Effects of monomethylarsonic and monomethylarsonous acid on evoked synaptic potentials in hippocampal slices of adult and young rats.

Arsenite and its metabolites, dimethylarsinic or dimethylarsinous acid, have previously been shown to disturb synaptic transmission in hippocampal slices of rats (Krüger, K., Gruner, J., Madeja, M.

Effects of dimethylarsinic and dimethylarsinous acid on evoked synaptic potentials in hippocampal slices of young and adult rats.

In this study, the effects of pentavalent dimethylarsinic acid ((CH(3))(2)AsO(OH); DMA(V)) and trivalent dimethylarsinous acid ((CH(3))(2)As(OH); DMA(III)) on synaptic transmission generated by the excitatory Schaffer collateral-CA1 synapse were tested in hippocampal slices of young (14-21 day-old) and adult (2-4 month-old) rats. Both compounds were applied in concentrations of 1 to 100 micromol/l. DMA(V) had no effect on the amplitudes of evoked fEPSPs or the induction of LTP recorded from the CA1 dendritic region either in adult or in young rats.

Effects of monomethyltin and dimethyltin compounds on heterologously expressed neuronal ion channels (Xenopus oocytes) and synaptic transmission (hippocampal slices).

The aim of this study was to investigate the effects of monomethyltin trichloride (MMT) and dimethyltin dichloride (DMT) on various neuronal ion channels heterologously expressed in Xenopus oocytes and on synaptic transmission in hippocampal slices of young (14-21 days old) and adult (2-4 months old) rats. The Xenopus oocyte expression system was chosen to allow direct assessment of the effects of MMT and DMT both on glutamate receptors sensitive to AMPA and NMDA and on various voltage-operated potassium and sodium channels. Hippocampal slices were used to analyze the effects of MMT and DMT on synaptic potentials generated by the important excitatory Schaffer collateral-CA1 synapse.

Effects of arsenite on long-term potentiation in hippocampal slices from young and adult rats.

The effects of trivalent arsenite were tested at the Schaffer collateral-CA1 synapse of adult (2-4 month) and young (14-21 days) rats. Exposure of 100micromol/l arsenite led to a slight and reversible reduction of the amplitudes of evoked excitatory postsynaptic field potentials in adult and young rats, while exposure of 0.1 and 1micromol/l arsenite had no effects.

Blockade and enhancement of glutamate receptor responses in Xenopus oocytes by methylated arsenicals.

Pentavalent and trivalent organoarsenic compounds belong to the major metabolites of inorganic arsenicals detected in humans. Recently, the question was raised whether the organic arsenicals represent metabolites of a detoxification process or methylated species with deleterious biological effects. In this study, the effects of trivalent arsenite (AsO(3) (3-); iA(III)), the pentavalent organoarsenic compounds monomethylarsonic acid (CH(3)AsO(OH)(2); MMA(V)) and dimethylarsinic acid ((CH(3))(2)AsO(OH); DMA(V)) and the trivalent compounds monomethylarsonous acid (CH(3)As(OH)(2), MMA(III)) and dimethylarsinous acid ((CH(3))(2)As(OH); DMA(III)) were tested on glutamate receptors and on voltage-operated potassium and sodium channels heterologously expressed in Xenopus oocytes.

Blockade of glutamatergic and GABAergic receptor channels by trimethyltin chloride.

1. Organotin compounds such as trimethyltin chloride (TMT) are among the most toxic of the organometallics. As their main target for toxicity is the central nervous system, the aim of the present study was to investigate the effects of TMT on receptor channels involved in various processes of synaptic transmission.

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.