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1.
ABSTRACT:   Wild adult maturing and immature female Japanese flounder Paralichthys olivaceus were collected in June 2004 and January 2005, respectively, to clarify a possible role of gonadotropin-releasing hormones (GnRHs) in reproduction. Levels of salmon GnRH (sGnRH), chicken GnRH-II (cGnRH-II) and sea bream GnRH (sbGnRH) in the brain and pituitary were examined by time-resolved fluoroimmunoassay. Three forms of GnRHs were detected in the discrete brain at various levels. In the pituitary of both maturing and immature fish, sbGnRH was abundant together with a pronounced amount of sGnRH, whereas cGnRH-II was almost below the detectable limit. In maturing fish, levels of sbGnRH were high in the telencephalon, hypothalamus and pituitary, while levels of sbGnRH of immature fish were very low in these regions. These results indicate that sbGnRH is mainly responsible for gonadotropin secretion, and that sbGnRH in the anterior part of the brain is associated with gonadal maturation in the Japanese flounder.  相似文献   

2.
Multiple forms of the gonadotropin-releasing hormone (GnRH) exist in teleost fish. A salmonid fish, masu salmon Oncorhynchus masou has salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II). sGnRH neurons were scattered from the olfactory nerve through the ventral telencephalon (VT) and the preoptic area (POA). sGnRH but not cGnRH-II was detected in the pituitary. sGnRH mRNA levels in the VT and the POA increased during gonadal maturation, suggesting that sGnRH neurons in these areas are involved in gonadal maturation. sGnRH neurons were first detected in a cluster near the olfactory epithelium 40 days after fertilization. sGnRH neurons were not detected in the brain by the olfactory epithelia lesion, suggesting that sGnRH neurons are derived from the olfactory epithelium. A pleuronectiform fish, barfin flounder Verasper moseri has sGnRH, cGnRH-II and seabream GnRH (sbGnRH). sGnRH and cGnRH-II-immunoreactive fibers were observed throughout the brain, but not in the pituitary. sbGnRH neurons were located in the POA and sent fibers to the pituitary, indicating that sbGnRH is involved in GTH secretion. Judging from the location of neuronal somata and their projections, it is indicated that three GnRH systems exist in the barfin flounder; the TN-, the MT- and the POA-GnRH system. However, in masu salmon, clear anatomical identification of the TN- and the POA-GnRH system is difficult, because the GnRH neurons located in the ventral forebrain are consecutive and the GnRH form produced in these neurons is the same (sGnRH). Thus, it is suggested in masu salmon that sGnRH neurons are derived from the olfactory epithelium, migrate into the brain and play different roles according to the location in the brain.  相似文献   

3.
ABSTRACT:   A pleuronectiform fish, the barfin flounder Verasper moseri , expresses three gonadotropin-releasing hormone (GnRH) forms in the brain: salmon GnRH (sGnRH), chicken GnRH-II (cGnRH-II) and seabream GnRH (sbGnRH). To clarify the effects of photoperiod on GnRH systems, changes in brain and pituitary GnRH peptide levels were examined using time-resolved fluoroimmunoassays. In experiment 1, 5-month-old male barfin flounder (mean total length 9.0 cm, body weight 11.0 g) were divided into short (8:16 h light : dark [L:D] cycle; lights on 08.00–16.00 hours) and long photoperiod (16:8 h L:D cycle; lights on 04.00–20.00 hours) groups in mid September and maintained until November under natural water temperature (19.3–15.2°C). Brain sGnRH concentrations were significantly higher in the 16:8 h L:D group than in the 8:16 h L:D group, whereas no significant differences were observed in total length, body weight, plasma testosterone concentration, brain cGnRH-II concentration and pituitary sbGnRH content. In experiment 2, 7-month-old male barfin flounder (mean total length 16.5 cm, body weight 76.8 g) were divided into short and long photoperiod groups in mid December and maintained until February under natural water temperature (12.5–6.6°C). Total length, body weight and condition factor were significantly greater in the 16:8 h L:D group than in the 8:16 h L:D group, whereas no significant differences were observed in plasma testosterone concentration and GnRH levels in the brain and pituitary. These results indicate that levels of sGnRH in barfin flounder are influenced by photoperiodic treatment dependent on water temperature and/or body size.  相似文献   

