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1.
Recent evidence has indicated the presence of IGF-I and IGF-I receptors in mammalian and teleost ovarian follicles. Since growth hormone (GH), which can be secreted from the pituitary concomitant with a gonadotropin as a response to gonadotropin-releasing hormone, generally acts to release IGF-I from tissues including the ovary, the effect of IGF-I itself on ovarian steroidogenesis and oocyte maturation was investigated in the model teleost, Fundulus heteroclitus. IGF-I was found to be without effect on ovarian follicle steroidogenesis, but initiated oocyte maturation in a dose-dependent manner even more rapidly and effectively than 17,20-dihydroxy-4-pregnene-3-one (DHP), the naturally occurring maturation-inducing steroid. IGF-II also induced oocyte maturation in a dose-dependent manner. IGF-I induction of oocyte maturation occurred in the absence of DHP production by the granulosa cells (which is normally stimulated by gonadotropin), and could be inhibited by cycloheximide but not actinomycin D, thus implicating the role of protein synthesis. These results suggest that GH-stimulated release of ovarian IGF-I may have an even more direct role than DHP on the reinitiation of oocyte maturation.  相似文献   

2.
In this article, an in vitro investigation was carried out to ascertain the roles of hormones and growth factor in the inductions of oocyte maturation and steroidogenesis of the postvitellogenic follicles in an Indian estuarine grey mullet, Mugil cephalus L. Oocyte maturation was evaluated by scoring the germinal vesicle breakdown (GVBD) percent of the postvitellogenic follicles. All the sex [17α,20β-dihydroxy-4-pregnane-3-one (DHP), estradiol 17β (E2), progesterone (P), 17α-OH progesterone (17-OH-P) and testosterone] and other [bovine-insulin and salmon-calcitonin, human chorionic gonadotropin (hCG), luteinizing hormone (LH) or hCG+DHP] hormones and insulin-like growth factor-I (IGF-I) significantly increased GVBD% in 9 h culture. DHP had a maximum effect (75 %) compared to other effectors. Some effectors (hCG: 82.14 %, LH: 78.94 %, hCG plus DHP: 81.81 %, E2: 80 % and IGF-I: 74.19 %) including DHP (79 %) further increased GVBD% in 15-h culture. All the hormones (except DHP) and IGF-I increased DHP, E2 and testosterone productions by the postvitellogenic ovarian follicles in vitro. DHP and testosterone productions were increased with the increase of incubation time from 9 h through 15 h. E2 production was not further increased beyond 12 h. DHP production was highest by hCG compared to other effectors. The hCG of all the test compounds was most effective in both the induction of GVBD% and steroid production. DHP is the most potent inducer of oocyte maturation in Indian estuarine flat head grey mullet. Involvement of estrogen in mullet oocyte maturation is indicated. hCG, like DHP, is equally potent and induces oocyte maturation via DHP production in vitro. hCG with DHP has synergistic action on oocyte maturation in mullet ovary. Interplay of several hormones (hCG, LH, and probably E2 and testosterone) and IGF-I on oocyte maturation is suggested in the mullet.  相似文献   

3.
Stenohaline freshwater fish with narrow salinity tolerance are susceptible to saline stress from global climate change and anthropogenic activities. The present study elucidated that saline exposure during the sensitive window of preparatory phase of oocyte maturation significantly affected gonadosomatic index, ovarian histology and morphometric features of oocytes in a stenohaline freshwater catfish, Heteropneustes fossilis (Bloch, 1794) in a dose (2 ppt, 5 ppt)—and duration (8, 24 days)‐dependent manner. The gonads of H. fossilis show annual maturation cycle. Loss of integrity of ovigerous lamellae, disruption of ovarian stroma, disrupted oolemma, ooplasmic vacuolization, damaged germinal vesicles and altered morphometry of previtellogenic oocytes, such as chromatin‐nucleolus, early perinucleolar and late perinucleolar, elucidated consistent effects of saline exposure except at 8 days exposure to 2 ppt of saline. Increased salinity might have affected the transmembrane ion/water transport and disrupted the osmotic balance in ovary that eventually led to impairment in growth of ovary and oocyte maturation. The susceptibility of ovary to comparatively less concentrations of saline exposure might be due to sensitiveness of ovary/oocytes during the early phase of growth. Fluctuating salinity along with other stressors can affect metabolic and growth rates, fecundity and ultimately survival of fish.  相似文献   

