| 1. |
- 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.
|
|
| 2. |
- 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.
|
|
| 3. |
- 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.
|
|
| 4. |
- 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.
|
|
| 5. |
- 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.
|
|
| 6. |
- 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.
|
|
| 7. |
- 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.
|
|
| 8. |
- 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.
|
|
| 9. |
- 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.
|
|
| 10. |
- 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.
|
|
