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Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology

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ISSN (Print) 1095-6433
Published by Elsevier

[2556 journals]

Cardiac hypertrophy and structural and metabolic remodeling related to seasonal dormancy in the first annual cycle in tegu lizards
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): Lilian Cristina da Silveira , Lucas Francisco R. do Nascimento , Alison Colquhoun , Augusto S. Abe , Silvia Cristina R. de Souza
  Morpho-functional adjustments in the heart of juvenile tegu lizards (Tupinambis merianae) were analyzed at distinct seasonal periods to investigate how the demands of growth and of energy saving are reconciled during the first annual cycle. The relative ventricular mass (Mv) was 31% and 69% larger in late autumn and winter dormancy, respectively, compared to early autumn. This effect did not persist during unfed arousal, suggesting that protein accumulates in the heart during hypometabolism and is degraded on arousal. Both the hypertrophy and the atrophy were disproportionate in the largest individuals. In contrast, Mv was smaller in lizards that were starved during spring activity compared to fed lizards, this effect being larger in smaller individuals. In late autumn and winter dormancy the spongy myocardium had 8% of the section area covered by lacunary spaces, which expanded after food intake during arousal and reached 29% in spring activity together with higher density of cardiomyocytes. Total and soluble proteins per mass unity were unchanged, and maximum activities of selected enzymes suggest sustained glycolytic and aerobic capacities during hypometabolism. Results indicate that important structural adjustments occur in the heart in anticipation of dormancy, and that the protein balance in the tissue is maintained at winter temperatures ~17°C.
  
  PubDate: 2013-05-21T02:03:35Z
Rapid effects of humidity acclimation on stress resistance in Drosophila melanogaster
- Abstract: Publication date: Available online 18 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Dau Dayal Aggarwal , Poonam Ranga , Bhawna Kalra , Ravi Parkash , Eugenia Rashkovetsky , Leonidas E. Bantis
  We tested the hypothesis whether developmental acclimation at ecologically relevant humidity regimes (40% and 75% RH) affects desiccation resistance of pre-adults (3rd instar larvae) and adults of Drosophila melanogaster Meigen (Diptera: Drosophilidae). Additionally, we untangled whether drought (40% RH) acclimation affects cold-tolerance in the adults of D. melanogaster. We observed that low humidity (40% RH) acclimated individuals survived significantly longer (1.6-fold) under lethal levels of desiccation stress (0-5% RH) than their counter-replicates acclimated at 75% RH. In contrast to a faster duration of development of 1st and 2nd instar larvae, 3rd instar larvae showed a delayed development at 40% RH as compared to their counterparts grown at 75% RH. Rearing to low humidity conferred an increase in bulk water, hemolymph content and dehydration tolerance, consistent with increase in desiccation resistance for replicates grown at 40% as compared to their counterparts at 75% RH. Further, we found a trade-off between the levels of carbohydrates and body lipid reserves at 40% and 75% RH. Higher levels of carbohydrates sustained longer survival under desiccation stress for individuals developed at 40% RH than their congeners at 75% RH. However, the rate of carbohydrates utilization did not differ between the individuals reared at these contrasting humidity regimes. Interestingly, our results of accelerated failure time (AFT) models showed substantial decreased death rates at a series of low temperatures (0, –2, or −4 °C) for replicates acclimated at 40% RH as compared to their counter-parts at 75% RH. Therefore, our findings indicate that development to low humidity conditions constrained on multiple physiological mechanisms of water-balance, and conferred cross-tolerance towards desiccation and cold stress in D. melanogaster. Finally, we suggest that the ability of generalist Drosophila species to tolerate fluctuations in humidity might aid in their existence and abundance under expected changes in moisture level in course of global climate change.
  
  PubDate: 2013-05-21T02:03:35Z
UCP4 expression changes in larval and pupal fat bodies of the beetle Zophobas atratus under adipokinetic hormone treatment
- Abstract: Publication date: Available online 17 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Malgorzata Slocinska , Nina Antos-Krzeminska , Marek Golebiowski , Mariola Kuczer , Piotr Stepnowski , Grzegorz Rosinski , Wieslawa Jarmuszkiewicz
  We investigated the influence of adipokinetic hormone (AKH), an insect neurohormone, on uncoupling protein 4 (ZaUCP4) expression and activity in larval and pupal fat body mitochondria of the beetle Zophobas atratus in relation to intermediary metabolism. Homologous Tenmo-AKH was administered to the beetle larvae and pupae as either a single dose or as two doses of 20 pmol during a 24 h interval. In the larval and pupal fat bodies, downregulation of ZaUCP4 expression at the mRNA and protein levels was observed 24 h and 48 h after AKH treatment, respectively. In both developmental stages, ZaUCP4 activity was lowered in fat body mitochondria 48 h after AKH treatment. In the AKH-injected larvae, changes in ZaUCP4 expression were accompanied by the mobilization of carbohydrate reserves, no change in the concentration of total lipids and an increase in the free fatty acid level. In contrast, AKH had no effect on carbohydrate metabolism in the pupal fat body but induced lipid mobilization. It seems that AKH influences ZaUCP4 expression by triggering multiple events and that it has different physiological roles in controlling intermediary metabolism in the fat body of the beetle larvae and pupae.
  
  PubDate: 2013-05-21T02:03:35Z
Fitting statistical models in bivariate allometry: Scaling metabolic rate to body mass in mustelid carnivores
- Abstract: Publication date: Available online 18 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Gary C. Packard
  The ongoing debate about methods for fitting the two-parameter allometric equation y = a x b to bivariate data seemed to be resolved recently when three groups of investigators independently reported that statistical models fitted by the traditional allometric method (i.e., by back-transforming a linear model fitted to log-log transformations) typically are superior to models fitted by standard nonlinear regression. However, the narrow focus for the statistical analyses in these investigations compromised the most important of the ensuing conclusions. All the investigations focused on two-parameter power functions and excluded from consideration other simple functions that might better describe pattern in the data; and all relied on Akaike’s Information Criterion instead of graphical validation to identify the better statistical model. My re-analysis of data from one of the studies (BMR vs. body mass in mustelid mammals) revealed (1) that the best descriptor for pattern in the data set is a straight line and not a two-parameter power function; (2) that a model with additive, normal, heteroscedastic error is superior to one with multiplicative, lognormal, heteroscedastic error; and (3) that Akaike’s Information Criterion is not a generally reliable metric for discriminating between models fitted to different distributions. These findings have apparent implications for interpreting the outcomes of all three of the aforementioned studies. Future investigations of allometric variation should adopt a more holistic approach to analysis and not be wedded to the traditional allometric method.
  
  PubDate: 2013-05-21T02:03:35Z
Physiological functions of osmolality and calcium ions on the initiation of sperm motility and swimming performance in redside dace, Clinostomus elongatus
- Abstract: Publication date: Available online 18 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Ian A.E. Butts , Sayyed Mohammad Hadi Alavi , Ali Mokdad , Trevor E. Pitcher
  Reproductive potential of fish stocks is critically dependent on sperm performance in an aquatic environment. The aim of this study is to test hypotheses, which govern the initiation of sperm motility and swimming performance, through physiological functions of osmolality and Ca2+ ion, in a threatened species of freshwater fish, the redside dace, Clinostomus elongatus. Spermatozoa motility was activated in either ionic or non-ionic media spanning a range of osmolalities. The role of Ca2+ channels on induction of spermatozoa motility and velocity were experimentally investigated by diluting sperm in media that contain various Ca2+ channel blockers. Results show that initiation of spermatozoa motility is a hypo-osmolality dependent mechanism. Inhibitors for L-type Ca2+ channels partially prohibited initiation of spermatozoa motility, while velocity was significantly reduced in both L-type and T-type Ca2+ channel blockers. Examination using W-7, an inhibitor for Ca2+-dependent calmodulin, showed significant decreases in spermatozoa motility and velocity. Involvement for Ca2+ in axonemal beating was confirmed by significant increases in velocity after adding Ca2+ into the activation media, while motility remained unchanged in Ca2+ supplemented activation media. Together, these findings suggest the involvement of Ca2+ in hypo-osmolality-dependent initiation of spermatozoa motility mediated by activation of Ca2+ binding protein in the axoneme of a freshwater fish sperm. Blocking Ca2+ exchange through L- or T-type Ca2+ channel influences flagellar beating force and leads to decrease in spermatozoa velocity.
  
  PubDate: 2013-05-21T02:03:35Z
Lipid digestion, absorption and uptake in Solea senegalensis
- Abstract: Publication date: Available online 14 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Pedro Borges , Françoise Medale , Vincent Veron , Maria dos Anjos Pires , Jorge Dias , Luísa M.P. Valente
  Dietary lipids are the major energy source for metabolic purposes in most fish species, and improve dietary protein utilization for growth. In a previous study we have reported a low tolerance of Senegalese sole juveniles to dietary lipid levels and suggested a maximal dietary inclusion level of 8% lipids for both optimal growth and nutrient utilization. The mechanisms behind this apparent poor utilization of the dietary lipids are still to be elucidated. The primary aim of the present study was to investigate the overall process of digestion and lipid absorption in relation to dietary lipid levels. Triplicate groups of twenty fish (mean initial mass 29g) were fed two isonitrogenous diets (54% of protein dry matter basis) with different lipid levels (L4 and L17, 4 and 17 % lipids dry matter basis), for 88days. Protein and lipid apparent digestibility coefficients as well as lipase activity were similar in both groups suggesting that Solea senegalensis has the ability to digest equally well a low fat or a high fat diet. Plasma triglycerides concentrations were significantly higher 5 and 16hours after feeding in fish fed the L17 compared to those fed L4, following dietary lipid supply, demonstrating effective lipid absorption. Expression of proteins related to lipid transport (microsomal triglyceride transfer protein), trafficking (Fatty acid binding protein 11) and fatty acid uptake (VLDL-r) was significantly higher in liver of fish fed the high fat diet 16h after the meal, but remained unchanged in muscle. In conclusion, it seems that high fat diets do not impair lipid digestion and absorption.
  
