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1.
The action of neuropeptide Y (NPY) and gonadotropin releasing hormone (s-GnRH) have been compared on the release of gonadotropin (GtH) by perifused rainbow trout pituitary glands sampled from freshly ovulated female rainbow trout. We have already demonstrated that NPY stimulated the secretion of GtH in vitro. The pituitary responses to s-GnRH and NPY were similar either after repeated 10 min infusions or a one hour prolonged application. In both cases, after the first application, the pituitary did not responded to subsequent secretagogues stimulations, and appeared to be desensitized. The stimulatory action of s-GnRH was partly inhibited (60%) by LH-RH antagonist (DpGlu1, DPhe2, DTrp3–6) LH-RH, which completely inhibited the response to NPY in perifused pituitary glands sampled from freshly ovulated females, but did not modify the response of pituitaries taken from vitellogenic animals in which NPY induced a transient inhibition of the GtH secretion. These results may indicate that the mode of action of NPY would differ between vitellogenic and matured animals. NPY also stimulated the GtH secretion from perifused pituitary dispersed cells prepared from pituitaries taken from freshly ovulated rainbow trout, indicating that NPY may act directly on the pituitary gonadotropic cells to stimulate GtH secretion.  相似文献   

2.
Vitellogenin (VTG) was purified from the plasma of estradiol-17β (E2) treated male brook trout (Salvelinus fontinalis; bt) using gel filtration and anion exchange chromatography. An antiserum to bt-VTG was raised in rabbits, then used to detect bt-VTG by Western blot analysis. Purified bt-VTG and its antibody were then used to develop an antibody-capture, competitive enzyme-linked immunosorbant assay (ELISA). Confirmation of the purified protein as bt-VTG was based on the characteristics of high molecular weight (∼562 kDa), dominant plasma protein in vitellogenic females and induction by exogenous E2 treatment in males. The antiserum recognized a major 184 kDa polypeptide as well as minor bt-VTG degradation products (150–66 kDa) in purified bt-VTG and in plasma from vitellogenic females. Low levels of antibody cross reactivity were shown with plasma from nonvitellogenic females, control rabbit serum, and several other antisera known to not contain VTG. The ELISA had a minimum detection limit of 8 ng ml−1 and intra- and inter-coefficients of variation less than 9% and 15%, respectively. The ELISA demonstrated parallel binding slopes among dilution curves of purified bt-VTG standard and plasma from diploid and triploid brook trout females. Using the ELISA, maximum plasma VTG levels of 93.5±33.6 mg ml−1 were detected in vitellogenic diploid females, whereas only 0.18±0.15 mg ml−1 were detected in triploid females of the same age (n=5 for each). Diploid and triploid males cohabitating with vitellogenic females showed measurable levels of plasma VTG during vitellogenesis in females (i.e., 0.17 and 0.06 mg ml−1, respectively (n=1)). This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
In vivo andin vitro techniques were used to examine the influence of various vertebrate peptides on growth hormone (GH) secretion in the goldfish. Tetradecapeptide somatostatin (SRIF-14) was found to inhibit GH secretionin vitro from perifused pituitary fragments, whereas similar concentrations of a salmonid SRIF peptide (sSRIF-25) did not affect GH secretion from the goldfish pituitary fragments. This indicates that SRIF receptors on the goldfish pituitary are very specific for SRIF-14-like peptides. Salmon gonadotropin (GTH)-releasing hormone (sGnRH) was found to elevate serum GH levels in male goldfish. The dopamine antagonist pimozide alone or injected in combination with sGnRH did not influence serum GH levels, although injection of pimozide alone significantly elevated serum GTH levels, in addition to potentiating the effects of sGnRH on GTH secretion. sGnRH stimulated GH secretion from goldfish pituitary fragmentsin vitro, indicating that sGnRH acts directly at the level of the pituitary to stimulate GH secretion in the goldfish. These results suggest that GnRH may also function as a GH-releasing factor in the goldfish, although the release-inhibitory factors for GH and GTH secretion do appear to be separate and distinct. Two human GH-releasing hormone (hGHRH) peptides were found to be ineffective in altering GH secretionin vitro from the perifused pituitary fragments. Consequently, a role for a mammalian GHRH-like peptide in the hypothalamic regulation of GH secretion in the goldfish remains questionable.  相似文献   