4.
To elucidate the role of gonadotropin-releasing hormone (GnRH) in gonadal maturation in wild female Japanese flounder Paralichthys olivaceus, we monitored changes in the levels of seabream GnRH (sbGnRH) in the olfactory bulb, telencephalon, hypothalamus, and pituitary during ovarian development together with changes in plasma levels of testosterone (T), estradiol-17β (E2), and 17α, 20β-dihydroxy-4-pregnen-3-one (DHP). Fish were caught offshore of the northern mainland of Japan in the Pacific Ocean at 3- to 4-week intervals between April and September by gill net. The netted fish were categorized into six groups based on ovarian stages: previtellogenic (April–early May), early yolk (April–late May), late yolk (late May–June), early spawning (June–August), late spawning (September), and termination (September) stages. The gonadosomatic index significantly increased from the previtellogenic to early spawning stages and decreased thereafter. In the olfactory bulb, no significant differences were observed in sbGnRH levels among the developmental stages. In contrast, sbGnRH levels in the telencephalon and hypothalamus were very high in the previtellogenic stage, lower in the early spawning stage, and relatively high in latter stages. sbGnRH levels in the pituitary were high in the previtellogenic stage and low in the early spawning stage. In addition, the relatively high levels of pituitary sbGnRH were found together with high plasma T, E2, and DHP levels in fish in the late yolk stage. These results indicate that sbGnRH in the telencephalon, hypothalamus, and pituitary is involved in ovarian maturation and that sbGnRH may play an important role in the initiation of ovarian recrudescence in wild Japanese flounder.  相似文献   

5.
Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL?1 (1.25 ng well?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.  相似文献   

6.
Macquarie perch (Macquaria australasica) is a freshwater percichthyid endemic to south-eastern Australia. In view of its conservation status (indeterminate), and its importance as a sport fish, natural stocks are replenished through a breeding programme using mature stock taken from the wild each year.This paper is the first of a series of investigations instigated to understand the underlying causes of the lack of response of Macquarie perch, caught from the wild and spawned and then tankreared for a year, to hypophysation techniques. In this paper, results of physical characteristics, proximate composition and ovarian histology of wild-caught and tank-reared fish (injected with salmon GnRHa and non-injected) are presented. Oocyte diameter distribution patterns indicate that Macquarie perch spawn once each year, and that in tank-reared fish oocyte maturation is incomplete with only a small proportion of oocytes reaching maturation. The mean (sd) gonadosomatic and hepatosomatic indices of wild fish were 11.25 (2.38) and 0.59 (0.10) and that of tank-reared fish were 4.84 (0.70) and 1.44 (0.09) respectively. These two parameters differed significantly (p<0.05) in the two groups of fish.Major differences also existed in the proximate composition of the liver and the way the liver components responded to GnRHa injection. The percent (sd) protein, lipid and ash by dry weight in the liver of wild injected fish were 57.02 (0.66), 30.63 (1.22) and 8.24 (0.05) respectively while in the liver of tank-reared uninjected fish these values were 30.87 (1.36), 24.59 (1.18) and 6.43 (0.13) respectively. When expressed as an absolute amount or an amount kg–1 body weight, all of moisture, protein, lipid, ash and nitrogen free extract were greater in tank-reared than wild fish. No significant differences were observed between wild and tank-reared fish in the composition of the body musculature or the oocytes.  相似文献   