  PubDate: 2013-05-17T03:36:02Z
Glycated hemoglobin is not an accurate indicator of glycemia in rainbow trout
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): A.E. Santin , A.J. Searle , V.D. Winston , M.S. Powell , R.W. Hardy , K.J. Rodnick
  Glycation occurs when glucose reacts non-enzymatically with proteins. This reaction depends upon time, ambient glucose concentration, and the molecular conformation of reactive amino acids. Little is known about protein glycation in fishes and the main objective of this study was to measure glycated hemoglobin (GHb) in rainbow trout, a glucose-intolerant species, under normoglycemic and hyperglycemic conditions. We also identified GHb isoforms in vivo and analyzed the structural environment surrounding potential glycation sites. Despite similar glycemia to healthy humans, GHb was an order of magnitude lower in rainbow trout (0.6%) compared with humans (6%) and was not affected by long-term hyperglycemia. Species differences in GHb appear to be related to differences in erythrocyte glucose, and differential expression and glycation of hemoglobin (Hb) isoforms may explain intraspecific differences in rainbow trout GHb. Computer analysis of glucose isomers (ringed-open and α- and β-pyranoses) interacting with the β-chain of rainbow trout HbI and HbIV, and human HbA did not reveal structural or energetic constraints for glucose binding (the initial step of glycation) for rainbow trout Hbs. Overall, there are significant differences between Hb glycation in humans and rainbow trout, and GHb does not appear to be an accurate indicator of glycemia over time in rainbow trout.
  
  PubDate: 2013-05-13T03:30:41Z
γ-Amino-butyric acid (GABA) receptor subunit and transporter expression in the gonad and liver of the fathead minnow (Pimephales promelas)
- Abstract: Publication date: Available online 12 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Katie Biggs , Jason S. Seidel , Alex Wilson , Christopher J. Martyniuk
  γ -Amino-butyric acid (GABA) is the major inhibitory neurotransmitter in the vertebrate central nervous system. GABA receptors and synthesizing enzymes have also been localized to peripheral tissues including the liver, oviduct, uterus and ovary of mammals but the distribution and role of GABA in peripheral tissues of fish has not been fully investigated. The objectives of this study were to (1) determine if mRNA encoding GABA synthesizing enzymes (glutamic acid decarboxylase 65 and 67; gad65 and gad67), GABA transporters, and GABAA receptor subunits are localized to liver and gonad of fathead minnow (Pimephales promelas) (FHM) (2) investigate the effects of GABA on ovarian 17β-estradiol (E2) production, and (3) measure transcript responses in the ovary after in vitro incubation to GABA. Real-time PCR assays were developed for gad65, gad67, vesicular GABA transporter (vgat) and GABA transporter 1 (gat1), and select GABAA receptor subunits (gabra1, gabra5, gabrb1, gabrb2, gabrg1, gabrg2). All transcripts were localized to the brain as expected; however transcripts were also detected in the liver, ovary, and testis of FHMs. In the female liver, gad65 mRNA was significantly higher in expression compared to the male liver. Transcripts for gad67 were highest in brain>gonad>liver and in the gonads, gad67 was significantly higher in expression than gad65 mRNA. In the liver and gonad, the relative abundance of the subunits followed a general trend of gabrb1 > gabrb2 = gabrg1 = gabrg2>gabra1 = gabra5. To explore the effects of GABA in the ovary, tissue explants from reproductive female FHMs were treated with GABA (10-10, 10-8 and 10-6 M) for 12h. GABA had no significant effect on 17β-estradiol production or on mRNA abundance for genes involved in ovarian steroidogenesis (e.g. 11βhsd, cyp17, cyp19a). There was a significant decrease in estrogen receptor 2a (esr2a) mRNA with 10-10 M GABA. This study begins to investigate the GABA system in non-neural tissues of teleost fish and addresses the broader topic regarding the peripheral roles of neurotransmitters.
  
  PubDate: 2013-05-13T03:30:41Z
Effect of short-term decrease in water temperature on body temperature and involvement of testosterone in steelhead and rainbow trout, Oncorhynchus mykiss
- Abstract: Publication date: Available online 12 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Go Miura , Arimune Munakata , Takashi Yada , Carl B. Schreck , David L.G. Noakes , Hiroyuki Matsuda
  The Pacific salmonid species Oncorhynchus mykiss is separated into a migratory form (steelhead trout) and a non-migratory form (rainbow trout). A decrease in water temperature is likely a cue triggering downstream behavior in the migratory form, and testosterone inhibits onset of this behavior. To elucidate differences in sensitivity to water temperature decreases between the migratory and non-migratory forms and effect of testosterone on the sensitivity, we examined two experiments. In experiment 1, we compared changes in body temperature during a short-term decrease in water temperature between both live and dead steelhead and rainbow trout. In experiment 2, we investigated effects of testosterone on body temperature decrease in steelhead trout. Water temperature was decreased by 3°C in 30min. The body temperature of the steelhead decreased faster than that of the rainbow trout. In contrast, there was no significant difference in the decrease in body temperature between dead steelhead and rainbow trout specimens. The body temperature of the testosterone-treated steelhead trout decreased more slowly than that of control fish. Our results suggest that the migratory form is more sensitive to decreases in water temperature than the non-migratory form. Moreover, testosterone might play an inhibitory role in sensitivity to such decreases.
  
  PubDate: 2013-05-13T03:30:41Z
Role of cutaneous surface fluid in frog osmoregulation
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): Erik Hviid Larsen , Hans Ramløv
  The study investigated whether evaporative water loss (EWL) in frogs stems from water diffusing through the skin or fluid secreted by mucous glands. Osmolality of cutaneous surface fluid (CSF) of Rana esculenta (Pelophylax kl. esculentus) subjected to isoproterenol or 30°C–34°C was 191±9.3 and 181±7.5mosm/kg, respectively, as compared to lymph osmolality of, 249±10mosm/kg. Cation concentrations of CSF were likewise independent of pre-treatment with averages of, [Na+]=65.5±5.1 and [K+]=14.9±1.6mmol/L, and lymph concentrations of 116mmol Na+/L and 5.1mmolK+/L. The relatively high [K+] confirms that CSF is produced by submucosal glands. Since the chemical energy of water of CSF was always higher than that of body fluids, diffusion of water would be from CSF to the interstitial fluid and not in the opposite direction. It is concluded that volume and composition of CSF are regulated by subepidermal exocrine gland secretion balanced by EWL into the atmosphere and ion reuptake by the epidermal epithelium. Previously discovered regulatory mechanisms of epithelial ion absorption, hitherto not ascribed a body function, fit well with a role in regulating turnover of CSF. As a regulated external physiological compartment, CSF would be of importance for the immune defenses that amphibians employ in protecting their skin.
  
  PubDate: 2013-05-13T03:30:41Z
Effect of Light at Night on oxidative stress markers in Golden spiny mice (Acomys russatus) liver
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): Lilach Ashkenazi , Abraham Haim
  Light at Night (LAN) suppresses melatonin (MLT) production, and effects metabolism, hormone secretion, gene expression and enzyme activity. Changes in antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD), can be used as an indication for oxidative stress level. We assayed activity and expression of these enzymes in the liver of Acomys russatus exposed to LAN and treated with MLT. Short day (SD)-acclimated A. russatus, was exposed to 30min of LAN for two, seven or 21 nights. MLT impact was assessed simultaneously with two and seven nights of LAN exposure. GPx and SOD activities were measured. Gpx1 expression was evaluated by RT-PCR. There was a significant increase in GPx activity following LAN exposure for all acclimation durations, GPx activity was elevated after two nights of LAN and MLT treatment, Gpx1 expression was elevated by MLT after seven nights of LAN. SOD activity increased after two nights of LAN in MLT-treated A. russatus, GPx activity increased with the duration of LAN acclimation, indicating changes in liver redox status. Our results suggest that LAN is a stressor that influences oxidative stress. As in the other studies, MLT increases antioxidant activities, presumably attenuating stress response, in order to restore homeostasis.
  
