| 11. |
- Blixt, Martin, 1977-, et al.
(författare)
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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
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 154:1-3, s. 41-47
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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)
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Hepatic insulin-like growth factor binding protein (igfbp) responses to food restriction in Atlantic salmon smolts
- 2016
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 233, s. 79-87
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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)
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Effects of estrogens on sex differentiation in Japanese quail and chicken
- 2009
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 163:1-2, s. 97-103
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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)
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New insights into the evolution of vertebrate CRH (corticotropin-releasing hormone) and invertebrate DH44 (diuretic hormone 44) receptors in metazoans
- 2014
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 209:SI, s. 162-170
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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)
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Acute stress rapidly decreases plasma testosterone in a free-ranging male songbird: Potential site of action and mechanism
- 2010
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Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 169:1, s. 82-90
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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)
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Isolation of Atlantic halibut pituitary hormones by continuous-elution electrophoresis followed by fingerprint identification, and assessment of growth hormone content during larval development
- 2007
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 150:2, s. 355-363
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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)
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Intermale competition in sexually mature arctic charr : effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior.
- 2000
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Ingår i: General and Comparative Endocrinology. - : Elsevier. - 0016-6480 .- 1095-6840. ; 118:3, s. 450-60
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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. |
- Elofsson, Ulf OE, et al.
(författare)
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Intermale competition in sexually mature arctic charr: Effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior
- 2000
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Ingår i: GENERAL AND COMPARATIVE ENDOCRINOLOGY. - 0016-6480. ; 118:3, s. 450-460
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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-k
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| 20. |
- Fahlman, Åsa
(författare)
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Cortisol and corticosterone independence in cortisol-dominant wildlife
- 2012
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 177, s. 113-119
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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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