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Nobata S, Sato K, Houki S, Ito M, Aoki Y, Kitagawa T, Hyodo S. Straightforward upriver migration to spawning sites by chum salmon Oncorhynchus keta homing to coastal short rivers in the Sanriku region. JOURNAL OF FISH BIOLOGY 2022; 100:748-757. [PMID: 35015295 DOI: 10.1111/jfb.14990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 12/31/2021] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
In chum salmon (Oncorhynchus keta) homed to the Sanriku region, Japan, most of the fish are matured in bays and spawn near river mouths in coastal short rivers; therefore, their upriver migration is extremely short, but their behavioural characteristics have remained unknown. Upriver migration in the Otsuchi River, a typical coastal river, was evaluated from behavioural and physiological aspects. Homing salmon tracked in Otsuchi Bay held in the inner bay for less than 1 day to more than 10 days before river entry. The varied holding duration was negatively correlated with plasma 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) concentration, an indicator of maturation. After river entry, however, most fish were captured in weirs near the river mouths within 2 days regardless of the DHP concentration. Of the 34 fish released in the river, on the contrary, eighteen and five fish were seen next day in the main spawning sites located at c. 1.5 km upstream and in the branch creek, respectively, and 85% of the fish held position there until their death. The mean survival time of released fish was 5.8 days. Plasma DHP level suggested that preparations for spawning were already completed at the timing of the release. Taken together, homing salmon completed spawning preparation in the bay, and then they moved to their spawning sites immediately after river entry and spawned there during their short remaining life. This upriver migration contrasts with those of other populations, such as early migrants and long river migrants, whose maturation is completed during upriver migration.
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Affiliation(s)
- Shigenori Nobata
- Division of Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Katsufumi Sato
- Division of Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
- International Coastal Marine Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Iwate, Japan
| | - Shouji Houki
- International Coastal Marine Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Iwate, Japan
| | - Motohiro Ito
- International Coastal Marine Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Iwate, Japan
| | - Yoshinori Aoki
- International Coastal Marine Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Iwate, Japan
| | - Takashi Kitagawa
- International Coastal Marine Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Iwate, Japan
| | - Susumu Hyodo
- Division of Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
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Nobata S, Kitagawa T, Houki S, Ito M, Aoki Y, Sato K, Hyodo S. Relationships between maturational status and migration behavior of homing chum salmon Oncorhynchus keta in inner bays of the Sanriku coast. Gen Comp Endocrinol 2021; 313:113896. [PMID: 34499908 DOI: 10.1016/j.ygcen.2021.113896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 08/31/2021] [Accepted: 09/01/2021] [Indexed: 10/20/2022]
Abstract
The correlations among gonad maturity and various homing behaviors of chum salmon, Oncorhynchus keta, were evaluated using acoustic tracking of tagged fish in Otsuchi Bay, Japan. There was a negative correlation between the time duration from release of tagged fish until river entry and the plasma 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) levels, an indicator of final maturation. Females with high DHP entered the rivers soon after the release, whereas females with low DHP (<10 ng/ml) took a few days to more than one week until river entry. Similar correlation was also found in males. A pattern of river entry correlated with maturational conditions was also observed in fish entering the rivers of neighboring bays. DHP concentrations of fish caught in the rivers were consistently higher. On the other hand, more than half of released salmon departed from the bay regardless of their plasma DHP level, suggesting that maturational status does not force homing adults to enter the most available nearest rivers. Fish entering the rivers experienced ambient temperatures less than 8 °C, which is approximately 5 °C lower than that of the bay. These results indicate that homing salmon hold their position in the bay until just before spawning, which may be attributable to low temperature avoidance. This characteristic type of river entry may be suitable to geographical features and thermal regimes of this region.
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Affiliation(s)
- Shigenori Nobata
- Division of Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
| | - Takashi Kitagawa
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Shouji Houki
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Motohiro Ito
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Yoshinori Aoki
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Katsufumi Sato
- Division of Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan; International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Susumu Hyodo
- Division of Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
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Qiang J, He J, Zhu JH, Tao YF, Bao JW, Yan Y, Xu P, Zhu X. Optimal combination of temperature and photoperiod for sex steroid hormone secretion and egg development of Oreochromis niloticus as determined by response surface methodology. J Therm Biol 2021; 97:102889. [PMID: 33863448 DOI: 10.1016/j.jtherbio.2021.102889] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/28/2021] [Accepted: 02/16/2021] [Indexed: 11/19/2022]
Abstract
For successful reproduction of farmed fish, it is important to understand the relationship between gonadal development and environmental factors such as temperature and photoperiod. In this study, we determined the effects of temperature (T) and photoperiod (Pp) on serum estradiol-17β (E2) and progesterone (P) contents, gonadosomatic index (GSI), and oocyte development in female tilapia. We used a central composite experimental design and response surface methodology. The experimental ranges were 18-36 °C for T and 0-24 h for Pp. The results show that the quadratic effects of T and Pp were highly significant for serum E2 and P contents, GSI, and the ratio of stage III to stage II oocytes (P < 0.01), and that the linear effects of T and Pp were also significant for these indicators (P < 0.05). The T × Pp interaction significantly affected serum E2 content (P < 0.05). Serum E2 and P content, GSI, and the ratio of stage III to stage II oocytes increased and then decreased with increasing T or Pp. The best combination of T and Pp for egg development was 28.6 °C/14.29 h. We observed the part of ovarian tissue containing stage V oocytes that are about to be discharged. Shortening the photoperiod or lowering the water temperature delayed the development of ovarian tissue so that most oocytes remained at stage II, and there were many atretic follicles. There were significant positive correlations between female GSI and serum E2, P, and the ratio of stage III to stage II oocytes. The results of this study provide a reference for the regulation of temperature and photoperiod to control broodstock gonadal maturation and hormone-induced broodstock spawning.
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Affiliation(s)
- Jun Qiang
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China; Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, 214081, China.
| | - Jie He
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China
| | - Jun-Hao Zhu
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China
| | - Yi-Fan Tao
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China
| | - Jin-Wen Bao
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China
| | - Yue Yan
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China
| | - Pao Xu
- Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, Jiangsu, China.
