Search USGS⌕ Search

SEARCH · Search USGS

Results for “General and Comparative Endocrinology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
USGS1985

The effects of cortisoland actinomycin D injections on choloride cells and branchial N+---K+-ATPase in rainbow trout (Salmo gairdneri)

Injections of cortisol, actinomycin D, or combined administration of the hormone and the antiobiotic did not effect rainbow trout ( Salmo gairdneri ) branchial Na + K + -ATPase activity. Numbers of chloride cells also did not change following cortisol and actinomycin D treatment. These results are discussed in light of a similar report concerning Atlantic salmon ( Salmo salar ).

General and Comparative Endocrinology↗
USGS1989

Plasma catecholamine concentrations in rainbow trout ( Salmo gairdneri ) at rest and after anesthesia and surgery

The effects of surgery and anesthesia on concentrations of plasma epinephrine (E), norepinephrine (NE), and dopamine (DA) were investigated in rainbow trout fitted with dorsal aorta cannulae. Baseline catecholamines (CA) concentrations, established in resting rainbow trout, were 1.55 ± 0.90 ϱmol/ml ( X ± SD) for E, 2.07 ± 1.26 for NE, and 1.33 ± 0.87 for DA. These values were based on the pooled analyses of five individual fish taken over seven different sampling periods. The E:NE ratio in resting fish was always less than 1.0. In a second experiment, fish were subjected to dorsal aorta cannulation and sequential blood samples were taken immediately after surgery, and 6, 24, and 48 hr later. Plasma E concentrations were 36 times greater than baseline values in the first sample; NE was 15 times greater and DA was 41 times greater. After surgery, plasma concentrations of all CAs fell rapidly but values were still higher than baseline 6 hr after surgery, then were near baseline at 24 and 48 hr after surgery. The E:NE ratio was about 3.0 immediately after surgery, dropped to 1.8 at 6 hr, and was about 1.0 at 24 and 48 hr. In a third experiment, plasma CAs were determined in a group of five animals anesthetized with tricaine methanesulfonate (100 mg/ml) to advanced anesthesia, and then allowed to recover in flowing well water over a 12-hr observation period. Plasma E and NE concentrations in the fish during early anes-thesia (1.14 ± 0.14 min) were not significantly different from preanesthesia values. During advanced anesthesia (2.31 ± 0.21 min), values for E and NE were significantly greater and continued to be elevated during the 12-hr recovery period. The E:NE ratio exceeded 1.0 during advanced anesthesia and for the rest of the experiment.

General and Comparative Endocrinology↗
USGS1991

Effects of prolacton chloride cells opercular membrane of seawater-adapted tilapia

Effects of prolactin on morphology and numbers of chloride cells in the opercular membrane of seawater-adapted tilapia ( Oreochromis mossambicus ) have been examined. Following five daily injections of ovine prolactin at a dose of 10 μg · g body wt −1 , blood samples were taken and opercular membranes were removed and stained with a fluorescent mitochondrial dye (dimethylaminostyrylethylpyridiniumiodine), a fluorescent derivative of ouabain (anthroylouabain), and a histological stain specific for the extensive tubular system of chloride cells (zinc-osmium-iodine). Mean plasma osmolarity and sodium increased 23–24% following prolactin injection. An increase in the relative frequency of chloride cells between 20 and 180 μm 2 in cross-sectional area and a decrease in the relative frequency of chloride cells greater than 180 μm 2 were observed following prolactin injections. Average cell size decreased 46–70% and cell height decreased 26–38% following prolactin injections. There was no significant change in cell density. Anthroylouabain staining was observed in both prolactin- and saline-injected fish, and no significant effect on Na + ,K + -adenosinetri-phosphatase activity was seen in either opercular membrane or gill tissue. The results demonstrate an effect of prolactin on chloride cell size and provide a morphological correlate for decreased secretory activity of chloride cells following prolactin injections.

