The radiation-induced bystander effect challenges the accepted paradigm of direct DNA damage in response to energy deposition driving the biological consequences of radiation exposure.With the bystander response, cells which have not been directly exposed to radiation respond to their neighbours being targeted. In our own studies we have used novel targeted microbeam approaches to specifically irradiate parts of individual cells within a population to quantify the bystander response and obtain mechanistic information. Using this approach it has become clear that energy deposited by radiation in nuclear DNA is not required to trigger the effect, with cytoplasmic irradiation required. Irradiated cells also trigger a bystander response regardless of whether they themselves live or die, suggesting that the phenotype of the targeted cell is not a determining factor. Despite this however, a range of evidence has shown that repair status is important for dealing with the consequences of a bystander signal. Importantly, repair processes involved in the processing of dsb appear to be involved suggesting that the bystander response involves the delayed or indirect production of dsb-type lesions in bystander cells. Whether these are infact true dsb or complexes of oxidised bases in combination with strand breaks and the mechanisms for their formation, remains to be elucidated.

Glow-discharge experiments were performed against water using a graphite rod as the anode and a silver thread as the cathode under an Ar atmosphere. UV-spectrum, FT-IR, 1H-NMR spectrum and GC-MS analyses of the solutions irradiated with plasma were studied. It was found that a small amount of carbon was transferred from anode into water and some organic compounds were produced by reaction between carbon and water. Among those, formic acid, acetic acid and propanoic acid were identified as the main products.

The observation of radiation-induced bystander responses, in which cells respond to their neighbors being irradiated, has important implications for understanding mechanisms of radiation action particularly after low-dose exposure. Much of this questions the current dogma of direct DNA damage driving response in irradiated systems. In this study, we have used a charged-particle microbeam to target individual helium ions (3He2) to individual cells within a population of radioresistant glioma cells cultured alone or in coculture with primary human fibroblasts. We found that even when a single cell within the glioma population was precisely traversed through its cytoplasm with one 3He2 ion, bystander responses were induced in the neighboring nonirradiated glioma or fibroblasts so that the yield of micronuclei was increased by 36% for the glioma population and 78% for the bystander fibroblast population. Importantly, the yield of bystander-induced micronuclei was independent of whether the cytoplasm or nucleus of a cell was targeted. The bystander responses were fully eliminated when the populations were treated with 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide or filipin, which scavenge nitric oxide (NO) and disrupt membrane rafts, respectively. By using the probe 4-amino-5-methylamino-2,7-difluorofluorescein, it was found that the NO level in the glioma population was increased by 15% after 1 or 10 cytoplasmic traversals, and this NO production was inhibited by filipin. This finding shows that direct DNA damage is not required for switching on of important cell-signaling mechanisms after lowdose irradiation and that, under these conditions, the whole cell should be considered a sensor of radiation exposure.

Discharge was performed against ammonia water using a graphite rod as the anode and a silver thread as the cathode under an Ar atmosphere. HPLC and thin layer chromatograph (TLC) analyses showed that three kinds of amino acids were produced in the reaction mixture. As the graphite anode is the solitary source of carbon in the system, it is considered that amino acids have been produced by synthetic reaction between graphite and ammonia water. Thus, our results provide a possible way of formation of amino acids from elemental carbon on the primitive earth. In ad-dition, the mechanism for the production of amino acids is discussed and the yields of different amino acids are pre- sented.

An arc-discharge was carried out to a mixture of ethanol and heavy water under a nitrogen atmosphere. GC-MS analysis showed that DCH2CH2OH and DOCH2CH2OH were produced. This result implies the decomposition of water molecules, which possibly serves as an initial step for the reaction in aqueous solution. In addition, CH3COOD and HOCH2CH2ND2 were also identified in the products, and it was considered that the "nitrogen deposition" effect was caused by capture of D from D2O with N