| | - Xiaowen Zhu
- Fisheries of College of Guangdong Ocean University, Zhanjiang, 524025, Guangdong, China
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Yazawa T, Inaba H, Imamichi Y, Sekiguchi T, Uwada J, Islam MS, Orisaka M, Mikami D, Ida T, Sato T, Miyashiro Y, Takahashi S, Khan MRI, Suzuki N, Umezawa A, Kitano T. Profiles of 5α-Reduced Androgens in Humans and Eels: 5α-Dihydrotestosterone and 11-Ketodihydrotestosterone Are Active Androgens Produced in Eel Gonads. Front Endocrinol (Lausanne) 2021; 12:657360. [PMID: 33833737 PMCID: PMC8021924 DOI: 10.3389/fendo.2021.657360] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 02/26/2021] [Indexed: 01/07/2023] Open
Abstract
Although 11-ketotestosterone (11KT) and testosterone (T) are major androgens in both teleosts and humans, their 5α-reduced derivatives produced by steroid 5α-reductase (SRD5A/srd5a), i.e., 11-ketodihydrotestosterone (11KDHT) and 5α-dihydrotestosterone (DHT), remains poorly characterized, especially in teleosts. In this study, we compared the presence and production of DHT and 11KDHT in Japanese eels and humans. Plasma 11KT concentrations were similar in both male and female eels, whereas T levels were much higher in females. In accordance with the levels of their precursors, 11KDHT levels did not show sexual dimorphism, whereas DHT levels were much higher in females. It is noteworthy that plasma DHT levels in female eels were higher than those in men. In addition, plasma 11KDHT was undetectable in both sexes in humans, despite the presence of 11KT. Three srd5a genes (srd5a1, srd5a2a and srd5a2b) were cloned from eel gonads. All three srd5a genes were expressed in the ovary, whereas only both srd5a2 genes were expressed in the testis. Human SRD5A1 was expressed in testis, ovary and adrenal, whereas SRD5A2 was expressed only in testis. Human SRD5A1, SRD5A2 and both eel srd5a2 isoforms catalyzed the conversion of T and 11KT into DHT and 11KDHT, respectively, whereas only eel srd5a1 converted T into DHT. DHT and 11KDHT activated eel androgen receptor (ar)α-mediated transactivation as similar fashion to T and 11KT. In contrast, human AR and eel arβ were activated by DHT and11KDHT more strongly than T and 11KT. These results indicate that in teleosts, DHT and 11KDHT may be important 5α-reduced androgens produced in the gonads. In contrast, DHT is the only major 5α-reduced androgens in healthy humans.
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Affiliation(s)
- Takashi Yazawa
- Department of Biochemistry, Asahikawa Medical University, Hokkaido, Japan
- *Correspondence: Takashi Yazawa,
| | - Hiroyuki Inaba
- Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan
- Freshwater Resources Research Center, Aichi Fisheries Research Institute, Aichi, Japan
| | - Yoshitaka Imamichi
- Department of Pharmacology, Asahikawa Medical University, Hokkaido, Japan
| | - Toshio Sekiguchi
- Noto Marine Laboratory, Institute of Nature and Environmental Technology, Division of Marine Environmental Studies, Kanazawa University, Ishikawa, Japan
| | - Junsuke Uwada
- Department of Biochemistry, Asahikawa Medical University, Hokkaido, Japan
| | | | - Makoto Orisaka
- Department of Obstetrics-Gynecology, University of Fukui, Fukui, Japan
| | - Daisuke Mikami
- Department of Nephrology, University of Fukui, Fukui, Japan
| | - Takanori Ida
- Center for Animal Disease Control, University of Miyazaki, Miyazaki, Japan
| | - Takahiro Sato
- Molecular Genetics, Institute of Life Sciences, Kurume University, Fukuoka, Japan
| | | | - Satoru Takahashi
- Department of Pediatrics, Asahikawa Medical University, Hokkaido, Japan
| | - Md. Rafiqul Islam Khan
- Department of Biochemistry, Asahikawa Medical University, Hokkaido, Japan
- Department of Pharmacy, University of Rajshahi, Rajshahi, Bangladesh
| | - Nobuo Suzuki
- Noto Marine Laboratory, Institute of Nature and Environmental Technology, Division of Marine Environmental Studies, Kanazawa University, Ishikawa, Japan
| | - Akihiro Umezawa
- Department of Reproduction, National Research Institute for Child Health and Development, Tokyo, Japan
| | - Takeshi Kitano
- Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan
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Nobata S, Kitagawa T, Tanaka K, Komatsu K, Aoki Y, Sato K, Takei Y, Hyodo S. Spreading of River Water Guides Migratory Behavior of Homing Chum Salmon Oncorhynchus keta in Otsuchi Bay, a Narrow Inlet with Multiple River Flows. Zoolog Sci 2019; 36:449-457. [PMID: 31833315 DOI: 10.2108/zs190026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 06/02/2019] [Indexed: 11/17/2022]
Abstract
The Sanriku-ria coast of Japan, a homing area for chum salmon, Oncorhynchus keta, is characterized by a large number of small closed bays into which one or multiple short rivers flow. The present behavioral investigation of chum salmon in this region was designed to gain deeper insight into the migration of chum salmon to their natal rivers. Eighty-three fish caught at the middle part of Otsuchi Bay were tracked using an acoustic transmitter in the narrow inlet into which flow three rivers: the Otsuchi, Koduchi, and Unosumai. The majority of 18 fish that entered the Unosumai River, which flows into the southwest side of the bay, directly approached the river along the southern coast. More than half of fish that entered the Otsuchi and Koduchi Rivers, which flow into the northwest side, also migrated into the inner bay via the southerly route, and then entered these rivers frequently after passing the mouth of the Unosumai River. In the inner bay, the salinity of sea surface water suggested that water from the three rivers circulates in a counterclockwise direction at a depth of less than 1.0 m, flowing eastwardly along the southern coast. The observed migratory paths of homing salmon in Otsuchi Bay thus correspond well with the counterflow of surface river water in the bay. The present results suggest that homing migration of salmon in the Sanriku narrow inlet is guided by natal river flows.
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Affiliation(s)
- Shigenori Nobata
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan,
| | - Takashi Kitagawa
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Kiyoshi Tanaka
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Kosei Komatsu
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.,Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 236-8648, Japan
| | - Yoshinori Aoki
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8, Akahama, Otsuchi, Kamihei, Iwate 028-1102, Japan
| | - Katsufumi Sato
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Yoshio Takei
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Susumu Hyodo
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
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Shahjahan M, Kitahashi T, Ando H. Temperature affects sexual maturation through the control of kisspeptin, kisspeptin receptor, GnRH and GTH subunit gene expression in the grass puffer during the spawning season. Gen Comp Endocrinol 2017; 243:138-145. [PMID: 27916574 DOI: 10.1016/j.ygcen.2016.11.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 11/25/2016] [Accepted: 11/30/2016] [Indexed: 01/31/2023]
Abstract
Water temperature is an environmental factor of primary importance that influences reproductive function in fish. To understand the molecular and physiological mechanisms underlying the regulation of reproduction by temperature, we examined changes in expression of genes encoding kisspeptin (kiss2), kisspeptin receptor (kiss2r) and three gonadotropin-releasing hormones (gnrh1, gnrh2 and gnrh3) in the brain and genes encoding gonadotropin (GTH) subunits (gpa, fshb and lhb) in the pituitary of grass puffer exposed to a low temperature (14°C), normal temperature (21°C) and high temperature (28°C) for 7days. In addition, the plasma levels of cortisol were examined after exposed to three temperature conditions. The gonadosomatic index was significantly decreased in both low and high temperature conditions. The levels of kiss2 and kiss2r mRNAs were significantly decreased at both low and high temperature conditions compared to normal temperature (control) condition. gnrh1 but not gnrh2 were significantly decreased in both temperature conditions, while gnrh3 showed a decreasing tendency in low temperature. Consequently, the levels of fshb and lhb mRNAs were significantly decreased in both low and high temperature conditions. Interestingly, the plasma levels of cortisol were significantly increased in low temperature but remain unchanged in high temperature, suggesting that the fish were under stress in the low temperature conditions but not in the high temperature conditions. Taken together, the present results indicate that anomalous temperature have an inhibitory effect on reproductive function through suppressing kiss2/kiss2r/gnrh1/fshb and lhb expression and these changes may occur in a normal physiological response as well as in a malfunctional stress response.
