P Swanson

Washington State University, Pullman, Washington, United States

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Publications (115)287.83 Total impact

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    ABSTRACT: The toxicokinetics of trenbolone was characterized during 500 ng/L water exposures in female rainbow trout (Oncorhynchus mykiss) and fathead minnows (Pimephales promelas). Related experiments measured various toxicodynamic effects of exposure. In both species, trenbolone was rapidly absorbed from the water and reached peak plasma levels within 8 hrs of exposure. Afterwards, trenbolone concentrations in trout (66-95 ng/ml) were 2-6 times higher compared to minnows (15-29 ng/ml), which was attributable to greater plasma binding in trout. During water exposures, circulating levels of estradiol (E2) rapidly decreased in both species to a concentration that was 25-40% of control values by 8-24 hrs of exposure and then remained relatively unchanged for the subsequent six days of exposure. In trout, changes in circulating levels of follicle stimulating hormone were also significantly greater after trenbolone exposure, relative to controls. In both species, the pharmacokinetics of injected E2-d3 was altered by trenbolone exposure with increased total body clearance and a corresponding decrease in elimination half-life. The unbound percentage of E2 in trout plasma was 0.25%, which was similar in pre- or post-vitellogenic female trout. Subsequent incubation with trenbolone caused the unbound percentage to significantly increase to 2.4 % in the pre-vitellogenic trout plasma. iTRAQ based toxicoproteomic studies in minnows exposed to 5, 50 and 500 ng/L trenbolone identified a total of 148 proteins with 19 down-regulated including vitellogenin and 18 up-regulated. Other down-regulated proteins were fibrinogens, α-2-macroglobulin and transferrin. Up-regulated proteins included amine oxidase, apolipoproteins, parvalbumin, complement system proteins and several uncharacterized proteins. The results indicate trenbolone exposure is a highly dynamic process in female fish with uptake and tissue equilibrium quickly established leading to both rapid and delayed toxicodynamic effects.
    Toxicological Sciences 09/2013; · 4.33 Impact Factor
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    ABSTRACT: Considerable research has been done on the effects of endocrine disrupting chemicals (EDCs) on reproduction and gene expression in the brain, liver and gonads of teleost fish, but information on impacts to the pituitary gland are still limited despite its central role in regulating reproduction. The aim of this study was to further our understanding of the potential effects of natural and synthetic estrogens on the brain-pituitary-gonad axis in fish by determining the effects of 17α-ethynylestradiol (EE2) on the pituitary transcriptome. We exposed sub-adult coho salmon (Oncorhynchus kisutch) to 0 or 12ng EE2/L for up to 6 weeks and effects on the pituitary transcriptome of females were assessed using high-throughput Illumina(®) sequencing, RNA-Seq and pathway analysis. After 1 or 6 weeks, 218 and 670 contiguous sequences (contigs) respectively, were differentially expressed in pituitaries of EE2-exposed fish relative to control. Two of the most highly up- and down-regulated contigs were luteinizing hormone β subunit (241-fold and 395-fold at 1 and 6 weeks, respectively) and follicle-stimulating hormone β subunit (-3.4-fold at 6 weeks). Additional contigs related to gonadotropin synthesis and release were differentially expressed in EE2-exposed fish relative to controls. These included contigs involved in gonadotropin releasing hormone (GNRH) and transforming growth factor-β signaling. There was an over-representation of significantly affected contigs in 33 and 18 canonical pathways at 1 and 6 weeks, respectively, including circadian rhythm signaling, calcium signaling, peroxisome proliferator-activated receptor (PPAR) signaling, PPARα/retinoid x receptor α activation, and netrin signaling. Network analysis identified potential interactions between genes involved in circadian rhythm and GNRH signaling, suggesting possible effects of EE2 on timing of reproductive events.
    Aquatic toxicology (Amsterdam, Netherlands) 08/2013; 142-143C:146-163. · 3.12 Impact Factor
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    Matthew R Baker, Penny Swanson, Graham Young
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    ABSTRACT: Exploitation of fisheries resources has unintended consequences, not only in the bycatch and discard of non-target organisms, but also in damage to targeted fish that are injured by gear but not landed (non-retention). Delayed mortality due to non-retention represents lost reproductive potential in exploited stocks, while not contributing to harvest. Our study examined the physiological mechanisms by which delayed mortality occurs and the extent to which injuries related to disentanglement from commercial gear compromise reproductive success in spawning stocks of Pacific salmon (Oncorhynchus spp.). We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries. Plasma cortisol levels correlated with the severity of disentanglement injury and were elevated in fish that developed infections related to disentanglement injuries. We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals. We demonstrate evidence for delayed or inhibited maturation in fish with disentanglement injuries. These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.
