By the app]ication of the protein A-gold technique fbr immunocytochemistry of the tilapia pituita... more By the app]ication of the protein A-gold technique fbr immunocytochemistry of the tilapia pituitaFy growth hormone (GH), our clectron micrographs revealed that the antigenicity of tilapia GH and the cyteplasmie structure were we}1 prese-,cd in the tissues fixcd with pcriodate-lysine-parafbrmaldehyde fo11owed by osmium tetroxide postfixation. Using the spccific antiserum against tilapia GH, the immunoreaetive gold particles of 20-40 nm in size wcre located on secrctory granules (200m300 nm in diameter) exclusively ofonc cell type in the proximal pars distalis identified as GH cells on the basis of their ultrastructural characteristics. This technique is considcred to be fairly eflicicnt for the detection of intracellular antigenic sitcs on ultrathin sections, K{pt worcts : immunoelectron microscopy, protcin A-go}d, teleost, pituitar}, gland, growth hormone,
Simultaneous immunoclectron microscopic localization of human chorionic gonadotropin (HCG) and hu... more Simultaneous immunoclectron microscopic localization of human chorionic gonadotropin (HCG) and human placental lactogen (HPL) was examincd on the same ultrathin section of hurnan chorionic villi by means of the double labeling technique. Using specific rabbit antisera against HCG and HPL fbllowed by goat anti-rabbit IgG-coated coHoidal gold of different sizes (IS nm and 5 nm), immunoreactions of HCG were concentrated on middie-sizecl secretory granules of 200-3eO nm and largc dense bodies of 500-1000 nm, whi}e those of HPL were exclu- sively located on small secretory granules of 80-180 nm, The present experiment provides clirect evidence for our previous data that HCG ancl HPL secrn to be stored in different granular components in the syncytiotrophoblast. . hurnan chorionic villi, syncytiotrophoblast, HCG, HPL, doubic immunoelectron microscopy,
The present study performed three experiments to establish a practical prevention strategy for th... more The present study performed three experiments to establish a practical prevention strategy for the ectoparasitic flagellate Ichthyobodo salmonis and ciliate Trichodina truttae in hatchery-reared juvenile chum salmon Oncorhynchus keta using dietary supplementation with oregano essential oil. Experiment 1 showed that a diet supplemented for 3 weeks with 0.02% oregano essential oil significantly prevented infection with I. salmonis and T. truttae in juveniles reared in small tanks. Experiment 2, in outdoor hatchery ponds, demonstrated that the oregano treatment completely prevented I. salmonis infection for 52 days and T. truttae infection for 38 days. Oregano-treated juvenile mortality attributable to infection with these protozoans also decreased to 7.6% of control juvenile mortality, confirming the utility of this treatment in cultured O. keta. Physiological analyses of the oregano-treated juveniles elucidated the treatment's safety in relation to their metabolism, osmoregulation, natural immunity and olfactory responses and also detected carvacrol (a major component of oregano essential oil which shows antimicrobial activity) on the skin. In experiment 3, exposure of the two protozoans to oregano essential oil revealed a weak antiparasitic action on the body surface of the juvenile O. keta. The overall results demonstrate that dietary oregano supplementation is a practical prevention strategy for I. salmonis and T. truttae in hatchery-reared juvenile O. keta and suggest the possibility that its anti-parasitic action is attributable to a component of the oil that emerges onto the skin of the body of the fish.
In the pituitary gland of silver females of the Japanese eel, Anguilla japonica, only one type of... more In the pituitary gland of silver females of the Japanese eel, Anguilla japonica, only one type of glandular cells was observed to be gonadotropic in nature. The gonadotrophs of the eels which were induced to mature by injections of salmon pituitaries showed a remarkable increase in size and in number as compared with those of untreated, immature females. The hypertrophied gonadotrophs revealed a prominent accumulation of secretory granules, which were increased also in size and in electron-density, an activated formation of granules, and a dilatation of cisternae of the rough endoplasmic reticulum_ No evident sign of secretion was detectable in the hypertrophied gonadotrophs of maturing eels. However, in the cells of the eel which had ovulated spontaneously, a distinct degranulation and a marked dilatation of cisternae of the rough endoplasmic reticulum occurred extensively, suggesting a release of hormonal contents from the cells. In the eels which had failed to ovulate following complete maturation, changes of pituitary gonadotrophs were not so prominent and uniform as those in the cells of the ovulating eel, implying a possible disturbance of the mechanism implicated in pituitary gonadotropin release in these fish.