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Affiliation(s)
- Md Shahjahan
- Sado Marine Biological Station, Faculty of Science, Niigata University, Sado, Niigata 952-2135, Japan
| | - Takashi Kitahashi
- Sado Marine Biological Station, Faculty of Science, Niigata University, Sado, Niigata 952-2135, Japan
| | - Hironori Ando
- Sado Marine Biological Station, Faculty of Science, Niigata University, Sado, Niigata 952-2135, Japan.
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Ornostay A, Marr J, Loughery JR, Martyniuk CJ. Transcriptional networks associated with 5-alpha-dihydrotestosterone in the fathead minnow (Pimephales promelas) ovary. Gen Comp Endocrinol 2016; 225:23-32. [PMID: 26344943 DOI: 10.1016/j.ygcen.2015.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 09/02/2015] [Accepted: 09/02/2015] [Indexed: 11/17/2022]
Abstract
Androgens play a significant role in regulating oogenesis in teleost fishes. The androgen dihydrotestosterone (DHT) is a potent non-aromatizable androgen involved in sexual differentiation in mammals; however, its actions are not well understood in teleost fish. To better characterize the physiological role of DHT in the fathead minnow (FHM) ovary on a temporal scale, in vitro assays for 17β-estradiol (E2) production were conducted in parallel with microarray analysis. Ovarian explants were incubated at different concentrations of DHT (10(-6), 10(-7), and 10(-8)M DHT) in three separate experiments conducted at 6, 9, and 12h. DHT treatment resulted in a rapid and consistent increase in E2 production from the ovary at all three time points. Therefore, DHT may act to shift the balance of metabolites in the steroidogenic pathway within the ovary. Major biological themes affected by DHT in the ovary in one or more of the time points included those related to blood (e.g. vasodilation, blood vessel contraction, clotting), lipids (e.g. lipid storage, cholesterol metabolism, lipid degradation) and reproduction (e.g. hormone and steroid metabolism). Gene networks related to immune responses and calcium signaling were also affected by DHT, suggesting that this androgen may play a role in regulating these processes in the ovary. This study detected no change in mRNA levels of steroidogenic enzymes (cyp19a1, star, 11βhsd, 17βhsd, srd5a isoforms), suggesting that the observed increase in E2 production is likely more dependent on the pre-existing gene or protein complement in the ovary rather than the de novo expression of transcripts. This study increases knowledge regarding the roles of DHT and androgens in general in the teleost ovary and identifies molecular signaling pathways that may be associated with increased E2 production.
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Affiliation(s)
- Anna Ornostay
- Department of Biology and Canadian Rivers Institute, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada
| | - Joshua Marr
- Department of Biology and Canadian Rivers Institute, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada
| | - Jennifer R Loughery
- Department of Biology and Canadian Rivers Institute, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada
| | - Christopher J Martyniuk
- Department of Biology and Canadian Rivers Institute, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada; Department of Physiological Sciences and Center for Environmental and Human Toxicology, UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA.
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8
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Ueda H. Physiological mechanisms of imprinting and homing migration in Pacific salmon Oncorhynchus spp. JOURNAL OF FISH BIOLOGY 2012; 81:543-558. [PMID: 22803723 DOI: 10.1111/j.1095-8649.2012.03354.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
After several years of feeding at sea, salmonids have an amazing ability to migrate long distances from the open ocean to their natal stream to spawn. Three different research approaches from behavioural to molecular biological studies have been used to elucidate the physiological mechanisms underpinning salmonid imprinting and homing migration. The study was based on four anadromous Pacific salmon Oncorhynchus spp., pink salmon Oncorhynchus gorbuscha, chum salmon Oncorhynchus keta, sockeye salmon Oncorhynchus nerka and masu salmon Oncorhynchus masou, migrating from the North Pacific Ocean to the coast of Hokkaido, Japan, as well as lacustrine O. nerka and O. masou in Lake Toya, Hokkaido, where the lake serves as the model oceanic system. Behavioural studies using biotelemetry techniques showed swimming profiles from the Bering Sea to the coast of Hokkaido in O. keta as well as homing behaviours of lacustrine O. nerka and O. masou in Lake Toya. Endocrinological studies on hormone profiles in the brain-pituitary-gonad axis of O. keta, and lacustrine O. nerka identified the hormonal changes during homing migration. Neurophysiological studies revealed crucial roles of olfactory functions on imprinting and homing during downstream and upstream migration, respectively. These findings are discussed in relation to the physiological mechanisms of imprinting and homing migration in anadromous and lacustrine salmonids.
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Affiliation(s)
- H Ueda
- Field Science Center for Northern Biosphere, Division of Biosphere Science, Graduate School of Environmental Science, Hokkaido University, Kita-ku, Sapporo, Hokkaido, Japan.
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9
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Martyniuk CJ, Denslow ND. Exploring androgen-regulated pathways in teleost fish using transcriptomics and proteomics. Integr Comp Biol 2012; 52:695-704. [PMID: 22596056 DOI: 10.1093/icb/ics072] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the environment, there are aquatic pollutants that disrupt androgen signaling in fish. Laboratory and field-based experiments have utilized omics technologies to characterize the molecular mechanisms underlying androgen-receptor agonism/antagonism. Transcriptomics and proteomics studies with 17β-trenbolone, a growth-promoting pharmaceutical found in water systems surrounding cattle feed lots, and androgens such as 17α-methyltestosterone and 17α-methyldihydrotestosterone, have been conducted in ovary and liver of fish that include the fathead minnow (FHM) (Pimephales promelas), common carp (Cyprinus carpio), Qurt medaka (Oryzias latipes), and zebrafish (Danio rerio). In this mini-review, we survey recent omics studies in fish and reveal that, despite the diversity of species and tissues examined, there are common cellular responses that are observed with waterborne androgenic treatments. Recurring themes in gene ontology include apoptosis, transport and oxidation of lipids, synthesis and transport of hormones, immune response, protein metabolism, and cell proliferation. However, we also discuss other mechanisms other than androgen receptor (AR) activation, such as responses to toxicant stress, estrogen receptor agonism, aromatization of androgens into estrogens, and inhibitory feedback mechanisms by high levels of androgens that may also explain molecular responses in fish. To further explore androgen-responsive protein networks, a sub-network enrichment analysis was performed on protein data collected from the livers of female FHMs exposed to 17β-trenbolone. We construct a putative AR-regulated protein/cell process network in the liver that includes B-lymphocyte differentiation, xenobiotic clearance, low-density lipoprotein oxidation, proliferation of smooth muscle cells, and permeability of blood vessels. We demonstrate that construction of protein networks can offer insight into cell processes that are potentially regulated by androgens.
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Affiliation(s)
- Christopher J Martyniuk
- Canadian Rivers Institute and Department of Biology, University of New Brunswick, Saint John, NB E2L 4L5, Canada.
