首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Many fish species display compensatory growth (CG), a phenomenon by which fasted fish grow faster during refeeding. However, most studies use a group‐housed fish approach that could be problematic in social fish when interaction between individuals is not considered or eliminated. Additionally, the growth hormone (GH)/insulin‐like growth factors’ (IGF‐1 and IGF‐2) axis is implicated in postnatal growth in vertebrates, but its relevance in CG is not fully understood. Thus, the aim of this work was to determine whether CG occurs in a social fish, Cichlasoma dimerus, using an individually held fish approach and secondly, to evaluate the GH/IGFs expression profile during refeeding by 3 days and 3 weeks. C. dimerus showed partial CG. The feed conversion efficiency (FCE) was higher in three‐day‐refed fish, which presented higher GH plasma and mRNA levels than controls but shown no differences in liver and muscle GH receptors (GHR1 and GHR2) and IGFs mRNA levels. Surprisingly, three‐week‐refed fish exhibited GHR1 and IGF‐2 increments, but a reduction in GHR2 expression in muscle. These results show a strong association between GH levels, growth rate and FCE during refeeding, and a long‐lasting effect of refeeding on muscular expression of GHRs and IGF‐2.  相似文献   

2.
  相似文献   

3.
  相似文献   

4.
Although gonadotrophins are major regulators of ovarian function in teleosts and other vertebrates, accumulating evidence indicates that the growth hormone (GH)-insulin-like growth factor (IGF) axis also plays an important role in fish reproduction. As a first step to understand the physiological role of the GH-IGF system in the ovarian development of starry flounder (Platichthys stellatus), the expression profiles of GH and IGF messenger RNAs (mRNAs) and plasma GH, IGF-I, estradiol-17β (E2), and testosterone (T) levels during the ovarian development were investigated. The developmental stages of ovaries were divided into five stages (II, III, IV, V, and VI) by histological analysis. The hepatosomatic index (HSI) and gonadosomatic index (GSI) values increased and peaked at stage IV and stage V, respectively, and then declined at stage VI. Pituitary GH mRNA levels decreased sharply at stage III and raised to top level at stage VI. The hepatic IGF-I mRNA levels ascended to maximum value at stage V and then declined significantly at stage VI. However, the hepatic IGF-II mRNA levels remained stable and increased significantly at stage VI. In contrast, the ovarian IGF-I mRNA levels increased gradually and peaked at stage VI. The ovarian IGF-II mRNA levels were initially stable and increased significantly at stage V until the top level at stage VI. Consistent with the pituitary GH mRNA levels, plasma GH levels reduced sharply at stage III and remained depressed until stage V and then raised remarkably at stage VI. Plasma IGF-I level peaked at stage V and then declined to initial level. Plasma E2 level peaked at stage IV and then dramatically descended to the basal level. Plasma T level peaked at stage V and then declined significantly back to the basal level. Based on statistical analysis, significant positive correlations between hepatic IGF-I mRNA and GSI, ovarian IGF-II mRNA and hepatic IGF-II mRNA, ovarian IGF-I mRNA and ovarian IGF-II mRNA, and plasma IGF-I and plasma T were observed, respectively. These results suggest that the GH-IGF system may be involved in the ovarian development of starry flounder; GH and IGFs appear to play distinct roles in the regulation of the ovarian development in paracrine/autocrine manners. These findings extend our knowledge of the roles of the GH-IGF axis on reproduction regulation in fish.  相似文献   

