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1.
  • Einarsdottir, Ingibjörg, 1951, et al. (författare)
  • Atlantic halibut growth hormone: structure and plasma levels of sexually mature males and females during photoperiod-regulated annual cycles
  • 2002
  • Ingår i: General and Comparative Endocrinology. - 0016-6480 .- 1095-6840. ; 127:1, s. 94-104
  • Tidskriftsartikel (refereegranskat)abstract
    • The main objectives of this study were to obtain the amino acid sequence of Atlantic halibut (Hippoglossus hippoglossus) growth hormone (hhGH) and compare it with other teleost species, to establish a radioimmunoassay to assess plasma hhGH levels and thus to gain information about possible biological functions and regulation by photoperiod. The hhGH gene was cloned and its amino acid sequence deduced from the cDNA. The mature hhGH protein consists of 186 amino acids. Comparison with other flatfish species as well as a species from a different order, the pufferfish, reveals that the sequence similarities of the mature hhGH with that of the barfin flounder, the Japanese flounder, the sole and the pufferfish are 99.5, 81.7, 74.2, and 65.2%, respectively. The sequence similarities appear to correctly reflect the gross phylogenetic relationships among these telcost species. A specific GH-RIA was developed for measurements of Atlantic halibut GH levels. Assessment of plasma GH levels in adult halibut revealed large gender differences, with GH levels frequently being an order of magnitude higher in males than females. The mean (+/-SEM) plasma GH for males kept on normal annual photoperiod were 25.2 +/- 6.11 ng ml(-1) and for females were 5.14 +/- 1.94 ng ml(-1). It appears likely that plasma growth hormone levels in Atlantic halibut can be inversely correlated to growth and metabolism. Shifting of the annual photoperiod cycles demonstrated that photoperiod in not a regulator of plasma GH levels in the Atlantic halibut. but further research is needed to assess whether GH plays a role in the reproduction of this marine teleost species. (C) 2002 Elsevier Science (USA). All rights reserved.
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2.
  • Larsson, D. G. Joakim, 1969, et al. (författare)
  • Regulation of androgen receptors in Atlantic croaker brains by testosterone and estradiol.
  • 2002
  • Ingår i: General and comparative endocrinology. - 0016-6480. ; 128:3, s. 224-30
  • Tidskriftsartikel (refereegranskat)abstract
    • A nuclear androgen receptor (AR1), distinctly different from the mammalian AR, has previously been identified in the brain of the Atlantic croaker, Micropogonias undulatus. Interestingly, brain AR1 levels were higher in gonadally recrudesced than in regressed fish. Therefore, the possible involvement of gonadal steroids in the regulation of brain AR1 levels was investigated in the present study. Saturation analysis of [3H]testosterone binding showed that brain AR1 levels were significantly reduced (2-3-fold) in either the nuclear or cytosolic fractions of both males and females three weeks after gonadectomy. Implantation of gonadectomized females with testosterone or estradiol-17beta one week prior to sampling resulted in physiological plasma steroid concentrations and restored brain AR1 levels to 60-105% of those in intact or sham-operated fish. These results suggest that gonadal factors, including both androgens and estrogens, are involved in the physiological regulation of brain androgen receptors in a teleost species during the reproductive cycle.
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3.
  • von Hofsten, Jonas, et al. (författare)
  • Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus)
  • 2003
  • Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 132:1, s. 96-102
  • Tidskriftsartikel (refereegranskat)abstract
    • Fushi tarazu factor-1 (FTZ-F1) genes belong to the nuclear receptor family 5A (NR5A). The distribution pattern of NR5A genes in teleosts suggests that they control functions separate to, or in addition to, those of other vertebrates. In mammals NR5A1 genes, including steroidogenic factor-1 (SF-1), are primarily involved in steroidogenesis. NR5A2 contain the alpha-fetoprotein transcription factor (FTF) genes, which protect mammalian embryos against maternal estrogens, and are involved in cholesterol transfer and metabolism. In this study we have analysed the expression of two Arctic char FTZ-F1 forms belonging to the NR5A2 group. The expression starts during early development and the transcripts are present in embryonic liver/pancreas and gonadal regions. The genes are up-regulated during embryogenesis as the embryo develops towards hatch, as shown by increased mRNA and protein levels. In adult Arctic char the FTZ-F1 forms are primarily located to tissues involved in steroidogenesis as well as cholesterol metabolism. Thus, a division of NR5A into SF-1 (NR5A1) and FTF (NR5A2) specific functions does not appear to have occurred in teleosts.
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4.
  • von Hofsten, Jonas, et al. (författare)
  • Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus)
  • 2003
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 132:1, s. 96-102
  • Tidskriftsartikel (refereegranskat)abstract
    • Fushi tarazu factor-1 (FTZ-F1) genes belong to the nuclear receptor family 5A (NR5A). The distribution pattern of NR5A genes in teleosts suggests that they control functions separate to, or in addition to, those of other vertebrates. In mammals NR5A1 genes, including steroidogenic factor-1 (SF-1), are primarily involved in steroidogenesis. NR5A2 contain the alpha-fetoprotein transcription factor (FTF) genes, which protect mammalian embryos against maternal estrogens, and are involved in cholesterol transfer and metabolism. In this study we have analysed the expression of two Arctic char FTZ-F1 forms belonging to the NR5A2 group. The expression starts during early development and the transcripts are present in embryonic liver/pancreas and gonadal regions. The genes are up-regulated during embryogenesis as the embryo develops towards hatch, as shown by increased mRNA and protein levels. In adult Arctic char the FTZ-F1 forms are primarily located to tissues involved in steroidogenesis as well as cholesterol metabolism. Thus, a division of NR5A into SF-1 (NR5A1) and FTF (NR5A2) specific functions does not appear to have occurred in teleosts.
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5.
  • Anderson, WG, et al. (författare)
  • Purification, characterization, and biological activity of insulins from dogfish, Scyliohinus canicula, and the hammerhead shark, Sphyrna lewini.
  • 2002
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 126:1, s. 113-122
  • Tidskriftsartikel (refereegranskat)abstract
    • Insulin was purified from pancreatic extracts of two elasmobranch species belonging to different families in the order Carcharhiniformes, the European spotted dogfish, Scyliorhinus canicula (Scyliorhinidae), and the hammerhead shark, Sphyrna lewini (Carcharhinidae). The amino acid sequence of dogfish insulin was established as A-chain GIVDHCCRNT(10) CSLYDLEGYC(20)NQ and B-chain LPSQHLCGSH(10)LVETLYFVCG(20)QKGFYYVPKV(30). The primary structure of hammerhead shark insulin was similar to that of dogfish insulin with only 2 amino acid substitutions at A8 (R --> H) and B30 (V --> I). The elasmobranch insulins were markedly different from human insulin (17 amino acid substitutions) but all the residues in human insulin that are believed to be important in determining the receptor binding conformation (B6, B8, B11, B13, B23, B24, B25, A2, A3, and A19) have been conserved in the elasmobranch insulins with the exception of the conservative substitution Phe --> Tyr at B25. Consistent with this, dogfish and human insulin showed almost identical binding affinity to the recombinant solubilized human insulin receptor (K-D values of 14.0 and 18.6 pM, respectively; relative potency 133%). Previous studies have shown that bovine insulin produces severe and sustained hypoglycemia in elasmobranchs but the effect is of slow onset. Bolus arterial injections of dogfish insulin (10 nmol (.) kg(-1)) into unanesthetized, fasting dogfish (n = 9) produced no changes in blood glucose, 3-hydroxybutyrate, and acetoacetate concentrations over a 4-h period. In a second series of experiments (n = 7), dogfish insulin (10 nmol (.) kg(-1)) produced a significant (P < 0.05) fall in blood glucose after 12 h that persisted for at least 48 h, but no change in ketone body concentrations. The data indicate that the metabolic actions of an endogenous elasmobranch insulin in an elasmobranch are similar to those previously described for mammalian insulin. (C) 2002 Elsevier Science (USA).
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6.
  • Andersson, E., et al. (författare)
  • Pituitary gonadotropin and ovarian gonadotropin receptor transcript levels: Seasonal and photoperiod-induced changes in the reproductive physiology of female Atlantic salmon (Salmo salar)
  • 2013
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 191, s. 247-258
  • Tidskriftsartikel (refereegranskat)abstract
    • In female Atlantic salmon kept at normal light conditions, pituitary follicle-stimulating hormone beta (fshb) transcript levels were transiently elevated one year before spawning, re-increased in February, and remained high during spawning in November and in post-ovulatory fish in December. The first increase in plasma 17b-estradiol (E-2), testosterone (T) and gonadosomatic index (GSI) was recorded in January; E-2 rose up to one month prior to ovulation, while T and GSI kept increasing until ovulation. Pituitary luteinizing hormone beta (lhb) transcript levels peaked at the time of ovulation. Except for transient changes before and after ovulation, ovarian follicle stimulating hormone receptor (fshr) transcript amounts were relatively stable at a high level. By contrast, luteinizing hormone receptor (lhcgr) transcript levels started out low and increased in parallel to GSI and plasma E-2 levels. Exposure to continuous light (LL) induced a bimodal response where maturation was accelerated or arrested. The LL-arrested females showed previtellogenic oil droplet stage follicles or primary yolk follicles only, and fshb and E-2 plasma levels collapsed while fshr increased. The LL-accelerated females showed elevated lhb transcript levels and slightly elevated E-2 levels during early vitellogenesis, and significantly elevated lhcgr E-2 and GSI levels in late vitellogenesis. We conclude that Fsh-dependent signaling stimulates recruitment into and the sustained development through vitellogenesis. Up-regulation of lhcgr gene expression during vitellogenesis may reflect an estrogenic effect, while elevated fshr gene expression following ovulation or during LL-induced arrestment may be associated with ovarian tissue remodeling processes. (C) 2013 Elsevier Inc. All rights reserved.