General and Comparative Endocrinology↗
USGS1991

Developmental differences in the responsiveness of gill Na+, K+ and -ATPase to cortisol salmonids

The ability of cortisol to increase gill Na + , K + -ATPase activity was examined in several salmonid species during development. Coho salmon ( Oncorhynchus kisutch ) parr were unresponsive to cortisol in vitro (10 μg/ml for 2 days) in November. Responsiveness was significant from January to March, peaking in January just prior to seasonal increases in gill Na + , K + -ATPase activity. Gill tissue became unresponsive to in vitro cortisol in April when in vivo gill Na + , K + -ATPase activity peaked. The ability of cortisol to stimulate gill, Na + , K + -ATPase activity in postemergent fry (2–3 months after hatching) was examined in chum ( O. keta ), chinook ( O. tschawytscha ), coho, and Atlantic salmon ( Salmo salar ). Initial levels of gill Na + , K + -ATPase activity were elevated in chum salmon, which normally migrate as fry. Cortisol (10 μg/ml for 4 days in vitro ) increased gill Na + , K + -ATPase activity in chum salmon fry (48% above initial levels), had a limited but significant effect in chinook salmon fry, and had no effect in coho and Atlantic salmon fry. In an in vivo experiment, Atlantic salmon previously exposed to simulated natural photoperiod (SNP) and continuous light (L24) received four cortisol injections of 2 μg · g −1 every third day. SNP fish responded with increased gill Na + , K + -ATPase activity (+66%), whereas L24 fish were not affected. Atlantic salmon presmolts with initially low levels of gill Na + , K + -ATPase activity responded to cortisol in vitro , whereas smolts with initially high levels of gill Na + , K + -ATPase activity were unresponsive. Triiodothyronine (0.01–10 μg/ml), prolactin (0.1–10 μg/ml), growth hormone (0.1–10 μg/ml), insulin (0.01–10 μg/ml), and bovine insulin-like growth factor I (0.01–1 μg/ml) did not affect gill Na + , K + -ATPase activity in vitro , individually or with cortisol (1–10 μg/ml). Thus, changes in responsiveness to cortisol occur during salmonid development, vary among species, and may be important in the heterochrony that characterizes the parr-smolt transformation.

General and Comparative Endocrinology↗
USGS1992

Stimulation of coho salmon growth by insulin-like growth factor I

The effect of insulin-like growth factor I on growth rate of coho salmon ( Oncorhynchus kisutch ) was examined. Juvenile coho salmon received implants of osmotic minipumps containing recombinant bovine insulin-like growth factor I (rbIGF-I) or saline for a period of 3 to 4 weeks. High doses of rbIGF-I (>0.13 μg · g −1 · d −1 ) resulted in hypoglycemia and death. In 2-year-old coho salmon, 0.09 μg · g −1 · d −1 rbIGF-I administered for 25 days doubled linear growth rate and increased growth rate in weight by 40%. In rapidly growing, 1-year-old coho salmon, growth rate was not altered by rbIGF-I at 0.01 or 0.05 μg · g −1 · d −1 for 31 days. In ration-limited fish exhibiting slow growth in the control group, rbIGF-I (0.02 to 0.12 μg · g −1 · d −1 ) increased linear growth rate by up to threefold and growth rate in weight by up to fourfold. The results indicate that exogenous treatment with mammalian IGF-I can stimulate coho salmon growth under some conditions, and that endogenous IGF-I may be an important factor in regulating growth of teleosts.

General and Comparative Endocrinology↗
USGS2004

Interaction of xenobiotics with estrogen receptors α and β and a putative plasma sex hormone-binding globulin from channel catfish ( Ictalurus punctatus )

Estrogens are important regulators of physiological functions. Although environmental contaminants (xenoestrogens) which interfere with estrogen signaling are of increasing concern, there is only limited information about their ability to interact with estrogen-binding proteins (SHBG) or receptors (ER). Recombinant ER?? and ?? were obtained after transient transfection of COS-7 cells with channel catfish ER cDNA. Plasma from adult female channel catfish was the source of SHBG. Tritiated estradiol ( 3H-E2) was used in standard radioligand-binding assays to characterize the binding properties of channel catfish SHBG (ccfSHBG) and to estimate the inhibition constants for various estrogenic compounds. Binding of 3H-E2 to ccfSHBG was saturable and of high affinity with a Kd (??SE) of 1.9??0.14nM and a Bmax of 14.3??2.4pmol/mg protein (n=3 assays). Additionally, ccfSHBG displayed binding specificity for androgens and estrogens. Endosulfan, 4-nonylphenol, and 4-octylphenol displaced 3H-E2 binding to ccfSHBG albeit only at very high concentrations, whereas dieldrin and atrazine showed little displacement activity even at the highest concentrations used. The synthetic estrogen ethynylestradiol had higher affinity than E2 for ccfSHBG. This finding differs from results with human and rainbow trout SHBG. The alkylphenolic compounds (4-octylphenol and 4-nonylphenol) displayed some ability to displace 3H-E2 binding from ER?? and ?? at high concentrations, but dieldrin and atrazine had little binding activity for both ER subtypes and endosulfan for ER??. The xenobiotics tested generally showed equivalent or greater affinity for ER?? than ER??, whereas natural estrogens had much greater affinity for ER?? than ER??. These observations suggest that results of studies using fish tissue ER extracts must be interpreted with caution, since both ER subtypes may be present, and that the binding of xenoestrogens to SHBG must be taken into account for proper assessment of endocrine disruption caused by environmental contaminants.