    PLoS ONE 08/2013; · 3.53 Impact Factor
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    ABSTRACT: Efforts to establish an aquaculture industry for sablefish (Anoplopoma fimbria) are constrained by reproductive dysfunction in wild-caught fish and by lack of reproduction of F1 females. Toward a better understanding of the reproductive dysfunction of captive broodstock, full-length cDNAs encoding the sablefish gonadotropin subunits (fshb, lhb and cga) and their receptors (fshr and lhcgr) were cloned, sequenced and quantitative real-time PCR assays developed. Sablefish gonadotropin subunits display some unique features, such as two additional Cys residues in the N-terminal region of Fshb and a lack of potential N-glycosylation sites in Fshb and Lhb, whereas Fshr and Lhcgr possess conserved structural characteristics described in other vertebrates. Wild females captured in fall completed gametogenesis in captivity the next spawning season, whereas females captured three months earlier, during summer, failed to mature. Interestingly, these wild non-maturing females exhibited similar reproductive features as prepubertal F1 females, including low levels of pituitary gonadotropin and ovarian receptor mRNAs and plasma sex steroids, and ovarian follicles arrested at the perinucleolus stage. In conclusion, this study described the cloning, molecular characterization and development of qPCR for sablefish gonadotropins and their receptors. Rearing conditions may impair vitellogenic growth of ovarian follicles in sablefish, compromising the reproductive success of broodstock.
    General and Comparative Endocrinology 07/2013; · 2.82 Impact Factor
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    Matthew R Baker, Penny Swanson, Graham Young
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    ABSTRACT: Exploitation of fisheries resources has unintended consequences, not only in the bycatch and discard of non-target organisms, but also in damage to targeted fish that are injured by gear but not landed (non-retention). Delayed mortality due to non-retention represents lost reproductive potential in exploited stocks, while not contributing to harvest. Our study examined the physiological mechanisms by which delayed mortality occurs and the extent to which injuries related to disentanglement from commercial gear compromise reproductive success in spawning stocks of Pacific salmon (Oncorhynchus spp.). We found evidence for elevated stress in fish injured via non-retention in gillnet fisheries. Plasma cortisol levels correlated with the severity of disentanglement injury and were elevated in fish that developed infections related to disentanglement injuries. We also analyzed sex steroid concentrations in females (estradiol-17β and 17,20β-dihydroxy-4-pregnen-3-one) to determine whether non-retention impairs reproductive potential in escaped individuals. We demonstrate evidence for delayed or inhibited maturation in fish with disentanglement injuries. These findings have important implications for effective conservation and management of exploited fish stocks and suggest means to improve spawning success in such stocks if retention in commercial fisheries is improved and incidental mortality reduced.
    PLoS ONE 01/2013; 8(7):e69615. · 3.53 Impact Factor
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    ABSTRACT: Follicle-stimulating hormone (Fsh) function in fishes is poorly understood. This study aimed to reveal Fsh-regulated genes in coho salmon previtellogenic ovarian follicles in vitro. Four suppression subtractive hybridization libraries were generated with RNA isolated from Fsh-treated and control follicles or follicle cell-enriched tissue fractions. Fsh induced steroidogenesis and dynamically upregulated several genes predominantly expressed in follicle cells, including WAP domain-containing protease, connexin 34.3, clusterin (clu1, clu2), fibronectin, wilms tumor 2-like, and influenza virus NS1A-binding protein a. Genes downregulated by Fsh included connective tissue growth factor, alcohol dehydrogenase 8-like, and serine/threonine-protein kinase pim-1. This study demonstrates for the first time in fishes that Fsh influences the expression of a unique suite of ovarian genes involved in processes like cell communication, survival and differentiation, and extracellular matrix remodeling. Collectively, these findings suggest that Fsh and/or steroids induce differentiation of granulosa cells and remodeling of the follicle in preparation for onset of vitellogenesis.