4.
Distinct expression of GnRH genes in the red seabream brain   总被引：1，自引：0，他引：1  
This paper reports the molecular cloning of a cDNA encoding the precursor of seabream gonadotropin-releasing hormone (prepro-sbGnRH) and the localization of salmon GnRH (sGnRH) and seabream GnRH (sbGnRH) expressing neurons in the brain of the red seabream (Pagrus major). The cloned prepro-sbGnRH cDNA has a 285 bps open reading frame encoding a 23 amino acid signal peptide, a 10 amino acid sbGnRH, the cleavage site (Gly-Lys-Arg), and a 59 amino acid GnRH-associated peptide. The expression of sGnRH and sbGnRH peptides, and prepro-sGnRH and prepro-sbGnRH mRNA were studied using immunocytochemistry and non-radioactive in situ hybridization, respectively. We found cell bodies that reacted positively with both the sGnRH cRNA probe and anti-sGnRH serum, but not with the sbGnRH cRNA probe or anti-sbGnRH serum in the ganglion of the terminal nerve. Cell bodies that reacted positively with the sbGnRH cRNA probe, anti-sbGnRH serum, and anti-sGnRH serum, but negatively with the sGnRH cRNA probe were found in the preoptic area (POA). Immunocytochemistry showed that a distinct bundle of axons arises in the POA which projected to the pituitary gland. These results suggest that sbGnRH is the most relevant hypophysiotropic form of GnRH.  相似文献   

5.
Effects of gonadotropin-releasing hormone (GnRH) on thyroxine (T4) release in vivo and in vitro were studied in barfin flounder Verasper moseri, masu salmon Oncorhynchus masou and goldfish Carassius auratus. Seabream GnRH (sbGnRH) at a dose of 200 ng/50 g body weight (BW) significantly increased plasma T4 levels 1 h after the in vivo injection in the barfin flounder, but thereafter the levels normalized. Salmon GnRH (sGnRH) significantly increased plasma T4 levels l h after the injection with a significant return to initial levels in male masu salmon and male goldfish. In contrast, sGnRH and cGnRH-II in barfin flounder, and cGnRH-II in male masu salmon and male goldfish were not effective in stimulating T4 release. To clarify direct involvement of GnRH in T4 release, dissected lower jaw including scattered thyroid follicles was incubated with sbGnRH (1 μg/well) in barfin flounder, and with two doses (0.1 and 1 μg/well) of sGnRH in masu salmon and goldfish in vitro. T4 concentrations of control were stable during 24 h. Incubation of lower jaw with high dose (1 μg/well) of GnRH significantly (P<0.05) increased T4 concentrations of incubation medium at 1 h in all experimental fishes. These results indicate that direct stimulation of T4 secretion by GnRH occurs widely in teleost fish.  相似文献   

6.
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7.
The brain of the pejerrey (Odontesthes bonariensis) has recently been shown to contain three forms of gonadotropin-releasing hormone (GnRH): salmon GnRH (sGnRH), chicken GnRH-II (cGnRH-II) and pejerrey GnRH (pjGnRH), nevertheless neuroanatomical studies on the distribution of these peptides are lacking. In this study we investigated the distribution of immunoreactive GnRH in the brain of adult pejerrey. Four different policlonal antisera and a monoclonal antibody against different GnRH variants were applied on cryosections and visualized using the ABC method. Three antisera (PBL#49, sGnRH#2 and cII741) revealed three different immunoreactive areas: the terminal nerve ganglion (at the junction between the olfactory bulbs and the anterior telencephalon), the preoptic area just anterior to the hypothalamus and the midbrain tegmentum. Fibers immunoreactive to GnRH were detected in different brain areas: the olfactory bulbs, the ventral thelencephalon, the hypothalamus, the mesencephalic area and an important innervation entering into the pituitary gland. Two other antibodies (LRH13 and s1668) labeled the two nuclei corresponding to the forebrain but not the midbrain tegmentum. As both antibodies have low crossreactivity to cGnRH-II, the data suggest that this group of cells express cGnRH-II. In summary, three different areas with immunoreactivity to GnRH were detected in the pejerrey brain. The distribution of sGnRH, pjGnRH and cGnRH-II expressing neurons, is discussed.  相似文献   

8.
Gonadotropin-releasing hormone (GnRH) molecular variants were characterized by gradient reverse phase high performance liquid chromatography (RP)-HPLC) from brain extracts of two perciforms with economic importance for Argentina and Uruguay. RP-HPLC fractions were tested in radioimmunoassays (RIAs) with both poly-specific and specific antisera. Both species showed the presence of the same three molecular forms, immunologically and chromatographically indistinguishable from sbGnRH, cGnRH-II and sGnRH. This study supports the hypothesis that their expression is a common pattern in perciforms.  相似文献   

