[Significance of the kinin system in thermal edema of the rat paw].
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Alpha-Globulins↗
Biomedical subjects
H Wiegand
Publications and source records attributed to H Wiegand.
[Consideration of natural mortality in bio-assay].
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Biological Assay↗
Detection of sub-miniature endplate potentials by harmonic analysis.
In phrenic nerve-diaphragm preparations from young rats and mice, long-term recordings of miniature endplate potentials (MEPPs) from single synapses were performed. Amplitude histograms obtained from these experiments were analysed with respect to the presence of multiple peaks which are believed to reflect quantal transmitter release. This was accomplished by subjecting MEPP amplitude histograms as well as matched random number histograms to Fourier analysis; harmonics in the MEPP amplitude distribution were considered valid only if they exceeded those of the random number distribution. In 9 out of 11 experiments, substantial evidence for the existence of preferred amplitudes was obtained; in two cases, however, it was completely missing. Applying our method to a series of promising MEPP amplitude histograms selected from the literature, we found a similar relationship between positive and negative results. We also noted a fairly constant relationship between the size of the elementary sub-MEPPs and the mean amplitude of the bell-MEPPs, named so according to the Gaussian shape of their amplitude distribution.
Animals↗
The action of thallium on the excitability of CA1 pyramidal cells in hippocampal slices.
The effect of thallium ions on central neuronal activity was investigated in hippocampal slice preparations from guinea pigs and rats using extra- and intracellular recording techniques. Thallium induced a reversible and concentration-dependent reduction of the orthodromically evoked compound action potential of CA1 pyramidal cells with only weak effects on either afferent fiber activity, postsynaptic potentials or antidromically evoked responses. The membrane potential and input resistance of the pyramidal cells were not impaired by thallium. In contrast, variations in the maintained spike activity and spontaneously occurring inhibitory postsynaptic potentials were observed. It is concluded, that in contrast to its presynaptic action in the peripheral nervous system, thallium has a predominant postsynaptic target site in the hippocampal slice preparation. It is suggested that the neurotoxic action of thallium is not mediated by an interaction with specific ion channels of the cell membrane, but rather by an unspecific influence on the intracellular metabolism of the CA1 pyramidal cell.
Action Potentials↗
The action of cobalt, cadmium and thallium on presynaptic currents in mouse motor nerve endings.
The action of cobalt, cadmium and thallium on presynaptic currents was investigated by recording extracellular potentials from mouse motor nerve terminals. Recorded waveforms consisted of two negative deflections preceded by a small positivity. The second negative deflection could be blocked by the potassium channel blockers tetraethylammonium (TEA) and 3,4-diaminopyridine (3,4-DAP). Application of either divalent cations (cobalt, cadmium) or monovalent thallous ions to the bath, even in mM concentrations, did not change these waveforms significantly. After application of high TEA and 3,4-DAP concentrations (10 mM and 250 microM, respectively), a prolonged positive-going wave arose, which could be blocked reversibly by bath application of cobalt and cadmium, but not thallium. The concentration-inhibition curve for cadmium suggested two apparent dissociation constants, whereas cobalt seemed to have only one apparent dissociation constant. It was concluded that the long-lasting positive wave is driven by calcium influx, since it was competitively antagonized by the application of cobalt and cadmium. A different, short-lasting positive wave arose using lower concentrations of potassium channel blockers, and this wave could not be blocked by cobalt, cadmium, or thallium.
4-Aminopyridine↗
Visual functions in 6-year-old children in relation to lead and mercury levels.
Within a larger comparative environmental health screening program in East and West Germany we investigated functions of the developing visual system in field experiments in a total of 384 children living in three different areas. Visual functions were assessed neurophysiologically by visual-evoked potentials (VEPs) and psychophysically by measuring the contrast sensitivity (CS). Blood lead concentrations and urinary mercury levels were used as markers of environmental and/or amalgam-derived exposure, respectively. The relationships among lead and mercury concentrations and the neurophysiological and psychophysical outcomes were investigated by means of linear regression analysis. After adjusting for confounding effects, statistically significant lead-related changes were found only for some of the VEP interpeak latencies, while some of the CS values were significantly reduced with increasing mercury concentrations. All other outcome variables were not significantly related to lead or mercury levels. It is concluded that even at blood lead levels in the range of 14 to 174 micrograms/l and at very low urinary mercury levels subtle changes in visual system functions can be measured.
Child↗