  PubDate: 2013-05-13T03:30:41Z
Feed intake and brain neuropeptide Y (NPY) and cholecystokinin (CCK) gene expression in juvenile cobia fed plant-based protein diets with different lysine to arginine ratios
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): Minh Van Nguyen , Ann-Elise Olderbakk Jordal , Marit Espe , Louise Buttle , Hung Van Lai , Ivar Rønnestad
  Cobia (Rachycentron canadum, Actinopterygii, Perciformes;10.5±0.1g) were fed to satiation with three plant-based protein test diets with different lysine (L) to arginine (A) ratios (LL/A, 0.8; BL/A, 1.1; and HL/A, 1.8), using a commercial diet as control for six weeks. The test diets contained 730gkg−1 plant ingredients with 505–529g protein, 90.2–93.9g lipidkg−1 dry matter; control diet contained 550g protein and 95g lipidkg−1 dry matter. Periprandial expression of brain NPY and CCK (npy and cck) was measured twice (weeks 1 and 6). At week one, npy levels were higher in pre-feeding than postfeeding cobia for all diets, except LL/A. At week six, npy levels in pre-feeding were higher than in postfeeding cobia for all diets. cck in pre-feeding cobia did not differ from that in postfeeding for all diets, at either time point. Cobia fed LL/A had lower feed intake (FI) than cobia fed BL/A and control diet, but no clear correlations between dietary L/A ratio and FI, growth and expression of npy and cck were detected. The data suggest that NPY serves as an orexigenic factor, but further studies are necessary to describe links between dietary L/A and regulation of appetite and FI in cobia.
  
  PubDate: 2013-05-09T03:30:50Z
Impact of cool versus warm temperatures on gestation in the aspic viper (Vipera aspis)
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): Catherine Louise Michel , Jean-Henri Pastore , Xavier Bonnet
  Previous experimental data suggested that digestion and growth rates are not impaired under cool constant temperature (23°C) in a viviparous snake (Vipera aspis). These results challenged the widespread notion that both elevated temperatures (e.g. 30°C) and temperature fluctuations are required for digestion and growth in temperate climate reptiles. Here, we investigated the impact of constant cool temperatures on another physiological performance that is crucial to population persisten gestation. At the time when reproductive females were midway through vitellogenesis, we placed ten reproductive and two non-reproductive female aspic vipers at each of two contrasted constant temperature conditions: cool (23°C) versus warm (28°C). Sixty percent of the females placed at 28°C gave birth to healthy offspring, suggesting that constant warm body temperatures were compatible with normal offspring production. Conversely, none of the cool females gave birth to healthy offspring. A blister disease affected exclusively cool pregnant females. Apparently, the combination of cool temperatures plus gestation was too challenging for such females. Our results suggest that reproduction is more thermally sensitive than digestion or growth, indeed gestation faltered under moderately cool thermal constraints. This sensitivity could be a crucial factor determining the capacity of this species to colonize different habitats.
  
  PubDate: 2013-05-09T03:30:50Z
Zinc transferrin stimulates red blood cell formation in the head kidney of common carp (Cyprinus carpio)
- Abstract: Publication date: Available online 7 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Yen-Hua Chen , Szu-Wei Fang , Sen-Shyong Jeng
  The common carp is one of the few fish able to tolerate extremely low oxygen levels. These fish store zinc in their digestive tract tissue and head kidney at concentrations of 300-500 μg/g of fresh tissue, which is 5-10 times higher than in other fish. Previous studies have indicated a link between the high zinc levels in the common carp and stress erythropoiesis. In this report, using suspension-cultured common carp head kidney cells with or without ZnCl2 supplementation, we found that zinc stimulated the proliferation of immature red blood cells; however, this effect was only observed when the culture was supplemented with carp serum. We identified the active component of carp serum to be transferrin. The zinc-transferrin complex interacts with the transferrin receptor and stimulates the proliferation of immature red blood cells. In addition, the growth rate of the immature red blood cells was regulated by the supplied ZnCl2 concentration. Under stress, the zinc in the common carp digestive tract tissue was released and used as a signal to induce red blood cell formation in the head kidney. This cell culture system might provide a means for exploring the regulatory role of zinc in hematopoietic cell growth.
  
  PubDate: 2013-05-09T03:30:50Z
Some euryhalinity may be more common than expected in marine elasmobranchs: The example of the South American skate Zapteryx brevirostris (Elasmobranchii, Rajiformes, Rhinobatidae)
- Abstract: Publication date: Available online 7 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Natascha Wosnick , Carolina A. Freire
  Elasmobranchs are essentially marine, but ~15% of the species occur in brackish or freshwater. The Brazilian marine coastal skate Zapteryx brevirostris, non-reported in nearby estuaries, was submitted to 35, 25, 15, and 5 psu, for 6 or 12 h (n=6). Plasma was assayed for osmolality, urea, and ions (Na+, Cl-, K+, Mg2+). Muscle water content was determined, and the rectal gland, kidney and gills were removed for carbonic anhydrase (CA) and Na+,K+-ATPase (NKA) activities. The skate survived to all treatments. Plasma osmolality and urea levels decreased respectively by 27% and 38% after 12 h in 5 psu (with respect to levels when in seawater), but plasma Na+, Cl-, and Mg2+were well regulated. Plasma K+ showed some conformation after 12 h. Muscle hydration was maintained. Branchial CA and NKA did not respond to salinity. Rectal gland NKA decreased upon seawater dilution, while renal NKA increased. This skate was shown to be partially euryhaline. The analysis of plasma urea of elasmobranchs in brackish and freshwater versus salinity and time - allied to the widespread occurrence of some euryhalinity in the group - led us to revisit the hypothesis of a brackish water habitat for elasmobranch ancestors.
  
  PubDate: 2013-05-09T03:30:50Z
Phenotypic flexibility in body mass, basal metabolic rate and summit metabolism in southern red bishops (Euplectes orix): Responses to short term thermal acclimation
- Abstract: Publication date: July 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 3
  Author(s): Tanja M.F.N. van de Ven , Nomakwezi Mzilikazi , Andrew E. McKechnie
  Avian basal metabolic rate (BMR) and summit metabolism (Msum) vary within individuals in response to seasonal acclimatization in free-ranging birds, and thermal acclimation under laboratory conditions. We examined relationships between acclimation air temperature (Tacc) and body mass (Mb), BMR and Msum in female southern red bishops (Euplectes orix) from a relatively mild coastal site and a seasonally colder, inland site. Following acclimation for 21days to Tacc =10, 22 or 35°C, Mb, BMR and Msum were all significantly and negatively related to Tacc. The significant relationship between BMR and Tacc did not remain after Mb was included as a covariate, whereas that between Msum and Tacc did. A subsequent reverse acclimation protocol, where bishops were acclimated to a second Tacc value and then re-acclimated to the first, revealed that short-term changes in Mb and BMR were completely reversible, but changes in Msum were only partially reversible. Following the reverse-acclimation protocol, metabolic expansibility (Msum/BMR) varied significantly with air temperature, being greatest at Tacc =35°C. Our data suggest that the intraspecific variation in seasonal metabolic variation previously reported for this species is at least partly driven by factors other than temperature.
  
  PubDate: 2013-05-05T03:32:22Z
Branchial O2 chemoreceptors in Nile tilapia Oreochromis niloticus: Control of cardiorespiratory function in response to hypoxia
- Abstract: Publication date: Available online 4 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Vivian M. Zeraik , Thiago C. Belão , Luiz Henrique Florindo , Ana L. Kalinin , F. Tadeu Rantin
  This study examined the distribution and orientation of gill O2 chemoreceptors in Oreochromis niloticus and their role in cardiorespiratory responses to graded hypoxia. Intact fish, and a group with the first gill arch excised (operated), were submitted to graded hypoxia and their cardiorespiratory responses (oxygen uptake - V ˙ O 2 , breathing frequency - f R, ventilatory stroke volume - V T, gill ventilation - V ˙ G , O2 extraction from the ventilatory current - EO2, and heart rate - f H) were compared. Their responses to bolus injections of NaCN into the bloodstream (internal) or ventilatory water stream (external) were also determined. The V ˙ O 2 of operated fish was significantly lower at the deepest levels of hypoxia. Neither reflex bradycardia nor ventilatory responses were completely abolished by bilateral excision of the first gill arch. EO2 of the operated group was consistently lower than the intact group. The responses to internal and external NaCN included transient decreases in f H and increases in f R and V amp (ventilation amplitude). These cardiorespiratory responses were attenuated but not abolished in the operated group, indicating that chemoreceptors are not restricted to the first gill arch, and are sensitive to oxygen levels in both blood and water.
  
  PubDate: 2013-05-05T03:32:22Z
Protein tyrosine phosphatase encoded in Cotesia plutellae bracovirus suppresses a larva-to-pupa metamorphosis of the diamondback moth, Plutella xylostella
- Abstract: Publication date: Available online 4 May 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): Jiwan Kim , Rahul Hepat , Daeweon Lee , Yonggyun Kim
  Parasitization by an endoparasitoid wasp, Cotesia plutellae, inhibits a larva-to-pupa metamorphosis of the diamondback moth, Plutella xylostella. This study tested an inhibitory effect of C. plutellae bracovirus (CpBV) on the metamorphosis of P. xylostella. Parasitized P. xylostella exhibited significantly reduced prothoracic gland (PTG) development at the last instar compared to nonparasitized larvae. Expression of the ecdysone receptor was markedly suppressed during the last instar larvae parasitized by C. plutellae. By contrast, expression of the insulin receptor significantly increased in the parasitized larvae. Microinjection of CpBV significantly inhibited the larva-to-pupa metamorphosis of nonparasitized larvae in a dose-dependent manner. Injection of CpBV also inhibited the expression of the ecdysone receptor and increased the expression of the insulin receptor. Individual CpBV segments were transiently expressed in its encoded genes in nonparasitized larvae and screened to determine antimetamorphic viral gene(s). Out of 21 CpBV segments, two viral segments (CpBV-S22 and CpBV-S27) were proved to inhibit larva-to-pupa metamorphosis by transient expression assay. RNA interference of each gene encoded in the viral segments was applied to determine antimetamorphic gene(s). Protein tyrosine phosphatase, early expressed gene, and four hypothetical genes were selected to be associated with the antimetamorphic activity of CpBV. These results suggest that antimetamorphosis of P. xylostella parasitized by C. plutellae is induced by inhibiting PTG development and subsequent ecdysteroid signaling with viral factors of CpBV.
  