    Molecular and Cellular Endocrinology 11/2012; · 4.04 Impact Factor
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    ABSTRACT: Exposure of female Atlantic salmon to elevated temperature can result in a dramatic reduction in egg fertility and embryo survival. Reductions in plasma 17β-estradiol (E2) levels are associated with much of the observed reduction in reproductive performance; however, the molecular basis for reduced E2 levels remains unknown. This study examined gene expression of ovarian steroidogenic enzymes and plasma levels of gonadotropins in maiden and repeat spawning Atlantic salmon exposed to higher than normal temperatures. Circulating levels of follicle stimulating hormone (Fsh) were significantly elevated in both maiden and repeat spawning fish maintained at 22 °C compared to 14 °C during vitellogenesis, but plasma luteinising hormone levels were mostly unaffected. In contrast, gene expression of the ovarian p450 aromatase a and cholesterol side chain cleavage protein were depressed at 22 °C compared to 14 °C. Hepatic gene expression of estrogen receptor alpha did not change with thermal challenge. The results show that the ovarian response to Fsh is inhibited at 22 °C, at least partly as a result of reduced expression of genes coding for steroidogenic enzymes.
    Aquaculture 03/2012; 334-337:205-212. · 2.01 Impact Factor
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    ABSTRACT: Captively reared adult Pacific salmon (Oncorhynchus spp.) released for natural spawning exhibit deficiencies in reproductive behavior. The effects of water current velocity in rearing tanks and gonadotropin-releasing hormone analogue (GnRHa) treatment on reproductive behavior of captively reared chinook salmon (Oncorhynchus tshawytscha) were examined. Treatment of females with GnRHa resulted in a significantly greater degree of nest guarding, earlier (more natural) onset of spawning, and higher frequency of aggression towards males. Current velocity did not significantly affect the female reproductive behaviors examined. Males reared under high current velocities (HV) spawned for the first time 2.4 days earlier, and alpha males reared in HV tanks defended their access to spawning females better than alpha males reared in low velocity (LV) tanks. Males reared in HV tanks had 34% lower protein content at the time of death than fish reared in LV tanks. Females reared in HV tanks had 38% lower lipid content, but the effects of current velocity were nonsignificant when accounting for significant random variation among tanks within treatments. Identifying and modifying environmental conditions that control hormonal changes during final maturation may lead to further improvements in reproductive performance of captively reared salmon.
    Canadian Journal of Fisheries and Aquatic Sciences 04/2011; 60(6):690-699. · 2.32 Impact Factor
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    ABSTRACT: Little is known about follicle-stimulating hormone (FSH) function during oocyte growth in fishes. The goal of this study was to gain a fundamental understanding of FSH action on ovarian follicles during early secondary oocyte growth by examining changes in ovarian gene expression and steroidogenesis in response to FSH. Coho salmon (Oncorhynchus kisutch) mid to late cortical alveolus stage follicles were incubated with or without salmon FSH in time-course and concentration-response experiments. Steroid levels were determined in the culture medium by immunoassay and levels of target ovarian mRNAs were determined by quantitative RT-PCR. Medium estradiol-17β (E2) levels increased in response to FSH and plateaued by 36h, while testosterone levels increased similarly but were lower and more variable than E2. Gonadotropin receptor transcripts were differentially regulated, with fshr and lhcgr being down- and up- regulated, respectively. Transcripts encoding proteins involved in steroidogenesis, such as star and hsd3b were significantly upregulated by FSH, whereas aromatase (cyp19a1a) mRNA was unaffected by FSH and declined over time in culture. A recently identified teleost gene, bmp16, was suppressed by FSH and an anti-apoptotic factor, clusterin 1 (clu1), was upregulated by FSH. Lesser FSH effects were observed on igf2, cyp11a1 and cyp17a1, which were stimulated, and igf1ra, inhbb, amh and apoe, which were suppressed. As evident by the significant increases in steroid production and transcripts for specific steroidogenesis-related proteins, FSH influences steroidogenesis during early secondary growth and may be a critical signal for puberty onset. Effects of FSH on ovarian anti-apoptotic and growth factor genes suggest roles for FSH in cell survival, growth and differentiation in teleosts.
