Subcellular localization of Na+/K+-ATPase isoforms resolved by in situ hybridization chain reaction in the gill of chum salmon at freshwater and seawater

The Na+/K+-ATPase (NKA) α1-isoforms were examined by in situ hybridization chain reaction (ISHCR) using short hairpin DNAs, and we showed triple staining of NKA α1a, α1b, and α1c transcripts in the gill of chum salmon acclimated to freshwater (FW) and seawater (SW). The NKA α1-isoforms have closely resembled nucleotide sequences, which could not be differentiated by conventional in situ hybridization. The ISHCR uses a split probe strategy to allow specific hybridization using regular oligo DNA, resulting in high specificity at low cost. The results showed that NKA α1c was expressed ubiquitously in gill tissue and no salinity effects were observed. FW lamellar ionocytes (type-I ionocytes) expressed cytoplasmic NKA α1a and nuclear NKA α1b transcripts. However, both transcripts of NKA α1a and α1b were present in the cytoplasm of immature type-I ionocytes. The developing type-I ionocytes increased the cytoplasmic volume and migrated to the distal region of the lamellae. SW filament ionocytes (type-II ionocytes) expressed cytoplasmic NKA α1b transcripts as the major isoform. Results from morphometric analysis and nonmetric multidimensional scaling indicated that a large portion of FW ionocytes was NKA α1b-rich, suggesting that isoform identity alone cannot mark the ionocyte types. Both immature or residual type-II ionocytes and type-I ionocytes were found on the FW and SW gills, suggesting that the chum salmon retains the potential to switch the ionocyte population to fit the ion-transporting demands, which contributes to their salinity tolerance and osmoregulatory plasticity.

Gene expression levels of synaptic exocytosis regulator synaptophysin in the brain and the olfactory organ of anadromous salmon

Anadromous Pacific salmon (genus Oncorhynchus) are known for their homing behavior based on olfactory imprinting, which is formed during their seaward migration. Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE/Snare) complex is a minimum unit of vesicle exocytosis from the pre-synaptic membrane. Its component genes (synaptosome-associated protein 25, syntaxin 1, and vesicle-associated membrane protein 2) are more strongly expressed in the olfactory nervous system (olfactory epithelium, olfactory bulb, and telencephalon) at the migration stages related to olfactory imprinting and/or retrieval in salmon. This study focused on the mRNA synthesis of synaptophysin (Syp), one of the Snare regulatory factors. syp is strongly expressed in chum salmon (Oncorhynchus keta) olfactory nervous system during the seaward migration and temporarily increased during the homeward migration. In reference to our previous studies, these expression changes were similar to the snare genes in the chum salmon. Therefore, syp and Snare component genes were synchronously expressed reflecting the development and short-term plasticity of the olfactory nervous system that is essential for olfactory imprinting.

Piscirickettsia salmonis shedding and tissue burden, and hematological responses during cohabitation infections in chum Oncorhynchus keta, pink O. gorbuscha and Atlantic salmon Salmo salar

BACKGROUND

Salmonid rickettsial septicemia is an emergent and geographically widespread disease of marine-farmed salmonids caused by infection with the water-borne bacterium Piscirickettsia salmonis. Very little is known about the route, timing, or magnitude of bacterial shedding from infected fish.

METHODOLOGY/PRINCIPAL FINDINGS

A cohabitation challenge model was used to assess shedding from chum Oncorhynchus keta, pink O. gorbuscha and Atlantic salmon Salmo salar. Infections in donor fish were established by intraperitoneal injection of P. salmonis. Naïve recipients were cohabitated with donor fish after which cumulative percent morbidity and mortality (CMM) was monitored, and bacterial burdens in kidney and in tank water were measured by qPCR. All donor fish died with mean days-to-death (MDD) among species ranging from 17.5 to 23.9. Among recipients, CMM ranged from 42.7% to 77.8% and MDD ranged from 49.7 to 56.4. In each trial, two peaks of bacterial DNA concentrations in tank water closely aligned with the MDD values of donor and recipient fish. Bacterial tissue burden and shedding rate, and plasma physiological parameters were obtained from individual donors and recipients. Statistically significant positive correlations between the shedding rate and P. salmonis kidney burden were measured in donor pink and in donor and recipient chum salmon, but not in donor or recipient Atlantic salmon. In Atlantic salmon, there was a negative correlation between kidney bacterial burden and hematocrit, plasma Ca++ and Mg++ values, whereas in infected chum salmon the correlation was positive for Na+ and Cl- and negative for glucose.

CONCLUSIONS

A dependency of bacterial shedding on species-specific patterns of pathogenesis was suggested. The coincidence of bacterial shedding with mortality will inform pathogen transmission models.