4.
The sperm duct epithelium of brook trout (Salvelinus fontinalis), mountedin vitro in Ussing-style epithelial chambers actively absorbs Na+ (measured as the short-circuit current, Isc) and secretes K+ (measured using86Rb+ as tracer). Dibutyryl-cyclic-adenosine monophosphate (db-cAMP) and 3-isobutyl-1-methylxanthine (IMX) produce a rapid, sustained stimulation of both ion transport processes, but the hormone connected to the response is unknown. Purified sockeye salmon CON A2 gonadotropin (GtH) produces a dose-dependent, rapid and sustained rise in Na+ uptake and K+ secretion. The time course, electrophysiological and transport characteristics are similar to those evoked by IMX. Carbohydrate-poor (chum salmon CON A1) GtH is ineffective. Pretreatment of fish with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) significantly increases milt volume but is without effect on resting or stimulated (IMX + db-cAMP) levels of sperm duct ion transport. This is the first indication of a direct, rapid action of GtH on ion transport by the vertebrate blood-testis barrier. The results suggest direct involvement of GtH in control of later stages of sperm maturation.  相似文献   

5.
The glutamate agonist, N-methyl-D,L-aspartate (NMA) stimulates the secretion of growth hormone (GH) from pituitary fragments in vitro and increases plasma GH levels in vivo in rainbow trout, Oncorhynchus mykiss (Flett et al. 1994; Holloway and Leatherland 1997a,b); however gonadal steroid hormones appear to modulate this response in experimental situations. This study examines whether steroid hormones also modulate the GH-regulatory actions of NMA during the normal reproductive cycle of rainbow trout by examining the relationship between the stage of sexual maturation and the pituitary release of GH in vitro in response to an NMA (10-8 M) challenge. NMA had no effect on mean GH release from the pituitary glands of fish that were immature (GSI <1.0), from males during early development (GSI 1.0-3.0), or from sexually mature males (with free running milt) and females (ovulated). However, NMA significantly increased GH release from pituitary glands taken from females during the early stages of gonadal growth (GSI 1.0-9.0) and from males and females sampled during the later stages of gonadal growth (males GSI 3.01-6.0; females GSI 9.01-15.0). The GH-stimulatory action of NMA in males and females progressed to a maximum effect during the late stages of gonadal growth, and disappeared in ovulated females and free running males. Moreover, in female fish, the maximal GH release in response to the NMA challenge is positively correlated with plasma 17β-estradiol levels; no such correlation was evident for plasma testosterone levels in males. Changes in the GH response to NMA during maturation while gonadal steroid levels fluctuate provides further evidence to suggest that the effects of NMA on GH secretion are intimately linked to endogenous gonadal steroid hormone levels. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

6.
In the present investigation, significant annual/seasonal variations were noticed in plasma and pituitary gonadotropin (GTH) which were correlated with gonado-somatic index, plasma estradiol-17β, and nuclear E2 receptor (NE2R) in the pituitary, hypothalamus and telencephalon. The NE2R concentrations and dissociation constant (k d) values showed significant seasonal variations with high values in the late preparatory phase and low values in the postspawning phase. The NE2R levels were the highest in the pituitary, followed by the hypothalamus and telencephalon in all the seasons. In the prespawning phase, ovariectomy (OVX) elicited a strong negative feedback on GTH secretion with a bimodal pattern of release and elevated the NE2R levels and k d values, without producing any significant change in the resting phase suggesting that E2 appears to exert differential feedbacks on GTH secretion.  相似文献   

