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  • Articles  (18)
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  • Springer  (13)
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  • 2015-2019
  • 1990-1994  (18)
  • 1990  (18)
  • Biology  (18)
  • Architecture, Civil Engineering, Surveying
  • Electrical Engineering, Measurement and Control Technology
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  • Articles  (18)
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  • 2015-2019
  • 1990-1994  (18)
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  • 1
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell suspension cultures of cowpea (Vigna sp.) were able to produce extracellular peroxidase. Different growth regulator concentrations induced different peroxidase activity in callus. The crude extracellular medium after four weeks of culture showed higher (6 times) specific peroxidase activity and higher thermo stability than commercial horse-radish peroxidase. The commercial production of peroxidase enzyme from cowpea by utilizing plant cell cultures is discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 153 (1990), S. 528-530 
    ISSN: 1432-072X
    Keywords: Anabaena ; Ferredoxin ; Flavodoxin ; Iron deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultures of the nitrogen-fixing cyanobacterium Anabaena variabilis PCC 6309 were grown under several iron concentrations, and changes in growth rates and chlorophyll and phycocyanin concentrations were determined. The total amount of ferredoxin present in the cells was found to be dependent on the concentration of iron in the media, as was the pattern distribution of the two different forms of the iron-sulfur protein described in this organism. Flavodoxin was not found to be present in these cells even when they were grown in the absence of added iron, indicating that this flavoprotein does not replace ferredoxin in this particular strain.
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  • 3
    ISSN: 1573-4919
    Keywords: cAMP-dependent protein kinase ; autophosphorylation ; limited proteolysis ; isoforms of regulatory subunits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Two forms of the regulatory subunit of the type II cAMP-dependent protein kinase (RII55 and RII52) were identified from bovine heart by gel electrophoretic behaviour. After autophosphorylation the RII55 isoform migrated more slowly (RII55/57) while the migration of RII52 isoform did not shift. Both isoforms showed different affinity for cAMP. The RII55/57 isoform was eluted from a cAMP-agarose column at 10 mM cAMP at low ionic strenght whereas the RII52 isoform required cAMP, plus 2 M NaCl. Partial proteolysis, using trypsin or formic acid, of autophosphorylated regulatory subunit isoforms resulted in different cleavage pattern as determined by peptide mapping. However, the V8125I-peptides patterns of both isoforms are quite similar. Incubation of partially purified holoenzyme with 10 nM [γ-32P]ATP (low ATP concentration) yielded a single band of Mr = 57,000 which corresponds to the RII55/57 isoform. The incubation, however, at 20 µM [γ-32P]ATP yielded two phosphobands corresponding to both RII55/57 and RII52 isoforms. The phosphorylation of RII52 took place with a lower efficiency and was more sensitive to the cAMP than the corresponding phosphorylation of the RII55/57.
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  • 4
    ISSN: 1573-4919
    Keywords: prolactin ; bromocryptine ; adipocytes and acini ; pentose phosphate shunt activity ; lipogenesis ; phospholipid turnover ; insulin responsiveness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Prolactin deficiency, induced by bromocryptine treatment, brought about reciprocal changes in the ability of adipocytes and acini isolated from lactating rats to synthesize lipids. The capacity to synthesize fatty acids and phospholipids decreased in the mammary gland and increased in adipocytes by bromocryptine treatment. In the mammary gland, the maximum potential activity of the pentose shunt as well as the specific activities of the pathway dehydrogenases were significantly reduced by bromocryptine treatment. Simultaneously, adipose tissue increased its lipogenic capacity but neither the maximum potential of the shunt nor the specific activities of the pentose phosphate shunt dehydrogenases were significantly changed with respect to the control lactating rats. Thus, a differential regulatory mechanism(s) of the pentose phosphate shunt activity appears to operate in these two tissues. Adipocytes from lactating rats showed a poor responsiveness to insulin in terms of lipid synthesis from glucose. In contrast, in adipocytes from bromocryptine treated rats insulin was able to increase lipid synthesis (105%). Sheep prolactin administration ‘in vivo’ partially reversed the effects of bromocryptine. These data suggest that prolactin mediates adipocytes resistance to insulin during lactation. Phospholipid synthesis, as occurred in fatty acid synthesis, is increased in adipose tissue and decreased in mammary gland by bromocryptine treatment. However, α-adrenergic stimulation increases phosphatidylinositol turnover to about the same percentages in both mammary gland acini and adipocytes from lactating rats independently of bromocryptine treatment.