    General and Comparative Endocrinology 03/2011; 171(1):52-63. · 2.82 Impact Factor
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    ABSTRACT: The objective of this investigation was to quantify pituitary thyroid stimulating hormone (TSH) β mRNA, pituitary and plasma TSH and plasma thyroid hormone levels during the parr-smolt transformation of Coho salmon that occurs in spring from February to May. The status of the pituitary-thyroid axis was assessed using an RNase protection assay for pituitary TSH β mRNA and radioimmunoassays for salmon pituitary and plasma TSH and thyroid hormones. TSH β mRNA was highest during late winter (February) (4.9 pg/μg DNA) and gradually declined during spring (2.3 pg/μg DNA). In contrast, pituitary and plasma TSH levels showed a small, but statistically non-significant change during smoltification. Despite minimal change in plasma TSH levels, characteristically large increases in plasma T4 (January-3.3 ng/ml to April-10.2 ng/ml) and significant, but modest increases in plasma T3 (February-2.4 ng/ml to April-5.8 ng/ml) were observed. Regression analysis showed a significant positive relationship between plasma T4 and T3 and negative relationship between plasma T3 and pituitary TSH β mRNA. However, all other relations were not significant. These data suggest a significant role for peripheral regulation (i.e. T4-T3 conversion, change in tissue sensitivity, hormone degradation rate) as well as evidence of central regulation via negative feedback at the level of the pituitary gland in regulation of thyroid activity in salmon. Furthermore, the increased thyroid sensitivity to TSH (shown previously), in the face of relatively constant plasma TSH levels, may be the major factor responsible for the increased thyroid activity observed during smoltification.
    General and Comparative Endocrinology 03/2011; 171(3):367-72. · 2.82 Impact Factor
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    ABSTRACT: Mechanisms regulating the normal progression of ovarian follicular growth versus onset of atresia in fishes are poorly understood. To gain a better understanding of these processes, we exposed immature female coho salmon (Oncorhynchus kisutch) to prolonged fasting to induce follicular atresia and monitored body growth, development of the ovarian follicles, changes in reproductive hormones, and transcripts for ovarian genes. Prolonged fasting reduced body and ovary weight and increased the appearance of atretic follicles relative to normally fed controls. Endocrine analyses showed that fasting reduced plasma insulin-like growth factor 1 (IGF1), estradiol-17β (E2), and pituitary, but not plasma, levels of follicle-stimulating hormone (FSH). Transcripts for ovarian fsh receptor (fshr) and steroidogenesis-related genes, such as steroidogenic acute regulatory protein (star), 3β-hydroxysteroid dehydrogenase (hsd3b), and P450 aromatase (cyp19a1a) were significantly lower in fasted fish. Ovarian expression of apoptosis-related genes, such as Fas-associated death domain (fadd), caspase 8 (casp8), caspase 3 (casp3), and caspase 9 (casp9) were significantly elevated in fasted fish compared to fed fish, indicating that apoptosis is involved in the process of atresia in this species. Interestingly, some genes such as fadd, casp8, casp3, and hsd3b, were differentially expressed prior to increases in the number of atretic follicles and reductions in hormone levels induced by fasting, and may therefore have potential as early indicators of atresia. Together these results suggest that prolonged nutritional stress may disrupt the reproductive system and induce follicular atresia in part via reductions in ovarian IGF and FSH signaling, and downstream effects on steroidogenesis-related genes and E2 production.
    General and Comparative Endocrinology 03/2011; 172(3):331-43. · 2.82 Impact Factor
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    ABSTRACT: Cited By (since 1996):25, Export Date: 23 March 2014, Source: Scopus
    General and Comparative Endocrinology 01/2011; 171(1):52-63. · 2.82 Impact Factor
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    ABSTRACT: Throughout oogenesis, cell-cell communication via gap junctions (GJs) between oocytes and surrounding follicle cells (theca and granulosa cells), and/or amongst follicle cells is required for successful follicular development. To gain a fundamental understanding of ovarian GJs in teleosts, gene transcripts encoding GJ proteins, connexins (cx), were identified in the coho salmon, Oncorhynchus kisutch, ovary. The spatiotemporal expression of four ovarian cx transcripts was assessed, as well as their potential regulation by follicle-stimulating hormone (FSH), luteinizing hormone (LH) and insulin-like growth factor 1 (IGF1). Salmonid ovarian transcriptomes were mined for cx genes. Four gene transcripts designated cx30.9, cx34.3, cx43.2, and cx44.9 were identified. Changes in gene expression across major stages of oogenesis were determined with real-time, quantitative RT-PCR (qPCR) and cx transcripts were localized to specific ovary cell-types by in situ hybridization. Further, salmon ovarian follicles were cultured with various concentrations of FSH, LH and IGF1 and effects of each hormone on cx gene expression were determined by qPCR. Transcripts for cx30.9 and cx44.9 were highly expressed at the perinucleolus (PN)-stage and decreased thereafter. In contrast, transcripts for cx34.3 and cx43.2 were low at the PN-stage and increased during later stages of oogenesis, peaking at the mid vitellogenic (VIT)-stage and maturing (MAT)-stage, respectively. In situ hybridization revealed that transcripts for cx34.3 were only detected in granulosa cells, but other cx transcripts were detected in both oocytes and follicle cells. Transcripts for cx30.9 and cx44.9 were down-regulated by FSH and IGF1 at the lipid droplet (LD)-stage, whereas transcripts for cx34.3 were up-regulated by FSH and IGF1 at the LD-stage, and LH and IGF1 at the late VIT-stage. Transcripts for cx43.2 were down-regulated by IGF1 at the late VIT-stage and showed no response to gonadotropins. Our findings demonstrate the presence and hormonal regulation of four different cx transcripts in the salmon ovary. Differences in the spatiotemporal expression profile and hormonal regulation of these cx transcripts likely relate to their different roles during ovarian follicle differentiation and development.