General and Comparative Endocrinology↗
USGS2005

Endocrine disruption of parr-smolt transformation and seawater tolerance of Atlantic salmon by 4-nonylphenol and 17β-estradiol

Sex steroids are known to interfere with the parr-smolt transformation of anadromous salmonids, and environmental estrogens such as nonylphenol have recently been implicated in reduced returns of Atlantic salmon in the wild. To determine the endocrine pathways by which estrogenic compounds affect smolt development and seawater tolerance, groups of juvenile Atlantic salmon were injected with one of five doses (0.5, 2, 10, 40 or 150 μg g −1 ) of branched 4-nonylphenol (NP), 2 μg g −1 of 17β- estradiol (E 2 ), or vehicle, during the parr-smolt transformation in April, and the treatment was repeated 4, 8, and 11 days after the first injection. Plasma was obtained for biochemical analysis 7 and 14 days after initiation of treatment. After 14 days of treatment, additional fish from each treatment group were exposed to seawater for 24 h to assess salinity tolerance. The E 2 treatment and the highest NP dose resulted in lower salinity tolerance and decreased plasma insulin-like growth factor I (IGF-I) levels, along with elevated levels of plasma vitellogenin and total calcium. Plasma growth hormone levels were elevated at intermediate NP doses only, and not affected by E 2 . After 7 days, plasma thyroxine (T 4 ) levels decreased in a strong, dose-dependent manner in response to nonylphenol, but after 14 days, this suppressive effect of T 4 occurred at the highest NP dose only. Similarly, E 2 decreased plasma T 4 levels at 7, but not 14 days. Plasma 3,3′,5-triodo- l -thyronine was reduced by E 2 and the highest NP dose after 7 and 14 days of treatment. Plasma cortisol levels were not affected by any of the treatments. The results indicate that the parr-smolt transformation and salinity tolerance can be compromised by exposure to estrogenic compounds. Suppression of plasma IGF-I levels is a likely endocrine pathway for the effects of estrogenic compounds on hypo-osmoregulatory capacity, and the detrimental effects of E 2 and NP on thyroid hormone levels are also likely to compromise the normal parr-smolt transformation of Atlantic salmon.

General and Comparative Endocrinology↗
USGS2006

Prolactin and growth hormone in fish osmoregulation

Prolactin is an important regulator of multiple biological functions in vertebrates, and has been viewed as essential to ion uptake as well as reduction in ion and water permeability of osmoregulatory surfaces in freshwater and euryhaline fish. Prolactin-releasing peptide seems to stimulate prolactin expression in the pituitary and peripheral organs during freshwater adaptation. Growth hormone, a member of the same family of hormones as prolactin, promotes acclimation to seawater in several teleost fish, at least in part through the action of insulin-like growth factor I. In branchial epithelia, development and differentiation of the seawater-type chloride cell (and their underlying biochemistry) is regulated by GH, IGF-I, and cortisol, whereas the freshwater-type chloride cell is regulated by prolactin and cortisol. In the epithelia of gastrointestinal tract, prolactin induces cell proliferation during freshwater adaptation, whereas cortisol stimulates both cell proliferation and apoptosis. We propose that control of salinity acclimation in teleosts by prolactin and growth hormone primarily involves regulation of cell proliferation, apoptosis, and differentiation (the latter including upregulation of specific ion transporters), and that there is an important interaction of these hormones with corticosteroids. ?? 2005 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗
USGS2006

Comparison of synthesis of 15α-hydroxylated steroids in males of four North American lamprey species