5.
Temporal changes in growth, plasma thyroid hormone, cortisol, growth hormone (GH) and non-esterified fatty acid (NEFA) concentrations, hepatic T3 content and hepatic 5-monodeiodinase activity were measured in rainbow trout (Oncorhynchus mykiss) subjected to a sustained fast for up to eight weeks, and during a four-week re-feeding period. The purpose of the study was to examine aspects of the endocrine control of energy partitioning processes characteristic of short-term (acute; fasting) and long-term (chronic; starvation) food-deprivation states in fish, and to explore the role of the thyroid hormones, cortisol and GH in the energy repartitioning that takes place during an acute anabolic (re-feeding) state following chronic food deprivation.Differences in growth rate between fed and fasted groups were evident after two weeks, but significant weight loss by the fasted groups was not evident until between four and six weeks into the fast. Hepatosomatic indices (HSIs) were significantly reduced in the fasted fish within seven days, and as early as two days in one study; recovery of the HSI in fasted fish was evident within three days of re-feeding. Liver protein content (expressed as % wet weight) was consistently depressed in the fasted fish in only one of the three studies. Liver total lipid content (expressed as % wet weight) was depressed in the fasted fish within two days of food deprivation. Because of the rapid and sustained decrease in the HSI of fasted fish, the hepatic total protein and lipid reserves, when considered on a body weight basis, were markedly lowered within the first few days of the fast. Plasma GH concentrations exhibited a bi-modal pattern of change, with a transient fall in levels, followed by a sustained increase in fasted fish. The indicators of interrenal activity were suggestive of a depressed pituitary-interrenal axis in fasted animals; plasma cortisol levels were elevated to levels of fed animals within one day of re-feeding. The indicators of thyroid hormone economy (plasma thyroid hormone levels, liver triiodothyronine content, hepatic 5-monodeiodinase (MD) activity, thyroid epithelial cell height) were similarly indicative of a depressed pituitary-thyroid axis in fasted animals, with recovery to levels of the fed animals within one week. Despite the compensatory changes in accumulation of reserves (as indicated by a compensatory increase in HSI), there were no apparent compensatory changes in any of the endocrine parameters evident during the re-feeding period.  相似文献   

6.
  相似文献   

7.
In vivo and in vitro approaches have been used to examine the role of dopamine (DA) as a growth hormone (GH)-releasing factor in the goldfish. DA stimulated GH release from perifused pituitary fragments of goldfish in a dose-dependent manner. The GH-releasing effect of DA was seasonal, being the highest in sexually regressed fish, intermediate in recrudescent fish, and the lowest in sexually mature (prespawning) fish. The GH response to DA was blocked by the D1 antagonist (+)SCH23390, confirming the involvement of D1 receptors in DA-stimulated GH release. In studies using static incubation of pituitary cells, somatostatin, a known physiological GH-release inhibitor in the goldfish, abolished the GH response to DA. Intraperitoneal injection of apomorphine, a non-selective DA agonist, also increased the plasma GH levels and enhanced the linear body growth of goldfish. These results strongly suggest that DA, by acting through DA D1 receptors, functions as a GH-releasing factor in the goldfish.  相似文献   

8.
Juvenile gilthead sea bream were fed to visual satiety with isonitrogenous diets based on fish meal and different plant ingredients (33–35% replacement) supplemented with free amino acids to meet the desired indispensable amino acid (IAA) profile and dispensable amino acid (DAA) content. In diets M and WB, IAA profile and DAA content resemble that of the muscle or whole body, respectively. In diets MGlu and WBGlu, DAA content was increased by adding -glutamic acid (Glu) and thus the IAA/DAA ratio varied from 1.13 (diet M) to 0.80 (diet WBGlu). Growth rates were not significantly different among experimental groups, but feed conversion ratio and nitrogen retention were impaired by the decrease of dietary IAA/DAA ratio. Postprandial ammonia excretion increased with the increase of dietary DAA content irrespective of IAA profile. Conversely, hepatic activity of glutamate dehydrogenase (GDH) was lower in fish fed diet WBGlu than in fish fed diet M. Hepatic growth hormone (GH) binding was not significantly affected by the dietary treatment, but circulating levels of insulin-like growth factor-I (IGF-I) and GH were, respectively, down- and up-regulated in fish fed diet WBGlu, which suggests some defect in the transmission of GH receptor signal. Fat retention and hepatic activities of lipogenic enzymes (glucose-6-phosphate dehydrogenase, G6PD; malic enzyme, ME) were decreased in fish fed diet MGlu. Key metabolic enzymes of hepatic glycolysis (glucokinase, GK) and gluconeogenesis (phosphoenolpyruvate carboxykinase, PEPCK) were also altered in this group of fish. Since soybean meal concentration was highest in diet MGlu, results on lipid and carbohydrate metabolism can be primarily attributed to this component of the diet. In contrast, data on growth performance, ammonia excretion and GH axis mainly reflect changes in the dietary amino acid profile, which reveals that a muscle IAA profile and a high IAA/DAA ratio are important in feeds for gilthead sea bream.  相似文献   