  PubDate: 2013-05-05T03:32:22Z
Relationship between brain and liver oxidative state and maximum lifespan potential of different fish species
- Abstract: Publication date: Available online 23 April 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  Author(s): A. Sanz , C.E. Trenzado , H. Botello Castro , M.J. López-Rodríguez , J.M. Tierno de Figueroa
  The aim of the present study is to determine whether a relationship exists between the maximum lifespan potential (MLSP) of different fish species (Squalius pyrenaicus, Cyprinus carpio, Carassius auratus, Luciobarbus sclateri and Oncorhynchus mykiss) and the oxidative state of brain and liver. For this purpose, the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST) and DT-diaphorase (NAD(P)H:quinone oxidoreductase1) were measured together with the lipid peroxidation degree (malondialdehyde, MDA) in liver and brain tissues of the collected species. Only the brain tissue manifested a higher activity of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione S-transferase in addition to a negative correlation between the values of MDA and MLSP among the different fish species. Hypotheses are proposed from the analysis of the obtained results that open new areas of research and converge on the importance of the theory of free radicals in the processes that condition the maximum life expectancy of an animal species.
  
  PubDate: 2013-04-23T03:37:18Z
Editorial Board
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  PubDate: 2013-04-23T03:37:18Z
The relationship between energy expenditure and speed during pedestrianlocomotion in birds: A morphological basis for the elevated y-intercept?
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  Author(s): Lewis G. Halsey
  The slope of the typically linear relationship between metabolic rate and walking speed represents the net cost of transport (NCOT). The extrapolated y-intercept is often greater than resting metabolic rate, thus representing a fixed cost associated with pedestrian transport including body maintenance costs. The full cause of the elevated y-intercept remains elusive and it could simply represent experimental stresses. The present literature-based study compares the mass-independent energetic cost of pedestrian locomotion in birds (excluding those with an upright posture, i.e. penguins), represented by the y-intercept, to a known predictor of cost of transport, hip height. Both phylogenetically informed and non-phylogenetically informed analyses were undertaken to determine if patterns of association between hip height, body mass, and the y-intercept are robust with respect to the method of analysis. Body mass and hip height were significant predictors of the y-intercept in the best phylogenetically-informed and non-phylogenetically informed models. Thus there is evidence that, in birds at least, the elevated y-intercept is a legitimate component of locomotion energy expenditure. Hip height is probably a good proxy of effective limb length and thus perhaps birds with greater hip heights have lower y-intercepts because their longer legs more efficiently accommodate body motion and/or because their limbs are more aligned with the ground reaction forces.
  
  PubDate: 2013-04-19T03:33:55Z
Preventive antioxidant responses to extreme oxygen level fluctuation in a subterranean crustacean
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  Author(s): M. Lawniczak , C. Romestaing , D. Roussel , C. Maazouzi , D. Renault , F. Hervant
  The principal aim of this work was to explore the responses of the groundwater crustacean Niphargus rhenorhodanensis to oxidative stress caused by short- and long-term drastic variations in oxygen level. To this end, we investigated thiobarbituric acid reactive substances (TBARS) levels and anti-oxidative enzyme (SOD and GPx) activities during 24h anoxia and post-anoxia recovery, and during 10days of severe hypoxia and post-hypoxia recovery. We observed a decrease in TBARS amounts during recovery from severe hypoxia. Parallel to these results, we observed an overactivation of SOD activity after a 24h anoxic stress. GPx activity measured at the end of anoxia or severe hypoxia and in the early hours of post-stress recovery also showed an overactivation compared to the control group. We can hypothesize that this overproduction of GPx corresponded to an anticipatory mechanism coping with the overproduction of reactive oxygen species (ROS) during the recovery phase in subterranean animals. This response could be considered as a major asset for life in alternately normoxic and hypoxic conditions, and therefore in extreme biotopes such as groundwaters.
  
  PubDate: 2013-04-19T03:33:55Z
In vitro response of putative fatty acid-sensing systems in rainbow trout liver to increased levels of oleate or octanoate
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  Author(s): Marta Librán-Pérez , Marcos A. López-Patiño , Jesús M. Míguez , José L. Soengas
  In a previous study we provided evidence for the presence in liver of rainbow trout of fatty acid (FA) sensing systems responding to changes in levels of oleate (long-chain FA) or octanoate (medium-chain FA). Since those effects could be attributed to an indirect effect, we have evaluated in the present study in vitro (in the absence of extrahepatic regulatory mechanisms) whether or not liver responds to changes in FA concentration in a way similar to that previously observed in vivo. Accordingly, liver slices were exposed to increased oleate or octanoate concentrations to evaluate changes in parameters related to FA metabolism, FA transport, nuclear receptors and transcription factors, ROS effectors, and glucose metabolism. The responses observed in vitro in liver were in general not coincident with those previously observed in vivo allowing us to suggest that FA sensing capacity of liver in vivo is of indirect nature and could be related among other reasons to an interaction with other endocrine systems and/or to FA sensing in hypothalamus.
  
  PubDate: 2013-04-15T03:33:12Z
Fish in hot water: Hypoxaemia does not trigger catecholamine mobilization during heat shock in rainbow trout (Oncorhynchus mykiss)
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  Author(s): S. Currie , E. Ahmady , M.A. Watters , S.F. Perry , K.M. Gilmour
  Rainbow trout (Oncorhynchus mykiss) exposed to an acute heat shock (1h at 25°C after raising water temperature from 13°C to 25°C over 4h) mount a significant catecholamine response. The present study investigated the proximate mechanisms underlying catecholamine mobilization. Trout exposed to heat shock in vivo exhibited a significant reduction in arterial O2 tension, but arterial O2 concentration was not affected by heat shock, nor was catecholamine release during heat shock prevented by prior and concomitant exposure to hyperoxia (to prevent the fall in arterial O2 tension). Thus, catecholamine mobilization probably was not triggered by impaired blood O2 transport. Heat-shocked trout also exhibited an elevation of arterial CO2 tension coupled with a fall in arterial pH, but these factors are not expected to trigger catecholamine release. The changes in blood O2 and CO2 tension occurred despite a significant hyperventilatory response to heat shock. Future studies should investigate whether catecholamine mobilization during heat shock in rainbow trout is triggered by a specific effect of high temperature activating the sympathetic nervous system via a thermosensitive transient receptor potential channel.
  
  PubDate: 2013-04-15T03:33:12Z
Role of brain nitric oxide in the cardiovascular control of bullfrogs
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  The goal of the present study was to determine if nitric oxide (NO) acting on the brain of bullfrog (Lithobates catesbeianus) is involved in arterial pressure and heart rate (HR) control by influencing sympathetic activity. We investigated the effect of intracerebroventricular injections of l-NMMA (a nonselective NO synthase inhibitor) on mean arterial blood pressure (MAP), HR and cutaneous vascular conductance (CVC) of pelvic skin after intravenous injection of α or β adrenergic blockers, prazosin or sotalol, respectively. Arterial pressure was directly measured by a telemetry sensor inserted in the aortic arch of animals. l-NMMA increased MAP, but did not change HR. This hypertensive response was inhibited by the pre-treatment with prazosin, but accentuated by sotalol. The effect of l-NMMA on MAP was also inhibited by i.v. injections of the ganglionic blocker, hexamethonium. Thus, NO acting on the brain of bullfrog seems to present a hypotensive effect influencing the sympathetic activity dependent on α and β adrenergic receptors in the periphery.
  
  PubDate: 2013-04-11T21:29:55Z
Development of sympathetic cardiovascular control in embryonic, hatchling, and yearling female American alligator (Alligator mississippiensis)
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  We used arterial tyramine injections to study development of sympathetic actions on in vivo heart rate and blood pressure in embryonic, hatching and yearling female American alligators. Tyramine is a pharmacological tool for understanding comparative and developmental sympathetic regulation of cardiovascular function, and this indirect sympathomimetic agent causes endogenous neuronal catecholamine release, increasing blood pressure and heart rate. Arterial tyramine injection in hatchling and yearling alligators caused the typical vertebrate response — rise in heart rate and blood pressure. However, in embryonic alligators, tyramine caused a substantial and immediate bradycardia at both 70% and 90% of embryonic development. This embryonic bradycardia was accompanied by hypotension, followed by a sustained hypertension similar to the hatchling and juvenile responses. Pretreatment with atropine injection (cholinergic receptor blocker) eliminated the embryonic hypotensive bradycardia, and phentolamine pretreatment (α-adrenergic receptor blocker) eliminated the embryonic hypotensive and hypertensive responses but not the bradycardia. In addition, hexamethonium pretreatment (nicotinic receptor blocker) significantly blunted embryos' bradycardic tyramine response. However, pretreatment with 6-hydroxydopamine, a neurotoxin that destroys catecholaminergic terminals, did not eliminate the embryonic bradycardia. Tyramine likely stimulated a unique embryonic response — neurotransmitter release from preganglionic nerve terminals (blocked with hexamethonium) and an acetylcholine mediated bradycardia with a secondary norepinephrine-dependent sustained hypertension. In addition, tyramine appears to stimulate sympathetic nerve terminals directly, which contributed to the overall hypertension in the embryonic, hatchling and yearling animals. Data demonstrated that humoral catecholamine control of cardiovascular function was dominant over the immature parasympathetic nervous system in developing alligator embryos, and suggested that sympathetic and parasympathetic nerve terminals were present and developing in ovo but were not tonically active.
  