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10
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Butts IAE, Love OP, Farwell M, Pitcher TE. Primary and secondary sexual characters in alternative reproductive tactics of Chinook salmon: Associations with androgens and the maturation-inducing steroid. Gen Comp Endocrinol 2012; 175:449-56. [PMID: 22172341 DOI: 10.1016/j.ygcen.2011.11.041] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Revised: 11/18/2011] [Accepted: 11/24/2011] [Indexed: 11/17/2022]
Abstract
The proximate mechanisms that underlie the evolution of within-sex variation in mating behavior, sexual characters and reproductive investment patterns are still poorly understood. Species exhibiting alternative reproductive tactics (ARTs) are ideal model systems to examine these mechanisms. Chinook salmon (Oncorhynchus tshawytscha) exhibits two distinct ARTs: hooknoses, which are large males that establish spawning dominance hierarchies via intense male-male competition and jacks, which are smaller precocious sneaking males that steal fertilizations via sperm competition. In this study, we examine plasma testosterone (T), 11-ketotestosterone (11-KT) and maturation-inducing steroid (MIS; 17α,20β-dihydroxy-4-pregnen-3-one) profiles of spawning hooknoses and jacks. Furthermore, we examine relationships between androgens and primary (gonad mass, gonadosomatic index and sperm traits) and secondary (total mass, body size, hump depth and kype length) sexual characters. Relationships between MIS and sperm traits are also examined. We found that hooknoses and jacks did not significantly differ in terms of plasma T, 11-KT or MIS concentrations. Moreover, we found significant positive relationships between levels of both androgens within each ART. There were no significant relationships between androgens, MIS and sperm traits. T and 11-KT concentrations co-varied positively with gonad investment and kype length in jacks. In hooknoses, 11-KT concentration was positively related to total mass, hump depth and condition factor. Overall, these findings suggest that there are differential androgen effects for each of the ARTs in Chinook salmon.
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Affiliation(s)
- Ian A E Butts
- Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 3P4.
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11
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Froehner S, Machado KS, Stefan E, Bleninger T, da Rosa EC, de Castro Martins C. Occurrence of selected estrogens in mangrove sediments. MARINE POLLUTION BULLETIN 2012; 64:75-79. [PMID: 22093257 DOI: 10.1016/j.marpolbul.2011.10.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 10/20/2011] [Accepted: 10/22/2011] [Indexed: 05/31/2023]
Abstract
This paper presents results related to the occurrence and distribution of estrogens along the Brazilian coast. Three mangrove areas were chosen to evaluate the presence of estrogens in surface sediments of mangrove forests. The presence of estrogens was observed in all studied sites. 17-α-Ethinylestradiol (EE2), a synthetic estrogen, was the most common and has been found in higher concentration (0.45-129.78 ng/g) compared to 17-β-estradiol (E1) and estrone (E2) (both being natural estrogens). The concentrations of E1 and E2 ranged from 0.02 to 49.27 ng/g and 0.03 to 39.77 ng/g, respectively. Theoretically, under anaerobic conditions EE2 can be reduced to E1 even in environments such as sediments of mangrove forests, which are essentially anaerobic. Even if the concentrations of estrogens seem to be insignificant in some samples, the effects remain uncertain.
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Affiliation(s)
- Sandro Froehner
- Department of Environmental Engineering, Federal University of Parana, Curitiba - PR 81531-980, Brazil.
| | - Karina Scurupa Machado
- Department of Environmental Engineering, Federal University of Parana, Curitiba - PR 81531-980, Brazil
| | - Elisa Stefan
- Department of Environmental Engineering, Federal University of Parana, Curitiba - PR 81531-980, Brazil
| | - Tobias Bleninger
- Department of Environmental Engineering, Federal University of Parana, Curitiba - PR 81531-980, Brazil
| | | | - César de Castro Martins
- Centro de Estudos do Mar, Federal University of Parana, Pontal do Parana - PR 83255-000, Brazil
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12
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Gillet C, Breton B, Mikolajczyk T, Bodinier P, Fostier A. Disruption of the secretion and action of 17,20β-dihydroxy-4-pregnen-3-one in response to a rise in temperature in the Arctic charr, Salvelinus alpinus. Consequences on oocyte maturation and ovulation. Gen Comp Endocrinol 2011; 172:392-9. [PMID: 21501615 DOI: 10.1016/j.ygcen.2011.04.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 03/29/2011] [Accepted: 04/03/2011] [Indexed: 11/25/2022]
Abstract
Plasma levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20βP), and the timing of ovulation were investigated in female Arctic charr (Salvelinus alpinus) reared at 5°C and at 10°C during the pre-spawning period. The effects of switching from 5 to 10°C, and from 10 to 5°C were also investigated. 17,20βP plasma levels were higher at 5°C than at 10°C. A switch from 10 to 5°C stimulated 17,20βP secretion, whereas a switch from 5 to 10°C had the opposite effect. Ovulation occurred spontaneously in the females kept at 5°C, and in those switched from 10 to 5°C. In contrast, ovulation was inhibited in females reared at 10°C, and in those switched from 5 to 10°C. Oocyte maturation at 5°C and at 10°C in the presence of LH or of 17,20βP was also investigated in vitro using donor females reared at 5 or 10°C. Both LH and 17,20βP stimulated oocyte maturation more effectively in oocytes incubated at 5°C than at 10°C. At both incubation temperatures, the rearing temperature of the donor females had a significant impact on their responsiveness to LH stimulation, but had no effect on their responsiveness to 17,20βP stimulation. In addition to the inhibition of LH secretion, which had already been reported, the results reported here show that in Arctic charr raising the temperature above the physiological range reduces both follicular responsiveness to LH stimulation and the sensitivity of oocytes to 17,20βP stimulation.
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Affiliation(s)
- C Gillet
- Institut National de la Recherche Agronomique, INRA, UMR Carrtel, Thonon les bains, France.
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Ueda H. Physiological mechanism of homing migration in Pacific salmon from behavioral to molecular biological approaches. Gen Comp Endocrinol 2011; 170:222-32. [PMID: 20144612 DOI: 10.1016/j.ygcen.2010.02.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 02/02/2010] [Accepted: 02/03/2010] [Indexed: 10/19/2022]
Abstract
The amazing abilities of Pacific salmon to migrate long distances from the ocean to their natal streams for spawning have been investigated intensively since 1950's, but there are still many mysteries because of difficulties to follow their whole life cycle and to wait their sole reproductive timing for several years. In my laboratory, we have tried to clarify physiological mechanisms of homing migration in Pacific salmon, using four anadromous Pacific salmon (pink, Oncorhynchus gorbuscha; chum, Oncorhynchus keta; sockeye, Oncorhynchus nerka; masu, Oncorhynchus masou) in the north Pacific Ocean as well as two lacustrine salmon (sockeye and masu) in Lake Toya and Lake Shikotsu, Hokkaido, Japan, where the lakes serve as a model "ocean". Three different approaches from behavioral to molecular biological researches have been conducted using these model fish. First, the homing behaviors of adult chum salmon from the Bering Sea to Hokkaido as well as lacustrine sockeye and masu salmon in Lake Toya were examined by means of physiological biotelemetry techniques, and revealed that salmon can navigate in open water using different sensory systems. Second, the hormone profiles in the brain-pituitary-gonadal (BPG) axis were investigated in chum salmon and lacustrine sockeye salmon during their homing migration by means of hormone specific time-resolved fluoroimmunoassay (TR-FIA) systems, and clarified that salmon gonadotropin-releasing hormone (sGnRH) plays leading roles on homing migration. Third, the olfactory functions of salmon were studied by means of electrophysiological, behavioral, and molecular biological techniques, and made clear that olfactory discriminating ability of natal stream odors. These results have discussed with the evolutional aspects of four Pacific salmon, sexual differences in homing profiles, and the possibility of dissolved free amino acids (DFAA) as natal stream odors for salmon.
