Fernando Galvez

University of California, Davis, Davis, CA, United States

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Publications (44)133.89 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Environmental salinity presents a key barrier to dispersal for most aquatic organisms, and adaptation to alternate osmotic environments likely enables species diversification. Little is known of the functional basis for derived tolerance to environmental salinity. We integrate comparative physiology and functional genomics to explore the mechanistic underpinnings of evolved variation in osmotic plasticity within and among two species of killifish; Fundulus majalis harbours the ancestral mainly salt-tolerant phenotype, whereas Fundulus heteroclitus harbours a derived physiology that retains extreme salt tolerance but with expanded osmotic plasticity towards the freshwater end of the osmotic continuum. Common-garden comparative hypo-osmotic challenge experiments show that F. heteroclitus is capable of remodelling gill epithelia more quickly and at more extreme osmotic challenge than F. majalis. We detect an unusual pattern of baseline transcriptome divergence, where neutral evolutionary processes appear to govern expression divergence within species, but patterns of divergence for these genes between species do not follow neutral expectations. During acclimation, genome expression profiling identifies mechanisms of acclimation-associated response that are conserved within the genus including regulation of paracellular permeability. In contrast, several responses vary among species including those putatively associated with cell volume regulation, and these same mechanisms are targets for adaptive physiological divergence along osmotic gradients within F. heteroclitus. As such, the genomic and physiological mechanisms that are associated with adaptive fine-tuning within species also contribute to macro-evolutionary divergence as species diversify across osmotic niches.
    Molecular Ecology 07/2013; 22(14):3780-3796. · 6.28 Impact Factor
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    ABSTRACT: The Deepwater Horizon oil rig disaster resulted in crude oil contamination along the Gulf coast in sensitive estuaries. Toxicity from exposure to crude oil can affect populations of fish that live or breed in oiled habitats as seen following the Exxon Valdez oil spill. In an ongoing study of the effects of Deepwater Horizon crude oil on fish, Gulf killifish ( Fundulus grandis ) were collected from an oiled site (Grande Terre, LA) and two reference locations (coastal MS and AL) and monitored for measures of exposure to crude oil. Killifish collected from Grande Terre had divergent gene expression in the liver and gill tissue coincident with the arrival of contaminating oil and up-regulation of cytochrome P4501A (CYP1A) protein in gill, liver, intestine, and head kidney for over one year following peak landfall of oil (August 2011) compared to fish collected from reference sites. Furthermore, laboratory exposures of Gulf killifish embryos to field-collected sediments from Grande Terre and Barataria Bay, LA, also resulted in increased CYP1A and developmental abnormalities when exposed to sediments collected from oiled sites compared to exposure to sediments collected from a reference site. These data are predictive of population-level impacts in fish exposed to sediments from oiled locations along the Gulf of Mexico coast.
    Environmental Science & Technology 05/2013; · 5.26 Impact Factor
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    ABSTRACT: The killifish Fundulus heteroclitus is abundant in osmotically dynamic estuaries and it can quickly adjust to extremes in environmental salinity. We performed a comparative osmotic challenge experiment to track the transcriptomic and physiological responses to two salinities throughout a time course of acclimation, and to explore the genome regulatory mechanisms that enable extreme osmotic acclimation. One southern and one northern coastal population, known to differ in their tolerance to hypo-osmotic exposure, were used as our comparative model. Both populations could maintain osmotic homeostasis when transferred from 32 to 0.4 p.p.t., but diverged in their compensatory abilities when challenged down to 0.1 p.p.t., in parallel with divergent transformation of gill morphology. Genes involved in cell volume regulation, nucleosome maintenance, ion transport, energetics, mitochondrion function, transcriptional regulation and apoptosis showed population- and salinity-dependent patterns of expression during acclimation. Network analysis confirmed the role of cytokine and kinase signaling pathways in coordinating the genome regulatory response to osmotic challenge, and also posited the importance of signaling coordinated through the transcription factor HNF-4α. These genome responses support hypotheses of which regulatory mechanisms are particularly relevant for enabling extreme physiological flexibility.