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7.
  • Benedet Perea, Susana, 1972, et al. (författare)
  • Pituitary and plasma growth hormone dynamics during sexual maturation of female Atlantic salmon
  • 2010
  • Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 167:1, s. 77-85
  • Tidskriftsartikel (refereegranskat)abstract
    • Growth hormone in fish regulates many important physiological processes including growth, metabolism and potentially reproduction. In salmonid fish, GH secretion is episodic with irregularly spaced GH peaks. Plasma GH reflects secretion episodes as well as the clearance rate of the hormone, and plasma levels may thus not always reflect the level of activation of the GH axis. This study measured the production dynamics of GH over a 17-month period in sexually maturing female Atlantic salmon which included final maturation and spawning. For the first time, the level of pituitary GH mRNA, pituitary GH protein and plasma GH protein were analyzed concurrently in the same individuals. mRNA and protein were extracted in parallel from the same samples with subsequent real time quantitative PCR to measure mRNA transcripts and radioimmunoassay to measure pituitary and plasma GH protein. Further, the effects of photoperiod manipulation on these parameters were studied. The results show no correlation between mRNA and protein levels except at some time points, and indicate that it is inappropriate to correlate pooled temporal data and averages in time series unless the relationship among the variables is stable over time. The results indicate complex and shifting relationships between pituitary GH mRNA expression, pituitary GH content and plasma GH levels, which could result from changes in clearance rather than secretion rate at different times and its episodic secretion. The study also suggests that there is a functionally important activation of the GH system during spring leading up to maturation and spawning.
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8.
  • Berg, A. H., et al. (författare)
  • Regulation of Arctic char (Salvelinus alpinus) egg shell proteins and vitellogenin during reproduction and in response to 17β-estradiol and cortisol
  • 2004
  • Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 135:3, s. 276-285
  • Tidskriftsartikel (refereegranskat)abstract
    • Estrogens induce both vitellogenin (Vtg) and egg shell (zona pellucida; ZP) protein synthesis in salmonids. However, while Vtg is strictly under estrogenic control, recent reports suggest that additional mechanisms are involved in ZP protein synthesis. During sexual maturation both estrogen and glucocorticoid levels increase in the circulation of female fish. As glucocorticoids have been shown to interfere with Vtg induction in fish we investigated whether cortisol (F) had similar effects on ZP regulation. In the present study we determined both the natural variation in Vtg and ZP during an annual reproductive cycle in female Arctic char (Salvelinus alpinus), and the effect of co-treatment of juvenile Arctic char with 17β-estradiol (E2) and F. During sexual maturation the expression of Vtg and ZP correlated to plasma levels of E2 and F. Determination of Vtg and ZP protein levels following co-treatment with E2 and F showed that F antagonized E2 induction of Vtg. However, F was observed to potentiate the expression of ZP protein in the same fish. These results indicate that in Arctic char Vtg and ZP proteins are not regulated by the same mechanisms and suggest that ZP protein expression does not necessarily imply exposure to estrogenic compounds alone, and may thus not be ideally suited as a biomarker of exposure to estrogenic compounds.
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9.
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10.
  • Björnsson, Björn Thrandur, 1952, et al. (författare)
  • Photoperiod regulation of plasma growth hormone levels during induced smoltification of underyearling Atlantic salmon.
  • 2000
  • Ingår i: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 119:1, s. 17-25
  • Tidskriftsartikel (refereegranskat)abstract
    • Earlier studies have established that increased daylength increases plasma growth hormone (GH) levels during spring smoltification of yearling Atlantic salmon. Recently, the Atlantic salmon aquaculture industry has started the production of underyearling ("summer") smolts. This involves fast juvenile growth on continuous light (24L), the transfer of juveniles over 8 cm in length to short day (12L) for 6 weeks in the summer, followed by transfer to 24L for another 6 weeks before transfer to seawater in late October. Three groups were studied in fresh water from July to the following May in order to elucidate the GH response to this photoperiod manipulation: one group was kept on 24L throughout (long-day group), while the other two groups were exposed to short day from July 15th. Of these, one was brought back onto long day on September 1st (winter group) while the other was kept on short day (short-day group). Plasma GH levels of the long-day group were around 1.6 ng/ml throughout the study. The short-day transfer suppressed GH levels to 0.7 ng/ml within 2 weeks (short-day and winter groups). The long-day transfer (winter group) increased GH levels to 11 ng/ml within 3 weeks, and this elevation of GH levels was sustained for about 3 months, before declining to pretreatment levels. The study demonstrates that underyearling Atlantic salmon react to increased daylength in a way similar to traditional yearling smolts. It also demonstrates for the first time that decreased daylength can suppress plasma GH levels in fish. It is concluded that winter photoperiod manipulation causes an out-of-season initiation and completion of the parr-smolt transformation of underyearling Atlantic salmon and that growth hormone plays a major role in this process.
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11.
  • Blixt, Martin, 1977-, et al. (författare)
  • Characterization of β-cell function of pancreatic islets isolated from bank voles developing glucose intolerance/diabetes : an animal model showing features of both type 1 and type 2 diabetes mellitus, and a possible role of the Ljungan virus
  • 2007
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 154:1-3, s. 41-47
  • Tidskriftsartikel (refereegranskat)abstract
    • Bank voles (Clethrionomys glareolus) kept in captivity develop diabetes mellitus to a significant extent. Also in wild bank voles, elevated blood glucose has been observed. A newly isolated picornavirus named Ljungan virus (LV) has been found in the pancreas of these bank voles. Moreover, LV infection in combination with environmental factors may cause glucose intolerance/diabetes (GINT/D) in normal mice. The aim of the present study was to investigate the functional characteristics of pancreatic islets, isolated from bank voles, bred in the laboratory but considered LV infected. About 20% of all males and females were classified as GINT/D following a glucose tolerance test. Of these animals the majority had become diabetic by 20 weeks of age, with a tendency towards an earlier onset in the males. GINT/D animals had increased serum insulin levels. Islets were tested on the day of isolation (day 0) and after 1 week of culture for their insulin content and their capacity to synthesize (pro)insulin, secrete insulin and metabolize glucose. Functional differences could be observed between normal and GINT/D animals as well as between genders. An elevated basal insulin secretion was observed on day 0 indicating β-cell dysfunction among islets isolated from diabetic males. In vitro culture could reverse some functional changes. The increased serum insulin level and the increased basal islet insulin secretion may suggest that the animals had developed a type 2 diabetes-like condition. It is likely that the putative stress imposed in the laboratory, maybe in combination with LV infection, can lead to an increased functional demand on the β-cells.
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12.
  • Breves, J. P., et al. (författare)
  • Hepatic insulin-like growth factor binding protein (igfbp) responses to food restriction in Atlantic salmon smolts
  • 2016
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 233, s. 79-87
  • Tidskriftsartikel (refereegranskat)abstract
    • The growth hormone (Gh)/insulin-like growth-factor (Igf) system plays a central role in the regulation of growth in fishes. However, the roles of Igf binding proteins (Igfbps) in coordinating responses to food availability are unresolved, especially in anadromous fishes preparing for seaward migration. We assayed plasma Gh, Igf1, thyroid hormones and cortisol along with igfbp mRNA levels in fasted and fed Atlantic salmon (Salmo solar). Fish were fasted for 3 or 10 days near the peak of smoltification (late April to early May). Fasting reduced plasma glucose by 3 days and condition factor by 10 days. Plasma Gh, cortisol, and thyroxine (T-4) were not altered in response to fasting, whereas Igf1 and 3,5,3'-triiodo-L-thyronine (T-3) were slightly higher and lower than controls, respectively. Hepatic igfbp1b1, -1b2, -2a,-2b1 and -2b2 mRNA levels were not responsive to fasting, but there were marked increases in igfbp1a1 following 3 and 10 days of fasting. Fasting did not alter hepatic igf1 or igf2; however, muscle igf1 was diminished by 10 days of fasting. There were no signs that fasting compromised branchial ionoregulatory functions, as indicated by unchanged Na+/K+-ATPase activity and ion pump/transporter mRNA levels. We conclude that dynamic hepatic igfbp1a1 and muscle igf1 expression participate in the modulation of Gh/Igf signaling in smolts undergoing catabolism.
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13.
