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BIOCHEMISTRY (192 journals)                  1 2     

AAPS PharmSciTech     Hybrid Journal   (Followers: 6)
Acetic Acid Bacteria     Open Access   (Followers: 1)
ACS Chemical Biology     Full-text available via subscription   (Followers: 249)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 13)
Acta Crystallographica Section D : Biological Crystallography     Hybrid Journal   (Followers: 8)
Acta Crystallographica Section F: Structural Biology Communications     Hybrid Journal   (Followers: 5)
Advances and Applications in Bioinformatics and Chemistry     Open Access   (Followers: 7)
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Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 10)
African Journal of Biochemistry Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 1)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 4)
American Journal of Biochemistry     Open Access   (Followers: 6)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 145)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
Amino Acids     Hybrid Journal   (Followers: 7)
Analytical Biochemistry     Hybrid Journal   (Followers: 171)
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Annual Review of Biochemistry     Full-text available via subscription   (Followers: 28)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Applied Biochemistry and Biotechnology     Hybrid Journal   (Followers: 18)
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Archives of Insect Biochemistry and Physiology     Hybrid Journal   (Followers: 1)
Archives Of Physiology And Biochemistry     Hybrid Journal   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Bangladesh Journal of Medical Biochemistry     Open Access   (Followers: 2)
BBA Clinical     Open Access  
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Biochemical and Biophysical Research Communications     Hybrid Journal   (Followers: 13)
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Biochemistry (Moscow) Supplement Series A: Membrane and Cell Biology     Hybrid Journal   (Followers: 4)
Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry     Hybrid Journal   (Followers: 4)
Biochemistry and Cell Biology     Full-text available via subscription   (Followers: 9)
Biochemistry and Molecular Biology Education     Hybrid Journal   (Followers: 3)
Biochemistry and Molecular Biology of Fishes     Full-text available via subscription   (Followers: 1)
Biochemistry Research International     Open Access   (Followers: 4)
Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids     Hybrid Journal   (Followers: 3)
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease     Hybrid Journal   (Followers: 17)
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Bioconjugate Chemistry     Full-text available via subscription   (Followers: 14)
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BioMolecular Concepts     Full-text available via subscription   (Followers: 2)
Bioscience, Biotechnology, and Biochemistry     Hybrid Journal   (Followers: 6)
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BMC Biochemistry     Open Access   (Followers: 8)
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Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Cell Biochemistry and Biophysics     Hybrid Journal   (Followers: 6)
Cell Biochemistry and Function     Hybrid Journal   (Followers: 3)
Cellular Physiology and Biochemistry     Open Access   (Followers: 3)
Central European Journal of Chemistry     Hybrid Journal   (Followers: 5)
ChemBioChem     Hybrid Journal   (Followers: 2)
Chemical and Biological Technologies for Agriculture     Open Access  
Chemical Biology & Drug Design     Hybrid Journal   (Followers: 23)
Chemical Engineering Journal     Hybrid Journal   (Followers: 18)
Chemical Senses     Hybrid Journal   (Followers: 1)
Chemical Speciation and Bioavailability     Full-text available via subscription   (Followers: 1)
Chemico-Biological Interactions     Hybrid Journal   (Followers: 2)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 5)
Chemistry & Biology     Full-text available via subscription   (Followers: 16)
Chemistry and Ecology     Hybrid Journal   (Followers: 1)
Clinical Biochemist Reviews     Full-text available via subscription   (Followers: 1)
Clinical Biochemistry     Hybrid Journal   (Followers: 3)
Clinical Chemistry and Laboratory Medicine     Full-text available via subscription   (Followers: 3)
Clinical Lipidology     Full-text available via subscription  
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: 4)
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: 8)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 2)
Current Chemical Biology     Hybrid Journal   (Followers: 2)
Current Opinion in Chemical Biology     Hybrid Journal   (Followers: 13)
Current Opinion in Lipidology     Hybrid Journal   (Followers: 2)
DNA Barcodes     Open Access  
Doklady Biochemistry and Biophysics     Hybrid Journal   (Followers: 2)
Doklady Chemistry     Hybrid Journal  
Egyptian Journal of Biochemistry and Molecular Biology     Full-text available via subscription  

        1 2     

Journal Cover Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
   [7 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1095-6433
     Published by Elsevier Homepage  [2563 journals]
  • The peptide hormone cholecystokinin modulates the tonus and compliance of
           the bulbus arteriosus and pre-branchial vessels of the rainbow trout
           (Oncorhynchus mykiss)
    • Abstract: Publication date: Available online 4 August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Henrik Seth , Michael Axelsson , Albin Gräns
      The bulbus arteriosus is a compliant structure between the ventricle and ventral aorta of teleost fish. It serves as a “wind-kessel” that dampens pressure variations during the cardiac cycle allowing a continuous flow of blood into the gills. The bulbus arteriosus receives sympathetic innervation and is affected by several circulating substances, indicating neurohumoral control. We have previously shown that the peptide hormone, cholecystokinin (CCK), affects the hemodynamics of the cardiovascular system in rainbow trout (Oncorhynchus mykiss) by increasing flow pulse amplitude without affecting cardiac output. We hypothesized that this could be explained by an altered tonus or compliance/distensibility of the bulbus arteriosus. Our results show that there is a substantial effect of CCK on the bulbus arteriosus. Concentrations of CCK that altered the cardiac function of in situ perfused hearts also contracted the bulbus arteriosus in vitro. Pressure–volume curves revealed a change in both the tonus and the compliance/distensibility of this structure. Furthermore, the stimulatory (constricting) effect of CCK was also evident in the ventricle and vasculature leading to the gills, but absent in the atrium, efferent branchial arteries and dorsal aorta. In conclusion, CCK alters the mechanical properties of the ventricle, bulbus arteriosus, ventral aorta and afferent gill vasculature, thus maintaining adequate branchial and systemic blood flow and pressure when cardiorespiratory demands change, such as after feeding.

      PubDate: 2014-08-08T00:31:18Z
  • How do measurement duration and timing interact to influence estimation of
           basal physiological variables of a nocturnal rodent?
    • Abstract: Publication date: Available online 7 August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): M.K. Connolly , C.E. Cooper
      Metabolic rate and evaporative water loss are two commonly measured physiological variables. It is therefore important, especially for comparative studies, that these variables (and others) are measured under standardised conditions, of which a resting state during the inactive phase is part of the accepted criteria. Here we show how measurement duration and timing affect these criteria and impact on the estimation of basal metabolic rate (oxygen consumption and carbon dioxide production) and standard evaporative water loss of a small nocturnal rodent. Oxygen consumption, carbon dioxide production and evaporative water loss all decreased over the duration of an experiment. Random assortment of hourly values indicated that this was an animal rather than a random effect for up to 11h. Experimental start time also had a significant effect on measurement of physiological variables. A longer time period was required to achieve minimal carbon dioxide consumption and evaporative water loss when experiments commenced earlier in the day, however experiments with earlier start times had a lower overall estimates of minimal oxygen consumption and carbon dioxide production. For this species, measurement duration of at least 8h, ideally commencing between before the inactive phase at 03:00h and 05:00h, is required to obtain minimal standard values for physiological variables. Up to 80% of recently published studies measuring basal metabolic rate and/or evaporative water loss of small nocturnal mammals may overestimate basal values due to insufficiently long measurement duration.

      PubDate: 2014-08-08T00:31:18Z
  • Editorial Board
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176

      PubDate: 2014-08-04T00:01:24Z
  • Immune responsiveness of Japanese quail selected for egg yolk testosterone
           content under severe protein restriction
    • Abstract: Publication date: Available online 30 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Zuzana Kankova , Monika Okuliarova , Michal Zeman
      Yolk testosterone concentrations vary in response to environmental conditions and different testosterone contents can subsequently modify the phenotypic traits of offspring. Apart from effects on growth, proactive behaviour and secondary sexual characteristics, the possible negative impacts of maternal testosterone on the immune system are often considered a limitation for its deposition. The effects of maternal testosterone can be modulated by postnatal environmental conditions, such as the availability of food resources. However, the majority of studies considering the effects of maternal testosterone on the immune system have been conducted under optimum conditions. In our study we evaluated the influence of genetic selection for high (HET) and low (LET) egg testosterone content in Japanese quail on immune responsiveness of offspring to phytohaemagglutinin (PHA) and lipopolysaccharide (LPS) stimulation under severe protein restriction. Protein restriction negatively influenced body weight and performance in the PHA-test. We observed an increase in Cort (corticosterone) and He/Ly (heterophil/lymphocyte ratio) after LPS, whilst no changes occurred in total IgY levels in the protein-restricted group. HET quails showed higher body mass and total IgY levels and lower He/Ly ratio than LET quails, whilst the PHA index and Cort concentration did not differ between lines. No interactions were found between protein restriction and genetic line. In conclusion, the immune response was not compromised under conditions of severe protein restriction in the faster growing HET line compared with the LET line. We hypothesise that the immune responsiveness of birds with higher yolk testosterone may be linked with other maternally-derived substances in a context-dependent manner.

      PubDate: 2014-08-04T00:01:24Z
  • A critical evaluation of automated blood gas measurements in comparative
           respiratory physiology
    • Abstract: Publication date: Available online 1 August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Christian Lind Malte , Sashia Lindhøj Jakobsen , Tobias Wang
      Precise measurements of blood gases and pH are of pivotal importance to respiratory physiology. However, the traditional electrodes that could be calibrated and maintained at the same temperature as the experimental animal are increasingly being replaced by new automated blood gas analyzers. These are typically designed for clinical use and automatically heat the blood sample to 37°C for measurements. While most blood gas analyzers allow for temperature corrections of the measurements, the underlying algorithms are based on temperature-effects for human blood, and any discrepancies in the temperature dependency between the blood sample from a given species and human samples will bias measurements. In this study we review the effects of temperature on blood gases and pH and evaluate the performance of an automated blood gas analyzer (GEM Premier 3500). Whole blood obtained from pythons and freshwater turtles was equilibrated in rotating Eschweiler tonometers to a variety of known PO2's and PCO2's in gas mixtures prepared by Wösthoff gas mixing pumps and blood samples were measured immediately on the GEM Premier 3500. The pH measurements were compared to measurements using a Radiometer BMS glass capillary pH electrode kept and calibrated at the experimental temperature. We show that while the blood gas analyzer provides reliable temperature-corrections for PCO2 and pH, PO2 measurements were substantially biased. This was in agreement with the theoretical considerations and emphasizes the need for critical calibrations/corrections when using automated blood gas analyzers.

