Observations and modelling of thoron and its progeny in the soil-atmosphere-plant system.

Samples of pasture vegetation, mainly Trifolium pratensis, were collected at the Botanic Garden of the University of Bologna during the period 1998-2000 and measured by gamma-spectrometry for determining thoron progeny. Concentrations of (212)Pb were between 1.5 and 20 Bq m(-2), with individual peaks up to 70 Bq m(-2). Soil samples were collected at the same location and physically characterised. Their chemical composition (particularly Th and U) was determined by X-ray fluorescence spectroscopy. Lead-212 on plants mainly originates from dry and wet deposition of this isotope generated in the lower atmosphere by the decay of its short-lived precursor (220)Rn, which is produced in the upper soil layers as a member of the natural thorium decay chain and exhales into the atmosphere. Concentrations of (220)Rn in the atmosphere depend on (1) the amount of Th present in soil, (2) the radon fraction which escapes from the soil minerals into the soil pore space, (3) its transport into the atmosphere, and (4) its redistribution within the atmosphere. The mobility of radon in soil pore space can vary by orders of magnitude depending on the soil water content, thus being the main factor for varying concentrations of (220)Rn and (212)Pb in the atmosphere. We present a simple model to predict concentrations of thoron in air and its progeny deposited from the atmosphere, which takes into account varying soil moisture contents calculated by the OPUS code. Results of this model show close agreement with our observations.

Bile acid kinetics in man studied by radio thin-layer chromatography and densitometry coupling.

A method based on coupling of the techniques of radioscanning a TLC plate and densitometry has been developed for the determination of pool sizes and fractional turnover rate of bile acids in man after intraduodenal administration of 14C-labelled acid. The validity of the method has been checked by comparison of the results obtained with those of an enzymatic spectrophotometric analysis, and a measurement of the radioactivity by liquid scintillation counting, after elution of the separated bile acid from a TLC plate. Advantages of the proposed method over the previous one include a reduced number of manipulations, the possibility of automation, a better reproducibility, and the possibility of elaborating the radiometric data obtained for the primary bile acid for better characterising its metabolism inside the enterohepatic circulation.

Mitochondrial respiratory chain features after gamma-irradiation.

Radiation provokes damage to DNA but also to membrane and protein structure. Radiolysis is a tool used very often in the study of free radical biological effects and of scavenger molecules effectiveness. Nitroimidazoles have been demonstrated to enhance the radiation effects on biological structures. The studies we have performed on isolated mitochondria irradiated, with and without nitroimidazoles, at a radiation dose equal to LD90, indicate that this treatment is not able to affect the structural and functional features investigated (ubiquinone-10, fatty acids, respiratory cytochrome levels or membrane fluidity and respiratory enzymatic activities), suggesting that an involvement of such externally produced radicals on membrane damage is unlikely. Moreover it was ascertained that the mitochondrial redox activities do not take part into the intracellular nitroimidazole reduction.

Interaction between reactive oxygen species and coenzyme Q10 in an aprotic medium: a cyclic voltammetry study.

The involvement of coenzyme Q (CoQ) as an antioxidant agent in several oxidative processes both in vitro and in vivo is nowadays pointed out by several biochemical and clinical studies, but the chemical mechanisms of this action are not yet unequivocally established. Electrochemistry provides very useful techniques for the analysis of the kinetics and thermodynamics, and mechanisms of chemical phenomena involving electron transfers, e.g. in the case of radical reactions. In the present study we used cyclic voltammetry to investigate the interactions between oxygen radicals and ubiquinone in aprotic medium, a condition similar to that existing in the biological membranes. The results obtained showed that ubiquinone is more easily reduced than oxygen, ruling out the possibility of an electron transfer from semiquinone to oxygen to produce superoxide radicals. On the contrary, it was demonstrated that fully reduced quinone is able to scavenge the superoxide radical, by reduction to peroxide ion, lowering actually the oxidative potential in the medium.

Reactivity of nitro-thiophene derivatives with electron and oxygen radicals studied by pulse radiolysis and polarographic techniques.

A new series of nitrothiophene derivatives have been synthetized and some of the physico-chemical parameters which can influence both their radiosensitizing efficiency and toxicity have been investigated. These include octanol/water partition coefficient (P), one-electron reduction potential (E7(1] and reactivity of the drugs towards primary radical species. For these studies, pulse radiolysis techniques and conventional polarography have been extensively used. Biological responses (both sensitization and toxicity) have been tested towards Chinese Hamster cells in vitro. The results are valuable in selecting, among the tested compounds, 5-NTMA, 5-NTM, 4- and 5-NTCA as the nitrohiophenes promising for in vivo applications.

Radioactivity in breast milk and placentas during the year after Chernobyl.

After the April 1986 nuclear reactor accident at Chernobyl in the Union of Soviet Socialist Republics, samples of human placenta and breast milk were tested for 1 year to determine the levels of radioactivity. The radionuclide iodine 131 was never beyond the detection limit of our gamma detector for both matrices. As to cesium isotopes 134 and 137, the highest levels detected in breast milk (6 Bq.L-1) and placenta (15.8 Bq.kg-1) were recorded in March 1987. Study data for breast milk and placenta are in agreement with the values calculated by means of double-compartment food-milk and food-placenta models. With regard to placental content, the cesium contribution to the average dose during the year after the Chernobyl accident was calculated to be 40 to 60 microSv.

Clinical trials with cyclophosphamide and misonidazole combination for maintaining treatment after radiation therapy of lung carcinoma.

Fifteen patients with inoperable non oat cell lung carcinoma, who had already been treated with telecobalt therapy in the mediastinum-hilar region, were treated with continuing therapy with misonidazole (MISO) and cyclophosphamide (Cy). MISO was administered in single doses of 1000 mg/m2 and 500 mg/m2, orally. Cy was administered in single doses of 500 mg/m2 and 250 mg/m2, i.v. This treatment was given every 4 weeks. All patients (15/15) suffered from hyporexia, nausea and vomiting within 48 hours from administration; furthermore, 2 patients had hemoragic cystitis, 2 had peripheral neurotoxicity, 3 had fever, and 2 had serious nervous depression. Leukopenia occurred in all patients immediately after drug administration, although it was not present in any patient by the time of the next administration. This clinical trial was concluded in December 1981. The follow-up at 18 months shows 7/15 cases of relapse (3 patients dead and 1 patient alive with recurrence, 2 patients dead and 1 patient alive with metastasis without recurrence). Eight of 15 patients are alive with progression of disease from 8 to 18 months.

Electrochemical and pulse radiolysis study of misonidazole and its azo and azoxy derivatives.

Pulse radiolysis experiments were carried out on methanolic solutions of misonidazole and its azo and azoxy derivatives in order to obtain the spectra of their radical anions. The rate constants for the reaction of these compounds with es- were 2.5 X 10(10), 2.3 X 10(10) and 1.9 X 10(10) M-1 s-1 respectively. The electrochemical properties of the compounds were studied with the aim of producing their radical anions by electrolysis in aprotic medium (DMF, 0.1 M TEAP ). The potentials at cathodic peaks were -1.05, -1.10 and -1.18 V for misonidazole, azo and azoxy derivatives, respectively. The decay of the radical anion of misonidazole, which produces nitrite ions, was studied in particular, the corresponding rate constant being 2.8 X 10(-4) s-1. The possibility of using electrochemistry in the study of these transient species is discussed.