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  Subjects -> BIOLOGY (Total: 2982 journals)
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BIOCHEMISTRY (231 journals)                  1 2 | Last

Showing 1 - 200 of 231 Journals sorted alphabetically
AAPS PharmSciTech     Hybrid Journal   (Followers: 5)
Acetic Acid Bacteria     Open Access   (Followers: 2)
ACS Central Science     Open Access   (Followers: 6)
ACS Chemical Biology     Full-text available via subscription   (Followers: 225)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
Acta Crystallographica Section D : Biological Crystallography     Hybrid Journal   (Followers: 8)
Acta Crystallographica Section F: Structural Biology Communications     Hybrid Journal   (Followers: 7)
Advances and Applications in Bioinformatics and Chemistry     Open Access   (Followers: 9)
Advances in Biological Chemistry     Open Access   (Followers: 7)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18)
African Journal of Biochemistry Research     Open Access   (Followers: 1)
African Journal of Chemical Education     Open Access   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
American Journal of Biochemistry     Open Access   (Followers: 8)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 66)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Polymer Science     Open Access   (Followers: 25)
Amino Acids     Hybrid Journal   (Followers: 7)
Analytical Biochemistry     Hybrid Journal   (Followers: 156)
Angiogenesis     Hybrid Journal   (Followers: 3)
Annals of Clinical Biochemistry     Hybrid Journal   (Followers: 7)
Annual Review of Biochemistry     Full-text available via subscription   (Followers: 52)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Applied Biochemistry and Biotechnology     Hybrid Journal   (Followers: 44)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 17)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 6)
Archives of Biochemistry and Biophysics     Hybrid Journal   (Followers: 20)
Archives of Insect Biochemistry and Physiology     Hybrid Journal  
Archives Of Physiology And Biochemistry     Hybrid Journal   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Avicenna Journal of Medical Biochemistry     Open Access  
Bangladesh Journal of Medical Biochemistry     Open Access   (Followers: 2)
BBA Clinical     Open Access  
BBR : Biochemistry and Biotechnology Reports     Open Access   (Followers: 4)
Biocatalysis     Open Access  
Biochemical and Biophysical Research Communications     Hybrid Journal   (Followers: 21)
Biochemical and Molecular Medicine     Full-text available via subscription   (Followers: 4)
Biochemical Compounds     Open Access  
Biochemical Engineering Journal     Hybrid Journal   (Followers: 15)
Biochemical Genetics     Hybrid Journal   (Followers: 3)
Biochemical Journal     Full-text available via subscription   (Followers: 25)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemical Society Transactions     Full-text available via subscription   (Followers: 4)
Biochemical Systematics and Ecology     Hybrid Journal   (Followers: 3)
Biochemistry     Full-text available via subscription   (Followers: 274)
Biochemistry & Pharmacology : Open Access     Open Access   (Followers: 3)
Biochemistry & Physiology : Open Access     Open Access  
Biochemistry (Moscow)     Hybrid Journal   (Followers: 4)
Biochemistry (Moscow) Supplement Series A: Membrane and Cell Biology     Hybrid Journal   (Followers: 3)
Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry     Hybrid Journal   (Followers: 3)
Biochemistry and Biophysics Reports     Open Access  
Biochemistry and Cell Biology     Full-text available via subscription   (Followers: 14)
Biochemistry and Molecular Biology Education     Hybrid Journal   (Followers: 6)
Biochemistry and Molecular Biology of Fishes     Full-text available via subscription   (Followers: 1)
Biochemistry Research International     Open Access   (Followers: 6)
Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids     Hybrid Journal   (Followers: 7)
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease     Hybrid Journal   (Followers: 14)
Biochimica et Biophysica Acta (BBA) - Molecular Cell Research     Hybrid Journal   (Followers: 8)
Biochimie     Hybrid Journal   (Followers: 7)
Biochimie Open     Open Access  
Bioconjugate Chemistry     Full-text available via subscription   (Followers: 29)
BioDrugs     Full-text available via subscription   (Followers: 7)
Bioelectrochemistry     Hybrid Journal   (Followers: 2)
Biofuels     Hybrid Journal   (Followers: 10)
Biogeochemistry     Hybrid Journal   (Followers: 13)
BioInorganic Reaction Mechanisms     Hybrid Journal   (Followers: 1)
Biokemistri     Open Access  
Biological Chemistry     Partially Free   (Followers: 23)
Biomaterials Research     Open Access   (Followers: 4)
Biomedicines     Open Access   (Followers: 1)
BioMolecular Concepts     Hybrid Journal   (Followers: 2)
Bioscience, Biotechnology, and Biochemistry     Hybrid Journal   (Followers: 24)
Biosimilars     Open Access   (Followers: 1)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 45)
Bitácora Digital     Open Access  
BMC Biochemistry     Open Access   (Followers: 14)
Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca : Food Science and Technology     Open Access  
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Cell Biochemistry and Biophysics     Hybrid Journal   (Followers: 6)
Cell Biochemistry and Function     Hybrid Journal   (Followers: 6)
Cellular Physiology and Biochemistry     Open Access   (Followers: 3)
ChemBioChem     Hybrid Journal   (Followers: 6)
Chemical and Biological Technologies for Agriculture     Open Access  
Chemical Biology & Drug Design     Hybrid Journal   (Followers: 20)
Chemical Engineering Journal     Hybrid Journal   (Followers: 33)
Chemical Senses     Hybrid Journal   (Followers: 1)
Chemical Speciation and Bioavailability     Open Access   (Followers: 1)
Chemico-Biological Interactions     Hybrid Journal   (Followers: 3)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry and Ecology     Hybrid Journal  
ChemTexts     Hybrid Journal  
Clinica Chimica Acta     Hybrid Journal   (Followers: 33)
Clinical Biochemist Reviews     Full-text available via subscription   (Followers: 1)
Clinical Biochemistry     Hybrid Journal   (Followers: 18)
Clinical Chemistry     Full-text available via subscription   (Followers: 67)
Clinical Chemistry and Laboratory Medicine     Hybrid Journal   (Followers: 59)
Clinical Lipidology     Full-text available via subscription   (Followers: 1)
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology     Hybrid Journal   (Followers: 5)
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 2)
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology     Hybrid Journal   (Followers: 8)
Comparative Biochemistry and Physiology Part D: Genomics and Proteomics     Hybrid Journal   (Followers: 3)
Comprehensive Biochemistry     Full-text available via subscription   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Current Chemical Biology     Hybrid Journal   (Followers: 2)
Current Medicinal Chemistry     Hybrid Journal   (Followers: 15)
Current Opinion in Chemical Biology     Hybrid Journal   (Followers: 26)
Current Opinion in Lipidology     Hybrid Journal   (Followers: 6)
DNA Barcodes     Open Access  
Doklady Biochemistry and Biophysics     Hybrid Journal   (Followers: 1)
Doklady Chemistry     Hybrid Journal  
Egyptian Journal of Biochemistry and Molecular Biology     Full-text available via subscription  
FABICIB     Open Access  
FEBS Letters     Hybrid Journal   (Followers: 55)
FEBS Open Bio     Open Access   (Followers: 3)
Fish Physiology and Biochemistry     Hybrid Journal   (Followers: 4)
Food & Function     Full-text available via subscription   (Followers: 5)
Foundations of Modern Biochemistry     Full-text available via subscription  
Free Radicals and Antioxidants     Full-text available via subscription   (Followers: 4)
Frontiers in Molecular Biosciences     Open Access   (Followers: 2)
Frontiers in Natural Product Chemistry     Hybrid Journal  
Global Biogeochemical Cycles     Full-text available via subscription   (Followers: 15)
Green Chemistry     Full-text available via subscription   (Followers: 9)
Histochemistry and Cell Biology     Hybrid Journal   (Followers: 4)
Indian Journal of Biochemistry and Biophysics (IJBB)     Open Access   (Followers: 3)
Indian Journal of Clinical Biochemistry     Hybrid Journal   (Followers: 1)
Indonesian Biomedical Journal     Open Access  
Insect Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 3)
International Journal of Biochemistry & Cell Biology     Hybrid Journal   (Followers: 8)
International Journal of Biochemistry and Biophysics     Open Access   (Followers: 1)
International Journal of Biological Chemistry     Open Access   (Followers: 4)
International Journal of Biomedical Nanoscience and Nanotechnology     Hybrid Journal   (Followers: 6)
International Journal of Food Contamination     Open Access  
International Journal of Plant Physiology and Biochemistry     Open Access   (Followers: 1)
International Journal of Plant Research     Open Access   (Followers: 3)
International Journal of Secondary Metabolite     Open Access   (Followers: 1)
Invertebrate Immunity     Open Access   (Followers: 1)
JBIC Journal of Biological Inorganic Chemistry     Hybrid Journal   (Followers: 5)
Journal of Microbial & Biochemical Technology     Open Access   (Followers: 2)
Journal of Applied Biology & Biotechnology     Open Access   (Followers: 2)
Journal of Bioactive and Compatible Polymers     Hybrid Journal   (Followers: 2)
Journal of Biochemistry     Hybrid Journal   (Followers: 44)
Journal of Biological Chemistry     Full-text available via subscription   (Followers: 189)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Carbohydrate Chemistry     Hybrid Journal   (Followers: 7)
Journal of Cellular Biochemistry     Hybrid Journal   (Followers: 5)
Journal of Chemical Biology     Hybrid Journal   (Followers: 1)
Journal of Chemical Neuroanatomy     Hybrid Journal  
Journal of Clinical Lipidology     Hybrid Journal   (Followers: 1)
Journal of Comparative Physiology B : Biochemical, Systemic, and Environmental Physiology     Hybrid Journal   (Followers: 4)
Journal of Drug Discovery and Therapeutics     Open Access  
Journal of Enzyme Inhibition and Medicinal Chemistry     Hybrid Journal   (Followers: 3)
Journal of Evolutionary Biochemistry and Physiology     Hybrid Journal  
Journal of Food and Drug Analysis     Open Access  
Journal of Forensic Toxicology and Pharmacology     Hybrid Journal   (Followers: 3)
Journal of Inborn Errors of Metabolism and Screening     Open Access  
Journal of Inorganic Biochemistry     Hybrid Journal   (Followers: 6)
Journal of Medical and Biomedical Sciences     Open Access  
Journal of Medical Biochemistry     Open Access   (Followers: 4)
Journal of Medicine and Biomedical Research     Open Access   (Followers: 1)
Journal of Molecular Biochemistry     Open Access   (Followers: 3)
Journal of Molecular Diagnostics     Hybrid Journal   (Followers: 7)
Journal of Neurochemistry     Hybrid Journal   (Followers: 3)
Journal of Nutritional Biochemistry     Hybrid Journal   (Followers: 7)
Journal of Pediatric Biochemistry     Hybrid Journal   (Followers: 1)
Journal of Peptide Science     Hybrid Journal   (Followers: 22)
Journal of Photochemistry and Photobiology B: Biology     Hybrid Journal   (Followers: 3)
Journal of Physiobiochemical Metabolism     Hybrid Journal   (Followers: 1)
Journal of Physiology and Biochemistry     Hybrid Journal   (Followers: 3)
Journal of Plant Biochemistry and Biotechnology     Hybrid Journal   (Followers: 6)
Journal of Steroid Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 2)
Journal of Virology & Antiviral Research     Hybrid Journal   (Followers: 5)
Journal of Wood Chemistry and Technology     Hybrid Journal   (Followers: 7)
La Rivista Italiana della Medicina di Laboratorio - Italian Journal of Laboratory Medicine     Hybrid Journal  
Lab on a Chip     Full-text available via subscription   (Followers: 34)
Marine Chemistry     Hybrid Journal   (Followers: 6)
Methods in Enzymology     Full-text available via subscription   (Followers: 11)
Molecular and Biochemical Parasitology     Hybrid Journal   (Followers: 2)
Molecular and Cellular Biochemistry     Hybrid Journal   (Followers: 6)
Molecular Aspects of Medicine     Hybrid Journal   (Followers: 2)
Molecular Informatics     Hybrid Journal   (Followers: 6)
Molecular inhibitors in targeted therapy     Open Access  
Moscow University Chemistry Bulletin     Hybrid Journal   (Followers: 1)
Mycology : An International Journal on Fungal Biology     Hybrid Journal   (Followers: 5)
Natural Products and Bioprospecting     Open Access   (Followers: 2)
Nature Chemical Biology     Full-text available via subscription   (Followers: 71)
Nature Communications     Open Access   (Followers: 166)
Neurosignals     Open Access  
NOVA     Open Access  
Novelty in Biomedicine     Open Access  
OA Biochemistry     Open Access   (Followers: 1)
OA Inflammation     Open Access  
Ocean Acidification     Open Access   (Followers: 3)
Organic & Biomolecular Chemistry     Full-text available via subscription   (Followers: 87)
Peptidomics     Open Access  
Pesticide Biochemistry and Physiology     Hybrid Journal   (Followers: 4)
Pflugers Archiv European Journal of Physiology     Hybrid Journal   (Followers: 3)

