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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: 259)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 13)
Acta Crystallographica Section D : Biological Crystallography     Hybrid Journal   (Followers: 8)
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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: 150)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 11)
Amino Acids     Hybrid Journal   (Followers: 7)
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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)
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Applied Organometallic Chemistry     Hybrid Journal   (Followers: 4)
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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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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: 18)
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Central European Journal of Chemistry     Hybrid Journal   (Followers: 5)
ChemBioChem     Hybrid Journal   (Followers: 2)
Chemical and Biological Technologies for Agriculture     Open Access  
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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: 14)
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
   Journal TOC RSS feeds Export to Zotero [7 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 1095-6433
     Published by Elsevier Homepage  [2563 journals]
  • Kisspeptin regulates the somatic growth-related factors of the cinnamon
           clownfish Amphiprion melanopus
    • Abstract: Publication date: Available online 15 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Na Na Kim , Young-Ung Choi , Heung-Sik Park , Choi Cheol Young Choi
      This study aimed to test the effects of kisspeptin (Kiss) on somatic growth in the cinnamon clownfish Amphiprion melanopus. We investigated the effects of Kiss treatment on the growth by measuring the mRNA expressions of the growth hormone (GH), insulin-like growth hormone factor (IGF-I), somatolactin (SL), and melatonin receptor (MT). The expression levels of GH and SL of the pituitary and IGF-I of the liver increased after Kiss treatment (in vivo and in vitro). In addition, the MT mRNA expression increased in the pituitary and brain after Kiss treatment (in vivo and in vitro). These results support the hypothesis that Kiss directly regulates the somatic growth-related factors, such as GH, SL, and MT, and IGF-I in the cinnamon clownfish. Further, injection of Kiss resulted in significantly higher levels of plasma melatonin than that in the control. We, therefore, conclude that Kiss plays a role in modulating growth and artificially induced rapid growth in cinnamon clownfish.

      PubDate: 2014-09-16T06:57:55Z
  • Peripheral chemoreceptors in fish: A brief history and a look ahead
    • Abstract: Publication date: Available online 16 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Michael G. Jonz , Peter C. Zachar , Dillon F. Da Fonte , Anna S. Mierzwa
      The story of control of cardiorespiratory reflexes by peripheral chemoreceptors includes a chapter on evolution in large part because of the work of Prof. William K. Milsom. Bill has reminded us to think comparatively about O2 and CO2/H+ sensing. We present a brief review of the fish gill and O2 chemoreceptors, as well as recent results from our laboratory, that were discussed at a symposium in honour of Prof. Milsom's extensive career. In a series of papers from the Milsom laboratory from 1986 to 1995, it was demonstrated that the fish gill is a major site of chemosensory discharge during hypoxia, and that this response is sensitive to multiple neurochemicals involved in chemosensing. These and other more recent studies by Bill and colleagues are now fundamental and have helped to shape the field as it is today. At the cellular level, we have shown that chemosensitive neuroepithelial cells (NECs) of the gills may possess unique adaptations compared to their mammalian homologues. In addition, we used injection of the styryl dye, FM1-43, to identify gill NECs in zebrafish and demonstrate increased vesicular activity in NECs in vitro during acute stimulation. In vivo, we have identified 5-HT2, 5-HT3, dopaminergic and nicotinic receptor activity involved in the hyperventilatory response in developing zebrafish. With this model we have also traced the fate of mitotic cells in the gills, and demonstrated the regeneration of resected gill filaments and replacement of O2-sensitive NECs.