Adult and young loaches, M isgurT/,us anguillicaudatus, of both sexes were exposed to continuous ... more Adult and young loaches, M isgurT/,us anguillicaudatus, of both sexes were exposed to continuous light for periods of 30 and 60 days during the postspawning period. The treatment caused a significant promotion of vitellogenesis and spermatogenesis in affected ovaries and testes of adult fish. In these fish, a remarkable activation of pituitary gonadotrophs of the vesicular cell type was observed electron microscopically. The vesicular cells showed a notable increase both in number and in size and, characteristically, a progressive expansion of their cytoplasmic vesicles. Pituitary gonadotrophs of the globular cell type were also observed to be activated under the influence of constant illumination, but the response was rather slight when compared with that of the vesicular cells even after 60 days of the treatment. In addition, exposure of young females 1i9 continuous light did efficiently induce a precocious differentiation of the vesicular cells in their pituitary glands, in parallel with a precocious occurrence of yolk accumulation in ovarian oocytes. The results indicate that the vesicular gonadotropic cells may be implicated primarily in the mechanism of vitellogenesis in females and spermatogenesis in males of the loach.
Here, we report the information about molecular and expression characterization of NR1 gene in ch... more Here, we report the information about molecular and expression characterization of NR1 gene in chum salmon for the first time. The complete NR1 subunit showed a large open-reading frame of 2844 bp in the total length of 3193 bp, and this cDNA contained a coding region encoding 948 amino acids and a stop codon. The organization of the NR1 subunit of chum salmon were similar of most other fishes, except C’ terminal. The expression of NR1 subunit was to show higher in the natal river near to the hatchery than near to the coast. We expect that the information reported herein may facilitate further investigations on the relationship between memory factors of natal rivers and homing mechanisms in Salmonidae.
Diadromous fishes are a frequent but poorly understood component of coastal riverine fish communi... more Diadromous fishes are a frequent but poorly understood component of coastal riverine fish communities in Australia. There are ~33 diadromous fishes found in Australian waters, mainly catadromous and amphidromous species. An extensive review of the literature identified major information gaps about the lifecycles and ecology of many of these species, with information on facultative diadromy, navigation, marine and early life stages being particularly limited. In many cases, this lack of information has led to poor management decisions and consequently many of the Australian diadromous species are under increasing threat from a range of environmental impacts. Much of the required information is difficult to obtain with traditional field surveys and, as a result, new and improved research tools and technologies, including telemetry, otolith chemistry, stable-isotope analysis (SIA) and functional magnetic resonance imaging (fMRI) are increasingly being applied. Key areas for research on...
The post-embedding immuno gold staining (IGS) technique was used for the ultrastructural localiza... more The post-embedding immuno gold staining (IGS) technique was used for the ultrastructural localization of glial fibrillary acidic protein (GFAP) in pituicytes and tanycytes of the neurohypophysis. IGS was applied to LR White embedded neurohypophyseal tissue of the Mongolian gerbil (Meriones unguiculatus), a species which contains abundant GFAP-positive pituicytes and tanycytes. GFAPimmunoreactivity could be demonstrated on pituicytic intermediate filaments (IF's) in situ. Thus, it was shown that pituicytes contain GFAP in its filamentous form, what had been a matter of speculation. At the ultrastructural level, gerbil tanycytes and tanycyte-like cells in the external zone of the median eminence were characterized by a great amount of densely packed IF's, which were labeled by both GFAP-or vimentin-antibodies. Sequential immunostaining of serial semithin sections with GFAP-and vimentin-antibodies revealed an invariable coexpression of the two IF proteins in somata and processes of these median eminence cells.
We investigated the origin of dissolved free amino acids (DFAA) in stream water focusing on biofi... more We investigated the origin of dissolved free amino acids (DFAA) in stream water focusing on biofilms in the river bed by means of incubation experiments in the laboratory. Stones were placed in the Toyohira River, Hokkaido, Japan, for 3 months, allowing formation of biofilms, and then incubated for 24 hours in the laboratory at stream water temperature. After incubation, the composition and concentrations of DFAA in the incubation solution and total hydrolyzed amino acids (THAA) in biofilms were measured by a high-performance liquid chromatography. The amount of chlorophyll a (Chl.a) and the number of bacteria were also measured. The DFAA concentration increased greatly in the biofilm incubation solution, but the DFAA composition (mole %) did not change relative to the inception of incubation, where it was similar to stream water. There was no correlation between the increase in DFAA concentration and the THAA concentration, Chl.a amount, or the number of bacteria in biofilms. These results suggest that biofilms are one of the major source of DFAA in stream water.
