Untersuchungen Über Auslösung und Hemmung der Regeneration beim Axolotl

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Isoenzyme pattern and subcellular localisation of enzymes involved in fumaric acid accumulation by Rhizopus oryzae

Summary Electrophoretic studies of fumarase and nicotine adenine dinucleotide (NAD)-malate dehydrogenase were carried out in the fumaric acid-accumulating fungus Rhizopus oryzae. The analyses revealed two fumarase isoenzymes, one localised solely in the cytosol and the other found both in the cytosol and in the mitochondrial fraction. The activity of the cytosolic isoenzyme of fumarase was higher during the acid production stage than during growth. Addition of cycloheximide inhibited fumaric acid production and decreased the activity of the cytosolic isoenzyme of fumarase. These results suggested that de novo protein synthesis is required for increase in the activity of the cytosolic isoenzyme and that such an increase in activity is essential for fumaric acid accumulation. Three distinct isoenzymes of NAD-malate dehydrogenase could be detected in R. oryzae. No changes were observed in the isoenzyme pattern of malate dehydrogenase during fumaric acid production.     

Redox-controlled,in vivo and in vitro phosphorylation of the α subunit of the light-harvesting complex I in Rhodobacter capsulatus

Labelling of Rhodobacter capsulatus cells with (³²P)Pi in a phototrophic culture results in phosphorylation of a membrane-bound polypeptide identified as the subunit of the LHI antenna complex of the photosynthetic apparatus. Phosphorylation of the same polypeptide was also observed by incubation of chromatophores with (³²P)ATP or under conditions of photophosphorylation with ADP and (³²P)Pi. The identity of the phosphorylated LHI- subunit was demonstrated by N-terminal protein sequencing of the phosphorylated polypeptide and by failure of labelling in LHI-defective mutants. Pre-aeration of the samples or addition of the oxidant potassium ferrcyanide stimulated the kinase activity whereas the presence of soluble cytoplasmic proteins impaired phosphorylation in an in vitro assay. No effect resulted from addition of reductants to the assay medium. The results indicate the presence of a membrane-bound protein kinase in R. capsulatus that phosphorylates the subunit of the LHI antenna complex under redox control.Abbreviations Pi inorganic phosphate - SDS-PAGE sodium dodecyl-sulfate polyacrylamide gel electrophoresis     

A burst of CO2 from photosynthesizing leaves after a temperature decrease under constant light conditions

A transient CO₂ burst from seedlings of some plant species was observed after a rapid temperature decrease. The magnitude of the CO₂ release depended on initial temperature, oxygen concentration and light intensity. To obtain a maximal value of CO₂ release, the temperature had to decrease by more than 8°C. The phenomenon was detected only in the light, and was confined to C₃ species. It was inhibited by low oxygen concentration, indicating its possible connection with photorespiration.     

Mire communities of Reykjanes peninsula,SW. Iceland (Plant communities of reykjanes peninsula,part I.)

In Reykjanes peninsula, mainly in the valley of Krísuvík, in all 6 mire associations were found, belonging to the alliancesEriophorion Scheuchzeri andCaricion canescentis-fuscae. Floristic, ecological and physiognomical differeces between the two alliances are discussed. Most of the associations seem to be restricted in their distribution to Iceland.     

Effect of lead on blood protoporphyrin levels of a group of ring teal ducks (Callonetta leucophrys)

This research determined the relationships between blood lead level and zinc protoporphyrin (ZnPROTO), protoporphyrin IX (PROTO), and free erythrocyte protoporphyrin (FEP) levels in a group of 18 ring teal ducks. Blood samples were drawn from two groups of ring teal ducks as part of the routine health maintenance program of the New York Zoological Park. One group of six teals had been exposed to what is believed to be lead-contaminated dust, while the second group of twelve teals was unexposed. Blood samples were analyzed for lead by flameless atomic absorption and for protoporphyrins by fluorescence. Blood lead level and log blood lead level had positive correlations with each of the protoporphyrins: the logarithmic correlations were better than the nonlogarithmic correlations, and PROTO correlated better than ZnPROTO. With one exception, PROTO levels were higher than ZnPROTO levels. The results suggest that PROTO, FEP, or ZnPROTO could serve as a biological indicator of lead poisoning in ring teal ducks.     

Structural analysis and molybdenum-dependent expression of the pAO1-encoded nicotine dehydrogenase genes of Arthrobacter nicotinovorans

The genes of nicotine dehydrogenase (NDH) were identified, cloned and sequenced from the catabolic plasmid pA01 of Arthrobacter nicotinovorans. In immediate proximity to this gene cluster is the beginning of the 6-hydroxy-L-niotine oxidase (6-HLNO) gene. NDH is composed of three subunits (A, B and C) of M_r 30011, 14924 and 87677. It belongs to a family of bacterial hydroxylases with a similar subunit structure; they have molybdopterin dinucleotide, FAD and Fe-S clusters as cofactors. Here the first complete primary structure of a bacterial hydroxylase is provided. Sequence alignments of each of the NDH subunits show similarities to the sequences of eukaryotic xanthine dehydrogenase (XDH) but not to other known molybdenum-containing bacterial enzymes. Based on alignment with XDH it is inferred that the smallest subunit (NDHB) carries an iron-sulphur cluster, that the middle-sized subunit (NDHA) binds FAD, and that the largest NDH subunit (NDHC) corresponds to the molybdopterin-binding domain of XDH. Expression of both the ndh and the 6-hlno genes required the presence of nicotine and molybdenum in the culture medium. Tungsten inhibited enzyme activity but not the synthesis of the enzyme protein. The enzyme was found in A. nicotinovorans cells in a soluble form and in a membrane-associated form. In the presence of tungsten the fraction of membrane-associated NDH increased.