        1 2 | Last

Journal Cover Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  [SJR: 0.939]   [H-I: 84]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1095-6433
   Published by Elsevier Homepage  [3031 journals]
  • Aquaporin in different moult stages of a freshwater decapod crustacean:
           expression and participation in muscle hydration control
    • Abstract: Publication date: Available online 9 March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Kamila Foguesatto, Robert T. Boyle, Monique T. Rovani, Carolina A. Freire, Marta M. Souza
      Crustaceans, during their moult cycle, at the stages of both pre-moult and post-moult, need water uptake. This movement of water creates a challenge for the regulation of cell volume. The cells of freshwater decapods require a high regulatory capacity to deal with hyposmotic stresses, given the need to face dilution of the haemolymph during their moult cycles. This study investigated the variation in the expression of water channels (aquaporins) along the moult cycle of a freshwater palaemonid shrimp, focusing on their role in cell volume regulation. Moults in Palaemonetes argentinus have been investigated along three stages of its moult cycle: intermoult, late pre-moult and recent post-moult. For the evaluation of tissue volume regulation, the weight of isolatedmuscle, subjected to isosmotic and hyposmotic salines, was followed for 60min. The expression of AQP during the different moult stages was evaluated by immunocytochemistry. Muscle from the three moult stages in isosmotic conditions showed the same pattern of tissue volume regulation. When muscle from animals in pre-moult and intermoult were submitted to hyposmotic stress they swell, followed by volume regulation, while in post-moult the regulation is compromised. The difference in volume regulatory control between pre-moult and post-moult may be related to a possible regulation of water channels, as AQP expression was equal at these stages. This study presents novel findings for crustaceans in general, in the demonstration that AQP expression changes during the moult cycle of a decapod crustacean, together with the regulation of cell volume with the participation of AQPs.

      PubDate: 2017-03-09T08:42:14Z
       
  • Hypoxia during embryonic development increases energy metabolism in
           normoxic juvenile chicks
    • Abstract: Publication date: Available online 7 March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Lara do Amaral-Silva, Carolina da S. Scarpellini, Paula Andrea Toro-Velasquez, Marcia H.M.R. Fernandes, Luciane H. Gargaglioni, Kênia C. Bícego
      Environmental changes during perinatal development can affect the postnatal life. In this sense, chicken embryos that experience low levels of O2 over a specific phase of incubation can have their tissue growth reduced and the ventilatory response to hypoxia blunted, at least until hatching. Additionally, exposure to low level of O2 after birth reduces the thermogenesis as well. In the present study, we tested the hypothesis that hypoxia over the third week of incubation affects the thermoregulation of juvenile chicks at an age when thermogenesis is already expected to be well-developed. To this end, we measured body temperature (Tb) and oxygen consumption ( V ̇ 0 2 ) under acute hypoxia or different ambient temperatures (Ta) of 1 and 10day-old chicks that have been exposed to 21% O2 for entire incubation (Nx) or to 15% O2 in the last week of incubation (Hx). We also assessed the thermal preference under normoxia or acute hypoxia of the older chicks from both incubation groups in a thermocline. Hypoxia over incubation reduced growth but did not affect the cold-induced thermogenesis in hatchlings. Regarding the juvenile Hx, present data indicate a catch up growth with higher resting V ̇ 0 2 , a thermal preference for warmer Tas and a possible higher thermal conductance. In conclusion, our results show that hypoxia over the third week of incubation can affect the thermoregulation at least until 10days after hatch in chickens.

      PubDate: 2017-03-09T08:42:14Z
       
  • The energetic, physiological, and behavioral response of lemon sharks
           (Negaprion brevirostris) to simulated longline capture
    • Abstract: Publication date: May 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 207
      Author(s): Ian A. Bouyoucos, Cory D. Suski, John W. Mandelman, Edward J. Brooks
      Commercial fisheries bycatch is a considerable threat to elasmobranch population recovery, and techniques to mitigate sub-lethal consequences can be improved with data on the energetic, physiological, and behavioral response of individuals to capture. This study sought to estimate the effects of simulated longline capture on the behavior, energy use, and physiological stress of juvenile lemon sharks (Negaprion brevirostris). Captive sharks equipped with acceleration biologgers were subjected to 1h of simulated longline capture. Swimming behaviors were identified from acceleration data using a machine-learning algorithm, energetic costs were estimated using accelerometer-calibrated relationships and respirometry, and physiological stress was quantified with point-of-care blood analyzers. During capture, sharks exhibited nine-fold increases in the frequency of burst swimming, 98% reductions in resting, and swam as often as unrestrained sharks. Aerobic metabolic rates during capture were 8% higher than for unrestrained sharks, and accounted for a 57.7% increase in activity costs when excess post-exercise oxygen consumption was included. Lastly, sharks exhibited significant increases in blood lactate and glucose, but no change in blood pH after 1h of capture. Therefore, these results provide preliminary insight into the behavioral and energetic responses of sharks to capture, and have implications for mitigating sub-lethal consequences of capture for sharks as commercial longline bycatch.

      PubDate: 2017-03-03T06:11:06Z
       
  • High rates of intestinal bicarbonate secretion in seawater tilapia
           (Oreochromis mossambicus)
    • Abstract: Publication date: May 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 207
      Author(s): I. Ruiz-Jarabo, S.F. Gregório, P. Gaetano, F. Trischitta, J. Fuentes
      Osmoregulation in fish is a complex process that requires the orchestrated cooperation of many tissues. In fish facing hyperosmotic environments, the intestinal absorption of some monovalent ions and the secretion of bicarbonate are key processes to favor water absorption. In the present study, we showed that bicarbonate levels in the intestinal fluid are several fold higher in seawater than in freshwater acclimated tilapia (Oreochromis mossambicus). In addition, we analyzed gene expression of the main molecular mechanisms involved in HCO3 – movements i.e. slc26a6, slc26a3, slc4a4 and v-type H-ATPase sub C in the intestine of tilapia acclimated to both seawater and freshwater. Our results show an anterior/posterior functional regionalization of the intestine in tilapia in terms of expression patterns, which is affected by environmental salinity mostly in the anterior and mid intestine. Analysis of bicarbonate secretion using pH-Stat in tissues mounted in Ussing chambers reveals high rates of bicarbonate secretion in tilapia acclimated to seawater from anterior intestine to rectum ranging between ~900 and ~1700nmolHCO3 – cm−2 h−1. However, a relationship between the expression of slc26a6, slc26a3, slc4a4 and the rate of bicarbonate secretion seems to be compromised in the rectum. In this region, the low expression of the bicarbonate transporters could not explain the high bicarbonate secretion rates here described. However, we postulate that the elevated v-type H-ATPase mRNA expression in the rectum could be involved in this process.

      PubDate: 2017-03-03T06:11:06Z
       
  • Effects of continuous white light and 12h white-12h blue light-cycles on
           the expression of clock genes in diencephalon, liver, and skeletal muscle
           in chicks
    • Abstract: Publication date: May 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 207
      Author(s): Kazuhisa Honda, Makoto Kondo, Daichi Hiramoto, Takaoki Saneyasu, Hiroshi Kamisoyama
      The core circadian clock mechanism relies on a feedback loop comprised of clock genes, such as the brain and muscle Arnt-like 1 (Bmal1), chriptochrome 1 (Cry1), and period 3 (Per3). Exposure to the light-dark cycle synchronizes the master circadian clock in the brain, and which then synchronizes circadian clocks in peripheral tissues. Birds have long been used as a model for the investigation of circadian rhythm in human neurobiology. In the present study, we examined the effects of continuous light and the combination of white and blue light on the expression of clock genes (Bmal1, Cry1, and Per3) in the central and peripheral tissues in chicks. Seventy two day-old male chicks were weighed, allocated to three groups and maintained under three light schedules: 12h white light-12h dark-cycles group (control); 24h white light group (WW group); 12h white light-12h blue light-cycles group (WB group). The mRNA levels of clock genes in the diencephalon were significantly different between the control and WW groups. On the other hand, the alteration in the mRNA levels of clock genes was similar between the control and WB groups. Similar phenomena were observed in the liver and skeletal muscle (biceps femoris). These results suggest that 12h white-12h blue light-cycles did not disrupt the circadian rhythm of clock gene expression in chicks.

      PubDate: 2017-03-03T06:11:06Z
       
  • Effects of aerial hypoxia and temperature on pulmonary breathing pattern
           and gas exchange in the South American lungfish, Lepidosiren paradoxa
    • Abstract: Publication date: Available online 3 March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Glauber S.F. da Silva, Daniela A.D.N. Ventura, Lucas A. Zena, Humberto Giusti, Mogens L. Glass, Wilfried Klein
      The South American lungfish Lepidosiren paradoxa is an obligatory air-breathing fish possessing well-developed bilateral lungs, and undergoing seasonal changes in its habitat, including temperature changes. In the present study we aimed to evaluate gas exchange and pulmonary breathing pattern in L. paradoxa at different temperatures (25 and 30°C) and different inspired O2 levels (21, 12, 10, and 7%). Normoxic breathing pattern consisted of isolated ventilatory cycles composed of an expiration followed by 2.4±0.2 buccal inspirations. Both expiratory and inspiratory tidal volumes reached a maximum of about 35ml.kg−1, indicating that L. paradoxa is able to exchange nearly all of its lung air in a single ventilatory cycle. At both temperatures, hypoxia caused a significant increase in pulmonary ventilation ( V ̇ E ), mainly due to an increase in respiratory frequency. Durations of the ventilatory cycle and expiratory and inspiratory tidal volumes were not significantly affected by hypoxia. Expiratory time (but not inspiratory) was significantly shorter at 30°C and at all O2 levels. While a small change in oxygen consumption ( V ̇ O 2 ) could be noticed, the carbon dioxide release ( V ̇ CO 2 , P =0.0003) and air convection requirement ( V ̇ E / V ̇ O 2 , P =0.0001) were significantly affected by hypoxia (7% O2) at both temperatures, when compared to normoxia, and pulmonary diffusion capacity increased about four-fold due to hypoxic exposure. These data highlight important features of the respiratory system of L. paradoxa, capable of matching O2 demand and supply under different environmental change, as well as help to understand the evolution of air breathing in lungfish.

