Penny Swanson

Washington State University, Pullman, Washington, United States

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Publications (116)287.58 Total impact

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    ABSTRACT: The function of follicle-stimulating hormone (Fsh) during oogenesis in fishes is poorly understood. Using coho salmon as a fish model, we recently identified a suite of genes regulated by Fsh in vitro and involved in ovarian processes mostly unexplored in fishes, like cell proliferation, differentiation, survival or extracellular matrix (ECM) remodeling. To better understand the role of these Fsh-regulated genes during oocyte growth in fishes, we characterized their mRNA levels at discrete stages of the ovarian development in coho salmon. While most of the transcripts were expressed at low levels during primary growth (perinucleolus stage), high expression of genes associated with cell proliferation (pim1, pcna, and mcm4) and survival (ddit4l) was found in follicles at this stage. The transition to secondary oocyte growth (cortical alveolus and lipid droplet stage ovarian follicles) was characterized by a marked increase in the expression of genes related to cell survival (clu1, clu2 and ivns1abpa). Expression of genes associated with cell differentiation and growth (wt2l and adh8l), growth factor signaling (inha), steroidogenesis (cyp19a1a) and the ECM (col1a1, col1a2 and dcn) peaked in vitellogenic follicles, showing a strong and positive correlation with transcripts for fshr. Other genes regulated by Fsh and associated with ECM function (ctgf, wapl and fn1) and growth factor signaling (bmp16 and smad5l) peaked in maturing follicles, along with increases in steroidogenesis-related gene transcripts. In conclusion, ovarian genes regulated by Fsh showed marked differences in their expression patterns during oogenesis in coho salmon. Our results suggest that Fsh regulates different ovarian processes at specific stages of development, likely through interaction with other intra- or extra-ovarian factors.
    PLoS ONE 01/2014; 9(12):e114176. · 3.53 Impact Factor
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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
    [Show abstract] [Hide abstract]
    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: Age of maturity (puberty) is a key component of the species-specific life history strategy in fish, which has evolved to achieve maximal reproductive fitness. In some fishes the age of puberty is highly plastic, but the underlying mechanisms involved are not understood. Development of reproductive competence relies on the integration of a wide variety of internal and external cues. These signals provide critical information on when an animal should reproduce: whether it is of sufficient size or energy status to reproduce (metabolic cues), whether conditions are optimal for reproductive success (environmental cues), and whether an appropriate mate is present (social cues). Although the mechanisms involved in integrating this information are not known, ultimately the onset and completion of puberty involves increases in brain gonadotropin-releasing hormone (GnRH) and subsequent effects on pituitary gonadotropins and gonadal physiology. In fishes, metabolic cues play an important role in puberty onset because of the large commitment of body energy reserves to the gonad. For capital breeders with long spawning migrations such as Pacific salmon, the physiological commitment to mature in a given year must be made well in advance of spawning and is influenced by body energy stores. In this talk, information on the timing of male puberty onset relative to the life history of three Oncorhynchus species will be presented. In males, puberty onset (defined by the initiation of spermatogenesis) involves the rapid proliferation of spermatogonia and expansion of seminiferous tubules in the testis. This was associated with an activation of pituitary follicle stimulating hormone (FSH) and luteinizing hormone (LH) subunit mRNAs and down regulation of testicular anti-mullerian hormone (AMH) mRNA. Fish showing high rates of spermatogonial proliferation and some meiotic germ cells (spermatocytes), had elevated plasma levels of 11-ketotestosterone (11-KT). The seasonal timing of puberty onset varied with species. In hatchery-reared spring Chinook salmon, for example, initiation of spermatogenesis occurred over several months, from late September through March. During this period metabolic status influenced the proportion of pubertal males. These data suggest that “maturation decisions” were being made in some fish a year in advance of spawning and if spermatogenesis was not initiated by the spring, it was delayed until subsequent years. Furthermore, because puberty onset was not synchronous, yet spermiation occurred only in the fall, our data suggest that the rate at which spermatogenesis is completed is not constant, and probably influenced by a variety of factors including genetics and environment.
