a damaged swimbladder (DED). In contrast to EF, in ED a significant elevation in transcript numbers of mitochondrial NADH dehydrogenase was observed. While in EF the transcriptional changes suggested that acid production and secretion was enhanced, in ED these changes appeared to be related to thickened tissue and thus elevated diffusion distances. The remarkable number of differentially expressed transcripts coding for proteins connected to cAMP-dependent signaling pathways indicated that metabolic control in gas gland cells includes cAMP-dependent pathways. In contrast to ED, in EF significant transcriptional changes could be related to the reconstruction of the extracellular matrix, while in ED tissue repair and inflammation was more pronounced. Surprisingly, in exercised eels hypoxia inducible transcription factor expression was elevated. In EF, a large number of genes related to the circadian clock were transcriptionally modified, which may be connected to the circadian vertical migrations observed during the spawning migration.
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Affiliation(s)
- Gabriel Schneebauer
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria
| | | | - Victoria Drechsel
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria
| | - Lasse Marohn
- Thünen Institute for Fisheries Ecology, Bremerhaven, Germany
| | - Klaus Wysujack
- Thünen Institute for Fisheries Ecology, Bremerhaven, Germany
| | | | - Ron Dirks
- Future Genomics Technologies, Leiden, The Netherlands
| | - Reinhold Hanel
- Thünen Institute for Fisheries Ecology, Bremerhaven, Germany
| | - Bernd Pelster
- Institute of Zoology, University of Innsbruck, Innsbruck, Austria
- Center for Molecular Biosciences, University Innsbruck, Innsbruck, Austria
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Dichiera AM, McMillan OJL, Clifford AM, Goss GG, Brauner CJ, Esbaugh AJ. The importance of a single amino acid substitution in reduced red blood cell carbonic anhydrase function of early-diverging fish. J Comp Physiol B 2020; 190:287-296. [PMID: 32146532 DOI: 10.1007/s00360-020-01270-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/27/2020] [Accepted: 02/12/2020] [Indexed: 02/07/2023]
Abstract
In most vertebrates, red blood cell carbonic anhydrase (RBC CA) plays a critical role in carbon dioxide (CO2) transport and excretion across epithelial tissues. Many early-diverging fishes (e.g., hagfish and chondrichthyans) are unique in possessing plasma-accessible membrane-bound CA-IV in the gills, allowing some CO2 excretion to occur without involvement from the RBCs. However, implications of this on RBC CA function are unclear. Through homology cloning techniques, we identified the putative protein sequences for RBC CA from nine early-diverging species. In all cases, these sequences contained a modification of the proton shuttle residue His-64, and activity measurements from three early-diverging fish demonstrated significantly reduced CA activity. Site-directed mutagenesis was used to restore the His-64 proton shuttle, which significantly increased RBC CA activity, clearly illustrating the functional significance of His-64 in fish red blood cell CA activity. Bayesian analyses of 55 vertebrate cytoplasmic CA isozymes suggested that independent evolutionary events led to the modification of His-64 and thus reduced CA activity in hagfish and chondrichthyans. Additionally, in early-diverging fish that possess branchial CA-IV, there is an absence of His-64 in RBC CAs and the absence of the Root effect [where a reduction in pH reduces hemoglobin's capacity to bind with oxygen (O2)]. Taken together, these data indicate that low-activity RBC CA may be present in all fish with branchial CA-IV, and that the high-activity RBC CA seen in most teleosts may have evolved in conjunction with enhanced hemoglobin pH sensitivity.
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Affiliation(s)
- Angelina M Dichiera
- Marine Science Institute, The University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX, 78373-5015, USA.
| | - Olivia J L McMillan
- Zoology Department, The University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
| | - Alexander M Clifford
- Scripps Institute of Oceanography, The University of California, San Diego, 9500 Gilman Drive #0202, La Jolla, CA, 92093-0202, USA
| | - Greg G Goss
- Department of Biological Sciences, The University of Alberta, 116 St. and 85 Ave., Edmonton, AB, T6G 2R3, Canada.,Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, V0R 1B0, Canada
| | - Colin J Brauner
- Zoology Department, The University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
| | - Andrew J Esbaugh
- Marine Science Institute, The University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX, 78373-5015, USA
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10
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Damsgaard C, Lauridsen H, Funder AM, Thomsen JS, Desvignes T, Crossley DA, Møller PR, Huong DT, Phuong NT, Detrich HW, Brüel A, Wilkens H, Warrant E, Wang T, Nyengaard JR, Berenbrink M, Bayley M. Retinal oxygen supply shaped the functional evolution of the vertebrate eye. eLife 2019; 8:52153. [PMID: 31820735 PMCID: PMC6904217 DOI: 10.7554/elife.52153] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 11/19/2019] [Indexed: 11/13/2022] Open
Abstract
The retina has a very high energy demand but lacks an internal blood supply in most vertebrates. Here we explore the hypothesis that oxygen diffusion limited the evolution of retinal morphology by reconstructing the evolution of retinal thickness and the various mechanisms for retinal oxygen supply, including capillarization and acid-induced haemoglobin oxygen unloading. We show that a common ancestor of bony fishes likely had a thin retina without additional retinal oxygen supply mechanisms and that three different types of retinal capillaries were gained and lost independently multiple times during the radiation of vertebrates, and that these were invariably associated with parallel changes in retinal thickness. Since retinal thickness confers multiple advantages to vision, we propose that insufficient retinal oxygen supply constrained the functional evolution of the eye in early vertebrates, and that recurrent origins of additional retinal oxygen supply mechanisms facilitated the phenotypic evolution of improved functional eye morphology.