      PubDate: 2017-03-03T06:11:06Z
       
  • Comparison of whole animal costs of protein synthesis among polar and
           temperate populations of the same species of gammarid amphipod
    • Abstract: Publication date: Available online 2 March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): S.P.S. Rastrick, N.M. Whiteley
      Protein synthesis can account for a substantial proportion of metabolic rate. Energetic costs of protein synthesis, should in theory, be the same in marine invertebrates from a range of thermal habitats, and yet direct measurements using inhibitors produce widely differing values, especially in the cold. The present study aimed to remove any potential confounding interspecific effects by determining costs of protein synthesis in two latitudinally separated populations of the same species (amphipod, Gammarus oceanicus) living in two different thermal regimes; polar vs cold-temperate. Costs of protein synthesis were determined in summer acclimatised G. oceanicus from Svalbard (79°N) at 5°C and from Scotland (58°N) at 13°C. Amphipods were injected with the protein synthesis inhibitor, cycloheximide (CHX), at 9 mmol l−1 in crab saline to give a tissue concentration of 0.05 mg CHX g−1 FW and left for 60 min before the injection of [3H] phenylalanine. After incubation for 120 min (180 min in total from initial injection), both whole-animal rates of oxygen uptake and absolute rates protein synthesis were significantly reduced in CHX-treated amphipods vs controls injected with saline. Both populations exhibited similar costs of protein synthesis of ~7 μmol O2 mg−1 protein which is close to the estimated theoretical minimum for peptide bond formation, and similar to the values obtained in cell-free systems. The study demonstrates that in G. oceanicus, costs of protein synthesis rates were not elevated in the cold but were fixed among polar and cold-temperate populations.

      PubDate: 2017-03-03T06:11:06Z
       
  • Corrigendum to “Usefulness of oxidative stress biomarkers evaluated in
           the snout scraping, serum and peripheral blood cells of Crocodylus
           moreletii from Southeast Campeche for assessment of the toxic impact of
           PAHs, metals and total phenols” (Comp. Biochem. Physiol. A 200C (2016)
           35–46)
    • Abstract: Publication date: Available online 1 March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Ricardo Dzul-Caamal, Abigail Hernández-López, Mauricio Gonzalez-Jáuregui, Sergio E. Padilla, M. Ivan Girón-Pérez, Armando Vega-López


      PubDate: 2017-03-03T06:11:06Z
       
  • Feather corticosterone during non-breeding correlates with multiple
           measures of physiology during subsequent breeding in a migratory seabird
    • Abstract: Publication date: Available online 24 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Graham D. Fairhurst, Louise Champoux, Keith A. Hobson, Jean-François Rail, Jonathan Verreault, Magella Guillemette, William A. Montevecchi, Pauline Brousseau, Catherine Soos
      Carry-over effects in migratory birds are likely mediated by physiological processes that are activated in response to environmental variation. Such processes affect body condition and/or reproductive success, and can include corticosterone (CORT) because this hormone responds to environmental stressors and influences energy balance. Few studies have considered how CORT levels during non-breeding relate to a broader physiological profile during subsequent breeding, and fewer still have considered measures other than body condition. To explore CORT's potential role in carry-over effects, we investigated the relationship between CORT and foraging ecology of northern gannets (Morus bassanus) during the non-breeding period, and tested for associations between these factors and variation in a suite of physiological and biochemical metrics during subsequent breeding. Northern gannets are the largest seabird top predator in the North Atlantic and were among the hardest hit by the Deepwater Horizon oil blowout in the Gulf of Mexico in 2010. We used light-level geolocators to confirm winter origins of individuals in our study. No interrelationships were found among levels of CORT from feathers grown during non-breeding (CORTf) and variation in foraging ecology, measured by stable isotopes of carbon (δ13C) and nitrogen (δ15N) from the same feathers. CORTf was correlated negatively with hematocrit and positively with triglyceride measured during subsequent incubation, and explained more variation in these variables than did body mass during incubation. These findings provide support for the hypothesis that energy management, measured using CORTf, during non-breeding carries over to influence physiological measures other than body condition. Gannets that previously wintered within the Gulf of Mexico in the years following the Deepwater Horizon oil blowout had higher levels of CORTf compared to birds that wintered along the Atlantic coast, suggesting an increased energetic cost associated with visiting the Gulf of Mexico. Our results indicate that CORT during non-breeding is associated with a broader physiological profile during subsequent breeding than previously reported in birds.

      PubDate: 2017-03-03T06:11:06Z
       
  • Erythrocyte heat shock protein responses to chronic (in vivo) and acute
           (in vitro) temperature challenge in diploid and triploid salmonids
    • Abstract: Publication date: April 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 206
      Author(s): Pillai V. Saranyan, Neil W. Ross, Tillmann J. Benfey
      This research investigated how ploidy level (diploid versus triploid) affects the heat shock protein (HSP) response in erythrocytes under different thermal stress regimes, both in vivo and in vitro, in Atlantic salmon (Salmo salar) and brook charr (Salvelinus fontinalis) in order to address the question of why triploids typically have reduced thermal tolerance. A preliminary study confirmed that identical volumes of diploid and triploid erythrocytes (which equates to a smaller number of larger cells for triploids compared to diploids) did not differ in total protein synthesis rates. After chronic (100d) acclimation of fish to 5, 15 and 25°C, triploid erythrocytes had lower HSP70, HSP90, heat shock factor 1 (HSF1) and ubiquitin (free and total) levels than diploids in both species. Furthermore, Atlantic salmon erythrocytes showed significantly higher protein breakdown (based on conjugated ubiquitin levels) in triploids than diploids after acute heat stress in vitro, but no significant difference was detected between ploidies after acute cold stress. These results indicate that: 1) triploid erythrocytes synthesize more total protein per cell than diploids as a result of increased cell size; 2) triploids have sufficient total HSP levels for survival under low stress conditions; and 3) the lower basal titres of HSPs in triploids may be a handicap when combating acute stress. Taken together, this suggests that triploids are limited in their ability to withstand thermal stress because of a reduced ability to maintain proteostasis under stressful conditions.

      PubDate: 2017-02-24T03:18:58Z
       
  • Nitrergic cardiovascular regulation in the African lungfish, Protopterus
           aethiopicus
    • Abstract: Publication date: Available online 17 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Renato Filogonio, William Joyce, Tobias Wang
      As a ubiquitous signaling molecule, nitric oxide (NO) exerts various important effects on the cardiovascular system and is involved in the regulation of vascular tone and myocardial metabolism in vertebrates. Lungfishes are closely related to tetrapods and provide an interesting possibility to understand the transition from water to land. Lungfishes are endowed with both systemic and pulmonary circulations, and their incompletely divided ventricle allows for blood to bypass either circuit. Lungfishes inhabit ephemeral waterbodies that may enforce prolonged aestivation during drought, throughout which nitric oxide synthase (NOS) expression is upregulated. To better understand the physiological relevance of NO on cardiovascular regulation in this transitory group, we measured vascular reactivity to muscarinic agonist acetylcholine, α and β-adrenergic agonists (phenylephrine and isoproterenol, respectively), or the NO donor, sodium nitroprusside (SNP) on four vessel segments—efferent branchial arteries, gill artery, ductus arteriosus and pulmonary artery—from the African lungfish, Protopterus aethiopicus. In a simultaneous study, we measured oxygen consumption and twitch force in myocardial preparations in the presence and absence of an NOS inhibitor (asymmetric dimethylarginine; ADMA). Only the ductus arteriosus vasodilated in response to SNP. Isoproterenol caused vasodilation, whereas acetylcholine and phenylephrine vasoconstricted all vessel segments. NOS inhibition decreased myocardial force relative to oxygen consumption, indicating a lowered efficiency. We provide novel evidence that NO affects the vasculature of lungfish that may be derived from perivascular nitrergic nerves limited to the ductus arteriosus. Our data also suggests that NO exerts a tonic dampening of myocardial oxygen consumption which may be particularly important during aestivation.

      PubDate: 2017-02-24T03:18:58Z
       
  • Significant association of cyp19a promoter methylation with environmental
           factors and gonadal differentiation in olive flounder Paralichthys
           olivaceus
    • Abstract: Publication date: Available online 17 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Zhaofei Fan, Yuxia Zou, Shuang Jiao, Xungang Tan, Zhihao Wu, DongDong Liang, Peijun Zhang, Feng You
      The sex ratio of olive flounder Paralichthys olivaceus is sensitive to temperature or exogenous hormone exposures in the period of gonadal differentiation. Among sex-related genes, cyp19a, encoding cytochrome P450 aromatase,exhibits significant sex-dimorphic expression pattern and plays an important role in fish gonadal differentiation and development. The present study investigated the expression levels and promoter methylation dynamics of cyp19a and its regulators (nr5a2 and nr0b1), and sex-steroid hormone levels during flounder gonadal differentiation under the treatments of high temperature and estradiol-17β (E2). The results showed that levels of flounder cyp19a expression and estradiol-17β were repressed by high temperature treatment during this period. The up-regulation of nr5a2 by E2 treatment may be related to the all-female formation, and up-regulation of nr0b1 by high temperature treatment may be associated with masculinization. Co-transfection assay indicated that nr5a2 and nr0b1 were antagonist regulators of cyp19a. Furthermore, cyp19a promoter exhibited significant demethylation phenomenon at early stage of ovarian differentiation. While, high temperature could repress the demethylation process, resulting in hypermethylation maintenance in cyp19a promoter. The hypermethylation promoter was able to suppress cyp19a expression by blocking the nr5a2-mediated transactivation activity in vitro. The DNA methylation of epigenetic modification in cyp19a promoter might be the vital way linking environmental factors and gonadal differentiation in flounder.

      PubDate: 2017-02-24T03:18:58Z
       
  • Nuclear and membrane progestin receptors in the European eel:
           characterization and expression in vivo through spermatogenesis
    • Abstract: Publication date: Available online 11 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Marina Morini, David S. Peñaranda, María C. Vílchez, Rasoul Nourizadeh-Lillabadi, Anne-Gaëlle Lafont, Sylvie Dufour, Juan F. Asturiano, Finn-Arne Weltzien, Luz Pérez
      Characterization of all the progestin receptor genes (PRs) found in the European eel has been performed. There were five membrane PRs (mPRs): mPRα (alpha), mPRAL1 (alpha-like1), mPRAL2 (alpha-like2), mPRγ (gamma), mPRδ (delta) and two nuclear PRs (nPRs or PGRs): pgr1 and pgr2. In silico studies showed that the C and E(F) domains of Pgr are well conserved among vertebrates whereas the A/B domain is not. Phylogeny and synteny analyses suggest that eel duplicated pgr (pgr1 and pgr2) originated from the teleost-specific third whole genome duplication (3R). mPR phylogeny placed three eel mPRs together with the mPRα clade, being termed mPRα, mPRAL1 and mPRAL2, while the other two eel mPRs clustered with mPRγ and mPRδ clades, respectively. The in vivo study showed differential expression patterns along the brain-pituitary-gonad axis. An increase in nPR transcripts was observed in brain (in pgr1) and pituitary (in pgr1 and pgr2) through the spermatogenesis, from the spermatogonia B/spermatocyte stage to the spermiation stage. In the testis, mPRγ, mPRδ and pgr2 transcripts showed the highest levels in testis with A spermatogonia as dominant germ cell, while the highest mPRα, mPRAL1 and mPRAL2 transcripts were observed in testis from spermiating males, where the dominant germ cell were spermatozoa. Further studies should elucidate the role of both nuclear and membrane progestin receptors on eel spermatogenesis.