7.
Goldfish,Carassius auratus, spawn several times within a spawning season. A gonadotropin (GtH) surge occurs at the time of ovulation in this cyprinid species. This ovulatory GtH surge mediates the processes of final oocyte maturation and ovulation, and occurs at the end of each spawning cycle. Within a cycle, there is a shift in the predominant plasma steroid from estradiol to testosterone, and finally 17α, 20β-dihydroxy-4-pregnen-3-one at the time of the ovulatory GtH surge. High levels of testosterone were always observed before ovulation. When ovariectomized or sexually regressed female goldfish were implanted with testosterone, they exhibited a GtH surge which was similar to those normally observed at ovulation. These results strongly suggest that elevated plasma testosterone is an important physiological requirement for the occurrence of the GtH surge.  相似文献   

8.
The role of gonadotropin (GTH) in the reproduction of the Japanese flounder, Paralichthys olivaceus, was studied by assessing the changes in the apparent activity of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the pituitary gland during gonadal maturation by immunohistochemical analyses. Corresponding changes in plasma levels of testosterone (T), estradiol-17β (E2), and 17α,20β-dihydroxy-4–pregnen-3-one (DHP) were also studied. Reared fish at the early spawning to termination stages were sampled from May to August and wild fish at the previtellogenic to termination stages were caught at 3- to 4-week intervals between April and September offshore from the northern mainland of Japan by gill nets. The gonadosomatic index of the reared fish decreased from the early spawning stage to the termination stage, while that of the wild fish increased significantly from the previtellogenic stage to the early spawning stage and decreased thereafter. In the reared fish, the immunostaining intensities of FSH and LH were high during the spawning period, accompanied by high plasma levels of T, E2, and DHP. In the wild fish, the immunostaining intensities of FSH and LH were low during the previtellogenic stage but increased during the maturing and spawning stages. These results indicate that both FSH and LH are likely associated with oocyte maturation in the Japanese flounder.  相似文献   

9.
Chalcalburnus tarichi is an endemic cyprinid species living in the Lake Van basin, in eastern Anatolia, Turkey. The present study was undertaken to determine which hormones induce oocyte maturation in C. tarichi. The levels of 17α,20β,21-trihydroxyprogesterone (20β-S), progesterone (P), 17α-hydroxyprogesterone (17α-HOP), 11-deoxycortisol (11-DOC), and 17α-hydroxy-20β-dihydroprogesterone (17,20β-P) were measured in fish caught from Lake Van and the Karasu River, and injected with human chorionic hormone (hCG) (1,000 and 1,500 IU/kg). Oocytes of fish caught from the lake were also incubated in vitro with different doses (50, 200, and 1,000 ng/ml) of 20β-S, 17α-HOP, 11-DOC, and 17,20β-P. 11-DOC was found to be the most effective hormone among those measured for inducing oocyte maturation in vivo and in vitro. 17,20β-P could not be determined in the plasma of any fish in vivo (P < 0.05). 1,000 IU/kg dose of hCG given by injection caused a statistically significant increase in all plasma hormone levels (P < 0.05). It was found that there was a significant decrease in the P level only at 1,500 IU/kg dose of hCG injected (P < 0.05), while the level of other hormones increased at this dose (P < 0.05). It was also determined that all the hormones were effective in germinal vesicle breakdown (GVBD) in in vitro oocyte culture (P < 0.05). However, 11-DOC was found to be the most effective hormone in GVBD at a dose of 200 ng/ml (70% GVBD). In conclusion, 11-DOC synthesized during final oocyte maturation in C. tarichi was found to be a potent inducer of GVBD, which shows that 11-DOC may be described as an oocyte maturation steroid in this species.  相似文献   

10.
Plasma estradiol-17 (E2), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E2 and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E2 and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.  相似文献   