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Affiliation(s)
- Christian Damsgaard
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.,Department of Zoology, University of British Columbia, Vancouver, Canada
| | - Henrik Lauridsen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Meinig School of Biomedical Engineering, Cornell University, Ithaca, United States
| | - Anette Md Funder
- Department of Forensic Medicine, Aarhus University, Aarhus, Denmark
| | | | - Thomas Desvignes
- Institute of Neuroscience, University of Oregon, Eugene, United States
| | - Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, United States
| | - Peter R Møller
- Section for Evolutionary Genomics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
| | - Do Tt Huong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho, Viet Nam
| | - Nguyen T Phuong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho, Viet Nam
| | - H William Detrich
- Department of Marine and Environmental Sciences, Marine Science Center, Northeastern University, Nahant, United States
| | - Annemarie Brüel
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Horst Wilkens
- Zoological Institute and Zoological Museum, University of Hamburg, Hamburg, Germany
| | - Eric Warrant
- Department of Biology, Lund University, Lund, Sweden
| | - Tobias Wang
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Jens R Nyengaard
- Core Center for Molecular Morphology, Section for Stereology and Microscopy, Centre for Stochastic Geometry and Advanced Bioimaging, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Michael Berenbrink
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Mark Bayley
- Section for Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
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11
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Schneebauer G, Mauracher D, Fiechtner B, Pelster B. Transcript levels of members of the SLC2 and SLC5 families of glucose transport proteins in eel swimbladder tissue: the influence of silvering and the influence of a nematode infection. FISH PHYSIOLOGY AND BIOCHEMISTRY 2018; 44:599-613. [PMID: 29327317 PMCID: PMC5862955 DOI: 10.1007/s10695-017-0456-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 12/05/2017] [Indexed: 06/07/2023]
Abstract
The rate of glucose metabolism has been shown to be correlated to glucose uptake in swimbladder gas gland cells. Therefore, it is assumed that in the European eel silvering, i.e., the preparation of the eel for the spawning migration to the Sargasso Sea, coincides with an enhanced capacity for glucose uptake. To test this hypothesis expression of all known glucose transport proteins has been assessed at the transcript level in yellow and in silver eels, and we also included Anguillicola crassus infected swimbladders. Glucose uptake by rete mirabile endothelial cells could be crucial for the countercurrent exchange capacity of the rete. Therefore, this tissue was also included in our analysis. The results revealed expression of ten different members of the slc2 family of glucose transporters, of four slc5 family members, and of kiaa1919 in gas gland tissue. Glucose transporters of the slc2 family were expressed at very high level, and slc2a1b made up about 80% of all slc2 family members, irrespective of the developmental state or the infection status of the eel. Overall, the slc5 family contributed to only about 8% of all detected glucose transport transcripts in gas gland tissue, and the slc2 family to more than 85%. In rete capillaries, the contribution of sodium-dependent glucose transporters was significantly higher, leaving only 66% for the slc2 family of glucose transporters. Neither silvering nor the infection status had a significant effect on the expression of glucose transporters in swimbladder gas gland tissue, suggesting that glucose metabolism of eel gas gland cells may not be related to transcriptional changes of glucose transport proteins.
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Affiliation(s)
- Gabriel Schneebauer
- Institute of Zoology, Leopold-Franzens-Universität Innsbruck, Technikerstr.25, 6020, Innsbruck, Austria
- Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - David Mauracher
- Institute of Zoology, Leopold-Franzens-Universität Innsbruck, Technikerstr.25, 6020, Innsbruck, Austria
- Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Birgit Fiechtner
- Institute of Zoology, Leopold-Franzens-Universität Innsbruck, Technikerstr.25, 6020, Innsbruck, Austria
- Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Bernd Pelster
- Institute of Zoology, Leopold-Franzens-Universität Innsbruck, Technikerstr.25, 6020, Innsbruck, Austria.
- Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
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Dietary electrolyte balance affects growth performance, amylase activity and metabolic response in the meagre (Argyrosomus regius). Comp Biochem Physiol B Biochem Mol Biol 2017; 211:8-15. [PMID: 28323073 DOI: 10.1016/j.cbpb.2017.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 03/10/2017] [Accepted: 03/10/2017] [Indexed: 12/30/2022]
Abstract
Dietary ion content is known to alter the acid-base balance in freshwater fish. The current study investigated the metabolic impact of acid-base disturbances produced by differences in dietary electrolyte balance (DEB) in the meagre (Argyrosomus regius), an euryhaline species. Changes in fish performance, gastric chyme characteristics, pH and ion concentrations in the bloodstream, digestive enzyme activities and metabolic rates were analyzed in meagre fed ad libitum two experimental diets (DEB 200 or DEB 700mEq/kg) differing in the Na2CO3 content for 69days. Fish fed the DEB 200 diet had 60-66% better growth performance than the DEB 700 group. Meagre consuming the DEB 200 diet were 90-96% more efficient than fish fed the DEB 700 diet at allocating energy from feed into somatic growth. The pH values in blood were significantly lower in the DEB 700 group 2h after feeding when compared to DEB 200, indicating that acid-base balance in meagre was affected by electrolyte balance in diet. Osmolality, and Na+ and K+ concentrations in plasma did not vary with the dietary treatment. Gastric chyme in the DEB 700 group had higher pH values, dry matter, protein and energy contents, but lower lipid content than in the DEB 200 group. Twenty-four hours after feeding, amylase activity was higher in the gastrointestinal tract of DEB 700 group when compared to the DEB 200 group. DEB 700 group had lower routine metabolic (RMR) and standard metabolic (SMR) rates, indicating a decrease in maintenance energy expenditure 48h after feeding the alkaline diet. The current study demonstrates that feeding meagre with an alkaline diet not only causes acid-base imbalance, but also negatively affects digestion and possibly nutrient assimilation, resulting in decreased growth performance.
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Storz JF. Gene Duplication and Evolutionary Innovations in Hemoglobin-Oxygen Transport. Physiology (Bethesda) 2017; 31:223-32. [PMID: 27053736 DOI: 10.1152/physiol.00060.2015] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During vertebrate evolution, duplicated hemoglobin (Hb) genes diverged with respect to functional properties as well as the developmental timing of expression. For example, the subfamilies of genes that encode the different subunit chains of Hb are ontogenetically regulated such that functionally distinct Hb isoforms are expressed during different developmental stages. In some vertebrate taxa, functional differentiation between co-expressed Hb isoforms may also contribute to physiologically important divisions of labor.