    Journal of Experimental Biology 04/2012; 215(Pt 8):1293-305. · 3.24 Impact Factor
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    Proceedings of the National Academy of Sciences 03/2012; 109(12):E679-E679. · 9.74 Impact Factor
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    ABSTRACT: The Gulf killifish (Fundulus grandis) is a euryhaline fish found in coastal marsh along the entire of Gulf of Mexico and southern Atlantic of coast of the United States. The objective of this study was to investigate the effects of salinity on embryogenesis in the Gulf killifish. Four recirculation systems at salinities of 0.4, 7, 15, and 30 g/L were maintained at a static temperature with flow-through trays, containing embryos (n = 39) placed in triplicate into each system. Throughout embryogenesis, the rate of development, ammonia and urea excretion, and heart rate were monitored. Percent hatch was recorded, and morphological parameters were measured for larvae at hatch. As salinity was increased, the rate of embryogenesis decreased. Salinity significantly affected percent hatch with an 80.0% ± 2.6% for 7 g/L and 39.1 ± 4.3, 45.4 ± 4.5, and 36.3% ± 12.0% for 0.4, 15, and 30 g/L, respectively. Salinity and stage of development significantly affected production of ammonia and urea. As salinity increased, the dominate metabolite end product changed from urea to ammonia. However, the 15 g/L salinity treatment had the two highest levels of urea recorded. Heart rate was unaffected by salinity but increased throughout embryogenesis and remained constant once embryos reached stages where hatching has been recorded. While mean total length was not affected by salinity, embryos incubated in 30 g/L produced larvae with significantly thicker body depth at hatch. The 0.4, 7, and 15 g/L salinity treatments all had similar mean hours to hatch. The 30 g/L treatment resulted in a significantly longer mean time to hatch and smaller body cavity area at hatch.
    Fish Physiology and Biochemistry 01/2012; 38(4):1071-82. · 1.55 Impact Factor
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    ABSTRACT: The biological consequences of the Deepwater Horizon oil spill are unknown, especially for resident organisms. Here, we report results from a field study tracking the effects of contaminating oil across space and time in resident killifish during the first 4 mo of the spill event. Remote sensing and analytical chemistry identified exposures, which were linked to effects in fish characterized by genome expression and associated gill immunohistochemistry, despite very low concentrations of hydrocarbons remaining in water and tissues. Divergence in genome expression coincides with contaminating oil and is consistent with genome responses that are predictive of exposure to hydrocarbon-like chemicals and indicative of physiological and reproductive impairment. Oil-contaminated waters are also associated with aberrant protein expression in gill tissues of larval and adult fish. These data suggest that heavily weathered crude oil from the spill imparts significant biological impacts in sensitive Louisiana marshes, some of which remain for over 2 mo following initial exposures.
    Proceedings of the National Academy of Sciences 09/2011; · 9.74 Impact Factor
  • Benjamin Dubansky, Brian Whitaker, Fernando Galvez
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    ABSTRACT: The larvae of unionid freshwater mussels (i.e., glochidia) undergo a parasitic stage requiring their attachment to the external epithelia of fish hosts, where they metamorphose into free-living juveniles. We describe the physiological effects in bluegill sunfish (Lepomis macrochirus) of infection with glochidia from the paper pondshell (Utterbackia imbecillis). Glochidia accumulation on bluegill increased dramatically at concentrations of 2000 glochidia liter(-1) and above, reaching a maximum attachment density of about 30 glochidia g(-1) fish at 4000 glochidia liter(-1). Plasma cortisol was the most sensitive indicator of biological effect to glochidial exposure, increasing significantly in hosts exposed to 2000 glochidia liter(-1) or greater. Glochidia were 31% more likely to undergo successful juvenile metamorphosis when attached to bluegill with elevated plasma cortisol, largely due to the enhanced survivorship of these larvae during the first 48 h after infection. We tested the hypothesis that glochidial attachment and juvenile metamorphosis were stimulated directly by plasma cortisol in fish hosts. Bluegill were given an intraperitoneal injection of cortisol, then infected with 1000 glochidia liter(-1) at 48 h after hormone supplementation. Cortisol-injected fish had a 42% increase in the number of attached glochidia g(-1) fish and a 28% increase in larval metamorphosis compared to sham-injected and control fish. We provide evidence that cortisol enhances glochidial metamorphosis on hosts by improving the retention of attached glochidia. This study gives insights into the influence of host physiology on glochidial attachment and juvenile mussel transformation.