Recent studies have provided evidence that 15α-hydroxytestosterone (15α-T) and 15α-hydroxyprogesterone (15α-P) are produced in vitro and in vivo in adult male sea lampreys ( Petromyzon marinus ), and that circulatory levels increase in response to injections with gonadotropin-releasing hormone ( GnRH ). We examined four species from the Petromyzontidae family including silver lampreys ( Ichthyomyzon unicuspis ), chestnut lampreys ( I. castaneus ), American brook lampreys ( Lethenteron appendix ), and Pacific lampreys ( Entosphenus tridentatus ) to determine if these unusual steroids were unique to sea lampreys or a common feature in lamprey species. In vitro production was examined through incubations of testis with tritiated precursors, and 15α-T and 15α-P production was confirmed in all species through co-elution with standards on both high performance liquid chromatography ( HPLC ) and thin layer chromatography . In vivo production was proven by demonstrating that HPLC-fractionated plasma had peaks of immunoreactive 15α-T and 15α-P that co-eluted with standards through using previously developed radioimmunoassays for 15α-T and 15α-P. The possible functionality of 15α-T and 15α-P was further examined in silver and Pacific lampreys by investigating the effect of injection of either type of lamprey GnRH on plasma concentrations of 15α-T and 15α-P. Injections with exogenous GnRH did not affect circulatory levels of either steroid in silver lampreys, and only GnRH III elicited higher levels of both steroids in Pacific lampreys. The 15α-hydroxylase enzyme(s) for steroids appeared to present in adult males of all species examined, but the question of whether 15α-hydroxylated steroids are functional in these lamprey species, and the significance of the 15- hydroxyl group, requires further research.

General and Comparative Endocrinology↗
USGS2007

Effects of larval-juvenile treatment with perchlorate and co-treatment with thyroxine on zebrafish sex ratios

The objective of this study was to determine the effect of larval-juvenile exposure to perchlorate, a thyroid hormone synthesis inhibitor, on the establishment of gonadal sex ratios in zebrafish. Zebrafish were exposed to untreated water or water containing perchlorate at 100 or 250 ppm for a period of 30 days starting at 3 days postfertilization (dpf). Recovery treatments consisted of a combination of perchlorate and exogenous thyroxine (T4; 10 nM). Thyroid histology was assessed at the end of the treatment period (33 dpf), and gonadal histology and sex ratios were determined in fish that were allowed an additional 10-day period of growth in untreated water. As expected, exposure to perchlorate caused changes in thyroid histology consistent with hypothyroidism and these effects were reversed by co-treatment with exogenous T4. Perchlorate did not affect fish survival but co-treatment with T4 induced higher mortality. However, relative to the corresponding perchlorate concentration, co-treatment with T4 caused increased mortality only at a perchlorate concentration of 100 ppm. Perchlorate alone or in the presence of T4 suppressed body length at 43 dpf relative to control values. Perchlorate exposure skewed the sex ratio toward female in a concentration-dependent manner, and co-treatment with T4 not only blocked the feminizing effect of perchlorate but also overcompensated by skewing the sex ratio towards male. Moreover, co-treatment with T4 advanced the onset of spermatogenesis in males. There was no clear association between sex ratios and larval survival or growth. We conclude that endogenous thyroid hormone plays a role in the establishment of gonadal sex phenotype during early development in zebrafish. ?? 2006 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗
USGS2007

Identification of plasma glucocorticoids in pallid sturgeon in response to stress