    American Fisheries Society 140th Annual Meeting; 09/2011
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    ABSTRACT: Wild steelhead (Oncorhynchus mykiss) typically spend two or more years in freshwater before migrating to sea, but hatchery steelhead are almost ubiquitously released as yearlings. Their large size at release coupled with life history pathways that include both male and female maturation in freshwater present ecological risks different from those posed by hatchery populations of Pacific salmon. Yearling hatchery reared steelhead that fail to attain minimum thresholds for smoltification or exceed thresholds for male maturation tend to ‘residualize’ (i.e., remain in freshwater). Residuals pose ecological risks including size-biased interference competition and predation on juvenile salmon and trout. Three hatchery populations of steelhead in Hood Canal, WA were reared under growth regimes designed to produce a more natural age at smoltification (age-2) to aid in rebuilding their respective natural populations. Mean smolt sizes and size variability at age-2 were within the range of wild smolts for two of the three populations. The third population reared at a different facility under similar temperatures exhibited high growth rate variability and high male maturation rates (20% of all released fish). Experimentally comparing age-1 and age-2 smolt programs will help identify optimal rearing strategies to reduce the genetic risk of domestication selection and reduce residualism rates and associated negative ecological effects on natural populations. Investigations of Winthrop National Fish Hatchery summer-run steelhead will measure a) selection on correlated behavioral traits (‘behavioral syndromes’), b) degree of smoltification, c) changes in hormones that regulate gonad growth at key developmental stages, and d) conduct extensive post-release monitoring of fish reared under each growth regime. KeywordsSteelhead trout–Fitness–Domestication–Ecological interactions–Residualism–Hatchery
    Environmental Biology of Fishes 05/2011; 94(1):29-44. · 1.31 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: Lean and siscowet morphotypes of lake trout Salvelinus namaycush in Lake Superior are thought to be genetically separate, but the reproductive isolating mechanism is unknown. The testicular and ovarian cycles and reproductive hormone levels of these morphotypes were determined from May to October in populations east and west of the Keweenaw Peninsula in southern Lake Superior. The gonadosomatic index (GSI) increased from August to October for lean and siscowet males and females east of the Keweenaw Peninsula and for siscowets west of the Keweenaw Peninsula. Circulating estradiol-17β (E2) levels and ovarian GSIs increased simultaneously in females of both morphotypes. However, circulating 11-ketotestosterone (11-KT) levels in lean and siscowet males were not significantly elevated until October even though testicular GSIs increased by August. Transcripts of the follicle stimulating hormone (FSH) beta subunit (an indirect measure of FSH activity) increased in lean and siscowet males and females during August and September, when GSIs were increasing for both morphotypes. The seasonal changes in GSIs and hormone levels indicate that both lean and siscowet individuals in southern Lake Superior populations undergo reproductive maturation at the same time in the fall; therefore, reproductive timing does not appear to genetically isolate the morphotypes in these populations. A proportion of the sampled females (lean lake trout: 54%; siscowets: 42%) exhibited no increase in GSI from August to October, strongly suggesting that in any given year some proportion of the population does not reproduce. This was also observed in males but at a lower percentage (19–20%). Fish that did not have maturing gonads from August to October also had lower E2 and 11-KT levels than maturing fish. Fecundity measured for lean and siscowet lake trout was not statistically different and was similar to historical values.Received November 13, 2010; accepted May 26, 2011
    Transactions of the American Fisheries Society 01/2011; 140(6):1472-1491. · 1.55 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. · 2.41 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

Publication Stats

4k Citations
287.58 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
    • Aristotle University of Thessaloniki
      Saloníki, Central Macedonia, Greece
  • 2004
    • Hokkaido University
      • Graduate School of Fisheries Sciences
      Sapporo-shi, Hokkaido, Japan
  • 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