      PubDate: 2014-08-04T00:01:24Z
  • Different stressors induce differential responses of the CRH-stress system
           in the gilthead sea bream (Sparus aurata)
    • Abstract: Publication date: Available online 1 August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Juan A. Martos-Sitcha , Yvette S. Wunderink , Justin Straatjes , Arleta K. Skrzynska , Juan M. Mancera , Gonzalo Martínez-Rodríguez
      The hypothalamus–pituitary–interrenal (HPI) axis, involved in the regulation of the neuroendocrine stress responses, presents important players such as corticotropin-releasing hormone (CRH, generally considered as the initiator of this pathway) and CRH-binding protein (CRH-BP, considered as an antagonist of CRH function). CRH and CRH-BP full-length cDNA sequences were obtained from Sparus aurata by screening a brain cDNA library, and their phylogenetic analysis as well as their roles during acute and chronic stress responses were assessed. mRNA expression levels and plasma cortisol concentrations were measured by RT qPCR and ELISA, respectively, in S. aurata juveniles submitted to: i) different environmental salinities in a short-time course response; and ii) food deprivation during 21days. In addition, osmoregulatory and metabolic parameters in plasma corroborated a clear reorganization depending on the stress source/period. Salinity transfer induced stress as indicated by enhanced plasma cortisol levels, as well as by up-regulated CRH and down-regulated CRH-BP expression values. On the other hand, food deprivation did not affect both expression levels, although plasma cortisol concentrations were enhanced. These results suggest that different stressors are handled through different stress pathways in S. aurata.

      PubDate: 2014-08-04T00:01:24Z
  • Changes in plasma concentrations of progesterone, dehydroepiandrosterone
           and corticosterone in response to acute stress of capture, handling and
           restraint in two subspecies of white-crowned sparrows
    • Abstract: Publication date: Available online 27 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Jesse S. Krause , David Dorsa , John C. Wingfield
      The aim of this study was to determine circulating patterns of the three major adrenal steroids in blood in response to stress during acute restraint handling in two subspecies of white-crowned sparrow (Zonotrichia leucophrys). Gambel’s white-crowned sparrows (Z.l. gambelii) are long distance migrants that breed at high latitudes and Nuttall’s white-crowned sparrows (Z.l. nuttalli) are residents of coastal California. Column partition chromatography was developed to separate progesterone, dehydroepiandrosterone (DHEA), and corticosterone from a small plasma sample. Each of these steroids has the capability to modulate the stress response through various mechanisms. For example, progesterone is bound to corticosterone binding globulin (CBG) with a higher affinity than corticosterone. If plasma levels of progesterone rise during acute stress, then this could displace corticosterone from CBG and increase the amount of biologically active, free, corticosterone in blood. Dehydroepiandrosterone (DHEA) has been implicated to have many anti-stress properties with the potential to mitigate some of the actions of corticosterone. Results indicate that progesterone levels in both subspecies are elevated in response to acute stress handling. DHEA levels declined in Gambel’s but did not change in Nuttall’s. Thus DHEA does not follow the same secretory pattern as in mammals. Corticosterone levels were elevated in response to acute stress handling in both subspecies. This study provides new insight into an integrated stress response among three steroids.

      PubDate: 2014-07-29T23:41:14Z
  • Sex-specific divergence for body size and desiccation-related traits in
           Drosophila hydei from the western Himalayas
    • Abstract: Publication date: Available online 18 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Bhawna Kalra , Ravi Parkash
      Sex-specific-differences are a widespread source of genetic variation in various Drosophila species. In the present study, we have examined desiccation survival in males and females of Drosophila hydei from colder and drier montane conditions of the western Himalayas (altitudinal populations; 600–2202m). In contrast with most other studies in drosophilids, D. hydei males exhibited comparatively higher desiccation resistance despite smaller body size compared to females. Accordingly, we tested the physiological basis of such adaptations in both sexes of D. hydei. Body size traits (wing length, wet weight and dry weight) were ~1.2 fold higher in females than males. However, desiccation resistance was 10 to 13h higher in males than females. These differences matched enhanced storage of trehalose content (~1.2 fold), higher hemolymph content (~1.2 fold) and enhanced cuticular lipid mass (~1.5 fold) in males than females. Water loss before succumbing to death (dehydration tolerance) was much higher in males (~81%) than females (~64%). A greater loss of hemolymph water until death under desiccation stress was associated with higher desiccation resistance in males. Further, there were lacks of differences in the rate of water loss, rate of trehalose utilization and rate of hemolymph depletion between the sexes in D. hydei. Therefore, sex-specific differences in desiccation resistance of D. hydei were independent of body size as well as the exhaustion of metabolite reserves and rather were caused by the higher dehydration tolerance as well as higher acquisition of hemolymph and trehalose contents.

      PubDate: 2014-07-26T23:36:34Z
  • Lipid metabolites as markers of fattening rate in a non-migratory
           passerine: Effects of ambient temperature and individual variation
    • Abstract: Publication date: Available online 24 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Isabelle Devost , Fanny Hallot , Myriam Milbergue , Magali Petit , François Vézina
      Plasma lipid metabolites such as triglycerides (TRIG) and glycerol (GLY) are used as indicators of fattening rate and nutritional condition in migratory birds. Requiring only one blood sample, they could also be used for studying daily and seasonal fattening rates in relation with habitat quality or weather variations in small species wintering in cold climates. Using captive black-capped chickadees (Poecile atricapillus) exposed to three experimental temperatures (0°C, 15°C, and 30°C), the goal of this experiment was to determine the relationship between plasma levels of both TRIG and GLY and fattening rate measured over periods varying from a few hours to the previous two days. Results showed that birds maintained in the cold had circulating metabolite levels 39–81% higher than those maintained at thermoneutrality, likely reflecting the size of their body fat reserves and that TRIG and total GLY were highly correlated across treatments. Fattening rate was also higher both at 0°C (+35%) and 30°C (+24%) relative to that measured at 15°C and, as expected, was positively correlated with metabolite levels across thermal treatments. However, despite a range of fattening rates similar to that observed at the other temperatures, the relationships were uncoupled at 30°C, implying that the technique may not be easily applicable at temperatures within or close to thermoneutrality. We also found a strong individual effect in the relationships between fattening rate and plasma TRIG levels, suggesting high individual consistency in these parameters in conditions of unrestricted food access such as in captivity. Our study therefore confirms that plasma TRIG and GLY levels can be used as relative indexes of condition and fattening rates in wintering passerines.

      PubDate: 2014-07-26T23:36:34Z
  • Non-invasive assessment of adrenocortical function in captive Nile
           crocodiles (Crocodylus niloticus)
    • Abstract: Publication date: Available online 24 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Stefanie B. Ganswindt , Jan G. Myburgha , Elissa Z. Cameron , Andre Ganswindt
      The occurrence of stress-inducing factors in captive crocodilians is a concern, since chronic stress can negatively affect animal health and reproduction, and hence production. Monitoring stress in wild crocodiles could also be beneficial for assessing the state of health in populations which are potentially threatened by environmental pollution. In both cases, a non-invasive approach to assess adrenocortical function as a measure of stress would be preferable, as animals are not disturbed during sample collection, and therefore sampling is feedback-free due to the absence of capture and handling. So far, however, such a non-invasive method has not been established for any crocodilian species. As an initial step, we therefore examined the suitability of two enzyme-immunoassays, detecting faecal glucocorticoid metabolites (FGMs) with a 11β,21-diol-20-one and 5β-3α-ol-11-one structure, respectively, for monitoring stress-related physiological responses in captive Nile crocodiles (Crocodylus niloticus). An adrenocorticotropic hormone (ACTH) challenge was performed on 10 sub-adult crocodiles, resulting in an overall increase in serum corticosterone levels of 272% above the pre-injection levels 5h post-injection. Saline-treated control animals (n=8) showed an overall increase of 156% in serum corticosterone levels 5h post-administration. Faecal samples pre- and post-injection could be obtained from three of the six individually housed crocodiles, resulting in FGM concentrations 136-380% above pre-injection levels, always detected in the first sample collected post-treatment (7–15 days post-injection). FGM concentrations seem comparatively stable at ambient temperatures for up to 72h post-defaecation. In conclusion, non-invasive hormone monitoring can be used for assessing adrenocortical function in captive Nile crocodiles based on FGM analysis.

      PubDate: 2014-07-26T23:36:34Z
  • Point mutagenesis reveals that a coiled-coil motif of CrV1 is required for
           entry to hemocytes to suppress cellular immune responses
    • Abstract: Publication date: Available online 26 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Sunil Kumar , Yonggyun Kim
      Various immunosuppressive factors are derived from polydnaviruses (PDVs) mutually symbiotic to some ichneumonid and braconid wasps. CrV1 was originally identified from a PDV called Cotesia rubecula bracovirus. CrV1 orthologs are reported in other Cotesia-associated PDVs, but not clearly understood in their physiological functions. This study determined a function of CrV1 encoded in C. plutellae bracovirus (CpBV). CpBV-CrV1 is the largest molecule among the known CrV1s and is predicted to possess three coiled-coil motifs. It was constitutively expressed in parasitized host, Plutella xylostella. In vivo transient expression of CpBV-CrV1 significantly impaired hemocyte nodule formation. However, its specific RNA interference significantly recovered the immune response. Two point mutations (Ala→Pro at 192nd and 196th positions) were designed to remove the main coiled-coil motif of CpBV-CrV1. When CpBV-CrV1 and the mutant CpBV-CrV1 were expressed in Sf9 cells, their proteins were synthesized and secreted into each culture medium. When each culture medium was overlaid on hemocytes of nonparasitized P. xylostella, an immunofluorescence assay showed that CpBV-CrV1 entered the hemocytes, but the mutant protein did not. The entered CpBV-CrV1 significantly inhibited hemocyte-spreading behavior by preventing F-actin formation. These results indicate that CpBV-CrV1 is an immunosuppressive factor of CpBV, in which its coiled-coil motif is essential.