9.
Gonadotropin-releasing hormone and gonadotropin in goldfish and masu salmon   总被引：1，自引：0，他引：1  
Reproductive activities in vertebrates are regulated by an endocrine system, consisting of the brain-pituitary-gonad axis. In teleosts, gonadotropin-releasing hormone (GnRH) in the brain stimulates gonadotropin (GTH) release in the pituitary gland, but because of lack of the portal vessel, it is not known when and how much GnRH is released for the regulation of GTH release. There are multiple molecular types of GnRH in teleosts and several distinct populations of GnRH neurons in the brain. However, we do not know which types and populations of GnRH neurons regulate reproductive activities. Here we summarize our recent studies on GnRH and GTH in masu salmon Oncorhynchus masou and goldfish Carassius auratus. Immunocytochemistry showed the location and molecular types of GnRH neurons. Salmon (sGnRH) and chicken-II GnRH (cGnRH-II) neuronal fibers were widely distributed in the brain of both masu salmon and goldfish. Only sGnRH fibers were observed in the pituitary of masu salmon, whereas both sGnRH and cGnRH-II fibers were observed in the goldfish pituitary, indicating that species specific GnRH profiles are involved in the regulation of pituitary function in teleosts. A series of experiments in masu salmon and goldfish suggest that among GnRH neuron populations GnRH neurons in the ventral telencephalon and the hypothalamus regulate GTH release, and that GnRH of the terminal nerve origin is not essential to gonadal maturation and ovulation. The biological function of other GnRH neurons remains unkown. Two GTHs appear to be characteristic of teleost; however, regulation of reproduction by these GTHs is a question that remains to be elucidated. In salmonid species, it is proposed that GTH I stimulates early gonadal development, whereas GTH II acts in later stages. When GTH expression was examined in goldfish, both GTH I and II mRNA levels in the pituitary gland showed increases in accordance with gonadal development, unlike the sequential expression of GTH subunits in salmonids. The expression of these GTH subunit mRNAs were affected by water temperature, starvation, and steroid hormones in goldfish, but in what manner these two GTHs regulate gonadal development remains to be clarified.  相似文献   

10.
The present study examined the differential mRNA expression levels of three forms of GnRH (sGnRH, pjGnRH and cGnRH-II) and two forms of GnRH receptor (pjGnRH-R I and pjGnRH-R II) in the brain, pituitary, and ovaries of pejerrey in relation to the reproductive status. The analysis revealed the presence of significant amounts of mRNA of the three GnRH forms while the ovaries showed only two (sGnRH and pjGnRH). The GnRH receptor II was found ubiquitously in the brain, pituitary, and ovaries while the form I was detected only in the brain. The levels of pjGnRH mRNA in the brain and pjGnRH-R II in the pituitary gland varied in correlation with the ovarian condition. However, brain sGnRH and pjGnRH-R I mRNA levels reached a maximum during early stages of ovarian development. In contrast, the brain levels of cGnRH-II mRNA showed no variation. The present study also shows a good correlation of ovarian sGnRH and pjGnRH-R II mRNA levels with the reproductive condition, suggesting that these molecules are may be involved in the regulation of pejerrey ovarian function.  相似文献   

11.
We examined the effects of gonadotropin-releasing hormone agonist (GnRHa) and testosterone (T) on the level of gonadotropin subunit mRNAs in the pituitary of ovariectomized or intact female red seabream. Ovariectomy induced increase of seabream (sb) GnRH, glycoprotein (GP) α and luteinizing hormone (LH) β mRNA levels. GnRHa treatment also stimulated GPα and LHβ mRNA levels. T treatment reduced GPα and LHβ mRNA expression probably via negative feedback action on sbGnRH. Both GnRHa and T treatment had no effect on follicle-stimulating hormone (FSH) β mRNA levels. These results suggest that the regulatory mechanisms of GPα and LHβ gene expression differ from those of FSHβ gene.  相似文献   