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Affiliation(s)
- Jay F Storz
- School of Biological Sciences, University of Nebraska, Lincoln, Nebraska
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Harter TS, Brauner CJ. The O 2 and CO 2 Transport System in Teleosts and the Specialized Mechanisms That Enhance Hb–O 2 Unloading to Tissues. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/bs.fp.2017.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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15
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Pelster B, Schneebauer G, Dirks RP. Anguillicola crassus Infection Significantly Affects the Silvering Related Modifications in Steady State mRNA Levels in Gas Gland Tissue of the European Eel. Front Physiol 2016; 7:175. [PMID: 27242549 PMCID: PMC4876612 DOI: 10.3389/fphys.2016.00175] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 05/02/2016] [Indexed: 11/20/2022] Open
Abstract
Using Illumina sequencing, transcriptional changes occurring during silvering in swimbladder tissue of the European eel have been analyzed by comparison of yellow and silver eel tissue samples. Functional annotation analysis based on GO terms revealed significant expression changes in a number of genes related to the extracellular matrix, important for the control of gas permeability of the swimbladder, and to reactive oxygen species (ROS) defense, important to cope with ROS generated under hyperbaric oxygen partial pressures. Focusing on swimbladder tissue metabolism, levels of several mRNA species encoding glucose transport proteins were several-fold higher in silver eels, while enzymes of the glycolytic pathway were not affected. The significantly higher steady state level of a transcript encoding for membrane bound carbonic anhydrase, however, suggested that CO2 production in the pentose phosphate shunt and diffusion of CO2 was of particular importance in silver eel swimbladder. In addition, the mRNA level of a large number of genes related to immune response and to sexual maturation was significantly modified in the silver eel swimbladder. The modification of several processes related to protein metabolism and transport, cell cycle, and apoptosis suggested that these changes in swimbladder metabolism and permeability were achieved by increasing cell turn-over. The impact of an infection of the swimbladder with the nematode Anguillicola crassus has been assessed by comparing these expression changes with expression changes observed between uninfected yellow eel swimbladder tissue and infected silver eel swimbladder tissue. In contrast to uninfected silver eel swimbladder tissue, in infected tissue the mRNA level of several glycolytic enzymes was significantly elevated, and with respect to extracellular matrix, several mucin genes were many-fold higher in their mRNA level. Modification of many immune related genes and of the functional categories “response to DNA damage stimulus” and “cellular response to stress” illustrated the damaging effect of the nematode infection. This study has identified a range of cellular processes in the swimbladder of silver eels that appear to be altered by nematode infection. These altered cellular processes could contribute to detrimental changes in swimbladder function that, in turn, may lead to impairment of spawning migration.
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Affiliation(s)
- Bernd Pelster
- Institute of Zoology, University of InnsbruckInnsbruck, Austria; Center for Molecular Biosciences, University of InnsbruckInnsbruck, Austria
| | - Gabriel Schneebauer
- Institute of Zoology, University of InnsbruckInnsbruck, Austria; Center for Molecular Biosciences, University of InnsbruckInnsbruck, Austria
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16
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Manconi B, Pellegrini M, Messana I, Sanna MT, Castagnola M, Iavarone F, Coluccia E, Giardina B, Olianas A. The hemoglobin system of the serpent eel Ophisurus serpens: structural and functional characterization. J Comp Physiol B 2013; 183:905-19. [PMID: 23632627 DOI: 10.1007/s00360-013-0759-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 04/08/2013] [Accepted: 04/16/2013] [Indexed: 11/27/2022]
Abstract
The hemoglobin system of the serpent eel Ophisurus serpens was structurally and functionally characterized with the aim of comparing it to the hemoglobin system of other fish species, as oxygen loading under the severe habitat conditions experienced by O. serpens could have necessitated specific adaptation mechanisms during evolution. The hemoglobin system of O. serpens includes one cathodic and four anodic components. The molecular mass of the α and β chains of the cathodic component as well as the 2 α and 4 β of the anodic components were determined. Analysis of the intact α and β chains from cathodic hemoglobin and their proteolytic digestion products by high-resolution MS and MS/MS experiments resulted in 92 and 95 % sequence coverage of the α and β globins, respectively. The oxygen binding properties of both hemoglobin components were analyzed with respect to their interactions with their physiological effectors. Stripped cathodic hemoglobin displayed the highest oxygen affinity among Anguilliformes with no significant effect of pH on O2-affinity. In the presence of both chloride and organic phosphates, O2-affinity was strongly reduced, and cooperativity was enhanced; moreover, cathodic hemoglobin contains two indistinguishable GTP-binding sites. Stripped anodic hemoglobins exhibited both low O2-affinity and low cooperativity and a larger Bohr effect than cathodic hemoglobin. The cathodic hemoglobin of O. serpens and the corresponding component of Conger conger share the greatest structural and functional similarity among hemoglobin systems of Anguilliformes studied to date, consistent with their phylogenetic relationship.
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Affiliation(s)
- Barbara Manconi
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria, 09042, Monserrato, CA, Italy
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Opazo JC, Butts GT, Nery MF, Storz JF, Hoffmann FG. Whole-genome duplication and the functional diversification of teleost fish hemoglobins. Mol Biol Evol 2012; 30:140-53. [PMID: 22949522 PMCID: PMC3525417 DOI: 10.1093/molbev/mss212] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Subsequent to the two rounds of whole-genome duplication that occurred in the common
ancestor of vertebrates, a third genome duplication occurred in the stem lineage of
teleost fishes. This teleost-specific genome duplication (TGD) is thought to have provided
genetic raw materials for the physiological, morphological, and behavioral diversification
of this highly speciose group. The extreme physiological versatility of teleost fish is
manifest in their diversity of blood–gas transport traits, which reflects the myriad
solutions that have evolved to maintain tissue O2 delivery in the face of
changing metabolic demands and environmental O2 availability during different
ontogenetic stages. During the course of development, regulatory changes in
blood–O2 transport are mediated by the expression of multiple,
functionally distinct hemoglobin (Hb) isoforms that meet the particular
O2-transport challenges encountered by the developing embryo or fetus (in
viviparous or oviparous species) and in free-swimming larvae and adults. The main
objective of the present study was to assess the relative contributions of whole-genome
duplication, large-scale segmental duplication, and small-scale gene duplication in
producing the extraordinary functional diversity of teleost Hbs. To accomplish this, we
integrated phylogenetic reconstructions with analyses of conserved synteny to characterize
the genomic organization and evolutionary history of the globin gene clusters of teleosts.