  • Brunström, Björn, et al. (författare)
  • Effects of estrogens on sex differentiation in Japanese quail and chicken
  • 2009
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 163:1-2, s. 97-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Estrogen production by the female avian embryo induces development of a female phenotype of the reproductive organs whereas the low estrogen concentration in the male embryo results in a male phenotype. Treatment of female embryos with exogenous estrogens disrupts Müllerian duct development resulting in malformations and impaired oviductal function. Exposure of male embryos to estrogens results in ovotestis formation and persisting Müllerian ducts in the embryos and testicular malformations, reduced semen production and partially developed oviducts in the adult bird. Furthermore, studies in Japanese quail show that the male copulatory behavior is impaired by embryonic estrogen treatment. Results from our experiments with selective agonists for ERalpha and ERbeta suggest that the effects of estrogens on the reproductive organs are mediated via activation of ERalpha. Abundant expression of ERalpha mRNA was shown in gonads and Müllerian ducts of early Japanese quail embryos. Both ERalpha and ERbeta transcripts were detected by real-time PCR in early embryo brains of Japanese quail indicating that both receptors may be involved in sex differentiation of the brain. However, in 9-day-old quail embryo brains in situ hybridization showed expression of ERbeta mRNA, but not of ERalpha mRNA, in the medial preoptic nucleus (POM) and the bed nucleus of the stria terminalis (BSTm), areas implicated in copulatory behavior of adult male quail. Furthermore, embryonic treatment with the selective ERalpha agonist propyl pyrazol triol (PPT) had no effect on the male copulatory behavior. These results suggest that ERbeta may be important for the effects of estrogens on brain differentiation.
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14.
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15.
  • Cardoso, João C R, et al. (författare)
  • New insights into the evolution of vertebrate CRH (corticotropin-releasing hormone) and invertebrate DH44 (diuretic hormone 44) receptors in metazoans
  • 2014
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 209:SI, s. 162-170
  • Tidskriftsartikel (refereegranskat)abstract
    • The corticotropin releasing hormone receptors (CRHR) and the arthropod diuretic hormone 44 receptors (DH44R) are structurally and functionally related members of the G protein-coupled receptors (GPCR) of the secretin-like receptor superfamily. We show here that they derive from a bilaterian predecessor. In protostomes, the receptor became DH44R that has been identified and functionally characterised in several arthropods but the gene seems to be absent from nematode genomes. Duplicate DH44R genes (DH44 R1 and DH44R2) have been described in some arthropods resulting from lineage-specific duplications. Recently, CRHR-DH44R-like receptors have been identified in the genomes of some lophotrochozoans (molluscs, which have a lineage-specific gene duplication, and annelids) as well as representatives of early diverging deuterostomes. Vertebrates have previously been reported to have two CRHR receptors that were named CRHR1 and CRHR2. To resolve their origin we have analysed recently assembled genomes from representatives of early vertebrate divergencies including elephant shark, spotted gar and coelacanth. We show here by analysis of synteny conservation that the two CRHR genes arose from a common ancestral gene in the early vertebrate tetraploidizations (2R) approximately 500 million years ago. Subsequently, the teleost-specific tetraploidization (3R) resulted in a duplicate of CRHR1 that has been lost in some teleost lineages. These results help distinguish orthology and paralogy relationships and will allow studies of functional conservation and changes during evolution of the individual members of the receptor family and their multiple native peptide agonists.
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16.
  • Deviche, Pierre J., et al. (författare)
  • Acute stress rapidly decreases plasma testosterone in a free-ranging male songbird: Potential site of action and mechanism
  • 2010
  • Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 169:1, s. 82-90
  • Tidskriftsartikel (refereegranskat)abstract
    • We used a free-ranging, seasonally breeding adult male songbird, the rufous-winged sparrow, Aimophila carpalis, to investigate the effects of acute stress-induced by capture followed by restraint, on the hypothalamo-pituitary–testicular axis. Intra- and interindividual comparisons revealed that males decreased their plasma testosterone (T) by 37–52% in response to acute stress. The decrease occurred within 15 min of capture and persisted for at least another 15 min. Within 15 min, the decrease in plasma T was not associated with a reduction in plasma luteinizing hormone (LH). Thirty minutes after capture and restraint, the decrease in plasma T either was likewise not associated with decreased plasma LH (intraindividual comparison) or concurred with a reduction in plasma LH (interindividual comparison). These observations indicate that effects of stress may have been mediated at the pituitary gland and also directly at the testicular levels. To address this question, we measured the hormonal response to an injection of the glutamate receptor agonist N-methyl-d,l-aspartate (NMA) to stimulate to stimulate the release of gonadotropin-releasing hormone (GnRH) or of GnRH to stimulate the release of LH. Treatment with NMA did not change plasma LH, presumably because the birds were in breeding condition and already secreting GnRH at a maximum rate. Administration of GnRH increased plasma LH equally in birds that were or were not stressed before the treatment. An injection of purified ovine LH (oLH) increased plasma T equally in birds that were or were not acutely stressed before the hormone injection. Thus, the observed acute stress-induced decrease in plasma T was apparently not mediated by decreased responsiveness of the pituitary gland to GnRH or of the testes to LH. Decreased plasma T following stress may involve a direct impairment of the testicular endocrine function.
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17.
  • Einarsdottir, Ingibjörg, 1951, et al. (författare)
  • Isolation of Atlantic halibut pituitary hormones by continuous-elution electrophoresis followed by fingerprint identification, and assessment of growth hormone content during larval development
  • 2007
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 150:2, s. 355-363
  • Tidskriftsartikel (refereegranskat)abstract
    • Continuous-elution electrophoresis (CEE) has been applied to separate putative hormones from adult Atlantic halibut pituitaries. Soluble proteins were separated by size and charge on Model 491 Prep Cell (Bio-Rad), where the homogenate runs through a cylindrical gel, and protein fractions are collected as they elute from the matrix. Protein fractions were assessed by SDS–PAGE and found to contain purified proteins of molecular size from 10 to 33 kDa. Fractions containing proteins with molecular weights of approximately 21, 24, 28 and 32 kDa, were identified as putative growth hormone (GH), prolactin, somatolactin and gonadotropins, respectively. These were analyzed further by mass spectrometry and identified with peptide mass protein fingerprinting. The CEE technique was used successfully for purification of halibut GH with a 5% yield, and appears generally well suited to purify species-specific proteins often needed for research in comparative endocrinology, including immunoassay work. Thus, the GH obtained was subsequently used as standards and iodination label in a homologous radioimmunoassay, applied to analyze GH content through larval development in normally and abnormally metamorphosing larvae. As GH is mainly found in the pituitary, GH contents were analyzed in tissue extracts from the heads only. The pituitary GH content increases proportionally to increased larval weight from first feeding to metamorphic climax. No difference in relative GH content was found between normal and abnormal larvae and it still remains to be established if GH has a direct role in metamorphosis.
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18.
  • Elofsson, Ulf, et al. (författare)
  • Intermale competition in sexually mature arctic charr : effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior.
  • 2000
  • Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 118:3, s. 450-60
  • Tidskriftsartikel (refereegranskat)abstract
    • Sexually mature Arctic charr (Salvelinus alpinus) males were allowed to interact in pairs for 4 days in the absence of females. Agonistic behavior was quantified, and at the end of the experiment, plasma levels of glucose, cortisol, testosterone (T), 11-ketotestosterone (11-KT), and 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha, 20beta-P) were determined alongside brain concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA, the major 5-HT metabolite), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC, a major DA metabolite). Plasma cortisol and glucose were significantly elevated in subordinate fish, and the number of aggressive acts received showed positive correlations with plasma levels of glucose on day 1, during the development of the dominance relationship, and of cortisol on day 4, when the dominance relationship was established. In contrast, plasma concentrations of T and 11-KT were significantly higher in dominant than in subordinate males, and there was a similar tendency in plasma concentrations of 17alpha,20beta-P. Further, plasma levels of these gonadal steroids were correlated with the number of aggressive acts performed on day 4, but not with the number of aggressive acts received. The plasma cortisol concentrations did not correlate with either 5-HIAA:5-HT or DOPAC:DA ratios in any of the brain parts analyzed. Plasma glucose levels showed positive correlations with brain 5-HIAA:5-HT ratios. Negative correlations were observed between 5-HIAA:5-HT ratios in the optic tectum and between plasma levels of T, 11-KT, and 17alpha,20beta-P. Telencephalic DOPAC/DA ratios displayed a negative correlation with plasma levels of T, 11-KT, and 17alpha,20beta-P, but only in dominant males.
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19.
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20.
  • Fahlman, Åsa (författare)
  • Cortisol and corticosterone independence in cortisol-dominant wildlife
  • 2012
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 177, s. 113-119
  • Tidskriftsartikel (refereegranskat)abstract
    • Species have traditionally been defined as cortisol-dominant or corticosterone-dominant, depending on the glucocorticoid that is reported. To assess the degree of covariance versus independence between cortisol and corticosterone, 245 serum samples belonging to 219 individuals from 18 cortisol-dominant, non-domesticated species (6 mammalian orders) were compared by mass spectrometry. In these samples, which were elevated above baseline, concentration ranges were overlapping for cortisol and corticosterone although cortisol was dominant in every sample except one of 17 bighorn sheep with a corticosterone-biased cortisol-to-corticosterone ratio of 0.17. As expected, cortisol and corticosterone were strongly associated among species (r(2) = 0.8; species with high absolute cortisol tend to have high absolute corticosterone concentrations), with wide variation in the species-average cortisol-to-corticosterone ratio (range 7.5-49) and an even wider ratio range across individuals (0.2-341). However, only 9 out of 13 species with >7 individuals showed a positive association between cortisol and corticosterone among individuals, and repeated measures of the cortisol-to-corticosterone ratio within individuals were weakly associated (CV range 3-136%). We conclude that corticosterone, although at lower concentrations, has the potential to signal independently of cortisol, and should be included in integrated endocrine models of stress responses. (C) 2012 Elsevier Inc. All rights reserved.
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21.