Cardiovascular Active Peptides of Marine Origin with ACE Inhibitory Activities: Potential Role as Anti-Hypertensive Drugs and in Prevention of SARS-CoV-2 Infection

Growing interest in hypertension-one of the main factors characterizing the cardiometabolic syndrome (CMS)-and anti-hypertensive drugs raised from the emergence of a new coronavirus, SARS-CoV-2, responsible for the COVID19 pandemic. The virus SARS-CoV-2 employs the Angiotensin-converting enzyme 2 (ACE2), a component of the RAAS (Renin-Angiotensin-Aldosterone System) system, as a receptor for entry into the cells. Several classes of synthetic drugs are available for hypertension, rarely associated with severe or mild adverse effects. New natural compounds, such as peptides, might be useful to treat some hypertensive patients. The main feature of ACE inhibitory peptides is the location of the hydrophobic residue, usually Proline, at the C-terminus. Some already known bioactive peptides derived from marine resources have potential ACE inhibitory activity and can be considered therapeutic agents to treat hypertension. Peptides isolated from marine vertebrates, invertebrates, seaweeds, or sea microorganisms displayed important biological activities to treat hypertensive patients. Here, we reviewed the anti-hypertensive activities of bioactive molecules isolated/extracted from marine organisms and discussed the associated molecular mechanisms involved. We also examined ACE2 modulation in sight of SARS2-Cov infection prevention.

Evaluation of growth status using endocrine growth indices, insulin-like growth factor (IGF)-I and IGF-binding protein-1b, in out-migrating juvenile chum salmon

This study aimed to utilize circulating insulin-like growth factor binding protein (IGFBP)-1b as a negative index of growth to evaluate the growth status of juvenile chum salmon (Oncorhynchus keta) in the ocean. First, rearing experiments using PIT-tagged juveniles were conducted to examine the relationship of circulating IGFBP-1b with growth rate of the fish in May and in June. The serum IGFBP-1b level negatively correlated with fish growth rate in both months, suggesting its utility as a negative index of growth. Next, the growth status of out-migrating juveniles in northeastern Hokkaido, Japan, was monitored for 3 years using the growth indices. Serum levels of IGF-I, a positive index of growth, in fish collected from the nearshore zone were low in May and high in June of all years. Levels of serum IGFBP-1b showed a trend opposite to that of serum IGF-I. However, the IGF-I/IGFBP-1b molar ratios well reflected the seasonal and regional trends. These findings suggest that the juveniles in June left the nearshore area under better growth conditions. The present study also suggests that the use of multiple growth indices would improve the sensitivity and accuracy to evaluate the current growth status of out-migrating juvenile chum salmon.

The Kuril Islands as a potential region for aquaculture: Trace elements in chum salmon

The Kuril Islands region is considered promising for development of salmon aquaculture. There are 41 salmon fish hatcheries in the Sakhalin Island and the Kuril Islands, 34 of them are hatcheries of the chum. Therefore, concentrations of six elements (Zn, Cu, Cd, Pb, As, and Hg) were determined in chum salmon were caught in this region. The contents of toxic elements (Cd, Pb, As, and Hg) don't exceed their maximum permissible concentrations (MPC) according to the Russian sanitary standards, but concentration of Pb are closely to MPC. Increased concentrations of Pb in wild chum have the natural origin. The unusual conditions of the Western Pacific are formed under the influence such factors as volcanism and upwelling.

The Olfactory Transcriptome and Progression of Sexual Maturation in Homing Chum Salmon Oncorhynchus keta

Reproductive homing migration of salmonids requires accurate interaction between the reception of external olfactory cues for navigation to the spawning grounds and the regulation of sexual maturation processes. This study aimed at providing insights into the hypothesized functional link between olfactory sensing of the spawning ground and final sexual maturation. We have therefore assessed the presence and expression levels of olfactory genes by RNA sequencing (RNAseq) of the olfactory rosettes in homing chum salmon Oncorhynchus keta Walbaum from the coastal sea to 75 km upstream the rivers at the pre-spawning ground. The progression of sexual maturation along the brain-pituitary-gonadal axis was assessed through determination of plasma steroid levels by time-resolved fluoroimmunoassays (TR-FIA), pituitary gonadotropin subunit expression and salmon gonadotropin-releasing hormone (sgnrh) expression in the brain by quantitative real-time PCR. RNAseq revealed the expression of 75 known and 27 unknown salmonid olfactory genes of which 13 genes were differentially expressed between fish from the pre-spawning area and from the coastal area, suggesting an important role of these genes in homing. A clear progression towards final maturation was characterised by higher plasma 17α,20β-dihydroxy-4-pregnen-3-one (DHP) levels, increased pituitary luteinizing hormone β subunit (lhβ) expression and sgnrh expression in the post brain, and lower plasma testosterone (T) and 17β-estradiol (E2) levels. Olfactomedins and ependymin are candidates among the differentially expressed genes that may connect olfactory reception to the expression of sgnrh to regulate final maturation.

Circulating insulin-like growth factor I in juvenile chum salmon: relationship with growth rate and changes during downstream and coastal migration in northeastern Hokkaido, Japan

Chum salmon (Oncorhynchus keta) migrate to the ocean in their first spring, and growth during early marine life is critical for survival. We examined the validity of circulating IGF-I and muscle RNA/DNA ratio as indices of growth rate using individually tagged juvenile chum salmon fed or fasted for 10 days. Serum IGF-I level was highly, positively correlated with individual growth rate. Muscle RNA/DNA ratio also showed a positive correlation, but its relation was not as high as that of IGF-I. We next measured these physiological parameters in chum salmon juveniles caught at river, estuary, port and nearshore of the northeastern Hokkaido, Japan, from May to June in 2013 and 2014, respectively. In both years, there was a trend that serum IGF-I levels were high in nearshore fish and low in river/estuarine fish in June. In contrast, muscle RNA/DNA ratio showed no clear temporal and spatial patterns. The present study shows that circulating IGF-I can be used as a growth index in juvenile chum salmon. Monitoring growth status using serum IGF-I suggests that growth of juvenile chum salmon in the survey area was activated when they left the coast.