      PubDate: 2014-09-16T06:57:55Z
  • Effects of hypoxia on ionic regulation, glycogen utilization and
           antioxidative ability in the gills and liver of the aquatic air-breathing
           fish Trichogaster microlepis
    • Abstract: Publication date: Available online 16 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Chun-Yen Huang , Hui-Chen Lin , Cheng-Huang Lin
      We examined the hypothesis that Trichogaster microlepis, a fish with an accessory air-breathing organ, uses a compensatory strategy involving changes in both behavior and protein levels to enhance its gas exchange ability. This compensatory strategy enables the gill ion-regulatory metabolism to maintain homeostasis during exposure to hypoxia. The present study aimed to determine whether ionic regulation, glycogen utilization and antioxidant activity differ in terms of expression under hypoxic stresses; fish were sampled after being subjected to 3 or 12 h of hypoxia and 12 h of recovery under normoxia. The air-breathing behavior of the fish increased under hypoxia. No morphological modification of the gills was observed. The expression of carbonic anhydrase II did not vary among the treatments. The Na+/K+-ATPase enzyme activity did not decrease, but increases in Na+/K+-ATPase protein expression and ionocyte levels were observed. The glycogen utilization increased under hypoxia as measured by glycogen phosphorylase protein expression and blood glucose level, whereas the glycogen content decreased. The enzyme activity of several components of the antioxidant system in the gills, including catalase, glutathione peroxidase, and superoxidase dismutase, increased in enzyme activity. Based on the above data, we concluded that T. microlepis is a hypoxia-tolerant species that does not exhibit ion-regulatory suppression but uses glycogen to maintain energy utilization in the gills under hypoxic stress. Components of the antioxidant system showed increased expression under the applied experimental treatments.

      PubDate: 2014-09-16T06:57:55Z
  • Antiviral activity of the inducible humoral immunity and its suppression
           by eleven BEN family members encoded in Cotesia plutellae bracovirus
    • Abstract: Publication date: Available online 16 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Ramjan Ali , Yonggyun Kim
      Upon parasitization by some endoparasitoids, polydnaviruses (PDVs) play a crucial role in inducing host immunosuppression. This study reports a novel immunosuppressive activity against humoral immune responses by BEN family genes encoded in Cotesia plutellae bracovirus (CpBV). A total of 11 BEN family members are encoded in 10 different CpBV DNA segments. When the CpBV segments were individually injected, specific BEN genes were expressed and suppressed the expression of antimicrobial peptide (AMP) and prophenoloxidase genes following bacterial challenge. The suppressive activities of the BEN genes were reversed by injection of the double-stranded RNA (dsRNA) specific to each BEN gene. The suppression of the AMP gene expressions by the BEN genes were also confirmed using an inhibition zone assay against Gram-positive and -negative bacterial growth. The significance of the suppressive activity of BEN genes against humoral immune responses was analyzed in terms of suppression of antiviral activity by the host humoral immunity. When CpBV was incubated with the plasma obtained from the larvae challenged with bacteria, the immunized plasma severely impaired the expression activity of the viral genes. However, an expression of BEN gene significantly rescued the viral gene expression by suppressing humoral immune response. These results suggest that BEN family genes of CpBV play a crucial role in defending the antiviral response of the parasitized Plutella xylostella by inhibiting humoral immune responses.

      PubDate: 2014-09-16T06:57:55Z
  • Seasonal variations in reproductive activity of the blue crab, Callinectes
           sapidus: Vitellogenin expression and levels of vitellogenin in the
           hemolymph during ovarian development
    • Abstract: Publication date: Available online 16 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Willawan Thongda , J. Sook Chung , Naoaki Tsutsui , Nilli Zmora , Anna Katenta
      In general, season affects the physiology and behavior of most animals. Warmer temperatures accelerate growth and reproduction of ectotherms, whereas these processes are slowed or halted in colder temperatures. Female blue crabs, Callinectes sapidus inhabiting the Chesapeake Bay, exhibit a seasonal migratory behavior that is closely tied with spawning and the release of larvae. To better understand reproductive activities of the migratory adult females, we examined two reproductive parameters of these crabs sampled monthly (April-December, 2006): the levels of vitellogenin (VtG) in the hemolymph and VtG expression in the hepatopancreas and ovary. The full-length cDNA of VtG (CasVtG-ova) has been isolated from the ovary. The putative CasVtG sequence found in the ovary is >99% identical to that of the hepatopancreas and is related most closely to the sequences reported in other crab species. In female C. sapidus, the hepatopancreas produces over 99% of the total VtG toward the ovarian development. Ovarian stages 2 and 3 in the sampled females are characterized by significant high levels of VtG in hemolymph and VtG expression in both the hepatopancreas and ovary. However, during the southbound migration in fall, females at ovarian stages 2 and 3 have decreased VtG levels, compared to those in spring and summer. The decreased vitellogenesis activity during the fall migration suggests seasonal adaptation to ensure successful spawning and the larval release.