These results were then integrated with available experimental data on functional
properties and developmental patterns of stage-specific gene expression. Our results
indicate that multiple α- and β-globin genes
were present in the common ancestor of gars (order Lepisoteiformes) and teleosts. The
comparative genomic analysis revealed that teleosts possess a dual set of TGD-derived
globin gene clusters, each of which has undergone lineage-specific changes in gene content
via repeated duplication and deletion events. Phylogenetic reconstructions revealed that
paralogous genes convergently evolved similar functional properties in different teleost
lineages. Consistent with other recent studies of globin gene family evolution in
vertebrates, our results revealed evidence for repeated evolutionary transitions in the
developmental regulation of Hb synthesis.
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Affiliation(s)
- Juan C Opazo
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
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Maqsood S, Benjakul S. Comparative studies on molecular changes and pro-oxidative activity of haemoglobin from different fish species as influenced by pH. Food Chem 2011. [DOI: 10.1016/j.foodchem.2010.07.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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20
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Buaniaw C, Siripongvutikorn S, Thongraung C. Effectiveness of ethanolic galangal extract (Alpinia galanga Linn.) on inhibition of lipid oxidation in fish muscle systems. Int J Food Sci Technol 2010. [DOI: 10.1111/j.1365-2621.2010.02415.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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21
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Olianas A, Meloni C, Messana I, Sanna MT, Castagnola M, Manconi B, Salvadori S, Giardina B, Pellegrini M. Striped mullet (Mugil cephalus) hemoglobin system: multiplicity and functional properties. J Comp Physiol B 2010; 181:187-97. [PMID: 21046405 DOI: 10.1007/s00360-010-0525-3] [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] [Received: 08/10/2010] [Revised: 10/14/2010] [Accepted: 10/17/2010] [Indexed: 11/28/2022]
Abstract
The most frequent (90%) phenotype of the hemoglobin system of M. cephalus presented two major hemoglobins, the more anodal HbI accounting for approximately 70% of the total. The two hemoglobin components separated by ion-exchange chromatography were analyzed by reverse-phase HPLC and electrospray ionization-mass spectrometry which revealed a more complex pattern: HbI consists in four different globins, two β (named β1 and β3) and two co-eluting α chains (α1 and α2); HbII consists in three globins, one β chain (named β2) and the same α1 and α2 present in HbI. The oxygen-binding properties of both hemoglobin components purified by DEAE cellulose were almost identical to those of the hemolysate: stripped hemoglobin showed a large Bohr effect which was enhanced by chloride ions and, at a larger extent, by organic phosphates which, at acidic pH values gave rise to the Root effect. A series of oxygen-binding experiments at increasing GTP concentrations was carried out in order to compare GTP-binding activities in the absence and presence of physiological amounts of chloride. The results indicated that hemoglobin do have two sites for GTP binding. In the absence of chloride, the two sites cannot be discriminated, whereas in the presence of chloride, a competition between the two anions occurred for both GTP-binding sites. The presence of multiple hemoglobin components with identical properties confirms that hemoglobin heterogeneity that often occurs in fish cannot be only explained as an evolutionary response to the physiological and/or environmental needs of the species.
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Affiliation(s)
- Alessandra Olianas
- Department of Sciences Applied to Biosystems, University of Cagliari, Cittadella Universitaria, 09042, Monserrato (CA), Italy
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Rummer JL, Roshan-Moniri M, Balfry SK, Brauner CJ. Use it or lose it? Sablefish, Anoplopoma fimbria, a species representing a fifth teleostean group where the βNHE associated with the red blood cell adrenergic stress response has been secondarily lost. J Exp Biol 2010; 213:1503-12. [DOI: 10.1242/jeb.038844] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Like most teleosts, sablefish (Anoplopoma fimbria Pallas 1814) blood exhibits a moderate Root effect (~35% maximal desaturation), where a reduction in blood pH dramatically reduces O2 carrying capacity, a mechanism important for oxygenating the eye and filling the swim bladder (SB) in teleosts. Although sablefish lack a SB, we observed a well-defined choroid rete at the eye. The adrenergically mediated cell swelling typically associated with a functional red blood cell (RBC) β-adrenergic Na+/H+ exchanger (βNHE), which would normally protect RBC pH, and thus O2 transport, during a generalized acidosis, was not observed in sablefish blood. Neither isoproterenol (a β-agonist) nor 8-bromo cAMP could elicit this response. Furthermore, RBC osmotic shrinkage, known to stimulate NHEs in general and βNHE in other teleosts such as trout and flounder, resulted in no significant regulatory volume increase (RVI), further supporting the absence of a functional RBC βNHE. The onset of the Root effect occurs at a much lower RBC pH (6.83–6.92) than in other teleosts, and thus RBC βNHE may not be required to protect O2 transport during a generalized acidosis in vivo. Phylogenetically, sablefish may represent a fifth group of teleosts exhibiting a secondary reduction or loss of βNHE activity. However, sablefish have not lost the choroid rete at the eye (unlike in the other four groups), which may still function with the Root effect to oxygenate the retina, but the low pH onset of the Root effect may ensure haemoglobin (Hb)-O2 binding is not compromised at the respiratory surface during a general acidosis in the absence of RBC βNHE. The sablefish may represent an anomaly within the framework of Root effect evolution, in that they possess a moderate Root effect and a choroid rete at the eye, but lack the RBC βNHE and the SB system.