  PubDate: 2013-04-11T21:29:55Z
Expression of aquaporin-3 and −8 mRNAs in the parr and smolt stages of sockeye salmon, Oncorhynchus nerka: Effects of cortisol treatment and seawater acclimation
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  This study aimed to examine the role of 2 aquaporin (AQP) isoforms (AQP3, and −8) in sockeye salmon (Oncorhynchus nerka) in response to a hyperosmotic challenge from freshwater to seawater (SW) during the parr and smoltification (smolt) stages. AQP3 mRNA was primarily detected in the osmoregulatory organs, such as gills, while AQP8 mRNA was primarily found in the intestine. These results suggested that AQP isoforms play a role in osmoregulation in specific osmoregulatory organs. Similarly, AQP3 mRNA expression in the gills (mean values:1.06±0.05 [parr] and 1.29±0.07 [smolt]) was significantly higher than AQP8 mRNA levels (parr: 0.04±0.003; smolt: 0.14±0.004), and in the intestine, AQP8 mRNA expression (parr: 0.89±0.007; smolt: 1.91±0.03) was significantly higher than AQP3 mRNA levels (parr: 0.24±0.006; smolt: 0.83±0.005); these expression patterns were similar in vivo and in vitro. Additionally, AQP mRNA levels were lower in cortisol treated than in control groups. Therefore, these results suggest that AQPs play important roles in the water absorption mechanisms associated with multiple AQP isoforms, and that cortisol enhances the hypo-osmoregulatory capacity of fish in SW, and also controls the expression of AQPs in a hyperosmotic environment.
  
  PubDate: 2013-04-11T21:29:55Z
Functional differentiation of pheromone-binding proteins in the common cutworm Spodoptera litura
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Pheromone-binding proteins (PBPs), a sub-family of odorant-binding proteins, are thought primarily to bind and transport the sex pheromones in moths. Considering multiple components of sex pheromone and multiple PBP genes exist in a single species, PBPs may contribute to the discrimination of different sex pheromone components. However, so far this discrimination is still unclear. Our previous ligand-binding assays showed that Spodoptera litura PBP1 (SlitPBP1) did not exhibit an obvious binding specificity among different sex pheromone components. In this study, binding specificity of the other two PBPs in S. litura (SlitPBP2 and SlitPBP3) was further investigated. As a result, SlitPBP2 was capable of binding all four sex pheromone components with similar affinities; whereas SlitPBP3 showed very weak binding affinities to them except Z9,E12–14:Ac. Similar results were also obtained from studied pheromone analogs, to which SlitPBP2 showed much stronger affinities than SlitPBP3. However, both SlitPBP2 and SlitPBP3 exhibited overall weaker affinities to sex pheromones and their analogs than SlitPBP1. In addition, quantitative real time PCR showed that three SlitPBP genes exhibited a very different sex-biased expression in adult antenna with male-biased for SlitPBP1 and SlitPBP2 while female-biased for SlitPBP3. Finally, ligand-binding assays indicated that the two SlitPBPs showed a similar pH-dependent conformational change as reported SlitPBP1, but these three SlitPBPs showed different behavior across a pH range or something similar. Taken together, our data suggest that in S. litura PBP1 and PBP2 may play critical roles in the perception of female sex pheromones, but do not show an obvious discriminative ability among different sex pheromone components; whereas PBP3 may have other functions.
  
  PubDate: 2013-04-11T21:29:55Z
Coping with sub-optimal water temperature: Modifications in fatty acid profile of barramundi as influenced by dietary lipid
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Metabolic responses to sub-optimal temperature deplete lipid depots, remodel membrane lipid and alter the fatty acid profile in the whole body and tissues of ectothermic vertebrates including fish. The magnitude of these changes may depend on dietary history including oil sources with different fatty acid compositions. Barramundi, Lates calcarifer (Perciformes, Latidae), a tropical ectothermic fish, was fed on diets either rich in dietary long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA) from fish oil, rich in stearidonic and γ-linolenic acid (SDA and GLA, respectively) from Echium plantagineum, or rapeseed oil deficient in LC-PUFA. Following 5weeks at the optimum temperature of 30°C when growth rates were comparable amongst dietary treatments, water temperature was dropped to 20°C for 1week for half of the animals and maintained at 30°C for the other half. Decreased temperature increased the liver and skeletal muscle content of LC-PUFA in fish fed on echium oil compared with rapeseed oil, while dietary LC-PUFA depots in fish oil fed-fish depleted rapidly in the week of sub-optimal temperature. The lipid unsaturation index of cellular membrane in the liver and muscle increased under low temperature at the same rate regardless of dietary oil. Therefore, rapid exposure of an ectothermic vertebrate to a lower and sub-optimal temperature caused significant modulation in fatty acid composition. We propose that the tolerance of barramundi, a representative of tropical farmed fish, to sub-optimal temperature will be enhanced when fatty acid substrates closer to the LC-PUFA are available in their diet.
  
  PubDate: 2013-04-11T21:29:55Z
Changes in brain arginine vasotocin, isotocin, plasma 11-ketotestosterone and cortisol in round goby, Neogobius melanostomus, males subjected to overcrowding stress during the breeding season
- Abstract: Publication date: June 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  In natural spawning grounds, breeding round goby, Neogobius melanostomus, males are exposed to various social stimuli, including high density of same-sex competitors and separation from females. We hypothesize that breeding males subjected to overcrowding in the wild experience high stress that affects their socio-sexual behavior and their relationships among conspecifics. We designed an experiment to mimic natural stimulation when highly aggregated breeding males are subjected to same-sex opponents. Males were sampled sequentially from experimental tank stocked at decreasing fish densities of 15 fish/m2, 9 fish/m2 and 4 fish/m2. We studied the effects of overcrowding on male behavior and selected hormones, brain arginine vasotocin (AVT) and isotocin (IT) and plasma 11-ketotestosterone (11-KT) and cortisol as these are known to play roles in reproduction and related social interactions. The highest brain AVT and plasma cortisol levels were measured in non-aggressive males kept in the overcrowded group of 15 fish/m2. IT level was elevated in fish kept at the lower density of 9 fish/m2, and at which the males began to display territoriality and aggression. The plasma level of 11-KT was similar in all the males. Brain AVT and IT and plasma cortisol along with behavioral observations can be applied as species-specific indicators of the well-being of round goby males.
  
  PubDate: 2013-04-11T21:29:55Z
trans-Resveratrol and ε-viniferin decrease glucose absorption in porcine jejunum and ileum in vitro
- Abstract: Available online 6 April 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  trans-Resveratrol and ε-viniferin are used as dietary supplements. They are reported to be supportive in preventing arteriosclerosis and diabetes and a previous study could demonstrate an inhibitory potential on sodium dependent glucose transport (SGLT1) in oocytes und mouse intestinal everted rings (Schulze et al., 2012, Genes Nutr. 6, S61). The in vitro effects of trans-resveratrol and ε-viniferin on intestinal glucose uptake in the porcine small intestines (Sus Scrofa) have not yet been evaluated. It was hypothesized that trans-resveratrol/ε-viniferin may have an adverse effect on porcine intestinal sodium dependent glucose uptake. The effects on electrogenic small intestinal glucose absorption and sodium dependent 3H-glucose uptake in brush border membrane vesicles (BBMV) were evaluated. Pieces of mucosa were mounted into Ussing chambers and were incubated with either trans-resveratrol (0.3mmol/L), ε-viniferin (0.3mmol/L), or ethanol. Sodium-dependent glucose absorption into BBMV was measured. 3H-glucose uptake studies were performed using the same concentrations of the respective substances. SGLT1 mediated glucose absorption was approximately 3-fold higher in ileum compared to jejunum. After preincubation with trans-resveratrol and ε-viniferin, glucose induced increases of short-circuit currents were significantly decreased. BBMV-studies revealed comparable results and glucose uptake was also significantly decreased. As the glucose transport/uptake was decreased after preincubation with either trans-resveratrol or ε-viniferin this active transport mechanism was directly influenced by inhibiting the SGLT1 transport system.
  