Compared to teleosts, little is known about the stress response in chondrosteans, and the glucocorticoid(s) most responsive to stress have never been definitively determined in sturgeon. In terms of cortisol production, pallid sturgeon (Scaphirhynchus albus) have a low physiological response to stress compared to other sturgeons (Acipenser sp.). Because of this, our null hypothesis was that cortisol is not the predominant glucocorticoid secreted in response to stress in pallid sturgeon. Our objective was to identify the putative glucocorticoids present in the plasma of pallid sturgeon during the stress response. Pallid sturgeon were subjected to a severe confinement stress (12 h) with an additional handling stressor for the first 6 h. Control fish were not subjected to confinement but were handled only to collect blood. Blood plasma was collected at time 0, 6, and 12 h. Gas chromatography/mass spectrometry was used to screen the plasma for the spectrum of glucocorticoids and determine the putative steroid secreted during the stress response. Cortisol was the primary glucocorticoid detected in stressed pallid sturgeon. In addition, the cortisol metabolites cortisone, alloTHE (5??-pregnane-3??,17??,21-triol-11,20-dione), allo-??-cortolone (3??,17??,20??,21-tetrahydro-5??-pregnan-11-one), and allo-??-cortolone (3??,17??,20??,21-tetrahydro-5??-pregnan-11-one) were detected. Plasma cortisol increased from a resting concentration of 0.67 ng/ml to 10.66 ng/ml at 6 h followed by a decrease to 6.78 ng/ml by 12 h. Plasma glucose increased significantly by time 6 and 12 h in both stressed and unstressed groups and remained elevated at time 12 h, while resting lactate concentrations were low to non-detectable and did not increase significantly with the stressor over time. Cortisol was the primary glucocorticoid synthesized and secreted in response to a stressor in pallid sturgeon. Though the proportional increase in plasma cortisol in stressed pallid sturgeon was lower than many other species of sturgeon, the concentration was high enough to elicit a secondary stress response as seen by changes in plasma glucose. ?? 2007 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗
USGS2008

Endocrine systems in juvenile anadromous and landlocked Atlantic salmon (Salmo salar): Seasonal development and seawater acclimation

The present study compares developmental changes in plasma levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and cortisol, and mRNA levels of their receptors and the prolactin receptor (PRLR) in the gill of anadromous and landlocked Atlantic salmon during the spring parr-smolt transformation (smoltification) period and following four days and one month seawater (SW) acclimation. Plasma GH and gill GH receptor (GHR) mRNA levels increased continuously during the spring smoltification period in the anadromous, but not in landlocked salmon. There were no differences in plasma IGF-I levels between strains, or any increase during smoltification. Gill IGF-I and IGF-I receptor (IGF-IR) mRNA levels increased in anadromous salmon during smoltification, with no changes observed in landlocked fish. Gill PRLR mRNA levels remained stable in both strains during spring. Plasma cortisol levels in anadromous salmon increased 5-fold in May and June, but not in landlocked salmon. Gill glucocorticoid receptor (GR) mRNA levels were elevated in both strains at the time of peak smoltification in anadromous salmon, while mineralocorticoid receptor (MR) mRNA levels remained stable. Only anadromous salmon showed an increase of gill 11??-hydroxysteroid dehydrogenase type-2 (11??-HSD2) mRNA levels in May. GH and gill GHR mRNA levels increased in both strains following four days of SW exposure in mid-May, whereas only the anadromous salmon displayed elevated plasma GH and GHR mRNA after one month in SW. Plasma IGF-I increased after four days in SW in both strains, decreasing in both strains after one month in SW. Gill IGF-I mRNA levels were only increased in landlocked salmon after 4 days in SW. Gill IGF-IR mRNA levels in SW did not differ from FW levels in either strain. Gill PRLR mRNA did not change after four days of SW exposure, and decreased in both strains after one month in SW. Plasma cortisol levels did not change following SW exposure in either strain. Gill GR, 11??-HSD2 and MR mRNA levels increased after four days in SW in both strains, whereas only the anadromous strain maintained elevated gill GR and 11??-HSD2 mRNA levels after one month in SW. The results indicate that hormones and receptors of the GH and cortisol axes are present at significantly lower levels during spring development and SW acclimation in landlocked relative to anadromous salmon. These findings suggest that attenuation of GH and cortisol axes may, at least partially, result in reduced preparatory upregulation of key gill ion-secretory proteins, possibly a result of reduced selection pressure for marine adaptations in landlocked salmon. ?? 2007 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗
USGS2008

Role of gap junctions and protein kinase A during the development of oocyte maturational competence in Ayu (Plecoglossus altivelis)