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Affiliation(s)
- Hiroshi Ueda
- Laboratory of Aquatic Bioresources and Ecosystem, Field Science Center for Northern Biosphere, Division of Biosphere Science, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido 060-0809, Japan.
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14
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Onuma TA, Makino K, Ando H, Ban M, Fukuwaka MA, Azumaya T, Urano A. Expression of GnRH genes is elevated in discrete brain loci of chum salmon before initiation of homing behavior and during spawning migration. Gen Comp Endocrinol 2010; 168:356-68. [PMID: 20470776 DOI: 10.1016/j.ygcen.2010.05.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 04/26/2010] [Accepted: 05/03/2010] [Indexed: 11/19/2022]
Abstract
Our previous studies suggested the importance of gonadotropin-releasing hormones (GnRHs) for initiation of spawning migration of chum salmon, although supporting evidence had been not available from oceanic fish. In farmed masu salmon, the amounts of salmon GnRH (sGnRH) mRNAs in the forebrain increased in the pre-pubertal stage from winter through spring, followed by a decrease toward summer. We thus hypothesized that gene expression for GnRHs in oceanic chum salmon changes similarly, and examined this hypothesis using brain samples from winter chum salmon in the Gulf of Alaska and summer fish in the Bering Sea. They were classified into sexually immature and maturing adults, which had maturing gonads and left the Bering Sea for the natal river by the end of summer. The absolute amounts of GnRH mRNAs were determined by real-time PCRs. The amounts of sGnRH mRNA in the maturing winter adults were significantly larger than those in the maturing summer adults. The amounts of sGnRH and chicken GnRH mRNAs then peaked during upstream migration from the coast to the natal hatchery. Such changes were observed in various brain loci including the olfactory bulb, terminal nerve, ventral telencephalon, nucleus preopticus parvocellularis anterioris, nucleus preopticus magnocellularis and midbrain tegmentum. These results suggest that sGnRH neurons change their activity for gonadal maturation prior to initiation of homing behavior from the Bering Sea. The present study provides the first evidence to support a possible involvement of neuropeptides in the onset of spawning migration.
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Affiliation(s)
- Takeshi A Onuma
- Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
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15
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Shahjahan M, Hamabata T, Motohashi E, Doi H, Ando H. Differential expression of three types of gonadotropin-releasing hormone genes during the spawning season in grass puffer, Takifugu niphobles. Gen Comp Endocrinol 2010; 167:153-63. [PMID: 20138178 DOI: 10.1016/j.ygcen.2010.01.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 01/28/2010] [Accepted: 01/31/2010] [Indexed: 11/26/2022]
Abstract
Grass puffer, Takifugu niphobles, has unique spawning behavior; spawning occurs on beach only for several days around new moon and full moon from spring to early summer. To investigate the role of gonadotropin-releasing hormone (GnRH) in the reproductive function, genes encoding three types of GnRHs, namely seabream GnRH (sbGnRH), chicken GnRH-II (cGnRH-II) and salmon GnRH (sGnRH), were cloned and changes in their mRNA amounts were examined over the spawning season. In addition, changes in the pituitary gonadotropin subunit mRNAs and the plasma steroid hormones were examined over the spawning season. Fishes were assessed at four reproductive stages, i.e., in December (early maturation), in April (maturing), in May (spawning), and in July (post-spawning). Moreover, spawning fish just after releasing eggs and sperm were taken at a spawning bed. The amounts of sbGnRH mRNA were substantially elevated in May and the spawning fish in both sexes, concomitant with considerable elevations of follicle-stimulating hormone and luteinizing hormone beta subunit mRNAs and plasma estradiol-17beta (E(2)) and testosterone (T) levels. There were strong positive correlations between the sbGnRH mRNA and the plasma E(2) and T levels over the spawning season in both sexes. The amounts of cGnRH-II mRNA showed no noticeable changes except for an increase in the post-spawning females. The amounts of sGnRH mRNA in the males were significantly increased in May, but they were low in the spawning males. In the females, sGnRH mRNA increased from the maturing stage and reached a maximum in the post-spawning stage, in which a positive correlation with the plasma cortisol levels was observed. These specific changes suggest that the expression of three types of GnRH genes is differentially regulated during the spawning season, and sex steroids may be important for the differential expression of GnRH genes.
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Affiliation(s)
- Md Shahjahan
- Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan
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16
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Onuma TA, Ban M, Makino K, Katsumata H, Hu W, Ando H, Fukuwaka MA, Azumaya T, Urano A. Changes in gene expression for GH/PRL/SL family hormones in the pituitaries of homing chum salmon during ocean migration through upstream migration. Gen Comp Endocrinol 2010; 166:537-48. [PMID: 20100485 DOI: 10.1016/j.ygcen.2010.01.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 10/19/2022]
Abstract
Gene expression for growth hormone (GH)/prolactin (PRL)/somatolactin (SL) family hormones in the pituitaries of homing chum salmon were examined, because gene expression for these hormones during ocean-migrating phases remains unclear. Fish were collected in the winter Gulf of Alaska, the summer Bering Sea and along homing pathway in the Ishikari River-Ishikari Bay water system in Hokkaido, Japan in autumn. The oceanic fish included maturing adults, which had developing gonads and left the Bering Sea for the natal river by the end of summer. The absolute amounts of GH, PRL and SL mRNAs in the pituitaries of the maturing adults in the summer Bering Sea were 5- to 20-fold those in the winter Gulf of Alaska. The amount of GH mRNA in the homing adults at the coastal seawater (SW) areas was smaller than that in the Bering fish, while the amount of PRL mRNA remained at the higher level until fish arrived at the Ishikari River. The gill Na(+),K(+)-ATPase activity in the coastal SW fish and the plasma Na(+) levels in the brackish water fish at the estuary were lowered to the levels that were comparable to those in the fresh water (FW) fish. In conclusion, gene expression for GH, PRL and SL was elevated in the pituitaries of chum salmon before initiation of homing behavior from the summer Bering Sea. Gene expression for GH is thereafter lowered coincidently with malfunction of SW adaptability in the breeding season, while gene expression for PRL is maintained high until forthcoming FW adaptation.
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Affiliation(s)
- Takeshi A Onuma
- Department of Animal and Marine Bioresource Science, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
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17
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Onuma TA, Makino K, Katsumata H, Beckman BR, Ban M, Ando H, Fukuwaka MA, Azumaya T, Swanson P, Urano A. Changes in the plasma levels of insulin-like growth factor-I from the onset of spawning migration through upstream migration in chum salmon. Gen Comp Endocrinol 2010; 165:237-43. [PMID: 19595688 DOI: 10.1016/j.ygcen.2009.07.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 06/29/2009] [Accepted: 07/01/2009] [Indexed: 10/20/2022]
Abstract
An increase in activity of the pituitary-gonadal axis (PG-axis) and gonadal development are essential for the onset of spawning migration of chum salmon from the Bering Sea. In the Bering Sea, fish with larger body sizes initiated gonadal development and commenced spawning migration to the natal river by the end of summer. We thus hypothesized that insulin-like growth factor-I (IGF-I), a somatotropic signal that interacts with the PG-axis, can be one of such factors responsible for the onset of migration, and examined changes in plasma levels and hepatic expression of IGF-I gene in oceanic and homing chum salmon in 2001-2003. The plasma IGF-I levels and corresponding body sizes in maturing adults, which had developing gonads, were significantly higher than those in immature fish in all years examined. Such increase in the plasma IGF-I levels in maturing fish was observed even in the Gulf of Alaska during February 2006, while coincident increase was not observed in the hepatic amounts of IGF-I mRNA. In autumn, the plasma IGF-I levels in homing adults decreased during upstream migration in the Ishikari River-Ishikari bay water system in Hokkaido, Japan. In conclusion, the plasma IGF-I levels increased with gonadal development when chum salmon migrated from the winter Gulf of Alaska to the summer Bering Sea. Circulating IGF-I may interact with the PG-axis and promote gonadal development that is inseparable from the onset of spawning migration. Circulating IGF-I levels were thereafter lowered in accordance with final maturation during upstream migration in the breeding season.