      PubDate: 2014-07-26T23:36:34Z
  • Exploring the consequences of mitochondrial differences arising through
           hybridization of sunfish
    • Abstract: Publication date: Available online 26 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): K. Mathers , J. Cox , Y. Wang , C.D. Moyes
      Previous studies have shown evidence of genomic incompatibility and mitochondrial enzyme dysfunction in hybrids of bluegill (Lepomis macrochirus Rafinesque) and pumpkinseed (L. gibbosus Linnaeus) sunfish (Davies et al., 2013 Physiol. Biochem. Zool. 85, 321–331). We assessed if these differences in mitochondria had an impact on metabolic processes that depend on mitochondrial function, specifically hypoxia tolerance and recovery from burst exercise. Bluegill, pumpkinseed, and their hybrids showed no difference in the critical oxygen tension (Pcrit) and no differences in tissue metabolites measured after exposure to 10% O2 for 30min. In contrast, loss of equilibrium (LOE) measurements showed that hybrids had reduced hypoxia tolerance and lacked the size-dependence in hypoxia tolerance seen in the parental species. However, we found no evidence of systematic differences in metabolite levels in fish after LOE. Furthermore, there were abundant glycogen reserves at the point of loss of equilibrium. The three genotypes did not differ in metabolite status at rest, showed an equal disruption at exhaustion, and similar metabolic profiles throughout recovery. Thus, we found no evidence of a mitochondria dysfunction in hybrids, and mitochondrial differences and oxidative metabolism did not explain the variation in hypoxia tolerance seen in the hybrid and two parental species.

      PubDate: 2014-07-26T23:36:34Z
  • Respiratory response to combined heat and hypoxia in the marine bivalves
           Pecten maximus and Mytilus spp.
    • Abstract: Publication date: September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 175
      Author(s): Sébastien Artigaud , Camille Lacroix , Vianney Pichereau , Jonathan Flye-Sainte-Marie
      Coastal ecosystems are increasingly disturbed by the increase of mean sea surface temperature and expansion of hypoxic areas. The objectives of the present work were to describe and compare the respiratory responses to combined heat and hypoxia in two bivalve species (Pecten maximus and Mytilus spp.) living in two contrasted coastal habitats (subtidal and intertidal, respectively). Results were consistent with the vertical zonation of both species. Mytilus spp. seemed to cope better with a temperature increase than P. maximus, which was found to be outside of its optimal thermal window at 25°C. Concerning respiratory responses to hypoxia at a given temperature, P. maximus displayed greater oxyregulation capacity that was maintained over a larger range of O2 levels, as compared to Mytilus spp. When acclimation temperatures increased, both species showed a decrease in their oxyregulation capacities alongside a reduction in aerobic performance, especially in P. maximus. The comparison between species suggests that subtidal species, such as P. maximus, might be more vulnerable to a combination of heat and hypoxia than intertidal species, such as Mytilus spp. Lastly, this study highlighted the utility of segmented linear models to estimate PcO2 and regulation percentages in marine organisms exposed to hypoxia.

      PubDate: 2014-07-26T23:36:34Z
  • Physiological strategies contributing to the coexistence of two predatory
           species of stoneflies: Dinocras cephalotes and Perla bipunctata
    • Abstract: Publication date: September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 175
      Author(s): A. Sanz , C.E. Trenzado , M.J. López-Rodríguez , J.M. Tierno de Figueroa
      Our study focuses on the oxidative state of two aquatic insects of the order Plecoptera belonging to the family Perlidae, namely Dinocras cephalotes (Curtis, 1827) and Perla bipunctata Pictet, 1833. These species are widely distributed throughout the Western Palearctic region and coexist in the stream where individuals for this study come from. We highlight the physiological strategies of these two different predator species of stoneflies, showing a higher accumulation of lipid reserves in P. bipunctata, higher glucose levels in the body tissues of D. cephalotes and a higher capacity of the antioxidant enzymes in P. bipunctata, what provides it a protection against oxidation of lipids, which are greater in this species. This leads to a similar oxidative state in both species. Based on these results is discussed how two close related species developing a very similar ecological role in the same habitat can achieve a similar fitness with differences in their physiological strategies.

      PubDate: 2014-07-26T23:36:34Z
  • Molecular characterization of a cDNA encoding red pigment-concentrating
           hormone in black tiger shrimp Penaeus monodon: Implication of its function
           in molt and osmoregulation
    • Abstract: Publication date: September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 175
      Author(s): Ponsit Sathapondecha , Sakol Panyim , Apinunt Udomkit
      Red pigment-concentrating hormone (RPCH) is a member of the AKH/RPCH peptide family present mainly in crustaceans and insects. Insect AKH is responsible for metabolic functions whereas RPCH plays a major role in the aggregation of red chromatophores in crustaceans. In this study, a full-length cDNA of RPCH of the black tiger shrimp, Penaeus monodon (PmRPCH) was cloned by Rapid Amplification of cDNA Ends strategies from the eyestalk RNA. A 770bp full-length PmRPCH cDNA harbored 279bp of an open reading frame encoding a signal peptide of 21 amino acid residues, an 8 amino acid mature RPCH peptide, followed by 61 amino acid residues of a RPCH precursor-related peptide. The highest levels of PmRPCH mRNA expression were detected in eyestalks while lower expression was found in other nervous tissues i.e. brain, thoracic ganglia and abdominal nerve cord. Expression of PmRPCH was transiently stimulated upon hypersalinity change within 12h suggesting its osmoregulatory function. During the molting cycle, PmRPCH in the eyestalk was expressed at the lowest level in the early pre-molt stage (D0), then gradually increased over the pre-molt period and reached the highest level in the late pre-molt (D4) and post-molt (AB) stages. RPCH peptide at a dose of 100pmol also increased gill Na+/K+ ATPase activity in 36–48h after injection. However, PmRPCH did not accelerate the duration of molting cycle. Our results provide the first evidence on the potential function of PmRPCH in molting, probably by mediating hemolymph osmolality and ion transport enzymes during the late pre-molt stage.

      PubDate: 2014-07-26T23:36:34Z
  • Bioenergetics in chicken embryo fibroblast cells: Evidence of lower proton
           leak in spontaneously immortalized chicken embryo fibroblasts compared to
           young and senescent primary chicken embryo fibroblast cells
    • Abstract: Publication date: September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 175
      Author(s): Kentu Lassiter , Sami Dridi , Alissa Piekarski , Elizabeth Greene , Billy Hargis , Byung-Whi Kong , Walter Bottje
      A spontaneously immortalized chicken embryo fibroblast (CEF) cell line (DF-1) is known to exhibit faster growth rate and greater sensitivity to oxidative stress compared to the primary parent CEF (pCEF1°) cells. Thus, major objectives of this study were to assess cell bioenergetics in pCEF1° and DF-1 cells under control conditions and in response to 4-hydroxy 2-nonenal (4-HNE) induced oxidative challenge. Cell bioenergetics were assessed by flux analysis of oxygen consumption rate (OCR). Under control conditions, DF-1 cells had higher OCR associated with ATP synthase activity and mitochondrial oxygen reserve capacity as well as lower OCR due to proton leak and non-mitochondrial cytochrome c oxidase activity. In response to 4-HNE (0 to 30μM), DF-1 cells were more sensitive to oxidant challenge than both young (passage 8) and senescent (passage 19) pCEF1° cells. Both passages 8 and 19 pCEF1° cells exhibited higher proton leak in response to 4-HNE, but this was not observed in DF-1 cells. Inducible proton leak occurs by 4-HNE stimulated activation of uncoupling protein (UCP) and adenine nucleotide translocase (ANT). From mRNA expression data indicated that ANT and avian UCP were down-regulated and up-regulated, respectively, in DF-1 compared to pCEF1° cells. Thus, we hypothesize that DF-1 cells are unable to increase proton leak due to lower expression of ANT, but not avian UCP, and this inability to increase proton leak contributes to greater susceptibility to oxidative stress of DF-1 cells compared to pCEF1° cells.

      PubDate: 2014-07-26T23:36:34Z
  • Corrigendum to “Variability in swimming performance and underlying
           physiology in rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo
           trutta)” [Comp. Biochem. Physiol., A 163 (2012) 350–356]
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Allison L. Ralph , Barbara I. Berli , Patricia Burkhardt-Holm , Keith B. Tierney

      PubDate: 2014-07-26T23:36:34Z
  • Editorial Board
    • Abstract: Publication date: September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 175

      PubDate: 2014-07-26T23:36:34Z
  • Digestive efficiencies are independent of gut passage times in rainbow
           skinks (Trachylepis margaritifer)
    • Abstract: Publication date: September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 175
      Author(s): Ashadee K. Miller , Barend F.N. Erasmus , Graham J. Alexander
      Constraints on physiological processes imposed on ectotherms by environmental temperatures can be severe, affecting many aspects of their biology. Included in the suite of physiological processes affected is gut motility, with below optimum temperatures generally resulting in slow gut passage. Trachylepis margaritifer (rainbow skink) however presents an unusual pattern whereby gut passage time decreases at a low temperature compared to when at an intermediate temperature. It has been suggested that this may be a ‘cutting-your-losses’ response whereby nutritional gain is sacrificed by voiding the digesta to reduce the risk of these rotting within the gut at these low temperatures, and if this is so, it should result in reduced digestive performance at 25°C. We tested this hypothesis by measuring appetite, apparent digestive efficiency (ADE) and apparent assimilation efficiency (AAE) in T. margaritifer. We found that although temperature significantly affected appetite and gut passage time, it did not affect digestive efficiency. Both ADE (>90%) and AAE (>80%) were high and temperature-independent across the range tested. Thus, the ‘cutting-your-losses’ hypothesis does not explain faster gut passage at 25°C. High digestive parameters could be maintained by increasing concentrations of digestive enzyme at low temperatures but remains to be tested in this species.