Meiotic resumption in teleost oocytes is induced by a maturation-inducing hormone (MIH). The sensitivity of oocytes to MIH, also known as oocyte maturational competence (OMC), is induced by LH via mechanisms that are not fully understood. A previous study of Ayu (Plecoglossus altivelis) showed the presence of functional heterologous gap junctions (GJs) between oocytes and their surrounding granulosa cells. The objectives of this study were to determine the role of ovarian GJs and of protein kinase A (PKA) during the acquisition of OMC. We examined the effects of the specific GJ inhibitor carbenoxolone (CBX) and 18??-glycyrrhetinic acid (??-GA) on the LH-(hCG)-dependent acquisition of OMC and on MIH-(17,20??-dihydroxy-4-pregnen-3-one)-dependent meiotic resumption; measured the cAMP content of ovarian follicles during the hCG-dependent acquisition of OMC; and determined the effects of PK activators and inhibitors on hCG-dependent OMC. Production of follicular cAMP increased during the hCG-dependent acquisition of OMC. Both GJ inhibitors and the PKA inhibitor H8-dihydrochloride, but not the PKC inhibitor GF109203X, suppressed the hCG-dependent acquisition of OMC in a dose-dependent manner. The PKA activator forskolin induced OMC with a similar potency to hCG. Unlike previous observations with teleosts where disruption of heterologous GJ either blocks or stimulates meiotic resumption, treatment with GJ inhibitors did not affect MIH-dependent meiotic resumption in maturationally competent follicles of Ayu. These observations suggest that ovarian GJs are essential for LH-dependent acquisition of OMC but not for MIH-dependent meiotic resumption, and that the stimulation of OMC by LH is mediated by cAMP-dependent PKA. They are also consistent with the view that a precise balance between GJ-mediated signals (positive or negative) and oocyte maturational readiness is required for hormonally regulated meiotic resumption. ?? 2007 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗
USGS2008

Effects of seawater acclimation on mRNA levels of corticosteroid receptor genes in osmoregulatory and immune systems in trout

Influence of environmental salinity on expression of distinct corticosteroid receptor (CR) genes, glucocorticoid receptor (GR)-1 and -2, and mineralcorticoid receptor (MR), was examined in osmoregulatory and hemopoietic organs and leucocytes of steelhead trout (Oncorhynchus mykiss). There was no significant difference in plasma cortisol levels between freshwater (FW)- or seawater (SW)-acclimated trout, whereas Na+, K+-ATPase was activated in gill of SW fish. Plasma lysozyme levels also showed a significant increase after acclimation to SW. In SW-acclimated fish, mRNA levels of GR-1, GR-2, and MR were significantly higher in gill and body kidney than those in FW. Head kidney and spleen showed no significant change in these CR mRNA levels after SW-acclimation. On the other hand, leucocytes isolated from head kidney and peripheral blood showed significant decreases in mRNA levels of CR in SW-acclimated fish. These results showed differential regulation of gene expression of CR between osmoregulatory and immune systems. ?? 2008 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗
USGS2008

Are we missing a mineralocorticoid in teleost fish? Effects of cortisol, deoxycorticosterone and aldosterone on osmoregulation, gill Na + ,K + -ATPase activity and isoform mRNA levels in Atlantic salmon

It has long been held that cortisol, acting through a single receptor, carries out both glucocorticoid and mineralocorticoid actions in teleost fish. The recent finding that fish express a gene with high sequence similarity to the mammalian mineralocorticoid receptor (MR) suggests the possibility that a hormone other than cortisol carries out some mineralocorticoid functions in fish. To test for this possibility, we examined the effect of in vivo cortisol, 11-deoxycorticosterone (DOC) and aldosterone on salinity tolerance, gill Na + ,K + -ATPase (NKA) activity and mRNA levels of NKA α1a and α1b in Atlantic salmon. Cortisol treatment for 6–14 days resulted in increased, physiological levels of cortisol, increased gill NKA activity and improved salinity tolerance (lower plasma chloride after a 24 h seawater challenge), whereas DOC and aldosterone had no effect on either NKA activity or salinity tolerance. NKA α1a and α1b mRNA levels, which increase in response to fresh water and seawater acclimation, respectively, were both upregulated by cortisol, whereas DOC and aldosterone were without effect. Cortisol, DOC and aldosterone had no effect on gill glucocorticoid receptor GR1, GR2 and MR mRNA levels, although there was some indication of possible upregulation of GR1 by cortisol (p = 0.07). The putative GR blocker RU486 inhibited cortisol-induced increases in salinity tolerance, NKA activity and NKA α1a and α1b transcription, whereas the putative MR blocker spironolactone had no effect. The results provide support that cortisol, and not DOC or aldosterone, is involved in regulating the mineralocorticoid functions of ion uptake and salt secretion in teleost fish.

