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        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  [2566 journals]
  • Seasonal variation in body mass, body temperature and thermogenesis in the
           Hwamei, Garrulax canorus
    • Abstract: Publication date: Available online 26 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Mei-Xiu Wu , Li-Meng Zhou , Li-Dan Zhao , Zhi-Jun Zhao , Wei-Hong Zheng , Jin-Song Liu
      The basal thermogenesis of birds is beginning to be viewed as a highly flexible physiological trait influenced by environmental fluctuations, particularly changes in ambient temperature (T a). Many birds living in regions with seasonal fluctuations in T a typically respond to cold by increasing their insulation and adjusting their metabolic rate. To understand these metabolic adaptations, body temperature (T b), metabolic rate (MR), thermal neutral zone (TNZ) and thermal conductance were measured within a range of temperatures from 5 to 40°C in free-living Hwamei, Garrulax canorus, in both winter and summer. Body mass was 61.2±0.3g in winter and 55.5±1.0g in summer, and mean T b was 41.6±0.1°C in winter and 42.3±0.1°C in summer. TNZ was between 28.3 and 35.1°C in winter and between 28.7 and 33.2°C in summer. The mean basal metabolic rate (BMR) within TNZ was 203.32±11.81ml O2 h-1 in winter and 168.99±6.45ml O2 h-1 in summer. Minimum thermal conductance was 3.73±0.09 joules g-1 h-1 °C-1 in winter and 3.26±0.06 joules g-1 h-1 °C-1 in summer. Birds caught in winter had higher body mass, MR, and more variable TNZ than those in summer. The increased winter BMR indicates improved ability to cope with cold and maintenance of a high T b. These results show that the Hwamei’s metabolism is not constant, but exhibits pronounced seasonal phenotypic flexibility associated with maintenance of a high T b.

      PubDate: 2014-09-28T11:03:11Z
  • mRNA levels of kisspeptins, kisspeptin receptors, and GnRH1 in the brain
           of chub mackerel during puberty
    • Abstract: Publication date: Available online 22 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Hirofumi Ohga , Hayato Adachi , Kojiro Matsumori , Ryoko Kodama , Mitsuo Nyuji , Sethu Selvaraj , Keitaro Kato , Shinji Yamamoto , Akihiko Yamaguchi , Michiya Matsuyama
      Kisspeptin (Kiss) and its cognate receptor (Kiss1R or GPR54), implicated in the neuroendocrine control of gonadotropin-releasing hormone (GnRH) secretion in mammals, have been proposed to be key factors in reproduction, with a special role during puberty. However, the mechanisms underlying the initiation of puberty in fish are poorly understood. The chub mackerel Scomber japonicus possesses two forms of Kiss (kiss1 and kiss2) and two Kiss receptor (kissr1 and kissr2) genes in the brain, which exhibit sexually dimorphic changes during the seasonal reproductive cycle. This indicates that the kisspeptin system plays an important role in gonadal recrudescence of chub mackerel; however, the involvement of kisspeptin system in the pubertal process has not been identified in this species. In the present study, we examined temporal patterns of kiss1, kiss2, kissr1, kissr2, and gnrh1 (hypophysiotropic GnRH form in this species) mRNA expression in chub mackerel brain during the pubertal process. In male fish, kiss2, kissr1 and kissr2 expression levels increased significantly at 14 weeks post-hatch (wph), synchronously with an increase in type A spermatogonial populations in the testis; kiss2 and gnrh1 expression levels significantly increased at 22 wph, just before the onset of meiosis in the testes. In female fish, kiss2 increased significantly at 14 wph, synchronously with an increase in number of perinucleolar oocytes in the ovary; kiss1 and kiss2 levels significantly increased concomitantly with an increase in the kissr1, kissr2, and gnrh1 levels at 24 wph, just before the onset of vitellogenesis in oocytes. The present results suggest positive involvement of the kisspeptin–GnRH system in the pubertal process in both chub mackerel sexes, as in mammals.