11.
Larval metamorphosis inducers of the sea cucumber Apostichopus japonicus were screened from physiologically active compounds. Doliolaria larvae completed their metamorphosis to juveniles in 120 h when treated with 5–10 μM of dopamine and l-DOPA, and 50 μM of l-adrenaline and l-noradrenaline. Doliolaria larvae had to be exposed to dopamine or l-DOPA for at least 24 h. D1-like dopamine receptor antagonists SKF87566 and LE300 (10 μM) inhibited metamorphosis by dopamine. However, the D2-like dopamine receptor antagonists sulpiride and nemonapride (10 μM) did not inhibit the effect of dopamine. The results suggest that D1-like dopamine receptors are involved in larval metamorphosis of the sea cucumber A. japonicus.  相似文献   

12.
Wild striped bass,Morone saxatilis, were collected from coastal waters and spawning areas to describe the endocrine correlates of oocyte development in non-captive, migratory fish. The fish were classified according to their most advanced oocytes. Serum levels of estradiol (E2), testosterone (T) and 17-20-dihydroxyprogesterone (DHP) were measured by radioimmunoassay (RIA). Females in the primary growth phase and early secondary growth phase (pre-vitellogenic) had low levels of plasma steroids, ovarian lipid content and gonadosomatic indices (GSIs). Significant increases in E2, T, ovarian lipid content and GSIs occurred during the vitellogenic phase. Maximum levels of all reproductive parameters were found in prespawning fish sampled in the Hudson River. Mean levels of E2, T, ovarian lipids and GSIs for these fish were 2.0±0.5 ng/ml, 3.0±0.3 ng/ml, 24±1 mg/g, and 5.6±0.3% (mean±SEM), respectively. In fish induced to spawn with human chorionic gonadotropin (HCG), DHP levels (1.9±0.4 ng/ml) were significantly elevated. Similar levels were found in two fish captured during the spawning season, suggesting that DHP may serve as the maturation-inducing steroid in this species.  相似文献   

13.
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   

14.
Effects of oral administration of l-thyroxine (T4) on growth performance, body composition, and some aspects of nutritional physiology were investigated in two slow-growing air-breathing fish (Channa punctatus and Heteropneustes fossilis) under laboratory conditions (LD 12:12 at 25°C). The results indicate that irrespective of the species, fish fed diets containing lower doses of T4 (up to 50 mg kg−1 of diet in C. punctatus and up to 100 mg kg−1 of diet in H. fossilis) showed significantly (P < 0.05) higher growth (in terms of live weight and length gain, specific growth rate, percentage gain in body weight and condition factor), low feed conversion ratio, high nutrient retention, high apparent protein digestibility, and high digestive enzyme activity. Viscero-somatic (VSI) and hepato-somatic (HSI) values were also high in fish fed on low dietary T4 levels. Liver glycogen levels decreased with the increase in the dietary T4 levels, indicating its utilization during growth. Muscle glycogen levels in H. fossilis coincided with high growth at 100 mg of T4. Observation of the postprandial excretion of metabolites (N–NH4 + and o-PO4 −) indicated significantly (P < 0.05) low levels in aquaria water where the fish were fed diets with low T4 levels. These studies further revealed that feeding fishes on higher T4 levels (above 50 mg in C. punctatus and above 100 mg in H. fossilis) not only repressed growth performance and nutrient retention, but also affected carcass composition by lowering protein accumulation (muscle and carcass protein) and energy assimilation. These studies revealed a biphasic action of thyroxine, i.e., the hormone at lower doses is anabolic, while at higher doses it acts as a catabolic agent, indicating that feeding fishes on higher doses can be detrimental to their growth and metabolism. In summary, the results of the present study show that feeding H. fossilis and C. punctatus on low doses of T4 enhances growth, decreases excretion of metabolites, and increases nitrogen retention. These observations suggest that T4 supplementation of the diet may have practical utility in the culture of slow-growing fish species.  相似文献   

