The uptake of Na-selenite in rat brain

Polyunsaturated fatty acids (PUFAs) occur in phospholipids of synapses of central nervous system (CNS). PUFAs may thus determine the fluidity of synaptosomal membranes and regulate neuronal transmission. It was therefore tempting to suggest an oxidative system in CNS protecting the membrane function, e.g., glutathione peroxidase (GSH-Px). In order to trace GSH-Px Wistar rats were loaded with 4800 kBq of⁷⁵Se sodium selenite. By means of gradient ultracentrifugation, particulate fractions of CNS were isolated and radioactivity as well as selenium dependent GSH-Px were estimated. The following data were obtained:

1. All fractions (myelin, synaptic vesicles, synaptosomes, mitochondria, and microsomes) contained⁷⁵Se.
2. After acetone precipitation of GSH-Px activity, fractionation on Sephadex G-150 revealed in all particulate fractions at least two peaks of radioactivity with GSH-Px activity.
3. The two GSH-Px peaks from the Sephadex filtration were freeze dried and applied on a hydrophobic T-gel column and eluted with decreasing molarity of ammonium sulfate from 1.5 to 0.05M. The first Sephadex peak with GSH-Px activity from myelin and the second peak with GSH-Px activity from synaptic vesicles could now be resolved into two different fractions of radioactivity on the T-gel. The remaining Sephadex G-150 peaks could only be resolved into one peak of radioactivity.
4. SDS-polyacrylamide gel electrophoresis of the T-gel peaks from all fractions showed a protein band with a mobility identical with that of human erythrocyte GSH-Px. The T-gel elution of myelin, synaptic vesicles and mitochondria gave rise to nearly pure CNS GSH-Px activity.

. The data presented support the idea that CNS fractions have membrane bound GSH-Px activity that may function as protecting enzymes towards oxidative stress in the brain.     

Monoclonal antibodies to epitopes shared by actin and vimentin obtained by paramyxovirus immunization

Three hybridoma clones producing IgM antibodies against actin were obtained from mice immunized with purified virions of paramyxoviruses. When tested on growing lung fibroblasts, ascites fluids of all clones stained in immunofluorescence cytoplasmic bundles of microfilaments, but also fibrillar networks. On colchicine-treated cells, perinuclear coils were seen in addition to microfilament bundles. In addition, one clone gave a pronounced speckled staining to the nuclei. Absorption of the ascites fluids with purified actin abolished all staining patterns. Using the Western blotting technique the antibodies reacted with both actin and vimentin polypeptides. DNase I abolished the staining of the actin filaments and of the nuclei, but left the vimentin pattern unimpaired. Thus, the monoclonal antibodies evidently reacted with epitopes common to actin and vimentin.     

CO2 environment,microclimate and photosynthetic characteristics of the moss Hylocomium splendens in a subarctic habitat

Summary In order to document the natural CO₂ environment of the moss Hylocomium splendens, and ascertain whether or not the moss was adapted to this, and its interactions with other microenvironmental factors, two studies were carried out. Firstly, the seasonal variations of CO₂ concentration, photosynthetically active radiation (PAR), tissue water content and temperature were measured in the natural microenvironment of H. splendens in a subarctic forest during the summer period (July–September). Secondly, the photosynthetic responses of the species to controlled CO₂ concentrations, PAR, temperature, and hydration were measured in the laboratory. CO₂ concentrations around the upper parts of the plant, when PAR was above the compensation point (30 mol m^–2 s^–1), were mostly between 400 and 450 ppm. They occasionally increased up to 1143 ppm for short periods. PAR flux densities below saturating light levels for photosynthesis (100 mol m^–2 s^–1), occurred during 65% (July), 76% (August) and 96% (September) of the hours of the summer period. The temperature optimum of photosynthesis was 20° C: this temperature coincided with PAR above the compensation point during 5%, 6% and 0% of the time in July, August and September, respectively. Optimal hydration of tissues was infrequent. Hence PAR, temperature and water limit CO₂ uptake for most of the growing season. Our data suggest that the higher than normal ambient CO₂ concentration in the immediate environment of the plant counteracts some of the limitations in PAR supply that it experiences in its habitat. This species already experiences concentrations of atmospheric CO₂ predicted to occur over the next 50 years.     

Biochemical characterization and DNA repair pathway interactions of Mag1-mediated base excision repair in Schizosaccharomyces pombe