    Biological Bulletin 04/2011; 220(2):97-106. · 1.23 Impact Factor
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    ABSTRACT: Adaptive variation tends to emerge clinally along environmental gradients or discretely among habitats with limited connectivity. However, in Atlantic killifish (Fundulus heteroclitus), a population genetic discontinuity appears in the absence of obvious barriers to gene flow along parallel salinity clines and coincides with a physiologically stressful salinity. We show that populations resident on either side of this discontinuity differ in their abilities to compensate for osmotic shock and illustrate the physiological and functional genomic basis of population variation in hypoosmotic tolerance. A population native to a freshwater habitat, upstream of the genetic discontinuity, exhibits tolerance to extreme hypoosmotic challenge, whereas populations native to brackish or marine habitats downstream of the discontinuity lose osmotic homeostasis more severely and take longer to recover. Comparative transcriptomics reveals a core transcriptional response associated with acute and acclimatory responses to hypoosmotic shock and posits unique mechanisms that enable extreme osmotic tolerance. Of the genes that vary in expression among populations, those that are putatively involved in physiological acclimation are more likely to exhibit nonneutral patterns of divergence between freshwater and brackish populations. It is not the well-known effectors of osmotic acclimation, but rather the lesser-known immediate-early responses, that appear important in contributing to population differences.
    Proceedings of the National Academy of Sciences 03/2011; 108(15):6193-8. · 9.74 Impact Factor
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    ABSTRACT: The rate of acid-stimulated and phenamil-sensitive sodium (Na(+)) uptake was measured in three different cell lineages: pavement cells (PVC), total mitochondrion-rich (MR) cell populations, and peanut lectin agglutinin-negative mitochondrion-rich cells (PNA(-) MR) isolated from the rainbow trout gill epithelium. Despite the presence of basal levels of Na(+) uptake in PVC, this transport was not enhanced by acidification, nor was it inhibited by independent treatment with bafilomycin (i.e., a V-type H(+)-ATPase inhibitor), phenamil (i.e., a specific inhibitor of ENaC), or Ag (a specific inhibitor of active Na(+) transport in fish). In contrast, Na(+) uptake in PNA(-) MR cells was increased by ~220% above basal levels following acidification of near 0.4 pH units in the presence of 1.0 mM external Na(+). Acid-stimulated Na(+) transport was entirely inhibited by both phenamil and bafilomycin. Silver (Ag) and copper (Cu), which are known to interfere with active Na(+) transport in fish, were also responsible for inhibiting acid stimulated Na(+) uptake in PNA(-) MR cells, but by themselves had no effect on basal Na(+) transport. Thus, we demonstrate that Ag specifically prevented acid-stimulated Na(+) uptake in PNA(-) MR cells in a dose-dependent manner. We also demonstrate rapid (<1 min) and significant inhibition of carbonic anhydrase (CA) by Ag in PNA(-) MR cells, but not in PVC. These data lend further support to the idea of a PNA(-) MR cell type as the primary site for Na(+) uptake in the freshwater (FW) gill phenotype of rainbow trout. Moreover, these findings provide support for the importance of intracellular protons in regulating the movement of Na(+) across the apical surface of the fish gill.
    Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 03/2011; 159(3):234-41. · 2.20 Impact Factor
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    ABSTRACT: Increased atmospheric CO(2) concentrations are causing greater dissolution of CO(2) into seawater, and are ultimately responsible for today's ongoing ocean acidification. We manipulated seawater acidity by addition of HCl and by increasing CO(2) concentration and observed that two coastal harpacticoid copepods, Amphiascoides atopus and Schizopera knabeni were both more sensitive to increased acidity when generated by CO(2). The present study indicates that copepods living in environments more prone to hypercapnia, such as mudflats where S. knabeni lives, may be less sensitive to future acidification. Ocean acidification is also expected to alter the toxicity of waterborne metals by influencing their speciation in seawater. CO(2) enrichment did not affect the free-ion concentration of Cd but did increase the free-ion concentration of Cu. Antagonistic toxicities were observed between CO(2) with Cd, Cu and Cu free-ion in A. atopus. This interaction could be due to a competition for H(+) and metals for binding sites.
    Marine pollution bulletin 09/2010; 60(12):2201-8. · 2.63 Impact Factor
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    ABSTRACT: We have studied intracellular pH (pHi) recovery in isolated trout gill mitochondrion-rich (MR) cells following acidification by the NH4Cl pre-pulse technique. Within a mixed MR cell population, one cell type displayed Na+-independent pHi recovery while the other cell type lacked a Na+-independent pHi recovery. Cells displaying Na+ independent recovery exhibited a significantly higher buffering capacity compared to cells lacking Na+-independent pHi recovery. Cells displaying Na+ independent recovery were identified as PNA+ (peanut lectin agluttinin binding) MR cells while those unable to recover were identified as PNA− (non-peanut lectin agluttinin binding) MR cells. Therefore, recovery from acidification in the absence of Na+ provides a direct functional marker for PNA+ and PNA− MR cells. Re-addition of Na+ to acidified cells resulted in a transient pHi recovery in both cell types. This event was abolished by amiloride (500 µM) but it was insensitive to phenamil (50 µM). The phorbol ester PMA (1 µM) potentiated the Na+ induced pHi recovery suggesting that activation by PKC is required for continuous Na+/H+ exchanger activity in trout gill MR cells. This study is the first functional description of pHi recovery in lectin-identified trout gill MR cells and provides insight into a putative cellular signaling mechanism that may control pHi regulation in the gill epithelium.
    Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology. 01/2010;
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    ABSTRACT: Evolutionary solutions to the physiological challenges of life in highly variable habitats can span the continuum from evolution of a cosmopolitan plastic phenotype to the evolution of locally adapted phenotypes. Killifish (Fundulus sp.) have evolved both highly plastic and locally adapted phenotypes within different selective contexts, providing a comparative system in which to explore the genomic underpinnings of physiological plasticity and adaptive variation. Importantly, extensive variation exists among populations and species for tolerance to a variety of stressors, and we exploit this variation in comparative studies to yield insights into the genomic basis of evolved phenotypic variation. Notably, species of Fundulus occupy the continuum of osmotic habitats from freshwater to marine and populations within Fundulus heteroclitus span far greater variation in pollution tolerance than across all species of fish. Here, we explore how transcriptome regulation underpins extreme physiological plasticity on osmotic shock and how genomic and transcriptomic variation is associated with locally evolved pollution tolerance. We show that F. heteroclitus quickly acclimate to extreme osmotic shock by mounting a dramatic rapid transcriptomic response including an early crisis control phase followed by a tissue remodeling phase involving many regulatory pathways. We also show that convergent evolution of locally adapted pollution tolerance involves complex patterns of gene expression and genome sequence variation, which is confounded with body-weight dependence for some genes. Similarly, exploiting the natural phenotypic variation associated with other established and emerging model organisms is likely to greatly accelerate the pace of discovery of the genomic basis of phenotypic variation.
