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[en] The effect of formation of single-strand non-reparable breaks in the DNA chain of plasmid pBR 322 under picosecond laser UV irradiation with the intensity of approximately 1013 W/m2 and lambda = 266-316 nm is studied. The breaks are shown to result from two-step excitation of DNA bases as well as from the formation of two-photon water radicals. The lower limit of quantum yield of single-strand breaks formation is approximately 10-5 - 10-6. (Auth.)
Journal
Photobiochemistry and Photobiophysics; ISSN 0165-8646; 
; v. 4(1-2); p. 87-93
; v. 4(1-2); p. 87-93
[en] The parvovirus Minute-Virus-of-Mice (MVM) was used to probe the DNA replication activities expressed by mouse fibroblasts. This system allowed us to study quantitatively the effect of UV-induced DNA lesions on the progression of DNA replication in vivo. MVM was UV-irradiated prior to infection. Pyrimidine dimers induced in the viral genome account for the reduced level of intracellular viral DNA synthesis, assuming that most of these lesions block viral DNA replication in unirradiated cells. The inhibition of damaged MVM DNA synthesis is less severe if the host cells themselves are irradiated prior to virus infection. This stimulation of viral DNA replication in pretreated cells might account for the UV-enhanced viral reactivation phenomenon, i.e. the increased survival of nuclear-replicating viruses propagated in cells preexposed to various genotoxic agents
[fr]
L'ADN du parvovirus Minute-Virus-of-Mice (MVM) a ete utilise comme sonde des activites de replication exprimees par les cellules de Souris. Ce systeme permet en particulier d'etudier quantitativement l'efficacite avec laquelle les lesions induites dans l'ADN expose au rayonnement UV bloquent le deroulement de sa replication in vivo. Le nombre de dimeres de pyrimidines induits dans le genome du virus MVM irradie avant l'infection rend compte du taux reduit de synthese intracellulaire de l'ADN viral si l'on considere que la majorite de ces lesions bloque la replication de l'ADN viral dans les cellules non irradiees. L'inhibition radioinduite de la synthese de l'ADN de MVM est moins prononcee si les cellules-hotes sont elles-memes irradiees avant l'infection. Cette stimulation de la replication de l'ADN viral dans les cellules pretraitees explique le phenomene de reactivation virale induite, c'est-a-dire l'augmentation de survie des virus a replication nucleaire dans les cellules preexposees a divers agents genotoxiquesJournal
Comptes Rendus des Seances de la Societe de Biologie et de ses Filiales; ISSN 0037-9026; ; v. 176(3); p. 395-401
; v. 176(3); p. 395-401
[en] This paper compares the RBE of a neutron beam produced by 50 MeV deuterons on beryllium [d(50)-Be] at the cyclotron CYCLONE of Louvain-La-Neuve and of a neutron beam produced by 34 MeV protons on beryllium [p(34)-Be] at the Hopital Regional d'Orleans. Early intestinal tolerance in mice was choosen as biological criterium; it is derived from LD50 determination after single and fractionated abdominal irradiation. For d(50)-Be neutrons, RBE was 1.8+-0.2 (with respect to 60Co γ-rays) for a single fraction. It increases up to 2.1+-0.2 for an irradiation in 2 fractions (3.5 h interval) and reaches 2.5+-0.3, 2.7+-0.3 and 2.5+-0.3 for irradiations in 10 fractions (7 and 3.5 h interval) and 20 fractions (3.5 h interval) respectively. RBE values observed for p(34)-Be neutrons (with respect to 60Co γ-rays) are not significantly different. For a single fraction RBE=1.7+-0.2 and for 2 fractions (3.5 h interval) RBE=2.0+-0.2
[fr]
Cet article compare l'EBR d'un faisceau de neutrons produit a partir de deutons de 50 MeV sur beryllium [d(50)-Be] au cyclotron CYCLONE de Louvain-La-Neuve avec celui d'un faisceau de neutrons produit a partir de protons de 34 MeV sur beryllium [p(34)-Be] au cyclotron de l'Hopital Regional d'Orleans. La tolerance intestinale precoce chez la souris a ete choisie comme critere biologique; elle est mesuree par la DL50 apres irradiation abdominale unique et fractionnee. Pour les neutrons d(50)-Be, l'EBR est egale a 1,8+-0,2 pour l'irradiation en dose unique (les rayons γ du 60Co sont pris comme reference). L'EBR augmente a 2,1+-0,2 pour une irradiation en 2 fractions (separees par 3,5 h) et atteint 2,5+-0,3, 2,7+-0,3 et 2,5+-0,3 respectivement pour des irradiations en 10 fractions (separees par 7 et 3,5 h) et en 20 fractions (separees par 3,5 h). Les valeurs d'EBR obtenues pour le faisceau de neutrons p(34)-Be ne sont pas significativement differentes. Pour l'irradiation a dose unique l'EBR=1,7+-0,2 et pour 2 fractions (separees par 3,5 h) l'EBR=2,0+-0,2Journal