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Affiliation(s)
- Takeshi A Onuma
- Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
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18
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Scott AP, Sumpter JP, Stacey N. The role of the maturation-inducing steroid, 17,20beta-dihydroxypregn-4-en-3-one, in male fishes: a review. JOURNAL OF FISH BIOLOGY 2010; 76:183-224. [PMID: 20738705 DOI: 10.1111/j.1095-8649.2009.02483.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The major progestin in teleosts is not progesterone, as in tetrapods, but 17,20beta-dihydroxypregn-4-en-3-one (17,20beta-P) or, in certain species, 17,20beta,21-trihydroxy-pregn-4-en-3-one (17,20beta,21-P). Several functions for 17,20beta-P and 17,20beta,21-P have been proposed (and in some cases proved). These include induction of oocyte final maturation and spermiation (milt production), enhancement of sperm motility (by alteration of the pH and fluidity of the seminal fluid) and acting as a pheromone in male cyprinids. Another important function, initiation of meiosis (the first step in both spermatogenesis and oogenesis), has only very recently been proposed. This is a process that takes place at puberty in all fishes and once a year in repeat spawners. The present review critically examines the evidence to support the proposed functions of 17,20beta-P in males, including listing of the evidence for the presence of 17,20beta-P in the blood plasma of male fishes and discussion of why, in many species, it appears to be absent (or present at low and, in some cases, unvarying concentrations); consideration of the evidence, obtained mainly from in vitro studies, for this steroid being predominantly produced by the testis, for its production being under the control of luteinizing hormone (gonadotrophin II) and, at least in salmonids, for two cell types (Leydig cells and sperm cells) being involved in its synthesis; discussion of the factors involved in the regulation of the switch from androgen to 17,20beta-P production that seems to occur in many species just at the time of spermiation; discussion of the effects of in vivo injection and application of 17,20beta-P (and closely related compounds) in males; a listing of previously published evidence that supports the proposed new function of 17,20beta-P as an initiator of meiosis; finally, discussion of the evidence for environmental endocrine disruption by progestins in fishes.
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Affiliation(s)
- A P Scott
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset, DT4 8UB, UK.
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Onuma TA, Sato S, Katsumata H, Makino K, Hu W, Jodo A, Davis ND, Dickey JT, Ban M, Ando H, Fukuwaka MA, Azumaya T, Swanson P, Urano A. Activity of the pituitary-gonadal axis is increased prior to the onset of spawning migration of chum salmon. ACTA ACUST UNITED AC 2009; 212:56-70. [PMID: 19088211 DOI: 10.1242/jeb.021352] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The activity of the pituitary-gonadal axis (PG axis) in pre-migratory and homing chum salmon was examined because endocrine mechanisms underlying the onset of spawning migration remain unknown. Pre-migratory fish were caught in the central Bering Sea in June, July and September 2001, 2002 and 2003, and in the Gulf of Alaska in February 2006. They were classified into immature and maturing adults on the basis of gonadal development. The maturing adults commenced spawning migration to coastal areas by the end of summer, because almost all fish in the Bering Sea were immature in September. In the pituitaries of maturing adults, the copy numbers of FSHbeta mRNA and the FSH content were 2.5- to 100-fold those of the immature fish. Similarly, the amounts of LHbeta mRNA and LH content in the maturing adults were 100- to 1000-fold those of immature fish. The plasma levels of testosterone, 11-ketotestosterone and estradiol were higher than 10 nmol l(-1) in maturing adults, but lower than 1.0 nmol l(-1) in immature fish. The increase in the activity of the PG-axis components had already initiated in the maturing adults while they were still in the Gulf of Alaska in winter. In the homing adults, the pituitary contents and the plasma levels of gonadotropins and plasma sex steroid hormones peaked during upstream migration from the coast to the natal hatchery. The present results thus indicate that the seasonal increase in the activity of the PG axis is an important endocrine event that is inseparable from initiation of spawning migration of chum salmon.
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Affiliation(s)
- Takeshi A Onuma
- Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
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Affiliation(s)
- Liliya Bykova
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, USA
| | - Lisa A. Holland
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, USA
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21
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Crossin GT, Hinch SG, Cooke SJ, Welch DW, Patterson DA, Jones SR, Lotto AG, Leggatt RA, Mathes MT, Shrimpton JM, Van Der Kraak G, Farrell AP. Exposure to high temperature influences the behaviour, physiology, and survival of sockeye salmon during spawning migration. CAN J ZOOL 2008. [DOI: 10.1139/z07-122] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since 1996, some populations of Fraser River sockeye salmon ( Oncorhynchus nerka Walbaum in Artedi, 1792) have begun spawning migrations weeks earlier than normal, and most perish en route as a result. We suspect that a high midsummer river temperature is the principal cause of mortality. We intercepted 100 sockeye during normal migration near a spawning stream and measured somatic energy and aspects of plasma biochemistry. Fish were then held at either 10 or 18 °C for 24 days. Before release, fish were biopsied again and implanted with acoustic transmitters. A group of biopsied but untreated control salmon were released at the same time. Sixty-two percent (8 of 13) of control salmon and 68% (21 of 31) of 10 °C salmon reached spawning areas. The 18 °C-treated fish were half as successful (35%; 6 of 17). During the holding period, mortality was 2 times higher and levels of Parvicapsula minibicornis (Kent, Whitaker and Dawe, 1997) infection were higher in the 18 °C-treated group than in the 10 °C-treated group. The only physiological difference between treatments was a change in gill Na+,K+-ATPase activity. This drop correlated negatively with travel times for the 18 °C-treated males. Reproductive-hormone levels and stress measures did not differ between treatments but showed significant correlations with individual travel times.