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Affiliation(s)
- Jodie L. Rummer
- Department of Zoology, University of British Columbia, No. 2370–6270 University Boulevard, Vancouver, BC, Canada, V6T 1Z4
| | - Mani Roshan-Moniri
- Department of Zoology, University of British Columbia, No. 2370–6270 University Boulevard, Vancouver, BC, Canada, V6T 1Z4
| | - Shannon K. Balfry
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Colin J. Brauner
- Department of Zoology, University of British Columbia, No. 2370–6270 University Boulevard, Vancouver, BC, Canada, V6T 1Z4
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23
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Cooper CA, Whittamore JM, Wilson RW. Ca2+-driven intestinal HCO(3)(-) secretion and CaCO3 precipitation in the European flounder in vivo: influences on acid-base regulation and blood gas transport. Am J Physiol Regul Integr Comp Physiol 2010; 298:R870-6. [PMID: 20130227 PMCID: PMC2853387 DOI: 10.1152/ajpregu.00513.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Accepted: 01/28/2010] [Indexed: 11/22/2022]
Abstract
Marine teleost fish continuously ingest seawater to prevent dehydration and their intestines absorb fluid by mechanisms linked to three separate driving forces: 1) cotransport of NaCl from the gut fluid; 2) bicarbonate (HCO(3)(-)) secretion and Cl(-) absorption via Cl(-)/HCO(3)(-) exchange fueled by metabolic CO(2); and 3) alkaline precipitation of Ca(2+) as insoluble CaCO(3), which aids H(2)O absorption). The latter two processes involve high rates of epithelial HCO(3)(-) secretion stimulated by intestinal Ca(2+) and can drive a major portion of water absorption. At higher salinities and ambient Ca(2+) concentrations the osmoregulatory role of intestinal HCO(3)(-) secretion is amplified, but this has repercussions for other physiological processes, in particular, respiratory gas transport (as it is fueled by metabolic CO(2)) and acid-base regulation (as intestinal cells must export H(+) into the blood to balance apical HCO(3)(-) secretion). The flounder intestine was perfused in vivo with salines containing 10, 40, or 90 mM Ca(2+). Increasing the luminal Ca(2+) concentration caused a large elevation in intestinal HCO(3)(-) production and excretion. Additionally, blood pH decreased (-0.13 pH units) and plasma partial pressure of CO(2) (Pco(2)) levels were elevated (+1.16 mmHg) at the highest Ca perfusate level after 3 days of perfusion. Increasing the perfusate [Ca(2+)] also produced proportional increases in net acid excretion via the gills. When the net intestinal flux of all ions across the intestine was calculated, there was a greater absorption of anions than cations. This missing cation flux was assumed to be protons, which vary with an almost 1:1 relationship with net acid excretion via the gill. This study illustrates the intimate link between intestinal HCO(3)(-) production and osmoregulation with acid-base balance and respiratory gas exchange and the specific controlling role of ingested Ca(2+) independent of any other ion or overall osmolality in marine teleost fish.
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Abstract
SUMMARY
Carbonic anhydrase (CA) is the zinc metalloenzyme that catalyses the reversible reactions of CO2 with water. CA plays a crucial role in systemic acid–base regulation in fish by providing acid–base equivalents for exchange with the environment. Unlike air-breathing vertebrates, which frequently utilize alterations of breathing (respiratory compensation) to regulate acid–base status, acid–base balance in fish relies almost entirely upon the direct exchange of acid–base equivalents with the environment (metabolic compensation). The gill is the critical site of metabolic compensation, with the kidney playing a supporting role. At the gill, cytosolic CA catalyses the hydration of CO2 to H+ and HCO3– for export to the water. In the kidney, cytosolic and membrane-bound CA isoforms have been implicated in HCO3– reabsorption and urine acidification. In this review, the CA isoforms that have been identified to date in fish will be discussed together with their tissue localizations and roles in systemic acid–base regulation.
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Affiliation(s)
- K. M. Gilmour
- Department of Biology and Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ottawa, ON, Canada
| | - S. F. Perry
- Department of Biology and Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ottawa, ON, Canada
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25
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26
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Berenbrink M. Historical reconstructions of evolving physiological complexity:O2 secretion in the eye and swimbladder of fishes. J Exp Biol 2007; 210:1641-52. [PMID: 17449830 DOI: 10.1242/jeb.003319] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe ability of some fishes to inflate their compressible swimbladder with almost pure oxygen to maintain neutral buoyancy, even against the high hydrostatic pressure several thousand metres below the water surface, has fascinated physiologists for more than 200 years. This review shows how evolutionary reconstruction of the components of such a complex physiological system on a phylogenetic tree can generate new and important insights into the origin of complex phenotypes that are difficult to obtain with a purely mechanistic approach alone. Thus, it is shown that oxygen secretion first evolved in the eyes of fishes, presumably for improved oxygen supply to an avascular, metabolically active retina. Evolution of this system was facilitated by prior changes in the pH dependence of oxygen-binding characteristics of haemoglobin (the Root effect) and in the specific buffer value of haemoglobin. These changes predisposed teleost fishes for the later evolution of swimbladder oxygen secretion, which occurred at least four times independently and can be associated with increased auditory sensitivity and invasion of the deep sea in some groups. It is proposed that the increasing availability of molecular phylogenetic trees for evolutionary reconstructions may be as important for understanding physiological diversity in the postgenomic era as the increase of genomic sequence information in single model species.
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Affiliation(s)
- Michael Berenbrink
- School of Biological Sciences, The University of Liverpool, Biosciences Building, Crown Street, Liverpool, UK.