      PubDate: 2014-07-26T23:36:34Z
  • Physiological and biochemical strategies for withstanding emersion in two
           galaxiid fishes
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Mauricio A. Urbina , Patrick J. Walsh , Jonathan V. Hill , Chris N. Glover
      The galaxiid fishes of the Southern hemisphere display variable tolerance to aerial exposure. Brown mudfish (Neochanna apoda), for example, pseudoaestivate, inhabiting moist soil for months at a time, whereas inanga (Galaxias maculatus) emerse under unfavourable water conditions, but only for periods of a few hours. This study sought to identify the physiological and biochemical strategies that determine emersion tolerance in these species. Nitrogenous waste excretion was measured before and after an experimental emersion period (14days for mudfish, 6h for inanga). Both species showed significantly elevated ammonia “washout” upon return to water, but no increase in plasma or muscle ammonia. Post-emersion urea levels were elevated in plasma and muscle in both fish, however the extent of the accumulation did not indicate significant de novo urea production. This was supported by the lack of carbamoyl phosphate synthetase activity in tissues. Consequently, mudfish metabolism was examined to determine whether changes in parameters such as oxygen consumption, carbon dioxide excretion, and/or altered metabolic costs (represented by the key ionoregulatory enzyme Na+, K+-ATPase; NKA) could explain emersion tolerance. Oxygen consumption rates, already very low in immersed mudfish, were largely maintained over the course of emersion. Carbon dioxide excretion decreased during emersion, and a small, but significant, decrease in NKA was noted. These data suggest that the extended emersion capacity of mudfish may result from a generally low metabolic rate that is maintained throughout aerial exposure via cutaneous gas exchange, and which limits the production of potentially toxic nitrogenous waste.

      PubDate: 2014-07-26T23:36:34Z
  • Cellular metabolic rates from primary dermal fibroblast cells isolated
           from birds of different body masses
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Ana Gabriela Jimenez , Joseph B. Williams
      The rate of metabolism is the speed at which organisms use energy, an integration of energy transformations within the body; it governs biological processes that influence rates of growth and reproduction. Progress at understanding functional linkages between whole organism metabolic rate and underlying mechanisms that influence its magnitude has been slow despite the central role this issue plays in evolutionary and physiological ecology. Previous studies that have attempted to relate how cellular processes translate into whole-organism physiology have done so over a range of body masses of subjects. However, the data still remains controversial when observing metabolic rates at the cellular level. To bridge the gap between these ideas, we examined cellular metabolic rate of primary dermal fibroblasts isolated from 49 species of birds representing a 32,000-fold range in body masses to test the hypothesis that metabolic rate of cultured cells scales with body size. We used a Seahorse XF-96 Extracellular flux analyzer to measure cellular respiration in fibroblasts. Additionally, we measured fibroblast size and mitochondrial content. We found no significant correlation between cellular metabolic rate, cell size, or mitochondrial content and body mass. Additionally, there was a significant relationship between cellular basal metabolic rate and proton leak in these cells. We conclude that metabolic rate of cells isolated in culture does not scale with body mass, but cellular metabolic rate is correlated to growth rate in birds.

      PubDate: 2014-07-26T23:36:34Z
  • The effects of constant and diel-fluctuating temperature acclimation on
           the thermal tolerance, swimming capacity, specific dynamic action and
           growth performance of juvenile Chinese bream
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Jing Peng , Zhen-Dong Cao , Shi-Jian Fu
      We investigated the effects of constant and diel-fluctuating temperature acclimation on the thermal tolerance, swimming capacity, specific dynamic action (SDA) and growth performance of juvenile Chinese bream (Parabramis pekinensis). The critical thermal maxima (CTmax ), critical thermal minima (CTmin ), lethal thermal maxima (LTmax ), lethal thermal minima (LTmin ), critical swimming speed (Ucrit ) and fast-start escape response after 30d acclimation to three constant temperatures (15, 20 and 25°C) and one diel-fluctuating temperature (20±5°C) were measured. In addition, feeding rate (FR), feeding efficiency (FE) and specific growth rate (SGR) were measured. The diel-fluctuating temperature group showed lower CTmin than the 20°C group but a similar CT max, indicating a wider thermal scope. SDA linearly increased with the temperature. Temperature variation between 20 and 25°C had little effect on either swimming or growth performance. However, fish in the 15°C group exhibited much poorer swimming and growth performance than those in the 20°C group. Ucrit decreased slightly under low acclimation temperature due to the pronounced improvement in swimming efficiency under cold temperature. Fish in the diel-fluctuating temperature group fed more but exhibited similar SGR compared to 20°C group, possibly due in part to an increase in energy expenditure to cope with the temperature fluctuation. The narrower thermal scope and lower CTmax of Chinese bream together with the conservation of CTmax with temperature acclimation, suggests that local water temperature elevations may have more profound effects on Chinese bream than on other fish species in the Three Gorges Reservoir.

      PubDate: 2014-07-26T23:36:34Z
  • The effects of poly-unsaturated fatty acids on the physiology of
           hibernation in a South American marsupial, Dromiciops gliroides
    • Abstract: Publication date: Available online 15 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Carolina Contreras , Marcela Franco , Ned J. Place , Roberto F. Nespolo
      Many mammals hibernate, which is a profound lethargic state of several weeks or months during winter, is a case that represents a transitory episode of hetherothermy. As with other cases of dormancy, the main benefit of hibernation seems to be energy saving. However, the depth and duration of torpor can be experimentally modified by the composition of food, especially by fattyacid composition. In eutherians, diets rich in unsaturated fatty acids (i.e., fatty acids with at least one double bond) lengthen torpor, reduce metabolism and permit hibernation at lower temperatures. Here we studied whether diets varying in fatty acid composition have an effect on the physiology of hibernation in a South American marsupial, Dromiciops gliroides. We designed a factorial experiment where thermal acclimation (two levels: natural versus constant temperature) was combined with diet acclimation: saturated (i.e., diets with high concentration of saturated fatty acids) versus unsaturated (i.e., diets with high concentration of unsaturated fatty acids). We measured energy metabolism in active and torpid individuals, as well as torpor duration, and a suite of 12 blood biochemical parameters. After a cafeteria test, we found that D. gliroides did not show any preference for a given diet. Also, we did not find effects of diet on body temperature during torpor, or its duration. However, saturated diets, combined with high temperatures provoked a disproportionate increase in fat utilization, leading to body mass reduction. Those animals were more active, and metabolized more fats than those fed with a high proportion of unsaturated fatty acids (=“unsaturated diets”). These results contrast with previous studies, which showed a significant effect of fatty acid composition of diets on food preferences and torpor patterns in mammals.

      PubDate: 2014-07-26T23:36:34Z
  • Changes in calpains and calpastatin in the soleus muscle of Daurian ground
           squirrels during hibernation
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Chen-Xi Yang , Yue He , Yun-Fang Gao , Hui-Ping Wang , Nandu Goswami
      We investigated changes in muscle mass, calpains, calpastatin and Z-disk ultrastructure in the soleus muscle (SOL) of Daurian ground squirrels (Spermophilus dauricus) after hibernation or hindlimb suspension to determine possible mechanisms by which muscle atrophy is prevented in hibernators. Squirrels (n=30) were divided into five groups: no hibernation group (PRE, n=6); hindlimb suspension group (HLS, n=6); two month hibernation group (HIB, n=6); twoday group after 90±12days of hibernation (POST, n=6); and forced exercise group (one time forced, moderate-intensity treadmill exercise) after arousal (FE, n=6). Activity and protein expression of calpains were determined by casein zymography and western blotting, and Z-disk ultrastructure was observed by transmission electron microscopy. The following results were found. Lower body mass and higher SOL muscle mass (mg) to total body mass (g) ratio were observed in HIB and POST; calpain-1 activity increased significantly by 176% (P =0.034) in HLS compared to the PRE group; no significant changes were observed in calpain-2 activity. Protein expression of calpain-1 and calpain-2 increased by 83% (P =0.041) and 208% (P =0.029) in HLS compared to the PRE group, respectively; calpastatin expression increased significantly by 180% (P <0.001) and 153% (P =0.007) in HIB and POST, respectively; the myofilaments were well-organized, and the width of the sarcomere and the Z-disk both appeared visually similar among the pre-hibernation, hibernating and post-hibernation animals. Inhibition of calpain activity and consequently calpain-mediated protein degradation by highly elevated calpastatin protein expression levels may be an important mechanism for preventing muscle protein loss during hibernation and ensuring that Z-lines remained ultrastructurally intact.