      PubDate: 2017-02-17T01:17:39Z
       
  • Molecular cloning, mRNA expression and characterization of membrane-bound
           hemoglobin in oriental river prawn Macrobrachium nipponense
    • Abstract: Publication date: Available online 10 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Shengming Sun, Fujun Xuan, Hongtuo Fu, Jian Zhu, Xianping Ge, Xugan Wu
      Most hemoglobins are respiratory proteins and are ubiquitous in animals, bacteria, fungi, protists, and plants. In this study, we describe a membrane-bound hemoglobin in the oriental river prawn Macrobrachium nipponense (MnHb), which also expresses hemocyanin. MnHb cDNA was cloned using the rapid amplification of cDNA ends (RACE) approach, which afforded a 1201bp gene encoding a 193 amino acid polypeptide. Bioinformatic evaluation suggested MnHb is membrane anchored by N-myristoylation, and immunofluorescence confirmed its location in the membrane of chief cells in the gill. The effect of hypoxia on MnHb expression was investigated, and reverse transcription PCR (RT-PCR) and Western blotting showed that MnHb was expressed almost exclusively in the gill. Quantitative RT-PCR revealed a significant increase in expression after 6h of hypoxia, and levels peaked at 24h due to oxidative stress. Exposure of cultured prawns to the stress inducer H2O2 significantly up-regulated the expression of MnHb in a dose-dependent manner. MnHb may have a role in protecting cell membrane lipids from damage by reactive oxygen species.

      PubDate: 2017-02-11T00:09:51Z
       
  • Molecular cloning, characterization, and temporal expression of the clock
           genes period and timeless in the oriental river prawn Macrobrachium
           nipponense during female reproductive development
    • Abstract: Publication date: Available online 10 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): SuHua Chen, Hui Qiao, HongTuo Fu, Shengming Sun, WenYi Zhang, ShuBo Jin, Yongsheng Gong, Sufei Jiang, Weiyi Xiong, YanWu
      The circadian clock is crucial for sustaining rhythmic biochemical, physiological, and behavioral processes in living creatures. In this study, we isolated and characterized two circadian clock genes in Macrobrachium nipponense, period (Mnper) and timeless (Mntim). The complete Mnper cDNA measures 4283bp in length with an open reading frame encoding 1292 amino acids, including functional domains such as PER-ARNT-SIM (PAS), cytoplasmic localization domain (CLD), TIM interaction site (TIS), and nuclear localization signal (NLS). The deduced Mntim protein comprises1540 amino acids with functional domains such as PER interaction site (PIS), NLS, and CLD. Tissue distribution analyses showed that the two genes were highly expressed in the eyestalk and brain in both males and females, as well as being expressed in the ovary. The expression profiles of Mnper and Mntim were determined in the eyestalk, brain, and ovary under simulated breeding season and non-breeding season conditions. The expression profiles of both Mnper and Mntim appeared to be unaffected in the eyestalk. However, the expression of both genes exhibited significant seasonal variations in the brain, and thus we assumed the brain to be their functional location. The expression profiles under different simulated seasons and the variations during different ovarian stages indicate that both genes might be involved with female reproduction. Especially the mRNA levels in the brain varied greatly during these stages indicating that the clock function in the brain is closely related to ovarian development and female reproduction. And the reproductive roles of clock genes need to be elucidated.

      PubDate: 2017-02-11T00:09:51Z
       
  • The influence of mechanical ventilation on physiological parameters in
           ball pythons (Python regius)
    • Abstract: Publication date: Available online 10 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Sashia L. Jakobsen, Catherine J.A. Williams, Tobias Wang, Mads F. Bertelsen
      Mechanical ventilation is widely recommended for reptiles during anesthesia, and while it is well-known that their low ectothermic metabolism requires much lower ventilation than in mammals, very little is known about the influence of ventilation protocol on the recovery from anesthesia. Here, 15 ball pythons (Python regius) were induced and maintained with isoflurane for 60min at one of three ventilation protocols (30, 125, or 250ml min−1 kg−1 body mass) while an arterial catheter was inserted, and ventilation was then continued on 100% oxygen at the specified rate until voluntary extubation. Mean arterial blood pressure and heart rate (HR) were measured, and arterial blood samples collected at 60, 80, 180min and 12 and 24h after intubation. In all three groups, there was evidence of a metabolic acidosis, and snakes maintained at 30ml min−1 kg−1 experienced an additional respiratory acidosis, while the two other ventilation protocols resulted in normal or low arterial PCO2. In general, normal acid-base status was restored within 12h in all three protocols. HR increased by 143±64% during anesthesia with high mechanical ventilation (250ml/min/kg) in comparison with recovered values. Recovery times after mechanical ventilation at 30, 125, or 250ml min−1 kg−1 were 289±70, 126±16, and 68±7min, respectively. Mild overventilation may result in a faster recovery, and the associated lowering of arterial PCO2 normalised arterial pH in the face of metabolic acidosis.

      PubDate: 2017-02-11T00:09:51Z
       
  • Effects of pinealectomy on the neuroendocrine reproductive system and
           locomotor activity in male European sea bass, Dicentrarchus labrax
    • Abstract: Publication date: Available online 8 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Mairi Cowan, José A. Paullada-Salmerón, José Fernando López-Olmeda, Francisco Javier Sánchez-Vázquez, José A. Muñoz-Cueto
      The seasonally changing photoperiod controls the timing of reproduction in most fish species, however, the transduction of this photoperiodic information to the reproductive axis is still unclear. This study explored the potential role of two candidate neuropeptide systems, gonadotropin-inhibitory hormone (Gnih) and kisspeptin, as mediators between the pineal organ (a principle transducer of photoperiodic information) and reproductive axis in male European sea bass, Dicentrarchus labrax. Two seven-day experiments of pinealectomy (Px) were performed, in March (end of reproductive season) and August (resting season). Effects of Px and season on the brain expression of gnih (sbgnih) and its receptor (sbgnihr), kisspeptins (kiss1, kiss2) and their receptors (kissr2, kissr3) and gonadotropin-releasing hormone (gnrh1, gnrh2, gnrh3) and the main brain receptor (gnrhr-II-2b) genes, plasma melatonin levels and locomotor activity rhythms were examined. Results showed that Px reduced night-time plasma melatonin levels. Gene expression analyses demonstrated a sensitivity of the Gnih system to Px in March, with a reduction in sbgnih in the mid-hindbrain, a region with bilateral connections to the pineal organ. In August, kiss2 levels increased in Px animals but not in controls. Significant differences in expression were observed for diencephalic sbgnih, sbgnihr, kissr3 and tegmental gnrh2 between seasons. Recordings of locomotor activity following surgery revealed a change from light-synchronised to free-running rhythmic behavior. Altogether, the Gnih and Kiss2 sensitivity to Px and seasonal differences observed for Gnih and its receptor, Gnrh2, and the receptor for Kiss2 (Kissr3), suggested they could be mediators involved in the relay between environment and seasonal reproduction.

      PubDate: 2017-02-11T00:09:51Z
       
  • An experimental evaluation of the role of the stress axis in mediating
           predator-prey interactions in wild marine fish
    • Abstract: Publication date: Available online 7 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Michael J. Lawrence, Erika J. Eliason, Jacob W. Brownscombe, Kathleen M. Gilmour, John W. Mandelman, Steven J. Cooke
      The hypothalamic-pituitary-interrenal (HPI) axis, through corticosteroid secretion, is an integral mechanism regulating internal homeostasis when vertebrates are faced with a stressor. However, continued HPI-axis stimulation can produce homeostatic overload, where corticosteroids are detrimental to organismal function. This overload condition may play an important role in mediating predator-prey interactions, because chronically/previously stressed animals may have higher rates of predator-induced mortality. However, the mechanism(s) underlying this observation are unknown. Using fish as models, we hypothesized that chronic stress would increase predation susceptibility owing to a poor physiological state (e.g. homeostatic overload) with corresponding sub-optimal changes in predator-avoidance behaviour. As cortisol is also required in low quantities to help regulate basic metabolic functions in fish, we expected that a glucocorticoid receptor antagonist (GR; e.g. homeostatic failure) may produce similar effects. Schoolmaster snapper (Lutjanus apodus) were given intraperitoneal implants of cocoa butter impregnated with nothing (sham; 5ml/kg body weight (BW)), cortisol (50mg/kg BW) or the GR antagonist RU486 (100mg/kg BW). At 24-h post-implantation, fish were tethered to the seafloor and observed for behavioural metrics associated with predation. Blood samples were collected from a subset of fish to assess the physiological consequences of the implants. Cortisol- and RU486-implanted fish both had significantly higher plasma cortisol concentrations than sham fish, with blood glucose and plasma urea being elevated only in the former. Further, anti-predator behaviours and predation mortality did not differ significantly among treatments. Despite changes in physiological state, predation susceptibility was unaffected, a finding that may reflect the complex relationships linking the physiology and behaviour of an organism as well as potential tethering artefacts.

      PubDate: 2017-02-11T00:09:51Z
       
  • Temperature dependent growth, feeding, nutritional condition and aerobic
           metabolism of juvenile spiny lobster, Sagmariasus verreauxi
    • Abstract: Publication date: Available online 5 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Quinn P. Fitzgibbon, Cedric J. Simon, Gregory G. Smith, Chris G. Carter, Stephen C. Battaglene
      We examined the effects of temperature on the growth, feeding, nutritional condition and aerobic metabolism of juvenile spiny lobster, Sagmariasus verreauxi, in order to determine if temperature acclimated aerobic scope correlates with optimum for growth and to establish the thermal tolerance window for this emerging aquaculture species. Juvenile lobsters (initial weight=10.95±0.47g) were reared (n =7) at temperatures from 11.0 to 28.5°C for 145days. All lobsters survived from 14.5 to 25.0°C while survival was reduced at 11.0°C (86%) and all lobsters died at 28.5°C. Lobster specific growth rate and specific feed consumption displayed a unimodal response with temperature peaking at 21.5°C. Lobster standard, routine and maximum metabolic rates, and aerobic scope all increased exponentially up to maximum non-lethal temperature. Optimum temperature for growth did not correspond to that for maximum aerobic scope suggesting that aerobic scope is not an effective predictor of the thermal optimum of spiny lobsters. Plateauing of specific feed consumption beyond 21.5°C suggests that temperature dependent growth of lobsters is limited by capacity to ingest or digest sufficient food to meet increasing maintenance metabolic demands at high temperatures. The nutritional condition of lobsters was not influenced by temperature and feed conversion ratio was improved at lower temperatures. These findings add to a growing body of evidence questioning the generality of aerobic scope to describe the physiological thermal boundaries of aquatic ectotherms and suggest that feed intake plays a crucial role in regulating performance at thermal extremes.