    Reproductive Biology and Endocrinology 01/2011; 9:52. · 2.14 Impact Factor
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    ABSTRACT: Cited By (since 1996):25, Export Date: 23 March 2014, Source: Scopus
    General and Comparative Endocrinology 01/2011; 171(1):52-63. · 2.82 Impact Factor
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    ABSTRACT: During adaptive radiations, animals colonize diverse environments, which requires adaptation in multiple phenotypic traits. Because hormones mediate the dynamic regulation of suites of phenotypic traits, evolutionary changes in hormonal signaling pathways might contribute to adaptation to new environments. Here we report changes in the thyroid hormone signaling pathway in stream-resident ecotypes of threespine stickleback fish (Gasterosteus aculeatus), which have repeatedly evolved from ancestral marine ecotypes. Stream-resident fish exhibit a lower plasma concentration of thyroid hormone and a lower metabolic rate, which is likely adaptive for permanent residency in small streams. The thyroid-stimulating hormone-β2 (TSHβ2) gene exhibited significantly lower mRNA expression in pituitary glands of stream-resident sticklebacks relative to marine sticklebacks. Some of the difference in TSHβ2 transcript levels can be explained by cis-regulatory differences at the TSHβ2 gene locus. Consistent with these expression differences, a strong signature of divergent natural selection was found at the TSHβ2 genomic locus. By contrast, there were no differences between the marine and stream-resident ecotypes in mRNA levels or genomic sequence in the paralogous TSHβ1 gene. Our data indicate that evolutionary changes in hormonal signaling have played an important role in the postglacial adaptive radiation of sticklebacks.
    Current biology: CB 12/2010; 20(23):2124-30. · 10.99 Impact Factor
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    ABSTRACT: An increase in activity of the pituitary–gonadal axis (PG-axis) and gonadal development are essential for the onset of spawning migration of chum salmon from the Bering Sea. In the Bering Sea, fish with larger body sizes initiated gonadal development and commenced spawning migration to the natal river by the end of summer. We thus hypothesized that insulin-like growth factor-I (IGF-I), a somatotropic signal that interacts with the PG-axis, can be one of such factors responsible for the onset of migration, and examined changes in plasma levels and hepatic expression of IGF-I gene in oceanic and homing chum salmon in 2001–2003. The plasma IGF-I levels and corresponding body sizes in maturing adults, which had developing gonads, were significantly higher than those in immature fish in all years examined. Such increase in the plasma IGF-I levels in maturing fish was observed even in the Gulf of Alaska during February 2006, while coincident increase was not observed in the hepatic amounts of IGF-I mRNA. In autumn, the plasma IGF-I levels in homing adults decreased during upstream migration in the Ishikari River-Ishikari bay water system in Hokkaido, Japan. In conclusion, the plasma IGF-I levels increased with gonadal development when chum salmon migrated from the winter Gulf of Alaska to the summer Bering Sea. Circulating IGF-I may interact with the PG-axis and promote gonadal development that is inseparable from the onset of spawning migration. Circulating IGF-I levels were thereafter lowered in accordance with final maturation during upstream migration in the breeding season.