  PubDate: 2013-04-08T06:20:01Z
Repeatability of baseline corticosterone and short-term corticosterone stress responses, and their correlation with testosterone and body condition in a terrestrial breeding anuran (Platymantis vitiana)
- Abstract: Available online 3 April 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  Repeatability of physiological response variables, such as the stress hormone corticosterone, across numerous sampling occasions is an important assumption for their use as predictors of behaviour, reproduction and fitness in animals. Very few studies have actually tested this assumption in free-living animals under uncontrolled natural conditions. Non-invasive urine sampling and standard capture handling protocol have enabled the rapid quantification of baseline corticosterone and short-term corticosterone stress responses in anuran amphibians. In this study, established non-invasive methods were used to monitor physiological stress and urinary testosterone levels in male individuals of the terrestrial breeding Fijian ground frog (Platymantis vitiana). Adult male frogs (n = 20) were sampled at nighttimes on three repeated occasions at intervals of 14 days during their annual breeding season on Viwa Island, Fiji. All frogs expressed urinary corticosterone metabolite responses to the capture and handling stressor, with some frogs showing consistently high urinary corticosterone responses than others. Ranks of corticosterone values at 0, 4 and 8 h, and the corrected rank were highly significant (r = 0.75 – 0.99) between the three repeated sampling occasions. Statistical repeatabilities were high for baseline corticosterone (r = 0.973) and for corticosterone values at 2 h (r = 0.862), 4 h (r = 0.861), 6 h (r = 0.820) and 8 h (r = 0.926), and also for the total (inclusive of baseline corticosterone values) and the corrected integrated responses (index of the acute response) [r = 0.867 and r = 0.870]. Urinary testosterone levels also showed high statistical repeatability (r = 0.78). Furthermore, variation in baseline and short-term corticosterone stress responses was greater between individuals than within individuals. Baseline urinary corticosterone was significantly negatively correlated with the corrected integrated corticosterone response (r = -0.3, p < 0.001) but non-significantly with body-condition (r = -0.04) and baseline urinary testosterone (r = -0.07). While, the corrected integrated corticosterone response was positively correlated (non-significantly) with baseline urinary testosterone (r = +0.04) and body-condition (r = +0.08). Urinary testosterone levels and body-condition were significantly negatively correlated (r = -0.23, p < 0.001). The results suggest that male frogs with higher levels of testosterone could have depleted energy reserve during the breeding period. The acute corticosterone responses help in replenishing energy that is needed for breeding and survival. The results also provide some support to the ‘cort-fitness’ hypothesis as highlighted by the negative correlation between baseline corticosterone and body-condition. It is most likely that the acute corticosterone response is adaptive and linked positively with reproductive fitness and survival in male anurans.
  
  PubDate: 2013-04-04T06:23:57Z
Thermoregulatory and metabolic responses to hypoxia in the oviparous lizard, Phrynocephalus przewalskii
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  The effects of hypoxia on behavioral thermoregulation, rate of heating and cooling, hysteresis of heart rate, and standard metabolic rate (SMR) were investigated in Phrynocephalus przewalskii, a small size toad headed lizard. Preferred temperature (Tb) descended when lizards were exposed to severe hypoxia (8% O2 and 6% O2) for 22h, and lizards were able to maintain preferred Tb after one week at 12% and 8% O2 respectively. The period of heating increased after being treated with hypoxia (12% and 8% O2) for one week. Hysteresis of heart rate appeared at any given body temperature and oxygen level except at 39°C and 40°C at 8% O2. SMR significantly increased after one-week acclimatization to 12% and 8% O2 when ambient temperature (Ta) was 25°C, however, it did not change at 35°C. Thus, we suggest that P. przewalskii has special thermoregulatory and metabolic mechanisms to acclimatize to the hypoxic environment.
  
  PubDate: 2013-04-04T06:23:57Z
The effect of stress and stress hormones on dynamic colour-change in a sexually dichromatic Australian frog
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Rapid colour changes in vertebrates have fascinated biologists for centuries, herein we demonstrate dynamic colour change in an anuran amphibian, the stony creek frog (Litoria wilcoxii), which turns from brown to bright (lemon) yellow during amplexus. We show this by comparing the colour of baseline (unpaired males) and amplecting (paired) males. We also investigate the possible role of stress and stress hormones on this colour change. Frogs were subjected to four different levels of stressors (handling, toe-clipping, saline injection and adrenocorticotropic hormone [ACTH] injection) and the colour change was measured using digital photography. A comparison of baseline colour and stress hormone (corticosterone) levels was also conducted to give further insight to this topic. From the images, the Red Blue Green (RGB) colour values were calculated, and a principal components analysis (PCA) was used to create a single colour metric (the major axis) as an index of colour in the visible spectrum. A moderate stressor (toe-clipping) led to a significant change in colour (within 10min) similar to that of amplecting males. Surprisingly, neither a mild stressor (handling and saline injection) nor the maximum stressor (handling and ACTH injection) led to a lightening response. This study confirms that the dynamic male colour change in this species in response to medium stressors adds new knowledge to the understanding of the functional mechanisms of dynamic colour change in amphibians.
  
  PubDate: 2013-04-04T06:23:57Z
Juvenile hormone regulates an expression of a late gene encoded in a polydnavirus, Cotesia plutellae bracovirus
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  An endoparasitoid wasp Cotesia plutellae encodes two host translation inhibitory factors (HTIFs) that are expressed in late larval stage of Plutella xylostella parasitized by C. plutellae. The late expressions of HTIFs seemed to be associated with decreasing titer of juvenile hormone (JH) at the last larval instar because an addition of pyriproxyfen (PYR, a JH analog) inhibited the late expression pattern of two HTIF genes. To understand their late expression control, promoter region of an HTIF gene called CpBV15α was cloned by inverse PCR. The cloned HTIF upstream region (1113bp) possessed a putative JH response element (JHRE) and other promoter elements. The putative promoter region was rejoined with an open reading frame of enhanced green fluorescence protein (EGFP). When the recombinant vector construct was injected into early third instar larvae of nonparasitized P. xylostella, it was expressed in fourth larval instar at 72h after injection, compared to relatively early expression in 24h after injection of control construct containing a baculovirus immediate-early promoter. However, recombinant EGFP construct lost the late expression pattern when its promoter region was incomplete by truncating JHRE region. PYR application inhibited EGFP expression of the recombinant construct, but gave little influence on truncated constructs. Interestingly, when the complete promoter construct was injected to pupal stage, its late expression pattern was lost and showed early expression pattern. However, an addition of PYR to pupae, which had been injected with the complete promoter construct, inhibited the reporter gene expression. These results suggest that late expression of a HTIF (CpBV15α) is controlled by its promoter, which is sensitive to host JH titer.
  
  PubDate: 2013-04-04T06:23:57Z
First evidence of the possible implication of the 11-deoxycorticosterone (DOC) in immune activity of Eurasian perch (Perca fluviatilis, L.): Comparison with cortisol
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Cortisol, the main corticosteroid in fish, is frequently described as a modulator of fish immune system. Moreover, 11-deoxycorticosterone (DOC) was shown to bind and transcriptionally activate the mineralocorticoid receptor and may act as a mineralocorticoid in fish. Immune modulations induced by intraperitoneal injections of these two corticosteroids were assessed in Eurasian perch juveniles. Cortisol and DOC were injected at 0.8mgkg−1 and 0.08mgkg−1 body weight respectively. Cortisol increased plasma lysozyme activity 72h post-injection, C-type lysozyme expression in spleen from 1 to 72h post-injection, and favoured blood neutrophils at the expense of a mixture of lymphocytes and thrombocytes. Moreover, 6h after injection, cortisol reduced expression levels of the pro-inflammatory cytokine TNF-α in spleen. DOC had no effects on the immune variables measured in plasma, but increased expression levels of C-type lysozyme and apolipoprotein A1 mRNA in both gills and spleen. Meanwhile, DOC stimulated its putative signalling pathway by increasing expression of mineralocorticoid receptor and 11β-hydroxysteroid dehydrogenase-2 in spleen. These results confirmed the role of cortisol as an innate, short term immune stimulator. For the first time, DOC is described as a possible immune stimulator in fish.
  
  PubDate: 2013-03-31T06:19:28Z
Responses of insulin-like growth factor (IGF)-I and two IGF-binding protein-1 subtypes to fasting and re-feeding, and their relationships with individual growth rates in yearling masu salmon (Oncorhynchus masou)
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Two subtypes of insulin-like growth factor binding protein (IGFBP)-1 are present in salmon blood and they are both up-regulated under catabolic conditions such as stress. The present study examined effects of fasting and re-feeding on IGFBP-1a (28-kDa form) and IGFBP-1b (22-kDa form) both at mRNA and protein levels along with IGF-I and RNA/DNA ratio in yearling masu salmon. Fish were individually tagged and assigned to one of three treatments: Fed, Fasted or Re-fed. Circulating IGF-I levels significantly decreased after fasting for 5weeks and were positively correlated with individual growth rates. Liver igf-1 mRNA levels were not affected by the treatment. Muscle RNA/DNA ratio did not respond to fasting nor showed correlations with growth rates. Circulating IGFBP-1a and IGFBP-1b increased during fasting and decreased after re-feeding. Both serum levels were inversely correlated with growth rates, while IGFBP-1b had consistent negative relationships with growth rates. Fasting/re-feeding also affected their mRNA levels in the liver. These results suggest that circulating IGF-I and IGFBP-1b could serve as positive and negative indices of growth, respectively, in masu salmon. Different sensitivities of IGBP-1a and IGFBP-1b may be useful to assess a broad range of catabolic conditions when they are combined.
  
