Quantification of CD59- mutants in human-hamster hybrid (AL) cells by flow cytometry.

Mutation assay is an important approach in evaluating the genotoxic risk of potentially harmful environmental chemicals. The human-hamster hybrid (A(L)) cell mutagenesis system, based on the complement/antibody-mediated cytotoxicity principle, has been used successfully to evaluate the mutagenic potential of a variety of environmental toxicants. The A(L) cells contain a standard set of CHO chromosomes and a single human chromosome 11, which expresses several cell surface proteins including CD59 encoded by the CD59 gene at 11p13.

A role for long-lived radicals (LLR) in radiation-induced mutation and persistent chromosomal instability: counteraction by ascorbate and RibCys but not DMSO.

Miazaki, Watanabe, Kumagai and their colleagues reported that induction of HPRT(-) mutants by X-rays in cultured human cells was prevented by ascorbate added 30min after irradiation. They attributed extinction of induced mutation to neutralization by ascorbate of radiation-induced long-lived mutagenic radicals (LLR), found using spectroscopy to have half-lives of minutes or hours. We find that post-irradiation treatment with ascorbate reduces, but does not eliminate, induction of CD59(-) mutants in human-hamster hybrid A(L) cells exposed to high-LET carbon-ions (LET of 100KeV/microm).

Dietary factors and cancer mortality among atomic-bomb survivors.

Dietary factors such as fruit and vegetables are thought to reduce the risk of cancer incidence and mortality. We investigated the effect of a diet rich in fruit and vegetables against the long-term effects of radiation exposure on the risk of cancer. A cohort of 36,228 atomic-bomb survivors of Hiroshima and Nagasaki, for whom radiation dose estimates were currently available, had their diet assessed in 1980.

Classical radiation biology dogma, bystander effects and paradigm shifts.

A classical dogma of radiation biology asserts that all effects of radiation on cells are due to it's direct, immediate actions. But evidence accumulated over the last 50 years shows that radiation also has, indirect 'non-target' actions including 'bystander' effects in which effects of radiation on cells or media are transported to cells or tissues that were not 'hit' by the radiation, leading to changes in their function. This important but heretical recognition of radiation actions has been referred to, probably incorrectly, as a 'paradigm shift.

Ascorbate, added after irradiation, reduces the mutant yield and alters the spectrum of CD59- mutations in A(L) cells irradiated with high LET carbon ions.

It has been reported that X-ray induced HPRT- mutation in cultured human cells is prevented by ascorbate added after irradiation. Mutation extinction is attributed to neutralization by ascorbate, of radiation-induced long-lived radicals (LLR) with half-lives of several hours. We here show that post-irradiation treatment with ascorbate (5 mM added 30 min after radiation) reduces, but does not eliminate, the induction of CD59- mutants in human-hamster hybrid A(L) cells exposed to high-LET carbon ions (LET of 100 KeV/microm).