      PubDate: 2017-02-11T00:09:51Z
       
  • Understanding evolutionary variation in basal metabolic rate: an analysis
           in subterranean rodents
    • Abstract: Publication date: Available online 4 February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Facundo Luna, Hugo Naya, Daniel E. Naya
      Understanding how evolutionary variation in energetic metabolism arises is central to several theories in animal biology. Basal metabolic rate (BMR) –i.e., the minimum rate of energy necessary to maintain thermal homeostasis in endotherms– is a highly informative measure to increase our understanding, because it is determined under highly standardized conditions. In this study we evaluate the relationship between taxa- and mass-independent (residual) BMR and ten environmental factors for 34 subterranean rodent species. Both conventional and phylogenetically informed analyses indicate that ambient temperature is the major determinant of residual BMR, with both variables inversely correlated. By contrast, other environmental factors that have been shown to affect residual BMR in endotherms, such as habitat productivity and rainfall, were not significant predictors of residual BMR in this group of species. Then, the results for subterranean rodents appear to support a central prediction of the obligatory heat model (OHM), which is a mechanistic model aimed to explain the evolution of residual BMR. Specifically, OHM proposes that during the colonization of colder environments, individuals with greater masses of metabolically expensive tissues (and thus with greater BMR) are favored by natural selection due to the link between greater masses of metabolically expensive tissues and physiological capacities. This way, natural selection should establishes a negative correlation between ambient temperature and both internal organ size and residual BMR.

      PubDate: 2017-02-04T23:14:40Z
       
  • Identification of the putative goldfish (Carassius auratus) magnesium
           transporter SLC41a1 and functional regulation in the gill, kidney, and
           intestine in response to dietary and environmental manipulations
    • Abstract: Publication date: Available online 24 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Vladimir Kodzhahinchev, Drago Kovacevic, Carol Bucking
      While magnesium requirements for teleost fish highlight the physiological importance of this cation for homeostasis, little is known regarding the molecular identity of transporters responsible for magnesium absorption or secretion. The recent characterization of the vertebrate magnesium transporter solute carrier 41a1 (SLC41a1) in the kidney of a euryhaline fish has provided a glimpse of possible moieties involved in piscine magnesium regulation. The present study obtained a novel SLC41a1 coding sequence for Carassius auratus and demonstrated ubiquitous expression in all tissues examined. Transcriptional regulation of SLC41a1 in response to dietary and environmental magnesium concentrations was observed across tissues. Specifically, decreased environmental magnesium correlated with decreased expression of SLC41a1 in the intestine, whereas the gill and kidney were unaffected. Dietary magnesium restriction correlated with decreased expression of SLC41a1 in the intestine and gill, while again no effects were detected in the kidney. Finally, elevated dietary magnesium correlated with increased expression of SLC41a1 in the kidney, while expression in the intestine and gill remained stable. Plasma magnesium was maintained in all treatments, and dietary assimilation efficiency increased with decreased dietary magnesium. Consumption of a single meal failed to impact SLC41a1 expression, and transcript abundance remained stable over the course of digestion in all treatments. Transcriptional regulation occurred between 7 and 14days following dietary and environmental manipulations and short-term regulation (e.g. <24h) was not observed. Overall the data supports transcriptional regulation of SLC41a1 reflecting a possible role in magnesium loss or secretion across tissues in fish.

      PubDate: 2017-01-29T22:40:01Z
       
  • An energetic perspective on tissue regeneration: The costs of tail
           autotomy in growing geckos
    • Abstract: Publication date: Available online 24 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Zuzana Starostová, Lumír Gvoždík, Lukáš Kratochvíl
      Tail autotomy is a crucial antipredatory lizard response, which greatly increases individual survival, but at the same time also compromises locomotor performance, sacrifices energy stores and induces a higher burden due to the ensuing response of regenerating the lost body part. The potential costs of tail autotomy include shifts in energy allocation and metabolic rates, especially in juveniles, which invest their energy primarily in somatic growth. We compared the metabolic rates and followed the growth of juvenile males with and without regenerating tails in the Madagascar ground gecko (Paroedura picta), a nocturnal ground-dwelling lizard. Geckos with intact tails and those that were regrowing them grew in snout-vent-length at similar rates for 22weeks after autotomy. Tail regeneration had a negligible influence on body mass-corrected metabolic rate measured at regular intervals throughout the regenerative process. We conclude that fast-growing juveniles under the conditions of unrestricted food can largely compensate for costs of tail loss and regeneration in their somatic growth without a significant impact on the total individual body mass-corrected metabolic rate.

      PubDate: 2017-01-29T22:40:01Z
       
  • Interspecific variation and plasticity in hemoglobin nitrite reductase
           activity and its correlation with oxygen affinity in vertebrates
    • Abstract: Publication date: Available online 18 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Frank B. Jensen, Rasmus A.H. Kolind, Natashia S. Jensen, Gabriella Montesanti, Tobias Wang
      Deoxygenated hemoglobin (Hb) is a nitrite reductase that reduces naturally occurring nitrite to nitric oxide (NO), supplying physiological relevant NO under hypoxic conditions. The nitrite reductase activity is modulated by the allosteric equilibrium between the R and T structures of Hb that also determines oxygen affinity. In the present study we investigated nitrite reductase activity and O2 affinity in Hbs from ten different vertebrate species under identical conditions to disclose interspecific variations and allow an extended test for a correlation between the rate constant for nitrite reduction and O2 affinity. We also tested plastic changes in Hb properties via addition of T-structure-stabilizing organic phosphates (ATP and GTP). The decay in deoxyHb during its reaction with nitrite was exponential-like in ectotherms (Atlantic hagfish, carp, crucian carp, brown trout, rainbow trout, cane toad, Indian python and red-eared slider turtle), while it was sigmoid in mammals (harbor porpoise and rabbit). Typically, hypoxia-tolerant species showed a faster reaction than intolerant species. Addition of ATP and GTP decreased O2 affinity and slowed the rate of nitrite reduction in a concentration-dependent manner. The initial second order rate constant of the deoxyHb-mediated nitrite reduction showed a strong curvilinear correlation with oxygen affinity among all ectothermic vertebrates, and the relationship also applied to plastic variations of Hb properties via organic phosphates. The relationship predicts high nitrite reductase activity in hypoxic tolerant species with high Hb-O2 affinity and reveals that the decrease in erythrocyte ATP and/or GTP during acclimation to hypoxia in ectotherms increases the erythrocyte NO generating capacity.

      PubDate: 2017-01-22T22:01:26Z
       
  • Ex utero Culture of Viviparous Embryos of the Lizard, Zootoca vivipara,
           Provides Insights into Calcium Homeostasis during Development
    • Abstract: Publication date: Available online 18 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Tom W. Ecay, James R. Stewart, Greg Wiessner, Benoit Heulin
      The chorioallantoic membrane resides adjacent to either the inner surface of the egg shell or uterine epithelium in oviparous and viviparous reptiles, respectively. Chorionic cells face the shell or uterine epithelium and transport calcium to underlying embryonic capillaries. Calcium transport activity of the chorioallantois increases in the final stages of development coincident with rapid embryonic growth and skeletal ossification. We excised embryos from viviparous Zootoca vivipara females at a stage prior to significant calcium accumulation and incubated them ex utero with and without calcium to test the hypothesis that chorioallantois calcium transport activity depends on developmental stage and not calcium availability. We measured calcium uptake by monitoring incubation media calcium content and chorioallantois expression of calbindin-D28K, a marker for transcellular calcium transport. The pattern of calcium flux to the media differed by incubation condition. Eggs in 0mM calcium exhibited little variation in calcium gain or loss. For eggs in 2mM calcium, calcium flux to the media was highly variable and was directed inward during the last 3days of the experiment such that embryos gained calcium. Calbindin-D28K expression increased under both incubation conditions but was significantly higher in embryos incubated with 2mM calcium. We conclude that embryos respond to calcium availability, yet significant calcium accumulation is developmental stage dependent. These observations suggest the chorioallantois exhibits a degree of functional plasticity that facilitates response to metabolic or environmental fluctuations.

      PubDate: 2017-01-22T22:01:26Z
       
  • Developmental changes and day-night expression of the
           gonadotropin-inhibitory hormone system in the European sea bass: Effects
           of rearing temperature
    • Abstract: Publication date: Available online 18 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): José A. Paullada-Salmerón, Guillaume Henri Loentgen, Mairi Cowan, María Aliaga-Guerrero, María del Carmen Rendón-Unceta, José A. Muñoz-Cueto
      The role of rearing temperature on fish development, sex differentiation and puberty has been largely addressed, but the impact of water temperature on the ontogeny of the main neuroendocrine systems controlling reproduction has received little attention. Gonadotropin-inhibitory hormone (Gnih) has been shown to act on gonadotropin-releasing hormone (Gnrh) neurons and on the pituitary to inhibit gonadotropin release and synthesis in vertebrates, including sea bass, Dicentrarchus labrax. In the present study we investigated the effects of rearing temperature during the thermosensitive period (5–60days post-fertilization, dpf) on the expression of the Gnih gene (gnih) and its receptor (gnihr). Animals were maintained under two different conditions, low temperature (LT, 15°C) or high temperature (HT, 21°C), throughout the thermosensitive period and sampled from 5 to 360 dpf at mid-light (ML) and mid-dark (MD). Our results showed significant effects of temperature on gnih and gnihr expression during the thermosensitive period, with higher transcript levels under LT condition. Some differences were also evident after the completion of the sex differentiation process. Moreover, we revealed daily variations in the developmental expression of gnih and gnihr, with higher diurnal mRNA levels at early stages (until 25 dpf), and a shift to higher nocturnal expression levels at 300–360 dpf, which corresponded with the beginning of the winter (reproductive season). To the best of our knowledge, this work represents the first study reporting the effects of rearing temperature on the transcription of Gnih system genes, as well as its daily variations during the development of a fish species.

      PubDate: 2017-01-22T22:01:26Z
       
  • Dual estrogenic regulation of the nuclear progestin receptor and
           spermatogonial renewal during gilthead seabream (Sparus aurata)
           spermatogenesis
    • Abstract: Publication date: Available online 15 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): François Chauvigné, Janmejay Parhi, Judith Ollé, Joan Cerdà
      Studies in teleosts suggest that progestins have crucial functions during early spermatogenesis. However, the role of the different progestin receptors in these mechanisms is poorly understood. In this work, we investigated the expression pattern and hormonal regulation of the classical nuclear progestin receptor (Pgr) in the gilthead seabream at three different stages of spermatogenesis: the resting (postspawning) phase, onset of spermatogenesis, and spermiation. Immunolocalization experiments using a seabream specific Pgr antibody revealed that the receptor was expressed in Sertoli and Leydig cells, and also in a subset of spermatogonia type A, throughout spermatogenesis. Short-term treatment of testis explants with 17β-estradiol (E2) increased pgr mRNA expression at all stages, while the progestin 17α,20β-dihydroxy-4-pregnen-3-one (17,20βP) had the opposite effect. At the resting stage, Sertoli cell Pgr expression was positively correlated with the occurrence of proliferating spermatogonia type A in the tubules, and both processes were incremented in vitro by E2 likely through the estrogen receptor alpha (Era) expressed in Sertoli and Leydig cells. In contrast, treatment with 17,20βP downregulated Pgr expression in somatic cells. The androgen 11-ketotestosterone (11-KT) upregulated pgr expression in Leydig cells and promoted the proliferation of mostly spermatogonia type B, but only during spermiation. No relationship between the changes in the cell type-specific expression of the Pgr with the entry into meiosis of germ cells was found. These data suggest a differential steroid regulation of Pgr expression during seabream spermatogenesis and the potential interplay of the E2/Era and 17,20βP/Pgr pathways for the maintenance of spermatogonial renewal rather than entry into meiosis.