  • Froiland, E., et al. (författare)
  • Seasonal appetite regulation in the anadromous Arctic charr: Evidence for a role of adiposity in the regulation of appetite but not for leptin in signalling adiposity
  • 2012
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 178:2, s. 330-337
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to investigate whether the seasonal feeding cycle of the anadromous Arctic charr (Salvelinus alpinus) is regulated by a lipostatic mechanism and if leptin (Lep) might act as an endocrine signal of adiposity. Offspring of anadromous Arctic charr with a body mass of 121 g were divided into two treatment groups; one was given feed in excess from March to November. and the other was fasted between April and early June and fed in excess thereafter. In the continuously fed group there was an 8-fold increase in body mass, and a doubling of percentage body fat, from March to August, after which there was no further increase. Fish in the other group lost weight and body fat during fasting, but grew rapidly on being fed, and had partially compensated for their deficit in body mass by August. Differences in percentage body fat between treatment groups were eliminated by August. providing evidence for a lipostatic regulation of feeding and energy homeostasis in Arctic charr. Neither liver total LepA gene expression nor plasma Lep concentrations correlated positively with fish adiposity, so there was no evidence that Lep acts as a signal of adiposity in this species. On the other hand, there was a strong increase in liver LepA1 gene expression at the end of the fasting period, concomitant with fat mobilization and increased plasma glucose, indicating that LepA1 may play a role in regulating metabolic processes associated with fasting. (C) 2012 Elsevier Inc. All rights reserved.
  •  
22.
  • Fuentes, E. N., et al. (författare)
  • Nutritional status modulates plasma leptin, AMPK and TOR activation, and mitochondrial biogenesis: Implications for cell metabolism and growth in skeletal muscle of the fine flounder
  • 2013
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 186, s. 172-180
  • Tidskriftsartikel (refereegranskat)abstract
    • Insight of how growth and metabolism in skeletal muscle are related is still lacking in early vertebrates. In this context, molecules involved in these processes, such as leptin, AMP-activated protein kinase (AMPK), target of rapamicyn (TOR), peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α, and oxidative phosphorylation complexes (OXPHOS), were assessed in the skeletal muscle of a fish species. Periods of fasting followed by a period of refeeding were implemented, using the fine flounder as a model (Paralichthys adspersus). This species exhibits remarkably slow growth and food intake, which is linked to an inherent growth hormone (GH) resistance and high circulating levels of leptin. Leptin increased during fasting concomitantly with AMPK activation, which was inversely correlated with TOR activation. On the other hand, AMPK was directly correlated with an increase in PGC-1α and OXPHOS complexes contents. Dramatic changes in the activation and content of these molecules were observed during short-term refeeding. Leptin, AMPK activation, and PGC-1α/OXPHOS complexes contents decreased radically; whereas, TOR activation increased significantly. During long-term refeeding these molecules returned to basal levels. These results suggest that there is a relation among these components; thus, during fasting periods ATP-consuming biosynthetic pathways are repressed and alternative sources of ATP/energy are promoted, a phenomenon that is reversed during anabolic periods. These results provide novel insight on the control of metabolism and growth in the skeletal muscle of a non-mammalian species, suggesting that both processes in fish muscle are closely related and coordinated by a subset of common molecules.
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23.
  • Fuentes, E. N., et al. (författare)
  • Plasma leptin and growth hormone levels in the fine flounder (Paralichthys adspersus) increase gradually during fasting and decline rapidly after refeeding
  • 2012
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 177:1, s. 120-127
  • Tidskriftsartikel (refereegranskat)abstract
    • In fish, recent studies have indicated an anorexigenic role of leptin and thus its possible involvement in regulation of energy balance and growth. In the present study, the effects of fasting and refeeding periods on plasma leptin levels were studied in the fine flounder, a flatfish with remarkably slow growth. To further assess the endocrine status of the fish during periods of catabolism and anabolism, plasma growth hormone (GH) levels were also analyzed. Under normal feeding condition, plasma leptin and CH levels remained stable and relatively high in comparison with other teleost species. For the three separate groups of fish, fasted for 2, 3, and 4 weeks, respectively, plasma leptin levels increase gradually, becoming significantly elevated after 3 weeks, and reaching highest levels after 4-week fasting. Plasma GH levels were significantly elevated after 2-week fasting. At the onset of refeeding, following a single meal, leptin levels decline rapidly to lower than initial levels within 2 h, irrespective of the length of fasting. Plasma GH also decline, the decrease being significant after 4, 24 and 2 h for the 2, 3 and 4-week fasted groups, respectively. This study shows that plasma leptin levels in the fine flounder are strongly linked to nutritional status and suggests that leptin secretion is regulated by fast-acting mechanisms. Elevated leptin levels in fasted fish may contribute to a passive survival strategy of species which experience natural food shortage periods by lowering appetite and limiting physical foraging activity. (C) 2012 Elsevier Inc. All rights reserved.
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24.
  • Fuentes, E. N., et al. (författare)
  • Regulation of skeletal muscle growth in fish by the growth hormone - Insulin-like growth factor system
  • 2013
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 192, s. 136-148
  • Tidskriftsartikel (refereegranskat)abstract
    • The growth hormone (GH)-insulin-like growth factor (IGF) system is the key promoter of growth in vertebrates; however, how this system modulates muscle mass in fish is just recently becoming elucidated. In fish, the GH induces muscle growth by modulating the expression of several genes belonging to the myostatin (MSTN), atrophy, GH, and IGF systems as well as myogenic regulatory factors (MRFs). The GH controls the expression of igf1 via Janus kinase 2 (JAK2)/signal transducers and activators of the transcription 5 (STAT5) signaling pathway, but it seems that it is not the major regulator. These mild effects of the GH on igf1 expression in fish muscle seem to be related with the presence of higher contents of truncated GH receptor1 (tGHR1) than full length GHR (flGHR1). IGFs in fish stimulate myogenic cell proliferation, differentiation, and protein synthesis through the MAPK/ERK and PI3K/AKT/TOR signaling pathways, concomitant with abolishing protein degradation and atrophy via the PI3K/AKT/FOXO signaling pathway. Besides these signaling pathways control the expression of several genes belonging to the atrophy and IGF systems. Particularly, IGFs and amino acid control the expression of igf1, thus, suggesting other of alternative signaling pathways regulating the transcription of this growth factor. The possible role of IGF binding proteins (IGFBPs) and the contribution of muscle-derived versus hepatic-produced IGF1 on fish muscle growth is also addressed. Thus, a comprehensive overview on the GH-IGF system regulating fish skeletal muscle growth is presented, as well as perspectives for future research in this field.
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25.
  • Fuentes, E. N., et al. (författare)
  • The TORC1/P70S6K and TORC1/4EBP1 signaling pathways have a stronger contribution on skeletal muscle growth than MAPK/ERK in an early vertebrate: Differential involvement of the IGF system and atrogenes
  • 2015
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 210, s. 96-106
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge about the underlying mechanisms, particularly the signaling pathways that account for muscle growth in vivo in early vertebrates is still scarce. Fish (Paralichthys adspersus) were fasted for 3 weeks to induce a catabolic period of strong muscle atrophy. Subsequently, fish were refed for 2 weeks to induce compensatory muscle hypertrophy. During refeeding, the fish were treated daily with either rapamycin (TORC blocker), P098059 (MEK blocker), or PBS (V; vehicle), or were untreated (C; control). Rapamycin and P098059 differentially impaired muscle cellularity in vivo, growth performance, and the expression of growth-related genes, and the inhibition of TORC1 had a greater impact on fish muscle growth than the inhibition of MAPK. Blocking TORC1 inhibited the phosphorylation of P70S6K and 4EBP1, two downstream components activated by TORC1, thus affecting protein contents in muscle. Concomitantly, the gene expression in muscle of igf-1, 2 and igfbp-4, 5 was down-regulated while the expression of atrogin-1, murf-1, and igfbp-2, 3 was up-regulated. Muscle hypertrophy was abolished and muscle atrophy was promoted, which finally affected body weight. TORC2 complex was not affected by rapamycin. On the other hand, the PD98059 treatment triggered ERK inactivation, a downstream component activated by MEK. mRNA contents of igf-1 in muscle were down-regulated, and muscle hypertrophy was partially impaired. The present study provides the first direct data on the in vivo contribution of TORC1/P70S6K, TORC1/4EBP1, and MAPK/ERK signaling pathways in the skeletal muscle of an earlier vertebrate, and highlights the transcendental role of TORC1 in growth from the cellular to organism level. (C) 2014 Elsevier Inc. All rights reserved.
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26.
