The hippocampal region of rats and mice after a single i.p. dose of clioquinol: loss of synaptic zinc, cell death and c-Fos induction.

Clioquinol (CQ) is able to chelate synaptic zinc, which can modulate excitatory and inhibitory neurotransmission. In humans, CQ was associated with cases of transient global amnesia (TGA) and with the neurodegenerative syndrome subacute myelo-optico-neuropathy (SMON). We examined the CQ induced loss of synaptic zinc, cell death and c-Fos induction in rats and mice. In rats, we found a strong reduction of histochemically reactive synaptic zinc no later than 4 h after the injection of the lowest dose of CQ (50 mg/kg) and, for all doses used, a return to control levels after 48 h. There was no evidence of cell death for any dose and up to 1 week after CQ injections. Only a slight induction of c-Fos was seen in the hippocampus for the higher doses used (100-200 mg/kg). In mice injected with 100 mg/kg, CQ also resulted in a fast loss of synaptic zinc. c-Fos was induced after 4 h in cell populations of the hippocampal region and other parts of the telencephalon, and substantially increased after 24 h. One day after the injection we found a pattern of cell loss (hilus, parts of CA3, CA1 and layer III of the medial entorhinal cortex) reminiscent of that seen in models of temporal lobe epilepsy. In conjunction with published data on the behavioral effects of zinc chelation and the modulatory effects of zinc in excitatory neurotransmission, our results indicate that the loss of synaptic zinc may have been involved in TGA and the neuropathology associated with SMON.

Prompt gamma neutron activation analysis of toxic elements in radioactive waste packages.

The French Alternative Energies and Atomic Energy Commission (CEA) and National Radioactive Waste Management Agency (ANDRA) are conducting an R&D program to improve the characterization of long-lived and medium activity (LL-MA) radioactive waste packages. In particular, the amount of toxic elements present in radioactive waste packages must be assessed before they can be accepted in repository facilities in order to avoid pollution of underground water reserves. To this aim, the Nuclear Measurement Laboratory of CEA-Cadarache has started to study the performances of Prompt Gamma Neutron Activation Analysis (PGNAA) for elements showing large capture cross sections such as mercury, cadmium, boron, and chromium. This paper reports a comparison between Monte Carlo calculations performed with the MCNPX computer code using the ENDF/B-VII.0 library and experimental gamma rays measured in the REGAIN PGNAA cell with small samples of nickel, lead, cadmium, arsenic, antimony, chromium, magnesium, zinc, boron, and lithium to verify the validity of a numerical model and gamma-ray production data. The measurement of a ∼20kg test sample of concrete containing toxic elements has also been performed, in collaboration with Forschungszentrum Jülich, to validate the model in view of future performance studies for dense and large LL-MA waste packages.

An improved method for the non-destructive characterization of radioactive waste by gamma scanning.

A method to improve the reliability and accuracy of activity results in segmented gamma scanning of radioactive waste drums with non-uniform isotope and matrix distribution has been developed. The improved method which is based on numerical simulations of the measured angular dependent count rate distribution during drum rotation in segmented gamma scanning has been validated through the measurement of Cs-137 and Co-60 activities in 13 real radioactive waste drums with heterogeneous activity and matrix distributions. The results were compared to that obtained for the conventional method assuming homogeneous activity and matrix distributions.