      PubDate: 2017-01-15T19:05:24Z
       
  • Glucose, Amino Acids and Fatty Acids Directly Regulate Ghrelin and
           NUCB2/Nesfatin-1 in the Intestine and Hepatopancreas of Goldfish
           (Carassius auratus) In Vitro
    • Abstract: Publication date: Available online 13 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Juan Ignacio Bertucci, Ayelén Melisa Blanco, Luis Fabián Canosa, Suraj Unniappan
      Ghrelin and nesfatin-1 are two peptidyl hormones primarily involved in food intake regulation. We previously reported that the amount of dietary carbohydrates, protein and lipids modulates the expression of these peptides in goldfish in vivo. In the present work, we aimed to characterize the effects of single nutrients on ghrelin and nesfatin-1 in the intestine and hepatopancreas. First, immunolocalization of ghrelin and NUCB2/nesfatin-1 in goldfish hepatopancreas cells was studied by immunohistochemistry. Second, the effects of 2 and 4h-long exposures of cultured intestine and hepatopancreas sections to glucose, L-tryptophan, oleic acid, linolenic acid (LNA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on ghrelin and nesfatin-1 gene and protein expression were studied. Co-localization of ghrelin and NUCB2/nesfatin-1 in the cytoplasm of goldfish hepatocytes was found. Exposure to glucose led to an upregulation of preproghrelin and a downregulation of nucb2/nesfatin-1 in the intestine. L-tryptophan mainly decreased the expression of both peptides in intestine and hepatopancreas. All fatty acids in general downregulated NUCB2/nesfatin-1 in the intestine, but only the longer and highly unsaturated fatty acids inhibit preproghrelin. EPA exposure led to a decrease in preproghrelin, and an increase in nucb2/nesfatin-1 expression in hepatopancreas after 2h. These results show that macronutrients exert a dose- and time-dependent regulation of ghrelin and nesfatin-1 in intestine and hepatopancreas. This study indicates that macronutrients modulate ghrelin and NUCB2/nesfatin-1, and suggests a role for these hormones in the digestive process and nutrient metabolism.

      PubDate: 2017-01-15T19:05:24Z
       
  • Na+/K+-ATPase activity in the anoxic turtle (Trachemys scripta) brain at
           different acclimation temperature
    • Abstract: Publication date: Available online 13 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Jonathan A.W. Stecyk, Anthony P. Farrell, Matti Vornanen
      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; 14 d 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.

      PubDate: 2017-01-15T19:05:24Z
       
  • Molecular characterization and functional analysis of a salmon louse
           (Lepeophtheirus salmonis, Krøyer 1838) heme peroxidase with a potential
           role in extracellular matrixes
    • Abstract: Publication date: Available online 11 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Aina-Cathrine Øvergård, Christiane Eichner, Frank Nilsen, Sussie Dalvin
      Heme peroxidases are the most abundant type of peroxidase catalyzing a H2O2-dependent oxidation of a wide variety of substrates. They are involved in numerous processes like the innate immune response, hormone and prostaglandin synthesis and crosslinking of proteins within extracellular matrixes (ECM) as well as molecules within the cuticle and chorion of arthropods and nematodes. In the present study, a Lepeophtheirus salmonis heme peroxidase (LsHPX) 1 was characterized. Amino acids in the active site of heme peroxidases were conserved, and the predicted protein sequence showed the highest similarity to genes annotated as chorion peroxidases and genes suggested to be involved in cuticle hardening or adhesion. LsHPX1 exhibited a dynamic expression during ontogenesis and during the nauplius molting cycle. Transcripts were localized to muscle cells near the muscle-tendon junction, in nerve tissue especially at neuromuscular junctions, subcuticular epithelium, subepithelial cells facing the hemolymph, exocrine glands within the subepithelial tissue and in isolated cells within the testis. Knock-down of LsHPX1 in nauplius larvae decreased the swimming activity of emerging copepodids. Histological analysis of knock-down animals revealed increased spacing between myofibers and changes in subepithelial and exocrine gland tissue. Considering these results, the potential role of LsHPX1 in crosslinking molecules of salmon louse ECMs is discussed.

      PubDate: 2017-01-15T19:05:24Z
       
  • Different age-dependent performance in Drosophila wild-type Canton-S and
           the white mutant w1118 flies
    • Abstract: Publication date: Available online 10 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Shuang Qiu, Chengfeng Xiao, R Meldrum Robertson
      Aging has significant effects on the locomotor performance of insects including Drosophila. Using a protocol for the high-throughput analysis of fly locomotion in a restricted space, we re-examined age-dependent behavioral characteristics in adult Drosophila. There are multiple important wild-type and background lines including the Canton-S strain and the w1118 strain, which has a null mutation of the white gene. Under standard rearing conditions, we found similar survival curves and median lifespans in Canton-S (50days) and w1118 (54days) strains, however, w1118 flies maintained stable body mass for up to 43days, whereas Canton-S flies gained body mass at young age, followed by a gradual decline. We also tested the behavioral performance of young and old flies. Compared with young w1118 flies (5–10days), old w1118 flies (40–45days) had an increased boundary preference during locomotion in small circular arenas, and increased speed of locomotor recovery from anoxia. Old Canton-S files, however, exhibited unchanged boundary preference and reduced recovery speed from anoxia relative to young flies. In addition, old w1118 flies showed decreased path length per minute and reduced 0.2s path increment compared with young flies, whereas old Canton-S flies displayed the same path length per minute and the same 0.2s path increment compared with young flies. We conclude that age-dependent behavioral and physiological changes differ between Canton-S and w1118 flies. These results illustrate that phenotypic differences between strains can change qualitatively, as well as quantitatively, as the animals age.

      PubDate: 2017-01-15T19:05:24Z
       
  • Salinity alters snakeskin and mesh transcript abundance and permeability
           in midgut and Malpighian tubules of larval mosquito, Aedes aegypti
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Sima Jonusaite, Andrew Donini, Scott P. Kelly
      This study examined the distribution and localization of the septate junction (SJ) proteins snakeskin (Ssk) and mesh in osmoregulatory organs of larval mosquito (Aedes aegypti), as well as their response to altered environmental salt levels. Ssk and mesh transcripts and immunoreactivity were detected in tissues of endodermal origin such as the midgut and Malpighian tubules of A. aegypti larvae, but not in ectodermally derived hindgut and anal papillae. Immunolocalization of Ssk and mesh in the midgut and Malpighian tubules indicated that both proteins are concentrated at regions of cell-cell contact between epithelial cells. Transcript abundance of ssk and mesh was higher in the midgut and Malpighian tubules of brackish water (BW, 30% SW) reared A. aegypti larvae when compared with freshwater (FW) reared animals. Therefore, [3H]polyethylene glycol (MW 400Da, PEG-400) flux was examined across isolated midgut and Malpighian tubule preparations as a measure of their paracellular permeability. It was found that PEG-400 flux was greater across the midgut of BW versus FW larvae while the Malpighian tubules of BW-reared larvae had reduced PEG-400 permeability in conjunction with increased Cl− secretion compared to FW animals. Taken together, data suggest that Ssk and mesh are found in smooth SJs (sSJs) of larval A. aegypti and that their abundance alters in association with changes in epithelial permeability when larvae reside in water of differing salt content. This latter observation suggests that Ssk and mesh play a role in the homeostatic control of salt and water balance in larval A. aegypti.

      PubDate: 2017-01-07T17:51:35Z
       
  • Geographic variation and within-individual correlations of physiological
           stress markers in a widespread reptile, the common garter snake
           (Thamnophis sirtalis)
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Eric J. Gangloff, Amanda M. Sparkman, Kaitlyn G. Holden, Caitlyn J. Corwin, Madeline Topf, Anne M. Bronikowski
      Characterizing the baseline and stress-induced hormonal, metabolite, and immune profiles of wild animals is important to assess the impacts of variable environments, including human-induced landscape changes, on organismal health. Additionally, the extent to which these profiles are coordinated across physiological systems within individuals remains an important question in understanding how stressors can differentially affect aspects of an individual's physiology. Here, we present data from wild populations of the common garter snake (Thamnophis sirtalis) on both baseline and stress-induced biomarkers: plasma corticosterone (CORT) concentration, plasma glucose concentration, and whole blood heterophil:lymphocyte ratio. Using a standardized restraint protocol with individuals from populations in disparate portions of this species' range – the Sierra Nevada Mountains of California and the plains of Iowa – we collected blood plasma samples at nine time points over three days. Both CORT and glucose response curves differed between georegions, with Iowa snakes attaining higher glucose concentration and maintaining elevated CORT and glucose levels for a longer duration. Additionally, both the total amount and proportional increases of CORT and glucose were lower in larger and therefore older snakes, suggesting ontogenetic shifts in stress perception or response. Within-individual correlation among the three physiological indicators was significant at the time of capture, absent after 3h in captivity, and partially restored after 3days in captivity, demonstrating the effect of stress on the relationships among these physiological systems. Together, these results provide further evidence for the great physiological flexibility of ectothermic tetrapods in maintaining homeostasis across a range of factors.

      PubDate: 2017-01-07T17:51:35Z
       
  • Extreme intra-clutch egg size dimorphism is not coupled with corresponding
           differences in antioxidant capacity and stable isotopes between eggs
    • Abstract: Publication date: Available online 4 January 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Maud Poisbleau, Michaël Beaulieu, Nina Dehnhard, Laurent Demongin, Gilles Lepoint, Nicolas Sturaro, Marcel Eens
      Oviparous females need to allocate resources optimally to their eggs in order to maximize their fitness. Among these resources, dietary antioxidants, acquired by females and transferred to the eggs during egg formation, can greatly affect the development and survival of the embryo and chick. In crested penguins, incubation starts after the second and last egg is laid and, as opposed to many other bird species, this egg hatches first, thereby enhancing the survival of the chick. Here, we assessed whether antioxidant and isotopic composition could underlie these differences between eggs within clutches of southern rockhopper penguins (Eudyptes chrysocome chrysocome). The second-laid egg had higher total antioxidant capacity than the first-laid egg, although this was not due to higher antioxidant concentration but to its higher mass. This suggests that resources are allocated by females at a constant rate in both eggs within clutches. Accordingly, we found a strong correlation for isotopic compositions between eggs suggesting that resources were allocated similarly to each egg within the clutch. Overall, we found little evidence for a significant role of antioxidant and isotopic compositions to explain differences in terms of embryo/chick development between eggs in crested penguins. However, since our results suggest a constant rate of antioxidant transfer from females to eggs, limiting the mass of the first-laid egg might represent a strategy for females to spare antioxidant defences and preserve self-maintenance.

      PubDate: 2017-01-07T17:51:35Z
       
  • Effects of seasonal acclimatization on action potentials and sarcolemmal
           K+ currents in roach (Rutilus rutilus) cardiac myocytes
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Ahmed Badr, Minna Hassinen, Mohamed F. El-Sayed, Matti Vornanen
      Temperature sensitivity of electrical excitability is a potential limiting factor for high temperature tolerance of ectotherms. The present study examines whether heat resistance of electrical excitability of cardiac myocytes is modified by seasonal thermal acclimatization in roach (Rutilus rutilus), a eurythermal teleost species. To this end, temperature dependencies of ventricular action potentials (APs), and atrial and ventricular K+ currents were measured from winter-acclimatized (WiR) and summer-acclimatized (SuR) roach. Under patch-clamp recording conditions, ventricular APs could be triggered over a wide range of temperatures (4–43°C) with prominent changes in resting membrane potential (RMP), AP duration and amplitude. In general, APs of SuR were slightly more tolerant to high temperatures than those of WiR, e.g. the break point temperature (T BP) of RMP was 37.6±0.4°C in WiR and 41±1°C in SuR (p<0.05). Of the two major cardiac K+ currents, the inward rectifier K+ current (IK1) was particularly heat resistant in both SuR (T BP 39.4±0.4°C) and WiR (T BP 40.0±0.4°C) ventricular myocytes. The delayed rectifier K+ current (IKr) was not as heat resistant as IK1. Surprisingly, IKr of WiR tolerated heat better (T BP 31.9±0.8°C) than IKr of SuR (T BP 24.1±0.5°C) (p<0.05). IKr (Erg2) channel transcripts of both atrial and ventricular myocytes were up-regulated in WiR. IK1 (Kir2) channel transcripts were not affected by seasonal acclimatization, although ventricular IK1 current was up-regulated in summer. Collectively, these findings show that thermal tolerance limits of K+ currents in isolated myocytes between seasonally acclimatized roach are much less pronounced than the heat sensitivity of ECG variables in intact fish.