  • Gong, Ningping, 1979, et al. (författare)
  • Impaired central leptin signaling and sensitivity in rainbow trout with high muscle adiposity
  • 2016
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 235, s. 48-56
  • Tidskriftsartikel (refereegranskat)abstract
    • The hormone leptin has been identified in all vertebrate classes, but its physiological roles in non-mammalian vertebrates are not well defined. To elucidate leptin regulation in energy homeostasis in a teleost fish species, this study compares hypothalamic and pituitary leptin signaling systems in energetically divergent rainbow trout lines selected for low (lean line, LL) and high (fat line, FL) muscle adiposity under feeding and starvation conditions. In fed fish, hypothalamic gene expression and protein density of the full-functional leptin receptor (LepRL), as well as a leptin binding protein (LepBP) expression, are lower in FL than LL fish. The FL fish have also lower activation of leptin-relevant signaling pathways involving protein kinase B (Akt) and extracellular signal-related kinase. These observations suggests impaired central leptin action in FL fish. During fasting, hypothalamic LepRL and LepBP expression, as well as active Akt levels are downregulated after one week, while pituitary LepRL expression is upregulated, in the LL fish only. After four weeks, hypothalamic LepRL protein levels return to normal levels in both fish lines and Akt is reactivated, although not to the same extent in FL as in LL fish, indicating that FL fish have low leptin sensitivity to nutritional changes. Neuropeptide Y and orexin expression is downregulated to similar levels in both fish lines after one-week fasting. The divergent leptin system profiles between the two fish lines demonstrate that phenotypic selection for high muscle adiposity affects leptin endocrinology, indicating regulatory roles for leptin in rainbow trout energy homeostasis. © 2016 Elsevier Inc.
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27.
  • Hallgren, Stefan, 1978-, et al. (författare)
  • Inhibition of cytochrome p450 brain aromatase reduces two male specific sexual behaviours in the male Endler guppy (Poecilia reticulata)
  • 2006
  • Ingår i: General and Comparative Endocrinology. - Amsterdam, The Netherlands : Elsevier. - 0016-6480 .- 1095-6840. ; 147:3, s. 323-328
  • Tidskriftsartikel (refereegranskat)abstract
    • In mammalian and avian vertebrate groups, androgens act as controlling agents on male aggression and courtship behaviour by their conversion to oestrogens by cytochrome P450 aromatase in well-defined brain regions. Despite the fact that bony fishes have exceptionally high brain aromatase activity, little is known about it’s possible regulatory effects on the reproductive behaviours of teleosts. In this study, Endler guppy males (Poecilia reticulata) were subjected to 26–29 days of 24-h exposure to two different concentrations (15 and 100 μg/L) of the aromatase inhibitor fadrozole in the water. Compared with the control males, two of three courtship activities in males exposed to the higher concentration were reduced when they were paired with receptive stimulus females. Reduction in brain aromatase activity was confirmed in both exposed groups with the use of the tritiated water assay.
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28.
  •  
29.
  • Henriksen, Rie, et al. (författare)
  • Maternal corticosterone elevation during egg formation in chickens (Gallus gallus domesticus) influences offspring traits, partly via prenatal undernutrition
  • 2013
  • Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 191, s. 83-91
  • Tidskriftsartikel (refereegranskat)abstract
    • The relationship between maternal stress during pregnancy in humans and the subsequent physical and mental health disorders in their children has inspired a wide array of studies on animal models. Almost all of these studies have used mammalian species, but more recently oviparous species in which the embryo develops outside the mothers body have received more attention. These new models facilitate disentangling of the underlying mechanism due to the accessibility of the prenatal environment, the egg. Studies in birds have found that maternal stress during egg formation induces phenotypic alterations in the offspring that hatch from these eggs. However, different offspring traits have been measured in different studies and potential underlying mechanisms are barely addressed. In this study we experimentally manipulated maternal corticosterone levels in laying hens. We found that mothers with experimentally elevated plasma corticosterone levels produced offspring that are smaller at hatching, less competitive, less fearful, have lower immunocompetence and higher plasma testosterone levels, as well as an alteration of visually guided behavioural lateralization. Earlier we have showed that eggs produced by these corticosterone treated mothers were lighter and contained lower concentrations of testosterone and progesterone in the yolk. While yolk hormones showed no correlation with any offspring traits, egg mass correlated positively with offsprings body mass from hatching until 10 days of age and hatching mass correlated positively with the offsprings ability to compete for food, indicating that prenatal under nutrition might mediate some effects of maternal stress.
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30.
  • Hildahl, Jon, 1976, et al. (författare)
  • Cloning of Atlantic halibut growth hormone receptor genes and quantitative gene expression during metamorphosis
  • 2007
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 151:2, s. 143-152
  • Tidskriftsartikel (refereegranskat)abstract
    • To gain insight into the possible regulatory role of the growth hormone (GH)-insulin-like growth factor I (IGF-I) system in flatfish metamorphosis, body GHR gene expression as well as IGF-I protein content was quantified in larval Atlantic halibut throughout metamorphosis (developmental stages 5–10). The cDNA of the full-length GH receptor (hhGHR) was cloned from adult liver and characterized. The hhGHR shows common features of a GHR, including a (Y/F)GEFS motif in the extracellular domain, a single transmembrane region, and an intracellular domain containing a Box 1 and Box 2. Additionally, a truncated GHR (hhGHRtr), similar to turbot and Japanese flounder GHRtr, was cloned and sequenced. These sequences are highly similar to the full-length and truncated GHRs in turbot (89%/86%) and Japanese flounder (93%/91%) with lower identity with other fish type I GHR (less-than-or-equals, slant81%) and type II GHRs (less-than-or-equals, slant58%). A quantitative real-time RT-PCR assay was used to measure hhGHR and hhGHRtr mRNA content in normally and abnormally metamorphosed individuals at six developmental stages, from early pre-metamorphosis to post-metamorphosis, when the fish is considered a juvenile. The level of hhGHR gene expression was highest at pre-metamorphic stage 6 and at stage 8 at the onset of metamorphosis, and then decreased during metamorphic climax and post-metamorphosis. Expression of hhGHRtr reached highest levels at stage 6 and then decreased to post-metamorphosis. The ratio of expression between the full-length and the truncated GHR (hhGHR:hhGHRtr) varied among stages and was highest at the onset of metamorphosis and at metamorphic climax. A radioimmunoassay was used to measure halibut IGF-I body content throughout metamorphosis. IGF-I increases from early metamorphosis to the onset of metamorphosis and then decreases towards post-metamorphosis. In comparison between normally and abnormally metamorphosing larvae, IGF-I content, hhGHR and hhGHRtr mRNA levels were reduced in the abnormal fish. These data indicate that the GH-IGF-I system either has a regulatory role in metamorphosis, or is being affected as a consequence of the abnormal metamorphosis.
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31.
  • Ingberg, Edvin, 1988-, et al. (författare)
  • Methods for long-term 17β-estradiol administration to mice
  • 2012
  • Ingår i: General and Comparative Endocrinology. - Maryland Heigths, USA : Elsevier. - 0016-6480 .- 1095-6840. ; 175:1, s. 188-193
  • Tidskriftsartikel (refereegranskat)abstract
    • Rodent models constitute a cornerstone in the elucidation of the effects and biological mechanisms of 17β-estradiol. However, a thorough assessment of the methods for long-term administration of 17β-estradiol to mice is lacking. The fact that 17β-estradiol has been demonstrated to exert different effects depending on dose emphasizes the need for validated administration regimens. Therefore, 169 female C57BL/6 mice were ovariectomized and administered 17β-estradiol using one of the two commonly used subcutaneous methods; slow-release pellets (0.18 mg, 60-day release pellets; 0.72 mg, 90-day release pellets) and silastic capsules (with/without convalescence period, silastic laboratory tubing, inner/outer diameter: 1.575/3.175 mm, filled with a 14 mm column of 36 μg 17β-estradiol/mL sesame oil), or a novel peroral method (56 μg 17β-estradiol/day/kg body weight in the hazelnut cream Nutella). Forty animals were used as ovariectomized and intact controls. Serum samples were obtained weekly for five weeks and 17β-estradiol concentrations were measured using radioimmunoassay. The peroral method resulted in steady concentrations within--except on one occasion--the physiological range and the silastic capsules produced predominantly physiological concentrations, although exceeding the range by maximum a factor three during the first three weeks. The 0.18 mg pellet yielded initial concentrations an order of magnitude higher than the physiological range, which then decreased drastically, and the 0.72 mg pellet produced between 18 and 40 times higher concentrations than the physiological range during the entire experiment. The peroral method and silastic capsules described in this article constitute reliable modes of administration of 17β-estradiol, superior to the widely used commercial pellets.
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32.
  • Jansson, Erika, et al. (författare)
  • Sex-dependent expression of anti-Müllerian hormone (amh) and amh receptor 2 during sex organ differentiation and characterization of the Müllerian duct development in Xenopus tropicalis
  • 2016
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 229, s. 132-144
  • Tidskriftsartikel (refereegranskat)abstract
    • Amphibian gonadal differentiation involves the action of sex steroids. Recent research indicates that the anti-Müllerian hormone (AMH) is involved in testicular development in some lower vertebrate species. For amphibians there is a lack of data on ontogenetic expression of the AMH receptor AMHR2/amhr2 and of progesterone receptors (PGRS/pgrs). Here we expand the knowledge on amphibian sex differentiation by characterizing ontogenetic mRNA levels of amh, amhr2, intracellular and membrane pgrs (ipgr and mpgr beta) and cytochrome P450 19a1 (cyp19a1) (ovarian marker) in the urogenital complex of the model species Xenopus (Silurana) tropicalis. Furthermore, we characterized the ontogenetic development of the Müllerian ducts (precursors of the female reproductive tract) histologically. The developmental period investigated spanned from beginning of gonadal differentiation, Nieuwkoop and Faber (NF) stage 51, to 4weeks post-metamorphosis. The Müllerian ducts were first observed at NF 64 in both sexes. Male-enhanced amh mRNA levels from NF 53/54 to 6days post-metamorphosis and female-enhanced cyp19a1 levels from NF 53 to 4weeks post-metamorphosis were noted. The sexually dimorphic mRNA level profile was more distinct for amh than for cyp19a1. The pgrs mRNA levels increased over the studied period and showed no sex differences. At later developmental stages, the amhr2 mRNA level was increased in putative females compared with males. Our findings suggest that AMH has a role in gonadal differentiation in X. tropicalis. We propose relative gonadal amh mRNA level as a testicular marker during early gonadal development in amphibians.