Location is everything: evaluating the effects of terrestrial and marine resource subsidies on an estuarine bivalve

Estuaries are amongst the world's most productive ecosystems, lying at the intersection between terrestrial and marine environments. They receive substantial inputs from adjacent landscapes but the importance of resource subsidies is not well understood. Here, we test hypotheses for the effects of both terrestrial- and salmon-derived resource subsidies on the diet (inferred from stable isotopes of muscle tissue), size and percent nitrogen of the soft-shell clam (Mya arenaria), a sedentary estuarine consumer. We examine how these relationships shift across natural gradients among 14 estuaries that vary in upstream watershed size and salmon density on the central coast of British Columbia, Canada. We also test how assimilation and response to subsidies vary at smaller spatial scales within estuaries. The depletion and enrichment of stable isotope ratios in soft-shell clam muscle tissue correlated with increasing upstream watershed size and salmon density, respectively. The effects of terrestrial- and salmon-derived subsidies were also strongest at locations near stream outlets. When we controlled for age of individual clams, there were larger individuals with higher percent nitrogen content in estuaries below larger watersheds, though this effect was limited to the depositional zones below river mouths. Pink salmon exhibited a stronger effect on isotope ratios of clams than chum salmon, which could reflect increased habitat overlap as spawning pink salmon concentrate in lower stream reaches, closer to intertidal clam beds. However, there were smaller clams in estuaries that had higher upstream pink salmon densities, possibly due to differences in habitat requirements. Our study highlights the importance of upstream resource subsidies to this bivalve species, but that individual responses to subsidies can vary at smaller scales within estuaries.

A chronic oral toxicity study of marine collagen peptides preparation from chum salmon (Oncorhynchus keta) skin using Sprague-Dawley rat

Due to the increased consumption of marine collagen peptides preparation (MCP) as ingredients in functional foods and pharmaceuticals, it was necessary to carry out safety requirements in the form of an oral chronic toxicity assessment. In order to define the oral chronic toxicity of MCP, a 24-month feeding study of MCP was carried out. Sprague-Dawley (S-D) rats at the age of four-week of both sexes were treated with MCP at the diet concentrations of 0%, 2.25%, 4.5%, 9% and 18% (wt/wt). The actual food intake and bodyweight of the individual animals were recorded periodically until sacrifice. Blood and urine samples were collected for serum chemistry evaluations and urinalysis. Throughout the experimental period, there was no toxicologically significant difference between the vehicle and MCP-treated animals with respect to the survival rate, body weight, food consumption, urinalysis, clinical biochemistry parameter and relative organ weight in either sex. Moreover, incidences of non-neoplastic lesions in MCP-treated groups did not significantly increase compared with the control group. Under the present experimental conditions, no higher risk of chronic toxic effects was observed in MCP-treated rats at the diet concentrations of 2.25%, 4.5%, 9% and 18% (wt/wt) than in the rats fed with basal rodent diet.

Oral administration of marine collagen peptides from Chum Salmon skin enhances cutaneous wound healing and angiogenesis in rats

BACKGROUND

A wound is a clinical entity which often poses problems in clinical practice. The present study was aimed to investigate the wound healing potential of administering marine collagen peptides (MCP) from Chum Salmon skin by using two wound models (incision and excision) in rats.

RESULTS

Ninety-six animals were equally divided into the two wound models and then within each model animals were randomly divided into two groups: vehicle-treated group and 2 g kg(-1) MCP-treated group. Wound closure and tensile strength were calculated. Collagen deposition was assessed by Masson staining and hydroxyproline measurement. Angiogenesis was assessed by immunohistological methods. MCP-treated rats showed faster wound closure and improved tissue regeneration at the wound site, which was supported by histopathological parameters pertaining to wound healing. MCP treatment improved angiogenesis and helped form thicker and better organised collagen fibre deposition compared to vehicle-treated group.

CONCLUSION

The results show the efficacy of oral MCP treatment on wound healing in animals.

Changes in gene expression for GH/PRL/SL family hormones in the pituitaries of homing chum salmon during ocean migration through upstream migration

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.

Reciprocal subsidies and food web pathways leading to chum salmon fry in a temperate marine-terrestrial ecotone

Stable isotope analysis was used to determine the relative proportions of terrestrial and marine subsidies of carbon to invertebrates along a tidal gradient (low-intertidal, mid-intertidal, high-intertidal, supralittoral) and to determine the relative importance of terrestrial carbon in food web pathways leading to chum salmon fry Oncorhynchus keta (Walbaum) in Howe Sound, British Columbia. We found a clear gradient in the proportion of terrestrially derived carbon along the tidal gradient ranging from 68% across all invertebrate taxa in the supralittoral to 25% in the high-intertidal, 20% in the mid-intertidal, and 12% in the low-intertidal. Stable isotope values of chum salmon fry indicated carbon contributions from both terrestrial and marine sources, with terrestrially derived carbon ranging from 12.8 to 61.5% in the muscle tissue of chum salmon fry (mean 30%). Our results provide evidence for reciprocal subsidies of marine and terrestrially derived carbon on beaches in the estuary and suggest that the vegetated supralittoral is an important trophic link in supplying terrestrial carbon to nearshore food webs.

