Life-history styles and somatic allocation in iteroporous arctic charr and semelparous pink salmon

Synopsis RNA/DNA ratios were used to estimate recent somatic allocation of spawning arctic charr,Salvelinus alpinus, and pink salmon,Oncorhynchus gorbuscha. Smaller arctic charr morphs had lower ratios than larger morphs. Larger male pink salmon had lower ratios than smaller males. Thus recent somatic allocation (anabolic metabolic activity and growth) is coupled with cumulative lifetime growth in iteroparous arctic charr, but is uncoupled in semelparous pink salmon. These data suggest that somatic investment in these species is being differentially effected by the energetic costs of reproduction.     

Novel set of multiplex assays (SalPrint15) for efficient analysis of 15 microsatellite loci of contemporary samples of the Atlantic salmon (Salmo salar)

We report the development of new PCR assays and loading panels for the Atlantic salmon using 15 microsatellite loci. A total of 8, 3 and 4 loci were coamplified in three separate PCRs using labelled primers and loaded on the ABI DNA analyzer in two separate panels. Amplified alleles were clearly typed, and easily interpretable results were obtained. The method was successfully applied in different laboratories, even when different types of DNA polymerase were employed. The method is useful for analysing paternity, population genetics and conservation as well as for selective breeding programmes.     

NMDA receptor subunit-dependent modulation by conantokin-G and Ala7-conantokin-G

The modulation of recombinant NMDA receptors by conantokin-G (con-G) and Ala7-conantokin-G (Ala7-Con-G) was investigated in Xenopus oocytes injected with capped RNA coding for NR1 splice variants and NR2 subunits using the two-electrode voltage clamp technique. Glutamate exhibited a marginally higher apparent affinity for NR2A-containing receptors than NR2B-containing receptors, regardless of the NR1 subunit present. Conantokins were bath applied to give cumulative concentration responses in the presence of 3 and 30 mum glutamate. Both contantokins exhibited biphasic concentration-response relationships at NR2A-containing NMDA receptors, producing potentiation at low conantokin concentrations and inhibition at high concentrations. These effects were stronger with glutamate concentrations near its EC50, and less marked at saturating concentrations. In contrast, the conantokin concentration-response relation was monophasic and inhibitory at NR2B-containing receptors. We conclude that the combinations of subunits that comprise the NMDA receptor complex influence conantokin and glutamate affinities and the nature of the responses to conantokins.     

Phosphorylation of human fibrinogen in vitro with cyclic 3',5'-AMP-stimulated protein kinase and (32P)ATP

Human fibrinogen was shown to be a substrate of the catalytic subunit of pig muscle cyclic 3′,5′-AMP-stimulated protein kinase $\text{in vitro}$. Maximally at least 6 mol of (³²P)phosphate per mol of fibrinogen was bound, preferentially to the α-chain.     

Estradiol-17β and nutritional status affect calcium balance, scale and bone resorption, and bone formation in rainbow trout, Oncorhynchus mykiss

The effects of estradiol-17β (E₂) on bone resorption and formation as well as its effects on scale resorption were investigated in rainbow trout in order to elucidate the role of the hormone in calcium mobilization from calcified tissues, and to clarify the importance of scale and bone as calcium reserves during sexual maturation. Furthermore, the effects of nutritional status on calcified tissues and E₂-induced calcium mobilization were studied. In fed as well as fasted rainbow trout, E₂ treatment increased scale osteoclastic activity measured as tartrate-resistant acid phosphatase activity, and reduced scale calcium content, suggesting that E₂ increases scale resorption in both the fed and fasted fish. Using histomorphometry, E₂ treatment was found to decrease pharyngeal bone resorption in fed, but not in fasted rainbow trout. The E₂ effect on rainbow trout bone is consistent with its physiological role in mammals and birds where E₂ has been reported to decrease bone resorption. It appears therefore that rainbow trout protect their skeleton and instead use scales as a source of calcium during E₂-induced calcium mobilization. The formation of pharyngeal bone was decreased by fasting, and the importance of the nutritional status for the activity of the bone cells in rainbow trout is therefore emphasized. Accepted: 8 May 1997     

Two methods to avoid the effect of endogenous protein inhibitors during the assay of protein kinase C activity in tissue extracts.

Using H1 as substrate the protein kinase C activity of rat liver cell sap was increased about fourfold by treatment with DEAE-cellulose at pH 7.5 at an intermediate ionic strength due to removal of protein inhibitors. The activity of cell sap from rat spleen, brain or muscle was about doubled by the same treatment. In contrast, when a specific synthetic peptide substrate was used the corresponding increase of enzyme activity was not obtained when the inhibitors were removed. This shows that this type of substrates should be preferred for reliable assays of protein kinase C in crude extracts. The possible role of the protein inhibitors for the substrate specificity of protein kinase C is briefly discussed.     

Determination of the optical purity of threonine and hydroxyproline by capillary gas chromatography on a chiral stationary phase

Summary Experimental conditions for the derivatization and resolution by GLC of all stereoisomers of threonine and 4-hydroxyproline are reported. Threonine was in two steps converted toN,O-bisisobutoxycarbonyl 2,2,2-trifluoroethyl ester derivatives, the second of which was performed under anhydrous conditions. As such the enantiomers could pairwise be separated by capillary gas chromatography on a Chirasil-Val column. SinceL- andD-threonine eluted much earlier than the corresponding allo forms, quantitative determination of the allothreonine content inD- orL-threonine down to the one percent level could be simply accomplished but also enantiomeric impurities could be determined. Unlike for threonine, the corresponding 4-hydroxyproline isomers could not all be resolved asN,O-bisisobutoxycarbonyl 2,2,2-trifluoroethyl esters on this column. Although diastereomers could still be separated, the allo pair cochromatographed and the resolution for theL- andD-isomers was low. Complete separation of the 4-hydroxyproline isomers could be accomplished asN,O-bisprotected isobutyl amides, the formation of which required three derivatization steps. These were used for the determination of allohydroxyproline.     

Stomach analyses of Baltic salmon from 1959–1962 and 1994–1997: possible relations between diet and yolk-sac-fry mortality (M74)

In recent years, Baltic Sea salmon Salmo salar have suffered high larval mortality (M74) which can be cured by thiamine treatment. Analyses of long term mortality records (1928–1998) from two salmon hatcheries suggest that before the 1970s M74 did not occur, or was less frequent. This indicates that varying M74 did not cause the long-term fluctuations of Baltic salmon catches in this period. The frequency of M74 has been correlated positively to the abundance of the salmon's primary prey, sprat Sprattus sprattus. Sprat, herring Clupea harengus and three-spined stickleback Gasterosteus aculeatus dominated the diet in both the periods of study, 1959–1962 and 1994–1997. The mean size of consumed sprat was significantly smaller in 1994–1997 compared with 1959–1962. Herring and, to a lesser extent, three-spined stickleback increased in the diet of salmon, while sprat appeared to constitute a smaller part of the diet in 1994–1997. The cause of M74 and the thiamine deficiency involved remains unknown, but is thought to be related to changes in thiamine or thiaminase content in forage fish, winter-feeding of salmon or general changes in the pelagic food web, caused by overfishing or eutrophication.