Application of combined high-performance thin-layer chromatography immunostaining and nanoelectrospray ionization quadrupole time-of-flight tandem mass spectrometry to the structural characterization of high- and low-affinity binding ligands of Shiga toxin 1.

Shiga toxin 1 (Stx1) represents an AB5 toxin produced by enterohemorrhagic Escherichia coli, which cause gastrointestinal diseases in humans that are often followed by potentially fatal systemic complications, such as acute encephalopathy and hemolytic uremic syndrome. The expression of the preferential Stx1 receptor, Gb3Cer/CD77 (Gal alpha1-4Gal beta1-4Glc beta1-1Cer), is one of the primary determinants of susceptibility to tissue injury. Due to the clinical importance of this life-threatening toxin, a combined strategy of preparative high-performance thin-layer chromatography (HPTLC) overlay assay and mass spectrometry was developed for the detection and structural characterization of Stx1-binding glycosphingolipids (GSLs).

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.

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.

NO chemiluminescence in exhaled air: interference of compounds from endogenous or exogenous sources.

Nitric oxide determination in exhaled air using chemiluminescence analysers is increasingly used, but may be affected by various other components of the air sample. The influence of several compounds originating from endogenous or exogenous sources on NO readings has been studied. Defined amounts of water vapour, carbon dioxide, acetone, heptane, acetonitrile, oxygen, nitrous oxide and enflurane were added to air samples with NO concentrations 0-250 parts per billion.

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.

Effects of 2-phenoxyethanol on N-methyl-D-aspartate (NMDA) receptor-mediated ion currents.

The actions were examined of 17 frequently used glycol ether compounds on the glutamate receptor-mediated ion currents. The receptors were expressed in Xenopus oocytes by injection of rat brain mRNA. Most of the 17 glycol ethers exerted no effects on the glutamate subreceptors activated by kainate and N-methyl-D-aspartate (NMDA), whereas 2-phenoxyethanol (ethylene glycol monophenyl ether) caused a considerable reduction of NMDA-induced membrane currents in a reversible and concentration-dependent manner.

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.

Effects of Pb2+ on delayed-rectifier potassium channels in acutely isolated hippocampal neurons.

Effects of Pb2+ on delayed-rectifier potassium channels in acutely isolated hippocampal neurons. J. Neurophysiol.

Effects of n-hexane and its metabolites on cloned voltage-operated neuronal potassium channels.

In order to study the mechanisms of acute n-hexane intoxication, the effects of n-hexane and its metabolites 2-hexanol, methyl-n-butyl ketone, 2,5-hexanediol and 2,5-hexanedione on the cloned voltage-operated potassium channels Kv1.1, Kv1.4, Kv2.

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.

Syn/anti isomerization of 2,4-dinitrophenylhydrazones in the determination of airborne unsymmetrical aldehydes and ketones using 2,4-dinitrophenylhydrazine derivation.

Aldehydes and ketones readily react with 2,4-dinitrophenylhydrazine (2,4-DNPH) to form the corresponding hydrazones. This reaction has been frequently used for the quantification of airborne carbonyl compounds. Since unsymmetrical aldehydes and ketones are known to form isomeric 2,4-dinitrophenylhydrazones (syn/ anti-isomers), the influence of isomerization on the practicability and accuracy of the 2,4-DNPH-method using 2,4-dinitrophenylhydrazine-coated solid sorbent samplers has been studied with three ketones (methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), and methyl isobutyl ketone (MIBK)).

[An example for stepwise reduction of work site-induced formaldehyde exposure in pathology].

Occupational formaldehyde exposure in pathology depends on the efficiency of the ventilation system in use and may reach concentrations considerably above the current threshold limit values. The reduction of formaldehyde exposure by stepwise improvement of the ventilation system at a pathologist's workplace is presented as an example in this paper. Assessment of formaldehyde concentration by personal air sampling at a workplace originally equipped with a hood ventilation system resulted in values of up to 4 ml/m3 in the pathologist's breathing zone.

Lead-induced blockage of kainate-sensitive receptor channels.

The effects of bivalent lead on ion channels activated by kainate and alpha-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.

Effects of lead on cloned voltage-operated neuronal potassium channels.

The action of lead (Pb2+) 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).

Exposure to formaldehyde and glutardialdehyde in operating theatres.

