In the present study, the effects of a thermal injury on the nitric oxide (NO)-ergic system was investigated in freely moving rats. Using a voltammetric method allowing direct and in situ NO measurements, a significant decrease in cortical NO concentration was observed during the 24 h following burning procedure. Since in the burning procedure halothane was employed, it was verified that this anaesthetic did not induce significant effect on cortical NO level. Experiments conducted in ex vivo conditions showed that blood NO and nitrites (NO2−) + nitrates (NO3−) concentrations increased strongly after burn injury while hypothalamic inducible NO-synthase (NOS2) mRNA level decreased significantly. A thermal injury was thus accompanied by a rapid impairment of the NO-ergic pathways, which might partly have been responsible for numerous changes occurring after burn injury.

The effects of a lethal gamma irradiation were investigated on cerebral NO-ergic system by using a voltammetric method in freely moving rats. It is reported that the cortical NO concentration increases right from the end of the radiation exposure (15 Gy) and reaches a maximal magnitude (+120%) 24 h later. A dose-effect relationship from 2 to 15 Gy for gamma-ray exposure has also been observed. The effects, obtained with either an NO synthase inhibitor nonselective for the different NO synthase isoforms or an NO synthase inhibitor selective for the constitutive isoform, suggest that the radiation-induced increase in NO is likely to be dependent on the inducible NO synthase isoform. Moreover, experiments performed under ex vivo conditions showed that the cortical mRNA level for Ca++-independent NO synthase, the brain NOS activity, and urinary nitrites/nitrates increased significantly 24 h after gamma-ray exposure. These results demonstrate that a supralethal wholebody irradiation alters the NO-ergic pathways. The increase in NO obtained under such conditions might constitute a good index of central nervous system radiosensitivity during the acute phase of the radiation syndrome. (C) 2003 by Radiation Research Society.

The effects of total-body irradiation on the permeability of rat striatal blood-brain barrier (BBB) to [3H]alpha-aminoisobutyric acid (AIBA) and [14C]sucrose were investigated using the microdialysis technique. Seven days, 3 and 6 weeks, and 3, 5, and 8 months after gamma exposure at a dose of 4.5 Gy, no modification of the permeability to both [3H]AIBA and [14C]sucrose was observed. But, in the course of the initial syndrome, we observed a significant but transient increase in the BBB permeability to the two markers between 3 and 17 h after exposure. A secondary transient "opening" of the BBB to [14C]sucrose was noticed about 28 h following irradiation without the corresponding increase in BBB permeability to [3H]AIBA. On the contrary, the transport of [3H]AIBA through the BBB was decreased between 33 and 47 h postradiation. In conclusion, our experiments showed early modifications of BBB permeability after a moderate-dose whole-body exposure. Confirmation of these results with other tracers, in another experimental model or in humans, would have clinical applications for designing appropriate pharmacotherapy in radiotherapy and treatment of accidental overexposure.

Chronic stress is known to induce immunological disorders. In the present study we examined the consequences of chronic restraint stress on the immune response to tetanus toxin in mice. We investigated the repartition of subsets of lymphoid cells in blood and spleen, the functional ability of lymphocytes to proliferate and to produce cytokines, and antibody titres against tetanus toxin following stress. We report discordance of the stimulation index of lymphocytes in the restraint group: the proliferating rate severely decreased following stimulation with a relevant antigen, whereas it increased with mitogen. Thus, we report a decrease in cytokine production with relevant antigen (interferon-gamma and interleukin-10), without a T helper type 1 and 2 secretion imbalance. Moreover, we observed an alteration in the humoral response, including a delay in isotype maturation and an immunoglobulin G1/G2a imbalance.

In an attempt to determine the consequences of total body radiation damage on learning and memory in the rat, twenty-eight male Wistar rats aged 4 months received 4.5 Gy total body gamma-irradiation (TBI) while 28 rats received sham irradiation. Sequential behavioral studies of negative reinforcement including a/ one- and b/ two-way avoidance tasks were undertaken. a/ One-way avoidance test: this test was performed before and after TBI. Prior to irradiation both groups were similar. At 20 days (D) and at 3 months post-TBI, irradiated rats had a significantly lower percentage of avoidance than controls but no statistical difference was found at 5 months post-TBI. b/ Two-way avoidance test: this test was performed only after TBI. At days 21, 22, 23, 24, (leaming) and at 4 or 6 months (recalls) post-TBI the mean percentage of avoidance was significantly lower in irradiated than in control rats. This study demonstrates that total-body exposure to 4.5 Gy gamma-irradiation induces behavioral dysfunction affecting learning and transitorily memory. These results suggest that a relatively low dose of total body irradiation can induce neurological complications, which persist 4-6 months later.

