Radionuclide Migration Experiments in Tuff Blocks/Underunsaturated and Saturated Conditions at a Scale of Up to 1 Metre

To complement migration experiments with non-radioactive tracers in the Busted Butte experimental facility (BBTF) at the Nevada Test Site, an exploratory migration experiment has been performed under unsaturated conditions in a {approx}0.3m x {approx}0.3m x {approx}0.3m block of tuff. Longer term migration experiments, up to 600 days, under unsaturated and saturated conditions in {approx}1 m3 blocks of tuff have recently been completed. Na-fluorescein, 3H (as tritiated water), 22Na, 60Co, 95mTc and/or 99Tc (as the pertechnetate anion), 137Cs, and 237Np were used as tracers in all three experiments. Under unsaturated conditions, Tc is transported slightly faster than 3H, while under saturated conditions, the chemical conditions became highly reducing, leading to significant retardation of Tc along the flow field. If chemically reducing conditions can be demonstrated to exist in the saturated zone downstream from the proposed repository, the geological formations underlying the proposed repository horizon can potentially act as a geological barrier to the transport of some multivalent radionuclides

Carbon-11-labeled daunorubicin and verapamil for probing P-glycoprotein in tumors with PET

One of the mechanisms for multidrug resistance (MDR) of tumors is an overexpression of the P-glycoprotein (P-gp). The cytostatic agent daunorubicin and the modulator verapamil were labeled with C-11 to probe P-gp with PET. Methods: Carbon-11-daunorubicin was prepared from (CCH2N2)-C-11 with an aldehyde precursor, followed by hydrolysis. Carbon-11-verapamil was synthesized by C-11-methylation. Both tracers were evaluated by investigating pharmacokinetics in rats and in vitro cell kinetics using human ovarian carcinoma cells. Results: Amounts of 111 MBq C-11-daunorubicin were prepared. Biodistribution studies of C-11-daunorubicin in male Wistar rats showed dose-dependent pharmacokinetics, whereas with C-11-verapamil the pharmacokinetics were dose independent. In in vitro experiments with cells, the ratio of accumulation of C-11-daunorubicin in drug sensitive/resistant cell lines was 16. Addition of verapamil resulted in increased accumulation of C-11-daunorubicin in the resistant cell line. The ratios of C-11-verapamil accumulation in drug-sensitive versus the MDR counterpart were 4-5. Conclusion: Carbon-11-daunorubicin and C-11-verapamil both have potential for in vivo probing of P-glycoprotein with PET