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33.
  • Jenni-Eiermann, Susanne, et al. (författare)
  • Are birds stressed during long-term flights? A wind-tunnel study on circulating corticosterone in the red knot
  • 2009
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 164:2-3, s. 101-106
  • Tidskriftsartikel (refereegranskat)abstract
    • During endurance flight most birds do not feed and have to rely on their body reserves. Fat and protein is catabolised to meet the high energetic demands. Even though the hormonal regulation of migration is complex and not yet fully understood. the adrenocortical hormone corticosterone crystallizes to play a major role in controlling physiological traits in migratory birds during flight. However, results from field studies are partially equivocal, not least because data from birds during endurance flight are hard to get and present mostly a momentary shot. A wind-tunnel experiment offered the possibility to measure repeatedly under controlled conditions the effect of long flights on the stress hormone corticosterone. In a long-distance migrating shorebird, the red knot Calidris canutus, we measured plasma concentrations of corticosterone within 3 min and after a restraint time of 30 min directly after 2 h and 10 h non-stop flights, respectively, and during rest. Baseline corticosterone levels were unchanged directly after the flights, indicating that endurance flight did not affect corticosterone levels. The adrenocortical response to restraint showed the typical rise in birds during rest, while birds after a 2 or 10 h flight substantially decreased plasma corticosterone concentrations. We suggest that the negative adrenocortical response to restraint after flight is part of the mechanism to reduce the proteolytic effect of corticosterone to save muscle protein and to avoid muscle damaging effects. (C) 2009 Elsevier Inc. All rights reserved.
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34.
  • Johansson, Marcus, 1982, et al. (författare)
  • Elevated plasma leptin levels of fasted rainbow trout decrease rapidly in response to feed intake
  • 2015
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 214, s. 24-29
  • Tidskriftsartikel (refereegranskat)abstract
    • Leptin has an anorexigenic effect in fish, indicating a role in regulation of growth and energy homeostasis. The study aimed to further clarify the physiological role of leptin in rainbow trout, specifically its short-term response to feed intake after a period of fasting. Utilizing a salmonid leptin radioimmunoassay, the study demonstrates differences in plasma leptin levels in fishes with different nutritional status and at the onset of feeding. Some of the fasted fish were clearly in a state of anorexia, and did not initiate feeding during the 72 h refeeding period. For those fish that did initiate feeding, both previously fed and fasted, plasma leptin levels rapidly decreased during the first 24 h in correlation with increased amount of food reaching the gastrointestinal tract, while non-feeding individuals retained a high plasma leptin levels. The data indicate that the leptin-induced anorexic state is broken after onset of feeding and that the regulatory mechanisms leading to decreased plasma leptin levels are linked to nutrient levels.
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35.
  • Johansson, Viktoria, 1972, et al. (författare)
  • Growth hormone-induced stimulation of swimming and feeding behaviour of rainbow trout is abolished by the D-1 dopamine antagonist SCH23390
  • 2005
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 141:1, s. 58-65
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of GH on various types of behaviour in fish are well documented although the underlying mechanisms are not fully understood. In rainbow trout, an involvement of the brain dopaminergic system in mediating the behavioural effects of GH has been indicated, as GH can alter the brain doparninergic activity. To further examine the role of the dopaminergic system in the mediation of GH effects on locomotion and foraging, GH- and sham-implanted juvenile rainbow trout were injected with the selective D, dopamine antagonist SCH23390 or vehicle. Swimming and feeding activity was then studied by direct observation. Brains were thereafter sampled and analysed for the content of serotonin, dopamine and their metabolites in the hypothalamus, optic tecturn, cerebellum, telencephalon, and brain stem. GH increased swimming activity as well as feed intake, effects which were abolished by SCH23390. By itself, the antagonist did not affect behaviour, nor did it affect the brain monoamines. In contrast, treatment with GH, with or without SCH23390, decreased the content of the dopamine metabolite homovanillic acid (HVA) in the optic tecturn and the cerebellum, as well as the serotomin content (5-HT) in the optic tectum. It is concluded that the D-1 dopamine receptor of the dopaminergic system appears to be of importance in the mediation of the effects of GH on behaviour. (C) 2004 Elsevier Inc. All rights reserved.
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36.
  • Jönsson, Elisabeth, 1968, et al. (författare)
  • Circulating levels of cholecystokinin and gastrin-releasing peptide in rainbow trout fed different diets.
  • 2006
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 148:2, s. 187-194
  • Tidskriftsartikel (refereegranskat)abstract
    • Cholecystokinin (CCK) and gastrin-releasing peptide (GRP) are gastrointestinal peptides thought to be important regulators of intake and digestion of food in vertebrates. In this study, pre- and postprandial plasma levels of CCK and GRP were measured in rainbow trout (Oncorhynchus mykiss) by the establishment of homologous radioimmunoassays, and the hormonal levels assessed in relation to dietary lipid:protein ratio and food intake. Fish were acclimated to either a high protein/low lipid diet (HP/LL diet; 14.1% lipids) or a normal protein/high lipid diet (NP/HL diet; 31.4% lipids). On three consecutive sampling days, radio-dense lead-glass beads were included in the diets for assessment of feed intake. Fish were terminally sampled for blood and stomach contents prior to feeding at time 0, and at 0.3, 1, 2, 4, 6, and 24 h after feeding. There was a postprandial elevation of plasma CCK levels, which was most evident after 4 and 6 h. Fish fed the NP/HL diet had higher plasma CCK levels compared with those fed the HP/LL diet. Plasma CCK levels were not affected by the amount of food ingested. GRP levels in plasma were not influenced by sampling time, diet, or feed intake. The results indicate that the endocrine release of gastrointestinal CCK is increased during feeding and may be further influenced by the dietary lipid:protein ratio in rainbow trout. Plasma GRP levels, on the other hand, appear not to be influenced by feeding or diet composition.
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37.
  • Jönsson, Elisabeth, 1968, et al. (författare)
  • Ghrelin decreases food intake in juvenile rainbow trout (Oncorhynchus mykiss) through the central anorexigenic corticotropin-releasing factor system
  • 2010
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 166:166, s. 39-46
  • Tidskriftsartikel (refereegranskat)abstract
    • Ghrelin stimulates pituitary growth hormone (GH) release, and has a key role in the regulation of food intake and adiposity in vertebrates. To investigate the central effect of native rainbow trout ghrelin (rtghrelin) on food intake in rainbow trout, as well as its possible mode of action, four groups of fish received a single injection into the third brain ventricle (i.c.v. injection): (1) control group (physiological saline) (2) ghrelin-treated group (2.0 ng rtghrelin g bwt−1), (3) group given the corticotropin-releasing hormone receptor antagonist α-helical CRF 9–41 (ahCRF) (4.0 ng g bwt−1) and (4) group receiving the same dose of both ghrelin and ahCRF. Food intake was assessed 1 h after treatment. In addition, the presence of the GHS-R (the ghrelin receptor) in the rainbow trout CNS was examined with Western blot. To investigate peripheral effects of ghrelin, rainbow trout received an intraperitoneal cholesterol-based implant with or without rtghrelin, and daily food intake was measured during 14 days. Weight and length were measured at the start and termination of the experiment and specific growth rates were calculated. Mesenteric fat stores, muscle and liver lipid content were analysed after the treatment period. Central ghrelin injections decreased food intake compared with controls, and treatment with ahCRF abolished the ghrelin-effect. Western blot analysis of the GHS-R revealed a single band at around 60 kDa in pituitary, hypothalamus, brain and stomach. Long-term peripheral ghrelin treatment decreased daily food intake compared with controls. This was reflected in a ghrelin-induced decrease in weight growth rate (p < 0.06). There was no effect of ghrelin on plasma GH levels or tissue fat stores. The conclusion from this study is that the GHS-R is indicated in the CNS in rainbow trout and that ghrelin may act there as an anorexigenic hormone, through a CRF-mediated pathway. Elevated peripheral ghrelin levels also seem to lead to decreased feed intake in the longer term.
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38.
  • Jönsson, Elisabeth, 1968 (författare)
  • The role of ghrelin in energy balance regulation in fish
  • 2013
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 187, s. 79-85
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge about the endocrine regulation of energy balance in fish is of interest for basic as well as aquaculture research. Ghrelin is a peptide hormone that was first identified in fish 10 years ago and has important roles in the control of food intake and metabolism. Both ghrelin and its receptor, the growth hormone secretagogue receptor (GHS-R), have been found in numerous fish species. Their tissue distributions support the idea that ghrelin has an integrative role in the regulation of energy balance at both the central nervous system level and systemic level. In tilapia and goldfish, ghrelin treatment appears to increase food intake and to stimulate lipogenesis and tissue fat deposition to promote a more positive energy status. In rainbow trout, on the other hand, ghrelin decreases food intake. Goldfish and rainbow trout are the fish species in which the mode of action of ghrelin on food intake has been most thoroughly investigated. The results from these studies indicate that ghrelin alters food intake by acting on well-known appetite signals, such as CRH, NPY and orexin, in the hypothalamus in a species-specific manner. In goldfish, sensory fibres of the vagus nerve convey the signal from gut-derived ghrelin to modulate appetite. The data also indicate that ghrelin may modulate foraging/swimming activity and the perception of food in fish. Results related to the effects of energy status, temperature, and stressors on plasma ghrelin/tissue ghrelin mRNA levels are occasionally inconsistent between short- and long-term studies, between the protein and mRNA, and between species. Recent data also imply a role of ghrelin in carbohydrate metabolism. More functional studies are required to understand the role of ghrelin and its mechanisms of action in the regulation of energy balance among fish.