      PubDate: 2014-07-26T23:36:34Z
  • Cholesterol deregulation induced by chronic corticosterone (CORT) stress
           in pectoralis major of broiler chickens
    • Abstract: Publication date: Available online 16 July 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Yujing Duan , Wenyan Fu , Song Wang , Yingdong Ni , Ruqian Zhao
      Chronic endogenous glucocorticoid (GC) excess in mammals is associated with metabolic dysfunction and dyslipidemia that are characterized by increased plasma triglyceride and total cholesterol (Tch) levels. However, the effects of chronic GC administration on cholesterol metabolism, particularly in muscle tissues of broiler chickens, are unknown. In this study, broiler chickens were treated chronically with vehicle (CON) or corticosterone (CORT) for 2weeks. Chronic CORT treatment significantly increased Tch levels in pectoralis major muscle (PMC) (p<0.001) as well as in leg muscle (p<0.01), and CORT enhanced triglyceride levels in the PMC (p<0.001). Real-time PCR results showed that HMGCR (p<0.05) mRNA expression was up-regulated by CORT in PMC, and 11β-HSD1 gene transcription (p=0.08) was not significantly downregulated, whereas glucocorticoid receptor (GR) mRNA expression, 11β-HSD2, CYP7A1, CYP27A1, ApoB and LDLR were unchanged by CORT (p>0.05). Western blot results showed that the levels of total GR (p=0.08) tended to be increased and nuclear GR protein (p<0.05) was increased in PMC by CORT administration. Parallel to an increase in gene expression, HMGCR protein expression in PMC was significantly increased (p<0.05) by CORT. Moreover, LDLR (p<0.05), ApoA1 (p=0.06) and 11β-HSD2 (p=0.07) protein expression in PMC tended to be increased by CORT compared to control. These results indicate that chronic CORT administration causes cholesterol accumulation in PMC tissues of broiler chickens by increasing cholesterol synthesis and uptake.

      PubDate: 2014-07-26T23:36:34Z
  • Enthalpic partitioning of the reduced temperature sensitivity of O2
           binding in bovine hemoglobin
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Roy E. Weber , Angela Fago , Kevin L. Campbell
      The oxygenation enthalpy of the heme groups of hemoglobin (Hb) is inherently exothermic, resulting in decreased Hb-O2 affinity with rising temperature. However, oxygenation is coupled with endothermic dissociation of allosteric effectors (e.g. protons, chloride ions and organic phosphates) from the protein, which reduces the overall oxygenation enthalpy. The evolution of Hbs with reduced temperature sensitivity ostensibly safeguards O2 unloading in cold extremities of regionally-heterothermic vertebrates permitting energy-saving reductions in heat loss. Ungulate (e.g. bovine) Hbs have long served as a model system in this regard in that they exhibit numerically low oxygenation enthalpies that are thought to correlate with the presence of an additional Cl− binding site (compared to human Hb) comprised of three cationic residues at positions 8, 76 and 77 of the β-chains of Hb. However, ungulate Hbs also exhibit distinctive amino acid exchanges at the N-termini of the β-chains that stabilize the low-affinity deoxystructure of the Hb, mimicking the action of organic phosphates. In order to assess the relative contributions from these two effects, we measured the temperature sensitivity of Hb-O2 affinity in bovine and human Hbs in the absence and presence of Cl− ions under strictly controlled pH conditions. The data indicate that Cl−-binding accounts for a minority (~30%) of the total reduction in the oxygenation enthalpy manifested in bovine compared to human Hb, whereas the majority of this reduction is ascribable to structural differences, including increased β-chain hydrophobicity that would increase the heat of oxygenation-linked conformational change in bovine Hb.

      PubDate: 2014-07-26T23:36:34Z
  • Chicken hatchlings prefer ambient temperatures lower than their
           thermoneutral zone
    • Abstract: Publication date: October 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 176
      Author(s): Paula Andrea Toro-Velasquez , Kênia C. Bícego , Jacopo P. Mortola
      We investigated whether or not the preferred ambient temperature (Tapref) of the 1-day old chicken hatchling, a precocial neonate with excellent locomotory capacity, clearly identifiable thermogenesis and independence from maternal care, coincides with the lower critical temperature (LCT) of thermoneutrality and minimal oxygen consumption ( V ˙ O 2 ). Tapref of single chicks measured in a thermocline (N =16) averaged 33.5±0.3°C (mode, 33.3±0.4°C). The same value was obtained in hatchlings studied in pairs. LCT was computed from the ambient temperature (Ta)– V ˙ O 2 relationship, constructed by slowly decreasing the Ta of a respirometer from 38 to 29°C over 2.5h, while continuously measuring V ˙ O 2 by an open-flow methodology; LCT averaged 36.4°C±0.3 or 36.8°C±0.4, depending on the method of computation. In all hatchlings Tapref was lower than LCT (P <0.001), by a magnitude that depended on the method of computation of the two variables, 2.8°C±0.3 (P <0.001) or 3.9°C±0.5. The Tapref-LCT difference implied that, at Tapref, V ˙ O 2 was higher than at thermoneutrality. We conclude that in the chicken hatchling thermal preference does not coincide with thermoneutrality, probably because during development what seems optimal from a thermoregulatory viewpoint may not necessarily be so for other regulatory functions.

      PubDate: 2014-07-26T23:36:34Z
  • PHA-induced inflammation is not energetically costly in the subterranean
           rodent Ctenomys talarum (tuco-tucos)
    • Abstract: Publication date: Available online 3 June 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Julieta L. Merlo , Ana P. Cutrera , Facundo Luna , Roxana R. Zenuto
      Immune activity has been proposed to be associated with substantial costs, due to trade-offs with other functions or activities that share common resources and contribute to an animal's fitness. However, direct estimates of the cost of mounting an immune response are few and have been performed mainly in birds. Thus, further work is needed to clarify the relative costs of different components of the immune system and the role of environmental and life-history traits in modulating the costs of resistance. Within the components of immunity, inflammation is considered to be associated with a larger energetic expenditure. Here, we evaluated the energetic cost of the inflammatory response to phytohemagglutinin (PHA) in a wild population of a subterranean rodent, Ctenomys talarum, and the trade-offs between immune activity and reproduction. C. talarum develops an inflammatory response to PHA, but contrary to our predictions, this response was not associated with an increase in oxygen consumption regardless of reproductive status or sex. Our study shows that an immune challenge may not always result in a detectable energetic cost. We discuss the possibility that other currencies could be underlying the cost, such as micro-or macronutrients requirements, autoimmunity or oxidative stress.

      PubDate: 2014-06-07T16:03:50Z
  • Are there different requirements for trace elements in eumelanin- and
           pheomelanin-based color production' A case study of two passerine
    • Abstract: Publication date: Available online 4 June 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Piotr Zduniak , Adrian Surmacki , Kiraz Erciyas-Yavuz , Maria Chudzińska , Danuta Barałkiewicz
      Melanin is the most common pigment in animal integuments including bird plumage. It has been shown that several trace elements may play roles in the production and signaling function of melanin-colored plumage. We investigated coloration and content of various metal elements in the rectrices of two insectivorous passerines, Common Redstarts (Phoenicurus phoenicurus) and Blackcaps (Sylvia atricapilla), which have eumelanin- and pheomelanin-based coloration, respectively. We hypothesized that 1) the two species would differ in concentrations of metals important in melanin synthesis (Ca, Fe, Cu, Zn), 2) differences in metal concentration levels would be related to feather coloration. Our study confirmed the first prediction and provides the first evidence that selected elements may play a greater role in pheomelanin than in eumelanin synthesis. Concentrations of three elements considered as important in melanin synthesis (Ca, Fe, Zn) were 52% to 93% higher in rusty colored Common Redstart feathers compared to the dark gray Blackcap feathers. However, element concentrations were not correlated with feather coloration or sex in either species. Our study suggests that, of the two melanin forms, pheomelanin synthesis may bear higher costs associated with the acquisition of specific elements or limited elements may create trade-offs between ornamentation and other physiological functions. Our findings warrant further investigations designed to better understand the roles of macro- and microelements in the synthesis of both forms of melanin.

      PubDate: 2014-06-07T16:03:50Z
  • Seasonal changes and endocrine regulation of pejerrey (Odontesthes
           bonariensis) oogenesis in the wild
    • Abstract: Publication date: Available online 2 June 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Mariano Elisio , Tomás Chalde , Leandro A. Miranda
      The goal of this study was to evaluate the essential components controlling the brain–pituitary–gonad axis during pejerrey (Odontesthes bonariensis) oogenesis in the wild. Ovarian developmental stages from vitellogenesis up to ovulation were associated with increasing day length and water temperatures below 21°C (winter and beginning of spring). Gonadal regression was observed when water temperature exceeded this value or when photoperiod decreased. Most females were arrested at primary growth stage during summer (high temperature) or at cortical alveoli stage between autumn and beginning of winter (short photoperiod). Plasma E2 and transcript levels of fshr, cyp19a1b and cyp19a1a increased during vitellogenesis, while fshb remained high at all vitellogenic stages. A significant correlation between plasma sex steroids (T and E2) and cyp19a1b as well as lhcgr transcript levels was observed during vitellogenesis, suggesting a steroid positive feedback. Gnrh-I, Gth subunits and lhcgr transcript levels increased significantly during late vitellogenesis and final maturation. Present results suggest that pejerrey vitellogenesis is controlled by Fsh/Fshr, stimulating gonadal aromatase and estradiol synthesis. Moreover, the increase of testosterone and estradiol during final vitellogenesis could induce coordinately the functioning of the Gnrh/Lh system (perhaps through brain P450 aromatase stimulation and brain estradiol increase) and the gonadal Lhcgr synthesis to promote the final maturation of oocytes. All these stimulation mechanisms of gonadal development would be possible only under permissive environmental conditions.

      PubDate: 2014-06-07T16:03:50Z
  • Acute exposure to a common suspended sediment affects the swimming
           performance and physiology of juvenile salmonids
    • Abstract: Publication date: Available online 6 June 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Barbara I. Berli , Matthew J.H. Gilbert , Allison L. Ralph , Keith B. Tierney , Patricia Burkhardt-Holm
      To study the effects of an acute exposure to turbidity generated by suspended sediment, we examined swimming performance (U crit) and related metabolic parameters in individual and groups of juvenile trout at three different concentrations of calcium carbonate. To investigate differences among strains or provenience, we compared one strain of rainbow trout (Oncorhynchus mykiss; RBT) and one strain of brown trout (Salmo trutta; BNT) from a common hatchery and one RBT strain from a separate hatchery. In general, trout swum individually or in groups exhibited a decrease in U crit as turbidity increased. Both RBT strains were more similar to each other and were impaired to a larger extent in swimming performance than BNT, which was less impacted. For groups, indicators of aerobic metabolism were elevated while those of anaerobic metabolism were depressed. Specifically, citrate synthase activities and glucose levels tended to be greater while plasma lactate and LDH activities were reduced. Lactate and LDH levels in individually swum trout under sediment exposure suggest a greater similarity of fish from the same provenience. We suggest that acute exposures to environmentally relevant turbidities generated by fine suspended sediment may cause a reduced U crit, and that these changes may be related to changes in the utilization of aerobic and anaerobic pathways.