This study investigated in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU... more This study investigated in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU) in masu salmon Oncorhynchus masou Brevoort. Underyearling fish were fed with RU for 16 months. Monthly changes in body growth, gonadal maturation and serum levels of sex steroids were monitored. Gonads were also incubated at 0, 1, 10, 100 and 1000 µg RU mL -1 Leibovitz's L-15 medium for 18 h. Levels of steroids in serum and cultured medium were measured. It was determined that RU-fed immature and mature males, when compared to control groups, showed significantly higher body growth during spring, summer, and the spawning period. Similarly, immature RU-fed females showed significantly higher fork length and body weight in autumn, spring and summer. Furthermore, RU-fed males showed significantly higher levels of serum testosterone (T) and 11-ketotestosterone (11-KT) levels in pre-spawning season, and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) in spawning season. In vitro RU incubation of gonads showed a dose-dependent and significant increase in T, 11-KT, estradiol-17β and DHP release in the medium. It appears that the causes of enhanced body growth and increased steroid production herein observed in salmonids are the physiologically active substances that may be contained in the mycelium of the fungus.
The olfactory system of salmonids is essential for imprinting and the subsequent homing migration... more The olfactory system of salmonids is essential for imprinting and the subsequent homing migration. Olfactory imprinting-related genes were identified in the olfactory system of 1-and 3-year-old lacustrine sockeye salmon (Oncorhynchus nerka) using a subtractive hybridization technique of representational difference analysis (cDNA-RDA). We have obtained a partial clone from a subtractive cDNA library of 1-year-old fish that contains a 756 bp open reading frame coding for a putative protein with 252 amino acid residues named the Sockeye salmon Olfactory system Imprinting related Gene (SOIG). By northern hybridization, the SOIG mRNA was only expressed in the olfactory epithelium and not in other tissues. In situ hybridization showed that the expression of SOIG mRNA was observed in the olfactory receptor cells and basal cells of the olfactory epithelium. This suggests that SOIG could have specific and important roles in olfactory system.
Preliminary information is presented on international cooperative salmon research conducted durin... more Preliminary information is presented on international cooperative salmon research conducted during the June-July 1997 cruise of the Oshoro maru. An objective of cooperative high-seas salmon research conducted under the North Pacific Anadromous Fish Commission Science Plan is salmon stock assessment through annual surveys along standard transects in the North Pacific Ocean and Bering Sea. Salmon surveys conducted aboard the Oshoro maru along 1800 longitude in the central North Pacific Ocean in June since 1978 have provided a valuable time series of fisheries and oceanographic data. This was the fourth consecutive year of cooperative Japan-U.S. sampling for salmon along a 145°W-longitude transect in the central Gulf of Alaska in early July. The primary objective of the 1997 cooperative research was to continue the collection of oceanographic and biological data along the 180°and 145°W transects. In 1997, mid-June mean sea surface temperatures (SSTs; 9.2°C) at gillnet fishing stations were 2.1°C cooler along the 180°transect and early July mean SSTs (12.4°C) were 2.5°C warmer along the 145°W transect than in 1996. This reverses a warming trend in mean SSTs at 180°stations and a cooling trend at 145°W stations that was observed over the previous three years. Catches by gillnet totaled 2,036 salmonids, including 225 salmonids (361 in 1996) in the central North Pacific Ocean (180°transect) and 1,811 salmonids (1,982 in 1996) in the Gulf of Alaska. At longline stations, 11 salmon (17 in 1996) in the central North Pacific Ocean and 28 salmon (33 salmon in 1996) in the Gulf of Alaska were tagged and released. One tagged sockeye salmon (maturing, age 1.2) released at 145°W, 54°N on 10 July was recovered in a commercial fishery in the San Juan Islands, Washington, on 12 August 1997. One coded-wire tagged steelhead (juvenile, age 1.0), which originated from a release of hatchery fish into a coastal Washington stream in 1997, was recovered at 145°W, 52°N on 8 July. Biological samples and data were collected for various other cooperative studies of salmon distribution, abundance, stock origins, maturity and growth, food habits, bioenergetics, and other aspects of ocean biology and ecology; results will be reported later.
