[Alpha emitters inhalation: detection by a process with flags]. / Intérêt de l'évaluation de l'inhalation des émetteurs alpha par la technique des drapeaux.

This work relates to the contaminated people survey (alpha emitters inhalation) with nasal mucus sample analysis. Alpha emitters detection by liquid wander on flags (blotting paper) was employed. Compared to the current technique with paper handkerchiefs, this process improves considerably the time, reduced to 10 min between the sampling's reception and the results of the analysis. The detection's sensitivity of the process is also higher. This process with flags concerns the occupational survey on people leaving an alpha contaminated area (nuclear power plant). It is also available to the monitoring of intervention teams leaving the contaminated area during the immediate response phase and the follow-on response phase (management of the crisis and site restoration).

Hair dosimetry following neutron irradiation.

Use of hair as a biological dosimeter of neutron exposure was proposed a few years ago. To date, the (32)S(n,p)(32)P reaction in hair with a threshold of 2.5 MeV is the best choice to determine the fast neutron dose using body activation. This information is essential with regards to the heterogeneity of the neutron transfer to the organism. This is a very important parameter for individual dose reconstruction from the surface to the deeper tissues. This evaluation is essential to the adapted management of irradiated victims by specialized medical staff. Comparison exercises between clinical biochemistry laboratories from French sites (the CEA and COGEMA) and from the IRSN were carried out to validate the measurement of (32)P activity in hair and to improve the techniques used to perform this examination. Hair was placed on a phantom and was irradiated at different doses in the SILENE reactor (Valduc, France). Different parameters were tested: variation of hair type, minimum weight of hair sample, hair wash before measurement, delivery period of results, and different irradiation configurations. The results obtained in these comparison exercises by the different laboratories showed an excellent correlation. This allowed the assessment of a dose-activity relationship and confirmed the feasibility and the interest of (32)P measurement in hair following fast neutron irradiation.

Effects of combined irradiation and doxorubicin treatment on cardiac function and antioxidant defenses in the rat.

Combined radiotherapy and chemotherapy have represented a major advance in the therapeutic management of cancer therapy. However, the combination of doxorubicin (DXR) and cardiac irradiation (IRR) could precipitate the unexpected expression of congestive heart failure. Oxidative lesions induced by IRR and DXR could represent one of the pathogenic factors of myocardial dysfunction. Our investigations were performed to evaluate in the rat: 1) cardiac functional changes, 2) cardiac and plasma peroxidative damage and antioxidant defenses variations, that occur 24 h (acute effects) and 30 d (middle term effects) following DXR treatment 1 mg/kg(-1)/day(-1) IP for 10 d and a 1 x 20 Gy cardiac gamma-irradiation. Our results showed that DXR affected heart reactivity as early as the end of its administration, although irradiation exerted no detectable effect. Antioxidant defenses disturbances in hearts of DXR treated rats were characterized by vitamins C and E decreases, catalase activity induction and an increase in lipid peroxidation. Moreover, plasma vitamin C consumption and the lower level of plasma lipid peroxidation attested to the efficient solicitation of antioxidant defenses that probably contributed to the preservation of cardiac function at 24 h. After 30 d, cardiac dysfunction became symptomatic at rest, resulting from DXR cardiac toxicity. In spite of the persistent activation of cardiac catalase activity, antioxidant deficiency and increased plasma and cardiac lipid peroxidation highlighted defenses overtaken. Thus, different physiopathological mechanisms are involved in heart disturbance at acute and middle terms, IRR and DXR acting on distinct targets without disclosing synergistic effects. After 30 d, cardiac and plasma biochemical abnormalities were emphasized by the combined DXR+IRR therapy, pointing out the severity of the damage. Oxidative damage to the heart induced both by irradiation and DXR, may be one of the pathogenic factors of myocardial dysfunction. There is the possibility that the deleterious effects might be limited by the use of pharmacologic antioxidant agents.

Effect of in vivo heart irradiation on the development of antioxidant defenses and cardiac functions in the rat.

During radiotherapy of thoracic tumors, the heart is often included in the primary treatment volume, and chronic impairment of myocardial function occurs. The cellular biomolecules are altered directly by radiation or damaged indirectly by free radical production. The purpose of this investigation was to evaluate the biochemical and functional responses of the rat heart to a single high dose of radiation. The effect of 20 Gy local X irradiation was determined in the heart of Wistar rats under general anesthesia. Mechanical performances were measured in vitro using an isolated perfused working heart model, and cardiac antioxidant defenses were also evaluated. Hearts were studied at 1 and 4 months after irradiation. This single dose of radiation induced a marked drop in the mechanical activity of the rat heart: aortic output was significantly reduced (18% less than control values) at 1 month postirradiation and remained depressed for the rest of the experimental period (21% less than control 4 months after treatment). This suggests the development of myocardial failure after irradiation. The decline of functional parameters was associated with changes in antioxidant defenses. The decrease in cardiac levels of vitamin E (-30%) was associated with an increase in the levels of Mn-SOD and glutathione peroxidase (+45.5% and +32%, respectively, at 4 months postirradiation). However, cardiac vitamin C and catalase levels remained constant. Since these antioxidant defenses were activated relatively long after irradiation, it is suggested that this was probably due to the production of free radical species associated with the development of inflammation.