      PubDate: 2014-09-16T06:57:55Z
  • High blood oxygen affinity in the air-breathing swamp eel Monopterus albus
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Christian Damsgaard , Inge Findorf , Signe Helbo , Yigit Kocagoz , Rasmus Buchanan , Do Thi Thanh Huong , Roy E. Weber , Angela Fago , Mark Bayley , Tobias Wang
      The Asian swamp eel (Monopterus albus, Zuiew 1793) is a facultative air-breathing fish with reduced gills. Previous studies have shown that gas exchange seems to occur across the epithelium of the buccopharyngeal cavity, the esophagus and the integument, resulting in substantial diffusion limitations that must be compensated by adaptations in others steps of the O2 transport system to secure adequate O2 delivery to the respiring tissues. We therefore investigated O2 binding properties of whole blood, stripped hemoglobin (Hb), two major isoHb components and the myoglobin (Mb) from M. albus. Whole blood was sampled using indwelling catheters for blood gas analysis and determination of O2 equilibrium curves. Hb was purified to assess the effects of endogenous allosteric effectors, and Mb was isolated from heart and skeletal muscle to determine its O2 binding properties. The blood of M. albus has a high O2 carrying capacity [hematocrit (Hct) of 42.4±4.5%] and binds O2 with an unusually high affinity (P 50 =2.8±0.4mmHg at 27°C and pH7.7), correlating with insensitivity of the Hb to the anionic allosteric effectors that normally decrease Hb-O2 affinity. In addition, Mb is present at high concentrations in both heart and muscle (5.16±0.99 and 1.08±0.19mg ∙ g wet tissue-1, respectively). We suggest that the high Hct and high blood O2 affinity serve to overcome the low diffusion capacity in the relatively inefficient respiratory surfaces, while high Hct and Mb concentration aid in increasing the O2 flux from the blood to the muscles.

      PubDate: 2014-09-12T05:16:16Z
  • Pigment granule translocation in red ovarian chromatophores from the
           palaemonid shrimp Macrobrachium olfersi (Weigmann, 1836): Functional roles
           for the cytoskeleton and its molecular motors
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Sarah Ribeiro Milograna , Márcia Regina Ribeiro , Munira Muhammad Abdel Baqui , John Campbell McNamara
      The binding of red pigment concentrating hormone (RPCH) to membrane receptors in crustacean chromatophores triggers Ca2+/cGMP signaling cascades that activate cytoskeletal motors, driving pigment granule translocation. We investigate the distributions of microfilaments and microtubules and their associated molecular motors, myosin and dynein, by confocal and transmission electron microscopy, evaluating a functional role for the cytoskeleton in pigment translocation using inhibitors of polymer turnover and motor activity in vitro. Microtubules occupy the chromatophore cell extensions whether the pigment granules are aggregated or dispersed. The inhibition of microtubule turnover by taxol induces pigment aggregation and inhibits re-dispersion. Phalloidin-FITC actin labeling, together with tannic acid fixation and ultrastructural analysis, reveals that microfilaments form networks associated with the pigment granules. Actin polymerization induced by jasplaquinolide strongly inhibits RPCH-induced aggregation, causes spontaneous pigment dispersion, and inhibits pigment re-dispersion. Inhibition of actin polymerization by latrunculin-A completely impedes pigment aggregation and re-dispersion. Confocal immunocytochemistry shows that non-muscle myosin II (NMMII) co-localizes mainly with pigment granules while blebbistatin inhibition of NMMII strongly reduces the RPCH response, also inducing spontaneous pigment dispersion. Myosin II and dynein also co-localize with the pigment granules. Inhibition of dynein ATPase by erythro-9-(2-hydroxy-3-nonyl) adenine induces aggregation, inhibits RPCH-triggered aggregation, and inhibits re-dispersion. Granule aggregation and dispersion depend mainly on microfilament integrity although microtubules may be involved. Both cytoskeletal polymers are functional only when subunit turnover is active. Myosin and dynein may be the molecular motors that drive pigment aggregation. These mechanisms of granule translocation in crustacean chromatophores share various features with those of vertebrate pigment cells.