The function of rhamnose-binding lectin in innate immunity by restricted binding to Gb3

L-rhamnose-binding lectins (RBLs) have been isolated from various kinds of fish and invertebrates and interact with various kinds of bacteria, suggesting RBLs are involved in various inflammatory reactions. We investigated the effect of RBLs from chum salmon (Oncorhynchus keta), named CSL1, 2 and 3, on the peritoneal macrophage cell line from rainbow trout (Oncorhynchus mykiss) (RTM5) and an established fibroblastic-like cell line derived from gonadal tissue of rainbow trout (RTG-2). CSLs were bound to the surface of RTM5 and RTG-2 cells and induced proinflammatory cytokines, including IL-1beta1, IL-1beta2, TNF-alpha1, TNF-alpha2 and IL-8 in both cells by recognizing globotriaosylceramide (Gb3). In addition, CSLs had an opsonic effect on RTM5 cells and this effect was significantly inhibited by L-rhamnose, indicating that CSLs enhanced their phagocytosis by binding to Gb3 on cell surfaces. This is the first finding that Gb3 plays a role in innate immunity by cooperating with natural ligands, RBLs.

[Differentiation of chum salmon Oncorhynchus keta Walbaum populations as revealed with microsatellite and allozyme markers: a comparison]

The character and extent of population differentiation in chum salmon Oncorhynchus keta from Sakhalin and Iturup were comparatively studied with 10 microsatellite and 12 allozyme markers. It was demonstrated with the example of allozyme polymorphism at the EstD locus that the effect of an individual locus with one major allele is capable of distorting the total picture of population differentiation. Multiallelic microsatellites were more efficient in revealing the genetic structure of chum salmon populations at the levels of differences between regional populations and between the stocks of individual rivers of the same region.

Kinetic properties of three isoforms of trypsin isolated from the pyloric caeca of chum salmon (Oncorhynchus keta)

Three isoforms of anionic chum salmon trypsin (ST-1, ST-2, and ST-3) were purified from the pyloric caeca of chum salmon (Oncorhynchus keta). The molecular weights of the three isoforms were about 24 kDa as determined by SDS-PAGE. The isoelectric points of ST-1, ST-2, and ST-3 were 5.8, 5.4, and 5.6, respectively. The apparent K(m) values of two isoforms (ST-1 and ST-2) for BAPA (benzoyl-L-arginine-p-nitroanilide) hydrolysis at 5, 15, 25 and 35 degrees C were slightly higher than that of the main isoform ST-3, depending on temperature. The turnover numbers, k(cat), of ST-1 and ST-2 were about twice as high as that of ST-3. Consequently, the catalytic efficiencies (k(cat)/K(m)) of ST-1 and ST-2 were more efficient than ST-3. There were marked differences in both apparent K(m) and k(cat) values of three anionic chum salmon trypsins as compared to bovine cationic trypsin. K(m) values of all chum salmon trypsins were approximately 10 times lower than those of bovine trypsin, depending on the temperature. The k(cat) values of all chum salmon trypsins were about 2- to 5-fold higher than those of bovine trypsin; therefore, the catalytic efficiencies (k(cat)/K(m)) of chum salmon trypsin were 20- to 40-fold more efficient than those of bovine trypsin. On the other hand, k(cat)/K(m) values of ST-1 for TAME (tosyl-L-arginine methyl ester) hydrolysis were lower than those of bovine trypsin, whereas k(cat)/K(m) values of ST-2 and ST-3 were comparable to those of bovine trypsin, depending on the temperature.

Application of laser ablation ICPMS to trace the environmental history of chum salmon Oncorhynchus keta

Trace element levels in otoliths of chum salmon Oncorhynchus keta were examined by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). A close linear relationship in the Sr:Ca ratios between EPMA (X-ray analysis with an electron microprobe) and LA-ICPMS analyses was found (p<0.0001), suggesting that the latter technique could be used to separate the marine and freshwater life phases. Mg:Ca, Cr:Ca, Zn:Ca and Ba:Ca ratios in either the core region or the oceanic growth zone of the otoliths varied among sites. These differences suggest that elemental compositions may reflect environmental variability among spawning (breeding) or habitat sites. Thus, those element ratios demonstrate the potential to be used to distinguish between fish spawning (breeding) sites and habitats for this species of salmon.

Unique disialosyl gangliosides from salmon kidney: Characterization of V3αFuc, IV3βGalNAc, II3(αNeuAc)2-Gg4Cer and its analogue with 4-O-acetyl-N-acetylneuraminic acid

Four unidentified acidic glycolipids (X3-X6) were isolated from the kidney of the Pacific salmon on an anion exchange column and by high performance liquid chromatography using a silica bead (Iatrobeads) column. Based on methylation analysis, chemical and enzymatic degradation, proton nuclear magnetic resonance spectroscopy and mass spectrometry, the glycon structure of X5 and X6 was identified as a unique disialosyl fucosyl-N-acetylgalactosaminyl ganglio-N-tetraose:Fucalpha3GalNAcbeta3Galbeta3GalNAcbeta4[NeuAcalpha8NeuAcalpha3] Galbeta4Glcbeta1Cer. NMR showed that X3 and X4 were analogues of X5 and X6 and contained O-acetyl groups on C4 of the outer N-acetylneuraminic acid, first disialosyl gangliosides containing 4-O-acetyl-N-acetylneuraminic acid. The ceramides of X3 and X5 contained predominantly C24: 1, and X4 and X6 contained saturated fatty acids (C14: 0, C16: 0 and C18: 0), whereas the long chain base was exclusively sphingenine. The concentrations of X3 and X4 were 0.13 and 0.16 nmol/g of kidney respectively and those of X5 and X6, were 0.07 nmol/g each.