      PubDate: 2014-09-23T08:53:25Z
  • Life stage-related differences in fatty acid composition of an obligate
           ectoparasite, the deer ked (Lipoptena cervi)—Influence of blood
           meals and gender
    • Abstract: Publication date: Available online 16 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Anne-Mari Mustonen , Reijo Käkelä , Tommi Paakkonen , Petteri Nieminen
      Metamorphosis and diet often influence fatty acid (FA) signatures (FAS) of insects. We investigated FAS in a hematophagous ectoparasite, the deer ked (Lipoptena cervi). Deer keds shed their wings upon attachment on the host and, thus, the FAS of an individual blood-fed imago/pupa in the fur of its host can be traced back to the blood FA profile of a single moose (Alces alces). Host blood and different life stages of deer keds were investigated for FA by gas chromatography. The FAS of life stages resembled each other more closely than the diet. Blood meals modified the FAS of both sexes but the FAS of the blood-fed females were closer to those of the prepupae/pupae. The parasitizing males had higher proportions of major saturated FA (SFA) and polyunsaturated FA (PUFA) than the females, which contained more monounsaturated FA (MUFA) with higher ratios of n-3/n-6 PUFA and unsaturated FA (UFA)/SFA. The proportions of 16:1n-7 were <1% in the blood but 18% (males) and 29% (females) in the blood-fed keds. Allocation of lipids to offspring by the females and possible accumulation of PUFA in male reproductive organs may have induced these sex-related differences. MUFA percentages and UFA/SFA ratios increased while SFA and many PUFA decreased from the reproducing females to the pupae. The diapausing pupae displayed lowered n-3/n-6 PUFA ratios and could have mobilized 16:0 and 18:3n-3 for the most fundamental metabolic processes. In conclusion, FAS are modified through the life stages of the deer ked possibly due to their different requirements.

      PubDate: 2014-09-20T08:14:15Z
  • Taking their breath away: Metabolic responses to low-oxygen levels in
           anchialine shrimps (Crustacea: Atyidae and Alpheidae)
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Justin C. Havird , Rebecca C. Vaught , Jeffrey R. Weeks , Yoshihisa Fujita , Michio Hidaka , Scott R. Santos , Raymond P. Henry
      Crustaceans generally act as oxy-regulators, maintaining constant oxygen uptake as oxygen partial pressures decrease, but when a critical low level is reached, ventilation and aerobic metabolism shut down. Cave-adapted animals, including crustaceans, often show a reduced metabolic rate possibly owing in part to the hypoxic nature of such environments. However, metabolic rates have not been thoroughly explored in crustaceans from anchialine habitats (coastal ponds and caves), which can experience variable oxygenic regimes. Here, an atypical oxy-conforming pattern of oxygen uptake is reported in the Hawaiian anchialine atyid Halocaridina rubra, along with other unusual metabolic characteristics. Ventilatory rates are near-maximal in normoxia and did not increase appreciably as PO2 declined, resulting in a decline in VO2 during progressive hypoxia. Halocaridina rubra maintained in anoxic waters survived for seven days (the duration of the experiment) with no measureable oxygen uptake, suggesting a reliance on anaerobic metabolism. Supporting this, lactate dehydrogenase activity was high, even in normoxia, and oxygen debts were quickly repaid by an unusually extreme increase in oxygen uptake upon exposure to normoxia. In contrast, four related anchialine shrimp species from the Ryukyu Islands, Japan, exhibited physiological properties consistent with previously studied crustaceans. The unusual respiratory patterns found in H. rubra are discussed in the context of a trade-off in gill morphology for osmoregulatory ion transport vs. diffusion of respiratory gasses. Future focus on anchialine species may offer novel insight into the diversity of metabolic responses to hypoxia and other physiological challenges experienced by crustaceans.

      PubDate: 2014-09-20T08:14:15Z
  • Editorial Board
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178

      PubDate: 2014-09-20T08:14:15Z
  • Sequence, genomic organization and expression of ghrelin receptor in grass
           carp, Ctenopharyngodon idellus
    • Abstract: Publication date: Available online 19 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): Wen-jing Cai , Xiao-chen Yuan , Yong-chao Yuan , Shou-qi Xie , Yuan Gong , Hang Su , Yang Qiao
      The growth hormone secretagogue-receptor (GHS-R) is an endogenous receptor for the gut hormone ghrelin. Here we report the identification and characterization of GHS-R1a in grass carp, Ctenopharyngodon idellus. The full-length GHS-R1a cDNA contained a 1803-bp coding domain sequence which encoded a peptide of 360 amino acid residues. Comparison analysis revealed that the amino acid sequences of GHS-R1a were highly conserved in vertebrates shared 97% amino acid identity with zebrafish (Danio rerio), 96% with jian carp (Cyprinus carpio var. Jian) and 93% with goldfish (Carassius auratus). The GHS-R1a showed the highest level of mRNA expression in the pituitary, followed by brain, liver, and lowest expression was observed in hindgut. Intraperitoneally injected with grass carp ghrelin (50, 100 and 150ng/g body weight (BW)), grass carp showed greater mRNA expression of GHS-R1a in the pituitary compared with saline injected at 0.5h post injection. It was observed that food deprivation could promote the expression of ghrelin and GHS-R1a in the pituitary, demonstrating that nutritional status can influence the expression of both ghrelin and GHS-R1a in the pituitary. After 2- or 4-week fast, plasma growth hormone (GH) increased, were positively correlated with ghrelin and GHS-R1a mRNA expression levels in the pituitary. These results suggested that the involvement of ghrelin/GHS-R1a systems in mediating the effects of nutritional status and ghrelin in grass carp.