      PubDate: 2014-09-12T05:16:16Z
  • Osmoregulation and branchial plasticity after acute freshwater transfer in
           red drum, Sciaenops ocellatus
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Caroline J. Watson , Wiolene M. Nordi , Andrew J. Esbaugh
      Red drum, Sciaenops ocellatus, is an estuarine-dependent fish species commonly found in the Gulf of Mexico and along the coast of the southeastern United States. This economically important species has demonstrated freshwater tolerance; however, the physiological mechanisms and costs related to freshwater exposure remain poorly understood. The current study therefore investigated the physiological response of red drum using an acute freshwater transfer protocol. Plasma osmolality, Cl−, Mg2+ and Ca2+ were all significantly reduced by 24h post-transfer; Cl− and Mg2+ recovered to control levels by 7days post-transfer. No effect of transfer was observed on muscle water content; however, muscle Cl− was significantly reduced. Interestingly, plasma and muscle Na+ content was unaffected by freshwater transfer. Intestinal fluid was absent by 24h post-transfer indicating cessation of drinking. Branchial gene expression analysis showed that both CFTR and NKCC1 exhibited significant down-regulation at 8 and 24h post-transfer, respectively, although transfer had no impact on NHE2, NHE3 or Na+, K+ ATPase (NKA) activity. These general findings are supported by immunohistochemical analysis, which revealed no apparent NKCC containing cells in the gills at 7days post transfer while NKA cells localization was unaffected. The results of the current study suggest that red drum can effectively regulate Na+ balance upon freshwater exposure using already present Na+ uptake pathways while also down-regulating ion excretion mechanisms.

      PubDate: 2014-09-12T05:16:16Z
  • The role of metabolism for understanding the altitudinal segregation
           pattern of two potentially interacting lizards
    • Abstract: Publication date: Available online 3 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Anamarija Žagar , Tatjana Simčič , Miguel A. Carretero , Al Vrezec
      Sympatric species belonging to the same ecological guild, that exhibit partial altitudinal segregation, can potentially interact when in areas of syntopic occurrence. Besides general species’ ecology, physiology can provide elusive answers about species interactions reflected in altitudinal patterns. Lizards Podarcis muralis and Iberolacerta horvathi subject to the rule of partial altitudinal segregation, while they strongly resemble in overall morphology and ecology (diet, daily and seasonal activity pattern), but show some degree of physiological dissimilarity. They have similar mean preferred body temperatures and its pattern of seasonal and daily variation but differ in the magnitude of seasonal variation. Since in ectotherms metabolism is highly dependent on body temperature, thermoregulation is expected to directly affect their metabolism. We compared metabolic rates of adult males of studied species from an area of sympatry, measured under two temperature regimes (20°C and 28°C) in search of interspecific differences in the response of metabolism to temperature change. Both species increased metabolic rates with temperature with a similar pattern. Secondly, we compared measures of electron transport activity from their tail tissues which provide values of species potential metabolic activity (enzymatic capacity). Species clearly differed in potential metabolic activity; I. horvathi attains higher values than P. muralis. No interspecific difference was detected in how species exploited this potential (calculated from the ratio of electron transport activity and metabolic rates). However, measures of electron transport activity showed higher potential metabolic activity of I. horvathi which together with the ability to thermoregulate more precisely could represent a higher competitive advantage over P. muralis in thermally more restrictive environments such as higher altitudes. Understanding of metabolism seems to provide valuable information for understanding recent distributional patterns as well as species interactions.