cDNA cloning and sequence analysis of preproendothelin-1 (PPET-1) from salmon, Oncorhynchus keta

The presence of endothelin (ET)-like immunoreactivity and the cardiovascular effects of mammalian ET-1 in fish have been reported. To identify ET-related peptides in fish, we screened the cDNA library of the salmon (Oncorhynchus keta) stomach by means of rapid amplification of cDNA ends, and we cloned cDNAs encoding an ET-related peptide. The salmon ET-related sequence of 21 amino acids is identical to the trout ET-1 peptide recently purified from kidney specimens of Oncorhynchus mykiss. The deduced amino acid sequence of salmon pre-proET-1 (PPET-1) comprises 244 amino acids, including a putative signal sequence and mature ET-1, as well as big ET-1 and ET-1-like sequences. This precursor, the first reported PPET-1 sequence for Salmoniformes, Teleostei, has low homology with the sequences of human, mouse, frog (Xenopus laevis), and zebrafish (Danio rerio) PPET-1 (26%, 29%, 24%, and 39%, respectively).

FATE OF NITROGEN IN RIPARIAN FOREST SOILS AND TREES: AN15N TRACER STUDY SIMULATING SALMON DECAY

We introduced an 15N-NH4+ tracer to the riparian forest of a salmon-bearing stream (Kennedy Creek, Washington, USA) to quantify the cycling and fate of a late-season pulse of salmon N and, ultimately, mechanisms regulating potential links between salmon abundance and tree growth. The 15N tracer simulated deposition of 7.25 kg of salmon (fresh) to four 50-m2 plots. We added NH4+ (the initial product of salmon carcass decay) and other important nutrients provided by carcasses (P, S, K, Mg, Ca) to soils in late October 2003, coincident with local salmon spawning. We followed the 15N tracer through soil and tree pools for one year. Biological uptake of the 15N tracer occurred quickly: 64% of the 15N tracer was bound in soil microbiota within 14 days, and roots of the dominant riparian tree, western red cedar (Thuja plicata), began to take up 15N tracer within seven days. Root uptake continued through the winter. The 15N tracer content of soil organic matter reached a maximum of approximately 52%, five weeks after the application, and a relative equilibrium of approximately 40% within five months. Six months after the addition, in spring 2004, at least 37% of the 15N tracer was found in tree tissues: approximately 23% in foliage, approximately 11% in roots, and approximately 3% in stems. Within the stems, xylem and phloem sap contained approximately 96% of the tracer N, and approximately 4% was in structural xylem N. After one year, at least 28% of the 15N tracer was still found in trees, and loss from the plots was only approximately 20%. The large portion of tracer N taken up in the fall and reallocated to leaves and stems the following spring provides mechanistic evidence for a one-year-lagged tree-growth response to salmon nutrients. Salmon nutrients have been deposited in the Kennedy Creek system each fall for centuries, but the system shows no evidence of nutrient saturation. Rates of N uptake and retention are a function of site history and disturbance and also may be the result of a legacy effect, in which annual salmon nutrient addition may lead to increased efficiency of nutrient uptake and use.

On a salmon (Oncorhynchus [corrected] keta) liver RNase, belonging to RNase T2 family: primary structure and some properties

A base-nonspecific and acid ribonuclease (RNase Ok2) was purified from the liver of a salmon (Oncorhnchus keta) to a homogeneous state by SDS-PAGE. The primary structure of RNase Ok2 was determined by protein chemistry and molecular cloning. The RNase Ok2 was a glycoprotein and consisted of 216 amino acid residues. Its molecular mass of protein moiety was 25,198, and its amino acid sequence showed that it belongs to the RNase T2 family of enzymes. The optimal pH of RNase Ok2 was around 5.5. The base preferences at the B1 and B2 sites were estimated from the rates of hydrolysis of 16 dinucleoside phosphates to be G>>A>U, C, and G>A>U>C respectively. In this enzyme, one of the three histidine residues which have been thought to be important for catalysis of RNase Rh, a typical RNase of this family of enzymes, His104 was replaced by tyrosine residue. Based on the results, the role of H104, which has been proposed to be a phosphate binding site with a substrate, was reconsidered, and we proposed a revised role of this His residue in the hydrolysis mechanism of RNase T2 family enzymes.

