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S Nordlund

Publications and source records attributed to S Nordlund.

At least 37 records · Page 2Linked to original sources
PubMed1993

Visiting public drinking places in Oslo: an application of the theory of planned behaviour.

This study was undertaken to describe and obtain better insight into pub-going in the Norwegian capital applying the theory of planned behaviour (TPB). The sample comprised 1053 persons aged between 16 and 71 years who visited public drinking places in Oslo. Two thirds of the sample were men. Data were collected by means of anonymous self-administered questionnaires. The majority of the respondents reported having visited a public drinking place at least once a week during the past 12 months. In the applied model, intention to visit a public drinking place during the next 14 days is considered to be a joint function of the attitude towards pub-going (Aact), subjective norms (SN), and perceived control over the behaviour (PBC). The goodness of fit (R2) of the model was 22%. The relative importance of the model's components were in descending order (beta): PBC, Aact and SN. Previous behaviour was included as a predictor in the TPB, and had a stronger effect upon intention than the model's original components. In conclusion, the TPB provided an adequate understanding of why pub and cafe guests frequent public drinking places. However, it is possible that the model over-simplifies the processes connected to pub-going and fails to describe the dynamics of the relationship between the individual and the environment.

Adolescent↗
PubMed1992

Studies on the effect of NAD(H) on nitrogenase activity in Rhodospirillum rubrum.

The effect of NAD(P) and analogs of this nucleotide on nitrogenase activity in Rhodospirillum rubrum has been studied. Addition of NAD+ to nitrogen fixing Rsp. rubrum leads to inhibition of nitrogenase. NADP+ has the same effect but NADH or analogs modified in the nicotinamide portion do not cause inhibition. In contrast to ammonium ions, addition of NAD+ leads to inhibition of nitrogenase in cells that have been N-starved under argon. The inhibitory effect of NAD+ is more pronounced at lower light intensities. Addition of NAD+ also leads to inhibition of glutamine synthetase, a phenomenon also occurring when "switch-off" is produced by the addition of effectors such as ammonium ions or glutamine. It is also shown that NAD+ is taken up by Rsp. rubrum cells.

NAD↗
PubMed1991

Low- and high-activity forms of glutamine synthetase from Rhodospirillum rubrum: sensitivity to feed-back effectors and activation of the low-activity form.

Glutamine synthetase from Rhodospirillum rubrum can be isolated in two forms, with low and high activity, respectively, depending on the concentration of combined nitrogen in the medium before harvest. The two forms have been studied with respect to their dependence on Mn2+ and Mg2+ in both the transferase and the biosynthetic assay. There is no difference in pH optimum between the forms in the biosynthetic assay. In addition the pH-optima for the two cations studied are very close, 7.4 (Mg2+) and 7.2 (Mn2+). It also shows that the activity of the low-activity form is higher than that of the high-activity form in the Mn(2+)-dependent biosynthetic assay. The two forms of Rsp. rubrum glutamine synthetase have also been studied with respect to their sensitivity towards feed-back effectors. In the transferase assay both forms are inhibited to essentially the same degree by alanine, glycine, histidine, AMP, CTP and UTP, CTP being the most effective of the nucleotides and of the amino acids alanine causes the highest inhibition. In the biosynthetic assay these effectors show different degrees of inhibition on the two different forms; the high-activity form being the most sensitive. The results are discussed in relation to properties of glutamine synthetase from Escherichia coli and other phototropic bacteria in which regulation of glutamine synthetase is known to be due to adenylylation. It is also shown that the low-activity form of Rsp. rubrum glutamine synthetase can be activated in crude extracts in a reaction that is inhibited by glutamine.

Enzyme Activation↗
PubMed1991

Purification and partial characterization of glutamate synthase from Rhodospirillum rubrum grown under nitrogen-fixing conditions.

Glutamate synthase, a key enzyme in ammonia assimilation, has been purified from the photosynthetic bacterium Rhodospirillum rubrum. The purification procedure involves ion-exchange chromatography, affinity chromatography and gel filtration. The recovery in the procedure is high (62%) and the specific activity is 21 mumol of NADPH oxidized/min per mg. The enzyme is specific for its substrates, and no activity was demonstrated with NADH or NH4+ ions substituting for NADPH and glutamine respectively. The enzyme is composed of two dissimilar subunits with molecular masses of 53 and 152 kDa, and it is shown that Cl- ions have an effect on the aggregation of the enzyme. Km values for the substrates are: NADPH, 16 microM; 2-oxoglutarate, 10 microM; and glutamine, 65 microM. The enzyme is inhibited by amidotransferase inhibitors at micromolar concentrations. The role of the enzyme in the metabolic regulation of nitrogenase is discussed.