    The Journal of heredity 01/2010; 102(5):499-511. · 2.05 Impact Factor
  • Nicolas R. Bury, Fernando Galvez, Chris M. Wood
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    ABSTRACT: The effects of independently altering chloride, calcium, and dissolved organic carbon (DOC) on the toxicity of silver (presented as AgNO3) were compared between rainbow trout (Oncorhynchus mykiss) and fathead minnows (Pimephales promelas). The 96-h median lethal concentration (LC50) toxicity tests for both species were performed under the same conditions, within the same containers. In addition, the effect of altering [Cl−] on silver-induced perturbations to body Na+ influx and gill silver load was studied. Toxicity tests were conducted in synthetic soft water (50 μM Na+, 50 μM Cl−, 50 μM Ca2+, 0.3 mg DOC/L). The [Cl−], [Ca2+], and [DOC] were adjusted by the addition of NaCl, CaNO3, or humic acid, respectively. On the basis of total silver, increasing [Cl−] over a range of 50 μM to 1,500 μM resulted in a 4.3-fold increase in the 96-h LC50 values (decrease in toxicity) for rainbow trout, but did not significantly affect the 96-h LC50 values for fathead minnows. Increasing water [Ca2+] (from 50 to 2,000 μM) had only a small influence (1.5-fold increase) on the 96-h LC50 values in either species. However, increasing DOC levels (from 0.3 to 5.8 mg DOC/L) significantly increased the 96-h LC50 values (2.7- to 4.1-fold increases) in both species. If the 96-h LC50 values are calculated on the basis of ionic silver, Ag+ (utilizing the aquatic geochemical computer program MINEQL+ ), then, in the case of rainbow trout, toxicity correlates to Ag+. However, this correlation does not exist for fathead minnows. Increasing [Cl− did not affect the degree of perturbation of Na+ influx during acute exposure (first 4 h) to 8 μg Ag/L in either species, nor did it affect the whole-body silver uptake rates, but it did reduce the gill silver load. These results demonstrate that differences exist in the way in which water chemistry ameliorates silver toxicity between rainbow trout and fathead minnows.
    Environmental Toxicology and Chemistry 11/2009; 18(1):56 - 62. · 2.62 Impact Factor
  • Fernando Galvez, Chris M. Wood
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    ABSTRACT: Static-renewal 7-d toxicity tests for silver nitrate (AgNO3) were performed with juvenile rainbow trout (Oncorhynchus mykiss Walbaum). The relative influences of calcium and chloride concentrations on median lethal time (LT50) were assessed. Calcium concentrations were controlled by adding either Ca(NO3)2 or CaSO4, whereas chloride concentrations were adjusted with either NaCl or KCl. For both calcium salts, a 100-fold elevation in concentration increased the LT50 approximately 10-fold. However, a 100-fold elevation in KCl ameliorated silver (Ag) toxicity at least 100-fold, while NaCl protected against Ag toxicity even more substantially, demonstrating the much greater protective effect of chloride relative to calcium. In a separate series of bioassays, fish were exposed to 0.92 μM Ag (100 μg/L as AgNO3) with varying amounts of NaCl titrated into each tank to alter the free [Ag+]. The 7-d LC50 occurred at a [NaCl] of 2,500 μM. Using MINEQL+ (a geochemical speciation program), the predicted free [Ag+] at this LC50 value is 0.0285 μM. Further bioassays were performed in which [chloride] was maintained at either 50 or 225 μM, while total [Ag] was independently varied from 0.0092 to 0.0694 μM (1.0–7.5 μg/L). The 7-d LC50 value was calculated at 0.0294 μM Ag (3.18 μg/L) at a chloride concentration of 50 μM, very similar to the free [Ag+] value of 0.031 μM calculated from an earlier LC50 test at a fixed [chloride] of 730 μM. According to MINEQL+, the estimated [Ag+] at this LC50 value is 0.0289 μM. Although a 7-d LC50 value could not be determined at 225 μM chloride, it was estimated at slightly above 0.0277 μM Ag+. Elevating chloride concentrations from 50 to 225 μM did not alter the accumulation of Ag in the liver. In addition, there were no significant differences in hepatic Ag accumulation between any of the Ag-exposed fish, irrespective of the total Ag concentration used during the exposure. Overall, Ag accumulated to approximately 185 μmol/kg wet weight in all Ag-exposed groups (approximately a 10-fold increase above controls). These results, together with a reanalysis of published data, suggest that Ag toxicity can be correlated with the free Ag ion [Ag+], and that any factors altering Ag+ availability (i.e., chloride) will be expected to modify acute Ag toxicity.
