Metabolic state of Zymomonas mobilis in glucose-, fructose-, and xylose-fed continuous cultures as analysed by 13C- and 31P-NMR spectroscopy.

The reasons for the well-known significantly different behaviour of the anaerobic, gram-negative, ethanologenic bacterium Zymomonas mobilis during growth on fructose (i.e. decreased growth and ethanol yields, increased by-product formation) as compared to that on its second natural substrate, glucose, have remained unexplained.

The anaerobic oxidation of ammonium.

From recent research it has become clear that at least two different possibilities for anaerobic ammonium oxidation exist in nature. 'Aerobic' ammonium oxidizers like Nitrosomonas eutropha were observed to reduce nitrite or nitrogen dioxide with hydroxylamine or ammonium as electron donor under anoxic conditions. The maximum rate for anaerobic ammonium oxidation was about 2 nmol NH4+ min-1 (mg protein)-1 using nitrogen dioxide as electron acceptor.

Identification of a thiamin-dependent synthase in Escherichia coli required for the formation of the 1-deoxy-D-xylulose 5-phosphate precursor to isoprenoids, thiamin, and pyridoxol.

In Escherichia coli, 1-deoxy-D-xylulose (or its 5-phosphate, DXP) is the biosynthetic precursor to isopentenyl diphosphate [Broers, S. T. J.

Propionate oxidation in Escherichia coli: evidence for operation of a methylcitrate cycle in bacteria.

Escherichia coli grew in a minimal medium on propionate as the sole carbon and energy source. Initially a lag phase of 4-7 days was observed. Cells adapted to propionate still required 1-2 days before growth commenced.

Bidirectional reaction steps in metabolic networks: II. Flux estimation and statistical analysis.

Metabolic carbon labelling experiments enable a large amount of extracellular fluxes and intracellular carbon isotope enrichments to be measured. Since the relation between the measured quantities and the unknown intracellular metabolic fluxes is given by bilinear balance equations, flux determination from this data set requires the numerical solution of a nonlinear inverse problem. To this end, a general algorithm for flux estimation from metabolic carbon labelling experiments based on the least squares approach is developed in this contribution and complemented by appropriate tools for statistical analysis.

Bidirectional reaction steps in metabolic networks: I. Modeling and simulation of carbon isotope labeling experiments.

The extension of metabolite balancing with carbon labeling experiments, as described by Marx et al. (Biotechnol. Bioeng.

Metabolic pathway of anaerobic ammonium oxidation on the basis of N studies in a fluidized bed reactor.

A novel metabolic pathway for anaerobic ammonium oxidation with nitrite as the electron acceptor has been elucidated using N-Iabelled nitrogen compounds. These experiments showed that ammonium was biologically oxidized with hydroxylamine as the most probable electron acceptor. The hydroxylamine itself is most likely derived from nitrite.

Constitutive expression in gal7 mutants of Kluyveromyces lactis is due to internal production of galactose as an inducer of the Gal/Lac regulon.

The induction process of the galactose regulon has been intensively studied, but until now the nature of the inducer has remained unknown. We have analyzed a delta gal7 mutant of the yeast Kluyveromyces lactis, which lacks the galactotransferase activity and is able to express the genes of the Gal/Lac regulon also in the absence of galactose. We found that this expression is semiconstitutive and undergoes a strong induction during the stationary phase.

Accurate determination of 13C enrichments in nonprotonated carbon atoms of isotopically enriched amino acids by 1H nuclear magnetic resonance.

A method for the accurate determination of 13C enrichments in nonprotonated carbon atoms of organic compounds that makes use of unresolved 13C satellites of proton(s) bonded to the vicinal carbon atom was developed. Using glutamate as a model molecule, this 1H nuclear magnetic resonance (NMR) inverse spin-echo difference spectroscopy method was calibrated for inversion efficiency and relaxation effects which were then shown to cause only a minor loss of the measured 13C satellite amplitude (2% for glutamate C-1 and 7% for glutamate C-5). The determination of 13C enrichments in nonprotonated glutamate carbon atoms by this method was shown to be more precise than 13C NMR.

The problem of overlapping glaucoma families in the Glaucoma Inheritance Study in Tasmania (GIST).

The Glaucoma Inheritance Study in Tasmania (GIST) is a population survey of Australia's island state, Tasmania (population 450,000). Its aim is to find families with autosomal dominant, adult-onset, primary open angle glaucoma (POAG) suitable for genetic linkage analysis. POAG is relatively common, affecting around 3% of the Australian population.

Development and application of a membrane cyclone reactor for in vivo NMR spectroscopy with high microbial cell densities.

A new bioreactor system has been developed for in vivo NMR spectroscopy of microorganisms under defined physiological conditions. This cyclone reactor with an integrated NMR flow cell is continuously operated in the magnet of a 400-MHz wide-bore NMR spectrometer system. The residence times of medium and cells are decoupled by a circulation-integrated cross-flow microfiltration module to achieve higher cell densities as compared to continuous fermentations without cell retention (increase in cell density up to a factor of 10 in steady state).