9.
The purpose of the study was to investigate whether dietary ration or diet composition influence the relationship between plasma growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) in Arctic charr (Salvelinus alpinus L.). The pattern of changes in plasma GH and IGF‐1 concentrations was examined in fish fed at different ration levels (0%, 0.35% and 0.70% BW day−1) for 5 weeks, and in fish fed diets containing different lipid:crude protein (LCP) ratios. Ration level significantly affected plasma GH and IGF‐1 concentrations; at 5 weeks the levels of both hormones in the food‐deprived group were significantly lower than in fish fed the 0.70% BW day−1 ration. Also, plasma IGF‐1 levels in fish of each ration treatment group were significantly correlated with individual final body weight; no such correlation was found for GH. To examine the effects of dietary LCP ratios, fish were fed for up to 18 weeks, with one of four formulated diets that had LCP ratios (dry matter basis) of 0.35 (Diet 1), 0.43 (Diet 2), 0.51 (Diet 3) or 0.59 (Diet 4), or a commercial diet (Diet 5) which had an LCP ratio of 0.38. Statistical differences in plasma GH and IGF‐1 concentrations were found only after 18 weeks. Growth hormone was significantly lower in fish fed Diets 1 and 2 compared with Diets 3 and 5, and IGF‐1 was significantly lower in fish fed Diet 1 compared with Diets 2 and 5. Significant correlations between plasma GH and IGF‐1 concentrations were found only for fish fed Diets 1 and 5, suggesting that the influence of diet composition on the relationship between GH and IGF‐1 varies with the dietary LCP ratio in this species. The decline in plasma IGF‐1 concentrations during food deprivation is similar to that described in other species; however, the unexpected decrease in plasma GH during food deprivation in this study may represent a species‐specific response.  相似文献   

10.
The biology of salmon growth hormone: from daylight to dominance   总被引：2，自引：0，他引：2  
The elucidation of the molecular structure of salmon growth hormone (GH) in the mid-1980's paved the way for a new era of endocrinological research. Establishment of homologous immuno- and receptor-assays have made studies of the secretion, tissue and plasma GH levels, GH turn-over and GH receptor concentrations possible. This overview attempts to summarize the present understanding of the biological roles of GH in salmon. Although the involvement of GH in the regulation of physiological processes throughout the salmon life history has yet to be comprehensively explored, the hormone has already been demonstrated to have several important functions. GH is a principal regulator of somatic growth in salmonids. The growth-stimulating effect of GH is probably integrated with that of insulin-like growth factor I (IGF-I), as in later vertebrates. GH stimulates protein synthesis and improves feed conversion during growth. The hormone also promotes lipid and glycogen breakdown as well as gluconeogenesis, functions which are probably of great importance during starvation when GH levels are seen to increase. During parr-smolt transformation of anadromous salmonids, circulating GH levels appear to be governed by environmental cues. Increasing springtime daylength elevates GH levels, and temperature modulates the photoperiod regulation of GH. The seawater-adapting role of GH during the parr-smolt transformation is complex. In freshwater, GH improves hypoosmoregulatory ability by stimulating branchial Na+,K+-ATPase activity and probably also acts in kidney and intestine. Following seawater entry, GH levels and turn-over increase transiently, probably to further increase seawater tolerance. Accumulating in vitro and in vivo data support the conclusion that GH is involved in the regulation of sexual maturation in salmonids although further studies are needed to establish the exact role of GH in this process. GH increases appetite but it is unclear whether the hormone effects the central nervous system directly, or acts indirectly through metabolic changes. GH increases swimming activity as well as dominant feeding behaviour and diminishes anti-predator behaviour of juvenile salmonids. The GH-induced changes of behavioural patterns imply that there exists an ecological trade-off between high growth rate and long-term survival which may explain why natural fish populations normally grow at sub-maximal rates. Current knowledge indicates that GH is an important and multi-functional hormone in salmon and a central mediator of seasonal changes in physiology and behaviour. The regulatory effects of GH are also of great applied interest as they are likely to affect both product quality in aquaculture and long-term survival of released fish.  相似文献   