Amino Acids↗
PubMed1991

Purification and partial characterization of a pyruvate oxidoreductase from the photosynthetic bacterium Rhodospirillum rubrum grown under nitrogen-fixing conditions.

A pyruvate oxidoreductase with the capacity to support pyruvate-dependent nitrogenase activity in vitro has been purified from the photosynthetic bacterium Rhodospirillum rubrum. The enzyme requires CoA for activity and is irreversibly inactivated by oxygen. The molecular properties and Km values for the substrates have been studied. In supporting nitrogenase activity addition of ferredoxin is required. Overall the enzyme is similar to the nif-specific pyruvate: flavodoxin oxidoreductase purified from Klebsiella pneumoniae.

Catalysis↗
PubMed1989

Purification and partial characterization of glutamine synthetase from the photosynthetic bacterium Rhodospirillum rubrum.

Glutamine synthetase (L-glutamate: ammonia ligase (ADP-forming), EC 6.3.1.2) from the photosynthetic bacterium Rhodospirillum rubrum grown under nitrogen fixing conditions has been purified to homogeneity. The purification procedure involves affinity chromatography on ADP-agarose type 2 as the major purification step. The recovery in the purification is 70%. The specific activity of the purified enzyme is about 10-times higher in the gamma-glutamyl transferase assay than in the coupled biosynthetic assay. The molecular weight was determined to 530,000 by native gradient polyacrylamide gel electrophoresis and to 500,000 by gel filtration. The subunits have an apparent molecular weight of 52,000. Glutamine synthetase isolated from Rsp. rubrum which had been exposed to ammonium ions ('switch-off') before harvest had about 20% of the transferase activity compared with the enzyme purified from nitrogen-starved cells. The low-activity form showed two bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Chromatography, Affinity↗
PubMed1987

Monocyte and iscom enhancement of cell-mediated response to cytomegalovirus.

Cell-mediated and humoral responses to cytomegalovirus were studied in a monkey model. Repeated low doses of virus antigen gave poor reactivities in both respects. High antigen doses gave a good humoral IgG response. When autologous monocytes were incubated with the CMV antigen as the immunizing injection, the specific cellular response to CMV antigen increased. The monocytes themselves did not contribute to the in vitro specific proliferation response. When iscoms were the carrier particles for CMV antigens, cellular response was even more strongly enhanced. In immunization schedules where specific cellular responses are important, we suggest that autologous monocytes or iscoms may be employed as antigen carriers.

Animals↗
PubMed1985

Properties and regulation of glutamine synthetase from Rhodospirillum rubrum.

Glutamine synthetase from Rhodospirillum rubrum was purified and characterized with respect to its pH optimum and the effect of Mg2+ on its active and inactive forms. Both adenine and phosphorus were incorporated into the inactive form of the enzyme, indicating covalent modification by AMP. The modification could not be removed by phosphodiesterase. Evidence for regulation of the enzyme by oxidation was obtained. Extracts from oxygen-treated cells had lower specific activities than did extracts from cells treated anaerobically. Glutamine synthetase activity was found to decrease in the dark in phototrophically grown cells; activity was recovered on re-illumination.

Adenine↗
PubMed1983

Incorporation of adenine into the modifying group of inactive iron protein of nitrogenase from Rhodospirillum rubrum.

Adenine was fed to cells of Rhodospirillum rubrum grown on glutamate. The adenine was found to be incorporated into the modifying group of the inactive form of iron protein. Adenine labelled in the 8-position ([8-3H]adenine) and the 2-position ([2-3H]adenine) was specifically incorporated into the electrophoretic 'upper-band' subunit of iron protein. Incorporation of label from the 2-position into many proteins was observed if histidine was not present in the medium. Label was removed by the activating enzyme for iron protein.

Adenine↗
PubMed1981

Conditions for cytomegalovirus stimulation of lymphocytes.