      PubDate: 2016-12-29T14:24:59Z
       
  • Rates of oxygen uptake increase independently of changes in heart rate in
           late stages of development and at hatching in the green iguana, Iguana
           iguana
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Marina R. Sartori, Augusto S. Abe, Dane A. Crossley, Edwin W. Taylor
      Oxygen consumption (VO2), heart rate (f H), heart mass (Mh) and body mass (Mb) were measured during embryonic incubation and in hatchlings of green iguana (Iguana iguana). Mean f H and VO2 were unvarying in early stage embryos. VO2 increased exponentially during the later stages of embryonic development, doubling by the end of incubation, while f H was constant, resulting in a 2.7-fold increase in oxygen pulse. Compared to late stage embryos, the mean inactive level of VO2 in hatchlings was 1.7 fold higher, while f H was reduced by half resulting in a further 3.6 fold increase in oxygen pulse. There was an overall negative correlation between mean f H and VO2 when data from hatchlings was included. Thus, predicting metabolic rate as VO2 from measurements of f H is not possible in embryonic reptiles. Convective transport of oxygen to supply metabolism during embryonic incubation was more reliably indicated as an index of cardiac output (COi) derived from the product of f H and Mh. However, a thorough analysis of factors determining rates of oxygen supply during development and eclosion in reptiles will require cannulation of blood vessels that proved impossible in the present study, to determine oxygen carrying capacity by the blood and arteriovenous oxygen content difference (A-V diff), plus patterns of blood flow.

      PubDate: 2016-12-29T14:24:59Z
       
  • A comparison of blood nitric oxide metabolites and hemoglobin functional
           properties among diving mammals
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Angela Fago, Daniel Garcia Parraga, Elin E. Petersen, Niels Kristensen, Lea Giouri, Frank B. Jensen
      The ability of marine mammals to hunt prey at depth is known to rely on enhanced oxygen stores and on selective distribution of blood flow, but the molecular mechanisms regulating blood flow and oxygen transport remain unresolved. To investigate the molecular mechanisms that may be important in regulating blood flow, we measured concentration of nitrite and S-nitrosothiols (SNO), two metabolites of the vasodilator nitric oxide (NO), in the blood of 5 species of marine mammals differing in their dive duration: bottlenose dolphin, South American sea lion, harbor seal, walrus and beluga whale. We also examined oxygen affinity, sensitivity to 2,3-diphosphoglycerate (DPG) and nitrite reductase activity of the hemoglobin (Hb) to search for possible adaptive variations in these functional properties. We found levels of plasma and red blood cells nitrite similar to those reported for terrestrial mammals, but unusually high concentrations of red blood cell SNO in bottlenose dolphin, walrus and beluga whale, suggesting enhanced SNO-dependent signaling in these species. Purified Hbs showed similar functional properties in terms of oxygen affinity and sensitivity to DPG, indicating that reported large variations in blood oxygen affinity among diving mammals likely derive from phenotypic variations in red blood cell DPG levels. The nitrite reductase activities of the Hbs were overall slightly higher than that of human Hb, with the Hb of beluga whale, capable of longest dives, having the highest activity. Taken together, these results underscore adaptive variations in circulatory NO metabolism in diving mammals but not in the oxygenation properties of the Hb.

      PubDate: 2016-12-29T14:24:59Z
       
  • Dynamic interactions between corticosterone, corticosteroid binding
           globulin and testosterone in response to capture stress in male breeding
           Eurasian tree sparrows
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Yaqing Li, Yanfeng Sun, Jesse S. Krause, Mo Li, Xuelu Liu, Weiwei Zhu, Yao Yao, Yuefeng Wu, Dongming Li
      In birds, corticosterone (CORT), testosterone (T), and corticosteroid binding globulin (CBG) are involved in modulating the trade-off between reproduction and survival. In response to acute stress, increased total plasma CORT is a ubiquitous phenomenon while T levels can decrease, or remain unchanged. Since CORT and T bind competitively with CBG in birds, the underlying regulatory mechanisms and consequences of their dynamic interactions remain largely unknown. Here, we studied the dynamic changes of total CORT, T, and CBG, and estimated free and bound CORT and T in response to capture stress in male Eurasian tree sparrows (Passer montanus) across the nest building, egg-laying, and nestling stages. We predicted that free, bound and total hormone concentrations would increase for CORT and decrease for T in response to acute stress, and the relative magnitude of these changes would vary with life history stage. We found that baseline and stressed-induced CORT values did not vary across breeding sub-stages. However, total and bound CORT increased with stress while free remained unchanged. Baseline levels of total, free and bound T were highest during the nest building and it was the only stage in which all measures of T were affected by stress. Regardless of breeding stage or restraint stress, we did not detect a significant correlation between CORT and T. CBG was found to be mostly unoccupied by steroid hormones under stress and stress-free conditions and this likely provided an adequate buffer for changes in free levels of CORT and T during unpredictable environmental perturbations.

      PubDate: 2016-12-29T14:24:59Z
       
  • Transcription of four Rhopalosiphum padi (L.) heat shock protein genes and
           their responses to heat stress and insecticide exposure
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Yuting Li, Qi Zhao, Xinle Duan, Chunman Song, Maohua Chen
      The bird cherry-oat aphid, Rhopalosiphum padi (L.), a worldwide destructive pest, is more heat tolerant than other wheat aphids, and it has developed resistance to different insecticides. Heat shock proteins (HSPs) play an important role in coping with environmental stresses. To investigate Hsp transcriptional responses to heat and insecticide stress, four full-length Hsp genes from R. padi (RpHsp60, RpHsc70, RpHsp70-1, and RpHsp70-2) were cloned. Four RpHsps were expressed during all R. padi developmental stages, but at varying levels. The mRNA levels of RpHsps were increased under thermal stress and reached maximal induction at a lower temperature (36°C) in the alate morph than in the apterous morph (37°C or 38°C). RpHsp expressions under heat stress suggest that RpHsp70-1 and RpHsp70-2 are inducible in both apterous and alate morphs, RpHsc70 is only heat-inducible in apterous morph, and RpHsp60 exhibits poor sensitivity to heat stress. The pretreatment at 37°C significantly increase both the survival rate and the RpHsps expression level of R. padi at subsequent lethal temperature. Under exposure to two sublethal concentrations (LC10 and LC30) of beta-cypermethrin, both RpHsp70-1 and RpHsp70-2 expressions were induced and reached a maximum 24h after exposure. In contrast, expression of RpHsp60 was not induced by either sublethal concentration of beta-cypermethrin. Moreover, the responses of RpHsp70-1 and RpHsp70-2 to heat shock were more sensitive than those to beta-cypermethrin. These results suggest that induction of RpHsp expression is related to thermal tolerance, and that RpHsp70-1 and RpHsp70-2 are the primary genes involved in the response to both heat and pesticide stress.

      PubDate: 2016-12-29T14:24:59Z
       
  • Nutritional status and functional digestive histology of the carnivorous
           Tasmanian devil (Sarcophilus harrisii)
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Hayley J. Stannard, Lydia Tong, Michelle Shaw, Monique Van Sluys, Bronwyn McAllan, David Raubenheimer
      Tasmanian devils (Sarcophilus harrisii) are the largest carnivorous marsupial in Australia. Currently many animals are being held in captivity as a management procedure to combat Devil Facial Tumor Disease. Only one published study thus far has investigated nutrition in Tasmanian devils, determining their maintenance energy requirements and digestibility on a rodent diet. More information is needed on Tasmanian devil nutritional and gastrointestinal function to aid in their management. Our study aimed to investigate the current nutritional status of Tasmanian devils in a captive population and functional morphology and histology of their gastrointestinal tract. Animals were maintained on a diet of kangaroo, rabbit, quail and chicken wings and digestibility of these items by the devils was high (>85% for dry matter, protein and lipid). Kangaroo and rabbit were high protein diet items while the quail and chicken wings provided high lipid to the diet, and carbohydrates were minimal (≤3% energy). Maintenance energy requirements were determined to be 620kJkg−0.75 d−1 with no significant difference between males and females. Opportunistic samples for gastrointestinal morphology were obtained from captive specimens. Tasmanian devils have a simple digestive tract similar to other dasyurid species. Both the morphology and histology of the gastrointestinal tract show specialization for a high protein carnivorous diet.

      PubDate: 2016-12-22T12:36:08Z
       
  • Effects of first exogenous nutrients on the mRNA levels of atrogin-1/MAFbx
           and GLUT1 in the skeletal muscles of newly hatched chicks
    • Abstract: Publication date: March 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 205
      Author(s): Daichi Ijiri, Saki Shimamoto, Mana Kawaguchi, Airi Furukawa, Kazuki Nakashima, Osamu Tada, Akira Ohtsuka
      The aim of this study was to examine the effects of first exogenous nutrients on the mRNA levels of muscle atrophy F-box (atrogin-1/MAFbx) and glucose transporters (GLUTs) in the skeletal muscles of newly hatched chicks with no feed experience. In experiment 1, newly hatched chicks had free access to feed or were fasted for the first 24h. The chicks having free access to feed for the first 24h increased their body weight and had decreased atrogin-1/MAFbx mRNA levels in their sartorius and pectoralis major muscles compared with the fasted chicks. In experiment 2, newly hatched chicks received a single feed via intubation into the crop. Three hours after intubation, levels of atrogin-1/MAFbx mRNA in the sartorius muscle were decreased whereas the plasma insulin concentration and phosphorylated AKT levels in the sartorius muscle were increased. In addition, the mRNA levels of GLUT1 and GLUT8 were increased in the sartorius muscle after the intubation. However, in the pectoralis major muscle, AKT phosphorylation and levels of atrogin-1/MAFbx, GLUT1 and GLUT8 mRNA were not affected 3h after intubation. The first exogenous nutrients increased the level of phosphorylated AKT in the sartorius muscle of newly hatched chicks, possibly because of the decrease in atrogin-1/MAFbx mRNA levels. Furthermore, the sartorius muscle in newly hatched chicks appeared to be more susceptible to the first feed compared with the pectoralis major muscle.

      PubDate: 2016-12-22T12:36:08Z
       
  • Intestinal response to salinity challenge in the Senegalese sole (Solea
           senegalensis)
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): I. Ruiz-Jarabo, A. Barany, I. Jerez-Cepa, J.M. Mancera, J. Fuentes
      Fish are continuously forced to actively absorb or expel water and ions through epithelia. Most studies have focused on the gill due to its role in Na+ and Cl− trafficking. However, comparatively few studies have focused on the changing function of the intestine in response to external salinity. Therefore, the present study investigated the main intestinal changes of long-term acclimation of the Senegalese sole (Solea senegalensis) to 5, 15, 38 and 55ppt. Through the measurement of short-circuit current (Isc) in Ussing chambers and biochemical approaches, we described a clear anterior/posterior functional regionalization of the intestine in response to salinity. The use of specific inhibitors in Ussing chamber experiments, revealed that the bumetanide-sensitive Na+/K+/Cl− co-transporters are the main effectors of Cl− uptake in both anterior intestine and rectum. Additionally, the use of the anion exchanger specific inhibitor, DIDS, showed a salinity/region dependency of anion exchanger function. Moreover, we also described ouabain-sensitive Na+/K+-ATPase (NKA) and Bafilomycin A1-sensitive H+-ATPase activities (HA), which displayed changes related to salinity and intestinal region. However, the most striking result of the present study is the description of an omeprazole-sensitive H+/K+-ATPase (HKA) in the rectum of Senegalese sole. Its activity was consistently measurable and increased at lower salinities, reaching rates even higher than those of the NKA. Together our results provide new insights into the changing role of the intestine in response to external salinity in teleost fish. The rectal activity of HKA offers an alternative/cooperative mechanism with the HA in the final processing of intestinal water absorption by apical titration of secreted bicarbonate.