11.
Growth hormone (GH), prolactin (PRL) and somatolactin (SL) are single chain proteins structurally and functionally related. Fish PRL and GH receptors (PRLR, GHR) have been characterized in several fish species. There is limited evidence of fish PRLR isoforms, but emerging data support the existence of different GHR variants. In gilthead sea bream, black sea bream, turbot and fugu, but not in zebrafish, GHR has retained an exclusive fish intron (10/10A). In gilthead sea bream and turbot, this intron is not alternatively spliced, but the black sea bream intron is either removed or retained during mRNA processing, resulting in a long GHR isoform with a 31 amino acid insertion that does not alter the open reading frame. This or any other GHR variant are not found in gilthead sea bream, but a truncated anchored form has been reported in turbot. The latter GHR isoform comprises extracellular and trans-membrane domains, the first 28 amino acids of the intracellular domain and 21 divergent amino acids before a stop codon. This GHR variant is the result of alternative splicing, being the 3′ UTR and the divergent sequence identical to the sequence of the 5′ end of the 9/10 intron. The physiological significance of different fish GHR isoforms remains unclear, but emerging data provide suitable evidence for season and nutrition related changes in the somatototropic axis activity. The up-regulation of circulating GH together with the decrease of plasma titres of insulin-like growth factor-I (IGF-I), an altered pattern of serum IGF binding proteins and a reduced expression of hepatic IGF-I and GHRs represent a mechanism conserved through vertebrate evolution. It secures the preferential utilization of mobilized substrates to maintain energy homeostasis rather than tissue growth. Somatolactin also changes as a function of season, ration size, dietary amino acid profile and dietary protein source creating opposite plasma GH and SL profiles. There is now direct evidence for a lipolytic effect of fish SL, acting at the same time as an inhibitory factor of voluntary food intake. Indeed, long-term feeding restriction results in the enlargement of the summer GH peak, whereas the SL rise coincident with shortened day length is delayed in juvenile fish until late autumn. These findings agree with the idea that SL may act as a marker of energy surplus, priming some particular process such as puberty onset. However, it remains unclear whether SL works through specific receptors and/or dimers or heterodimers of GH and PRL receptors.  相似文献   

12.
  相似文献   

13.
Growth hormone (GH) has recently been identified as co-gonadotropin regulating fish reproduction, hitherto, no effort has been made to see its effect on oocyte maturation in fishes, though some reports demonstrate the role of insulin like growth factor-I (IGF-I) in oocyte maturation in teleosts. Hence, effect of GH on oocyte maturation in post-vitellogenic H. fossilis has been worked out in the present study. Post-vitellogenic follicles in the ovarian tissue were challenged in vitro with H. fossilis pituitary homogenate (fPH), Clarias batrachus GH and GtH, barramundi IGF-I (IGF-I), 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) and testosterone alone, or in combination with IGF-I for 18 h at 26±1°C. Incubation of ovarian tissue with GH in the presence of actinomycin d or cycloheximide or barramundi IGF-I antiserum was also made separately. In general, oocyte maturation was induced by fPH, barramundi IGF-I, GtH, GH and DHP, which was augmented further by addition of barramundi IGF-I. Testosterone had no effect on GVBD. Actinomycin d, cycloheximide and anti barramundi IGF-I abolished the GH induced oocyte maturation. Present study suggests for the first time that GH has a role in egg maturation in fish.  相似文献   