  PubDate: 2013-03-31T06:19:28Z
Retinoid X receptor (RXR), estrogen receptor (ER) and other nuclear receptors in tissues of the mussel Mytilus galloprovincialis: Cloning and transcription pattern
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Bivalve molluscs accumulate chemical compounds from the environment that could cause alterations in lipid homeostasis and endocrine system. In vertebrates such cell processes are modulated by transcription factors belonging to the superfamily of nuclear receptors (NRs). The goal of this study was to clone fragments of mussel Mytilus galloprovincialis NR genes that could mediate cell responses such as peroxisome proliferation and endocrine disruption. PCR-based screening of mussel digestive gland cDNA using degenerate primers provided cDNA fragments or whole ORFs of retinoid X receptor (RXR), estrogen receptor (ER) and 5 proteins belonging to the NR1 subfamily highly similar to the arthropod ecdysone inducible protein E75. NR1G, whose whole ORF was cloned, is related to the nematode and trematode G group of NR1 receptors; NR1DEF is related to the D, E and F groups, and NR1Dv1, NR1Dv2 and NR1DΔ belong to the D group. mRNA transcripts for all these receptors were detected in gill, mantle and digestive gland. In all cases, except ER, transcript levels were lower in June than in January. NR1Dv1 and NR1DΔ did not show identical transcription levels, although both were at their lowest in digestive gland in June. On the contrary, NR1Dv2 and NR1DΔ transcription profiles were similar. Further studies are needed to determine the function(s) of mussel RXR, ER and novel NR1 subfamily receptors and their possible role in the regulation of physiological cell responses and/or adaptive response to xenobiotic exposures.
  
  PubDate: 2013-03-31T06:19:28Z
Thermal stress and cellular signaling processes in hemocytes of native (Mytilus californianus) and invasive (M. galloprovincialis) mussels: Cell cycle regulation and DNA repair
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  In a previous study using hemocytes from native and invasive congeners of Mytilus (Mytilus californianus and Mytilus galloprovincialis, respectively) we showed that DNA damage and cell signaling transduction processes related to the cellular stress response and apoptosis were induced by acute temperature stress. The present study extends this work by examining effects of acute heat- and cold stress on total hemocyte counts (THCs) and expression of key regulatory molecules involved in responding to stress: tumor suppressor factor (p53), cell cycle arrest activator (p21), and a DNA base excision repair enzyme (apurinic/apyrimidinic endonuclease (APE)). Hyperthermia (28°C, 32°C) led to significant decreases of THCs in both species. The extent of decrease in THC was temperature-, time-, and species-dependent; lower THC values were found in M. californianus, the more cold-adapted species. Western blot analyses of hemocyte extracts with antibodies specific for p53 protein, several site-specific phosphorylation states of p53, p21 protein, and APE indicated that heat- and cold (2°C) stress induced a time-dependent activation of stress-related proteins in response to DNA damage; these stress-induced changes could govern cell cycle arrest or DNA damage repair. Our results show that the downstream regulatory response to temperature-induced cell damage may play an important role in deciding cellular fate following heat- and cold stress. Compared to M. californianus, the more warm-adapted M. galloprovincialis appears to have a higher temperature tolerance due to a lesser reduction in THC, faster signaling activation and transduction, and stronger DNA repair ability following heat stress.
  
  PubDate: 2013-03-31T06:19:28Z
Rho participates in chemoreceptor-induced changes in morphology to hair bundle mechanoreceptors of the sea anemone, Nematostella vectensis
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Adjustable hair bundle mechanoreceptors located on anemone tentacles detect movements of nearby, swimming prey. The hair bundles are formed by numerous actin-based stereocilia that converge onto a single, central kinocilium. Interestingly, morphological and functional changes to the hair bundles are induced by activating chemoreceptors that bind prey-derived N-acetylated sugars and proline, respectively. Morphological changes to the hair bundles involve alterations to the actin cytoskeleton of stereocilia. A pharmacological activation of Rho induces hair bundles to elongate to lengths comparable to those normally induced by exposure to N-acetylneuraminic acid (NANA) and prevents shortening of hair bundles normally induced by proline. Rho inhibition prevents NANA-induced elongation, but does not prevent proline-induced shortening of hair bundles. Western blots feature a band similar in mass to that predicted for a Rho homolog in the genome of Nematostella. Immunocytochemistry localizes Rho in stereocilia of the hair bundle. Anemone hair bundles arise from multicellular complexes. Data from experiments using heptanol, a gap junction uncoupler, indicate that cell–cell communication is required in order for activated chemoreceptors to induce morphological changes to the hair bundles.
  
  PubDate: 2013-03-31T06:19:28Z
Spatial expression and functional flexibility of monocarboxylate transporter isoforms in the zebrafish brain
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  The present study provides in vivo evidence to prove the functional plasticity of monocarboxylate transporters (MCTs) in brains of vertebrates using zebrafish (Danio rerio) as a model. In the mammalian central nervous system (CNS), energy demands are largely met by oxidation of glucose. In recent studies, in addition to glucose, lactate is also considered an energy substrate for the CNS. Astrocytes were demonstrated to play an important role in transporting lactate as metabolic substrate from capillaries to neurons through monocarboxylate transporters (MCTs). The present study was to use zebrafish as an in vivo model to test the hypothesis of whether the various MCT homologs play differential roles in the development and functioning of the CNS. Using RT-PCR and double in situ hybridization coupling with immunocytochemical staining experiments, zebrafish MCTs1–4 were all found to be expressed in brains of embryos, and were further elucidated to be localized in both neurons and astrocytes. Loss-of-functions by morpholino knockdown further provided in vivo evidences to infer that zMCTs1, -2, and -4 may be involved in metabolite transport and functioning in the developing brain. Subsequent rescue experiments with capped mRNAs of specific isoforms further indicated that zMCT2 is an indispensable monocarboxylate-transporting route for CNS development and function in zebrafish. This information is essential for identifying proper candidates of MCT isoforms that are involved in the development and functioning of the CNS.
  
  PubDate: 2013-03-23T07:20:25Z
CO2-driven seawater acidification differentially affects development and molecular plasticity along life history of fish (Oryzias latipes)
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  Fish early life stages have been shown to react sensitive to simulated ocean acidification. In particular, acid–base disturbances elicited by altered seawater carbonate chemistry have been shown to induce pathologies in larval fish. However, the mechanisms underlying these disturbances are largely unknown. We used gene expression profiling of genes involved in acid–base regulation and metabolism to investigate the effects of seawater hypercapnia on developing Japanese ricefish (medaka; Oryzias latipes). Our results demonstrate that embryos respond with delayed development during the time window of 2–5dpf when exposed to a seawater pCO2 of 0.12 and 0.42kPa. This developmental delay is associated with strong down-regulation of genes from major metabolic pathways including glycolysis (G6PDH), Krebs cycle (CS) and the electron transport chain (CytC). In a second step we identified acid–base relevant genes in different ontogenetic stages (embryos, hatchlings and adults) and tissues (gill and intestine) that are up regulated in response to hypercapnia, including NHE3, NBCa, NBCb, AE1a, AE1b, ATP1a1a.1, ATP1a1b, ATP1b1a, Rhag, Rhbg and Rhcg. Interestingly, NHE3 and Rhcg expressions were increased in response to environmental hypercapnia in all ontogenetic stages and tissues tested, indicating the central role of these proteins in acid–base regulation. Furthermore, the increased expression of genes from amino acid metabolism pathways (ALT1, ALT2, AST1a, AST1b, AST2 and GLUD) suggests that energetic demands of hatchlings are fueled by the breakdown of amino acids. The present study provides a first detailed gene expression analysis throughout the ontogeny of a euryhaline teleost in response to seawater hypercapnia, indicating highest sensitivity in early embryonic stages, when functional ion regulatory epithelia are not yet developed.
  
  PubDate: 2013-03-23T07:20:25Z
The effects of body temperature and mass on the postprandial metabolic responses of the African egg-eating snakes Dasypeltis scabra and Dasypeltis inornata
- Abstract: June 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 2
  
  African egg-eating snakes (Dasypeltis) feed only on freshly laid bird eggs which they perforate within their esophagus before swallowing the liquid contents and regurgitating the empty shell. Compared to a snake’s typical intact meal, the liquid diet of Dasypeltis would expectedly generate a more moderate postprandial metabolic response and specific dynamic action (SDA). Free-ranging Dasypeltis feed over a range of ambient temperatures and thereby experience predicted temperature-dependent shifts in the duration and magnitude of their postprandial metabolic response. Such shifts would undoubtedly be shared among different species and age classes of Dasypeltis. To examine these expectations, we measured pre- and postprandial metabolic rates of adult Dasypeltis inornata and adult and neonate Dasypeltis scabra in response to liquid egg meals weighing 20% of snake body mass at 20, 25, 27, 30, and 32°C. With an increase in body temperature, postprandial metabolic profiles of neonate and adult snakes became narrower and shorter in duration. Specific dynamic action varied among temperature treatments, increasing from 20 to 32°C. Standard metabolic rate, postprandial peak metabolic rate, and SDA scaled with mass exponents that typically did not differ from 1.0. As expected, Dasypeltis digesting a liquid egg diet experienced a more modest postprandial response and SDA, expending on average only 10.6% of the meal’s energy on the breakdown, absorption, and assimilation of the egg meal, whereas other colubrids consuming intact rodent or fish meals expend on average 16.3% of the meal’s energy on digestion and assimilation. Actively foraging and feeding throughout the avian egg laying season enable Dasypeltis to survive when eggs are not available. The adaptive suite of traits that enable Dasypeltis to consume eggs of large relative size and ingest only the liquid contents may also be joined by physiological adaptations specific to their liquid diet and extended bouts of fasting.
  
