Ute Witting

Hepatitis A and hepatitis B vaccinations : immunogenicity of combined vaccine and of simultaneously or separately applied single vaccines

The vaccination success and side effects of hepatitis A and hepatitis B immunisation of health care employees when using a combined vaccine were compared to those observed with simultaneous or single immunisations. The immunological response of two groups of healthy participants (75 each) receiving either single HAV or HBV vaccination was compared with that of two groups (75 each) vaccinated either simultaneously with both vaccines or with the combined vaccine. There were no non or low responders with respect to hepatitis A vaccination. Only one participant failed to build up an anti-HBs titer after combined vaccination. The good tolerance of separate, simultaneous and combined vaccinations was confirmed. Both combined and simultaneous vaccination led to significantly higher anti-HAV titers than single immunisation, while markedly but not significantly higher anti-HBs titers were found only with simultaneous vaccination. Considering the additional advantage of the higher acceptance of only one injection with the combined vaccine, this vaccination should be recommended for employees at risk for both hepatitis A and hepatitis B.

Interferences of nitrogen dioxide in the determination of aldehydes and ketones by sampling on 2,4-dinitrophenylhydrazine-coated solid sorbent

SummaryThe influence of nitrogen oxides on the practicability and accuracy of the determination of aldehydes and ketones in air samples using the DNPH-method was examined. Nitrogen dioxide reacts with 2,4-dinitrophenylhydrazine and the reaction products were identified as 2,4-dinitrophenylazide (main product) and 2,4-dinitrochlorobenzene (by-product). They have a similar chromatographic behaviour in high performance liquid chromatography (HPLC) as formaldehyde-2,4-DNP-hydrazone. The chromatographic separation of the reaction products and formaldehyde-2,4-dinitrophenylhydrazone was performed using different gradient systems. Problems which occur in nitrogen dioxide-containing air samples are discussed.

Quantification of bacterial lipopolysaccharides (endotoxin) by GC–MS determination of 3-hydroxy fatty acids

A GC-MS method for the quantification of bacterial lipopolysaccharides (LPS, endotoxin) is presented. After hydrolytic cleavage of 3-hydroxy fatty acids (3-OH FAs) from the lipid A region of LPS, derivatisation of both the hydroxyl and the carboxyl group was performed in one step with a mixture of methyl-bis(trifluoracetamide)(MBTFA) and N-methyl-N-(tert-butyldimethylsilyl)trifluoracetamide (MTBSTFA). Using GC-MS in the EI mode with selected ion monitoring (SIM) for analysis, baseline separation of 3-OH FAs (and of possibly interfering 2-OH FAs) was achieved. The sensitivity of the method (LOD 7-50 pg/injection for the different 3-OH FAs investigated) allows for the efficient quantification of LPS in occupational and environmental samples. Degradation of 3-OH FAs as well as of their derivatives during sample preparation and GC-MS separation as a possible source of errors in analytical methods based on 3-OH FA determination is reported for the first time. Thermal elimination of water from the underivatised 3-OH FAs and of trifluoroacetic acid from the derivatives was identified as the cause of degradation. The resulting alpha,beta-unsaturated compounds showing the same mass spectra as the 3-OH FA derivatives were detected as more or less prominent satellite peaks. By using alkaline instead of acidic hydrolysis and cool on-column instead of split/splitless injection, elimination was reduced to an acceptable level.

Simultaneous determination of airborne acetaldehyde, acetone, 2-butanone, and cyclohexanone using sampling tubes with 2,4-dinitrophenylhydrazine-coated solid sorbent.

The 2,4-dinitrophenylhydrazine (2,4-DNPH) derivatization method mainly used for the determination of airborne formaldehyde was extended for acetaldehyde, acetone, 2-butanone, and cyclohexanone, the next four carbonyl compounds of industrial importance. Sampling devices and sampling conditions were adjusted for the respective limit value regulations. Analytical reliability criteria were established and compared to those of other recommended methods. With a minimum analytical range from one tenth to the 3-fold limit value in all cases and with relative standard deviations below 5%, the adjusted method meets all requirements for the reliable quantification of the four compounds in workplace air as well as in ambient air.