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Changes in the levels of pituitary mRNAs encoding GH, prolactin (PRL) and somatolactin (SL) were ... more Changes in the levels of pituitary mRNAs encoding GH, prolactin (PRL) and somatolactin (SL) were determined in pre-spawning chum salmon (Oncorhynchus keta) caught at a few key points along their homing pathway in 1994 and 1995. Furthermore, we analyzed relationships between expression of pituitary-specific POU homeodomain transcription factor (Pit-1/GHF-1) and GH/PRL/SL family genes. In 1994, seawater (SW) fish and matured fresh-water (FW) fish were sequentially captured at two points along their homing pathway, the coast and the hatchery. In addition to these two points, maturing FW fish were captured at the intermediate of the two points in 1995. The levels of hormonal mRNAs were determined by a quantitative dot blot analysis using single-stranded sense DNA as the standard. Relative levels of Pit-1/GHF-1 mRNAs were estimated by Northern blot analysis. In 1994, the levels of GH/PRL/SL family mRNAs except for PRL mRNA in the male FW fish were 1.8-4 times higher than those in the SW ...
The effects of external and surgically implanted radio transmitters on juvenile masu salmon were ... more The effects of external and surgically implanted radio transmitters on juvenile masu salmon were examined. External attachment of transmitters significantly decreased the survival of fish and caused a decreased U crit compared with surgical implantation. Although plasma cortisol, plasma glucose, and hematocrit values did not differ significantly among groups, it appears that the most suitable transmitter attachment method for juvenile masu salmon may be surgical implantation.
The upriver spawning migration of shishamo smelt Spirinchus lanceolatus tagged with nano-tag radi... more The upriver spawning migration of shishamo smelt Spirinchus lanceolatus tagged with nano-tag radio transmitters was investigated for both the eŠects of surgically implanted radio transmitters on swimming and spawning behavior in an experimental water tank and during the upriver spawning migration in the Mukawa River, Hok
By the app]ication of the protein A-gold technique fbr immunocytochemistry of the tilapia pituita... more By the app]ication of the protein A-gold technique fbr immunocytochemistry of the tilapia pituitaFy growth hormone (GH), our clectron micrographs revealed that the antigenicity of tilapia GH and the cyteplasmie structure were we}1 prese-,cd in the tissues fixcd with pcriodate-lysine-parafbrmaldehyde fo11owed by osmium tetroxide postfixation. Using the spccific antiserum against tilapia GH, the immunoreaetive gold particles of 20-40 nm in size wcre located on secrctory granules (200m300 nm in diameter) exclusively ofonc cell type in the proximal pars distalis identified as GH cells on the basis of their ultrastructural characteristics. This technique is considcred to be fairly eflicicnt for the detection of intracellular antigenic sitcs on ultrathin sections, K{pt worcts : immunoelectron microscopy, protcin A-go}d, teleost, pituitar}, gland, growth hormone,
Simultaneous immunoclectron microscopic localization of human chorionic gonadotropin (HCG) and hu... more Simultaneous immunoclectron microscopic localization of human chorionic gonadotropin (HCG) and human placental lactogen (HPL) was examincd on the same ultrathin section of hurnan chorionic villi by means of the double labeling technique. Using specific rabbit antisera against HCG and HPL fbllowed by goat anti-rabbit IgG-coated coHoidal gold of different sizes (IS nm and 5 nm), immunoreactions of HCG were concentrated on middie-sizecl secretory granules of 200-3eO nm and largc dense bodies of 500-1000 nm, whi}e those of HPL were exclu- sively located on small secretory granules of 80-180 nm, The present experiment provides clirect evidence for our previous data that HCG ancl HPL secrn to be stored in different granular components in the syncytiotrophoblast. . hurnan chorionic villi, syncytiotrophoblast, HCG, HPL, doubic immunoelectron microscopy,
The present study performed three experiments to establish a practical prevention strategy for th... more The present study performed three experiments to establish a practical prevention strategy for the ectoparasitic flagellate Ichthyobodo salmonis and ciliate Trichodina truttae in hatchery-reared juvenile chum salmon Oncorhynchus keta using dietary supplementation with oregano essential oil. Experiment 1 showed that a diet supplemented for 3 weeks with 0.02% oregano essential oil significantly prevented infection with I. salmonis and T. truttae in juveniles reared in small tanks. Experiment 2, in outdoor hatchery ponds, demonstrated that the oregano treatment completely prevented I. salmonis infection for 52 days and T. truttae infection for 38 days. Oregano-treated juvenile mortality attributable to infection with these protozoans also decreased to 7.6% of control juvenile mortality, confirming the utility of this treatment in cultured O. keta. Physiological analyses of the oregano-treated juveniles elucidated the treatment's safety in relation to their metabolism, osmoregulation, natural immunity and olfactory responses and also detected carvacrol (a major component of oregano essential oil which shows antimicrobial activity) on the skin. In experiment 3, exposure of the two protozoans to oregano essential oil revealed a weak antiparasitic action on the body surface of the juvenile O. keta. The overall results demonstrate that dietary oregano supplementation is a practical prevention strategy for I. salmonis and T. truttae in hatchery-reared juvenile O. keta and suggest the possibility that its anti-parasitic action is attributable to a component of the oil that emerges onto the skin of the body of the fish.