7.
This study provides quantitative data on the dynamics of protein sequestration into vitellogenic follicles of the rainbow trout, Salmo gairdneri. The ovarian uptake of both radiolabelled vitellogenin (VTG) and bovine serum albumin (BSA) were investigated in a homogenous population of maturing vitellogenic females. Ten fish were injected with 3H. VTG directly into the bloodstream. Concomitantly, five of these fish received an equal amount of 14C.BSA. Twenty two hours after injection, of the tissues sampled, the greatest proportions of 3H. VTG were present in the blood (into which the radio labels were administered) and in the ovary (up to 28% and 46% of that originally present in the blood, respectively). VTG uptake was both selective, rates of uptake far exceeding that of the 14C.BSA, and rapid. 3H. VTG was sequestered at rates of between 35 to 390 ng.mm2 follicle surface−1.h−1 in the different fish. The rates of VTG uptake into similarly sized follicles varied both between different sites within the ovary (by up to 30%) and also between the ovaries (by up to 38%) of an individual fish.  相似文献   

8.
The presence of a peptide closely related to porcine NPY has been demonstrated in the goldfish brain and pituitary by means of radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). The RIA data demonstrate that displacement curves of brain extracts are parallel to a porcine NPY standard and that in HPLC a compound present in brain extracts is co-eluted with porcine NPY. The distribution of this NPY-like factor within the central nervous system was studied by radioimmunoassay and immunohistochemistry. The results indicated that NPY has a widespread distribution with the highest concentrations being found in the telencephalon and diencephalon. In the pituitary gland, NPY immunoreactive terminals characterized at the electron microscope level were found in the different lobes and, in particular, in close association with the gonadotrophin (GTH) secreting cells. Using anin vitro perifusion system, it was shown that NPY causes a dose dependent increase of GTH release from anterior lobe fragments. These data indicate for the first time in teleosts that NPY is present and widely distributed in the brain and pituitary, and that among other putative functions, could be implicated in the multihormonal release of GTH from the pituitary.  相似文献   

9.
A total of 518 Gerres sp. were collected around Okinawa Island, Japan, from November 2002 to July 2005, with monthly sampling where the standard length of females (n=218) were 56.2–147.1 mm, and males (n=149) were 62.2–139.4 mm. The maximum ages observed for females were 5+ years and males were 4+ years, estimated by transverse sectioned sagittal otoliths. Mean marginal increment indicated that opaque rings were formed once a year during April to July. The standard length (SL; mm) — body wet weight (BW; g) relationships were described as BW=(3.26×10−5) SL2.97 and BW=(3.13×10−5) SL 2.98 for females and males, respectively, and the standard length at age described by von Bertalanffy growth function for females, L t=137.1(1−e−0.80[t+0.80]) and males, L t=127.3(1−e−0.82[t+0.93]).  相似文献   

10.
The present study was designed to obtain basic endocrine information on GTH I and GTH II in previtellogenic and prespermatogenic coho salmon (immature). Levels of GTH II in pituitary extracts were 6.5 ± 2.0 and 6.7 ± 2.0 pg/μg pituitary protein in male and female fish, respectively. In contrast, the pituitary content of GTH I was approximately 100-fold higher than GTH II (1.302 ± .22 and 1.173 ± .21 ng/μg pituitary protein in male and female fish, respectively). Plasma levels of GTH II in immature salmon were not detectable by RIA whereas plasma GTH I levels were approximately 0.62 ± 0.12 and 0.78 ± 0.13 ng/ml in male and female fish, respectively. Highly purified coho salmon GTH I and GTH II stimulated testicular testosterone production and ovarian estradiol productionin vitro in a similar manner, though GTH II appeared more potent than GTH I. Therefore, it appears that although the salmon pituitary contains predominantly GTH I prior to puberty, the gonad can respond to both GTH I and GTH II.  相似文献   