    Environmental Toxicology and Chemistry 10/2009; 16(11):2363 - 2368. · 2.62 Impact Factor
  • Christer Hogstrand, Fernando Galvez, Chris M. Wood
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    ABSTRACT: Static-renewal 168-h toxicity tests of silver nitrate (AgNO3), silver chloride (AgCln), and silver thiosulfate (Ag(S2O3)n) with juvenile rainbow trout (Oncorhyncus mykiss) were performed by standard methods. Because of low solubility of AgCl(s), bioassays for AgCln were performed in two separate ways. In one test series, AgCl(s) was added to freshwater and in another, AgCln(aq) was generated by adding AgNO3 to freshwater supplemented with 50 mM NaCl. Concentrations of Ag and metallothionein (MT) were analyzed in gills and livers offish that survived the exposures. Although Ag added as AgNO3 was found to be highly toxic to rainbow trout (168-h LC50 = 9.1 μg Ag L−1), the toxicities of the other Ag salts were low. The 168-h LC50 for Ag(S2O3)n was 137,000 μg Ag L−1 and no mortality was observed in AgCln (100,000 μg Ag L−1). Exposure to AgNO3, Ag(S2O3)n, or AgCln caused accumulation of Ag and induction of MT. Highest Ag levels were found in livers of trout exposed to 164,000 μg Ag L−1 as Ag(S2O3)n. In these fish, the hepatic Ag concentration was increased 335 times from the control value. The MT levels in gills and liver increased with the water Ag concentration and the highest level of MT was found in liver of fish exposed to Ag(S2O3)n.
    Environmental Toxicology and Chemistry 10/2009; 15(7):1102 - 1108. · 2.62 Impact Factor
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    ABSTRACT: The full-length cDNA sequence of a putative urea transporter (lfUT) of the facilitated diffusion UT-A type has been cloned from the African lungfish Protopterus annectens. The lfUT cDNA is 1990 bp in length and its open reading frame encodes a 409 amino acid long protein, with a calculated molecular mass of 44,723 Da. The sequence is closest to those of amphibians ( approximately 65% amino acid homology), followed by mammals and elasmobranchs ( approximately 60%), and then teleosts ( approximately 50%). lfUT was clearly expressed in gill, kidney, liver, skeletal muscle and skin. Upon re-immersion in water after 33 days of air exposure ('terrestrialization'), lungfish exhibited a massive rise in urea-N excretion which peaked at 12-30 h with rates of 2000-5000 micromol-N kg(-1) h(-1) (versus normal aquatic rates of <130 micromol-N kg(-1) h(-1)) and persisted until 70 h. This appears to occur mainly through the skin. Total 'excess' urea-N excretion amounted to approximately 81,000-91,000 micromol-N kg(-1) over 3 days. By real-time PCR, there was no difference in lfUT expression in the ventral abdominal skin between aquatic ammoniotelic controls and terrestrialized lungfish immediately after return to water (0 h), and no elevation of urea-N excretion at this time. However, skin biopsies revealed a significant 2.55-fold elevation of lfUT expression at 14 h, coincident with peak urea-N excretion. At 48 h, there was no longer any significant difference in lfUT mRNA levels from those at 0 and 14 h, or from aquatic fed controls. In accordance with earlier studies, which identified elevated urea-N excretion via the skin of P. dolloi with pharmacology typical of UT-A carriers, these results argue that transcriptional activation of a facilitated diffusion type urea transporter (lfUT) occurs in the skin during re-immersion. This serves to clear the body burden of urea-N accumulated during terrestrialization.