14.
瓦氏黄颡鱼生长激素基因克隆及其组织特异性表达分析   总被引：1，自引：1，他引：0  
生长激素(growth hormone,GH)对脊椎动物的生长发育及代谢具有重要作用。采用RT-PCR和RACE技术,克隆了瓦氏黄颡鱼垂体GH cDNA全长序列,应用real-time qPCR法对不同组织中GH mRNA的表达进行检测。序列分析表明,GH cDNA(GenBank登录号:GU395549)序列全长1 203 bp,其5’端非编码区77 bp、3’端非编码区523 bp,开放阅读框(open reading frame,ORF)603 bp,由此推导GH前体蛋白由200个氨基酸组成。同源性比较结果表明,瓦氏黄颡鱼与同目鱼类的GH编码序列同源性较高,与哺乳类和鸟类的同源性较低。Real-time qPCR结果显示,GH mRNA在垂体中的表达量最高,其次是脑、肌肉、肝脏、脂肪组织、胃、脾脏、卵巢或精巢,而在肾脏、心脏、鳃和肠中没有明显的表达。实验结果表明,GH基因在瓦氏黄颡鱼组织中广泛表达,提示GH可能以旁分泌或自分泌的方式对其生长和繁殖发挥重要作用。  相似文献   

15.
Using rainbow trout plasma protein (IGF-BP) which specifically binds human insulin-like growth factor (IGF) (Niu and Le Bail 1993), we have developed an assay to measure plasma IGF-like levels in different teleost species. Before the assay and to prevent interference by IGF-BP, IGF-like was extracted from all samples, using SP Sephadex C-25 in acidic conditions. After this treatment, contamination of the IGF fraction by IGF-BP which was estimated by binding assay, was approximately 5%, and was not detectable by western ligand blot. Human IGF-I was used as standard and labelled hormone. Sensitivity of the assay was 0.15–0.40 ng/ml (ED90) and ED50 was 1–3 ng/ml. hIGF-II crossreaction was partial and no significant displacement was observed with Insulin from different species or with other hormones. Inhibition curves were obtained with plasma IGF fractions (but not with tissue extracts) from teleost and mammals and are parallel to the standard curve. These results suggest that the protein binding assay can quantify an IGF-like factor in the plasma of teleost and that the binding sites of IGF are well conserved during vertebrate evolution. Using this IGF binding assay, IGF-like was measured in parallel with growth hormone (GH) in plasma from young rainbow trout killed every 1.5h throughout one day. The daily profiles for both hormones, which appear pulsatile, are similar. A significant correlation was observed between GH levels and IGF-like levels with a 1.5h delay. Analogous observations were obtained in individual catheterized adult rainbow trout. Although plasma GH levels differ greatly between fish, less variability is found with IGF-like. In a third experiment, rainbow trout were starved or submitted to bovine GH treatment for four weeks. Starved fish, in which plasma GH levels increased, had plasma IGF-like level significantly lower than in fed fish. In bGH injected fish, plasma IGF-like level was significantly higher than in non-injected fish. These results suggest that, as in mammals, IGF-like secretion depends on plasma GH level and could be modulated by the nutritional status of fish.  相似文献   

16.
Nile tilapia exhibits strong sexual growth dimorphism. The potential role of sex steroid hormones in sexual growth dimorphism is not fully understood. We investigated the effects of estradiol (E2) and testosterone (T) on growth rate, plasma sex hormones, and expression of growth hormone (GH)‐insulin‐like growth factor (IGF) axis genes and muscle regulatory factor (MRF) genes in female and male Nile tilapia. The results revealed that serum concentrations of E2 and T were significantly higher after correlative injection (P < 0.05). Compared to male fish, female fish had lower growth rates. E2 increased growth performance in females with no significant effects on males, whereas T significantly increased growth performance in males, with no significant effects on females. In females, E2 significantly increased expression of ghr1, ghr2, igf1, and igf2, while T decreased igf2 and increased ghr1 and ghr2 expression. In males, T increased expression of igf1, igf2, ghr1, and ghr2, and E2 decreased expression of igf1, ghr1, and ghr2. Additionally, E2 and T enhanced the expression of MRF genes (myod1, myod2, myog, and myf5) in female and male fish, respectively. The results suggest that sex steroid hormones play a role in sexual growth dimorphism by regulating the expression of GH‐IGF axis and MRF genes.  相似文献   