Embryonic and post-embryonic expression of arylalkylamine N-acetyltransferase and melatonin receptor genes in the eye and brain of chum salmon (Oncorhynchus keta)

Melatonin and arylalkylamine N-acetyltransferase (AANAT), the rate-limiting enzyme in melatonin synthesis, have taken on special importance in vertebrate circadian biology. Recent identification of genes encoding two AANAT (AANAT(1) and AANAT(2)) and two subtypes of melatonin receptor (Mel-R; Mel(1a) and Mel(1b)) in several fish species has led to rapid advances in characterizing the physiological roles of melatonin. In the present study, partial cDNAs encoding these four genes were cloned from the eye and brain of chum salmon (Oncorhynchus keta). Based on the nucleotide sequences, we developed highly sensitive real-time PCR systems for these four mRNAs. The development of daily rhythmicity in AANAT(1), AANAT(2), Mel(1a), and Mel(1b) transcript levels was examined in the eye and brain of chum salmon during embryonic and post-embryonic stages (from day -9 to day +180). In a parallel experiment, ocular and brain melatonin levels were measured by radioimmunoassay. Parallelism in developmental changes and in circadian rhythms of AANAT mRNAs and melatonin levels in the eye and the brain supports a hypothesis that the developmental increases of nocturnal melatonin levels results partly from the elevated transcription of AANAT genes. Moreover, abundant expression of AANAT and Mel-R mRNAs in the optic tectum, thalamus, hypothalamus, cerebellum, and eye indicates possible roles of melatonin in visual processing and neuroendocrine regulation, through which melatonin might be involved in migratory behavior of chum salmon.

Trypsin-catalysed synthesis of oligopeptide amides: comparison of catalytic efficiency among trypsins of different origin (bovine, Streptomyces griseus and chum salmon)

A procedure has been developed for the synthesis of oligopeptide amide using inverse substrates as acyl donors with amino acid amide instead of p-nitroanilide as acyl acceptor and trypsins of different origin (bovine, Streptomyces griseus and chum salmon trypsins) as the catalyst. The effectiveness of this procedure was demonstrated by the synthesis of a pentapeptide, Boc-[Leu5]-enkephalin amide, as a model compound. The method was the first enzymatic method shown to be successful at each successive coupling step for the synthesis of the oligopeptide. Bovine and chum salmon trypsins were superior to Streptomyces griseus trypsin as the catalyst.

Chum salmon trypsin-catalyzed preferential formation of peptides containing D-amino acid

Chum salmon trypsin-catalyzed peptide synthesis has been studied by using nine series of "inverse substrates," i.e., p-amidinophenyl, p- and m-guanidinophenyl, p- and m-(guanidinomethyl)phenyl, and four position isomers of guanidinonaphthyl esters derived from Nalpha-(tertbutyloxycarbonyl)amino acid as acyl donor components. They were found to couple with an acyl acceptor such as L-alanine p-nitroanilide to produce dipeptide in the presence of trypsin. All substrates tested in this study undergo less enantioselective coupling reaction, and the coupling product was the favorably obtained D-series rather than L-series (in the present case; Nalpha-Boc-D-Ala and Nalpha-Boc-L-Ala). The optimum condition for the coupling reaction was studied by changing the organic solvent, buffer solution, pH, and acyl acceptor concentration. It was found that the enzymatic hydrolysis of the resulting product was negligible.

Quantitative analysis of fushi tarazu factor 1 homolog messenger ribonucleic acids in the pituitary of salmon at different prespawning stages

Steroidogenic factor 1 (SF-1) or Ad4BP is a member of the fushi tarazu factor 1 (FTZ-F1) family and an orphan nuclear receptor that plays an important role in the hypothalamus-pituitary-gonadal axis and the adrenal cortex. Although its critical role in the differentiation of adrenals, gonads, and pituitary gonadotropes has been well demonstrated, regulatory function of SF-1 during sexual maturation is yet to be examined. To investigate the potential role of SF-1 in sexual maturation, expression of two salmon FTZ-F1 homolog genes, sFF1-I and sFF1-II, was examined in the pituitaries of chum and sockeye salmons, using specific and sensitive RNase protection assays. Only sFF1-I mRNA was found in the pituitary and other organs, such as the ovary, spleen, liver, brain, and skeletal muscle. In chum salmon during upstream migration from the bay to the hatchery, the level of sFF1-I mRNA in the male fish was increased on the midway in the river, where the levels of gonadotropin alpha- and II beta-subunit mRNAs were increased. In maturing sockeye salmon, the expression of the sFF1-I gene was elevated in the mature male fish, but the administration of GnRH analog did not further enhance the expression. These results indicate that sFF1-I gene expression in the pituitary is upregulated in maturing salmon, and this upregulation may not depend on GnRH.

Anionic trypsin from chum salmon: activity with p-amidinophenyl ester and comparison with bovine and Streptomyces griseus trypsins

An anionic trypsin from pyloric caeca of chum salmon (Oncorhynchus keta) was purified by ammonium sulfate and acetone fractionation followed by affinity chromatography, gel-filtration, and DEAE-anion exchange chromatography. The apparent molecular mass was about 24 kDa as determined by SDS-PAGE. The anionic chum salmon trypsin was moderately active toward esterase substrates such as tosyl-L-arginine methyl ester and tosyl-L-lysine methyl ester. Its amidase activity for benzoyl-L-arginine p-nitroanilide was comparative to those of bovine and Streptomyces griseus trypsins. Kinetic characteristics of anionic chum salmon, bovine, and Streptomyces griseus trypsins toward inverse substrate (p-amidinophenyl ester) were compared. Inverse substrate behaved as a specific substrate for anionic chum salmon trypsin with specific binding, efficient acylation, and relatively slow deacylation.