The Schizosaccharomyces pombe mag1 gene encodes a DNA repair enzyme with sequence similarity to the AlkA family of DNA glycosylases, which are essential for the removal of cytotoxic alkylation products, the premutagenic deamination product hypoxanthine and certain cyclic ethenoadducts such as ethenoadenine. In this paper, we have purified the Mag1 protein and characterized its substrate specificity. It appears that the substrate range of Mag1 is limited to the major alkylation products, such as 3-mA, 3-mG and 7-mG, whereas no significant activity was found towards deamination products, ethenoadducts or oxidation products. The efficiency of 3-mA and 3-mG removal was 5–10 times slower for Mag1 than for Escherichia coli AlkA whereas the rate of 7-mG removal was similar to the two enzymes. The relatively low efficiency for the removal of cytotoxic 3-methylpurines is consistent with the moderate sensitivity of the mag1 mutant to methylating agents. Furthermore, we studied the initial steps of Mag1-dependent base excision repair (BER) and genetic interactions with other repair pathways by mutant analysis. The double mutants mag1 nth1, mag1 apn2 and mag1 rad2 displayed increased resistance to methyl methanesulfonate (MMS) compared with the single mutants nth1, apn2 and rad2, respectively, indicating that Mag1 initiates both short-patch (Nth1-dependent) and long-patch (Rad2-dependent) BER of MMS-induced damage. Spontaneous intrachromosomal recombination frequencies increased 3-fold in the mag1 mutant suggesting that Mag1 and recombinational repair (RR) are both involved in repair of alkylated bases. Finally, we show that the deletion of mag1 in the background of rad16, nth1 and rad2 single mutants reduced the total recombination frequencies of all three double mutants, indicating that abasic sites formed as a result of Mag1 removal of spontaneous base lesions are substrates for nucleotide excision repair, long- and short-patch BER and RR.     

Fertile House Ssparrow X Tree Sparrow (Passer domesticus XPasser montanus) hybrids?

Summary Viability and a seemingly successful breeding of a F1 House Sparrow x Tree Sparrow hybrid are reported from islands off the coast of northern Norway. From two consecutive clutches of House Sparrow x Tree Sparrow hybrids recorded in 1995, only one of 7 chicks survived the first year. The surviving individual was later, in 1997, found attending the nest with a female House Sparrow and feeding the young in two consecutive clutches. Neither of the F2 hybrids were observed after fledging. Despite the fact that House Sparrows indulge in frequent extra pair copulation, we find it unlikely that both clutches fed by the male hybrid could have been fathered by a House Sparrow male and therefore conclude that the F1 male hybrid was fertile. The hybridisation may have been facilitated by the fragmented structure and small size (from 5 to 100 individuals) of the sub-populations found in our study area.

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Fertile Haus- x Feldsperling (Passer domesticus X Passer montanus) Hybride?

Zusammenfassung Wir berichten über die Überlebensfähigkeit und einen offenbar erfolgreichen Brutversuch eines F1 Haussperling x Feldsperling Hybriden auf Inseln vor der nordnorwegischen Küste. Aus zwei aufeinanderfolgenden Gelegen eines gemischten Haus-/Feldsperling Paares, die wir 1995 beobachtet hatten, überlebte nur eines von sieben Jungtieren das erste Jahr. Das überlebende Individuum nistete später, 1997, mit einem Haussperlingweibchen und fütterte die Jungen zweier aufeinanderfolgender Bruten. Keiner der F2 Hybriden wurde nach dem Schlüpfen beobachtet. Obwohl bei Haussperlingen Kopulationen außerhalb des Paares häufig sind, betrachten wir es als unwahrscheinlich, daß beide vom männlichen Hybriden gefütterten Bruten von einem Haussperlingmännchen gezeugt worden waren. Wir schließen deshalb, daß das F1 Hybridmännchen fruchtbar war. Die Hybridisierung könnte durch die fragmentierte Struktur und die kleine Größe (5 bis 100 Individuen) der lokalen Populationen erleichtert worden sein.

     

Soft Texture of Atlantic Salmon Fillets Is Associated with Glycogen Accumulation

Atlantic salmon (Salmo salar L.) with soft fillets are not suited for manufacturing high quality products. Therefore fillets with insufficient firmness are downgraded, leading to severe economic losses to the farming and processing industries. In the current study, morphological characteristics of salmon fillets ranging from soft to hard were analysed. Different microscopic techniques were applied, including novel methods in this field of research: morphometric image analysis, periodic acid Schiff staining, immunofluorescence microscopy, transmission electron microscopy and fourier transform infrared microscopy. The results showed that the myocytes of soft muscle had detached cells with mitochondrial dysfunctions, large glycogen aggregates and enlarged inter cellular areas, void of extracellular matrix proteins, including lower amounts of sulfated glycoproteins. Myofibre-myofibre detachment and disappearance of the endomysium in soft muscles coincided with deterioration of important connective tissue constituents such as Collagen type I (Col I), Perlecan and Aggrecan. In summary our investigations show for the first time an association between soft flesh of Atlantic salmon and massive intracellular glycogen accumulation coinciding with degenerated mitochondria, myocyte detachment and altered extracellular matrix protein distribution. The results are important for further understanding the etiology of soft salmon.     

Population properties affect inbreeding avoidance in moose

Mechanisms reducing inbreeding are thought to have evolved owing to fitness costs of breeding with close relatives. In small and isolated populations, or populations with skewed age- or sex distributions, mate choice becomes limited, and inbreeding avoidance mechanisms ineffective. We used a unique individual-based dataset on moose from a small island in Norway to assess whether inbreeding avoidance was related to population structure and size, expecting inbreeding avoidance to be greater in years with larger populations and even adult sex ratios. The probability that a potential mating event was realized was negatively related to the inbreeding coefficient of the potential offspring, with a stronger relationship in years with a higher proportion or number of males in the population. Thus, adult sex ratio and population size affect the degree of inbreeding avoidance. Consequently, conservation managers should aim for sex ratios that facilitate inbreeding avoidance, especially in small and isolated populations.