Inhibition in a microgravity environment of the recovery of Escherichia coli cells damaged by heavy ion beams during the NASDA ISS phase I program of NASA Shuttle/Mir mission no. 6.

We participated in a space experiment, part of the National Space Development Agency of Japan (NASDA) Phase I Space Radiation Environment Measurement Program, conducted during the National Aeronautics and Space Administration (NASA) Shuttle/Mir Mission No. 6 (S/MM-6) project. The aim of our study was to investigate the effects of microgravity on the DNA repair processes of living organisms in the in orbit. Heavy ion beam radiation- or ç-irradiation-damaged biological samples of Escherichia coli and the radioresistant bacterium Deinococcus radiodurans were prepared and placed in a biospecimen box, which was loaded into the RRMD III sensor unit of the Space Shuttle. Two identical sets of samples were left in the Spacehab's Payload Processing Facility (SPPF) in Florida, USA, as a control. (flight No. STS-84) was launched from NASA John F. Kennedy Space Center (KSC) in Florida, USA, on May 15, 1997. The mission duration was 9.22 days. An astronaut activated the biological samples in the biospecimen box in the Spacehab during orbit in order to start repair of the DNA damaged by heavy ion beams or ç-irradiation and the samples were incubated for 19 h 35 min at about 22ûC, the cabin temperature. The control specimens in the SPPF were subjected to the same treatment under terrestrial gravity. After returned to earth, we investigated cell recovery by comparing the repair of the radiation-damaged DNA of E. coli and D. radiodurans in the microgravity environment in space with that on Earth. The results indicated that the DNA repair process of E. coli, but not of D. radiodurans, cells was inhibited in a microgravity environment.

Relationship between LET and RBE values for Escherichia coli determined using carbon ion beams from the TIARA cyclotron and HIMAC synchrotron.

NASA: Researchers studied the effects of ion beams on cell lethality in two strains of Escherichia coli. Experiments were conducted on the wild-type strain and a DNA repair-deficient mutant strain that lacks the ability to repair DNA damage. A final aspect of the study was to examine the relationship between the linear energy transfer and relative biological effectiveness values for E. coli cell lethality and dose-response for decreasing the survival fraction to 10 percent.^ieng

Cellular effect of thermal neutron capture treatment using 10B1-para-boronophenylalanine: lethal effect on melanoma cells with different degrees of X-ray sensitivity.

We studied the effect of neutron capture treatment using 10B-compound on X-ray sensitive P-39 and X-ray resistant G-361 human melanoma cell lines, and found a high lethal effect of boron neutron capture therapy in comparison with conventional ionizing radiation. The P-39 line was sensitive to thermal neutron radiation, and extremely sensitive to bleomycin treatment, whereas the G-361 line was resistant to both forms of treatment; however, the two cell lines had similar sensitivity to thermal neutron radiation after pretreatment with 10B1-para-boronophenylalanine (10B1-BPA, 200 micrograms/ml medium). These results show that the thermal neutron capture products (a 7Li nucleus and alpha particle) are highly damaging and short range in tumor cells and thus more efficiently inactivate melanoma cells irrespective of x-ray sensitivity, than conventional X-ray-irradiation.