In the pituitary gland of silver females of the Japanese eel, Anguilla japonica, only one type of... more In the pituitary gland of silver females of the Japanese eel, Anguilla japonica, only one type of glandular cells was observed to be gonadotropic in nature. The gonadotrophs of the eels which were induced to mature by injections of salmon pituitaries showed a remarkable increase in size and in number as compared with those of untreated, immature females. The hypertrophied gonadotrophs revealed a prominent accumulation of secretory granules, which were increased also in size and in electron-density, an activated formation of granules, and a dilatation of cisternae of the rough endoplasmic reticulum_ No evident sign of secretion was detectable in the hypertrophied gonadotrophs of maturing eels. However, in the cells of the eel which had ovulated spontaneously, a distinct degranulation and a marked dilatation of cisternae of the rough endoplasmic reticulum occurred extensively, suggesting a release of hormonal contents from the cells. In the eels which had failed to ovulate following complete maturation, changes of pituitary gonadotrophs were not so prominent and uniform as those in the cells of the ovulating eel, implying a possible disturbance of the mechanism implicated in pituitary gonadotropin release in these fish.
Adult and young loaches, M isgurT/,us anguillicaudatus, of both sexes were exposed to continuous ... more Adult and young loaches, M isgurT/,us anguillicaudatus, of both sexes were exposed to continuous light for periods of 30 and 60 days during the postspawning period. The treatment caused a significant promotion of vitellogenesis and spermatogenesis in affected ovaries and testes of adult fish. In these fish, a remarkable activation of pituitary gonadotrophs of the vesicular cell type was observed electron microscopically. The vesicular cells showed a notable increase both in number and in size and, characteristically, a progressive expansion of their cytoplasmic vesicles. Pituitary gonadotrophs of the globular cell type were also observed to be activated under the influence of constant illumination, but the response was rather slight when compared with that of the vesicular cells even after 60 days of the treatment. In addition, exposure of young females 1i9 continuous light did efficiently induce a precocious differentiation of the vesicular cells in their pituitary glands, in parallel with a precocious occurrence of yolk accumulation in ovarian oocytes. The results indicate that the vesicular gonadotropic cells may be implicated primarily in the mechanism of vitellogenesis in females and spermatogenesis in males of the loach.
Here, we report the information about molecular and expression characterization of NR1 gene in ch... more Here, we report the information about molecular and expression characterization of NR1 gene in chum salmon for the first time. The complete NR1 subunit showed a large open-reading frame of 2844 bp in the total length of 3193 bp, and this cDNA contained a coding region encoding 948 amino acids and a stop codon. The organization of the NR1 subunit of chum salmon were similar of most other fishes, except C’ terminal. The expression of NR1 subunit was to show higher in the natal river near to the hatchery than near to the coast. We expect that the information reported herein may facilitate further investigations on the relationship between memory factors of natal rivers and homing mechanisms in Salmonidae.