Molecular cloning and expression of an otolith matrix protein cDNA from the rainbow trout, Oncorhynchus mykiss

The fish otolith is a hard tissue consisting of calcium carbonate and organic matrices. The matrix proteins play important roles in otolith formation, but little is known about the nature of these proteins. In this study, matrix proteins were extracted from the otoliths of rainbow trout, Oncorhynchus mykiss, and chum salmon, Oncorhynchus keta. EDTA-soluble matrix proteins were separated by SDS-PAGE, revealing two major components in the otoliths of both species with apparent molecular masses of 55 and 43 kDa. N-terminal and some internal amino acid sequences of the 55-kDa otolith matrix protein were determined. A cDNA fragment encoding this protein of O. mykiss was amplified by reverse transcription PCR using two degenerate primers designed from the amino acid sequences. A cDNA encoding this protein was obtained by screening a saccular cDNA library using the amplified cDNA fragment as a probe. Nucleotide sequence analysis revealed that the cDNA clone has a sequence of 2.5 kb and the open reading frame encoding 344 amino acid residues. Northern blot analysis showed that mRNA of this protein is expressed specifically in the sacculus, and consistently during the day.

A new vitamin E (alpha-tocomonoenol) from eggs of the Pacific salmon Oncorhynchus keta

A novel alpha-tocomonoenol 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyl-12-tridecenyl )-2H-1- benzopyran-6-ol[ having an unusual methylene unsaturation at the isoprenoid-chain terminus of alpha-tocopherol was isolated from the lipophilic fraction of chum salmon eggs. The structure of this marine-derived tocopherol (MDT) was established by spectral analyses. The peroxyl radical-trapping activities of MDT and alpha-tocopherol were compared in aqueous phosphatidylcholine liposomal suspension and in methanolic solution at 37 degrees C. The antioxidant activity of MDT was found to be identical to that of alpha-tocopherol under the experimental conditions of measurement.

The major acidic glycolipids from the kidney of the Pacific salmon (Oncorhynchus keta): characterization of a novel ganglioside, fucosyl-N-acetylgalactosaminyl-GM1

Two fractions of a major ganglioside from the kidney of the pacific salmon, Oncorhynchus keta, were eluted from a DEAE-Sephadex column in the monosialosyl fraction. The faster moving ganglioside (X1) on TLC was separated from the slower moving one (X2) by HPLC using a silica beads column. By methylation analysis, chemical and enzymatic degradation, reaction with monoclonal antibodies, LSIMS, and (1)H-NMR spectroscopy, X1 was determined to be a monosialosyl ganglioside belonging to the ganglio-series with a unique Fucalpha1-3GalNAc linkage at the nonreducing terminal: Fucalpha1-3GalNAcbeta1-3Galbeta1-3GalNAcbeta1-4[ NeuAcalpha2-3]Galbeta 1-4Glcbeta1-1Cer. Analysis of the lipophilic moiety indicated predominance of 24:1 fatty acid in combination with sphingenine. X2 was found to have a glycon structure identical to X1. The ceramide of X2 consisted predominantly of saturated fatty acids (18:0 and 16:0). The tissue concentrations of X1 and X2 in kidney were 3.7 and 2.8 nmol/g, respectively.

Miltpain, new cysteine proteinase from the milt of chum salmon, Oncorhynchus keta

A new cysteine proteinase, salmon miltpain, was isolated and purified from the milt of chum salmon (Oncorhynchus keta). Native molecular mass was estimated as 67,000 by gel filtration column chromatography (Shodex WS2003) and 22,300 by SDS-polyacrylamide gel electrophoresis. Isoelectoric point was determined to be 3.9 by isoelectric focusing. The first 15 amino acid residues in the N-terminal region were LPSFLY-AEMVGYNIL. The cysteine proteinase, which had a pH optimum of 6.0 for Z-Arg-Arg-MCA hydrolysis, required a thiol-reducing reagent for activation and was inhibited by E-64, iodacetamide, CA-074 Me, TLCK, TPCK and ZPCK. The cysteine proteinase exhibited unique substrate specificity toward paired basic residues such as Lys-Arg, Arg-Arg at the subsites of P2-P1 and had a K(m) of 16.3 microM and kcat of 20.3 s-1 with Z-Arg-Arg-MCA as substrate and a K(m) of 52.9 microM and kcat of 1.79 s-1 with Z-Phe-Arg-MCA. This proteinase was found to considerably hydrolyze basic proteins such as histone, salmine and clupaine but not milk casein.

Rapid liquid chromatographic method to distinguish wild salmon from aquacultured salmon fed synthetic astaxanthin

Analytical methods are needed to determine the presence of color additives in fish. We report a liquid chromatographic (LC) method developed to identify the synthetic form of the color additive astaxanthin in salmon, based on differences in the relative ratios of the configurational isomers of astaxanthin. The distributions of configurational isomers of astaxanthin in the flesh of wild Atlantic and wild Pacific salmon are similar, but significantly different from that in aquacultured salmon. Astaxanthin is extracted from the flesh of salmon, passed through a silica gel Sep-Pak cartridge, and analyzed directly by LC on a Pirkle covalent L-leucine column. No derivatization of the astaxanthin is required-an important advantage of our approach, which is a modification of our previously described method. This method can be used to distinguish between aquacultured and wild salmon. The method has general applicability and can also be used to identify astaxanthins derived from other sources such as Phaffia yeast and Haematococcus pluvialis algae.