      PubDate: 2014-06-07T16:03:50Z
  • The effects of exogenous cortisol on myostatin transcription in rainbow
           trout, Oncorhynchus mykiss
    • Abstract: Publication date: Available online 27 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Nicholas J. Galt , Jacob Michael Froehlich , Ethan A. Remily , Sinibaldo R. Romero , Peggy R. Biga
      Glucocorticoids (GCs) strongly regulate myostatin transcript levels in mammals via glucocorticoid response elements (GREs) in the myostatin promoter, and bioinformatics methods suggest that this regulatory mechanism is conserved among many vertebrates. However, the multiple myostatin genes found in some fishes may be an exception. In rainbow trout (Oncorhynchus mykiss), two genome duplication events have produced three putatively functional myostatin genes, myostatin-1a, -1b and -2a, which are ubiquitously and differentially expressed. In addition, in silico promoter analyses of the rainbow trout myostatin promoters have failed to identify putative GREs, suggesting a divergence in myostatin function. Therefore, we hypothesized that myostatin mRNA expression is not regulated by glucocorticoids in rainbow trout. In this study, both juvenile rainbow trout and primary trout myoblasts were treated with cortisol to examine the relationship between this glucocorticoid and myostatin mRNA expression. Results suggest that exogenous cortisol does not regulate myostatin-1a and -1b expression in vivo, as myostatin mRNA levels were not significantly affected by cortisol treatment in either red or white muscle tissue. In red muscle, myostatin-2a levels were significantly elevated in the cortisol treatment group relative to the control, but not the vehicle control, at both 12h and 24h post-injection. As such, it is unclear if cortisol was acting alone or in combination with the vehicle. Cortisol increased myostatin-1b expression in a dose-dependent manner in vitro. Further work is needed to determine if this response is the direct result of cortisol acting on the myostatin-1b promoter or through an alternative mechanism. These results suggest that regulation of myostatin by cortisol may not be as highly conserved as previously thought and support previous work that describes potential functional divergence of the multiple myostatin genes in fishes.

      PubDate: 2014-06-01T14:41:21Z
  • Adipose tissue and liver metabolic responses to different levels of
           dietary carbohydrates in gilthead sea bream (Sparus aurata)
    • Abstract: Publication date: Available online 26 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Marta Bou , Marijana Todorčević , Ramón Fontanillas , Encarnación Capilla , Joaquim Gutiérrez , Isabel Navarro
      This study analyzes the effects of replacing dietary lipids by carbohydrates and carbohydrates by fiber on gilthead sea bream growth, as well as lipid and glucose metabolism in adipose tissue and liver over the course of a 15-week feeding trial. Six different diets were formulated and fish were classified into two experimental groups sharing one diet. In the first group (LS), fish were fed four diets where lipids were reduced (23%–17%) by increasing carbohydrates (12%–28%) and, the second group (SF) consisted on three diets where the amount of carbohydrates (28%–11%) was exchanged at expenses of fiber (1%–18%). Differences in growth were not observed; nevertheless, the hepatosomatic index was positively related to dietary starch levels, apparently not due to enhanced hepatic lipogenesis, partly supported by unchanged G6PDH expression. In the LS group, lipogenic activity of adipose tissue was stimulated with low-lipid/high-carbohydrate diets by up-regulating G6PDH expression and a tendency to increase FAS, and promoted carbohydrate utilization versus fatty acid oxidation by modulating the transcription factors LXRα, PPARα and PPARβ expression. In the SF group, PPARs and LXRα increased parallel to fiber levels in adipose tissue. Furthermore, an adaptation of hepatic GK to dietary starch inclusion was observed in both groups; however, the lack of effects on G6Pase expression indicated that gluconeogenesis was not nutritionally regulated under the conditions examined. Overall, metabolic adaptations directed to an efficient use of dietary carbohydrates are present in gilthead sea bream, supporting the possibility of increasing the carbohydrate or fiber content in diets for aquaculture sustainability.

      PubDate: 2014-06-01T14:41:21Z
  • Editorial Board
    • Abstract: Publication date: August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 174

      PubDate: 2014-05-25T16:17:33Z
  • Ontogeny of non-shivering thermogenesis in Muscovy ducklings (Cairina
    • Abstract: Publication date: Available online 23 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Loïc Teulier , Jean-Louis Rouanet , Benjamin Rey , Damien Roussel
      In precocial birds, developing the capacity for early regulatory thermogenesis appears as a fundamental prerequisite for survival and growth in cold environments. However, the exact nature of these processes has not been thoroughly investigated. Several bird species, such as Muscovy ducks (Cairina moschata), develop muscular non-shivering thermogenesis when chronically exposed to cold. The aim of this study was to investigate the age-dependent development of non-shivering thermogenesis in ducklings reared either at thermoneutrality (25°C) or in the cold (4°C). Non-shivering thermogenesis was assessed weekly by simultaneously measuring whole body metabolic heat production and electromyographic activity during shivering at different temperatures ranging from 29°C to 0°C. We found that ducklings reared at thermoneutrality displayed a capacity for non-shivering thermogenesis during the first month of post-hatching life. This thermogenic mechanism increased further in ducklings chronically exposed to a cold environment, but it decreased over time when birds were kept in a thermoneutral environment.

      PubDate: 2014-05-25T16:17:33Z
  • Developmental acclimation to low or high humidity conditions affect
           starvation and heat resistance of Drosophila melanogaster
    • Abstract: Publication date: Available online 17 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Ravi Parkash , Poonam Ranga , Dau Dayal Aggarwal
      Populations of several Drosophila species originating from tropical humid localities are more resistant to starvation as well as heat than populations from high latitudes but mechanistic bases of such physiological changes are largely unknown. In order to test whether humidity levels affect starvation survival and heat resistance, we investigated developmental acclimation effects of low to high humidity conditions on the storage and utilization of energy resources, body mass, starvation survival, heat knockdown and heat survival of Drosophila melanogaster. Isofemale lines reared under higher humidity (85% RH) stored significantly higher level of lipids and showed greater starvation survival hours but flies were smaller in body size. In contrast, lines reared at high humidity evidenced reduced levels of body lipids and starvation resistance. Starvation resistance and lipid storage level were higher in females than in males. However, the rate of utilization of lipids under starvation stress was lower for lines reared under higher humidity. Adult flies of lines reared at 65% RH and acclimated under high or low humidity condition for 200h also showed changes in resistance to starvation and heat stress but such effects were significantly lower as compared with developmental acclimation. Isofemale lines reared under higher humidity showed greater heat knockdown time as well as heat-shock survival. These laboratory observations on developmental and adult acclimation effects of low versus high humidity conditions have helped in explaining seasonal changes (rainy versus autumn) in resistance to starvation and heat of the wild-caught flies of D. melanogaster. Thus, we may suggest that wet versus drier conditions significantly affect starvation and heat resistance of D. melanogaster.

      PubDate: 2014-05-25T16:17:33Z
  • Inhibition of the cardiac ATP-dependent potassium current by KB-R7943
    • Abstract: Publication date: Available online 17 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Denis V. Abramochkin , Matti Vornanen
      KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea) was developed as a specific inhibitor of the sarcolemmal sodium–calcium exchanger (NCX) with potential experimental and therapeutic use. However, in cardiomyocytes KB-R7943 also effectively blocks several K+ currents including the delayed rectifier, IKr. Recently, the background inward rectifier (IK1) and the acetylcholine-induced inward rectifier (IKACh) were shown to be sensitive to KB-R7943 block in mammalian and fish cardiomyocytes. In the present study we analyze the effects of KB-R7943 on the ATP-dependent potassium current (IKATP) recorded by whole-cell patch-clamp in ventricular cardiomyocytes from a mammal (mouse) and a fish (crucian carp). IKATP was induced by external application of a mitochondrial uncoupler CCCP (3×10−7 M) and internal perfusion of the cell with ATP-free pipette solution. A weakly inwardly rectifying current with a large outward component, recorded in the presence of CCCP, was blocked with 10−5 M glibenclamide by 56.1±4.6% and 56.9±3.6% in crucian carp and mouse ventricular myocytes, respectively. In fish cardiomyocytes IKATP was blocked by KB-R7943 with an IC50 value of 3.14×10−7 M, while in mammalian cells IC50 was 2.8×10−6 M (P<0.05). 10−5 M KB-R7943 inhibited CCCP-induced IKATP by 99.9±0.13% and 97.5±1.2% in crucian carp and mouse ventricular myocytes, respectively. In crucian carp the IKATP is about an order of magnitude more sensitive to KB-R7943 than the background IK1, but in mammals IKATP and IK1 are almost equally sensitive to KB-R7943. Therefore, the ability of KB-R7943 to block IKATP should be taken into account together with INCX inhibition when investigating possible cardioprotective effects of this compound.