The aim of this study was to evaluate the early-delayed effects of a low dose of the gamma acute radiation syndrome (1.5 Gy) on memory and on dopaminergic and serotoninergic metabolism in Swiss albino CD1 mice, of various ages (6, 10 and 20 weeks). At different times after irradiation (from 24 hr to three months), the mice were trained in a single-trial passive avoidance task and tested for retention either 24 hr or 5 days later. Their performance was compared to that of mice that were sham-irradiated. At the end of the behavioral test (days 3, 9, 30 and 93), the concentrations of dopamine (DA) and serotonin (5HT) and their metabolites were determined in hippocampus, anterior cortex and striatum of mice irradiated at the age of six weeks. No significant behavioral effect was observed whichever the age of the animals or the delay of observation. On the contrary at the moderate dose of 4.5 Gy we observed a significant memory deficit 9 days after the exposure. Considering the neurochemical study, in the striatum or in the frontal cortex, no significant modification was observed whichever the delay or the molecule. In the hippocampus slight modifications were noted: an increase (+144%, p = 0.002) in DA level on day 3 after exposure, and a decrease (-27%, p = 0.028) of 5HT level on day 30 post-irradiation. These modifications were only transient and not associated to modifications of the catabolites. This study demonstrates that total-body exposure to gamma radiation at low dose seems to induce only slight effects on the central nervous system.

Purpose: To investigate the effect of blood nitric oxide (NO) as a mediator of the neurovascular syndrome in rats following gamma-irradiation.Material and methods: Using a voltametric method together. with a carbon fibre based sensor, NO measurements were carried out in sham-irradiated and irradiated animals either in blood from the: abdominal aorta or in blood samples from the heart.Results: In in vitro conditions, properties of the probe were not altered by the ionizing radiation. Significant increases of +17% and + 25.6% were observed in the voltametric signal height at 90 min and 24 h respectively after a 15 Gy gamma-ray exposure. These effects were followed on days 3 and 4 by a progressive decrease in the signal height of 7% and 18% respectively. Dose-effect relationships were observed at 90 min and 24-h after exposure to gamma-rays in the. range of 3-15 Gy. Finally, the NO dependence on the measured voltametric signal was controlled by using inhibitors of the NO synthase (NOS) and by performing nitrate assays.Conclusions: Specific blood NO voltametric measurements are possible. Functional changes associated with NO after gamma-ray exposure are discussed.

Recovery from radiation-induced (RI) bone marrow aplasia depends on appropriate cytokine support. The early effects of exogenous cytokines at the hematopoietic stem and progenitor cell (HSPC) level following irradiation are still largely unknown, especially those of survival factors such as stem cell factor (SCF) and Flt-3 ligand (FL). This study was aimed at A) clarifying Fas/Fas-Ligand (Fas-L) implication in RI apoptosis of CD34+ cells and B) assessing the capacity of a combination of cytokines to mitigate RI apoptosis in HSPCs in vitro. We showed that most of in vitro gamma-irradiated CD34+ HSPCs incubated in a medium devoid of cytokines underwent progressive apoptosis-related changes from 6 h (i.e., decreased CD34 antigen expression, Annexin V binding); then Fas/Fas-L coexpression occurred from 10 h on. A strong DNA fragmentation, as assessed by TUNEL assay and propidium iodide staining, was observed at 24 h. Within a 2.5- to 6-Gy dose range, the RI apoptotic process finally led to 97% CD34+ cell death within 48 h with a complete loss of functionality. Unirradiated cells incubated in the same conditions displayed a significantly reduced apoptotic pattern. The early addition of a combination of SCF, FL, thrombopoietin, and interleukin 3 (4F) after cell irradiation prevented 15% (2.5 Gy) and 12% (4 Gy) of HSPCs, respectively, from RI apoptosis, whereas these cytokines used as single factors were inefficient. Furthermore, irradiated HSPCs (2.5 Gy) incubated with 4F in a serum-free culture system for seven days proliferated, giving rise to an increase in the number of total cells (x5.6-fold) and CD34+ cells (x4.2-fold) and to megakaryocytic and granulomonocytic precursors. These results show that the prevention of apoptosis in in vitro irradiated HSPCs depends on an early combination cytokine support. These data suggest that the early therapeutic administration of anti-apoptotic cytokines may be critical for preserving functional HSPCs from in vivo radiation damage.

L'apoptose, ou mort cellulaire programmee, est induite dans les lymphocytes par l'irradiation gamma. Apres une description de l'apoptose et de la necrose, autre processus de mort cellulaire, des methodes d'evaluation de l'apoptose sont rapportees. Certains radioprotecteurs qui ont une activite antioxydante participent a l'inhibition des processus apoptotiques. Par exemple, le zinc neutralise des caspases, lesquelles sont en relation avec des facteurs qui controlent la vie cellulaire. Trois facteurs essentiels sont abordes: la proteine p53, le recepteur Fas et la proteine Bcl-2, ces proteines etant impliquees dans la mort ou la survie des cellules apres une irradiation. La relation entre la modulation de l'expression de ces facteurs et la regeneration lymphocytaire est discutee.