      PubDate: 2016-11-30T09:28:34Z
       
  • Antioxidant responses in hibernating Chinese soft-shelled turtle
           Pelodiscus sinensis hatchlings
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): Wen-yi Zhang, Cui-juan Niu, Bo-jian Chen, Lin Yuan
      The antioxidant defense system protects turtles from oxidative stress during hibernation. The present study examined changes of the antioxidant enzymes both on mRNA level and enzyme activity level during hibernation of Chinese soft-shelled turtle Pelodiscus sinensis hatchlings. The upstream regulator NF-E2 related factor 2 (Nrf2) mRNA was also measured. Samples were taken at pre-hibernation (17.0°C, Mud temperature (MT)), hibernation (5.8°C, MT) and arousal (20.1°C, MT). Nrf2 exhibited a tissue-specific pattern of expression with a decrease in the brain, slight increase in the liver and heart during hibernation, and significant increase during arousal in all the three tissues. Superoxide dismutase (SOD) mRNA, catalase (CAT) mRNA, and glutathione peroxidase 3 (GPx3) mRNA exhibited a similar pattern as Nrf2 in the brain and liver during the entire hibernation period. Hepatic GPx4 mRNA level increased during hibernation and decreased during arousal, whereas it did not change in the heart. Cerebral SOD and CAT activities kept stable during the experimental period, but GPx activity decreased significantly during hibernation and arousal. Hepatic GPx enzyme activity did not change, whereas those of SOD and CAT exhibited a notable decrease during arousal. Malondialdehyde concentration did not increase during the hibernation process, indicating an effective protection of the antioxidant defense system.

      PubDate: 2016-11-23T05:31:06Z
       
  • Biological and environmental influence on tissue fatty acid compositions
           in wild tropical tunas
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): Fany Sardenne, Edouard Kraffe, Aurélien Amiel, Edwin Fouché, Laurent Debrauwer, Frédéric Ménard, Nathalie Bodin
      This study examined the fatty acid composition of three sympatric tropical tuna species (bigeye Thunnus obesus, yellowfin T. albacares and skipjack tuna Kastuwonus pelamis) sampled in the Western Indian Ocean in 2013. The fatty acid compositions of neutral and polar lipids, respectively involved in energy storage and cell membrane structure, were explored and compared in four tissues (red and white muscles, liver and gonads), according to biological (size, sex and maturity) and environmental (season and area) factors. The liver and the red muscle were the fattest tissues (i.e., higher levels of storage lipids) in all species and polar lipids were the lowest in the white muscle. Species and tissue types explained most differences in fatty acid compositions, while environmental factors had limited effects, except in the hepatic cell membrane where fatty acid composition varied with monsoons. Docosahexaenoic acid (22:6n-3) was the major fatty acid in both polar and neutral lipid fractions, especially in muscles. Eicosapentaenoic acid (20:5n-3) and oleic acid (18:1n-9) were in higher proportion in neutral than in polar lipids. Arachidonic acid (20:4n-6) and 22:6n-3, together with docosapentaenoic acid (22:5n-6) and stearic acid (18:0), showed preferential accumulation in polar lipids. 20:4n-6 was particularly involved in cell membranes of ovary and white muscle. Overall, an important inter-individual variability in fatty acid compositions of structural lipids was found within tissue types despite considering biological factors that are most likely to influence this type of lipids. It suggests that fatty acid profiles are influenced by individual-specific behaviors.

      PubDate: 2016-11-23T05:31:06Z
       
  • Dietary alpha-ketoglutarate promotes higher protein and lower
           triacylglyceride levels and induces oxidative stress in larvae and young
           adults but not in middle-aged Drosophila melanogaster
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): Maria M. Bayliak, Maria P. Lylyk, Halyna V. Shmihel, Oksana M. Sorochynska, Olesia I. Semchyshyn, Janet M. Storey, Kenneth B. Storey, Volodymyr I. Lushchak
      Alpha-ketoglutarate (AKG) is involved in multiple metabolic and regulatory pathways. In this work, the effects of AKG-supplemented diets on selected physiological responses and metabolic processes, including metabolism of reactive oxygen species, was assessed in larvae and adult (both 2 and 24days old) Drosophila melanogaster. Dietary supplementation with AKG resulted in dose-dependent effects on larval development, body composition and antioxidant status of third instar larvae. Larvae and young (2days post-eclosion) adult females fed on AKG shared similar metabolic changes such as higher total protein levels, lower triacylglyceride levels and higher values for oxidative stress indices, namely lipid peroxides and low molecular mass thiols. The latter indicated the development of oxidative stress which, in turn, may induce adaptive responses that can explain the higher resistance of AKG-fed young females to heat shock and hydrogen peroxide exposure. In contrast to young flies, middle-aged females (24days) on AKG-containing diet possessed higher total protein, glucose and triacylglyceride levels, whereas oxidative stress parameters were virtually the same as compared with control females of the same age. In parallel, females fed an AKG-supplemented diet showed lower fecundity, higher heat shock resistance but no change in oxidative stress resistance at middle age which in combination with levels of protein, glucose, and triacylglycerides can be considered as potentially beneficial AKG effects for aging organisms. To our best knowledge, this is the first study on age-matched AKG influence on animals' organism which shows that Drosophila may be used as a model for previous quick study in cost-efficient manner age-related AKG effects in mammals and humans.

      PubDate: 2016-11-23T05:31:06Z
       
  • Synchronization to light and mealtime of daily rhythms of locomotor
           activity, plasma glucose and digestive enzymes in the Nile tilapia
           (Oreochromis niloticus)
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): Bartira Guerra-Santos, José Fernando López-Olmeda, Bruno Olivetti de Mattos, Alice Borba Baião, Denise Soledade Peixoto Pereira, Francisco Javier Sánchez-Vázquez, Robson Bahia Cerqueira, Ricardo Castelo Branco Albinati, Rodrigo Fortes-Silva
      The light–dark cycle and feeding can be the most important factors acting as synchronizers of biological rhythms. In this research we aimed to evaluate synchronization to feeding schedule of daily rhythms of locomotor activity and digestive enzymes of tilapia. For that purpose, 120 tilapias (65.0±0.6g) were distributed in 12 tanks (10 fish per tank) and divided into two groups. One group was fed once a day at 11:00h (zeitgeber time, ZT6) (ML group) and the other group was fed at 23:00h (ZT18) (MD group). The fish were anesthetized to collect samples of blood, stomach and midgut at 4-hour intervals over a period of 24h. Fish fed at ML showed a diurnal locomotor activity (74% of the total daily activity occurring during the light phase) and synchronization to the feeding schedule, as this group showed anticipation to the feeding time. Fish fed at MD showed a disruption in the pattern of locomotor activity and became less diurnal (59%). Alkaline protease activity in the midgut showed daily rhythm with the achrophase at the beginning of the dark phase in both ML and MD groups. Acid protease and amylase did not show significant daily rhythms. Plasma glucose showed a daily rhythm with the achrophase shifted by 12h in the ML and MD groups. These results revealed that the feeding time and light cycle synchronize differently the daily rhythms of behavior, digestive physiology and plasma metabolites in the Nile tilapia, which indicate the plasticity of the circadian system and its synchronizers.

      PubDate: 2016-11-23T05:31:06Z
       
  • l-Leucine acts as a potential agent in reducing body temperature at
           hatching and affords thermotolerance in broiler chicks
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): Guofeng Han, Hui Yang, Mohammad A. Bahry, Phuong V. Tran, Phong H. Do, Hiromi Ikeda, Mitsuhiro Furuse, Vishwajit S. Chowdhury
      Thermal manipulation (TM) of incubation temperature causes metabolic alterations and contributes to improving thermotolerance in chicks post hatching. However, there has been no report on amino acid metabolism during TM and the part it plays in thermotolerance. In this study, we therefore first analyzed free amino acid concentrations in the embryonic brain and liver during TM (38.6°C, 6h/d during embryonic day (ED) 10 to ED 18). It was found that leucine (Leu), phenylalanine and lysine were significantly decreased in the embryonic brain and liver. We then chose l-Leu and other branched-chain amino acids (l-isoleucine (L-Ile) and l-valine (l-Val)) for in ovo injection on ED 7 to reveal their roles in thermoregulation, growth, food intake and thermotolerance in chicks. It was found that in ovo injection of l-Leu, but not of l-Ileu or l-Val, caused a significant decline in body temperature at hatching and increased food intake and body weight gain in broiler chicks. Interestingly, in ovo injection of l-Leu resulted in the acquisition of thermotolerance under high ambient temperature (35±1°C for 180min) in comparison with the control thermoneutral temperature (28±1°C for 180min). These results indicate that the free amino acid concentrations during embryogenesis were altered by TM. l-Leu administration in eggs caused a reduction in body temperature at hatching, and afforded thermotolerance in heat-exposed young chicks, further suggesting that l-Leu may be one of the key metabolic factors involved in controlling body temperature in embryos, as well as in producing thermotolerance after hatching.

      PubDate: 2016-11-23T05:31:06Z
       
  • Cortisol regulates nitric oxide synthase in freshwater and seawater
           acclimated rainbow trout, Oncorhynchus mykiss
    • Abstract: Publication date: February 2017
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 204
      Author(s): Lucie Gerber, Steffen S. Madsen, Frank B. Jensen
      Cortisol and nitric oxide (NO) are regulators of ion transport and metabolic functions in fish. In the gill, they show opposite effects on Na+/K+-ATPase (NKA) activity: cortisol stimulates NKA activity while NO inhibits NKA activity. We hypothesized that cortisol may impact NO production in osmoregulatory tissues by regulating NO synthase (NOS) expression. We evaluated the influence of cortisol treatment on mRNA expression of Nos1 and Nos2 in gill, kidney and middle intestine of both freshwater (FW) and seawater (SW) acclimated rainbow trout and found both tissue- and salinity-dependent effects. Nos2 expression was down-regulated in the gill by cortisol injection in both FW and SW trout. This was substantiated by incubating gill tissue with cortisol ex vivo. Similarly, cortisol injection significantly down-regulated Nos2 expression in kidney of SW fish but not in FW fish. In the middle intestine, Nos2 expression was up-regulated by cortisol injection in FW but unchanged in SW fish. Nos1 expression was up-regulated by cortisol injection in FW kidney and down-regulated in SW kidney, whereas it was unaffected in gill and middle intestine of FW and SW fish. Our data provide the first evidence that cortisol may influence NO production in fish by regulating Nos expression. Indeed, the down-regulation of Nos2 expression by cortisol in the gill may prevent the inhibitory effect of NO on NKA activity thereby furthering the stimulatory effect of cortisol on ion-transport.

      PubDate: 2016-11-17T03:37:58Z
       
 
 
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