Alberto Breccia

CHEMISTRY BY MICROWAVES

The pioneers of the application of microwaves into more canonic systems thought that it could produce similar effects in assisting the reactions carried out in research laboratories. In most cases it was soon evident that reactions were more rapid, cleaner and with an easier workup of the final material, saving a great deal of time [1]. These findings stimulated the diffusion of microwave ovens in many laboratories to take advantage of this instrument for their reactions.

On the chemical radioprotection by organic selenium compounds in vivo.

This paper deals with the radioprotection afforded by selenocystine, selenomethionine, colloidal selenium, selenoxanthene, selenoxanthone, and selenochromone in living rats. Our evaluation of radioprotection was based on the ability of the compounds to alleviate the mortality and the leukopenia occurring in rats exposed to irradiation of 600, 750, and 900 R. The results show that these compounds have an action similar to, and sometimes even superior to, that of cysteine. A preliminary study was made of the mechanism of action of the selenium derivatives by measurement of the retention of selenium in the blood, and its distribution at the subcellular level in the liver.

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.

Determination of metronidazole, misonidazole and its metabolite in serum and urine on RP-18 high-performance thin-layer chromatographic plates

Abstract A method for the determination of radiotherapeutic concentrations of metronidazole, misonidazole and its metabolite is described. The biological fluid (serum or urine) was deproteinized with acetone containing 2-nitroimidazole as internal standard, centrifuged and the supernatant evaporated under vacuum. The residue, dissolved in acetone, was applied to an HPTLC-RP-18 layer and, after development, quantitation was achieved with a scanning densitometer. The response was linear up to 180 μg/ml for all tested compounds and the detection limit was 0.5 μg/ml. Owing to its rapidity and sensitivity the method can be considered to be equivalent to high-performance liquid chromatography.

I. The Terpene Marrubiin

The biosynthesis of the diterpene marrubiin has been studied using some labelled possible precursors: [2-14C] mevalonate, [1-14C] acetate, [2-14C] acetate, [2-14C] pyruvate, [2,3-14C] succinate, [1,4-14C] succinate, [5-14C] ketoglutarate and [1,5-14C] citrate. Metabolism times of 24, 36, 48, 72 and 96 hours were used. The labelled compounds were supplied in solution to flowering white horehound (Marrubium vulgare L.), cut at the base of the stem. The incorporation results indicate that marrubiin undergoes a rapid turnover with a biological half life of about 24 hours. The rate of up-take of 14C from the prcursors is in the following order: [2-14C] mevalonate, [2-14C] acetate, [1-14C] acetate, [2-14C] pyruvate and [2,3-14C] succinate. Incorporation of 14C from the other compounds is negligible. If [2-14C] mevalonate is used, labelled marrubiin is formed 10 - 100 times more active than with the other precursors. The results suggest that all the precursors are degradated to acetic units through the Krebs cycle before their utilization, with the exception of mevalonate. Some samples of marrubiin (I) have been degradated chemically to the corresponding ketoderivative (II), in order to determine the distribution of radioactivity between the decahydronaphthalenic and furanic parts. The results are in good agreement with the distribution of the radioactivity in the molecule, as expected from the terpenoid structure of marrubiin.

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.

Thin-Layer Chromatographic Determination of 14C-Labelled and Unlabelled Cyclophosphamide

Abstract A thin layer-chromatographic method for the analysis of cyclophosphamide is described. The method involves the heating of the layer and the quantitation of the resulting fluorescent-U.V. absorbing derivative by densitometry. The limit of sensitivity of the assay is 50 ng applied to the layer and linearity is observed up to 2 μg. The method has been successfully applied to the determination of cyclophosphamide in plasma and to the determination of the specific of a radiolabe - ed sample.

Radio TLC in quality control and development of radiopharmaceuticals

Radio TLC has been used for determining the radiochemical purity and composition of two99mTc-radiopharmaceuticals, available as kits and commonly used for diagnostic imaging. Moreover, the same technique has been applied to detect impurities which decrease the specific activity of131I-derivatized dermatan sulfate, a new potential radiopharmaceutical, and for establishing the best labeling conditions.

Radiochemical and electrochemical studies of the interaction of Zn2+(65ZN) with the radiosensitizer misonidazole

Abstract Differential pulse polarography (DPP) of solutions containing misonidazole and zinc ions shows the disappearance of the reduction peak of the sensitizer and the appearance of a peak at a more positive potential, attribute to an eventual complex. None of the measurements performed has demonstrated the existence of a complex between zinc ions and the radiosensitizer misonidazole or some of its stable reduction products. To explain the results obtained by DPP, the electrolysis of misonidazole has been performed in the presence of 65 Zn oxalate, In this way it has been demonstrated that zinc ions interact with one or more short-lived reduction intermediates. These results suggest that zinc ions can play the role of scavengers of the toxic intermediates of nitroheterocyclic radiosensitizers produced by metabolic reduction. Experiments performed on Chinese hamster V79 cells, which have shown a decrease in the cytotoxicity of misonidazole and metronidazole in the presence of zinc ions, support this hypothesis.

Kinetic uptake of etanidazole in lung carcinoma and normal tissue in vivo

Thirty-four patients affected by primary pulmonary carcinoma or in a state of recurrence after surgery were analyzed and 2g/m2 of etanidazole was administered intravenously. After 30 min (group A), 60 min (group B), and 120 min (group C), both the bronchus affected by the carcinoma and the contralateral bronchus were biopsied. Of the 34 patients, 24 had histologically proven carcinoma and were enrolled in the study. Etanidazole determination was carried out with a polarographic method both in plasma and tissue. The results obtained indicate that the most favorable concentration of etanidazole in the tissue is at 30 min after administration and at this point is most beneficial when associated with radiotherapy. The tumor/plasma ratio of etanidazole examined in three phases is relatively higher than that noted with HPLC; however, it is compatible with the methodology used and previous studies carried out on other tumors.