Diadromous fishes are a frequent but poorly understood component of coastal riverine fish communi... more Diadromous fishes are a frequent but poorly understood component of coastal riverine fish communities in Australia. There are ~33 diadromous fishes found in Australian waters, mainly catadromous and amphidromous species. An extensive review of the literature identified major information gaps about the lifecycles and ecology of many of these species, with information on facultative diadromy, navigation, marine and early life stages being particularly limited. In many cases, this lack of information has led to poor management decisions and consequently many of the Australian diadromous species are under increasing threat from a range of environmental impacts. Much of the required information is difficult to obtain with traditional field surveys and, as a result, new and improved research tools and technologies, including telemetry, otolith chemistry, stable-isotope analysis (SIA) and functional magnetic resonance imaging (fMRI) are increasingly being applied. Key areas for research on...
The post-embedding immuno gold staining (IGS) technique was used for the ultrastructural localiza... more The post-embedding immuno gold staining (IGS) technique was used for the ultrastructural localization of glial fibrillary acidic protein (GFAP) in pituicytes and tanycytes of the neurohypophysis. IGS was applied to LR White embedded neurohypophyseal tissue of the Mongolian gerbil (Meriones unguiculatus), a species which contains abundant GFAP-positive pituicytes and tanycytes. GFAPimmunoreactivity could be demonstrated on pituicytic intermediate filaments (IF's) in situ. Thus, it was shown that pituicytes contain GFAP in its filamentous form, what had been a matter of speculation. At the ultrastructural level, gerbil tanycytes and tanycyte-like cells in the external zone of the median eminence were characterized by a great amount of densely packed IF's, which were labeled by both GFAP-or vimentin-antibodies. Sequential immunostaining of serial semithin sections with GFAP-and vimentin-antibodies revealed an invariable coexpression of the two IF proteins in somata and processes of these median eminence cells.
We investigated the origin of dissolved free amino acids (DFAA) in stream water focusing on biofi... more We investigated the origin of dissolved free amino acids (DFAA) in stream water focusing on biofilms in the river bed by means of incubation experiments in the laboratory. Stones were placed in the Toyohira River, Hokkaido, Japan, for 3 months, allowing formation of biofilms, and then incubated for 24 hours in the laboratory at stream water temperature. After incubation, the composition and concentrations of DFAA in the incubation solution and total hydrolyzed amino acids (THAA) in biofilms were measured by a high-performance liquid chromatography. The amount of chlorophyll a (Chl.a) and the number of bacteria were also measured. The DFAA concentration increased greatly in the biofilm incubation solution, but the DFAA composition (mole %) did not change relative to the inception of incubation, where it was similar to stream water. There was no correlation between the increase in DFAA concentration and the THAA concentration, Chl.a amount, or the number of bacteria in biofilms. These results suggest that biofilms are one of the major source of DFAA in stream water.
This study investigated in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU... more This study investigated in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU) in masu salmon Oncorhynchus masou Brevoort. Underyearling fish were fed with RU for 16 months. Monthly changes in body growth, gonadal maturation and serum levels of sex steroids were monitored. Gonads were also incubated at 0, 1, 10, 100 and 1000 µg RU mL -1 Leibovitz's L-15 medium for 18 h. Levels of steroids in serum and cultured medium were measured. It was determined that RU-fed immature and mature males, when compared to control groups, showed significantly higher body growth during spring, summer, and the spawning period. Similarly, immature RU-fed females showed significantly higher fork length and body weight in autumn, spring and summer. Furthermore, RU-fed males showed significantly higher levels of serum testosterone (T) and 11-ketotestosterone (11-KT) levels in pre-spawning season, and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) in spawning season. In vitro RU incubation of gonads showed a dose-dependent and significant increase in T, 11-KT, estradiol-17β and DHP release in the medium. It appears that the causes of enhanced body growth and increased steroid production herein observed in salmonids are the physiologically active substances that may be contained in the mycelium of the fungus.
The olfactory system of salmonids is essential for imprinting and the subsequent homing migration... more The olfactory system of salmonids is essential for imprinting and the subsequent homing migration. Olfactory imprinting-related genes were identified in the olfactory system of 1-and 3-year-old lacustrine sockeye salmon (Oncorhynchus nerka) using a subtractive hybridization technique of representational difference analysis (cDNA-RDA). We have obtained a partial clone from a subtractive cDNA library of 1-year-old fish that contains a 756 bp open reading frame coding for a putative protein with 252 amino acid residues named the Sockeye salmon Olfactory system Imprinting related Gene (SOIG). By northern hybridization, the SOIG mRNA was only expressed in the olfactory epithelium and not in other tissues. In situ hybridization showed that the expression of SOIG mRNA was observed in the olfactory receptor cells and basal cells of the olfactory epithelium. This suggests that SOIG could have specific and important roles in olfactory system.