      PubDate: 2014-09-06T03:54:40Z
  • The actions of the renin–angiotensin system on cardiovascular and
           osmoregulatory function in embryonic chickens (Gallus gallus domesticus)
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Casey A. Mueller , Dane A. Crossley II , Warren W. Burggren
      Using embryonic chickens (Gallus gallus domesticus), we examined the role of the renin–angiotensin system (RAS) in cardiovascular and osmotic homeostasis through chronic captopril, an angiotensin-converting enzyme (ACE) inhibitor. Captopril (5mgkg−1 embryo wet mass) or saline (control) was delivered via the egg air cell daily from embryonic day 5–18. Mean arterial pressure (MAP), heart rate (ƒH), fluid osmolality and ion concentration, and embryonic and organ masses were measured on day 19. Exogenous angiotensin I (ANG I) injection did not change MAP or ƒH in captopril-treated embryos, confirming ACE inhibition. Captopril-treated embryos were significantly hypotensive, with MAP 15% lower than controls, which we attributed to the loss of vasoconstrictive ANG II action. Exogenous ANG II induced a relatively greater hypertensive response in captopril-treated embryos compared to controls. Changes in response to ANG II following pre-treatment with phentolamine (α-adrenergic antagonist) indicated a portion of the ANG II response was due to circulating catecholamines in captopril-treated embryos. An increase in MAP and ƒH in response to hexamethonium indicated vagal tone was also increased in the absence of ACE activity. Captopril-treated embryos had lower osmolality, lower Na+ and higher K+ concentration in the blood, indicating osmoregulatory changes. Larger kidney mass in captopril-treated embryos suggests disrupting the RAS may stimulate kidney growth by decreasing resistance at the efferent arteriole and increasing the fraction of cardiac output to the kidneys. This study suggests that the RAS, most likely through ANG II action, influences the development of the cardiovascular and osmoregulatory systems.

      PubDate: 2014-09-06T03:54:40Z
  • Cold hardiness and deacclimation of overwintering Papilio zelicaon pupae
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Caroline M. Williams , Annegret Nicolai , Laura V. Ferguson , Mark A. Bernards , Jessica J. Hellmann , Brent J. Sinclair
      Seasonally-acquired cold tolerance can be reversed at warm temperatures, leaving temperate ectotherms vulnerable to cold snaps. However, deacclimation, and its underlying mechanisms, has not been well-explored in insects. Swallowtail butterflies are widely distributed but in some cases their range is limited by low temperature and their cold tolerance is seasonally acquired, implying that they experience mortality resulting from deacclimation. We investigated cold tolerance and hemolymph composition of Anise swallowtail (Papilio zelicaon) pupae during overwintering in the laboratory, and after four days exposure to warm temperatures in spring. Overwintering pupae had supercooling points around −20.5°C and survived brief exposures to −30°C, suggesting partial freeze tolerance. Overwintering pupae had hemolymph osmolality of approximately 920mOsm, imparted by high concentrations of glycerol, K+ and Na+. After exposure to spring warming, supercooling points increased to approximately −17°C, and survival of a 1h exposure to −20°C decreased from 100% to 0%. This deacclimation was associated with decreased hemolymph osmolality and reduced glycerol, trehalose, Na+ and Ca2+ concentrations. We compared cold tolerance of pupae to weather conditions at and beyond the species' northern range boundary. Minimum temperatures at the range boundary approached the lower lethal temperature of pupae, and were colder north of the range, suggesting that cold hardiness may set northern range limits. Minimum temperatures following warm snaps were likely to cause mortality in at least one of the past three years. Cold snaps in the spring are increasing in frequency as a result of global climate change, so are likely to be a significant source of mortality for this species, and other temperate ectotherms.