Cloning and sequence analysis of a cDNA encoding salmon (Onchorhynchus keta) liver transglutaminase

We isolated cDNA clones encoding a transglutaminase (TGase: EC 2.3.2.13) from a salmon (Onchorhynchus keta) cDNA library prepared from the liver. In the cDNA sequence combined, an open reading frame coding for a protein of 680 aa was found. The deduced sequence showed a considerable similarity (62.4%) to that of red sea bream TGase. By comparison of sequence similarity to other TGases, the structure of salmon TGase was like tissue type TGases, rather than membrane-associated type or plasma type TGases. As a structural feature of salmon TGase, 3 aa residues were substituted in the 25 aa sequence around the active site Cys residue, which is conserved among several tissue type TGases. The critical residues thought to form the catalytic-center triad (Cys272, His331, and Asp301) were found in the highly conserved region, but the region surrounding Tyr511, which corresponds to the residue participates in hydrogen-bond interactions of active center domain, was less similar to other TGases, except for red sea bream TGase. These finding suggests that the overall structure of fish TGase resembles tissue-type TGases, but has some unique structure.

Immunocytochemical localization of the Pit-1 protein in the pituitary of the rainbow trout (Oncorhynchus mykiss)

Pit-1 is a pituitary-specific transcription factor responsible for activating the growth hormone (GH) gene family. The localization of Pit-1 protein in the pituitary of rainbow trout was studied by immunocytochemical analysis. Fish Pit-1 was found to be extensively localized in the nuclei of cells in the proximal pars distalis (PPD), rostral pars distalis (RPD), and pars intermedia (PI). Sagittal sections were immunocytochemically double stained with antibodies against Pit-1, GH, prolactin (PRL), and somatolactin (SL). The results showed that Pit-1 protein was present in the GH-containing cells of the PPD, the PRL-containing cells of the RPD, and the SL-containing cells of the PI.

Changes of thyrotropin-releasing hormone concentration in the brain and levels of prolactin and thyroxin in the serum during spawning migration of the chum salmon Oncorhynchus keta

Changes in concentration of thyrotropin-releasing hormone (TRH) in various regions of the brain of female and male chum salmon Oncorhynchus keta during their spawning migration toward the home stream were examined to determine the physiological role of TRH. In the same specimens, serum levels of prolactin (PRL) and thyroxin (T4) were also examined and compared with the change of TRH concentration. TRH concentration in the olfactory bulb of males increased significantly just before the upstream migration or entering the river and dropped after entering the home stream. TRH concentration in the olfactory lobe was also slightly higher in Class 2 salmons with nuptial coloration captured in coastal water than in the other groups. TRH concentrations in hypothalamus and pituitary remained relatively low during the spawning migration. The change of TRH concentration in females was similar to that in males, but was smaller and with a wider range. The serum level of PRL was extremely low in both males and females collected in coastal waters (Classes 1 and 2) and increased after the fish entered the river. The serum level of T4 in both males and females tended to be low, as did the TRH concentration in the hypothalamus and pituitary. Immunohistochemistry of the brain using anti-proTRH serum revealed many proTRH cell bodies in the olfactory bulb and olfactory lobe. These results indicate that TRH in the homing salmon is produced mainly in the olfactory bulb and lobe and that its production may be related to changes in olfactory function during migration.

Gonadotropin-releasing hormone (GnRH): expression during salmon migration

In the seaward migrating chum salmon, immunocytochemical and in situ hybridization techniques revealed isolated GnRH neurons at the base of the nasal epithelium, along the nervus terminalis and as ganglia at the rostroventral (gROB) and caudalmost (GT) olfactory bulb. A novel GnRH ganglion was seen at the cribriform bone (gCB). GnRH immunoreactivity but not the hybridization signal was detected in the midbrain neurons. During the migratory period, there were trends towards an increase in GnRH mRNA in the gCB and the gROB and a significant surge in plasma thyroid hormones was also evident. Therefore, we hypothesise thyroid hormones might be crucial for the increased tendency of GnRH expression and the migratory behavior of chum salmon.

Monoclonal antibodies against the protein complex that contains the flagellar movement-initiating phosphoprotein of Oncorhynchus keta

We isolated and characterized several monoclonal antibodies against a protein complex containing the flagellar movement-initiating phosphoprotein (MIPP) that appears to play a crucial role in the initiation of flagellar movement in quiescent spermatozoa of Salmonid fish. The effects of the antibodies on the phosphorylation of MIPP, as well as on the initiation of movement, in model sperm cells were studied. Three monoclonal antibodies, namely, FMI7, FMI18, and FMI27, were found specifically to inhibit both the initiation of flagellar movement and the phosphorylation of MIPP. These antibodies did not recognize denatured MIPP; they only recognized the native antigen. FMI7 exclusively recognized the denatured form of a 38-kDa protein, which may possibly be a protein kinase responsible for the phosphorylation of MIPP. Immunofluorescence analysis in situ of model sperm cells with the antibodies showed that the antigen was localized predominantly in the basal structure of the spermatozoon. Thus, the results clearly demonstrate the involvement of MIPP in the initiation of flagellar movement and the control of flagellar motility.