Gamma radiation can induce cell death in lymphocytes. Apoptosis is characterized by numerous morphological, biochemical and molecular modifications measurable using various methods. Some radioprotectors have antioxidant properties and are able to inhibit radiation-induced DNA fragmentation and caspase activation. There are several caspases that cleave proteolytically many proteins and trigger phosphatidylserine externalization recognized by phagocytes. Three main proteins are involved in the regulation of radiation-induced apoptosis: p53, Fas and Bcl-2. The pharmacological regulation of cell death is discussed in order to investigate the subsequent effects related to cell regeneration following radiation injury.

L'image monolithique de la radiopathologie dont les mecanismes physiopathologiques sont reduits aux concepts classiques de « cellule cible» specifique avec mort cellulaire mitotique et apoptotique, se modifie grâce a l'accroissement de nos connaissances sur les communications intercellulaires. La radiobiologie cellulaire s'enrichit aujourd'hui de la radiobiologie « humorale » avec son concept de « reseau cible» tant au niveau des cellules que des messagers intercellulaires. Les desordres radio-induits observes au niveau de ces reseaux se concretisent dans la reaction inflammatoire qui est fortement impliquee dans l'evolution physiopathologique du syndrome aigu d'irradiation. Ces concepts d'une cascade perpetuelle de cytokines, sans periode de latence biologique et qui amenent aux effets tardifs radio-induits, sont particulierement illustres dans la pneumonie et la fibrose pulmonaire radio-induites.

The monolithic image of radiation pathology, the physiopathological mechanisms of which are limited to the conventional concept of specific "target cell" with mitotic and apoptotic cell death, is changing owing to our increasing knowledge about intercellular communications. The cellular radiationbiology is currently enriched by the "humoral" radiationbiology with its concept of "target network" including cells and intercellular messengers. The radiation-induced disorders observed in these networks take shape in the inflammatory reaction; which is largely involved, in the physiopathological development of the acute radiation syndrome. These concepts of a perpetual cascade of cytokines, leading to radiation-induced late effects with no biological latent period, are especially illustrated by the radiation-induced pneumonitis and pulmonary fibrosis.

1. To determine the acute effects of irradiation on the functionality of vessel, rat aortic rings were mounted in an organ bath for isometric tension measurements and irradiated (60Co, 1 Gy min(-1), 15 min). 2. Irradiation, which is without effect on non-contracted or endothelium-denuded vessels, led to an immediate and reversible increase in vascular tone on (-)-phenylephrine (1 microM)-precontracted aortic rings. The tension reached a plateau about 5 min after the beginning of irradiation. 3. The maximal radiation-induced contraction occurred on aortic rings relaxed by acetylcholine (ACh) (1 microM). In this condition, the addition of catalase (1000 u ml(-1)), which reduces hydrogen peroxide, and DMSO (0.1% v/v), which scavenges hydroxyl radical, had no influence on tension level while superoxide dismutase (SOD) (100 u ml(-1)), a superoxide anion scavenger, reduced the observed contraction. A similar result was obtained in the presence of indomethacin (10 microM), a cyclo-oxygenase blocker. 4. Pretreatment of rings with the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) (10-100 microM) inhibited the radiation-induced contraction. 5. This effect was dose rate-dependent and even occurred for a very low dose rate (0.06 Gy min(-1)). 6. The present results indicate that gamma-radiation induces an instantaneous vascular tone increase that is endothelium and dose rate-dependent. This effect is (i) maximal when nitric oxide (NO) is produced, (ii) greatly reduced by SOD and (iii) inhibited by L-NAME, suggesting a major involvement of complexes between NO and superoxide anion.

For many years, the adult central nervous system has been considered as radioresistant. Development of more sensitive and specific technics allowed to reconsider this concept. In this paper, we present the main experimental results obtained in our lab on early radio-induced neurochemical effects observed during the acute radiation syndrome.

Le système nerveux central adulte fut longtemps considéré comme très radiorésistant. Le développement de techniques sensibles et spécifiques a amené les radiobiologistes à réviser ce concept. Notre laboratoire s'est particulièrement intéressé aux perturbations neurochimiques induites au cours du syndrome initial d'irradiation globale aiguë. Nous présentons les principaux résultats expérimentaux obtenus sur les systèmes dopaminergique et cholinergique.

Programmed cell death or apoptosis is a process characterized by several morphological, biochemical and molecular events in response to physiological or pathological stimuli, such as gamma radiation. Free radicals being involved in many physiological and pathological processes, the aim of this study is to investigate the literature about the involvement of oxidative pathway during apoptotic process. As reported by several authors, the literature is abundant in this field and show the complexity of the network in which numerous molecules can regulate cell death and proliferation. However, reactive oxygen intermediate species (ROls) seem to play an important role in the induction of apoptosis as underlined by several reports. Regulation of cellular redox status may appear to be a key component which determines cell proliferation or apoptosis.