Comptes Rendus des Seances de la Societe de Biologie et de ses Filiales; ISSN 0037-9026; ; v. 176(3); p. 422-428
; v. 176(3); p. 422-428
[en] The survival time of golden hamsters (Mesocricetus auratus) after whole-body 60Co-γ-irradiation in the range of 600 to 200 000 rad was investigated. The two plateaus of the dose-survival curve which correspond to bone marrow and gastrointestinal death are similar to those of other species such as mice, rats and mongolian gerbils. A new plateau occurring 40-57 hours after doses of 30 000-60 000 rad, where there is a little reduction in survival time, has been found. It is in addition to the well recognized central nervous system (CNS) syndrome. This plateau is observed only in golden hamsters, presumably because of their relatively high resistance to CNS syndrome. Experiments involving partial body irradiation of the animals indicate that the target is in the cephalic one-third of abdomen. The new segment may well indicate a new type of acute somatic radiation injury different from the well known bone marrow, gastrointestinal and CNS syndromes. (author)
Journal
International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine; ISSN 0020-7616; ; v. 40(1); p. 87-94
; v. 40(1); p. 87-94
[en] Methods using 5 and 6 enzymes were devised to synthesize L-[11C]glutamic acid (GA) labeled on the carboxyl group of either the α-(AGA) or γ-(GGA) carbon atom. The distribution of the 11C-labeled AGA or GGA in rabbits was compared with that of L-[13N]glutamic acid. The results show that AGA was rapidly decarboxylated with loss of the 11C-label, and that GGA was also decarboxylated, but to a lesser degree. Thus, the radiolabel distribution may not reflect the distribution of the original compound. The results also demonstrate that positron labeled pharmaceuticals may be rapidly synthesized via complex enzymatic pathways. (author)
Journal
International Journal of Applied Radiation and Isotopes; ISSN 0020-708X; ; v. 33(8); p. 613-617
; v. 33(8); p. 613-617
[en] A compartmental model with five tissue compartments and two lung compartments has been developed to simulate the exhalation of an inert gas following (i) bolus intravenous injection of 133Xe in saline, (ii) bolus intravenous injection of 37Ar in saline, and (iii) the formation of 37Ar in bone tissue following fast neutron irradiation. The model was used to assess the probable effect that variations in individual physiology would have on measurements of body calcium by the 37Ar method. The likely errors arising from changes in physiology were found to be less than +-5%. The use of a recirculating breath collection system for collection of 37Ar could introduce larger than 5% if collection continued for one hour or more without extraction of the exhaled activity from the circuit. (author)
Journal
Physics in Medicine and Biology; ISSN 0031-9155; ; v. 27(9); p. 1105-1117
; v. 27(9); p. 1105-1117
[en] Satisfactory experimental models for preclinical prediction in cancerology must answer the following criteria: reproducibility of the method used for inducing tumors; clinical, pathological and kinetic similarity with the corresponding human tumors. We have developed a model of osteosarcoma locally induced by insoluble radioactive cerium chloride (144Ce Cl3) in Sprague Dawley rats. This method yields over 80% of bone tumors at the injection site, of which approximately half are histologically similar to human tumors. These tumors double their volume fairly slowly (in approximately 20 days); lung metastases occur both early and frequently (80% of animals). A transplantable tumor was developed from an induced osteosarcoma and adapted to the Curie strain. Transplantation in the bone, next to the bone, or under the skin is followed by widespread metastatic dissemination. The kinetics and histological features of the primary tumor are maintained. Tumor 85strontium uptake is similar to that seen in human osteosarcomas. These new models of osteosarcomas are being used for evaluating new cancer chemotherapeutic agents and interferon, etc