11.
The main serine proteinase inhibitors of rainbow trout (Oncorhynchuss mykiss) and common carp (Cyprinus carpio) blood plasma were isolated and purified. The investigated inhibitors, α1-proteinase inhibitor (α1-PI) and antithrombin III (AT III), act by forming stable complexes with target proteinases. The association rate constants k on for the interaction of fish plasma inhibitors with several serine proteinases have been determined: k on for both carp and rainbow trout α1-PI were >107 M−1 s−1 for human neutrophil elastase, and in the case of bovine trypsin and chymotrypsin k on values were 2.0–5.2 × 106 M−1 s−1. Association rate constants k on for the interaction of carp and rainbow trout AT III with bovine trypsin and thrombin were about 1.3 × 104–7.9 × 105 M−1 s−1 without and >107 M−1 s−1 in presence of heparin; so antithrombins require the presence of heparin to become effective proteinase inhibitors. The high degree of homology of the estimated amino acid sequences of fish inhibitors reactive site loops confirms their similarity with other proteinase inhibitors from the serpin family.  相似文献   

12.
A minimally invasive surgical technique (MIST) for the removal of ovulated eggs from Persian sturgeon Acipenser persicus was tested on broodstocks caught from the wild to determine whether it affected fecundity or hatching rates compared with the traditional stripping method of killing and removing the eggs (commonly used in hatchery). Morphological parameters of females, germinal vesicle (GV) position, weight of obtained egg, number of eggs/gram, fertilization rate, and percentage of hatching during incubation were not significantly different between the MIST and traditional stripping methods. Obtained ova were 4.8 ± 0.4 kg female−1 in the MIST and 4.6 ± 0.5 kg female−1 in traditional stripped groups, respectively; the fertilization rate was 83.4 ± 11.2% and 80.0 ± 7.2% in groups, respectively. The results of this study showed that the minimally invasive surgical technique approach is efficient, practical, and less stressful to Persian sturgeon broodstocks during artificial propagation than other reported egg collection procedures.  相似文献   

13.
A particulate fraction obtained from trout testis at the time of spermiation shows saturable binding sites for125I-labeled salmon gonadotropin (125I-GtH). Non-gonadal tissues (liver, muscle and spleen) did not demonstrate specific125I-GtH binding. The tracer's specific activity was determined by the self-displacement method (18 to 30 Ci/g). Maximal specific binding ability of125I-GtH varied from 20 to 30% of the labelled ligand added, depending on the hormone preparation. Specific binding of125I-GtH to 20 mg of the testis membrane varied from 40 to 85% of the total binding depending on the method of membrane prepratation, and was competitively inhibited by concentrations of unlabelled GtH ranging from ca 1 to 1000 ng/ml of incubate. Gonadotropin of mammalian origin, ovine TSH or salmon prolactin competed only weakly, or not at all, for testicular gonadotropin binding sites (relative potencies s-GtH>>FSH=hCG>s-PRL>bTSH). Scatchard analysis of equilibrium binding studies shows that saturable gonadotropin binding was due to a class of high affinity binding sites (sites I Ka3×1010 M–1) and possibly to a second class of lower affinity binding sites (sites II Ka=5 to 14×108 M–1). The binding capacity of sites I, as measured in enriched membrane preparations, was 45±18 fmoles/g of testis during the period of spermiation. The concentration of GtH required to obtain half maximal displacement of125I-GtH in the binding studies was of the same order of magnitude as the apparent ED50 for GtH stimulation of 11-Cetotestosterone (11KT) secretion by trout testesin vitro. Mammalian LH and FSH were 100 to 1000 folds less potent than salmor GtH to increase 11 KT secretion.  相似文献   

14.
Basal levels of plasma cortisol in unstressed salmonid fish are normally in the range 0–5 ng ml−1. An acute stress such as handling or 1 h confinement caused a temporary elevation of the plasma cortisol levels of both brown trout,Salmo trutta L., and rainbow trout,Salmo gairdneri Richardson, in the range 40–200 ng ml−1 with a return to basal levels within 24–48 h. The extent of the cortisol elevation in response to an acute stress was dependent upon both the species and strain of trout. Chronic stresses, such as prolonged confinement or crowding, resulted in an elevation of plasma cortisol levels to approximately 10 ng ml−1. Under these circumstances, blood cortisol levels remained elevated for periods of up to 4 weeks before acclimation finally occurred. It is shown, by means of intraperitoneal implantation of cortisol, that chronic elevation of plasma cortisol levels in the brown trout results in a dose-dependent increase in mortality due to common bacterial and fungal diseases. This effect is apparent at plasma cortisol levels as low as 10 ng ml−1, levels below those often reported as being representative of ‘unstressed’ fish. These findings are discussed in relation to the known immunosuppressive effects of corticosteroids in teleost fish.  相似文献   