15.
The relationship between plasma and ovarian levels of gonadal steroids was examined in two New Zealand fish species with multiple spawning cycles of differing length. Snapper (Pagrus auratus) have a daily cycle of oocyte development, ovulation and spawning, whereas demoiselles (Chromis dispilus) spawn over 2–3 days during a repeat spawning cycle of 7–9 days. Ovarian and plasma levels of the gonadal steroids 17β-estradiol (E2), testosterone (T), 17-hydroxyprogesterone (17P) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in reproductively active fish captured from the wild. Ovarian levels of E2, T and 17P changed in relation to spawning cycle and gonad stage in both snapper and demoiselles. E2 and T levels were detectable at all times, but highest during vitellogenesis in both species. Cyclic changes of 17P occurred in both species, and levels appeared to depend on the rate of conversion of 17P to other hormones. No changes in ovarian levels of 17,20βP were detected in relation to stage of the spawning cycle in snapper; however, ovarian levels of 17,20βP were highest in demoiselles before spawning when fish undergoing final oocyte maturation predominated. Plasma levels of E2 and T were strongly correlated with ovarian concentrations (r=0.850 and r=0.819 for E2 and T respectively) in demoiselles but there was poor correlation between ovarian and plasma levels of 17P and 17,20βP (r=0.004 and 0.273 respectively), or between ovarian and plasma levels of E2, T, 17P or 17,20βP of snapper (r=0.135, 0.277, 0.131 and 0.279). The poor correlation between plasma and ovarian levels of some steroid hormones suggests that plasma concentrations of steroids may not adequately reflect the reproductive status of the fish during short-term cyclic ovarian changes. It is suggested that this disparity is likely to be most marked in species with ovulatory periodicity of short duration.  相似文献   

16.
Germinal vesicle migration (GVM) and/or dissolution (GVD) were measured in goldfish oocytes, treated with 17α, 20β dihydroxyprogesterone (DHP) and other compounds considered to effect the cytoskeleton and oxidative phosphorylation,in vitro. Administration of DHP reinitiated meiotic maturation, increasing GVM and GVD in goldfish oocytes. Addition of 2,4-dinitrophenol (DNP) to the incubation medium significantly inhibited DHP-induced GVM and GVD. The DNP effect was found to be partially reversible after 24 h and could be reversed fully after a further delay of approximately 24h. Treatment of goldfish oocytes with demecolcine (DE; a colchicine derivative also known as colcemid) induces GVM to the micropyle without effecting GVD; while Cytochalasin-B which inhibits microfilament polymerization impairs both GVM and GVD. Administration of DNP, significantly inhibited DE-induced GVM, suggesting that GVM as well as GVD are dependent upon the process of oxidative phosphorylation. Addition of adenosine-5′ -triphosphate (ATP) at low concentrations (0.01–0.1 mM) did not effect DHP-induced or DNP-inhibited GVD in goldfish oocytes. The present results are consistent with the idea that migration of the oocyte nucleus during meiosis reinitiation has an energy requirement and involves participation by the cytoskeleton.  相似文献   

17.
In the present study, thiourea-induced thyroid hormone depletion and thyroxine (T4) ‘overdose’ were used as a strategy to understand the influence of thyroid hormones on ovarian recrudescence of juvenile (3-months-old), immature (8-months-old) and adult (1-year-old) air-breathing catfish, Clarias gariepinus. Thiourea-induced thyroid hormone depletion in juvenile catfish impaired ovarian development, but no significant effect was observed in immature catfish and during late stage of ovarian recrudescence of mature catfish. T4 treatment in females undergoing late stages of ovarian recrudescence induced rapid oocyte growth by promoting its early entry into maturational phase as evident from the presence of more number of vitellogenic and post-vitellogenic follicles, decrease in aromatse immunoreactivity and reduced estradiol–17β levels. Hence, thyroid hormones have an important role to play during early stages of ovarian development and vitellogenesis of catfish and also indicating that thyroid has a stage dependent effect on ovary.  相似文献   