    Journal of Experimental Biology 05/2009; 212(Pt 8):1202-11. · 3.24 Impact Factor
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    ABSTRACT: Natural organic matter (NOM) is an important constituent of aquatic environments; however, its influence on aquatic biota remains poorly studied. In the current study, NOM was isolated from nine different sites in southern Ontario, Canada, by the on-site treatment of water by reverse osmosis, followed by cation exchange. NOM from each site was reconstituted to 10 mg of C/L and pH 7.0 and exposed to either adult rainbow trout implanted with indwelling catheters or to in vitro primary cultures of the gill epithelium grown on semipermeable membranes. In both the in vivo and in vitro preparations, NOM was found to hyperpolarize transepithelial potential (TEP), with the magnitude of this change correlating extremely well to the absorptivity of the NOM at 340 nm, which is an index of its aromaticity. Gill hyperpolarization appeared to be independent of Ca2+ complexation by the NOM in all but two samples tested. We argue that NOM has direct actions on the ionic transport and/or permeability properties of fish gills. While NOM effects on the bioavailability of contaminants are well-known, NOM actions on such fundamental physiological properties of the gills have previously been overlooked. These may be of comparable or greater magnitude than commonly reported for other water-quality variables (e.g., hardness, pH, salinity) and therefore of critical importance in ecological understanding and risk assessment.
    Environmental Science and Technology 01/2009; 42(24):9385-90. · 5.26 Impact Factor
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    ABSTRACT: The zebrafish model system is ideal for studying nervous system development. Ultimately, one would like to link the developmental biology to various aspects of behavior. We are studying the consequences of nicotine exposure on nervous system development in zebrafish and have previously shown that chronic nicotine exposure produces paralysis. We also have made observations that the embryos moved in the initial minutes of the exposure as the bend rates of the musculature increased. This nicotine induced behavior manifests as an increase in the rate of spinal musculature bends, which spontaneously begin at ∼ 17 h post fertilization. The behavioral observations prompted the systematic characterization of nicotine-induced modulation of zebrafish embryonic motor output; bends of the trunk musculature.We first characterized embryonic motor output in zebrafish embryos with and without their chorions. We then characterized the motor output in embryos raised at 28 °C and 25 °C. The act of dechorionation along with temperature influenced the embryonic bend rate. We show that nicotine exposure increases embryonic motor output. Nicotine exposure caused the musculature bends to alternate in a left–right–left fashion. Nicotine was able to produce this phenotype in embryos lacking supraspinal input. We then characterize the kinetics of nicotine influx and efflux and demonstrate that nicotine as low as 1 μM can disrupt embryonic physiology. Taken together, these results indicate the presence of nicotinic acetylcholine receptors (nAChRs) associated with a spinal motor circuit early in embryogenesis.