General and Comparative Endocrinology↗
USGS2008

Effects of short-term acid and aluminum exposure on the parr-smolt transformation in Atlantic salmon (Salmo salar): Disruption of seawater tolerance and endocrine status

Episodic acidification resulting in increased acidity and inorganic aluminum (Ali) is known to interfere with the parr-smolt transformation of Atlantic salmon (Salmo salar), and has been implicated as a possible cause of population decline. To determine the extent and mechanism(s) by which short-term acid/Al exposure compromises smolt development, Atlantic salmon smolts were exposed to either control (pH 6.7-6.9) or acid/Al (pH 5.4-6.3, 28-64 ??g l-1 Ali) conditions for 2 and 5 days, and impacts on freshwater (FW) ion regulation, seawater (SW) tolerance, plasma hormone levels and stress response were examined. Gill Al concentrations were elevated in all smolts exposed to acid/Al relative to controls confirming exposure to increased Ali. There was no effect of acid/Al on plasma ion concentrations in FW however, smolts exposed to acid/Al followed by a 24 h SW challenge exhibited greater plasma Cl- levels than controls, indicating reduced SW tolerance. Loss of SW tolerance was accompanied by reductions in gill Na+,K+-ATPase (NKA) activity and Na+,K+,2Cl- (NKCC) cotransporter protein abundance. Acid/Al exposure resulted in decreased plasma insulin-like growth factor (IGF-I) and 3,3???,5???-triiodo-l-thyronine (T3) levels, whereas no effect of treatment was seen on plasma cortisol, growth hormone (GH), or thyroxine (T4) levels. Acid/Al exposure resulted in increased hematocrit and plasma glucose levels in FW, but both returned to control levels after 24 h in SW. The results indicate that smolt development and SW tolerance are compromised by short-term exposure to acid/Al in the absence of detectable impacts on FW ion regulation. Loss of SW tolerance during short-term acid/Al exposure likely results from reductions in gill NKA and NKCC, possibly mediated by decreases in plasma IGF-I and T3. ?? 2008 Elsevier Inc.

General and Comparative Endocrinology↗
USGS2008

Brain aromatase (Cyp19A2) and estrogen receptors, in larvae and adult pejerrey fish Odontesthes bonariensis: Neuroanatomical and functional relations

Although estrogens exert many functions on vertebrate brains, there is little information on the relationship between brain aromatase and estrogen receptors. Here, we report the cloning and characterization of two estrogen receptors, ?? and ??, in pejerrey. Both receptors' mRNAs largely overlap and were predominantly expressed in the brain, pituitary, liver, and gonads. Also brain aromatase and estrogen receptors were up-regulated in the brain of estradiol-treated males. In situ hybridization was performed to study in more detail, the distribution of the two receptors in comparison with brain aromatase mRNA in the brain of adult pejerrey. The estrogen receptors' mRNAs exhibited distinct but partially overlapping patterns of expression in the preoptic area and the mediobasal hypothalamus, as well as in the pituitary gland. Moreover, the estrogen receptor ??, but not ??, were found to be expressed in cells lining the preoptic recess, similarly as observed for brain aromatase. Finally, it was shown that the onset expression of brain aromatase and both estrogen receptors in the head of larvae preceded the morphological differentiation of the gonads. Because pejerrey sex differentiation is strongly influenced by temperature, brain aromatase expression was measured during the temperature-sensitive window and was found to be significantly higher at male-promoting temperature. Taken together these results suggest close neuroanatomical and functional relationships between brain aromatase and estrogen receptors, probably involved in the sexual differentiation of the brain and raising interesting questions on the origin (central or peripheral) of the brain aromatase substrate. ?? 2008 Elsevier Inc.

General and Comparative Endocrinology↗
USGS2009

Gene-expression signatures of Atlantic salmon's plastic life cycle

How genomic expression differs as a function of life history variation is largely unknown. Atlantic salmon exhibits extreme alternative life histories. We defined the gene-expression signatures of wild-caught salmon at two different life stages by comparing the brain expression profiles of mature sneaker males and immature males, and early migrants and late migrants. In addition to life-stage-specific signatures, we discovered a surprisingly large gene set that was differentially regulated-at similar magnitudes, yet in opposite direction-in both life history transitions. We suggest that this co-variation is not a consequence of many independent cellular and molecular switches in the same direction but rather represents the molecular equivalent of a physiological shift orchestrated by one or very few master regulators. ?? 2009 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