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.

Evidence has been accumulated for attached cells demonstrating that nonirradiated cells can have a response to the ionization events delivered to their neighbors. In the present study, we first investigated the bystander responses between suspension and neoplastic cells by coculturing L5178Y (LY) cells with human salivary gland (HSG) cells that had been irradiated with either 290 MeV/u carbon ions or X-rays. After this coculture, the survival of nonirradiated recipient LY cells showed dichotomous responses to the irradiation dose delivered to HSG cells. Apoptosis and necrosis were also produced in a 48 h subculture of the recipient LY cells, and their yield increased, but then had a tendency to decrease when the irradiation dose increased. Treatment of cells with PTIO, a nitric oxide specific scavenger, diminished apoptosis and necrosis of the recipient LY cells to the control level. As an oxidization product of NO, nitrite was detected in the coculture medium and its time course corresponded well to the decrease of the viability of irradiated HSG cells. Moreover, the relationship of the survival and the apoptotic and necrotic production of the recipient LY cells to the nitrite concentration followed a linear-quadratic model. The present findings of NO being involved in the radiation-induced bystander effect may have significance in terms of radiotherapy.

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.

Purpose: To investigate the signal factor and its function in the medium-mediated bystander eVect during heavy-ion irradiation of human salivary gland (HSG) neoplastic cells. Materials and methods: Unirradiated recipient HSG cells were co-cultivated with HSG donor cells irradiated with 290MeV/u carbon beams having diVerent LET values. Cell proliferation and micronucleus (MN) induction in recipient cells with and without treatment of a NO scavenger (PTIO) were measured and the concentration of nitrite in the co-culture medium was detected. As a direct control, the eVects of a nitric oxide (NO) generator (sper/NO) on cell proliferation and MN induction were also examined. Results: Increases in cell proliferation and MN induction were found in the recipient HSG cells as a result of co-culturing and cell proliferation was obviously enhanced during a further subculture. In comparison with 13 keV/mm, 100 keV/mm carbon-ion irradiation was found to be a more eYcient inducer of the medium-mediated bystander eVect. The treatment of cells by PTIO resulted in elimination of such eVects, which supports a rooxliedifzoartioNnOprionduthcteomf NedOiu,mni-tmriteediwaatesddebtyescttaenddienr theVeeccot.-cAulstuarne medium, and the dose–response for its concentration was similar to that of cell proliferation and MN induction in the recipient cells. When the HSG cells were treated by sper/NO with a concentration of less than 20 mm, cell proliferation was enhanced, whereas MN increased along with sper/NO concentration. Conclusion: NO participated in the medium-mediated bystander incideVects on cell proliferation and MN induction, depending on the LET of irradiation.

i per nuclear traversal, sug-gesting the existence of bystander effects. This low-dose sen-sitivity was increased when GJIC was enhanced by treating cells with 8-Br-cAMP, but it was partly reduced by treating cells with DMSO, an effective scavenger of reactive oxygen species (ROS). Moreover, no low-dose sensitivity was observed when cells were treated with 100 μM lindane, an inhibitor of GJIC. The survival of irradiated cells was increased by DMSO but was not influenced significantly by cAMP or lin- dane. On the other hand, G1-phase arrest was detected in the irradiated cells, and it was enhanced by cAMP. In contrast, this arrest was reduced or almost eliminated by DMSO or iindane, respectively, even when cells were irradiated with such a high dose that each cell received five nuclear traversals on average. Thus the bystander responses occurred after both low-dose and relatively high-dose irradiation. Our results in-dicated that both GJIC and ROS contributed to the radiation- induced bystander effect, but gap junctional channels might play an essential role by modulating the release of radiation-induced signaling factors.