[fr]
Les criteres des bons modeles experimentaux dans le domaine de la prediction preclinique en cancerologie sont: la reproductibilite de la methode d'induction des tumeurs, la ressemblance clinique, anatomopathologique et cinetique avec les tumeurs humaines correspondantes. Nous avons developpe un modele d'osteosarcome induit localement par le chlorure de cerium radioactif (144Ce Cl3) sous forme insoluble chez le rat Sprague Dawley. Cette methode permet d'obtenir plus de 80% de tumeurs osseuses au site d'injection dont la moitie environ correspond histologiquement a l'osteosarcome humain. Ces tumeurs ont un temps de doublement relativement long (20 jours environ) et metastasent tres frequemment (80% des animaux) et tres precocement au niveau du poumon. A partir d'un osteosarcome induit une tumeur transplantable a ete developpee et adaptee a la souche Curie. La greffe intra-osseuse, para-osseuse, ou sous-cutanee aboutit a une diffusion metastatique importante. Les caracteres histologiques et cinetiques de la tumeur primitive sont conserves. La tumeur fixe le 85strontium comme les osteocarsomes humains. Ces nouveaux modeles d'osteosarcomes sont utilises pour des essais therapeutiques: nouvelles drogues antimitotiques, interferon, etcJournal
Semaine des Hopitaux de Paris; ISSN 0037-1777; ; v. 58(28-29); p. 1684-1689
; v. 58(28-29); p. 1684-1689
[en] Analyses of the radiation effects in the survivors of the atomic bombings of Hiroshima and Nagasaki have employed the Tentative 1965 Dose Estimation (T65D). Revised dose estimates calculated using computer radiation transport codes and re-assessed radiation outputs from the weapons show major differences from T65D in the values of tissue kerma in air, both for the neutron and gamma radiation fields. These differences are more significant for the Hiroshima bomb. The bases for the T65D calculations and the recent evaluations of Loewe and Mendelsohn and Pace and Scott are outlined with a discussion of the reasons for the different values of tissue kerma obtained. A brief discussion is included of the basis of T65D 'transmission factors' and of tissue kerma to organ dose conversion factors, together with suggested changes that may be required. It is concluded that it would be premature to attempt re-analyses of observed effects until such time that the revision of dose estimation is completed. This revision is expected to last two years and will include reassessments of individual shielding factors and organ dose calculations. (author)
Journal
Radiation Protection Dosimetry; ISSN 0144-8420; ; v. 2(3); p. 127-139
; v. 2(3); p. 127-139
[en] The different methodological steps of the technical and economical assessment of the radiological protection are described. This consists in a presentation of the problems raised by: a) the identification of the protection options, of the criteria used in order to compare them (reduction of public and/or occupational risks, protection costs...); b) the quantitative evaluation of the criteria, and finally c) the use of various decision-aiding methods in view of comparing the protection options
[fr]
Les fifferentes etapes methodologiques de l'evaluation technico-economique de la protection radiologique sont decrites. On presente les problemes poses par: a) l'identification des options de protection et des criteres permettant leur comparaison (reduction des risques pour le public et/ou les travailleurs, couts de protection...); b) l'estimation quantitative des criteres; c) l'utilisation des diverses methodes d'aide a la decision dans le cadre de la comparaison des options de protectionJournal
Revue d'Epidemiologie et de Sante Publique; ISSN 0398-7620; ; v. 30(2); p. 237-248
; v. 30(2); p. 237-248
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