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39.
  • Kalliokoski, Otto, et al. (författare)
  • Distribution and time course of corticosterone excretion in faeces and urine of female mice with varying systemic concentrations
  • 2010
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 168:3, s. 450-454
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantification of corticosterone metabolites excreted in faeces and urine is increasingly being used for assessment of preceding corticosterone concentrations in the circulation. This is a promising approach to non-invasive stress assessment in laboratory rodents. It is however unknown whether the proportions of corticosterone metabolites excreted in faeces and urine may differ, depending on the concentration of corticosterone in blood. This uncertainty undermines the applicability of urinary and faecal corticosterone metabolite measurements as biomarkers for stress. Therefore, the terminal distribution and time course of corticosterone excretion, after intravenous injection of varying corticosterone concentrations, was investigated in female mice. Female BALB/c mice excreted 60% of all corticosterone in the urine with an approximate delay of 5 h from tail vein administration. The remaining 40% were excreted in faeces, with an approximate delay of 9 h from administration. The faecal/urinary excretion ratio, as well as time course of excretion, remained unaltered by administration of various doses of corticosterone covering the entire physiological range of serum corticosterone. Although currently untested for other strains of mice and species of animals, these findings add credence to the utility of faecal and urinary corticosterone as non-invasive biomarkers for physiological stress.
  •  
40.
  • Karlsson, Anna-Carin, et al. (författare)
  • A domestication related mutation in the thyroid stimulating hormone receptor gene (TSHR) modulates photoperiodic response and reproduction in chickens
  • 2016
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 228, s. 69-78
  • Tidskriftsartikel (refereegranskat)abstract
    • The thyroid stimulating hormone receptor gene (TSHR) has been suggested to be a "domestication locus" in the chicken. A strong selective sweep over TSHR in domestic breeds together with significant effects of a mutation in the gene on several domestication related traits, indicate that the gene has been important for chicken domestication. TSHR plays a key role in the signal transduction of seasonal reproduction, which is characteristically less strict in domestic animals. We used birds from an advanced intercross line between ancestral Red Junglefowl (RJF) and domesticated White Leghorn (WL) to investigate effects of the mutation on reproductive traits as well as on TSHB, TSHR, DIO2 and DIO3 gene expression during altered day length (photoperiod). We bred chickens homozygous for either the mutation (d/d) or wild type allele (w/w), allowing assessment of the effect of genotype at this locus while also controlling for background variation in the rest of the genome. TSHR gene expression in brain was significantly lower in both did females and males and did females showed a faster onset of egg laying at sexual maturity than wow. Furthermore, did males showed a reduced testicular size response to decreased day length, and lower levels of TSHB and DIO3 expression. Additionally, purebred White Leghorn females kept under natural short day length in Sweden during December had active ovaries and lower levels of TSHR and DIO3 expression compared to Red Junglefowl females kept under similar conditions. Our study indicates that the TSHR mutation affects photoperiodic response in chicken by reducing dependence of seasonal reproduction, a typical domestication feature, and may therefore have been important for chicken domestication.
  •  
41.
  • Kling, Peter, 1968, et al. (författare)
  • The role of GH in lipid homeostasis, energy utilization and partitioning in rainbow trout: interactions with ghrelin, leptin and insulin-like growth factor I
  • 2012
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 175:1, s. 153-162
  • Tidskriftsartikel (refereegranskat)abstract
    • The growth-promoting effects of in vivo growth hormone (GH) treatment were studied in relation to size and lipid content of energy stores including liver, mesentery, white muscle and belly flap in rainbow trout. In order to elucidate endocrine interactions and links to regulation of growth, adiposity and energy metabolism, plasma levels of GH, insulin-like growth factor I (IGF-I), leptin (Lep) and ghrelin, were assessed and correlated to growth and energy status. In addition tissue-specific expression of lepa1 mRNA was examined. Juvenile rainbow trout were implanted with sustained-release bovine GH implants and terminally sub-sampled at 1, 3 and 6 weeks. GH increased specific growth rate, reduced condition factor (CF) and increased feed conversion efficiency resulting in a redistribution of energy stores. Thus, GH decreased mesenteric (MSI) and liver somatic index (LSI). Lipid content of the belly flap increased following GH-treatment while liver and muscle lipid content decreased. Independent of GH substantial growth was accompanied by an increase in muscle lipids and a decrease in belly flap lipids. The data suggest that the belly flap may function as an energy buffering tissue during episodes of feeding and lean growth. Liver and muscle lipids were positively correlated to body weight, indicating a size-dependent change in adiposity. Hepatic lepa1 mRNA positively correlated to MSI and CF and its expression decreased following GH treatment, coinciding with decreased hepatic lipid content. Plasma Lep was positively correlated to MSI and belly flap lipid content, suggesting that Lep may communicate energy status. In summary, the observed GH tissue-specific effects on lipid metabolism in rainbow trout highlight the complex physiology of the energy reserves and their endocrine control.
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42.
  • Kobayashi, Yuki, et al. (författare)
  • Differential expressions of melanocortin receptor subtypes in melanophores and xanthophores of barfin flounder
  • 2010
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 168:1, s. 133-142
  • Tidskriftsartikel (refereegranskat)abstract
    • alpha-Melanocyte-stimulating hormone (alpha-MSH) is a member of the melanocortin (MC) family, and the MC receptor (MCR) is a member of the G protein-coupled receptor (GPCR) superfamily. We previously found that in barfin flounder, a flatfish, alpha-MSH with an acetyl group at the N-terminus stimulated pigment dispersion in xanthophores; however, this effect was not observed in melanophores. Therefore, the present study was undertaken to find which MCR subtypes are expressed in these pigment cells in order to elucidate how acetylation regulates activities of alpha-MSH-related peptides. Here, we also report the cloning of Mc1r and Mc5r from barfin flounder. Three types of cells-melanophores, xanthophores, and nonchromatophoric dermal cells-were isolated from the skin samples collected from the dorsal fin. These cells were then tested for the expression of Mc1r and Mc5r as well as Mc2r and Mc4r that we had previously cloned. Mc1r and Mc5r transcripts were detected in melanophores, and a sole Mc5r transcript was detected in xanthophores. We had previously found that the efficiency of alpha-MSH was higher than that of desacetyl-alpha-MSH for pigment dispersion in xanthophores. Acetylated MSH peptide may have increased binding affinity to MC5R, whereas alpha-MSH lacks melanin-dispersing activity. Increasing evidences indicate that many GPCRs form heterodimers, and this may affect the affinity of the ligand for the corresponding GPCR. Taken together, the expression of two different Mcr subtypes in melanophores may suggest that a heterodimer consisting of MC1R and MC5R may have a low binding affinity toward alpha-MSH. The present results clarify the types of MCRs that are expressed in melanophores and xanthophores of barfin flounder; furthermore, the results provide important clues about the functional regulation of alpha-MSH-related peptides.
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43.
  • Kobayashi, Yuki, et al. (författare)
  • Food deprivation increases the expression of melanocortin-4 receptor in the liver of barfin flounder, Verasper moseri
  • 2008
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 155:2, s. 280-287
  • Tidskriftsartikel (refereegranskat)abstract
    • The melanocortin (MC) system is composed of melanocyte-stimulating hormone, adrenocorticotropic hormone and their receptors. The MC system has a role in both pigmentation and the regulation of energy homeostasis, in which MC4R, one of the five MC receptors, has a key role. Interestingly, the barfin flounder (Pleuronectiformes) reared with a black background shows retarded growth compared to white background-reared fish, which could be associated with the MC system because of its dual role in regulating pigmentation and energy status. Here, we cloned MC4R and assessed the effects of feeding status on its expression in barfin flounder. Barfin flounder MC4R. was composed of 325 amino acids and showed the highest sequence identity to MC4R of fugu (85%), followed by rainbow trout (82%), zebrafish (79%), goldfish (78%), dogfish (71%), chickens (67%), humans (67%) and mice (65%). Among 18 different tissues examined, the predominant expression of MC4R was observed in the brain, liver, testis and ovary as detected with reverse transcription PCR. Food deprivation resulted in a 4-fold increase in the number of MC4R transcripts in the liver, whereas no change was observed in the brain between fasted fish and fed controls. These results suggest that the NIC system including MC4R is associated with energy homeostasis in barfin flounder and that peripheral tissues could play a role in this regulation.
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44.