  PubDate: 2013-03-23T07:20:25Z
Editorial Board
- Abstract: May 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 165, Issue 1
  
  PubDate: 2013-03-19T07:16:12Z
Heavy metals affect regulatory volume decrease (RVD) in nematocytes isolated from the jellyfish Pelagia noctiluca
- Abstract: Available online 14 March 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  The environmental contamination caused by heavy metals raises the question of their effect on biological systems. Among bio-indicators useful to monitor the toxicological effects of these chemicals, Cnidarians offer a unique model. Cnidarians possess highly specialized stinging cells, termed nematocytes, which respond to hyposmotic solution with well established homeostatic parameters as an acute osmotic phase (OP), leading to cell swelling, and then a slower regulatory volume decrease (RVD) phase, causing cell shrinkage. Here we report the effect of 65% artificial sea water (ASW) containing heavy metals, such as Cd, La, Co, Cu and Zn (concentrations comprised between 100 and 0.1μM) on both OP and RVD in nematocytes isolated from the jellyfish Pelagia noctiluca by 605mM NaSCN plus 0.01mM Ca2+. The exposure of the cells to Co and La inhibited RVD but not OP. However, Cu, Cd and Zn prevented the OP in a dose-dependent manner and, hence, also the detection of RVD. These results suggest that, in isolated nematocytes, heavy metal pollutants impair RVD either directly or indirectly through interference with the OP, thus negating RVD. Although further studies need to clarify the exact mechanisms whereby heavy metals exert their toxicity, it is evident that nematocytes of Cnidarians could serve as a model for ecotoxicological investigations.
  
  PubDate: 2013-03-15T22:29:06Z
Intraspecific variation in the metabolic scaling exponent in ectotherms: Testing the effect of latitudinal cline, ontogeny and transgenerational change in the land snail Cornu aspersum
- Abstract: Available online 6 March 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  The strong dependence of metabolic rates on body mass has attracted the interest of ecological physiologist, as it has important implications to many aspects of biology including species variations in body size, the evolution of life history, and the structure and function of biological communities. The great diversity of observed scaling exponents have lead some authors to conclude that there is no single universal scaling exponent, but instead it ranges from 2/3 to 1. Most of the telling evidence against the universality of power scaling exponents comes from ontogenetic changes. Nevertheless, there could be other sources of phenotypic variation that influence this allometric relationship at least at the intraspecific level. In order to explore the general concept of the metabolic scaling in terrestrial molluscs we tested the role of several biological and methodological sources of variation on the empirically estimated scaling exponent. Specifically, we measured a proxy of metabolic rate (CO2 production) in 421 individuals, during three generations, in three different populations. Additionally, we measured this scaling relationship in 208 individuals at five developmental stages. Our results suggest that the metabolic scaling exponent at the intraspecific level does not have a single stationary value, but instead it shows some degree of variation across geographic distribution, transgenerational change and ontogenetic stages. The major differences in the metabolic scaling exponent that we found were at different developmental stages of snails, because ontogeny involves increases in size at different rates, which in turn, generate differential energy demands.
  
  PubDate: 2013-03-08T22:25:42Z
The effects of diel-cycling hypoxia acclimation on the hypoxia tolerance, swimming capacity and growth performance of southern catfish (Silurus meridionalis)
- Abstract: Available online 6 March 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  To investigate the effects of diel-cycling hypoxia acclimation on the hypoxia tolerance, swimming and growth performance of juvenile southern catfish, we initially measured the critical oxygen tension (P crit), oxygen thresholds of aquatic surface respiration (ASR) and loss of equilibrium (LOE) of diel-cycling hypoxia-acclimated (15 d, 7:00–21:00, dissolved oxygen level (DO)=7.0±0.2mgL-1; 21:00–7:00, DO=3.0±0.2mgL-1) and non-acclimated (15 d, DO=7.0±0.2mgL-1) southern catfish at 25°C. We then measured the critical swimming speed (U crit) and metabolic rate (MR) of hypoxia-acclimated and non-acclimated fish (under both hypoxic and normoxic conditions). The feeding rate (FR), feeding efficiency (FE) and specific growth rate (SGR) of fish in hypoxia-acclimated and non-acclimated groups were also measured. The P crit, ASR and LOE of hypoxia-acclimated fish were significantly lower than those of non-acclimated fish. Hypoxia acclimation resulted in a significantly higher U crit when the individuals swam in hypoxia. The U crit, maximum metabolic rate (MMR) and metabolic scope (MS) of both the hypoxia-acclimated and non-acclimated fish all decreased with the decrease of DO. However, the U crit, MMR and MS decreased by 31, 43 and 54%, respectively, in non-acclimated fish, whereas these values decreased by 15, 28 and 29%, respectively, in hypoxia-acclimated fish, which suggests that hypoxia-acclimated fish were less sensitive to the DO decrease. The FR, FE and SGR all decreased by 21, 20 and 45%, respectively, in the hypoxia-acclimated group compared to the non-acclimated group. This result suggests that diel-cycling hypoxia acclimation improved the hypoxia tolerance and aerobic swimming performance of southern catfish, whereas impaired the growth performance. The high hypoxia tolerance and physiological plasticity to hypoxia-acclimated southern catfish may be related to its lower maintenance energy expenditure, sit-and-wait lifestyle and bottom-dwelling living environment condition (usually facing oxygen fluctuation). The growth performance of so-called ‘visceral type’ fish species, such as southern catfish, are more sensitive to hypoxia compared to other fish species because of their high peak post-prandial metabolic rate, which may be restrained by the limited aerobic metabolic scope in hypoxia.
  
  PubDate: 2013-03-08T22:25:42Z
Metabolic response to lipid infusion in fasting winter-acclimatized king penguin chicks (Aptenodytes patagonicus)
- Abstract: Available online 18 February 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  During the cold austral winter, king penguin chicks are infrequently fed by their parents and thus experience severe nutritional deprivation under harsh environmental conditions. These energetic constraints lead to a range of energy sparing mechanisms balanced by the maintenance of efficient thermogenic processes. The present work investigated whether the high thermogenic capacities exhibited by winter-acclimatized king penguin chicks could be related to an increase in lipid substrate supply and oxidation in skeletal muscle, the main site of thermogenesis in birds. To test this hypothesis, we examined i) the effect of an experimental rise in plasma triglyceride on the whole metabolic rate in winter-acclimatized (WA) and de-acclimatized king penguin chicks kept at thermoneutrality (TN), and ii) investigated the fuel preference of muscle mitochondria. In vivo, a perfusion of a lipid emulsion induced a small 10% increase of metabolic rate in WA chicks but not in TN group. In vitro, the oxidation rate of muscle mitochondria respiring on lipid-derived substrate was +40% higher in WA chicks than in TN, while no differences were found between groups when mitochondria oxidized carbohydrate-derived substrate or succinate. Despite an enhanced fuel selection towards lipid oxidation in skeletal muscle, a rise of circulating lipids per se was not sufficient to fully unravel the thermogenic capacity of winter-acclimatized king penguin chicks.
  
  PubDate: 2013-02-19T22:21:05Z
Hemoglobin concentrations in waders vary with their strategies of migration: A comparative analysis
- Abstract: Available online 17 February 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  The aim of this study was to determine whether blood oxygen capacity of waders varies with respect to migration at both inter-specific and individual level. To verify this hypothesis we measured hemoglobin concentration in 875 waders from 14 species during their autumn migration through central Poland. In most of the species we found an increase in the hemoglobin levels along with increasing fat loads during the stopover period, which suggests that individual birds are able to elevate their oxygen-carrying capacity of blood prior to departure on a migratory flight. Positive relationship between hemoglobin concentrations of waders and their fat loads was confirmed at the inter-specific level by the comparative analysis of independent contrasts. Comparative analysis also demonstrated that hemoglobin concentrations were positively related with theoretical flight range and mean refueling rate during stopovers. The results indicate that species travelling according to the strategy of energy-minimization (short-distance migrants, low fat reserves, low refueling rates) have lower blood oxygen capacity in comparison to time-selected species (long-distance migrants, high fat reserves, high refueling rates). It remains uncertain whether high hemoglobin levels in long-distance migrants are a fixed evolutionary trait or a temporal physiological adaptation associated with carrying considerable fat load.
  
  PubDate: 2013-02-19T22:21:05Z
Feeding and swimming modulate iono-and-hormonal regulation differently in goldfish, Carassius auratus and common carp, Cyprinus carpio
- Abstract: Available online 16 February 2013
  Publication year: 2013
  Source:Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
  
  Feeding and swimming can influence ion balance in fish. Therefore we investigated their impact on ionoregulation and its hormonal control in goldfish and common carp. As expected due to the osmorespiratory compromise, exhaustive swimming induced increases in gill Na+/K+ ATPase (NKA) activity in both species, resulting in stable levels of plasma ions. In contrast to our expectations, this only occurred in fed fish and feeding itself increased NKA activity, especially in carp. Fasting fish were able to maintain ion balance without increasing NKA activity, we propose that the increase in NKA activity is related to ammonia excretion rather than ion uptake per se. In goldfish, this increase in NKA activity coincided with a cortisol elevation while no significant change was found in carp. In goldfish, high conversion of plasma T4 to T3 was found in both fed and fasted fish resulting in low T4/T3 ratios, which increased slightly due to exhaustive swimming. In starved carp the conversion seemed much less efficient, and high T4/T3 ratios were observed. We propose that thyroid hormone regulation in carp was more related to its role in energy metabolism rather than ionoregulation. The present research showed that both species, whether fed or fasted, are able to sufficiently adapt their osmorepiratory strategy to minimise ions losses while maintaining gas exchange under exhaustive swimming.
  
  PubDate: 2013-02-19T22:21:05Z