15.
For studying the effect of LHRH-A2 hormone on the induction of final maturation and ovulation of Persian sturgeon, 71 matured females and 20 matured males were used. Five groups of breeders were injected with sturgeon pituitary gland hormone (50 mg per fish) and LHRH-A2 in dosages of 3.5, 7, 8 and 10 μg kg−1 for females and 3 and 5 μg kg−1 for males. Results showed that LHRH-A2 successfully induced final maturation and ovulation in females, and there was no significant difference between five groups of breeders in ovulation proportion, fertilization rate, survival rate of incubation, survival of yolk-sac absorption period and active feeding period of larvae. It can be concluded that the LHRH-A2 is a proper alternative for pituitary gland hormone in artificial propagation of Persian sturgeon.  相似文献   

16.
Rainbow trout were studied at different rearing densities, fish sizes and feeding frequencies so that we could evaluate the effect of these parameters on fin condition, growth and feed utilisation. In one study, two sizes of rainbow trout (18–70 g or 48–125 g), fed to near satiation at 17.7°C, were examined at two rearing densities (11–41 kg m−3 or 21–92 kg m−3). This study showed that the anal fin was healthier (P < 0.05) at low densities. In the second study rainbow trout were again fed to near satiation and grown from 50 g to 125 g in 16.4°C water, and they were fed either once daily or three times daily at two densities (18–45 kg m−3 or 54–124 kg m−3). Rainbow trout growth and feed utilisation were slightly but significantly (P < 0.05) reduced at high densities, while dorsal fin condition, surprisingly, was better (P < 0.0001) at the high densities. Possible explanations to these findings are discussed. Condition of the left pectoral fin was improved at once daily feeding (P < 0.05) compared with three feedings per day, at which fights for feed possibly are more frequent.  相似文献   

17.
Gravid brown trout (Salmo trutta) females were injected with various doses of a synthetic gonadotropin-releasing hormone analog (GnRHa), given with or without an injection of triiodothyronine (T3), in order to investigate the potential of T3 (a) to enhance the stimulatory effect of GnRHa on ovulation, and (b) to enhance the growth and survival of the produced progeny. From the time the hormonal treatments were initiated until ovulation was detected 5–38 days later, endogenous plasma T3 levels increased from an average of 3.6 to 11.6 ng ml−1. Injection with 20 mg T3 kg−1 body weight, further elevated plasma T3 levels at ovulation (16.0 ng ml−1. Mean time to ovulation was reduced significantly in fish injected with 10 μg kg−1 of GnRHa, whereas treatment with lower doses was ineffective. Injection with T3 did not enhance the ovulatory response of brown trout to GnRHa. Unfertilized eggs obtained from T3-injected females had a higher T3 content, suggesting a transfer of T3 from the maternal circulation into the oocytes. Maternal T3 injection had no effect on egg fertilization rates, embryo survival to eyeing and hatching, or the prevalence of abnormal larvae at the time of hatching. Length and weight gain of the progeny during yolk absorption was also not influenced by maternal T3 treatment. At the completion of yolk-sac absorption, progeny from females injected with T3 had a higher prevalence of skeletal abnormalities than controls. The results suggest that in teleosts like brown trout, which have high endogenous circulating T3 levels, treatment of females with T3 does not enhance responsiveness to GnRHa and it has the potential for deleterious effects on their offspring.  相似文献   