Preliminary information is presented on international cooperative salmon research conducted durin... more Preliminary information is presented on international cooperative salmon research conducted during the June-July 1997 cruise of the Oshoro maru. An objective of cooperative high-seas salmon research conducted under the North Pacific Anadromous Fish Commission Science Plan is salmon stock assessment through annual surveys along standard transects in the North Pacific Ocean and Bering Sea. Salmon surveys conducted aboard the Oshoro maru along 1800 longitude in the central North Pacific Ocean in June since 1978 have provided a valuable time series of fisheries and oceanographic data. This was the fourth consecutive year of cooperative Japan-U.S. sampling for salmon along a 145°W-longitude transect in the central Gulf of Alaska in early July. The primary objective of the 1997 cooperative research was to continue the collection of oceanographic and biological data along the 180°and 145°W transects. In 1997, mid-June mean sea surface temperatures (SSTs; 9.2°C) at gillnet fishing stations were 2.1°C cooler along the 180°transect and early July mean SSTs (12.4°C) were 2.5°C warmer along the 145°W transect than in 1996. This reverses a warming trend in mean SSTs at 180°stations and a cooling trend at 145°W stations that was observed over the previous three years. Catches by gillnet totaled 2,036 salmonids, including 225 salmonids (361 in 1996) in the central North Pacific Ocean (180°transect) and 1,811 salmonids (1,982 in 1996) in the Gulf of Alaska. At longline stations, 11 salmon (17 in 1996) in the central North Pacific Ocean and 28 salmon (33 salmon in 1996) in the Gulf of Alaska were tagged and released. One tagged sockeye salmon (maturing, age 1.2) released at 145°W, 54°N on 10 July was recovered in a commercial fishery in the San Juan Islands, Washington, on 12 August 1997. One coded-wire tagged steelhead (juvenile, age 1.0), which originated from a release of hatchery fish into a coastal Washington stream in 1997, was recovered at 145°W, 52°N on 8 July. Biological samples and data were collected for various other cooperative studies of salmon distribution, abundance, stock origins, maturity and growth, food habits, bioenergetics, and other aspects of ocean biology and ecology; results will be reported later.
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Changes in the levels of pituitary mRNAs encoding GH, prolactin (PRL) and somatolactin (SL) were ... more Changes in the levels of pituitary mRNAs encoding GH, prolactin (PRL) and somatolactin (SL) were determined in pre-spawning chum salmon (Oncorhynchus keta) caught at a few key points along their homing pathway in 1994 and 1995. Furthermore, we analyzed relationships between expression of pituitary-specific POU homeodomain transcription factor (Pit-1/GHF-1) and GH/PRL/SL family genes. In 1994, seawater (SW) fish and matured fresh-water (FW) fish were sequentially captured at two points along their homing pathway, the coast and the hatchery. In addition to these two points, maturing FW fish were captured at the intermediate of the two points in 1995. The levels of hormonal mRNAs were determined by a quantitative dot blot analysis using single-stranded sense DNA as the standard. Relative levels of Pit-1/GHF-1 mRNAs were estimated by Northern blot analysis. In 1994, the levels of GH/PRL/SL family mRNAs except for PRL mRNA in the male FW fish were 1.8-4 times higher than those in the SW ...
The effects of external and surgically implanted radio transmitters on juvenile masu salmon were ... more The effects of external and surgically implanted radio transmitters on juvenile masu salmon were examined. External attachment of transmitters significantly decreased the survival of fish and caused a decreased U crit compared with surgical implantation. Although plasma cortisol, plasma glucose, and hematocrit values did not differ significantly among groups, it appears that the most suitable transmitter attachment method for juvenile masu salmon may be surgical implantation.
The upriver spawning migration of shishamo smelt Spirinchus lanceolatus tagged with nano-tag radi... more The upriver spawning migration of shishamo smelt Spirinchus lanceolatus tagged with nano-tag radio transmitters was investigated for both the eŠects of surgically implanted radio transmitters on swimming and spawning behavior in an experimental water tank and during the upriver spawning migration in the Mukawa River, Hok
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