    General and Comparative Endocrinology 01/2010; · 2.82 Impact Factor
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    ABSTRACT: Igf1 and Igf2 stimulate growth and development of vertebrates. Circulating Igfs are produced by the liver. In mammals, Igf1 mediates the postnatal growth-promoting effects of growth hormone (Gh), whereas Igf2 stimulates fetal and placental growth. Hepatic Igf2 production is not regulated by Gh in mammals. Little is known about the regulation of hepatic Igf2 production in nonmammalian vertebrates. We examined the regulation of igf2 mRNA level by metabolic hormones in primary cultured coho salmon hepatocytes. Gh, insulin, the glucocorticoid agonist dexamethasone (Dex), and glucagon increased igf2 mRNA levels, whereas triiodothyronine (T(3)) decreased igf2 mRNA levels. Gh stimulated igf2 mRNA at physiological concentrations (0.25x10(-9) M and above). Insulin strongly enhanced Gh stimulation of igf2 at low physiological concentrations (10(-11) M and above), and increased basal igf2 (10(-8) M and above). Dex stimulated basal igf2 at concentrations comparable to those of stressed circulating cortisol (10(-8) M and above). Glucagon stimulated basal and Gh-stimulated igf2 at supraphysiological concentrations (10(-7) M and above), whereas T(3) suppressed basal and Gh-stimulated igf2 at the single concentration tested (10(-7) M). These results show that igf2 mRNA level is highly regulated in salmon hepatocytes, suggesting that liver-derived Igf2 plays a significant role in salmon growth physiology. The synergistic regulation of igf2 by insulin and Gh in salmon hepatocytes is similar to the regulation of hepatic Igf1 production in mammals.
    Journal of Endocrinology 12/2009; 204(3):331-9. · 4.06 Impact Factor
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    ABSTRACT: Insulin-like growth factor 1 (IGF1) is a key somatotropic hormone that may convey growth status to the reproductive endocrine system. This study examined effects of IGF1 alone or in combination with gonadotropin-releasing hormone (GnRH) on pituitary transcripts for GnRH receptor (GnRHR) variants, follicle-stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH), and IGF, as well as secretion of FSH in vitro. Three experiments were conducted with dispersed pituitary cells of prepubertal male coho salmon (Oncorhynchus kisutch) to determine the time course of the response to IGF1, IGF1 concentration response, and GnRH concentration response. IGF1 consistently elevated pituitary transcripts for gnrhr1 and the four gonadotropin subunits (fshb, lhb, cga1, and cga2) by day 10 of culture, while suppressing gh and igf2. Short-term treatment with GnRH (24h) induced minor increases in transcripts for fshb, cga1, and cga2, but suppressed lhb and strongly inhibited gnrhr1 expression. IGF1 significantly increased GnRH-stimulated FSH protein release by the pituitary cells, although not as robustly as previously observed in more reproductively advanced salmon. Our results demonstrate that IGF1 increases steady-state mRNA levels of gnrhr1 and four gonadotropin subunits, and may act alone or with GnRH to increase pituitary FSH release in male coho salmon, over 1year before puberty. These findings suggest that IGF1 may prime pituitary gonadotrope cells of prepubertal salmon to respond to GnRH by stimulating synthesis of GnRHR and FSH during puberty onset.
    General and Comparative Endocrinology 10/2009; 167(3):387-96. · 2.82 Impact Factor
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    ABSTRACT: The gonadotropins Fsh and Lh interact with their receptors (Fshr and Lhr, respectively) in a highly specific manner in mammals with little overlap in biological activities. In fish, the biological activities seem less clearly separated considering, for example, the steroidogenic potency of both Fsh and Lh. Important determinants of the biological activity are the specificity of hormone-receptor interaction and the cellular site of receptor expression. Here, we report the pharmacological characterization of Atlantic salmon Fshr and Lhr, identify receptor-expressing cells in the ovary, and validate receptor mRNA quantification systems. For the pharmacological studies, we used highly purified coho salmon gonadotropins and found that the Fshr preferentially responded to Fsh, but was also activated by approximately 6-fold higher levels of Lh. The Lhr was specific for Lh and did not respond to Fsh. Photoperiod manipulation was used to generate ovarian tissue samples with largely differing stages of maturation. Specific real-time, quantitative (rtq) PCR assays revealed up to 40-fold (fshr) and up to 350-fold (lhr) changes in ovarian expression levels, which correlated well with the differences in ovarian weight, histology, and circulating oestrogen levels recorded in January and June, respectively. Vitellogenic ovaries were used to localise receptor-expressing cells by in situ hybridization. Granulosa cells of small and large vitellogenic follicles were positive for both receptors. Also theca cells of small and large vitellogenic follicles expressed fshr mRNA, while only in large vitellogenic follicles theca cells were (weakly) positive for lhr mRNA. While only ovulatory Lh levels seem high enough to cross-activate the Fshr, expression by both receptors by granulosa and theca cells suggests that homologous ligand receptor interaction will prevail.