18.
The substrate specificity of brain acetylcholinesterase (AChE) in adult Carassius auratus fish and its sensitivity to carbamate insecticides were investigated in vitro. The results showed that the order of four substrates hydrolyzed by brain AChE in C. auratus was acetylthiocholine iodide > β-methylthiocholine iodide > propionylthiocholine iodide > butyrylthiocholine iodide, and the maximum velocity (V max) of AChE hydrolyzing acetylthiocholine iodide (ATCh) was the highest among the four substrates, and the V max values were 0.067 and 0.082 mmol min−1 mg−1 for male and female fish respectively. But their Michaelis–Menten constants (K m) were the lowest, only 0.071 and 0.072 mmol/l respectively. Compared with other carbamate insecticides, the sensitivity of brain AChE to carbofuran was the highest and the IC50 values were 1.04 × 10−6 mol/l for females and 1.17 × 10−6 mol/l for males. The inhibitory tendencies of eserine, methomyl, and aldicarb to brain AChE were very similar, and the percentage inhibition increased with time at the concentration of 1 × 10−6 mol/l. The order of inhibition potential of the three inhibitors from the highest to the lowest was eserine, aldicarb, and methomyl.  相似文献   

19.
The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1–7) and recently metamorphosed downstream migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15–0.55 μg.mg wet weight−1 in ammocoetes and metamorphosing stages 1–3 to 2.2–2.9 μg.mg−1 in stages 5–7 and to 8.8 μg.mg−1 in downstream migrants. The comparable values for ferritin iron were 0.06–0.26, 1.4–2.0, and 5.3 μg.mg−1. Superoxide dismutase activity fell sharply from 0.39 μg.mg−1 in large ammocoetes to between 0.07 μg.mg−1 in stage 1 and 0.15 μg.mg−1 in stage 6, before rising significantly to 0.26 μg.mg−1 in stage 7 and 0.35 μg.mg−1 in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity in the liver of non-trophic animals.  相似文献   

20.
The effects of thyrotropin-releasing hormone (TRH) on growth hormone (GH) and gonadotropin (GtH) release, and the influences of somatostatin (SRIF), the dopamine agonist apomorphine (APO) and extracellular calcium on basal and TRH-induced GH release were examined using an in vitro perifusion system for pituitary fragments of common carp (Cyprinus carpio). Five minute pulses of different dosages of TRH stimulated a rapid and dose-dependent increase in GH release from the perifused pituitary fragments with an ED50 of 9.7 ± 2.3 nM. TRH was ineffective on GtH release. SRIF significantly inhibited basal and TRH-induced GH release from the perifused pituitary fragments, and the effects of SRIF were dose-dependent. APO induced a dose-dependent increase in basal and TRH-stimulated GH release from the perifused pituitary fragments. Increasing the concentrations of extracellular calcium from 0 mM to 1.25 mM resulted in an increase in basal and TRH-induced GH release. The high dose of calcium (6.25 mM) caused a slight decrease in basal and TRH-induced GH release compared with those at a concentration of 1.25 mM.
Résumé Les effets de la thyrotropine (TRH) sur la sécrétion d'hormone de croissance (GH) et de gonadotropine (GTH), et de la somatostatine (SRIF), de l'apomorphine (APO), antagoniste dopaminergique, et du calcium extracellulaire sur les sécrétions basale et stimulée de GH ont été étudiées in vitro par périfusion, de fragments d'hypophyses de carpe (Cyprinus carpio). Des applications de 5 minutes de TRH à différentes concentrations induisent une stimulation rapide et dose dépendante de la sécrétion de GH (ED50 = 9.7 ± 2.3 nM). Le TRH est sans effet sur la sécrétion de GTH. Le SRIF inhibe la sécrétion basale de GH ainsi que la résponse hypophysaire à l'action du TRH. Son action est dose dépendante. L'apomorphine induit une augmentation dose dépendante de la sécrétion basale de GH et potentialise l'action du TRH sur la stimulation de la sécrétion de GH. Des effets équivalents sont induits par des concentrations croissantes de calcium extra cellulaire de 0 à 1.2 mM, alors qu'à une concentration de 6.25 mM des effets opposés sont obtenus.
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