Effects of lead on cloned voltage-operated neuronal potassium channels

The action of lead (Pb 2+) on cloned voltage-operated potassium channels of the rat brain was investigated in oocytes of Xenopus laevis. Pb2+ was found to decrease the potassium currents. This effect was due to a shift of the current-voltage relation in a positive direction (up to 30 mV). The Pb2+ effect appeared at a threshold concentration of about 0.1 μmol/l and was maximal at a concentration of about 30 μmol/l. At a potential of − 30 mV, the concentration needed for a 50% reduction of the potassium current was 1.0 μmol/l. The depressant effect of Pb2+ was obtained with all potassium channels tested (Kv1.1, Kv1.2, Kv1.4, Kv2.1, Kv3.4). It was minimal for the Kv2.1 channel and maximal for the Kv1.1 channel at potentials negative to 0 mV. An effect comparable with that of Pb2+ could not be induced by the application of magnesium or calcium. The external application of Pb2+ led to a decrease of potassium currents in outside-out but not in inside-out membrane patches. Overall, Pb2+ had a significant effect on the potassium channels which may contribute to the mechanisms of Pb2+ neurotoxicity.

Lead-induced blockade of kainate-sensitive receptor channels

The effects of bivalent lead on ion channels activated by kainate and α-amino-3-hydroxy-5-methyl-4-isoxazolpropionate (AMPA) were studied using Xenopus oocytes microinjected with mRNA from rat brain. Lead reduced kainate-induced membrane currents in a reversible and dose-dependent manner, without affecting membrane currents induced by AMPA. Lead decreased the kainate currents with a concentration of 0.1 μmol/l to 0.93 ± 0.01 and with a concentration of 100 μmol/l to 0.41 ± 0.04 of the control values. The blocking effect of lead on kainate responses was voltage dependent. The inhibition was strongest at - 90 mV to - 70 mV and became weaker at more positive membrane potentials. The effect of lead on the kainate-induced membrane currents remained unchanged when the concentration of kainate was increased. Hence lead probably represents a noncompetitive channel-blocking agent for non-N-methyl-d-aspartate (NMDA) receptor channels activated by kainate.

MMNTP-a new tailor-made modular derivatization agent for the selective determination of isocyanates and diisocyanates.

The synthesis of a new tailor-made derivatization agent for the selective determination of (di)isocyanates is presented. Starting from cyanuric chloride, the reagent 4-methoxy-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-(1-piperazine)(MMNTP) is synthesized by subsequent substitution of the three chlorine atoms. This new derivatization agent and the five urea derivatives of phenylisocyanate (PI), hexamethylene-diisocyanate (HDI), toluene-2,4-diisocyanate (2,4-TDI), toluene-2,6-diisocyanate (2,6-TDI) and methylenebisphenyl-4,4-diisocyanate (MDI) show good spectroscopic properties with small compound-to-compound variabilities (RSD([epsilon])= 5.3 %, RSD(relative fluorescence)= 9.4 %). Therefore, using UV detection, a single calibration is needed for the quantification of all diisocyanates and isocyanates respectively. For separation and analysis a HPLC method with a RP column and a binary gradient is presented. All derivatives are separated and show low limits of detection. In addition to the good spectroscopic properties and low limits of detection, good reactivity for the derivatizations at room temperature is observed. The aromatic diisocyanates can be measured immediately whereas aliphatic diisocyanates need 2 h incubation. These advantages make MMNTP a powerful and versatile derivatization agent for (di)isocyanates which is demonstrated by a real sample with solid phase sampling, where the reagent is coated on a sorbent.

Prediction of neurotoxic potency of hazardous substances with a modular in vitro test battery

Neurotoxic action was investigated on different model nervous systems linked to a modular in vitro test battery. Voltage operated potassium channels and glutamate operated ion channels expressed in oocytes of the clawed frog Xenopus laevis by injection of cRNA (cloned RNA) or mRNA, respectively, as well as isolated neurons and isolated neuronal networks from the buccal ganglia of the snail Helix pomatia, were used as consecutive modules of different complexity. Lead (Pb2+) was chosen as a known neurotoxic model substance to evaluate the suitability of the test battery to predict the neurotoxic potency of hazardous substances, to establish dose-response relationships, and to investigate the basic mechanisms involved in neurotoxicity. All modules delivered consistent results: potassium currents were reduced by lead with a threshold concentration of 0.1 mumol/l. Membrane currents elicited by the glutamate receptor agonists kainate were decreased by lead with a threshold concentration below 0.1 mumol/l, while currents elicited by the agonist AMPA were not affected. Action potentials generated by the isolated B4 snail neuron showed a decrease of potential amplitude and a prolongation of potential duration after application of lead. The neuronal network controlling the feeding activities of the snail reacted with a decrease of the frequency of the spontaneously generated feeding depolarisations, thus showing the direct neurotoxic effect of lead on body functions and behaviour.