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27
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Thongraung C, Benjakul S, Hultin HO. Effect of pH, ADP and muscle soluble components on cod hemoglobin characteristics and extractability. Food Chem 2006. [DOI: 10.1016/j.foodchem.2005.05.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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28
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Bonaventura C, Godette G, Stevens R, Brenowitz M, Henkens R. Overproduction of α Chains Provides a Proton-insensitive Component to the Bluefish Hemoglobin System. J Biol Chem 2005; 280:40509-14. [PMID: 16166086 DOI: 10.1074/jbc.m505353200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of alpha and beta chains and their post-translational assembly into alpha(2)beta(2) tetramers is fundamental to the formation and function of most vertebrate hemoglobins. There is a strong evolutionary bias that favors expression of equal amounts of the two types of chains, because cooperativity, pH sensitivity, and anionic control of function occurs only for the alpha(2)beta(2) tetramers. Remarkably, an over-production of alpha chains, as in the pathological condition known as beta thalassemia in humans, is adaptive rather than pathological in the bluefish hemoglobin system. The thalassemia of the bluefish is a novel means of providing for oxygen uptake and delivery when low pH conditions incapacitate the highly pH-sensitive Root effect hemoglobins of the fish. Although fish often have pH-insensitive along with highly pH-sensitive hemoglobins, having pH-insensitive alpha chain monomers in circulation is an unusual structural variation. The role of bluefish alpha chains in oxygen transport is enabled by their remarkably lower oxygen affinity relative to human alpha chains. This is the first reported case of a thalassemic condition that is maintained in a species as an adaptive advantage.
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Affiliation(s)
- Celia Bonaventura
- Nicholas School of the Environment and Earth Sciences, Duke University Marine Laboratory, Beaufort, North Carolina 28516, USA.
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29
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Waser W, Heisler N. Oxygen delivery to the fish eye: Root effect as crucial factor for elevated retinalPO2. J Exp Biol 2005; 208:4035-47. [PMID: 16244163 DOI: 10.1242/jeb.01874] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYAlthough the retina has one of the highest metabolic rates among tissues,certain teleost fishes lack any vascular supply to this organ which, in combination with the overall thickness of the organ, results in extremely long diffusion distances. As the only way to compensate for these obstacles, oxygen partial pressure (PO2) in the eyes of such fish is elevated far above atmospheric values. Although not supported by any direct evidence, the enhancement of PO2 is considered to be related to the Root effect, the release upon acidification of Hb-bound O2 into physical dissolution, possibly supported by counter-current multiplication similar to the loop of Henle.The present study evaluates the magnitude of intraocular PO2 enhancement under tightly controlled physiological conditions, to directly confirm the involvement of the Root effect on intraocular PO2 in the retina of rainbow trout Oncorhynchus mykiss. Intraocular PO2 was determined with special polarographic microelectrodes inserted into the eye. PO2profiles established in vivo by driving electrodes through the entire retina yielded average PO2 values between 10 mmHg (1.3 kPa) at the inner retinal surface and 382 mmHg (50.9 kPa) close to the outer retinal limit (Bruch's membrane). According to estimates on the basis of the diffusion distances determined from sections of the retina(∼436 μm at the site of PO2 measurement)and literature data on specific oxygen consumption, the in vivodetermined values would be sufficient to cover the oxygen demand of the retina with some safety margin.For a clear and direct in-tissue-test as to the involvement of the Root effect, an isolated in vitro eye preparation was established in order to avoid the problem of indirect blood supply to the eye from the dorsal aorta only via the pseudobranch, a hemibranch thought to modulate blood composition before entry of the eye. Any humoral effects (e.g. catecholamines)were eliminated by perfusing isolated eyes successively with standardized red blood cell (RBC) suspensions in Ringer, using trout (with Root) and human(lacking any Root effect) RBC suspension. To optimize perfusate conditions for maximal Root effect, the Root effect of trout RBCs was determined in vitro via graded acidification of individual samples equilibrated with standardized gas mixtures. During perfusion with trout RBC, PO2 at the outer retinal limit was 99 mmHg(13.2 kPa), but fell by a factor of 3.3 upon perfusion with human RBC in spite of higher total oxygen content (TO2 2.8 for trout vs 3.9 mmol l-1 for human RBC). Upon reperfusion with trout RBC, PO2 was restored immediately to the original value. This regularly observed pattern indicated a highly significant difference (P=0.003) between perfusion with trout (with Root effect;high retinal PO2) and perfusion with human (no Root effect; low retinal PO2) RBC suspension,thus clearly demonstrating that the Root effect is directly involved and a crucial prerequisite for the enhancement of PO2in the retina of the teleost eye.
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Affiliation(s)
- W Waser
- Department of Animal Physiology, Humboldt-Universität zu Berlin, 10115 Berlin, Germany.
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Weber RE, Fago A. Functional adaptation and its molecular basis in vertebrate hemoglobins, neuroglobins and cytoglobins. Respir Physiol Neurobiol 2005; 144:141-59. [PMID: 15556098 DOI: 10.1016/j.resp.2004.04.018] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2004] [Indexed: 11/17/2022]
Abstract
Hemoglobin (Hb), the paradigm for allosteric proteins through decades, has gained renaissance in recent years following discovery of globins or their genes in all living organisms and in all tissues of higher animals, and of new members of the globin family, such as neuroglobins, Ngb, found predominantly in neural and nerve tissues and cytoglobins, Cygb, that has unprecedented nuclear location. The recent progresses in this field have been prompted by the development of sophisticated techniques to probe molecular structure and functions, which have revealed novel functions, such as the scavenging and release of vasoactive nitric oxide and the regulation of cellular metabolism. This review deals with the functional adaptations and the underlying molecular mechanisms in globins and presents case examples of molecular adaptations encountered in vertebrates and agnathans.
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Affiliation(s)
- Roy E Weber
- Department of Zoophysiology, Institute of Biological Sciences, University of Aarhus, C.F. Møllers Alle 131, DK-8000 Aarhus C, Denmark.