      PubDate: 2014-09-06T03:54:40Z
  • The absence of ion-regulatory suppression in the gills of the aquatic
           air-breathing fish Trichogaster lalius during oxygen stress
    • Abstract: Publication date: Available online 3 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Chun-Yen Huang , Hsueh-Hsi Lin , Cheng-Huang Lin , Hui-Chen Lin
      The strategy for most teleost to survive in hypoxic or anoxic conditions is to conserve energy expenditure, which can be achieved by suppressing energy-consuming activities such as ion regulation. However, an air-breathing fish can cope with hypoxic stress using a similar adjustment, as in most teleost, or by enhancing gas exchange ability, both behaviorally and physiologically. In the present study, we examined Trichogaster lalius, an air-breathing fish without apparent gill modification, for their gill ion-regulatory abilities and glycogen utilization under a hypoxic treatment. We recorded air-breathing frequency, branchial morphology, and the expression of ion-regulatory proteins (Na+/K+-ATPase and vacuolar-type H+-ATPase) in the 1st and 4th gills and labyrinth organ (LO), and the expression of glycogen utilization (GP, glycogen phosphorylase protein expression and glycogen content) and other protein responses (catalase, CAT; carbonic anhydranse II, CAII; heat shock protein 70, HSP70; hypoxia-inducible factor-1α, HIF-1α; proliferating cell nuclear antigen, PCNA; superoxidase dismutase, SOD) in the gills of T. lalius after 3days in hypoxic and restricted conditions. In contrast to our study on other air-breathing species, no morphological modification of the 1st and 4th gills was observed. The air-breathing behavior of the fish and CAII protein expression both increased under hypoxia. Ion-regulatory abilities were not suppressed in the hypoxic or restricted groups, but glycogen utilization, indicated as GP protein expression, was enhanced within the groups. The expression of HIF-1α, HSP70 and PCNA did not vary among the treatments. Regarding the antioxidant system, decreased CAT enzyme activity was observed among the groups. In conclusion, during hypoxic stress, T. lalius did not significantly reduce energy consumption but enhanced gas exchange ability and glycogen expenditure.

      PubDate: 2014-09-06T03:54:40Z
  • Assessing stimulus and subject influences on auditory evoked potentials
           and their relation to peripheral physiology in green treefrogs (Hyla
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Nathan P. Buerkle , Katrina M. Schrode , Mark A. Bee
      Anurans (frogs and toads) are important models for comparative studies of communication, auditory physiology, and neuroethology, but to date, most of our knowledge comes from in-depth studies of a relatively small number of model species. Using the well-studied green treefrog (Hyla cinerea), this study sought to develop and evaluate the use of auditory evoked potentials (AEPs) as a minimally invasive tool for investigating auditory sensitivity in a larger diversity of anuran species. The goals of the study were to assess the effects of frequency, signal level, sex, and body size on auditory brainstem response (ABR) amplitudes and latencies, characterize gross ABR morphology, and generate an audiogram that could be compared to several previously published audiograms for green treefrogs. Increasing signal level resulted in larger ABR amplitudes and shorter latencies, and these effects were frequency dependent. There was little evidence for an effect of sex or size on ABRs. Analyses consistently distinguished between responses to stimuli in the frequency ranges of the three previously-described populations of afferents that innervate the two auditory end organs in anurans. The overall shape of the audiogram shared prominent features with previously published audiograms. This study highlights the utility of AEPs as a valuable tool for the study of anuran auditory sensitivity.

      PubDate: 2014-09-06T03:54:40Z
  • To each its own: Thermoregulatory strategy varies among neonatal polar
    • Abstract: Publication date: Available online 21 August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Linnea E. Pearson , Heather E.M. Liwanag , Mike O. Hammill , Jennifer M. Burns
      Cold environmental conditions and small body size often promote heat loss and may create thermoregulatory challenges for marine mammals born in polar regions. However, among polar-born phocid seal species there are variations in physical attributes and environmental conditions at birth, allowing for an interesting contrast in thermoregulatory strategy. We compared aspects of thermoregulatory strategies including morphometrics, sculp attributes (conductivity and resistance), nonshivering thermogenesis (NST via uncoupling protein 1; UCP1), and muscle thermogenesis (via enzyme activity) in neonatal harp (Pagophilus groenlandicus), hooded (Cystophora cristata), and Weddell seals (Leptonychotes weddellii). Harp seals are the smallest at birth (9.8±0.7kg), rely on lanugo (82.49±3.70% of thermal resistance), and are capable of NST through expression of UCP1 in brown adipose tissue (BAT). In contrast, hooded seal neonates (26.8±1.3kg) have 2.06±0.23cm of blubber, accounting for 38.19±6.07% of their thermal resistance. They are not capable of NST, as UCP1 is not expressed. The large Weddell seal neonates (31.5±4.9kg) rely on lanugo (89.85±1.25% of thermal resistance) like harp seals, but no evidence of BAT was found. Muscle enzyme activity was highest in Weddell seal neonates, suggesting they rely primarily on muscle thermogenesis. Similar total thermal resistance, combined with the marked differences in thermogenic capacity of NST and ST among species, strongly supports the idea that thermoregulatory strategy in neonate phocids is more closely tied to pups' surface area to volume ratio (SA:V) and potential for early water immersion rather than mass and ambient environmental conditions.