Studies by electron paramagnetic resonance of the importance of iron in the hydroxyl scavenging properties of ascorbic acid in plasma: effects of iron chelators.

Ascorbic acid is considered to be the most important antioxidant of plasma. Its oxidation leads to the ascorbyl free radical (AFR), detected by electron paramagnetic resonance (EPR) spectroscopy. The purpose of this study was to investigate by EPR the interaction of plasma AFR levels in different situations of oxidative stress. Our results showed that plasma AFR remains constant after rat feeding with vitamin C (5 mg or 50 mg per 100 g body weight). We also demonstrated that: (1) the ascorbyl free radical (AFR) level was increased after direct addition of iron Fe3+/EDTA to plasma, the optimal level was reached after addition of 8 microM Fe3+/EDTA (1:2); (2) this AFR production was associated with the formation of hydroxyl radicals. Iron chelators (deferrioxamine, a synthetic iron chelator and apotransferrine, a biological iron chelator) added just before the Fe3+/EDTA complex inhibited the increase of AFR signal induced by this complex. The scavenging effect of plasma was significantly correlated with the AFR production. Therefore, AFR, which is naturally present in plasma, could be used as an index of oxidative stress in which free radicals or adverse iron mobilisation are implicated.

Intramural neovascularization and haemorrhages are major long-term effects of intravascular gamma-radiation after stenting.

Structural changes that might influence the structural integrity of the vessel in response to intravascular brachytherapy (IVB) and stenting were examined, focus being on the importance of neovascularization in rabbit stented arteries. Stents were implanted in the infrarenal aortas of rabbits, immediately followed by gamma IVB or a sham radiation procedure, and the arteries harvested at 6 months. Labelling for von Willebrand factor showed an increase in adventitial and medial neovascularization in irradiated versus control arteries group (5.04+/-0.89 versus 1.51+/-0.23 mm(-2), respectively; p=0.004). Moreover, intramedial haemorrhages (free hemosiderin deposition) and inflammation (macrophages) were only observed in irradiated arteries. No significant change in expression of matrix metalloproteinase 1, 2 or 3 was observed between the irradiated and control group while collagen content decreased in the irradiated versus the control group (10.05%+/-1.48% versus 31.92%+/-3.12%, respectively; p<0.001). The study supports the hypothesis that IVB associated with stenting induces late deleterious effects on the medial layer, characterized by formation of intramural neovessels, haemorrhages and a decrease in collagen content.

PROCORAD's international intercomparisons highlight the evolution of techniques used to determine uranium in urine.

Inter-laboratory tests are a means of assessing the analytical coherence of medical laboratories. In radiotoxicology, this kind of exercise makes it possible to keep up with laboratory know-how and with the evolution and relative performances of analytical techniques. The intercomparison exercises organised by PROCORAD (Association for the Promotion of Quality Controls in Radiotoxicological Bioassays) provide an opportunity to compare and contrast radiochemistry and metrology for the in vitro analysis of urine and faeces. For uranium compounds, the development of new techniques such as inductively coupled plasma-mass spectrometry (ICP-MS), alpha spectrometry, and laser spectrofluorimetry makes it possible to compare the effectiveness of these protocols with respect to radiation protection monitoring, both in routine and special situations. Detection limits, flexibility, repeatability, reproducibility and isotopic quantification are the criteria considered in this study. The authors present the evolution of performances for the analysis of uranium in urine over the years. However, the goal of the laboratories taking part in these annual exercises is not only to check the accuracy of their results but also to have analytical discussions and the opportunity to exchange experiences that will enrich the group's general competence.

In vitro studies of interactions of NO. donor drugs with superoxide and hydroxyl radicals.