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  • 5
    ISSN: 1573-4919
    Keywords: counter-current distribution ; two-phase systems ; erythrocytes ; development ; bisphosphoglycerate mutase ; pyruvate kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary An inverse relationship between 2,3-bisphosphoglycerate levels and the ratio calculated from pyruvate kinase and bisphosphoglycerate mutase activities has been observed in red populations of rats during animal development. Counter-current distribution in aqueous two-phase systems of these cells populations shows a displacement of distribution profiles towards the high-numbered cavities of the rotor as animal ages. Heterogeneity of cells after distribution is only observed during the switching process from fetal to adult red cells taking place along the postnatal stage of development. Values for the pyruvate kinase/bisphosphoglycerate mutase ratio in these fractions suggest the separation of fetal (liver) from adult (bone marrow) red cells.
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  • 6
    ISSN: 1573-4935
    Keywords: adrenalectomy ; dexamethasone ; VIP ; cyclic AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The number of vasoactive intestinal peptide (VIP) receptors and the efficiency of VIP in the stimulation of cyclic AMP accumulation in rat jejunal epithelial cells increased after bilateral adrenalectomy. However, this condition increased neither receptor affinity nor VIP potency. In addition, jejunal VIP levels followed a parallel increase. These changes reversed to control conditions after glucocorticoid replacement with dexamethasone indicating that adrenalectomy modifies the intestinal VIP receptor/effector system and suggest a relationship between corticosteroids and VIP in the functions of intestinal epithelium.
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  • 7
    ISSN: 1617-4623
    Keywords: Rhizobium leguminosarum bv. phaseoli ; Glutamine synthetases ; Nitrogen metabolism ; glnT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using glnT DNA of Rhizobium meliloti as a hybridization probe we identified a R. leguminosarum biovar phaseoli (R. l. phaseoli) locus (glnT) expressing a glutamine synthetase activity in Klebsiella pneumoniae. A 2.2 kb DNA fragment from R. l. phaseoli was cloned to give plasmid pMW5a, which shows interspecific complementation of a K. pneumoniae glnA mutant. The cloned sequence did not show cross-hybridization to glnA or glnII, the genes coding for two glutamine synthetase isozymes of Rhizobium spp. While in previous reports on glnT of R. meliloti and Agrobacterium tumefaciens no glutamine synthetase activity was detected, we do find activity with the glnT locus of R. l. phaseoli. The glutamine synthetase (GSIII) activity expressed in a K. pneumoniae glnA strain from pMW5a shows a ratio of biosynthetic to transferase activity 103-fold higher than that observed for GSI or GSII. GSIII is similar in molecular weight and heat stability to GSI.
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  • 8
    ISSN: 1573-5079
    Keywords: Anabaena ; ferredoxin ; flavodoxin ; FPLC determination of ferredoxin and flavodoxin ; Iron deficiency ; Nitrogen fixation ; Photosynthesis ; strain differences in gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply. Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same Km values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 16 (1990), S. 2799-2815 
    ISSN: 1573-1561
    Keywords: Attractants ; Mexican fruit fly ; Diptera ; Tephritidae ; Anastrepha ludens ; host fruit ; yellow chapote ; Rutaceae ; Sargentia greggii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Chemicals from fermented chapote fruit were identified and evaluated as attractants for hungry adult Mexican fruit flies in laboratory and greenhouse bioassays. Twenty-eight chemicals identified from an attractive gas-chromatography fraction were as attractive as a chapote volatiles extract (CV) when mixed in the same amounts found in CV. Sixteen of the chemicals were slightly attractive to flies when tested individually. A mixture containing 15 of the chemicals by design and the 16th as an impurity, in arbitrary concentrations, was at least as attractive as the original CV. In a series of experiments, the number of chemicals was reduced to three by elimination of unnecessary components. The three-component mixture retained the attractiveness of the 15-component mixture. The three chemicals were 1,8-cineole, ethyl hexanoate, and hexanol (CEH). Attractiveness of the three-chemical mixture was equal to the sum of the attractiveness of the three individual components, suggesting that each chemical binds to a different receptor type that independently elicits partial attraction behavior. Optimal ratios were 10∶1∶1 of the three chemicals, respectively. Optimal test quantities ranged between 0.4–4Μg of 1,8-cineole and 40–400 ng each of ethyl hexanoate and hexanol applied to filter paper in the laboratory bioassays. A neat 10∶1∶1 mixture of the chemicals was 1.8 times more attractive than aqueous solutions ofTorula dried yeast and borax to starved 2-day-old flies when the lures were tested in competing McPhail traps in a large greenhouse cage.
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  • 10
    Publication Date: 1990-05-01
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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