12.
The roles of salmon GnRH (sGnRH) and gonadal steroid hormones in regulation of LH synthesis and release were examined in primary pituitary cell cultures of masu salmon (Oncorhynchus masou). Pituitaries were taken from fish at four reproductive stages: in March (initiation of sexual maturation); May (early maturation); July (pre-spawning); and September (spawning period). Amounts of LHβ subunit mRNA in the pituitary cells were determined by real-time PCR, and LH levels in the medium were determined by RIA. sGnRH and gonadal steroids including estradiol-17β (E2), testosterone (T) and 11-ketotestosterone (11-KT) were added to the cultures to examine their direct effects on LH response. sGnRH had no significant effect on LHβ mRNA levels at any stages, although a stimulatory trend was noted in March. In contrast, E2 and T considerably increased LHβ subunit mRNA levels in March and May during initial stages of maturation, and the effects were less pronounced in July and September. On the other hand, sGnRH stimulated LH release at all stages in the males and the effects were most prominent in July and September. E2 and T also stimulated LH release in July and September, but their effects were weaker than that of sGnRH. The present results indicate that sGnRH and gonadal steroids directly regulate LH synthesis and release in masu salmon pituitary cells: sGnRH mainly stimulates LH release in the late stage of sexual maturation; whereas, E2 and T are effective in stimulating LH synthesis at earlier stages of maturation.  相似文献   

13.
Levels of two types of gonadotropin-releasing hormone (salmon GnRH and chicken GnRH-II) in the brain and pituitary, and content of gonadotropin (GTHIβ and IIβ) in the pituitary were measured in male masu salmon from hatching to gonadal maturation for three years in order to clarify the involvement of GnRHs in precocious maturation. Underyearling precocious males were distinguishable in summer of year 1 and were marked by an increased GSI. Spermiation was observed among these individuals thereafter every autumn. Pituitary GTHIβ content in both precocious and immature males, and GTHIIβ content in precocious males showed seasonal fluctuations — high in autumn and low in winter. Pituitary GTHIIβ content was low in immature males. Pituitary sGnRH content in precocious males increased from spring to autumn during the three-year period. sGnRH concentrations in discrete brain areas showed seasonal changes — high during autumn to winter and low in summer. Concentrations in the olfactory bulbs and hypothalamus increased significantly in association with testicular maturation during year 3. sGnRH concentrations in the hypothalamus were significantly higher in precocious males than in immature males; this was possibly due to positive feedback of steroid hormones. cGnRH-II was undetectable in the pituitary and no distinct changes were observed in its concentration in the brain in relation to maturation. The phenomenon of underyearling precocious maturation is considered to be triggered before the onset of early summer. It is suggested that males which mature precociously are larger in size and contain much sGnRH in the pituitary before the outward signs of precocity appear; sGnRH may stimulate GTH II synthesis and induce precocious maturation.  相似文献   

14.
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   

15.
Immunohistochemical localization of orexin/hypocretin in the brain of a pleuronectiform fish, the barfin flounder Verasper moseri was examined as the first step in unraveling the possible function of the hormone in the brain. Orexin-A-like immunoreactive (ir) cell bodies were found to be located in the nucleus posterioris periventricularis (NPPv) of the hypothalamus, and orexin-A-like-ir fibers were detected not only in the hypothalamus but also extensively throughout the brain. The orexin-A-like-ir cell bodies did not project their fibers to the pituitary gland. Since melaninconcentrating hormone (MCH) and α-melanocyte-stimulating hormone (α-MSH) are suggested to regulate food intake in addition to orexin/hypocretin in the teleost fish, it was examined whether neural connections exist between orexin neurons and the MCH and α-MSH neurons in the barfin flounder brain by using double-staining immunohistochemistry. Some orexin-A-like-ir fibers were in close contact with the MCH-ir and α-MSH-ir cell bodies in the hypothalamus. Moreover, a few MCH-ir and α-MSH-ir fibers were in close contact with the orexin-A-like-ir cell bodies in the hypothalamus. These results suggest that reciprocal connections exist between the orexin and MCH neurons and between the orexin and α-MSH neurons in the brain of the barfin flounder.  相似文献   

16.
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   

17.
Levels of two moleculer types of gonadotropin-releasing hormone (GnRH), salmon GnRH (sGnRH) and chicken GnRH–II (cGnRH–II) in the various brain regions and pituitary gland of sockeye salmon (Oncorhynchus nerka) and chum salmon (O. keta) during smoltification and spawning migration, respectively, were measured using specific time-resolved fluoroimmunoassay (TR-FIA) systems. Changes in sGnRH levels in different brain regions tended to be specifically synchronized with serum thyroid hormone or pituitary gonadotropin (GTH) levels during smoltification and spawning migration, respectively. In contrast, cGnRH–II levels did not show such synchronized changes. SGnRH and cGnRH–II in various brain regions might have different roles during smoltification and spawning migration of salmonid fishes.  相似文献   