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Weber RE, Hourdez S, Knowles F, Lallier F. Hemoglobin function in deep-sea and hydrothermal-vent endemic fish: Symenchelis parasitica (Anguillidae) and Thermarces cerberus (Zoarcidae). J Exp Biol 2003; 206:2693-702. [PMID: 12819275 DOI: 10.1242/jeb.00475] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Deep-sea hydrothermal vents probably provide the harshest physico-chemical conditions confronting metazoan animals in nature. Given the absence of information on hemoglobin (Hb) function in hydrothermal-vent vertebrates, and the complex molecular and functional adaptations observed in hydrothermal-vent invertebrates, we investigated the oxygenation reactions of Hbs from the vent-endemic zoarcid Thermarces cerberus and the deep-sea anguillid Symenchelis parasitica from adjacent habitats. Electrophoretically cathodic and anodic isoHbs from S. parasitica exhibit radical differences in O(2) affinity and pH and organic phosphate (ATP) sensitivities, reflecting a division of labor as in other 'class II' fish that express both Hb types. Remarkably, the cathodic Hb (I) lacks chloride sensitivity, and the anodic Hb (II) shows anticooperativity near half-saturation at low temperature. T. cerberus isoHbs exhibit similar affinities and pH sensitivities ('class I' pattern) but much higher O(2) affinities than those observed in Hbs of the temperate, shallow-water zoarcid Zoarces viviparus, which, unless compensated, reveals markedly higher blood O(2) affinities in the former species. The temperature sensitivity of O(2) binding to T. cerberus Hbs and the anodic S. parasitica Hb, which have normal Bohr effects, is decreased by endothermic proton dissociation, which reduces the effects of ambient temperature variations on O(2) affinity. In the cathodic S. parasitica Hb, similar reduction appears to be associated with endothermic conformational changes that accompany the oxygenation reaction.
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Affiliation(s)
- Roy E Weber
- Department of Zoophysiology, C.F. Møllers Alle, Building 131, University of Aarhus, DK 8000 Aarhus C, Denmark.
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Role of deoxyhemoglobin in lipid oxidation of washed cod muscle mediated by trout, poultry and beef hemoglobins. Meat Sci 2002; 62:157-63. [DOI: 10.1016/s0309-1740(01)00242-x] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2001] [Revised: 11/20/2001] [Accepted: 11/20/2001] [Indexed: 11/23/2022]
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Pelster B. The generation of hyperbaric oxygen tensions in fish. NEWS IN PHYSIOLOGICAL SCIENCES : AN INTERNATIONAL JOURNAL OF PHYSIOLOGY PRODUCED JOINTLY BY THE INTERNATIONAL UNION OF PHYSIOLOGICAL SCIENCES AND THE AMERICAN PHYSIOLOGICAL SOCIETY 2001; 16:287-91. [PMID: 11719607 DOI: 10.1152/physiologyonline.2001.16.6.287] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Surprising inventiveness in the molecular interactions in fish hemoglobins that express the Root effect (decreased oxygen-carrying capacity at low pH) and in metabolic adaptations in swim bladder gas gland cells and retinal tissues causes local acidification of blood and generates hyperbaric oxygen tensions that drive oxygen into the swim bladder (regulating buoyancy) and ensures the oxygen supply to the avascularized retinae.
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Affiliation(s)
- B Pelster
- Institut für Zoologie und Limnologie, Universität Innsbruck, A-6020 Innsbruck, Austria
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Tamburrini M, Verde C, Olianas A, Giardina B, Corda M, Sanna MT, Fais A, Deiana AM, di Prisco G, Pellegrini M. The hemoglobin system of the brown moray Gymnothorax unicolor: structure/function relationships. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:4104-11. [PMID: 11454005 DOI: 10.1046/j.1432-1327.2001.02333.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Gymnothorax unicolor hemoglobin system is characterized by two components, called cathodic and anodic on the basis of their isoelectric point, which were separated by ion-exchange chromatography. The oxygen-binding properties of the purified components were studied in the absence and presence of chloride and/or GTP or ATP in the pH range 6.5-8.0. Stripped cathodic hemoglobin showed a small reverse Bohr effect, high oxygen affinity, and low co-operativity; the addition of chloride only caused a small decrease in oxygen affinity. In the presence of GTP or ATP, the oxygen affinity was dramatically reduced, the co-operativity increased, and the reverse Bohr effect abolished. Stripped anodic hemoglobin is characterized by both low oxygen affinity and co-operativity, and displayed a normal Bohr effect; the addition of chloride increased co-operativity, whereas ATP and GTP significantly modulated oxygen affinity at acidic pH values, enhancing the Bohr effect and giving rise to the Root effect. The complete amino-acid sequences of the alpha and beta chains of both hemoglobins were established; the molecular basis of the functional properties of the hemoglobins is discussed in the light of the primary structure and compared with those of other fish hemoglobins.
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Affiliation(s)
- M Tamburrini
- Institute of Protein Biochemistry and Enzymology, CNR, Naples, Italy
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Hourdez S, Lallier FH, De Cian MC, Green BN, Weber RE, Toulmond A. Gas transfer system in Alvinella pompejana (Annelida polychaeta, Terebellida): functional properties of intracellular and extracellular hemoglobins. Physiol Biochem Zool 2000; 73:365-73. [PMID: 10893176 DOI: 10.1086/316755] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2000] [Indexed: 11/03/2022]
Abstract
Alvinella pompejana is a tubicolous polychaete that dwells in the hottest part of the hydrothermal vent ecosystem in a highly variable mixture of vent (350 degrees C, anoxic, CO(2)- and sulfide-rich) and deep-sea (2 degrees C, mildly hypoxic) waters. This species has developed distinct-and specifically respiratory-adaptations to this challenging environment. An internal gas exchange system has recently been described, along with the report of an intracellular coelomic hemoglobin, in addition to the previously known extracellular vascular hemoglobin. This article reports the structure of coelomic hemoglobin and the functional properties of both hemoglobins in order to assess possible oxygen transfer. Coelomocytes contain a unique monomeric hemoglobin with a molecular weight of 14,810+/-1.5 Da, as determined by mass spectrometry. The functional properties of both hemoglobins are unexpectedly very similar under the same conditions of pH (6.1-8.2) and temperature (10 degrees -40 degrees C). The oxygen affinity of both proteins is relatively high (P50=0.66 Torr at 20 degrees C and pH 7), which facilitates oxygen uptake from the hypoxic environment. A strong Bohr effect (Phi ranging from -0.8 to -1.0) allows the release of oxygen to acidic tissues. Such similar properties imply a possible bidirectional transfer of oxygen between the two hemoglobins in the perioesophagal pouch, a mechanism that could moderate environmental variations of oxygen concentration and maintain brain oxygenation.