[The impact of parental divorce on the relationships of young adults].

"The 1993 Netherlands Fertility and Family Survey shows that parental divorce has an impact on (the attitudes towards) relationships of young adults. Children of divorced parents leave home at an earlier age and have a stronger preference for cohabitation. Once a relationship (cohabitation or marriage) has started, it is more likely to end in separation or divorce.

C3-carboxylation as an anaplerotic reaction in phosphoenolpyruvate carboxylase-deficient Corynebacterium glutamicum.

Phosphoenolpyruvate carboxylase (PEPCx) has recently been found to be dispensable as an anaplerotic enzyme for growth and lysine production of Corynebacterium glutamicum. To clarify the role of the glyoxylate cycle as a possible alternative anaplerotic sequence, defined PEPCx- and isocitrate-lyase (ICL)-negative double mutants of C. glutamicum wild-type and of the l-lysine-producing strain MH20-22B were constructed by disruption of the respective genes.

Short term effects of air pollution on emergency hospital admissions for respiratory disease: results of the APHEA project in two major cities in The Netherlands, 1977-89.

Study Objective: To assess the short term relationship between air pollution and the daily number of emergency hospital admissions for respiratory disease.

Design: Data were analysed using autoregressive Poisson regression allowing for overdispersion and controlling for possible confounding factors such as seasonal and other chronological variables, meteorological factors, and influenza epidemics.

Setting: The two major cities in The Netherlands-Amsterdam (694,700 inhabitants) and Rotterdam (576,200 inhabitants).

Evaluation of a fluorescence polarographic immunoassay with increased sensitivity for measurement of low concentrations of tobramycin in serum.

The limits of quantitation of the assay of tobramycin in serum by the fluorescence polarization immunoassay system marketed by Abbott Laboratories (TDxFLx system) are 0.1 and 10.0 mg/L.

Determination of the fluxes in the central metabolism of Corynebacterium glutamicum by nuclear magnetic resonance spectroscopy combined with metabolite balancing.

To determine the in vivo fluxes of the central metabolism we have developed a comprehensive approach exclusively based on the fundamental enzyme reactions known to be present, the fate of the carbon atoms of individual reactions, and the metabolite balance of the culture. No information on the energy balance is required, nor information on enzyme activities, or the directionalities of reactions. Our approach combines the power of (1)H-detected (13)C nuclear magnetic resonance spectroscopy to follow individual carbons with the simplicity of establishing carbon balances of bacterial cultures.

Reaction engineering methods to study intracellular metabolite concentrations.

The analysis of intracellular metabolite concentrations is of basic importance for metabolic engineering of microorganisms. In vivo NMR-spectroscopy as a non-invasive technique to measure intracellular metabolite concentrations and rapid sampling devices as invasive techniques are reviewed. The methods are discussed from a reaction engineering point of view.

In vivo stationary flux analysis by 13C labeling experiments.

Stationary flux analysis is an invaluable tool for metabolic engineering. In the last years the metabolite balancing technique has become well established in the bioengineering community. On the other hand metabolic tracer experiments using 13C isotopes have long been used for intracellular flux determination.

Anaerobic oxidation of ammonium is a biologically mediated process.

A newly discovered process by which ammonium is converted to dinitrogen gas under anaerobic conditions (the Anammox process) has now been examined in detail. In order to confirm the biological nature of this process, anaerobic batch culture experiments were used. All of the ammonium provided in the medium was oxidized within 9 days.

Influence of ethnic and geographic factors on the classic photoparoxysmal response in the electroencephalogram of epilepsy patients.

The classic photoparoxysmal response (CPPR) on photic stimulation in the electroencephalogram (EEG) of 128 patients with chronic epilepsy, constituting three different ethnic groups, was investigated. All patients were referred for routine clinical EEG investigation. There was a significantly higher occurrence in whites (2.

An early-onset recessive cerebellar disorder with distal amyotrophy and, in two patients, gross myoclonia: a probable ataxia telangiectasia variant.

We report a family of 4 siblings from a non-consanguineous marriage, presenting with an early onset recessive cerebellar ataxia and progressive distal limb wasting. Ocular or other telangiectasias were absent. There were neither frequent infections nor immunodeficiencies.

Ultrastructural localization of epidermal growth factor (EGF)-receptor transcripts in the cell nucleus using pre-embedding in situ hybridization in combination with ultra-small gold probes and silver enhancement.

A high-resolution in situ hybridization method is described for localizing epidermal growth factor (EGF)-receptor transcripts in nuclei of A431 epidermoid carcinoma cells. The method is based upon the use of ultra-small gold particles in combination with silver enhancement. The RNA of the EGF-receptor was detected mainly around the nucleoli.

[Two out of three young women use the pill].

Data from the 1993 Netherlands Fertility and Family Survey are analyzed. Results show that "three out of every four women aged 18-42 years use some method of birth control. Some 10% is pregnant or wants to become pregnant, 5% is infecund and 10% does not use a method for other reasons.