18.
Two gonadotropin releasing hormones (GnRHs) were identified in the African catfish: chicken GnRH-II (cGnRH-II) and catfish GnRH (cfGnRH). Immunological screening of HPLC fractions from pituitary extracts indicated a third GnRH which co-eluted with lamprey GnRH-III. However, mass determination and amino acid sequencing identified this material as isotocin. This underlines the risk of identifying multiple forms of GnRH in tissue extracts on the basis of immunoreactivity in HPLC fractions. In vivo and in vitro studies demonstrated that cGnRH-II is an over 100-fold more potent gonadotropin (GTH) secretagogue than cfGnRH. This correlates with the respective receptor affinities. The presence of both GnRHs in the pituitary gland suggests that they may modulate each other's GTH release activity. Sub-threshold or low doses of cGnRH-II partly inhibited cfGnRH-induced GTH II secretion. Conversely, combinations of sub-threshold or low doses of cfGnRH with effective doses of cGnRH-II led to increases in GTH II levels similar to those induced by cGnRH-II alone. Combinations of submaximally effective dose of the 2 peptides resulted in additive effects. Hence, both GnRHs participate in the regulation of GTH II release, and their relative concentrations may determine the overall effect. Immunocytochemistry, using anti-bodies against the respective recombinant GnRH associated peptides (GAPs), as well as in situ hybridization showed that cfGnRH neurones are scattered in the ventral forebrain and project into the pituitary gland, while cGnRH-II neurones are confined to the midbrain tegmentum and without projections to the pituitary gland. Transfection experiments with GnRH receptor cDNA shows ligand activation characteristics similar to those of the native GnRH-R. Autoradiographic studies and hormone release studies indicate that GnRH-Rs in the African catfish pituitary gland are restricted to the gonadotrophs.  相似文献   

19.
Gonadotropin (GTH) hormones are glycoprotein which stimulates gonadal maturation in vertebrates. Follicle stimulating hormone is involved in initiation of gametogenesis and regulation of gonadal growth. FSHβ has been cloned and characterized from the brain of Catla catla. The FSHβ full‐length of cDNA sequence of 523 bp comprised 3, 394 and 128 bp of 5′‐UTR, open reading frame (ORF) 3′‐UTR respectively. The coding region of C. catla FSHβ encoded a peptide of 130 amino acids. Phylogenetic analysis of C. catla FSHβ deduced amino acid sequence showed high similarity with Gobiocypris rarus followed by goldfish, Carassius auratus. The qPCR result shows that FSHβ mRNA is mainly expressed in pituitary while moderate and low expression was observed in testis and ovary respectively. Chitosan‐nanoconjugated kisspeptin‐10 (CK‐10) of particle size 125 nm, polydispersity index of 0.335 to 0.65 and zeta potential of ?34.95 mV were synthesized and evaluated at against naked kisspeptin‐10 for their reproductive hormonal profile. Treatment of fish with CK‐10 showed controlled and sustained surge of the reproductive hormones (FSH & LH) with peak at 12 h. The hormone levels of naked kisspeptin‐10 treated fish decline after 6 h. The sustained release of this CK‐10 will help in reducing maturation age, synchronization of ovulation and spawning in fish. This is the first report on use of chitosan‐nanoconjugated kisspeptin‐10 (CK‐10) for reproduction in fish.  相似文献   

20.
Vertebrate reproduction is under the neuroendocrine control of the hypothalamic decapeptide GnRH which synchronizes various reproductive events and influences other reproduction related aspects like spawning behavior and pheromonal action in fish. Multiple forms of GnRH peptides have been reported across diverse vertebrate and invertebrate classes. Here we report the partial seabream GnRH (sbGnRH) cDNA sequence cloned from the brain of Channa striatus (snake head murrel) a fresh water perciform with immense economic and medicinal value across Asiatic countries. sbGnRH mRNA was found in brain, gill and ovary of mature murrel with possible implications to the effect of GnRH on pheromonal phenomena and on reinitiation of oocyte meiosis. In keeping with the earlier reported role of GnRH in initiation of oocyte meiosis we here present evidence from RT-PCR, ICC demonstrating an increase in the level of sbGnRH mRNA in ovary from pre-vitellogenic to post-vitellogenic follicles.  相似文献   

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