17.
鱼生长激素基因在大肠杆菌中表达水平的研究   总被引：4，自引：1，他引：3  
采用聚合酶链反应（ＰＣＲ）技术对鲤和鲑生长激素ｃＤＮＡ的５‘端和３’端进行定向改造。将改造后的５种基因分别克隆到大肠杆菌表达质粒ｐＢＶ２２０进行原核表达，以研究鱼生长激素基因在大肠杆菌中的表达水平。实验结果表明：（１）核糖核蛋白体结合位点（ＳＤ）与起始密码子ＡＵＧ之间的距离对鱼生长激素的表达水平有影响；（２）鲑鱼生长激素基因的终止密码子ＵＡＧ可能不会有效终止该基因在大肠杆菌中翻译的进行而造成部分通  相似文献   

18.
In salmonids, growth hormone (GH) effectively promotes adaptation of freshwater (FW) fish to seawater (SW), but it has been unclear whether GH has osmoregulatory actions apart from those consequent to an increase in body size. Our objectives were first, to examine the minimum time and dose required for GH to enhance SW adaptation; and second, to optimize the conditions for the acute GH response in developing a convenient GH bioassay based on its plasma ion lowering effect. Trout showed markedly improved SW survival when transferred from fresh water 6, 24, or 48h after a single chum salmon GH injection (0.25 μg/g). Preadapting trout to 1/3 SW enhanced the plasma ion lowering effect of ovine GH (oGH) injected 48h before transfer of the fish to 80% SW. Endogenous plasma GH levels were elevated in control trout switched from low salinities to 80% SW but were depressed in oGH-injected fish after transfer. Under optimal test conditions (1/3 SW preadaptation, 48h pre-transfer injection, and 100% SW final challenge), the reduction in plasma Na+, Ca++, and Mg++ levels of oGH-injected fish was dose-dependent. The oGH doses giving minimum and maximum responses were 50 and 200 ng/g, respectively. In short, GH exerts acute osmoregulatory actions that promote SW adaptation in the absence of changes in body size. Compared with growth GH bioassays, the osmoregulatory assay is superior in economy of time, animal costs, and hormone quantity required and potentially in specificity.  相似文献   

19.
In African catfish the dopamine agonist apomorphine (APO) stimulates in vivo growth hormone (GH) release. The present study demonstrates that the potency of APO to stimulate plasma GH levels is affected by the nutritional status of the fish. The effect of starvation on APO induced GH release was investigated in sexually mature and immature catfish. Administration of APO clearly stimulated plasma GH levels in mature catfish that had been starved for 3 and 5 weeks, while no effect could be observed prior to starvation. This increased responsiveness to the GH stimulating action of APO was also demonstrated in fasted immature fish, though it was only evident in fish starved for a prolonged period (19 days or more). The importance of the duration of the starvation period suggests that the enhanced responsiveness is the result of physiological adaptations to starvation rather than an acute effect of food deprivation.  相似文献   

20.
In salmonids, growth hormone (GH) stimulates growth, appetite and the ability to compete for food. This study tested the hypothesis that increased GH levels in GH-transgenic coho salmon Oncorhynchus kisutch (Walbaum) increase competitive ability through higher feeding motivation. The transgenic strain of salmon used contained a gene construct consisting of the sockeye metallothionein-B promoter fused to the type 1 growth gene coding region. The transgenic animals (mean size = 250 g) were F1 individuals. In six consecutive feeding trials, the intake of contested food pellets by size-matched pairs consisting of one control (1 year older non-transgenic coho salmon) and one GH-transgenic coho salmon was compared. Pellets were provided sequentially until neither fish took three consecutive pellets; the identity of the fish taking each pellet was noted. Calculated on the three first pellets offered at each feeding trial, the transgenic coho salmon consumed 2.5 times more contested pellets than the controls, supporting the hypothesis that GH transgenesis increases the ability to compete for food. Overall, the transgenic fish consumed 2.9 times more pellets that the non-transgenic controls, indicating a high feeding motivation of the transgenic fish throughout the feeding trials. It appears that GH transgenesis and GH treatments can induce similar changes in the feeding behaviour of salmonids. Depending on how transgenic and wild individuals differ in other fitness-related characters, escaped GH transgenic fish may compete successfully with native fish in the wild.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号