Lymphocytes from healthy donors or from patients with chronic lymphocytic leukaemia were subjected to live or inactivated cytomegalovirus (CMV) or the mitogen phytohaemagglutinin. No early or late CMV antigens could be demonstrated in the lymphocytes, indicating that neither abortive nor replicative CMV infection takes place. Only cells from CMV antibody-positive leukaemic and non-leukaemic donors were stimulated by CMV to DNA synthesis, with a maximum on day 5. Cells from all individuals responded to phytohaemagglutinin stimulation, the peak of activity occurring on day 3. The stimulation with CMV occurred in T cells and was independent of early CMV antigen production, viral DNA synthesis, or viral replication. CMV is thus not an in vitro lymphocyte mitogen like Epstein-Barr virus but is a very potent antigen for memory T cells.

Antibodies, Viral↗
PubMed1979

Nitrogenase from Rhodospirillum rubrum. Relation between 'switch-off' effect and the membrane component. Hydrogen production and acetylene reduction with different nitrogenase component ratios.

Nitrogenase activity of 'membrane-free' extracts, produced from nitrogen-starved Rhodospirillum rubrum to which 4 mM NH4+ had been added is only about 10% of the activity in the control. The activity could be restored to 80% by including the membrane component, earlier found to activate R. rubrum nitrogenase, in the reaction mixture. The relation between this 'switch-off/switch-on' effect and the function of the membrane component is discussed. Hydrogen production catalyzed by R. rubrum nitrogenase is also dependent on activation by the membrane component. Hydrogen production is inhibited by acetylene but the degree of inhibition is dependent on the nitrogenase component ratio. The strongest inhibition is achieved at low MoFe protein/Fe protein rations. The ATP/2E- values are 4-5 at the component ratios giving the highest activity and increase at high MoFe protein/Fe protein ratios. CO inhibits acetylene reduction but has no effect on the hydrogen production.

Acetylene↗
PubMed1978

Properties of the nitrogenase system from a photosynthetic bacterium, Rhodospirillum rubrum.

Soluble nitrogenase from Rhodospirillum rubrum has been isolated and separated into its two components, the MoFe protein and the Fe protein. The MoFe protein has been purified to near homogeneity and has a molecular weight or 215 000. It contains two Mo, 25--30 Fe and 19--22 acid-labile sulphide and consists of four subunits, Mw 56 000. The Fe protein has a molecular weight 65 000. It contains approximately four Fe and four acid-labile sulphide and consists of two subunits, Mw 31 500. The highest specific activities for the purified components are 920 and 1260 nmol ethylene produced per min per mg protein, respectively. The purified components require the membrane component for activity (Nordlund, S., Eriksson, U. and Baltscheffsky, H. (1977) Biochim. Biophys. Acta 462, 187--195). Titration of the MoFe protein with the Fe protein shows saturation and excess MoFe protein over Fe protein is inhibitory. Addition of Fe2+ or Mn2+ to the reaction mixture increases the activity apparently through interaction with the membrane component.

Iron↗
PubMed1977

Necessity of a membrane component for nitrogenase activity in Rhodospirillum rubrum.

Acetylene reduction catalyzed by nitrogenase from Rhodospirillum rubrum has low activity and exhibits a lag phase. The activity can be increased by the addition of a chromatophore membrane component and the lag eliminated by preincubation with this component, which can be solubilized from chromatophores by treatment with NaCl. It is both trypsin- and oxygen-sensitive. Titration of the membrane component with nitrogenase and vice versa shows a saturation point. The membrane component interacts specifically with the Fe protein of nitrogenase, the interaction being ATP- and Mg2+-dependent.

Adenosine Triphosphate↗
PubMed1975

Regulation of nitrogenase synthesis in intact cells of Rhodospirillum rubrum: inactivation of nitrogen fixation by ammonia, L-glutamine and L-asparagine.

The synthesis of nitrogenase by intact cells of Rhodospirillum rubrum was repressed in N-free media supplemented with L-glutamine or L-asparagine, but was unaffected by the presence of L-glutamate, L-aspartate or L-histidine. Specific activities attained by cultures in supplemented media maintained under Ar-CO2 were 2 to 3 times higher than those in N-free medium under N2-CO2. A loss in total activity occurred both in cultures growing with N2 after maximum activity had been reached, and in cultures maintained under Ar when the gas phase was changed to N2. There was a rapid loss in nitrogen-fixing activity when low concentrations of NH4+, L-glutamine or L-asparagine were added to cultures with high activities, but this could be recovered in the absence of demonstrable protein synthesis. During growth, the degree of inactivation brought about by 0-5 mM-inactivator increased to 80 to 90%, and NH4+ excreted into the medium reached a maximum concentration towards the end of exponential growth.

Acetylene↗