Micro-irradiation techniques continue to be highly relevant to a number of radiobiological studies, due to their ability to deliver precise doses of radiation to selected individual cells (or sub-cellular targets) in vitro. The Gray cancer institute (GCI) ion microbeam uses a 1 lm diameter bore glass capillary to vertically collimate protons, or helium ions accelerated by a 4 MV Van de Graaff. Using 3He2+ ions, 99% of cells are targeted with an accuracy of

Nitric oxide (NO) is an important messenger molecule with multiple biological activities. In the present study, sper/NO, a NO generator, showed a biphasic effect on the proliferation of human salivary gland neoplastic (HSG) cells. Sper/NO of less than 20 lM stimulated cells to depart from the G2/M phase and so enhanced cell division and cell proliferation. But sper/NO at higher concentrations restrained cell proliferation and blocked cell-cycle progression. Cells were mainly arrested in the G2/M phase and S phase when they were treated with 100-200 and 300-500 lM sper/NO, respectively. Aspecial S-phase peak was detected in a histogram of the cell-phase distribution of sper/NO-treated HSG. When the concentration of sper/NO increased, the S-phase peak shifted from early the G2/M-phase to later the G1–S-phase boundary. Sper/NO-induced cell-cycle arrests were reversible when the cells were released from NO stress for 48 h and hence cell proliferation was recovered. In addition, micronucleus, but no apoptosis, was produced in the sper/NO-treated cells, and its yield tended to a saturation value with increasing concentrations of sper/NO. The sper/NO-induced effects were effectively eliminated or reduced by treating cells with PTIO, a NO-specific scavenger, indicating that NO is the main source of these effects.

By the method of gel electrophoresis, radiation-induced DNA single- and double-strand breaks (SSB, DSB) were studied with a model system of pBR322 solution in vitro in the presence of •OH radical scavengers, mannitol and TE (10-2 mol dm-3 Tris and 10-3 mol dm-3 ethylene diamine tetra-acetic acid). Experiments showed that SSB resulted from one-hit events of radiation energy deposition and DSB resulted from both one-hit and two-hit energy deposition events and so were distinguished into two classes of αDSB and βDSB. Moreover, α/β, where a is the number of DSB per unit dose induced in one irradiation event and β the number of DSB per unit squared dose induced by the combination of two independent SSB, was related to the scavenging capacity, s, and for σ<108 s-1, αDSB predominate over DSB. On the other hand, if σ<2´108 s–1, the measured G(αDSB) decreased in parallel with G(SSB), i.e., G(αDSB)/G(SSB) was a constant. When σ>2×108 s-1, G(αDSB) decreased slightly so that the ratio of αDSB to SSB evidently increased. Therefore, αDSB could be induced by the radical transfer mechanism for σ<2×108 s-1 and contrarily produced by the local multiply damaged sites (LMDS) mechanism for σ larger than this value. In addition, the distance for two independent complementary SSB forming αDSB was deduced, but no apparent variation of it was found in the wide σ range from ～105 to ～109 s-1, which shows that the DNA steric structure was not influenced by mannitol.

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.

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