    Toxicology and Applied Pharmacology. 01/2009;
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    Fernando Galvez, Tommy Tsui, Chris M Wood
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    ABSTRACT: The lack of a suitable flat epithelial preparation isolated directly from the freshwater fish gill has led, in recent years, to the development of cultured gill epithelia on semipermeable supports. To date, their minimal capacity to actively transport ions has limited their utility as ionoregulatory models. The current study describes a new method of culturing gill epithelia consisting either of an enriched population of pavement (PV) cells or a mixed population of PV cells and mitochondria-rich (MR) cells from the gills of adult rainbow trout. Although the cell culture approach is similar to the double-seeded insert (DSI) technique described previously, it makes use of Percoll density centrifugation to first separate populations of PV and MR cells, which are then seeded on cell culture supports in varying proportions on successive days so as to produce preparations enriched in one or the other cell types. Based on rhodamine staining, the MR cell-rich epithelia exhibited a threefold higher enrichment of MR cells compared to traditional DSI preparations. In general, MR cell-rich epithelia developed extremely high transepithelial resistances (TER; >30 kOmega cm(2)) and positive transepithelial potentials (TEP) under symmetrical conditions (i.e., L15 medium on both apical and basolateral sides). Apical exposure of cell cultures to freshwater reduced TER and produced a negative TEP in all the epithelial preparations, although MR cell-rich epithelia maintained relatively high TER and negative TEP for over 2 d under these asymmetrical conditions. Measurement of unidirectional Na(+) fluxes and application of the Ussing flux ratio criterion demonstrated active Na(+) uptake in PV cell-rich and MR cell-rich epithelia under both symmetrical and asymmetrical conditions. In comparison, Ca(2+) uptake and Na(+)/K(+)-ATPase activity were significantly elevated in MR cell-rich preparations relative to the traditional DSI or PV cell-rich cultures under symmetrical conditions. This new methodology enhances our ability to tailor cultured gill epithelia on semipermeable supports with different proportions of PV cells and MR cells, thereby illuminating the ionoregulatory functions of the two cell types.
    In Vitro Cellular & Developmental Biology - Animal 10/2008; 44(10):415-25. · 1.29 Impact Factor
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    ABSTRACT: Recent studies have shown that dietary Ca(2+) supplementation strongly inhibits uptake of Ca(2+) and Cd at the fish gill. To better understand the influence of dietary Ca(2+) on branchial Ca(2+) transport, we examined the expression of two trout gill calcium transporters during waterborne and dietary Cd exposure, at two different levels of dietary Ca(2+). Quantitative polymerase chain reaction (PCR) was used to monitor epithelial calcium channel (ECaC) and sodium-calcium exchange (NCX) mRNA levels following 7-28 days of exposure to these treatments. In brief, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to control, 3 microg/L waterborne Cd, 500 mg/kg dietary Cd, or a combined 3 microg/L waterborne plus 500 mg/kg dietary Cd exposure, supplemented with either 20 mg/g or 60 mg/g dietary calcium (Ca(2+)). Two-way analysis of variance was used to discern the main effects of Cd exposure and dietary Ca(2+) supplementation on ECaC and NCX mRNA levels. We found that dietary Ca(2+) supplementation decreased significantly ECaC mRNA expression on days 14 and 21. In comparison, NCX mRNA levels were not influenced by dietary Ca(2+) supplementation, but rather were significantly inhibited in the combined waterborne and dietary Cd exposure on day 7 alone. Statistical analysis found no interactive effects between Cd exposure and dietary Ca(2+) exposure at any time point, except for day 28. This study provides evidence of the importance of nutritional status on the transcriptional regulation of ion transport at the fish gill. We discuss the importance of diet and nutritional status to the development of new regulatory approaches, such as the biotic ligand model, which currently do not account for the significance of diet on metal bioavailability in aquatic organisms.
    Aquatic Toxicology 09/2007; 84(2):208-14. · 3.73 Impact Factor

Publication Stats

1k Citations
133.89 Total Impact Points

Institutions

  • 2012–2013
    • University of California, Davis
      • Department of Environmental Toxicology
      Davis, CA, United States
  • 2007–2013
    • Louisiana State University
      • Department of Biological Sciences
      Baton Rouge, LA, United States
    • Universidade Federal do Paraná
      • Departamento de Fisiologia
      Curitiba, Estado do Parana, Brazil
  • 2001–2011
    • University of Alberta
      • Department of Biological Sciences
      Edmonton, Alberta, Canada
  • 1998–2009
    • McMaster University
      • Department of Biology
      Hamilton, Ontario, Canada
  • 2002–2003
    • University of Waterloo
      • Department of Biology
      Waterloo, Ontario, Canada
  • 1999
    • University of Kentucky
      • Graduate Center for Toxicology
      Lexington, Kentucky, United States