      PubDate: 2014-09-02T02:29:30Z
  • Testing the heat-invariant and cold-variability tolerance hypotheses
           across geographic gradients
    • Abstract: Publication date: Available online 23 August 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Francisco Bozinovic , María J.M. Orellana , Sebastián I. Martel , José M. Bogdanovich
      Changes in temperature across geographic gradients can occur on a wide temporal range, from fluctuations within hours as a result of day-night to those over many years. These events will drive many organisms towards their physiological limits of thermal tolerance. Recently, many reports support a limited scope for adaptive evolutionary responses to high temperatures, meaning a conserved heat tolerance among ectotherms in general. We address this problem and tested the heat and cold tolerance invariant–variant hypotheses in terrestrial isopods. We studied five different populations of Porcellio laevis and three populations of Porcellio scaber, spanning 30° S latitudinal gradient in Chile. The heat tolerance of woodlice was conserved with little variation along latitude and environmental temperatures, but cold tolerance decreases significantly with environmental temperatures and latitudes. Indeed, a significant and negative correlation was observed between cold tolerance and latitude. Also, significant and positive correlations were observed among cold tolerance and environmental temperatures. Conversely, heat tolerance was not significantly correlated with any of the environmental temperatures tested neither with latitude. This macrophysiological pattern indicated that heat and cold-tolerances of species and populations not always change across geographical gradients meaning that thermal tolerance responses to high temperatures may be evolutionary constrained.

      PubDate: 2014-09-02T02:29:30Z
  • Editorial Board
    • Abstract: Publication date: November 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 177

      PubDate: 2014-09-02T02:29:30Z
  • Hearts of some Antarctic fishes lack mitochondrial creatine kinase
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): K.M. O'Brien , I.A. Mueller , J.I. Orczewska , K.R. Dullen , M. Ortego
      Creatine kinase (CK; EC functions as a spatial and temporal energy buffer, dampening fluctuations in ATP levels as ATP supply and demand change. There are four CK isoforms in mammals, two cytosolic isoforms (muscle [M-CK] and brain [B-CK]), and two mitochondrial isoforms (ubiquitous [uMtCK] and sarcomeric [sMtCK]). Mammalian oxidative muscle couples expression of sMtCK with M-CK, creating an energy shuttle between mitochondria and myofibrils. We hypothesized that the expression pattern and activity of CK would differ between hearts of red- and white-blooded Antarctic notothenioid fishes due to their striking differences in cardiac ultrastructure. Hearts of white-blooded icefishes (family Channichthyidae) have significantly higher mitochondrial densities compared to red-blooded species, decreasing the diffusion distance for ATP between mitochondria and myofibrils and potentially minimizing the need for CK. The distribution of CK isoforms was evaluated using western blotting and maximal activity of CK was measured in mitochondrial and cytosolic fractions and tissue homogenates of heart ventricles of red- and white-blooded notothenioids. Transcript abundance of sMtCK and M-CK was also quantified. Overall, CK activity is similar between hearts of red- and white-blooded notothenioids but hearts of icefishes lack MtCK and have higher activities of M-CK in the cytosol compared to red-blooded fishes. The absence of MtCK may compromise cardiac function under stressful conditions when ATP supply becomes limiting.

      PubDate: 2014-09-02T02:29:30Z
  • 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
  • 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
  • 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
  • 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
  • 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
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