      PubDate: 2014-05-25T16:17:33Z
  • Alterations in gill structure in tropical reef fishes as a result of
           elevated temperatures
    • Abstract: Publication date: Available online 23 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): A.J. Bowden , N.M. Gardiner , C.S. Couturier , J.A.W. Stecyk , G.E. Nilsson , P.L. Munday , J.L. Rummer
      Tropical regions are expected to be some of the most affected by rising sea surface temperatures (SSTs) because seasonal temperature variations are minimal. As temperatures rise, less oxygen dissolves in water, but metabolic requirements of fish and thus, the demand for effective oxygen uptake, increases. Gill remodelling is an acclimation strategy well documented in freshwater cyprinids experiencing large seasonal variations in temperature and oxygen as well as an amphibious killifish upon air exposure. However, no study has investigated whether tropical reef fishes remodel their gills to allow for increased oxygen demands at elevated temperatures. We tested for gill remodelling in five coral reef species (Acanthochromis polyacanthus, Chromis atripectoralis, Pomacentrus moluccensis, Dascyllus melanurus and Cheilodipterus quinquelineatus) from populations in northern Papua New Guinea (2° 35.765' S; 150° 46.193' E). Fishes were acclimated for 12–14 days to 29 and 31°C, encompassing their seasonal range (29–31°C), and 33 and 34°C to account for end-of-century predicted temperatures. We measured lamellar perimeter, cross-sectional area, base thickness, and length for five filaments on the 2nd gill arches and qualitatively assessed 3rd gill arches via scanning electron microscopy (SEM). All species exhibited significant differences in the quantitative measurements made on the lamellae, but no consistent trends with temperature were observed. SEM only revealed alterations in gill morphology in P. moluccensis. The overall lack of changes in gill morphology with increasing temperature suggests that these near-equatorial reef fishes may fail to maintain adequate O2 uptake under future climate scenarios unless other adaptive mechanisms are employed.

      PubDate: 2014-05-25T16:17:33Z
  • Ecophysiology of native and alien invasive clams in an ocean warming
    • Abstract: Publication date: Available online 15 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Patrícia Anacleto , Ana Luísa Maulvault , Vanessa M. Lopes , Tiago Repolho , Mário Diniz , Maria Leonor Nunes , António Marques , Rui Rosa
      Both climate change and biological invasions are among the most serious global environmental threats. Yet mechanisms underlying these eventual interactions remain unclear. The aim of this study was to undertake a comprehensive examination of the physiological and biochemical responses of native (Ruditapes decussatus) and alien invasive (Ruditapes philippinarum) clams to environmental warming. We evaluated thermal tolerance limits (CTMax), routine metabolic rates (RMR) and respective thermal sensitivity (Q10 values), critical oxygen partial pressure (Pcrit), heat shock response (HSP70/HSC70 levels), lipid peroxidation (MDA build-up) and antioxidant enzyme [glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD)] activities. Contrary to most studies that show that invasive species have a higher thermal tolerance than native congeners, here we revealed that the alien invasive and native species had similar CTMax values. However, warming had a stronger effect on metabolism and oxidative status of the native R. decussatus, as indicated by the higher RMR, HSP70/HSC70 and MDA levels, as well as GST, CAT and SOD activities. Moreover, we argue that the alien invasive clams, instead of up-regulating energetically expensive cellular responses, have evolved a less demanding strategy to cope with short-term environmental (oxidative) stress – pervasive valve closure. Although efficient during stressful short-term periods to ensure isolation and guarantee longer survival, such adaptive behavioural strategy entails metabolic arrest (and the enhancement of anaerobic pathways), which to some extent, will not be advantageous under the chronically warming conditions predicted in the future.

      PubDate: 2014-05-20T06:21:56Z
  • Derivation of a continuous myogenic cell culture from an embryo of common
           killifish, Fundulus heteroclitus
    • Abstract: Publication date: Available online 13 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Sarah J. Gignac , Nguyen T.K. Vo , Michael S. Mikhaeil , J. Andrew N. Alexander , Deborah L. MacLatchy , Patricia M. Schulte , Lucy E.J. Lee
      The common killifish or mummichog (Fundulus heteroclitus) is an estuarine teleost increasingly used in comparative physiology, toxicology and embryology. Their ability to withstand extreme environmental conditions and ease of maintenance has made them popular aquatic research organisms. Scientific advances with most popular model organisms have been assisted with the availability of continuous cell lines; however, cell lines from F. heteroclitus appears to be unavailable. The development of a killifish cell line, KFE-5, derived from the mid trunk region of a late stage embryo is described here. KFE-5 grows well in Leibovitz’s L-15 media with 10% fetal bovine serum (FBS). This cell line has been passaged over 60 times in a span of three years, and cells at various passages have been successfully cryopreserved and thawed. The cells are mostly fibroblastic but contain myogenic cells that differentiate into mono-, bi- and multi-nucleated striated myocytes. Immunofluorescence detection of muscle specific antigens such as α-actinin, desmin, myosin confirms KFE-5 as a myogenic cell line. KFE-5 has a temperature preference for 26-28°C and has been shown to withstand temperatures up to 37°C. The cell line responds to chemical signals including growth factors, hormones and extracellular matrix components. KFE-5 could thus be useful not only for mummichog’s thermobiology but also for studies in fish muscle physiology and development.

      PubDate: 2014-05-15T06:27:24Z
  • H2S exposure elicits differential expression of candidate genes in fish
           adapted to sulfidic and non-sulfidic environments
    • Abstract: Publication date: Available online 9 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Michael Tobler , Chathurika Henpita , Brandon Bassett , Joanna L. Kelley , Jennifer H. Shaw
      Disentangling the effects of plasticity, genetic variation, and their interactions on organismal responses to environmental stressors is a key objective in ecological physiology. We quantified the expression of five candidate genes in response to hydrogen sulfide (H2S) exposure in fish (Poecilia mexicana, Poeciliidae) from a naturally sulfide-rich environment as well as an ancestral, non-sulfidic population to test for constitutive and environmentally dependent population differences in gene expression patterns. Common garden raised individuals that had never encountered environmental H2S during their lifetime were subjected to short or long term H2S exposure treatments or respective non-sulfidic controls. The expression of genes involved in responses to H2S toxicity (cytochrome c oxidase, vascular endothelial growth factor, and cytochrome P450-2J6), H2S detoxification (sulfide:quinone oxidoreductase), and endogenous H2S production (cystathionine γ lyase) was determined in both gill and liver tissues by real time PCR. The results indicated complex changes in expression patterns that – depending on the gene – not only differed between organs and populations, but also on the type of H2S exposure. Populations differences, both constitutive and H2S exposure dependent (i.e., plastic), in gene expression were particularly evident for sulfide:quinone oxidoreductase, vascular endothelial growth factor, and to a lesser degree for cytochrome P450-2J6. Our study uncovered putatively adaptive modifications in gene regulation that parallel previously documented adaptive changes in phenotypic traits.

      PubDate: 2014-05-10T06:28:20Z
  • Evidence for intraspecific endocrine disruption of Geukensia demissa
           (Atlantic ribbed mussel) in an urban watershed
    • Abstract: Publication date: Available online 9 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Zachery M. Halem , Dustin J. Ross , Rachel L. Cox
      Populations undergo physiological adaptations in response to environmental stressors. Our five-year bio-monitoring study of the Bronx River Estuary demonstrates comparatively low dissolved oxygen concentrations in this urbanized watershed. Additionally, our current results establish altered hormonal levels, resulting from endocrine disruption, in Geukensia demissa (Atlantic ribbed mussel) from the Bronx River Estuary. No studies have yet investigated a correlation between low dissolved oxygen and endocrine disruption in field-collected bivalves. Testosterone, estradiol, and progesterone levels were collected from male and female mussels in the oxygen depleted Bronx River and well-oxygenated Greenwich Cove. Bronx River mussels exhibited higher testosterone levels and lower estradiol levels than Greenwich Cove mussels. The resulting abnormal hormonal ratio seems to indicate that environmental conditions in the Bronx River facilitate an allosteric inhibition of the cytochrome P450 aromatase enzyme, which aids conversion of testosterone to estradiol. Low progesterone levels suggest Bronx River mussels are experiencing a delay in sexual maturation, and morphometric data show a stalling of shell and tissue growth. To confirm that the mussels collected from both sites are the same species, the universal mitochondrial cytochrome c oxidase subunit I gene was analyzed, through DNA barcoding. Minimal sequential heterogeneity confirmed the mussels are the same species. Such findings suggest intraspecific divergence in various endocrine processes, resulting from environmentally induced stress.

      PubDate: 2014-05-10T06:28:20Z
  • Tracheole investment does not vary with body size among bumblebee (Bombus
           impatiens) sisters
    • Abstract: Publication date: Available online 9 May 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Jessica R. Vogt , Megan K. Dillon , Michael E. Dillon
      Body size is a key organism trait with critical implications for the physiology, life history, and ecology of organisms. Modern insects vary in body mass by over 6 orders of magnitude, but are small by comparison to many other metazoan taxa. The small size of modern insects may reflect limitations imposed by their open respiratory systems which rely, in part, on diffusion. Diffusion rates decline with distance such that, absent compensation, the capacity for larger insects to deliver oxygen to their tissues may be compromised. To compensate, larger grasshoppers, beetles, and bumblebees devote proportionally more of their body volume to the respiratory system, as demonstrated by hypermetric scaling of tracheal volume with body mass>1. Among bumblebee sisters, total respiratory volume scaled with mass2.6, but it is unclear at what level or levels of the tracheal system (main tracheal trunks, air sacs, tracheoles) bumblebees express this extreme hypermetry. Here we use transmission electron microscopy to examine morphology of tracheoles in bumblebee flight muscle among sister bumblebees varying nearly four-fold in body mass. Neither tracheole density nor tracheole diameter changed with body mass. The total cross-sectional area of tracheoles was also invariant with body mass. Together, these results reveal that bumblebees do not compensate for size-related limitations on oxygen delivery by increasing investment at the level of the tracheoles.