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Affiliation(s)
- G. T. Crossin
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - S. G. Hinch
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - S. J. Cooke
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - D. W. Welch
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - D. A. Patterson
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - S. R.M. Jones
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - A. G. Lotto
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - R. A. Leggatt
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - M. T. Mathes
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - J. M. Shrimpton
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - G. Van Der Kraak
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - A. P. Farrell
- Centre for Applied Conservation Research and Department of Forest Sciences, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
- Kintama Research Corporation, 10-1850 Northfield Road, Nanaimo, BC V9S 3B3, Canada
- Cooperative Resource Management Institute, Fisheries and Oceans Canada, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Faculty of Land and Food Systems and Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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22
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Furukuma S, Onuma T, Swanson P, Luo Q, Koide N, Okada H, Urano A, Ando H. Stimulatory Effects of Insulin-Like Growth Factor 1 on Expression of Gonadotropin Subunit Genes and Release of Follicle-Stimulating Hormone and Luteinizing Hormone in Masu Salmon Pituitary Cells Early in Gametogenesis. Zoolog Sci 2008; 25:88-98. [DOI: 10.2108/zsj.25.88] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 09/01/2007] [Indexed: 11/17/2022]
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23
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Makino K, Onuma TA, Kitahashi T, Ando H, Ban M, Urano A. Expression of hormone genes and osmoregulation in homing chum salmon: a minireview. Gen Comp Endocrinol 2007; 152:304-9. [PMID: 17336983 DOI: 10.1016/j.ygcen.2007.01.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 01/08/2007] [Accepted: 01/19/2007] [Indexed: 11/29/2022]
Abstract
Pacific salmon migrate from ocean through the natal river for spawning. Information on expression of genes encoding osmoregulatory hormones and migratory behavior is important for understanding of molecular events that underlie osmoregulation of homing salmon. In the present article, regulation of gene expression for osmoregulatory hormones in pre-spawning salmon was briefly reviewed with special reference to neurohypophysial hormone, vasotocin (VT), and pituitary hormones, growth hormone (GH) and prolactin (PRL). Thereafter, we introduced recent data on migratory behavior from SW to FW environment. In pre-spawning chum salmon, the hypothalamic VT mRNA levels increased in the males, while decreased in the females with loss of salinity tolerance when they were kept in SW. The amounts of GH mRNA in the pituitary decreased during ocean migration prior to entrance into FW. Hypo-osmotic stimulation by SW-to-FW transfer did not significantly affect the amount of PRL mRNA, but it was elevated in both SW and FW environments along with progress in final maturation. Behaviorally, homing chum salmon continued vertical movement between SW and FW layers in the mouth of the natal river for about 12h prior to upstream migration. Pre-spawning chum salmon in an aquarium, which allowed fish free access to SW and FW, showed that individuals with the lower plasma testosterone (T) and higher estradiol-17beta (E2) levels spent longer time in FW when compared with the SW fish. Taken together, neuroendocrine mechanisms that underlie salt and water homeostasis and migratory behavior from SW to FW may be under the control of the hypothalamus-pituitary-gonadal axis in pre-spawning salmon.
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Affiliation(s)
- Keita Makino
- Section of Biological Sciences, Hokkaido University Graduate School of Life Sciences, Sapporo, Hokkaido 060-0810, Japan
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24
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Onuma TA, Ando H, Koide N, Okada H, Urano A. Reproductive stage-related effects of salmon GnRH and sex steroid hormones on expression of genes encoding fushi tarazu factor 1 homolog and estrogen receptor alpha in masu salmon pituitary cells in vitro. Gen Comp Endocrinol 2007; 152:64-72. [PMID: 17418845 DOI: 10.1016/j.ygcen.2007.02.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Revised: 02/19/2007] [Accepted: 02/23/2007] [Indexed: 11/24/2022]
Abstract
Expression of genes encoding gonadotropin (GTH) subunits in the salmon pituitary was regulated by salmon gonadotropin-releasing hormone (sGnRH) and sex steroid hormones in a reproductive stage-dependent manner, probably through DNA-binding transcription factors. Direct effects of these hormones on expression of genes encoding salmon fushi tarazu factor 1 homolog (sFF1-I) and estrogen receptor alpha (ERalpha) were therefore examined by use of primary pituitary cell cultures of masu salmon at different reproductive stages. Pituitaries were collected in March (before initiation of gonadal maturation), in May (early maturing), in July (late maturing), and in September (spawning period). Amounts of sFF1-I and ERalpha mRNAs in the pituitary cells were determined by real-time polymerase chain reactions after a treatment with sGnRH, estradiol-17beta (E2), testosterone (T) or 11-ketotestosterone (11KT). The amounts of sFF1-I mRNA were elevated by E2 in the males, and by sGnRH and T in the females before initiation of gonadal maturation and at the early maturing stage. The amounts of ERalpha mRNA in the early maturing females were elevated by sGnRH. Effects of sGnRH were not significant at the late maturing and spawning stages. The amounts of ERalpha mRNA in the spawning males were halved by 11KT and E2, and those of sFF1-I and ERalpha mRNAs in the late maturing females were decreased by T and 11KT. These results indicated that responsiveness of sFF1-I and ERalpha genes to sGnRH and sex steroid hormones is seasonally variable in relation to reproductive stages. Expression of sFF1 and ERalpha genes should be stimulated at the early stages of gonadal maturation prior to increases in the amounts of GTH subunit mRNAs, while attenuated after the late maturing period when stored amounts of GTH subunit mRNAs reached near the maximum.
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Affiliation(s)
- Takeshi A Onuma
- Department of Animal and Marine Bioresource Science, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
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25
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Ando H, Luo Q, Koide N, Okada H, Urano A. Effects of insulin-like growth factor I on GnRH-induced gonadotropin subunit gene expressions in masu salmon pituitary cells at different stages of sexual maturation. Gen Comp Endocrinol 2006; 149:21-9. [PMID: 16765954 DOI: 10.1016/j.ygcen.2006.04.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Revised: 04/17/2006] [Accepted: 04/30/2006] [Indexed: 10/24/2022]
Abstract
Effects of insulin-like growth factor I (IGF-I) and salmon gonadotropin-releasing hormone (sGnRH) on expression of gonadotropin (GTH) subunit genes were examined using primary pituitary cell cultures of masu salmon (Oncorhynchus masou). Fishes were assessed at three reproductive stages, i.e., in April (early maturation), in June (maturing), and in September (spawning). Amounts of GTH subunit mRNAs in pituitary cells were determined using real-time PCR after incubation with IGF-I and/or sGnRH. IGF-I alone had almost no effects on three GTH subunit mRNAs in both sexes, except for decrease in follicle-stimulating hormone (FSH) beta mRNA in males in June. sGnRH alone was effective in stimulation of FSHbeta and luteinizing hormone (LH) beta gene expression in males in April. Thereafter it had no significant effects on GTH subunit mRNAs, although in September it tended to increase FSHbeta and LHbeta mRNAs in females. Co-administered IGF-I counteracted the sGnRH-induced expression of FSHbeta and LHbeta genes in males in April, but not in females in September. These results suggest that IGF-I is involved in direct regulation of GTH subunit genes during sexual maturation. In particular, IGF-I differently modulates sGnRH-induced GTH subunit gene expression, depending on reproductive stages.
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Affiliation(s)
- Hironori Ando
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
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26
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Scott AP, Katsiadaki I, Kirby MF, Thain J. Relationship between sex steroid and vitellogenin concentrations in flounder (Platichthys flesus) sampled from an estuary contaminated with estrogenic endocrine-disrupting compounds. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114 Suppl 1:27-31. [PMID: 16818243 PMCID: PMC1874175 DOI: 10.1289/ehp.8049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
High concentrations of vitellogenin (VTG; egg yolk protein) have previously been found in male flounder (Platichthys flesus) from several UK estuaries; these levels have been ascribed to the presence of estrogenic endocrine-disrupting compounds (EDCs). Gonadal abnormalities, including intersex, have also been recorded in these estuaries. However, there is no firm evidence to date that these two findings are causally linked or that the presence of estrogenic EDCs has any adverse population effects. In the present study, we examined the relationship between concentrations of VTG and sex steroids (11-oxo-testosterone in males and 17beta-estradiol in females) in specimens of flounder captured from the estuary of the River Mersey. We first questioned whether the high concentrations of VTG in male and immature female flounder were indeed caused by a direct effect of exogenous EDCs and not indirectly via the endogenous secretion of 17beta-estradiol. The data favored the direct involvement of estrogenic EDCs. We then questioned whether the presence of estrogenic EDCs not only stimulated inappropriate VTG synthesis but whether it might also have had a negative effect on endogenous steroid secretion. It should be noted that the predicted consequences of a drop in steroid secretion include smaller gonads, smaller oocytes, fewer numbers of sperm, and depressed spawning behavior. This question was more difficult to answer because of the strong effect of the seasonal reproductive cycle and stage of maturation on steroid concentrations. However, matched by month of capture and stage of maturation, both 17beta-estradiol in females and 11-keto-testosterone in males were in most cases significantly lower in those years when VTG concentrations were higher.