      PubDate: 2014-09-20T08:14:15Z
  • Critical windows in embryonic development: Shifting incubation
           temperatures alter heart rate and oxygen consumption of Lake Whitefish
           (Coregonus clupeaformis) embryos and hatchlings
    • Abstract: Publication date: Available online 16 September 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
      Author(s): J. Eme , C.A. Mueller , R.G. Manzon , C.M. Somers , D.R. Boreham , J.Y. Wilson
      Critical windows are periods of developmental susceptibility when the phenotype of an embryonic, juvenile or adult animal may be vulnerable to environmental fluctuations. Temperature has pervasive effects on poikilotherm physiology, and embryos are especially vulnerable to temperature shifts. To identify critical windows, we incubated whitefish embryos at control temperatures of 2°C, 5°C, or 8°C, and shifted treatments among temperatures at the end of gastrulation or organogenesis. Heart rate (fH) and oxygen consumption (V. o 2) were measured across embryonic development, and V. o 2 was measured in 1day-old hatchlings. Thermal shifts, up or down, from initial incubation temperatures caused persistent changes in fH and V. o 2 compared to control embryos measured at the same temperature (2°C, 5°C, or 8°C). Most prominently, when embryos were measured at organogenesis, shifting incubation temperature after gastrulation significantly lowered V. o 2 or fH. Incubation at 2°C or 5°C through gastrulation significantly lowered V. o 2 (42% decrease) and fH (20% decrease) at 8°C, incubation at 2°C significantly lowered V. o 2 (40% decrease) and fH (30% decrease) at 5°C, and incubation at 5°C and 8°C significantly lowered V. o 2 at 2°C (27% decrease). Through the latter half of development, V. o 2 and fH in embryos were not different from control values for thermally shifted treatments. However, in hatchlings measured at 2°C, V. o 2 was higher in groups incubated at 5°C or 8°C through organogenesis, compared to 2°C controls (43 or 65% increase, respectively). Collectively, these data suggest that embryonic development through organogenesis represents a critical window of embryonic and hatchling phenotypic plasticity. This study presents an experimental design that identified thermally sensitive periods for fish embryos.

      PubDate: 2014-09-20T08:14:15Z
  • Effects of salinity on metabolic rate and branchial expression of genes
           involved in ion transport and metabolism in Mozambique tilapia
           (Oreochromis mossambicus)
    • Abstract: Publication date: December 2014
      Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 178
      Author(s): Aris Zikos , Andre P. Seale , Darren T. Lerner , E. Gordon Grau , Keith E. Korsmeyer
      This study investigated the effects of two rearing salinities, and acute salinity transfer, on the energetic costs of osmoregulation and the expression of metabolic and osmoregulatory genes in the gill of Mozambique tilapia. Using automated, intermittent-flow respirometry, measured standard metabolic rates (SMRs) of tilapia reared in seawater (SW, 130mgO2 kg−1 h−1) were greater than those reared in fresh water (FW, 103mgO2 kg−1 h−1), when normalized to a common mass of 0.05kg and at 25±1°C. Transfer from FW to 75% SW increased SMR within 18h, to levels similar to SW-reared fish, while transfer from SW to FW decreased SMR to levels similar to FW-reared fish. Branchial gene expression of Na+–K+–2Cl− cotransporter (NKCC), an indicator of SW-type mitochondria-rich (MR) cells, was positively correlated with SMR, while Na+–Cl− cotransporter (NCC), an indicator of FW-type MR cells, was negatively correlated. Principal Components Analysis also revealed that branchial expression of cytochrome c oxidase subunit IV (COX-IV), glycogen phosphorylase (GP), and a putative mitochondrial biogenesis regulator in fish, peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), were correlated with a higher SMR, plasma osmolality, and environmental salinity, while expression of glycogen synthase (GS), PGC-1β, and nuclear respiratory factor 1 (NRF-1) had negative correlations. These results suggest that the energetic costs of osmoregulation are higher in SW than in FW, which may be related to the salinity-dependent differences in osmoregulatory mechanisms found in the gills of Mozambique tilapia.

      PubDate: 2014-09-20T08:14:15Z
  • 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
  • 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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