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  • 1
    Electronic Resource
    Electronic Resource
    Isolation and characterization of hydrogenase-negative mutants of Azorhizobium caulinodans ORS571 (1988)
    Springer
    Archives of microbiology 150 (1988), S. 595-599 
    Details
    ISSN: 1432-072X
    Keywords: Azorhizobium caulinodans ORS571 ; Hydrogenase ; Nitrogen fixation ; Chemostat cultures ; H2/N2 ratio ; ATP/2e value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydrogenase-negative (Hup-) mutants of Azorhizobium caulinodans ORS571 were isolated by means of Tn5 mutagenesis. The colony test used for screening for Hup- strains was based on the absence of reduction of triphenyltetrazolium chloride with hydrogen. Suspensions from cultures of the mutant strains grown under derepressing conditions did not use hydrogen with methylene blue or oxygen as the hydrogen acceptor. The mutants were shown to carry single Tn5 insertions at different locations in the A. caulinodans genome. Molar growth yields (corrected for poly-β-hydroxybutyrate formation) in chemostat cultures of the mutants were similar to those of the wild type. Molar growth yields of the mutants were not increased by passing additional hydrogen through chemostat cultures, which is in agreement with the hydrogenase-negative phenotype of the mutants. H2/N2 ratios (mol H2 formed per mol N2 fixed) were calculated from the hydrogen content of the effluent gas and the N-content of the bacterial dry weight. Low H2/N2 ratios (between 1.2 and 1.9) were found in both energy-limited (oxygen or succinate) cultures and in cultures limited by the supply of an anabolic substrate (Mg2+). ATP/2e values (mol ATP used at the transport of 2e to nitrogen or H+) were calculated from the H2/N2 ratios and the molar growth yields of nitrogen-fixing and ammonia-assimilating cultures. ATP/2e values were between 7 and 11. It was concluded that the calculated ATP/2e values comprise not only 4 mol ATP used at the transport of 2e through nitrogenase but also energy equivalents needed for reversed electron flow from NADH to the low-potential hydrogen donor used by nitrogenase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00408256
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolic and respiratory effects of enteral nutrition in patients during mechanical ventilation (1988)
    Springer
    Intensive care medicine 14 (1988), S. 206-211 
    Details
    ISSN: 1432-1238
    Keywords: Metabolic measurements ; Enteral nutrition ; Mechanical ventilation ; Weaning from the ventilator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of enteral feeding on O2-consumption ( $$\dot V_{O_2 } $$ ) and CO2-production ( $$\dot V_{CO_2 } $$ ) was studied in 9 ventilator-dependent patients, who were in a stable condition without signs of hypermetabolism. Resting energy expenditure (REE) in postabsorptive state was assessed and enteral feeding was started by continuous drip (480 kcal carbohydrate, 360 kcal vegetable fat and 160 kcal milkprotein: 6.4 g Nitrogen/ 1000 ml). Patients were given a moderate and a high caloric intake: 1.5 and 2.0 times REE. $$\dot V_{O_2 } $$ and $$\dot V_{CO_2 } $$ were measured for a 24 h period, beginning 7 h after the start of the dietary intake. Significant greater increases in $$\dot V_{O_2 } $$ , $$\dot V_{CO_2 } $$ and RQ were found during high caloric intake compared with the moderate caloric intake. $$\dot V_{O_2 } $$ , $$\dot V_{CO_2 } $$ and arterial blood-gases were measured in 4 patients during weaning from the ventilator. The increase in $$\dot V_{CO_2 } $$ induced by the high caloric feeding resulted in a rise in arterial CO2 tension (PaCO2) and respiratory distress. High caloric enteral nutrition can cause a significant increase in $$\dot V_{CO_2 } $$ inducing respiratory distress during weaning from the ventilator in patients with limited pulmonary reserves. Moderate caloric nutrition will be preferable to these patients in order to facilitate the weaning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00717989
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  • 3
    Electronic Resource
    Electronic Resource
    Enhanced lipolysis of myocardial triglycerides during low-flow ischemia and anoxia in the isolated rat heart (1989)
    Springer
    Basic research in cardiology 84 (1989), S. 165-173 
    Details
    ISSN: 1435-1803
    Keywords: Ischemia ; anoxia ; myocardial lipolysis ; reesterification ; freefatty acids ; redox state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We studied lipolysis in the isolated rat heart, measured as glycerol release during anoxia, low-flow ischemia and subsequent reperfusion. It was found that the rate of lipolysis was enhanced during ischemia/anoxia while the lipase activities in tissue extracts involved in the myocardial lipolysis and the amount of triglycerides were not affected. This indicates the dominant occurrence of a lipolysisreesterification principle in ischemic and anoxic tissue. A common observation of ischemia/anoxia is an increase in the tissue NADH/NAD+ ratio. Therefore we investigated the effect of lactate and malate, both of which enhance the tissue redox state on myocardial lipolysis. Perfusion in the presence of lactate (10 mM) and malate (10 mM) both stimulated myocardial lipolysis by about five times. This suggests that the rate of reesterification of product fatty acids to triglycerides, which is determined by the NADH/NAD+ ratio, because of the increased formation of glycerol 3-phosphate from dihydroxy acetone phosphate, plays an important role in the regulation of lipolysis. The existence of triglyceridefatty acid-triglyceride cycle is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01907926
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of the dissolved oxygen concentration and anabolic limitations on the behaviour of Rhizobium ORS571 in chemostat cultures (1986)
    Springer
    Antonie van Leeuwenhoek 52 (1986), S. 85-96 
    Details
    ISSN: 1572-9699
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chemostat cultures of Rhizobium ORS571 limited by the supply of oxygen or an anabolic substrate contained poly-β-hydroxybutyrate (PHB). Low amounts of PHB (about 10%) were present in ammonia- or nitrate-limited cultures; higher amounts were found in Mg++-limited cultures (about 20%) and in oxygen-limited nitrogen-fixing cultures (37%). A method is described to calculate YATP values (g PHB-free biomass · mol-1 ATP) from the Ysucc values (g dry wt·mol-1 succinate) measured. Ysucc and YATP values in cultures limited by the supply of an anabolic substrate and in the oxygen-limited ammonia-assimilating culture were much lower than the values found in the PHB-free succinate-limited cultures. This shows that uncoupling of growth and energy production occurred. Therefore, H2/N2 ratio (mol hydrogen formed per mol nitrogen fixed) in nitrogen-fixing cultures could not be calculated from the comparison of the YATP value found in the nitrogen-fixing culture and the value found in the corresponding ammonia-assimilating culture. Although the optimal dissolved oxygen concentration (d.o.c.) for nitrogen-fixing cultures of Rhizobium ORS571 is 5 or 10 μM, nitrogen-fixing cultures could be obtained up to a d.o.c. of 40 μM. Not only nitrogenase but also hydrogenase was active at this d.o.c. However, accumulation of PHB (10%) may indicate that cultures grown at unfavourable oxygen concentrations (15–40 μM O2) were N-limited rather than energy-limited, which may be the result of partial inactivation or repression of nitrogenase at a higher d.o.c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402690
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