The disinfection of operating theatres and adjoining areas is carried out with chemical disinfectants containing not only formaldehyde but also glutardialdehyde. The cleaning staff is therefore unavoidably exposed to these two substances. Adequate and correct evaluation of staff exposure must be based on exact quantification of these aldehydes in room air.

Evaluation of a new specific analysis of urinary delta-aminolevulinic acid in man.

A new specific method for urinary delta-aminolevulinic acid (ALA-U) measurement in man as a serial screening method for health control in occupational lead exposure was compared with a recommended, selective test (DAVIS method). The new test can be run fully automated, and the cost of material per sample is much lower than in the DAVIS method. ALA values obtained with this specific method were lower than those measured with the DAVIS method (= DAVIS values) in each case due to the elimination of interfering urinary compounds.

The tumor-protective effect of selenium in an experimental model.

The possibility of a tumor-protective effect of selenium on the growth of benzpyrene-induced sarcoma was studied in an assay with Balb/c mice. The animals received 4 parts/10(6) selenium in their drinking water for 12 months prior to subcutaneous injection of benzpyrene to induce sarcomas. In contrast to unpretreated controls, the selenium-exposed animals developed significantly less and smaller tumors in a given time.

Lead elimination of ICRF 158 in rats after chronic lead exposure.

Lead elimination by ICRF 158, a lipophilic derivative of ethylene-diaminetetra-acetate (EDTA), was investigated in rats after chronic lead exposure. The animals had received a lead concentration of 550 ppm in their drinking water for 140 days. Subsequent treatment with ICRF 158 for 30 days led to increased mobilization and elimination of incorporated lead, and the lead-induced inhibition of hemosynthesis was removed.

[Dose-dependent effects on phenobarbital on microsomal liver enzymes of chicken embryos (author's transl)].

Levels of cytochrome P-450 and the activities of amino-pyrinedemethylase and p-nitrophenol-UDP-glucuronyltransferase were measured in homogenates and microsomes of 16 to 19 day old chicken embryos exposed in ovo to phenobarbital. The activities of glucose-6-phosphatase were measured on the 19th day of incubation. After the highest dose of 3 X 8 mg phenobarbital, cytochrome P-450 increased 3-6fold, aminopyrinedemethylase activity 7fold and the activity of p-nitrophenol-UDP-glucuronyltransferase 3fold.

[Combined ultrastructural morphometric and biochemical investigations on the rat liver after ligation of the bile duct (author's transl)].

In the present study an ultrastructural morphometric analysis of the rat liver 1, 3 and 7 days after bile duct ligation was performed. Corresponding biochemical investigations included the determination of the cytochrom P 450 contents in the microsomal fraction. In the serum of the rats the activities of GOT and GPT were determined.

Side chain oxidation of ifosfamide in man.

Ifosfamide as well as its stable alkylating metabolites namely carboxy-Ifosfamide and two dechloroethylated compounds were determined in the urine of a patient with progredient lung carcinoma who had been treated with 6 g of the drug. Quantitative measurements were carried out using a colorimetric procedure which consists of TL-spectrophotometric determinations on sheets which had previously been sprayed with 4-pyridinaldehyde-2-benzothiazolylhydrazone. In the case investigated the Ifosfamide was found to have been converted largely into two dechloroethylated compounds (48%) and only a small portion of carboxy-Ifosfamide (2.

[Quantitative determination of cyclophosphamide, ifosfamide, and trofosfamide and their stable metabolites on TLC-plates with the aid of 4-pyridine-aldehyde-2-benzothiazolyl-hydrazone (PBH) (author's transl)].

Cyclophosphamide, ifosfamide, and trofosfamide can be analysed quantitatively together with their stable alkylating urine metabolites on TL-plates by means of the PBH-reagent (4-pyridine-aldehyde-2-benzothiazolyl-hydrazone). The method requires only 0.01 ml urine, but a careful standardisation is necessary by using reference substances.

Plaque development by vaccinia-viruses on the chicken chorio-allantois under the influence of cyclophosphamide.

The development of Vaccinia-virus plaques on the chorioallantois of embryonated eggs was studied under the influence of active cyclophosphamide metabolites. The viruses were inoculated on the 9th or the 13th incubation day. Cyclophosphamide was injected in doses of 62.