  • Kobayashi, Yuki, et al. (författare)
  • Melanocortin receptor subtypes in interrenal cells and corticotropic activity of α-melanocyte-stimulating hormones in barfin flounder, Verasper moseri
  • 2011
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 170:3, s. 558-568
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to characterize the pituitary-interrenal axis in barfin flounder, a flatfish. Adrenocorticotropic hormone (ACTH) and melanocortin 2 receptor (MC2R) have been shown to be indispensable substances in pituitary and interrenal cells for cortisol release, respectively. We previously identified ACTH in the pars distalis of the barfin flounder pituitary gland, and detected transcripts of Mc1r, Mc4r, and Mc5r in the head kidney wherein interrenal cells are located. We have now demonstrated the presence of MC2R, which is a specific receptor for ACTH, in interrenal cells by molecular cloning of Mc2r cDNA and in situ hybridization, and confirmation of the in vitro cortisol-releasing activity of ACTH. These results show the presence of a classical pituitary-interrenal axis in this fish. We also evaluated the role of α-melanocyte-stimulating hormone (α-MSH) and its related peptides. In situ hybridization was used to demonstrate the expression of Mc5r in interrenal cells; both desacetyl-α-MSH and diacetyl-α-MSH showed in vitro cortisol-releasing activities, while the activity of α-MSH was negligible. These findings indicate the presence of an additional pituitary-interrenal axis consisting of α-MSH-like peptides secreted from the neurointermediate lobe of the pituitary and MC5R in the interrenal cells. The cortisol-releasing activity of desacetyl-α-MSH and diacetyl-α-MSH, compared with the low activity of α-MSH, suggest a unique and specific functional role of these forms of MSH peptides. The interrenal co-expression of two subtypes of Mcrs may play a role in this specialization.
  •  
45.
  • Larhammar, Dan, et al. (författare)
  • Peptide hormone and receptor evolution
  • 2007
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 153:1-3, s. 147-
  • Tidskriftsartikel (refereegranskat)abstract
    • An important and fascinating theme that unifies both invertebrate and vertebrate endocrinologists is that of the evolution of peptide precursor and receptor genes. Peptide signalling plays a crucial role in processes that control decisive physiological events in organisms as divergent as yeast and mammals. The majority of small neuronal/endocrine peptides exert their functions via an interaction with heptahelical membrane receptors belonging to the G protein-coupled receptor superfamily, a large and diverse signal transducing protein category which has very ancient evolutionary roots. Most of the larger peptides and growth factors function via other well-conserved receptor classes that contain only a single transmembrane segment. The symposium on peptide hormone and receptor evolution brought together scientists studying peptide–receptor evolution in widely divergent metazoans. Two State-of-the-Art lectures gave overviews of current knowledge of peptide and receptor gene evolution. The sequencing and annotation of entire animal genomes constitutes a very exciting development that have already revolutionized the general views on metazoan macroevolution. The resulting burst of molecular data represents an impressive boost of novel opportunities for comparative and functional genomics research. Several vertebrate peptide and receptor families were described by Dan Larhammar to have multiplied in the 1–2 basal vertebrate tetraploidizations and in a third tetraploidization in ray-finned fishes before the radiation of teleosts. Families proposed to have multiplied in these events include NPY, tachykinins, opioid peptides, as well as the receptors for these three peptide families. The dynamics of coevolutionary change were discussed by Jozef Vanden Broeck based on several examples of peptide–receptor partners that show conservation across the protostomian–deuterostomian barrier. These examples include peptides belonging to the NPY, tachykinin, glycoprotein hormone and insulin-related peptide families, and their respective receptors. Additional examples of coevolution between peptides and their corresponding receptors in insects (the mosquito Aedes aegypti) and chelicerates (the tick Boophilus microplus) were presented by Ron Nachman. His detailed analysis of peptide receptor pharmacology has led to the production and selection of peptidomimetic compounds which specifically activate a particular receptor, while showing enhanced resistance against peptidases. This type of work may ultimately lead to the creation of novel, environmentally safe pest agents for insect management. In two other presentations, the evolution of two quite complex vertebrate peptide receptor systems were discussed. The five divergent and presumably ancient melanocortin receptors found in mammals have only three orthologues in the two sharks investigated so far (Angela Baron). Both the ά-MSH receptor MC1 and the ACTH receptor MC2 still remain to be identified or may have been lost or become widely divergent. The evolution of the large VIP/PACAP/secretin family (Florbela Vieira) involves duplicate PACAP genes in teleost fishes, whereas only a single VIP gene seems to exist. The PACAP gene and its chromosomal environment is more strongly conserved than the VIP gene. Invertebrates only have a single member most closely resembling PACAP. The concluding discussion largely revolved around the proposed tetraploidizations in early vertebrate evolution. While some hesitation still lingers, there is nevertheless no alternative explanation that can account better than the chromosome duplication (and tetraploidization) scenario for the extensive chromosome similarities and the high number of gene duplications that arose before gnathostomatous radiation. Additional gene duplications in early vertebrates were mentioned leading to the somatostatin 2-urotensin II gene pair and the somatostain 1-urotensin II-related peptide gene pair (Hervé Tostivint). Also the possible orthology relationships between peptides described in invertebrates, particularly insects, and vertebrates were discussed. Undoubtedly, definitive orthology relationships of neuropeptide precursor genes between protostomes and deuterostomes are often difficult to determine from sequence comparisons only, and will hopefully be aided by information on chromosome locations and gene neighbours.
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46.
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47.
  • Larsson, D. G. Joakim, 1969, et al. (författare)
  • Seasonal variations of vitelline envelope proteins, vitellogenin, and sex steroids in male and female eelpout (Zoarces viviparus).
  • 2002
  • Ingår i: General and comparative endocrinology. - : Elsevier BV. - 0016-6480. ; 125:2, s. 184-96
  • Tidskriftsartikel (refereegranskat)abstract
    • The seasonal variations of vitelline envelope proteins, vitellogenin (VTG), and reproductive steroids were investigated in feral male and female eelpout, Zoarces viviparus. 17beta-Estradiol was present in both sexes with a peak in prespawning fish of 2.6 ng/ml in males and 2.7 ng/ml in females. 11-Ketotestosterone peaked in June at 4.2 and 0.47 ng/ml in males and females, respectively. A surge of testosterone was seen in both sexes in August, just prior to spawning. All steroid levels were low during early pregnancy. The vitelline envelope of the eelpout is composed of two major and one minor protein with molecular weights of 50, 55, and 44 kDa, respectively. An antiserum raised against solubilized vitelline envelope from turbot (Scophthalmus maximus) cross-reacted strongly with the 50-kDa protein from the isolated vitelline envelope and a similar-sized protein in female plasma and plasma from estrogenized males. Interestingly, the 50-kDa protein was also present at low levels in males as demonstrated by ELISA and Western blotting. In males, the 50-kDa protein did not follow the seasonal changes in 17beta-estradiol, but instead showed an almost perfect negative correlation with water temperature. VTG was present in female plasma as shown by Western blotting, but VTG was not detectable in male plasma despite relatively high endogenous estrogen levels. This suggests that the VTG induction by estradiol may be modulated by other factors in the eelpout.
  •  
48.
  • Larsson, Tomas, et al. (författare)
  • Cloning and sequence analysis of the neuropeptide Y receptors Y5 and Y6 in the coelacanth Latimeria chalumnae
  • 2007
  • Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 150:2, s. 337-342
  • Tidskriftsartikel (refereegranskat)abstract
    • Two coelacanth species, Latimeria chalumnae and Latimeria menadoensis, the recently discovered second species, have a key evolutionary position at the divergence of bony fishes and tetrapods. Together with lungfishes, they are the only living species separating the species-rich tetrapods from the other major group of vertebrates, the ray-finned fishes. The coelacanth is therefore of great importance for comparisons of gene families that differ between these two groups, such as the neuropeptide Y (NPY) receptor family. In this work we have sequenced the full-length genes for two NPY receptors in Latimeria chalumnae. Phylogenetic analysis indicated that the two sequences are orthologs of the mammalian Y5 and Y6 receptors. The Y5 gene has been implicated in appetite stimulation in mammals but is absent from teleost fishes. The presence of the Y5 receptor in Latimeria together with phylogenetic analysis shows that Y5 existed before the separation of bony fishes and tetrapods. The Latimeria receptor has about 62 % identity to tetrapod Y5 sequences and contains the extended third intracellular loop with several highly conserved motifs that may be involved in signal transduction. The Latimeria Y6 receptor has about 60% identity to tetrapod Y6 sequences. The functional role of Y6 is unclear as the gene is seemingly functional in some mammals but is non-functional in others. The Y6 receptor is also missing in teleost fishes. Our results confirm an early vertebrate origin for all NPY receptor subtypes presently found in mammals followed by differential gene loss in the different classes of vertebrates.
  •  
49.
  • Lewander, Kerstin, et al. (författare)
  • Metabolic effects of insulin in the European eel, Anguilla anguilla L
  • 1976
  • Ingår i: General and Comparative Endocrinology. - 0016-6480 .- 1095-6840. ; 29:4, s. 455-467
  • Tidskriftsartikel (refereegranskat)abstract
    • Eels were injected intraperitoneally with insulin (100 IU/kg) and during 14 days the effects on different metabolites in blood, liver and muscle were studied. Exogenous insulin had a marked effect on carbohydrate metabolism. The observed changes (hypoglycemia, depletion of hepatic glycogen and an initial increase in muscle glycogen formation) indicate that insulin in eels induces effects on carbohydrate metabolism qualitatively similar to those found in mammals. Insulin also appears to have an important function in the regulation of lipid metabolism in eels, indicated by a rapid decrease in plasma FFA and a somewhat delayed decrease in other blood lipids. Protein metabolism and plasma inorganic ions were only slightly affected after insulin injection.
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50.
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