    General and Comparative Endocrinology 06/2009; 163(3):329-39. · 2.82 Impact Factor
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    ABSTRACT: Thyroid hormones (THs) regulate growth, morphological development, and migratory behaviors in teleost fish, yet little is known about the transcriptional dynamics of gene targets for THs in these taxa. Here, we characterized TH regulation of mRNAs encoding thyrotropin subunits and thyroid hormone receptors (TRs) in an adult teleost fish model, the fathead minnow (Pimephales promelas). Breeding pairs of adult minnows were fed diets containing 3,5,3'-triiodo-L-thyronine (T(3)) or the goitrogen methimazole for 10 days. In males and females, dietary intake of exogenous T(3) elevated circulating total T(3), while methimazole depressed plasma levels of total thyroxine (T(4)). In both sexes, this methimazole-induced reduction in T(4) led to elevated mRNA abundance for thyrotropin beta-subunit (tshbeta) in the pituitary gland. Fish treated with T(3) had elevated transcript levels for TR isoforms alpha and beta (tralpha and trbeta) in the liver and brain, but reduced levels of brain mRNA for the immediate-early gene basic transcription factor-binding protein (bteb). In the ovary and testis, exogenous T(3) elevated gene transcripts for tshbeta, glycoprotein hormone alpha-subunit (gphalpha), and trbeta, while not affecting tralpha levels. Taken together, these results demonstrate negative feedback of T(4) on pituitary tshbeta, identify tralpha and trbeta as T(3)-autoinduced genes in the brain and liver, and provide new evidence that tshbeta, gphalpha, and trbeta are THs regulated in the gonad of teleosts. Adult teleost models are increasingly used to evaluate the endocrine-disrupting effects of chemical contaminants, and our results provide a systemic assessment of TH-responsive genes during that life stage.
    Journal of Endocrinology 05/2009; 202(1):43-54. · 4.06 Impact Factor

Publication Stats

4k Citations
287.83 Total Impact Points

Institutions

  • 2006–2013
    • Washington State University
      Pullman, Washington, United States
  • 2000–2013
    • National Oceanic and Atmospheric Administration
      • • Resource Enhancement and Utilization Technologies Division
      • • Northwest Fisheries Science Center
      Seattle, WA, United States
  • 1987–2013
    • University of Washington Seattle
      • School of Aquatic and Fishery Sciences
      Seattle, WA, United States
  • 1993–2012
    • Northwest Fisheries Science Center
      Seattle, Washington, United States
    • Shizuoka University
      • Faculty of Science
      Shizuoka-shi, Shizuoka-ken, Japan
  • 1993–2010
    • National Marine Fisheries Service
      Silver Spring, Maryland, United States
  • 2009
    • University of Idaho
      Moscow, Idaho, United States
    • Kyushu University
      • Graduate School of Bioresource and Bioenvironmental Sciences
      Fukuoka-shi, Fukuoka-ken, Japan
  • 2004
    • Hokkaido University
      • Graduate School of Fisheries Sciences
      Sapporo-shi, Hokkaido, Japan
  • 1999
    • University of Stirling
      • Institute of Aquaculture
      Stirling, SCT, United Kingdom
  • 1998
    • Stockholm University
      • Department of Zoology
      Stockholm, Stockholm, Sweden
  • 1997
    • University of Barcelona
      • Departament de Fisiologia
      Barcelona, Catalonia, Spain
  • 1991–1993
    • Brunel University London
      अक्सब्रिज, England, United Kingdom
  • 1992
    • Kitasato University
      • Graduate School of Fisheries Sciences
      Edo, Tōkyō, Japan
  • 1990
    • Kyoto University
      • Primate Research Institute
      Kyoto, Kyoto-fu, Japan