18.
It has been established that secretion of gonadotropin (GtH) and growth hormone (GH) release in goldfish are both stimulated by GtH-releasing hormone (GnRH); in addition GtH secretion is inhibited by dopamine D2 mechanisms. In the present study, depletion of protein kinase C (PKC) in goldfish pituitary cells reduced the GtH and GH responses to GnRH and an activator of PKC in static culture. In perifusion studies, GtH released in response to sGnRH analog was greatly attenuated in PKC-depleted cells, however, hormone responses to forskolin were enhanced. Stimulation of dopamine D2 receptors reduced the GtH, but not the GH, responses elicited by PKC activators. These results indicate that PKC participates in the GtH and GH responses to natural neuroendocrine regulators in the goldfish.
Résumé Il a été établi que chez le poisson rouge, les sécrétions de gonadotropine (GtH) et d'hormone de croissance (GH) sont toutes les deux stimulées par la gonadolibérine (GnRH); de plus, la sécrétion de GtH est inhibée par des mécanismes dopaminergiques de type D2. Dans le présent travail, la déplétion de la teneur en protéine kinase C (PKC) dans des cellules hypophysaires de poisson rouge réduit les résponses en GtH et GH au GnRH et à un activateur de la PKC de cellules maintenues en incubation statique. Dans des cellules maintenues en périfusion et soumises à une déplétion en PKC, la GtH libérée en réponse à un analogue du sGnRH est fortement diminuée, cependent les réponses hormonales à la forskoline sont augmentées. La stimulation des récepteurs dopaminergiques D2 réduit, dans le cas d'action d'activateur de la PKC, la réponse en GtH mais pas en GH. Ces résultats indiquent que la PKC est impliquée dans les mécanismes de régulation de GtH et GH par des facteurs neuroendocriniens naturels.
  相似文献   

19.
A bioassay for insulin-like growth factor (IGF), based on the in vitro incorporation of [35S]-sulfate into gill arch tissue was used to study the hormonal regulation of proteoglycan synthesis in the goldfish (Carassius auratus). [35S]-sulfate incorporation into gill arch tissue was found to be time-dependent with maximal uptake occurring by 48h, suggesting that proteoglycan synthesis in this tissue was maintained for at least 48h in vitro. The addition of human recombinant IGF-I (IGF-I) to the incubation medium was found to significantly stimulate [35S]-sulfate uptake into the gill arches, whereas bovine growth hormone (GH) was without effect. Porcine insulin was also stimulatory, but results indicate that the effects of porcine insulin and IGF-I may be mediated by a single receptor system. Finally, arches from hypophysectomized fish were significantly less responsive to IGF-I than were arches from sham-operated fish. Furthermore, administration of ovine GH in vivo appeared to increase subsequent responsiveness in vitro. Together, these results provide evidence that the growth-promoting actions of GH in the goldfish may be mediated, at least in part, by a peptide related in structure to mammalian IGF-I.  相似文献   

20.
This study aimed to develop the consistent ovulation induction method in a pelagic egg spawning marine teleost, nibe croaker Nibea mitsukurii. Attempts to induce oocyte maturation and ovulation in nibe croaker using human chorionic gonadotropin (hCG; 0.5 IU g?1) resulted in the normal progression of oocyte maturation and hydration, but a failure to induce ovulation in many individuals. This ovulation disorder was similarly observed even when the dose of hCG was increased 10 times (5 IU g?1) or decreased to one tenth (0.05 IU g?1), indicating that it cannot be completely overcome solely by hCG administration. However, this ovulation disorder could be completely overcome by subsequent administration of 17,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) at the appropriate dose (0.5 μg g?1) and time (20 h after hCG administration). An increase in the number of individuals that ovulated due to DHP administration led to an increase in individuals producing larvae, resulting in an approximately threefold increase in the estimated number of larvae produced compared with the group of fish administered hCG alone. Thus, this ovulation induction method using DHP administration after hCG was demonstrated to overcome the ovulation disorder in nibe croaker and could be applicable to commercially important species with similar ovulation problems.  相似文献   

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