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Affiliation(s)
- S Hourdez
- Station Biologique de Roscoff, UPMC-Centre National de la Recherche Scientifique-INSU, BP 74, 29682 Roscoff Cedex, France.
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Würtz J, Salvenmoser W, Pelster B. Localization of carbonic anhydrase in swimbladder of European eel (Anguilla anguilla) and perch (Perca fluviatilis). ACTA PHYSIOLOGICA SCANDINAVICA 1999; 165:219-24. [PMID: 10090334 DOI: 10.1046/j.1365-201x.1999.00501.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The distribution of carbonic anhydrase in swimbladder tissue and especially in gas gland cells of the European eel (Anguilla anguilla) and the perch (Perca fluviatilis) was analysed using histochemical staining according to Hansson (1967), with modifications proposed by Riddersträle (1991). While in the European eel, gas gland cells are distributed as a single layered epithelium over the whole secretory part of the swimbladder, the gas gland of the perch consists of a compact, richly vascularized 'multilayered' epithelium, in which gas gland cells have contact with the swimbladder lumen via small channels. In spite of these differences in organization, membranes of gas gland cells near blood vessels are richly folded in both species. A strong histochemical staining for carbonic anhydrase was observed in these membrane foldings. With prolonged incubation times a positive reaction was also observed in the cytoplasm of gas gland cells. In addition, the vascular endothelium and the erythrocytes showed a positive histochemical reaction. No staining, however, was visible in apical membranes towards the lumen of the swimbladder. In the perch, swimbladder epithelial cells outside the gas gland showed no positive staining of carbonic anhydrase. The results thus indicate that carbonic anhydrase activity is especially concentrated in membranes facing blood vessels. This suggests that a rapid equilibrium of the CO2/HCO3- reaction in the intracellular as well as in the extracellular space is essential for swimbladder function.
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Affiliation(s)
- J Würtz
- Institut für Zoologie und Limnologie, Universität Innsbruck, Austria
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The Physiology of the Root Effect. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1546-5098(08)60260-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Pelster B, Burggren WW. Disruption of hemoglobin oxygen transport does not impact oxygen-dependent physiological processes in developing embryos of zebra fish (Danio rerio). Circ Res 1996; 79:358-62. [PMID: 8756015 DOI: 10.1161/01.res.79.2.358] [Citation(s) in RCA: 217] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Embryonic hemoglobin circulated by the developing heart in the early vertebrate embryo is widely assumed (without substantiation) to perform the same vital role of O2 carriage that it does in fetuses and adults. In order to challenge this assumption, we measured highly O2-dependent physiological variables like O2 consumption, cardiac performance, and initial swim bladder filling in the presence and absence of functional hemoglobin in the embryos and early larvae of the zebra fish, Danio ( = Brachydanio) rerio. Functional ablation of hemoglobin by carbon monoxide or phenylhydrazine did not reduce whole-animal O2 consumption, which was approximately 85 to 90 mumol.g-1.h-1. Similarly, no differences in heart variables like ventricular pressure development or heart rate, which increased from 135 to 175 bpm between stages 36h and 96h (indicating developmental stages 36 and 96 hours after fertilization, respectively), were observed in these experiments. Initial opening of the swim bladder was not influenced in the presence of CO-occupied hemoglobin but was significantly impaired when the embryonic hemoglobin was chemically modified by incubation with phenylhydrazine. That aerobic processes continue without hemoglobin O2 transport indicates the adequacy in the embryo of simple O2 diffusion alone even in developmental stages with extensive convective blood circulation generated by the heart.
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Affiliation(s)
- B Pelster
- Institut für Zoologie und Limnologie, Leopold-Franzens-Universität, Innsbruck, Austria
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Pelster B, Scheid P. Gegenstromkonzentrierung in der Schwimmblase Die Erzeugung hoher Gaspartialdr�cke durch das Zusammenspiel von zellul�rem Stoffwechsel und Organdurchblutung. Naturwissenschaften 1994. [DOI: 10.1007/bf01132678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Pelster B, Scheid P, Reeves RB. Kinetics of the Root effect and of O2 exchange in whole blood of the eel. RESPIRATION PHYSIOLOGY 1992; 90:341-9. [PMID: 1480844 DOI: 10.1016/0034-5687(92)90113-b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Oxygen transfer kinetics in blood of the eel (Anguilla rostrata, A. anguilla) were measured spectrophotometrically in thin blood layers covered by Gore-Tex membranes, which allowed fast changes of the gas phase at the blood surface (Heidelberger and Reeves, 1990 J. Appl. Physiol. 68: 1854-1864). The following main results were obtained for A. rostrata (similar values were measured for A. anguilla): (1) step change in PO2 of the gas phase between 0 and 37 kPa at low PCO2 (0.19 kPa, blood pH, 8.1; 20 degrees C) yielded mean half times (t(on)) for O2 uptake of 7.1 msec, and for O2 release (t(off)), of 42.8 msec. Similar values were obtained at high PCO2 (19 kPa; blood pH, 6.9), indicating O2 kinetics to be independent of pH and PCO2; (2) decreasing the high PO2 from 37 to 14 kPa significantly prolonged oxygen uptake kinetics, but release kinetics were unaltered; (3) changing PCO2 from 0.19 to 19 kPa at constant high PO2 (37 kPa) resulted in a reduction of hemoglobin oxygen saturation (SO2) (Root-off reaction), with t(off) averaging 44.8 msec; likewise, changing PCO2 from 19 to 0.19 kPa increased SO2 with t(on) averaging 64.8 msec (Root-on reaction). As these half times comprise reactions at the hemoglobin molecule and conversion between CO2 and H(+)/HCO3-, the Root effect kinetics of the hemoglobin molecule appear to be even faster. It is concluded that the O2 exchange kinetics of eel blood are comparable with those of human blood.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B Pelster
- Institut für Physiologie, Ruhr-Universität Bochum, FRG
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