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Affiliation(s)
- Alexander P Scott
- Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Weymouth, United Kingdom.
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27
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Onuma T, Ando H, Koide N, Okada H, Urano A. Effects of salmon GnRH and sex steroid hormones on expression of genes encoding growth hormone/prolactin/somatolactin family hormones and a pituitary-specific transcription factor in masu salmon pituitary cells in vitro. Gen Comp Endocrinol 2005; 143:129-41. [PMID: 16061071 DOI: 10.1016/j.ygcen.2005.03.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 02/28/2005] [Accepted: 03/07/2005] [Indexed: 11/23/2022]
Abstract
Expression of genes encoding growth hormone (GH), prolactin (PRL), and somatolactin (SL) in growing and maturing salmon was stimulated by gonadotropin-releasing hormone (GnRH) analog during particular periods of the life cycle. GnRH therefore appears to directly and/or indirectly regulate gene expression for GH, PRL, and SL in combination with the pituitary-gonadal axis, such as sex steroid hormones. Direct effects of salmon GnRH (sGnRH), estradiol-17beta (E2), testosterone, and 11-ketotestosterone (11KT) on the amounts of GH, PRL, and SL mRNAs were thus examined using primary pituitary cell cultures of masu salmon at the four reproductive stages. We also determined the amounts of mRNA encoding pituitary specific POU homeodomain transcription factor (Pit-1) by real-time polymerase chain reactions. The amounts of GH, PRL, and SL mRNAs in the control cells elevated with gonadal maturation, coincidently with those of Pit-1 mRNA. sGnRH at 1.0 nM elevated the amounts of all mRNAs examined in the pre-spawning females, whereas significant effects were not observed with 100 nM sGnRH at any reproductive stages. Sex steroid hormones had no significant effects before initiation of gonadal maturation and at the maturing stage. In the males, E2 tended to decrease the amounts of SL mRNA in the pre-spawning stage. In the females, E2 and 11KT increased the amounts of PRL and SL mRNAs in the pre-spawning stage, but halved those of PRL mRNA in the spawning stage. The amounts of Pit-1 mRNA changed coincidently with those of PRL and SL mRNAs at all examined stages. The effects of E2 alone were abolished by 100 nM sGnRH. The present results indicated that both sGnRH and steroid hormones directly modulate synthesis of Pit-1, and further expression of PRL and SL genes. sGnRH may indirectly regulate GH/PRL/SL family hormone genes through the pituitary-gonadal axis, particularly in the late stage of gametogenesis.
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Affiliation(s)
- Takeshi Onuma
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
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Onuma T, Higa M, Ando H, Ban M, Urano A. Elevation of gene expression for salmon gonadotropin-releasing hormone in discrete brain loci of prespawning chum salmon during upstream migration. ACTA ACUST UNITED AC 2005; 63:126-45. [PMID: 15702474 DOI: 10.1002/neu.20125] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Our previous studies suggested that salmon gonadotropin-releasing hormone (sGnRH) neurons regulate both final maturation and migratory behavior in homing salmonids. Activation of sGnRH neurons can occur during upstream migration. We therefore examined expression of genes encoding the precursors of sGnRH, sGnRH-I, and sGnRH-II, in discrete forebrain loci of prespawning chum salmon, Oncorhynchus keta. Fish were captured from 1997 through 1999 along their homing pathway: coastal areas, a midway of the river, 4 km downstream of the natal hatchery, and the hatchery. Amounts of sGnRH mRNAs in fresh frozen sections including the olfactory bulb (OB), terminal nerve (TN), ventral telencephalon (VT), nucleus preopticus parvocellularis anterioris (PPa), and nucleus preopticus magnocellularis (PM) were determined by quantitative real-time polymerase chain reactions. The amounts of sGnRH-II mRNA were higher than those of sGnRH-I mRNA, while they showed similar changes during upstream migration. In the OB and TN, the amounts of sGnRH mRNAs elevated from the coast to the natal hatchery. In the VT and PPa, they elevated along with the progress of final maturation. Such elevation was also observed in the rostroventral, middle, and dorsocaudal parts of the PM. The amounts of gonadotropin IIbeta and somatolactin mRNAs in the pituitary also increased consistently with the elevation of gene expression for sGnRH. These results, in combination with lines of previous evidence, indicate that sGnRH neurons are activated in almost all the forebrain loci during the last phases of spawning migration, resulting in coordination of final gonadal maturation and migratory behavior to the spawning ground.
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Affiliation(s)
- Takeshi Onuma
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
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29
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Saito D, Shi Q, Ando H, Urano A. Attenuation of diurnal rhythms in plasma levels of melatonin and cortisol, and hypothalamic contents of vasotocin and isotocin mRNAs in pre-spawning chum salmon. Gen Comp Endocrinol 2004; 137:62-8. [PMID: 15094336 DOI: 10.1016/j.ygcen.2004.02.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2004] [Revised: 02/09/2004] [Accepted: 02/23/2004] [Indexed: 10/26/2022]
Abstract
In the present study, diurnal changes in plasma levels of melatonin and cortisol, and hypothalamic contents of neurohypophysial hormone mRNAs were examined in pre-spawning chum salmon, Oncorhynchus keta. From late November to early December, homing fish were captured at two sites along their migratory pathway on the Sanriku coast, Japan. Fish captured in the seawater (SW) environment were transferred to SW aquaria, and fish captured in the freshwater (FW) environment were to FW aquaria. They were maintained under natural photoperiod of approximately 10L:14D and sacrificed at 4-h interval through 24-h period. Plasma levels of melatonin were determined by radioimmunoassay, while cortisol levels were determined by enzyme immunoassay. Hypothalamic contents of vasotocin and isotocin mRNAs were determined by quantitative dot-blot hybridization assay. The melatonin levels showed weak nocturnal elevations in the SW and FW males, and FW females. The levels were maximal at 22:00 and minimal at 10:00 or 14:00, however the amplitudes were smaller than those reported in the previous studies using immature salmonids. The levels of vasotocin and isotocin mRNAs were higher in the males at all time points. The mRNA levels, however, did not show any diurnal variations in either of group. The same applied to plasma cortisol levels. These results indicate that the diurnal endocrine rhythms were attenuated in pre-spawning chum salmon, in contrast to the prominent diurnal rhythms in immature salmonids.
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Affiliation(s)
- Daisuke Saito
- Division of Biological Sciences, Hokkaido University Graduate School of Science, Sapporo, Hokkaido 060-0810, Japan.
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