Nitric oxide (NO.) is a free radical characterized by a high spontaneous chemical reactivity with many other molecules including the superoxide radical (O2.-). This complex interaction may generate a peroxynitrite anion (ONOO-), which behaves as an important mediator of oxidative stress in many pathological states. In the present study, in vitro experiments were performed to assess directly the O2.- and hydroxyl (.OH) radical scavenging effects of various NO. donor drugs, i.e. sodium nitroprusside (SNP), sodium nitrite (NaNO2), molsidomine and SIN 1, at pH 7.4, 7 or 6. Concentrations of NO. in the incubation medium containing the different NO. donor drugs were measured by the assay based on the reaction of Fe-N-methyl-D-glucamine dithiocarbamate (MGD) with NO. that yields a stable spin-adduct measured by electron paramagnetic resonance (EPR). O2.- and .OH generation was characterized by EPR spin trapping techniques, using the spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). These free radicals were generated from the enzymatic system xanthine-xanthine oxidase, in phosphate buffer adjusted at pH 7.4, 7 and 6. Under these experimental conditions, SNP exhibited the strongest superoxide scavenging properties, characterized by IC50 values expressed in the micromolar range, which decreased at low pH. Addition of SNP (800 microM) to solution containing MGD and Fe2+ (5:1) at pH 7 4 produced a three line EPR spectrum which is identified to [(MGD)2-Fe2+-NO]. In control experiments no EPR signal was observed. We obtained the same results with NaNO2 and an augmentation of the spin-adduct level was noted with the prolongation of the incubation period. In return, molsidomine (2 mM) did not produce, in our conditions, a detectable production of NO.. NaNO2 displayed a significant superoxide scavenging effect only at pH 6, whilst neither molsidomine nor SIN 1 had any effect. Therefore, the superoxide scavenging properties of SNP, NaNO2, and molsidomine appeared to be closely related to their potential for NO release, which partially depends on the pH conditions. The behaviour of SIN 1 is more complicated, the speed of oxygen diffusion probably acting as a limiting factor in NO. formation in our conditions. The production of NO. was detected in presence of SIN 1. The intensity of the complex is comparable with the signal founded with NaNO2. By contrast, all molecules exhibited hydroxyl radical scavenging properties, highlighting the capacity of .OH to react with a wide range of molecules. In conclusion, considering the poor chemical reactivity of O2.-, the NO. donor drugs/O2.- interactions suggest a special relationship between these two radical species, which, in certain pathological states, could lead to the generation of cytotoxic end-products with strong oxidizing properties.

Effect of in vivo heart irradiation on coronary reactivity in the rat.

The frequent exposure of the heart to radiation during thoracic tumor radiotherapy often results in chronic impairment of myocardial function. The aim of the present investigation was to evaluate the effect of irradiation on coronary vascular tone in rat hearts exposed in vivo to a single dose of 20 Gy gamma rays. The ability of rat hearts to respond to changes in coronary reactivity was analyzed 1, 15, 30 and 60 days following cardiac irradiation, using the Langendorff model, after perfusion of either L-nitro-arginine (LNA), an inhibitor of nitric oxide synthetase or SIN 1, a nitric oxide donor drug. LNA-induced vasoconstriction and SIN 1-induced vasodilation were lost respectively 15 days and 30 days after irradiation, and associated with smooth muscle cell alterations observed in microscopy, but without any changes in myocardial MDA levels. Thus, our results suggest that 1) endothelium may represent an early and specific radiation target, characterized by radiation-induced vascular tone dysfunctions, with no detectable microscopical changes; 2) alterations are progressive, resulting first from endothelial damage, followed by smooth muscle cell injuries. In conclusion, a local cardiac irradiation induced cellular dysfunction, characterized by a loss of coronary reactivity without changes of the lipid peroxidation index in the hearts.

Direct evidence of caeruloplasmin antioxidant properties.

The chain-breaking antioxidant potential of caeruloplasmin and bovine serum albumin (BSA) has been investigated in comparison with other well-established antioxidants. Their Oxygen Radical Absorbing Capacity (ORAC), was measured by using beta-phycocyanin (beta-PC) as a fluorescent indicator protein, 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH) as a peroxyl radical generator and the water soluble vitamin E analogue, Trolox, as a reference standard. The relative peroxyl absorbing capacities/mole for Trolox, caeruloplasmin, heat-denatured caeruloplasmin (hCP), catalase, bovine serum albumin (BSA), superoxide dismutase (SOD), and deferoxamine were 1; 2.6; 3.3; 3.7; 1.2; 0.1; 0.2, respectively. Caeruloplasmin was far more effective as a peroxyl radical scavenger than SOD, deferoxamine and BSA, but slightly less effective than catalase. The peroxyl radical absorbing capacity of caeruloplasmin was enhanced by heat-denaturation of the protein. Electron paramagnetic resonance (EPR) spectroscopy using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trap, was applied in order to measure the scavenger abilities of caeruloplasmin on superoxide radical and hydroxyl radical production and the concentration required to inhibit by 50% oxygen free radical formation (IC50) was determined. The IC50 values of caeruloplasmin, hCP, and BSA for the superoxide radical were 12, 2, 260 microM and for the hydroxyl radical 15, 2, 200 microM. These results show that caeruloplasmin is an effective chain-breaking antioxidant for a variety of radicals, independently of its catalytic ferroxidase activity.