      PubDate: 2014-05-10T06:28:20Z
  • Euechinoidea and Cidaroidea respond differently to ocean acidification
    • Abstract: Publication date: Available online 29 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Marie Collard , Aurélie Dery , Frank Dehairs , Philippe Dubois
      The impact of the chemical changes in the ocean waters due to the increasing atmospheric CO2 depends on the ability of an organism to control extracellular pH. Among sea urchins, this seems specific to the Euechinoidea, sea urchins except Cidaroidea. However, Cidaroidea survived two ocean acidification periods: the Permian-Trias and the Cretaceous-Tertiary crises. We investigated the response of these two sea urchin groups to reduced seawater pH with the tropical cidaroid Eucidaris tribuloides, the sympatric euechinoid Tripneustes ventricosus and the temperate euechinoid Paracentrotus lividus. Both euechinoids showed a compensation of the coelomic fluid pH due to increased buffer capacity at reduced seawater pH. This was linked to an increased concentration of DIC in the coelomic fluid and thus of bicarbonate ions (most probably originating from the surrounding seawater as isotopic signature of the carbon - δ13C - were similar). On the other hand, the cidaroid showed no changes within the coelomic fluid. Moreover, the δ13C of the coelomic fluid did not match that of the seawater and was not significantly different between the urchins from the different treatments. Feeding rate was not affected in any species. While euechinoids are able to regulate their extracellular acid-base balance, many questions are still unanswered on the costs of this capacity. On the contrary, cidaroids do not seem affected by a reduced seawater pH. Further investigations need to be undertaken to cover more species, physiological and metabolic parameters in order to determine if energy trade-offs occur and how this mechanism of compensation is distributed among sea urchins.

      PubDate: 2014-04-30T06:27:37Z
  • Feeding induces translocation of vacuolar proton ATPase and pendrin to the
           membrane of leopard shark (Triakis semifasciata) mitochondrion-rich gill
    • Abstract: Publication date: Available online 16 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Jinae N. Roa , Christian L. Munévar , Martin Tresguerres
      In this study we characterized mitochondrion-rich (MR) cells and regulation of acid/base (A/B) relevant ion-transporting proteins in leopard shark (Triakis semifasciata) gills. Immunohistochemistry revealed that leopard shark gills posses two separate cell populations that abundantly express either Na+/K+-ATPase (NKA) or V-H+-ATPase (VHA), but not both ATPases together. Co-immunolocalization with mitochondrial Complex IV demonstrated, for the first time in shark gills, that both NKA- and VHA-rich cells are also MR cells, and that all MR cells are either NKA- or VHA-rich cells. Additionally we localized the anion exchanger pendrin to VHA-rich cells, but not NKA-rich cells. In starved sharks, VHA was localized throughout the cell cytoplasm and pendrin was present at the apical pole (but not in the membrane). However, in a significant number of gill cells from fed leopard sharks, VHA translocated to the basolateral membrane (as previously described in dogfish), and pendrin translocated to the apical membrane. Our results highlight the importance of translocation of ion-transporting proteins to the cell membrane as a regulatory mechanism for A/B regulation.

      PubDate: 2014-04-20T06:44:38Z
  • Expressional regulation of key hepatic enzymes of intermediary metabolism
           in European seabass (Dicentrarchus labrax) during food deprivation and
    • Abstract: Publication date: Available online 18 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Ivan Viegas , Albert Caballero-Solares , João Rito , Marina Giralt , Miguel A. Pardal , Isidoro Metón , John G. Jones , Isabel V. Baanante
      We hypothesized that the analysis of mRNA level and activity of key enzymes in amino acid and carbohydrate metabolism in a feeding/fasting/refeeding setting could improve our understanding of how a carnivorous fish, like the European seabass (Dicentrarchus labrax), responds to changes in dietary intake at the hepatic level. To this end cDNA fragments encoding genes for cytosolic and mitochondrial alanine aminotransferase (cALT; mALT), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) were cloned and sequenced. Measurement of mRNA levels through quantitative real-time PCR performed in livers of fasted seabass revealed a significant increase in cALT (8.5-fold induction) while promoting a drastic 45-fold down-regulation of PK in relation to the levels found in fed seabass. These observations were corroborated by enzyme activity meaning that during food deprivation an increase in the capacity of pyruvate generation happened via alanine to offset the reduction in pyruvate derived via glycolysis. After a 3-day refeeding period cALT returned to control levels while PK was not able to rebound. No alterations were detected in the expression levels of G6PDH while 6PGDH revealed to be more sensitive specially to fasting, as confirmed by a significant 5.7-fold decrease in mRNA levels with no recovery after refeeding. Our results indicate that in early stages of refeeding, the liver prioritized the restoration of systemic normoglycemia and replenishment of hepatic glycogen. In a later stage, once regular feeding is re-established, dietary fuel may then be channeled to glycolysis and de novo lipogenesis.

      PubDate: 2014-04-20T06:44:38Z
  • Assessing the energetic costs and trade-offs of a PHA-induced inflammation
           in the subterranean rodent Ctenomys talarum: Immune response in growing
    • Abstract: Publication date: Available online 12 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Ana Paula Cutrera , Facundo Luna , Julieta L. Merlo , María Belén Baldo , Roxana R. Zenuto
      A traditional approach used to assess whether immune defense is costly is to explore the existence of trade-offs between immunity and other functions; however, quantitative studies of the energetic costs associated with the activation of the immune system are scarce. We assessed the magnitude of a PHA-triggered immune response and the associated energetic costs in 60-day old Ctenomys talarum. We expected that the magnitude of the macroscopic inflammatory response to PHA is lower in young tuco-tucos compared with that of adults, given the allocation of substantial energy to growth, and that the magnitude of the inflammation is lower in male pups compared to females, due to the higher investment in growth of the larger sex. Concomitantly, we expected that the pups challenged with PHA show an increase in oxygen consumption compared to control animals and that a positive association exists between magnitude of the PHA-induced inflammation and oxygen consumption. Contrary to what was expected, young tuco-tucos mounted a higher inflammatory response compared with adults and there were no differences in the magnitude of this response between sexes. The inflammatory response induced by a PHA injection did not represent a significant energetic cost for young tuco-tucos. There were no differences in oxygen consumption between PHA-injected and control animals, and tuco-tucos that mounted a higher inflammatory response to PHA did not show higher oxygen consumption. Energy expenditure, however, is not the only physiological cost involved in trade-offs between immune response and various functions of the organism, and other currencies are discussed.

      PubDate: 2014-04-15T16:22:13Z
  • Adenosinergic regulation of the cardiovascular system in the red-eared
           slider Trachemys scripta
    • Abstract: Publication date: Available online 12 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): William Joyce , Tobias Wang
      Few studies have investigated adenosinergic regulation of the cardiovascular system in reptiles. The haemodynamic effect of a bolus intra-arterial adenosine injection (2.5μMkg−1) was investigated in nine anaesthetised red-eared sliders (Trachemys scripta). Adenosine caused a transient bradycardia, which was accompanied by systemic vasodilatation as evidenced by an increase in systemic flow and a decrease in systemic pressure. Meanwhile, pulmonary flow fell significantly. Both the bradycardia and increase in systemic conductance were significantly attenuated by theophylline (4mgkg−1), demonstrating an involvement of P1 receptors. These results suggest that adenosine is likely to play a significant role in reptile cardiovascular physiology. In turtles specifically, adenosinergic regulation may be particularly relevant during periods of apnoea.

      PubDate: 2014-04-15T16:22:13Z
  • Physiological indices of stress in wild and captive garter snakes:
           Correlations, repeatability, and ecological variation
    • Abstract: Publication date: Available online 5 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Amanda M. Sparkman , Anne M. Bronikowski , Shelby Williams , Shikha Parsai , Whitney Manhart , Maria G. Palacios
      Glucocorticoids and leukocyte ratios have become the most widespread variables employed to test hypotheses regarding physiological stress in wild and captive vertebrates. Little is known, however, regarding how these two indices of stress covary in response to stressors, their repeatability within individuals, and differences in response time upon capture. Furthermore, few studies compare stress indices between captive and wild populations, to assess potential alteration of stress physiology in captivity. To address these issues, we examined corticosterone (CORT) and heterophil to lymphocyte (H:L) ratios in two ecotypes of the garter snake Thamnophis elegans. We found that CORT and H:L ratios were not correlated within individuals, and both variables showed little or no repeatability over a period of months. CORT levels, but not H:L ratios, were higher for individuals sampled after ten min from the time of capture. However, both variables showed similar patterns of ecotypic variation, and both increased over time in gravid females maintained in captivity for four months. We suggest that CORT and H:L ratios are both useful, but disparate indices of stress in this species, and may show complex relationships to each other and to ecological and anthropogenic variables.

      PubDate: 2014-04-10T16:15:17Z
  • Phenotypic flexibility in passerine birds: Seasonal variation in fuel
           storage, mobilization and transport
    • Abstract: Publication date: Available online 3 April 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Eric T. Liknes , Christopher G. Guglielmo , David L. Swanson
      Winter acclimatization in small birds living in cold climates produces a winter phenotype characterized by upregulation of metabolic rates to meet enhanced thermoregulatory demands. We measured several key aspects of fuel storage, mobilization and transport in summer and winter to determine whether black-capped chickadees (Poecile atricapillus), white-breasted nuthatches (Sitta carolinensis), and house sparrows (Passer domesticus) seasonally modulate these attributes to meet enhanced winter thermoregulatory demands. In addition, we exposed birds to thermoneutral (control) and severe cold exposure treatments to determine whether acute cold exposure influenced fuel storage, mobilization or transport. Carcass lipid mass and pectoralis intramuscular lipid did not vary significantly between seasons or temperature treatments for any of the study species. Muscle glycogen varied significantly seasonally only for chickadee supracoracoideus and leg muscles, and did not vary among warm or cold treatments for any species. Pectoralis fatty acid binding protein (FABPc) was significantly elevated in winter for chickadees and nuthatches, but not for sparrows. Plasma metabolites showed little consistent variation in response to season or acute cold exposure. Thus, fuel storage and mobilization do not appear to be major targets of adjustment associated with seasonal metabolic flexibility in these species, but modulation of intracellular lipid transport by FABPc may be an important contributor to seasonal phenotypes in some species of small birds.

      PubDate: 2014-04-05T11:17:02Z
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